Inkjet head and inkjet recording device

Abstract

To provide an inkjet head and an inkjet recording device that can more reliably ensure the discharge stability of a nozzle part.SOLUTION: An inkjet head comprises a plurality of individual supply channels that individually supply ink from a common supply channel to a plurality of nozzle parts, and a plurality of individual circulation channels that individually discharge the ink from the plurality of nozzle parts to a common circulation channel, the individual pressure loss resistance of the plurality of individual circulation channels, for which the overall pressure loss resistance is greater than that of the plurality of individual supply channels, being made uniform, and the individual pressure loss resistance of the plurality of individual supply channels being made nonuniform so that the pressure of the plurality of nozzle parts is made uniform.SELECTED DRAWING: Figure 5B

Description

[Technical field]

[0001] The present invention relates to an inkjet head and an inkjet recording apparatus. [Background technology]

[0002] Inkjet recording devices have been known for some time, which perform drawing on a recording medium by ejecting (also called "ejecting") ink from nozzles in the nozzles while moving an inkjet head having multiple nozzles relative to a recording medium such as paper. Inkjet recording devices generally have multiple nozzles capable of storing ink therein and a supply flow path that supplies ink to the multiple nozzles, and the pressure in the nozzles is varied to eject the ink in the nozzles from the nozzles. Inkjet recording devices may also be provided with a circulation flow path (also called a discharge flow path) that recovers and resupplies a portion of the ink supplied to the nozzles in order to adjust the amount of ink supplied.

[0003] For example, in the inkjet recording device described in Patent Document 1, ink flows in opposite directions in a common supply flow path and a common circulation flow path that are parallel to each other and communicate with a plurality of nozzles arranged in the longitudinal direction, respectively. This makes the pressure loss resistance on the supply side and the pressure loss resistance on the circulation side equal at the position of each nozzle, canceling out the pressure distribution on both sides and equalizing the nozzle pressure in all nozzles.

[0004] Furthermore, for example, in the inkjet recording device described in Patent Document 2, the pressure loss in the multiple individual supply flow paths connecting the common supply flow path and each nozzle portion is made non-uniform due to differences in the lengths of the individual supply flow paths, etc., and the pressure loss in the multiple individual circulation flow paths connecting the common supply flow path and each nozzle portion is also made non-uniform due to differences in the lengths of the individual circulation flow paths, etc. This makes the pressure in all the nozzle portions uniform. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-61768 A [Patent Document 2] JP 2015-131475 A [Patent Document 3] International Publication No. 2018 / 08397 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to prevent the pressure generated in the nozzle from escaping to the discharge side flow path or propagating to other nozzles, a configuration may be adopted in which the pressure loss in the individual circulation flow path is made larger than the pressure loss in the individual supply flow path. One example of such a configuration is a configuration in which the cross-sectional area of ​​the individual circulation flow path is made relatively small and the cross-sectional area of ​​the individual supply flow path is made relatively large. This is based on the fact that as the cross-sectional area of ​​the pipe becomes smaller, the pressure loss of the fluid flowing through the pipe increases.

[0007] Regarding this point, for example, the inkjet recording device described in Patent Document 1 has a configuration in which the ink flows in opposite directions in the common supply flow path and the common circulation flow path, making the pressure loss resistance on the supply side and the discharge side equal. However, with this configuration, the pressure loss on the discharge side cannot be made greater than the pressure loss on the supply side, which poses the problem that it is not possible to prevent the pressure generated in the nozzle section as described above from escaping to the circulation flow path and propagating to other nozzle sections.

[0008] Also, for example, in the inkjet recording device described in Patent Document 2, a configuration is adopted in which the pressure loss between the individual flow paths is different on the supply side and the discharge side. However, in the configuration in which the cross-sectional area, etc., of the individual circulation flow paths is relatively small as described above, the individual circulation flow paths are very fine. Therefore, in consideration of the manufacturing cost and manufacturing variations, it is practically difficult to form the individual circulation flow paths in different shapes, etc., so as to obtain a desired pressure loss distribution. Therefore, there is a risk that it is not possible to suppress the pressure generated in the nozzle portion from escaping to the circulation flow path or propagating to other nozzle portions.

[0009] Furthermore, the pressure loss of the fluid flowing through the pipe increases in proportion to the viscosity of the fluid. Therefore, when high-viscosity ink is used in a conventional inkjet recording device, the pressure difference between the upstream side (inlet side) and downstream side of the common supply flow path becomes very large, and this pressure difference remains as a pressure difference between the nozzle parts (pressure distribution between the nozzle parts). If pressure distribution occurs between the nozzle parts when not ejecting, there are cases where the pressure of all the nozzle parts cannot be set within the desired range even when driven during ejection. As a result, there is a risk of ejection defects such as ink overflowing or air bubble entrapment in the nozzle parts.

[0010] Generally speaking, there is a certain limit to the improvement of ejection stability of the nozzle portion in conventional ink jet recording devices.

[0011] An object of the present invention is to provide an inkjet head and an inkjet recording apparatus that can more reliably ensure ejection stability of the nozzle portion. [Means for solving the problem]

[0012] One aspect of the inkjet head according to the present invention is a plurality of individual supply flow paths that individually supply ink to a plurality of nozzle portions from a common supply flow path; a plurality of individual circulation flow paths that individually discharge ink from the plurality of nozzles to a common circulation flow path, The individual pressure loss resistances of the multiple individual circulation flow paths, whose overall pressure loss resistance is greater than that of the multiple individual supply flow paths, are made uniform, and the individual pressure loss resistances of the multiple individual supply flow paths are made non-uniform so that the pressures in the multiple nozzle sections are made uniform.

[0013] One aspect of the inkjet recording apparatus according to the present invention is to The inkjet head has a drawing section that is equipped with the above-mentioned inkjet head, and supplies ink to the plurality of nozzle sections through the common supply flow path and the plurality of individual supply flow paths while circulating ink through the plurality of individual circulation flow paths and the common circulation flow path, and ejects ink from the plurality of nozzle sections to perform drawing. Effect of the Invention

[0014] According to the present invention, ejection stability of the nozzle portion can be more reliably ensured. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an inkjet printer equipped with an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing the main components of a control system of the inkjet printer. [Diagram 3] FIG. 3 is a diagram showing a schematic arrangement of inkjet heads in a head unit of an inkjet printer. [Figure 4] FIG. 4 is a perspective view showing the appearance of the ink-jet head. [Figure 5A] FIG. 5A is a diagram showing a schematic configuration of a main part of a cross section taken along the short side direction of a head chip in an inkjet head. [Figure 5B] FIG. 5B is a diagram showing a schematic configuration of a main part of a cross section along the longitudinal direction of a head chip in an inkjet head. [Figure 6] FIG. 6 is a diagram showing a schematic plan view of the nozzle periphery of an inkjet head. [Figure 7] FIG. 7 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of a head chip in an inkjet head according to a first modified example of the embodiment. [Figure 8] FIG. 8 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of a head chip in an inkjet head according to a second modified example of the embodiment. [Figure 9]FIG. 9 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of a head chip in an inkjet head according to a third modified example of the embodiment. [Figure 10] FIG. 10 is a diagram illustrating a planar configuration of the periphery of a nozzle in an inkjet head according to a fourth modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] [Inkjet printer 1] Fig. 1 is a diagram showing a schematic configuration of an inkjet printer equipped with an inkjet head according to the present embodiment, and Fig. 2 is a block diagram showing the main parts of a control system of the inkjet printer. The inkjet printer described below is an example of an inkjet recording device.

[0018] As shown in Figures 1 and 2, the inkjet printer 1 includes a transport unit 10, a supply unit 20, a discharge unit 30, an ink supply unit 40, a drawing unit 50, a reading unit 60, an operation display unit 70, an input / output interface 80, a control unit 90, etc.

[0019] The transport unit 10 has a plurality of members related to transport, such as a transport belt 11, a driving roller 12, and a driven roller 13. The transport unit 10 transports the recording medium M by the transport operation of the plurality of members, such as the transport belt 11. Specifically, in the transport unit 10, the transport belt 11 is stretched around the driving roller 12 and the driven roller 13, and is driven by driving the driving roller 12 to rotate. As a result, the recording medium M supplied from the supply unit 20 is transported to the drawing unit 50 while being placed on the transport surface 11a of the transport belt 11, and is transported to the discharge unit 30 after drawing (also referred to as image formation or printing) in the drawing unit 50.

[0020] The recording medium M may be any of various media capable of fixing the ink ejected from the inkjet head 55. The recording medium M may be, for example, a sheet-shaped medium such as paper, cloth (fabric), or resin. The recording medium M is not limited to a sheet-shaped medium, and may be a roll-shaped medium such as paper, cloth, or resin. An example of the resin recording medium M is a PCB (Printed Circuit Board) substrate. In the case of a PCB (Printed Circuit Board) substrate, drawing by the inkjet printer 1 can be applied to printing solder resist or marking ink on the PCB substrate. Other examples of the recording medium M that may be the subject of drawing include the metallic body of an automobile, building materials (exterior walls, roofing materials, tiles, etc.), and cans (metal cans for storing food, beverages, etc.). In the case of various building materials and various metal products, drawing by the inkjet printer 1 can be applied to painting on the various building materials and various metal products.

[0021] Further, while the conveying unit 10 is illustrated here as an example in which the conveying belt 11 conveys the recording medium M, the conveying unit 10 is not limited to the conveying belt 11 and may be configured to convey the recording medium M by a drum or roller.

[0022] The supply unit 20 has a supply stacking unit 21 that stacks and stores a plurality of recording media M, a supply conveying unit 22 that conveys the recording media M from the supply stacking unit 21 to the conveying unit 10, and the like. The supply stacking unit 21 is configured to be able to rise and fall, and when the topmost recording medium M is conveyed to the conveying unit 10 by the supply conveying unit 22, the supply stacking unit 21 rises so that the recording medium M that has become the topmost after the conveying can be conveyed to the supply conveying unit 22.

[0023] The discharge section 30 has a discharge stacking section 31 that stacks and stores a plurality of recording media M, a discharge conveying section 32 that conveys the recording media M discharged from the conveying section 10 to the discharge stacking section 31, and the like. The discharge stacking section 31 is configured to be capable of rising and lowering, and when the recording media M is conveyed from the discharge conveying section 32 to the discharge stacking section 31, the discharge stacking section 31 descends.

[0024] The supply conveying section 22 and the discharge conveying section 32 each have, for example, a plurality of rollers, and convey the recording medium M by rotating the rollers. The supply conveying section 22 and the discharge conveying section 32 are not limited to rollers, and may be configured with a belt, or may be configured with a combination of rollers and belts.

[0025] When a roll-shaped medium is used as the recording medium M, an unwinding roller on which the roll-shaped medium is stored in a wound state and a winding roller that winds up the roll-shaped medium are used instead of the supply stacking unit 21 and the discharge stacking unit 31. The roll-shaped medium is transported to the transport unit 10 by rotating the unwinding roller, and is wound up by the winding roller by rotating the winding roller.

[0026] A post-processing device that performs post-processing on the recording medium M on which an image is formed by the drawing unit 50 may be provided between the conveying unit 10 and the discharging unit 30. One of the post-processing devices is a fixing device that fixes the ink to the recording medium M. When, for example, an ultraviolet-curable ink is used as the ink, a fixing device is used that irradiates the recording medium M with ultraviolet rays to fix the ink to the recording medium M. When, for example, an aqueous ink or a solvent ink is used as the ink, a fixing device is used that fixes the ink to the recording medium M by a method such as drying. As the post-processing device, a device other than the fixing device, for example, a cutting device that cuts the recording medium M to a desired length, may be used.

[0027] The configurations of the transport section 10, the supply section 20, and the discharge section 30 can be modified in various ways depending on the type of recording medium M to be imaged.

[0028] The ink supply unit 40 is a device that supplies ink to a first sub-tank 52a of the drawing unit 50, which will be described later. The ink supply unit 40 has a main tank 41 and components (e.g., a pump, a valve, etc.) related to the supply of ink, which are not shown. The main tank 41 stores ink to be supplied to the first sub-tank 52a at room temperature. The ink supply unit 40 supplies ink from the main tank 41 to the first sub-tank 52a via a flow path 42 using a pump or the like (not shown).

[0029] In this embodiment, the ink used is a gel ink (phase transition ink) containing wax, which is a gel component that undergoes a reversible sol-gel phase transition due to temperature change. For example, an energy ray curable gel ink (e.g., an ultraviolet ray curable gel ink) that is in a gel state at room temperature and in a sol state at a temperature equal to or higher than the phase transition temperature when heated, and is cured by irradiation with energy rays can be used.

[0030] The heating unit 95 is disposed upstream of the drawing unit 50 in the transport direction T of the recording medium M, and heats the recording medium M transported by the transport belt 11 to a predetermined temperature. The heating unit 95 is connected to the control unit 90 (see FIG. 2) and is controlled by the control unit 90.

[0031] For example, the heating unit 95 has an infrared heater or the like, and when power is supplied to the infrared heater based on a control signal supplied from the control unit 90, the infrared heater generates heat and heats the recording medium M to a predetermined temperature. In this modified example, the predetermined temperature is a temperature equal to or higher than the phase transition temperature of the gel component of the gel ink. Depending on the type of ink used, the placement of the heating unit 95 may not be necessary. In the following description, "gel ink" will simply be referred to as "ink".

[0032] Here, a heating section 95 is disposed on the upper surface side of the conveyor belt 11, but instead of (or in addition to) the heating section 95, a heating section may be provided on the lower surface side of the conveyor belt 11, and the conveyor belt 11 may be heated to heat the recording medium M.

[0033] The drawing unit 50 has a carriage 51, a first sub-tank 52a, a second sub-tank 52b, flow paths 53a, 53b, and 53c, a head driving unit 54, and an inkjet head (hereinafter simply referred to as the head) 55 (see FIGS. 1 and 2).

[0034] 1, for the sake of simplicity, the ink supply units 40 and drawing units 50 for one color are shown, but the ink supply units 40 and drawing units 50 are arranged according to the number of colors to be used. For example, when four colors, yellow (Y), magenta (M), cyan (C), and black (K), are used, ink supply units 40 and drawing units 50 for four colors are arranged, and the drawing units 50 are arranged so as to be lined up at predetermined intervals along the transport direction T.

[0035] Further, a plurality of second sub-tanks 52b and heads 55 are connected to the downstream side of the first sub-tank 52a, but in FIG. 1, only one of each is shown for the sake of simplicity.

[0036] The carriage 51 is a housing that holds therein the first sub-tank 52a, the second sub-tank 52b, the flow paths 53a, 53b, 53c, the head driving unit 54, the head 55, and devices and members necessary for image formation. Although not shown, the carriage 51 also has an ink heating unit that heats the ink in the carriage 51 to a temperature equal to or higher than the phase transition temperature of the gel component of the ink and maintains that temperature.

[0037] The first sub-tank 52a is connected to the downstream side of the main tank 41. The first sub-tank 52a stores the ink supplied from the main tank 41 in the carriage 51. The ink in the sub-tank 52 is supplied to the second sub-tank 52b via a flow path 53a using a pump or the like (not shown) in the carriage 51.

[0038] A plurality of second sub-tanks 52b are connected to the downstream side of the first sub-tank 52a. The second sub-tank 52b stores the ink supplied from the first sub-tank 52a in the carriage 51. The ink in the second sub-tank 52b is supplied to a manifold 56 of the head 55, which will be described later, through a flow path 53b using a pump or the like (not shown) in the carriage 51. A part of the ink supplied to the manifold 56 is returned (recovered) to the second sub-tank 52b through a flow path 53c, and can be re-supplied to the manifold 56. That is, the ink circulates between the second sub-tank 52b and the manifold 56 through the flow paths 53b and 53c. The circulation flow paths also include a plurality of individual circulation flow paths 111a, a common circulation flow path 112b, and a vertical circulation flow path 112c, all of which will be described later (see FIGS. 5A, 5B, and 6).

[0039] Based on the control of a control unit 90 (described later), the head driving unit 54 outputs a driving voltage corresponding to the image data of the image to be formed to a piezoelectric element 58 of a head 55 (described later). The driving voltage from the head driving unit 54 drives the piezoelectric element 58, causing it to eject an amount of ink corresponding to the image data from a nozzle 59 of the head 55 (described later).

[0040] A plurality of heads 55 are connected to the downstream sides of the plurality of second sub-tanks 52b, respectively. That is, a plurality of second sub-tanks 52b and heads 55 are connected to the downstream sides of the first sub-tanks 52a.

[0041] The head 55 has a manifold 56 (an example of a common supply flow path), individual supply flow paths 57, piezoelectric elements 58, nozzles 59, individual circulation flow paths 111a, common circulation flow path 112b, and vertical circulation flow paths 112c (see FIGS. 5A, 5B, and 6). The head 55 has a plurality of nozzles 59, and the individual supply flow paths 57 and piezoelectric elements 58 are provided in accordance with the number of nozzles 59. In this embodiment, the nozzle portion 59a refers to a portion that includes the nozzles 59 and a space in the vicinity of the nozzles 59 that can temporarily store ink (see FIG. 5A).

[0042] The manifold 56 communicates with a plurality of individual supply flow paths 57, and ink supplied to the manifold 56 is supplied to the individual supply flow paths 57. A part or the whole of the individual supply flow path 57 is a chamber having an internal space capable of temporarily storing ink ejected from the nozzle 59. A piezoelectric element 58 is provided on a wall surface of the individual supply flow path 57. Moreover, one end of the nozzle 59 communicates with the individual supply flow path 57, and the other end is an open end.

[0043] A driving voltage is applied to the piezoelectric element 58 from the head driving unit 54. When the driving voltage is applied to the piezoelectric element 58 from the head driving unit 54, the piezoelectric element 58 deforms in response to the applied driving voltage, causing the individual supply flow path 57 to deform. The deformation of the individual supply flow path 57 imparts a pressure change to the ink in the individual supply flow path 57 that is supplied to the nozzle 59.

[0044] Therefore, when a drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 and the individual supply flow path 57 are deformed, causing a pressure change to be applied to the ink in the individual supply flow path 57, and as a result, the ink in the individual supply flow path 57 is ejected from the nozzle 59. In this manner, an image can be formed on the recording medium M by ejecting the ink from the nozzle 59.

[0045] In the carriage 51, the head 55 may be configured to be a single-pass (one-pass) type in which an image is formed by one scan, or may be configured to be a scan (multi-pass) type in which an image is formed by multiple scans. In the case of the single-pass type, the carriage 51 is provided with heads 55 in the width direction of the recording medium M (direction perpendicular to the conveying direction T of the recording medium M) in the number equal to the image formation width (see FIG. 3). As shown in FIG. 3, the multiple heads 55 are arranged in one or multiple rows with their longitudinal directions aligned with the width direction of the recording medium M, and in each head 55, the multiple nozzles 59 are arranged linearly or in a lattice pattern along the longitudinal direction of the head 55.

[0046] The reading unit 60 is disposed downstream of the drawing unit 50 in the transport direction T of the recording medium M, and reads an image (e.g., a predetermined pattern image) formed on the recording medium M transported by the transport belt 11. The reading unit 60 outputs the reading result of the predetermined pattern image to the control unit 90. The control unit 90 changes the image formation conditions, such as the image formation position and the driving conditions of the head 55, based on the reading result.

[0047] Although not shown, the inkjet printer 1 also includes a maintenance unit that performs maintenance such as cleaning of the head 55.

[0048] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal display or an organic EL (Electro Luminescence) display with a touch panel. The operation display unit 70 displays an operation menu for the user, information related to image data, various states of the inkjet printer 1, etc. The operation display unit 70 also includes a plurality of keys and receives various input operations from the user.

[0049] The input / output interface 80 mediates the transmission and reception of data between the external device 99 and the control unit 90. The input / output interface 80 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0050] The external device 99 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, and the like to the control unit 90 via the input / output interface 80 .

[0051] The control unit 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, a storage unit 94, etc.

[0052] The CPU 91 reads out various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various arithmetic processing. For example, the control unit 90 generates a drive signal for an image to be formed based on image data received from the input / output interface 80, and outputs the drive signal to the head 55.

[0053] The RAM 92 provides a working memory space for the CPU 91 and stores temporary data. The RAM 92 may include a non-volatile memory.

[0054] The ROM 93 stores various control programs and setting data executed by the CPU 91. Note that, instead of the ROM 93, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0055] The storage unit 94 stores print jobs and image data related to the print jobs input from an external device 99 via the input / output interface 80. As the storage unit 94, for example, a non-volatile semiconductor memory (so-called flash memory) or an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0056] The control unit 90 is connected to the transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, drawing unit 50, reading unit 60, operation display unit 70, input / output interface 80, heating unit 95, etc. The control unit 90 comprehensively controls the overall operation of the inkjet printer 1. The transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, drawing unit 50, reading unit 60, operation display unit 70, input / output interface 80, heating unit 95, etc. are controlled by the control unit 90 to execute predetermined processes.

[0057] The inkjet printer 1 having the above configuration supplies the recording medium M from the supply section 20 to the transport section 10 under the control of the control section 90, draws on the recording medium M transported to the transport section 10 using the drawing section 50, and transports the recording medium M with the image formed thereon to the discharge section 30.

[0058] [Head (inkjet head) 55] Next, the configuration of the inkjet head (head 55) according to this embodiment will be described. The configuration described here is the configuration of a single head 55. Note that all heads 55 in the inkjet printer 1 may have the same configuration, or the inkjet printer 1 may include heads 55 with configurations different from those described below.

[0059] FIG. 4 is a perspective view showing the appearance of the head 55. As shown in FIG.

[0060] The head 55 includes a housing 101 and an exterior member 102 that is fitted to the housing 101 at the bottom end of the housing 101, and the main components are housed inside the housing 101 and the exterior member 102. The exterior member 102 is provided with an inlet 103a through which ink is supplied from the outside, and outlets 103b and 103c through which ink is discharged to the outside. A manifold 56 connected to the inlet 103a is provided inside the exterior member 102. The exterior member 102 is also provided with a plurality of mounting holes 104 for mounting the inkjet head 100 to the base of the carriage 51.

[0061] Fig. 5A and Fig. 5B are diagrams showing the main configuration of the head chip in head 55. Fig. 5A is a diagram showing the main configuration of a cross section along the short side direction of the head chip, and Fig. 5B is a diagram showing the main configuration of a cross section along the long side direction of the head chip. Fig. 6 is a diagram showing the planar configuration of the periphery of the nozzles in head 55.

[0062] Components housed inside housing 101 and exterior member 102 of head 55 include head chip 110. As shown in Figures 5A and 5B, head chip 110 is configured by stacking and bonding multiple substrates (first substrate 111, second substrate 112, and third substrate 113). First substrate 111, second substrate 112, and third substrate 113 respectively become a lower layer, a middle layer, and an upper layer during use.

[0063] The first substrate 111 is provided with a plurality of nozzles 59, which are holes that each penetrate in the thickness direction (corresponding to the ink ejection direction, which is typically along the vertical direction), arranged in a row along the longitudinal direction. In the illustrated example, the number of nozzles 59 is six per example, but the number does not have to be six. The first substrate 111 may be a substrate made of a resin such as polyimide, or a substrate made of a metal such as SUS.

[0064] A liquid-repellent film containing a liquid-repellent material such as fluororesin particles is provided on the nozzle opening surface of the first substrate 111. By providing the liquid-repellent film, adhesion of ink and foreign matter to the nozzle opening surface can be suppressed, and the occurrence of ink discharge defects caused by the adhesion of the ink and foreign matter can be suppressed.

[0065] The first substrate 111 is also provided with a plurality of individual circulation channels 111a that communicate with the respective nozzles 59. The individual circulation channels 111a are grooves that extend parallel to each other in the short direction of the head 55 from the most downstream portion of the individual supply channel 57 that communicates with the corresponding nozzle 59, and all of them communicate with the common circulation channel 112a.

[0066] The second substrate 112 is provided with a plurality of individual supply flow paths 57 arranged in a row along the longitudinal direction, each of which is a hole penetrating in the thickness direction and communicates with a corresponding nozzle 59. In the illustrated example, the number of nozzles 59 is six per row, so the number of individual supply flow paths 57 is also six per row. In the following description, when the six individual supply flow paths 57 are to be distinguished from one another, they are referred to as individual supply flow paths 57-1, 57-2, 57-3, 57-4, 57-5, and 57-6, and when they are not to be distinguished from one another, they are simply referred to as "individual supply flow paths 57." The relative positions of the individual supply flow paths 57-1, 57-2, 57-3, 57-4, 57-5, and 57-6 are such that the larger the branch number of the reference symbol, the farther away they are from the inlet (inlet 103a) of the manifold 56, i.e., the further downstream of the manifold 56 they are.

[0067] Each of the individual supply channels 57 communicates with a manifold 56, which functions as a common supply channel, at its upstreammost portion. The individual supply channels 57 are separated by partitions having piezoelectric elements 58. The piezoelectric elements 58 are electrically connected to the head drive unit 54 by electrodes and wiring (not shown). The piezoelectric elements 58 are driven in response to a drive voltage signal applied from the head drive unit 54 via the electrodes and wiring, thereby repeatedly causing shear mode type displacements in the partitions of the individual supply channels 57, thereby fluctuating the pressure of the ink, and ejecting the ink from the nozzles 59 in response to the pressure fluctuations. That is, the head 55 according to this embodiment is an inkjet head that ejects shear mode type ink.

[0068] The second substrate 112 is, for example, a ceramic piezoelectric body (a member that deforms in response to the application of a voltage.) Examples of the piezoelectric body include PZT (lead zirconate titanate), lithium niobate, barium titanate, lead titanate, and lead metaniobate.

[0069] The second substrate 112 is provided with a common circulation channel 112a to which all of the individual circulation channels 111a communicate at their most downstream portions. The common circulation channel 112a is a groove extending along the longitudinal direction of the head 55 on the rear surface of the second substrate 112. The most downstream portion of the common circulation channel 112a communicates with a vertical circulation channel 112b also provided on the second substrate 112. The vertical circulation channel 112b communicates with the outlet 103c, enabling the circulation of ink.

[0070] A manifold 56 is provided on the third substrate 113, which extends along the longitudinal direction of the head 55 and communicates with all of the individual supply flow paths 57 at their upstream ends. The manifold 56 is a groove provided on the rear surface side of the third substrate 113. The third substrate 113 may be a substrate made of a resin such as polyimide, or a substrate made of a metal such as SUS.

[0071] The following describes the pressure loss resistance within the head 55. (1) The relationship between the pressure loss resistance of the individual supply flow passages 57 and the individual circulation flow passages 111a, (2) the relationship between the pressure loss resistance of the individual circulation flow passages 111a, and (3) the relationship between the pressure loss resistance of the individual supply flow passages 57 will be described later. Since known techniques described in, for example, Patent Document 3 can be applied to the detailed configuration within the head 55 that does not affect these relationships, detailed description thereof will be omitted here.

[0072] [Regarding flow path pressure loss resistance and pressure loss adjustment] The pressure loss ΔP in the individual supply flow passages 57 and the individual circulation flow passages 111a can be calculated by the following formula.

[0073]

number

[0074] Furthermore, in the case of a pipeline whose shape changes due to bending or width changes, the geometric loss coefficient ξ is used instead of the pipe friction coefficient (λ×l / d). In the case of bending, the geometric loss coefficient ξ increases as the bend angle increases, and in the case of shape changes, the coefficient increases as the difference in cross-sectional area before and after the shape change increases. If the flow path to be considered is composed of multiple flow path sections with different shapes, the pressure loss of the entire flow path to be considered can be estimated by adding up the pressure losses of each flow path section.

[0075] Moreover, the "pipes" in the formulas refer to the individual supply flow paths 57 or the individual circulation flow paths 111a, and the fluid refers to ink.

[0076] As can be seen from this formula, the pressure loss of the ink is proportional to the length of the individual supply flow path 57 (or the individual circulation flow path 111a). Furthermore, the pressure loss of the ink is inversely proportional to the diameter of the individual supply flow path 57 (or the individual circulation flow path 111a), and therefore inversely proportional to the cross-sectional area of ​​the individual supply flow path 57 (or the individual circulation flow path 111a). Furthermore, when the individual supply flow path 57 (or the individual circulation flow path 111a) has a shape other than a circular tube, the pressure loss of the ink is inversely proportional to the hydraulic diameter determined according to the cross-sectional aspect ratio of the individual supply flow path 57 (or the individual circulation flow path 111a). Furthermore, when there is a shape change in the individual supply flow path 57 (or the individual circulation flow path 111a), the pressure loss of the ink is proportional to the magnitude of the degree of the shape change.

[0077] Therefore, the resistance that causes pressure loss of the ink (hereinafter referred to as "pressure loss resistance") is determined based on the length, diameter (cross-sectional area), cross-sectional aspect ratio, and degree of shape change (e.g., bending angle) of the individual supply flow path 57 (or the individual circulation flow path 111a). Therefore, by adjusting at least one setting of the length, diameter (cross-sectional area), cross-sectional aspect ratio, and degree of shape change (e.g., bending angle) of the individual supply flow path 57 or the individual circulation flow path 111a, the pressure loss resistance can be easily adjusted and a desired pressure loss can be obtained.

[0078] [(1) Relationship between pressure loss resistance between the individual supply flow path 57 and the individual circulation flow path 111a] In this embodiment, by setting the cross-sectional areas of the individual supply flow paths 57 and the individual circulation flow paths 111a by the above-mentioned method, the overall pressure loss resistance of the multiple individual circulation flow paths 111a is made sufficiently smaller than the overall pressure loss resistance of the multiple individual supply flow paths 57. For example, the cross-sectional areas of all the individual circulation flow paths 111a are set sufficiently smaller than the cross-sectional areas of all the individual supply flow paths 57. This makes it possible to suppress the pressure generated in the nozzle portion 59a from escaping to the flow path on the discharge side or propagating to other nozzle portions 59a.

[0079] Here, the total pressure loss resistance is, for example, the average value of the pressure loss resistance. Specifically, the total pressure loss resistance of the individual supply flow paths 57 is the average value of the pressure loss resistance of all the individual supply flow paths 57-1 to 57-6, and the total pressure loss resistance of the individual circulation flow paths 111a is the average value of the pressure loss resistance of all the individual circulation flow paths 111a. It is preferable to set the total pressure loss resistance of the individual circulation flow paths 111a to be twice or more the total pressure loss resistance of the individual supply flow paths 57, since a significant difference can be generated between the pressure losses of both paths.

[0080] [(2) Relationship between pressure loss resistances between individual circulation channels 111a] In this embodiment, the pressure loss resistance is made uniform among the individual circulation channels 111a by setting the cross-sectional area of ​​each of the individual circulation channels 111a by the above-mentioned method. Here, for example, if the ratio (maximum / minimum) of the maximum value to the minimum value of the pressure loss resistance of the multiple individual circulation channels 111a is equal to or less than a predetermined value (for example, 1.1), the pressure loss resistance may be considered to be uniform among the individual circulation channels 111a. For example, the pressure loss resistance can be made uniform among the individual circulation channels 111a by making the length, diameter (cross-sectional area), cross-sectional aspect ratio, and degree of shape change (for example, bending angle) the same in all the individual circulation channels 111a, but if there is a difference in length, for example, another factor such as cross-sectional area may also be made different.

[0081] [(3) Relationship between pressure loss resistances between individual supply passages 57] In this embodiment, by setting the cross-sectional area and the like of each of the individual supply channels 57 according to the method described above, the pressure loss resistance is made non-uniform among the individual supply channels 57. Here, for example, if the pressure loss resistance of at least two of the plurality of individual supply channels 57 is different, it may be regarded that the pressure loss resistance is non-uniform among the individual supply channels 57. However, by making the pressure loss resistance non-uniform among the individual supply channels 57, it is desirable to make the pressures of the plurality of nozzle portions 59a uniform (the difference in the pressures of the plurality of nozzle portions 59a is made less than a predetermined value).

[0082] For example, as shown in FIG. 5B, the cross-sectional area of the individual supply channel 57 is enlarged (S1 < S2 < S3 < S4 < S5 < S6) by widening the diameter of the individual supply channel 57 or the like as the distance from the inlet of the manifold 56 increases. By doing so, the pressure loss resistance of the individual supply channel 57 communicating with the manifold 56 at a position relatively far from the inlet of the manifold 56 becomes smaller than the pressure loss resistance of the individual supply channel 57 communicating with the manifold 56 at a position relatively close to the inlet of the manifold 56. Thereby, the pressures of the plurality of nozzle portions 59a can be made uniform.

[0083] As described above, according to this embodiment, the inkjet head 55 includes a plurality of individual supply channels 57 that individually supply ink from the manifold 56 to the plurality of nozzle portions 59a, and a plurality of individual circulation channels 111a that individually discharge ink from the plurality of nozzle portions 59a to the common circulation channel 112a. The individual pressure loss resistances of the plurality of individual circulation channels 111a, whose overall pressure loss resistance is greater than that of the plurality of individual supply channels 57, are made uniform, and the individual pressure loss resistances of the plurality of individual supply channels 57 are made non-uniform so that the pressures of the plurality of nozzle portions 59a are made uniform. Thereby, the discharge stability of the nozzle portion 59a can be ensured more reliably.

[0084] In this embodiment, the inkjet printer 1 includes an inkjet head 55, and has a drawing section 50 that supplies ink to a plurality of nozzle portions 59a through a manifold 56 and a plurality of individual supply paths 57 while circulating ink through a plurality of individual circulation paths 111a and a common circulation path 112a, and ejects ink from the plurality of nozzle portions 59a to perform drawing. This makes it possible to perform drawing on the recording medium M while realizing the effects that can be achieved by the above-mentioned configuration of the inkjet head 55.

[0085] In recent years, various functions are required for inks used in inkjet recording devices, and as a result, the ink has become highly viscous or contains particles. In particular, when particles of a particle size are contained, polymer components are often further contained for particle dispersion in the ink, which tends to result in high viscosity. For example, when the ink used contains particles with a particle size of 0.5 μm or more in D90, the ink exhibits a significantly high viscosity. The particle size is the average diameter based on volume. In addition, the particle size measurement method is not particularly limited, but the particle size can be measured by an apparatus using a dynamic light scattering method or a laser diffraction method. For example, the Zetasizer series using the dynamic light scattering method manufactured by Malvern Panalytical and the Mastersizer series using the laser diffraction method manufactured by the same company can be suitably used.

[0086] The above-mentioned high-viscosity ink has a viscosity of, for example, 25 mPa·s or more. On the other hand, conventional inkjet recording devices are limited in the viscosity of ink that can be ejected, and the viscosity of ink that can be ejected is generally 15 to 20 mPa·s. Therefore, in recent years, there has been a demand for inkjet heads and inkjet recording devices that can stably eject even high-viscosity ink.

[0087] In this regard, in the inkjet head 55 according to the present embodiment, the individual pressure loss resistances of the individual supply flow paths 57 are made non-uniform so that the pressures of the nozzles 59a when not ejecting are uniform, and the pressure difference (pressure distribution) between the nozzles 59a is unlikely to remain when not ejecting. Therefore, the possibility of causing ejection defects such as ink overflow or air bubble entrapment at the nozzles 59a due to the pressure difference (pressure distribution) at the nozzles 59a is suppressed. Therefore, the inkjet head 55 according to the present embodiment and the inkjet printer 1 equipped with this inkjet head 55 can ensure ejection stability of the nozzles even when high viscosity ink is used. Incidentally, the pressure distribution of the nozzles 59a when not ejecting is within the range of -0.05 kPa to -1.0 kPa.

[0088] [Variation 1] FIG. 7 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of a head chip 110 in an inkjet head 55 according to a first modified example of the present embodiment.

[0089] In this modification, the pressure loss resistance of the multiple individual supply flow paths 57 is made non-uniform for each group consisting of one or more individual supply flow paths. More specifically, in this modification, the cross-sectional area of ​​the downstream group consisting of the individual supply flow paths 57-4, 57-5, and 57-6 communicating with the manifold 56 on the downstream side is formed to be larger than that of the upstream group consisting of the individual supply flow paths 57-1, 57-2, and 57-3 communicating with the manifold 56 on the upstream side (S6>S1), and thus the pressure loss resistance (average value) of the entire downstream group is lower than the pressure loss resistance (average value) of the entire upstream group. Even in this case, the same effect as in the present embodiment can be achieved. Moreover, since the structure of this modification is somewhat simpler than that of the present embodiment, dimensional control during manufacturing is easy, and there is also an effect of suppressing manufacturing costs and manufacturing variations.

[0090] [Variation 2] FIG. 8 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of head chip 110 in inkjet head 55 according to modified example 2 of the present embodiment.

[0091] In this modification, the individual supply flow paths 57 are made different in length, so that the pressure loss resistances of the individual supply flow paths 57 are made non-uniform. More specifically, in this modification, the length of the individual supply flow path 57 that communicates with the manifold 56 at a position farther away from the inlet of the manifold 56 is set to be shorter (L1>L2>L3>L4>L5>L6). This reduces the pressure loss resistance of the individual supply flow path 57 on the more downstream side. Even in this case, the same effect as in the present embodiment can be achieved. Moreover, the structure of this modification is easy to manufacture, since it is only necessary to make the upper surface portion of the second substrate 112 on which the manifold 56 is formed an inclined surface, and this also has the effect of suppressing manufacturing costs and manufacturing variations.

[0092] [Variation 3] FIG. 9 is a diagram showing a schematic configuration of a main part of a cross section taken along the longitudinal direction of a head chip 110 in an inkjet head 55 according to a third modification of the present embodiment.

[0093] In this modification, a throttle section (step) is provided in the middle of each of the individual supply flow paths 57, and the degree of reduction in the cross-sectional area caused by the throttle section is made different, so that the pressure loss resistance of each of the individual supply flow paths 57 is made non-uniform. More specifically, in this modification, the degree of reduction in the cross-sectional area caused by the throttle section of the individual supply flow path 57 that communicates with the manifold 56 at a position farther away from the inlet of the manifold 56 is set to be greater ((S1 / S6)<(S2 / S6)<(S3 / S6)<(S4 / S6)<(S5 / S6)<(S6 / S6)). This reduces the pressure loss resistance of the individual supply flow path 57 on the more downstream side. Even in this case, the same effect as in the present embodiment can be achieved.

[0094] [Variation 4] FIG. 10 is a diagram showing a schematic plan view of the nozzle periphery of an ink-jet head 55 according to a fourth modification of the present embodiment.

[0095] In this modification, the individual circulation flow paths 111a have, for example, a V-shaped bent portion. By having the bent portion in the individual circulation flow paths 111a, a certain pressure loss resistance can be ensured even for small-sized individual circulation flow paths 111a. However, in order to make the pressure loss resistance uniform among the individual circulation flow paths 111a, the bending angle of the bent portion is made uniform.

[0096] Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-mentioned specific embodiment. Various modifications and changes can be made to the specific examples described in the above embodiment within the scope of the gist of the present invention described in the claims.

[0097] The disclosures of the specification, drawings and abstract contained in Japanese application No. 2023-039518, filed on March 14, 2023, are incorporated herein by reference in their entirety. [Industrial Applicability]

[0098] INDUSTRIAL APPLICABILITY The present invention is useful as an inkjet head and an inkjet recording apparatus capable of improving the ejection stability of a nozzle portion. [Explanation of symbols]

[0099] 1. Inkjet printer 10. Conveyor 11 Conveyor belt 11a Conveying surface 12 Drive roller 13 Driven roller 20 Supply section 21 Supply loading section 22 Supply and conveying section 30 Discharge section 31 Discharge loading section 32 Discharge conveying section 40 Ink supply unit 41 Main Tank 42 Flow Path 50 Drawing section 51 Carriage 52a 1st Subtank 52b Second subtank 53a, 53b, 53c flow paths 54 Head drive unit 55 Inkjet head 56 Manifold (common supply flow path) 57 Individual supply channel 58 Piezoelectric element 59 Nozzle 59a Nozzle part 60 Reading unit 70 Operation display section 80 Input / Output Interface 90 Control section 91 CPU 92 RAM 93 ROM 94 Memory section 95 Heating section 99 External device 101 Case 102 Exterior parts 103a Inlet 103b, 103c Outlet 104 Mounting hole 110 Head Chip 111 First board 111a Individual circulation flow path 112 Second board 112a Common circulation flow path 112b Vertical circulation channel 113 Third Board

Claims

1. a plurality of individual supply flow paths that individually supply ink to a plurality of nozzle portions from a common supply flow path; a plurality of individual circulation flow paths that individually discharge ink from the plurality of nozzles to a common circulation flow path, The individual pressure loss resistances of the plurality of individual circulation flow paths, each of which has a larger overall pressure loss resistance than the plurality of individual supply flow paths, are made uniform, and the individual pressure loss resistances of the plurality of individual supply flow paths are made non-uniform so that pressures in the plurality of nozzle portions are made uniform. Inkjet head.

2. The total pressure drop resistance is an average value of the pressure drop resistances, an average value of the pressure drop resistance of the plurality of individual circulation flow paths is equal to or greater than twice the average value of the pressure drop resistance of the plurality of individual supply flow paths; 2. The ink-jet head according to claim 1.

3. one individual supply flow path communicating with the common supply flow path at a position relatively far from an inlet of the common supply flow path has a smaller pressure loss resistance than another individual supply flow path communicating with the common supply flow path at a position relatively close to the inlet of the common supply flow path; 2. The ink-jet head according to claim 1.

4. The pressure drop resistances of the individual supply flow paths are non-uniform with each group consisting of one or more individual supply flow paths as a unit.

2. The ink-jet head according to claim 1.

5. the plurality of individual supply flow paths include an upstream group consisting of one or more individual supply flow paths communicating with the common supply flow path on an upstream side thereof, and a downstream group consisting of one or more individual supply flow paths communicating with the common supply flow path on a downstream side thereof, and a total pressure drop resistance of the downstream group is reduced compared to a total pressure drop resistance of the upstream group.

5. The ink-jet head according to claim 4.

6. At least one of a length, a cross-sectional area, a bending angle, and a cross-sectional aspect ratio is made different between one individual supply flow path and another individual supply flow path, so that the pressure drop resistances of the individual supply flow paths are made non-uniform.

2. The ink-jet head according to claim 1.

7. At least one of the diameter of the throttle portion, the length of the throttle portion, and the number of the throttle portions is made different between one individual supply flow path and another individual supply flow path, so that the pressure loss resistances of the individual supply flow paths are made non-uniform.

2. The ink-jet head according to claim 1.

8. The plurality of individual circulation flow paths have bent portions.

2. The ink-jet head according to claim 1.

9. The bending angle of the bent portion is uniform.

9. The ink-jet head according to claim 8.

10. Due to the non-uniformity of the pressure loss resistance of each of the individual supply flow paths, the pressure distribution of the nozzle portions during non-ejection is within a range of −0.05 kPa to −1.0 kPa.

2. The ink-jet head according to claim 1.

11. when ink having a viscosity of 25 mPa·s or more is used, the pressures of the plurality of nozzle portions during non-ejection are made uniform by making the individual pressure loss resistances of the plurality of individual supply flow paths non-uniform; 2. The ink-jet head according to claim 1.

12. The ink used contains particles having a diameter of 0.5 μm or more in D90. The ink-jet head according to claim 11.

13. It is a shear mode inkjet head.

2. The ink-jet head according to claim 1.

14. a drawing unit comprising the inkjet head according to claim 1, supplying ink to the plurality of nozzle portions through the common supply flow path and the plurality of individual supply flow paths while circulating ink through the plurality of individual circulation flow paths and the common circulation flow path, and ejecting ink from the plurality of nozzle portions to perform drawing. Inkjet recording device.

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