JP2017161880A - Nip forming member, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a second nip forming member of a nip forming member that is not easily positionally displaced and deformed despite its small thickness.SOLUTION: A nip forming member 24 is formed of a base material 24a that forms its body and a second nip forming member 24b that has a higher thermal conductivity than that of the base material 24a and is disposed on a side of a nip part of the base material 24a along the longitudinal direction of the base material. The second nip forming member 24b includes a pair of side wall parts 24b2 and 24b3 that are bent to the opposite side of the nip part on the rotation upstream side and rotation downstream side of a fixing belt 21 to form a concave cross section that stores the base material 24a. Regulation parts 24b4 regulating separation of the base material 24a from the concave cross section are provided at some positions in the longitudinal direction of the side wall part 24b2 on the rotation upstream side.SELECTED DRAWING: Figure 4

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 or a printer, a belt-type fixing device with improved energy saving and first print time has been put into practical use. In this belt type fixing device, an endless fixing belt is heated by a heating member such as a halogen heater, but in recent years, a direct heating type in which a fixing belt having a reduced heat capacity is directly heated by a heating member (halogen heater) has become widespread. doing.

In this direct heating type, it is ideal to heat the fixing belt with a heating width that corresponds to the paper width size on a one-to-one basis. However, when a general halogen heater is used as the heating member, the paper width size is related to the cost. Actually, a smaller number of heaters (for example, a central heater and an end heater) can be used.

In the case where a small number of heaters are used in this way, the frequency of fixing is increased in a state where the fixing belt heating width is larger than the sheet width. In recent years, the heat capacity and thinning of fixing belts have been further reduced, so when high-speed continuous paper feeding is performed, the so-called end temperature rise (excess temperature of the low heat capacity and thin-walled fixing belt in the non-paper passing area outside the paper width). Temperature rise).

Therefore, for example, as in Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-194661, FIG. 10), a high heat conductive member is attached to a nip forming member that forms a fixing nip of a fixing device, so that an end when a small size paper is passed through. Conventionally, it has been practiced to reduce the temperature increase in the section.

In order to prevent the rise time and first print time from being delayed, it is necessary to reduce the heat capacity by reducing the thickness of the high thermal conductivity member. However, if the high thermal conductivity member is thin, displacement and deformation are likely to occur due to friction with the fixing belt. Further, fixing failure is likely to occur due to the positional deviation and deformation. The high thermal conductive member of Patent Document 1 has a concave cross section (FIG. 7), and the base material constituting the nip forming member main body is accommodated in the concave cross section using a predetermined jig. There was a risk of deformation.

Accordingly, an object of the present invention is to provide a highly heat conductive member that is less likely to be displaced or deformed even if it is thinned.

In order to solve the above-mentioned problems, the present invention provides a nip forming member disposed on the inner peripheral side of a rotatable endless fixing belt, wherein an opposing member disposed on the outer peripheral side of the fixing belt is configured to form the nip. In the nip forming member in which a nip portion is formed between the fixing belt and the opposing member by contacting the member, the nip forming member includes a nip forming first member constituting a nip forming member main body, A second nip forming member disposed on the nip portion side of the first nip forming member along the longitudinal direction of the first nip forming member, and the second nip forming member is disposed on the fixing belt. The rotating upstream side and the rotating downstream side have a pair of side wall portions bent to the opposite side to the nip portion, thereby forming a concave cross section that accommodates the first nip forming member, and the concave cross section and the nip A nip forming member, characterized in that it has a regulating portion for regulating separation of the formed first member in the longitudinal direction a part of the side wall portion of said rotary upstream.

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

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating an example of a fixing device used in an image forming apparatus. (A) is sectional drawing which looked at the stay and the nip formation member from the paper direction, (a) sectional view of (b), (b) is a cross-sectional view of a stay and a nip formation member. It is a perspective view of the nip forming member of FIG. FIG. 3 is a cross-sectional view of a nip forming member in the fixing device. It is BB sectional drawing of Drawing 5C showing the state where the substrate of a nip formation member is assembled to a high heat conduction member. It is a perspective view which shows the state which assembles | attaches the base material of a nip formation member to a high heat conductive member. It is a figure which shows the arrangement | positioning relationship between a heating member and a high heat conductive 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 heat 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, 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. In the center of the image forming apparatus 1, four image forming units 4Y, 4M, 4C, and 4K are provided. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It is the same structure except having.

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

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

A 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 member, four primary transfer rollers 31 as primary transfer members, 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 over 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 figure.

Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Each primary transfer roller 31 is connected to a power source, 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. Similarly to the primary transfer roller 31, a power source is connected to the secondary transfer roller 36 so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the secondary transfer roller 36. It has become.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed 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 container 2 is provided in the upper part of the printer main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 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 developing device 7 is connected to each of the toner bottles 2Y, 2M, 2C, 2K via the replenishment path. The toner is replenished.

On the other hand, at the lower part of the printer main body, a paper feed tray 10 that stores paper P as a recording medium, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided. Here, the recording medium includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. A manual paper feed mechanism may be provided on the side surface of the printer body.

In the printer main body, a transport path R is provided for discharging 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 transport members for transporting 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 onto the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper transport direction. Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. A discharge tray 14 for stocking sheets discharged outside the apparatus is provided on the upper surface of the printer main body.

(Basic printer operation)
Next, 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, the respective photoconductors 5 in the respective image forming units 4Y, 4M, 4C, and 4K are rotationally driven clockwise by the driving device, and the surface of each photoconductor 5 is predetermined by the charging device 6. It is uniformly charged to the polarity.

The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated 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 in the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is generated 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 could not be transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photoconductor 5 is neutralized by the static eliminator, and the surface potential is initialized.

In the lower part of the printer main 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 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 charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field 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 rotates, the transfer electric field formed in the secondary transfer nip causes a transfer on the intermediate transfer belt 30. The toner images are transferred onto the paper P all at once. At this time, the residual toner on the intermediate transfer belt 30 that could not be transferred onto the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container and collected.

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

The above description is an image forming operation when a full-color image is formed on a sheet. A single color image can be formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Two or three image forming units can be used to form a two-color or three-color image.

(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 includes a fixing belt 21 as a rotatable fixing rotator, and a pressure roller 22 as an opposing member that is rotatably provided to face the fixing belt 21.

Further, the fixing device 20 includes a halogen heater 23 (a central heater 23a and an end heater 23b) as heating members 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 serving as a support member for supporting 24. Further, the fixing device 20 includes a reflection member 26 that reflects the light emitted from the halogen heater 23 to the fixing belt 21, a temperature sensor 27 as a temperature detection member that detects the temperature of the fixing belt 21, and a sheet P from the fixing belt 21. A separating member 28 for separating the pressure roller, a pressure member for pressing the pressure roller 22 to the fixing belt 21, and the like.

The fixing belt 21 is composed of an endless belt member (including a film) having a thin wall and 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). Or it is comprised by the release layer of the outer peripheral side formed with polytetrafluoroethylene (PTFE) etc. Further, an elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

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

At the place where the pressure roller 22 and the fixing belt 21 are in pressure contact, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width. 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 to 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 may be a hollow roller. In that case, a heating member such as a halogen heater may be disposed inside the pressure roller 22. In addition, when there is no elastic layer, the heat capacity is reduced and the fixability is improved, but when the unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and uneven glossiness is formed on the solid portion 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 an elastic layer having a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided. The elastic layer 22b may be solid rubber, but if there is no heating member inside the pressure roller 22, sponge rubber may be used.

Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 21 is not easily taken away, thereby saving energy. Further, the fixing rotator and the counter rotator are not limited to being brought into pressure contact with each other, and may be configured to simply contact each other without applying pressure.

Each halogen heater 23 is fixed to the side plate of the fixing device 20 at both ends. Each halogen heater 23 is configured to generate heat by being output controlled by a power supply unit provided in the printer 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 such output control 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, IH, a resistance heating element, a carbon heater, or the like may be used as a heating member for heating the fixing belt 21.

The nip forming member 24 is disposed in a longitudinal shape over the axial direction of the fixing belt 21 or the axial direction of the pressure roller 22, and is fixedly supported by a stay 25. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, and a uniform nip width is obtained in the axial direction of the pressure roller 22. The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the bending prevention function of the nip forming member 24. However, the stay 25 may be made of resin. It is.

The nip forming member 24 is composed of a heat resistant member having a heat resistant temperature of 200 ° C. or higher. This prevents the nip forming member 24 from being deformed by heat in the toner fixing temperature range and ensures a stable state of the nip portion N, thereby stabilizing the output image quality. As the base material of the nip forming member 24, a general heat resistant resin can be used as will be described later with reference to FIG. In this embodiment, as will be described later, an 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 the surface thereof. When the fixing belt 21 rotates, the fixing belt 21 slides with respect to the low friction sheet, so that the driving 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 disposed between the stay 25 and the halogen heater 23. In the present 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 metal material having a high melting point.

By arranging the reflection member 26 in this way, the light emitted from the halogen heater 23 toward the stay 25 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, energy saving can be achieved.

Further, the reflective surface may be formed by subjecting the surface of the stay 25 on the side of the halogen heater 23 to mirror processing such as polishing or painting without providing the reflective member 26 as in the present embodiment. In addition, the reflectance of the reflecting surface of the reflecting member 26 or the stay 25 is desirably 90% or more.

Since the shape and material of the stay 25 cannot be freely selected in order to ensure the strength thereof, the weight of the selection of the shape and material is increased by providing the reflecting member 26 as in the present embodiment, and the reflecting member 26 is increased. And the stay 25 can be specialized for each function. Further, since the reflecting member 26 is provided between the halogen heater 23 and the stay 25, the position of the reflecting member 26 with respect to the halogen heater 23 is reduced, so that the fixing belt 21 can be efficiently heated.

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

In addition, the fixing device 20 according to the present embodiment is devised in various configurations in order to further improve energy saving and first print time. Specifically, the fixing belt 21 can be directly heated at a place other than the nip portion N by the halogen heater 23 (direct heating method). In the present embodiment, nothing is interposed between the halogen heater 23 and the left portion of the fixing belt 21 in FIG. 2, and the 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 made thinner and smaller in diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall 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 desirably 0.2 mm or less, and more desirably 0.16 mm or less. The diameter of the fixing belt 21 is desirably 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 configured to be equal. However, it is not limited to this configuration. For example, the fixing belt 21 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 22. In that case, since the curvature of the fixing belt 21 at 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 heat 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.

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

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

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

The heat 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 heat conductive 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 heat conductive member 24b to the base material 24a and the stay 25 is suppressed. Needless to say, the thermal conductivity of the substrate 24a is not limited to this.

As for the shape of the upper surface (stay facing surface) of the base material 24a, a plurality of first protrusions 24a2 arranged in two rows in the short direction are spaced apart and arranged in the longitudinal direction (FIG. 3A). FIG. 3A is a cross-sectional view taken along the line aa in FIG. Thus, by making the upper surface (stay-facing surface) of the base material 24a into a concavo-convex shape having protrusions arranged in the longitudinal direction, heat dissipation to the stay 25 side can be achieved while enabling pressure transmission from the stay 25 side to the nip portion. Can be suppressed. Therefore, the lighting rate of the halogen heater 23 can be reduced and the thermal efficiency and energy saving can be improved.

The first protrusions 24a2 are not limited to the shape arranged in two rows in the short direction and in a plurality of rows in the longitudinal direction as described above. That is, 1) a shape in which a plurality of first protrusions 24a2 in the short direction are arranged in the longitudinal direction, 2) a shape in which the first protrusions 24a2 in the short direction are arranged in one row, and 3) the first protrusions 24a2 can also have a staggered shape.

Further, a concave portion 70 having a triangular cross section is formed on the upper surface of the base material 24a as shown in FIG. The concave portion 70 is for engaging a regulating portion 24b4 of the high heat conductive member 24b described later. As shown in FIGS. 5A and 5B, the concave portion 70 is formed on the surface opposite to the nip portion N of the base material 24a. 24a has a bottom surface that is inclined with respect to the nip surface from the short direction nip inlet side toward the nip outlet side. 5B, when the base material 24a is inserted into the concave cross section of the high thermal conductive member 24b from the upper left side, the lower left corner of the bottom surface of the restricting portion 24b4 is directed toward the concave portion 70. Therefore, the inclination angle is equal to or greater 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 good thermal conductivity so that the end temperature 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 includes a copper-based material (for example, thermal conductivity 381 W / m · K) 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 base material, an iron-based SUS material (for example, thermal conductivity 19 W / m · K) or the like is used as the high thermal conductivity member 24b. Metal materials can also be used.

In the present embodiment, the high heat conductive member 24b is made of a copper-based material, and more specifically, the high heat 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, the high thermal conductivity member 24b is configured by bending a copper plate having such thermal conductivity. In the example of FIG. 3, the copper plate is bent and formed so that the high thermal conductive member 24 b has a concave cross section with a cross section perpendicular to the longitudinal direction. In addition, formation of a copper plate is not restricted to bending formation, Welding etc. may be sufficient.

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

For this reason, the high heat conductive member 24b is a thin layer member having a low heat capacity so as to prevent an increase in end temperature 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 heat conduction member 24b is thinned to minimize its heat capacity, and fixing failure due to a decrease in end temperature at the start of fixing is suppressed.

As shown in FIG. 5A, the high heat conduction member 24b has a bottom wall portion 24b1 as a first surface with a concave cross section as a nip portion facing surface, and side walls as second and third surfaces on the left and right in the width direction of the high heat conduction 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 paper direction. The height of the bent portion (the height of the side wall portions 24b2 and 24b3) is set to be equal to or greater than the vertical thickness of the base material 24a. In the illustrated example, the height Hs of the side wall portions 24b2 and 24b3 is constant, but the height Hs can be changed in the longitudinal direction of the high heat conducting member 24b. Thereby, the amount of heat released in the thickness direction of the high heat conductive member 24b can be adjusted by the position in the longitudinal direction, and the end temperature rise can be more appropriately suppressed.

In the present embodiment, in the case of the “A3 Nobi compatible fixing device”, the height Hs of the side wall portions 24b2 and 24b3 of the high heat conductive member 24b is set to 1. over the entire length in the longitudinal direction of the high heat conductive member 24b as shown in FIGS. The range is set to 0 mm to 1.9 mm. Here, the height Hs is a 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 and 24b3. A3 Nobi is a paper that is slightly larger than the standard size A3, and is a paper having a width of about 320 to 330 mm. However, there is no standard.

(Regulation Department)
A rectangle bent at a substantially right angle toward the downstream side of the rotation of the fixing belt 21, that is, an L-shaped cross section, at a part of the upper end of the side wall 24 b 2 on the inlet side of the nip portion (upstream side of the fixing belt 21) of the high heat conductive member 24 b. The restricting portion 24b4 is formed. As shown in FIG. 4, a plurality of the restriction portions 24 b 4 are formed at predetermined intervals a to c in the longitudinal direction of the high heat conductive member 24 b. The restricting portion 24b4 can be formed by bending or welding, but can be configured at a low cost without increasing the number of parts by bending a part of the high heat conductive member 24b as described above. Further, even if the restricting portion 24b4 is not bent at a right angle, the restricting portion 24b4 has an effect of preventing detachment as described below as long as the restricting portion 24b4 faces the bottom wall portion 24b1 of the substrate 24a.

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

By setting the length in the short direction of the restricting portion 24b4 to 2 mm, heat can be prevented from escaping to the back side of the nip through the restricting portion 24b4, and the base material 24a is placed in the concave cross section of the high heat conductive member 24b. At the time of insertion, the base material 24a is easily fitted and is not easily detached. In other words, the longer the length in the short direction of the restricting portion 24b4, the harder it is to fit the base material 24a. Therefore, it is necessary to enlarge the concave portion 70 of the base material 24a, and the strength of the base material 24a is sacrificed. On the other hand, the shorter the length in the short direction of the restricting portion 24b4, the easier it is to fit the base material 24a into the concave cross section of the high heat conductive member 24b, but the base material 24a is more easily detached.

The restricting portion 24b4 is engaged with the upper surface of the base material 24a opposite to the nip portion N on the upstream side of the rotation of the fixing belt 21, so that the friction with the fixing belt 21 is reduced even if the high heat conductive member 24b is thinned. Therefore, it is possible to suppress the displacement and deformation of the high thermal conductive member 24b. Further, the restricting portion 24b4 prevents the parts from being detached when the nip forming member 24 is assembled, and also improves the work efficiency of assembling 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 accommodated in the concave cross section of the high heat conducting member 24b from separating upward in FIG. 5A. Note that the fixing belt 21 may be provided on a part of the upper end of the side wall 24b3 on the downstream side of the rotation as shown in a circular frame in FIG. 5A instead of or together with the restriction 24b4 on the upstream side of the fixing belt 21. A rectangular restricting portion 24b6 bent substantially at a right angle toward the upstream side of the rotation may be formed.

A concave portion 70 that can be engaged with the front end side of the restricting portion 24b4 can be formed on the upper surface 24a1 of the base material 24a as required, as shown in FIGS. 3, 5A, and 5B. In the case where the restriction portion 24b6 is formed on the rotation downstream side of the fixing belt 21, the concave portion 70 can be formed as necessary at a position opposite to the restriction portion 24b6 on the opposite side of the base material 24a. Thereby, as will be described later, it is possible to suppress deterioration in image quality resulting from temperature unevenness in the longitudinal direction of the nip forming member 24.

By forming the concave portion 70, the base member 24a is inclined as shown in FIG. 5B and prevented from interfering with the restricting portion 24b4 when inserted into the concave cross section of the high thermal conductive member 24b as shown by an arrow. Is also possible. Of course, even if the restricting portion 24b4 is left at the position indicated by the solid line in FIG. 5A without forming the concave portion 70, the displacement and deformation of the high heat conductive member 24b can be suppressed.

The base material 24a in which the concave portion 70 is formed in this way 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 24a4 opposite to the edge 24a3 of the base material 24a draws an arcuate locus C1 while slidingly contacting the surface of the side wall 24b3. In addition, since the high heat conductive member 24b is thin, it is also possible to insert the base material 24a in a state where one or both of the side wall portions 24b2 and 24b3 are elastically bent outward. When such a method of inserting the base material 24a is used, the gap inside the side wall portion 24b3 shown in FIG. 5A is not necessarily required.

After the base material 24a is inserted into the concave cross section of the high thermal conductive member 24b, the regulating portion 24b4 is fitted into the concave portion 70 by being pressed and bent from above with a jig or the like as indicated by a broken line in FIG. 5A. Thereby, the base material 24a and the high heat conductive member 24b can be integrated, and the above-described positional deviation and deformation of the heat conductive member 24b are more reliably suppressed.

In addition, by leaving a gap between the front end side of the restricting portion 24b4 and the recessed portion 70, in the longitudinal direction of the base material 24a, a portion corresponding to the restricting portion 24b4 (a portion of the recessed portion 70) and a portion that is not The temperature can be made almost equal. That is, it is possible to leave the gap by leaving the restricting portion 24b4 at the position of the solid line in FIG. 5A or by slightly bending even when pressing and bending from above with a jig or the like. Thereby, it is possible to suppress a decrease in image quality resulting from temperature unevenness in the longitudinal direction of the nip forming member 24.

Further, since the restricting portion 24b4 is fitted into the concave portion 70, a later-described thrust stop between the base member 24a and the high heat conductive member 24b is also achieved, so that the both-end engaging portion 24b5 described later 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.

The length in the longitudinal direction of the nip forming member 24 is, for example, 300 mm or more in the case of an A3 Nobi width machine, and therefore, when the restricting portion 24b4 is only one central portion in the longitudinal direction, it is stable with the base material 24a in the entire longitudinal direction. It is difficult to keep the target engagement (hanging). Therefore, by installing a plurality of restricting portions 24b4 in the longitudinal direction of the high heat conducting member 24b (six in this embodiment), the catching property with the base material 24a is sufficiently strengthened in the longitudinal direction, BR>, S body. Yes.

By providing the restricting portion 24b4 in part as described above, the volume can be reduced. Thereby, it is not necessary to inadvertently increase the heat capacity other than the bottom wall portion 24b1 facing the nip portion N of the high heat conductive member 24b, and the thermal conductivity of the bottom wall portion 24b1 of the high heat conductive member 24b is more effectively increased. It can satisfy the necessary heat equalization function.

Further, by arranging the restricting portion 24b4 on the upstream side of the rotation of the fixing belt 21, the friction belt 15 rotates against the high heat conducting member 24b with a frictional resistance when the fixing belt 21 rotates in the arrow direction as shown in FIG. 5A. Even if the force in the direction of the arrow acts, the possibility that the base material 24a and the high thermal conductive member 24b are 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. Thereby, the stable sliding function of the low friction sheet interposed between the nip forming member 24 and the fixing belt 21 can be maintained over a long period of time, and the high-quality fixing function of the image forming apparatus 1 can be maintained. it can.

As shown in FIG. 4, the restriction portion 24 b 4 is formed such that the interval “a” on the center side in the longitudinal direction of the high heat conductive member 24 b is narrower than the interval “b” or the interval “c” on both ends in the longitudinal direction. Since the high heat conducting member 24b contacts the fixing belt 21 with the full width in the longitudinal direction, the bending force due to the largest frictional force acts on the central portion thereof, so the distance 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 heat conductive member 24b decreases as going outward in the longitudinal direction.

It is possible to increase the number of restricting portions 24b4 to further strengthen the connection with the base material. However, if the number of restricting portions 24b4 is increased too much, heat dissipation to the high heat conductive member 24b increases, thereby saving energy. Impairs sex. Therefore, in the present embodiment, the number of restricting portions 24b4 is six. By using six, the heat dissipation is within an allowable range, and the effect of suppressing the end temperature rise is also obtained.

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

By the engaging portion 24b5, it is possible to regulate displacement and deformation in the longitudinal direction of the high heat conductive member 24b and the base material 24a when assembled (thrust stop). Therefore, the assembly work efficiency of the nip forming member 24 can be improved in combination with the detachment restricting action 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 heat conductive member 24b, and from one side of the base material 24a toward the arrow direction, that is, obliquely downward from here. Is inserted so as to be hidden under the restricting portion 24b4. FIG. 5B is a BB cross section of FIG. 5C. Once the base material 24a falls within the concave cross section as shown in FIG. 5A, even if the base material 24a tries to float upward in the same figure, the lifting is prevented by the restricting portion 24b4. Therefore, the separation of the base material 24a from the concave cross section of the high heat conductive member 24b is restricted, the base material 24a and the high heat conductive member 24b are stabilized without being separated from each other, and the assembly of the nip forming member 24 can be smoothly advanced. .

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

Further, in place of the recess 70 described above, a recess 71 having the same shape and the same depth as the control portion 24b4 is formed in a portion where the control portion 24b4 is hooked as shown in FIG. You may make it fit 24b4 whole. By fitting the entirety of the restricting portion 24b4 into the recess 71, the protrusion of the restricting portion 24b4 can be eliminated from the upper surface 24a1 of the base material 24a, thereby increasing the distance from the stay 25 disposed above the base material 24a. It is possible to make the device compact. Moreover, since the thrust stop of the base material 24a and the high heat conductive member 24b can be achieved by fitting the restricting portion 24b4 into the recess 71, the 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.

(Relationship between 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 sizes of sheets to be passed through the fixing device 20 are indicated by A to D (A: postcard, A ′: A4 portrait, B: B4 portrait, C: A3 portrait, D: A3 Nobi).

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

The central heater 23 a has a heat generating portion (light emitting portion) h 1 on the center side in the width direction of the fixing belt 21, and the end heater 23 b has a heat generating portion (light emitting portion) h 2 on both ends in the width direction of the fixing belt 21. Inner end portions (end portions on the center side in the width direction of the fixing belt 21) of the heat generating portions h2 of the end heater 23b are arranged at positions corresponding to both end portions of the heat generating portion h1 of the central heater 23a.

The length Ls of the high heat conductive member 24b is such that both width direction outer end portions 24b-out are arranged in a range from the width direction inner end portion h2in of the heat generating portion h2 of the end heater 23b to the width direction outer end portion h2out. It is set to a length. Here, in this embodiment, the position of the width direction inner side edge part of the hole part 51 formed in the width direction both ends side of the high heat conductive member 24b is made into the width direction outer side edge part 24b-out of the said high heat conductive member 24b. Yes.

The hole 51 is provided to position the high heat 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 on the base material 24a into each hole 51, the high heat conductive member 24b is positioned in the width direction with respect to the base material 24a.

In the place where the hole 51 is formed, the area where the high heat conductive member 24b comes into contact with the fixing belt 21 is reduced, so that the heat conduction function from the place where the hole 51 is formed to the outside in the width direction is lowered. In particular, in the present embodiment, the paper conveyance direction length (recording medium conveyance direction length) L2 of the hole 51 is not less than half the paper conveyance direction length (recording medium conveyance direction length) L1 of the high thermal conductive member 24b. Therefore, the amount of heat conduction from the hole 51 to the outside 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 heat conduction member 24b is a portion that is expected to function mainly as a heat conduction portion. On the other hand, the region F on the outer side in the width direction from the hole portion 51 has a little heat conduction function 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 reasons described above, in the present embodiment, among the portions constituting the high heat conductive member 24b, the width direction outer end portion (hole portion 51) of the heat conductive portion (region E) where the original function as the heat conductive member is expected. The width direction inner side end portion) is set as the width direction outer side end portion 24b-out of the high heat conductive member 24b. Unlike the present embodiment, when the paper conveyance direction length L2 of the hole 51 is less than half of the paper conveyance direction length L1 of the high heat conductive member 24b, a portion (area) outside the width direction from the hole 51 (region). F) is also determined to function mainly as a heat conducting part. Therefore, in this case, the width direction outer end portion of the entire high heat conduction member 24b including the portion (region F) on the outer side in the width direction from the hole 51 is defined as the width direction outer end portion 24b-out of the high heat conduction member 24b. .

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. For example, the number of the restricting portions 24b4 can be increased or decreased from six according to the length of the nip forming member 24 or 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.

Furthermore, 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 heat conductive member 24b. The restricting portion 24b7 rises from the upper end of the side wall portion 24b3 and bends in an inverted U shape, and its distal end abuts on 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 inserted into the concave cross section of the high heat conducting member 24b as shown by the arrow, the restricting portion 24b7 guides the edge 24a4 of the base material 24a to the concave cross section. It has the function to do. When the base material 24a is inserted into the concave cross section, the tip of the restricting portion 24b7 contacts the upper surface 24a1 of the base material 24a, so that the base material 24a is prevented from detaching from the concave cross section, and the assembly of the nip forming member 24 is facilitated. Can proceed.

The downstream regulating portion 24b7 is preferably disposed between the upstream regulating portions 24b4 as shown in FIG. 7C. Thereby, the positional relationship between the base material 24a and the high heat conductive member 24b is maintained with high accuracy. Further, by arranging the upstream and downstream regulating portions 24b4 and 24b7 alternately in the longitudinal direction of the high thermal conductive member 24b as shown in FIG. 7C, the temperature rise characteristics can be made uniform in the longitudinal direction of the high thermal conductive member 24b. 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: Photoconductor 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: Metal core 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 heat conduction member (nip forming second member) 24b1: Bottom wall portion 24b2, 24b3: Side wall portion 24b4, 24b6: Restricting portion 24b5: Engaging portion 25: Stay 26: Reflecting member 27 : Temperature sensor 28: Separating 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 mark 70, 71: Recess

Japanese Patent Laying-Open No. 2015-194661

Claims (13)

A nip forming member disposed on the inner peripheral side of a rotatable endless fixing belt, wherein an opposing member disposed on the outer peripheral side of the fixing belt contacts the nip forming member, thereby In the nip forming member in which a nip portion is formed between the facing member and the nip forming member,
A nip forming first member constituting the nip forming member body;
A nip forming second member disposed 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 walls bent at the upstream side and the downstream side of the fixing belt so as to be opposite to the nip part, thereby forming a concave cross section for accommodating the nip forming first member. In addition, the nip forming member has a restricting portion for restricting the detachment between the concave cross section and the first nip forming member in a part of a longitudinal direction of the side wall portion on the upstream side of the rotation.   The nip forming member according to claim 1, wherein the restricting portion is formed at a plurality of locations in the longitudinal direction of the nip forming second member.   3. The nip forming member according to claim 2, wherein a mutual interval between the restricting portions is formed so that a center side in the longitudinal direction of the second nip forming member is narrower than both end sides in the longitudinal direction.   4. The height of the pair of side wall portions is higher than the thickness of the first nip forming member on both the upstream side and the downstream side of the rotation. 5. Nip forming member.   5. The nip forming member according to claim 1, wherein the restricting portion is bent from the side wall portion to the rotation downstream side of the fixing belt.   The nip forming member according to claim 5, wherein the restricting portion is a rectangle having a long side in the longitudinal direction of the nip forming second member.   The engaging part which engages with the longitudinal direction both ends of the said nip formation 1st member is formed in the longitudinal direction both ends of the said nip formation 2nd member, The any one of Claim 1 to 6 characterized by the above-mentioned. The nip forming member according to Item.   8. The mark according to claim 1, wherein a mark is provided on an upper surface of the first nip forming member opposite to the nip portion, and the mark corresponds to a position where the restricting portion is disposed. The nip forming member according to item 1.   The nip forming member according to any one of claims 1 to 8, wherein a concave portion into which the restricting portion can be fitted is formed on an upper surface of the first nip forming member opposite to the nip portion. . A nip forming member disposed on the inner peripheral side of a rotatable endless fixing belt, wherein an opposing member disposed on the outer peripheral side of the fixing belt contacts the nip forming member, thereby In the nip forming member in which a nip portion is formed between the facing member and the nip forming member,
A nip forming first member constituting the nip forming member body;
A nip forming second member disposed 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 walls bent at the upstream side and the downstream side of the fixing belt so as to be opposite to the nip part, thereby forming a concave cross section for accommodating the nip forming first member. And a nip having a restricting portion for restricting the detachment between the concave cross section and the first nip forming member at a part in the longitudinal direction of at least one of the side walls on the upstream side of the rotation or the downstream side of the rotation. Forming member.   The nip forming member according to any one of claims 1 to 10, wherein the nip forming second member has 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 disposed on the inner peripheral side of the fixing belt;
In the 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 with the fixing belt, the nip forming member includes:
A nip forming first member constituting the nip forming member body;
A nip forming second member disposed on the nip portion side of the nip forming first member along the longitudinal direction of the nip forming first member,
The second nip forming member has a concave cross section by having a pair of side walls bent at the upstream side and the downstream side of the fixing belt on the opposite side of the nip part. A fixing device having a restricting portion for restricting detachment from the first member at a part in a longitudinal direction of the side wall portion on the rotation upstream side. In an electrophotographic image forming apparatus in which a toner image is transferred to a recording medium and then fixed to form an image.
An image carrier held rotatably;
A charging device for charging the image carrier;
A latent image forming device that forms an electrostatic latent image on the image carrier charged by the charging device;
A developing device for developing 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 12, wherein the toner image transferred to the recording medium is fixed by the transfer device.

Images