Printing device and method

Abstract

Provided is a printing device capable of suppressing ink consumption while eliminating ink sedimentation.　A printer 1 includes a printing head 25 and ink flow paths 72K, 72Y, 72C and 72M. The printing head 25 has nozzles 26K, 26Y, 26C and 26M. The ink flow paths 72K, 72Y, 72C and 72M supply ink to the printing head 25. A CPU of the printer 1 executes sedimentation elimination processing. The sedimentation elimination processing involves executing an air inflow operation and a purge operation. The air inflow operation is an operation for causing air to flow into at least the printing head 25 from the nozzles 26K, 26Y, 26C and 26M. The purge operation is an operation for discharging ink from the nozzles 26K, 26Y, 26C and 26M, after the execution of the air inflow operation, to fill the ink flow paths 72K, 72Y, 72C and 72M and the printing head 25 with ink.

Description

Printing device and method

[0001] TECHNICAL FIELD This disclosure relates to printing devices and methods implemented in printing devices.

[0002] There are printing devices that print by ejecting ink onto a print medium. Particles contained in the ink may settle over time. If the settled particles cause stagnation in the ink flow within the ink ejection path, the printing device may experience ejection problems.

[0003] For example, the inkjet recording device described in Patent Document 1 inserts a hollow needle into an ink flow path and drives a pump to inject air bubbles into the ink flow path through the hollow needle. The surface of the recording head where the ejection ports are formed is sealed with a suction cap. By driving the pump, ink is sucked from the ejection ports. By sucking the ink, air bubbles adhering to the ink flow path are expelled from the ejection ports together with the air bubbles injected by the hollow needle. In this case, the volume of ink to be sucked can be reduced by the volume of the injected air bubbles.

[0004] JP 2015-100974 A

[0005] When considering using air bubbles injected with a hollow needle to flush out settled ink particles, there is a problem in that, depending on the position at which the air bubbles are injected within the ink flow path, a large amount of ink may be discharged before the air bubbles flowing through the ink flow path reach the ejection port, resulting in wasted ink consumption.

[0006] An object of the present disclosure is to provide a printing device that can reduce ink consumption while eliminating ink sedimentation.

[0007] One aspect of the present disclosure provides a printing device comprising: a print head having nozzles for ejecting ink; an ink flow path for supplying ink to the print head; an air inflow execution unit for executing an air inflow operation for injecting air from the nozzles into the print head and / or into the ink flow path; and a purge execution unit for filling the ink flow path and the print head with ink by executing a purge operation for discharging ink from the nozzles after the air inflow execution unit has executed the air inflow operation. The air flowing in from the nozzles by the air inflow operation pushes ink in the print head back into the ink flow path, eliminating ink sedimentation. In the purge operation, the print head is first discharged of air from the nozzles and then filled with ink. This reduces the amount of ink discharged from the nozzles. The printing device can reduce ink consumption while eliminating ink sedimentation.

[0008] The printing device may include a valve that can be switched between a first state in which the ink flow paths are connected and a second state in which the flow path resistance of the ink flow paths is greater than in the first state, and the air inflow execution unit may execute the air inflow operation by switching the valve to the second state and executing a flushing operation that discharges ink from the nozzles. By blocking the ink flow paths before executing the purging operation, the printing device can reliably create a negative pressure inside the print head. Therefore, air flowing in from the nozzles by the air inflow operation reliably pushes ink inside the print head back into the ink flow paths, eliminating ink sedimentation. Therefore, the printing device can reduce ink consumption while reliably eliminating ink sedimentation.

[0009] The printing device may include a back pressure application unit that applies back pressure to the print head and the ink flow path so that the ink flow path side of the print head is under low pressure, and the air inflow execution unit may set the valve to the second state, perform the flushing operation, and then perform the air inflow operation by setting the valve to the first state with the back pressure application unit applying back pressure to the print head and the ink flow path. By applying back pressure to the print head and the ink flow path, the printing device can more reliably create a negative pressure inside the print head. Therefore, air flowing in from the nozzles by the air inflow operation more reliably pushes ink inside the print head back into the ink flow path, eliminating ink sedimentation. Therefore, the printing device can more reliably eliminate ink sedimentation while suppressing ink consumption.

[0010] The printing device includes a valve switchable between a first state in which the ink flow paths are connected and a second state in which the flow path resistance of the ink flow paths is greater than in the first state; a cap member switchable between a sealed state in which the nozzle formation surface of the print head is covered and an open state in which the cap member is spaced from the nozzle formation surface; and a suction unit that performs a suction operation on the print head via the cap member. The air inflow execution unit may perform the air inflow operation by setting the cap member in the sealed state and the valve in the second state, causing the suction unit to perform the suction operation, and then setting the cap member in the open state. The purge execution unit may perform the purge operation by setting the valve in the first state after the air inflow execution unit has performed the air inflow operation. Since the ink flow paths are blocked and the suction-based purge operation reliably creates a negative pressure inside the print head, air flowing in from the nozzles by the air inflow operation reliably pushes ink inside the print head back into the ink flow paths, eliminating ink sedimentation. This allows the printing device to reliably eliminate ink sedimentation while reducing ink consumption.

[0011] The printing device includes a cap member that can be switched between a sealed state covering the nozzle formation surface of the print head and an open state spaced apart from the nozzle formation surface, and a suction unit that performs a suction operation on the print head via the cap member. The air inflow unit may perform the air inflow operation by placing the cap member in the sealed state, causing the suction unit to perform the suction operation, and then switching the cap member to the open state after a predetermined waiting time has elapsed. The purging operation creates a negative pressure inside the print head, causing air to flow into the print head from the nozzles during the air inflow operation. By waiting for the waiting time to elapse, the inflowing air can sufficiently push the ink inside the print head back into the ink flow path, eliminating ink sedimentation. This allows the printing device to reduce ink consumption while eliminating ink sedimentation. Furthermore, the printing device can eliminate ink sedimentation using only existing components, thereby achieving low costs.

[0012] The printing device may include an ink tank that stores ink and supplies ink to the print head via the ink flow path, and the air inflow execution unit may execute the air inflow operation by creating a low pressure on the ink flow path side of the print head due to a head difference between the ink tank and the print head. Because back pressure can be applied to the print head and the ink flow path due to the head difference between the print head and the ink tank, the printing device can achieve a configuration for eliminating ink sedimentation at low cost.

[0013] The printing device may include an ink tank that stores ink and supplies ink to the print head via the ink flow path, and a tank pump provided in the ink flow path, and the air inflow execution unit may execute the air inflow operation by driving the tank pump so that the ink flow path side of the print head is under low pressure. This allows the tank pump to be driven to apply back pressure to the ink tank, so the printing device can apply back pressure to the print head and the ink flow path. Therefore, the printing device can achieve a configuration for eliminating ink sedimentation at low cost.

[0014] The printing device may perform the air inflow operation by the air inflow execution unit and the purge operation by the purge execution unit again when a predetermined time has elapsed since the previous purge operation by the purge execution unit. By performing the purge operation, air inflow operation, and refilling operation each time the elapsed time has elapsed, the printing device can maintain a state in which maintenance has been performed to make it less likely for ink to settle.

[0015] Another aspect of the present disclosure is a method executed in a printing device having a print head with nozzles that eject ink and an ink flow path that supplies ink to the print head, the method comprising: an air inflow operation that causes air to flow from the nozzles into at least the print head and the ink flow path; and a purging operation that discharges ink from the nozzles after the air inflow operation is executed. This method can reduce ink consumption while eliminating ink sedimentation in the printing device.

[0016] FIG. 1 is a perspective view of the printer 1. FIG. 2 is a diagram of the ink flow path configuration in the initial state. FIG. 3 is a side view of the print head 25. FIG. 4 is a front view of the print head 25. FIG. 5 is a block diagram showing the electrical configuration of the printer 1. FIG. 6 is a flowchart of the implementation determination process. FIG. 7 is a flowchart of the sedimentation elimination process (first embodiment). FIG. 8 is a diagram showing the state when supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M are closed. FIG. 9 is a diagram showing the state when flushing is performed. FIG. 10 is a diagram showing the state when supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M are open. FIG. 11 is a diagram showing the state when a purge operation is performed. FIG. 12 is a front view of the print head 25 when flushing is performed. FIG. 13 is a front view of the print head 25 when a meniscus break occurs and the meniscus retracts. FIG. 14 is a front view of the print head 25 when air has backflowed enough to re-form a meniscus. FIG. 15 is a front view of the print head 25 when air has backflowed to the manifold 73K. FIG. 16 is a side view of the print head 25 when further air backflow occurs due to back pressure caused by opening the supply valve 84K. FIG. 17 is a side view of the print head 25 when a purge operation is performed and ink has flowed into the manifold 73K. FIG. 18 is a flowchart of the sedimentation elimination process (second embodiment). FIG. 19 is a diagram showing the process when suction is performed. FIG. 20 is a diagram showing the process when uncapping is performed. FIG. 21 is a flowchart of the sedimentation elimination process (third embodiment). FIG. 22 is a flowchart of the sedimentation elimination process (fourth embodiment). FIG. 23 is a diagram showing the process when the tank pumps 82K, 82Y, 82C, and 82M are driven to apply negative pressure to the subtanks 51K, 51Y, 51C, and 51M.

[0017] A printer 1 according to an embodiment of the present disclosure will be described with reference to the drawings. The lower left, upper right, lower right, upper left, upper side, and lower side of Fig. 1 are the front, rear, right, left, upper side, and lower side of the printer 1, respectively.

[0018] 1 is an inkjet printer that ejects ink onto a print medium (not shown) to perform printing. The print medium may be fabric, paper, or a T-shirt, for example. The printer 1 can print a color image on the print medium using, for example, five colors of ink: white (W), black (K), yellow (Y), cyan (C), and magenta (M).

[0019] Hereinafter, the white ink among the five color inks will be referred to as "white ink," and the four color inks of black, cyan, yellow, and magenta will be referred to as "black ink," "cyan ink," "yellow ink," and "magenta ink," respectively. When referring to black ink, cyan ink, yellow ink, and magenta ink collectively, or when no particular ink is specified, they will simply be referred to as "color ink." When referring to white ink and color inks collectively, or when no particular ink is specified, they will simply be referred to as "ink."

[0020] As shown in Figure 1, the printer 1 includes a transport unit 11 and a pair of guide rails 21. The transport unit 11 extends in the front-to-rear direction and supports a platen 15. A print medium (not shown) is placed on the upper surface of the platen 15. The platen 15 is transported in the front-to-rear direction along the transport unit 11 by driving a sub-scanning motor 32 shown in Figure 5. Therefore, in this embodiment, the front-to-rear direction is the sub-scanning direction.

[0021] The pair of guide rails 21 extend in the left-right direction and support a carriage 23. The carriage 23 is positioned above the platen 15. A print head 25 is mounted on the carriage 23. The number of print heads 25 is not limited to a specific number, but is six as an example. Note that Figure 1 shows only three print heads 25 lined up in the front-to-rear direction.

[0022] Each of the multiple print heads 25 ejects color ink, white ink, pretreatment agent, special paint, etc. when driven by a head drive unit 35 shown in Figure 5. The head drive unit 35 is, for example, a piezoelectric element. Since each of the multiple print heads 25 has the same structure, the structure of a print head 25 that ejects color ink will be described as an example.

[0023] The print head 25 has a rectangular parallelepiped shape. A nozzle forming surface 26 shown in FIG. 2 is provided on the underside of the print head 25. A plurality of nozzles are formed in the nozzle forming surface 26. In this embodiment, as an example, four nozzles 26K, 26Y, 26C, and 26M shown in FIG. 2 are formed in the nozzle forming surface 26. A head driving unit 35 is provided for each of the nozzles 26K, 26Y, 26C, and 26M. The head driving unit 35 is, for example, a piezoelectric element. When the head driving unit 35 is driven, the print head 25 ejects black ink, yellow ink, cyan ink, and magenta ink from the nozzles 26K, 26Y, 26C, and 26M, respectively.

[0024] 5, the carriage 23 is driven by a main scanning motor 31 to move left and right along the pair of guide rails 21. This causes the print head 25 to also move left and right. Therefore, in this embodiment, the left and right direction is the main scanning direction.

[0025] According to the above configuration, the printer 1 moves the platen 15 from front to rear by driving the sub-scanning motor 32 shown in Fig. 5. Then, while moving the platen 15 from rear to front by driving the sub-scanning motor 32 shown in Fig. 5, the printer 1 reciprocates the carriage 23 in the left-right direction by driving the main scanning motor 31 shown in Fig. 5. The print head 25 ejects ink while scanning in the left-right direction. In this way, the printer 1 prints an image on the print medium by ejecting ink from the print head 25 while transporting the print medium on the platen 15 in the front-to-back and left-to-right directions relative to the print head 25.

[0026] Caps 17 are provided to the left of the movement path of the platen 15 and below the movement path of the print heads 25. The number of caps 17 corresponds to the number of print heads 25, and is six in one example. The caps 17 are positioned in accordance with the arrangement positions of the print heads 25.

[0027] The cap 17 moves up and down by driving the cap motor 33 shown in FIG. 5. After printing is completed, the print head 25 is transported by the carriage 23 to the left side of the movement path of the platen 15. This positions the print head 25 above the cap 17. In this state, the cap motor 33 shown in FIG. 5 is driven, causing the cap 17 to move upward. In this case, the cap 17 covers the nozzle forming surface 26. This operation is called "capping." Driving the cap motor 33 causes the cap 17 to move downward and move away from the nozzle forming surface 26. This operation is called "uncapping." The cap 17 can be changed between a "sealed state" and an "open state." The sealed state is a state in which the cap 17 covers the nozzle forming surface 26. The open state is a state in which the cap 17 is separated from the nozzle forming surface 26.

[0028] As shown in Figure 1, a storage section 50 is provided on the right side of the printer 1. Multiple main tanks 52 are stored in the storage section 50. Multiple sub-tanks 51 are arranged on the right side of the printer 1, behind the guide rail 21. It is desirable that the multiple sub-tanks 51 be provided at the same height, but the orientation of the sub-tanks 51 in the horizontal direction is not limited.

[0029] Each of the plurality of main tanks 52 and sub-tanks 51 stores ink. In this embodiment, the main tanks 52 include main tanks 52K, 52Y, 52C, and 52M shown in Fig. 2. The sub-tanks 51 include sub-tanks 51K, 51Y, 51C, and 51M shown in Fig. 2.

[0030] An example of the flow path configuration for color inks will be described with reference to Figure 2. Hereinafter, the state in which the valves are closed will be referred to as the "closed state," and the state in which the valves are open will be referred to as the "open state." Valves in the closed state are illustrated as valves without diagonal lines, and valves in the open state are illustrated as valves with diagonal lines.

[0031] The printer 1 includes main tanks 52K, 52Y, 52C, and 52M, tank flow paths 71K, 71Y, 71C, and 71M, and sub-tanks 51K, 51Y, 51C, and 51M. The main tanks 52K, 52Y, 52C, and 52M store black ink, yellow ink, cyan ink, and magenta ink, respectively. The main tanks 52K, 52Y, 52C, and 52M are located at the most upstream position in the flow paths for the color inks.

[0032] The tank flow paths 71K, 71Y, 71C, and 71M are made of flexible tubes, for example. The upstream ends of the tank flow paths 71K, 71Y, 71C, and 71M are connected to the main tanks 52K, 52Y, 52C, and 52M, respectively. The downstream ends of the tank flow paths 71K, 71Y, 71C, and 71M are connected to the sub-tanks 51K, 51Y, 51C, and 51M, respectively.

[0033] Therefore, black ink, yellow ink, cyan ink, and magenta ink flow through the tank flow paths 71K, 71Y, 71C, and 71M from the main tanks 52K, 52Y, 52C, and 52M toward the sub-tanks 51K, 51Y, 51C, and 51M, respectively. The sub-tanks 51K, 51Y, 51C, and 51M store black ink, yellow ink, cyan ink, and magenta ink, respectively.

[0034] The tank flow paths 71K, 71Y, 71C, and 71M are provided with tank valves 81K, 81Y, 81C, and 81M, tank pumps 82K, 82Y, 82C, and 82M, and tank filters 83K, 83Y, 83C, and 83M, respectively. The tank valves 81K, 81Y, 81C, and 81M can be switched between a closed state and an open state by driving solenoids 811, 812, 813, and 814 shown in FIG. 5.

[0035] When the tank valves 81K, 81Y, 81C, and 81M are closed, they block the tank flow paths 71K, 71Y, 71C, and 71M, respectively. When the tank valves 81K, 81Y, 81C, and 81M are open, they connect the tank flow paths 71K, 71Y, 71C, and 71M, respectively.

[0036] The tank pumps 82K, 82Y, 82C, and 82M are provided upstream of the tank valves 81K, 81Y, 81C, and 81M. The tank pumps 82K, 82Y, 82C, and 82M are driven by pump motors 821, 822, 823, and 824 shown in FIG. 5 to suck black ink, yellow ink, cyan ink, and magenta ink from the main tanks 52K, 52Y, 52C, and 52M. The tank pumps 82K, 82Y, 82C, and 82M are driven by pump motors 821, 822, 823, and 824 shown in FIG. 5 to send the sucked black ink, yellow ink, cyan ink, and magenta ink to the sub-tanks 51K, 51Y, 51C, and 51M via the tank flow paths 71K, 71Y, 71C, and 71M, respectively.

[0037] The tank filters 83K, 83Y, 83C, and 83M are located upstream of the tank pumps 82K, 82Y, 82C, and 82M, and are replaceably attached to the tank flow paths 71K, 71Y, 71C, and 71M. The tank filters 83K, 83Y, 83C, and 83M are made of, for example, nonwoven fabric, woven fabric, resin film, or porous metal piece, and filter the ink.

[0038] The printer 1 is equipped with ink flow paths 72K, 72Y, 72C, and 72M. The ink flow paths 72K, 72Y, 72C, and 72M are formed, for example, from flexible tubes. The upstream ends of the ink flow paths 72K, 72Y, 72C, and 72M are connected to sub-tanks 51K, 51Y, 51C, and 51M, respectively. The downstream ends of the ink flow paths 72K, 72Y, 72C, and 72M are connected to the print head 25.

[0039] The ink flow paths 72K, 72Y, 72C, and 72M are flexible and can deform in response to the movement of the print head 25. The length from the upstream end to the downstream end of each of the ink flow paths 72K, 72Y, 72C, and 72M is longer than, for example, the length from the left end to the right end of the movement range of the print head 25.

[0040] Ink flow paths 72K, 72Y, 72C, and 72M are provided with supply valves 84K, 84Y, 84C, and 84M and supply filters 85K, 85Y, 85C, and 85M, respectively. The supply valves 84K, 84Y, 84C, and 84M can be switched between a closed state and an open state by driving solenoids 841, 842, 843, and 844 shown in FIG.

[0041] When the supply valves 84K, 84Y, 84C, and 84M are closed, they block the ink flow paths 72K, 72Y, 72C, and 72M, respectively. When the supply valves 84K, 84Y, 84C, and 84M are open, they connect the ink flow paths 72K, 72Y, 72C, and 72M, respectively.

[0042] The supply filters 85K, 85Y, 85C, and 85M are located downstream of the supply valves 84K, 84Y, 84C, and 84M, and are replaceably attached to the ink flow paths 72K, 72Y, 72C, and 72M. The supply filters 85K, 85Y, 85C, and 85M are made of, for example, nonwoven fabric, woven fabric, resin film, or porous metal piece, and filter the ink.

[0043] The printer 1 further includes a waste liquid tank 53 and a waste liquid flow path 73. The waste liquid tank 53 stores ink that has not been used in printing. The waste liquid flow path 73 is formed, for example, from a tube, and is flexible. One end of the waste liquid flow path 73 is connected to the cap 17. The other end of the waste liquid flow path 73 is connected to the waste liquid tank 53. Therefore, waste liquid flows through the waste liquid flow path 73 from the cap space 18 toward the waste liquid tank 53.

[0044] A waste liquid valve 86 and a waste liquid pump 87 are provided in the waste liquid flow path 73. The waste liquid valve 86 can be switched between a closed state and an open state by driving a solenoid 861 shown in Figure 5. When in the closed state, the waste liquid valve 86 blocks the waste liquid flow path 73. When in the open state, the waste liquid valve 86 opens the waste liquid flow path 73.

[0045] The waste liquid pump 87 is provided closer to the other end of the waste liquid flow path 73 (toward the waste liquid tank 53) than the waste liquid valve 86. The waste liquid pump 87 sucks waste liquid, air, etc. from the cap space 18 by driving a pump motor 871 shown in Fig. 5. The waste liquid pump 87 sends the sucked waste liquid, air, etc. through the waste liquid flow path 73 toward the waste liquid tank 53 by driving the pump motor 871 shown in Fig. 5.

[0046] The printer 1 includes an atmosphere communication channel 74. The atmosphere communication channel 74 is made of, for example, a tube and is flexible. One end of the atmosphere communication channel 74 is connected to the cap 17. The other end of the atmosphere communication channel 74 is open to the atmosphere 90.

[0047] An atmosphere communication valve 88 is provided in the atmosphere communication passage 74. The atmosphere communication valve 88 can be switched between a closed state and an open state by driving a solenoid 881 shown in FIG. 5. When in the closed state, the atmosphere communication valve 88 blocks the atmosphere communication passage 74. When in the open state, the atmosphere communication valve 88 opens the atmosphere communication passage 74.

[0048] 3 and 4, the flow path configuration within the print head 25 will be described in detail. In this embodiment, the flow path configuration for black ink supplied to nozzle 26K will be described as an example. The flow path configurations for supplying ink to the other nozzles 26Y, 26C, and 26M are the same as the flow path configuration for black ink supplied to nozzle 26K, so descriptions thereof will be omitted.

[0049] The print head 25 includes a manifold 73K, three individual flow paths 74K to 76K, and a nozzle 26K. The nozzle 26K includes, for example, three small holes 261K to 263K. Note that the nozzle 26K is composed of multiple small holes (for example, 70 holes), but in this embodiment, the nozzle 26K will be described as including only three small holes 261K to 263K.

[0050] The manifold 73K is a single flow path that extends linearly within the print head 25. The upstream end of the manifold 73K is connected to the downstream end of the ink flow path 72K. The manifold 73K branches from its downstream end into three individual flow paths 74K to 76K. The small holes 261K to 263K are provided in the nozzle forming surface 26. The downstream end of the individual flow path 74K communicates with the small hole 261K. The downstream end of the individual flow path 75K communicates with the small hole 262K. The downstream end of the individual flow path 76K communicates with the small hole 263K. A head driving unit 35 is provided for each of the small holes 261K to 263K.

[0051] As shown in FIG. 1, the print head 25 is positioned higher than the subtank 51. This creates a head difference between the print head 25 and the subtank 51. As a result, the ink flow paths 72K, 72Y, 72C, and 72M on the print head 25 side are under low pressure, and a predetermined back pressure is applied within the print head 25. This constantly creates a negative pressure within the print head 25. As a result, an ink meniscus is formed in each of the small holes 261K to 263K. In the printer 1, the negative pressure within the print head 25 is maintained at a level lower than the meniscus withstand pressure. The meniscus withstand pressure refers to the pressure at which the meniscus can withstand the negative pressure. When the head drive unit 35 is driven in this state, the print head 25 ejects black ink from the small holes 261K to 263K.

[0052] The electrical configuration of the printer 1 will be described with reference to Figure 5. The printer 1 is equipped with a control board 10. The control board 10 is provided with a CPU 41, ROM 42, RAM 43, and flash memory 44. The CPU 41 controls the printer 1 and is electrically connected to the ROM 42, RAM 43, and flash memory 44. The ROM 42 stores a control program that the CPU 41 uses to control the operation of the printer 1, information required by the CPU 41 when executing various programs, and the like. The RAM 43 temporarily stores various data used in the control program, and the like. The flash memory 44 is non-volatile and stores print data for printing, and the like.

[0053] The CPU 41 is electrically connected to the main scanning motor 31, sub-scanning motor 32, cap motor 33, head drive unit 35, solenoids 811 to 814, 841 to 844, 861, 881, pump motors 821 to 824, 871, and operation unit 37. The main scanning motor 31, sub-scanning motor 32, cap motor 33, head drive unit 35, solenoids 811 to 814, 841 to 844, 861, 881, and pump motors 821 to 824, 871 are driven under the control of the CPU 41.

[0054] The operation unit 37 is a touch panel or the like, and outputs information according to user operations to the CPU 41. By operating the operation unit 37, the user can input, to the printer 1, purge instructions for performing purging, and the like.

[0055] The implementation determination process will be described with reference to Figure 6. The implementation determination process determines whether or not to implement the sedimentation elimination process. The sedimentation elimination process is a process for pushing out ink from the ink flow paths in the print head 25, including settled particles. The specific process content will be described later. When the printer 1 is powered on, the CPU 41 reads an implementation determination program from the ROM 42 and executes this process.

[0056] The CPU 41 determines whether a predetermined time (e.g., four hours) has elapsed since the previous sedimentation elimination process (S1). The CPU 41 may measure the elapsed time since the previous sedimentation elimination process was completed, for example, using a timer (not shown). If the predetermined time has not elapsed (S1: NO), the CPU 41 terminates this process. If the predetermined time has elapsed (S1: YES), ink particles have settled in the manifold 73K to which the individual flow path 74K is connected (see FIG. 12). To eliminate particle settling, the CPU 41 executes the sedimentation elimination process (S2). After executing the sedimentation elimination process, the CPU 41 terminates this process.

[0057] The settling elimination process will be described. Four examples will be described in this embodiment. All four examples described below have in common the fact that they break the ink meniscus formed in the nozzles 26K, 26Y, 26C, and 26M (hereinafter referred to as meniscus break), draw air from the atmosphere into the print head 25, and then perform a purge operation. Note that the operation of causing a meniscus break and drawing air from the atmosphere into the ink flow path corresponds to the "air inflow operation" of this disclosure. The following four examples differ in the method of causing a meniscus break within the "air inflow operation."

[0058] First Embodiment A first embodiment will be described with reference to FIGS. 7 to 17. The sedimentation elimination process of the first embodiment involves flushing to cause a meniscus break. As shown in FIGS. 7 and 8, the CPU 41 closes the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M (S11). In this state, the CPU 41 executes flushing of the print head 25 (S12). Flushing is a maintenance operation that restores the ink ejection function of the nozzles 26K, 26Y, 26C, and 26M by driving the head drive unit 35 to eject ink from the nozzles 26K, 26Y, 26C, and 26M.

[0059] For example, when flushing is performed with supply valve 84K closed (see FIG. 12), ink is not supplied to nozzle 26K, and the negative pressure in the individual flow paths 74K, 75K, and 76K and manifold 73K increases. A similar phenomenon occurs in nozzles 26Y, 26C, and 26M. As a result, the negative pressure in the print head 25 increases.

[0060] If the negative pressure inside the print head 25 exceeds the meniscus's withstand pressure, a meniscus break occurs in the nozzles 26K, 26Y, 26C, and 26M. As shown in Figure 13, when the meniscus formed in the small hole 261K breaks, ink is drawn in by back pressure from the supply valve 84K side, causing the meniscus to retreat. As the meniscus retreats, air flows in from the nozzle 26K. As shown in Figure 14, after ink is drawn into the individual flow path 74K, a meniscus forms again, or the reverse flow continues until the negative pressure in the flow path is fully restored.

[0061] When flushing is complete, as shown in FIG. 10, the CPU 41 opens the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M (S13). As described above, because the print head 25 is located higher than the subtank 51, the back pressure from the subtank 51 further draws ink in. Then, as shown in FIGS. 15 and 16, when air backflows into the manifold 73K, the ink in the manifold 73K, including any settled particles, flows further back into the ink flow path 72K. A similar phenomenon occurs in the flow paths of the nozzles 26Y, 26C, and 26M. In this way, the flow paths within the print head 25 are replaced with air.

[0062] Next, as shown in Fig. 11, the CPU 41 caps the nozzle surface 26 and performs a purge operation with the nozzle surface 26 covered with the cap 17 (S14). By performing the purge operation, ink flows into the manifold 73K, which has been replaced with air, as shown in Fig. 17. As a result, the air in the manifold 73K is replaced with ink. Therefore, the sedimentation elimination process of the first embodiment can improve the replaceability of the ink flow path and the recovery performance against sedimentation. After the purge operation is completed, the CPU 41 ends this process.

[0063] Second Example A second example will be described with reference to Figures 18 to 20. In the sedimentation elimination process of the second example, the print head 25 is uncapped while the negative pressure inside the print head 25 is increased, causing a meniscus break. As shown in Figures 18 and 19, the CPU 41 caps the nozzle surface 26 (S21). With the nozzle surface 26 covered with the cap 17, the CPU 41 closes the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M (S22).

[0064] Next, the CPU 41 performs suction (S23). The CPU 41 applies negative pressure to the cap space 18 by driving the pump motor 871 shown in Figure 5, thereby suctioning ink from the nozzles 26K, 26Y, 26C, and 26M (see Figure 19). This increases the negative pressure inside the print head 25.

[0065] The CPU 41 then uncaps the print head 25 while the pressure inside is negative (S23). This causes a meniscus break because the pressure inside the print head 25 is lower than the pressure outside. This causes air in the atmosphere to flow into the print head 25 from the nozzles 26K, 26Y, 26C, and 26M, and backflow through the ink flow paths (see FIG. 20). This causes the ink flow paths, such as the manifold and individual flow paths inside the print head 25, to be filled with air.

[0066] Now that the state is the same as in the first embodiment, the CPU 41 opens the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M, and then executes a purge operation (S24). By executing the purge operation, ink flows into the manifold 73K, which has been replaced with air (see FIG. 17). As a result, the entire interior of the manifold 73K is replaced with ink. Therefore, even in the sedimentation elimination process of the second embodiment, the ink flow path replacement capability and recovery performance against sedimentation can be improved. After the purge operation is completed, the CPU 41 ends this process.

[0067] Third Embodiment A third embodiment will be described with reference to FIG. 21 . The settling elimination process of the third embodiment is a modification of the second embodiment. As in the second embodiment, the CPU 41 caps the nozzle forming surface 26 (S31). As described above, in the second embodiment, the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M are closed before suction is performed. In contrast, in the third embodiment, the CPU 41 performs suction while the supply valves 84K, 84Y, 84C, 84M, 81K, 81Y, 81C, and 81M are open (S32).

[0068] Next, the CPU 41 performs suction in S32 and then waits (S33). Here, in the case of a normal purge operation performed at the end of printing, for example, negative pressure is applied to the print head 25 to flush out the ink from the ink flow paths, and then the process waits until a first waiting time has elapsed, during which the cap space 18 returns to atmospheric pressure. In contrast, in S33, the CPU 41 performs suction in S32, then waits until a second waiting time, shorter than the first waiting time, has elapsed (S33), and uncaps the print head 25 after the second waiting time has elapsed (S34). When the second waiting time has elapsed, negative pressure remains within the print head 25. Uncapping the print head 25 in this state causes a meniscus break because the pressure inside the print head 25 is lower than the pressure outside. This causes atmospheric air to flow into the print head 25 through the nozzles 26K, 26Y, 26C, and 26M, replacing the flow paths within the print head 25 with air.

[0069] Since the state is now the same as in the first embodiment, the CPU 41 executes a purge operation (S35). By executing the purge operation, ink flows into the manifold 73K, which has been replaced with air. As a result, the inside of the manifold 73K is completely replaced with ink. Therefore, even in the sedimentation elimination process of the third embodiment, it is possible to improve the ink flow path replacement performance and the recovery performance against sedimentation. After the purge operation is completed, the CPU 41 ends this process.

[0070] Fourth Embodiment A fourth embodiment will be described with reference to FIGS. 22 and 23. In the sedimentation elimination process of the fourth embodiment, a meniscus break is caused by applying negative pressure to the subtanks 51K, 51Y, 51C, and 51M. As shown in FIGS. 22 and 23, the CPU 41 opens the tank valves 81K, 81Y, 81C, and 81M and the supply valves 84K, 84Y, 84C, and 84M (S41). Next, the CPU 41 drives the tank pumps 82K, 82Y, 82C, and 82M to suck ink from the subtanks 51K, 51Y, 51C, and 51M, respectively, thereby applying negative pressure to the subtanks 51K, 51Y, 51C, and 51M (S42).

[0071] When negative pressure is applied to the subtanks 51K, 51Y, 51C, and 51M, further negative pressure is applied inside the print head 25. If the negative pressure inside the print head 25 exceeds the meniscus withstand pressure, a meniscus break occurs in the nozzles 26K, 26Y, 26C, and 26M. This causes air in the atmosphere to flow into the print head 25 from the nozzles 26K, 26Y, 26C, and 26M and backflow through the ink flow paths 72K, 72Y, 72C, and 72M. As a result, the flow paths inside the print head 25 are replaced with air.

[0072] Since the state is now the same as in the first embodiment, the CPU 41 executes a purge operation (S43). By executing the purge operation, ink flows into the manifold 73K, which has been replaced with air. As a result, the inside of the manifold 73K is completely replaced with ink. Therefore, even in the sedimentation elimination process of the fourth embodiment, it is possible to improve the ink flow path replacement performance and the recovery performance against sedimentation. After the purge operation is completed, the CPU 41 ends this process.

[0073] In the fourth embodiment, negative pressure is applied to the subtanks 51K, 51Y, 51C, and 51M by driving the tank pumps 82K, 82Y, 82C, and 82M, but negative pressure may also be applied to the subtanks 51K, 51Y, 51C, and 51M by other methods. For example, in this embodiment, the main tank 52 is located lower than the subtank 51 (see FIG. 1), so simply opening the tank valves 81K, 81Y, 81C, and 81M causes the head difference between the main tank 52 and the subtank 51 to draw ink from the subtank 51 toward the main tank 52. This allows negative pressure to be applied to the subtank 51.

[0074] In the above description, the printer 1 is an example of a "printing device" in the present disclosure. The subtank 51 and the main tank 52 are examples of an "ink tank" in the present disclosure. The CPU 41 that executes the sedimentation elimination process is an example of an "air inflow execution unit" and a "purge execution unit" in the present disclosure. The supply valves 84K, 84Y, 84C, and 84M are examples of a "valve" in the present disclosure. The open state of the supply valves 84K, 84Y, 84C, and 84M is an example of a "first state" in the present disclosure, and the closed state is an example of a "second state" in the present disclosure. The subtank 51 is an example of a "back pressure application means" in the present disclosure. The cap 17 is an example of a "cap member" in the present disclosure. The waste liquid flow path 73 and the waste liquid pump 87 are examples of a "suction means" in the present disclosure. The second waiting time is an example of a "predetermined waiting time" in the present disclosure.

[0075] In the subsidence elimination process of the first embodiment shown in FIG. 7, steps S11 to S13 are an example of a process for executing the "air inflow operation" of the present disclosure. In the subsidence elimination process of the second embodiment shown in FIG. 18, steps S21 to S24 are an example of a process for executing the "air inflow operation" of the present disclosure. In the subsidence elimination process of the third embodiment shown in FIG. 21, steps S31 to S34 are an example of a process for executing the "air inflow operation" of the present disclosure. In the subsidence elimination process of the fourth embodiment shown in FIG. 22, steps S41 to S42 are an example of a process for executing the "air inflow operation" of the present disclosure.

[0076] As described above, the printer 1 of this embodiment includes a print head 25 and ink flow paths 72K, 72Y, 72C, and 72M. The print head 25 has nozzles 26K, 26Y, 26C, and 26M. The ink flow paths 72K, 72Y, 72C, and 72M supply ink to the print head 25. The CPU 41 of the printer 1 executes a sedimentation elimination process. The sedimentation elimination process executes an air inflow operation and a purge operation. The air inflow operation is an operation that injects air from the nozzles 26K, 26Y, 26C, and 26M into at least the print head 25 and the ink flow paths 72K, 72Y, 72C, and 72M. The purge operation is an operation that, after the air inflow operation, discharges ink from the nozzles 26K, 26Y, 26C, and 26M, thereby filling the ink flow paths 72K, 72Y, 72C, and 72M and the print head 25 with ink.

[0077] The air flowing in from the nozzles during the air inflow operation pushes the ink in the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, eliminating ink sedimentation. During the purging operation, air is first expelled from the nozzles 26K, 26Y, 26C, and 26M before the print head 25 is filled with ink. This means that only a small amount of ink is expelled from the nozzles 26K, 26Y, 26C, and 26M. The printer 1 can reduce ink consumption while eliminating ink sedimentation.

[0078] The printer 1 of the above embodiment includes supply valves 84K, 84Y, 84C, and 84M. The supply valves 84K, 84Y, 84C, and 84M can be switched between an open state and a closed state. In the open state, the ink flow paths 72K, 72Y, 72C, and 72M are in communication with each other. In the closed state, the flow path resistance of the ink flow paths 72K, 72Y, 72C, and 72M is greater than in the open state.

[0079] In the sedimentation elimination process of the first embodiment, the CPU 41 closes the supply valves 84K, 84Y, 84C, and 84M (S11) and performs a flushing operation (S12) to perform an air inflow operation. The flushing operation is an operation to discharge ink from the nozzles 26K, 26Y, 26C, and 26M. By closing the ink flow paths 72K, 72Y, 72C, and 72M before performing the purging operation, the printer 1 can reliably create a negative pressure inside the print head 25. Therefore, the air flowing in from the nozzles 26K, 26Y, 26C, and 26M by the air inflow operation reliably pushes the ink inside the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, eliminating ink sedimentation. As a result, the printer 1 can reliably eliminate ink sedimentation while suppressing ink consumption.

[0080] The printer 1 of the above embodiment is equipped with subtanks 51K, 51Y, 51C, and 51M. The subtanks 51K, 51Y, 51C, and 51M supply ink to the print head 25 via ink flow paths 72K, 72Y, 72C, and 72M. The subtanks 51K, 51Y, 51C, and 51M are located lower than the print head 25. Therefore, the subtanks 51K, 51Y, 51C, and 51M apply back pressure to the print head 25 and the ink flow paths 72K, 72Y, 72C, and 72M so that the pressure on the ink flow paths 72K, 72Y, 72C, and 72M side is lower than that on the print head 25. The CPU 41 closes the supply valves 84K, 84Y, 84C, and 84M to perform a flushing operation, and then opens the supply valves 84K, 84Y, 84C, and 84M while applying back pressure to the print head 25 and ink flow paths 72K, 72Y, 72C, and 72M, thereby performing an air inflow operation. By applying back pressure to the print head 25 and ink flow paths 72K, 72Y, 72C, and 72M, the printer 1 can more reliably create a negative pressure inside the print head 25. Therefore, the air flowing in from the nozzles 26K, 26Y, 26C, and 26M due to the air inflow operation more reliably pushes ink inside the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, eliminating ink sedimentation. This allows the printer 1 to more reliably eliminate ink sedimentation while reducing ink consumption.

[0081] The printer 1 of the above embodiment includes supply valves 84K, 84Y, 84C, and 84M, a cap 17, and a waste liquid pump 87. The cap 17 can be switched between a sealed state and an open state relative to the nozzle forming surface 26. The waste liquid pump 87 performs a suction operation on the print head 25 via the cap 17.

[0082] In the sedimentation elimination process of the second embodiment, the CPU 41 seals the cap 17 (S21) and closes the supply valves 84K, 84Y, 84C, and 84M (S22), causes the waste liquid pump 87 to perform a suction operation (S23), and then opens the cap 17 (S24), thereby performing an air inflow operation. After performing the air inflow operation, the CPU 41 opens the supply valves 84K, 84Y, 84C, and 84M and performs a purge operation (S25). By performing a suction operation with the supply valves 84K, 84Y, 84C, and 84M closed, negative pressure is reliably created within the print head 25. As a result, air flowing in from the nozzles 26K, 26Y, 26C, and 26M due to the air inflow operation reliably pushes ink in the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, thereby eliminating ink sedimentation. Therefore, the printer 1 can reliably eliminate ink sedimentation while reducing ink consumption.

[0083] In the sedimentation elimination process of the third embodiment, the CPU 41 seals the cap 17, causes the waste fluid pump 87 to perform a suction operation, and then, after a predetermined waiting time has elapsed, opens the cap 17 to perform an air inflow operation. The suction operation creates a negative pressure inside the print head 25, causing air to flow into the print head 25 through the nozzles 26K, 26Y, 26C, and 26M during the air inflow operation. By waiting for the waiting time to elapse, the inflowing air can sufficiently push the ink inside the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, eliminating ink sedimentation. This allows the printer 1 to reduce ink consumption while eliminating ink sedimentation. Furthermore, because the printer 1 can eliminate ink sedimentation using only existing components, it can achieve low costs.

[0084] The printer 1 includes subtanks 51K, 51Y, 51C, and 51M, main tanks 52K, 52Y, 52C, and 52M, and tank pumps 82K, 82Y, 82C, and 82M. The subtanks 51K, 51Y, 51C, and 51M store ink and supply it to the print head 25 via ink flow paths 72K, 72Y, 72C, and 72M. The main tanks 52K, 52Y, 52C, and 52M store ink to be supplied to the subtanks 51K, 51Y, 51C, and 51M and are connected to the subtanks 51K, 51Y, 51C, and 51M via the tank flow paths 71K, 71Y, 71C, and 71M. The tank pumps 82K, 82Y, 82C, and 82M are provided in the tank flow paths 71K, 71Y, 71C, and 71M, respectively.

[0085] In the sedimentation elimination process of the fourth embodiment, the CPU 41 executes an air inflow operation while driving the tank pumps 82K, 82Y, 82C, and 82M to apply back pressure to the subtanks 51K, 51Y, 51C, and 51M. By applying back pressure to the subtanks 51K, 51Y, 51C, and 51M, back pressure can be applied to the print head 25 and the ink flow paths 72K, 72Y, 72C, and 72M. This allows the printer 1 to create a further negative pressure within the print head 25. Therefore, the air flowing in from the nozzles 26K, 26Y, 26C, and 26M through the air inflow operation more reliably pushes ink within the print head 25 back into the ink flow paths 72K, 72Y, 72C, and 72M, eliminating ink sedimentation. This allows the printer 1 to more reliably eliminate ink sedimentation while reducing ink consumption.

[0086] The present disclosure is not limited to the above-described embodiment and various modifications are possible. In the flow path configuration of the printer 1 shown in Fig. 2, the number and positions of the filters can be freely changed.

[0087] In the settling elimination process of the above embodiment, the air inlet operation and the purge operation are performed simultaneously for the four nozzles, but they may also be performed individually for each of the four nozzles, for example.

[0088] In the first embodiment, in S11, the supply valves 84K, 84Y, 84C, and 84M are closed, but it is sufficient if the flow path resistance of the ink flow paths 72K, 72Y, 72C, and 72M is at least greater than when they are open, so the supply valves 84K, 84Y, 84C, and 84M do not have to be closed. For example, the flow path resistance can be increased simply by narrowing the flow path area of ​​each of the supply valves 84K, 84Y, 84C, and 84M.

[0089] In the first embodiment, by opening the supply valves 84K, 84Y, 84C, and 84M, a negative pressure is further applied to the print head 25 due to the head pressure difference between the subtank 51 and the print head 25. However, negative pressure may be applied in other ways. For example, negative pressure may be applied to the print head 25 by driving the tank pumps 82K, 82Y, 82C, and 82M to flow ink from the subtank 51 toward the main tank 52. Alternatively, the subtank 51 may be omitted, and the ink flow paths 72K, 72Y, 72C, and 72M on the side of the print head 25 may be under low pressure due to the head pressure difference between the main tank 52 and the print head 25. In this configuration, the main tank 52 corresponds to the "ink tank" in this disclosure.

[0090] Furthermore, in the above embodiment, the basic configuration of the printer 1 is such that the subtank 51 is located lower than the print head 25, but for example, the subtank 51 may be made movable in the vertical direction so that during a purge operation (when ink flows in), the subtank 51 is moved to a position below the print head 25. Furthermore, if the subtank 51 is omitted as described above, the main tank 52 may be made movable up and down.

[0091] Furthermore, while the above embodiment has been described using a print head 25 that ejects color inks as an example, the present disclosure is of course also applicable to print heads that eject white ink. The settling of ink particles can occur in pigment inks, for example, and it is known that white ink in particular settles more quickly than other color inks. Therefore, the present disclosure is particularly effective for print heads that eject white ink.

[0092] 1 Printer 25 Print head 26 Nozzle surface 26C, 26K, 26M, 26Y Nozzle 41 CPU 51 Sub-tank 52 Main tank 71C, 71K, 71M, 71Y Tank flow path 72C, 72K, 72M, 72Y Ink flow path 73 Waste liquid flow path 81C, 81K, 81M, 81Y Tank valve 82C, 82K, 82M, 82Y Tank pump 84C, 84K, 84M, 84Y Supply valve 87 Waste liquid pump

Claims

1. A printing device comprising: a print head having nozzles that eject ink; an ink flow path that supplies ink to said print head; an air inflow execution unit that executes an air inflow operation that causes air to flow from said nozzles into said print head and into said ink flow path, at least into said print head; and a purge execution unit that executes a purge operation to discharge ink from the nozzles after said air inflow execution unit has executed the air inflow operation, thereby filling said ink flow path and said print head with ink.

2. A printing device as described in claim 1, further comprising a valve that can be switched between a first state in which the ink flow path is connected and a second state in which the flow path resistance of the ink flow path is greater than in the first state, and wherein the air inflow execution unit executes the air inflow operation by switching the valve to the second state and executing a flushing operation to discharge ink from the nozzles.

3. A printing device as described in claim 2, further comprising a back pressure applying means for applying back pressure to the print head and the ink flow path so that the ink flow path side of the print head is under low pressure, and wherein the air inflow execution unit sets the valve to the second state, performs the flushing operation, and then performs the air inflow operation by setting the valve to the first state with the back pressure applying means applying back pressure to the print head and the ink flow path.

4. A printing device as described in claim 1, comprising: a valve switchable between a first state in which the ink flow paths are connected and a second state in which the flow path resistance of the ink flow paths is greater than in the first state; a cap member changeable between a sealed state covering the nozzle formation surface of the print head and an open state spaced apart from the formation surface; and suction means for performing a suction operation on the print head via the cap member, wherein the air inflow execution unit sets the cap member to the sealed state and the valve to the second state, causes the suction means to perform the suction operation, and then sets the cap member to the open state, thereby performing the air inflow operation; and the purge execution unit sets the valve to the first state and performs the purge operation after the air inflow execution unit has performed the air inflow operation.

5. A printing device as described in claim 1, comprising a cap member that can be changed to a sealed state covering the nozzle formation surface of the print head or an open state separated from the nozzle formation surface, and suction means that performs a suction operation on the print head via the cap member, wherein the air inflow execution unit sets the cap member to the sealed state, causes the suction means to perform the suction operation, and then, after a predetermined waiting time has elapsed, performs the air inflow operation by setting the cap member to the open state.

6. A printing device as described in claim 1, further comprising an ink tank that stores ink and supplies ink to the print head via the ink flow path, wherein the air inflow execution unit executes the air inflow operation by creating a low pressure on the ink flow path side relative to the print head due to a head difference between the ink tank and the print head.

7. A printing device as described in claim 1, comprising: an ink tank that stores ink and supplies ink to the print head via the ink flow path; and a tank pump provided in the ink flow path, wherein the air inflow execution unit executes the air inflow operation by driving the tank pump so that the ink flow path side relative to the print head is at low pressure.

8. A printing device as described in any one of claims 1 to 7, characterized in that when a predetermined time has elapsed since the previous purge operation was performed by the purge execution unit, the air inflow operation by the air inflow execution unit and the purge operation by the purge execution unit are performed again.

9. A method carried out in a printing device having a print head with nozzles that eject ink and an ink flow path that supplies ink to the print head, the method comprising: an air inflow operation that causes air to flow from the nozzles into the print head and into the ink flow path, at least into the print head; and a purging operation that expels ink from the nozzles after the air inflow operation has been carried out.

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