Inkjet printing apparatus, flow path resistance adjustment method, and printing method

Abstract

The present application provides an inkjet printing device, a flow path resistance adjustment method, and a printing method. The inkjet printing device includes: an inkjet head that performs printing by ejecting ink from a plurality of nozzles in a state in which an arrangement direction of the plurality of nozzles in a nozzle row in which the plurality of nozzles are arranged is a non-horizontal direction; an ink tank to which a pressure for delivering ink to the inkjet head or recovering ink from the inkjet head is applied; and an ink path that connects the ink tank and the inkjet head. The printing is performed in a state in which a parameter related to a flow path resistance of the ink path is set so that nozzle pressures of the plurality of nozzles are pressures within a prescribed range in which ink can be stably ejected, and ink flows at a flow rate required by the inkjet head.

Description

Technical Field

[0001] This invention relates to an inkjet printing apparatus, a flow path resistance adjustment method, and a printing method. Background Technology

[0002] An inkjet printing apparatus is known that is equipped with an inkjet head capable of ejecting ink in a horizontal direction and capable of printing on a surface orthogonal to the horizontal direction (e.g., the side of a carton).

[0003] In the inkjet printing apparatus described above, the nozzles in the nozzle array of the inkjet head are arranged in a direction orthogonal to the horizontal direction (vertical direction), and therefore the height positions of each nozzle are different. Consequently, the head difference between each nozzle and the ink tank connected to the inkjet head that supplies ink to the inkjet head, as well as the ink recovery tank that recovers ink from the inkjet head, are different.

[0004] This results in differences in nozzle pressure among the nozzles. Consequently, sometimes nozzles fail to eject ink consistently.

[0005] Japanese Patent Application Publication No. 2018-1687 describes a technique for printing by specifying the range of nozzles capable of stable ink ejection when printing by ejecting ink in a horizontal direction. Summary of the Invention

[0006] The technology described in Japanese Patent Application Publication No. 2018-1687 makes it difficult to print wide-format images in a single pass. Specifically, in wide-format inkjet heads used for single-pass printing of wide-format images, the large height difference between the upper and lower nozzles of the nozzle array results in a large difference in nozzle pressure corresponding to the head difference between the nozzles and the ink tank. Consequently, the range of nozzles capable of stable ink ejection becomes narrower relative to the width of the inkjet head, sometimes making it impossible to print the desired wide-format image in a single pass.

[0007] The same problem can occur when printing is performed by ejecting ink in a direction that is not perpendicular to the horizontal direction, even when an inkjet head is configured such that the nozzles in the nozzle array are arranged in a direction that is not horizontal.

[0008] The purpose of this invention is to provide an inkjet printing apparatus, a flow path resistance adjustment method, and a printing method that can print wide images in one pass when printing by ejecting ink in a direction that is not orthogonal to the horizontal direction.

[0009] The inkjet printing apparatus according to embodiments of the present invention includes: an inkjet head having a nozzle array with a plurality of nozzles arranged to eject ink, wherein the inkjet head ejects ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. Printing is performed when a parameter related to the flow path resistance is set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head. Here, the parameter related to the flow path resistance can be adjustable or pre-set (i.e., cannot be adjusted later).

[0010] The flow path resistance adjustment method according to embodiments of the present invention is used to adjust parameters related to the flow path resistance of the ink path in an inkjet printing apparatus, the inkjet printing apparatus comprising: an inkjet head having a nozzle array having a plurality of nozzles arranged to eject ink, the inkjet head ejecting ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank being pressured to supply ink to or recover ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The flow path resistance adjustment method includes adjusting the parameters related to the flow path resistance of the ink path to such that the nozzle pressure of each of the plurality of nozzles during printing is within a predetermined range capable of stably ejecting ink, and that ink flows at a flow rate required by the inkjet head. Here, the parameters related to the flow path resistance can be adjustable or controllable, or they can be pre-set (i.e., cannot be adjusted later).

[0011] A printing method, according to an embodiment of the present invention, is a printing method in an inkjet printing apparatus comprising: an inkjet head having a nozzle array of a plurality of nozzles arranged to eject ink, wherein the inkjet head ejects ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The printing method includes printing while a parameter related to the flow path resistance is set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head. Here, the parameter related to the flow path resistance can be an adjustable and controllable structure, or it can be a pre-set structure (i.e., one that cannot be adjusted later).

[0012] Based on the above structure, when printing by ejecting ink in a direction that is not orthogonal to the horizontal direction, wide-format images can be printed in one go. Attached Figure Description

[0013] Figure 1 This is a block diagram illustrating the structure of the inkjet printing apparatus according to the first embodiment.

[0014] Figure 2 yes Figure 1 The diagram shows a schematic structure of the conveyor section and head unit of the inkjet printing apparatus.

[0015] Figure 3 yes Figure 1 The diagram shows a schematic structure of the head unit and ink unit of the inkjet printing apparatus.

[0016] Figure 4 yes Figure 1 The diagram shows a schematic structure of the maintenance section of the inkjet printing unit.

[0017] Figure 5 yes Figure 1 The diagram shows a schematic structure of the ink unit of the inkjet printing device.

[0018] Figure 6 yes Figure 1 The diagram shows a fluid circuit model of the ink circulation section of the inkjet printing apparatus and the two inkjet heads connected to the ink circulation section.

[0019] Figure 7 This is a block diagram illustrating the structure of the inkjet printing apparatus according to the second embodiment.

[0020] Figure 8 yes Figure 7 The diagram shows a schematic structure of the conveyor section and head unit of the inkjet printing apparatus.

[0021] Figure 9 yes Figure 7 The diagram shows a schematic structure of the head unit and ink unit of the inkjet printing apparatus.

[0022] Figure 10 yes Figure 7 The diagram shows a schematic structure of the maintenance section of the inkjet printing unit.

[0023] Figure 11 yes Figure 7 The diagram shows a schematic structure of the ink unit of the inkjet printing device.

[0024] Figure 12 This is a diagram showing the flow path resistance table according to the second embodiment.

[0025] Figure 13 yes Figure 7 The diagram shows a fluid circuit model of the ink circulation section of the inkjet printing apparatus and the two inkjet heads connected to the ink circulation section. Detailed Implementation

[0026] In the following detailed description, numerous specific details are set forth for illustrative purposes to enable a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown schematically for the purpose of simplifying the drawings.

[0027] Embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that in all the drawings, the same or equivalent parts and components are labeled with the same or equivalent reference numerals, and the description of these parts and components is omitted or simplified. Furthermore, it should be noted that the drawings are schematic and differ from actual embodiments.

[0028] Reference Figures 1-6 The first embodiment of the present invention will be described below. Figure 1 This is a block diagram showing the structure of the inkjet printing apparatus 1 according to the first embodiment. Figure 2 yes Figure 1 The schematic diagram of the conveying section 2 and head units 3A to 3D of the inkjet printing apparatus 1 is shown. Figure 3 yes Figure 1 The schematic diagram shows the head unit 3A-3D and ink unit 4A-4C of the inkjet printing apparatus 1. Figure 4 yes Figure 1 A schematic diagram of the maintenance section 5 of the inkjet printing apparatus 1 shown. Figure 5 yes Figure 1 A schematic structural diagram of ink units 4A to 4C of the inkjet printing apparatus 1 shown. Figures 2-5 In this diagram, RT, LT, UP, DN, FR, and RR represent the right, left, up, down, forward, and backward directions, respectively. The up and down direction is the vertical direction, while the left and right and forward and backward directions are mutually orthogonal, and all are orthogonal to the up and down direction and parallel to the horizontal direction.

[0029] like Figure 1 As shown, the inkjet printing apparatus 1 includes a conveying unit 2, head units 3A to 3D, ink units 4A to 4C, a maintenance unit 5, and a control unit 6. Furthermore, sometimes the additional letters in the designations of the head units 3A to 3D, etc., are omitted for general description.

[0030] The conveying unit 2 moves the printing medium 7 in a conveying direction parallel to the horizontal direction. Figure 2The printing medium 7 is conveyed in the forward direction. The printing medium 7 has a printing surface 7a that is printed by the head unit 3. The printing surface 7a is a surface (vertical surface) that is orthogonal to the horizontal direction when the printing medium 7 is placed on the conveying unit 2 and conveyed. The printing medium 7 is, for example, a cardboard box.

[0031] Printing head units 3A to 3D eject ink onto the printing surface 7a of the printing medium 7 to perform printing. Printing head units 3A to 3D eject ink of different colors (e.g., black, cyan, magenta, and yellow) respectively. Figure 2 As shown, head units 3A to 3D are arranged along the conveying direction of the printing medium 7. Head units 3A to 3D have the same structure except for the color of the ink they eject.

[0032] Head unit 3 is able to Figure 4 The head unit 3 rotates between the printing position indicated by the solid line and the cleaning position indicated by the double-dotted line. The head unit 3 can be rotated manually or by a driving force such as a motor. Alternatively, the head unit 3 can be configured to move between the printing position and the cleaning position.

[0033] The printing position is the position of the head unit 3 when printing on the printing medium 7. The printing position is the position where the nozzle surface 11a of the inkjet head 11, described later, is orthogonal to the horizontal direction and parallel to the printing surface 7a of the printing medium 7 on the transport section 2.

[0034] The cleaning position is the position of the head unit 3 when cleaning the inkjet head 11. The cleaning position is the position where the nozzle surface 11a of the inkjet head 11 is horizontal.

[0035] Unless otherwise specified, the head unit 3 is set to be positioned in the printing position, and the vertical direction of the head unit 3 is the vertical direction of the head unit 3 in the state of being positioned in the printing position.

[0036] like Figure 3 , Figure 4 As shown, the head unit 3 includes a plurality of inkjet heads 11 and a head holder 12. In this embodiment, the head unit 3 includes six inkjet heads 11.

[0037] In the head unit 3, six inkjet heads 11 are arranged in a staggered manner along the vertical direction. That is, in the head unit 3, the six inkjet heads 11 arranged along the vertical direction are arranged in a manner that alternates between staggered positions in the rear-rear direction.

[0038] The inkjet head 11 ejects ink onto the printing surface 7a of the printing medium 7. The inkjet head 11 has a nozzle array 14 consisting of multiple ink-ejecting nozzles 13 arranged in a straight line at a predetermined spacing (see reference). Figure 5With the head unit 3 positioned in the printing position, the nozzles 13 in the nozzle array 14 are arranged in a direction orthogonal to the horizontal direction (vertical direction).

[0039] The nozzle 13 has an opening on the nozzle surface 11a of the inkjet head 11. The nozzle 13 ejects ink in a direction orthogonal to the nozzle surface 11a. That is, when the nozzle 13 prints on the printing surface 7a of the printing medium 7, it ejects ink in a horizontal direction.

[0040] The inkjet head holder 12 holds the inkjet heads 11. The inkjet head holder 12 holds each inkjet head 11 such that the nozzle faces 11a of all inkjet heads 11 are arranged in the same plane. A rotation shaft 15 is provided in the inkjet head holder 12, extending in a front-to-back direction parallel to the nozzle faces 11a and orthogonal to the arrangement direction of the nozzles 13. The head unit 3 is capable of rotating between a printing position and a cleaning position about the rotation shaft 15. Figure 4 In this configuration, a rotating shaft 15 is provided at the lower left end of the head holder 12 when the head unit 3 is in the printing position, but the position of the rotating shaft 15 is not restricted. For example, the rotating shaft 15 can be provided at the lower right end of the head holder 12 when the head unit 3 is in the printing position.

[0041] Ink units 4A-4C supply ink to inkjet heads 3A-3D. Ink unit 4A supplies ink to the first and second inkjet heads 11 from the bottom of each of inkjet heads 3A-3D. Ink unit 4B supplies ink to the third and fourth inkjet heads 11 from the bottom of each of inkjet heads 3A-3D. Ink unit 4C supplies ink to the fifth and sixth inkjet heads 11 from the bottom of each of inkjet heads 3A-3D.

[0042] exist Figure 3 In the diagram, only one head unit 3 is shown, and the illustrations of the other three head units 3 are omitted.

[0043] Ink unit 4 includes ink circulation sections 21A-21D, ink supply sections 22A-22D, pressure generation section 23, and four pressurized air paths 24 (see reference). Figure 5 ) and four negative pressure air paths 25 (refer to Figure 5 ).

[0044] Ink circulation units 21A to 21D circulate ink and supply ink to the inkjet heads 11. Ink circulation units 21A to 21D are respectively connected to two inkjet heads 11 in the head units 3A to 3D, which are arranged at different height positions, and supply ink to these two inkjet heads 11.

[0045] Specifically, ink circulation units 21A to 21D of ink unit 4A supply ink to the first and second inkjet heads 11 from the bottom in ink head units 3A to 3D, respectively. Ink circulation units 21A to 21D of ink unit 4B supply ink to the third and fourth inkjet heads 11 from the bottom in ink head units 3A to 3D, respectively. Ink circulation units 21A to 21D of ink unit 4C supply ink to the fifth and sixth inkjet heads 11 from the bottom in ink head units 3A to 3D, respectively.

[0046] like Figure 5 As shown, the ink circulation unit 21 includes a pressurized tank (ink tank) 31, a pressurized tank liquid level sensor 32, a negative pressure tank (ink tank) 33, a negative pressure tank liquid level sensor 34, a pressurized side ink path (ink path) 35, a negative pressure side ink path (ink path) 36, a pumping liquid path 37, and an ink pump 38.

[0047] The pressurized tank 31 stores the ink supplied to the inkjet head 11. A positive pressure for supplying ink to the inkjet head 11 is applied to the pressurized tank 31 by the pressure generating unit 23. The pressurized tank 31 is positioned lower than the lower inkjet head 11 (the lower side inkjet head 11) of the two inkjet heads 11 connected to the ink circulation unit 21 including the pressurized tank 31.

[0048] The pressure tank liquid level sensor 32 is used to detect whether the liquid level of ink in the pressure tank 31 has reached the reference height. The pressure tank liquid level sensor 32 outputs a "connected" signal when the liquid level in the pressure tank 31 is above the reference height, and outputs a "disconnected" signal when the liquid level is below the reference height.

[0049] The negative pressure tank 33 receives and stores ink that has not been consumed by the inkjet head 11. The negative pressure tank 33 stores ink supplied from the ink supply unit 22. The pressure generating unit 23 applies negative pressure to the negative pressure tank 33 to recover ink from the inkjet head 11. The negative pressure tank 33 is composed of a tank with the same shape as the pressurized tank 31 and is positioned at the same height as the pressurized tank 31.

[0050] The negative pressure tank liquid level sensor 34 is used to detect whether the liquid level of ink in the negative pressure tank 33 has reached the reference height. The reference height in the negative pressure tank 33 is the same as the reference height in the pressurized tank 31. The negative pressure tank liquid level sensor 34 outputs a "connected" signal when the liquid level in the negative pressure tank 33 is above the reference height, and outputs a "disconnected" signal when the liquid level is below the reference height.

[0051] The pressurized ink path 35 connects the pressurized tank 31 to the two inkjet heads 11. Ink supplied from the pressurized tank 31 to the two inkjet heads 11 flows in the pressurized ink path 35. The pressurized ink path 35 includes a pressurized common path 41, a pressurized upper head path (pressurized branch path) 42, and a pressurized lower head path (pressurized branch path) 43.

[0052] The pressurized side common path 41 is a common path for ink flowing from the pressurized tank 31 to the upper inkjet head 11 and from the pressurized tank 31 to the lower inkjet head 11. The upstream end of the pressurized side common path 41 in the ink circulation direction in the ink circulation section 21 is connected to the pressurized tank 31, and the downstream end is connected to the upstream end of the pressurized side upper head path 42 and the upstream end of the pressurized side lower head path 43.

[0053] The ink in the ink circulation section 21 circulates from the pressurized tank 31 along the pressurized side ink path 35 to the inkjet head 11 and from the inkjet head 11 back to the pressurized tank 31 via the negative pressure tank 33.

[0054] The pressurized upper head path 42 is a path for ink to flow from the pressurized common path 41 toward the upper inkjet head 11. The upstream end of the pressurized upper head path 42 in the ink circulation direction is connected to the downstream end of the pressurized common path 41 and the upstream end of the pressurized lower head path 43, and the downstream end of the pressurized upper head path 42 in the ink circulation direction is connected to the upper inkjet head 11.

[0055] The pressurized lower head path 43 is a path for ink to flow from the pressurized common path 41 toward the lower inkjet head 11. The upstream end of the pressurized lower head path 43 in the ink circulation direction is connected to the downstream end of the pressurized common path 41 and the upstream end of the pressurized upper head path 42, and the downstream end of the pressurized lower head path 43 in the ink circulation direction is connected to the lower inkjet head 11.

[0056] The negative pressure side ink path 36 connects the two inkjet heads 11 to the negative pressure tank 33. Ink that is not consumed by the two inkjet heads 11 flows in the negative pressure side ink path 36 and is recovered to the negative pressure tank 33. The negative pressure side ink path 36 includes a negative pressure side upper head path (negative pressure side branch path) 44, a negative pressure side lower head path (negative pressure side branch path) 45, and a negative pressure side common path 46.

[0057] The upper negative pressure head path 44 is a path for ink to flow from the upper inkjet head 11 toward the negative pressure side common path 46. The upstream end of the upper negative pressure head path 44 in the ink circulation direction is connected to the upper inkjet head 11, and the downstream end is connected to the upstream end of the negative pressure side common path 46 and the downstream end of the lower negative pressure head path 45.

[0058] The negative pressure side lower head path 45 is a path for ink to flow from the lower inkjet head 11 toward the negative pressure side common path 46. The upstream end of the negative pressure side lower head path 45 in the ink circulation direction is connected to the lower inkjet head 11, and the downstream end is connected to the upstream end of the negative pressure side common path 46 and the downstream end of the negative pressure side upper head path 44.

[0059] The common path 46 on the negative pressure side is a common path for ink flowing from the upper inkjet head 11 to the negative pressure tank 33 and for ink flowing from the lower inkjet head 11 to the negative pressure tank 33. The upstream end of the common path 46 on the negative pressure side in the ink circulation direction is connected to the downstream end of the upper negative pressure head path 44 and the downstream end of the lower negative pressure head path 45, and the downstream end of the common path 46 on the negative pressure side in the ink circulation direction is connected to the negative pressure tank 33.

[0060] The flow path resistances of the aforementioned pressurized upper head path 42, pressurized lower head path 43, negative pressure upper head path 44, and negative pressure lower head path 45 are set (adjusted) to ensure that the nozzle pressure of each nozzle 13 in the nozzle array 14 of the two inkjet heads 11 is within a stable ejection range (specified range), and that ink flows at the same flow rate required by both inkjet heads 11. The stable ejection range of nozzle pressure is the range of nozzle pressure within which the nozzle 13 can stably eject ink. The method for setting the flow path resistances of the pressurized upper head path 42, pressurized lower head path 43, negative pressure upper head path 44, and negative pressure lower head path 45 will be described later.

[0061] Pumping liquid path 37 is the path through which ink flows from negative pressure tank 33 to pressurized tank 31 via ink pump 38. The upstream end of pumping liquid path 37 in the ink circulation direction is connected to negative pressure tank 33, and the downstream end is connected to pressurized tank 31.

[0062] Ink pump 38 delivers ink from negative pressure tank 33 to pressurized tank 31. Ink pump 38 is located midway through the pumping liquid path 37.

[0063] Ink supply units 22A to 22D supply ink to ink circulation units 21A to 21D respectively. Ink supply unit 22 includes ink cartridge 51, ink supply path 52 and ink supply valve 53.

[0064] The ink cartridge 51 contains the ink used in printing using the inkjet head 11. The ink in the ink cartridge 51 is supplied to the negative pressure tank 33 of the ink circulation unit 21 via the ink supply path 52.

[0065] Ink supply path 52 connects ink cartridge 51 to negative pressure tank 33. In ink supply path 52, ink flows from ink cartridge 51 toward negative pressure tank 33.

[0066] The ink supply valve 53 opens and closes the ink flow path within the ink supply path 52. When supplying ink to the negative pressure tank 33, the ink supply valve 53 opens.

[0067] The pressure generating unit 23 generates pressure for ink circulation in the pressurized tank 31 and the negative pressure tank 33 of the ink circulation unit 21. Specifically, the pressure generating unit 23 draws air from the negative pressure tank 33 via the negative pressure air path 25 and sends air to the pressurized tank 31 via the pressurized air path 24, thereby applying positive pressure to the pressurized tank 31 and negative pressure to the negative pressure tank 33. The pressure generating unit 23 is common to ink circulation units 21A to 21D.

[0068] The pressurized air path 24 connects the pressure generating unit 23 to the air layer on the surface of the ink in the pressurized tank 31. Each pressurized air path 24 is provided corresponding to each ink circulation unit 21A to 21D.

[0069] The negative pressure air path 25 connects the pressure generating unit 23 to the air layer on the surface of the ink in the negative pressure tank 33. Each ink circulation unit 21A to 21D is provided with a negative pressure air path 25.

[0070] The maintenance unit 5 is used to clean the nozzle surface 11a of each inkjet head 11 of the head units 3A to 3D. The maintenance unit 5 can move between an extended position configured for cleaning the inkjet head 11 and a retracted position. The extended position is... Figure 4 The maintenance unit 5 shown is positioned directly below the head unit 3 in the cleaning position. The illustration of the maintenance unit 5 in the retracted position is omitted. Figure 4 As shown, the maintenance unit 5 includes an ink receiving unit 61 and a wiping component 62.

[0071] The ink receiving section 61 receives ink and other substances removed from the nozzle surface 11a by wiping with the wiping member 62 during the cleaning of the inkjet head 11.

[0072] The wiping member 62 wipes the nozzle surface 11a of the inkjet head 11 to remove ink and other substances from the nozzle surface 11a. In the maintenance unit 5, wiping members 62 are provided for wiping the three front inkjet heads 11 and the three rear inkjet heads 11 of the six inkjet heads 11 arranged in a staggered configuration, respectively, for the head units 3A to 3D. That is, eight wiping members 62 are provided in the maintenance unit 5.

[0073] The control unit 6 controls the operation of each part of the inkjet printing device 1. The control unit 6 is configured to include a CPU, RAM, ROM, hard disk, etc.

[0074] Next, the method for setting the flow path resistance of the pressurized upper head path 42, pressurized lower head path 43, negative pressure upper head path 44, and negative pressure lower head path 45 of the ink circulation unit 21 will be described.

[0075] Figure 6This is a fluid circuit model diagram of the ink circulation section 21 and the two inkjet heads 11 connected to the ink circulation section 21.

[0076] exist Figure 6 In the middle, P k P f These are the set pressures of the pressurized tank 31 and the negative pressure tank 33 during ink circulation (printing). During ink circulation, the pressure generating unit 23 adjusts the pressures of the pressurized tank 31 and the negative pressure tank 33 to P respectively. k P f .

[0077] P1 is the average nozzle pressure of the upper inkjet head 11, which is the nozzle pressure of the central nozzle 13 in the nozzle array 14 of the upper inkjet head 11. P2 is the average nozzle pressure of the lower inkjet head 11, which is the nozzle pressure of the central nozzle 13 in the nozzle array 14 of the lower inkjet head 11. Since a head difference is generated between the nozzles 13 in the upper inkjet head 11 and between the nozzles 13 in the lower inkjet head 11, the average nozzle pressure of the nozzles 13 in the upper inkjet head 11, i.e., P1, and the average nozzle pressure of the nozzles 13 in the lower inkjet head 11, i.e., P2, are used.

[0078] Q min It is the ink circulation flow rate required during ink circulation (printing).

[0079] R 0k It is the flow path resistance of the common path 41 on the pressurized side. R 0k It is a fixed value. R 1k This is the flow path resistance of the upper head path 42 on the pressurized side. R 2k It is the flow path resistance of the lower head path 43 on the pressurized side.

[0080] R 0f It is the flow path resistance of the common path 46 on the negative pressure side. R 0f It is a fixed value. R 1f It is the flow path resistance of the upper head path 44 on the negative pressure side. R 2f It is the flow path resistance of the lower head path 45 on the negative pressure side.

[0081] R Hk R is the flow path resistance from the ink inlet port inside the inkjet head 11 to the nozzle 13. Hf R is the flow path resistance from the nozzle 13 inside the inkjet head 11 to the ink outlet port. Hk R Hf It is a fixed value. R H It is the flow path resistance inside the inkjet head 11. H It is represented by the following formula (1).

[0082] R H =RHk +R Hf …(1)

[0083] R1 is the flow path resistance of the flow path formed by the upper head path 42 on the pressurized side, the upper inkjet head 11, and the upper head path 44 on the negative pressure side. R1 is represented by the following equation (2).

[0084] R1 = R 1k +R H +R 1f …(2)

[0085] R2 is the flow path resistance of the flow path formed by the pressurized side lower head path 43, the lower inkjet head 11, and the negative pressure side lower head path 45. R2 is represented by the following formula (3).

[0086] R2 = R 2k +R H +R 2f …(3)

[0087] R 12 It is the flow path resistance between the downstream end of the common path 41 on the pressurized side and the upstream end of the common path 46 on the negative pressure side. R 12 It is represented by the following formula (4).

[0088] R 12 =R1×R2 / (R1+R2)…(4)

[0089] When the flow path resistance of the entire path from the pressurized tank 31 through the inkjet head 11 to the negative pressure tank 33 is set as R, R is represented by the following equation (5).

[0090] R = R 0k +R 12 +R 0f …(5)

[0091] As mentioned above, the flow resistance R of the upper head path 42 on the pressurized side 1k The flow path resistance R of the lower head path 43 on the pressurized side 2k The flow path resistance R of the upper head path 44 on the negative pressure side 1f And the flow path resistance R of the lower head path 45 on the negative pressure side. 2f The nozzle pressure of each nozzle 13 in the nozzle array 14 of the two inkjet heads 11 is set to be within a stable ejection range, and the ink flows at the same flow rate required by the two inkjet heads 11.

[0092] Specifically, R 1k R 2k R 1f R 2f It is set to make the following equations (6) to (8) hold.

[0093] P1 = P2 = P typ …(6)

[0094] R1=R2…(7)

[0095] R = (P k -P f ) / Q min …(8)

[0096] Equation (6) above represents the condition for ensuring that the nozzle pressure of each nozzle 13 in the nozzle array 14 of the two inkjet heads 11 is within the stable ejection range. The reason for setting equation (6) as a condition is as follows.

[0097] In the ink circulation section 21 and the two inkjet heads 11 connected to the ink circulation section 21, if the following formula (9) holds, the nozzle pressure of each nozzle 13 of the nozzle array 14 in the two inkjet heads 11 becomes the pressure within the stable ejection range.

[0098] ΔP≥P Hh +|P1-P2|+Pσ…(9)

[0099] Here, ΔP is the upper limit of the stable ejection range (the maximum nozzle pressure P that can stably eject the product). max The lower limit of the stable ejection range (the minimum nozzle pressure P that can stably eject the product) and the lower limit of the stable ejection range. min The difference (P) max -P min ).

[0100] P Hh It refers to the head difference within the inkjet head 11. Specifically, P Hh The nozzle pressure P of the nozzle 13 at the downstream end of the nozzle array 14 of the inkjet head 11 is... nl The nozzle pressure P of the upper nozzle 13 nu The difference (P) nl -P nu ).

[0101] Pσ is the deviation (variance) of the nozzle pressure of the two inkjet heads 11. Pσ is determined by the performance of the pressure generating unit 23, the deviation of each component, etc.

[0102] As can be seen from equation (9), the smaller |P1-P2| is, the easier it is for equation (9) to hold true. Therefore, in this embodiment, as in equation (6), P1 is set to P2. As a result, the pressure difference based on the water head difference between the upper inkjet head 11 and the lower inkjet head 11 disappears, and equation (9) easily holds true. Here, in this embodiment, the ink circulation unit 21 and the inkjet head 11 are configured such that when P1 = P2, P HhPσ becomes the value that makes equation (9) true.

[0103] P in equation (6) typ This is the desired nozzle pressure value (target value) for the inkjet head 11. typ Set as P max With P min The values ​​between.

[0104] Equation (7) above represents the condition for ensuring that the ink flows at the same flow rate in both inkjet heads 11. Equation (8) above represents the condition for ensuring the ink flow rate required for printing by both inkjet heads 11. Setting equations (7) and (8) as conditions is to ensure that the ink flows at the required and the same flow rate in both inkjet heads 11.

[0105] When P1 is calculated from the pressure tank 31 side, P1 is represented by the following formula (10).

[0106]

Number 1

[0107]

[0108] P 1h It is the water head pressure of the upper inkjet head 11.

[0109] When P1 is calculated from the negative pressure tank 33 side, P1 is represented by the following formula (11).

[0110]

Number 2

[0111]

[0112] When P2 is calculated from the pressure tank 31 side, P2 is represented by the following formula (12).

[0113]

Number 3

[0114]

[0115] P 2h It is the water head pressure of the lower inkjet head 11.

[0116] When P2 is calculated from the negative pressure tank 33 side, P2 is represented by the following formula (13).

[0117]

Number 4

[0118]

[0119] Based on equations (1) to (13), we obtain equations (14) to (17).

[0120]

Number 5

[0121]

[0122]

[0123]

[0124]

[0125] The flow resistance R of the upper head path 42 on the pressurized side is calculated using equations (14) to (17). 1k The flow path resistance R of the lower head path 43 on the pressurized side 2k The flow path resistance R of the upper head path 44 on the negative pressure side 1f And the flow path resistance R of the lower head path 45 on the negative pressure side. 2f .

[0126] Specifically, the parameters related to the flow path resistance of this part are set such that they become the flow path resistance R obtained by equations (14) to (17). 1k R 2k R 1f R 2f Parameters related to flow path resistance include the length of the flow path, the diameter of the flow path, the shape of the tube, and the viscosity of the ink. The flow path resistance R is adjusted by changing at least one of these parameters. 1k R 2k R 1f R 2f For example, by adjusting at least one of the length, diameter, or shape of the flow path in the upper head path 42 on the pressurized side, the flow path resistance of the upper head path 42 on the pressurized side can be adjusted to R obtained by equation (14). 1k Regarding the flow path resistance R 2k R 1f R 2f Similarly, for example, the inkjet printing apparatus 1 includes a pressurized upper head path 42, a pressurized lower head path 43, a negative pressure upper head path 44, and a negative pressure lower head path 45, which are manufactured by adjusting (pre-setting) parameters related to flow path resistance as described above.

[0127] By setting the flow path resistance R as described above 1k R 2k R 1f R 2f On the upstream side of the inkjet head 11, the flow path resistance R of the pressurized lower head path 43 is... 2k The flow path resistance R of the upper head path 42 on the pressurized side 1k Large. On the lower flow side of the inkjet head 11, the flow resistance R of the negative pressure side lower head path 45 is large. 2fThe flow path resistance R of the upper head path 44 on the negative pressure side 1f Small. Moreover, the pressure difference based on the water head difference between the upper inkjet head 11 and the lower inkjet head 11 is eliminated.

[0128] Next, the operation of the inkjet printing device 1 will be explained.

[0129] When a printing job is input, the control unit 6 initiates ink circulation through the ink circulation units 21A-21D of the ink units 4A-4C. Specifically, the control unit 6 uses the pressure generating unit 23 of the ink units 4A-4C to generate a set pressure P for ink circulation in the pressure tank 31 and the negative pressure tank 33, respectively. k P f Thus, ink circulation in ink circulation units 21A to 21D begins, and ink flows from pressurized tank 31 through inkjet head 11 to negative pressure tank 33.

[0130] When the ink cycle begins, the control unit 6 initiates the printing operation. Specifically, the control unit 6 controls the transport of the printing medium 7 via the transport unit 2, and ejects ink from each inkjet head 11 of the head units 3A to 3D to print an image on the printing medium 7.

[0131] During the printing operation, ink is supplied from the pressurized tank 31 to the inkjet head 11, and any ink not consumed by the inkjet head 11 is recycled to the negative pressure tank 33. When the pressurized tank level sensor 32 is off and the negative pressure tank level sensor 34 is on, the control unit 6 drives the ink pump 38. This supplies ink from the negative pressure tank 33 to the pressurized tank 31. When the pressurized tank 31 is on, the control unit 6 stops the ink pump 38. In this way, the ink is circulated, and printing is performed.

[0132] When both the pressurized tank level sensor 32 and the negative pressure tank level sensor 34 are off, the control unit 6 opens the ink supply valve 53. This replenishes ink from the ink cartridge 51 to the negative pressure tank 33. When the negative pressure tank level sensor 34 is on, the control unit 6 closes the ink supply valve 53.

[0133] When printing based on the printing operation is completed, the control unit 6 controls the pressure generation unit 23 to end the ink circulation in the ink circulation units 21A to 21D.

[0134] Next, the operation of cleaning the nozzle surface 11a of the inkjet head 11 in the inkjet printing apparatus 1 will be described.

[0135] When head units 3A to 3D are positioned in the cleaning position, control unit 6 positions maintenance unit 5 in the unfolded position.

[0136] Next, the control unit 6 controls the pressure generating unit 23 of the ink units 4A to 4C to apply positive pressure for cleaning to the pressure tanks 31 of the ink circulation units 21A to 21D. As a result, ink is purged from the nozzles 13 of the inkjet head 11. At least a portion of the ink discharged from the nozzles 13 by the purging adheres to the nozzle surface 11a.

[0137] When the head unit 3 is positioned in the cleaning position, unlike when it is positioned in the printing position, the nozzles 13 in the nozzle array 14 are arranged horizontally, and all nozzles 13 are at the same height position, so there is no head difference between the nozzles 13. This is achieved by adjusting the flow path resistance R of the pressurized upper head path 42, pressurized lower head path 43, negative pressure upper head path 44, and negative pressure lower head path 45 as described above. 1k R 2k R 1f R 2f Therefore, the amount of ink discharged by the upper inkjet head 11 and the lower inkjet head 11 during purging is different, but they can still be purged.

[0138] After purging, the control unit 6 controls the maintenance unit to wipe the nozzle surface 11a of the inkjet head 11 using the wiping member 62. This removes dust and ink adhering to the nozzle surface 11a. As a result, the cleaning of the nozzle surface 11a of the inkjet head 11 is completed.

[0139] As explained above, in the inkjet printing apparatus 1, in the ink circulation section 21, parameters related to the flow path resistance of the pressure-side upper head path 42, the pressure-side lower head path 43, the negative pressure-side upper head path 44, and the negative pressure-side lower head path 45 are set such that the nozzle pressure of each nozzle 13 in the nozzle array 14 of the two inkjet heads 11 connected to the ink circulation section 21 is within a stable ejection range, and ink flows at the same flow rate required by the two inkjet heads 11.

[0140] Therefore, the ink flow rate required for printing can be ensured equally for both inkjet heads 11 through the common ink circulation section 21, and even if there is a head difference between the nozzles 13, the range of nozzles 13 capable of stable ink ejection can be suppressed from narrowing. Thus, according to the inkjet printing apparatus 1, the structure and control of the apparatus can be simplified, and wide-format images can be printed in one pass when printing with ink ejected in the horizontal direction. Furthermore, the head units 3A to 3D, which eject inks of different colors respectively, are arranged along the transport direction of the printing medium 7. Therefore, horizontal printing of full-color images on the sides of the printing medium 7 (e.g., three-dimensional objects such as cartons) is possible.

[0141] In the inkjet printing apparatus 1, printing is performed when the print head unit 3 is positioned in the printing position, and cleaning of the nozzle surface 11a of the print head 11 is performed when the print head unit 3 is positioned in the cleaning position. That is, in the inkjet printing apparatus 1, printing is performed with the nozzles 13 in the nozzle array 14 arranged in a vertical direction, and cleaning of the nozzle surface 11a is performed with the nozzles 13 arranged in a horizontal direction. This allows for the printing of wide-format images in a single pass, and also enables the print head 11 to be rotated and cleaned by blowing.

[0142] In the above implementation, in order to set the flow path resistance R 1k R 2k R 1f R 2f Set P1=P2 as a condition, but even if it is not P1=P2, it is sufficient to make the nozzle pressure of each nozzle 13 in each inkjet head 11 within the stable ejection range.

[0143] The pressure of the pressurized tank 31 and the negative pressure tank 33 can be used as parameters related to flow path resistance.

[0144] In the above embodiment, a structure is shown that ink is supplied to two inkjet heads 11 through an ink circulation unit 21, but it can also be configured to supply ink to one inkjet head through an ink circulation unit. In this case, the parameters related to the flow path resistance of the pressurized ink path connecting the pressure tank and the inkjet head, and the negative pressure ink path connecting the inkjet head and the negative pressure tank, are set such that the nozzle pressure of each nozzle is within a stable ejection range, and the ink flows at the flow rate required by the inkjet head. Even in this case, the ink flow rate required for printing can be ensured, and even if there is a head difference between the nozzles 13 in the inkjet head 11, the range of nozzles 13 capable of stable ink ejection can be suppressed from narrowing. Therefore, when printing by ejecting ink in the horizontal direction, wide-format images can be printed in one pass.

[0145] Alternatively, the structure can be configured to supply ink to three or more inkjet heads via an ink circulation unit. In this case, the parameters related to the flow path resistance of the multiple pressurized side branch paths and multiple negative pressure side branch paths connected to each inkjet head are set such that the nozzle pressure of each nozzle in the nozzle array of each inkjet head is within a stable ejection range, and the ink flows at the same flow rate required by each inkjet head.

[0146] The parameters related to the flow path resistance of the ink path can be adjusted to ensure that the nozzle pressure of each nozzle in the nozzle array of the inkjet head is within a stable ejection range and that the ink flows at the same flow rate required by each inkjet head. Alternatively, the flow path resistance itself can be adjusted.

[0147] In the above embodiment, an inkjet printing apparatus 1 was described in which inkjet heads 11 arranged in a direction orthogonal to the horizontal direction eject ink for printing. However, the invention is not limited thereto, and can be applied to inkjet printing apparatuses in which inkjet heads arranged in a direction other than the horizontal direction eject ink for printing in a direction not orthogonal to the horizontal direction, and where each nozzle has a different height position.

[0148] One implementation may have the following structure, for example.

[0149] The inkjet printing apparatus according to embodiments of the present invention includes: an inkjet head having a nozzle array of a plurality of nozzles arranged to eject ink, wherein the inkjet head ejects ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The printing is performed with parameters related to the flow path resistance of the ink path set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head.

[0150] The parameters related to the flow path resistance of the ink path can be preset to ensure that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that allows for stable ink ejection and that the ink flows at the flow rate required by the inkjet head.

[0151] The ink reservoir may include: a pressurized reservoir that stores ink supplied to the inkjet head and is subjected to a positive pressure for delivering ink to the inkjet head; and a negative pressure reservoir that receives ink not consumed by the inkjet head and is subjected to a negative pressure for recovering ink from the inkjet head. The ink path may include: a pressurized side ink path connecting the pressurized reservoir to the inkjet head; and a negative pressure side ink path connecting the inkjet head to the negative pressure reservoir. Parameters related to the flow path resistance of the pressurized side ink path and the flow path resistance of the negative pressure side ink path may be set to ensure that the nozzle pressure of each of the plurality of nozzles is within the specified range and that ink flows at the flow rate required by the inkjet head.

[0152] The inkjet head may include multiple inkjet heads configured at different height positions. The pressurized ink path may include multiple pressurized side branch paths respectively connected to the multiple inkjet heads. The negative pressure ink path may include multiple negative pressure side branch paths respectively connected to the multiple inkjet heads. Parameters related to the flow path resistance of each of the multiple pressurized side branch paths and the multiple negative pressure side branch paths may be set such that the nozzle pressure of each nozzle in the nozzle array of each of the multiple inkjet heads is within the specified range, and ink flows at the same flow rate required by each of the multiple inkjet heads.

[0153] The inkjet head can rotate around an axis extending in a direction parallel to the nozzle surfaces of the plurality of nozzle openings and orthogonal to the arrangement direction. Printing is performed when the arrangement direction is not horizontal, and cleaning of the nozzle surfaces is performed when the arrangement direction is horizontal.

[0154] The inkjet head may include: a first inkjet head that ejects ink of a first color onto a printing medium being conveyed in a conveying direction parallel to the horizontal direction; and a second inkjet head that ejects ink of a second color different from the first color onto the printing medium being conveyed in the conveying direction. The inkjet printing apparatus may further include: a first head unit including the first inkjet head; and a second head unit including the second inkjet head, the second head unit being disposed downstream of the first head unit in the conveying direction.

[0155] The inkjet head may include: a first inkjet head; and a second inkjet head disposed at a position higher than the first inkjet head. The printing can be performed with parameters related to the flow path resistance of the ink path set such that the average nozzle pressure of the plurality of nozzles of the first inkjet head is the same as the average nozzle pressure of the plurality of nozzles of the second inkjet head.

[0156] The flow path resistance adjustment method according to embodiments of the present invention is used to adjust parameters related to the flow path resistance of the ink path in an inkjet printing apparatus, the inkjet printing apparatus comprising: an inkjet head having a nozzle array having a plurality of nozzles arranged to eject ink, the inkjet head ejecting ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The flow path resistance adjustment method includes adjusting the parameters related to the flow path resistance of the ink path to such that the nozzle pressure of each of the plurality of nozzles during printing is within a predetermined range capable of stably ejecting ink, and that ink flows at a flow rate required by the inkjet head.

[0157] The flow path resistance adjustment method may further include: pre-adjusting the parameters related to the flow path resistance of the ink path so that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that enables stable ink ejection, and the ink flows at the flow rate required by the inkjet head.

[0158] A printing method, according to an embodiment of the present invention, is a printing method in an inkjet printing apparatus comprising: an inkjet head having a nozzle array of a plurality of nozzles arranged to eject ink, the inkjet head ejecting ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The printing method includes performing printing while a parameter related to the flow path resistance is set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head.

[0159] The printing method may further include: pre-setting the parameters related to the flow path resistance of the ink path to such that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that enables stable ink ejection, and printing is performed with ink flowing at the flow rate required by the inkjet head.

[0160] Next, refer to Figures 7-13 The second embodiment of the present invention will now be described. In the inkjet printing apparatus 1 according to the first embodiment, the narrowing of the nozzle range capable of stable ink ejection is suppressed, and wide-format images can be printed in one pass. Even in inkjet printing apparatuses where the flow path resistance of the ink is set as in the first embodiment, for example in structures where the inkjet head can be rotated and moved to change the ink ejection direction and the height position of the inkjet head is changed by rotation and movement, sometimes the flow path resistance of the ink becomes inappropriate by rotating and moving the inkjet head, thereby narrowing the nozzle range capable of stable ink ejection. As a result, sometimes it is impossible to print the desired wide-format image in one pass. The object of the second embodiment is to provide an inkjet printing apparatus, a flow path resistance adjustment method, and a printing method that can suppress the situation where wide-format images cannot be printed in one pass even when the height position of the inkjet head changes.

[0161] Figure 7 This is a block diagram showing the structure of the inkjet printing apparatus 101 according to the second embodiment. Figure 8 yes Figure 7The schematic structural diagram of the conveying section 102 and head units 103A to 103D of the inkjet printing apparatus 101 shown. Figure 9 yes Figure 7 A schematic structural diagram of the head unit 103A-103D and ink unit 108A-108C of the inkjet printing apparatus 101 shown. Figure 10 yes Figure 7 A schematic structural diagram of the maintenance section 109 of the inkjet printing apparatus 101 shown. Figure 11 yes Figure 7 A schematic structural diagram of the ink units 108A to 108C of the inkjet printing apparatus 101 shown. Figure 12 This is a graph showing the flow path resistance table 186. In Figures 8-11 In this diagram, RT, LT, UP, DN, FR, and RR represent the right, left, up, down, forward, and backward directions, respectively. The up and down direction is the vertical direction, while the left and right and forward and backward directions are mutually orthogonal, and all are orthogonal to the up and down direction and parallel to the horizontal direction.

[0162] like Figure 7 As shown, the inkjet printing apparatus 101 according to this embodiment includes a conveying unit 102, head units 103A to 103D, a rotation drive unit 104, a head angle detection unit 105, a lifting drive unit 106, a height position detection unit 107, ink units 108A to 108C, a maintenance unit 109, and a control unit 110. Furthermore, sometimes the additional letters in the designations of the head units 103A to 103D are omitted for general description.

[0163] The conveying unit 102 moves the printing medium 111 in a conveying direction parallel to the horizontal direction. Figure 8 (Forward direction) conveying. The printing medium 111 is, for example, a cardboard box. The printing medium 111 has a printable surface 111a that is printed by the head unit 103. Figure 8 In the example shown, the printing surface 111a is a surface orthogonal to the horizontal direction (vertical surface) in the state where the printing medium 111 is placed on the conveyor 102 and conveyed. In the inkjet printing apparatus 101, the printing surface 111a is not limited to a vertical surface; it can be a horizontal surface or a surface orthogonal to the horizontal direction. Figure 8 The lower right sloping surface in the middle.

[0164] Printing head units 103A to 103D eject ink onto the printing surface 111a of the printing medium 111 to perform printing. Printing head units 103A to 103D eject ink of different colors (e.g., black, cyan, magenta, and yellow) respectively. Figure 8 As shown, head units 103A to 103D are arranged along the conveying direction of the printing medium 111. Head units 103A to 103D have the same structure except for the color of the ink they eject.

[0165] Head unit 103 is capable of Figure 10 The inkjet head 103 rotates between a vertical state (shown by the solid line) and a horizontal state (shown by the double-dotted line). Head units 103A to 103D can rotate as a single unit. The vertical state is when the nozzle surface 121a of the inkjet head 121 (described later) is vertical, and the nozzles 123 (described later) are arranged in an up-down direction. The horizontal state is when the nozzle surface 121a is horizontal, and the nozzles 123 are arranged in a horizontal (left-right) direction. Whether in the vertical state, the horizontal state, or a state between the vertical and horizontal states where the nozzle surface 121a is tilted downwards to the right, head unit 103 can eject ink for printing. In other words, head unit 103 can eject ink for printing regardless of whether the nozzles 123 are arranged in a horizontal or non-horizontal direction.

[0166] Head units 103A to 103D can be raised and lowered as a single unit (can move along the vertical direction). In any of the following states: vertical, horizontal, and when the nozzle surface 121a is inclined to the lower right, head units 103A to 103D can be raised and lowered as a single unit.

[0167] like Figure 9 , Figure 10 As shown, the head unit 103 includes a plurality of inkjet heads 121 and a head holder 122. In this embodiment, the head unit 103 includes six inkjet heads 121.

[0168] In the head unit 103, the six inkjet heads 121 are arranged in a staggered manner in the arrangement direction of the nozzles 123 (vertical direction when the head unit 103 is vertical). Specifically, in the head unit 103, the six inkjet heads 121 are arranged in an alternating manner along the arrangement direction of the nozzles 123. That is, in the head unit 103, the six inkjet heads 121 arranged along the arrangement direction of the nozzles 123 are arranged in a manner where their positions are alternately staggered in the back-and-forth direction.

[0169] The inkjet head 121 ejects ink onto the printing surface 111a of the printing medium 111. The inkjet head 121 has a nozzle array 124 formed by multiple ink-ejecting nozzles 123 arranged in a straight line at a predetermined spacing (see reference). Figure 11 For example, when the head unit 103 is in a vertical state, the arrangement direction of the nozzles 123 in the nozzle array 124 becomes a direction orthogonal to the horizontal direction (vertical direction).

[0170] The nozzle 123 has an opening on the nozzle surface 121a of the inkjet head 121. The nozzle 123 ejects ink in a direction orthogonal to the nozzle surface 121a. That is, for example, when printing on the printing surface 111a of the printing medium 111 in a vertical state of the head unit 103, the nozzle 123 ejects ink in a horizontal direction.

[0171] The inkjet head holder 122 holds the inkjet head 121. The inkjet head holder 122 holds each inkjet head 121 in such a way that the nozzle faces 121a of all inkjet heads 121 are arranged in the same plane. A rotation shaft 125 is provided in the inkjet head holder 122, extending in a direction parallel to the nozzle faces 121a and orthogonal to the arrangement direction of the nozzles 123, i.e., a front-to-back direction. The inkjet head unit 103 is capable of rotating between a vertical and a horizontal position about the rotation shaft 125. As described above, since the inkjet head units 103A to 103D can rotate as a single unit, all inkjet heads 121 can rotate as a single unit.

[0172] exist Figure 10 In the vertical head unit 103, a rotating shaft 125 is provided at the lower left end of the head holder 122, but the position of the rotating shaft 125 is not restricted. For example, the rotating shaft 125 can be provided at the lower right end of the head holder 122 in the vertical head unit 103.

[0173] The rotation drive unit 104 rotates the head units 103A to 103D. The rotation drive unit 104 includes a motor, etc.

[0174] The head angle detection unit 105 detects the head angle. The head angle is the tilt angle of the nozzle surface 121a of the inkjet head 121. When the head unit 103 is in a vertical position, the head angle is 90 degrees, and when the head unit 103 is in a horizontal position, the head angle is 0 degrees.

[0175] The lifting drive unit 106 causes the head units 103A to 103D to move up and down. The lifting drive unit 106 includes a motor, etc. As described above, the head units 103A to 103D can be lifted and lowered as a single unit, so all the inkjet heads 121 can be lifted and lowered as a single unit.

[0176] The height position detection unit 107 detects the height position (vertical position) of the head units 103A to 103D. The height position of the head units 103A to 103D is the height position of the rotating shaft 125.

[0177] Ink units 108A-108C supply ink to inkjet heads 103A-103D. Ink unit 108A supplies ink to the first and second inkjet heads 121 from the bottom of each inkjet head unit 103A-103D. Ink unit 108B supplies ink to the third and fourth inkjet heads 121 from the bottom of each inkjet head unit 103A-103D. Ink unit 108C supplies ink to the fifth and sixth inkjet heads 121 from the bottom of each inkjet head unit 103A-103D.

[0178] exist Figure 9 Only one head unit 103 is shown in the diagram, and the illustrations of the other three head units 103 are omitted. The first, second, ..., sixth inkjet heads 121 from the bottom refer to the first, second, ..., sixth inkjet heads 121 from the bottom when the head unit 103 is set to the vertical position.

[0179] The ink unit 108 includes ink circulation sections 131A-131D, ink supply sections 132A-132D, a pressure generation section 133, and four pressurized air paths 134 (see reference). Figure 11 ) and four negative pressure air paths 135 (refer to) Figure 11 ).

[0180] The ink circulation units 131A to 131D circulate ink and supply ink to the inkjet head 121. The ink circulation units 131A to 131D are respectively connected to two inkjet heads 121 in the head units 103A to 103D and supply ink to these two inkjet heads 121.

[0181] Specifically, ink circulation units 131A to 131D of ink unit 108A supply ink to the first and second inkjet heads 121 from the bottom in ink head units 103A to 103D, respectively. Ink circulation units 131A to 131D of ink unit 108B supply ink to the third and fourth inkjet heads 121 from the bottom in ink head units 103A to 103D, respectively. Ink circulation units 131A to 131D of ink unit 108C supply ink to the fifth and sixth inkjet heads 121 from the bottom in ink head units 103A to 103D, respectively.

[0182] like Figure 11 As shown, the ink circulation unit 131 includes a pressurized tank (ink tank) 141, a pressurized tank liquid level sensor 142, a negative pressure tank (ink tank) 143, a negative pressure tank liquid level sensor 144, a pressurized side ink path (ink path) 145, a negative pressure side ink path (ink path) 146, adjusting valves 147-150 (adjusting unit), a pumping liquid path 151, and an ink pump 152.

[0183] The pressurized tank 141 stores the ink supplied to the inkjet head 121. A positive pressure for supplying ink to the inkjet head 121 is applied to the pressurized tank 141 by the pressure generating unit 133. The pressurized tank 141 is positioned lower than the lower inkjet head 121 (the lower inkjet head 121) of the two inkjet heads 121 connected to the ink circulation unit 131 including the pressurized tank 141, in the vertical state of the head unit 103.

[0184] Of the two inkjet heads 121 connected to the ink circulation unit 131, the inkjet head that is in a higher position when the head unit 103 is vertical is designated as the upper inkjet head 121, and the inkjet head that is in a lower position is designated as the lower inkjet head 121.

[0185] The pressure tank liquid level sensor 142 is used to detect whether the liquid level of ink in the pressure tank 141 has reached a reference height. The pressure tank liquid level sensor 142 outputs a "connected" signal when the liquid level in the pressure tank 141 is above the reference height, and outputs a "disconnected" signal when the liquid level is below the reference height.

[0186] The negative pressure tank 143 receives and stores ink that has not been consumed by the inkjet head 121. The negative pressure tank 143 stores ink supplied from the ink supply unit 132. A negative pressure is applied to the negative pressure tank 143 by the pressure generating unit 133 to recover ink from the inkjet head 121. The negative pressure tank 143 is constructed of a tank with the same shape as the pressurized tank 141 and is positioned at the same height as the pressurized tank 141.

[0187] The negative pressure tank liquid level sensor 144 is used to detect whether the liquid level of ink in the negative pressure tank 143 has reached the reference height. The reference height in the negative pressure tank 143 is the same as the reference height in the pressurized tank 141. The negative pressure tank liquid level sensor 144 outputs a "connected" signal when the liquid level in the negative pressure tank 143 is above the reference height, and outputs a "disconnected" signal when the liquid level is below the reference height.

[0188] The pressurized ink path 145 connects the pressurized tank 141 to the two inkjet heads 121. Ink supplied from the pressurized tank 141 to the two inkjet heads 121 flows in the pressurized ink path 145. The pressurized ink path 145 includes a pressurized common path 161, a pressurized upper head path (pressurized branch path) 162, and a pressurized lower head path (pressurized branch path) 163.

[0189] The pressurized side common path 161 is a common path for ink flowing from the pressurized tank 141 to the upper inkjet head 121 and from the pressurized tank 141 to the lower inkjet head 121. The upstream end of the pressurized side common path 161 in the ink circulation direction in the ink circulation section 131 is connected to the pressurized tank 141, and the downstream end is connected to the upstream end of the pressurized side upper head path 162 and the upstream end of the pressurized side lower head path 163.

[0190] The ink in the ink circulation section 131 circulates from the pressurized tank 141 along the pressurized side ink path 145 to the inkjet head 121 and from the inkjet head 121 back to the pressurized tank 141 via the negative pressure tank 143.

[0191] The pressurized upper head path 162 is a path for ink to flow from the pressurized common path 161 toward the upper inkjet head 121. The upstream end of the pressurized upper head path 162 in the ink circulation direction is connected to the downstream end of the pressurized common path 161 and the upstream end of the pressurized lower head path 163, and the downstream end of the pressurized upper head path 162 in the ink circulation direction is connected to the upper inkjet head 121.

[0192] The pressurized lower head path 163 is a path for ink to flow from the pressurized common path 161 toward the lower inkjet head 121. The upstream end of the pressurized lower head path 163 in the ink circulation direction is connected to the downstream end of the pressurized common path 161 and the upstream end of the pressurized upper head path 162, and the downstream end of the pressurized lower head path 163 in the ink circulation direction is connected to the lower inkjet head 121.

[0193] The negative pressure side ink path 146 connects the two inkjet heads 121 to the negative pressure tank 143. Ink that is not consumed by the two inkjet heads 121 flows in the negative pressure side ink path 146 and is recovered to the negative pressure tank 143. The negative pressure side ink path 146 includes a negative pressure side upper head path (negative pressure side branch path) 164, a negative pressure side lower head path (negative pressure side branch path) 165, and a negative pressure side common path 166.

[0194] The upper negative pressure head path 164 is a path for ink to flow from the upper inkjet head 121 toward the negative pressure side common path 166. The upstream end of the upper negative pressure head path 164 in the ink circulation direction is connected to the upper inkjet head 121, and the downstream end is connected to the upstream end of the negative pressure side common path 166 and the downstream end of the lower negative pressure head path 165.

[0195] The negative pressure side lower head path 165 is a path for ink to flow from the lower inkjet head 121 toward the negative pressure side common path 166. The upstream end of the negative pressure side lower head path 165 in the ink circulation direction is connected to the lower inkjet head 121, and the downstream end is connected to the upstream end of the negative pressure side common path 166 and the downstream end of the negative pressure side upper head path 164.

[0196] The common path 166 on the negative pressure side is a common path for ink flowing from the upper inkjet head 121 to the negative pressure tank 143 and for ink flowing from the lower inkjet head 121 to the negative pressure tank 143. The upstream end of the common path 166 on the negative pressure side in the ink circulation direction is connected to the downstream end of the upper negative pressure head path 164 and the downstream end of the lower negative pressure head path 165, and the downstream end of the common path 166 on the negative pressure side in the ink circulation direction is connected to the negative pressure tank 143.

[0197] Adjusting valves 147 to 150 respectively adjust the flow path resistance of the upper head path 162 on the pressurized side, the lower head path 163 on the pressurized side, the upper head path 164 on the negative pressure side, and the lower head path 165 on the negative pressure side. Adjusting valves 147 to 150 adjust the flow path resistance by adjusting the diameter of the flow path, which is a parameter related to the flow path resistance.

[0198] Pumping liquid path 151 is the path through which ink flows from negative pressure tank 143 to pressurized tank 141 via ink pump 152. The upstream end of pumping liquid path 151 in the ink circulation direction is connected to negative pressure tank 143, and the downstream end is connected to pressurized tank 141.

[0199] Ink pump 152 delivers ink from negative pressure tank 143 to pressurized tank 141. Ink pump 152 is located midway through the pumping path 151.

[0200] Ink supply units 132A to 132D supply ink to ink circulation units 131A to 131D respectively. Ink supply unit 132 includes ink cartridge 171, ink supply path 172 and ink supply valve 173.

[0201] The ink cartridge 171 contains the ink used in printing using the inkjet head 121. The ink in the ink cartridge 171 is supplied to the negative pressure tank 143 of the ink circulation unit 131 via the ink supply path 172.

[0202] Ink supply path 172 connects ink cartridge 171 to negative pressure tank 143. In ink supply path 172, ink flows from ink cartridge 171 toward negative pressure tank 143.

[0203] The ink supply valve 173 opens and closes the ink flow path within the ink supply path 172. When supplying ink to the negative pressure tank 143, the ink supply valve 173 is open.

[0204] The pressure generating unit 133 generates pressure for ink circulation in the pressurized tank 141 and the negative pressure tank 143 of the ink circulation unit 131. Specifically, the pressure generating unit 133 draws air from the negative pressure tank 143 via the negative pressure air path 135 and sends air to the pressurized tank 141 via the pressurized air path 134, thereby applying positive pressure to the pressurized tank 141 and negative pressure to the negative pressure tank 143. The pressure generating unit 133 is common to the ink circulation units 131A to 131D.

[0205] The pressurized air path 134 connects the pressure generating unit 133 to the air layer on the surface of the ink in the pressurized tank 141. Each pressurized air path 134 is provided corresponding to each ink circulation unit 131A to 131D.

[0206] The negative pressure air path 135 connects the pressure generating unit 133 to the air layer on the liquid surface of the ink in the negative pressure tank 143. Each of the ink circulation units 131A to 131D is provided with a negative pressure air path 135.

[0207] The maintenance unit 109 is used to clean the nozzle surface 121a of each inkjet head 121 of the head units 103A to 103D. The maintenance unit 109 is movable between an extended position configured for cleaning the inkjet head 121 and a retracted position. The extended position is... Figure 10 The maintenance section 109 shown is positioned directly below the head unit 103, which is horizontally arranged at a predetermined cleaning height. The illustration of the maintenance section 109 in its retracted position is omitted. Figure 10 As shown, the maintenance unit 109 includes an ink receiving unit 181 and a wiping component 182.

[0208] The ink receiving section 181 receives ink and the like that removed from the nozzle surface 121a by wiping with the wiping member 182 during the cleaning of the inkjet head 121.

[0209] The wiping member 182 wipes the nozzle surface 121a of the inkjet head 121 to remove ink and other substances from the nozzle surface 121a. In the maintenance unit 109, wiping members 182 are provided for wiping the three front inkjet heads 121 and the three rear inkjet heads 121 of the six inkjet heads 121 arranged in a staggered configuration, respectively, for the head units 103A to 103D. That is, eight wiping members 182 are provided in the maintenance unit 109.

[0210] The control unit 110 controls the operation of each part of the inkjet printing apparatus 101. The control unit 110 is configured to include a CPU, RAM, ROM, hard disk, etc.

[0211] Control unit 110 stores Figure 12The flow path resistance table 186 is shown. Flow path resistance table 186 shows the flow path resistance R of each ink unit 108A-108C during printing, considering the height position, head angle, and upper head path 162 on the pressure side of the head units 103A-103D. 1k The flow path resistance R of the lower head path 163 on the pressurized side 2k The flow path resistance R of the upper head path 164 on the negative pressure side 1f And the flow path resistance R of the lower head path 165 on the negative pressure side. 2f The associated tables are listed. Flow resistance table 186 stores the flow resistance R of the inkjet head 121 during cleaning. 1k R 2k R 1f R 2f The flow path resistance R will be described later. 1k R 2k R 1f R 2f For details.

[0212] During printing, the control unit 110 controls the adjusting valves 147-150 based on the height position and head angle of the head units 103A-103D and with reference to the flow path resistance table 186, in order to adjust the flow path resistance R in the ink circulation sections 131A-131D of the ink units 108A-108C. 1k R 2k R 1f R 2f During the cleaning of the inkjet head 121, the control unit 110 refers to the flow path resistance table 186 to control the adjusting valves 147-150 to reduce the flow path resistance R in the ink circulation sections 131A-131D of the ink units 108A-108C. 1k R 2k R 1f R 2f Adjust to the value used during cleaning.

[0213] Next, the flow path resistance R of the upper head path 162 on the pressurized side of the ink circulation section 131 mentioned above is... 1k The flow path resistance R of the lower head path 163 on the pressurized side 2k The flow path resistance R of the upper head path 164 on the negative pressure side 1f And the flow path resistance R of the lower head path 165 on the negative pressure side. 2f Please provide an explanation.

[0214] During printing, the nozzles 123 are arranged in a non-horizontal direction (the head angle is not 0 degrees), resulting in a water head difference between the nozzles 123. Furthermore, the two inkjet heads 121 connected to an ink circulation section 131 are at different heights. Even under these conditions, the flow path resistance R will still be... 1k R 2k R1f R 2f The value is set such that the nozzle pressure of each nozzle 123 in the nozzle array 24 of the inkjet head 121 is within the range (stable ejection range) where ink can be ejected stably, and the ink flows at the same flow rate required by each inkjet head 121.

[0215] Figure 13 This is a fluid circuit model diagram of the ink circulation unit 131 and the two inkjet heads 121 connected to the ink circulation unit 131.

[0216] exist Figure 13 In the middle, P k P f These are the set pressures of the pressurized tank 141 and the negative pressure tank 143 during ink circulation (printing). During ink circulation, the pressure of the pressurized tank 141 and the negative pressure tank 143 is adjusted to P by the pressure generating unit 133. k P f .

[0217] P1 is the average nozzle pressure of the upper inkjet head 121, and specifically the nozzle pressure of the central nozzle 123 in the nozzle array 124 of the upper inkjet head 121. P2 is the average nozzle pressure of the lower inkjet head 121, and also specifically the nozzle pressure of the central nozzle 123 in the nozzle array 124 of the lower inkjet head 121. Since a head difference exists between the nozzles 123 in both the upper and lower inkjet heads 121, the average nozzle pressure of the nozzles 123 in the upper inkjet head 121 (P1) and the average nozzle pressure of the nozzles 123 in the lower inkjet head 121 (P2) are used.

[0218] Q min It is the ink circulation flow rate required during ink circulation (printing).

[0219] R 0k It is the flow path resistance of the common path 161 on the pressurized side. R 0k It is a fixed value. R 1k As mentioned above, this is the flow path resistance of the upper head path 162 on the pressurized side. R 2k As mentioned above, this is the flow path resistance of the lower head path 163 on the pressurized side.

[0220] R 0f It is the flow path resistance of the common path 166 on the negative pressure side. R 0f It is a fixed value. R 1f As mentioned above, this is the flow path resistance of the upper head path 164 on the negative pressure side. R 2f As mentioned above, this is the flow resistance of the negative pressure side lower head path 165.

[0221] R HkR is the flow path resistance from the ink inlet port inside the inkjet head 121 to the nozzle 123. Hf R is the flow path resistance from the nozzle 123 inside the inkjet head 121 to the ink outlet port. Hk R Hf It is a fixed value. R H It is the flow path resistance within the inkjet head 121. R H It is represented by the following formula (1).

[0222] R H =R Hk +R Hf …(1)

[0223] R1 is the flow path resistance of the flow path formed by the upper head path 162 on the pressurized side, the upper inkjet head 121, and the upper head path 164 on the negative pressure side. R1 is represented by the following equation (2).

[0224] R1 = R 1k +R H +R 1f …(2)

[0225] R2 is the flow path resistance of the flow path through the pressurized side lower head path 163, the lower inkjet head 121, and the negative pressure side lower head path 165. R2 is represented by the following equation (3).

[0226] R2 = R 2k +R H +R 2f …(3)

[0227] R 12 R is the flow path resistance between the downstream end of the common path 161 on the pressurized side and the upstream end of the common path 166 on the negative pressure side. 12 It is represented by the following formula (4).

[0228] R 12 =R1×R2 / (R1+R2)…(4)

[0229] When the flow path resistance of the entire path from the pressurized tank 141 to the negative pressure tank 143 via the inkjet head 121 is set as R, R is represented by the following equation (5).

[0230] R = R 0k +R 12 +R 0f …(5)

[0231] As mentioned above, the flow path resistance R 1k R 2k R 1f R 2fThe nozzle pressure of each nozzle 123 in the nozzle array 124 of the two inkjet heads 121 is set to be within a stable ejection range, and ink flows at the same flow rate required by the two inkjet heads 121.

[0232] Specifically, R 1k R 2k R 1f R 2f It is set to make the following equations (6) to (8) true.

[0233] P1 = P2 = P typ …(6)

[0234] R1=R2…(7)

[0235] R = (P k -P f ) / Q min …(8)

[0236] Equation (6) above represents the condition for ensuring that the nozzle pressure of each nozzle 123 in the nozzle array 124 of the two inkjet heads 121 is within the stable ejection range. The reason for setting equation (6) as a condition is as follows.

[0237] In the ink circulation section 131 and the two inkjet heads 121 connected to the ink circulation section 131, if the following formula (9) holds, the nozzle pressure of each nozzle 123 of the nozzle array 124 in the two inkjet heads 121 becomes the pressure within the stable ejection range.

[0238] ΔP≥P Hh +|P1-P2|+Pσ…(9)

[0239] ΔP is the upper limit of the stable ejection range (the maximum nozzle pressure P that can stably eject the product). max The lower limit of the stable ejection range (the minimum nozzle pressure P that can stably eject the product) and the lower limit of the stable ejection range. min The difference (P) max -P min ).

[0240] P Hh It refers to the head difference within the inkjet head 121. Specifically, P Hh The nozzle pressure P of the nozzle 123 at the downstream end of the nozzle array 124 of the inkjet head 121 is... nl The nozzle pressure P of the upper nozzle 123 nu The difference (P) nl -P nu ).

[0241] Pσ is the deviation (variance) of the nozzle pressure of the two inkjet heads 121. Pσ is determined by the performance of the pressure generating unit 133, the deviation of each component, etc.

[0242] As can be seen from equation (9), the smaller |P1-P2| is, the easier it is for equation (9) to hold true. Therefore, in this embodiment, as in equation (6), P1 is set to P2. As a result, the pressure difference based on the water head difference between the upper inkjet head 121 and the lower inkjet head 121 disappears, and equation (9) easily holds true. In this embodiment, the ink circulation unit 131 and the inkjet head 121 are configured such that when P1 = P2, P Hh Pσ becomes the value that makes equation (9) true.

[0243] P in equation (6) typ This is the desired nozzle pressure value (target value) for the inkjet head 121. typ Set as P max With P min The values ​​between.

[0244] Equation (7) above represents the condition for ensuring that the ink flows at the same flow rate in both inkjet heads 121. Equation (8) above represents the condition for ensuring the ink flow rate required for printing by both inkjet heads 121. Setting equations (7) and (8) as conditions is to ensure that the ink flows at the required and the same flow rate in both inkjet heads 121.

[0245] When P1 is calculated from the pressure tank 141 side, P1 is represented by the following formula (10).

[0246]

Number 1

[0247]

[0248] P 1h It is the water head pressure of the upper inkjet head 121.

[0249] When P1 is calculated from the negative pressure tank 143 side, P1 is represented by the following formula (11).

[0250]

Number 2

[0251]

[0252] When P2 is calculated from the pressure tank 141 side, P2 is represented by the following formula (12).

[0253]

Number 3

[0254]

[0255] P 2h It is the water head pressure of the lower inkjet head 121.

[0256] When P2 is calculated from the negative pressure tank 143 side, P2 is represented by the following formula (13).

[0257]

Number 4

[0258]

[0259] Based on equations (1) to (13), we obtain equations (14) to (17).

[0260]

Number 5

[0261]

[0262]

[0263]

[0264]

[0265] The water head pressure P of the upper inkjet head 121 in equations (14) and (16) 1h And the water head pressure P of the lower inkjet head 121 in equations (15) and (17) 2h The height position varies depending on the height position of each inkjet head 121. The height position of each inkjet head 121 varies depending on the height position of the head unit 103 and the head angle.

[0266] In response, in the inkjet printing apparatus 101, the flow path resistance R of the ink circulation sections 131A-131D of the ink units 108A-108C is calculated in advance based on the height position and head angle of the head unit 103, i.e., based on the height position of each inkjet head 121. 1k R 2k R 1f R 2f Stored in Flow Path Resistance Table 186.

[0267] By controlling the flow path resistance R 1k R 2k R 1f R 2f With the values ​​calculated as described above set, when the nozzle 123 is not arranged horizontally (head angle is not 0 degrees), the flow path resistance R on the upstream side of the inkjet head 121, on the lower head path 163 of the pressurized side. 2k The flow path resistance R of the upper head path 162 on the pressurized side 1k Large. On the downstream side of the inkjet head 121, the flow resistance R of the negative pressure side lower head path 165 is... 2f The flow path resistance R of the upper head path 164 on the negative pressure side 1fSmall. Moreover, the pressure difference based on the head difference between the upper inkjet head 121 and the lower inkjet head 121 is eliminated.

[0268] During the cleaning of the inkjet head 121, the flow path resistance R is reduced. 1k R 2k R 1f R 2f The value is set to discharge the same predetermined amount of ink from each nozzle 123 of each inkjet head 121 by purging.

[0269] Purging is a process in which ink is delivered from the pressurized tank 141 to the two inkjet heads 121 via the pressurized ink path 145, causing ink to be discharged from each nozzle 123 of the two inkjet heads 121. In the inkjet printing apparatus 101, purging is performed with the head units 103A to 103D arranged horizontally at a predetermined cleaning height. During purging, a positive pressure for purging is applied to the pressurized tank 141, while the negative pressure tank 143 is set to an open state.

[0270] Therefore, P in equations (14) and (15) k Set as the positive pressure for purging, and P in equations (16) and (17) f Let the pressure be atmospheric pressure, and let P in equations (14) and (16) be... 1h and P in equations (15) and (17) 2h Let P in equations (14) to (17) be the value of the head units 103A to 103D in a horizontal state at a specified cleaning height position. typ Q min The nozzle pressure and circulation flow rate are set to values ​​that allow a specified amount of ink to be discharged through purging, respectively. The flow path resistance R during the cleaning of the inkjet head 121 is then calculated. 1k R 2k R 1f R 2f In the inkjet printing apparatus 101, the flow path resistance R during cleaning, calculated in this way, is... 1k R 2k R 1f R 2f Stored in Flow Path Resistance Table 186.

[0271] Next, the operation of the inkjet printing apparatus 101 will be explained.

[0272] During printing using the inkjet printing apparatus 101, the control unit 110 controls the rotation drive unit 104 and the lifting drive unit 106 to set the height position and head angle of the head units 103A to 103D to correspond to the height position and tilt angle of the printing surface 111a of the printing medium 111. The height position and head angle of the head units 103A to 103D corresponding to the height position and tilt angle of the printing surface 111a are input, for example, through user operation via an operation input unit (not shown).

[0273] In addition, the control unit 110, based on the set height position and head angle of the head units 103A to 103D, controls the adjusting valves 147 to 150 with reference to the flow path resistance table 186 to adjust the flow path resistance R in the ink circulation sections 131A to 131D of the ink units 108A to 108C. 1k R 2k R 1f R 2f In this way, the control unit 110 automatically adjusts the parameters related to the flow path resistance of the ink path in conjunction with the height position and head angle (i.e., position adjustment) of the set head units 103A to 103D.

[0274] Next, when a printing job is input, the control unit 110 starts ink circulation in the ink circulation sections 131A-131D of the ink units 108A-108C. Specifically, the control unit 110, through the pressure generating section 133 of the ink units 108A-108C, causes the pressure tank 141 and the negative pressure tank 143 to generate a set pressure P for ink circulation. k P f Thus, ink circulation in ink circulation units 131A to 131D begins, and ink flows from pressurized tank 141 to negative pressure tank 143 via inkjet head 121.

[0275] When the ink cycle begins, the control unit 110 begins the execution of the printing operation. Specifically, the control unit 110 controls the transport of the printing medium 111 via the transport unit 102, and ejects ink from each inkjet head 121 of the head units 103A to 103D to print an image on the printing medium 111.

[0276] During the printing operation, ink is supplied from the pressurized tank 141 to the inkjet head 121, and any ink not consumed by the inkjet head 121 is recycled to the negative pressure tank 143. When the pressurized tank level sensor 142 is off and the negative pressure tank level sensor 144 is on, the control unit 110 drives the ink pump 152. This supplies ink from the negative pressure tank 143 to the pressurized tank 141. When the pressurized tank 141 is on, the control unit 110 stops the ink pump 152. In this way, the ink is circulated, and printing is performed.

[0277] When both the pressurized tank level sensor 142 and the negative pressure tank level sensor 144 are off, the control unit 110 opens the ink supply valve 173. This replenishes ink from the ink cartridge 171 to the negative pressure tank 143. When the negative pressure tank level sensor 144 is on, the control unit 110 closes the ink supply valve 173.

[0278] When printing based on the printing operation is completed, the control unit 110 controls the pressure generating unit 133 to end the ink circulation in the ink circulation units 131A to 131D.

[0279] Next, the operation of cleaning the nozzle surface 121a of the inkjet head 121 in the inkjet printing apparatus 101 will be described.

[0280] When the inkjet head 121 is instructed to be cleaned, the control unit 110 controls the rotation drive unit 104 and the lifting drive unit 106 to position the inkjet head units 103A-103D horizontally at the cleaning height. Additionally, the control unit 110 refers to the flow path resistance table 186 to control the adjusting valves 147-150 to adjust the flow path resistance R in the ink circulation sections 131A-131D of the ink units 108A-108C. 1k R 2k R 1f R 2f Adjust to the value used during cleaning. Additionally, the control unit 110 positions the maintenance unit 109 in the extended position.

[0281] Next, the control unit 110 controls the pressure generating unit 133 of the ink units 108A to 108C to apply positive pressure for purging to the pressure tanks 141 of the ink circulation units 131A to 131D. The negative pressure tank 143 is set to be open to the atmosphere.

[0282] When a positive pressure for purging is applied to the pressurized tank 141, the same predetermined amount of ink is discharged from each nozzle 123 of each inkjet head 121. At least a portion of the ink discharged from the nozzle 123 by purging adheres to the nozzle surface 121a.

[0283] Next, the control unit 110 controls the maintenance unit 109 to wipe the nozzle surface 121a of the inkjet head 121 using the wiping member 182. This removes dust and other contaminants from the nozzle surface 121a along with any ink adhering to it. As a result, the cleaning of the inkjet head 121 is complete.

[0284] As explained above, in the inkjet printing apparatus 101, during printing, the control unit 110 controls the adjusting valves 147-150 in the ink circulation units 131A-131D of the ink units 108A-108C based on the height position and head angle of the head units 103A-103D, i.e., the height position of each inkjet head 121, to reduce the flow path resistance R. 1kR 2k R 1f R 2f The adjustment is made so that the nozzle pressure of each nozzle 123 in the nozzle array 124 of the two inkjet heads 121 connected to the ink circulation section 131 is within a stable ejection range, and the ink flows at the same flow rate required by the two inkjet heads 121.

[0285] Therefore, even if the height position of each inkjet head 121 changes due to changes in at least one of the height position or head angle of the head units 103A-103D, the ink flow rate required for printing can be ensured equally for the two inkjet heads 121 connected to the ink circulation unit 131, and even if there is a head difference between the nozzles 123, the range of nozzles 123 capable of stable ink ejection can be suppressed from narrowing. As a result, in a structure that simplifies the device structure and control by connecting two inkjet heads 121 to one ink circulation unit 131, the situation where wide-format images cannot be printed in one pass can be suppressed. In addition, the head units 103A-103D, which eject ink of different colors respectively, are arranged along the transport direction of the printing medium 111. Therefore, it is possible to perform transverse printing on the sides of the printing medium 111 (e.g., three-dimensional objects such as cartons) with full-color wide-format printing.

[0286] During the cleaning and purging process of the inkjet head 121, the control unit 110 controls the adjusting valves 147-150 to reduce the flow path resistance R in the ink circulation sections 131A-131D of the ink units 108A-108C. 1k R 2k R 1f R 2f The inkjet head 121 is adjusted so that each nozzle 123 of each inkjet head 121 discharges the same predetermined amount of ink. This prevents excessive ink discharge from the nozzles 123 of the inkjet head 121 due to purging, thus reducing ink waste.

[0287] In the above implementation, in order to calculate the flow path resistance R 1k R 2k R 1f R 2f Set P1=P2 as a condition, but even if it is not P1=P2, it is sufficient to set the nozzle pressure of each nozzle 123 in each inkjet head 121 to the pressure within the stable ejection range.

[0288] In the above embodiment, the flow path resistance R is adjusted by adjusting valves 147-150. 1k R 2k R 1f R 2f However, adjusting the flow path resistance R 1k R 2k R 1f R2f The method is not limited to this. For example, it can be the following structure: the upper head path 162 on the pressurized side, the lower head path 163 on the pressurized side, the upper head path 164 on the negative pressure side, and the lower head path 165 on the negative pressure side are respectively formed by the pipeline and the outer pipe. Air is delivered to the gap between the pipeline and the outer pipe by a pump, or air is drawn from the gap, thereby changing the inner diameter of the pipeline to adjust the flow resistance.

[0289] In the above implementation, in order to adjust the flow path resistance R 1k R 2k R 1f R 2f The diameter of the ink flow path is adjusted by adjusting valves 147 to 150. However, parameters related to flow path resistance other than the flow path diameter can also be adjusted. Besides the flow path diameter, parameters related to flow path resistance include the flow path length, pipe shape, ink viscosity, pressure of pressurized tank 141, and pressure of negative pressure tank 143. The flow path resistance R is adjusted by adjusting at least one of the following parameters: flow path length, flow path diameter, pipe shape, ink viscosity, pressure of pressurized tank 141, and pressure of negative pressure tank 143, using the adjustment unit for adjusting parameters related to flow path resistance. 1k R 2k R 1f R 2f That's all.

[0290] The device can be configured to allow manual rotation of the printhead units 103A to 103D. When the printhead units 103A to 103D are set to a horizontal position, the inkjet printing apparatus 101 enters a cleaning mode for cleaning the printhead 121. In this case, when in cleaning mode, parameters related to flow path resistance are adjusted to reduce the flow path resistance R. 1k R 2k R 1f R 2f The value should be the same as the value used when cleaning the inkjet head 121.

[0291] In the head unit 103, each inkjet head 121 can move independently along the arrangement direction of the nozzles 123. This movement can be performed manually or automatically by a drive unit using a motor or the like. When the arrangement direction of the nozzles 123 is not horizontal, the height position of the inkjet head 121 changes as it moves along the arrangement direction of the nozzles 123 within the head unit 103. Therefore, the flow path resistance R corresponding to the height position of the head unit 103, the head angle, and the position of each inkjet head 121 within the head unit 103 along the arrangement direction of the nozzles 123 is calculated in advance. 1k R 2k R 1f R 2fAnd keep it in the table, and refer to the table to adjust the flow path resistance R. 1k R 2k R 1f R 2f That's all.

[0292] In the above embodiment, the head unit 103 is configured to be able to rotate and move up and down, but it can also be configured to be able to perform only one of these actions. If the head unit 103 cannot rotate but can move up and down, the head angle can be set to any arbitrary angle. The rotation and movement of the head unit 103 can be performed manually.

[0293] It can be configured to not be able to perform at least one of the rotation and lifting actions of the head unit 103, but to be able to perform individual movement of the nozzles 123 of the inkjet head 121 along the arrangement direction. The head unit 103 can perform at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle surface 121a and orthogonal to the arrangement direction of the nozzles 123; vertical movement including movement when the arrangement direction of the nozzles 123 is not horizontal; and individual movement of each inkjet head 121 along the arrangement direction when the arrangement direction of the nozzles 123 is not horizontal. In addition, it is not limited to this, the height position of the inkjet head 121 can be changed.

[0294] In the above embodiment, a structure is shown that supplies ink to two inkjet heads 121 through an ink circulation unit 131, but a structure that supplies ink to one inkjet head through an ink circulation unit is also possible. In this case, during printing, based on the height position of the inkjet head, parameters related to the flow path resistance of the pressurized ink path connecting the pressurized tank and the inkjet head, and the negative pressure ink path connecting the inkjet head and the negative pressure tank, are adjusted so that the nozzle pressure of each nozzle is within a stable ejection range, and ink flows at the flow rate required by the inkjet head. During purging, parameters related to the flow path resistance of the pressurized ink path and the negative pressure ink path are adjusted so that each nozzle discharges the same predetermined amount of ink.

[0295] In this case, during printing, the required ink flow rate can be ensured, and even if there is a head difference between the nozzles 123 in the inkjet head 121, the range of nozzles 123 capable of stable ink ejection can be suppressed from narrowing, thus preventing the inability to print wide-format images in one pass. When cleaning the inkjet head 121, excessive ink discharge from the nozzles 123 of the inkjet head 121 by purging can be prevented, thus suppressing ink waste.

[0296] In the above embodiment, a structure is shown that supplies ink to two inkjet heads 121 through one ink circulation unit 131. However, it is also possible to supply ink to three or more inkjet heads through one ink circulation unit. In this case, during printing, based on the height position of each inkjet head, the parameters related to the flow path resistance of each of the multiple pressurized side branch paths and multiple negative pressure side branch paths connected to each inkjet head are adjusted so that the nozzle pressure of each nozzle in the nozzle array of each inkjet head is within a stable ejection range, and ink flows at the same flow rate required by each inkjet head. During purging, the parameters related to the flow path resistance of each of the multiple pressurized side branch paths and multiple negative pressure side branch paths are adjusted so that each nozzle of each inkjet head ejects the same predetermined amount of ink.

[0297] The parameters related to the flow path resistance of the ink path can be adjusted to make the nozzle pressure of each nozzle in the nozzle array of the inkjet head a pressure within a stable ejection range, and to allow the ink to flow at the same flow rate required by each inkjet head. The flow path resistance itself can also be adjusted.

[0298] One implementation may have the following structure, for example.

[0299] The inkjet printing apparatus according to embodiments of the present invention includes: an inkjet head having a nozzle array of a plurality of nozzles arranged to eject ink, wherein the inkjet head ejects ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The printing is performed with parameters related to the flow path resistance of the ink path set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head.

[0300] The inkjet printing apparatus may further include: an adjustment unit that adjusts parameters related to the flow path resistance of the ink path; and a control unit that controls the adjustment unit. The inkjet head can change its height position. During printing, the control unit controls the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the ink path to a pressure within a range that allows for stable ink ejection from each of the plurality of nozzles, and to allow ink to flow at the flow rate required by the inkjet head.

[0301] The ink canister may include: a pressurized canister that stores ink supplied to the inkjet head and is subjected to positive pressure for delivering ink to the inkjet head; and a negative pressure canister that receives ink not consumed by the inkjet head and is subjected to negative pressure for recovering ink from the inkjet head. The ink path may include: a pressurized side ink path connecting the pressurized canister to the inkjet head; and a negative pressure side ink path connecting the inkjet head to the negative pressure canister. The adjustment unit can adjust parameters related to the flow resistance of the pressurized side ink path and parameters related to the flow resistance of the negative pressure side ink path. The inkjet head may be capable of performing at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle faces of the plurality of nozzle openings and orthogonal to the arrangement direction; vertical movement including movement in a state where the arrangement direction is not horizontal; and movement along the arrangement direction in a state where the arrangement direction is not horizontal. During printing, the control unit can control the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the pressurized ink path and the flow path resistance of the negative pressure ink path so that the nozzle pressure of each of the plurality of nozzles is within the range that can stably eject ink, and the ink flows at the flow rate required by the inkjet head.

[0302] When the arrangement direction is horizontal, the control unit can perform a purging process to clean the inkjet head by feeding ink from the pressurized tank to the inkjet head via the pressurized ink path and discharging ink from the plurality of nozzles. During the purging process, the adjustment unit is controlled to adjust the parameters related to the flow resistance of the pressurized ink path and the parameters related to the flow resistance of the negative pressure ink path so that the plurality of nozzles discharge the same predetermined amount of ink.

[0303] The inkjet head may include a plurality of inkjet heads arranged in a staggered manner in the arrangement direction. The inkjet printing apparatus may also include a head unit including the plurality of inkjet heads. The pressurized side ink path may include a plurality of pressurized side branch paths respectively connected to the plurality of inkjet heads. The negative pressure side ink path may include a plurality of negative pressure side branch paths respectively connected to the plurality of inkjet heads. The head unit may be capable of performing at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle surface and orthogonal to the arrangement direction; vertical movement including movement in a state where the arrangement direction is not horizontal; and individual movement of each of the inkjet heads along the arrangement direction in a state where the arrangement direction is not horizontal. The adjustment unit may adjust parameters related to the flow path resistance of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths. During printing, the control unit can control the adjustment unit based on the height position of each of the plurality of inkjet heads to adjust the parameters related to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths so that the nozzle pressure of each of the plurality of nozzles in the nozzle array of each of the plurality of inkjet heads is within the range that can stably eject ink, and the ink flows at the same flow rate required by each of the plurality of inkjet heads.

[0304] The control unit can perform a purging process in which ink is supplied from the pressurized tank to the plurality of inkjet heads via the pressurized side ink path and ink is discharged from the plurality of nozzles of the plurality of inkjet heads, in a horizontal arrangement, to clean the plurality of inkjet heads. During the purging process, the adjustment unit is controlled to adjust the parameters related to the flow path resistance of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths so that the plurality of nozzles of the plurality of inkjet heads discharge the same predetermined amount of ink.

[0305] The inkjet head may include: a first inkjet head that ejects ink of a first color onto a printing medium being conveyed in a conveying direction parallel to the horizontal direction; and a second inkjet head that ejects ink of a second color different from the first color onto the printing medium being conveyed in the conveying direction. The inkjet printing apparatus may further include: a first head unit including the first inkjet head; and a second head unit including the second inkjet head, the second head unit being disposed downstream of the first head unit in the conveying direction.

[0306] The inkjet head may include: a first inkjet head; and a second inkjet head disposed at a position higher than the first inkjet head. The printing can be performed with parameters related to the flow path resistance of the ink path set such that the average nozzle pressure of the plurality of nozzles of the first inkjet head is the same as the average nozzle pressure of the plurality of nozzles of the second inkjet head.

[0307] The inkjet head can be positioned by at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle faces of the plurality of nozzle openings and orthogonal to the arrangement direction; vertical movement including movement when the arrangement direction is not horizontal; and movement along the arrangement direction when the arrangement direction is not horizontal. The control unit can control the adjustment unit in conjunction with the position adjustment to adjust the parameters related to the flow path resistance of the ink path.

[0308] The flow path resistance adjustment method according to embodiments of the present invention is used to adjust parameters related to the flow path resistance of the ink path in an inkjet printing apparatus, the inkjet printing apparatus comprising: an inkjet head having a nozzle array having a plurality of nozzles arranged to eject ink, the inkjet head ejecting ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The flow path resistance adjustment method includes adjusting the parameters related to the flow path resistance of the ink path to such that the nozzle pressure of each of the plurality of nozzles during printing is within a predetermined range capable of stably ejecting ink, and that ink flows at a flow rate required by the inkjet head.

[0309] In the flow path resistance adjustment method, the inkjet printing apparatus may include: an adjustment unit that adjusts parameters related to the flow path resistance of the ink path; and a control unit that controls the adjustment unit, wherein the inkjet head is capable of changing its height position. The flow path resistance adjustment method may include: during printing, the control unit controls the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the ink path to a pressure within a range that allows for stable ink ejection from each of the plurality of nozzles, and to allow ink to flow at the flow rate required by the inkjet head.

[0310] A printing method, according to an embodiment of the present invention, is a printing method in an inkjet printing apparatus comprising: an inkjet head having a nozzle array of a plurality of nozzles arranged to eject ink, the inkjet head ejecting ink from the plurality of nozzles in a non-horizontal orientation for printing; an ink tank subjected to pressure for supplying ink to or recovering ink from the inkjet head; and an ink path connecting the ink tank to the inkjet head. The printing method includes performing printing while a parameter related to the flow path resistance is set such that the nozzle pressure of each of the plurality of nozzles is within a predetermined range capable of stably ejecting ink, and ink flows at a flow rate required by the inkjet head.

[0311] In the printing method, the inkjet printing apparatus may include: an adjustment unit that adjusts parameters related to the flow path resistance of the ink path; and a control unit that controls the adjustment unit, wherein the inkjet head is capable of changing its height position. The printing method may include, during printing, the control unit controlling the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the ink path to a pressure within a range that allows for stable ink ejection from each of the plurality of nozzles, and to perform printing with ink flowing at the flow rate required by the inkjet head.

[0312] The embodiments of the present invention have been described above. However, the present invention can be embodied in other ways without departing from its spirit and essence. Therefore, these embodiments are illustrative in all respects and not restrictive, and the scope of the invention is indicated by the appended claims, not by the foregoing description, and all variations with the same meaning and scope as the claims are included within the scope of the invention.

[0313] Furthermore, the effects described in the embodiments of the present invention are merely examples of the best effects achieved by the present invention. Therefore, the effects of the present invention are not limited to those described in the embodiments of the present invention.

Claims

1. An inkjet printing apparatus, comprising: An inkjet head having a nozzle array of multiple nozzles arranged to eject ink, wherein the inkjet head ejects ink from the multiple nozzles in the nozzle array in a non-horizontal orientation to perform printing. Ink reservoir, which is subjected to pressure for supplying ink to or recovering ink from the inkjet head; and The ink path connects the ink tank to the inkjet head. in, The printing is performed with parameters related to the flow path resistance of the ink path set such that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that allows for stable ink ejection, and the ink flows at the flow rate required by the inkjet head. The parameters related to the flow path resistance of the ink path are preset to ensure that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that allows for stable ink ejection, and that the ink flows at the flow rate required by the inkjet head. The ink cartridge includes: A pressurized tank, which stores ink supplied to the inkjet head and is subjected to positive pressure for delivering ink to the inkjet head; and A negative pressure tank, which receives ink not consumed by the inkjet head and is subjected to negative pressure to recover the ink from the inkjet head. The ink path includes: A pressurized ink path that connects the pressurized tank to the inkjet head; and The negative pressure side ink path connects the inkjet head to the negative pressure tank. Parameters related to the flow path resistance of the pressurized ink path and parameters related to the flow path resistance of the negative pressure ink path are set to ensure that the nozzle pressure of each of the plurality of nozzles is within the specified range and that ink flows at the flow rate required by the inkjet head, the inkjet head comprising a plurality of inkjet heads disposed at different height positions. The pressurized ink path includes multiple pressurized branch paths that are respectively connected to the plurality of inkjet heads. The negative pressure side ink path includes multiple negative pressure side branch paths that are respectively connected to the multiple inkjet heads. The parameters relating to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths are set such that the nozzle pressure of each of the plurality of nozzles in the nozzle array of each of the plurality of inkjet heads is within the specified range, and ink flows at the same flow rate required by each of the plurality of inkjet heads.

2. The inkjet printing apparatus according to claim 1, characterized in that, The inkjet head is rotatable about an axis extending in a direction parallel to the nozzle surfaces of the plurality of nozzle openings and orthogonal to the arrangement direction. Printing is performed when the arrangement direction is not horizontal. With the arrangement direction horizontal, a purging process is performed to clean the nozzle surface.

3. The inkjet printing apparatus according to claim 1, characterized in that, It also has: The adjustment unit adjusts parameters related to the flow path resistance of the ink path; and The control unit controls the adjustment unit. The inkjet head can change its height position. During printing, the control unit controls the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the ink path so that the nozzle pressure of each of the plurality of nozzles is within a range that allows for stable ink ejection, and the ink flows at the flow rate required by the inkjet head.

4. The inkjet printing apparatus according to claim 3, characterized in that, The adjustment unit adjusts parameters related to the flow resistance of the pressurized ink path and parameters related to the flow resistance of the negative pressure ink path. The inkjet head is capable of performing at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle surfaces of the plurality of nozzle openings and orthogonal to the arrangement direction; This includes vertical movement when the arrangement direction is not horizontal; and movement along the arrangement direction when the arrangement direction is not horizontal. During printing, the control unit controls the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the pressurized ink path and the flow path resistance of the negative pressure ink path so that the nozzle pressure of each of the plurality of nozzles is within the range that can stably eject ink, and the ink flows at the flow rate required by the inkjet head.

5. The inkjet printing apparatus according to claim 4, characterized in that, With the arrangement direction horizontal, the control unit performs a purging process to clean the inkjet head, which involves feeding ink from the pressurized tank to the inkjet head via the pressurized ink path and discharging ink from the plurality of nozzles. During the purging process, the control unit controls the adjustment unit to adjust the parameters related to the flow resistance of the pressurized ink path and the flow resistance of the negative pressure ink path so that the plurality of nozzles discharge the same predetermined amount of ink.

6. The inkjet printing apparatus according to claim 4, characterized in that, The inkjet head includes a plurality of inkjet heads arranged in a staggered manner in the arrangement direction. The inkjet printing apparatus also includes a head unit comprising the plurality of inkjet heads. The pressurized ink path includes multiple pressurized branch paths that are respectively connected to the plurality of inkjet heads. The negative pressure side ink path includes multiple negative pressure side branch paths that are respectively connected to the multiple inkjet heads. The head unit is capable of performing at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle surface and orthogonal to the arrangement direction; This includes vertical movement when the arrangement direction is not horizontal; and individual movement of each inkjet head along the arrangement direction when the arrangement direction is not horizontal. The adjustment unit adjusts parameters related to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths. During printing, the control unit controls the adjustment unit based on the height position of each of the plurality of inkjet heads to adjust the parameters related to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths so that the nozzle pressure of each of the plurality of nozzles in the nozzle array of each of the plurality of inkjet heads is within the range that can stably eject ink, and the ink flows at the same flow rate required by each of the plurality of inkjet heads.

7. The inkjet printing apparatus according to claim 6, characterized in that, With the arrangement direction horizontal, the control unit performs a purging process to clean the multiple inkjet heads, which involves feeding ink from the pressurized tank to the multiple inkjet heads via the pressurized side ink path and discharging ink from the multiple nozzles of the multiple inkjet heads. During the purging process, the control unit controls the adjustment unit to adjust the parameters related to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths so that the plurality of nozzles of the plurality of inkjet heads each discharge the same predetermined amount of ink.

8. The inkjet printing apparatus according to claim 1 or 3, characterized in that, The inkjet head includes: A first inkjet head ejects ink of a first color onto a printing medium being conveyed in a conveying direction parallel to the horizontal direction; and The second inkjet head ejects ink of a second color, different from the first color, onto the printing medium being conveyed in the conveying direction. The inkjet printing device also features: The first head unit includes the first inkjet head; and The second head unit includes the second inkjet head, which is disposed downstream of the first head unit in the conveying direction.

9. The inkjet printing apparatus according to claim 1 or 3, characterized in that, The inkjet head includes: The first inkjet head; and The second inkjet head is positioned higher than the first inkjet head. The printing is performed when parameters related to the flow path resistance of the ink path are set such that the average nozzle pressure of the plurality of nozzles of the first inkjet head is the same as the average nozzle pressure of the plurality of nozzles of the second inkjet head.

10. The inkjet printing apparatus according to claim 3, characterized in that, The inkjet head can be positioned by at least one of the following actions: rotation about an axis extending in a direction parallel to the nozzle surface of the plurality of nozzle openings and orthogonal to the arrangement direction; This includes vertical movement when the arrangement direction is not horizontal; and movement along the arrangement direction when the arrangement direction is not horizontal. The control unit controls the adjustment unit in conjunction with the position adjustment to adjust the parameters related to the flow path resistance of the ink path.

11. An inkjet printing apparatus, comprising: An upper inkjet head and a lower inkjet head are arranged vertically. The upper inkjet head and the lower inkjet head have a nozzle array with multiple nozzles that eject ink. The upper inkjet head and the lower inkjet head eject ink from the multiple nozzles in the nozzle array in a non-horizontal direction to perform printing. Header path: and An ink canister, connected via the head path to the upper inkjet head and the lower inkjet head, is subjected to pressure for supplying ink to or recovering ink from the upper inkjet head and the lower inkjet head via the head path. in, The flow path resistance parameter of the printhead path is set based on the head difference between the upper and lower printheads to ensure that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that allows for stable ink ejection, and that ink flows at the required flow rate for both the upper and lower printheads. The flow path resistance parameter of the printhead path includes at least one of the length of the printhead path, the diameter of the printhead path, the shape of the printhead path, and the pressure of the ink canister. The printing is performed using a nozzle with a nozzle pressure determined by setting the flow path resistance parameter, which is within the specified range that enables stable ink ejection and generates the ink flow required for the upper and lower inkjet heads.

12. A printing method, which is a printing method in an inkjet printing apparatus, said inkjet printing apparatus comprising: An inkjet head having a nozzle array of multiple nozzles arranged to eject ink, wherein the inkjet head ejects ink from the multiple nozzles in the nozzle array in a non-horizontal orientation to perform printing. Ink reservoir, which is subjected to pressure for supplying ink to or recovering ink from the inkjet head; and The ink path connects the ink tank to the inkjet head. The ink cartridge includes: A pressurized tank that stores ink supplied to the inkjet head and is subjected to positive pressure for delivering ink to the inkjet head; as well as A negative pressure tank, which receives ink not consumed by the inkjet head and is subjected to negative pressure to recover the ink from the inkjet head. The ink path includes: A pressurized ink path that connects the pressurized tank to the inkjet head; and The negative pressure side ink path connects the inkjet head to the negative pressure tank. The inkjet head includes multiple inkjet heads configured at different height positions. The pressurized ink path includes multiple pressurized branch paths that are respectively connected to the plurality of inkjet heads. The negative pressure side ink path includes multiple negative pressure side branch paths that are respectively connected to the multiple inkjet heads. The printing method includes: printing with parameters related to the flow path resistance of each of the plurality of pressurized side branch paths and the plurality of negative pressure side branch paths set such that the nozzle pressure of each of the plurality of nozzles in the nozzle array of each of the plurality of inkjet heads is within a specified range that enables stable ink ejection, and printing is performed with ink flowing at the same flow rate required by each of the plurality of inkjet heads.

13. The printing method according to claim 12, characterized in that, The parameters related to the flow path resistance of the ink path are pre-set so that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range that allows for stable ink ejection, and printing is performed with ink flowing at the flow rate required by the inkjet head.

14. The printing method according to claim 12, characterized in that, The inkjet printing device also features: The adjustment unit adjusts parameters related to the flow path resistance of the ink path; and The control unit controls the adjustment unit. The inkjet head can change its height position. In the printing method, during printing, the control unit controls the adjustment unit based on the height position of the inkjet head to adjust the parameters related to the flow path resistance of the ink path to a pressure within a range that allows for stable ink ejection from each of the plurality of nozzles, and to flow ink at the flow rate required by the inkjet head for printing.

15. A printing method, which is a printing method in an inkjet printing apparatus, said inkjet printing apparatus comprising: An upper inkjet head and a lower inkjet head are arranged vertically. The upper inkjet head and the lower inkjet head have a nozzle array with multiple nozzles that eject ink. The upper inkjet head and the lower inkjet head eject ink from the multiple nozzles in the nozzle array in a non-horizontal direction to perform printing. Header path: and An ink canister, connected via the head path to the upper inkjet head and the lower inkjet head, is subjected to pressure for supplying ink to or recovering ink from the upper inkjet head and the lower inkjet head via the head path. in, The printing method includes: Based on the head difference between the upper and lower inkjet heads, the flow path resistance parameter of the printhead path is set such that the nozzle pressure of each of the plurality of nozzles during printing is within a specified range capable of stably ejecting ink, and the ink flows at the flow rate required by the upper and lower inkjet heads. The flow path resistance parameter of the printhead path includes at least one of the length of the printhead path, the diameter of the printhead path, the shape of the printhead path, and the pressure of the ink canister. Printing is performed using a nozzle with a nozzle pressure determined by setting the flow path resistance parameter, which is within the specified range that enables stable ink ejection and generates the ink flow required for the upper and lower inkjet heads.

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