JP5998497B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus using the same.

  Conventionally, in the image forming apparatus, a toner image formed on a photosensitive drum is transferred to a recording medium directly or via an intermediate transfer member, and an unfixed toner image transferred onto the recording medium is fixed by a fixing device. By doing so, a permanent image is obtained.

  By the way, as a fixing device used in such an image forming apparatus, for example, JP 2005-221719 A, JP 2007-072275 A, JP 2008-224874 A, JP 2011-059372 A, and the like. As disclosed, various types using an endless fixing belt have been proposed.

  In the fixing device according to the above Japanese Patent Application Laid-Open No. 2005-221719, for the purpose of smoothly transporting the recording medium by preventing the fixing belt from slipping, and for reliably peeling the recording medium from the fixing belt, The driving force in the circumferential direction is transmitted from the end drive member, and the cross-sectional shape of the pressing member is different between the paper passing area when the maximum size recording medium is used and the both ends being the non-paper passing area. At both ends, the contact surface of the pressing member when pressed by the pressure roll has substantially the same curvature as the contact surface of the end driving member and the fixing belt. is there.

  Further, in the fixing device according to the above Japanese Patent Application Laid-Open No. 2007-072275, for the purpose of stably separating the recording paper from the belt member, a heat insulating functional layer that prevents heat conduction is provided on the surface of the cylindrical body made of rigid body. A fixing roll configured to be coated, a belt member stretched around the fixing roll, a belt member that heats the belt member, a tension roll that stretches the belt member, and a pressure roller that is arranged to press the fixing roll And a pressure member covered with an elastic layer.

  Further, the fixing device according to the above-mentioned Japanese Patent Application Laid-Open No. 2008-224874 is intended to prevent the fixing member from shaking and wrinkling, and an endless fixing member that fixes the developer on the recording medium by being heated, A drive transmission member that is attached to the outer sides of both ends and to which a rotational force is transmitted; a holding member that is attached to the inner sides of both ends of the fixing member so as to face the drive transmission member and holds the cross-sectional shape of the fixing member in a substantially circular shape; It is comprised so that it may be equipped with.

  In addition, the image forming method according to Japanese Patent Application Laid-Open No. 2011-059372 has an object to provide an image forming method in which a fixing device capable of fixing at a heating temperature lower than the conventional one and a specific toner are combined. The fixing device includes a fixing member heated by a heating source and a pressure member disposed in pressure contact with the fixing member, and the recording medium is placed in a fixing nip formed by pressure contact between the fixing member and the pressure member. A fixing device for fixing an unfixed image on a recording medium to the recording medium by passing the toner, wherein the linear velocity of the fixing member and the pressure member is at least partially different, and the toner has a gap whose major axis is 0.2 μm or more. And having a porosity of 2 to 50% is used.

JP 2005-221719 A JP 2007-072275 A JP 2008-224874 A JP 2011-059372 A

  By the way, the problem to be solved by the present invention is a fixing device capable of avoiding damage to the elastic body layer of the pressure rotating body even when the fixing pressure is increased, and an image forming apparatus using the same. It is to provide.

That is, the invention described in claim 1 includes a heated endless belt,
A rotating body having an elastic layer on the surface side and rotating with the recording medium sandwiched between the endless belt and having an edge of the maximum sheet passing area of the recording medium as a boundary. The outer diameter outside the end of the maximum sheet passing area is formed so as to become smaller toward the end, and the outer diameter inside the end of the maximum sheet passing area of the recording medium is changed from the end to the center. A pressure rotator formed to have a smaller diameter as it goes,
Wherein is arranged inside the endless belt, Bei give a pressing member for pressing the endless belt and the pressure rotating body,
The pressure rotator is a fixing device that is pressed against a region including a maximum sheet passing region and a non-sheet passing region of the pressing member .

According to a second aspect of the present invention, the pressure rotating body is formed such that the outer diameter outside the end of the maximum sheet passing area of the recording medium changes linearly as it goes to the end. The fixing device according to claim 1.

According to a third aspect of the present invention, the pressing member is connected to the pressing rotor as the outer diameter outside the end of the maximum sheet passing area of the recording medium goes to the end. The fixing device according to claim 1, wherein the fixing device is formed in a shape along a bending curve that is deformed by pressure contact.

According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the endless belt has a heat generating layer and is heated by electromagnetic induction.

The invention described in claim 5, wherein the endless belt has its opposite ends the tubular member is mounted to, claims 1 to 4, I characterized in that it is driven to rotate through the tubular member The fixing device according to any one of the above.

According to a sixth aspect of the present invention, an image holding body for holding a toner image;
Transfer means for transferring the toner image held on the image holding member to a recording medium directly or via an intermediate transfer member;
A fixing means for fixing the toner image transferred onto the recording medium by the transfer means;
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

According to the first aspect of the present invention, it is possible to avoid damaging the elastic body layer of the pressure rotating body even when the fixing pressure is increased.
In addition, according to the first aspect of the present invention, wrinkles can be prevented from occurring on the recording medium.
Furthermore, according to the first aspect of the present invention, it is possible to suppress the pressure contact force from fluctuating from the maximum sheet passing area to the non-sheet passing area of the pressure rotating body.

  According to the second aspect of the invention, the configuration of the end portion of the pressure rotating body can be simplified.

According to the third aspect of the present invention, it is possible to suppress the pressure contact force from fluctuating from the maximum sheet passing area to the non-sheet passing area of the pressure rotating body.

According to the invention described in claim 4 , the endless belt can be heated in a short time.

According to the invention described in claim 5 , the endless belt can be reliably rotated.

According to the invention described in claim 6 , the life of the fixing device can be extended, and a good image can be formed over a long period of time.

1 is a cross-sectional configuration diagram illustrating a fixing device according to a first embodiment of the present invention. 1 is a configuration diagram illustrating an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied. FIG. FIG. 3 is a cross-sectional configuration diagram illustrating a fixing belt. It is a block diagram which shows the press-contact state of a press pad and a pressure roll. FIG. 3 is a configuration diagram illustrating an end portion of a fixing belt. It is a block diagram which shows a pressure roll. FIG. 5 is a cross-sectional view as indicated by an arrow in FIG. 4. It is a schematic diagram which shows the shape along the longitudinal direction of a press pad. 2 is a configuration diagram illustrating a fixing device. FIG. FIG. 6 is a cross-sectional configuration diagram illustrating a modified example of the fixing device. It is a schematic diagram which shows the measurement result of pressure distribution. It is a schematic diagram which shows the measurement result of pressure distribution. It is a schematic diagram which shows the measurement result of pressure distribution. It is a schematic diagram which shows the measurement result of pressure distribution. It is a block diagram which shows the fixing device which concerns on Embodiment 2 of this invention. It is a block diagram which shows a pressure roll.

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

Embodiment 1
FIG. 2 shows a tandem full-color image forming apparatus as an image forming apparatus to which the fixing device according to Embodiment 1 of the present invention is applied. The tandem full-color image forming apparatus includes an image reading apparatus and is configured to function as a full-color copying machine. However, the image reading apparatus may be omitted. The present invention is not limited to a tandem image forming apparatus, and is a monochrome image forming apparatus having only one photosensitive drum or a four-cycle full-color image forming apparatus. Is also applicable.

  In FIG. 2, reference numeral 1 denotes a main body of the image forming apparatus, and an image reading device 3 for reading an image of the document 2 is disposed at one upper end (left end in the illustrated example) of the image forming apparatus main body 1. ing. The image reading device 3 illuminates a document 2 placed on a platen glass 5 while being pressed by a document pressing member 4 with a light source 6, and reflects a reflected light image from the document 2 with a full rate mirror 7 and a half rate mirror 8. The image reading element 11 reads the image of the document 2 at a predetermined dot density by performing scanning exposure on the image reading element 11 made of a CCD or the like through a reduction optical system including the image forming lens 10 and the image forming lens 10. It is configured.

  The image of the document 2 read by the image reading device 3 is sent to the image processing device 12 as image data of three colors, for example, red (R), green (G), and blue (B) (for example, 8 bits each). In this image processing apparatus 12, predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. is performed on the image data of the document 2. Applied. In addition, image data that has been subjected to predetermined image processing by the image processing device 12 as described above is converted into cyan (C), magenta (M), yellow (Y), and black (K) by the image processing device 12. It is converted into four-color image data. Note that the color of the image data converted by the image processing device 12 is not limited to the image data of four colors of cyan (C), magenta (M), yellow (Y), and black (K), and high saturation cyan (HC). Or six colors including high saturation magenta (HM), etc., and the colors and saturations are arbitrary. Of course, the image data input to the image processing apparatus 12 may be sent from a personal computer or the like via a communication line (not shown).

  By the way, this embodiment is configured to include a plurality of image forming means for forming an image using toners having different colors or the same color and having different saturation and density.

  That is, inside the image forming apparatus main body 1 according to this embodiment, as shown in FIG. 2, as a plurality of image forming means, yellow (Y), magenta (M), cyan (C), black (K ), Four image forming units 13Y, 13M, 13C, and 13K corresponding to the respective colors are arranged in parallel at regular intervals along the horizontal direction.

  These four image forming units 13Y, 13M, 13C, and 13K are basically configured in the same manner except for the type of toner used, as shown in FIG. Along the photosensitive drum 14 as an image holding member driven at a predetermined rotational speed, a scorotron 15 as primary charging means for uniformly charging the surface of the photosensitive drum 14, and the photosensitive drum 14. An image exposure device 16 serving as a latent image forming unit that exposes an image corresponding to each color on the surface of the toner to form an electrostatic latent image, and a toner of a corresponding color formed on the electrostatic latent image formed on the photosensitive drum 14. The developing device 17 is a developing unit that develops the toner and the cleaning device 18 that cleans the transfer residual toner remaining on the surface of the photosensitive drum 14.

  In the image exposure apparatus 16, as shown in FIG. 2, the semiconductor laser 19 is modulated according to the image data, and the laser beam LB is emitted from the semiconductor laser 19 according to the image data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflecting mirrors 20 and 21, and the focal length is adjusted according to the scanning angle by an unshown f-θ lens. Then, scanning exposure is performed on the photosensitive drum 14 as an image holding member through a plurality of reflection mirrors 23 and 24. The image exposure device 16 is not limited to an apparatus that performs image scanning by deflecting and scanning the laser beam LB. For example, an LED eyelet in which a large number of LED light emitting elements are arranged along the axial direction of the photosensitive drum 14 is used. In the case of the image exposure device 16 using the LED eyelet, the image exposure device 16 is significantly larger than the image exposure device 16 that performs the image exposure by deflecting and scanning the laser beam LB. Therefore, it is possible to reduce the size of the entire image forming apparatus.

  The surface of each of the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, and 13K photoconductive drums 14Y, 14M, 14C, and 14K has scorotron 15Y, It is uniformly charged to a predetermined potential by 15M, 15C, and 15K. From the image processing device 12, image forming units 13Y, 13M, 13C, and 13K for image forming units 13Y, 13M, 13C, and 13K for yellow (Y), magenta (M), cyan (C), and black (K) are provided. Image data corresponding to each color is sequentially output to 16C and 16K. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted according to the image data from these image exposure apparatuses 16Y, 16M, 16C, and 16K are corresponding photosensitive drums 14Y and 14M. , 14C, 14K are scanned and exposed along the main scanning direction (axial direction of the photosensitive drum 14), and electrostatic latent images are formed on the surfaces of the photosensitive drums 14Y, 14M, 14C, 14K. The electrostatic latent images formed on the photosensitive drums 14Y, 14M, 14C, and 14K are respectively yellow (Y), magenta (M), and cyan (C) by the corresponding developing devices 17Y, 17M, 17C, and 17K. ) And black (K) toner images.

  Each color of yellow (Y), magenta (M), cyan (C), and black (K) sequentially formed on the photosensitive drums 14Y, 14M, 14C, and 14K of the image forming units 13Y, 13M, 13C, and 13K. As shown in FIG. 2, the toner image is transferred onto a primary transfer roll 26Y as a primary transfer unit on an intermediate transfer belt 25 as an intermediate transfer member disposed below each of the image forming units 13Y, 13M, 13C, and 13K. , 26M, 26C, and 26K, primary transfer is performed in a state of being superimposed on each other.

  The intermediate transfer belt 25 includes a driving roll 27, a driven roll 28, a tension applying roll 29, a driven roll 30, a back support roll 31 of the secondary transfer unit, and a plurality of rolls including a driven roll 32. The photosensitive drums 14Y, 14M, 14C, and 14K are driven along the direction of the arrow B by a drive roll 27 that is stretched over a predetermined tension and is rotated by a dedicated drive motor that is excellent in constant speed (not shown). It is driven to circulate at a predetermined speed substantially equal to the rotational speed (circumferential speed). As the intermediate transfer belt 25, for example, a flexible synthetic resin film such as polyimide or polyamideimide formed in an endless belt shape is used.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 25 in a multiple manner are transferred to the back support roll 31 via the intermediate transfer belt 25. The recording paper 34 that is secondarily transferred onto a recording paper 34 as a recording medium at a time by a secondary transfer roll 33 as a secondary transfer means that comes into pressure contact, and onto which the toner images of these colors are transferred, is transported in two successive steps. The belts 35 and 36 are conveyed to a fixing device 37 as fixing means according to the first embodiment. The recording paper 34 onto which the unfixed toner images of the respective colors are transferred is subjected to a fixing process with heat and pressure by a fixing device 37, as will be described later, and then discharged on the outside of the image forming apparatus main body 1. It is discharged onto the tray 38.

  As shown in FIG. 2, for example, the recording paper 34 is of a predetermined size or material from a paper feed tray 39 disposed at the bottom of the image forming apparatus main body 1. The paper is once transported to the resist roll 43 while being separated one by one through the paper transport path 42 provided with the roll 41. The recording paper 34 supplied from the paper feed tray 39 is sent to the secondary transfer position of the intermediate transfer belt 25 by a registration roll 43 that is rotationally driven in synchronization with the toner image on the intermediate transfer belt 25.

  The surface of the photosensitive drum 14 after the primary transfer of the toner image is cleaned by the cleaning device 18. Further, the intermediate transfer belt 25 after the secondary transfer of the toner image is cleaned by a belt cleaning device 44 whose surface is disposed at a position facing the driven roll 32.

  FIG. 1 is a cross-sectional configuration diagram showing a fixing device used in the image forming apparatus configured as described above.

  As shown in FIG. 1, the fixing device 37 forms an unfixed toner image T on a fixing belt 51 as a heated endless belt and a pressure contact portion (nip portion) N formed between the fixing belt 51. A pressure roll 52 as a pressure rotator rotating with the held recording paper 34 interposed therebetween, a pressure pad 53 as a pressure member for pressing the fixing belt 51 against the pressure roll 52, and the pressure pad 53 are supported. And a support member 54.

  Further, the fixing device 37 is disposed opposite to an outer peripheral surface located on the opposite side of the nip portion N of the fixing belt 51 with a predetermined gap therebetween, and an alternating magnetic field for heating the fixing belt 51 by electromagnetic induction heating. And an alternating magnetic field generating device 55 that generates heat and a heat storage member that is disposed in contact with the alternating magnetic field generating device 55 via the fixing belt 51 in a contact state and stores heat generated by the fixing belt 51. 56 and a peeling assisting member 57 for assisting the separation of the recording paper 34 from the fixing belt 51.

  The fixing belt 51 is formed in a thin cylindrical shape having an outer diameter of about 20 to 50 mm before being deformed by being pressed against the pressure roll 52. In this embodiment, the outer diameter of the fixing belt 51 is set. Is set to about 30 mm. As shown in FIG. 3, the fixing belt 51 includes, for example, a base layer 511, a heat generating layer 512, an elastic layer 513, and a surface release layer 514 sequentially stacked on the outer peripheral surface thereof. A protective layer may be provided on the outer periphery of 512, and its layer configuration is arbitrary.

  As the base layer 511, for example, a polyimide resin, which is a synthetic resin having high heat resistance, a metal material such as iron, nickel, copper, zirconium, cobalt, or a metal material thereof, and a thickness thereof is 10 to 10 mm. It is set to about 200 μm. In this embodiment, a polyimide resin having a thickness of 80 μm is used.

  The heat generating layer 512 is a layer that generates heat by the electromagnetic induction effect of the alternating magnetic field generated by the alternating magnetic field generator 55. As the heat generation layer 512, for example, a metal material made of a metal such as iron, cobalt, nickel, copper, aluminum, chromium, or an alloy thereof is used so that sufficient heat generation can be obtained by an eddy current due to electromagnetic induction. The material and thickness are selected in consideration of the resistance value. In this embodiment, copper having a thickness of about 5 μm is used.

  Further, the elastic layer 513 is made of an elastic body having heat resistance such as silicone rubber or fluororubber. The toner image held on the recording paper 34 as a recording medium is formed by laminating a plurality of color toners made of powder, and particularly in the case of a full-color image, the total amount of toner is large. Therefore, in order to uniformly heat and melt the toner image in the nip portion N of the fixing device 37, it is desirable that the surface of the fixing belt 51 be elastically deformed following the unevenness of the toner image on the recording paper 34. In this embodiment, a silicone rubber having a thickness of 100 to 600 μm, for example, 200 μm and a JIS-A hardness of 10 to 30 ° is used as the elastic layer 513.

  Further, the surface release layer 514 laminated on the surface of the elastic layer 513 is a layer that is in direct contact with the unfixed toner image held on the recording paper 34, and therefore a material having a high release property is used. . As this surface release layer 514, for example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether polymer), PTFE (polytetrafluoroethylene), silicone copolymer, or a composite layer thereof is used. If the surface release layer 514 is too thin, it is insufficient in terms of wear resistance, and the life of the fixing belt 51 is shortened. On the other hand, if the surface release layer 514 is too thick, the heat capacity of the fixing belt 51 becomes too large and the warm-up time becomes long. Therefore, in this embodiment, the thickness of the surface release layer 514 is set to 10 to 50 μm, for example, 30 μm in consideration of the balance between wear resistance and heat capacity.

  As shown in FIGS. 4 and 5, the fixing belt 51 configured as described above transmits a driving force to rotationally drive the fixing belt 51 to both end portions along the longitudinal direction (axial direction). A flange member 58 as a cylindrical member is attached in a state where it is fixed by means such as press fitting or adhesion. As shown in FIG. 5, these flange members 58 include a cylindrical portion 58 a that is inserted into the end portion of the fixing belt 51, and a cylindrical shape that is thicker than the cylindrical portion 58 a on the axially outer side of the fixing belt 51. And a drive part 58b in which the tooth surface of a gear such as a helical gear is integrally formed on the outer peripheral surface, and a radially outward ring between the cylindrical part 58a and the drive part 58b. And a flange portion 58c provided so as to protrude. Further, as shown in FIG. 5, the flange member 58 has both end portions along the longitudinal direction of the support member 54 via a bearing member 59 disposed on an inner peripheral surface extending from the cylindrical portion 58a to the drive portion 58b. It is rotatably supported by a columnar support portion 60 provided on the surface. As shown in FIG. 5 (b), the support portion 60 is provided with a fixing portion 61 having a rectangular cross section formed so as to protrude outward at both ends along the longitudinal direction of the support member 56. It has been.

  As the material constituting the flange member 58, so-called engineering having high mechanical strength and heat resistance, such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, LCP resin, etc. Plastics are suitable.

  On the other hand, as shown in FIG. 3, the pressure roll 52 has a cored bar member 521 formed in a cylindrical shape with a metal such as stainless steel or aluminum, and a thickness predetermined on the surface of the cored bar member 521. A heat-resistant elastic layer 522 made of silicone rubber or the like, and a PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene) coated on the surface of the elastic layer 522 with a heat of about 50 μm, for example. And a release layer 523 made of a material excellent in release properties such as a polymer). The pressure roll 52 is formed in, for example, a solid substantially cylindrical shape having an outer diameter of about 28 mm.

  Furthermore, in this embodiment, as the pressure roll 52, a small-diameter through-hole 524 penetrating along the axial direction is formed in the circumferential direction in the elastic body layer 522 made of a silicone sponge layer having a relatively small elastic modulus. A so-called SOLT roll (trade name) in which a plurality of layers are arranged at equal intervals along the outer periphery of the elastic body layer 522 and a release layer 523 made of a PFA tube is coated on the outer periphery of the elastic body layer 522 is used. Since the pressure roll 52 made of this SOLT roll has an elastic body layer 522 made of a silicone sponge layer having a relatively small elastic modulus on the surface side, it is a small diameter roll having a relatively small outer diameter. In addition, a relatively wide nip portion N (nip width) can be obtained and the diameter of the pressure roll 52 can be reduced, which is desirable.

  Further, since the pressure roll 52 has a plurality of through holes 524 in the elastic body layer 522, the heat capacity is relatively small and the heat insulating property is excellent, so that heat conduction from the fixing belt 51 is suppressed. At the start of heating, the temperature of the fixing belt 51 is quickly followed, so that the preheating time can be shortened. However, the pressurizing roll 52 is not limited to the SOLT roll (trade name), and may of course be a solid roll that does not have the through hole 524.

  As shown in FIG. 6, the pressure roll 52 is configured to suppress the occurrence of paper wrinkles on the recording paper 34 that passes through the nip portion N where the pressure roll 52 and the fixing belt 51 are pressed. The outer diameter of the maximum sheet passing region 52 is such that the outer diameter φA at the central portion along the axial direction is relatively small and the outer diameter φB at the end of the maximum passing region of the recording paper 34 is relatively large. Is set. The difference (φB−φA) between the outer diameter φA at the center of the pressure roll 52 and the outer diameter φB at the end of the maximum passage area of the recording paper 34 suppresses or prevents the occurrence of paper wrinkles on the recording paper 34. In order to do so, it is set to a predetermined value, and is set to about 50 μm to 100 μm, for example, 75 μm.

  The material of the pressing pad 53 that presses the fixing belt 51 and the pressure roll 52 is, for example, an elastic body having heat resistance such as silicone rubber or fluororubber. As shown in FIG. It is attached in a state of being fitted in a recess 62 provided at a position facing the pressure roll 52. The press pad 53 is a member that forms a nip portion N between the fixing belt 51 and the pressure roll 32 by being pressed against the pressure roll 52 via the fixing belt 51.

  The pressing pad 53 is made of an elastic body such as silicone rubber or fluororubber, for example, but the material constituting the pressing pad 53 is not limited to this and is a synthetic material having heat resistance and low thermal conductivity. For example, a heat-resistant resin such as a polyimide resin, a polyamide resin, a phenol resin, a PES resin (polyethersulfone), a PPS resin (polyphenylene sulfide), or an LCP (liquid crystal polymer) may be used. In this embodiment, as the material of the pressing pad 53, an elastic body having heat resistance such as silicone rubber or fluororubber is used.

  As shown in FIG. 4, the pressing pad 53 is provided over the sheet passing area (maximum sheet passing area) of the maximum size recording sheet 34 in the width direction of the fixing belt 51 and the non-sheet passing areas on both sides thereof. Both end surfaces are opposed to the inner surface of the flange member 58 with a small gap. The length of the elastic layer 522 of the pressure roll 52 is set to be approximately the same as the length including the maximum sheet passing area and the non-sheet passing area of the pressing pad 53. The pressure roll 52 is in pressure contact over the entire length.

  As shown in FIGS. 4 and 7A, the cross-sectional shape of the pressing pad 53 is such that the sheet passing area of the maximum size recording paper 34 is formed in the same shape, as shown in FIGS. As shown in the figure, the configuration is such that the shape smoothly changes from the paper passing area of the maximum size recording paper 34 toward the end. As shown in FIG. 7A, the cross-sectional shape of the maximum size sheet passing area of the pressing pad 53 is the same as the pre-nip area 53a which is the inlet side of the nip portion N positioned on the upstream side in the conveyance direction of the recording paper 34, and the recording. The shape is set to be different from that of the peeling nip region 53b on the outlet side of the nip portion N located on the downstream side in the conveyance direction of the paper 34. More specifically, the pre-nip region 53a of the pressing pad 53 is formed in a convex arc shape on the fixing belt 51 side whose surface on the pressure roll 52 side substantially follows the outer peripheral surface of the pressure roll 52, and is uniform and wide. A nip portion N is formed. On the other hand, in the peeling nip area 53b of the pressing pad 53, the surface of the pressure roll 52 is convex toward the pressure roll 52 side so that the radius of curvature of the fixing belt 51 passing through the peeling nip area 53b is reduced. It is formed so as to be pressed locally with a large nip pressure. With this configuration, a curl (down curl) in a direction away from the surface of the fixing belt 51 is formed on the recording paper 34 that passes through the peeling nip region 53 b, and the peeling from the surface of the fixing belt 51 to the recording paper 34 is promoted. As a result, after passing through the nip portion N, the recording paper 51 is deformed to form a down curl and is peeled off from the surface of the fixing belt 51 by its own rigidity.

  7B and 7C, the pressing pad 53 is formed so that its cross-sectional shape approaches an arc shape that follows the outer shape of the flange member 58 as it goes to the end in the axial direction. The end on the flange member 58 side is formed in an arc shape that is substantially the same shape as the outer shape of the flange member 58.

  Further, as shown in FIG. 7A, when the thickness T along the longitudinal direction of the maximum sheet passing region is constant, the pressing pad 53 has a support beam shape at both ends that presses against the pressing pad 53. The pressure roll 52 deforms the pressure pad 53 and the support member 54 that supports the pressure pad 53 into a curved shape, and the pressure contact force between the pressure pad 53 and the pressure roll 52 is in the axial direction of the pressure roll 52. The pressure at both ends along the line is high, the pressure at the central part is relatively low, and tends to be non-uniform along the axial direction of the pressure roll 52.

  Therefore, as shown in FIG. 8, the pressing pad 53 takes into account the bending of the pressing pad 53 and the support member 54 in advance, and the pressure contact force between the pressing pad 53 and the pressing roll 52 is maximum. In the paper region, the central portion is formed in a curved shape so that the central portion protrudes toward the pressure roll 52 relative to both end portions along the longitudinal direction so as to be substantially uniform along the axial direction. Yes.

  As shown in FIG. 3, the support member 54 has a rigidity such that the amount of deflection when receiving the pressure contact force from the pressure roll 52 via the pressing pad 53 is equal to or less than a predetermined value. It is formed in a rectangular cross section. The support member 54 is made of a material that does not affect or hardly gives influence to the induction magnetic field. For example, a heat resistant resin such as PPS (polyphenylene sulfide) mixed with glass fiber, a nonmagnetic metal material such as aluminum, or the like is used. Is used.

  Further, as shown in FIG. 8, the fixing device 37 includes a device frame 62 as a frame formed in an elongated rectangular shape. Fixing portions 61 provided at both ends of the support member 54 are fixed to the device frame 62, and the outer periphery of the support portion 60 of the support member 54 is attached to the outer periphery of the support member 54 as shown in FIG. A fixing belt 51 is rotatably mounted via a bearing member 59.

  Further, as shown in FIG. 9, the support frame 54 is attached to the device frame 62 in a state of being fixed through fixing portions 61 having a rectangular cross section provided integrally at both ends thereof. On the outer periphery of the support member 54, as shown in FIG. 5, a funnel member 58 of the fixing belt 51 is rotatable through a bearing member 59 inserted in the outer periphery of a support portion 60 formed in a columnar shape. It is supported.

  Further, as shown in FIG. 9, both end portions of a drive shaft 63 for rotationally driving the fixing belt 51 are rotatably attached to the device frame 62 via bearing members 64. The drive shaft 63 is attached with driven gears 65 that mesh with the drive portions 58 b of the flange members 58 located at both ends of the fixing belt 51 at both ends located inside the apparatus frame 62. In addition, a transmission gear 66 that transmits a driving force to the drive shaft 63 is attached to one end portion of the drive shaft 63 that is located outside the device frame 62, and a drive motor 67 is attached to the transmission gear 66. A drive gear 69 fixed to the rotary shaft 68 is meshed. The rotating shaft 68 of the drive motor 67 has a base end portion rotatably attached to the device frame 62 of the fixing device 37. The fixing device 37 rotates the drive motor 67 to transmit the rotational drive force of the drive motor 67 to the drive shaft 63 via the drive gear 69 and the transmission gear 66 and is attached to the drive shaft 63. The fixing belt 51 is rotated at a predetermined rotational speed by the drive portions 58b and 58b of the flange member 58 provided at both ends of the fixing belt 51 that rotates the driven gears 65 and 65 and meshes with the driven gears 65 and 65. Is driven to rotate.

  As described above, the fixing belt 51 is formed by laminating the base layer 511, the heat generating layer 512, the elastic layer 513, and the surface release layer 514 made of a metal material, a synthetic resin material, or the like. -It has flexibility and mechanical strength, and even when it receives rotational drive torque from the drive parts 58b, 58b of the flange member 58, buckling or the like does not occur. Driven smoothly and rotated.

  In the above embodiment, the case where only the fixing belt 51 is rotationally driven and the pressure roll 52 is pressed against the fixing belt 51 and driven to rotate is described. However, the rotational driving force of the drive motor 67 is described. It may be configured to transmit to the pressure roll 52 via a gear (not shown) so that both the fixing belt 51 and the pressure roll 52 are rotationally driven.

  As shown in FIG. 9, both ends of the rotary shaft 525 are rotatably supported by the apparatus frame 62 via bearing members 70, and the pressure roll 52 is arranged at both ends of the rotary shaft 525. The fixing spring 51 is pressed against the fixing belt 51 by a coil spring 71 as the biasing means. In this embodiment, as will be described later, in order to improve the productivity of the fixing device 37, the pressure contact force between the pressure roll 52 and the pressure pad 53 is set higher than the conventional one, and the two coil springs 71 are used. The total load is set to, for example, about 50 to 80 kgf. The bearing member 70 that rotatably supports the pressure roll 52 is held by a long hole (not shown) so as to be movable with respect to the device frame 62 of the fixing device 37 in a direction in contact with and away from the fixing belt 51. .

  The pressure roll 52 is configured to be movable in a direction in which it is pressed against or separated from the fixing belt 51 by a contact / separation mechanism (not shown), and is configured to separate the pressure roll 52 when heating of the fixing belt 51 is started. You may do it.

  As a specific configuration of the contact / separation mechanism 72, for example, as shown in FIG. 9, an arm member 73 that rotatably supports both ends of the rotation shaft 525 of the pressure roll 52 is provided. One end portion 73 a is rotatably supported around a fulcrum 74, and the other end portion 73 b is configured to be pressed by a coil spring 71 in a direction in pressure contact with the fixing belt 51. Further, an eccentric cam 76 that is rotationally driven by a rotating shaft 75 is disposed above the other end 73b of the arm member 73, and the eccentric cam 76 is rotationally driven at a predetermined timing. Thus, the other end 73 b of the arm member 73 may be pushed down so that the pressure roll 52 is separated from the fixing belt 51.

  Further, as shown in FIG. 3, a peeling assisting member 57 is provided on the downstream side of the nip portion N where the fixing belt 51 and the pressure roll 52 are in pressure contact with each other along the conveyance direction (arrow direction) of the recording paper 34. It has been. The separation assisting member 57 has a distal end portion 57 a that extends to the vicinity of the exit of the nip portion N, and a base end portion 57 b that is bent away from the conveyance path of the recording paper 34 that has been separated from the fixing belt 51. Is placed in the state where The separation assisting member 57 forcibly separates the recording sheet 34 that has not been separated from the fixing belt 51 due to the rigidity of the recording sheet 34 itself by the front end portion 57 a of the separation assisting member 57.

  Further, as shown in FIG. 3, an alternating magnetic field generator 53 arranged on the opposite side of the fixing belt 51 from the pressure roll 52 includes, for example, an exciting coil 80 for generating an alternating magnetic field and an exciting coil 80. Of the magnetic path of the alternating magnetic field generated by the holding member 81 that is held in a predetermined position in an arc shape and the exciting coil 80, the magnetic path is formed in a substantially arc shape that forms a magnetic path on the outer peripheral side of the fixing belt 51. An external magnetic path forming member 82 and an excitation circuit 83 that excites the excitation coil 80 by supplying a high-frequency current.

  The holding member 81 has a cross-sectional shape of an end surface located on the fixing belt 51 side formed in a concentric circular arc shape curved along the surface shape of the fixing belt 51, and a support surface for supporting the excitation coil 80 is provided. It is formed in an arc shape so that the distance from the fixing belt 51 becomes a predetermined value (for example, 0.5 to 2 mm). Moreover, as a material which comprises this holding member 81, heat resistant resin, such as heat resistant glass, a polycarbonate, polyether sulfone, PPS (polyphenylene sulfide), or the fiber reinforced heat resistant resin which mixed glass fiber with these, for example A nonmagnetic material having heat resistance such as the above is used.

  The exciting coil 80 is configured by winding, for example, 90 litz wires, each having a diameter of 0.17 mm, which are insulated from each other, wound in a hollow closed loop shape such as an oval shape, an elliptical shape, or a rectangular shape. Yes. The excitation coil 80 is supplied with a high-frequency current having a predetermined frequency from the excitation circuit 84, and an alternating magnetic field centered around a litz wire wound in a closed loop is generated around the excitation coil 80. The The frequency of the high-frequency current supplied from the excitation circuit 83 to the excitation coil 80 is set to 20 to 100 kHz, for example.

  In addition, the external magnetic path forming member 82 is made of, for example, a high permeability oxide or alloy material such as soft ferrite, ferrite resin, amorphous alloy (amorphous alloy), permalloy, or temperature-sensitive magnetic alloy. A magnetic body is used and functions as a magnetic path forming member located outside the fixing belt 51. In this external magnetic path forming member 82, the magnetic lines of force (magnetic flux) due to the alternating magnetic field generated by the excitation coil 80 cross the fixing belt 51 from the excitation coil 80 toward the heat generation control member 56. A path of magnetic lines of force (magnetic path) is formed so as to pass through and return to the exciting coil 80. In this way, by forming the magnetic path by the external magnetic path forming member 82, the alternating magnetic field (line of magnetic force) generated by the exciting coil 80 is concentrated in a region facing the external magnetic path forming member 82 of the fixing belt 51. . The external magnetic path forming member 82 is preferably made of a material that has a small loss due to magnetic path formation. Specifically, the external magnetic path forming member 82 is used in a form that reduces the eddy current loss (cutting off or dividing current paths due to recesses, etc.). It is desirable to use a material having a small hysteresis loss.

  Further, as shown in FIG. 3, a heat storage member 56 is disposed inside the fixing belt 51. The heat storage member 56 is a member that is disposed so as to face the alternating magnetic field generator 55 via the fixing belt 51, and has a heat storage function that conducts heat to the fixing belt 51 to compensate for the temperature drop of the fixing belt 51. is there. The heat storage member 56 is a member that forms a magnetic path inside the alternating magnetic field generated by the alternating magnetic field generator 55 and is made of a temperature-sensitive magnetic material whose magnetic permeability changes with temperature. A function for controlling the heat generation of the heat generation layer 512 is also provided. The heat storage member 56 is formed in an arc shape that follows the inner peripheral surface of the fixing belt 51, and the central angle of the arc-shaped portion along the inner peripheral surface of the fixing belt 51 is set to, for example, about 160 degrees. Is done. The heat generation control member 56 is fixed to the support member 54 with screws 85 via plate-like members 84 attached to both ends thereof.

  Further, a sliding member 86 made of a sheet-like member having a porous chamber structure impregnated with a lubricant is provided between the fixing belt 51 and the heat generation control member 56 in order to reduce sliding resistance therebetween. Is desirable.

  By the way, in the fixing device 37 configured as described above, the fixing pressure is increased as one means for improving the productivity determined by the number of recording sheets 34 fixed per unit time. It is conceivable that the pressing force with which the roll 52 presses is set higher than in the conventional case.

  However, when the pressure contact force between the fixing belt 51 and the pressure roll 52 is increased, the elastic layer 522 located in the non-sheet passing region of the pressure roll 52 may exceed the allowable stress limit and cause cohesive failure. It has been clarified by research by the present inventors.

  Therefore, in this embodiment, in order to avoid damaging the elastic body layer 522 of the pressure roll 52 even when the fixing pressure is increased, the pressure roll 52 is outside the maximum passage region of the recording paper 34. The outer diameter is configured so as to become smaller as it goes to the end.

  That is, as shown in FIG. 4, the pressure roll 52 is set to have a longer length in the axial direction than the paper passing area of the maximum size recording paper 34 used in the image forming apparatus. The both end portions along the axial direction of the pressure roll 52 are in pressure contact with the pressing pad 53 even in the non-sheet passing area outside the maximum sheet passing area.

  As shown in FIG. 6, the pressure roll 52 has an outer diameter of a non-sheet passing region positioned on the outer side in the axial direction from an end portion 526 of the maximum sheet passing region positioned in the center portion along the axial direction It is set so that the diameter decreases linearly from the end of the maximum sheet passing area toward the outside in the axial direction. At this time, the difference (φB−φC) between the outer diameter φB of the end of the maximum sheet passing area of the pressure roll 52 and the outer diameter φC of the end of the non-sheet passing area is the length of the non-sheet passing area. However, for example, it is set to about 0.5 to 2.0 mm, and in this embodiment, it is set to about φB−φC = 1.0 mm.

  Here, when the outer diameter φC of the end of the non-sheet passing area of the pressure roll 52 is set too small, the pressure contact force between the non-sheet passing area of the pressure roll 52 and the pressing pad 53 is locally increased. When the fixing belt 51 is rotationally driven via the flange member 58, the fixing belt 51 may be deformed between the fixing belt 51 and the pressure roll 52. It is good to set to about ~ 2.0 mm.

  Therefore, even when the pressure roll 52 is set so that the outer diameter of the non-sheet passing area becomes smaller from the end of the maximum sheet passing area toward the outer side in the axial direction, It is desirable to set the outer diameter φC of the end portion to be equal to or greater than a predetermined value.

  In the above configuration, in the image forming apparatus using the fixing device according to this embodiment, the elastic layer of the pressure rotating body is prevented from being damaged even when the fixing pressure is increased as follows. It is possible.

  In the image forming apparatus, as shown in FIG. 2, the photosensitive drums 14Y of the image forming units 13Y, 13M, 13C, and 13K for yellow (Y), magenta (M), cyan (C), and black (K) are provided. , 14M, 14C, and 14K, toner images of corresponding colors are formed according to image data, and yellow (Y), magenta (M), and magenta (M), formed on the photosensitive drums 14Y, 14M, 14C, and 14K, respectively. The cyan (C) and black (K) toner images are transferred onto the intermediate transfer belt 25 by the primary transfer rolls 26Y, 26M, 26C, and 26K, and then transferred from the intermediate transfer belt 25 to the secondary transfer roll 33. As a result, the image is secondarily transferred onto the recording paper 34 at once. Then, as described above, the recording paper 34 on which the unfixed toner images of the respective colors such as yellow (Y), magenta (M), cyan (C), and black (K) are held are conveyed to the fixing device 37 and fixed. Processing is performed.

  In the fixing device 37, almost simultaneously with the start of the operation for forming the toner image, as shown in FIG. 9, the driving motor 67 is activated to rotate the fixing belt 51, and as shown in FIG. In addition, power is supplied to the alternating magnetic field generator 55. When the fixing belt 51 passes through a heating region facing the alternating magnetic field generator 55, an eddy current is induced in the heat generating layer 512 by electromagnetic induction, and heat is generated by Joule heat due to eddy current loss of the eddy current. Heated.

  When the fixing belt 51 is heated to a predetermined fixing temperature, as shown in FIG. 3, the recording paper 34 holding the unfixed toner image T moves to the nip portion N where the fixing belt 51 and the pressure roll 52 are in pressure contact. The unfixed toner image T is heated, pressurized and melted while passing through the nip portion N to be fixed on the recording paper 34 as a permanent image.

  In the recording paper 34 on which the unfixed toner image T is fixed, the curvature of the pressing pad 53 changes from an upward convex shape to a downward convex shape in the vicinity of the exit of the nip portion N where the fixing belt 51 and the pressure roll 52 are pressed. The recording sheet 34 is peeled off from the fixing belt 51 by its waist (rigidity).

  By the way, in the fixing device 37, in order to improve productivity determined by the number of recording sheets 34 that can be fixed per unit time, the pressure contact force between the fixing belt 51 and the pressure roll 52 is higher than that of the conventional fixing device. Is set. Specifically, as shown in FIG. 9, the total load of the two coil springs 71 as the urging means for pressing the pressure roll 52 against the fixing belt 51 is about 50 to about 30 kgf. It is set to be significantly high at about 80 kgf.

  As described above, in the fixing device 37, the pressure contact force between the fixing belt 51 and the pressure roll 52 is set to be higher than that of the conventional one, so that the fixing belt 51 and the pressure roll 52 pass through the nip portion N where the pressure contact is made. By increasing the contact pressure between the fixing belt 51, the unfixed toner image T and the recording paper 34 with respect to the recording paper 34, the heat of the fixing belt 51 is efficiently transmitted to the unfixed toner image T and the recording paper 34. It is possible to greatly improve the fixing property.

  On the other hand, as shown in FIG. 9, the support member 54 that supports the pressing pad 53 has both end portions along the axial direction fixed to the device frame 62 of the fixing device 37, and the pressure roll 52 includes: Both end portions along the axial direction are pressed against the pressing pad 53 via the fixing belt 51.

  By the way, in this embodiment, as shown in FIG. 6, the pressure roll 52 is not passed through from the end 526 of the maximum sheet passing area located in the center along the axial direction. The outer diameter of the paper region is set so as to decrease linearly from the end 526 of the maximum paper passing region toward the outside in the axial direction. Therefore, in order to improve the productivity of the pressure roll 52, even if the pressure contact force between the fixing belt 51 and the pressure roll 52 is set higher than the conventional one, the non-sheet passing of the pressure roll 52 is not performed. It is possible to suppress the pressure contact force with the pressing pad 53 in the region from being excessive, and the pressure contact force between the fixing belt 51 and the pressure roll 52 can be held substantially uniformly over the end portions.

  Therefore, even when the pressure contact force between the fixing belt 51 and the pressure roll 52 is increased, the pressure contact force in the non-sheet passing region of the pressure roll 52 becomes excessive, and the elastic layer of the pressure roll 52 It is possible to avoid exceeding the allowable stress limit of 522, suppress the occurrence of cohesive failure in the elastic body layer 522 of the pressure roll 52, and extend the life of the pressure roll 52.

  Further, since it is possible to avoid an excessive pressure contact force in the non-sheet passing region of the pressure roll 52, the heat transfer to the end portion along the width direction of the fixing belt 51 is reduced, and the fixing belt 51 The temperature rise at the end along the width direction can be suppressed, and the life of the fixing belt 51 can be extended.

  Further, since the pressure contact force between the fixing belt 51 and the pressure roll 52 can be held substantially uniformly over the end portion thereof, the nip load is limited by effectively acting on the sheet passing area of the pressure roll 52. Good fixing performance can be obtained with a load.

Experimental Example In order to confirm the effect of the fixing device according to the first embodiment, the inventors made a prototype bench model of the fixing device 37 as shown in FIG. An experiment was conducted to measure the pressure distribution along the axial direction of the fixing nip N when the pressing force (total load) was set to 80 kgf. The pressure contact force between the fixing belt 51 and the pressure roll 52 is measured by interposing a tactile sheet that is an ultrathin sensor for measuring the pressure distribution between the nip N between the fixing belt 51 and the pressure roll 52. The pressure distribution between the nip N between the fixing belt 51 and the pressure roll 52 was measured.

  As shown in FIG. 6, the pressure roll 52 was set so that the difference between the outer diameter of the end of the maximum sheet passing area and the outer diameter of the non-sheet passing area was linearly reduced by 1 mm. A thing was used.

  FIG. 11 is a graph showing the results of the above experimental example.

  As can be seen from FIG. 11, in the fixing device 37 of this experimental example, although the surface pressure on the driving side of the fixing belt 51 is a little higher than the allowable surface pressure limit, It can be seen that the pressure contact pressure of the roll 52 can be made substantially constant including the non-sheet passing portions positioned at both ends in the axial direction, and the end portion of the elastic layer 522 when the pressure roll 52 is continuously driven. There was no damage.

Comparative Example As a comparative example, the inventors formed a cylindrical shape in which the outer diameter of the non-sheet passing region at both ends along the axial direction of the pressure roll 52 is equal to the outer diameter of the end of the maximum sheet passing region. In the conventional fixing device, the pressure distribution along the axial direction of the nip portion N is measured when the pressure contact force (total load) between the fixing belt 51 and the pressure roll 52 is set to 30 kgf, 50 kgf, and 80 kgf, respectively. An experiment was conducted to confirm whether or not the elastic layer 522 at the end of the pressure roll 52 is damaged when the fixing device 37 is continuously driven.

  12 to 14 are graphs showing the results of the comparative example.

  As is apparent from FIG. 12, when the pressure contact pressure between the fixing belt 51 and the pressure roll 52 is set to 80 kgf, there is a region where the surface pressure in the non-sheet passing region increases and exceeds the allowable surface pressure limit. I found out. Further, when the fixing device 37 was continuously driven, cohesive failure occurred at the end portion along the axial direction of the elastic layer 522 of the pressure roll 51.

  As is apparent from FIG. 13, when the pressure contact pressure between the fixing belt 51 and the pressure roll 52 is set to 50 kgf, the surface pressure of one non-sheet passing portion increases and exceeds the allowable surface pressure limit. It can be seen that there is an area. Further, when the fixing device was driven continuously, breakage occurred at the end portion along the axial direction of the pressure roll.

  On the other hand, as is apparent from FIG. 14, when the pressure contact pressure between the fixing belt 51 and the pressure roll 52 is set to 30 kgf, the surface pressure of the non-sheet passing portion is increased, but it is about the allowable surface pressure limit. I understand that. Further, even when the fixing device was driven continuously, no breakage occurred at the end portion along the axial direction of the pressure roll.

Embodiment 2
FIG. 15 shows a second embodiment of the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. In the second embodiment, the pressure rotator is shown in FIG. The pressing member is formed in a shape along a bending curve that is deformed by being pressed against the pressure rotating body as the outer diameter outside the maximum passage region of the recording medium goes to the end. ing.

  That is, in the second embodiment, as shown in FIG. 15, when the pressure roll 52 is brought into pressure contact with the pressure pad 53 via the fixing belt 51, it protrudes at both end portions along the axial direction of the pressure roll 52. When a load is applied to each of the rotating shafts, the surface of the pressing pad is deformed so as to bend according to the load applied to the rotating shaft of the pressure roll 52, as shown in FIG. This deformation deformation of the surface of the pressing pad is caused by structural mechanics as a modification example of a both-end support beam composed of a support member 54 having both ends fixed and a pressure roll 25 supported at both ends in pressure contact with the support member 54. It has been analyzed and found that the deflection curve of the pressure pad surface can be expressed as a quartic curve.

  Therefore, in the second embodiment, as shown in FIG. 16, the outer diameter of the non-sheet passing region of the pressure roll 52 is reduced toward the end portion based on a quartic curve that is a deflection curve of the pressing pad surface. It is comprised so that.

  By configuring in this way, it is possible to avoid an excessive pressure contact force in the non-sheet passing region of the pressure roll 52, and at the end of the pressure roll 52 along the axial direction of the elastic body layer 522. It is possible to suppress or prevent the occurrence of cohesive failure.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

  37: fixing device, 51: fixing belt, 52: pressure roll, 53: pressing pad, 54: support member.

Claims (6)

A heated endless belt;
A rotating body having an elastic layer on the surface side and rotating with the recording medium sandwiched between the endless belt and having an edge of the maximum sheet passing area of the recording medium as a boundary. The outer diameter outside the end of the maximum sheet passing area is formed so as to become smaller toward the end, and the outer diameter inside the end of the maximum sheet passing area of the recording medium is changed from the end to the center. A pressure rotator formed to have a smaller diameter as it goes,
Wherein is arranged inside the endless belt, Bei give a pressing member for pressing the endless belt and the pressure rotating body,
The fixing device according to claim 1, wherein the pressure rotator is pressed against an area including a maximum sheet passing area and a non-sheet passing area of the pressing member .   2. The pressurizing rotator is formed such that an outer diameter outside an end portion of a maximum sheet passing area of the recording medium changes linearly toward the end portion. Fixing device.   The pressurizing rotator follows a bending curve in which the pressing member is deformed by being pressed against the pressurizing rotator as the outer diameter outside the end of the maximum sheet passing area of the recording medium goes to the end. The fixing device according to claim 1, wherein the fixing device is formed in a different shape. The fixing device according to claim 1 , wherein the endless belt has a heat generating layer and is heated by electromagnetic induction. The fixing device according to claim 1 , wherein a cylindrical member is attached to both ends of the endless belt, and the endless belt is driven to rotate through the cylindrical member. An image carrier for holding a toner image;
Transfer means for transferring the toner image held on the image holding member to a recording medium directly or via an intermediate transfer member;
A fixing means for fixing the toner image transferred onto the recording medium by the transfer means;
An image forming apparatus using the fixing device according to claim 1 as the fixing unit.

Images