Inkjet recording device

Abstract

To improve image quality even when a recording medium is a medium having a high coefficient of thermal expansion.SOLUTION: An inkjet recording device includes: an image formation unit for forming an image by discharging an ultraviolet curable ink to a recording medium; and a positioning unit for positioning the recording medium before the recording medium is fed to the image formation unit. The image formation unit includes a heating unit for heating the recording medium carried on an outer peripheral surface of an image formation drum, where a preheating unit for preheating the recording medium before the recording medium is fed to the image formation unit is installed upstream of the positioning unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] In the field of inkjet recording devices, images are often formed using ultraviolet-curable ink (hereinafter referred to as UV ink) (see Patent Documents 1 and 2, etc.). An inkjet recording device according to the prior art includes an image forming unit that ejects UV ink onto a recording medium while conveying the recording medium in a conveyance direction to form an image. The image forming unit has an image forming drum that rotates while carrying the recording medium on its outer circumferential surface. The image forming drum has a plurality of claws on its outer circumferential surface that grip the leading edge of the recording medium. The outer circumferential surface of the image forming drum is provided with a plurality of suction portions that suck the recording medium. With the leading edge of the recording medium gripped by the plurality of claws, the recording medium is sucked by the plurality of suction portions, whereby the recording medium is supported on the outer circumferential surface of the image forming drum.

[0003] In image formation using UV ink, it is necessary to improve the wettability of the UV ink on the recording medium from the viewpoint of image quality, and the image forming unit has a heating unit that heats the recording medium carried on the outer peripheral surface of the image forming drum, and also has an inkjet head that ejects the UV ink onto the recording medium carried on the outer peripheral surface of the image forming drum. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5967237 [Patent Document 2] Patent No. 5811101 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the recording medium is a medium with a high thermal expansion coefficient, such as a resin sheet, heating the recording medium carried on the outer peripheral surface of the image forming drum can cause the recording medium to bulge due to thermal expansion between adjacent claws or suction portions. In such cases, the bulged portion of the recording medium may come into contact with the inkjet head, or the UV ink ejected from the inkjet head may land misaligned on the recording medium, resulting in a decrease in the image quality of the inkjet recording device.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inkjet recording apparatus that can improve image quality even when the recording medium has a high coefficient of thermal expansion. [Means for solving the problem]

[0007] One aspect of the inkjet recording apparatus of the present invention is an image forming unit that ejects ultraviolet curable ink onto a recording medium while conveying the recording medium in a conveyance direction, and forms an image; a stacking unit provided upstream of the image forming unit for stacking a plurality of recording media; a positioning unit that positions the recording medium supplied from the stacking unit before sending the recording medium to the image forming unit, The image forming unit includes: an image forming drum having a plurality of claws on its outer peripheral surface for gripping the leading edge of the recording medium, and a plurality of suction portions formed on its outer peripheral surface for suctioning the recording medium, the image forming drum rotating while carrying the recording medium on its outer peripheral surface; a heating unit that heats the recording medium carried on the outer peripheral surface of the image forming drum, Furthermore, a pre-heating section is provided upstream of the positioning section and pre-heats the recording medium before it is sent to the image forming section. [Effects of the Invention]

[0008] According to the present invention, the image quality of an inkjet recording apparatus can be improved even if the recording medium has a high thermal expansion coefficient. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic front view of an inkjet recording apparatus according to this embodiment. [Figure 2] FIG. 2 is an enlarged view of part II in FIG. [Figure 3] FIG. 3 is a schematic perspective view of the image forming drum. [Figure 4] FIG. 4 is a schematic bottom view of the head unit, showing a state in which multiple inkjet heads are attached to a carriage. [Figure 5] FIG. 5 is a schematic diagram illustrating another embodiment of the pre-heating unit. [Figure 6] FIG. 6 is a control block diagram of the inkjet recording apparatus according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] This embodiment will be described below with reference to the drawings. In this embodiment, the transport direction refers to the transport direction in which the recording medium is transported. The downstream side refers to the downstream side of the transport direction, and the upstream side refers to the upstream side of the transport direction. The transport width direction refers to the direction perpendicular to the transport direction. Furthermore, in this embodiment, the X-axis direction refers to the main scanning direction, which is the transport width direction. The Y-axis direction refers to the sub-scanning direction, which is the transport direction.

[0011] The configuration of an inkjet recording apparatus 10 according to this embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a schematic front view of the inkjet recording apparatus 10 according to this embodiment. FIG. 2 is an enlarged view of part II in FIG. 1. FIG. 3 is a schematic perspective view of the image forming drum 40. FIG. 4 is a schematic bottom view of the head unit 62, showing a state in which multiple inkjet heads 66 are attached to the carriage 64. FIG. 5 is a schematic view illustrating another aspect of the pre-heating section.

[0012] As shown in Fig. 1, the inkjet recording apparatus 10 according to this embodiment is a single-pass recording apparatus that forms (prints) an image on the recording medium P while moving the recording medium P in the transport direction. The recording medium P is a medium with a high coefficient of thermal expansion, such as a resin sheet (resin film) made of a resin such as polyethylene terephthalate resin, polyurethane resin, or polyethylene resin. In addition to media with a high coefficient of thermal expansion, various media such as plain paper, coated paper, or other paper, or fabric may also be used as the recording medium P.

[0013] The inkjet recording device 10 includes a device main body 12 that extends in the left-right direction in Fig. 1. The device main body 12 includes a center frame 14, a first side frame 16 disposed on one side of the center frame 14, and a second side frame 18 disposed on the other side of the center frame 14.

[0014] The center frame 14 is provided with an image forming unit 20 that ejects UV ink onto the recording medium P to form (print) an image while transporting the recording medium P in the transport direction. UV ink is ink that solidifies when irradiated with ultraviolet light during image formation. UV ink is in a gel state at room temperature and changes to a sol state when heated. The specific configuration of the image forming unit 20 will be described later.

[0015] 1 and 2, the first side frame 16 is provided with a first stacking section 22 for stacking a plurality of recording media P before image formation. The first stacking section 22 has a plate-shaped loading tray 24 for loading the recording media P, and the loading tray 24 is provided on the first side frame 16 so as to be movable in the vertical direction. The loading tray 24 is configured to move up and down depending on the amount of recording media P to be loaded, and the uppermost recording medium P is held at a predetermined height.

[0016] A transport section 26 is provided between the image forming section 20 and the first stacking section 22 to transport the recording medium P sent out from the loading tray 24 in the transport direction. The transport section 26 is arranged from the first side frame 16 to the center frame 14. The transport section 26 has a plurality of rotatable support rollers 28 and a plurality of endless belts 30 that are provided to be wound around the support rollers 28. Each support roller 28 extends in the X-axis direction (transport width direction), and the support rollers 28 are rotated by the drive of a transport motor (not shown). The belts 30 are arranged at intervals in the X-axis direction.

[0017] The conveying unit 26 is provided with a plurality of registration units 32 as positioning units that position the recording medium P supplied from the first stacking unit 22 before sending the recording medium P to the image forming unit 20. The registration units 32 are arranged at intervals in the X-axis direction, and each registration unit 32 has an abutment surface 32f for abutting the leading edge of the recording medium P. Each registration unit 32 is configured to be tiltable by a tilting motor (not shown) or a cam mechanism (not shown). The conveying unit 26 also has a plurality of conveying guides 34 that guide the recording medium P in the conveying direction between the first stacking unit 22 and the registration units 32. Each conveying guide 34 is arranged between adjacent belts 30.

[0018] The belt 30 is rotated by the rotation of the multiple support rollers 28, thereby transporting the recording medium P supplied from the loading tray 24 in the transport direction. The recording medium P is then positioned at a predetermined position on the transport unit 26 so that the leading edge of the recording medium P abuts against the abutment surfaces 32f of the multiple registration units 32 and is parallel to the X-axis direction. Then, the registration units 32 are tilted, and the belt 30 is rotated by the rotation of the multiple support rollers 28, thereby sending the recording medium P from the transport unit 26 to the image forming unit 20.

[0019] A supply unit 36 ​​serving as a medium supply unit that supplies the uppermost recording medium P stacked on the loading tray 24 to the transport unit 26 is provided above the first stacking unit 22 on the first side frame 16. In addition, a spray unit 38 serving as an air spray unit is provided near the first stacking unit 22 on the first side frame. The spray unit 38 sprays separating air to separate the uppermost recording medium P stacked on the loading tray 24 from the recording media P below it.

[0020] 1 to 3, the image forming unit 20 has an image forming drum 40 that rotates while carrying a recording medium P on its outer circumferential surface, and the image forming drum 40 is rotatably mounted on a center frame 14. With the recording medium P carried on the outer circumferential surface of the image forming drum 40, the image forming drum 40 is rotated by driving a rotary motor (not shown) for the image forming drum, thereby transporting the recording medium P in the transport direction.

[0021] The outer peripheral surface of the image forming drum 40 is formed with a plurality of (e.g., three) recesses 42 extending in the X-axis direction, and the recesses 42 are arranged at equal intervals along the outer peripheral surface of the image forming drum 40. Each recess 42 of the image forming drum 40 is provided with a plurality of first claws 44 that grip the leading end of the recording medium P in cooperation with the outer peripheral surface of the image forming drum 40, and the first claws 44 are arranged at intervals in the X-axis direction. In other words, the image forming drum 40 has a plurality of first claws 44 at a plurality of locations (e.g., three locations) on its outer peripheral surface, and the image forming drum 40 can support a plurality of (e.g., three) recording media P on its outer peripheral surface. The first claws 44 are configured to be switchable between an open state and a closed state. The first claws 44 grip the leading end of the recording medium P by switching from the open state to the closed state. The operation of the first claws 44 will be described later.

[0022] A plurality of first suction portions 46 that suction the recording medium P are provided on the outer peripheral surface of the image forming drum 40. The suction method of the plurality of first suction portions 46 may be either suction suction or electrostatic suction. With the plurality of first claw portions 44 gripping the leading end of the recording medium P, the plurality of first suction portions 46 suction the recording medium P, thereby supporting the recording medium P on the outer peripheral surface of the image forming drum 40. The operation of the plurality of first suction portions 46 will be described later.

[0023] The image forming unit 20 has a delivery drum 48 that delivers the recording medium P sent from the registration unit 32 side to the image forming drum 40, and the delivery drum 48 rotates while supporting the recording medium P on its outer circumferential surface. The delivery drum 48 is rotatably provided between the image forming drum 40 and the registration unit 32 in the center frame 14. The delivery drum 48 is configured to rotate in the direction opposite to the rotation direction of the image forming drum 40, in conjunction with the rotation of the image forming drum 40. The delivery drum 48 is configured to rotate one full rotation when the image forming drum 40 makes one-third of a rotation.

[0024] A recess 50 extending in the X-axis direction is formed on the outer peripheral surface of the transfer drum 48. A plurality of second claws 52 are provided in the recess 50 of the transfer drum 48 to grip the leading end of the recording medium P in cooperation with the outer peripheral surface of the transfer drum 48, and the plurality of second claws 52 are arranged at intervals in the X-axis direction. In other words, the transfer drum 48 has a plurality of second claws 52 on its outer peripheral surface. The plurality of second claws 52 are configured to be switchable between an open state and a closed state. The plurality of second claws 52 grip the leading end of the recording medium P by switching from the open state to the closed state. The operation of the plurality of second claws 52 will be described later.

[0025] A plurality of second suction sections 54 that suction the recording medium P are provided on the outer peripheral surface of the delivery drum 48. The suction method of the plurality of second suction sections 54 may be either suction suction or electrostatic suction. With the plurality of second claw sections 52 gripping the leading end of the recording medium P, the plurality of second suction sections 54 suction the recording medium P, thereby supporting the recording medium P on the outer peripheral surface of the delivery drum 48. The operation of the plurality of second suction sections 54 will be described later.

[0026] The image forming unit 20 has a swing arm 56 that supports the leading edge of the recording medium P sent out from the conveying unit 26. The swing arm 56 is provided in the center frame 14 between the conveying unit 26 and the delivery drum 48 so as to be able to swing. The swing arm 56 supports the recording medium P on the conveying unit 26 and delivers it to the delivery drum 48, allowing the multiple second claws 52 to grip the leading edge of the recording medium P.

[0027] The transfer drum 48 may be omitted from the configuration of the image forming unit 20. In this case, the swing arm 56 carries the recording medium P on the transport unit 26 and transfers it to the image forming drum 40. The transfer drum 48 and the swing arm 56 may also be omitted from the configuration of the image forming unit 20. In this case, the transport unit 26 transfers the recording medium P to the image forming drum 40 from its downstream end.

[0028] 1, the image forming unit 20 has a medium heating unit 58 for heating the recording medium P carried on the image forming drum 40, and the medium heating unit 58 is provided downstream of the delivery drum 48 in the center frame 14. The medium heating unit 58 is disposed opposite the outer circumferential surface of the image forming drum 40. The medium heating unit 58 has, for example, an infrared heater or the like, and heats the image forming drum 40 and the recording medium P so that the temperature of the recording medium P carried on the outer circumferential surface of the image forming drum 40 falls within a predetermined temperature range.

[0029] The image forming unit 20 has a temperature sensor 60 as a temperature detection unit that detects the temperature of the recording medium P carried on the image forming drum 40, and the temperature sensor 60 is provided immediately downstream of the medium heating unit 58 in the center frame 14. The temperature sensor 60 is disposed opposite the outer circumferential surface of the image forming drum 40. The temperature sensor 60 may be a non-contact type such as a thermopile sensor.

[0030] The image forming unit 20 may have a medium heating unit (not shown) for heating the recording medium P carried on the delivery drum 48. The image forming unit 20 may have a temperature sensor (not shown) as a temperature detection unit for detecting the temperature of the recording medium P carried on the delivery drum 48.

[0031] As shown in FIGS. 1 and 4, the image forming unit 20 has a plurality of head units 62 that form images by ejecting UV ink onto the recording medium P carried on the image forming drum 40. The plurality of head units 62 are arranged downstream of a temperature sensor 60 (medium heating unit 58). The plurality of head units 62 correspond to four colors of ink: yellow (Y), magenta (M), cyan (C), and black (K). The plurality of head units 62 corresponding to the four colors of ink, Y, M, C, and K, are arranged at intervals along the transport direction. Each head unit 62 is held by a respective carriage 64 that is provided on the center frame 14 so as to be movable in the main scanning direction. In other words, each head unit 62 is provided on the center frame 14 so as to be movable in the X-axis direction (main scanning direction) via the respective carriage 64.

[0032] Each head unit 62 has a plurality of inkjet heads 66 that eject UV ink onto the recording medium P, and the plurality of inkjet heads 66 are mounted on a carriage 64. A plurality of nozzles 66n for ejecting UV ink are formed at the tip of each inkjet head 66. The plurality of inkjet heads 66 are arranged, for example, in a staggered pattern along the X-axis direction. In other words, each head unit 62 constitutes a line head that includes a plurality of inkjet heads 66. Note that FIG. 4 conceptually illustrates the plurality of inkjet heads 66.

[0033] As shown in FIG. 1, the image forming unit 20 has a fixing unit 68 for fixing the UV ink onto the recording medium P, and the fixing unit 68 is provided downstream of the multiple head units 62 on the center frame 14. The fixing unit 68 is disposed opposite the outer circumferential surface of the image forming drum 40. The fixing unit 68 has a light-emitting unit that irradiates ultraviolet rays. The light-emitting unit of the fixing unit 68 irradiates ultraviolet rays onto the ink ejected onto the recording medium P, thereby curing the UV ink and fixing it to the recording medium P.

[0034] The image forming unit 20 has an image reading unit 70 that reads the image formed on the recording medium P, and the image reading unit 70 is provided downstream of the fixing unit 68 on the center frame 14. The image reading unit 70 is disposed opposite the outer circumferential surface of the image forming drum 40. The image reading unit 70 is configured by an in-line sensor in which multiple detection elements are arranged along the X-axis direction.

[0035] As shown in FIG. 1, the image forming unit 20 has a delivery unit 72 that transports the fixed recording medium P from the image forming drum 40 in the transport direction. The delivery unit 72 is provided across the center frame 14 and the second side frame 18. The delivery unit 72 has a plurality of rotatable support rollers 74, an endless belt 76 that is provided so as to be wound around the plurality of support rollers 74, and a transfer drum 78 that transfers the recording medium P from the image forming drum 40 to the belt 76. The transfer drum 78 is configured to rotate in a direction opposite to the rotation direction of the image forming drum 40 in conjunction with the rotation of the image forming drum 40. A transport motor (not shown) is driven to rotate the plurality of support rollers 74, causing the belt 76 to rotate, thereby transporting the recording medium P sent out from the image forming drum 40 in the transport direction.

[0036] As shown in Figures 1 and 2, in the image forming unit 20, the operations of the multiple first claw portions 44, the multiple first suction portions 46, the multiple second claw portions 52, and the multiple second suction portions 54 are performed as follows.

[0037] When the rotation of the transfer drum 48 positions the plurality of second claws 52 at a position corresponding to the swing arm 56 (the downstream end of the conveying section 26), the second claws 52 switch from an open state to a closed state and grip the leading end of the recording medium P carried by the swing arm 56. Then, while the transfer drum 48 rotates, the plurality of second suction sections 54 suction the recording medium P, allowing the transfer drum 48 to receive the recording medium P from the swing arm 56.

[0038] Next, when the rotation of the transfer drum 48 positions the plurality of second claw portions 52 at positions corresponding to the image forming drum 40, the second claw portions 52 switch from the closed state to the open state, and release the gripped state of the recording medium P. Then, as the transfer drum 48 rotates, the plurality of second suction portions 54 release the suctioned state of the recording medium P. Also, when the rotation of the image forming drum 40 positions the plurality of first claw portions 44 at positions corresponding to the transfer drum 48, the second claw portions 54 switch from the open state to the closed state, and grip the leading end of the recording medium P carried on the outer peripheral surface of the transfer drum 48. Then, as the image forming drum 40 rotates, the plurality of first suction portions 46 attract the recording medium P. This allows the recording medium P to be transferred from the transfer drum 48 to the image forming drum 40.

[0039] After the image is formed on the recording medium P, when the rotation of the image forming drum 40 positions the multiple first claw portions 44 at a position corresponding to the transfer drum 78, the multiple first claw portions 44 switch from the closed state to the open state, and release the gripped state of the recording medium P. Then, while the image forming drum 40 rotates, the multiple first suction portions 46 release the suction state of the recording medium P. This allows the recording medium P to be transferred from the image forming drum 40 to the transfer drum 78.

[0040] The image forming unit 20 may include a front-to-back reversing drum (not shown) for double-sided printing, as disclosed in, for example, JP-A-2021-120319.

[0041] 1, the second side frame 18 is provided with a second stacking section 80 for stacking a plurality of recording media P on which images have been formed. The second stacking section 80 has a plate-shaped loading tray 82 for loading the recording media P on which images have been formed. The second stacking section 80 stores the recording media P until the user removes the recording media P from the loading tray 82.

[0042] As shown in FIG. 2, the conveyance guide 34, located upstream of the registration unit 32, is provided with a pre-heating heater 84, which pre-heats the entire recording medium P before sending the recording medium P to the image forming unit 20. The pre-heating heater 84 may be an infrared heater. The pre-heating heater 84 heats the recording medium P on the conveyance unit 26 so that the temperature of the recording medium P reaches a predetermined target temperature. The predetermined target temperature may be the lower limit temperature of the predetermined temperature range, which is the heating temperature of the medium heating unit 58, or may be a temperature lower than the lower limit temperature of the predetermined temperature range. The predetermined target temperature is not limited to a specific temperature, but may be a temperature range having a certain width.

[0043] A temperature sensor 86 serving as a temperature detection unit that detects the temperature of the recording medium P on the conveyance unit 26 is provided above the conveyance unit 26 on the first side frame 16. The temperature sensor 86 may be a non-contact type such as a thermopile sensor.

[0044] Instead of providing the heater 84 as a pre-heating section in the conveyance guide 34, the spray unit 38 that sprays the separation air may be changed to a hot air spray unit 88 that serves as a hot air spray section that sprays hot air as the separation air flow. In other words, instead of using the heater 84 as a pre-heating section, the hot air spray unit 88 provided upstream of the registration section 32 may be used. In this case, a temperature sensor (not shown) may be provided above the first stacking section 22 in the first side frame 16 as a temperature detection section that detects the temperature of the uppermost recording medium P stacked on the loading tray 24.

[0045] 5, instead of using the heater 84 or the hot air injection unit as a pre-heating section, a hot air blower 92 that blows hot air into a cover member 90 that covers at least a part of the first stacking section 22 may be used. In other words, instead of using the heater 84 or the hot air injection unit 88 as a pre-heating section, a hot air blower 92 provided upstream of the registration section 32 may be used. In this case, a temperature sensor (not shown) may be provided at an appropriate position on the cover member 90 as a temperature detection section that detects the temperature of the uppermost recording medium P stacked on the loading tray 24.

[0046] As shown in FIGS. 2 and 5, a size detection unit 94 that detects the size of the recording medium P in the X-axis direction (width direction) is provided above the conveying unit 26 on the first side frame 16. The size detection unit 94 detects the size of the recording medium P in the X-axis direction after it has been heated to a predetermined target temperature. The size detection unit 94 may also detect the size of the recording medium P in the X-axis direction before it has been pre-heated by the heater 84. The size detection unit 94 has multiple reflective optical sensors arranged along the X-axis direction, and detects the difference in reflectance between the recording medium P and other components to detect the size of the recording medium P in the X-axis direction. Note that instead of detecting the size of the recording medium P in the X-axis direction, the size detection unit 94 may also detect the size of the recording medium P in the Y-axis direction (length direction). The size detection unit 94 may also detect the sizes of the recording medium P in both the X-axis and Y-axis directions.

[0047] The control configuration of the inkjet recording apparatus 10 according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a control block diagram of the inkjet recording apparatus 10 according to this embodiment.

[0048] 6, the inkjet recording apparatus 10 includes a control unit 96 that controls the image forming unit 20, the first stacking unit 22, the conveying unit 26, the registration unit 32, the supply unit 36, the ejection unit 38, and pre-heating units such as the heater 84. The control unit 96 is responsible for controlling the entire inkjet recording apparatus 10. The control unit 96 includes a CPU (Central Processing Unit) 98, a ROM (Read Only Memory) 100, and a RAM (Random Access Memory) 102. A storage unit 104 and a communication unit 106 are connected to the control unit 96.

[0049] The CPU 98 controls the overall operation of the inkjet recording apparatus 10. The CPU 98 reads out various control programs and setting data stored in the ROM 100, stores them in the RAM 102, and executes the programs to perform various arithmetic processing. The RAM 102 also provides the CPU 98 with a working memory space and stores temporary data. The RAM 102 may include a non-volatile memory.

[0050] When performing various types of arithmetic processing, the CPU 98 refers to various types of data stored in the storage unit 104. The storage unit 104 is configured by, for example, a nonvolatile semiconductor memory or a hard disk drive.

[0051] The storage unit 104 stores a predetermined target temperature to be heated by the heater 84 or the like as a pre-heating unit, in association with material information and thickness information of the recording medium P. When the storage unit 104 stores the predetermined target temperature, a table may be used. Furthermore, the storage unit 104 stores the thermal expansion coefficient of the recording medium P in association with size information of the recording medium P. When the storage unit 104 stores the thermal expansion coefficient of the recording medium P, a table may be used. The size information of the recording medium P is size information of the recording medium P in the X-axis direction (width direction), but may also be size information of the recording medium P in the Y-axis direction (length direction). The size information of the recording medium P may also be size information of the recording medium P in the X-axis and Y-axis directions.

[0052] The control unit 96 transmits and receives various data to and from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network) via the communication unit 106. The control unit 96 receives, for example, a print job transmitted from an external device, and controls the image forming unit 20 based on image data included in the print job. The communication unit 106 is configured, for example, by a communication control card such as a LAN card.

[0053] The control unit 96 is connected to temperature sensors 60, 86, etc. As a result, the control unit 96 monitors the temperature of the recording medium P being heated by the medium heating unit 58 based on the detection results from the temperature sensor 60. The control unit 96 monitors the temperature of the recording medium P being heated by a pre-heating unit such as the heater 84 based on the detection results from the temperature sensor 86, etc. In addition, the control unit 96 is connected to a size detection unit 94. As a result, the control unit 96 obtains size information of the recording medium P after being heated by a pre-heating unit such as the heater 84 based on the detection results from the size detection unit 94.

[0054] As shown in FIG. 6, the control unit 96 (CPU 98) has the following configuration by executing various control programs.

[0055] Based on the material information and thickness information of the recording medium P included in the print job, the control unit 96 acquires the predetermined target temperature stored in the storage unit 104. In other words, the control unit 96 acquires the predetermined target temperature stored in association with the material information and thickness information of the recording medium P included in the print job.

[0056] The control unit 96 controls the pre-heating unit such as the heater 84 based on the detection results from the temperature sensor 86 etc. so that the temperature of the recording medium P becomes a predetermined target temperature. In other words, the control unit 96 controls the heater 84 so that the temperature of the recording medium P detected by the temperature sensor 86 becomes the acquired predetermined target temperature. The control unit 96 may also control the hot air blower 88 so that the temperature of the recording medium P detected by the temperature sensor becomes the acquired predetermined target temperature. The control unit 96 may also control the hot air blower 92 so that the temperature of the recording medium P detected by the temperature sensor becomes the acquired predetermined target temperature.

[0057] Based on the size information of the recording medium P included in the print job, the control unit 96 acquires the thermal expansion coefficient of the recording medium P stored in the storage unit 104. In other words, the control unit 96 acquires the thermal expansion coefficient of the recording medium P associated with the size information of the recording medium P included in the print job.

[0058] The control unit 96 corrects the image size included in the image data in accordance with the thermal expansion of the recording medium P due to heating by a pre-heating unit such as the heater 84. Specifically, the control unit 96 calculates the amount of thermal expansion of the recording medium P due to heating by a pre-heating unit such as the heater 84, based on the acquired coefficient of thermal expansion of the recording medium P and the temperature of the recording medium P before and after heating by a pre-heating unit such as the heater 84. Then, the control unit 96 calculates a correction amount for correcting the image size based on the calculated amount of thermal expansion of the recording medium P, and corrects the image size taking that correction amount into account.

[0059] The control unit 96 may calculate a correction amount for correcting the image size based on the size of the recording medium before and after heating by a pre-heating unit such as the heater 84. In other words, the control unit 96 may calculate the amount of thermal expansion of the recording medium P caused by heating by a pre-heating unit such as the heater 84 based on the size of the recording medium before and after heating by a pre-heating unit such as the heater 84.

[0060] The control unit 96 controls the medium heating unit 58 based on the detection result from the temperature sensor 60 so that the temperature of the recording medium P carried on the image forming drum 40 falls within a predetermined temperature range.

[0061] As described above, the inkjet recording apparatus 10 according to this embodiment is configured such that a pre-heating unit, such as the heater 84, is provided upstream of the registration unit 32, which serves as a positioning unit. The pre-heating unit, such as the heater 84, pre-heats the entire recording medium P before the recording medium P is sent to the image forming unit 20. This allows the entire recording medium P to be thermally expanded in advance before the recording medium P is sent to the image forming unit 20. This prevents the recording medium P from rising between adjacent first claws 44 and first suction units 46 when the recording medium P supported on the outer peripheral surface of the image forming drum 40 is heated, even if the recording medium P is a medium with a high thermal expansion coefficient, such as a resin sheet. As a result, contact between the recording medium P and the inkjet head 66 and deviation in the impact of UV ink ejected from the inkjet head 66 on the recording medium P can be reduced.

[0062] In particular, when the image forming unit 20 has a transfer drum 48, when the recording medium P carried on the outer peripheral surface of the transfer drum 48 is heated, it is possible to prevent the recording medium P from rising between adjacent second claw portions 52 and second suction portions 54. Furthermore, by heating the recording medium P carried on the outer peripheral surface of the transfer drum 48, it is possible to further prevent the recording medium P from rising between adjacent first claw portions 44 and first suction portions 46 when the recording medium P carried on the outer peripheral surface of the image forming drum 40 is heated.

[0063] Therefore, according to the inkjet recording apparatus 10 of this embodiment, even if the recording medium P is a medium with a high thermal expansion coefficient such as a resin sheet, the image quality of the inkjet recording apparatus 10 can be improved.

[0064] Furthermore, according to the configuration of the inkjet recording apparatus 10 of this embodiment, as described above, the control unit 96 controls the pre-heating unit, such as the heater 84, based on the detection results from the temperature sensor 86, etc., so that the temperature of the recording medium P reaches a predetermined target temperature. Therefore, the entire recording medium P can be thermally expanded appropriately before being sent to the image forming unit 20. This makes it possible to further prevent the recording medium P from rising between adjacent first claw portions 44 and first suction portions 46 when the recording medium P held on the outer circumferential surface of the image forming drum 40 is heated. As a result, it is possible to further prevent contact between the recording medium P and the inkjet head 66 and deviation in the landing position of UV ink on the recording medium P.

[0065] Therefore, according to the inkjet recording apparatus 10 of this embodiment, even if the recording medium P is a medium with a high thermal expansion coefficient such as a resin sheet, the image quality of the inkjet recording apparatus 10 can be further improved.

[0066] Furthermore, according to the inkjet recording apparatus 10 of this embodiment, as described above, the control unit 96 acquires the predetermined target temperature stored in the storage unit 104 based on the material information and thickness information of the recording medium P. Therefore, even if the type of recording medium P to be printed is changed, the predetermined target temperature can be automatically set according to the changed recording medium P.

[0067] Therefore, according to the inkjet recording apparatus 10 of this embodiment, before the recording medium P is sent to the image forming unit 20, the heating operation of the pre-heating unit such as the heater 84 can be stably performed.

[0068] Furthermore, according to the inkjet recording apparatus 10 of this embodiment, as described above, the control unit 96 corrects the image size included in the image data in accordance with the thermal expansion of the recording medium P caused by heating by a pre-heating unit such as the heater 84. Therefore, it is possible to automatically adjust the image size in accordance with the thermal expansion of the recording medium P.

[0069] In particular, image size adjustment can be performed efficiently when the correction amount for correcting the image size is calculated based on the thermal expansion coefficient of the recording medium P and the temperature of the recording medium P before and after heating by a pre-heating unit such as the heater 84. Furthermore, image size adjustment can be performed efficiently when the correction amount for correcting the image size is calculated based on the size of the recording medium before and after heating by a pre-heating unit such as the heater 84.

[0070] Therefore, according to the inkjet recording apparatus 10 of this embodiment, the size of the image formed on the recording medium P can be stabilized.

[0071] Although the present embodiment has been specifically described above, the present invention is not limited to the specific embodiment described above. Various modifications and changes to the specific examples described in the above embodiment are possible within the scope of the gist of the present invention as defined in the claims. [Industrial Applicability]

[0072] The present invention is useful as an inkjet recording apparatus that can improve image quality even when the recording medium has a high thermal expansion coefficient. [Explanation of symbols]

[0073] 10. Inkjet recording device 12 Device body 14 Center Frame 16 First side frame 18 Second side frame 20 Image forming unit 22 First loading section 24 Loading tray 26 Conveyor 28 Support Roller 30 Belt 32 Registration section (positioning section) 32f Contact surface 34 Transport guide 36 Supply Unit 38 Injection unit (air injection part) 40 Image forming drum 42 recess 44 1st claw part 46 1st suction part 48 Delivery drum 50 recess 52 2nd claw part 54 2nd adsorption part 56 Swingarm 58 Medium heating section 60 Temperature sensor (first temperature detection unit) 62 Head Unit 64 Carriage 66 Inkjet head 68 Fixing section 70 Image reading unit 72 Delivery Department 74 Support Roller 76 Belt 78 Delivery drum 80 Second Loading Section 82 Loading tray 84 Heating heater (pre-heating section) 86 Temperature sensor (second temperature detection unit) 88 Warm air injection unit (warm air injection unit, pre-heating unit) 90 Cover member 92 Warm air blower (pre-heating section) 94 Size detection unit 96 Control Unit 98 CPU 100 ROM 102 RAM 104 Storage section 106 Communications Department

Claims

1. an image forming unit that ejects ultraviolet curable ink onto a recording medium while conveying the recording medium in a conveyance direction, and forms an image; a stacking unit provided upstream of the image forming unit for stacking a plurality of recording media; a positioning unit that positions the recording medium supplied from the stacking unit before sending the recording medium to the image forming unit, The image forming unit includes: an image forming drum having a plurality of claws on its outer peripheral surface for gripping the leading edge of the recording medium, and a plurality of suction portions for suctioning the recording medium on its outer peripheral surface, the image forming drum rotating while carrying the recording medium on its outer peripheral surface; a heating unit that heats the recording medium carried on the outer peripheral surface of the image forming drum, The image forming apparatus further includes a pre-heating unit provided upstream of the positioning unit and pre-heating the recording medium before sending it to the image forming unit. Inkjet recording device.

2. The image forming unit includes: a transfer drum having a plurality of second claws on its outer peripheral surface for gripping the leading edge of the recording medium, a plurality of second suction portions formed on its outer peripheral surface for suctioning the recording medium, the transfer drum rotating while carrying the recording medium on its outer peripheral surface, and the transfer drum transferring the recording medium sent from the positioning portion side to the image forming drum; The inkjet recording apparatus according to claim 1 .

3. a temperature detection unit that detects the temperature of the recording medium; 2. The inkjet recording apparatus according to claim 1, further comprising: a control unit that controls the pre-heating unit based on a detection result from the temperature detection unit so that the temperature of the recording medium becomes a target temperature.

4. a storage unit that stores the target temperature in association with material information and thickness information of the recording medium; the control unit acquires the target temperature stored in the storage unit based on material information and thickness information of the recording medium. The inkjet recording apparatus according to claim 3 .

5. the control unit controls the image forming unit based on the image data, and corrects the image size included in the image data in accordance with thermal expansion of the recording medium caused by heating by the pre-heating unit. The inkjet recording apparatus according to claim 3 .

6. a storage unit that stores the thermal expansion coefficient of the recording medium in association with size information of the recording medium; the control unit acquires a coefficient of thermal expansion of the recording medium based on size information of the recording medium, and calculates a correction amount for correcting the image size based on the acquired coefficient of thermal expansion of the recording medium and the temperatures of the recording medium before and after heating by the pre-heating unit. The inkjet recording apparatus according to claim 5 .

7. a size detection unit for detecting the size of the recording medium; the control unit calculates a correction amount for correcting the image size based on the size of the recording medium before and after heating by the pre-heating unit. The inkjet recording apparatus according to claim 5 .

8. the pre-heating unit is a heater provided in a transport guide that guides the recording medium in the transport direction between the stacking unit and the positioning unit; The inkjet recording apparatus according to claim 1 .

9. the pre-heating unit is a hot air injection unit that injects hot air as a separation air flow for separating the uppermost recording medium stacked on the stacking unit from the recording medium below it, The inkjet recording apparatus according to claim 1 .

10. The pre-heating unit is a hot air blower that blows hot air into a cover member that covers at least a portion of the loading unit. The inkjet recording apparatus according to claim 1 .

11. The recording medium is a resin film. The inkjet recording apparatus according to claim 1 .

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