Inkjet printing device

Abstract

An inkjet printing device is provided that can reduce ink ejection defects caused by drying and thickening of ink. [Solution] A heater 5 heats a platen 3 that supports a print medium P. Inkjet heads 41A, 41B eject ink onto the print medium P supported by the platen 3. A head lifting mechanism adjusts the distance between the inkjet heads 41A, 41B and the platen 3. A control unit 10 controls the head lifting mechanism for each of the inkjet heads 41A, 41B during a printing operation so that the distance between the inkjet head 41 and the platen 3 is wider during a period when there is no image data onto which ink is to be ejected than during a period when there is image data onto which ink is to be ejected.

Description

[Technical Field]

[0001] The present invention relates to inkjet printing devices. [Background technology]

[0002] In an inkjet printing device, ink ejection failure may occur due to drying and thickening of ink inside the nozzles that eject the ink.

[0003] For example, there is a serial inkjet printing device that performs printing while moving an inkjet head, in which a plurality of inkjet heads are arranged at different positions in the direction of movement.

[0004] In such an inkjet printing device, when one pass of printing begins, the inkjet heads begin ejecting ink sequentially, starting with the inkjet heads that are downstream in the direction of inkjet head movement. Therefore, the more upstream the inkjet heads are, the longer the idle running time becomes. The idle running of the inkjet heads is an operation in which the inkjet heads move without ejecting ink, in a state where there is no image data to eject ink onto.

[0005] Furthermore, when one pass of printing is completed, ink ejection is completed in sequence starting from the inkjet head on the downstream side, so the more downstream the inkjet head is, the longer the idle running time becomes.

[0006] When an inkjet head is idle, the ink inside the nozzles dries and thickens, which can lead to poor ink ejection from the nozzles. The longer the idle operation, the more likely such poor ink ejection occurs.

[0007] In particular, in inkjet printing devices that have a mechanism for heating the printing medium in order to dry the printing medium quickly, the ink inside the nozzles is likely to dry out and become thicker, which can easily lead to poor ink ejection as described above due to idle running.

[0008] A technology for suppressing ink ejection defects is disclosed in Patent Document 1. The printing device described in Patent Document 1 is equipped with a humidified air supply port that supplies humidified air to the support surface of a platen that supports a printing medium coated with a pretreatment liquid that contains a volatile component that reacts with ink.

[0009] This makes it possible to supply humidified air onto the printing medium when printing by ejecting ink from the nozzles of the head onto a printing medium coated with a pretreatment liquid, thereby making it difficult for the volatile components of the pretreatment liquid to volatilize and for the volatile components of the pretreatment liquid themselves to reach the nozzles, thereby preventing ink from coagulating due to a reaction between the ink in the nozzles and the volatile components of the pretreatment liquid, thereby preventing ink ejection defects. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2023-125791 Summary of the Invention [Problem to be solved by the invention]

[0011] The technique of Patent Document 1 can suppress ink ejection defects caused by a reaction between the ink and the volatile components of the pretreatment liquid, but is not effective against ink ejection defects caused by drying or thickening of the ink.

[0012] The present invention has been made in view of the above, and has an object to provide an inkjet printing apparatus that can reduce ink ejection defects caused by drying and thickening of ink. [Means for solving the problem]

[0013] In order to achieve the above object, the inkjet printing device of the present invention is characterized by comprising: a platen that supports a printing medium; a heating unit that heats the platen; a plurality of inkjet heads that eject ink onto the printing medium supported by the platen; an adjustment mechanism that adjusts the distance between each of the inkjet heads and the platen; and a control unit that controls the adjustment mechanism during printing operation so that, for each of the plurality of inkjet heads, the distance between the inkjet head and the platen is wider during periods when there is no image data onto which ink is to be ejected than during periods when there is image data onto which ink is to be ejected. [Effects of the Invention]

[0014] According to the inkjet printing apparatus of the present invention, it is possible to reduce ink ejection defects caused by drying and thickening of ink. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram of a head unit of the inkjet printing apparatus shown in FIG. [Figure 3] FIG. 2 is a control block diagram of the inkjet printing apparatus shown in FIG. [Figure 4] FIG. 10 is a diagram showing a state in which one inkjet head is disposed at a retracted position and the other inkjet head is disposed at a discharge position. [Figure 5] FIG. 10 is a diagram illustrating an example of the relationship between the distance from the platen and the air temperature. [Figure 6] FIG. 10 is a schematic configuration diagram of an inkjet printing apparatus according to a second embodiment. [Figure 7] FIG. 7 is a control block diagram of the inkjet printing apparatus shown in FIG. [Figure 8] FIG. 10 is a diagram showing a state in which one divided platen is disposed at a retracted position and the other divided platen is disposed at a reference position. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

[0017] The following embodiments are examples of devices that embody the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the materials, shapes, structures, arrangements, etc. of each component to those described below. The technical idea of ​​the present invention can be modified in various ways within the scope of the claims.

[0018] [First embodiment] FIG. 1 is a schematic diagram of an inkjet printing apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic diagram of a head unit of the inkjet printing apparatus shown in FIG. 1. FIG. 3 is a control block diagram of the inkjet printing apparatus shown in FIG. 1. In the following description, the up, down, front, and rear directions indicated by the arrows in FIG. 1 are defined as the up, down, front, and rear directions of the inkjet printing apparatus. Furthermore, the left and right directions as viewed from the front are defined as the left and right directions of the inkjet printing apparatus.

[0019] As shown in Figures 1 and 3, the inkjet printing device 1 according to the first embodiment includes a conveying section 2, a platen 3, a fan 4, a heater (corresponding to a heating section) 5, a main scanning drive guide 6, a main scanning drive motor 7, a head unit 8, a head lifting mechanism section (corresponding to an adjustment mechanism section) 9, a control section 10, and an exterior cover 11 that covers the head unit 8 and the like.

[0020] The transport unit 2 transports a printing medium P made of a strip of paper or the like. The transport unit 2 includes a supply drive motor 21, a transport roller 22, a pinch roller 23, a transport drive motor 24, a winding shaft 25, a winding drive motor 26, and printing medium guides 27 and 28.

[0021] The supply drive motor 21 rotates the core 31 of the printing medium roll 32, which is formed by winding the printing medium P around the core 31 in a roll shape. The printing medium roll 32 is disposed below the rear side of the platen 3.

[0022] The transport roller 22 transports the printing medium P unwound from the printing medium roll 32 toward the platen 3 while nipping the printing medium P between itself and the pinch roller 23. The transport roller 22 is disposed near the rear side of the platen 3.

[0023] The pinch roller 23 is in pressure contact with the transport roller 22 via the print medium P, and is rotated by the transport roller 22. The pinch roller 23 is disposed above the transport roller 22.

[0024] The transport drive motor 24 rotates the transport roller 22 .

[0025] The take-up shaft 25 takes up the printing medium P that is unwound from the printing medium roll 32 and transported via the platen 3. The take-up shaft 25 is disposed below the front side of the platen 3.

[0026] The winding drive motor 26 rotates the winding shaft 25 .

[0027] The print medium guide 27 guides the print medium P between the print medium roll 32 and the transport roller 22. The print medium guide 28 guides the print medium P between the platen 3 and the take-up shaft 25.

[0028] The platen 3 supports the print medium P. The platen 3 is formed in an elongated shape extending in the left-right direction. The platen 3 has a plurality of suction holes formed therein for suctioning air.

[0029] The fan 4 sucks air through the suction holes in the platen 3 to generate a suction force in the suction holes, thereby adsorbing the print medium P onto the platen 3 .

[0030] The heater 5 heats the platen 3. The heater 5 heats the platen 3 in order to quickly dry the printing medium P onto which ink has been ejected by warming the printing medium P. The heater 5 is disposed on the lower surface of the platen 3.

[0031] The main scanning drive guide 6 guides the head unit 8 to move in the left-right direction (main scanning direction). The main scanning drive guide 6 is formed in an elongated shape that extends in the left-right direction.

[0032] The main scanning drive motor 7 moves the head unit 8 in the left and right directions.

[0033] The head unit 8 ejects ink onto the print medium P while moving left and right (corresponding to a predetermined direction) to perform printing. The head unit 8 is movable between a position to the right of the right edge of the print medium P and a position to the left of the left edge of the print medium P. As shown in FIGS. 1 to 3, the head unit 8 includes inkjet heads 41A, 41B and a carriage 42. Note that the alphabetical subscripts in the reference numerals of the inkjet heads 41A, 41B, etc. may be omitted to refer to them collectively.

[0034] The inkjet head 41 has a plurality of nozzles (not shown) formed on a nozzle surface 41a, which is the lower surface facing the platen 3, and ejects ink from the nozzles.

[0035] 2, the two inkjet heads 41A and 41B are arranged in a staggered manner. That is, the inkjet heads 41A and 41B are spaced apart from each other in the left-right direction and are arranged at different positions in the front-to-rear direction. In this embodiment, the inkjet head 41B is arranged to the left and rear of the inkjet head 41A.

[0036] The carriage 42 holds the inkjet heads 41A and 41B. The carriage 42 is formed in a hollow box shape. The carriage 42 holds the inkjet heads 41A and 41B by inserting their lower ends into openings formed in a bottom plate 42a.

[0037] Note that the carriage 42 may be provided with a member against which the inkjet heads 41A, 41B are abutted in order to position the inkjet heads 41A, 41B at the ejection positions. This allows the inkjet heads 41A, 41B to be positioned at the ejection positions with high accuracy. Here, the ejection position of the inkjet head 41 is the height position when ejecting ink, which is the height position of the inkjet heads 41A, 41B in FIG. 2.

[0038] The head lifting mechanism 9 raises and lowers the inkjet heads 41A and 41B to adjust the distance between the inkjet heads 41A and 41B and the platen 3. The head lifting mechanism 9 raises and lowers the inkjet heads 41A and 41B individually, thereby making it possible to individually adjust the distance between the inkjet heads 41A and 41B and the platen 3. The head lifting mechanism 9 has a lifting mechanism such as a cam type or a ball screw type, and a motor (neither of which is shown) that drives the lifting mechanism.

[0039] The control unit 10 controls the overall operation of the inkjet printing apparatus 1. The control unit 10 is configured with a CPU, RAM, ROM, a hard disk, and the like.

[0040] Specifically, the control unit 10 moves the head unit 8 in the main scanning direction, ejects ink from the inkjet head 41 based on the image data of the print target, and performs one pass of printing, and then causes the transport unit 2 to transport the print medium P forward by a predetermined amount. Next, the control unit 10 moves the head unit 8 in the reverse direction, performs the next pass of printing, and then moves the print medium P forward by a predetermined amount. The control unit 10 prints an image on the print medium P by alternately repeating this one pass of printing and transporting the print medium P.

[0041] During this printing operation, the control unit 10 controls the head lifting mechanism 9 to increase the distance between the inkjet head 41 and the platen 3 during the idle period for each of the inkjet heads 41A and 41B compared to the non-idle period. Specifically, the control unit 10 controls the head lifting mechanism 9 to position each of the inkjet heads 41A and 41B at the aforementioned ejection position during the non-idle period. The control unit 10 also controls the head lifting mechanism 9 to position each of the inkjet heads 41A and 41B at a retracted position retracted above the ejection position during the idle period for each of the inkjet heads 41A and 41B.

[0042] Here, the idle period of the inkjet head 41 is a period during which the inkjet head 41 performs an idle operation. The idle operation of the inkjet head 41 is an operation in which the inkjet head 41 moves without performing an ink ejection operation in a state in which there is no image data to which ink is to be ejected.

[0043] The non-idling period of the inkjet head 41 is a period during which the inkjet head 41 has image data to eject ink onto, and during which the inkjet head 41 performs the ink ejection operation.

[0044] Next, the printing operation of the inkjet printing apparatus 1 will be described.

[0045] In the inkjet printing device 1, in a standby state before the start of a printing operation, the head unit 8 is disposed to the right of the right edge of the printing medium P or to the left of the left edge of the printing medium P. Here, it is assumed that the head unit 8 is disposed to the right of the right edge of the printing medium P.

[0046] When a command to start printing is given, the control unit 10 starts driving the fan 4 and heater 5. Here, the control unit 10 adjusts the temperature of the heater 5 so that the temperature of the platen 3 is a temperature that corresponds to the type of print medium P. The more difficult the type of print medium P is to dry, the higher the temperature of the platen 3 is set to.

[0047] Next, the control unit 10 controls the main scanning drive motor 7 to move the head unit 8 to the left, while controlling the inkjet head 41 based on the image data to eject ink, thereby printing the first pass.

[0048] In the printing operation of this first pass, the inkjet head 41B on the downstream side in the movement direction of the head unit 8 in this pass reaches the printing medium P, and then the inkjet head 41A on the upstream side reaches the printing medium P. The inkjet heads 41A and 41B perform an idle running operation until they each reach the printing medium P and start ejecting ink. During this idle running period when this idle running operation is being performed, the inkjet heads 41A and 41B are positioned at the retracted position.

[0049] Here, the control unit 10 sets the distance from the platen 3 during the inkjet head 41's idle period in accordance with the temperature of the platen 3, which is adjusted in accordance with the type of print medium P as described above. Specifically, the control unit 10 adjusts the retracted position of the inkjet head 41 to a position in accordance with the temperature of the platen 3. The higher the temperature of the platen 3, the higher the retracted position of the inkjet head 41 is set to. In other words, the higher the temperature of the platen 3, the greater the distance between the inkjet head 41 positioned in the retracted position and the platen 3.

[0050] The distance between the inkjet head 41 and the platen 3 during the idle period of the inkjet head 41, which depends on the temperature of the platen 3, is set to a distance that can prevent the ink in the nozzles from drying out and thickening while preventing the distance between the inkjet head 41 and the platen 3 from becoming excessively large. The distance between the inkjet head 41 and the platen 3 during the idle period of the inkjet head 41, which depends on the temperature of the platen 3, is set, for example, based on experiments.

[0051] When the idle period until the ink ejection operation starts ends in each of the inkjet heads 41A and 41B, the control unit 10 moves the inkjet heads 41A and 41B from the retracted position to the ejection position at the timing when the respective non-idle period starts.

[0052] For example, in the first pass printing operation, when the downstream inkjet head 41B reaches the printing medium P and the non-idle period begins, and the upstream inkjet head 41A is still in the idle period, as shown in Figure 4, the inkjet head 41A is positioned in the retracted position and the inkjet head 41B is positioned in the ejection position.

[0053] During the non-idling periods of the inkjet heads 41A and 41B, the ink ejection operation is performed by the inkjet heads 41A and 41B that are positioned at the ejection positions.

[0054] At the end of the printing operation of the first pass, the head unit 8 stops to the left of the left edge of the printing medium P. The inkjet heads 41A and 41B perform free running operation from the end of the ink ejection operation until the head unit 8 stops. Therefore, the control unit 10 moves the inkjet heads 41A and 41B from the ejection position to the retracted position at the timing when the ink ejection operation of each head is completed (the non-free running period is completed).

[0055] When the printing operation of the first pass is completed, the control unit 10 causes the transport unit 2 to transport the printing medium P forward by a predetermined amount.

[0056] Next, the control unit 10 moves the head unit 8 to the right, which is the opposite direction to the printing operation of the first pass, while controlling the inkjet head 41 to eject ink based on the image data, thereby printing the second pass.

[0057] During the printing operation of this second pass, the control unit 10 controls the inkjet heads 41A and 41B to be placed in the retracted position during the free-running period and to be placed in the ejection position during the non-free-running period, just as during the printing operation of the first pass described above.

[0058] When the printing operation of the second pass is completed, the control unit 10 causes the transport unit 2 to transport the printing medium P forward by a predetermined amount.

[0059] Thereafter, the control unit 10 performs printing on the printing medium P by alternately repeating the printing operation for one pass and the movement of the printing medium P in the same manner.

[0060] During one pass of printing, an idle period may occur during a non-idle period of inkjet heads 41A and 41B. Even during such an idle period, control unit 10 places inkjet heads 41A and 41B in the retracted position.

[0061] Furthermore, in a printing operation for one pass, at least one of the inkjet heads 41A and 41B may not have image data onto which ink is to be ejected for the entire period of one pass. For an inkjet head 41 that does not have image data onto which ink is to be ejected for the entire period of one pass, the entire period of one pass becomes an idle period, and therefore the control unit 10 positions the inkjet head 41 at the retracted position for the entire period of one pass.

[0062] When the inkjet head 41 runs idle, the ink inside the nozzles dries and thickens, which can result in poor ink ejection. In the inkjet printing device 1, the platen 3 is heated by the heater 5, and the heat from this increases the risk of poor ink ejection due to the ink drying and thickening inside the nozzles. Furthermore, when using ink with a high solvent evaporation rate or ink that dries quickly, such as ink with a high solid content or a high resin content, poor ink ejection due to the ink drying and thickening inside the nozzles is more likely to occur.

[0063] In contrast, in the inkjet printing device 1, as described above, the inkjet heads 41A and 41B are placed in the retracted positions during their respective idle periods, thereby increasing the distance between them and the platen 3 compared to non-idle periods. This makes the inkjet heads 41A and 41B less susceptible to the heat of the platen 3 during the idle periods, preventing the ink in the nozzles from drying out and thickening.

[0064] An example of the relationship between the distance from the platen 3 and the air temperature is shown in Fig. 5. In the example of Fig. 5, the temperature of the platen 3 is 45°C and the room temperature is 23.4°C.

[0065] The distance between the nozzle surface 41a of the inkjet head 41 at the ejection position and the platen 3 is, for example, 2 to 5 mm. Note that a distance of 2 to 5 mm between the inkjet head 41 and the platen 3 allows ink droplets of several picoliters to several tens of picoliters to be ejected with high precision at an ejection speed of about 5 to 10 m / s.

[0066] 5, when the platen 3 is heated, the temperature of the air is relatively high at a distance of about 2 to 5 mm from the platen 3, and therefore the temperature around the nozzle surface 41a of the inkjet head 41 at the ejection position is relatively high, which can cause the ink in the nozzles to dry out and become thicker.

[0067] 5, the air temperature drops significantly just by moving the head 10 to 15 mm away from the platen 3. Therefore, by increasing the distance between the nozzle surface 41a of the inkjet head 41 and the platen 3, it is possible to effectively prevent the ink in the nozzles from drying out and thickening.

[0068] As described above, in the inkjet printing apparatus 1, the control unit 10 controls the head lifting mechanism 9 for each of the inkjet heads 41A and 41B during printing operations so that the distance between the inkjet head 41 and the platen 3 is wider during the idle running period than during the non-idle running period. This makes the inkjet heads 41A and 41B less susceptible to the heat of the platen 3 during the idle running period, when the ink in the nozzles is likely to dry out and thicken. As a result, it is possible to reduce ink ejection defects caused by the ink drying out and thickening in the nozzles of the inkjet heads 41A and 41B.

[0069] Furthermore, in the inkjet printing device 1, the head lifting mechanism 9 moves the inkjet heads 41A and 41B individually to individually adjust the distance between the inkjet heads 41A and 41B and the platen 3. This makes it possible to increase the distance between each inkjet head 41 and the platen 3 during the idle period compared to the non-idle period.

[0070] Furthermore, in the inkjet printing device 1, the control unit 10 sets the distance from the platen 3 during the idle period of the inkjet head 41 in accordance with the temperature of the platen 3. This prevents the distance between the inkjet head 41 and the platen 3 from being excessively widened, and further reduces ink ejection defects caused by drying and thickening of the ink in the nozzles of the inkjet head 41.

[0071] [Second embodiment] Next, a second embodiment, which is a partial modification of the first embodiment, will be described.

[0072] Fig. 6 is a schematic diagram of an inkjet printing apparatus according to the second embodiment, and Fig. 7 is a control block diagram of the inkjet printing apparatus shown in Fig. 6.

[0073] As shown in Figures 6 and 7, the inkjet printing apparatus 1A of the second embodiment has a configuration in which the platen 3, fan 4, heater 5, and head lifting mechanism 9 of the inkjet printing apparatus 1 of the first embodiment described above are replaced with a platen 51, fans 52A and 52B, heaters 53A and 53B, and a platen lifting mechanism (corresponding to an adjustment mechanism) 54, respectively.

[0074] The platen 51 is obtained by dividing the platen 3 of the first embodiment into two in the front-to-rear direction and is composed of two divided platens 56A and 56B. The divided platens 56A and 56B are positioned opposite the inkjet heads 41A and 41B, respectively. A plurality of suction holes for suctioning air are formed in each of the divided platens 56A and 56B. The divided platens 56A and 56B can be raised and lowered independently.

[0075] Note that members against which the split platens 56A, 56B abut may be provided around the split platens 56A, 56B to position the split platens 56A, 56B at the reference position. This allows the split platens 56A, 56B to be positioned at the reference position with high precision. Here, the reference position of the split platen 56 is the height position of the split platen 56 when the inkjet head 41 corresponding to that split platen 56 performs an ink ejection operation, which is the height position of the split platens 56A, 56B in FIG. 6.

[0076] The fans 52A and 52B suck air through the suction holes of the divided platens 56A and 56B, respectively, to generate suction force in the suction holes, thereby attracting the print medium P onto the divided platens 56A and 56B.

[0077] The heaters 53A and 53B heat the divided platens 56A and 56B, respectively. The heaters 53A and 53B are disposed on the lower surfaces of the divided platens 56A and 56B, respectively.

[0078] The platen lifting mechanism 54 adjusts the distance between the inkjet heads 41A, 41B and the split platens 56A, 56B by raising and lowering the split platens 56A, 56B. By raising and lowering the split platens 56A, 56B individually, the platen lifting mechanism 54 can individually adjust the distance between the inkjet head 41A and the split platen 56A, and the distance between the inkjet head 41B and the split platen 56B. The platen lifting mechanism 54 has a lifting mechanism such as a cam type or a ball screw type, and a motor (neither of which is shown) that drives the lifting mechanism.

[0079] In the inkjet printing apparatus 1A, the control unit 10 controls the platen lifting mechanism 54 for each of the inkjet heads 41A and 41B during a printing operation so that the distance between the inkjet head 41 and the platen 51 (divided platen 56) is greater during the idle period than during the non-idle period. Specifically, the control unit 10 controls the head lifting mechanism 9 for each of the inkjet heads 41A and 41B so that the divided platen 56 corresponding to that inkjet head 41 is positioned at the reference position described above during the non-idle period. The control unit 10 also controls the platen lifting mechanism 54 for each of the inkjet heads 41A and 41B so that the divided platen 56 corresponding to that inkjet head 41 is positioned at a retracted position retracted downward from the reference position during the idle period.

[0080] For example, when inkjet head 41A is in an idling period and inkjet head 41B is in a non-idling period, split platen 56A is located at the retracted position and split platen 56B is located at the reference position, as shown in FIG.

[0081] During printing, the control unit 10 stops the fan 52 corresponding to the divided platen 56 that is positioned in the retracted position. When the divided platen 56 is positioned in the reference position, the control unit 10 drives the fan 52 corresponding to that divided platen 56 to attract the printing medium P to that divided platen 56.

[0082] Also, in the second embodiment, as in the first embodiment, the control unit 10 sets the distance between the inkjet head 41 and the platen 51 (split platen 56) during the inkjet head 41's idle period in accordance with the temperature of the platen 51 (split platen 56). In the second embodiment, the control unit 10 adjusts the retracted position of the split platen 56 to a position in accordance with the temperature of the platen 51. The retracted position of the split platen 56 is set to a lower position as the temperature of the platen 51 increases. In other words, the higher the temperature of the platen 51, the greater the distance between the inkjet head 41 and the split platen 56 arranged in the retracted position.

[0083] Even when at least one of the divided platens 56A, 56B is positioned in the retracted position, the transport roller 22, the pinch roller 23, and the print medium guides 27, 28 allow the print medium P to be transported.

[0084] As described above, in the inkjet printing apparatus 1A of the second embodiment, the control unit 10 controls the platen lifting mechanism 54 during printing operations to increase the distance between the inkjet head 41 and the platen 51 (split platen 56) for each of the inkjet heads 41A and 41B during the idle running period compared to the non-idle running period. As a result, in the second embodiment, as in the first embodiment, the inkjet heads 41A and 41B are less susceptible to the heat of the platen 51 during the idle running period, when the ink in the nozzles is likely to dry out and thicken. As a result, poor ink ejection caused by the ink drying out and thickening in the nozzles of the inkjet heads 41A and 41B can be reduced.

[0085] Furthermore, in the inkjet printing apparatus 1A, the platen lifting mechanism 54 moves the divided platens 56A, 56B individually to individually adjust the distance between the inkjet heads 41A, 41B and the platen 51. As a result, in the second embodiment, as in the first embodiment, it is possible to increase the distance between each inkjet head 41 and the platen 51 during the idle running period compared to the non-idle running period.

[0086] [Other embodiments] As described above, the present invention has been described by the first and second embodiments, but the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0087] In the second embodiment described above, a configuration was described in which inkjet heads 41A and 41B are arranged at different positions in a direction (front-to-back direction) perpendicular to the direction in which the head unit 8 moves (left-to-right direction), and split platens 56A and 56B corresponding to the inkjet heads 41A and 41B, respectively.

[0088] However, the number of inkjet heads and split platens is not limited to this. Furthermore, the number of inkjet heads and the number of split platens may be different. It is sufficient that the inkjet heads are arranged at one of a number of different positions equal to or less than the number of inkjet heads, and the platen is divided into a number of split platens corresponding to the positions in a direction perpendicular to the direction of movement of the inkjet heads. For example, four inkjet heads may be arranged in pairs at two different positions in a direction perpendicular to the direction of movement of the inkjet heads, and the platen may be divided into two split platens corresponding to these positions.

[0089] In the first and second embodiments described above, the distance between the inkjet head 41 and the platens 3, 51 during the idle period is set in accordance with the temperature of the platens 3, 51. However, the present invention is not limited to this, and for example, the distance between the inkjet head 41 and the platens 3, 51 during the idle period may be set to a fixed distance regardless of the temperature of the platens 3, 51.

[0090] In the first and second embodiments described above, the inkjet printing device 1 is a serial type in which two inkjet heads 41 are arranged in a staggered manner. However, the number and arrangement of the inkjet heads are not limited to this, and the inkjet printing device is not limited to a serial type.

[0091] For example, in a line-type inkjet head having multiple inkjet heads arranged in parallel, a platen, and a heating unit that heats the platen, during printing operation, for each of the multiple inkjet heads, during a period when there is no image data to be ejected onto, the inkjet head may be moved upward, thereby widening the distance between the inkjet head and the platen compared to during a period when there is image data to be ejected onto.

[0092] As such, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specifying matters according to the scope of the claims that are appropriate from the above description.

[0093] [Note] The present application discloses the following inventions.

[0094] (Appendix 1) a platen for supporting the print medium; a heating unit that heats the platen; a plurality of inkjet heads that eject ink onto a printing medium supported by the platen; an adjustment mechanism for adjusting a distance between each of the inkjet heads and the platen; a control unit that controls the adjustment mechanism unit to increase the distance between each of the inkjet heads and the platen during a period when there is no image data to be ejected with ink, compared to a period when there is image data to be ejected with ink; and An inkjet printing apparatus comprising:

[0095] (Appendix 2) The inkjet printing device described in Appendix 1, characterized in that the adjustment mechanism unit individually adjusts the distance between each inkjet head and the platen by moving each inkjet head individually.

[0096] (Appendix 3) the inkjet heads eject ink while moving in a predetermined direction; each of the inkjet heads is disposed at any one of a plurality of different positions in a direction perpendicular to the predetermined direction, the number of positions being equal to or less than the number of the inkjet heads; the platen is divided into a plurality of divided platens corresponding to the plurality of positions in a direction perpendicular to the predetermined direction, The inkjet printing device described in Appendix 1, characterized in that the adjustment mechanism unit individually adjusts the distance between each inkjet head and the platen by individually moving each divided platen.

[0097] (Appendix 4) The control unit controlling the heating unit to adjust the temperature of the platen according to the type of print medium; 4. The inkjet printing device according to claim 1, wherein the distance between the inkjet head and the platen during a period when there is no image data to be ejected with ink is set according to the temperature of the platen. [Explanation of symbols]

[0098] 1,1A Inkjet Printing Device 2. Conveyor section 3,51 Platen 4,52A,52B Fan 5, 53A, 53B heater 6 Main scanning drive guide 7 Main scanning drive motor 8 Head Unit 9 Head lifting mechanism 10 Control Unit 11 Exterior cover 21 Supply drive motor 22 Conveyor roller 23 Pinch roller 24 Transport drive motor 25 Winding shaft 26 Winding drive motor 27,28 Print Media Guide 31 Core body 32 rolls of printing media 41, 41A, 41B Inkjet head 42 Carriage 54 Platen lifting mechanism 56, 56A, 56B Split Platen

Claims

1. a platen for supporting the print medium; a heating unit that heats the platen; a plurality of inkjet heads that eject ink onto a printing medium supported by the platen; an adjustment mechanism for adjusting a distance between each of the inkjet heads and the platen; a control unit that controls the adjustment mechanism unit to increase the distance between each of the inkjet heads and the platen during a period when there is no image data to be ejected with ink, compared to a period when there is image data to be ejected with ink; and An inkjet printing apparatus comprising:

2. 2. The inkjet printing apparatus according to claim 1, wherein the adjustment mechanism adjusts the distance between each of the inkjet heads and the platen individually by moving each of the inkjet heads individually.

3. the inkjet heads eject ink while moving in a predetermined direction; each of the inkjet heads is disposed at any one of a plurality of different positions in a direction perpendicular to the predetermined direction, the number of positions being equal to or less than the number of the inkjet heads; the platen is divided into a plurality of divided platens corresponding to the plurality of positions in a direction perpendicular to the predetermined direction, 2. The inkjet printing apparatus according to claim 1, wherein the adjustment mechanism individually adjusts the distance between each of the inkjet heads and the platen by individually moving each of the divided platens.

4. The control unit controlling the heating unit to adjust the temperature of the platen according to the type of print medium; 4. The inkjet printing apparatus according to claim 1, wherein the distance between the inkjet head and the platen during a period when there is no image data to be ejected with ink is set in accordance with the temperature of the platen.

Images