JP3766930B2 - Fixing device - Google Patents

Description

【００４８】
図５より、オイル塗布量はいずれの塗布ローラにおいてもライフを通じて徐々に減少する傾向にあるが、オイル塗布ローラの表面粗さが小さい程オイル塗布量の減少幅が小さく、オイル塗布性能が安定していることがわかる。これは、表１に示したように、表面粗さが大きいサンプルでは、オイル塗布ローラ６１表面がオイル規制ブレード６７との摺動により表面粗さが小さくなり、性能に変化が発生するためである。後述するように、オイル塗布量が２０ｍｇ／Ａ４以上の場合、オイルゴーストが発生するといった問題があるが、初期の表面粗さＲａが１．１３μｍのサンプル１は、ライフ初期のオイル塗布量が２０ｍｇ／Ａ４以上となるためオイルゴーストが発生したり、またライフを通じてのオイル消費量が多くなるといった問題があり、オイル塗布ローラ６１の表面粗さＲａの上限としては１μｍ以下が望ましい。また、別の検討から、表面粗さＲａが０．１μｍ以下の場合は、オイル塗布量が１０ｍｇ／Ａ４以下となり、この場合、後述するようにオフセットが発生してしまうので、オイル塗布ローラ６１の表面粗さＲａの下限としては０．１μｍ以上となる。
【００４９】
なお、以上の表面粗さに関する結果は、オイル規制ブレード６７によりオイル塗布ローラ６１を２ｋｇ重で加圧（長さ２３０ｍｍ当たり）した場合の結果であるが、オイル塗布ローラ６１に大きな負荷を与えずかつ安定したオイル塗布を行える理想的な加圧条件（１〜３ｋｇ重（長さ２３０ｍｍ当たり））において同様の結果が得られた。
【００５０】
オイル塗布ローラ６１の表面粗さを上述の範囲（０．１μｍ以上１．０μｍ以下）内に設定するためには、オイル塗布ローラ６１の表面被覆層６１ｂが圧縮成形によるシリコンゴム材の場合には複数回（２回以上）研磨処理するのが有効（サンプル３）であり、また、表面被覆層がコーティング成形によるシリコンゴム材の場合には、未研磨で所望の表面粗さを得ることができる（サンプル４）。従って、本実施の形態においては，サンプル３若しくはサンプル４のオイル塗布ローラを使用する。
【００５１】
一方、表１からオイル塗布ローラ６１の種類によってオイル塗布フェルト６２のトナー汚れが大きく異なることがわかる。定着ローラ５１上にトナーが付着（オフセット）した場合、付着したトナーはオイル塗布ローラ６１にもある程度付着し、その結果オイル塗布フェルト６２がトナーで汚れる。表１の結果から、オイル塗布ローラ６１の表面粗さが小さい程オイル塗布ローラ６１上にトナーが付着しにくく、その結果オイル塗布フェルト６２のトナー汚れが少ないことがわかる。また、サンプル１及びサンプル２の比較から、表面粗さとしては両者に大きな差がないにもかかわらず、オイル塗布フェルト６２の汚れに大きな差が認められることから、サンプル１のＨＴＶシリコンゴムに比べサンプル２のＬＴＶシリコンゴムの方がトナーとの離型性に優れると考えられ、表面材質としてはＬＴＶシリコンゴムを用いるのが好ましい。
【００５２】
次に、オイル塗布ローラ６１表面が研磨処理されている場合の研磨方向とオイル塗布量の関係を調べた結果を表２に示す。
【００５３】
【表２】

【００５４】
オイル塗布ローラ６１表面を研磨処理した場合、研磨後のオイル塗布ローラ６１は周方向に表面摩擦力の方向性をもったものとなる。即ち、研磨後のオイル塗布ローラ６１表面は図６のような形状となり、Ｅ方向は摩擦力が大きく、その逆のＦ方向は摩擦力が小さくなる。本実験における研磨方向の順目方向とは、図７（ａ）のようにオイル塗布ローラ６１を定着ローラ５１及びオイル規制ブレード６７に対し摩擦力の小さい方向に配置した場合であり、また逆目方向とは図７（ｂ）のように摩擦力の大きい方向に配置した場合である。表２の結果から、オイル塗布ローラ６１の配設方向としては、順目方向に配設した方がライフ（６０、０００枚通紙後）による表面粗さの変化が小さく、オイル塗布量としても逆目方向と比較すると安定していることがわかる。
【００５５】
次に、本実施の形態によるオイル塗布ローラ６１の長手方向の表面粗さ分布とオイル塗布分布の関係について調べた結果を図８（ａ）に示す。上述したように、本実施の形態のオイル塗布ローラ６１は、中央部の表面粗さＲｃと両端部の表面粗さＲｅとが、Ｒｅ＞Ｒｃとなるよう研磨処理されている。比較例としてＲｅ＝Ｒｃとなるよう研磨処理したオイル塗布ローラ６１の長手方向の表面粗さ及びオイル塗布分布も図８（ｂ）に示す。
【００５６】
比較例ではオイル塗布量が中央部で多く、両端部で少ない分布となっている。これは加圧によるオイル規制ブレードのたわみにより、オイル塗布ローラに対するオイル規制ブレード６８の当接圧が中央部に比べて両端部で大きくなるためである。
【００５７】
これに対し、本実施の形態では、オイル塗布ローラ６１の表面粗さが中央部に比べて両端部が大きいため、比較例と比べて両端部でのオイル塗布量が多く、その結果オイル規制ブレード６１のたわみに起因するオイル塗布の不均一の影響が相殺される。したがって、ローラ長手方向で均一なオイル塗布分布が得られる。
【００５８】
オイル塗布ローラ６１の表面粗さを中央部に比べて両端部を大きく設定するための具体的方法としては、<img width="16" height="16" src="/Gaiji/gif16/0001.gif">研磨砥石やラッピングフィルム等の研磨手段の送り速度をローラ中央部に比べて両端部を速くする。<img width="16" height="16" src="/Gaiji/gif16/0002.gif">研磨回数を両端部に比べ中央部を多くする。等種々の方法があり、本発明においては上記いずれの方法を使用しても構わない。
【００５９】
次に、オイル塗布ローラ６１と定着ローラ５１との周速比と画像品質（特にオイルバンディング）との関係について実験結果を参照しながら詳しく説明する。表３は、オイル塗布ローラと定着ローラとの周速比とオイルバンディングの発生度合いとの関係を調べた結果である。
【００６０】
【表３】

【００６１】
この結果から、オイル塗布ローラ６１と定着ローラ５１との周速比Ｖｏ／Ｖｆとしては、Ｖｏ／Ｖｆ＝１が理想であることがわかる。しかしながら、定着ローラ５１やオイル塗布ローラ６１は通常加熱状態で使用され、その周速比は各々のローラのその時の温度状態により多少上下に変化する。従って、この周速比の変動を考慮した場合、表３の結果から周速比Ｖｏ／Ｖｆは、０．９５≦Ｖｏ／Ｖｆ≦１の範囲で使用するのが、オイルバンディングの発生を防止する上で望ましい。そこで、本実施の形態では、周速比Ｖｏ／Ｖｆ＝０．９７６となるように設定している。
【００６２】
次に、オイル塗布量と画像品質（特にオフセット及びオイルゴースト）との関係について、実験結果を参照しながら詳しく説明する。表４はオイル塗布量とオフセット及びオイルゴーストとの関係について調べた結果である。
【００６３】
【表４】

【００６４】
これより、オイル塗布量が２０ｍｇ／Ａ４以上になるとオイルゴーストによる画像欠陥が発生し、オイル塗布量が１０ｍｇ／Ａ４以下になるとオフセットによる画像欠陥が発生することがわかる。従って、オイル塗布量としては、１０ｍｇ／Ａ４〜２０ｍｇ／Ａ４の範囲にあるのが画像品質上適当であり、本実施の形態においてはオイル塗布ローラ表面粗さ、オイル粘度、オイル規制ブレード材質及び圧力等を調整することで、初期状態で１５．７ｍｇ／Ａ４、６０、０００枚通紙後で１２．３ｍｇ／Ａ４となるようオイル塗布量を設定している。
【００６５】
〔実施の形態２〕
次に、本発明の実施の形態２について図面を参照して説明する。ここで、本実施の形態は、オイル塗布フェルト以外の構成は実施の形態１と全く同じであるため、その同一部分については説明を省略する。
【００６６】
図９は本発明の実施の形態２におけるオイル塗布フェルト７２の構成を示した図である。実施の形態１で示したように、オイル塗布フェルトの材料としてＰＴＦＥ繊維等のフッ素系繊維を用いた場合、性能的には優れるが反面フッ素系繊維は製造が困難であり価格的に非常に高価であるという欠点がある。そこで、本実施の形態におけるオイル塗布フェルトは、図９のようにＰＴＦＥ繊維７２ａとアラミド繊維７２ｂの２種類の繊維を貼り合わせた２層構造のフェルトとなっており、ＰＴＦＥ繊維７２ａがオイル塗布フェルト６１と当接するように配設されている。ＰＴＦＥ繊維部７２ａの厚みは、０．５ｍｍ、アラミド繊維部７２ｂの厚みは１．５ｍｍで、ニードルパンチングにより繊維同士が絡み合った状態で強固に貼り合わされているため、オイル塗布ローラ６１との摺動によりフェルトのＰＴＦＥ繊維７２ａが抜け落ちたりする心配がなく、耐久性の点でも従来の１層構造のフェルトと同等の性能が得られる。またアラミド繊維はＰＴＦＥ繊維に比べて１／５程度の価格であり、製造が容易である。このため、本実施の形態のようにＰＴＦＥとしての性能が必要なオイル塗布ローラ６１との当接面にのみＰＴＦＥ繊維を使用することで、オイル塗布フェルトの価格をＰＴＦＥ繊維のみを使用したフェルトに比べて１／２以下に低減することができ、かつ、製造を容易とすることができる。なお、ここではアラミド繊維部を用いたが、耐熱性に富んだ繊維材料であれば使用することができる。
【００６７】
〔実施の形態３〕
実施の形態１，２においては、定着ローラを使用した定着装置について本発明を適用した場合について説明してきたが、定着ローラではなく定着ベルトを使用した定着装置においても本発明を適用できる。図１０に定着ベルトを使用した定着装置の概略断面図を示す。なお、オイル塗布装置については実施の形態１と同様であるので、説明は省略する。定着ベルト１０１は、駆動ローラ１０２及びテンションローラ１０３に掛け渡されており、テンションローラ１０３により所定の張力が加えられ、駆動ローラの駆動によい従動回転する。また定着ベルト１０１及び加圧ローラ１０４により定着ニップ部が形成されており、この定着ニップ部に未定着トナー像を有する記録紙を通過させることにより、トナーの定着を行なう。
【００６８】
定着ベルト１０１の加熱方法としては、▲１▼駆動ローラ１０２内に加熱源を設け、駆動ローラ１０２を介して加熱する方法、▲２▼定着ベルト１０１それ自身を発熱体で構成する方法、▲３▼定着ニップ部の定着ベルト１０１背面側に別途発熱源を設ける方法等種々の方法がある。
【００６９】
実験の結果、このようなベルト方式の定着装置においても実施の形態１及び２と同様の結果が得られ、本発明はベルト方式の定着装置においても適用できることがわかった。
【００７０】
なお、以上の実施の形態では、定着ローラ５１または定着ベルト１０１に接するオイル塗布ローラ６１にオイル塗布フェルト７２が当接することでオイル７０の供給を行っているが、定着ローラ５１または定着ベルトに直接接触してオイル７０を塗布してもよい。
【００７１】
【発明の効果】
以上のように、本発明の定着装置は、塗布ローラ表面の中心線平均粗さＲａが０．１μｍ≦Ｒａ≦１μｍであるため、ライフを通じてオイル塗布量の変化が少なく、オイル消費量が低減できる。
【００７２】
また、塗布ローラを定着部材に対して塗布ローラの周に沿う表面摩擦力が小さい方向に接触回転する関係に配しているため、ライフを通じてオイル塗布ローラの表面粗さの変化が小さく、オイル塗布量が安定しオイル消費量の低減や定着装置の信頼性の向上につながる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る定着装置の概略構成図である。
【図２】本発明の一実施の形態に係る定着装置の概略斜視図である。
【図３】図１に示す定着装置を備えたレーザープリンタの概略構成図である。
【図４】連続通紙エージング時のオイル塗布フェルト材質によるオイル塗布量変化を示す図である。
【図５】連続通紙エージング時のオイル塗布ローラ表面粗さによるオイル塗布量変化を示す図である。
【図６】オイル塗布ローラの研磨後の表面状態を示した図である。
【図７】オイル塗布ローラの研磨目による配置方向を示した図である。
【図８】オイル塗布ローラ長手方向の表面粗さ分布及びオイル塗布量分布を示した図である。
【図９】本発明の第２の実施の形態に係る定着装置の要部拡大図である。
【図１０】本発明の第３の実施の形態に係る定着装置の概略断面図である。
【図１１】従来の定着装置の概略断面図である。
【符号の説明】
５１ 定着ローラ
５２ 加圧ローラ
６１ オイル塗布ローラ
６２ オイル塗布フェルト
６３ オイル回収フェルト
６７ オイル規制ブレード
７０ シリコンオイル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device used in an electrophotographic apparatus using an electrophotographic process such as a copying machine, a facsimile, or a printer, and more particularly to a fixing apparatus used in an electrophotographic apparatus capable of full color printing.
[0002]
[Prior art]
Conventionally, as a fixing device used in an electrophotographic apparatus such as a copying machine or a printer, a toner image is melted by passing a recording paper having an unfixed toner image between a pair of heated and pressurized rollers. A heat roller fixing method for fixing to a recording paper is generally used. However, this heat roller fixing method has a problem that a so-called offset phenomenon in which the molten toner on the recording paper adheres to the roller is liable to occur. In particular, in a color electrophotographic apparatus, the color toner has poor releasability from the roller as compared with the conventional black toner, and the occurrence of the offset phenomenon is remarkable. Therefore, in current electrophotographic apparatus fixing devices, particularly color electrophotographic apparatus fixing devices, it is necessary to apply an anti-offset agent having a small surface energy such as silicone oil to the roller surface in order to prevent the offset phenomenon. It has become indispensable.
[0003]
Next, a general oil application device used in this type of fixing device will be described in detail with reference to FIG.
[0004]
The oil application device includes an oil application roller 61, an oil application felt 62, an oil regulating blade 68, an oil tank 69, and the like. The oil application felt 62 is arranged so that the upper end contacts the oil application roller 61 and the lower end is immersed in the oil 70 in the oil tank 69, and the oil 70 in the oil tank 69 is caused by the capillary phenomenon of the oil application felt 62. Is applied to the surface of the oil application roller 61. The oil applied to the surface of the oil application roller 61 is scraped off by the oil regulating blade 68 pressurized to the oil application roller 61 with a predetermined pressure and is made uniform to a predetermined amount, and then the oil application is performed. At the pressure contact portion B between the roller 61 and the fixing roller 51, it is transferred and applied to the surface of the fixing roller 51.
[0005]
Here, as the oil application felt 62, in order to reduce the supply amount of oil, as disclosed in JP-A No. 58-111963 (Patent Document 1) and the like, a fluorine-based porous material (for example, W.W. A method using a porous member of tetrafluoroethylene resin manufactured by L. GORE (trade name: GORE-TEX, etc.) has been proposed.
[0006]
[Patent Document 1]
JP 58-111963 A
[0007]
[Problems to be solved by the invention]
However, the conventional oil application apparatus has the following problems.
[0008]
(1) When toner adheres to the surface of the fixing roller (hereinafter, this phenomenon is referred to as offset), the toner adheres to the oil application felt through the oil application roller. As a result, the pores of the oil application felt made of a fluorine-based porous material are clogged with toner, and the oil cannot be supplied to the oil application roller.
[0009]
(2) The amount of oil applied to the oil application roller depends on the surface roughness of the oil application roller. If the surface roughness of the oil application roller is small, the amount of oil passing through the edge of the oil regulating blade decreases. The amount of oil applied to the oil application roller decreases, and vice versa.
[0010]
In the conventional oil application device, the surface roughness of the oil application roller decreases with use due to the sliding of the oil application roller and the oil regulating blade, so that the oil application amount gradually decreases throughout the life, resulting in an offset. Etc. occur. On the other hand, when it is attempted to secure an oil application amount that does not cause an offset throughout the life, the oil application amount in the initial stage of the life becomes excessively supplied, leading to an increase in oil consumption.
[0011]
(3) The amount of oil applied to the oil application roller also depends on the contact pressure between the oil regulating blade edge and the oil application roller. If the contact pressure is small, the oil application amount increases and decreases in the opposite case. .
[0012]
In the conventional oil application device, the contact pressure at both ends is usually larger than that at the center due to the deflection in the longitudinal direction of the oil regulating blade and the oil application roller, so that the oil application is not uniform in the longitudinal direction. As a result, image defects such as uneven gloss due to uneven application of oil and uneven transmission of OHP occur.
[0013]
(4) Since the oil application roller is in contact with the oil application felt, oil regulating blade, etc., it is necessary to forcibly drive with a large driving torque, but it is difficult to drive the oil application roller stably. Vibration is likely to occur at the drive gear pitch. As a result, oil application unevenness (hereinafter, this phenomenon is referred to as oil banding) corresponding to the drive gear pitch occurs in the vicinity of the drive gear side, resulting in image defects such as uneven gloss.
[0014]
(5) A phenomenon in which an offset occurs when the amount of oil applied is small, and conversely, if the amount of oil applied is too large, the image portion remains on the recording paper as a memory in the fixing roller cycle (hereinafter this phenomenon is referred to as oil ghost). Will occur. The cause of this oil ghost is that there is a large difference in the amount of oil on the fixing roller depending on whether the toner is absorbed by the toner between the image portion and the non-image portion. This is because even if the coating is applied again, this difference is not resolved and oil coating unevenness remains, resulting in image defects such as uneven gloss and uneven OHP transmittance.
[0015]
SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that can stably supply oil to a fixing roller.
[0016]
[Means for Solving the Problems]
The fixing device according to the present invention includes a fixing unit that fixes the unfixed toner image by heating and pressurizing a recording material having an unfixed toner image, and an intermediate coating unit that includes a roller in contact with the surface of the fixing unit. In a fixing device comprising: a release agent supply means for applying a release agent to the fixing means by supplying a release agent to the intermediate application means, the center line average roughness Ra of the surface of the intermediate application means However, 0.1 μm ≦ Ra ≦ 1 μm, and the intermediate coating unit is arranged so as to rotate in contact with the fixing unit and the leveling unit in a direction in which the surface frictional force along the circumferential direction is small. It is characterized by becoming.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
The first embodiment of the present invention will be described with reference to FIGS. 1 to 3 as follows. In this embodiment, the case where the fixing device is applied to a monochrome laser printer as an electrophotographic apparatus will be described, but the present invention is not limited to this.
[0018]
As shown in FIG. 3, the laser printer according to the present embodiment includes a paper feeding unit 10, an image forming apparatus 20, a laser scanning unit 30, and a fixing device 50.
[0019]
The laser printer having the above configuration conveys the paper P from the paper supply unit 10 to the image forming apparatus 20. In the image forming apparatus 20, a toner image is formed based on the laser beam 34 from the laser scanning unit 30, and the toner image is transferred to a sheet P as a conveyed recording material. Then, the paper P on which the toner image is transferred is conveyed to the fixing device 50 and the toner image is fixed to the paper P. Finally, the paper P on which the toner image has been fixed is discharged to the outside by paper transport rollers 41 and 42 provided on the downstream side of the paper transport of the fixing device 50. That is, the paper P is conveyed in the order of the paper feed tray 11, the image forming apparatus 20, and the fixing device 50 along the path of the arrow E shown in the drawing, and is discharged to the outside of the apparatus.
[0020]
The paper feed unit 10 includes a paper feed tray 11, a paper feed roller 12, a paper separation friction plate 13, a pressure spring 14, a paper detection actuator 15, a paper detection sensor 16, and a control circuit 17.
[0021]
The paper P mounted on the paper feed tray 11 receives a print command, and is fed one by one by the action of the paper feed roller 12, the paper separation friction plate 13, and the pressure spring 14, and is fed into the printer. The fed paper P tilts the paper detection actuator 15 and causes the paper detection optical sensor 16 to output it as an electrical signal to instruct the start of image printing. The control circuit 17 activated by the operation of the paper entry detection actuator 15 sends an image signal to the laser diode light emitting unit 31 of the laser scanning unit 30 to control lighting / non-lighting of the light emitting diode.
[0022]
The laser scanning unit 30 includes the laser diode light emitting unit 31, a scanning mirror 32, a scanning mirror motor 33, and reflection mirrors 35, 36, and 37.
[0023]
The scanning mirror 32 is rotated at a high speed and a constant speed by a scanning mirror motor 33. That is, in FIG. 3, the laser beam 34 scans in a direction perpendicular to the paper surface. The laser beam 34 irradiated from the laser diode light emitting unit 31 is irradiated to a later-described photoconductor 21 through reflection mirrors 36, 35, and 37. At this time, the laser beam 34 is selectively exposed on the photosensitive member 21 based on the lighting / non-lighting information from the control circuit 17.
[0024]
The image forming apparatus 20 includes a photoreceptor 21, a transfer roller 22, a charging member 23, a developing roller 24, a developing unit 25, and a cleaning unit 26.
[0025]
The laser beam 34 selectively discharges the surface charge of the photosensitive member previously charged by the charging member 23 to form an electrostatic latent image. The toner used for development is accumulated in the development unit 25. The toner provided with charge by appropriate agitation in the developing unit 25 adheres to the surface of the developing roller 24 and responds to the electrostatic latent image by the action of the developing bias voltage applied to the developing roller 24 and the electric field generated by the photoreceptor surface potential. A toner image can be formed on the photoreceptor 21.
[0026]
The paper P conveyed from the paper supply unit 10 is sandwiched between the photoconductor 21 and the transfer roller 22 and sent. The toner on the photoconductor 21 is electrically attracted and transferred onto the paper P by the action of an electric field applied by the transfer voltage applied to the transfer roller 22. At this time, the toner on the photoreceptor 21 is transferred to the paper P by the transfer roller 22, and the untransferred toner is collected by the cleaning unit 26.
[0027]
Thereafter, the paper P is conveyed to the fixing device 50. Therefore, an appropriate temperature and pressure are given by the pressure roller 52 and the fixing roller 51 maintained at 175 ° C. The toner is melted and fixed on the paper P to form a robust image.
[0028]
Then, the paper P is transported by the paper transport rollers 41 and 42 and discharged outside the apparatus.
[0029]
Next, the fixing device, which is a feature of the present invention, will be described in detail with reference to FIGS. FIG. 1 is a schematic sectional view of a fixing device of the present invention, and FIG. 2 is a schematic perspective view of an oil application device.
[0030]
The fixing roller 51 has a structure in which a release layer 51b made of silicon rubber is coated on the surface of an aluminum hollow core material 51a. The pressure roller 52 has a structure in which an elastic layer 52b made of silicon rubber is provided on the surface of a stainless steel core material 52a. The pressure roller 52 is pressed against the fixing roller 51 with a predetermined pressure by a pressure unit (not shown). Yes. A heater lamp 53 is disposed inside the fixing roller 51 and heats the surface of the fixing roller 51 to a predetermined temperature (175 ° C. in the present embodiment).
[0031]
The oil application device 60 includes an oil application roller 61, an oil application felt 62, an oil recovery felt 63, a felt pressure plate 64, a felt pressure plate support shaft 65, pressure springs 66a and 66b, an oil regulating blade 67, an oil tank 68, and a support. It consists of a frame 69. The oil tank 68 is filled with dimethyl silicone oil 70 (KF-96 manufactured by Shin-Etsu Chemical).
[0032]
The oil application roller 61 has a structure in which a surface of a stainless steel core 61a is covered with an LTV silicon rubber layer 61b having a thickness of 0.5 mm by compression molding, and is rotatably supported by a support frame 69. The surface roughness (centerline average roughness) Ra of the LTV silicon rubber layer 61b is set to 0.55 μm on the average in the longitudinal direction by performing the polishing process twice. However, a contrivance is made during the polishing process so that the surface roughness is different between the central portion and both end portions in the longitudinal direction of the oil application roller 61. In the oil application roller 61 in the present embodiment, Ra = 0. Polishing is performed so that Ra = 0.7 μm at 4 μm and both ends. The oil application roller 61 in the present embodiment is not limited to the above configuration. For example, after coating the surface of a stainless steel core material 61a with a 0.5 mm thick LTV silicon rubber layer 61b by compression molding, It may be formed by coating LTV silicon rubber (not shown) with a thickness of 0.04 mm. In this case, the roller surface may be unpolished, and the surface roughness Ra at this time is Ra = 0.26 μm on the average in the longitudinal direction.
[0033]
The oil application roller 61 is further pressed to the fixing roller 51 with a predetermined pressing force by a pressing unit (not shown), and the rotation direction of the fixing roller 51 (the direction of arrow C in the drawing) is driven by a driving unit (not shown). ) In the driven direction (in the direction of arrow D in the figure). However, the circumferential speed of the oil application roller 61 is set to be slightly slower than the circumferential speed of 85 mm / sec of the fixing roller 51 (a circumferential speed ratio of 0.976).
[0034]
The oil application felt 62 is a fiber made of tetrafluoroethylene resin (PTFE), and the oil recovery felt 63 is an aramid fiber (trade name Nomex manufactured by DuPont), both processed into a 2 mm thick felt shape. It is bonded through a 0.1 mm PET film 71. The two felts that have been bonded together have a structure in which the oil recovery felt 63 side is bonded to a felt pressing plate 64 made of SPCC (cold rolled steel plate) having a thickness of 1 mm and is integrally held. An oil tank 68 is disposed below the felt pressure plate 64, and the felt pressure plate 64 is rotatably supported by felt pressure plate support shafts 65a and 65b fixed to the upper surface of the oil tank 68.
[0035]
The length of the oil application felt 62 is set so that the upper end of the oil application felt 62 is in contact with the oil application roller 61 and the lower end of the oil application felt 62 is immersed in the oil 70 in the oil tank 68. Close to the blade 67, the lower end is inserted into the oil tank 68. However, the lower end of the oil recovery felt 63 is set to a length that does not come into contact with the oil level even when the oil tank 68 is 100% filled with oil. The felt holding plate 64 is pressed at a predetermined pressure in the direction of the oil application roller 61 by pressure springs 66a and 66b at both ends thereof. As a result, the oil application felt 62 is applied to the oil application roller 61 with a predetermined pressure. It is in contact.
[0036]
The oil regulating blade 67 is composed of a stainless steel blade holder 67a, a blade base material 68b made of fluoro rubber, and a blade coating material 67c made of a fluororesin sheet. The pressure is increased.
[0037]
In the oil application apparatus configured as described above, the oil 70 pumped up from the oil tank 68 by the capillary action of the oil application felt 62 is applied to the surface of the oil application roller 61. The oil 70 applied on the oil application roller 61 moves in the direction of the oil regulating blade 67 by the rotation of the oil application roller 61 (in the direction of arrow D in the figure). The oil 70 applied on the oil application roller 61 is scraped off by the edge portion A of the oil regulating blade 67 and is uniformized to a predetermined amount, and then the oil application roller 61 and the fixing roller 51 are separated. At the pressure contact portion B, the toner is transferred and applied to the surface of the fixing roller 51. The oil scraped off at the edge A of the oil regulating blade 67 is absorbed by the oil collecting felt 63 and is collected in the oil tank 68 through the PET film 60.
[0038]
Here, the oil-coated felt of the present invention will be described in detail with reference to experimental results.
[0039]
First, in the case of using porous PTFE as an oil application member (conventional example) and in the case of using a felt using PTFE fibers (invention), the change in oil application amount when continuous paper aging is performed is measured. The results will be described. The method for measuring the amount of oil applied was as follows. First, two OHP sheets are overlaid, passed through a pressure contact portion between the fixing roller and the pressure roller (hereinafter referred to as a fixing nip portion), and from the mass difference before and after the measurement of the OHP sheet in contact with the fixing roller, The amount of oil applied to the recording surface side was determined. The reason for using an OHP sheet is that when plain paper is used, the paper mass itself changes before and after the measurement due to the evaporation of the moisture in the paper due to heating at the pressure contact part. This is because it is difficult to determine the coating amount.
[0040]
FIG. 4 shows the measurement results for the change in the amount of oil applied in the conventional example and the present invention, obtained by the above measurement method. From the results shown in FIG. 4, in the conventional porous PTFE, the oil application amount suddenly decreased from the initial 16 mg / A4, resulting in an offset of 8 mg / A4 when 30,000 sheets were passed. . This is because porous PTFE cannot supply oil because the pores are clogged with toner even when the oil application surface is slightly stained with toner. On the other hand, in the felt using the PTFE fiber of the present invention, the oil application amount is 16 mg throughout the life because the oil supply is possible unless the application surface is completely covered with the toner even if the oil application surface is soiled with toner. / Stable around A4.
[0041]
Next, the oil application roller 61 of the present invention will be described in detail with reference to experimental results.
[0042]
First, as the surface coating layer 61 b of the oil application roller 61, the following four types of samples were measured for changes in the amount of oil applied due to continuous paper aging and contamination of the oil application felt 62. The results are shown in Table 1 and FIG.
[0043]
(1) Sample 1 obtained by compression-molding HTV (High Temperature Vulcanizing) silicon rubber (thickness 0.5 mm) and polishing the surface once.
[0044]
(2) Sample 2 obtained by compression molding LTV silicon rubber (thickness 0.5 mm) and polishing the surface once.
[0045]
(3) Sample 3 obtained by compression-molding LTV silicon rubber (thickness 0.5 mm) and polishing the surface twice.
[0046]
(4) Sample 4 obtained by compression-molding LTV silicon rubber (thickness 0.5 mm) and further coating the surface with LTV silicon rubber (thickness 0.04 mm).
[0047]
[Table 1]

[0048]
From FIG. 5, the oil application amount tends to gradually decrease over the life of any application roller. However, the smaller the surface roughness of the oil application roller, the smaller the decrease in the oil application amount and the more stable the oil application performance. You can see that This is because, as shown in Table 1, in the sample having a large surface roughness, the surface of the oil application roller 61 becomes small due to sliding with the oil regulating blade 67, and the performance is changed. . As will be described later, there is a problem that an oil ghost is generated when the oil application amount is 20 mg / A4 or more, but the sample 1 with an initial surface roughness Ra of 1.13 μm has an oil application amount of 20 mg at the initial stage of life. / A4 or more causes problems such as oil ghosting and increased oil consumption throughout the life. The upper limit of the surface roughness Ra of the oil application roller 61 is preferably 1 μm or less. Further, from another study, when the surface roughness Ra is 0.1 μm or less, the oil application amount is 10 mg / A4 or less, and in this case, an offset occurs as described later. The lower limit of the surface roughness Ra is 0.1 μm or more.
[0049]
The above-mentioned results regarding the surface roughness are the results when the oil application roller 61 is pressurized with 2 kg weight (per 230 mm length) by the oil regulating blade 67, but the oil application roller 61 is not subjected to a large load. Similar results were obtained under ideal pressure conditions (1 to 3 kg weight (per 230 mm length)) that enable stable oil application.
[0050]
In order to set the surface roughness of the oil application roller 61 within the above range (0.1 μm or more and 1.0 μm or less), when the surface coating layer 61b of the oil application roller 61 is a silicon rubber material by compression molding, It is effective (sample 3) to perform the polishing process a plurality of times (two times or more), and when the surface coating layer is a silicon rubber material formed by coating molding, a desired surface roughness can be obtained without polishing. (Sample 4). Therefore, in this embodiment, the oil application roller of sample 3 or sample 4 is used.
[0051]
On the other hand, it can be seen from Table 1 that the toner contamination of the oil application felt 62 varies greatly depending on the type of the oil application roller 61. When toner adheres (offset) on the fixing roller 51, the adhered toner adheres to the oil application roller 61 to some extent, and as a result, the oil application felt 62 is soiled with toner. From the results in Table 1, it can be seen that as the surface roughness of the oil application roller 61 is smaller, the toner is less likely to adhere to the oil application roller 61, and as a result, the toner contamination of the oil application felt 62 is less. In addition, comparison between Sample 1 and Sample 2 shows that there is a large difference in dirt on the oil-coated felt 62 even though there is no significant difference in surface roughness between the two. The LTV silicone rubber of sample 2 is considered to have better releasability from the toner, and it is preferable to use LTV silicone rubber as the surface material.
[0052]
Next, Table 2 shows the results of examining the relationship between the polishing direction and the amount of oil applied when the surface of the oil application roller 61 is polished.
[0053]
[Table 2]

[0054]
When the surface of the oil application roller 61 is polished, the polished oil application roller 61 has a direction of surface friction force in the circumferential direction. That is, the surface of the oil application roller 61 after polishing has a shape as shown in FIG. 6, and the friction force is large in the E direction and the friction force is small in the opposite F direction. The normal direction of the polishing direction in this experiment is a case where the oil application roller 61 is arranged in a direction in which the frictional force is small with respect to the fixing roller 51 and the oil regulating blade 67 as shown in FIG. A direction is a case where it arrange | positions in a direction with big frictional force like FIG.7 (b). From the results shown in Table 2, the oil application roller 61 is arranged in the normal direction with less change in surface roughness due to life (after passing 60,000 sheets). It can be seen that it is more stable than the reverse eye direction.
[0055]
Next, FIG. 8A shows the result of examining the relationship between the surface roughness distribution in the longitudinal direction of the oil application roller 61 according to this embodiment and the oil application distribution. As described above, the oil application roller 61 of this embodiment is polished so that the surface roughness Rc at the center and the surface roughness Re at both ends satisfy Re> Rc. As a comparative example, FIG. 8B also shows the surface roughness in the longitudinal direction and the oil application distribution of the oil application roller 61 that has been polished so that Re = Rc.
[0056]
In the comparative example, the oil application amount is large in the central portion and is small in both end portions. This is because the contact pressure of the oil regulating blade 68 against the oil application roller becomes larger at both ends than the center due to the deflection of the oil regulating blade due to pressurization.
[0057]
On the other hand, in this embodiment, since the surface roughness of the oil application roller 61 is larger at both ends compared to the central portion, the oil application amount at both ends is larger than that in the comparative example, and as a result, the oil regulating blade The effect of non-uniform oil application due to 61 deflection is offset. Therefore, a uniform oil application distribution can be obtained in the roller longitudinal direction.
[0058]
As a specific method for setting the surface roughness of the oil application roller 61 to be larger at both ends compared to the center, <img width = "16" height = "16" src = "/ Gaiji / gif16 / 0001.gif"> The feeding speed of the polishing means such as a polishing grindstone or a lapping film is increased at both ends compared to the center of the roller. <img width = "16" height = "16" src = "/ Gaiji / gif16 / 0002.gif"> Increase the number of polishing in the center compared to both ends. In the present invention, any of the above methods may be used.
[0059]
Next, the relationship between the peripheral speed ratio between the oil application roller 61 and the fixing roller 51 and the image quality (especially oil banding) will be described in detail with reference to experimental results. Table 3 shows the results of examining the relationship between the peripheral speed ratio between the oil application roller and the fixing roller and the degree of occurrence of oil banding.
[0060]
[Table 3]

[0061]
From this result, it is understood that Vo / Vf = 1 is ideal as the peripheral speed ratio Vo / Vf between the oil application roller 61 and the fixing roller 51. However, the fixing roller 51 and the oil application roller 61 are normally used in a heated state, and the peripheral speed ratio varies slightly up and down depending on the temperature state of each roller at that time. Therefore, when the fluctuation of the peripheral speed ratio is taken into consideration, the peripheral speed ratio Vo / Vf is used in the range of 0.95 ≦ Vo / Vf ≦ 1 from the results of Table 3 to prevent the occurrence of oil banding. Desirable above. Therefore, in the present embodiment, the peripheral speed ratio Vo / Vf = 0.976 is set.
[0062]
Next, the relationship between the oil application amount and the image quality (especially offset and oil ghost) will be described in detail with reference to experimental results. Table 4 shows the results of investigating the relationship between the oil application amount, offset, and oil ghost.
[0063]
[Table 4]

[0064]
From this, it can be seen that an image defect due to oil ghost occurs when the oil application amount is 20 mg / A4 or more, and an image defect due to offset occurs when the oil application amount is 10 mg / A4 or less. Accordingly, it is appropriate in terms of image quality that the oil application amount is in the range of 10 mg / A4 to 20 mg / A4. In this embodiment, the oil application roller surface roughness, oil viscosity, oil regulating blade material and pressure By adjusting the above, the oil application amount is set to 12.3 mg / A4 after passing 15.7 mg / A4, 60,000 sheets in the initial state.
[0065]
[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to the drawings. Here, since the configuration of the present embodiment is exactly the same as that of the first embodiment except for the oil application felt, the description of the same parts is omitted.
[0066]
FIG. 9 is a diagram showing a configuration of the oil application felt 72 according to the second embodiment of the present invention. As shown in the first embodiment, when a fluorine-based fiber such as PTFE fiber is used as the material for the oil-coated felt, the performance is excellent, but the fluorine-based fiber is difficult to manufacture and is very expensive in price. There is a drawback of being. Therefore, the oil-coated felt in the present embodiment is a two-layered felt in which two types of fibers, PTFE fiber 72a and aramid fiber 72b, are bonded as shown in FIG. 9, and PTFE fiber 72a is oil-coated felt. 61 is disposed so as to abut against the unit 61. The PTFE fiber portion 72a has a thickness of 0.5 mm, and the aramid fiber portion 72b has a thickness of 1.5 mm. As a result, there is no concern that the PTFE fiber 72a of the felt falls off, and the performance equivalent to that of the conventional one-layered felt can be obtained in terms of durability. Aramid fibers are about 1/5 the price of PTFE fibers and are easy to manufacture. For this reason, by using PTFE fiber only on the contact surface with the oil application roller 61 that requires performance as PTFE as in the present embodiment, the price of the oil application felt is changed to felt using only PTFE fiber. It can be reduced to ½ or less, and the manufacturing can be facilitated. In addition, although the aramid fiber part was used here, if it is a fiber material rich in heat resistance, it can be used.
[0067]
[Embodiment 3]
In the first and second embodiments, the case where the present invention is applied to a fixing device using a fixing roller has been described. However, the present invention can also be applied to a fixing device using a fixing belt instead of the fixing roller. FIG. 10 is a schematic sectional view of a fixing device using a fixing belt. Since the oil application device is the same as that of the first embodiment, the description thereof is omitted. The fixing belt 101 is stretched between a driving roller 102 and a tension roller 103, and a predetermined tension is applied by the tension roller 103, so that the fixing belt 101 is driven and rotated to drive the driving roller. Further, a fixing nip portion is formed by the fixing belt 101 and the pressure roller 104, and toner is fixed by passing a recording paper having an unfixed toner image through the fixing nip portion.
[0068]
As a heating method of the fixing belt 101, (1) a method of providing a heating source in the driving roller 102 and heating it through the driving roller 102, (2) a method of configuring the fixing belt 101 itself with a heating element, and (3) There are various methods such as a method of separately providing a heat source on the back side of the fixing belt 101 in the fixing nip portion.
[0069]
As a result of the experiment, it was found that the same results as those in the first and second embodiments were obtained in such a belt-type fixing device, and that the present invention can also be applied to the belt-type fixing device.
[0070]
In the above embodiment, the oil 70 is supplied by the oil application felt 72 coming into contact with the oil application roller 61 in contact with the fixing roller 51 or the fixing belt 101. However, the oil 70 is supplied directly to the fixing roller 51 or the fixing belt. Oil 70 may be applied in contact.
[0071]
【The invention's effect】
As described above, in the fixing device of the present invention, since the center line average roughness Ra of the coating roller surface is 0.1 μm ≦ Ra ≦ 1 μm, there is little change in the amount of oil applied throughout the life, and the oil consumption can be reduced. .
[0072]
Also, since the application roller is arranged in contact with the fixing member in a direction where the surface frictional force along the circumference of the application roller is small, the change in the surface roughness of the oil application roller is small throughout the life. The amount is stable, leading to a reduction in oil consumption and an improvement in the reliability of the fixing device.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention.
FIG. 2 is a schematic perspective view of a fixing device according to an embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a laser printer provided with the fixing device shown in FIG. 1;
FIG. 4 is a diagram showing a change in an oil application amount depending on an oil application felt material during continuous paper aging.
FIG. 5 is a diagram showing a change in the amount of oil applied due to the surface roughness of the oil application roller during continuous paper aging.
FIG. 6 is a diagram showing a surface state after polishing of an oil application roller.
FIG. 7 is a diagram showing the arrangement direction of the oil application roller according to the polishing marks.
FIG. 8 is a diagram showing a surface roughness distribution and an oil application amount distribution in the longitudinal direction of the oil application roller.
FIG. 9 is an enlarged view of a main part of a fixing device according to a second embodiment of the present invention.
FIG. 10 is a schematic cross-sectional view of a fixing device according to a third embodiment of the present invention.
FIG. 11 is a schematic cross-sectional view of a conventional fixing device.
[Explanation of symbols]
51 Fixing roller
52 Pressure roller
61 Oil application roller
62 Oiled felt
63 Oil recovery felt
67 Oil regulating blade
70 Silicone oil

Claims (6)

A fixing means for fixing the unfixed toner image by heating and pressurizing a recording material having an unfixed toner image, an intermediate coating means comprising a roller in contact with the surface of the fixing means, and a release agent for the intermediate coating means In a fixing device comprising a release agent supply means for applying a release agent to the fixing means by supplying,
The center line average roughness Ra of the intermediate coating means surface is 0.1 μm ≦ Ra ≦ 1 μm,
The fixing device, wherein the intermediate coating unit is arranged so as to contact and rotate in a direction in which a surface frictional force along a circumferential direction is small with respect to the fixing unit. An oil regulating blade is disposed in contact with the surface of the intermediate coating means, and the intermediate coating means rotates in contact with the oil regulating blade in a direction in which the surface frictional force along the circumferential direction is small. The fixing device according to claim 1, wherein the fixing device is arranged. 3. The fixing device according to claim 2, wherein LTV silicon rubber is used as a surface material of the intermediate application unit. The fixing device according to claim 1, wherein the intermediate application unit includes a single roller.   The intermediate coating means is composed of one roller, and the surface coating layer in contact with the release agent supply means is composed of LTV silicon rubber,
  The fixing device according to claim 1, wherein at least a surface of the release agent supply unit that is in contact with the intermediate coating unit is formed of a fluorine resin fiber. A fixing means for fixing the unfixed toner image by heating and pressurizing a recording material having an unfixed toner image, an intermediate coating means comprising a roller in contact with the surface of the fixing means, and a release agent for the intermediate coating means In a fixing device comprising a release agent supply means for applying a release agent to the fixing means by supplying,
The center line average roughness Ra of the intermediate coating means surface is 0.1 μm ≦ Ra ≦ 1 μm,
As the surface material of the intermediate application means, LTV silicon rubber is used,
The fixing device, wherein the intermediate coating unit is arranged so as to contact and rotate in a direction in which a surface frictional force along a circumferential direction is small with respect to the fixing unit.

Images