JP2003337488A - Heat fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly fix toner to a recording medium and to properly separate the recording medium fixed with the toner to be discharged in a heat fixing device for fixing toner to a recording medium. <P>SOLUTION: This heat fixing device for fixing an unfixed toner image to the recording medium 1 with heat is provided with a heating roller 12 having a heating element 11 inside; a fixing belt 10 wound around the heating roller and having a circumference longer than that of the heating roller; a pressing roller 13 press-contacted by the heating roller via the fixing belt, wherein a foam elastic body layer 13b, an elastic body layer 13c, and a release layer 13d are sequentially provided on a core bar 13a; and a pressing member 14 arranged on the inner side of a slacked part of the fixing belt formed on the side of a downstream in the carrying direction of the recording medium from at a press-contacting part between the heating roller and the pressing roller and pressed to the pressing roller via the fixing belt, wherein the radius of curvature of the recording medium at a delivery side is not more than 10 mm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device used to heat and fix an unfixed toner image on a recording medium in an image forming apparatus such as a copying machine or a printer. It is characterized in that the toner is sufficiently fixed on the recording medium even in the case of a full-color toner image, and the recording medium on which the toner image is fixed is appropriately separated from the fixing belt and the pressure roller. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a toner is supplied onto a recording medium and the toner is fixed on the recording medium by a fixing device.

Here, as such a fixing device, conventionally, as shown in FIG. 1, generally, a recording medium 1 to which toner t is supplied is guided between a pair of fixing rollers 2 and 3, and the pair of fixing rollers 2 and 3 is used. Toner t between the fixing rollers 2 and 3
Was fixed on the recording medium 1.

Further, as described above, the pair of fixing rollers 2,
In fixing the toner t on the recording medium 1 during the period of 3, the toner t is sufficiently fixed on the recording medium 1.
Heating elements 4 and 5 are provided in the fixing rollers 2 and 3, and the fixing rollers 2 and 3 are made of an elastic material such as rubber on the outer peripheral surfaces of the cored bars 2a and 3a made of metal. The fixing rollers 2 and 3 are provided with the elastic layers 2b and 3b, and the fixing rollers 2 and 3 are heated by the heat generating elements 4 and 5, and the fixing rollers 2 and 3 are pressed to each other. Elastic layers 2b, 3b provided on the outer peripheral portions of 2, 3
The length of the nip portion between them is increased so that the toner t is sufficiently heated and pressed to be fixed on the recording medium 1.

On the other hand, in recent years, the speed of the image forming apparatus as described above has been increased, and it has become necessary to sufficiently fix the toner t on the recording medium 1 at a high speed, and in a full-color image forming apparatus. In the case of the above, the toners t of a plurality of colors are supplied onto the recording medium 1 and the layer of the toner t becomes thick, and it is necessary to sufficiently fix the toner t having such a thick layer to the recording medium 1.

Here, in the fixing device as described above,
In order to sufficiently fix the toner t to the recording medium 1 at a high speed and to sufficiently fix the thickened toner t to the recording medium 1, the toner t is fixed between the fixing rollers 2 and 3. It became necessary to further increase the length of the nip part for heating and pressing.

In order to increase the length of the nip portion between the fixing rollers 2 and 3 as described above, the diameter of each of the fixing rollers 2 and 3 is increased or each of the fixing rollers 2 and 3 is increased. It is conceivable to increase the thickness of the elastic layers 2b and 3b provided on the outer peripheral portion of the sheet 3.

However, as described above, the fixing rollers 2, 3
When the diameter of is increased, the fixing device becomes larger,
There is a problem that the recording medium 1 is easily wound around the fixing roller 2 that comes into contact with the toner t. Further, when the thickness of the elastic layers 2b and 3b provided on the outer peripheral portions of the fixing rollers 2 and 3 is increased, it becomes difficult for heat to be transferred to the outer peripheral surfaces of the fixing rollers 2 and 3, so that the toner t is sufficiently supplied. The toner t cannot be sufficiently fixed on the recording medium 1 due to the inability to heat it, and a large amount of electric power is required to sufficiently heat the outer peripheral surfaces of the fixing rollers 2 and 3,
There were problems such as high running costs.

Therefore, in recent years, Japanese Patent Laid-Open No. 2000-2000
No. 89593, a fixing roller,
A fixing belt is stretched between a heating roller having a heater inside and pressed against the fixing belt from below to a pressure roller, and toner is applied to a nip portion between the fixing belt and the pressure roller. Is fed to the recording medium, and the toner is heated and pressed in this nip portion to fix the toner on the recording medium, and the recording medium having the toner thus fixed is discharged from the fixing roller side. It has been proposed to use a heat fixing device.

However, even in such a heat fixing device, there is a problem that the recording medium on which the toner is fixed tends to wind around the fixing belt which comes into contact with the toner, and when a toner image is formed on both sides of the recording medium. However, there is a problem in that the recording medium easily winds around the pressure roller, and particularly when a full-color toner image is formed on both surfaces of the recording medium, the above-mentioned winding is more likely to occur.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve various problems as described above in a heat fixing device for heating and fixing an unfixed toner image on a recording medium. Even if the toner image is a full-color toner image supplied with toner, the toner is sufficiently fixed on the recording medium, and the recording medium on which the toner image is fixed is properly separated from the fixing belt and the pressure roller. Is an issue.

[0012]

According to the present invention, in order to solve the above problems, in a heat fixing device for fixing an unfixed toner image on a recording medium by heating, a heating roller having a heating element therein; A fixing belt wound around the heating roller and having a peripheral length longer than that of the heating roller; pressed against the heating roller through the fixing belt, and a foamed elastic layer, an elastic layer, and A pressure roller on which a release layer is sequentially provided; disposed inside the slack portion of the fixing belt, which is formed on the downstream side in the recording medium conveyance direction from the pressure contact portion between the heating roller and the pressure roller. Then, a pressing member which is pressed by the pressure roller via the fixing belt and has a radius of curvature of 10 mm or less on the discharge side of the recording medium is provided.

Further, in the heat fixing device according to the present invention, the recording medium on which the unfixed toner image is formed is provided from the side of the heating roller having the heating element inside, the heating roller and the fixing belt which is laid across the pressing member. The unfixed toner image on the recording medium is heated and pressed between the heating roller and the pressure roller via the fixing belt while being guided between the fixing belt and the pressure roller. It is guided to a pressing member which is pressed against a pressure roller while being heated and pressed by the pressure roller, and the recording medium is pressed between the pressing member and the pressure roller via a fixing belt to record a toner image on the recording medium. Try to fix it on the medium.

By doing so, the unfixed toner image on the recording medium is heated and pressed in the long nip portion,
The unfixed toner image is sufficiently fixed on the recording medium, and even a full-color toner image in which toner of a plurality of colors is supplied and the toner layer is thick can be sufficiently fixed on the recording medium. Like Further, since the above-mentioned pressure roller is provided with the foamed elastic layer, the heat from the heating roller is also prevented from escaping through the pressure roller, and the unfixed toner image on the recording medium is efficiently heated, and the recording medium is efficiently heated. Will become fully established.

After fixing the toner image on the recording medium as described above, the recording medium is discharged from between the pressure roller and the fixing belt on the side of the pressing member.

In the heat fixing device according to the present invention, since the radius of curvature of the pressing member on the discharge side of the recording medium is 10 mm or less as described above, the recording medium on which the toner image is fixed as described above is used. Is easily separated from the fixing belt, and the recording medium is prevented from being wound around the fixing belt.

Further, in the heat fixing device according to the present invention, since the pressure roller is one in which the foamed elastic body layer, the elastic body layer and the release layer are sequentially provided on the core metal as described above is used. Even when the toner images are formed on both sides of the recording medium, the recording medium is prevented from being wound around the pressure roller. This is because the toner is prevented from adhering to the release layer of the pressure roller, and the pressure roller deforms significantly by the pressure applied by the pressure member, and the recording medium is not released when the pressure applied by the pressure member is released. It is considered that the recording medium is pushed in the direction away from the pressure roller due to the elastic restoring force of the elastic layer while being fed in the direction away from the pressure roller.

Further, in the present invention, since the elastic body layer is provided on the foamed elastic body layer in the pressure roller as described above, the foamed elastic body layer is largely deformed by the pressing by the pressing member as described above. However, the elastic restoring force of the elastic layer prevents the foamed elastic layer from being plastically deformed, and the durability is also improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A heating and fixing device according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

In the heat fixing device in this embodiment, as shown in FIG. 2, a fixing belt having a circumference longer than the heating roller 12 is provided on the outer circumference of the heating roller 12 in which the heating element 11 is provided. I'm trying to wrap around 10.

The heating roller 12 is pressed against the pressure roller 13 via the fixing belt 10, and the fixing belt 10 is formed on the downstream side of the pressure contact portion in the conveying direction of the recording medium 1. Inside the slack part of the
A roller-shaped pressing member 14 having a radius of 10 mm or less is arranged, and the pressing member 14 is pressed against the pressure roller 13.

In the heat fixing device of this embodiment, the heating roller 12 is rotated, and along with this, the fixing belt 10 is driven between the heating roller 12 and the pressing member 14, and Heating element 1 above
1, the fixing belt 10 is heated via the heating roller 12.

Then, in this state, the recording medium 1 supplied with the toner t is guided from the side of the heating roller 12 between the fixing belt 10 and the pressure roller 13, and the toner t supplied to the recording medium 1 is guided. Is heated and pressed between the heating roller 12 and the pressure roller 13 via the fixing belt 10, and the recording medium 1 is further fixed to the fixing belt 10 and the pressure roller 13.
While being heated and pressed between the pressure member 1 and the pressure member 14, the pressure roller 13 is guided between the pressure member 14 and the pressure member 1.
The recording medium 1 is pressed between the pressure roller 4 and the pressure roller 13 via the fixing belt 10 to fix the toner image on the recording medium 1. Thus, the recording medium 1 on which the toner t is fixed is fixed.
Are discharged from between the fixing belt 10 and the pressure roller 13 on the pressing member 14 side.

In the heat fixing device of this embodiment, the heating roller 12 is made of a material having excellent mechanical strength and thermal conductivity and formed into a cylindrical shape. For example, a metal such as aluminum, SUS, iron, copper, or brass, ceramics, fiber-reinforced metal, or the like can be used.

The heating element 11 is not particularly limited as long as it can be housed inside the heating roller 12, and for example, a halogen heater or the like can be used. Then, the surface temperature of the heating roller 12 is measured by a thermosensitive element (not shown) such as a thermistor or a temperature sensor, and based on this, the surface temperature of the heating roller 12 becomes constant by a control device (not shown). Are controlled.

On the other hand, the pressure roller 13 is formed into a cylindrical shape, and the foamed elastic layer 13b is formed on the outer periphery of the cored bar 13a.
The elastic layer 13c and the release layer 13d are sequentially provided.

The core metal 13a of the pressure roller 13
As in the case of the above heating roller 12, for example, a metal such as aluminum, SUS, iron, copper, brass, or the like,
It is possible to use those made of ceramics, fiber-reinforced metal, or the like.

Further, in the pressure roller 13, as the material of the foamed elastic body layer 13b provided on the outer periphery of the core metal 13a, for example, foamed silicone rubber or the like can be used.

As the foamed elastic layer 13b, it is preferable to use one having an average cell diameter of 150 to 300 μm. This is the foam elastic layer 1
When the average cell diameter in 3b is less than 150 μm, the heat insulating effect in the foamed elastic body layer 13b decreases, and the heat of the fixing belt 10 heated by the heating roller 12 easily escapes. This is because if it exceeds, the strength of the foamed elastic body layer 13b decreases and the durability deteriorates.

As for the hardness of the foamed elastic layer 13b, it is preferable to use one having an Asker C hardness of 20 to 60 degrees. This is the foam elastic layer 13
When the Asker C hardness in b is less than 20 degrees, the strength of the foamed elastic body layer 13b decreases and the durability deteriorates. On the other hand, when the Asker C hardness exceeds 60 degrees, the foamed elastic body layer 13b is deformed. The recording medium 1 supplied with the toner t cannot be sufficiently heated and pressed between the recording medium 1 and the heating roller 12 via the fixing belt 10, and the recording medium 1 is pressed by the pressure roller 13 This is because it becomes easier to wrap around.

When the thickness of the foamed elastic layer 13b is thin, the heat of the fixing belt 10 heated by the heating roller 12 can easily escape, and the foamed elastic layer 1 can be easily released.
The deformation of 3b is reduced, and the recording medium 1 to which the toner t is supplied cannot be sufficiently heated and pressed between the recording medium 1 and the heating roller 12 via the fixing belt 10.
When the recording medium 1 is easily wound around the pressure roller 13 and the foam elastic layer 13b becomes too thick, the recording medium 1 is fixed to the fixing belt 10 or the pressure roller 13.
It becomes easier to get around. Therefore, this foamed elastic body layer 1
The thickness of 3b is preferably in the range of 2 to 8 mm,
More preferably, it is in the range of 3 to 7 mm.

When providing the elastic body layer 13c on the foamed elastic body layer 13b, a known non-foaming elastic material can be used as the material thereof.
Silicone rubber, fluororubber, and the like can be used, and it is particularly preferable to use silicone rubber having a small surface tension and excellent elasticity and thermal stability. As such silicone rubber, RTV silicone rubber, HTV silicone rubber, etc. can be used. Specifically, polydimethyl silicone rubber (MQ), methylphenyl silicone rubber (PMQ), methyl vinyl silicone rubber ( VMQ), fluorosilicone rubber (FV
MQ) or the like can be used.

Further, in providing the elastic layer 13c in this way, if the elastic layer 13c is thin, the elastic restoring force in the elastic layer 13c becomes weak and the recording medium 1 is placed on the pressure roller 13. While the elastic foam layer 13b is easily wrapped around, and the elastic foam layer 13b is easily plastically deformed, the durability of the pressure roller 13 is deteriorated. On the other hand, when the elastic layer 13c becomes too thick, the elastic foam layer 13b described above is formed. The heat insulating effect due to is weakened, and the heat of the fixing belt 10 heated by the heating roller 12 easily escapes through the elastic layer 13c. For this reason, it is preferable that the thickness of the elastic layer 13c is in the range of 0.2 to 3 mm, and more preferably in the range of 0.5 to 2 mm.

Regarding the hardness of the elastic layer 13c, if the hardness becomes too high, the elastic layer 13c
Of the recording medium 1 to which the deformation of the toner is reduced and the toner t is supplied.
Cannot be sufficiently heated and pressed between the heating roller 12 and the fixing belt 10 and the recording medium 1 is easily wrapped around the pressing roller 13, while the hardness is low, The durability of the pressure roller 13 is reduced. Therefore, the hardness of the elastic layer 13c is
JIS-A hardness of 1 to 40 degrees, preferably 5 to 20 degrees,
More preferably, it should be in the range of 6 to 15 degrees.

Further, when the release layer 13d is provided on the elastic layer 13c, a fluororesin, a silicone rubber, a fluororubber or the like having low adhesion of the toner t can be used as the material thereof. Fluorine resin is preferably used.

As the above-mentioned fluororesin, for example, perfluoroalkoxy fluororesin (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FE
P), polyethylene tetrafluoroethylene (ETF
E), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), vinyl fluoride (PV
Fluorine-based resins such as F) can be used. Further, as the fluororubber, for example, vinylidene fluoride rubber,
Fluorosilicone rubber, tetrafluoroethylene / propylene rubber, tetrafluoroethylene / perfluorovinyl ether rubber, tetrafluoroethylene / perfluoro rubber and the like can be used.

The thickness of such a release layer 13d is
It is usually in the range of 5 to 100 μm, preferably 10 to 3
The range is 0 μm.

As the fixing belt 10 described above,
For example, a resin made of thermosetting polyimide, thermoplastic polyimide, polyamide, polyamide-imide, or the like, or one made of a metal such as nickel, stainless steel, or copper can be used. From the standpoint of improving heat resistance, abrasion resistance, chemical resistance, etc. of the fixing belt 10, it is preferable to use a thermosetting polyimide.
Further, in order to improve the thermal conductivity of the fixing belt 10, it is preferable to use one made of a metal such as nickel, stainless steel, or copper.

Then, in this fixing belt 10,
As shown in FIG. 2, when the release layer 10b is provided on the outer peripheral surface of the belt base material 10a made of the above materials, the toner t is prevented from adhering to the outer peripheral surface of the fixing belt 10. In addition, the recording medium 1 is properly separated from the fixing belt 10. As a material for such a release layer 10b, similar to the release layer 13d in the pressure roller 13 described above, a fluororesin, a silicone rubber, a fluororubber or the like having low adhesion of the toner t can be used. .

Further, in this fixing belt 10, as shown in FIG. 3, an elastic layer 10c is provided between the belt base material 10a made of the above material and the release layer 10b. The fixing belt 10 is the recording medium 1
The toner adheres well to the toner t above, and the occurrence of uneven fixing is suppressed. In addition, as a material of such an elastic layer 10c, the elastic layer 13c in the pressure roller 13 is used.
A known elastic material similar to the above can be used.

Here, when the elastic layer 10c is provided on the fixing belt 10 as described above, this elastic layer 1
If the thickness of 0c becomes too thick, the fixing belt 10
Since it takes time to sufficiently heat the elastic layer 10c, the thickness of the elastic layer 10c is preferably 500 μm or less, and more preferably 100 to 200 μm. When the release layer 10b is provided as described above, the thickness of the release layer 10b is 5 to 100 μm.
m, preferably 10 to 30 μm.

The circumference of the fixing belt 10 is longer than that of the heating roller 12 as described above, and the pressing member 14 is arranged inside the slack portion of the heating roller 12 so that the pressure roller 1 is pressed.
If it can be pressed against 3,
Generally, the circumference of the fixing belt 10 is set to the heating roller 1.
It is about 1.1 to 2.0 times the outer circumference of 2.

As the roller-shaped pressing member 14, a member made of a material having excellent mechanical strength is used, and for example, aluminum, SUS, iron, copper,
Metals such as brass, ceramics, and fiber reinforced metals are used.

In the heat fixing device of this embodiment, the pressing member 14 having a small radius of 10 mm or less as described above is pressed against the pressure roller 13 via the fixing belt 10, and the pressing member 14 is pressed. The recording medium 1 is pressed between the pressure roller 14 and the pressure roller 13 via the fixing belt 10 to fix the toner image on the recording medium 1. Thus, the recording medium 1 on which the toner t is fixed is fixed. Since the recording medium 1 is discharged from between the fixing belt 10 and the pressure roller 13 on the side of the pressing member 14, the recording medium 1 is fixed to the fixing belt 10.
Also, it is possible to suppress winding around the pressure roller 13.

When the roller-shaped pressing member 14 is used as described above, the recording medium 1 is the fixing belt 1.
The radius is preferably 4 to 4 in order to suppress the winding around 0.
A range of 10 mm, more preferably a range of 5 to 7 mm is used. Further, in this embodiment, the pressing member 14 in the shape of a roller is used, but the pressing member 14 is not limited to the one in the shape of such a roller, and the pressure roller is interposed via the fixing belt 10. It is also possible to use the one in which only the portion which is pressed by 13 and ejects the recording medium 1 has a roundness with a radius of curvature of 10 mm or less. In this case, the radius of curvature is preferably in the range of 2 to 10 mm, more preferably 3 to 8
Use the one in the range of mm.

Next, in the heat fixing device shown in FIG. 2, the fixing belt 10 has a thickness of 70 μm.
On the outer peripheral surface of the belt base material 10a made of a polyimide layer of m, an elastic layer 10c made of a silicone rubber layer having a thickness of 200 μm and a release layer 10b made of a silylperfluoroalkoxy fluororesin layer having a thickness of 30 μm are provided.
A cylindrical roller made of SUS having an outer diameter of 40 mm and a thickness of 1 mm is used as the heating roller 12 having a circumference of 148 mm.
As the above, a halogen heater was used, and as the pressing member 14, a SUS roller having a diameter of 10 mm was used.

Further, in the pressure roller 13 described above,
A cylindrical SUS with an outer diameter of 40 mm and a thickness of 3 mm
A foamed elastic body layer 13b made of silicone sponge having an Asker C hardness of 34 degrees, and J
An elastic layer 13c made of silicone rubber having an IS-A hardness of 10 degrees and a release layer 13d made of perfluoroalkoxy fluororesin having a thickness of 30 μm are provided.
Each pressure roller in which the thickness of the foam elastic body layer 13b and the elastic body layer 13c is changed is used.

(Experiment 1) In the heat fixing device of Experiment 1, the thickness of the foam elastic layer was set to 4 mm, and the thickness of the elastic layer was set to 0 as shown in Table 1 and FIG.
mm, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 m
m, 4 mm, and 5 mm pressure rollers were used.

Then, by rotating the heating roller,
While rotating the fixing belt, the heating element composed of the halogen heater is heated by applying an electric power of 700 W, and at a portion immediately before the fixing belt is nipped by the pressure roller and the heating roller. , The heating rate of the fixing belt in each heating and fixing device (° C / se
c) was measured, and the results are shown in Table 1 and FIG.

As a result, as the thickness of the elastic layer provided on the pressure roller becomes thicker, the temperature rising rate (° C./sec) of the fixing belt becomes slower.

Next, each heat fixing device using each of the above pressure rollers was replaced with a commercially available copying machine (CF-9 manufactured by Minolta Co., Ltd.).
No. 00) was mounted on a modified one, and image unevenness in the image fixed on the recording medium and separability of the recording medium were evaluated, and the results are shown in Table 1.

Here, regarding the image unevenness in the image fixed on the recording medium, as recording medium, A4 size plain paper (64 g / m ² ) and A4 size OHP sheet are used, and cyan toner and magenta toner are used. Ten solid images and half pattern images using yellow toner and black toner were fixed, and image unevenness in the fixed images was visually evaluated. Regarding the evaluation of the image unevenness, the case where there is no image unevenness in both the plain paper and the OHP sheet and the translucency of the OHP sheet is high is ⊚, and there is no image unevenness in the plain paper, and
○, if there is some image unevenness on the HP sheet
The case where slight image unevenness occurs on both the plain paper and the OHP sheet is indicated by Δ, and the case where image unevenness is severe on both the plain paper and OHP sheet is indicated by X.

Regarding the separability of the recording medium, an A4 size plain paper (64 g / m ² ) having a solid image of black toner already fixed on a portion other than 3 mm from the front end on the back surface was used as the recording medium. This plain paper was fed in the longitudinal direction, and 1000 sheets each having a solid image of black toner formed on a portion other than 3 mm from the leading end thereof were fixed, and the number of occurrences of jam was examined. Then, the separability is evaluated by ⊚ when no jam is generated, ◯ when one jam is generated, and Δ when two or four jams are generated.
The case where the occurrence of jams is 5 or more is indicated by x.

[0054]

[Table 1]

As a result, in the heat fixing device using the pressure roller provided with the elastic layer, the image in the fixed image is compared with the heat fixing device using the pressure roller not provided with the elastic layer. The occurrence of unevenness is suppressed, and the separability of the recording medium is also improved. Particularly, in a heat fixing device using a pressure roller provided with an elastic layer having a thickness of 0.5 mm or more, The occurrence of image unevenness in the fixed image was suppressed, and the separability of the recording medium was also improved.

The rate of temperature rise of the fixing belt (° C.
/ Sec), the thickness of the elastic layer provided on the pressure roller is preferably in the range of 0.2 to 3 mm, and the thickness of the elastic layer is 0.5 to 3 mm.
It was more preferable to have a range of 2 mm.

(Experiment 2) In the heat fixing apparatus of Experiment 2, the thickness of the elastic body layer was set to 1 mm, and the thickness of the foamed elastic body layer was set to 0 as shown in Table 2 and FIG.
mm, 2mm, 3mm, 5mm, 6mm, 7mm, 8m
m pressure rollers were used.

Then, in the same manner as in Experiment 1 above, the temperature rising rate (° C./sec) of the fixing belt in each heating and fixing device was measured, and the results are shown in Table 2 and FIG.

As a result, when the pressure roller provided with the elastic foam layer is used, the temperature rising rate (° C./° C.) of the fixing belt is higher than that when a pressure roller not provided with the elastic foam layer is used.
sec) was getting faster.

Further, as in the case of Experiment 1 described above, each of the above heat fixing devices was replaced with a commercially available copying machine (CF manufactured by Minolta Co., Ltd .: CF).
-900) was mounted on a modified product, and image unevenness in the image fixed on the recording medium and separability of the recording medium were evaluated, and the results are shown in Table 2.

[0061]

[Table 2]

As a result, in the heat fixing device using the pressure roller provided with the foam elastic layer having a thickness of 2 to 8 mm, the heat fixing device using the pressure roller not provided with the foam elastic layer is used. Compared with the above, the separability of the recording medium was improved. In particular, when a pressure roller provided with a foamed elastic layer having a thickness in the range of 3 to 7 mm, more preferably a foamed elastic layer having a thickness in the range of 3 to 6 mm is used, the recording medium is further separated. The sex was improved.

Further, the rate of temperature rise of the fixing belt (° C.
/ Sec), it was more preferable that the thickness of the elastic foam layer provided on the pressure roller was in the range of 5 to 7 mm.

In the heat fixing device of the above embodiment, the heating roller 12 is made of a material such as SUS having excellent mechanical strength and thermal conductivity.
It is also possible to use a roller having an elastic layer formed on the surface thereof. Further, as the elastic body layer, the same material and the same thickness as the elastic body layer 13a of the pressure roller 13 can be used. By using the heating roller 12 having the elastic layer in this way, the recording medium 1 can be held more softly at the nip portion with the pressure roller 13. Therefore, even when the fixing belt 10 that does not have the elastic layer as shown in FIG. 2 is used, the toner image is properly fixed and a high quality image can be obtained. .

[0065]

As described above in detail, in the heat fixing device of the present invention, the recording medium on which the unfixed toner image is formed is fed from the side of the heating roller having the heating element therein.
The unfixed toner image on the recording medium is guided between the heating roller and the pressure roller and the fixing belt spanning the heating member to heat and press the unfixed toner image between the heating roller and the pressure roller via the fixing belt. At the same time, it is guided to a pressing member that is pressed against the pressure roller while being heated and pressed between the fixing belt and the pressure roller, and further, between the pressing member and the pressure roller via the fixing belt. Pressurize the recording medium of
In fixing and discharging the toner image on this recording medium, a pressure roller having a foamed elastic body layer, an elastic body layer and a release layer sequentially provided on a core metal is used, and the recording medium is used as the pressing member. The one having a radius of curvature on the discharge side of 10 mm or less was used.

As a result, in the heat fixing device according to the present invention, the unfixed toner image on the recording medium is efficiently heated and pressed in the long nip portion so that the unfixed toner image is sufficiently fixed on the recording medium. As a result, a full-color toner image in which toner of multiple colors has been supplied and the toner layer has become thicker can be sufficiently fixed on the recording medium, and the recording medium on which the toner image has been fixed is used for fixing with a pressure roller. It is now properly ejected without wrapping around the belt.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a conventional fixing device that guides a recording medium supplied with toner between a pair of fixing rollers to fix the toner on the recording medium.

FIG. 2 is a schematic explanatory diagram of a heat fixing device according to an embodiment of the present invention.

FIG. 3 is a schematic explanatory view showing an example of a fixing belt used in the heat fixing device of the embodiment.

FIG. 4 is a schematic explanatory view showing another example of a fixing belt used in the heat fixing apparatus of the embodiment.

FIG. 5 is a graph showing the relationship between the thickness (mm) of the elastic layer provided on the pressure roller and the temperature rising rate (° C./sec) of the fixing belt in Experiment 1 of the present invention.

FIG. 6 is a graph showing the relationship between the thickness (mm) of the elastic foam layer provided on the pressure roller and the temperature rising rate (° C./sec) of the fixing belt in Experiment 2 of the present invention.

[Explanation of symbols]

1 recording medium 10 fixing belt 11 heating element 12 Heating roller 13 Pressure roller 13a core metal 13b Foamed elastic layer 13c elastic layer 13d Release layer 14 Pressing member t toner

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shozo Miyazaki             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Co., Ltd. (72) Inventor Toshiya Natsuhara             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Co., Ltd. (72) Inventor, Hoichi Sano             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Co., Ltd. F term (reference) 2H033 AA02 AA16 BA11 BA12 BA17                       BA20 BA21 BA25 BB02 BB18                       BB29 BB30 BB33 BB38

Claims (5)

[Claims] 1. A heating and fixing device for heating and fixing an unfixed toner image on a recording medium; a heating roller having a heating element therein; and a fixing roller wound around the heating roller and having a peripheral length longer than that of the heating roller. A belt; a pressure roller that is pressed against the heating roller via the fixing belt and has a foamed elastic body layer, an elastic body layer and a release layer sequentially provided on a core metal; It is arranged inside the slack portion of the fixing belt formed on the downstream side in the conveying direction of the recording medium from the pressure contact portion with the pressure roller, and is pressed by the pressure roller via the fixing belt. A heating and fixing device comprising: a pressing member having a radius of curvature of 10 mm or less on the discharge side of the recording medium. 2. The heat fixing device according to claim 1, wherein the foam elastic body layer in the pressure roller is made of foam silicone rubber. 3. The heat fixing device according to claim 1, wherein the foamed elastic body layer of the pressure roller has an average cell diameter of 150 to 300 μm. 4. The thickness of the elastic body layer in the pressure roller is in the range of 0.2 to 3 mm, and the thickness of the foamed elastic body layer is in the range of 2 to 8 mm. Item 5. The heat fixing device according to any one of Items 1 to 3. 5. The J of the elastic layer in the pressure roller.
The IS-A hardness is in the range of 1 to 40 degrees, and the Asker C hardness of the foamed elastic body layer is in the range of 20 to 60 degrees, The heating according to any one of claims 1 to 4. Fixing device.