Ink jet recording device

Abstract

To prevent fluttering of a conveying belt.SOLUTION: In an ink jet recording device, a distance between a central position of an ejection region R of a pre-processing head (5) in a conveyance direction and an axial position of an upstream support roller (25) is defined as a first reference distance (d1), and a distance between a central position of an ejection region R of a post-processing head (6) in the conveyance direction and an axial position of a downstream support roller (26) is defined as a second reference distance (d2). In this case, the reference distance (second reference distance (d2) in FIG. 7) of one of the pre-processing head (5) and the post-processing head (6) that ejects a smaller amount of liquid (post-processing head (6) in FIG. 7) is set to be smaller than the reference distance (first reference distance (d1) in FIG. 7) of the other that ejects a larger amount of liquid.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] An inkjet recording apparatus such as an inkjet printer includes an ink head that discharges ink droplets for image formation toward a recording medium. For example, when the recording medium is a fiber sheet such as a fabric or a knitted fabric or a plastic sheet, it may be necessary to apply a pretreatment liquid and a post-treatment liquid to the recording medium before and after discharging the ink droplets toward the recording medium. The pretreatment liquid is, for example, a treatment liquid for improving the fixability of ink droplets to the recording medium and the aggregability of ink pigments. The post-treatment liquid is, for example, a treatment liquid for enhancing the fastness of the printed image. In this case, the inkjet recording apparatus is provided with a treatment head that discharges droplets of the pretreatment liquid and the post-treatment liquid in addition to the ink head.

[0003] The ink head and each treatment head have a plurality of discharge holes that discharge droplets of the respective liquid to be discharged and a discharge surface through which the plurality of discharge holes open.

[0004] In the recording process, the recording medium is conveyed in a predetermined conveyance direction by a conveyance mechanism, and ink droplets and treatment droplets are discharged from the respective discharge holes of the ink head and each treatment head.

[0005] The conveyance mechanism includes an endless conveyance belt disposed at a position facing the ink head and each treatment head, and a driving roller and a driven roller.

[0006] The driving roller and the driven roller are arranged at intervals from each other in the conveyance direction. The conveyance belt has a conveyance surface disposed with a gap on the discharge side of the ink droplets with respect to the ink head, and circulates while being wound around the driving roller and the driven roller, thereby conveying the recording medium on the conveyance surface in the conveyance direction.

Summary of the Invention

[0007] An inkjet recording apparatus according to an aspect of the present disclosure includes a head group including an ink head having a discharge area for discharging an ink liquid, a pretreatment head having a discharge area for discharging a pretreatment liquid, and a post-treatment head having a discharge area for discharging a post-treatment liquid; a conveyance belt having a conveyance surface that faces the head group with a gap on the discharge area side and conveys a recording medium on the conveyance surface along the conveyance direction by circulating along the conveyance direction; a pair of rollers that are arranged at intervals in the conveyance direction and around which the conveyance belt is wound; and an upstream support roller and a downstream support roller that are arranged side by side in the conveyance direction between the pair of rollers and support the conveyance belt from the inner side of the belt. The pretreatment head, the ink head, and the post-treatment head are arranged in this order from the upstream side to the downstream side in the conveyance direction. When a first reference distance is a distance in the conveyance direction between a central position in the conveyance direction of the discharge area in the pretreatment head and an axial position of the upstream support roller, and a second reference distance is a distance in the conveyance direction between a central position in the conveyance direction of the discharge area in the post-treatment head and an axial position of the downstream support roller, either one of the first and second reference distances of the pretreatment head and the post-treatment head with a smaller amount of liquid discharged is smaller than the other of the first and second reference distances of the one with a larger amount of liquid discharged.

[0008] An inkjet recording apparatus according to another aspect of the present disclosure includes a head group including an ink head having a discharge area for discharging an ink liquid, a pretreatment head having a discharge area for discharging a pretreatment liquid, and a post-treatment head having a discharge area for discharging a post-treatment liquid; a conveyance belt having a conveyance surface that faces the head group with a gap on the discharge area side and conveys a recording medium on the conveyance surface along the conveyance direction by circulating along the conveyance direction; a pair of rollers that are arranged at intervals in the conveyance direction and around which the conveyance belt is wound; an upstream support roller and a downstream support roller that are arranged side by side in the conveyance direction between the pair of rollers and support the conveyance belt from the inner side of the belt. The pretreatment head, the ink head, and the post-treatment head are arranged in this order from the upstream side to the downstream side in the conveyance direction. The amount of the liquid discharged from the post-treatment head is set to be less than the amount of the liquid discharged from the pretreatment head. The distance in the conveyance direction between the center position in the conveyance direction of the discharge area of the pretreatment head and the axial position of the upstream support roller is set to be equal to the distance in the conveyance direction between the center position in the conveyance direction of the discharge area of the post-treatment head and the axial position of the downstream support roller. When viewed from a direction perpendicular to the conveyance surface of the conveyance belt, the entire discharge area of the post-treatment head is located within the roller-intermediate region sandwiched between the contact line with the upstream support roller and the contact line with the downstream support roller on the conveyance belt.

[0009] An inkjet recording apparatus according to another aspect of the present disclosure includes a head group including an ink head having a discharge area for discharging an ink liquid, a pretreatment head having a discharge area for discharging a pretreatment liquid, and a post-treatment head having a discharge area for discharging a post-treatment liquid, a conveyance belt having a conveyance surface facing the head group with a gap on the discharge area side and configured to convey a recording medium on the conveyance surface along the conveyance direction by orbiting along the conveyance direction, a pair of rollers arranged at intervals in the conveyance direction around which the conveyance belt is wound, and an upstream support roller and a downstream support roller arranged side by side in the conveyance direction between the pair of rollers and supporting the conveyance belt from the inner side of the belt. The pretreatment head, the ink head, and the post-treatment head are arranged in this order from the upstream side to the downstream side in the conveyance direction. The amount of the liquid discharged from the pretreatment head is set to be less than the amount of the liquid discharged from the post-treatment head. The distance in the conveyance direction between the central position in the conveyance direction of the discharge area of the pretreatment head and the axial position of the upstream support roller is set to be equal to the distance in the conveyance direction between the central position in the conveyance direction of the discharge area of the post-treatment head and the axial position of the downstream support roller. When viewed from a direction perpendicular to the conveyance surface of the conveyance belt, the entire discharge area of the pretreatment head is located within the roller-intermediate area sandwiched between the contact line with the upstream support roller and the contact line with the downstream support roller on the conveyance belt.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an inkjet recording apparatus according to each embodiment of the present disclosure will be described with reference to the drawings. In these embodiments, as a specific example of the inkjet recording apparatus, an inkjet printer including an ink head that ejects ink droplets for image formation onto a wide and long recording medium is exemplified. The inkjet printer is suitable for digital textile printing in which images such as characters and patterns are printed on a recording medium made of a fabric such as a woven or knitted fabric by an inkjet method. Of course, the inkjet recording apparatus according to the present disclosure can also be used for applications in which various inkjet images are printed on a recording medium such as a paper sheet or a resin sheet.

[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 apparatus) according to the first embodiment of the present disclosure, and FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1.

[0014] The inkjet printer 1 is a printer that prints an image on a wide and long workpiece W (recording medium) by an inkjet method, and includes a device frame 10, a workpiece conveyance unit 20 incorporated in the device frame 10, a carriage 3 disposed above the workpiece conveyance unit 20, and a rail support base 40 supported from below by the device frame 10.

[0015] In the present embodiment, the horizontal direction is the main scanning direction S during printing with respect to the workpiece W, and the direction from the rear to the front is the sub-scanning direction (the conveyance direction F of the workpiece W, which corresponds to the conveyance direction).

[0016] The device frame 10 forms a framework for mounting various components of the inkjet printer 1. The workpiece conveyance unit 20 is a mechanism that intermittently feeds (conveys) the workpiece W so that the workpiece W advances in the conveyance direction F from the rear to the front in the printing area where the inkjet printing process is performed. The carriage 3 mounts an ink head 4, a pre-treatment head 5, a post-treatment head 6, and a sub-tank 7, and reciprocates in the main scanning direction S (horizontal direction) that intersects (is orthogonal to) the conveyance direction F of the workpiece W during the inkjet printing process.

[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 horizontal width corresponding to the workpiece conveyance unit 20. The right frame 112 and the left frame 113 are respectively erected adjacent to the right and left of the central frame 111. A printing area A where printing processing is performed on the workpiece W is set between the right frame 112 and the left frame 113.

[0018] The central frame 111 has angular pipe members (not shown) connected to form a rectangular parallelepiped-shaped framework, 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 a rectangular plate-shaped side plate main body portion 111b disposed so as to close the left and right sides of the rectangular parallelepiped-shaped framework, and a side plate protruding portion 111c connected to the upper end portion of the side plate main body portion 111b and protruding above a conveyance belt 21 described later. The rail support base 40 is fixed to the upper end surface of the side plate protruding portion 111c.

[0019] At the front, rear, left, and right four corners on the lower surface of the central frame 111, moving casters 120 (only two of the front ones are shown in FIG. 1) are respectively attached.

[0020] Also, moving casters 120 (only one of which is shown in FIG. 1) are respectively attached to the central portion in the front-rear direction at the left end of the lower surface of the left frame 113 and to the central portion in the front-rear direction at the right end of the lower surface of the right frame 112.

[0021] As shown in FIG. 2, an adjustment bolt 123 is attached to each caster 120 with its head in contact with the floor surface. After an operator moves 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, 113 from the floor surface by rotationally adjusting the adjustment bolt 123.

[0022] The right frame 112 forms a maintenance area 13. The maintenance area 13 is an area where the carriage 3 is retracted when the printing process is not executed. In the maintenance area 13, cleaning processes, purge processes, etc. of the discharge holes n (FIG. 6) of the ink head 4, the pre-treatment head 5, and the post-treatment head 6 are performed, and a cap is fitted. The left frame 113 forms a turning area 14 for the carriage 3. The turning area 14 is an area where the carriage 3 that has mainly scanned the printing area A from right to left in the printing process temporarily enters when performing the main scanning in the reverse direction.

[0023] FIG. 3 is an enlarged side view showing the carriage mounting portion of the inkjet printer 1 as viewed from the left side. As shown in this figure, on the upper side of the apparatus frame 10, a left-right guide mechanism portion 15 for causing the carriage 3 to reciprocate in the left-right direction is assembled via a rail support base 40. The carriage 3 is attached to the left-right guide mechanism portion 15 via an up-down guide mechanism portion 16.

[0024] The up-down guide mechanism portion 16 has a pair of guide rails 161 (only one is shown in FIG. 3) that extend in the up-down direction and are arranged at intervals in the left-right direction, sliders 162 that are movably engaged with the respective guide rails 161 in the up-down direction, and a base plate 163 to which the pair of guide rails 161 are fixed. Two of the sliders 162 are respectively provided on each guide rail 161. The base plate 163 is a rectangular plate member having substantially the same left-right width as the carriage 3. The base plate 163 is fixed to a slider 152 of the left-right guide mechanism portion 15 described later.

[0025] The left-right guide mechanism portion 15 is fixed to the back surface (rear side surface) of the base plate 163 and holds the carriage 3 via the base plate 163 so as to be movable in the main scanning direction S (left-right direction). Specifically, the left-right guide mechanism portion 15 has a pair of guide rails 151 that extend in the left-right direction and are arranged at intervals in the up-down direction, and sliders 152 that are movably engaged with the respective guide rails 151 in the left-right direction. The guide rails 151 straddle the central 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). Two of the sliders 152 are respectively engaged with each guide rail 151. The base plate 163 of the up-down guide mechanism portion 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 on the base plate 163 so as to be movable in the up-down direction via the guide rails 161 and the sliders 162.

[0026] In the left and right guide mechanism section 15, a timing belt 153 (shown only in FIG. 1) is assembled so as to be capable of circulating and moving 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. The base plate 163 moves leftward or rightward while being guided by the pair of guide rails 151 as the timing belt 153 circulates and moves leftward or rightward. The timing belt 153 is driven to circulate by a carriage drive section composed of a motor or the like. The drive control of the carriage drive section is executed based on an operation program stored in advance by a controller (not shown).

[0027] [Configuration of Rail Support Base] As shown in FIG. 3, the rail support base 40 is a support base that supports the pair of guide rails 151 of the left and right guide mechanism section 15, and is arranged so as to straddle the upper end surfaces of the left and right side plates 111a (more specifically, the side - plate protruding portions 111c of the side plates 111a) of the central frame 111.

[0028] The rail support base 40 has a front side plate 41 to which the pair of guide rails 151 are fixed, a rear side plate 42 arranged at a distance behind the front side plate 41, two upper and lower connecting plates 43 connecting the front side plate 41 and the rear side plate 42, and left and right seat members 44 supporting the lower end portions of the front side plate 41 and the rear side plate 42. At both ends of the left and right seat members 44, adjustment bolts (not shown) whose heads abut against the upper end surfaces of the side plates 111a are attached, and the inclination of the rail support base 40 can be adjusted by rotating and adjusting these adjustment bolts.

[0029] [Configuration of Work Conveying Section] Returning to FIG. 2, the configuration of the work conveying section 20 will be described. The work conveying section 20 has a conveying 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 conveying belt 21 is wound around a driving roller 22 and a driven roller 23 and is configured to be rotatable in the front-rear direction. The upper surface of the conveying belt 21 functions as a conveying surface 21a for conveying the workpiece W (recording medium). The conveying 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 intervals 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 inside 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 (more specifically, the side plate main body 111b of the side plates 111a) of the central frame 111. The driving roller 22 is driven by a motor (not shown) to rotate the conveying belt 21. The driven roller 23 rotates following the rotation of the conveying belt 21 while applying tension to suppress slack to the conveying belt 21.

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

[0033] Upstream (in this example, rear side) of the feed roller 24, a workpiece supply and conveying mechanism (not shown) is provided. The feed roller 24 sandwiches the workpiece W supplied from this workpiece supply and conveying mechanism between itself and the conveying belt 21 and feeds it out to the downstream side (in this example, the front side). The fed-out workpiece W moves from the upstream side to the downstream side along with the circumferential movement of the conveying belt 21 and is carried into the printing area A (image forming position) facing the carriage 3.

[0034] The printing area A is located closer to the front side between the driving roller 22 and the driven roller 23 in a plan view. The upstream support roller 25 and the downstream support roller 26 extend in the left - right direction and are arranged at intervals in the front - rear direction between the driving roller 22 and the driven roller 23.

[0035] The upstream support roller 25 and the downstream support roller 26 support the lower surface of the conveyor belt 21 from the inner - circumferential 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 (more specifically, the side - plate main - body portions 111b of the side plates 111a) of the central frame 111.

[0036] The upper - end positions of the upstream support roller 25 and the downstream support roller 26 are at the same height as each other and are located slightly above the upper - end positions of the driving roller 22 and the driven roller 23. Thereby, the tension of the portion of the conveyor belt 21 between the upstream support roller 25 and the downstream support roller 26 (roller - between region U described later) can be increased to suppress the slack of the conveyor belt 21.

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

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

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

[0040] Flat surfaces 27b formed by D-cuts are formed at both upper and lower ends of the holder main body 27a when viewed from the axial direction. The lower flat surface 27b is used as a contact surface with the screw 291 in the roller tilt adjustment mechanism 29 described later.

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

[0042] The roller tilt adjustment mechanism 29 includes screws 291 (only the left side is shown in FIG. 5) respectively arranged below the left and right bearing holders 27, an adjustment block 292 with which the screws 291 are screwed, and a fixing nut 293 for fixing the screws 291. By adjusting the vertical position of the bearing holder 27 via the screws 291, the tilt of the downstream support roller 26 in the height direction (vertical direction) can be adjusted. The roller tilt 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. A screw hole 292a penetrating in the vertical direction is formed in the adjustment block 292, and the sweet potato screw 291 is screwed into the screw hole 292a and penetrates the adjustment block 292 vertically. The upper end surface of the sweet potato 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 sweet potato screw 291, the operator can move the bearing holder 27 up and down following the upper end position of the sweet potato screw 291. Then, by adjusting the vertical positions of the left and right bearing holders 27 that hold both ends of the downstream support roller 26, the operator can adjust the inclination of the downstream support roller 26 in the height direction (vertical direction).

[0044] [Configuration of the carriage] Next, the configuration of the carriage 3 will be described with reference to FIGS. 1 to 3. During the printing process, the carriage 3 is supported at a predetermined height by the vertical guide mechanism unit 16 and reciprocates in the main scanning direction S (the left-right direction in this embodiment), which intersects (orthogonal in this embodiment) the conveyance direction F, along the guide rail 151 of the left and right guide mechanism units 15.

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

[0046] The carriage body frame 30 has a rectangular vertical plate 30a fixed to the slider 162 of the vertical guide mechanism unit 16 and left and right side plates 30b connected to the edge portions on both the left and right sides of the vertical plate 30a, and has a U-shaped shape that is open to the front in plan view.

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

[0048] [Arrangement configuration of each head and sub-tank] FIG. 5 is a plan view showing the arrangement configuration of the heads 4 to 6 mounted on the upper surface of the head support plate 31 in the carriage 3, and FIG. 6 is a plan view showing the ejection surfaces Q of the heads 4 to 6.

[0049] As shown in FIG. 5, a head group including a plurality of ink heads 4 that eject ink droplets for image formation onto the workpiece W, a pretreatment head 5 that ejects droplets of a non-color-developing treatment liquid, and a post-treatment head 6 is attached to the upper surface of the head support plate 31.

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

[0051] Each of the heads 4 to 6 has a rectangular parallelepiped shape that is long in the front-rear direction in plan view, and they have the same configuration as each other. That is, each of the heads 4 to 6 includes a number (a plurality) of ejection holes n (so-called nozzles) that eject droplets of the ejection target liquid by an ejection method such as a piezo method using a piezo 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, these numerous ejection holes n are composed of two rows of ejection hole rows arranged in the main scanning direction S (left-right direction), and each ejection hole row is composed of a number (a plurality) of ejection holes n arranged at equal intervals in the conveyance direction F (front-rear direction). These ejection holes n open to the ejection surface Q, which 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 in one ejection operation from each ejection hole n of each of the heads 4 to 6 (in this example, for example, the volume ejected in response to a pulse of one cycle of the drive voltage) will be simply referred to as the "amount of ejected droplets".

[0052] In the present disclosure, the region on the discharge surface Q where the multiple discharge holes n are formed is referred to as the discharge region R. The discharge region R is defined by a pair of straight lines (lines L1 and L2 in the example of FIG. 6) that pass through the outer ends of the discharge holes n located on the outermost side in the conveyance direction F among the multiple discharge holes n and extend in the main scanning direction S, which is the direction orthogonal thereto, and a pair of straight lines (lines L3 and L4 in the example of FIG. 6) that pass through the outer ends of the discharge holes n located on the outermost side in the main scanning direction S among the multiple discharge holes n and extend in the conveyance direction F, which is the direction orthogonal thereto. In this example, the arrangement configurations (number, arrangement form, hole diameter, hole pitch) of the discharge holes n in each of the heads 4 to 6 are the same, and thus the shape and dimensions of the discharge region R are also the same.

[0053] As the ink liquid that is the discharge target liquid of the ink head 4, for example, an aqueous pigment ink liquid containing an aqueous solvent, a pigment, and a binder resin can be used. The plurality of ink heads 4 in the present embodiment include first to sixth ink heads 4A to 4F that each discharge different six-color ink liquids. For example, the first ink head 4A discharges orange ink droplets, the second ink head 4B discharges green ink droplets, the third ink head 4C discharges yellow ink droplets, the fourth ink head 4D discharges red ink droplets, the fifth ink head 4E discharges blue ink droplets, and the sixth ink head 4F discharges black ink droplets.

[0054] The ink heads 4A to 4F of various colors are mounted on the head support plate 31 of the carriage 3 so as to be arranged in the main scanning direction S. The ink heads 4A to 4F of various colors each have two heads. For example, the first ink head 4A is composed of an upstream head 4A1 arranged on the upstream side in the conveyance direction F and a downstream head 4A2 arranged on the downstream side of the upstream head 4A1 and shifted to the left side in the main scanning direction S. The ink heads 4B to 4F of other colors are the same. The upstream heads of these ink heads 4B to 4F are arranged in a line in the main scanning direction S at the same position as the upstream head 4A1 in the conveyance direction F, and the downstream heads are arranged in a line in the main scanning direction S at the same position as the downstream head 4A2 in the conveyance direction F. In this example, the upstream portions of the downstream heads 4A2 to 4F2 are inserted between the upstream heads A1 to 4F1. Thus, the ink heads 4 are arranged in a staggered pattern on the upper surface of the head support plate 31. Thereby, the ink heads 4 can be arranged at a high density in the conveyance direction F, and the size of the carriage 3 in the conveyance direction F can be reduced.

[0055] The pre-treatment head 5 and the post-treatment head 6 are arranged at positions different from those of the ink heads 4 in the conveyance direction F.

[0056] In the example of FIG. 5, one pre-treatment head 5 is arranged on the left side of the left end of the upstream ink head row (that is, the upstream ink heads 4A1 to 4F1). The pre-treatment head 5 is arranged on the upstream side of the ink heads 4 in the conveyance direction F. In other words, the pre-treatment head 5 is arranged such that the central position in the conveyance direction of the discharge area R is located upstream of the central position in the conveyance direction of the discharge area R of the upstream heads 4A1 to 4F1. The downstream portion of the pre-treatment head 5 is arranged at a position overlapping the upstream ink head row (that is, the upstream heads 4A1 to 4F1) in the conveyance direction F.

[0057] Similarly, in the example of FIG. 5, one post-treatment head 6 is disposed to the right of the right end of the downstream ink head row (i.e., the downstream heads 4A2 to 4F2). The post-treatment head 6 is disposed downstream of the ink head 4 in the conveyance direction F. That is, the post-treatment head 6 is arranged such that the central position of its discharge region R in the conveyance direction F is located downstream of the central position of the discharge regions R of the downstream heads 4A2 to 4F2. The upstream portion of the post-treatment head 6 is disposed at a position overlapping the downstream ink head row (i.e., the downstream heads 4A2 to 4F2) in the conveyance direction F.

[0058] The pre-treatment head 5 discharges droplets of a pre-treatment liquid (liquid to be discharged), which is for performing a predetermined pre-treatment on the workpiece W. The droplets of the pre-treatment liquid are discharged from the pre-treatment head 5 to a position on the workpiece W where ink liquid has not yet been discharged from the ink head 4. The pre-treatment liquid is a non-color-developing treatment liquid that does not develop color even when it adheres to the workpiece W, and is, for example, a treatment liquid that exhibits functions such as enhancing the fixing property of ink droplets to the workpiece W and the aggregating property of ink pigments. As such a pre-treatment liquid, a treatment liquid in which a binder resin is blended in a solvent, or a treatment liquid in which a cation resin that is positively charged is blended in a solvent, etc. can be used.

[0059] The post-treatment head 6 discharges droplets of a post-treatment liquid (liquid to be discharged), which is for performing a predetermined post-treatment on the workpiece W to which ink droplets have adhered. The post-treatment liquid is discharged from the post-treatment head 6 to a position on the workpiece W after ink droplets have been discharged from the ink head 4. The post-treatment liquid is similarly a non-color-developing treatment liquid that does not develop color even when it adheres to the workpiece W, and is a treatment liquid that exhibits a function of enhancing the fixing property and fastness (resistance to rubbing and scratching) of the ink image printed on the workpiece W by the ink head 4. As such a post-treatment liquid, a silicone-based treatment liquid, etc. can be used.

[0060] Here, the non-color-developing treatment liquid refers to a liquid that is not recognized by the human eye as having developed color when printed alone on a recording medium. The colors here include those with a chroma of 0, such as black, white, and gray. The non-color-developing treatment liquid is basically a transparent liquid. However, for example, when looking at 1 liter of the treatment liquid in a liquid state, it is not completely transparent and may appear slightly white or the like. Such a color is very faint and cannot be recognized by the human eye as having developed color when printed alone on a recording medium. Depending on the type of treatment liquid, there may be changes such as gloss on the recording medium when printed alone on the recording medium, but such a state is not color development.

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

[0062] Subsequently, the case where the pretreatment liquid and the post-treatment liquid are selectively discharged will be described. As described above, onto the portion of the work W where color is printed in accordance with the image, droplets of the pretreatment liquid, ink droplets, and droplets of the post-treatment liquid are discharged in this order. In this case, the ink droplets may be of one color or a plurality of colors. Basically, the pretreatment liquid and the post-treatment liquid are not discharged onto the portion where no color is printed, that is, the portion where no ink droplets are discharged.

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

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

[0065] [Printing method] The printing method executed by the inkjet printer 1 according to the present embodiment will be described. The inkjet printer 1 performs printing processing on the work W in a serial printing method. When the work W has a wide size, printing cannot be performed while continuously feeding the work W. In the serial printing method, the reciprocating movement of the carriage 3 equipped with the ink heads 4 of each color in the main scanning direction S and the intermittent feeding in the conveying direction F of the work W are repeated. In this example, in both the forward and return paths of the carriage 3, the discharge process of the droplets of the pre-treatment liquid by the pre-treatment head 5, the discharge process of the ink droplets by the ink head 4, and the discharge process of the droplets of the post-treatment liquid by the post-treatment head 6 are executed. Thus, printing processing is possible in both the forward and return movements. The reason why printing processing is possible in both the forward and return movements is that the pre-treatment head 5 and the post-treatment head 6 are arranged by shifting in the conveying direction F with respect to the ink head 4. If, in the carriage 3, the pre-treatment head 5, the ink head 4, and the post-treatment head 6 are arranged in a row in the main scanning direction S in this order, printing processing that can ensure the desired landing order of the pre-treatment liquid and the post-treatment liquid can be realized only in one of the forward or return movements. To enable printing processing in both directions, the pair of the pre-treatment head 5 and the post-treatment head 6 must be arranged on both sides of the array of the ink heads 4. In this case, the width of the carriage 3 in the main scanning direction S becomes large. Such an arrangement is not required in the present 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 pre-treatment head 5 and the post-treatment head 6 may set the amount of ejected droplets (in this example, the volume of droplets of the liquid to be ejected from each ejection hole n in one ejection operation) to different amounts according to the texture of the required printed image or the like. In this example, the post-treatment head 6 is set to have a smaller amount of the ejected droplets (volume) than the pre-treatment head 6. Specifically, in this example, when the amount of ejected droplets by the ink head 4 is X (pl), the amount of ejected droplets by the pre-treatment head 5 is set to the same amount as the ejected droplets by the ink head 4 (= X (pl)), and the amount of ejected droplets by the post-treatment head 6 is set to half of that amount (= X / 2 (pl)). Note that the amount of ejected droplets by each of the heads 4 to 6 described here is an example and is not limited to this.

[0067] When, as in this example, the amount of ejected droplets by the post-treatment head 6 is set to be smaller than the amount of ejected droplets by the pre-treatment head 5, a difference occurs in the spreading state when the respective ejected droplets land on the printing surface of the work W by the pre-treatment head 5 and the post-treatment head 6, which may lead to a deterioration in the image quality of the printed image. On the other hand, in this example, by devising the arrangement configuration of the upstream support roller 25 and the downstream support roller 26, the deterioration in the image quality of the printed image caused by the different amounts of ejected droplets by the pre-treatment head 5 and the post-treatment head 6 is suppressed.

[0068] [Explanation of the Arrangement Positions of the Upstream Support Roller and the Downstream Support Roller] FIG. 7 is an explanatory plan view seen from above the carriage 3 for explaining the arrangement positions of the upstream support roller 25 and the downstream support roller 26.

[0069] In this figure, reference numeral J1 indicates the axis of the upstream support roller 25, and reference numeral J2 indicates the axis of the downstream support roller 26. Further, reference numeral K1 indicates the center line in the conveyance direction F in the discharge area R of the pretreatment head 5 (specifically, a straight line passing through the center position in the conveyance direction F of the discharge area R and extending in the main scanning direction S), and reference numeral K2 indicates the center line in the conveyance direction F in the discharge area R of the post-treatment head 6 (specifically, a straight line passing through the center position in the conveyance direction F of the discharge area R and extending in the main scanning direction S).

[0070] The upstream support roller 25 and the downstream support roller 26 are arranged such that, in a plan view (viewed from the height direction perpendicular to the conveyance surface 21a of the conveyance belt 21), the entire discharge area R of the pretreatment head 5, the entire discharge area R of the ink head 4, and the entire discharge area R of the post-treatment head 6 are located (fit) within the inter-roller region U sandwiched between the contact lines (two straight lines that coincide with the axes J1 and J2 in a plan view) of both support rollers 25 and 26 on the conveyance belt 21.

[0071] That is, the upstream support roller 25 is arranged such that its axis J1 is located upstream of the center line K1 of the discharge area R of the pretreatment head 5 in the conveyance direction F. Further, the downstream support roller 26 is arranged such that its axis J2 is located downstream of the center line K2 of the discharge area R of the post-treatment head 6 in the conveyance direction F.

[0072] Here, when the distance in the conveyance direction F between the center line K1 of the discharge area R of the pretreatment 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 pretreatment head 5. Note that the reference distance means the distance to the nearer roller among 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 pretreatment 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 conveyance direction F from the upstream side to the downstream side 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 interval between 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 pretreatment 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, in the present embodiment, the reference distance (either the first reference distance d1 or the second reference distance d2, and in this example, the second reference distance d2) of the pretreatment head 5 and the post-treatment head 6, whichever has a smaller amount of ejected droplets (the post-treatment head 6 in this embodiment), is set to be smaller than the reference distance (the other of the first reference distance d1 and the second reference distance d2, and in this example, the first reference distance d1) of the one with a larger amount of ejected droplets (the pretreatment head 5 in this embodiment). That is, in the present embodiment, since the post-treatment head 6 has a smaller amount of ejected droplets than the pretreatment head 5, the second reference distance d2 is smaller than the first reference distance d1.

[0077] According to this configuration, even if the amounts of ejected droplets are different between the pretreatment head 5 and the post-treatment head 6, it is possible to suppress a decrease in the image quality of the printed image due to this.

[0078] That is, through intensive research, the inventors et al. arrived at the following ideas (i) and (ii). Specifically, (i) when the amount of ejected droplets ejected from the ejection 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 radial spread due to the droplets being crushed at the time of landing) is also small. Therefore, if the landing position of the ejected droplets deviates even slightly from the target position, the ejected droplets will not spread over the entire dot region targeted. (ii) Therefore, the inventors et al. arrived at the idea that when the amount of ejected droplets is small, the allowable deviation amount of the landing position is smaller compared to when it is large (when the droplet volume is large). As a result of applying this idea to the inkjet printer 1 of this embodiment, the inventors et al. reached the conclusion that the post-treatment head 6 has a smaller allowable deviation amount of the landing position because the amount of ejected droplets is smaller (the volume of the ejected droplets is smaller) compared to the pre-treatment head 5. Therefore, in order to reduce the deviation amount of the landing position of the ejected droplets by the post-treatment head 6, as described above, the second reference distance d2, which is the reference distance of the post-treatment head 6, is set to be smaller than the first reference distance d1, which is the reference distance of the pre-treatment head 5. Thereby, the position of the contact line between the downstream support roller 26 located on the post-treatment head 6 side and the conveyor belt 21 (that is, the position where it is difficult for the conveyor belt 21 to slacken) can be brought as close as possible to the region below the ejection region R of the post-treatment head 6 on the conveyor belt 21. Thereby, it is possible to suppress the conveyor belt 21 from slackening or fluttering below the post-treatment head 6. Therefore, even in the case where, as in this embodiment, the amount of ejected droplets by the post-treatment head 6 is small and the allowable deviation amount of the landing position of the ejected droplets allowed by the post-treatment head 6 is limited to a narrow range, it is possible to land the ejected droplets (post-treatment liquid) within that allowable range. Thus, the dot formation accuracy (the position accuracy of the dots formed after the ejected droplets land) by the post-treatment head 6 does not decrease compared to the pre-treatment head 5. In this way, in this embodiment, it is possible to suppress a difference in dot formation accuracy caused by the difference in the amount of ejected droplets between the pre-treatment head 5 and the post-treatment head 6, and consequently suppress a decrease in the image quality of the printed image.

[0079] In addition, in the present embodiment, in a plan view (when viewed from the height direction perpendicular to the conveyance surface 21a of the conveyance belt 21), the entire discharge region R of the pretreatment head 5, the entire discharge region R of the ink head 4, and the entire discharge region R of the post-treatment head 6 are located inside the inter-roller region U sandwiched between the contact lines of the upstream support roller 25 and the downstream support roller 26 on the conveyance belt 21 (a straight line that coincides with the axes J1 and J2 of both rollers 25 and 26 in a plan view). The positions of both support rollers 25 and 26 in the conveyance direction F are set.

[0080] According to this, the image quality of the printed image can be improved as much as possible. That is, in the inter-roller region U on the conveyance belt 21, since sufficient tension is applied to the conveyance belt 21 by the upstream support roller 25 and the downstream support roller 26, slack and fluttering are unlikely to occur. Therefore, in a plan view, by making the discharge region R of the pretreatment head 5, the discharge region R of the ink head 4, and the discharge region R of the post-treatment head 6 all fit within the inter-roller region U, the discharged droplets from each of the heads 4 to 6 can be made to land on the workpiece W in the inter-roller region U with little slack and fluttering. Thus, it is possible to further suppress the deterioration of the image quality of the printed image due to the slack and fluttering of the conveyance belt 21.

[0081] Further, in the present embodiment, the inkjet printer 1 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, the 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 region U between the rollers in the conveyor belt 21 and the ejection surface 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 ejection surface Q of each head 4 to 6 and the workpiece W on the conveyor belt 21 can be kept constant, suppressing the variation in the landing positions of the ejected droplets from each head 4 to 6, and thus improving the image quality of the printed image.

[0083] (Modification of the First Embodiment) FIG. 8 is a diagram corresponding to FIG. 7 showing a modification of the first embodiment. In this modification, the magnitude relationship of the amounts of ejected droplets by the pretreatment head 5 and the post-treatment head 6, and the magnitude relationship between the first reference distance d1 which is the reference distance of the pretreatment head 5 and the second reference distance d2 which is the reference distance of the post-treatment head 6 are different from those in the first embodiment. Note that the configuration other than this point is the same as that in the first embodiment, and in the following description, the same components as those in the first embodiment are denoted by the same reference numerals and the detailed description thereof is omitted.

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

[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 the amount of discharged droplets of the pretreatment head 5 is smaller than that of the post-treatment head 6 in this embodiment, so 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 side of the pretreatment head 5 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 below the discharge area R of the pretreatment head 5 in the conveyor belt 21. As a result, it is possible to suppress the conveyor belt 21 from sagging or fluttering below the pretreatment head 5. Therefore, even when, as in this modified example, the amount of discharged droplets by the pretreatment head 5 is small and the allowable range of deviation in the landing position is narrow, it is possible to land the discharged droplets (pretreatment droplets) within that allowable range. Accordingly, the dot formation accuracy of the pretreatment head 5 on the printing target surface of the workpiece W does not decrease compared to the post-treatment head 6.

[0088] Therefore, in this modified example, similar to the first embodiment, it is possible to suppress a decrease in the image quality of the printed image caused by the difference in the amount of discharged droplets between the pretreatment head 5 and the post-treatment head 6.

[0089] (Second Embodiment) FIG. 9 is a diagram corresponding to FIG. 7 showing the second embodiment. In this embodiment, the arrangement configuration of the upstream support roller 25 and the downstream support roller 26 is different from that of the first embodiment. Note that the configuration other than this point is the same as that of the first embodiment, and in the following description, the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof is omitted.

[0090] That is, in this embodiment, the amount of discharged droplets of the post-treatment head 6 is set to be less than the amount of discharged droplets of the pretreatment head 5, which is the same as in the first embodiment. However, as will be described below, the relative positional relationship between the upstream support roller 25 and the downstream support roller 26 with respect to each of the heads 4 to 6 is different from that of the first embodiment.

[0091] Specifically, in the present embodiment, in a plan view (when viewed from the height direction perpendicular to the conveyance surface 21a of the conveyance belt 21), the entire discharge region R of the post-treatment head 6 is located within the inter-roller region U sandwiched between the contact lines of the upstream support roller 25 and the downstream support roller 26 in the conveyance belt 21 (a straight line that coincides with the axes J1 and J2 of both rollers 25 and 26 in a plan view), and the entire discharge region R of the pre-treatment head 5 is located outside the inter-roller region U (on the upstream side in the conveyance direction F). The arrangement positions of the upstream support roller 25 and the downstream support roller 26 in the conveyance direction F are set accordingly.

[0092] And in the present embodiment, a first reference distance d1, which is the reference distance of the pre-treatment head 5 (that is, the distance between the center line K1 of the discharge region R of the pre-treatment head 5 and the axis J1 of the upstream support roller 25), and a second reference distance d2, which is the reference distance of the post-treatment head 6 (that is, the distance 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), are set to be equal (that is, d1 = d2).

[0093] [Effects of the Second Embodiment] According to the present embodiment, when the first reference distance d1 and the second reference distance d2, which are the respective reference distances between the pre-treatment head 5 and the post-treatment head 6, are set to be equal, it is possible to suppress a decrease in the image quality of a printed image caused by a difference in the amount of ejected droplets between the pre-treatment head 5 and the post-treatment head 6. That is, in the present embodiment, since the amount of ejected droplets by the post-treatment head 6 is set to be less than the amount of ejected droplets by the pre-treatment head 5 as in the first embodiment, the post-treatment head 6 has a narrower allowable range of landing positions of the ejected droplets that are allowed (in other words, higher landing position accuracy is required). Therefore, by disposing the post-treatment head 6, which requires such high landing position accuracy, in the region U between the rollers in a plan view, it is possible to suppress the slack and flutter of the conveyor belt 21 below the post-treatment head 6 and ensure the high landing position accuracy required for the post-treatment head 6. On the other hand, since the pre-treatment head 5 is disposed outside the region U between the rollers in a plan view, the landing position accuracy of the ejected droplets is lower than that of the post-treatment head 6. That is, outside the region U between the rollers of the conveyor belt 21, the belt tension decreases compared to the region U between the rollers, and a slight inclination in the conveying direction F (an inclination caused because the upper end positions of the two support rollers 25 and 26 are slightly higher than the upper end positions of the driving roller 22 and the driven roller 23) occurs, so that the conveying surface 21a is inclined and slackened. Therefore, for the pre-treatment head 5, since the printing process on the work W is executed outside the region U between the rollers, the landing position accuracy of the ejected droplets is lower than that of the post-treatment head 6. However, as described above, since the amount of ejected droplets of the pre-treatment head 5 is larger than that of the post-treatment head 6, the spreading amount after landing is also large, and the required landing position accuracy is lower than that of the post-treatment head 6. Therefore, even if the pre-treatment head 5 is disposed outside the region U between the rollers in a plan view, the image quality of the printed image does not deteriorate.

[0094] Therefore, in the present embodiment, similar to the first embodiment, it is possible to suppress a decrease in the image quality of a printed image caused by a difference in the amount of ejected droplets between the pre-treatment head 5 and the post-treatment head 6.

[0095] (Modification of the Second Embodiment) FIG. 10 is a view corresponding to FIG. 9 showing a modification of the second embodiment. In this modification, the relationship between the amounts of ejected droplets of the pretreatment head 5 and the post-treatment head 6, and the relative positional relationship between the pretreatment head 5, the post-treatment head 6, and the inter-roller region U in the conveying direction F are different from those of the second embodiment. Note that the configuration other than this point is the same as that of the second embodiment, and in the following description, the same components as those of the second embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted.

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

[0097] And, in this modification, as shown in FIG. 10, in a plan view (viewed from the height direction perpendicular to the conveying surface 21a of the conveying belt 21), the entire ejection region R of the pretreatment head 5 is positioned within the inter-roller region U, and the entire ejection region R of the post-treatment head 6 is positioned outside the inter-roller region U (downstream side in the conveying direction F). The arrangement positions of the upstream support roller 25 and the downstream support roller 26 in the conveying direction F are set.

[0098] And, in this modification, the first reference distance d1 which is the reference distance of the pretreatment head 5 (that is, the distance between the center line K1 of the ejection region R of the pretreatment 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-treatment head 6 (that is, the distance between the center line K2 of the ejection region R of the post-treatment head 6 and the axis J2 of the downstream support roller 26) are set to be equal (that is, d1 = d2).

[0099] [Operational Effects of the Modification of the Second Embodiment] According to this modification example, since the amount of ejected droplets by the pretreatment head 5 is set to be less than the amount of ejected droplets by the post-treatment head 6, the pretreatment head 5 has a smaller spread after the ejected droplets land compared to the post-treatment head 6, and thus the allowable deviation amount of the ejected droplets is also smaller (in other words, high landing position accuracy is required). In this modification example, by arranging the pretreatment head 5, which requires such high landing position accuracy, in the region U between the rollers where there is less slack and flutter of the conveyor belt 21 in a plan view, the landing position accuracy of the ejected droplets required for the pretreatment head 5 can be ensured. Therefore, similar to the second embodiment, it is possible to suppress a decrease in the image quality of the printed image caused by the difference in the amount of ejected droplets between the pretreatment head 5 and the post-treatment head 6.

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

[0101] (1) In each of the above embodiments and modifications, when identifying the processing head with the smaller amount of droplets of the ejection target liquid ejected from the ejection holes n among the pretreatment head 5 and the post-treatment head 6 and the processing head with the larger amount of droplets, an example in which the volume (pl) of the droplets is adopted as the amount of the droplets has been described. However, the present disclosure is not limited thereto, and the amount of the droplets may be the mass of the droplets.

[0102] (2) In each of the above embodiments and modification examples, the ejection holes n of each head 4 to 6 have been described with an example in which a large number of ejection holes n arranged in two rows (the number of ejection holes n in each row is the same) are regularly arranged in a lattice shape as shown in FIG. 6. However, the present disclosure is not limited thereto. For example, as shown in FIG. 11, the number of ejection holes n in each row does not have to be the same, and an irregular arrangement in which the positions of the ejection holes n at both ends in the conveyance direction F are shifted in the conveyance direction F as shown in the same figure may be used. Even in this case, the ejection region R shown by the two-dot chain line in FIG. 11 is defined in accordance with the definition of the ejection region R described in the above embodiment.

[0103] (3) In each of the above embodiments and each modification, the number and arrangement configuration of the discharge holes n of each of the heads 4 to 6 are the same as each other, but this is not restrictive, and they may be different from each other.

[0104] (4) In the second embodiment, the arrangement positions of the upstream support roller 25 and the downstream support roller 26 in the conveyance direction F are set so that the entire discharge region R of the pre-treatment head 5 is located outside (upstream side in the conveyance direction F) the region U between the rollers in plan view (see FIG. 9). However, this is not restrictive, and part or all of the discharge region R of the pre-treatment head 5 may be located within the region U between the rollers.

[0105] (5) In the modification of the second embodiment, the arrangement positions of the upstream support roller 25 and the downstream support roller 26 in the conveyance direction F are set so that the entire discharge region R of the post-treatment head 6 is located outside (downstream side in the conveyance direction F) the region U between the rollers in plan view (see FIG. 10). However, this is not restrictive, and part or all of the post-treatment head 6 may be located within the region U between the rollers.

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

[0107] (7) In each of the above-described embodiments and modifications, the ink head 4, the pre-treatment head 5, and the post-treatment head 6 are mounted on the carriage 3 that moves in the main scanning direction. However, the present invention is not limited to this, and the ink head 4, the pre-treatment head 5, and the post-treatment head 6 may be mounted on a fixed line head, and only the work W may be moved in the conveyance direction with respect to the line head.

Explanation of Signs

[0108] J1: Axis (axis of the upstream support roller) J2: Axis (axis of the downstream support roller) F: Conveyance direction R: Discharge area U: Area between rollers W: Work (recording medium) d1: First reference distance d2: Second reference distance n: Discharge hole 1: Inkjet printer (inkjet recording apparatus) 3: Carriage 4: Ink head 5: Pre-treatment head 6: Post-treatment head 21: Conveying belt 21a: Conveying surface 22: Driving roller (pair of rollers) 23: Driven roller (pair of rollers) 25: Upstream support roller 26: Downstream support roller 29: Roller inclination 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.

Images