Ink jet printer

Abstract

To suppress wasteful consumption of ink by reducing a difference in suction amount between a plurality of inks by reducing a viscosity difference between the plurality of inks in cleaning processing, and to suppress occurrence of color mixture by reducing a negative pressure difference between respective ink suction paths generated by suction of the plurality of inks.SOLUTION: The inkjet head is provided with a heating means such as a heater for heating a plurality of inks, and the plurality of inks are heated by the heating means in the cleaning process to reduce the viscosity difference between the plurality of inks.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an inkjet printer, and more particularly to an inkjet printer equipped with a cap unit used in a cleaning process for maintaining the ejection performance of inkjet nozzles in an inkjet head that ejects ink from inkjet nozzles using inkjet technology.

[0002] In this specification and the claims, the term "inkjet printer" refers to a variety of printers in general that utilize printing methods using inkjet technology through various conventionally known methods, including, for example, various continuous methods such as binary deflection methods or continuous deflection methods, and various on-demand methods such as thermal methods or piezoelectric element methods.

[0003] Furthermore, in this specification and the claims, "inkjet printer" includes both so-called two-dimensional printers, which eject printing ink toward a medium to print a two-dimensional image on the medium, and so-called three-dimensional printers (three-dimensional modeling devices), which eject binders, water, etc. onto powder material, etc., to harden the powder material and create a three-dimensional object.

[0004] Furthermore, in this specification and the claims, "media" includes not only various recording media made of paper such as plain paper, but also various media made of various materials such as resin materials such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), textiles, cloth, aluminum, iron, or wood.

[0005] Furthermore, in this specification and the claims, "ink" refers to not only various types of printing ink such as solvent-based pigment ink, water-based pigment ink, water-based dye ink, and ultraviolet-curable pigment ink, but also liquids such as binders and water used in three-dimensional modeling, and the term "ink" refers to all types of liquids that are sent to an inkjet head. [Background technology]

[0006] 2. Description of the Related Art Inkjet printers are generally well known, which perform a printing operation of forming an image on a medium by ejecting ink from inkjet nozzles formed in an inkjet head toward the medium using inkjet technology.

[0007] In such inkjet printers, as disclosed in, for example, JP 2020-138344 A, a so-called cap unit is provided as a device used for cleaning processes to maintain good ejection performance of the inkjet nozzles in the inkjet head.

[0008] Here, the cap unit is configured to include a cap member that is attached to cover the surface of the inkjet head where the inkjet nozzles are opened (inkjet nozzle surface) during standby for printing, and a suction pump connected to the cap member, and operates the suction pump to suck ink from the inkjet nozzles of the inkjet head, etc. Such a suction pump may be connected to the cap member via, for example, a cap tube.

[0009] The ink sucked by the suction pump is sent to a separately provided waste liquid tank, which may be connected to the suction pump via a waste liquid tube, for example.

[0010] Therefore, downstream of the cap member in an inkjet printer, two ink paths are provided: an ink suction path consisting of the cap member and a suction pump, etc., and a waste liquid path consisting of the suction pump and a waste liquid tube, etc.

[0011] In this specification and claims, ink paths located downstream of the cap member, such as the ink suction path and waste liquid path, will be collectively referred to as "ink paths downstream of the cap member."

[0012] In the conventional inkjet printers described above, a "suction process" and an "empty suction process" are performed as suction maintenance, which is a "cleaning process" for maintaining the ejection performance of the inkjet nozzles in the inkjet head.

[0013] That is, in the conventional inkjet printers described above, when the inkjet printer is on standby for printing, a cap member is attached to the inkjet nozzle surface, thereby forming an airtight space between the inkjet nozzle surface and the cap member.

[0014] When this sealed space is formed, the suction pump is operated to reduce the pressure inside the cap member, which in turn reduces the pressure inside the sealed space, causing the ink inside the inkjet head to be sucked out of the inkjet nozzle into the cap member and discharged, thereby maintaining good ejection performance of the inkjet nozzle.

[0015] In this way, the process of operating the suction pump at the "suction position" where the cap member is attached to the inkjet nozzle surface, and sucking the ink inside the inkjet head from the inkjet nozzle to the cap member and discharging it, is what is known as the "suction process" in cleaning processes, etc.

[0016] Furthermore, after the above-described suction process, in order to suck out ink accumulated in the cap member or to remove ink adhering to the inkjet nozzle face of the inkjet head, the cap member is released from the inkjet nozzle face and separated from the inkjet nozzle face, thereby opening the inside of the cap member and the sealed space to atmospheric pressure, and then the suction pump is operated.

[0017] In this way, by operating the suction pump at the "dry suction position" where the inside of the cap member and the sealed space are open to atmospheric pressure, it is possible to suck and discharge ink remaining in the cap member and remove ink adhering to the inkjet nozzle surface of the inkjet head, and the process of sucking and discharging ink remaining in the cap member and removing ink adhering to the inkjet nozzle surface of the inkjet head is what is known as "dry suction process" in cleaning processes, etc.

[0018] In this specification and claims, when there is no need to distinguish the "idle suction process" from the "suction process", the "idle suction process" will be collectively referred to simply as the "suction process".

[0019] Incidentally, conventional inkjet printers such as those described above employ a first printing method in which printing is performed by feeding multiple inks with different viscosities to multiple inkjet heads, respectively, and a second printing method in which printing is performed by feeding multiple inks with different viscosities to a single (single) inkjet head. In the first printing method, for example, the multiple inkjet heads include a first inkjet head and a second inkjet head, and the multiple inks with different viscosities include a first ink and a second ink, with the first ink being fed to the first inkjet head and the second ink being fed to the second inkjet head. In the second printing method, for example, the multiple inks with different viscosities include a first ink and a second ink, and the first ink and the second ink are fed to a single (single) inkjet head.

[0020] In inkjet printers that use the first or second printing method, when the cleaning process, which is the suction process or the empty suction process described above, is performed, various problems arise due to the difference in viscosity between the multiple inks, i.e., the difference in viscosity between each ink.

[0021] Specifically, because the amount of ink sucked by the suction pump differs depending on the viscosity of the ink, there is a difference in the amount of ink sucked between multiple inks, which results in the problem of ink being wasted and consumed in order to suck up a preset amount; and because the negative pressure in each ink suction path generated when the suction pump sucks each ink differs between multiple inks, a negative pressure difference occurs between each ink suction path, which causes the ink to flow backward and result in color mixing. [Prior art documents] [Patent documents]

[0022] [Patent Document 1] Japanese Patent Publication No. 2020-138344 Summary of the Invention [Problem to be solved by the invention]

[0023] The present invention has been made in consideration of the various problems with the prior art as described above, and its object is to provide an inkjet printer that reduces the difference in viscosity between multiple inks during cleaning processing, thereby reducing the difference in suction volume between the multiple inks and suppressing wasteful ink consumption, and that reduces the negative pressure difference between the ink suction paths that occurs when multiple inks are suctioned, thereby suppressing color mixing. [Means for solving the problem]

[0024] In order to achieve the above object, the inkjet printer according to the present invention is provided with a heating means, such as a heater, for heating the inks in the inkjet head, and by heating the inks with the heating means during the cleaning process, the viscosity difference between the inks is reduced.

[0025] Therefore, with the inkjet printer according to the present invention, the difference in viscosity between multiple inks is reduced during the cleaning process, thereby reducing the difference in suction volume between multiple inks and suppressing unnecessary ink consumption, and also reducing the negative pressure difference between each ink suction path that occurs when multiple inks are suctioned, thereby suppressing the occurrence of color mixing.

[0026] That is, an inkjet printer according to the present invention is an inkjet printer that uses inkjet technology to eject ink supplied to an ink supply path, comprising: a first inkjet head having inkjet nozzles that open to an inkjet nozzle face and eject a first ink supplied to the first ink supply path; a second inkjet head having inkjet nozzles that eject a second ink supplied to the second ink supply path; a first cap member attached to cover the inkjet nozzle face of the first inkjet head; and a second cap member attached to cover the inkjet nozzle face of the second inkjet head; a first heating means provided on the first inkjet head and that heats the first ink supplied to the first inkjet head; and a second heating means provided on the second inkjet head and that heats the second ink supplied to the second inkjet head; and heating elements connected to the first cap member and the second cap member and configured to heat the first ink supply path and the second inkjet head. the first ink jet head and the second ink jet head are supplied from the second ink supply path to the first ink jet head; storage means for storing information relating to viscosity changes associated with temperature changes for the first ink and the second ink; temperature determination means for determining, based on the information stored in the storage means, a temperature at which the viscosity of the first ink in the first ink jet head and the viscosity of the second ink in the second ink jet head become substantially the same; and heating control means for controlling at least one of the first heating means and the second heating means to a temperature at which the viscosity of the first ink in the first ink jet head and the viscosity of the second ink in the second ink jet head become substantially the same before the suction means starts suctioning the first ink supplied from the first ink supply path to the first ink jet head and the second ink supplied from the second ink supply path to the second ink jet head in a suction process.

[0027] An inkjet printer according to the present invention is an inkjet printer that uses inkjet technology to eject ink supplied to an ink supply path, and includes an inkjet head having first inkjet nozzles that open to an inkjet nozzle face and that eject a first ink supplied from a first ink supply path and a second inkjet nozzle that ejects a second ink supplied from a second ink supply path; a cap member that is attached to cover the inkjet nozzle face of the inkjet head; suction means that is connected to the cap member and that sucks the first ink and the second ink that are supplied to the inkjet head from the first ink supply path and the second ink supply path; and heating means that is provided in the inkjet head and that heats the first ink and the second ink that are supplied to the inkjet head. The inkjet head has a storage means for storing the temperature at which the viscosity of the first ink and the second ink becomes approximately the same, and a heating control means for controlling the heating means before the suction means starts suctioning the first ink and the second ink supplied from the first ink supply path and the second ink supply path to the inkjet head during the suction process, so that the temperatures of the first ink and the second ink become the temperatures stored in the storage means.

[0028] In the ink-jet printer according to the present invention, the case where the viscosities are substantially the same in the ink-jet printer according to the present invention described above includes a case where the viscosities are completely the same and a case where the viscosities are the same within a preset minute range of tolerance.

[0029] In addition, the ink jet printer according to the present invention is the ink jet printer according to the present invention described above, wherein the predetermined minute range of tolerance is within the range of ±0.2 mPa.s. [Effects of the Invention]

[0030] As the present invention is configured as described above, it is possible to reduce the difference in viscosity between multiple inks during cleaning processing, thereby reducing the difference in suction volume between multiple inks and suppressing unnecessary ink consumption, and it has the excellent effect of suppressing color mixing by reducing the negative pressure difference between each ink suction path that occurs when multiple inks are suctioned. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a perspective view illustrating a schematic configuration of an inkjet printer according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the inkjet head and its surroundings in the inkjet printer shown in FIG. [Figure 3] FIG. 3 is a block diagram illustrating the functional configuration of the microcomputer in the inkjet printer shown in FIG. 1, which is related to the implementation of the present invention. [Figure 4] Fig. 4(a) is a diagram showing the relationship between temperature and viscosity of an example first ink and a second ink used in the inkjet printer shown in Fig. 1. Fig. 4(b) is a graph based on the diagram shown in Fig. 4(a). [Figure 5] FIG. 5 is a diagram illustrating the configuration of an inkjet printer according to a second embodiment of the present invention, focusing on the configuration around the inkjet head. [Figure 6] FIG. 6 is a block diagram illustrating the functional configuration of a microcomputer in an inkjet printer according to a second embodiment of the present invention, which is related to the implementation of the present invention. [Figure 7] Figure 7(a) is a diagram showing the relationship between temperature and viscosity of an example first ink and a second ink used in an inkjet printer according to a second embodiment of the present invention, and Figure 7(b) is a graph based on the diagram shown in Figure 7(a). DETAILED DESCRIPTION OF THE INVENTION

[0032] An embodiment of an inkjet printer according to the present invention will be described in detail below with reference to the accompanying drawings.

[0033] (I) Inkjet printer according to a first embodiment of the present invention (I-1) Description of the configuration of an inkjet printer according to a first embodiment of the present invention FIG. 1 is a perspective view illustrating the outline of the configuration of an inkjet printer according to a first embodiment of the present invention.

[0034] FIG. 2 is a diagram illustrating the inkjet printer shown in FIG. 1, focusing on the inkjet head and its surroundings.

[0035] The overall configuration of an inkjet printer 10 according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. The inkjet printer 10 includes a fixed base member 14 that is supported by a base member 12 and extends in the main scanning direction.

[0036] Side members 16L and 16R are disposed on both the left and right ends of the base member 14, and a side unit 18 is disposed on the side of the side member 16R.

[0037] The inkjet printer 10 includes a central wall 20 that connects two side members 16L and 16R, and a guide rail 22 is disposed on the wall surface of the central wall 20 so as to extend in the main scanning direction.

[0038] Reference numeral 24 denotes a timing belt that is disposed parallel to the wall surface of the central wall 20 and is movable in the main scanning direction. A carriage 26 is fixedly disposed on the timing belt 24 and is slidably mounted on the guide rail 22. The carriage 26 is mounted with a first inkjet head 30A and a second inkjet head 30B as multiple inkjet heads, facing recording paper 28 as a medium positioned on the base member 14, and is also mounted with a first damper device 32A connected to the first inkjet head 30A and a second damper device 32B connected to the second inkjet head 30B.

[0039] The damper devices (first damper device 32A and second damper device 32B) described above are a conventionally known technology, and are sub-tanks arranged before the inkjet head in the ink supply path connecting the ink cartridge, which is the ink supply source, and the inkjet head in order to minimize ink pressure fluctuations in the inkjet head, and are generally arranged in the ink supply path of large inkjet printers.

[0040] The first inkjet head 30A is provided with first inkjet nozzles that open to a first inkjet nozzle surface 30Aa (not shown). Similarly, the second inkjet head 30B is provided with second inkjet nozzles that open to a second inkjet nozzle surface 30Ba (not shown).

[0041] In the inkjet printer 10, ink stored in the first ink cartridge 36A (in this specification and the claims, the ink stored in the first ink cartridge 36A will be referred to as the "first ink") is supplied to the first inkjet nozzles of the first inkjet head 30A via the first damper device 32A, and the supplied first ink is ejected from the first inkjet nozzles. Similarly, in the inkjet printer 10, ink stored in the second ink cartridge 36B (in this specification and the claims, the ink stored in the second ink cartridge 36B will be referred to as the "second ink") is supplied to the second inkjet nozzles of the second inkjet head 30B via the second damper device 32B, and the supplied second ink is ejected from the second inkjet nozzles.

[0042] Here, the viscosity of the first ink and the viscosity of the second ink are temperature dependent, as will be described later with reference to Figures 4(a) and (b), and the viscosity changes of the first ink and the second ink in response to temperature changes are different.

[0043] As shown in FIG. 2, the first inkjet head 30A is provided with a first heater 44A as heating means for heating the first ink supplied to the first inkjet head 30A, and similarly, the second inkjet head 30B is provided with a second heater 44B as heating means for heating the second ink supplied to the second inkjet head 30B.

[0044] The overall operation of the inkjet printer 10 is controlled by a microcomputer 34. The functional configuration of the microcomputer 34 related to the implementation of the present invention will be described in detail later with reference to the block diagram shown in FIG.

[0045] As described above, the inkjet printer 10 uses recording paper 28 as the medium. This recording paper 28 is a rolled medium having a predetermined length in the main scanning direction, which is the width direction, and is pulled out by a paper feeder (not shown) and supplied onto the base member 14, where it is transported in a direction perpendicular to the main scanning direction, i.e., in the longitudinal direction of the recording paper 28. The direction perpendicular to the main scanning direction, i.e., the transport direction of the recording paper 28 and the longitudinal direction of the recording paper 28, is referred to as the "sub-scanning direction."

[0046] In this inkjet printer 10, printing is performed on recording paper 28 under the control of a microcomputer 34.

[0047] That is, when the timing belt 24 moves as it is wound up under the control of the microcomputer 34, the carriage 26 moves back and forth in the forward direction (outward path) and the backward direction (return path) in the main scanning direction in accordance with the movement of the timing belt 24. As a result, the first damper device 32A, the second damper device 32B and the first inkjet head 30A and the second inkjet head 30B mounted on the carriage 26 move back and forth integrally in the forward direction (outward path) and the return path (return path) in the main scanning direction over the recording paper 28 supplied onto the base member 14 by the paper feeder, and printing is performed on the recording paper 28.

[0048] In the inkjet printer 10, a waste liquid tank 42 is disposed on the base member 14, and ink paths are formed from the first ink cartridge 36A and the second ink cartridge 36B, which are detachably disposed on the side unit 18, to the waste liquid tank 42 (see Figure 2).

[0049] The inkjet printer 10 is provided with a cap unit 38 including a first cap member 112A that is attached to and seals the first inkjet nozzle surface 30Aa where the openings of the first inkjet nozzles formed in the first inkjet head 30A are located, a second cap member 112B that is attached to and seals the second inkjet nozzle surface 30Ba of the second inkjet head 30B, and a single suction pump 114 connected to the first cap member 112A and the second cap member 112B, during a cleaning process operation to clean the first inkjet nozzle surface 30Aa of the first inkjet head 30A.

[0050] Reference numeral 40 denotes an operation panel equipped with controls 40a that allow an operator to control the operation of the inkjet printer 10. The operation panel 40 is provided with a display device 40b that displays the operating status of the inkjet printer 10.

[0051] Next, we will explain the two ink supply paths (liquid delivery paths) that run from the first ink cartridge 36A and the second ink cartridge 36B, which are ink supply sources detachably arranged in the side unit 18, through the first damper device 32A and the second damper device 32B to the first inkjet head 30A and the second inkjet head 30B.

[0052] These two ink supply paths, the first ink supply path 100A and the second ink supply path 100B, have the same configuration.

[0053] Specifically, the first ink supply path 100A includes a flexible ink supply tube 102, one end 102a of which is connected to communicate with the first ink cartridge 36A and the other end 102b of which is connected to communicate with the first damper device 32A. Similarly, the second ink supply path 100B includes a flexible ink supply tube 102, one end 102a of which is connected to communicate with the second ink cartridge 36B and the other end 102b of which is connected to communicate with the second damper device 32B.

[0054] The first ink cartridge 36A stores a first ink to be supplied to the first inkjet nozzles of the first inkjet head 30A, and is provided with a sensor (not shown) that detects the volume of the first ink stored in the first ink cartridge 36A. Similarly, the second ink cartridge 36B stores a second ink to be supplied to the second inkjet nozzles of the second inkjet head 30B, and is provided with a sensor (not shown) that detects the volume of the second ink stored in the second ink cartridge 36B.

[0055] Between one end 102a and the other end 102b of the ink supply tube 102 in the first ink supply path 100A and the second ink supply path 100B, a liquid supply pump 101 is disposed as a liquid supply means for pressurizing the first ink and the second ink in the first ink supply path 100A and the second ink supply path 100B and sending them to the first damper device 32A and the second damper device 32B, respectively. As this liquid supply pump 101, for example, various conventionally known pressure pumps such as a tube pump or a trochoid pump, which are conventionally known as rotary pumps, or a diaphragm pump, can be used, and therefore detailed description thereof will be omitted.

[0056] Rotary pumps such as tube pumps and trochoid pumps pressurize and pump ink by rotating rollers or gears inside the pump. In tube pumps and trochoid pumps, the unit liquid pumping capacity per unit rotation (unit operating amount) of the rollers or gears is set as a theoretical design value.

[0057] The first damper device 32A and the second damper device 32B are mounted on the carriage 26 together with the first inkjet head 30A and the second inkjet head 30B, and are provided with ink storage chambers that temporarily store the first ink and the second ink that have passed through the ink supply tubes 102. The first damper device 32A and the second damper device 32B absorb pressure fluctuations of the ink in the first ink supply path 100A and the second ink supply path 100B when the carriage 26 moves back and forth relative to the recording paper 28.

[0058] The first damper device 32A and the second damper device 32B are equipped with, for example, a detection lever serving as a negative pressure detection member that detects the negative pressure that fluctuates in accordance with changes in the storage volume of the first ink and the second ink in the ink storage chamber. The first damper device 32A and the second damper device 32B equipped with such a detection lever are well known technologies, as disclosed in, for example, Japanese Patent No. 5951091, and therefore a detailed description thereof will be omitted.

[0059] The inkjet printer 10 is provided with a first pressure sensor 118A and a second pressure sensor 118B as pressure detection means for detecting the pressure of the first ink and the second ink in the first ink supply path (liquid delivery path) 100A and the second ink supply path (liquid delivery path) 100B, respectively, for example, by constantly monitoring the displacement of the detection lever described above and constantly detecting the pressure values ​​of the first ink and the second ink in the ink storage chambers, or by constantly monitoring the pressure values ​​of the first ink and the second ink in the ink storage chambers and constantly detecting the pressure values ​​of the first ink and the second ink in the ink storage chambers.

[0060] The first pressure sensor 118A and the second pressure sensor 118B constantly detect the pressure values ​​of the first ink and the second ink in the ink storage chambers, and constantly output the detection results to the microcomputer .

[0061] As the first pressure sensor 118A and the second pressure sensor 118B, various types of sensors can be used as appropriate, such as an optical sensor that detects the displacement of the detection lever using light to detect the pressure value, a contact sensor that detects the displacement of the detection lever from the contact state of the detection lever to detect the pressure value, or a liquid pressure sensor that directly detects the pressure value of ink.

[0062] The pressure values ​​detected by the first pressure sensor 118A and the second pressure sensor 118B are output to the microcomputer 34, and the microcomputer 34 controls the operation, including starting and stopping, of the liquid delivery pump 101 and the suction pump 114 (described later) according to the pressure values ​​detected by the first pressure sensor 118A and the second pressure sensor 118B.

[0063] The first damper device 32A and the second damper device 32B are connected to a first inkjet head 30A and a second inkjet head 30B, which are equipped with a first inkjet nozzle and a second inkjet nozzle that communicate with the ink storage chambers of the first damper device 32A and the second damper device 32B, respectively. The first ink and the second ink stored in the first ink cartridge 36A and the second ink cartridge 36B are supplied to the first inkjet nozzle and the second inkjet nozzle of the first inkjet head 30A and the second inkjet head 30B, respectively, via the first damper device 32A and the second damper device 32B.

[0064] More specifically, the inkjet nozzles of the first inkjet head 30A are in communication with a first ink supply path 100A that includes a first damper device 32A, and similarly, the second inkjet nozzles of the second inkjet head 30B are in communication with a second ink supply path 100B that includes a second damper device 32B.

[0065] The first ink supplied to the first inkjet head 30A is ejected from the openings of the first inkjet head nozzles arranged in the first inkjet nozzle face 30Aa. Similarly, the second ink supplied to the second inkjet head 30B is ejected from the openings of the second inkjet head nozzles arranged in the second inkjet nozzle face 30Ba.

[0066] In the first damper device 32A and the second damper device 32B, the ink pressure in the ink storage chambers constituting the first ink supply path (liquid feed path) 100A and the second ink supply path (liquid feed path) 100B varies depending on the amount of ink stored in the ink storage chambers, so the amount of ink stored in the ink storage chambers can be determined based on the pressure values ​​detected by the first pressure sensor 118A and the second pressure sensor 118B as pressure detection means. For example, it can be determined whether the amount of ink stored in the ink storage chambers has reached a predetermined lower limit (predetermined amount) or a predetermined upper limit (full).

[0067] With the inkjet printer 10 having the above configuration, the liquid feed pump 101 and the suction pump 114 (described later) can be operated according to the amount of ink stored in the first damper device 32A and the second damper device 32B. This allows a predetermined amount of ink to be maintained in the ink storage chamber even when the inkjet printer 10 is printing on the medium 28, and allows ink to be stably supplied to the first inkjet head 30A and the second inkjet head 30B.

[0068] As described above, the inkjet printer 10 is provided with a cap unit 38 that caps the areas around the first inkjet nozzles formed on the first inkjet nozzle surface 30Aa of the first inkjet head 30A and caps the areas around the second inkjet nozzles formed on the second inkjet nozzle surface 30Ba of the second inkjet head 30B during the cleaning process operation for cleaning the first inkjet nozzle surface 30Aa of the first inkjet head 30A.

[0069] The cap unit 38 is configured to include a first cap member 112A that is attached to and seals the first inkjet nozzle surface 30Aa of the first inkjet head 30A, a second cap member 112B that is attached to and seals the second inkjet nozzle surface 30Ba of the second inkjet head 30B, and a suction pump 114 that can reduce the pressure inside the first cap member 112A and the second cap member 112B to suck ink from the first ink supply path 100A including the first inkjet head 30A and the second ink supply path 100B including the second inkjet head 30B. During a cleaning process operation to clean the first inkjet nozzle surface 30Aa of the first inkjet head 30A and the second inkjet nozzle surface 30Ba of the second inkjet head 30B, the suction pump 114 supplies negative pressure to the cap member 112A that seals the openings of the first inkjet nozzles formed in the first inkjet nozzle surface 30Aa of the first inkjet head 30A and the cap member 112B that seals the openings of the second inkjet nozzles formed in the second inkjet nozzle surface 30Ba of the second inkjet head 30B, thereby sucking ink from the first ink supply path 100A and the second ink supply path 100B.

[0070] Reference numeral 116A denotes a first cap tube, one end 116Aa of which is connected to the first cap member 112A, and the other end 116Ab of which is connected to the suction pump 114. Similarly, reference numeral 116B denotes a second cap tube, one end 116Ba of which is connected to the second cap member 112B, and the other end 116Bb of which is connected to the suction pump 114.

[0071] In the inkjet printer 10, the first cap member 112A, the second cap member 112B, the first cap tube 116A, the second cap tube 116B, and the suction pump 114 form an ink suction path 140 that forms an ink path downstream of the cap members.

[0072] Reference numeral 117 denotes a waste liquid tube, one end 117a of which is connected to the suction pump 114, and the other end 117b of which is connected to the waste liquid tank 42. In the inkjet printer 10, the suction pump 114 and the waste liquid tube 117 form a waste liquid path 150 that forms an ink path downstream of the cap member.

[0073] Here, the suction pump 114 may be a rotary pump such as a tube pump or a trochoid pump, or a vacuum pump, which are well known in the art.

[0074] Here, rotary pumps such as tube pumps and trochoid pumps are pumps that can be selectively controlled between a state in which suction force is generated by moving rollers or rotating gears inside the pump, a state in which the movement of the rollers inside the pump is stopped or the rotation of the gears is stopped at a predetermined position, releasing the suction force and opening it to the outside air (release state), and a state in which the movement of the rollers inside the pump is stopped or the rotation of the gears is stopped at a predetermined position, releasing the suction force and closing it off to the outside air.

[0075] Specifically, as the suction pump 114, a tube pump having a configuration similar to that of the tube pump disclosed in Japanese Patent No. 4857798 or the like can be used.

[0076] By operating the suction pump 114, the first ink and the second ink are sucked from the first inkjet head 30A and the second inkjet head 30B toward the waste liquid tank 42. The suction pump 114 can change the suction speed of the first ink and the second ink and the speed at which the waste liquid is sent.

[0077] The inkjet printer 10 moves the first cap member 112A using a stepping motor (not shown) so that the positional relationship between the first cap member 112A and the first inkjet head 30A can be freely changed relatively from a preset reference position (a position where suction processing and dry suction processing are not performed, which is the origin position when measuring the positional relationship between the first cap member 112A and the first inkjet head 30A, and where the first cap member 112A and the first inkjet nozzle surface 30Aa of the first inkjet head 30A are separated from each other) to a suction position when performing suction processing and to a dry suction position when performing dry suction processing. Similarly, the second cap member 112B is moved by a stepping motor (not shown) so that the positional relationship between the second cap member 112B and the second inkjet head 30B can be freely changed relatively from a preset reference position (a position where suction processing and dry suction processing are not performed, which is the origin position when measuring the positional relationship between the second cap member 112B and the second inkjet head 30B, and where the second cap member 112B and the second inkjet nozzle surface 30Ba of the second inkjet head 30B are separated from each other) to a suction position when performing suction processing and a dry suction position when performing dry suction processing.

[0078] In order to freely change the positional relationship between the first cap member 112A and the first inkjet head 30A and the positional relationship between the second cap member 112B and the second inkjet head 30B relative to each other, the mechanism for moving the first cap member 112A and the second cap member 112B by operating a stepping motor can use conventionally known technology disclosed in, for example, Japanese Patent No. 6437687, and therefore detailed description thereof will be omitted.

[0079] The microcomputer 34 controls the positions of the first cap member 112A and the second cap member 112B by rotating the stepping motor.

[0080] (I-2) Explanation of the functional configuration of the microcomputer in the inkjet printer according to the first embodiment of the present invention, related to the implementation of the present invention FIG. 3 is a block diagram illustrating the functional configuration of the microcomputer in the inkjet printer shown in FIG. 1 that is related to the implementation of the present invention.

[0081] Figure 4(a) shows a diagram illustrating the relationship between temperature and viscosity of an example of the first ink and the second ink used in the inkjet printer shown in Figure 1. Figure 4(b) shows a graph based on the diagram shown in Figure 4(a).

[0082] The microcomputer 34 is constructed to have a memory section 34a, a temperature determination section 34b, and a heater control section 34c as functional components related to the implementation of the present invention.

[0083] The storage unit 34a stores information about viscosity changes associated with temperature changes for each of the first ink and the second ink. Since various inks can be used as the first ink and the second ink, the storage unit 34a stores information about viscosity changes associated with temperature changes for each of the various inks. Specifically, the storage unit 34a stores, for example, information about the chart shown in FIG. 4(a) and information about the graph shown in FIG. 4(b).

[0084] When the cleaning process is initiated under the control of the microcomputer 34, the temperature determination unit 34b refers to the memory unit 34a and, before starting suction with the suction pump 114, determines the temperatures of the first ink and the second ink at which the viscosities of the first ink and the second ink are substantially the same, based on information regarding viscosity changes due to temperature changes of the first ink stored in the currently used first ink cartridge 36A and information regarding viscosity changes due to temperature changes of the second ink stored in the currently used second ink cartridge 36B. Here, "substantially the same" viscosities of the first ink and the second ink include cases where the viscosities are completely the same, i.e., completely identical, as well as cases where the viscosities are identical within a predetermined small tolerance (for example, a range of ±0.2 mPa.s).

[0085] Specifically, for example, if the information regarding the viscosity change of the first ink and the second ink due to temperature change is as shown in Figure 4(a) or 4(b), when the temperature of the first ink is 35°C and the temperature of the second ink is 45°C, the viscosity of the first ink and the viscosity of the second ink are 5.4 mPa.s, which are the same, and it is determined that the temperature of the first ink is 35°C and the temperature of the second ink is 45°C.

[0086] The heater control unit 34c controls the operation of the first heater 44A so that the temperature of the first ink becomes the temperature determined by the temperature determination unit 34b, and controls the operation of the second heater 44B so that the temperature of the second ink becomes the temperature determined by the temperature determination unit 34b.

[0087] (I-3) Explanation of the cleaning process in the inkjet printer according to the first embodiment of the present invention In the inkjet printer 10 having the above-described configuration, similar to conventional inkjet printers, the first ink and the second ink are supplied from the first ink cartridge 36A and the second ink cartridge 36B to their respective ink supply tubes 102 under the control of the microcomputer 34, and the first ink and the second ink are ejected onto the recording paper 28 from the first inkjet nozzles of the first inkjet head 30A and the second inkjet nozzles of the second inkjet head 30B, thereby performing a printing process onto the recording paper 28.

[0088] Furthermore, in the inkjet printer 10, as in conventional inkjet printers, the microcomputer 34 controls the suction pump 114 during the cleaning process to perform a suction process (including both the "suction process" and "empty suction process" described in detail above) to suck up the first ink and the second ink.

[0089] In the suction process of the inkjet printer 10, the following process is carried out before the suction pump 114 is operated to actually suck the first ink and the second ink.

[0090] That is, when the cleaning process is initiated under the control of the microcomputer 34, before suction by the suction pump 114 begins, the temperature determination unit 34b refers to the memory unit 34a and determines the temperature of the first ink and the temperature of the second ink at which the viscosity of the first ink and the viscosity of the second ink match, based on information regarding the viscosity change due to temperature change of the first ink currently in use and information regarding the viscosity change due to temperature change of the second ink currently in use.

[0091] That is, assuming that the information stored in memory unit 34a regarding the viscosity changes of the first ink and the second ink due to temperature changes is as shown in Figure 4(a) or 4(b), when the temperature of the first ink is 35°C and the temperature of the second ink is 45°C, the temperature determination unit 34b determines that the viscosity of the first ink and the viscosity of the second ink are approximately the same (match) at 5.4 mPa.s, and that the temperature of the first ink is 35°C and the temperature of the second ink is 45°C.

[0092] Next, the heater control unit 34c controls the operation of the first heater 44A so that the temperature of the first ink becomes the temperature determined by the temperature determination unit 34b, and controls the operation of the second heater 44B so that the temperature of the second ink becomes the temperature determined by the temperature determination unit 34b, thereby heating the first ink and the second ink to temperatures at which the viscosities of the first ink and the second ink become substantially the same (match). That is, according to the example of Figure 4(a) or 4(b), the heater control unit 34c controls the temperature of the first ink to 35°C, and controls the temperature of the second ink to 45°C.

[0093] Then, the heater control unit 34c heats the first ink and the second ink to temperatures at which the viscosities of the first ink and the second ink become substantially the same (match), and then starts suction using the suction pump 114. That is, according to the example shown in Figure 4(a) or 4(b), the temperature of the first ink reaches 35°C, the temperature of the second ink reaches 45°C, and the viscosities of the first ink and the second ink become substantially the same (match) at 5.4 mPa.s, after which suction using the suction pump 114 starts.

[0094] Therefore, in the suction process of the inkjet printer 10, the first heater 44A and the second heater 44B adjust the temperatures of the first ink and the second ink so that the viscosities of the first ink and the second ink are approximately the same, and then the suction pump 114 sucks the first ink and the second ink, so that the first ink and the second ink can be sucked equally from the first inkjet head 30A and the second inkjet head 30B.

[0095] Therefore, the first ink and the second ink are not wasted, and since no negative pressure difference occurs, color mixing due to backflow can be suppressed.

[0096] That is, according to the conventional technology, a single suction pump is used to suck up each inkjet head filled with ink of different viscosities during the suction process, but this results in differences in the amount of ink sucked up for each ink, resulting in wasted ink when trying to suck up the same amount, and also in the problem of backflow occurring due to negative pressure differences, resulting in color mixing. However, with the inkjet printer 10 according to the present invention, it is possible to prevent such problems from occurring.

[0097] (II) Inkjet printer according to a second embodiment of the present invention (II-1) Description of the configuration of an inkjet printer according to a second embodiment of the present invention FIG. 5 is a diagram illustrating the configuration of an inkjet printer according to a second embodiment of the present invention, focusing on the configuration around the inkjet head.

[0098] The inkjet printer according to the second embodiment and the inkjet printer 10 according to the first embodiment described above have similar configurations except for the configuration around the inkjet head and the functional configuration of the microcomputer 34. Therefore, in the following description of the inkjet printer according to the second embodiment, the configuration around the inkjet head and the functional configuration of the microcomputer 34 will be described, and a description of the other configurations and operations will be omitted.

[0099] First, the configuration around the inkjet head in the inkjet printer according to the second embodiment of the present invention will be described. The inkjet printer according to the second embodiment of the present invention includes a single inkjet head 300 as the inkjet head.

[0100] The inkjet head 300 is supplied with a plurality of inks, including a first ink from a first ink cartridge 360A and a second ink from a second ink cartridge 360B. The first ink is supplied to some of the inkjet nozzles (not shown) provided in the inkjet head 300, while the second ink is supplied to the inkjet nozzles of the inkjet head 300 that are not supplied with the first ink.

[0101] The inkjet head 300 is also provided with a heater 440 as a heating means for heating the first ink and the second ink.

[0102] The first ink and the second ink supplied to the inkjet head 300 are inks whose viscosities are approximately the same at a certain temperature. Such inks may be selected from existing inks, or may be newly designed inks whose viscosities are approximately the same at a certain temperature. Here, "approximately the same" ink viscosity includes not only completely identical inks, i.e., completely matching inks, but also inks that match within a predetermined small tolerance (for example, a range of ±0.2 mPa.s).

[0103] Reference numeral 112 denotes a cap member that is attached to and seals the inkjet nozzle surface 300a where the openings of the inkjet nozzles formed in the inkjet head 300 are located. Reference numeral 116 denotes cap tubes corresponding to the first cap tube 116A and the second cap tube 116B, with one end 116a connected to the cap member 112 and the other end 116b connected to the suction pump 114. Reference numeral 118 denotes pressure sensors corresponding to the first pressure sensor 118A and the second pressure sensor 118B.

[0104] (II-2) Explanation of the functional configuration of the microcomputer in the inkjet printer according to the second embodiment of the present invention FIG. 6 is a block diagram illustrating the functional configuration of a microcomputer in an inkjet printer according to a second embodiment of the present invention, which is related to the implementation of the present invention.

[0105] Figure 7(a) shows a diagram illustrating the relationship between temperature and viscosity of an example first ink and a second ink used in an inkjet printer according to a second embodiment of the present invention, and Figure 7(b) shows a graph based on the diagram shown in Figure 7(a).

[0106] The microcomputer 34 is constructed to have a memory section 340a and a heater control section 340b as functional components related to the implementation of the present invention.

[0107] The storage unit 340a stores the temperature at which the viscosity of the first ink and the viscosity of the second ink become substantially the same. The temperature stored in the storage unit 340a may be stored as a default value if the first ink and the second ink are both existing inks, or, if newly designed inks are used as the first ink or the second ink, the operator may use the operation unit 40a to input and store the temperature at which the viscosities become substantially the same.

[0108] Here, when the viscosity of the first ink and the viscosity of the second ink are "substantially the same," this includes not only being completely identical, i.e., being completely identical, but also being identical within a predetermined small tolerance range (for example, a range of ±0.2 mPa.s).

[0109] Specifically, for the first ink and the second ink, for example, if the information regarding the viscosity change of the first ink and the second ink due to temperature change is as shown in Figure 7(a) or Figure 7(b), 40°C, which is the temperature at which the difference (viscosity difference) between the viscosity of the first ink and the viscosity of the second ink becomes "0", is stored in memory unit 340a.

[0110] The heater control unit 340b controls the operation of the heater 440 so that the temperatures of the first ink and the second ink become the temperatures stored in the storage unit 340a.

[0111] (II-3) Explanation of the cleaning process in the inkjet printer according to the second embodiment of the present invention In the inkjet printer according to the second embodiment of the present invention, in the above-described configuration, as in conventional inkjet printers, the microcomputer 340 controls the suction pump 114 during the cleaning process to perform a suction process (including both the "suction process" and "empty suction process" described in detail above) to suck up the first ink and the second ink.

[0112] In the suction process of the inkjet printer according to the second embodiment of the present invention, the following process is carried out before the suction pump 114 is operated to actually suck the first ink and the second ink.

[0113] That is, when the cleaning process is initiated under the control of the microcomputer 340, before suction by the suction pump 114 begins, the heater control unit 340b controls the operation of the heater 440 based on the temperatures stored in the memory unit 340a so that the temperatures of the first ink and the second ink become the temperatures stored in the memory unit 340a.

[0114] For example, if the information regarding the viscosity change of the first ink and the second ink due to temperature change is as shown in Figure 7(a) or 7(b), "40°C" is stored in the memory unit, so the heater control unit 340b heats the first ink and the second ink by controlling the operation of the heater 440 so that the temperature of the first ink and the second ink becomes 40°C.

[0115] Then, the heater control unit 340c heats the first ink and the second ink to a temperature at which the viscosities of the first ink and the second ink become approximately the same (match) (for example, 40°C in the example shown in Figure 7(a) or Figure 7(b) above), and then suction by the suction pump 114 begins.

[0116] Therefore, in the inkjet printer according to the second embodiment of the present invention, in the suction process, the viscosities of the first ink and the second ink are adjusted to be approximately the same by heating with the heater 440, and then the first ink and the second ink are suctioned by the suction pump 114, so that the first ink and the second ink can be suctioned equally from the inkjet head 300.

[0117] Therefore, the first ink and the second ink are not wasted, and since no negative pressure difference occurs, color mixing due to backflow can be suppressed.

[0118] That is, with conventional technology, when inks of different viscosities are used in the same inkjet head, there is a problem that the amount of ink sucked out during the suction process differs, resulting in wasted ink being consumed in order to suck out the same amount, and there is also a problem that backflow occurs due to a negative pressure difference, resulting in color mixing.However, with the inkjet printer according to the second embodiment of the present invention, it is possible to suppress the occurrence of such problems.

[0119] (III) Explanation of the effects of the inkjet printer according to the first and second embodiments of the present invention As explained above, in the inkjet printer 10 according to the first embodiment of the present invention and the inkjet printer according to the second embodiment, the difference in viscosity between the multiple inks is reduced during the suction process, which reduces the difference in suction volume between the multiple inks and prevents unnecessary ink consumption, and also reduces the negative pressure difference between the ink suction paths caused by the suction of the multiple inks and prevents color mixing.

[0120] (IV) Description of other embodiments and modifications The above-described embodiment is merely an example, and the present invention can be embodied in various other forms. That is, the present invention is not limited to the above-described embodiment, and various omissions, substitutions, modifications, etc. can be made within the scope of the gist of the present invention.

[0121] For example, the above-described embodiment may be modified as shown in the following (IV-1) to (IV-4).

[0122] (IV-1) In the above-described embodiment, the plurality of inks is shown as two inks, a first ink and a second ink, but it goes without saying that the number of inks is not limited to two. That is, the plurality of inks used in an inkjet printer may be three or more inks. When three or more inks are used, the viscosities of all of the inks may be controlled to be uniform, or the necessary number of inks may be selected from the three or more inks and uniformed in viscosity.

[0123] (IV-2) In the above-described embodiments, a first embodiment in which the inkjet printer supplies a single ink to each of a plurality of inkjet heads and a second embodiment in which the inkjet printer supplies a plurality of inks to a single inkjet head are shown, but it goes without saying that the first embodiment and the second embodiment may coexist in the same inkjet printer.

[0124] (IV-3) In the above-described embodiment, the relationship between ink temperature and viscosity is shown in FIGS. 4(a)(b) and 7(a)(b) as specific examples, but it goes without saying that these are merely examples and are not limiting.

[0125] (IV-4) It goes without saying that the above-described embodiment and the various other embodiments and modifications shown in (IV-1) to (IV-3) above may be combined as appropriate. [Industrial Applicability]

[0126] The present invention can be used in inkjet printers, which are so-called two-dimensional printers that eject printing ink toward a medium to print a two-dimensional image on the medium, and inkjet printers, which are so-called three-dimensional printers (three-dimensional modeling devices), that eject binders, water, etc. onto powder material, etc., to harden the powder material and create a three-dimensional object. [Explanation of symbols]

[0127] 10. Inkjet printer 12 Base member 14 Base member 16L Side member 16R Side member 18 Side Unit 20 Central wall 22 Guide rail 24 Timing belt 26 Carriage 28 Recording Paper 30A 1st inkjet head 30Aa First inkjet nozzle surface 30B 2nd inkjet head 30Ba 2nd inkjet nozzle surface 32A First damper device 32B Second Imper Device 34 Microcomputer 34a Storage unit (storage means) 34b Temperature judgment section (temperature judgment means) 34c heater control unit (heating control means) 36A 1st ink cartridge 36B 2nd ink cartridge 38 Cap Unit 40 Operation Panel 40a Operator 40b Display device 42 Waste liquid tank 44A First heater (heating means) 44B Second heater (heating means) 100A First ink supply path 100B Second ink supply path 101 Liquid transfer pump 102 Ink supply tube 102a End 102b End 112 Cap member 112A first cap member 112B second cap member 114 Suction pump (suction means) 116 Cap Tube 116a End 116b End 116A First Cap Tube 116Aa End 116Ab End 116B Second Cap Tube 116Ba end 116Bb end 117 Waste tube 117a End 117b End 118 Pressure Sensor 118A First Pressure Sensor 118B Second pressure sensor 140 Ink suction path 150 Wastewater route 300 Inkjet Head 300a Inkjet nozzle surface 340a Storage unit (storage means) 340b Heater control unit (heating control means) 360A 1st ink cartridge 360B 2nd ink cartridge 440 Heater (heating means)

Claims

1. In an inkjet printer that ejects ink supplied to an ink supply path using inkjet technology, a first inkjet head having inkjet nozzles that open on an inkjet nozzle surface and that eject a first ink supplied to a first ink supply path, and a second inkjet head having inkjet nozzles that eject a second ink supplied to a second ink supply path; a first cap member attached to cover an inkjet nozzle surface of the first inkjet head and a second cap member attached to cover an inkjet nozzle surface of the second inkjet head; a first heating unit provided in the first inkjet head and configured to heat the first ink supplied to the first inkjet head, and a second heating unit provided in the second inkjet head and configured to heat the second ink supplied to the second inkjet head; a suction unit connected to the first cap member and the second cap member, and configured to suck the first ink supplied to the first inkjet head from the first ink supply path and the second ink supplied to the second inkjet head from the second ink supply path; a storage means for storing information regarding viscosity changes associated with temperature changes for the first ink and the second ink; a temperature determination unit that determines a temperature at which the viscosity of the first ink in the first inkjet head and the viscosity of the second ink in the second inkjet head become substantially the same, based on the information stored in the storage unit; and a heating control means for controlling at least one of the first heating means and the second heating means to a temperature at which a viscosity of the first ink in the first ink-jet head and a viscosity of the second ink in the second ink-jet head become substantially the same before the suction means starts suctioning the first ink supplied from the first ink supply path to the first ink-jet head and the second ink supplied from the second ink supply path to the second ink-jet head in a suction process; An inkjet printer comprising:

2. In an inkjet printer that ejects ink supplied to an ink supply path using inkjet technology, an inkjet head including first inkjet nozzles opening on an inkjet nozzle surface and configured to eject a first ink supplied from a first ink supply path and a second inkjet nozzles opening on an inkjet nozzle surface and eject a second ink supplied from a second ink supply path; a cap member attached to cover the inkjet nozzle surface of the inkjet head; a suction unit connected to the cap member, which sucks the first ink and the second ink supplied to the inkjet head from the first ink supply path and the second ink supply path; a heating unit provided in the inkjet head and configured to heat the first ink and the second ink supplied to the inkjet head; a storage means for storing a temperature at which the viscosity of the first ink and the viscosity of the second ink become substantially the same; a heating control means for controlling the heating means before the suction means starts suctioning the first ink and the second ink supplied to the inkjet head from the first ink supply path and the second ink supply path in a suction process, so that the temperatures of the first ink and the second ink become the temperatures stored in the storage means; An inkjet printer comprising:

3. 3. The inkjet printer according to claim 1, The case where the viscosities are substantially the same includes a case where the viscosities are completely the same and a case where the viscosities are the same with a predetermined small tolerance. An inkjet printer characterized by:

4. 4. The inkjet printer according to claim 3, The predetermined small range tolerance is within the range of ±0.2 mPa.s. An inkjet printer characterized by:

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