JP2019049762A - Fixation device - Google Patents

Abstract

To suppress the influence of an excessively high pressure peak at a fixation nip part on image quality and suppress the decrease in the life of a device.SOLUTION: In a fixation device that includes a heater holder 41 having a protrusion 41b that presses a recording material P with largest force among parts other than at least a central part of a fixation nip part N2 in the conveyance direction of the recording material P in the fixation nip part N2, a pressure roller 20 includes, in the axial direction, a first diameter part whose diameter is a first diameter and a second diameter part whose diameter is a second diameter larger than the first diameter, and the shortest distance from a part of the protrusion 41b in mutual pressure contact with the second diameter part to the central axis of the pressure roller 20 is longer than the shortest distance from a part of the protrusion 41b in mutual pressure contact with the first diameter part to the central axis of the pressure roller 20.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a fixing device.

  Conventionally, as a fixing device mounted on an image forming apparatus such as a copying machine or a laser beam printer, a film heating type is widely used. The film heating type fixing device has a ceramic heater as a heat source, a heat resistant fixing film, and a pressure roller. Further, the fixing device of the film heating type has a support member for supporting the fixing film on the inner peripheral surface side of the fixing film, and an inner circumferential nip portion is formed by the support member and the pressure roller via the fixing film. The fixing device having such a configuration forms a fixing nip portion by the fixing film and the pressure roller, and heats and fixes the unfixed toner image on the recording material while holding and conveying the recording material at the fixing nip portion.

  In addition, as a fixing device of a film heating method, a configuration is known in which a support member has a protruding portion that protrudes toward a pressure roller in an inner circumferential nip portion (Japanese Patent Application Laid-Open No. 2008-112118). By forming a portion having a high pressing force locally in the nip portion by the projecting portion, it is possible to improve the glossiness of the toner image fixed on glossy paper or the like without increasing the total pressing force.

  In addition, in order to form a peak of the pressure distribution on the downstream side in the conveyance direction of the recording material in the fixing nip portion, a configuration is known in which a projecting portion is provided on the downstream side in the conveyance direction of the recording material. Since the protruding portion is on the downstream side in the recording material conveyance direction, high pressure can be applied in a state where the toner image on the recording material is sufficiently softened or melted in the fixing nip portion, and the toner image is fixed on glossy paper or the like. It is possible to improve the glossiness of the toner image.

  On the other hand, as a pressure roller in the fixing device of the film heating type as described above, a pressure roller having a so-called reverse crown shape is known which has a shape in which the outer diameter gradually increases from the center to the end in the longitudinal direction. (Patent Document 2). This is intended to convey the recording material relatively faster as the recording material is conveyed at the fixing nip portion closer to the end compared to the central portion in the longitudinal direction. As described above, by increasing the conveyance speed of the end portion with respect to the central portion, it is possible to suppress the occurrence of distortion and bending of the recording material in the fixing nip portion, and to suppress the generation of wrinkles of the recording material.

Japanese Patent Application Laid-Open No. 10-198200 JP 2003-228246 A

  Here, in the configuration in which the protruding portion is provided on the support member, in the case where the protruding portion is provided on the upstream side or the downstream side in the conveyance direction of the recording material, there are the following problems. The width of the fixing nip portion (hereinafter, the fixing nip width) is not necessarily uniform in the longitudinal direction. When the fixing nip width is partially different in the longitudinal direction, the penetration amount of the protrusion is also partially different. Specifically, the penetration amount of the portion having a relatively wide nip width is higher than the penetration amount of the portion having a narrow fixing nip width. The difference in the amount of penetration is the difference in pressure peaks, and the higher the amount of penetration, the larger the pressure peak.

Therefore, when the width of the fixing nip at the end is relatively wider than that at the center (hereinafter referred to as a thick nip), the pressure peak is larger at the end than at the center. Conversely, in the case where the width of the fixing nip at the central portion is relatively wider than that at the end (hereinafter referred to as a medium thick nip), the pressure peak is larger at the central portion than at the end. In order to prevent the recording material from being wrinkled, it is preferable to intentionally form a thick nip, but in that case, as described above, a difference in pressure peak occurs between the end and the center.

  Such a difference in pressure peaks in the longitudinal direction results in a difference in glossiness of the toner image fixed on the recording material. The high pressure peak is high in gloss, and the low pressure peak is low in gloss. For example, in the thick nip configuration, the gloss at the end is high while the central gloss is low. . Such unevenness in glossiness causes the problem of lowering the image quality as unevenness of the image.

  Furthermore, the difference in pressure peak is also a difference in the amount of wear on the surface of the fixing film. The surface of the fixing film is gradually worn away by rubbing with the recording material. On the other hand, the higher the pressure peak, the larger the friction between the fixing film and the recording material, and the larger the amount of abrasion. Therefore, when there is a difference in the fixing nip width in the longitudinal direction, a difference also occurs in the amount of wear in the longitudinal direction. When the difference in the amount of abrasion occurs in the longitudinal direction as described above, unevenness occurs in the thickness of the fixing film in the longitudinal direction. Since the unevenness in thickness is the difference in the amount of heat transferred from the heater via the fixing film, the amount of heat given to the recording material is relatively large because the portion with a large amount of wear has a small thickness. If the difference in the amount of wear is large, the influence of partial heating unevenness can not be ignored. Then, this is also a problem that appears as unevenness of glossiness and unevenness of image.

  In addition, in the configuration in which a release layer is provided on the surface of the fixing film in order to prevent the toner image from being transferred onto the fixing film, the wear amount of the release layer on the surface affects the life. Specifically, when the release layer is completely lost by abrasion, the toner image adheres to the fixing film and does not peel off. Therefore, the faster the progress of wear of the release layer, the shorter the time until the complete release of the release layer, and the shorter the life of the device.

  By the way, regarding the wear of the surface of the fixing film, the portion corresponding to the edge of the end portion of the recording material tends to be the largest even if there is no unevenness in the longitudinal direction in the pressure peak. This is because the edge of the recording material is rough because it is a cut portion at the time of papermaking, and this rough portion is in linear contact with the fixing film at all times at the same position. In addition to this, since the portion corresponding to the edge of the recording material is a boundary with the non-sheet-passing portion of the recording material, it is also affected by the temperature rise of the non-sheet-passing portion when continuous sheet passing. The release layer of the fixing film may lose its abrasion resistance due to excessive heating such as non-sheet-passing temperature rise, depending on the material. Therefore, when such a release layer material is used, abrasion due to rubbing against the edge of the recording material is promoted. The portion corresponding to the edge of the recording material of the fixing film is scraped into a thin linear shape at first, and the wear gradually spreads toward the central portion of the fixing film starting from there. In the configuration of the thick nip, the pressure peak at the end is large, which further accelerates the wear of the portion corresponding to the edge of the recording material, and the life of the apparatus becomes shorter than the configuration of the middle thick nip.

  In view of the above problems, the present invention has an object to suppress the influence on the image quality due to the pressure peak in the fixing nip portion becoming excessively large, and to suppress the decrease in the life of the apparatus.

In order to achieve the above object, a fixing device according to the present invention is:
A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
The roller member has a first diameter portion having a first diameter and a second diameter portion having a second diameter larger than the first diameter in the axial direction of the roller member. ,
The shortest distance from the portion in pressure contact with the second diameter portion to the central axis in the protrusion is longer than the shortest distance from the portion in pressure contact with the first diameter portion to the central axis. Do.

Further, the fixing device according to the present invention is
A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
The roller member has a first diameter portion in which the width of the fixing nip portion in the transport direction is a first width in the axial direction of the roller member, and a second width larger than the first width. Has a second diameter,
The shortest distance from the portion in pressure contact with the second diameter portion to the central axis in the protrusion is longer than the shortest distance from the portion in pressure contact with the first diameter portion to the central axis. Do.

Further, the fixing device according to the present invention is
A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
In the axial direction of the roller member, the protrusion has a first protrusion with a first amount of protrusion and a second protrusion with a second amount of protrusion greater than the first amount of protrusion. Have
The second projecting portion may be provided farther from the central portion of the fixing nip portion in the transport direction than the first projecting portion.

  According to the present invention, it is possible to suppress the influence on the image quality due to the pressure peak in the fixing nip portion becoming excessively large, and to suppress the deterioration of the life of the apparatus.

FIG. 1 is a schematic cross-sectional view showing the entire configuration of an image forming apparatus according to the present embodiment. FIG. 2 shows a fixing device of Example 1 FIG. 2 is a schematic view showing a fixing device of Example 1 The figure which shows the pressure roller of Example 1 The figure which shows the shape of the fixing nip part of Example 1, and an inner surface nip part. The figure which shows the heater holder of Example 1, and a heater Sectional view showing the heater holder and the heater of Example 1 The figure explaining the positional relationship of the protrusion part with respect to the nip part of Example 1 Diagram showing a conventional heater holder and heater Cross-sectional view showing a heater holder and a heater of a conventional example The figure explaining the positional relationship of the projection part to the nip part of a prior art example Graph showing pressure distribution of Example 1 and Conventional Example Graph comparing longitudinal distribution with respect to glossiness of Example 1 and Conventional Example Graph comparing the conventional example and Example 1 with respect to the transition of the amount of wear The figure which shows the heater holder of Example 2, and a heater The figure which shows the positional relationship of the protrusion part with respect to the nip part of Example 2. Graph comparing the pressure distribution in the longitudinal direction by the protruding portion in Example 2 and Example 1 The figure which shows the heater holder of Example 3, and a heater The figure which shows the positional relationship of the protrusion part with respect to the nip part of Example 3. Graph comparing longitudinal distribution of pressure peaks of Examples 1 to 3 The figure which shows the positional relationship of the protrusion part with respect to the nip part of Example 4. The figure which looked at the heater holder of Example 4, and a heater from the heater attachment surface side The figure explaining the peak of the pressure of Example 5 The figure which shows the heater holder of Example 5, and a heater The figure which shows the shape of the fixing nip part in Example 6 The figure which compares and demonstrates the structure of Example 6 and the prior art example 2 Graph showing pressure distribution of Example 6 and Conventional Example 2 Diagram for explaining the seventh embodiment The figure which shows the nip formation member of Example 7 A schematic view of a pressure film type fixing device of Example 8.

  Hereinafter, with reference to the drawings, modes for carrying out the present invention will be exemplarily described in detail based on examples. However, the dimensions, materials, shapes, etc. of the components described in this embodiment should be changed as appropriate depending on the configuration of the apparatus to which the invention is applied and various conditions. That is, the scope of the present invention is not intended to be limited to the following embodiments.

(1) Overall Configuration of Image Forming Apparatus First, the overall configuration of an image forming apparatus according to an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the entire configuration of the image forming apparatus according to the present embodiment. The following description will be made using a full color laser beam printer (hereinafter simply referred to as a printer) 71 provided with a plurality of photosensitive drums 1 as an example of the image forming apparatus, but the present invention is not limited to this. It may be a monochrome copier or printer equipped with

  As shown in FIG. 1, the printer 71 mainly includes image forming stations 7Y, 7M, 7C, 7K corresponding to the respective colors of yellow Y, magenta M, cyan C, and black K, and an intermediate transfer belt 29, secondary. A transfer roller 63 and a fixing device 72 are provided. Hereinafter, in the case where distinction is not particularly required, the suffixes Y, M, C, and K given to reference numerals to indicate that they are elements provided for any color will be omitted.

  In the lower part of the printer 71, the cassette 61 is accommodated so as to be able to be pulled out. In the cassette 61, recording materials P such as paper are stacked and stored. The recording material P is fed from the paper feed cassette 61 by the pickup roller 62, separated by the feed / retard roller pair 14 one by one, and fed to the registration roller 15.

  Each image forming station 7 is provided with a photosensitive drum 1 as an image carrier, a charging device 2, a developing device 4, a cleaning blade 6 and a primary transfer portion 8. The charging device 2 uniformly charges the surface of the photosensitive drum 1. The developing device 4 has a developing roller 5 for attaching toner to the electrostatic latent image formed on the photosensitive drum 1 to form a toner image. The primary transfer portion 8 primarily transfers the toner image formed on the photosensitive drum 1 onto the intermediate transfer belt 29. The cleaning blade 6 removes toner remaining on the photosensitive drum 1 without being primarily transferred.

  Further, below the image forming station 7, a laser scanner 3Y is configured to irradiate the charged photosensitive drum 1 with a laser beam based on image information to form an electrostatic latent image on each photosensitive drum 1, 3M, 3C, 3K are arranged. The toner image on the intermediate transfer belt 29 transferred by the primary transfer portion 8 is secondarily transferred onto the recording material P by a secondary transfer portion N1 formed by the opposing roller 67 and the secondary transfer roller 63. The secondary transfer residual toner remaining on the intermediate transfer belt 29 without being transferred to the recording material P at the secondary transfer portion N1 is removed and collected by the belt cleaning device 66. The recording material P that has passed through the secondary transfer portion N1 then passes through the fixing device 72, and the toner image is fixed onto the recording material P.

  Thereafter, the recording material P on which the toner image is fixed is conveyed to the discharge roller pair 64. After passing through the discharge roller pair 64, the recording material P is discharged to the recording material loading unit 65. The printer 71 in the present embodiment can pass A3 size recording material, and the sheet supply possible width of the recording material P corresponds to 320 mm in the direction orthogonal to the transport direction.

Example 1
(2) Fixing Device Next, the fixing device according to the first embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 is a view showing the fixing device of Example 1, FIG. 2 (a) is a schematic cross-sectional view, and FIG. 2 (b) is an enlarged view of the vicinity of the fixing nip portion of FIG. . FIG. 3 is a schematic view of the fixing device of the first embodiment. In the following description, regarding the fixing device 72 and the members constituting the fixing device 72, the longitudinal direction is the axial direction of the pressure roller 20, that is, the direction orthogonal to the conveyance direction of the recording material P. The direction of the fixing device 72 in FIG. 2 is illustrated by rotating the direction of FIG. 1 by 90 degrees for the sake of convenience of the description.

  A fixing device 72 according to the first embodiment includes a fixing film 10 as a cylindrical flexible film member and a pressure roller 20 provided with a pressure roller 20 in pressure contact with the fixing film 10. Device of The pressure roller 20 is rotationally driven to cause the fixing film 10 to rotate. Then, the toner image on the recording material P is heated and fixed on the recording material P while the recording material P is nipped and conveyed in the fixing nip portion N2 formed by the fixing film 10 and the pressure roller 20.

  Further, as shown in FIGS. 2 and 3, the fixing device 72 includes a heater 30 as a heating body, a heater holder 41 as a holding member, a pressure stay 42 as a rigid pressure member, and a pressure application means as a pressure force urging means. A pressure means 43 and a fixing flange 45 as a regulating member are provided. The heater 30, the fixing film 10, the heater holder 41, the pressure stay 42, and the pressure roller 20 are all elongated members in the longitudinal direction. The fixing flange 45 regulates movement of the fixing film 10 in the longitudinal direction. The heater 30 and the heater holder 41 of the first embodiment correspond to the contact member of the present invention, and are provided in contact with the inner peripheral surface of the fixing film 10.

2-1) Fixing Film The fixing film 10 includes a base layer 11 formed in an endless film shape of a material having heat resistance and flexibility, and a release layer 12 provided on the outer peripheral surface of the base layer 11. And. In addition, an elastic layer 13 such as silicone rubber is provided on the outer peripheral surface of the base layer 11 with the inner peripheral surface side of the release layer 12 in order to improve fixability and image quality. By having the elastic layer 13, heat can be uniformly applied by wrapping the unfixed toner image T carried on the recording material P. However, if the thickness of the elastic layer 13 is too thick, the heat capacity is increased, and it takes time to reach the temperature necessary for fixing the toner image T to the recording material P, the temperature of the fixing film 10 The on-demand characteristic peculiar to the heating method is reduced. Therefore, the thickness of the elastic layer 13 is 50 μm or more and 500 μm or less. The thermal conductivity of the elastic layer 13 is preferably as high as possible, and is preferably 0.5 W / mK or more. In order to achieve such thermal conductivity, a thermally conductive filler such as ZnO, Al2O3, SiC, metallic silicon or the like is mixed into silicone rubber to adjust the thermal conductivity.

  The base layer 11 may be a thin-walled flexible endless belt made of a thin metal such as SUS or Ni having high thermal conductivity, or a heat-resistant resin such as polyimide, polyamide imide, or PEEK. . The outer surface of the base layer 11 is coated with a fluorine resin such as PFA, PTFE, FEP or the like separately or as a release layer 12 or a tube of the above-mentioned fluorine resin single product or a blend is coated. The thickness of the release layer 12 needs to be 5 μm or more from the viewpoint of durability. If the thickness of the releasing layer 12 is too thick, the thermal conductivity is lowered to adversely affect the fixing property, so the thickness needs to be 50 μm or less. In the fixing film 10 of Example 1, SUS is used as the material of the base layer 11, the thickness of the base layer 11 is 30 μm, and the inner diameter of the base layer 11 is 30 mm. The elastic layer 13 is made of silicone rubber having a thermal conductivity of 1.3 W / (m · K) and has a thickness of 275 μm. Further, as the release layer 12, a tube of PFA is used. The thickness of the release layer 12 is set to 20 μm in order to obtain good fixability.

2-2) Heater Holder The heater holder 41 is formed of a heat resistant resin such as liquid crystal polymer, phenol resin, PPS, PEEK or the like in a semicircular wedge shape in cross section. As shown in FIG. 2B, a concaved groove 41a is provided on the lower surface (the surface on the pressure roller 20 side) of the heater holder 41 along the longitudinal direction of the heater holder 41. Then, the heater 30 is held by the recessed groove 41a. The fixing film 10 is loosely fitted on the outer periphery of the heater holder 41. Both ends of the heater holder 41 in the longitudinal direction of the heater holder 41 with which the fixing film 10 is externally fitted are held at both ends of the device frame 27 (not shown).

  As shown in FIG. 2B, the heater holder 41 according to the first embodiment has a protrusion 41b on the downstream side in the conveyance direction of the recording material P in the fixing nip N2. The detailed shape of the protrusion 41 b will be described later.

2-3) Pressure Roller The pressure roller according to the first embodiment will be described with reference to FIGS. 2 (a) and 4. FIG. FIG. 4 is a view showing the pressure roller of the first embodiment. The pressure roller 20 is provided on the core shaft portion 21, at least one heat resistant elastic layer 22 provided on the outer peripheral surface of the core shaft portion 21, and on the outer peripheral surface of the heat resistant elastic layer 22. And the release layer 24 that is being The heat resistant elastic layer 22 can be made of, for example, a general heat resistant rubber elastic material such as silicone rubber or fluoro rubber. The release layer 24 is coated with a fluorine resin such as PFA, PTFE, or FEP separately or as a blend on the heat resistant elastic layer 22 or the tube of the fluorine resin separately or in a blend is coated on the heat resistant elastic layer 22. . In Example 1, an iron cored bar with a diameter of 22 mm was used as the cored bar 21, and silicone rubber with a thickness of 4 mm was used for the heat-resistant elastic layer 22. As the release layer 24, a 50 μm tube of PFA is coated.

As shown in FIG. 4, the pressure roller 20 of Example 1 has a reverse crown shape in which the diameter is larger at both end portions (second diameter portions) than at the central portion (first diameter portion) in the longitudinal direction. ing. Pressure roller 20
Reverse crown amount Cr of Example 1 where half of the difference between the diameter D2 (second diameter) of the end in the longitudinal direction and the diameter D1 (first diameter) of the central portion is the reverse crown amount Cr. Is 0.15 mm. By forming the pressure roller 20 in the reverse crown shape as described above, the conveyance speed of the recording material P by the rotation of the pressure roller 20 becomes faster in the vicinity of both ends than the central portion, and the recording material P is conveyed at the fixing nip portion. When you move the center part from the central part, it receives a force. Therefore, the generation of wrinkles in the recording material P can be suppressed.

2-4) Heater The heater 30 is a plate-like heating element that rapidly heats the fixing film 10 while being in contact with the inner peripheral surface of the fixing film 10. The heater 30 has a longitudinally elongated substrate. As the substrate, a ceramic substrate such as alumina or aluminum nitride, or a heat resistant resin substrate such as polyimide, PPS, or liquid crystal polymer can be used. On the back surface of the substrate (the surface on the opposite side to the pressure roller 20), a conductive heating resistance layer such as Ag / Pd (silver palladium), RuO 2, Ta 2 N, etc. is coated in a strip shape along the longitudinal direction of the substrate. It is formed. In addition, a glass coat is formed on the back surface of the substrate in order to ensure the protection and the insulation of the heat generating resistance layer. A sliding layer is provided on the surface of the substrate (the surface on the pressure roller 20 side) in order to improve the slidability of the substrate. As the sliding layer, a heat resistant resin such as polyimide or polyamideimide, a glass coat, or the like is used. In the first embodiment, the dimensions of the substrate of the heater 30 are 350 mm in the longitudinal direction, 10 mm in the short direction (the conveying direction of the recording material), and 0.6 mm in the thickness direction.

2-5) Pressurizing Stay The pressurizing stay 42 is formed in a U-shape in a downward cross-sectional shape by a material such as a metal having rigidity. The pressure stay 42 is disposed at the center of the upper surface (surface opposite to the pressure roller 20) of the heater holder 41 in the short direction inside the fixing film 10. The longitudinal ends of the pressure stay 42 are urged toward the axis of the pressure roller 20 by the pressure means 43 such as a pressure spring via the fixing flange 45 held by the device frame 27. Thus, the heater 30 is pressed against the surface of the pressure roller 20 through the fixing film 10.

  Then, as shown in FIG. 5, an inner surface nip N3 of a predetermined width is formed between the heater 30 and the fixing film 10, and a fixing nip N2 of a predetermined width is formed between the fixing film 10 and the pressure roller 20. It is formed. Hereinafter, for convenience of explanation, the inner surface nip N3 and the fixing nip N2 may be collectively referred to as a nip. The heat necessary for heating and fixing the toner image T is transmitted from the heater 30 to the fixing film 10 at the inner surface nip N3, and the heat is transmitted from the fixing film 10 to the recording material P at the fixing nip N2.

  FIG. 5 is a view showing the shapes of the fixing nip portion and the inner surface nip portion. In the fixing device of the first embodiment, as described above, the pressure roller 20 has a reverse crown shape, so the nip widths of the fixing nip portion N2 and the inner surface nip portion N3 differ in the longitudinal direction, and the end portion It is getting bigger.

2-6) Fixing Operation of Fixing Device The rotation drive / temperature adjustment control unit 44 as the control means shown in FIG. 3 executes a predetermined rotation drive control sequence according to the print command, and drives the motor M as a drive source. Then, the drive gear G provided at the longitudinal direction end of the core shaft portion 21 of the pressure roller 20 is rotated. As a result, the pressure roller 20 rotates at a predetermined circumferential speed. At this time, a rotational force that rotates in the direction opposite to the rotational direction of the pressure roller 20 acts on the fixing film 10 by the frictional force between the surface of the pressure roller 20 and the surface of the fixing film 10 in the fixing nip portion N2. Thereby, the fixing film 10 is driven to rotate the outer side of the heater holder 41 at substantially the same circumferential speed as the pressure roller 20 while the inner surface of the fixing film 10 contacts the sliding layer of the heater 30.

  Further, the rotation drive / temperature adjustment control unit 44 executes a predetermined temperature control sequence in accordance with the print command, and energizes the energization heat generation resistance layer of the heater 30. The energization heat generation resistance layer generates heat by the energization, and the heater 30 rapidly raises the temperature to heat the fixing film 10. The temperature of the fixing film 10 is detected by a thermistor 35 (see FIG. 2A) as a temperature detecting means provided inside the fixing film 10, and the thermistor 35 controls the temperature detection signal of the fixing film 10. Output to The thermistor 35 is disposed in a region through which the recording material P of various sizes usable for the printer 71 always passes. The rotational drive and temperature control unit 44 takes in a temperature detection signal from the thermistor 35, and controls energization of the energization heat generation resistance layer based on the temperature detection signal so that the fixing film 10 has a predetermined target temperature.

  As described above, the recording material P carrying the unfixed toner image T is guided along the entrance guide 28 to the fixing nip N 2 in a state where the temperature of the fixing film 10 is maintained at the predetermined target temperature. The sheet is nipped and conveyed by the pressure roller 20 and the pressure roller 20. In the conveyance process, the heat of the fixing film 10 heated by the heater 30 and the pressure of the fixing nip N2 are applied to the recording material P, and the toner image T is fixed on the surface of the recording material P by the heat and pressure. Ru. The recording material P which has passed through the fixing nip portion N 2 is separated from the fixing film 10 by curvature, and is discharged by the fixing discharge roller 26.

(3) Shape of Protrusive Portion 3-1) Shape of Protrusive Portion of First Embodiment The protrusion 41 b of the heater holder 41 of the first embodiment will be described in detail with reference to FIGS. 2 and 6 to 8. As shown in FIG. 2B, the protrusion 41b protrudes from the sliding surface by a protrusion amount h toward the central axis of the pressure roller 20 (toward the outer surface of the fixing film 10). In the fixing device of the first embodiment, the protrusion amount h is 0.2 mm. Here, the sliding surface refers to the surface of the heater 30 on which the fixing film 10 slides. The protruding portion 41 b presses the recording material P with the largest force among at least the fixing nip N 2 in the conveyance direction of the recording material P other than the central portion of the fixing nip N 2.

  FIG. 6 is a view showing the heater holder and the heater of Example 1, and FIG. 6 (a) is an external perspective view, and FIG. 6 (b) is a view seen from the heater mounting surface side. In the first embodiment, the position of the projecting portion 41 b provided in the heater holder 41 is different in the longitudinal direction, and the end portion is provided on the downstream side in the conveyance direction of the recording material P with respect to the central portion.

  7A and 7B are cross-sectional views showing the heater holder and the heater of Example 1, and FIG. 7A is a cross-sectional view of an end portion in the longitudinal direction, and FIG. 7B is a cross-sectional view of a central portion in the longitudinal direction. . The protruding portion 41 b is provided such that its leading end comes at a distance r 1 from the downstream end of the heater attachment groove 41 a of the heater holder 41 in the conveyance direction of the recording material P. Further, the distance from the downstream end of the inner surface nip portion N3 to the tip of the projecting portion 41b is s1. In the first embodiment, as shown in FIG. 7, the shortest distance from the protrusion 41b at the end in the longitudinal direction to the central axis O of the pressure roller 20 is x1, and from the protrusion 41b at the center in the longitudinal direction When the distance to the center axis O is x2, the relationship of x1> x2 is established.

  In the first embodiment, the position of the protruding portion 41b is determined based on the position of the inner surface nip portion N3. Specifically, the protrusion 41b is disposed such that the distance s1 is substantially equal at the center and at the end. In the configuration of the first embodiment, the protruding portion 41b is disposed downstream of the central portion with respect to the central portion because the inner surface nip portion N3 is larger in the end portion than in the central portion. That is, the distance r1 from the downstream end of the heater attachment groove 41a of the protrusion 41b is in the relation of central portion <end portion. In Example 1, the distance s1 is 2 mm.

FIG. 8 is a view for explaining the positional relationship between the fixing nip portion and the projecting portion with respect to the inner surface nip portion in the first embodiment. As shown in FIG. 8, the protrusion 41 b of the first embodiment is formed separately at the central portion 41 c and the end portions 41 d and 41 e. In the first embodiment, the length of the central portion 41c is 285 mm, and the length of both ends 41d and 41e is 20 mm.

  In the first embodiment, since the pressure roller 20 has a reverse crown shape, the inner surface nip portion N3 has a curved shape, and the nip width rapidly increases near the end. In the first embodiment, the protrusion 41 b is formed in a straight shape in the longitudinal direction with respect to such a curved nip shape. For this reason, in each area | region of the center part 41c of the protrusion part 41b, the edge parts 41d and 41e, all the distance s1 is not the same, but is slightly different.

  Therefore, in the first embodiment, the position where the distance s1 is equal at the center and the end is defined by A at the center and B at the end. That is, the position of the protrusion 41 b was set so that the distance s1 would be equal at the position A at the center and the position B at the end. Position A is a position corresponding to the center in the longitudinal direction. Position B is a position of 148.5 mm from position A. This is the position where the end of the paper passes when A4 size paper is traversed. The reason for this definition is that the A4 size recording material is most frequently used. However, the positions of the positions A and B are not limited to this. For example, the position B may be a position corresponding to the center in the longitudinal direction of the end 41 d (end 41 e) of the protrusion 41, that is, a position 152.5 mm from the position A in the first embodiment. The numerical values specifically shown in the first embodiment are optimized by the apparatus configuration, and are not limited to these numerical values.

3-2) Shape of Projection of Conventional Example The projection 41 b of the heater holder 41 of the conventional example will be described with reference to FIGS. 9 to 11. FIG. 9 is a view showing a heater holder and a heater according to the conventional example, and FIG. 9 (a) is an external perspective view, and FIG. 9 (b) is a view seen from the heater mounting surface side. The protrusion amount h of the protrusion 41b in the conventional example is 0.2 mm as in the first embodiment. FIG. 10 is a cross-sectional view showing a heater holder and a heater according to a conventional example, FIG. 10 (a) is a cross-sectional view of an end in the longitudinal direction, and FIG. 10 (b) is a cross-sectional view of a central portion in the longitudinal direction. FIG. 11 is a view for explaining the positional relationship between the fixing nip portion and the projecting portion with respect to the inner surface nip portion in the conventional example.

  In the conventional example, the projecting portions 41b are arranged at the same position longitudinally uniformly in the conveyance direction of the recording material. The distance r1 from the downstream end of the heater attachment groove 41a of the heater holder 41 to the tip of the projection 41b is equal at the central portion 41c and the end portions 41d and 41e. The distance s1 from the downstream end of the inner surface nip portion N3 to the projecting portion 41b is in the relation of central portion> end portion. In the conventional example, the values at the center and the end of the distance s1 are 2 mm and 1.7 mm, respectively.

(4) Effects of Example 1 Referring to FIG. 12, the effects of Example 1 are compared with those of the conventional example in terms of pressure distribution, glossiness, and wear resistance of the release layer 12 of the fixing film 10. While explaining. First, the pressure distribution in the conveyance direction of the recording material P will be described in comparison with the conventional example. FIG. 12 is a graph showing the pressure distribution in the fixing nip portion of Example 1 and the conventional example. FIG. 12A shows the pressure distribution of the fixing nip portion in the conveyance direction of the recording material P at the center portion A and the end portion B of the conventional example.

  There is a pressure peak C on the downstream side in the transport direction at both the longitudinal end and the center. The pressure peak C is formed by the protrusion 41 b of the heater holder 41. In the configuration of the conventional example, the pressure peak formed on the downstream side in the transport direction is larger than the central portion A because the amount of penetration of the protrusion 41b to the pressure roller 20 is larger at the end B than at the central portion A. .

FIG. 12B is a pressure distribution of the fixing nip portion in the conveyance direction of the recording material P at the center portion A and the end portion B of the first embodiment. In the first embodiment, since the protrusion 41b at the end B is shifted to the downstream of the recording material P in the conveyance direction than in the conventional example, the amount of penetration of the protrusion 41b into the pressure roller 20 becomes smaller. The peak is formed lower than in the conventional example. For this reason, the pressure by the protruding portion 41 b is substantially the same at the central portion A and the end portion B.

  FIG.12 (c) is the figure which compared the distribution of the longitudinal direction about the pressure peak of the downstream side of Example 1 and a prior art example. As illustrated, the first embodiment can make the difference between the pressure peaks at the center and the end smaller than in the conventional example. The difference in pressure peak appears as the difference in gloss of the toner image fixed on the recording material P.

  FIG. 13 is a graph comparing the distribution in the longitudinal direction with respect to the glossiness of Example 1 and the conventional example, but in Example 1, the difference between the pressure peaks at the center and the end can be made smaller than that of the conventional example. As a result, it has become possible to reduce the difference between the end and the center with respect to the gloss.

  Next, the durability of the fixing film 10 against the wear of the release layer 12 will be described in comparison with the conventional example. FIG. 14 is a graph comparing the conventional example and Example 1 with respect to the transition of the amount of wear in the portion where the releasing layer 12 of the fixing film 10 rubs against the edge of the recording material P. In the conventional example, since the pressure peak on the downstream side in the conveyance direction of the recording material P formed by the protruding portion 41 b is large, the progress of wear is fast. On the other hand, in Example 1, by setting the pressure peak on the downstream side lower than that of the conventional example, it is possible to suppress the progress of wear compared to the conventional example.

  As described above, the first embodiment can lower the pressure peak at the longitudinal end than in the conventional case, and can make the pressure peak substantially the same as the center. Therefore, in Example 1, it is possible to reduce the difference in glossiness between the center portion and the end portion and to improve the durability against abrasion of the release layer 12. As a result, the influence on the image quality can be suppressed, and the decrease in the life of the fixing device 72 can be suppressed.

  In the first embodiment, the position of the projection 41b is determined based on the distance s1 from the downstream end of the inner surface nip N3 to the tip of the projection 41b. However, the present invention is not necessarily limited to this method. The protrusions 41b may be disposed so that the longitudinal pressure peaks are substantially even, and may be determined, for example, by adjusting the position of the protrusions 41b according to the width of the fixing nip N2. The same applies to the following embodiments.

  As described above, in the projecting portion 41b, a portion in which the shortest distance x1 from the portion in pressure contact with the second diameter portion of the pressure roller 20 to the central axis O of the pressure roller 20 is in pressure contact with the first diameter portion The shortest distance x2 from the point to the central axis O is also shortened (see FIG. 7). The same applies to the other embodiments described below. In the first embodiment, specifically, the portion in pressure contact with the second diameter portion is provided downstream of the portion in pressure contact with the first diameter portion, in the conveyance direction of the recording material P. A configuration like this was realized. The second diameter portion is a portion having a diameter larger than that of the first diameter portion. In Example 1, the central portion of the pressure roller 20 corresponds to the first diameter portion, and both end portions have a second diameter. Corresponds to the department.

(Example 2)
Second Embodiment A second embodiment of the present invention will now be described with reference to FIGS. The basic configuration and operation of the fixing device of the second embodiment are the same as the fixing device of the first embodiment. Therefore, the elements having the same or corresponding functions and configurations as those of the fixing device of the first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted, and the characteristic points in the second embodiment will be described. The same applies to the following embodiments.

FIG. 15 is a view showing the heater holder and the heater of Example 2, FIG. 15 (a) is an external perspective view, and FIG. 15 (b) is a view seen from the heater mounting surface side. Similar to the first embodiment, the protrusion 41b of the second embodiment is formed downstream of the central portion of the recording material P in the conveyance direction, and the end portion is disposed more downstream than the central portion. ing. And the protrusion part 41b of Example 2 is not discontinuous in the boundary of the center part 41c and the edge parts 41d and 41e like the protrusion part 41b of Example 1, and as shown in FIG.15 (b) , Is formed continuously, and has a V shape.

  FIG. 16 is a view showing the positional relationship between the protruding portion 41b and the shapes of the fixing nip portion N2 and the inner surface nip portion N3 in the second embodiment. It is the same as that of the first embodiment that the inner surface nip portion N3 has a curved shape. The protrusion 41b of the second embodiment is formed along the downstream end of the inner surface nip portion N3 to a certain extent. Specifically, the protrusion 41b is disposed such that the distance s1 between the downstream end of the inner surface nip N3 and the protrusion 41b at the center A and the end B is equal, and the protrusion at the center A and the end B is It forms so that the part 41b may become on the same straight line. Therefore, as in the first embodiment, the distance s1 between the downstream end of the inner surface nip N3 and the projection 41b does not change suddenly at the boundary between the center 41c and the ends 41d and 41e.

  FIG. 17 is a graph comparing the pressure distribution in the longitudinal direction by the protruding portion 41 b of the second embodiment and the first embodiment. As illustrated, in the first embodiment, since the protrusion 41b has a discontinuous boundary between the central portion 41c and the end portions 41d and 41e, the distance s1 between the downstream end of the inner surface nip N3 and the protrusion 41b is the boundary The pressure peak suddenly changed near this boundary. On the other hand, in the second embodiment, since the protrusion 41b is continuously arranged without the boundary between the central portion 41c and the end portions 41d and 41e, the distance between the downstream end of the inner surface nip N3 and the protrusion 41b As in the first embodiment, s1 does not change suddenly. Therefore, in the second embodiment, the pressure peak can be gradually changed in the longitudinal direction. Therefore, in the second embodiment, the difference in pressure peak near the boundary between the central portion 41c and the end portions 41d and 41e as in the first embodiment can be improved, and an image with less unevenness of glossiness near this boundary can be obtained. become.

(Example 3)
Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 18 is a view showing the heater holder and the heater of Example 3, FIG. 18 (a) is an external perspective view, and FIG. 18 (b) is a view seen from the heater mounting surface side. The protrusion 41b of the third embodiment is not straight as in the first and second embodiments, but has a curved shape that draws a gentle curve. FIG. 19 is a view showing the positional relationship between the fixing nip N2 and the projection 41b with respect to the inner surface nip N3 in the third embodiment. As shown in FIG. 19, the inner surface nip portion N3 has a curved shape as in the first and second embodiments. In the third embodiment, the protrusion 41 b is formed to be curved along the nip shape. Specifically, the position of the protruding portion 41b was set such that the distance s1 between the downstream end of the inner surface nip portion N3 and the tip of the protruding portion 41b is equal over the entire longitudinal direction. Therefore, as in the first and second embodiments, the distances s1 are not equal only at limited positions such as the central portion A and the end portion B.

  FIG. 20: is the figure which compared the distribution of the longitudinal direction about the pressure peak of Examples 1-3. In the first and second embodiments, while the inner surface nip portion N3 is curved, the projecting portion 41b is formed in a straight line. For this reason, the distance s1 from the downstream end of the inner surface nip N3 to the tip of the projection 41b can not be made uniform in the longitudinal direction, and the pressure peak is slightly different in the longitudinal direction. Therefore, in Examples 1 and 2, the unevenness of the glossiness due to the pressure peak still occurs.

On the other hand, in the third embodiment, the protruding portion 41 b is also formed in a curved shape in accordance with the curved shape of the inner surface nip portion N3. As a result, the pressure peak formed by the protrusion 41 b can be made substantially the same throughout the longitudinal direction. That is, the difference between the pressure peaks in the longitudinal direction can be further improved than in the first and second embodiments, and an image having no unevenness in glossiness can be obtained in the entire longitudinal direction.

  In addition, the uniform pressure peak can further improve the wear unevenness in the longitudinal direction of the release layer of the fixing film 10. With respect to the wear of the recording material P due to the edge of the recording material P and the rubbing of the fixing film 10, in the configurations of the first and second embodiments, the maximum effect is obtained with respect to the size of the recording material P as a target. Conversely, the amount of wear other than the target size may be slightly larger than the target size. For example, in the configuration of the first embodiment, when the positions A and B at which the distances s1 are equal are determined with the A4 size as a target, other sizes such as longitudinal feeding of the B4 size, etc. There was a possibility that the amount of wear increased. However, in Example 3, since the pressure peak in the longitudinal direction is uniform, for example, the wear amount of the portion corresponding to the edge of the recording material P is made the same for recording materials of any size, not limited to A4 size. it can.

  As described above, in the third embodiment, the shape of the projecting portion 41b is also curved along the curved shape of the inner surface nip portion N3, thereby further reducing unevenness in pressure peak as compared with the first and second embodiments. , Glossiness and abrasion unevenness of the surface of the fixing film can be improved. In the third embodiment, the positions of the protrusions 41b are set so that the distance s1 from the downstream end of the inner surface nip N3 is equal over the entire longitudinal direction, but the distance s1 is necessarily equal over the entire longitudinal direction. There is no need. By curving the projecting portion 41b in accordance with the curved nip shape as in the third embodiment, it is possible to improve the unevenness of the glossiness and the unevenness of the abrasion amount of the releasing layer of the fixing film. Therefore, as described in the first embodiment, it is not necessary to determine the position of the protrusion 41b based on the distance s1, and the distance s1 may be different in the longitudinal direction within the allowable range.

(Example 4)
A fourth embodiment of the present invention will now be described with reference to FIGS. 21 and 22. FIG. 21 is a view showing the positional relationship between the fixing nip N2 and the projection 41b with respect to the inner surface nip N3 in the fourth embodiment. The nip widths of the fixing nip portion N2 and the inner surface nip portion N3 in Example 4 are different in the longitudinal direction, and the nip width (second width) at the central portion is larger than the nip width (first width) at the end portion. It is a medium thick nip. In order to make such a nip shape, the pressure applied to the central portion is made larger than the pressure applied to the end portion. Specifically, the thickness of the central portion of the heater holding surface of the heater holder 41 is larger than that of the both ends, so that the heater holding surface is convex toward the pressure roller 20 side. In Example 2, the diameter of the pressure roller 20 as a roller member is uniform in the longitudinal direction.

  For this reason, the amount of penetration of the heater 30 and the heater holder 41 into the pressure roller 20 is larger at the central portion than at the end, and as a result, the pressure applied to the central portion is larger than the pressure applied to the nip end. be able to. As described above, by setting the medium thickness nip, the wear amount of the portion corresponding to the edge of the recording material P in the releasing layer of the fixing film 10 can be obtained by using the thick nip as in Example 1 in which the pressure at the nip end is large. Can be suppressed more than the configuration of

  FIG. 22 is a view of the heater holder 41 and the heater 30 of the fourth embodiment as viewed from the heater mounting surface side. The central portion of the protrusion 41b of the fourth embodiment is disposed further downstream with respect to the end, and has a curved shape. In the fourth embodiment, the protrusion 41 b is formed to conform to the shape of the downstream end of the inner surface nip N 3. Specifically, the position of the protrusion 41b is set so that the distance s1 between the downstream end of the inner surface nip N3 and the tip of the protrusion 41b is equal over the entire longitudinal direction. By doing this, the pressure peak formed by the protrusion 41 b can be made substantially the same throughout the longitudinal direction. Therefore, it becomes possible to obtain an image without unevenness in glossiness in the entire longitudinal direction.

  In addition, uniform pressure peaks can be obtained, so that uneven wear in the longitudinal direction of the release layer of the fixing film 10 can be improved. When the projecting portion 41b is disposed straight in the longitudinal direction as in the conventional example described in the description of the first embodiment, the central portion of the distance s1 from the downstream end of the inner surface nip portion N3 to the projecting portion 41b is compared with the end portion. It becomes smaller. Therefore, the pressure peak formed by the projecting portion 41 b becomes large at the central portion in the longitudinal direction. As a result, the amount of wear of the release layer of the fixing film 10 at the central portion becomes large, and wear unevenness in the longitudinal direction has occurred. On the other hand, in the fourth embodiment, since uniform pressure peaks can be obtained in the longitudinal direction, wear at the central portion can be suppressed.

  As described above, in the fourth embodiment, the inner surface nip portion N3 has a medium thick nip shape, and along the curved shape of the inner surface nip portion N3, the shape of the projecting portion 41b is also curved. With such a configuration, unevenness in pressure peak can be reduced, and glossiness and abrasion unevenness on the surface of the fixing film can be improved. In addition, the shape of the protrusion part 41b is not limited to the curved shape. For example, the protrusion 41b may be linearly arranged, and the center portion may be shifted further downstream with respect to the end. In addition, the protrusion 41 b may be in the shape of a V in which the central portion is disposed further downstream with respect to the end.

(Example 5)
A fifth embodiment of the present invention will now be described with reference to FIGS. 23 and 24. FIG. 23 is a diagram for explaining the pressure peak of the fifth embodiment. FIG. 23A is an enlarged view of the nip portion of the fixing device in the fifth embodiment. FIG. 23B is a pressure distribution diagram of the recording material P in the conveyance direction at the inner nip portion of the fifth embodiment. As illustrated, in the fifth embodiment, the protrusion 41 b of the heater holder 41 is on the upstream side in the conveyance direction of the recording material P. In this case, the pressure distribution in the conveyance direction of the recording material P formed by the fixing film 10 and the pressure roller 20 has a pressure peak C on the upstream side of the conveyance direction of the recording material P.

  Thus, by providing the pressure peak on the upstream side in the conveyance direction of the recording material P, the surface of the fixing film 10 can be made to follow the pressure roller 20, and the upstream end of the fixing nip N2 and the inner nip N3. The distance of the upstream end of (hereinafter referred to as u3) can be increased. As a result, since the time for warming the recording material P is long while the recording material P reaches the inner surface nip portion N3, the preheating effect can be obtained, and good fixing property and glossiness can be obtained.

  FIG. 24 is a view showing the heater holder and the heater of Example 5, FIG. 24 (a) is an external perspective view, and FIG. 24 (b) is a view seen from the heater mounting surface side. The inner surface nip portion N3 has a curved shape as in the first to third embodiments, but the projecting portion 41b is formed along the nip shape. Specifically, the position of the protruding portion 41b was set such that the distance between the upstream end of the inner surface nip portion N3 and the protruding portion 41b (hereinafter referred to as s3) is equal over the entire longitudinal direction. As a result, the pressure peak formed by the protrusion 41 b can be made substantially the same throughout the longitudinal direction.

  Then, by obtaining an even pressure peak, it is possible to improve the amount of wear at the portion where the release layer of the fixing film 10 rubs against the end portion of the recording material P. As in the conventional example, when the projecting portion 41b is disposed straight in the longitudinal direction, the distance s3 from the upstream end of the inner surface nip portion N3 to the projecting portion 41b is smaller in the end portion than in the central portion. Therefore, the pressure peak formed by the protrusion 41 b becomes large at the longitudinal end. As a result, the progress of wear in the portion where the releasing layer of the fixing film 10 rubs against the edge of the recording material P is accelerated. On the other hand, in Example 5, since the pressure peak at the end can be made substantially the same as that at the center, the progress of wear at the portion where the release layer of the fixing film 10 rubs against the end of the recording material It can be suppressed more than before.

  Further, in Example 5, by obtaining uniform pressure peaks, it is possible to suppress unevenness of glossiness and fixability caused by pressure peaks, and obtain an image with less unevenness of glossiness and fixability in the entire longitudinal direction. Can. As described above, in the fifth embodiment, the pressure peak due to the protrusion 41 b can be made substantially the same in the entire longitudinal direction. Therefore, it is possible to suppress unevenness in glossiness and unevenness in fixing ability, and it is possible to improve the durability against abrasion of the release layer 12.

(Example 6)
Sixth Embodiment A sixth embodiment of the present invention will now be described with reference to FIGS. FIG. 26 is a diagram for comparing and explaining the configuration of the sixth embodiment and the second prior art. FIG. 26A is a view of the heater holder and the heater of Example 6 as viewed from the downstream side in the recording material conveyance direction, and FIG. 26B is a view as viewed from the heater mounting surface side. FIG. 26 (c) is a view of the heater holder and the heater of Conventional Example 2 as viewed from the heater mounting surface side.

  In the sixth embodiment, the protrusion amount of the protrusion 41 b of the heater holder 41 differs in the longitudinal direction, and the protrusion amount (second protrusion amount) of the end (second protrusion) is the center portion (first). The protrusion amount (first protrusion amount) is larger than the protrusion amount. In the sixth embodiment, the amount of protrusion h is 0.2 mm at the center and 0.35 mm at the end. By doing this, the recording material P after passing through the fixing nip portion N2 can be curved in the longitudinal direction, and can be formed in a convex shape on the fixing film 10 side. As a result, rigidity can be given in the longitudinal direction, and bending in the transport direction can be made difficult. Therefore, the behavior of the recording material P can be regulated, and the transportability of the recording material P can be stabilized. Further, as shown in FIG. 26 (b), in the projecting portion 41b in the sixth embodiment, the end portion (second projecting portion) is disposed more downstream than the central portion (first projecting portion), and the curve is gentle. It has a curved shape that draws

  Next, Conventional Example 2 as a comparative example to Example 6 will be described. Also in the heater holder 41 of Conventional Example 2, the protrusion amount h is different in the longitudinal direction as shown in FIG. 26A, and the end portion is larger than the central portion. Similar to the sixth embodiment, the protrusion amount h in the second prior art is 0.2 mm at the center and 0.35 mm at the end. In the second conventional example, as shown in FIG. 26C, the projecting portions 41b are arranged at the same position longitudinally uniformly in the conveyance direction of the recording material P.

  Here, FIG. 25 is a view showing the shape of the fixing nip portion N2 in the sixth embodiment. As shown, the nip width of the fixing nip N2 is uniform in the longitudinal direction. The thickness of the central portion in the longitudinal direction of the heater holding surface of the heater holder 41 is made larger than that at both ends, so that the fixing nip portion N2 is adjusted to have a straight nip shape. Even in such a straight nip shape, when the protrusion 41b is disposed straight in the longitudinal direction as in Conventional Example 2 and the protrusion amount h is made different in the longitudinal direction, the pressure peak by the protrusion 41b is the longitudinal direction Makes a difference. In the sixth embodiment, in order to suppress such a difference in pressure peak, the projecting portion 41b is disposed so that the end portion is further downstream with respect to the central portion, and has a curved shape that draws a gentle curve. .

  Hereinafter, specific effects of the sixth embodiment will be described in comparison with the second conventional example. FIG. 27 is a graph showing pressure distribution of Example 6 and Conventional Example 2. FIG. 27A is a graph showing the pressure distribution in the conveyance direction of the recording material P in the fixing nip portion N2 of the second conventional example. As illustrated, the pressure peak C is on the downstream side at both the end and the center. The pressure peak is formed by the protrusion 41 b of the heater holder 41. At the end, the amount h of protrusion of the protrusion 41 b is larger than that at the center, so the amount of penetration to the pressure roller 20 is large, and the pressure peak is larger than at the center.

On the other hand, FIG. 27B is a graph showing the pressure distribution in the conveyance direction of the recording material P in the fixing nip portion N2 of the sixth embodiment. In the sixth embodiment, since the end of the protrusion 41 b is disposed more downstream than the central portion, the amount of penetration of the protrusion 41 b at the end into the pressure roller 20 can be reduced. Therefore, as shown in FIG. 27 (b), the pressure peak can be formed lower than that of the second conventional example.

  Here, FIG. 27 (c) is a view showing the distribution in the longitudinal direction with respect to the pressure peaks of Example 6 and Conventional Example 2, but the pressure peak of Conventional Example 2 is gradually applied from the center to the end. Is getting bigger. For this reason, in Conventional Example 2, the glossiness of the recording material is higher at the end portions than in the central portion, causing unevenness in the glossiness. In Example 6, the pressure peaks at the end and the center can be made substantially the same, and the pressure peaks can be formed to be uniform in the longitudinal direction. That is, the pressure peak difference in the longitudinal direction can be improved as compared with the prior art example 2, and an image without unevenness in glossiness can be obtained in the entire longitudinal direction.

  Further, in Example 6, since the pressure peak can be made substantially the same throughout the longitudinal direction, abrasion of the release layer at the portion where the release layer of the fixing film 10 rubs against the edge of the recording material is improved. It can be made smaller than that. As described above, in the sixth embodiment, even when the protrusion amount h of the protrusion 41 b is different in the longitudinal direction, the shape of the protrusion 41 b is curved to reduce the difference in pressure peak in the longitudinal direction, It is possible to suppress unevenness in glossiness and the amount of abrasion of the release layer of the fixing film.

  In addition, the shape of the protrusion part 41b is not limited to the curved shape. For example, the protrusions 41b may be arranged in a straight line, and the central portion may be arranged further downstream with respect to the end. In addition, the protrusion 41 b may be in the shape of a V in which the central portion is disposed further downstream with respect to the end.

  Further, in the sixth embodiment, the case where the protrusion amount h of the protrusion 41b is higher at the end than at the center is described, but the protrusion amount h of the protrusion 41b is also higher when the center is higher than the end. The invention is applicable. The recording material P after passing through the fixing nip portion N2 can be curved in the longitudinal direction so as to be convex toward the pressure roller 20 by increasing the protrusion amount h of the central portion with respect to the end portion. As a result, rigidity can be given in the longitudinal direction, and bending in the transport direction can be made difficult. In such a case, the pressure peak difference between the end portion and the central portion can be made substantially the same by disposing the central protruding portion 41b having a large protrusion amount h downstream of the end protruding portion 41b. . The configuration of the sixth embodiment can also be applied to the case where the protrusion 41 b is disposed on the upstream side in the conveyance direction of the recording material P. In this case, the pressure peak in the longitudinal direction can be equalized by arranging the end portion of the protrusion 41 b further downstream with respect to the central portion.

(Example 7)
A seventh embodiment of the present invention will now be described with reference to FIGS. 28 and 29. Although the fixing device used in the description of Examples 1 to 6 uses the heater 30 as a heating body, the present invention is not limited to such a heating body. Other configurations may be employed as long as the pressure peak is formed by the projecting portion regardless of the heating method. For example, the present invention can be applied to a film heating method using electromagnetic induction as shown below.

  FIG. 28 is a view for explaining the seventh embodiment. FIG. 28A is a schematic cross-sectional view of a film heating type fixing device using electromagnetic induction according to a seventh embodiment. FIG. 28B is an enlarged view of a nip portion of the fixing device of the seventh embodiment. FIG. 28C is a view showing a pressure distribution in the conveyance direction of the recording material P in the fixing nip portion N2 of the seventh embodiment. The description of the same configuration as that of the first embodiment is omitted here.

  As shown in FIG. 28A, the fixing device of Example 7 includes a fixing film 512 as a cylindrical film member as an electromagnetic induction heat generating member, and a pressure roller 20 as a roller member pressed against the fixing film 512. And. The fixing film 512 has a heat generating layer which generates heat by the action of a magnetic field as a base layer, and has a laminated structure including an elastic layer and a releasing layer on the outer periphery thereof. Further, on the inner circumferential surface side of the fixing film 512, a nip forming member 510 as a contact member is provided. The nip forming member 510 has a cylindrical fixing film 512 loosely fitted thereon. Further, it comprises magnetic field generating means comprising an exciting coil 514 and a magnetic core (core material) 513 and disposed outside the fixing film 512.

  As the pressure roller 20 is rotationally driven, the cylindrical fixing film 512 rotates around the nip forming member 510, and the power to the exciting coil 514 causes the fixing film 512 to be in a state of being subjected to electromagnetic induction heat generation. Thereafter, the recording material P on which the unfixed toner image T is formed is introduced to the fixing nip portion N2 with the image surface facing upward, that is, facing the fixing film surface. Then, the image surface is held in close contact with the outer surface of the fixing film 512 and conveyed. In this process, the unfixed toner image T is heated and fixed on the recording material P by heating by the electromagnetic induction heat of the fixing film 10. When the recording material P passes through the fixing nip portion N2, the recording material P is separated from the outer surface of the fixing film 512 and discharged and conveyed.

  As shown in FIG. 28B, the nip forming member 510 in the seventh embodiment is in the longitudinal direction at a portion in contact with the inner peripheral surface of the fixing film 512 on the downstream side of the fixing nip N2 in the conveyance direction of the recording material P. It has a projecting portion 510b provided along. The protruding portion 510 b protrudes outward of the fixing film 512 by a protruding amount h beyond the minimal portion E of the press-contacting surface of the nip forming member 510 and the fixing film 512.

  Since the nip forming member 510 is not a plate-like heater as in the first to sixth embodiments, it can be shaped freely. Therefore, the surface of the nip forming member 510 in pressure contact with the inner surface of the fixing film 512 can be curved. Therefore, the pressure distribution in the conveyance direction of the recording material P formed at the fixing nip portion N2 is not the pressure distribution having two peaks as shown in Examples 1 to 6, but as shown in FIG. The distribution can be such that the pressure gradually increases toward the downstream side.

  FIG. 29 is a view showing the nip forming member of the seventh embodiment. Fig.29 (a) is the figure which looked at the nip formation member 510 of Example 7 from the nip formation surface side. The end of the protrusion 510b of the seventh embodiment is disposed further downstream in the recording material conveyance direction with respect to the center portion, and has a curved shape that draws a gentle curve. FIGS. 29 (b) and 29 (c) are cross-sectional views of the nip forming member 510 showing the positional relationship between the longitudinal direction end portion and the projecting portion 510b at the central portion. In the seventh embodiment, the position of the protrusion 510 b is defined by the distance from the center F of the fixing nip N 2. However, it is not limited to this method. Specifically, the protruding portion 510b is disposed such that the distance s4 is in the relation of central portion <end portion.

  In the configuration of the seventh embodiment, the protrusion 510 b is disposed downstream of the central portion of the protrusion 510 b by the extent that the nip width of the fixing nip N 2 is larger at the end than at the central portion. By arranging the protrusion 510 b in this manner, the amount of penetration of the protrusion 510 b into the pressure roller 20 can be made substantially the same in the entire longitudinal direction. As a result, the pressure peak formed by the protrusion 510 b can be made substantially the same throughout the longitudinal direction. Therefore, an image without unevenness in glossiness can be obtained in the entire longitudinal direction.

In addition, uniform pressure peaks can be obtained, so that uneven wear in the longitudinal direction of the release layer of the fixing film 10 can be improved. In addition, the shape of the protrusion part 510b is not limited to the curved shape. For example, the shape of the protrusion may be as described in the first embodiment or the second embodiment.
Moreover, even if it applies the invention described in Examples 4-6 to the film heating system using electromagnetic induction, the effect similar to Examples 4-6 can be acquired.

(Example 8)
Next, an eighth embodiment of the present invention will be described with reference to FIG. The present invention is also applicable to a pressure film type fixing device. FIG. 30 is a schematic view of a pressure film type fixing device of the eighth embodiment. Hereinafter, a pressure film type fixing device will be described with reference to FIG. The description of the same configuration as that of the first embodiment is omitted here.

  The fixing device of the eighth embodiment includes a heating member 531 such as a halogen heater inside, and has a fixing roll 532 as a roller member rotatably supported around a central axis. Further, a pressure member 530 as a film member supported in parallel to the axis of the fixing roll 532 and pressed against the fixing roll 532 is provided. The pressure member 530 is supported by the support member 533 and has a nip forming member 534 as an abutting member having a projecting portion on the downstream side in the conveyance direction of the recording material P on the inner circumferential surface side. Further, the nip forming member 534 is curved along the circumferential surface of the fixing roll 532. The present invention is also applied to a pressure film type fixing device that applies a pressure from the non-printing side to form a curved fixing nip along the circumferential surface of the fixing roll 532 from the first embodiment. The same effect as in Example 6 can be obtained.

DESCRIPTION OF SYMBOLS 10 ... Fixing film (film member), 20 ... Pressure roller (roller member), 41b ... Protrusion, 73 ... Fixing device

In order to achieve the above object, a fixing device according to the present invention is:
A tubular film member, which abuts against the abutment member on the inner peripheral surface of the film member, a roller member forming a fixing nip portion between both the film member and the abutment member via the film member the a, while nipping and conveying the recording material in the fixing nip, a fixing device for fixing a recording material an unfixed toner image formed on a recording material,
The contact member is a protruding portion that protrudes toward the roller member, and is the largest in the fixing nip portion at least among the portions other than the central portion of the fixing nip portion in the recording material conveyance direction. In a fixing device having a protrusion for pressing a recording material,
The roller member, in the axial direction of the roller member has a first diameter portion diameter is the first size, the second diameter portion diameter is greater than the first diameter,
Of said projecting portion, the second diameter portion and portion together form the fixing nip portion than said portion forming the fixing nip portion together with the first diameter portion of the protruding portion, the in the conveying direction It is characterized in that it is separated from the central portion of the fixing nip portion .

Claims (12)

A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
The roller member has a first diameter portion having a first diameter and a second diameter portion having a second diameter larger than the first diameter in the axial direction of the roller member. ,
The shortest distance from the portion in pressure contact with the second diameter portion to the central axis in the protrusion is longer than the shortest distance from the portion in pressure contact with the first diameter portion to the central axis. Fixing device. A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
The roller member has a first diameter portion in which the width of the fixing nip portion in the transport direction is a first width in the axial direction of the roller member, and a second width larger than the first width. Has a second diameter,
The shortest distance from the portion in pressure contact with the second diameter portion to the central axis in the protrusion is longer than the shortest distance from the portion in pressure contact with the first diameter portion to the central axis. Fixing device.   The portion of the protrusion which is in pressure contact with the second diameter portion is spaced apart from the central portion of the fixing nip portion in the transport direction than the portion of the protrusion which is in pressure contact with the first diameter portion. The fixing device according to claim 1 or 2, characterized in that:   3. The projection according to claim 1, wherein a portion of the protrusion in pressure contact with the second diameter portion has a smaller amount of protrusion than a portion of the protrusion in pressure contact with the first diameter portion. Fixing device as described.   The fixing according to any one of claims 1 to 4, wherein the first diameter portion is provided at an end portion in the axial direction, and the second diameter portion is provided at a central portion in the axial direction. apparatus.   The fixing according to any one of claims 1 to 4, wherein the second diameter portion is provided at an end portion in the axial direction, and the first diameter portion is provided at a central portion in the axial direction. apparatus.   The portion of the protrusion in contact with the second diameter portion is provided on the downstream side of the central portion of the fixing nip portion in the transport direction with respect to the portion of the protrusion in contact with the first diameter portion. The fixing device according to any one of claims 1 to 6, wherein the fixing device is provided.   The portion of the protrusion in contact with the second diameter portion is provided on the upstream side of the central portion of the fixing nip portion in the transport direction with respect to the portion of the protrusion in contact with the first diameter portion. The fixing device according to any one of claims 1 to 6, wherein the fixing device is provided.   The portion of the protrusion that contacts the second diameter portion and the portion of the protrusion that contacts the first diameter portion are continuously formed. The fixing device according to claim 1. A tubular film member, a contact member in contact with the inner circumferential surface of the film member, and the contact member are in pressure contact with each other via the film member, and a fixing nip portion is formed with the film member. A fixing device configured to fix an unfixed toner image to a recording material while nipping and conveying the recording material at the fixing nip portion.
The contact member is a projecting portion that protrudes toward the central axis of the roller member, and is the most in the fixing nip portion among the portions other than the central portion of the fixing nip portion in the conveyance direction of the recording material. In a fixing device having a projection for pressing the recording material with a large force,
In the axial direction of the roller member, the protrusion has a first protrusion with a first amount of protrusion and a second protrusion with a second amount of protrusion greater than the first amount of protrusion. Have
The fixing device according to claim 1, wherein the second protrusion is provided farther from the central portion of the fixing nip portion in the transport direction than the first protrusion.   The fixing device according to any one of claims 1 to 10, wherein the contact member includes a heating member configured to heat the film and a holding member configured to hold the heating member.   The fixing device according to claim 11, wherein the protrusion is formed on the holding member.

Images