Printing apparatus

Abstract

The present invention provides a printing apparatus that can produce high-quality printed materials while minimizing the use of ink whose viscosity has increased due to disuse. [Solution] The system includes an inkjet head 31 that ejects ink onto a printing medium to perform printing, an unused period measurement unit 50 that measures the unused period during which printing is not performed by the inkjet head 31, a temperature measurement unit 32 that measures the ambient temperature, an ink consumption measurement unit 51 that measures the amount of ink consumed for printing, and a control unit 5 that controls the drive voltage of the inkjet head 31 based on the unused period measured by the unused period measurement unit 50, the ambient temperature measured by the temperature measurement unit 32, and the ink consumption measured by the ink consumption measurement unit 51, when the unused period measured by the unused period measurement unit 50 is greater than or equal to a preset threshold.

Description

Technical Field

[0001] The present invention relates to a printing apparatus that performs printing processing by ejecting ink onto a printing medium.

Background Art

[0002] Conventionally, an inkjet printer is known as a printing apparatus that can perform on-demand printing of posters and large advertisements. In particular, a wide-format inkjet printer that can print on a wide roll-shaped substrate is known, and models equipped with solvent ink have been sold by various companies.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the idle time (non-use period) without using the printer becomes long, the solvent component volatilizes and permeates from the ink in the tube of the ink supply path that supplies ink from the ink bottle storing the ink to the inkjet head, or from the ink in the damper that suppresses the influence of the inertial force caused by the movement of the inkjet head, and it is known that the viscosity of the ink increases.

[0005] As a countermeasure against such an increase in the viscosity of the ink, it is known to use a tube with high gas barrier properties or to use a film membrane for the damper, but it cannot be completely suppressed.

[0006] Further, when printing processing is performed by driving the inkjet head as usual using the ink whose viscosity has increased in this way, the ejection speed of the ink ejected from the inkjet head decreases, the landing position of the ink is displaced, and the quality of the printed matter deteriorates.

[0007] It is also possible to discard the ink with increased viscosity from the tubes and dampers and replace it with ink of its original viscosity in the ink bottles, but the cost of discarded ink has a significant negative impact on the cost of printed materials. The larger the print width of the printer, the longer the tube length, and therefore the greater the amount of ink that increases in viscosity due to being left standing.

[0008] Furthermore, it is generally known that higher ambient temperatures increase the volatility of ink, which in turn makes it more likely for the ink's viscosity to increase.

[0009] In Patent Document 1, a method is proposed in which, when using ink containing volatile components, the temperature of the ink in the nozzle is detected by a temperature sensor, and the number of air-drive and pre-discharge operations are changed according to that temperature. However, even if multiple air-drive and pre-discharge operations are combined, if the amount of thickened ink is large, it takes an enormous amount of time to discharge, which is inefficient. Furthermore, as mentioned above, the cost of printed materials increases due to the disposal of the thickened ink.

[0010] In view of the above circumstances, the present invention aims to provide a printing apparatus that can produce high-quality printed materials while minimizing the use of ink whose viscosity has increased due to non-use. [Means for solving the problem]

[0011] The printing apparatus of the present invention comprises an ink ejection unit that ejects ink onto a printing medium and performs printing; an unused period measurement unit that measures the unused period during which printing is not performed by the ink ejection unit; a temperature measurement unit that measures the ambient temperature; an ink consumption measurement unit that measures the amount of ink consumed for printing; and a control unit that controls the drive voltage of the ink ejection unit based on the unused period measured by the unused period measurement unit, the ambient temperature measured by the temperature measurement unit, and the ink consumption measured by the ink consumption measurement unit, when the unused period measured by the unused period measurement unit is greater than or equal to a preset threshold. [Effects of the Invention]

[0012] According to the printing apparatus of the present invention, the period of non-use when printing is not performed, the ambient temperature, and the amount of ink consumed in the printing process are measured, and if the period of non-use exceeds a preset threshold, the drive voltage of the ink ejection unit is controlled based on the period of non-use, the ambient temperature, and the amount of ink consumed. As a result, high-quality printed materials can be obtained while minimizing the use of ink whose viscosity has increased due to non-use. [Brief explanation of the drawing]

[0013] [Figure 1] External perspective view showing a schematic configuration of an inkjet printing apparatus using one embodiment of the printing apparatus of the present invention. [Figure 2] Diagram showing the schematic configuration of the shuttle unit. [Figure 3] This diagram shows the connection relationship between the ink bottle, ink supply path, air damper, and inkjet head. [Figure 4] Figure 1 shows a block diagram illustrating the configuration of the control system for the inkjet printing apparatus. [Figure 5] This figure shows an example of a table illustrating the relationship between the period of non-use and ink viscosity at different ambient temperatures. [Figure 6] This figure shows an example of a table illustrating the relationship between ink viscosity and inkjet head drive voltage. [Figure 7] A flowchart illustrating an example of the operation of the inkjet printer shown in Figure 1. [Modes for carrying out the invention]

[0014] Hereinafter, an inkjet printing apparatus using an embodiment of the printing apparatus of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of this embodiment is characterized by controlling the drive voltage of the inkjet head. First, the configuration of the entire inkjet printing apparatus will be described. FIG. 1 is a schematic configuration diagram of the inkjet printing apparatus 1 of this embodiment. Note that the up, down, left, right, front, and rear directions indicated by arrows in FIG. 1 are the up, down, left, right, front, and rear directions in the inkjet printing apparatus 1.

[0015] As shown in FIG. 1, the inkjet printing apparatus 1 of this embodiment includes a shuttle base unit 2, a flat bed unit 3, and a shuttle unit 4.

[0016] The shuttle base unit 2 supports the shuttle unit 4 and moves the shuttle unit 4 in the front-rear direction (sub-scanning direction). Specifically, the shuttle base unit 2 includes a gantry portion 11 and a sub-scanning drive motor 12 (see FIG. 4).

[0017] The gantry portion 11 is formed in a rectangular frame shape and supports the shuttle unit 4. Sub-scanning drive guides 13A and 13B extending in the front-rear direction are formed on the left and right frames of the gantry portion 11, respectively. The sub-scanning drive guides 13A and 13B guide the shuttle unit 4 to move in the front-rear direction. The sub-scanning drive motor 12 moves the shuttle unit 4 in the front-rear direction.

[0018] The flat bed unit 3 supports the base material 15, which is a printing medium. The flat bed unit 3 is disposed in a rectangular parallelepiped-shaped recess formed inside the gantry portion 11 of the shuttle base unit 2. The flat bed unit 3 has a medium placement surface 3a, which is a horizontal surface on which the base material 15 is placed. The flat bed unit 3 has a lifting mechanism composed of a hydraulic drive mechanism (not shown), and is configured to be able to adjust the height of the medium placement surface 3a.

[0019] The shuttle unit 4 performs printing processing on the base material 15. FIG. 2 is a diagram showing the schematic configuration of the shuttle unit 4. As shown in FIG. 2, the shuttle unit 4 includes a housing 21, a main scanning drive guide 22, a main scanning drive motor 23 (see FIG. 4), a head lifting guide 24, a head lifting motor 25 (see FIG. 4), a head unit 26, a capping unit 66, a suction unit 28, an ink supply unit 29, and a temperature measurement unit 32.

[0020] The housing 21 houses each part such as the head unit 26. The housing 21 is formed in a portal shape that straddles the flat bed unit 3 in the left - right direction. The housing 21 is supported by the gantry portion 11 of the shuttle base unit 2 and is configured to be movable along the sub - scanning drive guides 13A and 13B.

[0021] The main scanning drive guide 22 guides the head unit 26 to move in the left - right direction (main scanning direction). The main scanning drive guide 22 is formed by an elongated member extending in the left - right direction. The head unit 26 is moved in the left - right direction by the main scanning drive motor 23.

[0022] The head lifting guide 24 guides the head unit 26 to move in the up - down direction. The head lifting guide 24 is formed from a member having an elongated shape in the up - down direction. The head lifting guide 24 is configured to be movable in the left - right direction along the main scanning drive guide 22 together with the head unit 26. The head unit 26 is lifted and lowered in the up - down direction by the head lifting motor 25.

[0023] The head unit 26 performs printing processing by discharging ink onto the base material 15 while moving in the left - right direction along the main scanning drive guide 22 as described above. The head unit 26 has four inkjet heads 31 as shown in FIG. 2. In the present embodiment, the inkjet head 31 corresponds to the ink discharge portion of the present invention.

[0024] The four inkjet heads 31 eject inks of different colors, such as C (cyan), M (magenta), Y (yellow), and K (black).

[0025] It is preferable to use a circulating head 31 that can circulate ink up to the vicinity of the nozzle. It is also preferable that the inkjet head 31 has a wide range of gradations, allowing the amount of ink ejected to be changed by the waveform of the drive voltage supplied to it. For example, the 508 series manufactured by SII Printec Co., Ltd. can be used as the inkjet head 31.

[0026] Furthermore, each inkjet head 31 is provided with an air damper 31a. The air damper 31a is provided between the end of the ink supply path 35 that supplies ink to each inkjet head 31 and each inkjet head 31.

[0027] The air damper 31a is designed to prevent the ink in the ink supply path 35 from moving due to the inertial force generated by the movement of the inkjet head 31, thereby preventing damage to the meniscus of the nozzle opening of the inkjet head 31, and absorbs the effects of the aforementioned inertial force. The ink flowing through the ink supply path 35 is supplied to the inkjet head 31 via the air damper 31a.

[0028] Furthermore, a capping unit 66 is provided on the ink ejection surface side of each inkjet head 31. The ink ejection surface is the surface on which the ink ejection ports of each nozzle of the inkjet head 31 are arranged.

[0029] Each capping unit 66 seals the ink ejection surface of each inkjet head 31 to prevent the ink ejection ports of each nozzle of the inkjet head 31 from drying out when the inkjet printing device 1 is in standby mode and not performing printing operations.

[0030] As shown in Figure 2, the capping unit 66 is installed inside the right end of the housing 21. When the head unit 26 moves to the standby position at the right end of the housing 21, it seals the ink ejection surface of the inkjet head 31.

[0031] The capping unit 66 moves up and down by a cap lifting motor 67 (see Figure 4). Specifically, the capping unit 66 moves up and down between a contact position in which it contacts the ink ejection surface of the inkjet head 31 and a retracted position below the contact position.

[0032] The suction unit 28, located below the capping unit 66, is used to suck up the ink accumulated in the capping unit 66. The suction unit 28 comprises a suction pipe 68, a suction pump 69, and a waste liquid tank 70.

[0033] One end of the suction pipe 68 is connected to the capping unit 66, and the other end of the suction pipe 68 is connected to the waste liquid tank 70. A suction pump 69 is installed for each end of the suction pipe 68.

[0034] The ink accumulated in the capping unit 66 is sucked up by the suction pump 69 and stored in the waste liquid tank 70 via the suction pipe 68.

[0035] The ink supply unit 29 is located inside the left end of the housing 21, as shown in Figure 2. The ink supply unit 29 includes four ink bottles 30, each storing one of the four colors of ink supplied to each inkjet head 31. The ink bottles 30 can be made of, for example, a rigid material with high gas barrier properties or an aluminum pouch. This allows the viscosity of the ink in the ink bottles 30 to be maintained at its initial viscosity regardless of the ambient temperature.

[0036] Figure 3 shows the connection relationship between one of the four ink bottles 30, the ink supply path 35, the air damper 31a, and the inkjet head 31. As shown in Figure 3, one end of the ink supply path 35 is connected to the ink bottle 30, and the air damper 31a and the inkjet head 31 are connected to the other end of the ink supply path 35. One end of the ink supply path 35 is also connected to the other three ink bottles 30, and the air damper 31a and the inkjet head 31 are connected to the other end of the ink supply path 35. In this embodiment, the ink bottle 30 corresponds to the storage unit of the present invention. A degassing module that reduces the amount of dissolved oxygen in the ink may be installed between the air damper 31a and the inkjet head 31. This increases the ejection stability and improves the stability of continuous printing.

[0037] Each ink supply path 35 is provided with an ink supply pump 33, and when the ink supply pump 33 is driven, the ink in the ink bottle 30 is supplied to the air damper 31a and the inkjet head 31 via the ink supply path 35.

[0038] The ink supply path 35 is provided within the housing 21 of the shuttle unit 4 shown in Figure 2, and extends from the left end to the right end of the housing 21. The ink supply path 35 is made of a tube made of polyethylene, for example, but is not limited to this; for example, a multilayer tube made of composite materials in layers may be used. This enhances the gas barrier properties and slows down the increase in viscosity due to the evaporation of the ink solvent.

[0039] For the ink, a general solvent ink can be used. Solvent ink can be prepared by dispersing the pigment in a main solvent such as glycol monoacetates or glycol ethers, and adding a solvent containing a binder resin that provides fixation to the substrate 15. Furthermore, it is preferable to use a solvent with a low boiling point from among highly safe solvents.

[0040] The temperature measurement unit 32 is equipped with a temperature sensor such as a thermistor and measures the temperature around the shuttle unit 4.

[0041] Figure 4 is a block diagram showing the control system of the inkjet printing apparatus 1 of this embodiment. The inkjet printing apparatus 1 includes a control unit 5 that controls the entire apparatus. The control unit 5 includes a CPU (Central Processing Unit), semiconductor memory, and a hard disk. The control unit 5 controls the various parts shown in Figure 4 by executing a program pre-stored in a storage medium such as semiconductor memory or a hard disk, and by operating electrical circuits.

[0042] In particular, the control unit 5 of this embodiment includes a non-use period measurement unit 50 and an ink consumption measurement unit 51.

[0043] The unused period measurement unit 50 measures the unused period during which no printing is performed. The unused period measurement unit 50 measures the unused period by counting clock signals. The unused period measurement unit 50 starts measuring the unused period from the time the printing process is completed, and resets the count to initialize when the ink whose viscosity has increased in the ink supply path 35 during the unused period is consumed and replaced with ink of initial viscosity. Ink of initial viscosity is the ink stored in the ink bottle 30. Since the change in ink viscosity does not occur rapidly, the unused period can be managed in hours rather than seconds or minutes.

[0044] The ink consumption measurement unit 51 measures the amount of ink consumed in the printing process. The ink consumption can be calculated, for example, by counting the number of dots formed on the substrate 15 based on the print data to be printed, and multiplying the number of dots by the amount of ink used to form one dot. The amount of ink used to form one dot may be calculated by multiplying the drive frequency of the inkjet head 31 by the amount of ink in one drop.

[0045] Furthermore, when the inkjet head 31 is purged to clean and maintain the ink ejection surface, the ink consumption measurement unit 51 also includes the amount of ink used during the purging operation in the ink consumption calculation.

[0046] The control unit 5 then controls the drive voltage of the inkjet head 31 based on the ambient temperature measured by the temperature measurement unit 32, the period of non-use measured by the non-use period measurement unit 50, and the ink consumption measured by the ink consumption measurement unit 51.

[0047] Specifically, when the printing process is started, the control unit 5 obtains the ambient temperature measured by the temperature measurement unit 32 and the unused period measured by the unused period measurement unit 50, and estimates the viscosity of the ink remaining in the ink supply path 35 based on the obtained ambient temperature and unused period. The control unit 5 has a table set in advance for each ambient temperature that shows the relationship between the unused period and the viscosity of the ink, for example, as shown in Figure 5, and the control unit 5 estimates the viscosity of the ink using the table shown in Figure 5, the unused period, and the ambient temperature.

[0048] Furthermore, the control unit 5 determines the drive voltage of the inkjet head 31 based on the ink viscosity estimated as described above. Specifically, the control unit 5 has a table pre-set that shows the relationship between ink viscosity and the drive voltage of the inkjet head 31, as shown in Figure 6. The table shown in Figure 6 shows the relationship between ink viscosity and drive voltage such that the ink ejection speed from the inkjet head 31 remains constant. Based on the table shown in Figure 6, the control unit 5 controls the inkjet head 31 so that the drive voltage increases as the estimated ink viscosity increases.

[0049] The control unit 5 uses the table shown in Figure 6 and the estimated ink viscosity to determine the drive voltage for the inkjet head 31, and supplies that drive voltage to the inkjet head 31 to perform the ink ejection operation.

[0050] The control unit 5 then acquires the ink consumption measured by the ink consumption measurement unit 51 and continues to control the drive voltage based on the estimated ink viscosity described above until the ink consumption reaches a preset threshold. The threshold for ink consumption is a value determined based on the amount of ink remaining in the ink supply path 35.

[0051] In other words, the control unit 5 monitors whether the ink with increased viscosity remaining in the ink supply path 35 has been consumed, and continues to control the drive voltage according to its viscosity until the ink remaining in the ink supply path 35 is consumed. When the ink remaining in the ink supply path 35 is consumed, ink with the initial viscosity is sequentially supplied to the ink supply path 35 from the ink bottle 30. That is, within the ink supply path 35, ink with increased viscosity is replaced with ink with the initial viscosity while the ink with increased viscosity is being consumed.

[0052] Furthermore, the ink with increased viscosity remains not only in the ink supply path 35 but also in the air damper 31a and the inkjet head 31. However, it is difficult to determine the boundary between the increased viscosity ink and the ink with its initial viscosity within the air damper 31a and the inkjet head 31. Therefore, in this embodiment, the drive voltage control based on the estimated ink viscosity continues until the ink in the ink supply path 35 is consumed, that is, until the ink with its initial viscosity reaches the air damper 31a.

[0053] Then, when the ink consumption reaches a preset threshold, that is, when the ink in the ink supply path 35 is replaced from ink of increased viscosity to ink of initial viscosity, the control unit 5 moves the head unit 26 to the capping unit 66, caps the inkjet head 31 with the capping unit 66, and drives the suction pump 69 to suck up and discard the remaining ink in the air damper 31a and the inkjet head 31.

[0054] Then, as described above, the control unit 5 discards the ink in the air damper 31a and the inkjet head 31, and then moves the head unit 26 again in the main scanning direction to resume the printing process. At this time, the drive voltage of the inkjet head 31 is switched from the drive voltage corresponding to the estimated ink viscosity described above to a preset drive voltage. The preset drive voltage is, for example, a drive voltage corresponding to the viscosity of the ink at its initial viscosity.

[0055] In this embodiment, as described above, after discarding the ink in the air damper 31a and the inkjet head 31, the drive voltage of the inkjet head 31 is switched to a preset drive voltage for the next scan of the head unit 26. However, this is not limited to this, and for example, the drive voltage may not be switched until the printing process of the ongoing print job is completed, and the drive voltage may be switched from the start of the print job to be performed immediately afterward.

[0056] Furthermore, if the viscosity of the ink estimated based on the period of non-use and ambient temperature exceeds a preset threshold, the control unit 5 may discard the ink in the ink supply path 35 and replace it with ink of initial viscosity before starting the printing process, rather than performing the printing process using the ink with increased viscosity in the ink supply path 35.

[0057] Specifically, if the estimated ink viscosity exceeds a preset threshold, the control unit 5 moves the head unit 26 to the capping unit 66, caps the inkjet head 31 with the capping unit 66, and drives the suction pump 69 to suck up and discard the ink remaining in the ink supply path 35, air damper 31a, and inkjet head 31.

[0058] Then, after discarding the ink, the control unit 5 drives the inkjet head 31 with a preset drive voltage (a drive voltage corresponding to the viscosity of the ink at its initial viscosity) to start the printing process. It is desirable that the estimated threshold value for ink viscosity used is, for example, the upper limit of the ink viscosity range in which the inkjet head 31 can normally eject ink, or a value increased by 5% from the initial viscosity. The ink viscosity range in which the inkjet head 31 can normally eject ink is a range that has been measured in advance as part of the specifications of the inkjet head 31, and can be determined from, for example, the manufacturer's recommended value, the specifications provided by the manufacturer, or the ejection observation results of the inkjet head 31.

[0059] Furthermore, the solvent ink used in the inkjet printing apparatus of this embodiment is preferably an ink having a viscosity in the low viscosity range within the ink viscosity range in which the inkjet head 31 can eject ink normally.

[0060] Specifically, for example, if the ink viscosity range in which the inkjet head 31 can normally eject is 7 mPa·s to 15 mPa·s, it is desirable to use a solvent ink with a viscosity of 7 mPa·s. By selecting the inkjet head 31, the ink viscosity range, and the viscosity of the solvent ink in this way, it becomes possible to ensure a longer time before the viscosity of the solvent ink rises outside the ink viscosity range, thereby further reducing ink waste due to thickening.

[0061] Furthermore, as mentioned above, the viscosity of the solvent ink is not limited to the lower limit of the ink viscosity range, but may be any viscosity lower than, for example, the median value of the ink viscosity range. Preferably, it is a viscosity in the low viscosity region of 1 / 3 of the lower limit of the ink viscosity range, and more preferably, it is a viscosity in the low viscosity region of 1 / 4 of the lower limit of the ink viscosity range.

[0062] Next, the printing operation of the inkjet printing apparatus 1 of this embodiment will be explained with reference to the flowchart shown in Figure 7.

[0063] In the inkjet printing apparatus 1, the shuttle unit 4 is positioned in a standby position when in standby mode before the start of printing. The standby position of the shuttle unit 4 is the position of the shuttle unit 4 shown by the solid line in Figure 1, which is the rear end of the frame portion 11 of the shuttle base unit 2.

[0064] In the standby state before the start of the printing process, the control unit 5 acquires the unused period measured by the unused period measurement unit 50 and the ambient temperature measured by the temperature measurement unit 32 (S10).

[0065] The control unit 5 then determines whether the period of non-use is greater than or equal to a preset threshold (S12). If the period of non-use is greater than or equal to a preset threshold (S12, YES), the control unit 5 estimates the viscosity of the ink remaining in the ink supply path 35 based on the period of non-use and the ambient temperature (S14). Next, the control unit 5 determines the drive voltage of the inkjet head 31 based on the estimated ink viscosity (S16).

[0066] When a print job is input, the control unit 5 controls the sub-scanning drive motor 12 to move the shuttle unit 4 from the standby position to the print processing start position. The print processing start position of the shuttle unit 4 is the position of the shuttle unit 4 shown by the dashed line in Figure 1, which is the front end of the frame portion 11 of the shuttle base unit 2. Prior to the input of a print job, the substrate 15 is placed on the media mounting surface 3a of the flatbed unit 3.

[0067] Next, the control unit 5 starts the printing process based on the input print job (S18). Specifically, the control unit 5 controls the main scanning drive motor 23 to move the head unit 26 in the main scanning direction, and based on the input print job, controls the inkjet head 31 with the drive voltage determined in S16 to eject ink, thereby performing one pass of printing.

[0068] Next, the control unit 5 controls the sub-scan drive motor 12 to move the shuttle unit 4 backward to the printing position for the next pass. Then, the control unit 5 again controls the main scan drive motor 23 to move the head unit 26 in the main scan direction (reverse direction) and print the next pass. The control unit 5 performs the printing process on the substrate 15 by alternately repeating the above-described process of printing one pass and moving the shuttle unit 4.

[0069] The control unit 5 then proceeds with the printing process as described above and obtains the amount of ink consumed by the printing process from the ink consumption measurement unit 51 (S20). When the amount of ink consumed reaches a preset threshold (S22, YES), that is, when the ink in the ink supply path 35 is replaced from ink of increased viscosity to ink of initial viscosity, the control unit 5 moves the head unit 26 to the capping unit 66, caps and sucks out the remaining ink in the air damper 31a and the inkjet head 31 (S24).

[0070] Then, as described above, the control unit 5 discards the ink in the air damper 31a and the inkjet head 31, and then moves the head unit 26 again in the main scanning direction to resume the printing process. At this time, the drive voltage of the inkjet head 31 is switched from the drive voltage corresponding to the estimated ink viscosity described above to a preset drive voltage (S26).

[0071] Then, the inkjet head 31 is driven at a preset drive voltage to continue printing until all printing processes are completed (S28, NO, S30). Once all printing processes are completed (S28, YES), the control unit 5 controls the sub-scan drive motor 12 to position the shuttle unit 4 in standby position.

[0072] In S12, if the period of non-use is shorter than a preset threshold (S12, NO), the control unit 5 starts printing by driving the inkjet head 31 with a preset drive voltage without performing the ink viscosity estimation described above (S32), and continues printing by driving the inkjet head 31 with a preset drive voltage until all printing is completed (S28, NO, S30). When all printing is completed (S28, YES), the control unit 5 controls the sub-scan drive motor 12 to place the shuttle unit 4 in the standby position.

[0073] Furthermore, although the above description of the operation shows the head unit 26 moving back and forth in the main scanning direction, the movement direction of the head unit 26 may be set to one direction. This has the effect of suppressing output variations compared to the case of reciprocating movement, and makes it easier to achieve accurate dot placement.

[0074] According to the inkjet printing apparatus 1 of the above embodiment, the period of non-use when printing is not performed, the ambient temperature, and the amount of ink consumed in the printing process are measured, and if the period of non-use exceeds a preset threshold, the drive voltage of the inkjet head 31 is controlled based on the period of non-use, the ambient temperature, and the amount of ink consumed. As a result, high-quality printed materials can be obtained while minimizing the use of ink whose viscosity has increased due to non-use.

[0075] Furthermore, in the inkjet printing apparatus 1 of the above embodiment, the drive voltage is increased as the viscosity of the ink, estimated based on the period of non-use and ambient temperature, increases. This makes it possible to maintain a constant ink ejection speed from the inkjet head 31, thereby maintaining the accuracy of ink placement on the substrate 15 and obtaining good quality printed materials.

[0076] Furthermore, in the inkjet printing apparatus 1 of the above embodiment, the control of the drive voltage based on the viscosity of the ink is continued until the amount of ink consumed reaches the amount of thickened ink in the ink supply path 35. As a result, the thickened ink in the ink supply path 35 can be ejected from the inkjet head 31 at an appropriate ink ejection speed, preventing misalignment of the ink droplets and enabling the production of high-quality printed materials.

[0077] Furthermore, in the inkjet printing apparatus 1 of the above embodiment, when the amount of ink consumed reaches a preset threshold, the ink in the air damper 31a and the inkjet head 31 is discarded. This ensures that the thickened ink in the air damper 31a and the inkjet head 31 is also properly discarded, and the printing process can then be started with ink of its initial viscosity.

[0078] Furthermore, in the inkjet printing apparatus 1 of the above embodiment, if the estimated viscosity of the ink exceeds a preset threshold, the ink in the ink supply path 35 is discarded. Therefore, if the viscosity of the thickened ink in the ink supply path 35 exceeds the ink viscosity range of the inkjet head 31, printing with the thickened ink can be avoided, and misalignment of the ink's landing position can be prevented.

[0079] Furthermore, in the inkjet printing apparatus of the above embodiment, if a solvent ink having a viscosity in the low viscosity range within the ink viscosity range in which the inkjet head 31 can eject normally is used, as described above, it becomes possible to ensure a longer time until the viscosity of the solvent ink rises outside the ink viscosity range, thereby further reducing ink waste due to thickening.

[0080] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments described above. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

[0081] The following further notes are disclosed regarding the present invention.

[0082] (Note 1) The printing apparatus of the present invention comprises an ink ejection unit that ejects ink onto a printing medium and performs printing; an unused period measurement unit that measures the unused period during which printing is not performed by the ink ejection unit; a temperature measurement unit that measures the ambient temperature; an ink consumption measurement unit that measures the amount of ink consumed for printing; and a control unit that controls the drive voltage of the ink ejection unit based on the unused period measured by the unused period measurement unit, the ambient temperature measured by the temperature measurement unit, and the ink consumption measured by the ink consumption measurement unit, when the unused period measured by the unused period measurement unit is greater than or equal to a preset threshold.

[0083] (Note 2) In the printing apparatus described in Appendix 1, the control unit can increase the drive voltage as the viscosity of the ink, estimated based on the period of non-use and ambient temperature, increases.

[0084] (Note 3) In the printing apparatus described in Appendix 1 or 2, the control unit can continue to control the drive voltage based on the viscosity of the ink until the amount of ink consumed reaches a preset threshold.

[0085] (Note 4) In the printing apparatus described in Appendix 3, the preset threshold value may be a value determined based on the amount of ink present in the ink path between the ink storage section and the ink ejection section.

[0086] (Note 5) In the printing apparatus described in Appendix 3 or 4, the control unit may discard the ink in the ink ejection unit when the amount of ink consumed reaches a preset threshold.

[0087] (Note 6) In the printing apparatus described in Appendix 4, the control unit estimates the viscosity of the ink based on the unused period measured by the unused period measurement unit and the temperature measured by the temperature measurement unit, and if the estimated viscosity of the ink exceeds a preset threshold, the control unit can discard the ink in the ink path.

[0088] (Note 7) In the printing apparatus described in any of the appendices 1 to 6, the ink may be a solvent ink having a viscosity in the low viscosity region within the normal ejection ink viscosity range of the ink ejection unit. [Explanation of Symbols]

[0089] 1. Inkjet printing device 2 Shuttle Base Units 3 Flatbed Units 3a Media placement surface 4 Shuttle Units 5. Control Unit 11. Base section 12 Sub-scanning drive motor 15 Base material 21 cabinets 22 Main scanning drive guide 23 Main scanning drive motor 24 Head Lifting Guide 25 Head lifting motor 13A, 13B Sub-scanning drive guide 26 Head Units 28 Suction part 29 Ink supply unit 30 ink bottles 31 Inkjet heads 31a Air damper 32 Temperature measurement unit 33. Ink supply pump 35. Ink supply path 50 Non-use period measurement section 51 Ink consumption measurement unit 66 Capping Units 67 Cap lifting motor 68 Suction tube 69 Suction pump 70 Waste liquid tank

Claims

1. An ink ejection unit that ejects ink onto a printing medium to perform printing, An unused period measurement unit that measures the period of time during which printing is not performed by the ink ejection unit, A temperature measuring unit that measures the ambient temperature, An ink consumption measuring unit for measuring the amount of ink used in the aforementioned printing process, A printing apparatus comprising a control unit that controls the drive voltage of the ink ejection unit based on the unused period measured by the unused period measurement unit, the ambient temperature measured by the temperature measurement unit, and the amount of ink consumed measured by the ink consumption measurement unit, when the unused period measured by the unused period measurement unit is greater than or equal to a preset threshold.

2. The printing apparatus according to claim 1, wherein the control unit increases the drive voltage as the viscosity of the ink, estimated based on the period of non-use and the ambient temperature, increases.

3. The printing apparatus according to claim 2, wherein the control unit continues to control the drive voltage based on the viscosity of the ink until the amount of ink consumed reaches a preset threshold.

4. The printing apparatus according to claim 3, wherein the preset threshold is a value determined based on the amount of ink present in the ink path between the ink storage unit and the ink discharge unit.

5. The printing apparatus according to claim 3, wherein the control unit discards the ink in the ink ejection unit when the amount of ink consumed reaches a preset threshold.

6. The printing apparatus according to claim 4, wherein the control unit estimates the viscosity of the ink based on the unused period measured by the unused period measurement unit and the temperature measured by the temperature measurement unit, and discards the ink in the ink path if the estimated viscosity of the ink exceeds a preset threshold.

7. The printing apparatus according to claim 1, wherein the ink is a solvent ink having a viscosity in the low viscosity region within the normal ejection ink viscosity range of the ink ejection unit.

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