JP5733606B2 - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

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JP5733606B2
JP5733606B2 JP2010253293A JP2010253293A JP5733606B2 JP 5733606 B2 JP5733606 B2 JP 5733606B2 JP 2010253293 A JP2010253293 A JP 2010253293A JP 2010253293 A JP2010253293 A JP 2010253293A JP 5733606 B2 JP5733606 B2 JP 5733606B2
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light
toner
image carrier
toner image
image
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JP2012103567A5 (en
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加余子 田中
加余子 田中
藤森　仰太
仰太 藤森
慶太 曽根
慶太 曽根
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Ricoh Co Ltd
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Description

本発明は、複写機、ファクシミリ、プリンタ等の画像形成装置に関するものである。   The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

従来、電源が投入された直後やプリントアウト枚数の累積が所定枚数に達したとき等の所定のタイミングに、正反射光と拡散反射光の両方を同時に検出可能な正反射光受光素子と拡散反射光受光素子とを有する光学的検出手段である光学センサを用いてプロセスコントロールなどの作像条件調整制御を実施する画像形成装置が知られている（例えば、特許文献１参照）。   Conventionally, a regular reflection light receiving element and diffuse reflection that can detect both specular reflection light and diffuse reflection light at the same time immediately after the power is turned on or when the cumulative number of printouts reaches a predetermined number. An image forming apparatus that performs image forming condition adjustment control such as process control using an optical sensor that is an optical detection unit having a light receiving element is known (for example, see Patent Document 1).

作像条件調整制御は、例えば次のように行われる。まず、光学センサの発光素子から発した光を像担持体である中間転写ベルトの表面の地肌部（トナーが付着していない部分）で反射させ、反射した正反射光を光学センサの正反射光受光素子で受光し正反射光に応じた出力値を出力する。次に、予め定められた形状の基準トナー像を感光体の表面に形成し、その基準トナー像を中間転写ベルト上に転写して、発光素子から発した光を基準トナー像で反射させ、反射した拡散反射光を拡散反射光受光素子で受光し拡散反射光に応じた出力値を出力する。そして、中間転写ベルト表面の地肌部における前記出力値を基準値として、この基準値と基準トナー像における前記出力値とを比較して基準トナー像のトナー濃度（単位面積あたりにおけるトナー付着量）を把握する。このようにして把握したトナー濃度に基づいて、そのトナー濃度が所望の濃度になるように、感光体の一様帯電電位、現像バイアス、感光体に対する光書込強度及び現像剤のトナー濃度の制御目標値などといった作像条件を調整する。このような作像条件調整制御により、長期に渡って安定した画像濃度のプリントアウトを行うことが可能になる。   The image forming condition adjustment control is performed as follows, for example. First, the light emitted from the light emitting element of the optical sensor is reflected by the background portion (the portion where the toner is not attached) on the surface of the intermediate transfer belt as an image carrier, and the reflected regular reflected light is reflected by the optical sensor. Light is received by the light receiving element and an output value corresponding to the specularly reflected light is output. Next, a reference toner image having a predetermined shape is formed on the surface of the photoconductor, the reference toner image is transferred onto the intermediate transfer belt, and the light emitted from the light emitting element is reflected by the reference toner image. The diffuse reflected light is received by the diffuse reflected light receiving element, and an output value corresponding to the diffuse reflected light is output. Then, using the output value at the background portion of the surface of the intermediate transfer belt as a reference value, the reference value and the output value of the reference toner image are compared, and the toner density (toner adhesion amount per unit area) of the reference toner image is determined. To grasp. Based on the toner density thus grasped, control of the uniform charging potential of the photosensitive member, the developing bias, the optical writing intensity to the photosensitive member, and the toner concentration of the developer so that the toner density becomes a desired density. Adjust imaging conditions such as target values. Such image forming condition adjustment control makes it possible to perform a printout with a stable image density over a long period of time.

しかしながら、光学センサに中間転写ベルトからの正反射光を受光する正反射光受光素子と、トナー像からの拡散反射光を受光する拡散反射光受光素子とをそれぞれ別個の受光素子で設けると、コストが増大するといった問題が生じる。   However, if the optical sensor is provided with a specular reflection light receiving element that receives specular reflection light from the intermediate transfer belt and a diffuse reflection light receiving element that receives diffuse reflection light from the toner image as separate light receiving elements, the cost is reduced. There arises a problem that increases.

本発明は以上の問題点に鑑みなされたものであり、その目的は、低コスト化を図りつつ、トナー濃度を検出できる画像形成装置を提供することである。   The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of detecting the toner density while reducing the cost.

上記目的を達成するために、請求項１の発明は、表面にトナー像を担持する像担持体と、前記像担持体の表面にトナー像を形成するトナー像形成手段と、該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学的検出手段による前記像担持体からの正反射光の検出値を用い、黒色とは異なる色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段によるトナー像からの拡散光の検出値を用いて、トナー濃度を算出することを特徴とするものである。
また、請求項２の発明は、表面にトナー像を担持する像担持体と、前記像担持体の表面にトナー像を形成するトナー像形成手段と、該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段による前記像担持体からの正反射光の出力値を用い、黒色とは異なる色のトナー像の濃度を算出する場合に前記光学検知検出手段による検出値の最大値を用いてトナー濃度を算出することを特徴とするものである。
また、請求項３の発明は、表面にトナー像を担持する像担持体と、前記像担持体の表面にトナー像を形成するトナー像形成手段と、該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段による前記像担持体からの正反射光の出力値を用い、黒色とは異なる色のトナー像の濃度を算出する場合には、前記光学的検知手段による予め設定された複数の検出タイミングそれぞれに対して、前記像担持体からの正反射光及びトナー像からの拡散反射光を受光した際の検出値から、前記像担持体からの正反射光を受光した際の検出値とを差し引いた差分値を算出し、前記差分値を累積した累積値を用いることを特徴とするものである。
また、請求項４の発明は、請求項３の画像形成装置において、上記光学的検出手段がトナー像からの拡散反射光を受光している時間を推定する推定手段を有しており、上記トナー濃度算出手段は、黒色とは異なる色のトナー像の濃度を算出する場合に前記推定手段の推定結果も用いることを特徴とするものである。
また、請求項５の発明は、請求項１、２、３または４の画像形成装置において、上記光学的検出手段と上記像担持体とのどちらか一方が互いの対向面に対して平行方向に移動可能であり、前記光学的検出手段による前記像担持体の検出方向が、前記光学的検出手段と前記像担持体とのどちらか一方の移動方向と平行であることを特徴とするものである。 In order to achieve the above object, an invention according to claim 1 is directed to an image carrier that carries a toner image on a surface, a toner image forming unit that forms a toner image on the surface of the image carrier, An optical detection means comprising: a light emitting means for irradiating light on a surface or a toner image carried on the surface; and a light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image; The detection value of the automatic detection means is separated into a specular reflection light component from the image carrier and a diffuse reflection light component from the toner image, and the toner of the toner image using the specular reflection light component and the diffuse reflection light component. A toner density calculating means for calculating the density, and a control for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculated value calculated by the toner density calculating means. Means and The distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the light receiving center of the light receiving means is the perpendicular line of the image carrier. The distance between the straight line intersecting the line and the point where the straight line intersects the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d can receive the specularly reflected light from the image carrier. The irradiation light opening angle from the light emission center that holds the specular reflection angle is θ1, and is the narrowest angle among the angles formed by the irradiation light opening angle θ1 and the straight line that intersects the light emission center among the perpendicular lines of the image carrier. The angle is θ2, the irradiation light opening angle from the light emission center is θ3, and the angle that is the narrowest angle among the angles formed by the straight line intersecting the light emission center and the irradiation light from the light emission center among the perpendicular lines of the image carrier Where d = (m1 m2) satisfy the relationship × {tan (θ1 + θ2) -tanθ2}, and, .theta.4 <.theta.2 and (θ3 + θ4)> (θ1 + θ2) and the meets at least one of relationships, the toner concentration calculating means, a black toner image When calculating the density of a toner image having a color different from black, at least using the detection value of the regular reflection light from the image carrier by the optical detection means. The toner density is calculated using the detected value of diffused light from the toner image .
According to a second aspect of the present invention, there is provided an image carrier that carries a toner image on the surface, toner image forming means that forms a toner image on the surface of the image carrier, and the surface of the image carrier and the image carrier. An optical detection means having a light emitting means for irradiating light on the toner image and a light receiving means for receiving reflected light reflected from the surface and the toner image irradiated from the light emitting means, and a detection value of the optical detection means Is divided into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner density of the toner image is calculated using the specularly reflected light component and the diffusely reflected light component Calculating means, and control means for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculated value calculated by the toner density calculating means, The vertical line of the image carrier That is, the distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the straight line that intersects the light receiving center of the light receiving means among the perpendicular lines of the image carrier. The distance of the straight line connecting the intersections with the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d holds the specular reflection angle at which the specular reflection light from the image carrier can be received. The opening angle of the irradiated light from the emission center is θ1, the angle that is the narrowest of the angles formed by the straight line intersecting the emission center of the perpendicular of the image carrier and the irradiation light opening angle θ1, is θ2, and the emission center When the opening angle of the irradiation light from is θ3 and the angle between the straight line intersecting the emission center of the perpendicular of the image carrier and the irradiation light from the emission center is θ4, d = (m1 + m2) × {tan (θ 1 + θ2) −tan θ2} and at least one of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2) is satisfied, and the toner density calculating unit calculates the density of the black toner image. Using at least the output value of the regular reflection light from the image carrier by the optical detection means, and using the maximum value of the detection value by the optical detection detection means when calculating the density of a toner image of a color different from black The toner density is calculated.
According to a third aspect of the present invention, there is provided an image carrier for carrying a toner image on the surface, a toner image forming means for forming a toner image on the surface of the image carrier, and the surface of the image carrier and the image carrier. An optical detection means having a light emitting means for irradiating light on the toner image and a light receiving means for receiving reflected light reflected from the surface and the toner image irradiated from the light emitting means, and a detection value of the optical detection means Is divided into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner density of the toner image is calculated using the specularly reflected light component and the diffusely reflected light component Calculating means, and control means for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculated value calculated by the toner density calculating means, The vertical line of the image carrier That is, the distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the straight line that intersects the light receiving center of the light receiving means among the perpendicular lines of the image carrier. The distance of the straight line connecting the intersections with the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d holds the specular reflection angle at which the specular reflection light from the image carrier can be received. The opening angle of the irradiated light from the emission center is θ1, the angle that is the narrowest of the angles formed by the straight line intersecting the emission center of the perpendicular of the image carrier and the irradiation light opening angle θ1, is θ2, and the emission center When the opening angle of the irradiation light from is θ3 and the angle between the straight line intersecting the emission center of the perpendicular of the image carrier and the irradiation light from the emission center is θ4, d = (m1 + m2) × {tan (θ 1 + θ2) −tan θ2} and at least one of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2) is satisfied, and the toner density calculating unit calculates the density of the black toner image. When calculating the density of a toner image having a color different from black using at least the output value of regular reflection light from the image carrier by the optical detection means, a plurality of preset values by the optical detection means are used. For each detection timing, from the detection value when the regular reflection light from the image carrier and the diffuse reflection light from the toner image are received, the detection value when the regular reflection light from the image carrier is received and The difference value is calculated by subtracting, and the accumulated value obtained by accumulating the difference value is used.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the optical detecting unit includes an estimating unit that estimates a time during which the diffusely reflected light from the toner image is received. The density calculating means uses the estimation result of the estimating means when calculating the density of a toner image having a color different from black.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first , second, third, or fourth aspect , one of the optical detection means and the image carrier is parallel to the opposing surfaces. It is movable, and the detection direction of the image carrier by the optical detection means is parallel to the movement direction of one of the optical detection means and the image carrier. .

本発明においては、光学的検出手段が有する受光手段で受光した反射光の検出値を、トナー濃度算出手段により前記正反射光成分と前記拡散反射光成分とに分離してトナー像のトナー濃度を算出することができる。これにより、像担持体からの正反射光を受光する正反射光受光手段と、トナー像からの拡散反射光を受光する拡散反射光受光手段とをそれぞれ別個で設ける必要がない。よって、受光手段の数を減らせる分、低コスト化を図ることができる。   In the present invention, the detected value of the reflected light received by the light receiving means included in the optical detecting means is separated into the regular reflected light component and the diffuse reflected light component by the toner density calculating means to obtain the toner density of the toner image. Can be calculated. Accordingly, it is not necessary to separately provide the regular reflection light receiving unit that receives the regular reflection light from the image carrier and the diffuse reflection light reception unit that receives the diffuse reflection light from the toner image. Therefore, the cost can be reduced by reducing the number of light receiving means.

以上、本発明によれば、低コスト化を図りつつ、トナー濃度を検出できるという優れた効果がある。   As described above, according to the present invention, there is an excellent effect that the toner density can be detected while reducing the cost.

パターン形成位置と光学センサの配設位置とを示した、中間転写ベルト近傍の拡大概略構成図。FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a pattern formation position and an optical sensor arrangement position. 実施形態に係るプリンタの概略構成図。1 is a schematic configuration diagram of a printer according to an embodiment. 像形成手段の概略構成図。FIG. 3 is a schematic configuration diagram of an image forming unit. パターン形成位置と光学センサの配設位置とを示した、中間転写ベルト近傍の拡大概略構成図。FIG. 3 is an enlarged schematic configuration diagram in the vicinity of an intermediate transfer belt showing a pattern formation position and an optical sensor arrangement position. 作像条件調整制御に係るブロック図。FIG. 3 is a block diagram related to image forming condition adjustment control. 光学センサの詳細図。Detailed view of the optical sensor. 光学センサの出力信号と、中間転写ベルトからの正反射光成分及びトナーからの拡散反射光成分との関係を示すグラフ。6 is a graph showing a relationship between an output signal of an optical sensor, a regular reflection light component from an intermediate transfer belt, and a diffuse reflection light component from toner. 光学センサ制御フロー図。Optical sensor control flowchart. 光学センサの出力値の時間変化を示す図。The figure which shows the time change of the output value of an optical sensor. トナー濃度算出制御に係るフローチャート。6 is a flowchart according to toner density calculation control.

以下、本発明を画像形成装置であるフルカラープリンタ（以下、プリンタという）１００に適用した場合の実施形態について説明する。
図２は、このプリンタ１００の概略構成を示す構成図である。このプリンタ１００は、図２に示すように、像形成手段としての各構成部材を収納する位置固定された装置本体と、転写材Ｓを収納する引き出し可能な給紙カセット２１とを備えている。装置本体の中央部には、イエロー（Ｙ）、シアン（Ｃ）、マゼンダ（Ｍ）、黒（Ｂｋ）の各色のトナー像を形成するための画像形成ユニット１Ｙ、１Ｃ、１Ｍ、１Ｂｋを備えている。以下、各符号の添字Ｙ、Ｃ、Ｍ、Ｂｋは、それぞれイエロー、シアン、マゼンダ、黒用の部材であることを示す。 Hereinafter, an embodiment in which the present invention is applied to a full-color printer (hereinafter referred to as a printer) 100 as an image forming apparatus will be described.
FIG. 2 is a configuration diagram showing a schematic configuration of the printer 100. As shown in FIG. 2, the printer 100 includes an apparatus main body that is fixed in position for storing each component as an image forming unit, and a drawable sheet cassette 21 that stores a transfer material S. An image forming unit 1Y, 1C, 1M, 1Bk for forming toner images of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) is provided at the center of the apparatus main body. Yes. Hereinafter, the subscripts Y, C, M, and Bk of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively.

図３は、像形成手段の概略構成を示す構成図である。図２及び図３に示すように本実施形態においては、像担持体としてのドラム状の感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋ、帯電手段としての帯電ローラ３Ｙ，３Ｃ，３Ｍ，３Ｂｋ、画像書込手段（露光手段）としてのレーザー露光装置２０及び現像手段としての現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋ、感光体表面の転写残トナーを除去するクリーニング装置６Ｙ，６Ｃ，６Ｍ，６Ｂｋを少なくとも有するユニットとして、各色の画像形成ユニット１Ｙ，１Ｃ，１Ｍ，１Ｂｋが複数組（本実施形態では４組）構成され、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）及びブラック（Ｂｋ）の各色の上記画像形成ユニット１Ｙ，１Ｃ，１Ｍ，１Ｂｋが、ループ状に走行する像担持体としての中間転写ベルト７の水平な張架面に対向して、その下部に左からＹ、Ｃ、Ｍ、Ｂｋの順に配設されている。また、各色の画像形成ユニット１Ｙ，１Ｃ，１Ｍ，１Ｂｋは４組とも同じ構成にしてある。   FIG. 3 is a configuration diagram showing a schematic configuration of the image forming means. As shown in FIGS. 2 and 3, in the present embodiment, drum-shaped photoreceptors 2Y, 2C, 2M, and 2Bk as image carriers, charging rollers 3Y, 3C, 3M, and 3Bk as charging means, and image writing As a unit having at least a laser exposure device 20 as means (exposure means), developing devices 4Y, 4C, 4M, and 4Bk as developing means, and cleaning devices 6Y, 6C, 6M, and 6Bk that remove transfer residual toner on the surface of the photoreceptor. The image forming units 1Y, 1C, 1M, and 1Bk for each color are configured in a plurality of groups (four in this embodiment), and the above-described colors for yellow (Y), magenta (M), cyan (C), and black (Bk) are described above. The image forming units 1Y, 1C, 1M, and 1Bk face the horizontal stretching surface of the intermediate transfer belt 7 as an image carrier that runs in a loop shape, and the left side of the image forming unit Y, are arranged C, M, in the order of Bk. The four image forming units 1Y, 1C, 1M, and 1Bk for each color have the same configuration.

帯電ローラ３Ｙ，３Ｃ，３Ｍ，３Ｂｋは、それぞれ所定の電位に保持されたトナーと同極性の帯電（本実施形態においてはマイナス帯電）によって感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋに対して帯電作用を行い、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋに一様な電位を与える。なお、帯電手段としては帯電ローラに限るものではなく、帯電ブラシや帯電チャージャ等の種々のものを適宜使用することができる。   The charging rollers 3Y, 3C, 3M, and 3Bk charge the photoreceptors 2Y, 2C, 2M, and 2Bk by charging with the same polarity as the toner held at a predetermined potential (negative charging in this embodiment). The uniform potential is applied to the photoreceptors 2Y, 2C, 2M, and 2Bk. The charging means is not limited to the charging roller, and various devices such as a charging brush and a charging charger can be used as appropriate.

レーザー露光装置２０は、帯電ローラ３Ｙ，３Ｃ，３Ｍ，３Ｂｋに対して感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの回転方向下流側で現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋの上流側を露光する。また、また、レーザー露光装置２０は、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの回転軸と平行に主走査方向に露光走査するように配置されている。   The laser exposure device 20 exposes the upstream sides of the developing devices 4Y, 4C, 4M, and 4Bk to the charging rollers 3Y, 3C, 3M, and 3Bk on the downstream side in the rotation direction of the photoreceptors 2Y, 2C, 2M, and 2Bk. Further, the laser exposure device 20 is arranged to perform exposure scanning in the main scanning direction in parallel with the rotation axes of the photoreceptors 2Y, 2C, 2M, and 2Bk.

レーザー露光装置２０は、例えば、半導体レーザー（ＬＤ）からなる光源と、コリメートレンズやシリンドリカルレンズ等からなるカップリング光学系（またはビーム整形光学系）と、回転多面鏡等からなる光偏向器と、光偏向器で偏向されたレーザー光を感光体２上に集光する結像光学系等からなり、別構成で設けた図示しない画像読み取り装置によって読み取られメモリに記録された各色の画像データ（あるいはパーソナルコンピュータ等の外部機器から入力された各色の画像データ）に従って強度変調されたレーザー光ＬＹ，ＬＣ，ＬＭ，ＬＢｋによって各色用の感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの感光層を像露光し、各色毎の静電潜像を形成する。なお、画像書込手段（露光手段）としては、上記のレーザー露光装置２０の他に、発光ダイオードアレイ（ＬＥＤアレイ）とレンズアレイ等を組み合わせたＬＥＤ書き込み装置なども用いることができる。   The laser exposure apparatus 20 includes, for example, a light source composed of a semiconductor laser (LD), a coupling optical system (or beam shaping optical system) composed of a collimating lens, a cylindrical lens, and the like, an optical deflector composed of a rotating polygon mirror, and the like. The image data of each color (or the image data (or the image data) read by an image reading device (not shown) provided in another configuration and recorded in the memory (or the like) is formed by an imaging optical system that condenses the laser light deflected by the optical deflector onto the photosensitive member 2. Image exposure of the photosensitive layers 2Y, 2C, 2M, and 2Bk for the respective colors with laser beams LY, LC, LM, and LBk intensity-modulated in accordance with image data of each color input from an external device such as a personal computer, An electrostatic latent image for each color is formed. As the image writing means (exposure means), in addition to the laser exposure apparatus 20 described above, an LED writing apparatus combining a light emitting diode array (LED array) and a lens array can be used.

感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋは、導電性円筒状支持体の表面に形成された下引き層上に、上記感光層として電荷発生層（下層）、電荷輸送層（上層）の順、またはこの逆の順にこれらの感光層が積層されている。また、上記電荷輸送層または上記電荷発生層の表面にさらに公知の表面保護層、例えば熱可塑性又は熱硬化性ポリマーを主体とするオーバーコート層などが形成されていてもよい。また、本実施形態では、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの導電性円筒状の支持体は接地されている。   The photoreceptors 2Y, 2C, 2M, and 2Bk are formed on the undercoat layer formed on the surface of the conductive cylindrical support, in the order of the charge generation layer (lower layer) and the charge transport layer (upper layer) as the photosensitive layer, or These photosensitive layers are laminated in the reverse order. Further, a known surface protective layer such as an overcoat layer mainly composed of a thermoplastic or thermosetting polymer may be formed on the surface of the charge transport layer or the charge generation layer. In the present embodiment, the conductive cylindrical supports of the photoreceptors 2Y, 2C, 2M, and 2Bk are grounded.

現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋは、感光体２の周面に対し所定の間隙を保ち、感光体２の回転方向と順方向に回転する円筒状の非磁性のステンレスあるいはアルミニウム材で形成された現像スリーブ４１Ｙ，４１Ｃ，４１Ｍ，４１Ｂｋを有し、現像装置４内部には各色毎の現像色に従いイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）及びブラック（Ｂｋ）の一成分あるいは二成分現像剤を収容している。本実施形態においては、一例として現像装置４内部にトナーと磁性キャリアとからなる二成分現像剤（本実施形態においてトナーはマイナス帯電）を収容しており、この場合、現像スリーブ４１内には、複数の固定磁石あるいは複数の磁極が着磁されたマグネットロールが配置される。また、各色の現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋには、容器内の現像剤を撹拌しながら搬送する撹拌・搬送部材４２や、各色のトナーボトル３７からトナーが補給される補給部４３が設けられている。さらに各色の現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋには、必要に応じて容器内の現像剤のトナー濃度を検出するトナー濃度センサ４４Ｙ，４４Ｃ，４４Ｍ，４４Ｂｋが設けられる。   The developing devices 4Y, 4C, 4M, and 4Bk are formed of a cylindrical non-magnetic stainless steel or aluminum material that maintains a predetermined gap with respect to the peripheral surface of the photoconductor 2 and rotates in the forward direction and the rotation direction of the photoconductor 2. Development sleeves 41Y, 41C, 41M, and 41Bk, and one or two components of yellow (Y), magenta (M), cyan (C), and black (Bk) in the developing device 4 according to the development color of each color. Contains component developer. In the present embodiment, as an example, a two-component developer composed of toner and a magnetic carrier (in this embodiment, the toner is negatively charged) is accommodated in the developing device 4. In this case, the developing sleeve 41 includes A plurality of fixed magnets or magnet rolls magnetized with a plurality of magnetic poles are arranged. Further, each color developing device 4Y, 4C, 4M, 4Bk is provided with an agitating / conveying member 42 for conveying the developer in the container while stirring, and a replenishing portion 43 for supplying toner from each color toner bottle 37. It has been. Further, the developing devices 4Y, 4C, 4M and 4Bk for the respective colors are provided with toner concentration sensors 44Y, 44C, 44M and 44Bk for detecting the toner concentration of the developer in the container as required.

各色の現像装置４Ｙ，４Ｃ，４Ｍ，４Ｂｋの現像スリーブ４１Ｙ，４１Ｃ，４１Ｍ，４１Ｂｋは図示しない突き当てコロ等により、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋのドラム面と所定の間隙、例えば１００［μｍ］から５００［μｍ］の間隙を開けて非接触に保たれており、その現像スリーブ４１Ｙ，４１Ｃ，４１Ｍ，４１Ｂｋに対して直流電圧と交流電圧とを重畳した現像バイアスを印加することにより、接触または非接触の反転現像を行い、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの表面上にトナー画像を形成する。   The developing sleeves 41Y, 41C, 41M, and 41Bk of the developing devices 4Y, 4C, 4M, and 4Bk for the respective colors are placed on the drum surface of the photoreceptors 2Y, 2C, 2M, and 2Bk and a predetermined gap, for example, 100 [ [mu] m] to 500 [[mu] m] is maintained in a non-contact state, and a developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeves 41Y, 41C, 41M, and 41Bk. Contact or non-contact reversal development is performed to form toner images on the surfaces of the photoreceptors 2Y, 2C, 2M, and 2Bk.

クリーニング装置６Ｙ，６Ｃ，６Ｍ，６Ｂｋは、例えばクリーニングブレード６１とクリーニングローラ（またはクリーニングブラシ）６２を有し、クリーニングブレード６１は、感光体表面のカウンタ方向に当接して設けられている。   The cleaning devices 6Y, 6C, 6M, and 6Bk include, for example, a cleaning blade 61 and a cleaning roller (or cleaning brush) 62, and the cleaning blade 61 is provided in contact with the counter direction of the photosensitive member surface.

中間転写体であり像担持体である中間転写ベルト７は、二次転写バックアップローラを兼ねる駆動ローラ８、支持ローラ９、テンションローラ１０ａ，１０ｂ及びバックアップローラ１１に内接して張架され、中間転写ベルト７の回転方向が図中の矢印で示す反時計方向になるように設けられている。   The intermediate transfer belt 7 that is an intermediate transfer member and an image carrier is stretched in contact with the driving roller 8 that also serves as a secondary transfer backup roller, the support roller 9, the tension rollers 10a and 10b, and the backup roller 11 to be intermediate transfer. The belt 7 is provided so that the rotation direction thereof is counterclockwise as indicated by an arrow in the drawing.

また、駆動ローラ８に対向して中間転写ベルト７を介して二次転写ローラ１４が設けられている。そしてベルトクリーニング装置１２のクリーニングブレード１２ａが支持ローラ９の位置の中間転写ベルト７に、カウンタ方向に当接して設けられている。また、同様に、中間転写ベルト７を挟んで各色毎の一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋが感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋに対向して設けられている。   Further, a secondary transfer roller 14 is provided through the intermediate transfer belt 7 so as to face the driving roller 8. A cleaning blade 12 a of the belt cleaning device 12 is provided in contact with the intermediate transfer belt 7 at the position of the support roller 9 in the counter direction. Similarly, primary transfer rollers 5Y, 5C, 5M, and 5Bk for each color are provided to face the photoreceptors 2Y, 2C, 2M, and 2Bk with the intermediate transfer belt 7 interposed therebetween.

この中間転写ベルト７は、体積抵抗が１０６［Ω・ｃｍ］から１０１２［Ω・ｃｍ］の無端ベルトであり、例えばポリカーボネート（ＰＣ）、ポリイミド（ＰＩ）、ポリアミドイミド（ＰＡＩ）、ポリビニリデンフルオライド（ＰＶＤＦ）、テトラフルオロエチレン−エチレン共重合体（ＥＴＦＥ）等の樹脂材料や、ＥＰＤＭ、ＮＢＲ、ＣＲ、ポリウレタン等のゴム材料にカーボン等の導電性フィラーを分散させたり、イオン性の導電材料を含有させたりしたものが用いられ、厚みは、樹脂材料の場合５０［μｍ］から２００［μｍ］程度、ゴム材料の場合は３００［μｍ］から７００［μｍ］程度の設定にすることが好ましい。なお、樹脂ベルト上にゴム層を設けたり、さらに表層にコーティング層を設けたりすることもある。また、中間転写ベルト７の表面にトナーが固着することを防止するためやクリーニング性の向上のために、ベルト表面にフッ素系樹脂等の離型剤または潤滑剤を塗布する手段を設けることもある。 This intermediate transfer belt 7 is an endless belt having a volume resistance of 10 6 [Ω · cm] to 10 12 [Ω · cm]. For example, polycarbonate (PC), polyimide (PI), polyamideimide (PAI), polyvinylidene Conductive fillers such as carbon are dispersed in resin materials such as fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), and rubber materials such as EPDM, NBR, CR, polyurethane, etc. A material containing a material is used, and the thickness is set to about 50 [μm] to 200 [μm] in the case of a resin material and about 300 [μm] to 700 [μm] in the case of a rubber material. preferable. A rubber layer may be provided on the resin belt, and a coating layer may be provided on the surface layer. Further, in order to prevent the toner from adhering to the surface of the intermediate transfer belt 7 or to improve the cleaning property, a means for applying a release agent such as a fluorine-based resin or a lubricant may be provided on the belt surface. .

中間転写ベルト７の駆動は図示しない駆動モータによる駆動ローラ８の回転によって行われる。駆動ローラ８は、例えばステンレス鋼等の導電性芯金（図示せず）の周面に、ポリウレタン、ＥＰＤＭ、シリコン等のゴムや樹脂材料にカーボン等の導電性フィラーを分散させた導電性または半導電性材料を被覆したものが用いられる。   The intermediate transfer belt 7 is driven by rotation of the drive roller 8 by a drive motor (not shown). The drive roller 8 is a conductive or semi-conductive material in which a conductive filler such as carbon is dispersed in a circumferential surface of a conductive metal bar (not shown) such as stainless steel, or a rubber or resin material such as polyurethane, EPDM, or silicon. A material coated with a conductive material is used.

一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋは、中間転写ベルト７を挟んで感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋに対向して設けられ、中間転写ベルト７と感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋとの間に転写域を形成する。一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋには、図示しない直流電源によりトナーと反対極性（本実施形態においてはプラス極性）の直流電圧を印加し、上記転写域に転写電界を形成することによって、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋ上に形成される各色のトナー像が中間転写ベルト７上に転写される。   The primary transfer rollers 5Y, 5C, 5M, and 5Bk are provided to face the photoreceptors 2Y, 2C, 2M, and 2Bk with the intermediate transfer belt 7 interposed therebetween, and the intermediate transfer belt 7 and the photoreceptors 2Y, 2C, 2M, and 2Bk are provided. A transfer zone is formed between the two. A DC voltage having a polarity opposite to that of the toner (plus polarity in the present embodiment) is applied to the primary transfer rollers 5Y, 5C, 5M, and 5Bk by a DC power source (not shown) to form a transfer electric field in the transfer area. Each color toner image formed on the photoreceptors 2Y, 2C, 2M, and 2Bk is transferred onto the intermediate transfer belt 7.

この各色毎の第１の転写手段である一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋは、例えば外径８［ｍｍ］のステンレス鋼等の導電性芯金（図示せず）の周面に、ポリウレタン、ＥＰＤＭ、シリコン等のゴム材料に、カーボン等の導電性フィラーを分散させたり、イオン性の導電材料を含有させたりして、体積抵抗が１０５［Ω・ｃｍ］から１０９［Ω・ｃｍ］程度のソリッド状態または発泡スポンジ状態で、厚さが５［ｍｍ］、ゴム硬度が２０［°］から７０［°］程度（Ａｓｋｅｒ−Ｃ）の半導電性弾性ゴム（図示しない）を被覆して形成される。 The primary transfer rollers 5Y, 5C, 5M, and 5Bk, which are the first transfer means for each color, are made of polyurethane on the peripheral surface of a conductive metal core (not shown) such as stainless steel having an outer diameter of 8 [mm], for example. , EPDM, silicon, or other rubber material is dispersed with a conductive filler such as carbon or an ionic conductive material, so that the volume resistance is from 10 5 [Ω · cm] to 10 9 [Ω · cm. A semi-conductive elastic rubber (not shown) having a thickness of 5 [mm] and a rubber hardness of 20 [°] to 70 [°] (Asker-C) in a solid or foamed sponge state. Formed.

転写材Ｓの表面に転写を行う二次転写ローラ１４は中間転写ベルト７を挟んで接地された駆動ローラ８に対向して設けられ、トナーの帯電極性とは反対極性（本実施形態においてはプラス極性）の直流電圧が直流電源によって印加され、中間転写ベルト７上に担持された重ね合わせトナー画像を転写材Ｓの表面に二次転写ローラ１４を介して転写する。   The secondary transfer roller 14 that performs transfer onto the surface of the transfer material S is provided to face the driving roller 8 that is grounded with the intermediate transfer belt 7 interposed therebetween, and has a polarity opposite to the toner charging polarity (in this embodiment, plus). (Polarity) DC voltage is applied by a DC power source, and the superimposed toner image carried on the intermediate transfer belt 7 is transferred to the surface of the transfer material S via the secondary transfer roller 14.

中間転写ベルト７上のカラートナー像を転写材Ｓ上に再転写する第２の転写手段である二次転写ローラ１４は、例えば外径１６［ｍｍ］のステンレス鋼等の導電性芯金の周面に、ポリウレタン、ＥＰＤＭ、シリコン等のゴム材料に、カーボン等の導電性フィラーを分散させたり、イオン性の導電材料を含有させたりして、体積抵抗が１０５［Ω・ｃｍ］から１０９［Ω・ｃｍ］程度のソリッド状態または発泡スポンジ状態で、厚さが７［ｍｍ］、ゴム硬度が２０［°］から７０［°］程度（Ａｓｋｅｒ−Ｃ）の半導電性弾性ゴム（図示しない）を被覆して形成される。この二次転写ローラ１４は一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋと異なり、トナーが接するため表面に半導電性のフッ素樹脂やウレタン樹脂等の離型性の良いものを被覆する場合がある。また、駆動ローラ８は前述したように、ステンレス鋼等の導電性芯金の周面に、ポリウレタン、ＥＰＤＭ、シリコン等のゴムや樹脂材料に、カーボン等の導電性フィラーを分散させたり、イオン性の導電材料を含有させたりした半導電性材料を、厚さが０．０５［ｍｍ］から０．５［ｍｍ］程度に被覆して形成される。 The secondary transfer roller 14 serving as a second transfer unit that re-transfers the color toner image on the intermediate transfer belt 7 onto the transfer material S has a circumference of a conductive metal core such as stainless steel having an outer diameter of 16 [mm]. On the surface, a volume resistance is 10 5 [Ω · cm] to 10 9 by dispersing a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, silicon, or containing an ionic conductive material. Semiconductive elastic rubber (not shown) having a thickness of 7 [mm] and a rubber hardness of about 20 [°] to 70 [°] (Asker-C) in a solid state or foamed sponge state of about [Ω · cm] ). Unlike the primary transfer rollers 5Y, 5C, 5M, and 5Bk, the secondary transfer roller 14 may come in contact with toner and may cover the surface with a good releasability such as semiconductive fluorine resin or urethane resin. Further, as described above, the driving roller 8 has a conductive core such as stainless steel dispersed on a peripheral surface of a conductive core metal such as polyurethane, EPDM, or silicon, or a conductive filler such as carbon, or an ionic property. A semiconductive material containing a conductive material is coated to a thickness of about 0.05 [mm] to 0.5 [mm].

感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋや中間転写ベルト７の表面に接したクリーニングブレード６１，１２ａは、板金ホルダー上に厚み１［ｍｍ］から３［ｍｍ］でＪＩＳ−Ａ硬度が６０［°］から８０［°］の板状のウレタンゴムを接着し、自由長が５［ｍｍ］から１２［ｍｍ］程度になるようにしたものであり、荷重５［ｇｆ］から５０［ｇｆ］程度で感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋや中間転写ベルト７に当接されている。また、ブレードが捲れあがらないようにブレード先端部にふっ素コーティングを施したり、相手側が帯電しないように導電性のウレタンゴムを使用したりすることもある。   The cleaning blades 61 and 12a in contact with the surfaces of the photoreceptors 2Y, 2C, 2M, and 2Bk and the intermediate transfer belt 7 have a thickness of 1 [mm] to 3 [mm] and a JIS-A hardness of 60 [°] on the sheet metal holder. To 80 [°] plate-like urethane rubber is bonded so that the free length becomes about 5 [mm] to about 12 [mm], and is sensitive to a load of about 5 [gf] to about 50 [gf]. It is in contact with the bodies 2Y, 2C, 2M, 2Bk and the intermediate transfer belt 7. In some cases, the blade tip is coated with fluorine to prevent the blade from rolling up or conductive urethane rubber is used so that the other side is not charged.

転写紙等の転写材Ｓは給紙カセット２１等から給紙ローラ２７により一枚ずつ搬送され、レジストローラ１３を経て二次転写ローラ１４と駆動ローラ８に挟まれた中間転写ベルト７に重ねられるように搬送され、二次転写部で中間転写ベルト７からトナー像の転写を受けて定着手段である定着装置１５に送られ、定着装置１５の定着ローラ１５ａと加圧ローラ１５ｂによる熱溶着による定着がなされて排紙部１８に排紙される。   The transfer material S such as transfer paper is conveyed one by one by a paper feed roller 27 from the paper feed cassette 21 or the like, and is superimposed on the intermediate transfer belt 7 sandwiched between the secondary transfer roller 14 and the drive roller 8 via the registration roller 13. The toner image is transferred from the intermediate transfer belt 7 at the secondary transfer portion and sent to the fixing device 15 as fixing means, and is fixed by heat welding between the fixing roller 15a and the pressure roller 15b of the fixing device 15. Is discharged to the paper discharge unit 18.

なお、本実施形態においては、感光体２Ｙ，２Ｃ，２Ｍ，２Ｂｋの帯電手段として帯電ローラ３Ｙ，３Ｃ，３Ｍ，３Ｂｋを用い、一次転写部材として一次転写ローラ５Ｙ，５Ｃ，５Ｍ，５Ｂｋを用いており、有害なオゾンの発生の抑制という観点からは好ましいが、これに限られるものでなく、コロトロン放電器を非接触の状態の帯電手段や一次転写手段として使うこともできる。   In the present embodiment, charging rollers 3Y, 3C, 3M, and 3Bk are used as charging means for the photoreceptors 2Y, 2C, 2M, and 2Bk, and primary transfer rollers 5Y, 5C, 5M, and 5Bk are used as primary transfer members. However, it is preferable from the viewpoint of suppressing the generation of harmful ozone, but is not limited to this, and the corotron discharger can be used as a charging means or a primary transfer means in a non-contact state.

また、上記二次転写部より中間転写ベルト７の回転方向下流側に、中間転写ベルト７における駆動ローラ１７への掛け回し箇所に対してそのおもて面側から所定の間隙を介して対向する、光学的検出手段としての光学センサ１６０を複数設けた光学センサユニット１６が配設されている（図４参照）。この光学センサユニット１６は、中間転写ベルト７上に形成された作像条件調整制御用のトナー濃度（トナー付着量）を階調的に変化させた複数のトナー像からなる階調パターンを検出することができる。具体的には、図４に示すように、光学センサユニット１６には、Ｂｋ色の階調パターンＳｋを検出する光学センサ１６０Ｂｋ、Ｍ色の階調パターンＳｍを検出する光学センサ１６０Ｍ、Ｃ色の階調パターンＳｃを検出する光学センサ１６０Ｃ、Ｙ色の階調パターンＳｙを検出する光学センサ１６０Ｙを備えている。（以下の説明において、各色の光学センサを区別しない場合は、色符号を削除して、説明を行う。）   Further, the intermediate transfer belt 7 is opposed to the portion where the intermediate transfer belt 7 is wound around the driving roller 17 from the front surface side through a predetermined gap on the downstream side in the rotation direction of the intermediate transfer belt 7 from the secondary transfer portion. An optical sensor unit 16 provided with a plurality of optical sensors 160 as optical detection means is disposed (see FIG. 4). The optical sensor unit 16 detects a gradation pattern composed of a plurality of toner images formed on the intermediate transfer belt 7 by changing the toner density (toner adhesion amount) for image formation condition adjustment control in gradation. be able to. Specifically, as shown in FIG. 4, the optical sensor unit 16 includes an optical sensor 160Bk that detects a Bk tone pattern Sk, an optical sensor 160M that detects an M tone pattern Sm, and a C color sensor. An optical sensor 160C for detecting the gradation pattern Sc and an optical sensor 160Y for detecting the Y gradation pattern Sy are provided. (In the following description, when the optical sensors of the respective colors are not distinguished, the description will be made with the color code deleted.)

図１に示すように、トナー状態検出装置である光学的検出手段の光学センサ１６０は、反射型の光学センサであり、光学センサ１６０と中間転写ベルト７それぞれの対向面（光学センサ１６０の底面１６０ａ及び中間転写ベルト７の表面）が平行となるように、光学センサ１６０が中間転写ベルト７の表面に対向して配設されている。そして、光学センサ１６０の発光部１６１から照射され中間転写ベルト７や中間転写ベルト７上のトナー像で反射された反射光を受光部１６２で受光し検出する。ここで、中間転写ベルト７には中間転写ベルト７の一部とみなせる部材などを含む（中間転写ベルト７に反射特性の異なる部材が加工されている場合など）。また、発光部１６１にはＬＥＤなどの光源を用いることができる。   As shown in FIG. 1, the optical sensor 160 of the optical detection means that is a toner state detection device is a reflection type optical sensor, and faces each of the optical sensor 160 and the intermediate transfer belt 7 (the bottom surface 160a of the optical sensor 160). The optical sensor 160 is disposed to face the surface of the intermediate transfer belt 7 so that the surface of the intermediate transfer belt 7 and the surface of the intermediate transfer belt 7 are parallel to each other. Then, the light receiving unit 162 receives and detects the reflected light that is irradiated from the light emitting unit 161 of the optical sensor 160 and reflected by the toner image on the intermediate transfer belt 7 or the intermediate transfer belt 7. Here, the intermediate transfer belt 7 includes a member that can be regarded as a part of the intermediate transfer belt 7 (a case where a member having different reflection characteristics is processed on the intermediate transfer belt 7 or the like). The light emitting unit 161 can be a light source such as an LED.

図５に作像条件調整制御に係るブロック図を示す。
光学センサ１６０から得られたアナログ信号は、ＡＤＣ（ＡＤコンバータ）１５１でのデジタル変換処理によってデジタル化されて、トナー濃度算出手段として機能するＣＰＵ１５２によりトナー濃度をＲＯＭ１５３やＲＡＭ１５４などに記憶された情報を用いて算出などにより推定し、その推定したトナー濃度に基づいて、そのトナー濃度が所望の濃度になるように、感光体２の一様帯電電位、現像バイアス、感光体２に対する光書込強度及び現像剤のトナー濃度の制御目標値などといった作像条件を調整する作像条件調整制御を制御デバイス１５５によって行う。これにより、長期に渡って安定した画像濃度のプリントアウトを行うことが可能になる。 FIG. 5 is a block diagram relating to image forming condition adjustment control.
The analog signal obtained from the optical sensor 160 is digitized by digital conversion processing in an ADC (AD converter) 151, and the information stored in the ROM 153, the RAM 154, and the like is stored in the ROM 153, the RAM 154, and the like by the CPU 152 functioning as a toner concentration calculation unit. And based on the estimated toner density, so that the toner density becomes a desired density, the uniform charging potential of the photosensitive member 2, the developing bias, the optical writing intensity with respect to the photosensitive member 2, and The control device 155 performs image forming condition adjustment control for adjusting image forming conditions such as a toner density control target value of the developer. This makes it possible to perform a printout with a stable image density over a long period of time.

光学センサ１６０の詳細図を図６に示す。
光学センサ１６０の発光部１６１の発光中心と受光部１６２とが中間転写ベルト７の表面に対向しており、中間転写ベルト７の垂線のうち発光中心と交わる直線とその直線が中間転写ベルト７と交わる点を結んだ直線の距離をｍ１、中間転写ベルト７の垂線のうち受光部１６２の受光中心と交わる直線とその直線が中間転写ベルト７と交わる点を結んだ直線の距離をｍ２、受光部１６２の受光領域をｄ、受光領域ｄが中間転写ベルト７からの鏡面反射光を受光可能な鏡面反射角度を保持する発光中心からの照射ビーム開き角度をθ１、中間転写ベルト７の垂線のうち発光中心と交わる直線と照射ビーム開き角度θ１との成す角のうち最も狭角である角度をθ２、発光中心からの照射ビーム開き角度をθ３、中間転写ベルト７の垂線のうち発光中心と交わる直線と発光中心からの照射ビームとの成す角のうち最も狭角である角度をθ４とした場合に、数１の関係を満たす。 A detailed view of the optical sensor 160 is shown in FIG.
The light emission center of the light emitting unit 161 and the light receiving unit 162 of the optical sensor 160 are opposed to the surface of the intermediate transfer belt 7. Of the perpendicular lines of the intermediate transfer belt 7, the straight line that intersects the light emission center and the straight line are the intermediate transfer belt 7. The distance of the straight line connecting the intersecting points is m1, the straight line intersecting the light receiving center of the light receiving unit 162 among the perpendicular lines of the intermediate transfer belt 7 and the distance of the straight line connecting the points where the straight line intersects the intermediate transfer belt 7 is m2, and the light receiving unit The light receiving area 162 is d, the light receiving area d holds the specular reflection angle at which the specular reflection light from the intermediate transfer belt 7 can be received, and the irradiation beam opening angle from the light emission center is θ1, and the light emission among the perpendicular lines of the intermediate transfer belt 7 is emitted. Of the angles formed by the straight line intersecting the center and the irradiation beam opening angle θ1, the narrowest angle is θ2, the irradiation beam opening angle from the light emission center is θ3, and light is emitted from the perpendicular of the intermediate transfer belt 7. And it intersects the straight line and the angle that is most narrow angle of an angle formed between the irradiation beam from the emission center when a .theta.4, satisfy formula 1 relationship.

Figure 0005733606
Figure 0005733606

本実施例に用いた各値は、ｍ１＝１０［ｍｍ］、ｍ２＝５［ｍｍ］、θ１＝７［度］、θ２＝１４［度］であり、受光部１６２の受光領域は、ｄ＝２［ｍｍ］となっている。このとき、発光部１６１からの光束は、θ３＝１０．１［度］、θ４＝１２［度］から成る領域で、中間転写ベルト７または中間転写ベルト７上のトナー像へ照射される。   The values used in this example are m1 = 10 [mm], m2 = 5 [mm], θ1 = 7 [degree], θ2 = 14 [degree], and the light receiving area of the light receiving unit 162 is d = 2 [mm]. At this time, the light beam from the light emitting unit 161 is irradiated onto the intermediate transfer belt 7 or the toner image on the intermediate transfer belt 7 in an area where θ3 = 10.1 [degrees] and θ4 = 12 [degrees].

上記の光学センサ１６０により、中間転写ベルト７上のトナー像を検出する。
光学センサ１６０による検知方向が図６に図示した矢印方向の場合、検知側である光学センサ１６０）が図中矢印方向に移動する場合や、被検知側である中間転写ベルト７が図中矢印方向に移動する場合が考えられるが、どちらが移動しても相対的な位置関係は同等となるので、本実施形態では中間転写ベルト７が図中矢印方向に移動する場合について説明する。 The toner image on the intermediate transfer belt 7 is detected by the optical sensor 160 described above.
When the detection direction by the optical sensor 160 is the arrow direction shown in FIG. 6, the optical sensor 160 on the detection side is moved in the arrow direction in the drawing, or the intermediate transfer belt 7 on the detection side is the arrow direction in the drawing. However, in this embodiment, the case where the intermediate transfer belt 7 moves in the direction of the arrow will be described.

中間転写ベルト表面の光沢度は、光沢度計：ＪＩＳ８７４１、２０度光沢度：Ｒｓ＝１００［％］、明度は、分光光度計：Ｘ−ｒｉｔｅ、Ｌａｂ：Ｌ＝５の場合、マゼンタトナー像を担持した中間転写ベルト７が、トナー状態検出状態の検知領域を通過すると、図７（ｉ）のような出力信号が得られた。これは、主に、中間転写ベルト７からの正反射光成分（ｉｉ）とトナーからの拡散反射光成分（ｉｉｉ）の合成によるものと考えた。   When the glossiness of the surface of the intermediate transfer belt is a gloss meter: JIS8741, 20 ° glossiness: Rs = 100 [%], and the brightness is a spectrophotometer: X-rite, Lab: L = 5, a magenta toner image is obtained. When the carried intermediate transfer belt 7 passed through the detection region of the toner state detection state, an output signal as shown in FIG. 7 (i) was obtained. This was considered to be mainly due to the combination of the regular reflection light component (ii) from the intermediate transfer belt 7 and the diffuse reflection light component (iii) from the toner.

中間転写ベルト７からの正反射光成分（ｉｉ）は、トナー像が無い状態では所定の出力信号を出力するが、トナー像が光学センサ１６０の正反射光を検知する検知領域内に入ってくると、中間転写ベルト地肌部からの正反射光が減少し、光学センサ１６０の正反射光を検知する検知領域内にから出ていくと、再び、中間転写ベルト地肌部からの正反射光が上昇する。   The specularly reflected light component (ii) from the intermediate transfer belt 7 outputs a predetermined output signal in the absence of a toner image, but the toner image enters a detection area where the optical sensor 160 detects specularly reflected light. Then, the regular reflection light from the intermediate transfer belt background portion decreases, and when the optical sensor 160 comes out of the detection area for detecting the regular reflection light, the regular reflection light from the intermediate transfer belt background portion increases again. To do.

トナーからの拡散反射光成分（ｉｉｉ）は、トナー像が光学センサ１６０の拡散反射光を検知する検知領域内に入ってくると、トナーによる拡散反射光が増え、トナー像が光学センサ１６０の拡散反射光を検知する検知領域内から出て行くと、トナーによる拡散反射光が減少する。   The diffuse reflection light component (iii) from the toner increases when the toner image enters the detection area where the optical sensor 160 detects the diffuse reflection light. When the light exits from the detection area for detecting the reflected light, the diffuse reflected light by the toner decreases.

ここで、本願発明者は、図７のロとニ及びニ’とロ’の、正反射光と拡散反射光の出力変化点のタイミングの差に着目した。そして、正反射光と拡散反射光の出力変化点に差があるということから、光学センサ１６０の一つの出力から正反射光成分と拡散反射光成分とを分離して、拡散反射光を取り出すことが可能であると考えるに至った。すなわち、光学センサ１６０から出力された同一の出力値から、正反射光成分と拡散反射光成分とを完全に分離させることが可能であると見出したのである。   Here, the inventor of the present application paid attention to the difference in the timing of the output change points of the regular reflection light and the diffuse reflection light between B and D and D 'and B' in FIG. Since there is a difference between the output change points of the specular reflected light and the diffuse reflected light, the specular reflected light component and the diffuse reflected light component are separated from one output of the optical sensor 160 to extract the diffuse reflected light. Came to think that is possible. That is, it has been found that the regular reflection light component and the diffuse reflection light component can be completely separated from the same output value output from the optical sensor 160.

光学センサ１６０が有する受光部１６２で受光した反射光の出力値（検出値）を、ＣＰＵ１５２により正反射光成分と拡散反射光成分とに分離してトナー像のトナー濃度を算出することができることで、中間転写ベルト７からの正反射光を受光する正反射光受光部と、トナー像からの拡散反射光を受光する拡散反射光受光部とをそれぞれ別個で設ける必要がなく、受光部の数を減らせる分、低コスト化を図ることができる。   By allowing the CPU 152 to separate the output value (detection value) of the reflected light received by the light receiving unit 162 of the optical sensor 160 into a regular reflected light component and a diffuse reflected light component, the toner density of the toner image can be calculated. Therefore, it is not necessary to separately provide a regular reflection light receiving unit that receives regular reflection light from the intermediate transfer belt 7 and a diffuse reflection light receiving unit that receives diffuse reflection light from the toner image. The cost can be reduced as much as possible.

ここで、正反射光成分と拡散反射光成分とを分離して、拡散反射光を抽出することが可能である条件としては、光学センサ１６０の正反射光を検知する検知領域と、光学センサ１６０の拡散反射光を検知する検知領域とが完全に一致しないことが重要になる。   Here, as conditions under which the specular reflection light component and the diffuse reflection light component can be separated and the diffuse reflection light can be extracted, a detection region for detecting the specular reflection light of the optical sensor 160 and the optical sensor 160 are included. It is important that the detection area for detecting the diffuse reflection light does not completely match.

光学センサ１６０より、中間転写ベルト７やトナー像に光が照射されると、正反射光は鏡面反射角を保持する受光範囲内でしか受光できない。一方、拡散反射光は空間に拡散するので、鏡面反射角にかかわらず受光領域へ突入することが可能である。このことから、数２と数３との少なくとも一方の関係を満たすことで、光学センサ１６０から出力された同一の出力値から、正反射光成分と拡散反射光成分とを分離して拡散反射光を抽出することが可能となる。   When light is irradiated from the optical sensor 160 to the intermediate transfer belt 7 or the toner image, the specularly reflected light can be received only within the light receiving range that maintains the specular reflection angle. On the other hand, the diffuse reflected light diffuses into the space, so that it can enter the light receiving region regardless of the specular reflection angle. Therefore, by satisfying at least one of the relations of Formula 2 and Formula 3, the specular reflected light component and the diffuse reflected light component are separated from the same output value output from the optical sensor 160, and the diffuse reflected light is separated. Can be extracted.

Figure 0005733606
Figure 0005733606

Figure 0005733606
Figure 0005733606

ここで、光学センサ１６０と中間転写ベルト７とのどちらか一方が互いの対向面に対して平行方向に移動可能であり、光学センサ１６０による中間転写ベルト７の検出方向が、光学センサ１６０と中間転写ベルト７とのどちらか一方の移動方向と平行であることで、数１の関係を満たし、且つ、数２と数３との少なくとも一方の関係を満たすことを維持することができる。   Here, either one of the optical sensor 160 and the intermediate transfer belt 7 can move in a direction parallel to the opposing surfaces, and the detection direction of the intermediate transfer belt 7 by the optical sensor 160 is intermediate between the optical sensor 160 and the intermediate transfer belt 7. By being parallel to one of the moving directions with respect to the transfer belt 7, it is possible to satisfy the relationship of Equation 1 and satisfy at least one of Equation 2 and Equation 3.

本実施例の場合、図７におけるイ−ロ間の出力は、光学センサ１６０の検知領域がベルト地肌部領域であることを意味している。図７におけるロ−ニ間の出力は、光学センサ１６０の検知領域にトナー像が突入しはじめ、非トナー像領域の中間転写ベルト７からの出力と、トナー像領域からの出力（拡散反射光）が混在し、また、正反射光受光領域にはまだトナー像が突入していないことを意味している。図７におけるニ−ニ’間の出力は、光学センサ１６０の正反射光受光領域にトナー像領域が突入していることを意味している。   In this embodiment, the output between the arrows in FIG. 7 means that the detection area of the optical sensor 160 is the belt background area. In the output between the ronies in FIG. 7, the toner image starts to enter the detection area of the optical sensor 160, the output from the intermediate transfer belt 7 in the non-toner image area, and the output from the toner image area (diffuse reflected light). Means that the toner image has not yet entered the regular reflection light receiving area. 7 indicates that the toner image area has entered the specularly reflected light receiving area of the optical sensor 160. In FIG.

したがって、ロ−ニ間の出力やニ’−ロ’間の出力の変化量が、トナーによる拡散反射光成分のみの出力の変化量と言え、この領域の情報を用いることで、トナー濃度を推定することができる。   Therefore, the output change between the lonely and the output between the two '--ro' can be said to be the change in the output of only the diffuse reflected light component by the toner, and the toner density is estimated by using the information in this region. can do.

ここで、黒色のトナーは光の大部分を吸収してしまう特性から、拡散光はほとんど得られない。すなわち、黒色のトナーは拡散反射光がほとんどないため正反射光が支配的になり、図７におけるロ−ニ間やニ’−ロ’間の領域での拡散反射光成分の出力がほとんどない。   Here, since the black toner absorbs most of the light, hardly any diffused light can be obtained. That is, since the black toner has almost no diffuse reflection light, the specular reflection light is dominant, and there is almost no output of the diffuse reflection light component in the region between the ronies and between the two '-ro' in FIG.

そこで、黒色のトナー像の場合には、ニ−ニ’間の領域の情報、言い換えれば、光学センサ出力の最小値を用いる。黒色のトナー像の場合には、検出時のノイズとなる拡散反射光がほとんどないことから、拡散反射光が入ってもよい構成をとることができる。すなわち、上述の光学センサ１６０で何ら問題はなく、逆に、従来のように拡散反射光を排除するような複雑な光学センサ１６０の構成（光路を絞ったり、アパーチャー形状を工夫したり）をとることで生じていた課題が解消されることになるため、黒色のトナー像の検知としても効果は大きい。   Therefore, in the case of a black toner image, information on the area between the knees, in other words, the minimum value of the optical sensor output is used. In the case of a black toner image, since there is almost no diffuse reflection light that becomes noise at the time of detection, a configuration in which diffuse reflection light may enter can be adopted. That is, there is no problem with the above-described optical sensor 160, and conversely, a complicated configuration of the optical sensor 160 that eliminates diffuse reflected light (throttle the optical path or devise the aperture shape) as in the prior art. This eliminates the problems that have arisen, and therefore has a great effect even when detecting a black toner image.

黒色とは異なる色のトナー像のトナー濃度推定方法としては、以下を考案した。
画像形成装置における光学センサ１６０の出力は、予め校正しておく必要がある。例えば、トナーがない地肌部やトナーや中間転写ベルト７とは別の基準体を光学センサ１６０で検知した際に、所定の出力となるようにしておく。ここで、光学センサ１６０の制御フローを図８に示す。光学センサ１６０による検知を行う際に光源であるＬＥＤをＯＮにし（Ｓ１）、ＬＥＤの出力が安定するＬＥＤ安定時間を待った後に（Ｓ２）、センサ出力を読み取り（Ｓ３）、その後、ＬＥＤをＯＦＦにして検知を終了する（Ｓ４）。 The following was devised as a method for estimating the toner density of a toner image having a color different from black.
The output of the optical sensor 160 in the image forming apparatus needs to be calibrated in advance. For example, when the optical sensor 160 detects a background portion where there is no toner or a reference body other than the toner or the intermediate transfer belt 7, a predetermined output is set. Here, the control flow of the optical sensor 160 is shown in FIG. When the detection by the optical sensor 160 is performed, the LED as the light source is turned on (S1), and after waiting for the LED stabilization time for the LED output to stabilize (S2), the sensor output is read (S3), and then the LED is turned off. Then, the detection ends (S4).

画像形成装置において、ＣＰＵ１５２でトナー濃度を推定するモードが実行されると、所定のタイミングより、光学センサ１６０によって中間転写ベルト表面やその表面に形成されたトナー像の検出を始める。   In the image forming apparatus, when the CPU 152 executes a mode for estimating the toner density, the optical sensor 160 starts detecting the surface of the intermediate transfer belt and the toner image formed on the surface at a predetermined timing.

画像形成装置は、少なくとも１色以上で１つ以上のトナー像を中間転写ベルト７上に作成する。作成されるトナー像としては、ベタパターンやラインパターンやディザパターンなど目的に応じて適正に設定するのが望ましい。   The image forming apparatus creates one or more toner images of at least one color on the intermediate transfer belt 7. It is desirable that the created toner image is appropriately set according to the purpose, such as a solid pattern, a line pattern, or a dither pattern.

作像された中間転写ベルト７上のトナー像が光学センサ１６０の検知領域内を順次通過する。トナー像の通過タイミングにあわせて、光学センサ１６０の出力値取得トリガ、サンプリング時間、サンプリング間隔、サンプリング数、が規定されている。取得した光学センサ１６０の出力をＶｐ（ｎ）；ｎ＝１，２，３・・・ｍ、（ｍは所定のサンプリング数）とする。   The formed toner image on the intermediate transfer belt 7 sequentially passes through the detection area of the optical sensor 160. The output value acquisition trigger, the sampling time, the sampling interval, and the sampling number of the optical sensor 160 are defined in accordance with the toner image passage timing. Let the acquired output of the optical sensor 160 be Vp (n); n = 1, 2, 3... M, where m is a predetermined sampling number.

光学センサ１６０が検出したＶｐ（ｎ）のうち出力が最大値となる値をＶｍａｘとする（図９参照）。そして、光学センサ１６０の出力値Ｖｍａｘあるいは出力値Ｖｍａｘを用いた算出値と、ＲＯＭ１５３が有している予め作成しておいたトナー濃度変換表とを参照して、トナー付着量を推定する。なお、光学センサ１６０の出力値Ｖｍａｘあるいは出力値Ｖｍａｘを用いた算出値をトナー濃度に変換する際に変換表ではなく変換式を用いても良い。   Of Vp (n) detected by the optical sensor 160, a value at which the output becomes the maximum value is defined as Vmax (see FIG. 9). Then, the toner adhesion amount is estimated with reference to the output value Vmax of the optical sensor 160 or a calculated value using the output value Vmax and a toner density conversion table prepared in advance in the ROM 153. Note that when converting the output value Vmax of the optical sensor 160 or the calculated value using the output value Vmax into the toner density, a conversion formula may be used instead of the conversion table.

ここで、１つのトナー像において光学センサ１６０の出力値Ｖｍａｘが複数得られる場合（光学センサ１６０によるトナー像の検知領域突入時や脱出時）は、例えば、それぞれをＶｍａｘ１、Ｖｍａｘ２とすると、トナー付着量変換表を作成する際に、Ｖｍａｘ１もしくはＶｍａｘ２もしくはＶｍａｘ１とＶｍａｘ２とを用いて算出される値（Ｖｍａｘ１とＶｍａｘ２の平均値など）のうち、トナー付着量と相関のよい値を採用するのが望ましい。   Here, when a plurality of output values Vmax of the optical sensor 160 are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that Vmax1 and Vmax2 respectively, toner adhesion When creating the amount conversion table, it is desirable to use a value having a good correlation with the toner adhesion amount among values calculated using Vmax1 or Vmax2 or Vmax1 and Vmax2 (such as an average value of Vmax1 and Vmax2). .

黒色とは異なる色のトナー像のトナー濃度推定方法の他例を説明する。
まず、中間転写ベルト地肌部の出力Ｖｓｇを検出するが、前述したように取得したＶｐ（ｎ）；ｎ＝１，２，３・・・ｍのうち、適正な値を使用する。この際、予め定めたＶｐ（ｎ）（光学センサ１６０により検出された中間転写ベルト地肌部に該当する位置の少なくとも１つ以上の所定の範囲のｎ）の平均値などで、中間転写ベルト地肌部の出力Ｖｓｇを算出するのが望ましい。 Another example of a toner density estimation method for a toner image having a color different from black will be described.
First, the output Vsg of the intermediate transfer belt background portion is detected, and an appropriate value is used among Vp (n); n = 1, 2, 3,. At this time, the intermediate transfer belt background portion is determined by an average value of a predetermined Vp (n) (n in a predetermined range of at least one position corresponding to the intermediate transfer belt background portion detected by the optical sensor 160). It is desirable to calculate the output Vsg.

Ｖｓｇ≦Ｖｐ（ｎ）の範囲において、数４に示すようにＶｓｇとＶｐ（ｎ）の差分を累積したものをＶｓとする。これにより、トナー像からの拡散反射光成分のみの出力情報を得ることができる。   In the range of Vsg ≦ Vp (n), Vs is obtained by accumulating the difference between Vsg and Vp (n) as shown in Equation 4. Thereby, output information of only the diffuse reflection light component from the toner image can be obtained.

Figure 0005733606
Figure 0005733606

すなわち、本構成例では、黒色とは異なる色のトナー像の濃度を算出する場合に、光学センサ１６０による予め設定された複数の検出タイミングそれぞれに対して、中間転写ベルトからの正反射光及びトナー像からの拡散反射光を受光した際の検出値から、中間転写ベルトからの正反射光を受光した際の検出値を差し引いた差分値を算出し、前記差分値を累積した累積値であるＶｓを用いる。これにより、トナー像からの拡散反射光成分のみの出力情報が得られるので、その情報から黒色とは異なる色のトナー像のトナー濃度（トナー付着量）算出が可能となる。   In other words, in this configuration example, when the density of a toner image having a color different from black is calculated, the specularly reflected light and toner from the intermediate transfer belt are respectively detected for a plurality of preset detection timings by the optical sensor 160. A difference value obtained by subtracting the detection value when the regular reflection light from the intermediate transfer belt is received from the detection value when the diffuse reflection light from the image is received is calculated, and Vs is a cumulative value obtained by accumulating the difference values. Is used. As a result, output information of only the diffuse reflection light component from the toner image can be obtained, so that it is possible to calculate the toner density (toner adhesion amount) of the toner image of a color different from black from the information.

そして、光学センサ１６０の出力値から算出されるＶｓと、ＲＯＭ１５３が有している予め作成しておいたトナー濃度変換表とを参照して、ＣＰＵ１５２がトナー濃度を推定する。なお、Ｖｓをトナー濃度に変換する際に変換表ではなく変換式を用いても良い。   The CPU 152 estimates the toner density with reference to Vs calculated from the output value of the optical sensor 160 and the toner density conversion table prepared in advance in the ROM 153. Note that a conversion formula may be used instead of a conversion table when converting Vs into toner density.

ここで、１つのトナー像において、Ｖｓが複数得られる場合（光学センサ１６０によるトナー像の検知領域突入時や脱出時）は、例えば、それぞれをＶｓ１、Ｖｓ２とすると、トナー濃度変換表を作成する際に、Ｖｓ１もしくはＶｓ２もしくはＶｓ１とＶｓ２を用いて算出される値（Ｖｓ１とＶｓ２の平均値や合計値など）のうち、トナー濃度と相関のよい値を採用するのが望ましい。   Here, when a plurality of Vs are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that Vs1 and Vs2 respectively, a toner density conversion table is created. At this time, it is desirable to employ a value having a good correlation with the toner density among the values calculated using Vs1, Vs2, or Vs1 and Vs2 (average value or total value of Vs1 and Vs2, etc.).

さらに、黒色とは異なる色のトナー像のトナー濃度推定方法の他例を説明する。
まず、中間転写ベルト地肌部の出力Ｖｓｇを検出するが、前述したように取得したＶｐ（ｎ）のうち、適正な値を使用する。この際、予め定めたＶｐ（ｎ）（地肌部に該当する少なくとも１つ以上の所定の範囲のｎ）の平均値などでＶｓｇを算出するのが望ましい。 Furthermore, another example of a toner density estimation method for a toner image having a color different from black will be described.
First, the output Vsg of the intermediate transfer belt background portion is detected, but an appropriate value is used among Vp (n) acquired as described above. At this time, it is desirable to calculate Vsg based on an average value of Vp (n) (at least one predetermined range of n corresponding to the background portion).

そして、最初にＶｐ（ｎ）＞Ｖｓｇとなった点をｔ１とし、Ｖｐが減少に転じた点をｔ２とすると、ＣＰＵ１５２により数５を用いてｔ２とｔ１との差分からΔｔ１を算出する。これにより、ＣＰＵ１５２によって光学センサ１６０がトナー像からの拡散反射光を受光している時間の一部を推定することができる。   Then, assuming that the point where Vp (n)> Vsg is first reached is t1, and the point where Vp starts to decrease is t2, the CPU 152 calculates Δt1 from the difference between t2 and t1 using Equation 5. Accordingly, the CPU 152 can estimate a part of the time during which the optical sensor 160 receives diffusely reflected light from the toner image.

Figure 0005733606
Figure 0005733606

そして、光学センサ１６０がトナー像からの拡散反射光を受光している時間の一部であるΔｔ１の範囲において、数６に示すようにＶｓｇとＶｐ（ｎ）の差分を累積したものをＶｓとする。これにより、トナー像からの拡散反射光成分のみの出力情報を得ることができる。   Then, in the range of Δt1, which is a part of the time during which the optical sensor 160 receives diffusely reflected light from the toner image, Vs is obtained by accumulating the difference between Vsg and Vp (n) as shown in Equation 6. To do. Thereby, output information of only the diffuse reflection light component from the toner image can be obtained.

Figure 0005733606
Figure 0005733606

そして、光学センサ１６０の出力値から算出されるＶｓと、ＲＯＭ１５３が有している予め作成しておいたトナー濃度変換表とを参照して、ＣＰＵ１５２がトナー濃度を算出して推定する。なお、Ｖｓをトナー濃度に変換する際に変換表ではなく変換式を用いても良い。   Then, the CPU 152 calculates and estimates the toner density with reference to Vs calculated from the output value of the optical sensor 160 and the toner density conversion table prepared in advance in the ROM 153. Note that a conversion formula may be used instead of a conversion table when converting Vs into toner density.

ここで、１つのトナー像において、Ｖｓが複数得られる場合（光学センサ１６０によるトナー像の検知領域突入時や脱出時）は、例えば、それぞれをＶｓ１やＶｓ２とすると、トナー濃度変換テーブルを作成する際に、Ｖｓ１もしくはＶｓ２もしくはＶｓ１とＶｓ２との両方を用いて算出される算出値（Ｖｓ１とＶｓ２の平均値や合計値など）のうち、トナー濃度と相関のよい値を採用するのが望ましい。   Here, when a plurality of Vs are obtained in one toner image (when the detection area of the toner image enters or exits by the optical sensor 160), for example, assuming that each is Vs1 or Vs2, a toner density conversion table is created. At this time, it is desirable to employ a value having a good correlation with the toner density among calculated values (average value or total value of Vs1 and Vs2) calculated using Vs1, Vs2, or both Vs1 and Vs2.

これらの方式で、黒色とは異なる色のトナー像のトナー濃度を算出し、黒色のトナー像はＶｓｐ＿ｍｉｎからトナー濃度を算出することで、単一のセンサで且つロバスト性の高いトナー濃度検知が可能となる。   With these methods, the toner density of a toner image of a color different from black is calculated, and the toner density of a black toner image is calculated from Vsp_min, so that it is possible to detect toner density with high robustness with a single sensor. It becomes.

図１０にトナー濃度算出制御に係るフローチャートの一例を示す。
まず、光学センサ１６０によって中間転写ベルト表面やその表面に予め形成された作像条件調整制御用のトナー像を検出する（Ｓ１）。次に、光学センサ出力から中間転写ベルト地肌部の出力をＣＰＵ１５２によって算出する（Ｓ２）。そして、光学センサ１６０によって検出されたトナー像が黒トナーを用いたものであった場合には（Ｓ３でＹＥＳ）、算出した中間転写ベルト地肌部の出力値を基準値として光学センサ出力の最小値をＣＰＵ１５２で算出し（Ｓ４）、前記最小値とＲＯＭ１５３が有しているトナー濃度変換表とを参照して、ＣＰＵ１５２が黒色のトナー像のトナー濃度を算出して推定し、トナー濃度を算出する一連の制御を終了する。一方、光学センサ１６０によって検出されたトナー像が黒色とは異なるトナーを用いたものであった場合には（Ｓ３でＮＯ）、算出した中間転写ベルト地肌部の出力値を基準値として光学センサ出力の最大値をＣＰＵ１５２で算出し（Ｓ６）、前記最大値とＲＯＭ１５３が有しているトナー濃度変換表とを参照して、ＣＰＵ１５２が黒色とは異なる色のトナー像のトナー濃度を算出して推定し、トナー濃度を算出する一連の制御を終了する。 FIG. 10 shows an example of a flowchart relating to toner density calculation control.
First, the surface of the intermediate transfer belt and a toner image for image forming condition adjustment control previously formed on the surface are detected by the optical sensor 160 (S1). Next, the CPU 152 calculates the output of the intermediate transfer belt background from the optical sensor output (S2). If the toner image detected by the optical sensor 160 uses black toner (YES in S3), the minimum value of the optical sensor output with the calculated output value of the intermediate transfer belt background as a reference value. Is calculated by the CPU 152 (S4), the CPU 152 calculates and estimates the toner density of the black toner image by referring to the minimum value and the toner density conversion table of the ROM 153, and calculates the toner density. A series of control ends. On the other hand, if the toner image detected by the optical sensor 160 uses a toner different from black (NO in S3), the calculated output value of the intermediate transfer belt background is used as a reference value to output the optical sensor. Is calculated by the CPU 152 (S6), and the CPU 152 calculates and estimates the toner density of the toner image having a color different from black by referring to the maximum value and the toner density conversion table of the ROM 153. Then, a series of control for calculating the toner density is completed.

そして、このように推定したトナー濃度に基づいて、そのトナー濃度が所望の濃度になるように、感光体２の一様帯電電位、現像バイアス、感光体２に対する光書込強度及び現像剤のトナー濃度の制御目標値などといった作像条件を調整する作像条件調整制御を制御デバイス１５５によって行うことで、長期に渡って安定した画像濃度のプリントアウトを行うことが可能になる。   Then, based on the toner density estimated in this way, the uniform charging potential of the photosensitive member 2, the developing bias, the optical writing intensity with respect to the photosensitive member 2, and the developer toner so that the toner concentration becomes a desired density. By performing the image forming condition adjustment control for adjusting the image forming condition such as the density control target value by the control device 155, it is possible to print out the image density stably for a long period of time.

以上、本実施形態によれば、画像形成装置において、表面にトナー像を担持する像担持体である中間転写ベルト７と、中間転写ベルト７の表面にトナー像を形成する画像形成ユニット１や一次転写ローラ５などからなるトナー像形成手段と、中間転写ベルト７の表面や前記表面に担持したトナー像に光を照射する発光手段である発光部１６１と発光部１６１から照射され前記表面やトナー像で反射した反射光を受光する受光手段である受光部１６２とを有する光学的検出手段である光学センサ１６０と、光学センサ１６０の検出値を、中間転写ベルト７から正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いてトナー像のトナー濃度を算出するトナー濃度算出手段であるＣＰＵ１５２と、ＣＰＵ１５２が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御をトナー像形成手段に行う制御手段である制御デバイスとを備える。これにより、光学センサ１６０に正反射光受光素子と拡散反射光受光素子とをそれぞれ別個の受光素子で設けることなく、正反射光成分の出力と拡散反射光成分の出力とを得ることができるので、低コスト化を図ることができる。
また、中間転写ベルト７の垂線のうち発光中心と交わる直線とその直線が中間転写ベルト７と交わる点を結んだ直線の距離をｍ１、中間転写ベルト７の垂線のうち受光中心と交わる直線とその直線が中間転写ベルト７と交わる点を結んだ直線の距離をｍ２、受光部１６２の受光領域をｄ、受光領域ｄが中間転写ベルト７からの鏡面反射光を受光可能な鏡面反射角度を保持する発光中心からの照射ビーム開き角度をθ１、中間転写ベルト７の垂線のうち発光中心と交わる直線と照射ビーム開き角度θ１との成す角のうち最も狭角である角度をθ２、発光中心からの照射ビーム開き角度をθ３、中間転写ベルト７の垂線のうち発光中心と交わる直線と発光中心からの照射ビームとの成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たすことで、光学センサ１６０の正反射光を検知する検知領域と、光学センサ１６０の拡散反射光を検知する検知領域とが完全に一致しないようにすることができる。よって、光学センサ１６０から出力された同一の出力値から、正反射光成分と拡散反射光成分とを分離することができる。
また、本実施形態によれば、光学センサ１６０と中間転写ベルト７とのどちらか一方が互いの対向面に対して平行方向に移動可能であり、光学センサ１６０による中間転写ベルト７の検出方向が、光学センサ１６０と中間転写ベルト７とのどちらか一方の移動方向と平行であることで、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たすことを維持することができる。
また、本実施形態によれば、ＣＰＵ１５２は、黒色のトナー像の濃度を算出する場合に少なくとも光学的検出手段によるトナー像からの正反射光の検出値を用い、黒色とは異なる色のトナー像の濃度を算出する場合に少なくとも光学検出手段によるトナー像からの拡散光の検出値を用いて、トナー濃度を算出することで、黒色とは異なる色のトナー像においては正反射光出力を含まない情報を用いるので、トナー濃度変動以外に起因する情報変動を低減させることができる。また、正反射光出力を拡散反射光のほとんどない黒色のトナー像にしか使用しないので、拡散反射光が入っても構わない、言い換えれば、ロバスト性のある正反射光学系を用いることができる。
また、本実施形態によれば、ＣＰＵ１５２は、黒色のトナー像の濃度を算出する場合に少なくとも光学検出手段による中間転写ベルト７からの正反射光の出力値を用い、黒色とは異なる色のトナー像の濃度を算出する場合に光学検知検出手段による検出値の最大値を用いてトナー濃度を算出する。受光光量が最大になったという情報は、トナー像が拡散光検知領域から正反射光検知領域へ入ったことがわかるので、拡散反射光検知領域のみの出力情報を用いることで、黒色とは異なる色のトナー像のトナー濃度算出が可能となる。
また、本実施形態によれば、ＣＰＵ１５２は、黒色のトナー像の濃度を算出する場合に少なくとも光学検出手段による中間転写ベルト７からの正反射光の出力値を用い、黒色とは異なる色のトナー像の濃度を算出する場合には、光学センサ１６０による予め設定された複数の検出タイミングそれぞれに対して、中間転写ベルト７からの正反射光及びトナー像からの拡散反射光を受光した際の検出値から、中間転写ベルト７からの正反射光を受光した際の検出値とを差し引いた差分値を算出し、前記差分値を累積した累積値を用いる。これにより、黒色とは異なる色のトナー像の濃度を算出する場合に、トナー像からの拡散反射光成分のみの出力情報が得られるので、その情報から黒色とは異なる色のトナー像のトナー濃度算出が可能となる。また、光学センサ１６０がトナー像からの拡散反射光を受光している時間を推定する推定手段でもあるＣＰＵ１５２の推定結果をも用いて、黒色とは異なる色のトナー像の濃度を算出するようにしても良い。 As described above, according to the present embodiment, in the image forming apparatus, the intermediate transfer belt 7 that is an image carrier that carries a toner image on the surface, the image forming unit 1 that forms a toner image on the surface of the intermediate transfer belt 7, and the primary A toner image forming unit comprising a transfer roller 5 and the like, a light emitting unit 161 which is a light emitting unit for irradiating light on the surface of the intermediate transfer belt 7 and a toner image carried on the surface, and the surface and toner image irradiated from the light emitting unit 161. An optical sensor 160 that is an optical detection unit having a light receiving unit 162 that receives the reflected light reflected by the optical sensor 160, and a detection value of the optical sensor 160 is obtained from a regular reflection light component and a toner image from the intermediate transfer belt 7. A CPU 152 which is a toner concentration calculation unit that calculates a toner concentration of a toner image using the specular reflection light component and the diffuse reflection light component. CPU152 and a control device which is a control unit for performing the toner image forming means control for adjusting the toner image forming conditions so that the desired toner density on the basis of the toner concentration calculation value calculated. As a result, the specular reflection light receiving element and the diffuse reflection light receiving element are not provided as separate light receiving elements in the optical sensor 160, so that the output of the specular reflection light component and the output of the diffuse reflection light component can be obtained. Cost reduction can be achieved.
Further, the distance straight line and the straight line intersecting the luminescent center of the straight line connecting the point of intersection between the intermediate transfer belt 7 of the normal of the medium between the transfer belt 7 m1, a straight line intersecting the light receiving center of the perpendicular of the intermediate transfer belt 7 The distance of the straight line connecting the points where the straight line intersects the intermediate transfer belt 7 is m2, the light receiving area of the light receiving unit 162 is d, and the light receiving area d maintains the specular reflection angle at which the specular reflected light from the intermediate transfer belt 7 can be received. The irradiation beam opening angle from the emission center to be emitted is θ1, the angle of the narrowest angle among the angles formed by the straight line intersecting the emission center of the perpendicular lines of the intermediate transfer belt 7 and the irradiation beam opening angle θ1 is θ2, and from the emission center When the opening angle of the irradiation beam is θ3 and the angle that is the narrowest of the angles formed by the straight line intersecting the emission center of the perpendicular line of the intermediate transfer belt 7 and the irradiation beam from the emission center is θ4, d = (m1 + m2) × {tan (θ1 + θ2) −tanθ2} is satisfied, and at least one of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2) is satisfied, so that the specularly reflected light of the optical sensor 160 is detected. The detection area and the detection area for detecting the diffusely reflected light of the optical sensor 160 can be prevented from being completely coincident with each other. Therefore, the regular reflection light component and the diffuse reflection light component can be separated from the same output value output from the optical sensor 160.
Further, according to the present embodiment, one of the optical sensor 160 and the intermediate transfer belt 7 can move in a direction parallel to the opposing surfaces, and the detection direction of the intermediate transfer belt 7 by the optical sensor 160 is determined. Since the optical sensor 160 and the intermediate transfer belt 7 are parallel to one of the moving directions, the relationship d = (m1 + m2) × {tan (θ1 + θ2) −tanθ2} is satisfied, and θ4 <θ2 ( It is possible to maintain that at least one of the relations θ3 + θ4)> (θ1 + θ2) is satisfied.
Further, according to the present embodiment, the CPU 152 uses at least the detection value of the regular reflection light from the toner image by the optical detection unit when calculating the density of the black toner image, and the toner image having a color different from black. When calculating the density of the toner, the toner density is calculated using at least the detection value of the diffused light from the toner image by the optical detection means, so that the toner image of a color different from black does not include the regular reflection light output. Since information is used, it is possible to reduce information fluctuation caused by other than toner density fluctuation. Further, since the regular reflection light output is used only for the black toner image having almost no diffuse reflection light, diffuse reflection light may be entered, in other words, a robust regular reflection optical system can be used.
Further, according to the present embodiment, the CPU 152 uses at least the output value of the regular reflection light from the intermediate transfer belt 7 by the optical detection unit when calculating the density of the black toner image, and uses a toner having a color different from black. When calculating the density of the image, the toner density is calculated using the maximum value detected by the optical detection and detection means. The information that the amount of received light is maximized is different from black because the toner image has entered the specular reflection light detection area from the diffuse light detection area, and the output information of only the diffuse reflection detection area is used. The toner density of the color toner image can be calculated.
Further, according to the present embodiment, the CPU 152 uses at least the output value of the regular reflection light from the intermediate transfer belt 7 by the optical detection unit when calculating the density of the black toner image, and uses a toner having a color different from black. When calculating the density of the image, detection is performed when regular reflection light from the intermediate transfer belt 7 and diffuse reflection light from the toner image are received at each of a plurality of preset detection timings by the optical sensor 160. A difference value obtained by subtracting the detected value when the regular reflection light from the intermediate transfer belt 7 is received is calculated from the value, and the accumulated value obtained by accumulating the difference value is used. As a result, when calculating the density of a toner image of a color different from black, output information of only the diffuse reflected light component from the toner image can be obtained. From this information, the toner density of the toner image of a color different from black is obtained. Calculation is possible. Also, the density of the toner image having a color different from black is calculated using the estimation result of the CPU 152 which is also an estimation means for estimating the time during which the optical sensor 160 receives diffusely reflected light from the toner image. May be.

１ 画像形成ユニット
２ 感光体
３ 帯電ローラ
４ 現像装置
５ 一次転写ローラ
６ クリーニング装置
７ 中間転写ベルト
８ 駆動ローラ
９ 支持ローラ
１０ａ テンションローラ
１０ｂ テンションローラ
１１ バックアップローラ
１２ ベルトクリーニング装置
１２ａ クリーニングブレード
１３ レジストローラ
１４ 二次転写ローラ
１５ 定着装置
１５ａ 定着ローラ
１５ｂ 加圧ローラ
１６ 光学センサユニット
１７ 駆動ローラ
１８ 排紙部
２０ レーザー露光装置
２１ 給紙カセット
２７ 給紙ローラ
３７ トナーボトル
４１ 現像スリーブ
４２ 撹拌・搬送部材
４３ 補給部
４４ トナー濃度センサ
６１ クリーニングブレード
１００ プリンタ
１５１ ＡＤＣ
１５２ ＣＰＵ
１５３ ＲＯＭ
１５４ ＲＡＭ
１５５ 制御デバイス
１６０ 光学センサ
１６０ａ 底面
１６１ 発光部
１６２ 受光部 DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photoconductor 3 Charging roller 4 Developing device 5 Primary transfer roller 6 Cleaning device 7 Intermediate transfer belt 8 Drive roller 9 Support roller 10a Tension roller 10b Tension roller 11 Backup roller 12 Belt cleaning device 12a Cleaning blade 13 Registration roller 14 Secondary transfer roller 15 Fixing device 15a Fixing roller 15b Pressure roller 16 Optical sensor unit 17 Drive roller 18 Paper discharge unit 20 Laser exposure device 21 Paper feed cassette 27 Paper feed roller 37 Toner bottle 41 Developing sleeve 42 Stirring / conveying member 43 Replenishment Unit 44 Toner concentration sensor 61 Cleaning blade 100 Printer 151 ADC
152 CPU
153 ROM
154 RAM
155 Control device 160 Optical sensor 160a Bottom surface 161 Light emitting unit 162 Light receiving unit

特開平３−２０９２８１号公報JP-A-3-209281

Claims (5)

表面にトナー像を担持する像担持体と、
前記像担持体の表面にトナー像を形成するトナー像形成手段と、
該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、
前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、
前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、
前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、
前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学的検出手段による前記像担持体からの正反射光の検出値を用い、黒色とは異なる色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段によるトナー像からの拡散光の検出値を用いて、トナー濃度を算出することを特徴とする画像形成装置。 An image carrier that carries a toner image on the surface;
Toner image forming means for forming a toner image on the surface of the image carrier;
Optical detection having light emitting means for irradiating light on the surface of the image carrier or a toner image carried on the surface, and light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image Means,
The detection value of the optical detection means is separated into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner image is obtained using the specularly reflected light component and the diffusely reflected light component. Toner concentration calculating means for calculating the toner concentration of
Control means for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculation value calculated by the toner density calculating means;
The distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the light receiving center of the light receiving means is the vertical line of the image carrier. The distance between the straight line intersecting the line and the point where the straight line intersects the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d can receive the specularly reflected light from the image carrier. The irradiation light opening angle from the light emission center that holds the specular reflection angle is θ1, and is the narrowest angle among the angles formed by the irradiation light opening angle θ1 and the straight line that intersects the light emission center among the perpendicular lines of the image carrier. The angle is θ2, the irradiation light opening angle from the light emission center is θ3, and the angle that is the narrowest angle among the angles formed by the straight line intersecting the light emission center and the irradiation light from the light emission center among the perpendicular lines of the image carrier Where d = (m1 + M @ 2) satisfy the relationship × {tan (θ1 + θ2) -tanθ2}, and, to meet at least one of the relationship .theta.4 between <.theta.2 and (θ3 + θ4)> (θ1 + θ2),
When calculating the density of the black toner image, the toner density calculation means uses at least the detection value of the regular reflection light from the image carrier by the optical detection means, and the density of the toner image having a color different from black When calculating the toner density, the toner density is calculated using at least the detection value of the diffused light from the toner image by the optical detection means . 表面にトナー像を担持する像担持体と、An image carrier that carries a toner image on the surface;
前記像担持体の表面にトナー像を形成するトナー像形成手段と、Toner image forming means for forming a toner image on the surface of the image carrier;
該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、Optical detection having light emitting means for irradiating light on the surface of the image carrier or a toner image carried on the surface, and light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image Means,
前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、The detection value of the optical detection means is separated into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner image is obtained using the specularly reflected light component and the diffusely reflected light component. Toner concentration calculating means for calculating the toner concentration of
前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、Control means for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculation value calculated by the toner density calculating means;
前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、The distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the light receiving center of the light receiving means is the vertical line of the image carrier. The distance between the straight line intersecting the line and the point where the straight line intersects the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d can receive the specularly reflected light from the image carrier. The irradiation light opening angle from the light emission center that holds the specular reflection angle is θ1, and is the narrowest angle among the angles formed by the irradiation light opening angle θ1 and the straight line that intersects the light emission center among the perpendicular lines of the image carrier. The angle is θ2, the irradiation light opening angle from the light emission center is θ3, and the angle that is the narrowest angle among the angles formed by the straight line intersecting the light emission center and the irradiation light from the light emission center among the perpendicular lines of the image carrier Where d = (m1 + M2) × {tan (θ1 + θ2) −tanθ2} and satisfy at least one of the relationship of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2),
前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段による前記像担持体からの正反射光の出力値を用い、The toner density calculation means uses at least the output value of the regular reflection light from the image carrier by the optical detection means when calculating the density of the black toner image,
黒色とは異なる色のトナー像の濃度を算出する場合に前記光学検知検出手段による検出値の最大値を用いてトナー濃度を算出することを特徴とする画像形成装置。An image forming apparatus, wherein when calculating the density of a toner image having a color different from black, the toner density is calculated using a maximum value detected by the optical detection detection means. 表面にトナー像を担持する像担持体と、An image carrier that carries a toner image on the surface;
前記像担持体の表面にトナー像を形成するトナー像形成手段と、Toner image forming means for forming a toner image on the surface of the image carrier;
該像担持体の表面や該表面に担持したトナー像に光を照射する発光手段と該発光手段から照射され該表面や該トナー像で反射した反射光を受光する受光手段とを有する光学的検出手段と、Optical detection having light emitting means for irradiating light on the surface of the image carrier or a toner image carried on the surface, and light receiving means for receiving reflected light irradiated from the light emitting means and reflected by the surface or the toner image Means,
前記光学的検出手段の検出値を、像担持体からの正反射光成分とトナー像からの拡散反射光成分とに分離し、前記正反射光成分や前記拡散反射光成分を用いて前記トナー像のトナー濃度を算出するトナー濃度算出手段と、The detection value of the optical detection means is separated into a specularly reflected light component from the image carrier and a diffusely reflected light component from the toner image, and the toner image is obtained using the specularly reflected light component and the diffusely reflected light component. Toner concentration calculating means for calculating the toner concentration of
前記トナー濃度算出手段が算出したトナー濃度算出値に基づいて所望のトナー濃度となるようにトナー像形成条件を調整する制御を前記トナー像形成手段に行う制御手段とを備え、Control means for controlling the toner image forming means to adjust a toner image forming condition so as to obtain a desired toner density based on the toner density calculation value calculated by the toner density calculating means;
前記像担持体の垂線のうち前記発光手段の発光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ１、前記像担持体の垂線のうち受光手段の受光中心と交わる直線とその直線が前記像担持体と交わる点を結んだ直線の距離をｍ２、前記受光手段の受光領域をｄ、前記受光領域ｄが前記像担持体からの鏡面反射光を受光可能な鏡面反射角度を保持する前記発光中心からの照射光開き角度をθ１、前記像担持体の垂線のうち前記発光中心と交わる直線と前記照射光開き角度θ１との成す角のうち最も狭角である角度をθ２、前記発光中心からの照射光開き角度をθ３、前記像担持体の垂線のうち前記発光中心と交わる直線と前記発光中心からの照射光との成す角のうち最も狭角である角度をθ４とした場合に、ｄ＝（ｍ１＋ｍ２）×｛ｔａｎ（θ１＋θ２）−ｔａｎθ２｝の関係を満たし、且つ、θ４＜θ２と（θ３＋θ４）＞（θ１＋θ２）との少なくとも一方の関係を満たし、The distance between the straight line that intersects the light emission center of the light emitting means and the straight line that intersects the point where the straight line intersects the image carrier is m1, and the light receiving center of the light receiving means is the vertical line of the image carrier. The distance between the straight line intersecting the line and the point where the straight line intersects the image carrier is m2, the light receiving area of the light receiving means is d, and the light receiving area d can receive the specularly reflected light from the image carrier. The irradiation light opening angle from the light emission center that holds the specular reflection angle is θ1, and is the narrowest angle among the angles formed by the irradiation light opening angle θ1 and the straight line that intersects the light emission center among the perpendicular lines of the image carrier. The angle is θ2, the irradiation light opening angle from the light emission center is θ3, and the angle that is the narrowest angle among the angles formed by the straight line intersecting the light emission center and the irradiation light from the light emission center among the perpendicular lines of the image carrier Where d = (m1 + M2) × {tan (θ1 + θ2) −tanθ2} and satisfy at least one of the relationship of θ4 <θ2 and (θ3 + θ4)> (θ1 + θ2),
前記トナー濃度算出手段は、黒色のトナー像の濃度を算出する場合に少なくとも前記光学検出手段による前記像担持体からの正反射光の出力値を用い、The toner density calculation means uses at least the output value of the regular reflection light from the image carrier by the optical detection means when calculating the density of the black toner image,
黒色とは異なる色のトナー像の濃度を算出する場合には、前記光学的検知手段による予め設定された複数の検出タイミングそれぞれに対して、前記像担持体からの正反射光及びトナー像からの拡散反射光を受光した際の検出値から、前記像担持体からの正反射光を受光した際の検出値とを差し引いた差分値を算出し、前記差分値を累積した累積値を用いることを特徴とする画像形成装置。When calculating the density of a toner image having a color different from that of black, for each of a plurality of detection timings set in advance by the optical detection means, the regular reflection light from the image carrier and the toner image Calculating a difference value obtained by subtracting a detection value when the regular reflection light from the image carrier is received from a detection value when the diffuse reflection light is received, and using a cumulative value obtained by accumulating the difference values. An image forming apparatus. 請求項３の画像形成装置において、The image forming apparatus according to claim 3.
上記光学的検出手段がトナー像からの拡散反射光を受光している時間を推定する推定手段を有しており、The optical detection means has an estimation means for estimating the time during which diffuse reflected light from the toner image is received;
上記トナー濃度算出手段は、黒色とは異なる色のトナー像の濃度を算出する場合に前記推定手段の推定結果も用いることを特徴とする画像形成装置。The image forming apparatus according to claim 1, wherein the toner density calculation unit uses the estimation result of the estimation unit when calculating the density of a toner image having a color different from black. 請求項１、２、３または４の画像形成装置において、
上記光学的検出手段と上記像担持体とのどちらか一方が互いの対向面に対して平行方向に移動可能であり、
前記光学的検出手段による前記像担持体の検出方向が、前記光学的検出手段と前記像担持体とのどちらか一方の移動方向と平行であることを特徴とする画像形成装置。 The image forming apparatus according to claim 1 , 2, 3, or 4 .
Either one of the optical detection means and the image carrier is movable in a direction parallel to the opposing surfaces;
An image forming apparatus, wherein a detection direction of the image carrier by the optical detector is parallel to a moving direction of one of the optical detector and the image carrier.
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