JPH10162944A - Heating apparatus and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating apparatus adopting a magnetic induction heating system and an upper and lower heating system, and perform efficient vertical heating by a low cost constitution. SOLUTION: This heating apparatus includes a nip part N formed by making pressure contact between a first rotating body 11 and a second rotating body 12. Both of the rotating bodies 11 and 12 exhibit magnetic induction heating properties. A heated material P introduced into the nip part N of the rotating bodies 11 and 12 is pinched and carried, and a magnetic field generated from an exciting coil 16 causes magnetic inductive heat generation in the rotating bodies 11 and 12, so that heat is applied to the heated material P. In this case, the exciting coil 16 centered at the nip part N of the rotating bodies 11 and 12 is a single coil formed in the rotating bodies 11 and 12. When viewed in a plane perpendicular to a rotation axis of the rotating body, the exciting coil 16 is closely wound in the neighborhood of the nip part N in the upstream of the rotating body in the rotational direction, and is not wound in the neighborhood of the nip part N in the downstream of the rotating body in the rotational direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a printer, a copying machine, a facsimile, etc., a recording material such as a transfer material sheet, printing paper, photosensitive paper (electrofax sheet), electrostatic recording paper, etc. A heat fixing device for fixing an unfixed developer image (unfixed toner image) formed and supported by a transfer (indirect) method or a direct method by an appropriate image forming process means such as recording or magnetic recording. As an image heating apparatus, a heating apparatus of a contact heating system such as a heat roller system, a film heating system, and a magnetic induction heating system is widely used.

A heating device of the heating roller type is a heating roller which is heated by a heat source such as a halogen lamp and is adjusted to a predetermined temperature, and a rotating roller pair of a pressing roller pressed against the heating roller (fixing roller). The recording medium as a heated material is introduced into a press-contact nip portion (fixing nip portion) of the two rollers and is nipped and conveyed, so that the unfixed developer image on the recording material surface is heated by the heat roller. Is heated and fixed.

A heating device of a film heating type is disclosed in
JP-A-3-313182, JP-A-1-263679, JP-A-2-15778, JP-A-4-44075, JP-A-4-44075-44083, JP-A-4-20
It has been proposed in, for example, Japanese Patent No. 4980-204984 and has been put to practical use.

In this apparatus, a material to be heated is brought into close contact with a heating body fixed and supported by a supporting member via a heat-resistant thin-walled film material (fixing film), and the film material is slidably moved to the heating body to heat the material. This is a system configuration in which heat of a body is given to a material to be heated via a film material. As a heating element, a ceramic substrate made of, for example, alumina (Al ₂ O ₃ ) or aluminum nitride (AlN) having characteristics such as heat resistance, insulation, and good thermal conductivity is used. A so-called ceramic heater having a resistive layer provided on the surface of the substrate and generating heat by energization as a basic structure can be used, and a thin film having a low heat capacity can be used as a film material. The heat transfer efficiency is higher than that of the heating device, the start-up of the device is quicker, the wait time can be reduced (quick start property: operated on demand), and power consumption can be reduced.

As an image heating apparatus using a magnetic induction heating method, Japanese Patent Publication No. 5-9027 discloses an eddy current generated in a core of a fixing roller by an alternating magnetic field, and the core or the fixing roller is magnetically induced by Joule heat. It has been proposed to generate heat.

FIG. 9 shows a schematic configuration of the apparatus. 50 ・
Reference numeral 54 denotes a pair of upper and lower fixing rollers and an elastic pressure roller which are arranged substantially in parallel and are brought into pressure contact with each other to form a nip portion N (fixing nip portion, heating nip portion). The fixing roller 50 mainly includes a cylindrical cored bar made of a ferromagnetic material as a magnetically induced heat-generating material. Generally, one or more desired functional layers such as a release layer and an elastic layer are formed on the outer peripheral surface thereof. You. The pressure roller 54 is composed of a core metal 54a and an elastic layer 54b formed concentrically and integrally around the core metal 54a, and is pressed against the fixing roller 50 side against the elasticity of the elastic layer 54b by pressing means (not shown). Thus, a nip portion N having a predetermined width is formed between the nip portion N and the fixing roller 50. The fixing roller 50 and the pressure roller 54 rotate in the directions indicated by arrows.

Reference numeral 51 denotes an exciting coil wound around an exciting iron core 52, which is disposed in a cylindrical core of the fixing roller 50. Reference numeral 53 denotes an auxiliary iron core, which is disposed outside the fixing roller so as to face an excitation iron core 52 of an excitation coil 51 disposed in a cylindrical core of the roller.
And the auxiliary iron core 53 to form a closed magnetic circuit. Excitation coil 51
A high-frequency AC current is applied from a drive power supply (not shown) to the AC power supply.
This acts on the cylindrical core of the fixing roller 50. Since the cylindrical core of the fixing roller 50 is made of a ferromagnetic material as a magnetically induced heat-generating material, an eddy current is generated in the cylindrical core of the fixing roller 50 by an alternating magnetic field, and the cylindrical core is formed. Generate heat due to Joule heat. That is, the fixing roller 50 is heated by magnetic induction. The temperature of the fixing roller 50 is adjusted to a predetermined fixing temperature by controlling the power supply from the driving power supply to the exciting coil 51 by a temperature control system including a temperature detecting unit (not shown).

The fixing roller 50 and the pressure roller 54
Is rotated, and the fixing roller 50 is magnetically induction-heated and the temperature is adjusted to a predetermined fixing temperature, and the recording material P carrying the unfixed toner image t as the material to be heated in the nip portion N has an image surface. Is introduced with the fixing roller 50 side, and is nipped and conveyed at the nip portion N. In the process of passing through the nip portion, the unfixed toner image t on the recording material P is heated and fixed as a permanent fixed image on the surface of the recording material P by heating by the fixing roller 50.

By utilizing the generation of the eddy current as described above, the fixing roller as the heating means can directly generate heat so that the heat generation position can be close to the toner image of the recording material as the material to be heated. There is an advantage that the heating efficiency can be increased as compared with the heating device of the system.

A heat fixing device in a full-color image forming apparatus is required to have a capability of sufficiently heating and melting a thick toner layer comprising a maximum of four layers of color toners. In order to heat the toner image via a rubber elastic layer for enclosing and uniformly melting the toner image, as a heating device of a magnetic induction heating system, a fixing roller as disclosed in Japanese Utility Model Laid-Open No. 54-19773 is used. U.S. Pat. No. 5,537,837, in which both the fixing roller and the pressure roller are provided with an excitation coil so that both the fixing roller and the pressure roller are heated by magnetic induction.
As disclosed in the specification of Japanese Patent No. 278618, there has been proposed a configuration in which a fixing roller having a small heat capacity is used and heated by an exciting member near a nip portion.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a magnetic induction heating type heating apparatus among the various types of heating apparatuses described above. More specifically, the present invention relates to an improvement in a heating device of a magnetic induction heating system and a vertical heating system.

That is, as in the above-described example of the heat fixing device in the full-color image forming apparatus, both heating (upper and lower heating) of two opposed pressure contact rotating members forming a nip portion for heating a recording material as a material to be heated. When the heating is performed by a magnetic induction heating method, the cost is increased in a configuration in which excitation coils are provided in both rotating bodies and a drive power supply is provided for each excitation coil.

An object of the present invention is to provide a heating apparatus of a magnetic induction heating system / upper / lower heating system, which can efficiently and vertically heat the heater at a low cost.

[0015]

According to the present invention, there is provided a magnetic induction heating type / vertical heating type heating apparatus characterized by the following constitutions:
And an image forming apparatus provided with the heating device as an image heating and fixing device.

(1) Pressing each other to form a nip portion,
It has first and second rotating bodies, each of which is magnetically induced and heat-generating, and introduces a material to be heated into the nip portions of the two rotating bodies, sandwiches and transports them, and rotates the two rotating bodies by a magnetic field generated from an exciting coil. In a heating device for heating the material to be heated by magnetic induction heating of a body, the exciting coil is formed in first and second rotating bodies around a nip portion of the first and second rotating bodies. A heating device comprising one coil.

(2) When viewed in a plane perpendicular to the rotation axis of the rotating body, the exciting coil is wound in a vicinity of the nip portion on the upstream side in the rotating direction of the rotating body. A heating device according to claim 1.

(3) When viewed in a plane perpendicular to the rotation axis of the rotating body, the exciting coil is not wound downstream of the rotating body in the rotation direction of the rotating body near the nip portion. A heating device according to claim 1.

(4) Pressing each other to form a nip portion,
It has first and second rotating bodies, each of which is magnetically induced and heat-generating, and introduces a material to be heated into the nip portions of the two rotating bodies, sandwiches and transports them, and rotates the two rotating bodies by a magnetic field generated from an exciting coil. A heating device for heating the material to be heated by magnetic induction heating of a body has an exciting coil for a first rotating body and an exciting coil for a second rotating body, and both exciting coils are provided with a single drive power supply. And a power supply switching unit between the two exciting coils.

(5) The material to be heated is a recording material carrying an image, and the apparatus is an image heating device for heating the image carried on the material to be recorded (1) to (4). A heating device according to any one of the above.

(6) The heating apparatus according to (5), wherein the image heating process is a heating and fixing process for an image on a recording material.

(7) An image forming means for forming and carrying an unfixed image on the recording material, and a heat fixing means for fixing the unfixed image on the recording material, wherein the heat fixing means are (1) to (4) An image forming apparatus, which is the heating apparatus according to any one of the above.

<Operation> That is, with respect to the heating device of the magnetic induction heating system and the upper and lower heating system, the excitation coil is a single coil formed in the first and second rotating bodies around the nip portion of the first and second rotating bodies. Thus, both the first and second rotating bodies can be magnetically induction-heated by the single excitation coil and the single drive power supply for the excitation coil, and a low cost configuration (single excitation coil / single drive Heating (up and down heating) of both the first and second rotating bodies can be efficiently performed by the power supply).

[0024] When viewed from a plane perpendicular to the rotation axis of the rotating body, the exciting coil is wound around the nip near the rotation direction of the rotating body. In the heat-fixing device, the unfixed image can be temporarily placed before the nip portion and the pre-drying of the recording material can be performed, and the toner scatters before the nip portion (image Tail)
Can be reduced.

[0025] When the exciting coil is viewed from a plane perpendicular to the rotation axis of the rotating body, the heating coil has a winding form that is not wound on the downstream side in the rotation direction of the rotating body in the vicinity of the nip portion. Can cool the toner on the recording material after passing through the nip portion, which is a heat fixing unit, and can prevent the recording material from winding around the rotating body.

[0026] An apparatus having an exciting coil for a first rotating body and an exciting coil for a second rotating body, both exciting coils being driven by a single drive power supply, and having an energization switching unit between the two exciting coils. With this configuration, the heating ratio of the first and second heating rotators can be switched with a low-cost configuration (single drive power supply), and efficient rotator heating becomes possible.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> (FIGS. 1 to 6) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic full-color printer.

Reference numeral 101 denotes an electrophotographic photosensitive drum as an image bearing member, which is an OPC (organic photosensitive member) / amorphous Se.
A photosensitive material layer made of amorphous Si or the like is formed on a cylindrical substrate (base) made of aluminum, nickel, or the like, and is rotated at a predetermined process speed (peripheral speed) in a counterclockwise direction indicated by an arrow.

The photosensitive drum 101 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

Next, a laser scanner 1 is provided on the charged surface.
The scanning exposure processing of the target image information by the laser beam 103 output from 10 is performed. Laser scanner 11
Numeral 0 outputs a laser beam 103 modulated (on / off) according to a time-series electric digital pixel signal of target image information from an image signal generator such as an image reader (not shown) to scan the surface of the rotating photosensitive drum. The electrostatic latent image corresponding to the target image information scanned and exposed on the surface of the rotating photosensitive drum 101 is formed by the scanning exposure. Reference numeral 109 denotes a photosensitive drum 1 which outputs an output laser beam from the laser scanner 110.
This is a mirror that deflects to the exposure position 01.

In the case of full-color image formation, scanning exposure and latent image formation are performed on a first color-separated component image of a target full-color image, for example, a yellow component image. Is developed as a yellow toner image by the operation of the yellow developing device 104Y. The yellow toner image is transferred to the surface of the intermediate transfer drum 105 at a primary transfer portion T1, which is a contact portion (or a close portion) between the photosensitive drum 101 and the intermediate transfer drum 105. After the transfer of the toner image to the surface of the intermediate transfer drum 105, the surface of the rotating photosensitive drum 101 is cleaned by the cleaner 107 by removing the adhered residue such as untransferred toner.

The above-described process cycle of charging, scanning exposure, development, primary transfer, and cleaning is performed by a second color separation component image (for example, a magenta component image, the magenta developing device 104M is operated) of a target full-color image. Third color separation component image (for example, cyan component image, cyan developing device 104C
Operates), a fourth color separation component image (for example, a black component image,
(The black developing unit 104BK is activated) for each color separation component image, and the yellow toner image, the magenta toner image, the cyan toner image,
The four color toner images, which are the black toner images, are sequentially transferred in a superimposed manner, and a color toner image corresponding to the target full-color image is synthesized and formed.

The intermediate transfer drum 105 has a medium resistance layer and a high resistance surface layer on a metal drum.
01 is rotated in the clockwise direction as indicated by an arrow at substantially the same peripheral speed as the photosensitive drum 101 in contact with or in proximity to the photosensitive drum 101, and a bias potential is applied to the metal drum of the intermediate transfer drum 105 to expose the photosensitive drum 101 with a potential difference from the photosensitive drum 101. The toner image on the drum 101 is transferred to the surface of the intermediate transfer drum 105.

The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to a secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106. The image is transferred onto the surface of the recording material P fed at a predetermined timing from a paper feeding unit (not shown) at T2. The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, and sequentially collectively transfers the composite color toner images from the surface of the intermediate transfer drum 105 to the recording material P.

The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105, introduced into an image heating device (heat fixing device) 100, and subjected to a heat fixing process for an unfixed toner image (image fixing). (Permanent fixing process) and is discharged as a full-color image-formed product to a discharge tray (not shown) outside the apparatus. The heat fixing device 100 will be described in detail in the following section (2).

After the transfer of the color toner image onto the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 by removing the adhered residue such as untransferred toner and paper dust. The cleaner 108 is normally kept in a non-contact state with the intermediate transfer drum 105, and is kept in a contact state with the intermediate transfer drum 105 in the process of performing the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. You.

The transfer roller 106 is always kept in a non-contact state with the intermediate transfer drum 105, and is transferred to the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The recording material P is held in contact with the recording material P.

A print mode for a mono-color image such as a black-and-white image can also be executed. Also, a double-sided image print mode or a multiple image print mode can be executed.

In the case of the double-sided image print mode, the recording material P on which the first-side image has been printed out of the heat fixing device 100 is turned upside down via a recirculation transport mechanism (not shown), and is returned to the secondary transfer portion T2 again. The toner image is transferred and transferred to the two surfaces, and is again introduced into the heat fixing device 100 to undergo a fixing process of the toner image on the two surfaces to output a double-sided image print.

In the case of the multiple image print mode, the recording material P on which the first image has been printed out of the heating and fixing device 100 is not turned upside down via a recirculation transport mechanism (not shown) and is again returned to the secondary transfer portion T2. And the toner image is transferred to the surface on which the first image has been printed, and is again introduced into the heat fixing device 100 and subjected to the second toner image fixing process, whereby a multiple image print is output. .

(2) Heat Fixing Apparatus 100 The heat fixing apparatus 100 of this embodiment employs a magnetic induction heating system using a cylindrical magnetic induction heat-generating film as a rotating body for heating a recording material as a material to be heated.・ Heating device of upper and lower heating system.

FIG. 2 is a schematic cross-sectional view of the heating and fixing apparatus 100, FIG. 3 is a vertical cross-sectional view of the apparatus with some parts omitted, FIG. 4 is a perspective view of a main part of the apparatus, and FIG. FIG.

Reference numerals 11 and 12 denote first and second two cylindrical magnetically induced heat-generating film members as heating rotators. Hereinafter, the first cylindrical magnetically induced heat generating film material is referred to as a fixing film, and the second cylindrical magnetically induced heat generating film material is referred to as a pressure film. This fixing film 11
The layer configuration of the pressure film 12 will be described later.

Reference numerals 13a and 13b denote first and second two cylindrical stays, each of which is a heat-resistant and rigid member made of a liquid crystal polymer, a phenol resin or the like.

The fixing film 11 has a first stay 13a.
In addition, the pressure film 12 is loosely fitted to the second stay 13b and supported by the second stay 13b.

A first stay 13a having the fixing film 11 fitted and supported externally and a second stay 13b having the pressure film 12 fitted and supported externally are arranged vertically parallel to the apparatus side plate (not shown). It is set up. First and second stays 13a
13b, both ends are held by a support member (not shown) in a non-rotating manner, and are pressed and urged by a pressing means (not shown) so that the fixing film 11 and the pressing film 12 are sandwiched and brought into pressure contact with each other. A nip portion N (fixing nip portion) having a width is formed.

Reference numeral 14 denotes a pressure film outer peripheral drive roller, which is arranged substantially in parallel with the pressure film 12 by holding both ends of the shaft portion 14a between the device side plates (not shown). Second stay 1 by pressing against the outer surface of the film
3b, the pressure film 12 is sandwiched. M is a driving means of the pressure film outer peripheral driving roller 14.

When the driving roller M is driven to rotate clockwise as shown by an arrow in FIG. 2 by the driving means M, the driving roller 14 is rotated by friction with the pressing film 12 pressed against the outer surface. A force is applied, and the pressure film 12 moves outwardly around the second stay 13b while the inner surface of the pressure film 12 slides in close contact with the outer surface of the second stay 13b in the fixing nip portion N and the vicinity thereof, as indicated by the arrow in the counterclockwise direction. In the direction, the driven rotation state is established with a peripheral speed substantially corresponding to the rotational peripheral speed of the drive roller 14.

When the pressure film 12 is rotated as described above, a rotational force acts on the fixing film 11 whose outer surface is in pressure contact with the pressure film 12 at the fixing nip N by frictional force. The inner surface of the fixing film 11 slides in close contact with the outer surface of the first stay 13a at the fixing nip portion N and in the vicinity thereof.
The outer periphery of a is rotated in a clockwise direction as indicated by an arrow with a peripheral speed substantially corresponding to the rotational peripheral speed of the pressurizing film 12 to be in a driven rotation state.

That is, when the pressure film outer peripheral drive rollers 14 are rotationally driven, they are brought into pressure contact with each other, so that the fixing nip portion N
The fixing film 11 and the pressure film 12, which are the magnetically induced heat-generating film material as the first and second heating rotators having formed thereon, are rotated. Lubricants such as heat-resistant grease are applied to the sliding contact between the inner surface of the fixing film 11 and the outer surface of the first stay 13a and the sliding contact between the inner surface of the pressing film 12 and the outer surface of the second stay 13b. , The frictional resistance is reduced and the fixing film 11
Smooth rotation of the pressure film 12 with low torque can be achieved.

Reference numeral 16 denotes an exciting coil as magnetic field generating means. In the apparatus of the present embodiment, the exciting coil 16 is provided around the fixing nip N formed by the fixing film 11 and the pressure film 12 as the first and second heating rotators. Cylindrical first supported external fitting
The first and second heating means are formed by alternately passing a single exciting coil wire and winding it in a coil shape on the stay 13a and the second stay 13b on which the pressure film 12 is externally supported. A single excitation coil is used for the fixing film 11 and the pressure film 12 as the rotating body for use. The excitation coil 16 is connected to a drive power supply (switching power supply) 20 whose oscillation circuit is variable in frequency.

Reference numerals 15a and 15b denote first and second exciting coil cores. In this embodiment, the first exciting coil core 15a is provided at a portion of the exciting coil 16 passing through the first stay 13a, and at a second position. The exciting coil core 15b is the exciting coil 1
No. 6 is a horizontally long plate-shaped member made of a ferromagnetic material such as ferrite, which is disposed in close proximity to a portion passing through the second stay 13b. In this example, the relative magnetic permeability is 25
00 was used.

Reference numeral 17 denotes a conductive chip thermistor having a low heat capacity as a temperature detecting means. In the apparatus of the present embodiment, the conductive chip thermistor 17 is located near the fixing nip N and is closer to the fixing film 11 and the pressure film 12 than the fixing nip N. It is arranged on the outer surface of the first stay 13a on the downstream side in the rotation direction. The output of the thermistor 17 is supplied to a control circuit (C
PU) 22.

The first and second 2
The layer configuration of the fixing film 11 and the pressure film 12, which are two cylindrical magnetically induced heat generating film materials, will be described with reference to a model diagram of FIG.

The fixing film 11 in this example is, in order from the inside to the outside of the cylinder, a heat insulating layer 11a, a heating layer 11b made of nickel and having a thickness of 50 μm, an elastic layer 11c made of silicone rubber, and a mold release of fluororesin. It is a four-layer laminated material of the layer 11d.

The pressure film 12 also has a heat insulating layer 12a, a heat generating layer 12b made of nickel and having a thickness of 50 μm, a heat resistant rubber such as silicone rubber or fluorine rubber, or a silicone rubber foamed in order from the inside to the outside of the cylinder. This is a four-layer laminate of an elastic layer 12c formed as described above and a release layer 12d of PFA, PTFE, FEP or the like. This pressurized film 1
The elastic layer 12c in No. 2 had a thickness of about 1 to 4 mm in order to form the fixing nip portion N having a required width.

Heat insulation layers 11a and 12a; heat generation layers 11b and 1
2b is a material layer for suppressing conduction of the heat of 2b to the inner surfaces of the fixing film 11 and the heating film 12. Fixing film 1
1. First and second stays 1 inside heating film 12
It is possible to prevent the temperature of the exciting coil 16 and the cores 15a and 15b as magnetic field generating means disposed in the 3a and 13b from being raised, and to perform stable heating. This heat insulating layer 11a
12a is a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES
Resin, PPS resin, PFA resin, PTFE resin, FEP
A heat-resistant resin such as a resin is preferred. 10 to 100 as thickness
0 μm is preferred. When the thickness is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient.

Heating layers 11b and 12b: magnetically induced heat-generating material layers (layers generating heat due to eddy current loss, metal layers, resistor layers, magnetic layers). Metals, metal compounds, organic conductors, and the like, which are good electric conductors having a thickness of about 1 to 100 μm, for example, nickel, and 10 ⁻⁵ to 10 ⁻¹⁰ Ω · m, for example. More preferably, a pure metal such as iron or cobalt having high magnetic permeability and exhibiting ferromagnetism or a compound thereof can be used.

Elastic layers 11c and 12c are material layers that function to enhance the fixability of the toner image by causing the film surface to follow the irregularities of the recording material and the toner layer. In particular, the present invention is effective for a heat fixing process of a color toner image layer of a superimposed four-color image having a thick toner layer. A heat-resistant material having good heat conductivity, such as silicone rubber, fluorine rubber, or fluorosilicone rubber, having a thickness of about 10 to 500 μm is used. If the hardness is too high, the unevenness of the recording material or the toner layer cannot be completely followed, causing uneven gloss of the image. Therefore, the hardness is 60
° (JIS-A) or less, more preferably 45 ° or less. As for the thermal conductivity σ, 6 × 10 ⁻⁴ to 2 × 10 ⁻³ (c
al / cm · s · deg). Thermal conductivity 6 × 10
If it is smaller than ⁻⁴ (cal / cm · s · deg), the thermal resistance is large, and the temperature rise in the surface layers of the fixing film 11 and the pressure film 12 becomes slow.

Release layers 11d and 12d; fixing film 11
And a material layer for enhancing the toner releasability on the surface of the pressure film 12. A material having good releasability and heat resistance, such as fluororesin such as PFA, PTFE, and FEP, silicone resin, silicone rubber, and fluororubber can be selected.
The thickness is preferably from 20 to 100 μm. If the thickness is less than 20 μm, there are problems such as uneven coating of the coating film, a portion having poor releasability, and insufficient heat resistance. On the other hand, if the thickness exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layers 11c and 12c is lost.

Thus, the pressure film outer peripheral drive roller 14
Are rotated to rotate the fixing film 11 and the pressure film 12, which are magnetically induced heat-generating film materials as first and second heating rotators, which are pressed against each other to form a fixing nip portion N. In the state in which the
A high-frequency AC current of 10 kHz to 1 MH, preferably 20 kHz to 800 kHz is supplied from the drive power supply 20, and the exciting coil 16 generates an alternating magnetic field.

The alternating magnetic field mainly acts on the heat generating layers 11b and 12b, which are the magnetically induced heat generating material layers of the fixing film 11 and the pressure film 12, in the fixing nip portion N and in the vicinity of the fixing nip portion. Heating layer 1
An eddy current flows inside 1b and 12b as if the change in the magnetic field is prevented.

This eddy current generates Joule heat corresponding to the resistance of the heat generating layers 11b and 12b,
That is, the fixing film 11 and the heating film 12 generate magnetically induced heat mainly in the fixing nip portion N and in the vicinity of the fixing nip portion, and the fixing nip portion N and the vicinity of the fixing nip portion are heated.

The heating temperature state of the fixing nip portion N is detected by the thermistor 17, and the detected temperature information is sent to the control circuit 22 via the A / D converter 21. Control circuit 2
2 sets the oscillator of the AC power supply of the drive power supply 20 to the optimum frequency based on the input temperature information, and controls the excitation coil 16 to apply an AC current of the optimum frequency to the excitation coil 16 so that the inside of the fixing nip N The temperature is controlled to a predetermined value.

A recording material P as a material to be heated is introduced between the fixing film 11 and the pressure film 12 in the fixing nip portion N, and is nipped and conveyed. Fixing film 11 and pressure film 1
2, the unfixed toner image t is heated and fixed on the surface of the recording material P by heating in a vertical heating method.

In the device 100 of the present embodiment, the exciting coil 16 as the magnetic field generating means has the first and second
A first stay 13a having a cylindrical shape and externally supporting the fixing film 11 around a fixing nip portion N formed by a fixing film 11 and a pressure film 12 as a heating rotator. A fixing film as a first and a second heating rotator formed by alternately passing a single long exciting coil wire through a second stay 13b on which the film 12 is externally supported and wound in a coil shape. A single excitation coil is provided for the pressure film 11 and the pressure film 12.

That is, both the fixing film 11 and the pressure film 12 as the first and second heating rotators are magnetically induction-heated by the single excitation coil 16. In this configuration, the upper and lower heating rotators 11 and 12 can be heated by a single excitation coil 16 and, at the same time, the magnetic field F generated by the excitation coil 16 is concentrated on the fixing nip portion N and its vicinity as shown in FIG. Since it is easy to perform the heating, the upper and lower heating rotating bodies 11 and 12 can be efficiently heated.

Actually, as in the configuration of this example, the single excitation coil 16 heats both the fixing film 11 and the pressure film 12 as the first and second heating rotary members by magnetic induction heating. A single excitation coil type heat fixing device (hereinafter referred to as device A), and a comparative example device, each of which independently excites a fixing film 11 and a pressure film 12 as first and second heating rotators. Place the coil,
The time required for heating and fixing with a heating / fixing device of an upper and lower independent excitation coil type (device B) having a drive power supply for each excitation coil was measured. Table 1 shows the results. However, process speed 105mm /
s, power consumption was 800 W, and the temperature regulation temperature was 190 ° C.

[0069]

[Table 1] As can be seen from Table 1, the apparatus A, that is, the apparatus having the configuration in which the single excitation coil 16 is formed around the fixing nip portion N is capable of fixing from the start of heating as compared with the apparatus B, that is, the apparatus of the upper and lower independent excitation coil system. It was found that the heating time was shortened and efficient heating was possible. In addition, the single excitation coil system becomes a single drive power source, and can reduce the cost of the apparatus.

In this embodiment, as a method of forming a single excitation coil 16 centering on the fixing nip portion N, a cylindrical first stay 13a on which the fixing film 11 is externally supported.
And a second stay 1 in which the pressurizing film 12 is externally supported.
3b, a single long exciting coil wire is alternately passed through and wound in a coil shape. As shown in FIG. 6, two exciting coil wires arranged in a predetermined number are manufactured 16a and 16b. One 16a is disposed in a cylindrical first stay 13a in which the fixing film 11 is externally supported, and the other 16b is disposed in a second stay 13b in which the pressing film 12 is externally supported. The exciting coil 16 can be formed by making both ends of the wires on the 16a and 16b sides electrically connected by the elbow connector 30 respectively.

<Second Embodiment> (FIG. 7) In this embodiment, a single excitation coil 16 formed around a fixing nip N in the heat fixing device of the first embodiment is formed as shown in FIG. In the fixing nip portion N, the number of windings is increased on the upstream side of the fixing film 11 and the pressure film 12 (hereinafter, referred to as the fixing nip portion upstream side), and on the downstream side (hereinafter, referred to as the fixing nip portion downstream side). The number of windings is reduced. Other configurations of the apparatus are the same as those of the heat fixing apparatus of the first embodiment, and the description thereof will not be repeated.

In the apparatus of this embodiment, since the exciting coil 16 is formed on the upstream side of the fixing nip portion, the preheating effect (heating before the fixing nip portion) makes it possible to temporarily attach the toner, thereby enabling tailing (fixing nip portion). (A phenomenon in which toner scatters due to water vapor at the time of intrusion) is improved. In addition, since the exciting coil 16 does not protrude downstream of the fixing nip, the amount of heat generated on the downstream side of the fixing nip is reduced, and the recording material (paper) is cooled and separated (the viscosity is reduced by toner cooling. Separation method).

Actually, a heating and fixing device (device C) in which the exciting coil 16 is formed on the upstream side of the fixing nip portion so as to have a preheating effect as in this embodiment is not provided with such a configuration. The tailing level was compared with the ineffective heating fixing device (hereinafter referred to as device D).
Table 2 shows the results. However, the fixing was performed under the conditions that the temperature was controlled at 190 ° C., the input power was 800 W, and the paper was passed 60 seconds after the start of heating.

[0074]

[Table 2] As can be seen from Table 2, the preheating effect was obtained and the tailing was improved by expanding the heating area to the upstream side of the fixing nip as shown in FIG.

Further, since the exciting coil 16 is formed on the upstream side of the fixing nip, the apparatus C has substantially no heating on the downstream side of the fixing nip. With a certain apparatus D, the separability of the recording material (paper) was evaluated. Table 3 shows the results.

[0076]

[Table 3] In the configuration in which the image is heated to the downstream side of the fixing nip portion, when the image having a high printing ratio is present up to the leading end of the paper as the recording material, the paper may be wound around the fixing film 11 as shown in FIG. In the configuration in which the downstream side of the fixing nip portion is not substantially heated, even when there is an image having a high printing ratio up to the leading edge of the paper, almost no paper wrapping occurs.

With the above configuration, the upper and lower heating rotators 11.
As a result, it was possible to improve the tailing due to the preheating effect and to cool and separate the paper downstream of the fixing nip.

<Third Embodiment> (FIG. 8) The apparatus of the present embodiment shown in FIG. 8 includes a first stay 13a and a second stay 13a.
13b, an excitation coil 16A for the fixing film 11 as a first heating rotator and an excitation coil 16B for the pressurizing film 12 as a second heating rotator are provided in each of the excitation coils 16A.・ 16B is a single beating power supply 2
The heating device is driven at 0 and has an energization switching unit 23 between the excitation coils 16A and 16B. With a low-cost configuration (single drive power supply), the heating ratio of the first and second heating rotators can be switched, and efficient heating of the rotator is possible. Other configurations of the apparatus are the same as those of the heat fixing apparatus 1 of the first embodiment, and a description thereof will not be repeated.

In this configuration, since the power supply switching unit 23 is provided between the exciting coils 16A and 16B in the vertical rotating bodies 11 and 12, the vertical rotating body 1 is changed according to the state of the heat fixing device 100.
The heating ratio of 1 and 12 can be changed, and efficient fixing can be performed.

For example, when the pressure film 12 is cold, the switching unit 23 is connected to the contact a and the upper and lower excitation coils 16A and 16B are connected in series, so that the two excitation coils 16A and 16B are connected. Electric current is applied to 16B, and upper and lower heating is performed. When the pressurized film 12 is sufficiently warm, the switching unit 23 is connected to the contact b, and the lower excitation coil 16B on the pressurized film 12 side is cut off from the drive power source 20, and the fixing film A current-carrying configuration may be adopted in which only the upper exciting coil 16A on the 11th side is energized and only the fixing film 11 is heated.

Actually, as in the apparatus of the present embodiment, the heat fixing device (device E) is provided with the power supply switching section 23 between the upper and lower excitation coils 16A and 16B so as to perform the above power supply control. ) And the upper and lower excitation coils 16A-1
The power required during fixing was measured with a heating and fixing device (hereinafter, referred to as device F) having no energization switching unit 23 between 6B and 6B.
Table 4 shows the results. The temperature control temperature of the fixing film 11 was 190 ° C., and the power consumption was represented by the average power when 100 sheets were continuously fixed.

[0082]

[Table 4] As can be seen from Table 4, the upper and lower excitation coils 16A and 16B
It can be seen that the power consumption can be reduced according to the device E having the device configuration in which the energization switching unit 23 is provided between them and the heating ratio of the upper and lower heating rotators 11 and 12 is changed depending on the state of the device.

With the above configuration, it is possible to efficiently heat the upper and lower heating rotators with a low cost configuration (single drive power supply).

<Others> 1) The layer configurations of the magnetically induced heating fixing film 11 and the pressure film 12 as the first and second heating rotators are not limited to the layer configurations of the embodiments. Of course. For example, a layer configuration in which the heat insulating layers 11a and 12a and / or the elastic layers 11c and 12c are omitted may be employed. The heat generating layers 11b and 12b may be used as a single film material. It is also possible to adopt a layer configuration in which another desired functional layer is added.

2) The first and second heating rotary members may be rigid cylinders (pipe-shaped roller members).

3) The configuration of the driving means for the first and second heating rotators can be designed in various forms.

4) The heating apparatus of the present invention is not only an image heating and fixing apparatus in the image forming apparatus and the like of the embodiment, but also an apparatus for heating a recording material carrying an image to improve surface properties such as gloss. It can be widely used as a heat treatment device such as a device for presumably attaching and a device for drying or heat laminating a sheet.

[0088]

As described above, according to the present invention,
About heating device of magnetic induction heating method, up and down heating method,
The excitation coil is a single coil formed in the first and second heating rotators around the nip portion of the first and second heating rotators. The first and second heating rotators can be magnetically induction-heated with a single drive power supply for the excitation coil, and the first and second heating rotators can be efficiently provided by a low cost configuration (single excitation coil / single drive power supply). Heating (up and down heating) of both of the second heating rotators becomes possible.

When viewed in a plane perpendicular to the rotation axis of the heating rotator, the excitation coil is wound in such a manner that the excitation coil is wound more upstream in the rotation direction of the heating rotator near the nip portion. The preheating effect (preheating effect of the material to be heated in front of the nip portion) is obtained, and in the heat fixing device, the non-fixed image can be assumed just before the nip portion and the pre-drying of the recording material can be performed. It is possible to reduce toner scattering (tailing of an image) in the foreground.

When the exciting coil is viewed in a plane perpendicular to the rotation axis of the heating rotator, the exciting coil has a winding form that is not wound in the vicinity of the nip portion on the downstream side in the rotation direction of the heating rotator. In the heat fixing device, the toner on the recording material after passing through the nip portion serving as the heat fixing unit can be cooled, and the recording material can be prevented from being wound around the heating rotating body.

The first exciting coil for the heating rotary member and the second exciting coil
By having an excitation coil for the heating rotator, the two excitation coils are driven by a single drive power supply, and by having a device configuration having an energization switching unit between the two excitation coils.
With a low-cost configuration (single drive power supply), the heating ratio of the first and second heating rotators can be switched, and efficient heating of the rotator is possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus (full-color image forming apparatus).

FIG. 2 is a schematic cross-sectional view of a heat fixing device.

FIG. 3 is a longitudinal cross-sectional model view of the apparatus with a middle part omitted.

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

FIG. 5 is an enlarged model diagram of a main part of FIG. 2;

FIG. 6 is an exploded perspective view of another configuration example of the exciting coil.

FIG. 7 is a schematic cross-sectional view of a heat fixing device according to a second embodiment.

FIG. 8 is a schematic cross-sectional view of a heat fixing device according to a third embodiment.

FIG. 9 is a schematic diagram illustrating a configuration of a conventional example of a heat-fixing device using a magnetic induction heating method.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 Heat induction fixing device of magnetic induction heating method / upper / lower heating method 11 Magnetic induction heat-generating fixing film (first heating rotator) 12 Magnetic induction heat-generating pressurized film (first heating rotator) 11a, 12a Thermal insulation Layers 11b and 12b Heat generation layer (magnetic induction heating material layer) 11c and 12c Elastic layer 11d and 11d Release layer 13a and 13b First and second stays 14 Outer peripheral drive roller 15 Core 16 Exciting coil 17 Thermistor 20 Drive power supply 21 A / D converter 22 Control circuit (CPU) 23 Excitation coil conduction switching unit

Claims (7)

[Claims] 1. A nip portion is formed by being pressed against each other, and has two first and second rotating bodies, each of which is magnetically induced and heat-generating, and a material to be heated is introduced into the nip portions of the two rotating bodies. A heating device for heating the material to be heated by magnetic induction heat generated by the two rotating bodies due to a magnetic field generated from the exciting coil; wherein the exciting coil is arranged around a nip portion between the first and second rotating bodies. A heating device comprising a single coil formed in first and second rotating bodies. 2. The method according to claim 1, wherein the exciting coil is wound in the vicinity of the nip portion in the vicinity of the nip portion on the upstream side in the rotation direction of the rotating body when viewed in a plane perpendicular to the rotation axis of the rotating body. A heating device as described. 3. The method according to claim 1, wherein the exciting coil is not wound near the nip portion on the downstream side in the rotation direction of the rotating body when viewed in a plane perpendicular to the rotation axis of the rotating body. A heating device as described. 4. A nip portion is formed by being pressed against each other, and has first and second rotating bodies each having magnetic induction heat generation property, and a material to be heated is introduced into the nip sections of both rotating bodies. A heating device for heating the material to be heated by magnetic induction heat generated by the two rotating bodies due to a magnetic field generated by the exciting coil; and an exciting coil for the first rotating body and an exciting coil for the second rotating body. A heating device having a coil, wherein the two excitation coils are driven by a single drive power supply, and further comprising an energization switching unit between the two excitation coils. 5. The recording medium according to claim 1, wherein the recording medium is a recording medium carrying an image, and the apparatus is an image heating apparatus for heating the recording image of the recording medium. A heating device according to any one of the preceding claims. 6. The heating apparatus according to claim 5, wherein the image heating process is a heating and fixing process for an image on a recording material. 7. An image forming means for forming and supporting an unfixed image on a recording material, and a heating and fixing means for fixing the unfixed image on the recording material, wherein the heating and fixing means is one of claims 1 to 4. An image forming apparatus, which is the heating device according to one of the above aspects.