Liquid discharge device and cleaning method

Abstract

To suppress backflow of liquid into a nozzle while reducing liquid adhering to a nozzle surface.SOLUTION: A liquid discharge device includes: a head for discharging liquid from a nozzle; a supply unit for supplying the liquid to the head and adjusting a pressure of the liquid at the head; a cap unit having a cap and an absorber housed in the cap; and a controller. The controller performs pressurization processing for pressurizing the liquid of the head and discharging the liquid from the nozzle of the head while having a nozzle surface of the head facing the absorber, and capping processing for covering the nozzle surface of the head with the cap and causing the absorber to absorb the liquid adhering to the nozzle surface of the head due to the pressurization processing, and reduces the pressure of the liquid of the head with the nozzle surface covered with the cap in the capping processing.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a cleaning method.

Background Art

[0002] Patent Document 1 describes pressurizing and depressurizing the ink in the head during cleaning of the head.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] After pressurizing the ink in the head, the ink that oozes out from the nozzles adheres to the nozzle surface of the head. If the liquid adhering to the nozzle surface drips from the nozzle surface, there is a risk of soiling the inside of the device. On the other hand, if the pressure of the ink in the head is reduced in order to reduce the liquid adhering to the nozzle surface, the liquid adhering to the nozzle surface may flow back into the nozzles, and there is a risk of color mixing of the ink in the nozzles.

[0005] An object of the present invention is to reduce the liquid adhering to the nozzle surface while suppressing the backflow of the liquid into the nozzles.

Means for Solving the Problems

[0006] The main invention for achieving the above object is a head that ejects liquid from nozzles, a supply unit that supplies the liquid to the head and adjusts the pressure of the liquid in the head, a cap unit having a cap and an absorber housed in the cap, a controller, comprising, the controller while making the nozzle surface of the head face the absorber, a pressurizing process of pressurizing the liquid of the head to eject the liquid from the nozzle of the head, covering the nozzle surface of the head with the cap, and a capping process of causing the absorber to absorb the liquid adhering to the nozzle surface of the head by the pressurizing process, performs, in the capping process, while the nozzle surface is covered with the cap, depressurizing the pressure of the liquid of the head, is a liquid ejection device.

[0007] Other features of the present invention will be clarified by the description in this specification.

Advantages of the Invention

[0008] According to the present invention, it is possible to suppress the backflow of the liquid into the nozzle while reducing the liquid adhering to the nozzle surface.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiment for Carrying Out the Invention

[0010] ===Embodiment=== <Basic Configuration> FIG. 1 is a schematic explanatory diagram of the liquid ejection device 1. FIG. 2 is a block diagram of the liquid ejection device 1.

[0011] The liquid ejection device 1 is a device that ejects liquid onto a medium M (such as printing paper, printing film, etc.). Here, the liquid ejection device 1 is a device (inkjet printer) that prints an image on the medium M. However, as long as the liquid ejection device 1 is a device that ejects liquid from the head 20, it does not have to be a device that prints an image on the medium M. That is, the liquid ejected from the head 20 is not limited to ink. The liquid ejection device 1 includes a moving unit 10 (a carriage unit 11 and a conveyance unit 12), a head 20, a supply unit 30, a cleaning unit 40 (a cap unit 50 and a wiper unit 60), and a controller 70.

[0012] The moving unit 10 is a unit that moves at least one of the medium M and the head 20. Here, the moving unit 10 includes a carriage unit 11 and a conveyance unit 12. The carriage unit 11 is a unit that moves the carriage 111 on which the head 20 is mounted in the scanning direction. The conveyance unit 12 is a unit that conveys the medium M in the conveyance direction. Note that the moving unit 10 is not limited to having a carriage unit 11 and a conveyance unit 12. For example, the moving unit 10 may be composed of a carriage unit 11 that moves the carriage 111 in a two-dimensional direction with respect to the fixed medium M. Also, the moving unit 10 may be composed of a conveyance unit 12 that conveys the medium M with respect to the fixed head 20.

[0013] FIG. 3 is an explanatory diagram of the head 20. The head 20 has a plurality of nozzles 211 for discharging liquid. The head 20 in the figure has four nozzle rows 21. Here, nozzle rows 21 for discharging liquids of different colors (here, inks) are provided. Specifically, a black ink nozzle row for discharging black ink, a cyan ink nozzle row for discharging cyan ink, a magenta ink nozzle row for discharging magenta ink, and a yellow ink nozzle row for discharging yellow ink are provided. Note that the number of nozzle rows 21 is not limited to four, and other numbers may also be used. Also, a plurality of nozzle rows 21 for discharging ink of the same color may be provided. In each nozzle row 21, a plurality of nozzles 211 are arranged in the conveyance direction. The nozzles 211 open at the nozzle surface 22 (the lower surface of the head 20) of the head 20, and liquid is discharged from the openings.

[0014] Each nozzle 211 is provided with a discharge driving unit (not shown). For example, the discharge driving unit is constituted by a piezo element. When the discharge driving unit is driven, droplets are discharged from the nozzle 211. Note that the discharge driving unit is not limited to a piezo element, and may be constituted by, for example, a heater or the like.

[0015] FIG. 4 is an explanatory view of the supply unit 30 and the cap unit 50. The supply unit 30 is a unit for supplying liquid to the head 20. The supply unit 30 includes a tank 31, a supply path 32, a liquid feed pump 33, a damper 34, and a pressure sensor 35. The tank 31 is a liquid supply source and is constituted by, for example, an ink cartridge. The supply path 32 is a liquid flow path between the tank 31 and the head 20 and is constituted by, for example, a tube. The liquid feed pump 33 is a pump for sending out liquid from the tank 31 to the head 20. Note that the liquid feed pump 33 also has a function of adjusting the pressure of the liquid in the head 20. When the liquid feed pump 33 is driven in the forward direction, the liquid in the head 20 is pressurized. When the liquid feed pump 33 is driven in the reverse direction, the liquid in the head 20 is depressurized. The damper 34 is a part for relaxing the pressure fluctuation of the liquid in the head 20. The damper 34 may also be called a sub-tank. The pressure of the liquid in the damper 34 may also be referred to as the pressure of the liquid in the head 20. The pressure sensor 35 measures the pressure of the liquid in the damper 34 (the pressure of the liquid in the head 20). The pressure sensor 35 outputs the measurement result to the controller 70. The controller 70 controls the liquid feed pump 33 based on the measurement result of the pressure sensor 35. For example, when ejecting droplets from the head 20, the driving of the liquid feed pump 33 is controlled based on the detection result of the pressure sensor 35 so that the pressure of the liquid in the head 20 becomes slightly lower than the atmospheric pressure so that the surface of the liquid (ink meniscus) on the nozzle surface 22 becomes concave. The supply unit 30 is provided for each nozzle row 21.

[0016] The cleaning unit 40 is a unit for cleaning the head 20. The cleaning unit 40 includes a cap unit 50 and a wiper unit 60 (see FIG. 2).

[0017] The cap unit 50 is a unit for covering the nozzle surface 22 of the head 20 with the cap 51. The cap unit 50 is used for the cleaning process as described later, but is also used to prevent the liquid in the nozzle 211 from drying by covering the nozzle surface 22 with the cap 51 when the liquid ejection device 1 is stopped. The cap unit 50 includes a cap 51, an absorber 52, a lifting mechanism 53, and a suction pump 54 (see Fig. 4). The cap 51 is a member that covers the nozzle surface 22 of the head 20.

[0018] The cap 51 is configured in a concave shape. In other words, the cap 51 is configured in a box shape with an open top. The cap 51 has a bottom and a wall portion rising from the periphery of the bottom, and the bottom and the wall portion form a housing portion (housing space). The absorber 52 is housed in the housing portion of the cap 51.

[0019] The absorber 52 is a member that absorbs liquid. The absorber 52 is housed in the cap 51. The upper surface of the absorber 52 is located slightly below the upper edge of the cap 51 (the upper edge of the wall portion). Thereby, when the upper edge of the cap 51 contacts the nozzle surface 22 of the head 20, a predetermined interval is formed between the absorber 52 and the nozzle surface 22. As described later, by bringing the liquid adhering to the nozzle surface 22 into contact with the absorber 52, the liquid on the nozzle surface 22 can be absorbed by the absorber 52.

[0020] The lifting mechanism 53 is a mechanism for changing the distance between the nozzle surface 22 of the head 20 and the cap 51. Here, the lifting mechanism 53 is configured to be able to lift the cap 51 (moveable in the vertical direction). However, the lifting mechanism 53 only needs to be configured to be able to lift at least one of the head 20 and the cap 51. The lifting mechanism 53 brings the head 20 and the cap 51 closer or farther apart along the vertical direction.

[0021] The suction pump 54 is a pump for sucking the liquid and air inside the cap 51. When the suction pump 54 is driven, the liquid (the liquid absorbed by the absorber 52) inside the cap 51 is sucked out. The liquid sucked out from the cap 51 by the suction pump 54 will be discharged to a waste liquid tank (not shown).

[0022] The wiper unit 60 is a unit for wiping the nozzle surface 22 of the head 20. As shown in FIG. 1, the wiper unit 60 is provided in the vicinity of the cap unit 50. The wiper unit 60 includes a wiper 61 (see FIG. 6E) and a lifting mechanism (not shown). The wiper 61 is a member for wiping the nozzle surface 22 of the head 20. For example, the wiper 61 is composed of a plate-shaped elastic member. When the lifting mechanism raises the wiper 61, the upper edge of the wiper 61 comes into contact with the nozzle surface 22. By moving the carriage 111 (head 20) with the wiper 61 in contact with the nozzle surface 22, the nozzle surface 22 can be wiped with the wiper 61. Note that the wiper unit 60 may be configured such that the wiper 61 moves in the scanning direction to wipe the nozzle surface 22.

[0023] The controller 70 is a control unit that controls the liquid ejection device 1. The controller 70 controls each unit of the liquid ejection device 1 (the moving unit 10, the head 20, the supply unit 30, the cleaning unit 40). The controller 70 includes an arithmetic processing device and a storage device (not shown). The arithmetic processing device is composed of, for example, a CPU, an MPU, etc. The storage device includes a RAM used for executing programs and a ROM for storing programs, etc. By the arithmetic processing device executing the programs stored in the storage device, various processes (printing processes, cleaning processes, etc.) will be executed. FIG. 2 shows the functional blocks of the controller 70. The controller 70 includes a printing processing unit 71 and a cleaning processing unit 72.

[0024] The printing processing unit 71 performs processing (printing processing) for printing on the medium M. For example, the printing processing alternately repeats a liquid ejection operation of driving the carriage unit 11 to move the head 20 in the scanning direction while ejecting liquid from the head 20 and a conveyance operation of driving the conveyance unit 12 to convey the medium M in the conveyance direction, and prints an image on the medium M.

[0025] The cleaning processing unit 72 performs processing (cleaning processing) for cleaning the head 20. The cleaning processing unit 72 includes a pressurizing processing unit 72A, a depressurizing processing unit 72B, a capping processing unit 72C, a wiping processing unit 72D, and a flushing processing unit 72E. Each processing unit (pressurizing processing unit 72A, depressurizing processing unit 72B, capping processing unit 72C, wiping processing unit 72D, and flushing processing unit 72E) is realized by the arithmetic processing unit constituting the controller 70 executing a program stored in the storage device. The processing performed by each processing unit will be described later.

[0026] <Cleaning Processing> FIG. 5 is a flowchart of the cleaning processing. FIGS. 6A to 6F are explanatory diagrams of the state of the cleaning processing.

[0027] As the cleaning processing, the controller 70 sequentially performs a pressurizing process (S001, see FIG. 6A), a depressurizing process (S002, see FIG. 6B), a capping process (S003, see FIGS. 6C and 6D), a wiping process (S004, see FIG. 6E), and a flushing process (S005, see FIG. 6F). Each process will be described below.

[0028] First, the controller 70 (pressure processing unit 72A) performs pressure processing (S001). The pressure processing is a process of pressurizing the liquid in the head 20 to discharge the liquid from the nozzle 211. At this time, the controller 70 moves the carriage 111 so that the nozzle surface 22 of the head 20 faces the absorber 52 of the cap unit 50. After the nozzle surface 22 of the head 20 faces the absorber 52 of the cap unit 50, the controller 70 drives the liquid feed pump 33 in the forward direction to pressurize the liquid in the head 20, making the pressure of the liquid in the head 20 higher than atmospheric pressure. Specifically, the controller 70 controls the liquid feed pump 33 based on the detection result of the pressure sensor 35 so that the pressure of the liquid in the head 20 becomes several kPa (for example, 3.0 kPa to 4.0 kPa) higher than atmospheric pressure. The pressure of the liquid in the head 20 during the pressure processing may be referred to as the "first pressure".

[0029] Incidentally, if the pressure of the liquid in the head 20 is about 100 kPa higher than atmospheric pressure, the liquid will jet out strongly from the nozzle 211. On the other hand, when the pressure of the liquid in the head 20 (first pressure) is about several kPa higher than atmospheric pressure, since the pressure difference is relatively small, the liquid will seep out from the nozzle 211 (it will not come out as if jetting).

[0030] Due to the pressure processing, the liquid that has seeped out from the nozzle 211 spreads wetly on the nozzle surface 22 due to surface tension. Further, when more liquid seeps out from the nozzle 211, as shown in Fig. 6A, the liquid will drip from the nozzle surface 22 (the liquid will drip from the nozzle surface 22). Since the pressure processing is performed with the nozzle surface 22 facing the absorber 52 of the cap unit 50, the liquid will drip from the nozzle surface 22 onto the absorber 52. The controller 70 drives the suction pump 54 during the pressure processing to discharge the liquid that has dripped into the cap 51.

[0031] Next, the controller 70 (pressure reduction processing unit 72B) performs pressure reduction processing (S002). The pressure reduction processing is a process of reducing the pressure of the liquid in the head 20. The controller 70 controls the liquid feed pump 33 to make the pressure of the liquid in the head 20 lower than the first pressure during the pressurization processing. The pressure of the liquid in the head 20 during the pressure reduction processing may be referred to as the "second pressure".

[0032] When the pressure of the liquid in the head 20 decreases from the first pressure to the second pressure due to the pressure reduction processing, the amount of the liquid flowing out from the nozzle 211 decreases compared with that during the pressurization processing, and the amount of the liquid dripping from the nozzle surface 22 is suppressed. As shown in FIG. 6B, during the pressure reduction processing, the liquid is in a state of adhering to the nozzle surface 22. Even during the pressure reduction processing, since a small amount of the liquid flows out from the nozzle 211 or the liquid wets and spreads on the nozzle surface 22, the liquid may drip during the pressure reduction processing. Therefore, similar to the pressurization processing, the pressure reduction processing is also performed in a state where the nozzle surface 22 faces the absorber 52 of the cap unit 50, and the liquid dripping from the nozzle surface 22 will fall onto the absorber 52. The controller 70 also drives the suction pump 54 during the pressure reduction processing to discharge the liquid dripping into the cap 51.

[0033] Next, the controller 70 (capping processing unit 72C) performs capping processing (S003). As shown in FIG. 6C, the capping processing is a process of covering the nozzle surface 22 with the cap 51 and bringing the liquid on the nozzle surface 22 into contact with the absorber 52. As shown in FIG. 6D, by performing the capping processing, the liquid adhering to the nozzle surface 22 can be absorbed by the absorber 52. Thereby, the amount of the liquid adhering to the nozzle surface 22 can be reduced. After separating the head 20 from the cap 51, the controller 70 drives the suction pump 54 to discharge the liquid in the cap 51 (see FIG. 6D). Note that the capping processing in S003 will be described in more detail later.

[0034] Next, the controller 70 (wipering processing unit 72D) performs a wiping process (S004). The wiping process is a process of wiping the nozzle surface 22 with the wiper 61. The controller 70 moves the carriage 111 to move the head 20 to the position of the wiper unit 60, and controls the lifting mechanism of the wiper unit 60 to raise the wiper 61. Then, as shown in FIG. 6E, the controller 70 moves the carriage 111 while bringing the wiper 61 into contact with the nozzle surface 22, and causes the wiper 61 to wipe the nozzle surface 22.

[0035] By the way, if the wiping process is performed with the nozzle surface 22 in a dry state, there is a risk of damaging the nozzle surface 22. On the other hand, since the above wiping process is performed with the liquid adhering to the nozzle surface 22, damage to the nozzle surface 22 can be suppressed. In other words, the above-described pressurization process is performed in order to perform a wet wiping process. Also, if the wiping process is performed immediately after the pressurization process, there is a risk that the liquid will drip while the head 20 moves to the position of the wiper unit 60 and contaminate the inside of the apparatus. Therefore, after the pressurization process and before the wiping process, the above-described depressurization process and capping process are performed.

[0036] Finally, the controller 70 (flushing processing unit 72E) performs a flushing process (S005). The flushing process is a process of discharging the liquid in the nozzle 211 by discharging droplets from the nozzle 211. At this time, the controller 70 moves the carriage 111 so that the nozzle surface 22 (nozzle 211) of the head 20 faces the absorber 52 of the cap unit 50. Then, as shown in FIG. 6F, the controller 70 drives the discharge driving unit (not shown; for example, a piezo element) of each nozzle 211 to discharge droplets from the nozzle 211. The controller 70 drives the suction pump 54 during the flushing process to discharge the liquid discharged to the cap 51 (and the absorber 52).

[0037] <Regarding the capping process (1)> When performing the above-described depressurization process, if the pressure of the liquid (second pressure) in the head 20 is made lower than the atmospheric pressure, the liquid (mixed-color ink) that has spread wet on the nozzle surface may flow back into the nozzle. For this reason, it is desirable that the second pressure be set to a pressure higher than the atmospheric pressure. However, if the pressure of the liquid (second pressure) in the head 20 during the depressurization process is set too high, the liquid will continue to ooze out from the nozzle 211 even after the depressurization process. As a result, when the head 20 moves between the cap unit 50 and the wiper unit 60 during the cleaning process, the liquid may drip from the nozzle surface 22, which may contaminate the inside of the apparatus. For this reason, the second pressure is set to be slightly higher than the atmospheric pressure. Specifically, during the depressurization process, the controller 70 controls the liquid feed pump 33 based on the detection result of the pressure sensor 35 so that the pressure of the liquid in the head 20 becomes several hundred Pa (for example, 0.5 kPa to 0.7 kPa) higher than the atmospheric pressure. Note that if the pressure of the liquid (second pressure) in the head 20 during the depressurization process is slightly higher than the atmospheric pressure, due to the flow path resistance, the outflow of the liquid from the nozzle 211 is almost stopped. On the other hand, during the flushing process, in order to eject liquid droplets from the head 20, it is necessary to set the pressure of the liquid in the head 20 to be slightly lower than the atmospheric pressure so that the surface of the liquid (ink meniscus) on the nozzle surface 22 becomes concave. The pressure of the liquid that allows liquid droplets to be ejected from the head 20 may be referred to as the "third pressure". Here, when the pressure of the liquid in the head 20 is set to the third pressure lower than the atmospheric pressure, if a large amount of liquid (mixed-color ink) flows back into the nozzle, it becomes necessary to eject a large amount of liquid during the flushing process. For this reason, when setting the pressure of the liquid in the head 20 to the third pressure, it is preferable to suppress the backflow of the liquid into the nozzle. Therefore, in the present embodiment, as described below, during the capping process, the pressure of the liquid in the head 20 is depressurized from the second pressure slightly higher than the atmospheric pressure to the third pressure slightly lower than the atmospheric pressure.

[0038] FIG. 7 is a flowchart of the capping process. The capping process shown in FIG. 7 is performed as the process of S003 in FIG. 5. That is, the capping process shown in FIG. 7 is performed after the pressure reduction process of S002 and before the wiping process of S004.

[0039] In the capping process (S003 in FIG. 5), first, the controller 70 (capping process unit 72C) controls the elevating mechanism 53 of the cap unit 50 to bring the head 20 and the cap 51 closer to each other until the upper edge of the cap 51 contacts the nozzle surface 22 of the head 20 (S011). As shown in FIG. 6C, when the upper edge of the cap 51 contacts the nozzle surface 22 of the head 20, the nozzle surface 22 is covered with the cap 51, and the absorber 52 and the nozzle surface 22 face each other with a predetermined interval therebetween, and the liquid adhering to the nozzle surface 22 comes into contact with the absorber 52. When the liquid adhering to the nozzle surface 22 comes into contact with the absorber 52, the liquid adhering to the nozzle surface 22 is absorbed by the absorber 52 (the liquid adhering to the nozzle surface 22 moves to the absorber 52).

[0040] Next, with the nozzle surface 22 covered with the cap 51 as shown in FIG. 6C, the controller 70 reduces the pressure of the liquid in the head 20 from the second pressure to the third pressure (S012). In the present embodiment, since the liquid adhering to the nozzle surface 22 is absorbed by the absorber 52 before the pressure of the liquid in the head 20 is reduced to the third pressure, the amount of the liquid flowing back to the nozzle 211 during the process of S012 can be suppressed. Note that the suction pump 54 is not driven in the state where the nozzle surface 22 is covered with the cap 51 as shown in FIG. 6C.

[0041] After reducing the pressure of the liquid in the head 20 to the third pressure, the controller 70 controls the elevating mechanism 53 of the cap unit 50 to separate the head 20 from the cap 51 (S013). By causing the absorber 52 to absorb the liquid adhering to the nozzle surface 22, the amount of liquid adhering to the nozzle surface 22 of the head 20 after separation from the cap 51 is reduced compared to the amount of liquid adhering to the nozzle surface 22 before the start of the capping process (see FIG. 6B). Thereby, the amount of liquid discharged during the flushing process (S005) can be suppressed.

[0042] Incidentally, when the pressure of the liquid in the head 20 is reduced from the second pressure to the third pressure after separating the head 20 from the cap 51 in S013 (when the process of S012 is performed after S013), the liquid oozing out from the nozzle 211 after separation cannot be absorbed by the absorber 52 and will accumulate on the nozzle surface 22. Therefore, it is advantageous to perform the process of S012 before the process of S013 in order to reduce the amount of liquid adhering to the nozzle surface 22.

[0043] After separating the head 20 from the cap 51, the controller 70 drives the suction pump 54 to discharge the liquid in the cap 51 (S014, see FIG. 6D). Note that the controller 70 will perform a wiping process after the capping process (S004 in FIG. 5).

[0044] As described above, in the capping process of the present embodiment, with the nozzle surface 22 covered by the cap 51 (see FIG. 6C), the pressure of the liquid in the head 20 is reduced (S012). Thereby, while reducing the liquid adhering to the nozzle surface 22, it is possible to suppress the backflow of the liquid into the nozzle 211.

[0045] <Regarding the capping process (2)> As shown in FIG. 6C, when the nozzle surface 22 is covered by the cap 51, the liquid adhering to the nozzle surface 22 comes into contact with the absorber 52. At this time, as shown in FIG. 6C, a liquid column is formed between the nozzle surface 22 and the absorber 52, and air may enter between the liquid columns. When the liquid adhering to the nozzle surface 22 comes into contact with the absorber 52, if the amount of the liquid adhering to the nozzle surface 22 exceeds the receiving capacity of the absorber 52, a liquid surface is formed on the upper surface of the absorber 52 (the state where the liquid surface is above the upper surface of the absorber 52). Thus, when the amount of the liquid adhering to the nozzle surface 22 exceeds the receiving capacity of the absorber 52, as shown in FIGS. 8A and 8B, bubbles may be formed in the liquid adhering to the head 20 after being separated from the cap 51. Then, when a wiping process (S004) is performed on the head 20 to which the liquid containing bubbles has adhered, as shown in FIG. 8C, the bubbles may splash and contaminate the inside of the apparatus. In the capping process of the modification example described below, it is possible to suppress the formation of bubbles in the liquid.

[0046] FIG. 9 is a flowchart of the capping process of the modification example. FIGS. 10A to 10F are explanatory diagrams of the state of the capping process of the modification example.

[0047] As shown in FIG. 10A, at the stage immediately before the capping process, the nozzle surface 22 faces the absorber 52 of the cap unit 50. Further, the liquid is adhering to the nozzle surface 22. The pressure of the liquid in the head 20 is set to a second pressure slightly higher than the atmospheric pressure.

[0048] In the capping process (S003 in FIG. 5), first, the controller 70 (capping process unit 72C) controls the lifting mechanism 53 of the cap unit 50 to bring the head 20 and the cap 51 closer to each other until the upper edge of the cap 51 contacts the nozzle surface 22 of the head 20 (S021). Similar to S011 described above, also in the process of S021, as shown in FIG. 10B, the liquid adhering to the nozzle surface 22 contacts the absorber 52, and the liquid adhering to the nozzle surface 22 is absorbed by the absorber 52 (the liquid adhering to the nozzle surface 22 moves to the absorber 52).

[0049] Next, the controller 70 controls the elevating mechanism 53 of the cap unit 50 to separate the head 20 from the cap 51 (S022). As already described, by causing the absorber 52 to absorb the liquid adhering to the nozzle surface 22, as shown in FIG. 10C, the amount of liquid adhering to the nozzle surface 22 of the head 20 after separation from the cap 51 can be reduced. However, as shown in FIGS. 8A and 8B, bubbles may be formed in the liquid adhering to the head 20 after separation from the cap 51.

[0050] Next, the controller 70 drives the suction pump 54 to discharge the liquid in the cap 51 (S023). As shown in FIG. 10D, the liquid absorbed by the absorber 52 in S021 is also discharged, and the receiving capacity of the absorber 52 is restored.

[0051] After the process of S023, the controller 70 performs the same processes as S011 to S014 described above (S011' to S014'). Note that the amount of liquid adhering to the nozzle surface 22 before the start of S011' is less than the amount of liquid adhering to the nozzle surface 22 before the start of the capping process (before the start of S021), and the receiving capacity of the absorber 52 has been restored by the process of S023. For this reason, in the process of S011', when the liquid adhering to the nozzle surface 22 comes into contact with the absorber 52, it is possible to suppress the formation of a liquid level on the upper surface of the absorber 52 (see FIG. 10E), and after the process of S013', it is possible to suppress bubbles from entering the liquid adhering to the head 20. Also, in the process of S011', when the liquid adhering to the nozzle surface 22 is absorbed by the absorber 52 (the absorber 52 with the restored receiving capacity), the bubbles disappear, so after the process of S013', it is possible to suppress bubbles from entering the liquid adhering to the head 20 (see FIG. 10F).

[0052] Even in the capping process of the modification example, with the nozzle surface 22 covered by the cap 51, the pressure of the liquid in the head 20 is reduced from a second pressure slightly higher than the atmospheric pressure to a third pressure slightly lower than the atmospheric pressure (S012’). Thereby, while reducing the liquid adhering to the nozzle surface 22, backflow of the liquid into the nozzle 211 can be suppressed. Even if the pressure of the liquid in the head 20 is not reduced in the state where the nozzle surface 22 is covered by the cap 51 (even if the process of S012’ is not performed), by performing the processes of S021 to S23 before the process of S011’, it is possible to suppress bubbles from entering the liquid adhering to the head 20 after the capping process.

[0053] ===Small brackets=== The liquid ejection device 1 of the present embodiment includes a head 20 that ejects liquid from the nozzle 211, a supply unit 30 that supplies liquid to the head 20 and can adjust the pressure of the liquid in the head 20, a cap unit 50 having a cap 51 and an absorber 52, and a controller 70. The controller 70 performs a pressurization process (S001) of pressurizing the liquid in the head 20 to eject the liquid from the nozzle 211, and a capping process (S003) of covering the nozzle surface 22 of the head 20 with the cap 51 and causing the absorber 52 to absorb the liquid adhering to the nozzle surface 22 by the pressurization process. The controller 70 of the present embodiment reduces the pressure of the liquid in the head 20 in the state where the nozzle surface 22 is covered by the cap 51 during the capping process (S012, S012’). Thereby, while reducing the liquid adhering to the nozzle surface 22, backflow of the liquid into the nozzle 211 can be suppressed.

[0054] After the pressurization process and before the capping process, the controller 70 of this embodiment performs a depressurization process of reducing the pressure of the liquid in the head 20 from a first pressure to a second pressure higher than the atmospheric pressure (S002). By performing the depressurization process, the amount of liquid flowing out from the nozzle 211 can be reduced. Note that if the pressure of the liquid in the head 20 is made lower than the atmospheric pressure before the capping process, the liquid adhering to the nozzle surface 22 may flow back into the nozzle 211. Therefore, it is desirable that the second pressure is higher than the atmospheric pressure. Then, in the capping process, the controller 70 depressurizes the pressure of the liquid in the head 20 from the second pressure to a third pressure lower than the atmospheric pressure with the nozzle surface 22 covered by the cap 51. Since the liquid adhering to the nozzle surface 22 is absorbed by the absorber 52 before the pressure of the liquid in the head 20 is depressurized to the third pressure, even if the pressure of the liquid in the head 20 is depressurized to a third pressure lower than the atmospheric pressure, the amount of liquid flowing back into the nozzle 211 can be suppressed.

[0055] In a modified example, in the capping process, the controller 70 performs the operation of bringing the head 20 and the cap 51 close to each other to cover the nozzle surface 22 with the cap 51 and separating the head 20 and the cap 51 from each other twice (refer to S021, S022, S011', and S013', FIGS. 10B, 10C, 10E, and 10F). Then, after separating the head 20 and the cap 51 (refer to S022, FIG. 10C), and before bringing the head 20 and the cap 51 close to each other again to cover the nozzle surface 22 with the cap 51 (refer to S011', FIG. 10E), the controller 70 discharges the liquid in the cap 51 by the suction pump 54 (refer to S023, FIG. 10D). Thereby, it is possible to suppress the entry of bubbles (refer to FIG. 8B) into the liquid adhering to the nozzle surface 22.

[0056] In the capping process shown in FIG. 9, the head 20 and the cap 51 are brought close to each other to cover the nozzle surface 22 with the cap 51, and the head 20 and the cap 51 are separated from each other twice. However, the number of repetitions of the proximity and separation of the head 20 and the cap 51 is not limited to two, and may be three or more. In the capping process, when the head 20 and the cap 51 are brought close to each other to cover the nozzle surface 22 with the cap 51 and the head 20 and the cap 51 are separated from each other a plurality of times, when the nozzle surface 22 is finally covered with the cap 51, it is desirable to reduce the pressure of the liquid in the head 20 from the second pressure to a third pressure lower than the atmospheric pressure. That is, in the process shown in FIG. 9, it is desirable to perform the processes of S011' to S014' (corresponding to the processes of S011 to S014 in FIG. 7) after repeating the processes of S021 to S023 a plurality of times. Thereby, the amount of liquid flowing back into the nozzle 211 can be suppressed.

[0057] By the way, when a wiping process (S004) is performed on the head 20 to which a liquid containing bubbles is attached, as shown in FIG. 8C, there is a risk that the bubbles will bounce and contaminate the inside of the apparatus. For this reason, when the wiping process is performed after the capping process, it is particularly effective to perform the capping process of the modified example.

[0058] ===Other Embodiments=== The above embodiments are presented as examples and do not limit the scope of the invention. The above configurations can be implemented in appropriate combinations, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The above embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0059] 1 Liquid discharge device, 10 Moving unit, 11 Carriage unit, 111 Carriage, 12 Conveying unit, 20 Head, 21 nozzle row, 211 nozzle, 22 nozzle surface, 30 supply unit, 31 tank, 32 supply path, 33 liquid feed pump, 34 damper, 35 pressure sensor, 40 cleaning unit, 50 cap unit, 51 cap, 52 absorber, 53 lifting mechanism, 54 suction pump, 60 wiper unit, 61 wiper, 70 controller, 71 printing processing section, 72 cleaning processing section, 72A pressurizing processing section, 72B depressurizing processing section, 72C capping processing section, 72D wiping processing section, 72E flushing processing section, M medium

Claims

1. A head that discharges a liquid from a nozzle, A supply unit that supplies the liquid to the head and adjusts the pressure of the liquid in the head, A cap unit having a cap and an absorber housed in the cap, A controller, Comprising, The controller, A pressurization process of pressurizing the liquid in the head to discharge the liquid from the nozzle while opposing the nozzle surface of the head to the absorber, A capping process of covering the nozzle surface of the head with the cap and absorbing the liquid adhering to the nozzle surface by the absorber by the pressurization process, Performing, In the capping process, while the nozzle surface is covered with the cap, depressurize the pressure of the liquid in the head, Liquid discharge device.

2. The liquid discharge device according to claim 1, The controller, After the pressurization process and before the capping process, perform a depressurization process of depressurizing the pressure of the liquid in the head from a first pressure to a second pressure higher than atmospheric pressure, In the capping process, while the nozzle surface is covered with the cap, depressurize the pressure of the liquid in the head from the second pressure to a third pressure lower than atmospheric pressure, Liquid discharge device.

3. The liquid discharge device according to claim 1 or 2, The cap unit has a suction pump that sucks the liquid in the cap, The controller, In the capping process, at least twice perform bringing the head and the cap close to each other to cover the nozzle surface with the cap and separating the head and the cap, After separating the head and the cap, before bringing the head and the cap close to each other again to cover the nozzle surface with the cap, discharge the liquid in the cap by the suction pump, Liquid discharge device.

4. The liquid discharge device according to claim 3, The controller performs a wiping process of wiping the nozzle surface with a wiper after the capping process, Liquid discharge device.

5. A head that discharges a liquid from a nozzle, A supply unit that supplies the liquid to the head and adjusts the pressure of the liquid in the head, A cap unit having a cap and an absorber housed in the cap, A cleaning method for a liquid discharge device comprising, While facing the nozzle surface of the head toward the absorber, a pressurizing process of pressurizing the liquid in the head to discharge the liquid from the nozzle; A capping process of covering the nozzle surface with the cap and causing the absorber to absorb the liquid adhering to the nozzle surface by the pressurizing process; are performed, and in the capping process, while the nozzle surface is covered with the cap, the pressure of the liquid in the head is reduced A cleaning method characterized by this.

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