JP3625864B2 - Image forming apparatus - Google Patents

Description

【００３５】
図１はこの発明の基礎となるレーザプリンタの構成を示す機能ブロック図である。
図１に示したレーザプリンタ１は、不揮発性メモリであるＥＥＰＲＯＭ３４に設けた頻度カウンタ２と、電源投入時に画素密度とモータ回転数の各初期値を決定する初期値決定手段３ａと、カウンタクリア手段４，初期値復帰手段５と、ＲＯＭ３２，ＲＡＭ３３，光書込制御回路４０及びモータドライバ４３とにより構成されている。
【００３６】
頻度カウンタ２は、それぞれ画素密度３００，４００，４８０，６００ｄｐｉ の使用回数を累算する個別カウンタ２ａ，２ｂ，２ｃ，２ｄとからなり、それらの内容はカウンタクリア手段４によってクリアされる。ＲＯＭ３２には予め画素密度Ｄとそれぞれ対応するモータ回転数Ｒのテーブルが予め格納されている。ＲＡＭ３３には初期値決定手段３ａが決定した画素密度とモータ回転数の各初期値が記憶される。
【００３７】
レーザプリンタ１の電源がオンになったことを示す信号が入力すると、初期値決定手段３ａは頻度カウンタ２の各個別カウンタ２ａ，２ｂ，２ｃ，２ｄの内容Ｆ３０，Ｆ４０，Ｆ４８，Ｆ６０を比較して、そのうちの最大値Ｆｍａｘ を示す画素密度Ｄを決定して、対応するモータ回転数Ｒとの組合せをＲＯＭ３２のテーブルから読出し、ＲＡＭ３３に各初期値として記憶させる。
【００３８】
次に初期値決定手段３ａは、初期値の決定が終了した時点でカウンタクリア手段４に信号を出力して、頻度カウンタ２（のすべての個別カウンタ２ａ〜２ｄ）をクリアさせるから、頻度カウンタ２は電源投入時から新しく頻度データを累算し始める。従って、初期値決定手段３ａは、常に前回の電源投入時以降の最新の頻度データによって初期値を決定することになる。
【００３９】
カウンタクリア手段４が頻度カウンタ２をクリアすると共に初期値復帰手段５に信号を出力すると、初期値復帰手段５は直ちにＲＡＭ３３に記憶された画素密度とモータ回転数の初期値を読出して、それぞれ光書込制御回路４０とモータドライバ４３に出力し、初期設定が行われる。モータドライバ４３は設定された初期値によってポリゴンモータ５４を回転させ、待機モードに入る。
【００４０】
それぞれ図示しないコントローラ２８を介してホストマシンから一連のプリント命令が入力すると、頻度カウンタ２の指定された画素密度に対応する個別カウンタの内容がインクリメントされ、また、ＲＯＭ３２に格納されているテーブルから指定された画素密度Ｄとそれに対応するモータ回転数Ｒが読出されて、それぞれ光書込制御回路４０とモータドライバ４３に設定される。
【００４１】
ＲＯＭ３２のテーブルから読出された画素密度Ｄとモータ回転数Ｒの設定値が、それぞれその直前のプリント命令による設定値又は初期値復帰手段５により設定された初期値と同じ場合はそのまま、異なる場合は光書込制御回路４０とモータドライバ４３は新しい設定値に切換えられてプリントジョブを実行する。
【００４２】
初期値復帰手段５は、プリントジョブの終了すなわちプリント命令の解除を検出すると、内蔵する図示しないタイマをスタートさせ、予め設定された時間内に次のプリント要求又は命令が入力しなければ、光書込制御回路４０とモータドライバ４３に設定された各設定値を解除して、ＲＡＭ３３に記憶されている各初期値に復帰させる。
【００４３】
したがって、図１に示したレーザプリンタは、電源投入毎に常に最新の頻度情報に基づいて画素密度とモータ回転数の初期値が決定され、プリント命令が入力すると指定された画素密度に応じてプリントジョブを実行するが、該プリントジョブ終了後に予め設定された時間内に次のプリント命令（又は要求）が入力しなければ、画素密度もモータ回転数も決定された初期値に復帰する。
そのため、プリント命令入力時における画素密度とモータ回転数の切換えの回数は、統計的に最も少くなり、スループットが向上する。
【００４４】
図５は、このレーザプリンタにおける初期値決定手段３ａであるＣＰＵ３１が実行する初期値決定のルーチンの一例をサブルーチン型式で示すフロー図である。
電源投入時に図５に示した初期値決定のサブルーチンにジャンプすると、先ずステップ１で画素密度３００ｄｐｉ の個別カウンタ２ａの内容である頻度Ｆ３０を読出して最大頻度Ｆｍａｘ とし、決定すべき画素密度の初期値ＤをＤ３０とする。
【００４５】
次に、ステップ２で個別カウンタ２ｂの内容であるＦ４０を読出し、ステップ３でＦｍａｘ と比較してＦ４０がＦｍａｘ より小さければステップ５にジャンプし、Ｆｍａｘ 以上であればステップ４に進んで、最大頻度Ｆｍａｘ をＦ４０に置換え、画素密度の初期値ＤをＤ４０としてステップ５に進む。
【００４６】
同様に、ステップ５で個別カウンタ２ｃからＦ４８を読出し、ステップ６でＦ４８がＦｍａｘ より小さければステップ８にジャンプし、否ならばステップ７でＦｍａｘ をＦ４８に置換え、初期値ＤをＤ４８にする。また、ステップ８で個別カウンタ２ｄからＦ６０を読出し、ステップ９でＦ６０がＦｍａｘ より小さければステップ１１にジャンプし、否ならばステップ１０でＦｍａｘ をＦ６０に置換え、初期値ＤをＤ６０にする。
【００４７】
ステップ１０までの段階で頻度が最大値を示す画素密度が初期値Ｄとして決定されるが、複数の画素密度の頻度が同じ最大値であった場合は、画素密度の大きい方が初期値Ｄとして選択される。もし、画素密度の小さい方を選択したければ、ステップ３，ステップ６，ステップ９の不等号「＞」をそれぞれ不等号「≧」に置換えればよい。
【００４８】
次に、ステップ１１でＦｍａｘ がゼロか否かを判定して否ならばステップ１３にジャンプし、ゼロであればステップ１２に進んで、初期値Ｄを予め設計段階で設定した初期値にしてステップ１３に進む。ステップ１３では、決定された画素密度の初期値Ｄに対応するモータ回転数ＲをＲＯＭ３２に格納されているテーブルから読出して、一対の初期値Ｄ，ＲとしてＲＡＭ３３に記憶させた後、リターンする。
【００４９】
この例では、初期値決定手段３ａがカウンタクリア手段４と組合されているが、初期値Ｄが決定されてから頻度カウンタ２がクリアされるから、一応問題はない。しかしながら、電源投入後に１度もプリント命令が入力しないで電源が切られると、頻度カウンタ２の個別カウンタ２ａ〜２ｄのすべての内容がゼロのままになっているから、再び電源が投入された時に、画素密度の初期値ＤがＤ６０（不等号を置換えた場合はＤ３０）になって了う。
【００５０】
それでも作動上の不都合は生じないが、図５に示したサブルーチンではステップ１１，ステップ１２を設け、Ｆｍａｘ がゼロの場合に設計値が初期値Ｄになるようにして、少しでもスループットが向上するようにしている。しかしながら、一般にカウンタクリア手段４が組合されていない場合は、ステップ１１及びステップ１２は不要であるから、削除した方がよい。
【００５１】
図６は、このようなカウンタクリア手段４が組合されていない一般的な画像形成装置における初期値決定手段３のルーチンの一例を示すサブルーチンである。図６に示した初期設定のサブルーチンは、図５に示したサブルーチンからステップ１１及びステップ１２を削除したものであり、その他のステップ番号はそのまま残して、説明を省略する。
【００５２】
図７はこの発明の一実施例であるレーザプリンタの構成を示す機能ブロック図である。
図７に示したレーザプリンタ１ａが、図１に示したレーザプリンタ１と異なる所は、初期値決定手段３ａ，カウンタクリア手段４，初期値復帰手段５をそれぞれ初期値決定手段３ｂ，カウンタ内容変更手段７，待機値復帰手段８に置換えると共に、ジョブカウンタ６を設け、ＲＡＭ３３に代えてＥＥＰＲＯＭ３４に画素密度とモータ回転数の（初期値及び）待機値を記憶させるようにしたことであり、その他の部分は同一符号を付して説明を省略する。
【００５３】
ジョブカウンタ６は新しいプリント命令が入力する度にその入力回数を累算して、その内容が予め設定した回数又はその倍数に達した時に初期値設定手段３ｂに信号を出力する。例えばジョブカウンタ６を８ビットの２進カウンタで構成し、オーバフローして出力されるキャリィをその出力信号とすれば、プリント命令が２５６回入力する度に信号が初期値決定手段３６に出力される。
【００５４】
初期値決定手段３ｂは、ジョブカウンタ６からの信号が入力すると、図６に示した初期値決定のサブルーチンに従って、頻度カウンタ２の各個別カウンタ２ａ〜２ｄの内容Ｆ３０〜Ｆ６０を比較して、そのうちの最大値Ｆｍａｘ を示す画素密度Ｄを決定して、対応するモータ回転数Ｒとの組合せをＲＯＭ３２のテーブルから読出し、ＥＥＰＲＯＭ３４に各初期値として記憶させる。
【００５５】
したがって上記の機能は、入力信号と初期値出力先とが異なるだけで、電源オンの信号により作用する図１に示した初期値決定手段３ａと同じであるが、この実施例の初期値決定手段３ｂは、さらに画素密度とモータ回転数の初期値から待機値を作成して、同じくＥＥＰＲＯＭ３４に記憶させる。
画素密度の待機値はその初期値と変らないが、モータ回転数の待機値はその初期より１段乃至２段低い値になっている。
【００５６】
【表２】

【００５７】
表２は、画素密度の初期値すなわち待機値にそれぞれ対応するモータ回転数の初期値，待機値Ａ，待機値Ｂの一例を示すテーブルであり、モータ回転数の待機値Ａは初期値より１段、待機値Ｂは初期値より２段低くそれぞれ設定した場合を示す。ただし、画素密度の初期値に対応するモータ回転数の初期値が、予め設定された複数段（この例では４段）のモータ回転数のうちの最も低く設定されたモータ回転数（この例ではＲ３０）のときは、それを待機値Ａ又はＢとしている。
また、ＥＥＰＲＯＭ３４には待機値Ａと待機値Ｂとが同時に記憶される訳ではなく、設計時にいずれか一方のみが記憶されるように設定されており、この実施例では待機値Ａが記憶される。
【００５８】
カウンタ内容変更手段７は、プリント命令が入力して指定された画素密度（例えば４００ｄｐｉ ）に対応する個別カウンタ（２ｂ）がインクリメントされた時に、インクリメントされた該個別カウンタ（２ｂ）の内容（Ｆ４０）を読出して、予め設定した限界値に達していたならば、該限界値以下に設定した除数によって各個別カウンタ２ａ〜２ｄの内容を除算した結果をそれぞれの新しい内容として交換する。
【００５９】
待機値復帰手段８は、プリントジョブの終了直後に図示しない内蔵タイマをスタートさせ、予め設定した時間内に次のプリント要求又は命令が入力しなければ、画素密度とモータ回転数の各設定値を解除してＥＥＰＲＯＭ３４に記憶されている各待機値に復帰させる。その機能は復帰対象がＲＡＭ３３の初期値かＥＥＰＲＯＭ３４の待機値かの差で、その他は初期値復帰手段５と全く同じである。
【００６０】
図８はカウンタ内容変更手段７であるＣＰＵ３１が実行する個別カウンタの内容変更のルーチンの一例を示すフロー図である。
それぞれ予め設定した限界値をＬ、除数をＪ（≦Ｌ）とし、またｎ＝０〜３としてＥＥＰＲＯＭ３４上の各個別カウンタ２ａ〜２ｄのアドレスＡをＡｎ、その内容をＦｎで示す。
【００６１】
図８に示したカウンタ内容変更のルーチンはプリント命令が入力した時にスタートし、先ずステップ２０で指定された画素密度に対応するアドレスＡｎの個別カウンタの内容Ｆｎをインクリメントした後、ステップ２１でその内容が限界値Ｌに達したか否かを判定し、否ならばエンドへ行く。限界値Ｌに達していればステップ２２に進んでｎ＝０にセットした後、ステップ２３に進む。
【００６２】
ステップ２３でアドレスＡｎの個別カウンタの内容Ｆｎを除数Ｊで除算し、ステップ２４でｎをインクリメントした後、ステップ２５に進んでｎが４になったか否か、すなわち全個別カウンタの内容が変更されたか否かを判定して、否ならばステップ２３に戻り、ｎ＝４であればエンドになる。
【００６３】
この実施例の効果が前述の例と異なる第１の点は、前述の例では少くとも１日１回電源がオン／オフされる場合は問題ないが、外部との通信回線を備えたＬＡＮ等のネットワークに接続されて電源オンのまま連続使用されると、頻度情報が変化しても初期値が変らず、そのうち各個別カウンタが次から次にオーバフローして、頻度情報が無意味になるという問題がある。しかしながら、この実施例ではプリント命令の入力回数によって初期値及び待機値が決定されるから、電源のオン／オフには無関係である。
【００６４】
第２の点は、個別カウンタ２ａ〜２ｄの内容に限界値Ｌを設定したから、いくら頻繁に使用されてもオーバフローすることがない。
さらに第３の点は、前述の例では頻度カウンタ２がクリアされることにより最新の頻度情報に基づいて初期値が決定される代りに、過去の頻度情報が全く失われて了う。しかしながら、この実施例では除数Ｊの設定如何によって過去の頻度情報を任意に生かすことが出来る。
【００６５】
すなわち、除数Ｊを限界値Ｌと等しく設定すれば、内容変更によって頻度最大の画素密度の個別カウンタのみ１で、他の個別カウンタは０になるから最大頻度の情報だけが残り、それ以降はそれに新しい情報が累算されることになる。また、除数Ｊを限界値Ｌ未満に設定すれば、過去の頻度情報は１／Ｊのウエイトで残り、以降はそれに新しい情報が累算されることになる。
【００６６】
第４の点は、モータ回転数の待機値をその初期値より１段（待機値Ａ）又は２段（待機値Ｂ）低く設定し、待機中はその待機値でポリゴンモータ５４を回転させているから、プリント命令が来てからポリゴンモータ５４が所定の回転数に安定するまでの立上り時間が余り長くならない範囲で、待機中のモータ回転に要する電力とそのための発熱を抑制し、ポリゴンモータ５４の寿命を延ばすことが出来る。
【００６７】
また、いずれの場合でも、設計時に設定した画素密度Ｄの設計値は、ＲＯＭ３２に格納して必要に応じて読出してもよいが、工場出荷時にＥＥＰＲＯＭ３４上のＤの設計値に対応する個別カウンタのみ任意の数に、その他の個別カウンタをゼロにしておけば、ユーザ側の最初の初期値又は初期値と待機値の決定が円滑に行われる。
【００６８】
【発明の効果】
以上説明したようにこの発明による画像形成装置は、プリントジョブの終了後所定時間内に次のプリント命令が入力しない場合に設定される画素密度とポリゴンモータの回転数の待機値を、ユーザによる画素密度の使用頻度に合せて設定できるので、スループットを大幅に改善することが出来る。
【図面の簡単な説明】
【図１】この発明の基礎となるレーザプリンタの構成を示す機能ブロック図である。
【図２】この発明の一実施例であるレーザプリンタの内部機構を示す概略構成図である。
【図３】図２に示したレーザプリンタの制御系の一例を示すブロック図である。
【図４】図２に示した光書込ユニットの要部斜視図である。
【図５】図１に示したレーザプリンタの初期値決定手段が実行する初期値決定のルーチンの一例をサブルーチン型式で示すフロー図である。
【図６】一般的な初期値決定手段が実行する初期値決定のルーチンの一例をサブルーチン型式で示すフロー図である。
【図７】この発明の一実施例であるレーザプリンタの構成を示す機能ブロック図である。
【図８】図７に示したレーザプリンタのカウンタ内容変更手段が実行するカウンタ内容変更のルーチンの一例を示すフロー図である。
【符号の説明】
１，１ａ：レーザプリンタ（画像形成装置）
２：頻度カウンタ
２ａ，２ｂ，２ｃ，２ｄ：個別カウンタ
３，３ａ，３ｂ：初期値決定手段
４：カウンタクリア手段 ５：初期値復帰手段
６：ジョブカウンタ ７：カウンタ内容変更手段
８：待機値復帰手段 ３１：ＣＰＵ
３４：ＥＥＰＲＯＭ（不揮発性メモリ）
４０：光書込制御回路（画像書込手段）
４３：モータドライバ（モータ制御手段）
５４：ポリゴンモータ[0001]
[Industrial application fields]
The present invention relates to an optical scanning type image forming apparatus using electrostatic latent image technology, and more particularly to an image forming apparatus capable of switching pixel density.
[0002]
[Prior art]
Generally, it is incorporated in a single host machine such as a personal computer or workstation, or in a printer, word processor (document editing / creating apparatus), facsimile, etc. connected as an external device to a network consisting of a plurality of host machines such as a LAN. There are image forming apparatuses such as built-in printers.
[0003]
Recently, the performance of printers has been rapidly improved in response to user demands for improving image quality and printing speed. Among them, an optical scanning printer using an electrostatic latent image technology and a laser as a light source, that is, Laser beam printers (abbreviated as laser printers for short) are distinguished by their high pixel density and high printing speed, so that they are often used both as external devices and built-in types.
[0004]
Furthermore, laser printers not only have a high pixel density, but also can change the pixel density relatively easily. Therefore, a device that can switch a plurality of pixel densities with a single printer in response to a command is commercially available. Yes. Normally, in such a printer, for example, one of a plurality of pixel densities is selected as a default or initial value at the time of designing.
[0005]
Therefore, when the printer is turned on, the optical writing control circuit and the polygon motor control circuit that drives the polygon mirror for scanning the laser beam rotate the image clock frequency corresponding to the selected pixel density (writing frequency). ) And the initial setting is performed so as to rise depending on the motor speed.
[0006]
When the pixel density is switched, the motor rotation speed is generally proportional to the pixel density, and the frequency of the image clock changes substantially proportional to the square of the pixel density. Of these, there is no problem because the switching of the image clock is performed electrically, but since the switching of the motor rotation speed is performed mechanically, it takes time to stabilize at a predetermined rotation speed. For this reason, some printers always rotate at a constant low rotation speed without stopping the motor in order to speed up the start-up of the motor in the standby mode waiting for the input of a print request.
[0007]
However, users rarely use all the pixel densities that the printer has, and in general, in printers connected to a single host machine, one pixel density is rarely two depending on the individual purpose of the operator. Is often used. Printers connected to a network such as a LAN specify the pixel density for each purpose by a plurality of operators. Therefore, the types of pixel density used are increased. However, the pixel density that is frequently used is one or two. Limited to about one.
[0008]
It is sufficient that the pixel density frequently used by the operator and the pixel density selected at the time of design match, but if they differ, the number of times of switching the pixel density inevitably increases. In particular, when connected to a LAN or the like, it is inevitable that the number of times of switching increases. Therefore, the time required for switching increases with the number of times of switching, and the work efficiency, that is, the throughput as the system is remarkably lowered.
[0009]
Therefore, for example, as disclosed in Japanese Patent Laid-Open No. 1-285349, a pixel density designation request for the next job is accepted even during execution of a print job (hereinafter also referred to simply as “job”). If switching is necessary, there has been a proposal to improve the throughput by starting the pixel density switching operation immediately after completion of the job being executed and accepting a print request for the next job during the operation.
[0010]
[Problems to be solved by the invention]
However, the above proposal is effective when job requests are continuously input. However, the first job after power-on and the job that is input with the standby time inserted are exactly the same as before. Therefore, there was a problem that the throughput was not improved.
[0011]
Rather, if a pixel density that is actually frequently used by the operator can be selected at the time of designing, it can be easily assumed that the throughput will be much improved. However, since each user's purpose of use varies, it is impossible to estimate the most frequently used pixel density by each user at the time of design, and it is statistically frequently used from conventional data. There is no other method than selecting.
[0012]
This invention has been made in view of the above points,When the next print command is not input within the specified time after the print job is completedPixel density set toAnd the standby value of the rotation speed of the polygon motor,A userPixel density byAccording to the frequency of useTo be able to setThe goal is to significantly improve throughput.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention sets image writing means for writing an image with a plurality of stages of pixel densities that can be switched in accordance with a pixel density designation command, and is set corresponding to each of the plurality of stages of pixel densities. In an optical scanning type image forming apparatus provided with motor control means for controlling rotation of a polygon motor by any of a plurality of stages of motor rotation speed,
An electrically rewritable non-volatile memory, a frequency counter comprising a plurality of individual counters for accumulating the number of times of use for each print job for each pixel density on the non-volatile memory, and each time a print command is input The job counter that accumulates the number of times of input and outputs a signal when the content reaches a preset number of times or a multiple thereof, and when the signal is input from the job counter, The initial value is determined by determining each initial value of the pixel density indicating the maximum value of the frequency and the preset motor rotation speed corresponding thereto.Decided asPixel density andIf the motor rotational speed determined as the initial value is the lowest motor rotational speed among the plurality of stages of motor rotational speed, the motor rotational speed is set otherwise.initial valueDecided asMotor speed set to one or two steps lower than motor speedEachAn initial value determining means for storing the standby value in the nonvolatile memory is provided.
[0014]
further,When the above print command is inputAmong a plurality of individual counters for each pixel density constituting the frequency counterWhen the individual counter corresponding to the specified pixel density is incremented, the individual counterCounter contents changing means for setting the result of dividing the contents of all the individual counters by the divisor set in advance below the limit value to the new contents of each individual counter when the contents of the counter reaches a preset limit valueIf the next print command is not input within a preset time after the end of the print job, the set values of the pixel density and the motor rotation number are canceled, and the respective values stored in the nonvolatile memory are stored. Standby value return means for returning to the standby value;Is provided.
[0015]
[Action]
The image forming apparatus configured as described above has an individual counter corresponding to the pixel density used for each print job among a plurality of individual counters for each pixel density constituting the frequency counter provided on the nonvolatile memory. Accumulate the number of uses. The initial value determining means determines the most frequently used pixel density indicated by the frequency counter and a preset motor rotation number corresponding thereto as each initial value,Determined as its initial valuePixel densityIs stored as a standby value, and if the motor rotational speed determined as the initial value is the lowest among the preset motor rotational speeds, the motor rotational speed is Otherwise, determined as the above initial valueMotor speed set to one or two steps lower than motor speedTheStore as standby value.
[0016]
And when the print command is input,Frequency counterWhen any one of the individual counters reaches the limit value, the contents of all the individual counters are divided by the divisor set below the limit value to obtain the new contents of each individual counter. As the counter overflows, the frequency data before the change of the counter contents is not lost, and is added to the frequency after the change with the weight of the reciprocal of the divisor to update each standby value.
If the next print command is not input within the preset time after the print job is completed, the set values of the pixel density and the motor speed are canceled and the standby values stored in the nonvolatile memory are set. Return.
[0017]
【Example】
FIG. 2 is a schematic diagram showing the internal mechanism of the laser printer according to one embodiment of the present invention.
In the laser printer 1 shown in FIG. 2, the paper 11 is fed by a paper feed roller 12 from one of the two upper and lower paper feed cassettes 10a and 10b, for example, a paper stack 11a on the upper paper feed cassette 10a. The sheet 11 is conveyed to the transfer position of the photosensitive drum 15 after being timed by the registration roller pair 13.
[0018]
The surface of the photosensitive drum 15 that is rotationally driven by the main motor 14 in the direction indicated by the arrow is charged by the charging charger 16 and scanned with a modulated spot from the optical writing unit 26 so that an electrostatic latent image is formed on the surface. It is formed. The formed latent image is visualized by attaching toner to the developing unit 17.
[0019]
The toner image is transferred by the transfer charger 18 onto the paper 11 conveyed by the registration roller pair 13. The sheet on which the toner image has been transferred is separated from the photosensitive drum 15 and then sent to the fixing unit 20 by the conveying belt 19 and is pressed against the fixing roller 20b by the pressure roller 20a and preheated with the pressure. Fixing is performed according to the temperature of the fixing roller 20b.
[0020]
The paper 11 exiting the fixing unit 20 is discharged by a paper discharge roller 21 to a paper discharge tray 22 provided on the side of the printer. On the other hand, the toner remaining on the photosensitive drum 15 is removed and collected by the cleaning unit 23.
A printed circuit board 24 on which a controller and an engine driver are mounted is disposed above the printer.
[0021]
FIG. 3 is a block diagram illustrating an example of a control system of the laser printer 1 illustrated in FIG. 2, and includes a controller 28 and an engine driver 30.
The controller 28 includes an MPU, ROM, RAM, I / O, etc. (not shown), converts image data including characters input from a host machine (not shown) into a bitmap, and synchronizes with an image clock WCLK input from the engine driver 30. The image processing unit outputs bitmap data DATA for each line to the engine driver 30.
[0022]
The main part of the engine driver 30 is electrically rewritable with a CPU 31 that controls each part of the engine driver 30, a ROM 32 that stores programs and constant data of various routines executed by the CPU 31, and a RAM 33 that stores variable data. The EEPROM 34, which is a non-volatile memory, and an I / O 35 to which a drive system 36 such as a motor and a solenoid constituting the engine driver 30 and various sensor groups 37 are connected are connected to each other via a bus 38.
[0023]
The engine driver 30 also includes an optical writing control circuit 40 that outputs an image clock WCLK having a frequency corresponding to the pixel density to the controller 28 in synchronization with a synchronization signal DETP output from a synchronization sensor 62 described later, and the control circuit. An LD driver 41 for turning on / off a laser diode (not shown) of the LD unit 50 with appropriate power in accordance with bitmap data DATA synchronized with the image clock WCLK input from the controller 28 via 40, and a polygon motor 54 described later. And a motor driver 43 that controls the motor to rotate at a constant speed at the motor speed set by the CPU 31, that is, the speed specified by the speed selection signals S0 to S2.
[0024]
FIG. 4 is a perspective view of a main part of the optical writing unit 26 shown in FIG.
The optical writing unit 26 includes an LD (laser diode) unit 50, a first cylinder lens 51, a first mirror 52, an imaging lens 53, a polygon motor 54, and a polygon mirror 55 rotated in the direction of arrow A. , A second mirror 57, a second cylinder lens 58, a third mirror 60, a condenser lens 61, and a synchronization sensor 62 as a light receiving element.
[0025]
The LD unit 50 includes a laser diode (not shown) and a collimator lens that converts a divergent beam emitted from the laser diode into a parallel light beam.
The first cylinder lens 51 has a function of shaping the parallel light beam emitted from the LD unit 50 in the sub-scanning direction on the photosensitive drum 15, and the imaging lens 53 is a parallel light beam reflected by the first mirror 52. Is converted into a convergent beam and made incident on the mirror surface 55 a of the polygon mirror 55.
[0026]
The polygon mirror 55 is an R polygon mirror formed by bending each mirror surface 55 a, and constitutes a post-object type rotary deflector 56 that does not use an fθ lens that is disposed between the polygon mirror 55 and the second mirror 57. .
The second mirror 57 reflects the light beam reflected and deflected by the rotating deflector 56 toward the photosensitive drum 15. The light beam reflected by the second mirror 57 passes through the second cylinder lens 58 and forms an image as a sharp spot on the main scanning line 15 a on the photosensitive drum 15.
[0027]
The third mirror 60 is disposed outside the scanning area on the photosensitive drum 15 by the light beam reflected by the rotary deflector 56 and reflects the incident light beam toward the synchronization sensor 62.
The light beam reflected by the third mirror 60 and collected by the condenser lens 61 is detected by a light receiving element such as a photodiode constituting the synchronization sensor 62 and is output from the synchronization sensor 62 as a synchronization signal DETP.
[0028]
In the laser printer 1 shown in FIGS. 2 to 4, the pixel density and the motor rotation number are set to respective initial values determined in advance in the initial setting after the power is turned on. When a print command is input from a host machine (not shown), the controller 28 outputs a print request signal RXD to the CPU 31 of the engine driver 30, and the CPU 31 outputs a signal TXD indicating the engine state to the controller 28.
[0029]
Subsequently, the pixel density designated via the controller 28 is input to the CPU 31, and the CPU 31 instructs the optical writing control circuit 40 on the pixel density and also notifies the motor driver 43 of the rotation speed selection signals S 0 to S 0 corresponding to the pixel density. S2 is output, and the optical writing control circuit 40 starts outputting the image clock WCLK synchronized with the synchronization signal DETP input from the synchronization sensor 62 at a frequency proportional to the square of the approximate pixel density according to the pixel density.
[0030]
As soon as the rotation speed selection signals S0 to S2 are input, the motor driver 43 outputs an acknowledge signal ACK to the CPU 31 and controls the polygon motor 54 so that the specified motor rotation speed is obtained. When a constant speed rotation state (lock state) stable at the motor rotation speed is entered, a lock signal LOK is output to the CPU 31 to notify that printing can be started.
[0031]
The optical writing control circuit 40 always outputs a clock having a frequency corresponding to each of a plurality of pixel densities by the built-in oscillation circuit, and outputs only a clock electrically selected according to the pixel density. However, since the polygon motor 54 is mechanically rotated, it takes time to stand up and become locked when it is stationary during standby.
[0032]
Especially when rising from a stationary state, not only excessive power is required in the initial stage, but also a pulse motor, a synchronous motor and the like need to be started at a low frequency at the start, so that the driver becomes complicated. Therefore, as described in the section of the prior art, a method of rotating the motor at a preset low number of revolutions during standby is used.
[0033]
Less thanIn the description ofCan be printed at four types of pixel densities of 600, 480, 400, and 300 dpi (dots / inch). As shown in Table 1, symbols indicating pixel density, motor rotation speed, and frequency are D, R, and F, respectively. And the upper two digits of the pixel density (in dpi) are attached to each. For example, the frequency F48 indicates the contents of the individual counter 2c that accumulates the number of times of use of 480 dpi of the frequency counter 2 including four individual counters.
[0034]
[Table 1]

[0035]
FIG. 1 illustrates the present invention.FoundationIt is a functional block diagram which shows the structure of a laser printer.
The laser printer 1 shown in FIG. 1 includes a frequency counter 2 provided in an EEPROM 34 which is a non-volatile memory, an initial value determining means 3a for determining initial values of pixel density and motor rotational speed when power is turned on, and counter clearing means. 4, initial value restoring means 5, ROM 32, RAM 33, optical writing control circuit 40, and motor driver 43.
[0036]
The frequency counter 2 is composed of individual counters 2a, 2b, 2c, and 2d that accumulate the number of times of use of pixel densities 300, 400, 480, and 600 dpi, respectively, and their contents are cleared by the counter clear means 4. In the ROM 32, a table of the motor rotation speed R corresponding to the pixel density D is stored in advance. The RAM 33 stores the initial values of the pixel density and the motor rotational speed determined by the initial value determining means 3a.
[0037]
When a signal indicating that the power of the laser printer 1 is turned on is input,initial valueThe determining means 3a compares the contents F30, F40, F48, F60 of the individual counters 2a, 2b, 2c, 2d of the frequency counter 2, determines the pixel density D indicating the maximum value Fmax, and determines the corresponding motor. The combination with the rotational speed R is read from the table of the ROM 32 and stored in the RAM 33 as each initial value.
[0038]
Next, the initial value determination means 3a outputs a signal to the counter clear means 4 when the determination of the initial value is completed to clear the frequency counter 2 (all of the individual counters 2a to 2d thereof). Starts accumulating new frequency data from power-on. Therefore, the initial value determining means 3a always determines the initial value based on the latest frequency data after the previous power-on.
[0039]
When the counter clear means 4 clears the frequency counter 2 and outputs a signal to the initial value return means 5, the initial value return means 5 immediately reads the initial values of the pixel density and the motor rotation speed stored in the RAM 33, and The data is output to the write control circuit 40 and the motor driver 43, and initial setting is performed. The motor driver 43 rotates the polygon motor 54 with the set initial value and enters a standby mode.
[0040]
When a series of print commands are input from the host machine via the controller 28 (not shown), the contents of the individual counter corresponding to the designated pixel density of the frequency counter 2 are incremented and designated from the table stored in the ROM 32. The pixel density D and the motor rotation speed R corresponding thereto are read out and set in the optical writing control circuit 40 and the motor driver 43, respectively.
[0041]
If the set values of the pixel density D and the motor rotation speed R read from the table of the ROM 32 are the same as the set values by the immediately preceding print command or the initial values set by the initial value restoring means 5, respectively, The optical writing control circuit 40 and the motor driver 43 are switched to the new set values and execute the print job.
[0042]
When detecting the end of the print job, that is, the cancellation of the print command, the initial value returning means 5 starts a built-in timer (not shown), and if the next print request or command is not input within a preset time, The setting values set in the loading control circuit 40 and the motor driver 43 are canceled, and the initial values stored in the RAM 33 are restored.
[0043]
Therefore, as shown in FIG.Laser printerEach time the power is turned on, the initial values of the pixel density and the motor rotation number are always determined based on the latest frequency information, and when a print command is input, the print job is executed according to the designated pixel density. If the next print command (or request) is not input within a preset time after the completion, both the pixel density and the motor rotational speed are restored to the determined initial values.
For this reason, the number of times of switching between the pixel density and the motor rotation number at the time of inputting the print command is statistically the smallest, and the throughput is improved.
[0044]
FIG.In this laser printerIt is a flowchart which shows an example of the routine of the initial value determination which CPU31 which is the initial value determination means 3a performs by a subroutine type | mold.
When jumping to the initial value determination subroutine shown in FIG. 5 when the power is turned on, first, in step 1, the frequency F30, which is the content of the individual counter 2a with a pixel density of 300 dpi, is read out to be the maximum frequency Fmax, and the initial value of the pixel density to be determined Let D be D30.
[0045]
Next, F40, which is the content of the individual counter 2b, is read in step 2, and compared with Fmax in step 3, if F40 is smaller than Fmax, the process jumps to step 5; Fmax is replaced with F40, the initial value D of the pixel density is set to D40, and the process proceeds to step 5.
[0046]
Similarly, in step 5, F48 is read from the individual counter 2c. In step 6, if F48 is smaller than Fmax, the process jumps to step 8. If not, Fmax is replaced with F48 in step 7, and the initial value D is set to D48. In step 8, F60 is read from the individual counter 2d. In step 9, if F60 is smaller than Fmax, the process jumps to step 11. If not, Fmax is replaced with F60 in step 10, and the initial value D is set to D60.
[0047]
The pixel density having the maximum frequency in the stage up to step 10 is determined as the initial value D, but when the frequency of a plurality of pixel densities is the same maximum value, the higher pixel density is set as the initial value D. Selected. If it is desired to select the lower pixel density, the inequality sign “>” in Step 3, Step 6 and Step 9 may be replaced with the inequality sign “≧”.
[0048]
Next, it is determined in step 11 whether or not Fmax is zero. If not, the process jumps to step 13, and if it is zero, the process proceeds to step 12, and the initial value D is set to the initial value set in advance in the design stage. Proceed to step 13. In step 13, the motor rotational speed R corresponding to the determined initial value D of the pixel density is read from the table stored in the ROM 32, stored in the RAM 33 as a pair of initial values D and R, and then the process returns.
[0049]
This exampleThen, the initial value determining means 3a is combined with the counter clearing means 4, but since the frequency counter 2 is cleared after the initial value D is determined, there is no problem. However, if the power is turned off without inputting a print command once after the power is turned on, all the contents of the individual counters 2a to 2d of the frequency counter 2 remain zero, so when the power is turned on again. The initial value D of the pixel density is D60 (D30 when the inequality sign is replaced).
[0050]
Still, there will be no inconvenience in operation, but the subroutine shown in FIG. 5 is provided with Steps 11 and 12 so that the design value becomes the initial value D when Fmax is zero so that the throughput is improved even a little. I have to. However, in general, when the counter clearing means 4 is not combined, step 11 and step 12 are unnecessary, and should be deleted.
[0051]
FIG. 6 is a subroutine showing an example of a routine of the initial value determining means 3 in a general image forming apparatus in which the counter clear means 4 is not combined. The initial setting subroutine shown in FIG. 6 is obtained by deleting step 11 and step 12 from the subroutine shown in FIG. 5, and other step numbers are left as they are, and description thereof is omitted.
[0052]
FIG. 7 shows the present invention.ExampleIt is a functional block diagram which shows the structure of the laser printer which is.
The laser printer 1a shown in FIG. 7 differs from the laser printer 1 shown in FIG. 1 in that the initial value determining means 3a, the counter clearing means 4, the initial value returning means 5 are changed to the initial value determining means 3b, and the counter contents are changed. In addition to replacing the means 7 and the standby value return means 8, a job counter 6 is provided, and the EEPROM 34 instead of the RAM 33 stores the pixel density and motor rotation speed (initial value) standby values. These parts are denoted by the same reference numerals and description thereof is omitted.
[0053]
Each time a new print command is input, the job counter 6Number of inputsAnd when the content reaches a preset number of times or a multiple thereof, a signal is output to the initial value setting means 3b. For example, if the job counter 6 is composed of an 8-bit binary counter and the carry output after overflow is the output signal, the signal is output to the initial value determining means 36 every time a print command is input 256 times. .
[0054]
When the signal from the job counter 6 is input, the initial value determining means 3b compares the contents F30 to F60 of the individual counters 2a to 2d of the frequency counter 2 according to the initial value determining subroutine shown in FIG. The pixel density D indicating the maximum value Fmax is determined, and the combination with the corresponding motor rotation speed R is read from the table of the ROM 32 and stored in the EEPROM 34 as each initial value.
[0055]
Therefore, the above function works only with the power-on signal, only the input signal and the initial value output destination are different.As shown in FIG.Same as the initial value determining means 3a,This exampleThe initial value determination means 3b further creates a standby value from the initial values of the pixel density and the motor rotation speed and stores the standby value in the EEPROM 34 as well.
The standby value of the pixel density does not change from the initial value, but the standby value of the motor rotation number is one or two steps lower than the initial value.
[0056]
[Table 2]

[0057]
Table 2 corresponds to the initial value of pixel density, that is, the standby value, respectively.motorIt is a table which shows an example of the initial value of rotation speed, standby value A, and standby value B. The case where the standby value A of motor rotation speed is set to one step from the initial value, and the standby value B is set to two steps lower than the initial value. Show. However,The initial value of the motor speed corresponding to the initial value of the pixel density is set to the lowest motor speed (R30 in this example) among the preset motor speeds of a plurality of stages (4 stages in this example). In this case, it is set as the standby value A or B.
Also,The EEPROM 34 does not store the standby value A and the standby value B at the same time, but is set so that only one of them is stored at the time of design. In this embodiment, the standby value A is stored.
[0058]
When the individual counter (2b) corresponding to the specified pixel density (for example, 400 dpi) is incremented by inputting the print command, the counter content changing means 7 increments the content (F40) of the individual counter (2b). When the limit value set in advance is reached, the contents obtained by dividing the contents of the individual counters 2a to 2d by the divisor set below the limit value are exchanged as new contents.
[0059]
The standby value return means 8 starts a built-in timer (not shown) immediately after the end of the print job, and if the next print request or command is not input within a preset time, the set values of the pixel density and the motor rotational speed are set. It cancels and it returns to each waiting value memorize | stored in EEPROM34. The function is the difference between whether the return target is the initial value of the RAM 33 or the standby value of the EEPROM 34, and the rest is exactly the same as the initial value return means 5.
[0060]
FIG. 8 is a flowchart showing an example of a routine for changing the contents of the individual counter executed by the CPU 31 which is the counter contents changing means 7.
The preset limit value is L, the divisor is J (≦ L), n = 0 to 3, the address A of each individual counter 2a to 2d on the EEPROM 34 is indicated by An, and the content thereof is indicated by Fn.
[0061]
The counter content change routine shown in FIG. 8 starts when a print command is input. First, the content Fn of the individual counter at the address An corresponding to the pixel density specified in step 20 is incremented, and then the content is displayed in step 21. It is determined whether or not the limit value L has been reached. If the limit value L has been reached, the process proceeds to step 22 to set n = 0, and then proceeds to step 23.
[0062]
In step 23, the content Fn of the individual counter at the address An is divided by the divisor J, and after incrementing n in step 24, the process proceeds to step 25, whether or not n becomes 4, that is, the content of all the individual counters is changed. If not, the process returns to step 23, and if n = 4, the end is reached.
[0063]
This exampleThe effect ofThe above exampleThe first difference is thatIn the above exampleThere is no problem if the power is turned on / off at least once a day, but the frequency information will change if it is connected to a network such as a LAN with an external communication line and used continuously. However, there is a problem that the initial value does not change, and each individual counter overflows from one to the next, and the frequency information becomes meaningless. However,In this exampleSince the initial value and the standby value are determined by the number of times the print command is input, it is irrelevant to turning on / off the power.
[0064]
The second point is that the limit value L is set in the contents of the individual counters 2a to 2d, and therefore no overflow occurs no matter how frequently used.
The third point is thatThe above exampleThen, by clearing the frequency counter 2, instead of determining the initial value based on the latest frequency information, the past frequency information is completely lost. However,This exampleThe past frequency information can be arbitrarily utilized depending on the setting of the divisor J.
[0065]
That is, if the divisor J is set equal to the limit value L, only the individual counter with the highest frequency pixel density is 1 by the content change and the other individual counters become 0, so only the maximum frequency information remains, and thereafter New information will be accumulated. If the divisor J is set to be less than the limit value L, the past frequency information remains with a weight of 1 / J, and new information is accumulated thereafter.
[0066]
The fourth point is that the standby value of the motor rotation speed is set one step (standby value A) or two steps (standby value B) lower than the initial value, and the polygon motor 54 is rotated at the standby value during standby. Therefore, the power required for the rotation of the motor during standby and the heat generation therefor are suppressed within a range in which the rising time from when the print command is received until the polygon motor 54 is stabilized at a predetermined rotational speed is not so long. Can extend the lifespan.
[0067]
Also,In any caseThe design value of the pixel density D set at the time of design may be stored in the ROM 32 and read as necessary. However, at the time of shipment from the factory, only the individual counter corresponding to the design value of D on the EEPROM 34 is set to an arbitrary number. If the individual counter is set to zero, the initial initial value or the initial value and the standby value on the user side can be determined smoothly.
[0068]
【The invention's effect】
As described above, the image forming apparatus according to the present invention isWhen the next print command is not input within the specified time after the print job is completedPixel density set toAnd the standby value of the rotation speed of the polygon motor,A userPixel density byAccording to the frequency of useBecause it can be setThroughput can be greatly improved.
[Brief description of the drawings]
FIG. 1 of the present inventionFoundationIt is a functional block diagram which shows the structure of a laser printer.
FIG. 2 is a schematic configuration diagram showing an internal mechanism of a laser printer according to an embodiment of the present invention.
3 is a block diagram showing an example of a control system of the laser printer shown in FIG.
4 is a perspective view of a main part of the optical writing unit shown in FIG. 2. FIG.
FIG. 5 shows in FIG.Laser printerIt is a flowchart which shows an example of the routine of the initial value determination which this initial value determination means performs by a subroutine format.
FIG. 6 is a flowchart showing an example of an initial value determining routine executed by a general initial value determining means in a subroutine format.
FIG. 7 shows the present invention.ExampleIt is a functional block diagram which shows the structure of the laser printer which is.
FIG. 8 is shown in FIG.Laser printerIt is a flowchart which shows an example of the routine of the counter content change which the counter content change means of FIG.
[Explanation of symbols]
1, 1a: Laser printer (image forming apparatus)
2: Frequency counter
2a, 2b, 2c, 2d: Individual counter
3, 3a, 3b: Initial value determining means
4: Counter clear means 5: Initial value return means
6: Job counter 7: Counter content changing means
8: Standby value return means 31: CPU
34: EEPROM (nonvolatile memory)
40: Optical writing control circuit (image writing means)
43: Motor driver (motor control means)
54: Polygon motor

Claims (1)

Image writing means for writing an image at a plurality of stages of pixel densities that can be switched in accordance with a pixel density designation command, and any of a plurality of stages of motor rotation speeds set corresponding to the plurality of stages of pixel densities, respectively. In an optical scanning type image forming apparatus provided with a motor control means for controlling the rotation of a polygon motor by
An electrically rewritable nonvolatile memory;
A frequency counter comprising a plurality of individual counters for accumulating the number of times of use for each pixel density for each print job on the nonvolatile memory;
A job counter that accumulates the number of times of input each time a print command is input and outputs a signal when the content reaches a preset number or a multiple thereof;
When the signal is input from the job counter, the pixel density indicating the maximum value among the frequencies according to the pixel density indicated by the frequency counter and the preset motor rotation speed corresponding thereto are determined as initial values, If the pixel density determined as the initial value and the motor rotation speed determined as the initial value are the lowest motor rotation speed among the motor rotation speeds of the plurality of stages, the motor rotation speed is set otherwise. the motor rotational speed set determined from the motor rotation speed 1 stage or 2-stage low as the initial value, the initial value determining means to be stored in the nonvolatile memory as respective standby value,
When an individual counter corresponding to a designated pixel density is incremented among a plurality of individual counters for each pixel density constituting the frequency counter when the print command is input, the contents of the individual counter are set in advance. If the value has been reached, the counter content changing means for dividing the contents of all the individual counters by the divisor set in advance below the limit value and making the new contents of each individual counter,
If the next print command is not input within a preset time after the end of the print job, the set values of the pixel density and the motor rotational speed are canceled, and the standby states stored in the nonvolatile memory An image forming apparatus comprising: a standby value return means for returning to a value.

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