Sheet conveying device and image forming apparatus having sheet conveying device

Abstract

To provide a sheet conveying device capable of efficiently heating a belt by a heating roller and suppressing meandering of the belt by a steering roller.SOLUTION: In the sheet conveying device, a tension roller 3311 is disposed so as to press a tension portion 3301Q of a drying belt 3301 tensioned by heating rollers 3351a and 3351b from the outside to the inside. A steering roller 3321 is disposed between a drive roller 3331 and the heating roller 3351a. In this way, a range in which a tension state of the drying belt 3301 changes when the tension roller 3311 moves can be limited to between the heating rollers 3351a and 3351b. As a result, although a belt winding angle of the heating rollers 3351a and 3351b increases with the movement of the tension roller 3311, the heating efficiency of the drying belt 3301 does not decrease compared to before the movement. On the other hand, since a belt winding angle of the steering roller 3321 remains unchanged from before the movement, belt meandering control is performed stably.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a sheet conveying device that conveys a sheet by a belt rotatably stretched around a plurality of rollers, and to an image forming apparatus equipped with the sheet conveying device. [Background technology]

[0002] Conventionally, in an image forming apparatus using an inkjet, in order to dry ink applied to a sheet, the sheet is heated via a belt that conveys the sheet. The belt is stretched by a plurality of rollers, such as a drive roller that rotates and drives the belt, a heating roller that heats the belt, a steering roller that suppresses meandering of the belt, and a tension roller that applies a certain tension to the belt. Conventionally, as in the apparatus described in Patent Document 1, the function of applying tension to the belt by the tension roller and the function of controlling meandering of the belt by the steering roller are separated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-90344 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the belt expands when heated by the heating roller, the belt circumference may become longer. If the belt circumference becomes longer, the tension of the belt will loosen if left as is. Therefore, when the belt circumference becomes longer, the tension roller moves from the inside to the outside, so that a certain tension is applied to the belt. However, when the tension roller moves, there is a risk that the tension state of the belt around the multiple rollers will change. In the device described in Patent Document 1, the belt winding angle around the steering roller and heating roller becomes smaller as the tension state of the belt changes with the movement of the tension roller, making the belt more likely to meander or making it difficult to heat the belt.

[0005] The present invention has been made in consideration of the above problems, and aims to provide a sheet conveying device that can efficiently heat the belt with a heating roller and suppress belt meandering with a steering roller even when the tension roller moves, and an image forming apparatus equipped with a sheet conveying device. [Means for solving the problem]

[0006] A sheet conveying device according to one embodiment of the present invention is a sheet conveying device that conveys a sheet, and includes an endless belt that rotates to convey a sheet, a first roller that tensions the belt downstream of a sheet conveying surface of the belt that conveys the sheet in relation to the rotation direction of the belt, a second roller that tensions the belt upstream of the rotation direction of the sheet conveying surface, a third roller that tensions the belt upstream of the second roller in the rotation direction, a steering roller that is arranged between the first roller and the third roller in relation to the rotation direction and tilts to move the belt in a width direction that intersects the rotation direction, and a tension roller that applies tension to the belt, wherein at least one of the second roller and the third roller is a heating roller that heats the belt, and the tension roller presses the tension portion of the belt, which is stretched between the second roller and the third roller, from the outside to the inside to apply tension to the belt. Effect of the Invention

[0007] According to the present invention, even if the tension roller moves, it is possible to realize efficient heating of the belt by the heating roller and suppression of meandering of the belt by the steering roller. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an inkjet recording apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a drying module. [Diagram 3] FIG. 2 is a perspective view showing the steering unit as viewed from the front side. [Figure 4] FIG. 4 is a perspective view showing the steering unit as viewed from the rear side. [Diagram 5] FIG. [Figure 6] FIG. 13 is a perspective view showing the tension unit in a state where the tension is released by one level. [Figure 7] FIG. 13 is a perspective view showing the tension unit in a state where the tension is released in two stages. [Figure 8] FIG. 4 is a diagram for explaining attachment of a tension unit. [Figure 9] FIG. 4 is a perspective view showing a support structure for the right door portion and a wiring structure for bundled wires. [Figure 10] FIG. 4 is a schematic cross-sectional view showing a belt tensioned state when the belt is inflated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, an image forming apparatus of this embodiment will be described with reference to FIG. 1. Here, as an example of the image forming apparatus, a so-called sheet-fed inkjet recording apparatus 100 that forms an image on a sheet using ink and a reaction liquid will be described. The sheet may be any recording material that can receive 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, and cloth.

[0010] In this specification, the side on which an operator stands when operating the inkjet recording apparatus 100 is referred to as the "front (or front)" and the opposite side is referred to as the "rear (or rear)". Additionally, the left side as viewed from the front is referred to as the "left" and the right side as viewed from the front is referred to as the "right".

[0011] <Inkjet recording device> 1, the inkjet recording apparatus 100 includes a feeding module 1000, a print 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 is subjected to various processes while being transported along a transport path in each module, and is finally discharged to the stacking module 7000.

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

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

[0014] The print module 2000 has a pre-imaging transport unit (not shown), a print belt unit 2200, and a recording unit 2300. The sheet S transported from the feeding module 1000 is transported to the print belt unit 2200 after the inclination and position of the sheet S are corrected by the pre-imaging transport unit.

[0015] A recording unit 2300 is disposed at a position facing the print belt unit 2200 with respect to the transport path of the sheet S. The recording unit 2300, which serves as an image forming unit, forms an image by ejecting ink from above onto the sheet S transported by the print belt using multiple recording heads. The sheet S is transported by suction using the print belt unit 2200, ensuring clearance with the recording heads. In this embodiment, a total of five line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black) and the reaction liquid are aligned along the transport direction of the sheet S.

[0016] The number of ink colors and recording heads is not limited to five. The inkjet method for ejecting ink can be a method using a heating element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS (Micro Electro Mechanical Systems) element, or the like. Each color of ink is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains a resin component of "0.1% by mass to 20.0% by mass" based on the total mass of the ink, water, a water-soluble organic solvent, a coloring material, wax, additives, and the like.

[0017] An in-line scanner (not shown) is disposed downstream in the transport direction of the recording unit 2300. The sheet S on which an image has been formed by the recording unit 2300 is transported by the print belt unit 2200 to an in-line scanner (not shown), which reads the image formed on the sheet S. Here, the misalignment and color density of the image formed on the sheet S are detected, and the image to be formed on the sheet S, its density, and the like are corrected based on the misalignment and color density of the image.

[0018] The drying module 3000 includes a cold air blowing unit 3100, a decoupling belt unit 3200, a drying belt unit 3300, and a hot air blowing unit 3400. The drying module 3000 reduces the liquid content of the ink applied to the sheet S in order to improve the fixation of the ink to the sheet S by the subsequent fixing module 4000.

[0019] The sheet S on which an image has been formed is transported to a decoupling belt unit 3200 disposed within the housing of the drying module 3000. In the decoupling belt unit 3200, frictional force is generated between the sheet S and the belt by wind pressure blown from above, 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, thereby preventing the sheet S from shifting when it is transported between the print belt unit 2010 and the decoupling belt unit 3200.

[0020] The sheet S conveyed from the decoupling belt unit 3200 is conveyed by a drying belt unit 3300 as a sheet conveying device, and ink applied to the sheet S is dried by blowing hot air from a hot air blowing unit 3400 arranged above the belt. The ink applied to the sheet S is heated by the drying module 3000 to promote evaporation of moisture, thereby suppressing the occurrence of so-called cockling, in which ink is scattered on the sheet S and a line like a border is formed around the periphery. The drying module 3000 may be any device that can heat and dry the sheet, but a hot air dryer or a heater is preferable. As the heater, for example, heating by an electric heating wire or an infrared heater is preferable from the viewpoint of safety and energy efficiency.

[0021] The fixing module 4000 has a fixing belt unit 4100. The fixing belt unit 4100 fixes the ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit 4110 and a lower belt unit 4120.

[0022] The cooling module 5000 has a cooling section 5100, and cools the high-temperature sheet S transported from the fixing module 4000. The cooling section 5100 cools the sheet S, for example, by taking in outside air with a fan into a cooling box to increase the pressure inside the cooling box, and blowing air from nozzles formed in a transport guide onto the sheet S. The cooling sections 5100 are disposed on both sides of the transport path of the sheet S, and can cool the sheet S from both sides.

[0023] The cooling module 5000 is also 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.

[0024] The inversion module 6000 has an inversion section 6400. The inversion section 6400 inverts the sheet S being conveyed, and changes 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 inversion module 6000.

[0025] 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. Thereafter, the sheet S passes through a double-sided conveyance path of 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 inversion unit 4200 that inverts the sheet S. The sheet S returned to the print module 2000 has an image formed with ink on the other side on which the image is not formed, and is discharged to the stacking module 7000 via the drying module 3000, the fixing module 4000, the cooling module 5000, and the inversion module 6000.

[0026] <Drying module> Next, the configuration of the drying module 3000 will be described with reference to Fig. 2. As shown in Fig. 2, in the decoupling belt unit 3200, the decoupling belt 3201 is stretched by a driving roller 3231, a tension roller 3211, and tension rollers 3270a and 3270b. Both ends of the driving roller 3231, the tension roller 3211, and the tension rollers 3270a and 3270b are rotatably supported by the front and rear plates of the decoupling belt unit 3200. Of these rollers, the tension roller 3211 is supported by a slide rail 3213 so as to be displaceable and rotatable in a predetermined direction, and applies tension to the decoupling belt 3201 by pressing the decoupling belt 3201 from the inside to the outside by the biasing force of a tension spring 3214.

[0027] The sheet S delivered from the print belt unit 2010 is sent to the decoupling belt unit 3200. When the sheet S is transported, the sheet S is pressed against the decoupling belt 3201 by air blown from the cold air blowing unit 3100 arranged above the decoupling belt unit 3200 and transported. The decoupling belt 3201 has numerous holes and is supported by a punching metal 3202 arranged inside the decoupling belt 3201. The punching metal 3202 has holes smaller than the holes in the decoupling belt 3201, allowing the air blown from the cold air blowing unit 3100 to locations other than the sheet S to escape. In addition, the decoupling belt 3201 is neutralized by a neutralization unit 3250 to prevent the decoupling belt 3201 from becoming charged due to friction between the sheet S and the decoupling belt 3201 and generating an excessive binding force on the sheet S.

[0028] The sheet S conveyed to the decoupling belt 3201 passes through an internal discharge guide 3240 and is sent to a drying belt unit 3300. An endless drying belt 3301 of the drying belt unit 3300 is stretched around a driving roller 3331, a heating roller 3351a, a heating roller 3351b, a tension roller 3311, and a steering roller 3321, which are rotatably fixed. The drying belt 3301 is driven by the rotation of the driving roller 3331.

[0029] In this embodiment, with respect to the rotation direction (arrow X direction) of the drying belt 3301, the drive roller 3331 as a first roller stretches and drives the drying belt 3301 downstream of the sheet transport surface 3301P that transports the sheet S of the drying belt 3301. The heating roller 3351b as a second roller stretches and heats the drying belt 3301 upstream (upstream in the rotation direction) of the sheet transport surface 3301P. The heating roller 3351a as a third roller stretches and heats the drying belt 3301 upstream of the heating roller 3351b.

[0030] The hot air blowing unit 3400 disposed above the drying belt unit 3300 blows hot air heated by a heater onto the drying belt unit 3300. A suction unit 3360 is provided on the inside of a sheet conveying surface 3301P of the drying belt 3301. In the suction unit 3360, a suction chamber 3361 is formed by a suction duct 3362 and the drying belt 3301, and a fan 3366 exhausts air to an exhaust duct 3367 to generate negative pressure in the suction chamber 3361. Since the drying belt 3301 has numerous small holes of about "φ0.4 mm" in size, the drying belt 3301 generates a force to attract the sheet S. The sheet S is transported on the sheet conveying surface 3301P of the drying belt 3301 by this suction force and the wind pressure from the hot air blowing unit 3400. Incidentally, inside the drying belt 3301, a number of rollers 3364 for supporting the drying belt 3301 are rotatably disposed at positions that do not impede the suction by the fan 3366.

[0031] During the process of conveying the sheet S by the drying belt 3301, the sheet S is heated by hot air blown from the hot air blowing unit 3400 and by the drying belt 3301, so that the ink applied to the sheet S is dried. The drying belt 3301 is heated by a heating roller 3351a and a heating roller 3351b. Inside the heating rollers 3351a and 3351b, a heater 3353 is provided for increasing the temperature of the heating rollers 3351a and 3351b. Outside the heating rollers 3351a and 3351b, a heater temperature detection sensor 3356 is provided for detecting the surface temperature of the heating rollers 3351a and 3351b. The temperature of the heater 3353 is controlled based on the detection result by the heater temperature detection sensor 3356 so that the temperature of the heating rollers 3351a and 3351b becomes a set temperature. Further, a non-contact belt temperature detection sensor 3343 such as an infrared sensor is provided to detect the temperature of the drying belt 3301 , and the detection result of the belt temperature detection sensor 3343 is reflected in the temperature setting of the heater 3353 .

[0032] In order to improve the heating efficiency of the drying belt 3301, it is effective to increase the contact area of ​​each of the heating rollers 3351a and 3351b with the drying belt 3301. In this embodiment, the heating roller 3351a is "φ110 mm" and the heating roller 3351b is "φ60 mm" which are larger diameter rollers than the other rollers to increase the contact area. As the drying belt 3301 is conveyed, the heat of the drying belt 3301 is dissipated by the atmosphere or other rollers that stretch it. Therefore, by arranging the heating rollers 3351b and 3351a upstream of the sheet conveying surface 3301P, the sheet S is efficiently heated.

[0033] In this embodiment, the tension roller 3311 contributes to improving the heating efficiency of the drying belt 3301. The tension roller 3311 presses the tension portion 3301Q of the drying belt 3301, which is tensioned by the heating rollers 3351a and 3351b, from the outside to the inside, thereby applying a certain tension to the drying belt 3301. The tension roller 3311 moves from the outside to the inside when the drying belt 3301 expands due to heat. At that time, as will be described in detail later, the winding angle between the heating rollers 3351a and 3351b and the drying belt 3301 is secured so as to suppress a change in the contact area between the heating rollers 3351a and 3351b and the drying belt 3301 compared to before the belt expansion.

[0034] The sheet S heated by the heating of the drying belt 3301 and the hot air from the hot air blowing unit 3400 is transported to the internal paper discharge unit 3340 and then discharged to the fixing module 4000 by the internal paper discharge roller 3345. In the drying module 3000, the hot air blowing unit 3401, the heating roller 3351a, and the heating roller 3351b raise the temperature of the drying belt unit 3300 to about "80°C". However, the decoupling belt unit 3200 is configured to blow non-heating air from the upper cold air blowing unit 3100, and the air blowing unit 3102 provided at the upper part of the connection with the drying belt unit 3300 exhausts and sucks in non-heating air, circulates air, and blocks the hot air from the hot air blowing unit 3400, so there is no large temperature rise and the impact is limited.

[0035] <Steering unit> Incidentally, when the sheet S is transported by the drying belt 3301, it is necessary to control the position of the drying belt 3301 in order to prevent a large deviation from occurring in the transport position of the sheet S in the width direction intersecting the rotation direction of the drying belt 3301. In this embodiment, a steering roller 3321 is disposed between the drive roller 3331 and the heating roller 3351a in relation to the rotation direction of the drying belt 3301, so that the position of the drying belt 3301 can be controlled (see FIG. 2). A steering unit 800 having the steering roller 3321 will be described using FIG. 3 and FIG. 4 with reference to FIG. 2. FIG. 3 shows the steering unit 800 as viewed from the front side, and FIG. 4 shows the steering unit 800 as viewed from the rear side.

[0036] As shown in FIG. 3, one end of the steering roller 3321 is rotatably supported by a steering arm 3323a, and the steering arm 3323a is provided on the front side plate 3303 so as to be rotatable around a rotation shaft 3326a. The steering motor 3324 supports an eccentric steering cam (not shown). A part of the steering arm 3323a is biased by a steering arm spring 3327 in a direction to abut against the steering cam. As the steering cam is rotated by the steering motor 3324, the steering arm 3323a rotates by the amount of eccentricity of the steering cam 3322. A flag 3328 is rotatably provided on the steering motor 3324 on the opposite side of the steering cam, and a flag sensor 3329 detects the flag 3328. The amount of rotation of the steering motor 3324 is controlled according to the detection result of the flag sensor 3329, and the amount of rotation of the steering roller 3321 is determined.

[0037] 4, the other end of the steering roller 3321 is rotatably supported by a steering arm 3323b, and the steering arm 3323b is provided on the rear side plate 3304 so as to be rotatable about a rotation shaft 3326b. The steering arm 3323b rotates so as to absorb the twist generated when the above-mentioned steering arm 3323a rotates, and does not greatly change the position of the steering roller 3321.

[0038] With this configuration, the steering arm 3323a rotates and tilts the steering roller 3321, thereby generating a thrust force in the width direction (rotation axis direction) on the drying belt 3301, thereby controlling the position of the drying belt 3301. Note that a configuration may be adopted in which the steering arm 3323b is fixed to the rear side plate 3304 without providing the rotation shaft 3326b, and the play of the support part 3330 that supports the steering roller 3321 absorbs the twist generated in the steering roller 3321 when the steering arm 3323a rotates.

[0039] <Tension unit> As described above, the tension roller 3311 presses the drying belt 3301 from the outside to the inside to apply a certain tension to the drying belt 3301. The tension unit 3310 having the tension roller 3311 will be described with reference to FIG. 2 and with reference to FIGS. 5 to 9.

[0040] 5 shows the tension unit 3310. The tension unit 3310 is a unit that can be attached to and detached from the drying belt unit 3300. The tension roller 3311 is rotatably supported by a tension arm 3312, and the tension arm 3312 is supported by a tension frame 3317 so as to be movable in a predetermined direction along a slide rail (not shown). The tension arm 3312 is biased by a plurality of tension springs 3314, so that the tension roller 3311 is biased in a biasing direction T1 from the outside to the inside via the tension arm 3312. In this embodiment, when the tension unit 3310 is incorporated into the drying belt unit 3300 and biases the drying belt 3301, a tension of, for example, "40 kgf" is applied to the drying belt 3301.

[0041] A large biasing force is required to tension the drying belt 3301 without slack, and in order to apply and release such a biasing force, the worker must use a large force to operate the tension unit 3310. To reduce the burden on the worker, the present embodiment has a two-stage pressure release mechanism using a lever.

[0042] As shown in Fig. 5, the tension lever 3316a is supported by a lever shaft 3316c extending in the direction of the rotation axis (width direction) of the tension roller 3311, and an eccentric cam (not shown) is provided on the lever shaft 3316c. When the tension lever 3316a is in the position shown in Fig. 5, the biasing force of the tension spring 3314 biases the tension arm 3312 in the biasing direction T1 via a link member (not shown).

[0043] Fig. 6 shows the tension unit in a state where the tension is released by one level. By moving the tension lever 3316a from the position shown in Fig. 5 to the position shown in Fig. 6, the eccentric cam pushes down the link member, so that the urging force of the tension spring 3314 is not transmitted to the tension arm 3312. However, by moving the tension lever 3316a to the position shown in Fig. 6, for example, about 60% of the urging force of the tension spring 3314 is released. At this time, the tension lever 3316b is in the tension applying position, so tension is still applied to the drying belt 3301. The tension lever 3316b is supported by a lever shaft 3316d that extends in the direction of the rotation axis (width direction) of the tension roller 3311, and an eccentric cam (not shown) is provided on the lever shaft 3316d.

[0044] Fig. 7 shows the tension unit in a state where the tension has been released in two stages. In the position of the tension lever 3316b shown in Fig. 6, the force of the tension spring 3314 urges the tension arm 3312 in the urging direction T1. By moving the tension lever 3316b from the position shown in Fig. 6 to the position shown in Fig. 7, the eccentric cam presses down the tension arm 3312, so that the urging force of the tension spring 3314 is not transmitted to the tension arm 3312. In other words, the remaining approximately 40% of the urging force of the tension spring 3314 is released. In this way, all tension applied to the drying belt 3301 is released, and the tension roller 3311 can be moved in the retracting direction T2. At this time, the tension arm 3312 that has been retracted enters the rotation trajectory of the abutting member 3319 that moves in conjunction with the operation of the lever shaft 3316c, thereby preventing the operator from making a mistake in the operating procedure of the tension levers 3316a and 3316b. Note that the structure used for applying and releasing tension is not limited to levers, and may be a structure for applying tension by stretching a wire, etc.

[0045] Next, the installation of the tension unit 3310 will be described with reference to Fig. 8. As shown in Fig. 8, the tension unit 3310, in which the tension roller 3311 is retracted by operating the tension levers 3316a and 3316b, is installed from the right side of the drying belt unit 3300. In order to facilitate the installation of the tension unit 3310, a right door portion 3380 is provided on the rear side plate 3304 so as to be rotatable about a rotation axis extending in the vertical direction. By opening the right door portion 3380, an opening 3301a of the tension unit 3310 is opened, and the tension unit 3310 can be inserted into the drying belt unit 3300 through the opened opening 3301a. In order to prevent the tension unit 3310 from hitting the drying belt 3301, the heating roller 3351a, and the heating roller 3351b when the tension unit 3310 is inserted, a guide plate 3318 that straddles the front plate 3303 and the rear plate 3304 is provided below the tension unit 3310. The tension unit 3310 is inserted along this guide plate 3318, whereby the tension unit 3310 is attached to a predetermined position within the drying belt unit 3300.

[0046] 9 shows the support structure of the right door part 3380 and the wiring structure of the bundled wires. After the tension unit 3310 is attached, the right door part 3380 is closed and held by the front plate 3303. The right door part 3380 is kept closed on the front plate 3303 by fitting with a positioning member 3381a provided on the heating roller 3351a side of the front plate 3303 and a positioning member 3381b provided on the heating roller 3351b side of the front plate 3303. In order to allow the tension unit 3310 to be inserted, an opening 3301a is formed in a U-shape between the heating rollers 3351a and 3351b in the front plate 3303 (see FIG. 8). Therefore, when only the front plate 3303 is supported, the weight of the heating roller 3351b causes a slight sagging only on the front plate 3303 side, which may disrupt the alignment of the heating roller 3351b that stretches the drying belt 3301. To prevent a decline in belt conveyance performance due to this disruption in the belt tension, the pitch of the positioning members 3381a and 3381b of the front plate 3303 is guaranteed by fitting with the right door portion 3380. This prevents the alignment of the heating roller 3351b from being disrupted, and prevents a decline in belt conveyance performance.

[0047] The right door 3380 is used as a cable path for the heater 3353. The heater 3353 is disposed within the heating rollers 3351a and 3351b, and both ends in the width direction are supported by the heater support parts 3354F and 3354R, respectively. In this embodiment, an AC voltage is applied to operate the heater 3353. Cables 3355a and 3355b for applying the AC voltage are connected to an electrical component part (not shown) of the drying module 3000 and both ends of the heater 3353 via relay connectors 3357a and 3357b.

[0048] Since the drying belt unit 3300 may be pulled out from the drying module 3000 during maintenance work, etc., the relay connector 3357a is configured to easily change the connection / disconnection of the bundle wires 3355a and 3355b. In addition, it is necessary to provide a path for the bundle wires 3355a and 3355b in the drying belt unit 3300, but it is difficult to route the bundle wires 3355a and 3355b near the tension unit 3310 to insert and remove the tension unit 3310. However, by providing a path for the bundle wires 3355a and 3355b in the right door portion 3380, the bundle wires can be routed along a short and simple path, and the bundle wires 3355a and 3355b can be retracted together with the right door portion 3380 by simply disconnecting the connection from the relay connector 3357b when inserting or removing the tension unit 3310. Therefore, by providing the right door portion 3380, it is possible to easily insert and remove the tension unit 3310 and handle the heater wires while maintaining the pitch between the heating rollers 3351a and 3351b at an appropriate position. Note that the above-mentioned wires 3355a and 3355b are not limited to AC wires that apply an alternating current voltage, and may be DC wires that apply a direct current voltage.

[0049] FIG. 10 shows the belt tension state when the belt expands. The temperature of the drying belt 3301 rises to about "approximately 80°C" due to the hot air from the hot air blowing unit 3400 (see FIG. 2) and heating by the heating rollers 3351a and 3351b. In this embodiment, a resin drying belt 3301 is used. Therefore, the linear expansion coefficient is "2 to 10×10 -5 ·K -1 When the belt circumference is 2600 mm, the drying belt 3301 can stretch by about 15 mm due to the effect of heat. In response to this stretching of the belt, the tension roller 3311 presses the drying belt 3301 further inward than before the belt stretched, and penetrates to the position shown by the dashed line in Fig. 10 (see 3311', 3301' in the figure).

[0050] As shown in Fig. 10, the tension roller 3311 biases the drying belt 3301 from the outside to the inside between the heating roller 3351a and the heating roller 3351b. The tension roller 3311 pushes the drying belt 3301 inward from a common circumstantial line E on the inside of the common circumstantial lines of the heating roller 3351a and the heating roller 3351b. The tension roller 3311 presses the drying belt 3301 so that the belt winding angle of the drying belt 3301 on the heating rollers 3351a and 3351b is "135° or more". It is preferable that the belt winding angle of the heating rollers 3351a and 3351b is close to "180°". For example, the tension roller 3311 may be moved to a position where the angle θ between the tension roller 3311 and the drying belt 3301 formed by tensioning the heating rollers 3351a and 3351b with respect to the biasing direction T1 of the tension roller 3311 becomes an acute angle (45° or less).

[0051] This improves the heating efficiency of the heating rollers 3351a and 3351b for the drying belt 3301, and also suppresses the effect of fluctuations in the belt winding angle of rollers other than the heating rollers 3351a and 3351b when the drying belt 3301 stretches due to temperature rise. For example, when the drying belt 3301 stretches by "20 mm," even if the intrusion position of the tension roller 3311 moves by "10 mm," the winding angle of the drying belt 3301 on rollers other than the heating rollers 3351a and 3351b does not change significantly.

[0052] In this way, when the tension roller 3311 is provided between the heating roller 3351a and the heating roller 3351b, the range in which the tension state changes due to the stretching of the drying belt 3301 is limited to between the heating roller 3351a and the heating roller 3351b. Also, since the tension roller 3311 moves in a direction in which the belt winding angle of the heating roller 3351a and the heating roller 3351b increases, the heating efficiency of the drying belt 3301 by the heating rollers 3351a and 3351b does not decrease compared to before the movement.

[0053] In order to increase the belt winding angle of each of the heating rollers 3351a and 3351b, it is preferable to move the tension roller 3311 in a direction C intersecting a straight line D connecting the rotation center of the heating roller 3351a and the rotation center of the heating roller 3351b. In addition, by moving the tension roller 3311 to the side of the roller with the greater heating output or the roller with the larger diameter, out of the heating rollers 3351a and 3351b, the heating efficiency of the drying belt 3301 can be improved.

[0054] As described above, in this embodiment, the tension roller 3311 is disposed to apply tension to the drying belt 3301 so as to press the tension portion 3301Q of the drying belt 3301 stretched by the heating rollers 3351a and 3351b from the outside to the inside. In addition, the steering roller 3321 is disposed between the driving roller 3331 and the heating roller 3351a to control the position of the drying belt 3301 in the rotation direction of the drying belt 3301. In this way, even if the tension roller 3311 moves when the drying belt 3301 expands due to the effect of heat and the belt stretches, the range in which the tension state of the drying belt 3301 changes can be limited to between the heating rollers 3351a and 3351b. Between the heating roller 3351a and the heating roller 3351b, the heating rollers 3351a and 3351b move in a direction in which the belt winding angle of the heating rollers 3351a and 3351b increases, so the heating efficiency of the drying belt 3301 by the heating rollers 3351a and 3351b does not decrease compared to before the movement. Even if the tension roller 3311 moves, the belt winding angle of the steering roller 3321 does not change, so the belt meandering control by the steering roller 3321 is stably performed without changing from before the belt movement. In this way, in this embodiment, even if the tension roller 3311 moves, it is possible to realize efficient heating of the drying belt 3301 by the heating rollers 3351a and 3351b and suppression of meandering of the drying belt 3301 by the steering roller 3321.

[0055] <Other embodiments> In the above-described embodiment, the resin drying belt 3301 is used, but the present invention is not limited to this, and a metal drying belt 3301 may be used. However, since the resin or rubber drying belt 3301 has a larger linear expansion coefficient than a metal drying belt, the above-described effect is more easily obtained.

[0056] In the above embodiment, the steering roller 3321 is displaced by the rotating steering arm 3323a to control the meandering of the belt, but the present invention is not limited to this. For example, an automatic centering mechanism that provides a regulating rib at the end of the drying belt 3301 to regulate the amount of meandering of the drying belt 3301, or a meandering control mechanism that generates a tension difference at the belt end may be used.

[0057] In the above embodiment, both the heating rollers 3351a and 3351b are heating rollers for heating the drying belt 3301, but at least one of the heating rollers 3351a and 3351b may be a heating roller. In this case, however, in order to efficiently heat the sheet S, it is preferable that the heating roller 3351b is the one that stretches the drying belt 3301 at a position closest to the sheet transport surface 3301P.

[0058] In the above embodiment, the heater 3353 is provided inside the heating rollers 3351a and 3351b, but this is not limited to the above. For example, the heater may be disposed on the outer periphery of the heating rollers 3351a and 3351b to heat them.

[0059] In the above embodiment, the inkjet recording apparatus 100 has been described as an example of an image forming apparatus, but the present invention is not limited to this. The present invention can also be applied to, for example, an electrophotographic image forming apparatus using toner, and can obtain the same effects as the present embodiment. [Explanation of symbols]

[0060] 100... image forming apparatus (inkjet recording apparatus), 2300... image forming section (recording section), 3300... sheet conveying apparatus (drying belt unit), 3301... drying belt, 3301P... sheet conveying surface, 3301Q... tension section, 3311... tension roller, 3321... steering roller, 3331... first roller (drive roller), 3351a... third roller (heating roller), 3351b... second roller (heating roller), S... sheet

Claims

1. A sheet conveying device for conveying sheets, An endless belt that rotates to transport the sheet, A first roller that tensions the belt downstream of the sheet conveying surface that conveys the sheet of the belt in the direction of rotation of the belt, In the aforementioned rotational direction, a second roller tensions the belt upstream of the sheet conveying surface and downstream of the first roller, In the aforementioned rotational direction, a third roller tensions the belt upstream of the second roller and downstream of the first roller, In the aforementioned rotational direction, a steering roller is positioned downstream of the first roller and upstream of the third roller, and tilts to move the belt in a width direction intersecting the rotational direction, The belt is provided with a tension roller that applies tension to the belt, At least one of the second roller and the third roller is a heating roller for heating the belt, The tension roller applies tension to the belt by pressing the tensioned portion of the belt, which is stretched by the second roller and the third roller, from the outside inward. A sheet conveying device characterized by the following features.

2. The tension roller is provided adjacent to the second roller and the third roller, Both the second roller and the third roller are heating rollers that heat the belt. The sheet conveying device according to feature 1.

3. The second roller is a heating roller that heats the belt. The sheet conveying device according to feature 1.

4. The tension roller extends the belt inward from the common outer tangent line of the second roller and the third roller that is inside the belt. The sheet conveying device according to feature 1.

5. The tension roller presses the belt so that the winding angle of the belt with respect to the heating roller is 135° or more. The sheet conveying device according to feature 4.

6. The tension roller moves in a direction that intersects the straight line connecting the rotation center of the second roller and the rotation center of the third roller. The sheet conveying device according to feature 1.

7. A sheet conveying device according to any one of claims 1 to 6, It comprises an image forming unit that forms an image on a sheet, An image forming apparatus characterized by the following features.

8. A first unit comprising the first roller, the second roller, the third roller, the steering roller, and the belt, and configured to be detachable, A second unit is provided detachably to the first unit, comprising the tension roller, an arm that rotatably supports the tension roller and is slidably supported, and a biasing member that biases the arm, The sheet conveying device according to feature 1.

9. The second unit comprises a tension lever that is movable between an allowable position that allows the tension roller to move to a position that applies tension to the belt, and a pressure release position that releases or reduces the pressure on the belt by the tension roller. The sheet conveying device according to feature 8.

10. The tension lever is a first tension lever, The second unit includes a second tension lever that is movable between a second allowable position that allows the tension roller to move to a position that applies tension to the belt, and a second pressure release position that releases or reduces the pressure on the belt by the tension roller. The sheet conveying device according to feature 9.

11. When the first tension lever is in the release position and the second tension lever is in the second release position, the arm restricts the first tension lever from moving to the allowable position. When the second tension lever moves to the second allowable position, the arm is moved by the biasing member, allowing the first tension lever to move to the allowable position. The sheet conveying device according to feature 10.

12. The first unit is provided with a protective cover capable of protecting the belt so that when the second unit is attached to the first unit, the second unit does not come into contact with at least a portion of the belt located between the second roller and the third roller. The sheet conveying device according to feature 8.

13. The first unit comprises a first side plate that rotatably supports one end of the first roller, and a second side plate that rotatably supports the other end of the first roller, The protective cover is provided between the second roller and the third roller, and spans the first side plate and the second side plate. The sheet conveying device according to feature 12.

14. The protective cover is a guide member capable of guiding the second unit when the second unit is attached to the first unit. The sheet conveying device according to feature 12.

15. A device body having an opening, The device body is provided with a door that opens and closes the opening for attaching and detaching the second unit, The first unit comprises a first side plate that rotatably supports one end of the second roller and the third roller, and a second side plate that rotatably supports the other end of the second roller and the third roller. The first side plate is provided with a notch at a position that overlaps with the second unit when viewed from a direction perpendicular to the first side plate. The door comprises a first fitting portion that engages with a portion of the first side plate located above the notch when the door is in the closed position that closes the opening, and a second fitting portion that engages with a portion of the first side plate located below the notch. The fitting is configured such that the distance between the centers of the second roller and the third roller is restricted by the door. The sheet conveying device according to feature 8.

16. A device body having an opening, The main body of the device is provided with a door that opens and closes the opening for attaching and detaching the second unit, The system includes a bundle of wires for supplying power to the heating roller, The first unit comprises a first side plate that rotatably supports one end of the second roller and the third roller, and a second side plate that rotatably supports the other end of the second roller and the third roller. The door is provided with a path for the wiring harness, and is configured to retract along with the door when the door is opened or closed. The sheet conveying device according to feature 8.

17. A hot air blowing device is provided opposite the sheet transport surface and capable of blowing hot air onto the sheet, wherein the hot air blowing device is configured to heat and dry the ink image formed on the recording material. The sheet conveying device according to feature 2.

18. A sheet conveying device for conveying sheets, The main body of the device, A first unit is detachably provided on the main body of the device, The unit comprises a second unit that is detachably attached to the first unit, The first unit is, An endless belt that rotates to transport the sheet, A first roller that tensions the belt downstream of the sheet conveying surface that conveys the sheet of the belt in the direction of rotation of the belt, In the aforementioned rotational direction, the upward flow on the sheet conveying surface and the second roller that tensions the belt downstream of the first roller, In the aforementioned rotational direction, a third roller tensions the belt upstream of the second roller and downstream of the first roller, At least one of the second roller and the third roller is a heating roller for heating the belt, The aforementioned second unit is A tension roller that applies tension to the belt, The tension roller is rotatably supported, and the arm is slidably supported, A biasing member that biases the arm, A sheet conveying device characterized by the following features.

Images