JP6712410B2 - Nip forming member, fixing device, and image forming apparatus - Google Patents

Description

The present invention relates to a nip forming member, a fixing device including the nip forming member, and an image forming apparatus including the fixing device.

As a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine and a printer, a belt-type fixing device having improved energy saving and fast print time has been put into practical use. This belt-type fixing device heats an endless fixing belt with a heating member such as a halogen heater. In recent years, a direct heating type in which a fixing belt having a low heat capacity is directly heated with a heating member (halogen heater) has become popular. doing.

In this direct heating type, it is ideal to heat the fixing belt with a heating width that corresponds one-to-one with the paper width size, but when using a general halogen heater as the heating member, the paper width size is It is the fact that a smaller number of heaters (for example, the central heater and the end heaters) are used for the number of heaters.

When a small number of heaters are used as described above, the frequency of fixing is increased with the heating width of the fixing belt being larger than the width of the sheet. In recent years, the heat capacity and the wall thickness of the fixing belt have been further reduced.Therefore, when high-speed continuous paper feeding is performed, the so-called edge temperature rise (excessive temperature) of the low heat capacity/thin fixing belt occurs in the non-paper passing area outside the paper width. Temperature rise) becomes severe.

Therefore, for example, as in Patent Document 1 (JP-A-2015-194661, FIG. 10), by attaching a high thermal conductive member to the nip forming member that forms the fixing nip of the fixing device, the end when small size paper is passed It has been conventionally performed to reduce the temperature rise in the section.

The high thermal conductivity member does not delay the start-up time and first print time, so it is necessary to reduce the heat capacity by thinning it.However, if the high thermal conductivity member is thin, it is likely to be displaced or deformed due to friction with the fixing belt. However, the misalignment or deformation easily causes a fixing failure. The high thermal conductive member of Patent Document 1 has a concave cross section (FIG. 7), and the base material forming the nip forming member main body is accommodated in the concave cross section using a predetermined jig. There was a risk of deformation.

Therefore, an object of the present invention is to provide a highly heat-conductive member that is unlikely to be displaced or deformed even if it is made thin.

In order to solve the above-mentioned problems, the present invention is a nip forming member arranged on the inner peripheral side of a rotatable endless fixing belt, wherein an opposing member arranged on the outer peripheral side of the fixing belt forms the nip. In the nip forming member in which a nip portion is formed between the fixing belt and the facing member by contacting the member, the nip forming member is a nip forming first member that constitutes a nip forming member main body, A nip forming second member arranged on the nip portion side of the nip forming first member along the longitudinal direction of the nip forming first member, wherein the nip forming second member is The rotation upstream side and the rotation downstream side have a pair of side wall portions that are bent to the side opposite to the nip portion to form a concave cross section for accommodating the nip forming first member, and the concave cross section and the nip forming first member. The nip forming member is characterized in that it has a restricting portion for restricting separation from the side wall portion in the longitudinal direction of the side wall portion on the rotation upstream side.

Since the nip forming member of the present invention has the nip forming second member in which the regulating portion is arranged on the upstream side of the rotation of the fixing belt, even if the thickness of the nip forming second member is reduced, the positional deviation and deformation thereof can be suppressed. it can.

1 is a schematic diagram of an image forming apparatus according to an exemplary embodiment of the present invention. FIG. 3 is a schematic diagram illustrating an example of a fixing device used in the image forming apparatus. FIG. 6A is a cross-sectional view of the stay and the nip forming member as seen from the sheet passing direction, and is a cross-sectional view taken along the line aa of FIG. 4 is a perspective view of the nip forming member of FIG. 3. FIG. FIG. 6 is a cross-sectional view of a nip forming member in the fixing device. FIG. 5C is a sectional view taken along line BB in FIG. 5C, showing a state in which the base material of the nip forming member is assembled to the high thermal conductivity member. It is a perspective view showing a state where a substrate of a nip forming member is assembled to a high thermal conductive member. It is a figure which shows the arrangement|positioning relationship of a heating member and a high thermal conductivity member. It is sectional drawing of the modification of a nip formation member. It is sectional drawing which shows the state which attaches a base material to a high thermal conductive member in a modification. It is a perspective view of the nip formation member of a modification.

(Image forming device)
A printer as an image forming apparatus according to an embodiment of the present invention, and a fixing device and a nip forming member used in the printer will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an electrophotographic color laser printer as an image forming apparatus. At the center of the image forming apparatus 1, four image forming units 4Y, 4M, 4C and 4K are provided. The image forming units 4Y, 4M, 4C and 4K contain developers of different colors of yellow (Y), magenta (M), cyan (C) and black (K) corresponding to the color separation components of the color image. The configuration is the same except that

Specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a toner on the surface of the photoconductor 5. And a cleaning device 8 for cleaning the surface of the photoconductor 5. In FIG. 1, reference numerals are given only to the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4K, and the other image forming units 4Y, 4M, and 4C are omitted. To do.

An exposure device 9 as a latent image forming device that exposes the surface of the photoconductor 5 to form an electrostatic latent image is disposed below the image forming units 4Y, 4M, 4C, and 4K. The exposure device 9 has a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc., and irradiates the surface of each photoconductor 5 with laser light based on image data. The exposure device 9 can also be configured as an LED exposure device.

The transfer device 3 is disposed above the image forming units 4Y, 4M, 4C and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as a primary transfer member, and a secondary transfer roller 36 as a secondary transfer member. The transfer device 3 further includes a secondary transfer backup roller 32, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

The intermediate transfer belt 30 is an endless belt, and is stretched around a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, the secondary transfer backup roller 32 is rotationally driven, so that the intermediate transfer belt 30 travels (rotates) in the direction indicated by the arrow in the drawing.

Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Further, a power source is connected to each primary transfer roller 31, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Further, similarly to the primary transfer roller 31, a power source is also connected to the secondary transfer roller 36 so that a predetermined DC voltage (DC) and/or AC voltage (AC) is applied to the secondary transfer roller 36. It has become.

The belt cleaning device 35 has a cleaning brush and a cleaning blade that are arranged so as to contact the intermediate transfer belt 30. The waste toner transfer hose extending from the belt cleaning device 35 is connected to the entrance of the waste toner container.

A bottle housing section 2 is provided on the upper part of the printer body, and four toner bottles 2Y, 2M, 2C and 2K containing replenishment toner are detachably mounted in the bottle housing section 2. A replenishment path is provided between each of the toner bottles 2Y, 2M, 2C, 2K and each of the developing devices 7, and each toner bottle 2Y, 2M, 2C, 2K is connected to each of the developing devices 7 through the replenishment path. Toner is replenished.

On the other hand, in the lower part of the printer body, there are provided a paper feed tray 10 that contains paper P as a recording medium, a paper feed roller 11 that carries out the paper P from the paper feed tray 10, and the like. Here, the recording medium includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, a manual sheet feeding mechanism may be provided on the side surface of the printer body.

Inside the printer body, a conveyance path R is provided for ejecting the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, a pair of timing rollers 12 serving as a transport member that transports the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 36 in the paper transport direction.

Further, a fixing device 20 for fixing the unfixed image transferred to the sheet P is disposed downstream of the position of the secondary transfer roller 36 in the sheet conveying direction. Further, on the downstream side of the fixing device 20 in the paper transport direction of the transport path R, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided. Further, a paper discharge tray 14 for stocking the paper discharged to the outside of the apparatus is provided on the upper surface of the printer body.

(Basic operation of the printer)
Subsequently, the basic operation of the printer according to the present embodiment will be described with reference to FIG. When the image forming operation is started, each photoconductor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotationally driven by the drive device in the clockwise direction in the figure, and the surface of each photoconductor 5 is predetermined by the charging device 6. Is uniformly charged to the polarity of.

The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoconductor 5. At this time, the image information exposed on each photoconductor 5 is monochromatic image information in which a desired full-color image is separated into color information of yellow, magenta, cyan, and black. By supplying toner to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, the electrostatic latent image is visualized as a toner image (visualization). ..

When the image forming operation is started, the secondary transfer backup roller 32 is rotationally driven counterclockwise in the figure, and the intermediate transfer belt 30 is circulated in the direction shown by the arrow in the figure. Then, a constant voltage or a constant-current-controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

After that, when the toner images of the respective colors on the photoconductors 5 reach the primary transfer nip as the photoconductors 5 rotate, the toner images on the photoconductors 5 are formed by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 30. In this way, a full-color toner image is carried on the surface of the intermediate transfer belt 30.

Further, the toner on each photoconductor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. After that, the surface of each photoconductor 5 is destaticized by the destaticizing device, and the surface potential is initialized.

At the lower part of the printer body, the paper feed roller 11 starts to rotate and the paper P is sent out from the paper feed tray 10 to the transport path R. The paper P sent out to the transport path R is timed by the timing roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, whereby a transfer electric field is formed in the secondary transfer nip.

Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 travels around, the transfer electric field formed at the secondary transfer nip causes the toner image on the intermediate transfer belt 30 to move. Toner images are collectively transferred onto the paper P. At this time, the residual toner on the intermediate transfer belt 30 that could not be completely transferred to the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to the waste toner container and collected.

After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed on the paper P by the fixing device 20. Then, the paper P is discharged to the outside of the apparatus by the paper discharge roller 13 and is stocked on the paper discharge tray 14.

The above description is an image forming operation when forming a full-color image on a sheet, but a single-color image is formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. It is also possible to form a two-color or three-color image by using two or three image forming units.

(Fixing device)
Next, the configuration of the fixing device 20 used in the printer will be described with reference to FIG. As shown in FIG. 2, the fixing device 20 has a fixing belt 21 as a rotatable fixing rotating body, and a pressure roller 22 as a facing member rotatably provided facing the fixing belt 21.

Further, the fixing device 20 includes a halogen heater 23 (a central heater 23a and an end heater 23b) as a heating member for heating the fixing belt 21, a nip forming member 24 disposed inside the fixing belt 21, and a nip forming member. And a stay 25 as a supporting member that supports 24. Further, in the fixing device 20, the reflection member 26 that reflects the light emitted from the halogen heater 23 to the fixing belt 21, the temperature sensor 27 as a temperature detecting member that detects the temperature of the fixing belt 21, and the sheet P from the fixing belt 21. And a pressure member for pressing the pressure roller 22 against the fixing belt 21.

The fixing belt 21 is composed of a thin endless belt member (including a film) having a low heat capacity and flexibility. Specifically, the fixing belt 21 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Alternatively, it is composed of a release layer on the outer peripheral side formed of polytetrafluoroethylene (PTFE) or the like. In addition, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer.

The pressure roller 22 includes a cored bar 22a, an elastic layer 22b formed on the surface of the cored bar 22a and made of foamable silicone rubber, silicone rubber, or fluororubber, and a PFA provided on the surface of the elastic layer 22b. Alternatively, the release layer 22c is made of PTFE or the like. The pressure roller 22 is pressed against the fixing belt 21 side by the pressing member and is in contact with the nip forming member 24 via the fixing belt 21.

At a position where the pressure roller 22 and the fixing belt 21 are in pressure contact with each other, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width. Further, the pressure roller 22 is configured to be rotationally driven by a drive source such as a motor provided in the printer body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate. When the paper P on which the toner image T is transferred is conveyed from the A1 direction to the nip portion N, the toner image T is fixed on the paper P at the nip portion N, and then the paper P is moved from the nip portion N in the A2 direction. It is supposed to be discharged.

In the present embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In that case, a heating member such as a halogen heater may be provided inside the pressure roller 22. In addition, when there is no elastic layer, the heat capacity becomes small and the fixability is improved, but when the unfixed toner is squeezed and fixed, the fine irregularities on the belt surface are transferred to the image, and uneven glossiness occurs in the solid part of the image. It can happen.

In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing the elastic layer having a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, so that it becomes possible to avoid uneven gloss. Although the elastic layer 22b may be solid rubber, sponge rubber may be used when there is no heating member inside the pressure roller 22.

Sponge rubber is more preferable because the heat insulating property is improved and the heat of the fixing belt 21 is not easily removed so that the energy is saved. Further, the fixing rotator and the counter rotator are not limited to being in pressure contact with each other, but may be configured to simply contact with each other without applying pressure.

Both ends of each halogen heater 23 are fixed to the side plates of the fixing device 20. Each of the halogen heaters 23 is configured to generate heat by being output-controlled by a power supply unit provided in the printer main body, and the output control is based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 27. Done. By controlling the output of the halogen heater 23, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature. In addition to the halogen heater, an IH, a resistance heating element, a carbon heater, or the like may be used as the heating member that heats the fixing belt 21.

The nip forming member 24 is arranged in a longitudinal shape across the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22, and is fixedly supported by the stay 25. As a result, it is possible to prevent the nip forming member 24 from bending due to the pressure of the pressure roller 22, and to obtain a uniform nip width in the axial direction of the pressure roller 22. The stay 25 is preferably made of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 24 from bending, but the stay 25 may be made of resin. Is.

Further, the nip forming member 24 is composed of a heat resistant member having a heat resistant temperature of 200° C. or higher. This prevents deformation of the nip forming member 24 due to heat in the toner fixing temperature range, ensures a stable state of the nip portion N, and stabilizes the output image quality. As the base material of the nip forming member 24, a general heat resistant resin can be used as described later with reference to FIG. In this embodiment, as will be described later, LCP having excellent heat resistance and moldability is used as the base material 24a of the nip forming member 24.

The nip forming member 24 has a low friction sheet on its surface. When the fixing belt 21 rotates, the fixing belt 21 slides on the low-friction sheet, so that the drive torque generated in the fixing belt 21 is reduced and the load due to the frictional force on the fixing belt 21 is reduced. As a material of the low-friction sheet, for example, Toyoflon (registered trademark) 401 manufactured by Toray Industries, Inc. is preferable.

The reflection member 26 is arranged between the stay 25 and the halogen heater 23. In this embodiment, the reflecting member 26 is fixed to the stay 25. Further, since the reflecting member 26 is directly heated by the halogen heater 23, it is desirable that the reflecting member 26 be formed of a high melting point metal material or the like.

By arranging the reflection member 26 in this way, the light emitted from the halogen heater 23 to the stay 25 side is reflected to the fixing belt 21. As a result, the amount of light applied to the fixing belt 21 can be increased, and the fixing belt 21 can be efficiently heated. Further, since it is possible to suppress the radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, it is possible to save energy.

Further, without providing the reflection member 26 as in the present embodiment, the surface of the stay 25 on the side of the halogen heater 23 may be mirror-finished by polishing or painting to form the reflection surface. Further, the reflectance of the reflecting surface of the reflecting member 26 or the stay 25 is preferably 90% or more.

Since the shape and material of the stay 25 cannot be freely selected in order to secure its strength, it is better to separately provide the reflecting member 26 as in the present embodiment because the weight of selection of the shape and material becomes wider, and the reflecting member 26. The stay 25 and the stay 25 can be specialized in their respective functions. Further, by providing the reflection member 26 between the halogen heater 23 and the stay 25, the position of the reflection member 26 with respect to the halogen heater 23 becomes closer, so that the fixing belt 21 can be efficiently heated.

Further, in order to further improve the heating efficiency of the fixing belt 21 due to the reflection of light, it is necessary to study the direction of the reflecting surface of the reflecting member 26 or the stay 25. For example, when the reflecting surface is arranged concentrically around the halogen heater 23, the light is reflected toward the halogen heater 23, and the heating efficiency is reduced accordingly. On the other hand, when a part or all of the reflecting surface is arranged so as to reflect light toward the fixing belt in a direction other than the halogen heater 23, the amount of light reflected toward the halogen heater 23 decreases. The heating efficiency by reflected light can be improved.

Further, the fixing device 20 according to the present embodiment has various structural measures for improving the energy saving property and the first print time. Specifically, the halogen heater 23 can directly heat the fixing belt 21 at a portion other than the nip portion N (direct heating method). In this embodiment, nothing is interposed between the halogen heater 23 and the left side portion of the fixing belt 21 in FIG. 2, and radiant heat from the halogen heater 23 is directly applied to the fixing belt 21 in that portion.

Further, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is thin and has a small diameter. Specifically, the thickness of each of the base material, the elastic layer, and the release layer constituting the fixing belt 21 is set in the range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the total thickness is set. It is set to 1 mm or less.

The diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 21 is preferably 0.2 mm or less, and more preferably 0.16 mm or less. The diameter of the fixing belt 21 is preferably 30 mm or less.

In this embodiment, the diameter of the pressure roller 22 is set to 20 to 40 mm, and the diameter of the fixing belt 21 and the diameter of the pressure roller 22 are made equal to each other. However, the configuration is not limited to this. For example, the diameter of the fixing belt 21 may be smaller than that of the pressure roller 22. In that case, since the curvature of the fixing belt 21 in the nip portion N is smaller than the curvature of the pressure roller 22, the paper P discharged from the nip portion N in the A2 direction is easily separated from the fixing belt 21.

(Nip forming member)
Next, the nip forming member 24 according to the embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 3, the nip forming member 24 includes a base material 24a as a nip forming first member and a high thermal conductive member 24b as a nip forming second member. The base material 24a constitutes the main body of the nip forming member 24, and is formed of a heat resistant resin described later.

The high thermal conductive member 24b is disposed on the lower surface (the surface facing the nip portion) of the base material 24a. As can be seen from FIGS. 3A and 3B, the high thermal conductive member 24b is arranged in non-contact with the stay 25 and the reflecting member 26 (see FIG. 2) arranged inside (upper) the stay 25. ing. Therefore, heat transfer from the high thermal conductivity member 24b to the stay 25 is prevented, and energy saving is not impaired. Similarly, heat transfer from the high thermal conductivity member 24b to the reflecting member 26 can be prevented, and energy saving can be maintained.

(Base material)
The base material 24a may be an inorganic material or an organic material that has lower thermal conductivity than the high thermal conductivity member 24b, has heat resistance with respect to the operating temperature, and can transmit pressure. Examples of such a material include inorganic materials such as ceramics, glass and aluminum, rubbers such as silicone rubber and fluororubber, PTFE (tetrafluoroethylene), PFA (tetrafluoroethylene/perfluoroalkoxy vinyl ether copolymer), ETFE (ethylene/tetrafluoroethylene copolymer), FEP (tetrafluoroethylene/hexafluoropropylene copolymer) and other fluororesins, PI (polyimide), PAI (polyamide imide), PPS (polyphenylene sulfide), Resins such as PEEK (polyetheretherketone), LCP (liquid crystal plastic, liquid crystal polymer), phenol resin, nylon, aramid, or a combination thereof can be used.

In the present embodiment, the base material 24a is formed of liquid crystal polymer (LCP) having excellent heat resistance and moldability. The heat resistant temperature of this LCP is preferably 350° C. or higher in order to withstand the rise in the end temperature when continuously passing a sheet of A6 length. Many of the conventional base materials 24a have a heat resistance of about 250° C., and it is necessary to improve the heat resistance against the rise in the end temperature.

The thermal conductivity of the base material 24a is, for example, 0.54 W/m·K, and this value is extremely smaller than the values of the high thermal conductivity member 24b, the stay 25, and the reflecting member 26. Therefore, a high heat insulating effect is obtained by the base material 24a, and heat transfer from the high thermal conductive member 24b to the base material 24a and the stay 25 is suppressed. Needless to say, the thermal conductivity of the base material 24a is not limited to this.

As for the shape of the upper surface (the stay facing surface) of the base material 24a, a plurality of first projections 24a2 arranged in two rows in the lateral direction are spaced apart from each other and arranged in the longitudinal direction (FIG. 3A). FIG. 3A is a sectional view taken along the line aa of FIG. In this way, by making the upper surface of the base material 24a (the stay facing surface) into an uneven shape having protrusions arranged in the longitudinal direction, it is possible to transmit pressure from the stay 25 side to the nip portion, and at the same time, to dissipate heat to the stay 25 side. Can be suppressed. Therefore, the lighting rate of the halogen heater 23 can be reduced to improve the thermal efficiency and energy saving.

The first protrusions 24a2 are not limited to the shape in which two rows are arranged in the lateral direction and a plurality of rows are arranged in the longitudinal direction as described above. That is, 1) a shape in which a plurality of first projections 24a2 arranged in one row in the lateral direction are arranged in the longitudinal direction, 2) a shape in which two first projections 24a2 arranged in two rows in the lateral direction are arranged in one row in the longitudinal direction, and 3) a first projection. It is also possible that zigzag arrangement of 24a2 is possible.

Further, as shown in FIG. 3B, a concave portion 70 having a triangular cross section is formed on the upper surface of the base material 24a. The concave portion 70 is for engaging the restriction portion 24b4 of the high thermal conductive member 24b, which will be described later, and as shown in FIGS. 5A and 5B, the concave portion 70 is formed on the surface of the substrate 24a opposite to the nip portion N. The bottom surface 24a has a bottom surface that is inclined with respect to the nip surface from the nip inlet side toward the nip outlet side. As shown in FIG. 5B, the inclination angle of the bottom surface is such that when the base material 24a is inserted into the concave cross section of the high thermal conductive member 24b from diagonally above the left, the bottom left corner of the restriction portion 24b4 faces the recess 70. Therefore, the inclination angle is equal to or more than the inclination angle of the base material 24a when the base material 24a is inserted.

(High thermal conductivity member)
On the other hand, the high thermal conductive member 24b is made of a material having a high thermal conductivity so that the temperature of the end portion of the fixing belt 21 does not rise. When the base material of the fixing belt 21 is a metal such as nickel or SUS, the high thermal conductive member 24b has a copper-based material (for example, thermal conductivity 381 W/mK) or an aluminum-based material (for example, thermal conductivity 236 W/m). -It is preferable to use a material having a high thermal conductivity such as K). When a resin material such as polyimide (thermal conductivity 0.29 W/m·K) is used for the fixing belt substrate, an iron-based SUS material (for example, thermal conductivity 19 W/m·K) or the like is used as the high thermal conductive member 24b. Metallic materials can also be used.

In this embodiment, the high thermal conductive member 24b is made of a copper-based material, and more specifically, the high thermal conductive member 24b is made of a copper-based material having a thermal conductivity of 236 w/(m·k) or more. In the present embodiment, a copper plate having such a thermal conductivity is bent and formed to form the high thermal conductivity member 24b. In the example of FIG. 3, the copper plate is formed by bending so that the high thermal conductive member 24b has a concave cross section in a cross section perpendicular to its longitudinal direction. The formation of the copper plate is not limited to bending and may be welding or the like.

The thickness or heat capacity of the high thermal conductive member 24b is set to a size that does not impair the temperature rising rise time or the first print time of the fixing belt 21. If the heat capacity of the high thermal conductive member 24b is too large, the amount of heat transferred from the fixing belt 21 is increased to prevent the temperature of the fixing belt 21 from rising, delaying the rising time and delaying the first print time, and turning on the halogen heater 23. The rate is increased and the energy saving property is impaired.

Therefore, the high heat conductive member 24b is a thin layer member having a low heat capacity to prevent the temperature rise of the end portion while ensuring energy saving. In the present embodiment, the thickness of the high thermal conductive member 24b is 1 mm or less, preferably 0.4 mm or less. In this way, the high thermal conductive member 24b is thinned to minimize its heat capacity, and fixing failure due to a decrease in the end temperature at the time of starting the fixing is suppressed.

As shown in FIG. 5A, in the high thermal conductive member 24b, the bottom wall portion 24b1 as the first surface of the concave cross section is a surface facing the nip portion, and the side walls as the second and third surfaces on the left and right in the width direction of the high thermal conductive member 24b. The portions 24b2 and 24b3 are bent at a predetermined height Hs toward the stay 25 so as to sandwich the base material 24a in the sheet passing direction. The height of the bent portion (height of the side wall portions 24b2, 24b3) is not less than the thickness of the base material 24a in the vertical direction. Although the height Hs of the side wall portions 24b2 and 24b3 is constant in the illustrated example, the height Hs can be changed in the longitudinal direction of the high thermal conductive member 24b. Thereby, the amount of heat released in the thickness direction of the high thermal conductive member 24b can be adjusted by the position in the longitudinal direction, and the temperature rise in the end portion can be suppressed more appropriately.

In the present embodiment, in the case of the “A3 non-fixing device”, the height Hs of the side wall portions 24b2, 24b3 of the high thermal conductive member 24b is 1. As shown in FIGS. 5A and 5B over the entire length in the longitudinal direction of the high thermal conductive member 24b. It is set in the range of 0 mm to 1.9 mm. Here, the height Hs is the height from the inner surface of the bottom wall portion 24b1 of the high thermal conductive member 24b to the upper ends of the side wall portions 24b2, 24b3. In addition, A3 novi is a sheet slightly larger than the standard size A3, and is a sheet having a width of 320 to 330 mm, but there is no standard.

(Regulatory Department)
A part of the upper end of the side wall portion 24b2 on the inlet side of the nip portion (upstream side of rotation of the fixing belt 21) of the high thermal conductive member 24b is substantially perpendicular to the downstream side of rotation of the fixing belt 21, that is, a rectangle bent in an L-shaped cross section. The restriction portion 24b4 is formed. As shown in FIG. 4, a plurality of the restriction portions 24b4 are formed at predetermined intervals a to c in the longitudinal direction of the high thermal conductive member 24b. The restriction portion 24b4 can be formed by bending or welding, but by forming a part of the high thermal conductive member 24b by bending as described above, it can be configured at low cost without increasing the number of parts. In addition, even if the restriction portion 24b4 is not bent at a right angle, if it is in a state of facing the bottom wall portion 24b1 of the base material 24a, a separation preventing effect described later is achieved.

The length in the lateral direction of the restriction portion 24b4 needs to be equal to or shorter than the thickness of the base material 24a and the height of the high heat conductive member 24b on the outlet side (left side in FIGS. 5A and 5B). Therefore, for example, when the thickness of the base material 24a and the height of the high thermal conductive member 24b on the outlet side are set to 2 mm, the lateral length of the restriction portion 24b4 can be set to 2 mm or less than 2 mm.

By setting the length of the restriction portion 24b4 in the short-side direction to 2 mm, it is possible to prevent heat from escaping through the restriction portion 24b4 and escaping to the back side of the nip, and at the same time, to arrange the base material 24a in the concave cross section of the high thermal conductive member 24b. At the time of insertion, the base material 24a is easy to fit and difficult to separate. That is, as the length of the restricting portion 24b4 in the short-side direction becomes longer, the base material 24a becomes harder to fit, so that it is necessary to make the concave portion 70 of the base material 24a larger, and the strength of the base material 24a is sacrificed. On the contrary, the shorter the length of the restriction portion 24b4 in the lateral direction is, the easier it is for the base material 24a to be fitted into the concave cross section of the high thermal conductive member 24b, but the base material 24a is more easily detached.

The restriction portion 24b4 engages with the upper surface of the base material 24a on the opposite side to the nip portion N on the upstream side of the rotation of the fixing belt 21, so that even if the high thermal conductive member 24b is thinned, friction with the fixing belt 21 occurs. Thus, it is possible to suppress the positional deviation and deformation of the high thermal conductive member 24b. Further, the restricting portion 24b4 prevents the parts from being separated during the assembly of the nip forming member 24, and also makes it possible to improve the work efficiency of the assembly of the nip forming member 24. That is, during the assembly of the nip forming member 24, the restricting portion 24b4 restricts the base material 24a housed in the concave cross section of the high thermal conductive member 24b from separating upward in FIG. 5A. Instead of the regulating portion 24b4 on the upstream side of the rotation of the fixing belt 21, or together with the regulating portion 24b4, as shown in the circular frame of FIG. 5A, the fixing belt 21 is formed on a part of the upper end of the side wall portion 24b3 on the downstream side of the rotation. You may form the rectangular regulation part 24b6 bent substantially at right angle toward the rotation upstream side.

If necessary, the upper surface 24a1 of the base material 24a may be provided with a recess 70 in which the distal end side of the restriction portion 24b4 is engageable, as shown in FIGS. 3, 5A, and 5B. When the regulation portion 24b6 is formed on the downstream side of the rotation of the fixing belt 21, the concave portion 70 can be formed at a position facing the regulation portion 24b6 on the opposite side of the base material 24a, if necessary. Thereby, as described later, it is possible to suppress the deterioration of the image quality due to the temperature unevenness of the nip forming member 24 in the longitudinal direction.

By forming the concave portion 70, it is possible to prevent the restriction portion 24b4 from becoming an obstacle when the base material 24a is inclined as shown in FIG. 5B and is inserted into the concave cross section of the high thermal conductive member 24b as shown by an arrow. Will also be possible. Of course, even if the restricting portion 24b4 is left at the position shown by the solid line in FIG. 5A without forming the recessed portion 70, it is possible to suppress the displacement and deformation of the high thermal conductive member 24b.

The base material 24a thus formed with the concave portion 70 is inserted in a horizontal state while rotating the base material 24a from a state in which the edge portion 24a3 on one side in FIG. 5B is applied to the inside of the base end portion of the regulating portion 24b4. FIG. 5A is after insertion. At the time of insertion, the edge portion 24a4 of the base material 24a opposite to the edge portion 24a3 draws an arcuate locus C1 while slidingly contacting the surface of the side wall portion 24b3. Since the high thermal conductive member 24b is thin, it is possible to insert the base material 24a with one or both of the side wall portions 24b2 and 24b3 elastically bent outward. When such a method of inserting the base material 24a is adopted, the gap inside the side wall portion 24b3 shown in FIG. 5A is not always necessary.

After the base material 24a is inserted into the concave cross section of the high thermal conductive member 24b, the regulating portion 24b4 is pressed from above with a jig or the like as shown by the broken line in FIG. With this, the base material 24a and the high thermal conductive member 24b can be integrated, and the positional deviation and deformation of the thermal conductive member 24b described above can be more reliably suppressed.

By leaving a gap between the tip end side of the regulation portion 24b4 and the concave portion 70, a portion corresponding to the regulation portion 24b4 (a portion of the concave portion 70) and a portion other than the portion are not formed in the longitudinal direction of the base material 24a. The temperature can be made almost equal by. That is, the gap can be left by leaving the restriction portion 24b4 at the position indicated by the solid line in FIG. 5A, or by slightly bending it even when it is pressed by a jig or the like from above and bent. As a result, it is possible to suppress the deterioration of the image quality due to the temperature unevenness of the nip forming member 24 in the longitudinal direction.

Further, by fitting the regulating portion 24b4 into the recess 70, it also serves as a thrust stop for the base material 24a and the high thermal conductive member 24b, which will be described later, and therefore it is possible to omit the both-end engaging portion 24b5, which will be described later. Further, since the concave portion 70 also functions as a mark of the triangular mark 60, the triangular mark 60 can be omitted.

Since the length of the nip forming member 24 in the longitudinal direction is, for example, 300 mm or more in the case of an A3 non-width machine, when the restricting portion 24b4 is only one position at the center in the longitudinal direction, it is stable with the base material 24a in the entire longitudinal direction. It is difficult to keep the mechanical engagement (hook). Therefore, by installing the regulating portions 24b4 at a plurality of locations (six locations in the present embodiment) in the longitudinal direction of the high thermal conductive member 24b, the longitudinal direction/BR>·S body can sufficiently secure the catching property with the base material 24a. There is.

The volume of the restriction portion 24b4 can be reduced by partially providing the restriction portion 24b4 as described above. Thereby, it is not necessary to inadvertently increase the heat capacity of the high thermal conductive member 24b other than the bottom wall portion 24b1 facing the nip portion N, and the thermal conductivity of the bottom wall portion 24b1 of the high thermal conductive member 24b can be more effectively enhanced. , It is possible to satisfy the required soaking function.

Further, by arranging the restricting portion 24b4 on the upstream side of the rotation of the fixing belt 21, the high thermal conductive member 24b is rubbed by the frictional resistance with the fixing belt 21 when the fixing belt 21 rotates in the direction of the arrow as shown in FIG. 5A. Even if a force in the direction of the arrow is applied, the possibility that the base material 24a and the high thermal conductive member 24b may be displaced or deformed can be reduced. Therefore, the positional relationship between the base material 24a and the high thermal conductive member 24b can be maintained with high accuracy. This makes it possible to maintain the stable sliding function of the low-friction sheet interposed between the nip forming member 24 and the fixing belt 21 for a long period of time, and to maintain the high-quality fixing function of the image forming apparatus 1. it can.

As shown in FIG. 4, the restriction portion 24b4 is formed so that the interval a on the longitudinal center side of the high thermal conductive member 24b is narrower than the interval b or the interval c on both longitudinal ends. Since the high thermal conductive member 24b is in contact with the fixing belt 21 in the entire width in the longitudinal direction, the bending force due to the largest frictional force acts on the central portion thereof, so that the interval a on the central side in the longitudinal direction is reduced corresponding to the bending force. ing. The distances b and c on both ends in the longitudinal direction may be equal, or the distance c on the outer side in the longitudinal direction may be slightly widened so that a<b<c. This is because the bending force due to the frictional force acting on the high thermal conductivity member 24b decreases as it goes outward in the longitudinal direction.

It should be noted that it is possible to increase the number of the restricting portions 24b4 to strengthen the connection with the base material. However, if the number of the restricting portions 24b4 is increased too much, the heat dissipation to the high thermal conductive member 24b increases and the energy saving is achieved. Impair sex. Therefore, in the present embodiment, the number of restricting portions 24b4 is set to six. By setting the number to 6, the heat dissipation falls within the allowable range and the effect of suppressing the end temperature rise can be obtained.

As shown in FIG. 4, rectangular engaging portions 24b5 capable of engaging with both ends of the base material 24a are formed at both ends of the high thermal conductive member 24b in the longitudinal direction. The engagement portion 24b5 is formed at both ends in the longitudinal direction of the bottom wall portion 24b1 at a substantially right angle, that is, in a direction away from the nip portion in an L-shaped cross section.

By the engagement portion 24b5, it is possible to control the positional deviation and deformation in the longitudinal direction of the high thermal conductive member 24b and the base material 24a when they are assembled (thrust stop). Therefore, the efficiency of assembling the nip forming member 24 can be improved in combination with the function of restricting the separation of the base material 24a by the restricting portion 24b4.

(Assembly of nip forming member)
To assemble the nip forming member 24, first, as shown in FIG. 5C, the base material 24a is arranged in parallel above the concave cross section of the high thermal conductive member 24b, and from here, one side of the base material 24a is directed in the arrow direction, that is, diagonally downward. Is inserted so as to go under the restriction portion 24b4. 5B is a BB cross section of FIG. 5C. Once the base material 24a fits within the concave cross section as shown in FIG. 5A, even if the base material 24a tries to float upward in FIG. 5A, the lifting is prevented by the restriction portion 24b4. Therefore, the detachment of the base material 24a from the concave cross section of the high thermal conductive member 24b is restricted, the base material 24a and the high thermal conductive member 24b are stable without separating from each other, and the assembly of the nip forming member 24 can be smoothly proceeded. ..

As shown in the enlarged view of FIG. 4, a triangular mark 60 may be formed in a concave shape or a convex shape at a portion of the upper surface 24a1 of the base material 24a where the restriction portion 24b4 is caught. This facilitates the positioning of the restriction portion 24b4 with respect to the base material 24a.

Further, as shown in FIG. 4C, in place of the recess 70 described above, a recess 71 having the same shape as the restriction 24b 4 and a constant depth is formed in the portion where the restriction 24b 4 is caught, and the recess 71 is provided with the restriction 71. The entire 24b4 may be fitted. By fitting the entire restricting portion 24b4 into the recess 71, it is possible to eliminate the protrusion of the restricting portion 24b4 on the upper surface 24a1 of the base material 24a, and thereby the distance to the stay 25 arranged above the base material 24a can be increased. The device can be made compact by packing. Further, fitting the regulation portion 24b4 into the recess 71 also serves as a thrust stopper for the base material 24a and the high thermal conductive member 24b, so that both-end engaging portions 24b5 can be omitted. Further, since the concave portion 70 also functions as a mark of the triangular mark 60, the triangular mark 60 can be omitted.

(Arrangement of halogen heater and high thermal conductivity member)
Finally, the positional relationship between the halogen heater 23 and the high thermal conductive member 24b will be described with reference to FIG. In FIG. 6, the width size of the paper that passes through the fixing device 20 is indicated by A to D (A: postcard, A′: A4 vertical, B: B4 vertical, C: A3 vertical, D: A3 novi).

The high thermal conductive member 24b is attached in parallel with the halogen heater 23. In the present embodiment, as the halogen heater 23, a central heater 23a and an end heater 23b having different heat generation regions are used. It is also possible to use a single heater as the halogen heater 23.

The central heater 23a has a heat generating portion (light emitting portion) h1 at the widthwise center of the fixing belt 21, and the end heater 23b has heat generating portions (light emitting portion) h2 at both widthwise ends of the fixing belt 21. The inner end (the end on the widthwise center side of the fixing belt 21) of each heat generating part h2 of the end heater 23b is arranged at a position corresponding to both ends of the heat generating part h1 of the central heater 23a.

As for the length Ls of the high thermal conductive member 24b, both widthwise outer ends 24b-out thereof are arranged in a range from the widthwise inner end h2in of the heat generating part h2 of the end heater 23b to the widthwise outer end h2out. It is set to the length. Here, in the present embodiment, the position of the widthwise inner end of the hole 51 formed at both widthwise both ends of the high heat conductive member 24b is defined as the widthwise outer end 24b-out of the high heat conductive member 24b. There is.

The hole 51 is provided for positioning the high thermal conductive member 24b with respect to the base material 24a of the nip forming member 24. By inserting a protrusion as a positioning portion provided in the base material 24a into each hole 51, the high thermal conductive member 24b is positioned in the width direction with respect to the base material 24a.

At the location where the hole 51 is formed, the area where the high thermal conductive member 24b comes into contact with the fixing belt 21 is small, so that the heat conduction function from the location where the hole 51 is formed to the outside in the width direction is low. In particular, in this embodiment, the length L2 of the hole 51 in the sheet conveying direction (recording medium conveying direction length) is more than half the sheet conveying direction length (recording medium conveying direction length) L1 of the high thermal conductive member 24b. Therefore, the amount of heat conduction from the hole 51 to the outer side in the width direction is reduced.

That is, in the present embodiment, the region E from the center in the width direction to the hole 51 in the width direction region of the high thermal conductive member 24b is a part mainly expected to function as a heat conducting portion. On the other hand, the region F on the outer side in the width direction from the hole 51 has a heat conduction function to some extent, but has a lower heat conduction function than the heat conduction portion, and is a portion mainly provided for the function as a positioning portion. is there.

For the above reason, in the present embodiment, the widthwise outer end portion (the hole portion 51) of the heat conducting portion (region E), which is expected to have an original function as the heat conducting member, of the portion configuring the high heat conducting member 24b. The inner end in the width direction) is the outer end 24b-out in the width direction of the high thermal conductive member 24b. Unlike the present embodiment, when the length L2 of the hole portion 51 in the sheet conveyance direction is less than half the length L1 of the high thermal conductive member 24b in the sheet conveyance direction, a portion (region) outside the hole 51 in the width direction is formed. It is determined that F) also mainly functions as a heat conducting portion. Therefore, in this case, the widthwise outer end portion of the entire high heat conductive member 24b including the portion (region F) on the widthwise outer side from the hole 51 is defined as the widthwise outer end portion 24b-out of the high heat conductive member 24b. ..

Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above embodiments and various modifications can be made within the scope of the technical idea described in the claims. For example, the number of the regulating portions 24b4 to be provided can be increased or decreased from six depending on the length of the nip forming member 24 and the like. Further, the shape of the restricting portion 24b4 is not limited to a rectangle, but can be changed to a square, a triangle, a trapezoid, or the like.

Further, as a modified example of the nip forming member 24, as shown in FIGS. 7A to 7C, a required number of regulating portions 24b7 may be formed on the side wall portion 24b3 on the downstream side of the high thermal conductive member 24b. The regulation portion 24b7 rises from the upper end of the side wall portion 24b3 and bends in an inverted U shape, and its tip portion abuts the upper surface 24a1 of the base material 24a as shown in FIG. 7A. In this modification, when the base material 24a is inclined as shown in FIG. 7B and is inserted into the concave cross section of the high thermal conductive member 24b as shown by the arrow, the regulating portion 24b7 guides the edge portion 24a4 of the base material 24a to the concave cross section. Have the function to When the base material 24a is inserted into the concave cross section, the tip of the regulating portion 24b7 abuts the upper surface 24a1 of the base material 24a, so that the base material 24a is prevented from coming off the concave cross section, and the assembly of the nip forming member 24 is smoothly performed. You can proceed to.

The downstream regulating portion 24b7 is preferably arranged between the upstream regulating portions 24b4 as shown in FIG. 7C. Thereby, the positional relationship between the base material 24a and the high thermal conductive member 24b is maintained with high accuracy. Further, by arranging the upstream side and the downstream side regulating portions 24b4 and 24b7 alternately in the longitudinal direction of the high thermal conductive member 24b as shown in FIG. 7C, the temperature rising characteristics can be made uniform in the longitudinal direction of the high thermal conductive member 24b. Therefore, it is possible to shorten the temperature rise time and the first print time.

1: Image forming device 2: Bottle storage unit 2Y, 2M, 2C, 2K: Toner bottle 3: Transfer device 4Y, 4M, 4C, 4K: Image forming unit 5: Photosensitive member 6: Charging device 7: Developing device 8: Cleaning Device 9: Exposure device 10: Paper feed tray 11: Paper feed roller 12: Timing roller 13: Paper discharge roller 14: Paper discharge tray 20: Fixing device 21: Fixing belt 22: Pressure roller 22a: Core bar 22b: Elastic layer 22c: Release layer 23: Halogen heater 23a: Central heater 23b: End heater 24: Nip forming member 24a: Base material (nip forming first member)
24a1: Upper surface 24a2: First protrusion 24b: High thermal conductive member (nip forming second member) 24b1: Bottom wall portions 24b2, 24b3: Side wall portions 24b4, 24b6: Restricting portion 24b5: Engaging portion 25: Stay 26: Reflecting member 27 : Temperature sensor 28: Separation member 30: Intermediate transfer belt 31: Primary transfer roller 32: Secondary transfer backup roller 33: Cleaning backup roller 34: Tension roller 35: Belt cleaning device 36: Secondary transfer roller 51: Hole 60: Triangular marks 70, 71: recess

JP, 2005-194661, A

Claims (11)

A nip forming member arranged on the inner peripheral side of a rotatable endless fixing belt, and an opposing member arranged on the outer peripheral side of the fixing belt comes into contact with the nip forming member, whereby the fixing belt and the fixing belt In the nip forming member in which a nip portion is formed between the opposing member and the nip forming member,
A nip forming first member constituting the nip forming member main body,
A nip forming second member arranged on the nip portion side of the nip forming first member along the longitudinal direction of the nip forming first member,
The nip forming second member has a pair of side wall portions on the upstream side and the downstream side of the rotation of the fixing belt, which are bent to the opposite side of the nip portion, thereby forming a concave cross section for accommodating the nip forming first member. Along with this, there are restricting portions for restricting separation between the concave section and the nip forming first member at a plurality of longitudinal positions of the side wall portion on the upstream side of rotation , and mutual intervals of the restricting portions are the nip forming first members . A nip forming member, characterized in that the center side in the longitudinal direction of the two members is formed narrower than the both end sides in the longitudinal direction . The nip forming member according to claim 1, wherein heights of the pair of side wall portions are higher than a thickness of the nip forming first member on both the rotation upstream side and the rotation downstream side. Nip forming member according to claim 1 or 2, wherein the regulating unit, characterized in that it is bent in the rotational downstream side of the fixing belt from the side wall portion. The nip forming member according to claim 3 , wherein the restricting portion is a rectangle having a long side in the longitudinal direction of the nip forming second member. The longitudinal ends of the nip forming second member, one of the four from claim 1, characterized in that the engagement portion engaged with longitudinal ends of the nip forming first member is formed 1 The nip forming member according to the item. Has a mark on the upper surface of the nip forming first member opposite to the nip portion, the mark is one of claims 1 to 5, characterized in that correspond to the position where the restricting unit is arranged The nip forming member according to item 1. The nip forming member according to any one of claims 1 to 6 , wherein a concave portion into which the regulating portion can be fitted is formed on an upper surface of the nip forming first member opposite to the nip portion. .. A nip forming member arranged on the inner peripheral side of a rotatable endless fixing belt, and an opposing member arranged on the outer peripheral side of the fixing belt comes into contact with the nip forming member, whereby the fixing belt and the fixing belt In the nip forming member in which a nip portion is formed between the opposing member and the nip forming member,
A nip forming first member constituting the nip forming member main body,
A nip forming second member arranged on the nip portion side of the nip forming first member along the longitudinal direction of the nip forming first member,
The nip forming second member has a pair of side wall portions on the upstream side and the downstream side of the rotation of the fixing belt, which are bent to the opposite side of the nip portion, thereby forming a concave cross section for accommodating the nip forming first member. Along with a plurality of regulating portions that regulate the separation between the concave cross section and the nip forming first member at a plurality of longitudinal side portions of the side wall portion on at least one of the rotation upstream side and the rotation downstream side , The nip forming member is characterized in that a mutual space is formed such that a central side in the longitudinal direction of the nip forming second member is narrower than both end sides in the longitudinal direction . The nip forming member according to any one of claims 1 to 8 , wherein the nip forming second member has a higher thermal conductivity than the nip forming first member. A rotatable endless fixing belt,
A heating member for heating the fixing belt,
A nip forming member arranged on the inner peripheral side of the fixing belt,
In a fixing device having a facing member that contacts the nip forming member from the outer peripheral side of the fixing belt and forms a nip portion between the fixing belt and the fixing belt, the nip forming member is
A nip forming first member constituting the nip forming member main body,
A nip forming second member arranged on the nip portion side of the nip forming first member along the longitudinal direction of the nip forming first member,
The nip forming second member forms a concave cross section by having a pair of side wall portions that are bent toward the opposite side to the nip portion on the rotation upstream side and the rotation downstream side of the fixing belt, and the concave cross section and the nip formation. The side wall portion on the upstream side of rotation has regulating portions for regulating separation from the first member at a plurality of locations in the longitudinal direction. A fixing device characterized by being formed narrower than both ends . In an electrophotographic image forming apparatus that forms an image by fixing a toner image after transferring it to a recording medium,
An image carrier rotatably held,
A charging device for charging the image carrier,
A latent image forming device for forming an electrostatic latent image on the image carrier charged by the charging device;
A developing device that visualizes the toner by attaching toner to the electrostatic latent image formed by the latent image forming device;
A transfer device for transferring the toner image visualized by the developing device to the recording medium;
An image forming apparatus comprising: the fixing device according to claim 10 for fixing the toner image transferred onto the recording medium by the transfer device.

Images