JP3903632B2 - Belt conveying apparatus and image forming apparatus - Google Patents

Description

【００６１】
ここで、Ｋは制御ゲインであり、Ｗは、図６に示す演算部２０ｅで算出されたエッジ位置ｅ（ｒ，ｎ）に基づいて算出されるウォーク量である。また、ＫＷは、少数第１位まで算出される値であり、ｉｎｔは、その少数第１位まで算出されたＫＷを整数化することを表す。
【００６２】
図７は、実施例１の画像形成装置が備えている中間転写ベルト１の位置ずれを是正するために実行される第１の中間転写ベルト位置調整モードのフローチャートを示す図、図８は、そのフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【００６３】
実施例１の画像形成装置において、第１の中間転写ベルト位置調整モードの実行が開始されると、中間転写ベルト１の回転が開始され、エッジセンサ１３により検出されたベルトエッジ信号に基づいて、図６に示す演算部２０ｅでエッジ位置ｅ（ｒ，ｎ）が算出される（ステップＳ１）。尚、ここでは、中間転写ベルト１の回転が開始してから最初にベルトホーム信号が検出された時点を、中間転写ベルト１の回転数０、すなわち中間転写ベルト１の１回転目が開始された時点とし、中間転写ベルト１の回転が開始してからベルトホーム信号が検出されるまでの間は、回転数ｒ＝−１と設定する。
【００６４】
ステップＳ１においてエッジ位置ｅ（ｒ，ｎ）が得られると、ステップＳ２に進み、そのステップＳ１で検出されたエッジ位置ｅ（ｒ，ｎ）の絶対値｜ｅ（ｒ，ｎ）｜が基準値Ｅ０より小さいか否かが判断される。ここで、基準値Ｅ０は、第１の中間転写ベルト位置調整モードを実行する前に中間転写ベルト１のエッジ位置を予め測定することにより得られた、その中間転写ベルト１のエッジプロファイルの最大値（ここでは０．４ｍｍ）に設定してある。尚、第１の中間転写ベルト位置調整モードの実行開始前に中間転写ベルト１を交換した場合等、第１の中間転写ベルト位置調整モードの実行開始前と実行開始後とでＥ０の値が異なる場合は、Ｅ０の値を、交換後の中間転写ベルト１に対応した値に変更すればよい。
【００６５】
ステップＳ２において、｜ｅ（ｒ，ｎ）｜＜Ｅ０（＝０．４ｍｍ）と判断されると、（１）式に示す制御ゲインＫ＝０に設定し、ステップモータ２１のステップ位置変化量Ｓを０にしたまま（すなわち、ステップモータ２１のステップ位置を固定することにより、ステアリングロール３の傾斜角度を固定する）、ステップＳ３に進み、ベルトホームセンサ１２からベルトホーム信号が出力されたか否かが判断される。ベルトホーム信号が出力されていないと判断されると、再度ステップＳ１に進み、ステップＳ２で｜ｅ（ｒ，ｎ）｜＜Ｅ０であると判断されつづける限り、ステップモータ２１のステップ位置変化量Ｓ＝０のまま、ステップＳ３でベルトホーム信号が出力されるまで、ステップＳ１〜ステップＳ３のループが繰り返し実行される。
【００６６】
図８（Ａ）に、中間転写ベルト１の回転数と、その中間転写ベルト１の位置ずれとの関係を示す。破線は、中間転写ベルト１のエッジ位置を示し、実線は、エッジ位置からエッジプロファイルが取り除くことにより算出されたその中間転写ベルト１自体の、基準位置からの位置ずれ量（ウォーク量）を示す。
【００６７】
ここでは、中間転写ベルト１の走行開始時（ｒ＝−１）において、エッジ位置は約１．０ｍｍであるため、ステップＳ２において、ステップＳ１で検出されたエッジ位置ｅ（ｒ，ｎ）が基準値Ｅ０（＝０．４ｍｍ）より大きい、すなわち、｜ｅ（ｒ，ｎ）｜≧Ｅ０と判断される。｜ｅ（ｒ，ｎ）｜≧Ｅ０と判断されると、ステップＳ４に進み、以下に示す（２）式を用いて、（１）式に示す制御ゲインＫを算出する。
【００６８】
【数２】

【００６９】
Ｋ０；定数
制御ゲインＫが算出されると、ステップＳ５に進み、上述した（１）式中のＫに（２）式を用いて算出されたＫを代入するとともに、（１）式中のＷにｅ（ｒ，ｎ）を代入してステップ位置変化量Ｓを算出し、その算出されたステップ位置変化量Ｓだけステップモータ２１のステップ位置を変更し、ステアリングロール３の傾斜角度を調整する。
【００７０】
つまり、実施例１の画像形成装置は、ステップＳ２において、エッジ位置ｅ（ｒ，ｎ）が、−０．４ｍｍ＜ｅ（ｒ，ｎ）＜０．４ｍｍの範囲にあるか否かを判断し、エッジ位置ｅ（ｒ，ｎ）がその範囲内に入った場合は、制御ゲインＫを０に設定してステアリングロール３の傾斜角度を固定し、中間転写ベルト１の位置の是正は行わず、一方、エッジ位置ｅ（ｒ，ｎ）がその範囲から外れた場合は、（２）式で表される制御ゲインＫをｅ（ｒ，ｎ）の値に応じて変化させてステアリングロール３の傾斜角度を制御し、中間転写ベルト１の位置の是正を積極的に行っている。つまり、実施例１の画像形成装置では、エッジ位置ｅ（ｒ，ｎ）が０．４ｍｍよりも大きい場合は、中間転写ベルト１のウォーク量が大きいと判断して、中間転写ベルト１の位置の是正を積極的に行っており、一方、エッジ位置ｅ（ｒ，ｎ）が０．４ｍｍよりも小さい場合は、中間転写ベルト１のウォーク量はそれほど大きくはないと判断して、中間転写ベルト１の位置の是正は行っていない。
【００７１】
このようにして中間転写ベルト１の位置の是正を行うと、中間転写ベルト１のウォーク量が大きいほど、ステップ位置変化量Ｓが大きくなる。このため、ステアリングロール３の傾斜角度が大きくなり、中間転写ベルト１の位置ずれに対する修正量が大きくなる。つまり、中間転写ベルト１のウォーク量が大きい場合は、その中間転写ベルト１の位置ずれに対する修正量が大きく、一方、中間転写ベルト１のウォーク量が小さい場合は、その中間転写ベルト１の位置ずれに対する修正量が小さく設定され、中間転写ベルト１のウォーク量に応じて、中間転写ベルト１の位置ずれを効果的に是正することができる。
【００７２】
ステップＳ５において、ステップ位置変化量Ｓが算出されたら、ステップＳ３に進み、ベルトホームセンサ１２からベルトホーム信号が出力されたか否かが判断される。ベルトホーム信号が出力されていないと判断されると、再度ステップＳ１に進み、ステップＳ２で｜ｅ（ｒ，ｎ）｜≧Ｅ０であると判断されつづける限り、ステップＳ３でベルトホーム信号が出力されるまで、ステップＳ１、Ｓ２、Ｓ４、Ｓ５、およびＳ３のループが繰り返し実行される。このループの実行により、中間転写ベルト１の位置ずれは小さくなり、ここでは、図８（Ａ）に示すように、ステップＳ３でベルトホーム信号が出力されたと判断された時点（ベルト回転数ｒ＝０）では、中間転写ベルト１のウォーク量は約０．４ｍｍである。
【００７３】
ステップＳ３でベルトホーム信号が出力されたと判断されると、中間転写ベルト１の回転数ｒ＝０、中間転写ベルト１の番地ｎ＝０に設定されステップＳ６に進み、回転数ｒ＝０、番地ｎ＝０におけるエッジ位置ｅ（０，０）が算出される。エッジ位置ｅ（０，０）が算出されると、ステップＳ７に進み、その算出されたエッジ位置ｅ（０，０）に基づいて、回転数ｒ＝０、番地ｎ＝０における中間転写ベルト１のウォーク量Ｗ（０，０）が算出される。このウォーク量Ｗ（０，０）は、以下の（３）式で表されるウォーク量Ｗ（ｒ，ｎ）において、ｒ＝０、ｎ＝０とすることにより算出される。
【００７４】
【数３】

【００７５】
Ｗ（ｒ，ｎ）は、回転数ｒ、番地ｎにおける、中間転写ベルト１のウォーク量である。従って、Ｗ（０，０）は、回転数ｒ＝０、番地ｎ＝０におけるウォーク量である。このＷ（０，０）は、エッジ位置ｅ（０，０）と、予め測定されたエッジプロファイルｐ（ｎ）のうちの番地ｎ＝０におけるｐ（０）との差分であり、この差分を算出することによりウォーク量Ｗ（０，０）が算出される。ウォーク量Ｗ（０，０）が算出されると、ステップＳ８に進み、（２）式を用いて、回転数ｒ＝０、番地ｎ＝０におけるＫ＝Ｋ０・（ｅ（０，０）−Ｅ０）が算出され、さらに、上述した（１）式のＫに、その算出されたＫ０・（ｅ（０，０）−Ｅ０）が代入されるとともに、ＷにステップＳ７で算出されたウォーク量Ｗ（０，０）が代入され、回転数ｒ＝０、番地ｎ＝０におけるステップ位置変化量Ｓ（０，０）が算出される。ステップ位置変化量Ｓ（０，０）が算出されると、ステップモータ２１は、その算出されたステップ位置変化量Ｓ（０，０）に対応するステップ数だけ回転してステップ位置を変更し、ステアリングロール３の傾斜角度が調整される。
【００７６】
ステップＳ８において、ステップ位置変化量Ｓ（０，０）が算出されたら、ステップＳ９に進み、中間転写ベルト１の走行を終了する旨の終了信号が入力されたか否かが判断される。終了信号が入力されていないと判断されると、ステップＳ１０に進み、番地ｎが、最大値Ｎ（ここでは５０）であるか否かが判断される。この時点では番地ｎ＝０であるので、最大値Ｎ（＝５０）ではないと判断され、ステップＳ１１で番地ｎがインクリメントされてｎ＝１となり、ステップＳ６に戻る。ステップＳ６に戻ると、今度は、中間転写ベルト１の回転数ｒ＝０、中間転写ベルト１の番地ｎ＝１におけるエッジ位置ｅ（０，１）が検出され、ステップＳ７、ステップＳ８それぞれで、回転数ｒ＝０、番地ｎ＝１におけるウォーク量Ｗ（０，１）、ステップ位置変化量Ｓ（０，１）が算出される。ステップモータ２１は、その算出されたステップ位置変化量Ｓ（０，１）に対応するステップ数だけ回転し、これにより、ステアリングロール３の傾斜角度が調整される。その後、ステップＳ９で、中間転写ベルト１の走行を終了する旨の終了信号が入力されていないと判断されるのであれば、この時点では番地ｎ＝１であるので、ステップＳ１０で、番地ｎが最大値Ｎ（＝５０）ではないと判断され、ステップＳ１１に進み、番地ｎがインクリメントされてｎ＝２となり、再度ステップＳ６に戻る。
【００７７】
以下同様にして、ステップＳ９で終了信号が入力されていないと判断されるのであれば、ステップＳ１０で、番地ｎが最大値Ｎ（＝５０）であると判断されるまで、ステップＳ６〜ステップＳ１１のループが繰り返し実行される。このループが繰り返し実行されることにより、中間転写ベルト１の回転数ｒ＝０と、中間転写ベルト１の番地ｎ＝０，１，２，……，５０それぞれとの組み合わせにおけるエッジ位置ｅ（０，０），ｅ（０，１），ｅ（０，２），……，ｅ（０，５０）が検出され、ステップモータ２１は、各エッジ位置ｅ（０，０），ｅ（０，１），ｅ（０，２），……，ｅ（０，５０）に基づいて求められたステップ位置変化量Ｓ（０，０），Ｓ（０，１），Ｓ（０，２），……，Ｓ（０，５０）それぞれに対応するステップ数だけ順次回転し、中間転写ベルト１のラテラル方向の位置が制御される。ここで、ステップＳ１０において、番地ｎが最大値Ｎ（＝５０）であると判断されると、ステップＳ３に戻り、ベルトホーム信号が出力されたら中間転写ベルト１の回転数ｒがインクリメントされｒ＝１となる。このインクリメントにより、中間転写ベルト１の１回転目が終了となる。図８（Ａ）に示すように、中間転写ベルト１が１回転し終えた時点では、中間転写ベルト１のウォーク量は、約０．２ｍｍである。
【００７８】
また、ステップＳ３においてｒ＝１にインクリメントされると、今度はその中間転写ベルト１の回転が２回転目に入り、再度ステップＳ６〜ステップＳ１１のループが繰り返し実行され、ｒ＝１（中間転写ベルト１の回転が２回転目）において、番地ｎ＝０，１，２，……，５０それぞれのときのステップ位置変化量Ｓ（１，０），Ｓ（１，１），Ｓ（１，２），……，Ｓ（１，５０）が求められ、ステップモータ２１が、それらステップ位置変化量Ｓ（１，０），Ｓ（１，１），Ｓ（１，２），……，Ｓ（１，５０）それぞれに対応するステップ数だけ順次回転する。ここで、ステップＳ１０において、番地ｎが最大値Ｎ（＝５０）であると判断されると、ステップＳ３に戻り、ベルトホーム信号が出力されたら中間転写ベルト１の回転数ｒがインクリメントされｒ＝２となる。このインクリメントにより、中間転写ベルト１の２回転目が終了となる。図８（Ａ）に示すように、中間転写ベルト１が２回転し終えた時点では、中間転写ベルト１のウォーク量は、ほぼ０ｍｍとなっている。
【００７９】
以下、同様にして、ｒが順次インクリメントされ、ステップモータ２１は、ｒ＝０，１，２，３……、ｎ＝０，１，２，……，５０それぞれの組合わせに対応したステップ位置変化量Ｓ（ｒ，ｎ）に対応するステップ数だけ回転し、中間転写ベルト１の位置が制御される。図８（Ａ）に示すように、中間転写ベルト１の位置ずれは、その中間転写ベルト１が２回転し終えたころに是正されていることがわかる。
【００８０】
尚、参考として、図８（Ｂ）に、中間転写ベルト１の回転数と、ステップモータ２１のステップ位置変化量Ｓ（ｒ，ｎ）との関係を示す。ここで、ステップ位置変化量Ｓ（ｒ，ｎ）は、中間転写ベルト１の回転数ｒにおいて、番地ｎ−１におけるステップモータ２１のステップ位置が、番地ｎにおけるステップモータ２１のステップ位置に変化するときのステップ位置の変化量である。また図８（Ｃ）に、中間転写ベルト１の回転数ｒと、ステップモータ２１のステップ位置との関係を示す。尚、ステップ位置は、回転数ｒ＝−１のときのステップモータ２１のステップ位置を基準位置としてある。
【００８１】
このように、実施例１の画像形成装置において、第１の中間転写ベルト位置調整モードを実行することにより、中間転写ベルト１の位置ずれが是正されるる。ここで、１０００分割のステップモータ２１を備えるが、第１の中間転写ベルト位置調整モードを有さない画像形成装置（比較例１）を用いた場合、中間転写ベルト１の位置がどのように制御されるかについて説明する。
【００８２】
図９は、比較例１の画像形成装置において、中間転写ベルトの位置ずれを是正するために実行されるフローチャートであり、図１０は、そのフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【００８３】
図９に示すフローチャートと、図７に示すフローチャートとの相違点は、図９に示すフローチャートが、図７に示すフローチャートのステップＳ１，Ｓ２，Ｓ４，Ｓ５を備えていない点のみである。尚、図９に示すフローチャートを実行するにあたり、中間転写ベルト１が回転し始めてから、最初にベルトホーム信号が出力されるまでの間、ステップモータ２１のステップ位置は所定のステップ位置に固定されている。また、比較例１の画像形成装置においても、実施例１と同様に、ステップモータのステップ位置変化量Ｓは上述した（１）式で表される。
【００８４】
図１０（Ａ）は、中間転写ベルト１の回転数と、エッジ位置および中間転写ベルトのウォーク量それぞれとの関係を示すグラフである。図８（Ａ）と図１０（Ａ）とを比較すると、中間転写ベルト１の回転を開始した時点（ｒ＝−１）でのウォーク量と、最も大きいウォーク量との差Ｚは、図８（Ａ）の方が小さい。従って、第１の中間転写ベルト位置調整モードを実行することにより、中間転写ベルト１の走行を開始してから、ベルトホーム信号が検出される間の、中間転写ベルト１のウォーク量Ｗが抑制されていることがわかる。
【００８５】
尚、参考として、図１０（Ｂ）に、中間転写ベルト１の回転数と、ステップモータのステップ位置変化量との関係を示し、図１０（Ｃ）に、中間転写ベルト１の回転数と、ステップモータのステップ位置との関係を示す。
【００８６】
（実施例２）
ここで、実施例２の画像形成装置の説明に先立って、図９に示すフローチャートにしたがって中間転写ベルトの位置を是正する、分解能１０００のステップモータを備えた比較例１の画像形成装置を用いたときに、中間転写ベルト１の回転を開始し、最初にベルトホーム信号が検出された時点以後の、中間転写ベルトのラテラル方向の位置ずれが是正される様子について説明する。
【００８７】
図１１は、比較例１の画像形成装置において、図９に示すフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれが是正される様子を示す図である。尚、図１１では、ベルトホーム信号が出力された時点での中間転写ベルトのウォーク量が０．２ｍｍの場合の例が示されている。
【００８８】
図１１（Ａ）は、中間転写ベルト１の回転数と、エッジ位置および中間転写ベルトのウォーク量それぞれとの関係、図１１（Ｂ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置変化量との関係、図１１（Ｃ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置との関係を示す。
【００８９】
図１１（Ａ）から、中間転写ベルト１の位置ずれは、その中間転写ベルト１が２回転し終えたころに是正されていることがわかる。
【００９０】
次に、比較例１の画像形成装置において、１０００分割のステップモータ２１の代わりに、１００分割のステップモータ２１を備えた画像形成装置（比較例２）を用意し、この比較例２の画像形成装置を用いたときの、中間転写ベルトのラテラル方向の位置ずれについて説明する。尚、比較例２の画像形成装置においても、ステップモータのステップ位置変化量Ｓは、上述した（１）式で表される。
【００９１】
図１２は、比較例２の画像形成装置において、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【００９２】
尚、ここでは、（１）式において、算出されたウォーク量Ｗ（ｒ，ｎ）に対して、ステップモータのステップ数変化量Ｓ（ｒ，ｎ）が小さい値に設定されるように、制御ゲインＫを小さい値に設定してある。
【００９３】
図１２（Ａ）は、中間転写ベルト１の回転数と、エッジ位置および中間転写ベルトのウォーク量それぞれとの関係、図１２（Ｂ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置変化量との関係、図１２（Ｃ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置との関係を示す。
【００９４】
図１２（Ａ）に示すように、中間転写ベルトのウォーク量は約−０．２ｍｍで飽和していしまい、位置ずれが是正されていないことがわかる。そこで、比較例２の画像形成装置において、（１）式で表されるステップ位置変化量Ｓの算出に用いられる制御ゲインＫを、図１２の場合における制御ゲインＫよりも大きい値に設定することによりステップモータのステップ数変化量を大きくしたときの、中間転写ベルトのラテラル方向の位置ずれの是正を試みた。
【００９５】
図１３は、そのときの中間転写ベルトのラテラル方向の位置ずれを示す図である。
【００９６】
図１３（Ａ）は、中間転写ベルト１の回転数と、エッジ位置および中間転写ベルトのウォーク量それぞれとの関係、図１３（Ｂ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置変化量との関係、図１３（Ｃ）は、中間転写ベルト１の回転数と、ステップモータのステップ位置との関係を示す。
【００９７】
制御ゲインＫを大きくしても、図１３（Ａ）に示すように、中間転写ベルトのウォーク量が約−０．１ｍｍで飽和していしまい、位置ずれが是正されていないことがわかる。
【００９８】
このように、比較例１の画像形成装置では、図１１（Ａ）に示すように、位置ずれが是正されているが、ステップモータ２１として高分解能のモータ（分解能１０００）を用いる必要があり、コストがかかるという問題がある。一方、比較例２の画像形成装置では、低コスト化を図るために、ステップモータ２１として低分解能のモータ（分解能１００）を用いているが、このような低分解能のモータでは、図１２（Ａ）、図１３（Ａ）に示すように、位置ずれを是正することができないという問題がある。そこで、減速機を用いて、低分解能のステップモータの分解能を高分解能にする方法が考えられるが、この方法では、減速機の精度等が問題となりステップモータの制御を高精度に行うことが難しい。
【００９９】
これに対し、実施例２の画像形成装置では、上述したように、低分解能のステップモータ（分解能１００）が用いられ、さらに、第２の中間転写位置調整モードが実行される。このように、第２の中間転写位置調整モードを実行することにより、高分解能のステップモータの代わりに低分解能のステップモータを用いても、中間転写ベルト１の位置ずれが精度よく是正される。以下に、その中間転写ベルト１の位置ずれが是正される原理について説明する。
【０１００】
図１４は、ステップモータのステップ位置と、中間転写ベルトが１回転する間のウォーク量の最大値（以下、ウォーク速度と呼ぶ）との関係を示すグラフである。
【０１０１】
図１４に示すように、ステップモータのステップ位置（すなわちステアリングロールの傾斜角度）とウォーク速度との間には直線Ｌで表される線形の対応関係がある。従って、ステップモータのステップ位置（ステアリングロールの傾斜角度）を正確に制御することにより、中間転写ベルト１のウォーク速度を０にできることがわかる。
【０１０２】
以下、実施例２において、ステップモータのステップ位置（ステアリングロールの傾斜角度）をどのように制御しているかについて説明する。
【０１０３】
図１５は、実施例２の画像形成装置が実行する第２の中間転写ベルト位置調整モードのフローチャートを示す図、図１６は、そのフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【０１０４】
中間転写ベルト１の回転が開始され、ステップＳ１でベルトホーム信号が出力されたと判断されると、中間転写ベルト１の回転数ｒ＝０、中間転写ベルト１の番地ｎ＝０にリセットされる。ここでは、図１６（Ａ）に示すように、ベルトホーム信号が出力された時点（ｒ＝０）での、ベルトのウォーク量は約０．２ｍｍである。ベルトホーム信号が出力されると、ステップＳ２に進み、回転数ｒ＝０、番地ｎ＝０におけるエッジ位置ｅ（０，０）が検出される。エッジ位置ｅ（０，０）が検出されると、ステップＳ３に進み、エッジ位置ｅ（０，０）とエッジプロファイルｐ（０）との差分から、回転数ｒ＝０、番地ｎ＝０におけるウォーク量Ｗ（０，０）を算出する。ウォーク量Ｗ（０，０）が算出されると、ステップＳ４に進み、その算出されたウォーク量Ｗ（０，０）に基づいて、回転数ｒ＝０、番地ｎ＝０において、中間転写ベルト１の位置ずれを是正するのに必要なステップ位置変化量Ｓ０（０，０）が算出される。このステップ位置変化量Ｓ０（０，０）は、以下の（４）式で表されるステップ位置変化量Ｓ０（ｒ，ｎ）において、ｒ＝０、ｎ＝０とすることにより算出される。
【０１０５】
【数４】

【０１０６】
このステップ位置変化量Ｓ０（ｒ，ｎ）は、回転数ｒ、番地ｎにおける、中間転写ベルト１の位置ずれを是正するのに必要なステップモータ２１のステップ位置変化量を、実施例２の画像形成装置が備えているステップモータ２１の分解能１００よりも高分解能である分解能１０００で算出したときのステップモータ２１のステップ位置変化量である。従って、（４）式で求められたステップ位置変化量Ｓ０をそのまま用いて、分解能１００のステップモータのステップ位置を変更しようとすると、分解能１００のステップモータ２１では本来設定できないステップ位置を新たなステップ位置と設定する場合が出てくる。そこで、（４）式で求められたステップ位置変化量Ｓ０に基づいて、分解能１００のステップモータ２１が設定可能なステップ位置のみを新たなステップ位置に設定するステップ位置変化量Ｓを算出する。そのステップ位置変化量Ｓは、以下のようにして算出される。
【０１０７】
ステップＳ４においてステップ位置変化量Ｓ０（０，０）が算出されると、ステップＳ５に進み、その算出されたステップ位置変化量Ｓ０（０，０）に基づいて、回転数ｒ＝０、番地ｎ＝０において、分解能１００のステップモータ２１が設定可能なステップ位置の中から１つのステップ位置Ａ（０，０）が設定される。このステップ位置Ａ（０，０）は、現在のステップ位置とのステップ位置変化量がステップＳ４で算出されたステップ位置変化量Ｓ０（０，０）に最も近いように設定される。このＡ（０，０）は、以下の（５）式で表されるステップ位置Ａ（ｒ，ｎ）において、ｒ＝０、ｎ＝０とすることにより算出される。
【０１０８】
【数５】

【０１０９】
Ａ（ｒ，ｎ）は、回転数ｒ、番地ｎにおける、ステップモータ２１のステップ位置である。
【０１１０】
（５）式から、Ａ（０，０）＝ｉｎｔ｛Ｓ０（０，０）｝となる。
【０１１１】
ステップＳ５において、Ａ（０，０）が算出されると、ステップＳ６に進み、その算出されたＡ（０，０）に基づいて、回転数ｒ＝０、番地ｎ＝０において、ステップモータのステップ位置を現在のステップ位置からステップ位置Ａ（０，０）にするのに必要なステップ位置変化量Ｓ（０，０）が算出される。このステップ位置変化量Ｓ（０，０）は、以下の（６）式で表されるステップ位置変化量Ｓ（ｒ，ｎ）において、ｒ＝０、ｎ＝０とすることにより算出される。
【０１１２】
【数６】

【０１１３】
だだし、ｎ−１；０以上の整数
つまり、Ｓ（０，０）＝ｉｎｔ｛Ａ（０，０）｝となる。
【０１１４】
このようにしてステップ位置変化量Ｓ（０，０）を算出し、その算出されたステップ位置変化量Ｓ（０，０）に対応したステップ数だけステップモータ２１を回転しステアリングロール３の傾斜角度を調整する。ステップＳ６において、ステップ位置変化量Ｓ（０，０）が算出されたら、ステップＳ７に進み、中間転写ベルト１の走行を終了する旨の終了信号が入力されたか否かが判断される。終了信号が入力されていないと判断されると、ステップＳ８に進み、番地ｎが、最大値Ｎ（ここでは５０）であるか否かが判断される。この時点では番地ｎ＝０であるので、最大値Ｎ（＝５０）ではないと判断され、ステップＳ９で番地ｎがインクリメントされてｎ＝１となり、ステップＳ２に戻る。ステップＳ２に戻ると、今度は、中間転写ベルト１の回転数ｒ＝０、中間転写ベルト１の番地ｎ＝１におけるエッジ位置ｅ（０，１）が検出され、ステップＳ３、ステップＳ４それぞれで、中間転写ベルト１の回転数ｒ＝０、中間転写ベルト１の番地ｎ＝１に対応したウォーク量Ｗ（０，１）、ステップ位置変化量Ｓ０（０，１）が算出される。その後、ステップＳ５に進み、（５）式を用いて、Ａ（０，１）を算出する。
【０１１５】

Ａ（０，１）が算出されたらステップＳ６に進み、（６）式を用いて、ステップ位置変化量Ｓ（０，１）を算出する。
【０１１６】

このようにして算出されたステップ位置変化量Ｓ（０，１）に対応したステップ数だけステップモータ２１を回動しステアリングロール３の傾斜角度を調整する。その後、ステップＳ７で、中間転写ベルト１の走行を終了する旨の終了信号が入力されていないと判断されるのであれば、この時点では番地ｎ＝１であるので、ステップＳ８で、番地ｎが最大値Ｎ（＝５０）ではないと判断され、ステップＳ９に進み、番地ｎがインクリメントされてｎ＝２となり、再度ステップＳ２に戻る。
【０１１７】
以下、ステップＳ７で、中間転写ベルト１の走行を終了する旨の終了信号が入力されていないと判断されるのであれば、ステップＳ８で、番地ｎが最大値Ｎ（＝５０）であると判断されるまで、ステップＳ２〜ステップＳ９のループが繰り返し実行される。このループが繰り返し実行されることにより、中間転写ベルト１の回転数ｒ＝０と、中間転写ベルト１の番地ｎ＝０，１，２，……，５０それぞれとの組み合わせにおけるエッジ位置ｅ（０，０），ｅ（０，１），ｅ（０，２），……，ｅ（０，５０）が検出され、ステップモータ２１は、各エッジ位置ｅ（０，０），ｅ（０，１），ｅ（０，２），……，ｅ（０，５０）に基づいて求められたステップ位置変化量Ｓ（０，０），Ｓ（０，１），Ｓ（０，２），……，Ｓ（０，５０）それぞれに対応したステップ数だけ順次回動し、中間転写ベルト１のラテラル方向の位置が制御される。ここで、ステップＳ８において、番地ｎが最大値Ｎ（＝５０）であると判断されると、ステップＳ１に戻り、ベルトホーム信号が出力されたら中間転写ベルト１の回転数ｒがインクリメントされｒ＝１となる。このインクリメントにより、中間転写ベルト１の、最初にベルトホーム信号を検出してからの１回転目が終了となる。図１６（Ａ）に示すように、中間転写ベルト１が１回転し終えた時点では、中間転写ベルト１のウォーク量は、約０．１ｍｍである。また、図１６（Ｃ）に示すように、ステップモータ２１のステップ位置は、回転数ｒが０から１になるまでの間に、−１、−２、−３、−２と変化している。
【０１１８】
また、ステップＳ１においてｒ＝１にインクリメントされると、今度はその中間転写ベルト１の回転が２回転目に入り、再度ステップＳ２〜ステップＳ９のループが繰り返し実行され、ｒ＝１（中間転写ベルト１の回転が２回転目）において、番地ｎ＝０，１，２，……，５０それぞれのときのステップ位置変化量Ｓ（１，０），Ｓ（１，１），Ｓ（１，２），……，Ｓ（１，５０）が求められ、ステップモータ２１が、それらステップ位置変化量Ｓ（１，０），Ｓ（１，１），Ｓ（１，２），……，Ｓ（１，５０）それぞれに対応したステップ数だけ順次回動する。ここで、ステップＳ８において、番地ｎが最大値Ｎ（＝５０）であると判断されると、ステップＳ１に戻り、ベルトホーム信号が出力されたら中間転写ベルト１の回転数ｒがインクリメントされｒ＝２となる。このインクリメントにより、中間転写ベルト１の２回転目が終了となる。図１６（Ａ）に示すように、中間転写ベルト１が２回転し終えた時点では、中間転写ベルト１のウォーク量は、ほぼ０ｍｍとなっている。また、図１６（Ｃ）に示すように、ステップモータ２１のステップ位置は、回転数ｒが１から２になるまでの間に、−２、−１、０と変化している。
【０１１９】
以下、同様にして、ｒが順次インクリメントされ、ステップモータ２１は、ｒ＝０，１，２，３……、ｎ＝０，１，２，……，５０それぞれの組合わせに対応したステップ位置変化量Ｓ（ｒ，ｎ）だけ順次回動し、中間転写ベルト１の位置が制御される。図１６（Ａ）に示すように、中間転写ベルト１の位置ずれは、その中間転写ベルト１が２回転し終えたころに是正されていることがわかる。
【０１２０】
実施例２の画像形成装置では、ステップＳ４において、ステップ位置変化量Ｓ０（ｒ，ｎ）を、実施例２の画像形成装置が備えているステップモータ２１の分解能１００よりも高分解能である分解能１０００で算出し、ステップＳ５において、その算出されたステップ位置変化量Ｓ０（ｒ，ｎ）と、ステップモータ２１のステップ位置Ａ（ｒ，ｎ−１）とに基づいて、ステップ位置Ａ（ｒ，ｎ）を算出し、ステップＳ６において、ステップモータ２１のステップ位置Ａ（ｒ，ｎ）と、ステップ位置Ａ（ｒ，ｎ−１）との差分を算出することにより、ステップモータ２１のステップ位置変化量Ｓ（ｒ，ｎ）を求めている。
【０１２１】
このように、そのステップモータ２１の分解能１００よりも高分解能である分解能１０００でステップモータ２１のステップ位置変化量Ｓ０（ｒ，ｎ）を求め、その算出されたステップ位置変化量Ｓ０（ｒ，ｎ）と、回転数ｒ，番地ｎ−１におけるステップモータ２１のステップ位置Ａ（ｒ，ｎ−１）とに基づいて、実施例２の画像形成装置が備えている分解能１００のステップモータ２１のステップ位置Ａ（ｒ，ｎ）を算出することにより、ステップモータ２１のステップ位置を、実施例２の画像形成装置が備えている分解能１００のステップモータ２１よりも高分解能である分解能１０００のステップモータのステップ位置に近づけることができる。従って、低分解能のステップモータを用いても、図１６（Ａ）に示すように、中間転写ベルト１の位置ずれが是正される。
【０１２２】
分解能１０００（高分解能）のステップモータのステップ位置を表す図１１（Ｃ）と、分解能１００（低分解能）のステップモータのステップ位置を表す図１２（Ｃ）、図１３（Ｃ）、および図１６（Ｃ）それぞれとを比較すると、図１６（Ｃ）に示すステップモータのステップ位置の軌跡が、図１１（Ｃ）に示すステップモータのステップ位置の軌跡に最も近いことがわかる（図１１（Ｃ）におけるステップ位置−３０は、図１２（Ｃ）、図１３（Ｃ）、および図１６（Ｃ）におけるステップ位置−３に相当する）。このように、低分解能のステップモータを用いても、そのステップモータのステップ位置を、高分解能のステップモータのステップ位置に近づけることにより、低コストで、その中間転写ベルト１の位置ずれを精度よく是正することができる。
【０１２３】
【発明の効果】
以上説明したように、本発明によれば、ベルトの位置ずれが大きくなってしまうことが抑制されたベルト搬送装置、およびそのベルト搬送装置を適用した画像形成装置が得られる。
【０１２４】
また、本発明によれば、低コストでベルトの位置を高精度に制御できるベルト搬送装置、およびそのベルト搬送装置を適用した画像形成装置替えられる。
【図面の簡単な説明】
【図１】本発明のベルト搬送装置の一実施形態を適用した、本発明の画像形成装置の一実施形態を示す概略構成図である。
【図２】エッジセンサの一例である接触型センサを示す概略構成図である。
【図３】エッジセンサの別の例である非接触型センサを示す概略構成図である。
【図４】図１に示す画像形成装置において、エッジセンサで検出される信号の経路を具体的に示した図である。
【図５】中間転写ベルトの蛇行が修正される様子の説明図である。
【図６】ステアリングロール３の傾斜角度を最適条件で細かく設定するシステムの一例を示す図である。
【図７】実施例１の画像形成装置が備えている中間転写ベルト１の位置ずれを是正するために実行される第１の中間転写ベルト位置調整モードのフローチャートを示す図である。
【図８】図７に示すフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【図９】比較例１の画像形成装置において、中間転写ベルトの位置ずれを是正するために実行されるフローチャートである。
【図１０】図９に示すフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【図１１】比較例１の画像形成装置において、図９に示すフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれが是正される様子を示す図である。
【図１２】比較例２の画像形成装置において、上述した（１）式に示す制御ゲインＫを小さい値に設定したときの中間転写ベルトのラテラル方向の位置ずれを示す図である。
【図１３】制御ゲインＫを、図１２の場合における制御ゲインＫよりも大きい値に設定したときの中間転写ベルトのラテラル方向の位置ずれを示す図である。
【図１４】ステップモータのステップ位置と、中間転写ベルトが１回転する間の位置ずれ量の最大値との関係を示すグラフである。
【図１５】実施例２の画像形成装置が実行する第２の中間転写ベルト位置調整モードのフローチャートを示す図である。
【図１６】図１５に示すフローチャート実行時における、中間転写ベルトのラテラル方向の位置ずれを示す図である。
【符号の説明】
１ 中間転写ベルト
１ａ エッジ
２ 駆動ロール
３ ステアリングロール
３ａ，１３ｅ，２２ｂ 他端
３ｂ，１３ｄ，２２ａ 一端
４ バックアップロール
５，６，７ アイドラーロール
８，９，１０，１１ 画像形成ユニット
８ａ，９ａ，１０ａ，１１ａ 感光体ドラム
８ｂ，９ｂ，１０ｂ，１１ｂ ラスタ走査器
８ｃ，９ｃ，１０ｃ，１１ｃ 帯電器
８ｄ，９ｄ，１０ｄ，１１ｄ 現像器
８ｅ，９ｅ，１３ｅ，１１ｅ 一次転写ロール
８ｆ，９ｆ，１３ｆ，１１ｆ クリーナ
１２ ベルトホームセンサ
１３ エッジセンサ
１３ｂ 接触子
１３ｃ，２４ 支軸
１３ｆ 変位センサ
１３ｇ ＬＥＤ
１３ｈ 光量センサ
１４ 用紙
１５ ピックアップロール
１６ ロール対
１７ 二次転写ロール
１８ 用紙搬送系
１９ 定着器
２０ ステアリング制御部
２０ａ コントローラ
２０ｂ 補償器
２０ｃ ステップモータドライバ
２０ｄ Ａ／Ｄ変換器
２０ｅ 演算部
２０ｆ 記憶部
２１ ステップモータ
２２ ステアリングアーム
２３ 偏心カム
２５ ステアリングモジュール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a belt conveyance device and an image forming apparatus.
[0002]
[Prior art]
In recent years, speeding up and downsizing of image forming apparatuses are desired, and a belt is attached to a toner carrier (for example, an intermediate transfer member or a photoreceptor) that carries a toner image or a paper carrier that carries a paper. There is an increasing demand for the image forming apparatus used. In an image forming apparatus using a belt, it is extremely important to suppress belt walking (meandering) in order to improve image quality. As a method for suppressing the walk of the belt, for example, the position in the width direction of the belt is detected by detecting the position in the width direction of the belt and controlling the tilt angle of the steering roll in accordance with the detected position of the belt. A steering system to be controlled can be considered. This steering system is a system that requires less force applied to the belt than the system in which the belt is guided by belt ribs or edge guides, and is suitable for suppressing the belt walk. In this method, the edge position of the belt in the belt width direction is detected by an edge sensor, and the edge position detected by the edge sensor is compared with the shape (edge profile) of the belt edge stored in advance, and the comparison result Based on the above, the positional deviation in the belt width direction is corrected.
[0003]
[Problems to be solved by the invention]
In this method, when comparing the edge position detected by the edge sensor and the edge profile of the belt stored in advance, the phase between the edge position detected by the edge sensor and the edge profile of the belt stored in advance. In order to prevent misalignment, a mark is usually provided at a predetermined position on the front or back surface of the belt, and at the timing when the mark is detected, the edge position detected by the edge sensor is sampled and compared with a pre-stored edge profile. Yes. Therefore, it cannot be compared with the edge profile after the belt is activated until the belt mark is detected. Here, for example, it is conceivable that the inclination angle of the steering roll is fixed to a predetermined angle after the belt is activated until the mark of the belt is detected. The predetermined angle is determined by the image forming apparatus. The angle is not necessarily appropriate for the usage environment. Therefore, a method of calculating the optimum tilt angle of the steering roll and fixing the tilt angle of the steering roll to the calculated tilt angle from when the belt is started until the belt mark is detected can be considered. . In this method, before the belt is newly driven, the optimum tilt angle of the steering roll when the belt is newly driven is calculated based on the inclination angle of the steering roll when the belt was last driven. . However, the belt has been stopped for a long time, or there have been environmental changes such as belt replacement or change of the installation location of the image forming apparatus. If it is larger than the positional deviation at the time of driving, when the belt starts to travel, there is a possibility that the positional deviation of the belt once increases immediately after the belt travels. At this time, if the positional deviation of the belt immediately after running the belt becomes extremely large, the belt position cannot be controlled, or in the worst case, the belt contacts the frame of the image forming apparatus main body. The belt may be damaged.
[0004]
In the steering method in which the position in the width direction of the belt is controlled by detecting the position in the width direction of the belt with an edge sensor and controlling the tilt angle of the steering roll in accordance with the detected position of the belt, In order to control the tilt angle of the roll, for example, a steering motor for driving the steering roll is prepared, and forward / reverse rotation is performed to forward / reverse the steering motor based on the position detected by the edge sensor and the control gain. It is conceivable to calculate the quantity S. For example, when a step motor is used as the steering motor, the forward / reverse rotation amount S needs to be obtained as an integer value. Here, when the resolution of the step motor is high (the number of steps of the motor is large), the step angle of the step motor can be set finely, and the belt position can be controlled with high accuracy.
[0005]
However, when a step motor with low resolution is used, the amount of change in the rotation angle of the motor when the motor rotates by one step is larger than the amount of change in the rotation angle for one step of the high-resolution step motor. Therefore, even in a low-resolution motor, if the forward / reverse rotation amount S for forward / reverse rotation of the motor is calculated using the same control gain as in the case of using a high-resolution motor, the amount of change in the rotation angle of the motor is consequently obtained. There is a problem that the position of the belt cannot be controlled well because it becomes large.
[0006]
As a countermeasure to this problem, it is conceivable to set the control gain to a small value when using a step motor with a low resolution. However, if the difference between the position detected by the edge sensor and the edge profile is very small, the amount of forward / reverse rotation of the motor S may be calculated as zero. That is, when the belt position deviation is very small, the change amount of the rotation angle of the step motor becomes zero, and there is a problem that the belt position cannot be controlled well.
[0007]
Therefore, as a method for controlling the position of the belt with high accuracy, there are a method using a high-resolution step motor (a micro-step type step motor) and a method of increasing the resolution of a low-resolution step motor by using a reduction gear. Though conceivable, the method using a high-resolution step motor has a problem that the cost is high because the control method of the step motor is complicated. On the other hand, in the method using a speed reducer, the accuracy of the speed reducer becomes a problem, and it is difficult to control the rotation angle of the step motor with high precision. There is a problem that the image to be easily deteriorated.
[0008]
In view of the above circumstances, an object of the present invention is to provide a belt conveyance device in which an increase in belt positional deviation is suppressed, and an image forming apparatus to which the belt conveyance device is applied.
[0009]
Another object of the present invention is to provide a belt conveyance device that can control the position of the belt with high accuracy at low cost, and an image forming apparatus to which the belt conveyance device is applied.
[0010]
[Means for Solving the Problems]
The first belt conveying device of the present invention comprises:
A belt that moves along a predetermined path,
A displacement detection means for detecting a displacement in the width direction of the belt from a predetermined reference movement path;
A steering member that corrects positional deviation in the width direction of the belt by changing the steering control position in contact with the belt;
Steering control means for changing the steering control position of the steering member stepwise with a predetermined first resolution;
Based on the positional deviation of the belt detected by the positional deviation detection means, a steering control position change amount for correcting the positional deviation in the width direction of the belt from the current steering control position of the steering roll, High-resolution change amount calculating means for calculating with a second resolution that is higher than the first resolution;
Steering control position calculating means for calculating a new steering control position based on the current steering control position of the steering member and the steering control position change amount calculated by the high resolution change amount calculating means; and
Based on the current steering control position of the steering member and the new steering control position calculated by the steering control position calculation means, the amount of change in the steering control position of the steering member is calculated with the first resolution. With low-resolution change amount calculation means,
The steering control means changes the steering control position of the steering member by the steering control position change amount calculated by the low resolution change amount calculation means.
[0011]
Here, in the first belt conveyance device of the present invention, the steering control means has a step motor, and the steering control position of the steering member is changed stepwise by rotating the step motor. It is preferable that
[0012]
According to another aspect of the present invention, there is provided an image forming apparatus for forming an image on a sheet by forming a toner image and finally transferring and fixing the toner image on a predetermined sheet.
A belt that moves along a predetermined path employed in a process of forming or conveying a toner image;
A displacement detection means for detecting a displacement in the width direction of the belt from a predetermined reference movement path;
A steering member that corrects positional deviation in the width direction of the belt by changing the steering control position in contact with the belt;
Steering control means for changing the steering control position of the steering member stepwise with a predetermined first resolution;
Based on the positional deviation of the belt detected by the positional deviation detection means, a steering control position change amount for correcting the positional deviation in the width direction of the belt from the current steering control position of the steering roll, High-resolution change amount calculating means for calculating with a second resolution that is higher than the first resolution;
Steering control position calculating means for calculating a new steering control position based on the current steering control position of the steering member and the steering control position change amount calculated by the high resolution change amount calculating means; and
Based on the current steering control position of the steering member and the new steering control position calculated by the steering control position calculation means, the amount of change in the steering control position of the steering member is calculated with the first resolution. With low-resolution change amount calculation means,
The steering control means changes the steering control position of the steering member by the steering control position change amount calculated by the low resolution change amount calculation means.
[0013]
The second belt conveying device of the present invention is
A belt that moves along a predetermined path,
An edge sensor for detecting an edge position of the belt in a direction intersecting the moving path of the belt;
A steering member that controls a moving path of the belt by changing a steering control position in contact with the belt;
Based on the edge position of the belt detected by the edge sensor and the control gain that can be freely changed, the positional deviation in the width direction of the belt from the current steering control position of the steering member is corrected. First change amount calculating means for obtaining a steering control position change amount for
Steering control means for changing the steering control position of the steering member by the steering control position change amount calculated by the first change amount calculation means;
The first change amount calculating means is characterized in that the control gain is changed in accordance with an edge position deviation amount from a predetermined reference position of the edge position detected by the edge sensor.
[0014]
Here, in the second belt conveyance device of the present invention, the first change amount calculation means has a control gain when the edge position deviation amount is within the predetermined range, compared with the case where the edge position deviation amount is out of the predetermined range. Is preferably changed to a small value including 0.
[0015]
Further, in the second belt conveyance device of the present invention, the belt is an endless belt, and moves cyclically along a predetermined circulation movement path.
Storage means for storing the belt edge profile;
Detecting means for detecting that a predetermined position of the belt has passed a predetermined position on the circulation movement path of the belt;
By correcting the edge position of the belt detected by the edge sensor with reference to the edge profile stored in the storage means, the positional deviation of the belt in the width direction from a predetermined reference movement path is calculated. And a positional deviation in the width direction of the belt from the current steering control position of the steering member based on the positional deviation in the width direction of the belt calculated by the positional deviation calculation means. A second change amount calculating means for obtaining a steering control position change amount of
The steering control means calculates the steering control position of the steering member from the first change amount calculating means until the detection by the detecting means after the belt starts moving. It is preferable that the position change amount is changed, and after the detection by the detection means, the steering control position change amount calculated by the second change amount calculation means is changed.
[0016]
The second image forming apparatus of the present invention is an image forming apparatus for forming an image on a sheet by forming a toner image and finally transferring and fixing the toner image on a predetermined sheet.
A belt that moves along a predetermined path employed in a process of forming or conveying a toner image;
An edge sensor for detecting an edge position of the belt in a direction intersecting the moving path of the belt;
A steering member that controls a moving path of the belt by changing a steering control position in contact with the belt;
Based on the edge position of the belt detected by the edge sensor and the control gain that can be freely changed, the positional deviation in the width direction of the belt from the current steering control position of the steering member is corrected. First change amount calculating means for obtaining a steering control position change amount for
Steering control means for changing the steering control position of the steering member by the steering control position change amount calculated by the first change amount calculation means;
The first change amount calculating means is characterized in that the control gain is changed in accordance with an edge position deviation amount from a predetermined reference position of the edge position detected by the edge sensor.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0018]
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention to which an embodiment of a belt conveying apparatus of the present invention is applied.
[0019]
The image forming apparatus includes an intermediate transfer belt 1. The intermediate transfer belt 1 is stretched with a predetermined tension by a drive roll 2, a steering roll 3, a backup roll 4, and idler rolls 5, 6, and 7. By this drive roll 2, the intermediate transfer belt 1 circulates and moves in an arrow direction (hereinafter referred to as process direction) P. The steering roll 3 is a roll for adjusting the position of the intermediate transfer belt 1 in the width direction (the direction perpendicular to the paper surface shown in FIG. 1; hereinafter referred to as the lateral direction).
[0020]
The image forming apparatus also includes four image forming units 8, 9, 10, and 11 corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). These four image forming units 8, 9, 10, 11 are arranged on the moving path of the intermediate transfer belt 1 so as to line up in the process direction P on the downstream side of the drive roll 2 and on the upstream side of the idler roll 5. ing.
[0021]
Each of the image forming units 8, 9, 10, and 11 is provided with photosensitive drums 8a, 9a, 10a, and 11a on which toner images are formed. Each of the photosensitive drums 8a, 9a, 10a, and 11a is supported by an image forming apparatus main body frame (not shown) so as to be rotatable in the direction of arrow D through the primary transfer position T1. The toner images formed on the photosensitive drums 8a, 9a, 10a, and 11a are transferred to the intermediate transfer belt 1 at the primary transfer position T1. Further, each of the image forming units 8, 9, 10, and 11 has raster scanners 8b, 9b, 10b, and 11b for exposing and scanning the surfaces of the photosensitive drums 8a, 9a, 10a, and 11a with a laser beam or the like. ing. Further, around each photosensitive drum 8a, 9a, 10a, and 11a, cleaners 8f, 9f, 10f, and 11f, chargers 8c, 9c, 10c, and 11c, and developing units 8d and 9d are arranged in the drum rotation direction D. , 10d, and 11d are disposed in order, and the primary transfer rolls 8e, 9e, 10e, and 11e are disposed between the photosensitive drums 8a, 9a, 10a, and 11a with the intermediate transfer belt 1 interposed therebetween. ing.
[0022]
Further, a mark (not shown) provided on the back surface of the intermediate transfer belt 1 is detected on the moving path of the intermediate transfer belt 1 downstream of the drive roll 2 and upstream of the primary transfer roll 8e. A belt home sensor 12 is disposed. Further, an edge sensor 13 is disposed on the moving path of the intermediate transfer belt 1 on the downstream side of the idler roll 5 and the upstream side of the steering roll 3. This edge sensor 13 relates to the edge of the intermediate transfer belt 1 with respect to the lateral direction R of the intermediate transfer belt 1 (perpendicular to the paper surface shown in FIG. 1; see FIGS. 2 and 3 described later). The position of the edge 1a shown in FIG. Signals output from the belt home sensor 12 and the edge sensor 13 are input to a steering control unit 20 (see FIG. 4 described later).
[0023]
FIG. 2 is a schematic configuration diagram illustrating a contact sensor which is an example of an edge sensor.
[0024]
The edge sensor 13 includes a contact 13b, and the contact 13b is supported so as to be rotatable in the Z direction around a support shaft 13c provided at an intermediate portion thereof. One end 13d of the contact 13b is kept in pressure contact with one edge 1a of the intermediate transfer belt 1 by a spring 13a with a pressure contact force of about 0.1N. A displacement sensor 13f that detects the displacement of the contact 13b in the Z direction is disposed at a position facing the other end 13e of the contact 13b.
[0025]
When the intermediate transfer belt 1 moves in the process direction P (perpendicular to the paper surface shown in FIG. 2), the intermediate transfer belt 1 meanders (movement in the lateral direction R) and the shape of the edge 1a itself of the intermediate transfer belt 1 As a result, the contact 13b of the edge sensor 13 is displaced in the Z direction around the support shaft 13c. At this time, the displacement amount of the contact 13b of the edge sensor 13 in the Z direction changes according to the displacement amount of the edge 1a of the intermediate transfer belt 1 in the lateral direction R. The signal output from the displacement sensor 13f fluctuates in accordance with the change in the amount of displacement, whereby the position in the lateral direction R of the edge 1a of the intermediate transfer belt 1 is continuously detected.
[0026]
FIG. 3 is a schematic configuration diagram showing a non-contact type sensor which is another example of the edge sensor.
[0027]
The edge sensor 13 is an LED (Light Emitting Diode) 13g with the edge 1a of the intermediate transfer belt 1 interposed therebetween, and a light amount sensor that detects the amount of light emitted from the LED 13g and passing beside the edge 1a of the intermediate transfer belt 1. 13h is arranged. When the intermediate transfer belt 1 moves in the process direction P, the edge sensor 13 is emitted from the LED 13g due to a change in the lateral direction R of the intermediate transfer belt 1 and the shape of the edge 1a of the intermediate transfer belt 1 itself. The amount of light passing through the side of the edge 1a of the belt 1 changes. Therefore, the position in the lateral direction R of the edge 1a of the intermediate transfer belt 1 is continuously detected.
[0028]
A signal detected by each edge sensor 13 is input to a steering control unit 20 described later. The steering control unit 20 changes the eccentric amount of the eccentric cam 23 (see FIG. 4 described later) based on the position in the lateral direction R of the edge 1a of the intermediate transfer belt 1 detected by the edge sensor 13, thereby the steering roll 3 is adjusted. By adjusting the inclination angle of the steering roll 3, the lateral displacement of the intermediate transfer belt 1 is corrected. The manner in which the lateral displacement of the intermediate transfer belt 1 is corrected will be described in detail later.
[0029]
Returning to FIG. 1, the description will be continued.
[0030]
In this image forming apparatus, the paper 14 on which an image is to be formed is stored in a paper feed cassette (not shown) and fed out one by one by a pickup roll 15 provided on the paper feed side of the paper feed cassette. The fed paper 14 is conveyed to the secondary transfer position T2 by following a path indicated by a broken line in the figure by a predetermined number of roll pairs 16. At the secondary transfer position T2, a secondary transfer roll 17 that is in contact with the intermediate transfer belt 1 is provided. The secondary transfer roll 17 is a roll that transfers the toner image transferred to the intermediate transfer belt 1 to the paper 14.
[0031]
The fixing device 19 fixes the toner image transferred to the paper 14 to the paper 14.
[0032]
Next, how the image forming apparatus having the above configuration corrects meandering of the intermediate transfer belt 1 will be described with reference to FIG.
[0033]
FIG. 4 is a diagram specifically showing a path of a signal detected by the edge sensor in the image forming apparatus shown in FIG.
[0034]
The image forming apparatus includes a steering arm 22. The steering arm 22 is rotatably supported at its intermediate portion by a support shaft 24. One end 22a of the steering arm 22 is rotatably connected to one end of the steering roll 3, and the other end 22b is press-contacted with an eccentric cam 23 fixed to the rotating shaft of the step motor 21. The step motor 21 is a motor whose rotation angle changes stepwise.
[0035]
The image forming apparatus also includes a steering control unit 20 that controls driving of the step motor 21.
[0036]
When the running of the intermediate transfer belt 1 is started, the edge sensor 13 detects the position of the edge of the intermediate transfer belt 1 in the lateral direction and outputs a belt edge signal E (t) (t; time) indicating the position. Output toward the steering control unit 20. The belt home sensor 12 detects the mark when the mark on the back surface of the intermediate transfer belt 1 passes over the belt home sensor 12 as the intermediate transfer belt 1 travels, and the mark is detected. Is output to the steering control unit 20. When the belt home signal output from the belt home sensor 12 is input to the steering control unit 20, the steering control unit 20 continuously samples the belt edge signal output from the edge sensor 13, and the sampled belt edge. Based on the signal, a control signal representing the rotation angle of the step motor 21 is output to the step motor 21. The step motor 21 rotates based on the control signal, the inclination angle of the steering roll 3 is controlled according to the rotation amount, and the meandering correction of the intermediate transfer belt 1 is performed.
[0037]
FIG. 5 is an explanatory diagram showing how the meandering of the intermediate transfer belt is corrected.
[0038]
5 (a), 5 (b), and 5 (c), sequentially from the left, a front view of the steering roll 3, a front view of the steering arm 22, and a side view of the step motor 21 to which the eccentric cam 23 is attached. It is shown.
[0039]
FIG. 5A shows a state in which the step motor 21 is stopped at a predetermined rotation angle, and the steering roll 3 is held substantially horizontal (the inclination is substantially zero) corresponding to the stop angle. The steering roll 3 is supported in a cantilever manner in which one end 3 b is pivoted (fixed) and the other end 3 a is movable by a steering arm 22.
[0040]
In the following, the rotation position of the step motor 21 corresponding to the rotation angle that can be taken by the step motor 21 is referred to as a step position, and each step position is determined from the reference step position when a certain step position is a reference step position. It is represented by the number of steps required to change to each step position. A change in the step position when the step motor 21 changes from the current step position to a new step position is referred to as a step position change amount.
[0041]
When the step motor 21 rotates from the state shown in FIG. 5A to change the step position and the eccentric cam 23 rotates counterclockwise as shown in FIG. 5B, the eccentric cam 23 is eccentric. The steering arm 22 rotates in the θ1 direction according to the position. As a result, the one end 3a of the steering roll 3 moves upward, and the inclination angle of the steering roll 3 changes by an angle corresponding to the step position change amount of the step motor 21. When one end 3 a of the steering roll 3 moves upward, the intermediate transfer belt 1 moves to the one end 3 a side of the steering roll 3.
[0042]
On the other hand, as shown in FIG. 5 (c), when the eccentric cam 23 rotates clockwise, the steering arm 22 rotates in the θ2 direction according to the eccentric position of the eccentric cam 23. The one end 3 a of the steering roll 3 is pushed down by the steering arm 22. At this time, the intermediate transfer belt 1 moves to the other end 3 b side opposite to the one end 3 a of the steering roll 3.
[0043]
In this image forming apparatus, as described above, the steering control unit 20 drives the step motor 21 based on the belt edge signal output from the edge sensor 13, whereby the tilt angle of the steering roll 3 is controlled and the intermediate transfer is performed. The meandering of belt 1 is corrected. In order to correct this meandering, a system for detecting the edge position of the intermediate transfer belt 1 with high accuracy and finely setting the tilt angle of the steering roll 3 based on the detection result is necessary. The image forming apparatus of the form includes the system. The system will be described below.
[0044]
FIG. 6 is a configuration diagram showing an example of the system.
[0045]
The controller 20a shown in FIG. 6 constitutes a part of the steering control unit 20 described above. The controller 20a includes a compensator 20b, a step motor driver 20c, an A / D converter 20d, a calculation unit 20e, and a storage unit 20f.
[0046]
The steering module 25 is a mechanical mechanism including the steering roll 3, the steering arm 22, the eccentric cam 23, and the support shaft 24. The belt module 30 stretches the intermediate transfer belt 1 and the intermediate transfer belt 1 described above. This is a mechanical mechanism including a roll such as a drive roll 2 to be provided.
[0047]
The A / D converter 20d included in the controller 20a converts the analog belt edge signal E (t) output from the edge sensor 13 into a digital signal and gives the digitized edge signal to the arithmetic unit 20e. . The computing unit 20e calculates an edge position e (r, n) from the digitized belt edge signal E (t) given from the A / D converter 20d. Hereinafter, r represents the number of rotations of the intermediate transfer belt 1 since the belt home signal was first detected, and n represents an address corresponding to a portion of the intermediate transfer belt 1 related to the process direction P. Here, n is an integer from 0 to 50. The storage unit 20f stores an edge profile p (n) representing the shape of the edge of the intermediate transfer belt 1 in a table format. This edge profile is an edge position measured by running the intermediate transfer belt 1 with the steering roll tilt angle fixed at a predetermined angle.
[0048]
Further, the compensator 20b included in the controller 20a is based on a positional deviation amount (hereinafter referred to as a walk amount) W (r, n) of the intermediate transfer belt 1 itself in the lateral direction from the reference position. The step position change amount S (r, n) of the step motor 21 necessary for correcting the positional deviation of the step motor 21 is calculated, and a control signal representing the step position change amount S (r, n) is output to the step motor driver 20c. To do. The step motor driver 20c drives the step motor 21 in accordance with the control signal output from the compensator 20b, and the tilt angle of the steering roll 3 constituting the steering module 25 is controlled by driving the step motor 21. The
[0049]
In the system configured as described above, the belt edge signal E (t) obtained by the detection of the edge sensor 13 is converted into a digital signal by the A / D converter 20d, and the rotational speed r, the address is converted by the arithmetic unit 20e. An edge position e (r, n) at n is generated.
[0050]
Next, using the edge profile p (n) stored in the storage unit 20f, the difference between the edge position e (r, n) acquired as described above and the corresponding edge profile p (n) is calculated. To do. As a result, the edge profile p (n) buried in the edge position e (r, n) is removed from the edge position e (r, n), and data representing the lateral position of the intermediate transfer belt 1 itself is obtained. Calculated. By calculating the difference between the calculated data and the reference position data REF representing the reference position of the intermediate transfer belt 1, the walk amount W (r, n) is obtained.
[0051]
The walk amount W (r, n) is compensated by the compensator 20b, and the step position change amount S (r, n) is calculated. The motor driver 20c changes the step position of the step motor 21 by the calculated step position change amount S (r, n). When the step position of the step motor 21 changes, the inclination angle of the steering roll 3 constituting the steering module 25 changes corresponding to the change in the step position. Thereby, the position of the intermediate transfer belt 1 in the lateral direction is controlled, and the meandering of the intermediate transfer belt 1 is suppressed.
[0052]
The image forming apparatus executes an image forming mode in which an image is formed on the paper 14 while correcting the meandering of the intermediate transfer belt 1 as described above. The image forming mode will be described below.
[0053]
When the image forming mode is executed, exposure light is emitted from the raster scanners 8b, 9b, 10b, and 11b (see FIG. 1) based on the image signal based on the belt home signal output from the belt home sensor 12. The electrostatic latent images are written on the surfaces of the photosensitive drums 8a, 9a, 10a, and 11a, respectively. Thereafter, the electrostatic latent images formed on the photosensitive drums 8a, 9a, 10a, and 11a are developed by the developing devices 8d, 9d, 10d, and 11d, and the photosensitive drums 8a, 9a, 10a, and 11a are respectively developed. In addition, yellow, magenta, cyan, and black toner images are formed. The toner images formed on the respective photosensitive drums 8a, 9a, 10a, and 11a are sequentially transferred and transferred onto the intermediate transfer belt 1 (primary transfer) at the primary transfer position T1, whereby the color toner is transferred onto the intermediate transfer belt 1. An image is formed. Thereafter, the color toner image is conveyed to the secondary transfer position T2 by the traveling of the intermediate transfer belt 1, and the paper 14 is also conveyed to the secondary transfer position T2. The color toner image conveyed to the secondary transfer position T2 is collectively transferred (secondary transfer) onto the paper 14 by the secondary transfer roll 17 disposed at the secondary transfer position T2. The sheet 14 on which the color toner image has been transferred is sent to a fixing unit 19 by a sheet conveying system 18 and subjected to fixing processing (heating, pressing, etc.) by the fixing unit 19, and the color transferred to the sheet 14 is transferred. The toner image is fixed on the paper 14. The paper 14 that has been subjected to fixing processing (heating, pressing, etc.) is discharged to a tray (not shown).
[0054]
The image forming apparatus configured as described above has two modes as the intermediate transfer belt position adjustment mode for adjusting the position of the intermediate transfer belt 1. One is a first intermediate transfer belt position adjustment mode which is performed after the rotation of the intermediate transfer belt 1 is started until the belt home signal is detected for the first time. The other is a belt home. This is a second intermediate transfer belt position adjustment mode performed after the signal is detected.
[0055]
【Example】
Examples will be described below.
[0056]
Two types of step motors were prepared as the step motor 21 described above. One is 100 divisions in which the rotation angle of the motor is changed stepwise at intervals of an angle R = 3.6 degrees corresponding to one division when 360 degrees are divided into 100 (hereinafter, this division number is referred to as the resolution of the step motor). The other is a step motor of 1000 divisions that changes the rotation angle of the motor stepwise at an interval of an angle R = 0.36 degrees corresponding to one division when 360 degrees are divided into 1000 divisions. Step motor.
[0057]
As the image forming apparatus of Example 1, an image forming apparatus provided with a 1000-division step motor 21 was prepared. In the image forming apparatus according to the first exemplary embodiment, only the first intermediate transfer belt position adjustment mode of the first and second intermediate transfer belt position adjustment modes is executed to adjust the position of the intermediate transfer belt 1. Further, an image forming apparatus provided with a 100-division step motor 21 was prepared as an image forming apparatus of Example 2. In the image forming apparatus according to the second exemplary embodiment, only the second intermediate transfer belt position adjustment mode of the first and second intermediate transfer belt position adjustment modes is executed to adjust the position of the intermediate transfer belt 1.
[0058]
Hereinafter, Examples 1 and 2 will be described in order.
[0059]
Example 1
In the image forming apparatus according to the first embodiment, when a control signal output from the steering control unit 20 is input to the step motor 21, the step position of the step motor 21 is as follows from the current step position (1 ) Changes by the step position change amount S obtained by the equation.
[0060]
[Expression 1]

[0061]
Here, K is a control gain, and W is a walk amount calculated based on the edge position e (r, n) calculated by the calculation unit 20e shown in FIG. Further, KW is a value calculated to the first decimal place, and int represents that the KW calculated to the first decimal place is converted to an integer.
[0062]
FIG. 7 is a flowchart illustrating a first intermediate transfer belt position adjustment mode executed to correct the positional deviation of the intermediate transfer belt 1 included in the image forming apparatus according to the first exemplary embodiment. FIG. FIG. 6 is a diagram illustrating a lateral displacement of the intermediate transfer belt during execution of the flowchart.
[0063]
In the image forming apparatus according to the first exemplary embodiment, when the execution of the first intermediate transfer belt position adjustment mode is started, the rotation of the intermediate transfer belt 1 is started, and based on the belt edge signal detected by the edge sensor 13, An edge position e (r, n) is calculated by the calculation unit 20e shown in FIG. 6 (step S1). Here, when the belt home signal is first detected after the rotation of the intermediate transfer belt 1 is started, the number of rotations of the intermediate transfer belt 1 is 0, that is, the first rotation of the intermediate transfer belt 1 is started. At the time point, the rotation speed r is set to −1 until the belt home signal is detected after the rotation of the intermediate transfer belt 1 is started.
[0064]
When the edge position e (r, n) is obtained in step S1, the process proceeds to step S2, and the absolute value | e (r, n) | of the edge position e (r, n) detected in step S1 is the reference value. It is determined whether or not it is smaller than E0. Here, the reference value E0 is the maximum value of the edge profile of the intermediate transfer belt 1 obtained by measuring the edge position of the intermediate transfer belt 1 in advance before executing the first intermediate transfer belt position adjustment mode. (Here, 0.4 mm). Note that, when the intermediate transfer belt 1 is replaced before the execution of the first intermediate transfer belt position adjustment mode, the value of E0 is different before and after the execution of the first intermediate transfer belt position adjustment mode. In this case, the value of E0 may be changed to a value corresponding to the replaced intermediate transfer belt 1.
[0065]
If it is determined in step S2 that | e (r, n) | <E0 (= 0.4 mm), the control gain K = 0 shown in the equation (1) is set, and the step position change amount S of the step motor 21 is set. (That is, the inclination angle of the steering roll 3 is fixed by fixing the step position of the step motor 21), the process proceeds to step S3, and whether the belt home signal is output from the belt home sensor 12 or not. Is judged. If it is determined that the belt home signal is not output, the process proceeds to step S1 again. As long as it is determined that | e (r, n) | <E0 in step S2, the step position change amount S of the step motor 21 is continued. The loop of step S1 to step S3 is repeatedly executed until the belt home signal is output in step S3 while = 0.
[0066]
FIG. 8A shows the relationship between the rotational speed of the intermediate transfer belt 1 and the positional deviation of the intermediate transfer belt 1. The broken line indicates the edge position of the intermediate transfer belt 1, and the solid line indicates the amount of positional deviation (walk amount) from the reference position of the intermediate transfer belt 1 itself calculated by removing the edge profile from the edge position.
[0067]
Here, since the edge position is about 1.0 mm when the intermediate transfer belt 1 starts running (r = −1), the edge position e (r, n) detected in step S1 is the reference in step S2. It is determined that the value is larger than the value E0 (= 0.4 mm), that is, | e (r, n) | ≧ E0. If it is determined that | e (r, n) | ≧ E0, the process proceeds to step S4, and the control gain K shown in the equation (1) is calculated using the following equation (2).
[0068]
[Expression 2]

[0069]
K0: Constant
When the control gain K is calculated, the process proceeds to step S5, where K calculated using the expression (2) is substituted for K in the above expression (1), and e ( r, n) is substituted to calculate the step position change amount S, the step position of the step motor 21 is changed by the calculated step position change amount S, and the tilt angle of the steering roll 3 is adjusted.
[0070]
That is, in step S2, the image forming apparatus according to the first embodiment determines whether the edge position e (r, n) is in a range of −0.4 mm <e (r, n) <0.4 mm. When the edge position e (r, n) falls within the range, the control gain K is set to 0 to fix the tilt angle of the steering roll 3, and the position of the intermediate transfer belt 1 is not corrected. On the other hand, when the edge position e (r, n) is out of the range, the control gain K expressed by the equation (2) is changed according to the value of e (r, n) to tilt the steering roll 3. The angle is controlled to positively correct the position of the intermediate transfer belt 1. That is, in the image forming apparatus according to the first exemplary embodiment, when the edge position e (r, n) is larger than 0.4 mm, it is determined that the walk amount of the intermediate transfer belt 1 is large, and the position of the intermediate transfer belt 1 is determined. On the other hand, when the correction is positively performed and the edge position e (r, n) is smaller than 0.4 mm, it is determined that the walk amount of the intermediate transfer belt 1 is not so large, and the intermediate transfer belt 1 The position is not corrected.
[0071]
When the position of the intermediate transfer belt 1 is corrected in this way, the step position change amount S increases as the walk amount of the intermediate transfer belt 1 increases. For this reason, the inclination angle of the steering roll 3 is increased, and the correction amount for the positional deviation of the intermediate transfer belt 1 is increased. That is, when the walk amount of the intermediate transfer belt 1 is large, the correction amount with respect to the positional deviation of the intermediate transfer belt 1 is large. On the other hand, when the walk amount of the intermediate transfer belt 1 is small, the positional deviation of the intermediate transfer belt 1 is large. The correction amount is set small, and the positional deviation of the intermediate transfer belt 1 can be effectively corrected according to the walk amount of the intermediate transfer belt 1.
[0072]
When the step position change amount S is calculated in step S5, the process proceeds to step S3, and it is determined whether or not the belt home signal is output from the belt home sensor 12. If it is determined that the belt home signal is not output, the process proceeds to step S1 again. As long as it is determined that | e (r, n) | ≧ E0 in step S2, the belt home signal is output in step S3. Until then, the loop of steps S1, S2, S4, S5 and S3 is repeatedly executed. By executing this loop, the positional deviation of the intermediate transfer belt 1 is reduced. Here, as shown in FIG. 8A, when it is determined in step S3 that the belt home signal has been output (belt rotation speed r = In 0), the walk amount of the intermediate transfer belt 1 is about 0.4 mm.
[0073]
If it is determined in step S3 that the belt home signal has been output, the rotational speed r of the intermediate transfer belt 1 is set to 0 and the address n of the intermediate transfer belt 1 is set to 0, and the process proceeds to step S6, where the rotational speed r = 0 and the address is set. An edge position e (0, 0) at n = 0 is calculated. When the edge position e (0, 0) is calculated, the process proceeds to step S7, and based on the calculated edge position e (0, 0), the intermediate transfer belt 1 at the rotation speed r = 0 and the address n = 0. The walk amount W (0, 0) is calculated. The walk amount W (0, 0) is calculated by setting r = 0 and n = 0 in the walk amount W (r, n) represented by the following equation (3).
[0074]
[Equation 3]

[0075]
W (r, n) is a walk amount of the intermediate transfer belt 1 at the rotation speed r and the address n. Therefore, W (0, 0) is the walk amount at the rotation speed r = 0 and the address n = 0. This W (0,0) is the difference between the edge position e (0,0) and p (0) at the address n = 0 in the edge profile p (n) measured in advance. By calculating, the walk amount W (0, 0) is calculated. When the walk amount W (0, 0) is calculated, the process proceeds to step S8, and using equation (2), K = K0 · (e (0, 0) − at the rotation speed r = 0 and the address n = 0. E0) is calculated, and the calculated K0 · (e (0,0) −E0) is substituted for K in the above-described equation (1), and the amount of walk calculated in step S7 is substituted for W. W (0, 0) is substituted, and the step position change amount S (0, 0) at the rotation speed r = 0 and the address n = 0 is calculated. When the step position change amount S (0, 0) is calculated, the step motor 21 rotates the number of steps corresponding to the calculated step position change amount S (0, 0) to change the step position, The inclination angle of the steering roll 3 is adjusted.
[0076]
When the step position change amount S (0, 0) is calculated in step S8, the process proceeds to step S9, where it is determined whether or not an end signal for ending the running of the intermediate transfer belt 1 is input. If it is determined that the end signal is not input, the process proceeds to step S10, and it is determined whether or not the address n is the maximum value N (here, 50). Since the address n = 0 at this time, it is determined that it is not the maximum value N (= 50). In step S11, the address n is incremented to n = 1, and the process returns to step S6. Returning to step S6, the edge position e (0, 1) at the rotation speed r = 0 of the intermediate transfer belt 1 and the address n = 1 of the intermediate transfer belt 1 is detected, and in steps S7 and S8, respectively. The walk amount W (0, 1) and the step position change amount S (0, 1) at the rotation speed r = 0 and the address n = 1 are calculated. The step motor 21 rotates by the number of steps corresponding to the calculated step position change amount S (0, 1), and thereby the inclination angle of the steering roll 3 is adjusted. Thereafter, if it is determined in step S9 that an end signal for ending the running of the intermediate transfer belt 1 has not been input, the address n = 1 at this time, so that the address n is determined in step S10. It is determined that the value is not the maximum value N (= 50), the process proceeds to step S11, the address n is incremented to n = 2, and the process returns to step S6 again.
[0077]
Similarly, if it is determined in step S9 that the end signal has not been input, steps S6 to S11 are performed until it is determined in step S10 that the address n is the maximum value N (= 50). This loop is repeatedly executed. By repeatedly executing this loop, the edge position e (0) in the combination of the rotational speed r = 0 of the intermediate transfer belt 1 and the addresses n = 0, 1, 2,. , 0), e (0, 1), e (0, 2),..., E (0, 50) are detected, and the step motor 21 detects the edge positions e (0, 0), e (0, 50). 1), e (0, 2),..., E (0, 50), step position change amounts S (0, 0), S (0, 1), S (0, 2), .., S (0, 50) are sequentially rotated by the number of steps corresponding to each, and the position of the intermediate transfer belt 1 in the lateral direction is controlled. If it is determined in step S10 that the address n is the maximum value N (= 50), the process returns to step S3, and when the belt home signal is output, the rotational speed r of the intermediate transfer belt 1 is incremented and r = 1 By this increment, the first rotation of the intermediate transfer belt 1 is completed. As shown in FIG. 8A, when the intermediate transfer belt 1 completes one rotation, the walk amount of the intermediate transfer belt 1 is about 0.2 mm.
[0078]
Further, when r = 1 is incremented in step S3, the rotation of the intermediate transfer belt 1 enters the second rotation this time, and the loop of steps S6 to S11 is repeated and r = 1 (intermediate transfer belt). 1 at the second rotation), the step position change amounts S (1, 0), S (1, 1), S (1, 2) when the addresses n = 0, 1, 2,. ),..., S (1, 50) are obtained, and the step motor 21 detects the step position change amounts S (1, 0), S (1, 1), S (1, 2),. Rotate sequentially by the number of steps corresponding to each (1, 50). If it is determined in step S10 that the address n is the maximum value N (= 50), the process returns to step S3, and when the belt home signal is output, the rotational speed r of the intermediate transfer belt 1 is incremented and r = 2. By this increment, the second rotation of the intermediate transfer belt 1 is completed. As shown in FIG. 8A, when the intermediate transfer belt 1 completes two rotations, the walk amount of the intermediate transfer belt 1 is almost 0 mm.
[0079]
In the same manner, r is sequentially incremented, and the step motor 21 has step positions corresponding to combinations of r = 0, 1, 2, 3..., N = 0, 1, 2,. The sheet is rotated by the number of steps corresponding to the change amount S (r, n), and the position of the intermediate transfer belt 1 is controlled. As shown in FIG. 8A, it can be seen that the positional deviation of the intermediate transfer belt 1 is corrected when the intermediate transfer belt 1 has completed two rotations.
[0080]
For reference, FIG. 8B shows the relationship between the rotation speed of the intermediate transfer belt 1 and the step position change amount S (r, n) of the step motor 21. Here, the step position change amount S (r, n) is such that the step position of the step motor 21 at the address n−1 changes to the step position of the step motor 21 at the address n at the rotation speed r of the intermediate transfer belt 1. This is the amount of change in the step position. FIG. 8C shows the relationship between the rotational speed r of the intermediate transfer belt 1 and the step position of the step motor 21. Note that the step position is based on the step position of the step motor 21 when the rotational speed r = −1.
[0081]
As described above, in the image forming apparatus according to the first exemplary embodiment, the first intermediate transfer belt position adjustment mode is executed, whereby the positional deviation of the intermediate transfer belt 1 is corrected. Here, in the case of using an image forming apparatus (Comparative Example 1) which includes the step motor 21 of 1000 divisions but does not have the first intermediate transfer belt position adjustment mode, how the position of the intermediate transfer belt 1 is controlled. Explain what will be done.
[0082]
FIG. 9 is a flowchart executed to correct the misalignment of the intermediate transfer belt in the image forming apparatus of Comparative Example 1, and FIG. 10 shows the lateral misalignment of the intermediate transfer belt when the flowchart is executed. FIG.
[0083]
The only difference between the flowchart shown in FIG. 9 and the flowchart shown in FIG. 7 is that the flowchart shown in FIG. 9 does not include steps S1, S2, S4, and S5 of the flowchart shown in FIG. In executing the flowchart shown in FIG. 9, the step position of the step motor 21 is fixed at a predetermined step position from when the intermediate transfer belt 1 starts to rotate until the belt home signal is first output. Yes. Also in the image forming apparatus of Comparative Example 1, the step position change amount S of the step motor is expressed by the above-described equation (1), as in Example 1.
[0084]
FIG. 10A is a graph showing the relationship between the rotation speed of the intermediate transfer belt 1 and the edge position and the walk amount of the intermediate transfer belt. Comparing FIG. 8A and FIG. 10A, the difference Z between the walk amount at the time when the rotation of the intermediate transfer belt 1 is started (r = −1) and the largest walk amount is shown in FIG. (A) is smaller. Therefore, by executing the first intermediate transfer belt position adjustment mode, the walk amount W of the intermediate transfer belt 1 is suppressed after the belt home signal is detected after the running of the intermediate transfer belt 1 is started. You can see that
[0085]
For reference, FIG. 10B shows the relationship between the rotational speed of the intermediate transfer belt 1 and the step position change amount of the step motor, and FIG. 10C shows the rotational speed of the intermediate transfer belt 1. The relationship with the step position of a step motor is shown.
[0086]
(Example 2)
Prior to the description of the image forming apparatus of Example 2, the image forming apparatus of Comparative Example 1 having a resolution of 1000 step motors that correct the position of the intermediate transfer belt according to the flowchart shown in FIG. 9 was used. In some cases, the lateral displacement of the intermediate transfer belt after the time when the rotation of the intermediate transfer belt 1 is started and the belt home signal is first detected will be corrected.
[0087]
FIG. 11 is a diagram illustrating how the lateral displacement of the intermediate transfer belt is corrected in the image forming apparatus of Comparative Example 1 when the flowchart illustrated in FIG. 9 is executed. FIG. 11 shows an example in which the walk amount of the intermediate transfer belt at the time when the belt home signal is output is 0.2 mm.
[0088]
FIG. 11A shows the relationship between the rotation speed of the intermediate transfer belt 1 and the edge position and the walk amount of the intermediate transfer belt. FIG. 11B shows the rotation speed of the intermediate transfer belt 1 and the step of the step motor. FIG. 11C shows the relationship between the rotational speed of the intermediate transfer belt 1 and the step position of the step motor.
[0089]
From FIG. 11A, it can be seen that the positional deviation of the intermediate transfer belt 1 is corrected when the intermediate transfer belt 1 has completed two rotations.
[0090]
Next, in the image forming apparatus of Comparative Example 1, an image forming apparatus (Comparative Example 2) provided with a 100-divided step motor 21 is prepared instead of the 1000-divided step motor 21, and the image formation of Comparative Example 2 is performed. The lateral displacement of the intermediate transfer belt when using the apparatus will be described. In the image forming apparatus of Comparative Example 2, the step position change amount S of the step motor is expressed by the above-described equation (1).
[0091]
FIG. 12 is a diagram illustrating the lateral displacement of the intermediate transfer belt in the image forming apparatus of Comparative Example 2.
[0092]
Here, in the expression (1), the control is performed so that the step number change amount S (r, n) of the step motor is set to a small value with respect to the calculated walk amount W (r, n). The gain K is set to a small value.
[0093]
12A shows the relationship between the rotational speed of the intermediate transfer belt 1 and the edge position and the amount of walk of the intermediate transfer belt. FIG. 12B shows the rotational speed of the intermediate transfer belt 1 and the step of the step motor. FIG. 12C shows the relationship between the rotational speed of the intermediate transfer belt 1 and the step position of the step motor.
[0094]
As shown in FIG. 12A, the walk amount of the intermediate transfer belt is saturated at about −0.2 mm, and it can be seen that the positional deviation is not corrected. Therefore, in the image forming apparatus of Comparative Example 2, the control gain K used for calculating the step position change amount S expressed by the equation (1) is set to a value larger than the control gain K in the case of FIG. Attempts were made to correct the lateral displacement of the intermediate transfer belt when the change amount of the step number of the step motor was increased.
[0095]
FIG. 13 is a diagram showing the lateral displacement of the intermediate transfer belt at that time.
[0096]
FIG. 13A shows the relationship between the rotation speed of the intermediate transfer belt 1 and the edge position and the walk amount of the intermediate transfer belt. FIG. 13B shows the rotation speed of the intermediate transfer belt 1 and the step of the step motor. FIG. 13C shows the relationship between the rotational speed of the intermediate transfer belt 1 and the step position of the step motor.
[0097]
Even when the control gain K is increased, as shown in FIG. 13A, the walk amount of the intermediate transfer belt is saturated at about −0.1 mm, and it is understood that the positional deviation is not corrected.
[0098]
As described above, in the image forming apparatus of Comparative Example 1, as shown in FIG. 11A, the positional deviation is corrected, but it is necessary to use a high-resolution motor (resolution 1000) as the step motor 21. There is a problem of cost. On the other hand, in the image forming apparatus of Comparative Example 2, a low resolution motor (resolution 100) is used as the step motor 21 in order to reduce the cost. However, in such a low resolution motor, FIG. ), As shown in FIG. 13A, there is a problem that the positional deviation cannot be corrected. Therefore, a method of increasing the resolution of the low-resolution step motor using a reduction gear is conceivable. However, in this method, the accuracy of the reduction gear becomes a problem and it is difficult to control the step motor with high accuracy. .
[0099]
In contrast, in the image forming apparatus according to the second embodiment, as described above, the low-resolution step motor (resolution 100) is used, and the second intermediate transfer position adjustment mode is executed. As described above, by executing the second intermediate transfer position adjustment mode, the positional deviation of the intermediate transfer belt 1 can be accurately corrected even when a low resolution step motor is used instead of the high resolution step motor. Hereinafter, the principle of correcting the positional deviation of the intermediate transfer belt 1 will be described.
[0100]
FIG. 14 is a graph showing the relationship between the step position of the step motor and the maximum value of the walk amount (hereinafter referred to as the walk speed) during one rotation of the intermediate transfer belt.
[0101]
As shown in FIG. 14, there is a linear correspondence represented by a straight line L between the step position of the step motor (ie, the tilt angle of the steering roll) and the walk speed. Accordingly, it can be seen that the walk speed of the intermediate transfer belt 1 can be reduced to 0 by accurately controlling the step position of the step motor (the tilt angle of the steering roll).
[0102]
Hereinafter, in the second embodiment, how the step position of the step motor (inclination angle of the steering roll) is controlled will be described.
[0103]
FIG. 15 is a flowchart illustrating a second intermediate transfer belt position adjustment mode executed by the image forming apparatus according to the second exemplary embodiment. FIG. 16 illustrates lateral displacement of the intermediate transfer belt when the flowchart is executed. FIG.
[0104]
When the rotation of the intermediate transfer belt 1 is started and it is determined in step S1 that the belt home signal has been output, the rotation speed r of the intermediate transfer belt 1 is reset to 0 and the address n of the intermediate transfer belt 1 is reset to 0. Here, as shown in FIG. 16A, the belt walk amount at the time when the belt home signal is output (r = 0) is about 0.2 mm. When the belt home signal is output, the process proceeds to step S2, and the edge position e (0, 0) at the rotation speed r = 0 and the address n = 0 is detected. When the edge position e (0, 0) is detected, the process proceeds to step S3, and from the difference between the edge position e (0, 0) and the edge profile p (0), the rotation speed r = 0 and the address n = 0. The walk amount W (0, 0) is calculated. When the walk amount W (0, 0) is calculated, the process proceeds to step S4. Based on the calculated walk amount W (0, 0), the intermediate transfer belt at the rotation speed r = 0 and the address n = 0. A step position change amount S0 (0, 0) necessary to correct the position shift of 1 is calculated. The step position change amount S0 (0, 0) is calculated by setting r = 0 and n = 0 in the step position change amount S0 (r, n) expressed by the following equation (4).
[0105]
[Expression 4]

[0106]
The step position change amount S0 (r, n) is the step position change amount of the step motor 21 required to correct the positional deviation of the intermediate transfer belt 1 at the rotation speed r and the address n. This is a step position change amount of the step motor 21 when calculated with a resolution 1000 higher than the resolution 100 of the step motor 21 provided in the forming apparatus. Therefore, if the step position change amount S0 obtained by the equation (4) is used as it is to change the step position of the step motor having the resolution 100, a step position that cannot be originally set by the step motor 21 having the resolution 100 is set as a new step. The case to set with the position comes out. Therefore, based on the step position change amount S0 obtained by the equation (4), a step position change amount S for setting only a step position that can be set by the step motor 21 with a resolution of 100 as a new step position is calculated. The step position change amount S is calculated as follows.
[0107]
When the step position change amount S0 (0, 0) is calculated in step S4, the process proceeds to step S5, and based on the calculated step position change amount S0 (0, 0), the rotation speed r = 0 and the address n When = 0, one step position A (0, 0) is set from among the step positions that can be set by the step motor 21 having a resolution of 100. The step position A (0, 0) is set so that the step position change amount with the current step position is closest to the step position change amount S0 (0, 0) calculated in step S4. This A (0,0) is calculated by setting r = 0 and n = 0 at the step position A (r, n) represented by the following equation (5).
[0108]
[Equation 5]

[0109]
A (r, n) is a step position of the step motor 21 at the rotation speed r and the address n.
[0110]
From equation (5), A (0,0) = int {S0 (0,0)}.
[0111]
When A (0, 0) is calculated in step S5, the process proceeds to step S6. Based on the calculated A (0, 0), the rotational speed r = 0 and address n = 0, A step position change amount S (0, 0) necessary to change the step position from the current step position to the step position A (0, 0) is calculated. The step position change amount S (0, 0) is calculated by setting r = 0 and n = 0 in the step position change amount S (r, n) expressed by the following equation (6).
[0112]
[Formula 6]

[0113]
However, n-1; an integer greater than or equal to 0
That is, S (0,0) = int {A (0,0)}.
[0114]
Thus, the step position change amount S (0, 0) is calculated, the step motor 21 is rotated by the number of steps corresponding to the calculated step position change amount S (0, 0), and the steering roll 3 is tilted. Adjust. When the step position change amount S (0, 0) is calculated in step S6, the process proceeds to step S7, where it is determined whether or not an end signal for ending the running of the intermediate transfer belt 1 is input. If it is determined that the end signal has not been input, the process proceeds to step S8, where it is determined whether the address n is the maximum value N (here, 50). Since the address n = 0 at this time, it is determined that it is not the maximum value N (= 50), the address n is incremented in step S9 to become n = 1, and the process returns to step S2. Returning to step S2, the edge position e (0, 1) at the rotation speed r = 0 of the intermediate transfer belt 1 and the address n = 1 of the intermediate transfer belt 1 is detected, and in steps S3 and S4, respectively. The walk amount W (0, 1) and the step position change amount S0 (0, 1) corresponding to the rotation speed r = 0 of the intermediate transfer belt 1, the address n = 1 of the intermediate transfer belt 1 are calculated. Then, it progresses to step S5 and A (0, 1) is calculated using (5) Formula.
[0115]

When A (0,1) is calculated, the process proceeds to step S6, and the step position change amount S (0,1) is calculated using the equation (6).
[0116]

The step motor 21 is rotated by the number of steps corresponding to the calculated step position change amount S (0, 1), and the tilt angle of the steering roll 3 is adjusted. Thereafter, if it is determined in step S7 that an end signal for ending the running of the intermediate transfer belt 1 has not been input, since address n = 1 at this time, the address n is determined in step S8. It is determined that the value is not the maximum value N (= 50), the process proceeds to step S9, the address n is incremented to n = 2, and the process returns to step S2.
[0117]
Hereinafter, if it is determined in step S7 that an end signal for ending the running of the intermediate transfer belt 1 has not been input, it is determined in step S8 that the address n is the maximum value N (= 50). Until this is done, the loop from step S2 to step S9 is repeatedly executed. By repeatedly executing this loop, the edge position e (0) in the combination of the rotational speed r = 0 of the intermediate transfer belt 1 and the addresses n = 0, 1, 2,. , 0), e (0, 1), e (0, 2),..., E (0, 50) are detected, and the step motor 21 detects the edge positions e (0, 0), e (0, 50). 1), e (0, 2),..., E (0, 50), step position change amounts S (0, 0), S (0, 1), S (0, 2), .., S (0, 50) are sequentially rotated by the number of steps corresponding to each, and the position of the intermediate transfer belt 1 in the lateral direction is controlled. If it is determined in step S8 that the address n is the maximum value N (= 50), the process returns to step S1, and when the belt home signal is output, the rotational speed r of the intermediate transfer belt 1 is incremented and r = 1 By this increment, the first rotation of the intermediate transfer belt 1 after the first detection of the belt home signal is completed. As shown in FIG. 16A, when the intermediate transfer belt 1 completes one rotation, the walk amount of the intermediate transfer belt 1 is about 0.1 mm. Further, as shown in FIG. 16C, the step position of the step motor 21 changes to −1, −2, −3, and −2 until the rotation speed r changes from 0 to 1. .
[0118]
Further, when r = 1 is incremented in step S1, the rotation of the intermediate transfer belt 1 enters the second rotation, and the loop of step S2 to step S9 is repeated and r = 1 (intermediate transfer belt). 1 at the second rotation), the step position change amounts S (1, 0), S (1, 1), S (1, 2) when the addresses n = 0, 1, 2,. ),..., S (1, 50) are obtained, and the step motor 21 detects the step position change amounts S (1, 0), S (1, 1), S (1, 2),. It is sequentially rotated by the number of steps corresponding to each (1, 50). If it is determined in step S8 that the address n is the maximum value N (= 50), the process returns to step S1, and when the belt home signal is output, the rotational speed r of the intermediate transfer belt 1 is incremented and r = 2. By this increment, the second rotation of the intermediate transfer belt 1 is completed. As shown in FIG. 16A, when the intermediate transfer belt 1 completes two rotations, the walk amount of the intermediate transfer belt 1 is almost 0 mm. Further, as shown in FIG. 16C, the step position of the step motor 21 changes to −2, −1, 0 until the rotational speed r changes from 1 to 2.
[0119]
In the same manner, r is sequentially incremented, and the step motor 21 has step positions corresponding to combinations of r = 0, 1, 2, 3..., N = 0, 1, 2,. The position of the intermediate transfer belt 1 is controlled by sequentially rotating the change amount S (r, n). As shown in FIG. 16A, it can be seen that the positional deviation of the intermediate transfer belt 1 is corrected when the intermediate transfer belt 1 has completed two rotations.
[0120]
In the image forming apparatus of the second embodiment, in step S4, the step position change amount S0 (r, n) is a resolution 1000 that is higher than the resolution 100 of the step motor 21 provided in the image forming apparatus of the second embodiment. In step S5, the step position A (r, n) is calculated based on the calculated step position change amount S0 (r, n) and the step position A (r, n-1) of the step motor 21. ) And the difference between the step position A (r, n) of the step motor 21 and the step position A (r, n-1) is calculated in step S6, whereby the step position change amount of the step motor 21 is calculated. S (r, n) is obtained.
[0121]
Thus, the step position change amount S0 (r, n) of the step motor 21 is obtained with a resolution 1000 higher than the resolution 100 of the step motor 21 and the calculated step position change amount S0 (r, n) is obtained. ) And the step position A (r, n-1) of the step motor 21 at the rotational speed r and the address n-1, the step of the step motor 21 with the resolution 100 provided in the image forming apparatus of the second embodiment. By calculating the position A (r, n), the step position of the step motor 21 is set to be higher than that of the step motor 21 with the resolution 100 of the image forming apparatus of the second embodiment. It is possible to approach the step position. Therefore, even when a low-resolution step motor is used, the positional deviation of the intermediate transfer belt 1 is corrected as shown in FIG.
[0122]
FIG. 11C showing the step position of the step motor with a resolution of 1000 (high resolution), and FIGS. 12C, 13C, and 16 showing the step position of the step motor with a resolution of 100 (low resolution). (C) Comparing with each, it can be seen that the locus of the step position of the step motor shown in FIG. 16C is closest to the locus of the step position of the step motor shown in FIG. ) Corresponds to step position -3 in FIGS. 12C, 13C, and 16C). As described above, even if a low-resolution step motor is used, the step position of the step motor is brought close to the step position of the high-resolution step motor, so that the positional deviation of the intermediate transfer belt 1 can be accurately performed at low cost. It can be corrected.
[0123]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a belt conveyance device in which an increase in the positional deviation of the belt is suppressed, and an image forming apparatus to which the belt conveyance device is applied.
[0124]
In addition, according to the present invention, a belt conveyance device that can control the position of the belt with high accuracy at low cost and an image forming apparatus to which the belt conveyance device is applied can be replaced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention to which an embodiment of a belt conveying apparatus of the present invention is applied.
FIG. 2 is a schematic configuration diagram showing a contact sensor as an example of an edge sensor.
FIG. 3 is a schematic configuration diagram showing a non-contact type sensor which is another example of the edge sensor.
4 is a diagram specifically showing a path of a signal detected by an edge sensor in the image forming apparatus shown in FIG. 1. FIG.
FIG. 5 is an explanatory diagram showing how the meandering of the intermediate transfer belt is corrected.
FIG. 6 is a diagram showing an example of a system for finely setting the tilt angle of the steering roll 3 under optimum conditions.
FIG. 7 is a flowchart illustrating a first intermediate transfer belt position adjustment mode that is executed in order to correct a positional deviation of the intermediate transfer belt 1 included in the image forming apparatus according to the first exemplary embodiment.
8 is a diagram showing a lateral displacement of the intermediate transfer belt during execution of the flowchart shown in FIG.
FIG. 9 is a flowchart executed in order to correct the positional deviation of the intermediate transfer belt in the image forming apparatus of Comparative Example 1;
10 is a diagram showing a lateral displacement of the intermediate transfer belt during execution of the flowchart shown in FIG. 9. FIG.
11 is a diagram illustrating a state in which the lateral displacement of the intermediate transfer belt is corrected when the flowchart illustrated in FIG. 9 is executed in the image forming apparatus of Comparative Example 1. FIG.
12 is a diagram showing a lateral displacement of the intermediate transfer belt when the control gain K shown in the above-described equation (1) is set to a small value in the image forming apparatus of Comparative Example 2. FIG.
13 is a diagram showing a lateral displacement of the intermediate transfer belt when the control gain K is set to a value larger than the control gain K in the case of FIG. 12. FIG.
FIG. 14 is a graph showing a relationship between a step position of a step motor and a maximum value of a positional deviation amount during one rotation of the intermediate transfer belt.
FIG. 15 is a flowchart illustrating a second intermediate transfer belt position adjustment mode executed by the image forming apparatus according to the second exemplary embodiment.
16 is a diagram showing a lateral displacement of the intermediate transfer belt during execution of the flowchart shown in FIG.
[Explanation of symbols]
1 Intermediate transfer belt
1a edge
2 Drive roll
3 Steering roll
3a, 13e, 22b The other end
3b, 13d, 22a
4 Backup roll
5, 6, 7 idler roll
8, 9, 10, 11 Image forming unit
8a, 9a, 10a, 11a Photosensitive drum
8b, 9b, 10b, 11b raster scanner
8c, 9c, 10c, 11c charger
8d, 9d, 10d, 11d Developer
8e, 9e, 13e, 11e Primary transfer roll
8f, 9f, 13f, 11f cleaner
12 Belt home sensor
13 Edge sensor
13b Contact
13c, 24 spindle
13f Displacement sensor
13g LED
13h Light quantity sensor
14 paper
15 Pickup roll
16 roll pairs
17 Secondary transfer roll
18 Paper transport system
19 Fixing device
20 Steering control unit
20a controller
20b compensator
20c step motor driver
20d A / D converter
20e arithmetic unit
20f storage unit
21 Step motor
22 Steering arm
23 Eccentric cam
25 Steering module

Claims (3)

A belt that moves along a predetermined path,
A displacement detection means for detecting a displacement in the width direction of the belt from a predetermined reference movement path;
A steering member for correcting a positional deviation in the width direction of the belt by changing a steering control position in contact with the belt;
Steering control means for stepwise changing the steering control position of the steering member with a predetermined first resolution;
A steering control position change amount for correcting a positional deviation in the width direction of the belt from a current steering control position of the steering roll, based on the positional deviation of the belt detected by the positional deviation detection means, High-resolution change amount calculating means for calculating with a second resolution that is higher than the first resolution;
A steering control position calculating means for calculating a new steering control position based on a current steering control position of the steering member and a steering control position change amount calculated by the high resolution change amount calculating means; and a current state of the steering member The low-resolution change amount calculation that calculates the change amount of the steering control position of the steering member with the first resolution based on the steering control position of the steering member and the new steering control position calculated by the steering control position calculation means With means,
The belt conveying device, wherein the steering control means changes a steering control position of the steering member by a steering control position change amount calculated by the low resolution change amount calculation means.   2. The belt conveyance according to claim 1, wherein the steering control means has a step motor, and rotates the step motor to change the steering control position of the steering member stepwise. apparatus. In an image forming apparatus for forming an image on a paper by forming a toner image and finally transferring and fixing the toner image on a predetermined paper,
A belt that moves along a predetermined path employed in a process of forming or conveying a toner image;
A displacement detection means for detecting a displacement in the width direction of the belt from a predetermined reference movement path;
A steering member for correcting a positional deviation in the width direction of the belt by changing a steering control position in contact with the belt;
Steering control means for stepwise changing the steering control position of the steering member with a predetermined first resolution;
A steering control position change amount for correcting a positional deviation in the width direction of the belt from a current steering control position of the steering roll, based on the positional deviation of the belt detected by the positional deviation detection means, High-resolution change amount calculating means for calculating with a second resolution that is higher than the first resolution;
A steering control position calculating means for calculating a new steering control position based on a current steering control position of the steering member and a steering control position change amount calculated by the high resolution change amount calculating means; and a current state of the steering member The low-resolution change amount calculation that calculates the change amount of the steering control position of the steering member with the first resolution based on the steering control position of the steering member and the new steering control position calculated by the steering control position calculation means With means,
The image forming apparatus, wherein the steering control means changes a steering control position of the steering member by a steering control position change amount calculated by the low resolution change amount calculation means.

Images