JPH0926715A - Image heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to subject an image to be heated to gentle heating over a wide range by providing an image heater with the region to be heated of a rotary heating member larger than nip width. SOLUTION: A coil 201 generates alternating magnetic flux by the alternating current supplied from an exciting circuit and the alternating magnetic flux is introduced to a ferrite core 202 t generate eddy current in the exothermic layer 101 of a fixing film 1. The eddy current generates Joule heat by the resistivity of the heating layer 101 to heat the recording paper P and the toner T on the recording paper P. An excitation coil 201 is so wound as to comply with the curved surface of the heating layer 101 on the upstream side from the nip and to comply with the ferrite core 202 on the downstream side from the nip. Namely, the generated magnetic flux arrives at the fixing film 1 at a high density and over a wide range on the upstream side from the nip. Conversely, the magnetic flux attains the lower density on the downstream side from the nip. The high-temp. region is settable widely on the upstream side from the nip of the fixing film 1 and is settable narrowly on the downstream side therefrom according thereto.

Description

Detailed Description of the Invention

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image heating apparatus for generating an eddy current using electromagnetic induction and heating the image.

[0002] This apparatus is a fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer and a facsimile, that is, a resin which is heat-meltable by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. The present invention relates to an apparatus for heat-fixing an unfixed toner image formed directly or indirectly on the surface of a recording material by using a toner made of the same as a permanent fixed image on the recording material surface.

[0003]

2. Description of the Related Art FIG. 12 is a view for explaining a conventional technique and is a schematic sectional view of a laser beam printer in which an electrophotographic technique is applied to a printer. The operation of this device will be described below.

The intensity of the laser beam from the scanner 13 is modulated by an image information signal sent from a host computer, and an electrostatic latent image is formed on the photosensitive drum 11. The intensity of the laser light and the irradiation spot diameter are properly set according to the resolution of the image forming apparatus and the desired image density, and the electrostatic latent image on the photosensitive drum 11 is the light portion potential V _L in the portion irradiated with the laser light. The other part is the primary charger 12
It is formed by being held at the dark portion potential V _D that is charged by. The photosensitive drum 11 rotates in the direction of the arrow, and the electrostatic latent images are sequentially developed by the developing device 14. The toner in the developing device 14 is a developing sleeve 140 which is a toner supply rotating body.
2 and the developing blade 1401, the toner height and tribo are controlled, and a uniform toner layer is formed on the developing sleeve 1402. The developing blade 1401 is usually made of metal or resin, and the resin blade is in contact with the developing sleeve 1402 with an appropriate contact pressure. The toner layer formed on the developing sleeve 1402 faces the photosensitive drum 11 as the developing sleeve 1402 itself rotates, and is V due to the electric field formed by the voltage V _dc applied to the developing sleeve 1402 and the surface potential of the photosensitive drum 11. Only the _L part is visualized selectively. The toner image on the photosensitive drum 11 is sequentially transferred by the transfer device 15 to the paper sent from the paper feeding device. As a transfer device, in addition to the corona charger shown in the figure, there is a transfer roller system which supplies current from a power supply to a conductive elastic rotating body to transfer the paper while applying transfer charge to paper. The paper on which the toner image has been transferred is sent to the fixing device 10 with the rotation of the photosensitive drum 11, and becomes a permanent fixed image by heating and pressing.

As an image heating apparatus represented by a heat fixing apparatus, a contact heating method such as a film heating method has been widely used in addition to the heat roller method shown in FIG.

Among them, as a fixing device of a device for forming a full-color image which is required to sufficiently heat and melt a maximum of four toner layers, a core metal of a fixing roller having a high heat capacity and a toner image are wrapped. The toner image is heated through the rubber elastic layer for uniform melting.

On the other hand, Japanese Patent Publication No. 5-9027 discloses that an eddy current is generated in a fixing roller by magnetic flux and heat is generated by Joule heat. By utilizing the generation of the eddy current, the heat generation position is determined by a toner image. And achieves a more efficient fixing process than a heat roller using a halogen lamp.

[0008]

However, in the above fixing device, there is a problem that the heat capacity of the fixing roller is large and not only the electric power required for heating becomes large but also the wait time becomes long.

When a fixing roller having a large heat capacity such as a full-color image recording apparatus is used, a delay occurs between the temperature control and the temperature rise on the surface of the fixing roller. Had occurred.

Further, the curvature of the fixing roller is determined by the restriction of the fixing ability, and there is a tendency that the curvature becomes small especially in a full-color image recording apparatus, and problems such as separation defects are likely to occur.

Further, in the fixing device disclosed in Japanese Patent Publication No. 5-9027, since the heat capacity of the fixing roller is large, it is necessary to concentrate the magnetic flux in the nip in order to raise the temperature of the nip portion with limited electric power. However, like the film heating type fixing device, there is no preheating effect, and there is a problem that tailing or fixing failure occurs.

An object of the invention according to the present application is to provide an image heating apparatus which consumes less power and can shorten the wait time. Even in a full-color image forming apparatus, the separability is ensured, and the tailing, the fixing failure, and the like are prevented. An object of the present invention is to provide a fixing device having high performance in which uneven gloss and offset do not occur.

[0013]

In order to achieve the above object, a first invention of the present application is a rotary heating member comprising a resistance material and a coating layer, and a rotary pressure member forming a nip with the rotary heating member. The heating region of the rotary heating member, which has a magnetic flux generating coil close to them and is heated by the alternating magnetic flux generated by the magnetic flux generating coil, is larger than the nip width.

In the above structure, by providing the heated area of the rotary heating member which is larger than the nip width, there is an effect of heating the image to be heated in a wide range and gently.

In addition to the characteristics of the first invention, the second invention of the present application is characterized in that the heated region of the rotary heating member is larger in the nip upstream than in the nip downstream.

In the above arrangement, the large heated area of the rotary heating member upstream of the nip has a preheating effect, and the small heated area of the rotary heating member downstream of the nip has a cooling separation effect.

Further, in addition to the features of the second invention, the third invention according to the present application is such that the winding manner of the magnetic flux generating coil viewed from a plane perpendicular to the central axis of rotation of the rotary heating member is the upstream and downstream of the nip. It is characterized by making it asymmetrical.

In the above structure, the asymmetric winding of the magnetic flux generating coil operates so that the magnitude of the magnetic flux that contributes to heat generation in the vicinity of the nip of the rotary heating member is increased upstream of the nip and decreased downstream of the nip.

Further, in addition to the features of the second invention, the fourth invention of the present application is such that the main magnetic flux generation direction (direction of the magnetic poles) of the magnetic flux generation coil as viewed in a plane perpendicular to the rotation center axis of the rotary heating member. (Corresponding to) is shifted to the upstream side of the nip.

In the above structure, the offset of the maximum magnetic flux generation direction of the magnetic flux generation coil operates so that the magnitude of the magnetic flux that contributes to heat generation in the vicinity of the nip of the rotary heating member is large upstream of the nip and small downstream of the nip.

Further, in addition to the features of the second invention, the fifth invention according to the present application is such that it is transparent to the upstream side of the nip on the outside of the rotary heating member as seen in a plane perpendicular to the central axis of rotation of the rotary heating member. It is characterized by arranging a member having a high magnetic susceptibility.

In the above structure, the member having high magnetic permeability operates so as to increase the magnitude of the magnetic flux that contributes to heat generation in the vicinity of the nip of the rotary heating member upstream of the nip.

Further, in addition to the features of the second invention, the sixth invention according to the present application has a nip between the rotary heating member and the magnetic flux generating coil as seen in a plane perpendicular to the central axis of rotation of the rotary heating member. A member having a low magnetic permeability is arranged on the downstream side of the.

In the above structure, the member having a low magnetic permeability operates so as to reduce the magnitude of the magnetic flux that contributes to heat generation in the vicinity of the nip of the rotary heating member, downstream of the nip.

The seventh invention according to the present application is characterized in that, in addition to the features of the first to sixth inventions, the rotary heating member has different curvatures inside and outside the nip.

In the above arrangement, the difference in curvature between the inside and outside of the nip operates so as to facilitate separation of the heated image from the rotary heating member.

The eighth invention of the present application is characterized in that, in addition to the features of the first to seventh inventions, a resistance material having ferromagnetism is used for the rotary heating member.

In the above structure, the resistance material having ferromagnetism operates so as to generate high Joule heat.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a view best showing the features of the present invention. In FIG. 1, 1 is a fixing film and 105 is a fixing film.
Reference numeral denotes an insulating film guide which does not hinder the passage of magnetic flux. The fixing film 1 rotates in the direction of the arrow while ensuring transport stability by the film guide 105. 201 is an exciting coil for generating an alternating magnetic flux, and 202 is a ferrite core for efficiently increasing the alternating magnetic flux generated by the exciting coil 201 around the nip.
Supported by 05.

An exciting circuit is connected to the exciting coil 201, and this exciting circuit can supply an alternating current of 50 KHz to the exciting coil 201. Reference numeral 3 denotes a pressure roller which is a 2 mm thick silicone rubber layer 302 on a core metal 301.
The fixing film 1 and the nip N are formed by being covered with elasticity. Further, the pressure roller 3 also serves as a drive roller for driving the fixing film 1 to rotate in the conveying direction of the recording material P.

The fixing film 1 will be described in detail with reference to FIG. The fixing film 1 is made of nickel and has a thickness of 5
The surface of the heating layer 101 having a thickness of 0 μm is covered with an elastic layer 102 made of silicone rubber, and the release layer 10 made of fluororesin is further provided.
It is covered with 3. As the heat generating layer 101, in addition to nickel, a metal which is a good electric conductor of 10 ⁻⁵ to 10 ⁻¹⁰ Ω · m,
Any metal compound or organic conductor may be used, and more preferably, a pure metal such as iron or cobalt having high magnetic permeability and exhibiting ferromagnetism or a compound thereof can be used. Heating layer 10
If the thickness of 1 is reduced, it will not be possible to secure a sufficient magnetic path,
The magnetic flux may leak to the outside to reduce the heat generation energy of the heating element itself, and if the thickness is increased, the heat capacity tends to increase and the time required for temperature rise tends to increase. Therefore, the thickness has an appropriate value depending on the values of specific heat, density, magnetic permeability, and resistivity of the material used for the heating element, and in this embodiment, it is 10 to 100 μm.
It was possible to obtain a temperature rising rate of 3 ° C./sec or more in the range of thickness. On the other hand, if the hardness of the elastic layer 102 is too high, the elastic layer 102 cannot follow irregularities of the recording material or the toner layer, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 102 is 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less. Regarding the thermal conductivity of the elastic layer 102, 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [cal / c
m · sec · deg. ] Is good. Thermal conductivity λ is 6 × 10
^-4 [cal / cm.sec.deg. ], The thermal resistance is large, and the temperature rise in the surface layer of the fixing film 1 becomes slow.

As the release layer 103, PFA, PTFE,
In addition to a fluororesin such as FEP, a material having good releasability and heat resistance such as a silicone resin, a silicone rubber, a fluororubber, and a silicone rubber can be selected. Release layer 10
3 preferably has a thickness of 20 to 100 μm.
If the thickness is less than 20 μm, there arises a problem that a portion having poor releasability is formed due to coating unevenness of the coating film and durability is insufficient. In addition, when the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 102 is lost.

Further, as shown in FIG. 4, a heat insulating layer 104 may be provided in the layer structure of the fixing film 1. Heat insulation layer 1
04 is preferably a heat-resistant resin such as a fluorine resin, a polyimide resin, a polyamide resin, a polyamide-imide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, and a FEP resin. Further, the thickness of the heat insulating layer 104 is preferably 10 to 1000 μm. When the thickness of the heat insulating layer 104 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if the thickness exceeds 1000 μm, the distance between the high magnetic permeability core 202 and the heat generating layer 101 increases, and the magnetic flux does not reach the heat generating layer 101 sufficiently. When the heat insulating layer 104 is provided, the heating of the exciting coil 201 and the ferrite core 202 due to the heat generated in the heat generating layer 101 can be prevented, so that stable heating can be performed.

The exciting coil 201 must generate an alternating magnetic flux sufficient for heating. For that purpose, it is necessary to have a low resistance component and a high inductance component. In this embodiment, as the core wire of the exciting coil 201, a high-frequency wire having a diameter of φ1 is used.
It is wound 20 times so as to go around the nip N as shown in FIG.

The coil 201 generates an alternating magnetic flux by the alternating current supplied from the exciting circuit, and the alternating magnetic flux is guided to the ferrite core 202 and the heat generating layer 101 of the fixing film 1.
Generate an eddy current. This eddy current generates Joule heat by the specific resistance of the heat generating layer 101, and the elastic layer 10
2. The recording material P and the toner T on the recording material P, which are conveyed to the nip N via the release layer 103, can be heated.

Although the fixing film 1 is driven by the pressure roller 3 in this embodiment, the film is driven by the driving roller 19 by applying tension to the fixing film 1 by the tension roller 20 as shown in FIG. Alternatively, a roll-up type film may be used.

The present invention focuses on the fact that a desired heating region can be easily set by providing a distribution in the density of the alternating magnetic flux.

In particular, in this embodiment, the distribution of the alternating magnetic flux density is realized by the winding method of the exciting coil 201. Specifically, the exciting coil 201 is wound along the curved surface of the heat generating layer 101 upstream of the nip N, and is wound along the ferrite core 202 downstream of the nip N. That is, the generated magnetic flux reaches the fixing film 1 in a high density and a wide range in the upstream of the nip, and on the contrary, has a low density in the downstream of the nip, and accordingly, the high temperature region is wide in the upstream of the nip of the fixing film 1 and in the downstream. The high temperature range can be set narrowly.

The operation and effect of the image heating apparatus of this embodiment when it is used as a fixing device of a four-color image forming apparatus will be described below together with the operation of the image forming apparatus.

FIG. 6 is a sectional view of an electrophotographic color printer using the present invention. 11 is a photosensitive drum made of an organic photosensitive member, 12 is a charging device for uniformly charging the photosensitive drum 11, and 13 is a signal from an image signal generator (not shown) for turning on / off a laser beam. And a laser optical box that forms an electrostatic latent image on the photosensitive drum 11. 1
101 is a laser beam, 1102 is a mirror. The electrostatic latent image on the photosensitive drum 11 is visualized by selectively attaching toner by the developing device 14. The developing device 14 includes a color developing device for yellow Y, magenta M, and cyan C, and a developing device B for black. The developing device 14 develops a latent image on the photosensitive drum 11 one by one, and transfers the toner image to the intermediate transfer drum 16. A color image is obtained by superimposing sequentially on the top. Intermediate transfer drum 16
Has a medium-resistance elastic layer and a high-resistance surface layer on a metal drum, and applies a bias potential to the metal drum to transfer a toner image by a potential difference from the photosensitive drum 11. On the other hand, the recording material P sent out from the sheet feeding cassette by the sheet feeding roller is sent between the transfer roller 15 and the intermediate transfer drum 16 so as to synchronize with the electrostatic latent image on the photosensitive drum 11. The transfer roller 15 transfers the toner image on the intermediate transfer drum 16 onto the recording material P by supplying a charge having a polarity opposite to that of the toner from the back surface of the recording material P. In this manner, the recording material P on which the unfixed toner image is placed is applied heat and pressure by the heat fixing device 10, is permanently fixed on the recording material P, and is discharged to a paper discharge tray (not shown). . The toner and paper dust remaining on the photosensitive drum 11 are removed by the cleaner 17, and the toner and paper dust remaining on the intermediate transfer drum 16 are removed by the cleaner 18. repeat.

The above-mentioned image heating device is used for the fixing device 10. The recording material P is gradually heated and enters the nip, and the toner image is fixed, separated at the nip outlet and rapidly cooled.

According to the configuration of this embodiment, the coil 20
The magnetic flux generated by No. 1 enables the operation of preheating the recording material P in order to sufficiently heat the fixing film 1 from the upstream of the nip, and abruptly weakens the magnetic flux to the fixing film 1 at the downstream of the nip. It enables quick cooling and separation of recording materials. Further, regarding the separation of the recording material, by making the heat generating layer 101 of the fixing film 1 sufficiently thin and forming a film shape, it is possible to facilitate the deformation of the fixing film 1 and change the curvature inside and outside the nip. We are trying to improve.

The state of heat generation distribution between the case of the conventional uniform coil arrangement and the case of the present embodiment is compared below, and the result of comparison of the fixing property and the frequency of occurrence of separation failure in that case is shown. Show. As the image forming apparatus, in a four-color image forming apparatus having a printing speed of 8 sheets of A4 size paper per minute,
The case where a solid image of three-color superposition is formed is shown as a representative. FIG. 7 shows the distribution of heat generation when the two are compared. According to the exciting coil of the present embodiment, as shown in the figure, the distribution of the magnetic force lines B is large in the wide range upstream of the nip and narrow in the downstream range of the nip. It is also confirmed that this action causes the heat value of the fixing film to be high in the upstream of the nip and low in the downstream of the nip. This effect appears as superiority or inferiority in fixability and separability, and the table below shows the results of tests on these. In the table below, "fixability" is represented by the difference in reflectance of image density before and after the adhesive tape is attached and peeled off, and "appropriate fixing temperature" is the fixability at which the value of the fixability is 5% or less. The temperature is a controlled temperature, and the "separation failure rate" is a rate at which a separation failure jam occurs when 80 g / m ² paper is passed.

[0044]

[Table 1]

As described above, according to the present invention, it is possible to realize an image forming apparatus having high fixing property and separability as compared with the case of using the conventional image heating device.

In this embodiment, since the toner containing the low-softening substance is used as the toner T, the oil fixing mechanism for preventing the offset is not provided in the heat fixing device.
An oil application mechanism may be provided when a toner containing no low-softening substance is used.

Although the four-color image forming apparatus has been described in the present embodiment, it may be applied to a monochrome or one-pass multi-color image forming apparatus. In this case, the elastic layer 102 can be omitted from the fixing film 1.

Further, as a development of this embodiment, a configuration as shown in FIG. 8 can be considered. In this development example, the pressure roller 3 is formed by covering the iron sleeve 301 with the elastic layer 302, and the exciting coil 38 is arranged in the pressure roller. This is a pressure coil core 203 having a heating layer and an exciting coil 203.
This is because the pressure roller 3 is directly heated by the eddy current induced in the core metal 301 of the pressure roller by the magnetic field generated in (1).

The magnetic field generated by the exciting coil 203 is applied to the core metal 3
In order to efficiently absorb 01, the exciting coil 203
The distance between the core metal 301 and the core metal 301 should be as short as possible.

Therefore, as shown in FIG. 8, the core metal 3 is made larger so that the area where the distance between the core metal 301 and the exciting coil 203 is close becomes large.
The exciting coil 203 was arranged along the curved surface 01.

Here, the exciting coil 201 and the exciting coil 2
Although an exciting circuit is connected to each of No. 03 and No. 03, the heat generation amounts of the fixing film 1 and the pressure roller 3 can be separately controlled by this. By separately controlling the heat generation amount of the fixing film 1 and the pressure roller 3, for example, for thick paper, the heat generation amount of the pressure roller 3 side is increased to supply a sufficient heat amount to the paper. Therefore, the fixing property can be improved. Further, it is possible to correct the difference in the amount of temperature drop due to the difference in heat capacity between the fixing film 1 and the pressure roller 3 during continuous printing, and more stable fixing performance can be obtained. In FIG. 8, the exciting coil 203 is not provided with a core, but a core may be provided. By providing the core, the magnetic flux density can be increased for the same number of windings of the exciting coil, so that a larger heat generation amount can be obtained.

Further, if the above-mentioned developed example is constructed at a lower cost, the exciting coil 203 and the exciting coil 201 can be connected in series. In this case, the inductance ratio between the fixing film 1 side and the pressure roller 3 side is arbitrarily selected by changing the winding ratio of the exciting coil 201 and the exciting coil 203, changing the frequency, changing the distance between the heat generating layer and the exciting coil, and the like. Therefore, the heat generation ratio of the fixing film 1 and the pressure roller 3 can be arbitrarily selected.

(Second Embodiment) FIG. 9 is a schematic sectional view showing another embodiment of the present invention. In the figure, the same reference numerals as those used above denote the same members. In the figure, reference numeral 203 denotes an aluminum magnetic flux blocking plate disposed on the downstream side of the nip, which blocks the magnetic flux generated by the exciting coil 201 and suppresses the heating of the fixing film 1 downstream of the nip. Magnetic flux blocking plate 203
For this, a non-magnetic metal plate is suitable. The required thickness varies depending on the frequency, but in this example, it is heated with an alternating magnetic flux of 50 KHz, in this case 0.5 mm or more,
A sufficient blocking effect was confirmed as in the above-described embodiment.

Although the magnetic flux blocking plate 203 is inserted between the film guide 105 and the exciting coil 201 in the present embodiment, it may be inserted between the fixing film 1 and the film guide 105. Particularly, when the magnetic flux blocking plate 201 is made of a material having a high thermal conductivity such as aluminum or copper, the effect of making the temperature distribution in the longitudinal direction of the fixing film 1 and the film guide 105 uniform can be obtained.

Since the magnetic flux blocking plate 201 makes the non-uniformity of the magnetic force lines due to the winding unevenness of the exciting coil 201 irrelevant in the downstream of the nip, it is possible to match the dimensional reference of the exciting coil 201 to the upstream side of the nip. Therefore, there is an advantage that the shape loss of the exciting coil 201 is reduced.

Although the effect of the magnetic flux blocking plate 201 has been described in the present embodiment, the fixing property and the separability can be further improved by applying the configuration of the first embodiment and its development example described above. I can hope.

(Third Embodiment) FIG. 10 is a schematic sectional view showing still another embodiment of the present invention.
In the figure, the same symbols as those used above indicate the same members.

In the present embodiment, the exciting coil 20
The main magnetic flux direction 1 (corresponding to the magnetic pole) 1 is shifted to the upstream side of the nip.

In this structure, the generated magnetic flux effectively heats the fixing film 1 over a wide range, and the maximum heat generation region of the fixing film 1 is arranged in the nip region and upstream thereof, so that the generated heat energy can be efficiently generated. Recording material P
Can be supplied to

Although the effect of the upstream side shift of the exciting coil 201 in the direction of the maximum magnetic flux has been described in the present embodiment, further fixing property and separation can be obtained by applying the configuration of the above-mentioned embodiment and its development example. It can be expected to improve sex.

(Fourth Embodiment) FIG. 11 is a schematic sectional view showing still another embodiment of the present invention.
In the figure, the same symbols as those used above indicate the same members.

In this embodiment, the magnetic flux guide plate 205 made of ferrite is arranged outside the fixing film 1 upstream of the nip. The magnetic flux guide plate 205 has the function of guiding the magnetic flux leaking to the outside of the fixing film 1 and guiding it to the upstream portion of the nip, and has the effect of increasing the amount of heat generation upstream of the nip.

As a further development of this embodiment, an auxiliary exciting coil is arranged at the position of the magnetic flux guide plate 205 to excite the magnetic flux generated by the exciting coil 201 in a direction that does not hinder the fixing film 1 upstream of the nip. A configuration that increases the amount of heat generation is possible. Such a structure is particularly effective when the heat generating layer 101 of the fixing film 1 is thicker than 50 μm.

[0064]

As described above, according to the first invention of the present application, by providing the heated region of the rotary heating member which is larger than the nip width, a wide range and gentleness with respect to the heated image can be obtained. An image heating device having high image heating ability can be realized.

According to the second invention of the present application,
A large heated area of the rotary heating member upstream of the nip has a preheating effect, and a small heated area of the rotary heating member downstream of the nip has an effect of providing a cooling separation effect. In addition to the effect of the first invention, a higher separability is achieved. It is possible to realize an image heating device having

According to the third to sixth inventions of the present application, in the effect of the second invention, the magnitude of the magnetic flux contributing to the heat generation in the vicinity of the nip of the rotary heating member is increased upstream of the nip, It has the effect of reducing the size downstream of the nip.

According to the seventh invention of the present application,
In addition to the effects of the first to sixth inventions, there is an effect of facilitating separation of the heated image from the rotary heating member.

The eighth invention according to the present application has the effect of generating high Joule heat in addition to the effects of the first to seventh inventions.

[Brief description of drawings]

FIG. 1 is a schematic sectional view illustrating a first embodiment of the present invention.

FIG. 2 is a perspective view of an exciting coil, a core and a stay according to the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of the fixing film according to the first embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of the fixing film according to the first embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a development example of the first embodiment of the present invention.

FIG. 6 is a schematic sectional view illustrating a color image forming apparatus using the image heating device of the present invention.

FIG. 7 is a diagram showing operations and effects of the first embodiment of the present invention.

FIG. 8 is a schematic sectional view showing a development example of the first embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view illustrating the second embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view illustrating a third embodiment of the present invention.

FIG. 11 is a schematic sectional view illustrating a fourth embodiment of the present invention.

FIG. 12 is a diagram showing a conventional example of the present invention.

[Explanation of symbols]

 1 Fixing Film 201 Excitation Coil 202 Core 3 Pressure Roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Kisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (8)

[Claims] 1. An image heating apparatus comprising: a rotary heating member comprising a resistance material and a coating layer; a rotary pressure member forming a nip with the rotary heating member; and a magnetic flux generating coil adjacent to these members. An image heating apparatus, wherein a heated region of the rotary heating member, which is heated by an alternating magnetic flux generated, is larger than a nip width. 2. The heated region of the rotary heating member is larger in the nip upstream than in the nip downstream.
Image heating equipment. 3. The image heating apparatus according to claim 2, wherein the winding method of the magnetic flux generating coil viewed in a plane perpendicular to the central axis of rotation of the rotary heating member is asymmetric in the upstream and downstream of the nip. 4. The image heating apparatus according to claim 2, wherein a main magnetic flux generating direction of the magnetic flux generating coil viewed from a plane perpendicular to a central axis of rotation of the rotary heating member is shifted to an upstream side of the nip. . 5. The image heating device according to claim 2, wherein a member having a high magnetic permeability is arranged outside the rotary heating member and on the upstream side of the nip when viewed in a plane perpendicular to the central axis of rotation of the rotary heating member. apparatus. 6. A member having a low magnetic permeability is arranged between the rotary heating member and the magnetic flux generating coil on the downstream side of the nip when viewed in a plane perpendicular to the central axis of rotation of the rotary heating member. The image heating apparatus according to claim 2. 7. The image heating apparatus according to claim 1, wherein the rotary heating member has different curvatures inside and outside the nip. 8. The image heating apparatus according to claim 1, wherein the resistance material has ferromagnetism.