Liquid injection device and maintenance method of liquid injection device

Abstract

This application relates to a liquid jetting device and a maintenance method for the liquid jetting device, which can reduce the deterioration of nozzle instability caused by maintenance operations of the liquid jetting device, including a pressurized discharge operation. The liquid jetting device includes a liquid jetting section having a common liquid chamber into which liquid can flow, multiple independent liquid chambers communicating with the common liquid chamber, nozzles communicating with the independent liquid chambers, nozzle faces through which the multiple nozzles open, and a jetting element. By driving the jetting element, the liquid can be jetted from the nozzle toward a medium. After performing a pressurized discharge operation by pressurizing the liquid in the common liquid chamber to discharge the liquid from the nozzle, the liquid jetting device determines whether the liquid can be jetted from the nozzle and performs a flushing operation by driving the jetting element corresponding to the nozzle that is determined to be able to jettison the liquid, thereby jetting the liquid from the nozzle.

Description

Technical Field

[0001] This invention relates to liquid jetting devices such as printers, and methods for maintaining such devices. Background Technology

[0002] Conventionally, as shown in Patent Document 1, an inkjet recording apparatus is known as an example of a liquid ejection device. This apparatus records ink by driving an ejection drive element disposed within the recording head to eject ink from a nozzle. The inkjet recording apparatus includes a pressure recovery unit, such as a pump, for a pressure ejection operation, during which the pressure within the recording head is increased to eject ink from the nozzle. Furthermore, after driving the pressure recovery unit, the inkjet recording apparatus drives the ejection drive element to perform a pre-ejection, thereby reducing the pressure remaining within the recording head after the pressure ejection operation.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-22167

[0004] However, as described in Patent Document 1, after the pressurization and discharge operation performed by driving the pressurization recovery unit, if the ejection drive element corresponding to the nozzle with an unstable state is driven for pre-ejection, there is a possibility that the unstable state of the nozzle may be further aggravated. Summary of the Invention

[0005] A liquid jetting device includes: a liquid jetting section having a common flow path through which liquid can flow, a plurality of independent liquid chambers communicating with the common flow path, nozzles communicating with the independent liquid chambers, nozzle surfaces open by the plurality of nozzles, and ejection elements, wherein the liquid jetting section can eject liquid from the nozzles toward a medium by driving the ejection elements; a pressurizing mechanism capable of pressurizing the liquid in the common flow path; a state detection section capable of detecting the state of either the nozzles or the independent liquid chambers; and a control section that performs: a pressurization discharge operation, in which the liquid is discharged from the nozzles by pressurizing the liquid in the common flow path by the pressurizing mechanism; a state detection operation, in which the state detection section detects the state after the pressurization discharge operation; and a flushing operation, in which the liquid is ejected from the nozzles by driving the ejection elements corresponding to the nozzles that are presumed to be capable of ejecting liquid based on the detection result of the state detection operation.

[0006] A maintenance method for a liquid injection device, wherein the liquid injection device includes a liquid injection section having a common flow path through which liquid can flow, a plurality of independent liquid chambers communicating with the common flow path, nozzles communicating with the independent liquid chambers, nozzle faces through which the plurality of nozzles open, and ejection elements, wherein the liquid injection section can eject liquid from the nozzles toward a medium by driving the ejection elements, and the maintenance method for the liquid injection device includes: performing a pressurization discharge operation, in which the liquid in the common flow path is pressurized to discharge the liquid from the nozzles; after the pressurization discharge operation, determining whether the liquid can be ejected from the nozzles; and performing a rinsing operation, in which the liquid is ejected from the nozzles by driving the ejection elements corresponding to the nozzles that are determined to be able to eject the liquid. Attached Figure Description

[0007] Figure 1 This is a schematic side view of the liquid injection device according to Embodiment 1.

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

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

[0010] Figure 4 It is a schematic cross-sectional view showing the liquid injection section and the liquid supply section.

[0011] Figure 5 It is along Figure 4 The cross-sectional view taken from line 4-4 in the image.

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

[0013] Figure 7 This is a diagram illustrating a computational model of simple harmonic motion assuming the residual vibration of the vibrating plate.

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

[0015] Figure 9 This is an explanatory diagram illustrating the relationship between bubble incorporation and residual vibration waveform.

[0016] Figure 10 It is a schematic cross-sectional view showing the pressurized discharge action.

[0017] Figure 11A It is a schematic cross-sectional view showing the pressure drop action.

[0018] Figure 11B It is a schematic cross-sectional view showing the pressure drop action.

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

[0020] Figure 13 It is a schematic cross-sectional view showing the rinsing action.

[0021] Figure 14 This is a flowchart illustrating an example of a cleaning process that includes a pressurized discharge action.

[0022] Figure 15A This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 1.

[0023] Figure 15B This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 1.

[0024] Figure 15C This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 1.

[0025] Figure 16A This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 3.

[0026] Figure 16B This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 3.

[0027] Figure 16C This is a schematic cross-sectional view illustrating the pressure drop flushing operation involved in Embodiment 3.

[0028] Explanation of reference numerals in the attached figures

[0029] 11 Liquid injection device; 12 Medium; 15 Liquid injection section; 17 Liquid supply source; 18 Mounting section; 19 Liquid supply section; 24 Nozzle; 25 Nozzle face; 30 Liquid supply flow path; 31 Liquid return flow path; 31a First return flow path; 31b Second return flow path; 32 Liquid storage section; 33 Circulation path; 34 Outlet pump; 38 Filter unit; 39 Flow mechanism; 39A Supply pump; 39B Return valve; 40 Pressure regulating device; 41 Storage opening valve; 4 2. Storage level detection unit; 45. On / off valve; 46. Choke valve; 48. Pressure regulating mechanism; 49. Pressing mechanism; 50. Liquid inlet; 51. Liquid outlet; 52. Main body; 53. Wall; 54. Through hole; 55. Filter component; 56. Diaphragm; 56a. First surface; 56b. Second surface; 57. Connecting path; 59. Supply valve; 60. Valve unit; 61. Pressure receiving part; 62. Upstream pressing component; 63. Downstream pressing component; 66. Pressure regulating chamber; 67. Expansion / contraction part; 68. Extrusion component. ; 69 Pressure regulating section; 70 Insertion hole; 71 Opening; 72 Air chamber; 74 Pressurization pump; 75 Connection path; 76 Pressure detection section; 77 Fluid pressure regulating section; 84 Filter; 85 Common liquid chamber; 85a Supply port; 86 Independent liquid chamber; 87 Vibrating plate; 88 Supply side connection path; 89 Ejection element; 90 Receiving chamber; 91 First discharge flow path; 92 Second discharge flow path; 93 Discharge liquid chamber; 94 Discharge side connection path; 96a First discharge port; 96b First discharge port Second outlet; 97a First return valve; 97b Second return valve; 98a First damper; 98b Second damper; 111 Control unit; 112 Detector group; 113 Spray status detection unit; 117 Memory; 118 Control circuit; 119 Drive circuit; 133 Wiping mechanism; 141 Strip component; 148 Opening; 151 Unwinding shaft; 152 Unwinding section; 153 Winding shaft; 154 Winding section; 157 Pushing section; 161 Wiping section; 162 Pull-out section. Detailed Implementation

[0030] 1. Implementation Method 1

[0031] Hereinafter, with reference to the accompanying drawings, an embodiment of the liquid jetting device and a method for maintaining the liquid jetting device will be described. The liquid jetting device is, for example, an inkjet printer that prints by jetting ink, a liquid, onto a medium such as paper. In the following description, liquid refers to ink used for printing, a processing liquid acting on the ink, etc.

[0032] In the accompanying drawings, it is assumed that the liquid injection device 11 is placed on a horizontal plane, with the Z-axis representing the direction of gravity and the X and Y axes representing the directions along the horizontal plane. The X, Y, and Z axes are orthogonal to each other. In the following description, the direction parallel to the Z-axis will also be referred to as the vertical direction Z. Figure 10 , Figure 11A , Figure 11B , Figure 12 , Figure 13 , Figures 15A to 15C as well as Figures 16A to 16C The liquid injection section 15 in the middle is along Figure 5 The cross-section taken from line 5-5 is shown.

[0033] like Figure 1 As shown, the liquid jetting device 11 includes a support platform 13 for supporting the medium 12 and a conveying section 14 for conveying the medium 12. The liquid jetting device 11 includes a liquid jetting section 15 for jetting liquid toward the medium 12 supported by the support platform 13 and a moving mechanism 16 for moving the liquid jetting section 15 in the scanning direction Xs.

[0034] like Figure 1 , Figure 2 As shown, the support stage 13 extends in the liquid jetting device 11 along the scanning direction Xs, which is also the width direction of the medium 12. In this embodiment, the scanning direction Xs is a direction parallel to the X-axis. The support stage 13 supports the medium 12 located at the printing position.

[0035] The conveying unit 14 includes a pair of conveyor rollers 21 for conveying the medium 12, a conveyor motor 22 for rotating the pair of conveyor rollers 21, and a guide plate 23 for guiding the medium 12. Multiple pairs of conveyor rollers 21 may be arranged along the conveying path of the medium 12. By driving the conveyor motor 22, the conveying unit 14 conveys the medium 12 along the surface of the support table 13. The conveying direction Yf of the conveying unit 14 for conveying the medium 12 is along the conveying path of the medium 12, and in the support table 13, it is along the surface in contact with the medium 12. In this embodiment, the conveying direction Yf is parallel to the Y-axis at the printing position.

[0036] The moving mechanism 16 includes: a guide shaft 26 extending in the scanning direction Xs; a carriage 27 holding the liquid jetting section 15 in a manner that allows for replacement of the liquid jetting section 15; and a carriage motor 28 for moving the carriage 27 along the guide shaft 26. The carriage 27 holds the liquid jetting section 15 in an orientation where the nozzle surface 25 is opposite to the support table 13 in the vertical direction Z. The liquid jetting section 15 jets, for example, various colored inks as liquids and processing liquids as liquids that promote ink fixing. The first cover 20a may also be configured to cover part of the moving path of the liquid jetting section 15. When the liquid jetting device 11 is configured such that the liquid jetting section 15 is exposed to the outside from the opened first cover 20a, the liquid jetting section 15 can be easily replaced.

[0037] The moving mechanism 16 causes the carriage 27 and the liquid jetting section 15 to reciprocate along the guide shaft 26 in the scanning direction Xs and in the opposite direction of the scanning direction Xs. That is, the liquid jetting device 11 of this embodiment is configured as a serial device in which the liquid jetting section 15 reciprocates along the X-axis.

[0038] like Figure 1 As shown, the liquid jetting apparatus 11 of this embodiment includes a liquid jetting section 15. The liquid jetting section 15 has a supply port 85a into which liquid flows, a second discharge port 96b into which liquid flows, 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, nozzle surfaces 25 through which the plurality of nozzles 24 open, and a jetting element. The liquid jetting section 15 of this embodiment jets liquid toward the medium 12 located at the printing position in the vertical direction Z by driving the jetting element, enabling printing on the medium 12. It should be noted that the number of liquid jetting sections 15 can also be two or more. In this case, the plurality of liquid jetting sections 15 can also be configured to be separated by a predetermined distance in the scanning direction Xs and staggered by a predetermined distance in the transport direction Yf.

[0039] like Figure 2 As shown, on the nozzle surface 25, a nozzle array L formed by multiple nozzles 24 arranged in the column direction Yr can also be arranged at certain intervals in a scanning direction Xs different from the column direction Yr. In this embodiment, the column direction Yr is along the direction parallel to the nozzle surface 25 and is consistent with the transport direction Yf at the printing position.

[0040] The liquid injection unit 15 of this embodiment has four nozzle rows L. Multiple nozzles 24 constituting a nozzle row L spray the same type of liquid. Among the multiple nozzles 24 constituting a nozzle row L, the nozzle 24 located upstream in the conveying direction Yf and the nozzle 24 located downstream in the conveying direction Yf are staggered in the scanning direction Xs.

[0041] like Figure 1 As shown, the liquid injection device 11 includes a mounting section 18 for detachably mounting a liquid supply source 17 that contains liquid, and a liquid supply section 19 for supplying liquid to the liquid injection section 15. The liquid injection device 11 includes a main body 20 composed of a housing, a frame, etc., and a first cover 20a and a second cover 20b that are installed on the main body 20 in an openable and closable manner.

[0042] The liquid supply source 17 is, for example, a container for holding liquid. The liquid supply source 17 can be a replaceable box or a tank that can be replenished with liquid. The liquid injection device 11 may also have multiple liquid supply units 19 corresponding to the type of liquid injected from the liquid injection unit 15. The liquid injection device 11 of this embodiment has four liquid supply units 19.

[0043] The liquid supply unit 19 includes a liquid supply flow path 30 connected to the supply port 85a in a manner capable of supplying liquid to the liquid injection unit 15. The liquid supply unit 19 also includes a liquid return flow path 31 connected to the second outlet 96b in a manner capable of returning the liquid supplied to the liquid injection unit 15 to the liquid supply flow path 30, and a liquid storage unit 32 for storing liquid. The liquid return flow path 31, together with the liquid supply flow path 30, can form a circulation path 33. The liquid storage unit 32 is connected to the liquid supply flow path 30 and the liquid return flow path 31 to form the circulation path 33. Figure 1 As shown, the liquid storage section 32 can be an open tank that allows the space inside the liquid storage section 32 to be open to the atmosphere, or it can be a flexible, sealed bag. Furthermore, the liquid injection device 11 includes the liquid storage section 32 such that the position of the liquid inside the liquid storage section 32 is lower than the nozzle surface 25 of the liquid injection section 15. Accordingly, pressure higher than the atmospheric pressure inside the liquid storage section 32 can be reduced and applied to the liquid injection section 15 through the liquid return flow path 31.

[0044] The liquid supply unit 19 is equipped with an outlet pump 34 that outlets liquid from the liquid supply source 17.

[0045] The liquid supply unit 19 includes a filter unit 38 for capturing air bubbles and foreign matter in the liquid. The filter unit 38 captures air bubbles and foreign matter in the liquid. The filter unit 38 is detachably installed in the liquid supply flow path 30. When the liquid injection 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.

[0046] The liquid supply unit 19 is equipped with an on / off valve 45. The on / off valve 45 is located between the outlet pump 34 and the liquid storage unit 32 in the liquid supply flow path 30. When the liquid discharged by the outlet pump 34 is supplied to the liquid injection unit 15, the on / off valve 45 is opened.

[0047] The liquid supply unit 19 includes a flow mechanism 39 that enables liquid to flow within the circulation path 33 and a pressure regulating device 40 that adjusts the pressure of the liquid supplied to the liquid injection unit 15. The flow mechanism 39 includes a supply pump 39A, which serves as a supply-side flow mechanism, located in the liquid supply flow path 30, and a return pump 39B, which serves as a return-side flow mechanism, located in the liquid return flow path 31. The supply pump 39A causes 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. By causing liquid to flow in the liquid supply flow path 30 along the supply direction A, the supply pump 39A can pressurize the fluid in the space communicating with the liquid supply flow path 30 in the liquid injection unit 15. Therefore, the supply pump 39A can be used as a pressurizing mechanism that can pressurize the liquid in the liquid injection unit 15, including the common flow path. The return pump 39B causes liquid to flow in the liquid return flow path 31 along the return direction B from the liquid injection unit 15 toward the liquid storage unit 32.

[0048] The supply pump 39A can be any pump capable of causing liquid to flow in the supply direction A within the liquid supply flow path 30. For example, if it is a reciprocating pump, it can also be a plunger pump or a diaphragm pump; if it is a rotary pump, it can also be a gear pump or a tubular pump. The return pump 39B can be any pump capable of causing liquid to flow in the return direction B within the liquid return flow path 31. For example, if it is a reciprocating pump, it can also be a plunger pump or a diaphragm pump; if it is a rotary pump, it can also be a gear pump or a tubular pump.

[0049] The liquid supply unit 19 has a second return valve 97b, which serves as a return valve, on the liquid return flow path 31. The return valve is located in the liquid return flow path 31 closer to the second outlet 96b of the liquid injection unit 15 than the return pump 39B. The return valve can be in a closed state, which prevents the flow of liquid in the liquid return flow path 31, and an open state, which allows the flow.

[0050] like Figure 2 As shown, the liquid jetting device 11 includes a maintenance unit 130 for maintaining the liquid jetting section 15. The maintenance unit 130 is located in a non-printing area, which is the area in the scanning direction Xs where the liquid jetting section 15 is not aligned with the medium 12 being transported. The maintenance unit 130 includes a liquid receiving section 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 also includes a waste liquid tray 138 located vertically below the area where the liquid jetting section 15 moves, and a waste liquid storage section 139 for storing waste liquid discharged from the liquid jetting section 15.

[0051] The position above the capping mechanism 136 is the starting position HP of the liquid spraying unit 15. The starting position HP is the starting point of the movement of the liquid spraying unit 15. The area above the wiping mechanism 133 is the wiping area WA.

[0052] In this embodiment, the position above the liquid receiving section 131 is the discharge position CP of the liquid injection section 15. When the liquid injection section 15 is in the discharge position CP, the nozzle surface 25 is opposite to the liquid receiving section 131. The liquid receiving section 131 is larger than the nozzle surface 25 in both the scanning direction Xs and the conveying direction Yf.

[0053] The liquid injection device 11 performs a pressurized discharge operation. In this pressurized discharge operation, the liquid injection section 15 is positioned at the discharge position CP, and the pressurization mechanism is driven to pressurize the liquid in the common flow path of the liquid injection section 15, thereby discharging the liquid from the nozzle 24. That is, the liquid receiving section 131 receives the liquid discharged by the pressurized discharge operation.

[0054] The liquid receiving unit 131 receives the liquid ejected from the nozzle 24 of the liquid ejection unit 15 by flushing. Flushing refers to the following action: for the purpose of preventing and eliminating clogging of the nozzle 24, liquid is forcibly discharged from the nozzle 24 independently of printing by driving the ejection element 89 of the liquid ejection unit 15.

[0055] The wiping mechanism 133 includes a strip-shaped member 141 capable of absorbing liquid. The wiping mechanism 133 includes: a holding portion 142 for holding the strip-shaped member 141; a base 143 for holding the holding portion 142 in a manner that allows it 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 for transmitting power to the winding motor 146. The holding portion 142 has an opening 148 that exposes the strip-shaped member 141. When the strip-shaped member 141 has a width of more than a nozzle surface 25 in the scanning direction Xs, the liquid jet section 15 can be efficiently maintained.

[0056] The retaining part 142 reciprocates along the Y-axis on the guide rail 144 by the power of the wiping motor 145. Specifically, the retaining part 142... Figure 2 The standby position indicated by the double-dotted line is... Figure 2The holding part 142 moves between the receiving positions shown by the solid line. When the wiping motor 145 is driven in forward rotation, the holding part 142 moves in a first wiping direction W1 parallel to the Y-axis, from the standby position toward the receiving position. When the wiping motor 145 is driven in reverse rotation, the holding part 142 moves in a second wiping direction W2 opposite to the first wiping direction W1, from the receiving position toward the standby position. In this embodiment, the first wiping direction W1 is consistent with the conveying direction Yf at the printing position.

[0057] The wiping mechanism 133 is capable of wiping the nozzle surface 25 of the liquid spraying section 15 located in the wiping area WA during at least one of the processes in which the holding section 142 moves in the first wiping direction W1 and the second wiping direction W2. The wiping action refers to the maintenance of wiping the nozzle surface 25 by wiping it with the strip member 141.

[0058] like Figure 2 , Figure 3 As shown, the wiping mechanism 133 includes an unwinding section 152 with an unwinding shaft 151 and a winding section 154 with a winding shaft 153. The unwinding section 152 holds the strip member 141 in a wound state. The strip member 141, unwound from the unwinding section 152, is conveyed to the winding section 154 along a 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 arranged sequentially from upstream along the conveying path of the strip 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 that they can rotate about the X-axis.

[0059] The winding shaft 153 is rotated by the drive of the winding motor 146. The winding section 154 winds the strip member 141 into a coil on the winding shaft 153.

[0060] In this embodiment, the pressing part 157 is a roller that winds the strip member 141. The pressing part 157 pushes the strip member 141, which is unwound from the unwinding part 152, from below to above, causing the strip member 141 to protrude from the opening 148. The portion of the strip member 141 that is pressed by the pressing part 157 becomes a wiping part 161 capable of wiping the nozzle surface 25. When the holding part 142 moves in the first wiping direction W1 or the second wiping direction W2, the pressing part 157 causes the strip member 141 to contact the nozzle surface 25 in a manner capable of wiping the nozzle surface 25. When the holding part 142 moves in the second wiping direction W2, the wiping mechanism 133 of this embodiment wipes the nozzle surface 25.

[0061] The wiping mechanism 133 has a pull-out portion 162, which is formed by pulling out the strip-shaped member 141 so that it is facing the nozzle surface 25 without contact. In this embodiment, the pull-out portion 162 is the 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 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 holding position, the liquid jetting device 11 positions the liquid jetting part 15 opposite the pull-out part 162, which can perform a pressurized discharge operation or a rinsing operation.

[0062] 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 pressure-reducing mechanism 167 for reducing pressure within 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 where the suction cover 164 contacts the liquid injection section 15 and surrounds the nozzle 24. The retracted position is where the suction cover 164 separates from the liquid injection section 15. The suction cover 164 may be configured to completely surround all nozzles 24 or to surround only a portion of the nozzles 24.

[0063] The liquid jetting device 11 can also perform suction cleaning as described below: the liquid jetting part 15 is positioned above the suction mechanism 134, and the suction cover 164 is positioned in the contact position and surrounds a nozzle array L, thereby depressurizing the suction cover 164 and discharging liquid from the nozzle 24. That is, the suction mechanism 134 can also contain the liquid discharged by suction cleaning.

[0064] The sealing 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. Driven by the standby motor 171, the standby holder 170 and the standby cover 169 move upward or downward. The standby cover 169 moves from a separated position (lower position) to a sealed position (upper position), contacting the liquid jet section 15 which is stopped at the initial position HP.

[0065] A standby cover 169, located in the sealing position, surrounds the opening of the nozzle 24. This maintenance of the standby cover 169 surrounding the opening of the nozzle 24 is called a standby cover. The standby cover is a type of cover. The standby cover prevents the nozzle 24 from drying out. The standby cover 169 can be configured to completely surround all nozzles 24, or it can be configured to surround only a portion of the nozzles 24.

[0066] Next, the liquid supply unit 19 will be described in detail.

[0067] like Figure 4 As shown, the outlet pump 34 includes a suction valve 35, a positive displacement pump 36, and a discharge valve 37. The suction valve 35 is located upstream of the positive displacement pump 36 in the liquid supply flow path 30, further upstream in the supply direction A. The discharge valve 37 is located downstream of the positive displacement pump 36 in the liquid supply flow path 30, further downstream in the supply direction A. The suction valve 35 and the discharge valve 37 are configured to allow the flow of liquid from upstream to downstream in the liquid supply flow path 30, while preventing the flow of liquid from downstream to upstream. The positive displacement pump 36 of the outlet pump 34 has a pump chamber 36b and a negative pressure chamber 36c divided by a flexible member 36a. The positive displacement pump 36 has a pressure reducing section 36d for reducing pressure in the negative pressure chamber 36c and a pressing member 36e disposed within the negative pressure chamber 36c and pressing the flexible member 36a toward the pump chamber 36b.

[0068] As the volume of the pump chamber 36b increases, the discharge pump 34 draws liquid from the liquid supply source 17 via the suction valve 35. The discharge pump 34 pressurizes the liquid within the pump chamber 36b by pressing the pump member 36e through the flexible member 36a. As the volume of the pump chamber 36b decreases, the discharge pump 34 ejects liquid into the liquid injection section 15 via the discharge valve 37. The pressurization pressure of the discharge pump 34 is set to a positive pressure higher than atmospheric pressure, for example, +50 kPa, based on the pressing force of the pump member 36e.

[0069] The liquid supply unit 19 includes a storage opening valve 41 that opens the space inside the liquid storage unit 32 to the atmosphere, a storage volume 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 inside the liquid storage unit 32. The stirring mechanism 43 includes a stirrer 43a disposed inside the liquid storage unit 32 and a rotating part 43b that rotates the stirrer 43a.

[0070] The liquid supply unit 19 includes an air inlet 44 that introduces air into the liquid supply flow path 30. The air inlet 44 includes a switching valve 44a disposed in the liquid supply flow path 30, an air inflow passage 44b connected to the switching valve 44a, and a one-way valve 44c disposed in the air inflow passage 44b. The switching valve 44a acts as a three-way valve, switching between connection and disconnection between the liquid supply flow path 30 and the air inflow passage 44b. The one-way valve 44c allows air to flow towards the liquid supply flow path 30 while preventing the flow of fluid from the liquid supply flow path 30 towards the outside. If the liquid supply flow path 30 is connected to the air inflow passage 44b, air can be introduced into the liquid supply flow path 30 through the air inflow passage 44b.

[0071] The liquid supply unit 19 is equipped with a choke valve 46. During suction cleaning performed by the suction mechanism 134, when choke suction is performed to reduce the pressure of the enclosed space including the liquid jet unit 15 and accumulate negative pressure, the choke valve 46 closes.

[0072] Next, the pressure regulating device 40 will be described in detail.

[0073] like Figure 4 As shown, the pressure regulating device 40 has a pressure regulating mechanism 48 that forms part of the liquid supply flow path 30 and a pressing mechanism 49 that changes the pressure regulating state of the pressure regulating mechanism 48. The pressure regulating mechanism 48 has a main body 52, which has a liquid inlet 50 into which liquid supplied from the liquid supply source 17 flows through the liquid supply flow path 30 and a liquid outlet 51 into which liquid can be contained.

[0074] The liquid supply path 30 and the liquid inlet 50 are separated by a wall 53 in the main body 52, but are connected by 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 path 30 is filtered by the filter member 55 and flows into the liquid inlet 50.

[0075] In the liquid outflow section 51, at least a portion of its wall surface is formed by a diaphragm 56. The diaphragm 56 bears the pressure of the liquid within the liquid outflow section 51 on its first surface 56a, which serves as the inner surface of the liquid outflow section 51. The diaphragm 56 bears atmospheric pressure on its second surface 56b, which serves as the outer surface of the liquid outflow section 51. Therefore, the diaphragm 56 is displaced in response to the pressure within the liquid outflow section 51. The volume of the liquid outflow section 51 changes due to the displacement of the diaphragm 56. The liquid inflow section 50 and the liquid outflow section 51 are connected to each other via a connecting path 57.

[0076] The pressure regulating mechanism 48 has a supply valve 59, which can be in a closed state (disconnecting the liquid inlet 50 from the liquid outlet 51) and an open state (connecting the liquid inlet 50 to the liquid outlet 51) in the communication path 57. In the closed state, it prevents the flow of liquid in the liquid supply path 30; in the open state, it allows the flow of liquid in the liquid supply path 30. The supply valve 59 opens when the pressure in the liquid injection section 15, for example, the pressure in the common flow path, becomes the same as or lower than a predetermined pressure. The supply valve 59 is located between the liquid storage section 32 and the liquid injection section 15 in the liquid supply path 30. Figure 4The supply valve 59 shown is in the closed state. The supply valve 59 has a valve portion 60 that can disconnect 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 can also be fixed to the diaphragm 56 separately from the supply valve 59 in a manner that contacts the supply valve 59.

[0077] An upstream pressing member 62 is disposed within the liquid inlet section 50. A downstream pressing member 63 is disposed within the liquid outlet section 51. Both the upstream pressing member 62 and the downstream pressing member 63 press in the direction that closes the supply valve 59. The supply valve 59 changes from a closed state to an open 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. This set value is, for example, set in the range of 1 kPa to 2 kPa.

[0078] The pressing force of the upstream pressing member 62 and the downstream pressing member 63 is set to create a negative pressure state within the liquid outlet 51, which is sufficient to form a concave meniscus at the 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 outlet 51 is 50 mm, the pressing force of the upstream pressing member 62 and the downstream pressing member 63 is set to create a pressure within the liquid outlet 51 within a range of -1 kPa to -2 kPa using a gauge. In this case, the gas-liquid interface is the boundary where the liquid and gas meet, and the meniscus is the curved liquid surface formed when the liquid meets the nozzle 24. Preferably, a concave meniscus suitable for liquid jetting is formed in the nozzle 24.

[0079] In this embodiment, when the supply valve 59 in the pressure regulating mechanism 48 is in the closed state, the pressure of 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 atmospheric pressure, for example, +50 kPa by a gauge pressure gauge.

[0080] In this embodiment, when the supply valve 59 in the pressure regulating mechanism 48 is in the closed state, the pressure of the liquid outlet 51 and the liquid downstream of the liquid outlet 51 is usually set to a negative pressure lower than atmospheric pressure.

[0081] If the liquid injection section 15 injects liquid, the liquid contained in the liquid outlet section 51 is supplied to the liquid injection section 15 via the liquid supply flow path 30. As a result, the pressure within the liquid outlet section 51 decreases. Consequently, if the pressure difference between the first surface 56a and the second surface 56b of the diaphragm 56 becomes the same as or greater than a set value, the diaphragm 56 flexes and deforms in a direction that reduces the volume of the liquid outlet section 51. As the pressure-bearing section 61 is pushed and moved along with the deformation of the diaphragm 56, the supply valve 59 becomes open, allowing the flow of liquid from the liquid inlet section 50 toward the liquid outlet section 51.

[0082] When the supply valve 59 is in the open state, the liquid in the liquid inlet 50 is pressurized by the supply pump 39A, thus supplying liquid from the liquid inlet 50 to the liquid outlet 51. As a result, the diaphragm 56 deforms to increase the volume of the liquid outlet 51. When the pressure difference between the first surface 56a and the second surface 56b of the diaphragm 56 becomes smaller than a set value, the supply valve 59 changes from the open state to the closed state. Consequently, the supply valve 59 prevents the flow of liquid from the liquid inlet 50 towards the liquid outlet 51.

[0083] As described above, the pressure regulating mechanism 48 regulates the pressure of the liquid supplied to the liquid injection section 15 by the displacement of the diaphragm 56, thereby regulating the pressure in the common flow path of the liquid injection section 15.

[0084] The pressing mechanism 49 includes an expansion / contraction section 67 forming a pressure regulating chamber 66 on the second surface 56b side of the diaphragm 56, a pressing member 68 for pushing the expansion / contraction section 67, and a pressure regulating section 69 capable of adjusting the pressure within the pressure regulating chamber 66. The expansion / contraction section 67 is formed in a balloon shape, for example, using rubber or resin. The expansion / contraction section 67 expands and contracts in response to the pressure adjustment of the pressure regulating chamber 66 by the pressure regulating section 69. The pressing member 68 is formed, for example, in a bottomed cylindrical shape. A portion of the expansion / contraction section 67 is inserted into an insertion hole 70 formed at the bottom of the pressing member 68.

[0085] The extrusion member 68 is mounted to the pressure regulating mechanism 48 such that its opening 71 is blocked by the pressure regulating mechanism 48. Thus, the extrusion 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 through the gap between the insertion hole 70 and the expansion / contraction portion 67. Therefore, atmospheric pressure acts on the second surface 56b of the diaphragm 56.

[0086] The pressure regulating unit 69 adjusts the pressure inside the pressure regulating chamber 66 to a level higher than the pressure in the air chamber 72, i.e., atmospheric pressure, thereby causing the expansion and contraction unit 67 to expand. By expanding the expansion and contraction unit 67 through the pressure regulating unit 69, 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 unit 67 of the pressing mechanism 49 pushes the portion of the diaphragm 56 that contacts the pressure-receiving portion 61, thereby forcibly opening the supply valve 59 of the pressure regulating mechanism 48. That is, the pressing mechanism 49 can be used as an opening mechanism capable of opening 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 connecting path 57.

[0087] like Figure 4 As shown, the pressure regulating unit 69 includes a pressure pump 74 for pressurizing fluids such as air and water, and a connection path 75 connecting the pressure pump 74 and the expansion / contraction unit 67. The pressure regulating unit 69 also includes a pressure detection unit 76 for detecting the pressure of the fluid within the connection path 75, and a fluid pressure regulating unit 77 for regulating the pressure of the fluid within the connection path 75.

[0088] The connection path 75 branches into multiple paths, each connecting to an expansion / contraction section 67 of a pressure regulating device 40. In this embodiment, the connection path 75 branches into four paths, each connecting to an expansion / contraction section 67 of a pressure regulating device 40. Fluid pressurized by the pressure pump 74 is supplied to each expansion / contraction section 67 via the connection path 75.

[0089] The fluid pressure regulating unit 77 can be a control valve that is controlled to open and close based on the pressure detected by the pressure sensing unit 76, or it can be a pressure relief valve 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 unit 77 opens, the fluid in the connection path 75 is released to the outside. In this way, the fluid pressure regulating unit 77 reduces the pressure of the fluid in the connection path 75.

[0090] Next, the liquid injection unit 15 and the liquid return flow path 31 connected to the liquid injection unit 15 in this embodiment will be described in detail.

[0091] like Figure 4As shown, the liquid injection unit 15 has a supply port 85a that allows liquid to flow into it. The supply port 85a is connected to the liquid supply flow path 30 in a manner that allows liquid to be supplied to the liquid injection unit 15. The liquid injection unit 15 has a common liquid chamber 85 that communicates with the supply port 85a as a common flow path. The height difference between the common liquid chamber 85 and the nozzle surface 25 is a level that can be disregarded in pressure calculations. The liquid injection unit 15 has a filter 84 that filters the supplied liquid, and the filtered liquid is ejected from the nozzle 24. The filter 84 captures air bubbles, foreign matter, etc., in the supplied liquid. The filter 84 is disposed in the common liquid chamber 85 that communicates with the liquid supply flow path 30.

[0092] The liquid injection unit 15 has multiple independent liquid chambers 86 communicating with a common liquid chamber 85. A nozzle 24 is provided corresponding to each independent liquid chamber 86. A portion of the wall of each independent liquid chamber 86 is formed by a vibrating plate 87. The common liquid chamber 85 and the multiple independent liquid chambers 86 are interconnected via a supply-side communication path 88. The multiple nozzles 24 communicate with the common liquid chamber 85 via their corresponding independent liquid chambers 86 and are open at nozzle faces 25. Therefore, the pressure within the common liquid chamber 85 is also referred to as the back pressure of the nozzle 24.

[0093] The liquid jetting unit 15 includes multiple ejection elements 89 and multiple receiving chambers 90 for receiving the ejection elements 89. The receiving chambers 90 are located at positions different from the common liquid chamber 85. Each receiving chamber 90 receives one ejection element 89. The ejection element 89 is disposed on the surface of the vibrating plate 87 opposite to the portion facing the individual liquid chamber 86. The liquid jetting unit 15 is provided in the liquid jetting device 11 such that by driving the ejection elements 89, the liquid in the individual liquid chamber 86 can be ejected as droplets from the multiple nozzles 24.

[0094] In this embodiment, the ejection element 89 is composed of a piezoelectric element that contracts when a driving voltage is applied. If the vibrating plate 87 deforms due to the contraction of the ejection element 89 caused by the application of the driving voltage, and then the driving voltage is released from the ejection element 89, the liquid in the independent liquid chamber 86, whose volume has changed, is ejected from the nozzle 24 as droplets.

[0095] like Figure 4 , Figure 5As shown, the liquid injection unit 15 has a first discharge outlet 96a and a second discharge outlet 96b, which allow the supplied liquid to be discharged to the outside without passing through the nozzle 24. The liquid injection unit 15 may also have a first discharge flow path 91 communicating with the first discharge outlet 96a, a second discharge flow path 92 communicating with the second discharge outlet 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 outlet 96a via the first discharge flow path 91, and with the supply port 85a via the independent liquid chamber 86 and the common liquid chamber 85. Furthermore, the common liquid chamber 85 communicates with the first discharge outlet 96a via the independent liquid chamber 86, the discharge liquid chamber 93, and the first discharge flow path 91, and with the second discharge outlet 96b via the second discharge flow path 92.

[0096] The discharge chamber 93 communicates with the multiple independent liquid chambers 86 via a discharge-side communication path 94 corresponding to each independent liquid chamber 86. Only one first discharge flow path 91 needs to be provided for each of the multiple independent liquid chambers 86 by providing the discharge chamber 93. That is, by providing the discharge chamber 93, it is not necessary to provide a first discharge flow path 91 for each independent liquid chamber 86. This simplifies the structure of the liquid injection unit 15. The liquid injection unit 15 may also have multiple first discharge flow paths 91, which communicate with the multiple independent liquid chambers 86.

[0097] like Figure 4 , Figure 5 As shown, the liquid return flow path 31 has a first return flow path 31a connected to the first outlet 96a in a manner that allows the liquid supplied to the liquid injection unit 15 to flow back to the liquid supply flow path 30, and a second return flow path 31b connected to the second outlet 96b. In this embodiment, the liquid return flow path 31 is configured such that the first return flow path 31a and the second return flow path 31b are combined. Alternatively, the liquid return flow path 31 may not be configured such that the first return flow path 31a and the second return flow path 31b are combined, and may be connected to the liquid storage unit 32 separately.

[0098] A first return valve 97a and a first damper 98a are provided as return valves on the first return flow path 31a. A second return valve 97b and a second damper 98b are provided as return valves on the second return flow path 31b. Alternatively, return pumps 39B may be provided on the first return flow path 31a and the second return flow path 31b respectively.

[0099] In the first return flow path 31a, the first damper 98a is positioned closer to the return pump 39B than the first return valve 97a. In the second return flow path 31b, the second damper 98b is positioned closer to the return pump 39B than the second return valve 97b. Both the first damper 98a and the second damper 98b are configured to store liquid. For example, one side of each damper 98a and the second damper 98b is formed of a flexible membrane, and the volume of the stored liquid is variable. By providing the first damper 98a and the second damper 98b, pressure fluctuations generated in the liquid injection section 15 when the liquid flows in the first return flow path 31a and the second return flow path 31b can be suppressed.

[0100] The liquid supply unit 19 can allow liquid to flow in either the first return flow path 31a or the second return flow path 31b, which are liquid return flow paths 31, by opening and closing the first return valve 97a and the second return valve 97b, which are return valves. For example, by opening the first return valve 97a and driving the return pump 39B, liquid in the common flow path of the liquid injection unit 15 can be discharged from the first discharge outlet 96a, which is the discharge port, to the first return flow path 31a, which is the liquid return flow path 31. Furthermore, for example, by opening the second return valve 97b and driving the return pump 39B, liquid in the common flow path of the liquid injection unit 15 can be discharged from the second discharge outlet 96b, which is the discharge port, to the second return flow path 31b, which is the liquid return flow path 31.

[0101] When the liquid in the common liquid chamber 85, which serves as a common flow path, is discharged into the liquid return flow path 31, the pressure in the common liquid chamber 85 of the liquid injection section 15 decreases. Liquid stored in the liquid outlet 51 of the pressure regulating mechanism 48 is then supplied to the common liquid chamber 85 of the liquid injection section 15 via the liquid supply flow path 30. Consequently, the pressure in the liquid outlet 51 decreases. Therefore, when the pressure difference between the pressure applied to the first surface 56a and the pressure applied to the second surface 56b of the diaphragm 56 becomes the same as or greater than a set value, the supply valve 59 becomes open, allowing the flow of liquid from the liquid inlet 50 towards the liquid outlet 51. As a result, the liquid supplied from the liquid supply flow path 30 to the liquid injection section 15 via the liquid inlet 50 flows back to the liquid supply flow path 30 via the liquid return flow path 31 and the liquid storage section 32.

[0102] Furthermore, when choke suction is performed by suction mechanism 134, the first return valve 97a and the second return valve 97b are closed together with the choke valve 46, making the liquid supply flow path 30 from the choke valve 46 to the liquid injection section 15, the liquid return flow path 31 from the liquid injection section 15 to the return valve, and the liquid injection section 15 a closed space.

[0103] Next, the electrical structure of the liquid injection device 11 will be described.

[0104] like Figure 6 As shown, the liquid injection device 11 includes a control unit 111 that uniformly controls the structural elements of the liquid injection device 11, and a detector group 112 controlled by the control unit 111. The detector group 112 includes an injection state detection unit 113 that can detect the state of the liquid in the liquid injection section 15 by detecting the vibration waveform of the independent liquid chamber 86. The detector group 112 monitors the condition inside the liquid injection device 11. The detector group 112 outputs the detection results to the control unit 111.

[0105] 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 the computer 120, which is an external device, and the liquid injection device 11. The drive circuit 119 generates drive signals that drive the ejection element 89.

[0106] CPU 116 is an arithmetic processing unit. Memory 117 is a storage device that stores the program of CPU 116 or a working area, and includes storage elements such as RAM and EEPROM. CPU 116 controls the conveying unit 14, moving mechanism 16, liquid supply unit 19, pressure regulating unit 69, maintenance unit 130, liquid injection unit 15, etc. of liquid injection device 11 via control circuit 118 according to the program stored in memory 117.

[0107] The detector assembly 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 jetting state detection unit 113 may also be configured as a circuit for detecting residual vibration of the independent liquid chamber 86. The jetting state detection unit 113 may also include a piezoelectric element constituting the ejection element 89.

[0108] Next, the method for inferring the state inside the independent liquid chamber 86 based on the detection results of the injection state detection unit 113 will be explained.

[0109] When a voltage is applied to the ejection element 89 according to a signal from the drive circuit 119, the vibrating plate 87 flexes and deforms. This causes a pressure fluctuation within the independent liquid chamber 86. Due to this fluctuation, the vibrating plate 87 vibrates briefly. This vibration is referred to as residual vibration. The state of the area 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 this residual vibration.

[0110] Figure 7 This is a diagram showing a calculation model of the simple harmonic motion of the residual vibration of the vibrating plate 87.

[0111] If the drive circuit 119 applies a drive signal to the ejection element 89, the ejection element 89 expands and contracts accordingly with the voltage of the drive signal. The vibrating plate 87 flexes accordingly with the expansion and contraction of the ejection element 89. As a result, the volume of the independent liquid chamber 86 contracts after expanding. At this time, due to the pressure generated inside the independent liquid chamber 86, a portion of the liquid filling the independent liquid chamber 86 is ejected from the nozzle 24 as droplets.

[0112] During the series of actions of the aforementioned vibrating plate 87, the vibrating plate 87 vibrates freely at its natural vibration frequency, which 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 vibrating plate 87. This free vibration of the vibrating plate 87 is residual vibration.

[0113] Figure 7 The calculation model for the residual vibration of the vibrating plate 87 shown is represented by pressure P, the aforementioned inertia m, compliance C, and flow path resistance r. If the calculation of volumetric velocity u is related to... Figure 7 The circuit is given a step response to pressure P, and the following equation is obtained.

[0114]

Mathematical Formula 1

[0115]

[0116]

[0117]

[0118] Figure 8 This is an illustration of the relationship between the viscosity increase of a 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 of the first half-wave in the residual vibration waveform. For example, when the liquid near nozzle 24 has dried, the viscosity of the liquid increases, i.e., it thickens. If the liquid thickens, the flow path resistance r increases, and therefore, the vibration period and the attenuation of the residual vibration increase.

[0119] Figure 9 This is an illustration of the relationship between bubble incorporation and residual vibration waveform. Figure 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 liquid flow path or the front end of nozzle 24, the inertia m of the liquid weight and the mixing of bubbles are correspondingly reduced compared to the normal state of nozzle 24. According to equation (2), if m decreases, the angular velocity ω increases, and therefore the vibration period shortens. That is, the vibration frequency increases.

[0120] It should be noted that the situation where air bubbles are mixed into the independent liquid chamber 86 includes the situation where air bubbles are mixed into the area of ​​the nozzle 24 in addition to the independent liquid chamber 86.

[0121] Furthermore, for example, the frequency of the vibration waveform detected when the independent liquid chamber 86 and nozzle 24 are filled with liquid and air bubbles are present is higher than the frequency of the vibration waveform detected when the independent liquid chamber 86 and nozzle 24 are filled with liquid and air bubbles are absent. The frequency of the vibration waveform detected when the independent liquid chamber 86 and nozzle 24 are filled with liquid and air bubbles are present is higher than the frequency of the vibration waveform detected when the independent liquid chamber 86 and nozzle 24 are filled with liquid and air bubbles are present. The larger the size of the air bubbles present in the independent liquid chamber 86 and nozzle 24 filled with liquid, the higher the frequency of the vibration waveform.

[0122] On the other hand, consider, for example, when liquid adheres to nozzle surface 25, and the liquid adhering to nozzle surface 25 is connected to the liquid inside nozzle 24, since the liquid adhering to nozzle surface 25 is connected to the liquid filling the independent liquid chamber 86 via nozzle 24, from the perspective of vibrating plate 87, the amount of liquid adhering to nozzle surface 25 is increased compared to normal, thereby increasing the liquid weight, i.e., the inertia m. Therefore, when the liquid adhering to nozzle surface 25 is connected to the liquid in independent liquid chamber 86, the frequency is lower than the normal frequency.

[0123] In addition, it is considered that if foreign matter such as paper dust adheres near the opening of nozzle 24, the amount of liquid in the independent liquid chamber 86 and the amount of liquid seeping out, as seen from the vibrating plate 87, will increase compared to normal, thus increasing the inertia m. The flow path resistance r is also considered to be increased due to the fibers of the paper dust adhering near the outlet of nozzle 24. Therefore, when paper dust adheres near the opening of nozzle 24, the frequency decreases compared to normal spraying, and the frequency of residual vibration increases compared to when the liquid thickens.

[0124] If the liquid becomes thickened, bubbles are introduced, or foreign matter adheres, the state within nozzle 24 and the independent liquid chamber 86 becomes abnormal. Typically, liquid will no longer be ejected from nozzle 24. Consequently, bad pixels appear in the image recorded on medium 12. Even if droplets are ejected from nozzle 24, there may be cases where the amount of droplets is small, or the droplets deviate from their flight direction and fail to land at the target location. Nozzles 24 exhibiting such poor ejection are called abnormal nozzles.

[0125] 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 injection state detection unit 113 detects the vibration waveform of the independent liquid chamber 86. The control unit 111 infers the state of the area including the independent liquid chamber 86 and the nozzle 24 communicating with the independent liquid chamber 86 based on the detection result of the injection state detection unit 113.

[0126] The control unit 111 infers whether the spraying state of the liquid spraying unit 15 is normal or abnormal based on the vibration waveform of the independent liquid chamber 86, which is the detection result of the spraying state detection unit 113. If the state within the independent liquid chamber 86 is abnormal, the control unit 111 infers whether the abnormality is due to the presence of air bubbles or to increased viscosity of the liquid. Based on the vibration waveform of the independent liquid chamber 86, the control unit 111 infers the total volume of air bubbles present in the independent liquid chamber 86 and the nozzle 24 communicating with it, as well as the degree of viscosity increase of the liquid in the independent liquid chamber 86 and the nozzle 24 communicating with it. Based on the vibration waveform of the independent liquid chamber 86, the control unit 111 infers whether liquid adheres to the nozzle surface 25 and whether the liquid adhering to the nozzle surface 25 is connected to the liquid inside the nozzle 24.

[0127] The control unit 111 can also infer whether the filter 84 is functioning properly based on the detection results detected by the injection status detection unit 113. If the filter 84 is clogged, the flow of liquid through the filter 84 is prone to stagnation. If the liquid flow stagnates, air will enter from the nozzle 24, and air bubbles are likely to accumulate in the independent liquid chamber 86. Therefore, the control unit 111 can also infer that the filter 84 is malfunctioning based on the abnormality caused by the detected air bubbles in the independent liquid chamber 86.

[0128] Specifically, for example, if the control unit 111 detects an anomaly caused by air bubbles in more than a specified number of independent liquid chambers 86, it may suspect that the filter 84 is malfunctioning. The specified number is, for example, a number that cannot be addressed by supplementary printing, in which liquid that should be sprayed from the malfunctioning nozzle is sprayed from the surrounding nozzles 24.

[0129] In this embodiment, the control unit 111 performs the printing action of forming characters and images on the medium 12 by alternating between the conveying action and the spraying action. The conveying action is the action of driving the conveying unit 14 to convey a unit amount of the medium 12, and the spraying action is the action of spraying liquid from the liquid spraying unit 15 onto the medium 12 while moving the carriage 27 in the scanning direction Xs.

[0130] Furthermore, within the pressing mechanism 49, the control unit 111 supplies pressurized fluid to the expansion and contraction section 67 by driving the pressurization pump 74. As a result of the expansion and contraction section 67 expanding, the diaphragm 56 displaces in a direction that reduces the volume of the liquid outlet 51, and the supply valve 59 becomes open. Thus, the control unit 111 controls the opening and closing of the supply valve 59 based on the driving of the pressing mechanism 49.

[0131] In the liquid jetting device 11, when the liquid flow stagnates, the liquid becomes prone to thickening or to accumulating air bubbles. In this case, abnormal nozzle conditions are more likely to occur. That is, the state of the independent liquid chamber 86 and the nozzle 24 becomes more prone to abnormalities. Therefore, in order to suppress the thickening of the liquid or to expel air bubbles, the control unit 111 is configured to perform maintenance operations to maintain the liquid jetting unit 15. In this embodiment, the control unit 111 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 suction cleaning as maintenance operations for the liquid jetting unit 15.

[0132] When no liquid is ejected from nozzle 24 during the printing operation, as a maintenance operation of liquid ejection unit 15, control unit 111 performs a first discharge operation to discharge the liquid in independent liquid chamber 86 toward liquid return flow path 31 via first discharge flow path 91 which communicates with independent liquid chamber 86. The first discharge operation is the operation of discharging the liquid in independent liquid chamber 86 toward liquid return flow path 31 via first discharge flow path 91 and first discharge outlet 96a.

[0133] During the printing operation, when liquid is not ejected from nozzle 24, for example, during the return of carriage 27 or between pages of media 12. The return of carriage 27 refers to the moment when carriage 27 moves back to its starting position HP. Between pages of media 12 refers to the time from when an image is printed on media 12 until the next media 12 reaches a position opposite to the liquid ejection unit 15. Control unit 111 performs the first discharge operation at such times.

[0134] In the first discharge operation, the control unit 111 draws liquid from the independent liquid chamber 86 from the first discharge flow path 91 side while maintaining the meniscus of the gas-liquid interface within the nozzle 24, thereby discharging the liquid toward the liquid return flow path 31. In this embodiment, the control unit 111 drives the return pump 39B with the first return valve 97a open to perform the first discharge operation. When the first discharge operation is performed by drawing liquid from the independent liquid chamber 86 from the first discharge flow path 91 side, the gas-liquid interface of the meniscus within the nozzle 24 moves toward the independent liquid chamber 86 side. As a result, at least a portion of the liquid within the nozzle 24 flows. This suppresses the thickening of the liquid within the nozzle 24.

[0135] Alternatively, if the control unit 111 performs a first discharge operation when it is deduced from the detection results of the jet state detection unit 113 that an abnormality has occurred in the state within the independent liquid chamber 86 due to the volume of bubbles present in the independent liquid chamber 86 and the nozzle 24 exceeding 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 jet state detection unit 113 when the volume of bubbles present in the independent liquid chamber 86 and the nozzle 24 reaches the set value.

[0136] The control unit 111 compares the vibration waveform of the independent liquid chamber 86 detected by the injection state detection unit 113 at time intervals to infer whether the state inside the independent liquid chamber 86 has improved. If it is inferred that the state inside the independent liquid chamber 86 has not improved, it performs a second discharge operation as a maintenance operation of the liquid injection unit 15, causing the liquid inside the independent liquid chamber 86 to be discharged from the nozzle 24 to the outside. The second discharge operation is the rinsing described above.

[0137] For example, if the state within the independent liquid chamber 86 does not improve even after the first discharge operation, the control unit 111 performs a second discharge operation to discharge the liquid from the nozzle 24 to the outside of the independent liquid chamber 86. In this case, after performing the first discharge operation based on the detection result of the jet state detection unit 113, the control unit 111 again detects the state within the independent liquid chamber 86 through the jet state detection unit 113. At this time, if the vibration waveform of the independent liquid chamber 86 suggests that the volume of air bubbles in the independent liquid chamber 86 and the nozzle 24 is increasing or the liquid is becoming more viscous, the control unit 111 considers that the state within the independent liquid chamber 86 has not improved and performs the second discharge operation.

[0138] For example, the control unit 111 may not perform the first discharge action based on the fact that the volume of the bubbles present 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 time expected for the bubbles to disappear has elapsed but the state in the independent liquid chamber 86 has not improved.

[0139] If, based on the detection results of the injection state detection unit 113, the number of independent liquid chambers 86 whose state is abnormal due to air bubbles present in the independent liquid chambers 86 and nozzles 24 exceeds a set number, the control unit 111 performs a third discharge operation as a maintenance operation of the liquid injection unit 15. This discharges the liquid in the common liquid chamber 85 towards the liquid return flow path 31 via the second discharge flow path 92 and the second discharge outlet 96b, which are connected to the common liquid chamber 85. In this embodiment, the third discharge operation is performed before the first discharge operation. The control unit 111 drives the return pump 39B with the second return valve 97b open to perform the third discharge operation. The set number is stored in the memory 117 of the control unit 111.

[0140] If the number of independent liquid chambers 86 suspected of having abnormal conditions due to air bubbles in the independent liquid chambers 86 and nozzles 24 exceeds a set number, it can be assumed that air bubbles exist in the common liquid chamber 85 that communicates with the multiple independent liquid chambers 86. In this case, since there is a possibility of continuously generating abnormal nozzles in the nozzle surface 25, it is difficult to perform supplementary printing. Therefore, if the number of independent liquid chambers 86 suspected of having abnormal conditions due to air bubbles in the independent liquid chambers 86 and nozzles 24 exceeds a set number, a third discharge operation is performed as a maintenance operation of the liquid jetting unit 15. As a result, the liquid in the common liquid chamber 85 where air bubbles are believed to exist can be discharged. In this embodiment, when air bubbles in the liquid discharged from the liquid jetting unit 15 circulate in the circulation path 33, they are released from the liquid into the air in the liquid storage unit 32.

[0141] During the printing operation, while liquid is being ejected from nozzle 24, as a maintenance operation of the liquid ejection unit 15, control unit 111 performs a fourth discharge operation, discharging the liquid in independent liquid chamber 86 towards liquid return flow path 31 at a flow rate smaller than that of the first discharge operation via first discharge flow path 91, which communicates with independent liquid chamber 86. In this embodiment, control unit 111 drives return pump 39B to perform the fourth discharge operation while the first return valve 97a is open. "While liquid is being ejected from nozzle 24 during the printing operation" refers, for example, to the time when an image is being printed on medium 12.

[0142] Because the flow rate of liquid flowing from the independent liquid chamber 86 towards the liquid return path 31 is smaller in the fourth discharge action compared to the first discharge action, the pressure within the independent liquid chamber 86 does not fluctuate significantly. By performing the fourth discharge action, even when liquid is being ejected from the nozzle 24 during the printing process, pressure fluctuations within the independent liquid chamber 86 and liquid viscosity increase can be suppressed. Liquid flow rate is the volume of liquid flowing per unit time.

[0143] When printing is not being performed, as a maintenance operation of the liquid jetting unit 15, the control unit 111 performs a fifth discharge operation, in which the liquid in the independent liquid chamber 86 is discharged toward the liquid return flow path 31 at a flow rate greater than that of the first discharge operation via the first discharge flow path 91, which communicates with the independent liquid chamber 86. In this embodiment, the control unit 111 drives the return pump 39B to perform the fifth discharge operation while the first return valve 97a is open. The fifth discharge operation is an operation in which the liquid in the independent liquid chamber 86 is discharged toward the liquid return flow path 31 at a flow rate greater than that of the first discharge operation via the first discharge flow path 91 and the first discharge outlet 96a with the nozzle surface 25 sealed by the suction cover 164.

[0144] When the flow rate of liquid flowing from the independent liquid chamber 86 toward the liquid return flow path 31 is increased by suction from the liquid return flow path 31 side, it is possible to draw in external gas through the nozzle 24. Conversely, 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 sealed with the suction cover 164, it is possible to prevent external gas from entering the independent liquid chamber 86 through the nozzle 24.

[0145] For the reasons stated above, if the nozzle surface 25 is sealed with the suction cap 164, the flow rate of liquid discharged from the independent liquid chamber 86 towards 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 injection section 15 can be maintained more effectively. When the suction cap 164 has an atmospheric opening valve, the fifth discharge operation is performed with the atmospheric opening valve closed.

[0146] It should be noted that when performing cyclic actions such as the first, third, fourth, and fifth discharge actions, or when the return valve is opened to perform cyclic actions, even when the valve is in a sealed state as in the fifth discharge action, pressure fluctuations due to liquid flow will occur in the common liquid chamber 85 and the independent liquid chamber 86. Furthermore, when the cyclic action is performed by driving the return pump 39B as in the first, third, fourth, and fifth discharge actions, the pressure in the common liquid chamber 85 and the independent liquid chamber 86 decreases. Therefore, it is preferable to start the first, third, fourth, and fifth discharge actions when the nozzle 24 has a curved surface, preferably when a concave curved surface is formed within the nozzle 24, to prevent liquid or air adhering to the nozzle surface 25 from flowing into the liquid return flow path 31 via the nozzle 24 during the cyclic action.

[0147] Furthermore, preferably, upon completion of the first, third, fourth, and fifth discharge operations, the control unit 111 stops driving the return pump 39B by gradually reducing the flow rate of liquid flowing from the liquid injection unit 15 towards the liquid return path 31. Moreover, during the cyclic operation of driving the return pump 39B as described in the first, third, fourth, and fifth discharge operations, if the return valve is abruptly closed to prevent liquid flow from the liquid injection unit 15 towards the liquid return path 31, the pressure in the common liquid chamber 85 and the independent liquid chamber 86 may sometimes increase. Therefore, it is preferable that upon completion of the first, third, fourth, and fifth discharge operations, the return valve is closed slowly to prevent pressure increases in the common liquid chamber 85 and the independent liquid chamber 86.

[0148] The liquid jetting device 11 can also perform a pressurized discharge operation when printing is not being performed. In this pressurized discharge operation, liquid is discharged from the nozzle 24 of the liquid jetting unit 15 by setting the pressure within the liquid jetting section 15, including the common flow path, to a pressure that is the same as or higher than the pressure capable of disrupting the meniscus formed in the nozzle 24. Figure 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, thereby opening the supply valve 59 of the pressure regulating mechanism 48. Then, a pressurized discharge operation is performed, supplying liquid pressurized by the supply pump 39A (which serves as a supply-side flow mechanism) to the pressure regulating mechanism 48 and the liquid injection section 15, thereby pressurizing the liquid in the liquid injection section 15, including the common liquid chamber 85, and discharging the liquid from the nozzle 24.

[0149] After the pressurized discharge operation, the pressure inside the liquid jetting section 15 is likely to become higher than during the printing operation. Therefore, when printing is performed after the pressurized discharge operation, the jetting of liquid from the nozzle 24 of the liquid jetting section 15 may become unstable. For example, the size of the droplets ejected from the nozzle 24 of the liquid jetting section 15 may not be the desired size, or the liquid may not be ejected at the appropriate time.

[0150] Therefore, in this embodiment, when a pressurization and discharge operation is performed, the control unit 111 performs a pressure reduction operation after the pressurization and discharge operation. During this pressure reduction operation, such as... Figure 11A , Figure 11BAs shown, when the control unit 111 stops supplying liquid to the liquid injection unit 15 via the pressurization mechanism and ceases supplying liquid to the liquid injection unit 15, it discharges liquid from the nozzle 24, thereby reducing the pressure in the liquid supply flow path 30 downstream of the liquid injection unit 15 and the pressure regulating mechanism 48. The pressure reduction operation continues until the pressure in the common liquid chamber 85, which serves as a common flow path, decreases and the discharge of liquid from the nozzle 24 stops.

[0151] When the pressure within the common liquid chamber 85 is set as the common flow path internal pressure, and the common flow path internal pressure during the printing action of ejecting liquid from the nozzle 24 towards the medium 12 is set as the ejection pressure, the ejection pressure is lower than atmospheric pressure and is maintained as a negative pressure that forms a concave meniscus within the nozzle 24, for example, -0.5 kPa to -3 kPa using a gauge. Conversely, after the pressure reduction action, the common flow path internal pressure is higher than atmospheric pressure, becoming a positive pressure that forms a convex meniscus within the nozzle 24, for example, +0.1 kPa to +1 kPa using a gauge. Furthermore, since the common flow path internal pressure during the pressurized discharge action needs to be the same as or higher than the pressure capable of disrupting the meniscus formed in the nozzle 24, it is, for example, +5 kPa to +50 kPa using a gauge. Therefore, the common flow path internal pressure during 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 during the pressurized discharge action but higher than the ejection pressure.

[0152] In addition, such as Figure 11A As shown, after the pressurization and discharge operation, the liquid discharged from nozzle 24 during the pressurization and discharge operation may sometimes remain attached to nozzle surface 25, covering the opening of nozzle 24. When a pressure reduction operation is performed while the liquid is attached to nozzle surface 25, covering the opening of nozzle 24, as... Figure 11B As indicated by the double-dotted arrow, the discharge of liquid from nozzle 24, and the dripping of liquid adhering to the nozzle surface 25 in a manner that covers the opening of nozzle 24, sometimes create liquid flow within the common liquid chamber 85, which serves as a common flow path. Then, due to this liquid flow, as... Figure 11B As shown by the dashed arrow, liquid adhering to the nozzle surface 25 in a manner that covers the opening of other nozzles 24 that communicate with the nozzle 24 via the common flow path may sometimes flow into the nozzle 24 in the liquid injection section 15, into the independent liquid chamber 86, and then into the common flow path.

[0153] Furthermore, since the pressure reduction operation is performed while the pressurized residue remains in the liquid injection section 15 during the pressurized discharge operation, when the pressure reduction operation is performed while allowing the flow of liquid in the liquid return flow path 31, foreign matter attached to the nozzle surface 25 that flows into the liquid injection section 15, including liquids of different types, may flow into the liquid return flow path 31 through the common flow path and the second discharge outlet 96b, which serves as the discharge outlet.

[0154] Therefore, the control unit 111 performs a pressure reduction operation when the flow of liquid in the liquid return flow path 31 is blocked. In this embodiment, the control unit 111 performs the pressure reduction operation while closing the first return valve 97a and the second return valve 97b, which are return valves provided in the liquid return flow path 31. As a result, even if foreign matter adhering to the nozzle surface 25, including liquids of different types, flows into the liquid injection section 15 during the pressure reduction operation, the inflow into the liquid return flow path 31 can be reduced.

[0155] Furthermore, after the pressure drop operation, the liquid injection device 11 performs a wiping action on the nozzle surface 25 while the flow of liquid in the liquid return path 31 is blocked. For example... Figure 12 As shown, in this embodiment, after the pressure reduction action, the control unit 111 drives the wiping mechanism 133 to perform the wiping action while the first return valve 97a and the second return valve 97b, which serve as return valves, are closed. Since the pressure in the common flow path becomes positive pressure after the pressure reduction action, forming a convex meniscus in the nozzle 24, when the meniscus is damaged during the wiping action, the liquid and air adhering to the nozzle surface 25 are less likely to flow into the liquid injection section 15 compared to when the meniscus is damaged when the pressure in the common flow path is the ejection pressure. Therefore, during the wiping action, the inflow of liquid and air adhering to the nozzle surface 25 into the liquid injection section 15 can be reduced, and the state of the nozzle surface 25 after the pressure reduction action can be adjusted. Furthermore, since the wiping action is performed while the flow of liquid in the liquid return flow path 31 is blocked, even if the meniscus formed in the nozzle 24 is damaged during the wiping action, the inflow of liquid and air adhering to the nozzle surface 25 into the liquid return flow path 31 through the nozzle 24 can also be reduced.

[0156] Furthermore, after the wiping action, the liquid jetting device 11 performs a rinsing action while the flow of liquid in the liquid return path 31 is blocked. For example... Figure 13As shown, in this embodiment, the control unit 111 performs a flushing operation to drive the ejection element 89 of the liquid injection unit 15 to eject liquid from the nozzle 24 while the first return valve 97a and the second return valve 97b, which are provided in the liquid return flow path 31 as return valves, are closed. This allows adjustment of the state of the nozzle 24 after the wiping operation. For example, if the pressure in the common flow path is higher than the ejection pressure after the wiping operation, the flushing operation can make the pressure in the common flow path equal to the ejection pressure, forming a concave meniscus in the nozzle 24. Furthermore, if foreign matter, liquids including different types of liquids, or air flow into the liquid injection unit 15, it can be discharged from the nozzle 24. In this case, for example, the flushing operation can also discharge liquid exceeding the liquid volume in the liquid injection unit 15 from the nozzle 24.

[0157] Furthermore, after the pressurized discharge operation, if the ejection element 89 corresponding to the nozzle 24, whose state is unstable, is driven to eject liquid from the nozzle 24, the unstable state of either the nozzle 24 or the independent liquid chamber 86 communicating with the nozzle 24 may be further aggravated. An unstable state of either the nozzle 24 or the independent liquid chamber 86 communicating with the nozzle 24 refers to, for example, the presence of air bubbles in either the liquid within the nozzle 24 or the independent liquid chamber 86, a high viscosity in either the liquid within the nozzle 24 or the independent liquid chamber 86, the presence of foreign matter near the opening of the nozzle 24, or the liquid adhering to the nozzle surface 25 being connected to the liquid within the nozzle 24 without forming a meniscus in the nozzle 24; that is, a state in which the nozzle is presumed to be abnormal based on the detection results of the ejection state detection unit 113. After the pressurized discharge operation, the liquid discharged from the nozzle 24 during the pressurized discharge operation may sometimes remain attached to the nozzle surface 25 in a manner that covers the opening of the nozzle 24. When the ejection element 89 corresponding to the nozzle 24, which is covered by liquid adhering to the nozzle surface 25 and does not form a curved surface, is driven to eject liquid from the nozzle 24, the liquid adhering to the nozzle surface 25 may increase due to pressure fluctuations generated within the independent liquid chamber 86, or air may be introduced from the opening of the nozzle 24 into the independent liquid chamber 86. As a result, the unstable state of either the nozzle 24 or the independent liquid chamber 86 communicating with the nozzle 24 may be further exacerbated.

[0158] Therefore, in this embodiment, the control unit 111 of the liquid injection device 11 performs a status detection operation and a flushing operation as a pressure reduction operation after the pressurization and discharge operation. In the status detection operation, the injection status detection unit 113, which serves as the status detection unit, detects the status of the nozzle 24 and the independent liquid chamber 86. In the flushing operation, the ejection element 89 corresponding to the nozzle 24, which is presumed to be a normal nozzle based on the detection result of the status detection operation, is driven, thereby causing the liquid to be ejected from the nozzle 24. It should be noted that in the following description, the flushing operation will also be referred to as the pressure reduction flushing operation.

[0159] In this embodiment, after the pressurization and discharge operation, the control unit 111 performs a state detection operation to determine the nozzle 24 capable of ejecting liquid, causing the ejection state detection unit 113 to detect the state of the nozzle 24 and the independent liquid chamber 86. During the state detection operation, the detection drive signal applied to each ejection element 89 is different from the ejection drive signal applied to the ejection element 89 to eject droplets from the nozzle 24, and is set to a specification that liquid will not be ejected from the nozzle 24. Furthermore, the pressure fluctuation generated in the independent liquid chamber 86 is smaller than the pressure fluctuation generated in the independent liquid chamber 86 when the ejection drive signal is applied to the ejection element 89.

[0160] In this embodiment, the control unit 111, based on the vibration waveform of the independent liquid chamber 86 detected by the jet state detection unit 113, estimates the position of the gas-liquid interface of the nozzle-side liquid connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side, thereby estimating whether liquid can be ejected from the nozzle 24. For example, if the estimated position of the gas-liquid interface of the nozzle-side liquid is located further vertically below the position of the meniscus when the nozzle 24 forms a convex meniscus, the control unit 111 estimates that the nozzle 24 is covered by liquid adhering to the nozzle surface 25 and cannot eject liquid. Furthermore, for example, if the estimated position of the gas-liquid interface of the nozzle-side liquid is within the range of the position of the gas-liquid interface when the nozzle 24 is maintained as a convex meniscus in the gravitational direction, the control unit 111 estimates that the nozzle 24 has a convex meniscus and liquid can be ejected. Furthermore, for example, if the position of the gas-liquid interface of the nozzle-side liquid is within the range of the position of the gas-liquid interface in the direction of gravity when the nozzle 24 is maintained as a concave curved liquid surface, the control unit 111 may assume that liquid can be ejected when the nozzle 24 has a concave curved liquid surface.

[0161] Furthermore, the control unit 111 can also estimate the position of the gas-liquid interface of the liquid on the nozzle side connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side and the pressure inside the common flow path based on the vibration waveform of the independent liquid chamber 86 detected by the injection state detection unit 113. For example, when liquid is ejected vertically downward from the nozzle 24 of the liquid injection unit 15, if the estimated position of the gas-liquid interface of the liquid on the nozzle side is located further vertically downward than the position of the gas-liquid interface when the nozzle 24 is maintained in a convex meniscus, the control unit 111 estimates that the pressure inside the common flow path is a positive pressure higher than the pressure of the convex meniscus that forms the liquid that can be ejected from the nozzle 24, for example, +1.1 kPa to +2 kPa using a gauge pressure gauge. Furthermore, for example, if the position of the gas-liquid interface of the nozzle-side liquid, as predicted, is within the range of the position of the gas-liquid interface in the direction of gravity when the nozzle 24 is maintained as a convex meniscus, the control unit 111 presumes that the pressure inside the common flow path is a predetermined pressure that is lower than the pressure inside the common flow path during the pressurized discharge operation and higher than the ejection pressure. Here, the predetermined pressure is the pressure that forms the convex meniscus capable of ejecting liquid from the nozzle 24, for example, +0.1 kPa to +1 kPa using a gauge pressure gauge. Furthermore, for example, if the position of the gas-liquid interface of the nozzle-side liquid, as predicted, is located inside the nozzle 24 further than the nozzle surface 25, the control unit 111 presumes that the pressure inside the common flow path is a negative pressure that forms the gas-liquid interface within the nozzle 24, for example, -0.1 kPa to -3.5 kPa using a gauge pressure gauge. Furthermore, for example, if the position of the gas-liquid interface of the nozzle-side liquid, as predicted, is within the range of the gas-liquid interface position when the nozzle 24 maintains a concave meniscus during the printing operation of ejecting liquid from the nozzle 24 toward the medium 12, the control unit 111 presumes that the pressure inside the common flow path is the ejection pressure, for example, -0.5 kPa to -3 kPa using a gauge pressure gauge. Furthermore, for example, if the position of the gas-liquid interface of the nozzle-side liquid, as predicted, is located inside the nozzle 24 in the gravity direction and is further vertically above the range of the gas-liquid interface position when the nozzle 24 maintains a concave meniscus during the printing operation of ejecting liquid from the nozzle 24 toward the medium 12, the control unit 111 presumes that the pressure inside the common flow path is a negative pressure lower than the ejection pressure, for example, -3.1 kPa to -3.5 kPa using a gauge pressure gauge.

[0162] After the initial state detection operation performed before the pressure drop flushing operation, the control unit 111 repeatedly performs the state detection operation. The control unit 111 may also apply a detection drive signal to the ejection element 89 corresponding to each nozzle 24 during the initial state detection operation and the state detection operation performed after droplets are ejected from the nozzle 24 during the pressure drop flushing operation. In this case, for example, for the nozzle 24 used for the pressure drop flushing operation, the state detection operation may be repeatedly performed by alternately applying the ejection drive signal and the detection drive signal to the ejection element 89.

[0163] Alternatively, during the initial state detection operation, the control unit 111 applies a detection drive signal to the ejection element 89 corresponding to each nozzle 24. Then, during subsequent state detection operations, the control unit 111 may apply a detection drive signal to the ejection element 89 corresponding to the nozzle 24 for nozzles 24 not used for the pressure drop flushing operation, and for nozzles 24 used for the pressure drop flushing operation, not apply a detection drive signal to the ejection element 89, but instead apply an ejection drive signal to the ejection element 89 to eject droplets from the nozzle 24. In this case, the control unit 111 may also repeat the state detection operation each time droplets are ejected from the nozzle 24 during the pressure drop flushing operation for nozzles 24 used for the pressure drop flushing operation.

[0164] Figures 15A-15C This is a schematic cross-sectional view illustrating the liquid jet section 15 of the pressure drop flushing operation according to Embodiment 1. For example, in... Figure 15A When multiple nozzles 24 are set to #1 to #6 as shown, in the case of... Figure 11A If a status detection operation is performed after the pressurized discharge operation, with the openings of nozzles 24 #1 to #6 covered by liquid adhering to the nozzle surface 25, the control unit 111 infers, based on the detection results of the status detection operation, that there are no nozzles 24 with curved surfaces, and therefore no nozzles 24 capable of ejecting liquid. Furthermore, in situations such as Figure 11B When the openings of nozzles 24 #1 and #6 are covered by liquid adhering to the nozzle surface 25, and the state detection operation is performed when nozzles 24 #2 to #5 have convex curved liquid surfaces, the control unit 111 infers from the detection results of the state detection operation that nozzles 24 #2 to #5 have convex curved liquid surfaces and that nozzles 24 #2 to #5 are nozzles 24 capable of ejecting liquid.

[0165] Next, as Figure 15AAs shown, the control unit 111 performs a pressure-reducing flushing operation by applying a spraying drive signal to drive the spraying elements 89 corresponding to nozzles 24 #2 to #5, which are presumed to be capable of spraying liquid. Therefore, after the pressurized discharge operation, by driving the spraying elements 89 corresponding to nozzles 24 #1 and #6, where liquid adhering to the nozzle surface 25 covers the opening of the nozzle 24 and does not form a meniscus, it is possible to reduce the increase of liquid adhering to the nozzle surface 25 or the introduction of air from the opening of the nozzle 24 into the independent liquid chamber 86. In other words, since the pressure-reducing flushing operation is performed using nozzles 24 #2 to #5 capable of spraying liquid after the pressurized discharge operation, the deterioration of the unstable state of the nozzles 24 in the liquid spraying unit 15 can be reduced through the maintenance operation of the liquid spraying unit 15. By ejecting liquid from nozzles 24 #2 to #5 during the pressure drop flushing action, the liquid in the liquid injection section 15 is discharged from nozzles 24 #2 to #5, causing a pressure drop in the common flow path. As a result, such as... Figure 15B As shown, the liquid adhering to the nozzle surface 25 in a manner that covers the openings of nozzles 24 of #1 and #6 flows into the liquid injection section 15 through nozzles 24 of #1 and #6, and the amount of liquid adhering to the nozzle surface 25 is reduced.

[0166] Considering that the state of the curved liquid surface formed in the nozzle 24 differs from that during the printing operation, the driving method (driving specification) of the ejector element 89 in the pressure-reducing flushing operation can be different from the driving method of the ejector element 89 in the flushing operation performed as a second discharge operation during the printing operation. As a result, for example, the size of the droplets ejected from the nozzle 24 in the pressure-reducing flushing operation can be smaller compared to the size of the droplets ejected from the nozzle 24 in the flushing operation as a second discharge operation. Furthermore, for example, the ejection velocity of the droplets ejected from the nozzle 24 in the pressure-reducing flushing operation can be faster compared to the ejection velocity of the droplets ejected from the nozzle 24 in the flushing operation as a second discharge operation.

[0167] In such Figure 15B When the state detection operation is performed under the conditions shown, since the nozzles 24 #1 to #5 have convex menisci, they are presumed to be nozzles 24 capable of ejecting liquid. However, in this embodiment, the control unit 111 continues to perform a pressure reduction flushing operation by driving the ejection elements 89 corresponding to the nozzles 24 #2 to #5 to eject liquid from the nozzles 24 #2 to #5 during the pressure reduction flushing operation. This causes the liquid in the liquid injection unit 15 to be discharged from the nozzles 24 #2 to #5, further reducing the pressure within the common flow path.

[0168] Then, based on the detection results of the executed state detection actions, it is inferred that it is as follows: Figure 15CWhen nozzles #1 to #6, which are multiple nozzles communicating with the common liquid chamber 85, have convex curved liquid surfaces as shown, the control unit 111 terminates the pressure reduction flushing operation. For example, the control unit 111 terminates the pressure reduction flushing operation if, based on the detection results of a state detection operation performed before the pressure reduction flushing operation, it is deduced that liquid can be ejected from nozzles #1 and #6, which are deduced to be unable to eject liquid. Alternatively, the control unit 111 may also terminate the pressure reduction flushing operation as follows: Figure 15C If, under the conditions shown, the detection results of the executed state detection operation indicate that a convex meniscus has formed on nozzles 24 #1 to #6, the pressure reduction flushing operation is terminated. Alternatively, the control unit 111 may terminate the pressure reduction flushing operation if, based on the detection results of the executed state detection operation, the pressure inside the common flow path becomes a predetermined pressure that is lower than the pressure inside the common flow path during the pressurized discharge operation but higher than the ejection pressure.

[0169] In addition, such as Figure 12 As shown, the control unit 111 drives the wiping mechanism 133 to perform a wiping action after the pressure drop flushing action. Since the pressure inside the common flow path becomes positive pressure after the pressure drop flushing action, forming a convex meniscus in the nozzle 24, the liquid and air adhering to the nozzle surface 25 are less likely to flow into the liquid injection section 15 compared to the cases where the meniscus is damaged during the wiping action or when the pressure inside the common flow path is the ejection pressure. Therefore, during the wiping action, the flow of air from the opening of the nozzle 24 into the liquid injection section 15 can be reduced, and the state of the nozzle surface 25 after the pressure drop action can be adjusted.

[0170] In addition, such as Figure 13As shown, after the pressure drop flushing action and the wiping action, the control unit 111 drives the ejection elements 89 corresponding to the nozzles 24 (#1 to #6) that communicate with the common liquid chamber 85 to perform the post-flushing action. This allows adjustment of the state of the nozzles 24 after the wiping action. For example, if the pressure inside the common flow path after the wiping action is a negative pressure higher than the ejection pressure, the post-flushing action can make the pressure inside the common flow path equal to the ejection pressure. Furthermore, since the post-flushing action is performed with the nozzles 24 having a curved liquid surface, the probability of liquid or air bubbles being introduced from the nozzles 24 and adhering to the nozzle surface 25 due to pressure fluctuations generated in the individual liquid chamber 86 is low. Therefore, during the post-rinsing operation, for nozzles 24 that are presumed to be abnormal nozzles due to the presence of air bubbles in either the nozzle 24 or the liquid in the independent liquid chamber 86, or due to high viscosity of either the nozzle 24 or the liquid in the independent liquid chamber 86, the corresponding ejection element 89 can be driven to eject during the post-rinsing operation. This improves the condition of either the nozzle 24 or the liquid in the independent liquid chamber 86 that is presumed to be abnormal. Furthermore, in the event that foreign matter, including different types of liquid, or air flows into the liquid injection section 15, it can be discharged from the nozzle 24 by performing the post-rinsing operation. In this case, for example, the post-rinsing operation can also discharge liquid exceeding the liquid volume in the liquid injection section 15 from the nozzle 24.

[0171] Next, refer to Figure 14 The flowchart shown illustrates the process executed by the control unit 111 of the liquid injection device 11 when performing maintenance operations including pressurization and discharge. In this embodiment, the process executed by the control unit 111 when performing maintenance operations including pressurization and discharge corresponds to the maintenance method of the liquid injection device 11. This series of processes executed by the control unit 111 can be performed according to each pre-set control cycle, or based on the detection results of the injection status detection unit 113, or manually by the operator of the liquid injection device 11.

[0172] like Figure 14 As shown, in step S11, the control unit 111 closes the first return valve 97a and the second return valve 97b to perform a pressurized discharge operation. Specifically, the control unit 111 controls the drive of the pressing mechanism 49, causing the diaphragm 56 to displace in the direction of decreasing volume in the liquid outlet 51, thereby opening the supply valve 59. In this way, by causing the pressurized liquid to flow into the liquid outlet 51, the liquid supply path 50, the common liquid chamber 85, the independent liquid chamber 86, and the nozzle 24, liquid is discharged from the nozzle 24. During the pressurized discharge operation, as... Figure 10As shown, liquid is continuously discharged from each nozzle 24.

[0173] Next, after the control unit 111 stops pressurizing the liquid injection section 15, which includes the common flow path, and ends the pressurization discharge operation, a pressure reduction flushing operation is performed in step S12. Specifically, the control unit 111 controls the drive of the pressing mechanism 49, causing the diaphragm 56 to move in the direction of increasing volume of the liquid outlet 51, thereby closing the supply valve 59 and ending the pressurization discharge operation. As a result, pressurized liquid is no longer supplied to the downstream side of the liquid outlet 51 of the pressure regulating mechanism 48, but because the positive pressure from the pressurization discharge operation remains in the liquid outlet 51, the liquid injection section 15, and the liquid supply flow path 30 between the liquid outlet 51 and the liquid injection section 15, liquid continues to flow out from the nozzle 24.

[0174] After the pressurization and discharge action, the control unit 111 repeatedly executes a state detection action, causing the injection state detection unit 113 to detect the state of either the nozzle 24 or the independent liquid chamber 86, in order to predict which nozzle 24 can eject liquid. For example, in such a case... Figure 11B As shown, when the openings of nozzles 24 #1 and #6 are covered by liquid adhering to the nozzle surface 25, and a state detection operation is performed while nozzles 24 #2 to #5 have convex menisci, the control unit 111 infers from the state detection operation results that nozzles 24 #2 to #5 have convex menisci and are nozzles 24 capable of ejecting liquid. Figure 15A As shown, the control unit 111 drives the ejection element 89 corresponding to the nozzles 24 #2 to #5, which are presumed to be capable of ejecting liquid, to perform a pressure reduction flushing operation.

[0175] Then, based on the detection results of the executed state detection actions, it is inferred that it is as follows: Figure 15C When nozzles #1 to #6, which are multiple nozzles communicating with the common liquid chamber 85, have convex curved liquid surfaces as shown, the control unit 111 terminates the pressure reduction flushing operation. For example, the control unit 111 terminates the pressure reduction flushing operation if, based on the detection results of a state detection operation performed before the pressure reduction flushing operation, it is deduced that liquid can be ejected from nozzles #1 and #6, which are deduced to be unable to eject liquid. Alternatively, the control unit 111 may also terminate the pressure reduction flushing operation as follows: Figure 15CIf, under the conditions shown, the control unit 111 determines that a convex meniscus has formed on nozzles 24 #1 to #6 based on the detection results of the executed state detection operation, the pressure reduction flushing operation is terminated. Alternatively, the control unit 111 may determine the position of the gas-liquid interface between the nozzle 24 and the liquid in the independent liquid chamber 86 based on the detection results of the executed state detection operation, and terminate the pressure reduction flushing operation if the pressure in the common flow path is determined to be a predetermined pressure that is lower than the pressure in the common flow path during the pressurized discharge operation and higher than the ejection pressure. Alternatively, the control unit 111 may determine that, based on the detection results of the executed state detection operation, liquid can be ejected from nozzles 24 #1 and #6, which were determined to be unable to eject liquid based on the detection results of the state detection operation performed before the pressure reduction flushing operation, and the pressure in the common flow path becomes a predetermined pressure that is lower than the pressure in the common flow path during the pressurized discharge operation and higher than the ejection pressure, the pressure reduction flushing operation is terminated.

[0176] After the pressure drop flushing action ends, the control unit 111 drives the wiping mechanism 113 in step S13 to perform a final wiping action to wipe the nozzle surface 25. The wiping action is performed with the first return valve 97a and the second return valve 97b in the closed state. Through this wiping action, liquid and foreign matter adhering to the nozzle surface 25 are removed.

[0177] Then, after the pressure reduction flushing action and the wiping action, in step S14, the control unit 111 drives the ejection elements 89 corresponding to the nozzles #1 to #6 of the plurality of nozzles 24 communicating with the common liquid chamber 85 to perform a post-flushing action as the final flushing action. The post-flushing action is performed with the first return valve 97a and the second return valve 97b in the closed state. By performing the post-flushing action, the state of the nozzles 24 after the wiping action can be adjusted. For example, if the pressure in the common flow path is higher than the ejection pressure after the wiping action, the post-flushing action can make the pressure in the common flow path equal to the ejection pressure. In addition, if foreign matter, liquid including different types of liquid, or air flows into the liquid injection section 15 after the pressurized discharge action, it can also be discharged from the nozzles 24 by performing the post-flushing action. In this case, for example, liquid exceeding the liquid volume in the liquid injection section 15 can also be discharged from the nozzles 24 by the post-flushing action. It should be noted that the driving method of the ejector element 89 in the post-rinse action can also be the same as the driving method of the ejector element 89 in the rinsing action, which is the second discharge action performed in the printing action.

[0178] As described above, the following effects can be obtained according to Embodiment 1.

[0179] The liquid injection device 11 includes: a liquid injection section 15 having a common liquid chamber 85 into which liquid can flow, a plurality of independent liquid chambers 86 communicating with the common liquid chamber 85, nozzles 24 communicating with the independent liquid chambers 86, nozzle surfaces 25 through which the plurality of nozzles 24 open, and an ejection element 89, wherein the liquid injection section 15 can eject the liquid from the nozzles 24 toward the medium 12 by driving the ejection element 89; a supply pump 39A and a pressure regulating device 40 as a pressurizing mechanism, which can pressurize the liquid in the common liquid chamber 85; and an injection state detection section 113, which can detect the nozzles 24 and The state of any of the independent liquid chambers 86; and the control unit 111, which performs: a pressurization discharge operation, in which the liquid in the common liquid chamber 85 is pressurized by the pressurization mechanism to discharge the liquid from the nozzle 24; a state detection operation, in which the jet state detection unit 113 detects the state after the pressurization discharge operation; and a pressure reduction flushing operation, in which the liquid is ejected from the nozzle 24 by driving the ejection element 89 corresponding to the nozzle 24 that is presumed to be able to eject the liquid based on the detection result of the state detection operation.

[0180] Therefore, since a pressure drop flushing action is performed by using a nozzle 24 that can eject liquid as a flushing action after the pressurized discharge action, the maintenance action of the liquid injection section 15 can reduce the deterioration of the unstable state of the nozzle 24 in the liquid injection section 15.

[0181] If the control unit 111 of the liquid injection device 11 determines, based on the detection result of the state detection operation performed after the liquid is ejected from the nozzle 24 during the rinsing operation, that the liquid can be ejected from the nozzle 24, which was previously thought to be unable to eject the liquid before the rinsing operation was performed, the rinsing operation is terminated. Accordingly, the ejection of liquid during the pressure reduction rinsing operation can be appropriately performed.

[0182] When the pressure of the liquid in the common liquid chamber 85 is set to the common flow path internal pressure, and the pressure of the common flow path when the liquid is ejected from the nozzle 24 toward the medium 12 is set to the ejection pressure, the control unit 111, based on the detection result of the state detection operation performed after the liquid is ejected from the nozzle 24 during the rinsing operation, deduces that the pressure of the common flow path is a predetermined pressure that is lower than the pressure of the common flow path during the pressurized discharge operation and higher than the ejection pressure. In this case, the control unit 111 ends the rinsing operation and performs a post-rinsing operation by driving the ejection element 89 corresponding to the plurality of nozzles 24 to eject the liquid from the plurality of nozzles 24. Accordingly, maintenance operations including the pressurized discharge operation can be performed efficiently.

[0183] The liquid jetting device 11 includes a wiping mechanism 133 capable of performing a wiping action on the nozzle surface 25. After the rinsing action, the control unit 111 of the liquid jetting device 11 drives the wiping mechanism 133 to perform the wiping action and performs the post-rinsing action. Accordingly, maintenance actions including pressurized discharge actions can be appropriately performed.

[0184] The maintenance method for the liquid jetting device 11 is as follows: the liquid jetting device includes a liquid jetting section 15, which has a common liquid chamber 85 into which liquid can flow, a plurality of independent liquid chambers 86 communicating with the common liquid chamber 85, nozzles 24 communicating with the independent liquid chambers 86, nozzle surfaces 25 through which the plurality of nozzles 24 open, and ejection elements 89. The liquid jetting section 15 can eject the liquid from the nozzles 24 toward the medium 12 by driving the ejection elements 89. The maintenance method for the liquid jetting device 11 includes: performing a pressurized discharge operation by pressurizing the liquid in the common liquid chamber 85 to discharge the liquid from the nozzles 24; after the pressurized discharge operation, determining whether the liquid can be ejected from the nozzles 24; and performing a pressure-reducing flushing operation as a flushing operation by driving the ejection elements 89 corresponding to the nozzles 24 that are determined to be able to eject the liquid to eject the liquid from the nozzles 24.

[0185] Therefore, since a pressure drop flushing action is performed by using a nozzle 24 that can eject liquid as a flushing action after the pressurized discharge action, the maintenance action of the liquid injection section 15 can reduce the deterioration of the unstable state of the nozzle 24 in the liquid injection section 15.

[0186] In the maintenance method of the liquid jetting device 11, the rinsing operation is terminated when a nozzle 24, which was presumed to be unable to jet out liquid before the rinsing operation was performed because its opening was covered by the liquid adhering to the nozzle surface 25, becomes capable of jetting liquid. Accordingly, the jetting of liquid during the pressure reduction rinsing operation can be appropriately performed.

[0187] In the maintenance method of the liquid injection device 11, when the pressure in the common liquid chamber 85 is set to the common flow path internal pressure, and the pressure in the common flow path when the liquid is ejected from the nozzle 24 toward the medium 12 is set to the ejection pressure, if the pressure in the common flow path becomes a predetermined pressure that is lower than the pressure in the common flow path during the pressurized discharge operation but higher than the ejection pressure, the flushing operation is terminated, and a post-flushing operation is performed to eject the liquid from the plurality of nozzles 24 by driving the ejection element 89 corresponding to the plurality of nozzles 24. Accordingly, maintenance operations including the pressurized discharge operation can be performed efficiently.

[0188] In the maintenance method of the liquid injection device 11, after the rinsing action, a wiping action is performed to wipe the nozzle surface 25, and then the post-rinsing action is performed. Accordingly, maintenance actions including pressurized discharge actions can be appropriately performed.

[0189] 2. Implementation Method Two

[0190] Next, the pressure drop flushing operation involved in Embodiment 2 will be described. The pressure drop flushing operation in this embodiment is a modification of the pressure drop flushing operation in Embodiment 1 described above. In this embodiment, the processing flow performed by the control unit 111 when performing the pressure drop flushing operation is equivalent to the maintenance method of the liquid injection device 11. It should be noted that, since this embodiment shows the pressure drop flushing operation in Embodiment 1 described above... Figure 15C And subsequently changed, therefore mainly regarding Figure 15B And will be explained thereafter.

[0191] Similar to implementation method one, such as Figure 15A As shown, the control unit 111 drives the ejection elements 89 corresponding to nozzles 24 #2 to #5, which are presumed to be capable of ejecting liquid, to perform a pressure-reducing flushing operation. During the pressure-reducing flushing operation, liquid is ejected from nozzles 24 #2 to #5, and the liquid in the liquid injection section 15 is discharged from nozzles 24 #2 to #5, causing a pressure drop in the common flow path. As a result, as... Figure 15B As shown, liquid adhering to the nozzle surface 25 in a manner that covers the openings of nozzles 24 of #1 and #6 flows into the liquid injection section 15 through nozzles 24 of #1 and #6, thereby reducing the amount of liquid adhering to the nozzle surface 25.

[0192] In such Figure 15B When the state detection operation is performed under the conditions shown, since convex menisci are formed in nozzles 24 #1 to #5, nozzles 24 #1 to #5 are presumed to be nozzles 24 capable of ejecting liquid. However, in this embodiment, the control unit 111 continues to perform a pressure reduction flushing operation by driving the ejection elements 89 corresponding to nozzles 24 #2 to #5 to eject liquid from nozzles 24 #2 to #5 during the pressure reduction flushing operation, causing the liquid in the liquid injection section 15 to be discharged from nozzles 24 #2 to #5, and further reducing the pressure in the common flow path.

[0193] In such Figure 15CWhen the state detection operation is performed under the conditions shown, convex menisci are formed in nozzles 24 #1 to #6, and nozzles 24 #1 to #6 are presumed to be able to eject liquid. However, unlike Embodiment 1, in this embodiment, the control unit 111 continues to perform a pressure reduction flushing operation by driving the ejection elements 89 corresponding to nozzles 24 #2 to #5 to eject liquid from nozzles 24 #2 to #5 during the pressure reduction flushing operation, causing the liquid in the liquid injection unit 15 to be discharged from nozzles 24 #2 to #5, and further reducing the pressure in the common flow path.

[0194] In this embodiment, by continuing the pressure reduction flushing action, the pressure inside the common flow path is further reduced from... Figure 15C If, based on the detection results of the executed state detection operation, it is deduced that a concave meniscus has formed within at least nozzles 24 #2 to #5, the control unit 111 terminates the pressure reduction flushing operation. For example, the control unit 111 may also, in the aforementioned state, deduce the position of the gas-liquid interface between the nozzle-side liquid and the liquid in the independent liquid chamber 86 on the nozzle 24 side based on the detection results of the state detection operation performed on the nozzles 24 used for the pressure reduction flushing operation. If the deduced position of the gas-liquid interface is located further inside the nozzle 24 than the nozzle surface 25, the control unit 111 may terminate the pressure reduction flushing operation if, based on the detection results of the executed state detection operation, it deduces the position of the gas-liquid interface between the nozzle-side liquid and the liquid in the independent liquid chamber 86 on the nozzle 24 side, and the pressure in the common flow path is deduced to be a negative pressure lower than atmospheric pressure.

[0195] Therefore, the control unit 111 of this embodiment does not perform... Figure 14Steps S13 and S14 in the flowchart shown. Furthermore, the pressure inside the common flow path when the pressure drop flushing operation ends can also be within the range of the ejection pressure. In this case, the control unit 111 can also estimate the position of the gas-liquid interface of the nozzle-side liquid connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side based on the detection results of the state detection operation. If the estimated position of the gas-liquid interface of the nozzle-side liquid is within the range of the position of the gas-liquid interface when the nozzle 24 maintains a concave curved liquid surface during the printing operation in the direction of gravity, where the liquid is ejected from the nozzle 24 towards the medium 12, the pressure drop flushing operation ends. Alternatively, the control unit 111 can also end the pressure drop flushing operation if the pressure inside the common flow path is estimated to be within the range of the ejection pressure based on the detection results of the state detection operation. Furthermore, if the nozzle surface 25 is provided with multiple nozzle rows L corresponding to various liquids, there is a possibility that liquids including different types of liquids may flow into the liquid injection section 15 after the pressurized discharge operation. In this situation, the control unit 111 can also discharge liquid exceeding the liquid volume in the liquid injection unit 15 from the nozzle 24 through a pressure reduction flushing action.

[0196] As described above, the following effects can be obtained according to Embodiment 2.

[0197] When the pressure of the liquid in the common liquid chamber 85 is set to the pressure inside the common flow path, the control unit 111 of the liquid injection device 11, based on the detection result of the state detection operation performed after the liquid is ejected from the nozzle 24 during the flushing operation, deduces that the gas-liquid interface formed on the nozzle 24 is located closer to the inside of the nozzle 24 than the nozzle surface 25, and then terminates the flushing operation. Accordingly, the ejection of liquid during the pressure reduction flushing operation can be appropriately performed.

[0198] In the maintenance method of the liquid injection device 11, the flushing operation is terminated when the gas-liquid interface formed on the nozzle 24 is located inside the nozzle 24, closer to the nozzle surface 25. Accordingly, the liquid can be appropriately ejected during the pressure reduction flushing operation.

[0199] 3. Implementation Method Three

[0200] Figures 16A-16C This is a schematic cross-sectional view of the liquid jetting unit 15 in the pressure drop flushing operation according to Embodiment 3. This embodiment is obtained by modifying the pressure drop flushing operation in Embodiment 1 described above. In this embodiment, the processing flow performed by the control unit 111 during the pressure drop flushing operation is equivalent to the maintenance method of the liquid jetting device 11.

[0201] For example, in such Figure 16A When multiple nozzles 24 are set to #1 to #6 as shown, in the case of... Figure 11A If a state detection operation is performed with the openings of nozzles 24 #1 to #6 covered by liquid adhering to the nozzle surface 25, the control unit 111 infers, based on the detection results of the state detection operation, that there are no nozzles 24 with curved surfaces, and therefore no nozzles 24 capable of ejecting liquid. Furthermore, in situations such as Figure 11B When the openings of nozzles 24 #1 and #6 are covered by liquid adhering to the nozzle surface 25, and the state detection operation is performed when nozzles 24 #2 to #5 have convex menisci, similar to Embodiment 1, the control unit 111 infers from the detection result of the state detection operation that nozzles 24 #2 to #5 have convex menisci and that nozzles 24 #2 to #5 are nozzles 24 capable of ejecting liquid.

[0202] Next, similar to Embodiment 1, the control unit 111 drives the ejection elements 89 corresponding to nozzles 24 #2 to #5, which are presumed to be capable of ejecting liquid, to perform a pressure-reducing flushing operation. By ejecting liquid from the nozzles 24 during the pressure-reducing flushing operation, the liquid in the liquid injection section 15 is discharged from nozzles 24 #2 to #5, and the pressure in the common flow path decreases. As a result, the liquid adhering to the nozzle surface 25 in a manner covering the openings of nozzles 24 #1 and #6 flows into the liquid injection section 15 through nozzles 24 #1 and #6, reducing the amount of liquid adhering to the nozzle surface 25. Figure 16A As shown, a convex curved liquid surface is formed at nozzle 24 of #1.

[0203] When a state detection operation is performed with nozzle 24 #1 having a convex meniscus, since nozzles 24 #1 to #5 also have convex menisci, nozzles 24 #1 to #5 are presumed to be nozzles capable of ejecting liquid. In this case, unlike Embodiment 1, as... Figure 16A As shown, in this embodiment, the control unit 111, in addition to the ejection drive of the ejection element 89 corresponding to the nozzles 24 of #2 to #5, also adds the ejection drive of the ejection element 89 corresponding to the nozzle 24 of #1 to continue the pressure reduction flushing operation. By ejecting liquid from the nozzles 24 of #1 to #5 during the pressure reduction flushing operation, the pressure inside the common flow path is further reduced.

[0204] As a result, when a state detection operation is performed with a reduced amount of liquid adhering to the nozzle surface 25 in a manner that covers the opening of nozzle 24 #6, and a convex meniscus is formed on nozzle 24 #6, since convex menisci are formed on nozzles 24 #1 to #6, nozzles 24 #1 to #6 are presumed to be nozzles 24 capable of ejecting liquid. In this case, unlike Embodiment 1, as... Figure 16BAs shown, in this embodiment, the control unit 111, in addition to the ejection drive of the ejection element 89 corresponding to the nozzles 24 #1 to #5, also adds the ejection drive of the ejection element 89 corresponding to the nozzle 24 #6 to continue the pressure reduction flushing operation. By ejecting liquid from the nozzles 24 #1 to #6 during the pressure reduction flushing operation, the pressure inside the common flow path is further reduced.

[0205] In this embodiment, such as Figure 16C As shown, when nozzles 24 #1 to #6 have concave menisci, the control unit 111 terminates the pressure drop flushing operation based on the detection result of the executed state detection action. For example, the control unit 111 may also terminate the pressure drop flushing operation based on the detection result of the state detection action. Figure 16C The detection result of the state detection operation performed under the state shown is used to estimate the position of the gas-liquid interface of the nozzle-side liquid connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side. If the estimated position of the gas-liquid interface of the nozzle-side liquid is located inside the nozzle 24 further than the nozzle surface 25, the pressure reduction flushing operation ends. Alternatively, the control unit 111 can also adjust the position based on the state detection result as shown. Figure 16C The detection result of the state detection operation performed under the state shown indicates the position of the gas-liquid interface of the liquid on the nozzle side connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side. If the pressure in the common flow path is estimated to be a negative pressure lower than atmospheric pressure, the pressure drop flushing operation ends. Alternatively, the control unit 111 can also determine the position of the gas-liquid interface based on the state detection result performed under the state shown. Figure 16C If the detection result of the state detection action performed under the state shown can be used to terminate the pressure reduction flushing action if the nozzles #1 and #6 24, which are presumed to be unable to eject liquid based on the detection result of the state detection action performed before the pressure reduction flushing action, eject liquid, and the position of the gas-liquid interface of the liquid on the nozzle side is located inside the nozzle 24 more than the nozzle surface 25.

[0206] Therefore, the control unit 111 of this embodiment does not perform... Figure 14 Steps S13 and S14 in the flowchart shown. Furthermore, the pressure within the common flow path at the end of the pressure drop flushing operation can also be within the range of the ejection pressure. In this case, the control unit 111 can also estimate the position of the gas-liquid interface of the nozzle-side liquid connected to the liquid in the independent liquid chamber 86 on the nozzle 24 side based on the detection results of the state detection operation. If the estimated position of the gas-liquid interface of the nozzle-side liquid is within the range of the gas-liquid interface position when the nozzle 24 maintains a concave curved liquid surface during the printing operation in which liquid is ejected from the nozzle 24 toward the medium 12 in the direction of gravity, the pressure drop flushing operation can be terminated. Alternatively, the control unit 111 can also terminate the pressure drop flushing operation if the pressure within the common flow path is estimated to be within the range of the ejection pressure based on the detection results of the state detection operation.

[0207] Furthermore, if the nozzle surface 25 is provided with multiple nozzle rows L corresponding to various liquids, there is a possibility that liquids of different types may flow into the liquid injection section 15 after the pressurized discharge operation. In such a case, the control unit 111 can continue the pressure reduction flushing operation after the pressure in the common flow path becomes within the range of the ejection pressure, thereby preventing... Figure 16C As indicated by the double-dotted arrow, liquid flows into the liquid jet section 15 through the supply port 85a, and liquid exceeding the amount of liquid in the liquid jet section 15 is discharged from the nozzle 24. Furthermore, the control unit 111 can also make the driving method of the ejection element 89 at this time the same as the driving method of the ejection element 89 in the rinsing operation, which is performed as a second discharge operation during the printing operation.

[0208] In addition, for example, such as Figure 16B As shown, when continuing the pressure reduction flushing operation by adding a spray drive for the spray element 89 corresponding to nozzle 24 #6 in addition to the spray drive for nozzles 24 #1 to #5, if the detection result of the executed state detection operation indicates that nozzle 24 #3 is an abnormal nozzle, the control unit 111 can continue the subsequent flushing operation by spraying the spray elements 89 corresponding to nozzles 24 other than #3. Furthermore, if, afterward, the flushing operation continues by spraying the spray elements 89 corresponding to nozzles 24 other than #3, and the detection result of the executed state detection operation indicates that nozzle 24 #3 has returned to a normal nozzle, the control unit 111 can continue the subsequent flushing operation by spraying the spray elements 89 corresponding to nozzles 24 #1 to #6.

[0209] As described above, the following effects can be obtained according to Embodiment 3.

[0210] The control unit 111 of the liquid injection device 11 terminates the rinsing operation if, based on the detection result of the state detection operation performed after the liquid is ejected from the nozzle 24 during the rinsing operation, it deduces that the gas-liquid interface formed on the nozzle 24 is located inside the nozzle 24, closer to the nozzle surface 25. Accordingly, the ejection of liquid during the pressure-reducing rinsing operation can be appropriately performed.

[0211] In the maintenance method of the liquid injection device 11, the flushing operation is terminated when the gas-liquid interface formed on the nozzle 24 is located inside the nozzle 24, closer to the nozzle surface 25. Accordingly, the liquid can be appropriately ejected during the pressure reduction flushing operation.

[0212] The above-described embodiments and other embodiments described below can be combined with each other to implement the invention without technical inconsistencies. The other embodiments will be described below.

[0213] The liquid jetting device 11 can have a different driving mode in the post-rinse action than the driving mode of the ejector element 89 in the rinsing action, which is performed as a second discharge action during the printing process, or the driving mode in the post-rinse action can be different from the driving mode of the ejector element 89 in the pressure-reducing rinsing action. As a result, for example, the size of the liquid droplets ejected in the post-rinse action may be smaller than the size of the liquid droplets ejected in the rinsing action, which is performed as a second discharge action, and larger than the size of the liquid droplets ejected in the pressure-reducing rinsing action. Furthermore, for example, the ejection speed of the liquid droplets ejected in the post-rinse action may be faster than the ejection speed of the liquid droplets ejected in the rinsing action, which is performed as a second discharge action, and slower than the ejection speed of the liquid droplets ejected in the pressure-reducing rinsing action.

[0214] The liquid injection device 11 may also include an electrothermal conversion element, such as a heater, capable of heating the liquid in the independent liquid chamber as the ejection element 89 of the liquid injection unit 15. 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, causing it to produce film boiling, thereby ejecting the liquid from the nozzle 24. In this case, the liquid injection device 11 may also include a temperature detection element as a state detection unit, arranged corresponding to the heater. Then, the control unit 111 determines whether liquid can be ejected from the nozzle 24 by comparing the highest temperature detected by the temperature detection element during liquid injection in the state of the independent liquid chamber 86 with a predetermined threshold, or by the difference in temperature change during liquid injection in the state of the independent liquid chamber 86.

[0215] The liquid jetting device 11 may also include an optical device capable of detecting the state of the nozzle surface 25, including the nozzle 24. For example, the liquid jetting device 11 may also include an optical sensor capable of measuring the distance in the gravitational direction between the nozzle surface 25 of the liquid jetting unit 15 and the gas-liquid interface of the liquid present at the position of the nozzle 24. The optical sensor can detect the position of the gas-liquid interface of the liquid present at the position of the nozzle 24, which is the state of the nozzle 24. In this case, the control unit 111 can also determine whether a meniscus is formed at the nozzle 24 based on the position of the gas-liquid interface of the liquid present at the position of the nozzle 24 detected by the optical sensor, and infer whether liquid can be ejected from the nozzle 24. Furthermore, the control unit 111 can infer whether the meniscus formed at the nozzle 24 is convex or concave based on the position of the gas-liquid interface of the liquid present at the position of the nozzle 24 detected by the optical sensor, and can also infer the internal pressure of the common flow path. Furthermore, for example, the liquid jetting device 11 may also include a camera capable of capturing images of the nozzle surface 25 of the liquid jetting unit 15. The camera can detect the liquid present at the position of the nozzle 24, which is the state of the nozzle 24. In this case, the control unit 111 can also infer the position of the liquid-gas interface at the nozzle 24 based on the color difference and color change within the nozzle 24 in the image of the nozzle surface 25 captured by the camera, and infer whether liquid can be ejected from the nozzle 24 and the pressure within the common flow path. Furthermore, the liquid jetting device 11 can also include an optical device serving as a state detection unit, which can move relative to the nozzle surface 25 of the liquid jetting unit 15. For example, the liquid jetting device 11 can mount an optical sensor or camera, which serves as the optical device, on the holding part 142 of the wiping mechanism 133 at a position capable of detecting the nozzle 24 of the liquid jetting unit 15. Thus, the control unit 111 can also drive and control the wiping mechanism 133 and the moving mechanism 16 to move the optical device relative to the nozzle surface 25 of the liquid jetting unit 15, thereby allowing the optical device to detect the state of the nozzle 24.

[0216] The liquid injection device 11 may also include a pressure sensor as a state detection unit capable of detecting the state of either the nozzle 24 or the independent liquid chamber 86. In this case, the pressure sensor can detect the pressure as the state of either the nozzle 24 or the independent liquid chamber 86. For example, the liquid injection section 15 of the liquid injection device 11 may also be provided with a separate piezoelectric element corresponding to the independent liquid chamber 86, separate from the piezoelectric element constituting the ejection element 89.

[0217] The liquid jetting device 11 may also include a pressure sensor capable of detecting the pressure within the common flow path. Since the pressure within the common flow path is substantially the same as the pressure of the liquid in the independent liquid chamber when the jetting element 89 is not driven to eject, the pressure sensor can detect the state of the independent liquid chamber. For example, the liquid jetting section 15 of the liquid jetting device 11 includes a pressure sensor that detects the pressure within the common liquid chamber 85, i.e., the pressure within the common flow path. Thus, the control unit 111 may terminate the pressure drop flushing operation based on the pressure within the common flow path detected by the pressure sensor. Alternatively, the control unit 111 may also infer whether liquid can be ejected from the nozzle 24 based on the pressure within the common flow path detected by the pressure sensor. In this case, for example, the control unit 111 may determine that liquid cannot be ejected from the nozzle 24 if the pressure within the common flow path detected by the pressure sensor is higher than the pressure at which the meniscus forms in the nozzle 24, and determine that liquid can be ejected from the nozzle 24 if the pressure within the common flow path detected by the pressure sensor is the same as the pressure at which the meniscus forms in the nozzle 24. Alternatively, the control unit 111 may infer the position of the gas-liquid interface between the liquid on the nozzle side and the liquid in the independent liquid chamber 86, and whether the meniscus formed on the nozzle 24 is convex or concave, based on the pressure inside the common flow path detected by the pressure sensor, and terminate the pressure drop flushing operation based on the inferred results. In this case, the control unit 111 may also infer the position of the liquid connected to the liquid in the independent liquid chamber 86 on the nozzle side and the pressure inside the common flow path without relying on the vibration waveform of the independent liquid chamber 86 detected by the jet state detection unit 113.

[0218] The liquid jetting device 11 can also terminate the pressure drop flushing operation after the pressurized discharge operation, assuming that a predetermined amount of liquid has been discharged from the nozzle 24 during the pressure drop flushing operation. For example, after the pressurized discharge operation, in order to keep the pressure in the common flow path within the range of the ejection pressure, assuming that the volume of the predetermined amount of liquid to be discharged from the nozzle 24 is PV cubic meters, the number of nozzles capable of ejecting liquid is assumed to be n nozzles, and the volume of a single droplet ejected from the nozzle 24 during the pressure drop flushing operation is DV cubic meters. In this case, the control unit 111 of the liquid jetting device 11 terminates the pressure drop flushing operation if, based on the number of times the ejection element 89 is driven during the pressure drop flushing operation, the total number of droplets ejected from the nozzle 24 becomes greater than PV / n / DV.

[0219] The liquid supply section 19 of the liquid injection device 11 may also lack a liquid return flow path 31. For example, the liquid supply section 19 of the liquid injection device 11 may also lack a liquid return flow path 31 connected to the first outlet 96a and the second outlet 96b of the liquid injection section 15. In this case, the liquid injection section 15 may also lack the first outlet 96a and the second outlet 96b. Furthermore, in this case, the control unit 111 does not perform drive control to switch the opening and closing states of the first return valve 97a and the second return valve 97b during the processing performed when performing maintenance operations including pressurization and discharge.

Claims

1. A liquid injection device, characterized in that, have: The liquid jetting unit has a common flow path through which liquid can flow in, multiple independent liquid chambers communicating with the common flow path, nozzles communicating with the independent liquid chambers, nozzle faces through which the multiple nozzles open, and a jetting element. The liquid jetting unit can jet the liquid from the nozzle toward the medium by driving the jetting element. The pressurization mechanism is capable of pressurizing the liquid within the common flow path; The status detection unit is capable of detecting the status of either the nozzle or the independent liquid chamber; as well as Control Department The control unit performs: The pressurized discharge action is achieved by pressurizing the liquid in the common flow path through the pressurizing mechanism, thereby discharging the liquid from the nozzle. The status detection action is performed after the pressurization and discharge action, causing the status detection unit to detect the status. as well as The rinsing action involves driving the ejection element corresponding to the nozzle that is presumed to be able to eject the liquid based on the detection result of the state detection action, thereby causing the liquid to be ejected from the nozzle, and not driving the ejection element corresponding to the nozzle that is presumed to be unable to eject the liquid.

2. The liquid injection device according to claim 1, characterized in that, If the control unit determines, based on the detection result of the state detection action performed after the rinsing action, that the liquid can be ejected from the nozzle that was presumed to be unable to eject the liquid before the rinsing action was performed, the rinsing action is terminated.

3. The liquid injection device according to claim 1, characterized in that, When the pressure of the liquid within the common flow path is set as the internal pressure of the common flow path, and the internal pressure of the common flow path when the liquid is ejected from the nozzle toward the medium is set as the ejection pressure, If the control unit deduces, based on the detection result of the state detection action performed after the flushing action, that the pressure inside the common flow path has become a predetermined pressure that is lower than the pressure inside the common flow path during the pressurized discharge action but higher than the ejection pressure, then the flushing action is terminated, and a post-flushing action is performed to eject the liquid from the plurality of nozzles by driving the ejection elements corresponding to the plurality of nozzles.

4. The liquid injection device according to claim 3, characterized in that, The liquid spraying device includes a wiping mechanism, which is capable of performing a wiping action to wipe the nozzle surface. The control unit drives the wiping mechanism to perform the wiping action after the rinsing action, and performs the post-rinsing action.

5. The liquid injection device according to claim 1, characterized in that, The control unit terminates the rinsing operation if it infers, based on the detection result of the state detection operation performed after the rinsing operation, that the gas-liquid interface formed on the nozzle is located closer to the inside of the nozzle than the nozzle surface.

6. A maintenance method for a liquid injection device, characterized in that, The liquid injection device includes a liquid injection section, which has a common flow path through which liquid can flow, multiple independent liquid chambers communicating with the common flow path, nozzles communicating with the independent liquid chambers, nozzle faces through which the multiple nozzles open, and an ejection element. The liquid injection section can eject the liquid from the nozzles toward the medium by driving the ejection element. The maintenance method for the liquid injection device includes: A pressurized discharge action is performed, in which the liquid in the common flow path is pressurized to discharge the liquid from the nozzle; After the pressurized discharge action, it is deduced whether the liquid can be ejected from the nozzle; and A rinsing action is performed in which the liquid is ejected from the nozzle by driving the ejection element corresponding to the nozzle that is presumed to be able to eject the liquid, and the ejection element corresponding to the nozzle that is presumed to be unable to eject the liquid is not driven.

7. The maintenance method for the liquid injection device according to claim 6, characterized in that, The rinsing action ends when a nozzle that was presumed to be unable to spray the liquid before the rinsing action was performed, due to the nozzle opening being covered by the liquid adhering to the nozzle surface, becomes capable of spraying the liquid.

8. The maintenance method for the liquid injection device according to claim 6, characterized in that, When the pressure of the liquid within the common flow path is set as the internal pressure of the common flow path, and the internal pressure of the common flow path when the liquid is ejected from the nozzle toward the medium is set as the ejection pressure, When the pressure inside the common flow path becomes a predetermined pressure that is lower than the pressure inside the common flow path during the pressurized discharge action but higher than the ejection pressure, the flushing action ends, and a post-flushing action is performed to eject the liquid from the plurality of nozzles by driving the ejection elements corresponding to the plurality of nozzles.

9. The maintenance method for the liquid injection device according to claim 8, characterized in that, After the rinsing action, a wiping action is performed to wipe the nozzle surface, followed by the post-rinsing action.

10. The maintenance method for the liquid injection device according to claim 6, characterized in that, The rinsing action ends when the gas-liquid interface formed at the nozzle is located further inside the nozzle than the nozzle surface.

Images