Liquid ejection device and maintenance method for liquid ejection device

Abstract

To provide a technique for a liquid ejection device that can clean nozzles efficiently and at low cost.SOLUTION: A liquid ejection device includes: a liquid ejection head which has a plurality of nozzles and a common liquid chamber part communicating with the nozzles; a liquid storage part which stores liquid; a first flow path which connects the common liquid chamber part and the liquid storage part; a second flow path which connects the common liquid chamber part and the liquid storage part; a check valve which is provided in the second flow path, blocks the flow of liquid from the liquid storage part to the common liquid chamber part and allows the flow from the common liquid chamber part to the liquid storage part; and pressurizing means which can selectively execute a first pressurizing operation in which liquid is pressurized to flow in the direction from the liquid storage part to the common liquid chamber part via the first flow path, and a second pressurizing operation in which liquid is pressurized to flow in the direction from the liquid storage part to the common liquid chamber part via the second flow path. The pressurizing means can execute a pressurizing discharge operation that executes the first pressurizing operation in a state where the check valve closes the second flow path by executing the second pressurizing operation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a liquid injection device and a maintenance method for the liquid injection device.

Background Art

[0002] In Patent Document 1, there is disclosed a printer including an ink cartridge, a head flow path which is a flow path for supplying the ink of the ink cartridge to a head, a nozzle for ejecting the ink in the head to the outside, a discharge path through which the ink discharged from the head without being ejected from the nozzle flows, and a three-way valve provided in the discharge path. The supply of ink from the ink cartridge to the head is performed by pressurizing the ink with a supply pump. In Patent Document 1, when the three-way valve closes the discharge path and the ink is pressurized by the supply pump, the ink staying in the head is forcibly ejected from the nozzle. Thereby, the nozzle is cleaned.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, for cleaning the nozzle, an on - off valve such as a three - way valve for closing the discharge path needs to be provided in the discharge path. When this on - off valve is a manual valve, since an operator needs to open and close the on - off valve each time cleaning is performed, the cleaning and the working efficiency of the printer decrease. On the other hand, when the on - off valve is a solenoid valve, electrical wiring arrangement and a control device are required, and the installation location and cost of the ink supply unit cost increase compared with a manual valve. Therefore, there is a need for a liquid injection device capable of cleaning the nozzle efficiently and at low cost.

Means for Solving the Problems

[0005] According to a first aspect of the present disclosure, a liquid ejecting apparatus is provided. The liquid ejecting apparatus includes a liquid ejecting head including a plurality of nozzles that eject liquid and a common liquid chamber portion that communicates with the plurality of nozzles, a liquid storage portion that stores liquid to be supplied to the common liquid chamber portion, a first flow path that communicates the common liquid chamber portion and the liquid storage portion, a second flow path that communicates the common liquid chamber portion and the liquid storage portion, a check valve provided in the second flow path that blocks a flow of liquid from the liquid storage portion toward the common liquid chamber portion and allows a flow from the common liquid chamber portion toward the liquid storage portion, and a pressurizing means that can selectively execute a first pressurizing operation of pressurizing the liquid so that the liquid flows from the liquid storage portion toward the common liquid chamber portion through the first flow path and a second pressurizing operation of pressurizing the liquid so that the liquid flows from the liquid storage portion toward the common liquid chamber portion through the second flow path, and the pressurizing means can execute a pressurizing discharge operation of executing the first pressurizing operation in a state where the check valve closes the second flow path by executing the second pressurizing operation.

[0006] According to a second aspect of the present disclosure, a method for maintaining a liquid ejecting apparatus is provided. The method for maintaining a liquid ejecting apparatus includes a liquid ejecting head including a plurality of nozzles that eject liquid and a common liquid chamber portion that communicates with the plurality of nozzles, a liquid storage portion that stores liquid to be supplied to the common liquid chamber portion, a first flow path that communicates the common liquid chamber portion and the liquid storage portion, a second flow path that communicates the common liquid chamber portion and the liquid storage portion, and a check valve provided in the second flow path that blocks a flow of liquid from the liquid storage portion toward the common liquid chamber portion and allows a flow from the common liquid chamber portion toward the liquid storage portion. The method for maintaining a liquid ejecting apparatus includes executing a pressurizing discharge operation of executing a first pressurizing operation of pressurizing the liquid so that the liquid flows from the liquid storage portion toward the common liquid chamber portion through the first flow path in a state where the check valve closes the second flow path by executing a second pressurizing operation of pressurizing the liquid in a direction from the liquid storage portion toward the common liquid chamber portion through the second flow path. BRIEF DESCRIPTION OF THE DRAWINGS

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] A. This Embodiment FIG. 1 is a diagram for explaining the liquid ejecting apparatus 1 of the present embodiment. In FIG. 1, an X-axis, a Y-axis, and a Z-axis orthogonal to each other are shown. In the present embodiment, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction. The liquid ejecting apparatus 1 ejects liquid as droplets onto the medium PM. In the present embodiment, the liquid is ink, and the liquid ejecting apparatus 1 is an inkjet printer. The liquid ejecting apparatus 1 includes a main tank 10, a first pump 11, a circulation mechanism 20, a conveyance mechanism 30, a moving mechanism 40, a liquid ejecting head 50, a first flow path 60, a second flow path 61, a first pressure acquisition unit 70, a second pressure acquisition unit 71, and a control unit 90 (not shown in FIG. 1).

[0009] The main tank 10 stores ink. In the present embodiment, the main tank 10 is composed of four ink cartridges that are detachable from the liquid injection device 1. Each ink cartridge contains ink of a different color. The type of ink is not particularly limited and may be a solvent-based ink or an aqueous ink. Note that as the main tank 10, an ink tank capable of replenishing ink, a film formed of a flexible film, or the like can be adopted. The first pump 11 supplies ink from the main tank 10 to the circulation mechanism 20 to replenish the circulation mechanism 20 with ink. The first pump 11 is controlled by the control unit 90.

[0010] FIG. 2 is a diagram for explaining the circulation mechanism 20 in the present embodiment. In FIG. 2, for ease of understanding, the main tank 10, the first pump 11, the liquid injection head 50, the first flow path 60, and the second flow path 61 are shown. The circulation mechanism 20 supplies ink to the liquid injection head 50. As shown in FIG. 2, the circulation mechanism 20 includes a liquid storage unit 210, a pressurizing means 220, and a decompression unit 230. comprises.

[0011] The liquid storage unit 210 stores ink. The liquid storage unit 210 stores the ink for supplying to the common liquid chamber 511 (to be described later) of the liquid injection head 50, the ink recovered from the liquid injection head 50, and the ink supplied from the main tank 10. In the present embodiment, the liquid storage unit 210 includes a first sub-tank 211, a second pump 212, a second sub-tank 213, and a relay flow path 214. The common liquid chamber 511 in the present embodiment is an example of a "common liquid chamber section".

[0012] The first sub-tank 211 stores the ink supplied to the liquid ejection head 50. The second pump 212 is controlled by the control unit 90 to supply the ink stored in the second sub-tank 213 to the first sub-tank 211. The second sub-tank 213 stores the ink recovered from the liquid ejection head 50. Also, the second sub-tank 213 stores the ink supplied from the main tank 10. The relay flow path 214 is a flow path that connects the first sub-tank 211 and the second sub-tank 213. A second pump 212 is provided in the relay flow path 214. The second pump 212 is, for example, a tube pump.

[0013] The pressurizing means 220 pressurizes the inside of the first sub-tank 211 and the inside of the second sub-tank 213, respectively. The pressurizing means 220 can execute a first pressurizing operation to pressurize the ink so that the ink flows in a direction from the first sub-tank 211 of the liquid storage unit 210 to the common liquid chamber 511 of the liquid ejection head 50 via the first flow path 60. Further, the pressurizing means 220 can execute a second pressurizing operation to pressurize the ink in a direction from the second sub-tank 213 of the liquid storage unit 210 to the common liquid chamber 511 of the liquid storage unit 210 via the second flow path 61. The pressurizing means 220 can selectively execute the first pressurizing operation and the second pressurizing operation. That is, the pressurizing means 220 can execute only one of the first pressurizing operation and the second pressurizing operation, and can also execute both the first pressurizing operation and the second pressurizing operation. The pressurizing means 220 can also execute neither the first pressurizing operation nor the second pressurizing operation. The first pressurizing operation and the second pressurizing operation are executed when the pressurizing means 220 is controlled by the control unit 90. For example, an electropneumatic regulator capable of pressure adjustment is used as the first regulator 222 and the second regulator 223 described later. By the control unit 90 controlling the electropneumatic regulator, the first pressurizing operation and the second pressurizing operation can be executed. Also, when a normal regulator is used, solenoid valves are provided between the compressor 221 and the first sub-tank 211, and between the compressor 221 and the second sub-tank 213, and by the control unit 90 controlling the opening and closing operations of the solenoid valves, the first pressurizing operation and the second pressurizing operation can be executed.

[0014] In this embodiment, the pressurizing means 220 is controlled by the control unit 90 to pressurize the ink in the first sub-tank 211 such that the pressure value acquired by the first pressure acquisition unit 70, which will be described later, is a predetermined pressure value. Further, the pressurizing means 220 is controlled by the control unit 90 to pressurize the ink in the second sub-tank such that the pressure value acquired by the second pressure acquisition unit 71, which will be described later, is a predetermined pressure value. Note that the pressure value acquired by the second pressure acquisition unit 71 is different from the pressure value acquired by the first pressure acquisition unit 70. The pressurizing means 220 includes a compressor 221, a first regulator 222, and a second regulator 223.

[0015] The compressor 221 pressurizes the ink in the first sub-tank 211 and the ink in the second sub-tank 213 with the generated compressed air. The compressor 221 can supply compressed air to either the first sub-tank 211 or the second sub-tank 213. Further, the compressor 221 can supply compressed air to both the first sub-tank 211 and the second sub-tank 213 simultaneously. The first regulator 222 reduces the pressure of the compressed air supplied from the compressor 221 to a certain pressure and supplies it to the first sub-tank 211. The second regulator 223 reduces the pressure of the compressed air supplied from the compressor 221 to a certain pressure and supplies it to the second sub-tank 213. The first pressurizing operation is an operation in which the compressor 221 and the first regulator 222 supply compressed air to the first sub-tank 211 under the control of the control unit 90. The second pressurizing operation is an operation in which the compressor 221 and the second regulator 223 supply compressed air to the second sub-tank 213 under the control of the control unit 90.

[0016] The decompression unit 230 decompresses the interior of the second sub-tank 213 under the control of the control unit 90. Thereby, the decompression unit 230 can cause the ink in the common liquid chamber 511 of the liquid ejection head 50 to flow into the second sub-tank 213 through the second flow path 61. The decompression unit 230 includes a vacuum pump 231 and a third regulator 232. The vacuum pump 231 decompresses the interior of the second sub-tank 213. The third regulator 232 adjusts the pressure of the decompression by the vacuum pump 231. When the decompression unit 230 is decompressing the interior of the second sub-tank 213, the pressurizing means 220 is controlled by the control unit 90 so as not to execute the second pressurizing operation.

[0017] The transport mechanism 30 shown in FIG. 1 transports the medium PM in the +Y direction. The transport mechanism 30 is controlled by the control unit 90. The moving mechanism 40 reciprocates the liquid ejection head 50 in the +X direction and the -X direction. The moving mechanism 40 is controlled by the control unit 90. The moving mechanism 40 includes a storage box 41 and a transport belt 42. The storage box 41 houses the liquid ejection head 50. The transport belt 42 has the storage box 41 fixed thereto. By moving in the X direction, the transport belt 42 can move the liquid ejection head 50 housed in the storage box 41 in the X direction.

[0018] FIG. 3 is a diagram for explaining the liquid ejection head 50. For convenience of understanding, in FIG. 3, the main tank 10, the first pump 11, the liquid storage unit 210, and the pressurizing means 220 are shown. The liquid ejection head 50 shown in FIG. 3 ejects ink onto the medium PM shown in FIG. 1. Specifically, the liquid ejection head 50 reciprocates in the X direction by the moving mechanism 40 shown in FIG. 1, thereby forming a predetermined image with ink on the surface of the medium PM. The liquid ejection head 50 is controlled by the control unit 90. In the present embodiment, as shown in FIGS. 1 and 3, the liquid ejection head 50 includes a flow path structure 500 and four head chips 510. The flow path structure 500 has a plurality of flow paths communicating with the four head chips 510. The flow path structure 500 has a first opening 540, a second opening 550, a check valve 560, and a flow path filter 570. Further, the flow path structure 500 forms a first inner flow path 60b of the first flow path 60 and a second inner flow path 61b of the second flow path 61, which will be described later. In FIG. 3, two head chips 510 are shown for convenience. The four head chips 510 have the same configuration.

[0019] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1. Before explaining each component of the flow path structure 500, the head chip 510 will be described. As shown in FIG. 4, the head chip 510 includes two common liquid chambers 511, a flow path forming member 513, a filter 514, a pressure chamber substrate 515, a nozzle plate 516, two vibration dampers 517, a piezoelectric element 518, a diaphragm 519, a protection substrate 520, a wiring substrate 521, a drive circuit 522, and two nozzle rows 523 corresponding to each of the two common liquid chambers 511.

[0020] FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4. FIG. 5 is a cross-sectional view passing through one of the two common liquid chambers 511. The common liquid chamber 511 is a portion into which the ink supplied from the first sub-tank 211 flows. As shown in FIG. 4, the common liquid chamber 511 communicates with the nozzle row 523. As shown in FIG. 5, the common liquid chamber 511 has a first liquid chamber opening 511a and a second liquid chamber opening 511b. The first liquid chamber opening 511a is an opening for circulating the ink supplied from the first sub-tank 211 into the common liquid chamber 511. The second liquid chamber opening 511b is an opening for discharging the ink in the common liquid chamber 511.

[0021] The flow path forming member 513 shown in FIG. 4 forms a flow path for supplying the ink in the common liquid chamber 511 to the nozzle row 523. The filter 514 catches foreign matters mixed in the ink while allowing the ink to pass through the flow path formed by the flow path forming member 513.

[0022] The pressure chamber substrate 515 forms a pressure chamber CB, which is a flow path for supplying ink to the nozzle row 523, in the same manner as the flow path forming member 513. The nozzle plate 516 is a plate-like member on which the nozzle row 523 is formed. The vibration absorber 517 absorbs fluctuations in the pressure of the ink in the common liquid chamber 511. The vibration absorber 517 constitutes the wall surface of the common liquid chamber 511. The vibration absorber 517 is, for example, a flexible resin film or a thin metal plate having flexibility. The surface of the vibration absorber 517 on the +Z direction side is joined to the flow path forming member 513 by an adhesive or the like.

[0023] The piezoelectric element 518 vibrates the diaphragm 519 to vary the pressure in the pressure chamber CB and eject the ink from the nozzle row 523. The piezoelectric element 518 is a passive element that deforms by a drive signal supplied by the drive circuit 522. The diaphragm 519 has the piezoelectric element 518 mounted thereon and vibrates in conjunction with the deformation of the piezoelectric element 518.

[0024] The protective substrate 520 protects the piezoelectric element 518 and reinforces the strength of the diaphragm 519. The protective substrate 520 is formed with a hole penetrating in the Z direction through which the wiring substrate 521 passes.

[0025] The wiring board 521 electrically connects the control unit 90 and the head chip 510. The drive circuit 522 supplies a drive voltage to the piezoelectric element 518. The drive circuit 522 is electrically connected to the wiring board 521. Based on a drive signal that is a signal from the control unit 90, the drive circuit 522 switches whether to supply at least a part of the waveform included in the drive signal as a pulse or not.

[0026] Each of the two nozzle rows 523 is a set of a plurality of nozzles N arranged linearly at intervals in the Y direction. The nozzle N ejects ink. The nozzle N is a hole formed in the nozzle plate 516 and allows ink to pass through. The plurality of nozzles N constituting one nozzle row 523 communicate with one common liquid chamber 511. As shown in FIG. 4, the two nozzle rows 523 are arranged at intervals in the X direction.

[0027] The first opening 540 shown in FIG. 3 is an opening for allowing the ink supplied from the first sub-tank 211 to flow into the liquid injection head 50. The first opening 540 is a flow path connection portion between the liquid storage portion 210 and the outside of the liquid injection head 50. The first opening 540 is connected to an end portion of the first internal flow path 60b that is an internal flow path of the liquid injection head 50 and an end portion of the first external flow path 60a that is an external flow path of the liquid injection head 50. The second opening 550 is an opening for allowing the ink to flow between the ink in the liquid injection head 50 and the second sub-tank 213. The second opening 550 is a flow path connection portion between the liquid storage portion 210 and the outside of the liquid injection head 50. The second opening 550 is connected to an end portion of the second internal flow path 61b that is an internal flow path of the liquid injection head 50 and an end portion of the second external flow path 61a that is an external flow path of the liquid injection head 50.

[0028] For the sake of convenience of understanding, before explaining the check valve 560 and the flow path filter 570, the first flow path 60, the second flow path 61, the first pressure acquisition unit 70, and the second pressure acquisition unit 71 will be described first. The first flow path 60 communicates the liquid storage unit 210 with the common liquid chamber 511. As shown in FIG. 3, the first flow path 60 communicates the first sub-tank 211 of the liquid storage unit 210 with the common liquid chamber 511. The first flow path 60 connects the first sub-tank 211 and the common liquid chamber 511. The first flow path 60 includes a first outer flow path 60a and a first inner flow path 60b.

[0029] The first outer flow path 60a is a flow path that connects the first sub-tank 211 of the liquid storage unit 210 and the first opening 540. The end of the first outer flow path 60a is connected to the first opening 540. The first inner flow path 60b is a flow path that connects the first opening 540 and the common liquid chamber 511. The end of the first inner flow path 60b is connected to the first opening 540. By connecting the first inner flow path 60b to the first opening 540 where the first outer flow path 60a is connected, the first flow path 60 communicates the first sub-tank 211 and the common liquid chamber 511. The first inner flow path 60b is arranged in the liquid ejection head 50. In the present embodiment, the first inner flow path 60b is a part of the flow path formed in the liquid ejection head 50. Note that the first inner flow path 60b may be a tube arranged in the liquid ejection head 50. The first inner flow path 60b branches toward the plurality of common liquid chambers 511 of each head chip 510. Although not shown, in the present embodiment, the first inner flow path 60b branches into a total of eight toward the respective common liquid chambers 511 of the four head chips 510.

[0030] The second flow path 61 communicates the liquid storage portion 210 and the common liquid chamber 511. Specifically, the second flow path 61 communicates the second sub-tank 213 of the liquid storage portion 210 and the common liquid chamber 511. The second flow path 61 is connected to the second sub-tank 213 and the common liquid chamber 511. Ink that has flowed into the common liquid chamber 511 via the first flow path 60 flows through the second flow path 61. Also, between the check valve 560 disposed in the second flow path 61 and the second sub-tank 213, when the second pressurization operation is executed, ink flows from the second sub-tank 213 toward the common liquid chamber 511. The second flow path 61 includes a second outer flow path 61a and a second inner flow path 61b.

[0031] The second outer flow path 61a is a flow path that connects the second sub-tank 213 of the liquid storage portion 210 and the second opening 550. The end of the second outer flow path 61a is connected to the second opening 550. The second inner flow path 61b is a flow path that connects the second opening 550 and the plurality of common liquid chambers 511. The end of the second inner flow path 61b is connected to the second opening 550. By connecting the second inner flow path 61b to the second opening 550 that connects to the second outer flow path 61a, the second flow path 61 communicates the second sub-tank 213 and the common liquid chamber 511. The second inner flow path 61b is disposed within the liquid ejection head 50. In the present embodiment, the second inner flow path 61b is a part of a flow path formed within the liquid ejection head 50. Note that the second inner flow path 61b may be a tube disposed within the liquid ejection head 50. The second inner flow path 61b branches toward each of the plurality of common liquid chambers 511 of each head chip 510. Although not shown, in the present embodiment, the second inner flow path 61b branches into a total of eight toward each of the eight common liquid chambers 511 of each of the four head chips 510.

[0032] The first pressure acquisition unit 70 acquires the pressure value of the ink in the first outflow path 60a. The first pressure acquisition unit 70 includes at least a pressure gauge. The first pressure acquisition unit 70 is provided in the middle of the first outflow path 60a. In the present embodiment, the first pressure acquisition unit 70 acquires the pressure value of the ink flowing into the liquid ejection head 50 at the first opening 540 that is connected to the end of the first inflow path 60b and is adjusted in consideration of the flow path resistance from the position where the first pressure acquisition unit 70 of the first outflow path 60a is provided to the first opening 540. The first pressure acquisition unit 70 transmits the acquired pressure value to the control unit 90. The second pressure acquisition unit 71 acquires the pressure value of the ink in the second flow path 61. In the present embodiment, the second pressure acquisition unit 71 includes at least a pressure gauge. The second pressure acquisition unit 71 is provided in the middle of the second outflow path 61a. The second pressure acquisition unit 71 acquires the pressure value of the ink flowing into or out of the liquid ejection head 50 at the second opening 550 that is connected to the end of the second inflow path 61b and is adjusted in consideration of the flow path resistance from the position where the second pressure acquisition unit 71 of the second outflow path 61a is provided to the second opening 550. The second pressure acquisition unit 71 transmits the acquired pressure value to the control unit 90. Note that the control unit 90 may perform adjustment taking into account the aforementioned flow path resistance on the pressure detected by the pressure gauge.

[0033] FIG. 6 is a diagram for explaining the shape of the check valve 560. The check valve 560 shown in FIG. 3 blocks the flow of ink from the second sub-tank 213 of the liquid storage unit 210 toward the common liquid chamber 511. Further, the check valve 560 allows the flow from the common liquid chamber 511 toward the second sub-tank 213. The check valve 560 is provided in the second flow path 61. In the present embodiment, the check valve 560 is provided in the second inflow path 61b. More specifically, the check valve 560 is provided in a portion of the second inflow path 61b before it branches toward each common liquid chamber 511 of the four head chips 510 as viewed from the second opening 550. As shown in FIG. 6, the check valve 560 of the present embodiment includes a valve body 561 and a valve body housing portion 562.

[0034] The valve body 561 has its position in the valve body housing portion 562 fluctuating depending on the ink flowing from the second sub-tank 213 toward each head chip 510 and the ink flowing from each head chip 510 toward the second sub-tank 213. The valve body 561 is a spherical object formed of a material having a specific gravity greater than that of the liquid. The valve body housing portion 562 allows the inflow of ink. The valve body housing portion 562 has a substantially cylindrical shape, and a through hole 563 is formed along the central axis. In the present embodiment, the check valve 560 is disposed at a position where the direction along the central axis of the valve body housing portion 562 is the vertical direction. The valve body 561 is disposed in the through hole 563. The through hole 563 includes a first through hole 563a, a second through hole 563b, and an inclined portion 563c. The valve body 561 is disposed in the first through hole 563a. The first through hole 563a is formed from one end of the valve body housing portion 562 toward the vicinity of the center, and has a diameter larger than the diameter of the valve body 561. The second through hole 563b is formed from the other end of the valve body housing portion 562 toward the vicinity of the center, and has a smaller diameter than the first through hole 563a. The second through hole 563b has a diameter smaller than the diameter of the valve body 561. The inclined portion 563c is the hypotenuse connecting the first through hole 563a and the second through hole 563b.

[0035] As shown by the arrow DA in A of FIG. 6, when pressure is applied to the ink in the direction from the second sub-tank 213 toward each head chip 510, the valve body 561 contacts the inclined portion 563c and closes the second through hole 563b. As a result, the check valve 560 is closed. On the other hand, when the pressure of the ink in the direction from each head chip 510 toward the second sub-tank 213 across the check valve 560 is greater than the ink pressure in the direction from the second sub-tank 213 toward each head chip 510, as shown in B of FIG. 6, the valve body 561 moves along the slope of the inclined portion 563c, and the ink flows from the second through hole 563b into the first through hole 563a as shown by the arrow DB.

[0036] The flow path filter 570 allows ink to flow through and catches foreign matter mixed in the ink. In the present embodiment, the flow path filter 570 is provided downstream of the portion of the first flow path 60 where the first pressure acquisition unit 70 acquires the pressure value. More specifically, the flow path filter 570 is provided in the portion of the first internal flow path 60b before it branches toward the common liquid chambers 511 of the respective four head chips 510.

[0037] FIG. 7 is a block diagram for explaining the control unit 90. The control unit 90 controls the operations of each component of the liquid ejecting device 1. In the present embodiment, the control unit 90 includes a CPU, a ROM, and a RAM. The CPU develops the programs stored in the ROM onto the RAM to exhibit various functions. In the present embodiment, the control unit 90 functions as a drive signal transmission unit 901, a drive control unit 902, a printing unit 903, a first liquid feeding unit 904, a second liquid feeding unit 905, a decompression control unit 906, a third liquid feeding unit 907, a fourth liquid feeding unit 908, a pressure acquisition unit 909, a circulation operation control unit 910, a pressurization discharge control unit 911, and a switching control unit 912.

[0038] The drive signal transmission unit 901 transmits a drive signal including a pulse to the drive circuit 522 shown in FIG. 4. The drive control unit 902 transmits a signal to the drive circuit 522 that designates whether or not to supply at least a part of the waveform included in the drive signal to the piezoelectric element 518 as a pulse. The printing unit 903 causes the liquid ejecting device 1 shown in FIG. 1 to execute a printing operation of performing printing on the medium PM based on an input received from the user via an interface group (not shown).

[0039] The first liquid delivery unit 904 shown in FIG. 7 transmits a first liquid delivery signal for causing the ink to be delivered from the main tank 10 to the second sub-tank 213 to the first pump 11 shown in FIG. 2. The second liquid delivery unit 905 transmits a second liquid delivery signal for causing the ink to be delivered from the second sub-tank 213 to the first sub-tank 211 via the relay flow path 214 to the second pump 212. The pressure reduction control unit 906 transmits a pressure reduction signal, which is a signal for reducing the pressure inside the second sub-tank 213, to the vacuum pump 231 and the third regulator 232. The third liquid delivery unit 907 transmits a first supply signal, which is a signal for supplying compressed air to the first sub-tank 211, to the compressor 221 of the pressurizing means 220 and the first regulator 222. By receiving the first supply signal, the pressurizing means 220 can execute the first pressurizing operation. The fourth liquid delivery unit 908 transmits a second supply signal, which is a signal for supplying compressed air to the second sub-tank 213, to the compressor 221 of the pressurizing means 220 and the second regulator 223. By receiving the second supply signal, the pressurizing means 220 can execute the second pressurizing operation. The pressure acquisition unit 909 receives pressure values from the first pressure acquisition unit 70 and the second pressure acquisition unit 71.

[0040] The circulation operation control unit 910 can cause the liquid ejection device 1 to execute a circulation operation. The circulation operation is an operation in which the pressurizing means 220 executes the first pressurizing operation and does not execute the second pressurizing operation, so that the ink is circulated in the order of the first sub-tank 211, the first flow path 60, the common liquid chamber 511 of each head chip 510, the second flow path 61, and the second sub-tank 213. In the present embodiment, the circulation operation is executed when the liquid ejection device 1 executes a printing operation or when a first switching operation or a second switching operation, which will be described later, is performed.

[0041] The circulation operation will be described with reference to FIGS. 2 and 3. The circulation operation can be executed by the circulation mechanism 20. The circulation operation control unit 910 notifies the third liquid feeding unit 907 that it should send a first supply signal, so that the third liquid feeding unit 907 sends the first supply signal to the pressurizing means 220. Thereby, the first pressurizing operation is executed by the pressurizing means 220. Further, the circulation operation control unit 910 notifies the decompression control unit 906 that the decompression in the second sub-tank 213 should be performed, so that the decompression control unit 906 sends a decompression signal to the decompression unit 230. Thereby, the ink in the liquid injection head 50 is recovered into the second sub-tank 213 through the second flow path 61. Further, the circulation operation control unit 910 notifies the second liquid feeding unit 905 that it should send a second liquid feeding signal. At this time, the circulation operation control unit 910 notifies the first liquid feeding unit 904 that it should send a first liquid feeding signal as necessary. In the present embodiment, in the circulation operation in the first switching operation and the second switching operation described later, ink is not ejected from the nozzle N. Note that, in the circulation operation in the first switching operation and the second switching operation, ink may be ejected from the nozzle N.

[0042] In the printing operation described above, while the same operation as the circulation operation is being executed, ink is ejected from the nozzle N. In this case, the drive control unit 902 sends a signal to the drive circuit 522 designating that at least a part of the waveform included in the drive signal is supplied as a pulse to the piezoelectric element 518. Further, the drive signal transmission unit 901 outputs a drive signal including a pulse to the drive circuit 522. Thereby, the diaphragm 519 vibrates in conjunction with the deformation of the piezoelectric element 518 of each head chip 510, and the pressure in the pressure chamber CB fluctuates, so that ink is ejected from the nozzle N.

[0043] The pressure discharge control unit 911 shown in FIG. 7 can cause the liquid injection device 1 to execute a pressure discharge operation. The pressure discharge operation is an operation in which the pressure means 220 executes the first pressurization operation in a state where the check valve 560 closes the second flow path 61 by executing the second pressurization operation. The pressure discharge operation will be described with reference to FIGS. 2 and 3. Specifically, the pressure discharge control unit 911 causes the fourth liquid supply unit 908 to transmit a second supply signal to the pressure means 220, causes the third liquid supply unit 907 to transmit a first supply signal to the pressure means 220, and causes the drive signal transmission unit 901 and the drive control unit 902 to transmit signals to the drive circuit 522, thereby causing the liquid injection device 1 to execute the pressure discharge operation. In the pressure discharge operation, in order to stabilize the ink pressurization to the first flow path 60 and the second flow path 61, it is preferable that the ink is not fed from the second sub-tank 213 to the first sub-tank 211 by the second pump 212.

[0044] FIG. 8 is an example of a flowchart of the pressure discharge operation. In step S10 of FIG. 8, the pressure discharge control unit 911 determines to execute the pressure discharge operation. When printing on the medium PM by the liquid injection device 1 is being performed, the printing operation is stopped and then the process of step S10 is executed. The execution of the pressure discharge operation is controlled by the pressure discharge control unit 911. The pressure discharge operation may be executed by the control unit 90 at intervals of a predetermined period, such as once every few days or once a week. Note that a circulation operation may be executed before the execution of step S10.

[0045] In step S20, the fourth liquid feeding unit 908 that has received the determination to execute the pressurized discharge operation from the pressurized discharge control unit 911 transmits the second supply signal to the pressurizing means 220, whereby the pressurizing means 220 executes the second pressurizing operation. By the second pressurizing operation, ink flows into the liquid ejection head 50 from the second sub-tank 213 through the second flow path 61. Since the check valve 560 is provided in the second flow path 61 as described above, when ink flows into the liquid ejection head 50 from the second sub-tank 213, the second flow path 61 is blocked by the check valve 560. When the circulation operation is being executed, the liquid feeding of the ink from the second sub-tank 213 to the first sub-tank 211 by the second pump 212 and the depressurization in the second sub-tank 213 by the depressurization unit 230 are stopped.

[0046] In step S30, the third liquid feeding unit 907 that has received the notification from the pressurized discharge control unit 911 transmits the first supply signal to the pressurizing means 220, whereby the pressurizing means 220 executes the first pressurizing operation. If the circulation operation has been executed before step S10, the pressurizing means 220 continues the first pressurizing operation. If the circulation operation has not been executed in step S20, the pressurizing means 220 executes the first pressurizing operation.

[0047] In step S40, the drive control unit 902 that has received the notification from the pressurized discharge control unit 911 transmits a signal specifying that at least a part of the waveform included in the drive signal is supplied as a pulse to the piezoelectric element 518 to the drive circuit 522. Further, the drive signal transmission unit 901 transmits a drive signal including a pulse to the drive circuit 522. The processes of steps S20 to S40 may be executed simultaneously.

[0048] Since the check valve 560 is closed by the second pressurizing operation, the ink in the second flow path 61 shown in FIG. 3 cannot pass through the check valve 560 and flow into the second sub-tank 213, and is blocked by the check valve 560. The pressure of the ink flowing into the common liquid chamber 511 of each head chip 510 becomes larger compared to when the pressurizing and discharging operation is not being executed, and the pressure of the ink passing through the filter 514 of each head chip 510 and reaching the nozzle row 523 becomes larger. As a result, when thickened ink, air bubbles, foreign matter mixed in from the outside, etc. are staying in the nozzle N, the pressure increases and the flow rate of the ink passing through the nozzle N increases, and due to the momentum of the ink, the ink containing the staying thickened ink, air bubbles, foreign matter mixed in from the outside, etc. is discharged from the nozzle N and dripped. Note that the ink containing the dripped thickened ink, air bubbles, foreign matter mixed in from the outside, etc. is collected in a waste liquid tank (not shown).

[0049] In the present embodiment, the pressurizing and discharging operation is executed in a state where the pressure value acquired by the second pressure acquisition unit 71 shown in FIG. 3 is equal to or less than the pressure value acquired by the first pressure acquisition unit 70. In other words, in the pressurizing and discharging operation, the pressure value at the second opening 550 is equal to or less than the pressure value at the first opening 540. Each of the third liquid feeding unit 907 and the fourth liquid feeding unit 908 that has received a notification to execute the pressurizing and discharging operation from the pressurizing and discharging control unit 911 transmits a signal to supply compressed air to the pressurizing means 220 at a predetermined pressure respectively. If the first pressure operation is being executed before the execution of step S10, the pressure of the ink flowing through the first flow path 60 may change.

[0050] Generally, when liquid flows through the liquid injection head 50 provided with the nozzle N, a pressure loss of the liquid occurs due to the resistance of the flow path in the liquid injection head 50. Further, in the present embodiment, a flow path filter 570 is provided in the first flow path 60. Due to the resistance of the flow path in the head chip 510 and the resistance of the flow path filter 570, the pressure value of the ink acquired by the first pressure acquisition unit 70 becomes smaller until it reaches the check valve 560. Therefore, even if the pressure value acquired by the second pressure acquisition unit 71 is equal to or less than the pressure value acquired by the first pressure acquisition unit 70, the closed state of the check valve 560 is maintained. Note that the pressure loss from the first sub-tank 211 to the check valve 560 through the first flow path 60 and each head chip 510 has been measured in advance. Even if the pressure value acquired by the second pressure acquisition unit 71 is equal to or less than the pressure value acquired by the first pressure acquisition unit 70, the pressure of the ink reaching the check valve 560 through the first flow path 60 and each head chip 510 is made smaller than the pressure of the ink reaching the check valve 560 from the second sub-tank 213 through the second flow path 61. Thus, the pressurizing means 220 is controlled by the control unit 90.

[0051] The switching control unit 912 shown in FIG. 7 causes the liquid injection device 1 to execute a first switching operation and a second switching operation. The first switching operation is an operation of switching from the circulation operation to the pressurization discharge operation. The pressurization discharge operation here is an operation in which, while the first pressurization operation is being executed, the second pressurization operation is executed so that the check valve 560 closes the second flow path 61, and the execution of the first pressurization operation is continued. The first switching operation may be executed when an input to execute the first switching operation is given to the liquid injection device 1 from the user via the interface group. Further, the control unit 90 may issue an instruction to execute the first switching operation based on a predetermined timing.

[0052] FIG. 9 is a flowchart for explaining the first switching operation. In step S10B of FIG. 9, under the control of the control unit 90, the liquid injection device 1 executes a circulation operation. In step S20B, under the control of the control unit 90, the liquid injection device 1 executes a pressurized discharge operation. In step S30B, under the control of the control unit 90, the pressurized discharge operation ends. Thereafter, the process ends. Hereinafter, the specific processes of steps S10B to S30B will be described.

[0053] FIG. 10 is a timing chart of the first switching operation. In FIG. 10, t represents time. At time t1, the circulation operation control unit 910 decides to execute the first switching operation. Also, the switching control unit 912 notifies the circulation operation control unit 910 to execute the circulation operation. At time t2, the circulation operation control unit 910 notifies the third liquid feeding unit 907 to transmit a first supply signal. Also, the circulation operation control unit 910 notifies the pressure reduction control unit 906 to transmit a pressure reduction signal. Although not shown, the circulation operation control unit 910 notifies the second liquid feeding unit 905 to transmit a second liquid feeding signal.

[0054] At time t3, the third liquid feeding unit 907 transmits a first supply signal to the pressurizing means 220. Also, the pressure reduction control unit 906 transmits a pressure reduction signal to the pressure reduction unit 230. At time t4, the first pressurizing operation is executed by the pressurizing means 220. Also, the second sub-tank 213 is depressurized by the pressure reduction unit 230. Further, although not shown, the ink in the second sub-tank 213 is supplied to the first sub-tank 211 by the second pump 212. The circulation operation is executed for a time pt1 which is a predetermined time.

[0055] At time t5, the switching control unit 912 notifies the pressure discharge control unit 911 to execute the pressure discharge operation. Further, the switching control unit 912 notifies the pressure reduction control unit 906 to stop transmitting the pressure reduction signal, and notifies the second liquid feeding unit 905 to stop the liquid feeding of the ink by the second pump 212. At time t6, the pressure discharge control unit 911 notifies the fourth liquid feeding unit 908 to transmit the second supply signal. Although not shown in FIG. 10, the pressure discharge control unit 911 further notifies the drive signal transmission unit 901 and the drive control unit 902 to transmit a signal to the drive circuit 522. At time t7, the fourth liquid feeding unit 908 transmits the second supply signal to the pressurizing means 220, and the drive signal transmission unit 901 and the drive control unit 902 transmit a signal to the drive circuit 522. Thereby, at time t8, the pressurizing means 220 executes the second pressurizing operation. Since the first pressurizing operation has already been executed, the pressure discharge operation is executed by the liquid injection device 1.

[0056] The switching control unit 912 determines that the first switching operation should end after a time pt2 which is a predetermined time, and at time t9, notifies the pressure discharge control unit 911 to stop the pressure discharge operation. At time t10, the pressure discharge control unit 911 notifies the third liquid feeding unit 907 and the fourth liquid feeding unit 908 to stop transmitting signals. At time t11, the third liquid feeding unit 907 and the fourth liquid feeding unit 908 stop transmitting signals, and thereafter the first pressurizing operation and the second pressurizing operation end. Also, although not shown, the discharge of the ink by the nozzle N also stops. Thereby, the pressure discharge operation ends.

[0057] In the first switching operation, the pressurizing means 220 is switched from the circulation operation in which the check valve 560 is not closed to the pressure discharge operation in which the check valve 560 is closed. The ink flowing from the common liquid chamber 511 toward the check valve 560 flows back in the common liquid chamber 511 when the check valve 560 is closed. Due to the water hammer action caused by this backflowing ink, compared with the mode of executing the pressure discharge operation from a state where the circulation operation is not executed, the liquid is discharged vigorously from the nozzle N, making it easier to discharge the solidified ink adhering in the nozzle N.

[0058] FIG. 11 is a flowchart for explaining the second switching operation. The second switching operation is an operation to switch from the pressurizing and discharging operation to the circulation operation. The second switching operation is executed when an input to execute the second switching operation is given to the liquid injection device 1 from the user via the interface group. In step S10C, under the control of the control unit 90, the liquid injection device 1 executes the pressurizing and discharging operation. Before the execution of step S10C, neither the printing operation nor the circulation operation is executed. In step S20C, under the control of the control unit 90, the liquid injection device 1 executes the circulation operation. In step S30C, under the control of the control unit 90, the circulation operation ends. Then, the process ends. Hereinafter, the specific processes of steps S10C to S30C will be described.

[0059] FIG. 12 is a timing chart of the second switching operation. In FIG. 12, t represents time. At time t21, the switching control unit 912 determines to execute the second switching operation. Further, the switching control unit 912 notifies the pressurizing and discharging control unit 911 to execute the pressurizing and discharging operation. At time t22, the pressurizing and discharging control unit 911 notifies the third liquid feeding unit 907 to transmit the first supply signal and notifies the fourth liquid feeding unit 908 to transmit the second supply signal. At time t23, the third liquid feeding unit 907 transmits the first supply signal to the pressurizing means 220, and the fourth liquid feeding unit 908 transmits the second supply signal to the pressurizing means 220. As a result, at time t24, the pressurizing means 220 executes the first pressurizing operation and the second pressurizing operation, so that the liquid injection device 1 executes the pressurizing and discharging operation. Although not shown in FIG. 12, while the pressurizing and discharging operation is being executed, ink continues to drip from the nozzles N of each head chip 510 by the drive signal transmitting unit 901 and the drive control unit 902. The pressurizing and discharging operation is executed for a predetermined time pt21.

[0060] At time t25, the switching control unit 912 notifies the pressure discharge control unit 911 to stop the pressure discharge operation. Also, the switching control unit 912 notifies the circulation operation control unit 910 to execute the circulation operation. At time t26, the pressure discharge control unit 911 notifies the fourth liquid feeding unit 908 to stop transmitting the second supply signal. Also, the circulation operation control unit 910 notifies the pressure reduction control unit 906 to transmit a pressure reduction signal. Although not shown in the figure, the circulation operation control unit 910 notifies the second liquid feeding unit 905 to transmit a second liquid feeding signal. As a result, the fourth liquid feeding unit 908 stops transmitting the second supply signal. Also, the pressure reduction control unit 906 transmits a pressure reduction signal to the pressure reduction unit 230, and the second liquid feeding unit 905 transmits a second liquid feeding signal to the second pump 212. At time t27, the pressure reduction unit 230 reduces the pressure of the second sub-tank 213, and the second pump 212 feeds ink from the second sub-tank 213 to the first sub-tank 211, whereby the liquid ejection device 1 executes the circulation operation.

[0061] The switching control unit 912 makes a determination to end the second switching operation after a time pt22 which is a predetermined time, and at time t28, notifies the circulation operation control unit 910 to stop the circulation operation. At time t29, the circulation operation control unit 910 notifies the third liquid feeding unit 907 to stop transmitting the first supply signal. Also, the circulation operation control unit 910 notifies the pressure reduction control unit 906 to stop transmitting the pressure reduction signal, and notifies the second liquid feeding unit 905 to stop transmitting the second liquid feeding signal. As a result, at time t30, the circulation operation ends.

[0062] In the second switching operation, from the state where the inflow of ink from the common liquid chamber 511 of each head chip 510 to the second sub-tank 213 of the liquid storage unit 210 is stopped due to the closing of the check valve 560, by switching to a circulation operation in which the second pressurization operation is not performed, the closing of the check valve 560 is released. For example, compared with the mode in which the circulation operation is executed from the state where the pressure discharge operation is not performed, the pressure of the ink flowing through the second flow path 61 immediately after the closing of the check valve 560 is released can be increased. As a result, the bubbles remaining in the ink in the common liquid chamber 511 of each head chip 510 can be efficiently discharged to the second sub-tank 213.

[0063] Also, in the present embodiment, as shown in FIG. 5, each head chip 510 of the liquid injection head 50 has a filter 514. Generally, it is known that a filter deteriorates due to the adhesion of foreign matter in the ink. Immediately after switching to the circulation operation from the state where the inflow of ink from the common liquid chamber 511 of each head chip 510 to the second sub-tank 213 of the liquid storage unit 210 is stopped, it is considered that the ink in the common liquid chamber 511 flows out vigorously toward the second sub-tank 213. At this time, it is considered that the foreign matter adhering to the first filter 514a and the second filter 514b is carried by the flowing-out ink and removed from the common liquid chamber 511. Thereby, it becomes possible to prevent the deterioration of the filter 514.

[0064] In the liquid ejecting apparatus 1 of the present embodiment, a pressure discharging operation can be executed. For example, in a mode where the second pressurizing operation is not executed and a manual valve or a solenoid valve is provided in the second flow path 61, with the second flow path 61 closed by the manual valve or the solenoid valve, when liquid is caused to flow through the first flow path 60, it is conceivable that ink is ejected from the nozzle N communicating with the common liquid chamber 511. According to the liquid ejecting apparatus 1 of the present embodiment, when the first pressurizing operation is executed by the pressurizing means 220 with the check valve 560 closing the second flow path 61 by the execution of the second pressurizing operation by the pressurizing means 220, ink is discharged from the nozzle N. Compared with a mode including a manual valve or a solenoid valve, cleaning of the nozzle N is performed efficiently and at low cost.

[0065] Further, since the check valve 560 can be provided inside the liquid ejecting head 50, when the liquid ejecting head 50 is assembled to the liquid ejecting apparatus 1, the check valve 560 can be simultaneously incorporated into the liquid ejecting apparatus 1. Therefore, compared with a mode of separately assembling the check valve 560 and the liquid ejecting head 50, the burden on the operator in the assembly is reduced. Further, since the check valve 560 is provided inside the liquid ejecting head 50, it is possible to reduce the inflow of foreign matter into the common liquid chamber 511 through the second internal flow path 61b.

[0066] Generally, when ink flows through the liquid injection head 50 provided with the nozzle N, a pressure loss of the ink occurs due to the resistance of the flow path in the liquid injection head 50. According to the liquid injection device 1 of the present embodiment, even if the pressure value at the second opening 550 is equal to or less than the pressure value at the first opening 540, the ink having a pressure smaller than the pressure when passing through the first opening 540 due to the resistance in the liquid injection head 50 flows into the first internal flow path 60b. If the pressure in the second flow path 61 is such that the check valve 560 closes the second flow path 61, the pressure of the ink flowing through the nozzle N becomes higher compared to the state where it is not blocked. Therefore, the ink staying in the nozzle N is discharged to the outside of the liquid injection device 1. Compared with the aspect where the pressure value at the second opening 550 is larger than the pressure value at the first opening 540, the pressure of the ink flowing through the check valve 560 via the second flow path 61 can be reduced. Therefore, breakage and deterioration of the check valve 560 can be suppressed.

[0067] Also, in the present embodiment, a flow path filter 570 through which liquid flows is provided in the first internal flow path 60b. A pressure loss occurs in the ink passing through the flow path filter 570 due to the resistance of the flow path filter 570. Therefore, even when the pressure value at the first opening 540 is larger than the pressure value at the second opening 550, it is considered that the pressure value of the ink reaching the check valve 560 becomes smaller than the pressure value at the second opening 550. For example, when the pressure value at the second opening 550 is made larger than the pressure value at the first opening 540, the check valve 560 is likely to be pushed in the direction from the liquid storage portion 210 toward the common liquid chamber portion. In the present embodiment, the valve body 561 of the check valve 560 is likely to be pushed in the direction of the arrow DA in FIG. 6. In the present embodiment, compared with the aspect where the flow path filter 570 is not provided, the pressure value at the second opening 550 can be reduced. As a result, deposition of pigments and the like, which are components of the ink, at the check valve 560 can be suppressed. In the present embodiment, deposition at the contact portion between the valve body 561 and the inclined portion 563c is suppressed. Therefore, the life of the check valve 560 can be extended.

[0068] B. Other Embodiments: B1. Other Embodiment 1: (1) In the above embodiment, the liquid is ink, and the liquid ejecting device 1 is an inkjet printer. For example, the liquid ejecting device may be various devices such as a facsimile machine or a copying machine. The use of the liquid ejecting device is not limited to printing, and it can be used as a device for ejecting a solution of a coloring material or a conductive material.

[0069] (2) In the above embodiment, the head chip 510 includes a common liquid chamber 511 to which the first internal flow path 60b and the second internal flow path 61b are connected, but it is not limited thereto. For example, the head chip may be configured to include a supply-side common liquid chamber into which ink supplied from the first sub-tank flows by being connected to the first internal flow path, a recovery-side liquid chamber into which ink that has not been ejected from the nozzle N flows, and an individual flow path that connects the supply-side liquid chamber and the recovery-side common liquid chamber and communicates with the nozzle. The recovery-side common liquid chamber is connected to the second internal flow path, and the ink in the recovery-side common liquid chamber received from the individual flow path during the circulation operation is recovered into the second sub-tank. In this aspect, the supply-side common liquid chamber and the recovery-side common liquid chamber are an example of the "common liquid chamber portion".

[0070] (3) In the above embodiment, the liquid ejecting head 50 includes four head chips 510, but it is not limited thereto. For example, the liquid ejecting head may include a number of head chips other than four, such as one or five.

[0071] (4) In the above embodiment, the valve body 561 is a spherical object, and the valve body housing portion 562 is formed with a first through hole 563a, a second through hole 563b, and an inclined portion 563c, but it is not limited thereto. For example, a check valve may be configured to include a lid-shaped valve body, a valve body housing portion having a first through hole and a second through hole with a diameter smaller than that of the first through hole. In this configuration, the lid-shaped valve body is disposed at a position in contact with the boundary between the first through hole and the second through hole. When pressure is applied in the direction from the second sub-tank toward the head chip, the valve body closes the boundary. As a result, the check valve is closed. On the other hand, when the pressure of the ink in the direction from the head chip toward the second sub-tank across the check valve is greater than the pressure of the ink in the direction from the second sub-tank toward the head chip, the valve body is separated from the boundary by the ink flowing from the head chip toward the second sub-tank. As a result, the ink flows into the second sub-tank.

[0072] (5) In the above embodiment, the pressurizing means 220 includes a compressor 221, a first regulator 222, and a second regulator 223, but it is not limited thereto. For example, the pressurizing means may include a first compressor and a first regulator for sending compressed air to the first sub-tank 211, and a second compressor and a second regulator for sending compressed air to the second sub-tank 213.

[0073] (6) In the above embodiment, the circulation mechanism 20 includes the pressurizing means 220, but it is not limited thereto. For example, the circulation mechanism may include a pressurizing means for pressurizing the first flow path for performing a circulation operation, separately from the pressurizing means for performing a first pressurizing operation for pressurizing the first flow path to execute a pressurizing and discharging operation.

[0074] B2. Other Embodiments 2: (1) In the above embodiment, the check valve 560 is provided in the second internal flow path 61b, but it is not limited thereto. For example, the check valve 560 may be provided in the second external flow path 61a.

[0075] (2) In the above embodiment, the check valve 560 is provided in a portion of the second internal flow path 61b before the branching. In this aspect, since the second flow path is blocked by one check valve, the cost of the liquid injection device can be suppressed. For example, a plurality of check valves may be provided in a portion of the second internal flow path after the branching.

[0076] B3. Other Embodiment 3: (1) In the above embodiment, the liquid injection device 1 includes a first pressure acquisition unit 70 and a second pressure acquisition unit 71. For example, in an aspect where the pressure value at the second opening is always controlled to be greater than the pressure value at the first opening, the liquid injection device may not include the first pressure acquisition unit and the second pressure acquisition unit.

[0077] (2) In the above embodiment, the pressurized discharge operation is performed in a state where the pressure value at the second opening 550 is less than or equal to the pressure value at the first opening 540, but it is not limited thereto. For example, the pressurized discharge operation may be performed in a state where the pressure value at the second opening is greater than the pressure value at the first opening.

[0078] (3) In the above embodiment, the first pressure acquisition unit 70 acquires the pressure value at the first opening 540, and the second pressure acquisition unit 71 acquires the pressure value at the second opening 550, but it is not limited thereto. For example, the first pressure acquisition unit may acquire the pressure value of the liquid flowing through the first flow path, and the second pressure acquisition unit may acquire the pressure value of the liquid flowing through the second flow path.

[0079] (4) In an embodiment where the liquid injection device includes two pressure acquisition units, one pressure acquisition unit acquires the pressure value of the liquid attempting to flow into the check valve on the head chip side of the second flow path with respect to the check valve, and the other pressure acquisition unit acquires the pressure value of the liquid attempting to flow into the check valve on the second sub-tank side of the second flow path with respect to the check valve. In this embodiment, the control unit can control the liquid injection device in real time such that in the pressurization and discharge operation, the pressure value acquired by the other pressure acquisition unit is equal to or greater than the pressure value acquired by one pressure acquisition unit. For example, considering the possibility of pressure loss occurring in the second flow path due to foreign matter adhering to the second flow path, the pressurization and discharge operation can be executed.

[0080] B4. Other Embodiment 4: (1) In the above embodiment, a flow path filter 570 through which ink flows is provided downstream of the portion of the first flow path 60 where the first pressure acquisition unit 70 acquires the pressure value, but this is not limiting. For example, the first flow path may not be provided with a flow path filter.

[0081] (2) For example, the flow path filter may be provided upstream of the portion of the first flow path where the first pressure acquisition unit acquires the pressure value. A plurality of filters may be provided both upstream and downstream of the portion of the first pressure acquisition unit where the pressure value is acquired.

[0082] B5. Other Embodiment 5: (1) In the above embodiment, the liquid injection device can execute the first switching operation, but this is not limiting. For example, the liquid injection device may not execute the first switching operation.

[0083] (2) In the above embodiment, when the first switching operation is executed, the pressurization and discharge operation is executed without an interval from the circulation operation, but this is not limiting. When the first switching operation is executed, the pressurization and discharge operation may be executed several seconds after the circulation operation.

[0084] (3) In the mode in which the first switching operation is executed, by making the pressure reduction in the second sub-tank by the pressure reduction unit during the circulation operation a negative pressure, ink vigorously flows into the liquid injection head. When switched to the pressurized discharge operation, the pressure of the ink flowing from the first liquid chamber portion and the second liquid chamber portion to the nozzles increases, and the ink staying in the nozzles is more easily discharged.

[0085] B6. Other Embodiment 6: (1) In the above embodiment, the liquid injection device can execute the second switching operation, but is not limited thereto. For example, the liquid injection device may not execute the second switching operation.

[0086] (2) In the above embodiment, when the second switching operation is executed, the circulation operation is executed without an interval from the pressurized discharge operation, but is not limited thereto. When the second switching operation is executed, the circulation operation may be executed several seconds after the pressurized discharge operation.

[0087] B7. Other Embodiment 7: In the above embodiment, the liquid storage unit 210 is composed of the first sub-tank 211, the second sub-tank 213, the second pump 212, and the relay flow path 214, but is not limited thereto. For example, in a mode in which the first sub-tank and the second sub-tank are partitioned by a partition in one tank, the circulation mechanism may not include the second pump and the relay flow path. Further, the liquid storage unit may be composed of a main tank, a first pump, a first sub-tank, a second sub-tank, a second pump, and a relay flow path. Further, a circulation mechanism may be constituted by a main tank as the liquid storage unit, a first outflow path connected to the main tank, a second outflow path connected to the main tank, and tube pumps provided in each of the first outflow path and the second outflow path. In this case, the tube pump provided in the first outflow path and the reversibly rotatable tube pump provided in the second outflow path are an example of the pressurizing means.

[0088] B8. Other Embodiment 8: Instead of using the first pressure acquisition unit 70 and the second pressure acquisition unit 71, a pressure acquisition unit capable of acquiring the pressure inside each of the first sub-tank and the second sub-tank may be provided, and the correlation between the pressure of the first pressure acquisition unit, the second pressure acquisition unit, the first sub-tank, and the second sub-tank may be measured in advance. A method of controlling the first pressurization operation and the second pressurization operation using the pressure values of the pressure acquisition units of the first sub-tank and the second sub-tank may also be used.

[0089] C. Other forms: The present disclosure is not limited to the above-described embodiments, and can be realized in various forms without departing from the gist thereof. For example, the present disclosure can also be realized by the following forms. The technical features in the above embodiments corresponding to the technical features in each of the following forms can be appropriately replaced or combined in order to solve part or all of the problems of the present disclosure or to achieve part or all of the effects of the present disclosure. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

[0090] (1) According to one embodiment of the present disclosure, a liquid injection device is provided. The liquid injection device includes a liquid injection head including a plurality of nozzles that inject liquid and a common liquid chamber portion communicating with the plurality of nozzles, a liquid storage portion that stores liquid to be supplied to the common liquid chamber portion, a first flow path that communicates the common liquid chamber portion and the liquid storage portion, a second flow path that communicates the common liquid chamber portion and the liquid storage portion, a check valve provided in the second flow path that blocks the flow of liquid from the liquid storage portion toward the common liquid chamber portion and allows the flow from the common liquid chamber portion toward the liquid storage portion, and a pressurizing means that can selectively execute a first pressurizing operation of pressurizing the liquid so that the liquid flows from the liquid storage portion toward the common liquid chamber portion via the first flow path and a second pressurizing operation of pressurizing the liquid so that the liquid flows from the liquid storage portion toward the common liquid chamber portion via the second flow path. The pressurizing means can execute a pressurizing discharge operation in which the first pressurizing operation is executed with the check valve closing the second flow path by executing the second pressurizing operation. For example, in an aspect where the second pressurizing operation is not executed and a manual valve or a solenoid valve is provided in the second flow path, it is conceivable that liquid is caused to flow through the first flow path with the second flow path closed by the manual valve or the solenoid valve, and liquid is injected from the nozzles communicating with the liquid chamber portion. According to the liquid injection device of this aspect, when the first pressurizing operation is executed by the pressurizing means with the check valve closing the second flow path by executing the second pressurizing operation by the pressurizing means, liquid is injected from the nozzles. Compared with the aspect including a manual valve or a solenoid valve, cleaning of the nozzles is performed efficiently and at low cost.

[0091] (2) In the liquid injection device of the above aspect, the second flow path may include a second outer flow path connecting the liquid storage portion and a second opening that is a flow path connection portion between the outside of the liquid injection head, and a second inner flow path connecting the second opening and the common liquid chamber portion within the liquid injection head, and the check valve may be provided in the second inner flow path. According to the liquid injection device of this form, a check valve can be provided inside the liquid injection head. Therefore, when assembling the liquid injection head to the liquid injection device, the check valve can be incorporated into the liquid injection device at the same time. As a result, compared with the mode of separately assembling the check valve and the liquid injection head, the burden on the operator during assembly is reduced.

[0092] (3) In the liquid injection device of the above form, the first flow path includes a first external flow path connecting the liquid storage part and a first opening which is a flow path connection part between the liquid injection head and the outside, and a first internal flow path inside the liquid injection head that connects the first opening and the common liquid chamber part. In the pressurized discharge operation, the pressure value at the second opening is equal to or less than the pressure value at the first opening, which may be a characteristic. Generally, when liquid flows through the inside of a liquid injection head equipped with a nozzle, a pressure loss of the liquid occurs due to the resistance of the flow path inside the liquid injection head. According to the liquid injection device of this form, even if the pressure value at the second opening is equal to or less than the pressure value at the first opening, ink with a pressure smaller than the pressure when passing through the first opening due to the resistance inside the liquid injection head flows into the first internal flow path. If the pressure of the second flow path is in a state where the check valve closes the second flow path, the pressure of the ink flowing through the nozzle becomes larger compared to the unblocked state. Therefore, the ink staying in the nozzle is discharged to the outside of the liquid injection device. Compared with the mode where the pressure value at the second opening is larger than the pressure value at the first opening, the pressure of the ink flowing through the second flow path to the check valve can be reduced. Therefore, damage and deterioration of the check valve can be suppressed.

[0093] (4) In the liquid injection device of the above form, a filter through which liquid flows may be provided in the first internal flow path. The liquid that has passed through the filter generates a pressure loss due to the resistance of the filter. Therefore, even when the pressure value at the first opening is greater than the pressure value at the second opening, it is considered that the pressure value of the ink reaching the check valve is smaller than the pressure value at the second opening. For example, when the pressure value at the second opening is made greater than the pressure value at the first opening, the check valve is more likely to be pushed in the direction from the liquid storage section to the common liquid chamber section. According to this type of liquid ejection device, compared with a mode in which no filter is provided, the pressure value at the second opening can be reduced. As a result, deposition of pigments and the like, which are components of the ink, on the check valve is suppressed. Therefore, the life of the check valve can be extended.

[0094] (5) In the liquid ejection device of the above-described embodiment, further, a circulation mechanism capable of executing a circulation operation for circulating the liquid in the order of the liquid storage section, the first flow path, the common liquid chamber section, the second flow path, and the liquid storage section may be provided, and a first switching operation for switching from the circulation operation to the pressurized discharge operation may be executable. According to this type of liquid ejection device, the pressurizing means can be switched from a circulation operation in which the check valve is not closed to a pressurized discharge operation in which the check valve is closed. The liquid that was flowing from the common liquid chamber section toward the check valve flows backward in the common liquid chamber section when the check valve is closed. Due to the water hammer action caused by this backward-flowing liquid, compared with a mode in which the pressurized discharge operation is executed from a state in which the circulation operation is not being performed, the liquid is discharged vigorously from the nozzle, making it easier to discharge the solidified ink adhering in the nozzle.

[0095] (6) In the liquid ejection device of the above-described embodiment, a circulation mechanism capable of executing a circulation operation for circulating the liquid in the order of the liquid storage section, the first flow path, the common liquid chamber section, the second flow path, and the liquid storage section may be provided, and a second switching operation for switching from the pressurized discharge operation to the circulation operation, which executes the circulation operation from the pressurized discharge operation, may be executable. According to the liquid injection device of this embodiment, from the state where the inflow of liquid from the common liquid chamber portion to the liquid storage portion is stopped due to the closing of the check valve, by switching to a circulation operation that does not execute the second pressurization operation, the closing of the check valve is released. For example, compared with the mode in which the circulation operation is executed from the state where the pressurization and discharge operation is not performed, the pressure of the liquid flowing through the second flow path immediately after the closing of the check valve is released can be increased. As a result, the bubbles remaining in the liquid in the common liquid chamber portion can be efficiently discharged to the liquid storage portion.

[0096] (7) In the liquid injection device of the above embodiment, the liquid storage portion includes a first sub-tank connected to the first flow path, a second sub-tank connected to the second flow path, and a relay flow path that communicates the first sub-tank and the second sub-tank. The liquid injection device may further include a decompression unit that decompresses the inside of the second sub-tank, and the pressurizing means pressurizes the inside of the first sub-tank and the second sub-tank, respectively.

[0097] (8) According to another aspect of the present disclosure, a method for maintaining a liquid injection device is provided. This method for maintaining a liquid injection device is a method for maintaining a liquid injection device including a liquid injection head including a plurality of nozzles for injecting liquid and a common liquid chamber portion communicating with the plurality of nozzles, and a liquid storage portion for storing liquid supplied to the common liquid chamber portion, and includes a first flow path for communicating the liquid storage portion and the common liquid chamber portion, and a check valve provided in a second flow path for communicating the common liquid chamber portion and the liquid storage portion, the check valve blocking the flow of liquid from the liquid storage portion to the common liquid chamber portion and allowing the flow from the common liquid chamber portion to the liquid storage portion. The method includes performing a first pressurization operation of pressurizing the liquid so that the liquid flows from the liquid storage portion to the common liquid chamber portion through the first flow path in a state where the check valve closes the second flow path by performing a second pressurization operation of pressurizing the liquid in a direction from the liquid storage portion to the common liquid chamber portion through the second flow path, and performing a pressurization and discharge operation.

[0098] The present disclosure can also be implemented in various forms other than a liquid ejecting apparatus and a maintenance method thereof. For example, it can be implemented in the form of a manufacturing method of a liquid ejecting apparatus, a control method of a liquid ejecting apparatus, a control method of a maintenance method of a liquid ejecting apparatus, a computer program for realizing the control method, a non-transitory recording medium recording the computer program, and the like.

Explanation of Signs

[0099] 1... Liquid ejecting apparatus, 10... Main tank, 11... First pump, 20... Circulation mechanism, 30... Conveying mechanism, 40... Moving mechanism, 41... Storage box, 42... Conveyor belt, 50... Liquid ejecting head, 60... First flow path, 60a... First external flow path, 60b... First internal flow path, 61... Second flow path, 61a... Second external flow path, 61b... Second internal flow path, 70... First pressure acquisition unit, 71... Second pressure acquisition unit, 90... Control unit, 210... Liquid storage unit, 211... First sub-tank, 212... Second pump, 213... Second sub-tank, 214... Relay flow path, 220... Pressurizing means, 221... Compressor, 222... First regulator, 223... Second regulator, 230... Pressure reducing unit, 231... Vacuum pump, 232... Third regulator, 500... Flow path structure, 510... Head chip, 511... Common liquid chamber, 511a... First liquid chamber opening, 511b... Second liquid chamber opening, 513... Flow path forming member, 514... Filter, 514a... First filter, 514b... Second filter, 515... Pressure chamber substrate, 516... Nozzle plate, 517... Vibration absorber, 518... Piezoelectric element, 519... Diaphragm, 520... Protection substrate, 521... Wiring substrate, 522... Driving circuit, 523... Nozzle row, 540... First opening, 550... Second opening, 560... Check valve, 561... Valve body, 562... Valve body housing, 563... Through hole, 563a... First through hole, 563b... Second through hole, 563c... Inclined portion, 570... Flow path filter, 901... Driving signal transmitting unit, 902... Driving control unit, 903... Printing unit, 904... First liquid feeding unit, 905... Second liquid feeding unit, 906... Pressure reducing control unit, 907... Third liquid feeding unit, 908... Fourth liquid feeding unit, 909... Pressure acquisition unit, 910... Circulation operation control unit, 911... Pressurizing and discharging control unit, 912... Switching control unit, CB... Pressure chamber, DA... Arrow, DB... Arrow, N... Nozzle, PM... Medium

Claims

1. A liquid injection head including a plurality of nozzles for injecting a liquid and a common liquid chamber portion communicating with the plurality of nozzles; A liquid storage portion for storing the liquid supplied to the common liquid chamber portion; A first flow path for communicating the common liquid chamber portion and the liquid storage portion; A second flow path for communicating the common liquid chamber portion and the liquid storage portion; A check valve provided in the second flow path for blocking the flow of the liquid from the liquid storage portion to the common liquid chamber portion and allowing the flow from the common liquid chamber portion to the liquid storage portion; Pressurizing means, A first pressurizing operation for pressurizing the liquid so that the liquid flows from the liquid storage portion to the common liquid chamber portion through the first flow path; Pressurizing means capable of selectively performing a second pressurizing operation for pressurizing the liquid from the liquid storage portion to the common liquid chamber portion through the second flow path; Comprising, The liquid injection device is characterized in that the pressurizing means can perform a pressurizing discharge operation in which the first pressurizing operation is performed with the check valve closing the second flow path by executing the second pressurizing operation.

2. The second flow path, A second outer flow path connecting the liquid storage portion and a second opening which is a flow path connection portion between the outside of the liquid injection head; A second inner flow path connecting the second opening and the common liquid chamber portion within the liquid injection head; Comprising, The liquid injection device according to claim 1, wherein the check valve is provided in the second inner flow path.

3. The first flow path, A first outer flow path connecting the liquid storage portion and a first opening which is a flow path connection portion between the outside of the liquid injection head; A first inner flow path connecting the first opening and the common liquid chamber portion within the liquid injection head; Comprising, In the pressurizing discharge operation, the pressure value at the second opening is equal to or less than the pressure value at the first opening. The liquid injection device according to claim 2.

4. The liquid injection device according to claim 3, wherein a filter through which the liquid flows is provided in the first inner flow path.

5. A circulation mechanism capable of performing a circulation operation for circulating the liquid in the order of the liquid storage portion, the first flow path, the common liquid chamber portion, the second flow path, and the liquid storage portion; The liquid injection device according to claim 1, characterized in that a first switching operation for switching from the circulation operation to the pressurizing discharge operation can be performed.

6. A circulation mechanism capable of performing a circulation operation for circulating liquid in the order of the liquid storage section, the first flow path, the common liquid chamber section, the second flow path, and the liquid storage section is provided. The liquid injection device according to claim 1, characterized in that it is a second switching operation for switching from the pressurized discharge operation to the circulation operation, and is capable of performing a second switching operation for executing the circulation operation from the pressurized discharge operation.

7. The liquid storage section includes a first sub-tank connected to the first flow path, a second sub-tank connected to the second flow path, and a relay flow path for communicating the first sub-tank and the second sub-tank. The liquid injection device further includes a decompression section for decompressing the inside of the second sub-tank. The pressurizing means pressurizes the inside of the first sub-tank and the inside of the second sub-tank respectively. The liquid injection device according to claim 1, characterized in that.

8. A liquid injection head including a plurality of nozzles for injecting liquid and a common liquid chamber section communicating with the plurality of nozzles, a first flow path for communicating the liquid injection head and a liquid storage section for storing the liquid supplied to the common liquid chamber section, and a second flow path for communicating the common liquid chamber section and the liquid storage section, provided with a check valve for blocking the flow of liquid from the liquid storage section to the common liquid chamber section and allowing the flow from the common liquid chamber section to the liquid storage section, a maintenance method for a liquid injection device, A pressurized discharge operation is performed by performing a first pressurizing operation for pressurizing the liquid so that the liquid flows from the liquid storage section to the common liquid chamber section through the first flow path in a state where the check valve closes the second flow path by performing a second pressurizing operation for pressurizing the liquid in a direction from the liquid storage section to the common liquid chamber section through the second flow path. The maintenance method for a liquid injection device is characterized in that.

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