Sheet conveying device

Abstract

To provide a configuration capable of forming a stable nip portion even in a configuration in which a pair of belts are movable between a separation position and a nip position.SOLUTION: An upper belt unit 410 includes an upper belt 411, an inlet roller 4110 and an outlet roller arranged to sandwich a nip portion, and an upper frame 414 supporting the inlet roller 4110 and the outlet roller. A lower belt unit 420 includes a lower belt 421, a lower frame 424, a pad supported by the lower frame 424 and in contact with an inner peripheral surface of the lower belt 421 in a nip portion to support the lower belt 421, and the like. The lower frame 424 is provided with an inlet abutment portion 424a against which an inlet roller bearing 4111 or an inlet roller bearing holder 4112 biased by an inlet roller pressure spring 4113 abuts when the upper belt unit 410 and the lower belt unit 420 form the nip portion.SELECTED DRAWING: Figure 13

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 belts, and the sheet is heated by a heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-15290 Summary of the Invention [Problem to be solved by the invention]

[0004] In a configuration in which a sheet is sandwiched and conveyed by a pair of belts, it is sometimes desirable to make the pressure at the nip formed by the pair of belts uniform. For example, when conveying a sheet on which an image is formed by ejecting ink, if the nip pressure is high, the ink on the sheet may adhere to the belt and peel off from the sheet. For this reason, it is conceivable to obtain uniform nip pressure by supporting the inside of one belt with a support member such as a pad and pressing the other belt against it.

[0005] Furthermore, in consideration of jam clearance, part replacement, and the like, a configuration may be adopted in which a pair of belts are moved relative to each other between a spaced apart position where they are spaced apart and a nip position where a sheet is nipped and conveyed. In this case, when one of the pair of belts is moved between the spaced apart position and the nip position, there is a risk that the relative positions of the pair of belts will vary due to manufacturing variations in parts, etc. If the relative positions of the pair of belts vary, one belt cannot be stably pressed against the other belt supported by a support member, and there is a risk that the formation of the nip portion will become unstable.

[0006] An object of the present invention is to provide a configuration that can form a stable nip portion even when a pair of belts is configured to be movable between a separation position and a nip position. [Means for solving the problem]

[0007] One aspect of the present invention is a sheet conveying device including a first belt unit having a rotating endless first belt and a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to nip and convey a sheet, wherein either the first belt unit or the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separated position where the first belt and the second belt are spaced apart from the nip position. the first belt unit includes the first belt, and a first roller and a second roller arranged to sandwich the nip portion in a rotation direction of the first belt; a plurality of first tension members that stretch the first belt; a first frame that supports the plurality of first tension members; a first bearing member that rotatably supports the first roller; a first holding member that holds the first bearing member movably relative to the first frame; and a first mounting member that urges the first holding member in a first direction so that the first roller presses an inner circumferential surface of the first belt outward. a second biasing member that biases the second holding member in a second direction so that the second roller presses the inner peripheral surface of the first belt outward; a second biasing member that biases the second holding member in a second direction so that the second roller presses the inner peripheral surface of the first belt outward; and the second belt unit includes the second belt, a plurality of second tension members that stretch the second belt, a second frame that supports the plurality of second tension members, and a second frame that is supported by the second frame and abuts against the inner peripheral surface of the second belt in the nip region. a first abutment portion provided on the second frame and abutting against the first bearing member or the first holding member urged in the first direction when the first belt unit and the second belt unit form the nip portion; and a second abutment portion provided on the second frame and abutting against the second bearing member or the second holding member urged in the second direction when the first belt unit and the second belt unit form the nip portion.

[0009] One aspect of the present invention is a sheet conveying device including a first belt unit having a rotating endless first belt and a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to nip and convey a sheet, wherein one of the first belt unit and the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separated position where the first belt and the second belt are spaced apart from the nip position. the first belt unit includes the first belt, and a first roller and a second roller arranged to sandwich the nip portion in the rotation direction of the first belt; a plurality of first tension members for tensioning the first belt, a first frame supporting the plurality of first tension members, a first bearing member for rotatably supporting the first roller, a first holding member for holding the first bearing member movably with respect to the first frame, a second bearing member for rotatably supporting the second roller, and a second holding member for holding the second bearing member movably with respect to the first frame. the second belt unit includes the second belt, a plurality of second tension members that stretch the second belt, a second frame that supports the plurality of second tension members, a support member that is supported by the second frame and that abuts against an inner circumferential surface of the second belt in the region of the nip portion to support the second belt, a first opposing portion that is provided on the second frame and faces the first bearing member or the first holding member in a state where the first belt unit and the second belt unit form the nip portion, and a second frame that is provided on the second frame and faces the first belt unit and the second belt unit. This sheet conveying device is characterized by having a second opposing portion that faces the second bearing member or the second holding member when the second belt unit forms the nip portion, and is equipped with a first fixing member that fixes the first holding member to the first frame when the first bearing member or the first holding member is positioned at a first predetermined position relative to the first opposing portion, and a second fixing member that fixes the second holding member to the first frame when the second bearing member or the second holding member is positioned at a second predetermined position relative to the second opposing portion.

[0010] One aspect of the present invention is a sheet conveying device including a first belt unit having a rotating endless first belt and a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to nip and convey a sheet, wherein one of the first belt unit and the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separated position where the first belt and the second belt are spaced apart from the nip position. a first tensioning member for tensioning the first belt; a first frame for supporting the first tensioning members; a first bearing member for rotatably supporting the first roller; a first holding member for holding the first bearing member movably relative to the first frame; a second bearing member for rotatably supporting the second roller; and a second biasing member that biases the second holding member in a second direction so that the second roller presses the inner peripheral surface of the first belt outward, and the second belt unit includes the second belt, a plurality of second tension members that stretch the second belt, a second frame that supports the plurality of second tension members, a support member that is supported by the second frame and abuts against the inner peripheral surface of the second belt in the nip portion region to support the second belt, and a support member that is provided on the second frame and supports the second belt, The sheet conveying device is characterized in that it has an opposing portion that faces the first bearing member or the first holding member when the nip portion is formed, and an abutting portion that is provided on the second frame and abuts against the second bearing member or the second holding member that is biased in the second direction when the first belt unit and the second belt unit form the nip portion, and is further characterized in that it is provided with a fixing member that fixes the first holding member to the first frame when the first bearing member or the first holding member is positioned at a predetermined position with respect to the opposing portion. [Effects of the Invention]

[0011] According to the present invention, even in a configuration in which a pair of belts are movable between a separation position and a nip position, a stable nip portion can be formed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming system according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the schematic configuration of a fixing module according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing the schematic configuration of a fixing belt unit according to the first embodiment. [Figure 4] FIG. 2 is a perspective view showing the configuration of a steering section of the fixing belt unit according to the first embodiment. [Figure 5] FIG. 2 is a plan view showing the relationship between the belt and the edge sensor according to the first embodiment. [Figure 6] FIG. 3 is a perspective view showing a first state in which an upper door unit of the fixing module according to the first embodiment is located at a closed position. [Figure 7] FIG. 10 is a perspective view showing a second state in which the upper door unit of the fixing module according to the first embodiment is positioned at the open position and the upper belt unit is positioned at the upper storage position. [Figure 8] 4 is a perspective view showing the gas spring in a state where the upper door unit of the fixing module according to the first embodiment is located at a closed position. FIG. [Figure 9] FIG. 10 is a perspective view showing a third state in which the upper door unit of the fixing module according to the first embodiment is positioned at the open position and the upper belt unit is positioned at the maintenance position. [Figure 10] 5A and 5B are diagrams showing a locking mechanism of the fixing module according to the first embodiment, in which FIG. 5A is a perspective view and FIG. 5B is a bottom view. [Figure 11] FIG. 10 is a cross-sectional side view showing the fixing module according to the first embodiment in a third state. [Figure 12]FIG. 10 is a perspective view showing a state in which the lower belt unit is located at a drawn-out position when the fixing module according to the first embodiment is in a third state. [Figure 13] FIG. 2 is an enlarged cross-sectional view of the vicinity of an inlet roller of the fixing belt unit according to the first embodiment. [Figure 14] FIG. 2 is an enlarged cross-sectional view of the vicinity of an outlet roller of the fixing belt unit according to the first embodiment. [Figure 15] FIG. 10 is a cross-sectional view showing a schematic configuration of a fixing belt unit according to a second embodiment. [Figure 16] FIG. 11 is an enlarged cross-sectional view of the vicinity of an inlet roller of a fixing belt unit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment The first embodiment will be described with reference to Figures 1 to 14. First, the schematic configuration of an image forming system according to this embodiment will be described with reference to Figure 1.

[0014] [Image formation system] The image forming system 1 as the image forming apparatus of this embodiment uses an inkjet recording method in which ink is ejected to form an image on a sheet, and is a so-called sheet-fed inkjet recording apparatus that forms an ink image on a sheet using two liquids: a reaction liquid and ink. The sheet may be any recording material that can accept ink, such as paper such as plain paper or cardboard, plastic film such as an overhead projector sheet, specially shaped sheets such as envelopes or index paper, or cloth.

[0015] 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 undergoes various processes as it is transported along the transport path within each module, and is finally discharged to the stacking module 7000.

[0016] The feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may each have separate housings, and these housings may be connected to form the image forming system 1. Alternatively, the feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may be arranged in a single housing.

[0017] The feeding module 1000 has storage cabinets 1500a, 1500b, and 1500c for storing sheets S, and the storage cabinets 1500a to 1500c are provided so as to be able to be pulled out toward the front side of the apparatus to store the sheets S. The sheets S are fed one by one in each of the storage cabinets 1500a to 1500c by a separation belt and a transport roller, and are transported to the print module 2000. The number of storage cabinets 1500a to 1500c is not limited to three, and there may be one, two, four or more.

[0018] The print module 2000, which serves as an image forming unit, includes a pre-imaging registration correction unit (not shown), a print belt unit 2010, and a recording unit 2020. The sheet S conveyed from the feeding module 1000 has its tilt and position corrected by the pre-imaging registration correction unit before being conveyed to the print belt unit 2010. The recording unit 2020 is positioned opposite the print belt unit 2010 with respect to the conveyance path. The recording unit 2020 is an inkjet recording unit that forms an image by ejecting ink onto the conveyed sheet S from above using a recording head. Multiple recording heads that eject ink are arranged along the conveyance direction. In this embodiment, the unit has a total of five line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), as well as reaction liquids. The sheet S is adsorbed and conveyed by the print belt unit 2010, ensuring clearance between the sheet S and the recording heads.

[0019] The number of ink colors and recording heads is not limited to the five mentioned above. The inkjet method can be a method using a heating element, a piezoelectric element, an electrostatic element, or a MEMS (Micro Electro Mechanical Systems) element. Each color of ink is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains 0.1% to 20.0% by mass of a resin component, water, a water-soluble organic solvent, coloring material, wax, additives, etc., based on the total mass of the ink.

[0020] When the sheet S on which an image is formed by the recording unit 2020 is transported by the print belt unit 2010, the misalignment and color density of the image formed on the sheet S are detected by an inline scanner (not shown) arranged downstream of the recording unit 2020 in the transport direction of the sheet S. Based on the misalignment and color density of the image, the image to be formed on the sheet S, its density, etc. are corrected.

[0021] 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 to improve the fixation of the ink to the sheet S by the subsequent fixing module 4000. The sheet S on which an image has been formed is transported to the decoupling section 3200 arranged within 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 air 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 as it 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 blowing hot air from the hot air blowing section 3400 arranged above the belt.

[0022] In this way, the drying module 3000 heats the ink and reaction liquid applied to the sheet S, promoting evaporation of the water, thereby preventing so-called cockling, in which ink splatters on the sheet S and leaves a fringe-like line around the periphery. The drying module 3000 may be any device capable of heat drying, but a hot air dryer or heater is preferred. Heating by an electric heating wire or infrared heater is preferred from the standpoint of safety and energy efficiency. The drying method may also be a combination of a method of applying hot air, a method of irradiating the surface of the sheet S with electromagnetic waves (such as ultraviolet or infrared rays), or a conductive heat transfer method using contact with a heating element.

[0023] The fixing module 4000 as a fixing system has a fixing belt unit 4100 as a fixing device. The fixing belt unit 4100 fixes ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit and a lower belt unit. The fixing belt unit 4100 will be described in detail later.

[0024] The cooling module 5000 has a plurality of cooling sections 5001, which cool the high-temperature sheet S transported from the fixing module 4000. The cooling sections 5001, for example, use a fan to draw outside air into a cooling box to increase the pressure inside the cooling box, and then cool the sheet S by blowing air out of the cooling box through a nozzle due to the pressure onto the sheet S. The cooling sections 5001 are arranged on both sides of the transport path of the sheet S, and cool both sides of the sheet S.

[0025] 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.

[0026] The reversing module 6000 has a reversing section 6400. The reversing section 6400 reverses the sheet S being conveyed, changing the orientation of the sheet S when it is discharged to the stacking module 7000. The stacking module 7000 has a top tray 7200 and a stacking section 7500, and stacks the sheet S conveyed from the reversing module 6000.

[0027] During double-sided printing, the sheet S is conveyed to a conveyance path below the cooling module 5000 by the conveyance path switching unit 5002. The sheet S then passes through a double-sided conveyance path including the fixing module 4000, the drying module 3000, the print module 2000, and the feeding module 1000, and is returned to the print module 2000. The double-sided conveyance section of the fixing module 4000 is provided with an inverting unit 4200 that inverts the sheet S. An image is formed with ink on the other side of the sheet S that has been returned to the print module 2000, and the sheet S is then discharged to the stacking module 7000 via the drying module 3000, the fixing module 4000, the cooling module 5000, and the inverting module 6000.

[0028] [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 above the fixing module 4000. The fixing belt unit 4100 has a substantially linear sheet transport path 400a 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 each drawing, the front side of the inkjet recording system 100 is represented as the front direction F, the rear side as the rear direction B, the right side as the right direction R, the left side as the left direction L, the upper side as the upward direction U, and the lower side as the downward direction D. An operation unit (not shown) operated by an operator is provided at the front side of the inkjet recording system 100.

[0029] 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 conveyor belt (first conveyor 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 detachably includes the 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 with an arc-shaped curved surface. The pad 423 is disposed so as to form a nip with the upper belt 411 via the lower belt 421.

[0030] 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 in the closed position and the upper belt unit 410 is in the upper storage position. At this time, the lower belt 421 sandwiches and conveys the sheet S together with the upper belt 411. 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, ink on the sheet S may adhere to the upper belt unit 410 and peel off from the sheet S. Therefore, the pressure is preferably 1 Pa to 2000 Pa, and more preferably 1 Pa to 200 Pa.

[0031] If the curvature of the pad 423 becomes large, the difference in the conveyance path between the front and back of the sheet S becomes large, which may cause friction between the sheet S and the belt. If the curvature of the pad 423 becomes large, there is a risk that the sheet S itself may memorize the curved shape and curl, so the radius of curvature of the pad 423 is desirably 50 mm or more. Furthermore, from the viewpoint of manufacturing precision, the radius of curvature of the pad 423 is desirably 100,000 mm or less. Due to these constraints, in this embodiment, the tension of the upper belt 411 is set to 200 N, the thickness is set to 0.3 mm, the curvature of the pad 423 is set to 30,000 mm, and the nip pressure is set to approximately 16 Pa.

[0032] By adopting this 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, sufficient heat transfer to the sheet S can be achieved by increasing the contact time between the sheet S and the upper belt unit 410. However, if the nip continues to form after sufficient heat transfer, ink may adhere to the upper belt 411 and peel off from the sheet S, or the upper belt 411 may rub against the sheet S, causing image distortion. Therefore, a long contact time is not desirable. Therefore, the time required for the leading edge of the sheet S to enter the nip entrance and exit the nip exit is preferably 0.5 to 4 seconds. 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 completely exit the nip exit is approximately 1.3 seconds. Furthermore, moisture is necessary for ink to penetrate into the sheet S, so when the sheet becomes hot, the upper belt 411 and the lower belt 421 are preferably made of a material that does not allow moisture to pass through so that the moisture evaporated from the surface of the sheet S does not escape through the upper belt 411 or the lower belt 421 that they come into contact with.

[0033] [Fusing 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, which serves 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 nipped and conveyed at the nip portion N, and pressure and heat are applied thereto, so that an image formed with ink is fixed to the sheet S1.

[0034] The upper belt unit 410 includes an endless upper belt 411 serving as a belt and a first belt, a plurality of tension rollers serving as a plurality of first tension members for tensioning the upper belt 411, and a first heating unit 4060a serving as a first heating device. The plurality of tension rollers include an entrance roller 4110 serving as a first roller, an exit roller 4120 serving as a second roller, a drive roller 4031a, a tension roller 4011a, a guide roller 4051a, and a steering roller 4021a. These rollers are arranged in order from upstream of a nip portion N in the rotation direction of the upper belt 411, thereby forming a rotational locus of the upper belt 411. The nip portion N is located between the entrance roller 4110 and the exit roller 4120. That is, the entrance roller 4110 and the exit roller 4120 are arranged to sandwich the nip portion N in the rotation direction of the upper belt 411. Each roller is supported by an upper frame 414, which serves as a first frame that is a housing of the upper belt unit 410. The first roller may be the exit roller 4120, and the second roller may be the entrance roller 4110. In short, the first roller and the second roller may be rollers that are arranged to sandwich the nip portion N.

[0035] The first heating unit 4060a is disposed inside the upper belt 411 and includes a first heater 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 main body 410a that includes the upper belt 411. The first belt unit main body 410a includes the upper belt 411, a plurality of rollers that stretch the upper belt 411, and an upper frame 414.

[0036] 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, which 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 region of the upper belt 411.

[0037] 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 disposed side by side in the rotation direction of the upper belt 411. In addition, a reflector 4052a is disposed so as to cover the periphery of the first heater portion 4061a except for the side facing the upper belt 411.

[0038] 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 first heater portions 4061a are open on the nip portion N side and so as to cover both widthwise ends of the first heater portions 4061a. This allows the reflecting plates 4052a to efficiently irradiate radiant heat from the first heater portions 4061a toward the nip portion N.

[0039] That is, in the upper belt unit 410, the predetermined region is a region (first region) within 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 plurality of first heater portions 4061a and the plurality of reflectors 4052a. This allows heat to be efficiently transferred to the sheet S passing through the nip portion N. In this embodiment, the region within the range of the nip portion N heated by the plurality of 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 in the conveyance direction of the sheet S passing through the nip portion N. That is, in this embodiment, the predetermined region of the upper belt unit 410 is the lower surface portion 411a.

[0040] The lower surface portion 411a is positioned opposite the lower belt 421, which is stretched between a nip upstream roller 426 and a nip downstream roller 427, among the tension rollers of the lower belt 421 described below, and is also positioned opposite an area where the lower belt 421 is supported by a pad 423 arranged 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.

[0041] The lower belt unit 420 includes an endless lower belt 421 serving as a belt and a second belt, a plurality of tension rollers serving as second tension members for tensioning the lower belt 421, and a second heating unit 4060b serving as a second heating device. The 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 upstream of the nip portion N in the rotation direction of the lower belt 421.

[0042] Furthermore, 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 as a third roller and the nip downstream roller 427 as a fourth roller are disposed so as to sandwich the nip portion N in the rotation direction of the lower belt 421. The pad 423 as a support member abuts against the inner circumferential surface of the lower belt 421 in the region of the nip portion N to support the lower belt 421. In other words, the nip upstream roller 426 and the nip downstream roller 427 are disposed on both sides of the pad 423 in the rotation direction of the lower belt 421. The distance between the nip upstream roller 426 and the nip downstream roller 427 is shorter than the distance between the entrance roller 4110 and the exit roller 4120. A rotational locus of the lower belt 421 is formed by these rollers and the pad 423. Each roller and pad 423 is supported by a lower frame 424 serving as a second frame that is a housing of the lower belt unit 420.

[0043] The second heating unit 4060b is disposed inside the lower belt 421, and includes a second heater 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 main body 420a that includes the lower belt 421. The second belt unit main body 420a includes the lower belt 421, a plurality of rollers that tension the lower belt 421, a pad 423, and a lower frame 424.

[0044] 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, which 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 region of the lower belt 421.

[0045] 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.

[0046] The reflectors 4052b are arranged in the same number as the second heater sections 4061b, corresponding to the second heater sections 4061b. The reflectors 4052b are formed so that the lower portions of the second heater sections 4061b are open and so that they cover both widthwise ends of the second heater sections 4061b. This allows the reflectors 4052b to efficiently irradiate the radiant heat from the second heater sections 4061b toward the lower portion of the lower belt 421.

[0047] That is, in the lower belt unit 420, the predetermined region is a region (second region) of the inner circumferential surface of the lower belt 421 that is outside the nip portion N, and in this embodiment, this region is a lower portion of the lower belt 421. Specifically, the region outside the nip portion N that is heated by the plurality of 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 region in the lower belt unit 420 is the lower surface portion 421a of the lower belt 421, and the lower surface portion 421a is the 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 therefore cannot directly heat the nip portion N as in the upper belt unit 410. For this reason, by arranging the plurality of second heater portions 4061b and the plurality of reflecting plates 4052b facing the lower surface portion 421a of the lower belt 421, the lower belt 421 is directly heated efficiently.

[0048] The lower surface portion 421a, which is the region of the lower belt 421 heated by the multiple second heaters 4061b and the multiple reflectors 4052b, is located upstream of the nip upstream guide roller 425 at the entrance of the nip portion N and the steering roller 4021b in terms of 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 tension roller 4011b that tension the lower portion of the lower belt 421 in terms of the rotation direction of the lower belt 421. Therefore, the multiple second heaters 4061b and the multiple reflectors 4052b can heat the lower belt 421 at a position relatively close to the nip portion N, and can efficiently transfer heat to the sheet S passing through the nip portion N.

[0049] 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 on the upper belt 411. In the lower belt unit 420, the tension roller 4011b and the guide roller 428 tension 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 on the lower belt 421.

[0050] The first heater portion 4061a and the second heater portion 4061b may be any heater that heats the belt by radiating heat, such as a halogen heater, and in this embodiment, these heaters are halogen heaters.

[0051] As described above, reflectors 4052a and 4052b are disposed around the first heater section 4061a and the second heater section 4061b to efficiently focus light onto the upper belt 411 and the lower belt 421, respectively. The reflectors 4052a and 4052b are made of, for example, a mirror-finished aluminum member to efficiently reflect light. The heater outputs of the multiple first heater sections 4061a and the multiple second heater sections 4061b are controlled based on temperatures detected by a temperature detector (not shown). This allows the upper belt 411 and the lower belt 421 to be maintained at appropriate temperatures.

[0052] In this embodiment, a halogen heater is used to directly heat the belt from the inside as a preferred example, but the heater may be a planar heating element or an induction heater. Alternatively, an aluminum heating roller with a built-in halogen heater may be brought into contact with the belt to indirectly heat it, or an external heating means may be used to heat the belt from the outside.

[0053] [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 upper belt unit 410 and the 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.

[0054] [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, which applies tension to the lower belt 421. The tension roller 4011b is arranged 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, of the nip upstream roller 426 and nip downstream roller 427 that form the nip portion N, the tension roller 4011b is arranged downstream of the nip downstream roller 427 in the rotation direction of the lower belt 421. Specifically, the tension roller 4011b is arranged further downstream of the drive roller 4031b, which is downstream of the nip downstream roller 427, in the rotation direction of the lower belt 421.

[0055] 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 the target length due to manufacturing variations or changes caused by usage conditions, tension roller 4011b can be pressed by the pressure member to stabilize the tensioned state of lower belt 421.

[0056] 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 in the rotation direction of the lower belt 421, the rollers are the tension roller 4011b, the guide roller 4051, the heating unit formed by the second heating unit 4060b, and the guide roller 428. By arranging the rollers in this embodiment, even if the position of the tension roller 4011b moves in the horizontal direction due to variations in the circumferential length of the lower belt 421, it is possible to suppress fluctuations 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.

[0057] [Steering roller] Next, the steering roller 4021b will be described with reference to Figs. 3 to 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 the steering roller 4021b for controlling the position of the lower belt 421 in the front-to-rear direction (forward direction F and rear direction B, width direction of the lower belt 421).

[0058] The steering roller 4021b is a roller made of metal, such as aluminum or iron. One front-rear end of the steering roller 4021b is rotatably supported by a fixed plate 4026b. The fixed plate 4026b is fastened to the lower frame 424 with screws 4027b or the like. The other front-rear end of the steering roller 4021b 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 portion of the steering arm 4023b, and the alignment of the steering roller 4021b can be changed by rotating the steering cam 4022b with a steering motor (not shown).

[0059] The fixing 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 fastening them again. For example, it is possible to fine-tune the optimal alignment position of the steering roller 4021b due to variations in the installation environment.

[0060] Furthermore, 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 posture of the steering roller 4021b. When the conveyed sheet S enters the nip portion N, the entry can be stabilized by conveying the posture of the sheet S along the lower belt 421.

[0061] 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.

[0062] First, an edge sensor 4025b is provided at one end of the lower belt 421 in the front-rear direction (the end on the forward direction F side in this embodiment), on the downward direction D side of the lower belt 421, in contact with the end surface of the lower belt 421 to detect the position of the lower belt 421 in the forward direction F. In the lower belt unit 420, the guide roller 428 is arranged so that the surface of the lower belt 421, which is 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. By providing the edge sensor 4025b between the tension roller 4011b and the guide roller 428, the influence of the belt locus due to variations in the circumferential length of the lower belt 421 on the edge sensor 4025b is reduced.

[0063] The rotation amount 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 that moves the edge sensor 4025b away from the lower belt 421 due to the frictional force it receives 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.

[0064] Meanwhile, an edge sensor 4025a is provided at the other end of the upper belt 411 in the front-rear direction (the end on the rearward direction B side in this embodiment), on the upper direction U side of the upper belt 411, in contact with the end surface of the upper belt 411 to detect the position of the upper belt 411 in the rearward direction B. In the upper belt unit 410, the guide roller 4051a is arranged so that the surface of the upper belt 411 stretched between the tension roller 4011a and the guide roller 4051a is approximately parallel to the moving direction (horizontal direction) of the tension roller 4011a. By providing the edge sensor 4025a between the tension roller 4011a and the guide roller 4051a, the influence of the belt locus due to variations in the circumferential length of the upper belt 411 on the edge sensor 4025a is reduced.

[0065] The rotation amount 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 that moves the edge sensor 4025a away from the upper belt 411 due to 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.

[0066] As shown in Figure 5, by arranging edge sensor 4025b at the end of the lower belt 421 on the forward F side and the portion on the downward D side, and edge sensor 4025a at the end of the upper belt 411 on the rear B side and the portion on the upward U side, it is possible to use edge sensors of the same shape for the upper belt 411 and the lower belt 421.

[0067] 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 its surface may be used to increase the frictional force and thereby improve steering performance. Also, although the steering roller is configured such that one end is fixed and the other end is moved to change the alignment, both ends may be supported movably to change the alignment.

[0068] [Drive roller] Next, the drive 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 the drive roller 4031b for applying a driving force to the lower belt 421.

[0069] The drive roller 4031b is a roller made of metal such as aluminum or iron. Both front and rear ends of the drive roller 4031b are rotatably supported by the lower frame 424, and the drive roller 4031b rotates when a drive force is input 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.

[0070] In this embodiment, the lower belt 421 and the upper belt 411 are rotated by the driving force applied independently by the driving rollers 4031a and 4031b. Note that, although the driving rollers in this embodiment are made of metal, rollers having a rubber layer such as heat-resistant rubber on the surface may also be used to increase the driving force by increasing the frictional force.

[0071] [Jam Clearance] If a sheet jams or slips in the sheet transport path 400a (FIG. 2) and the specified transport timing is deviated, the device detects the jam. In this case, the device automatically ejects the sheet S remaining in the sheet transport path 400a to the purge tray, but if the remaining sheet cannot be ejected to the purge tray, the user must remove the remaining sheet. The sheet S is conveyed while being sandwiched in the nip between the upper belt unit 410 and the lower belt unit 420, but if the sheet S remains in the nip when a jam occurs, the user must open the nip and remove the remaining sheet.

[0072] For this reason, either one of the upper belt unit 410 and the lower belt unit 420 is movable relative to the other belt unit between a nip position where the upper belt 411 and the lower belt 421 form a nip portion N, and a separated position where the upper belt 411 and the lower belt 421 are spaced apart from the nip position. In this embodiment, the upper belt unit 410 is movable relative to the lower belt unit 420 between the nip position and the separated position. This will be described in detail below.

[0073] As shown in FIGS. 6 to 8, the fixing module 4000 has an upper door unit 43 serving as a first housing that can be opened in the upward direction U. An upper belt unit 410 of the fixing belt unit 4100 is disposed inside the upper door unit 43, and the upper door unit 43 is configured to be able to open in the upward direction U together with the upper belt unit 410. The upper door unit 43 is rotatably connected to the device main body 400 by a support shaft 44 (see FIG. 8) provided on the rear side B of the device main body 400 serving as a second housing. The support shaft 44 serving as a rotation shaft is provided on the rear side of the device main body 400 in the sheet width direction (front-rear direction) that intersects with the sheet conveying direction, and is provided along the sheet conveying direction. The upper door unit 43 is provided rotatably with respect to the device main body 400 around the support shaft 44.

[0074] The upper door unit 43 has a handle 431 on the front side (F) of the apparatus main body 400, and is rotated and opened by pulling up the handle 431 in the upward direction (U). The upper door unit 43 is an example of a storage section, is provided separately from the upper belt unit 410, can store the upper belt unit 410, and can be displaced between a closed position (see FIG. 6) and an open position (see FIGS. 7 and 9) by rotating relative to the apparatus main body 400. In the closed position, the upper belt 411 and the lower belt 421 form a nip portion N at a nip position. In the open position, the upper belt 411 and the lower belt 421 are spaced apart from the nip position at a spaced position. In this embodiment, the upper door unit 43 is composed of a top plate and side plates and functions as an upper cover for the apparatus main body 400. Note that the upper door unit 43 is not limited to having only the function of a cover, and may be integrated with, for example, a display unit, an operation unit, and the like.

[0075] If a jam occurs, the user can lift up the handle 431 of the upper door unit 43 to open the upper door unit 43 upward to the separated position, and remove the sheets S remaining inside the apparatus main body 400 from the front of the apparatus. In this embodiment, a gas spring 45 is provided to improve the operability when the user opens and closes the upper door unit 43. The gas spring 45 biases the upper door unit 43 toward the open position.

[0076] In this embodiment, the upper door unit 43 is rotatable between a horizontal closed position and an open position inclined 30 degrees from the horizontal. When the opening angle of the upper door unit 43 is a first angle or less with respect to the horizontal, the gas spring 45 has a biasing force that rotates the upper door unit 43 and the upper belt unit 410 to the closed position due to their own weight. The upper door unit 43 is fixed in the closed position by abutting against an abutment portion (not shown) provided on the apparatus main body (housing) 400 due to the biasing force of its own weight. Here, the first angle is, for example, 5 degrees. Furthermore, when the opening angle of the upper door unit 43 is a second angle or more with respect to the horizontal, the gas spring 45 has a biasing force that rotates the upper door unit 43 to the open position. Here, the second angle is, for example, 20 degrees. Thus, by providing the gas spring 45, the upper door unit 43 can be automatically closed when the opening angle is 5 degrees or less and automatically opened when the opening angle is 20 degrees or more, improving operability.

[0077] In this embodiment, in order to improve operability, the reaction force of the gas spring 45 and the resultant force of the weight of the upper door unit 43 and the upper belt unit 410 are set so that a force acts in a direction toward the closed position when in the closed position. That is, the arrangement and load setting of the gas spring 45 are set in a direction that closes the upper door unit 43. However, the gas spring 45 may be set so that a force acts in a direction toward the open position (opening tendency) even when in the closed position, and the gas spring 45 may be fixed in the closed position by a latch mechanism or the like.

[0078] [Upper belt unit part replacement work] The upper belt unit 410 of the fixing belt unit 4100 is provided with components such as an upper belt 411, multiple tension rollers, a roller drive unit (not shown), a first heater unit 4061a, and a sensor (not shown). These components have a risk of failure during their product lifespan, and are therefore required to be replaceable in the market to accommodate periodic replacement or replacement due to accidental failure. In the commercial printing market, product availability is of utmost importance to users, so replacement work should be carried out quickly and reliably.

[0079] Therefore, in this embodiment, a configuration is adopted that allows parts of the upper belt unit 410 to be replaced with the upper door unit 43 open upward, and this configuration will be described with reference to Figures 9 to 11. When performing work such as part replacement, cleaning, or lubrication, a handle 431 arranged on the front side of the upper door unit 43 in the forward direction F is pulled up in the upward direction U, and the upper door unit 43 is rotated upward to open the sheet transport path 400a. The upper door unit 43 is held in an open position by a holding member (not shown) (see Figure 7).

[0080] 11, the fixing module 4000 has a first displacement portion 441 as a displacement portion. The first displacement portion 441 is provided to displace the upper belt unit 410 relative to the upper door unit 43 between an upper storage position (see FIG. 7) where the upper belt unit 410 is stored in the upper door unit 43 and a maintenance position (see FIGS. 9 and 11) where the upper belt unit 410 protrudes from the upper door unit 43. The first displacement portion 441 has a rotation shaft 46, a stopper 51 which is an example of a holding portion, and a gas spring 47.

[0081] The rotation shaft 46 is provided on the rear side of the upper door unit 43 when the upper door unit 43 is located at the closed position in the sheet width direction (front-rear direction), and is arranged along the sheet conveying direction. The upper belt unit 410 is provided rotatable around the rotation shaft 46. The upper belt unit 410, which is arranged inside the upper door unit 43, is supported rotatably relative to the upper door unit 43 by the rotation shaft 46 provided on the rear direction B side of the upper door unit 43. The upper belt unit 410 is fixed to the upper door unit 43 by a lock mechanism 50 (see FIGS. 10(a) and (b)) which is arranged on the front side of the upper door unit 43.

[0082] The configuration of the locking mechanism 50 will be described. The locking mechanism 50 has a locking lever 28, a pivot shaft 29, a locking member 30, and a locking hole 31. The locking lever 28 is provided so as to be rotatable within a predetermined angle around the pivot shaft 29, and the locking member 30 is fixed to the pivot shaft 29. As the locking lever 28 rotates, the pivot shaft 29 can rotate the locking member 30 from a locked position to an unlocked position. A locking hole 31 into which the pivot shaft 29 is inserted is formed on the upper door unit 43 side. The locking hole 31 is shaped so that the locking member 30 positioned at the unlocked angle can pass through it, and it becomes possible to unlock it at this position.

[0083] When the lock lever 28 of the lock mechanism 50 is turned to release the lock while the upper door unit 43 is open in the upward direction U, the upper belt unit 410 rotates about the rotation shaft 46, and the front side rotates downward due to the weight of the upper belt unit 410. In this way, the lock mechanism 50 switches between a locked state in which the upper belt unit 410 is fixed to the upper storage position relative to the upper door unit 43, and a released state in which the locked state is released and the upper belt unit 410 is allowed to rotate from the upper storage position to the maintenance position.

[0084] That is, the upper belt unit 410 is fixed to the upper storage position with respect to the upper door unit 43 by the locking mechanism 50. Note that this fixing mechanism does not have to be a locking mechanism as in this embodiment, and may be fastened by a fastening member such as a screw, or may be locked by another link mechanism, and the fixing configuration is not limited.

[0085] Furthermore, the upper belt unit 410 is fixed to the upper storage position relative to the upper door unit 43 by a locking mechanism that does not completely fix it but roughly supports it, and when the upper door unit 43 is closed, a part of the upper belt unit 410 comes into contact with a part of the device main body (housing) 400 or a part of the lower belt unit 420, etc., thereby fixing the position, or the upper belt unit 410 may be configured to abut against it due to its own weight.

[0086] The upper belt unit 410 hits a stopper 51 provided on the upper door unit 43 and stops rotating at the maintenance position. That is, the stopper 51 holds the upper belt unit 410 in the maintenance position when the upper door unit 43 is in the open position. The upper belt 411 can be pulled out toward the front of the device main body 400 in the sheet width direction when the upper door unit 43 is in the open position and the upper belt unit 410 is in the maintenance position. In this state, an operator can replace or perform maintenance on the upper belt 411.

[0087] 11, a gas spring 47 is provided between the upper door unit 43 and the upper belt unit 410. The gas spring 47 urges the upper belt unit 410 toward the upper storage position relative to the upper door unit 43 that is positioned in the open position. In particular, when the upper belt unit 410 is heavy, providing the gas spring 47 can improve operability.

[0088] In this embodiment, the gas spring 47 is disposed above the upper belt unit 410 and is fastened to a fixing member 48 in the upper door unit 43 and a fixing member 49 in the upper belt unit 410, thereby assisting the opening and closing operation of the upper belt unit 410. In this embodiment, the gas spring 47 is disposed above the upper belt unit 410, so that it does not interfere with the replacement work when replacing parts with the upper belt unit 410 open. In addition, the biasing force of the gas spring 47 is set so that the upper belt unit 410 does not lift up by itself due to a change in weight when a part is removed. In addition, the upper door unit 43 is held (locked) by a holding member (not shown) so that it does not close with the upper belt unit 410 in the open position.

[0089] The above-described upper door unit 43 and upper belt unit 410 can be displaced to the following first state, second state, and third state. In the first state, the upper door unit 43 is located in the closed position, and the upper belt unit 410 is located in the upper storage position, so that the upper belt 411 conveys the sheet S (see FIG. 6). In the second state, the upper door unit 43 is located in the open position, and the upper belt unit 410 is located in the upper storage position, so that the conveyance path for the sheet S is open (see FIG. 7). In the third state, the upper door unit 43 is located in the open position, and the upper belt unit 410 is located in the maintenance position, so that the upper belt 411 can be attached to and detached from the upper belt unit 410.

[0090] As described above, in the third state, the upper belt unit 410 is held in a substantially horizontal position, and in this state, it is possible to replace parts such as the upper belt 411, the tension roller 412, the heater 413, and the sensor, as well as to perform cleaning and lubrication work. This eliminates the need to remove the upper door or the exterior cover, significantly improving maintainability.

[0091] [Lower belt unit part replacement work] Next, part replacement and maintenance of the lower belt unit 420 will be described with reference to FIG. 12. The upper door unit 43 is placed in the open position, and the double-door front doors 401, 402 on the front side of the fixing module 4000 are opened. A fixing member (not shown) that fixes the lower belt unit 420 is removed, and the lower belt unit 420 is pulled out toward the front. This pulls out the lower belt unit 420, which is supported by slide rails 432, 433 whose longitudinal direction is the front-to-rear direction. In this pulled-out state, work such as part replacement, cleaning, and lubrication of the lower belt unit 420 can be performed.

[0092] In this embodiment, the slide rails 432, 433 are an example of a second displacement portion, and displace the lower belt unit 420 relative to the device body 400 between a lower storage position where the lower belt unit 420 is stored in the device body 400 and a drawn-out position where the lower belt unit 420 protrudes from the device body 400. Here, the drawn-out position is a position where the lower belt unit 420 protrudes from the device body 400 in the forward direction F in the sheet width direction, and where attachment and detachment of the lower belt 421 to and from the lower belt unit 420 is permitted. The lower belt unit 420 is permitted to move from the lower storage position to the drawn-out position when the upper door unit 43 is in the open position.

[0093] As described above, according to the fixing module 4000 of this embodiment, the upper door unit 43 and the upper belt unit 410 can be displaced to a third state in which the upper door unit 43 is in the open position and the upper belt unit 410 is in the maintenance position. This allows the upper belt 411 to be attached to and detached from the upper belt unit 410. In this state, parts such as the upper belt 411, the tension roller 412, the heater 413, and the sensor can be replaced, or cleaning and lubricating operations can be performed. This eliminates the need to remove the upper door or the exterior cover, significantly improving maintainability. This significantly improves the ease of maintenance during belt replacement and other maintenance operations. Furthermore, according to the fixing module 4000 of this embodiment, the upper belt unit 410 is held in a substantially horizontal position in the third state, further improving workability.

[0094] Furthermore, according to the fixing module 4000 of this embodiment, by pulling out the lower belt unit 420 toward the front side, the lower belt 421 can be attached to and detached from the lower belt unit 420. This improves the workability during maintenance, such as when replacing the belt.

[0095] [Nip details] Next, the formation section of the nip portion N will be described using FIGS. 13 and 14 with reference to FIG. 3. In order to provide a high-quality product in the fixing module 4000 described above, it is necessary to sufficiently heat the toner image on the sheet at a low temperature. Therefore, the nip portion N between the upper belt unit 410 and the lower belt unit 420 is required to have a wide nip area and to stably form a uniform nip with low nip pressure. To achieve this, it is necessary to stably press the upper belt 411 and the lower belt 421 against the pad 423 that supports the lower belt 421 from its inner circumferential surface in the nip portion N area.

[0096] On the other hand, in order to improve jam recovery and part replacement, if the upper belt unit 410 and the upper door unit 43 are configured to be movable between a closed position and an open position relative to the lower belt unit 420 and the device main body 400 so that the upper belt 411 can be moved between a nip position and a separated position relative to the lower belt 421, it is necessary to configure the device using multiple parts. For this reason, the relative positions of the upper belt unit 410 and the lower belt unit 420 may vary greatly due to manufacturing variations in parts, etc. As a result, it becomes difficult to stably press the upper belt 411 and the lower belt 421 against the pad 423, and there is a risk that the formation of the nip portion N may become unstable.

[0097] Therefore, in this embodiment, the following configuration is adopted to enable the stable formation of nip portion N. Fig. 13 is a partial enlarged view of the vicinity of entrance roller 4110, and Fig. 14 is a partial enlarged view of the vicinity of exit roller 4120. In lower belt unit 420, nip upstream roller 426 is disposed upstream of pad 423 that forms nip portion N in the rotation direction of lower belt 421, and nip downstream roller 427 is disposed downstream. In upper belt unit 410, entrance roller 4110 is disposed upstream of a portion that faces nip upstream roller 426 in the rotation direction of upper belt 411 when nip portion N is formed, and exit roller 4120 is disposed downstream of a portion that faces nip downstream roller 427.

[0098] When the upper belt unit 410 and the upper door unit 43 are moved to the open position, the upper belt 411 is spaced from the lower belt 421. In this state, the upper belt 411 is simply stretched by the tension of the tension roller 4011a, with no member abutting the inner surface of the upper belt 411 between the entrance roller 4110 and the exit roller 4120. On the other hand, when the upper belt unit 410 and the upper door unit 43 are moved to the closed position, the upper belt 411 is in a nip position with respect to the lower belt 421. In this state, the portion of the upper belt 411 stretched between the entrance roller 4110 and the exit roller 4120 is pressed against the pad 423, the nip upstream roller 426, and the nip downstream roller 427, forming a wide nip N with the lower belt 421 at low pressure.

[0099] Furthermore, the outer peripheral surfaces of nip upstream roller 426 and nip downstream roller 427 are arranged so as to be at approximately the same height as the sheet conveyance direction end of pad 423. This prevents the lower belt 421 and upper belt 411 from coming into strong contact with the end of pad 423 when nip portion N is formed, thereby preventing a local increase in nip pressure.

[0100] A backup plate 415 (see FIG. 2) is provided near the upper belt 411 corresponding to the area between the entrance roller 4110 and the exit roller 4120. The backup plate 415 is provided at a position approximately 5 mm to 10 mm away from the upper belt 411 to prevent the upper belt 411 from being significantly deformed and damaged when a user cleans the upper belt 411 in the open position or when the user unintentionally touches the upper belt 411. In other words, the backup plate 415 is positioned within a distance that allows it to be deformed by a predetermined external force without being damaged, and at a distance that prevents it from coming into contact with the upper belt 411 when the nip portion N is formed.

[0101] An entrance roller bearing 4111 and an exit roller bearing 4121 are provided at the ends of the entrance roller 4110 and the exit roller 4120, respectively, to rotatably support them. That is, the entrance roller bearing 4111, which serves as a first bearing member, rotatably supports the entrance roller 4110, and the exit roller bearing 4121, which serves as a second bearing member, rotatably supports the exit roller 4120. As long life is required for the entrance roller bearing 4111 and the exit roller bearing 4121, bearings filled with heat-resistant grease are used. Note that when the entrance roller 4110 corresponds to the second roller, the entrance roller bearing 4111 corresponds to the second bearing member, and the exit roller bearing 4121 corresponds to the first bearing member.

[0102] Furthermore, the inlet roller bearing 4111 and the outlet roller bearing 4121 are held by an inlet roller bearing holder 4112 and an outlet roller bearing holder 4122, respectively, and are supported so as to be movable relative to the upper frame 414. That is, the inlet roller bearing holder 4112, which serves as a first holding member, holds the inlet roller bearing 4111 relative to the upper frame 414 so as to be movable in a direction perpendicular to the rotation axis of the inlet roller 4110 (in the up-and-down direction in this embodiment). The outlet roller bearing holder 4122, which serves as a second holding member, holds the outlet roller bearing 4121 relative to the upper frame 414 so as to be movable in a direction swinging about a rotation shaft 4214. The rotation shaft 4214 is parallel to the rotation axis of the outlet roller 4120 and is disposed at a position offset from the outlet roller 4120.

[0103] Exit roller bearing holder 4122 is a member on an arm that is supported so as to be able to swing about rotating shaft 4124, and holds exit roller bearing 4121 on the tip side of the arm. Furthermore, when exit roller bearing holder 4122 swings around rotating shaft 4124 in this way, exit roller bearing 4121 moves substantially in the vertical direction. Note that when entrance roller 4110 corresponds to the second roller, entrance roller bearing holder 4112 corresponds to the second holding member, and exit roller bearing holder 4122 corresponds to the first holding member.

[0104] Furthermore, the inlet roller bearing holder 4112 and the outlet roller bearing holder 4122 are urged outward against the upper belt 411 by an inlet roller pressure spring 4113 and an outlet roller pressure spring 4123, respectively. That is, the inlet roller pressure spring 4113, which serves as a first urging member, urges the inlet roller bearing holder 4112 in a first direction so that the inlet roller 4110 presses the inner circumferential surface of the upper belt 411 outward. In the case of this embodiment, the first direction is a direction perpendicular to the rotation axis of the inlet roller 4110, which is the downward direction D in FIG. 13 . Specifically, the inlet roller pressure spring 4113 is a spring disposed in an elastically compressed state between the upper surface of the inlet roller bearing holder 4112 and the upper frame 414, and urges the inlet roller 4110 held by the inlet roller bearing holder 4112 downward.

[0105] Furthermore, the outlet roller pressure spring 4123 serving as a second biasing member biases the outlet roller bearing holder 4122 in a second direction so that the outlet roller 4120 presses the inner circumferential surface of the upper belt 411 outward. In this embodiment, the second direction is the direction in which the outlet roller bearing holder 4122 swings around the rotation shaft 4214, which is the downward direction D in FIG. 13. Specifically, the outlet roller pressure spring 4123 is disposed between the upper frame 414 and the base end of the arm-shaped outlet roller bearing holder 4122, and pulls the base end of the outlet roller bearing holder 4122 upward in FIG. 14, thereby biasing the outlet roller 4120, which is held at the tip end of the outlet roller bearing holder 4122, with the rotation shaft 4124 sandwiched therebetween, downward. When the entrance roller 4110 corresponds to the second roller, the entrance roller pressure spring 4113 corresponds to the second biasing member, and the exit roller pressure spring 4123 corresponds to the first biasing member.

[0106] The loads of the entrance roller pressure spring 4113 and the exit roller pressure spring 4123 are set to be stronger than the reaction force caused by the tension of the upper belt 411 generated by the tension roller 4011a. That is, when the upper belt unit 410 and the upper door unit 43 are moved to the open position, that is, when the upper belt 411 is in the separated position, the entrance roller 4110 and the exit roller 4120 are positioned outside the positions of the entrance roller 4110 and the exit roller 4120 when the nip portion N is formed, that is, when the upper belt 411 is in the nip position.

[0107] On the other hand, the lower frame 424 of the lower belt unit 420 is formed with an inlet abutment portion 424a and an outlet abutment portion 424b at positions corresponding to the outer circumferential surfaces of the inlet roller bearing 4111 and the outlet roller bearing 4121. That is, the inlet abutment portion 424a as a first abutment portion is provided on the lower frame 424 and abuts against the inlet roller bearing 4111 biased in the first direction when the upper belt unit 410 and the lower belt unit 420 form the nip portion N. Furthermore, the outlet abutment portion 424b as a second abutment portion is provided on the lower frame 424 and abuts against the outlet roller bearing 4121 biased in the second direction when the upper belt unit 410 and the lower belt unit 420 form the nip portion N.

[0108] Therefore, when the upper belt unit 410 and the upper door unit 43 are moved to the closed position, the outer circumferential surfaces of the entrance roller bearing 4111 and the exit roller bearing 4121 come into contact with the entrance abutment portion 424a and the exit abutment portion 424b, respectively. This determines the positions of the entrance rollers 4110 and the exit rollers 4120, which are supported by the entrance roller bearing 4111 and the exit roller bearing 4121, respectively, relative to the lower frame 424. Note that the members that abut against the entrance abutment portion 424a and the exit abutment portion 424b may be the entrance roller bearing holder 4112 and the exit roller bearing holder 4122. Also, the abutment portions on the entrance and exit sides may be configured so that the bearings on one side abut against the abutment portion and the holders on the other side abut against the abutment portion.

[0109] A pad 423, a nip upstream roller 426, and a nip downstream roller 427 are supported on a lower frame 424 of the lower belt unit 420. Therefore, by determining the positions of the entrance roller 4110 and the exit roller 4120 relative to the lower frame 424, the portion of the upper belt 411 stretched between the entrance roller 4110 and the exit roller 4120 is pressed with precision against the pad 423, the nip upstream roller 426, and the nip downstream roller 427. As a result, a nip portion N can be formed with precision between the upper belt 411 and the lower belt, and a wide, uniform nip portion N can be stably formed between the upper belt 411 and the lower belt 421 at low pressure.

[0110] In this embodiment, the outlet abutment portion 424b has an outer circumferential surface that serves as a cam surface made up of multiple curved surfaces with different radii. The outlet abutment portion 424b is fixed to an adjustment member 4241 that serves as a changer. The outlet abutment portion 424b is rotatable together with the adjustment member 4211 about a rotation shaft 4242. The rotation shaft 4242 is disposed parallel to the rotation axis of the nip downstream roller 427, and supports the outlet abutment portion 424b and the adjustment member 4241 rotatably relative to the lower frame 424. The adjustment member 4241 has an arc-shaped through hole 4243 that is centered on the rotation shaft 4242. By screwing a screw 4244 into the lower frame 424 through the through hole 4243, the adjustment member 4241 can be fixed at any angle.

[0111] Therefore, by rotating the outlet abutment portion 424b and the adjustment member 4241 around the rotation shaft 4242 and fixing them with the screws 4244, the position at which the cam surface of the outlet abutment portion 424b abuts against the outlet roller bearing 4121 changes, and the position of the outlet roller bearing 4121 relative to the lower frame 424 is changed. As a result, it is possible to adjust the amount of penetration of the outlet roller 4120 supported by the outlet roller bearing 4121 into the nip portion N. This makes it possible, for example, to reduce the amount of penetration of the outlet roller 4120 to further reduce stress on the sheet, or to increase the amount of penetration of the outlet roller 4120 to further improve the separation performance of sheets with a low basis weight, such as thin paper, from the belt. As a result, it is possible to handle a variety of media.

[0112] The adjustment member as described above may be provided on the inlet roller 4110 side. That is, a cam surface may be provided on inlet abutment portion 424a, and the position of this cam surface against inlet roller bearing 4111 may be changed to change the position of inlet roller bearing 4111 relative to lower frame 424. Therefore, it is sufficient if at least one of the abutment position of inlet abutment portion 424a against inlet roller bearing 4111 or inlet roller bearing holder 4112, and the abutment position of outlet abutment portion 424b against outlet roller bearing 4121 or outlet roller bearing holder 4122 can be changed.

[0113] In this way, by making it possible to change at least one of the abutting position of the inlet abutting portion 424a against the inlet roller bearing 4111 or the inlet roller bearing holder 4112 and the abutting position of the outlet abutting portion 424b against the outlet roller bearing 4121 or the outlet roller bearing holder 4122, it is possible to prevent the nip pressure from increasing excessively due to the thickness of the sheet. That is, when the nip portion N is formed between the upper belt 411 and the lower belt 421, the inlet roller 4110, the outlet roller 4120, the nip upstream roller 426, and the nip downstream roller 427, which are the rollers that form the nip portion N, are not provided with opposing rollers or members such as pads. In this embodiment, since the nip portion N is formed with an extremely low pressure, for example, if the intrusion amount of the inlet roller 4110 or the outlet roller 4120 is too large, the nip pressure of the sheet between the roller and the opposing portion of this roller may increase due to the thickness of the sheet. In response to this, by appropriately adjusting the intrusion amount of the entrance roller 4110 or the exit roller 4120, it is possible to obtain a uniform nip pressure stably even for thick sheets.

[0114] In this embodiment, the inlet roller bearing holder 4112 is formed into a holder shape that allows it to move linearly, and the outlet roller bearing holder 4122 is formed into a holder shape that allows it to rotate about the center of rotation, but the shape and configuration of the holders are not important as long as they can urge the rollers outward of the upper belt 411. For example, either holder may be configured to move linearly or rotate, or the inlet roller side may be configured to rotate, and the outlet roller side may be configured to move linearly.

[0115] Furthermore, as in this embodiment, the most accurate and suitable configuration is one in which the outer circumferential surfaces of the inlet roller bearing 4111 and the outlet roller bearing 4121 are directly abutted against the inlet abutment portion 424a and the outlet abutment portion 424b of the lower frame 424. However, since positioning with relatively high accuracy is possible with any member that moves linearly or rotates together with the inlet rollers 4110 and the outlet rollers 4120, an abutment shape may be provided in part of the inlet roller bearing holder 4112 or the outlet roller bearing holder 4122, and the abutment may be made against the inlet abutment portion 424a and the outlet abutment portion 424b.

[0116] According to this embodiment, it is possible to stably press the upper belt 411 and the lower belt 421 against the pad 423, and a wide and uniform nip can be formed at low pressure. Furthermore, as for the upper belt unit 410 as a whole, while being supported by the upper door unit 43, only the entrance roller bearing 4111 and the exit roller bearing 4121 are abutted against the entrance abutment portion 424a and the exit abutment portion 424b of the lower frame 424 by springs, so that the entrance roller bearing 4111 and the exit roller bearing 4121 can be accurately positioned without applying excessive load such as their own weight to them.

[0117] In the above-described embodiment, the lower frame 424 and the pad 423 are arranged in the lower belt unit 420, and the inlet roller 4110 and the outlet roller 4120 are arranged in the upper belt unit 410. However, the upper belt unit 410 and the lower belt unit 420 may be swapped, that is, the upper and lower belt units may be reversed. That is, even if the inlet roller and the outlet roller are arranged in the lower belt unit, and the upper frame and the pad having the abutment portion are arranged in the upper belt unit, the same effect can be obtained by adopting the same configuration as described above.

[0118] <Second embodiment> The second embodiment will be described with reference to FIG. 15. In the first embodiment described above, The configuration has been described in which the inlet roller bearing 4111 and the outlet roller bearing 4121 abut against the inlet abutment portion 424a and the outlet abutment portion 424b provided on the lower frame 424. In contrast, the fixing belt unit 4100A of this embodiment is configured so that the abutment portion 4231 provided on the pad 423A abuts against the upper frame 414. The other configurations and functions are the same as those of the first embodiment described above. For this reason, the same components as those in the first embodiment are denoted by the same reference numerals, and their description and illustration will be omitted or simplified, and the following description will focus on the differences from the first embodiment.

[0119] As in the first embodiment, configuring the inlet roller 4110 and the outlet roller 4120 to be movable and biased by springs is preferable because it is easier to achieve positioning accuracy relative to the pad 423 and the device is simpler. However, even with the configuration of this embodiment described below, the same effects as those of the first embodiment can be obtained. That is, the pad 423A as a support member is supported movably relative to the lower frame 424. The spring 4102 as a biasing member biases the pad 423A so that the pad 423A presses the inner circumferential surface of the lower belt 421 in the nip portion N region outward. In this embodiment, the spring 4102 biases the pad 423A in the upward direction U. The pad 423A is provided with an abutment portion 4231 that abuts against the upper frame 414 when the upper belt unit 410A and the lower belt unit 420A form the nip portion N.

[0120] In this embodiment, when the upper belt unit 410A and the upper door unit 43 are moved to the closed position, a part of the upper frame 414 abuts against the abutment portion 4231. This determines the positions of the entrance rollers 4110 and the exit rollers 4120, which are supported by the upper frame 414 via the entrance roller bearing 4111, the exit roller bearing 4121, and the like, relative to the pad 423A. As a result, the portion of the upper belt 411 stretched between the entrance roller 4110 and the exit roller 4120 is pressed against the pad 423 with precision, allowing the upper belt 411 and the lower belt to form a nip portion N with precision. This allows a wide nip and a uniform nip portion N to be stably formed between the upper belt 411 and the lower belt 421 at low pressure.

[0121] In the above description, the abutting portion 4231 is provided on the pad 423A, but the abutting portion 4231 may be provided on the lower frame 424. In such a configuration, the positions of the inlet rollers 4110 and the outlet rollers 4120 supported on the upper frame 414 via the inlet roller bearings 4111 and the outlet roller bearings 4121, etc., are determined relative to the lower frame 424. The pad 423A and the nip upstream roller 426 and the nip downstream roller 427 are supported on the lower frame 424. Therefore, by determining the positions of the inlet rollers 4110 and the outlet rollers 4120 relative to the lower frame 424, the portion of the upper belt 411 stretched between the inlet roller 4110 and the outlet roller 4120 is pressed against the pad 423, the nip upstream roller 426, and the nip downstream roller 427 with high precision. As a result, the nip N can be formed between the upper belt 411 and the lower belt with high precision, and a wide and uniform nip N can be stably formed between the upper belt 411 and the lower belt 421 at low pressure.

[0122] In this embodiment, the upper belt unit 410A and the lower belt unit 420A may be interchanged. That is, even if an upper frame having an abutting portion and a pad are arranged on the upper belt unit and this abutting portion abuts against the lower frame 424 of the lower belt unit, the same effect can be obtained by adopting the same configuration as above.

[0123] <Third embodiment> The third embodiment will be described with reference to FIG. 16. In the first embodiment described above, The configuration has been described in which the inlet roller bearing holder 4112 and the outlet roller bearing holder 4122 are biased by the inlet roller pressure spring 4113 and the outlet roller pressure spring 4123. In contrast, in the fixing belt unit 4100B of this embodiment, the inlet roller bearing holder 4112 and the outlet roller bearing holder 4122 are fixed in a positional state. The other configurations and operations are the same as those of the first embodiment described above. For this reason, the same components as those of the first embodiment are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment.

[0124] In the following, in this embodiment, the configuration of the inlet roller bearing holder is different from that of the first embodiment, so the inlet roller bearing holder will be described using the reference numeral "4112A." FIG. 16 is an enlarged view showing the vicinity of inlet roller 4110 in this embodiment. As in the first embodiment, an inlet roller bearing 4111 that rotatably supports inlet roller 4110 is provided at the end of inlet roller 4110. In addition, inlet roller bearing 4111 is held by inlet roller bearing holder 4112A. In this embodiment, inlet roller bearing holder 4112A is configured to be slidable in the vertical directions (upward direction U and downward direction D) in FIG. 16, and is fixed to upper frame 414 by screws 4114 that serve as fixing members (first fixing members).

[0125] The lower frame 424 is provided with an inlet facing portion 424aA as a facing portion (first facing portion) facing the inlet roller bearing 4111 when the upper belt unit 410B and the lower belt unit 420B form the nip portion N. The screws 4114 fix the inlet roller bearing holder 4112A to the upper frame 414 when the inlet roller bearing 4111 is positioned at a predetermined position (first predetermined position) with respect to the inlet facing portion 424aA. In this embodiment, the screws 4114 fix the inlet roller bearing holder 4112A to the upper frame 414 so that a gap (gap G) exists between the inlet roller bearing 4111 and the inlet facing portion 424aA when the upper belt unit 410B and the lower belt unit 420B form the nip portion N.

[0126] Such fixation with the screws 4114 is performed during assembly of the device, with the upper belt unit 410B and the lower belt unit 420B forming the nip portion N, and with a member having high precision and a thickness approximately equal to the gap G sandwiched between the inlet roller bearing 4111 and the inlet facing portion 424aA. After fixation with the screws 4114, removing this member makes it possible to obtain a gap with high precision between the inlet roller bearing 4111 and the inlet facing portion 424aA. The member facing the inlet facing portion 424aA may be the inlet roller bearing holder 4112A.

[0127] Furthermore, the configuration on the exit roller 4120 side may be the same as that of the first embodiment, or may be the same as that of the entrance roller 4110 side of this embodiment. In the case of the same configuration as that of the first embodiment, when the upper belt unit 410B and the lower belt unit 420B form the nip portion N, the exit roller bearing 4121 or the exit roller bearing holder 4122 abuts against the exit abutment portion 424b as an abutment portion.

[0128] On the other hand, if the configuration on the exit roller 4120 side is the same as the configuration on the inlet roller 4110 side described above, the exit abutment portion 424b corresponds to the second opposing portion. Hereinafter, the second opposing portion will be referred to as the exit opposing portion. That is, the exit opposing portion is provided on the lower frame 424, and faces the exit roller bearing 4121 or the exit roller bearing holder 4122 in a state where the upper belt unit 410B and the lower belt unit 420B form the nip portion N. Furthermore, with a screw as a second fixing member, the exit roller bearing holder 4122 is fixed to the upper frame 414 in a state where the exit roller bearing 4121 or the exit roller bearing holder 4122 is positioned at a second predetermined position with respect to the exit opposing portion.

[0129] In the case of this embodiment, when the upper belt unit 410B and the upper door unit 43 are moved to the closed position, the positional relationship between the entrance roller bearing 4111 and the entrance facing portion 424aA is fixed. If the configuration on the exit roller 4120 side is the same as in the first embodiment, the position of the exit roller 4120 relative to the lower frame 424 is determined, as in the first embodiment. Furthermore, if the configuration on the exit roller 4120 side is the same as the configuration on the entrance roller 4110 side of this embodiment, the positional relationship between the exit roller bearing 4121 and the exit facing portion is fixed when the upper belt unit 410B and the upper door unit 43 are moved to the closed position.

[0130] Therefore, in the present embodiment, as in the first embodiment, the positions of the entrance roller 4110 and the exit roller 4120 relative to the lower frame 424 are determined, and the portion of the upper belt 411 stretched between the entrance roller 4110 and the exit roller 4120 is pressed with precision against the pad 423, the nip upstream roller 426, and the nip downstream roller 427. As a result, the nip portion N can be formed with precision between the upper belt 411 and the lower belt, and a wide, uniform nip portion N can be stably formed between the upper belt 411 and the lower belt 421 at low pressure.

[0131] Furthermore, the configuration of the first embodiment does not require an adjustment process during assembly, as in this embodiment, and allows for accurate positioning of the inlet roller 4110 and the outlet roller 4120. On the other hand, while this embodiment requires an adjustment process during assembly, it allows for fine adjustment of the individual positioning positions to accommodate various media on the market, and is easily applicable to belt configurations with strong tension. Furthermore, in the first embodiment, the upper belt 411 with strong tension requires a strong biasing force from the spring that biases the inlet roller 4110 and the outlet roller 4120. However, in this embodiment, the inlet roller 4110 does not require a spring to bias the inlet roller 4110 because the inlet roller bearing holder 4112A is fixed to the upper frame 414 with the inlet roller bearing 4111 positioned relative to the inlet facing portion 424aA. If the outlet roller 4120 were configured in a similar manner, a spring to bias the outlet roller 4120 would also not be required.

[0132] In this embodiment, in order to provide an adjustable range, a predetermined gap G is provided so that the inlet roller bearing 4111 and the inlet facing portion 424aA do not come into contact with each other every time the upper belt unit 410 is opened or closed, but the gap G may be 0. In other words, when the upper belt unit 410 is in the closed position, the inlet roller bearing 4111 and the inlet facing portion 424aA may come into contact with each other.

[0133] In this embodiment, only the configuration around inlet roller bearing holder 4112A of inlet roller 4110 has been described, but only the configuration around outlet roller bearing holder 4122 of outlet roller 4120 may be the same as that described above. In other words, only one of the inlet rollers or the outlet rollers may be the same as that described above, or both may be the same as that described above.

[0134] Also in this embodiment, similarly to the above-described embodiments, the upper belt unit 410B and the lower belt unit 420B may be interchanged. Also, as in the third embodiment, the pad may be configured to be movable and fixed at a desired position.

[0135] <Other embodiments> In the above-described embodiments, the present invention has been described as being applied to the fixing belt units 4100, 4100A, and 4100B 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 also be applied to a cooling module 5000 (cooling device).

[0136] Furthermore, in the above-described embodiments, the present invention has been described as being applied to the inkjet recording system 100 as an image forming apparatus, but is not limited to this. For example, the present invention can be applied to an electrophotographic image forming apparatus that uses toner, and the same effects as those of the present embodiments can be obtained. [Explanation of symbols]

[0137] 1. Image forming system (image forming device) 43 Upper door unit (first cabinet) 400: Device body (second housing) 410, 410A, 410B...Upper belt unit (first belt unit) 411···Upper belt (first belt) 414···Upper frame (first frame) 420, 420A, 420B... Lower belt unit 420 (second belt unit) 421 Lower belt (second belt) 424 Lower frame (second frame) 423, 423A Pad (support member) 424a···Inlet abutment part (first abutment part) 424aA···Inlet facing part (facing part) 424b···Outlet abutment part (second abutment part) 426 Nip upstream roller (third roller) 427 Nip downstream roller (fourth roller) 4060a···First heating unit (first heating device) 4060b Second heating unit (second heating device) 4100, 4100A, 4100B....Fusing belt unit (sheet transport device) 4110 Entrance roller (first roller) 4111: Inlet roller bearing (first bearing member) 4112 Inlet roller bearing holder (first holding member) 4113 Entrance roller pressure spring (first biasing member) 4114 Screw (fixing member) 4120 Exit roller (second roller) 4121 Outlet roller bearing (second bearing member) 4122···Outlet roller bearing holder (second holding member) 4123: Exit roller pressure spring (second biasing member) 4124 Rotating shaft 4231···Butt section N...Nip section

Claims

1. a first belt unit having a rotating endless first belt; a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to sandwich and convey a sheet, a sheet conveying device in which one of the first belt unit and the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separation position where the first belt and the second belt are spaced apart from each other with respect to the nip position, The first belt unit is the first belt; a plurality of first tension members that tension the first belt, the first tension members including a first roller and a second roller that are arranged to sandwich the nip portion in the rotation direction of the first belt; a first frame supporting the plurality of first tension members; a first bearing member that rotatably supports the first roller; a first holding member that holds the first bearing member movably relative to the first frame; a first biasing member that biases the first holding member in a first direction so that the first roller presses the inner circumferential surface of the first belt outward; a second bearing member that rotatably supports the second roller; a second holding member that holds the second bearing member movably relative to the first frame; a second biasing member that biases the second holding member in a second direction so that the second roller presses the inner circumferential surface of the first belt outward, The second belt unit is the second belt; a plurality of second tension members for tensioning the second belt; a second frame supporting the plurality of second tension members; a support member supported by the second frame and in contact with an inner circumferential surface of the second belt in the nip region to support the second belt; a first abutment portion provided on the second frame, the first abutment portion abutting against the first bearing member or the first holding member biased in the first direction when the first belt unit and the second belt unit form the nip portion; a second abutment portion that is provided on the second frame and abuts against the second bearing member or the second holding member that is biased in the second direction when the first belt unit and the second belt unit form the nip portion; A sheet conveying device characterized by:

2. 2. The sheet conveying device according to claim 1, further comprising a change unit capable of changing at least one of the positions of the first abutment portion against the first bearing member or the first holding member and the position of the second abutment portion against the second bearing member or the second holding member.

3. the plurality of second tension members include a third roller and a fourth roller disposed on both sides of the support member in the rotation direction of the second belt, 2. The sheet conveying device according to claim 1, wherein the distance between the third roller and the fourth roller is shorter than the distance between the first roller and the second roller.

4. 2. The sheet conveying device according to claim 1, wherein the first holding member is movable relative to the first frame in a direction perpendicular to the rotation axis of the first roller.

5. The sheet conveying device according to claim 1, characterized in that the second holding member is movable relative to the first frame in a direction of swinging around a rotation axis that is parallel to the rotation axis of the second roller and positioned away from the second roller.

6. 2. The sheet conveying apparatus according to claim 1, wherein the first belt unit includes a first heating device for heating the first belt.

7. 2. The sheet conveying apparatus according to claim 1, wherein the second belt unit includes a second heating device for heating the second belt.

8. a first housing in which either the first belt unit or the second belt unit is disposed; a second housing in which the other of the first belt unit and the second belt unit is disposed; 2. The sheet conveying device according to claim 1, further comprising a rotation shaft that supports the first housing rotatably relative to the second housing so that the one belt unit can be moved between the nip position and the separation position.

9. a first belt unit having a rotating endless first belt; a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to sandwich and convey a sheet, a sheet conveying device in which one of the first belt unit and the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separation position where the first belt and the second belt are spaced apart from each other with respect to the nip position, The first belt unit is the first belt; a plurality of first tension members that tension the first belt, the first tension members including a first roller and a second roller that are arranged to sandwich the nip portion in the rotation direction of the first belt; a first frame supporting the plurality of first tension members; a first bearing member that rotatably supports the first roller; a first holding member that holds the first bearing member movably relative to the first frame; a second bearing member that rotatably supports the second roller; a second holding member that holds the second bearing member movably relative to the first frame, The second belt unit is the second belt; a plurality of second tension members for tensioning the second belt; a second frame supporting the plurality of second tension members; a support member supported by the second frame and in contact with an inner circumferential surface of the second belt in the nip region to support the second belt; a first opposing portion provided on the second frame, the first opposing portion opposing the first bearing member or the first holding member in a state in which the first belt unit and the second belt unit form the nip portion; a second opposing portion that is provided on the second frame and that faces the second bearing member or the second holding member in a state where the first belt unit and the second belt unit form the nip portion, a first fixing member that fixes the first holding member to the first frame in a state in which the first bearing member or the first holding member is positioned at a first predetermined position with respect to the first opposing portion; a second fixing member that fixes the second holding member to the first frame in a state in which the second bearing member or the second holding member is positioned at a second predetermined position with respect to the second opposing portion; A sheet conveying device characterized by:

10. the first fixing member fixes the first holding member to the first frame such that a first gap exists between the first bearing member or the first holding member and a first opposing portion in a state in which the first belt unit and the second belt unit form the nip portion; The sheet conveying device according to claim 9, characterized in that the second fixing member fixes the second holding member to the first frame so that a second gap exists between the second bearing member or the second holding member and a second opposing portion when the first belt unit and the second belt unit form the nip portion.

11. 10. The sheet conveying apparatus according to claim 9, wherein the first belt unit includes a first heating device for heating the first belt.

12. 10. The sheet conveying apparatus according to claim 9, wherein the second belt unit includes a second heating device for heating the second belt.

13. a first housing in which either the first belt unit or the second belt unit is disposed; a second housing in which the other of the first belt unit and the second belt unit is disposed; 10. The sheet conveying device according to claim 9, further comprising a rotation shaft that supports the first housing rotatably relative to the second housing so that the one belt unit can be moved between the nip position and the separation position.

14. a first belt unit having a rotating endless first belt; a second belt unit having a rotating endless second belt that forms a nip portion between the first belt and the second belt to sandwich and convey a sheet, a sheet conveying device in which one of the first belt unit and the second belt unit is movable relative to the other belt unit between a nip position where the first belt and the second belt form the nip portion and a separation position where the first belt and the second belt are spaced apart from each other with respect to the nip position, The first belt unit is the first belt; a plurality of first tension members that tension the first belt, the first tension members including a first roller and a second roller that are arranged to sandwich the nip portion in the rotation direction of the first belt; a first frame supporting the plurality of first tension members; a first bearing member that rotatably supports the first roller; a first holding member that holds the first bearing member movably relative to the first frame; a second bearing member that rotatably supports the second roller; a second holding member that holds the second bearing member movably relative to the first frame; a second biasing member that biases the second holding member in a second direction so that the second roller presses the inner circumferential surface of the first belt outward, The second belt unit is the second belt; a plurality of second tension members for tensioning the second belt; a second frame supporting the plurality of second tension members; a support member supported by the second frame and in contact with an inner circumferential surface of the second belt in the nip region to support the second belt; a facing portion provided on the second frame, the facing portion facing the first bearing member or the first holding member in a state in which the first belt unit and the second belt unit form the nip portion; an abutment portion that is provided on the second frame and abuts against the second bearing member or the second holding member that is biased in the second direction when the first belt unit and the second belt unit form the nip portion, a fixing member that fixes the first holding member to the first frame in a state where the first bearing member or the first holding member is positioned at a predetermined position with respect to the opposing portion; A sheet conveying device characterized by:

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