Image forming apparatus, lifespan determination method, and lifespan determination program

Abstract

To provide an image formation apparatus, service life determination method and service life determination program which can accurately determine the service life of an ink jet head.SOLUTION: An image formation apparatus comprises: an ink jet head which has a storage part that stores phase transition ink and forms an image on a recording medium by discharging the phase transition ink; a drive condition change unit which changes a drive condition of the ink jet head in a case of discharging the phase transition ink on the basis of the first reading result of a pattern image formed by the ink jet head; a state change estimation unit which estimates the occurrence of a state change of the phase transition ink in the storage part when the changed drive condition satisfies a prescribed condition; and a determination unit which determines whether or not the ink jet head reaches the end of the service life on the basis of whether or not the occurrence of the state change is estimated.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a lifespan determination method, and a lifespan determination program. [Background technology]

[0002] Inkjet image forming apparatuses (hereinafter referred to as inkjet image forming apparatuses) are known that eject ink onto a recording medium such as paper to form an image on the recording medium. In inkjet image forming apparatuses, the quality of the images formed by the inkjet heads (hereinafter simply referred to as heads) that eject the ink deteriorates over time. For example, the heads have piezoelectric elements for ejecting ink, and deterioration of the piezoelectric elements over time reduces the amount of ink ejected, resulting in a decrease in the quality (density) of the images formed.

[0003] Therefore, in order to maintain the quality of the images formed, conventional inkjet image forming devices adjust the head driving conditions (e.g., the driving voltage applied to the piezoelectric element) so that an appropriate amount of ink is ejected.

[0004] In conventional inkjet image forming devices, if the head driving conditions are adjusted but the ink is not ejected at an appropriate amount, the head is determined to have reached the end of its life and is replaced with a new head. For example, Patent Document 1 discloses an inkjet image forming device that predicts and determines the life of the head by determining changes in the head driving conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-69311 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the ink ejected from the head includes gel ink (phase-transition ink) containing a gel component that undergoes a reversible sol-gel phase transition in response to temperature changes. In inkjet image forming devices that use gel ink, the gel component concentration of the gel ink stored in the head reservoir can become high depending on the usage conditions, etc. When gel ink in this state is ejected from the head, gel ink with a high gel component concentration does not expand to the specified dot diameter due to increased pinning. Therefore, it is necessary to adjust the head driving conditions to maintain the quality of the formed image.

[0007] Even when the head operating conditions are adjusted due to a change in the concentration of the gel component in the gel ink rather than due to deterioration of the head over time, conventional inkjet image forming devices such as those shown in Patent Document 1 predict and determine the life of the head based on the change in the head operating conditions. As a result, there is a risk that the head may be judged to have reached the end of its life due to a change in the head operating conditions caused by a change in the concentration of the gel component in the gel ink, even though the head is not actually at the end of its life. If this determination is made, the head may be unnecessarily replaced with a new one even though the head is not actually at the end of its life, resulting in increased costs.

[0008] An object of the present invention is to provide an image forming apparatus, a lifespan determination method, and a lifespan determination program that are capable of accurately determining the lifespan of an inkjet head. [Means for solving the problem]

[0009] The image forming apparatus according to the present invention comprises: an inkjet head having a reservoir for storing a phase change ink and ejecting the phase change ink to form an image on a recording medium; a drive condition changing unit that changes a drive condition of the inkjet head when ejecting the phase change ink based on a first reading result of a pattern image formed by the inkjet head; a state change estimation unit that estimates the occurrence of a state change of the phase change ink in the reservoir when the changed driving condition satisfies a predetermined condition; a determination unit that determines whether the inkjet head has reached the end of its life depending on whether the occurrence of the state change is estimated; Equipped with.

[0010] The lifespan determination method according to the present invention comprises the steps of: forming a pattern image on a recording medium by ejecting the phase change ink from an inkjet head having a reservoir for storing the phase change ink; changing a driving condition of the inkjet head when ejecting the phase change ink based on a first reading result of the formed pattern image; If the modified driving conditions satisfy a predetermined condition, an occurrence of a change in state of the phase change ink in the reservoir is estimated; Whether the inkjet head has reached the end of its life is determined depending on whether the occurrence of the state change is estimated.

[0011] The lifespan determination program according to the present invention comprises: On the computer, forming a pattern image on a recording medium by ejecting the phase change ink from an ink jet head having a reservoir for storing the phase change ink; changing a driving condition of the inkjet head when ejecting the phase change ink based on a first reading result of the formed pattern image; if the modified driving conditions satisfy a predetermined condition, estimating the occurrence of a change in state of the phase change ink in the reservoir; a process of determining whether the inkjet head has reached the end of its life depending on whether the occurrence of the state change is estimated; Execute the following. [Effects of the Invention]

[0012] According to the present invention, the life of an inkjet head can be determined with high accuracy. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 2 is a block diagram showing a main part of a control system of the image forming apparatus shown in FIG. 1. FIG. [Figure 3] 10A and 10B are diagrams illustrating changes in ink droplets ejected from an inkjet head when the number of ejections (degree of deterioration) of the inkjet head is different. [Figure 4] 10 is a graph showing the relationship between the number of ink ejections and the optimum voltage applied to a piezoelectric element of an inkjet head. [Figure 5] 10A and 10B are diagrams illustrating changes in ink droplets ejected from an inkjet head when the concentration of gel components contained in the ink is different. [Figure 6] 10 is a graph showing the relationship between the number of ink ejections and the optimum voltage applied to a piezoelectric element of an inkjet head for ink containing an appropriate concentration of gel component and ink containing a high concentration of gel component. [Figure 7] 2 is a flowchart illustrating a lifespan determination method performed in the image forming apparatus shown in FIG. [Figure 8] 8 is a flowchart illustrating a modified example of the lifespan determination method shown in FIG. 7. [Figure 9] 1A and 1B are diagrams illustrating ink droplets ejected from an inkjet head onto a recording medium at room temperature and at a temperature equal to or higher than the phase transition temperature for ink containing an appropriate concentration of gel component and ink containing a high concentration of gel component. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0015] [Image forming equipment] 1 is a diagram showing a schematic configuration of an inkjet printer 100 (image forming apparatus according to the present invention) according to this embodiment. FIG. 2 is a block diagram showing the main parts of a control system of the inkjet printer 100.

[0016] As shown in Figures 1 and 2, the inkjet printer 100 includes a conveying unit 10, a supply unit 20, a discharge unit 30, an ink supply unit 40, an image forming unit 50, a reading unit 60, an operation display unit 70, an input / output interface 80, a control unit 90, and the like.

[0017] The conveying unit 10 has a plurality of members related to conveyance, such as a conveying belt 11, a driving roller 12, and a driven roller 13. The conveying unit 10 conveys the recording medium M by the conveying operation of the plurality of members, such as the conveying belt 11. Specifically, in the conveying unit 10, the conveying belt 11 is stretched over the driving roller 12 and the driven roller 13, and is driven by driving the driving roller 12 to rotate. As a result, the recording medium M supplied from the supplying unit 20 is conveyed to the image forming unit 50 while placed on the conveying surface 11a of the conveying belt 11, and after an image is formed (printed) in the image forming unit 50, the recording medium M is conveyed to the discharging unit 30.

[0018] The recording medium M can be any of various media capable of fixing ink ejected from the inkjet head 55 described below, such as sheet-like paper, cloth (woven fabric), resin, etc. Note that the recording medium M is not limited to sheet-like media, and may also be roll-like media such as paper, cloth, resin, etc.

[0019] Also, here, as an example, a conveying unit 10 that conveys the recording medium M using a conveying belt 11 is shown, but the conveying unit 10 is not limited to a conveying belt 11 and may be configured to convey the recording medium M using a drum or roller.

[0020] The supply unit 20 has a supply stacking unit 21 that stacks and stores a plurality of recording media M, a supply conveying unit 22 that conveys and supplies the recording media M from the supply stacking unit 21 to the conveying unit 10, etc. The supply stacking unit 21 is configured to be able to rise and fall, and when the topmost recording medium M is conveyed to the conveying unit 10 by the supply conveying unit 22, the supply stacking unit 21 rises so that the recording medium M that has become the topmost after the conveying can be conveyed to the supply conveying unit 22.

[0021] The discharge section 30 has a discharge stacking section 31 that stores a stack of multiple recording media M, and a discharge conveying section 32 that conveys the recording media M discharged from the conveying section 10 to the discharge stacking section 31. The discharge stacking section 31 is configured to be able to rise and fall, and when the recording media M is conveyed from the discharge conveying section 32 to the discharge stacking section 31, the discharge stacking section 31 descends.

[0022] The supply conveying section 22 and the discharge conveying section 32 have, for example, a plurality of rollers, and convey the recording medium M by rotating the rollers. The supply conveying section 22 and the discharge conveying section 32 are not limited to rollers, and may be configured with a belt, or may be configured with a combination of rollers and belts.

[0023] When a roll-shaped medium is used as the recording medium M, an unwinding roller on which the roll-shaped medium is stored in a wound state and a winding roller that winds up the roll-shaped medium are used instead of the supply stacking unit 21 and the discharge stacking unit 31. The roll-shaped medium is transported to the transport unit 10 by rotating the unwinding roller, and is wound up onto the winding roller by rotating the winding roller.

[0024] A post-processing device may be provided between the conveying unit 10 and the discharging unit 30 to perform post-processing on the recording medium M on which an image has been formed by the image forming unit 50. One example of the post-processing device is a fixing device that fixes ink to the recording medium M. When, for example, ultraviolet-curable ink is used as the ink, a fixing device is used that irradiates ultraviolet light onto the recording medium M to fix the ink to the recording medium M. When, for example, water-based ink or solvent ink is used as the ink, a fixing device is used that fixes the ink to the recording medium M by a method such as drying. Furthermore, a device other than a fixing device, such as a cutting device that cuts the recording medium M to a desired length, may also be used as the post-processing device.

[0025] The ink supply unit 40 is a device that supplies ink to a sub-tank 52 of the image forming unit 50, which will be described later, and includes a main tank 41 and components (e.g., a pump, a valve, etc.) related to ink supply, which are not shown. The main tank 41 stores ink to be supplied to the sub-tank 52 at room temperature. The ink supply unit 40 uses a pump or the like (not shown) to supply ink from the main tank 41 to the sub-tank 52 via the flow path 42.

[0026] In this embodiment, the ink used is a gel ink (phase transition ink) containing wax, a gel component that undergoes a reversible sol-gel phase transition in response to a temperature change. For example, an energy beam curable gel ink (e.g., ultraviolet-curable gel ink) that is in a gel state at room temperature, in a sol state when heated to a temperature equal to or higher than the phase transition temperature, and that is cured by irradiation with energy beams can be used.

[0027] The image forming unit 50 includes a carriage 51, a sub-tank 52, flow paths 53a and 53b, a head driving unit 54, an inkjet head (hereinafter simply referred to as a head) 55, and the like (see FIGS. 1 and 2).

[0028] 1, for the sake of simplicity, the ink supply units 40 and image forming units 50 for one color are shown, but the ink supply units 40 and image forming units 50 are arranged according to the number of colors to be used. For example, when four colors, yellow (Y), magenta (M), cyan (C), and black (K), are used, ink supply units 40 and image forming units 50 for four colors are arranged, and the image forming units 50 are arranged so as to be lined up at predetermined intervals along the transport direction T.

[0029] Carriage 51 is a housing that holds subtank 52, flow paths 53a and 53b, head drive unit 54, head 55, and other devices and components required for image formation. Although not shown, carriage 51 also has an ink heating unit that heats the gel ink in carriage 51 to a temperature equal to or higher than the phase transition temperature of the gel component of the gel ink and maintains that temperature.

[0030] Subtank 52 (storage section in the present invention) stores gel ink supplied from main tank 41 within carriage 51. The gel ink in subtank 52 is supplied to manifold 56 of head 55 (described later) via flow path 53a using a pump or the like (not shown) within carriage 51. The gel ink supplied to manifold 56 is returned to subtank 52 via flow path 53b. In other words, flow paths 53a and 53b form a circulation flow path that circulates gel ink between subtank 52 and manifold 56.

[0031] Based on the control of a control unit 90 (described later), the head driving unit 54 outputs a driving voltage corresponding to the image data of the image to be formed to a piezoelectric element 58 of a head 55 (described later). The driving voltage from the head driving unit 54 drives the piezoelectric element 58, causing it to eject an amount of gel ink corresponding to the image data from a nozzle 59 of the head 55 (described later).

[0032] The head 55 has a manifold 56, pressure chambers 57, piezoelectric elements 58, nozzles 59, etc. The head 55 has a plurality of nozzles 59, and the pressure chambers 57 and piezoelectric elements 58 are provided in accordance with the number of nozzles 59.

[0033] Manifold 56 communicates with a plurality of pressure chambers 57, and gel ink supplied to manifold 56 is supplied to pressure chambers 57. Pressure chamber 57 is a space in which gel ink to be ejected is stored, and a piezoelectric element 58 is provided on the wall surface of pressure chamber 57. One end of nozzle 59 communicates with pressure chamber 57, and the other end is an open end.

[0034] A drive voltage is applied to the piezoelectric element 58 from the head drive unit 54. When the drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 deforms in accordance with the applied drive voltage, which deforms the pressure chamber 57. The deformation of the pressure chamber 57 causes a pressure change in the gel ink in the pressure chamber 57 that is supplied to the nozzle 59.

[0035] Therefore, when a drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 and the pressure chamber 57 are deformed, causing a pressure change in the gel ink inside the pressure chamber 57, and as a result, the gel ink inside the pressure chamber 57 is ejected from the nozzle 59. In this way, by ejecting the gel ink from the nozzle 59, an image can be formed on the recording medium M being transported.

[0036] In the carriage 51, the heads 55 may be configured to be a single-pass (one-pass) type that forms an image in one scan, or a scan (multi-pass) type that forms an image in multiple scans. In the single-pass type, the carriage 51 is provided with heads 55 in the width direction of the recording medium M (the direction perpendicular to the conveying direction T of the recording medium M), the number of which corresponds to the image formation width.

[0037] The reading unit 60 is disposed downstream of the image forming unit 50 in the conveying direction T of the recording medium M, and reads an image (for example, a predetermined pattern image) formed on the recording medium M conveyed by the conveyor belt 11. The reading unit 60 outputs the reading result of the predetermined pattern image to the control unit 90. The control unit 90 changes the image forming conditions, for example, the image forming position and the driving conditions of the head 55, based on the reading result.

[0038] Although not shown, the inkjet printer 100 also includes a maintenance unit that performs maintenance such as cleaning of the head 55.

[0039] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal display with a touch panel or an organic EL (Electro Luminescence) display. The operation display unit 70 displays an operation menu for the user, information related to image data, various states of the inkjet printer 100, etc. The operation display unit 70 also has a plurality of keys and accepts various input operations from the user.

[0040] The input / output interface 80 mediates the transmission and reception of data between the external device 200 and the control unit 90. The input / output interface 80 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0041] The external device 200 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, and the like to the control unit 90 via the input / output interface 80 .

[0042] The control unit 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, a storage unit 94, and the like.

[0043] The CPU 91 reads out various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various arithmetic processing. For example, the control unit 90 generates a drive signal for an image to be formed based on image data received from the input / output interface 80, and outputs the drive signal to the head 55.

[0044] The RAM 92 provides a working memory space for the CPU 91 and stores temporary data. The RAM 92 may include a non-volatile memory.

[0045] The ROM 93 stores various control programs and setting data executed by the CPU 91. Note that, instead of the ROM 93, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0046] The storage unit 94 stores print jobs and image data related to the print jobs input from the external device 200 via the input / output interface 80. As the storage unit 94, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0047] The control unit 90 is connected to the transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, image forming unit 50, reading unit 60, operation and display unit 70, input / output interface 80, etc. The control unit 90 controls the overall operation of the inkjet printer 100. The transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, image forming unit 50, reading unit 60, operation and display unit 70, input / output interface 80, etc. are controlled by the control unit 90 to execute predetermined processes.

[0048] The inkjet printer 100 having the above configuration supplies the recording medium M from the supply section 20 to the conveying section 10 under the control of the control section 90, forms an image on the recording medium M conveyed to the conveying section 10 in the image forming section 50, and conveys the recording medium M with the image formed thereon to the discharge section 30.

[0049] In this embodiment, the control unit 90 changes the drive conditions of the head 55 when ejecting gel ink based on the first read result below, which is the read result read by the reading unit 60 (the drive condition change unit of the present invention). The drive condition change unit is provided as a function of the control unit 90, and is provided as a program executed by the control unit 90, for example.

[0050] 3 is a diagram illustrating the change in droplets of gel ink ejected from head 55 when the number of ejections (degree of deterioration) of head 55 is different. Also, FIG. 4 is a graph showing the relationship between the number of ejections of gel ink and the optimum drive voltage applied to piezoelectric element 58 of head 55.

[0051] The quality of the images formed by head 55 changes due to deterioration over time of head 55. For example, as piezoelectric element 58 deteriorates over time due to the number of ejections, the amount of gel ink ejected from head 55 decreases, the gel ink droplets become smaller (see droplets D1 → D2 in FIG. 3), and the quality (density) of the images formed decreases.

[0052] Therefore, in order to maintain the quality of the formed image, the control unit 90 (drive condition change unit) adjusts the drive conditions of the head 55 based on the first read result so that the gel ink is ejected in an appropriate amount. For example, based on the image density and droplet dot diameter, which are the first read result, the drive voltage to the piezoelectric element 58, which is the drive condition of the head 55, is adjusted to obtain an optimal voltage so that the pattern image to be formed has a gel ink ejection amount that will become the reference pattern image.

[0053] 4, if the drive conditions of the head 55 satisfy predetermined conditions, for example, if the optimum drive voltage of the piezoelectric element 58 exceeds the upper voltage limit, it will no longer be possible to eject the gel ink in an appropriate amount even if the drive voltage of the piezoelectric element 58 is adjusted. In this case, the head 55 is deemed to have reached the end of its life, and is replaced with a new head 55.

[0054] In the case of gel ink, depending on the usage conditions, the concentration of the gel component of the gel ink stored in the sub-tank 52 in the carriage 51 may become high.

[0055] 5 is a diagram illustrating the change in droplets of gel ink ejected from head 55 when the concentration of gel component contained in the gel ink differs. Also, FIG. 6 is a graph showing the relationship between the number of times gel ink is ejected and the optimal drive voltage applied to piezoelectric element 58 of head 55 for gel ink containing a gel component of an appropriate concentration and gel ink containing a gel component of a high concentration (>appropriate concentration).

[0056] When the concentration of the gel component of the gel ink increases, the pinning ability increases, and therefore the droplets of gel ink ejected from head 55 do not expand to the specified dot diameter (see droplets D3→D4 in FIG. 5).

[0057] Therefore, to maintain the quality of the formed image, it is necessary to adjust the driving conditions of head 55. Specifically, as described above, based on the first reading results (image density, droplet dot diameter), the driving conditions of head 55 (for example, the driving voltage to piezoelectric element 58) are adjusted so that the gel ink is ejected in an appropriate amount.

[0058] Even if the drive conditions of the head 55 (the drive voltage of the piezoelectric element 58) are adjusted in this way due to a change in the concentration of the gel component of the gel ink, the life of the head will be predicted and determined based on the change in the drive conditions of the head 55, as shown in Figure 6. Therefore, there is a risk that the life of the head will be erroneously determined to be the end of its life, even though it is not actually the end of its life, due to a change in the drive conditions of the head 55 caused by a change in the concentration of the gel component of the gel ink. If this determination is made, the head 55 will be unnecessarily replaced with a new one even though the life of the head 55 is not actually the end of its life, resulting in increased costs.

[0059] Therefore, in this embodiment, the inkjet printer 100 is equipped with a state change estimation unit and a determination unit, which will be described below. The state change estimation unit estimates the occurrence of a state change of the gel ink in the subtank 52 when the driving conditions of the head 55 satisfy predetermined conditions. Furthermore, the determination unit determines whether the head 55 has reached the end of its life depending on whether the occurrence of a state change is estimated.

[0060] The state change estimation unit is provided as a function of the control unit 90, and is provided, for example, as a program executed by the control unit 90. When the drive conditions of the head 55 satisfy predetermined conditions, specifically when the optimal voltage of the piezoelectric element 58 exceeds the upper voltage limit, the state change estimation unit estimates that a state change has occurred in the gel ink in the subtank 52. The state change estimation of the occurrence of a state change in the gel ink in the subtank 52 is performed by determining whether a change in the concentration of the gel component of the gel ink has occurred based on the usage history of the head 55 (the period of use of the head 55, the number of times ink has been ejected from the head 55).

[0061] The determination unit is also provided as a function of the control unit 90, and is provided, for example, as a program executed by the control unit 90. The determination unit determines whether the head 55 has reached the end of its life depending on whether the state change estimation unit has estimated the occurrence of a state change, that is, whether a change in the concentration of the gel component of the gel ink has occurred. Even if the optimal voltage of the piezoelectric element 58 exceeds the upper voltage limit, if a change in the concentration of the gel component of the gel ink has occurred, the determination unit determines that the head 55 has not reached the end of its life.

[0062] An example of a method for determining the lifespan of a head 55, which is implemented in an inkjet printer 100 equipped with the above-described state change estimation unit and determination unit, will be described with reference to Fig. 7. Fig. 7 is a flowchart illustrating the method for determining the lifespan implemented in the inkjet printer 100. The method for determining the lifespan shown in Fig. 7 is executed as a lifespan determination program in the control unit 90, which is a computer.

[0063] (Step S11) The control unit 90 controls the image forming unit 50 to form a pattern image on the recording medium M using the head 55. As the pattern image, a dot pattern is used so that the image density and dot diameter can be measured by the reading unit 60, as will be described below.

[0064] (Step S12) The control unit 90 uses the reading unit 60 to read the pattern image formed on the recording medium M, and obtains the first reading result (image density and dot diameter).

[0065] (Step S13) The control unit 90 determines whether there is an image defect caused by improper gel ink ejection based on the acquired first reading results (image density and dot diameter). For example, if the image density or dot diameter of the dot pattern cannot be properly acquired, it determines that there is an image defect caused by improper gel ink ejection. If it determines that there is an image defect (YES), it proceeds to step S14, and if it determines that there is no image defect (NO), it proceeds to step S15.

[0066] (Step S14) The control unit 90 uses the maintenance unit to clean the head 55. After cleaning the head 55, the process returns to step S11, and steps S11 to S13 are executed again. If cleaning is to be executed a predetermined number of times in succession, the control unit 90 may, for example, cause the operation display unit 70 to notify an error by a message or sound.

[0067] (Step S15) The control unit 90 (drive condition change unit) adjusts the drive conditions of the head 55 (drive voltage of the piezoelectric element 58) based on the acquired first read results (image density and dot diameter). Specifically, based on the image density and dot diameter, the drive voltage of the piezoelectric element 58 is adjusted so that the amount of gel ink ejected will be such that the pattern image to be formed is a reference pattern image. In this case, for example, if the image density is lower than the reference, the drive voltage is adjusted in a direction to increase the ejection amount, and if the image density is higher than the reference, the drive voltage is adjusted in a direction to decrease the ejection amount.

[0068] (Step S16) The control unit 90 checks whether the adjusted drive voltage of the piezoelectric element 58 is less than a predetermined voltage. For example, as shown in FIG. 6, it checks whether the adjusted drive voltage of the piezoelectric element 58 is less than a predetermined voltage upper limit.

[0069] If the drive voltage of the adjusted piezoelectric element 58 is less than the predetermined voltage (YES), it can be determined that the head 55 is not at the end of its life, and the series of steps ends. On the other hand, if the drive voltage of the adjusted piezoelectric element 58 is not less than the predetermined voltage (NO), that is, if the drive voltage is equal to or greater than the predetermined voltage, it is possible that the head 55 has reached the end of its life, and so the process proceeds to step S17.

[0070] (Step S17) The control unit 90 (condition change estimation unit) checks whether a value relating to the usage history of the head 55 is equal to or greater than a predetermined value. For example, the control unit 90 stores the period of use of the head 55 and the number of times ink has been ejected, for example, in the memory unit 94. At this time, if ink other than gel ink is used, it is desirable that the period of use of the head 55 and the number of times ink has been ejected also include the period of use of ink other than gel ink and the number of times ink has been ejected. Then, if the adjusted drive voltage of the piezoelectric element 58 is equal to or greater than the predetermined voltage (NO in step S16), in step S17, the control unit 90 checks the period of use of the head 55 and the number of times ink has been ejected, by referring to the memory unit 94.

[0071] If the value relating to the usage history of head 55 is equal to or greater than the predetermined value (YES), it can be determined that head 55 has reached the end of its life, and the process proceeds to step S23. On the other hand, if the value relating to the usage history of head 55 is not equal to or greater than the predetermined value (NO), that is, if the value is less than the predetermined value, it is possible that the drive voltage has exceeded the predetermined voltage due to the concentration of the gel component of the gel ink, and the process proceeds to step S18.

[0072] For example, if the period of use of head 55 is equal to or longer than a predetermined period of use, or the number of times ink has been ejected is equal to or greater than a predetermined number of times, it can be determined that head 55 has reached the end of its life, and the process proceeds to step S23. On the other hand, if the period of use of head 55 is shorter than the predetermined period of use, or the number of times ink has been ejected is less than a predetermined number of times, there is a possibility that the drive voltage has exceeded a predetermined voltage due to the concentration of the gel component of the gel ink, and the process proceeds to step S18.

[0073] In this way, the control unit 90 estimates that a change in the state of the gel ink has occurred by checking whether the numerical value relating to the usage history of the head 55 is equal to or greater than a predetermined numerical value. Estimating that a change in the state of the gel ink has occurred means that an abnormality in the gel ink in the carriage 51 is detected, and in that case, the following step S18 is carried out to refresh (reset) the gel ink in the carriage 51.

[0074] (Step S18) The control unit 90 refreshes (discharges) the gel ink inside the carriage 51. Specifically, the control unit 90 controls the head 55 (head drive unit 54) to perform a discharge operation in which the gel ink stored in the subtank 52 is discharged from the nozzles 59 of the head 55. At this time, the gel ink discharged from the nozzles 59 is collected, for example, in a collection tank provided in the maintenance unit.

[0075] In this way, the gel ink in the sub-tank 52 is discharged outside the carriage 51, and gel ink is supplied from the main tank 41 of the ink supply unit 40 to the sub-tank 52, so that the gel ink in the carriage 51 is automatically refreshed (reset).

[0076] (Step S19) After refreshing the gel ink in the carriage 51, the control unit 90 controls the image forming unit 50 to cause the head 55 to form a pattern image on the recording medium M. As described above, a dot pattern is used as the pattern image.

[0077] (Step S20) The control unit 90 uses the reading unit 60 to read the pattern image formed on the recording medium M, and obtains the first reading result (image density and dot diameter).

[0078] (Step S21) The control unit 90 (driving condition changing unit) adjusts the driving conditions of the head 55 (driving voltage of the piezoelectric element 58) based on the acquired first reading result (image density and dot diameter).

[0079] (Step S22) The control unit 90 (determination unit) checks whether the adjusted drive voltage of the piezoelectric element 58 is less than a predetermined voltage. For example, as shown in Fig. 6, it checks whether the adjusted drive voltage of the piezoelectric element 58 is less than a predetermined voltage upper limit.

[0080] If the drive voltage of the adjusted piezoelectric element 58 is less than the predetermined voltage (YES), it can be determined that the head 55 has not reached the end of its life, and the series of steps ends. On the other hand, if the drive voltage of the adjusted piezoelectric element 58 is not less than the predetermined voltage (NO), that is, if the drive voltage is equal to or greater than the predetermined voltage, it can be determined that the head 55 has reached the end of its life, and the process proceeds to step S23.

[0081] (Step S23) The control unit 90 ends the series of procedures by causing the operation and display unit 70 to notify the replacement of the head 55 by a message or sound. Upon receiving the notification of the replacement of the head 55, the operator will carry out the head 55 replacement work.

[0082] As described above, in this embodiment, the inkjet printer 100 includes a state change estimation unit and a determination unit. The state change estimation unit estimates the occurrence of a state change of the gel ink in the subtank 52 when the drive conditions of the head 55 satisfy predetermined conditions, and the determination unit determines whether the head 55 has reached the end of its life depending on whether the occurrence of a state change is estimated.

[0083] Furthermore, in this embodiment, the state change estimation unit estimates the occurrence of a state change of the gel ink based on the usage history of the head 55.

[0084] According to this embodiment configured as described above, even if the optimal voltage of the piezoelectric element 58 exceeds the upper voltage limit, the life of the head 55 is determined by determining whether a change in the concentration of the gel component of the gel ink has occurred based on the usage history of the head 55.

[0085] Conventional inkjet image forming apparatuses such as those shown in Patent Document 1 do not take into account changes in the state of gel ink, and therefore may make inaccurate estimates of the lifespan of the head 55. In contrast, in the present embodiment, changes in the state of gel ink (changes in the concentration of the gel component) are taken into account when determining the lifespan of the head 55, making it possible to accurately determine the lifespan of the head 55. As a result, it is possible to appropriately notify the user when it is time to replace the head 55, eliminating the need to replace the head 55 with a new one and preventing increases in costs.

[0086] <Variation 1> An inkjet printer 100 of this modified example will be described with reference to Figures 1 and 2. In addition to the configuration described in the above embodiment, the inkjet printer 100 of this modified example further includes a heating unit 110, as indicated by the long dotted line in Figures 1 and 2.

[0087] The heating section 110 is disposed upstream of the image forming section 50 in the conveying direction T of the recording medium M, and heats the recording medium M conveyed by the conveyor belt 11 to a predetermined temperature. The heating section 110 is connected to the control section 90 (see FIG. 2) and is controlled by the control section 90.

[0088] For example, the heating unit 110 has an infrared heater or the like, and power is supplied to the infrared heater based on a control signal supplied from the control unit 90, causing the infrared heater to generate heat and heat the recording medium M to a predetermined temperature. In this modified example, the predetermined temperature is a temperature equal to or higher than the phase transition temperature of the gel component of the gel ink.

[0089] Here, the heating section 110 is arranged on the upper surface side of the conveying belt 11, but instead of (or in addition to) the heating section 110, a heating section may be arranged on the lower surface side of the conveying belt 11, and the conveying belt 11 may be heated to heat the recording medium M.

[0090] A method for determining the lifespan of the head 55 performed in the inkjet printer 100 of this modified example will be described with reference to Fig. 8. Fig. 8 is a flowchart illustrating this modified example, which is a modification of the lifespan determination method shown in Fig. 7.

[0091] The lifespan determination method of this modified example is the same as the lifespan determination method shown in Fig. 7 except for step S17. Therefore, the same procedures of steps S11 to S16 and steps S18 to S23 are not described in Fig. 8. Furthermore, to avoid duplication, the description of the same procedures of steps S11 to S16 and steps S18 to S23 is also omitted here.

[0092] In step S17 shown in Figure 7, as described above, the control unit 90 (state change estimation unit) estimates the occurrence of a state change in the gel ink by checking whether the numerical value related to the usage history of the head 55 is greater than or equal to a predetermined numerical value.

[0093] On the other hand, in this modified example, the control unit 90 (state change estimation unit) estimates the occurrence of a state change of the gel ink based on the results of a second read of a pattern image formed on a recording medium M heated to a temperature equal to or higher than the phase transition temperature of the gel component. Estimating the occurrence of a state change of the gel ink in this modified example will be described below with reference to steps S17-1 to S17-4 shown in Figure 8. The lifespan determination method shown in Figure 8 is also executed as a lifespan determination program in the control unit 90, which is a computer.

[0094] (Step S17-1) In step S16 above, if the adjusted drive voltage of the piezoelectric element 58 is equal to or higher than the predetermined voltage, the control unit 90 controls the heating unit 110 to heat the recording medium M to a temperature equal to or higher than the phase transition temperature of the gel component.

[0095] (Step S17-2) The control unit 90 controls the image forming unit 50 to cause the head 55 to form a pattern image on the recording medium M. As the pattern image, a dot pattern is used, as described above.

[0096] (Step S17-3) The control unit 90 uses the reading unit 60 to read the pattern image formed on the recording medium M and obtains a second reading result.

[0097] (Step S17-4) The control unit 90 (determination unit) checks whether the value of the second reading result is equal to or greater than a predetermined value. In this modification, the value of the second reading result is, for example, the dot diameter of a gel ink droplet when the gel ink is ejected under predetermined driving conditions.

[0098] Here, the numerical values ​​relating to the second reading result will be explained with reference to Fig. 9, taking the dot diameter of gel ink droplets as an example. Fig. 9 is a diagram illustrating gel ink droplets ejected from head 55 onto recording medium M at room temperature and onto recording medium M at a temperature equal to or higher than the phase transition temperature, for gel ink containing an appropriate concentration of gel component and gel ink containing a high concentration of gel component.

[0099] When gel ink is ejected onto the recording medium M under predetermined driving conditions, the dot diameter of the ejected gel ink droplets varies depending on the concentration of the gel component of the gel ink, the temperature of the recording medium M, and the like.

[0100] When the concentration of the gel component of the gel ink is appropriate and the temperature of the recording medium M is room temperature, the dot diameter of a gel ink droplet D11 when the gel ink is ejected under specified driving conditions is defined as d11. Also, when the concentration of the gel component of the gel ink is appropriate and the temperature of the recording medium M is a temperature equal to or higher than the phase transition temperature of the gel component, the dot diameter of a gel ink droplet D12 when the gel ink is ejected under specified driving conditions is defined as d12.

[0101] When the temperature of the recording medium M is equal to or higher than the phase transition temperature of the gel component, the gel ink droplets D12 expand to a dot diameter equivalent to that of ink without a gel component. In other words, the dot diameter d12 of the droplets D12 becomes larger than the dot diameter d11 of the droplets D11.

[0102] In addition, when the concentration of the gel component of the gel ink is high (>optimum concentration) and the temperature of the recording medium M is room temperature, the dot diameter of a gel ink droplet D13 when the gel ink is ejected under specified driving conditions is defined as d13. In addition, when the concentration of the gel component of the gel ink is high and the temperature of the recording medium M is a temperature equal to or higher than the phase transition temperature of the gel component, the dot diameter of a gel ink droplet D14 when the gel ink is ejected under specified driving conditions is defined as d14.

[0103] When the concentration of the gel component of the gel ink is high, the pinning ability is increased compared to when the concentration of the gel component of the gel ink is appropriate, and the dot diameter d13 of the gel ink droplet D13 does not expand to the dot diameter d11 of the gel ink droplet D11. In other words, the dot diameter d13 of the droplet D13 is smaller than the dot diameter d11 of the droplet D11.

[0104] Even if the gel ink has a high concentration of gel component, when the temperature of the recording medium M is equal to or higher than the phase transition temperature of the gel component, the gel ink droplets D14 will expand to a dot diameter equivalent to that of ink containing no gel component. In other words, the dot diameter d14 of droplets D14 will be larger than the dot diameter d13 of droplets D13 and larger than the dot diameter d11 of droplets D11.

[0105] On the other hand, if the head 55 is deteriorated (the piezoelectric element 58 is deteriorated), the actual amount of gel ink ejected will be small even if the gel ink is ejected under specified driving conditions. Therefore, even if the temperature of the recording medium M is equal to or higher than the phase transition temperature of the gel component, the dot diameter of the ejected gel ink droplets will not be as large as droplets D12 and D14 shown in FIG. 9. In this modified example, focusing on this point, the occurrence of a change in the state of the gel ink is estimated by comparing the dot diameter of the pattern image acquired in step S17-3 with, for example, the dot diameter d11 of droplet D11. Specifically, if the dot diameter of the pattern image acquired in step S17-3 is equal to or larger than the dot diameter d11 of droplet D11, the occurrence of a change in the state of the gel ink (an increase in the concentration of the gel component) can be estimated.

[0106] Therefore, when the concentration of the gel component of the gel ink is appropriate and the temperature of the recording medium M is room temperature, the dot diameter d11 of the gel ink droplet D11 when a predetermined amount of gel ink is ejected is measured in advance. The measured dot diameter d11 is then stored in the memory unit 94 as a predetermined value.

[0107] It is also possible to measure in advance the dot diameter d11 of the gel ink droplet D11 when different amounts of gel ink are ejected, and store in the storage unit 94 the correspondence between the ejection amount and the dot diameter d11 as a table.

[0108] Then, in step S17-4 described above, when checking whether the numerical value relating to the second reading result is equal to or greater than a predetermined numerical value, the control unit 90 compares the dot diameter of the pattern image acquired in step S17-3 with the dot diameter d11 stored in the memory unit 94. The control unit 90 checks whether the dot diameter of the pattern image acquired in step S17-3 is equal to or greater than the dot diameter d11 stored in the memory unit 94.

[0109] Then, if the dot diameter of the pattern image acquired in step S17-3 is equal to or greater than the dot diameter d11 stored in memory unit 94 (YES), control unit 90 proceeds to step S18. In other words, since there is a possibility that the drive voltage has exceeded a predetermined voltage due to the concentration of the gel component of the gel ink, control unit 90 proceeds to step S18. On the other hand, if the dot diameter of the pattern image acquired in step S17-3 is not equal to or greater than the dot diameter d11 stored in memory unit 94 (NO), it can be determined that head 55 has reached the end of its life, and control unit 90 proceeds to step S23.

[0110] In this way, the control unit 90 estimates that a change in the state of the gel ink has occurred by checking whether the dot diameter of the pattern image acquired in step S17-3 is equal to or greater than the dot diameter d11 stored in the memory unit 94. Estimating that a change in the state of the gel ink has occurred means that an abnormality in the gel ink in the carriage 51 is detected, and in this case, the above-mentioned step S18 is also carried out to refresh (reset) the gel ink in the carriage 51.

[0111] Although the explanation here has been given using the dot diameter of the gel ink droplets as an example of the numerical value relating to the second reading result, the image density may also be used as the numerical value relating to the second reading result. Even when the image density is used as the numerical value relating to the second reading result, it is possible to estimate the occurrence of a change in the state of the gel ink in the same way as in the case of the dot diameter.

[0112] As described above, in this modified example, the state change estimation unit estimates the occurrence of a state change in the gel ink based on the second reading result of the pattern image formed by the head 55 on the recording medium M heated to a temperature above the phase transition temperature of the gel ink.

[0113] According to this modified example configured as above, even if the optimal voltage of the piezoelectric element 58 exceeds the upper voltage limit, the lifespan of the head 55 is determined by determining whether or not a change in the concentration of the gel component of the gel ink has occurred based on the results of the second read of the pattern image. In this way, the lifespan of the head 55 is determined taking into account the change in the state of the gel ink (change in the concentration of the gel component), so the lifespan of the head 55 can be determined with high accuracy. As a result, it is possible to appropriately notify the user when it is time to replace the head 55, which prevents unnecessary replacement with a new head 55 and prevents increases in costs.

[0114] The above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or main features thereof. [Explanation of symbols]

[0115] 10 Conveying section 11 Conveyor belt 11a Conveying surface 12 Drive roller 13 Driven roller 20 Supply section 21 Supply loading section 22 Supply and conveying section 30 Discharge section 31 Discharge loading section 32 Discharge and conveyance section 40 Ink supply unit 41 Main Tank 42 Flow path 50 Image forming unit 51 Carriage 52 Subtank 53a, 53b flow path 54 Head drive unit 55 Inkjet head 56 Manifold 57 Pressure Chamber 58 Piezoelectric element 59 nozzle 60 Reading unit 70 Operation display section 80 Input / Output Interface 90 Control Unit 100 Inkjet Printer 110 Heating section 200 External device

Claims

1. an inkjet head having a reservoir for storing a phase change ink and ejecting the phase change ink to form an image on a recording medium; a drive condition changing unit that changes a drive condition of the inkjet head when ejecting the phase change ink based on a first reading result of a pattern image formed by the inkjet head; a state change estimation unit that estimates the occurrence of a state change of the phase change ink in the reservoir when the changed driving condition satisfies a predetermined condition; a determination unit that determines whether the inkjet head has reached the end of its life depending on whether the occurrence of the state change is estimated; An image forming apparatus comprising:

2. the state change estimation unit estimates the occurrence of a state change of the phase change ink based on a usage history of the inkjet head; The image forming apparatus according to claim 1 .

3. the usage history is the period of time during which the inkjet head has been used; The image forming apparatus according to claim 2 .

4. the usage history is the number of times ink is ejected by the inkjet head; The image forming apparatus according to claim 2 .

5. the state change estimation unit estimates the occurrence of a state change of the phase change ink based on a second reading result of a pattern image formed by the inkjet head on the recording medium heated to a temperature equal to or higher than the phase change temperature of the phase change ink; The image forming apparatus according to claim 1 .

6. the state change estimation unit estimates that a state change has occurred in the phase change ink when the value related to the usage history is less than a predetermined value; The image forming apparatus according to claim 2 .

7. the state change estimation unit estimates that a state change has occurred in the phase change ink when the value of the second reading result is equal to or greater than a predetermined value; The image forming apparatus according to claim 5 .

8. The pattern image is formed of a dot pattern. The image forming apparatus according to claim 1 .

9. The reading result is the density of the pattern image. The image forming apparatus according to claim 8 .

10. the read result is the dot diameter of the phase change ink constituting the pattern image; The image forming apparatus according to claim 8 .

11. the drive condition changing unit changes the drive conditions based on the first reading result so that the pattern image formed by the inkjet head becomes a reference pattern image. The image forming apparatus according to claim 1 .

12. the inkjet head has nozzles for ejecting the phase change ink, and piezoelectric elements that deform in response to an applied drive voltage and impart a pressure change to the phase change ink supplied to the nozzles; the driving condition is the driving voltage applied to the piezoelectric element; The image forming apparatus according to claim 1 .

13. the predetermined condition is that the driving voltage is equal to or higher than a predetermined voltage; The image forming apparatus according to claim 12.

14. a control unit that controls the inkjet head to perform a discharge operation of discharging the phase change ink stored in the storage unit from the nozzle when it is determined that the inkjet head has not yet reached the end of its life; 14. The image forming apparatus according to claim 12 or 13.

15. forming a pattern image on a recording medium by ejecting the phase change ink from an inkjet head having a reservoir for storing the phase change ink; changing a driving condition of the inkjet head when ejecting the phase change ink based on a first reading result of the formed pattern image; If the modified driving conditions satisfy a predetermined condition, an occurrence of a change in state of the phase change ink in the reservoir is estimated; determining whether the inkjet head has reached the end of its life depending on whether the occurrence of the state change is estimated; Lifespan determination method.

16. On the computer, forming a pattern image on a recording medium by ejecting the phase change ink from an ink jet head having a reservoir for storing the phase change ink; changing a driving condition of the inkjet head when ejecting the phase change ink based on a first reading result of the formed pattern image; if the modified driving conditions satisfy a predetermined condition, estimating the occurrence of a change in state of the phase change ink in the reservoir; a process of determining whether the inkjet head has reached the end of its life depending on whether the occurrence of the state change is estimated; A lifespan determination program that executes the above.

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