JP3857344B2 - Heater - Google Patents

Description

【０００１】
【発明の属する技術分野】
本発明は、画像形成用電子写真プロセスにおいて、感光ドラムから被印刷体上に転写されたトナーを熱定着する場合に好適に用いられる加熱ヒータおよびこれを用いた加熱装置に関する。このような電子写真プロセスは、乾式複写機、レーザープリンタ、ＬＥＤプリンタ、ファクシミリの印字部等に広く応用されている。
【０００２】
【従来の技術】
画像形成用の電子写真プロセスにおけるトナー定着部の小型化、軽量化を図るとともに、使用可能温度への昇温時間の短縮化と省電力化を図るために、筒型回転ローラ式の定着用加熱ヒータとして内装されるハロゲンランプに替えて絶縁基板上に発熱体を帯状に配置してなる加熱ヒータを用い得ることが日経エレクトロニクス１９９３年の９−１３号に開示されている。
【０００３】
そのような加熱ヒータは、図３の斜視図に示すように、矩形短冊状の絶縁基板１１の上面に、長辺方向に延びる所定長さの発熱抵抗体１２を酸化ルテニウムを含む抵抗用ペーストを印刷及び焼成することにより形成する一方、この発熱抵抗体１２の両端部に一部重なるようにして電極１３、１３を銀ペースト等の導体ペーストを印刷及び焼成することにより形成し、更に発熱抵抗体１２の温度を検出するためのサーミスタ（図示せず）を実装した後、発熱抵抗体１２を保護する保護層（図示せず）をガラスペーストの印刷及び焼成によって形成することにより加熱ヒータは製造されている。
【０００４】
【発明が解決しようとする課題】
近年、この種の電子写真プロセスには高速化、高画質化が要求されつつあり、そのような要望に応えるために、前述のような加熱ヒータにおいては発熱抵抗体１２の短辺方向の幅を広く形成している。このような加熱ヒータの幅寸法の増大により、発熱抵抗体１２に対する被印刷体の搬送速度を同一な値に設定した場合は、発熱抵抗体１２との接触時間が長くなるのでトナーに高融点タイプを用いることができ、高画質印字が可能となる。
【０００５】
又、発熱抵抗体１２に対する被印刷体の搬送速度を速くした場合でも、発熱抵抗体１２と被印刷体との接触時間を従来とほぼ同一に設定でき、従来と同様な定着性を維持したままで高速印字が可能になる、
しかしながら、前述のような加熱ヒータは発熱抵抗体１２が印刷及び焼成により形成されており、その断面が図４（ａ）に示すような形状となっているので、横断面を示す図４の中央部ａの部分と端部ｂの部分とでは幅寸法を同一とした場合であっても発熱抵抗体１２の厚さが異なり、ａの部分のほうがｂの部分に比べて単位幅当たりの抵抗値が大きく、加熱ヒータに電流を印加した場合に図４（ｂ）に示すように厚さ寸法の大きいａの部分の発熱量は厚さ寸法の小さいｂの部分の発熱量より多くなる。それにより、発熱抵抗体１２の横断面方向の位置により発熱温度にばらつきが生じ、被印刷体へのトナーの定着むらが生じやすいという問題があった。
【０００６】
又、加熱ヒータの発熱抵抗体１２の短辺方向の寸法を大きくしても発熱抵抗体１２の発熱温度は、図４（ｂ）に示すように幅方向中央部に集中したままで端部にまで広がっておらず、発熱抵抗体の幅方向の寸法を拡大したにも拘らず高速高画質対応が可能な加熱ヒータが得られないという問題があった。
本発明は、温度ばらつきの少ない構造を有し、高速高画質対応が可能な加熱ヒータを提供することを目的とする。
【０００７】
【課題を解決するための手段】
前述の問題点を解決するために、本願の請求項１に記載した発明は、長尺状の絶縁基板の表面に長辺方向に抵抗用ペーストを印刷及び焼成することによって帯状の発熱抵抗体を形成して、当該発熱抵抗体の幅方向における中央部の厚さ寸法が前記発熱抵抗体の幅方向における両端部の厚さ寸法より大きく形成された加熱ヒータにおいて、前記帯状の発熱抵抗体の幅方向両端部に前記発熱抵抗体の長手方向に沿って追加抵抗膜が前記抵抗用ペーストと同一の材料により形成されていて、前記発熱抵抗体の幅方向における中央部の厚さ寸法が前記発熱抵抗体の幅方向における両端部の厚さ寸法と前記追加抵抗膜の厚さ寸法との和とほぼ等しくされていることを特徴としている。
【０００８】
この構成によれば、発熱抵抗体及び追加抵抗膜が同一の材料により形成され、かつ発熱抵抗体の幅方向における中央部の厚さ寸法が発熱抵抗体の幅方向における両端部の厚さ寸法と追加抵抗膜の厚さ寸法との和とほぼ等しくされているために、加熱ヒータの短辺方向（切断面方向）の抵抗値のバラつきを抑制することができ、ひいては発熱量のバラツキを抑制することができる。
【０００９】
【実施の形態】
以下本発明の加熱ヒータの実施例を図面を用いて説明する。
図１（ａ）は本発明の加熱ヒータの一実施例を示す平面図で、アルミナセラミックよりなる長尺状の絶縁基板１の表面に酸化ルテニウムを含む抵抗用ペーストを印刷及びこれを焼成して発熱抵抗体２が形成されている。この発熱抵抗体２は絶縁基板１の短辺方向の中央部に長辺方向に沿って帯状に形成されている。
【００１０】
そして、この発熱抵抗体２の基板短辺方向、即ち抵抗体幅方向の両端部上に、その長手方向に沿って前述の抵抗用ペーストを印刷及びこれを焼成して追加抵抗膜３が形成される。
この実施例において追加抵抗膜３は平面視で帯状に形成したが、これに変えて図１（ｂ）に示すように、追加抵抗膜３をその幅が長手方向の中央部に対して両端部が幅広形状で発熱抵抗体２を部分的に挟んで対向するように形成してもよい。
【００１１】
追加抵抗膜３をこのように形成することにより、発熱抵抗体２で発生する熱エネルギーがその両端部に形成された電極を介して放熱され、発熱抵抗体２の長辺方向両端部分での発熱量が中央部分に比べて少なくなってしまうことを有効に防止できる。即ち、追加抵抗膜３の長辺方向の両端部分の幅寸法を中央部分に比べて広くすることで、発熱抵抗体２の両端側での損失熱エネルギーを追加抵抗膜３の幅広部分で補うこととなり、加熱ヒータの発熱エネルギーを長辺方向で更に均等化することが可能となる。
【００１２】
追加抵抗膜３を形成したら、発熱抵抗体２の長辺方向の両端部にそれぞれ連なるように銀ペースト等の導電ペーストを印刷及びこれを焼成して一対の電極４、４を形成する。そして、発熱抵抗体２と追加抵抗膜３との一体化による抵抗値をトリミング等により調整した後、一対の電極４、４が部分的に露出するようにサーマルヘッドの発熱抵抗体の保護層に従来より用いられている周知のガラスペーストを印刷及びこれを焼成して保護膜５を形成する。
【００１３】
上述の実施例では、発熱抵抗体の長辺方向の両端に電極が配置された構成の加熱ヒータを示したが、絶縁基板の一端側に電極を配置し長辺方向の他端側で発熱抵抗体が折り返すような形状、若しくは他端側に折り返し用の電極（発熱抵抗体以外とは外部と接続され無い）を有する形状の発熱抵抗体を有する加熱ヒータに適用しても良い。
【００１４】
尚、本発明は上述の実施例に記載の形成方法、形状及び材料等の構成に特に限定されるものではない。
【００１５】
【発明の効果】
上述のように、帯状の発熱抵抗体の短辺方向両端部に、発熱抵抗体の長辺方向に沿って追加抵抗膜を形成することにより、図２（ａ）に示すように加熱ヒータの短辺方向におけるＡの位置の厚さ寸法とＢの位置の厚さ寸法とがほぼ等しく形成でき、加熱ヒータの使用時での短辺方向の抵抗値ばらつきが少なくなる。
【００１６】
それにより、加熱ヒータの電極に電流を印加して発熱抵抗体及び追加抵抗膜を発熱させると、図２（ｂ）に示すように発熱部の幅方向の両端部近傍に亘り発熱温度にばらつきがなくなるので、被印刷体へのトナーの定着ムラが発生しにくくなり、高画質印字に対応することが可能になるだけでなく、トナーの定着可能な温度より加熱ヒータの発熱時の温度が上回る領域が発熱抵抗体の全幅とほぼ等しくなる。このため、発熱抵抗体に対する被印刷体の搬送速度を従来と同一な値にすることにより、発熱抵抗体と被印字体との接触時間が長くなるのでトナーに高融点タイプを用いることができ、高画質印字が可能となるという効果を有する。又、発熱抵抗体に対する被印刷体の搬送速度を速くしても、発熱抵抗体と被印字体との接触時間が同じ程度になるので同様に定着させることができ、高速度印字が可能になるという効果を有する。
【００１７】
更に、発熱抵抗体の長辺方向に沿って形成された追加抵抗膜は、幅方向の寸法を長手方向の中央部より両端部が幅広に形成することにより、発熱抵抗体と追加抵抗膜との合成した抵抗値が長辺方向両端部が中央部より高くなる。
それにより、加熱ヒータの電極に電流を印加して発熱抵抗体及び追加抵抗膜を発熱させると、長辺方向両端部が中央部に比べて発熱温度は高くなるが、電極を介して放熱される熱エネルギーと相殺されて幅方向に加えて長手方向の加熱ヒータの温度分布も略均一となり、被印刷体に対するトナーの定着ムラをより一層防止することが可能となるという効果を有する。
【図面の簡単な説明】
【図１】本発明の加熱ヒータを示す平面図
【図２】図１の本発明の加熱ヒータの一部断面図
【図３】従来の加熱ヒータを示す斜視図
【図４】図３の従来の加熱ヒータの一部断面図
【符号の説明】
１・・・・絶縁基板
２・・・・発熱抵抗体
３・・・・追加抵抗膜
４・・・・電極
５・・・・保護膜
出願人 ローム株式会社[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heater suitably used for heat-fixing toner transferred from a photosensitive drum onto a printing medium in an electrophotographic process for image formation, and a heating apparatus using the same. Such an electrophotographic process is widely applied to a dry copying machine, a laser printer, an LED printer, a facsimile printing unit, and the like.
[0002]
[Prior art]
In order to reduce the size and weight of the toner fixing part in the electrophotographic process for image formation, and to shorten the heating time to the usable temperature and to save power, the cylindrical rotating roller type fixing heating Nikkei Electronics 1993 No. 9-13 discloses that a heater in which a heating element is arranged in a strip shape on an insulating substrate can be used instead of a halogen lamp installed as a heater.
[0003]
In such a heater, as shown in the perspective view of FIG. 3, a resistance paste containing ruthenium oxide is applied to a heating resistor 12 having a predetermined length extending in the long side direction on the upper surface of a rectangular strip-like insulating substrate 11. While forming by printing and baking, electrodes 13 and 13 are formed by printing and baking a conductive paste such as silver paste so as to partially overlap both ends of the heating resistor 12, and further the heating resistor. After the thermistor (not shown) for detecting the temperature of 12 is mounted, the heater is manufactured by forming a protective layer (not shown) for protecting the heating resistor 12 by printing and baking glass paste. ing.
[0004]
[Problems to be solved by the invention]
In recent years, high speed and high image quality are being demanded for this type of electrophotographic process. In order to meet such a demand, in the heater as described above, the width of the heating resistor 12 in the short side direction is increased. Widely formed. Due to such an increase in the width of the heater, when the conveyance speed of the printing medium with respect to the heating resistor 12 is set to the same value, the contact time with the heating resistor 12 becomes longer, so the toner has a high melting point type. Can be used, and high-quality printing is possible.
[0005]
In addition, even when the conveyance speed of the printing medium with respect to the heating resistor 12 is increased, the contact time between the heating resistor 12 and the printing medium can be set to be almost the same as the conventional one, and the fixing property similar to the conventional one is maintained. Enables high-speed printing.
However, in the heater as described above, the heating resistor 12 is formed by printing and baking, and the cross section thereof has a shape as shown in FIG. Even when the width dimension is the same between the portion a and the end b, the thickness of the heating resistor 12 is different, and the resistance value per unit width is greater in the a portion than in the b portion. When a current is applied to the heater, as shown in FIG. 4B, the calorific value of the portion a having a large thickness dimension is larger than the calorific value of the portion b having a small thickness dimension. As a result, there is a problem in that the heat generation temperature varies depending on the position of the heat generating resistor 12 in the cross-sectional direction, and uneven toner fixing to the printing medium tends to occur.
[0006]
Further, even if the dimension in the short side direction of the heating resistor 12 of the heater is increased, the heating temperature of the heating resistor 12 is concentrated at the center in the width direction as shown in FIG. However, there is a problem that a heater capable of high-speed and high-quality correspondence cannot be obtained even though the widthwise dimension of the heating resistor is increased.
An object of the present invention is to provide a heater having a structure with little temperature variation and capable of high speed and high image quality.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention described in claim 1 of the present application is that a strip-shaped heating resistor is formed by printing and baking a resistance paste in the long side direction on the surface of a long insulating substrate. In the heater formed and formed such that the thickness dimension of the central portion in the width direction of the heating resistor is larger than the thickness dimension of both end portions in the width direction of the heating resistor, the width of the band-shaped heating resistor said additional resistive film along the longitudinal direction of the heating resistors are formed of the same material as the resistor paste to opposite end portions, wherein the thickness of the central portion in the width direction of the heating resistor heating resistor It is characterized by being substantially equal to the sum of the thickness dimension of both end portions in the width direction of the body and the thickness dimension of the additional resistive film .
[0008]
According to this configuration, the heating resistor and the additional resistance film are formed of the same material, and the thickness dimension of the central portion in the width direction of the heating resistor is equal to the thickness dimension of both ends in the width direction of the heating resistor. Since it is almost equal to the sum of the thickness of the additional resistance film, variation in the resistance value in the short side direction (cutting surface direction) of the heater can be suppressed, and thus variation in heat generation can be suppressed. be able to.
[0009]
Embodiment
Embodiments of the heater according to the present invention will be described below with reference to the drawings.
FIG. 1A is a plan view showing an embodiment of a heater according to the present invention, in which a resistance paste containing ruthenium oxide is printed on the surface of a long insulating substrate 1 made of alumina ceramic and fired. A heating resistor 2 is formed. The heating resistor 2 is formed in a strip shape along the long side direction at the center of the insulating substrate 1 in the short side direction.
[0010]
Then, on the both ends of the heating resistor 2 in the short-side direction of the substrate, that is, in the width direction of the resistor, the above-mentioned resistance paste is printed along the longitudinal direction and fired to form the additional resistance film 3. The
In this embodiment, the additional resistive film 3 is formed in a band shape in plan view, but instead, as shown in FIG. 1B, the additional resistive film 3 has a width at both end portions with respect to the central portion in the longitudinal direction. However, they may be formed so as to face each other with the heating resistor 2 partially sandwiched therebetween.
[0011]
By forming the additional resistance film 3 in this manner, the heat energy generated in the heating resistor 2 is radiated through the electrodes formed at both ends thereof, and heat is generated at both ends in the long side direction of the heating resistor 2. It is possible to effectively prevent the amount from being reduced compared to the central portion. That is, by increasing the width dimension of both end portions in the long side direction of the additional resistance film 3 as compared with the central portion, the loss heat energy at both ends of the heating resistor 2 is compensated by the wide portion of the additional resistance film 3. Thus, the heat generation energy of the heater can be further equalized in the long side direction.
[0012]
After the additional resistance film 3 is formed, a pair of electrodes 4 and 4 are formed by printing and baking a conductive paste such as silver paste so as to be connected to both ends of the heating resistor 2 in the long side direction. Then, after adjusting the resistance value due to the integration of the heating resistor 2 and the additional resistance film 3 by trimming or the like, the protective layer of the heating head heating resistor is exposed so that the pair of electrodes 4 and 4 are partially exposed. The protective film 5 is formed by printing a well-known glass paste used conventionally and baking it.
[0013]
In the above-described embodiment, the heater having the configuration in which the electrodes are arranged at both ends in the long side direction of the heating resistor is shown. However, the electrode is arranged on one end side of the insulating substrate and the heating resistor is arranged at the other end side in the long side direction. The present invention may be applied to a heater having a heating resistor having a shape in which the body is folded or a shape having a folding electrode (other than the heating resistor is not connected to the outside) on the other end side.
[0014]
In addition, this invention is not specifically limited to structure, such as a formation method, a shape, and a material as described in the above-mentioned Example.
[0015]
【The invention's effect】
As described above, by forming an additional resistance film along the long side direction of the heating resistor at both ends in the short side direction of the belt-like heating resistor, as shown in FIG. The thickness dimension at the position A in the side direction and the thickness dimension at the position B can be formed substantially equal, and variations in resistance value in the short side direction when using the heater are reduced.
[0016]
As a result, when a current is applied to the electrode of the heater to generate heat in the heating resistor and the additional resistance film, the heating temperature varies near both ends in the width direction of the heating portion as shown in FIG. This eliminates the possibility of uneven toner fixation on the substrate, making it possible to support high-quality printing, as well as a region where the temperature when the heater heats up is higher than the temperature at which the toner can be fixed. Becomes substantially equal to the entire width of the heating resistor. For this reason, by making the conveyance speed of the printing medium with respect to the heating resistor the same value as before, the contact time between the heating resistor and the printing body becomes longer, so the high melting point type can be used for the toner, This has the effect of enabling high-quality printing. Also, even if the conveyance speed of the printing medium with respect to the heating resistor is increased, the contact time between the heating resistor and the printing medium becomes the same, so that the fixing can be performed in the same manner, and high-speed printing is possible. It has the effect.
[0017]
Furthermore, the additional resistive film formed along the long side direction of the heating resistor is formed such that the widthwise dimension is wider at both ends than the central part in the longitudinal direction, so that the heating resistor and the additional resistive film are The combined resistance value is higher at both ends in the long side direction than at the center.
As a result, when current is applied to the electrode of the heater to heat the heating resistor and the additional resistance film, the heat generation temperature at both ends in the long side direction is higher than that at the center, but heat is radiated through the electrode. The temperature distribution of the heater in the longitudinal direction as well as in the width direction is offset substantially by being offset by the thermal energy, and it is possible to further prevent the toner from being unevenly fixed to the printing medium.
[Brief description of the drawings]
1 is a plan view showing a heater according to the present invention. FIG. 2 is a partial cross-sectional view of the heater according to the present invention shown in FIG. 1. FIG. 3 is a perspective view showing a conventional heater. Sectional view of the heater of the machine 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Heating resistor 3 ... Additional resistance film 4 ... Electrode 5 ... Protective film applicant ROHM Co., Ltd.

Claims (1)

長尺状の絶縁基板の表面に長辺方向に抵抗用ペーストを印刷及び焼成することによって帯状の発熱抵抗体を形成して、当該発熱抵抗体の幅方向における中央部の厚さ寸法が前記発熱抵抗体の幅方向における両端部の厚さ寸法より大きく形成された加熱ヒータにおいて、
前記帯状の発熱抵抗体の幅方向両端部に前記発熱抵抗体の長手方向に沿って追加抵抗膜が前記抵抗用ペーストと同一の材料により形成されていて、前記発熱抵抗体の幅方向における中央部の厚さ寸法が前記発熱抵抗体の幅方向における両端部の厚さ寸法と前記追加抵抗膜の厚さ寸法との和とほぼ等しくされていることを特徴とする加熱ヒータ。A strip-shaped heating resistor is formed by printing and baking a resistance paste in the long side direction on the surface of the long insulating substrate, and the thickness dimension of the central portion in the width direction of the heating resistor is the heat generation In the heater formed larger than the thickness dimension of both ends in the width direction of the resistor,
Said additional resistive film along the longitudinal direction of the heating resistors are formed of the same material as the resistor paste both widthwise ends of the strip-like heating resistor, the central portion in the width direction of the heating resistor heating heater of thickness dimension, characterized in that it is substantially equal to the sum of the thickness of both end portions and the thickness dimension of the additional resistive film in the width direction of the heating resistor.

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