Fixing device and image forming apparatus

Abstract

To prevent excessive increase in the temperature of a reflecting member, and prevent delay in the time until recovery to an operating state.SOLUTION: A fixing device of the present invention comprises: a rotating fixing member; a pressure member that is in contact with the outer peripheral surface of the fixing member to form a nip part, and applies a pressure to a recording material passing through the nip part; a heat source that is arranged inside the fixing member; and a reflecting member that has a reflecting part reflecting radiation heat from the heat source toward the inner peripheral surface of the fixing member, and an applied pressure receiving part receiving the pressure applied by the pressure member through the fixing member, wherein the reflecting part and the applied pressure receiving part are integrally or thermally connected to each other. The fixing device further has a heat insulating member between the fixing member and the applied pressure receiving part of the reflecting member. The heat insulating member is present only in a paper feeding area of the recording medium and not present in non-paper feeding areas at both ends, or has a notch shape.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus.

Background Art

[0002] Electrophotographic image forming apparatuses such as copiers and printers are provided with a fixing device that fixes a toner image on a recording material such as paper. Various methods are used for this fixing device, and as a general method, the sliding belt method is known.

[0003] For example, Patent Document 1 discloses a fixing device having a rotating fixing member, a pressing member that contacts the fixing member to form a nip portion, a heat source, a reflecting portion that reflects radiant heat from the heat source toward the fixing member, and a pressure receiving portion that receives the pressing force of the pressing member via the fixing member, either integrally or thermally connected, and the pressure receiving portion contacts the fixing member via a highly slidable sliding member.

[0004] Since the above fixing device reflects radiant heat at the reflecting portion, the fixing member can be efficiently heated. Further, since the reflecting portion and the pressure receiving portion are integrally or thermally connected, the heat of the reflecting portion can be prevented from escaping to the fixing member or the like, and an excessive temperature rise of the reflecting portion (reflecting member) can be suppressed.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, on the other hand, when the fixing device returns from a cold state to an operating state, the fixing member having a smaller heat capacity than the reflecting member rises in temperature faster, so the heat of the fixing member escapes to the reflecting member, and there is a possibility that the return time of the fixing device may be delayed.

[0006] Therefore, an object of the present invention is to provide a fixing device that can suppress an excessive temperature rise of a reflecting member and also suppress a delay in the return time to an operating state.

Means for Solving the Problems

[0007] The above problem is solved by a fixing device including a rotating fixing member, a pressing member that contacts an outer peripheral surface of the fixing member to form a nip portion and presses a recording material passing through the nip portion, a heat source disposed inside the fixing member, a reflecting member including a reflecting portion that reflects radiant heat from the heat source toward an inner peripheral surface of the fixing member, and a pressure receiving portion that receives a pressing force of the pressing member via the fixing member, wherein the reflecting member has a heat insulating member between the pressure receiving portion of the reflecting member and the fixing member, and the heat insulating member exists exclusively in a paper passing area of the recording material and does not exist in non-paper passing areas at both ends or is in a notch shape.

Advantages of the Invention

[0008] According to the present invention, an excessive temperature rise of the reflecting member can be suppressed, and a delay in the return time to the operating state can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. Hereinafter, an embodiment in which the present invention is applied to a laser printer (hereinafter referred to as a "printer"), which is an electrophotographic image forming apparatus, will be described.

[0011] This image forming apparatus 1 includes an image forming unit 100 that forms an image on a sheet P as a recording material. The image forming unit 100 is a tandem type image forming apparatus in which image forming units 10Y, 10M, 10C, and 10K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are arranged along the rotation direction of an intermediate transfer belt 20 as an intermediate transfer member. Each of the image forming units 10Y, 10M, 10C, and 10K includes a photoreceptor 11Y, 11M, 11C, and 11K as a latent image carrier.

[0012] In addition, each of the image forming units 10Y, 10M, 10C, and 10K includes a charging device as charging means, an optical writing device 9 as electrostatic latent image forming means, and a developing device as developing means around the photoreceptors 11Y, 11M, 11C, and 11K. Further, around the photoreceptors 11Y, 11M, 11C, and 11K, a primary transfer device as primary transfer means and a cleaning device as cleaning means are also provided.

[0013] The charging device uniformly charges the surface of the photoreceptor to a predetermined potential, and the optical writing device 9 exposes the surface of the photoreceptor uniformly charged by the charging device according to image information to write an electrostatic latent image. The developing device creates a toner image by a developing process of attaching toner of each color (Y, M, C, K) to the electrostatic latent image on the photoreceptor. The primary transfer device transfers the toner image on the photoreceptor onto the intermediate transfer belt 20, and the cleaning device removes and cleans the residual transferred toner on the photoreceptor.

[0014] The toner images of each color formed on the photoreceptors 11Y, 11M, 11C, and 11K are primarily transferred onto the intermediate transfer belt 20 by the primary transfer device so as to overlap each other, and a color toner image is formed on the intermediate transfer belt 20. The color toner image on the intermediate transfer belt 20 is conveyed to the opposing area (secondary transfer area) with the secondary transfer device 30 as the intermediate transfer belt 20 rotates.

[0015] On the other hand, a paper feed cassette 60 as a paper feed unit for feeding the held paper P is arranged below the image forming unit 100. The paper P is fed one by one from the paper feed cassette 60 by the pickup roller 61. Then, along the conveyance path, the paper P is conveyed to the secondary transfer area by the registration roller pair 62.

[0016] The color toner image on the intermediate transfer belt 20 is secondarily transferred onto the paper P conveyed by the registration roller pair 62 at a predetermined timing in the secondary transfer area by the secondary transfer device 30. The paper P on which the color toner image is formed is then conveyed to a fixing device 40 as a fixing means, and the color toner image is fixed on the paper P by the action of heat and pressure. The paper P after fixing is conveyed along the conveyance path and discharged to the paper discharge tray 50 by the paper discharge roller 63.

[0017] FIG. 2 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. The fixing device 40 includes a fixing belt 42 that is a rotating fixing member, a pressure roller 41 that is a pressing member, and a heat source 43 (a halogen heater in the example of the figure) disposed inside the fixing belt 42, and performs fixing by heating and pressing.

[0018] Further, inside the fixing belt 42, a nip forming member 45 held by a fixing stay 44 that is a stay member is arranged. The nip forming member 45 forms a nip portion with the pressure roller 41 with the fixing belt 42 interposed therebetween.

[0019] The nip forming member 45 is a sliding member disposed on the nip surface and is composed of a soaking member 45a that is a heat transfer member and a resin pad 45b that supports it. One of the roles of the resin pad 45b is heat insulation, which suppresses the heat absorption of the fixing belt 42 to the fixing stay 44 via the nip forming member 45 and suppresses the increase in warm-up time and TEC value.

[0020] The soaking member 45a is, for example, in the shape of a pad extending in the width direction of the fixing belt 42. This soaking member 45a is disposed to average the temperature in the axial direction of the fixing belt. That is, it takes heat from a location with a high temperature of the fixing belt 42 and transfers the taken heat to a location with a low temperature of the fixing belt 42 to equalize the temperature in the axial direction of the fixing belt 42.

[0021] In the configuration of FIG. 2, the shape of the nip portion is flat, but it may also be a concave shape or other shapes. By forming a concave nip, the discharge direction of the leading edge of the paper becomes closer to the pressure roller 41, and the separability of the paper from the fixing belt 42 is improved, so the occurrence of jams is suppressed.

[0022] The soaking member 45a is a metal member such as aluminum or copper with high thermal conductivity of 50 [W / m·K] or more, and a coating with excellent sliding performance is applied to the surface of the soaking member 45a. Examples of the coating material include resin-based ones such as polyimide resin, fluororesin, polyphenylene sulfide resin, or saturated polyester resin. Alternatively, glass fiber, carbon, graphite, fluorinated graphite, carbon fiber, molybdenum disulfide, or fluororesin may be mixed into such a resin-based coating material.

[0023] In addition, a metal-based material can also be used as the coating material. Examples of the metal-based coating material include molybdenum disulfide, nickel, and composite plating of nickel and fluororesin. Further, examples of the metal-based coating material also include anodized aluminum or anodized aluminum impregnated with resin or metal. In addition, ceramics can also be used as the coating material. Examples of the ceramics used as the coating material include silicon carbide ceramics, silicon nitride ceramics, alumina ceramics, and those mixed with molybdenum disulfide, fluororesin, etc.

[0024] In addition, an anodized layer is formed on the surface layer of the soaking member 45a formed of aluminum or an aluminum alloy, and molybdenum disulfide generated by secondary electrolysis is filled in the micropores of the anodized layer from the deepest part to the outermost surface of the micropores, etc. are also effective.

[0025] The soaking member 45a having a high thermal conductivity in the present embodiment is made of a material having a thermal conductivity equal to or higher than that of aluminum and is processed as described above. Thus, the soaking member 45a having a high thermal conductivity is made.

[0026] The pressure roller 41 abuts on the outer peripheral surface of the fixing belt 42 to form a nip portion, and presses the recording material passing through the nip portion. The pressure roller 41 has a silicone rubber layer provided on the outer periphery of a metal roller, and a release layer (PFA or PTFE layer) is provided on the surface of the silicone rubber layer to obtain releasability. In addition, the pressure roller 41 is pressed against the fixing belt side by a spring or the like, and the rubber layer is compressed and deformed to have a predetermined nip width.

[0027] The driving force is transmitted to the pressure roller 41 through a gear from a driving source such as a motor provided in the image forming apparatus 1, and the pressure roller 41 rotates. The fixing belt 42 rotates by being driven by the driving force transmitted from the pressure roller 41 at the nip portion.

[0028] The pressure roller 41 may be a solid roller, but a hollow one is preferred because it has a smaller heat capacity. Also, the pressure roller 41 may have a heating source such as a halogen heater. The silicone rubber layer may be solid rubber, but if there is no heater inside the pressure roller, sponge rubber may be used. Sponge rubber is more desirable because it enhances heat insulation and makes it difficult for the heat of the fixing belt to be taken away.

[0029] The fixing belt 42 is an endless belt (or film) based on a metal belt such as nickel or SUS or a resin material such as polyimide. The surface layer of the fixing belt 42 has a release layer such as a PFA or PTFE layer to provide release properties so that toner does not adhere.

[0030] There may be an elastic layer formed of a silicone rubber layer or the like between the base material and the release layer of the fixing belt 42. When there is no silicone rubber layer, the heat capacity becomes small and the fixing property is improved, but when fixing an unfixed image by pressing it down, there is a problem that fine irregularities on the belt surface are transferred to the image and traces like orange peel remain on the solid part of the image. To improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, fine irregularities are absorbed and the orange peel image is improved.

[0031] The fixing stay 44 is a hollow pipe-shaped metal body made of a metal such as aluminum, iron, or stainless steel. In this embodiment, the fixing stay 44 is square, but it may have other cross-sectional shapes. It prevents the nip forming member 45 that receives pressure from the pressure roller 41 from deflecting so as to obtain a uniform nip width in the axial direction.

[0032] Two heat sources 43 for raising the temperature of the fixing belt 42 are provided inside the fixing belt 42. In this embodiment, the heat source 43 is a halogen heater, and the fixing belt 42 is directly heated by the radiant heat of the heat source 43 from the inner peripheral side. Here, the heat source 43 only needs to be able to heat the fixing belt 42, and it may be an IH coil, a resistance heating element, a carbon heater, or the like.

[0033] Further, inside the fixing belt 42, a reflecting member 48 as a reflector for reflecting heat toward the fixing belt side is disposed to minimize the loss of radiant heat from the heat source 43. The reflecting member 48 is based on a high-purity aluminum material as a metal member, and a high-brightness aluminum or the like having a plurality of enhanced reflection films and protective films formed on the surface layer so as to obtain a high reflectance, for example, a reflectance of 95% or more, is used. Depending on the configuration, a material obtained by vapor-depositing silver on an aluminum plate to further improve the reflectance may also be used.

[0034] Note that the reflectance in this embodiment was measured using a spectrophotometer (ultraviolet-visible-infrared spectrophotometer UH4150 manufactured by Hitachi High-Technologies Corporation) at an incident angle of 5°.

[0035] The reflecting member 48 of this embodiment has a reflecting portion 48a that reflects radiant heat toward the inner peripheral surface of the fixing belt 42, and a pressure receiving portion 48b that receives the pressing force of the pressing roller 41. The reflecting portion 48a is disposed between the heat source 43 and the fixing stay 44. The pressure receiving portion 48b is disposed in a manner sandwiched between a heat equalizing member 45a that is a sliding member and a resin pad 45b.

[0036] Furthermore, a heat insulating member 49 for reducing heat conduction between the two is provided between the pressure receiving portion 48b and the heat equalizing member 45a. This heat insulating member 49 is a characteristic configuration of the present invention, and its details will be described below.

[0037] FIG. 3 is a perspective view showing the configuration of a heat insulating member according to an embodiment of the present invention. Although only one end portion is shown in FIG. 3, the other end portion has the same configuration. Also, the heat equalizing member 45a is omitted.

[0038] As shown in FIG. 3, the heat insulating member 49 is exclusively in the paper passing area (central area of the pressure receiving portion 48b) of the recording material and does not exist in the non-paper passing area (end area of the pressure receiving portion 48b), or is in a notch shape.

[0039] As a result, the heat transfer path in the paper passage area becomes the pressure receiving part 48b - heat insulating member 49 - heat equalizing member 45a - fixing belt 42, and the heat conduction between the fixing belt 42 and the pressure receiving part 48b can be blocked (or reduced).

[0040] On the other hand, the heat transfer path in the non - paper passage areas at both ends becomes the pressure receiving part 48b - heat equalizing member 45a - fixing belt 42, and the heat transfer between the fixing belt 42 and the pressure receiving part 48b can be made larger than that in the paper passage area.

[0041] The heat insulating member 49 is provided exclusively in the central area (paper passage area) and not in the both - end areas (non - paper passage areas) (see FIG. 3), but a metal member 52 having the same thickness as the heat insulating member 49 may be provided in the both - end areas (see FIG. 4). Thereby, the pressure distribution in the central area and the end areas can be made uniform, and in the both - end areas, the heat of the reflecting member 48 (pressure receiving part 48b) can be efficiently transferred to the heat equalizing member 45a.

[0042] Subsequently, the operation and effects of the fixing device 40 of the present embodiment will be described.

[0043] (Suppression of temperature rise of the reflecting member) In a conventional fixing device, as shown in FIG. 5 for example, the reflecting member 148 did not have a pressure receiving part 48b. The reflectivity of the reflecting member 148 is about 95 - 98%, and since the reflecting member itself also absorbs the radiant heat from the heat source 143, its temperature gradually rises. Particularly, when a large amount of continuous paper passage (fixing) is performed, the temperature of the reflecting member 148 rises to about 300°C - 400°C.

[0044] Generally, when a certain amount of heat load or more is applied to the reflecting member, the aluminum or silver layer discolors. When that happens, not only does the reflectivity decrease and the original performance cannot be exhibited, but in the worst case, there is a risk of leading to safety problems. Therefore, in the conventional configuration, it is necessary to limit the operating rate so that such a temperature is not reached, which has been a bottleneck for improving productivity.

[0045] On the other hand, the reflecting member 48 of the present embodiment has a pressure receiving portion 48b that extends in a region receiving the pressing force from the pressing roller 41 between the heat sink member 45a (heat insulating member 49) and the resin pad 45b (see FIGS. 2 and 3).

[0046] Since the reflecting member 48 is made of aluminum as a metal member having good thermal conductivity as described above, the heat absorbed by the reflecting portion 48a quickly moves to the entire component (pressure receiving portion 48b). The heat that has moved to the pressure receiving portion 48b moves directly or via the heat insulating member 49 to the heat sink member 45a. Since the heat sink member 45a is formed of a member having high thermal conductivity, it can efficiently transfer heat from the pressure receiving portion 48b.

[0047] The heat transmitted to the heat sink member 45a is transmitted to the fixing belt 42 and used for toner melting. The main heat flow is shown by arrows in FIG. 6. Thereby, an excessive temperature rise of the reflecting member 48 can be suppressed. Further, since the heat absorbed by the reflecting member 48 can be used for toner melting, power consumption can be reduced.

[0048] (Suppression of delay in return time) As described above, the fixing device 40 of the present embodiment can suppress an excessive temperature rise of the reflecting portion 48a (reflecting member 48). However, on the other hand, when the fixing device returns from a cold state to an operating state, such as at startup or when returning from a stopped state, there is a concern that a delay may occur in the return time because the pressure receiving portion 48b of the reflecting member 48 takes away the heat of the fixing belt 42. This is because the fixing belt 42 has a lower heat capacity than the pressure receiving portion 48b and the fixing belt 42 rises in temperature first.

[0049] The fixing device 40 of the present embodiment (particularly, the heat insulating member 49 that exists exclusively in the paper passing area of the recording material and does not exist in the non-paper passing area or is in a cutout shape) is also effective in suppressing the delay in the return time.

[0050] FIG. 7 is a matrix diagram showing the operation and effects of the fixing device according to an embodiment of the present invention. FIG. 7 is a matrix of the central region where the heat insulating member is present or the end region where it is not present and the heat storage state (cold or hot) of the fixing device, showing the operation and effects.

[0051] (A) End region × Cold The heat of the fixing belt 42 in the end region (non-paper passing region) is taken away (moves) to the reflecting member 48 via the heat equalizing member 45a. However, since it is a non-paper passing region, the influence on the return time is slight (no problem).

[0052] (B) Central region × Cold The heat of the fixing belt 42 in the central region (paper passing region) is less likely to be taken away (moved) to the reflecting member 48 by the heat insulating member 49. Therefore, the temperature rise rate of the fixing belt 42 does not slow down, and the delay of the return time can be suppressed.

[0053] (C) End region × Hot The heat of the reflecting member 48 in the end region (non-paper passing region) moves to the fixing belt 42 via the heat equalizing member 45a. Therefore, an excessive temperature rise of the reflecting member 48 can be suppressed.

[0054] (D) Central region × Hot The heat of the reflecting member 48 in the central region (paper passing region) is less likely to move to the fixing belt 42 due to the heat insulating member 49. However, since the heat can move to the fixing belt 42 via the end region ((C) reference), an excessive temperature rise of the reflecting member 48 can be suppressed.

[0055] As described above, the fixing device of the present embodiment can suppress an excessive temperature rise of the reflecting member and can also suppress a delay in the return time to the operating state.

[0056] Subsequently, an advantageous configuration will be described.

[0057] The heat insulation member 49 is preferably a sheet-shaped member containing silica aerogel. Silica aerogel is a general term for silica gels with extremely high porosity and low density (generally, about 0.10 to 0.20 g / cm 3 degree), and depending on its structure, it can have heat insulation properties as high as that of air. By using this material as the heat insulation member 49, heat conduction between the pressure receiving portion 48b of the reflecting member 48 and the heat equalizing member 45a can be blocked (or significantly reduced) in the paper passing area where the heat insulation member 49 is present.

[0058] Also, the paper passing area of the recording material where the heat insulation member 49 is provided is preferably within the maximum paper width range. It is possible to achieve both high suppression of excessive temperature rise of the reflecting member 48 and suppression of delay in the return time to the operating state.

[0059] Since the heat equalizing member 45a is a metal part and has a high thermal conductivity, the amount of heat transfer in the longitudinal direction is also large. As shown in Fig. 8(a), even if the heat of the fixing belt 42 in the central region (paper passing area) is made difficult to transfer to the reflecting member 48 by the heat insulation member 49, the heat of the heat equalizing member 45a can move from the central region to the end region and then to the reflecting member 48.

[0060] Therefore, as shown in Fig. 8(b), the heat equalizing member 45a is configured to sandwich a member 54 having a lower thermal conductivity than the heat equalizing member 45a at positions corresponding to both longitudinal ends of the heat insulation member 49. Thereby, the heat of the heat equalizing member 45a moving from the central region to the end region can be suppressed, and as a result, the heat escaping to the reflecting member 48 can be suppressed.

[0061] The heat equalizing member 45a is coated with a coating having excellent sliding performance as described above to reduce the friction coefficient with respect to the inner peripheral surface of the fixing belt 42. In particular, it is preferably lower than the friction coefficient with respect to the inner peripheral surface of the fixing belt 42 on the surface of the pressure receiving portion 48b.

[0062] As a result, compared with the case where the pressure receiving portion 48b of the reflecting member 48 is brought into contact with the inner peripheral surface of the fixing belt 42, the sliding resistance of the fixing belt 42 can be reduced. Therefore, the torque for rotating the fixing belt 42 can be decreased, and wear of the inner peripheral surface of the fixing belt 42 can be suppressed.

[0063] As described above, the present invention has been described in detail using the embodiments. These embodiments are merely examples and can be used with various modifications without departing from the gist of the invention. For example, the embodiments and the modification examples may be combined with each other.

[0064] In addition, the effects described in the embodiments of the present invention merely list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

[0065] Aspects of the present invention are as follows, for example. (Aspect 1) A rotating fixing member, A pressing member that abuts against the outer peripheral surface of the fixing member to form a nip portion and presses a recording material passing through the nip portion, A heat source disposed inside the fixing member, A reflecting member having a reflecting portion that reflects radiant heat from the heat source toward the inner peripheral surface of the fixing member and a pressure receiving portion that receives the pressing force of the pressing member via the fixing member, wherein the reflecting portion and the pressure receiving portion are integrally or thermally connected, In a fixing device comprising: There is a heat insulating member between the pressure receiving portion of the reflecting member and the fixing member, The heat insulating member is present exclusively in the paper passing area of the recording material and is not present in the non-paper passing areas at both ends or is in a notch shape, characterized in that it is a fixing device. (Aspect 2) The fixing device according to aspect 1, wherein the heat insulating member is a member formed in a sheet shape and containing silica aerogel. (Aspect 3) The fixing device according to aspect 1 or 2, wherein the paper passing area is within the maximum paper width range. (Aspect 4) The fixing device according to any one of Aspects 1 to 3, characterized in that metal members having the same thickness as the heat insulating member in the paper passage area are provided in the non-paper passage areas at both ends. (Aspect 5) The fixing device according to any one of Aspects 1 to 4, characterized in that a sliding member having high slidability with respect to the inner peripheral surface of the fixing member is provided between the heat insulating member and the fixing member. (Aspect 6) The fixing device according to Aspect 5, characterized in that the sliding member is formed of a member having a higher thermal conductivity than the heat insulating member. (Aspect 7) The fixing device according to Aspect 5 or 6, characterized in that the sliding member has members having a lower thermal conductivity than the sliding member at positions corresponding to both ends in the longitudinal direction of the heat insulating member. (Aspect 8) An image forming apparatus including the fixing device according to any one of Aspects 1 to 7.

Explanation of Reference Numerals

[0066] 1 Image forming apparatus 9 Optical writing device 10C, 10K, 10M, 10Y Image forming units 11C, 11K, 11M, 11Y Photoreceptors 20 Intermediate transfer belt 30 Secondary transfer device 40 Fixing device 41 Pressing roller 42 Fixing belt 43, 143 Heat sources 44 Fixing stay 45 Nip forming member 45a Heat equalizing member 45b Resin pad 48, 148 Reflective members 48a Reflection part 48b Pressure receiving part 49 Heat insulating member 50 Paper discharge tray 52 Metal member 54 (Low thermal conductivity) member 60 Sheet Feeding Cassette 61 Pickup Roller 62 Registration Roller Pair 63 Discharge Roller 100 Image Forming Unit Paper for P

Prior Art Documents

Patent Documents

[0067]

Patent Document 1

Claims

1. A rotating fixing member, a pressing member that abuts against an outer peripheral surface of the fixing member to form a nip portion and presses a recording material passing through the nip portion, a heat source disposed inside the fixing member, a reflecting member having a reflecting portion that reflects radiant heat from the heat source toward an inner peripheral surface of the fixing member and a pressure receiving portion that receives a pressing force of the pressing member via the fixing member, wherein the reflecting portion and the pressure receiving portion are integrally or thermally connected; and in a fixing device comprising: a heat insulating member is provided between the pressure receiving portion of the reflecting member and the fixing member, the heat insulating member exists exclusively in a paper passing area of the recording material and does not exist in non-paper passing areas at both ends or is in a notch shape, characterized in that it is a fixing device.

2. The fixing device according to claim 1, wherein the heat insulating member is a member formed in a sheet shape and containing silica aerogel.

3. The fixing device according to claim 1, wherein the paper passing area is within a maximum paper width range.

4. The fixing device according to claim 1, characterized in that metal members having the same thickness as the heat insulating member in the paper passing area are provided in the non-paper passing areas at both ends.

5. The fixing device according to claim 1, characterized in that a sliding member having high slidability with respect to an inner peripheral surface of the fixing member is provided between the heat insulating member and the fixing member.

6. The fixing device according to claim 5, wherein the sliding member is formed of a member having a higher thermal conductivity than the heat insulating member.

7. The fixing device according to claim 6, wherein the sliding member has a member having a lower thermal conductivity than the sliding member at positions corresponding to both longitudinal ends of the heat insulating member.

8. An image forming apparatus comprising the fixing device according to any one of claims 1 to 7.

Images