JPH08234600A - Heating device and image forming device - Google Patents

Abstract

PURPOSE: To provide a heating device capable of simplifying the heat control while shortening the time for elevating temp. at the rising time of an image forming device, and preventing the temp. rise in a non paper passing part, an image defect due to change of the roller peripheral speed, and the generation of corrugation of a recording material originated from difference of nipping part width difference in the length direction. CONSTITUTION: A heat resistive film 10 in a endless belt state is put over a stay 13 supporting the heater 12, and a thin metallic sleeve 11 formed into a thin hollow cylindrical shape consisting of iron, SUS, nickel and so on is held in press contact with the heater 12 through the heat resistive film 10. Then, the thickness (t) of thin metallic sleeve 11 is elastically deformed by pressing it with contact, and set in an area possible to form the nip part, by the elasticity caused by the elastic deformation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus adopting an electrophotographic system, an electrostatic recording system or the like, and more specifically, a heating member and a pressure member arranged in pressure contact with each other. The present invention relates to a heating device configured by, and an image forming apparatus including the heating device.

[0002]

2. Description of the Related Art Conventionally, many electrophotographic copying machines, printers and the like employ a contact heating type heat roller fixing method or an energy saving type film heating method, which have good thermal efficiency and safety, as fixing means. ing.

The heat fixing device of the heat roller fixing system has a heating roller (fixing roller) as a heating member and an elastic pressure roller as a pressure member pressed against the heating roller as a basic structure. Then, the unfixed image (toner image) is formed on the pressure contact nip portion (fixing nip portion) of the pair of rollers.
By introducing the material to be recorded (transfer material sheet, electrostatic recording paper, electrofax paper, printing paper, etc.) that has formed and carried the nip portion of the pressure contact nip portion, heat from the heating roller and the pressure contact nip portion are introduced. The unfixed image is fixed on the surface of the recording material as a permanently fixed image by heat and pressure under the pressure of.

Further, a film heating type fixing device is disclosed in, for example, JP-A-63-313182 and JP-A-2-157.
878, 4-44075 to 44083, 4-20498.
Nos. 0-204984 and the like, in which a heat-resistant film (fixing film) is brought into close contact with a heating member by a pressure member (elastic roller) and slid and conveyed, and the heat-resistant fixing film is sandwiched between the heating member and the heating member. A recording material carrying an unfixed image is introduced between the heat-resistant film and the pressure member in the pressure-contact nip portion formed by the pressure member, and the pressure-contact nip portion is conveyed together with the heat-resistant film, It is an apparatus for fixing an unfixed image as a permanent image on a recording material by heat from a heating member applied through a heat resistant film and pressing force of a pressure contact nip portion.

Since a film heating type fixing device can use a low heat capacity linear heating element as a heating member and a thin film having a low heat capacity as a heating member, power saving and weight time reduction (quick startability) can be achieved. ) Is possible.

Further, an induction heating system has been proposed as another heating device of a power saving type. The induction heating method is
A film in which a metal thin film and a heat-resistant release layer are sequentially formed on a heat-resistant resin formed into a film, an exciting coil arranged inside the film, and an exciting coil arranged in pressure contact with the film to drive the coil. It has a backup roller and induction heats a metal thin film layer of a film by an eddy current generated when the exciting coil is energized. A recording material is passed between the film and the backup roller to heat and pressurize, The unfixed image on the recording material is fixed by heat and pressure as a permanently fixed image.

The induction heating system heats the metal layer inside the film closer to the recording material, and like the film heating system, heat is generated only in the pressure contact nip portion, so that the thermal efficiency is high, and the power saving and the wait time are shortened (quick). Startability)
In addition, since the film has a certain degree of rigidity, it is a fixing method capable of speeding up with a simple structure.

The conventional heat fixing device as described above heats and presses the recording material at the press nip portion which is composed of the heating member and the pressing member, and each of the pressing members has elasticity. A body roller is used, and a pressure contact nip portion having a predetermined width is formed between the body roller and the heating body by elastic deformation of the body roller.

[0009]

However, in the above conventional example, when an elastic roller is used as the pressing member, the following phenomenon may occur.

(1) The elastic roller (pressure roller) is made of a cored bar and a heat-resistant rubber such as silicone rubber molded on the elastic layer, or a sponge elastic layer formed by foaming silicone rubber. Since a heat-resistant release layer made of fluororesin, etc. is sequentially formed, the elastic layer needs to have a certain thickness to form a pressure contact nip portion having a desired width. In some cases, the heat capacity became large and it took a certain period of time for the roller temperature to rise. Especially when the temperature of the pressure roller, which is the pressure member, is low immediately after the apparatus is started up, almost no heat is applied to the recording material from the pressure roller, and conversely, much heat from the heating member is absorbed by the pressure roller. In some cases, the amount of heat applied to the toner image on the recording material is insufficient, and the fixability of the toner image, which changes depending on the total amount of heat applied from both the heating member and the pressure member, deteriorates.

Therefore, in the conventional heat roller type heat fixing device, in order to secure sufficient fixing property immediately after the device is started up, the temperature range of the pressure roller is predicted by the time after the device is started up, the paper passing state and the like. However, it was necessary to change the fixing temperature.

Further, in the fixing device adopting the film heating method or the induction heating method, as shown in FIG. 13, the proper temperature range of the heat resistant film which can achieve both the fixability and the high temperature offset may be narrowed, and the heat resistance may be high. The temperature of the film may change depending on the pressure roller temperature.Therefore, in order to keep the heat-resistant film temperature within the appropriate temperature range, set the target temperature of the heating element immediately after startup to high, The heating member (heater) is turned off (or turned on) for a certain period between
However, complicated control of the heating member may be required, such as predicting the temperature of the pressure roller from the temperature change amount during that period and setting the fixing temperature for each sheet.

(2) Heat roller system, film heating system,
Alternatively, in an induction heating type heating device, a recording material having a width smaller than the maximum width of the recording material that can be introduced into the device (small size recording material) is continuously introduced and passed through the heating treatment. As a result, the heating member portion of the pressure contact nip portion formed between the heating member and the pressure member, which corresponds to the area through which the recording material passes (paper passing area), is heated by the temperature control system. Heat is compensated and maintained at a predetermined temperature, whereas the heating member portion for the area where the recording material does not pass (non-sheet passing area) does not consume heat for heating the recording material. The temperature of the heating member part, the pressing member part, and the heat-resistant film part corresponding to this non-paper passing area accumulates,
A so-called "non-sheet-passing portion temperature rise" phenomenon may occur in which the temperature rises above the paper-passing area maintained and controlled at a predetermined temperature.
By using an elastic roller made of heat-resistant rubber or the like having poor heat conductivity as the pressing member, this phenomenon of temperature increase in the non-sheet passing portion may be promoted. If the temperature rise of this non-paper feed area is remarkable, it may cause heat damage to the pressure elastic body, heat resistant film and other members around the temperature rise area. When a recording material having a size larger than that of the recording material is passed, heating unevenness of the recording material may occur due to temperature unevenness of the pressure contact nip portion, and uneven glossiness and fixing unevenness of the image may occur.

(3) Further, since the elastic roller made of heat-resistant rubber or the like has a large coefficient of thermal expansion, the roller outer diameter in the sheet passing area and the roller outer diameter in the sheet non-passing area are caused by the temperature rise in the sheet non-passing portion. An outer diameter difference may occur, and when a large-sized recording material is passed in this state, an abnormal image such as paper wrinkles may occur.

(4) In the case of an apparatus in which the pressure elastic roller is a driving roller for conveying the recording material or the heat resistant film, the conveying speed of the recording material or the heat resistant film is the peripheral speed of the driving roller. Therefore, if the thermal expansion of the pressure elastic roller as the driving roller is large, the peripheral speed may change. For example, in the case of the image heating fixing device of the image forming apparatus,
When the recording material straddles the image heating section such as the image transfer section and the image heating and fixing device, the recording material is pulled by the image heating and fixing device and the formed image stretches or the image blurs. I have something to do. Furthermore, if there is a difference in outer diameter in the longitudinal direction of the elastic roller due to a temperature rise in the non-paper passing area, etc., there may be a speed difference in the film transport speed between the paper passing area and the non-paper passing area. However, problems such as damage due to buckling may occur.

(5) Further, when the elastic roller is pressed against the fixing member by the pressing means in the longitudinal direction of the elastic roller, the pressing roller having a small diameter exerts a pressing force toward both end portions in the longitudinal direction due to the bending of the shaft. Since the width of the nip portion is increased, the width of the nip portion is different in the longitudinal direction, and may be larger toward the both end portions than in the central portion. This causes a difference in the pressure applied to the recording material that is nipped and conveyed between the nip between the central portion and the both ends, and excessive pressure is applied to the end portion of the recording material, so that the fiber stretches and the end portion of the recording material Rippling sometimes occurred.

The first invention according to the present application solves the above-mentioned problems, and in the heating device of the heat roller system, the temperature control can be simplified while shortening the temperature rising time when the device is started up. An object of the present invention is to provide a heating device that does not cause image defects due to a temperature increase in a non-sheet passing portion, a change in roller peripheral speed, and waviness of a recording material due to a difference in nip width in the longitudinal direction.

The second invention according to the present application solves the above-mentioned problems, and in the film type heating device, the temperature control time can be simplified while shortening the temperature rising time at the time of starting the device. It is an object of the present invention to provide a heating device that does not generate image defects due to a change in the roller non-passage area, a change in the roller peripheral speed, abnormal running of the film, and waviness of the recording material due to the difference in the longitudinal direction of the nip width I am trying.

Further, a third invention according to the present application solves the above-mentioned problems, and in an induction heating type heating device, it is possible to simplify the temperature control while shortening the temperature rising time at the time of starting the device. It is an object of the present invention to provide a heating device which does not generate a temperature rise in a non-sheet passing portion, an image defect due to a change in roller peripheral velocity, and a waviness of a recording material due to a difference in a width direction of a nip portion.

Further, the fourth invention according to the present application achieves the above-mentioned object, is capable of forming a nip by elastic deformation and elastic force generated by the elastic deformation, has appropriate rigidity, and is rotated by pressure. Another object of the present invention is to provide a heating device having a roller that does not buckle.

Further, a fifth invention according to the present application is, in the above-mentioned fourth invention, an object of the present invention to provide a heating device which does not generate dirt such as toner on the roller surface.

The sixth invention according to the present application is the same as the fourth invention, wherein a desired nip width can be obtained even when the roller has a small diameter, or even when the pressure is low. An object of the present invention is to provide a heating device that can make black and halftone fixing properties more uniform, and can obtain a high-quality image without graze.

Further, the seventh invention to the ninth invention according to the present application can simplify the temperature control while shortening the waiting time when the apparatus is started up, and can increase the temperature of the non-sheet passing portion and the roller circumference. An object of the present invention is to provide an image forming apparatus capable of forming a good image without causing an image defect due to a change in speed and waviness of a recording material due to a difference in nip width in a longitudinal direction.

Further, the tenth invention of the present application achieves the above-mentioned object, and is capable of forming a nip by elastic deformation and elastic force generated by the elastic deformation, has appropriate rigidity, and is rotated by pressure. Another object of the present invention is to provide an image forming apparatus provided with a heating device that does not buckle.

Further, an eleventh invention of the present application is, in the above-mentioned tenth invention, an object of the invention is to provide an image forming apparatus which does not generate dirt such as toner on the roller surface.

The twelfth invention of the present application is the tenth invention, wherein the desired nip width can be obtained even when the diameter of the roller is small, or even when the pressure is low. An object of the present invention is to provide an image forming apparatus which can make black and halftone fixing properties more uniform, and can obtain a high-quality image without graze.

[0027]

According to a first invention of the present application, the above object is provided with a heating member and a pressing member which are arranged so as to be in pressure contact with each other. In the heating device for heating the recording material in the pressure contact nip portion formed by, at least one of the heating member and the pressure member is formed of a thin sleeve, and the pressure contact nip portion is elastically deformed of the thin sleeve, And the elastic force generated by the elastic deformation.

According to the second invention of the present application,
The above-mentioned object includes a heating member, a heat-resistant film that is endlessly movable while slidingly contacting the heating member, and a pressure member that slides and conveys the heat-resistant film while closely contacting the heating member. The recording material is introduced into the pressure contact nip portion between the heating member and the pressure member formed by sandwiching the heat resistant film, and the pressure contact nip portion is conveyed together with the heat resistant film. In a film heating type heating device for applying heat to a recording material through a heat resistant film, the pressing member is formed of a thin sleeve, and the press contact nip portion is elastically deformed and This is achieved by being formed by the elastic force generated by the deformation.

Further, according to the third invention of the present application, the above object is to provide a rotating body, an exciting coil provided inside the rotating body, and an arrangement so as to make pressure contact with the rotating body. A pressure member that forms a pressure contact nip portion with a predetermined width between the rotor and the rotating body, and the eddy current generated in the rotor causes the pressure contact nip portion to generate heat, and the recording material is heated in the pressure contact nip portion. In the heating device, the pressing member is formed by a thin sleeve, and the pressure contact nip portion is formed by elastic deformation of the thin sleeve and elastic force generated by the elastic deformation.

According to the fourth invention of the present application,
The above-mentioned object is any one of the above-mentioned first to third inventions, wherein the thin-walled sleeve has a wall thickness t, a radius r, a Young's modulus of a member forming the thin-walled sleeve E, and a Poisson's ratio ν. if you did this,

[0031]

## EQU00003 ## It is achieved by satisfying 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5 .

Further, according to the fifth invention of the present application, the above object is achieved by providing the heat-resistant release layer on the surface layer of the metal sleeve in the thin sleeve in the fourth invention.

According to a sixth invention of the present application, in the above-mentioned fourth invention, the thin sleeve has a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer on the surface layer of the metal sleeve. This is achieved by being sequentially formed.

Further, according to the seventh invention of the present application,
The purpose is to develop an image bearing member having a photosensitive layer, an exposing means for exposing the image bearing member according to image information, and an electrostatic latent image formed on the image bearing member by the exposure with a developer. A developing device, a transfer device for transferring the developer image to the recording material, and a heating device provided with a heating member and a pressing member arranged so as to be in pressure contact with each other are provided, and the developer image is formed. In an image forming apparatus for forming an image by heating a recording material in a pressure contact nip portion formed by the heating member and a pressing member of the heating device, at least one of the heating member and the pressing member of the heating device. Is formed of a thin sleeve, and the pressure contact nip portion is formed by elastic deformation of the thin sleeve and elastic force generated by the elastic deformation.

According to the eighth invention of the present application,
The purpose is to develop an image bearing member having a photosensitive layer, an exposing means for exposing the image bearing member according to image information, and an electrostatic latent image formed on the image bearing member by the exposure with a developer. A developing device, a transfer device for transferring a developer image to a recording material, and a pressing member for slidingly transporting a heat-resistant film which is endlessly movable while slidingly contacting a heating member while closely adhering to the heating member. And a heating device having
The recording material on which the developer image is formed is introduced into the pressure contact nip portion between the heating member and the pressure member formed by sandwiching the heat resistant film, and the pressure contact nip portion together with the heat resistant film is introduced. In the image forming apparatus which conveys the heat of the heating member to the recording material through the heat resistant film to form an image, the pressing member of the heating device is formed of a thin sleeve, The nip portion is achieved by the elastic deformation of the thin sleeve and the elastic force generated by the elastic deformation.

Further, according to the ninth invention of the present application, the above object is to provide an image bearing member having a photosensitive layer, an exposing means for exposing the image bearing member according to image information, and an image by the exposure. A developing device that develops an electrostatic latent image formed on a carrier with a developer, a transfer device that transfers the developer image onto a recording material, and a rotating body provided with an exciting coil inside to press and rotate the rotating body. And a heating device having a pressure member that forms a pressure contact nip portion of a predetermined width with the body, and heats the recording material on which the developer image is formed by the eddy current generated in the rotating body. In an image forming apparatus for forming an image by heating in a pressure contact nip portion, the pressure member of the heating device is formed of a thin sleeve, and the pressure contact nip portion is elastically deformed by the thin wall sleeve and by the elastic deformation. Due to the elastic force generated It is accomplished by being formed.

According to a tenth invention of the present application, the object is the thin-walled sleeve according to any one of the seventh to ninth inventions, wherein the thin-walled sleeve has a wall thickness t, a radius r, When the Young's modulus of the member forming the thin sleeve is E and the Poisson's ratio is ν,

[0038]

## EQU00004 ## It is achieved by satisfying 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5 .

Further, according to the eleventh invention of the present application,
In the tenth aspect of the invention, the above object is achieved by providing the heat-resistant release layer on the surface layer of the metal sleeve of the thin sleeve.

According to a twelfth invention of the present application, in the above-mentioned tenth invention, the thin sleeve has a heat-resistant elastic layer and a heat-resistant release layer each having a thickness of 1.0 mm or less on the surface layer of the metal sleeve. It is achieved by sequentially forming.

[0041]

According to the first to third inventions of the present application, the recording material is passed through a pressure contact nip portion formed by the heating member and the pressure member pressed against the heating member, and the recording material is undetermined. In a heat fixing device that heats and presses a formed image to fix it as a permanent image on the recording material, a thin sleeve is used for at least one of a pressure member and a heating member, and elastic deformation of the thin sleeve causes elastic deformation. Since the pressure contact nip having a desired width is formed by the elastic force, it operates as follows.

(1) When a thin sleeve is used as the pressing member, or when a thin sleeve is used as the heating member and a good heat conductive rigid member is used as the pressing member, both the pressing member and the heating member are thin. In the case of using the sleeve, the heat capacity of the member formed of the thin-walled sleeve is small in any case, the temperature of the member rises quickly when the device is started up, and the startup time of the heating device is shortened. Further thereafter, the temperature of the member is maintained at a constant value like the temperature of the heating member, and sufficient fixing property is secured immediately after the apparatus is started up at the steady-state temperature in the conventional heating method. Is lower than in the past and it is not necessary to provide a plurality of target temperatures for fixing, and the control of the heating member is further simplified.

(2) When a thin sleeve is used for at least one of the pressure member and the heating member, and when a rigid member having good heat conductivity is used as the pressure member by using the thin sleeve on the heating member side. Since the heat conductivity in the longitudinal direction of the pressure contact nip portion is increased and a small-sized recording material passes through, the temperature rise in the non-passage area of the recording material becomes small and the temperature unevenness also becomes small. No uneven glossiness or uneven fixing of the image occurs, and members disposed near the area are not damaged by heat.

(3) Further, since the thermal expansion coefficient of the pressing member is small and the outer diameter is stable, the conveying speed and the conveying property of the recording material and the film are stable, and the wrinkles of the recording material and the elongation of the image are increased.・
Image problems such as blurring, film deviation and damage do not occur.

(4) The thin-walled sleeve has appropriate rigidity and forms a flat nip portion uniformly in the longitudinal direction, so that the nip width becomes uniform and is applied to the recording material, but the pressure is even in the longitudinal direction. Therefore, waviness does not occur at the edge of the recording material.

According to the fourth invention of the present application,
In any one of the first to third inventions, when the thin sleeve has a wall thickness t, a radius r, a Young's modulus of a member forming the thin sleeve is E, and a Poisson's ratio is ν,

[0047]

[Equation 5] 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5

By satisfying the condition, the nip can be formed by the elastic deformation of the thin sleeve and the elastic force generated by the elastic deformation, and the nip can have appropriate rigidity, and the sleeve does not buckle even when it is rotated under pressure.

Further, according to the fifth invention of the present application, in the above-mentioned fourth invention, the thin-walled sleeve has a heat-resistant release layer on the surface layer of the metal sleeve, and therefore exhibits good releasability.

According to the sixth invention of the present application, in the above-mentioned fourth invention, the thin sleeve has a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer sequentially formed on the surface layer of the metal sleeve. Therefore, the desired nip width can be obtained even when the sleeve has a small diameter or even when the pressure is low. Further, the wrapping of the sleeve makes the fixing properties such as solid black and halftone more uniform, thereby obtaining a high-quality image without greasiness.

Further, according to the seventh invention to the ninth invention of the present application, the heating device according to any one of the first invention to the third invention is used for heating a visible image of a recording material. Since the image forming apparatus is equipped with the above, the standby time at the time of starting the apparatus is shortened, the temperature control is simplified, the temperature of the non-sheet passing portion is increased, the image is defective due to the change of the roller peripheral speed, and the nip width in the longitudinal direction is increased. A good image is formed without causing waviness of the recording material due to the difference.

According to a tenth invention of the present application, in any one of the seventh to ninth inventions described above,
A thin sleeve has a wall thickness t, a radius r, a Young's modulus of a member forming the thin wall sleeve E, and a Poisson's ratio ν,

[0053]

[Equation 6] 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5

By satisfying the condition, the nip can be formed by the elastic deformation of the thin-walled sleeve and the elastic force generated by the elastic deformation, and the nip can have an appropriate rigidity, and the sleeve does not buckle even under the pressure rotation, which is excellent. Image formation is performed.

Further, according to the eleventh invention of the present application, in the tenth invention, since the heat-resistant release layer is provided on the surface layer of the metal sleeve of the thin-walled sleeve, the thin sleeve exhibits good releasability. Image formation is performed.

According to the twelfth invention of the present application, in the above-mentioned tenth invention, the thin sleeve has a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer sequentially formed on the surface layer of the metal sleeve. Therefore, the desired nip width can be obtained even when the sleeve has a small diameter or even when the pressure is low. Further, the wrapping of the sleeve makes the fixing properties such as solid black and halftone more uniform, thereby forming a high-quality image without greasiness.

[0057]

FIG. 6 shows an example of an image forming apparatus according to the present invention. In FIG. 6, reference numeral 1 is a photosensitive drum as an image carrier, which is formed by forming a photosensitive material such as OPC, amorphous Se, or amorphous Si on a cylindrical substrate such as aluminum or nickel. The photosensitive drum 1 is rotationally driven in the direction of the arrow, and the surface thereof is first uniformly charged by a charging roller 2 as a charging device. Next, the laser beam 3 which is the exposure means is turned on according to the image information.
/ OFF control is performed to perform scanning exposure, and an electrostatic latent image is formed on the photosensitive drum 1. This electrostatic latent image is developed and visualized by the phenomenon device 4. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and it is often used in combination with image exposure and reversal developing. The visualized toner image is transferred from the photosensitive drum 1 onto a transfer material P which is a recording material supplied and conveyed at a predetermined timing by a transfer roller 5 which is a transfer device. The transfer material P holding the toner image is conveyed to the fixing device 6, heated and pressed in the nip portion of the fixing device 6 and fixed on the transfer material P to form a permanent image. On the other hand, the transfer residual toner remaining on the photosensitive drum 1 after the transfer is removed from the surface of the photosensitive drum 1 by the cleaning device 7. Hereinafter, a specific example of the fixing device to which the present invention is applied will be described.

(First Embodiment) FIG. 1 is a schematic sectional view of a film heating type fixing device to which the first embodiment of the present invention is applied.

In FIG. 1, 10 is a heat-resistant film (fixing film) in the form of an endless belt, which is fitted onto a semi-arcuate film guide member (stee) 13 in such a manner that it has a margin in its circumferential length. ing.

The film 10 has a total thickness of 100 μm in order to reduce the heat capacity and improve the quick start property.
m or less, preferably 40 μm or less and 20 μm or more,
PTFE, PF with heat resistance, releasability, strength, durability, etc.
A, PPS or other single layer film, or polyimide, polyamide imide, PEEK, PES or other film surface with PT
It is a composite layer film or the like coated with FE, PFA, FEP or the like as a release layer.

Reference numeral 11 denotes a thin metal sleeve as a pressing member, which is a sleeve formed by molding a metal such as iron, SUS or nickel into a thin hollow cylinder. The thin metal sleeve 11
The thickness t is required to be set in a range in which a nip can be formed by elastic deformation and an elastic force generated by the elastic deformation, which has appropriate rigidity, and which is not buckled by pressure rotation. The proper range is defined by the range of pressure (buckling pressure) that causes buckling when a thin cylinder receives external pressure,
When the radius of the thin-walled metal sleeve 11 is r, the Young's modulus of the constituent material of the thin-walled metal sleeve 11 is E, and the Poisson's ratio is ν, it is expressed by the following relational expression. (Quoted from "Contemporary Material Engineering" (Ohm).

[0062]

[Equation 7] 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5

For example, nickel is used as a constituent material,
When making a thin metal sleeve having a radius r = 10.0 [mm], the appropriate values of the thickness of the sleeve are: Young's modulus E of nickel = 20.0 [N / m ² ] and Poisson's ratio ν = 0.3.
0 [N / m ² ] and the above equation, 60 μm <t <150 μm
The thickness is within the range, and an arbitrary wall thickness may be selected within the range.

Further, as shown in FIG. 2, the thin metal sleeve 11 may have a structure in which the surface layer of the metal sleeve 11a is covered with a heat-resistant release layer 11b made of a fluororesin such as PFA or PTFE. In that case, in order not to impair the good thermal conductivity of the thin metal sleeve 11, it is preferable that the heat-resistant release layer 11b has a thickness of 50 μm or less.

As shown in FIG. 4, the thin metal roller 11 has flanges 51 inserted at both ends and fixed by adhesion, and a shaft 53 is passed in the roller longitudinal direction via a bearing 52 provided in the center of the flange. It is arranged in pressure contact with the heating body 12 as a heating member shown in FIG. 1 by a pressure spring 55 via a bearing 53 and a bearing 54 with a pressure of 5 to 10 kgf.

The length of the thin metal roller 11 in the longitudinal direction needs to be longer than that of the heating body 12 in order to form a uniform nip. Specifically, as shown in FIG. Distance X to the end face of the insertion part is 3.0m
It is preferably m or more. Further, at least one of the flanges 42 is a gear flange, and the driving means (not shown) rotationally drives the thin metal sleeve 11 via the gear flange.

In FIG. 1, the film 10 is rotated at a predetermined peripheral speed by the rotation of the thin metal sleeve 11 so as to be in contact with the surface of the heating body 12 in the clockwise direction indicated by the arrow at least during image fixing and sliding on the surface of the heating body 12. At the time, that is, at a peripheral speed substantially the same as the transport speed of the transfer material P carrying the unfixed toner image T transported from the image forming section (A) side, it is rotationally driven without wrinkles.

The heating element 12 includes an energization heating element (resistive heating element) 12a as a heat source that generates heat by power feeding, and the temperature is raised by the heat generation of the energization heating element 12a. Therefore, when the heating body 12 is heated by the power supply to the energization heating body 12a and the film 10 is rotationally driven, the thin metal sleeve 11 is elastically deformed and the elastic force generated by the elastic deformation causes the heating body 12 to Of the pressure nip N (fixing nip) formed between the film 10
When the transfer material P is introduced between the thin metal sleeve 11 and the thin metal sleeve 11, the transfer material P comes into close contact with the film 10 and passes through the fixing nip portion N in an overlapping state with the film.

In the course of the transfer material P passing through the fixing nip portion, heat energy is applied to the transfer material P from the heating body 12 through the film 10 so that the unfixed toner image T on the transfer material P is heated and fused and fixed. After passing through the fixing nip, the material P is separated from the film 10 and discharged.

In FIG. 7, a polyimide film having a film thickness of 20 μm as a heat-resistant film and a release layer made of PFA having a thickness of 15 μm are formed on the surface layer of a metal sleeve formed by molding nickel as a pressing member to a thickness of 90 μm. Fig. 8 shows the transition of the film temperature and the pressure member temperature when the temperature of the heating element was controlled to 160 ° C with a heating device using a coated thin metal sleeve. The transition of the temperature of the heat-resistant film in the paper-passing portion and the non-paper-passing portion in the case of performing is shown.

The vertical axis of FIG. 7 is the temperature of each member, the horizontal axis is the elapsed time from the start-up of the apparatus, the line A in the graph indicates the boundary temperature at which high-temperature offset occurs, and the line B indicates that fixing failure occurs. Shows the boundary temperature, line A and line B
The temperature range sandwiched between is the proper temperature range of the heat-resistant film in which sufficient fixability can be secured at each time after the apparatus is started up and high-temperature offset does not occur. As shown in the figure, by using a thin nickel sleeve as the pressing member, the temperature rise of the heat resistant film at the time of starting the device becomes faster than in the case of the conventional configuration using the elastic roller as the pressing member. This temperature became almost constant. This is because the heat capacity of the pressure member is reduced and the thermal conductivity is improved by using a thin sleeve, the temperature of the pressure member facing the nip rises quickly, and after the temperature rises, it follows the control of the heater. However, since the temperature is kept substantially constant, the temperature of the heat-resistant film is also kept substantially constant even if the target temperature of the heating element is kept constant. Therefore, in the heat fixing device to which the present invention is applied, a good image can be obtained which satisfies the fixability at a constant target fixing temperature and does not cause high temperature offset.
Control of setting the target temperature for each sheet by F (or ON) is not required, and the heater control can be simplified.

Further, since the heat conduction in the longitudinal direction of the nip portion becomes good, the temperature difference ΔT between the paper passing portion and the non-paper passing portion becomes small even after the continuous passing of small size paper, as shown in FIG. No uneven gloss or uneven fixing due to uneven temperature at the nip portion occurred.

Further, since the nickel sleeve has a small coefficient of thermal expansion, the transfer material conveying speed is stable, and as described above, the temperature rise of the non-sheet passing portion is small, so that the heat-resistant film is also stable in conveying and the image such as elongation There were no problems or damage to the film. Even if a small-diameter shaft having a diameter of 6.0 mm is used as the pressing member, since the structure for transmitting the flexure generated in the shaft does not exist between the sleeve and the shaft, the nip width is formed uniformly in the entire longitudinal direction. Rippling did not occur at the edges of the transfer material.

In the structure of this embodiment, the temperature detecting element 1
Since the No. 4 can be installed on the inner surface of the nip of the thin metal sleeve 11 whose temperature is closer to that of the nip portion, not on the back surface of the conventional heating body, more reliable temperature control is possible.

Further, as shown in FIG. 3, the thin metal sleeve 11 may have a structure in which a thin elastic layer 11c made of heat resistant rubber such as silicone rubber is provided on the metal sleeve 11a. When a thin elastic layer is provided on the metal sleeve in this way,
A small diameter sleeve, a desired nip width with a low pressure can be obtained, and since it has the effect of wrapping the toner from the back side of the transfer material, the fixability of solid black and halftone becomes more uniform, and high quality without greasiness etc. You can get the image of. At this time, the thickness of the thin elastic layer 11c is preferably 1.0 m or less so as not to impair the thermal conductivity of the thin metal sleeve 11.

(Second Embodiment) In this embodiment, a thin metal sleeve is applied as a pressing member of an induction heating type heat fixing device.

FIG. 9 is a schematic sectional view of an induction heating type fixing device adopting this embodiment.

Reference numeral 20 is a heat generating film as a heating member, which is made of polyimide, polyamide imide, PEEK, PE.
A film base material 20a having a thickness of 10 μm to 100 μm is formed of a resin such as S, PPS, PFA, PTFE or FEP,
Fe, Co and Ni, Cu, and
A metal layer 20b of Cr or the like was formed to a thickness of 1 μm to 100 μm, and a releasable layer 20c was formed on the outer layer again by coating a heat-resistant resin having a good releasability such as PFA, PTFE, FEP silicone resin or the like alone or coating it. It is a thing.

Reference numeral 21 denotes a coil, which is formed by winding it around an iron core. Reference numeral 23 denotes a sliding plate that supports the coil and guides the movement of the film 20 and slides the film. It is preferable to apply grease, oil or the like on the surface of the film 20 using glass or the like having a small friction resistance. Alternatively, the sliding member may be configured by the core material 22 as a smooth surface.

Reference numeral 11 denotes a thin metal sleeve as a pressing member, which has the same structure as that of the above embodiment. The thin metal sleeve 11 is placed in pressure contact with the core member 21 by a pressure means (not shown) at a predetermined pressure, and a film is formed between the thin metal sleeve 11 and the core member 21 due to elastic deformation of the metal sleeve and elastic force generated by the elastic deformation. A pressure contact nip portion having a desired width is formed through the thin metal sleeve 11, and the thin metal sleeve 11 is driven by a driving means (not shown), and the film 20 is rotated by the thin metal sleeve 11.

An alternating current is applied to the coil 21 from an exciting circuit (not shown), whereby the magnetic flux indicated by the arrow H is repeatedly generated and extinguished around the coil 21. This magnetic flux H
The core material 22 is configured so that the crosses the conductive layer of the film 20. When a fluctuating magnetic field traverses a magnetic body, eddy currents are generated in the conductor so as to create a magnetic field that prevents changes in the magnetic field. This eddy current is indicated by arrow A. Due to the skin effect, this eddy current almost concentrates on the surface of the conductive layer on the side of the coil 21 and generates heat with power proportional to the skin resistance of the film conductive layer 20b, and heats only the pressure contact nip portion.

A temperature detecting element 24 is arranged in sliding contact on the surface of the inner surface of the thin metal sleeve 11 facing the pressure contact nip portion. Since the temperature of the inner surface of the thin metal sleeve 11 facing the nip is almost the same as the temperature of the film surface facing the pressure contact nip, the energization control means for energizing the exciting coil based on the detection result of the temperature detecting element. (Not shown) to control the temperature of the fixing nip portion to a desired value.

The transfer material P carrying the unfixed toner image is conveyed together with the film 20 by the thin metal sleeve 11, and is heated / pressurized in the pressure contact nip portion to heat-fix the unfixed toner image T on the transfer material P. Then, the image is fixed on the transfer material to form a permanently fixed image.

In this embodiment, the same effect as in the first embodiment can be obtained by using the thin metal sleeve as the pressing member. Further, the thin metal sleeve itself has the same heat generation principle as that of the metal layer in the film. Since the heat is generated by the induction heating, the fixing temperature can be set lower.

(Third Embodiment) This embodiment is a heating device of a heating roller system using a thin metal sleeve as a pressing member. FIG. 10 shows a schematic sectional view of the device.

In the figure, 30 is a heating roller as a heating member having a halogen heater therein, 11 is a thin metal sleeve, and the heating roller 30 and the thin metal sleeve 1 are provided.
1 are arranged in parallel vertically and the thin metal sleeve 11 is arranged in pressure contact with the heating roller 30 with a predetermined pressure in the same manner as in the above-mentioned embodiment.

Reference numeral N denotes a pressure contact nip portion formed by elastic deformation of the thin metal sleeve 11 caused by pressure contact between the heating roller 30 and the thin metal sleeve 11 and elastic force generated by the elastic deformation. The heating roller 30 is rotationally driven in the clockwise direction by a driving means (not shown), and the thin metal sleeve 11 is driven to rotate.

The heating roller 30 has a heat-resistant release layer 32b made of a fluororesin such as PFA or PTFE on a cored bar 32a made of aluminum, stainless steel or the like which is processed into a hollow cylindrical shape to improve releasability from toner. It is a covered structure.

The thin metal sleeve 11 has the same structure as that of the above-mentioned embodiment.

The temperature detecting element 3 is provided on the surface of the heating roller 30.
2 is provided, the temperature detecting element detects the temperature of the surface of the heating roller 30, and the heater driving means (not shown) keeps the surface of the heating roller at a predetermined temperature based on the detection result. Turn on / off the halogen heater 31
FF is controlled.

Transfer material P carrying an unfixed toner image T
Is nipped and conveyed in the pressure contact nip portion N, and is heated and pressed to heat and melt the toner and fix the toner on the transfer material to obtain a permanently fixed image.

Also in this embodiment, the same effect as that of the above-mentioned embodiment can be obtained by using the thin metal sleeve as the pressing member.

When an elastic roller having an elastic layer of silicone rubber or the like is used as the pressing member, the heat from the heating source at the time of starting the apparatus is consumed for heating both the heating roller and the elastic roller. Although it took about 1 minute to start up, with the configuration as shown in this embodiment, most of the heat from the heating source at the time of start-up is spent to heat the heating roller core metal, The time required for raising can be reduced to about 2/3 in proportion to the conventional case.

(Fourth Embodiment) This embodiment is a heating device of a heating roller type using a thin metal sleeve as a heating roller and a rigid roller having good thermal conductivity as a pressing member.

FIG. 11 shows a schematic sectional view of the apparatus.

In the figure, 41 is a thin metal sleeve as a heating member having a halogen heater 44 inside, and 40 is a good heat conductive roller as a pressing member.

The good heat conductive roller 40 is arranged in pressure contact with the thin metal sleeve 41 at a predetermined pressure by a pressing means (not shown).

The thin-walled metal sleeve 41 comprises a metal sleeve 41a made of iron, SUS, nickel or the like, and a thin heat-resistant elastic body 41c made of silicone rubber or the like, PFA, PT.
It is a hollow rotating body in which a heat-resistant release layer 41b made of FE, FEP or the like is sequentially formed.

The good heat conductive roller 40 includes nylon 6, nylon 66, polyethylene terephthalate, and polyptyrene in which a core metal 40a made of iron, SUS or the like is mixed with about 30 to 40% of heat resistant reinforcing fiber such as glass short fiber. Heat-resistant elastic layer 40b made of heat-resistant cured resin such as terephthalate or polyphenylene sulfide, heat-resistant polymer such as silicone resin, fluororesin, polyimide, aromatic polyamide, polybenzimidazole, or inorganic solid heat insulating material such as foam glass. , A metal layer 40c made of a good thermoelectric metal such as aluminum is sequentially formed.

Reference numeral N denotes a pressure contact nip portion formed by elastic deformation of the thin metal sleeve 41 caused by pressure contact between the good heat conductive roller 40 and the thin metal sleeve 41, and elastic force generated by the elastic deformation.

As shown in FIG. 11, the thin metal sleeve 41 has flanges 44 inserted and adhered at both ends, and one of the flanges serves as a gear, which is driven by a driving means (not shown) via the flange gear. The good thermal conductor roller 40 is driven to rotate in the direction of the arrow, and rotates in accordance with this.

A temperature detecting element 43 is disposed on the surface of the thin metal sleeve 41. The temperature detecting element detects the temperature of the surface of the thin metal sleeve 41, and the surface of the thin metal sleeve 41 is determined based on the detection result. The halogen heater 44 is ON / OFF controlled by a heater driving means (not shown) so as to maintain the temperature.

Transfer material P carrying an unfixed toner image T
Is nipped and conveyed in the pressure contact nip portion and heated and pressed to heat and melt the toner, and the toner is fixed on the transfer material P to obtain a permanently fixed image.

Also in this embodiment, the thin metal sleeve is used as the heating member, and the press contact nip portion is formed by the elastic elastic deformation of the thin metal sleeve and the elastic force generated by the elastic deformation, and the press member has high thermal conductivity. By using a metal roller, the heat capacity of the entire heating device can be reduced, the thermal conductivity in the longitudinal direction of the nip part can be increased, and the device startup time can be shortened and the temperature rise in the non-sheet passing area can be reduced. No damage to internal parts. Further, since a uniform nip is formed in the longitudinal direction, waviness does not occur at the end portion of the transfer material as in the above-described embodiment.

Further, as shown in the enlarged view of the pressure contact nip portion in FIG. 12, the fixing property is improved due to the toner wrapping effect by the thin heat resistant elastic layer provided on the thin metal sleeve 41, and the fixing temperature is low. Becomes possible.

[0106]

As described above, the first aspect of the present application
According to the invention, the recording material on which the unfixed image is formed passes through a nip portion formed by a heating member that is maintained at a predetermined temperature and a pressing member that is pressed against the heating member. In the heating device which heats and pressurizes the unfixed image to fix it as a permanent image on the recording material,
When a thin sleeve is used as the pressing member and a nip is formed between the thin sleeve and the heating member by elastic deformation of the thin sleeve and the elastic force generated by the elastic deformation, or the thin sleeve is used as the heating member and good thermal conductivity of a rigid body is obtained. The following effects can be obtained by forming a nip between the pressurizing member and the elastic deformation of the thin sleeve and the elastic force generated by the elastic deformation.

(1) When the thin sleeve is used as the pressing member, or when the thin sleeve is used as the heating member and the good thermal conductive rigid member is used as the pressing member, the heat capacity of the pressing member is small. Since the temperature of the pressure member rises quickly when the device is started up, and the temperature of the pressure member can be maintained at a constant value after that, it depends on the time from the device startup and the paper passing state. Since it is not necessary to provide a plurality of target temperatures for fixing, control of the heating member can be simplified.

(2) In the case where the thin-walled sleeve is used as the pressing member, the thin-walled sleeve is used as the heating member, and the good thermal conductive rigid member is used as the pressing member, the thermal conductivity in the longitudinal direction of the nip portion is obtained. Since the temperature rise is small, the temperature rise in non-sheet passing is small, and the temperature unevenness is also small, so that it is possible to prevent uneven glossiness of the image, uneven fixing, and the like, and it is also possible to prevent damage to the members near the non-sheet passing temperature rising part due to heat.

(3) Further, since the thermal expansion coefficient of the pressing member is small and the outer diameter is stable, the transport speed and transportability of the recording material and the heat resistant film are stable, and wrinkles of the recording material and image Image problems such as stretching and blurring, and damage to the heat-resistant film can be prevented.

(4) Since the thin sleeve has an appropriate rigidity and acts to uniformly form a flat nip portion in the longitudinal direction, the nip width becomes uniform and the pressure applied to the recording material is increased. Is uniform in the longitudinal direction, and it is possible to prevent waviness at the edge of the recording material.

According to the fourth invention of the present application,
In any one of the first to third inventions, when the thin sleeve has a wall thickness t, a radius r, a Young's modulus of a member forming the thin sleeve is E, and a Poisson's ratio is ν,

[0112]

[Equation 8] 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5

By satisfying the above condition, it is possible to provide a sleeve in which a nip can be formed by elastic deformation of the thin sleeve and an elastic force generated by the elastic deformation, and which has appropriate rigidity and which is not buckled even by pressure rotation.

Further, according to the fifth invention of the present application, in the fourth invention, since the heat-resistant releasing layer is provided on the surface layer of the metal sleeve of the thin-walled sleeve, good releasing property can be obtained. I can.

According to the sixth invention of the present application,
In the fourth aspect of the invention, the thin-walled sleeve has the heat-resistant elastic layer and the heat-resistant release layer with a thickness of 1.0 mm or less sequentially formed on the surface layer of the metal sleeve.
Alternatively, a desired nip width can be obtained even with a low pressure. Further, the wrapping of the sleeve makes the fixing properties such as solid black and halftone more uniform, so that a high-quality image without greasiness can be obtained.

Furthermore, the seventh to ninth inventions of the present application
According to the invention, the image forming apparatus is equipped with the heating device according to any one of the first to third inventions as a heating device for heating the visible image of the recording material. Time is shortened, temperature control is simplified, image failure due to temperature rise in non-sheet passing area, change in roller peripheral speed, wavy recording material due to difference in nip width in the longitudinal direction, and good image quality Can be formed.

According to the tenth invention of the present application, in any one of the seventh to ninth inventions described above,
A thin sleeve has a wall thickness t, a radius r, a Young's modulus of a member forming the thin wall sleeve E, and a Poisson's ratio ν,

[0118]

[Equation 9] 1.19 × 10 ^-6 <{E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5

By satisfying the condition, the nip can be formed by the elastic deformation of the thin sleeve and the elastic force generated by the elastic deformation, and the nip can have appropriate rigidity, and the sleeve can be prevented from buckling due to the pressure rotation. Therefore, good image formation can be performed.

Further, according to the eleventh invention of the present application, in the tenth invention, since the heat-resistant release layer is provided on the surface layer of the metal sleeve of the thin-walled sleeve, good releasability can be obtained. Therefore, good image formation can be performed.

According to the twelfth aspect of the present invention, in the tenth aspect of the invention, the thin-walled sleeve has a metal sleeve surface layer on which a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer are sequentially formed. Therefore, the desired nip width can be obtained even when the sleeve has a small diameter or even when the pressure is low. Further, by enclosing the sleeve, the fixing properties such as solid black and halftone can be made more uniform, and a high-quality image without greasiness can be formed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a heating device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the thin-layer metal sleeve of the first embodiment according to the present invention.

FIG. 3 is a schematic sectional view of a thin-layer metal sleeve of the first embodiment according to the present invention.

FIG. 4 is a perspective view of the thin-layer metal sleeve of the first embodiment according to the present invention.

FIG. 5 is a schematic cross-sectional view of the thin-layer metal sleeve of the first embodiment according to the present invention.

FIG. 6 is a schematic diagram of an image forming apparatus to which the present invention is applied.

FIG. 7 is a graph showing changes in temperature of a heating member and a pressure member.

FIG. 8 is a graph showing temperature transitions of a sheet passing portion and a non-sheet passing portion when a small size sheet is passed.

FIG. 9 is a schematic sectional view of a heating device of a second embodiment according to the present invention.

FIG. 10 is a schematic sectional view of a heating device of a third embodiment according to the present invention.

FIG. 11 is a schematic sectional view of a heating apparatus of a fourth embodiment according to the present invention.

FIG. 12 is an enlarged cross-sectional view of a nip portion of a heating device according to a fourth example of the present invention.

FIG. 13 is a graph showing a temperature transition of a heat fixing device constituent member of a conventional heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 3 Laser beam (exposure means) 4 Developing device 5 Transfer roller (transfer device) 6 Fixing device 10 Heat resistant film 11,41 Thin metal sleeve (thin sleeve) 11a, 41a Metal sleeve 11b, 41b Heat-resistant release layer 11c, 41c Thin elastic layer 12 Heating body (heating member) 20 Exothermic film (heating member) 30 Heating roller (heating member) 40 Good thermal conductive roller (pressurizing member) N Pressure contact nip P Transfer material ( Recording material)

Claims (12)

[Claims] 1. A heating device comprising a heating member and a pressure member arranged so as to be in pressure contact with each other, wherein a recording material is heated in a pressure contact nip portion formed by the heating member and the pressure member. At least one of the member and the pressing member is formed of a thin sleeve, and the pressure contact nip portion is formed by elastic deformation of the thin sleeve and elastic force generated by the elastic deformation. . 2. A heating member, a heat-resistant film disposed so as to be endlessly movable while slidingly contacting the heating member, and a pressure member for slidingly transporting the heat-resistant film while closely contacting the heating member. The recording material is introduced into the pressure-contact nip portion between the heating member and the pressure member formed by sandwiching the heat-resistant film, and the recording material is conveyed through the pressure-contact nip portion together with the heat-resistant film. In a heating device of a film heating system for applying the heat of No. 1 to a recording material through a heat resistant film, the pressing member is formed of a thin sleeve, and the press nip portion is elastically deformed of the thin sleeve, and A heating device formed by an elastic force generated by elastic deformation. 3. A rotating body, an exciting coil provided inside the rotating body, and a pressing nip portion having a predetermined width formed between the rotating body and the rotating body so as to be in pressure contact with the rotating body. In a heating device that has a pressure member and heats the recording material at the pressure contact nip portion by the eddy current generated in the rotating body, the pressure member is formed of a thin sleeve. The heating device is characterized in that the press contact nip portion is formed by elastic deformation of the thin sleeve and an elastic force generated by the elastic deformation. 4. The thin sleeve has a wall thickness of t, a radius of r,
When the Young's modulus of the member forming the thin sleeve is E and the Poisson's ratio is ν, the following equation is obtained: 1.19 × 10 ⁻⁶ <{E / 4 (1-ν ² )} (t / r) ³ <1.85 The heating device according to any one of claims 1 to 3, wherein x10 ^-5 is satisfied. 5. The heating device according to claim 4, wherein the thin-walled sleeve is provided with a heat-resistant release layer on the surface layer of the metal sleeve. 6. The heating device according to claim 4, wherein the thin sleeve has a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer sequentially formed on the surface layer of the metal sleeve. 7. An image carrier having a photosensitive layer, exposure means for exposing the image carrier according to image information, and an electrostatic latent image formed on the image carrier by the exposure with a developer. A developing device for pressing, a transfer device for transferring the developer image onto the recording material, and a heating device provided with a heating member and a pressing member arranged in pressure contact with each other are provided to form the above-mentioned developer image. In an image forming apparatus for forming an image by heating a recording material to be recorded in a pressure contact nip portion formed by the heating member and the pressing member of the heating device, at least the heating member or the pressing member of the heating device. One is formed of a thin-walled sleeve, and the pressure contact nip portion is formed by elastic deformation of the thin-walled sleeve and an elastic force generated by the elastic deformation. 8. An image carrier having a photosensitive layer, exposure means for exposing the image carrier according to image information, and an electrostatic latent image formed on the image carrier by the exposure with a developer. A developing device for pressing, a transfer device for transferring a developer image onto a recording material, and a heat-resistant film disposed so as to be endlessly movable while slidingly contacting a heating member. A heating device provided with a member, the recording material on which the developer image is formed is introduced into a pressure contact nip portion between the heating member and the pressure member, which are formed by sandwiching the heat resistant film. In the image forming apparatus, the heat of the heating member is conveyed along with the heat-resistant film and the heat of the heating member is applied to the recording material through the heat-resistant film to form an image. Is formed of a thin sleeve The image forming apparatus is characterized in that the pressure contact nip portion is formed by elastic deformation of the thin-walled sleeve and an elastic force generated by the elastic deformation. 9. An image bearing member having a photosensitive layer, an exposing means for exposing the image bearing member according to image information, and an electrostatic latent image formed on the image bearing member by the exposure with a developer. A developing device for pressing, a transfer device for transferring a developer image to a recording material, and a pressurizing member that presses a rotating body having an exciting coil inside to form a pressure contact nip portion with a predetermined width between the rotating body and the rotating body. An image forming apparatus including a heating device including a member, wherein the recording material on which the developer image is formed is heated at a pressure nip portion generated by eddy current generated in the rotating body to form an image, The image forming apparatus is characterized in that the pressing member of the heating device is formed of a thin sleeve, and the pressure contact nip portion is formed by elastic deformation of the thin sleeve and an elastic force generated by the elastic deformation. . 10. The thin-walled sleeve has a wall thickness of t, a radius of r, a Young's modulus of a member forming the thin-walled sleeve of E, and a Poisson's ratio of ν: 1.19 × 10 ⁻⁶ <{ The image forming apparatus according to any one of claims 7 to 9, wherein E / 4 (1-ν ² )} (t / r) ³ <1.85 × 10 ^-5 is satisfied. 11. The image forming apparatus according to claim 10, wherein the thin sleeve is provided with a heat-resistant release layer on the surface layer of the metal sleeve. 12. The image forming apparatus according to claim 10, wherein in the thin-walled sleeve, a heat-resistant elastic layer having a thickness of 1.0 mm or less and a heat-resistant release layer are sequentially formed on the surface layer of the metal sleeve.