JP2000162912A - Image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the problem caused by the temperature rising of a paper non-passing part by preventing or mitigating the temperature rising of the paper non-passing part of an image heating device in the image heating device of an electromagnetic induction heating system and an image forming device provided with the image heating device. SOLUTION: In this image heating device 100 which has a magnetic flux generating means having an exciting coil 3 and a magnetic material core 4 and an induction heating element 1 executing electromagnetic induction heat generation by the action of the generated magnetic flux of the magnetic flux generating means and which heats an image on a recording material by the heat of the induction heating element 1 by introducing and carrying the recording material to a heating part N, the characteristic (Curie temperature) of the magnetic material cores 4 (4C, 4B and 4C) arranged in a direction orthogonal with the carrying direction of the recording material is set to be different according to the position of the direction orthogonal with the carrying direction of the recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electromagnetic (magnetic) induction heating type image heating apparatus and an image forming apparatus provided with the image heating apparatus.

[0002]

2. Description of the Related Art For example, in an image forming apparatus using a transfer type electrophotographic process, an unfixed toner image formed and supported on an electrophotographic photosensitive member surface as an image carrier by an electrophotographic process is used as a transfer material as a recording material. And the unfixed toner image transferred to the transfer material is heat-fixed as a permanent fixed image by a heat fixing device as an image heating device, and the transfer material is output as an image formed product. The toner is a melting and fixing visible powder composed of a resin, a magnetic material, a colorant, and the like.

As a fixing device, a heat roller type device has been widely used. This fixing device includes a rotating roller pair of a fixing roller (heat roller) which has a built-in heat source such as a halogen lamp and is heated and controlled to a predetermined fixing temperature, and a pressing roller, and a pressure contact nip portion ( This is a device that heats and fixes an unfixed toner image to the surface of the recording material by heat and pressure by introducing a recording material on which an unfixed toner image is formed and carried as a material to be heated into a fixing nip portion and nipping and conveying the recording material. .

[0006] Further, a fixing device in which a fixing roller is heated by an electromagnetic induction heating method has been proposed. this is,
An eddy current is generated in a conductive layer (induction heating element) provided on the inner surface of the fixing roller by a magnetic flux generated by an exciting coil as a magnetic flux generating means, and heat is generated by Joule heat to heat and control the fixing roller to a predetermined fixing temperature. is there.

[0005] In such a fixing device of the electromagnetic induction heating system, a heat generating source (induction heating element) can be placed very close to the toner, so that it is compared with a fixing device of a heat roller system using a conventional halogen lamp. In addition, the time required for the temperature of the surface of the fixing roller to reach an appropriate temperature for fixing when the fixing device is started can be shortened. Another feature is that the heat transfer path from the heat generation source to the toner is short and simple, so that the heat efficiency is high.

[0006]

In the above-described fixing device of the electromagnetic induction heating type, the characteristic that the time required for the temperature of the fixing roller surface to reach an appropriate temperature for fixing when the fixing device is started can be shortened. Therefore, the heat capacity of the fixing roller is preferably as small as possible.

Therefore, if a thin fixing roller having a small heat capacity is used, it is difficult to transfer heat in the direction of the rotation axis. For example, small-sized paper (recording material) is continuously passed through the apparatus and a large amount of fixing processing is performed. In such a case, a large temperature difference may occur between a portion of the fixing roller surface where the paper contacts (paper passing portion) and a portion where the paper does not contact (non-paper passing portion) (temperature rise in the non-paper passing portion).

Further, if the temperature of the fixing roller is controlled at the paper passing portion, the temperature of the non-paper passing portion greatly exceeds the temperature suitable for fixing, so that the thermal deterioration of each member of the fixing device progresses or the fixing at the non-paper passing portion. There has been a problem that hot offset of toner to the roller surface occurs.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image heating apparatus of an electromagnetic induction heating type and an image forming apparatus provided with the image heating apparatus. An object of the present invention is to solve the above-mentioned problems caused by the temperature rise of the paper section.

[0010]

According to the present invention, there is provided an image heating apparatus and an image forming apparatus having the following constitutions.

(1) A magnetic flux generating means having an exciting coil and a magnetic core, and an induction heating element for generating electromagnetic induction by the action of the magnetic flux generated by the magnetic flux generating means. In an image heating apparatus that heats an image on a recording material by the heat of an induction heating element, the characteristics of a magnetic core disposed in a direction perpendicular to the recording material conveyance direction are made different depending on the position in the direction perpendicular to the recording material conveyance direction. An image heating device, characterized in that:

(2) The image heating apparatus according to (1), wherein the magnetic core has a different Curie temperature in a direction perpendicular to the recording material conveying direction.

(3) When the recording material is introduced and conveyed to the apparatus on the basis of the center, a magnetic core having a lower Curie temperature at both ends in a direction perpendicular to the recording material conveyance direction than the central portion is used. The image heating apparatus according to claim 1, wherein:

(4) When the recording material is introduced and conveyed to the apparatus on the basis of the center, the magnetic core uses a magnetic core having a Curie temperature of 240 ° C. at the center in the direction perpendicular to the recording material conveyance direction. The image heating apparatus according to (1) or (2), wherein a magnetic core having a Curie temperature of 200 ° C. is used in the section.

(5) The image heating apparatus according to any one of (1) to (4), wherein the induction heating element is a rotating body.

(6) The method according to any one of (1) to (4), wherein the induction heating element is a rotating body, and the exciting coil of the magnetic flux generating means and the magnetic core are present inside the rotating body. The image heating device according to claim 1.

(7) The method according to any one of (1) to (4), wherein the induction heating element is a rotating body, and the exciting coil of the magnetic flux generating means and the magnetic core are present outside the rotating body. The image heating device according to claim 1.

(8) Any one of (1) to (7), including a rotary pressurizing member which forms a recording material nipping and conveying nip portion by contacting the induction heating element directly or via a heat transfer material in the heating section. The image heating device according to claim 1.

(9) The image heating device according to any one of (1) to (8), which is an image heating fixing device for heating and fixing an image as a permanent image on a recording material.

(10) An image forming apparatus comprising the image heating device according to any one of (1) to (9).

<Operation> a) That is, in the image heating apparatus of the electromagnetic induction heating type, regarding the magnetic flux generating means having the exciting coil and the magnetic core, the characteristics of the magnetic core arranged in the direction orthogonal to the recording material conveyance direction Is different depending on the position in the direction orthogonal to the recording material conveyance direction, and acts to change the amount of heat generated by the induction heating element in the direction orthogonal to the recording material conveyance direction without a complicated mechanism.

[0022] Thus, it is possible to prevent or reduce the temperature rise of the non-sheet passing portion of the apparatus with a simple configuration at low cost, and to solve the problem caused by the temperature rise of the non-sheet passing portion.

B) The configuration in which the magnetic cores have different Curie temperatures in the direction perpendicular to the recording material transport direction is used when the magnetic cores arranged in the direction perpendicular to the recording material transport direction exceed their respective Curie temperatures. It acts to reduce the heat generation efficiency and prevents the surface temperature of the induction heating element from becoming abnormally high locally in a direction orthogonal to the recording material conveyance direction of the induction heating element without a complicated mechanism.

As a result, when the induction heating element is locally heated to a high temperature and the magnetic core becomes higher than the Curie temperature due to the heat, the heat generation efficiency at that position is reduced and the surface temperature of the induction heating element becomes abnormally high. And a good quality heated image can be obtained.

C) When the recording material is introduced and conveyed to the apparatus on the basis of the center, a magnetic core having a lower Curie temperature at both ends in a direction perpendicular to the recording material conveying direction than the central portion is used. The configuration is such that when both ends of the induction heating element become higher than the temperature suitable for image heating, the heat causes the magnetic cores arranged at both ends in the direction orthogonal to the recording material conveyance direction to rise and the Curie temperature or higher. And the heat generation efficiency at both ends is reduced, and the surface temperature of the induction heating element at both ends in the direction orthogonal to the recording material conveyance direction is prevented from becoming abnormally high without a complicated mechanism.

In this way, for example, when a large amount of small-sized recording material continuously passes through and the both ends of the induction heating element, which is a non-paper-passing portion, greatly exceed the temperature suitable for image heating, the recording material conveyance direction may be used. When the magnetic cores located at both ends in the direction perpendicular to the temperature rise and become higher than the Curie temperature, the heat generation efficiency of that part is reduced to prevent an abnormally high temperature, and the thermal deterioration of each member of the device is prevented. It is possible to prevent toner hot offset in advancing or a non-sheet passing portion.

D) Characteristics of the magnetic core that acts to change the amount of heat generated by the induction heating element in a direction perpendicular to the recording material conveyance direction include magnetic permeability in addition to the Curie temperature.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (FIGS. 1 to 3) FIGS. 1 and 2 are enlarged views of a main part of a fixing device 100 as an image heating device of an electromagnetic induction heating type in this embodiment. It is a horizontal section model diagram and a vertical section model diagram. FIG. 3 is an exploded perspective view of an excitation coil as a magnetic flux generating means and a magnetic core.

The fixing device 100 includes a fixing roller 1 that is heated by electromagnetic induction as a fixing rotating member, and a pressing rotating member that is disposed below the fixing roller 1 and presses the recording material P against the fixing roller 1. The main component is an elastic pressure roller 2, and an excitation coil 3 and a magnetic core 4 as magnetic flux generating means inserted and disposed inside the fixing roller 1.

The fixing roller 1 is a cylindrical roller made of a thin induction heating element having a reduced heat capacity. In this example, the outer diameter is 4
This is an iron cylinder having a thickness of 0 [mm] and a thickness of 0.7 [mm]. In order to improve the release property of the surface using this as a core metal, for example, PTFE10 to 50 [μm], PFAl0 to 5
A layer of 0 [μm] may be provided.

As another material (induction heating element) of the fixing roller 1, a material having a relatively high magnetic permeability μ and an appropriate resistivity ρ, such as a magnetic material (magnetic metal) such as magnetic stainless steel, is used. You may. Further, among non-magnetic materials, conductive materials such as metals can be used by making the material into a thin film.

The pressure roller 2 has a 5 [mm] thick Si rubber layer on the outer periphery of an iron core having an outer diameter of 20 [mm] and improves the surface releasability similarly to the fixing roller 1. For example, PTFE10 to 50 [μm] or PFAl0 to 50 [μm]
m], and is an elastic roller having an outer diameter of 30 [mm].

The fixing roller 1 and the pressure roller 2 are vertically pressed against each other so that the bearings 6, 6,
A fixing nip portion (heating nip portion) N having a predetermined width is formed between the two by being freely rotatable via 7.7. The pressure roller 2 is pressed in the rotation axis direction of the fixing roller 1 by a mechanism (not shown) using a spring or the like. The pressure roller 2 is loaded with about 30 [kg weight], and in this case, the nip width of the press contact nip portion N is about 6 [mm]. However, depending on circumstances, the nip width may be changed by changing the load.

Reference numeral 8 denotes a drive gear integrally mounted on one end of the fixing roller 1. The fixing roller 1 receives the rotational force of a driving source (not shown) via the driving gear 8, and the clock shown by an arrow in FIG. It is rotationally driven at a predetermined peripheral speed in the direction. The pressure roller 2 rotates following the frictional force between the pressure roller 2 and the fixing roller 1 in the fixing nip portion N.

The exciting coil 3 as a magnetic flux generating means and the magnetic core 4 are formed on the lower surface side of a horizontally long heat-resistant resin support stay 5 extending in the rotation axis direction of the fixing roller and penetrating the inside of the cylindrical fixing roller 1. It is fixed and held.

For example, the excitation coil 3, the magnetic core 4, and the support stay 5 are entirely covered with a heat-shrinkable tube to hold the excitation coil 3 and the magnetic core 4 on the support stay 5. Excitation coil 3 for support stay 5
The means for fixing and holding the magnetic core 4 is not particularly limited.

Then, the support stay 5 holding the excitation coil 3 and the magnetic core 4 fixed therein is inserted into the inner space of the cylindrical fixing roller 1, and both longitudinal ends of the support stay 5 are fixed to the stationary member 10 on the apparatus housing side. 10 is fixedly supported. Excitation coil 3
The magnetic core 4 and the support stay 5 are not in contact with the inner surface of the fixing roller 1.

The exciting coil 3 is made of an insulated wire and wound and formed into a horizontally long boat shape having a substantially semicircular cross section with an outer shape substantially corresponding to the inner surface of the cylindrical fixing roller 1. The fixing roller 1 is located substantially corresponding to the lower half surface of the inner surface of the fixing roller 1.

The exciting coil 3 must generate an AC magnetic flux sufficient for heating, but for that purpose, it is necessary to reduce the resistance component and increase the inductance component. In this example, the excitation coil 3 was formed by winding around the fixing nip N using a high-frequency insulated wire in which several thin wires were used as the core wire. Considering the case where heat was transferred to the winding, a heat-resistant material was used for the coating.

The magnetic material core 4 is formed by assembling a horizontally long plate-shaped member made of a magnetic material into a substantially T-shaped cross section. The magnetic core 4 is located at a substantially central portion of the exciting coil 3 having a horizontally long boat shape. The lower surface of the vertical portion of the body core 4 is located at a position corresponding to the fixing nip portion N. The magnetic core 4 serves to efficiently guide the AC magnetic flux generated from the exciting coil 3 to the induction heating element constituting the fixing roller 1.

A material having high magnetic permeability and low loss is used as the material of the magnetic core 4. In the case of an alloy such as permalloy, an eddy current loss in the core increases at high frequencies, so that a laminated structure may be used. The core is used to increase the efficiency of the magnetic circuit and for magnetic shielding.

The exciting coil 3 has a high frequency converter 21
Is connected. The high-frequency converter 21 applies an alternating (alternating) current of 10 to 100 [kHz] to the exciting coil 3 and supplies electric power of 100 to 2000 [W].

Reference numeral 11 denotes a temperature sensor, which is disposed so as to be in contact with the surface of the fixing roller 1, and a detection signal of the temperature sensor 11 is input to the control circuit 22.
The control circuit 22 controls the high-frequency converter 21 based on the detected temperature information input from the temperature sensor 11 to increase or decrease the power supply to the exciting coil 3 so that the surface temperature of the fixing roller 1 becomes a predetermined constant temperature. Automatic control.

Reference numeral 12 denotes a recording material transport guide, which is arranged at a position for guiding the recording material P, which carries the unfixed toner image t and is transported, to a nip portion N between the fixing roller 1 and the pressure roller 2. .

Reference numeral 13 denotes a separation claw, which is disposed in contact with the surface of the fixing roller 1 and forcibly separates and removes a jam when the recording material P adheres to the fixing roller 1 after passing through the nip portion N. This is to prevent it.

The exciting coil 3 generates an alternating magnetic flux by the alternating current supplied from the high-frequency converter 21, and the alternating magnetic flux is guided to the magnetic core 4 to fix the fixing nip N
To generate an eddy current in the induction heating element constituting the fixing roller 1 in the fixing nip portion N. The eddy current generates Joule heat due to the specific resistance of the induction heating element. That is, by supplying an alternating current to the exciting coil 3, the fixing roller 1 is brought into an electromagnetic induction heating state.

The surface temperature of the fixing roller 1 is determined by a temperature sensor 1
By controlling the power supply from the high-frequency converter 21 to the exciting coil 3 by the control circuit 22 including 1, the temperature is controlled to a predetermined fixing temperature. In order to increase the heat generation of the fixing roller 1, it is preferable to increase the frequency or the amplitude of the alternating current.

The fixing roller 1 is driven to rotate, and the pressure roller 2 is driven to rotate accordingly, so that an alternating current is supplied from the high-frequency converter 21 to the exciting coil 3 so that the fixing roller 1 is heated by electromagnetic induction to fix the image. In a state in which the surface temperature of the roller 1 rises to a predetermined value and the temperature is controlled, a recording in which an unfixed toner image t as a material to be heated is carried between the rotating fixing roller 1 and the pressing roller 2 in the fixing nip portion N. By the introduction of the recording material P, the recording material P comes into close contact with the surface of the fixing roller 1 and passes through the fixing nip portion N. In the process of passing the fixing nip portion, the recording material P and the recording material P are heated by the heat of the fixing roller 1. The unfixed toner image t is heated, and the toner image is heated and fixed.

The recording material P that has passed through the fixing nip N is separated from the fixing roller 1 at the exit side of the fixing nip N and conveyed.

In this embodiment, the recording material P is introduced into the fixing device 100 on a central basis. O is the center paper passing reference line. A is a paper-passing area of a large-size recording material (maximum-size recording material that can be passed through the apparatus), B is a paper-passing area of a small-size recording material, and C and C are small-size recording materials. This is a non-sheet passing area portion that occurs when the sheet is touched. In this embodiment, non-sheet passing areas C and C that occur when a small-size recording material is used are generated on both sides of the sheet passing area B of the small-size recording material because the sheet passing is based on the center. .

With the above-described configuration, while the fixing device is on standby, the surface temperature of the fixing roller 1 is set to a predetermined 190 [° C.] optimum for fixing.
When the temperature is controlled at about the same temperature, 200
A power supply of about [W] is required. At that time, the temperature of the exciting coil 3 becomes about 210 [° C.] and the temperature of the magnetic core 4 becomes about 200 [° C.]. When a large number of fixing processes are continuously performed at a speed of about 30 sheets per minute, it is necessary to supply power of about 450 [W] to the exciting coil 3, and at that time, the temperature of the exciting coil 3 is about 230 [° C.] The temperature of the magnetic core 4 becomes about 220 [° C.]. Therefore, the Curie temperature of the magnetic core 4 is set at 22
It must be 0 [° C] or more. If the temperature of the magnetic core 4 exceeds the Curie temperature, the power-to-heat conversion efficiency is extremely reduced at the extremely high temperature.

As described above, when a small amount of paper (recording material) is continuously passed through the apparatus and a large amount of fixing processing is performed, for example, the paper passing portion B on which the paper on the surface of the fixing roller comes into contact.
Then, a large temperature difference may occur between the non-sheet passing portions C and C that do not come into contact with each other (non-sheet passing portion temperature rise). Further, the temperature of the fixing roller surface temperature is measured by a temperature sensor
When the temperature is controlled based on the temperature detected in step 1, the small-size paper is passed through the center reference in the rotation axis direction of the fixing roller.
The center of the fixing roller is approximately 190 mm, which is optimal for fixing.
Although the temperature is maintained at [° C.], the surface temperature of the fixing roller at the non-paper passing portions C and C where the paper does not always contact at both ends in the rotation axis direction of the fixing roller becomes as high as 240 ° C. at the maximum. Sisters,
This is undesirable because it promotes thermal deterioration of peripheral members and causes hot offset of the toner to the fixing roller surface.

Therefore, in the present embodiment, in order to prevent or alleviate such a temperature rise in the non-sheet passing portion, the magnetic core 4 of the magnetic flux generating means is moved in the direction of the rotation axis of the fixing roller to pass a small-size recording material. The structure is divided into three parts: a part 4B corresponding to the area part B and parts 4C and 4C corresponding to the non-sheet passing area parts C and C on both sides of the part 4B. The magnetic material core has a Curie temperature of 240 ° C., and a portion 4C / C corresponding to the non-paper passing region C / C.
A 4C magnetic core having a Curie temperature of 220 [° C.] was used.

That is, in the paper passing area B of the small-size recording material, the temperature of the magnetic core 4B in the portion corresponding to the paper passing area is always lower than the Curie temperature of the magnetic core. The fixing roller portions corresponding to the area portions can be efficiently heated by electromagnetic induction, while the non-sheet passing area portions C and C on both sides thereof are used as the magnetic cores 4C and 4C corresponding to the non-sheet passing area portions. Since the magnetic core having a lower Curie temperature than the magnetic core 4B in the portion corresponding to the paper passing area is used, when fixing a large amount of small-sized paper continuously in a large amount, it is necessary to use both ends of the fixing roller. Certain non-paper passing area C
When the temperature of C rises due to the temperature rise in the non-sheet passing area, the magnetic cores 4C and 4C in the portion corresponding to the non-sheet passing area also become high in temperature. The heat generation efficiency at the fixing roller part decreases, and eventually,
It is possible to prevent the non-sheet passing areas C and C on both ends of the fixing roller from becoming abnormally high in temperature.

The exciting coil 3 and the magnetic core 4 as the magnetic flux generating means can be disposed outside the fixing roller 1.

<Second Embodiment> In this embodiment, in the fixing device 100 of the first embodiment, a heat-resistant resin supporting the excitation coil 3 as a magnetic flux generating means and the magnetic core 4 is used. The resulting support stay 5 is made of aluminum.

By using an aluminum member having a high thermal conductivity as the support stay 5, heat generated in the exciting coil 3 and the magnetic core 4 is transported through the aluminum support stay 5 having a high thermal conductivity. Since heat can be radiated from both ends of the support stay, the temperature of the exciting coil 3 and the magnetic core 4 can be reduced by about 20 ° C.

As a result, the Curie temperature of the magnetic core 4 can be lowered. In this embodiment, the magnetic core of the portion 4B corresponding to the paper passing area B has a Curie temperature of 220 ° C.
4C corresponding to the non-sheet passing area C, C
A 4C magnetic core having a Curie temperature of 200 ° C. was used.

The magnetic field generated by the exciting coil 3 is shielded from the aluminum support stay 5 by the horizontal plate portion of the T-shaped magnetic core 4 in cross section. There is no worry about fever.

In this embodiment, the support stay 5 for supporting the excitation coil 3 and the magnetic core 4 is made of aluminum, so that the temperature of the excitation coil 3 and the magnetic core 4 can be reduced when the resin support stay is used. Since the temperature can be lowered, the Curie temperature of the magnetic core 4 can be lowered, so that it is not necessary to use a special magnetic material, and the inexpensive magnetic core 4 can be used. Can be lowered, so that it is not necessary to use a special coil having high heat resistance, and an inexpensive exciting coil can be used.

<Third Embodiment> (FIG. 4) In this embodiment, the fixing device 100 of the above-described first or second embodiment is divided into three parts in the direction of the rotation axis of the fixing roller. Each of the magnetic core portions 4B corresponding to the paper passing area B of the recording material and the magnetic core portions 4C corresponding to the non-paper passing areas C on both sides thereof.
B and C are spaced apart from each other with a gap α of about 1 mm as shown in FIG.

In the present embodiment, the presence of the gap α makes it possible to make the temperature difference more noticeable when a temperature difference occurs between the three magnetic core portions 4C, 4B, and 4C. When a large amount of paper is continuously fixed, for example, when the end of the fixing roller, which is the non-paper passing area C where the paper does not contact, greatly exceeds the temperature suitable for fixing, the non-paper passing area C・ Magnetic core part 4C corresponding to C
The temperature of 4C also rises and exceeds the Curie temperature, so that the heat generation efficiency at the end of the fixing roller decreases, and the magnetic core 4
The mechanism of lowering the fixing roller temperature at the positions C and 4C can be made more effective.

<Fourth Embodiment> (FIG. 5) FIG. 5 is a model diagram of a main part of another configuration example of the fixing device 100 of the electromagnetic induction heating system. 14 is a heater holder, 15 is an induction heating element such as an iron plate as a heater fixed and held downward on the heater holder 14, and 16 is a heat-resistant fixing film that slides and moves on the lower surface of the fixed induction heating element 15 described above. Reference numeral 2 denotes an elastic pressure roller. The elastic pressure roller 2 presses the downward surface of the induction heating element 15 with the fixing film 16 interposed therebetween to form a nip portion N. The induction heating element 15 generates electromagnetic induction heat by a magnetic flux generated from a magnetic flux generating means including the exciting coil 3 and the magnetic core 4.

Then, the fixing film 1 in the nip portion N
When the recording material P carrying the unfixed toner image t is introduced between the pressure roller 6 and the pressure roller 2 and is conveyed while nipping the nip portion N together with the fixing film 16, the heat of the induction heating element 15 is transferred to the fixing film 16. The toner image t is heated and pressurized and fixed on the surface of the recording material P. The recording material P passing through the nip portion N is sequentially separated from the surface of the fixing film 16 and is discharged and conveyed.

The present invention can of course be applied to such a case where the induction heating element is a fixed type device.

<Fifth Embodiment> (FIG. 6) FIG. 6 is a schematic structural diagram of an example of an image forming apparatus provided with the fixing device 100 of the first embodiment. The image forming apparatus of this embodiment is a transfer type electrophotographic apparatus.

Reference numeral 31 denotes a drum-type electrophotographic photosensitive member which is driven to rotate at a predetermined peripheral speed (process speed) in the clockwise direction of the arrow. The photoreceptor 31 is uniformly charged to a predetermined polarity and potential by a charging roller 32 as a charging unit during the rotation process, and then receives an image exposure L by an unillustrated exposure unit on the uniformly charged surface. As a result, an electrostatic latent image corresponding to the exposure image is formed on the surface of the rotating photoconductor 31.

Next, the electrostatic latent image is subjected to regular development or reverse development as a toner image by the developing means 33, and the toner image is transferred to a transfer nip portion T, which is a pressure contact portion between the photosensitive member 31 and the transfer roller 34, not shown. The image is sequentially transferred onto a transfer material P as a recording material fed at a predetermined control timing from a paper supply unit.

The transfer material P having passed through the transfer nip T
Is separated from the surface of the photoreceptor 31, introduced into the fixing device 100, subjected to the fixing process of the toner image, and discharged.

After the transfer material is separated, the surface of the photoreceptor 31 is subjected to removal of residual substances such as transfer residual toner by the cleaning device 35, and is repeatedly subjected to image formation.

<Others> 1) Excitation coil 3 and magnetic core 4 as magnetic flux generating means
May be disposed outside the fixing roller 1.

2) The exciting coil 3 may be provided with a shape-retaining member (bobbin) as necessary to prevent its shape from being lost.

3) It is a matter of course that the standard for passing the recording material can be the one-side standard.

4) The image heating device of the present invention is not limited to the fixing device of each embodiment, but may be a device for heating a recording material carrying an image to improve the surface properties such as gloss, or a device for assuming an image. It can be widely used as a means or a device for heating a material to be heated, such as a heating device, a device for heating and drying a material to be heated, and a laminating device.

5) Unfixed toner image t on recording material P
The formation principle and process are not limited and are optional.

[0076]

As described above, according to the present invention, in the image heating apparatus of the electromagnetic induction heating type and the image forming apparatus provided with the image heating apparatus, it is possible to prevent the non-sheet passing portion of the image heating apparatus from heating up. It is possible to alleviate the problem caused by the temperature rise in the non-sheet passing portion, thereby reducing the problem.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic cross-sectional view of a fixing device according to a first embodiment.

FIG. 2 is a longitudinal sectional model view of the same device.

FIG. 3 is an exploded perspective view of an excitation coil and a magnetic core as a magnetic flux generating means.

FIG. 4 is a schematic longitudinal sectional view of a fixing device according to a third embodiment.

FIG. 5 is a schematic diagram of a main part of a fixing device according to a fourth embodiment.

FIG. 6 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to a fifth embodiment.

[Explanation of symbols]

1 ············································································································· , 13 ... Separating claws, 21 ... High frequency converter, 2
2. Control circuit, P, recording material, t, unfixed toner image

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 AA03 AA09 AA30 AA32 BA25 BA27 BB12 BB19 BE06 CA27 3K059 AA08 AA14 AB00 AB19 AB20 AB23 AB27 AB28 AC10 AC33 AC34 AC37 AC73 AD03 AD07 AD26 AD34 AD35 AD37 BD02 CD02 CD44 CD52 CD75 CD75

Claims (10)

[Claims] A magnetic flux generating means having an exciting coil and a magnetic core; and an induction heating element for generating electromagnetic induction by the action of the magnetic flux generated by the magnetic flux generating means. In an image heating apparatus for heating an image on a recording material by heat of a heating element, characteristics of a magnetic core arranged in a direction perpendicular to a recording material conveyance direction are made different depending on a position in a direction perpendicular to the recording material conveyance direction. An image heating device characterized by the above-mentioned. 2. The image heating apparatus according to claim 1, wherein the magnetic cores have different Curie temperatures in a direction perpendicular to the recording material conveyance direction. 3. A magnetic core having a lower Curie temperature at both ends in a direction perpendicular to the recording material transport direction than at the central portion when the recording material is introduced and transported into the apparatus on the basis of the center. The image heating apparatus according to claim 1, wherein: 4. When a recording material is introduced and conveyed to the apparatus on the basis of a center, a magnetic core having a Curie temperature of 240 ° C. is used at a central portion in a direction orthogonal to the recording material conveying direction. The image heating apparatus according to claim 1, wherein a magnetic core having a Curie temperature of 200 ° C. is used. 5. The image heating apparatus according to claim 1, wherein the induction heating element is a rotating body. 6. The method according to claim 1, wherein the induction heating element is a rotating body, and the exciting coil of the magnetic flux generating means and the magnetic core are present inside the rotating body. Image heating equipment. 7. The method according to claim 1, wherein the induction heating element is a rotating body, and the exciting coil of the magnetic flux generating means and the magnetic core are present outside the rotating body. Image heating equipment. 8. The rotating pressurizing member for forming a recording material nipping and conveying nip portion by contacting the induction heating element directly or via a heat transfer material in the heating section. Image heating equipment. 9. The image heating device according to claim 1, wherein the image heating device is an image heating fixing device that heats and fixes an image on a recording material as a permanent image. 10. An image forming apparatus comprising the image heating device according to claim 1. Description: