JP2016212215A - Fixing device and image forming apparatus - Google Patents

Fixing device and image forming apparatus Download PDF

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JP2016212215A
JP2016212215A JP2015094757A JP2015094757A JP2016212215A JP 2016212215 A JP2016212215 A JP 2016212215A JP 2015094757 A JP2015094757 A JP 2015094757A JP 2015094757 A JP2015094757 A JP 2015094757A JP 2016212215 A JP2016212215 A JP 2016212215A
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temperature
fixing belt
magnetic field
fixing
magnetic
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内藤　康隆
Yasutaka Naito
康隆 内藤
小西　正孝
Masataka Konishi
正孝 小西
剛 春原
Takeshi Haruhara
剛 春原
敏行 宮田
Toshiyuki Miyata
敏行 宮田
英一郎 徳弘
Eiichiro Tokuhiro
英一郎 徳弘
照代 竜崎
Teruyo Ryuzaki
照代 竜崎
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Fujifilm Business Innovation Corp
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Fuji Xerox Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To suppress an excessive increase in temperature of a temperature-sensitive magnetic member compared with a case where only blocking parts extending in the direction of movement of a fixing member are formed in the temperature-sensitive magnetic member.SOLUTION: A fixing device comprises: a fixing belt that can perform circulation movement and has a conductive layer heated by electromagnetic induction to fix a toner onto a sheet; an exciting coil that generated an AC magnetic field intersecting with the conductive layer of the fixing belt; and a temperature-sensitive magnetic member 64 that includes a plurality of first slits 641 that face the exciting coil across the fixing belt, are inclined with respect to the direction of movement of the fixing belt, and block an eddy current from the AC magnetic field generated by the exciting coil, and a plurality of second slits 642 that are inclined to the opposite side of the first slits 641 with respect to the direction of movement and block the eddy current from the AC magnetic field, and has a magnetic characteristic changing between ferromagnetism and paramagnetism according to temperature and transmits the AC magnetic field when the magnetic characteristic is ferromagnetism.SELECTED DRAWING: Figure 9

Description

本発明は、定着装置および画像形成装置に関する。   The present invention relates to a fixing device and an image forming apparatus.

従来技術として、特許文献１には、定着ベルトと、交流磁界を生成する磁界生成部材と、定着ベルトを挟んで磁界生成部材と対向し磁界生成部材にて生成された交流磁界を誘導して磁路を形成する感温磁性部材とを備える定着装置が開示されている。
この定着装置では、感温磁性部材の過剰な温度上昇を抑制するために、感温磁性部材に、定着ベルトの移動方向に沿って延び渦電流の流れを遮断する遮断部を設け、感温磁性部材に発生するジュール熱を低く抑えている。 As a conventional technique, Patent Document 1 discloses a fixing belt, a magnetic field generating member that generates an alternating magnetic field, and an alternating magnetic field generated by the magnetic field generating member that opposes the magnetic field generating member across the fixing belt to magnetize the magnetic field. A fixing device including a temperature-sensitive magnetic member that forms a path is disclosed.
In this fixing device, in order to suppress an excessive increase in temperature of the temperature-sensitive magnetic member, the temperature-sensitive magnetic member is provided with a blocking portion that extends along the moving direction of the fixing belt and blocks the flow of eddy currents. The Joule heat generated in the member is kept low.

特開２０１０−１９７６１７号公報JP 2010-197617 A

ところで、感温磁性部材に定着ベルトの移動方向に沿って延びる遮断部を形成した定着装置では、感温磁性部材と定着ベルトとの間の空間において、定着ベルトの軸方向への空気の移動は起こりにくい。この場合、感温磁性部材と定着ベルトとの間の空間への感温磁性部材の放熱が起こりにくく、感温磁性部材の温度が過剰に上昇しやすい。
本発明は、感温磁性部材に定着部材の移動方向に延びる遮断部のみを形成する場合と比較して、感温磁性部材の過剰な温度上昇を抑制することを目的とする。 By the way, in the fixing device in which the temperature-sensitive magnetic member is formed with the blocking portion extending along the moving direction of the fixing belt, the movement of air in the axial direction of the fixing belt is not performed in the space between the temperature-sensitive magnetic member and the fixing belt. Hard to happen. In this case, heat dissipation of the temperature-sensitive magnetic member to the space between the temperature-sensitive magnetic member and the fixing belt is difficult to occur, and the temperature of the temperature-sensitive magnetic member tends to rise excessively.
An object of the present invention is to suppress an excessive temperature rise of the temperature-sensitive magnetic member as compared with a case where only the blocking portion extending in the moving direction of the fixing member is formed on the temperature-sensitive magnetic member.

請求項１に係る発明は、導電層を有し、当該導電層が電磁誘導加熱されることで記録材にトナーを定着する循環移動可能な定着部材と、前記定着部材の前記導電層と交差する交流磁界を生成する磁界生成部材と、前記定着部材を挟んで前記磁界生成部材と対向し、前記定着部材の移動方向に対し傾斜し当該磁界生成部材にて生成された交流磁界による渦電流を遮断する複数の第１遮断部と当該移動方向に対し当該第１遮断部とは反対側に傾斜し当該交流磁界による渦電流を遮断する複数の第２遮断部とを有し、磁気特性が温度に応じて強磁性と常磁性との間で変化して磁気特性が強磁性の場合に当該交流磁界を透過させる感温磁性部材とを備える定着装置である。
請求項２に係る発明は、複数の前記第１遮断部と複数の前記第２遮断部とは、前記移動方向の下流に向かうに従い互いに近づく方向に延びることを特徴とする請求項１に記載の定着装置である。
請求項３に係る発明は、前記第１遮断部および前記第２遮断部は、それぞれ、前記感温磁性部材を切欠くことにより形成されることを特徴とする請求項１または２に記載の定着装置である。
請求項４に係る発明は、導電層を有し、当該導電層が電磁誘導加熱されることで記録材にトナーを定着する循環移動可能な定着部材と、前記定着部材の前記導電層と交差する交流磁界を生成する磁界生成部材と、前記定着部材を挟んで前記磁界生成部材と対向し、磁気特性に応じて強磁性と常磁性との間で変化し、磁気特性が強磁性の場合に当該磁界生成部材にて生成された交流磁界を透過させ、当該定着部材との間に当該定着部材の移動方向に直交する第１方向に向かう気流と当該第１方向とは反対の第２方向に向かう気流とを発生させる気流発生部を有する感温磁性部材とを備える定着装置である。
請求項５に係る発明は、前記気流発生部は、前記第１方向に向かう気流と前記第２方向に向かう気流とを衝突させ乱流を発生させることを特徴とする請求項４に記載の定着装置である。
請求項６に係る発明は、トナー像を形成するトナー像形成手段と、前記トナー像形成手段によって形成された前記トナー像を記録材上に転写する転写手段と、請求項１乃至５のいずれか１項に記載の定着装置とを備える画像形成装置である。 According to a first aspect of the present invention, there is provided a conductive layer, and the conductive layer that is circulated and movable to fix the toner on the recording material by electromagnetic induction heating, and the conductive layer of the fixing member intersects with the conductive layer. A magnetic field generating member that generates an alternating magnetic field, and the magnetic field generating member that faces the fixing member and is inclined with respect to the moving direction of the fixing member to block eddy currents generated by the alternating magnetic field generated by the magnetic field generating member And a plurality of second blocking sections that are inclined to the opposite side of the first blocking section with respect to the moving direction and block eddy currents due to the alternating magnetic field, and the magnetic characteristics are dependent on temperature. Accordingly, the fixing device includes a temperature-sensitive magnetic member that changes between ferromagnetism and paramagnetism and transmits the AC magnetic field when the magnetic characteristics are ferromagnetism.
The invention according to claim 2 is characterized in that the plurality of first blocking portions and the plurality of second blocking portions extend in directions closer to each other as they go downstream in the moving direction. It is a fixing device.
The invention according to claim 3 is characterized in that the first blocking portion and the second blocking portion are each formed by cutting out the temperature-sensitive magnetic member. Device.
According to a fourth aspect of the present invention, there is provided a conductive layer, and the conductive layer is electromagnetically heated so that the toner can be circulated and moved, and the conductive layer of the fixing member intersects the conductive layer. A magnetic field generating member that generates an alternating magnetic field, and facing the magnetic field generating member across the fixing member, changes between ferromagnetism and paramagnetism according to the magnetic characteristics, and when the magnetic characteristics are ferromagnetic The AC magnetic field generated by the magnetic field generating member is transmitted, and the air flow toward the first direction perpendicular to the moving direction of the fixing member and the second direction opposite to the first direction are transmitted to the fixing member. And a temperature-sensitive magnetic member having an airflow generation unit that generates an airflow.
The invention according to claim 5 is characterized in that the airflow generation unit collides the airflow directed in the first direction and the airflow directed in the second direction to generate turbulent flow. Device.
The invention according to claim 6 is a toner image forming means for forming a toner image, a transfer means for transferring the toner image formed by the toner image forming means onto a recording material, and any one of claims 1 to 5. An image forming apparatus comprising the fixing device according to item 1.

請求項１に係る発明によれば、感温磁性部材に定着部材の移動方向に延びる遮断部のみを形成する場合と比較して、感温磁性部材の過剰な温度上昇を抑制することができる。
請求項２に係る発明によれば、第１遮断部と第２遮断部とが移動方向の下流に向かうに従い互いに離れる方向に延びる場合と比較して、感温磁性部材と定着部材との間の空気の移動を促進することが可能となる。
請求項３に係る発明によれば、感温磁性部材を切欠かない場合と比較して、感温磁性部材からの放熱を促進することが可能となる。
請求項４に係る発明によれば、感温磁性部材に定着部材の移動方向に延びる遮断部のみを形成する場合と比較して、感温磁性部材の過剰な温度上昇を抑制することができる。
請求項５に係る発明によれば、乱流を発生させない場合と比較して、感温磁性部材と定着部材との間の空気の移動を促進することが可能となる。
請求項６に係る発明によれば、感温磁性部材に定着部材の移動方向に延びる遮断部のみを形成する場合と比較して、感温磁性部材の過剰な温度上昇を抑制することができる。 According to the first aspect of the present invention, it is possible to suppress an excessive temperature rise of the temperature-sensitive magnetic member as compared with the case where only the blocking portion extending in the moving direction of the fixing member is formed on the temperature-sensitive magnetic member.
According to the second aspect of the present invention, the first blocking portion and the second blocking portion are disposed between the temperature-sensitive magnetic member and the fixing member as compared with the case where the first blocking portion and the second blocking portion extend in directions away from each other toward the downstream of the moving direction. It becomes possible to promote the movement of air.
According to the invention which concerns on Claim 3, it becomes possible to accelerate | stimulate the thermal radiation from a temperature sensitive magnetic member compared with the case where a temperature sensitive magnetic member is not notched.
According to the invention which concerns on Claim 4, compared with the case where only the interruption | blocking part extended in the moving direction of a fixing member is formed in a temperature sensitive magnetic member, the excessive temperature rise of a temperature sensitive magnetic member can be suppressed.
According to the invention which concerns on Claim 5, compared with the case where a turbulent flow is not generated, it becomes possible to promote the movement of the air between a temperature-sensitive magnetic member and a fixing member.
According to the invention which concerns on Claim 6, compared with the case where only the interruption | blocking part extended in the moving direction of a fixing member is formed in a temperature sensitive magnetic member, the excessive temperature rise of a temperature sensitive magnetic member can be suppressed.

本実施の形態が適用される画像形成装置の構成例を示した図である。1 is a diagram illustrating a configuration example of an image forming apparatus to which the exemplary embodiment is applied. 本実施の形態の定着装置の構成を示す図である。1 is a diagram illustrating a configuration of a fixing device according to an exemplary embodiment. 本実施の形態の定着装置の構成を示す図である。1 is a diagram illustrating a configuration of a fixing device according to an exemplary embodiment. 定着ベルトの層構成を説明する図である。FIG. 3 is a diagram illustrating a layer configuration of a fixing belt. 本実施の形態の内部加熱ユニットの構成を示した斜視図である。It is the perspective view which showed the structure of the internal heating unit of this Embodiment. （ａ）〜（ｂ）は、ＩＨヒータにより生成された磁力線の状態を示した図である。(A)-(b) is the figure which showed the state of the magnetic force line produced | generated by the IH heater. 本実施の形態が適用される感温磁性部材の構成を説明する図である。It is a figure explaining the structure of the temperature-sensitive magnetic member to which this Embodiment is applied. 感温磁性部材に形成されるスリットによる渦電流の流れを分断する作用を説明する図であるIt is a figure explaining the effect | action which interrupts the flow of the eddy current by the slit formed in a temperature-sensitive magnetic member. （ａ）〜（ｂ）は、感温磁性部材に形成されるスリットにより発生する気流を説明する図である。(A)-(b) is a figure explaining the airflow which generate | occur | produces with the slit formed in a temperature-sensitive magnetic member. 感温磁性部材の他の構成を示した図である。It is the figure which showed the other structure of the temperature-sensitive magnetic member.

以下、添付図面を参照して、本発明の実施の形態について詳細に説明する。
＜画像形成装置の説明＞
図１は本実施の形態が適用される画像形成装置の構成例を示した図である。図１に示す画像形成装置１は、所謂タンデム型のカラープリンタであり、画像データに基づき画像形成を行う画像形成部１０、画像形成装置１全体の動作を制御する制御手段の一例としての制御部３０、画像形成装置１に対して供給される用紙Ｐを保持する用紙保持部４０、画像が形成された用紙Ｐを積載する用紙積載部４５を備えている。さらには、例えばパーソナルコンピュータ（ＰＣ）３や画像読取装置（スキャナ）４等との通信を行って画像データを受信する通信部４１、通信部４１にて受信された画像データに対し予め定めた画像処理を施す画像処理部４２を備えている。さらにまた、画像形成装置１は、表示パネルなどにより構成されユーザからの情報を受け付けるとともにユーザに対して情報を表示する表示部の一例としてのユーザインタフェース（ＵＩ）３４を備えている。 Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Description of Image Forming Apparatus>
FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus to which the exemplary embodiment is applied. An image forming apparatus 1 illustrated in FIG. 1 is a so-called tandem color printer, and includes an image forming unit 10 that forms an image based on image data, and a control unit as an example of a control unit that controls the operation of the entire image forming apparatus 1. 30, a paper holding unit 40 that holds the paper P supplied to the image forming apparatus 1, and a paper stacking unit 45 that stacks the paper P on which an image is formed. Further, for example, a communication unit 41 that receives image data by communicating with a personal computer (PC) 3 or an image reading device (scanner) 4, and a predetermined image for the image data received by the communication unit 41. An image processing unit 42 for performing processing is provided. Further, the image forming apparatus 1 includes a user interface (UI) 34 as an example of a display unit that is configured by a display panel and receives information from the user and displays information to the user.

画像形成部１０は、一定の間隔を置いて並列的に配置されるトナー像形成手段の一例である４つの画像形成ユニット１１Ｙ、１１Ｍ、１１Ｃ、１１Ｋ（「画像形成ユニット１１」とも総称する）を備えている。各画像形成ユニット１１は、静電潜像を形成してトナー像を保持する感光体ドラム１２、感光体ドラム１２の表面を予め定めた電位で帯電する帯電器１３、帯電器１３によって帯電された感光体ドラム１２を各色画像データに基づき露光するＬＥＤ（Light Emitting Diode）プリントヘッド１４、感光体ドラム１２上に形成された静電潜像を現像する現像器１５、転写後の感光体ドラム１２表面を清掃するドラムクリーナ１６を備えている。
画像形成ユニット１１各々は、現像器１５に収納されるトナーを除いて同様に構成され、それぞれがイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、黒（Ｋ）のトナー像を形成する。 The image forming unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (also collectively referred to as “image forming unit 11”), which are examples of toner image forming units that are arranged in parallel at regular intervals. I have. Each image forming unit 11 is charged by a photosensitive drum 12 that forms an electrostatic latent image and holds a toner image, a charger 13 that charges the surface of the photosensitive drum 12 at a predetermined potential, and a charger 13. An LED (Light Emitting Diode) print head 14 that exposes the photosensitive drum 12 based on each color image data, a developing device 15 that develops an electrostatic latent image formed on the photosensitive drum 12, and the surface of the photosensitive drum 12 after transfer A drum cleaner 16 is provided.
Each of the image forming units 11 is configured in the same manner except for the toner stored in the developing device 15, and each forms a toner image of yellow (Y), magenta (M), cyan (C), and black (K). .

また、画像形成部１０は、各画像形成ユニット１１の感光体ドラム１２にて形成された各色トナー像が多重転写される中間転写ベルト２０、各画像形成ユニット１１にて形成された各色トナー像を中間転写ベルト２０に順次転写（一次転写）する一次転写ロール２１を備えている。さらに、中間転写ベルト２０上に重畳して転写された各色トナー像を記録材（記録紙）である用紙Ｐに一括転写（二次転写）する二次転写ロール２２、二次転写後の中間転写ベルト２０表面を清掃するベルトクリーナ２５、二次転写された各色トナー像を用紙Ｐ上に定着させる定着手段（定着装置）の一例としての定着装置６０を備えている。なお、本実施の形態の画像形成装置１では、中間転写ベルト２０、一次転写ロール２１、および二次転写ロール２２により転写手段が構成される。   The image forming unit 10 also receives the intermediate transfer belt 20 onto which the color toner images formed on the photosensitive drums 12 of the image forming units 11 are transferred, and the color toner images formed on the image forming units 11. A primary transfer roll 21 that sequentially transfers (primary transfer) to the intermediate transfer belt 20 is provided. Further, a secondary transfer roll 22 that batch-transfers (secondary transfer) each color toner image transferred onto the intermediate transfer belt 20 onto a sheet P that is a recording material (recording paper), and intermediate transfer after the secondary transfer. A belt cleaner 25 for cleaning the surface of the belt 20 and a fixing device 60 as an example of fixing means (fixing device) for fixing each color-transferred toner image on the paper P are provided. In the image forming apparatus 1 of the present embodiment, the intermediate transfer belt 20, the primary transfer roll 21, and the secondary transfer roll 22 constitute a transfer unit.

本実施の形態の画像形成装置１では、制御部３０による動作制御の下で、次のようなプロセスによる画像形成処理が行われる。すなわち、ＰＣ３やスキャナ４からの画像データは通信部４１にて受信され、画像処理部４２により予め定めた画像処理が施された後、各色の画像データとなって各画像形成ユニット１１に送られる。そして、例えば黒（Ｋ）色トナー像を形成する画像形成ユニット１１Ｋでは、感光体ドラム１２が矢印Ａ方向に回転しながら帯電器１３により予め定めた電位で帯電され、画像処理部４２から送信された黒（Ｋ）色画像データに基づきＬＥＤプリントヘッド１４が感光体ドラム１２を走査露光する。それにより、感光体ドラム１２上には黒（Ｋ）色画像に関する静電潜像が形成される。感光体ドラム１２上に形成された黒（Ｋ）色静電潜像は現像器１５により現像され、感光体ドラム１２上に黒（Ｋ）色トナー像が形成される。同様に、画像形成ユニット１１Ｙ、１１Ｍ、１１Ｃにおいても、それぞれイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）の各色トナー像が形成される。   In the image forming apparatus 1 of the present embodiment, under the operation control by the control unit 30, image forming processing is performed by the following process. That is, the image data from the PC 3 or the scanner 4 is received by the communication unit 41, subjected to predetermined image processing by the image processing unit 42, and then sent to each image forming unit 11 as image data of each color. . In the image forming unit 11K that forms, for example, a black (K) toner image, the photosensitive drum 12 is charged at a predetermined potential by the charger 13 while rotating in the direction of arrow A, and is transmitted from the image processing unit 42. The LED print head 14 scans and exposes the photosensitive drum 12 based on the black (K) color image data. As a result, an electrostatic latent image relating to a black (K) color image is formed on the photosensitive drum 12. The black (K) electrostatic latent image formed on the photosensitive drum 12 is developed by the developing device 15, and a black (K) toner image is formed on the photosensitive drum 12. Similarly, yellow (Y), magenta (M), and cyan (C) toner images are formed in the image forming units 11Y, 11M, and 11C, respectively.

各画像形成ユニット１１の感光体ドラム１２に形成された各色トナー像は、一次転写ロール２１により矢印Ｂ方向に移動する中間転写ベルト２０上に順次静電転写（一次転写）され、各色トナーが重畳された重畳トナー像が形成される。中間転写ベルト２０上の重畳トナー像は、中間転写ベルト２０の移動に伴って二次転写ロール２２が配置された領域（二次転写部Ｔ）に搬送される。重畳トナー像が二次転写部Ｔに搬送されると、そのタイミングに合わせて用紙保持部４０から用紙Ｐが二次転写部Ｔに供給される。そして、重畳トナー像は、二次転写部Ｔにて二次転写ロール２２が形成する転写電界により、搬送されてきた用紙Ｐ上に一括して静電転写（二次転写）される。   Each color toner image formed on the photosensitive drum 12 of each image forming unit 11 is sequentially electrostatically transferred (primary transfer) onto the intermediate transfer belt 20 that moves in the direction of arrow B by the primary transfer roll 21, and each color toner is superimposed. A superimposed toner image is formed. The superimposed toner image on the intermediate transfer belt 20 is conveyed to a region (secondary transfer portion T) where the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves. When the superimposed toner image is conveyed to the secondary transfer unit T, the paper P is supplied from the paper holding unit 40 to the secondary transfer unit T in accordance with the timing. The superimposed toner image is collectively electrostatically transferred (secondary transfer) onto the conveyed paper P by the transfer electric field formed by the secondary transfer roll 22 in the secondary transfer portion T.

その後、重畳トナー像が静電転写された用紙Ｐは、定着装置６０まで搬送される。定着装置６０に搬送された用紙Ｐ上のトナー像は、定着装置６０によって熱および圧力を受け、用紙Ｐ上に定着される。そして、定着画像が形成された用紙Ｐは、画像形成装置１の排出部に設けられた用紙積載部４５に搬送される。
一方、一次転写後に感光体ドラム１２に付着しているトナー（一次転写残トナー）、および二次転写後に中間転写ベルト２０に付着しているトナー（二次転写残トナー）は、それぞれドラムクリーナ１６、およびベルトクリーナ２５によって除去される。
このようにして、画像形成装置１での画像形成処理がプリント枚数分のサイクルだけ繰り返し実行される。 Thereafter, the paper P on which the superimposed toner image is electrostatically transferred is conveyed to the fixing device 60. The toner image on the paper P conveyed to the fixing device 60 receives heat and pressure by the fixing device 60 and is fixed on the paper P. Then, the paper P on which the fixed image is formed is conveyed to a paper stacking unit 45 provided in the discharge unit of the image forming apparatus 1.
On the other hand, the toner (primary transfer residual toner) adhering to the photosensitive drum 12 after the primary transfer and the toner (secondary transfer residual toner) adhering to the intermediate transfer belt 20 after the secondary transfer are respectively drum cleaner 16. , And the belt cleaner 25.
In this way, the image forming process in the image forming apparatus 1 is repeatedly executed for the number of printed sheets.

＜定着装置の構成の説明＞
次に、本実施の形態の定着装置６０について説明する。
図２および図３は本実施の形態の定着装置６０の構成を示す図であり、図２は正面図、図３は図２におけるＩＩＩ−ＩＩＩ断面図である。
まず、断面図である図３に示すように、定着装置６０は、用紙Ｐにトナー像を定着する定着部材の一例としての定着ベルト６１と、定着ベルト６１の外周側において、定着ベルト６１に対向するように配置された加圧ロール６２と、定着ベルト６１の内周側に設けられるとともに、定着ベルト６１を介して加圧ロール６２から押圧され、加圧ロール６２との間にニップ部Ｎを形成する押圧パッド６３と、定着ベルト６１の外周側に設けられ、定着ベルト６１からの用紙Ｐの剥離を補助する剥離補助部材１７３とを備えている。さらに、定着装置６０は、定着ベルト６１の外周側に設けられ、定着ベルト６１を電磁誘導加熱するＩＨヒータ８０と、定着ベルト６１の内周側に設けられ、ＩＨヒータ８０とともに定着ベルト６１を加熱する内部加熱ユニット７０と、を備えている。 <Description of Fixing Device Configuration>
Next, the fixing device 60 of the present embodiment will be described.
2 and 3 are diagrams showing the configuration of the fixing device 60 of the present embodiment, FIG. 2 is a front view, and FIG. 3 is a sectional view taken along line III-III in FIG.
First, as shown in FIG. 3, which is a cross-sectional view, the fixing device 60 faces a fixing belt 61 as an example of a fixing member that fixes a toner image on a sheet P, and the fixing belt 61 on the outer peripheral side of the fixing belt 61. The pressure roll 62 is arranged on the inner peripheral side of the fixing belt 61 and is pressed from the pressure roll 62 via the fixing belt 61, and a nip portion N is formed between the pressure roll 62 and the pressure roll 62. A pressing pad 63 to be formed and a peeling assisting member 173 provided on the outer peripheral side of the fixing belt 61 and assisting the peeling of the paper P from the fixing belt 61 are provided. Further, the fixing device 60 is provided on the outer peripheral side of the fixing belt 61 and is provided on the inner peripheral side of the fixing belt 61 by heating the fixing belt 61 together with the IH heater 80 provided by electromagnetic induction heating of the fixing belt 61. An internal heating unit.

＜定着ベルトの説明＞
図４は、定着ベルト６１の層構成を説明する図である。定着ベルト６１は、原形が円筒形状の無端のベルト部材で構成され、例えば原形（円筒形状）時の直径が３０ｍｍ、幅方向長が３７０ｍｍに形成されている。また、図４に示したように、定着ベルト６１は、内周側から、基材層６１１、基材層６１１の上に積層された導電層の一例としての導電発熱層６１２、トナー像の定着性を向上させる弾性層６１３、最上層に被覆された表面離型層６１４が積層された多層構造のベルト部材である。したがって、本実施の形態においては、定着ベルト６１の内周側において基材層６１１が内部加熱ユニット７０の後述する感温磁性部材６４と接触し、定着ベルト６１の外周側において表面離型層６１４が加圧ロール６２およびＩＨヒータ８０に対向している。 <Description of fixing belt>
FIG. 4 is a diagram illustrating the layer configuration of the fixing belt 61. The fixing belt 61 is formed of an endless belt member having an original cylindrical shape, and has a diameter of 30 mm and a length in the width direction of 370 mm in the original shape (cylindrical shape), for example. As shown in FIG. 4, the fixing belt 61 includes a base material layer 611, a conductive heat generating layer 612 as an example of a conductive layer laminated on the base material layer 611, and a toner image fixing from the inner peripheral side. It is a belt member having a multilayer structure in which an elastic layer 613 for improving the property and a surface release layer 614 coated on the uppermost layer are laminated. Therefore, in the present embodiment, the base material layer 611 comes into contact with a temperature-sensitive magnetic member 64 described later of the internal heating unit 70 on the inner peripheral side of the fixing belt 61, and the surface release layer 614 on the outer peripheral side of the fixing belt 61. Faces the pressure roll 62 and the IH heater 80.

基材層６１１は、導電発熱層６１２を支持するとともに、定着ベルト６１全体としての機械的強度を形成する耐熱性のシート状部材で構成される。また、基材層６１１は、ＩＨヒータ８０にて生成された交流磁界が感温磁性部材６４まで作用するように、磁界を通過させる物性（比透磁率、固有抵抗）を持った材質、厚さで形成される。一方、基材層６１１自身は、磁界の作用により発熱しないか、または発熱し難く構成される。
具体的には、基材層６１１として、例えば、厚さ３０〜２００μｍ（好ましくは５０〜１５０μｍ）の非磁性ステンレススチール等の非磁性金属や、厚さ６０〜２００μｍの樹脂材料等が用いられる。 The base material layer 611 is composed of a heat-resistant sheet-like member that supports the conductive heat generating layer 612 and forms the mechanical strength of the entire fixing belt 61. In addition, the base material layer 611 is made of a material having a physical property (relative magnetic permeability, specific resistance) that allows the magnetic field to pass therethrough so that the AC magnetic field generated by the IH heater 80 acts to the temperature-sensitive magnetic member 64, and the thickness. Formed with. On the other hand, the base material layer 611 itself is configured not to generate heat or hardly generate heat due to the action of a magnetic field.
Specifically, as the base material layer 611, for example, a nonmagnetic metal such as nonmagnetic stainless steel having a thickness of 30 to 200 μm (preferably 50 to 150 μm), a resin material having a thickness of 60 to 200 μm, or the like is used.

導電発熱層６１２は、ＩＨヒータ８０（図３参照）にて生成される交流磁界によって電磁誘導加熱される電磁誘導発熱体層である。すなわち、導電発熱層６１２は、ＩＨヒータ８０からの交流磁界が厚さ方向に通過することにより、渦電流を発生させる層である。
通常、ＩＨヒータ８０に交流電流を供給する励磁回路８８（図３参照）の電源として、安価に製造できる汎用電源が使用される。そのため、ＩＨヒータ８０により生成される交流磁界の周波数は、一般に、汎用電源による２０ｋＨｚ〜１００ｋＨｚとなる。それにより、導電発熱層６１２は、周波数２０ｋＨｚ〜１００ｋＨｚの交流磁界が侵入し通過するように構成される。 The conductive heating layer 612 is an electromagnetic induction heating element layer that is electromagnetically heated by an alternating magnetic field generated by the IH heater 80 (see FIG. 3). That is, the conductive heat generating layer 612 is a layer that generates an eddy current when the AC magnetic field from the IH heater 80 passes in the thickness direction.
Usually, a general-purpose power source that can be manufactured at low cost is used as a power source for the excitation circuit 88 (see FIG. 3) that supplies an alternating current to the IH heater 80. Therefore, the frequency of the alternating magnetic field generated by the IH heater 80 is generally 20 kHz to 100 kHz by a general-purpose power source. Thereby, the conductive heat generating layer 612 is configured such that an alternating magnetic field having a frequency of 20 kHz to 100 kHz enters and passes therethrough.

導電発熱層６１２に交流磁界が侵入できる領域は、交流磁界が１/ｅに減衰する領域である「表皮深さ（δ）」として規定され、次の（１）式から導かれる。（１）式において、ｆは交流磁界の周波数（例えば、２０ｋＨｚ）、ρは固有抵抗値（Ω・ｍ）、μｒは比透磁率である。
そのため、導電発熱層６１２の厚さは、周波数２０ｋＨｚ〜１００ｋＨｚの交流磁界が導電発熱層６１２に侵入し通過するように、（１）式で規定される導電発熱層６１２の表皮深さ（δ）よりも薄く構成される。また、導電発熱層６１２を構成する材料として、例えば、Ａｕ、Ａｇ、Ａｌ、Ｃｕ、Ｚｎ、Ｓｎ、Ｐｂ、Ｂｉ、Ｂｅ、Ｓｂ等の金属や、これらの金属合金が用いられる。 The region where the alternating magnetic field can enter the conductive heat generating layer 612 is defined as “skin depth (δ)”, which is a region where the alternating magnetic field attenuates to 1 / e, and is derived from the following equation (1). (1) In the equation, f is the AC magnetic field frequency (e.g., 20 kHz), [rho is resistivity (Omega · m), the mu r is the relative permeability.
Therefore, the thickness of the conductive heat generating layer 612 is determined by the skin depth (δ) of the conductive heat generating layer 612 defined by the equation (1) so that an AC magnetic field having a frequency of 20 kHz to 100 kHz penetrates and passes through the conductive heat generating layer 612. It is configured to be thinner. Further, as a material constituting the conductive heat generating layer 612, for example, metals such as Au, Ag, Al, Cu, Zn, Sn, Pb, Bi, Be, and Sb, and metal alloys thereof are used.

Figure 2016212215
Figure 2016212215

具体的には、導電発熱層６１２として、厚さ２μｍ〜２０μｍ、固有抵抗値２．７×１０−８Ω・ｍ以下の例えばＣｕ等の非磁性金属（比透磁率が概ね１の金属）が用いられる。
また、定着ベルト６１が定着設定温度まで加熱されるまでに要する時間（以下、「ウォームアップタイム」）を短縮する観点からも、導電発熱層６１２は、薄層に構成される。 Specifically, as the conductive heating layer 612, a nonmagnetic metal such as Cu (a metal having a relative permeability of about 1) having a thickness of 2 μm to 20 μm and a specific resistance value of 2.7 × 10 −8 Ω · m or less is used. Used.
Also, from the viewpoint of shortening the time required for the fixing belt 61 to be heated to the fixing set temperature (hereinafter referred to as “warm-up time”), the conductive heat generating layer 612 is configured as a thin layer.

次に、弾性層６１３は、シリコーンゴム等の耐熱性の弾性体で構成される。定着対象となる用紙Ｐに保持されるトナー像は、粉体である各色トナーが積層して形成されている。そのため、ニップ部Ｎにおいてトナー像の全体に均一に熱を供給するには、用紙Ｐ上のトナー像の凹凸に倣って定着ベルト６１表面が変形することが好ましい。そこで、弾性層６１３には、例えば厚みが１００μｍ〜６００μｍ、硬度が１０°〜３０°（ＪＩＳ−Ａ）のシリコーンゴムが用いられる。
表面離型層６１４は、用紙Ｐ上に保持された未定着トナー像と直接接触するため、離型性の高い材質が使用される。例えば、ＰＦＡ(テトラフルオロエチレンパーフルオロアルキルビニルエーテル重合体)、ＰＴＦＥ(ポリテトラフルオロエチレン)、シリコーン共重合体、またはこれらの複合層等が用いられる。表面離型層６１４の厚さとしては、薄すぎると、耐摩耗性の面で充分でなく、定着ベルト６１の寿命を短くする。その一方で、厚すぎると、定着ベルト６１の熱容量が大きくなりすぎ、ウォームアップタイムが長くなる。そこで、表面離型層６１４の厚さとして、耐摩耗性と熱容量とのバランスを考慮し、１μｍ〜５０μｍが用いられる。 Next, the elastic layer 613 is composed of a heat-resistant elastic body such as silicone rubber. The toner image held on the sheet P to be fixed is formed by laminating each color toner as powder. Therefore, in order to supply heat uniformly to the entire toner image at the nip portion N, it is preferable that the surface of the fixing belt 61 is deformed following the unevenness of the toner image on the paper P. Therefore, for example, a silicone rubber having a thickness of 100 μm to 600 μm and a hardness of 10 ° to 30 ° (JIS-A) is used for the elastic layer 613.
Since the surface release layer 614 is in direct contact with the unfixed toner image held on the paper P, a material having a high release property is used. For example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether polymer), PTFE (polytetrafluoroethylene), silicone copolymer, or a composite layer thereof is used. If the thickness of the surface release layer 614 is too thin, it is not sufficient in terms of wear resistance, and the life of the fixing belt 61 is shortened. On the other hand, if it is too thick, the heat capacity of the fixing belt 61 becomes too large and the warm-up time becomes long. Therefore, the thickness of the surface release layer 614 is 1 μm to 50 μm in consideration of the balance between wear resistance and heat capacity.

＜加圧ロールの説明＞
加圧ロール６２は、定着ベルト６１に対向するように配置され、定着ベルト６１に従動して図３の矢印Ｄ方向に、例えば１４０ｍｍ／ｓのプロセススピードで回転する。そして、加圧ロール６２と押圧パッド６３とにより定着ベルト６１を挟持した状態でニップ部Ｎを形成し、このニップ部Ｎに未定着トナー像を保持した用紙Ｐを通過させることで、熱および圧力を加えて未定着トナー像を用紙Ｐに定着する。
加圧ロール６２は、例えば直径１８ｍｍの中実のアルミニウム製コア（円柱状芯金）６２１と、コア６２１の外周面に被覆された例えば厚さ５ｍｍのシリコーンスポンジ等の耐熱性弾性体層６２２と、さらに例えば厚さ５０μｍのカーボン配合のＰＦＡ等の耐熱性樹脂被覆または耐熱性ゴム被覆による離型層６２３とが積層されて構成される。そして、加圧ロール６２は、押圧バネ６８（図２参照）により例えば２５ｋｇｆの荷重で定着ベルト６１を介して押圧パッド６３を押圧している。 <Description of pressure roll>
The pressure roll 62 is disposed so as to face the fixing belt 61 and rotates in the direction of arrow D in FIG. 3 at a process speed of 140 mm / s, for example, following the fixing belt 61. Then, a nip portion N is formed in a state where the fixing belt 61 is sandwiched between the pressure roll 62 and the pressing pad 63, and the sheet P holding the unfixed toner image is passed through the nip portion N, so that the heat and pressure To fix the unfixed toner image on the paper P.
The pressure roll 62 includes, for example, a solid aluminum core (cylindrical metal core) 621 having a diameter of 18 mm, and a heat-resistant elastic body layer 622 such as a silicone sponge having a thickness of 5 mm, which is coated on the outer peripheral surface of the core 621. Further, for example, a release layer 623 made of a heat-resistant resin coating such as PFA containing carbon having a thickness of 50 μm or a heat-resistant rubber coating is laminated. The pressure roll 62 presses the pressing pad 63 via the fixing belt 61 with a load of 25 kgf, for example, by a pressing spring 68 (see FIG. 2).

＜押圧パッドの説明＞
押圧パッド６３は、シリコーンゴムやフッ素ゴム等の弾性体やＬＣＰ、ＰＰＳ（ポリフェニレンサルファイド）等の耐熱性樹脂で構成され、図３に示すように加圧ロール６２と対向する位置にてホルダ６５に支持される。そして、押圧パッド６３は、定着ベルト６１を介して加圧ロール６２から押圧される状態で配置され、加圧ロール６２との間でニップ部Ｎを形成する。 <Description of pressing pad>
The pressing pad 63 is made of an elastic body such as silicone rubber or fluorine rubber, or a heat resistant resin such as LCP or PPS (polyphenylene sulfide), and is attached to the holder 65 at a position facing the pressure roll 62 as shown in FIG. Supported. The pressing pad 63 is disposed in a state of being pressed from the pressure roll 62 via the fixing belt 61, and forms a nip portion N with the pressure roll 62.

なお、本実施の形態では、押圧パッド６３による剥離の補助手段として、ニップ部Ｎの下流側に、剥離補助部材１７３を配置している。剥離補助部材１７３は、ニップ部Ｎよりも用紙搬送方向下流側において、定着ベルト６１に向かって延びる剥離バッフル１７１と、剥離バッフル１７１を支持するホルダ１７２とから構成される。そして、ニップ部Ｎの出口にて押圧パッド６３により用紙Ｐに形成されたカール部分を剥離バッフル１７１により支持することで、用紙Ｐが定着ベルト６１方向に向かうことを抑制する。   In the present embodiment, a peeling assisting member 173 is arranged on the downstream side of the nip portion N as a peeling assisting means by the pressing pad 63. The peeling assisting member 173 includes a peeling baffle 171 that extends toward the fixing belt 61 and a holder 172 that supports the peeling baffle 171 on the downstream side of the nip portion N in the sheet conveyance direction. Then, the curled portion formed on the paper P by the pressing pad 63 at the exit of the nip portion N is supported by the peeling baffle 171, thereby suppressing the paper P from moving toward the fixing belt 61.

＜ＩＨヒータの説明＞
続いて、ＩＨヒータ８０について説明する。本実施の形態のＩＨヒータ８０は、定着ベルト６１の導電発熱層６１２に交流磁界を作用させて電磁誘導加熱する。
図３に示すように、本実施の形態のＩＨヒータ８０は、定着ベルト６１の外周面に沿って設けられる支持体８１と、支持体８１に支持されるとともに支持体８１を介して定着ベルト６１に対向して設けられ、交流磁界を生成する磁界生成部材の一例としての励磁コイル８２と、支持体８１に支持されるとともに励磁コイル８２に対向して設けられ、励磁コイル８２にて生成された交流磁界の磁路を形成する磁心８４とを備えている。また、本実施の形態のＩＨヒータ８０は、励磁コイル８２上に設けられ、励磁コイル８２を支持体８１上に固定する弾性支持部材８３と、支持体８１に取り付けられるとともに、励磁コイル８２、弾性支持部材８３および磁心８４を囲んで設けられ、磁界を遮蔽するシールド８５と、磁心８４とシールド８５との間に設けられ、磁心８４を支持体８１側に加圧する加圧部材８６と、励磁コイル８２に交流電流を供給する励磁回路８８とを備えている。
また、本実施の形態のＩＨヒータ８０は、図３に示すように、定着ベルト６１を介して、定着ベルト６１の内周側に設けられる内部加熱ユニット７０の後述する感温磁性部材６４と対向している。 <Description of IH heater>
Next, the IH heater 80 will be described. The IH heater 80 of the present embodiment applies electromagnetic induction heating to the conductive heat generating layer 612 of the fixing belt 61 to perform electromagnetic induction heating.
As shown in FIG. 3, the IH heater 80 of the present embodiment includes a support 81 provided along the outer peripheral surface of the fixing belt 61, a support 81 supported by the support 81, and the fixing belt 61 via the support 81. And an excitation coil 82 as an example of a magnetic field generating member that generates an alternating magnetic field, and supported by the support 81 and provided opposite to the excitation coil 82, and generated by the excitation coil 82. And a magnetic core 84 that forms a magnetic path of an alternating magnetic field. In addition, the IH heater 80 of the present embodiment is provided on the excitation coil 82, and is attached to the support body 81 and the elastic support member 83 that fixes the excitation coil 82 on the support body 81. A shield 85 that surrounds the support member 83 and the magnetic core 84, shields the magnetic field, a pressure member 86 that is provided between the magnetic core 84 and the shield 85, and pressurizes the magnetic core 84 toward the support 81, and an excitation coil And an exciting circuit 88 for supplying an alternating current to 82.
Further, as shown in FIG. 3, the IH heater 80 of the present embodiment is opposed to a temperature-sensitive magnetic member 64 described later of an internal heating unit 70 provided on the inner peripheral side of the fixing belt 61 via the fixing belt 61. doing.

支持体８１は、定着ベルト６１の移動方向に直交する方向（以下では、定着ベルト６１の幅方向という）を長手方向とし、定着ベルト６１の全幅に亘って定着ベルト６１と対向して設けられる。
さらに、支持体８１は、図３に示すように、断面が定着ベルト６１の表面形状に沿って湾曲した形状で形成され、励磁コイル８２を支持する上部面が定着ベルト６１の表面と予め定められた間隙（例えば、０．５ｍｍ〜２ｍｍ）を保つように設定されている。
支持体８１を構成する材質としては、例えば、ポリカーボネート、ポリエーテルサルフォン、ＰＰＳ（ポリフェニレンサルファイド）等の耐熱性樹脂、またはこれらにガラス繊維を混合した耐熱性樹脂、耐熱ガラス等の耐熱性のある非磁性材料が用いられる。 The support 81 is provided so as to face the fixing belt 61 over the entire width of the fixing belt 61 with the direction perpendicular to the moving direction of the fixing belt 61 (hereinafter referred to as the width direction of the fixing belt 61) as the longitudinal direction.
Further, as shown in FIG. 3, the support 81 is formed in a shape whose cross section is curved along the surface shape of the fixing belt 61, and the upper surface supporting the exciting coil 82 is predetermined as the surface of the fixing belt 61. The gap is set so as to maintain a gap (for example, 0.5 mm to 2 mm).
Examples of the material constituting the support 81 include heat-resistant resins such as polycarbonate, polyethersulfone, and PPS (polyphenylene sulfide), or heat-resistant resins obtained by mixing glass fibers with these materials, and heat-resistant glass. A non-magnetic material is used.

励磁コイル８２は、相互に絶縁された例えば直径０．１７ｍｍの銅線材を例えば９０本束ねたリッツ線が、定着ベルト６１の幅方向が長手方向となるような長円形状や楕円形状、長方形状等の中空きの閉ループ状に巻かれて構成される。そして、励磁コイル８２に励磁回路８８から予め定めた周波数の交流電流が供給されることにより、励磁コイル８２の周囲には、閉ループ状に巻かれたリッツ線を中心とする交流磁界が生成される。励磁回路８８から励磁コイル８２に供給される交流電流の周波数は、一般に、上記した汎用電源により生成される２０ｋＨｚ〜１００ｋＨｚが用いられる。
弾性支持部材８３は、例えばシリコーンゴム等やフッ素ゴム等の弾性体で構成されたシート状部材である。弾性支持部材８３は、励磁コイル８２が支持体８１に密着して固定されるように、励磁コイル８２を支持体８１に対して押圧するように設定されている。 The exciting coil 82 is composed of, for example, 90 litz wires that are bundled with, for example, 90 copper wires having a diameter of 0.17 mm and are formed in an oval shape, an elliptical shape, or a rectangular shape in which the width direction of the fixing belt 61 is the longitudinal direction. It is configured to be wound in a closed loop with a hollow space. Then, when an alternating current having a predetermined frequency is supplied to the exciting coil 82 from the exciting circuit 88, an alternating magnetic field centered around a litz wire wound in a closed loop is generated around the exciting coil 82. . Generally, the frequency of the alternating current supplied from the excitation circuit 88 to the excitation coil 82 is 20 kHz to 100 kHz generated by the general-purpose power source.
The elastic support member 83 is a sheet-like member made of an elastic body such as silicone rubber or fluorine rubber. The elastic support member 83 is set to press the excitation coil 82 against the support 81 so that the excitation coil 82 is fixed in close contact with the support 81.

磁心８４は、複数が隣接する磁心８４との間に間隙を有するように、定着ベルト６１の幅方向に複数が並んで設けられる。そして、それぞれの磁心８４は、断面が定着ベルト６１の断面形状に沿って湾曲するとともに、定着ベルト６１の移動方向を長手方向とする弓状の形状を有している。そして、それぞれの磁心８４は、支持体８１により位置決めされている。
また、図３に示すように、定着ベルト６１の移動方向に沿った磁心８４の長さは、後述する感温磁性部材６４の定着ベルト６１の移動方向に沿った長さよりも短く構成される。これにより、磁心８４から放射される磁力線Ｈ（後述する図６（ａ）〜図６（ｂ）参照）のＩＨヒータ８０周辺への漏洩が減り、力率が向上する。さらには、定着装置６０を構成する金属製部材への電磁誘導を抑え、定着ベルト６１（導電発熱層６１２）での発熱効率が高まる。 A plurality of magnetic cores 84 are provided side by side in the width direction of the fixing belt 61 so that a plurality of magnetic cores 84 have a gap between adjacent magnetic cores 84. Each magnetic core 84 has a cross-sectional shape that is curved along the cross-sectional shape of the fixing belt 61, and has an arcuate shape in which the moving direction of the fixing belt 61 is a longitudinal direction. Each magnetic core 84 is positioned by a support body 81.
As shown in FIG. 3, the length of the magnetic core 84 along the moving direction of the fixing belt 61 is configured to be shorter than the length along the moving direction of the fixing belt 61 of the temperature-sensitive magnetic member 64 described later. Thereby, the leakage of the magnetic field lines H radiated from the magnetic core 84 (see FIGS. 6A to 6B described later) to the periphery of the IH heater 80 is reduced, and the power factor is improved. Furthermore, electromagnetic induction to the metal member constituting the fixing device 60 is suppressed, and the heat generation efficiency of the fixing belt 61 (conductive heat generation layer 612) is increased.

磁心８４を形成する材料としては、例えばソフトフェライト、フェライト樹脂、非晶質合金（アモルファス合金）、やパーマロイ、感温磁性合金等の高透磁率の酸化物や合金材質で構成される強磁性体が用いられる。磁心８４は、励磁コイル８２にて生成された交流磁界による磁力線Ｈ（磁束）を内部に誘導し、磁心８４から支持体８１を介して定着ベルト６１を横切って感温磁性部材６４方向に向かい、感温磁性部材６４の中を通過して支持体８１を介して磁心８４に戻るといった磁力線Ｈの通路（磁路）を形成する。すなわち、励磁コイル８２にて生成された交流磁界が磁心８４の内部と感温磁性部材６４の内部とを通過するように構成して、磁力線Ｈが定着ベルト６１と励磁コイル８２とを内部に包み込むような閉磁路を形成する。それにより、励磁コイル８２にて生成された交流磁界の磁力線Ｈは、定着ベルト６１のうち磁心８４と対向する領域に集中される。   As a material for forming the magnetic core 84, for example, a ferromagnetic material composed of a high permeability oxide or alloy material such as soft ferrite, ferrite resin, amorphous alloy (amorphous alloy), permalloy, temperature-sensitive magnetic alloy, etc. Is used. The magnetic core 84 induces a magnetic force line H (magnetic flux) due to the alternating magnetic field generated by the exciting coil 82, travels from the magnetic core 84 to the direction of the temperature-sensitive magnetic member 64 across the fixing belt 61 via the support 81, A path (magnetic path) of magnetic lines of force H passing through the temperature-sensitive magnetic member 64 and returning to the magnetic core 84 via the support 81 is formed. That is, the AC magnetic field generated by the excitation coil 82 is configured to pass through the inside of the magnetic core 84 and the inside of the temperature-sensitive magnetic member 64, and the magnetic field line H wraps the fixing belt 61 and the excitation coil 82 inside. Such a closed magnetic circuit is formed. As a result, the magnetic field lines H of the alternating magnetic field generated by the exciting coil 82 are concentrated on the region of the fixing belt 61 facing the magnetic core 84.

＜内部加熱ユニットの説明＞
続いて、内部加熱ユニット７０の構成について説明する。図５は、本実施の形態の内部加熱ユニット７０の構成を示した斜視図である。
図３および図５に示すように、本実施の形態の内部加熱ユニット７０は、定着ベルト６１の内周側において定着ベルト６１に非接触状態で配置され、ＩＨヒータ８０の励磁コイル８２により生成された交流磁界を誘導して磁路を形成する感温磁性部材６４を備えている。また、内部加熱ユニット７０は、定着ベルト６１の内周面に接触して設けられ、定着ベルト６１の温度を検知する温度検知センサ７１、７２と、感温磁性部材６４に設けられた孔６４５を介して定着ベルト６１の内周面に対向し、感温磁性部材６４が高温になった場合に、汎用電源から励磁回路８８への通電を遮断するサーモスタット７３と、を備えている。さらに、内部加熱ユニット７０は、感温磁性部材６４、温度検知センサ７１、７２およびサーモスタット７３を支持するホルダ６５を備えている。 <Description of internal heating unit>
Next, the configuration of the internal heating unit 70 will be described. FIG. 5 is a perspective view showing the configuration of the internal heating unit 70 of the present embodiment.
As shown in FIGS. 3 and 5, the internal heating unit 70 of the present embodiment is disposed in a non-contact state with the fixing belt 61 on the inner peripheral side of the fixing belt 61, and is generated by the excitation coil 82 of the IH heater 80. A temperature-sensitive magnetic member 64 that induces an alternating magnetic field to form a magnetic path is provided. The internal heating unit 70 is provided in contact with the inner peripheral surface of the fixing belt 61, and includes temperature detection sensors 71 and 72 that detect the temperature of the fixing belt 61 and a hole 645 provided in the temperature-sensitive magnetic member 64. And a thermostat 73 that opposes the inner peripheral surface of the fixing belt 61 and interrupts energization from the general-purpose power supply to the excitation circuit 88 when the temperature-sensitive magnetic member 64 becomes hot. Furthermore, the internal heating unit 70 includes a holder 65 that supports the temperature-sensitive magnetic member 64, the temperature detection sensors 71 and 72, and the thermostat 73.

＜感温磁性部材の説明＞
次に、感温磁性部材６４について説明する。図３に示すように、感温磁性部材６４は、定着ベルト６１の内周面に倣った円弧形状で形成され、外周面が定着ベルト６１の内周面とは予め定めた間隙（例えば、０．５ｍｍ〜１．５ｍｍ）を有するように近接し、且つ定着ベルト６１に対して非接触で配置される。感温磁性部材６４を定着ベルト６１に近接して配置することで、感温磁性部材６４の温度は、定着ベルト６１の温度に対応して変化するようになっている。一方、感温磁性部材６４を定着ベルト６１に非接触で配置することで、画像形成装置１のメインスイッチがオンされ、定着ベルト６１が定着設定温度まで加熱される際に、定着ベルト６１の熱が感温磁性部材６４に流入するのを抑制して、ウォームアップタイムの短縮を図ることが可能となる。 <Description of temperature-sensitive magnetic member>
Next, the temperature-sensitive magnetic member 64 will be described. As shown in FIG. 3, the temperature-sensitive magnetic member 64 is formed in an arc shape that follows the inner peripheral surface of the fixing belt 61, and the outer peripheral surface is a predetermined gap (for example, 0) from the inner peripheral surface of the fixing belt 61. .. 5 mm to 1.5 mm) and close to the fixing belt 61 without contact. By arranging the temperature-sensitive magnetic member 64 close to the fixing belt 61, the temperature of the temperature-sensitive magnetic member 64 changes in accordance with the temperature of the fixing belt 61. On the other hand, by disposing the temperature-sensitive magnetic member 64 on the fixing belt 61 in a non-contact manner, the main switch of the image forming apparatus 1 is turned on and the fixing belt 61 is heated when the fixing belt 61 is heated to the fixing set temperature. Can be prevented from flowing into the temperature-sensitive magnetic member 64, and the warm-up time can be shortened.

そして、感温磁性部材６４は、その磁気特性の透磁率が急変する温度である「透磁率変化開始温度」が、各色トナー像が溶融する定着設定温度以上であって、定着ベルト６１の弾性層６１３や表面離型層６１４の耐熱温度よりも低い温度範囲内に設定された材質で構成される。すなわち、感温磁性部材６４は、定着設定温度を含む温度領域において強磁性と非磁性（常磁性）との間を可逆的に変化する特性（「感温磁性」）を有する材質で構成される。それにより、感温磁性部材６４は、強磁性を呈する透磁率変化開始温度以下の温度範囲において磁路形成部材として機能し、ＩＨヒータ８０にて生成され定着ベルト６１を透過した磁力線を内部に誘導して、感温磁性部材６４の内部を通過する磁路を形成する。そして、感温磁性部材６４は、定着ベルト６１とＩＨヒータ８０の励磁コイル８２（後段の図６参照）とを内部に包み込むような閉磁路を形成する。一方、透磁率変化開始温度を超える温度範囲においては、感温磁性部材６４は、ＩＨヒータ８０にて生成され定着ベルト６１を透過した磁力線を、感温磁性部材６４の厚さ方向に横切るように透過させる。それにより、ＩＨヒータ８０にて生成され定着ベルト６１を透過した磁力線は、感温磁性部材６４を透過してＩＨヒータ８０に戻る磁路を形成する。   The temperature-sensitive magnetic member 64 has a “permeability change start temperature”, which is a temperature at which the magnetic permeability of the magnetic characteristics changes suddenly, equal to or higher than a fixing set temperature at which each color toner image melts, and the elastic layer of the fixing belt 61. It is comprised with the material set in the temperature range lower than the heat-resistant temperature of 613 and the surface release layer 614. FIG. That is, the temperature-sensitive magnetic member 64 is made of a material having a characteristic (“temperature-sensitive magnetism”) that reversibly changes between ferromagnetic and non-magnetic (paramagnetic) in a temperature range including the fixing set temperature. . As a result, the temperature-sensitive magnetic member 64 functions as a magnetic path forming member in a temperature range that is equal to or lower than the permeability change start temperature exhibiting ferromagnetism, and induces the magnetic field lines generated by the IH heater 80 and transmitted through the fixing belt 61 to the inside. Thus, a magnetic path passing through the inside of the temperature-sensitive magnetic member 64 is formed. The temperature-sensitive magnetic member 64 forms a closed magnetic path that encloses the fixing belt 61 and the exciting coil 82 of the IH heater 80 (see FIG. 6 at a later stage). On the other hand, in the temperature range exceeding the permeability change start temperature, the temperature-sensitive magnetic member 64 crosses the magnetic field lines generated by the IH heater 80 and transmitted through the fixing belt 61 in the thickness direction of the temperature-sensitive magnetic member 64. Make it transparent. Thereby, the magnetic lines of force generated by the IH heater 80 and transmitted through the fixing belt 61 form a magnetic path that passes through the temperature-sensitive magnetic member 64 and returns to the IH heater 80.

なお、ここでの「透磁率変化開始温度」とは、透磁率（例えば、ＪＩＳ Ｃ２５３１で測定される透磁率）が連続的に低下を開始する温度であり、例えば感温磁性部材６４等の部材を透過する磁束量（磁力線の数）が変化し始める温度点をいう。したがって、透磁率変化開始温度は、物質が磁性を消失する温度であるキュリー点に近い温度となるが、キュリー点とは異なる概念を有するものである。   The “permeability change start temperature” here is a temperature at which the magnetic permeability (for example, the magnetic permeability measured by JIS C2531) starts to decrease continuously. For example, a member such as the temperature-sensitive magnetic member 64 This is the temperature point at which the amount of magnetic flux that passes through (the number of lines of magnetic force) starts to change. Therefore, the permeability change start temperature is close to the Curie point, which is the temperature at which the substance loses magnetism, but has a different concept from the Curie point.

感温磁性部材６４に用いる材質としては、定着設定温度として用いられる例えば１４０℃〜２４０℃の範囲内に透磁率変化開始温度が設定された例えばＦｅ−Ｎｉ合金（パーマロイ）等の二元系整磁鋼やＦｅ−Ｎｉ−Ｃｒ合金等の三元系の整磁鋼等が用いられる。例えば、Ｆｅ−Ｎｉの二元系整磁鋼においては約Ｆｅ６４％、Ｎｉ３６％（原子数比）とすることで２２５℃前後に透磁率変化開始温度を設定することができる。このようなパーマロイや整磁鋼等の金属合金等は、成型性や加工性に優れ、伝熱性も高く安価である等の理由から、感温磁性部材６４に適する。その他の材質としては、Ｆｅ、Ｎｉ、Ｓｉ、Ｂ、Ｎｂ、Ｃｕ、Ｚｒ、Ｃｏ、Ｃｒ、Ｖ、Ｍｎ、Ｍｏ等からなる金属合金が用いられる。
また、感温磁性部材６４は、ＩＨヒータ８０により生成された交流磁界（磁力線）に対する表皮深さδ（上記（１）式参照）よりも厚い厚さで形成される。具体的には、例えばＦｅ−Ｎｉ合金を用いた場合には２００μｍ〜８００μｍ程度に設定される。 The material used for the temperature-sensitive magnetic member 64 is, for example, a binary system such as an Fe—Ni alloy (permalloy) in which a magnetic permeability change start temperature is set within a range of 140 ° C. to 240 ° C. used as a fixing set temperature. A ternary shunt steel such as magnetic steel or Fe—Ni—Cr alloy is used. For example, in the Fe-Ni binary magnetic shunt steel, the permeability change start temperature can be set around 225 ° C. by setting it to about Fe 64% and Ni 36% (atomic ratio). Such metal alloys such as permalloy and magnetic shunt steel are suitable for the temperature-sensitive magnetic member 64 because they are excellent in moldability and workability, have high heat conductivity, and are inexpensive. As other materials, a metal alloy made of Fe, Ni, Si, B, Nb, Cu, Zr, Co, Cr, V, Mn, Mo or the like is used.
Further, the temperature-sensitive magnetic member 64 is formed with a thickness greater than the skin depth δ (see the above formula (1)) with respect to the AC magnetic field (lines of magnetic force) generated by the IH heater 80. Specifically, for example, when an Fe—Ni alloy is used, the thickness is set to about 200 μm to 800 μm.

＜ホルダの説明＞
図３および図５に示すように、ホルダ６５は、定着ベルト６１の内周側に設けられ、押圧パッド６３、感温磁性部材６４、温度検知センサ７１、７２およびサーモスタット７３を支持する。そして、ホルダ６５は、押圧パッド６３が加圧ロール６２からの押圧力を受けた状態で、押圧パッド６３の撓み量が一定量以下となるように、剛性の高い材料で構成される。それにより、ニップ部Ｎにおける定着ベルト６１の幅方向の圧力（ニップ圧）の均一性を維持している。さらに、本実施の形態の定着装置６０では、電磁誘導を用いて定着ベルト６１を加熱する構成を採用していることから、ホルダ６５は、誘導磁界に影響を与えないか、または与え難い材料であり、かつ、誘導磁界から影響を受けないか、または受け難い材料で構成される。例えば、ガラス混入ＰＰＳ（ポリフェニレンサルファイド）等の耐熱性樹脂や、例えばＡｌ、Ｃｕ、Ａｇ等の非磁性金属材料等が用いられる。 <Description of holder>
As shown in FIGS. 3 and 5, the holder 65 is provided on the inner peripheral side of the fixing belt 61 and supports the pressing pad 63, the temperature-sensitive magnetic member 64, the temperature detection sensors 71 and 72, and the thermostat 73. The holder 65 is made of a material having high rigidity so that the bending amount of the pressing pad 63 becomes a certain amount or less in a state where the pressing pad 63 receives the pressing force from the pressing roll 62. Thereby, the uniformity of the pressure (nip pressure) in the width direction of the fixing belt 61 at the nip portion N is maintained. Further, since the fixing device 60 of the present embodiment employs a configuration in which the fixing belt 61 is heated using electromagnetic induction, the holder 65 is made of a material that does not affect or hardly gives influence to the induced magnetic field. It is made of a material that is not affected or hardly affected by the induced magnetic field. For example, a heat-resistant resin such as glass-mixed PPS (polyphenylene sulfide) or a nonmagnetic metal material such as Al, Cu, or Ag is used.

＜温度検知センサの説明＞
温度検知センサ７１、７２は、定着ベルト６１の内周面に接触して設けられ、定着ベルト６１の温度を検知する。本実施の形態では、定着ベルト６１の幅方向中央部（ニップ部Ｎにおける最小通紙領域に対応する位置）に一方の温度検知センサ７１が配置され、定着ベルト６１における幅方向の一方の端部（ニップ部Ｎにおける最小通紙領域よりも端部側に対応する位置）に他方の温度検知センサ７２が配置されている。
なお、それぞれの温度検知センサ７１、７２は、図５に示すように、ばね部材７１ａ、７２ａを介してホルダ６５によって支持されている。そして、それぞれの温度検知センサ７１、７２は、ばね部材７１ａ、７２ａにより定着ベルト６１の内周面に押圧されるようになっている。 <Explanation of temperature detection sensor>
The temperature detection sensors 71 and 72 are provided in contact with the inner peripheral surface of the fixing belt 61 and detect the temperature of the fixing belt 61. In the present embodiment, one temperature detection sensor 71 is disposed at the center in the width direction of the fixing belt 61 (a position corresponding to the minimum sheet passing area in the nip portion N), and one end of the fixing belt 61 in the width direction. The other temperature detection sensor 72 is disposed (a position corresponding to the end side of the minimum sheet passing region in the nip portion N).
In addition, as shown in FIG. 5, each temperature detection sensor 71 and 72 is supported by the holder 65 via the spring members 71a and 72a. The temperature detection sensors 71 and 72 are pressed against the inner peripheral surface of the fixing belt 61 by spring members 71a and 72a.

温度検知センサ７１、７２としては、例えばサーミスタ式の温度検知センサを用いることができる。温度検知センサ７１、７２として使用するサーミスタ式の温度検知センサとしては、例えば、温度の上昇に対して抵抗が減少するＮＴＣ（Negative Temperature Coefficient）サーミスタ、温度の上昇に対して抵抗が増加するＰＴＣ（Positive Temperature Coefficient）サーミスタ、温度の上昇に対して抵抗が減少するが特定の温度範囲で感度が良好となるＣＴＲ（Critical Temperature Resistor）サーミスタ等の種々のサーミスタを使用することができる。   As the temperature detection sensors 71 and 72, for example, a thermistor type temperature detection sensor can be used. As the thermistor type temperature detection sensors used as the temperature detection sensors 71 and 72, for example, an NTC (Negative Temperature Coefficient) thermistor whose resistance decreases as the temperature rises, or a PTC ( Various thermistors such as a positive temperature coefficient (CTR) thermistor and a CTR (Critical Temperature Resistor) thermistor whose resistance decreases with an increase in temperature but has a good sensitivity in a specific temperature range can be used.

そして、詳細については後述するが、本実施の形態では、通常、温度検知センサ７１、７２により検知される定着ベルト６１の温度に応じて、励磁回路８８（図３参照）を介して励磁コイル８２（図３参照）に供給する電力を決定している。   Although details will be described later, in the present embodiment, the exciting coil 82 is normally connected via the exciting circuit 88 (see FIG. 3) according to the temperature of the fixing belt 61 detected by the temperature detecting sensors 71 and 72. The power supplied to (see FIG. 3) is determined.

＜サーモスタットの説明＞
サーモスタット７３は、感温磁性部材６４に設けられた孔６４５を介して定着ベルト６１に対向し、感温磁性部材６４の温度が過度に上昇した場合に、励磁回路８８への電力の供給を遮断するために設けられる。
サーモスタット７３は、例えば、熱膨張率の異なる２種の金属板が積層されたバイメタルにより構成される。具体的には、サーモスタット７３は、例えば、鉄とニッケルとの合金（インバー）からなる第１の金属板と、鉄とニッケルとを含む合金にクロムやマンガン等の金属を添加した第２の金属板とが積層されたバイメタル等により構成される。
そして、サーモスタット７３は、感温磁性部材６４が過度に高温になった場合に第１の金属板と第２の金属板との熱膨張率の差によって変形することにより、励磁回路８８への電力の供給を遮断する。 <Explanation of thermostat>
The thermostat 73 faces the fixing belt 61 through a hole 645 provided in the temperature-sensitive magnetic member 64, and cuts off the power supply to the excitation circuit 88 when the temperature of the temperature-sensitive magnetic member 64 rises excessively. To be provided.
The thermostat 73 is made of, for example, a bimetal in which two types of metal plates having different thermal expansion coefficients are stacked. Specifically, the thermostat 73 is, for example, a first metal plate made of an alloy (invar) of iron and nickel, and a second metal obtained by adding a metal such as chromium or manganese to an alloy containing iron and nickel. It is composed of bimetal or the like on which plates are laminated.
The thermostat 73 deforms due to the difference in thermal expansion coefficient between the first metal plate and the second metal plate when the temperature-sensitive magnetic member 64 becomes excessively high in temperature, thereby supplying power to the excitation circuit 88. Shut off the supply.

＜定着ベルトの駆動機構の説明＞
次に、定着ベルト６１の駆動機構について説明する。
正面図である図２に示したように、内部加熱ユニット７０のホルダ６５（図３参照）の軸方向両端部には、定着ベルト６１の両端部の断面形状を円形に維持しながら定着ベルト６１を周方向に回転駆動するエンドキャップ部材６７が固定されている。そして、定着ベルト６１は、両端部からエンドキャップ部材６７を介した回転駆動力を直接的に受けて、例えば１４０ｍｍ／ｓのプロセススピードで図３の矢印Ｃ方向に回転移動する。
エンドキャップ部材６７を構成する材質としては、機械的強度や耐熱性の高い所謂エンジニアリングプラスチックスが用いられる。例えば、エンドキャップ部材６７を構成する材質としては、フェノール樹脂、ポリイミド樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ＰＥＥＫ樹脂、ＰＥＳ樹脂、ＰＰＳ樹脂、ＬＣＰ樹脂等が用いられる。 <Description of Fixing Belt Drive Mechanism>
Next, a driving mechanism for the fixing belt 61 will be described.
As shown in FIG. 2 which is a front view, the fixing belt 61 is provided at both ends in the axial direction of the holder 65 (see FIG. 3) of the internal heating unit 70 while keeping the cross-sectional shape of both ends of the fixing belt 61 circular. An end cap member 67 that rotates and rotates in the circumferential direction is fixed. The fixing belt 61 directly receives the rotational driving force from both ends via the end cap member 67, and rotates and moves in the direction of arrow C in FIG. 3 at a process speed of 140 mm / s, for example.
As a material constituting the end cap member 67, so-called engineering plastics having high mechanical strength and heat resistance are used. For example, as a material constituting the end cap member 67, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, LCP resin, or the like is used.

そして、図２に示すように、定着装置６０では、駆動モータ９０からの回転駆動力が伝達ギヤ９１、９２を介してシャフト９３に伝達され、シャフト９３に結合された伝達ギヤ９４、９５から両エンドキャップ部材６７に伝達される。それによって、エンドキャップ部材６７から定着ベルト６１に回転駆動力が伝わり、エンドキャップ部材６７と定着ベルト６１とが一体となって回転駆動される。
このように、定着ベルト６１が定着ベルト６１の両端部から駆動力を直接受けて回転するので、定着ベルト６１は安定して回転する。 As shown in FIG. 2, in the fixing device 60, the rotational driving force from the drive motor 90 is transmitted to the shaft 93 via the transmission gears 91 and 92, and both are transmitted from the transmission gears 94 and 95 coupled to the shaft 93. It is transmitted to the end cap member 67. As a result, a rotational driving force is transmitted from the end cap member 67 to the fixing belt 61, and the end cap member 67 and the fixing belt 61 are integrally rotated.
Thus, the fixing belt 61 rotates by receiving the driving force directly from both ends of the fixing belt 61, so that the fixing belt 61 rotates stably.

＜定着ベルトが発熱する状態の説明＞
引き続いて、ＩＨヒータ８０により生成された交流磁界によって定着ベルト６１が発熱する状態を説明する。図６（ａ）〜（ｂ）は、ＩＨヒータ８０により生成された磁力線の状態を示した図であって、図６（ａ）は、定着ベルト６１（感温磁性部材６４）の温度が透磁率変化開始温度以下の温度範囲にある場合の磁力線（Ｈ）の状態を示し、図６（ｂ）は、定着ベルト６１（感温磁性部材６４）の温度が透磁率変化開始温度を超えた温度範囲にある場合の磁力線（Ｈ）の状態を示している。 <Description of the state in which the fixing belt generates heat>
Subsequently, a state in which the fixing belt 61 generates heat by the alternating magnetic field generated by the IH heater 80 will be described. FIGS. 6A and 6B are diagrams showing the state of the lines of magnetic force generated by the IH heater 80. FIG. 6A shows the temperature of the fixing belt 61 (temperature-sensitive magnetic member 64). FIG. 6B shows the state of the lines of magnetic force (H) in the temperature range below the magnetic permeability change start temperature, and FIG. 6B shows the temperature at which the temperature of the fixing belt 61 (temperature-sensitive magnetic member 64) exceeds the magnetic permeability change start temperature. The state of the lines of magnetic force (H) in the range is shown.

まず、上記したように、感温磁性部材６４の透磁率変化開始温度は、各色トナー像を定着する定着設定温度以上であって定着ベルト６１の耐熱温度以下となる温度範囲内（例えば、２２０℃〜２４０℃）に設定されている。そして、定着ベルト６１の温度が透磁率変化開始温度以下の状態にある場合には、定着ベルト６１に近接する感温磁性部材６４の温度も定着ベルト６１の温度に対応して、透磁率変化開始温度以下となる。そのため、感温磁性部材６４は強磁性を呈するので、ＩＨヒータ８０により生成された交流磁界の磁力線Ｈは、定着ベルト６１を透過した後、感温磁性部材６４の内部を広がり方向に沿って通過する磁路を形成する。ここでの「広がり方向」とは、感温磁性部材６４の厚さ方向と直交する方向を意味する。   First, as described above, the permeability change start temperature of the temperature-sensitive magnetic member 64 is within a temperature range that is equal to or higher than the set fixing temperature for fixing each color toner image and equal to or lower than the heat resistance temperature of the fixing belt 61 (for example, 220 ° C. ˜240 ° C.). When the temperature of the fixing belt 61 is equal to or lower than the magnetic permeability change start temperature, the temperature of the temperature-sensitive magnetic member 64 adjacent to the fixing belt 61 is also started corresponding to the temperature of the fixing belt 61. Below temperature. Therefore, since the temperature-sensitive magnetic member 64 exhibits ferromagnetism, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 pass through the fixing belt 61 and then pass through the inside of the temperature-sensitive magnetic member 64 along the spreading direction. To form a magnetic path. Here, the “spreading direction” means a direction orthogonal to the thickness direction of the temperature-sensitive magnetic member 64.

図６（ａ）に示すように、定着ベルト６１の温度が透磁率変化開始温度以下の温度範囲にある場合には、ＩＨヒータ８０により生成された交流磁界の磁力線Ｈは、定着ベルト６１を交差して透過し、感温磁性部材６４の内部を広がり方向（厚さ方向と直交する方向）に沿って通過する磁路を形成する。そのため、定着ベルト６１の導電発熱層６１２を横切る領域での単位面積あたりの磁力線Ｈの数（磁束密度）は多くなる。   As shown in FIG. 6A, when the temperature of the fixing belt 61 is in a temperature range equal to or lower than the magnetic permeability change start temperature, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 cross the fixing belt 61. Thus, a magnetic path that passes through the inside of the temperature-sensitive magnetic member 64 along the spreading direction (direction orthogonal to the thickness direction) is formed. Therefore, the number of magnetic field lines H (magnetic flux density) per unit area in the region crossing the conductive heat generating layer 612 of the fixing belt 61 increases.

すなわち、ＩＨヒータ８０の磁心８４から磁力線Ｈが放射されて定着ベルト６１の導電発熱層６１２を横切る領域Ｒ１、Ｒ２を通過した後、磁力線Ｈは強磁性体である感温磁性部材６４の内部に誘導される。そのため、定着ベルト６１の導電発熱層６１２を厚さ方向に横切る磁力線Ｈは感温磁性部材６４の内部に進入するように集中し、領域Ｒ１、Ｒ２での磁束密度は高くなる。また、感温磁性部材６４の内部を広がり方向に沿って通過した磁力線Ｈが再び磁心８４に戻るに際しても、導電発熱層６１２を厚さ方向に横切る領域Ｒ３では、感温磁性部材６４内の磁位の低い部分から集中して磁心８４に向けて発生する。そのため、定着ベルト６１の導電発熱層６１２を厚さ方向に横切る磁力線Ｈは、感温磁性部材６４から集中して磁心８４に向かうこととなり、領域Ｒ３での磁束密度も高くなる。   That is, after the magnetic field lines H are radiated from the magnetic core 84 of the IH heater 80 and pass through the regions R1 and R2 across the conductive heat generating layer 612 of the fixing belt 61, the magnetic field lines H enter the inside of the temperature-sensitive magnetic member 64 which is a ferromagnetic material. Be guided. Therefore, the magnetic field lines H crossing the conductive heat generating layer 612 of the fixing belt 61 in the thickness direction are concentrated so as to enter the inside of the temperature-sensitive magnetic member 64, and the magnetic flux density in the regions R1 and R2 increases. Further, even when the magnetic field lines H that have passed through the inside of the temperature-sensitive magnetic member 64 along the spreading direction return to the magnetic core 84 again, in the region R3 that crosses the conductive heating layer 612 in the thickness direction, the magnetic field in the temperature-sensitive magnetic member 64 is increased. It is concentrated toward the magnetic core 84 from the lower part. Therefore, the magnetic force lines H that cross the conductive heat generating layer 612 of the fixing belt 61 in the thickness direction are concentrated from the temperature-sensitive magnetic member 64 toward the magnetic core 84, and the magnetic flux density in the region R3 is also increased.

磁力線Ｈが厚さ方向に横切る定着ベルト６１の導電発熱層６１２では、単位面積当たりの磁力線Ｈの数（磁束密度）の変化量に比例した渦電流Ｉが発生する。それにより、図６（ａ）に示したように、磁束密度の変化量が大きい領域Ｒ１、Ｒ２および領域Ｒ３では、大きな渦電流Ｉが発生する。導電発熱層６１２に生じた渦電流Ｉは、導電発熱層６１２の固有抵抗値Ｒと渦電流Ｉの二乗の積であるジュール熱Ｗ（Ｗ＝Ｉ２Ｒ）を発生させる。それにより、大きな渦電流Ｉが発生した導電発熱層６１２では、大きなジュール熱Ｗが発生する。
このように、定着ベルト６１の温度が透磁率変化開始温度以下の温度範囲にある場合には、磁力線Ｈが導電発熱層６１２を横切る領域Ｒ１、Ｒ２や領域Ｒ３において大きな熱が発生する。それにより、定着ベルト６１は加熱される。 In the conductive heating layer 612 of the fixing belt 61 where the magnetic lines H cross in the thickness direction, an eddy current I proportional to the amount of change in the number of magnetic lines H per unit area (magnetic flux density) is generated. Accordingly, as shown in FIG. 6A, a large eddy current I is generated in the regions R1, R2 and R3 where the amount of change in magnetic flux density is large. The eddy current I generated in the conductive heat generation layer 612 generates Joule heat W (W = I 2 R), which is the product of the specific resistance value R of the conductive heat generation layer 612 and the square of the eddy current I. Thereby, a large Joule heat W is generated in the conductive heat generating layer 612 where the large eddy current I is generated.
As described above, when the temperature of the fixing belt 61 is in the temperature range equal to or lower than the permeability change start temperature, large heat is generated in the regions R1 and R2 and the region R3 where the magnetic lines H cross the conductive heat generating layer 612. Thereby, the fixing belt 61 is heated.

ところで、本実施の形態の定着装置６０では、定着ベルト６１の内周面側において定着ベルト６１に近接させて感温磁性部材６４を配置している。これにより、励磁コイル８２にて生成された磁力線Ｈを内部に誘導する磁心８４と、定着ベルト６１を厚さ方向に横切って透過した磁力線Ｈを内部に誘導する感温磁性部材６４とが近接した構成を実現している。このため、ＩＨヒータ８０（励磁コイル８２）により生成された交流磁界は、磁路が短いループを形成するので、磁路内での磁束密度や磁気結合度は高まる。それにより、定着ベルト６１の温度が透磁率変化開始温度以下の温度範囲にある場合、定着ベルト６１にはさらに効率的に熱が発生する。   By the way, in the fixing device 60 of the present embodiment, the temperature-sensitive magnetic member 64 is disposed in the vicinity of the fixing belt 61 on the inner peripheral surface side of the fixing belt 61. As a result, the magnetic core 84 that guides the magnetic lines of force H generated by the exciting coil 82 and the temperature-sensitive magnetic member 64 that guides the magnetic lines of force H that have passed through the fixing belt 61 in the thickness direction are close to each other. The configuration is realized. For this reason, since the alternating magnetic field generated by the IH heater 80 (excitation coil 82) forms a loop with a short magnetic path, the magnetic flux density and the magnetic coupling degree in the magnetic path increase. Accordingly, when the temperature of the fixing belt 61 is in a temperature range equal to or lower than the magnetic permeability change start temperature, heat is more efficiently generated in the fixing belt 61.

＜定着ベルトの昇温を抑制する機能の説明＞
一方、誘導加熱により定着ベルト６１の温度が上昇し、例えばニップ部Ｎ（図３参照）において用紙が搬送されない非通紙部に対応する領域において、定着ベルト６１の温度が透磁率変化開始温度を超えた場合には、定着ベルト６１に近接する感温磁性部材６４の温度も定着ベルト６１の温度に対応して、透磁率変化開始温度を超える。この場合、感温磁性部材６４は比透磁率が１に近づき、強磁性体としての性質が消失する。感温磁性部材６４の比透磁率が低下して１に近づくことで、ＩＨヒータ８０にて生成された交流磁界の磁力線Ｈは感温磁性部材６４の内部に誘導されず、感温磁性部材６４を透過するようになる。このため、定着ベルト６１の導電発熱層６１２を通過した後の磁力線Ｈは拡散し、導電発熱層６１２を横切る磁力線Ｈの磁束密度は低下する。これにより、導電発熱層６１２で発生する渦電流Ｉは減少して、定着ベルト６１での発熱量（ジュール熱Ｗ）が低減される。この結果、定着ベルト６１の過剰な温度上昇が抑えられ、定着ベルト６１の損傷が抑制される。 <Description of function for suppressing temperature rise of fixing belt>
On the other hand, the temperature of the fixing belt 61 rises due to induction heating. For example, in the region corresponding to the non-sheet passing portion where the sheet is not conveyed in the nip portion N (see FIG. 3), the temperature of the fixing belt 61 becomes the magnetic permeability change start temperature. If it exceeds, the temperature of the temperature-sensitive magnetic member 64 adjacent to the fixing belt 61 also exceeds the permeability change start temperature corresponding to the temperature of the fixing belt 61. In this case, the temperature-sensitive magnetic member 64 has a relative magnetic permeability close to 1, and the properties as a ferromagnetic material disappear. When the relative permeability of the temperature-sensitive magnetic member 64 decreases and approaches 1, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 are not induced inside the temperature-sensitive magnetic member 64, and the temperature-sensitive magnetic member 64. Will become transparent. For this reason, the magnetic field lines H after passing through the conductive heat generating layer 612 of the fixing belt 61 are diffused, and the magnetic flux density of the magnetic field lines H crossing the conductive heat generating layer 612 is reduced. As a result, the eddy current I generated in the conductive heat generation layer 612 is reduced, and the heat generation amount (Joule heat W) in the fixing belt 61 is reduced. As a result, an excessive temperature rise of the fixing belt 61 is suppressed, and damage to the fixing belt 61 is suppressed.

ところで、その後、定着ベルト６１の温度が感温磁性部材６４の透磁率変化開始温度よりも低くなると、感温磁性部材６４の温度も透磁率変化開始温度よりも低くなる。それにより、感温磁性部材６４は再び強磁性に変化して磁力線Ｈが感温磁性部材６４に誘導されるので、導電発熱層６１２に渦電流Ｉが多く流れるようになる。これにより、定着ベルト６１が再び加熱されるようになる。   By the way, after that, when the temperature of the fixing belt 61 becomes lower than the magnetic permeability change start temperature of the temperature-sensitive magnetic member 64, the temperature of the temperature-sensitive magnetic member 64 also becomes lower than the magnetic permeability change start temperature. As a result, the temperature-sensitive magnetic member 64 changes to ferromagnetic again, and the lines of magnetic force H are induced in the temperature-sensitive magnetic member 64, so that a large amount of eddy current I flows through the conductive heat generation layer 612. As a result, the fixing belt 61 is heated again.

図６（ｂ）に示すように、定着ベルト６１の温度が、例えば非通紙領域において上昇し透磁率変化開始温度を超えた温度範囲にある場合には、感温磁性部材６４の比透磁率が低下する。このため、ＩＨヒータ８０により生成された交流磁界の磁力線Ｈは、感温磁性部材６４を容易に透過するように変化する。これにより、ＩＨヒータ８０（励磁コイル８２）により生成された交流磁界の磁力線Ｈは、磁心８４から定着ベルト６１側に向けて拡散するように放射されるようになる。   As shown in FIG. 6B, when the temperature of the fixing belt 61 is in a temperature range that rises in the non-sheet passing region and exceeds the magnetic permeability change start temperature, for example, the relative magnetic permeability of the temperature-sensitive magnetic member 64. Decreases. For this reason, the magnetic field line H of the alternating magnetic field generated by the IH heater 80 changes so as to easily pass through the temperature-sensitive magnetic member 64. Accordingly, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 (excitation coil 82) are radiated so as to diffuse from the magnetic core 84 toward the fixing belt 61 side.

すなわち、ＩＨヒータ８０の磁心８４から磁力線Ｈが放射されて定着ベルト６１の導電発熱層６１２を横切る領域Ｒ１、Ｒ２では、磁力線Ｈは感温磁性部材６４に誘導され難いため、放射状に拡散する。それにより、定着ベルト６１の導電発熱層６１２を厚さ方向に横切る磁力線Ｈの磁束密度（単位面積当たりの磁力線Ｈの数）が減少する。また、磁力線Ｈが再び磁心８４に戻る際に導電発熱層６１２を厚さ方向に横切る領域Ｒ３でも、拡散した広い領域から磁力線Ｈが磁心８４に戻ることとなるため、定着ベルト６１の導電発熱層６１２を厚さ方向に横切る磁力線Ｈの磁束密度が減少する。
そのため、定着ベルト６１の温度が透磁率変化開始温度を超える温度範囲にある場合には、領域Ｒ１、Ｒ２や領域Ｒ３において導電発熱層６１２を厚さ方向に横切る磁力線Ｈの磁束密度が減少することとなる。それにより、磁力線Ｈが厚さ方向に横切る導電発熱層６１２に発生する渦電流Ｉは減り、定着ベルト６１に発生するジュール熱Ｗは減少する。この結果、定着ベルト６１の温度は低下する。 That is, in the regions R1 and R2 where the magnetic force lines H are radiated from the magnetic core 84 of the IH heater 80 and cross the conductive heat generating layer 612 of the fixing belt 61, the magnetic force lines H are difficult to be guided to the temperature-sensitive magnetic member 64 and thus diffuse radially. As a result, the magnetic flux density (number of magnetic force lines H per unit area) of the magnetic field lines H crossing the conductive heat generating layer 612 of the fixing belt 61 in the thickness direction decreases. Further, even in the region R3 that crosses the conductive heat generating layer 612 in the thickness direction when the magnetic force line H returns to the magnetic core 84 again, the magnetic force line H returns to the magnetic core 84 from the diffused wide region. The magnetic flux density of the magnetic field lines H crossing 612 in the thickness direction decreases.
Therefore, when the temperature of the fixing belt 61 is in a temperature range exceeding the permeability change start temperature, the magnetic flux density of the magnetic field lines H that cross the conductive heating layer 612 in the thickness direction decreases in the regions R1, R2, and R3. It becomes. As a result, the eddy current I generated in the conductive heating layer 612 where the magnetic field lines H cross in the thickness direction is reduced, and the Joule heat W generated in the fixing belt 61 is reduced. As a result, the temperature of the fixing belt 61 decreases.

＜感温磁性部材の昇温を抑制するための構成＞
ここで、感温磁性部材６４の過剰な温度上昇を抑える機能を果たすには、感温磁性部材６４の長手方向の領域毎の温度が、それに対向する定着ベルト６１の長手方向の領域毎の温度に対応して変化し、上記した定着ベルト６１の温度を検知する検出部としての機能を果たす必要がある。
そのために、感温磁性部材６４自身に関しては、磁力線Ｈによって誘導加熱され難い構成が採用される。すなわち、定着ベルト６１の温度が透磁率変化開始温度以下であり、感温磁性部材６４が強磁性を呈する状態であっても、ＩＨヒータ８０からの磁力線Ｈの中には、感温磁性部材６４を厚さ方向に横切る磁力線Ｈは存在する。それにより、感温磁性部材６４内部には弱い渦電流Ｉが発生しており、感温磁性部材６４自身においても若干の発熱が生じる。そのため、例えば、大量の画像形成が連続して行われた場合等には、感温磁性部材６４に熱が蓄積され、通紙領域でも感温磁性部材の温度が上昇傾向を呈する。それにより、渦電流損やヒステリシス損が大きく磁力線Ｈの通過により発熱し易い感温磁性部材６４では、状況によっては、定着ベルト６１の温度が透磁率変化開始温度を超えていなくとも、感温磁性部材６４が通紙領域における定着ベルト６１の温度上昇を抑えるように機能してしまう場合がある。そこで、感温磁性部材６４の温度と定着ベルト６１の温度との対応関係が維持され、感温磁性部材６４が定着ベルト６１の温度を検知する検知部として精度良く機能するために、感温磁性部材６４自身に発生するジュール熱Ｗを抑える必要がある。 <Configuration for suppressing temperature rise of temperature-sensitive magnetic member>
Here, in order to perform the function of suppressing the excessive temperature rise of the temperature-sensitive magnetic member 64, the temperature of each region in the longitudinal direction of the temperature-sensitive magnetic member 64 is the temperature of each region in the longitudinal direction of the fixing belt 61 facing it. It is necessary to fulfill a function as a detection unit for detecting the temperature of the fixing belt 61 described above.
Therefore, regarding the temperature-sensitive magnetic member 64 itself, a configuration that is difficult to be induction-heated by the magnetic field lines H is adopted. That is, even if the temperature of the fixing belt 61 is equal to or lower than the permeability change start temperature and the temperature-sensitive magnetic member 64 exhibits ferromagnetism, the temperature-sensitive magnetic member 64 is included in the magnetic force lines H from the IH heater 80. There is a magnetic field line H that crosses in the thickness direction. As a result, a weak eddy current I is generated inside the temperature-sensitive magnetic member 64, and a slight amount of heat is generated in the temperature-sensitive magnetic member 64 itself. Therefore, for example, when a large amount of image formation is continuously performed, heat is accumulated in the temperature-sensitive magnetic member 64, and the temperature of the temperature-sensitive magnetic member tends to increase even in the paper passing region. Thereby, in the temperature-sensitive magnetic member 64 that has large eddy current loss and hysteresis loss and easily generates heat due to the passage of the magnetic lines of force H, depending on the situation, even if the temperature of the fixing belt 61 does not exceed the permeability change start temperature, The member 64 may function to suppress the temperature increase of the fixing belt 61 in the paper passing area. Therefore, the correspondence between the temperature of the temperature-sensitive magnetic member 64 and the temperature of the fixing belt 61 is maintained, and the temperature-sensitive magnetic member 64 functions as a detection unit that detects the temperature of the fixing belt 61 with high accuracy. It is necessary to suppress the Joule heat W generated in the member 64 itself.

そこで、まず第１として、感温磁性部材６４は、磁力線Ｈによって誘導加熱され難い物性（固有抵抗値および透磁率）を持った材質が選定される。
また、第２として、感温磁性部材６４の厚さは、少なくとも透磁率変化開始温度以下の温度範囲にて磁力線Ｈが感温磁性部材６４の厚さ方向に横切り難いように、強磁性を呈する状態での表皮深さδよりも厚く形成される。 Therefore, first, the temperature-sensitive magnetic member 64 is selected from a material having physical properties (specific resistance value and magnetic permeability) that are difficult to be induction-heated by the magnetic field lines H.
Second, the thickness of the temperature-sensitive magnetic member 64 exhibits ferromagnetism so that the magnetic field lines H are difficult to cross in the thickness direction of the temperature-sensitive magnetic member 64 at least in the temperature range below the permeability change start temperature. It is formed thicker than the skin depth δ in the state.

さらに、第３として、感温磁性部材６４には、磁力線Ｈによって発生する渦電流Ｉの流れを分断する複数のスリット６４０が形成される。誘導加熱され難いように感温磁性部材６４の材質や厚さを選定しても、感温磁性部材６４内部に発生する渦電流Ｉを０とすることは困難である。そこで、感温磁性部材６４に発生した渦電流Ｉの流れを複数のスリット６４０により分断することで、渦電流Ｉを減少させて、感温磁性部材６４に発生するジュール熱Ｗを低く抑えている。
さらに、本実施の形態では、複数のスリット６４０により、定着ベルト６１と感温磁性部材６４との間の空間において、感温磁性部材６４の長手方向に沿った方向に向かう気流を発生させ、感温磁性部材６４が気流により冷却されやすくしている。 Third, the temperature-sensitive magnetic member 64 is formed with a plurality of slits 640 that divide the flow of the eddy current I generated by the lines of magnetic force H. Even if the material and thickness of the temperature-sensitive magnetic member 64 are selected so that induction heating is difficult, it is difficult to set the eddy current I generated in the temperature-sensitive magnetic member 64 to zero. Therefore, by dividing the flow of the eddy current I generated in the temperature-sensitive magnetic member 64 by the plurality of slits 640, the eddy current I is reduced and the Joule heat W generated in the temperature-sensitive magnetic member 64 is kept low. .
Further, in the present embodiment, the plurality of slits 640 generate an air flow in the direction along the longitudinal direction of the temperature-sensitive magnetic member 64 in the space between the fixing belt 61 and the temperature-sensitive magnetic member 64, thereby The warm magnetic member 64 is easily cooled by the airflow.

＜感温磁性部材のスリットの説明＞
図７（ａ）〜（ｃ）は、本実施の形態が適用される感温磁性部材６４の構成を説明する図である。図７（ａ）は、ホルダ６５に取り付けられた状態の感温磁性部材６４の斜視図であり、図７（ｂ）は、感温磁性部材６４を図７（ａ）のＶＩＩＢ方向から見た図であり、図７（ｃ）は、感温磁性部材６４を図７（ｂ）のＶＩＩＣ方向から見た図である。
また、図８は、感温磁性部材６４に形成されるスリット６４０による渦電流Ｉの流れを分断する作用を説明する図であり、感温磁性部材６４を上方（図７（ｂ）におけるＶＩＩＣ方向）から見た図に対応する。さらに、図９（ａ）〜（ｂ）は、感温磁性部材６４に形成されるスリット６４０により発生する気流を説明する図である。
なお、図７（ａ）〜（ｃ）、図８および図９（ａ）〜（ｂ）においては、サーモスタット７３（図５参照）を設置するための孔６４５（図５参照）の記載を省略している。 <Description of temperature-sensitive magnetic member slit>
7A to 7C are diagrams illustrating the configuration of the temperature-sensitive magnetic member 64 to which the present embodiment is applied. FIG. 7A is a perspective view of the temperature-sensitive magnetic member 64 attached to the holder 65, and FIG. 7B is a view of the temperature-sensitive magnetic member 64 from the VIIB direction of FIG. 7A. FIG. 7C is a view of the temperature-sensitive magnetic member 64 viewed from the VIIC direction of FIG. 7B.
FIG. 8 is a diagram for explaining the action of dividing the flow of the eddy current I by the slit 640 formed in the temperature-sensitive magnetic member 64. The temperature-sensitive magnetic member 64 is located above (in the VIIC direction in FIG. 7B). Corresponds to the figure seen from). Further, FIGS. 9A to 9B are views for explaining airflow generated by the slit 640 formed in the temperature-sensitive magnetic member 64. FIG.
7A to 7C, FIG. 8, and FIGS. 9A to 9B, the description of the hole 645 (see FIG. 5) for installing the thermostat 73 (see FIG. 5) is omitted. doing.

本実施の形態の感温磁性部材６４に形成されるそれぞれのスリット６４０は、図７（ａ）〜（ｃ）に示すように、定着ベルト６１の移動方向（図７（ａ）〜（ｃ）における矢印Ｃ方向）に対して傾斜して設けられる。具体的には、複数のスリット６４０は、定着ベルト６１の移動方向に対して第１方向に傾斜した複数の第１スリット６４１と、定着ベルト６１の移動方向に対して第１方向とは異なる第２方向に傾斜した複数の第２スリット６４２とを含んでいる。   As shown in FIGS. 7A to 7C, each slit 640 formed in the temperature-sensitive magnetic member 64 of the present embodiment has a moving direction of the fixing belt 61 (FIGS. 7A to 7C). In the direction of arrow C). Specifically, the plurality of slits 640 includes a plurality of first slits 641 inclined in the first direction with respect to the moving direction of the fixing belt 61 and a first direction different from the first direction with respect to the moving direction of the fixing belt 61. A plurality of second slits 642 inclined in two directions are included.

複数の第１スリット６４１は、予め定めた間隙を隔てて感温磁性部材６４の長手方向に等間隔に形成されている。そして、図７（ｃ）に示すように、それぞれの第１スリット６４１は、感温磁性部材６４を上方から見た場合に、定着ベルト６１の移動方向の上流側から下流側に向かうに従い左側から右側に向かうように形成されている。
同様に、複数の第２スリット６４２は、予め定めた間隙を隔てて感温磁性部材６４の長手方向に等間隔に形成されている。そして、図７（ｃ）に示すように、それぞれの第２スリット６４２は、感温磁性部材６４を上方から見た場合に、定着ベルト６１の移動方向の上流側から下流側に向かうに従い右側から左側に向かうように形成されている。 The plurality of first slits 641 are formed at equal intervals in the longitudinal direction of the temperature-sensitive magnetic member 64 with a predetermined gap therebetween. As shown in FIG. 7C, each of the first slits 641 is formed from the left side as the temperature-sensitive magnetic member 64 is viewed from the upper side toward the downstream side in the moving direction of the fixing belt 61. It is formed to go to the right side.
Similarly, the plurality of second slits 642 are formed at equal intervals in the longitudinal direction of the temperature-sensitive magnetic member 64 with a predetermined gap therebetween. As shown in FIG. 7C, each of the second slits 642 is formed from the right side as the temperature-sensitive magnetic member 64 is viewed from above, from the upstream side to the downstream side in the moving direction of the fixing belt 61. It is formed to go to the left side.

そして、図７（ａ）〜（ｃ）に示すように、第１スリット６４１と第２スリット６４２とは、定着ベルト６１の移動方向の上流側から下流側に向かうに従い、互いに近づくように形成されている。言い換えると、第１スリット６４１および第２スリット６４２は、定着ベルト６１の移動方向の上流側から下流側に向かうに従い、感温磁性部材６４の長手方向中央部に向かうようになっている。   7A to 7C, the first slit 641 and the second slit 642 are formed so as to approach each other from the upstream side to the downstream side in the moving direction of the fixing belt 61. ing. In other words, the first slit 641 and the second slit 642 are directed toward the center in the longitudinal direction of the temperature-sensitive magnetic member 64 from the upstream side to the downstream side in the moving direction of the fixing belt 61.

続いて、感温磁性部材６４に発生した渦電流Ｉの流れを分断する機能について説明する。
本実施の形態の感温磁性部材６４に形成される複数のスリット６４０（第１スリット６４１、第２スリット６４２）は、図８に示すように、磁力線Ｈによって発生する渦電流Ｉの流れる方向に対して交差している。そのため、スリット６４０が無い場合には感温磁性部材６４の長手方向の全体に亘って大きな渦となって流れる渦電流（図８破線）が、スリット６４０により分断される。これにより、スリット６４０を形成した場合には、感温磁性部材６４内を流れる渦電流Ｉ（図８実線）は、スリット６４０とスリット６４０との間の領域内での小さな渦となり、全体として渦電流Ｉの電流量は低減される。この結果、感温磁性部材６４での発熱量（ジュール熱Ｗ）は、スリット６４０を設けない場合と比較して減少し、発熱し難い構成が実現する。したがって、複数のスリット６４０は、渦電流を分断（遮断）する遮断部として機能する。 Subsequently, the function of dividing the flow of the eddy current I generated in the temperature-sensitive magnetic member 64 will be described.
The plurality of slits 640 (the first slit 641 and the second slit 642) formed in the temperature-sensitive magnetic member 64 of the present embodiment are arranged in the direction in which the eddy current I generated by the lines of magnetic force H flows as shown in FIG. Crosses against each other. Therefore, when there is no slit 640, the eddy current (broken line in FIG. 8) that flows as a large vortex over the entire length of the temperature-sensitive magnetic member 64 is divided by the slit 640. As a result, when the slit 640 is formed, the eddy current I flowing through the temperature-sensitive magnetic member 64 (solid line in FIG. 8) becomes a small vortex in the region between the slit 640 and the slit 640, and the vortex as a whole. The amount of current I is reduced. As a result, the amount of heat generated by the temperature-sensitive magnetic member 64 (Joule heat W) is reduced as compared with the case where the slit 640 is not provided, and a configuration that hardly generates heat is realized. Therefore, the plurality of slits 640 function as a blocking unit that divides (blocks) the eddy current.

続いて、図９および上述した図３を用いて、感温磁性部材６４のスリット６４０により生じる気流について説明する。
上述したように、本実施の形態の定着装置６０では、感温磁性部材６４は、定着ベルト６１の内周面に対して予め定めた間隙を介して配置され、感温磁性部材６４と定着ベルト６１との間には空間が設けられている。
これにより、画像形成装置１（図１参照）のメインスイッチがオンされて定着ベルト６１が矢印Ｃ方向に回転され、感温磁性部材６４に対して定着ベルト６１が移動すると、図３に示すように、感温磁性部材６４と定着ベルト６１との間の空間において定着ベルト６１の移動方向に向かう気流Ｇが生じる。 Next, the airflow generated by the slit 640 of the temperature-sensitive magnetic member 64 will be described using FIG. 9 and FIG. 3 described above.
As described above, in the fixing device 60 of the present embodiment, the temperature-sensitive magnetic member 64 is disposed with a predetermined gap with respect to the inner peripheral surface of the fixing belt 61, and the temperature-sensitive magnetic member 64 and the fixing belt are arranged. A space is provided between the unit 61 and the unit 61.
As a result, the main switch of the image forming apparatus 1 (see FIG. 1) is turned on, the fixing belt 61 is rotated in the direction of arrow C, and the fixing belt 61 moves relative to the temperature-sensitive magnetic member 64, as shown in FIG. In addition, an airflow G is generated in the space between the temperature-sensitive magnetic member 64 and the fixing belt 61 in the moving direction of the fixing belt 61.

ここで、上述したように、スリット６４０の第１スリット６４１および第２スリット６４２は、定着ベルト６１の移動方向に対して異なる方向に傾斜して設けられている。これにより、定着ベルト６１の回転により発生した気流Ｇは、第１スリット６４１および第２スリット６４２に案内され、定着ベルト６１の移動方向に対して傾斜した方向に進行する。
言い換えると、本実施の形態では、第１スリット６４１および第２スリット６４２により、定着ベルト６１の移動方向に交差し互いに異なる方向に向かう気流が生じる。具体的には、定着ベルト６１の回転により、感温磁性部材６４と定着ベルト６１との間には、第１スリット６４１に案内されることで感温磁性部材６４の長手方向の一端側から他端側（図９では左から右）に向かう第１気流Ｇ１と、第２スリット６４２に案内されることで感温磁性部材６４の他端側から一端側（図９では右から左）に向かう第２気流Ｇ２とが生じる。 Here, as described above, the first slit 641 and the second slit 642 of the slit 640 are provided to be inclined in different directions with respect to the moving direction of the fixing belt 61. Accordingly, the airflow G generated by the rotation of the fixing belt 61 is guided by the first slit 641 and the second slit 642 and proceeds in a direction inclined with respect to the moving direction of the fixing belt 61.
In other words, in the present embodiment, the first slit 641 and the second slit 642 generate airflows that cross the moving direction of the fixing belt 61 and travel in different directions. Specifically, the rotation of the fixing belt 61 causes the temperature-sensitive magnetic member 64 and the fixing belt 61 to be guided from one end side in the longitudinal direction of the temperature-sensitive magnetic member 64 by being guided by the first slit 641. The first airflow G1 heading toward the end side (left to right in FIG. 9) and the second slit 642 guide the head from the other end side to the one end side (right to left in FIG. 9). A second airflow G2 is generated.

これにより、本実施の形態では、例えば感温磁性部材６４に対して定着ベルト６１の移動方向に沿ったスリット６４０のみを形成する場合と比較して、感温磁性部材６４と定着ベルト６１との間での空気の移動量が多くなる。この結果、感温磁性部材６４に生じた熱が、感温磁性部材６４と定着ベルト６１との間の空気へ放出されやすくなり、感温磁性部材６４の過剰な温度上昇が抑制される。   Accordingly, in the present embodiment, for example, the temperature-sensitive magnetic member 64 and the fixing belt 61 are compared with the case where only the slit 640 along the moving direction of the fixing belt 61 is formed on the temperature-sensitive magnetic member 64. The amount of air movement between them increases. As a result, heat generated in the temperature-sensitive magnetic member 64 is easily released to the air between the temperature-sensitive magnetic member 64 and the fixing belt 61, and an excessive temperature rise of the temperature-sensitive magnetic member 64 is suppressed.

さらに、本実施の形態では、第１スリット６４１と第２スリット６４２とを定着ベルト６１の移動方向の下流側に向かうに従い感温磁性部材６４の長手方向中央部に向かうように設けることで、第１スリット６４１に案内される第１気流Ｇ１と第２スリット６４２に案内される第２気流Ｇ２とが、感温磁性部材６４と定着ベルト６１との間で衝突するようになっている。そして、図９に示すように、第１気流Ｇ１と第２気流Ｇ２とが衝突することで、感温磁性部材６４と定着ベルト６１との間の空間に乱流Ｇｔが生じる。
これにより、乱流Ｇｔが生じない場合と比較して、感温磁性部材６４と定着ベルト６１との間での空気の移動量が大きくなり、感温磁性部材６４からの放熱がより促進される。この結果、本構成を採用しない場合と比較して、感温磁性部材６４の過剰な温度上昇がより抑制される。 Furthermore, in the present embodiment, the first slit 641 and the second slit 642 are provided so as to be directed toward the center in the longitudinal direction of the temperature-sensitive magnetic member 64 toward the downstream side in the moving direction of the fixing belt 61. The first air flow G 1 guided by the first slit 641 and the second air flow G 2 guided by the second slit 642 collide between the temperature-sensitive magnetic member 64 and the fixing belt 61. As shown in FIG. 9, the first air flow G <b> 1 and the second air flow G <b> 2 collide to generate a turbulent flow Gt in the space between the temperature-sensitive magnetic member 64 and the fixing belt 61.
Thereby, compared with the case where the turbulent flow Gt does not occur, the amount of air movement between the temperature-sensitive magnetic member 64 and the fixing belt 61 is increased, and the heat radiation from the temperature-sensitive magnetic member 64 is further promoted. . As a result, an excessive temperature rise of the temperature-sensitive magnetic member 64 is further suppressed as compared with the case where this configuration is not adopted.

なお、本実施の形態では、感温磁性部材６４を、定着ベルト６１の軸方向（感温磁性部材６４の長手方向）に一体の部材としたが、例えば感温磁性部材６４を定着ベルト６１の軸方向に複数の部材に分割して構成してもよい。図１０は、感温磁性部材６４の他の構成を示した図である。図１０に示すよう例では、感温磁性部材６４が、定着ベルト６１の軸方向に並ぶ２つの部材６４Ａ、６４Ｂにより構成されている。そして、図１０に示す例では、感温磁性部材６４を構成する２つの部材６４Ａ、６４Ｂのそれぞれに、複数の第１スリット６４１および複数の第２スリット６４２を設けている。   In this embodiment, the temperature-sensitive magnetic member 64 is an integral member in the axial direction of the fixing belt 61 (the longitudinal direction of the temperature-sensitive magnetic member 64). You may divide | segment into several members and to comprise in an axial direction. FIG. 10 is a view showing another configuration of the temperature-sensitive magnetic member 64. In the example shown in FIG. 10, the temperature-sensitive magnetic member 64 is composed of two members 64 </ b> A and 64 </ b> B arranged in the axial direction of the fixing belt 61. In the example shown in FIG. 10, a plurality of first slits 641 and a plurality of second slits 642 are provided in each of the two members 64 </ b> A and 64 </ b> B constituting the temperature-sensitive magnetic member 64.

これにより、図１０に示した例においても、感温磁性部材６４の部材６４Ａと定着ベルト６１との間、および部材６４Ｂと定着ベルト６１との間のそれぞれに、第１スリット６４１に案内される第１気流Ｇ１（図９参照）と、第２スリット６４２に案内される第２気流Ｇ２（図９参照）とが生じる。これにより、感温磁性部材６４と定着ベルト６１との間での空気の移動量が多くなり、感温磁性部材６４の過剰な温度上昇が抑制される。   Accordingly, also in the example shown in FIG. 10, the first slit 641 is guided between the member 64A of the temperature-sensitive magnetic member 64 and the fixing belt 61 and between the member 64B and the fixing belt 61. A first airflow G1 (see FIG. 9) and a second airflow G2 (see FIG. 9) guided by the second slit 642 are generated. As a result, the amount of air movement between the temperature-sensitive magnetic member 64 and the fixing belt 61 increases, and an excessive temperature rise of the temperature-sensitive magnetic member 64 is suppressed.

また、図１０に示した例では、感温磁性部材６４の部材６４Ａと定着ベルト６１との間、および部材６４Ｂと定着ベルト６１との間のそれぞれにおいて、第１気流Ｇ１と第２気流Ｇ２とが衝突し乱流Ｇｔ（図９参照）が生じる。これにより、本構成を採用しない場合と比較して、感温磁性部材６４の過剰な温度上昇がより抑制される。   In the example shown in FIG. 10, the first air flow G1 and the second air flow G2 are respectively provided between the member 64A of the temperature-sensitive magnetic member 64 and the fixing belt 61 and between the member 64B and the fixing belt 61. Collide with each other to generate a turbulent flow Gt (see FIG. 9). Thereby, compared with the case where this structure is not employ | adopted, the excessive temperature rise of the temperature-sensitive magnetic member 64 is suppressed more.

なお、図示は省略するが、例えば感温磁性部材６４を定着ベルト６１の軸方向に２つの部材に分割して構成する場合、一方の部材に複数の第１スリット６４１のみを設け、他方の部材に複数の第２スリット６４２を設けてもよい。この場合であっても、感温磁性部材６４全体としては、第１スリット６４１と第２スリット６４２との双方を有することになるため、上述した例と同様に、感温磁性部材６４の過剰な温度上昇を抑制する効果が得られる。   Although illustration is omitted, for example, when the temperature-sensitive magnetic member 64 is divided into two members in the axial direction of the fixing belt 61, only the first slits 641 are provided on one member, and the other member is provided. A plurality of second slits 642 may be provided. Even in this case, since the temperature-sensitive magnetic member 64 as a whole has both the first slit 641 and the second slit 642, the excess of the temperature-sensitive magnetic member 64 is the same as in the above-described example. The effect of suppressing the temperature rise is obtained.

１…画像形成装置、１０…画像形成部、６０…定着装置、６１…定着ベルト、６４…感温磁性部材、６４０…スリット、６４１…第１スリット、６４２…第２スリット DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Image forming part, 60 ... Fixing apparatus, 61 ... Fixing belt, 64 ... Temperature-sensitive magnetic member, 640 ... Slit, 641 ... 1st slit, 642 ... 2nd slit

Claims (6)

導電層を有し、当該導電層が電磁誘導加熱されることで記録材にトナーを定着する循環移動可能な定着部材と、
前記定着部材の前記導電層と交差する交流磁界を生成する磁界生成部材と、
前記定着部材を挟んで前記磁界生成部材と対向し、前記定着部材の移動方向に対し傾斜し当該磁界生成部材にて生成された交流磁界による渦電流を遮断する複数の第１遮断部と当該移動方向に対し当該第１遮断部とは反対側に傾斜し当該交流磁界による渦電流を遮断する複数の第２遮断部とを有し、磁気特性が温度に応じて強磁性と常磁性との間で変化して磁気特性が強磁性の場合に当該交流磁界を透過させる感温磁性部材と
を備える定着装置。 A fixing member having a conductive layer and capable of circulating movement for fixing the toner to the recording material by electromagnetic induction heating of the conductive layer;
A magnetic field generating member that generates an alternating magnetic field that intersects the conductive layer of the fixing member;
A plurality of first blocking portions that face the magnetic field generating member across the fixing member, are inclined with respect to the moving direction of the fixing member, and block eddy currents caused by an alternating magnetic field generated by the magnetic field generating member and the movement A plurality of second interrupting portions that incline to the opposite side of the first interrupting portion with respect to the direction and interrupt eddy currents due to the alternating magnetic field, and have a magnetic property between ferromagnetic and paramagnetic depending on temperature And a temperature-sensitive magnetic member that transmits the AC magnetic field when the magnetic characteristics are ferromagnetic. 複数の前記第１遮断部と複数の前記第２遮断部とは、前記移動方向の下流に向かうに従い互いに近づく方向に延びることを特徴とする請求項１に記載の定着装置。   The fixing device according to claim 1, wherein the plurality of first blocking units and the plurality of second blocking units extend in a direction approaching each other toward a downstream side in the moving direction. 前記第１遮断部および前記第２遮断部は、それぞれ、前記感温磁性部材を切欠くことにより形成されることを特徴とする請求項１または２に記載の定着装置。   The fixing device according to claim 1, wherein each of the first blocking unit and the second blocking unit is formed by cutting out the temperature-sensitive magnetic member. 導電層を有し、当該導電層が電磁誘導加熱されることで記録材にトナーを定着する循環移動可能な定着部材と、
前記定着部材の前記導電層と交差する交流磁界を生成する磁界生成部材と、
前記定着部材を挟んで前記磁界生成部材と対向し、磁気特性に応じて強磁性と常磁性との間で変化し、磁気特性が強磁性の場合に当該磁界生成部材にて生成された交流磁界を透過させ、当該定着部材との間に当該定着部材の移動方向に直交する第１方向に向かう気流と当該第１方向とは反対の第２方向に向かう気流とを発生させる気流発生部を有する感温磁性部材と
を備える定着装置。 A fixing member having a conductive layer and capable of circulating movement for fixing the toner to the recording material by electromagnetic induction heating of the conductive layer;
A magnetic field generating member that generates an alternating magnetic field that intersects the conductive layer of the fixing member;
An AC magnetic field generated by the magnetic field generation member that faces the magnetic field generation member across the fixing member, changes between ferromagnetism and paramagnetism according to magnetic characteristics, and the magnetic characteristics are ferromagnetic. And an air flow generation unit that generates an air flow in a first direction orthogonal to the moving direction of the fixing member and an air flow in a second direction opposite to the first direction. A fixing device including a temperature-sensitive magnetic member. 前記気流発生部は、前記第１方向に向かう気流と前記第２方向に向かう気流とを衝突させ乱流を発生させることを特徴とする請求項４に記載の定着装置。   The fixing device according to claim 4, wherein the airflow generation unit collides the airflow directed in the first direction and the airflow directed in the second direction to generate a turbulent flow. トナー像を形成するトナー像形成手段と、
前記トナー像形成手段によって形成された前記トナー像を記録材上に転写する転写手段と、
請求項１乃至５のいずれか１項に記載の定着装置と
を備える画像形成装置。 Toner image forming means for forming a toner image;
Transfer means for transferring the toner image formed by the toner image forming means onto a recording material;
An image forming apparatus comprising: the fixing device according to claim 1.
JP2015094757A 2015-05-07 2015-05-07 Fixing device and image forming apparatus Pending JP2016212215A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10990046B2 (en) * 2019-05-31 2021-04-27 Kyocera Document Solutions Inc. Fixing device having heater holding member with inclined slits

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10990046B2 (en) * 2019-05-31 2021-04-27 Kyocera Document Solutions Inc. Fixing device having heater holding member with inclined slits

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