JPH0830126A - Heating device and image forming device - Google Patents

Abstract

PURPOSE:To prevent a conductive member from being damaged by bend by uniformizing the temperature distribution of the conduction member in the longitudinal direction of a heating part for a body to be heated and preventing the conductive material from being twisted because of the non-uniformity of thermal expansion of a pressure member in the longitudinal direction of the heating part for the body to be heated in the heating device of an electromagnetic induction heating system. CONSTITUTION:This device is the heating device of an electromagnetic induction system for heating the body to be heated P in tight contact with the conductive member 17 with the generated heat of the conductive member 17 by an eddy current A generated in the conductive member 17 by making magnetic field H act on thc conductive member 17(17b) by magnetic field generating means 21 and 22. A member 25A having good thermal conduction over thc longitudinal direction of the heating part for the body to be heated is arranged on a surface on an opposite side to a side where the conductive member part comes in to tight contact with the body to be heated at the heating part N for the body to be heated.

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 equipped with the heating device as an image heating device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device, a recording machine, etc., it is necessary to use an electrophotographic, electrostatic recording, magnetic recording, etc. Directly or indirectly on the surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image support by using a toner made of a heat-meltable resin by the image forming process means. An image heating and fixing device as a heating device for heating and fixing an unfixed toner image corresponding to the target image information formed by the (transfer) method as a permanently fixed image on the surface of the recording material carrying the toner image. Is a heat roller type fixing device using a heat roller,
A contact-type fixing device such as a fixing device using a film heating method is widely used.

(A) A heat roller type apparatus is composed of a metal heat roller having a heating element such as a halogen heater therein and a pressure roller having elasticity for pressure contact with the metal heat roller. By passing a recording material as an object to be heated through a fixing nip portion which is a portion, a toner image is heated and pressure-fixed.

However, in such a heat roller system, since the heat capacity of the roller is large, it takes a very long time to raise the temperature of the roller surface to a predetermined fixing temperature.
Therefore, in order to quickly execute the image output operation, the roller surface must be controlled to a certain standby temperature even during non-image output.

(B) A film heating type apparatus is disclosed in Japanese Patent Laid-Open No.
JP-A-3-313182, JP-A-2-157878, JP-A-4-44075, and JP-A-4-2049.
It is proposed in Japanese Patent Publication No. 80. That is, it has a heating body (generally referred to as a ceramic heater, hereinafter referred to as a heater) and a heat-resistant film that moves in close contact with the heater. It is a heating device that moves the position and applies the thermal energy of the heater to the object to be heated through the film. It has a pressurizing member that brings the film and the object to be heated into close contact with the heater.

In the image fixing operation, a recording material as a heated body is introduced and passed between the film and the pressing member in the fixing nip portion formed by pressing the heater and the pressing member with the film interposed therebetween. The heating is performed by heating the surface of the recording material on which the developed image is carried with a heater through a film to apply thermal energy to the unfixed toner image to soften and melt the toner.

In such a film heating type apparatus,
Since a heater having a low heat capacity can be used, the wait time can be shortened (quick start) as compared with the heat roller method. Further, since the quick start is possible, it is not necessary to raise the temperature of the heater in advance, so that it is possible to reduce the power consumption and prevent the temperature rise inside the machine.

The film heating type heating device has the advantages as described above and is effective as an image heating and fixing device. However, the film interposed between the heater, which is a heating body, and the heated body has a thermal resistance. It was also an inclusion that impairs thermal efficiency.

That is, in the conventional film heating system, since the heater indirectly heats the object to be heated through the film, there is still room for improvement in terms of heating efficiency. For example, if the film thickness is increased in order to increase the strength of the film, it becomes difficult to quickly supply the heat of the heater to the object to be heated. Further, since the film itself has a heat insulating property, the heat generated by the heater, which should originally be transmitted to the outer surface of the film, is accumulated inside the film. That is, when a high-rigidity film is used, heat conduction becomes poor and the heat capacity of the film becomes large, so that a rapidly heatable state cannot be achieved. If the film is thin, rigidity cannot be obtained, a film running control mechanism is required, and the device becomes large and has a complicated configuration. The material of the film that requires heat resistance is limited. Further, since the resin film has a good heat insulating property, heat is accumulated inside the film, and heat resistance is required also for the parts arranged inside the film, which makes it necessary to use expensive and limited materials.

(C) Therefore, the present applicant previously proposed 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 so as to improve the thermal efficiency. There is.

This is a conductive member (inductive magnetic material, magnetic metal material, magnetic field absorbing conductive material) which changes a magnetic field generated by combining a core material which is a magnetic body and a coil in an exciting circuit and moves in the magnetic field. ) Is to generate an eddy current in the conductive layer in the film. 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 is in close contact with the object to be heated generates heat, and the thermal efficiency is excellent.

FIG. 10 is a schematic view of an example of the heating device of the electromagnetic induction heating system / film heating system.

Reference numeral 21 denotes an exciting coil as a magnetic field generating means, which is formed by winding around a core material (magnetic material, core) 22. Reference numeral 23 is a stay that supports the core material and also serves as a film guide. Reference numeral 25 is a film pressure plate (first pressure member) arranged below the core member 22, and is made of glass having a relatively small friction resistance with respect to the film 17 as a conductive member (heat generating member) described later. ing.

Reference numeral 17 is an endless (cylindrical, seamless) heat-resistant film having a conductive layer as a conductive member, and includes a film base layer 17a, a conductive layer 17b, and a release layer 1.
7c is a three-layer structured film. The film 17 is loosely fitted onto the assembly (electromagnetic induction heating structure) including the coil 21, the core member 22, the stay 23, and the pressure plate 25.

Reference numeral 24 is a pressure roller (second pressure member), which is constructed by winding silicone rubber, fluororubber or the like around the core metal. The pressure roller 24 is arranged so as to sandwich the film 17 with a predetermined pressing force by bearing means / urging means (not shown) so as to be in pressure contact with the lower surface of the film pressure plate 25. A film 17 is sandwiched between them to form a pressure contact nip portion (heated body heating portion, fixing nip portion).

The pressure roller 24 is rotationally driven in the counterclockwise direction indicated by the arrow by the driving means. This pressure roller 2
The rotational force acts on the film 17 due to the frictional force between the roller 24 and the outer surface of the film 17 due to the rotational driving of the film 5, so that the film 17 slides in close contact with the lower surface of the pressure plate 25 and the assembly 2
It rotates around 1, 22, 23, and 25.

With such a structure, a current is applied to the coil 21 at a predetermined frequency from an exciting circuit (not shown), whereby a magnetic flux indicated by an arrow H is repeatedly generated and extinguished around the coil 21. The core material 22 is configured such that the magnetic flux H crosses the conductive layer 17b of the film 17.

When a fluctuating magnetic field traverses a conductor, it produces a magnetic field which impedes changes in the magnetic field.
Eddy current is generated in the conductive layer 17b of No. 7. Due to the skin resistance of the conductive layer 17b of the film 17, the eddy current causes the conductive layer 17b of the film to generate heat with electric power proportional to the skin resistance.

Since heat is generated directly near the surface layer of the film 17 in this manner, there is an advantage that heating can be performed rapidly regardless of the thermal conductivity and heat capacity of the film base layer 17a. In addition, rapid heating that does not depend on the thickness of the film 17 can be realized.

Thus, in the state where the film 17 is rotated by the rotation of the pressure roller 24 and the film 17 (17b) is heated by the electromagnetic induction heating, the film 17 and the pressure roller 24 in the pressure contact nip portion are The recording material P as an object to be image-fixed is introduced from an image forming section (not shown) between the two, and is conveyed while sandwiching the pressure contact nip portion together with the film 17 so that the film 17 is heated by electromagnetic induction. Heat is applied to the recording material P, and the unfixed toner image T on the recording material P is heated and fixed on the surface of the recording material P. The recording material P passing through the pressure contact nip portion is separated from the surface of the film 1 and conveyed.

This system is fundamentally different from the conventional film heating system in that the film itself directly generates heat, and therefore the heating efficiency does not decrease even if the film thickness is increased.

[0022]

The electromagnetic induction heating type / film heating type heating device of the above (c) has the following problems.

.. Due to variations in the film thickness of the conductive layer of the film as the conductive member (heat generating member), distribution of the magnetic field in the longitudinal direction, and the like, the temperature distribution of the film in the paper-passing area of the heated object tends to become uneven.

[0024]. Damage to the conductive film layer caused by deformation or fatigue due to pressure.

[0025]. When small size paper is continuously passed as the object to be heated, the film temperature difference between the paper passing area and the non-paper passing area is 100.
deg or more. Due to this temperature difference, the amount of thermal expansion of the pressure roller becomes non-uniform in the longitudinal direction, and there is a possibility that the film conveying force will be different and the film will be twisted and damaged.

Therefore, the present invention solves the above problems (1) to (3) in the heating apparatus of the electromagnetic induction heating type, that is, makes the temperature distribution of the conductive member uniform in the longitudinal direction of the heating target heating section, It is an object of the present invention to prevent the conductive member from being broken due to bending, and to prevent the conductive member from being twisted due to uneven thermal expansion of the pressing member in the longitudinal direction of the heated portion of the body to be heated.

[0027]

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

(1) An electromagnetic induction system in which a magnetic field is applied to the conductive member by the magnetic field generating means to heat the object to be heated that is brought into close contact with the conductive member by the heat generated by the eddy current generated in the conductive member. A heating device, characterized in that a member having good thermal conductivity is disposed over the length of the heating target heating portion on the surface of the heating target heating portion opposite to the heating target contact side of the conductive member portion. apparatus.

(2) The heating device according to (1), wherein the member having good thermal conductivity has a curvature on a surface in contact with the conductive member.

(3) The heating device according to (1) or (2), wherein the member having good thermal conductivity is in contact with the heat radiating member at the non-sheet-passing side end of the heating target sheet width region.

(4) The conductive member is a rotating body, and the magnetic field generating means and a member having good thermal conductivity are arranged inside the rotating body and contact the inner surface of the rotor of the member having good thermal conductivity. The surface has a convex shape in the same direction as the rotating body, and the heating device according to any one of (1) to (3).

(5) The heating apparatus according to (4), wherein the surface of the member having good thermal conductivity that contacts the inner surface of the rotor has the same curvature as the inner surface of the rotor.

(6) The heating device according to (4), wherein the surface of the member having good thermal conductivity, which is in contact with the inner surface of the rotator, has a curvature larger than that of the inner surface of the rotator.

(7) The heating device according to any one of (1) to (6), wherein the member having good thermal conductivity has a roller shape.

(8) The heating device according to any one of (1) to (7), wherein the member having good thermal conductivity is not in contact with the magnetic field generating means.

(9) The member having good thermal conductivity is characterized in that an elastic layer is provided on the surface in contact with the conductive member (1).
The heating device according to any one of (1) to (8).

(10) The surface of the member having good thermal conductivity that contacts the conductive member has a crown shape in a direction orthogonal to the moving direction of the conductive member (1) to (9).
The heating device according to any one of 1.

(11) The heating device according to any one of (1) to (10), wherein the conductive member is a moving member having an end.

(12) The heating device according to any one of (1) to (11), wherein the conductive member is a laminated member including a conductive layer or a member itself conductive.

(13) The method according to any one of (1) to (12), further comprising a conductive member or a pressing member for bringing the conductive member and the object to be heated into close contact with a member having good thermal conductivity. Heating device.

(14) The pressing member is a rotating body that is rotationally driven or driven to rotate (13).
The heating device according to.

(15) The object to be heated 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 (1) to (). The heating device according to 14).

(16) An image forming apparatus comprising the heating device according to any one of (1) to (14) as an image heating device.

[0044]

In other words, by disposing a member having good thermal conductivity in the longitudinal direction of the heated body heating portion on the surface of the conductive member portion of the heated body heating portion opposite to the side where the heated body adheres. The non-uniformity of the temperature distribution of the conductive member in the longitudinal direction of the heated part of the heated body caused by the variation in the film thickness of the conductive member or the distribution of the magnetic field in the longitudinal direction of the heated part of the heated body causes the good thermal conductivity of the member. The temperature distribution of the conductive member in the paper passing area can be made uniform by being corrected by the diffusion of heat along the length of the member.

For the same reason, the temperature rise in the non-sheet-passing portion when the small-sized object to be heated is continuously passed is also reduced by lowering the temperature difference between the sheet-passing portion and the non-sheet-passing portion.

The reduction of the temperature rise in the non-sheet-passing portion is achieved by providing a heat-dissipating member in contact with the non-sheet-passing-side end of the sheet-passing width region of the heated body of the member having good thermal conductivity. The heat is prevented from being stored in the section, which makes it more effective.

Further, the contact surface of the good thermal conductive member with the conductive member has a convex shape in the same direction as the conductive member surface, has the same curvature as the conductive member surface, or has a curvature larger than the conductive member surface. By doing so, it is possible to form the nip without forming a forcibly bent portion in the conductive member, so that bending stress does not act on the conductive member or is alleviated, and damage due to bending of the conductive member is prevented and durable. The property is improved.

[0048]

【Example】

<Embodiment 1> (FIGS. 1 and 2) FIG. 1 shows an example of a heating device of the present embodiment (electromagnetic induction heating system.
FIG. 3 is a schematic diagram showing a configuration of a film heating type image heating apparatus). The same components and parts as those in FIG. 10 are designated by the same reference numerals, and the repeated description will be omitted.

(1) Magnetic field generating means 21 and 22 Iron is used for the core material 22. Also, film 1
In order to increase the heat generation of the conductive layer 17b of No. 7, by using a material such as ferrite or permalloy having a high magnetic permeability and a low residual magnetic flux density, the magnetic flux generated by the coil 21 is increased or the change of the magnetic flux is increased. The current flowing through the film may be increased.

In this embodiment, a U-shaped core 22 is used, a coil 21 is long in the axial direction of the film as shown in FIG. 2, and a magnetic flux H passing vertically through the film 17 is used.
Was generated to heat the film 17 (17b) as a conductive member. Of course, the core material 22 may be of E type, I type, or the like as in the device of FIG. 10, and these may be combined, or the dimensions and materials may be changed without combination. .

The stay 23 is made of liquid crystal polymer, phenol resin or the like, and a rubbing plate for guiding the film is attached to the side surface.

(2) Film 17 The rotating body film 17 as a conductive member (heat generating member) is
Polyimide, polyamide imide, PEEK, PES, PPS, PFA, PTFE, with a thickness of 10 μm to 100 μm
A heat-resistant resin such as FEP is used as a base layer (base material) 17a, and a conductive layer 17b is provided on the outer periphery of the base layer 17a (on the pressure contact surface side of the heated body).
Of Fe, Co, or a metal such as Ni, Cu, or Cr is formed to a thickness of 1 μm to 100 μm by plating or the like. Further, a release layer 17c is formed on the free surface of the conductive layer 17b by mixing or independently coating a heat-resistant resin having a good toner release property such as PFA, PTFE, FEP or silicone resin as a surface layer. It has a layered structure.

In this example, the film base layer 17a and the conductive layer 1
Although 7b is a separate layer, the film base layer 17a itself may be a conductive layer.

If the thickness of the conductive layer 17b is less than 1 μm, most of the electromagnetic energy cannot be absorbed by the conductive layer 17b, resulting in poor energy efficiency and the problem that the leaked magnetic field heats other metal parts. Occurs. On the other hand, in the conductive layer 17b having a thickness exceeding 100 μm, the film 1
There is a problem that the rigidity of 7 becomes too high and heat is transferred by heat conduction in the conductive layer, so that it becomes difficult to warm the release layer 17c.

If the resistance value of the conductive layer 17b is too small, the heat generation efficiency when an eddy current is generated deteriorates. Therefore, the specific volume resistivity of the conductive layer 17b is 1.5 × 10 5 in a 20 ° C. environment.
^-8 Ωm or more is preferable. (3) Heating principle The exciting coil 21 receives an alternating current (10k) from the exciting circuit 28.
(Hz to 500 kHz) is applied, whereby the magnetic flux indicated by the arrow H is repeatedly generated and extinguished around the coil 21. The core material 22 is configured such that the magnetic flux H crosses the conductive layer 17b of the film 17.

When a fluctuating magnetic field traverses a conductor, an eddy current A is generated in the conductor so as to generate a magnetic field that hinders the change of the magnetic field.

Due to the skin effect, this eddy current mostly flows concentratedly on the surface of the conductive layer 17b on the side of the exciting coil 21, and heat is generated by electric power proportional to the skin resistance R _S of the film conductive layer 17b.

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

[0059]

[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 this point of view, the non-magnetic metal is used as the conductive layer 17
It is presumed that it is difficult to heat when used for b, but when the thickness t of the conductive layer 17b is thinner than the skin depth δ, R _S ≈ρ / t, and therefore heating is possible.

The frequency of the alternating current applied to the exciting coil 21 is preferably 10 to 500 kHz. Above 10 kHz, the absorption efficiency into the conductive layer 17b improves,
Up to kHz, 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 generated when energized. If the frequency is 200 kHz or less, the loss generated in the exciting circuit is small and the radiation noise to the surroundings is small.

When an alternating current of 10 to 500 kHz is applied to the conductive layer 17b, the skin depth is about several μm to several hundreds of μm at room temperature to 200 ° C. Actually conductive layer 17
If the thickness of b is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed by the conductive layer 17b, 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 17b having a thickness of more than 100 μ, the rigidity of the film 17 becomes too high, and heat is transferred by heat conduction in the conductive layer 17b, which causes a problem that the release layer 17c is hard to warm. In addition, manufacturing time and cost are increased. Therefore, the thickness of the conductive layer 17b is preferably 1 to 100 μm.

To increase the heat generation of the conductive layer 17b, I
_It suffices to increase _f, and for that purpose, the magnetic flux generated by the exciting coil 21 may be strengthened or the change of the magnetic flux may be increased. As this method, the number of windings of the coil 21 may be increased, or the core material 22 of the exciting coil 21 may be ferrite or permalloy having a high magnetic permeability and a low residual magnetic flux density.

In this embodiment, the conductive layer 17b of the film 17 is used.
Was 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 17b. 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, or nickel having a high transmittance is attached, the electromagnetic energy generated by the exciting coil 2 is 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 17b of the film 17 is made of not only metal but also conductive, 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.

In this embodiment, the direction of the magnetic field is the film 17
The magnetic field may be run in the conductive layer 17b in parallel with the layer surface.

As a material for forming the conductive layer 17b,
When the Curie temperature used is that required for fixing, the Curie temperature is heated, and when the Curie temperature approaches, the specific heat increases and the internal energy is changed, so that the self-temperature control becomes possible. When the temperature exceeds the Curie temperature, the spontaneous magnetization disappears, whereby the magnetic field generated in the conductive layer 17b decreases below the Curie temperature, so that the eddy current decreases and works to suppress heat generation, so that the self-temperature control is possible. Become. The Curie point is 100 ° C to 200 depending on the softening point of the toner.
C is preferred.

Alternatively, since the combined inductance between the exciting coil 21 and the film 17 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 21 and control the temperature. Is.

As the material of the core material 22 of the coil 21, 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 22 starts to rise. As a result, the inductance of the exciting coil 21 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 high frequency side and energy is consumed as power loss of the exciting circuit. As a result, the energy supplied to the coil 21 is reduced and runaway is prevented. Specifically, the Curie point is 100
It is good to select at ℃ to 250 ℃.

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.

(4) Film pressure plate 25A The film pressure plate 25A (first pressure member) on the inner surface side of the film, which is the side where the magnetic field generating means 21 and 22 are arranged, is made of a good heat-conductive material such as ceramic. The member has conductivity.

A lubricant such as grease oil is preferably applied to the surface of the pressure plate 25A as a member having good thermal conductivity in order to reduce the frictional resistance with the film 17. Further, a member having a relatively good sliding property such as a thin glass plate may be adhered to the contact surface of the pressure plate 25A with the film 17.

If this pressure plate 25A is a conductive member, the pressure plate 25A will generate heat due to the energy of the magnetic force that causes the metal layer 17b of the film 17 to generate heat, and the energy necessary for fixing will be sufficient. Since the pressure plate 25A is not applied to the layer 17b, the pressure plate 25A needs to be made of a material having good thermal conductivity and in which eddy current is not generated.

In this embodiment, the thermal conductivity is 0.004 (cal /
cm 2 sec ℃ or more Al ₂ O ₃ ceramic (width 40 m
m, thickness 2 mm, length 220 mm) was used, but the filler was dispersed in the resin to achieve a thermal conductivity of 0.004 (cal / cm · s).
Materials with a temperature above ec · ° C) may be used.

With such a structure, the film conductive layer 1
It is possible to correct the unevenness of the temperature distribution of the film in the longitudinal direction caused by the variation of the film thickness of 7b and the distribution of the magnetic field in the longitudinal direction, and to make the temperature distribution of the film in the paper passing area uniform.

Further, when small-size paper is continuously fed, the pressure roller temperature of the non-sheet-passing portion where the heat energy is not absorbed by the paper as the object to be heated is about 270 ° C., and the heat-resistant temperature of the pressure roller 24 is high. It exceeds 240-250 ° C. The pressure plate 25A of this embodiment also has an effect of reducing the temperature rise in the non-sheet passing portion.

In order to obtain the effect of increasing the thermal conductivity in the longitudinal direction of the pressure plate 25A and reducing the temperature rise in the non-sheet passing portion, the length of the pressure plate 25A is L, the cross-sectional area is S, the thermal conductivity is ρ, and the consumption is ρ. Power W
Then

[0084]

[Equation 1] It was found from the study by the present inventors that the relationship of 1 should be satisfied.

When the pressure plate 25A of the present embodiment constructed so as to satisfy this relational expression is used and small-size paper is continuously fed, the pressure roller temperature of the non-paper passing portion is approximately 230 ° C. It could be kept within the heat resistant temperature of 24.

That is, since the pressure plate 25A made of ceramic having good heat conductivity is arranged on the inner surface of the film 17 so that the temperature distribution in the longitudinal direction of the film becomes uniform, the temperature distribution in the longitudinal direction of the film becomes uneven. It is possible to prevent defective fixing and uneven gloss. The pressure plate 25A, which is a member having good thermal conductivity, is attached to the stay 23 including the core material 22, and the film 17 together with the stay 23 is pressed by the pressure roller 24 (second pressure) by a pressure mechanism (not shown). Member). Alternatively, the pressure plate 25A may be directly provided with a pressure mechanism. Alternatively, the pressure may be applied from the pressure roller 24 toward the pressure plate 25.

Although the film pressing plate 25A and the stay 23 are separate members here, they may be integrated using the same material. This is advantageous in terms of cost because the number of parts is reduced and the assemblability is improved.

(5) Energizing system 28 is an exciting circuit for energizing the exciting coil 21, and 27
Is a safety element such as a temperature fuse and a thermoswitch which are brought into contact with the core member 22 of the exciting coil 21 and are interposed in series in this energizing path. This safety element 27 serves to cut off the energization to the exciting coil 21 when the temperature rises excessively. The safety element 27 for preventing the runaway is not warmed normally even if a low operating temperature is used, so that it does not spontaneously cut off, and since the operating temperature is low at the time of an abnormality, the power supply is quickly stopped, so it is safer than in the past. Is.

Reference numeral 26 is a thermistor which is in contact with the surface of the pressure roller 24, and serves to detect the temperature of the pressure roller 24 and control the current applied to the exciting coil 21.
That is, the exciting circuit 28 is controlled by the regulator 29 based on the temperature detected by the thermistor 26, and the exciting coil 21
The value of the current applied to is controlled. When the pressure roller 24 is cold and the temperature detected by the thermistor 26 is low, the duty ratio of energization is reduced. That is, when the pressure roller 24 is cold, full-wave current is energized, but as it warms up, the amount of heating can be adjusted by gradually turning off at even the ON timing and thinning the energization. The thermistor 26 includes a non-contact surface of the pressure plate 25A (a back surface of the pressure plate) and a core member 2.
It is also possible to provide it on 2.

With such a configuration, an alternating current is applied to the exciting coil 21 from the exciting circuit 28, whereby the magnetic flux indicated by the arrow H is repeatedly generated and extinguished around the exciting coil 21.

As in the apparatus shown in FIG. 10, the pressure roller 24 rotates the film 17 and the electromagnetic induction heating heats the film 17 (17b). (Heating part heating part,
A recording material P as an object to be image-fixed, which is an object to be heated, is introduced between a film 17 of a fixing nip portion) and a pressure roller 24 from an image forming portion (not shown), and a pressure contact nip portion N is formed together with the film 17. The heat of the film 17 (17b) heated by electromagnetic induction is applied to the recording material P by being nipped and conveyed, and the unfixed toner image T on the recording material P is heated and fixed on the surface of the recording material P. Is. The recording material P passing through the pressure nip portion N is separated from the surface of the film 17 and conveyed.

Although the film pressure plate 25A is in contact with the core material 22 in the apparatus of this embodiment shown in FIG. 1, it may be noncontact. In that case, for example, if the stay 23 and the pressure plate 25A are separate members, the stay 23 may be fixedly arranged in the heating device, and the film 17 may be pressed only by the pressure plate 25A. Further, when the stay 23 and the pressure plate 25A are the same member, it is sufficient to simply attach the core member 22 to the stay 23 apart from the pressure plate 25A.

As described above, since heat is generated directly near the surface layer of the film 17, the film base layer (base material) 17
There is an advantage that heating can be performed rapidly regardless of the thermal conductivity and heat capacity of a. That is, the film base material (base layer) of the film 17 as a conductive member (heating member) has only to work thermally as a heat insulating material, and is more preferable than a film heating type device using a film as a conventional heat conductor. The selection branch of the material spreads. Also, since it does not depend on the thickness of the film 17,
Since the rigidity of the film 17 is improved for speeding up, even if the base layer 17a of the film 17 is thickened, it can be quickly heated to the fixing temperature.

In this embodiment, the film heating is explained, but
The film as the heating member may be a roller body.

The apparatus of this embodiment is not limited to the fixing apparatus, but is widely used for heating objects such as an apparatus for heating a recording material carrying an image to modify the surface properties such as gloss and a hypothetical wearing apparatus. It can be used as means and device. It can also be used in a device for heating and drying while conveying a sheet-like material.

<Embodiment 2> (FIG. 3) In this embodiment, as shown in FIG. 3, the film pressure plate 25A as a member having good thermal conductivity is not a flat plate like the device of the embodiment (FIG. 1). However, the contact surface with the inner surface of the film 17 has a convex shape in the same direction as the shape of the film.

In the flat pressure plate 25A as in the apparatus of the first embodiment, there is a high risk of premature damage of the film 17 due to bending, but the film contact surface of the pressure plate 25A is the inner surface of the film as in this embodiment. By adopting a shape that follows the curvature, it is possible to form a nip without forming a bent portion in the film and prevent damage to the film. here,
The curvature of the film contact surface of the film pressing plate 25A is 0, that is, any curvature may be used as long as it has a curvature in the same direction as the film, but is preferably equal to or more than the curvature of the inner surface of the film.

When the curvature of the pressure plate 25A is equal to or larger than the curvature of the film 17, the film 17 can be rotationally driven while maintaining a shape close to a standing shape where no external force is applied,
Damage is hard to occur.

Also in the case of the apparatus of this example, the film pressure plate 2
By using 5A as a member having good thermal conductivity by using ceramics having good thermal conductivity, the temperature distribution in the longitudinal direction of the film becomes uniform, and the occurrence of defective fixing and uneven gloss caused by uneven temperature distribution is prevented. You can

<Embodiment 3> (FIG. 4) In this embodiment, in order to prevent the film 17 from being twisted or damaged due to the temperature rise in the non-sheet-passing area when a small-sized paper is continuously fed,
A member having good thermal conductivity similar to that of the second embodiment is used for the pressure plate 25A on the inner surface of the film, and the non-sheet passing portion end of the pressure plate 25A (the non-sheet passing side end portion of the heating target sheet passing width region). The heat dissipation member 30 is arranged.

It has been known that the main cause of the twist in the film 17 is that the thermal expansion of the pressure roller 24 in the longitudinal direction becomes uneven.

For example, when a small-sized recording material P such as an envelope is continuously passed as an object to be heated, the recording material is not passed through the non-sheet passing area (non-sheet passing portion) B of the film 17 or the pressure roller 24. Since the heat is not taken away, the temperature gradually rises when the paper is continuously passed, and the temperature difference from the paper passing area (paper passing portion) A becomes 100 deg or more. Due to this temperature difference, the amount of thermal expansion of the pressure roller 24 becomes non-uniform, and a difference in roller outer diameter occurs in the axial direction, resulting in a difference in the feed amount of the film 17.

In particular, when the recording material is heated in a one-sided standard configuration in which one side end of the recording material is conveyed as a reference, for example, in a device having a maximum width of A4 size, B5 size or 100 mm width.
This phenomenon becomes remarkable because the non-sheet passing area B of about 40 mm to 110 mm is formed when the envelope is passed.

The apparatus (image heating and fixing apparatus) used in this embodiment has a one-sided reference configuration. The end portion of the recording material is conveyed along the conveyance reference surface a.

Reference numeral 30 denotes a heat radiating member for releasing the amount of heat of the small size paper non-passing area B to the outside of the pressure roller to reduce the temperature difference between the small size paper passing area A and the non-paper passing area B. It is connected to the non-sheet-passing side end of the pressure plate 25. In this embodiment, aluminum having good heat conductivity is used as the heat dissipation member 30 in order to enhance the heat dissipation effect. The shape is 2 mm in wall thickness,
It is a disk with a diameter of 15 mm.

Thus, the apparatus of the present embodiment provided with the heat dissipation member 30 as described above and the apparatus excluding the heat dissipation member 30 from this apparatus are each passed through a small-sized recording material to perform heat treatment. Then, the temperature of the pressure roller 24 and the twist of the film 17 were tested.

In this case, the temperature of the film surface in the sheet passing area A is controlled to 130 ° C. in both the apparatus with and without the heat radiating member 30, and the sheet passing area A is not passed. Envelopes (width 10
5mm x length 241mm) process speed 11.4
Paper was continuously fed at π mm / sec and a paper gap of 296 mm.

The temperature of the pressure roller 24 was measured by pressing a thermocouple under the pressure roller with a pad. The measurement point is 11 mm from the transport reference surface a on the paper passing side, and 2 on the non-paper passing side.
It is at 07 mm.

In the case of the apparatus excluding the heat radiating member 30, the number of continuous paper feeds was 40 and the temperature difference ΔT between the paper feed area A and the non-paper feed area B of the pressure roller 24 was ΔT = 115 deg.

According to the experiments conducted by the present inventors, the pressure roller 2
When the temperature difference ΔT of 4 becomes about ΔT ≧ 110 deg, the film 17 starts to wrinkle and twists.

Next, an experiment similar to the above was conducted by using the apparatus of this embodiment equipped with the heat dissipation member 30 as shown in FIG.

The result is ΔT = 107 de when 40 sheets are continuously fed.
g, and film twist did not occur.

In this way, the non-sheet passing area B of the pressure roller 24
The temperature rise is reduced because the heat energy accumulated on the non-paper passing area B side where the heat energy is not absorbed by the recording material when passing the small size paper is passed through the heat radiating member 30 through the pressure plate 25A having good thermal conductivity. This is because it is transmitted to and is radiated.

From the above, by using the heating device having the structure shown in this embodiment, it is possible to prevent the film from being twisted and prevent the heating device from being damaged.

<Embodiment 4> (FIG. 5) In the heating apparatus of this embodiment, the film pressure plate 25A as a member having good thermal conductivity has a crown shape in the longitudinal direction as shown in FIG. This crown is a pressure plate 25
Even if A is a flat plate as in Example 1, it can be attached in the same manner even if it has a curvature as in Example 2. Further, the crown amount of the pressure plate 25A can be optimally selected according to the material, thickness, width, pressing force, etc. of the pressure plate 25A.

The heating device presses the pressure plate 25A or the stay 23 from both ends thereof against the pressure roller 24 by a pressure mechanism (not shown). When the pressure plate 25A has a straight shape in the longitudinal direction as in the first and second embodiments, the pressing force is naturally high at both ends and becomes lower toward the center. This appears as a nip shape as it is, and the nip is wide at the end and narrow at the center. The imbalance of the nip width in the longitudinal direction causes unevenness in the heating amount of the recording material in the longitudinal direction, and there is a possibility that offset may occur due to excessive fixing in the wide nip portion, or improper fixing may occur in the narrow nip portion. However, when the pressure plate 25A is provided with a crown as in the present embodiment, the pressure applied at both ends and the pressure applied at the center are averaged, so that the nip width can be made uniform.

<Embodiment 5> (FIG. 6) In this embodiment, a thin elastic member 25a as shown in FIG. 6 is provided on the contact surface of the film pressure plate 25A as a member having good thermal conductivity with the film 17. It is pasted. For the elastic member 25a, rubber having high heat resistance such as silicone rubber or fluororubber can be used. A sheet 25b of heat-resistant resin such as PFA or PTFE is adhered to the surface of the elastic member 25a in order to improve the slidability between the pressure plate 25A and the film 17. In this embodiment, the pressure plate 25A has a curvature as in the second embodiment.

With the above-mentioned structure, the nip formation sandwiching the film 17 is formed by the pressure roller 24 and the elastic layer 25a.
Since the pressure is applied between the pressure plates 25A having a gap, the nip can be made wider, and the heating capacity of the recording material P can be improved.

<Embodiment 6> (FIG. 7) In this embodiment, the shape of the core material 22 is U-shaped, and the film 17 is placed in the space corresponding to the valley between the two walls of the pressure roller 24.
A film pressure roller 25B, which is a member having good thermal conductivity, is arranged in pressure contact with the.

The film pressure roller 25B is the film pressure plate 25 as a member having good thermal conductivity in the above-mentioned embodiment.
Like A, it is made of a ceramic having good thermal conductivity.

The film pressure roller 25B is made of the core material 22.
Is not in contact with. Therefore, the film pressure roller 2
5B forms a nip by being pressed against the pressure roller 24 by sandwiching the film 17 from there by a pressure mechanism provided in a bearing portion (not shown). The film pressure roller 25B is rotated by being driven to rotate the film 17.

By thus pressing the film 17 not by the plate but by the rotating body, the slidability of the film 17 is improved and the film 17 is less likely to slip. This is also an effective means for preventing damage to the film 17 due to metal fatigue.

It goes without saying that the film pressure roller 25B can be provided with a crown as in the third embodiment. Further, the elastic layer 25a as in Example 4 can be provided on the surface of the film pressure roller 25B.

<Embodiment 7> (FIG. 8) (a), (b), and (c) of FIG. 8 show another example of the configuration of the heating device of the electromagnetic induction heating system.

(A) is the electromagnetic induction heating structure 21.
As an endless belt-shaped conductive member between the three members of 22, 23, and 25, the lower surface of the film pressure plate 25A as a member having good thermal conductivity, the driving roller 31, and the driven roller (tension roller) 32. The film 17 is stretched around and the driving roller 31 drives the film 17 to rotate. Reference numeral 33 denotes a pressure roller that is pressed against the lower surface of the pressure plate 25 with the film 17 interposed therebetween, and is driven to rotate as the film 17 rotates.

(B) is the electromagnetic induction heating structure 21.
Driving the film 17 as an endless belt-shaped conductive member between the lower surface of the film pressure plate 25A, which is a member having good thermal conductivity, and the driving roller 31 of 22.23.25. The roller 31 is rotationally driven.

In the case of (c), the film 17 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 34 side. Body 21, 22, 23
25 is configured to run at a predetermined speed to the winding shaft 35 side via the lower surface of the film pressure plate 25A as a member having good thermal conductivity.

<Embodiment 8> (FIG. 9) In this embodiment, for example, an outline of an example of an image forming apparatus in which the heating apparatus of the electromagnetic induction heating system of the above-described Embodiment 1 is used as an image heating fixing apparatus (image heating apparatus) 55 It is a block diagram. The image forming apparatus of this example is a laser beam printer using an electrophotographic process.

Reference numeral 41 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 41 is rotationally driven in the clockwise direction indicated by the arrow at a predetermined peripheral speed (process speed), and in the course of the rotation, the primary charger 42 uniformly charges the negative dark potential V _D.

Reference numeral 43 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 41, which has been negatively and uniformly charged by the primary charger 42 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 the exposed portion rotates. An electrostatic latent image corresponding to the target image information is formed on the surface of the exposure drum 41.

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

The developing device 44 has a developing sleeve 44a which is driven to rotate, and the outer peripheral surface of the sleeve is coated with a thin layer of toner having a negative charge to face the surface of the photosensitive drum 41. Absolute value is photosensitive drum 4
Since the developing bias voltage V _DC that is smaller than the dark potential V _{D of} 1 and larger than the bright potential V _L is applied, the toner on the sleeve 44a is transferred only to the portion of the light potential V _L of the photosensitive drum 41. 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 45 is fed out and fed one by one by the paper feed roller 46, and the conveyance guide 4
7, a nip portion (transfer portion) 52 between the photosensitive drum 41 and the transfer roller 50 as a transfer member which is brought into contact with the photosensitive drum 41 and a transfer bias is applied by the power source 51 via the pair of registration rollers 48 and the pre-transfer guide 49. The toner image on the surface of the photosensitive drum 41 is sequentially transferred to the surface of the fed recording material P by being fed at an appropriate timing synchronized with the rotation of the photosensitive drum 41. Transfer roller 50 as transfer member
The resistance value of 10 ⁸ to 10 ⁹ Ωm is suitable.

The recording material P that has passed through the transfer section 52 is separated from the surface of the photosensitive drum 41, and is fixed by the conveyance guide 54 to the fixing device 55.
Then, the transferred toner image is fixed and is output to the paper discharge tray 56 as an image formed product (print). The surface of the photosensitive drum 41 after separation of the recording material is a cleaning device 53.
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.

[0135]

As described above, according to the present invention, in the heating apparatus of the electromagnetic induction heating system, the temperature distribution of the conductive member (film) in the longitudinal direction of the heated portion of the object to be heated can be made uniform. . Further, damage due to bending of the conductive member can be prevented, and the durability of the device can be improved. It was possible to prevent the conductive member from being twisted due to the non-uniform thermal expansion of the pressure roller in the longitudinal direction of the heating portion.

[Brief description of drawings]

FIG. 1 is a model diagram showing a schematic configuration of a heating apparatus (electromagnetic induction heating type / film heating type image heating / fixing apparatus) according to a first embodiment.

FIG. 2 is a perspective view of an exciting coil as a magnetic field generating means and a core material.

FIG. 3 is a model diagram showing a schematic configuration of a heating device according to a second embodiment.

FIG. 4 is a partially cutaway model diagram of a heating device according to a third embodiment.

FIG. 5 is a side model view of a film pressing plate having a crown shape (Example 4).

FIG. 6 is a model diagram of a main part of a heating device according to a fifth embodiment.

FIG. 7 is a schematic diagram showing a schematic configuration of a heating device of Example 6.

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

FIG. 9 is a schematic configuration diagram of an example of an image forming apparatus (Example 8).

FIG. 10 is a model diagram showing a schematic configuration of an example of an electromagnetic induction heating type / film heating type heating device (image heating and fixing device).

[Explanation of symbols]

17 Heat Resistant Film as Conductive Member (Heating Member) 17a Film Base Layer (Base Material) 17b Conductive Layer (Heating Layer) 17c Release Layer 21 Excitation Coil 22 Coil Core Material 23 Stay 24 Film Pressing Roller 25 / 25A / 25B Good Thermally conductive film pressure plate or film pressure roller 26 Thermistor (temperature detection element) 27 Safety element 28 Excitation circuit 29 Regulator 30 Heat dissipation member

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Daizo Fukuzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Atsuyoshi Abe 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Kenichi Ogawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (16)

[Claims] 1. An electromagnetic induction heating method for heating an object to be heated, which is brought into close contact with the conductive member by heat generation of the conductive member caused by an eddy current generated in the conductive member by applying a magnetic field to the conductive member by the magnetic field generation means. A heating device, characterized in that a member having good thermal conductivity is arranged on the surface of the electrically conductive member portion of the heated portion of the heated object opposite to the contact side of the heated object, over the length of the heated portion of the heated object. . 2. The heating device according to claim 1, wherein the member having good thermal conductivity has a curvature on a surface in contact with the conductive member. 3. The heating device according to claim 1, wherein the member having good thermal conductivity is in contact with the heat radiating member at a non-sheet-passing side end of a heating target sheet passing width region. 4. The conductive member is a rotating body, and the magnetic field generating means and a member having good thermal conductivity are arranged inside the rotating body, and the surface of the member having good thermal conductivity is in contact with the inner surface of the rotor. The heating device according to claim 1, wherein the heating device has a convex shape in the same direction as the rotating body. 5. The heating device according to claim 4, wherein a surface of the member having good thermal conductivity that contacts the inner surface of the rotator has the same curvature as the inner surface of the rotator. 6. The heating device according to claim 4, wherein a surface of the member having good thermal conductivity that is in contact with the inner surface of the rotator has a curvature equal to or larger than the inner surface of the rotator. 7. The heating device according to claim 1, wherein the member having good thermal conductivity has a roller shape. 8. The heating device according to claim 1, wherein the member having good thermal conductivity is not in contact with the magnetic field generating means. 9. The heating device according to claim 1, wherein the member having good thermal conductivity is provided with an elastic layer on a surface in contact with the conductive member. 10. The member according to claim 1, wherein a surface of the member having good thermal conductivity that contacts the conductive member has a crown shape in a direction orthogonal to a moving direction of the conductive member. Heating device. 11. The heating device according to claim 1, wherein the conductive member is an end member that travels and moves. 12. The heating device according to claim 1, wherein the conductive member is a laminated member including a conductive layer or a member that is itself conductive. 13. The heating device according to claim 1, further comprising a pressure member for bringing the conductive member or the conductive member and the object to be heated into close contact with a member having good thermal conductivity. apparatus. 14. The heating device according to claim 13, wherein the pressing member is a rotating body that is rotationally driven or driven to rotate. 15. The object 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.
The heating device according to 4. 16. An image forming apparatus comprising the heating device according to any one of claims 1 to 14 as an image heating device.