JP6740333B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device.

2. Description of the Related Art Conventionally, a film heating type is widely used as a fixing device mounted on an image forming apparatus such as a copying machine or a laser beam printer. The film heating type fixing device includes a ceramic heater as a heat source, a heat-resistant fixing film, and a pressure roller. Further, the film heating type fixing device has a supporting member for supporting the fixing film on the inner peripheral surface side of the fixing film, and the supporting member and the pressure roller form an inner peripheral nip portion via the fixing film. In the fixing device having such a configuration, a fixing nip portion is formed by the fixing film and the pressure roller, and the unfixed toner image on the recording material is heated and fixed while the recording material is nipped and conveyed by the fixing nip portion.

Further, as a film heating type fixing device, a configuration is known in which a supporting member has a protruding portion protruding toward a pressure roller in an inner peripheral nip portion (Patent Document 1). By forming a locally high pressure portion in the nip portion by the protrusion portion, it is possible to improve the glossiness of the toner image fixed on glossy paper or the like without increasing the total pressure.

In addition, a configuration is known in which a protrusion is provided on the downstream side in the recording material conveyance direction in order to form a pressure distribution peak in the fixing nip portion on the downstream side in the recording material conveyance direction. Since the protruding portion is located on the downstream side in the conveying direction of the recording material, 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 film heating type fixing device as described above, there is known a pressure roller having a shape in which the outer diameter gradually increases in the longitudinal direction from the central portion to the end portion, that is, a so-called reverse crown-shaped pressure roller. (Patent Document 2). This is intended to convey the recording material relatively faster as the recording material is conveyed in the fixing nip portion as it approaches the end portion than in the central portion in the longitudinal direction. In this way, by increasing the transport speed of the end portion with respect to the central portion, it is possible to suppress the occurrence of distortion or bending of the recording material in the fixing nip portion and suppress the occurrence of wrinkles in the recording material.

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

Here, in the configuration in which the protrusion is provided on the support member, when the protrusion is provided on the upstream side or the downstream side in the transport direction of the recording material, there are the following problems. The width of the fixing nip portion (hereinafter, the fixing nip width) is not always 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 amount of intrusion in the portion where the nip width is relatively large is higher than the amount of invasion in the portion where the fixing nip width is narrow. The difference in the amount of intrusion becomes the difference in the pressure peak, and the higher the amount of intrusion, the larger the pressure peak.

Therefore, when the fixing nip width of the end portion is relatively wider than that of the central portion (hereinafter referred to as thick nip), the pressure peak is larger at the end portion than at the central portion. On the contrary, when the fixing nip width of the central portion is relatively wider than that of the end portion (hereinafter, referred to as thick nip), the pressure peak is larger in the central portion than in the end portion. From the viewpoint of preventing wrinkling of the recording material, it is preferable to intentionally form a thick nip, but in that case, there is a difference in pressure peak between the end portion and the central portion as described above.

Such a difference in pressure peak in the longitudinal direction becomes a difference in glossiness of the toner image fixed on the recording material. The glossiness is high where the pressure peak is high and low when the pressure peak is low. For example, in the case of a thick nip structure, the glossiness at the end is high but the glossiness at the center is low. .. Such unevenness in glossiness causes a problem that the image quality deteriorates as unevenness in the image.

Further, the difference in pressure peak also causes the difference in the amount of abrasion on the surface of the fixing film. The surface of the fixing film is gradually worn due to the friction with the recording material. On the other hand, the higher the pressure peak, the greater the friction between the fixing film and the recording material, and the greater the amount of wear. Therefore, if there is a difference in the fixing nip width in the longitudinal direction, a difference in the amount of wear also occurs in the longitudinal direction. If there is a difference in the amount of wear in the longitudinal direction as described above, the thickness of the fixing film becomes uneven in the longitudinal direction. Since the unevenness of the thickness causes a difference in the amount of heat transmitted from the heater through the fixing film, the amount of heat applied to the recording material is relatively large due to the small thickness at a portion having a large amount of wear. If this difference in wear amount is large, the effect of partial heating unevenness cannot be ignored. Then, this is also a problem that appears as uneven glossiness and uneven image.

Further, in a structure 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 due to abrasion, the toner image adheres to the fixing film and cannot be peeled off. Therefore, the faster the abrasion of the release layer, the shorter the time until the release layer is completely lost, and the shorter the life of the device.

By the way, regarding the abrasion of the surface of the fixing film, the portion corresponding to the edge of the edge of the recording material tends to be the most even in the state where the pressure peak has no unevenness in the longitudinal direction. This is because the edge of the recording material is rough because it is a cut portion at the time of paper making, and this rough portion is always in linear contact with the fixing film at the same position. In addition to this, since the portion corresponding to the edge of the recording material is the 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 during continuous sheet feeding. Depending on the material of the release layer of the fixing film, the abrasion resistance may be deteriorated due to excessive heating such as temperature rise in the non-sheet passing portion. Therefore, when such a release layer material is used, the abrasion due to the rubbing of the edge of the recording material is promoted. The portion of the fixing film corresponding to the edge of the recording material is initially scraped into a thin linear shape, and eventually the wear gradually spreads from there to the central portion of the fixing film. With the thick nip structure, the pressure peak at the end portion is large, so that the wear of the portion corresponding to the edge of the recording material is further promoted, and the life of the apparatus becomes shorter than that of the medium thick nip structure.

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

In order to achieve the above object, the fixing device according to the present invention is
A tubular film member, an abutting member that comes into contact with the inner peripheral surface of the film member, and a roller member that forms a fixing nip portion between the film member and the abutting member via the film member, A fixing device for fixing an unfixed toner image formed on a recording material to the recording material while nipping and conveying the recording material at the fixing nip portion,
The abutting member is a projecting portion that projects toward the roller member, and has the largest force in at least a portion of the fixing nip portion other than the central portion of the fixing nip portion in the recording material conveyance direction. In a fixing device having a protrusion that presses the recording material,
The roller member has a first diameter part having a diameter of a first size and a second diameter part having a diameter larger than the first diameter part in the axial direction of the roller member,
A portion of the protruding portion that forms a pressure peak of the fixing nip portion with the second diameter portion is smaller than a portion of the protruding portion that forms a pressure peak of the fixing nip portion with the first diameter portion. It is characterized in that it is separated from the central portion of the fixing nip portion in the transport direction.
Further, the fixing device according to the present invention,
A tubular film member, an abutting member that comes into contact with the inner peripheral surface of the film member, and a roller member that forms a fixing nip portion between the film member and the abutting member via the film member, A fixing device for fixing an unfixed toner image formed on a recording material to the recording material while nipping and conveying the recording material at the fixing nip portion,
The abutting member is a projecting portion that projects toward the roller member, and has the largest force in at least a portion of the fixing nip portion other than the central portion of the fixing nip portion in the recording material conveyance direction. In a fixing device having a protrusion that presses the recording material,
The inner surface nip portion, which is the contact area between the film member and the contact member, is located at a position different from the first area whose width in the transport direction is the first width and the first area in the axial direction of the roller member. And a second region having a larger width in the transport direction than the first region,
A second portion of the protrusion that forms a pressure peak of the fixing nip portion together with a portion of the roller member corresponding to the second region of the inner surface nip portion is a portion of the inner surface nip portion of the protrusion portion. It is characterized in that it is farther from the central portion of the fixing nip portion in the transport direction than the first portion forming the pressure peak of the fixing nip portion together with the portion of the roller member corresponding to the first region.

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

Schematic cross-sectional view showing the overall configuration of the image forming apparatus according to the present embodiment FIG. 1 illustrates a fixing device according to a first exemplary embodiment. Schematic diagram showing the fixing device of Embodiment 1. FIG. 3 is a diagram showing a pressure roller of Example 1. FIG. 3 is a diagram showing the shapes of a fixing nip portion and an inner surface nip portion of Embodiment 1. The figure which shows the heater holder and heater of Example 1. Sectional drawing which shows the heater holder and heater of Example 1. 6A and 6B are views for explaining the positional relationship of the protruding portion with respect to the nip portion according to the first embodiment. Diagram showing a conventional heater holder and heater Sectional drawing which shows the heater holder and heater of a prior art example. The figure explaining the positional relationship of the protrusion part with respect to the nip part of a prior art example. Graph showing pressure distribution of Example 1 and conventional example Graph comparing the longitudinal distribution of glossiness of Example 1 and the conventional example A graph comparing the conventional example and the example 1 with respect to changes in the amount of wear The figure which shows the heater holder and heater of Example 2. FIG. 6 is a diagram showing a positional relationship of a protrusion with respect to a nip portion of Embodiment 2. The graph which compared the pressure distribution of the longitudinal direction by the protrusion part of Example 2 and Example 1. The figure which shows the heater holder and heater of Example 3. FIG. 6 is a diagram showing a positional relationship of a protrusion with respect to a nip portion in Embodiment 3. The graph which compared the distribution of the longitudinal direction about the pressure peak of Examples 1-3. FIG. 10 is a diagram showing a positional relationship of a protrusion with respect to a nip portion of Embodiment 4. The figure which looked at the heater holder and heater of Example 4 from the heater mounting surface side. The figure explaining the peak of the pressure of Example 5. The figure which shows the heater holder and heater of Example 5. FIG. 6 is a diagram showing the shape of a fixing nip portion in Embodiment 6. The figure which compares and compares the structure of Example 6 and the prior art 2. Graph showing pressure distributions of Example 6 and Conventional Example 2 FIG. 6 is a diagram illustrating Example 7. FIG. 6 is a diagram showing a nip forming member of Example 7. A schematic view of a pressure film type fixing device of Example 8.

MODES FOR CARRYING OUT THE INVENTION Modes for carrying out the present invention will be exemplarily described in detail below based on embodiments with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed 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 sectional view showing the overall configuration of the image forming apparatus according to this embodiment. Hereinafter, as an example of the image forming apparatus, a full-color laser beam printer (hereinafter, simply referred to as a printer) 71 including a plurality of photosensitive drums 1 will be described, but the present invention is not limited to this, and the photosensitive drum 1 It may be a monochrome copier or printer provided with one.

As shown in FIG. 1, the printer 71 mainly includes image forming stations 7Y, 7M, 7C and 7K corresponding to yellow Y, magenta M, cyan C, and black K, an intermediate transfer belt 29, and a secondary transfer belt. A transfer roller 63 and a fixing device 72 are provided. In the following description, the subscripts Y, M, C, and K given to the reference numerals to represent the elements provided for any of the colors will be omitted unless particularly distinguished.

A cassette 61 is housed in the lower part of the printer 71 so that it can be pulled out. A recording material P such as paper is stacked and accommodated in the cassette 61. The recording material P is fed from the paper feed cassette 61 by the pickup roller 62, separated sheet by sheet by the feed/retard roller pair 14, 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 that forms a toner image by attaching toner to the electrostatic latent image formed on the photosensitive drum 1. 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 the toner remaining on the photosensitive drum 1 without being primarily transferred.

Further, below the image forming station 7, a laser scanner 3Y that irradiates the charged photosensitive drums 1 with a laser beam based on image information to form an electrostatic latent image on each photosensitive drum 1, 3M, 3C and 3K are arranged. The toner image on the intermediate transfer belt 29 transferred by the primary transfer section 8 is secondarily transferred onto the recording material P by the secondary transfer section N1 formed by the counter 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 the secondary transfer portion N1 then passes through the fixing device 72, and the toner image is fixed on the recording material P.

The recording material P on which the toner image has been fixed is then 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 stacking unit 65. The printer 71 in this embodiment can pass an A3 size recording material, and the width of the recording material P that can be passed 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. 2A and 2B are views showing the fixing device of Embodiment 1, FIG. 2A is a schematic sectional view, and FIG. 2B is an enlarged view of the vicinity of the fixing nip portion of FIG. 2A. .. FIG. 3 is a schematic diagram of the fixing device according to the first exemplary embodiment. In the following description, with respect to the fixing device 72 and the members constituting the fixing device 72, the longitudinal direction is a direction orthogonal to the axial direction of the pressure roller 20, that is, the conveying direction of the recording material P. Note that in FIG. 2, the orientation of the fixing device 72 is illustrated by rotating the orientation of FIG. 1 by 90 degrees for convenience of description.

The fixing device 72 according to the first exemplary embodiment includes a fixing film 10 as a cylindrical flexible film member and a pressure roller 20 provided in pressure contact with the fixing film 10, and is a pressure roller driving type/film heating type. Device. The pressure roller 20 is rotationally driven, and the fixing film 10 is driven to rotate. Then, in the fixing nip portion N2 formed by the fixing film 10 and the pressure roller 20, the toner image on the recording material P is heated and fixed on the recording material P while nipping and conveying the recording material P.

In addition, 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 pressing force urging means. It has a pressure means 43 and a fixing flange 45 as a regulating member. Each of the heater 30, the fixing film 10, the heater holder 41, the pressure stay 42, and the pressure roller 20 is a member elongated in the longitudinal direction. The fixing flange 45 regulates the movement of the fixing film 10 in the longitudinal direction. The heater 30 and the heater holder 41 of the first embodiment have a configuration corresponding 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 of an endless film made of a material having heat resistance and flexibility, and a release layer 12 provided on the outer peripheral surface of the base layer 11. Have and. Further, in order to improve fixing property and image quality, an elastic layer 13 such as silicone rubber is provided on the outer peripheral surface of the base layer 11 and between the inner peripheral surface side of the release layer 12. Since the elastic layer 13 is provided, the unfixed toner image T carried on the recording material P is wrapped and the heat can be uniformly applied. However, if the elastic layer 13 is too thick, the heat capacity becomes large, and it takes time to bring the temperature of the fixing film 10 to the temperature necessary for fixing the toner image T to the recording material P, and thus the film. The on-demand property peculiar to the heating method is deteriorated. Therefore, the thickness of the elastic layer 13 is 50 μm or more and 500 μm or less. The higher the thermal conductivity of the elastic layer 13, the more preferable it is, and it is preferable that it is 0.5 W/mK or more. In order to achieve such thermal conductivity, a thermally conductive filler such as ZnO, Al2O3, SiC or metallic silicon is mixed in the silicone rubber to adjust the thermal conductivity.

As the base layer 11, a thin metal such as SUS or Ni having high thermal conductivity, or a heat-resistant resin such as polyimide, polyamide-imide or PEEK formed into a thin flexible endless belt may be used. .. The release layer 12 is coated on the outer peripheral surface of the base layer 11 with a fluororesin such as PFA, PTFE, and FEP as a single product or a blend, or is coated with a tube of the fluororesin single product or a blended product. From the viewpoint of durability, the release layer 12 needs to have a thickness of 5 μm or more. Further, if the release layer 12 is too thick, the thermal conductivity is lowered and the fixability is adversely affected. Therefore, it is necessary to set the thickness to 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. As the release layer 12, a PFA tube 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 made of a heat-resistant resin such as liquid crystal polymer, phenol resin, PPS, PEEK, etc. and has a semicircular cross-section gutter shape. As shown in FIG. 2B, a groove 41a having a concave shape is provided on the lower surface of the heater holder 41 (the surface on the pressure roller 20 side) along the longitudinal direction of the heater holder 41. The heater 30 is held by the recessed groove 41a. The fixing film 10 is loosely fitted around the heater holder 41. The heater holder 41 to which the fixing film 10 is fitted is held at both ends in the longitudinal direction of the heater holder 41 at both ends (not shown) of the apparatus frame 27.

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

2-3) Pressure Roller The pressure roller according to the first exemplary embodiment will be described with reference to FIGS. FIG. 4 is a diagram illustrating the pressure roller of the first embodiment. The pressure roller 20 includes a 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 an outer peripheral surface of the heat resistant elastic layer 22. And the release layer 24 is provided. For the heat resistant elastic layer 22, a general heat resistant rubber elastic material such as silicone rubber or fluororubber can be used. The release layer 24 is formed by coating a fluororesin such as PFA, PTFE, FEP or the like on the heat-resistant elastic layer 22 as a single product or a blend, or by coating the heat-resistant elastic layer 22 with a tube of the fluororesin single product or a blended product. .. In Example 1, an iron cored bar having a diameter of 22 mm was used as the cored bar 21, and a silicone rubber having a thickness of 4 mm was used for the heat resistant elastic layer 22. As the release layer 24, a PFA tube is covered with 50 μm.

As shown in FIG. 4, the pressure roller 20 of Example 1 has an inverted crown shape in which the diameter is larger at both end portions (second diameter portion) than in the central portion (first diameter portion) in the longitudinal direction. ing. Pressure roller 20
If the half of the difference between the diameter D2 (second diameter) of the end portion in the longitudinal direction and the diameter D1 (first diameter) of the central portion is defined as the reverse crown amount Cr, the reverse crown amount Cr of the first embodiment is obtained. Is 0.15 mm. By thus forming the pressure roller 20 in the shape of an inverted crown, the conveyance speed of the recording material P due to the rotation of the pressure roller 20 becomes higher in the vicinity of both ends than in the central portion, and the recording material P is conveyed in the fixing nip portion. When it is pulled, it receives the force of being pulled from the center toward both ends. Therefore, it is possible to suppress the occurrence of wrinkles on the recording material P.

2-4) Heater The heater 30 is a plate-shaped heating element that rapidly heats the fixing film 10 while contacting the inner peripheral surface of the fixing film 10. The heater 30 has a substrate elongated in the longitudinal direction. 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 (the surface opposite to the pressure roller 20) of the substrate, an electric heating resistance layer of Ag/Pd (silver palladium), RuO2, Ta2N, etc. is applied in a strip shape along the longitudinal direction of the substrate. Is formed. Further, a glass coat is formed on the back surface of the substrate in order to protect the energization heating resistance layer and ensure insulation. A sliding layer is provided on the surface of the substrate (the surface on the pressure roller 20 side) for the purpose of improving the slidability of the substrate. As the sliding layer, a heat resistant resin such as polyimide or polyamide imide, or a glass coat is used. In the first embodiment, the size of the substrate of the heater 30 is 350 mm in the longitudinal direction, 10 mm in the lateral direction (recording material conveying direction), and 0.6 mm in the thickness direction.

2-5) Pressurizing Stay The pressing stay 42 is made of a material such as metal having rigidity and formed in a U-shape with a downward cross section. The pressure stay 42 is arranged inside the fixing film 10 at the center of the upper surface of the heater holder 41 (the surface opposite to the pressure roller 20) in the lateral direction. Then, both 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 apparatus frame 27. As a result, the heater 30 is pressed against the surface of the pressure roller 20 via the fixing film 10.

Then, as shown in FIG. 5, an inner surface nip portion N3 having a predetermined width is formed between the heater 30 and the fixing film 10, and a fixing nip portion N2 having a predetermined width is formed between the fixing film 10 and the pressure roller 20. It is formed. Note that, for convenience of description, the inner surface nip portion N3 and the fixing nip portion N2 may be collectively referred to as a nip portion hereinafter. Heat necessary for heating and fixing the toner image T is transferred from the heater 30 to the fixing film 10 at the inner surface nip portion N3, and transferred from the fixing film 10 to the recording material P at the fixing nip portion N2.

FIG. 5 is a diagram showing the shapes of the fixing nip portion and the inner surface nip portion. In the fixing device according to the first exemplary embodiment, since the pressure roller 20 has the inverted crown shape as described above, the nip widths of the fixing nip portion N2 and the inner surface nip portion N3 are different in the longitudinal direction, and the nip width of the end portion is larger than that of the central portion. Is getting bigger.

2-6) Fixing Operation of Fixing Device The rotation drive/temperature control unit 44 as a control unit shown in FIG. 3 executes a predetermined rotation drive control sequence in response to a print command, and drives the motor M that is a drive source. Then, the drive gear G provided at the longitudinal 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 peripheral speed. At that time, due to 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, a rotational force that rotates in the opposite direction to the rotational direction of the pressure roller 20 acts on the fixing film 10. As a result, the fixing film 10 is driven to rotate at the same peripheral speed as the pressure roller 20 outside the heater holder 41 while the inner surface of the fixing film 10 contacts the sliding layer of the heater 30.

Further, the rotation drive/temperature control unit 44 executes a predetermined temperature control sequence in response to the print command, and energizes the energization heating resistance layer of the heater 30. Due to the energization, the energization heating resistance layer generates heat and the heater 30 rapidly rises in 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 outputs a temperature detection signal of the fixing film 10 to the control unit 44. Output to. The thermistor 35 is arranged in an area through which the recording materials P of various sizes usable by the printer 71 definitely pass. The rotation drive/temperature control unit 44 takes in a temperature detection signal from the thermistor 35 and controls the energization of the energization heat generating resistance layer based on the temperature detection signal so that the fixing film 10 reaches a predetermined target temperature.

In this way, in the state where the temperature of the fixing film 10 is maintained at the predetermined target temperature, the recording material P carrying the unfixed toner image T is guided to the fixing nip portion N2 along the entrance guide 28, and the fixing film 10 is held. It is nipped and conveyed by the pressure roller 20 and the pressure roller 20. In the conveying process, heat of the fixing film 10 heated by the heater 30 and pressure of the fixing nip portion 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. It The recording material P that has passed through the fixing nip portion N2 is curvature-separated from the fixing film 10 and is discharged by the fixing paper discharge roller 26.

(3) Shape of Protruding Part 3-1) Shape of Protruding Part of Embodiment 1 The protruding part 41b 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 projecting portion 41b projects toward the central axis of the pressure roller 20 (toward the outer surface of the fixing film 10) by a projecting amount h from the sliding surface. In the fixing device of Embodiment 1, the protrusion amount h is 0.2 mm. Here, the sliding surface means a surface of the heater 30 on which the fixing film 10 slides. The protruding portion 41b presses the recording material P with the largest force among at least a portion of the fixing nip portion N2 other than the central portion of the fixing nip portion N2 in the transport direction of the recording material P.

6A and 6B are views showing the heater holder and the heater of the first embodiment, FIG. 6A is an external perspective view, and FIG. 6B is a view seen from the heater mounting surface side. In the first embodiment, the position of the protruding portion 41b included in the heater holder 41 is different in the longitudinal direction, and the end portion is provided on the downstream side in the transport direction of the recording material P with respect to the central portion.

7A and 7B are cross-sectional views showing a heater holder and a heater according to the first embodiment. 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 41b is provided so that its tip is located at a position at a distance r1 from the downstream end of the heater mounting groove 41a of the heater holder 41 in the recording material P transport direction. The distance from the downstream end of the inner surface nip portion N3 to the tip of the protruding portion 41b is s1. Then, in Example 1, 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 central axis O is x2, the relationship is x1>x2.

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 protruding portion 41b is arranged so that the distance s1 is substantially equal in the central portion and the end portion. In the configuration of the first embodiment, the end portion of the inner surface nip portion N3 is larger than the central portion, so that the end portion of the projecting portion 41b is arranged downstream of the central portion. That is, the distance r1 of the protruding portion 41b from the downstream end of the heater mounting groove 41a has a relationship of central portion<end portion. In the first embodiment, the distance s1 is 2 mm.

FIG. 8 is a diagram illustrating a positional relationship between the fixing nip portion and the inner surface nip portion of the protruding portion according to the first embodiment. As shown in FIG. 8, the protruding portion 41b of the first embodiment is formed separately in the central portion 41c and the end portions 41d and 41e. In Example 1, the length of the central portion 41c was 285 mm, and the length of both end portions 41d and 41e was 20 mm.

In Example 1, since the pressure roller 20 has an inverted crown shape, the inner surface nip portion N3 has a curved shape, and the nip width rapidly increases near the end portion. In the first embodiment, the protruding portion 41b is linearly formed in the longitudinal direction with respect to such a curved nip shape. Therefore, the distances s1 are not the same but slightly different in the respective regions of the central portion 41c and the end portions 41d and 41e of the protruding portion 41b.

Therefore, in the first embodiment, the position where the distance s1 is equal in the central portion and the end portion is defined by A in the central portion and B in the end portion. That is, the position of the protrusion 41b is set so that the distance s1 is equal at the position A at the center and at the position B at the end. The position A is a position corresponding to the center in the longitudinal direction. Position B is a position 148.5 mm from position A. This is the position where the paper edge passes when A4 size paper is fed laterally. The reason for this definition is that the recording material of A4 size is used most frequently. 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 of the end 41d (end 41e) of the protrusion 41 in the longitudinal direction, that is, a position 152.5 mm from the position A in the first embodiment. It should be noted that the numerical values specifically shown in the first embodiment are optimized by the device configuration and are not limited to these numerical values.

3-2) Shape of Conventional Projection Part With reference to FIGS. 9 to 11, the conventional projection part 41b of the heater holder 41 will be described. 9A and 9B are views showing a heater holder and a heater of a conventional example, FIG. 9A is an external perspective view, and FIG. 9B 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. 10A and 10B are sectional views showing a heater holder and a heater of a conventional example, FIG. 10A is a sectional view of an end portion in the longitudinal direction, and FIG. 10B is a sectional view of a central portion in the longitudinal direction. FIG. 11 is a diagram illustrating a positional relationship between the fixing nip portion and the inner surface nip portion of the projecting portion in the conventional example.

In the conventional example, the protrusions 41b are arranged at the same position in the longitudinal direction uniformly in the recording material conveyance direction. The distance r1 from the downstream end of the heater mounting groove 41a of the heater holder 41 to the tip of the protruding portion 41b is equal in 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 has a relationship 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 Next, referring to FIG. 12, the effects of Example 1 were compared with the conventional example in terms of pressure distribution, glossiness, and durability of the release layer 12 of the fixing film 10 against abrasion. While explaining. First, the comparison result of the pressure distribution in the conveying direction of the recording material P with the conventional example will be described. 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 in the fixing nip portion in the conveyance direction of the recording material P at the central 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 in both the longitudinal end portion and the central portion. The pressure peak C is formed by the protruding portion 41b of the heater holder 41. In the configuration of the conventional example, since the amount of protrusion 41b entering the pressure roller 20 at the end portion B is larger than at the central portion A, the pressure peak formed on the downstream side in the transport direction is larger than at the central portion A. ..

On the other hand, FIG. 12B shows the pressure distribution in the fixing nip portion in the conveyance direction of the recording material P at the central portion A and the end portion B of the first embodiment. In the first embodiment, the protruding portion 41b at the end B is shifted to the downstream side in the conveying direction of the recording material P as compared with the conventional example. The peak is formed lower than in the conventional example. Therefore, the pressure by the protruding portion 41b is almost the same in the central portion A and the end portion B.

FIG. 12C is a diagram comparing the longitudinal pressure distributions of the pressure peaks on the downstream side of Example 1 and the conventional example. As shown in the figure, the first embodiment can reduce the difference in pressure peak between the central portion and the end portion as compared with the conventional example. This pressure peak difference appears as a difference in glossiness of the toner image fixed on the recording material P.

Further, FIG. 13 is a graph comparing the distributions in the longitudinal direction regarding the glossiness of Example 1 and the conventional example. In Example 1, the difference between the pressure peaks at the central portion and the end portions can be made smaller than that in the conventional example. Therefore, it is possible to reduce the difference in glossiness between the edge and the center.

Next, the result of comparison of the durability of the fixing film 10 against wear of the release layer 12 with the conventional example will be described. FIG. 14 is a graph comparing the conventional example and the example 1 with respect to changes in the amount of wear in the part where the release 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 transport direction of the recording material P formed by the protruding portion 41b is large, the progress of wear is fast. On the other hand, in Example 1, the pressure peak on the downstream side was made lower than that of the conventional example, so that it is possible to suppress the progress of wear as compared with the conventional example.

As described above, in the first embodiment, the pressure peak at the end in the longitudinal direction can be made lower than that in the conventional case, and the pressure peak can be made almost the same as that at the central portion. Therefore, in Example 1, it is possible to reduce the difference in glossiness between the central portion and the end portion and to improve the durability performance against wear of the release layer 12. As a result, it is possible to suppress the influence on the image quality and prevent the life of the fixing device 72 from being shortened.

In addition, in the first embodiment, the position of the protruding portion 41b is determined based on the distance s1 from the downstream end of the inner surface nip portion N3 to the tip of the protruding portion 41b, but the method is not necessarily limited thereto. It suffices that the protrusions 41b are arranged so that the pressure peaks in the longitudinal direction are substantially equal, and for example, it may be determined by adjusting the position of the protrusions 41b according to the width of the fixing nip portion N2. This also applies to the subsequent examples.

As described above, in the projecting portion 41b, 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 the portion in pressure contact with the first diameter portion. From the center axis O to the shortest distance x2 (see FIG. 7). The same applies to the other embodiments described below. In the first embodiment, specifically, by providing the portion in pressure contact with the second diameter portion with respect to the portion in pressure contact with the first diameter portion on the downstream side in the transport direction of the recording material P, Realized a configuration like this. The second diameter portion is a portion having a larger diameter than the first diameter portion, and in the first embodiment, the central portion of the pressure roller 20 corresponds to the first diameter portion, and both end portions have the second diameter portion. Corresponds to the department.

(Example 2)
Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The basic configuration and operation of the fixing device of the second embodiment are the same as those of the fixing device of the first embodiment. Therefore, elements having the same or equivalent functions and configurations as those of the fixing device of the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted, and characteristic points of the second embodiment will be described. This also applies to the subsequent examples.

15A and 15B are views showing a heater holder and a heater according to the second embodiment, FIG. 15A is an external perspective view, and FIG. 15B is a view seen from the heater mounting surface side. Similar to the first embodiment, the protruding portion 41b of the second embodiment is formed on the downstream side of the central portion of the recording material P in the transport direction, and the end portion of the protruding portion 41b is disposed on the downstream side of the central portion. ing. Then, the protruding portion 41b of the second embodiment is not discontinuous at the boundary between the central portion 41c and the end portions 41d and 41e like the protruding portion 41b of the first embodiment, and as shown in FIG. , Is continuously formed and has a dogleg shape.

FIG. 16 is a diagram showing the positional relationship of the protrusions 41b with respect to the shapes of the fixing nip portion N2 and the inner surface nip portion N3 in the second embodiment. As in the first embodiment, 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 some extent. Specifically, the protrusion 41b is arranged so that the distance s1 between the downstream end of the inner surface nip portion N3 at the central portion A and the end B and the protrusion 41b is equal, and the protrusions at the central portion A and the end B are arranged. The portion 41b is formed so as to be on the same straight line. Therefore, unlike the first embodiment, the distance s1 between the downstream end of the inner surface nip portion N3 and the protruding portion 41b does not suddenly change at the boundary between the central portion 41c and the end portions 41d and 41e.

FIG. 17 is a graph comparing the pressure distributions in the longitudinal direction by the protruding portions 41b of the second embodiment and the first embodiment. As illustrated, in the first embodiment, the protrusion 41b has a discontinuous boundary between the central portion 41c and the end portions 41d and 41e. The pressure peak suddenly changed near this boundary. On the other hand, in the second embodiment, since the protrusion 41b is arranged continuously without the boundary between the central portion 41c and the ends 41d and 41e, the distance between the downstream end of the inner surface nip portion N3 and the protrusion 41b. s1 does not change suddenly as in the first embodiment. Therefore, in Example 2, the pressure peak can be gently changed in the longitudinal direction. Therefore, in the second embodiment, it is possible to improve the difference in the pressure peak near the boundary between the central portion 41c and the end portions 41d and 41e as in the first embodiment, and it is possible to obtain an image with less uneven glossiness near the boundary. become.

(Example 3)
Next, a third embodiment of the present invention will be described with reference to FIGS. 18A and 18B are views showing a heater holder and a heater of Example 3, FIG. 18A is an external perspective view, and FIG. 18B is a view seen from the heater mounting surface side. The protruding portion 41b of the third embodiment has a curved shape that draws a gentle curve, rather than the straight shape as in the first and second embodiments. FIG. 19 is a diagram showing the positional relationship between the fixing nip portion N2 and the inner surface nip portion N3 of the protrusion 41b 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 protruding portion 41b is formed to be curved so as to follow the nip shape. Specifically, the position of the protruding portion 41b is 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, the distances s1 are not equal only at limited positions such as the central portion A and the end portions B as in the first and second embodiments.

20: is the figure which compared the distribution of the longitudinal direction about the pressure peak of Examples 1-3. In Examples 1 and 2, the inner surface nip portion N3 was curved, whereas the protruding portion 41b was formed linearly. Therefore, the distance s1 from the downstream end of the inner surface nip portion N3 to the tip of the protrusion 41b cannot be made uniform in the longitudinal direction, and a slight difference in the pressure peak occurs in the longitudinal direction. Therefore, in Examples 1 and 2, unevenness in glossiness due to the pressure peak still occurred.

On the other hand, in the third embodiment, the protruding portion 41b 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 41b can be made substantially the same in the entire longitudinal direction. That is, the difference in the pressure peak in the longitudinal direction can be further improved as compared with Examples 1 and 2, and an image having no unevenness in glossiness in the entire longitudinal direction can be obtained.

Further, by obtaining a uniform pressure peak, it is possible to further improve the uneven wear of the release layer of the fixing film 10 in the longitudinal direction. With respect to the abrasion of the recording material P due to the rubbing of the fixing film 10, the configurations of Examples 1 and 2 have the maximum effect on the size of the target recording material P. 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 distance s1 is equal to each other are determined by targeting the A4 size, the B4 size is fed longitudinally, and when other sizes are passed, the A4 size is more than There was a possibility that the amount of wear would increase. However, in the third embodiment, since the pressure peaks in the longitudinal direction are uniform, it is possible to make the amount of wear of the portion corresponding to the lip of the recording material P the same for recording materials of all sizes, not limited to A4 size, for example. it can.

As described above, in the third embodiment, the protrusion 41b is also curved along the curved shape of the inner surface nip portion N3, so that the unevenness of the pressure peak is further reduced as compared with the first and second embodiments. It is possible to improve glossiness and uneven wear of the surface of the fixing film. In the third embodiment, the position of the protruding portion 41b is set so that the distance s1 from the downstream end of the inner surface nip portion N3 is equal in the entire longitudinal direction, but the distance s1 is not necessarily equal in the entire longitudinal direction. No need. By curving the protruding portion 41b according to the curved nip shape as in the third embodiment, it is possible to improve the unevenness in glossiness and the uneven wear amount of the release layer of the fixing film. Therefore, it is not always necessary to determine the position of the protrusion 41b based on the distance s1 as described in the first embodiment, and the distance s1 may be different in the longitudinal direction as long as it is within the allowable range.

(Example 4)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 21 is a diagram showing the positional relationship between the fixing nip portion N2 and the inner surface nip portion N3 of the protrusion 41b in the fourth embodiment. The nip widths of the fixing nip portion N2 and the inner surface nip portion N3 in the fourth embodiment are different in the longitudinal direction, and the nip width at the central portion (second width) is larger than the nip width at the end portions (first width). It has a thick nip. In order to obtain 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 made larger than that of both end portions so that the heater holding surface is convex toward the pressure roller 20 side. In the second embodiment, the pressure roller 20 as a roller member has a uniform diameter in the longitudinal direction.

Therefore, the amount of penetration of the heater 30 and the heater holder 41 into the pressure roller 20 is larger in the central portion than in the end portions, and as a result, the pressure applied to the central portion is larger than the pressure applied to the nip end portion. be able to. As described above, by using the medium-thick nip, the wear amount of the portion corresponding to the edge of the recording material P in the release layer of the fixing film 10 can be adjusted to be the thick nip as in Example 1 where the pressure at the nip end is large. It can be suppressed more than the configuration.

22: is the figure which looked at the heater holder 41 and the heater 30 of Example 4 from the heater attachment surface side. The projecting portion 41b of the fourth embodiment has a central portion arranged more downstream than the end portion and has a curved shape. In the fourth embodiment, the protrusion 41b is formed so as to follow the shape of the downstream end of the inner surface nip portion N3. Specifically, the position of the protruding portion 41b is set so 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. By doing so, the pressure peak formed by the protruding portion 41b can be made substantially the same in the entire longitudinal direction. Therefore, it is possible to obtain an image in which the glossiness is uniform in the entire longitudinal direction.

Further, by obtaining a uniform pressure peak, it is possible to improve the uneven wear of the release layer of the fixing film 10 in the longitudinal direction. When the protrusion 41b is arranged straight in the longitudinal direction as in the conventional example described in the description of the first embodiment, the distance s1 from the downstream end of the inner surface nip portion N3 to the protrusion 41b is smaller in the central portion than in the end portion. Get smaller. Therefore, the pressure peak formed by the protrusion 41b becomes large in 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 was increased, and uneven wear in the longitudinal direction occurred. On the other hand, in Example 4, since a uniform pressure peak is obtained in the longitudinal direction, wear in 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 the protruding portion 41b is also formed in a curved shape along the curved shape of the inner surface nip portion N3. With such a configuration, it is possible to reduce unevenness of the pressure peak and improve glossiness and uneven wear of the fixing film surface. The shape of the protruding portion 41b is not limited to the curved shape. For example, the protruding portion 41b may be linearly arranged, and the central portion may be shifted further downstream from the end portion. In addition, the protrusion 41b may be arranged in a dogleg shape by disposing the central portion on the downstream side with respect to the end portion.

(Example 5)
Next, a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 23 is a diagram illustrating a pressure peak of the fifth embodiment. FIG. 23A is an enlarged view of the nip portion of the fixing device according to the fifth exemplary embodiment. FIG. 23B is a pressure distribution diagram of the recording material P in the conveyance direction of the inner surface nip portion of the fifth embodiment. As illustrated, in the fifth embodiment, the protruding portion 41b of the heater holder 41 is on the upstream side in the transport direction of the recording material P. In this case, the pressure distribution in the transport 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 in the transport direction of the recording material P.

By thus providing the pressure peak on the upstream side in the conveying 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 portion N2 and the inner surface nip portion N3. The distance (hereinafter, referred to as u3) at the upstream end of the can be increased. As a result, the preheating effect can be obtained because the time for warming the recording material P becomes long before the recording material P reaches the inner surface nip portion N3, and good fixability and glossiness can be obtained.

24A and 24B are views showing a heater holder and a heater of Example 5, FIG. 24A is an external perspective view, and FIG. 24B 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 protrusion 41b is formed along the nip shape. Specifically, the position of the protruding portion 41b is set so that the distance (hereinafter, referred to as s3) from the upstream end of the inner surface nip portion N3 to the protruding portion 41b is equal over the entire longitudinal direction. As a result, the pressure peak formed by the protrusion 41b can be made substantially the same in the entire longitudinal direction.

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

Further, in Example 5, by obtaining a uniform pressure peak, it is possible to suppress unevenness in glossiness and fixability due to the pressure peak, and obtain an image with little unevenness in glossiness and fixability in the entire longitudinal direction. You can As described above, in the fifth embodiment, the pressure peak due to the protruding portion 41b can be made substantially the same in the entire longitudinal direction. Therefore, it is possible to suppress unevenness of glossiness and unevenness of fixability, and it is possible to improve durability performance against wear of the release layer 12.

(Example 6)
Next, a sixth embodiment of the present invention will be described with reference to FIGS. FIG. 26 is a diagram for explaining a comparison between the configurations of the sixth embodiment and the second conventional example. 26A is a view of the heater holder and the heater of the sixth embodiment as seen from the downstream side in the recording material conveyance direction, and FIG. 26B is a view as seen from the heater mounting surface side. In addition, FIG. 26C 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 41b of the heater holder 41 is different in the longitudinal direction, and the protrusion amount (second protrusion amount) of the end portion (second protrusion portion) is the central portion (first protrusion). The protrusion amount is larger than the protrusion amount (first protrusion amount). In the sixth embodiment, the protrusion amount h is 0.2 mm at the center and 0.35 mm at the ends. By doing so, the recording material P that has passed through the fixing nip portion N2 can be curved in the longitudinal direction to have a convex shape on the fixing film 10 side. As a result, rigidity can be provided in the longitudinal direction, and bending in the transport direction can be suppressed. 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. 26B, in the projecting portion 41b in the sixth embodiment, the end portion (second projecting portion) is arranged more downstream than the central portion (first projecting portion), and a gentle curve is formed. It has a curved shape.

Next, Conventional Example 2 as a comparative example with respect to Example 6 will be described. Also in the heater holder 41 of the second conventional example, the protruding amount h is different in the longitudinal direction as shown in FIG. 26A, and the end portion is larger than the central portion. The protrusion amount h in the second conventional example is 0.2 mm at the central portion and 0.35 mm at the end portions, as in the sixth embodiment. Then, in Conventional Example 2, as shown in FIG. 26C, the protrusions 41b are arranged at the same position in the lengthwise direction in the transport direction of the recording material P.

Here, FIG. 25 is a diagram showing the shape of the fixing nip portion N2 in the sixth embodiment. As illustrated, the nip width of the fixing nip portion N2 is uniform in the longitudinal direction. The fixing nip portion N2 was adjusted to have a straight nip shape by making the thickness of the central portion of the heater holding surface of the heater holder 41 in the longitudinal direction larger than that of both ends. Even in such a straight nip shape, when the protrusions 41b are arranged straight in the longitudinal direction and the protrusion amount h is varied in the longitudinal direction as in the second conventional example, the pressure peaks of the protrusions 41b cause the longitudinal peak. Makes a difference. In the sixth embodiment, in order to suppress such a difference in pressure peak, the projecting portion 41b is arranged so that the end portion is on the downstream side with respect to the central portion, and has a curved shape that draws a gentle curve. ..

Hereinafter, the specific effect of the sixth embodiment will be described in comparison with the conventional example 2. FIG. 27 is a graph showing pressure distributions 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 Conventional Example 2. As shown, there is a pressure peak C on the downstream side at both the end and the center. This pressure peak is formed by the protruding portion 41b of the heater holder 41. At the end portion, the protrusion amount h of the protrusion portion 41b is larger than that in the center portion, so that the intrusion amount into the pressure roller 20 is large and the pressure peak is larger than that in the center portion.

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 41b is arranged on the downstream side with respect to the center, the amount of the protrusion 41b entering the pressure roller 20 at the end can be reduced. Therefore, as shown in FIG. 27B, the pressure peak can be formed lower than that in the second conventional example.

Here, FIG. 27C is a diagram 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 gradually increases from the central portion to the end portion. Is getting bigger. For this reason, in Conventional Example 2, the glossiness of the recording material was higher at the edges than at the center, and uneven glossiness occurred. 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 more than in Conventional Example 2, and an image with no unevenness in glossiness can be obtained in the entire longitudinal direction.

Further, in Example 6, since the pressure peaks can be made substantially the same in the entire region in the longitudinal direction, the abrasion of the release layer in the portion where the release layer of the fixing film 10 rubs against the edge of the recording material is prevented from the abrasion of the conventional example 2. Can be smaller than. As described above, in the sixth embodiment, even when the protrusion amount h of the protrusion 41b differs in the longitudinal direction, the difference in the pressure peak in the longitudinal direction is reduced by forming the protrusion 41b in a curved shape. It is possible to suppress uneven glossiness and the amount of wear of the release layer of the fixing film.

The shape of the protrusion 41b is not limited to the curved shape. For example, the protruding portions 41b may be arranged linearly, and the central portion may be displaced further downstream from the end portions. In addition, the protrusion 41b may be arranged in a dogleg shape by disposing the central portion on the downstream side with respect to the end portion.

Further, in the sixth embodiment, the case where the protrusion amount h of the protruding portion 41b is higher at the end portion than at the central portion has been described, but also when the protruding amount h of the protrusion portion 41b at the central portion is higher than that at the end portion. The present invention is applicable. By increasing the protrusion amount h of the central portion with respect to the end portion, the recording material P that has passed through the fixing nip portion N2 can be curved in the longitudinal direction and can have a convex shape on the pressure roller 20 side. As a result, rigidity can be provided in the longitudinal direction, and bending in the transport direction can be suppressed. In such a case, by disposing the central protruding portion 41b having a large protruding amount h downstream of the end protruding portion 41b, the pressure peak difference between the end portion and the central portion can be made substantially the same. .. The configuration of the sixth embodiment can be applied to the case where the protruding portion 41b is arranged on the upstream side in the transport direction of the recording material P. In this case, the pressure peak in the longitudinal direction can be made uniform by arranging the projecting portion 41b such that the end portion is arranged more downstream than the central portion.

(Example 7)
Next, a seventh embodiment of the present invention will be described with reference to FIGS. 28 and 29. The fixing device used in the description of Examples 1 to 6 uses the heater 30 as a heating body, but the present invention is not limited to such a heating body. Other configurations may be used as long as the pressure peaks are formed by the protrusions 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 diagram for explaining the seventh embodiment. 28A is a schematic cross-sectional view of a film heating type fixing device using electromagnetic induction according to the seventh embodiment. FIG. 28B is an enlarged view of the nip portion of the fixing device according to the seventh embodiment. FIG. 28C is a diagram showing the pressure distribution in the conveyance direction of the recording material P in the fixing nip portion N2 of the seventh embodiment. Note that the description of the same configuration as that of the first embodiment is omitted here.

As shown in FIG. 28A, in the fixing device of Example 7, a fixing film 512 as a cylindrical film member as an electromagnetic induction heating member, and a pressure roller 20 as a roller member in pressure contact with the fixing film 512. And have. The fixing film 512 has a laminated structure in which a heat generating layer that generates heat by the action of a magnetic field is used as a base layer, and an elastic layer and a release layer are provided on the outer periphery thereof. Further, a nip forming member 510 as a contact member is provided on the inner peripheral surface side of the fixing film 512. The nip forming member 510 is loosely fitted with a cylindrical fixing film 512. Further, it has a magnetic field generating means which is composed of an exciting coil 514 and a magnetic core (core material) 513 and is arranged outside the fixing film 512.

The pressure roller 20 is rotationally driven, and accordingly, the cylindrical fixing film 512 rotates around the nip forming member 510, and the fixing film 512 is heated by electromagnetic induction by supplying power to the exciting coil 514. After that, the recording material P on which the unfixed toner image T is formed is introduced into the fixing nip portion N2 with the image surface facing upward, that is, facing the fixing film surface. Then, the image surface is nipped and conveyed in a state of being in close contact with the outer surface of the fixing film 512, and in this process, the unfixed toner image T is heated and fixed on the recording material P by heating by the electromagnetic induction heat generation of the fixing film 10. When the recording material P passes through the fixing nip portion N2, it 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 according to the seventh embodiment extends in the longitudinal direction at a portion of the fixing nip portion N2 that is in contact with the inner peripheral surface of the fixing film 512 on the downstream side in the conveying direction of the recording material P. It has the protrusion part 510b provided along it. The protruding portion 510b protrudes toward the outside of the fixing film 512 by a protruding amount h from the minimum portion E of the pressure contact surface between the nip forming member 510 and the fixing film 512.

Since the nip forming member 510 is not a plate-shaped heater as in the first to sixth embodiments, it can be freely shaped. Therefore, in the nip forming member 510, the surface that comes into pressure contact with the inner surface of the fixing film 512 can be a curved surface. Therefore, the pressure distribution in the transport 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. In addition, the distribution can be such that the pressure gradually increases toward the downstream side.

FIG. 29 is a diagram illustrating a nip forming member according to the seventh embodiment. FIG. 29A is a diagram of the nip forming member 510 of Example 7 as viewed from the nip forming surface side. The projecting portion 510b of the seventh embodiment has a curved shape that draws a gentle curve, with the end portion being arranged in the recording material conveyance direction with respect to the central portion, further downstream. 29(b) and 29(c) are cross-sectional views of the nip forming member 510 showing the positional relationship between the longitudinal end portion and the central protruding portion 510b, respectively. In the seventh embodiment, the position of the protruding portion 510b is defined by the distance from the center F of the fixing nip portion N2. However, the method is not limited to this. Specifically, the protrusions 510b are arranged so that the distance s4 is in the relationship of central portion<end portion.

In the configuration of the seventh embodiment, the end portion of the protruding portion 510b is arranged on the downstream side of the central portion because the nip width of the fixing nip portion N2 is larger at the end portion than at the central portion. By disposing the protrusion 510b in this manner, the amount of the protrusion 510b entering 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 510b can be made substantially the same in the entire longitudinal direction. Therefore, it is possible to obtain an image in which the glossiness is not uneven in the entire longitudinal direction.

Further, by obtaining a uniform pressure peak, it is possible to improve the uneven wear of the release layer of the fixing film 10 in the longitudinal direction. The shape of the protrusion 510b is not limited to the curved shape. For example, you may make it the shape of the protrusion part as described in Example 1 or Example 2.
Moreover, even if the invention described in Examples 4 to 6 is applied to a film heating method using electromagnetic induction, the same effects as those in Examples 4 to 6 can be obtained.

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

The fixing device according to the eighth embodiment includes a heating body 531 such as a halogen heater therein and a fixing roll 532 as a roller member rotatably supported around a central axis. Further, it has a pressing member 530 as a film member that is supported in parallel with the axis of the fixing roll 532 and is pressed against the fixing roll 532. The pressing member 530 is supported by the supporting member 533, and has a nip forming member 534 as an abutting member having a protrusion on the downstream side in the transport direction of the recording material P on the inner peripheral surface side. The nip forming member 534 is curved in a shape along the peripheral surface of the fixing roll 532. The present invention is also applied to a fixing device of a pressure film type which forms a curved fixing nip along the peripheral surface of the fixing roll 532 by applying pressure from the non-printing surface side, and the first to third embodiments are performed. The same effect as in Example 6 can be obtained.

10... Fixing film (film member), 20... Pressure roller (roller member), 41b... Projection portion, 73... Fixing device

Claims (16)

A tubular film member, an abutting member that comes into contact with the inner peripheral surface of the film member, and a roller member that forms a fixing nip portion between the film member and the abutting member via the film member, A fixing device for fixing an unfixed toner image formed on a recording material to the recording material while nipping and conveying the recording material at the fixing nip portion,
The abutting member is a projecting portion that projects toward the roller member, and has the largest force in at least a portion of the fixing nip portion other than the central portion of the fixing nip portion in the recording material conveyance direction. In a fixing device having a protrusion that presses the recording material,
The roller member has a first diameter part having a diameter of a first size and a second diameter part having a diameter larger than the first diameter part in the axial direction of the roller member,
A portion of the protruding portion that forms a pressure peak of the fixing nip portion with the second diameter portion is smaller than a portion of the protruding portion that forms a pressure peak of the fixing nip portion with the first diameter portion. A fixing device, wherein the fixing device is separated from a central portion of the fixing nip portion in the transport direction. A portion of the protrusion that forms a pressure peak of the fixing nip portion with the second diameter portion protrudes more than a portion of the protrusion that forms a pressure peak of the fixing nip portion with the first diameter portion. The fixing device according to claim 1, wherein the fixing device has a large amount. The fixing device according to claim 1 or 2, wherein the first diameter portion is provided at an axial end portion of the roller member, and the second diameter portion is provided at a central portion in the axial direction. apparatus. 3. The fixing device according to claim 1, wherein the second diameter portion is provided at an axial end portion of the roller member, and the first diameter portion is provided at a central portion in the axial direction. apparatus. The portion of the protruding portion that forms the pressure peak of the fixing nip portion with the second diameter portion has a greater area than the portion of the protruding portion that forms the pressure peak of the fixing nip portion with the first diameter portion. The fixing device according to any one of claims 1 to 4, wherein the fixing device is provided on a downstream side of a central portion of the fixing nip portion in the transport direction. The portion of the protruding portion that forms the pressure peak of the fixing nip portion with the second diameter portion has a greater area than the portion of the protruding portion that forms the pressure peak of the fixing nip portion with the first diameter portion. The fixing device according to any one of claims 1 to 4, wherein the fixing device is provided on an upstream side of a central portion of the fixing nip portion in the transport direction. A portion of the protrusion that forms a pressure peak of the fixing nip portion with the second diameter portion and a portion of the protrusion that forms a pressure peak of the fixing nip portion with the first diameter portion are continuous. The fixing device according to claim 1, wherein the fixing device is formed on the fixing device. When the fixing device is viewed in a direction substantially perpendicular to the surface of the fixing nip portion , the protrusion that forms a pressure peak of the fixing nip portion together with the roller member is curved. Item 8. The fixing device according to any one of items 1 to 7. A tubular film member, an abutting member that comes into contact with the inner peripheral surface of the film member, and a roller member that forms a fixing nip portion between the film member and the abutting member via the film member, A fixing device for fixing an unfixed toner image formed on a recording material to the recording material while nipping and conveying the recording material at the fixing nip portion,
The abutting member is a projecting portion that projects toward the roller member, and has the largest force in at least a portion of the fixing nip portion other than the central portion of the fixing nip portion in the recording material conveyance direction. In a fixing device having a protrusion that presses the recording material,
The inner surface nip portion, which is the contact area between the film member and the contact member, is located at a position different from the first area whose width in the transport direction is the first width and the first area in the axial direction of the roller member. And a second region having a larger width in the transport direction than the first region,
A second portion of the protrusion that forms a pressure peak of the fixing nip portion together with a portion of the roller member corresponding to the second region of the inner surface nip portion is a portion of the inner surface nip portion of the protrusion. The fixing is characterized in that it is farther from the central portion of the fixing nip portion in the transport direction than the first portion forming a pressure peak of the fixing nip portion together with the portion of the roller member corresponding to the first region. apparatus. The fixing device according to claim 9, wherein the second portion has a larger protrusion amount than the first portion. The fixing device according to claim 9, wherein the second portion is provided on the downstream side of the fixing nip portion in the transport direction with respect to the first portion. The fixing device according to claim 9, wherein the second portion is provided on the upstream side of the fixing nip portion in the transport direction with respect to the first portion. 13. The fixing device according to claim 9, wherein the second portion and the first portion are continuously formed. When the fixing device is viewed in a direction substantially perpendicular to the surface of the fixing nip portion, the protrusion that forms a pressure peak of the fixing nip portion together with the roller member is curved. Item 14. The fixing device according to any one of items 9 to 13. The contact member has a heater, the heater also fixing device according to any one of claims 1 to 14, characterized in that in contact with the inner peripheral surface of the film member. The fixing device according to claim 15 , wherein the protruding portion protrudes toward the roller member from a surface of the heater that is in contact with the film member.

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