Inkjet recording device

Abstract

In an inkjet recording device, when the distance between the center position in the transport direction of the discharge area R of the pre-processing head (5) and the axial position of the upstream support roller (25) is defined as a first reference distance (d1), and the distance between the center position in the transport direction of the discharge area (R) of the post-processing head (6) and the axial position of the downstream support roller (26) is defined as a second reference distance (d2), the reference distance (second reference distance (d2) in FIG. 7) of the pre-processing head (5) or post-processing head (6) which discharges a smaller amount of liquid (post-processing head (6) in FIG. 7) is set smaller than the reference distance (first reference distance (d1) in FIG. 7) of the head which discharges a larger amount of liquid.

Description

[Technical field]

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

[0002] An inkjet recording device such as an inkjet printer includes an ink head that ejects ink droplets for forming an image onto a recording medium. For example, when the recording medium is a fiber sheet such as a woven or knitted fabric or a plastic sheet, it may be necessary to apply a pretreatment liquid or a posttreatment liquid to the recording medium before and after ejecting the ink droplets onto the recording medium. The pretreatment liquid is, for example, a treatment liquid for improving the fixation of the ink droplets onto the recording medium and the coagulation of the ink pigment. The posttreatment liquid is, for example, a treatment liquid for improving the robustness of the printed image. In this case, the inkjet recording device includes, in addition to the ink head, a treatment head that ejects droplets of the pretreatment liquid and the posttreatment liquid.

[0003] The ink head and each processing head have a plurality of ejection holes for ejecting droplets of the respective ejection target liquids, and an ejection surface in which the plurality of ejection holes open.

[0004] During recording processing, the recording medium is transported in a predetermined transport direction by a transport mechanism, and ink droplets and processing liquid droplets are ejected from the ejection holes of the ink head and each processing head.

[0005] The transport mechanism includes an endless transport belt disposed in a position facing the ink head and each processing head, a drive roller, and a driven roller.

[0006] The drive roller and the driven roller are disposed at a distance from each other in the transport direction. The transport belt has a transport surface disposed at a distance from the ink droplet ejection side of the ink head, and transports the recording medium on the transport surface in the transport direction by rotating while being wrapped around the drive roller and the driven roller. Summary of the Invention

[0007] An inkjet recording apparatus according to one aspect of the present disclosure includes a head group including an ink head having an ejection region for ejecting an ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid, a conveyor belt having a conveying surface facing the head group with a gap on the ejection region side and moving in a circular movement along a conveying direction to convey a recording medium on the conveying surface along the conveying direction, a pair of rollers arranged at an interval from each other in the conveying direction and around which the conveyor belt is wound, and an upstream support roller and a downstream support roller arranged side by side in the conveying direction between the pair of rollers and supporting the conveyor belt from an inner side of the belt. and a support roller, the pre-processing head, the ink head, and the post-processing head are arranged in this order from the upstream side to the downstream side in the transport direction, and when a distance in the transport direction between a center position in the transport direction of the ejection area in the pre-processing head and an axial position of the upstream support roller is defined as a first reference distance, and a distance in the transport direction between a center position in the transport direction of the ejection area in the post-processing head and an axial position of the downstream support roller is defined as a second reference distance, one of the first and second reference distances from the pre-processing head or the post-processing head ejecting a smaller amount of liquid is smaller than the other of the first and second reference distances from the pre-processing head or the post-processing head ejecting a larger amount of liquid.

[0008] According to another aspect of the present disclosure, there is provided an inkjet recording apparatus comprising: a head group including an ink head having an ejection region for ejecting ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid; a transport belt having a transport surface facing the head group with a gap on the ejection region side and transporting a recording medium on the transport surface along the transport direction by moving in a circular movement along the transport direction; a pair of rollers arranged at an interval from each other in the transport direction and around which the transport belt is wound; and an upstream support roller and a downstream support roller arranged side by side in the transport direction between the pair of rollers and supporting the transport belt from an inner side of the belt; The processing heads are arranged in this order from the upstream side to the downstream side in the transport direction, the amount of liquid ejected from the post-processing head is set to be less than the amount of liquid ejected from the pre-processing head, the distance in the transport direction between the center of the transport direction of the ejection area of ​​the pre-processing head and the axial position of the upstream support roller is set to be equal to the distance in the transport direction between the center of the transport direction of the ejection area of ​​the post-processing head and the axial position of the downstream support roller, and when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the post-processing head is located within the inter-roller area of ​​the transport belt between the contact line with the upstream support roller and the contact line with the downstream support roller.

[0009] An inkjet recording apparatus according to another aspect of the present disclosure includes a head group including an ink head having an ejection region for ejecting ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid, a transport belt having a transport surface facing the head group with a gap on the ejection region side and transporting a recording medium on the transport surface along the transport direction by moving in a circular movement along the transport direction, a pair of rollers arranged at an interval from each other in the transport direction and around which the transport belt is wound, and an upstream support roller and a downstream support roller arranged side by side in the transport direction between the pair of rollers and supporting the transport belt from an inner side of the belt, the pre-processing heads are arranged in this order from the upstream side to the downstream side in the transport direction, the amount of liquid ejected from the pre-processing head is set to be less than the amount of liquid ejected from the post-processing head, the distance in the transport direction between the center position in the transport direction of the ejection area of ​​the pre-processing head and the axial position of the upstream support roller is set to be equal to the distance in the transport direction between the center position in the transport direction of the ejection area of ​​the post-processing head and the axial position of the downstream support roller, and when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the pre-processing head is located within the inter-roller area of ​​the transport belt between the contact line with the upstream support roller and the contact line with the downstream support roller. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing the overall configuration of an inkjet printer (inkjet recording apparatus) according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is an enlarged side view showing the carriage mounting location of the inkjet printer as viewed from the left side. [Figure 4]FIG. 4 is a side view, including a partial cross section, showing the support structure at the left end of the downstream support roller. [Diagram 5] FIG. 5 is a schematic plan view of the carriage as viewed from above. [Figure 6] FIG. 6 is a schematic plan view showing the ejection surfaces of the ink head, the pre-treatment head, and the post-treatment head. [Figure 7] FIG. 7 is an explanatory plan view for explaining the positional relationship between each head mounted on a carriage, and the upstream support rollers and downstream support rollers. [Figure 8] FIG. 8 is a view corresponding to FIG. 7 and showing a modified example of the first embodiment. [Figure 9] FIG. 9 is a view corresponding to FIG. 7 and showing the second embodiment. [Figure 10] FIG. 10 is a view corresponding to FIG. 9 (or FIG. 7) and shows a modified example of the second embodiment. [Figure 11] FIG. 11 is a view corresponding to FIG. 6 and showing another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the following, an inkjet recording apparatus according to each embodiment of the present disclosure will be described with reference to the drawings. In these embodiments, an inkjet printer equipped with an ink head that ejects ink droplets for forming an image on a wide and long recording medium is exemplified as a specific example of an inkjet recording apparatus. Inkjet printers are suitable for digital textile printing that uses an inkjet method to print images such as characters and patterns on a recording medium made of fabric such as woven fabric or knitted fabric. Of course, the inkjet recording apparatus according to the present disclosure can also be used for printing various inkjet images on recording media such as paper sheets and resin sheets.

[0012] (First embodiment)

[0013] [Overall configuration of inkjet printer] FIG. 1 is a perspective view showing the overall configuration of an inkjet printer 1 (an example of an inkjet recording device) according to a first embodiment of the present disclosure, and FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG.

[0014] The inkjet printer 1 is a printer that prints images on a wide and long workpiece W (recording medium) using an inkjet method, and includes an equipment frame 10, a workpiece transport section 20 incorporated in the equipment frame 10, a carriage 3 positioned above the workpiece transport section 20, and a rail support base 40 supported from below by the equipment frame 10.

[0015] In this embodiment, the left-right direction is the main scanning direction S when printing on the workpiece W, and the direction from rear to front is the sub-scanning direction (the transport direction F of the workpiece W, which corresponds to the transport direction).

[0016] The device frame 10 forms a framework for mounting various components of the inkjet printer 1. The work transport unit 20 is a mechanism that intermittently feeds (transports) the work W so that the work W progresses in a transport direction F from rear to front in a printing area where inkjet printing processing is performed. The carriage 3 is equipped with an ink head 4, a pre-processing head 5, a post-processing head 6, and a sub-tank 7, and moves back and forth in a main scanning direction S (left-right direction) that intersects (is perpendicular to) the transport direction F of the work W during the inkjet printing processing.

[0017] The device frame 10 includes a central frame 111, a right frame 112, and a left frame 113. The central frame 111 forms a framework for mounting various components of the inkjet printer 1, and has a left-right width corresponding to the work transport section 20. The right frame 112 and the left frame 113 are erected to the right and left, respectively, of the central frame 111. Between the right frame 112 and the left frame 113, a printing area A is set up where printing processing is performed on the work W.

[0018] The central frame 111 has rectangular pipe members (not shown) connected to form a rectangular parallelepiped skeleton, and left and right side plates 111a that face each other in the left-right direction and form the left and right side surfaces of the central frame 111. As shown in Fig. 2, the left and right side plates 111a have rectangular side plate main body parts 111b arranged to close both the left and right sides of the rectangular parallelepiped skeleton, and side plate protruding parts 111c connected to the upper ends of the side plate main body parts 111b and protruding above the conveyor belt 21 described below. The rail support base 40 is fixed to the upper end surfaces of the side plate protruding parts 111c.

[0019] Casters 120 (only the two at the front and rear are shown in FIG. 1) are attached to the four corners of the lower surface of the central frame 111 for mobility.

[0020] In addition, a caster 120 (only one is shown in FIG. 1) for mobility is attached to the center in the front-rear direction at the left end of the underside of the left frame 113, and to the center in the front-rear direction at the right end of the underside of the right frame 112.

[0021] 2, an adjustment bolt 123 is attached to each caster 120 with its head in contact with the floor surface. After moving the inkjet printer 1 to a predetermined position via the casters 120, the operator can adjust the height and inclination of each of the frames 111, 112, and 113 from the floor surface by rotating the adjustment bolt 123.

[0022] The right frame 112 forms the maintenance area 13. The maintenance area 13 is an area where the carriage 3 is retracted when the printing process is not being performed. In the maintenance area 13, cleaning processes, purging processes, etc. are performed on the ejection holes n (FIG. 6) of the ink head 4, pre-processing head 5, and post-processing head 6, and the ejection holes are also capped. The left frame 113 forms a turn-around area 14 for the carriage 3. The turn-around area 14 is an area where the carriage 3 temporarily enters when it performs a main scan in the opposite direction after performing a main scan in the opposite direction from right to left in the printing process.

[0023] 3 is an enlarged side view showing the carriage mounting location of the inkjet printer 1 as seen from the left side. As shown in this figure, a left-right guide mechanism 15 for causing the carriage 3 to reciprocate left and right is attached via a rail support base 40 to the upper side of the device frame 10. The carriage 3 is attached to this left-right guide mechanism 15 via a top-bottom guide mechanism 16.

[0024] The vertical guide mechanism 16 has a pair of guide rails 161 (only one of which is shown in FIG. 3) that extend in the vertical direction and are aligned laterally with a gap therebetween, sliders 162 that engage with each guide rail 161 so as to be movable in the vertical direction, and a base plate 163 to which the pair of guide rails 161 are fixed. Each guide rail 161 is provided with two sliders 162. The base plate 163 is a rectangular plate material having approximately the same left-right width as the carriage 3. The base plate 163 is fixed to a slider 152 of the horizontal guide mechanism 15, which will be described later.

[0025] The left-right guide mechanism 15 is fixed to the rear surface (rear side surface) of the base plate 163, and holds the carriage 3 movably in the main scanning direction S (left-right direction) via the base plate 163. Specifically, the left-right guide mechanism 15 has a pair of guide rails 151 that extend in the left-right direction and are arranged vertically at an interval, and sliders 152 that engage with each guide rail 151 movably in the left-right direction. The guide rails 151 straddle the center frame 111 and the left and right frames 112, 113, and extend over the entire left-right direction of the inkjet printer 1 (see FIG. 1). The two sliders 152 engage with each guide rail 151. The base plate 163 of the up-down guide mechanism 16 is attached to the front side surface (right side surface in FIG. 2) of each slider 152. As described above, the carriage 3 is held by this base plate 163 movably in the up-down direction via the guide rails 161 and the sliders 162.

[0026] A timing belt 153 (shown only in FIG. 1) is attached to the left-right guide mechanism 15 so as to be movable in a circulating manner in the left-right direction (main scanning direction S). The timing belt 153 is an endless belt, and is fixed to the base plate 163. As the timing belt 153 moves in a circulating manner in the left-right direction, the base plate 163 moves in a circulating manner while being guided by the pair of guide rails 151. The timing belt 153 is driven to rotate by a carriage drive unit consisting of a motor and the like. The drive control of the carriage drive unit is executed by a controller (not shown) based on an operating program stored in advance.

[0027] [Rail support configuration] As shown in FIG. 3, the rail support base 40 is a support base that supports a pair of guide rails 151 of the left and right guide mechanism parts 15, and is arranged across the upper end surfaces of the left and right side plates 111a (more specifically, the side plate protrusions 111c of the side plates 111a) of the central frame 111.

[0028] The rail support base 40 has a front plate 41 to which the pair of guide rails 151 are fixed, a rear plate 42 arranged behind the front plate 41 with a gap therebetween, two upper and lower connecting plates 43 that connect the front plate 41 and the rear plate 42, and left and right seat members 44 that support the lower ends of the front plate 41 and the rear plate 42. An adjustment bolt (not shown) whose head abuts against the upper end surface of the side plate 111a is attached to each of both ends of the left and right seat members 44, and the inclination of the rail support base 40 can be adjusted by rotating and adjusting the adjustment bolt.

[0029] [Work transport section configuration] 2, a description will be given of the configuration of the work transport section 20. The work transport section 20 has a transport belt 21, a driving roller 22, a driven roller 23, a feed roller 24, an upstream support roller 25, and a downstream support roller 26.

[0030] The conveyor belt 21 is configured to be able to rotate in the front-rear direction while being wound around a driving roller 22 and a driven roller 23. The upper surface of the conveyor belt 21 functions as a conveying surface 21a for conveying a workpiece W (recording medium). The conveyor belt 21 supplies the workpiece W to the printing area A by rotating in the front-rear direction.

[0031] The driving roller 22 and the driven roller 23 extend in the left-right direction and are arranged at an interval from each other in the front-rear direction. In this example, the driving roller 22 is arranged at the front end of the central frame 111, and the driven roller 23 is arranged at the rear end within the central frame 111. Both ends of the driving roller 22 and the driven roller 23 are rotatably supported by the left and right side plates 111a of the central frame 111 (more specifically, the side plate main body parts 111b of the side plates 111a). The driving roller 22 is driven by a motor (not shown) to rotate the conveyor belt 21. The driven roller 23 rotates following the rotation of the conveyor belt 21 while applying tension to the conveyor belt 21 to suppress slack.

[0032] The feed roller 24 is disposed slightly forward of the driven roller 23 and in contact with the conveying surface 21a (upper surface) of the conveyor belt 21. Both ends of the feed roller 24 are rotatably supported by the left and right side plates 111a of the central frame 111 (more specifically, by the side plate protrusions 111c of the left and right side plates 111a).

[0033] A work supply transport mechanism (not shown) is provided upstream of the feed roller 24 (rear in this example), and the feed roller 24 sandwiches the work W supplied by the work supply transport mechanism between the feed roller 24 and the transport belt 21 and delivers it downstream (front in this example). The delivered work W moves from the upstream side to the downstream side as the transport belt 21 rotates, and is carried into a printing area A (image forming position) facing the carriage 3.

[0034] In a plan view, the printing area A is located toward the front between the drive roller 22 and the driven roller 23. The upstream support roller 25 and the downstream support roller 26 are disposed between the drive roller 22 and the driven roller 23, extending in the left-right direction and spaced apart in the front-rear direction.

[0035] The upstream support roller 25 and the downstream support roller 26 support the lower surface of the conveyor belt 21 from the inner peripheral side of the belt below the printing area A. Both the upstream support roller 25 and the downstream support roller 26 are rotatably supported by the left and right side plates 111a of the central frame 111 (more specifically, the side plate main body portions 111b of the side plates 111a).

[0036] The upper ends of the upstream support roller 25 and the downstream support roller 26 are located at the same height as each other and are located slightly above the upper ends of the drive roller 22 and the driven roller 23. This increases the tension in the portion of the conveyor belt 21 between the upstream support roller 25 and the downstream support roller 26 (an inter-roller region U described below), thereby suppressing slack in the conveyor belt 21.

[0037] 3, both ends of the upstream support roller 25 and the downstream support roller 26 are supported by bearings (not shown) held in bearing holders 27. Each bearing holder 27 is fixed to the left and right side plates 111a of the central frame 111 using four bolts 11.

[0038] 4 is a side view including a partial cross section showing the support structure of the left end portion of the downstream support roller 26. As shown in this figure, the bearing holder 27 has a cylindrical holder main body 27a with a bearing fitted on its inner circumferential surface, and a spigot portion 27c protruding from one end face in the thickness direction of the holder main body 27a.

[0039] A bearing is fitted to the inner peripheral surface of the holder main body 27a. The spigot portion 27c is fitted to a through hole 111d formed in the side plate 111a of the central frame 111 so as to be slightly movable (for example, about 1 mm to 2 mm) in the vertical direction. This through hole 111d is formed in an oblong shape that is slightly long in the vertical direction.

[0040] At both upper and lower ends of the holder body 27a, flat surfaces 27b are formed by D-cutting when viewed from the axial direction. The lower flat surface 27b is used as a contact surface for a set screw 291 in the roller inclination adjustment mechanism 29 described later.

[0041] In this example, the roller inclination adjustment mechanism 29 is provided only to the downstream support roller 26, which is closer to the front side of the inkjet printer 1, out of the upstream support roller 25 and the downstream support roller 26.

[0042] The roller inclination adjustment mechanism 29 has set screws 291 (only the left side is shown in FIG. 5) arranged on the undersides of the left and right bearing holders 27, respectively, an adjustment block 292 into which the set screws 291 screw, and a fixing nut 293 for fixing the set screws 291, and makes it possible to adjust the inclination of the downstream support roller 26 in the height direction (up and down direction) by adjusting the up and down position of the bearing holder 27 via the set screws 291. The roller inclination adjustment mechanism 29 corresponds to an adjustment mechanism for adjusting the parallelism between the upstream support roller 25 and the downstream support roller 26.

[0043] Specifically, the adjustment block 292 is fixed to the outer surfaces of the left and right side plates 111a with bolts. The adjustment block 292 is formed with a screw hole 292a penetrating in the vertical direction, and the set screw 291 is screwed into the screw hole 292a and penetrates the adjustment block 292 in the vertical direction. The upper end surface of the set screw 291 abuts against the lower flat surface 27b of the bearing holder 27 as described above. By loosening the fixing nut 293 and rotating the set screw 291, the worker can move the bearing holder 27 up and down following the upper end position of the set screw 291. Thus, the worker can adjust the vertical positions of the left and right bearing holders 27 that hold both ends of the downstream support roller 26, thereby adjusting the inclination of the downstream support roller 26 in the height direction (vertical direction).

[0044] [Carriage configuration] Next, the configuration of the carriage 3 will be described with reference to Figures 1 to 3. During printing, the carriage 3 reciprocates along guide rails 151 of the left-right guide mechanism 15 in a main scanning direction S (left-right direction in this embodiment) that intersects with the transport direction F (orthogonal in this embodiment) while being supported at a predetermined height by the up-down guide mechanism 16.

[0045] Specifically, the carriage 3 includes a carriage main body frame 30 and a head support plate 31 connected to the carriage main body frame 30. An ink head 4, a pre-processing head 5, and a post-processing head 6 are mounted on the upper surface of the head support plate 31. The carriage main body frame 30 and the head support plate 31 may be integrally formed, or may be formed from separate members.

[0046] The carriage main body frame 30 has a rectangular vertical plate 30a fixed to the slider 162 of the upper and lower guide mechanism part 16, and left and right side plates 30b connected to the left and right edge portions of the vertical plate 30a, and has a U-shape that is open to the front when viewed in a plane.

[0047] The head support plate 31 is a plate-like member that holds the heads 4 to 6 described above, and is disposed so as to close the lower end side of the carriage body frame 30.

[0048] [Layout of heads and subtanks] FIG. 5 is a plan view showing the arrangement of the heads 4 to 6 mounted on the upper surface of the head support plate 31 of the carriage 3, and FIG.

[0049] As shown in FIG. 5, a group of heads is attached to the upper surface of the head support plate 31, including multiple ink heads 4 that eject ink droplets for forming an image onto the workpiece W, and a pre-treatment head 5 and a post-treatment head 6 that eject droplets of non-colorable treatment liquid.

[0050] The pre-treatment head 5, the ink head 4, and the post-treatment head 6 are disposed in this order from the upstream side to the downstream side in the transport direction F.

[0051] Each of the heads 4 to 6 has a rectangular parallelepiped shape elongated in the front-rear direction in a plan view, and has the same configuration as each other. That is, each of the heads 4 to 6 has a large number (plurality) of ejection holes n (so-called nozzles) that eject droplets of the ejection target liquid by an ejection method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, and an ink passage (not shown) that guides the ejection target liquid to the ejection holes n. As shown in FIG. 6, the large number of ejection holes n are composed of two rows of ejection holes aligned in the main scanning direction S (left-right direction), and each ejection hole row is composed of a large number (plurality) of ejection holes n aligned at equal intervals in the transport direction F (front-rear direction). These ejection holes n open to an ejection surface Q that is the lower end surface of each of the heads 4 to 6. In the following description, the amount of droplets of the ejection target liquid ejected from each of the ejection holes n of each of the heads 4 to 6 in one ejection operation (in this example, for example, the volume ejected in response to one period of the pulse of the driving voltage) is simply referred to as the "amount of ejected droplets".

[0052] In the present disclosure, the region in the discharge surface Q where the numerous discharge holes n are formed is referred to as the discharge region R. The discharge region R is defined as a region surrounded by a pair of straight lines (straight lines L1 and L2 in the example of FIG. 6) that pass through the outer end of the discharge hole n located at the outermost position in the transport direction F among the numerous discharge holes n and extend in the main scanning direction S that is the perpendicular direction to the outer end of the discharge hole n located at the outermost position in the main scanning direction S among the numerous discharge holes n and extend in the transport direction F that is the perpendicular direction to the outer end of the discharge hole n (straight lines L3 and L4 in the example of FIG. 6). In this example, the arrangement configuration (number, arrangement form, hole diameter, hole pitch) of the discharge holes n in each of the heads 4 to 6 is the same, and therefore the shape and dimensions of the discharge region R are also the same.

[0053] The ink liquid to be ejected by the ink head 4 may be, for example, a water-based pigment ink liquid containing a water-based solvent, a pigment, and a binder resin. In this embodiment, the ink heads 4 include first to sixth ink heads 4A to 4F that eject six different color ink liquids. For example, the first ink head 4A ejects orange ink droplets, the second ink head 4B ejects green ink droplets, the third ink head 4C ejects yellow ink droplets, the fourth ink head 4D ejects red ink droplets, the fifth ink head 4E ejects blue ink droplets, and the sixth ink head 4F ejects black ink droplets.

[0054] The ink heads 4A to 4F of each color are mounted on the head support plate 31 of the carriage 3 so as to be aligned in the main scanning direction S. Each of the ink heads 4A to 4F of each color has two heads. For example, the first ink head 4A is composed of an upstream head 4A1 arranged on the upstream side of the transport direction F, and a downstream head 4A2 arranged downstream of the upstream head 4A1 and shifted to the left side of the main scanning direction S. The ink heads 4B to 4F of the other colors are similar. Each of the upstream heads of these ink heads 4B to 4F is aligned in a row in the main scanning direction S at the same position as the upstream head 4A1 in the transport direction F, and each of the downstream heads is aligned in a row in the main scanning direction S at the same position as the downstream head 4A2 in the transport direction F. In this example, the upstream parts of the downstream heads 4A2 to 4F2 are inserted between the upstream heads A1 to 4F1. The ink heads 4 are then arranged in a staggered pattern on the upper surface of the head support plate 31. This allows the ink heads 4 to be arranged at high density in the transport direction F, thereby making it possible to reduce the size of the carriage 3 in the transport direction F.

[0055] The pre-treatment head 5 and the post-treatment head 6 are disposed at positions different from the ink head 4 in the transport direction F.

[0056] In the example of FIG. 5, one pre-treatment head 5 is disposed to the left of the left end of the upstream ink head row (i.e., the upstream ink heads 4A1-4F1). The pre-treatment head 5 is disposed upstream of the ink heads 4 in the transport direction F. In other words, the pre-treatment head 5 is disposed such that the center position in the transport direction of the ejection region R is located upstream of the center positions in the transport direction of the ejection regions R of the upstream heads 4A1-4F1. The downstream portion of the pre-treatment head 5 is disposed at a position that overlaps with the upstream ink head row (i.e., the upstream heads 4A1-4F1) in the transport direction F.

[0057] 5, one post-processing head 6 is disposed to the right of the right end of the downstream ink head row (i.e., downstream heads 4A2-4F2). The post-processing head 6 is disposed downstream of the ink heads 4 in the transport direction F. That is, the post-processing head 6 is disposed such that the center position of its ejection region R in the transport direction F is located downstream of the center positions of the ejection regions R of the downstream heads 4A2-4F2. The upstream portion of the post-processing head 6 is disposed at a position that overlaps with the downstream ink head row (i.e., downstream heads 4A2-4F2) in the transport direction F.

[0058] The pretreatment head 5 ejects droplets of a pretreatment liquid (liquid to be ejected) for performing a predetermined pretreatment on the workpiece W. The droplets of the pretreatment liquid are ejected from the pretreatment head 5 to positions on the workpiece W where ink liquid has not yet been ejected from the ink head 4. The pretreatment liquid is a non-coloring treatment liquid that does not develop color even when attached to the workpiece W, and is a treatment liquid that exhibits functions such as increasing the fixation of ink droplets to the workpiece W and the coagulation of ink pigments. As such a pretreatment liquid, a treatment liquid in which a binder resin is blended in a solvent, or a treatment liquid in which a positively charged cationic resin is blended in a solvent, can be used.

[0059] The post-treatment head 6 ejects droplets of post-treatment liquid (liquid to be ejected) for performing a predetermined post-treatment on the workpiece W to which the ink droplets have been attached. The post-treatment liquid is ejected from the post-treatment head 6 to a position on the workpiece W after the ink droplets have been ejected from the ink head 4. The post-treatment liquid is a non-coloring treatment liquid that does not develop color even when it adheres to the workpiece W, and has the function of increasing the fixability and robustness (resistance to rubbing and scraping) of the ink image printed on the workpiece W by the ink head 4. A silicone-based treatment liquid or the like can be used as such a post-treatment liquid.

[0060] Here, the non-coloring treatment liquid refers to a treatment liquid that is not recognized as colored by the naked eye when printed alone on a recording medium. The color here includes colors with a saturation of 0, such as black, white, and gray. The non-coloring treatment liquid is basically a transparent liquid, but when, for example, 1 liter of treatment liquid is viewed in liquid form, it is not completely transparent and may appear slightly white. Such a color is very light, so when printed alone on a recording medium, it is not recognized as colored by the naked eye. Note that, depending on the type of treatment liquid, when printed alone on a recording medium, a change such as glossiness may occur on the recording medium, but such a state is not colored.

[0061] In this embodiment, the pre-treatment liquid and the post-treatment liquid may be ejected onto substantially the entire surface of the workpiece W, or the pre-treatment liquid and the post-treatment liquid may be ejected selectively in accordance with the image to be printed, similar to the ink liquid.

[0062] Next, a case where the pretreatment liquid and the posttreatment liquid are selectively ejected will be described. As described above, droplets of the pretreatment liquid, ink droplets, and droplets of the posttreatment liquid are ejected in this order onto the portion of the workpiece W where colors are printed according to an image. In this case, the ink droplets may be of one color or of multiple colors. Basically, the pretreatment liquid and the posttreatment liquid are not ejected onto the portion where no color is printed, i.e., the portion where the ink droplets are not ejected.

[0063] Openings 31a (see FIG. 5) are provided in the head support plate 31 at locations where the heads 4 to 6 are arranged. The ink heads 4, pre-processing heads 5 and post-processing heads 6 are assembled to the head support plate 31 so as to be fitted into the respective openings 31a. From each opening 31a, a discharge surface Q (see FIG. 6, described later) of each head 4 to 6 is exposed. The discharge surface Q exposed from each opening 31a faces the transport surface 21a of the transport belt 21.

[0064] The sub-tank 7 (shown only in FIG. 1) is supported by the carriage 3 above the heads 4, 5, 6 via a holding frame (not shown). A sub-tank 7 is provided corresponding to each of the heads 4, 5, 6. Each sub-tank 7 is supplied with ink or treatment liquid from a cartridge (not shown) containing ink and treatment liquid or a main tank, and supplies these to each of the heads 4, 5, 6. Each sub-tank 7 and the heads 4, 5, 6 are connected by pipes (not shown).

[0065] [Print method] A printing method performed by the inkjet printer 1 according to this embodiment will be described. The inkjet printer 1 performs printing processing on the workpiece W using a serial printing method. If the workpiece W has a wide size, printing cannot be performed while continuously feeding the workpiece W. In the serial printing method, the carriage 3 carrying the ink heads 4 of each color moves back and forth in the main scanning direction S, and the workpiece W is intermittently fed in the transport direction F. In this example, the pre-treatment head 5 ejects droplets of the pre-treatment liquid, the ink head 4 ejects droplets of the ink, and the post-treatment head 6 ejects droplets of the post-treatment liquid, in both the forward and return paths of the carriage 3. In this way, printing processing is possible in both the forward and return paths. The reason why printing processing is possible in both the forward and return paths is that the pre-treatment head 5 and the post-treatment head 6 are shifted in the transport direction F relative to the ink head 4. If the pre-treatment head 5, ink head 4, and post-treatment head 6 were aligned in this order in the main scanning direction S on the carriage 3, printing that ensures the desired landing order of the pre-treatment liquid and post-treatment liquid could only be achieved in one of the forward or backward movements. To enable bidirectional printing, the pair of pre-treatment head 5 and post-treatment head 6 must be arranged on both sides of the ink head 4 array. In this case, the width of the carriage 3 in the main scanning direction S would increase. This arrangement is unnecessary in this embodiment, so the width of the carriage 3 in the main scanning direction S can be reduced.

[0066] As described above, in the all-in-one type inkjet printer 1 in which the ink head 4, the pre-treatment head 5, and the post-treatment head 6 are mounted on one carriage 3, the amount of the discharged droplets (in this example, the volume of the droplets of the discharge target liquid discharged from each discharge hole n in one discharge operation) may be set to different amounts in the pre-treatment head 5 and the post-treatment head 6 depending on the required texture of the printed image. In this example, the amount (volume) of the discharged droplets of the post-treatment head 6 is set to be smaller than that of the pre-treatment head 6. Specifically, in this example, when the amount of the discharged droplets of the ink head 4 is X (pl), the amount of the discharged droplets of the pre-treatment head 5 is set to the same amount (=X (pl)) as the amount of the discharged droplets of the ink head 4, and the amount of the discharged droplets of the post-treatment head 6 is set to half that amount (=X / 2 (pl)). Note that the amount of the discharged droplets of each head 4 to 6 described here is an example and is not limited thereto.

[0067] If the amount of droplets discharged by the post-processing head 6 is set to be less than the amount of droplets discharged by the pre-processing head 5 as in this example, there will be a difference in the extent to which the droplets discharged by the pre-processing head 5 and the post-processing head 6 spread when they land on the printing surface of the workpiece W, which may result in a deterioration in the quality of the printed image. In response to this, in this example, the arrangement of the upstream support rollers 25 and the downstream support rollers 26 is devised to suppress the deterioration in the quality of the printed image caused by the difference in the amount of droplets discharged by the pre-processing head 5 and the post-processing head 6.

[0068] [Explanation of the arrangement of the upstream support rollers and downstream support rollers] FIG. 7 is an explanatory plan view seen from above the carriage 3, for explaining the positions of the upstream support rollers 25 and the downstream support rollers 26. As shown in FIG.

[0069] In this figure, the symbol J1 indicates the axis of the upstream support roller 25, and the symbol J2 indicates the axis of the downstream support roller 26. Furthermore, the symbol K1 indicates the center line in the transport direction F of the discharge region R of the pre-processing head 5 (more specifically, a straight line that passes through the center position of the discharge region R in the transport direction F and extends in the main scanning direction S), and the symbol K2 indicates the center line in the transport direction F of the discharge region R of the post-processing head 6 (more specifically, a straight line that passes through the center position of the discharge region R in the transport direction F and extends in the main scanning direction S).

[0070] The upstream support roller 25 and the downstream support roller 26 are arranged so that, in a planar view (viewed from a height direction perpendicular to the conveying surface 21a of the conveying belt 21), the entire ejection area R of the pre-processing head 5, the entire ejection area R of the ink head 4, and the entire ejection area R of the post-processing head 6 are located (fitted) within the inter-roller area U sandwiched between the contact lines of both support rollers 25, 26 on the conveying belt 21 (two straight lines that coincide with the axis lines J1, J2 in a planar view).

[0071] That is, the upstream support roller 25 is disposed so that its axis J1 is located upstream of the center line K1 of the discharge region R of the pre-processing head 5 in the transport direction F. The downstream support roller 26 is disposed so that its axis J2 is located downstream of the center line K2 of the discharge region R of the post-processing head 6 in the transport direction F.

[0072] Here, when the distance in the conveyance direction F between the center line K1 of the discharge area R of the pre-treatment head 5 and the axis J1 of the upstream support roller 25 is defined as the first reference distance d1, and the distance in the conveyance direction F between the center line K2 of the discharge area R of the post-treatment head 6 and the axis J2 of the downstream support roller 26 is defined as the second reference distance d2, the relationship d2 < d1 is satisfied. In other words, it can be said that the post-treatment head 6 has a smaller reference distance than the pre-treatment head 5. Note that the reference distance means the distance to the closer one of the two support rollers 25 and 26 as seen from each of the treatment heads 5 and 6. In this example, the distance ratio H (= d2 / d1) obtained by dividing the second reference distance d2 (the reference distance of the post-treatment head 6) by the first reference distance d1 (the reference distance of the pre-treatment head 5) is set within a range of, for example, 0.85 to 0.90.

[0073] [Operation and Effect of the First Embodiment] As described above, the inkjet printer 1 of the present embodiment includes an upstream support roller 25 and a downstream support roller 26 that are arranged in the upstream side to the downstream side in the conveyance direction F between the drive roller 22 and the driven roller 23 and support the conveyance belt 21 from the inner side of the belt.

[0074] According to this, by supporting the conveyance belt 21 from below (the inner side of the belt) by the upstream support roller 25 and the downstream support roller 26, it is possible to suppress the fluttering of the conveyance belt 21 between the drive roller 22 and the driven roller 23 and improve the image quality of the printed image.

[0075] Here, from the viewpoint of improving the image quality of the printed image, it is preferable to arrange the upstream support roller 25 and the downstream support roller 26 near both ends of the printing area A. However, if the amount (the volume of the droplets in this example) of the droplets of the liquid to be discharged is different between the pre-treatment head 5 and the post-treatment head 6, there is a problem that relatively small droplets cannot land at the target position and the image quality of the printed image deteriorates.

[0076] In contrast to this, in this embodiment, the positions of the upstream support roller 25 and the downstream support roller 26 in the transport direction F are set so that the reference distance (either the first reference distance d1 or the second reference distance d2, in this example the second reference distance d2) of the pre-processing head 5 or the post-processing head 6 which ejects a smaller amount of droplets (in this embodiment the post-processing head 6) is smaller than the reference distance (the other of the first reference distance d1 or the second reference distance d2, in this example the first reference distance d1) of the pre-processing head 5 which ejects a larger amount of droplets (in this embodiment the pre-processing head 5). That is, in this embodiment, since the post-processing head 6 ejects a smaller amount of droplets than the pre-processing head 5, the second reference distance d2 is smaller than the first reference distance d1.

[0077] According to this configuration, even if the amount of droplets ejected by the pre-treatment head 5 and the post-treatment head 6 differs, it is possible to prevent deterioration in the quality of the printed image due to this difference.

[0078] That is, the inventors, after intensive research, arrived at the following ideas (i) and (ii). Specifically, (i) when the amount of droplets discharged from the discharge holes n of each head 4 to 6 is small (when the volume of the droplets is small), the degree of spread of the droplets after landing on the printing surface of the workpiece W (the degree of spread in the radial direction due to the droplets being crushed when landing) is also small, so if the landing position of the discharged droplets is even slightly deviated from the target position, the discharged droplets do not spread over the entire target dot area. (ii) Therefore, when the amount of the discharged droplets is small, the allowable amount of deviation of the landing position is smaller than when the amount of the discharged droplets is large (when the droplet volume is large). Then, the inventors applied this idea to the inkjet printer 1 of this embodiment, and concluded that the amount of the discharged droplets of the post-processing head 6 is smaller than that of the pre-processing head 5 (the volume of the discharged droplets is small), and therefore the allowable amount of deviation of the landing position is also smaller. Therefore, in order to reduce the amount of deviation in the landing position of the discharged droplets by the post-processing head 6, the inventors set the second reference distance d2, which is the reference distance of the post-processing head 6, to be smaller than the first reference distance d1, which is the reference distance of the pre-processing head 5, as described above. This allows the position of the contact line between the downstream support roller 26 located on the post-processing head 6 side and the conveyor belt 21 (i.e., the position where the conveyor belt 21 is unlikely to become loose) to be as close as possible to the area of ​​the conveyor belt 21 below the discharge area R of the post-processing head 6. This makes it possible to prevent the conveyor belt 21 from becoming loose or fluttering below the post-processing head 6. Therefore, even if the amount of discharged droplets by the post-processing head 6 is small and the amount of deviation in the landing position of the discharged droplets allowed by the post-processing head 6 is limited to a narrow range as in this embodiment, it is possible to land the discharged droplets (post-processing liquid) within the allowable range. Therefore, the dot formation accuracy by the post-processing head 6 (the position accuracy of the dots formed after the discharged droplets land) does not decrease compared to the pre-processing head 5. In this way, in this embodiment, it is possible to suppress differences in dot formation accuracy caused by differences in the amount of ejected droplets between the pre-processing head 5 and the post-processing head 6, and ultimately to suppress deterioration in image quality of the printed image.

[0079] In addition, in this embodiment, the positions of the conveying direction F of both support rollers 25, 26 are set so that, in a planar view (viewed from a height direction perpendicular to the conveying surface 21a of the conveying belt 21), the entire ejection area R of the pre-processing head 5, the entire ejection area R of the ink head 4, and the entire ejection area R of the post-processing head 6 are located inside the inter-roller area U sandwiched between the contact lines of the upstream support roller 25 and the downstream support roller 26 on the conveying belt 21 (a straight line that coincides with the axis lines J1, J2 of both rollers 25, 26 in a planar view).

[0080] This can improve the image quality of the printed image as much as possible. That is, in the inter-roller region U of the conveyor belt 21, the upstream support roller 25 and the downstream support roller 26 provide sufficient tension to the conveyor belt 21, so that slackness and fluttering are unlikely to occur. Therefore, by making the discharge area R of the pre-treatment head 5, the discharge area R of the ink head 4, and the discharge area R of the post-treatment head 6 all fit within the inter-roller region U in a plan view, the discharged droplets from each head 4 to 6 can be landed on the workpiece W in the inter-roller region U where slackness and fluttering are minimal. Therefore, deterioration in the image quality of the printed image caused by slackness and fluttering of the conveyor belt 21 can be further suppressed.

[0081] In this embodiment, the inkjet printer 1 also includes a roller inclination adjustment mechanism 29 for adjusting the parallelism between the upstream support roller 25 and the downstream support roller 26.

[0082] According to this, an operator can adjust the parallelism between the upstream support roller 25 and the downstream support roller 26 via the roller inclination adjustment mechanism 29, thereby adjusting the parallelism between the inter-roller region U of the conveyor belt 21 and the discharge surfaces Q of the heads 4 to 6 mounted on the carriage 3 to a predetermined parallelism. Therefore, regardless of the position of the carriage 3 in the main scanning direction, the distance between the discharge surfaces Q of the heads 4 to 6 and the workpiece W on the conveyor belt 21 can be kept constant, suppressing variation in the landing positions of the discharged droplets from the heads 4 to 6, and ultimately improving the image quality of the printed image.

[0083] (Modification of the first embodiment) Fig. 8 is a view equivalent to Fig. 7 showing a modified example of the first embodiment. In this modified example, the magnitude relationship between the amounts of droplets discharged by the pre-processing head 5 and the post-processing head 6, and the magnitude relationship between the first reference distance d1 which is the reference distance of the pre-processing head 5 and the second reference distance d2 which is the reference distance of the post-processing head 6 are different from those in the first embodiment. Note that the configuration other than this point is the same as in the first embodiment, and in the following description, the same components as in the first embodiment are denoted by the same reference symbols and detailed description thereof will be omitted.

[0084] That is, in this modified example, the amount of droplets ejected by the pre-processing head 5 is set to be less than the amount of droplets ejected by the post-processing head 6. In this example, when the amount of droplets ejected by the ink head 4 is X (pl), the amount of droplets ejected by the pre-processing head 5 is set to half that amount (=X / 2(pl)), and the amount of droplets ejected by the post-processing head 6 is set to the same amount (=X(pl)) as the amount of droplets ejected by the ink head 4. Note that this example of setting the amount of droplets ejected is just one example and is not limited to this.

[0085] And in this modified example, as shown in FIG. 8, the first reference distance d1 (the distance in the conveyance direction F between the center line K1 of the discharge region R of the pretreatment head 5 and the axis J1 of the upstream support roller 25) is set to be smaller than the second reference distance d2 (the distance in the conveyance direction F between the center line K2 of the discharge region R of the post-treatment head 6 and the axis J2 of the downstream support roller 26) (that is, d1 < d2). In other words, the reference distance of the pretreatment head 5 is smaller than that of the post-treatment head 6. In this example, the distance ratio H (= d1 / d2) obtained by dividing the first reference distance d1, which is the reference distance of the pretreatment head 5, by the second reference distance d2, which is the reference distance of the post-treatment head 6, is set within the range of, for example, 0.85 to 0.90.

[0086] [Operation and Effect of the Modified Example of the First Embodiment] As described above, in this modified example, the amounts of discharged droplets of the pretreatment head 5 and the post-treatment head 6 are different from each other, and the reference distance (either the first reference distance d1 or the second reference distance d2, and in this example, the first reference distance d1) of the one with the smaller amount of discharged droplets (the pretreatment head 5 in this example) among the pretreatment head 5 and the post-treatment head 6 is smaller than the reference distance (the other of the first reference distance d1 and the second reference distance d2, and in this example, the second reference distance d2) of the one with the larger amount of discharged droplets (the post-treatment head 6 in this example). That is, the positions of the upstream support roller 25 and the downstream support roller 26 in the conveyance direction F are set such that. That is, in this embodiment, since the pretreatment head 5 discharges fewer droplets than the post-treatment head 6, the first reference distance d1 is smaller than the second reference distance d2.

[0087] According to this configuration, the contact line between the upstream support roller 25 located on the pre-processing head 5 side and the conveyor belt 21 (i.e., the position where slack is unlikely to occur in the conveyor belt 21) can be brought as close as possible to the area of ​​the conveyor belt 21 below the discharge area R of the pre-processing head 5. This makes it possible to prevent the conveyor belt 21 from loosening or fluttering below the pre-processing head 5. Therefore, even if the amount of droplets discharged by the pre-processing head 5 is small and the allowable range of the deviation of the landing position is narrow as in this modified example, it is possible to land the discharged droplets (pre-processing droplets) within that allowable range. Therefore, the dot formation accuracy of the pre-processing head 5 on the printing surface of the workpiece W is not reduced compared to the post-processing head 6.

[0088] Therefore, in this modified example, similar to the first embodiment, degradation in the quality of the printed image caused by the difference in the amount of droplets ejected by the pre-treatment head 5 and the post-treatment head 6 can be suppressed.

[0089] Second embodiment Fig. 9 is a view showing a second embodiment, which corresponds to Fig. 7. In this embodiment, the arrangement of the upstream support rollers 25 and the downstream support rollers 26 is different from that of the first embodiment. Note that the other configurations are the same as those of the first embodiment, and in the following description, the same components as those of the first embodiment are denoted by the same reference numerals and detailed description thereof will be omitted.

[0090] That is, in this embodiment, the amount of droplets ejected from the post-processing head 6 is set to be less than the amount of droplets ejected from the pre-processing head 5, which is similar to the first embodiment. However, as described below, the relative positional relationship of the upstream support roller 25 and the downstream support roller 26 to each of the heads 4 to 6 differs from that of the first embodiment.

[0091] Specifically, in this embodiment, the positions of the upstream support roller 25 and the downstream support roller 26 in the conveying direction F are set so that, in a planar view (viewed from a height direction perpendicular to the conveying surface 21a of the conveying belt 21), the entire discharge area R of the post-processing head 6 is located within the inter-roller area U sandwiched between the contact line of the upstream support roller 25 and the downstream support roller 26 on the conveying belt 21 (a straight line that coincides with the axis lines J1, J2 of both rollers 25, 26 in a planar view), and the entire discharge area R of the pre-processing head 5 is located outside the inter-roller area U (upstream of the conveying direction F).

[0092] In this embodiment, the first reference distance d1, which is the reference distance of the pre-processing head 5 (i.e., the distance between the center line K1 of the discharge area R of the pre-processing head 5 and the axis J1 of the upstream support roller 25), and the second reference distance d2, which is the reference distance of the post-processing head 6 (i.e., the distance between the center line K2 of the discharge area R of the post-processing head 6 and the axis J2 of the downstream support roller 26), are set to be equal (i.e., d1 = d2).

[0093] [Effects of the second embodiment] According to this embodiment, when the first reference distance d1 and the second reference distance d2, which are the reference distances between the pre-processing head 5 and the post-processing head 6, are set equal to each other, it is possible to suppress deterioration in the quality of the printed image caused by the difference in the amount of droplets discharged between the pre-processing head 5 and the post-processing head 6. That is, in this embodiment, as in the first embodiment, the amount of droplets discharged by the post-processing head 6 is set smaller than the amount of droplets discharged by the pre-processing head 5, so that the post-processing head 6 has a narrower allowable range of the landing position of the droplets that can be allowed (in other words, high landing position accuracy is required). Therefore, by disposing the post-processing head 6, which requires such high landing position accuracy, in the inter-roller region U in a plan view, it is possible to suppress slackness and fluttering of the conveyor belt 21 below the post-processing head 6 and ensure the high landing position accuracy required of the post-processing head 6. On the other hand, since the pre-processing head 5 is disposed outside the inter-roller region U in a plan view, the landing position accuracy of the droplets discharged is lower than that of the post-processing head 6. That is, outside the inter-roller region U of the conveyor belt 21, the belt tension is lower than that in the inter-roller region U, and a slight inclination occurs in the conveying direction F (the inclination occurs because the upper end positions of the support rollers 25, 26 are slightly higher than the upper end positions of the driving roller 22 and the driven roller 23), so that the conveying surface 21a is inclined or loose. Therefore, the pre-processing head 5 executes the printing process on the workpiece W outside the inter-roller region U, so the landing position accuracy of the discharged droplets is lower than that of the post-processing head 6, but as described above, the amount of discharged droplets of the pre-processing head 5 is larger than that of the post-processing head 6, so the amount of spread after landing is also large, and the required landing position accuracy is lower than that of the post-processing head 6. Therefore, even if the pre-processing head 5 is arranged outside the inter-roller region U in a plan view, the image quality of the printed image is not deteriorated.

[0094] Therefore, in this embodiment, similarly to the first embodiment, deterioration in the quality of the printed image caused by the difference in the amount of droplets ejected by the pre-treatment head 5 and the post-treatment head 6 can be suppressed.

[0095] (Modification of the second embodiment) Fig. 10 is a view equivalent to Fig. 9, showing a modified example of the second embodiment. In this modified example, the magnitude relationship of the ejected droplet amounts between the pre-processing head 5 and the post-processing head 6, and the relative positional relationship between the pre-processing head 5, the post-processing head 6, and the inter-roller region U in the transport direction F are different from those in the second embodiment. Note that the configuration other than this point is the same as in the second embodiment, and in the following description, the same components as in the second embodiment are denoted by the same reference numerals and detailed description thereof will be omitted.

[0096] That is, in this modified example, the amount of droplets ejected by the pre-processing head 5 is set to be less than the amount of droplets ejected by the post-processing head 6. In this modified example, when the amount of droplets ejected by the ink head 4 is X (pl), the amount of droplets ejected by the pre-processing head 5 is set to half the amount of droplets ejected by the ink head 4 (=X / 2(pl)), and the amount of droplets ejected by the post-processing head 6 is set to the same amount (=X(pl)) as the amount of droplets ejected by the ink head 4. Note that this example of setting the amount of droplets ejected is just one example and is not limited to this.

[0097] In this modified example, as shown in FIG. 10, the positions of the upstream support roller 25 and the downstream support roller 26 in the conveying direction F are set so that, in a planar view (viewed from a height direction perpendicular to the conveying surface 21a of the conveying belt 21), the entire discharge area R of the pre-processing head 5 is located within the inter-roller area U, and the entire discharge area R of the post-processing head 6 is located outside the inter-roller area U (downstream in the conveying direction F).

[0098] In this modified example, the first reference distance d1, which is the reference distance of the pre-processing head 5 (i.e., the distance between the center line K1 of the discharge area R of the pre-processing head 5 and the axis J1 of the upstream support roller 25), and the second reference distance d2, which is the reference distance of the post-processing head 6 (i.e., the distance between the center line K2 of the discharge area R of the post-processing head 6 and the axis J2 of the downstream support roller 26), are set to be equal (i.e., d1=d2).

[0099] [Effects of the Modification of the Second Embodiment] According to this modification, the amount of droplets discharged by the pre-processing head 5 is set to be smaller than the amount of droplets discharged by the post-processing head 6, so that the pre-processing head 5 spreads less after the droplets land compared to the post-processing head 6, and therefore the allowable deviation of the droplets is smaller (in other words, high landing position accuracy is required). In this modification, the pre-processing head 5, which requires such high landing position accuracy, is arranged in the inter-roller region U, where the conveyor belt 21 is less loose and fluttering in plan view, so that the landing position accuracy of the droplets required for the pre-processing head 5 can be ensured. Therefore, as in the second embodiment, it is possible to suppress the deterioration of the image quality of the printed image caused by the difference in the amount of droplets discharged by the pre-processing head 5 and the post-processing head 6.

[0100] (Other embodiments) The inkjet printer 1 (inkjet recording apparatus) according to an embodiment of the present disclosure has been described above, but the present disclosure is not limited to this, and for example, the following modified embodiments can be adopted.

[0101] (1) In each of the above embodiments and variations, an example has been described in which the volume of a droplet (pl) is used as the amount of the droplet when identifying the pre-processing head 5 and the post-processing head 6 which ejects a smaller amount of droplets of the liquid to be ejected from the ejection hole n, and the post-processing head which ejects a larger amount of the droplet. However, this is not limited to this, and the amount of the droplet may be the mass of the droplet.

[0102] (2) In the above-described embodiments and modified examples, the ejection holes n of each head 4 to 6 are arranged in two rows of a large number of ejection holes n (each row has the same number of ejection holes n) in a regular lattice pattern as shown in Fig. 6, but the present invention is not limited to this, and for example, as shown in Fig. 11, the number of ejection holes n in each row does not have to be the same, and the ejection holes n may be irregularly arranged such that the positions of the ejection holes n at both ends of the transport direction F are shifted in the transport direction F as shown in the same figure. Even in this case, the ejection area R indicated by the two-dot chain line in Fig. 11 is specified according to the definition of the ejection area R described in the above-described embodiments.

[0103] (3) In each of the above-described embodiments and modifications, the heads 4 to 6 have the same number of ejection holes n and the same arrangement, but this is not limited to the above and may be different from each other.

[0104] (4) In the second embodiment, the upstream support roller 25 and the downstream support roller 26 are positioned in the conveying direction F so that the entire discharge area R of the pre-processing head 5 is located outside the inter-roller area U (upstream of the conveying direction F) in a planar view (see Figure 9), but this is not limited to this, and part or the entire discharge area R of the pre-processing head 5 may be located within the inter-roller area U.

[0105] (5) In the modified example of the second embodiment, the positions of the upstream support roller 25 and the downstream support roller 26 in the conveying direction F are set so that the entire discharge area R of the post-processing head 6 is located outside the inter-roller area U (downstream in the conveying direction F) in a planar view (see FIG. 10 ). However, this is not limited to this, and part or all of the post-processing head 6 may be located within the inter-roller area U.

[0106] (6) In each of the above-described embodiments and modified examples, the ink heads 4 are arranged in two rows in the transport direction F, but this is not limited thereto, and they may be arranged in one row or three or more rows. Also, while one each of the pre-treatment head 5 and post-treatment head 6 is arranged, two or more pre-treatment heads 5 or post-treatment heads 6 may be arranged side by side in the main scanning direction, or two or more pre-treatment heads 5 or post-treatment heads 6 may be arranged side by side in the transport direction F. In the latter case, it is considered that the positional relationship between the upstream support roller 25 and downstream support roller 26 described above is applied to the pre-treatment head 5 and post-treatment head 6 closest to the ink head 4 in the transport direction F.

[0107] (7) In each of the above embodiments and variations, the ink head 4, pre-processing head 5 and post-processing head 6 are mounted on a carriage 3 that moves in the main scanning direction, but this is not limited to this. The ink head 4, pre-processing head 5 and post-processing head 6 may be mounted on a fixed line head and only the workpiece W may be moved in the transport direction relative to the line head. [Explanation of symbols]

[0108] J1: Axis (axis of the upstream support roller) J2: Axis (axis of downstream support roller) F: Transport direction R:Discharge area U: Area between rollers W: Work (recording medium) d1: 1st reference distance d2: 2nd reference distance n:Discharge hole 1: Inkjet printer (inkjet recording device) 3: Carriage 4: Ink head 5: Pre-treatment head 6: Post-processing head 21: Conveyor belt 21a: conveying surface 22: Drive roller (pair of rollers) 23: Driven roller (pair of rollers) 25: Upstream support roller 26: Downstream support roller 29: Roller tilt adjustment mechanism (adjustment mechanism)

Claims

1. a head group including an ink head having an ejection region for ejecting ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid; a conveyor belt having a conveyance surface facing the head group with a gap on the ejection region side, and moving in a circular movement along a conveyance direction to convey a recording medium on the conveyance surface along the conveyance direction; a pair of rollers arranged at an interval in the conveying direction and around which the conveying belt is wound; an upstream support roller and a downstream support roller that are arranged side by side in the conveying direction between the pair of rollers and support the conveying belt from an inner side of the belt, the pre-treatment head, the ink head, and the post-treatment head are disposed in this order from the upstream side to the downstream side in the transport direction, When a distance in the transport direction between a center position in the transport direction of the ejection region of the pre-processing head and an axial position of the upstream support roller is defined as a first reference distance, and a distance in the transport direction between a center position in the transport direction of the ejection region of the post-processing head and an axial position of the downstream support roller is defined as a second reference distance, An inkjet recording device, wherein one of the first and second reference distances of the pre-treatment head and the post-treatment head ejecting a smaller amount of liquid is smaller than the other of the first and second reference distances of the pre-treatment head and the post-treatment head ejecting a larger amount of liquid.

2. 2. The ink jet recording apparatus according to claim 1, An inkjet recording device, wherein, when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the pre-treatment head, the entire ejection area of ​​the ink head, and the entire ejection area of ​​the post-treatment head are located within an inter-roller area on the transport belt between a contact line with the upstream support roller and a contact line with the downstream support roller.

3. 2. The ink jet recording apparatus according to claim 1, The inkjet recording apparatus further comprises an adjustment mechanism for adjusting the parallelism between the upstream support roller and the downstream support roller.

4. 4. The inkjet recording apparatus according to claim 1, an inkjet recording apparatus, wherein one of the pre-treatment head and the post-treatment head which ejects a smaller amount of liquid is the post-treatment head;

5. 4. The inkjet recording apparatus according to claim 1, an inkjet recording apparatus, wherein one of the pre-treatment head and the post-treatment head which ejects a smaller amount of liquid is the pre-treatment head;

6. a head group including an ink head having an ejection region for ejecting an ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid; a conveyor belt having a conveying surface facing the head group with a gap on the ejection region side, the conveyor belt moving in a circular movement along a conveying direction to convey a recording medium on the conveying surface along the conveying direction; and a pair of rollers arranged at an interval from each other in the conveying direction and around which the conveyor belt is wound; an upstream support roller and a downstream support roller that are arranged side by side in the conveying direction between the pair of rollers and support the conveying belt from an inner side of the belt, the pre-treatment head, the ink head, and the post-treatment head are disposed in this order from the upstream side to the downstream side in the transport direction, the amount of liquid discharged from the post-treatment head is set to be smaller than the amount of liquid discharged from the pre-treatment head, a distance in the transport direction between a center position in the transport direction of the discharge region of the pre-treatment head and an axial position of the upstream support roller is set equal to a distance in the transport direction between a center position in the transport direction of the discharge region of the post-treatment head and an axial position of the downstream support roller, An inkjet recording device, wherein, when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the post-processing head is located within an inter-roller area on the transport belt between a contact line with the upstream support roller and a contact line with the downstream support roller.

7. 7. The ink jet recording apparatus according to claim 6, An inkjet recording device, wherein, when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the post-processing head is located within the inter-roller area, while at least a portion of the ejection area of ​​the pre-processing head is located outside the inter-roller area.

8. a head group including an ink head having an ejection region for ejecting ink liquid, a pre-treatment head having an ejection region for ejecting a pre-treatment liquid, and a post-treatment head having an ejection region for ejecting a post-treatment liquid; a conveyor belt having a conveying surface facing the head group with a gap on the ejection region side, the conveying belt moving in a circular movement along a conveying direction to convey a recording medium on the conveying surface along the conveying direction; and a pair of rollers arranged at an interval from each other in the conveying direction, around which the conveying belt is wound; an upstream support roller and a downstream support roller that are arranged side by side in the conveying direction between the pair of rollers and support the conveying belt from an inner side of the belt, the pre-treatment head, the ink head, and the post-treatment head are disposed in this order from the upstream side to the downstream side in the transport direction, the amount of liquid discharged from the pre-treatment head is set to be smaller than the amount of liquid discharged from the post-treatment head, a distance in the transport direction between a center position in the transport direction of the discharge region of the pre-treatment head and an axial position of the upstream support roller is set equal to a distance in the transport direction between a center position in the transport direction of the discharge region of the post-treatment head and an axial position of the downstream support roller, An inkjet recording device, wherein, when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the pretreatment head is located within an inter-roller area of ​​the transport belt between a contact line with the upstream support roller and a contact line with the downstream support roller.

9. 9. The ink jet recording apparatus according to claim 8, An inkjet recording device, wherein, when viewed from a direction perpendicular to the transport surface of the transport belt, the entire ejection area of ​​the pre-processing head is located within the inter-roller region, while at least a portion of the ejection area of ​​the post-processing head is located outside the inter-roller region.

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