Sheet conveyance device

Abstract

To provide a configuration capable of suppressing deterioration of cleaning performance even if the length in the width direction of an upper belt 411 is increased.SOLUTION: In the width direction of a sheet, when the lengths of the portions where cleaning rollers 801 and 802 are in contact with an upper belt 411 are W1 and W2, and the length of the maximum size sheet is WL, the conditions W1<WL and W2<WL are satisfied. In addition, the cleaning rollers 801 and 802 are disposed at positions offset from each other in the rotational direction of the upper belt 411, and are disposed at positions offset from each other in the width direction such that a part of the cleaning roller 801 in the width direction and a part of the cleaning roller 802 in the width direction overlap with each other in the rotational direction of the upper belt 411.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a sheet transport device that transports a sheet. [Background technology]

[0002] Patent Document 1 describes a configuration in which a sheet is sandwiched and conveyed by a pair of rotating bodies, and the configuration includes two cleaning members that contact the rotating bodies to clean the rotating bodies. The two cleaning members have surface layers with different releasability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-74756 A Summary of the Invention [Problem to be solved by the invention]

[0004] Even in a configuration in which two cleaning members are brought into contact with a rotating body to clean the rotating body as in Patent Document 1, when the compatible sheet size of the device increases and the width of the rotating body increases, the width of the two cleaning members also increases, which may cause the two cleaning members to bend and reduce the cleaning performance of the central portion of the rotating body in the width direction.

[0005] An object of the present invention is to provide a configuration capable of suppressing a decrease in cleaning performance even when the length of the rotating body in the width direction is increased. [Means for solving the problem]

[0006] One aspect of the present invention includes a first rotating body, a second rotating body that forms a nip portion for sandwiching and conveying a sheet on which an image is formed between the first rotating body, and a first cleaning member and a second cleaning member that contact the surface of the first rotating body to clean deposits on the surface. With respect to the width direction of the sheet that intersects the conveyance direction of the sheet in the nip portion, the length of the portion where the first cleaning member contacts the first rotating body is W1, the length of the portion where the second cleaning member contacts the first rotating body is W2, and the length of the sheet with the maximum size conveyed in the nip portion is WL. When WL is defined, W1 < WL and W2 < WL are satisfied. The first cleaning member and the second cleaning member are arranged at positions shifted from each other with respect to the rotation direction of the first rotating body, and a part of the width direction of the first cleaning member and a part of the width direction of the second cleaning member overlap with each other with respect to the rotation direction of the first rotating body. The sheet conveyance device is characterized in that they are arranged at positions shifted from each other with respect to the width direction.

Effect of the Invention

[0007] According to the present invention, even if the length in the width direction of the rotating body increases, it is possible to suppress a decrease in cleaning performance.

Brief Description of the Drawings

[0008] [Figure 1] Schematic cross-sectional view showing the schematic configuration of the image forming system according to the first embodiment. [Diagram 2] Schematic cross-sectional view showing the schematic configuration of the fixing module according to the first embodiment. [Diagram 3] Schematic cross-sectional view showing the schematic configuration of the fixing belt unit according to the first embodiment. [Figure 4] Perspective view showing the configuration of the steering portion of the fixing belt unit according to the first embodiment. [Diagram 5] Plan view showing the relationship between the belt and the edge sensor according to the first embodiment. [Figure 6] Perspective view showing the arrangement of the cleaning roller unit in the upper belt unit according to the first embodiment. [Figure 7] FIG. 4 is an enlarged perspective view showing a mounting portion of a cleaning roller unit in the upper belt unit according to the first embodiment. [Figure 8] FIG. 2 is a perspective view of a cleaning roller unit according to the first embodiment. [Figure 9] 9 is a perspective view of the cleaning roller unit according to the first embodiment, seen from the opposite side to that in FIG. 8. [Figure 10] FIG. 4 is a perspective view showing an arrangement of a cleaning roller in the upper belt unit according to the first embodiment. [Figure 11] FIG. 11 is a plan view showing an arrangement of cleaning rollers in an upper belt unit according to a modification of the first embodiment. [Figure 12] FIG. 11 is a plan view showing the arrangement of cleaning rollers in an upper belt unit according to a second embodiment. [Figure 13] FIG. 13 is a plan view showing an arrangement of cleaning rollers in an upper belt unit according to a modification of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 the present embodiment will be described with reference to Figure 1.

[0010] [Image formation system] The image forming system 1 as the image forming apparatus of this embodiment uses an inkjet recording method of ejecting ink 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, namely, a reaction liquid and ink. The sheet may be any recording material that can receive ink, such as paper such as plain paper or thick paper, plastic film such as an overhead projector sheet, specially shaped sheets such as an envelope or index paper, and cloth.

[0011] 1, the image forming system 1 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 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 image forming system 1. 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 of the apparatus 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 as an image forming section has a pre-imaging registration correction section (not shown), a print belt unit 2010, and a recording section 2020. The sheet S conveyed from the feeding module 1000 has its inclination and position corrected by the pre-imaging registration correction section and is conveyed to the print belt unit 2010. The recording section 2020 is disposed at a position facing the print belt unit 2010 with respect to the conveying path. The recording section 2020 is an inkjet recording section that forms an image by discharging ink onto the conveyed sheet S from above with a recording head. A plurality of recording heads that discharge ink are arranged along the conveying direction. In this embodiment, in addition to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), a total of five line-type recording heads corresponding to the reaction liquid are provided. The sheet S is attracted and conveyed by the print belt unit 2010, so that a clearance between the sheet S and the recording head is ensured.

[0015] The number of ink colors and recording heads is not limited to the above five. The inkjet method may 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.

[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 in-line scanner (not shown) disposed 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 formed on the sheet S, the density, etc. are corrected.

[0017] The drying module 3000 includes a decoupling section 3200, a drying belt unit 3300, and a hot air blowing section 3400. The drying module 3000 reduces the liquid content of the ink and reaction liquid applied to the sheet S in order to improve the fixation of the ink to the sheet S by the subsequent fixing module 4000. The sheet S on which an image is formed is transported to a decoupling section 3200 arranged in the drying module 3000. In the decoupling section 3200, frictional force is generated between the sheet S and the belt by the wind pressure of the wind blown from above, and the sheet S is 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 the sheet S is transported between the print belt unit 2010 and the decoupling section 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 hot air blowing from the hot air blowing section 3400 arranged above the belt.

[0018] In this way, the ink and reaction liquid applied to the sheet S are heated by the drying module 3000 to promote evaporation of the moisture, thereby preventing so-called cockling, in which ink splatters on the sheet S and creates a border-like line around the periphery. The drying module 3000 may be any device capable of heating and drying, but a hot air dryer or heater is preferable. As the heater, for example, an electric heating wire or an infrared heater is preferable from the viewpoint of safety and energy efficiency.

[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 the ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit and a lower belt unit. The fixing belt unit 4100 will be described in detail later.

[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 section 5001, for example, takes in outside air into a cooling box with a fan to increase the pressure inside the cooling box, and cools the sheet S by blowing air from the cooling box through a nozzle due to the pressure against the sheet S. The cooling sections 5001 are disposed 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 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.

[0023] During double-sided printing, the sheet S is transported to a transport path below the cooling module 5000 by the transport path switching unit 5002. Thereafter, the sheet S passes through a double-sided transport 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 transport 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.

[0024] [Fixing module] Next, the fixing module 4000 will be described in detail with reference to FIG. 2. FIG. 2 is a schematic diagram showing the fixing module 4000. A fixing belt unit 4100 is provided on the upper part of the fixing module 4000. The fixing belt unit 4100 has a substantially linear sheet transport path 401 for receiving the sheet S discharged from the drying module 3000, performing fixing, and then delivering the sheet S to the cooling module 5000. In addition, in each drawing, the front side of the inkjet recording system 100 is represented as the front direction F, the rear side is represented as the rear direction B, the right side is represented as the right direction R, the left side is represented as the left direction L, the upper side is represented as the upper direction U, and the lower side is represented as the lower direction D. In addition, an operation unit (not shown) operated by an operator is provided on the front side of the inkjet recording system 100.

[0025] The fixing belt unit 4100 includes an upper belt unit 410 and a lower belt unit 420. The upper belt unit 410 is disposed vertically above the lower belt unit 420. The upper belt unit 410 includes an upper belt 411, which is an example of a fixing belt and a conveying belt (first conveying belt), and a tension roller 4011a that applies tension to the upper belt 411. That is, the upper belt unit 410 is an example of a belt unit (first belt unit), and includes a detachable upper belt 411 that conveys the sheet S. The lower belt unit 420 is an example of a second belt unit, and includes a lower belt 421, a tension roller 422 that applies tension to the lower belt 421, and a pad 423 having an arc-shaped curved surface. The pad 423, which serves as a nip portion forming member, is disposed so as to form a nip with the upper belt 411 via the lower belt 421.

[0026] The sheet S is conveyed while being sandwiched in the nip between the upper belt unit 410 and the lower belt unit 420. That is, the lower belt 421 is an example of a rotating body and a second conveyor belt, and is disposed opposite the upper belt unit 410 when the upper door unit 43 is located in the closed position and the upper belt unit 410 is located in the upper storage position. At this time, the sheet S is sandwiched together with the upper belt 411 and conveyed. The pressure of the nip is determined by the tension and thickness of the upper belt 411 and the curvature of the pad 423. If the pressure of the nip is too high, the ink of the sheet S may adhere to the upper belt unit 410 and the ink may peel off from the sheet S. Therefore, the pressure is preferably 1 Pa to 2000 Pa, and more preferably 1 Pa to 200 Pa.

[0027] When the curvature of the pad 423 becomes large, the difference in the conveying path between the front and back of the sheet S becomes large, and there is a possibility that friction will occur between the sheet S and the belt. When the curvature of the pad 423 becomes large, there is a possibility that a phenomenon will occur in which the sheet S itself memorizes the curved shape and curls, so it is desirable that the curvature radius of the pad 423 is 50 mm or more. Also, from the viewpoint of manufacturing precision, it is desirable that the curvature radius of the pad 423 is 100,000 mm or less. Due to these constraints, in this embodiment, the tension of the upper belt 411 is 200 N, the thickness is 0.3 mm, the curvature of the pad 423 is 30,000 mm, and the nip pressure is about 16 Pa.

[0028] By adopting such a configuration, uniform pressure can be applied even in a wide nip. As a result, even when the temperature of the upper belt unit 410 is set to the melting point of wax or the boiling point of water, the contact time between the sheet S and the upper belt unit 410 can be increased to sufficiently transfer heat to the sheet S. However, if the nip continues to be formed after the heat is sufficiently transferred, a phenomenon occurs in which ink adheres to the upper belt 411 and peels off the sheet S, or the upper belt 411 and the sheet S rub against each other, causing a disturbance in the image, so a contact time that is too long is not preferable. Therefore, it is desirable that the time required for the leading edge of the sheet S to enter the entrance of the nip and exit the exit of the nip is 0.5 s to 4 s. In this embodiment, a pad 423 with a length of 900 mm in the sheet transport direction is used, the sheet S is transported at 700 mm / s, and the time required for the leading edge of the sheet S to exit the exit of the nip from the entrance of the nip is about 1.3 s. Since moisture is necessary for ink to penetrate into the sheet S, it is preferable that the upper belt 411 and the lower belt 421 are impermeable to prevent moisture evaporated from the surface of the sheet S from escaping through the upper belt 411 or the lower belt 421 that they come into contact with when the sheet becomes hot.

[0029] [Fuser belt unit] Next, the fixing belt unit 4100 of this embodiment will be described with reference to Fig. 3. As shown in Fig. 3, the fixing belt unit 4100 as a sheet conveying device and a fixing device includes an upper belt unit 410 as a first belt unit and a lower belt unit 420 as a second belt unit, and a nip portion N is formed by pressing an upper belt 411 of the upper belt unit 410 and a lower belt 421 of the lower belt unit 420 together. A sheet S1 is sandwiched and conveyed at the nip portion N, and pressure and heat are applied thereto, so that an image formed by ink is fixed to the sheet S1.

[0030] The upper belt unit 410 includes an endless upper belt 411 as a first rotating body and a first belt, a plurality of tension rollers as a plurality of first tension members for tensioning the upper belt 411, and a first heating unit 4060a as a heating unit and a first heating device. The plurality of tension rollers are an entrance roller 4110, an exit roller 4120, a driving roller 4031a, a tension roller 4011a, a guide roller 4051a, and a steering roller 4021a. These rollers are arranged in order from the upstream of the nip portion N with respect to the rotation direction of the upper belt 411, and the upper belt 411 forms a rotation trajectory by this. In addition, the nip portion N exists between the entrance roller 4110 and the exit roller 4120. Each roller is supported by an upper frame 414 which is a housing of the upper belt unit 410.

[0031] The first heating unit 4060a is disposed inside the upper belt 411, and includes a first heater section 4061a, a reflecting member, and a reflecting plate 4052a as the first reflecting member. The first heating unit 4060a is detachable from the first belt unit body 410a having the upper belt 411. The first belt unit body 410a includes the upper belt 411, a plurality of rollers that stretch the upper belt 411, and an upper frame 414.

[0032] The first heater section 4061a is disposed in a non-contact manner with the upper belt 411 and along the width direction of the upper belt 411 that intersects with the rotation direction of the upper belt 411, and radiates heat to heat the upper belt 411. The reflector 4052a is disposed along the width direction and reflects the radiant heat of the first heater section 4061a toward a predetermined area of ​​the upper belt 411.

[0033] In this embodiment, the first heating unit 4060a of the upper belt unit 410 is disposed inside the upper belt 411 and above the nip portion N, and heats the upper belt 411 from the inside. The first heating unit 4060a has a plurality of first heater portions 4061a. In this embodiment, three first heater portions 4061a are arranged side by side in the rotation direction of the upper belt 411. In addition, a reflecting plate 4052a is arranged so as to cover the periphery of the first heater portion 4061a except for the side facing the upper belt 411.

[0034] The reflecting plates 4052a are arranged in the same number as the first heater portions 4061a in correspondence with the first heater portions 4061a. The reflecting plates 4052a are formed so that the nip portion N side of the first heater portions 4061a is open and so as to cover both ends of the first heater portions 4061a in the width direction. This allows the radiant heat of the first heater portions 4061a to be efficiently irradiated toward the nip portion N by the reflecting plates 4052a.

[0035] That is, in the upper belt unit 410, the predetermined area is an area (first area) in the range of the nip portion N on the inner circumferential surface of the upper belt 411, and the nip portion N is directly heated by the multiple first heater portions 4061a and the multiple reflectors 4052a. This allows heat to be efficiently transferred to the sheet S passing through the nip portion N. In this embodiment, the area in the range of the nip portion N heated by the multiple first heater portions 4061a is the inner circumferential surface (lower surface portion) of the upper belt 411, and is the lower surface portion 411a located upstream of the center position of the nip portion N with respect to the conveying direction of the sheet S passing through the nip portion N. That is, in this embodiment, the predetermined area in the upper belt unit 410 is the lower surface portion 411a.

[0036] The lower surface portion 411a is located opposite to the lower belt 421 stretched between a nip upstream roller 426 and a nip downstream roller 427, among the tension rollers of the lower belt 421 described later, and is also located opposite to an area where the lower belt 421 is supported by a pad 423 disposed between these rollers. This allows the distance between the lower surface portion 411a of the upper belt 411 and the first heating unit 4060a to be kept approximately constant regardless of the rotation of the upper belt 411.

[0037] The lower belt unit 420 includes an endless lower belt 421 as a second rotating body and a second belt, a plurality of tension rollers as a plurality of second tension members for tensioning the lower belt 421, and a second heating unit 4060b as a second heating device. The plurality of tension rollers are a nip upstream guide roller 425, a nip upstream roller 426, a nip downstream roller 427, a drive roller 4031b, a tension roller 4011b, a guide roller 4051b, a guide roller 428, and a steering roller 4021b. These rollers are arranged in order from the upstream of the nip portion N in the rotation direction of the lower belt 421.

[0038] Further, a nip portion N exists between the nip upstream roller 426 and the nip downstream roller 427, and a pad 423 is disposed therebetween. That is, the nip upstream roller 426 and the nip downstream roller 427 are disposed so as to sandwich the nip portion N in the rotation direction of the lower belt 421. The pad 423 as a nip portion forming member abuts against the inner peripheral surface of the lower belt 421 in the region of the nip portion N to support the lower belt 421, thereby forming the nip portion N between the upper belt 411 and the lower belt 421. The lower belt 421 has a rotational trajectory formed by the rollers and the pad 423. The rollers and the pad 423 are supported by a lower frame 424 which is a housing of the lower belt unit 420.

[0039] The second heating unit 4060b is disposed inside the lower belt 421, and includes a second heater portion 4061b, a reflecting member, and a reflecting plate 4052b as the second reflecting member. The second heating unit 4060b is detachable from the second belt unit body 420a having the lower belt 421. The second belt unit body 420a includes the lower belt 421, a plurality of rollers that stretch the lower belt 421, a pad 423, and a lower frame 424.

[0040] The second heater section 4061b is disposed in a non-contact manner with the lower belt 421 and along the width direction of the lower belt 421 that intersects with the rotation direction of the lower belt 421, and radiates heat to heat the lower belt 421. The reflector 4052b is disposed along the width direction and reflects the radiant heat of the second heater section 4061b toward a predetermined area of ​​the lower belt 421.

[0041] In this embodiment, the second heating unit 4060b of the lower belt unit 420 is disposed inside the lower belt 421 and below the nip portion N, and heats the lower belt 421 from the inside. The second heating unit 4060b has a plurality of second heater portions 4061b. In this embodiment, two second heater portions 4061b are disposed side by side in the rotation direction of the lower belt 421. In addition, a reflector 4052b is disposed so as to cover the periphery of the second heater portion 4061b except for the side facing the lower belt 421.

[0042] The reflecting plates 4052b are arranged in the same number as the second heater sections 4061b in correspondence with the second heater sections 4061b. The reflecting plates 4052b are formed so that the lower sides of the second heater sections 4061b are open and so as to cover both ends of the second heater sections 4061b in the width direction. This allows the radiant heat of the second heater sections 4061b to be efficiently irradiated toward the lower portion of the lower belt 421 by the reflecting plates 4052b.

[0043] That is, in the lower belt unit 420, the predetermined area is an area (second area) of the inner circumferential surface of the lower belt 421 that is outside the nip portion N, and in this embodiment, it is the lower part of the lower belt 421. Specifically, the area outside the nip portion N that is heated by the second heaters 4061b is the inner circumferential surface (lower surface portion) of the lower belt 421 between the guide roller 4051b and the guide roller 428 with respect to the rotation direction of the lower belt 421. That is, the predetermined area in the lower belt unit 420 is the lower surface portion 421a of the lower belt 421, and the lower surface portion 421a is a surface on which the lower belt 421 is stretched in a substantially horizontal direction between the guide roller 4051b and the guide roller 428. As described above, the lower belt unit 420 is provided with the pad 423 at a position corresponding to the nip portion N, and cannot directly heat the nip portion N like the upper belt unit 410. For this reason, by arranging a plurality of second heater portions 4061b and a plurality of reflecting plates 4052b facing the lower surface portion 421a of the lower belt 421, the lower belt 421 is directly heated efficiently.

[0044] The lower surface portion 421a, which is an area of ​​the lower belt 421 heated by the multiple second heater portions 4061b and the multiple reflectors 4052b, is located on the upstream side of the nip upstream guide roller 425 at the entrance of the nip portion N and the steering roller 4021b in the rotation direction of the lower belt 421. The lower surface portion 421a is located downstream of the center position between the guide roller 428 and the tension roller 4011b that tension the lower portion of the lower belt 421 in the rotation direction of the lower belt 421. Therefore, the multiple second heater portions 4061b and the multiple reflectors 4052b can heat the lower belt 421 at a position relatively close to the nip portion N, and the heat can be efficiently transferred to the sheet S passing through the nip portion N.

[0045] As described above, in the upper belt unit 410, the pad 423 keeps the distance between the upper belt 411 and the first heating unit 4060a approximately constant regardless of the rotation of the upper belt 411. This stabilizes the thermal effect from the first heater section 4061a to the upper belt 411. In the lower belt unit 420, the tension roller 4011b and the guide roller 428 stretch the lower belt 421 upstream and downstream of the second heating unit 4060b, so that the distance between the lower belt 421 and the second heating unit 4060b is kept approximately constant regardless of the rotation of the lower belt 421. This stabilizes the thermal effect from the second heater section 4061b to the lower belt 421.

[0046] The first heater portion 4061a and the second heater portion 4061b may be any heater that heats the belt by radiating heat, for example, a halogen heater. In this embodiment, these heaters are halogen heaters.

[0047] As described above, the reflectors 4052a and 4052b are arranged around the first heater section 4061a and the second heater section 4061b to efficiently collect light onto the upper belt 411 and the lower belt 421, respectively. The reflectors 4052a and 4052b are made of, for example, mirror-finished aluminum members to efficiently reflect light. The heater outputs of the first heater sections 4061a and the second heater sections 4061b are controlled based on the temperature detected by a temperature detector (not shown). This allows the upper belt 411 and the lower belt 421 to be kept at an appropriate temperature.

[0048] In this embodiment, as a preferred example, the belt is directly heated from the inside by a halogen heater, but the heater may be a sheet heating element or an IH heater. Also, the belt may be indirectly heated by contacting a heating roller made of aluminum or the like containing a halogen heater with the belt, or an external heating means may be used to heat the belt from the outside.

[0049] [About the tension rollers of each belt unit] We will now explain the tension rollers 4011a and 4011b, steering rollers 4021a and 4021b, and drive rollers 4031a and 4031b of the above-mentioned upper belt unit 410 and lower belt unit 420. Since the functions of these rollers are the same in the upper belt unit 410 and the lower belt unit 420, the following explanation will be given taking the rollers of the lower belt unit 420 as an example.

[0050] [Tension roller] First, the tension roller 4011b will be described with reference to FIG. 3. Of the multiple tension rollers provided in the lower belt unit 420, one roller is the tension roller 4011b that applies tension to the lower belt 421. The tension roller 4011b is disposed on the surface (downward direction D) opposite to the surface (upward direction U) that forms the nip portion N, and tensions the lower belt 421. In this embodiment, the tension roller 4011b is disposed downstream of the nip downstream roller 427, which is one of the nip upstream roller 426 and the nip downstream roller 427 that form the nip portion N, in the rotation direction of the lower belt 421. Specifically, the tension roller 4011b is disposed further downstream of the drive roller 4031b that is downstream of the nip downstream roller 427 with respect to the rotation direction of the lower belt 421.

[0051] Furthermore, tension roller 4011b is supported so as to be movable in a predetermined direction (in this embodiment, the direction of the arrow shown in FIG. 3), and is pressurized by a pressure member (e.g., a spring) (not shown). For example, if the circumferential length of lower belt 421 varies from a target length due to manufacturing variations or changes caused by usage conditions, tension roller 4011b is pressed by the pressure member, so that the tensioned state of lower belt 421 can be stabilized.

[0052] Specifically, in this embodiment, the tension roller 4011b of the lower belt unit 420 is configured to be supported so as to be movable in the horizontal direction (left direction L and right direction R). The tension roller 4011b is arranged so that, from the upstream side of the rotation direction of the lower belt 421, the tension roller 4011b, the guide roller 4051, the heating section by the second heating unit 4060b, and the guide roller 428 are arranged. By arranging in this embodiment, even if the position of the tension roller 4011b moves in the horizontal direction due to the variation in the circumferential length of the lower belt 421, it is possible to suppress the variation in the distance between the second heating unit 4060b and the lower belt 421. Meanwhile, the tension roller 4011a of the upper belt 411 is also configured to be supported so as to be movable in the horizontal direction.

[0053] [Steering roller] Next, the steering roller 4021b will be described with reference to Fig. 3 to Fig. 5. Fig. 4 is a schematic perspective view showing the vicinity of the steering roller of the fixing belt unit 4100. Fig. 5 is a plan view showing the relationship between the upper belt 411 (lower belt 421) and the edge sensor 4025a (4025b). Of the multiple tension rollers provided in the lower belt unit 420, one roller is a steering roller 4021b for controlling the position of the lower belt 421 in the front-rear direction (forward direction F and rear direction B, width direction of the lower belt 421).

[0054] The steering roller 4021b is a roller made of metal such as aluminum or iron. One end of the steering roller 4021b in the front-rear direction is rotatably supported by a fixed plate 4026b. The fixed plate 4026b is fastened to the lower frame 424 by screws 4027b or the like. The other end of the steering roller 4021b in the front-rear direction is rotatably supported by a steering arm 4023b. The steering arm 4023b is supported by the lower frame 424 so as to be rotatable about a rotation center 4024b. A steering cam 4022b having an eccentric radius abuts against a part of the steering arm 4023b, and the alignment of the steering roller 4021b can be changed by rotating the steering cam 4022b by a steering motor (not shown).

[0055] The fixed plate 4026b is configured so that the rotation center position of the steering roller 4021b can be moved by loosening the screws 4027b to the lower frame 424, and the alignment can be adjusted by refastening the screws. For example, it is possible to fine-tune the optimal alignment position of the steering roller 4021b depending on the variation in the installation environment.

[0056] Further, a nip upstream guide roller 425 is disposed downstream of the steering roller 4021b provided in the lower belt unit 420 in the rotation direction of the lower belt 421. This is to stabilize the trajectory of the lower belt 421 immediately before the nip portion N, regardless of the attitude of the steering roller 4021b. When the conveyed sheet S enters the nip portion N, the sheet S is conveyed so that its attitude is aligned with the lower belt 421, thereby stabilizing the entry.

[0057] Next, the control of the front-rear position of the lower belt 421 by the steering roller 4021b will be described with reference to Figures 4 and 5. Here, the upper belt unit 410 and the lower belt unit 420 have slightly different configurations, so each will be described separately.

[0058] First, an edge sensor 4025b is provided at one end of the lower belt 421 in the front-rear direction (the end on the front direction F side in this embodiment) on the lower direction D side of the lower belt 421 to contact the end face of the lower belt 421 and detect the position of the lower belt 421 in the front direction F. In the lower belt unit 420, the guide roller 428 is arranged so that the surface of the lower belt 421 stretched by the tension roller 4011b and the guide roller 428 is approximately parallel to the moving direction (horizontal direction) of the tension roller 4011b. The edge sensor 4025b is provided between the tension roller 4011b and the guide roller 428 to reduce the influence of the belt locus due to the variation in the circumferential length of the lower belt 421 on the edge sensor 4025b.

[0059] The amount of rotation of the steering cam 4022b is controlled based on the detection value of the edge sensor 4025b. The rotation center 4028b of the edge sensor 4025b is set so that when the lower belt 421 rotates, the edge sensor 4025b receives a force in a direction in which the edge sensor 4025b moves away due to a frictional force from the lower belt 421. As a result, the load acting between the edge sensor 4025b and the end face of the lower belt 421 can be reduced.

[0060] Meanwhile, at the other end of the upper belt 411 in the front-rear direction (the end on the rear direction B side in this embodiment), an edge sensor 4025a is provided on the upper direction U side of the upper belt 411 in contact with the end face of the upper belt 411 to detect the position of the upper belt 411 in the rear direction B. In the upper belt unit 410, the guide roller 4051a is arranged so that the surface of the upper belt 411 stretched by the tension roller 4011a and the guide roller 4051a is approximately parallel to the moving direction (horizontal direction) of the tension roller 4011a. The edge sensor 4025a is provided between the tension roller 4011a and the guide roller 4051a to reduce the influence of the belt locus due to the circumferential length variation of the upper belt 411 on the edge sensor 4025a.

[0061] The amount of rotation of the steering cam 4022a is controlled based on the detection value of the edge sensor 4025a. The rotation center 4028a of the edge sensor 4025a is set so that when the upper belt 411 rotates, the edge sensor 4025a receives a force in a direction in which the edge sensor 4025a moves away due to a frictional force from the upper belt 411. As a result, the load acting between the edge sensor 4025a and the end face of the upper belt 411 can be reduced.

[0062] As shown in FIG. 5, by arranging edge sensor 4025b at the end of lower belt 421 on the forward direction F side and the portion on the downward direction D side, and edge sensor 4025a at the end of upper belt 411 on the rear direction B side and the portion on the upward direction U side, it becomes possible to use edge sensors of the same shape for upper belt 411 and lower belt 421.

[0063] In addition, although the steering roller in this embodiment is a metal roller, a roller having a rubber layer such as heat-resistant rubber on the surface may be used to increase the frictional force and thereby improve steering performance. Also, although one end of the steering roller is fixed and the alignment is changed by moving the other end, both ends may be supported movably to change the alignment.

[0064] [Drive roller] Next, the driving roller 4031b will be described with reference to Fig. 3. Of the multiple tension rollers provided in the lower belt unit 420, one roller is a driving roller 4031b for applying a driving force to the lower belt 421.

[0065] The driving roller 4031b is a roller made of metal such as aluminum or iron. Both ends of the driving roller 4031b in the front-rear direction are rotatably supported by the lower frame 424, and the driving roller 4031b rotates by inputting a driving force using a drive transmission mechanism (not shown) such as a gear or a timing belt, and rotates the lower belt 421 in a predetermined direction by frictional force.

[0066] In this embodiment, the lower belt 421 and the upper belt 411 are rotated by applying a driving force to them independently from the driving rollers 4031a and 4031b. Note that, although the driving rollers in this embodiment are made of metal, a roller having a rubber layer such as heat-resistant rubber on its surface may be used to increase the driving force by increasing the frictional force.

[0067] [Cleaning roller unit] The fixing belt unit 4100 of this embodiment has a cleaning roller unit 600 for cleaning the upper belt 411 of the upper belt unit 410. The cleaning roller unit 600 will be described with reference to Figs. 6 to 11. As shown in Fig. 6, the cleaning roller unit 600 is arranged on the upper belt 411 for cleaning off adhesions such as ink and paper dust adhering to the belt. In this embodiment, the cleaning roller unit 600 having cleaning rollers 801 and 802 described later is arranged at a position facing a guide roller 4051a, which is one of the tension rollers of the upper belt unit 410, across the upper belt 411.

[0068] 7 is an enlarged perspective view showing a mounting portion of the cleaning roller unit 600 in the upper belt unit 410. The cleaning roller unit 600 has a cleaning roller support plate 601 that supports cleaning rollers 801, 802. The cleaning roller support plate 601 is attached to a front side plate 602, which is a front side plate of the upper frame 414 of the upper belt unit 410, with screws 701A, 701B. The cleaning roller support plate 601 is also supported by inserting insertion portions 702A, 702B, 702C into a rear side plate 603, which is a rear side plate of the upper frame 414. That is, the cleaning roller unit 600 is supported by the upper frame 414.

[0069] Figures 8 and 9 are perspective views showing a detailed configuration of the cleaning roller unit 600. Figure 8 is a perspective view of the cleaning roller unit 600 in a state where it is attached to the upper belt unit 410 as shown in Figure 7, as viewed from the side indicated by the arrow α. Also, Figure 9 is a perspective view of the cleaning roller unit 600 as viewed from the side where the cleaning rollers 801 and 802 are attached, that is, from the opposite side to Figure 8 (the side indicated by the arrow β).

[0070] In the cleaning roller unit 600, a cleaning roller 801 as a first cleaning member and a cleaning roller 802 as a second cleaning member are attached to the surface of the cleaning roller support plate 601 on the arrow β side. The cleaning rollers 801 and 802 are attached to the cleaning roller support plate 601 via pressure springs (not shown) as urging members, via cleaning roller holders 803A, 803B, 804A, and 804B, which are respectively attached to the cleaning roller support plate 601. The cleaning rollers 801 and 802 are urged toward the upper belt 411 by the pressure springs.

[0071] 10 is a perspective view showing the arrangement of cleaning rollers 801, 802 in the upper belt unit 410. As described above, the cleaning rollers 801, 802 are arranged so as to be pressed against the cleaning roller support plate 601 toward the upper belt 411 by a pressure spring (not shown). The cleaning rollers 801, 802 come into contact with the surface of the upper belt 411 to clean off any deposits on the surface.

[0072] Here, the fixing belt unit 4100 of the present embodiment is also capable of handling large-sized sheets that are long in the width direction of the sheet intersecting the sheet conveying direction at the nip portion N. For this reason, the width directions of the upper belt 411 and the lower belt 421 are also long. If the width direction length of the cleaning roller is increased to clean the upper belt 411 having such a long width direction, the cleaning roller will bend due to contact with the rotating upper belt 411. That is, the cleaning roller receives a frictional force from the upper belt 411. At this time, since both ends in the rotation axis direction are supported by the cleaning roller support plate, the cleaning roller is bent so that the center part in the rotation axis direction protrudes in the rotation direction of the upper belt 411 more than both ends.

[0073] This makes the contact of the central portion of the cleaning roller in the direction of its rotation axis with the upper belt 411 unstable. Since the cleaning roller is arranged so that the direction of its rotation axis is along the width direction, there is a risk that the cleaning performance of the central portion of the width direction of the upper belt 411 may decrease. Small sheets also pass through the central portion of the width direction of the upper belt 411, so that small sheets in particular are easily soiled. Therefore, in this embodiment, the following configuration is adopted.

[0074] 10, the cleaning rollers 801 and 802 are disposed at positions offset from each other in the rotation direction of the upper belt 411. The cleaning rollers 801 and 802 are also disposed at positions offset from each other in the width direction such that a part of the cleaning roller 801 in the width direction and a part of the cleaning roller 802 in the width direction overlap with each other in the rotation direction of the upper belt 411.

[0075] The cleaning rollers 801, 802 have rotating shafts 801a, 802a whose both ends are rotatably supported by cleaning roller holders 803A, 803B, 804A, 804B (Figure 9), and roller portions 801b, 802b arranged around the rotating shafts 801a, 802a and in contact with the upper belt 411.

[0076] Also, when the length in the width direction of the portion where the roller part 801b of the cleaning roller 801 is in contact with the upper belt 411 is W1, the length in the width direction of the portion where the roller part 802b of the cleaning roller 802 is in contact with the upper belt 411 is W2, and the length in the width direction of the sheet with the maximum size conveyed in the nip part N is WL, W1 < WL and W2 < WL are satisfied. For this reason, when the length in the width direction of the upper belt 411 is WB, W1 < WB and W2 < WB are also satisfied. That is, in the present embodiment, the lengths in the width direction of the roller parts 801b and 802b of the cleaning rollers 801 and 802 are made shorter than the width of the sheet with the maximum size, respectively.

[0077] Note that the entire roller parts 801b and 802 do not have to be in contact with the upper belt 411. For example, if the cleaning rollers 801 and 802 are arranged such that the end parts of the roller parts 801b and 802b protrude outside the upper belt 411, among the roller parts 801b and 802b, the part inside from the end part protruding from the upper belt 411 becomes the part in contact with the upper belt 411. In the present embodiment, the cleaning rollers 801 and 802 are arranged such that the front end part of the roller part 801b protrudes forward from the upper belt 411 and the rear end part of the roller part 802b protrudes rearward from the upper belt 411.

[0078] In the present embodiment, by arranging the cleaning rollers 801 and 802 in this way, in the entire area in the width direction (front-rear direction) of the upper belt 411, either the roller parts 801b and 802b of the cleaning rollers 801 and 802 are in contact with the surface of the upper belt 411. Note that the end parts of the roller parts 801b and 802b may be made to be inside the upper belt 411. Even in this case, the range where both the roller parts 801b and 802b are in contact with the upper belt 411 is made to be at least larger than the width of the sheet with the maximum size.

[0079] Therefore, in this embodiment, the contact area of ​​the cleaning rollers 801, 802 together with the upper belt 411 is set to be larger than at least the maximum sheet width. That is, when the widthwise length of the area where a part of the cleaning roller 801 and a part of the cleaning roller 802 overlap is W3, the relationship (W1+W2)-W3>WL is satisfied.

[0080] However, if the length of the contact portion of the cleaning rollers 801, 802 with the upper belt 411 is made larger than the maximum sheet width, the cleaning rollers 801, 802 will bend as described above, resulting in a decrease in cleaning performance. For this reason, in this embodiment, the length of the contact portion of the cleaning rollers 801, 802 with the upper belt 411 is made smaller than the maximum sheet width, making it difficult for the cleaning rollers 801, 802 to bend.

[0081] On the other hand, it is necessary to avoid the occurrence of uncleaned portions in the region of the upper belt 411 through which the sheet passes by shortening the length of the cleaning rollers 801 and 802. Furthermore, although it is conceivable to arrange the portions of the cleaning rollers 801 and 802 that contact the upper belt 411 so that the gap between them in the width direction is zero, this is not realistic considering the component tolerance. For this reason, in this embodiment, as shown in FIG. 10, a part of the width direction of the cleaning roller 801 and a part of the width direction of the cleaning roller 802 are overlapped in the rotation direction of the upper belt 411. That is, the cleaning rollers 801 and 802 are arranged so that the roller portions 801b and 802b partially overlap when viewed from the rotation direction of the upper belt 411.

[0082] In the case of this embodiment, the length WB in the width direction of the upper belt 411 is, for example, 400 mm, and the lengths W1 and W2 in the width direction of the portions where the roller parts 801b and 802 are in contact with the upper belt 411 are, for example, 320 mm. W3 in FIG. 10 is the length in the width direction of the region where a part in the width direction of the cleaning roller 801 and a part in the width direction of the cleaning roller 802 overlap, and is, for example, 240 mm. Also, the length in the width direction of the sheet with the maximum size is, for example, 364 mm. Therefore, W1 < WL and W2 < WL are satisfied.

[0083] Also, in the case of this embodiment, when the length in the width direction of the smallest-size sheet conveyed in the nip part is defined as WS, the length in the width direction (overlap length) W3 of the region where the cleaning rollers 801 and 802 overlap is longer than WS. That is, W3 > WS is satisfied. The length WS in the width direction of the smallest-size sheet is, for example, 210 mm. For this reason, for small-size sheets passing near the center in the width direction of the upper belt 411, the cleaning effect by the two cleaning rollers 801 and 802 can be obtained. Therefore, the cleaning performance of small-size sheets can be further improved.

[0084] Note that, for example, even if the length in the width direction of the smallest-size sheet is 210 mm (A5), if it is desired to improve the cleaning performance for sheets with a size of 297 mm (A4) or more in the width direction, for example, the overlap length W3 may be set to 297 mm or more. For example, this is the case when the usage frequency of the smallest-size sheets is low. The main point is that the overlap length W3 may be set as appropriate in consideration of the usage frequency of the sheets in the apparatus.

[0085] 11, if there is no need to focus on improving cleaning performance for a particular size, the lengths W1 and W2 of the cleaning rollers 801, 802 in contact with the upper belt 411 may be set to, for example, 210 mm, and the length (overlap length) W3 of the area where the cleaning rollers 801, 802 overlap in the rotation direction of the upper belt 411 may be set to, for example, 20 mm. By shortening the overlap length W3 in this way, the length of each of the cleaning rollers 801, 802 can be shortened, and deflection of the cleaning rollers 801, 802 can be further suppressed.

[0086] As described above, in this embodiment, the lengths W1 and W2 of the cleaning rollers 801 and 802 in contact with the upper belt 411 are smaller than the maximum sheet size width WL. Therefore, compared to the case where the cleaning rollers are in contact for a length longer than the maximum sheet size width WL, it is possible to suppress the cleaning rollers from being deflected. Also, in this embodiment, a part of the width direction of the cleaning roller 801 and a part of the width direction of the cleaning roller 802 are overlapped in the rotation direction of the upper belt 411, so that even if the cleaning rollers 801 and 802 are shortened, the surface of the upper belt 411 can be cleaned over a wide range. In particular, since (W1+W2)-W3>WL is satisfied, the area of ​​the upper belt 411 through which the sheet passes can be cleaned more reliably.

[0087] In addition, in this embodiment, since the inner end of the cleaning roller 801 contacts the upper belt 411, there is a risk that the ink or other deposits collected by the cleaning roller 801 will be discharged in the width direction at the inner end of the cleaning roller 801 on the upstream side of the rotation direction of the upper belt 411. However, since the cleaning roller 802 is arranged so as to overlap the cleaning roller 802 on the downstream side of the inner end of the cleaning roller 801, the deposits discharged in the width direction from the cleaning roller 801 can be collected by the cleaning roller 802. Note that, since the deposits are collected at the inner end of the cleaning roller 802 by the upstream cleaning roller 801, the phenomenon of deposits being discharged in the width direction from the inner end of the cleaning roller 802 does not occur. For this reason, the configuration of this embodiment, including the fixing belt unit 4100 of this embodiment, is preferably applicable to a fixing device that fixes an image on a sheet.

[0088] <Second embodiment> The second embodiment will be described with reference to Figs. 12 and 13. In the above-mentioned first embodiment, a configuration in which the surface of the upper belt 411 is cleaned by two cleaning rollers 801, 802 has been described. In contrast, in this embodiment, a configuration in which the surface of the upper belt 411 is cleaned by three cleaning rollers 801, 802, and 803. Other configurations and functions are the same as those of the above-mentioned first embodiment. For this reason, the same reference numerals are used for configurations similar to those of the first embodiment, and explanations and illustrations are omitted or simplified, and the following description will focus on the points that are different from the first embodiment.

[0089] As shown in FIG. 12, the cleaning roller unit 600A of the present embodiment includes a cleaning roller 803 as a third cleaning member in addition to a cleaning roller 801 as a first cleaning member and a cleaning roller 802 as a second cleaning member. Similar to the cleaning rollers 801 and 802, the cleaning roller 803 also contacts the surface of the upper belt 411 to clean the deposits on the surface. Further, the cleaning roller 803 also has a rotating shaft whose both ends are rotatably supported by cleaning roller holders 803A, 803B, 804A, 804B (FIG. 9), and a roller portion 803b disposed around the rotating shaft and contacting the upper belt 411.

[0090] Further, the cleaning roller 803 is disposed at a position shifted in the width direction and a position shifted in the rotation direction of the upper belt 411 with respect to the cleaning rollers 801 and 802. Here, let the length in the width direction of the portion where the roller portion 801b of the cleaning roller 801 contacts the upper belt 411 be W1, the length in the width direction of the portion where the roller portion 802b of the cleaning roller 802 contacts the upper belt 411 be W2, and the length in the width direction of the portion where the roller portion 803b of the cleaning roller 803 contacts the upper belt 411 be W4. In this case, W1 < WL, W2 < WL, and W4 < WL are satisfied, and W1 < WB, W2 < WB, and W4 < WB are also satisfied. Note that WL is the length in the width direction of the sheet having the maximum size conveyed in the nip portion N, and WB is the length in the width direction of the upper belt 411.

[0091] Also, a part in the width direction of the cleaning roller 803 and a part in the width direction of the cleaning roller 801 that does not overlap with the cleaning roller 802 overlap in the rotation direction of the upper belt 411. That is, the cleaning roller 801 is disposed on the center side in the width direction with respect to the cleaning rollers 802 and 803, and both ends in the width direction of the cleaning roller 801 overlap with the inner ends of the cleaning rollers 802 and 803 in the rotation direction of the upper belt 411.

[0092] In addition, if the widthwise length of the area where part of the cleaning roller 801 and part of the cleaning roller 802 overlap in the widthwise direction is W5 and the widthwise length of the area where part of the cleaning roller 801 and part of the cleaning roller 803 overlap in the widthwise direction is W6, then (W1+W2+W3)-(W5+W6)>WL is satisfied.

[0093] In this embodiment, the lengths W2 and W4 of the cleaning rollers 802 and 803 in contact with the upper belt 411 are 150 mm, and the length W1 of the cleaning roller 801 in contact with the upper belt 411 is 160 mm. In addition, the length W5 of the area where the cleaning rollers 801 and 802 overlap in the rotation direction of the upper belt 411 is 30 mm, and the length W6 of the area where the cleaning rollers 801 and 803 overlap in the rotation direction of the upper belt 411 is 30 mm.

[0094] On the other hand, in the case of another example of this embodiment shown in FIG. 13, the lengths W2 and W4 of the cleaning rollers 802 and 803 in contact with the upper belt 411 are 230 mm, and the length W1 of the cleaning roller 801 in contact with the upper belt 411 is 240 mm. Also, the length of the area where two or more of the cleaning rollers 801, 802, and 803 overlap with respect to the rotation direction of the upper belt 411, that is, the widthwise length W1 of the central cleaning roller 801 is 240 mm, which is greater than the widthwise length WS (e.g., 210 mm) of the minimum sheet size. That is, W1>WS is satisfied. Also, in the configuration of FIG. 13, all of the cleaning rollers 801, 802, and 803 overlap with respect to the rotation direction of the upper belt 411 at a part in the width direction.

[0095] In this embodiment, by further arranging a cleaning roller 803 in addition to the cleaning rollers 801 and 802, the lengths W1, W2, and W4 of the cleaning rollers 801, 802, and 803 in contact with the upper belt 411 can be made smaller than in the first embodiment with respect to the width WL of the maximum sheet size. This makes it possible to further suppress the bending of the cleaning rollers 801, 802, and 803. Also, by increasing the number of cleaning rollers in this way, it is possible to easily accommodate cases where it is desired to further expand the sheet size that can be handled by the fixing device by lengthening the width direction length of the fixing members such as the upper belt 411.

[0096] Also, as in another example of this embodiment, by arranging the cleaning rollers 801, 802, and 803 so that all the cleaning rollers overlap in a portion of the width direction in the rotation direction of the upper belt 411, the length of the overlapping area of ​​each cleaning roller is increased. Therefore, the cleaning performance can be improved while suppressing the width direction length of the cleaning rollers. Also, by making the length W1 of the portion where the central cleaning roller 801 contacts the upper belt 411 longer than the width direction length WS of the minimum size sheet, the cleaning performance for the minimum size sheet can be improved.

[0097] <Other embodiments> In the above-mentioned first embodiment, a configuration in which two cleaning rollers are arranged has been described, and in the second embodiment, a configuration in which three cleaning rollers are arranged has been described, but even if four or more cleaning rollers are arranged, similar effects can be obtained as long as the relationship between the cleaning rollers satisfies the above-mentioned first or second embodiment. In addition, in the present invention, the first rotating body has been described as the upper belt 411, but the first rotating body may be the lower belt 421. That is, the lower belt unit 420 may be provided with a cleaning roller unit as described in the above-mentioned first and second embodiments.

[0098] In addition, in each of the above-described embodiments, the cleaning roller is disposed on the belt, but the same effect can be obtained as long as the rotating body is not a belt but is a rotating body. For example, the present invention may be applied to a configuration in which the cleaning roller is disposed on the fixing roller. Furthermore, each cleaning member may be a scraper or a blade other than a roller.

[0099] In addition, in each of the above-mentioned embodiments, the present invention has been described as being applied to a fixing belt unit as a sheet conveying device, but the sheet conveying device of the present invention is not limited to this, and can be applied to a device having a pair of belts on both sides of the sheet conveying surface. For example, the present invention can be applied to a cooling module 5000 (cooling device), and the rotating body can be applied not only to a fixing belt or fixing roller, but also to a cooling belt or cooling roller that cools a sheet.

[0100] In addition, in each of the above-described embodiments, the case where the inkjet recording system 100 is applied as an image forming apparatus has been described, but the present invention is not limited to this. For example, the present invention can be applied to an electrophotographic image forming apparatus using toner, and the same effects as those of the present embodiment can be obtained. [Explanation of symbols]

[0101] 1. Image forming system (image forming device) 411: Upper belt (first rotating body, first belt) 421...Lower belt (2nd rotating body, 2nd belt) 801: Cleaning roller (first cleaning member) 802: Cleaning roller (second cleaning member) 803: Cleaning roller (third cleaning member) 4060a···First heating unit (heating section) 4100··· Fixing belt unit (sheet transport device) N...Nip part

Claims

1. A first rotating body; a second rotating body that forms a nip portion between the first rotating body and the second rotating body to nip and convey a sheet on which an image is formed; a first cleaning member and a second cleaning member that come into contact with a surface of the first rotating body to clean deposits on the surface, With respect to a width direction of the sheet intersecting with the conveying direction of the sheet in the nip portion, when a length of a portion where the first cleaning member is in contact with the first rotating body is W1, a length of a portion where the second cleaning member is in contact with the first rotating body is W2, and a length of a maximum size sheet conveyed in the nip portion is WL, W1<WL and W2<WL are satisfied, The first cleaning member and the second cleaning member are disposed at positions shifted from each other in a rotation direction of the first rotating body, and are disposed at positions shifted from each other in the width direction such that a portion of the first cleaning member in the width direction and a portion of the second cleaning member in the width direction overlap with each other in the rotation direction of the first rotating body. A sheet conveying device comprising:

2. When a length in the width direction of an area where a part of the first cleaning member and a part of the second cleaning member in the width direction overlap is W3 and a length in the width direction of a sheet of a minimum size that is transported through the nip portion is WS, W3>WS is satisfied.

2. The sheet transport device according to claim 1.

3. When a length in the width direction of an area where a part of the first cleaning member and a part of the second cleaning member in the width direction overlap each other is defined as W3, the relationship (W1+W2)-W3>WL is satisfied.

2. The sheet transport device according to claim 1.

4. The first cleaning member and the second cleaning member are rollers.

2. The sheet transport device according to claim 1.

5. a third cleaning member that comes into contact with a surface of the first rotating body to clean deposits on the surface, When the length in the width direction of the portion of the third cleaning member that is in contact with the first rotating body is W4, W4<WL is satisfied, The third cleaning member is disposed at a position shifted with respect to the first cleaning member and the second cleaning member in the rotation direction of the first rotating body, and is disposed at a position shifted with respect to the first cleaning member in the width direction such that a part of the third cleaning member in the width direction and a part of the first cleaning member in the width direction that does not overlap with the second cleaning member overlap with each other in the rotation direction of the first rotating body.

2. The sheet transport device according to claim 1.

6. When a length in the width direction of a region where a part of the first cleaning member and a part of the second cleaning member overlap in the width direction is W5 and a length in the width direction of a region where a part of the first cleaning member and a part of the third cleaning member overlap in the width direction is W6, (W1+W2+W3)-(W5+W6)>WL is satisfied.

6. The sheet transport device according to claim 5,

7. When the length in the width direction of a sheet of a minimum size that can be conveyed through the nip portion is WS, W1>WS is satisfied.

6. The sheet transport device according to claim 5,

8. The first cleaning member, the second cleaning member, and the third cleaning member are all overlapped with each other in a part in the width direction with respect to the rotation direction of the first rotating body.

6. The sheet transport device according to claim 5,

9. The third cleaning member is a roller.

6. The sheet transport device according to claim 5,

10. The first rotating body is an endless first belt that is stretched around a plurality of first tension members, The second rotating body is an endless second belt stretched around a plurality of second tension members.

2. The sheet transport device according to claim 1.

11. The heating unit further includes a heating unit for heating the first rotating body.

2. The sheet transport device according to claim 1.

Images