JP2003114583A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device having an external heating means which is constituted so that toner hardly infiltrates into an external heating member and can be removed by making a sheet of paper pass even if the toner infiltrates thereinto, an image defect caused by offset is avoided and excellent fixing property is maintained over a long period. SOLUTION: This fixing device has: a fixing member 100 coming into contact with transfer material 18 carrying unfixed developer and capable of heating the material 18; and an external heating member 102 coming into contact with the surface 109a of the fixing member without coming into contact with the material 18 and heating the surface 109a. In the device, a cleaning member does not abut on the surface 109c of the external heating member, and the releasing property of the surface 109c is made higher than that of the surface 109a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer and a copying machine, and a fixing device used in such an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, various systems such as an electrophotographic system, a thermal transfer system, and an inkjet system have been used as an image forming apparatus. Among them, the one using the electrophotographic method is superior to the other methods in terms of high speed, high image quality, and quietness, and is widely adopted as an image forming engine for copying machines and page printers.

In the electrophotographic system, electrostatic force is used,
An image formed by toner particles is formed on a transfer material such as paper. The fixing device melts and fixes the toner image on the transfer material to form a stable image. An electrophotographic color image forming apparatus will be described below as an example to explain a toner image forming principle in the electrophotographic method and a conventional example of a fixing device.

FIG. 4 is a schematic block diagram of a color image forming apparatus using an electrophotographic system as an example of the image forming apparatus. The system shown in the figure is a system known as an intermediate transfer system among electrophotographic systems.

First, the photosensitive drum 1, which is an image carrier, is rotationally driven in the direction shown by the arrow, and its surface is uniformly charged to -600V by the charger 2. After that, a latent image corresponding to an image is formed on the surface of the photosensitive drum 1 by the scanning light 4 from the laser exposure optical system 3 and the like. The potential of the latent image portion formed by exposure with scanning light is approximately -200V. On the other hand, each color developing device 5 (black), 6 containing a toner which is a developer
(Magenta), 7 (cyan), and 8 (yellow) are arranged on the rotor 22 near the photosensitive drum 1 as shown in the figure,
By rotating the rotor 22 every 90 °, the rotor 22 is sequentially arranged at the developing position facing the photosensitive drum 1.

Assuming that the developing device 5 faces the photosensitive drum 1, a certain amount of negatively charged toner is supplied onto the developing roller 5a, which is a developer carrying member provided in the developing device 5. In addition, a developing bias is applied to the developing roller 5a by a power source (not shown). By setting the developing bias to an appropriate value between the charging potential and the exposure portion potential, it is possible to perform the development in which the toner is selectively attached to the latent image on the photosensitive drum 1.

The monochromatic image thus formed on the photosensitive drum 1 is sequentially transferred onto the intermediate transfer belt 9 which rotates at substantially the same speed as the photosensitive drum 1 in the direction indicated by the arrow. At the time of transfer, a power supply 19 is applied to the transfer roller 10 which is a transfer unit that holds the intermediate transfer belt 9 between the photosensitive drum 1 and the photosensitive drum 1.
Transfer bias of positive polarity (200V to 700
V) is being applied. The toner remaining on the surface of the photosensitive drum 1 after the transfer is removed by the cleaner 17.

Each of the other developing devices 6, 7 and 8 has a developing roller similar to the developing roller 5a. In the above process, each color developing device 5 is synchronized with the rotation of the intermediate transfer belt 9.
8 are sequentially performed, and when a color image of four colors is formed on the intermediate transfer belt 9, the secondary transfer roller 11 of the transfer unit is contacted via the transfer material 18 and is applied from the power source 20. The color image is secondarily transferred onto the transfer material 18 all at once by the positive polarity bias (1 kv).

When the above process is completed, the toner remaining after the secondary transfer is removed by the cleaner 13, and the intermediate transfer belt 9 is decharged by a decharging charger (not shown). AC corona charging is often used as the static eliminator.
Further, in order to improve the charge removal efficiency, it is common to provide an electrode on the back surface of the intermediate transfer belt 9. The intermediate transfer belt 9
Is wound around the tension roller 16, the drive roller 15, and the secondary transfer counter roller 12.

The intermediate transfer belt 9 usually has a thickness of 70 μm.
m to 200 μm, volume resistivity 10 ¹¹ Ωcm to 10 ¹⁶ Ω
cmd PVdF, polyamide, polyimide, PE
Resin film belts such as T and polycarbonate and 0.5
A few dozen μ thick on a low resistance base layer of rubber with a thickness of about 2 mm
It is possible to use a rubber belt or the like provided with a high-resistivity resin layer having good mold releasability.

The full-color toner image, which is the developer image transferred onto the transfer material 18, is then fixed on the transfer material 18 by passing through the fixing device 21, and becomes an output image of the device.

Next, a schematic structure of Conventional Example 1 which is an example of a conventional fixing device used as the fixing device 21 of FIG. 4 is shown in FIG.
Will be described in detail.

In the fixing device of Conventional Example 1, a fixing member (fixing roller) 100 and a pressing member (pressing roller) 101, which are heating rollers as two types of temperature-controlled heating members.
The transfer material 18 on which the unfixed developer image 104, which is the above-described full-color toner image, is allowed to pass through the contact nip 110 thereof.

At this time, the unfixed developer image 104 is heated and pressed to be fixed on the transfer material 18. Here, the unfixed developer image 104 is formed on the surface of the transfer material 18 on the fixing roller 100 side. In addition, here, both rollers 10
Regarding the members constituting 0 and 101, for example, a heater as a member of the fixing roller 100 is described as a heater 106a, and a heater as a member of the fixing roller 101 is described as a heater 106b. Both 106a and 106b will be shown. The other members of the fixing roller 100 and the pressure roller 101 are also represented by the same method.

Each of the rollers 100 and 101 is provided with a halogen heater 106 at the center thereof, and the radiant energy generated by the heater 106 is transferred to the rollers 100 and 101.
Inside, the aluminum core metal 107 surrounding the heater 106 absorbs the heat, and each roller 100, 101 is heated.

In order to satisfactorily melt the toner and fix it on the transfer material 18, the fixing roller 100 and the pressure roller 10 are used.
Since it is necessary to secure the first contact nip 110, the rollers 100 and 101 have a thickness of 2 m around the aluminum core metal 107.
An elastic layer 108 made of silicon rubber of m is provided.

Further, in order to prevent the toner and paper powder from sticking to the surfaces of the rollers 100 and 101, the outermost surface layer which is the surface of the rollers 100 and 101 is a coating layer 109 made of a highly releasable resin such as PFA or PTFE. It is formed in.

On the other hand, in the case of the roller having the elastic layer 108 as in such an example, the distance from the portion of the heater 106 that collects the radiation and generates heat becomes far from the roller surface, which causes the following problems.

That is, from the continuous portion to the rollers 100, 10
When the heat of the surface 1 is rapidly removed, the heat supplied from the core metal 107 due to the heat conduction cannot keep up with the heat, and the rollers 100, 101
The temperature of the surface is lowered, resulting in poor fixing.

When strong heating is performed to compensate for the temperature drop on the surface, the silicone rubber elastic layer 108 near the core metal 107 is formed.
Temperature rises too fast and accelerates deterioration.

Such inconvenience becomes more severe as the roller diameter is smaller and the elastic layer 108 is thicker when the transfer material 18 is supplied at the same speed.

In order to solve the above problems, a method of heating the fixing roller from the outside has been proposed. FIG. 6 shows a structure of a conventional example 2 which is an example of a fixing device of such a system.

In FIG. 6, an external heating member (external heating roller) 102, which is a heating roller that abuts on the surface of the fixing roller 100 and does not touch the transfer material 18 and directly heats the surface of the fixing roller 100, is provided. .

The external heating roller 102 is the fixing roller 10.
0 or a halogen heater 106c similar to the pressure roller 101
It is composed of an aluminum core bar 107c provided at the center.

The heat energy taken from the surface of the fixing roller 100 by passing the paper by the external heating roller 102 can be replenished directly from the surface, and even when the paper is continuously passed, the roller 10
0,101 It is difficult to cause a temperature drop on the surface.

[0026]

However, in the fixing device of the second conventional example, the toner is melted in the fixing nip 110, and the following force relationship is established. 1. Cohesive force between toners> Adhesive force between toner and fixing roller, pressure roller 2. Adhesive force between toner and transfer material> Adhesive force between toner on fixing roller and pressure roller surface

As a result, the toner is fixed on the surface 109 of the fixing roller.
It does not adhere to a and is fixed to the transfer material 18.

On the other hand, when the image forming apparatus detects an abnormality such as a jam, the operation of the apparatus is stopped, and the roller heating by the heater 106 is stopped for ensuring safety. At that time, if the transfer material 18 on which the unfixed toner 104 is placed exists in the fixing nip 110, the above-mentioned force relationship is broken due to the temperature decrease of the rollers 100 and 101, and the fixing roller 100 and the pressure roller 101 are broken.
Toner may adhere to the surface (offset).
Further, it is sufficiently possible that toner adheres to the roller during the jam processing by the user.

In the case of the fixing device of Conventional Example 1 shown in FIG. 5,
The surfaces of the fixing roller 100 and the pressure roller 101 may be contaminated with the offset toner for the above reason. However, when the apparatus returns to the normal state, the above force relationship is established again, and the fixing roller 100 is first fed. The offset toner on the pressure roller 101 is fixed again on the transfer material 18 and can be removed from the roller.

However, in the case of the fixing device of the second conventional example shown in FIG. 6, the offset toner due to a jam or the like also wraps around on the external heating roller 102, and the transfer material is transferred even in the first sheet passing after the jam. It is not possible to remove all of the toner on the external heating roller 102 that is not in direct contact with 18. The toner on the external heating roller 102 gradually returns to the fixing roller 100, and each time it is mixed and fixed with the image toner on the transfer material 18, there is a big problem.

In order to prevent the above inconvenience, there has been proposed a method of removing the offset toner by providing a cleaning member 115 which contacts the fixing roller 100 and the external roller 102 as in the conventional example 3 shown in FIG. Becomes larger,
In addition to the complication, the user needs to regularly replace the cleaning member.

Therefore, an object of the present invention is to prevent the toner from wrapping around the external heating member in the fixing device having the external heating means, and even if the toner wraps around, it is possible to remove the toner with one sheet of paper, and it is possible to use the offset. (EN) Provided is a fixing device which avoids image defects and maintains good fixing properties for a long period of time.

[0033]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the first aspect of the present invention includes a fixing member that contacts an unfixed developer-carrying transfer material and heats the transfer material, and a fixing member that does not contact the transfer material but contacts the fixing member surface. An external heating member for heating the surface of the fixing member by means of an external heating member, the external heating member surface does not come into contact with the cleaning member, and the releasing property is higher than the releasing property of the fixing member surface. A fixing device characterized by the above.

The second aspect of the present invention includes an image bearing member and means for transferring the developer image formed on the image bearing member onto a transfer material, and an image provided with the fixing device of the first aspect of the present invention. A forming apparatus is provided.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION A fixing device and an image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 The structure of the image forming apparatus in this embodiment is the same as the structure of the image forming apparatus shown in FIG. 4 and its explanation is omitted. Here, the detailed configuration, the difference from the conventional example, and the effect of this embodiment of the fixing device, which is the characteristic part of the present invention, will be described.

The structure of the fixing device in this embodiment is shown in FIG. In the fixing device, the halogen heater 106 is provided inside.
It has three heating rollers (a fixing roller 100, a pressure roller 101, and an external heating roller 102) including a, 106b, and 106c. Similar to the configuration of the second conventional example, the arrangement is such that the transfer material 18 is sandwiched between the contact nip portions 110 and the unfixed developer image 104 is formed on the transfer material 18 toward the fixing roller 100. The fixing roller 100 and the pressure roller 101 are arranged in the
The external heating roller 102 is arranged on the fixing roller 100 so as not to come into contact with the fixing roller 100.

No cleaning member or the like is provided. The fixing roller 100 and the pressure roller 101 are in contact with each other at a predetermined pressure (40 kgf, 20 kgf), and the fixing roller 100 and the external heating roller 102 are in contact with each other.

Further, the rollers 100, 101, 1
Reference numeral 02 has a temperature detection means (not shown) such as a thermistor, and each heater 1 is based on the temperature detection information by them.
The lighting of 06 is controlled and the temperature is adjusted.

In this embodiment, the pressure roller 101 and the fixing roller 100 both have a diameter of 40 mm, the external heating roller 102 has a diameter of 25 mm, and the roller lengths are 234 mm for the fixing roller 100 and 228 mm for the pressure roller 101.
The external heating roller 102 has a length of 228 mm.

Each of the fixing roller 100 and the pressure roller 101 has a thickness of about 2 outside the hollow aluminum roller core 107.
A silicon rubber elastic layer 108 having a thickness of 20 mm is provided, and a high release layer 109 having a thickness of 20 μm, which is a surface layer forming a surface, is provided outside the elastic layer 108. Additives such as red iron oxide and silica are added to the silicone rubber forming the elastic layer 108 in order to improve thermal conductivity, and the rubber hardness is adjusted to 8 degrees (test piece hardness JIS A).

The external heating roller 102 has a hollow aluminum roller 107c provided with a coating layer (surface layer) 109c having a thickness of 20 μm and formed of a highly releasable material.

The fixing roller 100 is rotationally driven in the arrow direction at a peripheral speed of about 120 mm / s by a driving means (not shown), and the other rollers 101 and 102 are driven to rotate. After the transfer process, the transfer material 18 holding the unfixed developer image 104 on the upper side in the drawing is conveyed in the direction of the arrow and enters the fixing device,
Contact nip 11 for fixing roller 100 and pressure roller 101
Pass 0 (about 9 mm). In the nip 110, the transfer material 18 is heated and pressed to fix the image.

In this embodiment, the surface layer (front surface) 109a of the fixing roller 100 and the surface layer (surface) of the outer roller 102.
Although both 109c are formed of a high release layer, each of them adopts a surface layer formed of a different material (material).
The releasability of the surface of the external heating roller 102 is set higher than the releasability of the surface of 00.

More specifically, in this embodiment, the fixing roller surface layer 109a is made of fluororubber, and the external heating roller surface layer 109c is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) resin.

In order to determine the releasability of the roller surface used in this embodiment, a contact angle measuring device (CA manufactured by Kyowa Interface Science Co., Ltd.
Using a -X roll type (trade name), the contact angle of pure water was measured by a liquid solution method.

As a result, the surface 109a of the fixing roller 100
The contact angles of pure water on the outer heating roller 102 surface 109c and the outer heating roller 102 surface were 100 ° and 110 °, respectively.
That is, the external heating roller surface 109c has higher releasability than the fixing roller surface 109a.

As described above, by making the releasability of the surface of the external heating roller 102 higher than that of the surface of the fixing roller 100, the offset toner adhered to the surface of the fixing roller 100 due to a jam or the like is less likely to get around to the external heating roller 102.

Further, the image forming apparatus of the present embodiment is provided with the cleaning mode in which the transfer material can be passed through the fixing device after the occurrence of the jam in the fixing portion and before the normal image formation. Therefore, even when the toner is rotated around, after returning to the normal state, the offset toner is returned to the fixing roller 100 due to the difference in releasability, and all the toner is transferred onto the transfer material 18 that has passed through after the jam by the cleaning mode. Is discharged. As a result, it is possible to prevent image defects from occurring on the second and subsequent sheets.

In the examples of the present specification, the releasability of the fixing roller and the external heating roller was judged by measuring the contact angle using pure water as a sample, but other materials such as alcohol and oil are used as the sample. May be used.

Further, the image forming apparatus is not limited to the one shown in FIG. 4, but may be a single color image forming apparatus, an apparatus using no intermediate transfer member, or an electrostatic recording type.

Embodiment 2 The structure of the image forming apparatus in this embodiment is also the same as that of the image forming apparatus already described in FIG. The schematic structure of the fixing device in this embodiment is also the same as that of the first embodiment, and the duplicated description will be omitted.

In this embodiment, as the surface layer (front surface) 109a of the fixing roller 100 and the surface layer (front surface) 109c of the external heating roller 102, high releasable layers made of the same material are provided. The releasability of the external heating roller 102 surface was set higher than the releasability of the surface of the fixing roller 100 by changing the amount or material of the contaminants added to the material of each high release layer.

More specifically, in this embodiment, both the fixing roller surface layer 109a and the external heating roller surface layer 109c are made of PFA resin as a material, and the difference in releasability is set as follows.

That is, the outer heating roller surface layer 109c is made of pure PFA resin, while the fixing roller surface layer 10 is formed.
In the case of 9a, a minute amount of carbon fine particles were dispersed in the PFA resin as a contaminant.

Generally, the PFA resin has a high mold release property, but if another substance (having a lower mold release property) is mixed, the mold release property is lowered. Due to the properties of the roller, the contaminant is preferably stable even at high temperatures, and carbon was selected as the contaminant in order to prevent offset and the like due to electrification of the roller surface.

As a result, the contact angles of pure water on the fixing roller surface 109a and the external heating roller surface 109c were 100 ° and 110 °, respectively.

As described above, in the present embodiment, the releasability of the surface of the external heating roller is adjusted by adjusting the amount of the contaminants added to the material or the material of the fixing roller and the external heating roller. By making the height higher than the surface of the fixing roller, it becomes difficult for the external heating roller to get around due to jams or the like as in the first embodiment. Also, for example, even when the toner wraps around, after returning to the normal state, the offset toner is returned to the fixing roller due to the difference in releasability, and after the jam, the offset toner is entirely discharged onto the first transfer material. As a result, it is possible to prevent image defects from occurring on the second and subsequent sheets.

Embodiment 3 The configuration of the image forming apparatus in this embodiment is also the same as in Embodiments 1 and 2.
Similarly to the above, the configuration is the same as that of the image forming apparatus already shown in FIG. Further, the schematic configuration of the fixing device in this embodiment is almost the same as in the first and second embodiments. Here, reference will be made to FIG. 1 and redundant description will be omitted.

In this embodiment, both the surface of the fixing roller 100 and the surface of the external heating roller 102 are formed by a high release layer.
By adopting surface layers having different surface properties, the releasability of the external heating roller surface was set higher than the releasability of the fixing roller surface.

More specifically, in this embodiment, the fixing roller surface layer 109a and the external heating roller surface layer 109c are both PF.
The fixing roller surface layer 109a has a surface roughness (Rz value) of 6 μm, and the external heating roller surface layer 10 is formed of A resin.
The surface roughness (Rz value) of 9c was set to 1 μm, and the surface roughness of the fixing roller surface layer 109a was set to be larger than the surface roughness of the surface layer 109c of the external heating roller 102.

Here, the surface roughness (R
z value) is a surface roughness measuring instrument SE- manufactured by Kosaka Laboratory Ltd.
The value measured using 3400 (trade name) was used.

By doing so, the surface layer of the fixing roller having a larger surface roughness has a larger surface area at the portion in contact with the toner, so that the adhesive force between the toner and the surface layer is increased and the releasability to the toner is increased. descend. As a result, the releasability of the outer heating roller surface layer having a smaller surface roughness can be relatively increased.

In the first and second embodiments, the contact angle is measured to determine the releasability of the surface layer. However, when the surface roughness is different as in this example, it is difficult to perform the same determination, and therefore the contact angle measurement was not performed.

As described above, the surface roughness of the fixing roller and the external heating roller is adjusted so that the releasability of the external heating roller surface is higher than that of the fixing roller surface. As a result, it becomes difficult for the offset toner attached to the surface of the fixing roller to flow around to the external heating roller. Further, even if the toner has rotated around, after returning to the normal state, the offset toner is returned to the fixing roller due to the difference in releasability, and is completely discharged onto the transfer material that has passed through after the jam. As a result, it is possible to prevent image defects from occurring on the second and subsequent sheets.

Example 4 In Examples 1 to 3, the fixing roller 100 and the pressure roller 10 were used.
Both have heaters 106 built in, but each roller 1
The heater 106 in 00 and 101 is optional.
Further, as long as the external heating member is in contact with the surface of the fixing roller 100, a member other than the roller may be adopted as the external heating member. Some examples are shown below.

FIG. 2 shows an example in which a plate-shaped fixed ceramic heater 111 is adopted as an external heating member. The ceramic heater 111 has a width of 10 mm, and is brought into contact with the fixing roller 100 by a pressing means (not shown) with the releasable surface 119 as a contact surface. Since the heater 111, which is the external heating member, directly heats the surface of the fixing roller 100, efficient heating can be performed.

Further, FIG. 3 shows the external heating member 102.
As an example, an endless thin film 112 having a ceramic heater 113 inside is adopted. The film 112 has a base layer 116 made of a polyimide resin having a thickness of 50 μm and a surface layer 117 made of a high release material such as PFA. And, it slides on the film guide 114 and rotates in the direction of the arrow. This external heating member is the fixing roller surface 109a as in FIG.
In addition to efficient heating, the heater 113 is in contact with the fixing roller 100 via the rotatable film 112, so that the driving force of the fixing roller 100 can be reduced.

Even when these external heating members are adopted, the features of the present invention are learned, and in the fixing device of FIG. 2, the contact surface 11 of the ceramic heater 111 with the fixing roller 100.
9 and the fixing roller surface layer 109a, or in the fixing device of FIG. 3, the film surface layer 117 and the fixing roller surface layer 109
The material or the surface roughness of a is adjusted so that the contact surface 119 of the external heating member (ceramic heater) 111 or the film surface layer 117 of the external heating member 102 has higher releasability than the surface layer 109a of the fixing roller 100. By doing so, it is possible to obtain the same effects as those described in the first to third embodiments, and it is possible to prevent the occurrence of defects in the output images of the second and subsequent sheets after the jam restoration.

[0070]

As described above, the fixing device and the image forming apparatus of the present invention include a fixing member capable of heating a transfer material,
An external heating member that contacts the fixing member surface and heats the contact surface without contacting the transfer material.
There is no contact of the cleaning member against it, and by making the releasability of the surface higher than the releasability of the fixing member, it becomes difficult for the offset toner adhering to the surface of the fixing roller due to a jam or the like to flow around to the external heating roller, and Even when it wraps around, it is immediately returned to the fixing roller and then returned onto the first transfer material after the jam is released. As a result, image defects are prevented from occurring on the second and subsequent sheets, so that image defects due to offset can be avoided, and good fixability can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a fixing device of the present invention.

FIG. 2 is a cross-sectional view showing another example of the fixing device of the present invention.

FIG. 3 is a cross-sectional view showing another example of the fixing device of the present invention.

FIG. 4 is a schematic configuration diagram showing an image forming apparatus of the present invention.

FIG. 5 is a cross-sectional view showing a fixing device of Conventional Example 1.

FIG. 6 is a cross-sectional view showing a fixing device of Conventional Example 2.

FIG. 7 is a sectional view showing a fixing device of Conventional Example 3.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 18 Transfer material 21 Fixing device 100 Fixing roller (fixing member) 101 Pressure roller 102 External heating roller (external heating member) 104 Unfixed developer image 106 Halogen heater 107 Core metal 108 Elastic layer 109 Release layer 109a Release layer (fixing member surface) 109c Release layer (external heating member surface) 110 Nip part (contact surface) 111, 113 Ceramic heater 112 Film (external heating member) 114 Film guide 115 Cleaning member 116 Film base layer 117 Film Surface Layer (External Heating Member Surface) 119 Ceramic Heater Surface (External Heating Member Surface)

Claims (9)

[Claims] 1. A fixing member for contacting a transfer material carrying an unfixed developer and heating the transfer material, and a fixing member surface for contacting the fixing member surface without contacting the transfer material. In the fixing device having an external heating member for heating, the surface of the external heating member does not come into contact with the cleaning member, and the releasability is higher than the releasability of the surface of the fixing member. apparatus. 2. On the surface of the external heating member, the type of material forming the surface or the added contaminant, or
The fixing device according to claim 1, wherein the ratio of the amount of the raw material to the amount of the added contaminant is different from that of the surface of the fixing member. 3. The fixing device according to claim 1, wherein the surface of the external heating member has a larger contact angle with respect to pure water than the surface of the fixing member. 4. The fixing device according to claim 1, wherein the surface roughness of the external heating member and the surface roughness of the fixing member are different from each other. 5. The fixing device according to claim 1, wherein the external heating member is a heating roller. 6. The external heating member is a fixed heater in contact with the fixing member.
The fixing device according to any one of 1. 7. The external heating member is a thin film,
The fixing device according to any one of claims 1 to 4, further comprising a fixed heater inscribed in the thin film. 8. An image carrier, and a means for transferring the developer image formed on the image carrier to a transfer material.
An image forming apparatus comprising the fixing device according to any one of 1. 9. The cleaning mode according to claim 8, further comprising a cleaning mode for passing the transfer material through the fixing device after the device main body detects an abnormality and stops and before normal image formation is resumed. Image forming apparatus.