JP4532684B2 - Inkjet recording device - Google Patents

Description

【００４１】
また、この駆動を行う記録ヘッドの等価回路の構成を図７に示している。各ノズルに対応してインクを吐出させるための吐出エネルギー発生素子（ここに示す例および以下の実施形態においてはその１例として発熱抵抗素子を用いて説明する。）７０１が配されている。
【００４２】
ここで駆動ブロック番号は、１つのイべントの中で駆動される順番を表わしている。すなわち、１，２，３，…，８（図７では、ＢＡ，ＢＢ，…，ＢＨ）の順に駆動される。この３２個のノズルを有する記録ヘッドを使用して、各パス８ノズル送りで４パスのマルチパス記録によって画像を記録すると、８ラスタ周期で同じ駆動ブロックに属するノズルを使用することになる。以下の表２は、各パスにおけるラスタの記録に使用されるノズルと駆動ブロックとを示している。
【００４３】
【表２】

【００４４】
この従来例では同じラスタを記録するのに、同じ駆動ブロックに属するノズルのみを使用することとなる。その結果、上記で図５に関して説明した、駆動ブロックに依存した、周期的圧力変動に起因する濃度ムラが重ね合わされ、より顕著に現れてしまう。
【００４５】
図６は、本実施形態における、インクジェット記録ヘッドのノズル列（ａ）、各ノズルの駆動信号（ｂ）および各ノズルから吐出された飛翔インク滴（ｃ）を、図４と同様に模式的に示した図である。また、図８から図１０に、本実施形態の駆動を行うためのＩＣ内部の回路、記録ヘッドの等価回路およびブロックの駆動信号のタイミングチャートをそれぞれ示している。図６（ａ）において、インクジェット記録ヘッドのノズル列５００は、３２個のノズルからなり、これらのノズルは図中上から８個を単位として、第１セクションから第４セクションまで４つのセクションに分けられている。
【００４６】
更にこれらの各セクション内の８個の各ノズルは、８つの駆動ブロックの一つに属しており、記録の際にはブロック毎に時分割で駆動される。すなわち、同じブロックのノズルは同時に駆動される。
【００４７】
図８から図１０の回路図およびタイミングチャートを用いて、実施形態の記録ヘッドの回路および駆動タイミングンについて以下に具体的に説明する。図８は本実施形態の記録ヘッドを駆動するためのＩＣの内部回路図であり、図９は図８に示す構成のＩＣを用いて駆動される本実施形態の記録ヘッドの透過回路図であり、図１０は図９の記録ヘッドを駆動する信号のタイミングチャートである。
【００４８】
本実施形態では、記録ヘッドを１回主走査方向にスキャンしながら記録を行うと、８ピッチ分副走査方向に移動させた後、主走査方向にスキャンしながら次の行の記録を行う。同時に吐出を行うノズル間の最小距離は８ピッチである。すなわち同一周期内に８種類の駆動タイミングＢＡ，ＢＢ，ＢＣ，ＢＤ，ＢＥ，ＢＦ，ＢＧ，ＢＨを持ち（図１０参照）、これが各ノズルに割り当てられている。図９でＣＬＫはクロック信号、ＬＡはラッチ信号であり８ビット分のデータがシフトレジスタにたまるとラッチに送られる。
【００４９】
Ｂ１，Ｂ２，…，Ｂ８は記録信号ラインであり、１ビット目から８ビット目まで割り当てられる。ＯＵＴ１〜ＯＵＴ８は出力信号端子である。
【００５０】
図９で、ＩＣ１はノズル番号１〜８からの吐出、ＩＣ２はノズル番号９〜１６からの吐出、ＩＣ３はノズル番号１７〜２４からの吐出、ＩＣ４はノズル番号２５〜３２からの吐出をそれぞれ担当する。図９に示されるように、各ＩＣ毎にラインＢ１〜Ｂ８に供給される駆動タイミング信号ＢＡ，ＢＢ，…，ＢＨの組合わせが異なっている。例えば、ＩＣ１においてラインＢ１には駆動タイミング信号ＢＡ、Ｂ２にはＢＨ、Ｂ３にはＢＧ、Ｂ４にはＢＦ、Ｂ５にはＢＥ、Ｂ６にはＢＤ、Ｂ７にはＢＣ、Ｂ８にはＢＢがそれぞれ割り当てられているが、ＩＣ２においてラインＢ１には駆動タイミング信号ＢＨ、Ｂ２にはＢＡ、Ｂ３にはＢＢ、Ｂ４にはＢＣ、Ｂ５にはＢＤ、Ｂ６にはＢＥ、Ｂ７にはＢＦ、Ｂ８にはＢＧがそれぞれ割り当てられている（表３参照）。
【００５１】
このような記録ヘッドを用いて、副走査方向８ピッチ送りで４パス記録を行ったとき、記録媒体上の各画素が属する行（ラスター）がどの駆動タイミング信号によってどのノズルから吐出されたインク滴で構成されるのかを示したのが表４である。
【００５２】
本実施形態においては、３２本のノズルを駆動するために４個のＩＣを用いているが、ＩＣの種類としては一種類でありながら、各ＩＣの出力ＯＵＴｎ（ｎ＝１〜８）は異なるタイミングで駆動されている。このように構成すると、ＩＣの種類を増やすことなく本発明の要件を満たすように駆動タイミングを変えることができるので、生産コストの面で有利である。
【００５３】
なお、本実施形態においては、１つのＩＣ内で１つのノズルを駆動するために駆動タイミングを１つ要したが、ノズル数の多い記録ヘッドの場合には、本発明の要件を満たす範囲であれば、同一ＩＣで駆動されるノズルの内、少なくとも１つ以上のノズルに同一の駆動タイミングを割り当ててもよい（例えば、ラインＢ１〜Ｂ８の８つの駆動タイミング信号の入力を持つ１つのＩＣで８つ以上のノズルを駆動する場合など）。
【００５４】
図示した例では、駆動ブロックのノズルへの割り当ては、以下の表３に示すようになっており、従来例のように周期的ではない。そして、第１駆動ブロックから第８駆動ブロックまで昇順に、図６（ｂ）に示すパルス状の駆動信号３００によって順次駆動され、各ノズルから駆動信号に対応して図６（ｃ）に示すようにインク滴１００が吐出される。
【００５５】
【表３】

【００５６】
本実施形態では、表３に示したように各駆動ブロックのノズルへの割り当てが各ノズルグループ毎に異なっており、非同期的になっているので、上記従来例と同様に、各パス８ノズル送りの４パスのマルチパス記録を行う場合、各ラスタの記録に使用されるノズルは下記の表４のようになる。
【００５７】
【表４】

【００５８】
この表からも解るように、表２で示される従来の場合と異なり、本実施形態の場合、各ラスタにおいて記録に使用される４つの駆動ブロックの番号はいずれも異なっている。また更に、上記で図５に関して説明したように、前半の駆動ブロックはインクの吐出量が多く、後半の駆動ブロックはインクの吐出量が少なくなる傾向がある。これに対して本実施形態では、各ラスタを記録するのに、前半または後半の駆動ブロックだけとはならないようにノズルに駆動ブロックを割り当てている。
【００５９】
この場合、各ラスタを記録する４回の記録パスのうち、２つの記録パスでは前半の駆動ブロックを使用し、２つの記録パスでは後半の駆動ブロックを使用するのが好ましい。本実施形態では、８つの駆動ブロックの前半に属する駆動ブロックと後半に属する駆動ブロックとが交互となるようにしている。例えば、ラスタ１に関して記録に使用する駆動ブロックは、パス１からパス４まで順に、１、８、５、４となっており、ラスタ２の記録に使用する駆動ブロックは、パス１からパス４まで順に、８、１、４、５となっている。
【００６０】
更に、本実施形態では、記録に使用する４つの駆動ブロックのブロック番号の合計値が、いずれのラスタでも１８となり等しい。また、４つの記録パスのうち、前半２つの記録パスで使用する２つの駆動ブロックのブロック番号の合計値と、後半２つの記録パスで使用する２つの駆動ブロックのブロック番号の合計値とはいずれも９となっている。このようにすると、前半２つの対と後半２つの対とを組み合わせて、４つの駆動ブロックの割り当てを単純化することができる。
【００６１】
なお、表３および表４に示した、各ノズルと駆動ブロックとの対応、および各ラスタの記録に使用する駆動ブロックの対応は、上記において図２に関して説明した、記録ヘッド１７０８に対して記録データの供給制御を行うゲートアレイ（Ｇ．Ａ．）１７０４によって管理・制御される。
【００６２】
このように本実施形態では、各ラスタを記録するのに使用する駆動ブロックをバランスよく分配することにより、４回の記録パスで、各記録端で使用される駆動ブロックに依存するインク吐出量に起因する記録濃度のバラツキを補償して、濃度ムラを低減することができる。すなわち、濃い濃度の記録と淡い濃度の記録が交互に行われるので、４回の記録を重ね合わせたものは、ラスタ間での濃度差が相殺されて、いずれのラスタでも略等しい平均的な濃度となり、記録品質が向上する。
【００６３】
なお、以上の実施形態において、記録ヘッドから吐出される液滴はインクであるとして説明し、さらにインクタンクに収容される液体はインクであるとして説明したが、その収容物はインクに限定されるものではない。例えば、記録画像の定着性や耐水性を高めたり、その画像品質を高めたりするために記録媒体に対して吐出される処理液のようなものがインクタンクに収容されていても良い。
【００６４】
また、先の実施形態においてはインクを吐出するための吐出エネルギー発生素子として発熱抵抗体を取り上げて説明したが、これに限らずピエゾ等の素子であっても良い。
【００６５】
以上の実施形態は、特にインクジェット記録方式の中でも、インク吐出を行わせるために利用されるエネルギーとして熱エネルギーを発生する手段（例えば電気熱変換体やレーザ光等）を備え、前記熱エネルギーによりインクの状態変化を生起させる方式を用いることにより記録の高密度化、高精細化が達成できる。
【００６６】
その代表的な構成や原理については、例えば、米国特許第４７２３１２９号明細書、同第４７４０７９６号明細書に開示されている基本的な原理を用いて行うものが好ましい。この方式はいわゆるオンデマンド型、コンティニュアス型のいずれにも適用可能であるが、特に、オンデマンド型の場合には、液体（インク）が保持されているシートや液路に対応して配置されている電気熱変換体に、記録情報に対応していて膜沸騰を越える急速な温度上昇を与える少なくとも１つの駆動信号を印加することによって、電気熱変換体に熱エネルギーを発生せしめ、記録ヘッドの熱作用面に膜沸騰を生じさせて、結果的にこの駆動信号に１対１で対応した液体（インク）内の気泡を形成できるので有効である。
【００６７】
この気泡の成長、収縮により吐出用開口を介して液体（インク）を吐出させて、少なくとも１つの滴を形成する。この駆動信号をパルス形状とすると、即時適切に気泡の成長収縮が行われるので、特に応答性に優れた液体（インク）の吐出が達成でき、より好ましい。
【００６８】
このパルス形状の駆動信号としては、米国特許第４４６３３５９号明細書、同第４３４５２６２号明細書に記載されているようなものが適している。なお、上記熱作用面の温度上昇率に関する発明の米国特許第４３１３１２４号明細書に記載されている条件を採用すると、さらに優れた記録を行うことができる。
【００６９】
記録ヘッドの構成としては、上述の各明細書に開示されているような吐出口、液路、電気熱変換体の組み合わせ構成（直線状液流路または直角液流路）の他に熱作用面が屈曲する領域に配置されている構成を開示する米国特許第４５５８３３３号明細書、米国特許第４４５９６００号明細書を用いた構成も本発明に含まれるものである。加えて、複数の電気熱変換体に対して、共通するスロットを電気熱変換体の吐出部とする構成を開示する特開昭５９−１２３６７０号公報や熱エネルギーの圧力波を吸収する開口を吐出部に対応させる構成を開示する特開昭５９−１３８４６１号公報に基づいた構成としても良い。
【００７０】
さらに、記録装置が記録できる最大記録媒体の幅に対応した長さを有するフルラインタイプの記録ヘッドとしては、上述した明細書に開示されているような複数記録ヘッドの組み合わせによってその長さを満たす構成や、一体的に形成された１個の記録ヘッドとしての構成のいずれでもよい。
【００７１】
加えて、上記の実施形態で説明した記録ヘッド自体に一体的にインクタンクが設けられたカートリッジタイプの記録ヘッドのみならず、装置本体に装着されることで、装置本体との電気的な接続や装置本体からのインクの供給が可能になる交換自在のチップタイプの記録ヘッドを用いてもよい。
【００７２】
また、以上説明した記録装置の構成に、記録ヘッドに対する回復手段、予備的な手段等を付加することは記録動作を一層安定にできるので好ましいものである。これらを具体的に挙げれば、記録ヘッドに対してのキャッピング手段、クリーニング手段、加圧あるいは吸引手段、電気熱変換体あるいはこれとは別の加熱素子あるいはこれらの組み合わせによる予備加熱手段などがある。また、記録とは別の吐出を行う予備吐出モードを備えることも安定した記録を行うために有効である。
【００７３】
さらに、記録装置の記録モードとしては黒色等の主流色のみの記録モードだけではなく、記録ヘッドを一体的に構成するか複数個の組み合わせによってでも良いが、異なる色の複色カラー、または混色によるフルカラーの少なくとも１つを備えた装置とすることもできる。
【００７４】
以上説明した実施の形態においては、インクが液体であることを前提として説明しているが、室温やそれ以下で固化するインクであっても、室温で軟化もしくは液化するものを用いても良く、あるいはインクジェット方式ではインク自体を３０°Ｃ以上７０°Ｃ以下の範囲内で温度調整を行ってインクの粘性を安定吐出範囲にあるように温度制御するものが一般的であるから、使用記録信号付与時にインクが液状をなすものであればよい。
【００７５】
加えて、積極的に熱エネルギーによる昇温をインクの固形状態から液体状態への状態変化のエネルギーとして使用せしめることで積極的に防止するため、またはインクの蒸発を防止するため、放置状態で固化し加熱によって液化するインクを用いても良い。いずれにしても熱エネルギーの記録信号に応じた付与によってインクが液化し、液状インクが吐出されるものや、記録媒体に到達する時点では既に固化し始めるもの等のような、熱エネルギーの付与によって初めて液化する性質のインクを使用する場合も本発明は適用可能である。
【００７６】
このような場合インクは、特開昭５４−５６８４７号公報あるいは特開昭６０−７１２６０号公報に記載されるような、多孔質シート凹部または貫通孔に液状または固形物として保持された状態で、電気熱変換体に対して対向するような形態としてもよい。本発明においては、上述した各インクに対して最も有効なものは、上述した膜沸騰方式を実行するものである。
【００７７】
なお、本発明は、複数の機器（例えばホストコンピュータ、インタフェイス機器、リーダ、プリンタなど）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、複写機、ファクシミリ装置など）に適用してもよい。
【００７８】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体（または記録媒体）を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはCPUやMPU）が記憶媒体に格納されたプログラムコードを読み出し実行することによっても、達成されることは言うまでもない。この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているオペレーティングシステム(OS)などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００７９】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるメモリに書込まれた後、そのプログラムコードの指示に基づき、その機能拡張カードや機能拡張ユニットに備わるCPUなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【００８０】
【発明の効果】
以上説明したように、本発明によれば、各ラスタを記録するのに使用する駆動ブロックをバランスよく分配することにより、複数回の記録パスにおいて、各記録タイミングに依存するインク吐出量の差に起因する記録濃度のバラツキを補償して、濃度ムラを低減することができる。すなわち、濃い濃度の記録と淡い濃度の記録が交互に行われるので、複数回の記録を重ね合わせたものは、ラスタ間での濃度差が相殺されて、いずれのラスタでも略等しい平均的な濃度となり、記録品質が向上するという効果がある。
【図面の簡単な説明】
【図１】本発明の代表的実施形態であるインクジェット記録装置の構成を示す外観斜視図である。
【図２】図１のプリンタの制御部の構成を示すブロック図である。
【図３】インクカートリッジの構成を示す外観斜視図である。
【図４】従来のインクジェット記録ヘッドのノズル列、各ノズルの駆動信号および各ノズルから吐出された飛翔インク滴を模式的に示した図である。
【図５】全ノズルからインク滴を周期的に吐出させる駆動信号と、その時のメニスカス面の状態とを時間に関して示したグラフである。
【図６】本発明のインクジェット記録ヘッドのノズル列、各ノズルの駆動信号および各ノズルから吐出された飛翔インク滴を模式的に示した図である。
【図７】従来の記録ヘッドの等価回路の例を示す回路図である。
【図８】本発明の実施形態の記録ヘッド駆動用ＩＣの内部構成を示す回路図である。
【図９】図８のＩＣで駆動される本発明の実施形態の記録ヘッドの等価回路の回路図である。
【図１０】図９の記録ヘッドに供給される信号のタイミングチャートである。
【符号の説明】
ＩＪＨ 記録ヘッド
１００ インク滴
３００ 駆動信号
５００ ノズル列[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus and a recording head driving method of the apparatus, and in particular, records a recording head having a plurality of nozzles arranged in a predetermined direction and ejecting ink droplets from each in a direction substantially orthogonal to the nozzle arrangement direction. The present invention relates to an ink jet recording apparatus that performs recording by scanning a medium, and a recording head driving method of the apparatus.
[0002]
[Prior art]
For example, as an information output device in a word processor, personal computer, facsimile, or the like, there is a printer that records information such as desired characters and images on a recording medium such as paper or film.
[0003]
As a printer recording method, various methods such as a dot impact method, a thermal method, and an ink jet method are known. The ink jet recording method is one of so-called non-impact recording methods. Noise generation at the time is negligibly small, high-speed recording and recording on various recording media are possible, and so-called plain paper is fixed without requiring special processing, and high definition A cheap image can be obtained.
[0004]
Because of such advantages, recording apparatuses using the ink jet system have been rapidly spread over the past few years as recording apparatuses in copiers, facsimiles, word processors and the like as well as printers as peripheral devices for computers.
[0005]
Ink-jet printing methods that are widely used today include an electrothermal conversion element (heater) method and a piezoelectric element (piezo) method, both of which are electrical. Ink droplet ejection is controlled by a signal.
[0006]
The principle of ink droplet ejection using an electrothermal conversion element is that an electric signal is given to the electrothermal conversion element to instantaneously boil ink in the vicinity of the electrothermal conversion element (film boiling), and the phase change of the ink at that time Ink droplets are ejected at a high speed by the rapid bubble growth caused by the above. For this reason, there are advantages such as a simple structure of the ink jet recording head and easy integration of nozzles.
[0007]
Ink jet recording heads often have a plurality of nozzles for discharging ink and discharge pressure generating elements in order to perform high density recording. Normally, these multiple nozzles are first divided into a predetermined number of nozzles at physical positions, and further divided into drive blocks within each section, and separate division that causes the discharge pressure generating elements to be time-division driven for each drive block. A drive system is adopted. This divided driving method is an effective method for reducing the size of the power source for driving the head and the power source members such as connectors and cables.
[0008]
In addition, in the case of an inkjet recording head using an electrothermal conversion element, the power source for the discharge pressure generating element is a voltage value fluctuation in order to perform stable discharge in consideration of the characteristics of the electrothermal conversion element and ink. Therefore, it is not preferable to increase the capacity of the power source. The above-described separation / division driving method is also effective for satisfying such a demand for power supply.
[0009]
Hereinafter, the case where the ink jet recording head is driven by the separation and division driving method will be described in more detail with reference to the drawings.
[0010]
FIG. 4 schematically shows the nozzle row (a) of the inkjet recording head, the drive signal (b) of each nozzle, and the flying ink droplet (c) ejected from each nozzle. In FIG. 4A, the nozzle row 500 of the ink jet recording head is composed of, for example, 32 nozzles, and these nozzles are divided into four sections from the first section to the fourth section in units of eight from the top in the figure. It is divided.
[0011]
Further, each of the eight nozzles in each section belongs to one of the eight drive blocks, and is driven in a time division manner for each block during recording. That is, the nozzles in the same block are driven simultaneously.
[0012]
In the illustrated example, the first, ninth, seventeenth, and twenty-fifth nozzles of the nozzle array 500 are the first drive block, and the second, tenth, eighteenth, and twenty-sixth nozzles are the eighth drive block. Moreover, it is periodically assigned to each drive block. Then, the first drive block to the eighth drive block are sequentially driven by the pulsed drive signal 300 shown in FIG. 4B in ascending order, and each nozzle is shown in FIG. 4C corresponding to the drive signal. Ink droplets 100 are discharged.
[0013]
In addition, each nozzle has a unique peculiarity regarding the ejection direction of ink drops, the amount of ejected liquid, and the like. Such nozzle-specific wrinkles may adversely affect the recorded image and cause streaks or unevenness. In order to reduce such an adverse effect on a recorded image, a multi-pass recording method for recording an image by scanning a recording area a plurality of times with an inkjet recording head so that the same raster is recorded by two or more different nozzles Is used.
[0014]
[Problems to be solved by the invention]
In an ink jet recording apparatus, it is desirable to always keep ink in a stable discharge state. However, when ink is discharged by a discharge pressure generating element, pressure fluctuations caused by ink discharge may cause a common liquid chamber to be discharged. In some cases, the ink in the adjacent liquid path is vibrated. For this reason, when the discharge pressure generating elements disposed in the adjacent liquid paths are continuously driven, the discharge becomes unstable due to the pressure fluctuation, and the discharge liquid amount changes.
[0015]
When the amount of discharged liquid changes, it causes dark and light unevenness in the recorded image. Such fluctuations in the amount of discharged liquid due to fluctuations in ink pressure become more conspicuous as the number of nozzles that are continuously driven simultaneously increases, and the distance from the ink supply b and the common liquid chambers communicating with the respective discharge ports. The shape and the position and size of residual bubbles in the common liquid chamber are also greatly affected.
[0016]
In addition, when the number of nozzles driven at the same time changes greatly, the ink flow velocity into the liquid chamber fluctuates, and the fluctuation vibrates the meniscus surface of the nozzle through the common liquid chamber. As a result, the ejection becomes unstable and the amount of ejected ink changes, resulting in uneven density in the recorded image.
[0017]
Regarding the change in the discharge amount, it has been found by the inventors' experiment that the shaded portion of the recorded image depends on the drive block. FIG. 5 is a graph showing a drive signal for ejecting ink droplets from all nozzles at regular intervals and a distance from the meniscus orifice at that time with respect to time. As shown, for the first half drive blocks 1 to 3, the meniscus position is convex with respect to the orifice surface, and for the second half drive blocks 6 and 7, the meniscus position is concave with respect to the orifice surface. As shown, the meniscus state is specified for each drive block. The unevenness of the meniscus directly corresponds to the discharge amount.
[0018]
As described above, the ejection pressure generating elements are driven in a time-sharing manner, and are usually periodically arranged on the recording head substrate in a predetermined order. Accordingly, there arises a problem that periodic density unevenness of the recorded image occurs due to the periodic fluctuation of the ink pressure. In particular, when recording an image by multi-pass printing, if the combination of nozzle drive blocks that scan the same raster is composed only of blocks with a large ejection amount, the density unevenness of the recorded image becomes more prominent.
[0019]
In order to reduce the influence on the recorded image due to such a pressure change of the ink in the liquid chamber, the common liquid chamber is widened, or the physical distance between adjacent ejection pressure generating elements and the driving time interval are set. It has been made longer. This makes it difficult to further reduce the size of the recording head and increase the recording speed.
[0020]
The present invention has been made in view of the above circumstances, and an ink jet recording apparatus and a recording head driving method for an ink jet recording apparatus that can reduce density unevenness of a recorded image caused by periodic fluctuations in ink pressure. The purpose is to provide.
[0021]
[Means for Solving the Problems]
The ink jet recording apparatus of the present invention that achieves the above object uses a recording head having n sections (n is an integer of 2 or more) having n sections (m is an integer of 2 or more) that eject ink. In an inkjet recording apparatus that performs multi-pass recording by scanning each recording area n times with nozzles of different sections, n circuits provided corresponding to each of the n sections for driving the nozzles; A supply unit configured to configure m blocks including nozzles selected from each of the n sections, and to supply a drive timing signal for time-division driving the m blocks in a predetermined drive order; When the number of m nozzles in the n sections is numbered in the driving order in which the blocks are driven in a time-sharing manner, The supply means and the n circuits are connected so that the drive timing signal is supplied so that the numbers assigned to the n nozzles that record the same raster in each recording area are different when performing It is characterized by .
[0023]
That is, in the ink jet recording apparatus of the present invention, when performing multi-pass recording in which recording is performed by scanning a plurality of times, the nozzles used for recording the same raster in the driving method in which the nozzles are time-division driven at a plurality of timings. , Drive at the timing of at least two different blocks.
[0024]
As a result, by distributing the drive blocks used for printing each raster in a well-balanced manner, it is possible to compensate for variations in print density due to differences in the amount of ink ejection depending on each print timing in multiple print passes. Thus, density unevenness can be reduced. In other words, since dark density recording and light density recording are performed alternately, the overlap between multiple recordings cancels out the density difference between the rasters, and the average density is almost the same for all rasters. As a result, the recording quality is improved.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0026]
FIG. 1 is an external perspective view showing an outline of the configuration of an ink jet recording apparatus IJRA which is a typical embodiment of the present invention. In FIG. 1, the carriage HC that engages with the spiral groove 5004 of the lead screw 5005 that rotates via the driving force transmission gears 5009 to 5011 in conjunction with the forward / reverse rotation of the drive motor 5013 has a pin (not shown). It is supported by the guide rail 5003 and reciprocates in the directions of arrows a and b. On the carriage HC, an integrated ink jet cartridge IJC incorporating a recording head IJH and an ink tank IT is mounted.
[0027]
A paper pressing plate 5002 presses the recording paper P against the platen 5000 in the moving direction of the carriage HC. Reference numerals 5007 and 5008 denote photo-couplers which are home position detectors for confirming the presence of the carriage lever 5006 in this region and switching the rotation direction of the motor 5013.
[0028]
Reference numeral 5016 denotes a member that supports a cap member 5022 that caps the front surface of the recording head IJH. Reference numeral 5015 denotes a suction unit that sucks the inside of the cap, and performs suction recovery of the recording head through the cap opening 5023. Reference numeral 5017 denotes a cleaning blade, and reference numeral 5019 denotes a member that enables the blade to move in the front-rear direction, and these are supported by a main body support plate 5018. Needless to say, the blade is not in this form, and a known cleaning blade can be applied to this example.
[0029]
Reference numeral 5021 denotes a lever for starting suction for suction recovery, which moves in accordance with the movement of the cam 5020 engaged with the carriage, and the driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching. Is done.
[0030]
These capping, cleaning, and suction recovery are configured so that desired processing can be performed at their corresponding positions by the action of the lead screw 5005 when the carriage comes to the home position side region. As long as the above operation is performed, any of these can be applied to this example.
[0031]
Next, a control configuration for executing the recording control of the above-described apparatus will be described.
[0032]
FIG. 2 is a block diagram showing the configuration of the control circuit of the inkjet recording apparatus IJRA. In the figure showing a control circuit, 1700 is an interface for inputting a recording signal, 1701 is an MPU, 1702 is a ROM for storing a control program executed by the MPU 1701, 1703 is various data (the recording signal and recording data supplied to the head). Etc.). Reference numeral 1704 denotes a gate array (GA) that controls supply of recording data to the recording head 1708, and also performs data transfer control among the interface 1700, MPU 1701, and RAM 1703. Reference numeral 1710 denotes a carrier motor for conveying the recording head 1708, and 1709 denotes a conveyance motor for conveying the recording paper. Reference numeral 1705 denotes a head driver for driving the recording head, and reference numerals 1706 and 1707 denote motor drivers for driving the transport motor 1709 and the carrier motor 1710, respectively.
[0033]
The operation of the control configuration will be described. When a recording signal enters the interface 1700, the recording signal is converted into recording data for printing between the gate array 1704 and the MPU 1701. The motor drivers 1706 and 1707 are driven, and the recording head is driven according to the recording data sent to the head driver 1705 to perform recording.
[0034]
Here, the control program executed by the MPU 1701 is stored in the ROM 1702. However, the control program can be changed from a host computer connected to the recording apparatus by further adding an erasable / writeable storage medium such as an EEPROM. It can also be configured as follows.
[0035]
As described above, the ink tank IT and the recording head IJH may be integrally formed to constitute a replaceable ink cartridge IJC. However, the ink tank IT and the recording head IJH can be separated from each other. Then, only the ink tank IT may be exchanged when the ink runs out.
[0036]
FIG. 3 is an external perspective view showing the configuration of the ink cartridge IJC in which the ink tank and the head can be separated. In the ink cartridge IJC, as shown in FIG. 3, the ink tank IT and the recording head IJH can be separated at the position of the boundary line K. When the ink cartridge IJC is mounted on the carriage HC, an electrode (not shown) for receiving an electric signal supplied from the carriage HC side is provided, and by this electric signal, the recording head IJH as described above is provided. Is driven to eject ink.
[0037]
In FIG. 3, reference numeral 500 denotes an ink discharge port array. The ink tank IT is provided with a fibrous or porous ink absorber for holding the ink, and the ink is held by the ink absorber.
[0038]
Next, the driving method of the recording head in this embodiment will be described in detail. Here, a description will be given in comparison with the conventional example, taking as an example a recording head having eight drive blocks and four sections, that is, 8 × 4 = 32 nozzles.
[0039]
The nozzle configuration of the recording head of the conventional example is the configuration as shown in FIG. 4A described above, and the nozzle numbers and the drive block numbers correspond as shown in Table 1 below.
[0040]
[Table 1]

[0041]
Further, FIG. 7 shows the configuration of an equivalent circuit of the recording head that performs this driving. An ejection energy generating element for ejecting ink corresponding to each nozzle (which will be described using a heating resistor element as an example in the example shown here and in the following embodiments) 701 is disposed.
[0042]
Here, the drive block number represents the order of driving in one event. That is, it is driven in the order of 1, 2, 3,..., 8 (BA, BB,..., BH in FIG. 7). When an image is recorded by multi-pass printing of 4 passes with 8 pass of each pass using the print head having 32 nozzles, nozzles belonging to the same drive block are used in 8 raster cycles. Table 2 below shows the nozzles and drive blocks used for raster printing in each pass.
[0043]
[Table 2]

[0044]
In this conventional example, only the nozzles belonging to the same drive block are used to record the same raster. As a result, the density unevenness caused by the periodic pressure fluctuation depending on the drive block described above with reference to FIG. 5 is superimposed and appears more prominently.
[0045]
FIG. 6 schematically shows the nozzle row (a) of the ink jet recording head, the drive signal (b) of each nozzle, and the flying ink droplet (c) ejected from each nozzle in the present embodiment, as in FIG. FIG. FIGS. 8 to 10 show timing charts of the internal circuit of the IC, the equivalent circuit of the recording head, and the driving signal of the block for driving the present embodiment, respectively. In FIG. 6A, the nozzle array 500 of the ink jet recording head is composed of 32 nozzles, and these nozzles are divided into four sections from the first section to the fourth section, with the eight nozzles from the top as a unit. It has been.
[0046]
Further, each of the eight nozzles in each section belongs to one of the eight drive blocks, and is driven in a time division manner for each block during recording. That is, the nozzles in the same block are driven simultaneously.
[0047]
With reference to the circuit diagrams and timing charts of FIGS. 8 to 10, the circuit and drive timing of the recording head of the embodiment will be specifically described below. FIG. 8 is an internal circuit diagram of an IC for driving the recording head of the present embodiment, and FIG. 9 is a transmission circuit diagram of the recording head of the present embodiment driven using the IC having the configuration shown in FIG. FIG. 10 is a timing chart of signals for driving the recording head of FIG.
[0048]
In this embodiment, when recording is performed while the recording head is scanned once in the main scanning direction, the recording is performed for the next row while scanning in the main scanning direction after being moved in the sub scanning direction by 8 pitches. The minimum distance between nozzles that discharge simultaneously is 8 pitches. That is, eight types of drive timings BA, BB, BC, BD, BE, BF, BG, and BH are provided in the same cycle (see FIG. 10), and these are assigned to each nozzle. In FIG. 9, CLK is a clock signal, LA is a latch signal, and when 8-bit data is accumulated in the shift register, it is sent to the latch.
[0049]
B1, B2,..., B8 are recording signal lines, which are assigned from the 1st bit to the 8th bit. OUT1 to OUT8 are output signal terminals.
[0050]
In FIG. 9, IC1 is responsible for ejection from nozzle numbers 1-8, IC2 is responsible for ejection from nozzle numbers 9-16, IC3 is responsible for ejection from nozzle numbers 17-24, and IC4 is responsible for ejection from nozzle numbers 25-32. To do. As shown in FIG. 9, the combinations of the drive timing signals BA, BB,..., BH supplied to the lines B1 to B8 are different for each IC. For example, in IC1, line B1 is assigned drive timing signal BA, B2 is assigned BH, B3 is assigned BG, B4 is assigned BF, B5 is assigned BE, B6 is assigned BD, B7 is assigned BC, and B8 is assigned BB. However, in IC2, drive timing signal BH for line B1, BA for B2, BB for B3, BC for B4, BD for B5, BE for B6, BF for B7, BG for B8 Are assigned (see Table 3).
[0051]
When such a recording head is used to perform four-pass recording at a pitch of 8 pitches in the sub-scanning direction, the ink droplets ejected from which nozzle by which drive timing signal the row (raster) to which each pixel on the recording medium belongs. Table 4 shows whether they are configured as follows.
[0052]
In this embodiment, four ICs are used to drive 32 nozzles, but the output OUTn (n = 1 to 8) of each IC is different, although there is only one type of IC. Driven with timing. Such a configuration is advantageous in terms of production cost because the drive timing can be changed so as to satisfy the requirements of the present invention without increasing the types of ICs.
[0053]
In this embodiment, one drive timing is required to drive one nozzle in one IC. However, in the case of a print head having a large number of nozzles, it may be within a range that satisfies the requirements of the present invention. For example, among the nozzles driven by the same IC, the same drive timing may be assigned to at least one or more nozzles (for example, 8 in one IC having eight drive timing signal inputs of lines B1 to B8). Such as driving more than one nozzle).
[0054]
In the illustrated example, the allocation of the drive blocks to the nozzles is as shown in Table 3 below, and is not periodic as in the conventional example. Then, the first drive block to the eighth drive block are sequentially driven by the pulse-like drive signal 300 shown in FIG. 6B in ascending order, and each nozzle corresponds to the drive signal as shown in FIG. 6C. Ink droplets 100 are discharged.
[0055]
[Table 3]

[0056]
In this embodiment, as shown in Table 3, the allocation of nozzles in each drive block is different for each nozzle group and is asynchronous. When performing the 4-pass multi-pass printing, the nozzles used for printing each raster are as shown in Table 4 below.
[0057]
[Table 4]

[0058]
As can be seen from this table, unlike the conventional case shown in Table 2, in this embodiment, the numbers of the four drive blocks used for recording in each raster are all different. Further, as described above with reference to FIG. 5, the first drive block tends to have a large amount of ink discharge, and the latter drive block tends to have a small amount of ink discharge. On the other hand, in the present embodiment, in order to record each raster, the drive blocks are assigned to the nozzles so that the raster blocks are not limited to the first half or the second half.
[0059]
In this case, out of the four recording passes for recording each raster, it is preferable to use the first driving block in two recording passes and use the second driving block in two recording passes. In the present embodiment, the drive blocks belonging to the first half of the eight drive blocks and the drive blocks belonging to the second half are alternated. For example, the drive blocks used for recording with respect to raster 1 are 1, 8, 5, 4 in order from pass 1 to pass 4, and the drive blocks used for recording raster 2 are from pass 1 to pass 4. In order, they are 8, 1, 4, and 5.
[0060]
Furthermore, in this embodiment, the total value of the block numbers of the four drive blocks used for recording is equal to 18 in any raster. Of the four recording passes, the sum of the block numbers of the two driving blocks used in the first two recording passes and the sum of the block numbers of the two driving blocks used in the second two recording passes are any. Is also nine. In this way, it is possible to simplify the assignment of the four drive blocks by combining the first two pairs and the second two pairs.
[0061]
The correspondence between the nozzles and the drive blocks and the correspondence of the drive blocks used for printing each raster shown in Tables 3 and 4 is the recording data for the print head 1708 described above with reference to FIG. Are controlled and controlled by a gate array (GA) 1704 that controls the supply of the data.
[0062]
As described above, in this embodiment, by distributing the drive blocks used for printing each raster in a balanced manner, the ink ejection amount depending on the drive block used at each printing end is obtained in four printing passes. Density unevenness can be reduced by compensating for the resulting recording density variation. That is, since the dark density recording and the light density recording are alternately performed, the overlap between the four recordings cancels out the density difference between the rasters, and the average density is almost the same for all rasters. As a result, the recording quality is improved.
[0063]
In the above embodiment, the liquid droplets ejected from the recording head have been described as ink, and the liquid stored in the ink tank has been described as ink. However, the storage is limited to ink. It is not a thing. For example, a treatment liquid discharged to the recording medium may be stored in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.
[0064]
In the previous embodiment, the heating resistor has been described as an ejection energy generating element for ejecting ink. However, the present invention is not limited to this, and an element such as a piezo may be used.
[0065]
The above embodiment includes means (for example, an electrothermal converter, a laser beam, etc.) that generates thermal energy as energy used for performing ink discharge, particularly in the ink jet recording system, and the ink is generated by the thermal energy. By using a system that causes a change in the state of recording, it is possible to achieve higher recording density and higher definition.
[0066]
As its typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recording information and applying a rapid temperature rise exceeding the film boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface of the liquid, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed.
[0067]
By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, since the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve discharge of a liquid (ink) having particularly excellent responsiveness.
[0068]
As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.
[0069]
As the configuration of the recording head, in addition to the combination configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting surface The configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which is disposed in a bending region, are also included in the present invention. In addition, Japanese Patent Application Laid-Open No. 59-123670, which discloses a configuration in which a common slot is used as a discharge portion of an electrothermal transducer, or an opening that absorbs a pressure wave of thermal energy is discharged to a plurality of electrothermal transducers. A configuration based on Japanese Patent Laid-Open No. 59-138461 disclosing a configuration corresponding to each part may be adopted.
[0070]
Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is satisfied by a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration or a configuration as a single recording head formed integrally may be used.
[0071]
In addition to the cartridge-type recording head in which the ink tank is integrally provided in the recording head itself described in the above embodiment, it can be electrically connected to the apparatus body by being attached to the apparatus body. A replaceable chip type recording head that can supply ink from the apparatus main body may be used.
[0072]
In addition, it is preferable to add recovery means, preliminary means, and the like for the recording head to the configuration of the recording apparatus described above because the recording operation can be further stabilized. Specific examples thereof include a capping unit for the recording head, a cleaning unit, a pressurizing or sucking unit, an electrothermal converter, a heating element different from this, or a preheating unit using a combination thereof. In addition, it is effective to provide a preliminary ejection mode for performing ejection different from recording in order to perform stable recording.
[0073]
Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrated or may be a combination of a plurality of colors. An apparatus having at least one of full colors can also be provided.
[0074]
In the embodiment described above, the description is made on the assumption that the ink is a liquid, but it may be an ink that is solidified at room temperature or lower, or an ink that is softened or liquefied at room temperature, Alternatively, the ink jet method generally controls the temperature of the ink so that the viscosity of the ink is within a stable discharge range by adjusting the temperature within a range of 30 ° C. or higher and 70 ° C. or lower. It is sufficient if the ink sometimes forms a liquid.
[0075]
In addition, it is solidified in a stand-by state in order to actively prevent temperature rise by heat energy as energy for changing the state of ink from the solid state to the liquid state, or to prevent ink evaporation. Ink that is liquefied by heating may be used. In any case, by applying heat energy according to the application of thermal energy according to the recording signal, the ink is liquefied and liquid ink is ejected, or when it reaches the recording medium, it already starts to solidify. The present invention can also be applied to the case of using ink having the property of being liquefied for the first time.
[0076]
In such a case, the ink is held as a liquid or solid in a porous sheet recess or through-hole as described in JP-A-54-56847 or JP-A-60-71260, It is good also as a form which opposes with respect to an electrothermal converter. In the present invention, the most effective one for each of the above-described inks is to execute the above-described film boiling method.
[0077]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.
[0078]
Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0079]
Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0080]
【The invention's effect】
As described above, according to the present invention, by distributing the drive blocks used for printing each raster in a well-balanced manner, the difference in ink discharge amount depending on each printing timing can be obtained in a plurality of printing passes. Density unevenness can be reduced by compensating for the resulting recording density variation. In other words, since dark density recording and light density recording are performed alternately, the overlap between multiple recordings cancels out the density difference between the rasters, and the average density is almost the same for all rasters. Thus, the recording quality is improved.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing a configuration of an ink jet recording apparatus which is a representative embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a control unit of the printer of FIG.
FIG. 3 is an external perspective view showing a configuration of an ink cartridge.
FIG. 4 is a diagram schematically showing nozzle rows of a conventional ink jet recording head, drive signals for each nozzle, and flying ink droplets ejected from each nozzle.
FIG. 5 is a graph showing a driving signal for periodically ejecting ink droplets from all nozzles and a state of a meniscus surface at that time with respect to time.
FIG. 6 is a diagram schematically showing nozzle rows of the ink jet recording head of the present invention, drive signals for each nozzle, and flying ink droplets ejected from each nozzle.
FIG. 7 is a circuit diagram illustrating an example of an equivalent circuit of a conventional recording head.
FIG. 8 is a circuit diagram showing an internal configuration of a printhead driving IC according to an embodiment of the present invention.
9 is a circuit diagram of an equivalent circuit of a recording head according to an embodiment of the present invention driven by the IC of FIG.
10 is a timing chart of signals supplied to the recording head of FIG.
[Explanation of symbols]
IJH recording head 100 ink droplet 300 drive signal 500 nozzle array

Claims (4)

  Using a recording head having n sections (m is an integer of 2 or more) that includes m nozzles (m is an integer of 2 or more) that eject ink, each recording area is scanned n times by nozzles of different sections. In an inkjet recording apparatus that performs multipass recording,
  N circuits provided corresponding to each of the n sections for driving the nozzle;
  A supply unit configured to configure m blocks including nozzles selected from each of the n sections, and to supply a drive timing signal for time-division driving the m blocks in a predetermined drive order;
N, which records the same raster in each recording area when performing multi-pass recording when the m nozzles in the n sections are numbered in the driving order in which the blocks are time-division driven. An ink jet recording apparatus, wherein the supply means and the n circuits are connected so that drive timing signals are supplied so that the numbers assigned to the nozzles are different.   2. The ink jet recording apparatus according to claim 1, wherein the numbers assigned to the n nozzles that record the same raster are constituted by pairs of numbers belonging to the first half and numbers belonging to the second half.   3. The ink jet recording apparatus according to claim 1, wherein a total of numbers assigned to n nozzles that record the same raster is equal among m rasters.   4. The recording head according to claim 1, wherein the recording head is a recording head that discharges ink by using thermal energy, and includes an electrothermal transducer for generating thermal energy for each nozzle. The ink jet recording apparatus according to any one of the above.

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