JP3076882B2 - Thermal fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing apparatus used in an electrophotographic copying machine or a recording apparatus, and more particularly, to a method in which a toner image is thermally fixed on a sheet and paper wrinkles occur when the sheet is conveyed. The present invention relates to a heat fixing device suitable for preventing the occurrence of heat.

[0002]

2. Description of the Related Art In general, a heat fixing device has a temperature of, for example, 5 degrees.
It is used in an environment where the humidity varies widely, such as ~ 35 [deg.] C and a humidity of 15-90%, and the mechanical properties of the paper used in the apparatus vary greatly according to the environmental change. Moreover, the paper temperature is 180 ° C to 200 ° C from the ambient temperature.
Is rapidly heated to the fixing temperature, and the paper is easily deformed and wrinkles are easily generated. There are many deformation modes of paper wrinkles, and paper has a complicated appearance.

Conventionally, a heat roller using a pressure roller having a uniform outer diameter as well as a heating roller having a uniform outer diameter, and fixing a toner image on a sheet while pressing and transporting the roller between the rollers. It is well known that the paper is easily deformed in the transport direction, that is, vertical wrinkles are easily generated. Many inventions have been made to solve this vertical wrinkle problem.

For example, Japanese Unexamined Patent Publication (Kokai) No. 60-128472 discloses an inverted crown-shaped heating roller whose outer diameters at both ends are larger than that of a central portion. A heat roller fixing device that reduces the occurrence of paper wrinkles by intersecting axes with each other is disclosed. As described in this publication, in a heat fixing device simply installed in parallel with an inverted crown-shaped heating roller and a pressure contact roller having a uniform outer diameter, the outer diameter of both ends of the heating roller is increased. Thus, the vertical wrinkles of the paper can be prevented, but the horizontal wrinkles in the direction crossing the transport direction of the paper, such as the phenomenon that the side of the paper is wavy or the paper is deformed on the ribs, are easily generated. Therefore, the invention disclosed in Japanese Patent Application Laid-Open No. 60-128472 is
In order to prevent lateral wrinkles, a heating roller and a pressure roller are crossed with each other. However, when the inverted crown-shaped heating roller and the pressing roller having a uniform outer diameter are crossed with each other, the transport direction of the sheet tends to be unstable.

In Japanese Utility Model Laid-Open Publication No. 1-155072,
An inverted crown-shaped heating roller whose outer diameter at both ends is larger than that of the center and a positive crown-shaped pressure roller whose outer diameters at both ends are smaller than that of the center are built in the heating roller. There is disclosed an invention in which the generation of paper wrinkles is reduced by controlling the plurality of heat sources to change the shape of the pressing roller to an optimal state. However, the paper wrinkle prevention mechanism of the present invention tends to be too complicated as a whole device configuration.

[0006]

In the above-mentioned prior art, in the heat-fixing roller setting device in which a heating roller having an inverted crown shape and a pressure-contact roller having a uniform outer diameter are crossed with each other in an axis, a sheet of paper is formed. There is a problem that the transport direction is likely to be unstable. In addition, a reverse crown-shaped heating roller and a normal crown-shaped pressure roller are used, and a plurality of heat sources incorporated in the heating roller are controlled to perform pressure welding. In the paper wrinkle prevention mechanism that changes the shape of the roller to an optimal state, there is a problem that the apparatus becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat fixing device capable of preventing the occurrence of paper wrinkles such as a paper waving phenomenon with a simple device configuration.

[0008]

To achieve the above object, according to the Invention The thermal fixing device of the present invention includes a heating roller outer diameter of large inverted crown shape from the central portion of the built both ends a heat source, the heating b - and uniform pressure roller is arranged parallel to that outer diameter La, heating b - a first driving means for driving the La or pressure roller, said pressure being sandwiched between the heating roller and the pressure roller <br In a heat fixing device provided with a sheet discharging means for discharging the sheet on which the toner image is fixed by the heat roller to the downstream side, the sheet discharging means includes a plurality of driving rollers arranged in the width direction of the sheet.
Roller, and the drive roller is arranged to face the drive roller.
A plurality of driven rollers for nipping the paper between them, and a driving roller
Drive means for driving the driven roller and each of the driven rollers
And pressing means for pressing against the drive roller side.
Pressure on both sides of the paper in the width direction of the paper.
It is characterized by being relatively strong in the center.

The heating roller is made of fluororesin.
The pressing roller is covered with silicone rubber and driven
Rollers are rubber with a high coefficient of friction, driven rollers have a coefficient of friction
It is preferable that each of them is made of an engineering plastic having a low hardness.

Further, the heat fixing device of the present invention has a built-in heating source.
The outer diameter of both ends is larger than that of the center.
A heating roller and an outer diameter arranged in parallel with the heating roller
Driving uniform pressure roller and heating roller or pressure roller
The first driving means, and a gap between the heating roller and the pressure roller.
Paper having the toner image fixed by the heating roller
Fixing device provided with a paper discharging means for discharging paper to the downstream side
, The paper discharge means is arranged in the width direction of the paper
Multiple discharge belts running in the paper transport direction and discharge belts
The paper is sandwiched between the discharge belt
Driven rollers, and a second driven roller for driving the discharge belt.
Driving means and each of the driven rollers separately on the discharge belt side
And a pressing means for pressing, wherein the pressing force of the pressing means is made relatively stronger at both ends in the width direction of the paper than at the center in the width direction of the paper.

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

According to the above construction, the heating roller has an inverted crown shape in which the outer diameters of both ends are larger than the center, so that the transport amount at both ends of the paper is smaller than the transport amount at the central portion of the paper. The difference in the transport amount between the end portion and the center portion of the sheet acts to spread both end portions of the sheet on the upstream side (entrance side) of the heating roller, thereby preventing vertical wrinkling of the sheet. Due to the difference in the amount of conveyance, lateral wrinkling and waving are likely to occur at both ends of the sheet on the downstream side (exit side) of the heating roller.

Regarding the sheet discharging means provided on the downstream side of the heating roller and the pressure roller, in the heat fixing device of the present invention , the outer peripheral speed of the driving roller driven by the driving means is the paper conveying speed by the heating roller and the pressure roller. It is set to be faster, and to the pressing force applied to the drive roller which is set lower than in holding force of the sheet by the heating roller and the pressure roller, the drive roller is a tension in the conveying direction while slipping on the sheet And transport the paper.

[0020]

In the heat fixing device of the present invention, the pressing force applied to the driving roller at the center of the sheet by the pressing means is set to be stronger than the driving rollers at both ends in the sheet width direction. A relatively strong tension is applied to the central portion in the width direction of the sheet rather than the sheet portion, thereby preventing lateral wrinkles and waving occurring at both ends of the sheet.

[0022]

The sheet discharging means includes a driving roller and a driven roller.
Instead of rollers, a discharge belt can be adopted
You. In this manner, the same effect as the above-described paper discharging means is obtained in that a relatively strong tension is applied to the central portion in the width direction of the paper from both ends in the width direction of the paper, and as a result, similarly, Prevents horizontal wrinkling and waving at both ends of the paper.

[0024]

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a heat fixing device according to an embodiment of the present invention. The heat fixing device of this embodiment includes a heating roller 1 having a built-in heating source 3, an outer diameter of both ends is larger than that of a central portion, and has an inverted crown shape and both ends are rotatably supported by bearings (not shown). A pressure roller 2 having a uniform outer diameter and installed in parallel with the heating roller 1 and rotatably supported by a bearing (not shown); and a pressure means (not shown) for pressing the pressure roller 2 against the heating roller 1. A heating roller driving means as a first driving means (not shown) for driving the heating roller 1 via a gear 4 provided at an end of the heating roller 1; A discharge means for discharging the sheet 20 sandwiched and sent out by the roller 1 and the pressure roller 2 further downstream. The surface of the heating roller 1 is coated with a fluorine resin, and the surface of the pressing roller 2 is coated with a silicone rubber. The heating source 3 is, for example, a halogen lamp.

The discharging means includes a heating roller 1 and a pressing roller 2
A drive discharge roller 50 provided on the surface side of the sheet 20 and a driven discharge roller 51 that faces the drive discharge roller 50 and the sheet 20 to face each other; A discharge roller driving means (not shown) is provided as second driving means (not shown) that rotationally drives the discharge roller 50 via a gear 53 provided at an end thereof.

The drive discharge roller 50 has two central drive rollers 5 provided at the center in the width direction on the upper side of the paper 20.
0b and two side drive rollers 50a provided at both ends in the width direction. A driven discharge roller 51 located below the paper 20 is a roller group of a central driven roller 51b paired with the central driving roller 50b and a side driven roller 51a paired with the side driving roller 50a. It is composed of The center drive roller 50b and the side drive roller 50a are each fixedly attached to the shaft 54, and are integrally driven by a discharge roller drive unit. On the other hand, the center driven roller 51b and the side driven roller 51
a is separately pressed upward by a spring 52b and a spring 52a, respectively, and is rotated by being driven by each of the center drive roller 50b and the side drive roller 50a. Each of the drive discharge roller 50 and the driven discharge roller 51 is made of engineering plastics having a low coefficient of friction.

Further, as a feature of the present embodiment, the outer diameters of the central driving roller 50b and the central driven roller 51b at the center of the paper are different from those of the side driving roller 5 at the end on the paper side.
0a, which is larger than the outer diameter of the side driven roller 51a.

Next, the operation of the heat fixing device having the above configuration will be described. The heating roller 1 is heated by the heating means 3 and is driven by the heating roller driving means while sandwiching the sheet 20 between the heating roller 1 and the pressing roller 2 to rotate in the direction of arrow a. The press roller 2 rotates in the direction of arrow b following the heating roller 1. The paper 20 is heated by the heating roller 1 and the pressure roller.
The unfixed toner (not shown) on the sheet 20 is heated by the heating roller 1 to be melted and fixed on the sheet 20 in accordance with the rotation of the roller 2. Pressure roller 2
Is from 0.2 kg / cm (2 N / cm) to 2.0
Heating boiler with a sufficiently high linear pressure of kg / cm (20 N / cm)
Since the paper 20 is pressed by the roller 1, the transport amount of the paper 20 at the center in the width direction of the paper is small, and the paper 20 is transported at both ends in the width direction of the paper in accordance with the outer diameter of the heating roller 1 having an inverted crown shape. The amount is large. This difference in the amount of conveyance acts as a force to spread the sheet 20 in the direction perpendicular to the sheet conveyance direction at the entrance side of the heating roller 1, thereby preventing vertical wrinkles generated on the sheet. However,
Since the paper 20 is rapidly heated to about 200 ° C. by the heating roller 1, paper wrinkles due to the difference in the transport amount are likely to be generated on the downstream side of the heating roller.

Center drive roller 50b and side drive roller 5
0a is a drive discharge roller composed of a total of four roller groups, two each.
The transport speed of the roller 50 is set at a high speed of about 5% to 30% on average on the transport speed of the heating roller 1. However, the central driven roller 51b and the side driven rollers are two in total and four in total. The pressing force of the driven discharge rollers 51 composed of the roller groups is a light load of about 200 g (2N), and slips against the paper 20, so that the transport speed of the paper 20 is determined by the heating roller. You. However, since the outer diameter of the center roller 50b in the width direction is larger than the outer diameter of the end roller 50a in the width direction, it occurs at both ends of the sheet 20 downstream of the heating roller 1. Paper wrinkles can be prevented by relatively strongly pulling the looseness of the paper, particularly at the center of the paper 20.

Table 1 shows the results of a paper transport experiment performed using the thermal fixing device shown in FIG. Hereinafter, description will be given based on Table 1. Table 1 is a table showing experimental conditions and experimental results.

[0033]

[Table 1]

As an experimental condition, the case where the outer diameter of the driving discharge roller 50 is variously changed is shown. As an experimental condition other than the driving discharge roller, the outer diameter of the heating roller is 23 m.
m, the outer diameter of the pressure roller is 19 mm, the pressing force of the pressure roller is 0.45 kg / cm (4.5 N / cm), and the paper width is 2
At 57 mm, the total pressing force of the pressure roller is 11.6 kg (11
3N). The inverse crown amount of the heating roller is 0.1 mm in diameter. The set temperature of the heating roller is 200 ° C. to clarify the tendency of paper deformation.
The experiment was conducted at a higher temperature. Experiments were conducted with respect to two types of heating roller setting speeds, 30 mm / s and 60 mm / s.

The driving speeds of the side driving roller 50b and the center driving roller 50a constituting the driving discharge roller 50 with respect to the set speed of the heating roller are different depending on the respective rollers. , 16% at 13.8 mm, 1
The speed increase is 20% at 4.4 mm and 27% at 15.3 mm.

The experimental results shown in Table 1 were obtained by evaluating the waving of the paper. The crosses in the table indicate that the waving is too large to be used for general use. Those that can be used, the double circles in the table indicate those that have a small degree of undulation and can be sufficiently used.

Hereinafter, the experiment Nos. The experimental results will be discussed in accordance with the following. Experiment No. 1-1 to No. 1 1-3
Is a side drive roller 50a as a comparative example as in the conventional apparatus.
And the center drive roller 50a have the same outer diameter, and the outer diameters are 13.0 mm, 13.8 mm, and 14.0 mm, respectively. Paper transport speed is 60mm
In the case of / s, there is a wave, but the paper can be used for a while. However, when the sheet conveying speed is 30 mm / s, the sheet is so wavy that it cannot withstand general use. Although the cause of the change in the wavy state of the paper due to the difference in the paper transport speed is unknown, it can be seen that the three comparative examples have insufficient performance especially at low speeds.

No. 1-4 is also a comparative example, and the side drive roller 5
0a and the outer diameter of the central drive roller 50b was 13.0 mm. Contrary to the present invention, the drive discharge roller is such that the rollers at both ends have the same diameter. Is larger than some rollers. This combination had the worst results in Table 1 for both the paper conveyance speeds of 60 mm / s and 30 mm / s, which had many waves and could not withstand general use.

No. Nos. 1-5 and No. 1; 1-6 are the experimental results of the present invention. The outer diameter of the drive discharge roller is such that the outer diameter of the central drive roller 50b is equal to the side drive roller 50a.
The driving speed is set to be relatively high at the central portion of the sheet. No. 1-5, the side drive roller 50b has a diameter of 13.0 mm, and the center drive roller 50a has a diameter of 1
Although the paper has a diameter of 4.4 mm and has a wavy shape at both the sheet conveying speeds of 30 mm / s and 60 mm / s, it reaches a level that can be used for a while. No. In Nos. 1-6, the average drive speed of the drive discharge roller is No. 1 when the side drive roller 50a has a diameter of 13.8 mm and the center drive roller 50b has a diameter of 15.3 mm. It is set faster than 1-5. In this case, the degree of the undulation was slight and the situation was sufficient for use.

Next, a second experiment was performed to confirm the effects of the present invention. Table 2 shows the results. Table 2 is a table showing experimental results of the present invention and a comparative example, and is a result of an experiment conducted at a high temperature and a high humidity of 35 ° C. and 90% Rh in a bad environment in which paper is likely to wrinkle.

[0041]

[Table 2]

In the experiment, the degree of influence on paper wrinkles was examined by changing the amount of reverse crown of the heating roller. Those described as Comparative Examples in Table 2 correspond to Nos. In Table 1. No. 1-1 of the conventional apparatus using the side drive roller and the central drive roller in the conventional apparatus and the one described as the present invention are described in Table 1.
The side drive roller and the center drive roller shown in 1-5 are used. The paper transport speed is 60 mm / s. In this experiment, the state of wrinkles was examined by passing 20 sheets each.

In Table 2, Experiment No. When the reverse crown amount of the heating roller indicated by 2-1 was 0 mm, horizontal wrinkles did not occur on the paper, but vertical wrinkles occurred. The frequency of occurrence of vertical wrinkles on the paper in the conventional example and the present invention is considered to be substantially the same. This indicates that the frequency of vertical wrinkles does not change depending on the shape of the driving discharge roller. In other words, since the crown amount of the heating roller is dominant with respect to the vertical wrinkle, even if a slight tension is applied to the central portion of the paper downstream of the heating roller, the influence on the vertical wrinkle is not affected. It indicates that there is no.

Experiment No. The reverse crown amount of 2-2 is 0.0
When the width is 5 mm, no wrinkles or vertical wrinkles occur on the paper, and the performance is satisfied. The conventional example also shows that the occurrence of sheet wrinkling can be reduced by appropriately selecting the heat fixing conditions.

Experiment No. Inverse crown amount of 2-3 is 0.1
At 0 mm, no vertical wrinkles occurred on the paper, but rib-like horizontal wrinkles sometimes occurred. Overall, the frequency of occurrence of vertical wrinkles in the conventional example and the present invention was almost the same in 0 out of 20 sheets. However, in the conventional example, horizontal wrinkles occurred, whereas in the present invention, horizontal wrinkles occurred. There were no outbreaks. This indicates that the shape of the drive discharge roller of the present invention, that is, the frequency of occurrence of side wrinkles is reduced by pulling the center of the sheet relatively more strongly than the side edges.

As described above, according to the drive discharge roller according to the present invention, the lateral wrinkling and the waving phenomenon of the paper can be effectively and significantly reduced. Become wider. In addition, there is a characteristic that the side wrinkles and the vertical wrinkles opposite to the waving phenomenon do not have the side effect of increasing the frequency of occurrence.

Although the drive discharge roller of FIG. 1 is composed of four rollers and has different diameters at the center and both ends, the outer diameter of the center is used. It is apparent that the same operation and effect as in FIG. 1 can be obtained even if a positive crown-shaped integrated drive discharge roller having a larger diameter than both ends is used.

(Second Embodiment) A second embodiment of the present invention will be described. In the first embodiment shown in FIG. 1, a drive discharge roller including a central drive roller having a large outer diameter and a side drive roller having a small outer diameter is used. On the other hand, this embodiment uses a drive discharge roller in which the center drive roller and the side drive roller have the same diameter. Other configurations are the same as those of the first embodiment. In this embodiment, both the side drive roller 50a and the center drive roller 50b are set to have a diameter of 13.0 mm. The pressed spring force of the driven roller group pressed corresponding to each drive roller group is the central drive roller 50b.
500g (5N) for the central driven roller pressed against the side, and 200g for the side driven roller pressed against the side driving roller.
It is set higher than (2N). The conditions for the paper transport experiment were the same as those described in the first embodiment, except that the set temperature of the heating roller was 200 ° C., and the driving speed was 30 mm / s and 60 mm / s.

According to the results of this experiment, no occurrence of wrinkles or undulations was observed on the paper, and it was found that there was a remarkable effect on the prevention of paper wrinkles as compared with the conventional apparatus.

(Third Embodiment) Here, a third embodiment will be described. In the third embodiment, as in the second embodiment, the driving discharge roller is constituted by a center driving roller and a side driving roller having the same diameter, and is constituted by four rollers shown in FIG. At the center of each of the discharge roller and the driven discharge roller, another driving discharge roller and a driven discharge roller opposed thereto are further added.

Unlike in FIG. 1, the diameter of the drive discharge roller 50 increased to five is 13.1 in both the end roller 50a and the center roller 50b in this embodiment as in the second embodiment. 0mm
Is set to the diameter. The pressed spring force of the driven roller group pressed corresponding to each drive discharge roller group is:
Both the center driven roller and the end driven roller are 200 g (2
N). Other configurations are the same as those of the first embodiment.

With respect to the third embodiment, a paper transport experiment was performed under the same conditions as those for the second embodiment.
The results of this experiment show that, because the force density at the center of the paper increased, no rib-like lateral wrinkles or waving were observed on the paper, and that the increase in the force density at the center of the paper was effective in preventing paper wrinkles. all right.

Embodiment 4 Here, a fourth embodiment will be described with reference to FIG. In the fourth embodiment, a discharge belt rotating in the transport direction of the sheet 20 is used in place of the driving discharge roller 50 of the first embodiment. That is, in the discharge belt, two drive pulleys 60b located at the center in the width direction of the paper 20 and two drive pulleys located at both ends in the width direction of the paper 20 are provided on the drive shaft 64 on the upstream side. 6
0a, and two central drive pulleys 60b and two side drive pulleys 60a are also fixed to the downstream support shaft 65, similarly to the drive shaft 64. A central belt 66a is wound around the center of the paper and a side belt 66b is wound around the paper at each of the four pairs of pulleys that form a pair at the upstream and downstream sides, and belt tension mechanisms 67 are provided at both ends of the support shaft. A central driven pulley 51b has a spring 52 below the central drive pulley 60b with a central belt 66b interposed therebetween.
b, and each side driving pulley 60
A center driven pulley 51b is pressed against a by a spring 52b across the side belt 66a.

In the heat fixing device of this embodiment, similarly to the center drive roller 50b and the side drive roller 50a in the first embodiment, the diameter of the pulley center drive pulley 60b is made larger than the diameter of the side drive pulley 60a. As a result of the paper transport experiment shown in Tables 1 and 2, as in the first embodiment, no occurrence of rib-like horizontal wrinkles or waving was observed on the paper, and it was found that the paper was effective in preventing paper wrinkles. . That is, it was found that the use of the belt was effective in preventing paper wrinkling similarly to the roller.

(Embodiment 5) The heat fixing device of the fifth embodiment differs from the device of the fourth embodiment in that the center drive pulley 60b and the side drive pulley 60a have the same outer diameter.
The pressing force of the central driven roller 51b on the side driving pulley 60b is stronger than the pressing force of the side driven roller 51a on the side driving pulley 60a.

Using the heat fixing device of the fifth embodiment, the second
As a result of performing an experiment similar to the experiment using the apparatus of the example, no occurrence of rib-like horizontal wrinkles or waving was observed on the paper, and it was found that the paper was effective in preventing paper wrinkles.

(Embodiment 6) The heat fixing device of the sixth embodiment is the same as the device of the fifth embodiment except that the central drive pulley 60b, the central driven roller 51b, the central belt 66b and the spring 51b are added.
It is a set added. An experiment was carried out in the same manner as the experiment using the apparatus of the third embodiment using this heat fixing device, and as a result, there was also an effect of preventing paper wrinkles.

In the heat fixing device shown in FIG. 3, a discharge belt is used instead of the driving discharge roller of the first embodiment, and a driven discharge roller is used.
Driven belt (consisting of driven pulleys 61a and 62b, belts 66a and 66b, and springs 62a and 62b)
Is used. As a result of carrying out paper transport experiments using the heat fixing device shown in FIG. 3 under the same conditions as those of the fourth to sixth embodiments, no rib-like lateral wrinkles or undulations were found on the paper in the same manner. It was found that paper wrinkles were effective. From the above, it can be seen that the effect of preventing paper wrinkles is the same regardless of whether the driven or driven sheet discharging means is a belt or a roller.

[0059]

According to the present invention, by applying a relatively strong tension to the center of the sheet from the side of the sheet at the exit side of the heating roller, wrinkles generated on the sheet can be prevented. Thus, it is possible to provide a heat fixing device that is more stable in performance than conventional ones.

[Brief description of the drawings]

FIG. 1 is a perspective view of a heat fixing device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a heat fixing device according to a fourth embodiment of the present invention.

FIG. 3 is a perspective view of a heat fixing device according to a seventh embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Heating roller 2 Pressure roller 3 Heating source 4 Gear 20 Paper 50 Drive discharge roller 50a Drive roller 50b Central drive roller 51 Driven discharge roller 51a Driven roller 51b Central driven roller 52a, 52b, 62a, 62b Spring 53 Gear 54, 64 Drive shaft 65 Support shaft 60a Side drive pulley 60b Central drive pulley 66a Side belt 66b Central belt

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Junichi Matsuno 502, Kandate-cho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hitachi, Ltd. (56) References JP-A-3-31159 (JP, A) JP-A-60- 50547 (JP, A) JP-A-2-286559 (JP, A) JP-A-58-77353 (JP, U) JP-A-59-82259 (JP, U) (58) Fields investigated (Int. Cl. ^7, DB name) G03G 13/20 G03G 15/00 510 - 534 G03G 15/20

Claims (3)

(57) [Claims] And 1. A heating roller outer diameter of large inverted crown shape from the central portion of the built both ends a heat source, the heating Russia - and uniform pressure roller is arranged parallel to that outer diameter La, the <br/> heating b - a first driving means for driving the La or the pressure roller, the sheet on which the toner image by holding by the <br/> heating roller is fixed between the pressure roller and the heating roller A sheet discharging unit that discharges the sheet to a downstream side, wherein the sheet discharging unit includes a plurality of sheets arranged in a width direction of the sheet.
A drive roller, the drive roller being arranged to face the drive roller,
A plurality of driven rollers for nipping the paper between the driven rollers,
Second driving means for driving the driving roller, and the driven
Pressing each roller separately to the drive roller side
Wherein the pressing force of the pressing means is relatively increased at both ends in the width direction of the sheet and more at the center in the width direction of the sheet. 2. The heating roller is made of fluororesin,
The pressure roller is covered with silicone rubber,
The driving roller is a rubber with a high coefficient of friction, and the driven roller is
Engineering plastics with low coefficient of friction
Thermal fixing device according to claim 1, characterized in that it is configured that. 3. A heating roller outer diameter of large inverted crown shape from the central portion of the built both ends a heat source, the heating Russia - and uniform pressure roller is arranged parallel to that outer diameter La, the <br/> heating b - a first driving means for driving the La or the pressure roller, the sheet on which the toner image is fixed by sandwiching by the <br/> heated roller between the pressure roller and the heating roller in the heat fixing device that includes a sheet discharge means for discharging to the downstream side, the sheet discharge unit, transportable paper are arranged in the width direction of the paper
A plurality of discharge belts traveling in a feeding direction, and the discharge belt
Is arranged so as to face the sheet and pinch the sheet between the discharge belt and the discharge belt.
And a second driven roller for driving the discharge belt.
, And each of the driven rollers is separately discharged.
And a pressing unit for pressing the belt toward the belt, wherein the pressing force of the pressing unit is relatively increased at both ends in the width direction of the sheet and at the center in the width direction of the sheet.