JP2004205434A - Image forming apparatus, and manufacturing method, reforming method and sound evaluating method of image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively cope with the noise on the basis of an objective sound evaluation even if the image forming speed has several different modes. <P>SOLUTION: The sound generated from an image forming apparatus is measured to lead out a discomfort probability P with the predetermined estimation formula on the basis of a mental acoustic parameter obtained from a result of the measurement. Each part of the apparatus is designed so that the lead-out discomfort probability P satisfies the predetermined condition (step S1) to manufacture the image forming apparatus restricted in generation of uncomfortable noise (step S2). The image forming apparatus allowing to reduce the uncomfortableness to be given to a person by the generated operation noise is thereby provided. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

上記式の導出に用いた心理音響パラメータ値の平均値を、上記式（ｆ）に代入するとともに、そのときのＰ＝０．５と定義することにより、音の不快さの確率を予測する音質評価式を導出し、導出した音質評価式を用いて音質評価を行うことを特徴とする音質評価方法である。
【００８５】
請求項３１にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価である不快確率そのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。
【００８６】
また、請求項３２にかかる発明は、画像形成対象シートに対して画像を形成する画像形成装置の製造方法であって、画像形成装置が画像形成時に発する複数種類の音に対して一対比較法による評価を行い、かかる評価による２音の不快確率を目的変数とし、心理音響パラメータ値の差を説明変数として重回帰分析を行い、その結果から音質の不快確率に関する下記の式（ｆ）を導出し、
【数１】

上記式の導出に用いた心理音響パラメータ値の平均値を、上記式（ｆ）に代入するとともに、そのときのＰ＝０．５と定義することにより、音の不快さの確率を予測する音質評価式を導出し、導出した音質評価式を用い、その音質評価式による音質評価が所定の条件を満たすよう装置各部を設計し、当該設計内容にしたがって画像形成装置を製造することを特徴とする画像形成装置の製造方法である。
【００８７】
請求項３２にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価である不快確率のそのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。そして、このようにして得られた音質評価式による音質評価が所定の条件を満たすよう装置各部が設計された画像形成装置が製造されるので、つまり不快な音をほとんど発しない画像形成装置を提供することができる。
【００８８】
また、請求項３３にかかる発明は、画像形成対象シートに対して画像を形成する画像形成装置を改造する方法であって、画像形成装置が画像形成時に発する複数種類の音に対して一対比較法による評価を行い、かかる評価による２音の不快確率を目的変数とし、心理音響パラメータ値の差を説明変数として重回帰分析を行い、その結果から音質の不快確率に関する下記の式（ｆ）を導出し、
【数１】

上記式の導出に用いた心理音響パラメータ値の平均値を、上記式（ｆ）に代入するとともに、そのときのＰ＝０．５と定義することにより、音の不快さの確率を予測する音質評価式を導出し、導出した音質評価式を用いて改造対象となる画像形成装置の発する音の音質評価を行い、かかる音質評価結果に基づいて改造対象となる前記画像形成装置の構成を改造することを特徴とする画像形成装置の改造方法である。
【００８９】
また、請求項３３にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価である不快確率そのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。そして、このようにして得られた音質評価式を用いた画像形成装置が発する音の音質評価に基づいて、その装置構成を改造する。したがって、良好な音質評価が得られる、つまり不快な音をほとんど発しない画像形成装置を提供することができる。
【００９０】
【発明の実施の形態】
以下に添付図面を参照して、この発明にかかる画像形成装置、画像形成装置の製造方法、画像形成装置の改造方法および音質評価方法の好適な実施の形態を詳細に説明する。
【００９１】
Ａ．画像形成装置の構成
図１は、一般的な画像形成装置の全体構成を示す図である。本発明は、このような一般的な画像形成装置が発する騒音を評価し、その評価に基づき当該騒音が人に与える不快感を低減するための対策をなす改造方法であり、かかる改造方法についての説明に先立ち、一般的な画像形成装置の構成について説明する。
【００９２】
図１に示す画像形成装置は、電子写真方式を採用したディジタルカラープリンタであり、光学ユニット１と、感光体ユニット３と、現像ユニット４と、転写ユニット５と、定着ユニット４６と、給紙部１１０とを備えている。
【００９３】
画像形成時には、当該画像形成装置の最下部に配置された給紙部１１０に収容された画像形成対象シート（印刷用紙やＯＨＰシート等も含むが、以下用紙とする）が図の右下側から左斜め上側へ上がる所定の搬送経路に沿って搬送させられる。このように搬送される用紙は、給紙部１１０から繰り出されて、給紙部１１０の上方側に図の右下から左上側への斜め方向の搬送経路に沿って搬送される。この間、用紙は同様に搬送経路に沿って並んで配置される４つの感光体ユニット３および現像ユニット４と転写ユニット５との間を通過させられ、所定の画像が転写される。かかる画像転写がなされた用紙は、感光体ユニット３、現像ユニット４および転写ユニット５のさらに左斜め上側に配置される定着ユニット４６へ搬送され、定着ユニット４６によって転写画像が定着させられる。
【００９４】
図２に示すように、光学ユニット１は、図２の右下から左上方向といった斜め方向である用紙搬送路に沿って延在するユニットであって、その方向に沿って配置されるハウジング１１を有している。ハウジング１１の上部には、４つの色毎のレーザダイオード（ＬＤ）１７（Ｂｋ：ブラック），１８（Ｃ：シアン），１９（Ｍ：マゼンダ），２０（Ｙ：イエロー）が取り付けられている。
【００９５】
また、ハウジング１１には、主操作ライン操作のためのポリゴンミラーモータ２、ドット位置補正のための２層ｆθレンズ２１，２２、面倒れ補正を行うための長尺ＷＴＬレンズ２３，２４，２５，２６、図示せぬレーザビーム径補正のためのシリンダレンズ等が取り付けられている。
【００９６】
ポリゴンミラーモータ２には、上下２枚の６面ミラー２７が一体となって形成されており、このポリゴンミラー２７にＬＤ１７，１８，１９，２０が発したレーザ光が照射される。
【００９７】
各色に対応するＬＤ１７，１８，１９，２０は、用紙の搬送タイミングにあわせて発光し、その光（図中太線で示す）がシリンダレンズ、ポリゴンミラー２７、２層ｆθレンズ２１，２２、長尺ＷＴＬレンズ２３，２４，２５，２６を経由して各色の感光体ドラム２８に照射される。
【００９８】
なお、ブラックに対応するＬＤユニット１７については、２ビーム方式のものを採用することが好ましい。すなわち、２ビーム方式のＬＤを採用することで、モノクロ画像形成時に２ビームを同時に書き込むことができ、ポリゴンミラーモータ２の回転数を抑えながら、かつ迅速な書き込みを行うことができるからである。このようにポリゴンミラーモータ２の回転数を低減することで、騒音が抑制されるといった効果や、モータの寿命が延びるといった効果も得られる。例えば、カラーモードで印刷する場合にポリゴンミラー２７の回転数が２９５２８rpm（revolutions per minute）で印刷速度２８ppm（pages per minute）であるが、モノクロ印刷時にはポリゴンミラー２７の回転数が２１８５０rpmと回転速度が小さいにもかかわらず、印刷速度３８ppmとなるといった具合である。
【００９９】
図１に戻り、この画像形成装置における感光体ユニット３、現像ユニット４および転写ユニット５の構成について説明する。同図に示すように、この画像形成装置は、４連ドラムのタンデム作像方式を採用した装置であり、この方式を採用することでフルカラー印刷モードおよびモノクロ印刷モードの印刷速度を向上させている。また、上述したように感光体ユニット３、現像ユニット４および転写ユニット５を斜めに配置することで設置スペースを小さくし、これにより装置全体を小型にしている。
【０１００】
感光体ユニット３、現像ユニット４は、それぞれ各色で独立したユニットとなっている。つまり、マゼンダ（Ｍ）用の感光体ユニット３および現像ユニット４、シアン（Ｃ）用の感光体ユニット３および現像ユニット４、イエロー（Ｙ）用の感光体ユニット３および現像ユニット４、ブラック（Ｂｋ）用の感光体ユニット３および現像ユニット４があり、これらが図１の右下側から左上側に上記順序で並んで配置されている。なお、Ｂｋ用を除いたＭ用、Ｃ用、Ｙ用の感光体ユニット３は全く同一の構成であるため、新しいユニットであればどの色用（Ｍ、Ｃ、Ｙ）に用いるようにしてもよい。
【０１０１】
転写ユニット５は、上述した順序で斜め方向に配置される感光体ユニット３および現像ユニット４の下方側に、当該斜め方向に沿って延在するユニットであり、その斜め方向に沿うよう配置されている。転写ユニット５は、複数のローラと、当該ローラに巻き掛けられたエンドレスの転写ベルト２９とを有している。図示せぬモータによってローラが回転させられることにより転写ベルト２９が図中半時計回りに回転させられ、給紙部１１０から送り出された用紙はかかる転写ベルト２９に載って図の右下側から左上側に搬送させられる。また、転写ユニット５の搬送方向の下流側（図の左上側）には、Ｐセンサ６が配置されており、かかるＰセンサ６が転写ベルト２９上に形成されたＰセンサパターンの濃度を検知し、かかる検知結果が制御に利用される。
【０１０２】
ここで、図３にある色に対応する感光体ユニット３および現像ユニット４の断面図を示す。同図に示すように、感光体ユニット３は、感光体ドラム２８（例えばφ３０）を有している。感光体ドラム２８は中空円柱状であり、後述する駆動機構によって図中時計回りに回転させられるようになっている。
【０１０３】
感光体ドラム２８の上方側には帯電ローラ３６（例えば、φ１１）が配置されている。帯電ローラ３６は、その表面が感光体ドラム２８の表面から０．０５mm程度離間した位置に配置されている。そして、帯電ローラ３６は、感光体ドラム２８と逆方向、つまり図中半時計周りに回転させられ、感光体ドラム２８の面上に均一な電荷を印加している。
【０１０４】
また、帯電ローラ３６の上方側にはクリーニングブラシ３７が配置されている。感光体ドラム２８の左斜め上側にはクリーニングブラシ３９およびカウンターブレード３８が配置され、これらによって感光体ドラム２８のクリーニングがなされる。
【０１０５】
また、クリーニングブラシ３９の左側には、廃トナー回収コイル４０が配置されており、かかる廃トナー回収コイル４０によって回収された廃トナーは、図１に示す廃トナーボルト１６に搬送されるようになっている。
【０１０６】
次に、現像ユニット４は、乾式２成分磁気ブラシ現像方式を採用したものであり、現像ローラ３０と、現像ドクタ３１と、搬送スクリュー左３２と、搬送スクリュー右３３と、トナー濃度センサ３４と、剤カートリッジ３５とを備える。
【０１０７】
次に、図４を参照しながら感光体ユニット３の駆動機構について説明する。感光体ユニット３は、各色毎に設けられており、４つのユニットがあるが、Ｍ用、Ｃ用、Ｙ用（カラー用）の３つの感光体ユニット３と、Ｂｋ用の感光体ユニット３とは別々の駆動機構によって駆動されるようになっている。すなわち、カラー用の感光体ユニット３の駆動は、カラードラム駆動モータ４１を駆動源とし、この駆動力を伝達するギヤ４３，４４、ジョイント４５とによって行われる。
【０１０８】
一方、ブラック用の感光体ユニット３の駆動は、別の黒ドラム駆動モータ４２を駆動源とし、この駆動力を伝達する別のギヤ４４、ジョイント４５によって行われる。したがって、カラーモード印刷時には、カラードラム駆動モータ４１のみが動作し、黒ドラム駆動モータ４２は停止している。一方、モノクロモード印刷時には、黒ドラム駆動モータ４２のみが動作し、カラードラム駆動モータ４１は停止している。なお、カラードラム駆動モータ４１および黒ドラム駆動モータ４２はステッピングモータである。
【０１０９】
図５および図６に示すように、この定着ユニット４６は、ベルト定着方式を採用したものであり、ベルトは定着ローラと比べて熱容量が小さいことから、この方式を採用することで、定着ローラを用いる方式よりもウォームアップ時間の短縮、待機時のローラ設定温度を低下できる等のメリットがある。
【０１１０】
この定着ユニット４６は、画像が転写された用紙を加熱・加圧し、用紙上にトナー像を定着させるものであり、定着ベルト１３と、オイル塗布ユニット４７とを有している。オイル塗布ユニット４７内には、ジェルがオイルから染み出し、これが塗布フェルト４８から塗布ローラ４９に供給される。そして、塗布ローラ４９が回転しながら定着ベルト１３に微量のシリコーンオイルを塗布している。このように定着ベルト１３にオイルを塗布することで、定着ベルト１３と用紙とが剥離しやすくなるようにしている。なお、かかるオイル塗布ユニット４７による塗布動作は、用紙が１枚搬送される毎になされるようになっており、図示せぬソレノイドやスプリングを有する機構によって、用紙１枚が搬送される都度オイル塗布ユニット４７が駆動され、定着ベルト１３と接触させられる。一方、用紙１枚が通過すると、上記機構によってオイル塗布ユニット４７が定着ベルト１３から離間させられるようになっている。
【０１１１】
また、図５に示すように、定着ベルト１３の用紙搬送方向上流側には、クリーニングローラ５０が設けられており、かかるクリーニングローラ５０が定着ベルト１３上の汚れを吸着し、これによりベルトクリーニングがなされる。
【０１１２】
以上が定着ユニット４６の構成であり、かかる定着ユニット４６を通過した用紙は、搬送ローラによって図1に示す本体トレー５１に搬送される。
【０１１３】
次に、図７を参照しながら給紙部１１０の構成について説明する。かかる給紙部１１０は、第１トレー９と、第２トレー１０と、手差し給紙トレー８といった３つのトレーを有している。これらの各トレーは、トレーに収容された用紙を送り出す方式として、ＦＲＲ給紙方式を採用している。ＦＲＲ給紙方式による送り出し機構は、給紙トレー内に積層された用紙束中から送り出された用紙を一枚づつに分離する為に、給紙方向に回転駆動される給紙コロに対して逆転コロを当接させた構成となっている。
【０１１４】
この構成の下、逆転コロは、給紙コロとは逆方向へ向かう弱いトルクがトルクリミッタを介して付与されているため、給紙コロと接触している状態、或は一枚の用紙が両コロ間に進入した状態では給紙コロに連れ回りする一方で、給紙コロと離間した状態、或は２枚以上の用紙が両コロ間に進入した状態では逆回転する。このため、重送用紙の進入時には逆転コロに接する側の用紙は給紙方向下流側へ戻されて、重送が防止されることとなる。
【０１１５】
第１トレー９に収容された用紙は、第１給紙ユニット５１によって１枚分離されて第１トレー９から送り出される。そして、送り出された用紙は、中継ローラ５３によって搬送され、搬送ローラ５５に到達する。ここで、用紙は搬送ローラ５５によってターンさせられながら、左斜め上方側のレジストローラ７に向けて搬送される。
【０１１６】
搬送された用紙は、停止しているレジストローラ７に突き当たり、これにより用紙の斜行が補正される。そして、感光体ユニット３等による画像形成工程とのタイミング調整を行い、所定のタイミングで図示せぬレジストクラッチがつながれてレジストローラ７が駆動され、用紙が転写ユニットへ向けて搬送される。以降用紙は、上述したように転写ベルト２９によって搬送され、所定の画像転写等の処理がなされる。
【０１１７】
なお、第２トレー１０に収容された用紙の送り出しは、第２給紙ユニット５２、中継ローラ５４によって搬送ローラ５５に向けて用紙が搬送され、その後は第１トレー９に収容された用紙と同様である。また、手差しトレー８にセットされた用紙は、給紙ユニット５６によってレジストローラ７に向けて搬送され、以降は上記第１トレー９からの用紙搬送と同様である。
【０１１８】
次に、上述したように第１トレー９および第２トレー１０から用紙を送り出す第１給紙ユニット５１および第２給紙ユニットを駆動する構成について説明する。図８に示すように、これらの両ユニットは、１つのステッピングモータ５６によって駆動されており、各々のユニットへの駆動力伝達は第１給紙クラッチ５７および第２給紙クラッチ５８を介して行われる。すなわち、第１トレー９から用紙を送り出すときは第１給紙クラッチ５７のみがつながれた状態となり、第２トレー１０から用紙を送り出すときは第２給紙クラッチ５８のみがつながれた状態となる。
【０１１９】
この画像形成装置は、上述したようにカラー用感光体ユニット３等を有しており、モノクロ印刷のみならず、カラー印刷もできるようになっている。より具体的には、表１に示すように、「モノクロモード」、「カラーモード▲１▼」、「カラーモード▲２▼」、「ＯＨＰ／厚紙モード」といった４つの印刷モードを有しており、ユーザが操作部等を操作してモードを選択した場合、その選択にしたがって図示せぬ当該画像形成装置の制御部（動作制御手段）が装置各部を制御し、その動作モードで各部を動作させる。この画像形成装置では、制御部がユーザに選択されたモードによって画像形成速度を３種類（182.5mm/s＝38ppm（pages per minute）、125.0mm/s＝28ppm、62.5mm/s＝14ppm）に切り替えるようになっている。すなわち、選択された動作モードによってステッピングモータ５６、黒ドラム駆動モータ４２、カラードラム駆動モータ４１といったモータの回転速度を変化させるよう制御しているのである。
【表１】

ここで、高解像度の「カラーモード▲２▼」や「ＯＨＰ／厚紙モード」では、印刷速度（画像形成速度）が１４ppmであるのに対し、「モノクロモード」では印刷速度が３８ppmであり、３倍近い速度差がある。このような大きな速度差を１つのモータで実現するため、この画像形成装置では用紙搬送機構系等の駆動源としてステッピングモータを採用している。
【０１２０】
Ｂ．音質評価手法
本発明は、上記のような画像形成装置が発する騒音を評価し、その評価に基づき当該騒音が人に与える不快感を低減するための対策をなす改造方法であり、以下、上記構成の画像形成装置が画像形成時に発する騒音を評価する手法について説明する。
【０１２１】
音質を評価する方法としては、シェッフェの一対比較法により得られた実験結果から音質を予測できる音質評価式を導出するというものが考えられる。一対比較法は、画像形成装置の発する音のように、絶対的な評価が困難な刺激に対して、２つの刺激の対をつくる。そして、評価を行いたい刺激の全組み合わせで対をつくり、その評点の差を求め、刺激各々について相対的な平均評点を与えるというものである。この方法は、人間が１つの刺激に対して評価をするのは困難であるが、２つの刺激を比較してどちらがよいか悪いかを判断することは比較的容易になし得る点に着目したものである。
【０１２２】
例えば、３つの刺激Ａ１、Ａ２、Ａ３がある場合、それぞれの刺激モデルを、
ｙ１＝μ＋α１、ｙ２＝μ＋α２、ｙ３＝μ＋α３
とする。なお、簡略化のため、このモデルは総平均μと主効果αｉ（ｉ＝１，２，３）のみで構成されているものとする。また、実験計画法のパラメータ推定のために必要な一般的な制約と同様に、主効果の総和は０とする。
α１＋α２＋α３＝０‥‥（１）
【０１２３】
絶対的な評価ができないということは、μの値についての見当がつかないということなので、直接にｙ１、ｙ２、ｙ３が測定できないということであるが、上述したように２つの刺激の差をとることでμが消えて、主効果のみの差で表せることになる。
ｙ１−ｙ２＝（μ＋α１）−（μ＋α２）＝α１−α２‥‥（２）
ｙ１−ｙ３＝（μ＋α１）−（μ＋α３）＝α１−α３‥‥（３）
ｙ２−ｙ３＝（μ＋α２）−（μ＋α３）＝α２−α３‥‥（４）
【０１２４】
ここで、（２）＋（３）は、
２ｙ１−（ｙ２＋ｙ３）＝２α１−（α２＋α３）
であるが、上記制約式（１）により
２ｙ１−（ｙ２＋ｙ３）＝３α１
となる。つまり、各刺激の効果を取り出すことができる。そして、このときの各刺激の効果を、画像形成装置が持つ物理的特性の差によって、１次の関数で表すとすれば、
α１−α２＝ｂ（ｘ１−ｘ２）‥‥（５）
という関係が得られる。ここで、ｂは定数であり、ｘｉは、ｉ＝１，２，３‥‥ｎである。切片は２つの刺激の差をモデル化するので相殺される。
【０１２５】
そこで、評点の差（一対比較法実験により得られた一対の音の評点の差）を目的変数に、複数の物理的特性値（心理音響パラメータ等）の差を説明変数群とし、重回帰分析を行えば、評価の差を予測するモデルが得られることになる。すなわち、比較したい２つの音が有する物理的特性値を入力すると、２つの音がどのくらい不快さが異なるかといった評価の差の予測が出力できるモデルが得られる。
【０１２６】
本発明者は、以上のような評価の差の予測モデルとは別に、音質評価の予測モデルとして、以下の多重ロジスティック回帰モデルを適用することとした。
【数２】

（ｆ）式は、上記のように音Ａｉと音Ａｊとの優劣の差を予測するものではなく、音Ａｉと音Ａｊの優劣の勝敗を確率Ｐｉｊ、（１−Ｐｉｊ）として予測するものである。
【数３】

ここで、Ｐｉｊは、試料となる音の対（Ａｉ、Ａｊ）とを比較した際に音Ａｉが不快と感じる確率であり、（１−Ｐｉｊ）は音Ａｊが不快と感じる確率である。これらの確率は、πｉを試料となる音Ａｉが不快とされた度数、πｊを試料となる音Ａｊが不快とされた度数とすれば容易に求めることができる。そして、確率Ｐｉｊは、二項分布にしたがうことが統計的に知られているので、その期待値が心理音響特性に影響を受けるという仮定が成り立つのであれば、上記（ｆ）式の乗法モデルを用いることが合理的である。多重ロジスティック回帰モデルは、母確率Ｐｉｊを予測するモデルであるから、予測されるＰｉｊは０〜１の範囲の値となり、その値は指標として合理的である。
【０１２７】
したがって、本発明者は上記の多重ロジスティック回帰モデルを音質評価のモデルとすることした。ここで、本発明における音質評価モデルの導出過程の説明に先立ち、ロジスティック回帰モデルについて簡単に説明しておく。
【０１２８】
画像形成装置の発する音の不快さの原因としてラウドネスがあり、説明を簡単にするためにその原因がラウドネスのみにあるとする。この場合、２つの試料となる音（Ａ１、Ａ２）について、どちらが不快な音であるかをｎ人が比較したときに、各々の音のラウドネスに差がなければＡ１とＡ２の各々が不快とされる確率は５０％であることが期待される。
【０１２９】
そして、音Ａ１よりも音Ａ２のラウドネスが１（sone）小さいとき、音Ａ２が不快であると答えた確率が２５％になったとする。さらに、音Ａ１よりも音Ａ２のラウドネスが２（sone）小さくなると、音Ａ２が不快であると答える確率はさらに２５％下がり、０％になるとは考えられない。すなわち、ラウドネスが１（sone）小さくなることで、不快と答える確率が２５％下がったと考えるのではなく、ラウドネスを１（sone）小さくすることで、不快と答える確率が５０％から２５％に、つまり半分になったと考えるのが自然である。したがって、ラウドネスが２（sone）小さくなると不快と答える確率は２５×（１／２）＝１２．５％となると考えるのである。
【０１３０】
このように音質改善効果には、加法性が成立するのではなく、乗法性が成立するのである。乗法性が成立する場合には、対数ｌｎ（ｐ）をとると加法性が成立する。また、歩留りのように１００％の限界を挑戦する場合には、−ｌｎ（１−ｐ）をとればよい。この２つの対数を組み合わせた
ｚ＝ｌｎ（ｐ）−ｌｎ（１−ｐ）＝ｌｎ（ｐ／１−ｐ）‥‥（７）
をロジット変換と呼ぶ。そして、この逆変換は、
ｐ＝exp（ｚ）／（１＋exp（ｚ））＝１／（１＋exp（−ｚ））
である。このことは、０から１までの確率ｐにＳ字型曲線（シグモイド関数）をあてはめたとき、その曲線をロジスティック分布の累積分布関数で近似していることになる。
【０１３１】
図９に示すグラフは、ロジット変換による効果を示すものである。同図に示すように、ロジット変換後には、確率ｐについて線形性が成り立つことがわかる。したがって、ｚを目的変数として、通常の回帰分析を適用してｚを推定し、上記（６）式の逆変換によりｐの推定値を求めることができるのである。このように不良率や割合であるｐを目的変数とする予測では、ｐ＝ｒ／ｎをロジット変換し、それを目的変数として回帰分析すればよく、これをロジスティック回帰分析という。なお、ｒは不良数、ｎは検査数である。ただし、ｒが０またはｎのときは、ｚを求めることができないので、
ｚ＝ｌｎ（（ｒ＋１／２）／（ｎ−ｒ＋１／２））
とする。この変換を経験ロジットと呼ぶ。
【０１３２】
なお、この変換のままでは、ｎの数が大きい場合もｎが小さい場合も同等に扱うことになるので、ｎの大きさに対応した重み付けを行う必要がある。特に、ｐの値が０または１の近傍となる場合には、ロジットｚの分散が大きくなり不都合である。これらの点を考慮したのがロジスティック回帰分析である。
【０１３３】
以上がロジスティック回帰分析についての説明であり、本発明者は、かかるロジスティック回帰分析を利用して音質評価式を導出し、その評価式を用いて音質評価を行うこととした。以下、実際に行った実験等を下にその過程を詳細に説明することとする。
【０１３４】
画像形成装置の音質評価実験と音質評価式導出の流れは以下のとおりである。
（１）画像形成装置の動作音の採取
（２）動作音の分析
（３）採取した動作音から供試音の作成
（４）供試音の心理音響パラメータの測定
（５）供試音による一対比較法実験
（６）不快音源の特定
（７）差モデルの分析データの作成
（８）評点の差を予測する式を導出
（９）評点を予測するモデル式（音質評価式）の導出
（１０）導出した音質評価式の検証
【０１３５】
以下、上記過程の詳細について説明する。
（１）画像形成装置の動作音の採取
画像形成装置の動作音の採取は、ヘッドアコースティックス社製ダミーヘッドHMS（Head Measurement System）IIIを用い、バイノーラル（両耳覚）録音を行った。このようにバイノーラル録音を行い、専用ヘッドフォンで再生することで、実際に人間が機械の発生する音を聞いたときの感覚で再現できるからである。また、上述したように被測定機器である画像形成装置は、動作モードに応じて３種類の画像形成速度で画像形成動作を実行するものであり、これらの３つの動作モードごとに以下のような測定条件で測定を行った（図１０参照）。
・録音環境‥‥半無響室
・ダミーヘッド２０３の耳の位置（収音位置）２０４‥‥高さ１．２ｍ、被測定機器２０１端面からの水平距離ほぼ１ｍ（１±０．０３）、幅方向は機器中央位置
・録音方向‥‥前面（画像形成装置の操作部２０２がある面）、後面、左右面の４方向
・録音モード‥‥ＦＦ（フリー・フィールド：無響室用）
・ＨＰフィルタ‥‥２２Ｈｚ
【０１３６】
なお、ダミーヘッドの高さを１．２ｍとしたのは、最近の画像形成装置の利用の仕方として、ユーザが着席した状態でパーソナルコンピュータ等から指示を出すケースが多いことを考慮したものである。もちろん、人間が立っている状態を考慮して１．５ｍの高さにダミーヘッドを設置してもよい。
【０１３７】
ところで、画像形成装置が発する音は、方向ごとに異なるのが通常である。種々のモータの配置位置や、用紙の搬送経路、排紙口の位置などが装置中心にあるわけではなく、分散配置されているからである。よって、ある音源（モータ等）が発する音は右面側ではよく聞こえるが、左面側ではよく聞こえないといったように各方向ごとに採取される音も異なるものとなる。後述する実験に使用する供試音はどの方向で採取したものであってもよいが、一対比較実験を行う際にはいずれか１つの方向で採取したものに統一する必要がある。そこで、本実験では、前面側においてユーザが最も聞く機会が多いであろうと考えられる一方で、通常画像形成装置の後面側は壁にあわせて設置される後面側の音を聞く機会がほとんどないと考えられるので、前面側で採取したものを供試音として利用することとした。
【０１３８】
（２）動作音の分析
次に、上述したように採取した各モードの動作時における画像形成装置の動作音の分析を行った。
【０１３９】
まず、「カラーモード▲１▼」、つまり印刷速度が２８ppmで動作したときの騒音を分析すると、図１１に示すような分析結果が得られた。図１１上側は時間軸上で採取した音を表現したものであり、図１１下側は周波数軸上で採取した音を表現したものである。この結果から、７つの主要な音源を抽出した。まず、時間軸上で定着ユニット４６の定着オイル塗布衝撃音を抽出した。そして、周波数軸上では、カラー現像駆動系音、給紙ステッピングモータ音、帯電音、ドラム駆動ステッピングモータ音、ポリゴンミラーモータ音、用紙摺動音を抽出した。
【０１４０】
次に、「カラーモード▲２▼」、つまり印刷速度が１４ppmで動作したときの騒音を分析すると、図１２に示すような分析結果が得られた。図１２上側は時間軸上で採取した音を表現したものであり、図１２下側は周波数軸上で採取した音を表現したものである。この結果から、主要な音源として、時間軸上では定着オイル塗布衝撃音を抽出し、周波数軸上では給紙ステッピングモータ音、帯電音、ドラム駆動モータ音、ポリゴンミラーモータ音、用紙摺動音を抽出した。
【０１４１】
次に、「モノクロモード」、つまり印刷速度３８ppmで動作したときの騒音を分析すると、図１３に示すような分析結果が得られた。図１３上側は時間軸上で採取した音を表したものであり、図１３下側は周波数軸上で採取した音を表したものである。この結果から、主要な音源として、時間軸上では定着オイル塗布衝撃音を抽出し、周波数軸上では、現像駆動系音、帯電音、ドラム駆動ステッピングモータ音、用紙摺動音を抽出した。
【０１４２】
（３）採取した動作音から供試音の作成
次に、上述したように機器前面側の位置で採取した音をヘッドアコースティックス社製の音質解析ソフトウェアである「ArtemiS」を利用し、採取した音の加工を行った。
【０１４３】
本実験において行った音の加工方法としては、採取した原音から印刷動作１サイクル期間中の音を切り出した。そして、１サイクル期間中の音のうち、上述したように抽出した主要音源に関する部分に対して周波数軸上または時間軸上でフィルタ処理を施し、これらの部分を減衰または強調する処理を行った。すなわち、１つのモードで抽出された音源の音につき３つの水準の音（強調・原音・減衰）を作成した。
【０１４４】
なお、上述したように画像形成装置の前後左右側で採取される音は各々異なるが、このような４方向の音から得られる心理音響パラメータ値の範囲よりも、本実験で作成した前面側で採取した音を強調、減衰して得られる３つの供試音から得られる心理音響パラメータ値の範囲の方が広いことが確認されている。すなわち、本実験のように前面側で採取した音を強調、減衰して得られる３つの音を用いて主観的評価実験を行うことで、４方向で採取した音から得られる音の特性をカバーする音質評価式が得られることになり、当該音質評価式により４方向における不快さを算出することもできる。
【０１４５】
以上のように前面側で採取した音を元に、３つの動作モードごとに抽出した主要音源の発する音から３つの水準の音（強調、原音、減衰）を作成すると、各モードについて抽出した音源の水準が異なる組み合わせをＬ９直行表に基づいて９音作成した。主観的評価実験では、総当りの比較実験を行う必要があるので、９音の場合、７２通りの比較実験を行うことになる。
【０１４６】
ここで、表２は「カラーモード▲１▼」、つまり印刷速度２８ppmで動作したときに採取された音から抽出された主要音源（７つ）について作成した３水準の音を、Ｌ９直行表に基づいて割り付けて９つの供試音を作成した結果を示す。このように直行表に割り付けるとこで、各因子（音源の水準変化）間に相関がないため、他の因子の変化を無視して分析が可能となる。
【表２】

かかる表（以下の表も同様）において、「−１」は音をほぼ聞こえなくなるまで減衰して作成した音であり、「０」は原音そのままのレベルの音であり、「１」は原音と比較してレベルの違いがはっきりとわかるまで強調した音である。例えば、表２における供試音「カラー２８ppm▲９▼」は、すべての音源について「０」がついているので、すべてが原音のままであることを示す。
【０１４７】
なお、表２においては、後述する比較法実験により得られた各供試音の主観的評価値を併記している。
【０１４８】
次に、表３は「カラーモード▲２▼」、つまり印刷速度１４ppmで動作したときに採取された音から抽出された主要音源（６つ）について作成した３水準の音を、Ｌ９直行表に基づいて割り付けた結果を示す。ただし、帯電音、ドラム駆動ステッピングモータ音、ポリゴンミラーモータ音は、同じトーナリティ成分の音であるため、各々の供試音について同水準のレベルとした。給紙ステッピングモータ音もトーナリティ成分であるが、これについては間欠的に発生する音であるため、上記のモータ音とは個別に水準を振ることとした。
【表３】

また、表４は「モノクロモード」、つまり印刷速度３８ppmで動作したときに採取された音から抽出された主要音源（５つ）について作成した３水準の音を、Ｌ９直行表に基づいて割り付けた結果を示す。ただし、帯電音およびドラム駆動ステッピングモータ音は同じトーナリティ成分の音であるため、各々の供試音について同水準のレベルとした。
【表４】

また、本実験においては、上記３つのモードを混合したときに前面で採取された音から得られる、心理音響パラメータであるラウドネス値、シャープネス値、トーナリティ値およびインパルシブネス値から３つの水準の音（強調、原音、減衰）を作成し、これらの音をＬ９直行表に基づいて割り付けて供試音を作成した。その結果を表５に示す。
【表５】

なお、ラウドネス値の割り付けについては、「モノクロモード」印刷速度３８ppmについては強調したものを、「カラーモード▲１▼」印刷速度２８ppmについては中間のものを、「カラーモード▲２▼」印刷速度１４ppmについては減衰したものをそれぞれ割り付けることとした。すなわち、印刷速度に応じてラウドネスの各水準値を割り付けた。また、表中のかっこ内の数値は、各々のパラメータ値を示している。本実験では印刷速度（ppm）がどのような影響を与えるか、つまり印刷速度の効果についても確認を行うため、印刷速度とラウドネス値が完全に比例して変化するようではその効果を分析できない。したがって、表５に示すように、ラウドネス値は同じ水準であっても１（sone）程度の差をつけ、聞こえの大きさの違いがでるようにした。
以上が採取した動作音から供試音を作成する過程の詳細である。
【０１４９】
（４）供試音の心理音響パラメータの測定
次に、上述したように作成した供試音について、上記ヘッドアコースティックス社製の音質解析ソフトウェア「ArtemiS」を用い心理音響パラメータを求めた。この音質解析ソフトウェアでは、心理音響パラメータを求める際に、様々な設定を選択することができるのであるが、今回の実験ではデフォルトの設定を採用した。
【０１５０】
例えば、ラウドネスについては、「Caluculation method」として「FFT/ISO0532」、「Filter/ISO0532」および「FFT/HEAD」が選択できるが、デフォルトの「FFT/ISO0532」を採用し、「Spectrum Size」はデフォルトの「４０９６」で行った。シャープネスについては、「Caluculation method」はデフォルトの「FFT/ISO532」を採用し、「Sharpness method」は、「Aures」，「von Bismarck」のうち、デフォルトの「Aures」を採用した。「Spectrum Size」はデフォルトの「４０９６」で行なった。他の心理音響パラメータはラウドネスと相関があり、ラウドネスの設定によって自動的に変化する。
【０１５１】
以上のように設定した音質解析ソフトウェアを用い、上記（３）の過程で作成した供試音の心理音響パラメータ値を求めた。その結果を表６に示す。
【表６】

【０１５２】
（５）供試音による一対比較法実験
次に、上記のように作成した供試音を評価してもらう被験者を集め、被験者に各モードごと（「カラーモード▲１▼」、「カラーモード▲２▼」、「モノクロモード」および「混合モード」）に作成した供試音▲１▼〜▲９▼を一対比較してどちらが不快であるかを判定させた。
【０１５３】
かかる比較実験の際、９つの供試音から２つの供試音のすべての組み合わせを抽出し、Ｎ人の被験者が組み合わせのすべてを比較する。すなわち、１つのモードで９つの供試音があるわけであるから、７２通りの組み合わせがあり、これらについて被験者に比較をさせる。したがって、供試音▲１▼と供試音▲２▼という組み合わせについての評価と、供試音▲２▼と供試音▲１▼という組み合わせについての評価は別であり、このように聞く順序が異なる組み合わせについても実験対象となる。
【０１５４】
そして、この比較では、例えば供試音▲１▼と供試音▲２▼とを比較し、その被験者が供試音▲１▼を不快と評価した場合には「１点」、供試音▲２▼が不快であった場合には「−１点」とし、結果を集計して統計処理を行った結果、９つの供試音に対して−１〜１の範囲で相対的な主観評価値を得た。なお、かかる主観評価値は表２〜表５に併記している。上記のような評価を行っているので、この主観評価値は大きい方が不快であることを意味する。
【０１５５】
ここで、９つの供試音のすべての組み合わせの対について、比較順序が異なる場合も含めて比較実験を行うことが好ましいが、実験回数を減らすために供試音から得られる心理音響パラメータの重要性等を考慮して抽出した重要な供試音対についてのみ比較実験を行うようにしてもよい。
【０１５６】
なお、上述した一対比較法実験では、一対比較による評価をどちらが不快であるかを選択するものとし、同程度の不快さという判断をしないことを条件としている。そして、このような実験データを用いて後述する音質評価式を求めるようにしているが、シェッフェの方法とその改良方法（芳賀変法、浦変法、中屋変法）については累積ロジスティック回帰モデルを使用し、またブラドレー・テリー法では以下に説明する音質評価式を使用し、あらゆる一対比較法の実験データについても適用することができる。
【０１５７】
（６）不快音源の特定
次に、不快音源の特定を、「カラーモード▲１▼」、「カラーモード▲２▼」および「モノクロモード」の３つのモードについて実施した実験結果ごとに行った。ここで、図１４〜図２８は、表２〜表４に示される各音源の水準（強調、原音、減衰）と、主観評価値との関係をグラフに示したものである。このグラフにおいては、縦軸は主観評価値αであり、上にいくほど不快であることを意味する。グラフの横軸は音源の水準、つまり音圧レベル水準であり、「−１」は音源を減衰、「０」は原音のまま、「＋１」は音源を強調したものである。
【０１５８】
また、各図中の「Ｒ²」は寄与率であり、「Ｒ」は相関関数である。ここで、寄与率とは、不快さに対してその音源が何パーセント寄与しているかを示すものである。図１４に示す結果の場合、定着オイル塗布衝撃音が不快さに５１％寄与していることを示す。すなわち、音源のレベル変化と、主観評価値（不快さ）の変化の相関が高ければ、寄与率は大きくなるのである。なお、１つのモードにおける各音源の寄与率の合計は１００％になるが、四捨五入等の関係で正確に１００％になっていないものもある。
【０１５９】
図１４〜図２０に示される「カラーモード▲１▼」の各音源の寄与率を参照すると、カラー現像駆動音系、給紙ステッピングモータ音、帯電音、ポリゴンミラーモータ音はほとんど不快さに寄与していないことがわかる。しかし、後の分析により、給紙ステッピングモータ音、帯電音、ポリゴンミラーモータ音の３音源はトーナリティ（純音）成分と関係が強く、実際には不快だが、純音の周波数が近い場合は同時に対策しないとあまり不快さが改善されないことがわかった。したがって、他のモードでは、これらの音源については各供試音で同一水準とすることにした（上記（３）の過程および表３、表４参照）。このため、音源のうち、カラー現像駆動音のみが不快さにほとんど寄与していないので騒音対策の必要がないと考えられる。ただし、音響パワーレベルによる評価では改善が必要な場合もある。
【０１６０】
一方、「カラーモード▲１▼」において最も不快さに寄与しているのは、定着オイル塗布衝撃音であり、その次に寄与しているのは用紙摺動音である。
【０１６１】
図２１〜図２４に示される「カラーモード▲２▼」の不快音源分析結果によると、定着オイル塗布衝撃音４３％、用紙摺動音３５％、給紙ステッピングモータ音１７％、帯電音、ポリゴンミラーモータ音およびドラム駆動モータ音の３音源の合計が３％であった。
【０１６２】
図２５〜図２８に示される「モノクロモード」の不快音源分析結果によると、定着オイル塗布衝撃音４３％、用紙摺動音３５％、帯電音とドラム駆動モータ音の合計が１０％、現像駆動音系は３％であった。
【０１６３】
以上のような分析結果からは、現像駆動系の音以外の音源は不快さに寄与しており、これらの音源について騒音対策を施せば不快さを軽減させることができることがわかる。
【０１６４】
（７）差モデルの分析データ作成
次に、上記（５）の一対比較法実験により取得した実験結果を用い、２音を比較したときにそれぞれの音を不快に感じる確率を求める。より具体的には、Ａ音（先に提示した音）と、Ｂ音（後に提示した音）を比較し、不快に感じた音の人数を全被験者数で割った値を算出する。例えば、被験者が４０人であった場合において、Ａ音（先提示音）とＢ音（後提示音）を比較して、Ａ音が不快であると判断した人が３０人、Ｂ音が不快であると判断した人が１０人であるとすると、このときのＡ音およびＢ音を不快に感じる確率をそれぞれ以下のように求める。
Ａ音不快確率＝３０／４０、Ｂ音不快確率＝１０／４０
【０１６５】
このように求めた不快確率は、２つの音の物理量（心理音響パラメータ等）の差に基づいて、次の（８）の過程で行われる２つの音の不快確率の差を予測するモデルの作成に用いられる。また、当該予測モデルの作成に用いられる、物理量（心理音響パラメータ）の差、つまり対比した供試音と供試音の心理音響パラメータ値（表６参照）の差とを、すべての供試音の組み合わせ（１モードあたり７２通り、４つのモードがあるため２８８通り）を算出する。
【０１６６】
以上のように算出した評点の差と心理音響パラメータ値との差の結果（差モデルの分析データ）の一部を表７に示す。かかる表７は「カラーモード▲１▼」の供試音についての結果の一部（供試音▲１▼と供試音▲２▼〜▲９▼の比較結果）である。
【表７】

（８）２音の不快確率を予測する式を導出
【０１６７】
次に、上述した（７）の過程において求めた２音の不快確率と、音の物理量（心理音響パラメータ）の差とを用い、多重ロジスティック回帰分析を行った。
【０１６８】
多重ロジスティック回帰分析は、統計解析ソフトウェア「ＪＭＰ （ＳＡＳ Ｉｎｓｔｉｔｕｔｅ Ｉｎｃ の登録商標）」または「ＳＰＳＳ （ＳＰＳＳ Ｉｎｃの登録商標）」等を利用して行なうことができる。上記表７のデータ（不快確率および心理音響パラメータ値の差等）を、「ＪＭＰ 」に入力し、説明変数（心理音響パラメータ値の差）を選択しながら分析を実行することにより、ロジスティック回帰係数や選択した説明係数のＰ値や式の寄与率等の統計的な結果がアウトプットされる。ここで、Ｐ値は有意差検定の確率のことであり、５％以下で有意、５％以上で有意でない（関係ない）と判断する。
【０１６９】
今回は、評点の差のモデルであるので、切片を０に固定し、統計解析ソフト『JMPバージョン4J』によって有意な心理音響パラメータを選択した。変数選択の結果、ラウドネス，シャープネス，トーナリティ，インパルシブネスが選択された。変数として選択した4つの心理音響パラメータの偏回帰係数（重回帰分析時の回帰係数）を表８に示す。
【表８】

なお、上記表８に示すように、回帰分析結果としては、選択した４つのパラメータの偏回帰係数に加え、９５％以上の信頼性をもつ偏回帰係数の上限値および下限値（つまり、９５％以上の信頼性をもつ偏回帰係数の範囲）も含まれている。これらの上限値および下限値は、偏回帰係数の推定値に、それぞれ対応する標準偏差の約２倍の値（２σ）を±したものである。偏回帰係数の値はいずれも正であるため、パラメータ値の差が正方向に大きくなればなるほど、不快さの差も大きくなることがわかる。
【０１７０】
上記の多重ロジスティック回帰分析の結果を用い、上記（ｆ）式のexp内が以下の−ｚとなるモデル式を作成した。
【数４】

z=＋0.80742768×（ｘラウドネスi−ｘラウドネスj）
＋1.3807×（ｘシャープネスi−ｘシャープネスj）
＋9.0486×（ｘトーナリティi−ｘトーナリティj）
＋5.5916×（ｘインパルシブネスi−ｘインパルシブネスj）・・・(ｇ)
以上のようにして２つの音の心理音響パラメータ値を代入することにより、２音を比較した時の不快確率を算出できる非線形式が導出できた。
【０１７１】
ここで、図２９に一対の２音を比較したときの不快確率の実測値と、上記モデル式を用いて導出した予測値との散布図を示す。図示のように、不快さの寄与率も９２％と高く、このモデル式の信頼性が高いことがわかる。
【０１７２】
（９）不快確率を予測する音質評価式の導出
上記のように導出したモデルでは、２音を比較したときの不快確率を予測することができるが、音質評価において最終的に必要となるのは単独の音の不快確率である。そこで、以下のようにして、上記２音を比較したときの不快確率を予測するモデルから、取り出したある１つの音に対して母集団の中での相対的な不快確率を求めることができる音質評価式を導出した。
【０１７３】
まず、上記（ｆ）式の（ｇ）に、各心理音響パラメータとして実験に使用した以下のような各供試音の平均値を代入して、そのときの不快確率ｐ＝０．５、つまり各パラメータ値が平均的である場合の音を、母集団のその他の音と比較した場合の不快確率を５０％と定義した。
【０１７４】
各心理音響パラメータ値の平均値を代入するから、
ｘラウドネス０＝7.067804
ｘシャープネス０＝2.27953527947254
ｘトーナリティ０＝0.115442108655561
ｘインパルシブネス０＝0.606150659026989
であり、よって、
0.5＝1/｛1+exp（-［+0.80742768（ラウドネス値i−7.067804）
+1.38073296（シャープネス値i−2.27953527947254）
+9.04860954（トーナリティ値i−0.115442108655561）
+5.59160971（インパルシブネス値i−0.606150659026989）］｝
となる。
【０１７５】
ここで、expの中身をｚとすると、
0.5＝1/1＋exp（-ｚ）
0.5×｛1＋exp（-ｚ））｝＝1
0.5×exp（-ｚ）＝0.5
exp（-ｚ）＝1
【０１７６】
そして、両辺に対数をとると、
ln｛exp（-ｚ）｝＝ln1＝0
-ｚ＝0
ｚ＝0
よって、
ｚ＝0＝［+0.80742768（ラウドネス値i−7.067804）+1.38073296（シャープネス値i−2.27953527947254）+9.04860954（トーナリティ値i−0.115442108655561）+5.59160971（インパルシブネス値i−0.606150659026989）］
となる。よって、
ｚ＝+0.80742768×ラウドネス値i+1.38073296×シャープネス値i+9.04860954×トーナリティ値i+5.59160971×インパルシブネス値i-13.28811895
となる。したがって、単独の供試音に対して、不快に感じる確率を予測するモデル式（ｄ）に変換できる。
不快確率Ｐ＝１／（１＋exp（−ｚ））
z＝＋0.80742768×（ラウドネス）＋1.38073296×（シャープネス）＋9.04860954×（トーナリティ）＋5.59160971×（インパルシブネス）−13.28811895・・・・・・・・・・・・・・・（ｄ）
【０１７７】
このように導出した（ｄ）式を不快確率Ｐを予測する音質評価式として用いることができる。
【０１７８】
今回は、全データの平均値を基準値に使ったが、環境変化により基準値を変更することが可能である。また、改良前の画像形成装置の音から得られる心理音響パラメータ値を基準値として、改良後の画像形成装置の発する音の不快確率を算出することも可能である。
【０１７９】
以上のようにして導出された上記（ｄ）式は、平均値からのずれによる優劣の確率の変化を推定するものであり、音の物理量の平均値を入力した場合の確率は０．５として計算している。この確率が大きくなるにつれて不快さが増すことになる。この音質評価式を用いることで確率Ｐが所定の確率以下になる心理音響パラメータの条件を求めることができる。
【０１８０】
また、上記（ｄ）式から、各心理音響パラメータに対応する音の要素を低減すれば、つまり▲１▼聞こえの大きさを小さくする（ラウドネス）、▲２▼高周波成分を少なくする（シャープネス）、▲３▼純音成分を少なくする（トーナリティ）、▲４▼衝撃音を小さくする（インパルシブネス）、ことにより不快さを低減させることができることがわかる。
【０１８１】
なお、上記（８）で説明したように、表８に示す回帰分析結果として取得した９５％以上の信頼性をもつ偏回帰係数の範囲とするので、切片の範囲もそれぞれの偏回帰係数の上限値と下限値とを代入して得られる値となる（下限値代入時切片は-12.47284396、上限値代入時切片は-14.10339529）。
【０１８２】
この範囲内で係数および切片が取りうるとして上記（ｄ）式を変形すると、以下の式（ａ）が得られる。
不快確率Ｐ＝１／（１＋exp（−ｚ））
ｚ＝ Ａ×（ラウドネス値）＋Ｂ×（シャープネス値）＋Ｃ×（トーナリティ値）＋Ｄ×（インパルシブネス値）＋Ｅ
0.76545285≦Ａ≦ 0.84940259
1.27685159≦Ｂ≦ 1.48461447
8.11323413≦Ｃ≦ 9.98398583
5.30484579≦Ｄ≦ 5.87837423
-14.10339529≦Ｅ≦ -12.47284396‥‥（ａ）
【０１８３】
かかる（ａ）式を不快確率Ｐを予測する音質評価式として用いることができる。
【０１８４】
また、表８に示す結果に基づいて上記（ａ）式は回帰係数のとり得る値に幅を持たせたものであるが、表８に示す回帰係数の推定値を固定した場合（つまり各心理音響パラメータに乗算する係数を固定した場合）、ｚに±２σを加えたものが、９５％の信頼区間の範囲を示すものとなる。ここで、σは誤差の標準偏差である。
【０１８５】
ｚの標準誤差はを求め方は、まず実測した不快さの確率ｐを用い、上記（７）式によりｚを導出する一方で、統計解析ソフトウェア「ＪＭＰ （ＳＡＳ Ｉｎｓｔｉｔｕｔｅ Ｉｎｃ の登録商標）」等を用いてｚの予測値を導出する。そして、実測値から求められたｚと、予測値のｚとの関係を散布図にプロットし、上記統計解析ソフトウェアを用いて、その差（誤差）の標準偏差を求めることができる。
【０１８６】
このような作業を行った結果、誤差の標準偏差σ＝0.721307が得られた。
【０１８７】
よって、この誤差の範囲を含んだ式は、以下の（ｃ）式のようになる。
不快確率Ｐ＝１／（１＋exp（−ｚ±２σ））
z＝＋0.80742768×（ラウドネス）＋1.38073296×（シャープネス）＋9.04860954×（トーナリティ）＋5.59160971×（インパルシブネス）−13.28811895
σ＝0.721307‥‥（ｃ）
【０１８８】
上記（ｃ）式を不快確率Ｐを予測する音質評価式として用いることもできる。また、上述したように求めた誤差の標準偏差σを用い、以下のような式によって不快確率を求めることも考えられる。
不快確率Ｐ＝１／（１＋exp（−ｚ））±２σ
【０１８９】
しかしながら、この式を用いて不快確率を導出した場合、導出される不快確率Ｐの範囲が０〜１までの範囲を超えてしまうことがあり、不快確率を予測する式としては不適当である。
【０１９０】
（１０）導出した音質評価式の検証
次に、上記のように導出した不快確率Ｐの予測式（音質評価式）の予測精度を検証することとした。
【０１９１】
この検証としては、不快確率Ｐの実測値と、上記音質評価式（ｄ）を用いて導出した予測値とを比較することにより行った。不快確率Ｐの実測値は各動作モードごとに実際に実験を行わなくては求まらないため、上記４つのモード「カラーモード▲１▼」、「カラーモード▲２▼」、「モノクロモード」、「混合モード」）ごとに実験を行って不快確率の実測値を求めるとともに、これらに対応する予測値を音質評価式を用いて導出することとした。
【０１９２】
不快確率の実測値としては、各供試音の不快指数の和を全体の評価数で割った値を用いる。より具体的には、「カラーモード▲１▼」の供試音に関する実験においては、不快確率の分母は以下の値となる。実験を３５人で実施した場合、各供試音については９音の各々について、他の８音と比較するので、
８音×２（比較順序の入れ替え）×３５人＝５６０人となる。
【０１９３】
一方、分子は、例えば「カラーモード▲１▼」の供試音▲１▼を例にとって説明すると、他の供試音▲２▼〜▲９▼と比較した際（順序逆も含む）に供試音▲１▼を不快と判断した人数が、それぞれ１０人、２０人、２０人、１９人、１９人、５０人、５人、５人であれば、その和１４８人が分子となる。
【０１９４】
よって、この場合「カラーモード▲１▼」の供試音▲１▼の不快確率の実測値は４８／５６０＝０．２６となる。
【０１９５】
以上のような手順で４つのモードのそれぞれの供試音ごとに不快確率の実測値を求めるとともに、音の物理量（心理音響パラメータ）を上記音質評価式（ｄ）に代入することで予測値を得る。このようにして、各モードの各供試音についての実測不快確率と予測確率とを求めることができ、その結果を表９に示す。
【表９】

そして、この結果をプロットしたグラフを図３０に示す。同図に示すように、このグラフの傾きはほぼ１であり、寄与率も高い。したがって、４つの実験、つまり４つのモードのいずれであっても実験上記式（ｄ）によって導出される評点の予測値の精度が高いと考えられる。
【０１９６】
なお、検証のための予測値の導出にあたっては、実験ごと（モードごと）の心理音響パラメータの平均値から切片（＝E）を求め、それを切片とした（ｄ）式を若干変形した式をモードごとに導出し、導出した式を用いて予測値を求めることとした。このような調整を行ったのは、各実験による実測値と予測値とを比較して、当該予測値の精度を検証する必要があったからであるが、検証を行わない場合にはこのような調整を行うことなく、上記（ｄ）式を音質評価式として用いることができる。表１０に参考のために、その調整値を示す。「全体平均との差」の値を各モードの平均値を代入して求めた切片の値に加算すると、上記式（ｄ）と同様の式となる。
【表１０】

さて、上述した検証で明らかなように、音質評価式（ｄ）によって求められる予測確率の精度が高いと考えられるが、このように得られた不快確率Ｐがどのくらいの値になると人が不快と感じるかが重要である。そこで、これを確認するため次のような実験を行った。すなわち、被験者に供試音▲１▼〜▲９▼をすべて聞いてもらった後、再び１音づつ聞いてもらい、各々の供試音について不快さを３段階評価するという実験を行い、表１１、表１２、表１３に示す結果を得た。なお、表１１は「カラーモード▲１▼」の供試音についての実験結果、表１２は「カラーモード▲２▼」についての実験結果、表１３は「モノクロモード」についての実験結果である。
【表１１】

【表１２】

【表１３】

なお、表中「Ａ」は許容できる音、「Ｃ」は許容できない音、「Ｂ」はその中間ぐらいの音という評価である。そして、「Ａ」と評価された音の予測不快確率（式（ｄ）に算出された値）のうち、最も大きな値を許容値とすると、各モードのppmおよび画像形成速度（mm/s）ごとの許容値は表１４に示すようになる。
【表１４】

図３１は表１４に示される結果に基づき、ppm値と許容値との関係を近似させたグラフである。かかる近似式は、
Ｐ≦0.3383Ｌｎ（ppm）−0.8103‥‥（ｂ）
である。
【０１９７】
また、図３２は表１４に示される結果に基づき、画像形成速度（mm/s）と許容値との関係を近似させたグラフである。かかる近似式は、
Ｐ≦0.3201Ｌｎ（mm/s）−1.2402‥‥（ｅ）
である。
【０１９８】
以上のように上記式（ｄ）、（ｃ）または（ａ）式を利用することで、実際に主観的な評価実験を行うことなく、音の物理量から取得できる心理音響パラメータ値等を取得するだけで人が不快と感じる不快確率Ｐを求めることができる。そして、上述した条件式（ｂ）（ｄ）により、画像形成速度（mm/sやppm）が異なる複数の動作モードを有する機器であっても、各モードごとに求めた不快確率Ｐがどのような値であれば不快さを感じさせないかを判断することができる。
【０１９９】
以上が画像形成装置が発する音の質を評価する方法、および当該音質評価に用いる音質評価式の導出方法である。
【０２００】
Ｃ．改造方法
上述したように本発明は、上記のような画像形成装置が発する騒音を評価し、その評価に基づき当該騒音が人に与える不快感を低減するための対策をなす改造方法であり、以下、上記構成の画像形成装置を改造し、画像形成装置が発する音が人に不快感を与えることを低減するための対策の具体例について説明する。
【０２０１】
まず、画像形成装置が発する音を評価するため、上述した（１）と同様の手法で画像形成装置が発する音を採取する。ここで、採取位置は、ＩＳＯ７７７９に規定されている近在者位置（図１１照）であり、基準箱の水平面の投影から1.00±0.03ｍの距離で、高さは床上1.2±0.03mまたは1.50±0.03mの位置である。
【０２０２】
また、図１０に示すように、操作部のある前面、左右面および後面といった４面側すべてについて音の採取を行い、各々の収音結果から心理音響パラメータを取得して不快確率Ｐを上記音質評価式により求め、各面ごとの不快確率Ｐが許容値内か否かを判定するようにしてもよいし、前面のみ、あるいはいずれか１の面側のみで採取した収音結果から不快確率Ｐを求めて判定を行うようにしてもよい。また、４面側で採取した音から得られた心理音響パラメータ値の平均値を導出し、かかる平均値から求めた不快確率Ｐが許容値内か否かを判定するようにしてもよい。
【０２０３】
なお、４面側のいずれに位置する人が不快さを感じないようにさせるためには４面側すべての位置で音を採取することが好ましいが、１面のみ、特に最も人が位置する可能性が高い前面側での音を採取することでも十分な評価ができる。
【０２０４】
以上のようにして求めた不快確率Ｐが上述した許容値を超える場合には、人が不快であると感じているおそれが非常に高いので、かかる不快確率Ｐが許容値以下となるよう装置各部に種々の改造を施す。一方、不快確率Ｐが許容値以下である場合には、人が不快に感じるおそれは少なく、特に騒音対策を施す必要はないと判断することができる。
【０２０５】
上述したように不快確率Ｐは、聞こえの大きさを小さくする（ラウドネス）、高周波成分を少なくする（シャープネス）、純音成分を少なくする（トーナリティ）、衝撃音を小さくする（インパルシブネス）といった対策を施すことにより小さくすることができ、これを小さくすることで人に与える不快さを低減できることになる。よって、以下においては、上記の心理音響パラメータを低減させるための具体的な対策例について説明する。
【０２０６】
（１）トーナリティ（純音成分）の低減対策
（１−１）ドラム駆動ステッピングモータ音の低減
まず、トーナリティの低減対策例について説明する。トーナリティの低減対策としては、ドラム駆動ステッピングモータ音を低減する方法がある。図１１、図１２および図１３に示すように、いずれの動作モードにおいてもドラム駆動モータの音が発生している。そして、この音はステッピングモータへの入力パルスの周波数成分を多く含むものである。
【０２０７】
図３３および図３４は改造前のカラードラム駆動モータ４１と黒ドラム駆動モータ４２とを含むドラム駆動機構を示す図である。これらの図に示すように、カラードラム駆動モータ４１、黒ドラム駆動モータ４２、ギヤ４３，４４はモータブラケット５９によって保持されている。
【０２０８】
モータブラケット５９は、板金を絞り加工等で強度を持たせた部材である。そして、曲げ加工により当該画像形成装置の筐体取り付け部（ねじ穴等）が形成されており、モータブラケット５９はこの取り付け部において筐体に固定されている。
【０２０９】
モータブラケット５９には、並んで配置される４つのギヤ４４が回転可能に保持されている。これらのギヤ４４のうち、図３３の最も右側のギヤ４４と黒ドラム駆動モータ４２のモータ軸に取り付けられたギヤ６１とが歯合されている。これにより黒ドラム駆動モータ４２によってギヤ４４が回転させられ、これに伴ってモノクロ画像形成用の感光体ドラム２８（図３参照）が回転させられるようになっている。
【０２１０】
また、上記のギヤ４４以外の３つのギヤ４４のうち図３２の左側の２つのギヤ４４は、カラードラム駆動モータ４１のモータ軸６２によって回転させられる。また、左から２番目のギヤ４４と３番目のギヤ４４とはともに中継ギヤ４３に歯合されており、これにより２番目のギヤ４４の回転に伴って３番目のギヤ４４が回転させられる。つまり、カラードラム駆動モータ４１の回転に伴って３つのギヤ４４が回転させられ、これによりＣ用、Ｍ用、Ｙ用の感光体ドラム２８（図３参照）が同時に回転させられるようになっている。
【０２１１】
以上のような感光体ドラムを駆動するためのギヤはモジュール０．５でギヤの軸間距離を設計値に正確にあわせることができるよう、モータの取り付けに対して特殊な防振構造等を採用していない。つまり、黒ドラム駆動モータ４２およびカラードラム駆動モータ４１は直接モータブラケット５９に取り付けられて固定されている。
【０２１２】
このようにモータをモータブラケット５９に直接取り付けることによって動作時のモータの振動がモータブラケット５９に固体伝搬し、増幅されて放射される。これに起因して発せられる音は、ドラム駆動モータであるステッピングモータの駆動周波数成分を多く含む音である。
【０２１３】
このようなステッピングモータの駆動周波数成分が顕著な音の発生を低減するため、図３５に示すように、カラードラム駆動モータ４１および黒ドラム駆動モータ４２を防振ゴムマウント６０を介してモータブラケット６５に取り付けるようにする。すなわち、この防振ゴムマウント６０は、上記のように発生する音を低減させる低減手段となる。
【０２１４】
防振ゴムマウント６０としては、例えば株式会社ＮＯＫ製のステッピングモータマウントを使用することができ、後述する騒音対策による効果を試す試験においては当該ステッピングモータマウントを使用している。
【０２１５】
モータブラケット６５とドラム駆動モータとの間に防振ゴムマウント６０を介在させたドラム駆動機構について図３６および図３７を参照しながら説明する。防振ゴムマウント６０をドラム駆動モータとモータブラケット６５の間に介在させると、各ギヤの軸間距離の精度が悪化する。このため、このドラム駆動機構では、モータ軸を直接ギヤに歯合させるのではなく、モータ軸からタイミングベルト機構を介してギヤ４４等に駆動力を伝達する構成とした。
【０２１６】
より具体的には、カラードラム駆動モータ４１および黒ドラム駆動モータ４２のモータ軸にはそれぞれタイミングプーリ６６，６７を取り付け、かかるタイミングプーリ６６，６７に巻きかけられたタイミングベルト７０によって２段ギヤ／プーリ６３，６４にモータの駆動力を伝達する。つまり、モータ軸の回転に伴って２段ギヤ／プーリ６３，６４を回転させる。
【０２１７】
かかる２段ギヤ／プーリのギヤは上述したドラム駆動用のギヤ４４に歯合されている。これにより上記改造前の構成と同様、ドラム駆動モータの回転に伴ってギヤ４４を回転させることができ、感光体ドラム２８（図３参照）を回転させることができる。
【０２１８】
モータブラケット６５は、モータを保持する部分（図３７の下側の部分）がその上の部分よりもモータと反対側に突出するよう曲げ加工がなされている。かかる突出部分にできた空間に防振ゴムマウント６０がモータブラケット６５と接するよう配置され、防振ゴムマウント６０のモータブラケット６５と反対側にモータ（４１，４２）がそのモータ軸がモータブラケット６５の反対側（図３７の左側）の面に突出するよう配置される。このようにモータブラケット６５とモータとを直接保持する構造とせず、防振ゴムマウント６０を介在させて保持する構造としている。
【０２１９】
本構成では、２段ギヤ／プーリ６３，６４がモータブラケット６５の図３７の左側（ギヤ４４が配置される側）に配置されるので、モータ軸はその分だけ図３７の左側の位置まで突出させる必要がある。しかしながら、上記のようにモータブラケット６５に突出部分を作ることで、モータの配置位置そのものを図３７の左側にすることでき、これによりモータ軸を長くする必要がなくなる。よって、モータ軸を長くすることで生じるおそれのあるモータ軸の偏心やそれに起因した騒音発生等を抑制することができる。
【０２２０】
なお、本構成においては、２段ギヤ／プーリ６３，６４を取り付けるためのスタッド６９の強度を大きくすることが好ましい。スタッド６９の強度が不足している場合には、ギヤ４４と２段ギヤ／プーリとが偏心しながら噛み合うこととなり、ベアリング７０を介してドラム軸６８も偏心することになる。ドラム軸６８の偏心は用紙に形成される画像に影響を与えることがあり、かかる不具合を起こさないため、スタッド６９の強度を大きくする必要があるからである。
【０２２１】
また、上述した防振ゴムマウント以外にも、モータの振動をある程度吸収することができる弾性体を用いるようにしてもよい。
以上がドラム駆動ステッピングモータ音の低減対策である。
【０２２２】
（１−２）給紙用ステッピングモータ音の低減
次に、給紙用のステッピングモータ音の低減対策について説明する。上述したように上記画像形成装置の給紙機構系の駆動モータは、ステッピングモータ５６であり（図８参照）、かかるステッピングモータの駆動を制御することでトレーからの用紙搬送を行うようになっている。このモータ音の低減対策としては、ステッピングモータ５６の駆動制御内容を以下のようにする方法があり、以下その制御内容について説明する。
【０２２３】
図３８は、ステップ角θ０で駆動されるステッピングモータのロータの動きを説明するための図である。ステッピングモータのステップ角は機械構造的に決められるものであり、通常はかかるステップ角θづつロータが一度に移動するのでかかるステップ角θが大きい場合にはその動きが滑らかではなく、振動等が生じこれが騒音の原因となる。
【０２２４】
そこで、本構成では、図示のように電子回路による制御によって機械的構造によってきめられているステップ角θよりも小さいステップ角でステッピングモータを駆動する、いわゆるマイクロステップ駆動を行うようにする。すなわち、励磁相の１相に供給する電流値を徐々に増加させる一方で、他の１相へ供給する電流値を徐々に低下させるといった電流供給制御を行うことで（図３８の▲１▼〜▲５▼参照）、ステップ角θよりも小さいステップ角での駆動を可能とし、その動きを滑らかにして騒音を低減しようというのである。
【０２２５】
また、図３９は、ステッピングモータのマイクロステップ駆動の１つである１−２相励磁のシーケンスを示す図である。１−２相励磁は、コイルを１相づつ励磁する１相励磁とコイルを２相づつ励磁する２相励磁を交互に繰り返す励磁方式であり、この励磁方式を用いてステッピングモータを駆動した場合、モータのステップ角が１／２となり、通常の駆動を行うよりもロータの動きが滑らかになり、振動を低減することができる。
【０２２６】
（１−３）ポリゴンミラーモータ音の低減
次に、ポリゴンミラーモータが発する音を低減するための対策について図４０を参照しながら説明する。同図に示すように、この対策では、ポリゴンミラーモータ２の近傍にヘルムホルツ共鳴器７１を取り付けている。より具体的には、ポリゴンミラーモータ２を保持するハウジング１１の上部にヘルムホルツ共鳴器７１を取り付けている。
【０２２７】
ヘルムホルツ共鳴器７１は、体積Ｖ１の空洞７２を形成するための空洞形成部材７２ａを有している。空洞形成部材７２ａはハウジング１１と一体になって形成されており、そのポリゴンミラーモータに対向する位置にある部分には空洞７２に通じる開口穴７３（断面積Ｓｂ）が形成されている。ここで、開口穴７３が形成された部分の板厚がＴｂであるとすると、かかる開口穴７３は一般的なヘルムホルツ共鳴器における、長さＴｂ、開口面積Ｓｂの短管に相当することになり、この構造体はヘルムホルツ共鳴器７１として機能するのである。
【０２２８】
この構成の下、ポリゴンミラーモータ２が駆動され、その振動によって開口穴７３の入り口に音圧が作用すると、開口穴７３（短管）内の空気（媒質）が一体運動を行い、空洞７２内の空気に圧力変化を生じさせる。このような現象は、開口穴７３（短管）内の空気を質点、空洞７２内の空気の体積変化による圧力変化をバネと仮定すると、力学系の質点−バネモデルと等価となり、後述する周波数（ヘルムホルツ共鳴周波数）に対して共振（共鳴）が生じることとなる。つまり、このヘルムホルツ共鳴周波数の音響エネルギーが空洞７２に閉じ込められるので外部空間にとっては音が低減されることになるのである。
【０２２９】
ここで、ヘルムホルツ共鳴周波数Ｆｈ（Ｈｚ）は次式により算出される。
Ｆｈ＝Ｃ／２π（Ｓｂ／（Ｖ１・Ｔｂ））^1/2
Ｃ：音速
【０２３０】
すなわち、開口穴７３の開口面積Ｓｂ、長さＴｂ（つまりハウジング１１の開口穴７３が設けられる部分の板厚）、空洞形成部材７２ａによって形成される空洞７２の体積Ｖ１を変化させることによって共鳴周波数Ｆｈ、つまり低減させたい音の周波数を変化させることができる。そこで、ポリゴンミラーモータ２を駆動したときに発生する音のうち最もレベルが大きくなる周波数に合致するよう上記各部の寸法等の設計を行うようにすれば、ポリゴンミラーモータ２の発する音を効果的に低減させることができる。
【０２３１】
なお、上述した騒音測定結果からは（図１１〜図１３参照）、カラーモード時にはポリゴンミラーモータ音が騒音として抽出されるものの、モノクロモード時には当該音はあまり騒音としては目立ったものとなっていない。このような場合には上記のようにカラーモード時にポリゴンミラーモータが発する音のうち、最もレベルが大きくなる周波数にヘルムホルツ共鳴周波数が合致するよう各部の寸法等を決定すればよい。一方、モノクロモード時に他の周波数のレベルが大きいような場合には、この周波数が共鳴周波数となるようなヘルムホルツ共鳴器を別途設けるようにすればよい。
【０２３２】
また、上記のように対応する周波数ごとにヘルムホルツ共鳴器を併設するようにしてもよいが、カラーモード時とモノクロモード時で開口穴７３の開口面積Ｓｂを変化させる機構を設けるようにしてもよい。例えば、開口穴７３をある程度ふさぐ位置とふさがない位置との間で移動可能なふた部材等を設け、かかるふた部材をモードに応じて移動させることで、各々のモード時における共鳴周波数を各々のモード時にレベルが大きくなる周波数と合致するよう可変させるようにしてもよい。
【０２３３】
（１−４）帯電音の低減
次に、帯電音の低減対策について説明する。帯電音とは、以下のようにして発生する音である。すなわち、帯電ローラ３６が感光体ドラム２８を帯電する際には（図３参照）、一般にバイアス電圧の交流成分に起因して帯電ローラ３６の表面と感光体ドラム２８の表面との間に引力と斥力が交互に作用し、両者の間に振動を生じさせる。この振動によって感光体ドラム２８が放射する音が帯電音であり、当該音は周波数の高い耳障りな純音であり、一般的に交流成分の周波数とその整数倍の周波数成分（高調波成分）からなる。
【０２３４】
このような帯電音の低減対策について図４１および図４２を参照しながら説明する。図４１に示すように、帯電音対策がなされた感光体ドラム２８の中空部分には、制振部材７４が配置されている。制振部材７４は、感光体ドラム２８の軸方向に延びる中空円筒状の基部７５と、当該基部７５から放射状に突出する複数の羽根部７６とを有しており、基部７５の中心軸が感光体ドラム２８の中心軸と略一致するよう配置される。
【０２３５】
制振部材の各羽根部７６の先端が感光体ドラム２８の内面に圧接しており、これにより制振部材７４が感光体ドラム２８内において保持されている。ここで、羽根部７６は、ゴム、樹脂またはこれらを含む材料、例えばウレタンゴムを含む材料、ポリプロピレン樹脂、ポリアミド樹脂などの熱可塑性樹脂材料等の弾性材料によって構成されていることが好ましい。羽根部７６として弾性材料を用いることによって、羽根部７６の先端がその弾性力によって感光体ドラム２８に圧接され、保持される。したがって、接着剤等による接着作業や位置だし作業が不要であるので、取り付け作業および取り出し作業が容易となるからである。
【０２３６】
上記のように感光体ドラム２８の内面側に羽根部７６が圧接するよう制振部材７４を配置することで、かかる制振部材７４が感光体ドラム２８の振動を抑制するよう作用する。したがって、上述した帯電ローラ３６による帯電の際に生じる感光体ドラム２８の振動を抑制することができる。また、このように感光体ドラム２８の振動を抑制するための部材が感光体ドラム２８の内部に設置されているので、新たに制振部材を設置するスペースをとる等の対策を施す必要がない。
【０２３７】
なお、感光体ドラム２８の振動を抑制して騒音を低減する手段としては、上記構成の制振部材７４に限らず、感光体ドラム２８の中空部分に金属柱を嵌合するといった対策を施すようにしてもよく、市販されている制振材（例えば、横浜ゴム株式会社製ハマダンパーなど）を貼り付ける等するようにしてもよい。
【０２３８】
（２）シャープネス（高周波成分）の低減対策
（２−１）用紙摺動音の低減
次に、シャープネス（高周波成分）の低減対策について説明する。シャープネスの低減対策としては、用紙摺動音を低減する方法がある。なお、用紙摺動音とは、搬送される用紙が部材等と摺動することによって生じる音である。
【０２３９】
上述したように第１トレー９または第２トレー１０に収容された用紙は、第１給紙ユニット５１または第２給紙ユニット５２によって各トレーから繰り出され、中継ローラ５３および搬送ローラ５５によってレジストローラ７の位置まで搬送される（図７参照）。
【０２４０】
ここで、図４３は、第１トレー９または第２トレー１０に収容された用紙を搬送して画像形成を行うとき（通常のプリント時）と、用紙を搬送せずにプリントを行うとき（フリーラン時）とで画像形成装置が発する騒音を測定して周波数分析（１／３オクターブバンド分析）した結果を示す。図４４は、この分析結果に示される通常のプリント時とフリーラン時の騒音から得られる各周波数帯域の音圧レベル差を示すグラフである。
【０２４１】
すなわち、図４４に示す周波数帯域ごとの音圧レベルは、用紙を第１トレー９または第２トレー１０から送り出して搬送するか否かに起因する、画像形成装置が発する騒音内容の差であり、用紙を搬送することによって図４４に示すように各周波数帯域で音圧レベルが増加していることを意味する。
【０２４２】
図４４に示すグラフから、通常のプリント時とフリーラン時とで３（ｄＢ）以上の差があるのは、２００〜２５０Ｈｚを中心とした帯域と、３．１５ｋＨｚ以上の帯域の２つである。なお、３ｄＢ以上の差は、音響エネルギーが２倍以上の差があることになる。
【０２４３】
以上の分析結果を検討すると、２００〜２５０Ｈｚを中心とした帯域の成分は、用紙とレジストローラ７が衝突する際に発生する音に起因するものであることがわかった。一方、３．１５ｋＨｚ以上の周波数帯域の成分は、用紙搬送時に用紙が部材等に摺動することで発生する音に起因するものであることがわかった。また、１２．５ｋＨｚ〜１６ｋＨｚを中心とした帯域では、７（ｄＢ）以上の差があり、またこの帯域はシャープネス値に与える影響が大きい。このことから、用紙摺動音の低減を図ることが騒音対策として効果的であることがわかる。以下、給紙ユニット、中継ローラ５３および搬送ローラ５５によって搬送される用紙の摺動音を低減するための対策について図４５を参照しながら説明する。
【０２４４】
同図に示すように、搬送ローラ５５は、複数のコロを軸に通したローラであり、用紙搬送路を挟んで対向配置されるローラ５５ａとローラ５５ｂとを有している。そして、搬送路Ａに沿って搬送される用紙（第１トレー９から繰り出された用紙）、または搬送路Ｂに沿って搬送される用紙（第２トレー１０から繰り出された用紙）はかかるローラ５５ａ、５５ｂ間に案内され、ローラ５５ａ、５５ｂによってレジストローラ７に向けて搬送される。
【０２４５】
搬送ローラ５５の近傍には、用紙を所定の経路に沿って搬送するためのガイド部材８０，８１，８２が配置されている。
【０２４６】
ガイド部材８０は、ローラ５５ａとともに搬送路Ａに沿って搬送される用紙をローラ５５ａ、５５ｂ間に案内する空間を形成する。また、ガイド部材８０は、ガイド部材８１とともに搬送路Ｂに沿って搬送される用紙をローラ５５ａ、５５ｂ間に向けて案内する空間を形成する。
【０２４７】
ガイド部材８０の搬送方向下流側（図４５の上側）の部分には、用紙搬送方向（図の上下方向）に延びる可踏性シート（例えばマイラーシート）からなる案内部材７７が取り付けられている。この案内部材７７は搬送路Ａ，Ｂから搬送される用紙をローラ５５ａ、５５ｂ間に向けて案内する。
【０２４８】
図４６に示すように、案内部材７７の先端部分における、ローラ５５ａと交錯しないようローラ５５ａが配置される位置には、切り欠き部分７７ａが裁断等することで形成されており、これにより用紙をその先端部分に接触させて確実にローラ５５ａ、５５ｂ間に向けて案内する。
【０２４９】
したがって、図４７に示すように搬送路Ａからの用紙は、案内部材７７の先端部分に摺動しながら搬送されることになる。従来の一般的な案内部材７７は、可撓性シートを所定形状にせん断することによって作製されており、その先端部分（せん断部分）にはバリが出ているのが通常である。このようなバリを１枚づつ取り除くのは非常に困難な作業であり、コストと時間を要することになる。したがって、通常はこのような作業は行われず、バリがある先端部分と用紙が摺動することで耳障りな騒音を発生してしまう。
【０２５０】
そこで、本構成では、図４８に示す構成の案内部材７７を採用することで、上記のような用紙と案内部材７７の先端部分が摺動することに起因する耳障りな騒音を低減することができる。
【０２５１】
図４９に示すように、従来の可撓性シートからなる案内部材は、所定の形状にせん断した厚さｔの可撓性シートをそのまま案内部材７７０としているものであり、用紙が摺動する先端部分はせん断部分となっている。これに対し、図４８に示す構成では、厚さｔ／２の可撓性シートを折り曲げて２枚重ねとしその折り曲げ部分が案内部材７７の先端部分となるようにしている。このような構成の案内部材７７を採用することで、上記のように搬送される用紙が摺動する先端部分は折り曲げ部分であり、せん断加工がなされていない部分であり、かつ滑らかなＲ形状となる。よって、上記のようなせん断加工部分にみられるバリに起因する耳障りな騒音の発生を低減することができるのである。また、２枚重ねとした厚みも従来の案内部材７７０と同様の厚みとなるため、必要とされる弾性力を発揮することもでき、案内部材としての機能に支障をきたすこともない。
【０２５２】
（３）インパルシブネス（衝撃成分）の低減対策
上記構成の画像形成装置においては、インパルシブネスの発生はほとんど定着オイル塗布音に起因するものである（図１１〜図１３参照）。定着オイル塗布音は、上述した構成の画像形成装置では、オイル消費量の増加を抑制するため、用紙が搬送されると、その都度オイル塗布ユニット４７を駆動して定着ベルト１３と接触させる構成を採用している（図６参照）。このような用紙が搬送されるごとになされる接触・離間の音が衝撃的に発生するので不快感を与えることになる。
【０２５３】
このような定着オイル塗布音による騒音問題は、画像形成のために用いるトナーとして、オイルレストナーを使用することで解消することができる。すなわち、かかるオイルレストナーはトナーにワックスが包含されているので、上述したようにオイル塗布作業を行わなくても、定着ベルトと用紙との乖離性がよい。このため、オイル塗布ユニット４７を利用する必要がなく、上述したオイル塗布ユニット４７と定着ベルト１３との接離に起因する衝撃音の発生を防止することができる。なお、オイルレストナーを使用するにあたっては、感光体ユニット３等の作像プロセス構成をオイルレストナーに適するよう修正する必要がある。
以上が不快確率Ｐを低減するための対策の具体例である。
【０２５４】
本発明者は、上記のような対策を施した画像形成装置が発する音を、対策前の画像形成装置が発する音を測定した際と同様の条件で測定し、その測定結果から対策の効果を検討した。なお、以下において比較する測定結果は、各々画像形成装置を「カラーモード▲１▼」で動作させたときに画像形成装置の前面側で音を採取することで得られたものである。
【０２５５】
図５０に、対策後の騒音の分析結果を示す。同図に示す対策後の分析結果と、対策前の分析結果（図１１参照）を比較すると、給紙ステッピングモータ音は１０（ｄｂ）程度低減され、帯電音は約５（ｄＢ）、ドラム駆動モータ音は約８（ｄＢ）低減され、ポリゴンミラーモータ音も１０（ｄＢ）程度低減されている。また、定着オイル塗布音もなくなった。以上のことから、上記対策を施すことによって各音源の発する音を低減させることができることがわかる。
【０２５６】
また、対策後と対策前の測定結果から得られた心理音響パラメータ値および上記音質評価式（ｄ）による音質評価値の比較結果を表１５に示す。
【表１５】

この表からわかるように、対策後の音質評価値、つまり不快確率は「−０．２３」であり、表１４に示される「カラーモード▲１▼」の許容値「−０．２６」よりも小さい。したがって、上記の対策によってほとんど不快感を与えることがないよう画像形成装置の改造がなされたものといえる。
【０２５７】
Ｄ．本発明の適用例
なお、本発明は、上記のように導出した音質評価式を用い、画像形成装置の音質評価を行い、かかる評価結果（不快確率Ｐ）が所定の条件を満たすような画像形成装置を提供できるようにするものである。したがって、本発明は、図５１に示すように、新製品の開発・製造の際に適用することができる。
【０２５８】
具体的には、上記音質評価式による音質評価（不快確率Ｐ）が所定の条件を満たすよう、画像形成装置の装置各部にどのような構成を採用するかを設計する（Ｓ１：設計過程）。そして、画像形成装置の発する音から得られる不快確率Ｐが所定の条件を満たすようになされた設計内容にしたがって画像形成装置を製造する（Ｓ２：製造過程）。このような製造工程を経ることで、不快な騒音をほとんど発しない画像形成装置を製造することができ、かかる画像形成装置をユーザに提供することができる。
【０２５９】
また、一旦販売等した画像形成装置の騒音対策として本発明を適用することもできる。すなわち、すでに販売等した画像形成装置が発する音を上記のように測定し、その測定結果から上記音質評価式を用いて不快確率Ｐを導出する。そして、導出した不快確率Ｐが所定の条件を満たすか否かを検討し、満たしている場合には不快な騒音をほとんど発していないと考えられるので改造は不要であると判断する。一方、導出された不快確率Ｐが所定の条件を満たさない場合には、不快確率Ｐが所定の条件を満たすよう、画像形成装置の各部に対し、上述したような種々の改造を施す。これにより不快な騒音をほとんど発しない画像形成装置を提供することができる。
【０２６０】
【発明の効果】
以上説明したように、請求項１にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６１】
また、請求項２にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６２】
また、請求項３にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６３】
また、請求項４にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、画像形成速度に対応した（ｅ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６４】
また、請求項５にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６５】
また、請求項６にかかる発明によれば、画像形成装置が発する音から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように構成されているので、当該画像形成装置の発する音がユーザに不快感を与えることを低減することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６６】
また、請求項７にかかる発明によれば、動作制御手段によって選択されたどの動作モードで動作している場合にも、その動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６７】
また、請求項８にかかる発明によれば、画像形成装置のユーザが通常位置する可能性が高い画像形成装置の前面側の位置で収音した結果から得られた確率Ｐが、上述した条件を満たすようになっているので、画像形成装置の動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２６８】
また、請求項９にかかる発明によれば、画像形成装置の４方向で収音された音から確率Ｐを導出し、その平均値が条件を満たしているので、どの方向にユーザがいてもその動作音がユーザに与える不快感を平均的に緩和することができる。
【０２６９】
また、請求項１０にかかる発明によれば、画像形成装置の少なくとも１方向側において収音した音から導出した確率Ｐが条件を満たしているので、その方向側にいるユーザに対して、画像形成装置の動作音が不快感を与えることを低減することができるという効果が得られる。
【０２７０】
また、請求項１１にかかる発明によれば、画像形成装置の前後左右方向のすべての方向側で収音された音から導出される確率Ｐが条件を満たしているので、ユーザはどの方向側にいても画像形成装置の動作音が当該ユーザに不快感を与えることを低減できるという効果が得られる。
【０２７１】
また、請求項１２にかかる発明によれば、低減手段により画像形成時に画像形成装置が発する音を低減することができ、これにより画像形成装置が発する音から導出される確率Ｐが条件を満たし、画像形成装置の発する音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２７２】
また、請求項１３にかかる発明によれば、ステッピングモータ動作時の振動が直接ブラケット部材に伝達されず、弾性体によって吸収されるので、ブラケット部材に伝達される振動が低減され、この振動に起因して発生する音を低減できるという効果が得られる。
【０２７３】
また、請求項１４にかかる発明によれば、ステッピングモータをマイクロステップ駆動することで、通常の機械的に定まるステッピングモータのステップ角よりも小さい角度のステップ角でステッピングモータを駆動することができる。これによりステッピングモータのロータ駆動が滑らかになり、振動の発生を抑制することができ、動作音を低減させることができるという効果が得られる。
【０２７４】
また、請求項１５にかかる発明によれば、ヘルムホルツ共鳴器は、その形状寸法等から定まるヘルムホルツ共鳴周波数の音成分をその空洞内に閉じ込める、つまりその共鳴周波数の音成分を減衰させる機能を有する。したがって、モータが発する音の主な周波数成分に対応する共鳴周波数を有するヘルムホルツ共鳴器を近傍に設置することでモータの発生音が装置外部に漏れる量を低減できるという効果が得られる。
【０２７５】
また、請求項１６にかかる発明によれば、像坦持体に帯電手段が帯電させる際には、その帯電作用によって像坦持体が振動し、これに起因して音が発生するが、その像担持体に生じる振動を制振部材によって抑制することができ、発生音を低減することができる。また、制振部材は像担持体の内部に配置されるため、新たな設置スペース等を用意する必要もないという効果が得られる。
【０２７６】
また、請求項１７にかかる発明によれば、案内部材における可撓性シートの折り曲げた部分が搬送される画像形成対象シートと接するようになっているので、当該接触により発生する音を低減することができる。すなわち、可撓性シートを所定の寸法にする場合、通常裁断されるが、可撓性シートの裁断部分にはバリ等があり、この部分が画像形成対象シートと接すると耳障りな音が発生する。これに対し、この発明では、上記のように裁断部分ではなく折り曲げ部分が画像形成対象シートと接するようになっているので、耳障りな音の発生を低減することができるという効果が得られる。
【０２７７】
また、請求項１８にかかる発明によれば、ワックスを含むトナーを用いることで、画像形成における定着過程の際に、定着部材と画像形成対象シートの乖離性を向上させるために定着部材に対してオイル塗布等の作業を行う必要がない。よって、かかるオイル塗布作業に伴って発生する音を低減することができるという効果が得られる。
【０２７８】
また、請求項１９にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２７９】
また、請求項２０にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８０】
また、請求項２１にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８１】
また、請求項２２にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８２】
また、請求項２３にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８３】
また、請求項２４にかかる発明によれば、画像形成装置の設計の際に、その画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部を設計しており、かかる設計内容に基づいた画像形成装置が製造される。したがって、動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を製造して提供する場合であっても、その動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８４】
また、請求項２５にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８５】
また、請求項２６にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８６】
また、請求項２７にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、１分あたりの画像形成対象シートの出力数値に対応した条件（ｂ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｂ）が画像形成対象シートの出力値によって変動するので、その出力値つまり複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８７】
また、請求項２８にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ａ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ａ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８８】
また、請求項２９にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｃ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ｃ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２８９】
また、請求項３０にかかる発明によれば、改造対象となる画像形成装置が発する音の収音結果から得られる心理音響パラメータ値を用い音質評価式（ｄ）によって導出される確率Ｐが、画像形成速度に対応した条件（ｅ）に合致するように装置各部の構成を改造している。したがって、この改造によって画像形成装置の動作音がユーザに不快感を与えることを低減できる画像形成装置を製造してユーザに提供することができる。また、条件（ｅ）が画像形成速度によって変動するので、複数の動作モード等を有しており、各モードで画像形成速度が変動する装置を改造する場合であっても、改造後の装置動作音から得られるパラメータ値を１つの音質評価式（ｄ）を用いて確率Ｐを求めることができるとともに、かかる確率Ｐが速度に応じて変動する条件を満たしているので、どのモードで動作しても動作音がユーザに不快感を与えることを低減できるという効果が得られる。
【０２９０】
また、請求項３１にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価そのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。
【０２９１】
請求項３２にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価そのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。そして、このようにして得られた音質評価式による音質評価が所定の条件を満たすよう装置各部が設計された画像形成装置が製造されるので、つまり不快な音をほとんど発しない画像形成装置を提供することができるという効果が得られる。
【０２９２】
また、請求項３３にかかる発明によれば、まず２音の不快確率と心理音響パラメータ値の差との関係に関する式を求めてから、その式から音の評価そのものを予測する音質評価式を導出しているので、比較的多くの実験を行うことなく精度の高い音質評価式の導出することができ、結果として音質評価に関する作業が簡易となるという効果が得られる。そして、このようにして得られた音質評価式を用いた画像形成装置が発する音の音質評価に基づいて、その装置構成を改造する。したがって、良好な音質評価が得られる、つまり不快な音をほとんど発しない画像形成装置を提供することができるという効果が得られる。
【図面の簡単な説明】
【図１】画像形成装置の全体構成を示す正断面図である。
【図２】前記画像形成装置の光学ユニットの構成を示す図である。
【図３】前記画像形成装置の感光体ユニットおよび現像ユニットの構成を示す図である。
【図４】前記感光体ユニットの感光体ドラムを駆動するための構成を示す分解斜視図である。
【図５】前記画像形成装置の定着ユニットを示す斜視図である。
【図６】前記定着ユニットの構成を示す正断面図である。
【図７】前記画像形成装置の給紙部の構成を示す正断面図である。
【図８】前記給紙部の駆動構成を示す斜視図である。
【図９】ロジット変換の内容を説明するためのグラフである。
【図１０】音質評価式を導出するために画像形成装置の発する音を測定する際の測定条件を説明するための図である。
【図１１】前記画像形成装置が１つのモードで動作しているときの前記測定により得られた音の分析結果を示す図である。
【図１２】前記画像形成装置が他のモードで動作しているときの前記測定により得られた音の分析結果を示す図である。
【図１３】前記画像形成装置がその他のモードで動作しているときの前記測定により得られた音の分析結果を示す図である。
【図１４】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図１５】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図１６】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図１７】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図１８】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図１９】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２０】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２１】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２２】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２３】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２４】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２５】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２６】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２７】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２８】画像形成装置の発する音から抽出した音源の水準（強調、原音、減衰）と、主観評価値との関係を示したグラフである。
【図２９】本発明の一過程において、導出した音の不快確率の差を算出できるモデル式を用いて求めた予測値と、実測値とをプロットした散布図である。
【図３０】画像形成装置の動作モードごとに、本発明によって導出した音質評価式を用いて求めた予測した不快確率の値と、実測値とを比較プロットしたグラフである。
【図３１】実験結果から導かれるppm値と、上記音質評価式によって導出された指数の許容値との関係を示すグラフである。
【図３２】実験結果から導かれる画像形成速度と、上記音質評価式によって導出された指数の許容値との関係を示すグラフである。
【図３３】本発明にかかる改造方法の具体例の１つを説明するための図であって、改造前の感光体ドラム駆動機構の構成を示す斜視図である。
【図３４】改造前の感光体ドラムを駆動するための駆動モータの取り付け構造を説明するための図である。
【図３５】改造後の感光体ドラムを駆動するための駆動モータの取り付け構造を説明するための図である。
【図３６】改造後の感光体ドラム駆動機構の構成を示す斜視図である。
【図３７】改造後の感光体ドラム駆動機構の構成を示す側面図である。
【図３８】本発明にかかる改造方法の具体例の１つを説明するための図であって、給紙用ステッピングモータの駆動制御内容を説明するための図である。
【図３９】本発明にかかる改造方法の具体例の１つを説明するための図であって、給紙用ステッピングモータをマイクロステップ駆動する際の励磁シーケンスを示す図である。
【図４０】本発明にかかる改造方法の具体例の１つを説明するための図であって、ポリゴンミラーモータ近傍に設けられたヘルムホルツ共鳴器を示す断面図である。
【図４１】本発明にかかる改造方法の具体例の１つを説明するための図であって、感光体ドラムの振動を抑制するための構成を示す図である。
【図４２】前記感光体ドラムの振動を抑制するための構成を示す分解斜視図である。
【図４３】用紙を搬送して画像形成動作を行ったときと、用紙を搬送しないで画像形成動作をおこなったとき（フリーラン時）とで画像形成装置が発する音の周波数帯域ごとの音圧レベルを示す図である。
【図４４】用紙を搬送して画像形成動作を行ったときと、用紙を搬送しないで画像形成動作をおこなったとき（フリーラン時）とで画像形成装置が発する音の周波数帯域ごとの音圧レベルの差を示す図である。
【図４５】画像形成装置の給紙部の構成を示す図である。
【図４６】前記給紙部の構成要素である搬送ローラと、用紙を案内する可撓性シートからなる案内部材との位置関係を示す図である。
【図４７】前記給紙部の前記案内部材近傍の拡大図である。
【図４８】騒音対策がなされた前記案内部材の構成を示す図である。
【図４９】騒音対策がなされていない案内部材の構成を示す図である。
【図５０】本発明にかかる改造方法によって対策がなされた画像形成装置の発する音の分析結果を示す図である。
【図５１】本発明にかかる画像形成装置の製造過程を示すフローチャートである。
【符号の説明】
１ 光学ユニット
２ ポリゴンミラーモータ
３ 感光体ユニット
４ 現像ユニット
５ 転写ユニット
７ レジストローラ
９ 第１トレー
１０ 第２トレー
１１ ハウジング
１３ 定着ベルト
２７ ポリゴンミラー
２８ 感光体ドラム
２９ 転写ベルト
３６ 帯電ローラ
４１ カラードラム駆動モータ
４２ 黒ドラム駆動モータ
４３ 中継ギヤ
４４ ギヤ
４６ 定着ユニット
４７ オイル塗布ユニット
４８ 塗布フェルト
４９ 塗布ローラ
５１ 第１給紙ユニット
５２ 第２給紙ユニット
５３ 中継ローラ
５４ 中継ローラ
５５ａ ローラ
５５ｂ ローラ
５５ 搬送ローラ
５６ ステッピングモータ
５９ モータブラケット
６０ 防振ゴムマウント
６３，６４ プーリ
６５ モータブラケット
６６，６７ タイミングプーリ
７０ タイミングベルト
７１ ヘルムホルツ共鳴器
７２ 空洞
７２ａ 空洞形成部材
７３ 開口穴
７４ 制振部材
７７ 案内部材
８０，８１，８２ ガイド部材
１１０ 給紙部
２０１ 被測定機器
２０２ 操作部
２０３ ダミーヘッド
７７０ 案内部材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, a method for manufacturing an image forming apparatus, a method for modifying an image forming apparatus, and a method for evaluating sound quality.
[0002]
[Prior art]
In an office or the like, various apparatuses equipped with an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus are installed. In this type of image forming apparatus, many parts are mechanically connected. Further, the image forming apparatus has a motor for driving these mechanisms and the like. During the image forming operation, operation sounds of respective parts of the apparatus are generated, and the operation sounds give a discomfort to a user or the like. It can be a problem.
[0003]
At present, as a method of evaluating the noise of office equipment, a method based on a sound power level and a sound pressure level is generally used (such as ISO7779). However, in the method of evaluating noise based on the sound power level or the like, the correlation between the evaluation and the subjective discomfort of humans may not be very good, and even if the evaluation based on the above criteria is good. However, there are many things that make people feel uncomfortable.
[0004]
For example, when a human hears two sounds having the same sound pressure level but different frequency distribution and presence / absence of an impact sound, the discomfort of each sound is different. Become. Therefore, even when the sound pressure level is low, a sound containing a high frequency component, a pure tone component, or the like may be uncomfortable.
[0005]
In this way, it is thought that it is necessary to evaluate the sound quality and take noise measures in consideration of the noise from office equipment, rather than simply taking measures based on the sound power level and sound pressure level. .
[0006]
Conventionally, as a noise countermeasure technology of an image forming apparatus, a masking sound generating function for masking an operation sound at the time of image formation is mounted on the image forming apparatus, and a noise is generated by generating a masking sound during an image forming operation. There is an attempt to reduce it (see, for example, Patent Document 1).
[0007]
Further, as a technique for evaluating the quality of a sound emitted when the image forming apparatus operates, there are the following techniques.
[0008]
For example, among various sounds emitted by the image forming apparatus, only a "go sound" which is low-frequency random noise generated with respect to an airflow such as an exhaust sound can be evaluated (see Patent Document 2), a scanner, and the like. It is possible to evaluate only the "keening sound" generated by the motor or the charging device (see Patent Document 3), and to evaluate only the "shear sound" which is high-frequency random noise generated due to paper rubbing or the like. Only those that can be targeted (see Patent Document 4) and those that can be evaluated only as “won-won sounds” consisting of pure sounds having peaks at a plurality of adjacent frequencies due to a beat of a drive mechanism or the like. (See Patent Document 5).
[0009]
In addition, a technique is disclosed in which the annoyance felt by a person by including a pure tone, a beat, a low frequency component, a high frequency component, and the like is referred to as smoothness, and the smoothness can be evaluated (see Patent Document 6).
[0010]
In addition, a sound quality evaluation method and the like that can evaluate the sound quality of a noise generated from office equipment in consideration of the influence on a human subjective feeling is disclosed (see Patent Document 7).
[0011]
Also disclosed is an image forming apparatus that acquires a discomfort index based on a loudness value and a sharpness value obtained from a sound generated from the image forming apparatus, and devises a paper transport mechanism such that the acquired discomfort index satisfies a predetermined condition. (See Patent Document 8).
[0012]
[Patent Document 1]
JP-A-9-193506
[Patent Document 2]
JP-A-10-232163
[Patent Document 3]
JP-A-10-253440
[Patent Document 4]
JP-A-10-253442
[Patent Document 5]
JP-A-10-267742
[Patent Document 6]
JP-A-10-267743
[Patent Document 7]
JP 2001-336975 A
[Patent Document 8]
JP-A-2002-128316
[0013]
[Problems to be solved by the invention]
However, in an image forming apparatus equipped with the above-described masking sound generation function, a noise level may be increased because a masking sound is generated in addition to a sound generated by the apparatus during operation. In addition, it is necessary to newly install a device that is completely unrelated to the image forming operation, such as a masking generator (a speaker, a control device, a sound source, and the like). There is also the problem of increased costs, and it is hard to say that it is an effective noise countermeasure.
[0014]
Further, in the various sound quality evaluation techniques described above, a specific sound quality can be evaluated with respect to the operation sound of the image forming apparatus, and an evaluation can be performed in consideration of a subjective feeling of a person. However, these technologies do not specify how to use this evaluation to take measures against noise.
[0015]
By the way, in order to evaluate sound quality and take measures against noise based on the evaluation result, it is necessary to quantitatively measure the sound quality and measure how much the sound quality has been improved before and after the measure.
[0016]
However, since sound quality is not a physical quantity, quantitative measurement cannot be performed. Therefore, it is difficult to set a value or the like that is a target for improvement. In the case of sound quality evaluation by humans, expressions such as "improved" and "slightly improved" are used.Also, due to individual differences, evaluation differs depending on the person and whether the obtained result is general. Judgment is also difficult.
[0017]
Incidentally, psychoacoustic parameters are known as physical quantities for evaluating sound quality. Representative examples of the psychoacoustic parameters include the following (for example, the 7th Design Engineering and System Division Lecture Meeting of the Japan Society of Mechanical Engineers), aiming for a breakthrough in design and systems toward the 21st century! "" November 10, 1997, "Sound and Vibration and Design, Color and Design (1)", Division No. 089B).
(1) Loudness (sone): size of hearing
(2) Sharpness (acum): relative distribution of high frequency components
(3) Tonality (tu): articulation, relative distribution of pure tone components
4) Roughness (asper): Sound roughness
5) Fractionation strings (vacil): fluctuation intensity, beat
(6) Impulse Shibness (iu): Impact
7) Relative approach: Sense of fluctuation
[0018]
As these parameter values increase, discomfort tends to increase.
[0019]
Sounds generated from apparatuses such as copiers and printers include sounds of various timbres because these apparatuses have complicated mechanisms. That is, it is conceivable that a low-frequency heavy sound, a high-frequency high-pitched sound, a sound generated by impact, and the like are generated from a plurality of sound sources such as a motor, a solenoid, and paper while changing over time. Humans judge whether sound emitted from such an image forming apparatus is unpleasant or not by comprehensively judging which part of the sound is particularly unpleasant. Is considered to have been weighted. That is, it is considered that not all of the above-mentioned various psychoacoustic parameters affect human discomfort at the same rate, but there are parameters having a large influence and parameters having a small influence.
[0020]
Among the above-mentioned prior arts, there is one in which a discomfort index is acquired based on a loudness value and a sharpness value, and a paper transport mechanism is devised so that the acquired discomfort index satisfies a predetermined condition (Patent Document 8). This technique is considered to take the above points into consideration.
[0021]
However, in recent image forming apparatuses, there are those capable of selecting the resolution of an image and those capable of both a color image and a monochrome image. In addition, there are devices that perform different operations depending on differences in the quality of paper to be printed, and devices that can set a printing speed. Thus, many of the recent image forming apparatuses have a plurality of operation modes. As described above, in an apparatus having a plurality of operation modes, the operation of each part of the apparatus differs depending on the operation mode, resulting in different noises and the like, and particularly when the printing speed changes, the rotation speed of the motor changes. The frequency component of the sound generated differs depending on the sound, and the sound generated from various mechanisms also changes. This change may cause a difference in the sound source or the like for which a person feels discomfort.
[0022]
Therefore, for noise suppression in an image forming apparatus having a plurality of operation modes, complicated work such as performing sound quality evaluation for each operation mode such as a different printing speed is performed, and discomfort is caused when operating in any operation mode. It is necessary to take noise countermeasures so as not to give any noise, but the above technique does not take such points into consideration.
[0023]
The present invention has been made in view of the above, and even when there are a plurality of modes having different image forming speeds, an image forming apparatus in which noise countermeasures are performed based on objective sound quality evaluation, such an image forming apparatus is provided. It is an object of the present invention to obtain a manufacturing method, a method for modifying the image forming apparatus, and a sound quality evaluation method.
[0024]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an image forming apparatus for forming an image on an image forming target sheet, wherein sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. Loudness value, sharpness value, tonality value, impulsiveness value of psychoacoustic parameters obtained from the sound emitted by the image forming apparatus when forming an image on the image forming target sheet, and the image per minute Using the output numerical value (ppm) of the sheet to be formed (A4 size lateral direction), the probability P calculated by the following equation (a) satisfies the following condition (b).
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus characterized in that:
[0025]
According to the first aspect of the invention, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is the output numerical value of the image forming target sheet per minute. Since the configuration is such that the condition (b) corresponding to the condition (b) is satisfied, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates depending on the speed, the mode in which the operation is performed Even so, it is possible to reduce that the operation sound gives the user discomfort.
[0026]
According to a second aspect of the present invention, there is provided an image forming apparatus for forming an image on an image forming target sheet, wherein the sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. A loudness value, a sharpness value, a tonality value, and an impulseness value of psychoacoustic parameters obtained from a sound emitted by the image forming apparatus when an image is formed on a target sheet, and the image forming target sheet (A4 Using the output value (ppm) in the horizontal direction of the size, the probability P calculated by the following equation (c) satisfies the following condition (b).
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus characterized in that:
[0027]
According to the invention according to claim 2, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is the output numerical value of the image forming target sheet per minute. Since the configuration is such that the condition (b) corresponding to the condition (b) is satisfied, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, the mode in which the operation is performed Even so, it is possible to reduce that the operation sound gives the user discomfort.
[0028]
According to a third aspect of the present invention, there is provided an image forming apparatus for forming an image on an image forming target sheet, wherein the sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. A loudness value, a sharpness value, a tonality value, and an impulseness value of psychoacoustic parameters obtained from a sound emitted by the image forming apparatus when an image is formed on a target sheet, and the image forming target sheet (A4 Using the output numerical value (ppm) in the horizontal direction (size), the probability P calculated by the following equation (d) satisfies the following condition (b).
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus characterized in that:
[0029]
According to the invention according to claim 3, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is the output numerical value of the image forming target sheet per minute. Since the configuration is such that the condition (b) corresponding to the condition (b) is satisfied, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (d), and since the probability P satisfies the condition that fluctuates according to the speed, the mode in which mode the operation is performed Even so, it is possible to reduce the discomfort of the user due to the operation sound.
[0030]
According to a fourth aspect of the present invention, there is provided an image forming apparatus for forming an image on an image forming target sheet, wherein the sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. A loudness value, a sharpness value, a tonality value, and an impulseness value of psychoacoustic parameters obtained from a sound emitted by the image forming apparatus when an image is formed on a target sheet, and an image forming speed (v : Mm / s) and the probability P calculated by the following equation (a) satisfies the following condition (e):
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus characterized in that:
[0031]
According to the invention according to claim 4, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound emitted by the image forming apparatus matches (e) corresponding to the image forming speed. Therefore, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained by using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is inconsistent with the user in any mode. Pleasant feeling can be reduced.
[0032]
According to a fifth aspect of the present invention, there is provided an image forming apparatus for forming an image on an image forming target sheet, wherein the sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. A loudness value, a sharpness value, a tonality value, and an impulseness value of psychoacoustic parameters obtained from a sound emitted by the image forming apparatus when an image is formed on a target sheet, and an image forming speed (v : Mm / s) and the probability P calculated by the following equation (c) satisfies the following condition (e):
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus characterized in that:
[0033]
According to the invention according to claim 5, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound emitted by the image forming apparatus is determined by the condition (e) corresponding to the image forming speed. Since it is configured to match, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is inconsistent with the user in any mode. Pleasant feeling can be reduced.
[0034]
According to a sixth aspect of the present invention, there is provided an image forming apparatus for forming an image on a sheet on which an image is to be formed, wherein the sound is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus. A loudness value, a sharpness value, a tonality value, and an impulseness value of psychoacoustic parameters obtained from a sound emitted by the image forming apparatus when an image is formed on a target sheet, and an image forming speed (v : Mm / s) and the probability P calculated by the following equation (d) satisfies the following condition (e):
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus characterized in that:
[0035]
According to the invention according to claim 6, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound emitted by the image forming apparatus is determined by the condition (e) corresponding to the image forming speed. Since it is configured to match, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained by using one sound quality evaluation formula (d), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is not affected by the user in any mode. Pleasant feeling can be reduced.
[0036]
Further, according to a seventh aspect of the present invention, in the configuration of the first aspect, any one of a plurality of operation modes is selected to form an image on the image forming target sheet. An operation control unit for controlling each unit of the apparatus is provided, and the probability P satisfies the condition regardless of the operation mode in any of the plurality of operation modes.
[0037]
According to the seventh aspect of the present invention, it is possible to reduce the discomfort to the user due to the operation sound when operating in any of the operation modes selected by the operation control means.
[0038]
According to an eighth aspect of the present invention, in the configuration according to any one of the first to sixth aspects, the sound collection position is a nearby person position defined in ISO (International Organization For Standardization) 7779. The probability P calculated from at least the sound collection result of the sound in the front direction of the device satisfies the condition.
[0039]
According to the invention according to claim 8, the probability P obtained from the result of sound pickup at the position on the front side of the image forming apparatus where the user of the image forming apparatus is likely to be normally located satisfies the above-described condition. Therefore, it is possible to reduce the possibility that the operation sound of the image forming apparatus gives the user discomfort.
[0040]
According to a ninth aspect of the present invention, in the configuration according to any one of the first to sixth aspects, the sound collection position is a nearby person position specified in ISO (International Organization For Standardization) 7779. The average value of the probability P calculated from each of the sound collection results of the sounds in four directions of the front, rear, left, and right of the device satisfies the above condition.
[0041]
According to the ninth aspect, the probability P is derived from the sounds collected in four directions of the image forming apparatus, and the average value satisfies the condition. Discomfort to the user can be reduced on average.
[0042]
According to a tenth aspect of the present invention, in the configuration according to any one of the first to sixth aspects, the sound pickup position is a nearby person position specified in ISO (International Organization For Standardization) 7779. The probability P calculated from at least one of the sound collection results in the front, rear, left, and right directions of the device satisfies the above condition.
[0043]
According to the tenth aspect of the present invention, the probability P derived from the sound collected in at least one direction of the image forming apparatus satisfies the condition. It is possible to reduce the discomfort caused by the operation sound.
[0044]
According to an eleventh aspect of the present invention, in the configuration according to any one of the first to sixth aspects, the sound pickup position is a nearby person position specified in ISO (International Organization For Standardization) 7779. In addition, all the probabilities P calculated from each of the sound collection results of the sounds in the four directions of the front, rear, left, and right of the device satisfy the above condition.
[0045]
According to the eleventh aspect, the probability P derived from the sound collected in all the front, rear, left, and right directions of the image forming apparatus satisfies the condition, so that the user can be in any direction. The operation sound of the image forming apparatus can reduce the discomfort of the user.
[0046]
According to a twelfth aspect of the present invention, in the configuration according to any one of the first to eleventh aspects, the image processing apparatus further includes a reduction unit configured to reduce a sound emitted from the apparatus when forming an image on the image forming target sheet. Features.
[0047]
According to the twelfth aspect of the present invention, the noise generated by the image forming apparatus at the time of image formation can be reduced by the reducing unit, whereby the probability P derived from the sound generated by the image forming apparatus satisfies the condition, It is possible to reduce discomfort caused by the sound emitted from the device to the user.
[0048]
According to a thirteenth aspect of the present invention, in the configuration of the twelfth aspect, a stepping motor that drives a predetermined portion when forming an image on the image forming target sheet, and a bracket member that holds the stepping motor are provided. Furthermore, it is characterized in that the reduction means has an elastic body interposed between the stepping motor and the bracket member.
[0049]
According to the thirteenth aspect of the present invention, since the vibration during the operation of the stepping motor is not directly transmitted to the bracket member but is absorbed by the elastic body, the vibration transmitted to the bracket member is reduced. Generated sound can be reduced.
[0050]
According to a fourteenth aspect of the present invention, in the configuration of the twelfth aspect, the image forming apparatus further includes a stepping motor that drives a predetermined portion when forming an image on the image forming target sheet, and the reducing unit includes the stepping motor. It is characterized by having a drive control means for driving the motor in a micro step.
[0051]
According to the fourteenth aspect of the present invention, the stepping motor is driven by micro-stepping, so that the stepping motor can be driven at a step angle smaller than the step angle of the ordinary mechanically determined stepping motor. As a result, the rotor driving of the stepping motor becomes smooth, vibration can be suppressed, and operation noise can be reduced.
[0052]
According to a fifteenth aspect of the present invention, in the configuration of the twelfth aspect, the apparatus further comprises a motor for driving a predetermined portion at the time of forming an image on the image forming target sheet, And a Helmholtz resonator disposed at
[0053]
According to the invention according to claim 15, the Helmholtz resonator has a function of confining the sound component of the Helmholtz resonance frequency determined by its shape and size in the cavity, that is, attenuating the sound component of the resonance frequency. Therefore, by installing a Helmholtz resonator having a resonance frequency corresponding to the main frequency component of the sound generated by the motor in the vicinity, it is possible to reduce the amount of sound generated by the motor leaking out of the device.
[0054]
According to a sixteenth aspect of the present invention, in the configuration of the twelfth aspect, the image forming apparatus further includes a columnar image carrier having a hollow portion, and a charging unit configured to charge a surface of the image carrier. The reduction means has a vibration suppression member for suppressing vibration of the image carrier in a hollow portion of the image carrier.
[0055]
According to the invention according to claim 16, when the charging means charges the image carrier, the image carrier vibrates due to the charging action, and a sound is generated due to the vibration. Vibration generated in the body can be suppressed by the vibration damping member, and generated sound can be reduced. Further, since the vibration damping member is disposed inside the image carrier, it is not necessary to prepare a new installation space or the like.
[0056]
According to a seventeenth aspect of the present invention, in the configuration according to the twelfth aspect, the guide member is a flexible sheet that guides the image forming target sheet along a predetermined transport path, and is conveyed. The image forming apparatus further includes a guide member having an end in contact with the image forming target sheet and a bent portion of the flexible sheet.
[0057]
According to the seventeenth aspect of the present invention, since the bent portion of the flexible sheet in the guide member comes into contact with the image forming target sheet to be conveyed, the sound generated by the contact can be reduced. . That is, when the flexible sheet is made to have a predetermined size, the flexible sheet is usually cut. However, the cut portion of the flexible sheet has burrs and the like, and when this portion comes in contact with the image forming target sheet, an unpleasant sound is generated. . On the other hand, in the present invention, since the bent portion, not the cut portion, comes into contact with the image forming target sheet as described above, generation of harsh sound can be reduced.
[0058]
An eighteenth aspect of the present invention is the image forming apparatus according to the twelfth aspect, wherein the toner used for forming an image on the image forming target sheet is a toner containing wax.
[0059]
According to the invention according to claim 18, by using a toner containing wax, oil is applied to the fixing member in order to improve the dissociation between the fixing member and the sheet to be image-formed during the fixing process in the image formation. There is no need to perform such operations. Therefore, it is possible to reduce the noise generated with the oil application operation.
[0060]
According to a nineteenth aspect of the present invention, there is provided a method of manufacturing an image forming apparatus for forming an image on an image forming target sheet, the method comprising: The loudness value, the sharpness value, the tonality value, the impulsiveness value of the psychoacoustic parameters obtained from the sound emitted by the image forming apparatus when performing image formation on the image-collected sheet to be picked up, Using the output numerical value (ppm) of the image forming target sheet (A4 size horizontal direction), each part of the apparatus is designed so that the probability P calculated by the following equation (a) satisfies the following condition (b). Design steps,
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
And a manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step.
[0061]
According to the nineteenth aspect, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P meets the condition (b) corresponding to the output numerical value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (a), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0062]
According to a twentieth aspect of the present invention, there is provided a method of manufacturing an image forming apparatus for forming an image on an image forming target sheet, the method comprising: The loudness value, the sharpness value, the tonality value, the impulsiveness value of the psychoacoustic parameter obtained from the sound emitted by the image forming apparatus when performing image formation on the image forming target sheet that is collected, Using the output numerical value (ppm) of the image forming target sheet (A4 size horizontal direction), each part of the apparatus is designed so that the probability P calculated by the following equation (c) satisfies the following condition (b). Design steps,
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
And a manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step.
[0063]
According to the twentieth aspect, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P meets the condition (b) corresponding to the output numerical value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (c), and the probability P satisfies the condition that varies depending on the speed. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0064]
According to a twenty-first aspect of the present invention, there is provided a method for manufacturing an image forming apparatus for forming an image on an image forming target sheet, the method comprising: The loudness value, the sharpness value, the tonality value, the impulsiveness value of the psychoacoustic parameter obtained from the sound emitted by the image forming apparatus when performing image formation on the image forming target sheet that is collected, Using the output numerical value (ppm) of the image forming target sheet (A4 size lateral direction), each part of the apparatus is designed such that the probability P calculated by the following equation (d) satisfies the following condition (b). Design steps,
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A manufacturing step of manufacturing an image forming apparatus according to the design content made by the design step;
A method for manufacturing an image forming apparatus, comprising:
[0065]
According to the twenty-first aspect, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P meets the condition (b) corresponding to the output numerical value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (d), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0066]
The invention according to claim 22 is a method of manufacturing an image forming apparatus for forming an image on an image forming target sheet, wherein the image is collected at a sound collecting position approximately 1 m away from the end face of the image forming apparatus to be manufactured. A loudness value, a sharpness value, a tonality value, an impulsiveness value of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image-formed sheet to be sounded, and the image-formed sheet A design step of designing each part of the device so that the probability P calculated by the following equation (a) satisfies the following condition (e) using the image forming speed (v: mm / s) with respect to
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
And a manufacturing step of manufacturing the image forming apparatus according to the design contents performed in the designing step.
[0067]
According to the invention of claim 22, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P satisfies the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0068]
According to a twenty-third aspect of the present invention, there is provided a method of manufacturing an image forming apparatus for forming an image on an image forming object sheet, wherein the image is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. A loudness value, a sharpness value, a tonality value, an impulsiveness value of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet to be sounded, and the image forming target sheet A design step of designing each part of the apparatus such that the probability P calculated by the following equation (c) satisfies the following condition (e) using the image forming speed (v: mm / s) with respect to
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
And a manufacturing step of manufacturing the image forming apparatus according to the design contents performed in the designing step.
[0069]
According to the twenty-third aspect, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P satisfies the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0070]
The invention according to claim 24 is a method of manufacturing an image forming apparatus for forming an image on an image forming target sheet, wherein the image is collected at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. A loudness value, a sharpness value, a tonality value, an impulsiveness value of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet to be sounded, and the image forming target sheet A design step of designing each unit of the apparatus such that the probability P calculated by the following equation (d) satisfies the following condition (e) using the image forming speed (v: mm / s) with respect to
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
And a manufacturing step of manufacturing the image forming apparatus according to the design contents performed in the designing step.
[0071]
According to the twenty-fourth aspect, when designing the image forming apparatus, the probability derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that P satisfies the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P by using one sound quality evaluation formula (d), and since the probability P satisfies the condition of fluctuating according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0072]
According to a twenty-fifth aspect of the present invention, there is provided a method for remodeling an image forming apparatus for forming an image on an image forming target sheet, wherein the image forming apparatus is provided at a sound collection position substantially 1 m away from an end face of the remodeling target image forming apparatus. A sound collecting step of collecting sound emitted by the image forming apparatus when forming an image on the image forming target sheet; and a loudness value and a sharpness value of a psychoacoustic parameter obtained from a sound collecting result in the sound collecting step. Using the tonality value, the impulseness value, and the output numerical value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (a) is A modification step of modifying the configuration of the device so as to satisfy the condition (b) of
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising:
[0073]
According to the invention according to claim 25, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is one minute The configuration of each part of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the modification can be used to calculate the probability P using one sound quality evaluation formula (a), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0074]
According to a twenty-sixth aspect of the present invention, there is provided a method for modifying an image forming apparatus for forming an image on an image forming target sheet, wherein the image forming apparatus is provided at a sound collection position approximately 1 m away from an end surface of the image forming apparatus to be modified. A sound collecting step of collecting sound emitted by the image forming apparatus when forming an image on the image forming target sheet; and a loudness value and a sharpness value of a psychoacoustic parameter obtained from a sound collecting result in the sound collecting step. Using the tonality value, the impulseness value, and the output value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (c) is A modification step of modifying the configuration of the device so as to satisfy the condition (b) of
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising:
[0075]
According to the invention according to claim 26, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is one minute The configuration of each part of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the remodeling can be used to determine the probability P using one sound quality evaluation formula (c), and the condition that the probability P varies according to the speed is satisfied. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0076]
The invention according to claim 27 is a method for remodeling an image forming apparatus for forming an image on an image forming target sheet, wherein the image forming apparatus is provided at a sound collection position approximately 1 m away from an end face of the image forming apparatus to be remodeled. A sound collecting step of collecting sound emitted by the image forming apparatus when forming an image on the image forming target sheet; and a loudness value and a sharpness value of a psychoacoustic parameter obtained from a sound collecting result in the sound collecting step. Using the tonality value, the impulseness value, and the output value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (d) is A modification step of modifying the configuration of the device so as to satisfy the condition (b) of
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising:
[0077]
According to the invention according to claim 27, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is one minute The configuration of each part of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the modification can be used to calculate the probability P using one sound quality evaluation formula (d), and the condition that the probability P varies according to the speed is satisfied. Therefore, it is possible to reduce the discomfort of the operation sound to the user regardless of the operation mode.
[0078]
Further, according to the invention according to claim 28, there is provided a method of remodeling an image forming apparatus for forming an image on an image forming target sheet, wherein a sound collection position approximately 1 m away from an end face of the image forming apparatus to be remodeled. A sound collecting step of collecting sound emitted by the image forming apparatus when forming an image on the image forming target sheet, and a loudness value and a sharpness of a psychoacoustic parameter obtained from a sound collecting result in the sound collecting step. Using the value, tonality value, impulsiveness value, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (a) is determined by the following condition (e). A) modifying the configuration of the device to satisfy
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising:
[0079]
According to the invention according to claim 28, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is determined by the image forming speed The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to (1). Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0080]
The invention according to claim 29 is a method for remodeling an image forming apparatus that forms an image on a sheet on which an image is to be formed, wherein the sound collecting position is approximately 1 m away from an end face of the image forming apparatus to be remodeled. A sound collecting step of collecting sound emitted by the image forming apparatus when performing image formation on the image forming target sheet, and a loudness value, a sharpness value of a psychoacoustic parameter obtained from a sound collecting result in the sound collecting step, Using the tonality value, the impulsiveness value, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (c) is determined by the following condition (e). Modification steps to modify the configuration of the device to meet
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising:
[0081]
According to the invention according to claim 29, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is determined by the image forming speed The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to (1). Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0082]
The invention according to claim 30 is a method of remodeling an image forming apparatus that forms an image on a sheet on which an image is to be formed, wherein the image forming apparatus is formed at a sound collection position approximately 1 m away from an end face of the image forming apparatus to be remodeled. A sound collection step of collecting sound emitted by the image forming apparatus when forming an image on the target sheet; and a loudness value, a sharpness value, and a tonality value of a psychoacoustic parameter obtained from a sound collection result in the sound collection step. , The probability P calculated by the following equation (d) using the impulsiveness value and the image forming speed (v: mm / s) with respect to the image forming target sheet satisfies the following condition (e). A modification step for modifying the configuration of the device;
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising:
[0083]
According to the invention according to claim 30, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is determined by the image forming speed. The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to (1). Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P by using one sound quality evaluation formula (d), and since the probability P satisfies the condition of fluctuating according to the speed, it is possible to operate in any mode. Also, it is possible to reduce that the operation sound gives the user discomfort.
[0084]
The invention according to claim 31 is a method for evaluating a sound emitted at the time of image formation by an image forming apparatus that forms an image on an image forming target sheet, wherein the image forming apparatus includes a plurality of types of sounds emitted at the time of image formation. The sound is evaluated by the paired comparison method, logistic regression analysis is performed using the discomfort probability of the two sounds based on the evaluation as the objective variable, and the difference between the psychoacoustic parameter values as the explanatory variable. Equation (f) is derived,
(Equation 1)

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound This is a sound quality evaluation method characterized by deriving an evaluation formula and performing sound quality evaluation using the derived sound quality evaluation formula.
[0085]
According to the thirty-first aspect of the present invention, a sound quality evaluation expression for obtaining a relation between the discomfort probability of two sounds and the difference between psychoacoustic parameter values, and then predicting the discomfort probability itself, which is a sound evaluation, from the expression. Is derived, it is possible to derive a highly accurate sound quality evaluation expression without performing a relatively large number of experiments, and as a result, it is possible to obtain an effect that work related to sound quality evaluation is simplified.
[0086]
The invention according to claim 32 is a method of manufacturing an image forming apparatus for forming an image on an image forming target sheet, wherein a plurality of types of sounds emitted by the image forming apparatus at the time of image formation are determined by a pair comparison method. An evaluation is performed, a multiple regression analysis is performed using the discomfort probability of two sounds based on the evaluation as an objective variable, and the difference between psychoacoustic parameter values as an explanatory variable, and the following formula (f) relating to the discomfort probability of sound quality is derived from the result. ,
(Equation 1)

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound Deriving an evaluation formula, using the derived sound quality evaluation formula, designing each unit of the apparatus such that the sound quality evaluation by the sound quality evaluation formula satisfies predetermined conditions, and manufacturing an image forming apparatus according to the design contents. 6 is a method for manufacturing an image forming apparatus.
[0087]
According to the thirty-second aspect of the present invention, first, an expression relating to the relationship between the discomfort probability of two sounds and the difference between psychoacoustic parameter values is obtained, and then the sound quality evaluation for estimating the discomfort probability itself, which is the sound evaluation, from the expression. Since the equations are derived, a highly accurate sound quality evaluation equation can be derived without performing a relatively large number of experiments, and as a result, the effect of simplifying the work related to sound quality evaluation can be obtained. Then, an image forming apparatus in which each part of the apparatus is designed so that the sound quality evaluation based on the sound quality evaluation formula obtained in this way satisfies predetermined conditions is manufactured, that is, an image forming apparatus that hardly emits unpleasant sound is provided. can do.
[0088]
The invention according to claim 33 is a method for remodeling an image forming apparatus that forms an image on an image forming target sheet, wherein the image forming apparatus uses a pair comparison method for a plurality of types of sounds emitted during image formation. The regression analysis is performed using the discomfort probability of two sounds based on the evaluation as an objective variable and the difference between psychoacoustic parameter values as an explanatory variable, and the following formula (f) regarding the discomfort probability of sound quality is derived from the result. And
(Equation 1)

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound Deriving an evaluation formula, performing a sound quality evaluation of the sound generated by the image forming apparatus to be remodeled using the derived sound quality evaluation formula, and remodeling the configuration of the image forming apparatus to be remodeled based on the sound quality evaluation result. A method for remodeling an image forming apparatus.
[0089]
According to the thirty-third aspect of the present invention, first, an expression relating to the relationship between the discomfort probability of two sounds and the difference between psychoacoustic parameter values is obtained, and then the disparity probability which is the evaluation of sound is predicted from the expression. Since the evaluation formula is derived, it is possible to derive a high-precision sound quality evaluation formula without performing a relatively large number of experiments, and as a result, it is possible to obtain an effect that the work related to the sound quality evaluation is simplified. Then, based on the sound quality evaluation of the sound generated by the image forming apparatus using the sound quality evaluation formula thus obtained, the apparatus configuration is modified. Therefore, it is possible to provide an image forming apparatus that can obtain good sound quality evaluation, that is, hardly emits unpleasant sound.
[0090]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of an image forming apparatus, a method for manufacturing an image forming apparatus, a method for modifying an image forming apparatus, and a method for evaluating sound quality according to the present invention will be described below in detail with reference to the accompanying drawings.
[0091]
A. Configuration of image forming apparatus
FIG. 1 is a diagram illustrating an entire configuration of a general image forming apparatus. The present invention is a remodeling method for evaluating noise generated by such a general image forming apparatus, and taking measures to reduce discomfort caused to the person by the noise based on the evaluation. Prior to the description, a configuration of a general image forming apparatus will be described.
[0092]
The image forming apparatus shown in FIG. 1 is a digital color printer adopting an electrophotographic system, and includes an optical unit 1, a photoreceptor unit 3, a developing unit 4, a transfer unit 5, a fixing unit 46, and a paper feeding unit. 110.
[0093]
At the time of image formation, an image forming target sheet (including a printing sheet and an OHP sheet, etc., but hereinafter referred to as a sheet) accommodated in a sheet feeding unit 110 arranged at the bottom of the image forming apparatus is viewed from the lower right side of the figure. The sheet is conveyed along a predetermined conveying path that goes upward and diagonally to the left. The sheet conveyed in this manner is fed out of the sheet feeding unit 110 and is conveyed to the upper side of the sheet feeding unit 110 along a diagonal conveying path from the lower right to the upper left in FIG. During this time, the sheet is also passed between the four photoreceptor units 3 and the developing unit 4 and the transfer unit 5 which are similarly arranged along the transport path, and a predetermined image is transferred. The sheet on which the image has been transferred is conveyed to a fixing unit 46 disposed on the upper left side of the photoconductor unit 3, the developing unit 4 and the transfer unit 5, and the transferred image is fixed by the fixing unit 46.
[0094]
As shown in FIG. 2, the optical unit 1 is a unit that extends along a sheet conveyance path that is oblique, such as from the lower right to the upper left in FIG. 2, and includes a housing 11 that is arranged along that direction. Have. Laser diodes (LD) 17 (Bk: black), 18 (C: cyan), 19 (M: magenta), and 20 (Y: yellow) are attached to the upper part of the housing 11 for each of the four colors.
[0095]
Further, the housing 11 includes a polygon mirror motor 2 for operating a main operation line, two-layer fθ lenses 21 and 22 for dot position correction, and long WTL lenses 23, 24, 25 for correcting surface tilt. 26, a cylinder lens and the like (not shown) for correcting the laser beam diameter are attached.
[0096]
The polygon mirror motor 2 is integrally formed with two upper and lower six-surface mirrors 27, and the polygon mirror 27 is irradiated with laser beams emitted from LDs 17, 18, 19, and 20.
[0097]
The LDs 17, 18, 19, and 20 corresponding to the respective colors emit light in synchronization with the sheet conveyance timing, and the light (shown by a bold line in the drawing) is transmitted to a cylinder lens, a polygon mirror 27, a two-layer fθ lens 21, 22, a long one. The photosensitive drums 28 of the respective colors are irradiated via the WTL lenses 23, 24, 25, 26.
[0098]
In addition, it is preferable to employ a two-beam type LD unit 17 for black. That is, by employing a two-beam type LD, two beams can be simultaneously written at the time of monochrome image formation, and quick writing can be performed while the number of rotations of the polygon mirror motor 2 is suppressed. By reducing the number of rotations of the polygon mirror motor 2 in this manner, an effect of suppressing noise and an effect of extending the life of the motor can be obtained. For example, when printing in the color mode, the rotation speed of the polygon mirror 27 is 29528 rpm (revolutions per minute) and the printing speed is 28 ppm (pages per minute). Despite being small, the printing speed is 38 ppm.
[0099]
Returning to FIG. 1, the configurations of the photoconductor unit 3, the developing unit 4, and the transfer unit 5 in the image forming apparatus will be described. As shown in the figure, this image forming apparatus is an apparatus that employs a tandem image forming method with four drums, and the printing speed in a full-color print mode and a monochrome print mode is improved by adopting this method. . Further, as described above, the photoreceptor unit 3, the developing unit 4, and the transfer unit 5 are arranged obliquely to reduce the installation space, thereby reducing the size of the entire apparatus.
[0100]
The photoconductor unit 3 and the developing unit 4 are independent units for each color. That is, the photosensitive unit 3 and the developing unit 4 for magenta (M), the photosensitive unit 3 and the developing unit 4 for cyan (C), the photosensitive unit 3 and the developing unit 4 for yellow (Y), and the black (Bk) 1) and a developing unit 4 are arranged in the above order from the lower right side to the upper left side in FIG. Since the photoconductor units 3 for M, C, and Y, except for Bk, have exactly the same configuration, a new unit may be used for any color (M, C, Y). Good.
[0101]
The transfer unit 5 is a unit that extends along the oblique direction below the photoconductor unit 3 and the developing unit 4 that are obliquely arranged in the order described above, and is arranged along the oblique direction. I have. The transfer unit 5 has a plurality of rollers and an endless transfer belt 29 wound around the rollers. When the rollers are rotated by a motor (not shown), the transfer belt 29 is rotated counterclockwise in the figure, and the paper sent from the paper supply unit 110 is placed on the transfer belt 29 and is moved from the lower right to the upper left in the figure. To the side. A P sensor 6 is disposed on the downstream side (upper left side in the drawing) of the transfer unit 5 in the transport direction, and the P sensor 6 detects the density of the P sensor pattern formed on the transfer belt 29. The detection result is used for control.
[0102]
Here, a cross-sectional view of the photoconductor unit 3 and the developing unit 4 corresponding to a certain color in FIG. 3 is shown. As shown in the figure, the photoconductor unit 3 has a photoconductor drum 28 (for example, φ30). The photoconductor drum 28 has a hollow cylindrical shape, and is configured to be rotated clockwise in the figure by a driving mechanism described later.
[0103]
A charging roller 36 (for example, φ11) is disposed above the photosensitive drum 28. The charging roller 36 is disposed at a position where the surface thereof is separated from the surface of the photosensitive drum 28 by about 0.05 mm. Then, the charging roller 36 is rotated in a direction opposite to the photosensitive drum 28, that is, counterclockwise in the figure, and applies a uniform charge on the surface of the photosensitive drum 28.
[0104]
Further, a cleaning brush 37 is disposed above the charging roller 36. A cleaning brush 39 and a counter blade 38 are disposed on the upper left side of the photoconductor drum 28, and the photoconductor drum 28 is cleaned by these.
[0105]
Further, a waste toner collecting coil 40 is disposed on the left side of the cleaning brush 39, and the waste toner collected by the waste toner collecting coil 40 is transported to the waste toner bolt 16 shown in FIG. ing.
[0106]
Next, the developing unit 4 employs a dry two-component magnetic brush developing method, and includes a developing roller 30, a developing doctor 31, a transport screw left 32, a transport screw right 33, a toner density sensor 34, And an agent cartridge 35.
[0107]
Next, a drive mechanism of the photoconductor unit 3 will be described with reference to FIG. The photoconductor unit 3 is provided for each color, and there are four units. There are three photoconductor units 3 for M, C, and Y (for color), and a photoconductor unit 3 for Bk. Are driven by different driving mechanisms. That is, the color photoconductor unit 3 is driven by the color drum drive motor 41 as a drive source, and by the gears 43 and 44 and the joint 45 for transmitting the drive force.
[0108]
On the other hand, the photoconductor unit 3 for black is driven by another black drum drive motor 42 as a drive source, and by another gear 44 and a joint 45 for transmitting this drive force. Therefore, during color mode printing, only the color drum drive motor 41 operates, and the black drum drive motor 42 is stopped. On the other hand, at the time of monochrome mode printing, only the black drum drive motor 42 operates, and the color drum drive motor 41 is stopped. The color drum drive motor 41 and the black drum drive motor 42 are stepping motors.
[0109]
As shown in FIGS. 5 and 6, the fixing unit 46 employs a belt fixing method, and since the belt has a smaller heat capacity than the fixing roller, the fixing unit employs the belt fixing method. There are merits such as a shorter warm-up time and a lower set roller temperature during standby than the method used.
[0110]
The fixing unit 46 heats and presses the sheet on which the image has been transferred, and fixes the toner image on the sheet. The fixing unit 46 includes the fixing belt 13 and the oil application unit 47. In the oil application unit 47, the gel oozes out of the oil and is supplied from the application felt 48 to the application roller 49. A small amount of silicone oil is applied to the fixing belt 13 while the application roller 49 rotates. By applying oil to the fixing belt 13 in this manner, the fixing belt 13 and the paper are easily separated. The application operation by the oil application unit 47 is performed every time one sheet of paper is conveyed. Each time one sheet of paper is conveyed by a mechanism having a solenoid or a spring (not shown), the oil is applied. The unit 47 is driven and brought into contact with the fixing belt 13. On the other hand, when one sheet passes, the oil application unit 47 is separated from the fixing belt 13 by the above mechanism.
[0111]
As shown in FIG. 5, a cleaning roller 50 is provided on the upstream side of the fixing belt 13 in the paper transport direction, and the cleaning roller 50 absorbs dirt on the fixing belt 13 so that the belt cleaning is performed. Done.
[0112]
The above is the configuration of the fixing unit 46, and the sheet that has passed through the fixing unit 46 is transported to the main body tray 51 shown in FIG. 1 by the transport rollers.
[0113]
Next, the configuration of the sheet feeding unit 110 will be described with reference to FIG. The paper feed unit 110 has three trays such as a first tray 9, a second tray 10, and a manual feed tray 8. Each of these trays employs an FRR paper feeding system as a system for sending out the sheets stored in the tray. The FRR paper feeding mechanism reverses the paper feed roller that is driven to rotate in the paper feed direction in order to separate the paper fed from the paper stack stacked in the paper feed tray one by one. It has a configuration in which rollers are abutted.
[0114]
Under this configuration, since the reverse rotation roller is applied with a weak torque directed in the opposite direction to the paper supply roller via the torque limiter, the reverse rotation roller is in contact with the paper supply roller, or when one sheet In the state in which the sheet has entered between the rollers, the sheet rotates along with the sheet feeding roller, while in the state in which the sheet is separated from the sheet feeding roller, or in a state in which two or more sheets have entered between both rollers, it rotates in the reverse direction. For this reason, when the multi-feed paper enters, the paper in contact with the reverse rotation roller is returned to the downstream side in the paper feeding direction, and the double feed is prevented.
[0115]
The sheets stored in the first tray 9 are separated by the first sheet feeding unit 51 and sent out from the first tray 9. Then, the fed sheet is transported by the relay roller 53 and reaches the transport roller 55. Here, the sheet is conveyed toward the registration roller 7 on the upper left side while being turned by the conveyance roller 55.
[0116]
The conveyed sheet collides with the stopped registration roller 7, whereby the skew of the sheet is corrected. Then, the timing of the image forming process by the photoreceptor unit 3 and the like is adjusted. At a predetermined timing, a registration clutch (not shown) is connected to drive the registration roller 7, and the sheet is conveyed to the transfer unit. Thereafter, the sheet is conveyed by the transfer belt 29 as described above, and is subjected to predetermined processing such as image transfer.
[0117]
The paper stored in the second tray 10 is sent out in the same manner as the paper stored in the first tray 9 after the paper is transported toward the transport roller 55 by the second paper feed unit 52 and the relay roller 54. It is. The paper set on the manual tray 8 is conveyed toward the registration roller 7 by the paper supply unit 56, and thereafter, the same as the conveyance of the paper from the first tray 9 described above.
[0118]
Next, a configuration for driving the first paper supply unit 51 and the second paper supply unit that feed out the paper from the first tray 9 and the second tray 10 as described above will be described. As shown in FIG. 8, both of these units are driven by one stepping motor 56, and transmission of driving force to each unit is performed via a first paper feed clutch 57 and a second paper feed clutch 58. Is That is, when the paper is fed from the first tray 9, only the first paper feed clutch 57 is engaged, and when the paper is fed from the second tray 10, only the second paper feed clutch 58 is engaged.
[0119]
This image forming apparatus has the color photoreceptor unit 3 and the like as described above, and can perform not only monochrome printing but also color printing. More specifically, as shown in Table 1, there are four print modes such as "monochrome mode", "color mode (1)", "color mode (2)", and "OHP / cardboard mode". When the user operates the operation unit or the like to select a mode, a control unit (operation control unit) of the image forming apparatus (not shown) controls each unit of the apparatus according to the selection, and operates each unit in the operation mode. . In this image forming apparatus, the control unit sets the image forming speed to three types (182.5 mm / s = 38 ppm (pages per minute), 125.0 mm / s = 28 ppm, and 62.5 mm / s = 14 ppm) according to the mode selected by the user. It is designed to switch. That is, the control is performed so that the rotational speeds of the stepping motor 56, the black drum drive motor 42, and the color drum drive motor 41 are changed according to the selected operation mode.
[Table 1]

Here, the printing speed (image forming speed) is 14 ppm in the high-resolution “color mode 2” and “OHP / thick paper mode”, while the printing speed is 38 ppm in the “monochrome mode”. There is nearly twice the speed difference. In order to realize such a large speed difference with a single motor, this image forming apparatus employs a stepping motor as a drive source for a paper transport mechanism system or the like.
[0120]
B. Sound quality evaluation method
The present invention is a remodeling method for evaluating the noise generated by the image forming apparatus as described above and taking measures to reduce the discomfort caused to the person by the noise based on the evaluation. A method for evaluating the noise generated by the apparatus during image formation will be described.
[0121]
As a method of evaluating the sound quality, a method of deriving a sound quality evaluation formula capable of predicting the sound quality from an experimental result obtained by the Scheffe pairwise comparison method may be considered. In the pair comparison method, a pair of two stimuli is created for a stimulus whose absolute evaluation is difficult, such as a sound emitted from an image forming apparatus. Then, pairs are formed with all combinations of stimuli to be evaluated, the difference between the scores is obtained, and a relative average score is given for each stimulus. This method focuses on the point that it is difficult for a human to evaluate one stimulus, but it is relatively easy to compare two stimuli to determine which is better or worse. It is.
[0122]
For example, if there are three stimuli A1, A2 and A3, each stimulus model is
y1 = μ + α1, y2 = μ + α2, y3 = μ + α3
And For simplification, it is assumed that this model is composed of only the total average μ and the main effect αi (i = 1, 2, 3). In addition, the total sum of the main effects is set to 0, similarly to the general constraint necessary for estimating the parameters of the experimental design.
α1 + α2 + α3 = 0 ‥‥ (1)
[0123]
The fact that the absolute evaluation cannot be performed means that there is no idea about the value of μ, so that it is not possible to directly measure y1, y2, and y3, but the difference between the two stimuli is taken as described above. As a result, μ disappears and can be represented by the difference of only the main effect.
y1−y2 = (μ + α1) − (μ + α2) = α1−α2 ‥‥ (2)
y1−y3 = (μ + α1) − (μ + α3) = α1−α3 ‥‥ (3)
y2−y3 = (μ + α2) − (μ + α3) = α2−α3） (4)
[0124]
Here, (2) + (3) is
2y1- (y2 + y3) = 2α1- (α2 + α3)
However, according to the above constraint equation (1),
2y1- (y2 + y3) = 3α1
Becomes That is, the effect of each stimulus can be extracted. Then, assuming that the effect of each stimulus at this time is represented by a first-order function by a difference in physical characteristics of the image forming apparatus,
α1−α2 = b (x1−x2) ‥‥ (5)
Is obtained. Here, b is a constant, and xi is i = 1, 2, 3 ‥‥ n. The intercept is canceled because it models the difference between the two stimuli.
[0125]
Therefore, multiple regression analysis is performed using the difference between the scores (the difference between the scores of a pair of sounds obtained by the paired comparison experiment) as the objective variable and the differences between a plurality of physical characteristic values (such as psychoacoustic parameters) as the explanatory variables. Is performed, a model for predicting the difference between the evaluations is obtained. That is, when a physical characteristic value of two sounds to be compared is input, a model capable of outputting a prediction of a difference in evaluation as to how discomfort the two sounds differ is obtained.
[0126]
The present inventor has decided to apply the following multiple logistic regression model as a prediction model for sound quality evaluation, separately from the prediction model for the evaluation difference as described above.
(Equation 2)

The expression (f) does not predict the difference between the superiority of the sound Ai and the sound Aj as described above, but predicts the victory of the superiority of the sound Ai and the sound Aj as the probability Pij, (1−Pij). is there.
(Equation 3)

Here, Pij is a probability that the sound Ai is uncomfortable when the sound pair (Ai, Aj) to be sampled is compared, and (1-Pij) is a probability that the sound Aj is uncomfortable. These probabilities can be easily obtained by setting πi as the frequency at which the sound Ai serving as a sample is made unpleasant, and πj as the frequency at which the sound Aj serving as a sample is made unpleasant. Since the probability Pij is statistically known to follow the binomial distribution, if the assumption that the expected value is affected by the psychoacoustic characteristic holds, the multiplicative model of the above equation (f) is used. It is reasonable to use. Since the multiple logistic regression model is a model for predicting the population probability Pij, the predicted Pij has a value in the range of 0 to 1, and the value is reasonable as an index.
[0127]
Therefore, the present inventor has adopted the above-described multiple logistic regression model as a model for sound quality evaluation. Before describing the process of deriving the sound quality evaluation model in the present invention, a logistic regression model will be briefly described.
[0128]
It is assumed that loudness is a cause of the discomfort of the sound generated by the image forming apparatus, and for the sake of simplicity, the loudness is the only cause. In this case, when n persons compare two sounds (A1 and A2) to be uncomfortable sounds, if there is no difference in loudness of each sound, each of A1 and A2 is uncomfortable. Is expected to be 50%.
[0129]
When the loudness of the sound A2 is smaller than the sound A1 by 1 (sone), the probability that the sound A2 is unpleasant is 25%. Further, when the loudness of the sound A2 is smaller than the sound A1 by 2 (sone), the probability that the sound A2 is uncomfortable is further reduced by 25% and is not considered to be 0%. In other words, instead of considering that the loudness decreases by 1 (sone), the probability of responding to discomfort decreases by 25%, by decreasing the loudness by 1 (sone), the probability of responding to discomfort decreases from 50% to 25%. In other words, it is natural to think that it has been reduced by half. Therefore, it is considered that when the loudness is reduced by 2 (sone), the probability of answering discomfort is 25 × (１ ／) = 12.5%.
[0130]
In this way, the sound quality improvement effect does not have the additive property but the multiplicative property. In the case where the multiplicity is satisfied, the logarithm ln (p) is obtained, and the additivity is satisfied. Further, in the case where the limit of 100% is challenged like the yield, -ln (1-p) may be taken. Combined these two logarithms
z = ln (p) -ln (1-p) = ln (p / 1-p) ‥‥ (7)
Is called logit transformation. And this inverse transformation is
p = exp (z) / (1 + exp (z)) = 1 / (1 + exp (−z))
It is. This means that when an S-shaped curve (sigmoid function) is applied to a probability p from 0 to 1, the curve is approximated by a cumulative distribution function of a logistic distribution.
[0131]
The graph shown in FIG. 9 shows the effect of the logit transform. As shown in the figure, it can be seen that linearity holds for the probability p after the logit transformation. Therefore, z can be estimated by applying ordinary regression analysis using z as the target variable, and an estimated value of p can be obtained by the inverse transformation of the above equation (6). In the prediction using the defect rate or the ratio p as the target variable, logistic transformation of p = r / n may be performed and a regression analysis may be performed using the target variable as logarithmic regression analysis. Note that r is the number of defects and n is the number of inspections. However, when r is 0 or n, z cannot be obtained.
z = ln ((r + ／) / (n−r + ／))
And This transformation is called empirical logit.
[0132]
It should be noted that if this conversion is used as it is, the case where the number of n is large and the case where n is small will be treated equally, so it is necessary to perform weighting corresponding to the size of n. In particular, when the value of p is close to 0 or 1, the variance of the logit z increases, which is inconvenient. Logistic regression analysis takes these points into account.
[0133]
The above is the description of the logistic regression analysis, and the inventor has derived a sound quality evaluation formula using the logistic regression analysis, and performed sound quality evaluation using the evaluation formula. Hereinafter, the process will be described in detail with reference to actually performed experiments and the like.
[0134]
The flow of the sound quality evaluation experiment and the derivation of the sound quality evaluation formula of the image forming apparatus are as follows.
(1) Collection of operation sound of image forming apparatus
(2) Analysis of operation sound
(3) Creating test sounds from collected operation sounds
(4) Measurement of psychoacoustic parameters of test sound
(5) Pair comparison experiment using test sound
(6) Identification of unpleasant sound source
(7) Creation of difference model analysis data
(8) Deriving an equation for predicting the difference between the scores
(9) Derivation of model formula (sound quality evaluation formula) for predicting score
(10) Verification of derived sound quality evaluation formula
[0135]
Hereinafter, the details of the above process will be described.
(1) Collection of operation sound of image forming apparatus
The operation sound of the image forming apparatus was collected by binaural (binaural) recording using a dummy head HMS (Head Measurement System) III manufactured by Head Acoustics. This is because by performing binaural recording in this way and reproducing the sound with a dedicated headphone, the sound can be reproduced as if a human actually heard the sound generated by the machine. Further, as described above, the image forming apparatus which is the device to be measured executes an image forming operation at three types of image forming speeds in accordance with the operation mode, and the following operation is performed for each of these three operation modes. The measurement was performed under the measurement conditions (see FIG. 10).
・ Recording environment ‥‥ Semi-anechoic room
The position of the ear of the dummy head 203 (sound pickup position) 204 ‥‥ 1.2 m, the horizontal distance from the end surface of the device under test 201 is approximately 1 m (1 ± 0.03), and the width direction is the center position of the device
Recording direction: four directions: front (the surface where the operation unit 202 of the image forming apparatus is located), rear, and left and right
・ Recording mode @FF (free field: for anechoic room)
・ HP filter @ 22Hz
[0136]
The reason why the height of the dummy head is set to 1.2 m is to take into account the fact that, in recent years, the use of an image forming apparatus is such that a user often gives an instruction from a personal computer or the like in a seated state. . Of course, a dummy head may be installed at a height of 1.5 m in consideration of a state where a person is standing.
[0137]
By the way, the sound emitted by the image forming apparatus usually differs for each direction. This is because the arrangement positions of various motors, the transport path of the paper, the position of the paper discharge port, and the like are not located at the center of the apparatus, but are distributed. Therefore, sounds emitted from a certain sound source (such as a motor) are often heard on the right side, but are not heard well on the left side, so that sounds collected in each direction are different. The test sound used in the experiment described later may be collected in any direction, but it is necessary to unify the sample sound in any one direction when performing the paired comparison experiment. Therefore, in this experiment, it is considered that the user will most often hear the front side, while the rear side of the image forming apparatus usually has little opportunity to hear the rear side sound that is installed along with the wall. Therefore, we decided to use what was collected on the front side as the test sound.
[0138]
(2) Analysis of operation sound
Next, the operation sound of the image forming apparatus during the operation of each mode collected as described above was analyzed.
[0139]
First, the noise when operating in "color mode (1)", that is, when the printing speed was 28 ppm, was analyzed, and the analysis result as shown in FIG. 11 was obtained. The upper part of FIG. 11 represents sounds collected on the time axis, and the lower part of FIG. 11 represents sounds collected on the frequency axis. From these results, seven main sound sources were extracted. First, the impact sound of the fixing oil application of the fixing unit 46 was extracted on the time axis. On the frequency axis, a color development drive system sound, a paper feeding stepping motor sound, a charging sound, a drum driving stepping motor sound, a polygon mirror motor sound, and a paper sliding sound are extracted.
[0140]
Next, when the noise when operating in "color mode (2)", that is, when operating at a printing speed of 14 ppm, was analyzed, an analysis result as shown in FIG. 12 was obtained. The upper part of FIG. 12 represents sounds collected on the time axis, and the lower part of FIG. 12 represents sounds collected on the frequency axis. Based on this result, the main sound source is the fusing oil application impact sound on the time axis, and the paper feeding stepping motor sound, charging sound, drum drive motor sound, polygon mirror motor sound, and paper sliding sound on the frequency axis. Extracted.
[0141]
Next, when analyzing the noise in the “monochrome mode”, that is, when operating at a printing speed of 38 ppm, an analysis result as shown in FIG. 13 was obtained. The upper part of FIG. 13 shows sounds collected on the time axis, and the lower part of FIG. 13 shows sounds collected on the frequency axis. From these results, as the main sound source, the impact sound of the fixing oil application was extracted on the time axis, and the development drive system sound, the charging sound, the drum driving stepping motor sound, and the paper sliding sound were extracted on the frequency axis.
[0142]
(3) Creating test sounds from collected operation sounds
Next, as described above, the sound collected at the position on the front side of the device was processed using "ArtemiS" which is sound quality analysis software manufactured by Head Acoustic's.
[0143]
As a sound processing method performed in this experiment, a sound during one cycle of the printing operation was cut out from the collected original sound. Then, of the sounds in one cycle period, a filter process was performed on the frequency axis or the time axis for the portion related to the main sound source extracted as described above, and a process of attenuating or enhancing these portions was performed. That is, three levels of sound (emphasis, original sound, and attenuation) were created for the sound of the sound source extracted in one mode.
[0144]
Note that, as described above, the sounds collected on the front, rear, left, and right sides of the image forming apparatus are different from each other, but the range of the psychoacoustic parameter values obtained from such four-directional sounds is smaller on the front side created in this experiment. It has been confirmed that the range of psychoacoustic parameter values obtained from three test sounds obtained by emphasizing and attenuating the collected sound is wider. In other words, by performing a subjective evaluation experiment using three sounds obtained by emphasizing and attenuating the sound collected on the front side as in this experiment, the characteristics of the sound obtained from the sound collected in four directions are covered. As a result, the discomfort in four directions can be calculated using the sound quality evaluation formula.
[0145]
As described above, based on the sound collected on the front side, three levels of sound (emphasis, original sound, attenuation) are created from the sound emitted by the main sound source extracted for each of the three operation modes. Nine sounds were created based on the L9 orthogonal table. In the subjective evaluation experiment, it is necessary to perform a round robin comparison experiment, so that in the case of 9 sounds, 72 comparison experiments are performed.
[0146]
Here, Table 2 shows, in the L9 orthogonal table, “color mode (1)”, that is, three levels of sounds created for the main sound sources (seven) extracted from the sounds collected when operating at a printing speed of 28 ppm. The result of creating nine test sounds based on the assignment based on the test sound is shown. By allocating to the orthogonal table in this manner, since there is no correlation between the respective factors (changes in the level of the sound source), the analysis can be performed ignoring changes in other factors.
[Table 2]

In this table (the same applies to the following tables), "-1" is a sound created by attenuating the sound until it is almost inaudible, "0" is a sound of the original sound level, and "1" is a sound of the original sound. The sound is emphasized until the difference in level is clearly understood. For example, the test sound “color 28 ppm (9)” in Table 2 indicates that all sound sources are the original sound because “0” is attached to all sound sources.
[0147]
In Table 2, the subjective evaluation values of the test sounds obtained by the comparative experiment described later are also shown.
[0148]
Next, Table 3 shows “Color Mode 2”, that is, three levels of sounds created for the main sound sources (six) extracted from the sounds collected when operating at a printing speed of 14 ppm, in an L9 orthogonal table. The result of the assignment based on this is shown. However, the charging sound, the drum driving stepping motor sound, and the polygon mirror motor sound are sounds having the same tonality component, and therefore, each test sound was set to the same level. The paper feeding stepping motor sound is also a tonality component, but since it is a sound that occurs intermittently, the level is set separately from the above-mentioned motor sound.
[Table 3]

Table 4 shows three levels of sounds created for the main sound source (five) extracted from the sounds sampled when operating in the "monochrome mode", that is, at a printing speed of 38 ppm, based on the L9 orthogonal table. The results are shown. However, since the charging sound and the drum driving stepping motor sound are sounds of the same tonality component, each of the test sounds has the same level.
[Table 4]

Also, in this experiment, three levels of sound were obtained from the loudness value, sharpness value, tonality value, and impulseness value, which are psychoacoustic parameters, obtained from the sound taken at the front when the above three modes were mixed. (Emphasis, original sound, attenuation) were created, and these sounds were assigned based on the L9 orthogonal table to create a test sound. Table 5 shows the results.
[Table 5]

As for the loudness value assignment, the "monochrome mode" printing speed of 38 ppm is emphasized, the "color mode (1)" printing speed of 28 ppm is intermediate, and the "color mode (2)" printing speed of 14 ppm. As for, it was decided to allocate the attenuated ones respectively. That is, each loudness level value is assigned according to the printing speed. Numerical values in parentheses in the table indicate respective parameter values. In this experiment, the effect of the printing speed (ppm), that is, the effect of the printing speed is also checked. Therefore, the effect cannot be analyzed if the printing speed and the loudness value change completely in proportion. Therefore, as shown in Table 5, even if the loudness value is the same level, a difference of about 1 (sone) is provided so that a difference in the size of hearing is obtained.
The above is the details of the process of creating the test sound from the collected operation sounds.
[0149]
(4) Measurement of psychoacoustic parameters of test sound
Next, psychoacoustic parameters of the test sound created as described above were determined using the sound quality analysis software “ArtemiS” manufactured by Head Acoustic Co., Ltd. With this sound quality analysis software, various settings can be selected when obtaining psychoacoustic parameters, but default settings were adopted in this experiment.
[0150]
For example, for loudness, "FFT / ISO0532", "Filter / ISO0532" and "FFT / HEAD" can be selected as the "Caluculation method", but the default "FFT / ISO0532" is used, and "Spectrum Size" is the default. "4096". Regarding the sharpness, the "Caluculation method" adopted the default "FFT / ISO532", and the "Sharpness method" adopted the default "Aures" of "Aures" and "von Bismarck". "Spectrum Size" was performed with the default "4096". Other psychoacoustic parameters are correlated with loudness and change automatically with loudness settings.
[0151]
Using the sound quality analysis software set as described above, the psychoacoustic parameter value of the test sound created in the process (3) was obtained. Table 6 shows the results.
[Table 6]

[0152]
(5) Pair comparison experiment using test sound
Next, subjects who had the test sounds created as described above evaluated were collected, and the subjects were asked for each mode (“color mode (1)”, “color mode (2)”, “monochrome mode” and “mixed mode”. A pair of the test sounds (1) to (9) created in the "mode") was compared to determine which was unpleasant.
[0153]
In such a comparative experiment, all combinations of two test sounds are extracted from nine test sounds, and N subjects compare all of the combinations. That is, since there are nine test sounds in one mode, there are 72 combinations, and the subject is made to compare them. Therefore, the evaluation of the combination of the test sound (1) and the test sound (2) is different from the evaluation of the combination of the test sound (2) and the test sound (1). Experiments are also performed on combinations with different.
[0154]
In this comparison, for example, the test sound (1) is compared with the test sound (2), and if the subject evaluates the test sound (1) as unpleasant, "1 point" If (2) was unpleasant, it was set to "-1 point", the results were totaled, and statistical processing was performed. As a result, the relative subjective evaluation in the range of -1 to 1 for the nine test sounds. Value obtained. The subjective evaluation values are also shown in Tables 2 to 5. Since the above evaluation is performed, a larger subjective evaluation value means a more unpleasant one.
[0155]
Here, it is preferable to perform a comparison experiment including a case where the comparison order is different for all pairs of combinations of the nine test sounds. However, in order to reduce the number of experiments, the importance of the psychoacoustic parameters obtained from the test sounds is important. The comparison experiment may be performed only on important test sound pairs extracted in consideration of the characteristics and the like.
[0156]
In the paired comparison experiment described above, the evaluation based on the paired comparison is to select which is unpleasant, and is conditioned on not judging the same degree of discomfort. The sound quality evaluation formula described later is determined using such experimental data. The Scheffe's method and its improved methods (Haga modified method, Ura modified method, Nakaya modified method) are based on the cumulative logistic regression model. In the Bradley-Terry method, a sound quality evaluation formula described below is used, and the present invention can be applied to experimental data of any paired comparison method.
[0157]
(6) Identification of unpleasant sound source
Next, an unpleasant sound source was specified for each of the results of experiments performed in three modes of "color mode (1)", "color mode (2)", and "monochrome mode". Here, FIGS. 14 to 28 are graphs showing the relationship between the level (emphasis, original sound, attenuation) of each sound source shown in Tables 2 to 4 and the subjective evaluation value. In this graph, the vertical axis is the subjective evaluation value α, and the higher the value, the more unpleasant it is. The horizontal axis of the graph is the level of the sound source, that is, the sound pressure level level. “−1” attenuates the sound source, “0” is the original sound, and “+1” emphasizes the sound source.
[0158]
In addition, “R^Two"Is a contribution ratio, and" R "is a correlation function. Here, the contribution ratio indicates what percentage the sound source contributes to discomfort. The results shown in FIG. 14 indicate that the fixing oil application impact noise contributes 51% to discomfort. That is, the higher the correlation between the change in the level of the sound source and the change in the subjective evaluation value (discomfort), the greater the contribution ratio. Note that the sum of the contribution rates of the sound sources in one mode is 100%, but there is a case where the sum does not reach 100% due to rounding or the like.
[0159]
Referring to the contribution ratio of each sound source in the "color mode (1)" shown in FIGS. 14 to 20, the color development driving sound system, the paper feeding stepping motor sound, the charging sound, and the polygon mirror motor sound almost contribute to discomfort. You can see that they haven't. However, according to the later analysis, the three sound sources of the paper feeding stepping motor sound, the charging sound, and the polygon mirror motor sound have a strong relationship with the tonality (pure sound) component, and are actually uncomfortable. It turned out that the discomfort was not much improved. Therefore, in other modes, these sound sources are set to the same level for each test sound (see the process of (3) and Tables 3 and 4). For this reason, it is considered that there is no need for noise countermeasures since only the color development driving sound among the sound sources hardly contributes to discomfort. However, the evaluation based on the sound power level may need improvement.
[0160]
On the other hand, in the “color mode {circle around (1)}”, the most unpleasant noise is the impulsive oil application impact noise, and the second most significant noise is the paper sliding noise.
[0161]
According to the results of the unpleasant sound source analysis of “color mode {circle around (2)}” shown in FIGS. 21 to 24, the fixing oil application impact sound 43%, the paper sliding noise 35%, the paper feed stepping motor noise 17%, the charging noise, the polygon The sum of the three sound sources of the mirror motor sound and the drum drive motor sound was 3%.
[0162]
According to the results of the uncomfortable sound source analysis in the “monochrome mode” shown in FIGS. 25 to 28, the fixing oil application impact noise 43%, the paper sliding noise 35%, the sum of the charging noise and the drum driving motor noise 10%, the development driving The sound system was 3%.
[0163]
From the above analysis results, it can be seen that sound sources other than the sound of the developing drive system contribute to discomfort, and if these sound sources are subjected to noise countermeasures, the discomfort can be reduced.
[0164]
(7) Create analysis data for difference model
Next, the probability that each sound is uncomfortable when two sounds are compared is calculated using the experimental result obtained by the paired comparison method experiment (5). More specifically, the sound A (the sound presented earlier) and the sound B (the sound presented later) are compared, and a value obtained by dividing the number of unpleasant sounds by the total number of subjects is calculated. For example, when there are 40 subjects, the sound A (first presentation sound) and the sound B (back presentation sound) are compared, and 30 persons who judge that the sound A is unpleasant and the sound B is unpleasant. If it is assumed that there are 10 persons, the probability that the sound A and the sound B are unpleasant at this time is obtained as follows.
Sound A discomfort probability = 30/40, Sound B discomfort probability = 10/40
[0165]
The discomfort probability obtained in this way is based on the difference between the physical quantities (psychological acoustic parameters and the like) of the two sounds, and creates a model for predicting the difference between the discomfort probabilities of the two sounds performed in the following process (8). Used for In addition, the difference between physical quantities (psychological acoustic parameters) used for creating the prediction model, that is, the difference between the test sound and the psychoacoustic parameter value of the test sound (see Table 6) is used for all the test sounds. (72 patterns per mode, 288 patterns because there are 4 modes) are calculated.
[0166]
Table 7 shows a part of the result of the difference between the score calculated as described above and the psychoacoustic parameter value (analysis data of the difference model). Table 7 shows a part of the results of the test sound in the “color mode (1)” (comparison result between the test sound (1) and the test sounds (2) to (9)).
[Table 7]

(8) Deriving an equation to predict the discomfort probability of two sounds
[0167]
Next, multiple logistic regression analysis was performed using the discomfort probability of the two sounds obtained in the process (7) and the difference between the physical quantities (psychological and acoustic parameters) of the sounds.
[0168]
Multiple logistic regression analysis can be performed using statistical analysis software “JMP (registered trademark of SAS Institute Inc)” or “SPSS (registered trademark of SPSS Inc)” or the like. The logistic regression coefficient is obtained by inputting the data in Table 7 (such as the discomfort probability and the difference between psychoacoustic parameter values) into “JMP” and executing an analysis while selecting the explanatory variable (difference between psychoacoustic parameter values). Statistical results such as the P value of the selected explanatory coefficient and the contribution of the equation are output. Here, the P value is the probability of a significant difference test, and is determined to be significant at 5% or less and not significant at 5% or more (irrelevant).
[0169]
In this case, since the model is a model of the difference between the scores, the intercept was fixed to 0, and significant psychoacoustic parameters were selected by the statistical analysis software “JMP version 4J”. As a result of variable selection, loudness, sharpness, tonality and impulsiveness were selected. Table 8 shows partial regression coefficients (regression coefficients during multiple regression analysis) of the four psychoacoustic parameters selected as variables.
[Table 8]

As shown in Table 8, as a result of the regression analysis, in addition to the partial regression coefficients of the selected four parameters, the upper and lower limits of the partial regression coefficient having a reliability of 95% or more (that is, 95% The range of the partial regression coefficient with the above reliability) is also included. The upper limit value and the lower limit value are obtained by adding ± 2 times (2σ) of the corresponding standard deviation to the estimated value of the partial regression coefficient. Since the values of the partial regression coefficients are all positive, it can be seen that as the parameter value difference increases in the positive direction, the discomfort difference also increases.
[0170]
Using the results of the multiple logistic regression analysis described above, a model expression was created in which exp in the above expression (f) is -z below.
(Equation 4)

z = + 0.80742768 × (x loudness i−x loudness j)
+ 1.3807 × (x sharpness i−x sharpness j)
+ 9.0486 × (x tonality i−x tonality j)
+5.5916 x (x impulsiveness i-x impulsiveness j) ... (g)
By substituting the psychoacoustic parameter values of the two sounds as described above, a non-linear equation that can calculate the discomfort probability when comparing the two sounds can be derived.
[0171]
Here, FIG. 29 shows a scatter diagram of the actually measured value of the discomfort probability when comparing a pair of two sounds and the predicted value derived using the above model formula. As shown, the contribution rate of the discomfort is as high as 92%, which indicates that the reliability of this model formula is high.
[0172]
(9) Derivation of sound quality evaluation formula to predict discomfort probability
With the model derived as described above, the discomfort probability when comparing two sounds can be predicted, but what is ultimately required in sound quality evaluation is the discomfort probability of a single sound. Therefore, a sound quality that can determine the relative discomfort probability in the population for one extracted sound from a model that predicts the discomfort probability when comparing the two sounds as described below. An evaluation formula was derived.
[0173]
First, the average value of each of the following test sounds used in the experiment as the psychoacoustic parameters is substituted into (g) of the above equation (f), and the discomfort probability p = 0.5 at that time, that is, The discomfort probability was defined as 50% when the sound when each parameter value was average was compared with the other sounds in the population.
[0174]
Substituting the average value of each psychoacoustic parameter value,
x loudness 0 = 7.067804
x sharpness 0 = 2.27953527947254
x Tonality 0 = 0.115442108655561
x impulseness 0 = 0.606150659026989
So,
0.5 = 1 / ｛1 + exp (-[+ 0.80742768 (loudness value i−7.067804)
+1.38073296 (Sharpness value i−2.27953527947254)
+9.04860954 (tonality value i−0.115442108655561)
+5.59160971 (Impulsiveness value i−0.606150659026989)]｝
Becomes
[0175]
Here, if the content of exp is z,
0.5 = 1/1 + exp (-z)
0.5 × {1 + exp (-z)) = 1
0.5 × exp (-z) = 0.5
exp (-z) = 1
[0176]
And if we take logarithms on both sides,
ln {exp (-z)} = ln1 = 0
-z = 0
z = 0
Therefore,
z = 0 = [+ 0.80742768 (loudness value i−7.067804) +1.38073296 (sharpness value i−2.27953527947254) +9.04860954 (tonality value i−0.115442108655561) +5.59160971 (impulsiveness value i−0.606150659026989)]
Becomes Therefore,
z = + 0.80742768 × Loudness value i + 1.38073296 × Sharpness value i + 9.04860954 × Tonality value i + 5.59160971 × Impulsiveness value i-13.28811895
Becomes Therefore, a single test sound can be converted into the model formula (d) for predicting the probability of feeling uncomfortable.
Discomfort probability P = 1 / (1 + exp (-z))
z = +0.80742768 x (loudness) + 1.80773296 x (sharpness) + 9.04860954 x (tonality) + 5.59160971 x (impulsiveness)-13.28811895 d)
[0177]
The equation (d) derived in this way can be used as a sound quality evaluation equation for estimating the discomfort probability P.
[0178]
This time, the average value of all data was used as the reference value, but it is possible to change the reference value due to environmental changes. Further, it is also possible to calculate the discomfort probability of the sound emitted from the image forming apparatus after the improvement using the psychoacoustic parameter value obtained from the sound of the image forming apparatus before the improvement as the reference value.
[0179]
The above equation (d) derived as described above is for estimating a change in the probability of superiority or inferiority due to a deviation from the average value, and the probability when the average value of the physical quantity of the sound is input is assumed to be 0.5. I'm calculating. As this probability increases, discomfort increases. By using this sound quality evaluation formula, a condition of a psychoacoustic parameter at which the probability P becomes equal to or less than a predetermined probability can be obtained.
[0180]
From the above equation (d), if the elements of the sound corresponding to each psychoacoustic parameter are reduced, that is, (1) the size of the hearing is reduced (loudness), and (2) the high frequency component is reduced (sharpness). It can be seen that (3) reducing pure tone components (tonality) and (4) reducing impact sound (impulsiveness) can reduce discomfort.
[0181]
As described in the above (8), since the partial regression coefficient range having the reliability of 95% or more obtained as the regression analysis result shown in Table 8 is set, the range of the intercept is also the upper limit of each partial regression coefficient. This is a value obtained by substituting the value and the lower limit (intercept at the time of substituting the lower limit is -12.47284396, and intercept at the time of substituting the upper limit is -14.10339529).
[0182]
If the above equation (d) is modified assuming that coefficients and intercepts can be taken within this range, the following equation (a) is obtained.
Discomfort probability P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.76545285 ≦ A ≦ 0.84940259
1.27685159 ≦ B ≦ 1.48461447
8.11323413 ≦ C ≦ 9.98398583
5.30484579 ≦ D ≦ 5.87837423
-14.10339529 ≦ E ≦ -12.47284396 ‥‥ (a)
[0183]
Equation (a) can be used as a sound quality evaluation equation for estimating the discomfort probability P.
[0184]
Further, based on the results shown in Table 8, the above equation (a) gives a range to the values that the regression coefficients can take, but when the estimated values of the regression coefficients shown in Table 8 are fixed (that is, each When the coefficient for multiplying the acoustic parameter is fixed), the value obtained by adding ± 2σ to z indicates the range of the 95% confidence interval. Here, σ is the standard deviation of the error.
[0185]
The standard error of z is obtained by first using the actually measured probability of discomfort p to derive z by the above equation (7), and using statistical analysis software “JMP (registered trademark of SAS Institute Inc)” or the like. Is used to derive a predicted value of z. Then, the relationship between z obtained from the actually measured value and z of the predicted value is plotted on a scatter diagram, and the standard deviation of the difference (error) can be obtained using the statistical analysis software.
[0186]
As a result of performing such an operation, a standard deviation σ of error was obtained as 0.721307.
[0187]
Therefore, the expression including the range of the error is as the following expression (c).
Discomfort probability P = 1 / (1 + exp (-z ± 2σ))
z = +0.80742768 x (loudness) + 1.80773296 x (sharpness) + 9.04860954 x (tonality) + 5.59160971 x (impulsiveness)-13.28811895
σ = 0.721307 ‥‥ (c)
[0188]
The above equation (c) can also be used as a sound quality evaluation equation for estimating the discomfort probability P. It is also conceivable to use the standard deviation σ of the error obtained as described above to calculate the discomfort probability by the following equation.
Discomfort probability P = 1 / (1 + exp (-z)) ± 2σ
[0189]
However, when the discomfort probability is derived using this formula, the range of the derived discomfort probability P may exceed the range of 0 to 1, which is inappropriate as a formula for predicting the discomfort probability.
[0190]
(10) Verification of derived sound quality evaluation formula
Next, the prediction accuracy of the prediction formula (sound quality evaluation formula) for the discomfort probability P derived as described above was verified.
[0191]
This verification was performed by comparing the actually measured value of the discomfort probability P with the predicted value derived using the above sound quality evaluation formula (d). Since the actual measurement value of the discomfort probability P cannot be obtained without actually performing an experiment for each operation mode, the above four modes “color mode (1)”, “color mode (2)”, and “monochrome mode” , "Mixed mode"), an actual measurement of the discomfort probability was obtained, and the corresponding predicted values were derived using a sound quality evaluation formula.
[0192]
As the actually measured value of the discomfort probability, a value obtained by dividing the sum of the discomfort indexes of the test sounds by the overall evaluation number is used. More specifically, in the experiment on the test sound in “color mode (1)”, the denominator of the discomfort probability is as follows. When the experiment is performed by 35 people, each test sound is compared with the other eight sounds for each of the nine sounds.
Eight sounds × 2 (replacement of comparison order) × 35 people = 560 people.
[0193]
On the other hand, the numerator, for example, using the test sound (1) of the “color mode (1)” as an example, when compared with other test sounds (2) to (9) (including the reverse order) If the number of persons who judge test sound (1) as unpleasant is 10, 20, 20, 19, 19, 50, 5, 5 or 5, respectively, the sum of 148 is the numerator.
[0194]
Therefore, in this case, the actually measured value of the discomfort probability of the test sound (1) in the “color mode (1)” is 48/560 = 0.26.
[0195]
The predicted value is obtained by substituting the physical quantity (psychological acoustic parameter) of the sound into the above sound quality evaluation equation (d) while obtaining the actually measured value of the discomfort probability for each test sound in each of the four modes in the above procedure. obtain. In this way, the actually measured discomfort probability and the predicted probability for each test sound in each mode can be obtained, and the results are shown in Table 9.
[Table 9]

And the graph which plotted this result is shown in FIG. As shown in the figure, the slope of this graph is almost 1, and the contribution ratio is high. Therefore, it is considered that the accuracy of the predicted value of the score derived by the above-described experiment (d) is high in the four experiments, that is, in any of the four modes.
[0196]
In deriving a predicted value for verification, an intercept (= E) is obtained from an average value of psychoacoustic parameters for each experiment (for each mode), and an equation obtained by slightly modifying equation (d) using the intercept as an intercept is obtained. It was derived for each mode, and the predicted value was determined using the derived formula. This adjustment was made because it was necessary to verify the accuracy of the predicted value by comparing the actually measured value and the predicted value from each experiment. The above equation (d) can be used as a sound quality evaluation equation without adjustment. Table 10 shows the adjusted values for reference. When the value of “difference from the overall average” is added to the intercept value obtained by substituting the average value of each mode, the equation becomes the same as the above equation (d).
[Table 10]

Now, as is clear from the above-described verification, it is considered that the accuracy of the prediction probability obtained by the sound quality evaluation formula (d) is high, but the value of the discomfort probability P obtained in this way indicates that a person is uncomfortable. It is important to feel. Therefore, the following experiment was performed to confirm this. That is, after the subject heard all the test sounds (1) to (9), they were asked to listen again one by one, and an experiment was performed to evaluate the discomfort for each of the test sounds in three stages. , Tables 12 and 13 were obtained. Table 11 shows the experimental results for the test sound in "color mode (1)", Table 12 shows the experimental results for "color mode (2)", and Table 13 shows the experimental results for "monochrome mode".
[Table 11]

[Table 12]

[Table 13]

In the table, "A" is an acceptable sound, "C" is an unacceptable sound, and "B" is an intermediate sound. Then, assuming that the largest value among the predicted discomfort probabilities of the sound evaluated as “A” (the value calculated in the equation (d)) is an allowable value, the ppm in each mode and the image forming speed (mm / s) Table 14 shows the permissible values for each.
[Table 14]

FIG. 31 is a graph in which the relationship between the ppm value and the allowable value is approximated based on the results shown in Table 14. Such an approximate expression is
P ≦ 0.3383Ln (ppm) -0.8103 ‥‥ (b)
It is.
[0197]
FIG. 32 is a graph in which the relationship between the image forming speed (mm / s) and the allowable value is approximated based on the results shown in Table 14. Such an approximate expression is
P ≦ 0.3201Ln (mm / s) -1.2402 ‥‥ (e)
It is.
[0198]
As described above, by using the above equations (d), (c) or (a), a psychoacoustic parameter value or the like that can be obtained from a physical quantity of sound is obtained without actually performing a subjective evaluation experiment. The discomfort probability P at which a person feels uncomfortable can be obtained only by the above. According to the above-mentioned conditional expressions (b) and (d), even if the device has a plurality of operation modes having different image forming speeds (mm / s and ppm), the discomfort probability P obtained for each mode is determined. With such a value, it can be determined whether or not the user feels uncomfortable.
[0199]
The above is the method for evaluating the quality of the sound emitted by the image forming apparatus and the method for deriving the sound quality evaluation formula used for the sound quality evaluation.
[0200]
C. Modification method
As described above, the present invention is a remodeling method that evaluates noise generated by an image forming apparatus as described above, and takes measures to reduce discomfort caused to the person by the noise based on the evaluation. A description will be given of a specific example of a measure for modifying the image forming apparatus having the above configuration and reducing a noise generated by the image forming apparatus from giving a discomfort to a person.
[0201]
First, in order to evaluate the sound emitted from the image forming apparatus, the sound emitted from the image forming apparatus is collected in the same manner as in (1) described above. Here, the sampling position is a nearby position (see FIG. 11) specified in ISO7777, a distance of 1.00 ± 0.03 m from the horizontal plane projection of the reference box, and a height of 1.2 ± 0.03 m or 1.50 m above the floor. The position is ± 0.03m.
[0202]
Further, as shown in FIG. 10, sound is collected on all four sides such as the front side, left and right side and rear side where the operation unit is located, and psychoacoustic parameters are obtained from each sound pickup result to determine the discomfort probability P with the above sound quality. It may be determined by an evaluation formula to determine whether or not the discomfort probability P for each surface is within an allowable value. Alternatively, the discomfort probability P may be determined from the sound collection results collected only on the front surface or only one of the surfaces. May be determined. Alternatively, an average value of the psychoacoustic parameter values obtained from the sounds collected on the four sides may be derived, and it may be determined whether or not the discomfort probability P calculated from the average value is within an allowable value.
[0203]
In order to prevent a person located on any of the four sides from feeling uncomfortable, it is preferable to collect sound at all positions on the four sides. Sufficient evaluation can also be obtained by collecting sound on the front side, which is highly likely.
[0204]
If the discomfort probability P obtained as described above exceeds the above-mentioned permissible value, there is a very high possibility that a person feels discomfort. To various modifications. On the other hand, when the discomfort probability P is equal to or less than the allowable value, it is possible to judge that there is little possibility that the person feels uncomfortable, and it is not necessary to take noise countermeasures.
[0205]
As described above, the discomfort probability P is a measure such as reducing the size of hearing (loudness), reducing high-frequency components (sharpness), reducing pure tone components (tonality), and reducing impact sound (impulsiveness). , It is possible to reduce the size, and by reducing the size, it is possible to reduce the discomfort given to a person. Therefore, a specific countermeasure example for reducing the psychoacoustic parameter will be described below.
[0206]
(1) Measures to reduce tonality (pure sound components)
(1-1) Reduction of drum drive stepping motor sound
First, an example of a tonality reduction measure will be described. As a measure for reducing tonality, there is a method of reducing drum drive stepping motor sound. As shown in FIGS. 11, 12 and 13, the sound of the drum drive motor is generated in any of the operation modes. This sound contains many frequency components of the input pulse to the stepping motor.
[0207]
FIGS. 33 and 34 are views showing a drum drive mechanism including a color drum drive motor 41 and a black drum drive motor 42 before remodeling. As shown in these figures, the color drum drive motor 41, the black drum drive motor 42, and the gears 43 and 44 are held by a motor bracket 59.
[0208]
The motor bracket 59 is a member in which sheet metal is given strength by drawing or the like. A casing mounting portion (such as a screw hole) of the image forming apparatus is formed by bending, and the motor bracket 59 is fixed to the casing at the mounting portion.
[0209]
Four gears 44 arranged side by side are rotatably held by the motor bracket 59. Of these gears 44, the rightmost gear 44 in FIG. 33 meshes with a gear 61 attached to the motor shaft of the black drum drive motor 42. Thus, the gear 44 is rotated by the black drum drive motor 42, and accordingly, the photosensitive drum 28 (see FIG. 3) for forming a monochrome image is rotated.
[0210]
Further, of the three gears 44 other than the gear 44 described above, the two gears 44 on the left side in FIG. 32 are rotated by the motor shaft 62 of the color drum drive motor 41. Further, the second gear 44 and the third gear 44 from the left are meshed with the relay gear 43, whereby the third gear 44 is rotated with the rotation of the second gear 44. That is, the three gears 44 are rotated with the rotation of the color drum drive motor 41, whereby the C, M, and Y photoconductor drums 28 (see FIG. 3) are simultaneously rotated. I have.
[0211]
The gears for driving the photosensitive drum as described above employ a special anti-vibration structure for the motor mounting so that the center distance of the gears can be accurately adjusted to the design value in module 0.5. I haven't. That is, the black drum driving motor 42 and the color drum driving motor 41 are directly attached to and fixed to the motor bracket 59.
[0212]
By directly attaching the motor to the motor bracket 59 in this manner, the vibration of the motor during operation propagates to the motor bracket 59, and is amplified and radiated. The sound generated due to this is a sound that contains a large amount of drive frequency components of the stepping motor that is the drum drive motor.
[0213]
As shown in FIG. 35, the color drum drive motor 41 and the black drum drive motor 42 are connected to the motor bracket 65 via a vibration-proof rubber mount 60 in order to reduce the generation of a sound in which the drive frequency component of the stepping motor is remarkable. Attach to That is, the anti-vibration rubber mount 60 serves as a reducing unit that reduces the sound generated as described above.
[0214]
As the anti-vibration rubber mount 60, for example, a stepping motor mount manufactured by NOK Co., Ltd. can be used, and the stepping motor mount is used in a test for testing the effect of noise suppression described later.
[0215]
A drum drive mechanism in which a vibration-proof rubber mount 60 is interposed between the motor bracket 65 and the drum drive motor will be described with reference to FIGS. 36 and 37. If the anti-vibration rubber mount 60 is interposed between the drum drive motor and the motor bracket 65, the accuracy of the distance between the shafts of the respective gears deteriorates. For this reason, in this drum drive mechanism, the driving force is transmitted from the motor shaft to the gear 44 and the like via the timing belt mechanism, instead of directly meshing the motor shaft with the gear.
[0216]
More specifically, timing pulleys 66 and 67 are attached to the motor shafts of the color drum driving motor 41 and the black drum driving motor 42, respectively. The driving force of the motor is transmitted to the pulleys 63 and 64. That is, the two-stage gear / pulley 63, 64 is rotated with the rotation of the motor shaft.
[0217]
The gear of the two-stage gear / pulley is meshed with the gear 44 for driving the drum. Thus, similarly to the configuration before the remodeling, the gear 44 can be rotated with the rotation of the drum drive motor, and the photosensitive drum 28 (see FIG. 3) can be rotated.
[0218]
The motor bracket 65 is bent so that a portion for holding the motor (the lower portion in FIG. 37) protrudes to a side opposite to the motor than a portion thereabove. The anti-vibration rubber mount 60 is arranged in the space formed by the protruding portion so as to be in contact with the motor bracket 65, and the motors (41, 42) are mounted on the motor shaft 65 on the opposite side of the anti-vibration rubber mount 60 from the motor bracket 65. 37 (left side in FIG. 37). In this manner, the structure is not such that the motor bracket 65 and the motor are directly held, but is held with the vibration-proof rubber mount 60 interposed therebetween.
[0219]
In this configuration, since the two-stage gears / pulleys 63 and 64 are arranged on the left side of the motor bracket 65 in FIG. 37 (on the side where the gear 44 is arranged), the motor shaft protrudes by that amount to the left side in FIG. Need to be done. However, by forming the protruding portion on the motor bracket 65 as described above, the position of the motor itself can be set to the left side in FIG. 37, so that it is not necessary to lengthen the motor shaft. Therefore, it is possible to suppress eccentricity of the motor shaft, which may be caused by making the motor shaft longer, noise generation due to the eccentricity, and the like.
[0220]
In this configuration, it is preferable to increase the strength of the stud 69 for attaching the two-stage gear / pulley 63, 64. If the strength of the stud 69 is insufficient, the gear 44 and the two-stage gear / pulley mesh with each other while being eccentric, and the drum shaft 68 is also eccentric via the bearing 70. This is because the eccentricity of the drum shaft 68 may affect an image formed on a sheet and does not cause such a problem, so that the strength of the stud 69 needs to be increased.
[0221]
Further, an elastic body that can absorb the vibration of the motor to some extent may be used in addition to the above-described anti-vibration rubber mount.
These are the measures for reducing the noise of the drum drive stepping motor.
[0222]
(1-2) Reduction of Stepping Motor Sound for Feeding
Next, measures for reducing the noise of the stepping motor for sheet feeding will be described. As described above, the driving motor of the paper feeding mechanism system of the image forming apparatus is the stepping motor 56 (see FIG. 8), and the sheet is conveyed from the tray by controlling the driving of the stepping motor. I have. As a countermeasure for reducing the motor noise, there is a method of controlling the drive of the stepping motor 56 as follows. The control will be described below.
[0223]
FIG. 38 is a diagram for explaining the movement of the rotor of the stepping motor driven at the step angle θ0. The step angle of the stepping motor is determined mechanically. Usually, the rotor moves by one step angle θ at a time. If the step angle θ is large, the movement is not smooth, and vibration occurs. This causes noise.
[0224]
Therefore, in this configuration, so-called micro-step driving, in which the stepping motor is driven at a step angle smaller than the step angle θ determined by the mechanical structure under the control of the electronic circuit as illustrated, is performed. That is, by performing current supply control such that the current value supplied to one of the excitation phases is gradually increased, while the current value supplied to the other one phase is gradually reduced ((1) to (1) in FIG. 38). (Refer to (5)), it is possible to drive at a step angle smaller than the step angle θ, to reduce the noise by smoothing the movement.
[0225]
FIG. 39 is a diagram showing a sequence of a 1-2-phase excitation which is one of the micro-step driving of the stepping motor. The 1-2-phase excitation is an excitation method in which one-phase excitation for exciting the coil one phase at a time and two-phase excitation for exciting the coil two phases each are alternately repeated. When a stepping motor is driven using this excitation method, The step angle of the motor is reduced to 、, so that the movement of the rotor becomes smoother than in the case of normal driving, and vibration can be reduced.
[0226]
(1-3) Reduction of polygon mirror motor sound
Next, measures for reducing the sound generated by the polygon mirror motor will be described with reference to FIG. As shown in the figure, in this measure, a Helmholtz resonator 71 is mounted near the polygon mirror motor 2. More specifically, a Helmholtz resonator 71 is mounted on the upper part of the housing 11 holding the polygon mirror motor 2.
[0227]
The Helmholtz resonator 71 has a cavity forming member 72a for forming a cavity 72 having a volume V1. The cavity forming member 72a is formed integrally with the housing 11, and an opening hole 73 (cross-sectional area Sb) communicating with the cavity 72 is formed in a portion of the cavity forming member 72a at a position facing the polygon mirror motor. Here, assuming that the thickness of the portion where the opening 73 is formed is Tb, the opening 73 corresponds to a short tube having a length Tb and an opening area Sb in a general Helmholtz resonator. This structure functions as the Helmholtz resonator 71.
[0228]
Under this configuration, when the polygon mirror motor 2 is driven and a sound pressure acts on the entrance of the opening hole 73 due to the vibration, the air (medium) in the opening hole 73 (short pipe) moves integrally, and Causes a pressure change in the air. This phenomenon is equivalent to a mass-spring model of a dynamic system, assuming that the air in the opening 73 (short pipe) is a mass point and the pressure change due to the volume change of the air in the cavity 72 is a spring. Resonance (resonance) occurs with respect to the Helmholtz resonance frequency). That is, the acoustic energy of the Helmholtz resonance frequency is confined in the cavity 72, so that the sound is reduced for the external space.
[0229]
Here, the Helmholtz resonance frequency Fh (Hz) is calculated by the following equation.
Fh = C / 2π (Sb / (V1 · Tb))^1/2
C: speed of sound
[0230]
That is, the resonance frequency is changed by changing the opening area Sb of the opening hole 73, the length Tb (that is, the plate thickness of the portion where the opening hole 73 of the housing 11 is provided), and the volume V1 of the cavity 72 formed by the cavity forming member 72a. Fh, that is, the frequency of the sound to be reduced can be changed. Therefore, if the dimensions and the like of the above components are designed so as to match the frequency at which the level becomes highest among the sounds generated when the polygon mirror motor 2 is driven, the sound generated by the polygon mirror motor 2 can be effectively reduced. Can be reduced.
[0231]
From the above noise measurement results (see FIGS. 11 to 13), although the polygon mirror motor sound is extracted as noise in the color mode, the sound is not so noticeable in the monochrome mode. . In such a case, the dimensions and the like of each part may be determined so that the Helmholtz resonance frequency matches the highest frequency among the sounds emitted by the polygon mirror motor in the color mode as described above. On the other hand, when the level of another frequency is large in the monochrome mode, a Helmholtz resonator having this frequency as a resonance frequency may be separately provided.
[0232]
As described above, a Helmholtz resonator may be provided for each corresponding frequency, or a mechanism for changing the opening area Sb of the opening 73 between the color mode and the monochrome mode may be provided. . For example, a lid member or the like that is movable between a position where the opening hole 73 is closed to some extent and a position where the opening hole 73 is not closed is provided, and the resonance frequency in each mode is set to each mode by moving the lid member according to the mode. It may be made variable so as to coincide with the frequency at which the level increases sometimes.
[0233]
(1-4) Reduction of charging noise
Next, measures for reducing the charging noise will be described. The charging sound is a sound generated as follows. That is, when the charging roller 36 charges the photosensitive drum 28 (see FIG. 3), an attractive force is generally generated between the surface of the charging roller 36 and the surface of the photosensitive drum 28 due to the AC component of the bias voltage. The repulsive forces act alternately, causing vibration between the two. The sound radiated by the photosensitive drum 28 due to this vibration is a charged sound, which is a harsh pure sound having a high frequency, and generally includes a frequency of an AC component and a frequency component (harmonic component) that is an integral multiple thereof. .
[0234]
Such measures for reducing the charging noise will be described with reference to FIGS. 41 and 42. As shown in FIG. 41, a vibration damping member 74 is disposed in a hollow portion of the photosensitive drum 28 in which a measure against the charging noise is taken. The vibration damping member 74 has a hollow cylindrical base 75 extending in the axial direction of the photosensitive drum 28, and a plurality of blades 76 radially protruding from the base 75. The central axis of the base 75 is photosensitive. It is arranged so as to substantially coincide with the central axis of the body drum 28.
[0235]
The tip of each blade 76 of the vibration damping member is in pressure contact with the inner surface of the photosensitive drum 28, whereby the vibration damping member 74 is held inside the photosensitive drum 28. Here, it is preferable that the blade portion 76 is made of an elastic material such as rubber, resin or a material containing these, for example, a material containing urethane rubber, or a thermoplastic resin material such as polypropylene resin or polyamide resin. By using an elastic material for the blade portion 76, the tip of the blade portion 76 is pressed against and held by the photosensitive drum 28 by its elastic force. Therefore, since the bonding operation and the positioning operation using an adhesive or the like are not required, the mounting operation and the removing operation are facilitated.
[0236]
By arranging the damping member 74 such that the blade portion 76 is pressed against the inner surface of the photosensitive drum 28 as described above, the damping member 74 acts to suppress the vibration of the photosensitive drum 28. Therefore, it is possible to suppress the vibration of the photosensitive drum 28 that occurs at the time of charging by the charging roller 36 described above. Further, since the member for suppressing the vibration of the photosensitive drum 28 is provided inside the photosensitive drum 28, it is not necessary to take a measure such as taking a space for newly installing a vibration damping member. .
[0237]
The means for suppressing the vibration of the photosensitive drum 28 to reduce the noise is not limited to the vibration damping member 74 having the above-described configuration, and a countermeasure such as fitting a metal column into the hollow portion of the photosensitive drum 28 may be taken. Alternatively, a commercially available damping material (for example, Hama Damper manufactured by Yokohama Rubber Co., Ltd.) may be attached.
[0238]
(2) Measures to reduce sharpness (high-frequency components)
(2-1) Reduction of paper sliding noise
Next, measures for reducing sharpness (high-frequency components) will be described. As a measure for reducing sharpness, there is a method of reducing paper sliding noise. Note that the paper sliding noise is a sound generated when the transported paper slides on a member or the like.
[0239]
As described above, the paper stored in the first tray 9 or the second tray 10 is fed out of each tray by the first paper supply unit 51 or the second paper supply unit 52, and the registration roller is transported by the relay roller 53 and the transport roller 55. 7 (see FIG. 7).
[0240]
Here, FIGS. 43A and 43B show a case where the sheet stored in the first tray 9 or the second tray 10 is transported to form an image (at the time of normal printing) and a case where printing is performed without transporting the sheet (free). 4 shows the results of frequency analysis (１ ／ octave band analysis) of the noise generated by the image forming apparatus during the run. FIG. 44 is a graph showing the sound pressure level differences in the respective frequency bands obtained from the noises during normal printing and during the free run shown in the analysis results.
[0241]
That is, the sound pressure level for each frequency band shown in FIG. 44 is a difference in noise content generated by the image forming apparatus due to whether or not a sheet is sent out from the first tray 9 or the second tray 10 and conveyed. It means that the sound pressure level is increased in each frequency band as shown in FIG. 44 by conveying the paper.
[0242]
From the graph shown in FIG. 44, there are two or more differences of 3 (dB) between the normal printing and the free run in the band centered at 200 to 250 Hz and the band at 3.15 kHz or more. . Note that a difference of 3 dB or more means that the acoustic energy has a difference of 2 times or more.
[0243]
Examination of the above analysis results revealed that the components in the band centered at 200 to 250 Hz were caused by the sound generated when the paper and the registration roller 7 collided. On the other hand, it has been found that the component in the frequency band of 3.15 kHz or more is caused by the sound generated when the paper slides on a member or the like during paper transport. In a band centered on 12.5 kHz to 16 kHz, there is a difference of 7 (dB) or more, and this band has a large effect on the sharpness value. This indicates that reducing the sliding noise of the paper is effective as a countermeasure against noise. Hereinafter, measures for reducing the sliding noise of the sheet conveyed by the sheet feeding unit, the relay roller 53, and the conveying roller 55 will be described with reference to FIG.
[0244]
As shown in the figure, the transport roller 55 is a roller having a plurality of rollers passed through a shaft, and has a roller 55a and a roller 55b which are arranged to face each other with the paper transport path therebetween. The roller 55a is used for the sheet conveyed along the conveyance path A (the sheet fed from the first tray 9) or the sheet conveyed along the conveyance path B (the sheet fed from the second tray 10). , 55b, and is conveyed toward the registration roller 7 by the rollers 55a, 55b.
[0245]
Guide members 80, 81, and 82 for transporting the sheet along a predetermined path are arranged near the transport roller 55.
[0246]
The guide member 80 forms a space for guiding the sheet conveyed along the conveyance path A together with the roller 55a between the rollers 55a and 55b. Further, the guide member 80 forms a space for guiding the sheet conveyed along the conveyance path B together with the guide member 81 toward the space between the rollers 55a and 55b.
[0247]
A guide member 77 made of a treadable sheet (for example, a mylar sheet) extending in the sheet conveyance direction (vertical direction in the figure) is attached to a portion of the guide member 80 on the downstream side in the conveyance direction (upper side in FIG. 45). The guide member 77 guides the sheet conveyed from the conveyance paths A and B toward between the rollers 55a and 55b.
[0248]
As shown in FIG. 46, a cutout portion 77a is formed by cutting or the like at a position where the roller 55a is arranged so as not to cross the roller 55a at the leading end portion of the guide member 77. By contacting the leading end, the guide is reliably guided between the rollers 55a and 55b.
[0249]
Accordingly, as shown in FIG. 47, the paper from the transport path A is transported while sliding on the leading end of the guide member 77. The conventional general guide member 77 is manufactured by shearing a flexible sheet into a predetermined shape, and burrs are usually formed at a tip portion (shear portion) thereof. Removing such burrs one by one is a very difficult task, which requires cost and time. Therefore, such an operation is not usually performed, and the paper slides on the leading end portion where the burr is generated, thereby generating annoying noise.
[0250]
Therefore, in this configuration, by employing the guide member 77 having the configuration shown in FIG. 48, it is possible to reduce the harsh noise caused by the sliding of the paper and the leading end portion of the guide member 77 as described above. .
[0251]
As shown in FIG. 49, the guide member made of a conventional flexible sheet is a guide member 770 that is a flexible sheet having a thickness t that has been sheared into a predetermined shape and is used as a guide member 770. The part is a shearing part. On the other hand, in the configuration shown in FIG. 48, a flexible sheet having a thickness of t / 2 is folded to form two sheets, so that the bent portion becomes the distal end portion of the guide member 77. By employing the guide member 77 having such a configuration, the leading end portion where the paper conveyed as described above slides is a bent portion, a portion that has not been subjected to shearing, and has a smooth R shape. Become. Therefore, it is possible to reduce the generation of harsh noise caused by burrs in the sheared portion as described above. Further, since the thickness of the two sheets is also the same as that of the conventional guide member 770, the required elastic force can be exhibited, and the function as the guide member is not hindered.
[0252]
(3) Measures to reduce impulsiveness (impact component)
In the image forming apparatus having the above configuration, the generation of impulsiveness is almost caused by the fixing oil application sound (see FIGS. 11 to 13). In the image forming apparatus having the above-described configuration, the fixing oil application sound is controlled such that the oil application unit 47 is driven to make contact with the fixing belt 13 each time a sheet is conveyed in order to suppress an increase in oil consumption. (See FIG. 6). Such a contact / separation sound generated every time a sheet is conveyed is generated in a shocking manner, thereby giving a feeling of discomfort.
[0253]
Such a noise problem due to the fixing oil application noise can be solved by using an oilless toner as the toner used for image formation. That is, since the oil-less toner contains wax in the toner, the divergence between the fixing belt and the sheet is good without performing the oil application operation as described above. Therefore, it is not necessary to use the oil application unit 47, and it is possible to prevent the generation of the impact noise caused by the contact and separation between the oil application unit 47 and the fixing belt 13 described above. When using the oilless toner, it is necessary to modify the image forming process configuration of the photoconductor unit 3 and the like so as to be suitable for the oilless toner.
The above is a specific example of the measure for reducing the discomfort probability P.
[0254]
The inventor measures the sound emitted by the image forming apparatus having taken the above measures under the same conditions as when measuring the sound emitted by the image forming apparatus before the measure, and determines the effect of the measure from the measurement result. investigated. Note that the measurement results to be compared below were obtained by collecting sound on the front side of the image forming apparatus when each of the image forming apparatuses was operated in the “color mode (1)”.
[0255]
FIG. 50 shows an analysis result of the noise after the countermeasure. Comparing the analysis result after the countermeasure shown in the figure with the analysis result before the countermeasure (see FIG. 11), the sound of the sheet feeding stepping motor is reduced by about 10 (db), the charging noise is about 5 (dB), and the drum drive is performed. The motor sound is reduced by about 8 (dB), and the polygon mirror motor sound is also reduced by about 10 (dB). In addition, the sound of fixing oil application disappeared. From the above, it can be seen that the sound produced by each sound source can be reduced by taking the above measures.
[0256]
Table 15 shows comparison results of the psychoacoustic parameter values obtained from the measurement results before and after the countermeasure and the sound quality evaluation value by the above sound quality evaluation formula (d).
[Table 15]

As can be seen from this table, the sound quality evaluation value after the countermeasure, that is, the discomfort probability is “−0.23”, which is smaller than the allowable value “−0.26” of “color mode (1)” shown in Table 14. small. Therefore, it can be said that the image forming apparatus has been remodeled so that the above countermeasure hardly causes discomfort.
[0257]
D. Example of application of the present invention
The present invention can provide an image forming apparatus in which the sound quality of an image forming apparatus is evaluated using the sound quality evaluation formula derived as described above, and the evaluation result (discomfort probability P) satisfies a predetermined condition. It is to make. Therefore, the present invention can be applied to the development and manufacture of a new product as shown in FIG.
[0258]
Specifically, what kind of configuration is adopted in each unit of the image forming apparatus so that the sound quality evaluation (discomfort probability P) based on the sound quality evaluation formula satisfies a predetermined condition (S1: design process). Then, the image forming apparatus is manufactured in accordance with the design contents in which the discomfort probability P obtained from the sound emitted from the image forming apparatus satisfies a predetermined condition (S2: manufacturing process). Through such a manufacturing process, an image forming apparatus that hardly emits unpleasant noise can be manufactured, and such an image forming apparatus can be provided to a user.
[0259]
Further, the present invention can be applied as a measure against noise of an image forming apparatus once sold or the like. That is, the sound generated by the image forming apparatus already sold or the like is measured as described above, and the discomfort probability P is derived from the measurement result using the above sound quality evaluation formula. Then, it is examined whether or not the derived discomfort probability P satisfies a predetermined condition, and if it satisfies, it is considered that almost no unpleasant noise is emitted, so it is determined that the modification is unnecessary. On the other hand, when the derived discomfort probability P does not satisfy the predetermined condition, various modifications as described above are performed on each unit of the image forming apparatus so that the discomfort probability P satisfies the predetermined condition. This makes it possible to provide an image forming apparatus that hardly emits unpleasant noise.
[0260]
【The invention's effect】
As described above, according to the first aspect of the present invention, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is determined as follows. Since the configuration is such that the condition (b) corresponding to the output numerical value of the sheet to be formed is met, it is possible to reduce the possibility that the sound generated by the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates depending on the speed, the mode in which the operation is performed Even so, an effect is obtained that it is possible to reduce the discomfort caused by the operation sound to the user.
[0261]
According to the second aspect of the present invention, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is equal to the probability of the image forming target sheet per minute. Since the configuration is such that the condition (b) corresponding to the output numerical value is met, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, the mode in which the operation is performed Even so, an effect is obtained that it is possible to reduce the discomfort caused by the operation sound to the user.
[0262]
According to the third aspect of the present invention, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is equal to the probability P of the image forming target sheet per minute. Since the configuration is such that the condition (b) corresponding to the output numerical value is met, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (b) varies depending on the output value of the image forming target sheet, even if the apparatus has the output value, that is, a plurality of operation modes, and the image forming speed fluctuates in each mode, even if the apparatus has an The parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (d), and since the probability P satisfies the condition that fluctuates according to the speed, the mode in which mode the operation is performed Even so, an effect is obtained that it is possible to reduce the discomfort caused by the operation sound to the user.
[0263]
According to the invention of claim 4, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound emitted by the image forming apparatus corresponds to the image forming speed (e). Therefore, it is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained by using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is inconsistent with the user in any mode. The effect that it is possible to reduce pleasure can be obtained.
[0264]
According to the fifth aspect of the present invention, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is a condition (e) corresponding to the image forming speed. ), It is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is inconsistent with the user in any mode. The effect that it is possible to reduce pleasure can be obtained.
[0265]
According to the sixth aspect of the present invention, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound emitted from the image forming apparatus is a condition (e) corresponding to the image forming speed. ), It is possible to reduce the possibility that the sound emitted from the image forming apparatus gives the user discomfort. Further, since the condition (e) varies depending on the image forming speed, even if the device has a plurality of operation modes and the image forming speed fluctuates in each mode, the parameter value obtained from the operation sound is not changed. The probability P can be obtained by using one sound quality evaluation formula (d), and since the probability P satisfies the condition that fluctuates according to the speed, the operation sound is not affected by the user in any mode. The effect that it is possible to reduce pleasure can be obtained.
[0266]
Further, according to the invention according to claim 7, it is possible to obtain an effect that it is possible to reduce the discomfort to the user due to the operation sound when operating in any operation mode selected by the operation control means. .
[0267]
Further, according to the invention according to claim 8, the probability P obtained from the result of sound pickup at the position on the front side of the image forming apparatus where the user of the image forming apparatus is likely to be normally located is determined by the above condition. Since the condition is satisfied, the effect that the operation sound of the image forming apparatus gives the user uncomfortable feeling can be reduced.
[0268]
According to the ninth aspect of the present invention, the probability P is derived from the sounds collected in four directions of the image forming apparatus, and the average value satisfies the condition. The discomfort given to the user by the operation sound can be reduced on average.
[0269]
According to the tenth aspect, the probability P derived from the sound collected in at least one direction of the image forming apparatus satisfies the condition. An effect is obtained that it is possible to reduce the discomfort caused by the operation sound of the device.
[0270]
According to the eleventh aspect of the present invention, the probability P derived from the sound collected in all directions in the front, rear, left and right directions of the image forming apparatus satisfies the condition. However, the effect that the operation sound of the image forming apparatus gives the user discomfort can be reduced.
[0271]
According to the twelfth aspect of the present invention, the sound generated by the image forming apparatus at the time of image formation can be reduced by the reducing unit, whereby the probability P derived from the sound generated by the image forming apparatus satisfies the condition, An effect is obtained that it is possible to reduce the occurrence of discomfort to the user due to the sound emitted from the image forming apparatus.
[0272]
According to the thirteenth aspect of the present invention, since the vibration during the operation of the stepping motor is not directly transmitted to the bracket member but is absorbed by the elastic body, the vibration transmitted to the bracket member is reduced. Thus, the effect that the sound generated by the noise can be reduced can be obtained.
[0273]
According to the fourteenth aspect of the present invention, the stepping motor can be driven at a step angle smaller than the step angle of the ordinary mechanically determined stepping motor by microstep driving the stepping motor. As a result, the rotor driving of the stepping motor becomes smooth, the generation of vibration can be suppressed, and the effect of reducing the operation noise can be obtained.
[0274]
According to the fifteenth aspect of the present invention, the Helmholtz resonator has a function of confining a sound component having a Helmholtz resonance frequency determined by its shape and size in a cavity, that is, attenuating a sound component having the resonance frequency. Therefore, by installing a Helmholtz resonator having a resonance frequency corresponding to the main frequency component of the sound generated by the motor in the vicinity, the effect of reducing the amount of sound generated by the motor leaking out of the device can be obtained.
[0275]
Further, according to the invention according to claim 16, when the charging means charges the image carrier, the image carrier vibrates due to the charging action, and a sound is generated due to the vibration. Vibration generated in the image carrier can be suppressed by the vibration damping member, and generated noise can be reduced. Further, since the vibration damping member is disposed inside the image carrier, there is an effect that it is not necessary to prepare a new installation space or the like.
[0276]
According to the seventeenth aspect of the present invention, since the bent portion of the flexible sheet in the guide member comes into contact with the image forming target sheet to be conveyed, the sound generated by the contact can be reduced. Can be. That is, when the flexible sheet is made to have a predetermined size, the flexible sheet is usually cut. However, the cut portion of the flexible sheet has burrs and the like, and when this portion comes in contact with the image forming target sheet, an unpleasant sound is generated. . On the other hand, in the present invention, since the bent portion, not the cut portion, comes into contact with the image forming target sheet as described above, it is possible to obtain an effect that generation of harsh sound can be reduced.
[0277]
According to the eighteenth aspect of the present invention, by using a toner containing a wax, the fixing member can be separated from the image forming target sheet in order to improve the separation property between the fixing member and the image forming target sheet during the fixing process in image formation. There is no need to perform operations such as oil application. Therefore, the effect that the noise generated by the oil application operation can be reduced can be obtained.
[0278]
According to the nineteenth aspect, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed such that the probability P is in accordance with the condition (b) corresponding to the output value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (a), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0279]
According to the twentieth aspect of the present invention, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed such that the probability P is in accordance with the condition (b) corresponding to the output value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (c), and the probability P satisfies the condition that varies depending on the speed. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0280]
According to the invention of claim 21, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed such that the probability P is in accordance with the condition (b) corresponding to the output value of the image forming target sheet per minute, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (b) varies depending on the output value of the image forming target sheet, an apparatus having the output value, that is, a plurality of operation modes and the like, in which the image forming speed varies in each mode is manufactured and provided. Even in this case, the parameter value obtained from the operation sound can be used to determine the probability P using one sound quality evaluation formula (d), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0281]
According to the invention of claim 22, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that the probability P matches the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0282]
According to the twenty-third aspect, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that the probability P matches the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0283]
According to the invention of claim 24, when designing the image forming apparatus, the image quality is derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus. Each part of the apparatus is designed so that the probability P matches the condition (e) corresponding to the image forming speed, and the image forming apparatus is manufactured based on the design contents. Therefore, it is possible to manufacture an image forming apparatus that can reduce the discomfort of the user due to the operation sound, and provide the user with the image forming apparatus. Further, since the condition (e) varies depending on the image forming speed, even if the apparatus has a plurality of operation modes and the like and manufactures and provides an apparatus in which the image forming speed fluctuates in each mode, the operation is not affected. The parameter value obtained from the sound can be used to determine the probability P by using one sound quality evaluation formula (d), and since the probability P satisfies the condition of fluctuating according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0284]
According to the invention according to claim 25, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is 1 The configuration of each unit of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet per minute. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the modification can be used to calculate the probability P using one sound quality evaluation formula (a), and the probability P satisfies the condition that varies according to the speed. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0285]
According to the twenty-sixth aspect, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is 1 The configuration of each unit of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet per minute. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the remodeling can be used to determine the probability P using one sound quality evaluation formula (c), and the condition that the probability P varies according to the speed is satisfied. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0286]
According to the twenty-seventh aspect, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound generated by the image forming apparatus to be remodeled is 1 The configuration of each unit of the apparatus is modified so as to meet the condition (b) corresponding to the output numerical value of the image forming target sheet per minute. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. In addition, since the condition (b) varies depending on the output value of the sheet on which the image is to be formed, the output value, that is, a plurality of operation modes and the like is provided, and the apparatus in which the image forming speed varies in each mode is modified. However, the parameter value obtained from the device operation sound after the modification can be used to calculate the probability P using one sound quality evaluation formula (d), and the condition that the probability P varies according to the speed is satisfied. Therefore, it is possible to reduce the effect of the operation sound on the user regardless of the operation mode.
[0287]
According to the twenty-eighth aspect, the probability P derived by the sound quality evaluation formula (a) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is represented by the image The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to the forming speed. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (a), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0288]
According to the invention according to claim 29, the probability P derived by the sound quality evaluation formula (c) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is represented by the image The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to the forming speed. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P using one sound quality evaluation formula (c), and since the probability P satisfies the condition that fluctuates according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0289]
According to the invention according to claim 30, the probability P derived by the sound quality evaluation formula (d) using the psychoacoustic parameter value obtained from the sound collection result of the sound emitted by the image forming apparatus to be remodeled is represented by The configuration of each part of the apparatus is modified so as to meet the condition (e) corresponding to the forming speed. Therefore, it is possible to manufacture and provide the user with an image forming apparatus capable of reducing the user's discomfort due to the operation sound of the image forming apparatus due to this modification. Further, since the condition (e) varies depending on the image forming speed, the apparatus has a plurality of operation modes and the like, and even if the device in which the image forming speed varies in each mode is modified, the operation of the device after the modification is performed. The parameter value obtained from the sound can be used to determine the probability P by using one sound quality evaluation formula (d), and since the probability P satisfies the condition of fluctuating according to the speed, it is possible to operate in any mode. Also, the effect that the operation sound gives the user unpleasant feeling can be reduced.
[0290]
According to the thirty-first aspect of the present invention, first, an expression relating to the relationship between the discomfort probability of two sounds and the difference between psychoacoustic parameter values is obtained, and a sound quality evaluation expression for estimating the sound evaluation itself is derived from the expression. Therefore, it is possible to derive a highly accurate sound quality evaluation expression without performing a relatively large number of experiments, and as a result, it is possible to obtain an effect that the work related to sound quality evaluation is simplified.
[0291]
According to the invention according to claim 32, first, an expression relating to the relationship between the discomfort probability of two sounds and the difference between psychoacoustic parameter values is obtained, and a sound quality evaluation expression for estimating the sound evaluation itself is derived from the expression. Therefore, it is possible to derive a highly accurate sound quality evaluation expression without performing a relatively large number of experiments, and as a result, it is possible to obtain an effect that the work related to sound quality evaluation is simplified. Then, an image forming apparatus in which each part of the apparatus is designed so that the sound quality evaluation based on the sound quality evaluation formula obtained in this way satisfies predetermined conditions is manufactured, that is, an image forming apparatus that hardly emits unpleasant sound is provided. The effect is obtained.
[0292]
According to the invention of claim 33, first, an expression relating to the relationship between the discomfort probability of two sounds and the difference between psychoacoustic parameter values is obtained, and then a sound quality evaluation expression for estimating the sound evaluation itself is derived from the expression. Therefore, it is possible to derive a highly accurate sound quality evaluation expression without performing a relatively large number of experiments, and as a result, it is possible to obtain an effect that the work related to sound quality evaluation is simplified. Then, based on the sound quality evaluation of the sound generated by the image forming apparatus using the sound quality evaluation formula thus obtained, the apparatus configuration is modified. Therefore, it is possible to obtain an effect that an excellent image quality evaluation can be obtained, that is, an image forming apparatus that hardly emits unpleasant sound can be provided.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing the entire configuration of an image forming apparatus.
FIG. 2 is a diagram illustrating a configuration of an optical unit of the image forming apparatus.
FIG. 3 is a diagram illustrating a configuration of a photoconductor unit and a developing unit of the image forming apparatus.
FIG. 4 is an exploded perspective view showing a configuration for driving a photosensitive drum of the photosensitive unit.
FIG. 5 is a perspective view showing a fixing unit of the image forming apparatus.
FIG. 6 is a front sectional view showing a configuration of the fixing unit.
FIG. 7 is a front sectional view illustrating a configuration of a sheet feeding unit of the image forming apparatus.
FIG. 8 is a perspective view showing a driving configuration of the paper feeding unit.
FIG. 9 is a graph for explaining the contents of logit conversion.
FIG. 10 is a diagram for explaining measurement conditions when measuring a sound emitted from the image forming apparatus in order to derive a sound quality evaluation formula.
FIG. 11 is a diagram illustrating an analysis result of a sound obtained by the measurement when the image forming apparatus is operating in one mode.
FIG. 12 is a diagram illustrating an analysis result of a sound obtained by the measurement when the image forming apparatus is operating in another mode.
FIG. 13 is a diagram illustrating an analysis result of a sound obtained by the measurement when the image forming apparatus is operating in another mode.
FIG. 14 is a graph showing a relationship between a level of a sound source (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 15 is a graph showing a relationship between a level of a sound source (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 16 is a graph showing a relationship between a level (emphasis, original sound, attenuation) of a sound source extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 17 is a graph showing a relationship between a level of a sound source (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 18 is a graph showing a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 19 is a graph showing a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 20 is a graph showing a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 21 is a graph illustrating a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 22 is a graph showing a relationship between a level (emphasis, original sound, attenuation) of a sound source extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 23 is a graph showing a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 24 is a graph showing a relationship between a level of a sound source (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 25 is a graph showing the relationship between the sound source level (emphasis, original sound, attenuation) extracted from the sound emitted from the image forming apparatus and the subjective evaluation value.
FIG. 26 is a graph showing a relationship between a level of a sound source (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 27 is a graph showing the relationship between the level of a sound source (emphasis, original sound, attenuation) extracted from the sound emitted from the image forming apparatus and the subjective evaluation value.
FIG. 28 is a graph showing a relationship between a sound source level (emphasis, original sound, attenuation) extracted from a sound emitted from the image forming apparatus and a subjective evaluation value.
FIG. 29 is a scatter diagram in which a predicted value obtained by using a model formula capable of calculating a difference in the discomfort probability of a derived sound and an actually measured value in one process of the present invention are plotted.
FIG. 30 is a graph in which a predicted discomfort probability value obtained by using the sound quality evaluation formula derived according to the present invention and an actually measured value are compared and plotted for each operation mode of the image forming apparatus.
FIG. 31 is a graph showing a relationship between ppm values derived from experimental results and allowable values of indices derived by the above sound quality evaluation formula.
FIG. 32 is a graph showing a relationship between an image forming speed derived from an experimental result and an allowable value of an index derived by the above sound quality evaluation formula.
FIG. 33 is a view for explaining one specific example of the remodeling method according to the present invention, and is a perspective view showing a configuration of a photosensitive drum driving mechanism before remodeling.
FIG. 34 is a diagram for explaining a mounting structure of a drive motor for driving the photosensitive drum before remodeling.
FIG. 35 is a view for explaining a mounting structure of a drive motor for driving the photoconductor drum after the remodeling.
FIG. 36 is a perspective view showing a configuration of a photoconductor drum driving mechanism after remodeling.
FIG. 37 is a side view showing the configuration of the photosensitive drum drive mechanism after the remodeling.
FIG. 38 is a diagram for explaining one specific example of the remodeling method according to the present invention, and is a diagram for explaining the drive control content of the sheet feeding stepping motor.
FIG. 39 is a diagram for explaining one specific example of the remodeling method according to the present invention, and is a diagram illustrating an excitation sequence when the sheet-feeding stepping motor is microstep-driven.
FIG. 40 is a view for explaining one specific example of the modification method according to the present invention, and is a cross-sectional view showing a Helmholtz resonator provided near a polygon mirror motor.
FIG. 41 is a view for explaining one specific example of the remodeling method according to the present invention, and is a view showing a configuration for suppressing vibration of the photosensitive drum.
FIG. 42 is an exploded perspective view showing a configuration for suppressing vibration of the photosensitive drum.
FIG. 43 shows the sound pressure for each frequency band of the sound generated by the image forming apparatus when an image forming operation is performed by conveying a sheet and when an image forming operation is performed without conveying a sheet (during a free run). It is a figure showing a level.
FIG. 44 shows the sound pressure of the sound generated by the image forming apparatus for each frequency band when a sheet is conveyed to perform an image forming operation and when an image forming operation is performed without conveying a sheet (during a free run). It is a figure showing a level difference.
FIG. 45 is a diagram illustrating a configuration of a sheet feeding unit of the image forming apparatus.
FIG. 46 is a diagram showing a positional relationship between a transport roller as a component of the paper feeding unit and a guide member formed of a flexible sheet for guiding a sheet.
FIG. 47 is an enlarged view of the vicinity of the guide member of the paper feeding unit.
FIG. 48 is a diagram showing a configuration of the guide member in which noise countermeasures have been taken.
FIG. 49 is a diagram showing a configuration of a guide member in which noise countermeasures are not taken.
FIG. 50 is a diagram showing an analysis result of a sound emitted from the image forming apparatus for which measures have been taken by the remodeling method according to the present invention.
FIG. 51 is a flowchart showing a manufacturing process of the image forming apparatus according to the present invention.
[Explanation of symbols]
1 Optical unit
2 Polygon mirror motor
3 Photoconductor unit
4 Developing unit
5 Transfer unit
7 Registration roller
9 First tray
10 Second tray
11 Housing
13 Fixing belt
27 Polygon mirror
28 Photoconductor drum
29 Transfer belt
36 Charging roller
41 Color drum drive motor
42 black drum drive motor
43 Relay gear
44 gears
46 Fusing unit
47 Oil application unit
48 Coated Felt
49 Application roller
51 1st paper feed unit
52 Second paper feed unit
53 Relay roller
54 Relay roller
55a roller
55b roller
55 transport roller
56 stepper motor
59 Motor bracket
60 Anti-vibration rubber mount
63, 64 pulley
65 Motor bracket
66,67 Timing pulley
70 Timing belt
71 Helmholtz resonator
72 cavities
72a Cavity forming member
73 Opening hole
74 Damping member
77 Guide member
80, 81, 82 Guide member
110 Paper feed unit
201 Equipment under test
202 Operation unit
203 dummy head
770 Guide member

Claims (33)

An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the value, the tonality value, the impulseness value, and the output value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (a) is: P = 1 / (1 + exp (−z)) which satisfies the following condition (b)
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus comprising: An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the values, tonality values, impulsiveness values, and output numerical values (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (c) is: P = 1 / (1 + exp (−z ± 2σ)) that satisfies the following condition (b):
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus comprising: An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the values, tonality values, impulsiveness values, and output numerical values (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability P calculated by the following equation (d) is: P = 1 / (1 + exp (−z)) which satisfies the following condition (b)
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
An image forming apparatus comprising: An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the value, tonality value, impulsiveness value, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (a) is determined by the following condition (e). ) Satisfying P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus comprising: An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the values, tonality values, impulsiveness values, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (c) is determined by the following condition (e). ) Satisfying P = 1 / (1 + exp (−z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus comprising: An image forming apparatus that forms an image on an image forming target sheet,
Loudness values and sharpness of psychoacoustic parameters obtained from sounds emitted by the image forming apparatus when performing image formation on the image forming target sheet collected at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus. Using the value, the tonality value, the impulseness value, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (d) is represented by the following condition (e). ) Satisfying P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
An image forming apparatus comprising: Any one of a plurality of operation modes, comprising an operation control means for controlling each unit of the apparatus in order to form an image on the image forming target sheet,
7. The image forming apparatus according to claim 1, wherein the probability P satisfies the condition regardless of the operation mode of the plurality of operation modes. 8. The sound pickup position is a nearby person position defined in ISO (International Organization For Standardization) 7779, and at least the probability P calculated from a sound pickup result of sound in the front direction of the device satisfies the condition. The image forming apparatus according to any one of claims 1 to 6, wherein The sound pickup position is a nearby person position defined in ISO (International Organization For Standardization) 7779, and the average value of the probability P calculated from each of sound pickup results of four directions of front, rear, left, and right of the device is The image forming apparatus according to claim 1, wherein the condition is satisfied. The sound pickup position is a nearby person position defined in ISO (International Organization For Standardization) 7779, and the probability P calculated from a sound pickup result of at least one of the front, rear, left, and right directions of the device is the sound pickup position. The image forming apparatus according to claim 1, wherein a condition is satisfied. The sound pickup position is a nearby person position specified in ISO (International Organization For Standardization) 7779, and all the probabilities P calculated from each of sound pickup results in four directions of front, rear, left and right of the device are calculated. The image forming apparatus according to claim 1, wherein the condition is satisfied. The image forming apparatus according to claim 1, further comprising a reduction unit configured to reduce a sound generated by the apparatus when forming an image on the image forming target sheet. A stepping motor that drives a predetermined portion when forming an image on the image forming target sheet,
And a bracket member for holding the stepping motor,
13. The image forming apparatus according to claim 12, wherein the reduction unit has an elastic body disposed between the stepping motor and the bracket member. The image forming apparatus further includes a stepping motor that drives a predetermined portion when forming an image on the image forming target sheet,
13. The image forming apparatus according to claim 12, wherein the reduction unit includes a drive control unit that drives the stepping motor by microstepping. The image forming apparatus further includes a motor that drives a predetermined portion when forming an image on the image forming target sheet,
13. The image forming apparatus according to claim 12, wherein the reduction unit has a Helmholtz resonator disposed near the motor. Further comprising a columnar image carrier having a hollow portion, and a charging unit for charging the surface of the image carrier,
The image forming apparatus according to claim 12, wherein the reduction unit includes a vibration suppression member that suppresses vibration of the image carrier in a hollow portion of the image carrier. A guide member made of a flexible sheet for guiding the image forming target sheet along a predetermined conveyance path, and an end portion of the flexible sheet that is in contact with the conveyed image forming target sheet is a bent portion of the flexible sheet. The image forming apparatus according to claim 12, further comprising a guiding member. 13. The image forming apparatus according to claim 12, wherein the toner used for forming an image on the image forming target sheet is a toner containing wax. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the values, sharpness values, tonality values, impulsiveness values, and output values (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability calculated by the following equation (a). A design step of designing each part of the device so that P satisfies the following condition (b):
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the value, sharpness value, tonality value, impulsiveness value, and the output numerical value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability calculated by the following equation (c). A design step of designing each part of the device so that P satisfies the following condition (b):
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the value, sharpness value, tonality value, impulsiveness value, and the output numerical value (ppm) of the image forming target sheet (A4 size lateral direction) per minute, the probability calculated by the following formula (d). A design step of designing each part of the device so that P satisfies the following condition (b):
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the values, sharpness values, tonality values, impulsiveness values, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (a) is as follows: A design step of designing each part of the device to satisfy the condition (e);
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the values, sharpness values, tonality values, impulsiveness values, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (c) is as follows: A design step of designing each part of the apparatus so as to satisfy the condition (e);
P = 1 / (1 + exp (-z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
Loudness of a psychoacoustic parameter obtained from a sound emitted by the image forming apparatus when an image is formed on the image forming target sheet picked up at a sound collecting position approximately 1 m away from an end face of the image forming apparatus to be manufactured. Using the value, sharpness value, tonality value, impulsiveness value, and the image forming speed (v: mm / s) for the image forming target sheet, the probability P calculated by the following equation (d) is as follows: A design step of designing each part of the apparatus so as to satisfy the condition (e);
P = 1 / (1 + exp (-z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A manufacturing step of manufacturing the image forming apparatus in accordance with the design contents performed in the designing step. A method for modifying an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Loudness value, sharpness value, tonality value, impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and the output numerical value of the image formation target sheet (A4 size horizontal direction) per minute ( ppm) and a modification step of modifying the configuration of the device so that the probability P calculated by the following equation (a) satisfies the following condition (b): P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising: A method for modifying an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Loudness value, sharpness value, tonality value, impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and the output numerical value of the image formation target sheet (A4 size horizontal direction) per minute ( ppm) and a modification step of modifying the configuration of the device so that the probability P calculated by the following equation (c) satisfies the following condition (b): P = 1 / (1 + exp (−z ± 2σ) ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising: A method for modifying an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Loudness value, sharpness value, tonality value, impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and the output numerical value of the image formation target sheet (A4 size horizontal direction) per minute ( ppm) and a modification step of modifying the configuration of the device so that the probability P calculated by the following equation (d) satisfies the following condition (b): P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3383Ln (ppm) −0.8103 ‥‥ (b)
14 ≦ ppm ≦ 38
A method for remodeling an image forming apparatus, comprising: A remodeling method of an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Using a loudness value, a sharpness value, a tonality value, an impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and an image forming speed (v: mm / s) for the image forming target sheet. And a modification step of modifying the configuration of the device so that the probability P calculated by the following equation (a) satisfies the following condition (e): P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
0.765545285 ≦ A ≦ 0.849440259
1.27685159 ≦ B ≦ 1.484641447
8.111323413 ≦ C ≦ 9.998398585
5.30484579 ≦ D ≦ 5.878737243
−14.10339529 ≦ E ≦ −1.472284396 ‥‥ (a)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising: A remodeling method of an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Using a loudness value, a sharpness value, a tonality value, an impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and an image forming speed (v: mm / s) for the image forming target sheet. And a modification step of modifying the configuration of the apparatus so that the probability P calculated by the following equation (c) satisfies the following condition (e): P = 1 / (1 + exp (−z ± 2σ))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895
σ: standard deviation = 0.721307 ‥‥ (c)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising: A remodeling method of an image forming apparatus that forms an image on an image forming target sheet,
A sound collecting step of collecting a sound emitted by the image forming apparatus when performing image formation on the image forming target sheet at a sound collecting position approximately 1 m away from an end surface of the image forming apparatus to be remodeled;
Using a loudness value, a sharpness value, a tonality value, an impulsiveness value of psychoacoustic parameters obtained from the sound pickup result in the sound pickup step, and an image forming speed (v: mm / s) for the image forming target sheet. And a modification step of modifying the configuration of the apparatus so that the probability P calculated by the following equation (d) satisfies the following condition (e): P = 1 / (1 + exp (−z))
z = A × (loudness value) + B × (sharpness value) + C × (tonality value) + D × (impulsiveness value) + E
A = 0.807472768
B = 1.38073296
C = 9.04860954
D = 5.591609971
E = -13.28811895 ‥‥ (d)
P ≦ 0.3201Ln (v) -1.2042 ‥‥ (e)
62.5 ≦ v ≦ 185
A method for remodeling an image forming apparatus, comprising: A method for evaluating a sound emitted during image formation by an image forming apparatus that forms an image on an image forming target sheet,
The image forming apparatus evaluates a plurality of types of sounds emitted at the time of image formation by a pair comparison method,
A logistic regression analysis is performed using the discomfort probability of two sounds based on the evaluation as a target variable and the difference between psychoacoustic parameter values as an explanatory variable, and the following formula (f) regarding the discomfort probability of sound quality is derived from the result,

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound Deriving the evaluation formula,
A sound quality evaluation method characterized by performing sound quality evaluation using the derived sound quality evaluation formula. A method for manufacturing an image forming apparatus that forms an image on an image forming target sheet,
The image forming apparatus evaluates a plurality of types of sounds emitted at the time of image formation by a pair comparison method,
A logistic regression analysis is performed using the discomfort probability of two sounds based on the evaluation as a target variable and the difference between psychoacoustic parameter values as an explanatory variable, and the following formula (f) regarding the discomfort probability of sound quality is derived from the result,

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound Deriving the evaluation formula,
Using the derived sound quality evaluation formula, each part of the device is designed so that the sound quality evaluation by the sound quality evaluation formula satisfies a predetermined condition,
A method for manufacturing an image forming apparatus, wherein the image forming apparatus is manufactured according to the design contents. A method for modifying an image forming apparatus that forms an image on an image forming target sheet,
The image forming apparatus evaluates a plurality of types of sounds emitted at the time of image formation by a pair comparison method,
A logistic regression analysis is performed using the discomfort probability of two sounds based on the evaluation as a target variable and the difference between psychoacoustic parameter values as an explanatory variable, and the following formula (f) regarding the discomfort probability of sound quality is derived from the result,

By substituting the average of the psychoacoustic parameter values used in deriving the above equation into the above equation (f) and defining P = 0.5 at that time, a sound quality that predicts the probability of discomfort of the sound Deriving the evaluation formula,
Using the derived sound quality evaluation formula, evaluate the sound quality of the sound emitted by the image forming apparatus to be remodeled,
A method for remodeling an image forming apparatus, comprising remodeling the configuration of the image forming apparatus to be remodeled based on the sound quality evaluation result.

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