Inkjet recording device

Abstract

To provide a configuration capable of suppressing a change of a conveyance force in a decoupling part 3200 on the downstream side of a recording part according to a sheet size.SOLUTION: A decoupling part 3200 includes: a belt 3201 formed with a plurality of holes; a duct 3262 arranged inside the belt 3201 such that an opening part 3264 is opened toward a rear side of a conveyance surface of a sheet of the belt 3201; and a suction fan that sucks air inside the duct 3262 to suck the sheet to the conveyance surface. When a suction length being a length in a width direction of a region where a range formed with a plurality of holes in the belt 3201 and the opening part 3264 overlap is defined as L1, a length in the width direction of the sheet having the minimum size is defined as L2, and a length in the width direction of the sheet having the maximum size is defined as L3, L2<L1<L3 is satisfied.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus that forms an image on a sheet with ink and transports the sheet on which the image has been formed. [Background technology]

[0002] Inkjet recording devices that form images using ink include those configured to eject ink from an image forming unit onto a conveyed sheet to form an image on the sheet, and then convey the sheet to a downstream conveying unit (see, for example, Patent Document 1). In the case of the configuration described in Patent Document 1, the conveying unit employs a configuration in which the sheet is adsorbed to a belt by air suction and conveyed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-69782 Summary of the Invention [Problem to be solved by the invention]

[0004] If a configuration is adopted in which the conveying section that conveys the sheet downstream of the image forming section adsorbs the sheet to the belt by air suction and conveys it, the area where the suction area of ​​the belt overlaps with the sheet changes depending on the size of the sheet, and the conveying force of the belt on the sheet changes, which may cause the image to be distorted during image formation in the upstream image forming section.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a configuration capable of suppressing a change in conveying force in a conveying section downstream of an image forming section depending on the sheet size. [Means for solving the problem]

[0006] One aspect of the present invention includes a first conveyance unit that conveys a sheet, an image forming unit that discharges ink onto the sheet conveyed by the first conveyance unit to form an image on the sheet, and a second conveyance unit that is disposed on the downstream side of the image forming unit with respect to the conveyance direction of the sheet in the first conveyance unit, receives the sheet conveyed by the first conveyance unit, and further conveys it to the downstream side in the conveyance direction. The second conveyance unit includes an endless belt formed with a plurality of holes, a plurality of tensioning members that tension the belt to form a conveyance surface for conveying the sheet on the outer peripheral surface of the belt, a duct disposed inside the belt such that an opening faces the back side of the conveyance surface of the belt, a suction unit that sucks air in the duct to adsorb the sheet to the conveyance surface, and a drive unit that rotates the belt to convey the sheet adsorbed to the conveyance surface. A region where the range in which the plurality of holes are formed in the belt and the opening overlap when viewed from a direction perpendicular to the conveyance surface on the conveyance surface, and a suction length that is the length in the width direction of the sheet intersecting the conveyance direction in a range of a predetermined length from the upper end of the opening with respect to the conveyance direction is defined as L1. When the length in the width direction of the smallest-size sheet on which image formation is possible by the image forming unit is L2, and the length in the width direction of the largest-size sheet on which image formation is possible by the image forming unit is L3, an inkjet recording apparatus characterized by satisfying L2 < L1 < L3.

Advantages of the Invention

[0007] According to the present invention, it is possible to suppress a change in the conveyance force in the conveyance unit on the downstream side of the image forming unit according to the sheet size.

Brief Description of the Drawings

[0008] [Figure 1] Schematic cross-sectional view of the overall configuration of the image forming system according to the first embodiment. [Figure 2] Schematic cross-sectional view of the overall configuration of the drying module according to the first embodiment. [Figure 3] (a) Perspective view showing a part of the decoupling unit according to the first embodiment cut away, (b) Cross-sectional view taken along line C-C of (a). [Figure 4] FIG. 2 is a cross-sectional view showing a schematic configuration of a decoupling unit and its periphery according to the first embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing a schematic configuration of the periphery of a connection portion between a print module and a drying module according to the first embodiment. [Figure 6] FIG. 4 is a schematic cross-sectional view of the decoupling unit and its surroundings showing a state in which a sheet has reached a rear guide from a print belt unit according to the first embodiment. [Figure 7] FIG. 3 is a schematic cross-sectional view of the decoupling unit and its surroundings, showing a state in which a sheet has reached the decoupling unit from the print belt unit according to the first embodiment. [Figure 8] FIG. 3 is a schematic cross-sectional view of the decoupling unit and its surroundings, showing a state in which a sheet straddles a print suction unit and a decoupling suction unit according to the first embodiment. [Figure 9] FIG. 3 is a schematic cross-sectional view of the decoupling portion and its surroundings, showing a state in which a sheet has reached a drying belt unit from the decoupling portion according to the first embodiment. [Figure 10] FIG. 2 is a schematic plan view showing a state in which a minimum size sheet is conveyed by a decoupling unit according to the first embodiment. [Figure 11] FIG. 2 is a schematic plan view showing a state in which a maximum size sheet is conveyed by a decoupling unit according to the first embodiment. [Figure 12] FIG. 10 is a schematic plan view showing a state in which a maximum size sheet is conveyed by a decoupling unit according to a second embodiment. [Figure 13] FIG. 10 is a cross-sectional view showing a schematic configuration of the periphery of a connection between a print module and a drying module according to a second embodiment. [Figure 14] FIG. 10 is a control block diagram of a suction fan according to a third embodiment. [Figure 15] FIG. 11 is a schematic plan view showing a state in which a short sheet is conveyed by a decoupling unit according to a third embodiment. [Figure 16] FIG. 11 is a schematic plan view showing a state in which a long sheet is conveyed by a decoupling unit according to a third embodiment. [Figure 17]10 is a flowchart of suction pressure control of a decoupling suction unit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment The first embodiment will be described with reference to Figures 1 to 11. First, the schematic configuration of an image forming system according to this embodiment will be described with reference to Figure 1.

[0010] [Image formation system] The inkjet recording apparatus 100 as the image forming system of this embodiment uses an inkjet recording method in which ink is ejected to form an image on a sheet, and is a so-called sheet-fed inkjet recording apparatus that forms an ink image on a sheet using two liquids: a reaction liquid and ink. The sheet may be any recording material that can accept ink, such as paper such as plain paper or cardboard, plastic film such as an overhead projector sheet, specially shaped sheets such as envelopes or index paper, or cloth.

[0011] 1, the inkjet recording apparatus 100 of this embodiment includes a feeding module 1000, a printing module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inverting module 6000, and a stacking module 7000. The sheet S supplied from the feeding module 1000 undergoes various processes as it is transported along the transport path within each module, and is finally discharged to the stacking module 7000.

[0012] The feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may each have separate housings, and these housings may be connected to form the inkjet recording apparatus 100. Alternatively, the feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may be arranged in a single housing.

[0013] The feeding module 1000 has storage cabinets 1500a, 1500b, and 1500c for storing sheets S, and the storage cabinets 1500a to 1500c are provided so as to be able to be pulled out toward the front side of the apparatus to store the sheets S. The sheets S are fed one by one in each of the storage cabinets 1500a to 1500c by a separation belt and a transport roller, and are transported to the print module 2000. The number of storage cabinets 1500a to 1500c is not limited to three, and there may be one, two, four or more.

[0014] The print module 2000 includes a pre-imaging registration correction unit (not shown), a print belt unit 2010 as a first transport unit, and a recording unit 2020 as an image forming unit. The sheet S transported from the feeding module 1000 has its tilt and position corrected by the pre-imaging registration correction unit before being transported to the print belt unit 2010. The recording unit 2020 is positioned opposite the print belt unit 2010 with respect to the transport path. The recording unit 2020 is an inkjet recording unit that forms an image by ejecting ink onto the transported sheet S from above using a recording head. Multiple recording heads that eject ink are arranged along the transport direction. In this embodiment, the unit has a total of five line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), as well as reaction liquids. The sheet S is adsorbed and transported by the print belt unit 2010, ensuring clearance between the sheet S and the recording heads.

[0015] The number of ink colors and recording heads is not limited to the five mentioned above. The inkjet method can be a method using a heating element, a piezoelectric element, an electrostatic element, or a MEMS (Micro Electro Mechanical Systems) element. Each color of ink is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains 0.1% to 20.0% by mass of a resin component, water, a water-soluble organic solvent, coloring material, wax, additives, etc., based on the total mass of the ink.

[0016] When the sheet S on which an image is formed by the recording unit 2020 is transported by the print belt unit 2010, the misalignment and color density of the image formed on the sheet S are detected by an inline scanner (not shown) arranged downstream of the recording unit 2020 in the transport direction of the sheet S. Based on the misalignment and color density of the image, the image to be formed on the sheet S, its density, etc. are corrected.

[0017] The drying module 3000 includes an air blowing unit 3100, a decoupling unit 3200 as a second conveying unit, a drying belt unit 3300, and a hot air blowing unit 3400. The drying module 3000 reduces the liquid content of the ink and reaction liquid applied to the sheet S to improve the fixation of the ink to the sheet S by the subsequent fixing module 4000. The sheet S on which an image has been formed is transported to the decoupling unit 3200 arranged within the drying module 3000. In the decoupling unit 3200, frictional force is generated between the sheet S and the belt due to the wind pressure blown from above by the air blowing unit 3100, causing the sheet S to be transported by the belt. In this way, the sheet S placed on the belt is transported by frictional force, preventing the sheet S from shifting as it is transported between the print belt unit 2010 and the decoupling unit 3200. The sheet S transported from the decoupling section 3200 is adsorbed and transported by the drying belt unit 3300, and the ink and reaction liquid applied to the sheet S are dried by blowing hot air from the hot air blowing section 3400 arranged above the belt.

[0018] In this way, the drying module 3000 heats the ink and reaction liquid applied to the sheet S, promoting evaporation of the water, thereby preventing so-called cockling, in which ink splatters on the sheet S and leaves a fringe-like line around the periphery. The drying module 3000 may be any device capable of heat drying, but a hot air dryer or heater is preferred. Heaters that heat air are preferably, for example, electric heating wires or infrared heaters, from the standpoints of safety and energy efficiency. Furthermore, the drying method may be a combination of a method of applying hot air, a method of irradiating the surface of the sheet S with electromagnetic waves (such as ultraviolet or infrared rays), or a conductive heat transfer method using contact with a heating element.

[0019] The fixing module 4000 as a fixing system has a fixing belt unit 4100 as a fixing device. The fixing belt unit 4100 fixes ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit and a heated lower belt unit.

[0020] The cooling module 5000 has a plurality of cooling sections 5001, which cool the high-temperature sheet S transported from the fixing module 4000. The cooling sections 5001, for example, use a fan to draw outside air into a cooling box to increase the pressure inside the cooling box, and then cool the sheet S by blowing air out of the cooling box through a nozzle due to the pressure onto the sheet S. The cooling sections 5001 are arranged on both sides of the transport path of the sheet S, and cool both sides of the sheet S.

[0021] The cooling module 5000 is provided with a transport path switching unit 5002. The transport path switching unit 5002 switches the transport path of the sheet S depending on whether the sheet S is transported to the reversing module 6000 or to a double-sided transport path for double-sided printing, in which images are formed on both sides of the sheet S.

[0022] The reversing module 6000 has a reversing section 6400. The reversing section 6400 reverses the sheet S being conveyed, changing the orientation of the sheet S when it is discharged to the stacking module 7000. The stacking module 7000 has a top tray 7200 and a stacking section 7500, and stacks the sheet S conveyed from the reversing module 6000.

[0023] During double-sided printing, the sheet S is conveyed to a conveyance path below the cooling module 5000 by the conveyance path switching unit 5002. The sheet S then passes through a double-sided conveyance path including the fixing module 4000, the drying module 3000, the print module 2000, and the feeding module 1000, and is returned to the print module 2000. The double-sided conveyance section of the fixing module 4000 is provided with an inverting unit 4200 that inverts the sheet S. An image is formed with ink on the other side of the sheet S that has been returned to the print module 2000, and the sheet S is then discharged to the stacking module 7000 via the drying module 3000, the fixing module 4000, the cooling module 5000, and the inverting module 6000.

[0024] [Drying module] Next, the drying module 3000 will be described in detail with reference to FIGS. 2 and 3(b). FIG. 2 is a schematic cross-sectional view of the drying module 3000, and FIG. 3(a) is a perspective view of a decoupling unit 3200, with a portion of a belt 3201 and a punched metal 3202 (described later) cut away. FIG. 3(b) is a diagram schematically illustrating the cross-sectional configuration of the decoupling unit 3200. As shown in FIGS. 1, 3(a), and 3(b), the front side of the inkjet recording apparatus 100 is represented as the front direction F, the rear side as the rear direction B, the right side as the right direction R, the left side as the left direction L, the upper side as the upper direction U, and the lower side as the lower direction D. An operating unit (not shown) operated by an operator is provided at the front side of the inkjet recording apparatus 100. The sheet is transported from right to left in the left-right direction.

[0025] In this embodiment, as described above, the drying module 3000 includes the air blowing unit 3100, the decoupling unit 3200 as the second conveying unit, the drying belt unit 3300, and the hot air blowing unit 3400. As shown in Fig. 1, the decoupling unit 3200 is disposed downstream of the recording unit 2020 in the sheet conveying direction of the print belt unit 2010 (the direction of arrow A in Fig. 2), and receives the sheet conveyed by the print belt unit 2010 and conveys it further downstream in the conveying direction.

[0026] The decoupling unit 3200 includes an endless belt (second belt) 3201, a drive roller 3231, a tension roller 3211, tension rollers 3270a and 3270b, a punched metal support member 3202, a decoupling suction unit 3260, and a drive motor 3232 serving as a drive unit (second drive unit). The belt 3201 is tensioned by the drive roller 3231, the tension roller 3211, and the tension rollers 3270a and 3270b. The tension roller 3270a and the drive roller 3231, serving as multiple tension members (multiple second tension members), tension the belt 3201 so that a conveying surface (second conveying surface) α, which is a surface for conveying a sheet, is formed on the outer circumferential surface of the belt 3201. The sheet conveying surface α of the belt 3201 is supported from its back surface by the punched metal support member 3202. That is, the punched metal 3202 as a support member is disposed between an opening 3264 of a duct 3262 (described later) and the belt 3201, and supports the back side of the conveying surface α of the belt 3201.

[0027] As shown in FIG. 3( a), the drive roller 3231 and the tension rollers 3270a, 3270b are rotatably supported by a front side plate 3203 and a rear side plate 3204. The front side plate 3203 is a side plate located on the F side of the decoupling unit 3200, and the rear side plate 3204 is a side plate located on the B side of the decoupling unit 3200. The front-to-rear direction of the decoupling unit 3200 is approximately parallel to the rotation axis direction of the various rollers such as the drive roller 3231 described above. The front side plate 3203 and the rear side plate 3204 are connected by a middle plate 3206 located in the front-to-rear direction. The front side plate 3203, the rear side plate 3204, and the middle plate 3206 form a frame of the decoupling unit 3200.

[0028] 2, tension roller 3211 is supported by slide rail 3213 so as to be displaceable in a predetermined direction and rotatable. The predetermined direction is a direction in which belt 3201 is pushed from the inside to the outside. Furthermore, tension roller 3211 is biased in the predetermined direction by the biasing force of tension spring 3214. As a result, tension roller 3211 biases belt 3201 from the inside, thereby applying tension to belt 3201.

[0029] In this embodiment, the tension roller 3211 also functions as a steering roller that controls the position of the belt 3201 in the width direction (the sheet width direction intersecting the sheet conveyance direction, the rotation axis direction of the drive roller 3231). For this reason, one end of the tension roller 3211 in the rotation axis direction is supported by a steering arm (not shown) that rotates around a rotating part (not shown). The steering arm rotates around the rotating part by controlling the rotation amount of a steering motor (not shown) having an eccentric steering cam in accordance with the detection result of an edge sensor 3225 that detects the end position of the belt 3201 in the width direction. As a result, the tension roller 3211 tilts with respect to the drive roller 3231, and the width direction position of the belt 3201 is controlled. This prevents the belt 3201 from meandering.

[0030] As shown in FIGS. 3(a) and 3(b), a plurality of holes (first holes) 3207 are formed in the belt 3201. Furthermore, as shown in FIG. 3(b), a plurality of holes (second holes) 3208 smaller than the holes 3207 in the belt 3201 are formed in the perforated metal 3202. By forming the plurality of holes 3207 in the belt 3201 and the plurality of holes 3208 in the perforated metal 3202 in this way, air can be sucked from the outside to the inside of the belt 3201 by a decoupling suction unit 3260 arranged inside the belt 3201, and the sheet S can be adsorbed to the conveying surface α of the belt 3201. Then, by driving the belt 3201 to rotate via the drive roller 3231 by the drive motor 3232, the sheet S can be conveyed while being adsorbed to the belt 3201.

[0031] Furthermore, to prevent the sheet S attracted to the belt 3201 from floating up, which would reduce the force of attraction of the sheet S to the belt 3201, an air blowing section 3100 is disposed above the decoupling section 3200 as a blowing section that blows air toward the conveying surface α of the belt 3201. The air blowing section 3100 has a plurality of air blowing units 3101 arranged in a line along the sheet conveying direction. Each of the plurality of air blowing units 3101 is capable of blowing air toward the conveying surface α of the belt 3201. The sheet S is pressed against the belt 3201 by the air blown from the plurality of air blowing units 3101, and the sheet S is conveyed by the belt 3201 in the conveying direction.

[0032] Air blown from the air blowing unit 3101 onto areas other than the sheet S can escape through holes 3208 in the punched metal. In this embodiment, the holes 3207 in the belt 3201 and the holes 3208 in the punched metal are provided as circular holes at equal intervals, but they may be arranged at unequal intervals, or may be provided in a shape other than circular. In addition, to prevent the belt 3201 from becoming charged due to friction between the sheet S and the belt 3201 and generating excessive binding force, the belt 3201 is neutralized by a neutralization unit 3250. The neutralization unit 3250 has a neutralization needle 3251 that is in sliding contact with or close to the belt 3201.

[0033] The sheet S conveyed from the decoupling unit 3200 is guided by an internal discharge guide 3240 and sent to a drying belt unit 3300 located downstream of the decoupling unit 3200 in the sheet conveying direction. The drying belt unit 3300 includes an endless belt 3301, a drive roller 3331, a tension roller 3311, heating rollers 3351a and 3351b, a steering roller 3321, a plurality of rollers 3364, a drying suction unit 3360, etc.

[0034] The belt 3301 is stretched over a drive roller 3331, heating rollers 3351a and 3351b, a tension roller 3311, and a steering roller 3321, each of which is rotatably supported. The tension roller 3311 is displaced in a predetermined direction to apply tension to the belt 3301. The belt 3301 is rotated by the drive roller 3331, which is driven by a motor (not shown). A hot air blowing section 3400 is disposed above the drying belt unit 3300. The hot air blowing section 3400 has multiple hot air blowing units 3401 arranged in a row along the sheet conveyance direction. The multiple hot air blowing units 3401 blow hot air heated by heaters onto the sheet conveyance surface β of the belt 3301. As a result, the ink-coated sheet S conveyed from the decoupling section 3200 is pressed against the belt 3301 by the hot air, and the ink on the sheet S is dried.

[0035] A dry suction unit 3360 is provided inside the belt 3301. The dry suction unit 3360 forms a suction chamber 3361 with a suction duct 3362 and the belt 3301, and a fan 3366 below exhausts air to an exhaust duct 3367, generating negative pressure in the suction chamber 3361. Because multiple small holes, e.g., 0.4 mm in diameter, are formed in the belt 3301, an attraction force that attracts the sheet S is generated in the belt 3301 above the dry suction unit 3360. This attraction force, along with the air pressure from the hot air blowing unit 3400, holds the sheet S to the belt 3301 and transports it. To support the belt 3301 in a predetermined position, multiple rollers 3364 are rotatably arranged in the dry suction unit 3360. This configuration supports the belt 3301 from the inside without interfering with the suction by the fan 3366.

[0036] In the process of conveying the sheet S by the drying belt unit 3300, the ink is dried by the blowing of hot air from the hot air blowing unit 3400 and the heat from the belt 3301. The belt 3301 is heated by a belt heating unit 3350 consisting of a heating roller 3351a and a heating roller 3351b. A heater 3353 is disposed inside each of the heating rollers 3351a and 3351b. The heating of each heater 3353 raises the temperature of the heating rollers 3351a and 3351b, and each heater 3353 is controlled so that the set temperature is reached based on the detection result of a roller temperature detection sensor 3356 that detects the temperature of each roller.

[0037] Heating by such heater 3353 consumes a lot of power, so in order to reduce the power consumption of the product, it is necessary to efficiently raise the temperature of belt 3301 and sheet S. Increasing the contact area of ​​belt 3301 with heating rollers 3351a and 3351b is effective in improving the temperature raising efficiency of belt 3301. In this embodiment, the diameter of heating roller 3351a is set to φ110 mm, and the diameter of heating roller 3351b is set to φ60 mm, which are large diameters, to increase the contact area with belt 3301.

[0038] Furthermore, the heat imparted to the belt 3301 from the heating rollers 3351a and 3351b is dissipated by contact with the atmosphere and the rollers tensioning the belt 3301 as the belt 3301 is transported. Therefore, in order to efficiently transfer heat from the belt 3301 to the sheet S, it is effective to arrange the belt heating unit 3350 upstream of the conveying surface β of the belt 3301 in the rotation direction of the belt 3301. In this embodiment, of the pair of rollers tensioning the belt 3301 to form the conveying surface β of the sheet, the roller located upstream in the sheet conveying direction is the heating roller 3351b, and the heating roller 3351a is arranged further upstream of the heating roller 3351b in the rotation direction of the belt 3301.

[0039] Furthermore, tension roller 3311 is biased against belt 3301 from outside between heating rollers 3351a and 3351b, allowing the belt to wrap around heating rollers 3351a and 3351b at a nearly 180° angle. This is intended to improve the temperature rise efficiency of belt 3301 and to minimize the effect of fluctuations in the belt tension position when belt 3301 stretches due to temperature rise. If belt 3301 stretches by 20 mm, the insertion position of tension roller 3311 only moves 10 mm, and the wrap angle of belt 3301 around other rollers does not change significantly. This improves both the temperature rise efficiency of belt 3301 and the heat transfer efficiency from belt 3301 to sheet S, while also stabilizing the belt tension state.

[0040] The temperature rise of the belt 3301 is detected by a non-contact belt surface temperature detection sensor 3343 such as an infrared sensor, and the difference from the set temperature is determined by the control unit and reflected in the temperature setting of the heater 3353. Note that the heating roller 3351b is not limited to a roller that stretches the belt 3301 to form the sheet conveying surface, but may be a roller located upstream in the rotation direction of the belt 3301 from a roller or support member that stretches the belt 3301 to form the sheet conveying surface β. Also, in this embodiment, the belt 3301 may be made of metal, but using a material made of resin or rubber has a larger linear expansion coefficient and is therefore more effective in preventing the belt 3301 from stretching.

[0041] In this embodiment, a resin belt 3301 is used, but a metal belt having high durability and large heat capacity may also be used. The sheet S is heated by the temperature rise via the belt 3301 and by the hot air from the hot air blowing unit 3400, and is then transported to the internal discharge unit 3340, and is then discharged to the fixing module 4000 by the internal discharge rollers 3345.

[0042] In the drying module 3000, the belt 3301 is heated to approximately 80°C by the hot air blowing unit 3400 and heating rollers 3351a and 3351b. Meanwhile, in the decoupling unit 3200, the air blowing unit 3100 blows unheated air onto the belt 3201. However, an air blowing unit 3102 is provided above the connection between the decoupling unit 3200 and the drying belt unit 3300. The air blowing unit 3102 exhausts and sucks in unheated air to circulate the air, blocking the hot air from the hot air blowing unit 3400 between the decoupling unit 3200 and the drying belt unit 3300. Therefore, the hot air blowing unit 3400 does not cause a large temperature rise in the decoupling unit 3200, and the impact of the hot air blowing unit 3400 is also limited.

[0043] In the above description, the belt heating unit 3350 is configured with two rollers, the heating roller 3351a and the heating roller 3351b. However, the belt heating unit 3350 may be configured to include a heating roller or heating unit other than these two rollers.

[0044] [Suction configuration of decoupling part] 3(a) and 3(b), the configuration of the decoupling suction unit 3260 of the decoupling section 3200 will be described. The decoupling suction unit 3260 has a duct (second duct) 3262 and a suction fan 3261 as a suction section (second suction section). The duct 3262 is disposed inside the belt 3201 so that an opening (second opening) 3264 faces the back side of the conveying surface α of the belt 3201. The suction fan 3261 sucks air inside the duct 3262 (inside the duct) to adsorb the sheet onto the conveying surface α.

[0045] The above-mentioned middle plate 3206 is disposed inside the belt 3201 in the front-to-rear direction. The middle plate 3206 is provided with a suction fan 3261. One or more suction fans 3261 are provided. In this embodiment, three suction fans 3261 are disposed side by side in the sheet conveyance direction. The suction fan 3261 may be a sirocco fan or an axial flow fan, but in this embodiment, an axial flow fan is used and is disposed so that the rotation axis direction of the fan is in the vertical direction.

[0046] A wall formed by a part of the middle plate 3206 and duct walls 3262a and 3262b is erected around the suction fan 3261, and a duct 3262 is formed by the pair of duct walls 3262a arranged on both sides in the front-to-rear direction, the pair of duct walls 3262b arranged on both sides in the left-to-right direction, and part of the middle plate 3206. An opening 3264 is formed in these duct walls 3262a and 3262b on the side opposite the middle plate 3206. The opening 3264 is located close to the perforated metal 3202 and functions as a suction port that sucks air outside the belt 3201 through the multiple holes 3207 and 3208 in the belt 3201 and adsorbs the sheet onto the conveying surface α. The duct 3262 has an opening 3264 located close to the punched metal 3202, so that a substantially closed space is formed between the opening 3264 and the punched metal 3202, thereby enabling efficient sucking of air outside the belt 3201.

[0047] The suction fan 3261 rotates and exhausts the air in the duct 3262, creating a negative pressure inside the duct 3262, which sucks the sheet S through the holes 3208 in the punched metal 3202 and the holes 3207 in the belt 3201. Because the belt 3201, which is stretched around a roller, comes into contact with the punched metal 3202, suction is performed from the area where the holes 3208 in the punched metal 3202, the holes 3207 in the belt 3201, and the opening 3264 overlap. Hereinafter, this area will also be referred to as the suction area.

[0048] The suction region is a region where the region where the plurality of holes 3207 are formed in the belt 3201, the region where the plurality of holes 3208 are formed in the perforated metal 3202, and the opening 3264 overlap when viewed on the conveying surface α from a direction perpendicular to the conveying surface α (in the vertical direction in this embodiment). Note that if the perforated metal 3202 is omitted, the suction region is a region where the region where the plurality of holes 3207 are formed in the belt 3201 and the opening 3264 overlap when viewed on the conveying surface α from a direction perpendicular to the conveying surface α.

[0049] By performing suction from the suction region as described above, the sheet S placed on the belt 3201 is attracted to the belt 3201 and is transported in accordance with the movement of the belt 3201. The suction pressure Pd of the decoupling suction unit 3260 is set to approximately 10 Pa or more and 30 Pa or less.

[0050] The air exhausted from the suction fan 3261 is discharged below the middle plate 3206 and exits the decoupling unit 3200 through the lower end or holes of the belt 3201. However, if a large amount of air is sucked in by the suction fan 3261, the air may not be able to smoothly exit through the ends or holes of the belt 3201. In this case, the exhaust volume of the suction fan 3261 may decrease, which may result in a decrease in the negative pressure in the duct 3262. For this reason, this embodiment employs a configuration in which an exhaust fan 3263 is provided to further exhaust air from the space exhausted by the suction fan 3261 to the outside of the decoupling unit 3200. The exhaust fan 3263 exhausts air, for example, to the rear side of the device.

[0051] [Sheet transport configuration around the decoupling section] 4 and 5, a description will be given of the conveying configuration of the sheet S around the decoupling unit 3200 and the recording unit 2020. A print belt unit 2010 and the recording unit 2020 are arranged upstream of the decoupling unit 3200 in the sheet conveying direction A. The print belt unit 2010 has an endless belt (first belt) 4, a drive roller 41, multiple tension rollers 42, 43, and 44 (see FIG. 1), a print suction unit 5, a drive motor 45 as a first drive unit, and the like.

[0052] The belt 4 is tensioned by a drive roller 41 and multiple tension rollers 42, 43, and 44. The tension roller 42 and the drive roller 41, which serve as multiple first tension members, tension the belt 4 so that a conveying surface (first conveying surface) γ, which is a surface for conveying a sheet, is formed on the outer circumferential surface of the belt 4. The belt 4 is rotated by the drive roller 41, which is driven by a drive motor 45. The belt 4 has multiple holes formed therein. A print suction unit 5 is provided inside the belt 4.

[0053] The print suction unit 5 has a duct (first duct) 51 and a suction fan 52 as a first suction section. The duct 51 is disposed inside the belt 4 so that an opening (first opening) 53 faces the back side of the conveyance surface γ of the belt 4. The suction fan 52 sucks air inside the duct 51 (inside the duct) to adsorb the sheet to the conveyance surface γ. The suction fan 52 rotates and exhausts the air inside the duct 51, creating negative pressure inside the duct 51, which then sucks the sheet S through the holes in the belt 4. In this way, the sheet S placed on the belt 4 is adsorbed to the belt 4 and transported in accordance with the movement of the belt 4.

[0054] A recording section (head section) 2020 as an image forming section is provided opposite the print belt unit 2010, and ejects ink onto the sheet S attracted to the conveying surface γ of the belt 4 to form an image on the sheet S. A print suction unit 5 sucks the sheet S with a suction force of approximately 500 Pa so that the position of the sheet S relative to the recording section 2020 does not change during image formation, and so that the sheet S does not come into contact with the recording section 2020 due to floating of the sheet S.

[0055] A rear guide 6 serving as a guide unit is provided between the print belt unit 2010 and the decoupling unit 3200, and an air blowing unit 3101 is provided above the rear guide 6. That is, the rear guide 6 is disposed downstream of the print belt unit 2010 and upstream of the decoupling unit 3200 in the conveying direction, and guides the sheet S conveyed by the print belt unit 2010 to the decoupling unit 3200. The air blowing unit 3101 serves as a blowing unit that blows air onto the conveying surface α of the belt 3201 of the decoupling unit 3200, and is disposed so as to blow air onto the conveying surface α of the belt 3201 and onto the upstream side of the conveying surface α in the conveying direction. Therefore, air is also blown from the air blowing unit 301 onto the rear guide 6.

[0056] 6 to 9, the behavior of the sheet S as it is transported from the print belt unit 2010 to the drying belt unit 3300 will be described. The sheet S is attracted to and transported by the belt 4 of the print belt unit 2010, and is released from the suction restraint at the point where it passes through the print suction unit 5, losing its holding force on the belt 4. The sheet S separates from the belt 4 due to the curvature of the drive roller 41 that stretches the belt 4 and a separation mechanism (not shown) that abuts against the surface of the belt 4, and is transported to the rear guide 6 by the conveying force Fp at the point where the sheet S is still being restrained (see FIG. 6).

[0057] When the leading end of the sheet S is not sucked and constrained, the air blowing unit 3101 presses the sheet S against the belt 4 and the rear guide 6 from above the sheet S. This prevents the sheet S from lifting due to the running wind generated by transporting the sheet S, and brings the belt 4 into contact with the sheet S. As a result, the conveyance posture of the sheet S can be stabilized, the suction force by the print suction unit 5 is stabilized, and the variation in the conveyance force Fp by the print belt unit 2010 can be suppressed. The blowing pressure onto the rear guide 6 is about 500 Pa, which is weaker than the 1000 Pa of the warm air blowing unit 3400.

[0058] The leading end of the sheet S that has passed through the rear guide 6 reaches the belt 3201 of the decoupling unit 3200. Until the leading end of the sheet S reaches the decoupling suction unit 3260, the conveyance force Fd of the sheet S by the decoupling unit 3200 is only the conveyance force Fd1 caused by the frictional force generated between the sheet S and the belt 3201 due to the wind pressure of the air blowing unit 3101, and it is conveyed in a state where the conveyance force Fp by the print belt unit 2010 is overwhelmingly high "Fd1 < Fp" (see Fig. 7).

[0059] When the leading end of the sheet S reaches the decoupling suction unit 3260, in addition to the conveyance force Fd1 due to the wind pressure of the air blowing unit 3101, a belt conveyance force Fd2 due to the suction force of the decoupling suction unit 3260 is generated (see Fig. 8). At this time, if the combined force of the conveyance force Fd1 in the wind pressure at the decoupling unit 3200 and the conveyance force Fd2 by the decoupling suction unit 3260 exceeds the conveyance force Fp of the print belt unit 2010 with respect to the sheet S, the conveyance speed of the sheet S switches from the print belt unit 2010 to the driving speed of the decoupling unit 3200, and the conveyance speed of the sheet changes.

[0060] When image formation is performed on the sheet S by the recording unit 2020 on the print belt unit 2010, or such a speed variation of the sheet occurs while the formed image is detected by an in-line scanner (not shown), the image is distorted and the image quality deteriorates. In order to prevent this phenomenon, it is required that the conveying force Fp of the print belt unit 2010 exceeds the conveying force Fd (=Fd1 + Fd2) by the decoupling unit 3200, that is, "Fd1 + Fd2 < Fp" in the state where the sheet S is being imaged and the image is being detected.

[0061] Therefore, in this embodiment, it is arranged such that Fd < Fp. This will be described with reference to FIG. 5. First, in the print belt unit 2010, the recording unit 2020 is arranged to face the conveying surface γ on the upstream side of the downstream end of the opening 53 of the duct 51 with respect to the conveying direction. That is, with respect to the conveying direction of the sheet, the downstream end X1 of the recording unit 2020 is arranged on the upstream side of the downstream end X2 of the opening 53. Further, of the opening 53 of the duct 51, the opening area of the portion downstream of the downstream end X1 of the recording unit 2020 with respect to the conveying direction is Sp, and the suction pressure of the suction fan 52 (the pressure for sucking air from the duct 51 by all the suction fans 52) is Pp. Furthermore, in the decoupling unit 3200, the opening area of the opening 3264 of the duct 3262 is Sd, and the suction pressure of the suction fan 3261 (the pressure for sucking air from the duct 3262 by all the suction fans 3261) is Pd.

[0062] In this case, the conveying force Fp of the print belt unit 2010 can be expressed as Pp × Sp. Also, the belt conveying force Fd2 due to the suction force of the decoupling suction unit 3260 can be expressed as Pd × Sd. Therefore, in this embodiment, at least, it is arranged such that Pd × Sd < Pp × Sp. And even when the conveying force Fd1 due to the wind pressure of the air blowing unit 3101 is added to Pd × Sd, Pp × Sp is made larger.

[0063] Specifically, the suction pressure Pd of the decoupling suction unit 3260 is set to between approximately 10 Pa and 30 Pa, and the suction pressure Pp of the print suction unit 5 is set to a large value of approximately 500 Pa, thereby establishing the above-mentioned relationship between the conveying forces. In other words, the suction pressure Pd of the suction fan 3261 is lower than the suction pressure Pp of the suction fan 52.

[0064] Furthermore, the conveying speed of the belt 3201 of the decoupling unit 3200 is set to be approximately 3% faster than the conveying speed of the belt 4 of the print belt unit 2010. In other words, the peripheral speed of the belt 3201 is faster than the peripheral speed of the belt 4. This makes it possible to suppress fluctuations in the conveying force Fd2 of the sheet S when the sheet S is held across the print belt unit 2010 and the decoupling unit 3200, which can occur when a loop is generated in the sheet S due to speed fluctuations caused by component tolerances or the like, making the posture of the sheet S unstable.

[0065] Furthermore, by causing the belt 3201 of the decoupling unit 3200 to pull the sheet S held by the belt 4 of the print belt unit 2010, the sheet holding force on the decoupling unit 3200 side becomes lower than the holding force on the print belt unit 2010 side, and a state of dynamic friction is maintained between the belt 3201 and the sheet S. As a result, the friction force between the sheet S and the belt 3201 becomes lower than that during static friction, so that the conveying force Fd of the decoupling unit 3200 can be kept low and stable even if the blowing pressure of the air blowing unit 3101 from above or the suction pressure of the decoupling suction unit 3260 is increased. Creating such a sheet holding state reduces image distortion during image formation due to fluctuations in the speed of the sheet S.

[0066] When the trailing edge of the sheet S passes through the recording unit 2020 and the inline scanner (not shown), any speed fluctuations in the sheet S do not affect the image quality. After that point, the trailing edge of the sheet S passes through the print suction unit 5, and the conveying force Fd by the decoupling unit 3200 becomes dominant. With the sheet S no longer constrained by the print belt unit 2010, the tension between the units of the sheet S is eliminated, and a static friction state is created between the sheet S and the belt 3201 of the decoupling unit 3200, and the sheet S is conveyed in this state.

[0067] The sheet S conveyed by the decoupling unit 3200 is released from the suction-induced restraint on the belt 3201 at the point where it passes through the decoupling suction unit 3260. Then, the curvature of the drive roller 3231 causes the leading edge of the sheet S to separate from the belt 3201, and the sheet is delivered to the internal discharge guide 3240. The internal discharge guide 3240 is disposed downstream of the decoupling unit 3200 and upstream of the drying belt unit 3300 in the conveying direction, and guides the sheet S conveyed by the decoupling unit 3200 to the drying belt unit 3300.

[0068] Furthermore, an air blowing unit 3102 blows air at approximately 600 Pa onto the internal discharge guide 3240 from above the internal discharge guide 3240. The air blown onto the internal discharge guide 3240 generates frictional resistance between the sheet S and the internal discharge guide 3240, but the area of ​​the sheet S that is in contact with the belt 3201 and the internal discharge guide 3240 with a large contact area ratio is restrained by the belt 3201 by the air blowing unit 3101 and suction by the decoupling suction unit 3260. Therefore, a sufficiently large conveying force Fd is generated by the belt 3201, and the sheet S is conveyed on the internal discharge guide 3240 without decelerating. Then, the leading edge of the sheet S reaches the dry suction unit 3360 of the drying belt unit 3300 (see FIG. 9).

[0069] The dry suction unit 3360 generates a suction force Pf of approximately 1500 Pa, which is a stronger suction force than the decoupling suction unit 3260. Therefore, when the sheet S reaches the dry suction unit 3360 and is conveyed a short distance, the conveying force of the sheet S is dominated by the conveying force Ff of the dry belt unit 3300, and the setting is "Ff>Fd."

[0070] In this embodiment, a total of five air blowing units 3101 and ventilation units 3102 are arranged above the decoupling section 3200 and the internal discharge guide 3240. Of these air blowing units 3101 and ventilation units 3102, the most upstream unit in the conveying direction, which is arranged above the rear guide 6, has an air pressure of 500 Pa, and the four downstream units, which are arranged above the belt 3201 of the decoupling section 3200, all have an equal air pressure of 600 Pa blowing from the blowing holes onto the sheet.

[0071] If the air pressure of the air blowing unit 3101 arranged above the rear guide 6 is set too high, the friction between the sheet S and the rear guide 6 increases, thereby increasing the conveyance resistance of the sheet S. As a result, a delay in conveyance of the sheet S may occur when the sheet S is transferred from the print belt unit 2010 to the decoupling unit 3200. On the other hand, if the air pressure of the air blowing unit 3101 arranged above the decoupling unit 3200 is too low, the friction between the sheet and the belt 3201 of the decoupling unit 3200 decreases, causing slippage between the sheet S and the belt 3201 and potentially causing a conveyance delay of the sheet S. For this reason, in this embodiment, the air pressure of only the air blowing unit 3101 arranged above the rear guide 6, which is the most upstream unit in the conveyance direction, is set lower than the air pressure of the four downstream air blowing units 3101 and the air blowing unit 3102 arranged above the belt 3201.

[0072] Furthermore, the air pressure of the five air blowing units 3101 and air blowing units 3102 may be gradually increased toward the downstream side in the conveyance direction of the sheet S, as long as the air pressure of the five air blowing units 3101 and air blowing units 3102 is smaller than the air pressure of 1000 Pa of the hot air blowing unit 3401 (see FIG. 2). If the air pressure of the hot air blowing unit 3401 located at the most upstream position in the conveyance direction of the sheet differs greatly from the air pressure of the air blowing unit 3102 located at the most downstream position in the conveyance direction of the sheet, a sudden air flow occurs in the direction opposite to the conveyance direction between the hot air blowing unit 3401 located at the most upstream position in the conveyance direction and the air blowing unit 3102 located at the most downstream position in the conveyance direction, causing the sheet to lift up and likely resulting in conveyance problems. For this reason, it is preferable to gradually increase the wind pressure of the air blowing unit 3101 and the air blowing unit 3102 toward the downstream side in the conveying direction, thereby reducing the wind pressure difference between the warm air blowing unit 3401 located at the most upstream side in the sheet conveying direction and the air blowing unit 3102 located at the most downstream side in the sheet conveying direction.

[0073] [Suction length and sheet width] Next, the relationship between the widthwise length (suction length) of the suction area of ​​the decoupling unit 3200 and the widthwise length (sheet width) of the sheet will be described with reference to FIGS. 10 and 11. The decoupling unit 3200 transports the sheet S between the print belt unit 2010 and the drying belt unit 3300 with a weaker force than the respective transport forces in order to stably transfer the sheet S between them. Since the inkjet recording apparatus 100 transports sheets S of various sizes, the area where the sheet S overlaps with the suction area on the belt 3201 of the decoupling unit 3200 (hereinafter referred to as the "suction area") varies depending on the size of the sheet S, which may result in differences in transport force. Therefore, the suction force of the decoupling suction unit 3260 is set so that the sheet S can be transported stably even when the suction area is small and the transport force is weak.

[0074] However, if a sheet S with a large suction area is conveyed, the suction force corresponding to the small suction area described above may suck the sheet S more than necessary as the suction area increases, which may result in an excessively large conveying force. If the conveying force generated by the decoupling section 3200 becomes stronger than the conveying force of the print belt unit 2010, speed fluctuations may occur when the sheet S is transferred, which may lead to image distortion during image formation. Therefore, in this embodiment, the following configuration is adopted to address the above concerns.

[0075] Here, L1 is the suction length, which is the widthwise length of the suction region within a range of a predetermined length from the top end of the opening 3264 in the conveyance direction (in this embodiment, the entire length of the opening 3264 in the conveyance direction), L2 is the widthwise length of the smallest size sheet on which an image can be formed by the recording unit 2020, and L3 is the widthwise length of the largest size sheet on which an image can be formed by the recording unit 2020. The suction length L1 is the length of the shortest region among the widthwise length of the region in which the multiple holes 3207 are formed in the belt 3201, the widthwise length of the region in which the multiple holes 3208 are formed in the perforated metal 3202, and the widthwise length of the opening 3264. In this embodiment, since the widthwise length of the opening 3264 is the shortest, the suction length L1 is the widthwise length of the opening 3264. In other words, it is the distance between a pair of duct walls 3262a arranged on both sides in the front-to-rear direction.

[0076] 10 is a top view of the decoupling unit 3200, schematically illustrating a state in which a sheet S(min) having a minimum sheet width (L2) in a direction substantially perpendicular to the conveying direction A of the sheet S as envisioned in the inkjet recording apparatus 100 is being conveyed on the belt 3201 of the decoupling unit 3200. FIG. 11 is a top view of the decoupling unit 3200, schematically illustrating a state in which a sheet S(max) having a maximum sheet width (L3) in a direction substantially perpendicular to the conveying direction A of the sheet S as envisioned in the inkjet recording apparatus 100 is being conveyed.

[0077] As shown in FIG. 10, in a direction substantially orthogonal to the conveyance direction A of the sheet S (the front-rear direction and the width direction of the apparatus), the suction length L1 of the decoupling unit 3200 is set to be larger than the width L2 of the sheet S(min). Since the sheet S(min) with a small width L2 has a small suction area, the conveyance force by the belt 3201 is small. Therefore, in order to efficiently and stably convey the sheet S(min), it is desirable to suck the entire width of the sheet with an optimal pressure. Therefore, in the present embodiment, the suction length L1 is made larger than the width L2 of the sheet S(min).

[0078] Also, as shown in FIG. 11, the suction length L1 of the decoupling unit 3200 is set to be smaller than the width L3 of the sheet S(max). As described above, if the suction area of the sheet S(max) with a large width becomes too large, the conveyance force by the belt 3201 may increase and speed fluctuations may occur. Therefore, in the present embodiment, by making the suction length L1 smaller than the width L3 of the sheet S(max), it is possible to suppress an excessive increase in the conveyance force while securing the suction area required for the conveyance force, and to suppress the conveyance force within an appropriate range.

[0079] Thus, in the present embodiment, the suction length L1 is set so as to satisfy "L2 < L1 < L3". Thereby, the change in the conveyance force due to the difference in the width direction of the sheet S can be suppressed. That is, it is possible to suppress the conveyance force in the decoupling unit 3200 from changing according to the sheet size. As a result, it is possible to suppress the occurrence of speed fluctuations when the sheet S is transferred from the print belt unit 2010 to the decoupling unit 3200 depending on the sheet size, and to suppress the deterioration of the image quality.

[0080] <Second Embodiment> The second embodiment will be described with reference to Figures 12 and 13. In the first embodiment described above, the width direction length of the opening 3264 of the duct 3262 in the decoupling section 3200 was the same throughout the conveying direction. In contrast, in this embodiment, the width direction length of the opening 3264A is changed midway through the conveying direction. Since the other configurations and functions are the same as those of the first embodiment described above, the same configurations will be assigned the same reference numerals and explanations and illustrations will be omitted. The following description will focus on the differences from the first embodiment.

[0081] In this embodiment, the opening 3264A of the duct 3262A in the decoupling unit 3200A serving as the second transfer unit has a first opening portion 3264A1 and a second opening portion 3264A2. The first opening portion 3262A1 is a portion corresponding to a range of a predetermined length D from the upper end of the opening 3264A in the transfer direction. The second opening portion 3262A2 is located downstream of the first opening portion 3262A1 in the transfer direction and is a portion whose length in the width direction is shorter than that of the first opening portion 3262A1.

[0082] That is, in this embodiment, duct 3262A has a pair of duct walls 3262c provided on both front-rear sides of a portion corresponding to first opening portion 3262A1 and a pair of duct walls 3262d provided on both front-rear sides of a portion corresponding to second opening portion 3262A2. In this embodiment, too, the shortest length among the widthwise length of the region where multiple holes 3207 are formed in belt 3201, the widthwise length of the region where multiple holes 3208 are formed in punched metal 3202, and the widthwise length of opening 3264A is opening 3264A. Therefore, the widthwise length of first opening portion 3262Aa1 is defined as suction length L1, and the widthwise length of second opening portion 3262A2 is defined as suction length L4. Suction length L1 is the distance between the pair of duct walls 3262c, and suction length L4 is the distance between the pair of duct walls 3262d. In other words, in this embodiment, the distance between the pair of duct walls 3262d is shorter than the distance between the pair of duct walls 3262c.

[0083] FIG. 12 is a top view of the decoupling unit 3200A schematically showing a state in which a sheet S(max) having the maximum width direction length (L3) of the sheet S assumed in the inkjet recording apparatus 100 of the present embodiment is being conveyed. FIG. 12 is different from FIGS. 10 and 11 of the above-described first embodiment in that the suction lengths are set to be different lengths at the upstream and downstream of the conveyance of the sheet S. That is, in the first embodiment, the suction length is the same width L1 from the upstream to the downstream, whereas in the case of the present embodiment, the suction length of the first opening portion 3262A1 on the upstream side is L1, and the suction length of the second opening portion 3262A2 on the downstream side is set to L4 which is shorter than L1.

[0084] Here, as the sheet S conveyed from the print belt unit 2010 to the decoupling unit 3200A is conveyed from the upstream to the downstream, the suction area increases, and accordingly the conveyance force also increases. In the present embodiment shown in FIG. 12, by making the suction length L4 of the downstream second opening portion 3262A2 shorter than the suction length L1 of the upstream first opening portion 3262A1, it is possible to suppress an increase in the suction area of the sheet S conveyed to the downstream, and it is possible to suppress an increase in the conveyance force.

[0085] In the present embodiment, the suction lengths L1 and L4 are set so as to satisfy “L2 < L4 < L1 < L3”. Thereby, the present embodiment can achieve further suppression of changes in the conveyance force due to the difference in the width direction of the sheet S, and thus can be said to be a more preferable configuration from the viewpoint of conveyance. That is, in the case of the present embodiment, regardless of the width of the sheet, the sheet can be stably conveyed by the decoupling unit 3200A, and image defects such as image misregistration can be more suppressed in the print module 2000.

[0086] Note that the arrangement of the second opening portion 3262A2 in the conveyance direction is not limited to the central portion in the conveyance direction of the sheet S as shown in FIG. 12, and it may be at least within the width in the conveyance direction of the sheet S. Further, the second opening portion may be arranged by dividing the opening 3264A so as to have a width of L4.

[0087] Here, the position of the second opening portion 3242A2 in the transport direction will be described with reference to Fig. 13. Fig. 13 shows a configuration in which the print module 2000 has an inspection device 2021, such as an inline scanner, disposed downstream in the transport direction of the recording unit 2020. The inspection device 2021 detects the image formed by the recording unit 2020 and inspects for color shift and the like, and the recording unit 2020 corrects the ink ejection timing and the like based on the detection results of the inspection device 2021.

[0088] As shown in FIG. 13 , in the print module 2000, the inspection device 2021 is disposed upstream of the downstream end of the opening 53 of the duct 51 in the conveying direction so as to face the conveying surface γ. That is, in the sheet conveying direction, the downstream end X3 of the inspection device is disposed upstream of the downstream end X2 of the opening 53. In this case, the boundary between the first opening portion 3242A1 and the second opening portion 3242A2 in the conveying direction is preferably located 420 mm from the downstream end X3 of the inspection device 2021, which is the conveying length of, for example, an A3-sized sheet of paper. Incidentally, if the inspection device 2021 is not present, the boundary is preferably located 420 mm from the downstream end X1 of the recording unit 2020 in the conveying direction, which is the conveying length of, for example, an A3-sized sheet of paper. In this embodiment, the boundary between the first opening portion 3242A1 and the second opening portion 3242A2 in the conveying direction is preferably located 320 mm from the upstream end X4 of the opening 3242A in the conveying direction. That is, it is preferable that the predetermined length D is 320 mm.

[0089] That is, the position in the conveyance direction at the boundary between the first opening portion 3242A1 and the second opening portion 3242A2 is preferably set to the position of the length of the sheet with the longest length in the width direction among the sheets on which image formation can be performed by the recording unit 2020, starting from the downstream end of the inspection device 2021 or the recording unit 2020. In addition, if the relationship between the sheet conveyance force of the print belt unit 2010 and the sheet conveyance force of the decoupling unit 3200A can satisfy Pd×Sd<Pp×Sp described above, the position at the above-mentioned boundary can be set as appropriate. For example, it can be set as appropriate according to the suction pressure, suction area of the print belt unit 2010 and the decoupling unit 3200A, and the length of the sheet with a high assumed usage frequency.

[0090] <Third Embodiment> The third embodiment will be described with reference to FIGS. 14 to 17. In each of the above-described embodiments, the suction pressure of the decoupling units 3200 and 3200A is constant regardless of the length of the sheet in the conveyance direction. In contrast, in this embodiment, the suction pressure of the decoupling unit 3200B is changed according to the length of the sheet in the conveyance direction. Since the other configurations and operations are the same as those of the first embodiment or the second embodiment described above, the same reference numerals will be given to the same configurations below, and the description and illustration will be omitted. Hereinafter, the description will focus on the differences from the first embodiment and the second embodiment.

[0091] As shown in FIG. 14, the suction fan 3261 serving as a suction unit (second suction unit) is controlled by a control unit 8001. The control unit 80001 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each unit by reading a program corresponding to a control procedure stored in the ROM. The RAM also stores working data and input data, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned programs. The control unit 80001 may control the entire inkjet recording apparatus 100, or may control the drying module 3000. The operation unit 8000 allows the user to perform various settings for the inkjet recording apparatus 100, such as inputting information about the type of sheet.

[0092] In the inkjet recording apparatus 100, it is assumed that not only sheets S of different widths as described above but also various sheets S of different lengths in the conveyance direction are conveyed. For this reason, in this embodiment, the suction pressure of the suction fan 3261 can be changed according to the length of the sheet. That is, the control unit 8001 can control the rotation speed of the suction fan 3261. In other words, the control unit 8001 can control the suction pressure of the suction fan 3261. Then, based on sheet information (e.g., sheet size) input from the operation unit 8000, the control unit 8001 can change the suction pressure of the suction fan 3261 to a first suction pressure when the length of the sheet in the conveyance direction is a first length, or to a second suction pressure lower than the first suction pressure when the length of the sheet in the conveyance direction is a second length longer than the first length.

[0093] Next, a specific description will be given using Figures 15 and 16. Figure 15 is a top view of decoupling unit 3200B, which schematically shows a state in which sheet S1 having a short length in the transport direction (first length) is being transported. Figure 16 is a top view of decoupling unit 3200B, which schematically shows a state in which sheet S2 having the same width as sheet S1 in Figure 15 but a long length in the transport direction (second length) is being transported.

[0094] As shown in FIG. 15, a sheet S1 having a short length in the transport direction has a small suction area (shaded area in the figure) and a small transport force. Therefore, the suction force of the suction fan 3261 is set so that even a sheet S1 having a small transport force can be stably transported. In contrast, as shown in FIG. 16, a sheet S2 having a long length in the transport direction has a large suction area (shaded area in the figure) and a larger transport force, so it is possible that the suction pressure will have a greater effect on speed fluctuations than a sheet S1 having a short length in the transport direction. Therefore, in order to be less susceptible to speed fluctuations and to achieve even more stable transport, it is desirable that even a sheet S2 having a long length in the transport direction has a transport force similar to that of a sheet S1 having a short length in the transport direction.

[0095] Therefore, in this embodiment, in order to maintain a similar conveying force regardless of the length in the conveying direction, a mechanism is provided that can adjust the setting of the suction pressure Pd in ​​the belt 3201 of the decoupling unit 3200B according to the length in the conveying direction. Specifically, before the sheet S is conveyed to the decoupling unit 3200B, the control unit 8001 acquires information about the length of the sheet S from an operation unit 8000 that acquires the length of the sheet S in the conveying direction, and the control unit 8001 controls the suction fan 3261 arranged inside the belt 3201 so that the suction pressure Pd is "low" (second suction pressure) for the sheet S2 that is long in the conveying direction, and so that the suction pressure Pd is "high" (first suction pressure) for the sheet S1 that is short in the conveying direction.

[0096] The control unit 8001 may acquire information about the sheet size based on information input from an external device other than the operation unit 8000, such as a personal computer connected to the inkjet recording apparatus 100.

[0097] The above-mentioned control will be explained using the flowchart in Fig. 17. As shown in Fig. 17, the user inputs the sheet size through the operation unit 8000 of the inkjet recording apparatus 100 (S01). Then, the inkjet recording apparatus 100 starts the sheet transport operation (S02). The control unit 8001 determines the suction pressure Pd corresponding to the sheet size input in S01 (S03). Thereafter, the sheet S is transported to the decoupling unit 3200B (S04).

[0098] The method for acquiring the length of the sheet S is not limited to input from the operation unit 8000 or an external device, and may also be, for example, conversion from a detection sensor that can detect the transport timing during transport of the sheet S. For example, a detection sensor may detect the leading and trailing ends of the sheet upstream of the decoupling unit 3200B in the transport direction, and the control unit 8001 may determine the length of the sheet to be next transported to the decoupling unit 3200B from the detection signal of this detection sensor.

[0099] In this manner, in this embodiment, even when the lengths of the sheets S in the conveying direction are different, the sheets S can be conveyed with similar conveying forces, and a more desirable configuration can be obtained that can achieve even more stable conveyance. That is, regardless of the length of the sheet in the conveying direction, the decoupling unit 3200B can stably convey the sheet, and the occurrence of image defects such as image misalignment in the print module 2000 can be further suppressed. [Explanation of symbols]

[0100] 4··· Belt (1st Belt) 41: Drive roller (first tension member) 42... Tension roller (first tension member) 45 Drive motor (first drive unit) 51 Duct (first duct) 52 Suction fan (first suction section) 53 Opening (first opening) 100 Inkjet recording device 2010 Print belt unit (first conveyor) 2020 Recording section (image forming section) 3100···Air blowing unit (blowout unit) 3200, 3200A, 3200B... Decoupling section (second transfer section) 3201 Belt (Second Belt) 3202 Punching metal (supporting member) 3207···Hole (first hole) 3208···hole (second hole) 3231 Drive roller (tension member, second tension member) 3232 Drive motor (drive unit, second drive unit) 3261···Suction fan (suction section, second suction section) 3262···Duct (Second Duct) 3264, 3264A...Opening (second opening) 3264A1...1st opening part 3264A2...Second opening part 3270a... Tension roller (tension member, second tension member) 8001 Control unit α···Transport surface (second transport surface) γ···Transport surface (first transport surface)

Claims

1. a first conveying unit that conveys a sheet; an image forming unit that ejects ink onto the sheet conveyed by the first conveying unit to form an image on the sheet; a second conveying unit that is disposed downstream of the image forming unit in a sheet conveying direction of the first conveying unit, receives the sheet conveyed by the first conveying unit, and conveys the sheet further downstream in the sheet conveying direction; The second transport unit is an endless belt having a plurality of holes formed therein; a plurality of tension members that tension the belt and form a conveying surface on the outer circumferential surface of the belt for conveying a sheet; a duct disposed inside the belt such that an opening thereof opens toward the back side of the conveying surface of the belt; a suction unit that sucks air inside the duct to adsorb the sheet onto the conveying surface; a drive unit that drives the belt to rotate and thereby convey the sheet attracted to the conveying surface, The area where the range where the plurality of holes are formed in the belt and the opening overlap when viewed from a direction perpendicular to the conveying surface, and when a suction length which is the widthwise length of the sheet intersecting the conveying direction within a predetermined length range from the upper end of the opening in the conveying direction is defined as L1, the widthwise length of a sheet of a minimum size on which an image can be formed by the image forming unit is defined as L2, and the widthwise length of a sheet of a maximum size on which an image can be formed by the image forming unit is defined as L3, L2<L1<L3 fulfill An inkjet recording apparatus characterized by:

2. a support member disposed between the opening of the duct and the belt, the support member supporting a back side of the conveying surface of the belt; When the plurality of holes are defined as a plurality of first holes, a plurality of second holes are formed in the support member, The suction length is the widthwise length of an area where the range in which the plurality of first holes are formed in the belt, the range in which the plurality of second holes are formed in the support member, and the openings overlap when viewed from a direction perpendicular to the conveying surface.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

3. The length of the opening in the width direction is L1.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

4. The opening has a first opening portion corresponding to the range of the predetermined length from the upper end in the transport direction, and a second opening portion located downstream of the first opening portion in the transport direction and having a length in the width direction shorter than that of the first opening portion.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

5. When the length of the first opening portion in the width direction is L1 and the length of the second opening portion in the width direction is L4, L2<L4<L1<L3 fulfill 5. The inkjet recording apparatus according to claim 4,

6. Further, a control unit capable of controlling the suction unit is provided, The control unit is capable of changing the suction pressure of the suction unit to a first suction pressure when the length of the sheet in the conveying direction is a first length, and to a second suction pressure lower than the first suction pressure when the length of the sheet in the conveying direction is a second length longer than the first length.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

7. a blowing unit that blows air toward the conveying surface of the belt, The blowing unit blows air onto the conveying surface and an upstream side of the conveying surface in the conveying direction.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

8. a guide unit that is disposed downstream of the first conveying unit and upstream of the second conveying unit in the conveying direction and that guides the sheet conveyed by the first conveying unit to the second conveying unit, The blowing section blows air toward the conveying surface at a blowing pressure greater than the blowing pressure at the guide section.

8. The inkjet recording apparatus according to claim 7,

9. The first transport unit is an endless first belt having a plurality of holes formed therein; a plurality of first tension members that tension the first belt and form a first conveying surface on an outer circumferential surface of the first belt for conveying a sheet; a first duct disposed inside the first belt such that a first opening faces a back side of the first conveying surface of the first belt; a first suction unit that sucks air in the first duct to adsorb the sheet onto the first conveying surface; a first driving unit that rotates and drives the first belt to convey the sheet attracted to the first conveying surface, the image forming unit ejects ink onto the sheet attracted to the first transport surface; the belt is a second belt, the plurality of tension members are a plurality of second tension members, the opening is a second opening, the duct is a second duct, the conveying surface is a second conveying surface, the suction unit is a second suction unit, The drive unit is a second drive unit.

2. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

10. The suction pressure of the second suction unit is lower than the suction pressure of the first suction unit.

10. The inkjet recording apparatus according to claim 9,

11. The peripheral speed of the second belt is faster than the peripheral speed of the first belt.

10. The inkjet recording apparatus according to claim 9,

12. the image forming unit is disposed so as to face the first transport surface upstream of a downstream end of the first opening in the transport direction; When the opening area of ​​the first opening at a portion downstream of the downstream end of the image forming unit in the conveying direction is Sp, the suction pressure of the first suction unit is Pp, the opening area of ​​the second opening is Sd, and the suction pressure of the second suction unit is Pd, Pd x Sd < Pp x Sp fulfill 10. The inkjet recording apparatus according to claim 9,

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