JP2006030350A

JP2006030350A - Fixing device and image forming apparatus

Info

Publication number: JP2006030350A
Application number: JP2004205610A
Authority: JP
Inventors: Tomoe Ariga; 友衛有賀; Takeshi Ikuma; 健井熊
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2004-07-13
Filing date: 2004-07-13
Publication date: 2006-02-02

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deflection in the shaft direction of a belt stretching and laying member and the creep deformation thereof so as to form a uniform stable fixing nip all over the area in the shaft direction. <P>SOLUTION: The fixing device is equipped with a thermal fixing roll 1, a pressure roll 2 pressed against the thermal fixing roll, a heat resistant belt 3 wound round the outer periphery of the pressure roll and moving while it is held between the thermal fixing roll and the pressure roll, and the belt stretching and laying member 4 for stretching and laying the heat resistant belt, and fixes an unfixed toner image formed on sheet material by arranging the belt stretching and laying member at a position where the nip is formed by winding the heat resistant belt round the thermal fixing roll side from a tangent L at a pressing part between the thermal fixing roll and the pressure roll on a more upstream side in the moving direction of the heat resistant belt than the pressing part. An elastic supporting member 5 is disposed between the pressure roll 2 and the belt stretching and laying member 4, and a plurality of springs 6 are disposed in the shaft direction between the belt stretching and laying member 4 and the elastic supporting member 5, then the elastic supporting member 5 is provided with a pressing part 5d pressing while applying the rotational force of the pressure roll to the nip part between the fixing roll and the heat resistant belt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、熱定着ロールと、該熱定着ロールに押圧する加圧ロールと、該加圧ロールの外周に捲着され前記熱定着ロールとの間に挟持されて移動する耐熱ベルトと、該耐熱ベルトを張架するベルト張架部材とを備え、シート材上に形成した未定着トナー像を定着する定着装置に関する。 The present invention includes a heat fixing roll, a pressure roll that presses against the heat fixing roll, a heat-resistant belt that is attached to the outer periphery of the pressure roll and is sandwiched and moved between the heat fixing roll, and the heat-resistant roll. The present invention relates to a fixing device that includes a belt stretching member that stretches a belt and fixes an unfixed toner image formed on a sheet material.

複写機やプリンタ、ファクシミリ等の画像形成装置に搭載され転写材上に未定着のトナー像を接触加熱定着する加熱ロール型定着装置として、表面に弾性体が被覆され加熱源を内蔵して回転可能にした熱定着ロールと、複数の支持ロールによって張架された無端の耐熱ベルトと、耐熱ベルトを熱定着ロールの廻りに所定角度だけ巻き付けてニップ領域を形成させると共にそのニップ領域の出口に他の部分よりも大きな圧力を局部的に加えて熱定着ロール表面の弾性体に歪みを生じさせる圧力手段とを設け、ニップ部からのシート材の排出を容易にした定着装置（例えば、特許文献１参照）、無端の耐熱ベルトの内側に突出部が設けられた押圧部材を配設し、接触ニップ域の微小圧力領域を減少させるようにした定着装置（例えば、特許文献２参照）などが提案されている。 Mounted on image forming devices such as copiers, printers, and facsimiles, it is a heated roll type fixing device that heats and fixes unfixed toner images on a transfer material. A heat fixing roll, an endless heat-resistant belt stretched by a plurality of support rolls, and a heat-resistant belt is wound around the heat-fixing roll by a predetermined angle to form a nip region and another outlet is provided at the exit of the nip region. A fixing device that applies pressure larger than the portion locally to cause distortion on the elastic body on the surface of the heat fixing roll, and facilitates discharge of the sheet material from the nip portion (see, for example, Patent Document 1) ), A fixing device in which a pressing member provided with a protrusion is provided inside the endless heat-resistant belt so as to reduce a minute pressure region in the contact nip region (for example, Patent Document 2) Irradiation), and the like have been proposed.

これらは、複数の支持ロールとその回転軸受が必要で、定着装置が複雑で大型化するだけでなく、高価にし、必然的に当該定着装置を搭載した画像形成装置を複雑、大型化、高価にする。しかも、耐熱ベルトの周長が長くなり、所定の経路で移動する時に、複数の支持ロールによって熱エネルギーが奪われ、周長の長さに応じて自然放熱が増える。そのため、所定の温度に到達するまでの時間が多く必要になり、電源オン時から定着可能になるまでの所謂ウォーミングアップ時間を長く要することになり、好ましくない。 These require a plurality of support rolls and their rotating bearings, which not only makes the fixing device complicated and large, but also makes it expensive, and inevitably makes the image forming apparatus equipped with the fixing device complicated, large and expensive. To do. Moreover, when the perimeter of the heat-resistant belt becomes long and moves along a predetermined path, the heat energy is taken away by the plurality of support rolls, and the natural heat dissipation increases according to the length of the perimeter. For this reason, it takes a long time to reach a predetermined temperature, and a so-called warm-up time from when the power is turned on to when fixing is required is not preferable.

また、熱定着ロールに対して耐熱ベルトをニップ形成可能な角度だけ巻き付けてニップ部出口で他の部分より大きな圧力を局部的に加え熱定着ロールの弾性層に歪みを形成させる構成では、シート材が熱定着ロールに巻き付くのを抑制するには好適であるが、弾性層の歪みに沿って排出されるシート材は、この歪みに倣ってカールしたり、局部的な高圧力のために皺発生などの変形をもたらす。 In the configuration in which the heat-resistant belt is wound around the heat-fixing roll at an angle capable of forming a nip, and a pressure larger than other portions is locally applied at the exit of the nip portion to form a strain in the elastic layer of the heat-fixing roll. The sheet material discharged along the strain of the elastic layer curls along the strain or is locally damaged by high pressure. It causes deformation such as occurrence.

他に、ロール間に設定した圧力によってロールを撓ませてロールに接するニップ長を形成し、このニップ間に未定着トナー像を担持したシート材を通過させて定着させ、シート材の特性に合わせロールの駆動速度として、第１の速度か第２の速度かを選択して駆動する定着装置（例えば、特許文献３参照）が提案されているが、ロールの熱容量が大きくてウォーミングアップ時間を長く要して好ましくないばかりでなく、圧力によってロールを撓ませて形成した長ニップ間を通過するシート材は、前者の装置と同様、この圧力によるストレスが大きくてカールや皺などのシート材変形を引き起こす。 In addition, the roll is deflected by the pressure set between the rolls to form a nip length in contact with the roll, and a sheet material carrying an unfixed toner image is passed between the nips and fixed to match the characteristics of the sheet material. There has been proposed a fixing device (for example, see Patent Document 3) that selects and drives the roll speed as the first speed or the second speed. However, the roll has a large heat capacity and requires a long warm-up time. Not only is this not preferable, but the sheet material that passes between the long nips formed by bending the roll with pressure, like the former device, is stressed by this pressure and causes deformation of the sheet material such as curls and wrinkles. .

そこで、上記のような課題を解決するものとして、張架部材を耐熱ベルトの移動方向上流側で熱定着ロールと加圧ロールとの押圧部の接線より熱定着ロールに耐熱ベルトを巻き付けてニップを形成する位置に配置して揺動可能に支持することにより、熱ロール型定着装置の構造の単純化、小型化、コスト低減を可能にし、ウォーミングアップ時間を短縮でき、シート材へのストレスを小さくしてカールの発生や皺発生など排出されるシート材の変形を抑制できるようにした定着装置（例えば、特許文献４参照）を提案している。
特許第３０８４６９２号公報特許第３４８０２５０号公報特公平８−４０２３５号公報特開平２００４−４２３４号公報 Therefore, as a solution to the above-described problem, the nip is formed by winding the heat-resistant belt around the heat-fixing roll from the tangent line of the pressing portion between the heat-fixing roll and the pressure roll at the upstream side in the moving direction of the heat-resistant belt. By placing it at the forming position and supporting it in a swingable manner, the structure of the heat roll type fixing device can be simplified, reduced in size and cost can be reduced, the warm-up time can be shortened, and the stress on the sheet material can be reduced. A fixing device (see, for example, Patent Document 4) that can suppress deformation of the discharged sheet material such as curling and wrinkling is proposed.
Japanese Patent No. 3084692 Japanese Patent No. 3480250 Japanese Patent Publication No. 8-40235 Japanese Patent Laid-Open No. 2004-4234

しかしながら、これまでに提案されている上記従来の各定着装置の構造では、定着特性の向上策としては有効な手段となっているが、熱定着ロールや加圧ロールの軸方向、つまり長手方向の全域にわたって安定した接触ニップ域を形成するのに十分ではない。すなわち、接触ニップ域は、押圧により熱定着ロールや加圧ロールの軸撓み、あるいは押圧部材、張架部材の曲がりや反り、軸方向の捻じれなどの変形と微妙な関係にあるため、これらの影響を受け、接触ニップ域が不安定になるのを解消するのが難しく、定着特性が向上できないのが現状である。 However, the structure of each of the conventional fixing devices proposed so far is an effective means for improving the fixing characteristics, but in the axial direction of the heat fixing roll and the pressure roll, that is, in the longitudinal direction. It is not sufficient to form a stable contact nip area throughout. That is, the contact nip area has a delicate relationship with deformation such as axial bending of the heat fixing roll or pressure roll by pressing, or bending or warping of the pressing member or stretching member, and twisting in the axial direction. Under the present circumstances, it is difficult to eliminate the instability of the contact nip area, and the fixing characteristics cannot be improved.

また、熱定着ロールが発する約２００℃程度の高温の影響を受けてクリープ変形をきたす場合があり、特にウオーミングアップ時間の短縮に効用のある熱容量の小さなプラスチックス素材で形成した張架部材の場合にはこの現象が顕著に現れ、安定した定着ニップの形成に好ましくない場合が生じる。 In addition, creep deformation may occur under the influence of a high temperature of about 200 ° C. generated by the heat fixing roll, particularly in the case of a stretch member formed of a plastic material having a small heat capacity that is effective for shortening the warm-up time. This phenomenon appears remarkably, and there are cases where it is not preferable for the formation of a stable fixing nip.

本発明は、上記従来の課題を解決するものであって、ベルト張架部材で耐熱ベルトを張架して熱定着ロールと加圧ロールとの押圧部の接線より熱定着ロールに耐熱ベルトを巻き付けてニップを形成する接触ニップ域を簡単な構成により安定化し均一な安定した定着ニップが形成可能とし定着特性を向上させるものである。 The present invention solves the above-described conventional problems, in which a heat-resistant belt is stretched by a belt-stretching member, and the heat-resistant belt is wound around the heat-fixing roll from the tangent of the pressing portion between the heat-fixing roll and the pressure roll. Thus, the contact nip area for forming the nip can be stabilized with a simple configuration, and a uniform and stable fixing nip can be formed to improve the fixing characteristics.

そのために本発明の定着装置は、熱定着ロールと、該熱定着ロールに押圧する加圧ロールと、該加圧ロールの外周に捲着され前記熱定着ロールとの間に挟持されて移動する耐熱ベルトと、該耐熱ベルトを張架するベルト張架部材とを備え、前記ベルト張架部材を、熱定着ロールと加圧ロールとの押圧部より耐熱ベルトの移動方向上流側で、かつ耐熱ベルトが押圧部接線より熱定着ロール側に巻き付けてニップを形成する位置に配置し、シート材上に形成した未定着トナー像を定着する定着装置であって、前記加圧ロールとベルト張架部材との間に弾性支持部材を配設し、前記ベルト張架部材と弾性支持部材間の軸方向に複数のスプリングを配設し、前記加圧ロールの回転力を前記定着ロールと耐熱ベルトのニップ部に押圧する押圧部を前記弾性支持部材に設けたことを特徴とする。
また、前記弾性支持部材の加熱ロール側には、加熱ロールと耐熱ベルトの厚みを含む曲率と同一の曲面が形成され、該曲面の先端は、加熱ロールと加圧ロールとのニップ部に近接するように構成されていることを特徴とする。
また、前記前記スプリングの軸芯を通る線は、加圧ロールの回転軸の軸芯から加熱ロールに対して外側にずらした位置を通る線上とし、スプリング付勢力の分力が耐熱ベルトを加熱ロールに押圧する方向としたことを特徴とする。
また、前記ベルト張架部材には、熱定着ロールとの押圧部に平坦面が形成されていることを特徴とする。
また、前記弾性支持部材の内面には、加圧ロールの外周面と略同一の曲率面を有する突起状の摺接面が形成され、該摺接面を介して加圧ロールに摺接するように構成したことを特徴とする。
また、前記摺接面に対向する位置に前記スプリングを配置したことを特徴とする。
また、前記弾性支持部材の内面周方向両側に曲面状の摺接面を形成し、該摺接面を介して加圧ロールに摺接するように構成したことを特徴とする。
また、前記ベルト張架部材は、前記熱定着ロールに前記耐熱ベルトの内側から軽押圧する方向にバネ付勢する軽押圧付勢手段を配置したことを特徴とする。
また、前記ベルト張架部材は、前記耐熱ベルトの摺動面の中央近傍が端部より凸状に突出したクラウン形状であることを特徴とする。 Therefore, the fixing device of the present invention includes a heat fixing roll, a pressure roll that presses against the heat fixing roll, and a heat resistance that is attached to the outer periphery of the pressure roll and is sandwiched between the heat fixing roll and moves. A belt and a belt stretching member that stretches the heat-resistant belt, and the belt stretching member is located upstream of the pressing portion between the heat fixing roll and the pressure roll in the moving direction of the heat-resistant belt, and the heat-resistant belt is A fixing device that is placed at a position where a nip is formed by wrapping around a pressing portion tangent to a heat fixing roll side, and fixes an unfixed toner image formed on a sheet material, comprising: the pressure roll and a belt stretching member An elastic support member is disposed between the plurality of springs in the axial direction between the belt stretching member and the elastic support member, and the rotational force of the pressure roll is applied to the nip portion of the fixing roll and the heat-resistant belt. The pressing part to be pressed Characterized in that provided on the support member.
A curved surface having the same curvature including the thickness of the heating roll and the heat-resistant belt is formed on the heating roll side of the elastic support member, and the tip of the curved surface is close to the nip portion between the heating roll and the pressure roll. It is comprised as follows.
The line passing through the axis of the spring is on a line passing through a position shifted outward from the axis of the rotary shaft of the pressure roll with respect to the heating roll. It is characterized by the direction of pressing.
Further, the belt stretching member is characterized in that a flat surface is formed at a pressing portion with the heat fixing roll.
In addition, a protrusion-like sliding contact surface having a curvature surface substantially the same as the outer peripheral surface of the pressure roll is formed on the inner surface of the elastic support member, and is in sliding contact with the pressure roll through the sliding contact surface. It is characterized by comprising.
Further, the spring is disposed at a position facing the sliding contact surface.
In addition, a curved slidable contact surface is formed on both sides in the circumferential direction of the inner surface of the elastic support member, and the elastic support member is configured to slidably contact the pressure roll via the slidable contact surface.
Further, the belt stretching member is characterized in that a light pressing urging means for urging a spring in a direction of light pressing from the inside of the heat-resistant belt is arranged on the heat fixing roll.
Further, the belt stretching member has a crown shape in which the vicinity of the center of the sliding surface of the heat-resistant belt protrudes from the end portion in a convex shape.

本発明によれば、加圧ロールとベルト張架部材との間に弾性支持部材を配設し、ベルト張架部材と弾性支持部材間に軸方向に複数のスプリングを配設し、前記複数のスプリングの付勢力を異ならせることにより、ベルト張架部材の軸方向撓みやクリープ変形を防止し、軸方向全域にわたって均一な安定した定着ニップを形成することができる。また、ベルト張架部材には、各スプリングの付勢力に応じた力が作用し、耐熱ベルトに張力が付与されると同時に、加圧ロールの回動力は摺接面との摩擦力によって弾性支持部材に伝達され、押圧部を介して耐熱ベルトを加熱ロールに押圧させることができるので、熱定着ロールとベルト張架部材の押圧した部位と、熱定着ロールに加圧ロールをを押圧した部位との中間部位では、耐熱ベルトが熱定着ロールに巻き付けられて押圧状態が連続した定着ニップを形成することができる。 According to the present invention, an elastic support member is disposed between the pressure roll and the belt stretching member, and a plurality of springs are disposed in the axial direction between the belt stretching member and the elastic support member. By varying the urging force of the spring, it is possible to prevent the belt stretching member from being bent in the axial direction and creep deformation, and to form a uniform and stable fixing nip throughout the entire axial direction. In addition, a force corresponding to the urging force of each spring acts on the belt stretching member, and tension is applied to the heat-resistant belt. At the same time, the rotational force of the pressure roll is elastically supported by the frictional force with the sliding contact surface. Since the heat-resistant belt can be pressed against the heating roll through the pressing portion via the pressing portion, the pressed portion of the heat fixing roll and the belt stretching member, and the portion where the pressure roll is pressed against the heat fixing roll, In the intermediate portion, a heat-resistant belt is wound around the heat-fixing roll to form a fixing nip in which the pressing state is continuous.

以下、本発明の実施の形態を図面を参照しつつ説明する。図１は本発明に係る定着装置の１実施形態を示し、図１（Ａ）は図１（Ｂ）のＸ−Ｘ線に沿って切断し矢印方向に見た断面図、図１（Ｂ）は図１（Ａ）のＹ−Ｙ線に沿って切断し矢印方向に見た断面図であり、装置の右半分は省略している。図２はベルト張架部材の加圧ロール側から見た斜視図、図３は弾性支持部材の斜視図、図４は定着ニップ部を拡大して示す図である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows one embodiment of a fixing device according to the present invention. FIG. 1A is a cross-sectional view taken along the line XX of FIG. FIG. 4 is a cross-sectional view taken along the line YY in FIG. 1A and viewed in the direction of the arrow, with the right half of the device omitted. 2 is a perspective view of the belt stretching member as viewed from the pressure roll side, FIG. 3 is a perspective view of the elastic support member, and FIG. 4 is an enlarged view of the fixing nip portion.

図１において、熱定着ロール１は、外径２５ｍｍ程度、肉厚０．７ｍｍ程度のパイプ材をロール基材１ｂとして、その外周に厚み０．４ｍｍ程度の弾性体１ｃを被覆して形成し、ロール基材１ｂの内部に加熱源として１０５０Ｗ、２本の柱状ハロゲンランプ１ａを内蔵して回転可能にしたものである。加圧ロール２は、例えば外径２５ｍｍ程度、肉厚０．７ｍｍ程度のパイプ材をロール基材、さらには、その外周に厚み０．２ｍｍ程度の弾性体を被覆して形成し、熱定着ロール１と加圧ロール２の圧接力を１０ｋｇ以下、ニップ長を１０ｍｍ程度で構成し、熱定着ロール１に対向して配置し、図示矢印方向に回転可能にした構造になっている。加圧ロール２の両端の回転軸２ａは、図１（Ｂ）に示すように左右のフレーム７に軸受７ａを介して回転自在に支持されている。 In FIG. 1, a heat fixing roll 1 is formed by covering a pipe member having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm as a roll base material 1b, and an elastic body 1c having a thickness of about 0.4 mm on its outer periphery. The roll base 1b has a built-in 1050W as a heating source and two columnar halogen lamps 1a that can be rotated. The pressure roll 2 is formed by, for example, forming a pipe material having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm by coating a roll base material, and further covering an outer periphery of the elastic body having a thickness of about 0.2 mm. The pressure contact force between No. 1 and the pressure roll 2 is 10 kg or less, the nip length is about 10 mm, and it is arranged to face the heat fixing roll 1 so as to be rotatable in the direction of the arrow shown. As shown in FIG. 1B, the rotary shafts 2a at both ends of the pressure roll 2 are rotatably supported by the left and right frames 7 via bearings 7a.

本実施形態によれば、熱定着ロール１および加圧ロール２の外径を２５ｍｍ程度の小径に構成しているため、定着後のシート材Ｓが熱定着ロール１または耐熱ベルト３に巻き付くこともないので、シート材Ｓを強制的に剥がすための手段を不要になる。また、熱定着ロール１の弾性体１ｃの表層には約３０μｍのＰＦＡ層を設ければ、その分だけ剛性が向上し略均一な弾性変形をして所謂水平ニップが形成されて熱定着ロール１の周速に対して耐熱ベルト３またはシート材Ｓの搬送速度に差異が生じることもなく、極めて安定した画像定着が可能となる。 According to this embodiment, since the outer diameters of the heat fixing roll 1 and the pressure roll 2 are configured to be as small as about 25 mm, the sheet material S after fixing is wound around the heat fixing roll 1 or the heat-resistant belt 3. Therefore, a means for forcibly peeling the sheet material S becomes unnecessary. If a PFA layer of about 30 μm is provided on the surface of the elastic body 1 c of the heat fixing roll 1, the rigidity is improved by that amount and a substantially uniform elastic deformation is formed to form a so-called horizontal nip, thereby forming the heat fixing roll 1. Thus, there is no difference in the conveying speed of the heat-resistant belt 3 or the sheet material S with respect to the peripheral speed, and extremely stable image fixing is possible.

本実施形態においては、熱定着ロール１の内部に２本の加熱源１ａを内蔵しており、このハロゲンランプの発熱エレメントを異なった配置に構成して選択的に点灯すると、後述する耐熱ベルト３が熱定着ロール１に巻き付いた定着ニップ部位とベルト張架部材４が熱定着ロール１に摺接する部位のような異なった条件や、幅の広いシート材と幅の狭いシート材とのように異なった条件下での温度コントロールを容易に行うことができる。 In the present embodiment, two heat sources 1a are built in the heat fixing roll 1, and when the heating elements of the halogen lamp are configured in different arrangements and selectively lit, a heat-resistant belt 3 described later. Different conditions such as a fixing nip portion wound around the heat fixing roll 1 and a portion where the belt stretching member 4 is in sliding contact with the heat fixing roll 1, or a wide sheet material and a narrow sheet material. Temperature can be easily controlled under different conditions.

耐熱ベルト３は、熱定着ロール１と加圧ロール２との間に挟持されて加圧ロール２とベルト張架部材４の外周に張架され移動可能になったエンドレスのベルトであり、例えば０．０３ｍｍ以上の厚みを有するステンレス管やニッケル電鋳管等の金属管、ポリイミドやシリコン等の耐熱樹脂等管で構成される。 The heat-resistant belt 3 is an endless belt that is sandwiched between the heat fixing roll 1 and the pressure roll 2 and is stretched around the outer periphery of the pressure roll 2 and the belt stretching member 4 so as to be movable. It is composed of a metal tube such as a stainless steel tube or a nickel electroformed tube having a thickness of 0.03 mm or more, and a heat-resistant resin tube such as polyimide or silicon.

ベルト張架部材４は、熱定着ロール１と加圧ロール２のニップ部よりもシート材Ｓの搬送方向上流側に配設されるとともに、加圧ロール２の回転軸２ａを中心として矢印方向に揺動可能に配設されている。また、ベルト張架部材４は、シート材Ｓが定着ニップを非通過の状態において耐熱ベルト３を熱定着ロール１の接線方向に張架する構成にし、耐熱ベルト３の内側から熱定着ロール１を平坦な面４ｃで軽押圧する（図２、図４参照）。シート材Ｓが定着ニップに進入する初期位置で定着圧力が大きいと進入がスムーズに行われなくて、シート材Ｓの先端が折れた状態で定着される場合があるが、耐熱ベルト３を熱定着ロール１の接線方向に張架する構成にすると、シート材Ｓの進入がスムーズに成される導入口部が形成でき、安定したシート材Ｓの進入が可能になる。 The belt stretching member 4 is disposed on the upstream side in the conveying direction of the sheet material S from the nip portion between the heat fixing roll 1 and the pressure roll 2, and in the direction of the arrow about the rotation shaft 2 a of the pressure roll 2. It is arranged so that it can swing. The belt stretching member 4 is configured to stretch the heat-resistant belt 3 in the tangential direction of the heat-fixing roll 1 in a state where the sheet material S does not pass through the fixing nip, and the heat-fixing roll 1 is attached from the inside of the heat-resistant belt 3. Lightly press on the flat surface 4c (see FIGS. 2 and 4). If the fixing pressure is large at the initial position where the sheet material S enters the fixing nip, the entry may not be smoothly performed and the sheet material S may be fixed with the leading end of the sheet material S broken. When the roll 1 is stretched in the tangential direction, an introduction port portion in which the sheet material S can smoothly enter can be formed, and the sheet material S can be stably entered.

ベルト張架部材４は、耐熱ベルト３の内周に嵌挿して加圧ロール２および弾性支持部材５と協働して耐熱ベルト３に張力ｆを付与すると共に、耐熱ベルト３を熱定着ロール１に巻き付けてニップを形成する位置に配置した、略半月状のベルト摺動部材（耐熱ベルト３はベルト張架部材４上を摺動する）である。弾性支持部材５は、軸方向断面が円弧状の部材であり、両端には加圧ロール２とベルト張架部材４に延びるフランジ５ａが形成され、内面には加圧ロール２に対する円弧突起状の摺接面５ｂが形成され、摺接面５ｂを介して加圧ロール２に摺接されるように構成されいる。また、弾性支持部材５の加熱ロール１側には、加熱ロール１と耐熱ベルト３の厚みを含む曲率と同一の曲面からなる押圧部５ｄが形成され、押圧部５ｄの先端５ｅは、加熱ロール１と加圧ロール２とのニップ部に近接するように構成されている。 The belt stretching member 4 is fitted on the inner periphery of the heat-resistant belt 3 to apply tension f to the heat-resistant belt 3 in cooperation with the pressure roll 2 and the elastic support member 5, and the heat-resistant belt 3 is attached to the heat fixing roll 1. A belt-shaped sliding member (a heat-resistant belt 3 slides on the belt stretching member 4) arranged at a position where it is wound around the belt to form a nip. The elastic support member 5 is a member having an arc-shaped cross section in the axial direction, formed with flanges 5a extending to the pressure roll 2 and the belt stretching member 4 at both ends, and having an arc-shaped projection with respect to the pressure roll 2 on the inner surface. A sliding contact surface 5b is formed, and is configured to be in sliding contact with the pressure roll 2 via the sliding contact surface 5b. Further, on the heating roll 1 side of the elastic support member 5, a pressing portion 5d having the same curved surface as the curvature including the thickness of the heating roll 1 and the heat-resistant belt 3 is formed, and the tip 5e of the pressing portion 5d is connected to the heating roll 1 And the pressure roll 2 are configured to be close to each other.

また、弾性支持部材５の摺接面５ｃに対向する位置にスプリング配設孔４ｂが形成され、スプリング配設孔４ｂにはスプリング６が配設されている。そして、加圧ロール２およびベルト張架部材４が弾性支持部材５のフランジ５ａ間に位置するように配設し、加圧ロール２に対して弾性支持部材５およびベルト張架部材４を位置決めしている。この構成により、ベルト張架部材４には、各スプリング６の付勢力に応じた張力が作用し、耐熱ベルト３に張力ｆが付与される。同時に、加圧ロール２の回動力は摺接面５ｂとの摩擦力によって弾性支持部材５に伝達され、押圧部５ｄを介して耐熱ベルト３を加熱ロール１に押圧させることができる。なお、図４においてフランジ５ａに矢印Ｐ方向にバネ力を作用させるようにすれば押圧部５ｄの押圧力をさらに増大させることができる。 A spring disposition hole 4b is formed at a position facing the sliding contact surface 5c of the elastic support member 5, and a spring 6 is disposed in the spring disposition hole 4b. The pressure roll 2 and the belt stretching member 4 are disposed so as to be positioned between the flanges 5 a of the elastic support member 5, and the elastic support member 5 and the belt stretching member 4 are positioned with respect to the pressure roll 2. ing. With this configuration, a tension corresponding to the urging force of each spring 6 acts on the belt stretching member 4 and a tension f is applied to the heat-resistant belt 3. At the same time, the rotational force of the pressure roll 2 is transmitted to the elastic support member 5 by the frictional force with the sliding contact surface 5b, and the heat-resistant belt 3 can be pressed against the heating roll 1 via the pressing portion 5d. In FIG. 4, if the spring force is applied to the flange 5a in the direction of arrow P, the pressing force of the pressing portion 5d can be further increased.

図５は、図１の定着装置の変形例を示す断面図である。図１においては、弾性支持部材５の内面には加圧ロールの外周面と略同一の曲率面を有する突起状の摺接面５ｂが形成され、摺接面５ｂを介して加圧ロール２に摺接するように構成しているが、本例においては、弾性支持部材５の内面周方向両側に曲面状の摺接面５ｂを形成し、摺接面５ｂを介して加圧ロール２に摺接するように構成している。前記摺接面５ｂは、加圧ロール２の外周面に沿って２つの位置で摺接してベクトル合力で前記加圧ロールの外周面に沿って前記ベルト張架部材を摺接させている。 FIG. 5 is a cross-sectional view showing a modification of the fixing device of FIG. In FIG. 1, a protrusion-like sliding contact surface 5b having a curvature surface substantially the same as the outer peripheral surface of the pressure roll is formed on the inner surface of the elastic support member 5, and is formed on the pressure roll 2 via the sliding contact surface 5b. In this example, curved contact surfaces 5b are formed on both sides in the circumferential direction of the inner surface of the elastic support member 5, and in contact with the pressure roll 2 via the contact surface 5b. It is configured as follows. The slidable contact surface 5b is slidably contacted at two positions along the outer peripheral surface of the pressure roll 2 and slidably contacts the belt stretching member along the outer peripheral surface of the pressure roll with a vector resultant force.

加圧ロール２の外周に捲着し熱定着ロール１との間に挟持し移動する耐熱ベルト３をベルト張架部材４により張架し熱定着ロール１に巻き付けてニップを形成する場合、ベルト張架部材４は、軸方向に撓みが生じたり、約２００℃程度の高温になる熱定着ロール１の影響を受けてクリープ変形が生じたりする。特にベルト張架部材４をウォーミングアップタイムの短縮に効用のあるものとして、熱容量の小さなプラスチック素材で形成した場合に、この現象が顕著に現れ安定した定着ニップの形成に好ましくない。本実施形態においては、ベルト張架部材４には、軸方向全域にわったて各スプリング６の付勢力に応じた張力が作用するため、このような軸方向の撓みやクリープ変形を所定の許容幅で防止できるので、軸方向全域にわたって均一な安定した定着ニップが形成可能となる。 When a heat-resistant belt 3 that is attached to the outer periphery of the pressure roll 2 and is sandwiched and moved between the heat-fixing roll 1 is stretched by the belt-stretching member 4 and wound around the heat-fixing roll 1, a belt tension is formed. The frame member 4 is deflected in the axial direction, or creep deformation occurs due to the influence of the heat fixing roll 1 having a high temperature of about 200 ° C. In particular, when the belt stretching member 4 is made of a plastic material having a small heat capacity as effective for shortening the warm-up time, this phenomenon appears remarkably and is not preferable for forming a stable fixing nip. In the present embodiment, the belt tension member 4 is subjected to a tension according to the urging force of each spring 6 over the entire region in the axial direction. Since it can be prevented by the width, a uniform and stable fixing nip can be formed over the entire axial direction.

ベルト張架部材４は、耐熱ベルト３が摺動する軸方向の中央近傍がやや凸状に突出したクラウン形状とすることにより、中央近傍で耐熱ベルト３に付与する張力ｆを大きくなるようにし、耐熱ベルト３の端部への寄りや蛇行をなくし、耐熱ベルト３がベルト張架部材４の摺動面を滑らかに摺動でき、ベルト張架部材４が変形して略真直な状態を得るようにすることもできる。このクラウン形状は、耐熱ベルト３の張架方向のみならず、熱定着ロール１に軽押圧する方向においても形成しておくことも安定した定着ニップの形成に有効である。 The belt stretching member 4 has a crown shape in which the vicinity of the center in the axial direction in which the heat-resistant belt 3 slides protrudes slightly convex so that the tension f applied to the heat-resistant belt 3 near the center is increased. The heat-resistant belt 3 can be smoothly slid on the sliding surface of the belt stretching member 4 and the belt stretching member 4 is deformed so as to obtain a substantially straight state. It can also be. This crown shape is effective not only in the direction in which the heat-resistant belt 3 is stretched but also in the direction in which the heat-fixing roll 1 is lightly pressed, so that a stable fixing nip can be formed.

また、ベルト張架部材４は、耐熱ベルト３が熱定着ロール１と加圧ロール２との押圧部接線Ｌより熱定着ロール１側に巻き付けてニップを形成する位置に配置される。突壁４ｄは、ベルト張架部材４の一端または両端に突設され、耐熱ベルト３が一方に寄った場合にこの突壁４ｄに当接して寄り規制を行うためのものである。スプリング９は、ベルト張架部材４の突壁４ｄの熱定着ロール１と反対側端部のフレームとの間に配設され、ベルト張架部材４を耐熱ベルト３の内側から熱定着ロール１に軽押圧する方向にバネ付勢する軽押圧付勢手段であり、このスプリング９によりベルト張架部材４の平坦な面４ｃが耐熱ベルト３の内側から熱定着ロール１に軽押圧され、熱定着ロール１に摺接して位置決めされる。 The belt stretching member 4 is disposed at a position where the heat-resistant belt 3 is wound around the pressing portion tangent L between the heat fixing roll 1 and the pressure roll 2 toward the heat fixing roll 1 to form a nip. The protruding wall 4d protrudes from one end or both ends of the belt stretching member 4, and when the heat-resistant belt 3 approaches one side, the protruding wall 4d comes into contact with the protruding wall 4d to regulate the deviation. The spring 9 is disposed between the heat fixing roll 1 of the projecting wall 4 d of the belt stretching member 4 and the frame at the opposite end, and the belt stretching member 4 is connected to the heat fixing roll 1 from the inside of the heat-resistant belt 3. This is a light pressure biasing means for biasing the spring in the light pressure direction. The flat surface 4c of the belt stretching member 4 is lightly pressed from the inside of the heat-resistant belt 3 to the heat fixing roll 1 by the spring 9, and the heat fixing roll. 1 and is positioned in sliding contact.

ベルト張架部材４と熱定着ロール１の相対的な位置関係は、加圧ロール２とベルト張架部材４に耐熱ベルト３を張架して張力を付与した状態で決定付けられ、微細な関係においては、熱定着ロール１に対して軸方向に平行な状態ではなく、所謂スキューした相対関係であったり、ベルト張架部材４の反りや曲がりなどの真直性に影響されたりする。このような場合、耐熱ベルト３の内側から熱定着ロール１に軽押圧するベルト張架部材４の部位が円筒状の曲面になっていると、耐熱ベルト３の内側から熱定着ロール１にベルト張架部材４が軽押圧する部位における定着ニップの様相が均一に形成できない場合がある。しかし、上記のようにベルト張架部材４が耐熱ベルト３の内側から熱定着ロール１に軽押圧する部位を平坦な面４ｃで形成すると、この部位での定着ニップの不均一な状態を緩和することができ、好ましい定着ニップの形成が容易にできる。 The relative positional relationship between the belt tension member 4 and the heat fixing roll 1 is determined in a state in which the heat-resistant belt 3 is stretched between the pressure roll 2 and the belt tension member 4 and tension is applied, and a fine relationship is established. However, it is not in a state parallel to the axial direction with respect to the heat fixing roll 1, but is a so-called skewed relative relationship, or is affected by straightness such as warping or bending of the belt stretching member 4. In such a case, if the belt tension member 4 that is lightly pressed from the inside of the heat-resistant belt 3 to the heat-fixing roll 1 has a cylindrical curved surface, the belt tension is applied from the inside of the heat-resistant belt 3 to the heat-fixing roll 1. There is a case where the fixing nip aspect cannot be uniformly formed at the portion where the frame member 4 is lightly pressed. However, if the portion where the belt stretching member 4 is lightly pressed against the heat fixing roll 1 from the inside of the heat-resistant belt 3 is formed on the flat surface 4c as described above, the uneven state of the fixing nip at this portion is alleviated. And a preferable fixing nip can be easily formed.

さらに、ベルト張架部材４が軽押圧する部位で安定したニップが形成されれば、耐熱ベルト３の張力から生じる摺動摩擦力に対応して耐熱ベルト３とベルト張架部材４の摺動摩擦力が付加されることにより、加圧ロール２で耐熱ベルト３を駆動する場合、熱定着ロール１にベルト張架部材４が軽押圧する部位と熱定着ロール１に加圧ロール２が押圧する部位との中間領域（定着ニップの中間領域）では、耐熱ベルト３が弾性支持部材５の曲面５ｄで押圧され熱定着ロール１に巻き付けされた押圧状態の連続した定着ニップを形成できるので、より安定した定着ニップの形成が可能になる。 Furthermore, if a stable nip is formed at a site where the belt tension member 4 is lightly pressed, the sliding friction force between the heat resistant belt 3 and the belt stretching member 4 corresponds to the sliding friction force generated from the tension of the heat resistant belt 3. In addition, when the heat-resistant belt 3 is driven by the pressure roll 2, a portion where the belt stretching member 4 is lightly pressed against the heat fixing roll 1 and a portion where the pressure roll 2 is pressed against the heat fixing roll 1. In the intermediate region (intermediate region of the fixing nip), since the heat-resistant belt 3 is pressed by the curved surface 5d of the elastic support member 5 and wound around the heat fixing roll 1, a continuous fixing nip can be formed. Can be formed.

耐熱ベルト３を加圧ロール２とベルト張架部材４により張架して加圧ロール２で安定して駆動するには、加圧ロール２と耐熱ベルト３との摩擦係数をベルト張架部材４と耐熱ベルト３との摩擦係数より大きく設定するとよいが、摩擦係数に関しては異物の侵入や摩耗などによって不安定になる場合がある。これに対し、加圧ロール２と耐熱ベルト３の巻き付け角よりベルト張架部材４と耐熱ベルト３の巻き付け角が小さくなるように、また、加圧ロール２の径よりベルト張架部材４の径が小さくなるように設定すると、耐熱ベルト３がベルト張架部材４を摺動する長さが短くなり、経時変化や外乱などに対する不安定要因から回避でき耐熱ベルト３を加圧ロールで安定して駆動することができる。 In order to stretch the heat-resistant belt 3 by the pressure roll 2 and the belt stretching member 4 and drive it stably with the pressure roll 2, the friction coefficient between the pressure roll 2 and the heat-resistant belt 3 is set to the belt stretching member 4. However, the friction coefficient may become unstable due to the intrusion or wear of foreign matter. On the other hand, the winding angle of the belt tension member 4 and the heat-resistant belt 3 is smaller than the winding angle of the pressure roll 2 and the heat-resistant belt 3, and the diameter of the belt tension member 4 is smaller than the diameter of the pressure roll 2. Is set to be small, the length that the heat-resistant belt 3 slides on the belt stretching member 4 is shortened, and it is possible to avoid unstable factors against changes with time, disturbances, etc. Can be driven.

シート材Ｓは、ベルト張架部材４が熱定着ロール１に軽押圧される位置をニップ初期位置として耐熱ベルト３と熱定着ロール１との間を通過することで未定着トナー像が定着され、熱定着ロール１に加圧ロール２が押圧する位置をニップ終了位置として押圧部接線Ｌの方向に排出される。 The sheet material S is fixed on the unfixed toner image by passing between the heat-resistant belt 3 and the heat fixing roll 1 with the position where the belt stretching member 4 is lightly pressed against the heat fixing roll 1 as the initial nip position. The position where the pressure roll 2 presses against the heat fixing roll 1 is discharged as the nip end position in the direction of the pressing portion tangent L.

本実施形態において、ベルト張架部材４は、耐熱ベルト３を摺動させる非回転部材であり、回転部材ではないので軸受等が不要になるので、支持構造が簡単になる。加えてベルト張架部材４を略半月状とすることにより、加圧ロール２側にその半月欠方向を向けてベルト張架部材４を配置し、加圧ロール２に対して極限まで接近した配置が可能になる。このことによりまた、耐熱ベルト３の周長を短縮して構成することが可能になる。したがって、熱ロール型定着装置を簡単な構造にして小型で安価にすることができる。 In the present embodiment, the belt stretching member 4 is a non-rotating member that slides the heat-resistant belt 3, and since it is not a rotating member, a bearing or the like is not required, so that the support structure is simplified. In addition, by arranging the belt tension member 4 in a substantially half-moon shape, the belt tension member 4 is arranged on the pressure roll 2 side in the direction of the half-moon notch, and is arranged close to the pressure roll 2 to the limit. Is possible. This also makes it possible to configure the heat-resistant belt 3 with a reduced circumferential length. Therefore, the heat roll type fixing device can be made simple and small and inexpensive.

耐熱ベルト３は、必要最小限の経路で移動するので、加熱源を内蔵して回転可能な熱定着ロール１とのニップ部で加熱され、所定の経路で移動する時に奪われる熱エネルギーを最小限に抑えることができる。さらに、周長を短くすることができるので、自然放熱による温度低下も少なく、電源オン時から所望の温度に到達して定着可能になるまでの所謂ウォーミングアップ時間の短縮が可能になる。しかも、耐熱ベルト３は、図１に示すように加圧ロール２とベルト張架部材４の協働によって張力が付与されて熱定着ロール１に巻き付けてニップを形成しているので、容易にニップ長を長く構成することができ、構造が簡単になり小型で安価にすることができる。 Since the heat-resistant belt 3 moves along the minimum necessary path, it is heated at the nip portion with the heat fixing roll 1 that has a built-in heating source and can be rotated, and the thermal energy lost when moving along the predetermined path is minimized. Can be suppressed. Furthermore, since the perimeter can be shortened, there is little temperature drop due to natural heat dissipation, and so-called warm-up time from when the power is turned on to when a desired temperature is reached and fixing becomes possible can be shortened. In addition, as shown in FIG. 1, the heat-resistant belt 3 is tensioned by the cooperation of the pressure roll 2 and the belt stretching member 4 and is wound around the heat fixing roll 1 to form a nip. The length can be increased, the structure is simplified, and the size can be reduced and the cost can be reduced.

また、シート材Ｓの上に形成した未定着トナー像を安定して定着するには、未定着トナー像を十分に溶融して定着することが必須であり、所望の温度と溶融時間を必要とするが、本発明による構成では、図１に示すように耐熱ベルト３をベルト張架部材４で張架して張力を付与し熱定着ロール１に巻き付けてニップを形成し、耐熱ベルト３の内側から押圧する加圧ロール２で押圧すると共に、ベルト張架部材４で軽押圧することにより、ニップ長を長く構成するために熱定着ロール１の表面に被覆した弾性体を大きく歪ませてニップ長を長くするような手段は必要ないので、弾性体の厚みは薄く構成可能である。しかも、弾性体を歪ませるために加圧ロール２の圧接圧力を大きく設定する必要もなく、未定着トナー像を担持したシート材Ｓが熱定着ロール１と耐熱ベルト３の間を通過するときに通過するシート材へのストレスが小さいので、未定着トナー像の定着後に排出されるシート材に皺発生などのシート材Ｓの変形が抑制される。 Further, in order to stably fix the unfixed toner image formed on the sheet material S, it is essential to sufficiently melt and fix the unfixed toner image, and a desired temperature and melting time are required. However, in the configuration according to the present invention, as shown in FIG. 1, the heat-resistant belt 3 is stretched by a belt stretching member 4 to apply tension, and is wound around the heat fixing roll 1 to form a nip. In order to make the nip length longer, the elastic body coated on the surface of the heat fixing roll 1 is greatly distorted by pressing with the pressure roll 2 that is pressed from the belt and by lightly pressing with the belt stretching member 4 so that the nip length Therefore, the elastic body can be made thin. In addition, it is not necessary to set the pressure contact pressure of the pressure roll 2 large in order to distort the elastic body, and when the sheet material S carrying the unfixed toner image passes between the heat fixing roll 1 and the heat-resistant belt 3. Since the stress on the passing sheet material is small, deformation of the sheet material S such as wrinkles on the sheet material discharged after fixing the unfixed toner image is suppressed.

したがって、熱ロール型定着装置の機械的剛性アップは不要であるばかりでなく、熱定着ロール１の薄肉厚化が可能であり、加熱源から耐熱ベルト３を加熱する加熱速度が向上する。また、加圧ロール２も同様に薄肉厚化が可能であり、熱容量を小さく構成できるので、耐熱ベルト３からの熱エネルギー吸収が小さく、電源オン時から所望の温度に到達して定着可能になるまでの所謂ウォーミングアップ時間の短縮が可能である。 Therefore, not only the mechanical rigidity of the heat roll type fixing device is not required, but also the heat fixing roll 1 can be thinned, and the heating speed for heating the heat-resistant belt 3 from the heating source is improved. Similarly, the pressure roll 2 can be made thin and thick, and the heat capacity can be made small. Therefore, the heat energy absorption from the heat-resistant belt 3 is small, and it can be fixed by reaching a desired temperature when the power is turned on. It is possible to shorten the so-called warm-up time.

図６はベルト張架部材を耐熱ベルトの移動方向上流側に配置した場合のニップ通過位置と定着圧力の変化を示す図であり、定着圧力の変化の様子を、厚めのシート材は点線で、標準厚のシート材は実線で、薄めのシート材は２点鎖線でそれぞれ示している。
ベルト張架部材４を耐熱ベルト３の移動方向上流側に配置した場合には、ベルト張架部材４を熱定着ロール１に軽押圧すると、図（ａ）に示すように厚めのシート材で、ニップ初期位置での定着圧力がアップする。全体としては、シート材厚によって定着圧力に差が生じるが、ニップ領域において、ニップ初期位置から一定の定着圧力になり、ニップ終了位置で加圧ロール２による押圧で定着圧力が高くなる。また、ベルト張架部材４を揺動可能にすると、図（ｂ）に示すようにシート材厚にかかわらず所定の定着圧力になり、ベルト張架部材４の位置を切り換え耐熱ベルト３が熱定着ロール１に巻き付く角度（ニップ領域）を変えるようにすると、図（ｃ）に示すようにニップ開始位置が切り替わるので、圧力差は生じるがその差は小さくなる。 FIG. 6 is a diagram showing changes in the nip passage position and the fixing pressure when the belt stretching member is arranged on the upstream side in the movement direction of the heat-resistant belt. The change in the fixing pressure is indicated by the dotted line for the thick sheet material. The standard thickness sheet material is indicated by a solid line, and the thin sheet material is indicated by a two-dot chain line.
When the belt tension member 4 is arranged on the upstream side in the movement direction of the heat-resistant belt 3, when the belt tension member 4 is lightly pressed against the heat fixing roll 1, a thick sheet material as shown in FIG. Fixing pressure at the initial nip position increases. As a whole, there is a difference in the fixing pressure depending on the sheet material thickness, but in the nip region, the fixing pressure is constant from the initial position of the nip, and the fixing pressure is increased by pressing with the pressure roll 2 at the nip end position. Further, when the belt stretching member 4 is made swingable, a predetermined fixing pressure is obtained regardless of the sheet material thickness as shown in FIG. When the wrapping angle (nip region) around the roll 1 is changed, the nip start position is switched as shown in FIG. 3C, so that a pressure difference is generated but the difference is reduced.

上記実施の形態によれば、耐熱ベルト３が必要最小限の経路で移動するので、耐熱ベルト３は、加熱源を内蔵して回転可能な熱定着ロール１とのニップ部で加熱され、所定の経路で移動する時に奪われる熱エネルギーを最小限に抑えることができると共に、周長を短くすることができるので、自然放熱による温度低下も少なく、電源オン時から所望の温度に到達して定着可能になるまでの所謂ウォーミング時間の短縮が可能である。 According to the above-described embodiment, the heat-resistant belt 3 moves along the necessary minimum path. Therefore, the heat-resistant belt 3 is heated at the nip portion with the rotatable heat fixing roll 1 with a built-in heating source, The thermal energy lost when moving along the route can be minimized and the circumference can be shortened, so there is little temperature drop due to natural heat dissipation, and it can be fixed by reaching the desired temperature from the time the power is turned on. It is possible to shorten the so-called warming time until it becomes.

上記のようにベルト張架部材４と弾性支持部材５との間に複数のスプリング６を配置して耐熱ベルト３に張力を付与する構成にすると、複数のスプリング６の付勢力の選択組み合わせによってベルト張架部材４の軸方向の定着圧力分布は、種々選択可能であり、目的に応じて設定すればよい。 When a plurality of springs 6 are arranged between the belt stretching member 4 and the elastic support member 5 to apply tension to the heat-resistant belt 3 as described above, the belt is selected by a combination of biasing forces of the plurality of springs 6. Various fixing pressure distributions in the axial direction of the tension member 4 can be selected and may be set according to the purpose.

図７（ａ）は複数のスプリング６の付勢力を、等分布定着圧力になるように選択配置したものである。シート材上に形成した未定着トナー像を定着ニップ部を通過させて定着した時に、定着強度や定着光沢等の定着特性は定着ニップ部の温度と圧力によって左右される。従って、等分布定着圧力に構成することにより定着特性はシート材全域にわたって均一な定着画像を得ることができる。 FIG. 7A shows an arrangement in which the urging forces of the plurality of springs 6 are selected and arranged so as to obtain an evenly distributed fixing pressure. When an unfixed toner image formed on a sheet material is fixed by passing through the fixing nip portion, fixing characteristics such as fixing strength and fixing gloss depend on the temperature and pressure of the fixing nip portion. Therefore, a uniform fixed image can be obtained over the entire area of the sheet material by configuring at an evenly distributed fixing pressure.

図７（ｂ）は複数のスプリング６の付勢力を、中央部が大きく両端部が小さい定着圧力分布になるように選択配置したものである。加熱ロール１、加圧ロール２、ベルト張架部材の軸撓みが生じると、中央部の定着圧力が低下して好ましくない状態が生じるが、複数のスプリング６の付勢力を、ベルト張架部材４の中央部が大きく両端部を小さく設定することにより、定着特性はシート材全域にわたって均一な定着画像を得ることができる。 FIG. 7B shows the urging force of the plurality of springs 6 selectively arranged so that the fixing pressure distribution is large at the center and small at both ends. If the heating roll 1, the pressure roll 2, and the belt stretching member are bent, the fixing pressure at the center portion is lowered and an unfavorable state occurs. However, the biasing force of the plurality of springs 6 is applied to the belt stretching member 4. By setting the central portion of the sheet to be large and the both end portions to be small, it is possible to obtain a fixed image having a uniform fixing characteristic over the entire sheet material.

図７（ｃ）は複数のスプリング６の付勢力を、両端部が大きく中央部が小さい定着圧力分布になるように選択配置したものである。シート材上に形成した未定着トナー像を定着ニップ部を通過させて定着した時に、定着圧力とシート材搬送力のバランスによってシート材の中央部にシワなどが発生して好ましくない場合がある。この場合の対策として一般的には加圧ロールまたは加熱ロールの外径の中央部を細くした逆クラウン形状のロール対を用いてシート材の両端部の搬送力を大きくして対応するものであるが、本実施形態によれば、複数のスプリング６の付勢力を、ベルト張架部材４の両端部が大きく中央部を小さくなるように設定することにより、両端部のシート材搬送力を高めることができ、上記の加圧ロールまたは加熱ロールの外径の中央部を細くした逆クラウン形状のロール対を用いてシート材の両端部の搬送力を大きくしてシート材の中央部に発生するシワ防止を行う内容と同等の効果を発揮することができる。 In FIG. 7C, the urging forces of the plurality of springs 6 are selectively arranged so that the fixing pressure distribution is large at both ends and small at the center. When an unfixed toner image formed on a sheet material is fixed by passing through the fixing nip portion, wrinkles or the like may occur in the center portion of the sheet material due to the balance between the fixing pressure and the sheet material conveyance force. As a countermeasure in this case, generally, a pair of rolls having a reverse crown shape in which the central portion of the outer diameter of the pressure roll or the heating roll is narrowed is used to increase the conveying force at both ends of the sheet material. However, according to the present embodiment, the urging force of the plurality of springs 6 is set so that both ends of the belt stretching member 4 are large and the center is small, thereby increasing the sheet material conveying force at both ends. Wrinkles generated at the center portion of the sheet material by increasing the conveying force at both ends of the sheet material using the reverse crown-shaped roll pair in which the center portion of the outer diameter of the pressure roll or heating roll is thinned. The effect equivalent to the content to prevent can be exhibited.

図７（ｄ）は複数のスプリング６の付勢力を、ベルト張架部材４の両端部と中央部で大きくなるように設定した場合で、図７（ｂ）、（ｃ）を併せた定着圧力分布を有し、中央部の定着圧力を高め両端部でのシート材搬送力を高めることができる。 FIG. 7D shows a case where the urging forces of the plurality of springs 6 are set so as to increase at both end portions and the central portion of the belt stretching member 4, and the fixing pressure in which FIGS. 7B and 7C are combined. It has a distribution, and can increase the fixing pressure at the center and increase the sheet material conveying force at both ends.

図８は、本発明に係る定着装置の他の実施形態を示す図１と同様の図である。なお、以下の説明で前記実施形態と同一の構成については同一番号を付けて説明を省略する。
本実施形態においては、スプリング６の軸芯を通る線は、加圧ロール２の回転軸２ａの軸芯２ｂから加熱ロール１に対して外側にずらした位置２ｃを通る線上としている。これによりベルト張架部材４を付勢する方向は、付勢力の分力が耐熱ベルト３を加熱ロール１に押圧する方向になっている。このことにより、ベルト張架部材４に付与される付勢力の分力が耐熱ベルト３を熱定着ロール１に軽押圧する押圧力に付加される。熱定着ロール１にベルト張架部材４が軽押圧する部位と熱定着ロール１に加圧ロール２が押圧する部位との中間領域（定着ニップの中間領域）では、耐熱ベルト３が熱定着ロール１に巻き付けされた押圧状態の連続した定着ニップを形成できるので、より安定した定着ニップの形成が可能になる。 FIG. 8 is a view similar to FIG. 1 showing another embodiment of the fixing device according to the present invention. In the following description, the same components as those in the above embodiment are denoted by the same reference numerals and description thereof is omitted.
In the present embodiment, the line passing through the axis of the spring 6 is on the line passing through the position 2 c shifted outward from the axis 2 b of the rotary shaft 2 a of the pressure roll 2 with respect to the heating roll 1. Accordingly, the direction in which the belt stretching member 4 is urged is a direction in which the component force of the urging force presses the heat-resistant belt 3 against the heating roll 1. As a result, the component force of the urging force applied to the belt stretching member 4 is added to the pressing force for lightly pressing the heat-resistant belt 3 against the heat fixing roll 1. In an intermediate region (intermediate region of the fixing nip) between a portion where the belt stretching member 4 is lightly pressed against the heat fixing roll 1 and a portion where the pressure roll 2 is pressed against the heat fixing roll 1, the heat resistant belt 3 is the heat fixing roll 1. Since a continuous fixing nip wound in a pressed state can be formed, a more stable fixing nip can be formed.

図９は本発明に係る画像形成装置の１実施の形態を示す全体構成の模式的断面図である。図中、１０は画像形成装置、１０ａはハウジング、１０ｂは扉体、１１は紙搬送ユニット、１５はクリーニング手段、１７は像担持体、１８は画像転写搬送手段、２０は現像手段、２１はスキャナ手段、２１ｂは回転多面鏡、２９は転写ベルトユニット、３０は給紙ユニット、４０は定着手段、Ｗは露光ユニット、Ｄは画像形成ユニットを示す。 FIG. 9 is a schematic cross-sectional view of the overall configuration showing an embodiment of an image forming apparatus according to the present invention. In the figure, 10 is an image forming apparatus, 10a is a housing, 10b is a door, 11 is a paper transport unit, 15 is a cleaning means, 17 is an image carrier, 18 is an image transfer transport means, 20 is a developing means, and 21 is a scanner. Means, 21b is a rotary polygon mirror, 29 is a transfer belt unit, 30 is a paper feed unit, 40 is fixing means, W is an exposure unit, and D is an image forming unit.

本実施形態の画像形成装置１０は、ハウジング１０ａと、ハウジング１０ａの上部に形成された排紙トレイ１０ｃと、ハウジング１０ａの前面に開閉自在に装着された扉体１０ｂを有し、ハウジング１０ａ内には、露光ユニット（露光手段）Ｗ、画像形成ユニットＤ、画像転写搬送手段を有する転写ベルトユニット２９、給紙ユニット３０が配設され、扉体１０ｂ内には紙搬送ユニット１１が配設されている。各ユニットは、本体に対して着脱可能な構成であり、メンテナンス時等には一体的に取り外して修理または交換を行うことが可能な構成になっている。 The image forming apparatus 10 of the present embodiment includes a housing 10a, a paper discharge tray 10c formed on the top of the housing 10a, and a door body 10b that is attached to the front surface of the housing 10a so as to be openable and closable. 1 includes an exposure unit (exposure means) W, an image forming unit D, a transfer belt unit 29 having an image transfer and conveyance means, and a paper feed unit 30, and a paper conveyance unit 11 is arranged in the door body 10b. Yes. Each unit has a configuration that can be attached to and detached from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.

画像形成ユニットＤは、複数（本実施形態では４つ）の異なる色の画像を形成する画像形成ステーションＹ（イェロー用），Ｍ（マゼンタ用），Ｃ（シアン用），Ｋ（ブラック用）を備えている。そして、各画像形成ステーションＹ，Ｍ，Ｃ，Ｋには、それぞれ、感光ドラムからなる像担持体１７と、像担持体１７の周囲に配設された、コロナ帯電手段からなる帯電手段１９および現像手段２０を有する。これら各画像形成ステーションＹ，Ｍ，Ｃ，Ｋは、転写ベルトユニット２９の下側に斜めアーチ状のラインに沿って像担持体１７が上向きになるように並列配置されている。なお、各画像形成ステーションＹ，Ｍ，Ｃ，Ｋの配置順序は任意である。 The image forming unit D includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality (four in this embodiment) of different color images. I have. In each of the image forming stations Y, M, C, and K, an image carrier 17 that is a photosensitive drum, a charging unit 19 that is a corona charging unit and a developing unit that are disposed around the image carrier 17 are provided. Means 20 are included. These image forming stations Y, M, C, and K are arranged in parallel on the lower side of the transfer belt unit 29 so that the image carrier 17 faces upward along an oblique arched line. The order of arrangement of the image forming stations Y, M, C, and K is arbitrary.

転写ベルトユニット２９は、ハウジング１０ａの下側に配設され図示しない駆動源により回転駆動される駆動ローラ１２と、駆動ローラ１２の斜め上方に配設される従動ローラ１３と、バックアップローラ（テンションローラ）１４と、これら３本、少なくとも２本のローラ間に張架されて図示矢印方向（反時計方向Ｘ）へ循環駆動される中間転写ベルトからなる画像転写搬送手段１８と、画像転写搬送手段１８の表面に当接するクリーニング手段１５とを備えている。従動ローラ１３、バックアップローラ１４および画像転写搬送手段１８は、駆動ローラ１２に対して図で左側に傾斜する方向に配設され、これにより画像転写搬送手段１８駆動時のベルト搬送方向Ｘが下向きになるベルト面１８ａが下方に位置し、搬送方向が上向きになるベルト面１８ｂが上方に位置するようにされている。 The transfer belt unit 29 is disposed below the housing 10a and is driven to rotate by a drive source (not shown), a driven roller 13 disposed obliquely above the drive roller 12, and a backup roller (tension roller). ) 14, an image transfer conveyance means 18 comprising an intermediate transfer belt that is stretched between these three or at least two rollers and driven to circulate in the direction indicated by the arrow (counterclockwise direction X), and an image transfer conveyance means 18 And a cleaning means 15 that abuts against the surface. The driven roller 13, the backup roller 14, and the image transfer / conveying means 18 are disposed in a direction inclined to the left in the drawing with respect to the driving roller 12, so that the belt conveying direction X when driving the image transfer / conveying means 18 is downward. The belt surface 18a is positioned below, and the belt surface 18b whose transport direction is upward is positioned above.

したがって、各画像形成ステーションＹ，Ｍ，Ｃ，Ｋも駆動ローラ１２に対して図で左側に傾斜する方向に配設されることになる。そして、像担持体１７は、アーチ状のラインに沿って画像転写搬送手段１８の搬送方向下向きのベルト面１８ａに接触し、図示矢印に示すように画像転写搬送手段１８の搬送方向に回転駆動される。可撓性を有する無端スリーブ状の画像転写搬送手段１８は、像担持体１７に対して上側から被せるように略同一の巻き付け角度で接触させるため、像担持体１７と画像転写搬送手段１８との間の接触圧やニップ幅は、テンションローラ１４により画像転写搬送手段１８に付与される張力、像担持体１７の配置間隔、巻き付け角度（アーチの曲率）などを制御することにより調整することができる。 Accordingly, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left in the drawing with respect to the driving roller 12. Then, the image carrier 17 contacts the belt surface 18a facing downward in the transport direction of the image transfer transport unit 18 along the arched line, and is rotationally driven in the transport direction of the image transfer transport unit 18 as indicated by the arrows in the figure. The The flexible endless sleeve-shaped image transfer / conveyance means 18 is brought into contact with the image carrier 17 from substantially the same wrapping angle so as to be covered from above, so that the image carrier 17 and the image transfer / conveyance means 18 are in contact with each other. The contact pressure and the nip width can be adjusted by controlling the tension applied to the image transfer / conveying means 18 by the tension roller 14, the arrangement interval of the image carrier 17, the winding angle (arch curvature), and the like. .

駆動ローラ１２は、２次転写ローラ３９のバックアップローラを兼ねている。駆動ローラ１２の周面には、例えば厚さ３ｍｍ程度、体積抵抗率が１０5 Ω・ｃｍ以下のゴム層が形成されており、金属製の軸を介して接地することにより、２次転写ローラ３９を介して供給される２次転写バイアスの導電経路としている。また、駆動ローラ１２は、その径を従動ローラ１３、バックアップローラ１４の径より小さくすることにより、２次転写後の記録紙が記録紙自身の弾性力で剥離し易くすることができる。また、従動ローラ１３を後述するクリーニング手段１５のバックアップローラとして兼用させている。 The drive roller 12 also serves as a backup roller for the secondary transfer roller 39. For example, a rubber layer having a thickness of about 3 mm and a volume resistivity of 10 5 Ω · cm or less is formed on the peripheral surface of the drive roller 12, and the secondary transfer roller 39 is grounded through a metal shaft. The conductive path of the secondary transfer bias supplied via Further, by making the diameter of the driving roller 12 smaller than the diameters of the driven roller 13 and the backup roller 14, the recording paper after the secondary transfer can be easily separated by the elastic force of the recording paper itself. Further, the driven roller 13 is also used as a backup roller for the cleaning means 15 described later.

１次転写部材１６は、トナー像を順次重ねて転写して画像を形成する転写バイアス印加手段として、画像転写搬送手段の内側に接する位置に配置しているが、単に画像転写搬送手段への通電を確保可能な手段として接すればよいので、例えば画像転写搬送手段に接して従動回転する導電性ローラやリジッドな接触子、あるいは板バネ等の導電性弾性部材、樹脂等の繊維群によって形成した導電性ブラシ等でも構成可能である。 The primary transfer member 16 is disposed at a position in contact with the inner side of the image transfer / conveyance means as a transfer bias applying means for forming an image by sequentially superimposing and transferring the toner images. For example, a conductive roller or a rigid contactor rotated in contact with the image transfer conveying means, a conductive elastic member such as a leaf spring, or a conductive group formed by a fiber group such as a resin. It can also be configured with a nature brush or the like.

上記のように本実施形態の画像形成装置では、複数の像担持体１７を並列配置し、各像担持体１７に対して略同一の巻き付け角度を有する姿勢で可撓性を有する無端スリーブ状の画像転写搬送手段１８を接触配置して少なくとも２本のローラ１２、１３に張架して回転駆動し、画像転写搬送手段１８には、いずれかのローラ１２、１３によって張力を付与して像担持体１７のトナー像を順次重ねて転写する構造に構成し、略同一の巻き付け角度に応じて像担持体１７と画像転写搬送手段１８との接触部に、容易に略同一のニップを形成し、接触圧力も略同一にする。 As described above, in the image forming apparatus according to the present embodiment, a plurality of image carriers 17 are arranged in parallel, and the endless sleeve-like shape is flexible with a posture having substantially the same winding angle with respect to each image carrier 17. The image transfer / conveying means 18 is placed in contact and is stretched and rotated around at least two rollers 12 and 13. The image transfer / conveying means 18 is tensioned by any of the rollers 12 and 13 to carry the image. The toner image of the body 17 is configured to be sequentially superimposed and transferred, and substantially the same nip is easily formed at the contact portion between the image carrier 17 and the image transfer conveying means 18 according to substantially the same winding angle. The contact pressure is also substantially the same.

クリーニング手段１５は、搬送方向下向きのベルト面１８ａ側に設けられ、二次転写後に画像転写搬送手段１８の表面に残留しているトナーを除去するクリーニングブレード１５ａと、回収したトナーを搬送するトナー搬送部材１５ｂを備えている。クリーニングブレード１５ａは、従動ローラ１３への画像転写搬送手段１８の巻きかけ部において画像転写搬送手段１８に当接されている。また、画像転写搬送手段１８の裏面には、後述する各画像形成ステーションＹ，Ｍ，Ｃ，Ｋの像担持体１７に対向して１次転写部材１６が当接され、１次転写部材１６には転写バイアスが印加されている。 The cleaning unit 15 is provided on the side of the belt surface 18a facing downward in the transport direction, and a cleaning blade 15a that removes toner remaining on the surface of the image transfer transport unit 18 after the secondary transfer, and a toner transport that transports the collected toner A member 15b is provided. The cleaning blade 15 a is in contact with the image transfer / conveyance means 18 at a portion where the image transfer / conveyance means 18 is wound around the driven roller 13. Further, a primary transfer member 16 is brought into contact with the back surface of the image transfer conveying unit 18 so as to face an image carrier 17 of each of the image forming stations Y, M, C, and K described later. A transfer bias is applied.

露光手段Ｗは、斜め方向に配設された画像形成ユニットＤの斜め下方に形成された空間に配設されている。また、露光手段Ｗの下部でハウジング１０ａの底部には給紙ユニット３０が配設されている。露光手段Ｗは、全体がケースに収納され、ケースは、搬送方向下向きのベルト面の斜め下方に形成される空間に配設されている。ケースの底部には、ポリゴンミラーモータ２１ａ、ポリゴンミラー（回転多面鏡）２１ｂからなる単一のスキャナ手段２１を水平に配設されるとともに、各色の画像信号により変調される複数のレーザ光源２３からのレーザビームをポリゴンミラー２１ｂで反射させ各像担持体上に偏向走査する光学系Ｂには、単一のｆ−θレンズ２２および各色の走査光路が像担持体１７にそれぞれ非平行になって折り返すように複数の反射ミラー２４が配設されている。 The exposure means W is disposed in a space formed obliquely below the image forming unit D disposed in the oblique direction. A paper feeding unit 30 is disposed below the exposure unit W and at the bottom of the housing 10a. The exposure means W is entirely housed in a case, and the case is disposed in a space formed obliquely below the belt surface facing downward in the transport direction. A single scanner means 21 comprising a polygon mirror motor 21a and a polygon mirror (rotating polygon mirror) 21b is horizontally disposed at the bottom of the case, and a plurality of laser light sources 23 modulated by image signals of respective colors. In the optical system B that reflects and scans the laser beam by the polygon mirror 21b and deflects and scans the image carrier, the single f-θ lens 22 and the scanning light path of each color are not parallel to the image carrier 17 respectively. A plurality of reflecting mirrors 24 are arranged so as to be folded.

本実施形態においては、装置下方に走査光学系Ｂを配置し、しかも、スキャナ手段２１をケースの底部に配置することにより、ポリゴンモータ２１ａ自身がケース全体に与える振動を最小限にし、振動源であるポリゴンモータ２１ａの数を一つにすることによりケース全体に与える振動を最小限にする。また、各画像ステーションＹ，Ｍ，Ｃ，Ｋは斜め方向に配設し、かつ像担持体１７を斜めアーチ状のラインに沿って上向きに並列配置してトナー貯留容器２６を斜め下方に傾斜して配置している。 In the present embodiment, the scanning optical system B is disposed below the apparatus, and the scanner means 21 is disposed at the bottom of the case to minimize the vibration that the polygon motor 21a itself gives to the entire case. By reducing the number of polygon motors 21a to one, vibration applied to the entire case is minimized. Further, the image stations Y, M, C, and K are arranged in an oblique direction, and the image carrier 17 is arranged in parallel upward along an oblique arched line so that the toner storage container 26 is inclined obliquely downward. Arranged.

給紙ユニット３０は、記録媒体が積層保持されている給紙カセット３５と、給紙カセット３５から記録媒体を一枚ずつ給送するピックアップローラ３６を備えている。紙搬送ユニット１１は、二次転写部への記録媒体の給紙タイミングを規定するゲートローラ対３７（一方のローラはハウジング１０ａ側に設けられている）と、駆動ローラ１２および画像転写搬送手段１８に圧接される二次転写手段としての二次転写ローラ３９と、主記録媒体搬送路３８と、定着手段４０と、排紙ローラ対４１と、両面プリント用搬送路４２を備えている。 The paper feed unit 30 includes a paper feed cassette 35 in which recording media are stacked and held, and a pickup roller 36 that feeds the recording media from the paper feed cassette 35 one by one. The paper transport unit 11 includes a gate roller pair 37 (one roller is provided on the housing 10a side) that regulates the timing of feeding the recording medium to the secondary transfer unit, the drive roller 12, and the image transfer transport means 18. A secondary transfer roller 39 as a secondary transfer unit that is pressed against the main body, a main recording medium conveyance path 38, a fixing unit 40, a discharge roller pair 41, and a duplex printing conveyance path 42 are provided.

本実施形態においては、転写ベルトの搬送方向上向きのベルト面１８ｂの斜め上方に形成される空間、換言すれば、転写ベルトに対して画像形成ステーションと反対側の空間に定着手段４０を配設することが可能になり、露光手段Ｗ、画像転写搬送手段１８、画像形成手段への熱伝達を低減することができ、各色の色ずれ補正動作を行う頻度を少なくすることができる。特に、露光手段Ｗは、定着手段４０から最も離れた位置にあり、走査光学系部品の熱による変位を最小限にすることができ、色ズレを防ぐことができる。また、画像転写搬送手段１８を駆動ローラ１２に対して傾斜する方向に配設しているため、図で右側空間に広いスペースが生じその空間に定着手段４０を配設することができ、コンパクト化を実現することができると共に、定着手段４０で発生する熱が、左側に位置する露光ユニットＷ、画像転写搬送手段１８および各画像形成ステーションＹ，Ｍ，Ｃ，Ｋへ伝達されるのを防止することができる。画像形成ユニットＤの左側下部の空間に露光ユニットＷを配置することができるため、画像形成手段の駆動系がハウジング１０ａへ与える振動による、露光ユニットＷの走査光学系Ｂの振動を最小限に抑えることができ、画質の劣化を防止することができる。 In the present embodiment, the fixing unit 40 is disposed in a space formed obliquely above the belt surface 18b facing upward in the transfer belt conveyance direction, in other words, in a space opposite to the image forming station with respect to the transfer belt. Therefore, heat transfer to the exposure unit W, the image transfer conveyance unit 18, and the image formation unit can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced. In particular, the exposure means W is located farthest from the fixing means 40, and the displacement of the scanning optical system components due to heat can be minimized, thereby preventing color misregistration. Further, since the image transfer conveying means 18 is arranged in a direction inclined with respect to the drive roller 12, a large space is generated in the right side space in the figure, and the fixing means 40 can be arranged in the space, thereby making the apparatus compact. And the heat generated by the fixing unit 40 is prevented from being transmitted to the exposure unit W, the image transfer / conveying unit 18 and the image forming stations Y, M, C, and K located on the left side. be able to. Since the exposure unit W can be arranged in the lower left space of the image forming unit D, the vibration of the scanning optical system B of the exposure unit W due to the vibration applied to the housing 10a by the drive system of the image forming means is minimized. And deterioration of image quality can be prevented.

上記実施形態では、中間転写ベルトを画像転写搬送手段１８として像担持体１７に接触させる構成としたが、表面にシート材を吸着して搬送移動し、該シート材の表面にトナー像を順次重ねて転写して画像を形成搬送するシート材搬送ベルトを画像転写搬送手段１８として像担持体１７に接触させる構成としてもよい。この場合、上記各実施形態と異なるのは、画像転写搬送手段１８であるシート材搬送ベルトのベルト搬送方向が像担持体１７に接触する下面で逆方向の上向きになることである。 In the above embodiment, the intermediate transfer belt is configured to come into contact with the image carrier 17 as the image transfer conveyance unit 18. However, the sheet material is adsorbed and conveyed on the surface, and the toner images are sequentially superimposed on the surface of the sheet material. Alternatively, a sheet material conveying belt that forms and conveys an image by transferring the image may be configured to contact the image carrier 17 as the image transfer conveying means 18. In this case, the difference from each of the above embodiments is that the belt conveyance direction of the sheet material conveyance belt which is the image transfer conveyance means 18 is upward in the opposite direction on the lower surface in contact with the image carrier 17.

以上、本発明の実施形態について説明したが、本発明はこれに限定されるものではなく、種々の変形が可能である。例えば上記実施形態では、各トナー色の現像器を並べて配置したタンデム式のカラー画像形成装置やその定着装置について説明したが、各トナー色の現像器をロータリーフレームに搭載してロータリー式のカラー画像形成装置、モノカラー、モノクロの画像形成装置やその定着装置についても同様に適用できることはいうまでもない。 As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation is possible. For example, in the above-described embodiment, the tandem color image forming apparatus in which the developing units for each toner color are arranged side by side and the fixing device thereof have been described. However, the developing unit for each toner color is mounted on a rotary frame and a rotary type color image is provided. Needless to say, the present invention can be similarly applied to a forming apparatus, a mono-color and monochrome image forming apparatus, and a fixing device thereof.

本発明の定着装置の１実施形態を説明するための図である。1 is a diagram for explaining an embodiment of a fixing device of the present invention. FIG. 図１のベルト張架部材の加圧ロール側から見た斜視図である。It is the perspective view seen from the pressure roll side of the belt stretching member of FIG. 図１の弾性支持部材の斜視図である。It is a perspective view of the elastic support member of FIG. 図１の定着ニップ部を拡大して示す図である。FIG. 2 is an enlarged view showing a fixing nip portion of FIG. 1. 図１の定着装置の変形例を示す図である。FIG. 8 is a diagram illustrating a modification of the fixing device in FIG. 1. ニップ通過位置と定着圧力の変化を示す図である。It is a figure which shows the change of a nip passage position and fixing pressure. 定着圧力分布を示す図である。It is a figure which shows fixing pressure distribution. 本発明の他の実施形態を説明するための図である。It is a figure for demonstrating other embodiment of this invention. 本発明に係る画像形成装置の例を示す模式的断面図である。1 is a schematic cross-sectional view illustrating an example of an image forming apparatus according to the present invention.

Explanation of symbols

１…熱定着ロール、２…加圧ロール、３…耐熱ベルト、４…ベルト張架部材
４ｂ…スプリング配設孔、４ｃ…平坦面、
５…弾性支持部材、５ａ…フランジ、５ｂ…摺接面、５ｄ…押圧部
６…スプリング、Ｓ…シート材、Ｌ…押圧部接線 DESCRIPTION OF SYMBOLS 1 ... Thermal fixing roll, 2 ... Pressure roll, 3 ... Heat-resistant belt, 4 ... Belt tension member 4b ... Spring arrangement | positioning hole, 4c ... Flat surface,
5 ... elastic support member, 5a ... flange, 5b ... sliding contact surface, 5d ... pressing part 6 ... spring, S ... sheet material, L ... pressing part tangent

Claims

A heat-fixing roll, a pressure roll that presses against the heat-fixing roll, a heat-resistant belt that is attached to the outer periphery of the pressure roll and is sandwiched and moved between the heat-fixing roll, and the heat-resistant belt is stretched A belt stretching member that is arranged on the upstream side in the moving direction of the heat-resistant belt from the pressing portion between the heat fixing roll and the pressure roll, and the heat-resistant belt is located on the heat fixing roll side from the tangent to the pressing portion. A fixing device that is disposed at a position where a nip is formed by winding, and fixes an unfixed toner image formed on a sheet material,
An elastic support member is disposed between the pressure roll and the belt stretching member, a plurality of springs are disposed in an axial direction between the belt stretching member and the elastic support member, and a rotational force of the pressure roll. A fixing device comprising: a pressing portion that presses the nip portion between the fixing roll and the heat-resistant belt on the elastic support member.

The pressing portion has a curved surface that has the same curvature as the heating roll and the thickness of the heat-resistant belt, and the tip of the curved surface is configured to be close to the nip portion between the heating roll and the pressure roll. The fixing device according to claim 1, wherein:

The line passing through the axis of the spring is a line passing through a position shifted outward from the axis of the rotary shaft of the pressure roll with respect to the heating roll, and the component force of the spring biasing force presses the heat-resistant belt against the heating roll. The fixing device according to claim 1, wherein the fixing device is in a direction in which the fixing device moves.

The fixing device according to claim 1, wherein the belt stretching member has a flat surface at a pressing portion with the heat fixing roll.

On the inner surface of the elastic support member, a protruding sliding contact surface having substantially the same curvature surface as the outer peripheral surface of the pressure roll is formed, and is configured to be in sliding contact with the pressure roll through the sliding contact surface. The fixing device according to claim 1, wherein

The fixing device according to claim 5, wherein the spring is disposed at a position facing the sliding contact surface.

5. A curved sliding contact surface is formed on both sides of the inner surface of the elastic support member in the circumferential direction, and the elastic support member is configured to be in sliding contact with the pressure roll through the sliding contact surface. The fixing device according to 1.

8. The belt tension member according to claim 1, wherein a light pressing biasing means for biasing a spring in a direction of light pressing from the inside of the heat-resistant belt is disposed on the heat fixing roll. Fixing device.

The fixing device according to claim 1, wherein the belt stretching member has a crown shape in which the vicinity of the center of the sliding surface of the heat-resistant belt protrudes from the end.

An image forming apparatus comprising the fixing device according to claim 1.