JP3890833B2 - Color image forming position shift detection device and image forming device using the same - Google Patents

Description

となる。これは距離換算で０．５５ｍｍであり、非常に小さな値で良いことがわかる。ここでの検出の中心タイミングＬ２は、実際に検出された第１のパターンのタイミングから第２のパターンまでの設計値で設定される。
【００７３】
以下、３番目以降のパターン及び他の色のカラーレジずれ検出用パターンも同様に、検出領域と検出の中心タイミングが設定される。
【００７４】
一方、第１番目のパターンが検出できなかった場合には、パターンが検出されるまで以下の検出領域の計算を行い、パターンの検出領域を設定する。また、検出の中心タイミングは、そのパターンに応じた設計値で設定する。
【００７５】

【００７６】
パターンが検出されてからすぐ次のパターンが検出されなかった場合、その後のパターン検出は、以下の検出領域を設定する。
【００７７】

【００７８】
この場合の検出中心タイミングは、検出済みパターンの実測タイミングからそのパターンまでの間隔の設計値で設定する。
【００７９】
なお、検出領域１は第１パターンにも適用でき、検出領域２は第１パターンが検出された後の第２パターンにも適用できる。
【００８０】
このように、カラーレジずれ検出用パターン５０が検出できるまでは、許容ずれ量と速度誤差を考慮した広い検出範囲と、基準タイミングより検出中心をそれぞれ設定する。カラーレジずれ検出用パターン５０が検出された後の同色のパターンでは、検出されたタイミングを基に新たに速度変動とその色の周期的変動分を考慮した狭い検出範囲と、検出されたパターンの検出タイミングより中心値をそれぞれ設定すれば良い。
【００８１】
これにより、図１０に示すように、大幅にカラーレジずれ検出用パターン５０の検出領域を狭く設定することが可能となり、中間転写ベルト２５上の傷や汚れなどによるノイズの影響や、パターン検出器６０の光量やパターンの濃度変動などによって、レジずれ検出用パターンの誤検出が生じるのを確実に防止することができ、しかも、レジずれ検出用パターンをサンプリングする際の信頼性や対ノイズ性を向上することが可能となる。
【００８２】
なお、上記カラーレジずれ検出用パターンやパターン検出手段は、前記実施の形態のものに限定されるものではなく、カラープリンタ／カラーファクシミリ等における他のカラーレジずれ検出用パターンやパターン検出手段であっても良いことは勿論である。
【００８３】
実施の形態２
図１２はこの発明の実施の形態２を示すものであり、前記実施の形態１と同一の部分には同一の符号を付して説明すると、この実施の形態２では、実施の形態１と異なり、中間転写体ベルト上に各画像形成ユニットで形成されたトナー像を一旦多重に転写するのではなく、転写材担持体としての転写材搬送ベルト９０上に担持された転写用紙３４上に、各画像形成ユニットで形成されたトナー像を直接多重に転写するように構成したものである。
【００８４】
なお、図中、９１、９２は転写材搬送ベルト９０を張架する駆動ロールと従動ロール、９３は転写材搬送ベルト９０上に転写用紙３４を搬送するための用紙搬送ロールを示すものである。
【００８５】
その他の構成及び作用は、前記実施の形態１と同様であるので、その説明を省略する。
【００８６】
実施の形態３
図１３はこの発明の実施の形態３を示すものであり、この実施の形態３では、実施の形態１と異なり、像担持体としての感光体ドラム上に、当該感光体ドラムの１回転毎に順次色の異なるトナー像を形成し、このトナー像を中間転写体上に互いに重ね合わせた状態で転写するように構成したものである。
【００８７】
図１３はこの発明の実施の形態３に係る画像形成装置としてのカラー電子写真複写機を示すものである。
【００８８】
図１３において、１０１はカラー電子写真複写機の本体を示すものであり、このカラー電子写真複写機本体１０１の上部には、原稿１０２を１枚ずつ分離した状態で自動的に搬送する自動原稿搬送装置１０３と、当該自動原稿搬送装置１０３によって搬送される原稿１０２の画像を読み取る原稿読取装置１０４が配設されている。この原稿読取装置１０４は、プラテンガラス１０５上に載置された原稿１０２を光源１０６によって照明し、原稿１０２からの反射光像を、フルレートミラー１０７及びハーフレートミラー１０８、１０９及び結像レンズ１１０からなる縮小光学系を介してＣＣＤ等からなる画像読取素子１１１上に走査露光して、この画像読取素子１１１によって原稿２の色材反射光像を所定のドット密度（例えば、１６ドット／ｍｍ）で読み取るようになっている。
【００８９】
上記原稿読取装置４によって読み取られた原稿２の色材反射光像は、例えば、赤（Ｒ）、緑（Ｇ）、青（Ｂ）（各８ｂｉｔ）の３色の原稿反射率データとして画像処理装置１１２に送られ、この画像処理装置１１２では、原稿２の反射率データに対して、シェーデイング補正、位置ズレ補正、明度／色空間変換、ガンマ補正、枠消し、色／移動編集等の所定の画像処理が施される。
【００９０】
そして、上記の如く画像処理装置１１２で所定の画像処理が施された画像データは、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（ＢＫ）（各８ｂｉｔ）の４色の原稿色材階調データとしてＲＯＳ１１３（Ｒａｓｔｅｒ Ｏｕｔｐｕｔ Ｓｃａｎｎｅｒ）に送られ、このＲＯＳ１１３では、原稿色材階調データに応じてレーザー光による画像露光が行われる。
【００９１】
上記カラー電子写真複写機本体１０１の内部には、色の異なる複数のトナー像を形成可能な画像形成手段Ａが配設されている。この画像形成手段Ａは、主として、静電潜像が形成される像担持体としての感光体ドラム１１７と、前記感光体ドラム１１７上に形成された静電潜像を現像して色の異なる複数のトナー像を形成可能な現像手段としてのロータリー方式の現像装置１１９とから構成されている。
【００９２】
上記ＲＯＳ１１３は、図１３に示すように、図示しない半導体レーザーを原稿再現色材階調データに応じて変調し、この半導体レーザーからレーザー光ＬＢを階調データに応じて出射する。この半導体レーザーから出射されたレーザー光ＬＢは、回転多面鏡１１４によって偏向走査され、ｆ・θレンズ１１５及び反射ミラー１１６を介して像担持体としての感光体ドラム１１７上に走査露光される。
【００９３】
上記ＲＯＳ１１３によってレーザー光ＬＢが走査露光される感光体ドラム１１７は、図示しない駆動手段によって矢印方向に沿って所定の速度で回転駆動されるようになっている。この感光体ドラム１１７の表面は、予め一次帯電用のスコロトロン１１８によって所定の極性（例えば、マイナス極性）及び電位に帯電された後、原稿再現色材階調データに応じてレーザー光ＬＢが走査露光されることによって静電潜像が形成される。上記感光体ドラム１１７上に形成された静電潜像は、イエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（ＢＫ）の４色の現像器１１９Ｙ、１１９Ｍ、１１９Ｃ、１１９ＢＫを備えたロータリー方式の現像装置１１９によって、例えば、感光体ドラム１１７の帯電極性と同極性のマイナス極性に帯電したトナー（帯電色材）によって反転現像され、所定の色のトナー像となる。尚、上記感光体ドラム１１７上に形成されたトナー像は、必要に応じて転写前帯電器１２０によってマイナス極性の帯電を受け、電荷量が調整されるようになっている。
【００９４】
上記感光体ドラム１１７上に形成された各色のトナー像は、当該感光体ドラム１１７の下部に配置された中間転写体としての中間転写ベルト１２１上に、第１の転写手段としての１次転写ロール１２２によって多重に転写される。この中間転写ベルト１２１は、駆動ロール１２３、従動ロール１２４ａ、テンションロール１２４ｂ及び２次転写手段の一部を構成する対向ロールとしてのバックアップロール１２５によって、感光体ドラム１１７の周速と同一の移動速度で矢印方向に沿って回動可能に支持されている。
【００９５】
上記中間転写ベルト１２１上には、形成する画像の色に応じて、感光体ドラム１１７上に形成されるイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（ＢＫ）の４色のすべて又はその一部のトナー像が、一次転写ロール１２２によって順次重ね合わせた状態で転写される。この中間転写ベルト１２１上に転写されたトナー像は、所定のタイミングで２次転写位置へと搬送される記録媒体としての転写用紙１２６上に、中間転写ベルト１２１を支持するバックアップロール１２５と、当該バックアップロール１２５に圧接する第２の転写手段の一部を構成する２次転写ロール１２７の圧接力及び静電吸引力によって転写される。上記転写用紙１２６は、図１３に示すように、カラー電子写真複写機本体１０１内の下部に配置された複数の記録媒体収容部材としての給紙カセット１２８、１２９、１３０、１３１の何れかから、所定のサイズのものがフィードロール１２８ａ、１２９ａ、１３０ａ、１３１ａによって給紙される。給紙された転写用紙１２６は、複数の搬送ロール１３２及びレジストロール１３３によって、所定のタイミングで中間転写ベルト１２１の２次転写位置まで搬送される。そして、上記転写用紙１２６には、上述したように、２次転写手段としてのバックアップロール１２５と２次転写ロール１２７とによって、中間転写ベルト１２１上から所定の色のトナー像が一括して転写されるようになっている。
【００９６】
また、上記中間転写ベルト１２１上から所定の色のトナー像が転写された転写用紙１２６は、中間転写ベルト１２１から分離された後、搬送ベルト１３４によって定着装置１３５へと搬送され、この定着装置１３５によって熱及び圧力でトナー像が転写用紙１２６上に定着され、片面複写の場合には、そのまま排紙トレイ１３６上に排出されてカラー画像の複写工程が終了する。
【００９７】
一方、両面複写の場合には、第１面（表面）にカラー画像が形成された転写用紙１２６を、そのまま排紙トレイ１３６上に排出せずに、図示しない反転ゲートによって下向きに搬送方向が変更され、３つのロールが圧接されたトリロール１３７及び反転ロール１３８によって、反転通路１３９へと一旦搬送される。そして、上記転写用紙１２６は、今度は逆転する反転ロール１３８によって両面用通路１４０へと搬送され、この両面用通路１４０に設けられた搬送ロール１４１によってレジストロール１３３まで一旦搬送されて停止する。転写用紙１２６は、中間転写ベルト１２１上のトナー像と同期して、再度レジストロール１３３によって搬送が開始され、当該転写用紙１２６の第２面（裏面）に対してトナー像の転写・定着工程が行われた後、排出トレイ１３６上に排出されるようになっている。
【００９８】
なお、図１３中、１４２は転写工程が終了した後の感光体ドラム１１７の表面から残留トナーや紙粉等を除去するためのクリーニング装置、１４３は中間転写ベルト１２１の清掃を行うための中間転写ベルト用クリーナー、１４４は手差しトレイをそれぞれ示している。
【００９９】
その他の構成及び作用は、前記実施の形態１と同様であるので、その説明を省略する。
【０１００】
【発明の効果】
以上説明したように、この発明によれば、レジずれ検出用パターンの誤検出が生じるのを確実に防止することができ、しかも、レジずれ検出用パターンをサンプリングする際の信頼性や対ノイズ性を向上することが可能なカラー画像形成位置ずれ検出装置及びこれを用いた画像形成装置を提供することができる。
【図面の簡単な説明】
【図１】 図１はこの発明の実施の形態１に係るカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図２】 図２はこの発明の実施の形態１に係るカラー画像形成位置ずれ検出装置を適用した画像形成装置としてのデジタルカラー複写機を示す構成図である。
【図３】 図３はこの発明の実施の形態１に係るカラー画像形成位置ずれ検出装置を適用した画像形成装置としてのデジタルカラー複写機を示す構成図である。
【図４】 図４は中間転写ベルトを示す斜視図である。
【図５】 図５はこの発明の実施の形態１に係るカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図６】 図６はこの発明の実施の形態１に係るカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図７】 図７はパターン検出器を示す斜視構成図である。
【図８】 図８はパターン検出器の検出状態を示す説明図である。
【図９】 図９はカラーレジずれ補正回路を示すブロック図である。
【図１０】 図１０はカラーレジずれ補正回路の検出誤差の検出状態を示す説明図である。
【図１１】 図１１はこの発明の実施の形態２に係るカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図１２】 図１２はこの発明の実施の形態３に係るカラー画像形成位置ずれ検出装置を適用した画像形成装置としてのデジタルカラー複写機を示す構成図である。
【図１３】 図１３はこの発明の実施の形態４に係るカラー画像形成位置ずれ検出装置を適用した画像形成装置としてのデジタルカラー複写機を示す構成図である。
【図１４】 図１４は従来のカラー画像形成位置ずれ検出装置を使用したカラー画像形成装置を示す構成図である。
【図１５】 図１５は従来のカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図１６】 図１６は従来のカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンを示す説明図である。
【図１７】 図１７は従来のカラー画像形成位置ずれ検出装置で使用されるカラーレジずれ検出用パターンの検出タイミングを示す説明図である。
【図１８】 図１８はカラーレジずれ検出用パターンの誤検出状態を示す説明図である。
【符号の説明】
５０：カラーレジずれ検出用パターン、５０Ｋ：第１のマーク、５０Ｙ：第２のマーク、Ａ：検出領域、Ｂ２：検出領域。[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system, an electrostatic recording system, etc., and in particular, in a color image forming apparatus, controls registration as an image forming position of each color. The present invention relates to a registration control system.
[0002]
[Prior art]
In recent years, documents processed in offices and the like have been rapidly colored, and image forming apparatuses such as copying machines, printers, and facsimiles that handle these documents have also been rapidly colored. Currently, these color devices have been further improved in image quality and speed as the quality of office processing in offices and the like has become higher and faster. As a color device that can meet such a requirement, for example, each color forming unit has black (K), yellow (Y), magenta (M), and cyan (C), and each image forming unit is formed. Various so-called tandem type color image forming apparatuses have been proposed and actually commercialized, which form multiple color images by transferring images of different colors onto a transfer material or intermediate transfer member to be conveyed. .
[0003]
Examples of this type of tandem color image forming apparatus include the following. As shown in FIG. 14, the tandem type color image forming apparatus includes a black image forming unit 200K that forms a black (K) image and a yellow image forming unit 200Y that forms a yellow (Y) image. And a magenta color image forming unit 200M for forming a magenta (M) color image and a cyan color image forming unit 200C for forming a cyan (C) color image. These four image forming units 200K, 200Y, 200M, and 200C are horizontally arranged at a predetermined interval. Further, the toners sequentially formed by the respective image forming units are formed below the black (K), yellow (Y), magenta (M), and cyan (C) image forming units 200K, 200Y, 200M, and 200C. An intermediate transfer belt 201 that transfers images in a state where they are superimposed on each other is disposed so as to be rotatable along the direction of the arrow. The intermediate transfer belt 201 is formed, for example, by forming a flexible synthetic resin film such as polyimide in a strip shape, and connecting both ends of the synthetic resin film formed in a strip shape by means of welding or the like. Configured. Therefore, as shown in FIG. 15, the intermediate transfer belt 201 inevitably has a seam portion 201a which is a connecting portion of the synthetic resin film.
[0004]
The black (K), yellow (Y), magenta (M), and cyan (C) image forming units 200K, 200Y, 200M, and 200C are all configured in the same manner, and these four image forming units 200K, In 200Y, 200M, and 200C, as described above, black, yellow, magenta, and cyan toner images are sequentially formed. The image forming units 200K, 200Y, 200M, and 200C for the respective colors are provided with a photosensitive drum 202. The surface of the photosensitive drum 202 is uniformly charged by a primary charging scorotron 203, and then image exposure is performed. The apparatus 204 scans and exposes image forming laser light according to image information, and forms an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 202 is developed with toner of each color of black, yellow, magenta, and cyan by the developing units 205 of the image forming units 200K, 200Y, 200M, and 200C. Thus, visible toner images are formed, and these visible toner images are transferred onto the intermediate transfer belt 201 by the transfer charger 206 in a state of being superimposed on each other. The black, yellow, magenta, and cyan toner images transferred onto the intermediate transfer belt 201 are transferred onto the transfer sheet 207 in a lump and then subjected to a fixing process by the fixing device 208. A color image is formed.
[0005]
In FIG. 14, reference numeral 209 denotes a photoreceptor cleaner, and 210 denotes an intermediate transfer belt cleaner.
[0006]
By the way, the tandem type color image forming apparatus configured in this manner is a system in which toner images sequentially formed by a plurality of image forming units 200K, 200Y, 200M, and 200C are transferred onto the intermediate transfer belt 201 in a multiple manner. Therefore, the transfer speed of the images formed by the image forming units 200K, 200Y, 200M, and 200C for each color is easily shifted, and the alignment of the images for each color, that is, color registration is possible. Tends to deteriorate frequently and it is difficult to maintain high image quality. This is due to manufacturing tolerances and mounting tolerances of the image exposure apparatuses 204K, 204Y, 204M, and 204C or the image forming units 200K, 200Y, 200M, and 200C as an initial one, and over time. As a result, the members constituting each of the image forming units 200K, 200Y, 200M, and 200C are thermally expanded or displaced due to a change in the internal temperature of the color image forming apparatus or an external force applied to the color image forming apparatus. Due to such as. Among these, a change in internal temperature and an external force are inevitable. For example, a daily operation such as a transfer paper replenishing operation or a paper jam recovery applies an external force to the color image forming apparatus.
[0007]
Therefore, as a conventional technique, as shown in FIG. 15, a pattern 211 for detecting a color registration shift (hereinafter abbreviated as “color registration shift”) is formed on the intermediate transfer belt 201, and this color is formed. Various techniques for sampling the registration error detection pattern 211 by the detector 212 and correcting the registration error of the toner images of the respective colors have already been proposed and introduced into actual machines.
[0008]
As a technique for detecting these color registration shifts, the registration shift detection pattern for detecting the registration shift amount is characterized to increase the size of a detector that reads the registration shift detection pattern. The present applicant has already proposed a technique that can cope with both fine adjustment and coarse adjustment (Japanese Patent Application No. 10-264154).
[0009]
In the image forming apparatus according to Japanese Patent Application No. 10-264154, an image on the image carrier has a first line segment arranged at a predetermined angle with a process direction which is a moving direction of the surface of the image carrier, Pattern forming means for forming a registration error detection pattern comprising a second component arranged symmetrically with the first line segment across an imaginary line orthogonal to the process direction on an image output unit, and rotation of the image carrier Sometimes, the pattern reading means for sequentially reading the first component and the second line segment of the registration error detection pattern formed on the image carrier at a predetermined position, and the first line segment by the pattern reading means and And a registration error detection unit configured to detect a registration error amount of the image output unit based on a reading result of the second line segment.
[0010]
In the case of the image forming apparatus according to the above-mentioned Japanese Patent Application No. 10-264154, a registration error detection pattern as shown in FIG. The registration deviation amount of the image output unit is detected by sequentially forming the pattern on the transfer belt 201 along the process direction and detecting these registration deviation detection patterns with a pattern detector.
[0011]
At this time, as shown in FIG. 16, the timing for sampling the registration deviation detection pattern is the time from the detection reference timing, and the sampling start and the detection area are set. The region where the registration error detection pattern 211 is sampled is set so that the pattern can be reliably detected even if the registration error detection pattern 211 is shifted by an allowable maximum value in consideration of the pattern shift amount. There is a need.
[0012]
By the way, in the technique disclosed in the above Japanese Patent Application No. 10-264154, when the output of the registration deviation detection pattern 211 to be sampled is set to be as long as one round of the intermediate transfer belt 201, for example, the registration deviation is detected. Due to manufacturing accuracy, temperature / time-dependent changes, etc., between the design speed and the actual speed of the photosensitive drum forming the detection pattern 211 and the intermediate transfer belt 201 to which the registration deviation detection pattern 211 is transferred. Considering that a difference occurs in the pattern, it is necessary to set a wider sampling area as the pattern is located on the downstream side in the process direction, that is, as the time from the detection reference timing becomes longer. Alternatively, when the sampling area is constant, it is necessary to set in advance the sampling area from the top in anticipation of the deviation due to the speed error when sampling the pattern again located on the most downstream side in the process direction. is there.
[0013]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. That is, in the technique disclosed in the above Japanese Patent Application No. 10-264154, it is considered that the actual speed of the photosensitive drum and the intermediate transfer belt 201 differs from the design speed due to manufacturing accuracy, temperature / aging change, and the like. If the sampling area for sampling the registration error detection pattern is set wider as the pattern is located on the downstream side in the process direction, the regular pattern located before and after the pattern to be sampled may be detected incorrectly. There is a problem that the side of the pattern that should not be detected is sampled. In addition, if the sampling area for sampling the registration error detection pattern is set wider, it becomes more susceptible to noise such as dirt and scratches on the belt during sampling, and the reliability when sampling the registration error detection pattern is increased. In addition, there is a problem that the noise resistance is lowered.
[0014]
This problem will be described more specifically. Now, as shown in FIG. 17, a sampling color registration detection pattern 211 is formed using a sample start signal (in this case, for the sake of simplicity, this signal and the start of pattern output have the same timing) as a trigger. Image information for output is output, and a color registration error detection pattern 211 as shown in FIG. 16 is sequentially formed on the intermediate transfer belt 201 from the black image forming unit 200K to the yellow image forming unit 200Y. . The first black color registration deviation detection pattern 211K formed on the intermediate transfer belt 201 reaches the position of the pattern detector 212 after a predetermined time TA has elapsed.
[0015]
Here, assuming that the detection area necessary for detecting the leading black color registration deviation detection pattern 211K is A,
A = TA ± {(allowable deviation) × 2 + (deviation due to speed error at TA)}
= 700 ÷ 250 ± (10 ÷ 250 + 700 ÷ 250 × 0.0002)
= (2.8 ± 0.0458) sec
[0016]
Here, the speed setting value of the intermediate transfer belt 201 is 250 mm / sec, the length of one circumference of the intermediate transfer belt 201 is 2000 mm, the distance from the exposure position of the first image forming unit 200K to the pattern detector 212 is 700 mm, The allowable deviation amount is set to 5 mm in both the main and sub scanning directions, and the belt speed fluctuation rate is set to 0.0002.
[0017]
Note that doubling the permissible deviation amount means a necessary detection range in the case of a deviation of 5 mm in both the main and sub scanning directions due to the characteristics of the registration deviation detection pattern. The timing of the detection center is set by the design time from the reference timing until the leading pattern 211K reaches the pattern detector 60.
[0018]
On the other hand, when the color registration error detection pattern 211 is formed over the entire circumference of the intermediate transfer belt 201, if the detection area (time) necessary for detecting the final color registration error detection pattern 211 is Bend, The detection area Bend is
Bend = TB ± {(allowable deviation) × 2 + (deviation due to speed error in TB)}
= 2700 ÷ 250 ± (10 ÷ 250 + 2700 ÷ 250 × 0.0002)
= (10.8 ± 0.0616) sec
It becomes.
[0019]
That is, in order to reliably detect the final pattern, it is necessary to sample ± 0.0616 sec in terms of time and ± 15.4 mm equivalent in terms of design speed distance. In order to prevent erroneous detection of the reverse-side pattern under this condition, it is necessary to take measures such as increasing the pattern interval so that the erroneous detection timing does not enter this detection region. That is, if only the allowable deviation amount is taken into consideration, an interval of 10 mm is sufficient, but an interval of 30 mm or more is required. This is a problem that leads to a decrease in the number of color registration misalignment detection patterns 211 that can be formed in one rotation of the intermediate transfer belt 201, that is, a decrease in frequency. Further, the fact that the detection area of the color registration misalignment detection pattern 211 is wide causes the problem that it is easily affected by noise such as scratches and dirt on the intermediate transfer belt 201 as described above.
[0020]
On the other hand, when the amount of light of the pattern detection means for detecting the registration error detection pattern, the density of the registration error detection pattern, or the like changes, as shown in FIG. There has been a problem that erroneous detection occurs due to erroneous detection.
[0021]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention can reliably prevent misdetection of a registration error detection pattern, Furthermore, it is an object of the present invention to provide a color image forming position shift detection device capable of improving the reliability and noise resistance when sampling a registration shift detection pattern and an image forming apparatus using the same.
[0022]
[Means for Solving the Problems]
  In order to solve the above problems, the invention described in claim 1 isA first sensor having a first detection angle inclined obliquely with respect to the moving direction of the detection target, and detecting a first color image forming position shift detection pattern;
A second sensor having a second detection angle different from the first detection angle and detecting a second color image formation position shift detection pattern;
In a color image formation misregistration detection device comprising:
A first color image formation misregistration detection pattern formed substantially along the detection angle of the first sensor and formed between the detection position by the first sensor and the detection position by the second sensor. When,
A second sensor formed substantially along a detection angle of the second sensor and formed between a detection position by the first sensor and a detection position by the second sensor;Color image formation position shift detection pattern
  Formed on the surface of the object to be detected,
  After the first color image formation misregistration detection pattern is detected by the first sensor or after the second color image formation misregistration detection pattern is detected by the second sensor, the detection is performed. Next, the first or second color image formation misregistration detection pattern is selected according to the position of the already detected color image formation misregistration detection pattern and the design time from the detected color image formation misregistration detection pattern. The detection area for detecting the detection target surface of the first color image formation position deviation detection pattern and the second color image formation position deviation detection pattern, which are ideal at the position of the first sensor, A second color image forming position deviation detection pattern that is set narrower than the interval along the moving direction and is ideal at the position of the second sensor Set narrower than the most closely spaced along said movement direction of the detected object surface and the first color image forming position shift detecting patternThis is a color image forming position deviation detecting device.
[0023]
According to the first aspect of the present invention, the previous color image formation misregistration detection pattern is detected in the detection area of the plurality of color image formation misregistration detection patterns sequentially formed on the surface of the detection target. In such a case, the color image formation misregistration detection pattern is set based on the detected color image formation misregistration detection pattern, so that the detection area of the color image formation misregistration detection pattern can be set significantly narrower. It is possible to erroneously detect other color image formation misregistration detection patterns, avoid the influence of noise due to scratches or dirt on the surface of the detection target, and cause misdetection of the registration misregistration detection pattern. In addition, it is possible to reliably prevent the misregistration, and it is possible to improve reliability and noise resistance when sampling the registration error detection pattern.
[0024]
In the invention described in claim 2, a color image can be formed by transferring multiple toner images of different colors onto an intermediate transfer member or a transfer material carried on a transfer material carrier. Image forming apparatus,
  A first sensor having a first detection angle inclined obliquely and detecting a first color image formation position shift detection pattern;
A second sensor having a second detection angle different from the first detection angle and detecting a second color image forming position shift detection pattern;
With
A first color image formation misregistration detection pattern formed substantially along the detection angle of the first sensor and formed between the detection position by the first sensor and the detection position by the second sensor. When,
A second color image formation misregistration detection pattern formed substantially along the detection angle of the second sensor and formed between the detection position by the first sensor and the detection position by the second sensor. The
Formed on the surface of the intermediate transfer member or transfer material carrier,
After the first color image formation misregistration detection pattern is detected by the first sensor or after the second color image formation misregistration detection pattern is detected by the second sensor, the detection is performed. Next, the first or second color image formation misregistration detection pattern is selected according to the position of the already detected color image formation misregistration detection pattern and the design time from the detected color image formation misregistration detection pattern. The detection area for detecting the detection target surface of the first color image formation position deviation detection pattern and the second color image formation position deviation detection pattern, which are ideal at the position of the first sensor, A second color image forming position deviation detection pattern that is set narrower than the interval along the moving direction and is ideal at the position of the second sensor Set narrower than the most closely spaced along the moving direction of the intermediate transfer member or a transfer material bearing member surface with the first color image forming position shift detecting patternAn image forming apparatus characterized by the above.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0027]
Embodiment 1
FIG. 2 is a schematic configuration diagram showing a tandem type color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
[0028]
In FIG. 2, reference numeral 1 denotes a main body of a tandem type digital color copying machine, and an original reading device 4 for reading an image of the original 2 is disposed on the upper end of one end of the digital color copying machine main body 1. ing. In the digital color copying machine main body 1, image forming units 13K, 13Y, 13M, and 13C for black (K), yellow (Y), magenta (M), and cyan (C) are horizontally arranged. Are arranged at regular intervals. Further, below the four image forming units 13K, 13Y, 13M, and 13C, an intermediate transfer belt 25 that transfers toner images of respective colors sequentially formed by these image forming units in a state of being superimposed on each other, It is arrange | positioned so that rotation is possible along the arrow direction. The toner images of each color transferred onto the intermediate transfer belt 25 in a multiple manner are collectively transferred onto a transfer paper 34 as a transfer material fed from a paper feed cassette 39 or the like, and then a fixing unit 37. Thus, the toner image is fixed on the transfer paper 34 and discharged to the outside.
[0029]
FIG. 3 shows in more detail the configuration of the tandem type color electrophotographic copying machine as the image forming apparatus according to the first embodiment of the present invention.
[0030]
Here, the configuration of the present invention will be described using a tandem type color electrophotographic copying machine, but the present invention is also effective in a color printer / facsimile. The same applies to the second and third embodiments.
[0031]
In FIG. 3, reference numeral 1 denotes a main body of a tandem type digital color copying machine. A platen cover 3 that presses a document 2 onto a platen glass 5 is disposed on an upper portion of one end side of the digital color copying machine main body 1. A document reading device 4 that reads an image of the document 2 placed on the platen glass 5 is provided. The document reader 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and reflects a reflected light image from the document 2 from a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. The image reading element 11 composed of a CCD or the like is scanned and exposed through a reduction optical system, and the color material reflected light image of the document 2 is formed at a predetermined dot density (for example, 16 dots / mm) by the image reading element 11. It is configured to read.
[0032]
The color material reflected light image of the document 2 read by the document reader 4 is, for example, IPS 12 (three-color document reflectance data of red (R), green (G), and blue (B) (each 8 bits)). In this IPS 12, the reflectance data of the document 2 is subjected to predetermined corrections such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. Image processing is performed.
[0033]
The image data that has been subjected to the predetermined image processing by the IPS 12 as described above has four color original color material levels of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 bits). As described below, black (K), yellow (Y), magenta (M), and cyan (C) image forming units 13K, 13Y, 13M, and 13C ROSs 14K, 14Y, and 14M, as described below. , 14C (Raster Output Scanner), and these ROSs 14K, 14Y, 14M, and 14C perform image exposure with laser light in accordance with document color material gradation data of a predetermined color.
[0034]
Incidentally, inside the tandem type digital color copying machine main body 1, as described above, four image forming units 13K, 13Y of black (K), yellow (Y), magenta (M), and cyan (C) are provided. , 13M, 13C are arranged in parallel in the horizontal direction with a certain interval.
[0035]
These four image forming units 13K, 13Y, 13M, and 13C are all configured in the same manner, and are roughly divided into a photosensitive drum 15 that rotates at a predetermined rotational speed in the direction of the arrow, and the photosensitive drum 15. A primary charging scorotron 16 that uniformly charges the surface of the photosensitive drum 15, an ROS 14 that forms an electrostatic latent image by exposing an image corresponding to each color on the surface of the photosensitive drum 15, and a photosensitive drum 15. The developing unit 17 develops the electrostatic latent image and the cleaning device 18.
[0036]
As shown in FIG. 3, the ROS 14 modulates the semiconductor laser 19 according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser 19 according to the gradation data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflection mirrors 20 and 21, and again carries an image via the reflection mirrors 20 and 21 and the plurality of reflection mirrors 23 and 24. Scanning exposure is performed on the photosensitive drum 15 as a body.
[0037]
From the IPS 12, image data of each color is supplied to the image forming units 13K, 13Y, 13M, and 13C of ROS 14K, 14Y, 14M, and 14C of each color of black (K), yellow (Y), magenta (M), and cyan (C). Are sequentially output, and laser beams LB emitted from these ROSs 14K, 14Y, 14M, and 14C in accordance with image data are scanned and exposed on the surfaces of the respective photosensitive drums 15K, 15Y, 15M, and 15C, and electrostatic latent An image is formed. The electrostatic latent images formed on the photosensitive drums 15K, 15Y, 15M, and 15C are respectively black (K), yellow (Y), magenta (M), and cyan by the developing units 17K, 17Y, 17M, and 17C. It is developed as a toner image of each color of (C).
[0038]
Black (K), yellow (Y), magenta (M), and cyan (C) are sequentially formed on the photosensitive drums 15K, 15Y, 15M, and 15C of the image forming units 13K, 13Y, 13M, and 13C. The toner images of the respective colors are transferred in multiple by primary transfer rolls 26K, 26Y, 26M, and 26C onto an intermediate transfer belt 25 as an intermediate transfer member disposed below each of the image forming units 13K, 13Y, 13M, and 13C. The The intermediate transfer belt 25 is wound around the drive roll 27, the stripping roll 28, the steering roll 29, the idle roll 30, the backup roll 31, and the idle roll 32 with a constant tension. A drive roll 27 that is rotationally driven by a dedicated drive motor with excellent constant speed (not shown) is circulated at a predetermined speed in the direction of the arrow. As the transfer belt 25, for example, a flexible synthetic resin film such as polyimide is formed in a band shape, and both ends of the synthetic resin film formed in the band shape are connected by means such as welding, thereby providing an endless belt. What was formed in the shape is used. Therefore, as shown in FIG. 4, the intermediate transfer belt 25 inevitably has a seam portion 25a which is a connecting portion of the synthetic resin film.
[0039]
The black (K), yellow (Y), magenta (M), and cyan (C) toner images transferred onto the transfer belt 25 in a multiple manner are transferred to the backup roll 31 by a secondary transfer roll 33. The transfer sheet 34 that has been secondarily transferred onto the transfer sheet 34 by the pressure contact force and electrostatic force and onto which the toner images of the respective colors have been transferred is conveyed to the fixing device 37 by the two conveyance belts 35 and 36. The transfer paper 34 onto which the toner images of the respective colors have been transferred undergoes a fixing process with heat and pressure by a fixing device 37 and is discharged onto a discharge tray 38 provided outside the copying machine main body 1.
[0040]
As shown in FIG. 3, the transfer paper 34 has a predetermined size from any one of a plurality of paper feed cassettes 39, 40, 41, and a pair of paper feed rollers 42 and a pair of paper transport rollers 43, 44. , 45 is temporarily transported to the registration roll 47 via a paper transport path 46. The transfer paper 34 supplied from any one of the paper feed cassettes 39, 40, 41 is sent onto the intermediate transfer belt 25 by a registration roll 47 that is rotationally driven at a predetermined timing.
[0041]
Then, in the four image forming units 13K, 13Y, 13M, and 13C of black, yellow, magenta, and cyan, as described above, the black, yellow, magenta, and cyan toner images are respectively predetermined. It is formed sequentially at the timing.
[0042]
The photosensitive drums 15K, 15Y, 15M, and 15C, after the toner image transfer process is completed, the residual toner and paper dust are removed by the cleaning devices 18K, 18Y, 18M, and 18C, and the next image formation is performed. Prepare for the process. Further, residual toner is removed from the intermediate transfer belt 25 by a belt cleaner 48.
[0043]
By the way, in this embodiment, a color registration error detection pattern 50 is formed on the intermediate transfer belt 25 at a predetermined timing, and the color registration error detection pattern 50 is detected, and each image forming unit 13K, After correcting the color registration misalignment of 13Y, 13M, and 13C, a color image is formed.
[0044]
As shown in FIG. 5, the color registration misalignment detection pattern 50 includes a first line segment M1 arranged at a predetermined angle θ with the process direction of the intermediate transfer belt 25, and the process direction of the intermediate transfer belt 25. A first line segment M1 and a second line segment M2 arranged symmetrically with respect to a virtual line perpendicular to the line are used. The first line segment M1 and the second line segment M2 are formed by the same image forming unit (same color). The color registration misalignment detection pattern 50 configured as described above is, for example, in the order of black, yellow, magenta, cyan, black, yellow, magenta, cyan,. Formed over the entire circumference.
[0045]
The color registration deviation detection pattern 50 is read by a detector set at a predetermined pattern detection position, more specifically, a registration gap detection pattern (shown by a broken line) in an ideal state at a predetermined interval. It has become. Accordingly, when the intermediate transfer belt 25 moves in the process direction, the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25 has the first line segment M1 at timing A and the second line segment M2. Are read at timing B, respectively. The pattern detection position may be an intermediate position in the lateral direction of the ideal registration error detection pattern.
[0046]
Here, assuming that the distance from the reference point set on the intermediate transfer belt 25 in advance to the timing A is DA and the distance from the reference point to the timing B is DB, the lateral shift amount Lerr of the registration shift detection pattern 50. Corresponds to the difference between DA and DB since the first line segment M1 and the second line segment M2 are arranged symmetrically. That is, assuming that the difference between DA and DB when the registration deviation detection pattern in the ideal state is read is DW, the lateral direction deviation amount Lerr is obtained by the following equation (1).
Lerr = | (DB-DA-DW) × 0.5 | × tan θ (1)
[0047]
The DW at this time is obtained by multiplying the length of the first line segment M1 or the second line segment M2 by cos θ if a detector is arranged at the lateral direction intermediate position of the registration deviation detection pattern 50 in the ideal state. Identified.
[0048]
On the other hand, the process direction deviation amount Perr of the registration deviation detection pattern 50 with respect to the detector can also be obtained based on DA and DB. That is, assuming that the intermediate timing between timing A and timing B when reading the registration deviation detection pattern 50 in the ideal state is Pnom, and the distance from the reference point to the timing Pnom is DPnom, the process direction deviation amount Perr is Since the first line segment M1 and the second line segment M2 are arranged symmetrically, it is obtained by the following equation (2).
Perr = 0.5 × (DA + DB) −DPnom (2)
[0049]
That is, the registration deviation detection pattern 50 including the first line segment M1 and the second line segment M2 symmetrical to the first line segment M1 is formed, and this is read by a detector at a predetermined position. The process direction deviation amount Perr and the lateral direction deviation amount Lerr can be obtained.
[0050]
FIG. 6 is a conceptual diagram showing a color registration error detection pattern 50 formed in the image forming apparatus according to the first embodiment. In the figure, the solid line indicates the color registration misalignment detection pattern actually formed, and the broken line indicates the color registration misalignment detection pattern in the ideal state.
[0051]
As described above, the color registration misalignment detection pattern 50 includes the first line segment M1 and the second line segment M2 symmetrical to the first line segment M1. However, as shown in FIG. 6, the first line segment M1 and the second line segment M2 each have an angle of approximately 45 degrees with respect to the process direction of the intermediate transfer belt 25, and further fine adjustment. In order to make it possible to cope with both a deviation amount of about several hundred μm that can be accommodated with a coarse deviation and a registration deviation amount of about 5 mm, for example, which needs to be adjusted, the first line segment M1 and the second line The size of the minute M2 in the lateral direction is, for example, about 15 mm.
[0052]
The color registration misalignment detection patterns 50 are formed at both ends in the width direction of the intermediate transfer belt 25, for example, as shown in FIG.
[0053]
As described above, the color registration misalignment detection patterns 50 formed on the intermediate transfer belt 25 are detected by the pattern detectors 60 disposed at both ends in the width direction of the intermediate transfer belt 25 as shown in FIG. Is done.
[0054]
Each pattern detector 60 is a so-called split (bi-cell) type detector having a pair of photocells D1 and D2 for improving reading accuracy. However, each of these photocells D1 and D2 is arranged in a substantially C shape, and one of them is arranged along the first line segment M1 at an angle of about 45 degrees with the process direction. Are arranged symmetrically with the one along the second line segment M2.
[0055]
Each pattern detector 60 is installed at a position having a predetermined relationship with the registration deviation detection pattern 50 in an ideal state. Specifically, in each pattern detector 60, the intermediate position between the photocells D1 and D2 matches the intermediate position in the lateral direction when the registration deviation detection pattern 50 to be read is in an ideal state. .
[0056]
In such a pattern detector 60, when the intermediate transfer belt 25 moves in the process direction at the belt speed V, the photocell D1 displays the first line segment M1 at timing A as shown in FIG. The cell D2 detects the second line segment M2 at the timing B, respectively.
[0057]
Here, TA is the time from the timing (reference timing) when the reference point on the intermediate transfer belt 25 passes through the photocells D1 and D2 to the timing A, TB is the time from the reference point to the timing B, and the process direction. The pattern reference timing (center timing of the registration error detection pattern in an ideal state) is Pnom, and the lateral size of the registration error detection pattern 50 is W, and the distance between the photocells D1 and D2 Is SW, the lateral direction deviation amount Lerr and the process direction deviation amount Perr of the registration deviation detection pattern 50 are symmetrical with respect to the first line segment M1 and the second line segment M2, and both are approximately in the process direction. Since they are arranged with an angle of 45 degrees, they are obtained by calculation using functions shown in the following equations (3) and (4).
Lerr = | V × (TB−TA) | × 0.5 (3)
Perr = {0.5 × (TA + TB) −SW / 2−Pnom} × V (2)
[0058]
Based on the registration deviation detection pattern 50, the lateral direction deviation amount Lerr and the process direction deviation amount Perr are obtained, and each image forming unit is instructed to correct the image formation position based on the result. To prevent the output image quality from deteriorating.
[0059]
FIG. 7 is a perspective view showing the pattern detector 60 for detecting the color registration deviation.
[0060]
In FIG. 7, reference numeral 61 denotes a housing of the pattern detector 60, and 62 a and 62 b denote two light emitting elements that respectively illuminate the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25. Reference numerals 63b, 64a, and 64b denote two sets of light receiving elements that respectively receive reflected light from different mountain-shaped marks 51 of the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25. As the two light emitting elements 62a and 62b, for example, LEDs that emit light having a specific wavelength or light having a predetermined wavelength distribution are used. These light emitting elements 62a and 62b are arranged on the intermediate transfer belt 25. These one detection positions are arranged so as to illuminate from opposite diagonal directions inclined by a predetermined angle. The two sets of light receiving elements 63a, 63b and 64a, 64b are arranged in such a manner that the center portions are in contact with each other and the both end portions are inclined downward by a predetermined angle with respect to the horizontal direction. 63b and 64a and 64b, and the light receiving elements 63a, 63b and 64a and 64b are set so that the detection timing and the detection angle of the reflected light are different from each other, as shown in FIG.
[0061]
As shown in FIG. 8, when the pattern detector 60 detects the color registration deviation detection pattern 50 formed on the intermediate transfer belt 25, the first and second lines of the color registration deviation detection pattern 50 are detected. Due to the minute M1 or M2, as shown in FIG. 8 (a), one of the light receiving elements 63b outputs a smooth mountain-shaped waveform first, and after some delay, the other light receiving element 63a also As shown in FIG. 8B, a smooth mountain-shaped waveform is output. Then, by amplifying the waveforms output from these two light receiving elements 63b and 63a, or by taking the difference and then amplifying it, as shown in FIG. After falling, an output waveform that rises in a large mountain shape is obtained. Therefore, by taking the difference between the waveforms output from the two light receiving elements 63a and 63b, as shown in FIG. 8D, it is possible to detect a color registration deviation without using a high-precision sensor such as a CCD. It becomes possible to detect the linear mark 51 of the pattern 50 with high resolution and high accuracy.
[0062]
FIG. 9 is a block diagram showing an embodiment of the color registration misalignment correction apparatus according to the first embodiment.
[0063]
In FIG. 9, reference numeral 70 denotes a CPU for controlling the image forming operation of the tandem type digital color copying machine and the detection and calibration operation of the color registration misalignment, and 71 denotes the image forming operation executed by the CPU 70, the detection of the color registration misalignment, and ROM storing software programs for controlling the calibration operation, etc. 72 is an LED driver for lighting the LEDs constituting the light emitting elements 62a and 62b of the pattern detector 60, 73 is a light receiving element 63a of the pattern detector 60, PWM circuit (pulse width modulation circuit) 60 for controlling the threshold value for sampling data at 63b, 64a and 64b, and 60 at the three ends of the intermediate transfer belt 25 in the width direction, for example, at three ends (if necessary, both end portions 74, a pattern detector for detecting a color registration misalignment detection pattern formed on the A counter for measuring a time interval between predetermined pulses (rising) at the time of detecting a color registration error detection pattern output from these pattern detectors 60 based on a reference clock pulse, 75 is also based on a command from the CPU 70 Then, the original 2 is transferred to the ROSs 14Y, 14M, 14C, and 14BK of the image forming units 13Y, 13M, 13C, and 13BK of yellow (Y), magenta (M), cyan (C), and black (BK) at a predetermined timing. An image output circuit for outputting image information for forming the color registration error detection pattern 50 or an image output circuit 76 for outputting the color registration error detection pattern 50, respectively, indicates a registration pattern storage ROM for storing the image information of the color registration error detection pattern 50 in advance. is there.
[0064]
In this embodiment, the CPU 70 controls the image forming operation of the tandem type digital color copying machine, or immediately after the tandem type digital color copying machine is turned on, or the copying machine. The CPU 70 moves onto the intermediate transfer belt 25 at a predetermined timing such as when the temperature in the main body 1 changes by a predetermined temperature or more, when a predetermined number of copies are made by the copying machine, when the front cover is opened and closed, and so on. A color registration misalignment detection pattern 50 as shown in FIGS. 4 to 6 is formed, and this color registration misalignment detection pattern 50 is detected by the pattern detector 60 to be a target for a reference color pattern. Detects how much the color registration shift detection pattern 50 formed by the image forming units 13Y, 13M, and 13C is shifted. , And is configured to perform a control to calibrate the color shift.
[0065]
By the way, as shown in FIG. 9, the CPU 70 outputs predetermined image information to the ROSs 14K, 14Y, 14M, and 14C of the image forming units 13K, 13Y, 13M, and 13C of the respective colors via the image output circuit 75. As a result, a color registration deviation detection pattern 50 as shown in FIGS. 4 to 6 is repeatedly formed on the intermediate transfer belt 25.
[0066]
When detecting the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25 by the pattern detector 60, if the sampling area is set too wide, a regular pattern positioned before and after the pattern to be sampled is erroneously set. There is a risk of detecting or sampling the side of the pattern that should not be detected. In addition, if the sampling area for sampling the registration error detection pattern is set wider, it becomes more susceptible to noise such as dirt and scratches on the belt during sampling, and the reliability when sampling the registration error detection pattern is increased. It also leads to a reduction in noise resistance.
[0067]
Therefore, in the first embodiment, as shown in FIG. 10, the color registration shift for sampling is triggered by a sample start signal (in this case, for the sake of simplicity, this signal and the pattern output start are set at the same timing). Image information for forming the detection pattern 50 is output, and the color registration deviation detection pattern 50 as shown in FIG. 6 is sequentially transferred from the black image forming unit 13K to the yellow image forming unit 13Y. Sequentially formed on the belt 25. As shown in FIG. 11, the first black color registration deviation detection pattern 50K formed on the intermediate transfer belt 25 reaches the position of the pattern detector 60 after a predetermined time TA has elapsed.
[0068]
Here, as shown in FIG. 1, assuming that a detection area A necessary for detecting the leading black color registration deviation detection pattern 50K is A, this detection area A is:
A = TA ± {(allowable deviation) × 2 + deviation due to speed error in TA)}
= 700 ÷ 250 ± (10 ÷ 250 + 700 ÷ 250 × 0.0002)
= (2.8 ± 0.0458) sec
It becomes.
[0069]
Here, the speed setting value of the intermediate transfer belt 25 is 250 mm / sec, the length of one turn of the intermediate transfer belt 25 is 2000 mm, the distance from the exposure position of the first image forming unit 13K to the pattern detector 60 is 700 mm, The allowable deviation amount is set to 5 mm in both the main and sub scanning directions, and the belt speed fluctuation rate is set to 0.0002.
[0070]
Note that doubling the permissible deviation amount means a necessary detection range when the registration deviation detection pattern 50 is deviated by 5 mm in both the main and sub scanning directions. The detection center timing L is set by the design time until the leading pattern 50K reaches the pattern detector 60 from the reference timing.
[0071]
Next, when the first black color registration error detection pattern 50K is detected by the pattern detector 60, the CPU 70 detects the detection area of the next black color registration error detection pattern 50K of the same color. Therefore, it is not necessary to consider the color registration misregistration amount, and it is set by the deviation due to the speed error in the distance between the first and second black color registration misregistration detection patterns 50K and the periodic variation of the color misregistration. Can do.
[0072]
That is, if the detection area of the second pattern of the same color as the color where the first pattern is detected is B2, this detection area B2 is
B2 = ± {(shift due to speed error from pattern 1 to 2) + (color shift periodic variation from pattern 1 to 2)}
It can be expressed as Here, when the distance from the pattern 1 to 2 is 200 mm, and the periodic variation of the color shift of this pattern is 150 μm, the detection region B2 is

It becomes. This is 0.55 mm in terms of distance, and it can be seen that a very small value is sufficient. Here, the detection center timing L2 is set as a design value from the timing of the first pattern actually detected to the second pattern.
[0073]
Hereinafter, the detection area and the detection center timing are set in the same manner for the third and subsequent patterns and the color registration deviation detection patterns for other colors.
[0074]
On the other hand, if the first pattern cannot be detected, the following detection area is calculated until the pattern is detected, and the pattern detection area is set. Further, the detection center timing is set with a design value corresponding to the pattern.
[0075]

[0076]
When the next pattern is not detected immediately after the pattern is detected, the following detection areas are set for the subsequent pattern detection.
[0077]

[0078]
In this case, the detection center timing is set as a design value of the interval from the actual measurement timing of the detected pattern to the pattern.
[0079]
The detection area 1 can also be applied to the first pattern, and the detection area 2 can also be applied to the second pattern after the first pattern is detected.
[0080]
Thus, until the color registration deviation detection pattern 50 can be detected, the detection center is set based on the wide detection range considering the allowable deviation amount and the speed error, and the reference timing. In the same color pattern after the color registration misalignment detection pattern 50 is detected, a narrow detection range that newly considers the speed fluctuation and the periodic fluctuation of the color based on the detected timing, and the detected pattern The center value may be set based on the detection timing.
[0081]
As a result, as shown in FIG. 10, the detection area of the color registration misalignment detection pattern 50 can be set to be significantly narrow, the influence of noise due to scratches and dirt on the intermediate transfer belt 25, the pattern detector, and the like. It is possible to reliably prevent misdetection of the registration error detection pattern due to the light amount of 60 and the density variation of the pattern, and to improve reliability and noise resistance when sampling the registration error detection pattern. It becomes possible to improve.
[0082]
The color registration misalignment detection pattern and pattern detection means are not limited to those of the above-described embodiment, but are other color registration misalignment detection patterns and pattern detection means in a color printer / color facsimile or the like. Of course, it may be.
[0083]
Embodiment 2
FIG. 12 shows a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals, and the second embodiment is different from the first embodiment. The toner images formed by the image forming units on the intermediate transfer body belt are not transferred once in a multiple manner, but on the transfer paper 34 carried on the transfer material transport belt 90 as a transfer material carrier. In this configuration, the toner images formed by the image forming unit are directly transferred in multiple layers.
[0084]
In the figure, reference numerals 91 and 92 denote driving rolls and driven rolls that stretch the transfer material conveyance belt 90, and 93 denotes a paper conveyance roll for conveying the transfer paper 34 onto the transfer material conveyance belt 90.
[0085]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0086]
Embodiment 3
FIG. 13 shows a third embodiment of the present invention. In the third embodiment, unlike the first embodiment, on the photosensitive drum as the image carrier, every rotation of the photosensitive drum. In this configuration, toner images of different colors are sequentially formed, and the toner images are transferred onto the intermediate transfer member in a state of being superimposed on each other.
[0087]
FIG. 13 shows a color electrophotographic copying machine as an image forming apparatus according to Embodiment 3 of the present invention.
[0088]
In FIG. 13, reference numeral 101 denotes a main body of a color electrophotographic copying machine, and an automatic document transport for automatically transporting the original 102 in a state of being separated one by one on the upper part of the main body 101 of the color electrophotographic copying machine. An apparatus 103 and an original reading apparatus 104 that reads an image of the original 102 conveyed by the automatic original conveying apparatus 103 are provided. The document reader 104 illuminates a document 102 placed on a platen glass 105 with a light source 106, and reflects a reflected light image from the document 102 from a full-rate mirror 107, half-rate mirrors 108 and 109, and an imaging lens 110. The image reading element 111 composed of a CCD or the like is scanned and exposed through the reduction optical system, and the color material reflected light image of the original 2 is scanned at a predetermined dot density (for example, 16 dots / mm) by the image reading element 111. It is supposed to read.
[0089]
The color material reflected light image of the document 2 read by the document reading device 4 is subjected to image processing, for example, as document reflectance data of three colors of red (R), green (G), and blue (B) (8 bits each). The image processing apparatus 112 sends predetermined correction data such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. to the reflectance data of the document 2. Image processing is performed.
[0090]
The image data subjected to the predetermined image processing by the image processing apparatus 112 as described above is an original of four colors of yellow (Y), magenta (M), cyan (C), and black (BK) (8 bits each). The color material gradation data is sent to a ROS 113 (Raster Output Scanner), and the ROS 113 performs image exposure with laser light in accordance with the original color material gradation data.
[0091]
An image forming unit A capable of forming a plurality of toner images having different colors is disposed inside the color electrophotographic copying machine main body 101. This image forming means A mainly develops a photosensitive drum 117 as an image carrier on which an electrostatic latent image is formed and a plurality of different colors by developing the electrostatic latent image formed on the photosensitive drum 117. And a rotary type developing device 119 as developing means capable of forming a toner image.
[0092]
As shown in FIG. 13, the ROS 113 modulates a semiconductor laser (not shown) according to the original reproduction color material gradation data, and emits a laser beam LB from the semiconductor laser according to the gradation data. The laser beam LB emitted from the semiconductor laser is deflected and scanned by the rotary polygon mirror 114, and is scanned and exposed on the photosensitive drum 117 as an image carrier through the f · θ lens 115 and the reflecting mirror 116.
[0093]
The photosensitive drum 117 on which the laser beam LB is scanned and exposed by the ROS 113 is rotationally driven at a predetermined speed in the direction of the arrow by a driving unit (not shown). The surface of the photosensitive drum 117 is charged in advance with a predetermined polarity (for example, negative polarity) and potential by the primary charging scorotron 118, and then the laser beam LB is scanned and exposed in accordance with the original reproduction color material gradation data. As a result, an electrostatic latent image is formed. The electrostatic latent image formed on the photosensitive drum 117 includes four color developing devices 119Y, 119M, 119C, and 119BK of yellow (Y), magenta (M), cyan (C), and black (BK). The rotary developing device 119 reversely develops, for example, with a toner (charged color material) charged to a negative polarity that is the same polarity as the charged polarity of the photosensitive drum 117 to form a toner image of a predetermined color. The toner image formed on the photosensitive drum 117 is negatively charged by the pre-transfer charger 120 as necessary to adjust the amount of charge.
[0094]
The toner images of the respective colors formed on the photosensitive drum 117 are transferred onto a primary transfer roll as a first transfer unit on an intermediate transfer belt 121 as an intermediate transfer member disposed below the photosensitive drum 117. Multiple transfer is performed by 122. The intermediate transfer belt 121 is moved at the same moving speed as the peripheral speed of the photosensitive drum 117 by a driving roll 123, a driven roll 124a, a tension roll 124b, and a backup roll 125 as an opposing roll constituting a part of the secondary transfer means. It is supported so as to be rotatable along the arrow direction.
[0095]
On the intermediate transfer belt 121, four colors of yellow (Y), magenta (M), cyan (C), and black (BK) are formed on the photosensitive drum 117 according to the color of the image to be formed. All or part of the toner image is transferred in a state of being sequentially superimposed by the primary transfer roll 122. The toner image transferred onto the intermediate transfer belt 121 is transferred to a secondary transfer position at a predetermined timing on a transfer sheet 126 as a recording medium, a backup roll 125 that supports the intermediate transfer belt 121, Transfer is performed by the pressure contact force and electrostatic attraction force of the secondary transfer roll 127 that constitutes a part of the second transfer unit that is in pressure contact with the backup roll 125. As shown in FIG. 13, the transfer sheet 126 is fed from any one of a plurality of sheet feeding cassettes 128, 129, 130, and 131 serving as recording medium accommodation members disposed in the lower part of the color electrophotographic copying machine main body 101. Paper of a predetermined size is fed by feed rolls 128a, 129a, 130a, 131a. The fed transfer sheet 126 is transported to the secondary transfer position of the intermediate transfer belt 121 by a plurality of transport rolls 132 and registration rolls 133 at a predetermined timing. Then, as described above, a predetermined color toner image is transferred onto the transfer sheet 126 from the intermediate transfer belt 121 by the backup roll 125 and the secondary transfer roll 127 as secondary transfer means. It has become so.
[0096]
The transfer sheet 126 onto which the toner image of a predetermined color is transferred from the intermediate transfer belt 121 is separated from the intermediate transfer belt 121 and then conveyed to the fixing device 135 by the conveying belt 134. Thus, the toner image is fixed on the transfer sheet 126 by heat and pressure, and in the case of single-sided copying, the toner image is directly discharged onto the discharge tray 136 and the color image copying process is completed.
[0097]
On the other hand, in the case of duplex copying, the transfer sheet 126 on which the color image is formed on the first surface (front surface) is not discharged onto the discharge tray 136 as it is, but the conveyance direction is changed downward by a reversing gate (not shown). Then, the tri-roll 137 and the reverse roll 138 with which the three rolls are pressed are temporarily transported to the reverse passage 139. Then, the transfer sheet 126 is conveyed to the double-sided passage 140 by the reversing roll 138 which is now reversed, and is temporarily conveyed to the registration roll 133 by the conveying roll 141 provided in the double-sided passage 140 and stopped. The transfer sheet 126 is started to be conveyed again by the registration roll 133 in synchronization with the toner image on the intermediate transfer belt 121, and the transfer / fixing process of the toner image is performed on the second surface (back surface) of the transfer sheet 126. After being performed, it is discharged onto the discharge tray 136.
[0098]
In FIG. 13, reference numeral 142 denotes a cleaning device for removing residual toner, paper dust, and the like from the surface of the photosensitive drum 117 after the transfer process is completed, and reference numeral 143 denotes an intermediate transfer for cleaning the intermediate transfer belt 121. Belt cleaners 144 indicate manual feed trays.
[0099]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0100]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent misdetection of the registration error detection pattern, and further, reliability and noise resistance when sampling the registration error detection pattern. A color image forming position shift detecting device capable of improving the image quality and an image forming apparatus using the same can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a color registration misalignment detection pattern used in a color image formation position misalignment detection apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position deviation detecting apparatus according to Embodiment 1 of the present invention is applied.
FIG. 3 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position shift detecting apparatus according to Embodiment 1 of the present invention is applied.
FIG. 4 is a perspective view showing an intermediate transfer belt.
FIG. 5 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the first embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the first embodiment of the present invention.
FIG. 7 is a perspective configuration diagram showing a pattern detector.
FIG. 8 is an explanatory diagram showing a detection state of the pattern detector.
FIG. 9 is a block diagram illustrating a color registration error correction circuit.
FIG. 10 is an explanatory diagram illustrating a detection state of a detection error of the color registration misalignment correction circuit.
FIG. 11 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the second embodiment of the present invention.
FIG. 12 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position deviation detecting apparatus according to Embodiment 3 of the present invention is applied.
FIG. 13 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming positional deviation detecting apparatus according to Embodiment 4 of the present invention is applied.
FIG. 14 is a block diagram showing a color image forming apparatus using a conventional color image forming position deviation detecting device.
FIG. 15 is an explanatory diagram showing a color registration misalignment detection pattern used in a conventional color image formation misregistration detection apparatus.
FIG. 16 is an explanatory diagram showing a color registration misalignment detection pattern used in a conventional color image formation misregistration detection apparatus.
FIG. 17 is an explanatory diagram showing detection timing of a color registration misalignment detection pattern used in a conventional color image formation misregistration detection apparatus.
FIG. 18 is an explanatory diagram showing an erroneous detection state of a color registration misalignment detection pattern.
[Explanation of symbols]
50: Color registration misalignment detection pattern, 50K: first mark, 50Y: second mark, A: detection area, B2: detection area.

Claims (2)

A first sensor having a first detection angle inclined obliquely with respect to the moving direction of the detection target, and detecting a first color image forming position shift detection pattern;
A second sensor having a second detection angle different from the first detection angle and detecting a second color image formation position shift detection pattern;
In a color image formation misregistration detection device comprising:
A first color image formation misregistration detection pattern formed substantially along the detection angle of the first sensor and formed between the detection position by the first sensor and the detection position by the second sensor. When,
A second color image formation misregistration detection pattern formed substantially along the detection angle of the second sensor and formed between the detection position by the first sensor and the detection position by the second sensor. The
Formed on the surface of the object to be detected,
After the first color image formation misregistration detection pattern is detected by the first sensor or after the second color image formation misregistration detection pattern is detected by the second sensor, the detection is performed. Next, the first or second color image formation misregistration detection pattern is selected according to the position of the already detected color image formation misregistration detection pattern and the design time from the detected color image formation misregistration detection pattern. The detection area for detecting the detection target surface of the first color image formation position deviation detection pattern and the second color image formation position deviation detection pattern, which are ideal at the position of the first sensor, A second color image forming position deviation detection pattern that is set narrower than the interval along the moving direction and is ideal at the position of the second sensor Color image forming position shift detecting apparatus is characterized in that set narrower than the most closely spaced along the moving direction of the detection object surface of the first color image forming position shift detecting pattern. An image forming apparatus capable of forming a color image by transferring multiple toner images of different colors onto an intermediate transfer member or a transfer material carried on a transfer material carrier,
A first sensor having a first detection angle inclined obliquely with respect to the moving direction of the detection target, and detecting a first color image forming position shift detection pattern;
A second sensor having a second detection angle different from the first detection angle and detecting a second color image formation position shift detection pattern;
With
A first color image formation misregistration detection pattern formed substantially along the detection angle of the first sensor and formed between the detection position by the first sensor and the detection position by the second sensor. When,
A second color image formation misregistration detection pattern formed substantially along the detection angle of the second sensor and formed between the detection position by the first sensor and the detection position by the second sensor. The
Formed on the surface of the intermediate transfer member or transfer material carrier,
After the first color image formation misregistration detection pattern is detected by the first sensor or after the second color image formation misregistration detection pattern is detected by the second sensor, the detection is performed. Next, the first or second color image formation misregistration detection pattern is selected according to the position of the already detected color image formation misregistration detection pattern and the design time from the detected color image formation misregistration detection pattern. The detection area for detecting the detection target surface of the first color image formation position deviation detection pattern and the second color image formation position deviation detection pattern, which are ideal at the position of the first sensor, A second color image forming position deviation detection pattern that is set narrower than the interval along the moving direction and is ideal at the position of the second sensor Color image forming position shift detecting apparatus is characterized in that set narrower than the most closely spaced along the moving direction of the intermediate transfer member or a transfer material bearing member surface with the first color image forming position shift detecting pattern .

Images