Inkjet printer

Abstract

Provided is an inkjet printer capable of suppressing a deterioration in the print quality of a medium caused by floating of the medium and variation in head gap, and reducing the manufacturing cost of a platen.　In the inkjet printer, a suction hole group 15b having a large number of suction holes 15a for suctioning a medium placed on a platen 15 is formed in the platen 15, the suction holes 15a being arranged in a main scanning direction. A linear groove 15c that is linear and recessed from the upper surface of the platen 15 and extends in the main scanning direction is formed in a part of the platen 15 where the suction hole group 15b is formed. Only the linear groove 15c is formed, as a groove for suctioning the medium, on the upper surface of the platen 15.

Description

Inkjet printer

[0001] The present invention relates to an inkjet printer that prints on a medium.

[0002] Inkjet printers that print on long media are known (see, for example, Patent Document 1). The inkjet printer described in Patent Document 1 includes an ink head that ejects ink onto the media, a carriage on which the ink head is mounted, a head movement mechanism that moves the carriage in the main scanning direction, a platen (support table) on which the media is placed during printing, and an adsorption device that adsorbs the media placed on the platen to the platen. The upper surface of the platen is a flat support surface that supports the media.

[0003] In the inkjet printer described in Patent Document 1, first to fifth grooves recessed downward are formed on the support surface of the platen. The first to fifth grooves are linear grooves extending in the main scanning direction. A number of suction holes are formed within the first to fifth grooves for sucking the medium. In this inkjet printer, the first and second grooves are aligned in the sub-scanning direction. A number of connecting grooves connecting the first and second grooves are formed on the support surface. The connecting grooves are linear grooves inclined with respect to the main scanning direction and the sub-scanning direction.

[0004] In the inkjet printer described in Patent Document 1, suction holes are formed in the first through fifth grooves, which are linear and long in the main scanning direction, making it difficult for the suction holes to be blocked by the medium placed on the support surface. Therefore, in this inkjet printer, the medium is sucked through the entire first through fifth grooves. Furthermore, in this inkjet printer, the medium is sucked through a connecting groove formed between the first and second grooves. Therefore, in this inkjet printer, it is possible to prevent the medium placed on the platen from floating up, thereby preventing a decrease in print quality of the medium due to the medium floating up.

[0005] Japanese Patent Application Laid-Open No. 2022-160826

[0006] On the other hand, in the inkjet printer described in Patent Document 1, because a connecting groove is formed between the first groove and the second groove, there is a risk that the distance between the portion of the medium placed on the platen between the first groove and the second groove and the underside of the inkjet head that ejects the ink may vary. In other words, with this inkjet printer, there is a risk that the head gap may vary between the first groove and the second groove.

[0007] Therefore, even though the inkjet printer described in Patent Document 1 can prevent a decrease in print quality of the medium due to lifting of the medium, there is a risk that print quality of the medium will decrease due to variations in the head gap between the first groove and the second groove. Also, in the inkjet printer described in Patent Document 1, multiple connecting grooves that are inclined with respect to the main scanning direction and the sub-scanning direction are formed between the first groove and the second groove, which may increase the manufacturing costs of the platen.

[0008] Therefore, an object of the present invention is to provide an inkjet printer that can suppress deterioration in print quality of a medium caused by floating of the medium and variations in the head gap, and can reduce the manufacturing costs of the platen.

[0009] In order to solve the above problems, the inkjet printer of the present invention comprises an inkjet head that ejects ink onto a medium, a platen that is positioned below the inkjet head and on which the medium is placed during printing, and a suction mechanism that sucks the medium placed on the platen onto the platen, the platen having a group of suction holes formed therein that are arranged in the main scanning direction, which is the width direction of the medium, for sucking the medium placed on the platen, the group of suction holes being for sucking the medium placed on the platen, the group of suction holes being arranged in the main scanning direction, which is the width direction of the medium, the portion of the platen where the group of suction holes is formed having linear grooves that are recessed from the top surface of the platen and extend in the main scanning direction, and the platen having only linear grooves formed as grooves recessed from the top surface of the platen.

[0010] In the inkjet printer of the present invention, linear grooves extending in the main scanning direction are formed in the portion of the platen where the suction hole group is formed, making it difficult for the suction holes to be blocked by the medium placed on the platen. This allows the medium to be sucked across the entire linear groove. This prevents the medium placed on the platen from floating up, thereby preventing a decrease in print quality due to the medium floating up. Furthermore, in the inkjet printer of the present invention, only linear grooves are formed in the platen as grooves recessed from the top surface of the platen, eliminating the head gap variation between the first and second grooves as seen in the inkjet printer described in Patent Document 1. This prevents a decrease in print quality due to head gap variation.

[0011] Furthermore, in the present invention, because only linear grooves are formed in the platen as grooves recessed from the top surface of the platen, it is possible to reduce the manufacturing costs of the platen compared to when multiple connecting grooves are formed between the first groove and the second groove, as in the inkjet printer described in Patent Document 1. In this way, the present invention makes it possible to suppress deterioration in print quality of the medium due to lifting of the medium, suppress deterioration in print quality of the medium due to variations in the head gap, and reduce the manufacturing costs of the platen.

[0012] In addition, when a heater for heating the medium is built into the platen, if multiple connection grooves are formed between the first groove and the second groove as in the inkjet printer described in Patent Document 1, the medium and the platen do not come into contact in the areas where the connection grooves are formed, making it difficult to achieve a uniform temperature distribution in the heated medium. In contrast, in the present invention, it is easier to achieve a uniform temperature distribution in the heated medium compared to when multiple connection grooves are formed between the first groove and the second groove.

[0013] In the present invention, the inkjet printer includes, for example, a heater for heating the medium before printing. According to the inventor's investigations, when the medium before printing is heated, the medium tends to stretch depending on the thickness and type of the medium, which can cause the medium placed on the platen to easily lift up. However, with the present invention, it is possible to prevent the medium placed on the platen from lifting up even when the medium before printing is heated.

[0014] In the present invention, for example, the platen is formed with four suction hole groups and four linear grooves spaced apart in the vertical direction and in the sub-scanning direction perpendicular to the main scanning direction, and the depth of the linear grooves is 0.3 mm or less.

[0015] As described above, the inkjet printer of the present invention can suppress deterioration in print quality of the medium caused by medium lifting and head gap variations, and can also reduce the manufacturing costs of the platen.

[0016] 4 is a side view for explaining the configuration of an inkjet printer according to an embodiment of the present invention. FIG. 5 is a perspective view of the platen shown in FIG. 1. FIG. 6 is a plan view of a portion of the platen shown in FIG. 2. FIG. 7 is an enlarged view of a portion E in FIG. 4.

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] (Overall Configuration of Inkjet Printer) FIG. 1 is a side view for explaining the configuration of an inkjet printer 1 according to an embodiment of the present invention.

[0019] The inkjet printer 1 (hereinafter referred to as "printer 1") of this embodiment is, for example, a commercial inkjet printer. The printer 1 includes a printing mechanism 3 that prints on a long medium 2 (sheet-like medium 2) such as paper, fabric, or a resin sheet, a medium transport mechanism 4 that transports the medium 2, a payout roll holding unit 6 that holds a payout roll 5 that is the medium 2 wound into a roll before printing, a take-up roll holding unit 8 that holds a take-up roll 7 that is the medium 2 wound into a roll after printing, and a heater 9 that heats the medium 2 before printing.

[0020] If the Y direction in FIG. 1, which is perpendicular to the up-down direction (vertical direction), is defined as the "left-right direction," then the width direction of the medium 2 coincides with the left-right direction. In the following description, the X direction in FIG. 1, which is perpendicular to the up-down and left-right directions, is defined as the "front-to-back direction." Furthermore, the X1 direction in FIG. 1, which is one side of the front-to-back direction, is defined as the "front" side, and the X2 direction in FIG. 1, which is the opposite side, is defined as the "rear" side. In this embodiment, the left-to-right direction (Y direction) is the main scanning direction, and the front-to-back direction (X direction) is the sub-scanning direction.

[0021] The printing mechanism 3 includes an inkjet head 12 (hereinafter referred to as "head 12") that ejects ink onto the medium 2, a carriage 13 on which the head 12 is mounted, a carriage drive mechanism that moves the carriage 13 back and forth in the main scanning direction (left and right direction), and a support frame (Y bar) 14 that supports the carriage 13 so that it can move left and right. The head 12 ejects ink downward. A plurality of nozzles that eject ink are formed on the underside of the head 12. The head 12 includes a piezoelectric element (piezo element) that ejects ink from the nozzles. The carriage drive mechanism includes, for example, a belt that is partially fixed to the carriage 13, a pulley around which the belt is stretched, and a motor that rotates the pulley.

[0022] In this embodiment, the ink ejected from the head 12 is ultraviolet-curable UV ink. The carriage 13 is equipped with an ultraviolet irradiator (not shown) that irradiates ultraviolet rays toward the medium 2 to cure the UV ink ejected from the head 12. The ultraviolet irradiator is equipped with an ultraviolet LED chip. The carriage 13 is also equipped with an ink heating mechanism (not shown) that heats the UV ink to reduce its viscosity. The ink heating mechanism heats the UV ink supplied to the head 12.

[0023] The printing mechanism 3 also includes a platen 15 on which the medium 2 is placed during printing, a platen frame 16 that supports the platen 15 from below, and a suction mechanism 17 that sucks the medium 2 placed on the platen 15 onto the platen 15. The platen 15 is located below the head 12 and the carriage 13. The platen 15 is formed in an elongated shape that is long and narrow in the left-right direction. The platen 15 is formed with a number of suction holes 15a (see FIG. 3) that suck the medium 2 placed on the platen 15. The suction holes 15a penetrate the platen 15 in the up-down direction. A number of suction holes 15a are formed throughout almost the entire area of ​​the platen 15. The thickness direction of the medium 2 when printing is performed by the printing mechanism 3 coincides with the up-down direction. The specific configuration of the platen 15 will be described later.

[0024] The platen frame 16 is formed in the shape of a rectangular groove (square groove) that is elongated in the left-right direction. The platen frame 16 is formed by bending a thin metal plate such as a steel plate into the rectangular groove shape. The top surface of the platen frame 16 is open. The platen 15 is fixed to the upper end of the platen frame 16, and the top surface of the platen frame 16 is closed by the platen 15. A space is formed inside the platen frame 16, defined by the platen frame 16 and the platen 15. The suction hole 15a is connected to this space.

[0025] The suction mechanism 17 includes multiple suction fans 18 disposed below the platen frame 16. The suction fans 18 are fixed to the bottom surface of the platen frame 16. The suction fans 18 suck air from the space defined by the platen frame 16 and the platen 15. That is, when the suction fans 18 are activated, the air inside the space defined by the platen frame 16 and the platen 15 is exhausted. Once the air inside the space defined by the platen frame 16 and the platen 15 is exhausted, the medium 2 is sucked onto the upper surface of the platen 15, and the medium 2 is held by the platen 15. The suction fans 18 are activated when printing on the medium 2.

[0026] The medium transport mechanism 4 transports the long medium 2 in the longitudinal direction of the medium 2. The medium transport mechanism 4 includes a transport roller 19 and a pad roller 20 that is disposed opposite the transport roller 19 and is biased toward the transport roller 19. The transport roller 19 and the pad roller 20 are disposed behind the platen 15. The transport roller 19 is connected to a drive mechanism that rotates the transport roller 19. The drive mechanism includes a motor as a drive source. The medium 2 is transported while sandwiched between the transport roller 19 and the pad roller 20. The medium 2 before printing is transported from the rear side to the top surface of the platen 15, and the medium 2 after printing is transported from the top surface of the platen 15 to the front side.

[0027] The payout roll holding unit 6 is disposed below the printing mechanism 3. The payout roll holding unit 6 includes a rotary shaft 23 that is inserted into the inner periphery of the payout roll 5. The take-up roll holding unit 8 is disposed below the printing mechanism 3. The take-up roll holding unit 8 includes a rotary shaft 24 that is inserted into the inner periphery of the take-up roll 7 and a drive mechanism that rotates the rotary shaft 24. The heater 9 is disposed between the feed roller 19 and pad roller 20 and the payout roll holding unit 6 in the transport direction of the medium 2. The heater 9 is covered by a cover. The heater 9 heats the medium 2 that is moving toward the platen 15.

[0028] (Configuration of Platen) Fig. 2 is a perspective view of the platen 15 shown in Fig. 1. Fig. 3 is a plan view of a portion of the platen 15 shown in Fig. 2. Fig. 4 is a side view of the platen 15 shown in Fig. 2. Fig. 5 is an enlarged view of part E in Fig. 4.

[0029] As described above, the platen 15 is formed in an elongated shape that is long and narrow in the left-right direction. The upper surface of the platen 15 serves as a medium placement surface on which the medium 2 is placed. As described above, the platen 15 is formed with a large number of suction holes 15a that penetrate the platen 15 in the up-down direction. The platen 15 also has suction hole groups 15b formed with a large number of suction holes 15a arranged in the left-right direction. In this embodiment, four suction hole groups 15b are formed in the platen 15 and are spaced apart in the front-to-rear direction (sub-scanning direction). Two of the four suction hole groups 15b are positioned adjacent to each other in front of the center of the platen 15 in the front-to-rear direction, and the remaining two suction hole groups 15b are positioned adjacent to each other behind the center of the platen 15 in the front-to-rear direction.

[0030] In the portion of the platen 15 where the suction hole groups 15b are formed, linear grooves 15c are formed that are recessed downward from the top surface of the platen 15 and extend in the left-right direction. That is, the suction hole groups 15b are formed within the linear grooves 15c. As described above, in this embodiment, four suction hole groups 15b are formed in the platen 15, spaced apart in the front-rear direction. Therefore, four linear grooves 15c are formed in the platen 15, spaced apart in the front-rear direction. That is, the linear grooves 15c are formed in all portions of the platen 15 where the suction hole groups 15b are formed. The hatched portions in FIG. 3 are the linear grooves 15c. The linear grooves 15c are long grooves that extend from the left end to the right end of the platen 15 in the left-right direction. That is, the linear grooves 15c are formed across the entire area of ​​the platen 15 in the left-right direction.

[0031] The linear grooves 15c are formed in shallow angular groove (square groove) shapes. The suction holes 15a are formed, for example, at the center positions of the linear grooves 15c in the front-rear direction. The width (front-rear direction width) of the linear grooves 15c is larger than the inner diameter of the suction holes 15a. For example, the width of the linear grooves 15c is about five times the inner diameter of the suction holes 15a. The depth D of the linear grooves 15c (specifically, the depth D of the linear grooves 15c from the top surface of the platen 15; see FIG. 5 ) is 0.3 mm or less. Only four linear grooves 15c are formed in the platen 15 as grooves recessed from the top surface of the platen 15. In other words, only the linear grooves 15c are formed in the top surface of the platen 15 as grooves for sucking the medium.

[0032] (Major Effects of the Present Embodiment) As described above, in the present embodiment, linear grooves 15c extending in the left-right direction are formed in the portion of the platen 15 where the suction hole groups 15b are formed, making it difficult for the suction holes 15a to be blocked by the medium 2 placed on the platen 15. As a result, in the present embodiment, the medium 2 can be sucked by the entire linear groove 15c. Therefore, in the present embodiment, it is possible to prevent the medium 2 placed on the platen 15 from floating up, and as a result, it is possible to prevent a decrease in the print quality of the medium 2 due to the medium 2 floating up.

[0033] In this embodiment, the heater 9 heats the medium 2 before printing, which can cause the medium 2 to stretch easily depending on the thickness and type of the medium 2, making the medium 2 placed on the platen 15 more likely to float up. However, in this embodiment, even if the medium 2 before printing is heated, it is possible to prevent the medium 2 placed on the platen 15 from floating up.

[0034] Furthermore, according to the inventor's investigations, in this embodiment, the UV ink ejected from the head 12 is heated by the ink heating mechanism, reaction heat is generated in the UV ink ejected onto the medium 2, and the substrate of the UV LED chip generates heat when ultraviolet light is irradiated onto the medium 2. As a result, the medium 2 placed on the platen 15 is heated by these factors, and depending on the thickness and type of the medium 2, the medium 2 is likely to stretch, causing the medium 2 placed on the platen 15 to easily lift up. Furthermore, according to the inventor's investigations, when a thin, inelastic, and brittle medium 2 is used, when the medium 2 is made of vinyl chloride, or when the ambient temperature of the printer 1 is low, the medium 2 placed on the platen 15 is likely to lift up. However, in this embodiment, it is possible to prevent the medium 2 placed on the platen 15 from lifting up.

[0035] In this embodiment, only linear groove 15c is formed in platen 15 as a groove recessed from the top surface of platen 15. Therefore, in this embodiment, there is no variation in the head gap between the first groove and the second groove, as in the inkjet printer described in Patent Document 1. Therefore, in this embodiment, it is possible to suppress deterioration in print quality of the medium 2 due to variation in the head gap. Furthermore, in this embodiment, because only linear groove 15c is formed in platen 15 as a groove recessed from the top surface of platen 15, it is possible to reduce the manufacturing cost of the platen 15 compared to the inkjet printer described in Patent Document 1, which has multiple connecting grooves formed between the first groove and the second groove.

[0036] (Other Embodiments) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0037] In the above-described embodiment, the linear grooves 15c do not have to be formed across the entire area of ​​the platen 15 in the left-right direction. Also, in the above-described embodiment, the depth D of the linear grooves 15c may be greater than 0.3 mm. Furthermore, in the above-described embodiment, two or three suction hole groups 15b spaced apart in the front-to-rear direction may be formed in the platen 15, or five or more suction hole groups 15b may be formed in the platen 15. Even in this case, the same number of linear grooves 15c as the number of suction hole groups 15b are formed. Also, in the above-described embodiment, the printer 1 may be provided with a heater for heating the medium 2 after printing. Also, the printer 1 does not have to be provided with a heater 9.

[0038] REFERENCE SIGNS LIST 1 Printer (inkjet printer) 2 Medium 9 Heater 12 Head (inkjet head) 15 Platen 15a Suction hole 15b Suction hole group 15c Linear groove 17 Suction mechanism D Depth of linear groove X Sub-scanning direction Y Main scanning direction

Claims

1. An inkjet printer comprising: an inkjet head which ejects ink onto a medium; a platen which is positioned below the inkjet head and on which the medium is placed during printing; and a suction mechanism for sucking the medium placed on the platen into the platen; wherein the platen is formed with a group of suction holes which are arranged in a main scanning direction which is the width direction of the medium and which suck the medium placed on the platen, the group of suction holes being arranged in a main scanning direction which is the width direction of the medium; in the portion of the platen where the group of suction holes is formed, a linear groove which is recessed from the top surface of the platen and extends in the main scanning direction; and wherein the top surface of the platen is formed with only the linear groove as a groove for sucking the medium.

2. An ink jet printer according to claim 1, further comprising a heater for heating said medium before printing.

3. An inkjet printer as described in claim 1 or 2, characterized in that the platen is formed with four groups of suction holes and four straight grooves arranged at intervals in the vertical direction and in the sub-scanning direction perpendicular to the main scanning direction.

4. The ink-jet printer according to claim 1 or 2, wherein the depth of said straight grooves is 0.3 mm or less.

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