JP2006293283A - Endless belt, fixing device, image forming apparatus and method, and method for manufacturing endless belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of paper wrinkling and to suppress the wear down of a belt surface and the damage of belt edges as well relating to the endless belt, the surface of which is relatively pressed by a rotationally driving rotor and a nip region to hold a recording sheet in-between is formed between the surface and the rotor, and which circulates in follow up to the rotation of the rotor. <P>SOLUTION: The endless belt has a largest external diameter part 126 which is disposed between each of both edges 123 and a transverse direction central part 122 orthogonal to the circulating direction thereof and has the largest external diameter, and a reduced diameter part 127 which is gradually reduced in the external diameter from the largest external diameter part 126 respectively toward both edges 123. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an endless belt in which a surface is relatively pressed against a rotating body that is driven to rotate, a nip region is formed in which the sheet is sandwiched between the rotating body, and the endless belt circulates following the rotation of the rotating body. The present invention relates to a fixing device that includes a belt and fixes an unfixed toner image on a sheet, an image forming device that includes the fixing device, an image forming method that is performed in the image forming device, and a method for manufacturing the endless belt.

  Among image forming apparatuses such as copiers, printers, and facsimiles that employ an electrophotographic system, a fixing device that fixes an unfixed toner image transferred onto a sheet such as paper to a recording sheet is provided. As one of the fixing devices, a nip region is formed by bringing the peripheral surfaces of a pair of rotatable rotating members into contact with each other, and a sheet carrying an unfixed toner image is passed through the nip region, so It is known to apply heat and pressure to a received toner image to fix an unfixed toner image on a sheet. For example, a so-called roll-roll type fixing device using a heating roll having a heat source therein and a pressure roll provided with an elastic layer is known as a pair of rotatable rotating bodies. However, in this roll-roll type fixing device, a thick elastic layer is also provided on the heating roll in order to form a nip region having a predetermined length or more. For this reason, there is a problem that the heat capacity of the heating roll increases, and the time until the heating roll is raised from room temperature to a fixable temperature (hereinafter referred to as “warm-up time”) becomes long. Accordingly, a so-called roll-belt type fixing device in which the pressure roll is replaced with an endless belt has been proposed (see, for example, Patent Document 1).

  FIG. 1 is a schematic diagram showing an example of a conventional roll-belt type fixing device.

  A fixing device 200 shown in FIG. 1 has a heating roll 210 with a built-in heat source, an endless fixing belt 220 stretched between three support rolls 221, 222, and 223, and a back surface side of the fixing belt 220. The main part is constituted by the pressed pad 230 having elasticity.

  The heating roll 210 has a cylindrical core 211 inside, and is driven to rotate in the direction of the arrow in the figure by a motor (not shown). An elastic layer 212 is formed on the surface of the core 211, and the surface of the elastic layer 212 is covered with a release layer 213. That is, the surface of the heating roll 210 is formed by the release layer 213. Inside the core 211, a halogen lamp 214 is disposed as a heating source. Further, around the heating roll 210, a release agent coating device 240 for applying a release agent oil, a cleaning device 250 for cleaning the roll surface, and the surface of the heating roll 210 are heated in contact with the surface. An external heating device 260, a peeling claw 270 for peeling the paper after fixing, and a temperature sensor 280 for controlling the temperature of the surface of the heating roll 210 are provided.

  The surface of the fixing belt 220 is pressed against the heating roll 210 and circulates following the rotation of the heating roll 210. A heater lamp 2211 is disposed inside one of the three support rolls 221, 222, and 223 that stretches the fixing belt 220. The surface of the fixing belt 220 is pressed against the heating roll 210 by a pressing pad 230 having elasticity and a support roll 223 disposed in the vicinity of the pressing pad 230 to form a nip region N.

  In FIG. 1, the toner image T is transferred onto the paper P by a transfer device (not shown) on the right side of the drawing, and the unfixed toner image T is carried toward the nip region N of the fixing device 200 shown in FIG. The paper P is conveyed. As the paper P enters the nip region N and passes through the nip region N, the unfixed toner image T is heated and pressurized, and the unfixed toner image T is fixed on the paper P.

  In the roll-belt type fixing device 200 shown in FIG. 1, the portion of the fixing belt 220 that is in pressure contact with the peripheral surface of the heat-fixing roll 10 has a shape along the peripheral surface of the heat-roller 210. The nip region N is formed more easily than the roll-roll type fixing device. For this reason, in the heating roll 210 shown in FIG. 1, the thickness of the elastic layer 212 can be suppressed thinner than that of the heating and fixing roll provided in the roll-roll type fixing device, and the warm-up time can be shortened.

  However, a problem with such a roll-belt type fixing device 200 is that paper wrinkles are likely to occur. The occurrence of paper wrinkles is likely to be a problem even in a roll-roll type fixing device. However, in the roll-roll type fixing device, the rotation axis of the roll is larger than the nip width of the roll in the center in the extending direction of the rotation axis. By widening the nip width at the end in the extending direction of the paper, a speed difference is given to the transport speed of the paper, and the speed difference is used to pull the paper at the entrance side of the nip area in the width direction perpendicular to the transport direction. I give power to prevent it. On the other hand, in the roll-belt type fixing device, the pressure application member 230 shown in FIG. 1 is shaped, and the pressure distribution in the nip region N is differentiated in the width direction of the sheet so that the speed difference is made in the sheet conveyance speed. However, the sliding resistance between the low friction layer 233 of the pressure applying member 230 and the back surface of the fixing belt 220 is inevitably increased in the long-term use, and the fixing belt 220 is heated by the heating roll 210. It becomes difficult to follow the rotation of. In this case, paper wrinkles are likely to occur without causing the above-described speed difference. Further, in the heating roll 210 shown in FIG. 1, the thickness of the elastic layer 212 is suppressed to be thinner than that of the heating and fixing roll provided in the roll-roll type fixing device. It has become.

  FIG. 2 is a cross-sectional view showing a belt proposed in Patent Document 2 as a fixing belt of the fixing device shown in FIG. 1, and FIG. 3 was proposed in Patent Document 3 as a fixing belt of the fixing device shown in FIG. It is sectional drawing which shows a belt.

  In both FIG. 2 and FIG. 3, the width direction of the fixing belts 300 and 400 is the left-right direction in the figure, and this width direction is hereinafter sometimes referred to as the axial direction. 2 and 3 show the paper P that passes through the nip region N shown in FIG. 1, and the passing direction of the paper P is perpendicular to the paper surface. The left-right direction corresponds to the width direction of the paper P orthogonal to the transport direction.

  FIG. 2 and FIG. 3 schematically show the fixing belts 300 and 400 taken along the axial direction of the fixing belt 300. The fixing belt inevitably moves in the axial direction while circulating. On both sides in the axial direction of the fixing belt 300 shown in FIG. 2, a regulating member 510 provided in the fixing device is shown. The regulating member 510 shown in FIG. 2 is supported by the frame 501 of the fixing device, and prevents the circulating fixing belt 300 from moving in the axial direction by entering the axial end portions 301 of the fixing belt 300. Is. Further, sensors 520 provided in the fixing device are shown on both sides in the axial direction of the fixing belt 400 shown in FIG. The sensor 520 shown in FIG. 3 detects that the circulating fixing belt 400 has moved in the axial direction. For example, if the fixing belt 400 shown in FIG. 3 moves to the right side of the drawing, the sensor 520 shown on the right side of the drawing detects the movement of the fixing belt 300 in the axial direction, and the fixing belt 300 is not shown in the drawing. To the left.

  In the fixing belt 300 shown in FIG. 2, the central portion 302 in the width direction has the smallest outer diameter, and the outer diameter gradually increases from the central portion 302 toward both edges 303. It is the maximum outer diameter.

  A fixing belt 400 shown in FIG. 3 is provided with a first straight portion 404 whose outer diameter is substantially constant in the width direction at the center in the width direction. The outer diameter of the first straight portion 404 is the fixing diameter shown in FIG. The belt 400 has a minimum outer diameter. Moreover, the 2nd straight part 405 whose outer diameter is substantially constant in the width direction is provided also in each width direction both ends. The second straight portion 405 continues to the edge 403 of the fixing belt 400, and the outer diameter of the second straight portion 405 is the maximum outer diameter of the fixing belt 400 shown in FIG. From the first straight portion 404 to the second straight portions 405 at both ends, the outer diameter gradually increases.

  Also, a release layer is provided on the surface of any of the fixing belts 300 and 400 shown in FIG. 2 and FIG. 3 to enhance the releasability from paper and toner.

  2 and 3, the width of the fixing belts 300 and 400 is longer than the width of the paper P, and when the paper P is sandwiched in the nip region N, the paper P of the fixing belt 300 and 400 is fixed. The portion on the outer side in the width direction that is not in contact with the sheet is in contact with the surface of the heating roll 210 (see FIG. 1) that is rotationally driven. A slip in the circulation direction is likely to occur between the sheet P and the sheet P. For this reason, the speed in the width direction of the fixing belts 300, 400 between the fixing belts 300, 400 between the outer portion in the width direction that is not in contact with the paper P and the portion in contact with the end in the width direction of the paper P. Due to the difference, the part of the fixing belt 300 or 400 that is in contact with the end in the width direction of the paper P is likely to be worn away from the release layer provided on the surface thereof. When the release layers of the fixing belts 300 and 400 are worn, image quality defects due to toner adhesion to the endless belt 220 and paper jams may occur.

Further, in the fixing belt 300 with the edge 303 expanded as shown in FIG. 2, when the edge 303 is pressed against the regulating member 510 by moving in the axial direction, the edge 303 is easily expanded, and the edge 303 of the fixing belt 300 is damaged. It will happen. The edge damage is caused by pressing the edge 403 against the sensor 520 even in the fixing belt 400 having a substantially constant outer diameter up to the edge 403 shown in FIG.
JP-A-9-34291 JP-A-3-110137 JP 2002-14560 A

  In view of the above circumstances, the present invention includes an endless belt that suppresses the generation of paper wrinkles and also prevents the belt surface from being worn and the edge of the belt from being damaged, and the endless belt. It is an object of the present invention to provide a fixing device for fixing to a sheet, an image forming apparatus provided with the fixing device, an image forming method implemented in the image forming apparatus, and a method for manufacturing the endless belt.

The endless belt of the present invention that solves the above object forms a nip region in which a surface is relatively pressed against a rotary member that is rotationally driven and sandwiches a recording sheet with the rotary member. In an endless belt that follows and circulates,
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
And a reduced diameter portion having an outer diameter that gradually decreases from the maximum outer diameter portion toward both edges.

  Even if the endless belt of the present invention is pressed toward the rotating body, the rotating body is pressed toward the endless belt so that the endless belt is relatively pressed toward the rotating body. It may be.

Here, the endless belt has a width longer than the length in the width direction of the recording sheet,
A mode in which the maximum outer diameter portion is a portion provided in the vicinity of the both edges in the width direction of the recording sheet sandwiched in the nip region is preferable.

  The shape of the endless belt of the present invention is a shape that can easily give a speed difference in the width direction to the conveyance speed of the recording sheet sandwiched in the nip region. That is, both end portions in the width direction of the recording sheet sandwiched in the nip region are more firmly sandwiched between the rotating body and the vicinity of the maximum outer diameter portion than the central portion in the width direction of the recording sheet. Even if the endless belt becomes difficult to follow the rotation of the rotating body, a speed difference in the width direction occurs in the recording sheet conveyance speed between the central portion and both ends of the recording sheet. Cheap. For this reason, the recording sheet is pulled in the width direction, and generation of paper wrinkles is suppressed. In addition, the shape of the endless belt of the present invention is also a shape that suppresses a difference in speed in the width direction from the circulation speed of the endless belt. That is, both ends in the width direction of the recording sheet are in contact with the vicinity of the maximum outer diameter portion, and the area near the maximum outer diameter portion moves within the area of the endless belt in contact with the recording sheet. This is an area that is most easily driven by the recording sheet, and the slip in the circulation direction hardly occurs between the recording sheet and the recording sheet. For this reason, it is suppressed that the endless belt surface is worn. Furthermore, the edge of the endless belt is not easily expanded by the reduced diameter portion, and the endless belt is prevented from being damaged.

In the endless belt of the present invention, when the outer diameters of both edges are R1, the outer diameter of the maximum outer diameter portion is R2, and the outer diameter of the central portion in the width direction is R3,
R2> R1 ≧ R3 Formula (1)
It is preferable to satisfy the relationship represented by the above formula (1),
Furthermore, it is preferable to have a straight portion whose outer diameter is substantially constant in the width direction at the center portion in the width direction.

  By doing so, it becomes easy to manufacture an endless belt.

Here, in the endless belt of the present invention, the surface may be formed on a base material made of a thin metal film having a thickness of 20 μm to 80 μm, or of the polyimide resin and the polyamide resin. The said surface may be formed on the base material which consists of any one resin.

Furthermore, in the endless belt of the present invention, an aspect in which the maximum outer diameter portion is the thickest part is preferable, or
This endless belt is formed by laminating a plurality of layers in the thickness direction, and has an inner diameter substantially constant in the width direction,
The maximum outer diameter portion is a portion formed by increasing the thickness of any one of the plurality of layers,
It is also preferable that the reduced diameter portion is a portion formed by gradually reducing the thickness of any one of the plurality of layers toward both edges.

  By adopting these aspects, even if a speed difference in the width direction occurs in the circulation speed of the endless belt, the maximum outer diameter portion is not easily worn away, and the product life of the endless belt is extended. Moreover, according to the latter aspect, the endless belt can be easily manufactured because the inner diameter is substantially constant.

The fixing device of the present invention that solves the above object passes a recording sheet carrying an unfixed toner image through a predetermined nip region to apply heat and pressure to the unfixed toner image. In a fixing device for fixing a toner image to the recording sheet,
Rotating body that rotates,
A nip region is formed in which the recording sheet is sandwiched between the rotating body and the surface is relatively pressed against the rotating body, the endless belt that circulates following the rotation of the rotating body, and the nip region is heated. Heating means,
The endless belt is
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
It has a reduced diameter part where the outer diameter is gradually reduced from the maximum outer diameter part toward each of both edges.

  The rotating body referred to here may be in the form of a roll or a belt (hereinafter the same).

  According to the fixing device of the present invention, the generation of paper wrinkles can be suppressed, and the endless belt surface can be prevented from being worn and the edge of the endless belt can be prevented from being damaged.

  In the fixing device of the present invention, it is preferable that the endless belt is made of a heat resistant resin that maintains a predetermined strength even when receiving heat from the heating means.

Further, in the fixing device of the present invention, the endless belt has better releasability between the base layer and both the toner constituting the toner image and the recording sheet than the material constituting the base layer. It is also preferable that it has a multilayer structure including at least a surface layer that is provided on the base layer and constitutes the surface, made of a heat-resistant material that maintains a predetermined strength even when receiving heat from the heating means, Moreover,
The endless belt has a heat resistant elastic layer between the base layer and the surface layer, which is more elastically deformable than the base layer and maintains a predetermined strength even when receiving heat from the heating means. More preferably.

In addition, the endless belt has a substantially constant inner diameter in the width direction,
The maximum outer diameter portion is a portion formed by increasing the thickness of at least one of the base layer, the heat-resistant elastic body layer, and the surface layer,
The reduced diameter portion is a portion formed by gradually reducing the thickness of at least one of the base layer, the heat resistant elastic body layer, and the surface layer toward both edges. Even more preferred.

An image forming apparatus of the present invention that solves the above object transfers a toner image carried on a toner image carrying body carrying a toner image onto a recording sheet, and the recording sheet on which the toner image is transferred Image formation in which an image is formed on the recording sheet by applying heat to the unfixed toner image by passing through a predetermined nip region and applying pressure, and fixing the unfixed toner image on the recording sheet. In the device
A rotating body that is driven to rotate, an endless belt that forms a nip region in which a recording sheet is sandwiched between the rotating body and the surface is relatively pressed against the rotating body, and circulates following the rotation of the rotating body; and A fixing device having a heating means for heating the nip region;
The endless belt is
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
It has a reduced diameter part where the outer diameter is gradually reduced from the maximum outer diameter part toward each of both edges.

  The image forming apparatus of the present invention is provided with a fixing device that suppresses the occurrence of paper wrinkles and prevents the endless belt surface from being worn and the edge of the endless belt from being damaged.

The image forming method of the present invention that solves the above-described object is to transfer a toner image carried on a toner image carrying body carrying a toner image onto a recording sheet, and to transfer the recording sheet onto which the toner image is transferred. Image formation in which an image is formed on the recording sheet by applying heat to the unfixed toner image by passing through a predetermined nip region and applying pressure, and fixing the unfixed toner image on the recording sheet. In the method
A toner image carrying step for carrying a toner image on the toner image carrier;
A transfer step of transferring the toner image carried on the toner image carrier onto a recording sheet;
A toner image is formed in a nip region that is heated between a rotating member that rotates and a surface that is relatively pressed against the rotating member and that circulates following the rotation of the rotating member. A fixing step for fixing the unfixed toner image to the recording sheet by applying heat and pressure to the unfixed toner image transferred to the recording sheet by passing the recording sheet onto which the toner image has been transferred. Have
The fixing step includes, as the endless belt, a maximum outer diameter portion having a maximum outer diameter provided between each edge and a center portion in the width direction orthogonal to the circulation direction, and both edges from the maximum outer diameter portion. This is a step of fixing the unfixed toner image onto the recording sheet by using one having a reduced diameter portion whose outer diameter gradually decreases toward each.

  According to the image forming method of the present invention, in the fixing step, the generation of paper wrinkles is suppressed and the endless belt surface is prevented from being worn and the edge of the endless belt is damaged.

  The toner image carrier here may be a photoconductor or an intermediate transfer member.

In the first endless belt manufacturing method of the present invention that solves the above-described object, the surface is relatively pressed against a rotating member that is rotationally driven, and a nip region is formed between which the recording sheet is sandwiched. In the method of manufacturing an endless belt that circulates following the rotation of the rotating body,
The maximum outer diameter portion provided between each edge and the central portion in the width direction perpendicular to the circulation direction, and the outer diameter gradually decreases from the maximum outer diameter portion toward each edge. An annular body forming step of forming an annular body on the surface of the core body having a reduced diameter portion, the outer peripheral shape of which follows the shape of the surface;
And a removing step of removing the annular body formed on the surface of the core body from the core body.

Here, in the first endless belt manufacturing method, the annular body forming step is a step of applying a coating liquid to the surface of the core body and drying the coating liquid applied to the surface of the core body. Or you can
In the annular body forming step, an outer diameter of the core body is approximately uniform in the axial direction and the sleeve that shrinks when heated is heated, the sleeve that is extrapolated to the core body is heated, and the sleeve It may be a step of shrinking the sleeve until the inner peripheral surface is in contact with the surface of the core.

In the second endless belt manufacturing method of the present invention that solves the above-described object, a surface is relatively pressed against a rotating member that is rotationally driven, and a nip region is formed between which the recording sheet is sandwiched. In the method of manufacturing an endless belt that circulates following the rotation of the rotating body,
By supplying the solution toward the surface of the core having a cylindrical surface whose outer diameter is substantially uniform in the axial direction and changing the supply amount of the solution, both the edges and the circulation direction are provided on the surface. A maximum outer diameter portion having a maximum outer diameter and a reduced diameter portion having an outer diameter gradually decreasing from the maximum outer diameter portion toward each of both edges. An annular body forming step of forming an annular body having,
And a removing step of removing the annular body formed on the surface of the core body from the core body.

  Here, in the second endless belt manufacturing method, the annular body forming step rotates the core body around the axis while keeping the axis of the core body horizontal. A nozzle that discharges the solution on the surface and its core are moved relative to each other in the axial direction of the core, and at least one of the discharge amount of the nozzle and the relative moving speed of the nozzle and the core The maximum outer diameter portion with the largest outer diameter provided between the both edges and the central portion in the width direction orthogonal to the circulation direction and both edges from the maximum outer diameter portion And a step of forming an annular body having a reduced diameter portion whose outer diameter gradually decreases toward.

  The nozzle may be moved with respect to the core, or the core may be moved with respect to the nozzle.

  Further, in the second endless belt manufacturing method, in the annular body forming step, the core body is immersed in the solution so that the axis is vertical, and the core body is pulled up from the solution in the vertical direction. By moving the core body and the solution relative to each other and changing the relative moving speed of the core body and the solution, the edges of the core body are orthogonal to both edges and the circulation direction. An annular portion having a maximum outer diameter portion having a maximum outer diameter and a reduced diameter portion in which the outer diameter gradually decreases from the maximum outer diameter portion toward each of both edges. It may be a step of forming a body.

  The core may be pulled up from the solution in the vertical direction, or the solution may be pulled down from the core in the vertical direction.

  The endless belt of the present invention is manufactured by both the first endless belt manufacturing method and the second endless belt manufacturing method.

  According to the present invention, there is provided an endless belt that suppresses the generation of paper wrinkles and prevents the belt surface from being worn and the edge of the belt from being damaged. A fixing device for fixing, an image forming apparatus provided with the fixing device, an image forming method implemented in the image forming apparatus, and a method for manufacturing the endless belt can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 4 is a diagram showing a schematic configuration of a full-color image forming apparatus corresponding to an embodiment of the image forming apparatus of the present invention.

  The image forming apparatus 1 shown in FIG. 4 incorporates a roll-belt type fixing device 100 corresponding to an embodiment of the fixing device of the present invention. The image forming apparatus 1 also includes a photosensitive drum 10 and an intermediate transfer belt 20. The photosensitive drum 10 rotates clockwise. The intermediate transfer belt 20 is arranged so as to be stretched between a plurality of support rolls and to come into contact with the surface of the photosensitive drum 10. In the image forming apparatus 1, the primary transfer roll 40 is disposed at a position facing the photosensitive drum 10 with the intermediate transfer belt 20 interposed therebetween. The portion where the photosensitive drum 10 and the intermediate transfer belt 20 are in contact is the primary transfer position.

  A developing rotary 50 is disposed around the photosensitive drum 10 on the upstream side of the primary transfer position. The developing rotary 50 is provided with a developing device (not shown) that stores colored toners of black (BK), yellow (Y), magenta (M), and cyan (C). Although not shown, a charger, an optical writing unit, a cleaning device, and a charge eliminating device are disposed around the photosensitive drum 10.

  A bias roll 60 as a secondary transfer member is provided around the intermediate transfer belt 20 on the downstream side of the primary transfer position. Further, at a position facing the bias roll 60 with the intermediate transfer belt 20 interposed therebetween, A backup roll 70 is provided. In the image forming apparatus 1, the position sandwiched between the bias roll 60 and the backup roll 70 is the secondary transfer position, and the secondary transfer position includes a paper feed tray group 80 that stores sheets of each size. Paper to be supplied, paper placed on the manual feed table 81, an OHP sheet, or the like is sent.

  Hereinafter, the image forming apparatus 1 shown in FIG. 4 will be described in more detail with reference to FIG. 4 and FIG. 5 while adding a description of the image forming method performed in the image forming apparatus 1 shown in FIG.

  FIG. 5 is a flowchart showing an image forming method performed in the image forming apparatus shown in FIG.

  The image forming method shown in FIG. 5 corresponds to an embodiment of the image forming method of the present invention. The image forming apparatus 1 shown in FIG. 4 receives image signals of four colors of yellow, magenta, cyan, and black. When these image signals are input, in the image forming apparatus 1, the surface of the photosensitive drum 10 is uniformly charged by a charger, and then, according to the cyan image signal in the input image information. An electrostatic latent image is formed on the surface of the photosensitive drum 10 by irradiating the photosensitive drum 10 with laser light from the optical writing unit, and the electrostatic latent image formed on the surface of the photosensitive drum 10 is developed. Development is carried out by a developing device containing cyan toner provided in the rotary 50, and a cyan toner image is formed on the surface of the photosensitive drum 10 (cyan toner image forming step S1 shown in FIG. 5). Next, the cyan toner image on the photosensitive drum 10 is primarily transferred to the intermediate transfer belt at the primary transfer position (cyan toner image primary transfer step S2 shown in FIG. 5). From the surface of the photosensitive drum 10 after the cyan toner image is primarily transferred to the intermediate transfer belt 20, the residual toner is removed by the cleaning device, and the residual charge is removed by the static eliminator.

  Subsequently, this time, a magenta toner image is similarly formed on the surface of the photosensitive drum 10 (magenta toner image forming step S3 shown in FIG. 5), and this magenta toner image is transferred to the intermediate transfer belt at the primary transfer position. Then, the toner image is primarily transferred to the intermediate transfer belt 20 so as to overlap with the cyan toner image that has been primarily transferred first (Magenta toner image primary transfer step S4 shown in FIG. 5).

  Thereafter, a yellow toner image and a black toner image are sequentially formed (yellow toner image forming step S5 and black toner image forming step S7 shown in FIG. 5), and firstly transferred to the intermediate transfer belt 20 at the primary transfer position. The primary transfer is sequentially performed so as to overlap with the toner image (yellow toner image primary transfer step S6 and black toner image primary transfer step S8 shown in FIG. 5). By doing so, the intermediate transfer belt 20 carries toner images that are overlapped in the order of cyan, magenta, yellow, and black from the belt surface side. Therefore, the intermediate transfer belt 20 corresponds to an example of a toner image carrier referred to in the image forming apparatus of the present invention, and a series of steps from Step S1 to Step S8 shown in FIG. This corresponds to an example of an image carrying step.

  Subsequently, the overlapping toner image is secondarily transferred to a sheet at a secondary transfer position sandwiched between the bias roll 60 and the backup roll 70 (secondary transfer step S9 shown in FIG. 5). Therefore, the secondary transfer step S9 shown in FIG. 5 corresponds to an example of a transfer step in the image forming method of the present invention. Thus, the toner image is transferred to the paper, and the paper on which the toner image is transferred is sent to the fixing device 100. In the fixing device 100, a sheet carrying an unfixed toner image is passed through a predetermined nip region so that heat is applied to the unfixed toner image and pressure is applied to fix the unfixed toner image on the sheet (FIG. 5). Fixing step S10). The sheet on which the toner image is fixed is discharged to a discharge tray 90 provided in the image forming apparatus 1.

  FIG. 6 is a diagram showing a schematic configuration of a fixing device incorporated in the image forming apparatus shown in FIG.

  In FIG. 6, the recording paper P carrying the unfixed toner image T is conveyed from the right side to the left side in the drawing. A fixing device 100 shown in FIG. 6 is a roll-belt type fixing device provided with a fixing belt 120 corresponding to an embodiment of an endless belt of the present invention. Unlike the fixing device 200 shown in FIG. 1, the fixing device 100 employs a so-called free belt nip system in which a fixing belt is not stretched. A fixing device 100 shown in FIG. 6 is in contact with a heating roll 110 having a built-in heating source, an endless fixing belt 120, and an inner surface side of the fixing belt 120, and the fixing belt 120 along the surface of the heating roll 110. The pressure applying member 130 that presses the main portion constitutes a main part, and a nip region N is formed between the heating roll 110 and the fixing belt 120 to sandwich the recording paper P carrying the unfixed toner image T.

  The heating roll 110 has a cylindrical core 111 inside, and is rotationally driven in the direction of arrow B in the figure by a motor (not shown). An elastic layer 112 is formed on the surface of the core 111, and the surface of the elastic layer 112 is covered with a release layer 113. That is, the surface of the heating roll 110 is formed by the release layer 113.

  As the core 111, a metal cylinder having high thermal conductivity such as iron, aluminum, and stainless steel can be used. The outer diameter and thickness of the core 111 differ in strength and thermal conductivity depending on the material used. The core 111 in this embodiment is an iron cylinder having a thickness of 0.5 mm and an outer diameter of 25 mm.

  As a material of the elastic layer 112, a material having elasticity and high heat resistance is preferable. In particular, it is preferable to use an elastic material such as rubber or elastomer having a rubber hardness of about 25 to 40 ° (JIS-A hardness), and specific examples include silicone rubber and fluororubber. The thickness of the elastic layer 3 is preferably about 0.3 to 1.0 mm, although it depends on the rubber hardness of the material used. The elastic layer 112 in the present embodiment is made of silicone rubber having a thickness of 0.6 mm and a rubber hardness of 30 ° (JIS-A hardness).

  As the release layer 113, it is particularly preferable to use a fluororesin in consideration of release properties and wear resistance. As the fluororesin, fluororesins such as PFA (perfluoroalkyl vinyl ether copolymer resin), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer resin) can be used. From the viewpoint of workability, PFA is preferred. The thickness of the release layer 113 is preferably 5 to 50 μm. When the thickness of the release layer 113 is less than 5 μm, abrasion of the release layer 113 may occur due to friction between the end of the paper P in the width direction perpendicular to the conveyance direction and the heating roll 110. On the other hand, when the thickness exceeds 50 μm, the surface hardness of the release layer 113 is increased, and image quality defects such as gloss unevenness may appear. As a method for forming the release layer 113, any conventionally known method can be adopted. For example, a method of covering the tube may be used, or a resin to be formed is dissolved or dispersed in an appropriate solvent. An application method in which the liquid is applied by a dip coating method, a spray coating method, a roll coating method, a bar coating method, a spin coating method, or the like may be used. The release layer 113 in this embodiment is formed by covering the elastic layer 112 formed on the surface of the core 111 with a tubular PFA having a thickness of 30 μm.

  Inside the core 111, a halogen lamp 114 is disposed as a heating source. As long as the heating source heats the nip region N, for example, an external heating roll 260 for externally heating the heating roll 210 as shown in FIG. 1 or a support roll 221 as shown in FIG. It may be a heater lamp 2211 that is built in and heats the fixing belt 220. Further, the fixing belt 120 itself may also serve as a heating source by electromagnetic induction heating or the like. A temperature sensor 180 is disposed on the surface of the heating roll 110, and the temperature of this surface is measured. Then, the halogen lamp 114 is feedback-controlled by a temperature controller (not shown) based on the measurement signal of the temperature sensor 180, and the surface temperature of the heating roll 110 is adjusted to be substantially constant.

  The surface of the fixing belt 120 is pressed against the heating roll 110 and circulates in the direction of arrow C following the rotation of the heating roll 110. The fixing belt 120 is in contact with the heating roll 110 so as to be wound at a predetermined angle, and a nip region N is formed between the fixing belt 120 and the heating roll 110. The winding angle of the fixing belt 120 around the heating roll 110 is preferably about 15 to 45 ° so as to ensure a sufficiently wide (long) nip region, although it depends on the rotation speed of the heating roll 110. In the fixing belt 120 shown in FIG. 6, the shape and size of the pressure applying member 130 are designed so that the winding angle is 27 °. A more detailed description of the fixing belt 120 will be described later.

  The pressure applying member 130 includes a low-friction sheet 131, an elastic member 132 provided below the low-friction sheet 131, and a support frame 133 that supports them from below. The elastic member 132 is formed from the upper end of the support frame 133. It is arranged in a protruding state.

  The low friction sheet 131 is a sheet having a smaller frictional resistance than the elastic member 132 and is made of a low friction material that is hard and flexible. As the material of the low friction sheet 131, various materials such as metals, ceramics, and resins can be adopted. Specifically, polyethersulfone (PES), polybutylene terephthalate (heat resistant resin) In addition to PBT), liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), natural materials such as 6-nylon or 6,6-nylon, and materials obtained by adding carbon or glass fiber to these materials Can be used.

  The actual hardness of the surface of the low friction sheet 131 needs to be higher than the actual hardness of the surface of the heating roll 110 in order to deform the elastic layer 112 of the heating roll 110 and improve the releasability. The hardness is preferably 80 ° or more, more preferably 95 ° or more.

  The flexibility required for the low friction sheet 131 needs to be a level of flexibility that follows the bending of the heating roll 110 with almost no reaction force in the vicinity of the fixing set temperature. As a material physical property, it is preferable that it is 5 GPa or less in the bending elastic modulus in use temperature. However, it is not limited only to this value, and it is necessary to consider the mechanical rigidity such as thickness and side slits, that is, it is necessary to consider the entire part.

  As the elastic member 132, a long solid sheet material, a modified solid product, a modified tube product, a foamed rubber sheet, or the like can be used. Examples of the material include silicone rubber, fluoro rubber, urethane, natural rubber, SBR, IR, and the like. Can give. Note that a plurality of springs may be used as the elastic member 132 instead of the rubber member. The elastic member 132 is required to have sufficient flexibility. Specifically, the required hardness of the elastic member 132 is a range of about 10 to 70 degrees in terms of JIS-A hardness, preferably about 20 to 50 degrees, and more preferably about 30 to 50 degrees. preferable. If it is less than 10 °, the amount of deformation of the rubber becomes too large and the nip position becomes unstable, and if it exceeds 70 °, the hardness is too high to ensure sufficient flexibility. Further, the thickness of the elastic member 132 is not particularly limited, but the average thickness is preferably in the range of about 2 to 6 mm, and more preferably in the range of about 3 to 5 mm. In particular, the thickness of the protruding portion from the support frame 133 is preferably in the range of about 0.3 to 1.2 mm on average, and more preferably in the range of about 0.5 to 1.0 mm.

  The support frame 133 urges the entire pressure applying member 130 toward the axis of the heating roll 110 by a load from a spring (not shown). A belt traveling guide 134 is attached to the support frame 133 so as to restrict slack in the circulation direction of the fixing belt 120 and to rotate smoothly.

  Further, in the fixing device 100 shown in FIG. 6, a peeling unit 170 is provided on the downstream side of the nip region N in the rotation direction of the heating roll 110 in order to ensure higher sheet peeling properties. In the peeling means 170 shown in FIG. 6, the release sheet 171 is held by the holding member 172 in a direction (reverse) opposite to the rotation direction of the heating roll 110 with a slight gap provided on the surface of the heating roll 110. ing.

  The paper P carrying the unfixed toner image T is conveyed toward the nip region N of the fixing device 100. As the sheet P enters the nip region N and passes through the nip region N, the unfixed toner image T is applied with heat from the halogen lamp 114 and pressure acting on the nip region N. The image T is fixed on the paper P.

  Next, the fixing belt 120 shown in FIG. 6 will be described in detail. The fixing belt 120 shown in FIG. 6 has a laminated structure in which a plurality of layers are laminated in the thickness direction.

  FIG. 7 is a diagram schematically showing a cross section of the fixing belt shown in FIG.

  The fixing belt 120 shown in FIG. 7 is formed by laminating a base layer 1201, a heat-resistant elastic body layer 1202, and a surface layer 1203 in this order.

  The base layer 1201 shown in FIG. 7 may be a layer made of a thin metal film or a layer made of a heat-resistant resin that maintains a predetermined strength even when it receives heat from the halogen lamp 114 shown in FIG. . Examples of the heat resistant resin include a polyimide resin and a polyamide resin from the viewpoint of strength and dimensional stability at a high temperature, and a polyimide resin is more preferable in terms of film formability. The base layer 1201 made of polyimide is manufactured using a polyimide precursor solution. Examples of the manufacturing method include a centrifugal molding method in which a polyimide precursor solution is applied to the inner surface of a cylindrical body and dried while rotating, an inner surface coating method in which the polyimide precursor solution is developed on the inner surface of the cylindrical body, There is an outer surface coating method in which a solution is applied to the outer surface of a core body as shown in 91027.

  The thickness of the base layer 1201 is required to be 20 μm or more from the viewpoint of required strength in use (for belt breakage / wrinkle / buckling), and is preferably 200 μm or less from the viewpoint of flexibility and heat capacity. And 50 μm or more and 100 μm or less is more preferable.

  In the case where the base layer 1201 is a layer made of a thin metal film, the thickness is preferably 150 μm or less, more preferably 20 μm or more and 80 μm or less. Examples of the base layer 1201 made of a thin film metal material include a stainless steel belt and an endless nickel belt formed by electroforming. In the electroforming method, a metal is deposited on a conductive mother mold (electric mold, mold) by electroplating or electroless plating, and then the metal is peeled off from the mother mold to obtain a product. When the matrix is a metal, a surface treatment for peeling is performed, and when the matrix is a non-metal, a conductive treatment for plating is performed. According to this electroforming method, the shape of the matrix can be faithfully and accurately copied, and a highly accurate product can be obtained. The width, inner diameter, and the like of the endless electroformed nickel belt can be appropriately determined depending on the application, and are not particularly limited.

  The heat resistant elastic body layer 1202 is a layer that is more elastically deformed than the base layer 1201 and maintains a predetermined strength even when receiving heat from the halogen lamp 114 shown in FIG. As a material used for the heat resistant elastic body layer 1202, it is preferable to use silicon rubber or fluororubber from the viewpoint of heat resistance. From the viewpoint of being able to achieve both material hardness and rebound resilience, and from the viewpoint of film formability, silicone rubber, It is more preferable to use liquid silicone rubber (LSR). The thickness of the heat resistant elastic body layer 1292 is preferably 2 mm or less, and more preferably 0.5 mm or less. This is because the purpose of using a fixing belt instead of a roll is to save energy (shortening the warm-up time), and rubber such as silicone rubber has very poor thermal conductivity, and increasing the thickness makes the thermal efficiency worse. It is.

  The surface layer 1203 is a layer constituting the surface of the fixing belt 120 and is made of a heat-resistant rubber such as a fluorine resin or silicone rubber. The surface layer 1203 is more releasable from both the paper and the toner image after fixing than the material constituting the base layer 1201, and has a predetermined strength even when receiving heat from the halogen lamp 114 shown in FIG. It is preferable to use a layer made of a heat-resistant material to be maintained. Examples of such heat-resistant materials having releasability include polytetrafluoroethylene (hereinafter referred to as “PTFE”), perfluoroalkyl vinyl ether copolymer (hereinafter referred to as “PFA”), tetrafluoroethylene hexafluoride. And propylene copolymer (hereinafter referred to as “FEP”). When a fluororesin is used for the surface layer 1203, the thickness is preferably 10 μm or more and 100 μm or less, and more preferably 15 μm or more and 50 μm or less. This is because 10 μm is necessary in consideration of abrasion due to paper passing, and the material of the fluororesin used for the surface layer is expensive, and the coating operation for forming the layer needs to be applied twice as the film becomes thicker. There is a problem such as becoming, and it is preferable to suppress it to 100 μm or less.

  In addition, by providing the release agent coating apparatus 240 for applying the release agent oil shown in FIG. 1, higher releasability can be ensured.

  Next, the shape of the fixing belt 120 shown in FIG. 6 will be described.

  FIG. 8 is a sectional view of the entire fixing belt shown in FIG.

  In FIG. 8, the width direction of the fixing belt 120 is the left-right direction in the figure, and this width direction is hereinafter sometimes referred to as the axial direction. Further, FIG. 8 shows the paper P passing through the nip region N shown in FIG. In FIG. 8, the passage direction of the paper P is a direction perpendicular to the paper surface, and the left-right direction in the figure corresponds to the width direction of the paper perpendicular to the transport direction.

  FIG. 8 schematically shows a cross-section of the fixing belt 120 along the axial direction of the fixing belt 120. The fixing belt 120 shown in FIG. A regulating member 550 provided in the fixing device 100 shown is shown. The restricting member 550 is supported by the frame 505 of the fixing device 100 and prevents the circulating fixing belt 120 from moving in the axial direction by entering the both ends 121 in the axial direction of the fixing belt 120. .

  The fixing belt 120 shown in FIG. 8 has a width longer than the length of the paper P in the width direction, and both edges P1 in the width direction of the paper P shown in FIG. It is located between the center part 122 in the width direction. In the fixing belt 120 shown in FIG. 8, a portion slightly from the center than both edges P1 in the width direction of the paper P is the maximum outer diameter portion 126 having the maximum outer diameter. Further, the fixing belt 120 is provided with a reduced diameter portion 127 in which the outer diameter is gradually reduced from the maximum outer diameter portion 126 toward the respective edges 123. That is, the fixing belt 120 shown in FIG. 8 has a uniform thickness, the maximum outer diameter portion 126 is the most swelled shape, and both edges 123 are swelled. Further, in the fixing belt 120 shown in FIG. 8, the outer diameter gradually decreases from the maximum outer diameter portion 126 toward the center portion 122 in the width direction, and the outer diameter is the smallest at the center in the width direction.

Here, assuming that the outer diameters of both edges 123 of the fixing belt 120 are R1, the outer diameter of the maximum outer diameter portion 126 is R2, and the outer diameter that is the smallest at the center in the width direction is R3, the fixing shown in FIG. Belt 120 is
R2>R1> R3 Formula (A)
The relationship represented by the above formula (A) is satisfied.

  The relationship of R1> R3 in the above formula (A) may be R1 = R3.

  The difference between the outer diameter of the maximum outer diameter portion 126 that is the smallest in the width direction R2 and the outer diameter R3 is preferably 15 μm or more in order to sufficiently exhibit the effect of preventing paper wrinkles described later. . However, if the difference in the outer diameter is too large, on the contrary, a speed difference in the width direction is generated in the paper conveyance speed, and there is a case where the paper wave / image unevenness called loose is likely to occur. The maximum allowable limit of the outer diameter difference varies depending on the outer diameter of the fixing belt, the specifications of the fixing device, and the use conditions of the image forming apparatus (paper used, printing speed, etc.).

  The fixing belt 120 shown in FIG. 8 has a base layer 1201 as an inner peripheral surface of the fixing belt 120 with the thicknesses of the base layer 1201, the heat resistant elastic body layer 1202, and the surface layer 1203 shown in FIG. 120 is shaped from the back side. As a method for forming the shape from the back side of the base layer 120, in the case of a fixing belt made of heat-resistant resin, it can be realized by the following method.

  In the case where the heat-resistant resin is a polyimide resin, a polyimide precursor solution is prepared by preparing a core having an outer diameter obtained by subtracting a desired film thickness from the outer diameters of R1, R2, and R3 described above. By applying the precursor solution on the outer surface of the core and baking it, a fixing belt having the above-described outer diameter shapes of R1, R2, and R3 can be obtained. As another method, the polyimide precursor is applied and fired on the outer surface of the core body having a constant outer diameter in the axial direction by the above-mentioned outer surface coating method, or the substantially constant inner diameter is set by the inner surface coating method. The polyimide endless belt having a substantially constant outer diameter and film thickness was obtained by coating and firing on the inner surface of the core body, and then had the same outer diameter shape as that of R1, R2, and R3 described above. By extrapolating to the core body and then heating again to about the firing temperature, the endless belt contracts and adheres closely to the core body, and a fixing belt having the above-described outer diameter shapes of R1, R2, and R3 can be obtained.

  The shape of the fixing belt 120 shown in FIG. 8 described above is a shape that can easily make a speed difference in the width direction to the conveyance speed of the paper sandwiched in the nip region N (see FIG. 6). That is, each end portion in the width direction of the paper P sandwiched in the nip region N is more firmly between the heating roll 110 (see FIG. 6) and the maximum outer diameter portion 126 than the central portion in the width direction of the paper P. Even if the fixing belt 120 does not easily follow the rotation of the heating roll 110, there is a speed difference in the width direction between the central portion and both end portions of the paper P in the width direction. Prone to occur. For this reason, the paper P is pulled in the width direction, and the occurrence of paper wrinkles is suppressed. Further, the shape of the fixing belt 120 shown in FIG. 8 is also a shape that suppresses a difference in speed in the width direction from the circulation speed of the fixing belt 120. That is, both end portions in the width direction of the paper P are in contact with the maximum outer diameter portion 126, and the area of the maximum outer diameter portion 126 is a sheet that moves in the area of the fixing belt 120 in contact with the paper. In this region, slip in the circulation direction is unlikely to occur with the paper P. For this reason, it is possible to prevent the surface of the fixing belt 120 from being worn. Further, the edge 123 of the fixing belt 120 is not easily expanded by the reduced diameter portion 127, and the edge 123 of the fixing belt 120 is prevented from being pressed against the regulating member 550 and being damaged.

  Next, a modification of the fixing belt 120 shown in FIG. 6 will be described.

  9 is a cross-sectional view of the whole belt showing a first modification of the fixing belt shown in FIG. 6, and FIG. 10 is a cross-sectional view of the whole belt showing a second modification of the fixing belt shown in FIG.

  9 and 10 also show the fixing belts 600 and 700 and the paper P in the same manner as in FIG. That is, FIG. 9 and FIG. 10 each schematically show a state in which the fixing belts 600 and 700 are sectioned along the axial direction of the fixing belts 600 and 700. 9 and 10 also show sensors 560 provided in the fixing device on both sides in the axial direction of the fixing belts 600 and 700, respectively. The sensor 560 detects that the circulating fixing belts 600 and 700 have moved in the axial direction from the normal position, and when the sensor 560 detects the movement of the fixing belts 600 and 700 in the axial direction. The fixing belts 600 and 700 are returned to their normal positions by a mechanism (not shown).

  In both the fixing belt 600 shown in FIG. 9 and the fixing belt 700 shown in FIG. 10, there are maximum outer diameter portions 606 and 706 having the maximum outer diameter between both edges 603 and 703 and the width direction centers 602 and 702. Also provided are reduced diameter portions 607 and 707 in which the outer diameter gradually decreases from the maximum outer diameter portions 606 and 706 toward both edges 603 and 703, respectively. In addition, both the fixing belts 600 and 700 satisfy the relationship represented by the above formula (A).

  The fixing belts 600 and 700 shown in FIGS. 9 and 10 are different from the fixing belt 120 shown in FIG. 8 in that straight portions 604 and 704 having an outer diameter substantially constant in the width direction are provided at the center in the width direction. There is in point. These fixing belts 600 and 700 are easily manufactured by the straight portions 604 and 704.

  Further, the fixing belt 600 shown in FIG. 9 has a uniform thickness, whereas the fixing belt 600 shown in FIG. 10 has a non-uniform thickness in the width direction. Further, the fixing belt 600 shown in FIG. 9 has a different inner diameter in the width direction, whereas the fixing belt 700 shown in FIG. 10 has a substantially constant inner diameter in the width direction. In a fixing belt made of a thin film metal, it is difficult to form a shape including the inner peripheral surface side of the belt. Therefore, it is preferable to make the inner diameter substantially constant. As shown in FIG. 7, the fixing belt 700 shown in FIG. 10 is also formed by laminating a base layer, a heat-resistant elastic body layer, and a surface layer in the order of description in the thickness direction. In the fixing belt 700 shown in FIG. 10, the maximum outer diameter portion 706 is the thickest portion, and the inner diameter of the base layer is substantially constant in the width direction. A maximum outer diameter portion 706 shown in FIG. 10 is a portion formed by increasing the thickness of any one of the plurality of layers. By doing so, even if a speed difference in the width direction occurs in the circulation speed of the fixing belt 700 shown in FIG. 10, the maximum outer diameter portion 706 is hardly worn and the product life of the fixing belt is extended. Further, the reduced diameter portion 707 shown in FIG. 10 is a portion formed by gradually reducing the thickness of any one of the plurality of layers toward both edges 703.

  As in the fixing belt 700 shown in FIG. 10, in order to change the film thickness of the base layer, the heat-resistant elastic body layer, and the surface layer while making the inner diameter of the base layer substantially constant, a known coating technique is used. It can be realized by changing the amount of adhesion at the time.

  The maximum outer diameter portion may have a constant width in the width direction between the edge of the fixing belt and the width direction central portion 122. In addition, recently, a fixing device using electromagnetic induction heat generation has been developed. However, the fixing belt of the present embodiment may have an electromagnetic induction heat generation layer such as copper or nickel. Furthermore, the fixing belt of this embodiment can also be applied to a fixing device shown in FIG. 1 in which the fixing belt is stretched by a support roll.

  Next, a method for manufacturing the fixing belt 120 shown in FIG. 8 and the fixing belt 600 shown in FIG. 9 will be described.

  Here, first, the maximum outer diameter portion provided between each of the edges and the center portion in the width direction orthogonal to the circulation direction, and the outer diameter from the maximum outer diameter portion toward the both edges respectively. A core body (hereinafter referred to as a special core body) having a diameter-reduced portion that is gradually reduced is prepared, and an annular body whose outer peripheral shape follows the shape of the surface is formed on the surface of the special core body ( Annular body forming step). Next, the annular body formed on the surface of the special core is removed from the special core (removal process). By doing so, the fixing belt 120 shown in FIG. 8 and the fixing belt 600 shown in FIG. 9 are manufactured.

  Next, a method for manufacturing the fixing belt 700 shown in FIG. 10 will be described.

In order to manufacture the fixing belt 700 shown in FIG. 10, a core body (hereinafter referred to as a general core body) having a cylindrical surface whose outer diameter is substantially uniform in the axial direction may be prepared. Then, by supplying the solution toward the surface of the general core and changing the supply amount of the solution, it is provided on the surface of the general core between each of the edges and the central portion in the width direction orthogonal to the circulation direction. Forming an annular body having a maximum outer diameter portion having a maximum outer diameter and a reduced diameter portion in which the outer diameter gradually decreases from the maximum outer diameter portion toward both edges (annular body forming step). . Next, the annular body formed on the surface of the general core is removed from the general core (removal process).
(Example)
Hereinafter, the embodiment of the present invention will be described in more detail using examples. The present invention is not limited to the following examples.
Example 1
As a polyimide (PI) precursor solution, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine were synthesized in N-methylpyrrolidone and had a solid content concentration of 18% ( A solution having a viscosity of about 20 Pa · s was prepared.

  An element tube having an outer diameter of 70 mm and a length of 400 mm was heated at 350 ° C. for 10 minutes and allowed to cool naturally, and then the surface was cut to have a minimum outer diameter Rs = 67.9 mm with a width of 70 mm at the center in the axis direction. A portion is formed so that the outer diameter linearly increases from both ends of the minimum outer diameter portion toward both ends of the core body, and the maximum outer diameter Rm = 60 mm from both ends of the raw tube. After forming 68.0, the outer diameter was linearly decreased toward both ends of the raw tube, and an aluminum cylinder having a diameter of 67.93 mm at both ends of the raw tube was obtained. Next, this aluminum cylinder is roughened to Ra 0.8 μm by blasting with spherical alumina particles, and then a silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the surface. The core was subjected to baking treatment at 300 ° C. for 1 hour. This core corresponds to an example of the above-described special core.

  Subsequently, a spin coating process was performed.

  FIG. 11 is a diagram illustrating a state in which the spin coating process is performed.

  In the spin coating process here, the core body 80 was rotated at 120 rpm with the axial direction of the core body 80 being horizontal. The spatula 81 is made of polyethylene having a width of 20 mm and a thickness of 1 mm, and has elasticity. This was pressed against the core body 80, and the PI precursor solution was discharged from the container 82 through a nozzle 83 having a diameter of 4 mm at an air pressure of 0.4 MPa and a discharge amount of 20 ml / min. When the PI precursor solution passed through the spatula 81, the spatula 81 was expanded and a gap was created between the spatula 81 and the core body 80. Next, the nozzle 83 and the spatula 81 were applied by moving from one end of the core body 80 to the other end at a speed of 180 mm / min. Under this condition, the nozzle 83 and the spatula 81 were moved by 1.5 mm per rotation of the core. When discharging the PI precursor solution, 5 mm of uncoated portions were provided at both ends of the core body 80.

  Subsequently, the drying process was implemented. In this drying step, the core was put in a drying furnace at 100 ° C. while rotating at 20 rpm. When taken out after 60 minutes, a PI precursor film having a thickness of about 150 μm was formed, and the residual solvent was about 40% (mass ratio). In this state, the film could not be removed from the core. In addition, there was a gap between the end film and the core due to slight contraction of the end film.

  Next, a conical lid was attached to one end of the core, and a 20 mm wide polyester tape (trade name: No. 31B, manufactured by Nitto Denko) was applied over the entire circumference to cover the exposed portion of the core and the PI precursor film. .

  Next, a water-based fluororesin dispersed coating process was performed.

  FIG. 12 is a diagram illustrating a state in which the water-based fluororesin dispersion coating process is performed.

  In the water-based fluororesin-dispersed coating step here, the water-based fluororesin-dispersed coating 91 (concentration 55 wt%, viscosity 600 mPa · s, containing ethanol in addition to water as a solvent), as shown in FIG. A 480 mm coating tank 92 was placed. As shown in FIG. 12, an external tank 93 having a capacity equal to or larger than the volume of the core body 80 to be coated is provided outside the coating tank 92, and receives the fluororesin dispersion overflowed from the upper part of the coating tank 92. The reservoir 94 is supplied from the external tank 93 to the coating tank 92 by the pump 94 to circulate the fluororesin dispersion. In this way, it is possible to reduce the total amount of the expensive fluororesin dispersion rather than providing another paint tank outside and circulate, as well as foaming due to the overflow of the fluororesin dispersion overflowing from the top of the coating tank. There is also an advantage that is difficult to occur. A viscosity adjusting liquid adding device 96 for adjusting the viscosity of the fluororesin dispersion liquid was added so as to be dropped into the circulation path 95 or the external tank 93, and a filter 97 for removing foreign substances was further added.

This water-based fluororesin-dispersed paint has an average particle size of high melt viscosity (27.0 × 10 ^{4 to} 29.0 × 10 ⁴ poise; 2.7 × 10 ^{4 to} 2.9 × 10 ⁴ Pa · s: 380 ° C.). Of an average particle diameter of 18 μm PFA powder having a diameter of 0.2 μm PFA and a low melt viscosity (3.0 × 10 ⁴ v5.0 × 10 ⁴ poise; 0.3 × 10 ^{4 to} 0.5 × 10 ⁴ Pa · s: 380 ° C.) It is a mixed type (PFA powder / PFA fine particle = 37/63) fluororesin solution. As a solvent, in addition to water 33% by mass (dispersion is 100% by weight), ethyl alcohol 0.5% by mass (same as above), t- Butanol 3.5 mass%, solid content of fluororesin is 51 mass% (same), surfactant 2 mass% (same), thickener 5 mass% (same). Here, 4% by mass (same as above) of barium sulfate (manufactured by Sakai Chemical Co., Ltd .: BMH-60: average particle size of 5 μm, large particles of 15 μm or more is 2% by mass or less) is added to the dispersion. Using. Although barium sulfate particles are added here, carbon particles or mica powder can be added depending on the purpose.

  At the upper part of the coating tank 92, an annular air blower 98 for annularly blowing an air flow of 5 m / min toward the upper 45 ° was attached to promote drying of the coating film. When the concentration of the fluororesin dispersion increases due to evaporation of the solvent, a mixture of water and volatile solvent at a certain ratio (here, the ratio of water 5 to ethanol 5) is used for viscosity adjustment. Added and adjusted with the liquid addition device 96.

  The core body 80 was made vertical in the coating tank 92, and the upper PI precursor film was immersed by leaving 15 mm. Next, while applying an air flow, the core body 80 was pulled up at a uniform speed of 0.15 m / min to form a PFA coating film.

  After the completion of the pulling, the polyester tape was removed, and the lower lid was removed, followed by drying at 80 ° C. for 10 minutes.

  Next, a heating and firing step was performed. In this heating and baking step, heating was performed at 150 ° C. for 20 minutes, 220 ° C. for 20 minutes, and 380 ° C. for 40 minutes to form a PI resin film, and the PFA coating film was baked. A series of processes from the spin coating process to the heating and firing process corresponds to an example of the annular body forming process using the special core described above, and by performing each process so far, the outer peripheral shape is the core surface. An annular body along the shape was formed on the surface of the core body.

  After the annular body cooled to room temperature, a removal process was performed, and the annular body was removed from the core body. A fixing belt having a shape as shown in FIG. 9 having a length of 340 mm and a PFA layer having a thickness of 35 μm on a PI resin endless belt having a thickness of 80 μm is obtained by cutting both ends of the annular body removed from the core body by 30 mm. Obtained. This fixing belt is provided with a maximum outer diameter portion at a position 40 mm in the width direction from both edges of the fixing belt, and the outer diameter R2 of this maximum outer diameter portion was 68.20 mm. The outer diameter R1 of each edge of the fixing belt was 68.17 mm, and the outer diameter R3 of the straight portion at the center in the width direction of the fixing belt was 68.10 mm.

This fixing belt is set in a fixing device having the same configuration as the fixing device in which the fixing belt is stretched by a support roll shown in FIG. 1, and double-sided printing is performed using P paper A3 size (manufactured by Fuji Xerox Office Supply). However, no paper wrinkle occurred, and even after 300,000 sheets were passed through this paper passing test, the wear at the end of the fixing belt was small, and the decrease in film thickness at the end of the paper passing was 9 μm ( The wear rate is 0.030 μm / Kpv), and the film thickness of the surface layer remains sufficiently. Even when a sheet having a width larger than the A3 sheet passing width is passed, the glossiness of the image is not visually changed and is a streak-like shape. There was no image quality defect. In addition, during the paper passing test, there is no abnormal noise due to buckling failure of the edge of the fixing belt, and even if the edge of the fixing belt after the paper passing test is visually observed, the belt edge is spread. There wasn't.
(Example 2)
An element tube with an outer diameter of 70 mm and a length of 400 mm is heated at 350 ° C. for 10 minutes and naturally cooled, and then the surface is cut to prepare a cylindrical body with an outer diameter (φ68.2 mm) substantially uniform in the axial direction. Then, the polyimide (PI) precursor solution is applied to the outer surface of the cylindrical body in the same manner as in Example 1, dried, and the fluororesin dispersion is applied and dried. A PI resin film was formed by heating for 20 minutes, 220 ° C. for 20 minutes, and 340 ° C. for 30 minutes, and the PFA coating film was baked. After cooling to room temperature, the PFA coating film was removed from the cylindrical body to obtain a sleeve having an outer diameter of 68.5 mm. This sleeve contracts when heated. Thereafter, the sleeve was extrapolated to the following core body, heated at 380 ° C. for 40 minutes, and contracted until the inner peripheral surface of the sleeve was in contact with the surface of the core body (extrapolation step). The core used here has a length of 400 mm, and the shape thereof is provided with a portion having a width of 60 mm and a minimum outer diameter Rs = 67.9 mm in the central portion in the axial direction of the core, and the core from both ends of the minimum outer diameter portion. Give the shape so that the outer diameter increases almost linearly toward both ends of the body, and after forming the maximum outer diameter Rm = 68.0 mm at a position 70 mm from both ends of the core, toward the both ends of the core Thus, this corresponds to an example of the above-described special core in which the outer diameter is linearly reduced and Re = 67.95 mm at both ends of the core. The extrapolation process performed here corresponds to an example of the annular body forming process using the above-described special core body, and by performing this extrapolation process, the annular body whose outer shape conforms to the shape of the core body surface. Was formed on the surface of the core.

  Then, the whole core was cooled, a removal process was performed, and the annular body was removed from the core. The length of the annular body removed from the core body was cut by 30 mm to a length of 340 mm, and a fixing belt having a shape shown in FIG. 9 having a 35 μm thick PFA layer on an 80 μm thick PI resin endless belt was obtained. . This fixing belt is provided with a maximum outer diameter portion at a position 40 mm in the width direction from both edges of the fixing belt, and the outer diameter R2 of this maximum outer diameter portion was 68.20 mm. The outer diameter R1 of each edge of the fixing belt was 68.16 mm, and the outer diameter R3 of the straight portion at the center in the width direction of the fixing belt was 68.10 mm.

This fixing belt was set in a fixing device having the same configuration as the fixing device on which the fixing belt shown in FIG. 1 is stretched, and double-sided printing was performed using P paper A3 size (manufactured by Fuji Xerox Office Supply). No wrinkles occurred, and even after passing 300,000 sheets in this paper passing test, the wear at the end of the fixing belt was small, and the film thickness reduction at the end of the paper passing was 10 μm (a wear rate of 0. 0 mm). 034 μm / Kpv), and the film thickness of the surface layer remains sufficiently. Even when a paper having a width larger than the A3 paper passing width is passed, the glossiness of the image is not visually changed and no streak-like image quality defect is observed. It was outbreak. In addition, during the paper passing test, there is no abnormal noise due to buckling failure of the edge of the fixing belt, and even if the edge of the fixing belt after the paper passing test is visually observed, the belt edge is spread. There wasn't.
(Example 3)
An element tube having an outer diameter of 70 mm and a length of 400 mm was heated at 350 ° C. for 10 minutes and naturally cooled, and then the surface was cut to prepare a core body having an outer diameter of φ67.9 mm. The outer diameter of the core is uniform in the axial direction, and the core corresponds to an example of the above-described general core. A polyimide (PI) precursor solution was applied to the outer surface of the core body in the same manner as in Example 1 and dried, followed by dip coating with a fluororesin dispersion (dip coating step). In this dip coating process, the core body was made vertical in the coating tank 92 shown in FIG. 12, and the upper PI precursor film was left so as to leave 15 mm. Next, while the air flow is applied, the core body starts to be pulled up at a speed of 0.15 m / min at first, and the pulling speed is gradually increased to 0.4 m / min until the core body comes out of the 70 mm coating tank liquid surface. The pulling speed is increased, and then the pulling speed is gradually decreased until the core comes out of the liquid surface of the 170 mm coating tank, and the pulling speed is increased at a constant speed of 0.1 m / min from 170 mm to 230 mm. Gradually raise the pulling speed until it reaches a point where the pulling speed becomes 0.4 m / min at 330 mm, gradually lowering the pulling speed until the core is completely lifted from the coating tank, and at the lower end of the core, the pulling speed is increased. A PFA coating film was formed while changing the pulling speed at a speed of 0.15 m / min. When the pulling speed of the core body is changed in this way, the supply amount of the solution supplied toward the surface of the core body changes. After the completion of the pulling, the polyester tape was removed, and the lower lid was removed, followed by drying at 80 ° C. for 10 minutes.

  Next, as a heating and baking step, heating was performed at 150 ° C. for 20 minutes, 220 ° C. for 20 minutes, and 380 ° C. for 40 minutes to form a PI resin film, and the PFA coating film was baked. A series of steps from applying and drying the PI precursor solution to this heating and firing step corresponds to an example of the annular body forming step using the above-described general core, and the core is obtained by performing each step so far. An annular body was formed on the body surface.

  After the annular body cooled to room temperature, a removal process was performed, and the annular body was removed from the core body. A fixing belt having a shape shown in FIG. 10 having a length of 340 mm and a PFA layer on an 80 μm thick PI resin endless belt was obtained by cutting both ends of the annular body removed from the core body by 30 mm. The film thickness of the PFA layer of this fixing belt was 25 μm at the straight portion at the center in the width direction, 35 μm at each edge, and 45 μm at a position 40 mm from the both edges of the belt in the width direction. The inner diameter of the fixing belt is uniform, and by providing a film pressure distribution in the width direction of the PFA layer as described above, the maximum outer diameter portion is provided at a position 40 mm in the width direction from both edges of the fixing belt. Yes. That is, the position where the width of the PFA layer is 40 mm from both edges of the fixing belt is the thickest part of the PFA layer. The outer diameter R2 of the maximum outer diameter portion is 68.19 mm, the outer diameter R1 of each edge of the fixing belt is 68.17 mm, and the outer diameter R3 of the straight portion at the center in the width direction of the fixing belt is 68.15 mm. Met.

This fixing belt was set in a fixing device having the same configuration as the fixing device shown in FIG. 1, and double-sided printing was performed using P paper A3 size (manufactured by Fuji Xerox Office Supply Co.). Even after passing 300,000 sheets in the sheet passing test, the wear at the end of the fixing belt is small, and the film thickness reduction amount at the end of the sheet is 8 μm (wear rate 0.027 μm / Kpv). The film thickness of the surface layer also remained sufficiently, and even when a paper having a width larger than the A3 paper passing width was passed, the glossiness of the image was not visually changed and a streak-like image quality defect did not occur. In addition, during the paper passing test, there is no abnormal noise due to buckling failure of the edge of the fixing belt, and even if the edge of the fixing belt after the paper passing test is visually observed, the belt edge is spread. There wasn't.
Example 4
A core tube having an outer diameter of 32 mm and a length of 400 mm is heated at 350 ° C. for 10 minutes and naturally cooled, and then the surface is cut to obtain a core body having an outer diameter (φ29.9 mm) substantially uniform in the axial direction (described above) Corresponding to an example of a general core) was prepared, and a polyimide precursor solution was applied to the surface of the core by the same spin coating method as in Example 1 (rotary coating process). In this spin coating process, when the nozzle 83 shown in FIG. 11 is moved from one end of the core toward the other end, the discharge amount of the nozzle 83 is changed. That is, the polyimide precursor solution is first discharged from the nozzle 83 at a discharge amount of 22 ml / min, and the discharge amount is gradually increased so that the discharge amount becomes 25 ml / min when the nozzle 83 moves to the position of 70 mm. It was. Next, when the nozzle 83 moves to the position of 170 mm, the discharge amount is gradually decreased so that the discharge amount becomes 22 ml / min. The discharge amount until the nozzle 83 reaches the position of 230 mm from the position of 170 mm. Was kept constant at 22 ml / min. Subsequently, when the nozzle 83 moves to a position of 330 mm, the discharge amount is gradually increased so that the discharge amount becomes 25 ml / min. Finally, when the nozzle 83 reaches the other end of the core body, the discharge amount is increased. The discharge rate was gradually reduced to 22 ml / min. When the discharge amount of the polyimide precursor solution is changed in this way, the supply amount of the solution supplied toward the core surface changes. Note that the moving speed of the nozzle 83 may be changed. After the application was completed, drying was performed in the same manner as in Example 1 to obtain a PI precursor film.

  Next, an aqueous fluororesin dispersion is applied in the same manner as in Example 1, dried, and then heated and fired at 150 ° C. for 20 minutes, 220 ° C. for 20 minutes, and 340 ° C. for 30 minutes. The PI resin film was formed and the PFA coating film was baked. A series of steps from the spin coating step to the heating and firing step corresponds to an example of the annular body forming step using the above-described general core body, and the annular body is formed on the surface of the core body by carrying out each step so far. Been formed.

  After the annular body cooled to room temperature, a removal process was performed to remove the annular body from the core body. The both ends of the annular body removed from the core body were cut by 30 mm to make the length 340 mm, and a fixing belt having the shape shown in FIG. 10 having a PFA layer having a thickness of 35 μm on the PI resin endless belt was obtained. The film thickness of the PI resin endless belt corresponding to the base layer of this fixing belt is 80 μm at the straight portion at the center in the width direction, 90 μm at each edge, and 100 μm at the position 40 mm in the width direction from both edges of the belt. Met.

  As a result, the outer diameter R3 of the straight portion at the center portion in the width direction of the fixing belt is 30.15 mm, the outer diameter R1 at each edge is 30.17 mm, and the maximum outer diameter is 40 mm from both edges in the width direction. The outer diameter R2 of the diameter portion was 30.19 mm.

This fixing belt is set in a fixing device having the same configuration as the fixing device of the free belt nip method without stretching the fixing belt shown in FIG. 6, and double-sided printing is performed using P paper A3 size (manufactured by Fuji Xerox Office Supply). Although the paper wrinkle did not occur, even after 300,000 sheets were passed through this paper passing test, the wear at the end of the fixing belt was small, and the film thickness reduction at the end of the paper passing was 5 μm (Abrasion rate is 0.050 μm / Kpv), and the film thickness of the surface layer remains sufficiently. Even when a paper having a width larger than the A3 paper passing width is passed, the glossiness of the image is not visually changed and is a streak shape. No image quality defects occurred. In addition, during the paper passing test, there is no abnormal noise due to buckling failure of the edge of the fixing belt, and even if the edge of the fixing belt after the paper passing test is visually observed, the belt edge is spread. There wasn't.
(Example 5)
A core corresponding to an example of the same special core as the core used in Example 1 is prepared, and the same method as in Example 1 is applied, but the spin coating process is performed without applying the fluororesin. By doing so, only the PI film was formed.

  Thereafter, 95 parts by mass of polyol vulcanization type fluororubber G-702 (Daikin Kogyo Co., Ltd.) and 5 parts by mass of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd.) as a metal oxide are dissolved in a mixed solvent of MEK and MIBK. After adding 30 parts by mass of Lubron L-5F (manufactured by Daikin) as a low molecular weight tetrafluoroethylene resin fine particle and stirring and dispersing it well, the solution was applied to the surface of the PI film. Firing was performed to form a fluorine rubber layer having a thickness of 200 μm. A series of steps from the spin coating step to the fluororubber layer forming step corresponds to an example of the annular body forming step using the above-described special core, and by performing each step so far, the outer peripheral shape is An annular body along the shape of the core surface was formed on the core surface.

  After the annular body cooled to room temperature, a removal process was performed, and the annular body was removed from the core body. The fixing belt shown in FIG. 9 has a length of 340 mm by cutting both ends of the annular body removed from the core body to 340 mm, and has a 200 μm-thick fluororubber layer on an 80 μm-thick PI resin endless belt. Got. The outer diameter R3 of the straight portion at the center portion in the width direction of this fixing belt is 68.40 mm, the outer diameter R1 at each edge is 68.45 mm, and the maximum outer diameter portion is 40 mm from both edges in the width direction. The outer diameter R2 of this was 68.50 mm.

The fixing belt shown in FIG. 1 was set in a fixing device having the same configuration as the fixing device on which the fixing belt is stretched, and double-sided printing was performed using P paper A3 size (manufactured by Fuji Xerox Office Supply). No paper wrinkles occurred, and even after 300,000 sheets of this paper passing test were passed, there was little wear at the end of the fixing belt, and the decrease in film thickness at the end of the paper passing was 12 μm (wear rate 0) .040 μm / Kpv), and the film thickness of the surface layer remains sufficiently. Even when a sheet having a width larger than the A3 sheet passing width is passed, the glossiness of the image is not visually changed and a streak-like image quality defect is also observed. It did not occur. In addition, during the paper passing test, there is no abnormal noise due to buckling failure of the edge of the fixing belt, and even if the edge of the fixing belt after the paper passing test is visually observed, the belt edge is spread. There wasn't.
(Comparative Example 1)
A core tube having an outer diameter of 70 mm and a length of 400 mm is heated at 350 ° C. for 10 minutes and naturally cooled, and then the surface is cut to prepare a core body having an outer diameter (φ67.9 mm) substantially uniform in the axial direction. Then, a polyimide (PI) precursor solution was applied to the outer surface of the core body in the same manner as in Example 1, dried, a fluororesin dispersion was applied, dried, and heated and fired.

  After cooling to room temperature, the coating is removed from the core, and the length is 340 mm by cutting both ends by 30 mm, and a 35 μm thick PFA layer is provided on an 80 μm thick PI resin endless belt, and the outer diameter is approximately φ68. A 1 mm straight fixing belt was obtained. That is, this fixing belt has a uniform outer diameter in the width direction.

When this fixing belt is set in the fixing device shown in FIG. 1 and double-sided printing is performed using P paper A3 size (manufactured by Fuji Xerox Office Supply Co., Ltd.), a paper wrinkle is generated by 3%, and a sign of the occurrence of paper wrinkle. 10% of image unevenness at a high image density (a shape in which water droplets hang down) occurred. In addition, after passing 300,000 sheets in this paper passing test, the film thickness reduction amount at the end of the fixing belt to be passed becomes 25 μm (wear rate 0.080 μm / Kpv), and the film thickness of the surface layer is still Although it remained, when a paper having a width larger than the A3 paper passing width was passed, the image glossiness of the worn portion was changed and a streak-like image quality defect occurred. Thereafter, as a result of continuing the 100,000 sheet passing test, a part of the surface layer at the end of the fixing belt passing through the paper was worn away, and toner and paper dust adhered. Further, when the edge of the fixing belt after the paper passing test was visually observed, it was confirmed that the belt edge spread.
(Comparative Example 2)
Prepare the same core as the core used in Example 4, apply a polyimide (PI) precursor solution to the outer surface of the core in the same manner as in Example 1, dry, then apply a fluororesin dispersion, and dry The heating and baking step was performed.

  After cooling to room temperature, the film is removed from the core, and both ends are cut by 30 mm to make the length 340 mm, and the 35 μm thick PFA layer is provided on the 80 μm thick PI resin endless belt. A 1 mm straight endless belt was obtained. That is, as with the fixing belt of Comparative Example 1, this fixing belt also has an outer diameter that is uniform in the width direction.

When this fixing belt is set in a fixing device having the same configuration as the fixing device of the free belt nip type shown in FIG. 6 and double-sided printing is performed using P paper A3 size (manufactured by Fuji Xerox Office Supply Co., Ltd.), 6% of wrinkles occurred, and 12% of image unevenness (a shape in which water droplets drip) at a high image density, which was a sign of paper wrinkles, occurred. In addition, after passing 300,000 sheets in this paper passing test, the film thickness reduction amount at the end portion of the fixing belt to be passed becomes 22 μm (wear rate 0.070 μm / Kpv), and the film thickness of the surface layer is Although still remaining, when a paper having a width larger than the A3 paper passing width was passed, the image glossiness of the worn portion was changed, and a streak-like image quality defect occurred. Further, when the edge of the fixing belt after the paper passing test was visually observed, it was confirmed that the belt edge spread.
(Comparative Example 3)
An element tube having an outer diameter of 32 mm and a length of 400 mm was heated at 350 ° C. for 10 minutes and allowed to cool naturally, and then the surface was cut to have a minimum outer diameter Rs = 29.9 mm with a width of 70 mm at the center in the axis direction of the element tube. A portion is formed so that the outer diameter linearly increases from both ends of the minimum outer diameter portion toward both ends of the core body, and the maximum outer diameter Rm = 30.0 mm is set at both ends of the core body. A belt having a polyimide layer and a fluororesin layer was produced by the same production method as in Example 1 except that the formed aluminum cylinder was prepared.

  As a result, the fixing belt has a 35 μm thick PFA layer on an 80 μm thick PI resin endless belt, the outer diameter of the straight portion at the center in the width direction is 30.1 mm, and the outer diameters of both edges are 30.2 mm. Got. That is, the fixing belt is not provided with the reduced diameter portion shown in each of FIGS.

  When this fixing belt is set in a fixing device having the same configuration as the fixing device of the free belt nip type shown in FIG. 6, double-sided printing is performed using P paper A3 size (manufactured by Fuji Xerox Office Supply Co.). Did not occur. However, when 30,000 sheets were passed through this sheet passing test, the edge of the fixing belt spreads out, and overcoming the restriction member (see FIGS. 2 and 8) that restricts the movement of the fixing belt in the axial direction. Then, abnormal noise occurred. Further, the amount of decrease in the film thickness at the sheet passing end of the fixing belt at that time is 11 μm (abrasion rate 0.36 μm / Kpv). The wear rate was such that the surface layer was worn.

  From the above results, it was found that by using the endless belt of the present invention, the generation of paper wrinkles can be suppressed and the belt surface can be prevented from being worn and the belt edge can be prevented from being damaged.

It is a schematic block diagram which shows an example of the conventional roll-belt type fixing device. FIG. 2 is a cross-sectional view showing a belt proposed in Patent Document 2 as a fixing belt of the fixing device shown in FIG. 1. It is sectional drawing which shows the belt proposed in patent document 3 as a fixing belt of the fixing device shown in FIG. 1 is a diagram illustrating a schematic configuration of a full-color image forming apparatus corresponding to an embodiment of an image forming apparatus of the present invention. 5 is a flowchart showing an image forming method performed in the image forming apparatus shown in FIG. FIG. 5 is a diagram illustrating a schematic configuration of a fixing device incorporated in the image forming apparatus illustrated in FIG. 4. FIG. 7 is a diagram schematically showing a cross section of the fixing belt shown in FIG. 6. FIG. 7 is a cross-sectional view of the entire fixing belt shown in FIG. 6. FIG. 7 is a cross-sectional view of the entire belt showing a first modification of the fixing belt shown in FIG. 6. FIG. 7 is a cross-sectional view of the entire belt showing a second modification of the fixing belt shown in FIG. 6. It is a figure which shows a mode that the spin-coating process is implemented. It is a figure which shows a mode that the water-system fluororesin dispersion coating process is implemented.

Explanation of symbols

  1: image forming apparatus, 10: photosensitive drum, 20: intermediate transfer belt, 40: primary transfer roll, 50: development rotary, 60: bias roll, 70: backup roll, 80: paper feed tray group, 81: manual feed 90: discharge tray, 100: fixing device, 110: heating roll, 114: halogen lamp, 120, 600, 700: fixing belt, 1201: base layer, 1202: heat resistant elastic layer, 1203: surface layer, 121: Axial ends, 122: widthwise central part, 123: both edges, 126: maximum outer diameter part, 127: reduced diameter part, 130: pressure applying member, 170: peeling means, 550: regulating member, N: nip region

Claims (6)

In an endless belt that circulates following the rotation of the rotating body by forming a nip region in which the recording sheet is sandwiched between the rotating body and the surface relatively pressed against the rotating body.
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
An endless belt, comprising: a reduced diameter portion having an outer diameter that gradually decreases from the maximum outer diameter portion toward both edges. In a fixing device for fixing the unfixed toner image to the recording sheet by applying heat and pressure to the unfixed toner image by passing a recording sheet carrying the unfixed toner image through a predetermined nip region ,
Rotating body that rotates,
An endless belt that circulates following the rotation of the rotating body is formed by forming a nip area in which a recording sheet is sandwiched between the rotating body and a surface relatively pressed against the rotating body, and heating the nip area Heating means,
The endless belt,
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
A fixing device having a reduced diameter portion in which the outer diameter gradually decreases from the maximum outer diameter portion toward both edges. The toner image carried on the toner image carrier that carries the toner image is transferred onto a recording sheet, and the recording sheet on which the toner image has been transferred passes through a predetermined nip region to form an unfixed toner image. In an image forming apparatus for forming an image on the recording sheet by applying heat and pressure, and fixing the unfixed toner image on the recording sheet,
A rotating body that is driven to rotate, an endless belt that forms a nip region in which a recording sheet is sandwiched between the rotating body and the surface is relatively pressed against the rotating body, and circulates following the rotation of the rotating body; and A fixing device having heating means for heating the nip region;
The endless belt,
A maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a width direction central portion orthogonal to the circulation direction;
An image forming apparatus comprising: a reduced diameter portion having an outer diameter gradually reduced from the maximum outer diameter portion toward both edges. The toner image carried on the toner image carrier that carries the toner image is transferred onto a recording sheet, and the recording sheet on which the toner image has been transferred passes through a predetermined nip region to form an unfixed toner image. In an image forming method of forming an image on the recording sheet by applying heat and pressure, and fixing the unfixed toner image on the recording sheet,
A toner image carrying step for carrying a toner image on the toner image carrier;
A transfer step of transferring the toner image carried on the toner image carrier onto a recording sheet;
The toner image is transferred to a nip region formed between the rotating body that rotates and the surface of the endless belt that circulates following the rotation of the rotating body that is relatively pressed against the rotating body. A fixing step of fixing the unfixed toner image to the recording sheet by applying heat and pressure to the unfixed toner image transferred to the recording sheet by passing the recording sheet.
The fixing step includes, as the endless belt, a maximum outer diameter portion having a maximum outer diameter provided between each of the edges and a center portion in the width direction orthogonal to the circulation direction, and both edges from the maximum outer diameter portion. An image forming method comprising the step of fixing the unfixed toner image onto the recording sheet using a portion having a reduced diameter portion whose outer diameter gradually decreases toward each. In the method of manufacturing an endless belt that forms a nip region in which a recording sheet is sandwiched between the rotating body and a surface that is relatively pressed against the rotating body, and follows the rotation of the rotating body.
A maximum outer diameter portion having a maximum outer diameter provided between each edge and the central portion in the width direction orthogonal to the circulation direction, and the outer diameter gradually decreases from the maximum outer diameter portion toward each edge. An annular body forming step in which an outer peripheral shape forms an annular body along the shape of the surface on the surface of the core body having a reduced diameter portion;
A method for producing an endless belt, comprising: a step of removing an annular body formed on a surface of the core body from the core body. In the method of manufacturing an endless belt that forms a nip region in which a recording sheet is sandwiched between the rotating body and a surface that is relatively pressed against the rotating body, and follows the rotation of the rotating body.
By supplying a solution toward the surface of the core having a cylindrical surface whose outer diameter is substantially uniform in the axial direction and changing the supply amount of the solution, both edges and the circulation direction are supplied to the surface. A maximum outer diameter portion having a maximum outer diameter and a reduced diameter portion in which the outer diameter is gradually reduced from the maximum outer diameter portion toward both edges. An annular body forming step of forming an annular body having,
A method for producing an endless belt, comprising: a step of removing an annular body formed on a surface of the core body from the core body.

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