JPH0816007A - Heating apparatus and image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent metal members and parts outside of an apparatus main body and inside of a conductive member from being heated by magnetic fluxes which permeate the conductive member without being absorbed in the conductive member or leak out of the end part of an exciting coil of a magnetic field generating means in the longitudinal direction without acting on the conductive member, regading an electromagnetic induction heating-type heating apparatus. CONSTITUTION:A heating apparatus is electromagnetic induction heating-type wherein a magnetic field of magnetic field generating means 2, 3 is made to act on a conductive member 4 which is either fixed or movable to generate an eddy current in the conductive member and a material to be heated is heated by heat generation in the conductive member due to the eddy current. Magnetic flux shielding members 8, 9 to shield leaking magnetic fluxes are installed, the magnetic fluxes are generated by an exciting coil 3 of the magnetic field generating means 2, 3 and do not reach the conductive member or permeate the conductive member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic (magnetic) induction heating type heating device and an image forming apparatus provided with the heating device as an image heating device.

[0002]

2. Description of the Related Art Conventionally, for example, a heating device for a recording material for heating and fixing an image, that is, a copying machine, a laser beam printer,
In image forming apparatuses such as a facsimile, a microfilm reader printer, an image display (display) device, and a recording machine, a toner made of a heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. A visible image (unfixed) corresponding to the target image information formed by the direct method or the indirect (transfer) method on the surface of the recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) The heat roller system has been widely used as an image heating and fixing device (image heating device) for performing heat fixing processing as a permanently fixed image on the surface of a recording material carrying the image).

In this system, a metallic fixing roller having a heater inside and a pressure roller having elasticity to press against the metallic fixing roller are basically constructed, and a recording material is introduced and passed through a fixing nip portion formed by the pair of rollers. By doing so, the toner image is heated and pressure-fixed.

However, in such a heat roller system,
Since the heat capacity of the fixing roller is large, it took a very long time to raise the surface of the fixing roller to the fixing temperature. Therefore, there is a problem that the roller surface must be temperature-controlled to a certain temperature even when the machine is not used in order to promptly execute the image output operation.

That is, it takes a long time to warm up, and it is necessary to provide a standby state to keep the fixing roller heated in order to speed up the first print.

[0006] Also, various methods and configurations such as a flash heating method, an oven heating method, and a hot plate heating method are known and put into practical use. US Patent No. 35787
A belt heating system is also known as described in Japanese Patent Specification No. 97.

[0007]. Recently, a film heating type heating device, that is, a fixedly supported heating body (thermal heater)
And a heat-resistant film that is conveyed while being pressed against the heater, and a pressurizing member that adheres the heated material to the heater through the film, and applies the heat of the heater to the heated material through the film. The device having the configuration described above has come to be used.

According to the applicant's previous proposal, for example, Japanese Patent Laid-Open No.
JP-A-3-313182, JP-A-2-157878, JP-A-4-44075, and JP-A-4-2049.
The method and apparatus disclosed in Japanese Patent No. 80 belong to this, and a thin heat-resistant film (fixing film) as a heat conductor.
A moving means for moving the film, a heating body arranged to be fixedly supported on one side of the film with the film inside, and a heating body arranged on the other side of the film so as to face the heating body. And a pressure member for closely contacting the developed image bearing surface of the recording material to be image-fixed through the film, and the film is conveyed and introduced between the film and the pressure member at least when image fixing is performed. The recording material to be recorded is to be moved in the forward direction at the same speed as the recording material to be fixed, and is passed through a fixing nip portion formed by pressure contact between a heating member and a pressing member with the traveling moving film interposed therebetween. The developed image bearing surface of the material is heated by the heating body through the film to apply thermal energy to the developed image to soften / melt it, and then the film after passing through the fixing point and the recording material are separated at the separation point. It is a device based on that.

As the pressing member, generally, a roller body made of silicone rubber or fluororubber having excellent heat resistance and releasing property is often used.

Such a film heating type heating device is a device for heating a recording material carrying an image to modify the surface property (such as polishing), a device for post-treatment, or a sheet-like material for conveying. It can also be used as a device for heating and drying.

In such a film heating type heating device, a heater having a low heat capacity can be used as a heater. Therefore, it is possible to save power and shorten the wait time (quick start) as compared with the conventional contact heating method such as the heat roller method and the belt heating method.
In addition, the ability to do a quick start eliminates the need for preheating (heating during standby) during non-printing operations.
It is also possible to save power in a comprehensive sense.

However, such a film heating type heating device also has the following problems.

A. When a thick film having high rigidity is used for durability and speeding up, heat conduction becomes poor and the heat capacity of the film becomes large, so that a rapidly heatable state cannot be achieved. That is, the thick film becomes a thermal resistance and impairs the heat transfer from the heater to the recording material which is the material to be heated, and the energy saving and quick start characteristics which are the features of the film heating type apparatus are impaired.

B. However, if the film is thin, rigidity cannot be obtained and a film traveling control mechanism is required, resulting in a large device and a complicated configuration.

C. The material of the film that requires heat resistance is limited. In addition, since the resin film has good heat insulation, all the heat of the heater does not transfer to the outer surface of the film and heats up the inside (heat accumulation inside the film), so heat resistance is also required for the parts placed inside the film. Therefore, it is necessary to use expensive and limited materials.

.. Therefore, the inventors of the present invention have conducted research on a heating device of an electromagnetic induction heating system / film heating system in which the film itself does not generate heat resistance by heating the film itself to improve the thermal efficiency.

This is to change the magnetic field generated in the exciting circuit by combining magnetic field generating means, for example, a core material which is a magnetic body and an exciting coil. That is, by applying a high frequency to the coil, a magnetic field is repeatedly generated and extinguished in the film as a conductive member (inductive magnetic material, magnetic field absorbing conductive material) that moves in the generated magnetic field, and an eddy current is generated in the conductive layer in the film. It is what is generated. This eddy current is converted into heat (Joule heat) by the electric resistance of the conductive layer, and as a result, only the film that adheres to the material to be heated generates heat,
Excellent thermal efficiency.

That is, when a fluctuating magnetic field traverses the conductor, an eddy current is generated in the conductive layer of the film so as to generate a magnetic field that prevents the change of the magnetic field. This eddy current causes the skin resistance of the conductive layer of the film to generate heat in the conductive layer of the film with an electric power proportional to the skin resistance. Since heat is generated directly near the surface layer of the film, there is an advantage that heating can be performed rapidly regardless of the thermal conductivity and heat capacity of the film base layer. In addition, rapid heating that does not depend on the film thickness can be realized.

This makes it possible to increase the thickness of the film base layer with high rigidity without impairing energy saving and quick start properties, and to cope with durability and speeding up.

[0020]

However, such a heating device of the electromagnetic induction heating type is not absorbed by the conductive member such as a film having a conductive layer in the magnetic flux generated from the exciting coil of the magnetic field generating means. Magnetic flux leaks even if it penetrates through the conductive member, or magnetic flux leaks in the longitudinal direction from the end of the exciting coil of the magnetic field generation means, and heats the metal members and parts outside the device body and inside the conductive member. There was a possibility that

Therefore, the present invention has an object to solve this problem in an electromagnetic induction heating type apparatus.

[0022]

The present invention is a heating device and an image forming apparatus characterized by the following configurations.

(1) Heating of an electromagnetic induction heating system in which a magnetic field of a magnetic field generating means is applied to a fixed or moving conductive member to heat a material to be heated by heat generation of the conductive member by an eddy current generated in the conductive member A heating device comprising a magnetic flux shielding member that shields a magnetic flux that is generated from the exciting coil of the magnetic field generating means and that does not reach the conductive member or penetrates the conductive member.

(2) The heating device according to (1), wherein the moving conductive member is a rotating body or a moving end member.

(3) The heating device according to (1) or (2), wherein the conductive member is a laminated member including a conductive layer or a member itself conductive.

(4) The heating device according to any one of (1) to (3), further comprising a pressure member for directly or indirectly adhering the member to be heated to the conductive member.

(5) The pressurizing member is a pressurizing rotary member which is rotationally driven or driven to rotate (4).
The heating device according to.

(6) The material to be heated is a recording material carrying an image to be heat-treated, and an image heating device for heating the image on the recording material (1) to (). The heating device according to any one of 5).

(7) An image forming apparatus comprising the heating device according to any one of (1) to (6) as an image heating device.

[0030]

[Function] A magnetic flux shield that penetrates the conductive member without being absorbed by the conductive member, or shields (absorbs) a leaked magnetic flux that does not act on the conductive member in the longitudinal direction from the end of the exciting coil of the magnetic field generating means. By providing the member, it is possible to prevent the metal member / part on the outside of the apparatus main body or the inside of the conductive member from being heated by the leakage magnetic flux.

[0031]

【Example】

<Example 1> (Figs. 1 to 5) (1) Overall schematic configuration of apparatus Fig. 1 is a schematic cross-sectional view showing the configuration of an example of an electromagnetic induction heating apparatus according to the present invention. An example heating device is
An image heating and fixing device of an electromagnetic induction heating system and a film heating system, which uses a rotating endless film having a conductive layer as a conductive member. FIG. 2 is an enlarged model view of the nip portion, FIG. 3 is a perspective view in which a middle portion of a core material (magnetic field generating means) and an exciting coil are omitted, FIG. 4 is a perspective view of a main part of the device, and FIG. It is a longitudinal cross-sectional view of a main part.

Reference numeral 1 denotes a substantially U-shaped film inner surface guide stay having an upward cross section, and this stay 1 is a liquid crystal polymer.
An exciting coil 3 made of a phenol resin or the like, which is wound around a core material (E-shaped core) 2 as a magnetic field generating means, is housed inside. A rubbing plate is attached to a portion of the stay 1 that comes into contact with the film 4 as a conductive member. The core material 2 is a core such as ferrite, permalloy, or iron core.

The stay 1, the core member 2 and the exciting coil 3
The assembly (electromagnetic induction heating structure) is a horizontally long member having a longitudinal direction in a direction intersecting (orthogonal) with the conveying (moving) direction of the film 4 and the recording material (heating material) P.

A heat-resistant film 4 having a conductive layer, which is an endless shape (cylindrical shape, seamless) as a conductive member (heating member) and has a conductive layer, is loosely fitted on the outside of the assemblies 1, 2, and 3 as a conductive member. There is.

Reference numeral 5 is a pressure roller, which is formed by coating the core metal with silicone rubber, fluororubber or the like. The pressure roller 5 sandwiches the film 4 against the lower surface of the stay 1 with a predetermined pressing force by bearing means and urging means (not shown), and sandwiches the film 4 between the lower surface of the stay and the lower surface of the stay. Pressure contact nip part (heat generation area, fixing nip part) N
To form.

The pressure roller 5 is rotationally driven by the drive means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the film 4 due to the frictional force between the roller and the outer surface of the film due to the rotational driving of the pressure roller 5, and the film 4 slides in close contact with the lower surface of the stay 1 to rotate around the stay 1. .
In this case, it is preferable to apply a lubricant such as grease or oil between the lower surface of the stay 1 and the inner surface of the film 4.

The film 4 as a conductive member has a thickness of 10 μm to 100 μm as shown in the layer structure model diagram of FIG.
Polyimide / Polyamideimide / PEEK / PES /
A heat-resistant resin such as PPS / PEA / PTFE / FEP is used as the base layer 4a of the endless film, and a conductive layer 4b is formed on the outer periphery of the base layer 4a (on the pressure contact surface side of the material to be heated) as a layer of iron or cobalt by plating. For example, nickel, copper,
A metal layer such as chromium is formed with a thickness of 1 μm to 100 μm. Furthermore, a release layer 4c is formed by mixing or independently coating a heat-resistant resin having a good toner release property such as PFA, PTFE, FEP, or a silicone resin on the free surface of the conductive layer 4b as an outermost layer (surface layer). It has a three-layer structure. In this example, the film base layer 4a and the conductive layer 4b are separate layers, but the film base layer 4a itself may be the conductive layer.

When a current is applied to the exciting coil 3 from an exciting circuit (not shown), the conductive layer 4b of the film 4 generates heat by electromagnetic induction heating.

Reference numeral 6 denotes a thermistor which is a temperature detecting element for detecting the surface temperature of the pressure roller 5, and controls the current value applied to the exciting coil 3 based on the temperature detected by the thermistor 6. When the pressure roller 5 is cold and the temperature detected by the thermistor 6 is low, the duty ratio of energization is increased, and when the detected temperature is high, the duty ratio of energization is decreased. For example, when the pressure roller 5 is cold, it is energized with a full wave, but as it gets warmer, the heating amount can be adjusted by gradually turning it off and thinning the energization even at the ON timing. The thermistor 6 may be provided on the film non-sliding surface of the stay 1 or on the core material 2.

Reference numeral 7 is a safety element such as a temperature fuse or a thermoswitch that cuts off energization to the exciting coil 3 when the temperature rises excessively. The safety element 7 does not normally warm even if it is used with a low operating temperature, so that it does not spontaneously break. In addition, since the operating temperature is low when an abnormality occurs, the energization is quickly stopped, which is safe.

Thus, when the film 4 is rotated by the rotation of the pressure roller 5 and a current is applied from the exciting circuit to the exciting coil 3 to heat the conductive layer 4b of the film 4, the pressure contact nip portion N is formed. The recording material P as a material to be heated is introduced into the surface of the recording material P, and the recording material P comes into close contact with the surface of the film 4 and passes through the pressure contact nip portion N together with the film. The unfixed toner image T applied to the toner is heat-fixed T ′. The recording material P passing through the pressure nip portion N is separated from the surface of the film 4 and conveyed.

Reference numerals 8/8 and 9/9 are leakage magnetic flux shielding members. This will be explained in section (3).

(2) Heating principle The exciting coil 3 is connected to an exciting circuit (not shown) from 10 KHz to 5 KHz.
An alternating current (alternating current) is applied at a frequency of 00 KHz, and as a result, the magnetic flux indicated by the arrow H is repeatedly generated and extinguished around the coil 3 as shown in the model diagrams of FIGS. The core material 2 is formed so that the magnetic flux H crosses the conductive layer 4b of the film 4.
Is configured.

When a fluctuating magnetic field traverses in a conductor, eddy currents are generated in the conductor so as to create a magnetic field that impedes changes in the magnetic field. This eddy current is indicated by arrow A (FIG. 2).

Due to the skin effect, this eddy current almost concentrates on the surface of the conductive layer 4b on the coil 3 side, and heat is generated by power proportional to the skin resistance R _S of the film conductive layer 4b.

R _S is the skin depth obtained from the angular frequency ω, the magnetic permeability μ, and the specific resistance ρ.

[0047]

[Outside 1] Can be expressed as

Therefore, by increasing R _S or increasing I _f , the power can be increased and the amount of heat generation can be increased.

To increase R _S , the frequency ω may be increased, or a material having a high magnetic permeability μ and a material having a high specific resistance ρ may be used.

From now on, the nonmagnetic metal is added to the conductive layer 4b.
It is presumed that it is difficult to heat when used for the conductive layer 4
When the thickness t of b is smaller than the skin depth δ, R _S ≈ρ / t, and thus heating is possible.

The frequency of the alternating current applied to the exciting coil 3 is preferably 10 to 500 kHz. At 10 kHz or higher, the absorption efficiency into the conductive layer 4b is improved, and 500 kHz
Up to z, an exciting circuit can be assembled using inexpensive elements.

Further, if the frequency is 20 kHz or more, the sound exceeds the audible range and no sound is produced when energized. If the frequency is 200 kHz or less, the loss generated in the exciting circuit is small.

The skin thickness depends on the material, temperature and frequency, but is generally 10 KHz to 500 KHz, and is generally several μm to several hundreds μm at room temperature to 200 ° C.

When the thickness of the conductive layer 4b is actually smaller than 1 μm, most of the electromagnetic energy cannot be absorbed by the conductive layer 4b, resulting in poor energy efficiency.

There is also a problem that the leaked magnetic field heats other metal parts.

On the other hand, in the conductive layer 4b having a thickness of more than 100 μ, the rigidity of the film 4 becomes too high, and heat is transferred by the heat conduction in the conductive layer 4b, so that the release layer 4c is hard to warm. In addition, manufacturing time and cost are increased.

Therefore, the thickness of the conductive layer 4b is 1 to 100 μm.
Is preferred.

To increase the heat generation of the conductive layer 4b, I _f
Is increased, and for that purpose, the magnetic flux generated by the coil 3 may be strengthened or the change of the magnetic flux may be increased. As this method, the number of windings of the coil 3 may be increased, or the core material 2 of the coil 3 may be ferrite, permalloy, or the like having a high magnetic permeability and a low residual magnetic flux density.

If the resistance value of the conductive layer 4b of the film 4 is too small, the heat generation efficiency when an eddy current is generated deteriorates. Therefore, the low specific volume efficiency of the conductive layer 4b is 1.
It is preferably 5 × 10 ⁻⁸ Ωm or more.

In this embodiment, the conductive layer 4b of the film 4 is formed by plating, but it may be formed by vacuum vapor deposition, sputtering or the like. As a result, aluminum or metal oxide alloy that cannot be plated can be used for the conductive layer 4b. However, it is preferable to perform the plating treatment in order to obtain a layer thickness of 1 to 100 μm because the plating treatment can easily obtain the film thickness.

For example, when a ferromagnetic material such as iron, cobalt, nickel or the like having a high transmittance is attached, the electromagnetic energy generated by the exciting coil 3 can be easily absorbed, the heating can be efficiently performed, and the magnetism leaked out of the machine is small. It also reduces the impact on peripheral devices. Moreover, it is better to select one of these with high and low efficiency.

The conductive layer 4b of the film 4 is made of not only metal but also conductive and high magnetic permeability particles and whiskers dispersed in an adhesive for bonding the surface release layer to the low thermal conductive base material. It may be used as a conductive layer.

For example, manganese, titanium, chromium, iron,
Particles of copper, cobalt, nickel or the like, particles of these alloys such as ferrite or oxide, or whiskers can be mixed with conductive particles such as carbon and dispersed in an adhesive to form a conductive layer.

As described above, since heat is directly generated near the surface layer of the film 4, there is an advantage that heating can be performed rapidly regardless of the thermal conductivity and heat capacity of the film base material (base layer) 4a. Further, since it does not depend on the thickness of the film 4, in order to improve the rigidity of the film 4 for speeding up, the film 4
Even if the base material 4a is thickened, it can be quickly heated to the fixing temperature.

Further, since the film base material 4a is a resin having a low thermal conductivity, it has a good heat insulating property, and it can be insulated from a coil having a large heat capacity such as a coil inside the film, so that there is little loss of heat even when continuous printing is performed. , Energy efficient. Moreover, heat is not transmitted to the coil 3 in the film, and the performance of the coil does not deteriorate.

Since the thermal efficiency is improved, the temperature rise in the apparatus can be suppressed and the influence on the image forming portion of the image forming apparatus such as an electrophotographic apparatus using the heating apparatus as an image heating and fixing apparatus can be reduced.

(3) Leakage Magnetic Flux Shielding In the apparatus according to the present embodiment, the film 4 has a weak magnetic flux outside the nip portions on both longitudinal sides of the nip portion N, as indicated by the broken line a'in FIG. The leakage magnetic flux penetrating the conductive layer 4b of FIG. Further, as indicated by a broken line b'in FIG. 5, the magnetic fluxes at both longitudinal end portions of the exciting coil 3 leak to the outside of the film through the openings at both end portions of the cylindrical film 4 without traversing the film 4. Such leakage magnetic fluxes a'and b'can cause eddy currents to heat up the metal members and parts on the outside of the main body of the device and on the inside of the film, which is a conductive member, and can improve the efficiency of power consumption. Absent.

Therefore, in the present embodiment, the magnetic flux shielding member 8 is provided near the outside of the nip on both sides of the length of the nip N and outside the film so as to be substantially parallel to the length of the film. A'is shielded a (shown by a solid line). The shield members 8 and 8 preferably have high resistance and high magnetic permeability, and are preferably made of, for example, Ferayitch or Permalloy, and their length is longer than that of the exciting coil 3 to generate magnetic flux. It is preferable that the coil is arranged on the pressure roller side with respect to the coil as much as possible.

Further, by disposing disk-shaped magnetic flux shielding members 9 on the both longitudinal ends of the exciting coil 3 and inside the cylindrical film 4 as a conductive member, the leakage magnetic flux b ′ Was shielded b (shown by a solid line). This shielding member 9
9 also preferably has a high resistance and a high magnetic permeability, and is preferably made of, for example, ferric or permalloy. There is no particular restriction on the diameter and the like, and the plate is not limited to a circular shape as long as it can shield the leakage magnetic flux b ′, and may be an elliptical or polygonal plate. It is desirable that the shielding members 9 and 9 are included in the inner space of the film 4.

Either one of the shielding members 8 and 8 and 9 and 9 may be provided, or a shielding member may be provided at a required portion other than these (for example, 8 in FIG. 1). ′ ・
8 ') is also possible. It is also possible to arrange the shielding member in such a form as to entirely surround the outside of the cylindrical film 4.

In this embodiment, the direction of the magnetic field is perpendicular to the film 4. However, the magnetic field may be run in the conductive layer 4b parallel to the layer surface.

When a material having a Curie temperature required for fixing is used as the material for forming the conductive layer 4b, the specific heat increases when the Curie temperature approaches the Curie temperature and the internal energy is changed, so that self-temperature control is possible. Become. When the Curie temperature is exceeded, the spontaneous magnetization disappears, whereby the magnetic field generated in the conductive layer 4b decreases below the Curie temperature, and therefore the eddy current decreases and works to suppress heat generation, so that self-temperature control is possible. Become. The Curie point is preferably 100 ° C. to 200 ° C. according to the softening point of the toner.

Alternatively, since the combined inductance between the exciting coil 3 and the film 4 changes greatly near the Curie temperature, it is possible to detect the temperature on the side of the exciting circuit that applies a high frequency to the coil 3 and control the temperature. Is.

As the material of the core material 2 of the coil 3, it is preferable to use one having a low Curie point.

When the carrying operation of the apparatus is stopped and a so-called runaway state where heating control is impossible is performed, the temperature of the core material 2 starts to rise. As a result, the inductance of the exciting coil 3 seems to have increased from the viewpoint of the circuit that generates the high frequency. Therefore, when the exciting circuit tries to match the frequency, it gradually changes to the higher frequency side and energy is consumed as power loss of the exciting circuit. As a result, the energy supplied to the coil 3 is reduced and runaway is prevented. Specifically, the Curie point is 100 ° C
It is recommended to select at ~ 250 ° C.

If the temperature is 100 ° C. or lower, the temperature rises even if the temperature is lower than the melting point of the toner and the inside of the film is thermally insulated, so that the runaway prevention is apt to malfunction. In the above embodiment, the film heating is explained, but a heat roller using a core material having low thermal conductivity may be used.

However, since a higher magnetic flux density can be obtained when the exciting coil and the conductive layer are closer to each other, it is preferable to use a thin film heating system of a low heat conductive base material.

Although the E-shaped core material 2 is used in the embodiment, I-type and U-shaped core materials may be used. In addition, these may be combined, or the dimensions and materials may be changed for each without combining them.

<Embodiment 2> (FIG. 6) In this embodiment, the magnetic field generating means are arranged vertically facing each other, facing each other or in contact with each other, and a field coil plate 10 as a coil and an induction magnetic material. Is an electromagnetic induction heating structure (heater) made of the magnetic metal material 11 as described above. The electromagnetic induction heating structures 10 and 11 are attached to the magnetic metal material 1.
1 is exposed downward and is fitted into the substantially central portion of the lower surface of the film inner surface guide stay 12 having a substantially semicircular cross-section formed of a thermosetting resin or the like and having rigidity and heat resistance along the guide longitudinal direction. It is attached and held.

Reference numeral 13 is an endless heat-resistant film, which is loosely fitted onto the film inner surface guide stay 12 including the electromagnetic induction heating structures 10 and 11, and the film 13 is electromagnetically induced by the pressure roller 5. It is pressed against the lower surface of the magnetic metal material 11 of the heating structures 10 and 11. The film 13 is not provided with a conductive layer.

The pressure roller 5 is rotationally driven in the counterclockwise direction indicated by the arrow by the driving means M, and the rotational force acts on the film 13 by the frictional force between the roller and the film outer surface due to the rotational drive of the pressure roller 5. Then, the film 13 is brought into close contact with the lower surface of the magnetic metal material 11 to slide and rotate.

The high frequency magnetic field generated from the magnetic field coil of the field coil plate 10 is magnetically coupled to the magnetic metal material 11, and the magnetic metal material 11 is heated by the eddy current loss caused by magnetism,
The heat generated by the magnetic metal material 11 heats the heat resistant film 13 that closely moves to the magnetic metal material 11.

Thus, an image as a material to be heated is fixed between the film 13 and the pressure roller 5 in the pressure contact nip portion N formed by the magnetic metal material 11 and the pressure roller 5 with the film 13 interposed therebetween. The recording material P to be recorded is introduced from an image forming section (not shown) and is nipped and conveyed together with the film 13 in the pressure contact nip portion N, whereby the heat of the magnetic metal material 10 is transferred to the film 1.
The unfixed toner image T on the recording material P, which is applied to the recording material P via 3, is heated and fixed on the surface of the recording material P. The recording material P passing through the pressure contact nip portion N is the film 13
Is separated from the surface and is transported.

Also in the apparatus of this example, the same effect as that of the first embodiment can be obtained by disposing the leakage magnetic flux shielding members 8, 8 and 9 and 9 similarly to the first embodiment.

<Embodiment 3> (FIG. 7) FIGS. 7 (a), (b) and (c) show another example of the configuration of the electromagnetic induction heating type heating device.

(A) is an electromagnetic induction heating structure 1.2.
The film 4 serving as an endless belt-shaped conductive member is suspended and stretched between the three members of the lower surface of the stay 1 of 3, the driving roller 15, and the driven roller (tension roller) 16, and the film is formed by the driving roller 15. 4 is rotationally driven. Reference numeral 16 denotes a pressure roller that is pressed against the lower surface of the stay with the film 4 interposed therebetween, and is driven to rotate as the film 4 rotates.

In (b), the electromagnetic induction heating structure 1
A film 4 as an endless belt-shaped conductive member is suspended and stretched between the lower surface of the 2.3 stay 1 and the two members of the drive roller 12 and is rotationally driven by the drive roller 15.

In (c), the film 4 as the conductive member is not an endless belt-shaped one, but a long end film wound in a roll is used, and this is an electromagnetic induction heating structure from the feeding shaft 17 side. The body 1, 2, 3 is configured to run at a predetermined speed toward the winding shaft 18 side via the stay lower surface.

<Embodiment 4> (FIG. 8) In this embodiment, for example, an outline of an example of an image forming apparatus using the heating apparatus of the electromagnetic induction heating system of the above-described Embodiment 1 as an image heating fixing apparatus (image heating apparatus) 35 It is a block diagram. The image forming apparatus of this example is a laser beam printer using an electrophotographic process.

Reference numeral 21 is a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image supporting member (first image supporting member). The photosensitive drum 21 is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed), and in the course of the rotation, the primary charger 22 uniformly charges the negative dark potential V _D.

Reference numeral 23 denotes a laser beam scanner which emits a laser beam L modulated in accordance with a time series electric digital pixel signal of target image information input from a host device such as an image reading device, a word processor and a computer (not shown). Then, the surface of the photosensitive drum 21, which has been negatively and uniformly charged by the primary charger 22 as described above, is scanned and exposed by the laser beam, so that the potential absolute value of the exposed portion becomes small and becomes the bright potential V _{L and} rotates. An electrostatic latent image corresponding to the target image information is formed on the surface of the exposure drum 21.

Next, the latent image is subjected to reversal development (laser exposure section V
Toner is attached to _L ) to make it visible.

The developing device 24 has a developing sleeve 24a which is rotationally driven, and the outer peripheral surface of the developing sleeve 24 is coated with a thin layer of toner having a negative charge to face the surface of the photosensitive drum 21. Absolute value is photosensitive drum 2
By applying the developing bias voltage V _DC which is smaller than the dark potential V _{D of} 1 and larger than the bright potential V _L , the toner on the sleeve 24 a is transferred only to the portion of the light potential V _L of the photosensitive drum 21. The latent image is visualized (reversal development).

On the other hand, the recording material (second image carrier, transfer paper) P stacked and set on the paper feed tray 25 is fed out and fed one by one by the paper feed roller 26, and conveyed by the conveyance guide 27 and the resist. Via the roller pair 28 and the pre-transfer guide 29, the photosensitive drum 21 is exposed to the nip portion (transfer portion) 32 with the transfer roller 30 which is brought into contact with the photosensitive drum 21 and a transfer bias is applied by the power supply 31. The toner image on the surface side of the photosensitive drum 21 is sequentially transferred onto the surface of the fed recording material P by being fed at an appropriate timing synchronized with the rotation of the drum 21. The transfer roller 30 as a transfer member preferably has a resistance value of about 10 ⁸ to 10 ⁹ Ωm.

The recording material P that has passed through the transfer portion 32 is separated from the surface of the photosensitive drum 21, and is fixed by the conveyance guide 34 to the fixing device 35.
Then, the transferred toner image is fixed and is output to the discharge tray 36 as an image formed product (print). The surface of the photosensitive drum 21 after the recording material is separated is cleaned by a cleaning device 33.
Then, the residual toner on the surface of the photosensitive drum such as residual toner after transfer is removed, and the surface is cleaned to be repeatedly used for image formation.

[0096]

As described above, according to the present invention, in an electromagnetic induction heating type heating device or an image heating device (image heating and fixing device), the conductive member is not absorbed but penetrates the conductive member or generates a magnetic field. Shields (absorbs) the leakage magnetic flux leaking from the end of the exciting coil of the means without acting on the conductive member in the longitudinal direction.
By providing the magnetic flux shielding member for preventing the heating, it is possible to prevent the metal member / part on the outside of the main body of the apparatus or the inside of the conductive member from being heated by the leakage magnetic flux, and the intended purpose is well achieved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electromagnetic induction heating device according to a first embodiment.

[Figure 2] Enlarged model view of the nip part

FIG. 3 is a perspective view of a core member and an exciting coil with an intermediate portion omitted.

FIG. 4 is a perspective view of the main part of the device.

FIG. 5 is a vertical cross-sectional view of the main part of the device.

FIG. 6 is a schematic diagram of another configuration example of the heating device (Example 2)

7 (a), (b), and (c) are schematic diagrams of another example of the configuration of the heating device (Example 3).

FIG. 8 is a schematic configuration diagram of an example of an image forming apparatus (Example 4).

[Explanation of symbols]

 1 Guide Inner Surface of Film 2/3 Core Material and Excitation Coil as Magnetic Field Generating Means 4 Film as Conductive Member 4a Film Base Layer 4b Conductive Layer 4c Release Layer 5 Pressure Roller N Pressure Contact Nip P Recording as Heated Material Material 6 Temperature detection element (thermistor) 7 Safety element (temperature fuse, thermo switch, etc.) 8.9 Leakage magnetic flux shielding member

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Manabu Takano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Daizo Fukuzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Atsushi Abe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A heating device of an electromagnetic induction heating system for heating a material to be heated by causing a magnetic field of a magnetic field generating means to act on a fixed or moving conductive member to generate heat of the conductive member by an eddy current generated in the conductive member. The heating device is provided with a magnetic flux shielding member that shields a leakage magnetic flux that is generated from the exciting coil of the magnetic field generating means and does not reach the conductive member or penetrates the conductive member. 2. The heating device according to claim 1, wherein the moving conductive member is a rotating body or an end member that travels and moves. 3. The heating device according to claim 1, wherein the conductive member is a laminated member including a conductive layer or a member which is itself conductive. 4. The heating device according to claim 1, further comprising a pressing member for directly or indirectly adhering the member to be heated to the conductive member. 5. The heating device according to claim 4, wherein the pressurizing member is a pressurizing rotary member that is rotationally driven or driven to rotate. 6. The heating target material is a recording material carrying an image to be heat-treated, and is an image heating device for heating the image on the recording material. The heating device according to any one of 1. 7. An image forming apparatus comprising the heating device according to any one of claims 1 to 6 as an image heating device.