JP4194186B2 - Image heating device - Google Patents

Description

【００９１】
表１のようにｄ＝１５ｍｍで濃度低下率が２０％以上となり、良好な定着性を得ることができないが、ｄ＝１０ｍｍでは濃度低下率が８〜１５％となり、実用レベルでは問題のない良好な定着性がえられる。
【００９２】
従って、これらより磁性コア５の間隙を１０ｍｍ以下とすることで、定着性を満足する温調温度を定着フィルム６に与えることが出来る。
【００９３】
次に磁性コア５ａと磁性コア５ｂの各々の間隙の重なり距離Ｌを図８に示すように間隙Ｏに意図的に設けて、空回転温調（定着スピード：１００ｍｍ／ｓ、定着温度１８０℃）した場合の間隙Ｏ近辺の定着フィルム（スリーブ）６の長手温度分布を測定したところ、図９に示す様な結果が得られた。図９において、横軸は複数の分割磁性部材の配列を内包した誘導発熱体の長手方向である。
【００９４】
これによるとＬ＝３ｍｍのとき間隙Ｏに当たる定着フィルム６の温度は設定温調温度どおり１８０℃を示し、Ｌ＝５ｍｍでは１７５℃、Ｌ＝７ｍｍでは１７０となり、温度低下している事が判る。従って先ほどの距離ｄの温調温度で１７５℃以上で良好な定着性が得られているため、磁性コア５ａと磁性コア５ｂの間隙重なり距離Ｌも５ｍｍ以内とすることで、定着性に影響ない温調温度を定着フィルム６に与えることが出来る。
【００９５】
また、本例においては記録材に関する情報は外部の画像信号発生装置（コンピュータ等）から得る例を示したが、装置内に紙サイズ検知機構等のセンサーを設け、これにより検知された情報を記憶して、これを用いる事もできる。
【００９６】
また、本例は４色カラー画像形成装置について説明してきたが、モノクロ画像形成装置に利用しても良い。
【００９７】
この場合は定着フィルム６において弾性層６ｂを省略することができる。
【００９８】
なお、図１０は分割の磁性コア５ａと５ｂの長手方向の端面が同一磁路上に配置されている形態の場合を示したものであり、この形態の場合は磁性コア５ａ・５ｂの切れ目では磁場が不均一になり、電磁誘導発熱体の長尺方向に温度ムラが発生して、定着不良や光沢ムラという問題が発生していた。
【００９９】
〈実施形態例２〉（図１１・図１２）
図１１は本実施形態例２における磁束発生手段４・５の斜視図、図１２は磁性コア５の側面図である。
【０１００】
本実施形態例の装置は前述実施形態例１の装置との対比において、図１１・図１２に示すように、磁束発生手段４・５の磁性コア５の形状及び配置が異なる点を除いて同じである。
【０１０１】
即ち、磁性コア５ａ、５ｂの形状を平行四辺形及び台形にして、磁性コア５ａ、５ｂの間隙が同一磁路上にないように配してあり、励磁コイル４により発生した交番磁束のほとんどが磁性コア５ａ、５ｂ内を通過する構成となっている。
【０１０２】
つまり、分割の各磁性コア５ａ、５ｂの隣の磁性コアと対向する面が円筒状定着フィルム６の回転軸線に垂直な同一平面上にない形態のものである。
【０１０３】
このような形状の磁性コア５ａ、５ｂを配置することによっても実施形態例１と同様に定着フィルム６の電磁誘導発熱層６ａにおける磁束を均一にすることができる構成となり、より高速な画像形成装置に向いている。
【０１０４】
〈実施形態例３〉（図１３・図１４）
図１３は本実施形態例３における磁束発生手段４・５の斜視図、図１４は磁性コア５の側面図である。
【０１０５】
本実施形態例の装置は前述実施形態例１の装置との対比において、図１３・図１４に示すように、磁束発生手段４・５の磁性コア５の形状及び配置が異なる点を除いて同じである。
【０１０６】
即ち、磁性コア５ａ、５ｂの形状を三角形にして、磁性コア５ａ、５ｂの間隙が同一磁路上にないように配してあり、励磁コイル４により発生した交番磁束のほとんどが磁性コア５ａ、５ｂ内を通過する構成となっている。
【０１０７】
このような形状の磁性コア５ａ、５ｂを配置することによっても実施形態例１と同様に定着フィルム６の電磁誘導発熱層６ａにおける磁束を均一にすることができる構成となり、より高速な画像形成装置に向いている。
【０１０８】
〈その他〉
ａ）磁性コア５の５ａまたは５ｂの一方または両方の接続面を図１５に示す（Ａ）、（Ｂ）、（Ｃ）、（Ｄ）及び（Ｅ）のような形状にしても良い。
【０１０９】
これらの場合においても実施例形態１及び２と同様に定着フィルム６の電磁誘導発熱層６ａにおける磁束を均一にすることができる構成となる。
【０１１０】
特に（Ａ）の形状は鍵状になっているため磁性コア５が固定され、磁性コア５の間隙が広がることがないという効果もある。
【０１１１】
ｂ）定着フィルム６はエンドレスベルト状のものを二つ以上の部材間に懸回張設して加圧ローラ或いは加圧ローラ以外の駆動手段で回転駆動する装置構成であっても良い。
【０１１２】
また、定着フィルム６は電磁誘導発熱層６ａの無い耐熱性フィルム材にし、これを電磁誘導発熱体の面に摺動移動させ、電磁誘導発熱体は磁束発生手段４・５により電磁誘導発熱させて耐熱性フィルム材を介した該電磁誘導発熱体からの熱により被加熱材を加熱する装置構成にすることもできる。
【０１１３】
定着フィルム６または上記の耐熱性フィルム材は、ロール巻きにした長尺の有端フィルム材にし、これを繰り出し軸側から加熱部を経由させて巻き取り軸側へ所定の速度で走行させる装置構成にすることもできる。
【０１１４】
ｃ）誘導発熱体に薄肉の磁性材料からなるローラを用いることもできる。
【０１１５】
この場合も薄肉であるが故発生しやすい非通紙部の過昇温を、本発明の効果により顕著に改善することができる。
【０１１６】
ｄ）励磁コイル４等からなる磁束発生手段を定着フィルム６等の誘導発熱体の外周囲に配した装置であっても良い。
【０１１７】
ｅ）本発明において、加熱装置には実施形態例の画像加熱定着装置に限られず、画像を担持した記録材を加熱してつや当の表面性を改質する像加熱装置、仮定着する像加熱装置、その他、被加熱材の加熱乾燥装置、加熱ラミネート装置など、広く被加熱材を加熱処理する手段・装置が含まれる。
【０１１８】
ｆ）加圧部材はローラ以外のも、例えばベルト部材などの回転体にすることができる。
【０１１９】
ｇ）記録材に対するトナー像の形成原理・手段は任意である。
【０１２０】
【発明の効果】
以上説明したように、本発明によれば、電磁誘導加熱方式の像加熱装置において、磁性コアのコストを抑えつつ発熱体の母線方向の温度分布ムラを抑えることができる。
【図面の簡単な説明】
【図１】 実施形態例１における画像形成装置の概略構成図
【図２】 画像加熱定着装置の横断面模型図
【図３】 磁束発生手段の斜視図
【図４】 交番磁束の発生の様子および磁路を模式的に表した図
【図５】 （ａ）及び（ｂ）はそれぞれ定着フィルム（誘導発熱体フィルム）の層構成模型図
【図６】 （ａ）は磁性コアの形状と配置を示す側面図、（ｂ）はその部分の拡大図
【図７】 実施形態例１の定着フィルム表面の長手温度分布を示す図
【図８】 磁性コアの間隙の配置を示す側面拡大図
【図９】 磁性コアの間隙の重なり距離による定着フィルム表面の長手温度分布を示す図
【図１０】 分割の磁性コアの長手方向の端面が同一磁路上に配置されている形態の場合を示した図
【図１１】 実施形態例２における磁束発生手段の斜視図
【図１２】 磁性コアの形状と配置を示す側面図
【図１３】 実施形態例３における磁束発生手段の斜視図
【図１４】 磁性コアの形状と配置を示す側面図
【図１５】 （Ａ）、（Ｂ）、（Ｃ）、（Ｄ）及び（Ｅ）は磁性コアの分割面の形状と配置を示す横側面図
【符号の説明】
１０・・加熱定着装置、１・・加熱アセンブリ、２・・加圧ローラ、３・・円筒状フィルムガイド部材、４・・励磁コイル、５・・磁性コア、６・・定着フィルム、Ｃ・・交番磁束、ｄ・・磁性コアの間隙距離、Ｌ・・磁性コアの間隙重なり距離[0001]
BACKGROUND OF THE INVENTION
  The present invention, ElectricMagnetic (magnetic) induction heating methodStatue ofThe present invention relates to a heating device.
[0002]
[Prior art]
For convenience, an image heating and fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, and a fax machine will be described as an example.
[0003]
  The image heating and fixing device in the image forming apparatus is a toner made of a heat-meltable resin or the like by an appropriate image forming process such as electrophotography, electrostatic recording, and magnetic recording in an image forming unit of the image forming apparatus. The toner image formed by the direct method or the indirect (transfer) method on the surface of the recording material using the developer)HardIt is an apparatus that performs heat fixing processing as a received image.
[0004]
Conventionally, as such an image heating and fixing device, there are various methods such as a heat roller method, a film heating method, and an electromagnetic induction heating method.
[0005]
a. Heat roller method
This consists of a rotating roller pair of a fixing roller (heat roller) and a pressure roller that are heated and adjusted to a predetermined fixing temperature by incorporating a heat source such as a halogen lamp, and a pressure nip (fixing nip) of the roller pair. In this case, an unfixed toner image is heated and fixed on the surface of the recording material by introducing a recording material on which an unfixed toner image is formed and supported as a material to be heated and sandwiching and conveying the recording material.
[0006]
However, this apparatus has problems such as a large heat capacity of the fixing roller, a large amount of power required for heating, and a long wait time (waiting time from when the apparatus power is turned on until the print output is enabled).
[0007]
In the case of a fixing device for a full-color image device, since the ability to sufficiently heat and melt a maximum of four toner layers is required, the fixing roller has a core metal having a high heat capacity and encloses the toner layer. In order to melt uniformly, a rubber elastic material is provided on the outer periphery of the core metal, and the toner image is heated through the rubber elastic layer.
[0008]
In particular, in the case of an apparatus using a fixing roller having a large heat capacity, a delay occurs between the temperature adjustment of the fixing roller and the temperature increase of the roller surface, which causes problems such as fixing failure, uneven gloss, and offset. It was.
[0009]
b. Film heating method
This has a heating element and a film whose one surface slides on this heating element and the other surface moves in contact with the recording medium, and heat from the heating element is applied to the recording material through the film. This is a device that heat-fixes an unfixed toner image on the surface of a recording material (Japanese Patent Laid-Open Nos. 63-313182, 2-157878, 4-44075-44083, 20420-204984, etc.) .
[0010]
Such a film heating type apparatus can use a low heat capacity ceramic heater or the like as a heating element, and a heat resistant thin thin heat capacity film as a heating element, and a heat roller type apparatus using a fixing roller having a large heat capacity. Compared to, there are advantages such as being able to save power and shortening the wait time, have quick start characteristics, and can suppress the temperature rise in the machine.
[0011]
  c. Electromagnetic induction heating method
  This uses an electromagnetic induction heating element as a heating element, an electric conductor (excitation coil) shaped to circulate a part of the generated magnetic flux around the electromagnetic induction heating element, and a plurality of magnetic members (magnetic core) divided in the longitudinal direction. An eddy current generated in the electromagnetic induction heating element by applying a magnetic field by means of a magnetic flux (magnetic field) generating means comprising a kind of high permeability memberBased onThis is a device that heats and fixes a toner image on a recording material surface as a heated material by Joule heat generation.
[0012]
Japanese Examined Patent Publication No. 7-319312 discloses a heat roller type device that electromagnetically heats a ferromagnetic fixing roller. The heat generating position can be close to the fixing nip portion, and a halogen lamp is used as a heat source. It achieves a more efficient fixing process than the conventional heat roller system.
[0013]
[Problems to be solved by the invention]
  Electromagnetic induction heating methodStatue ofIn the heating device, a high permeability member divided as a magnetic member of the magnetic flux generating means is used, so that the magnetic field becomes non-uniform at the break (gap of 5 mm or more), and in the longitudinal direction of the electromagnetic induction heating element. Temperature unevenness has occurred, causing problems such as poor fixing and uneven gloss.
[0014]
As a method of solving this problem, a method of using a non-divided high permeability member can be considered, but it is difficult to inexpensively manufacture a high permeability member of 300 mm or more from the A3 size correspondence, Since the high magnetic permeability member becomes very high in temperature, there is a problem that warping and chipping occur and the magnetic field distribution becomes non-uniform.
[0015]
Therefore, it is possible to shorten the wait time with low power consumption, prevent the temperature unevenness in the longitudinal direction of the fixing nip of the heating rotator, and increase the speed and durability. There is a demand for an inexpensive electromagnetic induction heating type heating apparatus or image heating apparatus that can be used and having high performance that does not cause poor fixing, uneven gloss, and offset, and an image forming apparatus equipped with the heating apparatus.
[0016]
  The present invention can meet such a demand., ElectricMagnetic induction heating type image heating devicePlaceIt is to provide.
[0017]
[Means for Solving the Problems]
  The present invention is an image heating apparatus having the following configuration.
A cylindrical heating element having a heating layer that generates heat due to eddy currents generated by electromagnetic induction, a magnetic core arranged so that the longitudinal direction thereof is parallel to the generatrix of the heating element, and the direction of magnetic flux generated by energization An excitation coil having a plurality of turns wound around the length of the magnetic core so as to be perpendicular to the bus bar of the heating element, and is generated by energization of the excitation coil and is guided by the magnetic core. In the image heating apparatus, an eddy current is generated in the heat generating layer by the action of the magnetic flux, and the toner image on the recording material is heated by the heat of the heating element that generates heat by the action of the eddy current.
  The magnetic core isThe cross-sectional shape when viewed from one end side of the busbar is T-shaped,A plurality of divided magnetic cores are arranged in a line parallel to the bus bar.The side portion of the T-shape when viewed from one end of the busbarThe first column,MultipleThe divided magnetic cores are aligned in parallel to the bus bar.The vertical side portion of the T-shape when viewed from one end of the busbarA second row, and all gaps between the plurality of divided magnetic cores in the first row and all gaps between the plurality of divided magnetic cores in the second row are 10 mm or less, An image characterized in that all the gaps in the first row and all the gaps in the second row do not overlap in the direction of the generatrix, or even if they overlap, the overlap distance is 5 mm or less. Heating device.
  According to the present invention, it is possible to suppress uneven temperature distribution in the bus bar direction of the heating element while suppressing the cost of the magnetic core.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
<Embodiment Example 1> (FIGS. 1 to 8)
(1) Example of image forming apparatus
FIG. 1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic full color printer.
[0035]
Reference numeral 11 denotes an electrophotographic photosensitive drum (image bearing member) made of an organic photosensitive member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed (peripheral speed).
[0036]
The photosensitive drum 11 is subjected to a uniform charging process with a predetermined polarity and potential by a charging device 12 such as a charging roller during the rotation process.
[0037]
  Next, a laser beam LB output from a laser optical box (laser scanner) 13 is applied to the charging surface., PaintingA scanning exposure process of image information is performed. The laser optical box 13 is supplied from an image signal generator such as a computer (not shown).PaintingA laser beam LB modulated (on / off) corresponding to a time-series electric digital pixel signal of image information is output to scan and expose the photosensitive drum surface. By this scanning exposure, the photosensitive drum 11 surface is scanned and exposed. ShiPaintingAn electrostatic latent image corresponding to the image information is formed. A mirror 13 a reflects the output laser beam from the laser optical box 13 to the exposure position of the photosensitive drum 11.
[0038]
  For full-color image formationTheThe first color separation component image of the color image, for example, the yellow component image, is subjected to scanning exposure and latent image formation, and the latent image is developed as a yellow toner image by the operation of the yellow developing device 14Y of the four-color developing device 14. Is done.
[0039]
The yellow toner image is transferred onto the surface of the intermediate transfer drum 16 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 11 and the intermediate transfer drum 16.
[0040]
The surface of the photosensitive drum 11 after the transfer of the toner image to the surface of the intermediate transfer drum 16 is cleaned by the cleaner 17 after removal of adhered residues such as transfer residual toner.
[0041]
  The process cycle of charging, scanning exposure, development, primary transfer, and cleaning is as described above.TheSecond (for example, magenta component image, magenta developer 14M is activated), third (for example, cyan component image, cyan developer 14C is activated), and fourth (for example, black component image, black developer 14BK is activated) ) Are sequentially executed, and toner images of four colors, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image, are sequentially superimposed and transferred onto the surface of the intermediate transfer drum 16.TheA color image corresponding to the color image is synthesized and formed.
[0042]
The intermediate transfer drum 16 has a middle-resistance elastic layer and a high-resistance surface layer on a metal drum. The intermediate transfer drum 16 is in contact with or close to the photosensitive drum 11 at the same peripheral speed as that of the photosensitive drum 11. The toner image on the side of the photoconductor drum 11 is transferred to the surface of the intermediate transfer drum 16 by a potential difference from the photoconductor drum 11 by applying a bias potential to the metal drum.
[0043]
  The color toner image synthesized on the surface of the intermediate transfer drum 16 is not shown on the secondary transfer portion T2 in the secondary transfer portion T2 which is a contact nip portion between the intermediate transfer drum 16 and the transfer roller 15. Sent from the paper feeder at the specified timingAs a material to be heatedTransfer is performed on the surface of the recording material (transfer material) P.
[0044]
The transfer roller 15 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images sequentially from the surface of the intermediate transfer drum 16 to the recording material P side.
[0045]
The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 16, introduced into an image heating and fixing device (image heating device) 10, and subjected to a heating and fixing process for an unfixed toner image. The sheet is discharged as an image formed product to a discharge tray (not shown) outside the apparatus.
[0046]
The image heating and fixing device 10 is an electromagnetic induction heating type device according to the present invention. The fixing device 10 will be described in detail in the next section (2).
[0047]
The intermediate transfer drum 16 after the color toner image has been transferred to the recording material P is cleaned by the cleaner 18 after removal of adhering residues such as transfer residual toner and paper dust.
[0048]
The cleaner 18 is always held in a non-contact state with the intermediate transfer drum 16, and is brought into contact with the intermediate transfer drum 16 during the secondary transfer of the color toner image from the intermediate transfer drum 16 to the recording material P. Retained.
[0049]
In addition, the transfer roller 15 is always held in a non-contact state with the intermediate transfer drum 16 and is in contact with the intermediate transfer drum 16 during the secondary transfer of the color toner image from the intermediate transfer drum 16 to the recording material P. Kept in a state.
[0050]
  From an image signal generator (computer) (not shown)PaintingInformation about the recording material P (paper size, paper thickness, special paper information, etc.) can be attached to the image information.
[0051]
Based on this information, the image forming apparatus selects a suitable recording material P by a paper feeding unit (not shown) and performs the above-described paper feeding operation, and stores information relating to this recording material in the storage device 101 (FIG. 3) in the apparatus. And used as a control parameter for the image heating and fixing apparatus 10.
[0052]
(2) Image heating and fixing device 10
2 is a schematic cross-sectional view of the image heating and fixing apparatus 10, and FIG. 3 is a perspective view of magnetic flux generation means (magnetic flux generation apparatus).
[0053]
The fixing device 10 mainly includes a heating assembly 1 and a pressure roller 2 as a rotary pressure member.
[0054]
  The heating assembly 1 includes a cylindrical film guide 3, an exciting coil 4 and magnetic core (magnetic member, high magnetic permeability member) 5 as magnetic flux generating means disposed in the inner space thereof, and a cylindrical film guide 3 loosely fitted outside. And a cylindrical (seamless) fixing film (sleeve) 6 as an induction heating element.As described below, the fixing film 6 is a cylindrical heating element having a heat generating layer that generates heat due to eddy current generated by electromagnetic induction. The magnetic core 5 is arranged so that its longitudinal direction is parallel to the generatrix of the fixing film 6. The exciting coil 4 is obtained by winding a plurality of turns around the length of the magnetic core 5 so that the direction of magnetic flux generated by energization is perpendicular to the bus of the fixing film 6.
[0055]
The pressure roller 2 is an elastic roller composed of a core metal 2a and a 2 mm-thick silicone rubber layer 2b covering the outer periphery of the core metal.
[0056]
The heating assembly 1 and the pressure roller 2 are brought into pressure contact with each other and assembled in an apparatus housing (not shown), and a fixing nip (heating nip) portion N having a predetermined width is formed between the two 1 and 2. In the fixing nip portion N, the inner surface of the fixing film 6 is in close contact with the lower surface of the cylindrical film guide member 3.
[0057]
The pressure roller 2 is rotationally driven in the clockwise direction indicated by the arrow in FIG. 2 by the driving means M (pressure roller drive type), and a fixing nip is formed between the roller 2 and the outer surface of the fixing film 6 by the rotational driving of the pressure roller 2. A rotational force acts on the fixing film 6 by the frictional force in the portion N, and the fixing film 6 rotates in the counterclockwise direction of the arrow around the outer periphery of the cylindrical film guide member 3.
[0058]
  The exciting coil 4 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit 40 (FIG. 3), and the alternating magnetic flux is guided to the magnetic core 5 to generate an eddy current in an electromagnetic induction heat generating layer to be described later of the fixing film 6. . The eddy current generated in the electromagnetic induction heat generating layer of the fixing film 6 generates Joule heat by the specific resistance of the electromagnetic induction heat generating layer. That is, by supplying an alternating current to the exciting coil 4,An eddy current is generated in the electromagnetic induction heating layer by the action of the magnetic flux generated by this energization and guided by the magnetic core 5, and the action of this eddy current causesThe fixing film 6 enters an electromagnetic induction heat generation state.The toner image on the recording material is heated by the heat of the fixing film 6.
[0059]
FIG. 4 schematically shows the state of generation of the alternating magnetic flux and the magnetic path, and C represents a part of the generated magnetic flux. The magnetic path is on the cross section of the magnetic core 5 (5a, 5b). In the apparatus of this example, it is on a plane perpendicular to the rotation axis of the cylindrical fixing film.
[0060]
The temperature of the fixing nip portion N is controlled to a predetermined fixing temperature by controlling the alternating current supplied from the exciting circuit 40 to the exciting coil 4 by a control circuit 100 including a temperature detection hand-drawn (not shown).
[0061]
Thus, in the state where the fixing film 6 is rotated by the rotation of the pressure roller 2 and the alternating current is supplied to the exciting coil 4 and the temperature of the fixing nip portion N rises to a predetermined temperature and is adjusted in temperature. A recording material P carrying an unfixed toner image t as a material to be heated is introduced between the N rotation fixing film 6 and the pressure roller 2 so that the recording material P is placed on the outer surface of the fixing film 6. The recording material P and the unfixed toner image t are heated by the heat generated by the electromagnetic induction heating of the fixing film 6 in the process of passing through the fixing nip N together with the fixing film 6. Then, the toner image is heat-fixed.
[0062]
The recording material P that has passed through the fixing nip N is separated from the outer surface of the fixing film 6 on the exit side of the fixing nip N and conveyed.
[0063]
a. Cylindrical film guide member 3
In the heating assembly 1, the cylindrical film guide member 3 is an insulating and heat resistant member that does not prevent the passage of magnetic flux, supports the exciting coil 4 and the magnetic core 5, and rotates on the outside of the member 3. 6 serves to guide the inner surface of the fixing film 6 to ensure the rotation stability of the fixing film 6.
[0064]
b. Excitation coil 4
The exciting coil 4 of the present example is formed by winding an outer long boat shape in which the outer shape substantially corresponds to the inner surface of the cylindrical film guide member 3 using an insulating coated conductor. The substantially lower half surface of the inner surface receives the outer surface and is inserted into the cylindrical film guide member 3.
[0065]
The exciting coil 4 must generate an alternating magnetic flux sufficient for heating. For this purpose, it is necessary to make the resistance component low and the inductance component high.
[0066]
In this example, the exciting coil 4 is configured by winding 12 turns so as to go around the fixing nip portion N using a high-frequency φ1 insulation-coated conductive wire in which fine wires are bundled as a core wire.
[0067]
An excitation circuit 40 is connected to the excitation coil 4, and the excitation circuit 40 can supply an alternating current of 50 KHz to the excitation coil 4.
[0068]
c. Fixing film 6
The fixing film 6 is a cylindrical member including an electromagnetic induction heat generating layer, has an inner diameter slightly larger than the outer diameter of the cylindrical film guide member 3, and is loosely fitted on the cylindrical film guide member 3.
[0069]
FIG. 5A is a layer configuration model diagram of the fixing film 6. The fixing film 6 of this example includes an electromagnetic induction heating layer 6a on the inner side (cylindrical film guide member 3 side), an elastic layer 6b on the outer side, and a release layer on the outer side (surface layer; on the pressure roller 2 side). 6c is a three-layer composite layer structure.
[0070]
The heat of the electromagnetic induction heat generating layer 6a is transferred to the recording material P conveyed to the fixing nip N through the elastic layer 6b and the release layer 6c to heat the recording material P and the toner image t on the recording material. .
[0071]
The heat generating layer 6a is a material layer having electromagnetic induction heat generating property that generates Joule heat by an eddy current caused by the action of an alternating magnetic flux.^-Five-10^-Ten Any metal, metal compound, or organic conductor that is a good electrical conductor of Ω · cm may be used. More preferably, a pure metal such as iron or cobalt that exhibits high permeability and ferromagnetism or a compound thereof can be used.
[0072]
If the thickness of the heat generating layer 6a is reduced, a sufficient magnetic path cannot be secured, the magnetic flux leaks to the outside, and the heat generating energy of the heating element itself may be reduced. Tend to be longer. Accordingly, the thickness has an appropriate value depending on the specific heat, density, magnetic permeability, and resistivity of the material used for the heat generating layer 6a. In practice, when operated as a heat fixing device, a temperature increase rate of 3 deg / sec or more could be obtained as the surface temperature of the fixing film 6 within a thickness range of 10 to 100 μm.
[0073]
The elastic layer 6b is a rubber layer such as silicone rubber. In this example, the elastic layer 6b is provided to improve the fixing of a color toner image composed of a maximum of four toner layers. Wraps and melts uniformly.
[0074]
If the elastic layer 6b has an excessively high hardness, the unevenness of the recording material or the toner layer cannot be fully tracked, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 6b is preferably 60 ° (JIS-A; JIS-K (using A type measuring device)) or less, more preferably 45 ° or less.
[0075]
Regarding the thermal conductivity λ of the elastic layer 6b, it is 6 × 10.^-Four~ 2x10^-3[Ca1 / cm · sec · deg. ] Is good. Thermal conductivity λ is 6 × 10^-Four[Ca1 / cm · sec · deg. Smaller than], the thermal resistance is large, and the temperature rising rate on the surface of the fixing film is slow.
[0076]
The thickness of the elastic layer 6b is preferably 100 to 300 μm. If the thickness is less than 100 μm, spot-like gloss unevenness is likely to occur when the ratio of evening images is large as in a color image forming apparatus. A large thermal gradient is generated between the heat generating layer 6a and the heat generating layer 6a, and the elastic layer is likely to be thermally deteriorated.
[0077]
The release layer 6c prevents toner from adhering to the surface of the fixing film, and has good release properties and heat resistance such as fluorine resin such as PFA, PTFE, FEP, silicone resin, silicone rubber, fluorine rubber, and silicone rubber. The material can be selected.
[0078]
The thickness of the release layer 6c is preferably 20 to 100 [mu] m. If the thickness is less than 20 [mu] m, there arises a problem that a poorly releasable part is formed due to coating unevenness of the coating film or the durability is insufficient. Further, when the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin release layer, the hardness becomes too high and the effect of the elastic layer 6b is lost.
[0079]
The fixing film 6 used in this example is a three-layer composite layer composed of a heat-generating layer 6a made of nickel having a thickness of 50 μm, an elastic layer 6b made of silicone rubber having a thickness of 300 μm, and a release layer 6c made of fluororesin having a thickness of 30 μm. It is a film.
[0080]
Further, as shown in FIG. 5B, the fixing film 6 may be a four-layer fixing film 6 in which a heat insulating layer 6d is provided inside the heat generating layer 6a in the above layer structure.
[0081]
The heat insulating layer 6d is preferably a heat-resistant resin such as a fluororesin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, or FEP resin.
[0082]
The thickness of the heat insulating layer 6d is preferably 10 to 1000 μm. When the thickness of the heat insulating layer 6d is smaller than 10 μm, the heat insulating effect cannot be obtained and the durability is insufficient. If it exceeds 1000 μm, the distance from the magnetic core 5 to the heat generating layer 6a increases, and the magnetic flux does not sufficiently reach the heat generating layer 6a.
[0083]
When the heat insulating layer 6d is provided, it is possible to prevent the exciting coil 4 and the magnetic core 5 from being heated by heat generated in the heat generating layer 6a, so that stable heating can be performed.
[0084]
d. Magnetic core 5
The magnetic core 5 is a horizontally long divided ferrite core, and is disposed at a substantially central portion of the horizontally long boat-shaped exciting coil 4 and supported by the cylindrical film guide member 3. The magnetic core 5 serves to efficiently guide the alternating magnetic flux generated from the exciting coil 4 to the fixing film 6.
[0085]
  In this example, the divided surfaces of the two types of magnetic cores 5a and 5b divided as shown in FIG. 6 are arranged so as not to overlap. In other words, the end face in the longitudinal direction of the divided magnetic core 5a and the end face in the longitudinal direction of the similarly divided magnetic core 5b are arranged so as not to be located on the same magnetic path. As described above, the magnetic path is on the cross section of the magnetic core 5 (5a, 5b). In the apparatus of this example, it is on a plane perpendicular to the rotation axis of the cylindrical fixing film.
  That is, the magnetic core 5 isThe cross-sectional shape when viewed from one end of the bus of the fixing film 6 is T-shaped,A plurality of divided magnetic cores 5a are arranged in a line parallel to the bus of the fixing film 6.The side portion of the T-shape when viewed from one end of the busbarThe first row 5a, 5a, and so on, DoubleSeveral divided magnetic cores 5b are arranged in a line parallel to the bus.The vertical side portion of the T-shape when viewed from one end of the busbarAnd the second row 5b, 5b,. As described later, all the gaps between the plurality of divided magnetic cores in the first row 5a, 5a,... And all the gaps between the plurality of divided magnetic cores in the second row 5b, 5b,. .., And all the gaps in the first row 5 a, 5 a, and all the gaps in the second row 5 b, 5 b,. The distance is 5 mm or less.
[0086]
  With this configuration,Since the magnetic flux generated by the exciting coil 4 can pass through the magnetic core, which is a high permeability member,While suppressing the cost of the magnetic core, it is possible to suppress uneven temperature distribution in the direction of the bus of the heating element.
[0087]
The gap between the split magnetic cores (the gap between the end faces of the split magnetic cores) is obtained when the idling temperature is adjusted (fixing speed: 100 mm / s, fixing temperature 180 ° C.) by changing the distance d of the gap O in FIG. When the longitudinal temperature distribution of the fixing film (sleeve) 6 near the gap O was measured, the result as shown in FIG. 7 was obtained. In FIG. 7, the horizontal axis is the longitudinal direction of the induction heating element including an array of a plurality of divided magnetic members.
[0088]
  According to this, it hits the gap O when d = 5 mm.RudeThe temperature of the film 6 shows 180 ° C. according to the set temperature control temperature, 175 ° C. when d = 10 mm, and 170 when d = 15 mm. This is because the magnetic flux generated in the exciting coil 4 is interrupted in the gap O portion of the magnetic core 5, so that the portion of the fixing film 6 where the magnetic flux does not hit does not generate heat.
[0089]
Table 1 shows the fixability (Xerox 4020/105 g paper, LTR size) of the evening image (5 mm × 5 mm square) at that time. In the fixability evaluation, the density reduction rate by the rubbing test was adopted.
[0090]
[Table 1]

[0091]
As shown in Table 1, when d = 15 mm, the density reduction rate is 20% or more, and good fixability cannot be obtained. However, when d = 10 mm, the density reduction rate is 8-15%, and there is no problem at a practical level. Fixability is obtained.
[0092]
Therefore, by setting the gap between the magnetic cores 5 to 10 mm or less, a temperature adjustment temperature satisfying the fixing property can be given to the fixing film 6.
[0093]
Next, an overlap distance L between the gaps of the magnetic core 5a and the magnetic core 5b is intentionally provided in the gap O as shown in FIG. 8 to adjust the idling temperature (fixing speed: 100 mm / s, fixing temperature 180 ° C.). When the longitudinal temperature distribution of the fixing film (sleeve) 6 near the gap O was measured, the result as shown in FIG. 9 was obtained. In FIG. 9, the horizontal axis is the longitudinal direction of the induction heating element including an array of a plurality of divided magnetic members.
[0094]
  According to this, it hits the gap O when L = 3mmRudeThe temperature of the film 6 shows 180 ° C. as the set temperature control temperature, 175 ° C. when L = 5 mm, and 170 when L = 7 mm. Accordingly, good fixability is obtained at a temperature control temperature of 175 ° C. or more at the temperature d of the previous distance d. Therefore, the gap overlap distance L between the magnetic core 5a and the magnetic core 5b is also within 5 mm, so that the fixability is not affected. The temperature control temperature can be given to the fixing film 6.
[0095]
In this example, the information about the recording material is obtained from an external image signal generation device (computer or the like). However, a sensor such as a paper size detection mechanism is provided in the device to store the detected information. And this can be used.
[0096]
In this example, the four-color image forming apparatus has been described, but the present invention may be used for a monochrome image forming apparatus.
[0097]
In this case, the elastic layer 6 b can be omitted in the fixing film 6.
[0098]
FIG. 10 shows a case in which the longitudinal end faces of the divided magnetic cores 5a and 5b are arranged on the same magnetic path. In this case, the magnetic field at the break of the magnetic cores 5a and 5b is shown. Becomes uneven, temperature unevenness occurs in the longitudinal direction of the electromagnetic induction heating element, and problems such as poor fixing and gloss unevenness occur.
[0099]
<Embodiment 2> (FIGS. 11 and 12)
FIG. 11 is a perspective view of the magnetic flux generating means 4 and 5 in the second embodiment, and FIG. 12 is a side view of the magnetic core 5.
[0100]
The apparatus of the present embodiment is the same as the apparatus of the first embodiment except that the shape and arrangement of the magnetic cores 5 of the magnetic flux generating means 4 and 5 are different as shown in FIGS. It is.
[0101]
That is, the magnetic cores 5a and 5b are parallelograms and trapezoids so that the gaps between the magnetic cores 5a and 5b are not on the same magnetic path, and most of the alternating magnetic flux generated by the exciting coil 4 is magnetic. The structure passes through the cores 5a and 5b.
[0102]
That is, the surface facing the adjacent magnetic core of each of the divided magnetic cores 5 a and 5 b is not on the same plane perpendicular to the rotation axis of the cylindrical fixing film 6.
[0103]
By arranging the magnetic cores 5a and 5b having such a shape, the magnetic flux in the electromagnetic induction heat generating layer 6a of the fixing film 6 can be made uniform as in the first embodiment, and a higher-speed image forming apparatus. Suitable for.
[0104]
<Embodiment 3> (FIGS. 13 and 14)
FIG. 13 is a perspective view of the magnetic flux generation means 4 and 5 in the third embodiment, and FIG. 14 is a side view of the magnetic core 5.
[0105]
The apparatus of the present embodiment is the same as the apparatus of the first embodiment except that the shape and arrangement of the magnetic cores 5 of the magnetic flux generating means 4 and 5 are different as shown in FIGS. It is.
[0106]
That is, the magnetic cores 5a and 5b are triangular in shape so that the gaps between the magnetic cores 5a and 5b are not on the same magnetic path, and most of the alternating magnetic flux generated by the exciting coil 4 is magnetic cores 5a and 5b. It is configured to pass through.
[0107]
By arranging the magnetic cores 5a and 5b having such a shape, the magnetic flux in the electromagnetic induction heat generating layer 6a of the fixing film 6 can be made uniform as in the first embodiment, and a higher-speed image forming apparatus. Suitable for.
[0108]
<Others>
a) One or both of the connection surfaces of 5a or 5b of the magnetic core 5 may be shaped as shown in (A), (B), (C), (D) and (E) in FIG.
[0109]
In these cases, the magnetic flux in the electromagnetic induction heat generating layer 6a of the fixing film 6 can be made uniform as in the first and second embodiments.
[0110]
In particular, since the shape of (A) is key-shaped, the magnetic core 5 is fixed, and the gap between the magnetic cores 5 does not widen.
[0111]
b) The fixing film 6 may have an apparatus configuration in which an endless belt-shaped belt is suspended between two or more members and is rotationally driven by a pressure roller or a driving means other than the pressure roller.
[0112]
The fixing film 6 is made of a heat-resistant film material without the electromagnetic induction heating layer 6a, and is slid on the surface of the electromagnetic induction heating element. The electromagnetic induction heating element is heated by electromagnetic induction by the magnetic flux generating means 4 and 5. It can also be set as the apparatus structure which heats a to-be-heated material with the heat from this electromagnetic induction heat generating body through a heat resistant film material.
[0113]
The fixing film 6 or the above heat-resistant film material is a long end film material wound in a roll, and this device travels at a predetermined speed from the feeding shaft side to the winding shaft side via the heating unit. It can also be.
[0114]
c) A roller made of a thin magnetic material may be used for the induction heating element.
[0115]
In this case as well, the excessive temperature rise of the non-sheet passing portion which is thin and easily occurs can be remarkably improved by the effect of the present invention.
[0116]
d) A device in which magnetic flux generating means including the exciting coil 4 or the like is arranged around the outer periphery of the induction heating element such as the fixing film 6 may be used.
[0117]
e) In the present invention, the heating device is not limited to the image heating and fixing device of the embodiment, but an image heating device that heats a recording material carrying an image to modify the surface property of the gloss, and an image heating device that is assumed In addition, there are widely included means / devices for heat-treating the material to be heated, such as a heating / drying device for the material to be heated, and a heating laminating device.
[0118]
f) The pressure member can be a rotating body such as a belt member other than the roller.
[0119]
g) The principle and means for forming the toner image on the recording material are arbitrary.
[0120]
【The invention's effect】
  As explained above, according to the present invention,In the image heating apparatus of the electromagnetic induction heating method, temperature distribution unevenness in the bus bar direction of the heating element can be suppressed while suppressing the cost of the magnetic core.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first exemplary embodiment.
FIG. 2 is a schematic cross-sectional view of an image heating and fixing device.
FIG. 3 is a perspective view of magnetic flux generation means.
FIG. 4 is a diagram schematically showing an alternating magnetic flux generation state and a magnetic path.
FIGS. 5A and 5B are model diagrams of the layer structure of a fixing film (induction heating element film), respectively.
6A is a side view showing the shape and arrangement of a magnetic core, and FIG. 6B is an enlarged view of the portion.
FIG. 7 is a graph showing the longitudinal temperature distribution on the surface of the fixing film of Embodiment 1
FIG. 8 is an enlarged side view showing the arrangement of gaps in the magnetic core.
FIG. 9 is a graph showing the longitudinal temperature distribution on the surface of the fixing film according to the overlapping distance of the gaps of the magnetic core.
FIG. 10 is a diagram showing a case in which the longitudinal end faces of the divided magnetic cores are arranged on the same magnetic path
FIG. 11 is a perspective view of magnetic flux generation means in the second embodiment.
FIG. 12 is a side view showing the shape and arrangement of a magnetic core.
FIG. 13 is a perspective view of magnetic flux generation means in Embodiment 3;
FIG. 14 is a side view showing the shape and arrangement of a magnetic core.
15 (A), (B), (C), (D) and (E) are lateral side views showing the shape and arrangement of the split surfaces of the magnetic core.
[Explanation of symbols]
10 .... Heat fixing device, 1 .... Heat assembly, 2 .... Pressure roller, 3 .... Cylindrical film guide member, 4 .... Excitation coil, 5 .... Magnetic core, 6 .... Fusing film, C .. Alternating magnetic flux, d ·· Magnetic core gap distance, L · · Magnetic core gap overlap distance

Claims (1)

A cylindrical heating element having a heating layer that generates heat due to eddy currents generated by electromagnetic induction, a magnetic core arranged so that the longitudinal direction thereof is parallel to the generatrix of the heating element, and the direction of magnetic flux generated by energization An excitation coil having a plurality of turns wound around the length of the magnetic core so as to be perpendicular to the bus bar of the heating element, and is generated by energization of the excitation coil and is guided by the magnetic core. In the image heating apparatus, an eddy current is generated in the heat generating layer by the action of the magnetic flux, and the toner image on the recording material is heated by the heat of the heating element that generates heat by the action of the eddy current.
The magnetic core has a T-shaped cross-sectional shape when viewed from one end side of the bus bar, and a plurality of divided magnetic cores are arranged in a line in parallel to the bus bar, and one end side of the bus bar When viewed from one end side of the bus, the first row constituting the horizontal portion of the T-shape when viewed from the side, and a plurality of divided magnetic cores are aligned in parallel to the bus A second row constituting a vertical side portion of the T-shape, and all gaps between the plurality of divided magnetic cores in the first row and the plurality of divided magnetic cores in the second row All the gaps between them are 10 mm or less, and all the gaps in the first row and all the gaps in the second row do not overlap in the direction of the generatrix or even if they overlap, the overlap distance is An image heating apparatus characterized by being 5 mm or less.

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