JP2000098772A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregularities in a toner image caused by the expansion of air and the generation of water vapor in a belt nip part where a fixing roll is brought in press-contact with a belt, and also, to control a belt walk without damaging the endless belt with a simple constitution, as for a fixing device for fixing the toner image carried on a recording material by heating and pressurizing. SOLUTION: The endless belt 20 which is stretched between a pressure roll 40 and supporting rolls 41 and 42 so as to travel around the rolls is brought into press contact with the circumferential surface of the fixing roll 1. As for the endless belt 20, a cylindrical belt substrate 21 is formed by spirally laminating a sheet-like film, and an elastic layer 22 is laminated on the circumferential surface of the substrate 21. Thus, the strength of the endless belt 20 is increased, so that the tension of the belt can be increased so as to make a pressure working on the belt nip higher. Besides, the belt walk is controlled by making the edges of the endless belt 20 abut on guide members arranged on both sides, and also, the belt is prevented from buckling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which is used in an image forming apparatus utilizing an electrophotographic method, such as a copying machine, a printer and a facsimile, and which fixes an unfixed toner image on a recording sheet by heating. More specifically, the present invention relates to a belt nip type fixing device having a heating member and a belt pressing member.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, it is necessary to fix an unfixed toner image formed on a recording sheet to a permanent image. As such a fixing means, a solvent fixing method, a pressure fixing method, a heat fixing method and the like are conventionally known.

[0003] However, the solvent fixing method has a problem of odor and hygiene because the solvent vapor emanates. Further, the pressure fixing method has disadvantages in that the fixing property is poor as compared with other fixing methods and the pressure-sensitive toner is expensive. Due to these factors, both have not been put to practical use at present. For this reason, a heat fixing method in which the toner is melted by heating and thermally fused to the recording sheet has been widely adopted.

[0004] As an apparatus of the heat fixing method, a heat roll type fixing apparatus is widely known, and as shown in FIG.
A main part is constituted by a fixing roll 110 having a heat source and a pressure roll 120 arranged in pressure contact with the fixing roll. The fixing roll 110 is provided with a heater 114 inside a cylindrical cored bar 111, a heat resistant rubber coating layer 112 formed on the outer peripheral surface of the cored bar, and a release layer 113 formed on the surface thereof. The pressure roll 120 is provided with a heater 124 inside a cylindrical metal core 121, and a heat-resistant elastic layer 122 and a surface coating layer 123 are formed on the outer peripheral surface of the metal core. Then, the fixing roll 110 and the pressure roll 12
Between 0 and 0, the sheet carrying the unfixed toner image is passed, and the unfixed toner image is heated and pressed to be fixed on the sheet. This fixing device is currently most widely used because of its higher thermal efficiency and less risk of burning of paper due to paper jam compared to other heat fixing methods such as heat radiation fixing method.

As an improved type of the fixing device of the heat fixing type,
Japanese Patent Application Laid-Open No. 5-150679 proposes a fixing device using an endless belt 140 as shown in FIG. 4 instead of a pressure roll. This fixing device supports an endless belt 140 stretched around a plurality of support rolls 141, 142, 143 so as to be able to rotate around the fixing roll 130 so as to be pressed against the fixing roll 130. The sheet carrying the toner image is transported.

In such a fixing device, since the nip can be relatively widened by using the endless belt 140, the heating time is prolonged, and more heat can be given to the toner. Therefore, it is possible to increase the speed or reduce the size of the device. Also,
It is suitable for a color copying machine and a color printer which need to form a multilayer toner into a desired color.

In this fixing device, the elastic layer 13 made of silicone rubber is provided on the surface of the fixing roll 130.
2 is formed, and the elastic layer 132 is locally distorted in the press-contact area by receiving the press-contact force of the support roll 141. That is, since the surface speed of the elastic layer 132 locally increases, a small deviation occurs between the sheet and the fixing roll 130 in the pressure contact region of the support roll 141.

[0008] The toner in a high temperature state tends to adhere to the fixing roll 130, but this shift causes a small slip at the interface between the toner and the fixing roll 130, and the adhesion of the toner to the fixing roll 130 decreases. It is thought that it is reduced. In addition, silicone oil is applied to the fixing roll 130 as a release agent so that toner does not easily adhere.

As a result, the sheet carrying the toner image is separated from the fixing roll 130 against the adhesive force between the toner and the fixing roll 130. Since the adhesive force between the fused toner and the fixing roll 130 depends on the surface chemical properties of both, the behavior of whether or not the paper is peeled depends on the type and amount of the toner, the surface material of the fixing roll, and the like. According to this fixing device, the sheet can be peeled from the fixing roll without using a peeling means such as a peeling claw (hereinafter, referred to as self-stripping). For this reason, self-stripping can be easily performed even on a thin paper sheet having a weak stiffness and hardly peeling off, or a sheet sheet with a large amount of toner attached.

[0010]

However, the fixing device using the endless belt has two major problems as described below. (1) In the case where a heat-fusing toner, which is currently the mainstream, is used, the sheet must be heated to melt the toner and be fixed on the sheet. At the time of this heating, air and water vapor expand from inside the warmed paper or toner layer.
Such air or water vapor is generated when the paper carrying the toner image is heated in the nip, and between the fixing roll and the paper or between the endless belt and the paper until the paper passes through the nip. Continue to intervene. And
When the paper has passed through the nip, it is discharged outside.

Therefore, when the pressure in the nip is low, the expansion of the air or water vapor cannot be suppressed, and a sufficient pressure for fixing the toner to the paper cannot be provided. In addition, the paper is in the nip,
In a state where the toner is not fixed, air bubbles such as air and water vapor in the toner layer and the paper move around, so that the unfixed toner may move. This causes bleeding, misalignment, and disorder of the image.

In a roll pair type fixing device using only a fixing roll and a pressure roll without using an endless belt, such a problem is small because the pressure in the nip is sufficiently large. However, in a fixing device of a belt nip type, the pressure is low. As the size is reduced, the toner image may be disturbed by bubbles, which is a problem.

As the endless belt used in such a fixing device, a thermosetting or thermoplastic polyimide seamless belt is mainly used from the viewpoint of heat resistance and strength. It is only necessary to increase the belt tension by further increasing the strength of the endless belt and improve the pressure in the nip.However, a polyimide seamless belt involves molding difficulties when trying to form a thick belt, and the thickness is increased. About 100 μm is a practical limit. Further, in consideration of mass productivity, the limit is about 75 μm in thickness. This does not provide enough pressure in the nip. An endless belt is also conceivable by bonding both ends of a sheet-like film, but a high pressure portion and a low pressure portion are generated due to the step of the seam portion, which also causes trouble at the time of fixing.

In order to solve such a problem, a fixing device described in Japanese Patent Application Laid-Open No. 9-34291 has been proposed. As shown in FIG. 5, the fixing device includes a pressure assist pad 165 having a contact surface that can be substantially aligned with the outer peripheral surface of the fixing roll 150 inside the endless belt 160. Is pressed toward the fixing roll 150. Further, when the endless belt 160 is pressed by the pressure assist pad 165, the pressure Pn within the belt nip, the temperature Tn inside the belt nip, the environmental temperature To, and the atmospheric pressure Po are expressed as Pn ≧ Po (Tn / To-1) is established. With such a configuration, it is possible to apply a pressure sufficient to suppress the expansion of air or water vapor to the entire nip, and it is possible to solve the problem that the toner image is disturbed as described above.

However, in the fixing device shown in FIG.
The fixing roller 150 is rotated by a drive motor (not shown), and the endless belt 160 is rotated by following the fixing roller. The inner peripheral surface of the endless belt 160 slides with the pressure auxiliary pad 165. The endless belt 160 is rotated against the rotation.
The inner peripheral surface of the endless belt 160 and the pressure assist pad 16
Although measures are taken to reduce the coefficient of friction in No. 5, the drive motor of the fixing roll 150 still requires a large torque. For this reason, the size of the motor is increased, which leads to an increase in the size of the copier / printer. There is also a problem that the electric power of the motor increases.

Further, since the endless belt 160 is rotated against a large frictional force, the fixing roll 15 is rotated.
Large stress is also applied to the elastic layer 152 and the release layer 153 of the zero, and the elastic layer and the release layer of the endless belt 160, which causes problems such as tearing and peeling of the elastic layer and the release layer.

(2) In a fixing device using an endless belt, there is a problem that the endless belt is shifted in accordance with the misalignment of the fixing roll and the belt supporting roll. Since the fixing roll and the support roll cannot be completely parallelized in the manufactured device, the belt walk cannot be completely eliminated. Therefore, when the endless belt is offset, a mechanism for restoring the offset is required. 4 and 5
Has a belt detecting means (not shown) for detecting the deviation of the endless belt 160 in the width direction of the endless belt 160, and the belt supporting roll 162 is provided in accordance with the detection signal. The belt walk is regulated by displacing the.

However, the above-described mechanism is not preferable because it requires a belt detecting means, a mechanism for displacing the belt support roll 162, a motor, and the like, which leads to an increase in cost and an increase in the size of the apparatus.

On the other hand, a structure that can control the belt walk by abutting the edge of the endless belt is very simple and is desirable in terms of cost. In this case, since the thickness is small, the belt edge does not have strength and causes buckling of the belt edge.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent a toner image from being disturbed by applying a sufficient pressure to the inside of a belt nip and to increase the height of an endless belt. An object of the present invention is to provide a fixing device capable of extending the life, and to provide a fixing device capable of restricting the deviation of the belt with a simple configuration without causing buckling of the belt edge.

[0021]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a first fixing member having a built-in heat source and having an endless peripheral surface moving around; And a second fixing member which moves circumferentially while being pressed against the circumferential surface of the first fixing member, and the unfixed toner image is carried on a nip portion where the two fixing members are pressed against each other. A fixing device that conveys a sheet and heats and presses the unfixed toner image on a surface on a side in contact with the first fixing member to fix the unfixed toner image on the recording sheet; At least one of the fixing members is an endless belt, and the endless belt is formed on a cylindrical substrate formed by spirally laminating a plurality of layered sheet-like thin films, and is formed on an outer peripheral surface of the substrate. Elastic layer It shall have.

In such a fixing device, the endless belt has a cylindrical base body in which a plurality of end-shaped sheet-like thin films are spirally laminated, and compared with a conventional single-layer member. Thus, an endless belt having a large thickness and a high strength can be obtained. For this reason, the tension when the endless belt is stretched can be increased, and the nip pressure between the endless belt and the fixing member can be increased. As a result, expansion of the air and water vapor in the sheet and the toner image in the nip can be suppressed, and the unfixed toner image can be prevented from being disturbed by the expanded bubbles. Further, the endless belt can apply a pressing force to a wide area in the nip, and the toner image on the recording sheet passing through the nip can be reliably applied by applying pressure to the toner image. Therefore, it is possible to obtain a good fixed image without image disturbance and to cope with an increase in the speed of the apparatus.

Further, as described in claim 2, it is desirable that the elastic layer has a thickness larger than that of the sheet-like thin film. The tubular substrate is formed by spirally laminating a plurality of end-formed sheet-like thin films, and a step is formed at the beginning and end of winding of the sheet. Is relatively small. By providing the elastic layer thicker than the sheet-like thin film on the outer peripheral surface of the base, the step portion of the base is absorbed by the elastic layer on the surface when the endless belt is pressed against the fixing member. For this reason, the pressure of the belt nip can be made substantially uniform, and image quality deterioration at the time of fixing can be prevented.

As described in claim 3, it is preferable that at least two or more layers of the base are laminated at any part in the circumferential direction of the endless belt. As described above, the thickness of a single-layer endless belt is limited to about 100 μm due to difficulties in molding.
An endless belt having a substantially uniform thickness of not less than 00 μm can be formed.

The material of the sheet-like thin film can be appropriately selected from known materials, but from the viewpoint of tensile strength and coefficient of thermal expansion, it is preferable to use an aromatic polyamide as described in claim 4. desirable. With an endless belt made of an aromatic polyamide, sufficient strength can be obtained even when the tension at the time of stretching is increased, and it is possible to prevent the endless belt from being torn, broken, stretched, and the like.

According to a fifth aspect of the present invention, a guide member is provided outside the edge portion in the width direction of the endless belt to correct the deviation of the belt by abutting the endless belt. In the fixing device, the endless belt is shifted depending on the misalignment of the support member and the fixing member of the endless belt, but by hitting the edge of the endless belt against the guide member,
The deviation of the endless belt is regulated, and the orbital movement can be stably performed. At this time, by using the endless belt having a large strength, buckling of the edge portion at the time of abutting can be prevented.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic configuration diagram illustrating a fixing device according to an embodiment of the present invention. FIG. 1 (b)
FIG. 2 is a schematic configuration diagram showing an endless belt used in the fixing device. The fixing device includes a fixing roll 10 having a built-in heating source, an endless belt 20 arranged to be in pressure contact with the fixing roll 10, a pressing roll 40 for stretching the endless belt 20, and two support rolls 41. , 42 constitute a main part.

The fixing roll 10 has an elastic layer 12 and a release layer 13 formed around a metal core 11, and the core 11 is an aluminum cylinder having an outer diameter of 47 mm and a length of 350 mm. . An HTV having a rubber hardness of 45 ° (JIS-A) is formed on the surface of the core 11 as the elastic layer 12.
(High Temperature Vulcanization) An RTV (Room Temperature Vulcaniza) having a thickness of 2 μm and a release layer 13 formed of silicone rubber having a thickness of 2 mm.
tion) Silicone rubber is dip coated. The release layer 13 is finished to a surface close to a mirror state.

The core 11 may be made of metal such as iron or SUS, instead of aluminum. Further, as the elastic layer 12, another material having high heat resistance can be used. As the release layer 13, besides silicone rubber, fluorine rubber, PFA (perfluoroalkoxy vinyl ether copolymer resin), PTFE (polytetrafluoroethylene),
Fluororesins such as FEP (ethylene tetrafluoride hexafluoropropylene copolymer resin) can be used. The elastic layer 1
Rubber hardness of 2 is a spring type A made by Teclock.
This is the result of measurement with a die hardness tester according to JIS K6301 with a load of 1,000 gf added.

An output 8 as a heating source is provided inside the core 11.
A 50 W halogen lamp 14 is fixedly supported. Further, a temperature sensor 15 is arranged close to the surface of the fixing roll 10, and the temperature of the surface of the fixing roll 10 is measured. Then, based on the measurement signal of the temperature sensor 15,
Halogen lamp 1 by a temperature controller (not shown)
4 is feedback-controlled so that the surface of the fixing roll 10 is adjusted to 150 ° C.

In the vicinity of the fixing roll 10, a release agent supply device (not shown) is provided. A fixed amount of the release agent is always supplied from the release agent supply device to the surface of the fixing roll 10. This prevents a part of the toner from being offset to the fixing roll 10 when the unfixed toner is fixed on the sheet. As the release agent supplied by the release agent supply device, dimethyl silicone oil having a viscosity of 300 cs (trade name “KF-96”: manufactured by Shin-Etsu Chemical Co., Ltd.)
Is used.

As shown in FIG. 1B, the endless belt 20 comprises a belt substrate 21 and an elastic layer 22 laminated thereon, and the belt substrate 21 is made of an aromatic polyamide having a thickness of 15 μm. The sheet is wound into a cylindrical shape having a diameter of 60 mm to form a thick base material. 5 μm thick PFA is used as an adhesive between the aromatic polyamide sheets. PFA is obtained by coating the surface of an aromatic polyamide sheet in advance, winding the sheet in a cylindrical shape, and heating and firing the sheet to bond the sheets. By laminating about 10 layers of the aromatic polyamide sheet [the number of layers is omitted in FIG.
A belt substrate 21 having a thickness of μm is formed. that time,
10m between the start and end of the sheet
m so that they are overlapped and polished so that the steps are reduced. On the belt base material 21, as an elastic layer 22, R
TV (Room Temperature Vulcanization) silicone rubber is coated with a thickness of 100 μm.

In the case of an endless belt of a polyimide resin generally used conventionally, the thickness is usually 40 to 75 μm, and if the thickness is more than 100 μm, uniformity of the thickness cannot be obtained, so that it is difficult to manufacture. Becomes On the other hand, in the present embodiment, a thin aromatic polyamide sheet is formed by spirally winding and laminating the aromatic polyamide sheet.
m can be easily made. Since the sheet itself is as thin as about 15 μm (about 20 μm even when adhered), the step between the start and end of winding is small. Further, since the elastic layer 22 is provided on the belt substrate 21, this step does not cause any problem. In addition, in the present embodiment, the start portion of the sheet and the end portion of the sheet are overlapped and polished by about 10 mm, so that the thickness of the belt can be made more uniform.

The thin film sheet used for the endless belt 20 can be used as long as it is a resin having heat resistance. The aromatic polyamide has a tensile strength of 30 to 50 [kg / mm ² ] and a tensile modulus of 1000 to 1900 [kg / mm ² ]. mm ² ], which is preferable since the strength of the material is excellent. In contrast, the thermosetting polyimide has a tensile strength of 25 [kg / mm ² ] and a tensile modulus of 300 [kg / mm ² ], and the PET has a tensile strength of 25 [kg / mm ^2]. ] And a tensile modulus of 400 [kg / mm ² ], which indicates that the aromatic polyamide is superior. Due to these properties, aromatic polyamide is 20 μm
It is also an advantage that the following thin film sheets are excellent in productivity.

The thermal expansion coefficient of the aromatic polyamide is 2 ×
10 ⁻⁶ [mm / mm / ° C.], coefficient of thermal expansion of thermosetting polyimide is 20 × 10 ⁻⁶ [mm / mm / ° C.], coefficient of thermal expansion of PET is 12 ×
10 ⁻⁶ [mm / mm / ° C.], indicating that the thermal expansion of the aromatic polyamide is small. Generally, when an endless belt is used as a fixing device, the belt is undulated when the belt is locally heated at a nip portion. However, it can be said that aromatic polyamide is unlikely to undulate, which is a great advantage.

The endless belt 20 includes a pressing roll 40
The support rolls 41 and 42 are stretched with a tension of 40 kgf and are pressed by the fixing roll 10. The winding angle of the endless belt 20 around the fixing roll 10 is 45 °
And the width of the nip in the circumferential direction of the belt is about 20.
mm.

The pressing roll 40 is a stainless steel roll having a diameter of 23 mm, and is provided at the nip exit portion (downstream of the nip in the paper transport direction) at the endless belt 2.
The fixing roll 10 is pressed against the fixing roll 10 with a load of 40 kg. Here, about 5% is added to the elastic layer 12 of the fixing roll 10.
And the surface speed of the fixing roll 10 is changed to cause a slight displacement at the interface between the fixing roll and the toner, thereby improving the peeling performance.

The nip formed by the pressure roll 40 is 3 mm, and the pressure in this area is about 6.0 kg / cm ² . The pressure at the portion where the nip is formed only by the endless belt 20 is about 2.0 kg / cm ² .

The fixing roller 10 is driven to rotate at a peripheral speed of 300 mm / sec by a motor (not shown), and the endless belt 20 moves around following the rotation of the fixing roller 10. The duel time at the time of fixing is 66 msec.

Further, in the fixing device, as shown in FIG. 1A, a belt edge guide member 45 for regulating the deviation of the endless belt 20 is provided between the support roll 40 and the support roll 42. . As illustrated in FIG. 2A, the belt edge guide member 45 has two members supported substantially in parallel at both ends in the width direction of the endless belt 20, and has a concave shape facing the edge portion of the endless belt 20. It has a cross section. Then, the edge of the endless belt 20 abuts to control the belt walk.

Next, the operation of the fixing device will be described. In the image forming process, the toner image 71 is transferred onto the sheet 70 by a transfer device (not shown), and the sheet 70 is conveyed from the right side of the figure toward the nip. The paper 70 enters the nip where the fixing roll 10 and the endless belt 20 are pressed against each other. Then, the fixing roll 10 is controlled by the pressure acting on the nip and the halogen lamp 14.
The toner image 71 is formed by the heat given through the
Settled on top.

If the pressure in the nip is not sufficient, the paper 70 is heated while passing through the nip, so that the air and water vapor contained in the paper and the toner layer expand. Then, the air or water vapor becomes bubbles in the belt nip, and disturbs the unfixed toner image.

However, in the fixing device of this embodiment, since the belt strength is increased by the endless belt 20 of the lamination type, it is possible to increase the belt tension. That is, the pressing force of the endless belt 20 against the fixing roll 10 also increases, and the pressure of the belt nip can be increased. As a result, the expansion of air and water vapor in the paper and the toner layer can be suppressed, and the unfixed toner image can be prevented from being disturbed by the expanded bubbles.

At the same time, a pressing force can be applied between the endless belt 20 and the fixing roll 10 in a wide area in the belt nip, so that a sufficient pressure is applied to the toner image 71 on the sheet 70 passing through the nip. It is possible to fix by working. That is, it is possible to reliably fix the toner image while preventing the toner image from being disturbed. Further, since a sliding member such as a pad which comes into contact with the endless belt is not used, a problem due to an increase in torque does not occur.

Further, in the fixing device, the belt edge guide members 45 are provided at both ends in the width direction of the endless belt 20, and when the endless belt 20 abuts against one belt edge guide member 45 by walking, the endless belt The 20 walks are regulated, and it is possible to make a round trip in a stable place.

Next, the result of an experiment for examining the relationship between the tension of the endless belt and the disturbance of the toner image will be described. In the above-mentioned fixing device, an experiment was conducted in which the tension of the endless belt was changed in five stages of 10 kgf to 50 kgf, and the state of occurrence of disturbance of the toner image was investigated. Table 1 shows the nip pressure and the state of disturbance of the toner image at this time. In Table 1, a circle indicates that the image quality is good without any disturbance of the toner image, and a cross indicates that the disturbance of the toner image has occurred.

[0047]

[Table 1]

Further, an experiment was conducted in which four endless belts having different thicknesses were used, and the strength of the belt when the tension was changed in five steps was investigated. Table 2 shows the results. In Table 2, the mark “○” indicates that there is no problem in the strength of the endless belt, and the mark “X” indicates that tearing, tearing, elongation, etc. of the endless belt have occurred. Below margin

[0049]

[Table 2]

As a result of the above experiment, in Table 1, as the tension increases, the pressure in the nip increases and the belt tension becomes 3
It can be seen that at 0 kgf or more, the disturbance of the toner image does not occur. Also, from Table 2, the thickness of the belt base material is 100 μm.
In the following cases, the belt is damaged by the tension of 30 kgf,
It can be seen that it cannot withstand the belt tension for preventing the image quality from being disturbed. When the thickness of the belt base material is 150 μm or more, sufficient strength is obtained even when the belt tension is increased, and it is understood that the reliability is high. From the above, it can be seen that the pressure of the belt nip can be increased and the toner image can be prevented from being disturbed by using the lamination type endless belt in which the thin film sheet is spirally wound to have a predetermined thickness.

Next, the results of an experiment in which the material and thickness of the endless belt were changed and the buckling force of the belt was examined will be described. As the belt base material, a thermosetting polyimide and an aromatic polyamide having different thicknesses are used. In the fixing device shown in FIG. 1, the buckling force of each belt is applied while applying a tension of 40 kg to the endless belt. It was measured. The buckling force of the belt here is when the endless belt stretched with a tension of 40 kg hits the belt edge guide member,
Each belt shows the minimum force to cause buckling.
This buckling force was measured by a strain gauge attached to the belt edge guide member. Table 3 shows the results.

[0052]

[Table 3]

In the above-described fixing device, the degree of deviation of the belt differs depending on the degree of misalignment of the alignment of the fixing roll 10, the pressing roll 40, and the supporting rolls 41 and 42, but the design intersection of the fixing device is maximized. When the deviation force of the belt generated when touched was measured, it was about 500
N. Therefore, as shown in Table 3, thermosetting polyimide and aromatic polyamide of 150 μm or less have a problem in the strength of the endless belt, but have a thickness of 200 μm.
If the aromatic polyamide is used, the belt can sufficiently withstand the biasing force of the belt. By using such an endless belt, it becomes possible to abut the edge of the belt against the belt edge guide member and to control the deviation of the belt.

[0054]

As described above, according to the present invention,
It is possible to increase the tension of the lamination type endless belt and press it against the fixing member, thereby suppressing expansion of the air and water vapor in the paper and the toner layer. For this reason, the generation of air bubbles in the belt nip can be suppressed, and the unfixed toner can be prevented from being disturbed by the air bubbles. At the same time,
Since a large pressure can be exerted over a large area in the belt nip, it is possible to reliably fix the toner on the sheet passing through the belt nip. Therefore, it is possible to obtain a good image by preventing the toner image from being disturbed at the time of fixing, and it is possible to cope with an increase in the speed and size of the apparatus. Furthermore, since the laminated type endless belt can also increase the strength against buckling, the belt can be prevented from being biased by an edge guide method in which a belt edge is abutted. Therefore, the walking regulation mechanism of the endless belt is simplified, and a small size and low cost can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a fixing device according to an embodiment of the present invention and an endless belt used in the fixing device.

FIG. 2 is a longitudinal sectional view of the fixing device shown in FIG. 1;

FIG. 3 is a schematic configuration diagram illustrating a first example of a conventional fixing device.

FIG. 4 is a schematic configuration diagram illustrating a second example of a conventional fixing device.

FIG. 5 is a schematic configuration diagram illustrating a third example of a conventional fixing device.

[Explanation of symbols]

 ... Fixing roll, 11... Core, 12... Elastic layer, 13... Release layer, 14... Halogen lamp, 15. ..Temperature sensor, 20 ... Endless belt, 40 ... Press-contact roll, 41 ... Support roll, 42 ... Support roll, 45 ... Belt edge guide Member, 70, paper, 71, toner image

Claims (5)

[Claims] 1. A first fixing member having a built-in heat source and having an endless peripheral surface moving around, and a second fixing member having an endless peripheral surface being pressed against the peripheral surface of the first fixing member to move around. A recording sheet carrying an unfixed toner image in a nip portion where the two fixing members are pressed against each other, and the unfixed toner is conveyed on the surface in contact with the first fixing member. In a fixing device for fixing an image on the recording sheet by heating and pressing the image, at least one of the first fixing member and the second fixing member is an endless belt, and the endless belt is an endless sheet. Cylindrical substrate formed by laminating a plurality of spirally-shaped thin film films,
And an elastic layer formed on an outer peripheral surface of the base. 2. The fixing device according to claim 1, wherein the elastic layer has a thickness greater than that of the sheet-like thin film. 3. The fixing device according to claim 1, wherein at least two or more layers of the base are laminated at any part in a circumferential direction of the endless belt. 4. The fixing device according to claim 1, wherein the sheet-like thin film is formed of an aromatic polyamide. 5. The endless belt according to claim 1, further comprising a guide member outside the edge portion in the width direction of the endless belt, the guide member abutting against the endless belt to regulate the deviation of the belt. The fixing device according to any one of the above.