JPH1064670A - Heater and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater capable of heating with uniform temperature distribution so as to prevent inferior fixing, uneven glossiness, and offset when the heater is applied to an image forming device by correcting an end part magnetic field generated by an exciting coil. SOLUTION: A fixing film represented by 1 is composed of a heating layer 101, an elastic layer 102, and a mold release layer 103. An exciting coil is represented by 201, and a ferrite core by 202 a pressing roller is represented by 3 that forms a nip N through pressure contact with a lower face of a film guide 105 via the fixing film 1. An alternating magnet flux generated by the exciting coil 201 is led to the ferrite core 202, an eddy current is generated in the heating layer 101 of the fixing film, and a recording material P that is a heated material to be carried to the nip N by the heat generated by the eddy current and a toner T on the recording material P is heated. The energizing coil 201 is improved in that the number of turns at an end part 201c is greater than that at the center in the widthwise direction of the heated material P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a heating apparatus that heats a heating section by generating eddy current loss using electromagnetic induction and an image forming apparatus including the heating apparatus. The heating device is a fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, that is, an appropriate image forming process means such as electrophotography, electrostatic recording, and magnetic recording. The present invention is suitable for an apparatus that heat-fixes an unfixed toner image formed directly or indirectly on the surface of a recording material using a toner as a permanent fixed image on the surface of the recording material.

[0002]

2. Description of the Related Art As a heating device represented by a heat fixing device, a so-called contact heating system such as a heat roller system or a film heating system has been widely used.

Among them, in a fixing device of an image forming apparatus for forming a full-color image, which is required to be capable of sufficiently heating and melting a maximum of four toner layers, a core metal of a fixing roller having a high heat capacity or a toner image is formed. The toner image is heated via a rubber elastic layer or the like for wrapping and uniformly melting.

In such an apparatus, since an intervening member such as a metal core or a rubber elastic layer is provided, if a good fixing property is ensured, the heat source and the material to be heated tend to separate from each other, and the efficiency is increased. It was difficult.

On the other hand, Japanese Patent Publication No. 5-9027 discloses an electromagnetic heating type heating device in which an eddy current is generated in a fixing roller by magnetic flux and heat is generated by Joule heat, and the generation of the eddy current is utilized. The heat generation position can be close to the toner image, and a fixing process with higher efficiency than a heat roller using a halogen lamp has been achieved.

[0006]

However, in the heating device of the electromagnetic heating system, the material to be heated is heated due to the heat radiation at the end of the heating section and the generation of magnetic flux at the end and at the center. Was sometimes non-uniform. For this reason, problems such as poor fixing, uneven gloss and offset have occurred in the image forming apparatus provided with the heating device.

An object of the present invention is to maintain a uniform temperature distribution in the width direction of a material to be heated in a heating unit in a heating device.
Another object of the present invention is to achieve high performance without defective fixing, uneven gloss and offset even in an image forming apparatus provided with the heating device.

[0008]

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

(1) A fixed or moving heating member, a magnetic field generating means for generating an alternating magnetic field and causing the heating member to generate heat by the action of the magnetic field, and a pressing member for pressing the heating member to form a nip A heating device that conveys and passes the material to be heated through the nip to heat the material to be heated, wherein the magnetic field is generated when a direction perpendicular to the direction of material to be heated is taken as a width direction of the material to be heated. The density of the magnetic flux generated by the means is changed in the width direction of the material to be heated of the heating member, so that the temperature distribution of the nip in the width direction of the material to be heated is made uniform.

(2) A fixed or moving heating member, a magnetic field generating means for generating an alternating magnetic field and causing the heating member to generate heat by the action of the magnetic field, and a pressing member for pressing the heating member to form a nip. A heating device that conveys and passes the material to be heated through the nip to heat the material to be heated, wherein the magnetic field is generated when a direction perpendicular to the direction of material to be heated is taken as a width direction of the material to be heated. The heating device is characterized in that the magnetic flux density is higher at the end of the heating member than at the center of the heating member in the width direction of the material to be heated.

(3) The heating device according to (1) or (2), wherein the magnetic field generating means has a larger number of turns at an end portion than at a central portion in a width direction of a material to be heated of the exciting coil for generating a magnetic field. .

(4) The magnetic field generating means is characterized in that a correction core is disposed near an end of the exciting coil for generating a magnetic field in the width direction of the material to be heated, and the magnetic flux is concentrated. The heating device according to any one of 3).

(5) The heating device according to any one of (1) to (4), wherein the developer image carried on the recording material is heated.

(6) An image forming means for carrying a developer image on a recording material and a heating device according to any one of (1) to (4) as an image heating device for heating the developer image. And an image forming apparatus.

That is, at both ends of the coil,
Increasing the number of turns, generating more magnetic flux compared to the center, or disposing correction cores near both ends of the coil,
By guiding the magnetic flux to the heating section without scattering it to the heating section at the end, the distribution of the magnetic flux generated by the magnetic field generating means is appropriately set, and the temperature distribution in the width direction of the heating member is made uniform. can do.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 (1) Overall Configuration of Heating Device FIG. 1A is a schematic cross-sectional view showing a schematic configuration of a fixing device of the present invention, FIG. (c) is a schematic sectional view of the fixing film. In FIG. 1, reference numeral 1 denotes a fixing film, 105 denotes an insulating film guide which does not hinder the passage of magnetic flux.
5 rotates in the direction of the arrow while ensuring transport stability. 201 is an exciting coil for generating an alternating magnetic flux,
Reference numeral 202 denotes a ferrite core for efficiently increasing the alternating magnetic flux generated by the excitation coil 201 around the nip, and is supported by the film guide 105.

An excitation circuit is connected to the excitation coil 201, and this excitation circuit can supply an alternating current of 50 KHz to the excitation coil 201. Reference numeral 3 denotes a pressure roller which is a 2 mm thick silicone rubber layer 302 on a core metal 301.
The nip N is formed by applying pressure to the lower surface of the film guide 105 via the fixing film 1 to provide elasticity. The pressure roller 3 also functions as a drive roller that rotates the fixing film 1 in the conveying direction (X-axis direction in the drawing) of the recording material P as the material to be heated.

The heating device supplies an alternating current from the excitation circuit to the coil 201 to generate an alternating magnetic flux. The alternating magnetic flux is guided to the ferrite core 202 and the eddy current flows to the heating layer 101 of the fixing film 1. Generate. This eddy current generates Joule heat due to the specific resistance of the heat generating layer 101, and heats the recording material P conveyed to the nip N via the elastic layer 102 and the release layer 103 and the toner T on the recording material P. .

(2) Fixing Film 1 The fixing film 1 will be described. In the fixing film 1, the surface of a heating layer 101 made of nickel as a heating element and having a thickness of 50 μm is covered with an elastic layer 102 made of silicone rubber. Of the mold release layer 103.

As the heat generating layer 101, besides nickel,
A metal, a metal compound, or an organic conductor which is an electric conductor of 0 ^-5 to 10 ^-10 Ω · m may be used. More preferably, pure metal such as iron or cobalt having high magnetic permeability (having ferromagnetism) or Those compounds can be used.

If the thickness of the heat generating layer 101 is too small, a sufficient magnetic path cannot be secured, and magnetic flux may leak to the outside, and the heat generated by the heat generating element itself may be reduced. When the thickness is large, the heat capacity tends to be large, and the time required for temperature rise tends to be long. Therefore, the thickness of the heat generating layer 101 has an appropriate value depending on the specific heat, density, magnetic permeability, and resistivity of the material used for the heat generating element. In the present embodiment, the thickness of the heat generating layer 101 is 3 ° C./sec or more in the thickness range of 10 to 100 μm. A heating rate could be obtained.

If the hardness of the elastic layer 102 is too high, the unevenness of the recording material or the toner layer cannot be completely followed, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 102 is 60 ° (JIS-A) or less, more preferably 4 ° (JIS-A).
5 ° (JIS-A) or less is preferable. The thermal conductivity λ of the elastic layer 102 is 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [cal
/ Cm · sec · deg. ] Is good. Thermal conductivity λ is 6 ×
10 ^-4 [cal / cm · sec · deg. ], The thermal resistance is large, and the temperature rise in the surface layer of the fixing film 1 becomes slow.

As the release layer 103, PFA, PTFE,
In addition to a fluororesin such as FEP, a material having good releasability and heat resistance, such as a silicone resin, a silicone rubber, and a fluororubber, can be selected. The thickness of the release layer 103 is 20
To 100 μm, and the thickness of the release layer 103 is 20
If it is smaller than μm, problems occur such as uneven coating of the coating film during production, resulting in portions having poor releasability, and insufficient durability. Further, if the thickness of the release layer exceeds 100 μm, there arises a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 102 is reduced.

(3) Excitation Coil 201 (FIG. 2) The excitation coil 201 must generate an alternating magnetic flux sufficient for heating. For this purpose, it is necessary to reduce the resistance component and increase the inductance component. . In this embodiment, a high-frequency φ1 bundle of thin wires is used as the core wire of the excitation coil 201, and the core coil 202 is wound 12 times as shown in FIG.

In contrast to the conventional single-turn coil 202 'as shown in FIG.
As shown in (a), one wire is continuously wound, and the number of turns at both ends is greater than the number of turns (12 times) at the center. That is, the number of turns at the end is increased so as to correct the loss at the end having a weak magnetic field restraining force, and the magnetic flux density is partially increased.

Such a conventional excitation coil 201 'and the excitation coil 201 of this embodiment are provided in a heating device having the same other configuration, and the magnetic flux density in the longitudinal direction and the longitudinal direction of the nip N temperature (the material to be heated) 2 (b),
This is shown in FIG.

FIG. 2 (b) shows a conventional excitation coil 201 '.
As shown in the figure, the magnetic flux density is substantially constant over the longitudinal direction, and the temperature of the nip N is low at both ends due to the weak magnetic flux and light flux at the width direction end of the heating member and the large amount of heat radiation. ing.

On the other hand, in the excitation coil 201 of the present embodiment, as shown in FIG. 3B, the magnetic flux density at the longitudinal end is higher than that at the center, so that the entire area of the nip N in the longitudinal direction is increased. A uniform temperature distribution is obtained. At this time, FIG.
In the region E shown in FIG.
The temperature of the nip N has almost no effect and is negligible.

Further, in order to secure a magnetic path as shown in FIG. 5, the ferrite core can be made more effective by extending the ferrite core to the portion of the correction coil 201c.

<Embodiment 2> (FIGS. 6 and 7) As another embodiment, as shown in FIG.
A ferrite core 203 of the same material as the core 202 is placed at the end of the core, and a magnetic path is secured for the magnetic flux diverging from the end to prevent the divergence of the magnetic field and make the magnetic flux density at the end equal to or more than the central part. It is possible to do.

Further, as shown in FIG.
In addition, by providing the correction core 203, the distribution of the magnetic flux can be set more effectively.

<Embodiment 3> (FIG. 8) FIGS. 8 (a), (b) and (c) of FIG.
01 shows another embodiment.

(A) has a main portion 201a for heating the heating member and a correction portion 201b opposite to the main portion 201a. Is attenuated by the correction unit 201b, and the magnetic flux density at the end is relatively increased.

In the case of (b), the main part 201a is
The correction section 201b is set to the forward direction at the end in the width direction of the material to be heated, and the reverse direction is set at the center, to more effectively correct the magnetic flux distribution.

The ones (c) is n pieces of coils 201 ₁ ～201 _n series or parallel (shown in series) to the heated material width direction are juxtaposed and connected to the coil of the central portion 201 ₂
Coil 201 of the end portion than the ~201 _{n-1 1,} 201 _n
Has increased the number of turns.

<Embodiment 4> (FIG. 9) FIGS. 9A, 9B and 9C show other examples of the configuration of the heating apparatus of the electromagnetic induction heating system.

(A) is a stay (film guide)
An endless belt-like shape is formed between three members, that is, the lower surface of the electromagnetic induction heating structure R (the lower surface of the stay 105) having the core 105, the excitation coil 201, the core 202, and the like, the driving roller 45, and the driven roller (tension roller) 46. The film 1 as a conductive member is stretched and stretched to form a drive roller 45.
And the film 1 is driven to rotate. 3
Reference numeral denotes a pressure roller pressed against the lower surface of the stay with the film 1 interposed therebetween, and is driven to rotate as the film 1 rotates.

In the case of (b), the film 1 as an endless belt-shaped conductive member is suspended between the lower surface of the stay of the electromagnetic induction heating structure R and the driving roller 45, and rotated by the driving roller 45. It is of a configuration for driving.

In the case of (c), the film 1 as the conductive member is not an endless belt-like film, but a long end film wound in a roll, which is fed out from the shaft 48 side by an electromagnetic induction heating structure. It is configured to run at a predetermined speed toward the winding shaft 49 via the lower surface of the stay of the body R.

Fifth Embodiment (FIG. 10) In this embodiment, for example, an outline of an example of an image forming apparatus using the heating device of the electromagnetic induction heating system of the first embodiment as an image heating fixing device (heating device) 10 will be described. It is a block diagram. The image forming apparatus of the present embodiment is a laser beam printer using an electrophotographic process.

Reference numeral 11 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image bearing member (first image bearing member). The photosensitive drum 11 is driven to rotate at a predetermined peripheral speed (process speed) in a counterclockwise direction indicated by an arrow, and is uniformly charged to a predetermined negative dark potential VD by the primary charger 12 during the rotation process.

Reference numeral 13 denotes a laser beam scanner, which converts a laser beam L modulated according to a time-series electric digital pixel signal of target image information input from a host device (not shown) such as an image reading device, a word processor, and a computer. Then, the surface of the photosensitive drum 11 negatively and uniformly charged by the primary charger 12 as described above is scanned and exposed by the laser beam, so that the absolute value of the potential of the exposed portion is reduced and becomes the bright potential VL, and the rotation exposure is performed. An electrostatic latent image corresponding to the target image information is formed on the surface of the drum 11.

Next, the latent image is reversal-developed with a powder toner negatively charged by the developing device 14 (laser exposure section V
L is toner-adhered) and is visualized.

The developing device 14 has a developing sleeve 1402 and a developing blade 1401 which are driven to rotate. The developing blade 1401 is usually made of metal or resin. 140
2 is in contact with an appropriate contact pressure. Then, the toner height and tribo are controlled by the developing sleeve 1402 and the developing blade 1401,
A uniform toner layer having a negative charge is formed at 402 and faces the surface of the photosensitive drum 11, and the sleeve 1402 has an absolute value smaller than the dark potential VD of the photosensitive drum 11 and larger than the bright potential VL. Due to the application of the bias voltage VDC, the toner on the sleeve 1402 is transferred only to the portion of the photosensitive drum 11 having the bright potential VL, and the latent image is visualized (reversal development).

On the other hand, a recording material (second image carrier, transfer paper) P loaded and set on a paper feed tray 25 is fed out one by one by a paper feed roller 26, and is conveyed by a conveyance guide 27 and a resist. The transfer bias is supplied to a position (transfer portion) between the photosensitive drum 11 and the transfer device 15 via the roller pair 28 and the pre-transfer guide 29 at an appropriate timing synchronized with the rotation of the photosensitive drum 11, and the transfer bias is changed. The toner image on the surface of the photosensitive drum 11 is sequentially transferred to the surface of the recording material P passing through the transfer section by the transfer device 15 to which the voltage is applied.

The recording material P that has passed through the transfer section is separated from the surface of the photosensitive drum 11 and introduced into the fixing device 10 by the transport guide 34, where the transferred toner image is fixed, and discharged as an image formed product (print). Output to the tray 36. After the recording material is separated, the surface of the photosensitive drum 11 is cleaned by the cleaning device 33 to remove the residual toner such as toner remaining after transfer, and the surface is cleaned and repeatedly used for image formation.

<Others> In each of the above embodiments, an example in which a film is provided with a heating layer as a heating member has been described.
A film in which the film itself is composed of a heating element (metal sleeve or the like) or a roller type in which an alternating magnetic flux acts on a metal roller may be used.

A conductive (preferably ferromagnetic) flat plate fixed and supported is used, and a pressing member is pressed against the flat plate directly or via a film to form a nip, and an alternating magnetic flux is applied to the flat plate. A configuration may be adopted in which heat is applied to generate heat, and heat treatment is performed on the material to be heated passing through the nip.

[0049]

As described above, according to the invention of the present application, the end magnetic field generated by the exciting coil is corrected,
Thus, it is possible to achieve the provision of a heating device capable of making the distribution of the calorific value of the heating section in the width direction of the material to be heated uniform, and an image forming apparatus provided with the heating device.

Further, high performance without defective fixing, uneven gloss and offset can be achieved in the image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a model diagram showing a schematic configuration of a heating device according to a first embodiment.

FIG. 2 is an explanatory diagram of a magnetic field generation distribution and a nip temperature distribution in a single-turn excitation coil.

FIG. 3 is an explanatory diagram of a magnetic field generation distribution and a nip temperature distribution in the end correction winding excitation coil.

FIG. 4 is an explanatory view of an end of an exciting coil.

FIG. 5 is a schematic cross-sectional view of the excitation coil and the core, showing another configuration of the excitation coil.

FIG. 6 is a schematic diagram illustrating an end configuration of a magnetic field generating unit according to a second embodiment.

FIG. 7 is a schematic diagram illustrating an end configuration of a magnetic field generating unit according to a second embodiment.

FIG. 8 is a schematic configuration diagram of another embodiment of the excitation coil.

FIG. 9 is a schematic configuration diagram of another embodiment of the heating device.

FIG. 10 is a schematic configuration diagram of an image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing film 101 Heat generation layer 102 Elastic layer 103 Release layer 105 Film guide 201 Excitation coil 202 Core 203 Correction core 3 Pressure roller 301 Core metal 302 Silicone rubber 10 Fixing device 11 Photosensitive drum 12 Primary charger 13 Scanner 14 Developing device 1401 developing blade 1402 developing sleeve 15 transfer device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideo Nanataki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (6)

[Claims] 1. A fixed or moving heating member, a magnetic field generating means for generating an alternating magnetic field and causing the heating member to generate heat by the action of the magnetic field, and a pressing member for pressing the heating member to form a nip; A heating device that conveys and passes the material to be heated through the nip to heat the material to be heated, wherein the direction perpendicular to the direction of conveying the material to be heated is the width direction of the material to be heated, and the magnetic field generating means The density of the magnetic flux generated by the heating member is changed in the width direction of the material to be heated of the heating member to make the temperature distribution of the nip in the width direction of the material to be heated uniform. 2. A heating member which is fixed or movable, a magnetic field generating means for generating an alternating magnetic field and causing the heating member to generate heat by the action of the magnetic field, and a pressing member for pressing the heating member to form a nip. A heating device that conveys and passes the material to be heated through the nip to heat the material to be heated, wherein the direction perpendicular to the direction of conveying the material to be heated is the width direction of the material to be heated, and the magnetic field generating means A heating device characterized in that the magnetic flux density at the end of the heating member is higher than that at the center of the heating member in the width direction of the material to be heated. 3. The heating apparatus according to claim 1, wherein said magnetic field generating means has a larger number of turns at an end portion than at a central portion in a width direction of a material to be heated of said exciting coil for generating a magnetic field. 4. The magnetic field generating means according to claim 1, wherein a correction core is arranged near an end of the exciting coil for generating a magnetic field in a width direction of the material to be heated, and the magnetic flux is concentrated.
The heating device according to claim 3. 5. The heating apparatus according to claim 1, wherein the developer image carried on the recording material is subjected to a heat treatment. 6. The heating device according to claim 1, wherein the image forming unit carries a developer image on a recording material, and the image heating device heats the developer image. An image forming apparatus comprising: