JP2000112269A - Fixing device - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a fixing device capable of exhibiting high fixability using a liquid developer containing a non-volatile solvent. SOLUTION: In a fixing device for thermally fixing an unfixed image formed on recording paper 4 using a liquid developer containing a non-volatile solvent, a heating roller 1 having a heat source 3 therein and driven to rotate is provided. And a plurality of backup rollers 2 installed opposite to the heating roller. The backup roller presses the recording paper toward the heating roller by a pressing force of 50 g / cm per unit length in the axial direction. By setting as follows, the contact pressure between the recording paper and the heating roller is sufficiently suppressed, and the offset amount of the toner adhering on the heating roller after fixing is reduced.

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 a copying machine, a facsimile, and a printer.
The present invention relates to an image forming apparatus including a fixing device having a heating roller and a supporting roller facing the heating roller and using a liquid developer containing a non-volatile solvent.

[0002]

2. Description of the Related Art As a fixing method of a conventional general fixing device, there is a heat roller fixing method having a heating roller and a pressure roller. In this fixing method, one or both of a heating roller and a pressure roller are formed of an elastic body such as rubber or sponge, and a nip is formed by a pressing force between these rollers. Then, the unfixed image is fixed by passing the recording medium having the unfixed image adhered between the rollers. In a fixing device using this fixing method, it is necessary to form the nip width larger in order to improve the fixing property, so that the pressing force between the rollers is increased, or the heating roller or the pressure roller is used. Is configured to have a low hardness. But,
In order to increase the pressing force between the rollers, the strength of these rollers must be increased. For this reason, it is necessary to increase the volume of the core of these rollers, but when increasing the strength of the heating roller, the heat capacity of the heating roller itself increases, so that the rise time of the fixing device becomes longer. I will. In addition, when the hardness of the roller made of an elastic material such as rubber or sponge is reduced, permanent deformation occurs and a problem occurs in durability.

Conventionally, in order to solve the above-mentioned problems, fixing systems such as a heat belt fixing system and a thermal film fixing system have been proposed. In these fixing systems, a nip width can be formed sufficiently large even under a low pressing force, so that stable fixing properties can be achieved. Also,
It is known that the offset of the developer can be reduced by devising a heat transfer process between a heated belt or a film and a recording medium even with respect to a problem related to toner offset. . However, the mechanisms of the heat belt fixing method and the heat film fixing method are complicated as compared with the above-described heat roller fixing method, and have a disadvantage that a belt shift that does not occur in the heat roller fixing method occurs. Further, when the driving speed is increased due to the complexity of the mechanism and the shift toward the belt, stability is lacking, which is disadvantageous in increasing the fixing speed, which has been desired in recent years.

The above-mentioned conventional fixing device is mainly intended to be applied to a case where an image is formed using a dry developer or a liquid developer using a volatile solvent. It is also possible to form an image with a liquid developer containing a non-volatile solvent using such a fixing device, and the above-mentioned disadvantages, disadvantages, and beneficial effects similarly occur. But,
In this case, a new problem occurs when a liquid developer containing a nonvolatile solvent is used.

[0005] In recent years, research on full-color image formation has been actively conducted. However, in order to obtain a high-quality image during full-color image formation, it is necessary to enhance the color developability of a color image. Since the color developability of this color image depends on the mixing properties of the toners of each color forming the color image, when forming a full-color image, the average particle diameter of the toner is generally smaller than that of a dry developer. Suitable is a wet type developer capable of performing the following. This is because the wet developer has a higher mixing property than the dry developer. Further, a wet developer is more advantageous than a dry developer in that the amount of toner required for image formation can be sufficiently reduced.

[0006]

Conventionally, when an unfixed image is fixed by a fixing device using a dry developer, a large amount of heat is applied and a large pressure is applied to fix the image and at the same time to fix a color image. The coloring was enhanced. On the other hand, a fixing device using a wet developer generally does not need to apply a large pressure at the time of fixing an image, and can improve the color developability only by heating. When a liquid developer containing a non-volatile solvent is used among the above-mentioned wet type developers, the presence of the non-volatile solvent transferred onto the recording medium greatly affects the fixability. In this case, it is necessary to absorb the non-volatile solvent remaining on the recording medium into the recording medium, or to remove the non-volatile solvent using a roller or the like that comes into contact with the image surface of the recording medium. Absorption of the non-volatile solvent in the recording medium is promoted by heating the non-volatile solvent remaining on the recording medium by heating the recording medium, for example, and reducing the viscosity of the non-volatile solvent. It is possible. Therefore, in order to improve the fixability, it is necessary to heat the above-mentioned nonvolatile solvent for a sufficient time. In this case,
It is not necessary to heat the entire recording medium, and it is sufficient if at least the carrier liquid adhering on the recording medium and the surface layer of the image surface of the recording medium are heated.

Further, when a liquid developer containing a non-volatile solvent is used as described above, the phenomenon that the offset amount of the toner increases as the contact pressure between the heating roller and the recording medium during image fixing increases. Has been confirmed by For this reason, it is necessary to widen the heating area while sufficiently suppressing the contact pressure in order to obtain a high-quality image.

The present invention has been made in view of the above background, and it is an object of the present invention to have a simple structure, a small size, and a high fixing property using a liquid developer containing a non-volatile solvent. To provide a fixing device that can perform the fixing.

[0009]

In order to achieve the above object, the invention according to claims 1 to 6 is directed to a method in which a part or all of a carrier liquid is formed on a recording medium by using a liquid developer which is a non-volatile solvent. In a fixing device for thermally fixing an unfixed image formed, a heating roller, heating roller driving means for driving the heating roller, and a plurality of supporting rollers provided in the circumferential direction opposite to the heating roller. The support roller presses the recording medium toward the heating roller with a pressing force of 5 mm per unit length in the axial direction of the support roller.
It is characterized by being set to 0 g / cm or less. In this fixing device, since the same supporting roller as the pressing roller in the heat roller fixing method is used,
The height of the fixing device can be reduced, and the structure thereof can be configured very easily as compared with the heat belt fixing method or the heat film fixing method. However, the supporting roller in this fixing device mainly forms a conveyance path of the recording medium and aims to guide the recording medium. It is not intended to fix the image.

Further, by setting the pressing force per unit length in the axial direction of the support roller to 50 g / cm or less, the contact pressure of the recording medium with respect to the heating roller can be sufficiently suppressed, and after the fixing, the heating roller can be heated. It is possible to reduce the amount of offset of the toner adhering on the top. Furthermore,
Although a very weak force is applied, pressing the recording medium against the heating roller can ensure the close contact between the heating roller and the recording medium. By ensuring such adhesion, the heat transfer efficiency between the heating roller and the recording medium can be improved. Thereby, an unfixed image on the recording medium can be efficiently fixed.
In particular, when fixing a color image, the color developability of the color image can be enhanced. Also, since a plurality of the supporting rollers are arranged in the circumferential direction of the heating roller, a wide heating area can be secured, and a sufficient time for heating the non-volatile solvent remaining on the recording medium is secured. can do. In this case, in the fixing region formed between the heating roller and the support roller, the recording medium is bent by the pressure of the support roller at a portion that comes into contact with each support roller, while the recording medium is bent at other portions. Thereby, it comes into contact with the heating roller.

Further, even when one or all of the pressures of the support rollers are set to 0 g / cm, since a plurality of these support rollers are installed in the circumferential direction so as to face the heating roller, fixing is performed. Contact between the recording medium and the heating roller in the area is realized by bending of the recording medium. Due to the bending of the recording medium, the adhesion between the recording medium and the heating roller is ensured, and the heat transfer efficiency therebetween can be improved. Further, by ensuring the adhesion in this way, the adhesive force between the carrier liquid on the recording medium and the heating roller and the shearing stress of the carrier liquid act to ensure the transportability of the recording medium. Can be. When one or all of the pressures of the support rollers are set to 0 g / cm as described above, at least until the leading end of the recording medium reaches the inside of the fixing area, that is, the recording medium is bent. Until the recording medium comes into contact with the heating roller, it is necessary to separately provide a conveying means for conveying the recording medium.

In particular, a second aspect of the present invention is the fixing device of the first aspect, wherein a gap is provided between the support roller and the heating roller. In this fixing device, since a gap is provided between the support roller and the heating roller, when the gap is larger than the thickness of the recording medium passing therethrough, that is, when one or all of the support rollers are heated. When the pressure is set to 0 g / cm,
The contact between the recording medium and the heating roller in the fixing area is realized by bending of the recording medium. By this bending, it is possible to ensure the adhesion between the heating roller and the recording medium,
The heat transfer efficiency between them can be improved, and the transportability of the recording medium can be ensured. In particular,
When the supporting roller and the heating roller are completely separated from each other, the two rollers are in a non-contact state, and the heat from the heating roller does not directly propagate to the supporting roller,
It is possible to reduce the amount of heat required in the fixing device and to shorten the warm-up time.

According to a third aspect of the present invention, in the fixing device of the second aspect, a step portion having an outer diameter larger than an outer diameter of a fixing portion of the heating roller is provided at both ends of the heating roller. The above-mentioned gap is formed. In this fixing device, since the gap is formed by the step portions provided at both ends of the heating roller, there is no need to strictly adjust the arrangement of the support roller and the pressing force, and the gap is formed with a simple configuration. can do.
Further, since the heating roller is generally thinned in order to reduce its heat capacity, its roundness is reduced, and its cross section may be deformed into an elliptical shape.
Even in such a case, since the gap is formed by contacting the support roller with the step, the gap can be stably maintained constant. Also, since the contact between the heating roller and the support roller is only at the above-mentioned stepped portion,
Heat transmitted from the heating roller to the support roller can be reduced. In particular, if the portion of the supporting roller that contacts the step portion of the heating roller is formed of a heat insulating material, it is possible to further suppress the heat from the heating roller from being transmitted to the supporting roller.
It is possible to reduce the warm-up time of the fixing device.

The invention of claim 4 is the invention of claim 2 or 3
Wherein the gap in the axial direction of the heating roller is not less than 20 μm and not more than 500 μm. When manufacturing the above-mentioned heating roller and supporting roller, it is practically difficult to keep the true axiality within about 10 μm. Therefore, in order to keep these rollers separated, at least 20 μm
It is necessary to form a gap. Thus, if the gap is set to 20 μm or more, the heating roller and the supporting roller can be stably brought into a non-contact state, and the heat from the heating roller can be directly transmitted to the supporting roller. Therefore, the warm-up time of the fixing device can be reduced. Further, when the gap is 500 μm or more, the contact state between the heating roller and the recording medium is deteriorated, and it is impossible to secure the adhesion. Therefore, if the gap is set to 500 μm or less, the adhesion between them can be ensured, and the transportability of the recording medium can be ensured. When the gap is set to be larger than the thickness of the recording medium, the contact between the recording medium and the heating roller in the fixing area is realized by bending of the recording medium. On the other hand, when the gap is set smaller than the thickness of the recording medium, for example, when the pressing force of the support roller is realized by using a spring, the stroke length of the spring is reduced as compared with the case where no gap is provided. Therefore, lower pressure can be realized.

According to a fifth aspect of the present invention, in the fixing device of the first, second, third, or fourth aspect, the relationship between the outer diameter D of the heating roller and the outer diameter d of the support roller is 0 <d / D ≦ 0.5. As the value of d / D is larger, that is, as the outer diameter d of the supporting roller is larger than the outer diameter D of the heating roller, it becomes more difficult to transfer a sheet between a plurality of supporting rollers. There is a problem that the recording medium passes between adjacent support rollers without passing between the support roller and the heating roller. This problem tends to occur particularly during conveyance of a thin recording medium. In view of this problem, in this fixing device,
Each support roller arranged in the circumferential direction of the heating roller,
The heating roller is formed so as to have an outer diameter of half or less. Since the number of the support rollers disposed in the fixing region on the outer peripheral portion of the heating roller increases as the outer diameter of the support roller decreases, at least d / D ≦ 0.5, so that the design of the fixing device can be improved. In addition, a plurality of, preferably three or more, support rollers can be provided in a necessary limited fixing area, so that a recording medium can be stably conveyed.

[0016] The invention of claim 6 is based on claims 1, 2,
In the fixing device according to any one of the third, fourth, and fifth fixing devices, a support roller driving unit that drives the support roller is provided. In this fixing device, since the supporting roller is also driven to rotate together with the heating roller, the stability of recording medium conveyance in the fixing area can be further improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the fixing device according to the present invention is used as a fixing device of an image forming apparatus will be described below. FIG. 1 is a side view illustrating a schematic configuration of the fixing device according to the first embodiment. This fixing device is provided with a heating roller 1, a driving motor (not shown) as a heating roller driving unit for driving the heating roller, and four heating rollers arranged in a circumferential direction of the heating roller so as to face an outer peripheral surface of the heating roller. And a backup roller 2 as a supporting roller. The heating roller 1 is formed by coating a surface of a hollow cylindrical member with a fluororesin layer such as tetrafluoroethylene-perfluoroalkylvinyl copolymer (PFA) or polytetrafluoroethylene (PTFE). . Also, this heating roller 1
A halogen lamp tube 3 as a heat source is installed in the hollow portion. The halogen lamp tube 3 is set so that the surface temperature of the heating roller 1 becomes a predetermined temperature.
The power supply is controlled by a power supply control device (not shown). Each backup roller 2 disposed on the outer periphery of the heating roller 1 has an outer diameter d corresponding to 2/5 of the outer diameter D of the heating roller 1 and has a surface similar to that of the heating roller 1. Use the one coated with a fluororesin layer.

As described above, since the outer diameters of the heating roller 1 and the backup roller 2 are set so that d / D = 0.4, the outer diameter of the heating roller 1 in the limited fixing region is limited. The four backup rollers 2 can be arranged in the same manner. In addition, these backup rollers 2
Are arranged so as to be very close to each other, so that the recording paper 4 as a recording medium passing through the fixing area can be stably conveyed along the surface of the heating roller 1.

At the both ends of each backup roller 2, the backup roller is connected to the heating roller 1.
A spring member 5 is attached as urging means for urging to the side. The spring member 5 is configured to press the backup roller 2 against the heating roller 1 with a sufficiently weak force. Thus, the backup roller 2
Is small, the contact pressure of the recording paper 4 with the heating roller 1 can be kept sufficiently low, and the offset amount of the toner adhering on the heating roller after fixing can be reduced. Further, the contact between the recording paper 4 and the heating roller 1 in the fixing area is realized by the pressing force of the backup roller at a portion where the recording paper comes into contact with each backup roller 2 and by the bending of the recording paper at other portions. Is done. Therefore, the adhesion between the heating roller 1 and the recording paper 4 is sufficiently ensured in the entire fixing area, and the recording paper can be brought into contact with the heating roller 1 for a long time.

Next, a second embodiment of the fixing device according to the present invention will be described. FIG. 2 is a side view illustrating a schematic configuration of the fixing device according to the second embodiment. The heating roller 1, the backup roller 2 and the spring member 5 in this fixing device are the same as those in the first embodiment, but the heating roller and the backup roller have a configuration in which their rotating shafts protrude from both ends in the axial direction. ing. The fixing device according to the present embodiment has two stoppers 6 formed of fan-shaped plates.
Are provided, and their acute angles are
Are respectively fixed to the protruding portions at both ends of the rotating shaft. Further, the curved portion of the stopper 6 is supported by projecting portions at both ends of the rotation shaft of each backup roller 2. Accordingly, the backup roller 2 moves toward the heating roller 1 by the urging action of the spring member 5, but the movement is prevented by the stopper 6, and the backup roller 2 is held at a predetermined position. Thereby, the backup roller 2
G between the surface of the heating roller 1 and the surface of the heating roller 1
Is formed. The gap G is set to be about 100 μm in the present embodiment.

Here, the above fixing device has a thickness of 100 μm.
A case where an unfixed image formed on the recording paper 4 of m or less is fixed will be described. FIG. 3A is a diagram showing a state in which the leading end of the recording paper 4 is located in the fixing area, and FIG.
FIG. 4 is a diagram showing a state in which the leading end of the recording paper has passed through a fixing area. In the fixing area formed between the heating roller 1 and the backup roller 2, the backup roller applies the recording paper 4 to the heating roller 1 as shown in these drawings.
The conveyance is performed while changing the conveyance direction along the circumferential direction. For this reason, the portion of the recording paper 4 located in the fixing area is in a curved state. At this time, when this portion is bent, a portion that is in contact with the heating roller 1 is formed on the recording paper 4. Thereby, the adhesion between the heating roller 1 and the recording paper 4 can be ensured. In this case, the recording paper 4
Since the heating roller 1 is heated almost without pressure, the offset amount of the toner on the heating roller 1 can be extremely reduced. Further, by ensuring the adhesion between the heating roller 1 and the recording paper 4, the heat transfer efficiency between them can be improved, and the fixing can be performed efficiently. Further, by ensuring the above-mentioned adhesion, the recording paper 4
The adhesive force between the upper carrier liquid and the heating roller 1 is exhibited,
The adhesive force and the shearing stress of the carrier liquid act to ensure the transportability of the recording paper.

Further, the above fixing device has a thickness of 100 μm.
Even when the unfixed image formed on the recording paper 4 is fixed, the stroke length of the spring member is reduced by the gap G between the heating roller 1 and each backup roller 2 according to the first embodiment. The contact pressure of the recording paper 4 against the heating roller 1 can be further reduced as compared with the case where the gap G is not provided.

Further, since the heating roller 1 and the backup roller 2 are completely separated from each other during non-fixing, the heating roller 1 heated by the halogen lamp tube 3 for warm-up is used as the backup roller. The roller 2 does not lose heat. Therefore,
The thermal warm-up time of the heating roller 1 can be shortened, and unnecessary power consumption can be prevented.

Next, a modification of the gap forming mechanism of the second embodiment will be described. FIG. 4 is a front view of the heating roller according to the present modification. The heating roller 7 in this modification is also formed of a hollow cylindrical member whose surface is coated with a fluororesin layer, similarly to the heating roller described above. In the vicinity of both ends of the heating roller 7, a step portion 8 having an outer diameter larger than the outer diameter of the central portion is provided.
The step portion 8 is formed by thickly coating only the vicinity of both ends of the heating roller during the fluororesin coating in the manufacturing process of the heating roller 7. Alternatively, the step 8 may be formed by, for example, temporarily coating the entire heating roller with a thicker fluororesin and then cutting the central portion.

To shorten the thermal warm-up time of the heating roller 7, it is necessary to sufficiently reduce the heat capacity of the heating roller. In order to reduce the heat capacity of the heating roller 7, it is effective to reduce the thickness of the heating roller. However, the roundness of the heating roller decreases as the thickness of the heating roller decreases. When the roundness of the heating roller 7 is reduced in this way, the contact pressure between the heating roller and the recording paper 4 becomes uneven in the circumferential direction of the heating roller, and a local offset occurs in a portion where the contact pressure is large. appear. Further, due to the uneven contact pressure, the fixing property deteriorates due to insufficient heat propagation in a portion where the recording paper 4 is separated from the heating roller 1.

However, since the gap in this modification is formed by bringing the backup roller into contact with the step 8 of the heating roller 7, even if the roundness of the heating roller is poor, This gap can be stably maintained constant. Further, since the contact between the heating roller 7 and the backup roller is only at the stepped portion 8, the heat transmitted from the heating roller to the backup roller can be reduced.

In the fixing device according to the two embodiments described above, if a drive motor is provided as a supporting roller driving means for rotating the backup roller 2 and the backup roller is driven to rotate together with the heating roller,
Smooth and stable recording paper conveyance can be realized.
As such a supporting roller driving unit, for example, gears are attached to both ends of the heating roller that is driven to rotate and both ends of the backup roller, and the gears are meshed with each other, so that the backup roller is driven by the rotation driving force of the heating roller. It may be configured to be driven to rotate.

[0028]

Next, an embodiment in which the fixing device according to the present invention is used as a fixing device of an electrophotographic copying machine will be described. The configuration of the fixing device in this embodiment is the same as that described in the second embodiment. In the present embodiment, a heating roller formed by coating a surface of a hollow aluminum pipe having a thickness of 700 μm and an outer diameter Dφ30 mm with a fluororesin at a thickness of 30 μm is used. Each backup roller is formed by coating a surface of a stainless steel roller with a fluororesin and having an outer diameter d of 12 mm. That is, the relationship between the heating roller and the backup roller is set so that d / D = 0.4. Each of the heating roller and each backup roller has an axial length of 320 mm. Each backup roller is pressed against the heating roller at 1000 gf using a spring member attached thereto. If this fixing device is used to fix any paper generally used in the printing field, for example, thin glossy paper used for advertisements and thick non-glossy paper used for business cards, etc. And a good fixing effect could be obtained.

Using this fixing device, two experiments were conducted while changing the gap length between the heating roller and the backup roller. The first experimental example is a measurement of the surface temperature of the backup roller with respect to the gap length. In this experimental example, the surface temperature at one point of the backup roller when the heating roller was set to 140 ° C. and the heating roller and the backup roller were simultaneously rotated for a certain period of time, for a case where the gap length was 40 μm or less. It was measured. This measurement result is shown in FIG.
Considering this result, when the gap length is 20 μm or less, the surface temperature of the backup roller becomes extremely high. This is considered to be due to the mechanical accuracy of the heating roller and the backup roller, where these rollers are in local contact. Therefore, in order to reduce the amount of heat supplied unnecessary for fixing, the gap length needs to be set to 20 μm or more.

The second experimental example is an inspection of image fixability on recording paper with respect to the gap length. In this experimental example, using a recording paper of the same quality having a thickness of 50 μm, 90 μm, and 120 μm, the image fixing property when the gap length was 1 mm or less was examined. FIG. 6 shows the test results. Considering this result, the larger the gap length, the more the fixability tends to deteriorate. In particular, when the gap length was 500 μm or more, the fixability deteriorated rapidly. It is considered that the deterioration of the fixing property is caused by insufficient contact between the recording paper and the heating roller. In addition, with the deterioration of the fixing property, the conveyance property of the recording paper also deteriorated. Therefore, in order to achieve stable fixability to any of the above-described recording papers, the gap length is set to 500 μm.
m. It is considered that the upper limit of the gap length slightly changes depending on the type of recording paper (difference in stiffness, etc.) and the outer diameter of the heating roller.

[0031]

According to the first to sixth aspects of the present invention, the structure is simple and compact, the offset amount can be reduced, the heat transfer efficiency can be improved, and high fixing performance can be achieved. There is an excellent effect that it can be done.

In particular, according to the second and third aspects of the invention, there is an excellent effect that the warm-up time can be reduced.

According to the invention of claim 4, there is an excellent effect that the above-mentioned effects can be obtained to the maximum.

According to the fifth and sixth aspects of the present invention, there is an excellent effect that the recording medium can be stably conveyed.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a schematic configuration of a fixing device according to a first embodiment.

FIG. 2 is a side view illustrating a schematic configuration of a fixing device according to a second embodiment.

FIGS. 3A and 3B are side views of a fixing device for explaining conveyance of a recording sheet according to a second embodiment.

FIG. 4 is a front view of a heating roller in a modification of the gap forming mechanism of the second embodiment.

FIG. 5 is a graph showing a measurement result of a surface temperature of a backup roller with respect to a gap length in a first experimental example.

FIG. 6 is a graph showing fixability with respect to gap length in a second experimental example.

[Explanation of symbols]

 1 7 Heating roller 2 Backup roller 3 Halogen lamp tube 4 Recording paper 5 Spring member 6 Stopper 8 Step

Claims (6)

[Claims] A fixing device for thermally fixing an unfixed image formed on a recording medium using a liquid developer in which part or all of a carrier liquid is a non-volatile solvent, a heating roller, Heating roller driving means for driving the roller,
A plurality of support rollers provided in the circumferential direction so as to face the heating roller, and a pressing force for pressing the recording medium toward the heating roller by the support roller is a unit in an axial direction of the support roller. A fixing device wherein the length is set to 50 g / cm or less. 2. A fixing device according to claim 1, wherein a gap is provided between said support roller and said heating roller. 3. The fixing device according to claim 2, wherein the gap is formed by providing a stepped portion having an outer diameter larger than the outer diameter of the fixing portion of the heating roller at both ends of the heating roller. Characteristic fixing device. 4. The fixing device according to claim 2, wherein the gap in the axial direction of the heating roller is not less than 20 μm and not more than 500 μm. 5. The fixing device according to claim 1, wherein the outer diameter D of the heating roller and the outer diameter d of the supporting roller.
A relation of 0 <d / D ≦ 0.5. 6. A fixing device according to claim 1, further comprising a support roller driving means for driving said support roller.