Liquid injection device and maintenance method of liquid injection device

Abstract

The present application provides a liquid injection device and a maintenance method for the liquid injection device, which can reduce the amount of foreign matter attached to the nozzle surface and the amount of liquid flowing into the liquid return flow path. The liquid injection device comprises: a liquid injection portion having a supply port, a second discharge port, a plurality of nozzles, and a nozzle surface opened by the plurality of nozzles, and ejecting the liquid from the plurality of nozzles; a liquid supply flow path connected to the supply port to supply the liquid to the liquid injection portion; and a liquid return flow path connected to the second discharge port to allow the liquid supplied to the liquid injection portion to flow back to the liquid supply flow path. After the liquid injection device performs a pressurized discharge action of pressurizing the liquid in the liquid injection portion and causing the liquid to be discharged from the nozzle, the liquid injection device performs a pressure reduction action of reducing the pressure in the liquid injection portion while the flow of the liquid in the liquid return flow path is blocked.

Description

Technical Field

[0001] The present invention relates to a liquid ejecting device such as a printer and a maintenance method of the liquid ejecting device. Background Art

[0002] Conventionally, as shown in Patent Document 1, there is known a liquid ejection device as an example of a liquid ejection device, wherein the liquid ejection device ejects ink as an example of a liquid supplied from a sub-tank as an example of a liquid storage section via a liquid supply flow path from a nozzle of a liquid ejection head as an example of a liquid ejection section to perform printing. The liquid ejection head is connected to the sub-tank via a liquid return flow path so that the ink can circulate, and a purge pump as an example of a pressurizing mechanism is provided on the liquid supply flow path, and the purge pump can perform a pressurized discharge action of forcibly supplying ink to the liquid ejection head and discharging it from the nozzle. Then, after performing the pressurized discharge action, the liquid ejection device reduces the pressure in the liquid ejection head by performing a circulation action.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2012-30496

[0004] However, as in the liquid ejection device described in Patent Document 1, there is the following technical problem: when a pressure reducing action is performed by performing a circulation action to reduce the pressure in the liquid ejection head after a pressurized ejection action, ink remaining on the nozzle surface where the nozzle is opened due to the pressurized ejection action flows into the liquid return flow path through the liquid ejection head during the pressure reducing action. Summary of the invention

[0005] A liquid ejection device, comprising: a liquid ejection unit having a supply port for liquid to flow in, a discharge port for liquid to flow out, a common flow path communicating with the supply port and the discharge port, an independent liquid chamber communicating with the common flow path, a nozzle communicating with the independent liquid chamber, a nozzle face opened by a plurality of the nozzles, and an ejection element, wherein the liquid ejection unit ejects the liquid in the independent liquid chamber from the nozzle toward a medium by driving the ejection element; a liquid supply flow path connected to the supply port to supply the liquid to the liquid ejection unit; and a liquid return flow path connected to the discharge port to return the liquid supplied to the liquid ejection unit to the liquid supply port. A flow path reflux; a pressurizing mechanism, which pressurizes the liquid in the liquid injection section; a return valve, which is arranged in the liquid return flow path and can be in a closed valve state that prevents the flow of the liquid and an open valve state that allows the flow of the liquid; and a control section, which performs a pressurized discharge action and a pressure reduction action, and performs the pressure reduction action in a state where the return valve is closed. In the pressurized discharge action, the control section causes the pressurizing mechanism to pressurize the liquid in the liquid injection section so that the liquid is discharged from the nozzle. In the pressure reduction action, the control section causes the pressurizing mechanism to stop the pressurization in the liquid injection section.

[0006] A maintenance method for a liquid injection device, wherein the liquid injection device comprises: a liquid injection portion having a supply port for liquid to flow in, a discharge port for liquid to flow out, a common flow path communicating with the supply port and the discharge port, an independent liquid chamber communicating with the common flow path, a nozzle communicating with the independent liquid chamber, a nozzle face opened by a plurality of the nozzles, and a spraying element, wherein the liquid injection portion sprays the liquid in the independent liquid chamber from the nozzle toward a medium by driving the spraying element; a liquid supply flow path connected to the supply port to supply the liquid to the liquid injection portion; and a liquid return flow path connected to the discharge port to cause the liquid supplied to the liquid injection portion to flow back to the liquid supply flow path, wherein the maintenance method comprises: performing a pressurized discharge action of pressurizing the liquid in the liquid injection portion to discharge the liquid from the nozzle; and after the pressurized discharge action, performing a pressure reducing action of reducing the pressure in the liquid injection portion in a state where the flow of the liquid in the liquid return flow path is blocked. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a side view schematically showing the liquid ejecting device according to the first embodiment.

[0008] Figure 2 is a schematic top view of the maintenance unit.

[0009] Figure 3is a schematic side view of the wiping mechanism.

[0010] Figure 4 It is a cross-sectional view schematically showing a liquid ejecting portion and a liquid supplying portion.

[0011] Figure 5 is along Figure 4 A cross-sectional view taken along line 4-4.

[0012] Figure 6 is a block diagram showing the electrical structure of the liquid ejecting device.

[0013] Figure 7 1 is a diagram showing a calculation model that assumes simple harmonic motion of residual vibration of a vibration plate.

[0014] Figure 8 This is an explanatory diagram for explaining the relationship between the viscosity increase of liquid and the residual vibration waveform.

[0015] Fig. 9 This is an explanatory diagram for explaining the relationship between bubble mixing and the residual vibration waveform.

[0016] Fig.10 It is a cross-sectional view schematically showing the pressurized discharge operation.

[0017] Fig.11A It is a cross-sectional view schematically showing the pressure reduction operation.

[0018] Fig. 11B It is a cross-sectional view schematically showing the pressure reduction operation.

[0019] Fig.12 It is a cross-sectional view schematically showing the wiping action.

[0020] Fig.13 It is a cross-sectional view schematically showing the flushing action.

[0021] Fig.14 This is a flowchart showing an example of the cleaning process including the pressurized discharge operation.

[0022] Fig.15 It is a cross-sectional view schematically showing the pressure reducing operation according to the second embodiment.

[0023] Fig.16 It is a cross-sectional view schematically showing the pressure reducing operation according to the third embodiment.

[0024] Fig.17 It is a cross-sectional view schematically showing a liquid ejecting portion, a liquid supplying portion, and a pressurized discharge operation according to a fourth embodiment.

[0025] Fig.18This is a cross-sectional view schematically showing the liquid ejecting section, the liquid supply section, and the pressurized discharge operation according to the fifth embodiment.

[0026] Description of Reference Numerals

[0027] 11, 511, 611 liquid ejecting device; 12 medium; 13 support platform; 14 conveying part; 15, 515 liquid ejecting part; 16 moving mechanism; 17 liquid supply source; 18 mounting part; 19, 519, 619 liquid supply part; 20 main body; 20a first cover; 20b second cover; 21 conveying roller pair; 22 conveying motor; 23 guide plate; 24 nozzle; 25 nozzle surface; 26 guide shaft; 27 carriage; 28 carriage motor; 30 liquid supply flow path; 30m connecting part; 31, 531, 631 liquid return flow path; 31a first return flow path; 31b second return flow path; 32 liquid storage part; 33 circulation path; 34 derivation pump; 35 suction valve; 36 displacement pump; 36a flexible member; 36b pump chamber ; 36c negative pressure chamber; 36d pressure reducing portion; 36e pressing member; 37 discharge valve; 38 filter unit; 39, 539 flow mechanism; 39A supply pump; 39B, 539B return valve; 40, 540, 640 pressure regulating device; 41 storage release valve; 42 storage amount detection portion; 43 stirring mechanism; 43a stirring rod; 43b rotating portion; 44 air introduction portion; 44a switching valve; 44b air inflow channel; 44c check valve; 45 opening and closing valve; 46 choke valve; 48 pressure regulating mechanism; 49 pressing mechanism; 50 liquid inflow portion; 51 liquid outflow portion; 52 main body; 53 wall; 54 through hole; 55 filter member; 56 diaphragm; 56a first surface; 56b second surface; 57 communication path; 59 Supply valve; 60 valve portion; 61 pressure receiving portion; 62 upstream side pressing member; 63 downstream side pressing member; 66 pressure regulating chamber; 67 expansion and contraction portion; 68 extrusion member; 69 pressure regulating portion; 70 insertion hole; 71 opening portion; 72 air chamber; 74 pressure pump; 75 connection path; 76 pressure detection portion; 77 fluid pressure regulating portion; 84 filter; 85 common liquid chamber as a common flow path; 85a supply port; 86 independent liquid chamber; 87 vibration plate; 88 supply side communication path; 89 ejection element; 90 storage chamber; 91 first discharge flow path; 92 second discharge flow path; 93 discharge liquid chamber; 94 discharge side communication path; 96a first discharge port as a discharge port; 96b second discharge port as a discharge port; 97a return valve a first return valve as a return valve; 97b a second return valve as a return valve; 98a a first damper; 98b a second damper; 111 a control unit; 112 a detector group; 113 an ejection state detection unit; 115 an interface unit; 116 a CPU; 117 a memory; 118 a control circuit; 119 a drive circuit; 120 a computer; 130 a maintenance unit; 131 a liquid receiving unit; 133 a wiping mechanism; 134 a suction mechanism; 136 a capping mechanism; 138 a waste liquid tray; 139 a waste liquid storage unit; 141 a belt-shaped member; 142 a holding unit; 143 a base unit; 144 a guide rail; 145 a wiping motor; 146 a winding motor; 147 a power transmission mechanism; 148 an opening; 151 a unwinding shaft; 152 an unwinding unit; 153 a winding shaft;154 winding portion; 155 upstream roller; 156 tension roller; 157 pushing portion; 158 limiting roller; 159 first horizontal roller; 160 second horizontal roller; 161 wiping portion; 162 pulling portion; 164 suction cover; 165 suction holder; 166 suction motor; 167 decompression mechanism; 169 standby cover; 170 standby holder; 171 standby motor; 599 pressure sensor; 700 pressure regulating mechanism; 701 liquid storage chamber; 702 air chamber; 703 partition wall; 704 air flow path; 705 air pump; 706 pressure detector; 707 pressure regulator; A supply direction; B return direction; CP discharge position; HP starting position; W1 first wiping direction; W2 second wiping direction; WA wiping area; Xs scanning direction; Yf conveying direction; Z vertical direction; DETAILED DESCRIPTION

[0028] 1. Implementation Method 1

[0029] Hereinafter, a first embodiment of a liquid ejection device and a maintenance method of the liquid ejection device will be described with reference to the accompanying drawings. The liquid ejection device is, for example, an inkjet printer that ejects ink, which is an example of a liquid, onto a medium such as paper to perform printing. In the following description, liquid refers to ink used for printing, a treatment liquid acting on the ink, and the like.

[0030] In the drawings, it is assumed that the liquid ejection device 11 is placed on a horizontal plane, the Z axis represents the direction of gravity, and the X axis and the Y axis represent the direction along the horizontal plane. The X axis, the Y axis, and the Z axis are orthogonal to each other. In the following description, the direction parallel to the Z axis is also referred to as the vertical direction Z. Fig.10 , Fig.11A , Fig. 11B , Fig.12 , Fig.13 , Fig.15 , Fig.16 , Fig.17 as well as Fig.18 The liquid ejection portion 15 is along Figure 5 The cross section taken along line 5-5 is shown.

[0031] like Figure 1 As shown, the liquid ejecting device 11 includes a support table 13 supporting a medium 12 and a conveying unit 14 conveying the medium 12. The liquid ejecting device 11 includes a liquid ejecting unit 15 ejecting liquid toward the medium 12 supported by the support table 13 and a moving mechanism 16 capable of moving the liquid ejecting unit 15 in a scanning direction Xs.

[0032] like Figure 1 , Figure 2As shown, the support table 13 extends in the scanning direction Xs which is also the width direction of the medium 12 in the liquid ejecting device 11. The scanning direction Xs in this embodiment is a direction parallel to the X axis. The support table 13 supports the medium 12 at the printing position.

[0033] The conveying unit 14 includes a conveying roller pair 21 for conveying the medium 12, a conveying motor 22 for rotating the conveying roller pair 21, and a guide plate 23 for guiding the medium 12. A plurality of conveying roller pairs 21 may be provided along the conveying path of the medium 12. By driving the conveying motor 22, the conveying unit 14 conveys the medium 12 along the surface of the support table 13. The conveying direction Yf in which the conveying unit 14 conveys the medium 12 is a direction along the conveying path of the medium 12, and is a direction along the surface of the support table 13 with which the medium 12 contacts. The conveying direction Yf in this embodiment is parallel to the Y axis at the printing position.

[0034] The moving mechanism 16 includes: a guide shaft 26 provided to extend in the scanning direction Xs; a carriage 27 for holding the liquid ejecting unit 15 in such a manner that the liquid ejecting unit 15 can be replaced; and a carriage motor 28 for moving the carriage 27 along the guide shaft 26. The carriage 27 holds the liquid ejecting unit 15 in a posture in which the nozzle surface 25 is opposite to the support table 13 in the vertical direction Z. The liquid ejecting unit 15 ejects, for example, a plurality of color inks as liquid and a processing liquid as a liquid for promoting the fixing of the ink. The first cover 20a may also be provided to cover a part of the moving path of the liquid ejecting unit 15. When the liquid ejecting device 11 is provided so that the liquid ejecting unit 15 is exposed to the outside from the opened first cover 20a, the liquid ejecting unit 15 can be easily replaced.

[0035] The moving mechanism 16 reciprocates the carriage 27 and the liquid ejector 15 in the scanning direction Xs and the opposite direction of the scanning direction Xs along the guide shaft 26. That is, the liquid ejector 11 of this embodiment is configured as a serial type device in which the liquid ejector 15 reciprocates along the X axis.

[0036] like Figure 1As shown, the liquid ejection device 11 of this embodiment includes a liquid ejection unit 15. The liquid ejection unit 15 includes a supply port 85a that allows liquid to flow into the liquid ejection unit 15, a second discharge port 96b that serves as a discharge port that allows liquid to flow out of the liquid ejection unit 15, a common flow path communicating with the supply port 85a and the second discharge port 96b, a plurality of nozzles 24 communicating with the common flow path, a nozzle surface 25 opened by the plurality of nozzles 24, and an ejection element. The liquid ejection unit 15 of this embodiment ejects liquid toward the medium 12 at the printing position in the vertical direction Z by driving the ejection element, and can print on the medium 12. It should be noted that the number of liquid ejection units 15 may be more than two. In this case, the plurality of liquid ejection units 15 may also be configured to be separated by a specified distance in the scanning direction Xs and staggered by a specified distance in the conveying direction Yf.

[0037] like Figure 2 As shown, on the nozzle surface 25, a plurality of nozzle rows L formed by a plurality of nozzles 24 arranged in the row direction Yr may be arranged at regular intervals in the scanning direction Xs different from the row direction Yr. The row direction Yr in this embodiment is a direction along the nozzle surface 25 parallel to the Y axis, and coincides with the conveying direction Yf at the printing position.

[0038] The liquid ejecting unit 15 of the present embodiment has four nozzle rows L. The plurality of nozzles 24 constituting one nozzle row L eject the same type of liquid. Among the plurality of nozzles 24 constituting one nozzle row L, the nozzles 24 located upstream in the conveying direction Yf and the nozzles 24 located downstream in the conveying direction Yf are formed to be shifted in position in the scanning direction Xs.

[0039] like Figure 1 As shown, the liquid ejecting device 11 includes a mounting portion 18 to which a liquid supply source 17 containing liquid is detachably mounted, and a liquid supply portion 19 capable of supplying liquid to the liquid ejecting portion 15. The liquid ejecting device 11 includes a main body 20 composed of a housing, a frame, etc., and a first cover 20a and a second cover 20b mounted on the main body 20 in an openable and closable manner.

[0040] The liquid supply source 17 is, for example, a container for containing liquid. The liquid supply source 17 may be a replaceable cartridge or a tank for replenishing liquid. The liquid ejecting device 11 may also include a plurality of liquid supply units 19 in a manner corresponding to the type of liquid ejected from the liquid ejecting unit 15. The liquid ejecting device 11 of this embodiment includes four liquid supply units 19.

[0041] The liquid supply unit 19 includes a liquid supply passage 30 connected to the supply port 85a so as to supply liquid to the liquid injection unit 15. The liquid supply unit 19 includes a liquid return passage 31 connected to the second discharge port 96b so as to return the liquid supplied to the liquid injection unit 15 to the liquid supply passage 30, and a liquid storage unit 32 for storing liquid. The liquid return passage 31 can form a circulation passage 33 together with the liquid supply passage 30. The liquid storage unit 32 is connected to the liquid supply passage 30 and the liquid return passage 31 to form a circulation passage 33. Figure 1 As shown, the liquid storage section 32 may be an open tank that opens the space in the liquid storage section 32 to the atmosphere, or may be a flexible sealed bag. In addition, the liquid ejecting device 11 includes the liquid storage section 32 in such a manner that the position of the liquid in the liquid storage section 32 is lower than the nozzle surface 25 of the liquid ejecting section 15. Thus, the pressure higher than the atmospheric pressure in the liquid storage section 32 can be reduced to act on the liquid ejecting section 15 through the liquid return flow path 31.

[0042] The liquid supply unit 19 includes a delivery pump 34 that delivers the liquid from the liquid supply source 17 .

[0043] The liquid supply unit 19 is provided with a filter unit 38 for capturing bubbles and foreign matter in the liquid. The filter unit 38 captures bubbles and foreign matter in the liquid. The filter unit 38 is detachably mounted on the liquid supply flow path 30. When the liquid ejecting device 11 is configured such that the filter unit 38 is exposed to the outside from the opened second cover 20b, the filter unit 38 can be easily replaced.

[0044] The liquid supply unit 19 includes an on-off valve 45. The on-off valve 45 is provided between the delivery pump 34 and the liquid storage unit 32 in the liquid supply flow path 30. When the liquid delivered by the delivery pump 34 is supplied to the liquid ejecting unit 15, the on-off valve 45 is opened.

[0045] The liquid supply unit 19 includes a flow mechanism 39 capable of flowing the liquid in the circulation path 33 and a pressure regulating device 40 for regulating the pressure of the liquid supplied to the liquid ejecting unit 15. The flow mechanism 39 includes a supply pump 39A as a supply-side flow mechanism provided in the liquid supply flow path 30 and a return pump 39B as a return-side flow mechanism provided in the liquid return flow path 31. The supply pump 39A causes the liquid to flow in the liquid supply flow path 30 along the supply direction A from the liquid storage unit 32 toward the liquid ejecting unit 15. The supply pump 39A causes the liquid to flow in the supply direction A in the liquid supply flow path 30, thereby pressurizing the fluid in the space in the liquid ejecting unit 15 that communicates with the liquid supply flow path 30. Therefore, the supply pump 39A can be used as a pressurizing mechanism that can pressurize the liquid in the liquid ejecting unit 15 including the common flow path. The return pump 39B causes the liquid to flow in the liquid return flow path 31 along the return direction B from the liquid ejecting unit 15 toward the liquid storage unit 32.

[0046] The supply pump 39A may be any pump capable of causing the liquid to flow in the supply direction A in the liquid supply flow path 30, and for example, if it is a reciprocating pump, it may be a plunger pump or a diaphragm pump, and if it is a rotary pump, it may be a gear pump or a tube pump. The return pump 39B may be any pump capable of causing the liquid to flow in the return direction B in the liquid return flow path 31, and for example, if it is a reciprocating pump, it may be a plunger pump or a diaphragm pump, and if it is a rotary pump, it may be a gear pump or a tube pump.

[0047] The liquid supply unit 19 includes a second return valve 97b as a return valve on the liquid return flow path 31. The return valve is provided at a position closer to the second discharge port 96b of the liquid ejection unit 15 than the return pump 39B in the liquid return flow path 31. The return valve can be in a closed state to prevent the flow of liquid in the liquid return flow path 31 and an open state to allow the flow.

[0048] like Figure 2 As shown, the liquid ejecting device 11 includes a maintenance unit 130 for performing maintenance on the liquid ejecting unit 15. The maintenance unit 130 is provided in a non-printing area, which is an area where the liquid ejecting unit 15 is not opposed to the medium 12 being transported in the scanning direction Xs. The maintenance unit 130 includes a liquid receiving unit 131 for receiving liquid discharged from the nozzle 24, a wiping mechanism 133, a suction mechanism 134, and a capping mechanism 136. The maintenance unit 130 includes a waste liquid tray 138 provided vertically below the moving area where the liquid ejecting unit 15 moves, and a waste liquid storage unit 139 for storing waste liquid discharged from the liquid ejecting unit 15.

[0049] The position above the capping mechanism 136 is the home position HP of the liquid ejecting unit 15. The home position HP is the starting point of the movement of the liquid ejecting unit 15. The area above the wiping mechanism 133 is the wiping area WA.

[0050] In this embodiment, the position above the liquid receiving portion 131 is the discharge position CP of the liquid ejecting portion 15. When the liquid ejecting portion 15 is at the discharge position CP, the nozzle surface 25 faces the liquid receiving portion 131. The liquid receiving portion 131 is larger than the nozzle surface 25 in the scanning direction Xs and the conveying direction Yf.

[0051] The liquid ejecting device 11 performs a pressurized discharge operation in which the liquid ejecting unit 15 is located at the discharge position CP and the pressurizing mechanism is driven to pressurize the liquid in the common flow path of the liquid ejecting unit 15 and discharge the liquid from the nozzle 24. That is, the liquid receiving unit 131 receives the liquid discharged by the pressurized discharge operation.

[0052] The liquid receiving portion 131 receives the liquid ejected from the nozzle 24 of the liquid ejecting portion 15 by flushing. Flushing refers to the action of forcibly discharging the liquid from the nozzle 24 regardless of printing by driving the ejection element 89 of the liquid ejecting portion 15 for the purpose of preventing or eliminating clogging of the nozzle 24.

[0053] The wiping mechanism 133 includes a belt-shaped member 141 capable of absorbing liquid. The wiping mechanism 133 includes: a holding portion 142 that holds the belt-shaped member 141; a base portion 143 that holds the holding portion 142 in a manner that allows the holding portion 142 to move in a first wiping direction W1 and a second wiping direction W2 opposite to the first wiping direction W1; and a pair of guide rails 144 extending along the Y axis. The wiping mechanism 133 may also include a wiping motor 145, a winding motor 146, and a power transmission mechanism 147 that transmits power from the winding motor 146. The holding portion 142 has an opening 148 that exposes the belt-shaped member 141. When the belt-shaped member 141 has a width greater than the nozzle surface 25 in the scanning direction Xs, the liquid ejecting portion 15 can be efficiently maintained.

[0054] The holding part 142 is reciprocated along the Y axis on the guide rail 144 by the power of the wiping motor 145. Figure 2 The standby position indicated by the double-dashed line is Figure 2When the wiping motor 145 is driven forward, the holding portion 142 moves in a first wiping direction W1 parallel to the Y axis from the standby position toward the accommodating position. When the wiping motor 145 is driven reversely, the holding portion 142 moves in a second wiping direction W2 opposite to the first wiping direction W1 from the accommodating position toward the standby position. The first wiping direction W1 in this embodiment is consistent with the conveying direction Yf at the printing position.

[0055] The wiping mechanism 133 can wipe the nozzle surface 25 of the liquid ejecting unit 15 located in the wiping area WA during at least one of the process in which the holding unit 142 moves in the first wiping direction W1 and the process in which the holding unit 142 moves in the second wiping direction W2. The wiping operation refers to maintenance in which the nozzle surface 25 is wiped by the belt-shaped member 141.

[0056] like Figure 2 , Figure 3 As shown, the wiping mechanism 133 includes: an unwinding section 152 having an unwinding shaft 151 and a winding section 154 having a winding shaft 153. The unwinding section 152 holds the belt-like member 141 in a rolled state. The belt-like member 141 unwound from the unwinding section 152 is conveyed to the winding section 154 along the conveying path. The wiping mechanism 133 includes an upstream roller 155, a tension roller 156, a pressing section 157, a limiting roller 158, a first horizontal roller 159, and a second horizontal roller 160, which are arranged in order from upstream along the conveying path of the belt-like member 141. The holding section 142 supports the unwinding shaft 151, the upstream roller 155, the tension roller 156, the pressing section 157, the limiting roller 158, the first horizontal roller 159, the second horizontal roller 160, and the winding shaft 153 so as to be rotatable with the X axis as the axial direction.

[0057] The winding shaft 153 is rotated by the driving of the winding motor 146. The winding unit 154 winds the belt-shaped member 141 around the winding shaft 153 in a roll shape.

[0058] The pressing portion 157 of this embodiment is a roller around which the belt-shaped member 141 is wound. The pressing portion 157 pushes the belt-shaped member 141 unwound from the unwinding portion 152 from the bottom to the top, so that the belt-shaped member 141 protrudes from the opening 148. The portion of the belt-shaped member 141 pressed by the pressing portion 157 becomes the wiping portion 161 that can wipe the nozzle surface 25. When the holding portion 142 moves in the first wiping direction W1 or the second wiping direction W2, the pressing portion 157 brings the belt-shaped member 141 into contact with the nozzle surface 25 so that the nozzle surface 25 can be wiped. When the holding portion 142 moves in the second wiping direction W2, the wiping mechanism 133 of this embodiment wipes the nozzle surface 25.

[0059] The wiping mechanism 133 includes a pull-out portion 162 formed by pulling out the belt-shaped member 141 so as to face the nozzle surface 25 without contact. The pull-out portion 162 of this embodiment is a portion between the first horizontal roller 159 and the second horizontal roller 160. The pull-out portion 162 is larger than the nozzle surface 25 in the scanning direction Xs and the conveying direction Yf. Figure 2 The storage position of the holding part 142 shown by the solid line is the position where the liquid receiving part 131 and the pull-out part 162 are arranged in the scanning direction Xs. When the holding part 142 is in the storage position, the liquid ejecting device 11 makes the liquid ejecting part 15 face the pull-out part 162, and can perform pressurized discharge operation or flushing.

[0060] like Figure 2 As shown, the suction mechanism 134 includes a suction cover 164, a suction holder 165, a suction motor 166 for reciprocating the suction holder 165 along the Z axis, and a decompression mechanism 167 for reducing the pressure in the suction cover 164. The suction motor 166 moves the suction cover 164 between a contact position and a retracted position. The contact position is a position where the suction cover 164 contacts the liquid ejecting unit 15 and surrounds the nozzle 24. The retracted position is a position where the suction cover 164 is separated from the liquid ejecting unit 15. The suction cover 164 may be a structure that completely surrounds all the nozzles 24, or a structure that surrounds a part of the nozzles 24.

[0061] The liquid ejecting device 11 may also perform suction cleaning as follows: the liquid ejecting portion 15 is positioned above the suction mechanism 134, the suction cover 164 is positioned at a contact position and surrounds one nozzle row L, and the pressure in the suction cover 164 is reduced, thereby discharging the liquid from the nozzle 24. That is, the suction mechanism 134 may also contain the liquid discharged by the suction cleaning.

[0062] The capping mechanism 136 includes a standby cover 169, a standby holder 170, and a standby motor 171 that reciprocates the standby holder 170 along the Z axis. The standby holder 170 and the standby cover 169 move upward or downward by the drive of the standby motor 171. The standby cover 169 moves from the separation position, which is the lower position, to the capping position, which is the upper position, and contacts the liquid ejecting portion 15 that stops at the home position HP.

[0063] The standby cap 169 located at the capping position surrounds the opening of the nozzle 24. In this way, the maintenance of the standby cap 169 surrounding the opening of the nozzle 24 is called standby capping. Standby capping is a type of capping. By standby capping, the drying of the nozzle 24 is suppressed. The standby cap 169 may be a structure that completely surrounds all the nozzles 24, or a structure that surrounds a part of the nozzles 24.

[0064] Next, the liquid supply unit 19 will be described in detail.

[0065] like Figure 4 As shown, the outlet pump 34 includes a suction valve 35, a displacement pump 36, and a discharge valve 37. The suction valve 35 is located in the liquid supply flow path 30 at a position more upstream than the displacement pump 36 in the supply direction A. The discharge valve 37 is located in the liquid supply flow path 30 at a position more downstream than the displacement pump 36 in the supply direction A. The suction valve 35 and the discharge valve 37 are configured to allow the flow of liquid from the upstream to the downstream in the liquid supply flow path 30, and to prevent the flow of liquid from the downstream to the upstream. The displacement pump 36 included in the outlet pump 34 includes a pump chamber 36b and a negative pressure chamber 36c divided by a flexible member 36a. The displacement pump 36 includes a decompression portion 36d for decompressing the negative pressure chamber 36c and a pressing member 36e provided in the negative pressure chamber 36c and pressing the flexible member 36a toward the pump chamber 36b side.

[0066] The delivery pump 34 draws liquid from the liquid supply source 17 through the suction valve 35 as the volume of the pump chamber 36b increases. The delivery pump 34 presses the liquid in the pump chamber 36b via the flexible member 36a by the pressing member 36e, thereby pressurizing the liquid. The delivery pump 34 ejects the liquid to the liquid ejecting portion 15 via the ejection valve 37 as the volume of the pump chamber 36b decreases. The pressure with which the delivery pump 34 pressurizes the liquid is set to a positive pressure higher than the atmospheric pressure, for example, +50 kPa in gauge pressure, according to the pressing force of the pressing member 36e.

[0067] The liquid supply unit 19 includes a storage opening valve 41 that opens the space in the liquid storage unit 32 to the atmosphere, a storage amount detection unit 42 that detects the amount of liquid stored in the liquid storage unit 32, and a stirring mechanism 43 that can stir the liquid in the liquid storage unit 32. The stirring mechanism 43 includes a stirring rod 43a provided in the liquid storage unit 32 and a rotating unit 43b that rotates the stirring rod 43a.

[0068] The liquid supply section 19 includes an air introduction section 44 for introducing air into the liquid supply flow path 30. The air introduction section 44 includes a switching valve 44a provided on the liquid supply flow path 30, an air inflow channel 44b connected to the switching valve 44a, and a one-way valve 44c provided on the air inflow channel 44b. The switching valve 44a serves as a three-way valve to switch the connection and non-connection between the liquid supply flow path 30 and the air inflow channel 44b. The one-way valve 44c allows the flow of air toward the liquid supply flow path 30, while preventing the flow of fluid from the liquid supply flow path 30 toward the outside. If the liquid supply flow path 30 is connected to the air inflow channel 44b, air can be introduced into the liquid supply flow path 30 through the air inflow channel 44b.

[0069] The liquid supply unit 19 includes a choke valve 46. When choke suction is performed to depressurize the closed space including the liquid ejecting unit 15 and accumulate negative pressure during suction cleaning by the suction mechanism 134, the choke valve 46 is closed.

[0070] Next, the pressure regulating device 40 will be described in detail.

[0071] like Figure 4 As shown, the pressure regulating device 40 includes a pressure regulating mechanism 48 constituting a part of the liquid supply flow path 30 and a pressing mechanism 49 for changing the pressure regulating state of the pressure regulating mechanism 48. The pressure regulating mechanism 48 includes a main body 52 formed with a liquid inflow portion 50 into which the liquid supplied from the liquid supply source 17 via the liquid supply flow path 30 flows, and a liquid outflow portion 51 capable of accommodating the liquid inside.

[0072] The liquid supply flow path 30 and the liquid inlet 50 are separated by a wall 53 provided in the main body 52, and communicate with each other through a through hole 54 formed in the wall 53. The through hole 54 is covered by a filter member 55. Therefore, the liquid in the liquid supply flow path 30 is filtered by the filter member 55 and flows into the liquid inlet 50.

[0073] In the liquid outflow portion 51, at least a part of the wall surface thereof is constituted by a diaphragm 56. The diaphragm 56 bears the pressure of the liquid in the liquid outflow portion 51 with a first surface 56a as the inner surface of the liquid outflow portion 51. The diaphragm 56 bears the atmospheric pressure with a second surface 56b as the outer surface of the liquid outflow portion 51. Therefore, the diaphragm 56 is displaced in accordance with the pressure in the liquid outflow portion 51. The volume of the liquid outflow portion 51 changes due to the displacement of the diaphragm 56. The liquid inflow portion 50 and the liquid outflow portion 51 are communicated with each other through a communication path 57.

[0074] The pressure regulating mechanism 48 includes a supply valve 59, which can be in a closed state in which the liquid inflow portion 50 and the liquid outflow portion 51 are disconnected in the communication path 57, and in an open state in which the liquid inflow portion 50 and the liquid outflow portion 51 are communicated. In the closed state, the flow of the liquid in the liquid supply flow path 30 is blocked, and in the open state, the flow of the liquid in the liquid supply flow path 30 is allowed. When the pressure in the liquid ejecting portion 15, for example, the pressure in the common flow path becomes equal to or lower than the prescribed pressure, the supply valve 59 is opened. The supply valve 59 is provided between the liquid storage portion 32 and the liquid ejecting portion 15 in the liquid supply flow path 30. Figure 4The supply valve 59 is shown in a closed state. The supply valve 59 includes a valve portion 60 capable of shutting off the communication path 57 and a pressure receiving portion 61 that receives pressure from the diaphragm 56. The supply valve 59 is moved by being pushed by the diaphragm 56 through the pressure receiving portion 61. The pressure receiving portion 61 may be fixed to the diaphragm 56 separately from the supply valve 59 so as to contact the supply valve 59.

[0075] The upstream pressing member 62 is provided in the liquid inflow portion 50. The downstream pressing member 63 is provided in the liquid outflow portion 51. Both the upstream pressing member 62 and the downstream pressing member 63 press in the direction of closing the supply valve 59. The supply valve 59 changes from a closed valve state to an open valve state when the pressure applied to the first surface 56a is lower than the pressure applied to the second surface 56b and the difference between the pressure applied to the first surface 56a and the pressure applied to the second surface 56b becomes the same as or greater than a set value. The set value is set, for example, in the range of 1 kPa to 2 kPa.

[0076] The pressing force of the upstream pressing member 62 and the downstream pressing member 63 is set so that the pressure in the liquid outflow portion 51 becomes a negative pressure state within a range that can form a concave meniscus as a gas-liquid interface in the nozzle 24. For example, considering that the pressure applied to the second surface 56b is atmospheric pressure, and the height difference between the common flow path and the liquid outflow portion 51 is 50 mm, the pressing force of the upstream pressing member 62 and the downstream pressing member 63 is set so that the pressure in the liquid outflow portion 51 is in the range of -1kPa to -2kPa in gauge pressure. In this case, the gas-liquid interface is the boundary where the liquid meets the gas, and the meniscus is the curved liquid surface formed by the liquid meeting the nozzle 24. It is preferable to form a concave meniscus suitable for the injection of the liquid in the nozzle 24.

[0077] In this embodiment, when the supply valve 59 in the pressure regulating mechanism 48 is in the closed state, the pressure of the liquid in the liquid inlet 50 and the liquid upstream of the liquid inlet 50 is usually set by the supply pump 39A to a positive pressure higher than the atmospheric pressure, for example, +50 kPa in gauge pressure.

[0078] In the present embodiment, when the supply valve 59 in the pressure regulating mechanism 48 is in the closed valve state, the pressure of the liquid in the liquid outflow portion 51 and the liquid downstream of the liquid outflow portion 51 is usually set to a negative pressure lower than the atmospheric pressure.

[0079] When the liquid ejection unit 15 ejects liquid, the liquid contained in the liquid outflow unit 51 is supplied to the liquid ejection unit 15 via the liquid supply flow path 30. As a result, the pressure in the liquid outflow unit 51 decreases. Thus, if the difference between the pressure applied to the first surface 56a of the diaphragm 56 and the pressure applied to the second surface 56b becomes equal to or greater than the set value, the diaphragm 56 is flexed and deformed in a direction that reduces the volume of the liquid outflow unit 51. When the pressure receiving unit 61 is pushed and moved along with the deformation of the diaphragm 56, the supply valve 59 is in an open valve state that allows the flow of liquid flowing from the liquid inflow unit 50 toward the liquid outflow unit 51.

[0080] When the supply valve 59 is in the open state, the liquid in the liquid inlet 50 is pressurized by the supply pump 39A, so that the liquid is supplied from the liquid inlet 50 to the liquid outflow portion 51. As a result, the diaphragm 56 is deformed so as to increase the volume of the liquid outflow portion 51. When the difference between the pressure applied to the first surface 56a of the diaphragm 56 and the pressure applied to the second surface 56b becomes smaller than the set value, the supply valve 59 changes from the open state to the closed state. As a result, the supply valve 59 blocks the flow of the liquid flowing from the liquid inlet 50 to the liquid outflow portion 51.

[0081] As described above, the pressure adjustment mechanism 48 adjusts the pressure of the liquid supplied to the liquid ejecting portion 15 by the displacement of the diaphragm 56 , thereby adjusting the pressure in the common flow path in the liquid ejecting portion 15 .

[0082] The pressing mechanism 49 includes an expansion and contraction portion 67 that forms a pressure regulating chamber 66 on the second surface 56b side of the diaphragm 56, a pressing member 68 that pushes the expansion and contraction portion 67, and a pressure regulating portion 69 that can adjust the pressure in the pressure regulating chamber 66. The expansion and contraction portion 67 is formed in a balloon shape, for example, by rubber, resin, etc. The expansion and contraction portion 67 expands and contracts as the pressure regulating portion 69 adjusts the pressure in the pressure regulating chamber 66. The pressing member 68 is formed in a bottomed cylindrical shape, for example. A portion of the expansion and contraction portion 67 is inserted into an insertion hole 70 formed at the bottom of the pressing member 68.

[0083] The pressing member 68 is attached to the pressure regulating mechanism 48 in such a manner that the opening 71 is blocked by the pressure regulating mechanism 48. Thus, the pressing member 68 forms an air chamber 72 covering the second surface 56b of the diaphragm 56. The air chamber 72 communicates with the external space via the gap between the insertion hole 70 and the expansion / contraction portion 67. Therefore, the atmospheric pressure acts on the second surface 56b of the diaphragm 56.

[0084] The pressure regulating portion 69 expands the expansion and contraction portion 67 by regulating the pressure in the pressure regulating chamber 66 to a pressure higher than the pressure of the air chamber 72, that is, the atmospheric pressure. The expansion and contraction portion 67 is expanded by the pressure regulating portion 69, so that the pressing mechanism 49 presses the diaphragm 56 in a direction that reduces the volume of the liquid outflow portion 51. At this time, the expansion and contraction portion 67 of the pressing mechanism 49 pushes the portion of the diaphragm 56 that contacts the pressure receiving portion 61, so that the supply valve 59 of the pressure regulating mechanism 48 is forced to be in an open valve state. That is, the pressing mechanism 49 can be applied as a valve opening mechanism that can open the supply valve 59. The area of ​​the portion of the diaphragm 56 that contacts the pressure receiving portion 61 is larger than the cross-sectional area of ​​the communication path 57.

[0085] like Figure 4 As shown, the pressure regulating unit 69 has a pressure pump 74 for pressurizing a fluid such as air or water, and a connection path 75 connecting the pressure pump 74 and the expansion / contraction unit 67. The pressure regulating unit 69 has a pressure detecting unit 76 for detecting the pressure of the fluid in the connection path 75, and a fluid pressure regulating unit 77 for regulating the pressure of the fluid in the connection path 75.

[0086] The connection path 75 is branched into a plurality of paths, each of which is connected to the expansion and contraction parts 67 of the plurality of pressure regulating devices 40. The connection path 75 of this embodiment is branched into four paths, each of which is connected to the expansion and contraction parts 67 of the four pressure regulating devices 40. The fluid pressurized by the pressure pump 74 is supplied to each expansion and contraction part 67 via the connection path 75.

[0087] The fluid pressure regulating part 77 may be a control valve that is controlled to open and close based on the pressure detected by the pressure detecting part 76, or may be a pressure relief valve that is configured to automatically open when the pressure of the fluid in the connection path 75 becomes higher than a predetermined pressure. When the fluid pressure regulating part 77 opens, the fluid in the connection path 75 is released to the outside. In this way, the fluid pressure regulating part 77 reduces the pressure of the fluid in the connection path 75.

[0088] Next, the liquid ejecting section 15 and the liquid return flow path 31 connected to the liquid ejecting section 15 in the present embodiment will be described in detail.

[0089] like Figure 4As shown, the liquid ejection portion 15 has a supply port 85a that enables liquid to flow into the liquid ejection portion 15. The supply port 85a is connected to the liquid supply flow path 30 in a manner that enables liquid to be supplied to the liquid ejection portion 15. The liquid ejection portion 15 has a common liquid chamber 85 as a common flow path that communicates with the supply port 85a. The height difference between the common liquid chamber 85 and the nozzle surface 25 is a level that can be ignored when converting pressure. The liquid ejection portion 15 has a filter 84 that filters the supplied liquid, and the liquid filtered by the filter 84 is ejected from the nozzle 24. The filter 84 captures bubbles, foreign matter, etc. in the supplied liquid. The filter 84 is arranged in the common liquid chamber 85 that communicates with the liquid supply flow path 30.

[0090] The liquid ejection unit 15 includes a plurality of independent liquid chambers 86 communicating with the common liquid chamber 85. One nozzle 24 is provided corresponding to one independent liquid chamber 86. A portion of the wall surface of the independent liquid chamber 86 is formed by a vibration plate 87. The common liquid chamber 85 and the plurality of independent liquid chambers 86 communicate with each other via a supply-side communication path 88. The plurality of nozzles 24 communicate with the common liquid chamber 85 via the corresponding independent liquid chambers 86 and open at the nozzle surface 25. Therefore, the pressure in the common liquid chamber 85 is also referred to as the back pressure of the nozzle 24.

[0091] The liquid ejection unit 15 includes a plurality of ejection elements 89 and a plurality of storage chambers 90 for storing the ejection elements 89. The storage chambers 90 are arranged at positions different from the common liquid chamber 85. One storage chamber 90 stores one ejection element 89. The ejection element 89 is provided on the surface of the vibration plate 87 opposite to the portion facing the independent liquid chamber 86. The liquid ejection unit 15 is provided in the liquid ejection device 11 in such a manner that the liquid in the independent liquid chamber 86 can be ejected as droplets from the plurality of nozzles 24 by driving the ejection element 89.

[0092] The ejection element 89 of this embodiment is composed of a piezoelectric element that contracts when a driving voltage is applied. If the application of the driving voltage to the ejection element 89 is terminated after the vibration plate 87 is deformed due to the contraction of the ejection element caused by the application of the driving voltage, the liquid in the independent liquid chamber 86 whose volume has changed is ejected from the nozzle 24 as droplets.

[0093] like Figure 4 , Figure 5As shown, the liquid ejection unit 15 has a first discharge port 96a and a second discharge port 96b as discharge ports that enable the supplied liquid to be discharged to the outside without passing through the nozzle 24. The liquid ejection unit 15 may also have a first discharge flow path 91 communicating with the first discharge port 96a, a second discharge flow path 92 communicating with the second discharge port 96b, and a discharge liquid chamber 93 connecting the first discharge flow path 91 and the independent liquid chamber 86. Thus, the discharge liquid chamber 93 communicates with the first discharge port 96a via the first discharge flow path 91, and communicates with the supply port 85a via the independent liquid chamber 86 and the common liquid chamber 85. In addition, the common liquid chamber 85 communicates with the first discharge port 96a via the independent liquid chamber 86, the discharge liquid chamber 93, and the first discharge flow path 91, and communicates with the second discharge port 96b via the second discharge flow path 92.

[0094] The discharge liquid chamber 93 communicates with the plurality of independent liquid chambers 86 via the discharge side communication path 94 provided for each independent liquid chamber 86. It is sufficient to provide one first discharge flow path 91 for the plurality of independent liquid chambers 86 by providing the discharge liquid chamber 93. That is, by providing the discharge liquid chamber 93, it is not necessary to provide the first discharge flow path 91 for each independent liquid chamber 86. Thus, the structure of the liquid ejecting unit 15 can be simplified. The liquid ejecting unit 15 may also have a plurality of first discharge flow paths 91, which communicate with the plurality of independent liquid chambers 86.

[0095] like Figure 4 , Figure 5 As shown, the liquid return flow path 31 includes a first return flow path 31a connected to the first discharge port 96a and a second return flow path 31b connected to the second discharge port 96b in a manner that the liquid supplied to the liquid injection portion 15 can flow back to the liquid supply flow path 30. The liquid return flow path 31 of this embodiment is configured such that the first return flow path 31a and the second return flow path 31b merge. The liquid return flow path 31 may also be connected to the liquid storage portion 32 separately without merging the first return flow path 31a and the second return flow path 31b.

[0096] The first return flow path 31a is provided with a first return valve 97a and a first damper 98a as return valves. The second return flow path 31b is provided with a second return valve 97b and a second damper 98b as return valves. A return pump 39B may be provided on each of the first return flow path 31a and the second return flow path 31b.

[0097] In the first return flow path 31a, the first damper 98a is arranged at a position closer to the return pump 39B than the first return valve 97a. In the second return flow path 31b, the second damper 98b is arranged at a position closer to the return pump 39B than the second return valve 97b. The first damper 98a and the second damper 98b are configured to store liquid. For example, one side of the first damper 98a and the second damper 98b is formed by a flexible film, and the volume of the stored liquid is variable. By providing the first damper 98a and the second damper 98b, it is possible to suppress the pressure fluctuation generated in the liquid injection portion 15 when the liquid flows in the first return flow path 31a and the second return flow path 31b.

[0098] The liquid supply unit 19 can make the liquid flow through any of the first return flow path 31a and the second return flow path 31b as the liquid return flow path 31 by opening and closing the first return valve 97a and the second return valve 97b as the return valves. For example, by opening the first return valve 97a as the return valve and driving the return pump 39B, the liquid in the common flow path of the liquid ejecting unit 15 can be discharged from the first discharge port 96a as the discharge port to the first return flow path 31a as the liquid return flow path 31. In addition, for example, by opening the second return valve 97b as the return valve and driving the return pump 39B, the liquid in the common flow path of the liquid ejecting unit 15 can be discharged from the second discharge port 96b as the discharge port to the second return flow path 31b as the liquid return flow path 31.

[0099] When the liquid in the common liquid chamber 85 as the common flow path is discharged to the liquid return flow path 31, the pressure in the common liquid chamber 85 of the liquid ejecting portion 15 decreases, and the liquid contained in the liquid outflow portion 51 of the pressure regulating mechanism 48 is supplied to the common liquid chamber 85 of the liquid ejecting portion 15 via the liquid supply flow path 30. Thus, the pressure in the liquid outflow portion 51 decreases. Thus, when the difference between the pressure applied to the first surface 56a of the diaphragm 56 and the pressure applied to the second surface 56b becomes equal to or greater than the set value, the supply valve 59 becomes an open valve state that allows the flow of liquid from the liquid inflow portion 50 toward the liquid outflow portion 51. As a result, the liquid supplied from the liquid supply flow path 30 to the liquid ejecting portion 15 via the liquid inflow portion 50 flows back to the liquid supply flow path 30 via the liquid return flow path 31 and the liquid storage portion 32.

[0100] In addition, when choke suction is performed by the suction mechanism 134, the first return valve 97a and the second return valve 97b are closed together with the choke valve 46, so that the liquid supply path 30 from the choke valve 46 to the liquid injection part 15, the liquid return path 31 from the liquid injection part 15 to the return valve, and the liquid injection part 15 become closed spaces.

[0101] Next, the electrical structure of the liquid ejecting device 11 will be described.

[0102] like Figure 6 As shown, the liquid ejecting device 11 includes a control unit 111 that controls the components of the liquid ejecting device 11 in a unified manner and a detector group 112 controlled by the control unit 111. The detector group 112 includes an ejection state detection unit 113 that can detect the ejection state of the liquid of the liquid ejecting unit 15 by detecting the vibration waveform of the independent liquid chamber 86. The detector group 112 monitors the conditions in the liquid ejecting device 11. The detector group 112 outputs the detection result to the control unit 111.

[0103] The control unit 111 includes an interface unit 115, a CPU 116, a memory 117, a control circuit 118, and a drive circuit 119. The interface unit 115 transmits and receives data between a computer 120 as an external device and the liquid ejecting apparatus 11. The drive circuit 119 generates a drive signal for driving the ejection element 89.

[0104] The CPU 116 is a calculation processing device. The memory 117 is a storage device that ensures an area or a work area for storing the program of the CPU 116, and has a storage element such as a RAM and an EEPROM. The CPU 116 controls the conveying unit 14, the moving mechanism 16, the liquid supply unit 19, the pressure regulating unit 69, the maintenance unit 130, the liquid ejecting unit 15, etc. of the liquid ejecting device 11 via the control circuit 118 according to the program stored in the memory 117.

[0105] The detector group 112 may include, for example, a linear encoder for detecting the movement of the carriage 27 and a medium detection sensor for detecting the medium 12. The ejection state detection unit 113 may be a circuit for detecting the residual vibration of the independent liquid chamber 86. The ejection state detection unit 113 may include a piezoelectric element constituting the ejection element 89.

[0106] Next, a method of estimating the state in the independent liquid chamber 86 based on the detection result of the injection state detection unit 113 will be described.

[0107] When a voltage is applied to the ejection element 89 according to a signal from the drive circuit 119, the vibration plate 87 is flexed and deformed. As a result, a pressure change occurs in the independent liquid chamber 86. Due to this change, the vibration plate 87 vibrates for a moment. This vibration is called residual vibration. The state of the range including the independent liquid chamber 86 and the nozzle 24 communicating with the independent liquid chamber 86 can be inferred based on the state of the residual vibration.

[0108] Figure 7 1 is a diagram showing a calculation model assuming simple harmonic motion of residual vibration of vibration plate 87 .

[0109] When the drive circuit 119 applies a drive signal to the ejection element 89, the ejection element 89 expands and contracts in accordance with the voltage of the drive signal. The vibration plate 87 bends in accordance with the expansion and contraction of the ejection element 89. As a result, the volume of the independent liquid chamber 86 expands and then contracts. At this time, due to the pressure generated in the independent liquid chamber 86, a part of the liquid filling the independent liquid chamber 86 is ejected from the nozzle 24 as droplets.

[0110] During the above-mentioned series of actions of the vibration plate 87, the vibration plate 87 freely vibrates at a natural vibration frequency, and the natural vibration frequency is determined by the shape of the flow path of the liquid flow, the flow path resistance r based on the viscosity of the liquid, the inertia m based on the weight of the liquid in the flow path, and the compliance C of the vibration plate 87. The free vibration of the vibration plate 87 is a residual vibration.

[0111] Figure 7 The calculation model of the residual vibration of the vibration plate 87 shown in FIG. 8 is represented by the pressure P, the inertia m mentioned above, the compliance C and the flow path resistance r. Figure 7 The circuit gives a step response at pressure P, and the following formula is obtained.

[0112]

Mathematical formula 1

[0113]

[0114]

[0115]

[0116] Figure 8 This is a diagram for explaining the relationship between the viscosity increase of the liquid and the residual vibration waveform. Figure 8 The horizontal axis represents time t, and the vertical axis represents the magnitude of the residual vibration. Figure 8 Em is the wave height value of the first half wave in the residual vibration waveform. For example, when the liquid near the nozzle 24 has dried, the viscosity of the liquid increases, that is, the viscosity increases. If the liquid viscosity increases, the flow path resistance r increases, so the vibration period and the attenuation of the residual vibration increase.

[0117] Fig. 9 It is an explanatory diagram of the relationship between bubble mixing and the residual vibration waveform. Fig. 9 The horizontal axis represents time t, and the vertical axis represents the magnitude of the residual vibration. For example, when bubbles are mixed into the flow path of the liquid or the front end of the nozzle 24, the inertia m of the liquid weight is reduced in accordance with the mixing of bubbles compared to the normal state of the nozzle 24. According to formula (2), if m decreases, the angular velocity ω increases, and therefore the vibration period is shortened. That is, the vibration frequency increases.

[0118] Note that the case where air bubbles are mixed into the independent liquid chamber 86 includes the case where air bubbles are mixed into a region including the nozzle 24 in addition to the independent liquid chamber 86 .

[0119] Furthermore, for example, the frequency of the vibration waveform detected in a state where bubbles exist in the independent liquid chamber 86 filled with liquid and the nozzle 24 is higher than the frequency of the vibration waveform detected in a state where bubbles do not exist in the independent liquid chamber 86 filled with liquid and the nozzle 24. The frequency of the vibration waveform detected in a state where the independent liquid chamber 86 and the nozzle 24 are filled with air is higher than the frequency of the vibration waveform detected in a state where bubbles exist in the independent liquid chamber 86 filled with liquid and the nozzle 24. The larger the size of the bubbles existing in the independent liquid chamber 86 filled with liquid and the nozzle 24, the higher the frequency of the vibration waveform.

[0120] On the other hand, for example, when liquid is attached to the nozzle surface 25 and the liquid attached to the nozzle surface 25 is connected to the liquid in the nozzle 24, the liquid attached to the nozzle surface 25 is connected to the liquid filled in the independent liquid chamber 86 via the nozzle 24. Therefore, from the perspective of the vibration plate 87, the liquid attached to the nozzle surface 25 increases compared to the normal state, and the liquid weight, that is, the inertia m increases. Therefore, when the liquid attached to the nozzle surface 25 is connected to the liquid in the independent liquid chamber 86, the frequency is lowered compared to the normal frequency.

[0121] In addition, if foreign matter such as paper dust adheres to the vicinity of the opening of the nozzle 24, the amount of liquid in the independent liquid chamber 86 and the liquid seeping out increases from the vibration plate 87 compared to normal, and thus the inertia m increases. It is considered that the flow path resistance r increases due to the fibers of the paper dust attached to the vicinity of the outlet of the nozzle 24. Therefore, when the paper dust adheres to the vicinity of the opening of the nozzle 24, the frequency decreases compared to normal ejection, and the frequency of the residual vibration increases compared to when the liquid is thickened.

[0122] If the liquid is thickened, bubbles are mixed in, or foreign matter is fixed, the state of the nozzle 24 and the independent liquid chamber 86 becomes abnormal, and the liquid is typically no longer ejected from the nozzle 24. As a result, a bad pixel is generated in the image recorded on the medium 12. Even if droplets are ejected from the nozzle 24, there may be a small amount of droplets, or the flight direction of the droplets may deviate and fail to land at the target position. The nozzle 24 that has such a poor ejection is called an abnormal nozzle.

[0123] As described above, the residual vibration of the independent liquid chamber 86 communicating with the abnormal nozzle is different from the residual vibration of the independent liquid chamber 86 communicating with the normal nozzle 24. Therefore, the ejection state detection unit 113 detects the vibration waveform of the independent liquid chamber 86. The control unit 111 estimates the state of the range including the independent liquid chamber 86 and the nozzle 24 communicating with the independent liquid chamber 86 based on the detection result of the ejection state detection unit 113.

[0124] The control unit 111 estimates whether the ejection state of the liquid ejection unit 15 is normal or abnormal based on the vibration waveform of the independent liquid chamber 86 as the detection result of the ejection state detection unit 113. When the state in the independent liquid chamber 86 is abnormal, it is estimated that the nozzle 24 communicating with the independent liquid chamber 86 is an abnormal nozzle. The control unit 111 estimates whether the state in the independent liquid chamber 86 is abnormal due to the presence of bubbles or the state in the independent liquid chamber 86 is abnormal due to the thickening of the liquid based on the vibration waveform of the independent liquid chamber 86. The control unit 111 estimates the total volume of bubbles existing in the independent liquid chamber 86 and the nozzle 24 communicating with the independent liquid chamber 86, and the degree of thickening of the liquid in the independent liquid chamber 86 and the nozzle 24 communicating with the independent liquid chamber 86 based on the vibration waveform of the independent liquid chamber 86. The control unit 111 estimates whether the liquid is attached to the nozzle surface 25 and the liquid attached to the nozzle surface 25 is connected to the liquid in the nozzle 24 based on the vibration waveform of the independent liquid chamber 86.

[0125] The control unit 111 may also infer whether the filter 84 is normal based on the detection result detected by the injection state detection unit 113. If the filter 84 is clogged, the flow of the liquid passing through the filter 84 is likely to stagnate. If the flow of the liquid is stagnant, air will enter from the nozzle 24, and bubbles are likely to accumulate in the independent liquid chamber 86. Therefore, the control unit 111 may also infer that the filter 84 is abnormal based on the abnormality caused by the bubbles in the independent liquid chamber 86 detected.

[0126] Specifically, for example, the control unit 111 infers that the filter 84 has an abnormality when an abnormality caused by bubbles occurs in a predetermined number or more of the plurality of independent liquid chambers 86. The predetermined number is, for example, a number that cannot be handled by supplementary printing in which liquid to be ejected from the abnormal nozzle is compensated by liquid ejected from the surrounding nozzles 24.

[0127] In this embodiment, the control unit 111 performs a printing action to form characters and images on the medium 12 by alternating a conveying action and a spraying action. The conveying action is an action of driving the conveying unit 14 to convey the medium 12 by a unit conveying amount, and the spraying action is an action of spraying liquid from the liquid spraying unit 15 to the medium 12 while moving the slide 27 in the scanning direction Xs.

[0128] In addition, the control unit 111 drives the pressure pump 74 in the pressing mechanism 49 to supply pressurized fluid to the expansion and contraction portion 67. As a result of the expansion of the expansion and contraction portion 67, the diaphragm 56 is displaced in a direction that reduces the volume of the liquid outflow portion 51, and the supply valve 59 is in an open state. In this way, the control unit 111 performs opening and closing control of the supply valve 59 based on the driving of the pressing mechanism 49.

[0129] In the liquid injection device 11, when the flow of the liquid stagnates, the liquid becomes easy to increase in viscosity or accumulate bubbles. In this case, it becomes easy to produce abnormal nozzles. That is, the state of the independent liquid chamber 86 and the nozzle 24 becomes easy to become abnormal. Therefore, in order to suppress the increase in viscosity of the liquid or discharge bubbles, the control unit 111 is configured to perform a maintenance operation for maintaining the liquid injection unit 15. The control unit 111 of this embodiment is configured to perform a first discharge operation, a second discharge operation, a third discharge operation, a fourth discharge operation, a fifth discharge operation, a pressurized discharge operation, and a suction cleaning as maintenance operations of the liquid injection unit 15.

[0130] When liquid is not ejected from the nozzle 24 during the printing operation, the control unit 111 performs a first discharge operation to discharge the liquid in the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 communicating with the independent liquid chamber 86 as a maintenance operation of the liquid ejecting unit 15. The first discharge operation is an operation to discharge the liquid in the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 and the first discharge port 96a.

[0131] The time when the liquid is not ejected from the nozzle 24 during the printing operation refers to, for example, the time when the carriage 27 returns or between pages of the medium 12. The time when the carriage 27 returns refers to the time when the carriage 27 moves to return to the home position HP. Between pages of the medium 12 refers to the time from when an image is printed on the medium 12 until the next medium 12 reaches a position opposite to the liquid ejecting unit 15. The control unit 111 executes the first ejection operation at such a time.

[0132] In the first discharge operation, the control unit 111 sucks the liquid in the independent liquid chamber 86 from the first discharge flow path 91 side in a manner that the curved liquid surface of the gas-liquid interface in the nozzle 24 is maintained, thereby discharging the liquid toward the liquid return flow path 31. The control unit 111 of this embodiment drives the return pump 39B in a state where the first return valve 97a is opened, and performs the first discharge operation. When the first discharge operation is performed by sucking the liquid in the independent liquid chamber 86 from the first discharge flow path 91 side, the gas-liquid interface of the curved liquid surface in the nozzle 24 moves toward the independent liquid chamber 86 side. As a result, at least a portion of the liquid in the nozzle 24 flows. As a result, the viscosity increase of the liquid in the nozzle 24 can be suppressed.

[0133] The control unit 111 may also execute the first discharge operation when it is inferred based on the detection result of the ejection state detection unit 113 that the state in the independent liquid chamber 86 is abnormal because the bubbles existing in the independent liquid chamber 86 and the nozzle 24 have a volume greater than a set value. The set value is stored in the memory 117 of the control unit 111. The memory 117 stores, for example, the vibration waveform detected by the ejection state detection unit 113 when the bubbles existing in the independent liquid chamber 86 and the nozzle 24 have a volume reaching the set value.

[0134] The control unit 111 compares the vibration waveforms of the independent liquid chamber 86 detected by the ejection state detection unit 113 at intervals to estimate whether the state in the independent liquid chamber 86 has improved, and when it is estimated that the state in the independent liquid chamber 86 has not improved, the control unit 111 performs a second discharge operation to discharge the liquid in the independent liquid chamber 86 from the nozzle 24 to the outside as a maintenance operation of the liquid ejecting unit 15. The second discharge operation is the above-mentioned flushing.

[0135] For example, when the state in the independent liquid chamber 86 is not improved even after the first discharge operation is performed, the control unit 111 performs a second discharge operation to discharge the liquid in the independent liquid chamber 86 to the outside from the nozzle 24. In this case, after the control unit 111 performs the first discharge operation based on the detection result of the ejection state detection unit 113, the control unit 111 again detects the state in the independent liquid chamber 86 through the ejection state detection unit 113. At this time, when it is estimated based on the vibration waveform of the independent liquid chamber 86 that the volume of the bubbles in the independent liquid chamber 86 and the nozzle 24 is increasing or the viscosity of the liquid is progressing, the control unit 111 determines that the state in the independent liquid chamber 86 is not improved, and performs the second discharge operation.

[0136] For example, the control unit 111 may not perform the first discharge action if the volume of the bubbles in the independent liquid chamber 86 and the nozzle 24 is less than a set value, and may perform the second discharge action if the state in the independent liquid chamber 86 has not improved after the time when the bubbles are expected to disappear has passed.

[0137] When the number of independent liquid chambers 86 whose states are abnormal due to bubbles in the independent liquid chambers 86 and the nozzles 24 is greater than a set number, the control unit 111 performs a third discharge operation as a maintenance operation of the liquid ejecting unit 15, in which the liquid in the common liquid chamber 85 is discharged toward the liquid return flow path 31 via the second discharge flow path 92 connected to the common liquid chamber 85 and the second discharge port 96b, based on the detection result of the ejection state detection unit 113. In the present embodiment, the third discharge operation is performed before the first discharge operation is performed. The control unit 111 drives the return pump 39B in a state where the second return valve 97b is opened to perform the third discharge operation. The set number is stored in the memory 117 of the control unit 111.

[0138] When the number of independent liquid chambers 86 in which it is presumed that the state in the independent liquid chamber 86 is abnormal due to the bubbles existing in the independent liquid chamber 86 and the nozzle 24 is greater than the set number, it is considered that there are bubbles in the common liquid chamber 85 that communicates with the plurality of independent liquid chambers 86. In this case, since there is a possibility that abnormal nozzles are continuously generated in the nozzle surface 25, it is difficult to perform supplementary printing. For this reason, when the number of independent liquid chambers 86 in which it is presumed that the state in the independent liquid chamber 86 is abnormal due to the bubbles existing in the independent liquid chamber 86 and the nozzle 24 is greater than the set number, the third discharge action is performed as a maintenance action of the liquid ejection unit 15. Thus, the liquid in the common liquid chamber 85 in which bubbles are considered to exist can be discharged. In the present embodiment, when the bubbles in the liquid discharged from the liquid ejection unit 15 circulate in the circulation path 33, they are released from the liquid into the air in the liquid storage unit 32.

[0139] When the liquid is ejected from the nozzle 24 during the printing operation, the control unit 111 performs a fourth discharge operation to discharge the liquid in the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 communicating with the independent liquid chamber 86 at a flow rate smaller than that of the first discharge operation as a maintenance operation of the liquid ejecting unit 15. In the present embodiment, the control unit 111 drives the return pump 39B in a state where the first return valve 97a is opened to perform the fourth discharge operation. When the liquid is ejected from the nozzle 24 during the printing operation, for example, refers to the timing when an image is being printed on the medium 12.

[0140] Since the flow rate of the liquid flowing from the independent liquid chamber 86 toward the liquid return flow path 31 in the fourth discharge operation is smaller than that in the first discharge operation, the pressure in the independent liquid chamber 86 does not change greatly. By performing the fourth discharge operation, even when the liquid is being ejected from the nozzle 24 during the printing process, it is possible to suppress the change in the pressure in the independent liquid chamber 86 and the increase in the viscosity of the liquid. The flow rate of the liquid is the volume of the liquid flowing per unit time.

[0141] When the printing operation is not performed, as a maintenance operation of the liquid ejecting unit 15, the control unit 111 performs a fifth discharge operation to discharge the liquid in the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 communicating with the independent liquid chamber 86 at a flow rate greater than that of the first discharge operation. In the present embodiment, the control unit 111 drives the return pump 39B in a state where the first return valve 97a is opened to perform the fifth discharge operation. The fifth discharge operation is an operation to discharge the liquid in the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 and the first discharge port 96a at a flow rate greater than that of the first discharge operation in a state where the nozzle surface 25 is capped by the suction cap 164.

[0142] When the flow rate of the liquid flowing from the independent liquid chamber 86 toward the liquid return flow path 31 is increased by suctioning the inside of the independent liquid chamber 86 from the liquid return flow path 31, there is a possibility that external air is sucked in from the nozzle 24. In contrast, when the liquid in the independent liquid chamber 86 is discharged toward the liquid return flow path 31 via either the first discharge flow path 91 or the second discharge flow path 92 connected to the independent liquid chamber 86, if the nozzle surface 25 is covered with the suction cap 164, it is possible to suppress the external air from entering the independent liquid chamber 86 through the nozzle 24.

[0143] For the above reasons, if the nozzle surface 25 is capped with the suction cap 164, the flow rate of the liquid discharged from the independent liquid chamber 86 toward the liquid return flow path 31 via the first discharge flow path 91 connected to the independent liquid chamber 86 can be increased. Therefore, by performing the fifth discharge operation, the liquid ejecting unit 15 can be more effectively maintained. In the case where the suction cap 164 has an atmospheric release valve, the fifth discharge operation is performed in a state where the atmospheric release valve is closed.

[0144] It should be noted that when a circulation operation such as the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation is performed, or the return valve is opened to perform the circulation operation, even in the capping state as in the fifth discharge operation, pressure fluctuations due to the flow of liquid will occur in the common liquid chamber 85 and the independent liquid chamber 86. In addition, when the circulation operation is performed by driving the return pump 39B as in the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation, the pressure in the common liquid chamber 85 and the independent liquid chamber 86 becomes low. Therefore, it is preferable to start the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation in a state where a meniscus is formed in the nozzle 24, preferably in a state where a concave meniscus is formed in the nozzle 24, so as to prevent the liquid and air attached to the nozzle surface 25 from flowing into the liquid return flow path 31 through the nozzle 24 as the circulation operation is performed.

[0145] In addition, it is preferable that, when the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation are completed, the control unit 111 stops driving the return pump 39B so that the flow rate of the liquid flowing from the liquid ejecting unit 15 to the liquid return flow path 31 is gradually reduced. In addition, in the circulation operation performed by driving the return pump 39B as in the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation, if the return valve is suddenly closed to prevent the flow of the liquid from the liquid ejecting unit 15 to the liquid return flow path 31, the pressure in the common liquid chamber 85 and the independent liquid chamber 86 may increase. Therefore, it is preferable that, when the first discharge operation, the third discharge operation, the fourth discharge operation, and the fifth discharge operation are completed, the return valve is slowly closed to prevent the pressure in the common liquid chamber 85 and the independent liquid chamber 86 from increasing.

[0146] The liquid ejection device 11 may also perform a pressurized ejection operation when not performing a printing operation. In this pressurized ejection operation, the pressure in the liquid ejection unit 15 including the common flow path is set to a pressure equal to or higher than the pressure capable of destroying the meniscus formed in the nozzle 24, thereby ejecting liquid from the nozzle 24 of the liquid ejection unit 15. Fig.10 As shown, in this embodiment, the control unit 111 causes the pressing mechanism 49 of the pressure regulating device 40 to push the diaphragm 56, and opens the supply valve 59 of the pressure regulating mechanism 48. As a result, the liquid pressurized by the supply pump 39A as the supply-side flow mechanism is supplied to the pressure regulating mechanism 48 and the liquid ejecting unit 15, and the liquid in the liquid ejecting unit 15 including the common liquid chamber 85 is pressurized, thereby performing a pressurized discharge operation in which the liquid is discharged from the nozzle 24.

[0147] After the pressure discharge operation is performed, the pressure in the liquid ejecting unit 15 tends to become higher than during the printing operation. Therefore, when the printing operation is performed after the pressure discharge operation is performed, the ejection of the liquid from the nozzle 24 of the liquid ejecting unit 15 may become unstable. For example, the size of the liquid droplets ejected from the nozzle 24 of the liquid ejecting unit 15 may not reach the desired size, or the liquid may not be ejected at the timing when it should be ejected.

[0148] Therefore, in this embodiment, when the pressurized discharge operation is performed, the control unit 111 performs a pressure reduction operation after the pressurized discharge operation. In this pressure reduction operation, Fig.11A , Fig. 11BAs shown, the control unit 111 stops the supply of liquid to the liquid ejecting unit 15 through the pressurizing mechanism and discharges liquid from the nozzle 24 without supplying liquid to the liquid ejecting unit 15, thereby reducing the pressure in the liquid ejecting unit 15 and the liquid supply flow path 30 on the downstream side of the pressure regulating mechanism 48. The pressure reduction operation is performed until the pressure in the common liquid chamber 85 as the common flow path is reduced and the discharge of liquid from the nozzle 24 is stopped.

[0149] When the pressure in the common liquid chamber 85 is set as the common flow path internal pressure, and the common flow path internal pressure during the printing operation of ejecting liquid from the nozzle 24 toward the medium 12 is set as the ejection pressure, the ejection pressure is lower than the atmospheric pressure and maintained as a negative pressure that forms a concave meniscus in the nozzle 24, for example, -0.5kPa to -3kPa in gauge pressure. In contrast, the common flow path internal pressure after the pressure reduction operation is higher than the atmospheric pressure and becomes a positive pressure that forms a convex meniscus in the nozzle 24, for example, +0.1kPa to +1kPa in gauge pressure. In addition, since the common flow path internal pressure in the pressurized discharge operation needs to be the same as or higher than the pressure that can destroy the meniscus formed in the nozzle 24, it is, for example, +5kPa to +50kPa in gauge pressure. Therefore, the common flow path internal pressure in the pressurized discharge operation is higher than the ejection pressure, and the common flow path internal pressure after the pressure reduction operation is lower than the common flow path internal pressure in the pressurized discharge operation and higher than the ejection pressure.

[0150] In addition, if Fig.11A As shown in FIG. 1 , after the pressurized discharge operation is performed, the liquid discharged from the nozzle 24 during the pressurized discharge operation may be retained in a state of being attached to the nozzle surface 25 in a manner covering the opening of the nozzle 24. When the pressure reduction operation is performed in a state where the liquid is attached to the nozzle surface 25 in a manner covering the opening of the nozzle 24, as shown in FIG. Fig. 11B As shown by the double-dashed arrow, the discharge of the liquid from the nozzle 24 and the drop of the liquid adhering to the nozzle surface 25 in a manner covering the opening of the nozzle 24 may sometimes generate a flow of the liquid in the common liquid chamber 85 as a common flow path. Then, due to the flow of the liquid, as shown in FIG. Fig. 11B As shown by the dotted arrow, the liquid attached to the nozzle surface 25 in a manner covering the openings of other nozzles 24 connected to the nozzle 24 via the common flow path sometimes flows into the nozzle 24 in the liquid injection section 15, the independent liquid chamber 86, and then flows into the common flow path.

[0151] Furthermore, since the pressure reducing action is performed while the pressure in the pressurized discharge action remains in the liquid injection portion 15, when the pressure reducing action is performed while allowing the flow of liquid in the liquid return flow path 31, during the pressure reducing action, foreign matter attached to the nozzle surface 25 and liquids including different types of liquids that flow into the liquid injection portion 15 may flow into the liquid return flow path 31 through the common flow path and the second discharge port 96b serving as a discharge port.

[0152] Therefore, the control unit 111 performs the pressure reduction operation in a state where the flow of the liquid in the liquid return flow path 31 is blocked. In the present embodiment, the control unit 111 performs the pressure reduction operation in a state where the first return valve 97a and the second return valve 97b as return valves provided in the liquid return flow path 31 are closed. Thus, even if foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid ejecting unit 15 during the pressure reduction operation, the inflow into the liquid return flow path 31 can be reduced.

[0153] In addition, after the pressure reduction operation, the liquid ejecting device 11 performs a wiping operation to wipe the nozzle surface 25 in a state where the flow of the liquid in the liquid return flow path 31 is blocked. Fig.12 As shown, in this embodiment, the control unit 111 drives the wiping mechanism 133 to perform the wiping operation after the pressure reduction operation in a state where the first return valve 97a and the second return valve 97b as return valves are closed. Since the internal pressure of the common flow path after the pressure reduction operation becomes a positive pressure that forms a convex meniscus on the nozzle 24, when the meniscus is destroyed during the wiping operation, the liquid and air attached to the nozzle surface 25 are less likely to flow into the liquid ejecting unit 15 than when the meniscus is destroyed when the internal pressure of the common flow path is the ejection pressure. Therefore, during the wiping operation, the liquid and air attached to the nozzle surface 25 can be reduced from flowing into the liquid ejecting unit 15, and the state of the nozzle surface 25 after the pressure reduction operation can be adjusted. In addition, since the wiping operation is performed in a state where the flow of the liquid in the liquid return flow path 31 is blocked, when the meniscus formed on the nozzle 24 is destroyed during the wiping operation, the liquid and air attached to the nozzle surface 25 can be reduced from flowing into the liquid return flow path 31 through the nozzle 24.

[0154] In addition, after the wiping action, the liquid ejecting device 11 performs a flushing action in a state where the flow of the liquid in the liquid return flow path 31 is blocked. Fig.13As shown, in the present embodiment, the control unit 111 drives the ejection element 89 of the liquid ejection unit 15 to eject liquid from the nozzle 24 while the first return valve 97a and the second return valve 97b as return valves provided in the liquid return flow path 31 are closed. Thus, the state of the nozzle 24 after the wiping action can be adjusted. For example, in a case where the internal pressure of the common flow path after the wiping action is higher than the ejection pressure, the internal pressure of the common flow path can be made to become the ejection pressure by the flushing action, and a concave meniscus can be formed in the nozzle 24. In addition, in the case where foreign matter, liquid including a different type of liquid, and air flow into the liquid ejection unit 15, they can also be discharged from the nozzle 24. In this case, for example, liquid exceeding the amount of liquid in the liquid ejection unit 15 can also be discharged from the nozzle 24 by the flushing action.

[0155] Next, refer to Fig.14 The flowchart shown in FIG. 1 illustrates the process flow of the process executed when the control unit 111 of the liquid injection device 11 performs a maintenance operation including a pressurized discharge operation in this embodiment. In this embodiment, the process flow of the process executed when the control unit 111 performs a maintenance operation including a pressurized discharge operation is equivalent to the maintenance method of the liquid injection device 11. The series of processes executed by the control unit 111 may be executed in each control cycle set in advance, may be executed based on the detection result of the injection state detection unit 113, or may be manually executed by the user (operator) of the liquid injection device 11.

[0156] like Fig.14 As shown, the control unit 111 closes the first return valve 97a and the second return valve 97b to perform a pressurized discharge operation (step S11). In detail, the control unit 111 controls the driving of the pressing mechanism 49 to displace the diaphragm 56 in a direction to reduce the volume of the liquid outflow portion 51, thereby opening the supply valve 59. In this way, the pressurized liquid is caused to flow into the liquid outflow portion 51, the liquid supply passage 50, the common liquid chamber 85, the independent liquid chamber 86, and the nozzle 24, thereby discharging the liquid from the nozzle 24. In the pressurized discharge operation, as shown in FIG. Fig.10 As shown, liquid is discharged continuously from each nozzle 24.

[0157] Next, the control unit 111 performs a pressure reduction operation (step S12) by causing the pressurizing mechanism to stop pressurizing the liquid ejection unit 15 including the common flow path. In detail, the control unit 111 controls the driving of the pressing mechanism 49 to displace the diaphragm 56 in the direction of increasing the volume of the liquid outflow unit 51, thereby causing the supply valve 59 to be in a closed valve state. As a result, the pressurized liquid is no longer supplied to the downstream side of the liquid outflow unit 51 of the pressure regulating mechanism 48, but since the positive pressure in the pressurized discharge operation remains in the liquid outflow unit 51, the liquid ejection unit 15, and the liquid supply flow path 30 between the liquid outflow unit 51 and the liquid ejection unit, the liquid continues to flow out of the nozzle 24. In the pressure reduction operation, the amount of liquid flowing out of the nozzle 24 per unit time is less than that in the pressurized discharge operation. The pressure reduction operation is performed until the outflow of liquid from the nozzle 24 stops.

[0158] Once a predetermined time has passed since the start of the pressure reduction operation, the control unit 111 determines that the outflow of the liquid from the nozzle 24 has stopped. For example, the predetermined time is set based on the waiting time required from the start of the pressure reduction operation to the stop of the outflow of the liquid from the nozzle 24, which is previously obtained based on experimental results. When the viscosity of the liquid increases, the waiting time becomes longer. Therefore, the control unit 111 may also change the waiting time by estimating the viscosity of the liquid based on the vibration waveform of the independent liquid chamber 86 detected by the injection state detection unit 113.

[0159] Alternatively, the control unit 111 may also infer whether the outflow of the liquid from the nozzle 24 has stopped based on the vibration waveform of the independent liquid chamber 86 detected by the ejection state detection unit 113. For example, the control unit 111 may also determine that the outflow of the liquid from the nozzle 24 has stopped when it is inferred from the vibration waveform of the independent liquid chamber 86 that the position of the liquid in the nozzle 24 has become the same as the position of the convex meniscus. In addition, for example, the control unit 111 may also determine that the outflow of the liquid from the nozzle 24 has stopped when the change in the vibration waveform of the independent liquid chamber 86 caused by the decrease in the amount of liquid attached to the nozzle surface 25 and connected to the liquid in the nozzle 24 has stopped.

[0160] Furthermore, for example, the control unit 111 may determine that the outflow of the liquid from the nozzle 24 has stopped when the pressure change in the independent liquid chamber 86 caused by the discharge of the liquid from the nozzle 24 and the dripping of the liquid adhering to the nozzle face 25 so as to cover the opening of the nozzle 24 is no longer detected by the ejection state detection unit 113. Furthermore, for example, when the vibration waveform from the independent liquid chamber 86 communicating with one nozzle 24 to the independent liquid chamber 86 communicating with other adjacent nozzles 24 changes from a detected state to a non-detected state, the control unit 111 may infer that the state in which the openings of one nozzle 24 and other nozzles 24 are covered by the liquid adhering to the nozzle face 25 has been eliminated, and determine that the outflow of the liquid from the nozzle 24 has stopped.

[0161] After the outflow of the liquid from the nozzle 24 stops, the control unit 111 drives the wiping mechanism 133 to perform a wiping operation to wipe the nozzle surface 25 (step S13). It should be noted that in the following description, the wiping operation is also referred to as a post-wiping operation. The post-wiping operation is performed in a state where the first return valve 97a and the second return valve 97b are in a closed valve state. Through this post-wiping operation, the liquid and foreign matter attached to the nozzle surface 25 are removed.

[0162] Then, the control unit 111 drives the ejection element 89 of the liquid ejection unit 15 to perform a flushing action to eject the liquid from the nozzle 24 (step S14). It should be noted that in the following description, the flushing action is also referred to as a post-flushing action. The post-flushing action is performed with the first return valve 97a and the second return valve 97b in a closed valve state. Through this post-flushing action, the state of the nozzle 24 after the wiping action can be adjusted. For example, in a case where the internal pressure of the common flow path after the wiping action is higher than the ejection pressure, the internal pressure of the common flow path can be made to become the ejection pressure through the flushing action. In addition, in the case where different liquids, including foreign bodies such as air, flow into the liquid ejection unit 15 due to the pressure drop action, they can also be discharged from the nozzle 24. It should be noted that the driving method of the ejection element 89 in the post-flushing action can also be the same as the driving method of the ejection element 89 in the flushing action as the second ejection action performed in the printing action.

[0163] As described above, according to the first embodiment, the following effects can be obtained.

[0164] The liquid ejection device 11 comprises: a liquid ejection unit 15 having a supply port 85a through which liquid can flow, a first discharge port 96a and a second discharge port 96b as discharge ports through which the liquid can flow out, a common liquid chamber 85 as a common flow path communicating with the supply port 85a, the first discharge port 96a and the second discharge port 96b, an independent liquid chamber 86 communicating with the common liquid chamber 85, a nozzle 24 communicating with the independent liquid chamber 86, a nozzle face 25 in which a plurality of nozzles 24 open, and an ejection element 89, wherein the liquid ejection unit 15 can eject the liquid in the independent liquid chamber 86 from the nozzle 24 toward the medium 12 by driving the ejection element 89; a liquid supply flow path 30 connected to the supply port 85a in a manner capable of supplying the liquid to the liquid ejection unit 15; and a liquid return flow path 31 in a manner capable of returning the liquid supplied to the liquid ejection unit 15 to the liquid ejection unit 15. The liquid is connected to the first discharge port 96a and the second discharge port 96b in a manner that the liquid refluxes to the liquid supply path 30; the supply pump 39A as a pressurizing mechanism, which can pressurize the liquid in the liquid injection section 15; a return valve, which is arranged in the liquid return path 31 and can be in a closed valve state that prevents the flow of the liquid and an open valve state that allows the flow; and a control unit 111, the control unit 111 performs a pressurized discharge action and a pressure reduction action. In the pressurized discharge action, the control unit 111 causes the pressurizing mechanism to pressurize the liquid in the liquid injection section 15 so that the liquid is discharged from the nozzle 24. In the pressure reduction action, the control unit 111 causes the pressurizing mechanism to stop the pressurization in the liquid injection section 15 while the return valve is closed, so that the pressure in the liquid injection section 15 is reduced.

[0165] Accordingly, in the event that foreign matter attached to the nozzle surface 25 or liquid including different types of liquids flows into the liquid injection portion 15 from the opening of the nozzle 24 during the pressure reduction action, since the pressure reduction action is performed while blocking the flow of liquid in the liquid return path 31, the flow of the liquid into the liquid injection portion 15 into the liquid return path 31 can also be reduced.

[0166] The liquid ejection device 11 is provided with a wiping mechanism 133 capable of performing a wiping operation for wiping the nozzle surface 25. After the pressure drop operation, the control unit 111 drives the wiping mechanism 133 to perform the wiping operation in a state where the return valve is closed. Thus, the state of the nozzle surface 25 after the pressure drop operation can be adjusted. In addition, since the wiping operation is performed in a state where the flow of liquid in the liquid return flow path 31 is blocked, when the meniscus formed on the nozzle 24 is destroyed during the wiping operation, it is also possible to reduce the liquid and air attached to the nozzle surface 25 from flowing into the liquid return flow path 31 through the nozzle 24.

[0167] The control unit 111 of the liquid ejecting device 11 performs a flushing operation after the wiping operation by driving the ejection element 89 in a state where the return valve is closed to eject the liquid from the nozzle 24. In this way, the state of the nozzle 24 after the wiping operation can be adjusted. In addition, when foreign matter, liquid including a different type of liquid, or air flows into the liquid ejecting unit 15, it can also be discharged from the nozzle 24.

[0168] When the pressure of the liquid in the common liquid chamber 85 as the common flow path is set as the common flow path internal pressure, and the common flow path internal pressure when the liquid is ejected from the nozzle 24 toward the medium 12 is set as the ejection pressure, the common flow path internal pressure in the pressurized discharge operation is higher than the ejection pressure, and the common flow path internal pressure after the pressure reduction operation is lower than the common flow path internal pressure in the pressurized discharge operation and higher than the ejection pressure. Accordingly, when the pressurized discharge operation, the pressure reduction operation, and the wiping operation are performed, foreign matter attached to the nozzle surface 25, liquid including a different type of liquid, and air can be reduced from flowing into the liquid ejection unit 15 from the opening of the nozzle 24.

[0169] The liquid ejection device 11 further includes: a liquid storage portion 32, which stores the liquid supplied to the liquid ejection portion 15 and is connected to the liquid supply flow path 30 and the liquid return flow path 31; and a supply valve 59, which is provided between the liquid storage portion 32 in the liquid supply flow path 30 and the liquid ejection portion 15 and can be in a closed valve state to prevent the flow of the liquid and an open valve state to allow the flow, and the supply pump 39A as the pressurizing mechanism is provided between the liquid storage portion 32 in the liquid supply flow path 30 and the supply valve 59, and the control portion 111 performs the pressurized discharge action by opening the supply valve 59 and supplies the liquid to the liquid ejection portion 15, and performs the pressure reduction action by closing the supply valve 59. Accordingly, the pressurized discharge action and the pressure reduction action can be performed by opening and closing the supply valve 59.

[0170] The liquid ejection device 11 further includes a return pump 39B as a return side flow mechanism which is provided between the return valve and the liquid storage unit 32 in the liquid return flow path 31 and can discharge the liquid from the discharge port. The supply valve 59 opens when the pressure in the common flow path becomes equal to or lower than a predetermined pressure, and the control unit 111 causes the return pump 39B as the return side flow mechanism to discharge the liquid from the discharge port. Accordingly, by causing the return side flow mechanism to discharge the liquid from the discharge port, the supply valve 59 can be opened, and the liquid supplied from the liquid supply flow path 30 to the liquid ejection unit 15 can flow back to the liquid supply flow path 30 via the liquid return flow path 31.

[0171] The control unit 111 of the liquid injection device 11 closes the return valve before performing the pressurized discharge operation. Accordingly, by stopping the pressurization of the common flow path in the liquid injection unit 15 by the pressurizing mechanism, a pressure reduction operation can be performed in a state where the flow of liquid in the liquid return flow path 31 is blocked after the pressurized discharge operation.

[0172] The maintenance method of a liquid injection device is used to maintain a liquid injection device 11, wherein the liquid injection device 11 includes: a liquid injection portion 15, which has a supply port 85a for liquid to flow in, a first discharge port 96a and a second discharge port 96b as discharge ports for the liquid to flow out, a common liquid chamber 85 as a common flow path communicating with the supply port 85a, the first discharge port 96a and the second discharge port 96b, an independent liquid chamber 86 communicating with the common liquid chamber 85, a nozzle 24 communicating with the independent liquid chamber 86, a nozzle face 25 in which a plurality of nozzles 24 are opened, and a spray element 89, wherein the liquid in the independent liquid chamber 86 can be discharged from the nozzle 24 toward the nozzle 24 by driving the spray element 89. The medium 12 is ejected; a liquid supply flow path 30, which is connected to the supply port 85a in a manner capable of supplying the liquid to the liquid injection portion 15; and a liquid return flow path 31, which is connected to the first discharge port 96a and the second discharge port 96b in a manner capable of returning the liquid supplied to the liquid injection portion 15 to the liquid supply flow path 30. The maintenance method includes: performing a pressurized discharge action to pressurize the liquid in the liquid injection portion 15 so that the liquid is discharged from the nozzle 24; and after the pressurized discharge action, performing a pressure reducing action to reduce the pressure in the liquid injection portion 15 in a state where the flow of the liquid in the liquid return flow path 31 is blocked.

[0173] Accordingly, in the event that foreign matter attached to the nozzle surface 25 or liquid including different types of liquids flows into the liquid injection portion 15 from the opening of the nozzle 24 during the pressure reduction action, since the pressure reduction action is performed while blocking the flow of liquid in the liquid return path 31, the flow of the liquid into the liquid injection portion 15 into the liquid return path 31 can also be reduced.

[0174] The maintenance method of the liquid ejecting device performs a wiping operation to wipe the nozzle surface 25 after the pressure reduction operation while the flow of the liquid in the liquid return flow path 31 is blocked. Thus, the state of the nozzle surface 25 after the pressure reduction operation can be adjusted. In addition, since the wiping operation is performed while the flow of the liquid in the liquid return flow path 31 is blocked, even if the meniscus formed on the nozzle 24 is destroyed during the wiping operation, the liquid attached to the nozzle surface 25 and the air flowing into the liquid return flow path 31 through the nozzle 24 can be reduced.

[0175] The maintenance method of the liquid ejecting device performs a flushing operation of driving the ejection element 89 to eject the liquid from the nozzle 24 in a state where the flow of the liquid in the liquid return flow path 31 is blocked after the wiping operation. In this way, the state of the nozzle 24 after the wiping operation can be adjusted. In addition, when foreign matter, liquid including a different type of liquid, or air flows into the liquid ejecting portion 15, it can also be discharged from the nozzle 24.

[0176] In the maintenance method of the liquid ejection device, when the pressure of the liquid in the common liquid chamber 85 as the common flow path is set as the common flow path internal pressure, and the common flow path internal pressure when the liquid is ejected from the nozzle 24 toward the medium 12 is set as the ejection pressure, the common flow path internal pressure in the pressurized discharge operation is higher than the ejection pressure, and the common flow path internal pressure after the pressure reduction operation is lower than the common flow path internal pressure in the pressurized discharge operation and higher than the ejection pressure. Accordingly, when the pressurized discharge operation, the pressure reduction operation, and the wiping operation are performed, foreign matter attached to the nozzle surface 25, liquid including a different type of liquid, and air can be reduced from flowing into the liquid ejection unit 15 from the opening of the nozzle 24.

[0177] 2. Implementation Method 2

[0178] Fig.15 2 is a cross-sectional view schematically showing the pressure reduction operation according to Embodiment 2. This embodiment changes the pressure reduction operation in Embodiment 1 described above.

[0179] The liquid injection device 11 may also perform a flushing action during the pressure drop action. In the present embodiment, the control unit 111 performs a pressure drop action including a flushing action after the pressurized discharge action. In the present embodiment, the process flow of the processing performed by the control unit 111 when performing the pressure drop action is equivalent to the maintenance method of the liquid injection device 11. In detail, the control unit 111 performs a flushing action of driving the ejection element 89 of the liquid injection unit 15 to eject liquid from the nozzle 24 during the pressure drop action in the above-mentioned embodiment 1. It should be noted that in the following description, the flushing action is also referred to as a pressure drop flushing action.

[0180] Considering that the state of the meniscus formed in the nozzle 24 is different from that during the printing operation, the driving method of the ejection element 89 in the pressure drop flushing operation may be different from the driving method of the ejection element 89 in the flushing operation performed as the second discharge operation during the printing operation. As a result, for example, the size of the droplets ejected in the pressure drop flushing operation may be smaller than the size of the droplets ejected in the flushing operation as the second discharge operation. In addition, for example, the ejection speed of the droplets ejected in the pressure drop flushing operation may be faster than the ejection speed of the droplets ejected in the flushing operation as the second discharge operation. The pressure drop operation is performed until the outflow of the liquid from the nozzle 24 stops.

[0181] The number of times the ejection element 89 is driven in the pressure drop flushing action may be set based on the time required for the pressure drop action calculated in advance based on experimental results, etc. Alternatively, the ejection element 89 may be driven intermittently in the pressure drop flushing action. During the pressure drop action, when the ejection element 89 is not driven, the control unit 111 estimates whether the discharge of the liquid from the nozzle 24 has stopped based on the vibration waveform of the independent liquid chamber 86 detected by the injection state detection unit 113, and continues to drive the ejection element 89 until the outflow of the liquid from the nozzle 24 stops.

[0182] When the ejection elements 89 corresponding to all the nozzles 24 communicating with the common liquid chamber 85 as a common flow path are driven in order to perform the pressure reduction flushing action during the pressure reduction action, as shown in FIG. Fig.15 In this way, liquid droplets are not ejected from the nozzle 24 whose opening is covered by the liquid attached to the nozzle surface 25, but liquid droplets are ejected sequentially from the nozzle 24 where a convex meniscus is formed due to the dripping of the liquid attached to the nozzle surface 25. Fig.15 As shown by the double-dashed arrow, due to the ejection of the droplets from the nozzle 24, a flow of liquid is generated in the common liquid chamber 85 as the common flow path, and the liquid attached to the nozzle surface 25 in a manner that covers the openings of other nozzles 24 that communicate with the nozzle 24 via the common flow path is as shown in FIG. Fig.15 As shown by the dotted arrow, sometimes it flows into the liquid injection portion 15.

[0183] In this embodiment, similarly to the first embodiment, the control unit 111 performs the pressure reduction operation while closing the first return valve 97a and the second return valve 97b as return valves provided in the liquid return flow path 31. Thus, the flushing operation is performed during the pressure reduction operation, and even when foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid ejecting unit 15 during the pressure reduction operation, the inflow into the liquid return flow path 31 can be reduced.

[0184] As described above, according to the second embodiment, the following effects can be obtained.

[0185] The control unit 111 of the liquid injection device 11 performs the flushing action during the pressure drop action. In addition, the maintenance method of the liquid injection device 11 performs the flushing action during the pressure drop action. Accordingly, by ejecting droplets from the nozzle 24 caused by the flushing action, the pressure drop in the liquid injection unit 15 during the pressure drop action can be promoted. In addition, since the pressure drop action including the flushing action is performed in a state where the flow of liquid in the liquid return flow path 31 is blocked, when foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid injection unit 15 during the pressure drop action, the inflow into the liquid return flow path 31 can also be reduced.

[0186] 3. Implementation Method 3

[0187] Fig.16 2 is a cross-sectional view schematically showing the pressure reduction operation according to Embodiment 3. This embodiment changes the pressure reduction operation in Embodiment 1 described above.

[0188] The liquid ejection device 11 may also perform a wiping action during the pressure drop action. In the present embodiment, the control unit 111 performs a pressure drop action including a wiping action after the pressurized discharge action. In detail, the control unit 111 drives the wiping mechanism 133 to perform the wiping action during the pressure drop action in the above-mentioned embodiment 1. It should be noted that in the following description, the wiping action is also referred to as a pressure drop wiping action. In the pressure drop wiping action, the pushing force of the pushing portion 157 used to make the belt-shaped member 141 contact the nozzle surface 25 may be smaller than the pushing force in the post-wiping action. Alternatively, in the pressure drop wiping action, the belt-shaped member 141 may be contacted with the liquid attached to the nozzle surface 25 instead of being contacted with the nozzle surface 25 to perform wiping. The pressure drop action is performed until the outflow of the liquid from the nozzle 24 stops.

[0189] In this case, the control unit 111 can determine that the outflow of liquid from the nozzle 24 has stopped by the completion of the pressure drop wiping action, or it can infer whether the outflow of liquid from the nozzle 24 has stopped based on the vibration waveform of the independent liquid chamber 86 detected by the injection state detection unit 113 after the pressure drop wiping action is completed.

[0190] When performing a pressure drop wiping action during a pressure drop action, such as Fig.16 In this way, the strip-shaped member 141 as the wiping portion 161 of the wiping mechanism 133 comes into contact with the liquid attached to the nozzle surface 25, and the liquid attached to the nozzle surface 25 is collected by the strip-shaped member 141. Fig.16 As shown by the double-dashed arrow, the liquid attached to the nozzle surface 25 in a manner covering the opening of the nozzle 24 is collected by the belt-shaped member 141, thereby generating a flow of liquid in the common liquid chamber 85 as a common flow path, as shown in FIG. Fig.16 As shown by the dotted arrow in FIG. 1 , the liquid attached to the nozzle surface 25 may flow into the liquid ejecting portion 15 so as to cover the opening of another nozzle 24 communicating with the nozzle 24 via the common flow path.

[0191] In this embodiment, similarly to the above-mentioned embodiment 1, the control unit 111 performs a pressure drop operation while closing the first return valve 97a and the second return valve 97b as return valves provided in the liquid return flow path 31. Thus, a wiping operation is performed during the pressure drop operation, and when foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid injection unit 15 during the pressure drop operation, the inflow into the liquid return flow path 31 can be reduced. In addition, the control unit 111 of the liquid injection device 11 performs a wiping operation during the pressure drop operation. Accordingly, the pressure drop in the liquid injection unit 15 during the pressure drop operation can be promoted.

[0192] 4. Implementation Method 4

[0193] Fig.17 1 is a cross-sectional view schematically showing a liquid supply unit, a liquid ejection unit, and a pressurized discharge operation in a liquid ejection device according to a fourth embodiment. Fig.17 The embodiment 1 is obtained by using the liquid ejecting section 515 and the liquid supplying section 519 shown in the figure. It should be noted that the same reference numerals are used for the same components as those in the first embodiment, and repeated descriptions are omitted.

[0194] like Fig.17 As shown, the liquid ejection unit 515 is provided with a pressure sensor 599. The pressure sensor 599 detects the pressure in the common liquid chamber 85, that is, the internal pressure of the common flow path. The liquid ejection unit 515 of this embodiment does not have the first discharge port 96a of the liquid ejection unit 15 in the first embodiment. Therefore, the liquid ejection unit 515 may not have the first discharge flow path 91 and the discharge liquid chamber 93 of the liquid ejection unit 15.

[0195] like Fig.17As shown, the liquid supply unit 519 includes a pressure regulating device 540, a liquid return flow path 531, and a flow mechanism 539. The liquid supply unit 519 of this embodiment is obtained by replacing the pressure regulating device 40, the liquid return flow path 31, and the flow mechanism 39 in the above-mentioned embodiment 1 with a pressure regulating device 540, a liquid return flow path 531, and a flow mechanism 539.

[0196] The pressure regulating device 540 regulates the pressure of the liquid supplied to the liquid ejecting portion 515. The pressure regulating device 540 of this embodiment is obtained by removing the pressing mechanism 49 from the pressure regulating device 40 of the first embodiment.

[0197] The liquid return flow path 531 can form a circulation path 33 together with the liquid supply flow path 30. The liquid return flow path 531 connects the second discharge port 96b as a discharge port to the connection portion 30m between the liquid storage portion 32 and the on-off valve 45 in the liquid supply flow path 30 in such a manner that the liquid supplied to the liquid ejecting portion 515 can flow back to the liquid supply flow path 30. The liquid return flow path 531 of this embodiment does not include the return valve included in the liquid return flow path 31 in the first embodiment.

[0198] The flow mechanism 539 enables the liquid in the circulation path 33 to flow. The flow mechanism 539 has a return pump 539B as a return-side flow mechanism provided in the liquid return flow path 531. The return pump 539B is provided in the liquid return flow path 531 at a position closer to the second discharge port 96b than the connection portion 30m. The flow mechanism 539 of this embodiment is obtained by replacing the return pump 39B as the return-side flow mechanism in the above-mentioned embodiment 1 with the return pump 539B.

[0199] The return pump 539B can make the liquid flow in the liquid return flow path 531 along the return direction B from the liquid ejecting portion 515 toward the liquid supply path 30 and the pressurizing direction C toward the liquid ejecting portion 515. The return pump 539B can be applied as a pressurizing mechanism that can pressurize the liquid in the liquid ejecting portion 515 including the common flow path by making the liquid flow in the pressurizing direction C. The return pump 539B blocks the flow of the liquid in the liquid return flow path 531 when not driven. The return pump 539B may also be a tube pump, for example.

[0200] The liquid ejection device 511 performs a pressurized ejection operation of ejecting liquid from the nozzle 24 of the liquid ejection unit 515 by setting the pressure in the liquid ejection unit 515 including the common flow path to a pressure equal to or higher than the pressure capable of destroying the meniscus formed in the nozzle 24. Fig.17As shown, in this embodiment, the control unit 111 drives the return pump 539B as a pressurizing mechanism to make the liquid flow in the pressurizing direction C, pressurizes the liquid in the liquid ejecting unit 515 including the common liquid chamber 85, and discharges the liquid from the nozzle 24. In this case, the control unit 111 performs the pressurizing discharge operation by driving and controlling the return pump 539B as a pressurizing mechanism.

[0201] Next, the liquid ejection device 511 stops the pressurized discharge action and performs a pressure reduction action. Specifically, the control unit 111 stops the drive of the return pump 539B. The return pump 539B blocks the flow of the liquid in the liquid return flow path 531 when it is not driven. Therefore, after the pressurized discharge action, the pressure reduction action is performed in a state where the flow of the liquid in the liquid return flow path is blocked. In this case, the control unit 111 performs the pressure reduction action by stopping the drive of the return pump 539B as a pressurizing mechanism. The pressure reduction action is performed until the discharge of the liquid from the nozzle 24 stops.

[0202] When the internal pressure of the common flow path detected by the pressure sensor 599 reaches a pressure at which a convex meniscus is formed in the nozzle 24 , the control unit 111 determines that discharge of the liquid from the nozzle 24 has stopped.

[0203] As described above, according to the fourth embodiment, the control unit 111 of the liquid injection device 511 can perform a pressurized discharge action by causing the return pump 539B serving as a pressurizing mechanism to pressurize the liquid in the liquid injection unit 515, and can perform a pressure reduction action in a state where the flow of liquid in the liquid return flow path 531 is blocked by stopping the drive of the return pump 539B serving as a pressurizing mechanism.

[0204] Furthermore, in the fourth embodiment, similarly to the above-mentioned first embodiment, since the pressure reduction action is performed in a state where the flow of liquid in the liquid return flow path 531 is blocked, when foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid injection portion 515 from the opening of the nozzle 24 during the pressure reduction action, the flow of the liquid flowing into the liquid injection portion 515 into the liquid return flow path 531 can be reduced.

[0205] 5. Implementation Method 5

[0206] Fig.18 1 is a cross-sectional view schematically showing a liquid supply unit, a liquid ejection unit, and a pressurized discharge operation in a liquid ejection device according to a fifth embodiment. Fig.18It should be noted that the same reference numerals are used for the same structural parts as those in the first embodiment, and repeated descriptions are omitted.

[0207] like Fig.18 As shown, the liquid supply unit 619 includes a liquid return channel 631 and a pressure regulator 640. The liquid supply unit 619 of this embodiment is obtained by replacing the liquid return channel 31 and the pressure regulator 40 in the first embodiment with a liquid return channel 631 and a pressure regulator 640.

[0208] The liquid return flow path 631 can form a circulation path 33 together with the liquid supply flow path 30. The liquid return flow path 631 connects the first discharge port 96a and the second discharge port 96b, which are not shown, as discharge ports to the liquid supply source 17 in a manner that the liquid supplied to the liquid ejector 15 can flow back to the liquid supply flow path 30. In the present embodiment, the liquid supply source 17 is connected to the liquid supply flow path 30 and the liquid return flow path 631 to form the circulation path 33.

[0209] A first return valve 97a as a return valve, a first return pump 39Ba as a return pump 39B, and a first damper 98a may be provided on the first return flow path 31a. A second return valve 97b as a return valve, a second return pump 39Bb as a return pump 39B, and a second damper 98b may be provided on the second return flow path 31b.

[0210] The pressure regulating device 640 includes a pressure regulating mechanism 700 capable of pressurizing the liquid in the liquid ejecting unit 15 including the common liquid chamber 85 as the common flow path. The pressure regulating device 640 of this embodiment is obtained by replacing the pressing mechanism 49 in the first embodiment with the pressure regulating mechanism 700.

[0211] The pressure regulating mechanism 700 includes a liquid storage chamber 701 , an air chamber 702 , a partition wall 703 , an air flow path 704 , an air pump 705 , a pressure detector 706 , and a pressure regulator 707 .

[0212] The liquid storage chamber 701 is configured to store liquid and is provided in the liquid supply flow path 30 at a position between the liquid outflow portion 51 of the pressure regulating device 640 and the supply port 85 a of the liquid ejecting portion 15 .

[0213] The air chamber 702 is disposed adjacent to the liquid storage chamber 701 .

[0214] The partition wall 703 is flexible and partitions the liquid storage chamber 701 and the air chamber 702. Therefore, for example, when the pressure in the air chamber 702 becomes higher than the pressure in the liquid storage chamber 701, the partition wall 703 deforms, the volume of the air chamber 702 increases, and the volume of the liquid storage chamber 701 decreases.

[0215] The air flow path 704 is provided to communicate with the air chamber 702 .

[0216] The air pump 705 is configured to supply air to the air chamber 702 and to suck air from the air chamber 702. The air pump 705 is provided in the air flow path 704. By driving the air pump 705, when air is supplied to the air chamber 702, the pressure in the air chamber 702 and the liquid storage chamber 701 increases, and when air is sucked from the air chamber 702, the pressure in the air chamber 702 and the liquid storage chamber 701 decreases.

[0217] The pressure detector 706 is configured to detect the pressure in the air chamber 702. The pressure detector 706 is provided in the air flow path 704 at a position between the air chamber 702 and the air pump 705. The air chamber 702 is separated from the liquid storage chamber 701 by a flexible partition wall 703. The liquid storage chamber 701 communicates with the common liquid chamber 85 as a common flow path of the liquid ejecting section 15 via the liquid supply flow path 30. Thus, the pressure detector 706 can detect the internal pressure of the common flow path via the liquid storage chamber 701 and the liquid supply flow path 30.

[0218] The pressure regulator 707 is configured to regulate the pressure in the air chamber 702. The pressure regulator 707 may also be provided in the air flow path 704 at a position between the air pump 705 and the pressure detector 706. The pressure regulator 707 may also be provided with a relief valve, for example. In this case, when the pressure in the air chamber 702 becomes higher than the set pressure, the relief valve of the pressure regulator 707 automatically opens to release the air in the air chamber 702 to the outside. In this way, the pressure regulator 707 reduces the pressure in the air chamber 702 for regulation.

[0219] The air chamber 702 is separated from the liquid storage chamber 701 by a flexible partition wall 703. The liquid storage chamber 701 communicates with the common liquid chamber 85, which is a common flow path of the liquid injection section 15, via the liquid supply flow path 30. Thus, the pressure regulating mechanism 700 can pressurize the liquid in the liquid injection section 15 including the common liquid chamber 85 by driving the air pump 705. In addition, the pressure regulating mechanism 700 can drive the air pump 705 based on the pressure detected by the pressure detector 706, and can adjust the internal pressure of the common flow path of the liquid injection section 15 to a specified pressure. In addition, for example, when the volume of the liquid storage chamber 701 is increased from Fig.18When the state of the double dotted line shown increases to the state shown by the solid line, the pressure regulating mechanism 700 drives the air pump 705 based on the pressure detected by the pressure detector 706, and adjusts the pressure in the air chamber 702 to a negative pressure within the range in which the supply valve 59 of the pressure regulating mechanism 48 is opened and the curved liquid surface formed in the nozzle 24 is not destroyed.

[0220] The liquid ejection device 611 performs a pressurized ejection operation of ejecting liquid from the nozzle 24 of the liquid ejection unit 15 by setting the pressure in the liquid ejection unit 15 including the common flow path to a pressure equal to or higher than the pressure capable of destroying the meniscus formed in the nozzle 24. Fig.18 As shown, in this embodiment, the control unit 111 closes the first return valve 97a and the second return valve 97b, and drives the air pump 705 of the pressure regulating mechanism 700 to supply air to the air chamber 702, thereby pressurizing the liquid in the liquid storage chamber 701 through the air chamber 702. Then, the liquid in the liquid storage chamber 701 is supplied to the liquid ejecting unit 15, and the liquid in the common liquid chamber 85 is pressurized, thereby causing the liquid to be discharged from the nozzle 24. In this case, the control unit 111 performs the pressurized discharge operation by driving and controlling the pressure regulating mechanism 700 as a pressurizing mechanism.

[0221] Next, the liquid ejection device 611 stops the pressurized discharge operation and performs a pressure reduction operation. Specifically, the control unit 111 stops the driving of the air pump 705. In this case, the control unit 111 performs the pressure reduction operation by driving and controlling the pressure regulating mechanism 700. The pressure reduction operation is performed until the discharge of the liquid from the nozzle 24 stops.

[0222] The control unit 111 may determine that the discharge of liquid from the nozzle 24 is stopped when the internal pressure of the common flow path detected by the pressure detector 706 of the pressure regulating mechanism 700 reaches a pressure at which a convex meniscus is formed in the nozzle 24 .

[0223] In addition, the liquid ejection device 611 may also drive the pressure regulating mechanism 700 to perform a pressure reduction operation after the pressurized discharge operation. Specifically, the control unit 111 may also drive and control the air pump 705 based on the pressure detected by the pressure detector 706 to draw air from the air chamber 702, thereby reducing the internal pressure of the common flow path to a pressure at which a convex curved liquid surface is formed.

[0224] As described above, according to the fifth embodiment, the control unit 111 of the liquid ejecting device 611 can perform a pressurizing discharge operation by driving and controlling the pressure regulating mechanism 700 as a pressurizing mechanism, and can perform a pressure reducing operation by driving and controlling the pressure regulating mechanism 700.

[0225] Furthermore, in the fifth embodiment, similarly to the above-mentioned first embodiment, since the pressure reduction action is performed in a state where the flow of liquid in the liquid return flow path 631 is blocked, when foreign matter attached to the nozzle surface 25 or liquid including a different type of liquid flows into the liquid injection portion 15 from the opening of the nozzle 24 during the pressure reduction action, the flow of the liquid into the liquid injection portion 15 into the liquid return flow path 631 can be reduced.

[0226] The above-mentioned embodiment and other embodiments described below can be implemented in combination with each other within the scope of no technical contradiction. Other embodiments will be described below.

[0227] If the liquid ejection device can pressurize the pressure in the liquid ejection part including the common flow path to a pressure equal to or higher than the pressure that can destroy the concave meniscus in the nozzle by driving the pressurizing mechanism, the pressurized discharge action can also be performed in a state where the liquid in the liquid return flow path is allowed to flow. For example, in the first embodiment, the control unit 111 performs a pressurized discharge action in which the supply valve 59 is opened in a state where either the first return valve 97a or the second return valve 97b as the return valve is opened, and the liquid pressurized by the supply pump 39A is supplied to the pressure regulating mechanism 48 and the liquid ejection part 15, and the liquid in the liquid ejection part 15 including the common liquid chamber 85 is pressurized, so that the liquid is discharged from the nozzle 24. Next, the control unit 111 closes the first return valve 97a and the second return valve 97b, and closes the supply valve 59, so that the pressurized discharge action is stopped, and a pressure drop action is performed. In this case, since the pressure reduction operation is performed while the flow of liquid in the liquid return flow path 31 is blocked, it is also possible to reduce the inflow of foreign matter attached to the nozzle surface 25 and liquid including different types of liquid into the liquid return flow path 31 through the liquid injection portion 15.

[0228] The liquid injection device may not have a supply-side flow mechanism. For example, in the first embodiment, when the liquid injection device 11 does not have a supply pump 39A as a supply-side flow mechanism in the flow mechanism 39, the control unit 111 may drive the outlet pump 34 to allow the liquid to flow in the liquid supply flow path 30 along the supply direction A from the liquid storage unit 32 toward the liquid injection unit 15. In this case, the outlet pump 34 can be used as a pressurizing mechanism that can pressurize the liquid in the liquid injection unit 15 including the common flow path. In addition, when the supply valve 59 in the pressure regulating mechanism 48 is in a closed valve state, the control unit 111 may drive the outlet pump 34 to set the pressure of the liquid upstream of the pressure regulating mechanism 48 to a positive pressure higher than the atmospheric pressure. In addition, at this time, it is better to close the storage opening valve 41 of the liquid storage unit 32 first.

[0229] The liquid ejection device may not include a liquid storage portion. For example, in the first embodiment, the liquid ejection device 11 may not include a liquid storage portion 32, and the liquid return flow path 31 may connect the second discharge port 96b as a discharge port to the connection portion between the supply pump 39A as a supply-side flow mechanism and the on-off valve 45 in the liquid supply flow path 30 in a manner that enables the liquid supplied to the liquid ejection portion 15 to flow back to the liquid supply flow path 30. In addition, in this case, the liquid ejection device 11 may not include a return pump 39B as a return-side flow mechanism, and the control unit 111 may drive the supply pump 39A in a state where the first return valve 97a and the second return valve 97b as return valves are opened and the on-off valve 45 is closed, thereby causing the liquid to flow in the circulation path 33 along the supply direction A and the return direction B. In addition, the control unit 111 may drive the supply pump 39A in a state where the first return valve 97a and the second return valve 97b serving as return valves are closed and the on-off valve 45 is opened, thereby causing the liquid to flow in the liquid supply flow path 30 in the supply direction A and pressurizing the liquid in the liquid supply flow path 30. In addition, the control unit 111 may open the supply valve 59 to perform a pressurized discharge operation.

[0230] For example, in the first embodiment, the liquid injection device can also drive the return pump 39B through the control unit 111 while the first return valve 97a and the second return valve 97b serving as return valves are opened, so that the liquid flows in the circulation path 33 along the supply direction A and the return direction B, and the first return valve 97a and the second return valve 97b are suddenly closed to stop the flow of the liquid, thereby pressurizing the pressure in the liquid injection unit 15 to perform a pressurized discharge action.

[0231] The liquid injection device 11 may also be provided with a pressure sensor capable of detecting the pressure in the common liquid chamber 85, i.e., the internal pressure of the common flow path, as a pressure regulating device 40, as in the fourth embodiment, and a control valve capable of controlling an open valve state that allows the flow of liquid in the liquid supply flow path 30 and a closed valve state that prevents the flow of liquid as a pressure regulating device 40. The control valve may also be an electromagnetic valve such as a solenoid valve. In this case, the control unit 111 may also control the opening and closing of the control valve so that the internal pressure of the common flow path detected by the pressure sensor is within the range of the ejection pressure. In addition, the control valve 111 may also perform a pressurized discharge action by opening the control valve, and perform a pressure drop action by opening the control valve and stopping the pressurized discharge action.

[0232] The liquid ejection device 11 may not include the expansion and contraction portion 67 in the pressing mechanism 49, but may open and close the supply valve 59 by regulating the pressure in the air chamber 72 directly connected to the connection path 75 through the pressure regulating portion 69. In this case, the control portion 111 may drive the pressure pump 74 of the pressure regulating portion 69 to increase the pressure in the air chamber 72, thereby opening the supply valve 59 to perform the pressurized discharge operation, and drive the fluid pressure regulating portion 77 of the pressure regulating portion 69 to reduce the pressure in the air chamber 72, thereby closing the supply valve to stop the pressurized discharge operation and start the pressure reduction operation. In addition, the pressure pump 74 may be enabled to suck the air in the air chamber 72, and the control portion 111 may drive the fluid pressure regulating portion 77 of the pressure regulating portion 69 during the pressure reduction operation to reduce the pressure in the air chamber 72, thereby promoting the pressure reduction in the liquid ejection portion 15 during the pressure reduction operation.

[0233] The liquid injection device may also include a pressure regulating valve as a return valve disposed in the liquid return flow path. For example, in the fifth embodiment, the liquid injection device 611 may also set the first return valve 97a and the second return valve 97b as return valves to the same structure as the pressure regulating mechanism 48, and set the liquid return flow path so that the liquid flows from the discharge port of the liquid injection portion 15 into the liquid inlet portion, and in the return direction B in the liquid return flow path, the liquid outflow portion is located downstream of the liquid inflow portion. Accordingly, when the liquid does not flow in the return direction B due to the drive of the return side flow mechanism, since the return valve does not open, the control unit 111 can drive and control the pressurizing mechanism, thereby being able to perform a pressurized discharge action in a state where the flow of the liquid in the liquid return flow path is blocked. In addition, when the liquid supplied to the liquid ejecting portion 15 is caused to flow back to the liquid supply passage 30, for example, when the control unit 111 drives the first return pump 39Ba as the return side flow mechanism, the pressure of the first return passage 31a decreases and the first return valve 97a opens, and the liquid in the liquid ejecting portion 15 flows back to the liquid supply passage 30 via the first return passage 31a. In addition, the pressure in the liquid outflow portion where the return valve is opened may be set to a negative pressure lower than the pressure that breaks the concave meniscus formed in the nozzle 24 and higher than the pressure at which the supply valve 59 is opened, for example, in the range of -2 kPa to -3 kPa in gauge pressure. Accordingly, for example, when the control unit 111 drives the second return pump 39Bb as the return side flow mechanism, the supply valve 59 and the second return valve 97b open, and the liquid supplied from the liquid supply passage 30 to the liquid ejecting portion 15 flows back to the liquid supply passage 30 via the second return passage 31b.

[0234] The liquid injection device may perform pressure drop flushing in the pressure drop action of the second embodiment until the internal pressure of the common flow path reaches a negative pressure, or may perform pressure drop flushing until the internal pressure of the common flow path reaches within the range of the ejection pressure. For example, the control unit 111 performs pressure drop flushing in the pressure drop action until a concave meniscus is formed in the nozzle 24 based on the vibration waveform of the independent liquid chamber 86 detected by the ejection state detection unit 113, and ends the pressure drop action. In the case where the pressure drop flushing is performed until the internal pressure of the common flow path reaches within the range of the ejection pressure, the internal pressure of the common flow path after the pressure drop action becomes lower than the internal pressure of the common flow path in the pressurized discharge action and becomes the same as the ejection pressure.

[0235] The liquid ejection device may perform the pressure drop wiping action in the pressure drop action of the third embodiment until the internal pressure of the common flow path reaches a negative pressure, or may perform the action until the internal pressure of the common flow path reaches within the range of the ejection pressure. For example, the control unit 111 performs the pressure drop wiping action in the pressure drop action until a concave meniscus is formed in the nozzle 24 based on the vibration waveform of the independent liquid chamber 86 detected by the ejection state detection unit 113, and ends the pressure drop action. In the case where the pressure drop wiping action is performed until the internal pressure of the common flow path reaches within the range of the ejection pressure, the internal pressure of the common flow path after the pressure drop action becomes lower than the internal pressure of the common flow path in the pressurized discharge action and becomes the same as the ejection pressure.

[0236] The liquid ejecting device may make the driving mode in the post-flushing action different from the driving mode of the ejection element 89 in the flushing action as the second ejection action performed during the printing process, and may make the driving mode in the post-flushing action different from the driving mode of the ejection element 89 in the pressure drop flushing action. As a result, for example, the size of the liquid droplets ejected in the post-flushing action may be smaller than the size of the liquid droplets ejected in the flushing action as the second ejection action, and may be larger than the size of the liquid droplets ejected in the pressure drop flushing action. In addition, for example, the ejection speed of the liquid droplets ejected in the post-flushing action may be faster than the ejection speed of the liquid droplets ejected in the flushing action as the second ejection action, and may be slower than the ejection speed of the liquid droplets ejected in the pressure drop flushing action.

[0237] The liquid ejecting device may also include a temperature sensor capable of detecting the temperature of the liquid in the liquid ejecting portion. For example, the liquid ejecting portion 15 of the liquid ejecting device 11 may include a temperature sensor capable of detecting the temperature in, for example, the common liquid chamber 85 or the independent liquid chamber 86, and the control portion 111 may estimate the viscosity in the independent liquid chamber 86 communicating with the common liquid chamber 85 and in the nozzle 24 based on the temperature of the liquid in the liquid ejecting portion 15 detected by the temperature sensor.

[0238] The liquid injection device may also include an electrothermal conversion element such as a heater that can heat the liquid in the independent liquid chamber 86 as an ejection element of the liquid injection unit. For example, the control unit 111 of the liquid injection device 11 may heat the liquid in the independent liquid chamber 86 by driving the heater of the liquid injection unit 15 to cause film boiling, thereby causing the liquid to be ejected from the nozzle 24. In this case, the liquid state detection unit 113 may also compare the maximum temperature of the liquid during injection detected by the temperature detection element directly below the heater with a predetermined threshold value, or detect the injection state based on the difference in temperature changes. In addition, the liquid state detection unit 113 may also detect the injection state by flight detection using an optical element. The control unit 111 may also combine the state detection in the independent liquid chamber 86 with the results of the flight detection using an optical element to infer the injection state of the liquid of the liquid injection unit 15.

Claims

1. A liquid injection device, characterized in that: have: A liquid ejecting unit having a supply port for liquid to flow in, a discharge port for liquid to flow out, a common flow path communicating with the supply port and the discharge port, an independent liquid chamber communicating with the common flow path, a nozzle communicating with the independent liquid chamber, a nozzle face where a plurality of nozzles are opened, and an ejection element, wherein the liquid ejecting unit ejects the liquid in the independent liquid chamber from the nozzle toward a medium by driving the ejection element; a liquid supply flow path connected to the supply port to supply the liquid to the liquid ejecting portion; a liquid return flow path connected to the discharge port so that the liquid supplied to the liquid ejecting portion flows back to the liquid supply flow path; a pressurizing mechanism for pressurizing the liquid in the liquid ejecting portion; a return valve, disposed in the liquid return flow path, and capable of being in a closed valve state for preventing the flow of the liquid and an open valve state for allowing the flow of the liquid; as well as Control Department, The control unit performs a pressurized discharge action and a pressure reducing action, and performs the pressure reducing action while the return valve is closed. In the pressurized discharge action, the control unit causes the pressurizing mechanism to pressurize the liquid in the liquid injection unit so that the liquid is discharged from the nozzle. In the pressure reducing action, the control unit causes the pressurizing mechanism to stop the pressurization in the liquid injection unit.

2. The liquid ejecting device according to claim 1, wherein: The liquid ejecting device includes a wiping mechanism that performs a wiping operation to wipe the nozzle surface. The control unit drives the wiping mechanism to perform the wiping operation in a state where the return valve is closed after the pressure reducing operation.

3. The liquid ejecting device according to claim 2, wherein: The control unit executes a flushing operation of driving the ejection element to eject the liquid from the nozzle, and executes the flushing operation in a state where the return valve is closed after the wiping operation.

4. The liquid ejecting device according to claim 3, wherein: The control unit performs the flushing operation during the pressure reducing operation.

5. The liquid ejecting device according to any one of claims 1 to 4, characterized in that: When the pressure in the common flow path is set as the common flow path internal pressure, and the common flow path internal pressure when the liquid is ejected from the nozzle toward the medium is set as the ejection pressure, the common flow path internal pressure in the pressurized discharge action is higher than the ejection pressure, and the common flow path internal pressure after the pressure reduction action is lower than the common flow path internal pressure in the pressurized discharge action and higher than the ejection pressure.

6. The liquid ejecting device according to any one of claims 1 to 4, characterized in that: The liquid injection device further comprises: a liquid storage portion storing the liquid supplied to the liquid ejecting portion, the liquid storage portion being connected to the liquid supply flow path and the liquid return flow path; and a supply valve disposed between the liquid storage portion and the liquid ejecting portion in the liquid supply flow path and capable of being in a closed valve state for preventing the flow of the liquid and an open valve state for allowing the flow of the liquid, The pressurizing mechanism is provided between the liquid storage portion and the supply valve in the liquid supply flow path. The control unit performs the pressurizing and discharging operation in a state where the supply valve is opened, and performs the pressure reducing operation in a state where the supply valve is closed.

7. The liquid ejecting device according to claim 6, wherein: The liquid ejecting device further includes a return-side flow mechanism, which is provided between the return valve and the liquid storage portion in the liquid return flow path and discharges the liquid from the discharge port. When the pressure in the common flow path becomes equal to or lower than a predetermined pressure, the supply valve opens. The control unit causes the return-side flow mechanism to discharge the liquid from the discharge port.

8. The liquid ejecting device according to any one of claims 1 to 4, characterized in that: The control unit closes the return valve before performing the pressurized discharge operation.

9. The liquid ejecting device according to claim 1, wherein: The liquid ejecting device includes a wiping mechanism that performs a wiping operation to wipe the nozzle surface. During the pressure reduction operation, the control unit drives the wiping mechanism in a state where the return valve is closed to perform the wiping operation.

10. A method for maintaining a liquid injection device, characterized in that: The liquid injection device comprises: A liquid ejecting unit having a supply port for liquid to flow in, a discharge port for liquid to flow out, a common flow path communicating with the supply port and the discharge port, an independent liquid chamber communicating with the common flow path, a nozzle communicating with the independent liquid chamber, a nozzle face where a plurality of nozzles are opened, and an ejection element, wherein the liquid ejecting unit ejects the liquid in the independent liquid chamber from the nozzle toward a medium by driving the ejection element; a liquid supply flow path connected to the supply port to supply the liquid to the liquid ejecting portion; as well as a liquid return flow path connected to the discharge port so that the liquid supplied to the liquid ejecting portion flows back to the liquid supply flow path; The maintenance method comprises: performing a pressurized discharge operation of pressurizing the liquid in the liquid ejecting portion so as to discharge the liquid from the nozzle; as well as After the pressurized discharge operation, a pressure reducing operation is performed to reduce the pressure in the liquid ejecting section in a state where the flow of the liquid in the liquid return flow path is blocked.

11. The maintenance method of the liquid injection device according to claim 10, characterized in that: After the pressure reducing operation, a wiping operation of wiping the nozzle surface is performed in a state where the flow of the liquid in the liquid return flow path is blocked.

12. The maintenance method of the liquid injection device according to claim 11, characterized in that: After the wiping operation, a flushing operation is performed in which the discharge element is driven to discharge the liquid from the nozzle in a state in which the flow of the liquid in the liquid return flow path is blocked.

13. The maintenance method of the liquid injection device according to claim 12, characterized in that: The flushing action is performed during the pressure reducing action.

14. The maintenance method of a liquid injection device according to any one of claims 10 to 13, characterized in that: When the pressure in the common flow path is set as the common flow path internal pressure, and the common flow path internal pressure when the liquid is ejected from the nozzle toward the medium is set as the ejection pressure, the common flow path internal pressure in the pressurized discharge action is higher than the ejection pressure, and the common flow path internal pressure after the pressure reduction action is lower than the common flow path internal pressure in the pressurized discharge action and higher than the ejection pressure.

15. The maintenance method of the liquid injection device according to claim 12, characterized in that: During the pressure reducing operation, a wiping operation of wiping the nozzle surface is performed in a state where the flow of the liquid in the liquid return flow path is blocked.

Images