Inkjet printer

Abstract

Since the ink in the protruding portion connecting the ink supply device and the print head chip, etc. is not heated, the viscosity of the ink increases, and sometimes the fluidity cannot be maintained. The inkjet printer (1) for solving the above problems includes: an inkjet head (300) for ejecting ink; a protruding portion (310) that is provided to protrude relative to the inkjet head (300) and through which ink flows toward the inkjet head (300); and an ink flow path portion (6) for supplying ink to the protruding portion (310). The ink flow path portion (6) includes an ink heating module (200) for heating the ink. A conduction portion (210) is disposed adjacent to the outside of the protruding portion (310). The conduction portion (210) is formed on the ink heating module (200) itself or is formed independently of the ink heating module (200) and is used for conducting heat from the ink heating module (200).

Description

[0001] This application is a divisional application of an international application with an international filing date of November 16, 2020 (date of entry into the Chinese national phase: March 28, 2022), an international application number of PCT / JP2020 / 042569 (national application number: 202080068127.0), and an invention title of "Inkjet Printer". Technical Field

[0002] The present invention relates to an inkjet printer.

[0003] The present invention relates to an inkjet printer having a pair of inkjet heads. Background Art

[0004] For printing in which ink having a relatively high viscosity is ejected by an inkjet printer, the ink is heated in a flow path for supplying the ink to an inkjet head to reduce its viscosity and improve its fluidity, and then the heated ink is supplied to the inkjet head for the above-mentioned printing.

[0005] Patent Document 1 describes a technique of an inkjet print head package having: an ink supply section having a preheating plate; a print head chip or the like having an auxiliary heater; and an ink hose connecting an ink supply device and the print head chip or the like.

[0006] Conventionally, an ink supply device for supplying ink to a print head chip has been known (for example, refer to Patent Document 1). This ink supply device has a preheating plate and a preheating heater, and the preheating plate and the preheating heater heat the ink supplied to the print head chip. The ink heated by the ink supply device is supplied to the print head chip. The print head chip ejects the ink supplied through an ink supply port through a plurality of nozzles.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-213061 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] Since the ink is not heated at the protruding portion connecting the ink supply device and the print head chip or the like, the viscosity of the ink increases, and sometimes the fluidity cannot be maintained.

[0012] The present invention has been made in view of such problems.

[0013] An inkjet head such as a general printhead chip moves relative to a recording medium in a main scanning direction, and a plurality of nozzles are arranged in a nozzle row that is arranged in a sub-scanning direction orthogonal to the main scanning direction. In addition, for an inkjet head, there is a case where an ink supply port is provided on one side in the sub-scanning direction with respect to the nozzle row. Moreover, in order to make the nozzle row longer in the sub-scanning direction, there is a case where two inkjet heads are used and two nozzle rows are arranged in the sub-scanning direction. In this case, generally, two ink supply ports provided on the two inkjet heads are respectively arranged on one side in the sub-scanning direction with respect to the nozzle row.

[0014] Here, in the nozzle row, compared with the nozzles on the other side in the sub-scanning direction that are farther from the ink supply port, the nozzles on one side in the sub-scanning direction that are closer to the ink supply port have an unstable ink temperature just after the ink starts to be ejected. This is because when the ink in the inkjet head is heated by an ink heater provided in the inkjet head, the temperature distribution of the ink becomes uneven. Therefore, for the nozzles on the side closer to the ink supply port, just after the ink starts to be ejected, the deviation of the ink ejection speed is larger than that of the nozzles on the side farther from the ink supply port. In other words, for the nozzles on the side farther from the ink supply port, just after the ink starts to be ejected, the deviation of the ink ejection speed is smaller than that of the nozzles on the side closer to the ink supply port.

[0015] In two nozzle rows arranged along the sub-scanning direction, in one nozzle row, the nozzles on the other nozzle row side become the nozzles on the side closer to the ink supply port. On the other hand, in the other nozzle row, the nozzles on the one nozzle row side become the nozzles on the side farther from the ink supply port. This is because two ink supply ports provided on the two inkjet heads are respectively arranged on the same side in the sub-scanning direction with respect to each nozzle row. Therefore, the nozzles on the side closer to the ink supply port and the nozzles on the side farther from the ink supply port in the two nozzle rows in the sub-scanning direction are combined in a continuous manner or an overlapping manner. As a result, the nozzles with a large deviation of the ink ejection speed are paired with the nozzles with a small deviation of the ink ejection speed. Thus, it is easy to generate stripes caused by density, that is, banding, which may lead to a decrease in image quality.

[0016] Then, an object of the present invention is to provide an inkjet printer capable of improving image quality.

[0017] Solution for solving the problem

[0018] An inkjet printer for solving the above problems includes: an inkjet head for ejecting ink; a protruding portion that is provided to protrude relative to the inkjet head and through which the ink flows toward the inkjet head; and an ink flow path portion for supplying the ink to the protruding portion. The ink flow path portion includes an ink heating module for heating the ink. Adjacent to the outside of the protruding portion, a conduction portion is disposed, which is formed on the ink heating module itself or independently of the ink heating module and is used for conducting heat from the ink heating module.

[0019] An inkjet printer for solving the above problems includes: an inkjet head for ejecting ink; a protruding portion that is provided to protrude relative to the inkjet head and through which the ink flows toward the inkjet head; and an ink flow path portion for supplying the ink to the protruding portion. The ink flow path portion includes an ink heating module for heating the ink. The ink heating module includes a heating flow path through which the ink flows. The protruding portion includes a protruding flow path through which the ink flows inside. The flow path cross-sectional area of the protruding flow path is smaller than the flow path cross-sectional area of the heating flow path.

[0020] The inkjet printer of the present invention is an inkjet printer that performs printing by relatively moving a recording medium and an inkjet head that ejects ink onto the recording medium. The inkjet head includes: a nozzle row formed by arranging a plurality of nozzles in a single direction; an ink supply port formed on one end side of the nozzle row; and an ink heater for heating the ink. The inkjet printer includes a pair of the inkjet heads, and the pair of inkjet heads are arranged such that the nozzle rows of the pair of inkjet heads are offset in position in the same direction with the other ends approaching each other compared to the one ends.

[0021] According to this structure, it is possible to make the nozzles on the side farther from the ink supply port of the two nozzle rows arranged with a position offset approach each other. That is, it is possible to make the nozzles with a smaller deviation in ink ejection speed approach each other. Therefore, it is possible to suppress the generation of stripes caused by density unevenness, that is, banding, and improve the image quality of the object to be printed.

[0022] In addition, preferably, the inkjet printer further includes a heating module disposed upstream of each inkjet head in the flow direction of the ink for heating the ink supplied to the ink supply port.

[0023] According to this structure, it is possible to heat the ink supplied to the inkjet head, and thus it is possible to suppress unevenness in the temperature of the ink in the inkjet head.

[0024] Further, preferably, when the pair of inkjet heads simultaneously perform a printing operation on the recording medium, the other end portions of the nozzle rows of one inkjet head and the other inkjet head in the pair of inkjet heads are close to each other, and are regarded as a nozzle row obtained by continuous connection of the nozzle row of one inkjet head and the nozzle row of the other inkjet head in the pair of inkjet heads.

[0025] According to this structure, it is possible to use a pair of inkjet heads to print on the recording medium with a longer nozzle row obtained by continuous connection of a pair of nozzle rows.

[0026] Further, preferably, the inkjet printer further includes a control unit for controlling the printing operation of the inkjet head. In the control unit, a multi-pass method is used in which multiple main scanning operations corresponding to multi-pass printing are performed on each position of the recording medium, so that each inkjet head performs printing on the printing medium. And, in each pass of the multi-pass printing performed on each position of the recording medium, mask data, which is data specifying pixels to which ink droplets should be ejected, is used, and the inkjet head ejects ink droplets to the pixels specified by the mask data. In the mask data, the nozzles on the closer other end portion side of the nozzle rows of the pair of inkjet heads have a higher usage frequency, and the nozzles on the one end portion side of the nozzle row have a lower usage frequency.

[0027] According to this structure, it is possible to set the nozzles with a higher nozzle usage frequency as the nozzles with a smaller deviation in the ink ejection speed. Therefore, it is possible to increase the usage frequency of the nozzles with higher ink ejection stability, and on the other hand, it is possible to reduce the usage frequency of the nozzles with lower ink ejection stability. Therefore, it is possible to stably eject ink onto the recording medium.

[0028] Further, preferably, the pair of inkjet heads have the same structure, and in the plane in which each inkjet head moves relative to the recording medium, the pair of inkjet heads are arranged in a point-symmetrical manner with a phase difference of 180 degrees centered on a symmetrical point.

[0029] According to this structure, by arranging the pair of inkjet heads in a point-symmetrical manner, it is possible to make the pair of inkjet heads have the same structure, so it is possible to suppress an increase in device cost.

[0030] Further, preferably, the ink is an ultraviolet curable ink curable by ultraviolet rays.

[0031] According to this structure, even when the ink is an ultraviolet curable ink, it is possible to improve the image quality of the object to be printed.

[0032] Effects of the Invention

[0033] In the inkjet printer according to the present invention, by heating the protruding portion with the heat transfer portion, an increase in the ink viscosity at the protruding portion is suppressed, and thus, the fluidity of the ink can be ensured. Description of the Drawings

[0034] Figure 1 is a perspective view of the inkjet printer of this embodiment.

[0035] Figure 2 is a schematic front view of the carriage of the inkjet printer of this embodiment.

[0036] Figure 3 is a right side cross-sectional view of the main part of the inkjet printer of this embodiment.

[0037] Figure 4 is a conceptual diagram showing the heat transfer area of the ink at the heating flow path and the protruding flow path of this embodiment.

[0038] Figure 5 is a cross-sectional view showing the shape of the protruding flow path of a modified example of this embodiment.

[0039] Figure 6 is a perspective view of the inkjet printer of this embodiment.

[0040] Figure 7 is a schematic diagram schematically showing the structure near the inkjet head.

[0041] Figure 8 is a top view showing the inlet side of the inkjet head.

[0042] Figure 9 is a top view showing the nozzle surface side of the inkjet head.

[0043] Figure 10 is an explanatory diagram showing the ejection frequency of the ink at the nozzle row. Detailed Description of the Embodiment

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the present invention is not limited to these embodiments.

[0045] <Inkjet Printer>

[0046] Hereinafter, with reference to Figure 1 and Figure 2 the inkjet printer of this embodiment will be described. Figure 1 is a perspective view of the inkjet printer of this embodiment. Figure 2 is for explaining Figure 1 the structure of the main part of the inkjet printer shown.

[0047] An inkjet printer 1 (hereinafter referred to as "printer 1") ejects UV (Ultra Violet) ink from an inkjet head 300 (hereinafter referred to as "head 300") onto a print medium 3 to perform printing. As Figure 2 shown, the printer 1 includes: a head unit 2, a platen 4, a carriage 5, an ink storage unit 7, a storage unit connection part 9, a hose 10, and a carriage drive unit 11.

[0048] In the following description, the conveyance direction of the print medium 3 is set as the X direction, the direction in which the head 300 moves is set as the Y direction, and the direction orthogonal to the X direction and the Y direction is set as the Z direction. Additionally, in the X direction, the front direction of the printer 1 in Figure 1 is set as the X+ direction, and the back direction of the printer 1 is set as the X− direction. Further, in the Y direction, the left side direction of the printer 1 in Figure 1 is set as the Y+ direction, and the right side direction of the printer 1 is set as the Y− direction. Moreover, in the Z direction, the direction opposite to the vertical direction of the printer 1 in Figure 1 is referred to as the Z+ direction, and the vertical direction of the printer 1 is referred to as the Z− direction. Additionally, the plane formed by the X direction and the Y direction is referred to as the XY plane. The direction along the XY plane is referred to as the horizontal direction.

[0049] As Figure 1 shown, the ink storage unit 7 is installed in the storage unit connection part 9 with the outlet facing downward. The ink in the ink storage unit 7 flows through the hose 10 installed in the storage unit connection part 9 and is supplied to a pressure control unit 100 mounted on the carriage 5. Here, the height of the ink storage unit 7 installed in the storage unit connection part 9 is located at a position higher than that of the pressure control unit 100. In addition, the ink storage unit 7 and the storage unit connection part 9 may also be mounted on the carriage 5.

[0050] The ink storage unit 7 is made of a flexible material. The ink storage unit 7 is airtightly installed in the storage unit connection part 9. The ink storage unit 7 is configured to maintain a constant pressure of the air inside when the remaining amount of ink decreases.

[0051] The ink supplied from the storage unit connection part 9 having the ink storage unit 7 contains UV ink. The viscosity of the UV ink has a high temperature dependence, being at a relatively high viscosity at normal temperature, but the viscosity decreases when heated. That is, the UV ink can improve its fluidity by heating. Here, the UV ink refers to ink having the property of curing when irradiated with UV.

[0052] The UV ink contains pigments as colorants, monomers as materials for forming a coating film through polymerization, a photoinitiator that absorbs UV light to initiate the polymerization reaction of the monomers, and a regulator for adjusting the printed ink, and has ultraviolet curability. When the UV ink is irradiated with ultraviolet rays, the photoinitiator reacts to initiate the polymerization reaction of the monomers, thereby curing.

[0053] One end of the hose 10 is connected to the storage unit connection part 9, and the other end of the hose 10 is connected to the pressure control part 100 of the nozzle unit 2. The hose 10 bends in the horizontal direction to follow the movement of the carriage 5 in the Y+ direction or the Y− direction.

[0054] The nozzle unit 2 ejects ink onto the platen 4 described later. As Figure 2 shown, the nozzle unit 2 has: a pressure control part 100, an ink heating module 200, a conduction part 210, a nozzle 300, and a protrusion 310. The nozzle unit 2 is mounted on the carriage 5 described later.

[0055] The pressure control part 100 causes the ink supplied from the ink storage part 7 to flow toward the ink heating module 200. The pressure control part 100 has a control flow path 110 for the ink to flow through, a buffer 120, and a back suction device 130. The pressure control part 100 is arranged at a position lower than the ink storage part 7. Here, using Figure 2 the head difference h between the height of the ink level in the ink storage part 7 shown and the height of the ink at the inlet of the pressure control part 100, the ink flows from the ink storage part 7 to the pressure control part 100.

[0056] When the flow rate of the ink supplied from the ink storage part 7 during ink flow is larger than the amount of ink ejected from the nozzle 300, the pressure control part 100 holds the remaining ink in the buffer by increasing the capacity of the buffer 120. In addition, when the flow rate of the ink supplied from the ink storage part 7 is smaller than the amount of ink ejected from the nozzle 300, the pressure control part 100 supplies the ink held in the buffer by reducing the capacity of the buffer 120. Thus, it is possible to cope with a sharp increase or decrease in the amount of ink ejected from the nozzle 300. In addition, when the ink is not ejected from the nozzle 300, the pressure control part 100 uses the back suction device 130 to increase the volume of the buffer 120 and performs an operation of slightly returning the ink between the pressure control part 100 and the nozzle 300.

[0057] <Ink Heating Module>

[0058] The ink heating module 200 is used to heat the ink supplied from the pressure control part 100. As Figure 3As shown, the ink heating module 200 has a heating flow path 220 for ink circulation inside. The heating flow path 220 connects the inlet 222 and the connection port 230. The ink heating module 200 has a connection end face 232 continuous from the connection port 230. The ink heating module 200 has a hole 234 for installing the sealing member 260 on the connection end face 232. The ink heating module 200 is provided with a sheet heater 240 on the side surface. The ink heating module 200 is fixed by fastening the fixing part 250 to the carriage 5 with threaded parts.

[0059] According to Figure 3 , the heating flow path 220 that the ink heating module 200 has inside includes a first heating path 224 along the Z - direction from the inlet 222, a second heating path 226 continuous from the first heating path 224 and along the X+ direction, and a third heating path 228 continuous from the second heating path 226 and along the Z - direction to reach the connection port 230. The ink heating module 200 having the heating flow path 220 is heated by the sheet heater 240 described later. That is, the ink flowing through the heating flow path 220 is heated by the heating flow path 220, and its viscosity decreases, thereby improving fluidity.

[0060] In the following description, unless otherwise specified, the heating flow path 220 refers to the third heating path 228. The flow path diameter dimension of the heating flow path 220 is expressed as d 1 . The flow path diameter dimension d of the heating flow path 220 1 For example, is It is also possible that the ink heating module 200 has a plurality of heating flow paths 220, and is configured to supply ink to each heating flow path 220 from a plurality of ink storage parts 7 via a pressure control part 100.

[0061] In this embodiment, the flow path cross - sectional shape of the heating flow path 220 is a circular shape having a flow path diameter dimension d 1 , and the flow path cross - sectional shape of the protruding flow path 312 is a circular shape having a flow path diameter dimension d 2 will be described. However, the flow path cross - sectional shapes of the heating flow path 220 and the protruding flow path 312 are not limited to circular shapes. That is, when the flow path cross - sectional shapes of the heating flow path 220 and the protruding flow path 312 are shapes other than circular shapes, their respective flow path cross - sectional shapes can be made equivalent to circular shapes having a flow path diameter dimension d 1 and a flow path diameter dimension d 2 of a circular shape, and applied to this embodiment. Here, for the diameter dimension in the case where the flow path cross - sectional shape is made equivalent to a circular shape, for example, it is calculated by making the area of the equivalent circular shape equal to the area of the flow path cross - sectional shape.

[0062] The material of the ink heating module 200 can use a material that easily conducts heat, such as aluminum alloy. For the ink heating module 200, for example, after the overall shape is processed by die casting, the inlet 222, the heating flow path 220, the connection port 230, the hole 234, and the connection end face 232 are set by machining. The unnecessary holes and the like generated by machining are appropriately closed.

[0063] The sheet heater 240 is used to heat the ink heating module 200. The sheet heater 240 has flexibility and is mainly arranged on the side surface of the ink heating module 200. Specifically, according to Figure 3 , the sheet heater 240 is arranged along the second heating path 226 from the end face in the X− direction to the end face in the X+ direction of the ink heating module 200, and covers the side surface in the Y+ direction of the ink heating module 200.

[0064] The sheet heater 240 is formed, for example, by covering the heating wire from both sides with silicone rubber. In addition, the sheet heater 240 is provided with a temperature sensor. The sheet heater 240 can adjust the temperature by adjusting the supply voltage. The temperature sensor can also be arranged on the ink heating module 200. The power output of the sheet heater 240 is, for example, 36W. In addition, the set temperature of the sheet heater 240 is, for example, 48°C.

[0065] <Sealing member>

[0066] As Figure 3 shown, the sealing member 260 seals and connects the ink heating module 200 and the protrusion 310. The sealing member 260 is, for example, an annular sealing ring. The sealing ring (sealing member) 260 is installed in the hole 234 of the ink heating module 200. The outer diameter dimension of the sealing ring 260 corresponds to the inner diameter dimension of the hole 234. The inner diameter dimension of the sealing ring 260 corresponds to the outer diameter dimension of the protrusion 310.

[0067] When the conduction part 210 is fixed to the ink heating module 200, the sealing ring 260 installed in the hole 234 is pressed by the end face 216 and deformed, so that its position is restricted relative to the hole 234. Moreover, when the nozzle 300 is installed on the carriage 5, the front end of the protrusion 310 penetrates through the inner circumference of the sealing ring 260 and is connected to the connection port 230. At this time, the protrusion 310 presses the surface of the inner circumference of the sealing ring 260 with the surface of the outer circumference of the protrusion 310. The sealing ring 260 deformed due to the protrusion 310 blocks the gap between the outer circumferential surface of the front end part of the protrusion 310 and the hole 234. Thus, the protruding flow path 312 is connected to the heating flow path 220.

[0068] <Ink flow path part>

[0069] As Figure 2As shown, the ink flow path section 6 includes: an ink storage section 7, a storage section connection section 9, a hose 10, a pressure control section 100, and an ink heating module 200.

[0070] <Protrusion>

[0071] As Figure 3 shown, the protrusion 310 is provided to protrude with respect to the nozzle 300 described later. The protrusion 310 has an inner protrusion flow path 312 for allowing ink to flow toward the nozzle 300. As Figure 3 shown, the protrusion flow path 312 is connected to the heating flow path 220. The protrusion 310 causes the ink to flow from the ink flow path section 6 to the nozzle 300.

[0072] The protrusion 310 is configured in a tube shape and has an outer peripheral surface and an inner peripheral surface. The flow path formed by the inner peripheral surface of the protrusion 310 is the protrusion flow path 312. The inner diameter dimension of the inner peripheral surface of the protrusion flow path 312 is d 2 . The protrusion 310 is made of resin and is produced by, for example, injection molding. The flow path cross-sectional area of the protrusion flow path 312 is configured to be smaller than the flow path cross-sectional area of the heating flow path 220. In the present embodiment, the case where the protrusion flow path 312 has a circular shape with a flow path diameter dimension d 2 is described, but the protrusion flow path 312 is not limited to a circular shape.

[0073] <Inkjet Head>

[0074] The nozzle 300 ejects the ink conveyed from the protrusion 310 onto the print medium 3. As Figure 3 shown, the nozzle 300 has inside it: a built-in heater 320, nozzles 330, ink chambers 340, a substrate 350, a heat insulator 352, a radiator 354, a fan 356, and a nozzle cover 360. The nozzle 300 is disposed on the bottom surface of the carriage 5 so as to face the platen 4.

[0075] The nozzles 330 are provided on the surface of the nozzle 300 that faces the platen 4 and are used for ejecting ink. The nozzles 330 have: a plurality of ejection holes (not shown) arranged, a piezoelectric element (not shown) for ejecting the ink from the ejection holes, a substrate 350 for controlling the piezoelectric element, and a heat insulator 352. The heat insulator 352 is disposed between the built-in heater 320 and the substrate 350. The ejection of the ink from the ejection holes of the nozzles 330 is controlled by the substrate 350 for controlling the piezoelectric element. The substrate 350 has a radiator 354 and a fan 356 on the surface opposite to the surface in contact with the heat insulator 352. The built-in heater 320 is configured in the same way as the sheet heater 240. The set temperature of the built-in heater 320 is, for example, 45°C.

[0076] The ink chamber 340 supplies ink from the protrusion 310 to the entire surface of the nozzle 330. The ink chamber 340 is provided between the nozzle 330 and the built-in heater 320 and faces the surface of the nozzle 330. That is, the surface of the ink chamber 340 in the Z+ direction contacts the built-in heater 320, and the surface of the ink chamber 340 in the Z− direction contacts the nozzle 330. In the ink chamber 340, the ink heated by the built-in heater 320 is supplied to the nozzle 330. The ink in the print head 300 is heated by the built-in heater 320 to maintain a state with high fluidity.

[0077] <Conduction part>

[0078] The conduction part 210 is used to heat the protrusion 310. The conduction part 210 is integrally formed with the ink heating module 200, so that heat transfer is easily performed from the ink heating module 200. The conduction part 210 of this embodiment is a member independent of the ink heating module 200. As Figure 3 shown, the conduction part 210 is arranged on the connection end face 232 of the ink heating module 200. The material of the conduction part 210 is made of a material that is easy to conduct heat, for example, aluminum alloy. The material of the conduction part 210 can also be made of the same material as the ink heating module 200.

[0079] As Figure 3 shown, the conduction part 210 is configured in a cylindrical shape and has an outer circumference 212 and an inner circumference 214 of the conduction part 210. The diameter dimension of the inner circumference 214 of the conduction part 210 becomes a dimension corresponding to the outer diameter dimension of the protrusion 310 described later. The diameter dimension of the inner circumference 214 of the conduction part 210 becomes a dimension corresponding to the outer diameter dimension of the protrusion 310. The conduction part 210 can surround the periphery of the protrusion 310 in a manner adjacent to the periphery of the protrusion 310.

[0080] The end face 216 of the conduction part 210 is precisely ground. The conduction part 210 has a mounting hole (not shown) and is fixed to the ink heating module 200 by tightening from the lower side (Z− direction side) of the mounting hole using a threaded member. In addition, the conduction part 210 can also have a positioning structure relative to the ink heating module 200. The conduction part 210 can also have a fitting structure, for example. Thereby, the conduction part 210 can be simply positioned relative to the ink heating module 200.

[0081] In addition, in the present embodiment, the case where the conduction part 210 is a member independent of the ink heating module 200 has been described, but the structure of the conduction part 210 is not limited thereto. That is, the conduction part 210 may also be a part of the member of the ink heating module 200. Also in this case, the conduction part 210, which is a part of the member of the ink heating module 200, is disposed adjacent to the protruding part 310. In addition, also in this case, the conduction part 210 may be disposed so as to surround the periphery of the protruding part 310 adjacent to the periphery of the protruding part 310.

[0082] In the present embodiment, the case where the conduction part 210 has a cylindrical shape has been described, but the shape of the conduction part 210 is not limited thereto. It is only necessary that the conduction part 210 is disposed adjacent to the protruding part 310. Here, "disposed adjacent" means that the protruding part 310 is disposed beside the conduction part 210, meaning that the distance between the protruding part 310 and the conduction part 210 is close to the extent that heat can be transferred between the protruding part 310 and the conduction part 210, including the state of contact. The conduction part 210 may also be composed of a plurality of structural bodies.

[0083] According to Figure 3 , the conduction part 210 is disposed adjacent to the protruding part 310 between the ink heating module 200 and the carriage 5, but the position where the conduction part 210 is disposed is not limited thereto. The conduction part 210 may also be disposed adjacent to the protruding part 310 between the ink heating module 200 and the nozzle 300. Thus, the conduction part 210 can heat the protruding part 310 over a longer distance. In this case, the carriage 5 has a hole with a diameter larger than the outer diameter 212 of the conduction part 210 for the conduction part 210 to pass through.

[0084] A nozzle unit 2 is mounted on the carriage 5. The carriage 5 may have a plurality of nozzle units 2. The carriage 5 is guided by a guide rail 12 within the entire width range in the Y direction of the printing medium 3 and is moved in the Y+ direction or the Y− direction by a carriage drive unit 11. The carriage 5 has a control unit (not shown) for controlling a later-described sheet heater 240, a built-in heater 320, etc., and a UV irradiator (not shown) for curing the ejected UV ink.

[0085] As described above, the carriage drive unit 11 moves the carriage 5 in the Y+ direction or the Y− direction. The carriage drive unit 11 can adjust the moving speed of the carriage 5 and can stop it with high stop position accuracy. The carriage drive unit 11 includes, for example, a belt-pulley mechanism unit (not shown) and a motor.

[0086] The printing medium 3 is placed on the platen 4. The platen 4 has a conveying roller 8 for conveying the printing medium 3 in the conveying direction (X+ direction). The platen 4 performs an intermittent operation of conveying the printing medium 3 a certain length in the conveying direction (X+ direction) corresponding to the printing operation.

[0087] As Figure 2 shown, the printing medium 3 is placed on the platen 4. The printing medium 3 is installed in the printer 1 in a wound state, and is pulled out and placed on the platen 4 corresponding to the printing operation. The material of the printing medium 3 is, for example, paper, cloth, or resin film. The printing medium 3 may also be configured to be installed in the printer 1 in a single-sheet state and supplied corresponding to the printing operation.

[0088] <Regarding heat transfer>

[0089] Hereinafter, the structure in which the heat from the ink heating module 200 heats the ink by means of the conduction part 210 and the protruding part 310 will be described. First, the heat from the ink heating module 200 heated by the sheet heater 240 is transferred to the conduction part 210 through the contact part between the connection end face 232 and the end face 216 of the conduction part 210. The heat transferred from the ink heating module 200 to the end face 216 diffuses in the conduction part 210 due to heat conduction, and the temperature of the conduction part 210 rises.

[0090] The heat is transferred to the protruding part 310 by using the conduction part 210 disposed adjacent to the protruding part 310. The heat transfer from the conduction part 210 to the protruding part 310 is mainly carried out by heat conduction through the contact part between the inner periphery 214 of the conduction part 210 and the outside of the protruding part 310. When the inner periphery 214 of the conduction part 210 does not contact the outside of the protruding part 310, the heat transfer from the conduction part 210 to the protruding part 310 is mainly carried out by heat transfer or heat radiation from the inner periphery 214 of the conduction part 210 to the outside of the protruding part 310.

[0091] Regarding the transfer of heat from the protruding part 310 to the ink flowing in the protruding flow path 312, first, the heat transferred from the conduction part 210 to the protruding part 310 conducts heat in the protruding part 310, and the temperature of the protruding part 310 rises. Here, afterwards, the heat is transferred from the wall surface of the protruding flow path 312 with the increased temperature to the ink flowing in the protruding flow path 312. The transfer of heat from the wall surface of the protruding flow path 312 to the ink flowing in the protruding flow path 312 is carried out by heat transfer. Thus, the heat of the ink heating module 200 is transferred to the protruding flow path 312 through the conduction part 210 and the protruding part 310, and the ink flowing in the protruding flow path 312 is heated.

[0092] <Regarding the flow path cross-sectional area>

[0093] Hereinafter, with reference to Figure 4Describe the relationship between the protruding flow path 312 and the heating flow path 220. Here, the density of the ink in the flow path from the ink flow path section 6 to the nozzle 300 can be regarded as constant. In addition, the flow rate of the ink in the flow path from the ink flow path section 6 to the nozzle 300 is constant. Therefore, in the flow path with a smaller cross-sectional area, the flow velocity of the flowing ink is faster than that in the flow path with a larger cross-sectional area. In this case, as Figure 4 shown, when the flow velocity of the ink flowing in the heating flow path 220 is set to v 1 , and the flow velocity of the ink flowing in the protruding flow path 312 is set to v 2 , it is represented by the following formula (1).

[0094] v 2 / v 1 =A 1 / A 2 ··· Formula (1)

[0095] Regarding the cross-sectional area of the flow path, a specific description will be given with reference to Figure 3 . As Figure 3 and Figure 4 shown, the flow path diameter dimension d 2 of the protruding flow path 312 is smaller than the flow path diameter dimension d 1 of the heating flow path 220. That is, the cross-sectional area A 2 of the protruding flow path 312 is smaller than the cross-sectional area A 1 of the heating flow path 220. For the heating flow path 220, when the flow path diameter dimension d 1 is , the cross-sectional area A 1 of the heating flow path 220 is approximately 3.8 mm 2 . For the protruding flow path 312, when the flow path diameter dimension d 2 is , the cross-sectional area A 2 is approximately 2 mm 2 .

[0096] In this case, if the cross-sectional area A 1 of the heating flow path 220 and the cross-sectional area A 2 of the protruding flow path 312 are substituted into formula (1) and the flow velocity v 2 of the ink in the protruding flow path 312 is calculated, then it is approximately 1.9 times the flow velocity v 1 of the ink flowing in the heating flow path 220. Thus, by making the cross-sectional area A 2 of the protruding flow path 312 smaller than the cross-sectional area A 1 of the heating flow path 220, the fluidity can be increased in the protruding flow path 312 compared to the heating flow path 220.

[0097] From another perspective, when making the flow path cross-sectional area A of the protruding flow path 312 2 smaller than the flow path cross-sectional area A of the heating flow path 220 1 , the residence time of the ink in the protruding flow path 312 is shorter than the residence time of the ink in the heating flow path 220. Therefore, the time for heat energy to transfer between the protruding portion 310 and the ink flowing through the protruding flow path 312 is shorter than the time for heat energy to transfer between the heating flow path 220 and the ink flowing through the heating flow path 220.

[0098] This situation will be specifically described. When the temperature T of the ink flowing through the protruding flow path 312 2 is higher than the temperature T of the heating flow path 220 and the protruding flow path 312 0 , the heat energy possessed by the ink flowing through the protruding flow path 312 is transferred to the protruding portion 310. In this embodiment, the flow path diameter dimension d of the protruding flow path 312 2 is smaller than the flow path diameter dimension d of the heating flow path 220 1 . Therefore, the flow velocity v of the ink flowing through the protruding flow path 312 2 is faster than the flow velocity v of the ink flowing through the heating flow path 220 1 . Thus, the residence time of the ink in the protruding flow path 312 is shorter, and the amount of heat energy released from the ink passing through the protruding flow path 312 is suppressed. By reducing the decrease in the ink temperature in the protruding flow path 312, the increase in the ink viscosity is suppressed, and the fluidity of the ink is ensured.

[0099] When the temperature T of the ink flowing through the protruding flow path 312 2 is lower than the temperature T of the protruding flow path 312 0 , the ink flowing through the protruding flow path 312 receives heat energy from the protruding flow path 312. Thereby, the viscosity of the ink in the protruding portion 310 is decreased, and the fluidity can be improved.

[0100] In addition, when the heat transfer area where the ink per unit volume V in the heating flow path 220 receives heat energy from the wall surface of the heating flow path 220 is set as R 1 , and the heat transfer area where the ink per unit volume V in the protruding flow path 312 receives heat energy from the wall surface of the protruding flow path 312 is set as R 2 , Equation (2) is obtained. Here, for the case where the height (length in the Z direction) of the ink per unit volume V in the heating flow path 220 is set as L 1 , and the height (length in the Z direction) of the ink per unit volume V in the protruding flow path 312 is set as L 2 , the heat transfer area R 1 is πd 1 L 1 , and the heat transfer area R 2 is πd 2 L 2 .

[0101] R 2 = (d 1 / d 2 )·R 1 ··· Equation (2)

[0102] That is, the heat transfer area R where the ink per unit volume V in the protruding flow path 312 receives heat energy from the wall surface of the protruding flow path 312 2 is larger than the heat transfer area R where the ink receives heat energy from the wall surface of the heating flow path 220 1 . Thus, in the protruding flow path 312, the ink is heated more efficiently than in the heating flow path 220

[0103] Here, by making the flow path diameter size d of the protruding flow path 312 2 configured to be smaller than the flow path diameter size d of the heating flow path 220 1 , in the protruding portion 310 disposed adjacent to the conduction portion 210 through which heat is transferred from the ink heating module 200, the temperature T of the protruding flow path 312 0 is higher than the temperature T of the ink flowing through the protruding portion 310 2 . Therefore, in the protruding flow path 312, the ink can be heated efficiently

[0104] <Regarding the shape of the protruding flow path>

[0105] Next, the shape of the protruding flow path 312 will be described. In Figure 3 , the shape of the protruding flow path 312 is represented by the same flow path diameter size d over the entire length of the protruding portion 310 2 , but it is not limited thereto. The flow path diameter size of the protruding portion 310 may be smaller than the flow path diameter size d of the heating flow path 220 at least in part of the entire length of the protruding portion 310 1 . Thus, the flow velocity of the ink flowing through the protruding flow path 312 becomes faster than that of the ink in the heating flow path 220, and therefore the fluidity of the ink can be improved

[0106] In addition, regarding the shape of the protruding flow path 312 of the protruding portion 310, for example Figure 5 as shown, it may be that in the portion of the protruding portion 310 facing the connection end face 232, there is a portion having a flow path diameter size d in the shape of a throttle hole 2 , and the other portions are configured to have the same flow path diameter size as the flow path diameter size d of the heating flow path 220 1 . Alternatively, it may be that the protruding portion 310 has a flow path diameter size d on the surface in contact with the connection end face 232 of the protruding portion 310 2 , and for example, uniformly expands from the flow path diameter size d 2 to the flow path diameter size d of the heating flow path 220 over the entire length 1The flow path diameter dimension of the protrusion 310 changes in the same diameter dimension manner. Additionally, it can also be that the flow path diameter dimension of the protrusion 310 is d on the surface of the protrusion 310 that contacts the connection end face 232 2 , for example, and is steppedly enlarged to the flow path diameter dimension d of the heating flow path 220 over the entire length 2 in a manner that changes to the same dimension 1 as the flow path diameter dimension of the heating flow path 220

[0107] <Other Embodiments>

[0108] <Assembly Method>

[0109] The assembly method of the nozzle unit 2 of the printer 1 of the present invention will be described. The nozzle 300 is assembled with respect to the ink heating module 200 mounted on the carriage 5. That is, the sealing member 260 is disposed in the hole 234 of the ink heating module 200, and the conduction part 210 is fixed to the ink heating module 200 to position the sealing member 260. Then, the protrusion 310 of the nozzle 300 is installed from the lower side. The protrusion 310 penetrates through the opening provided in the carriage 5 and the inner periphery of the conduction part 210 and is connected to the connection port 230 of the ink heating module 200. Here, the sealing surface at the front end of the protrusion 310 is sealed by pressing the inner periphery of the sealing member 260. Then, the nozzle 300 is fixed with respect to the carriage 5

[0110] <Protrusion with Sealing Member>

[0111] The sealing member 260 may not be installed on the ink heating module 200 but on the front end portion of the protrusion 310. In this case, the conduction part 210 is configured as a member independent of the ink heating module 200. The sealing member 260 is installed on the front end portion of the protrusion 310 disposed adjacent to the conduction part 210 in advance. That is, the conduction part 210 is provided for the protrusion 310 in a manner that it is located between the sealing member 260 and the nozzle 300. Then, the protrusion 310 having the conduction part 210 and the sealing member 260 is installed on the ink heating module 200

[0112] Hereinafter, the embodiments of the present invention will be described in detail based on the drawings. In addition, the present invention is not limited by this embodiment. Additionally, among the structural elements in the following embodiments, there are structures that can be replaced and are easily replaceable by those skilled in the art, or substantially the same structures. Moreover, the structural elements described below can be appropriately combined. Additionally, in the case of having multiple embodiments, the respective embodiments can also be combined

[0113] [This Embodiment]

[0114] The inkjet printer 91 of the present embodiment (hereinafter also simply referred to as the printer 91) is a device that prints an image on a medium 92 as a recording medium by an inkjet method. As the medium 92, for example, a non-permeable medium made of metal, resin, etc. that is non-permeable to ink, or a permeable medium made of cloth, paper, etc. that is permeable to ink can be applied, and any material can be applied as long as it is a medium 92 capable of forming an image. In addition, as the ink, for example, an ultraviolet curable ink (UV ink) that is cured by ultraviolet rays is applied. The UV ink of the present embodiment is an ink having a high viscosity in a temperature range of normal temperature (for example, 15°C to 25°C). Next, refer to Figures 6 to 10 Describe the printer 91.

[0115] Figure 6 is a perspective view of the inkjet printer of the present embodiment. Figure 7 is a schematic diagram schematically showing the structure near the inkjet head. Figure 8 is a top view showing the inlet side of the inkjet head. Figure 9 is a top view showing the nozzle surface side of the inkjet head. Figure 10 is an explanatory diagram showing the ejection frequency of the ink at the nozzle row.

[0116] As Figure 6 and Figure 7 shown, the printer 91 includes: an inkjet head 93 (hereinafter also simply referred to as the head 93), a carriage 94, a platen 95, a heating module 96, a pressure regulating unit 97, a carriage driving unit 98, a guide rail 99, an ink tank 910, and a control unit 915. Here, in Figure 6 and Figure 7 the X direction is the direction in which the medium 92 is conveyed and becomes the sub-scanning direction. The Y direction is the direction in which the inkjet head 93 moves and becomes the main scanning direction. The Z direction is a direction orthogonal to the main scanning direction and the sub-scanning direction, and for example, is a vertical direction when the plane including the main scanning direction and the sub-scanning direction is a horizontal plane.

[0117] The head 93 is provided on the carriage 94 and ejects UV ink toward the medium 92. The head 93 has a nozzle row 921a, and the nozzle row 921a includes a plurality of nozzles 921 arranged in the X direction (sub-scanning direction). In addition, in the head 93, a plurality of nozzle rows 921a are provided according to the types of colors used. For example, nozzle rows 921a corresponding to four colors of CMYK are arranged in the Y direction. Two (a pair) of these heads 93 are provided on the carriage 94. When viewed from the Y direction (main scanning direction), the ends of the two nozzle rows 921a of the two heads 93 face each other in the X direction, and a longer nozzle row 921a connected in the X direction is formed.

[0118] The platen 95 is disposed opposite to the print head 93 in the Z direction. A medium 92 is placed on the platen 95. The platen 95 heats the placed medium 92 and heats the ink ejected onto the medium 92 via the medium 92, thereby promoting the drying of the ink.

[0119] In addition to mounting the print head 93, the carriage 94 also mounts a heating module 96 and a pressure regulating unit 97. The carriage drive unit 98 moves the carriage 94 along the guide rail 99. The guide rail 99 is disposed to extend in the Y direction, and the carriage drive unit 98 moves the carriage 94 in the Y direction. At this time, the carriage 94 moved by the carriage drive unit 98 moves the print head 93, the heating module 96, and the pressure regulating unit 97 integrally. In addition, the print head 93, the heating module 96, and the pressure regulating unit 97 are integrally configured as a print head unit 911.

[0120] The heating module 96 is disposed on the upstream side of the print head 93 in the ink flow direction. The heating module 96 warms the UV ink supplied to the print head 93 by heating it, thereby reducing the viscosity of the ink supplied to the print head 93.

[0121] Ink is supplied from the ink tank 910 to the pressure regulating unit 97 via the ink supply line 912. The ink tank 910 is disposed at a position above the pressure regulating unit 97 and supplies ink to the pressure regulating unit 97 using the head difference. The pressure regulating unit 97 regulates the pressure of the ink supplied to the heating module 96. The pressure regulating unit 97 is a mechanical pressure buffer such as a pressure buffer disclosed in Japanese Patent Application Laid-Open No. 2012-232595, for example. Specifically, the pressure regulating unit 97 regulates the pressure of the ink so that the ink chamber formed inside the print head 93 becomes negative pressure.

[0122] The control unit 915 is connected to the print head 93, the heating module 96, and the carriage drive unit 98. The control unit 915 includes, for example, an integrated circuit such as a CPU (Central Processing Unit). The control unit 915 performs the following controls: ink ejection control performed by the print head 93, ink heating control performed by the heating module 96, and movement control of the print head 93 in the main scanning direction performed by the carriage drive unit 98.

[0123] In the above inkjet printer 91, the ink first flows out from the ink tank 910 to the ink supply line 12 and flows into the pressure regulating unit 97 via the ink supply line 12. The ink whose pressure has been regulated in the pressure regulating unit 97 is supplied to the heating module 96. The ink is heated in the heating module 96 and its viscosity decreases, and then it is supplied toward the print head 93. Next, the print head 93 ejects ink toward the medium 92 while moving in the Y direction.

[0124] Next, refer to Figure 8 and Figure 9A description will be given of the vicinity of the inkjet head 93. As described above, two inkjet heads 93 are mounted on the carriage 94, and the inkjet head 93 is mounted on the bottom plate 926. As Figure 8 and Figure 9 shown, the two nozzles 93 are arranged and configured at a predetermined gap in the main scanning direction with respect to the bottom plate 926. In addition, the two nozzles 93 are arranged such that their two nozzle rows 921a are arranged in the sub-scanning direction when viewed from the main scanning direction, so that their positions in the sub-scanning direction are different. When viewed from the main scanning direction, the ends of the two nozzle rows 921a arranged in the sub-scanning direction overlap each other.

[0125] Each of the nozzles 93 has a nozzle row 921a composed of a plurality of nozzles 921, an ink supply port 925, and an ink heater 927. The ink heated by the heating module 96 flows into the ink supply port 925. The ink supply port 925 is provided on one side in the sub-scanning direction with respect to the nozzle row 921a. A plurality of ink supply ports 925 are provided according to the type of color used. For example, ink supply ports 925 corresponding to the four colors of CMYK are arranged in the Y direction.

[0126] The ink heater 927 heats the ink inside the nozzle 93. The ink heater 927 reduces the viscosity of the ink by heating the ink flowing inside the nozzle 93.

[0127] Here, since the ink supply port 925 is provided on one side in the sub-scanning direction with respect to the nozzle row 921a, in the nozzle row 921a, one side in the sub-scanning direction is the side closer to the ink supply port 925, and the other side in the sub-scanning direction is the side farther from the ink supply port 925. That is to say, the flow path length of the nozzle 921 on the side closer to the ink supply port 925 from the ink supply port 925 is shorter, and the flow path length of the nozzle 921 on the side farther from the ink supply port 925 from the ink supply port 925 is longer. In the case of such a nozzle 93, since the flow path length of the nozzle 921 on the side closer to the ink supply port 925 is shorter, the heating of the ink is insufficient when the ink is just ejected, and the ejection speed of the ink deviates compared with the nozzle 921 on the side farther from the ink supply port 925.

[0128] As Figure 8As shown, two nozzles 93 are arranged at a prescribed interval in the main scanning direction. In addition, the two nozzles 93 are arranged such that their respective ink supply ports 925 are located on the outer sides in the sub-scanning direction. That is, the ink supply ports 925 of the respective nozzles 93 are arranged at both ends in the sub-scanning direction with respect to two nozzle rows 921a connected in the sub-scanning direction. That is, the two nozzles 93 are arranged adjacent to each other in the sub-scanning direction such that the ends on the other side (the side away from the ink supply port 925) of their nozzle rows 921a approach each other. That is to say, when the two nozzles 93 simultaneously perform a printing operation on the medium 92, the ends on the other side are made to approach each other in such a way that it is regarded as a nozzle row formed by continuously connecting the nozzle rows 921a of the two nozzles 93 respectively. Therefore, among the two nozzle rows 921a arranged in the sub-scanning direction, the nozzle 921 on the side of one nozzle row 921a closer to the other nozzle row 921a becomes the nozzle 921 on the side away from the ink supply port 925. Similarly, among the two nozzle rows 921a arranged in the sub-scanning direction, the nozzle 921 on the side of the other nozzle row 921a closer to one nozzle row 921a becomes the nozzle 921 on the side away from the ink supply port 925. Moreover, for the two nozzle rows 921a, in the sub-scanning direction, the nozzles 921 on the side away from the ink supply port 925 face each other, and thus, the nozzles 921 with a smaller deviation in ink ejection speed face each other.

[0129] In addition, as Figure 8 and Figure 9 shown, the two nozzles 93 have the same structure and are arranged in a point-symmetrical manner with a 180-degree phase difference centered on the symmetrical point P in the plane including the X direction and the Y direction. That is to say, in the plane including the X direction and the Y direction, one nozzle 93 is located at a position rotated 180 degrees with respect to the other nozzle 93 centered on the symmetrical point P. Therefore, the nozzle rows 921a corresponding to the four colors of CMYK of the two nozzles 93 are also arranged in a point-symmetrical manner with a 180-degree phase difference centered on the symmetrical point P.

[0130] Next, with reference to Figure 10 , the ink ejection control by the control unit 915 will be described. The control unit 915 performs printing using a multi-pass method, and in this multi-pass method, multiple main scanning operations corresponding to the multi-pass printing are performed for each position of the medium 92. The main scanning operation refers to an operation of ejecting ink droplets onto the medium 92 while moving the nozzle 93 in the main scanning direction.

[0131] Specifically, the printer 91 performs printing, for example, using a multi-pass method with the number of printing passes set to N (N is an integer of 2 or more). The number of printing passes N is, for example, 4 or more, and preferably 8 or more. In addition, in this case, the nozzles 921 in the nozzle rows 921a of the respective nozzles 93 are allocated corresponding to each pass of printing from the first pass to the Nth pass.

[0132] For example, when the number of printing passes is N, the plurality of nozzles 921 arranged in the sub-scanning direction of the nozzle row 921a are divided into N regions each having the same number of nozzles. Further, for the nozzle row 921a divided into N regions, in cooperation with the conveyance of the medium 92 in the sub-scanning operation, the printing for each pass from the first pass to the Nth pass is sequentially assigned starting from the region that first overlaps with the medium 92. Here, the sub-scanning operation refers to the operation of conveying the medium 92 relative to the print head 93 in the sub-scanning direction. Further, the control unit 915 sets the movement amount in one sub-scanning operation to the width of the arrangement of the nozzles 921 corresponding to one pass of printing (width in the sub-scanning direction), that is, the paper feed width. This paper feed width is the width in the sub-scanning direction of each of the N divided regions. Further, the control unit 915 causes the print head 93 to perform the sub-scanning operation during the interval of the main scanning operation of the print head 93. As a result, each time the main scanning operation is performed, the control unit 915 causes the region of the medium 92 facing the print head 93 to be offset by an amount corresponding to the paper feed width in the sub-scanning direction. Further, in each main scanning operation, the nozzles 921 in each region of the nozzle row 921a perform printing corresponding to the corresponding pass of printing.

[0133] Further, in the control of the printing corresponding to each pass of printing, the control unit 915 selects the pixels for which ink droplets should be ejected. More specifically, for example, in each pass of printing in the multi-pass printing performed at each position of the medium 92, the control unit 915 uses mask data that is data specifying the pixels for which ink droplets should be ejected, and causes each print head 93 to eject ink droplets for the pixels specified by the mask data. As a result, the control unit 915 performs multi-pass printing using the mask data. That is, the control unit 915 controls the ejection frequency of the ink ejected from the nozzle row 921a of the print head 93 as the ejection control of the print head 93 by using the mask data when performing the main scanning operation. By controlling the ejection frequency of the ink, the control unit 915 suppresses the generation of stripes formed in the main scanning direction and forms an image with smooth gradation. As such control of the ejection frequency of the ink, there is MAPS (Mimaki Advanced Pass System).

[0134] Here, when printing is performed in a multi-pass manner using two print heads 93, the mask data used for each pass of printing in the multi-pass printing, for example, becomes Figure 10 the pattern shown. Figure 10 The mask data shown becomes mask data in a pattern in which the nozzle usage frequency continuously changes in the sub-scanning direction, in other words, mask data in a pattern in which the concentration of the ink ejected onto the medium 92 continuously changes.

[0135] In Figure 10In the mask data shown, with respect to the entire length of two nozzle rows 921a arranged in the sub-scanning direction, the usage frequency (concentration) of the nozzles at the center in the sub-scanning direction is made higher than that of the nozzles on both sides thereof. In other words, in Figure 10 the mask data shown, the nozzles on the closer other end side (the side away from the ink supply port 925) of the nozzle rows 921a of the two print heads 93 have a higher usage frequency, and the nozzles on one end side (the side closer to the ink supply port 925) of the nozzle rows 921a have a lower usage frequency. Moreover, for the ejection frequency of the ink controlled using Figure 10 the mask data shown, in the entire length of the above nozzle rows 921a, the usage frequency of the nozzles at the center in the sub-scanning direction is set to the maximum (peak), the usage frequency of the nozzles at both ends in the sub-scanning direction is set to zero, and it becomes a triangular pattern that gradually decreases from the center in the sub-scanning direction to both sides by a certain value. In addition, this triangular pattern may also be a trapezoidal shape. If the usage frequency of the nozzles at the center in the sub-scanning direction is made higher than that of the nozzles on both sides in the sub-scanning direction, the pattern shape of the nozzle usage frequency may be any shape.

[0136] In the present embodiment, since the ejection control of the ink is performed using the above mask data, the nozzles 921 with a higher nozzle usage frequency become the nozzles on the side away from the ink supply port 925, and the nozzles 921 with a lower nozzle usage frequency become the nozzles 921 on the side closer to the ink supply port 925. Therefore, the nozzles 921 with a higher nozzle usage frequency become the nozzles 921 with a smaller deviation in the ink ejection speed, and the nozzles 921 with a lower nozzle usage frequency become the nozzles 921 with a larger deviation in the ink ejection speed.

[0137] As described above, according to the present embodiment, among the two nozzle rows 921a arranged in the sub-scanning direction, the nozzles 921 on the side away from the ink supply port 925 can be combined with each other. That is, they can be combined in such a way that the nozzles 921 on the side with a smaller deviation in the ink ejection speed and higher ink ejection stability are continuous or overlapping with each other in the sub-scanning direction. Therefore, it is possible to hardly generate streaks caused by shading, that is, banding, and it is possible to improve the image quality of the medium 92.

[0138] In addition, according to the present embodiment, since the ink supplied to the ink supply port 925 of the print head 93 can be heated by the heating module 96, unevenness in the ink temperature inside the print head 93 can be suppressed.

[0139] In addition, according to the present embodiment, since two print heads 93 are used, the medium 92 can be printed using the longer nozzle row obtained by the continuity of the two nozzle rows 921a.

[0140] In addition, according to the present embodiment, the nozzle 921 with a relatively high nozzle usage frequency can be made into a nozzle 921 with a relatively small deviation in the ejection speed of the ink. Therefore, the usage frequency of the nozzle 921 with relatively high ink ejection stability can be increased. On the other hand, the usage frequency of the nozzle 921 with relatively low ink ejection stability can be reduced, so that the ink can be stably ejected onto the medium 92.

[0141] In addition, according to the present embodiment, two nozzles 93 are arranged point-symmetrically, so that the two nozzles 93 can be made into the same structure, and thus an increase in the device cost can be suppressed.

[0142] In addition, according to the present embodiment, even when using UV ink, an improvement in the image quality with respect to the medium 92 can be achieved.

[0143] In addition, in the present embodiment, UV ink is adopted, but the ink used is not limited to UV ink. Further, in the present embodiment, two nozzles 93 having the same structure are arranged point-symmetrically, but two nozzles 93 having different structures may also be used.

[0144] Explanation of reference numerals

[0145] 1, inkjet printer; 2, nozzle unit; 3, printing medium; 4, platen; 5, carriage; 6, ink flow path portion; 7, ink storage portion; 8, conveying roller; 9, storage portion connection portion; 10, hose; 11, carriage drive portion; 12, guide rail; 100, pressure control portion; 110, control flow path; 120, buffer; 130, anti-suction device; 200, ink heating module; 210, conduction portion; 212, outer periphery of the conduction portion; 214, inner periphery of the conduction portion; 216, end face of the conduction portion; 220, heating flow path; 222, inlet; 224, first heating path; 226, second heating path; 228, third heating path; 230, connection port; 232, connection end face; 234, hole; 240, sheet heater; 250, fixing portion; 260, sealing member; 300, nozzle (inkjet head); 310, protruding portion; 312, protruding flow path; 320, built-in heater; 330, nozzle; 340, ink chamber; 350, substrate; 352, heat insulator; 354, radiator; 356, fan; 360, nozzle cover; A 1 , flow path cross-sectional area of the heating flow path; A 2 , flow path cross-sectional area of the protruding flow path; d 1 , flow path diameter dimension of the heating flow path; d 2 , inner diameter dimension of the protruding portion, flow path diameter dimension of the protruding flow path; V, unit volume of the ink; R 1 , heat transfer area of the heating flow path; R 2 , heat transfer area of the protruding flow path; T 0, the temperatures of the heating flow path and the protruding flow path; T1, the temperature of the ink in the heating flow path; T 2 , the temperature of the ink in the protruding flow path; 91, an inkjet printer; 92, a medium; 93, an inkjet head; 94, a carriage; 95, a platen; 96, a heating module; 97, a pressure regulating unit; 98, a carriage driving unit; 99, a guide rail; 910, an ink tank; 911, a print head unit; 912, an ink supply line; 915, a control unit; 921, a nozzle; 921a, a nozzle row; 925, an ink supply port; 926, a bottom plate; 927, an ink heater.

Claims

1. An inkjet printer that performs printing by relatively moving a recording medium and an inkjet head that ejects ink onto the recording medium. Characterized in that the inkjet head has: a nozzle row formed by arranging a plurality of nozzles in a single row in the same direction; an ink supply port formed on the end side of the nozzle row; and an ink heater for heating the ink. The inkjet printer includes a pair of the inkjet heads. The pair of inkjet heads are arranged with a positional offset in the same direction such that the end portions of the nozzle rows of the pair of inkjet heads are separated from each other in the same direction and the other end portions are close to each other in the same direction.

2. The inkjet printer according to claim 1, wherein the inkjet printer further includes a heating module provided upstream of each inkjet head in the flow direction of the ink for heating the ink supplied to the ink supply port.

3. The inkjet printer according to claim 1, wherein when the pair of inkjet heads simultaneously perform a printing operation with respect to the recording medium, the other end portions of the nozzle rows of one inkjet head and the other inkjet head in the pair are close to each other, so as to be regarded as a nozzle row obtained by continuous connection of the nozzle row of one inkjet head and the nozzle row of the other inkjet head in the pair.

4. The inkjet printer according to claim 1, wherein the inkjet printer further includes a control unit for controlling the printing operation of the inkjet head. In the control unit, by using a multi-pass method of performing multiple main scanning operations corresponding to multi-pass printing on each position of the recording medium, each inkjet head performs printing with respect to the recording medium. And, in each pass of the multi-pass printing performed on each position of the recording medium, using mask data that is data specifying pixels where ink droplets should be ejected, ink droplets are ejected from each inkjet head for the pixels specified by the mask data. In the mask data, the nozzles on the closer other end side of the nozzle rows of the pair of inkjet heads have a higher usage frequency, and the nozzles on the end side of the nozzle rows have a lower usage frequency.

5. The inkjet printer according to claim 1, wherein the pair of inkjet heads have the same structure, and in the plane where each inkjet head relatively moves with respect to the recording medium, the pair of inkjet heads are arranged in a point-symmetric manner with a 180-degree phase difference centered on a symmetric point.

6. The inkjet printer according to claim 1, wherein the ink is an ultraviolet curable ink curable by ultraviolet rays.

Images