JP4110774B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of previously preventing a separation defect of a recording paper, a spatter of toner, etc., caused by an insufficient static elimination due to a variation of performance of a static elimination needle such as discharging performance, static elimination performance, etc., in a static eliminator. <P>SOLUTION: The image forming apparatus is provided with a control means for measuring a discharge initiating voltage Vh1 when the static elimination needle is not used and a discharge initiating voltage Vh2 at the predetermined step after the static elimination needle is used e.g. when a cartridge is replaced, and indicating an alarm for prompting a user to clean or replace the static elimination needle based on a difference between both discharge initiating voltages. <P>COPYRIGHT: (C)2003,JPO

Description

【００６９】
この表１から明らかなように、未使用時の放電開始電圧（−２５００Ｖ）に対しプリント枚数が増加するにつれて放電開始電圧が徐々に変動（増加）し、プリント枚数が２００ｋ枚を超える頃になると、剥離不良やトナー飛び散りが発生するようになる。
【００７０】
そこで、このような特性があることに鑑み、前記警告表示を行う際の判断基準である閾値Ｍについては、交換用の警告表示を行うために「８００（Ｖ）」に設定し、また清掃用の警告表示を行うためには「５００（Ｖ）」に設定した。この閾値Ｍはいずれも、放電開始電圧の差分が超えて、プリント枚数が１５０ｋ枚に達する前の段階で警告表示が行われるような値であるため、剥離不良やトナー飛び散りが発生する時期（プリント枚数が２００ｋ枚を超えるとき）よりも前に、除電針６０の清掃や交換を行うことが可能となる。
【００７１】
［実施の形態２］
図１０乃至図１２は、実施の形態２に係るプリンタの要部構成を示すものである。この実施の形態に係るプリンタは、除電装置６の警告表示に関する制御内容の一部を変更した以外は実施の形態１に係るプリンタと同じ構成からなるものである。
【００７２】
すなわち、このプリンタでは、制御装置７により、実施の形態１の場合と同様に除電装置６における除電針６０の清掃又は交換を促す警告表示を行うか否かの判断に当たり、除電針６０の針状電極板６１の未使用時における放電開始電圧Ｖｈ１の測定結果に基づいて除電用電源装置６５から印加する除電用電圧Ｖｅの基準値（Ｖ_std１）を設定するとともに、その電極板６１のプロセスカートリッジ交換時における放電開始電圧Ｖｈ２の測定結果に基づいて除電用電圧Ｖｅの基準値（Ｖ_std２）を再設定し、その双方の基準値（Ｖ_std１、Ｖ_std２）の差分に基づいて上記電極板６１に関する警告表示を行うように設定している（図１０）。
【００７３】
まず、電極板６１の未使用時における除電用電圧Ｖｅの基準値（Ｖ_std１）の設定は、図１１のステップＳ１０〜Ｓ１６で示すように、未使用時における放電開始電圧Ｖｈ１の測定を実施の形態１の場合（図７のステップＳ１０〜Ｓ１６）と同様に行った後、その放電開始電圧Ｖｈ１を除電用電圧Ｖｅの初期段階の基準値Ｖ_std１として設定する（Ｓ５０）。この設定した基準値Ｖ_std１については制御装置７の記憶部に記憶保持される。
【００７４】
これにより、プリンタ（除電装置６）単位で存在し得る、針状電極板６１の製造上における形状寸法の誤差や取り付け状態の誤差があっても、初期段階における放電開始電圧Ｖｈ１を実測してプリンタ（除電装置６）固有の除電用電圧Ｖｅの基準値Ｖ_stdを決定することにより、初期誤差に左右されることなく予定通りの放電特性ひいては除電性能を得ることが可能になる。ちなみに、このプリンタでは、次にカートリッジ交換時までの間は、その設定した基準値Ｖ_std１に所定の係数ｋ（例えばｋ＝０．６）を乗じた電圧、すなわち０．６・Ｖ_std１を除電用電圧Ｖｅとして実際に印加する。
【００７５】
一方、カートリッジ交換時における除電用電圧Ｖｅの基準値（Ｖ_std２）の設定は、図１２のステップＳ２０〜Ｓ２９で示すように、カートリッジ交換時における放電開始電圧Ｖｈ２の測定を実施の形態１の場合（図８のステップＳ２０〜Ｓ２９）と同様に行った後、その放電開始電圧Ｖｈ２（補正係数ｄｍを乗じたもの）を除電用電圧Ｖｅのカートリッジ交換時の基準値Ｖ_std２として設定する（Ｓ６０）。この再設定した基準値Ｖ_std２については制御装置７の記憶部に初期段階の基準値に置き換えて記憶保持される。
【００７６】
これにより、針状電極板６１がトナー等の付着により経時的に汚染されることがあっても、プロセスカートリッジ１０の交換時における放電開始電圧Ｖｈ２を実測してプリンタ（除電装置６）固有の使用後で所定の時期における除電用電圧Ｖｅの基準値Ｖ_std２（＝ｄｍ・Ｖｈ２）を決定することにより、経時変動に左右されることなく予定通りの放電特性ひいては除電性能を得ることが可能になる。ちなみに、このカートリッジ交換後においては、その再設定した基準値Ｖ_std２に所定の係数ｋ（例えばｋ＝０．６）を乗じた電圧、すなわち０．６・Ｖ_std２を除電用電圧Ｖｅとして実際に印加する。
【００７７】
そして、制御装置７では、図１０に示すように、プロセスカートリッジ１０が新品のものに交換されたことが検知されると（Ｓ４０）、未使用時における除電用電圧Ｖｅの基準値Ｖ_std１とカートリッジ交換時の除電用電圧Ｖｅの基準値Ｖ_std２を読み出した後（Ｓ４１）、その基準値Ｖ_std１、Ｖ_std２の差分（＝｜Ｖ_std２｜−｜Ｖ_std１｜）を求め、その差分が予め設定した閾値Ｍより大きくなるか否かが判別される（Ｓ４２）。
【００７８】
この際、その差分が閾値Ｍよりも大きいと判断されると、針状電極板６１の放電性能（ひいては除電性能）が低下したとみなし、表示装置８を介して必要な警告表示をする（Ｓ４３）。警告表示は、除電針６０の清掃を促す警告メッセージ（例えば「除電針を清掃してください」）又は除電針６０の交換を促す警告メッセージ（例えば「除電針を交換してください」）が表示される。閾値Ｍは、例えば交換用の警告表示を行う場合には「１５００（Ｖ）」に設定し、また、清掃用の警告表示を行う場合には「１０００（Ｖ）」に設定される。
【００７９】
表２は、このプリンタにおける除電装置６の性能の推移状態について行った実験の測定結果を示すものである。
【００８０】
この実験は、除電針（ＤＴＳ）６０に印加する除電用電圧Ｖｅとして、プリント枚数５０ｋ枚ごとに測定した放電開始電圧に基づいて（再）設定する各基準値（＝放電開始電圧）に係数ｋ＝０．６を乗じた電圧を印加した以外は実施の形態１における実験と同じ条件で行っている。
【００８１】
【表２】

【００８２】
この表２から明らかなように、未使用時の放電開始電圧（−２５００Ｖ）に対しプリント枚数が増加するにつれて放電開始電圧が徐々に変動（増加）するが、除電用電圧Ｖｅとして再設定する基準値にもとづく電圧を印加するようにしているため、プリント枚数が３００ｋ枚を超える頃になると、剥離不良やトナー飛び散りが発生し始めるようになる。この点、プリント枚数が２００ｋ枚を超える頃に剥離不良等が発生し始めていた実施の形態１における実験結果（表１）と比べると、その剥離不良等の発生時期を遅らせることができ、これにより、除電針６０の使用可能な期間を、本来その性能低下が発生し始めているにもかかわらずある程度延長できることが確認された。
【００８３】
また、このような特性があることに鑑み、前記警告表示を行う際の判断基準である閾値Ｍについては、交換用の警告表示を行うために「１５００（Ｖ）」に設定し、また清掃用の警告表示を行うためには「１０００（Ｖ）」に設定した。特に、この各警告表示を行う判断基準用の閾値Ｍに関しては、実施の形態１における閾値と比べると、前記した除電針６０の使用可能な期間を基準値の再設定によりある程度延長できることに起因して、警告表示を行う判断基準となる差分の値を大きめに設定して電極部材のライフを擬似的に伸ばして有効利用できることが確認された。
【００８４】
ここで、表２に示されるように、プリント枚数が３００ｋ枚及び３５０ｋ枚において放電開始電圧が「−４０００Ｖ」のままとなりプリント枚数２５０ｋ枚のときの放電開始電圧と同じになっているが、これは、除電用電源装置６５の電源容量の最大値が−４０００Ｖであって、これ以上の高電圧を印加できないことによるものである。したがって、このときの放電開始電圧は放電開始とみなす電流値（Ｉｘ）の「−５μＡ」に達する前のものであるため、そのときに印加した除電用電圧Ｖｅは本来印加すべきものに比べて少なめの電圧になっている。
【００８５】
この実施の形態２では、除電用電圧の基準値を再設定による補正をしながら除電針６０の汚染による性能劣化を補うことにより剥離不良等の不具合の発生時期を遅らせ、除電針６０の使用可能な時期についてもある程度延長できるが、その反面、除電用電源装置６５の電源容量の最大値（Ｖ_MAX）との関係から、初期時の放電開始電圧の値（基準値にも相当する）の大きさや警告表示の判断基準である閾値Ｍの設定内容によっては、カートリッジ交換時等における放電開始電圧の測定時に印加する測定用電圧が電源容量の最大値では足りず正確に測定することができなくなり、その結果、閾値Ｍを超える場面がなくなり、警告表示ができなくなるおそれもある。
【００８６】
そこで、このような除電用電源装置６５の電源容量を考慮しながら警告表示を行うか否かの判断を行う観点から、図１３に示すように、除電用印加電圧の基準値の設定時に測定する放電開始電圧の値が電源容量の最大値（Ｖ_MAX）以上になるか否かを判断し（Ｓ７０）、その最大値以上である場合には、さらに放電開始電圧測定時の電流値Ｉｎが放電開始とみなす電流値Ｉｘ未満であるか否かを判断し（Ｓ７１）、その電流値Ｉｘ未満であると判断された場合には、前記した各警告表示を、前記閾値Ｍを超えるか否かの判断結果よりも優先して行うように構成するとよい。このような警告表示の判断は、例えば、カートリッジ交換時の基準値を再設定する過程（図１２のステップＳ２７）で測定する放電開始電圧のデータを援用して並行処理するように構成する。
【００８７】
ちなみに、実施の形態１、２においては、除電針６０が、図３に示すように針状電極板６１と電極ホルダー板６２とが一体となって取り外し可能である構造を採用しているため、除電針６０の交換を行う際には、電極ホルダー板６２も同時に交換されることになる。
【００８８】
これにより、このプリンタにおける転写部位と転写部４とを結ぶ中継用の用紙搬送路５ｂのように円弧状に湾曲した経路形態（Ｃ字型の経路）になっている場合には、特に、転写部から通過排出された記録用紙Ｐの後端部が湾曲状態で搬送される反動により転写部位を排出した直後に除電針６０側に触れた状態で移動し、電極ホルダー６２の保護用突出部６２ａに接触しながら通過しやすく、この接触通過が長期にわたり繰り返されることによって保護用突出部６２ａの接触部が次第に磨耗して図４ｂ中に示す二点鎖線Ｃの上部側が削れてなくなり、保護突出部６２ａの上端部に尖鋭な角部６２ｃが形成されることになるが、かかる角部６２ｃが形成された電極ホルダー６２も除電針６０の交換と同時に新しいものに交換される。この結果、かかる角部６２ｃと記録用紙Ｐとの接触時に異常放電が起こってトナー飛び散り等が発生するという不具合を回避することができる。
【００８９】
なお、実施の形態１では、環境条件について環境検知センサ１８により検知する場合を例示したが、この検知センサ１８に代えて、湿度や温度等の環境変化に伴って変化する転写ロール１５ａの抵抗値を間接的に測定した結果を利用して検知するようにしてもよい。図１８は、転写用電源装置１５ｂから転写ロール１５ａに電圧を印加したときの電流値を調べた場合における電圧−電流特性を示すものである。この図に示すように、電圧−電流特性は各環境条件によって異なることから、電源装置１５ｂから一定の測定用電圧を印加したときの電流値を計測すれば、環境条件を判断することができる。
【００９０】
また、実施の形態１では、除電針の電極板６１の経時的な放電開始電圧Ｖｈ２の測定をプロセスカートリッジ交換時に行うように設定したが、これ以外の時期に行うように設定することも可能であり、例えば、電源投入時ごとに実行するように設定してもよい。
【００９１】
【発明の効果】
以上説明したように、本発明の画像形成装置によれば、除電用の電極部材の未使用段階及び所定経過段階における放電開始電圧性能の測定結果に基づいてその電極部材に関する警告表示がなされるため、かかる電極部材の放電性能ひいては除電性能の変動に伴う除電不足に起因する記録媒体の剥離不良や現像剤（トナー）のトナーの飛び散り等の発生を未然に防ぐことができる。
【００９２】
したがって、このような画像形成装置にあっては、除電不足に起因した記録媒体の剥離不良や現像剤飛び散り等の不具合の発生が確実に防止され、かかる不具合の発生がない良好な画像形成を行うことが可能となる。
【図面の簡単な説明】
【図１】 実施の形態１に係るプリンタを示す概要図。
【図２】 図１のプリンタの要部を示す拡大断面図。
【図３】 図２においてプロセスカートリッジを取り外した後の除電装置を含む部位を示す断面図。
【図４】 除電装置の除電針の構成を示すもので、（ａ）はその感光ドラムとの位置関係などを示す正面図、（ｂ）は（ａ）のＢ−Ｂ線断面図。
【図５】 除電装置などの制御系の構成を示す説明図。
【図６】 放電開始電圧の差分に基づく警告表示を行うための制御内容を示すフローチャート。
【図７】 電極板の未使用時における放電開始電圧を測定するための制御内容を示すフローチャート。
【図８】 経過段階（カートリッジ交換時）における放電開始電圧を測定するための制御内容を示すフローチャート。
【図９】 未使用時の放電開始電圧の測定時における各動作を示すタイミンチャート。
【図１０】 除電用電圧の基準値の差分に基づく警告表示を行うための制御内容を示すフローチャート。
【図１１】 初期段階の放電開始電圧に基づく除電用電圧の基準値を設定するための制御内容を示すフローチャート。
【図１２】 経過段階（カートリッジ交換時）の放電開始電圧に基づく除電用電圧の基準値を再設定するための制御内容を示すフローチャート。
【図１３】 電源装置の電源容量を考慮した警告表示を行うための制御内容を示すフローチャート。
【図１４】 感光ドラムとの離間距離を異にする場合における除電針の電極部材に関する電圧−電流特性の測定結果を示すグラフ図。
【図１５】 新品時及び一定使用後における除電針の電極部材（ｄ＝４．５ｍｍ）に関する電圧−電流特性の測定結果を示すグラフ図。
【図１６】 新品時及び一定使用後における除電針の電極部材（ｄ＝５．０ｍｍ）に関する電圧−電流特性の測定結果を示すグラフ図。
【図１７】 測定時の環境条件が異なる場合における除電針の電極部材に関する電圧−電流特性の測定結果を示すグラフ図。
【図１８】 測定時の環境条件が異なる場合における転写ロールに関する電圧−電流特性の測定結果を示すグラフ図。
【符号の説明】
７…制御装置（制御手段）、８…表示装置、１１…感光ドラム（像担持体）、１５…転写装置（転写手段）、６０…除電針（電極部材）、６１…針状電極板（電極本体）、６２…電極ホルダー（電極保持部材）、６２ａ…保護用突出部、６５…除電用電源装置（電圧印加手段）、Ｖｈ１…未使用時の放電開始電圧、Ｖｈ２…カートリッジ交換時（使用後の所定段階）の放電開始電圧、Ｐ…記録用紙（記録媒体）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, or a multi-function machine that forms an image made of a developer, and more particularly, to a static eliminating device that neutralizes a recording medium such as a recording sheet on which the image is finally formed. The present invention relates to an image forming apparatus provided.
[0002]
[Prior art]
In an image forming apparatus using an electrophotographic method or the like, an image (toner image) made of a developer is formed on an image carrier such as a photoconductor by an electrophotographic process according to image information, and the image is then recorded on a recording medium. An image is formed on a recording medium by transferring the image directly or via an intermediate transfer member and fixing the image on the recording medium thereafter or simultaneously. In this case, the transfer of the image to the recording medium is mainly performed by utilizing an electrostatic action, and in recent years, a roll that passes the recording medium in a state of pressing the recording medium against the image carrier or the intermediate transfer body. This is performed by using a transfer means having a configuration in which a contact-type transfer member having a form or the like is arranged and a transfer voltage is applied to the transfer member.
[0003]
In such an image forming apparatus, a static eliminator is disposed for the purpose of neutralizing a recording medium immediately after transfer (including reduction of charged charges). The static eliminator generally includes a recording medium and an electrode member disposed in a state where the transfer member can approach and oppose the recording medium in the width direction at the time of conveyance at a position near the downstream side in the recording medium feeding direction. What is comprised with the voltage application means which applies the predetermined voltage for static elimination to an electrode member is used. Among these, as the electrode member, a plate-like member (so-called static elimination needle) whose tip end facing the recording medium has a sharp shape such as a saw blade is often used.
[0004]
By the way, when using this static elimination apparatus, it is said that the static elimination performance is likely to change due to fluctuations in the use environment conditions governed by temperature and humidity, and it is difficult to maintain the proper static elimination performance. When the static elimination performance fluctuates (particularly decreases), the recording medium immediately after transfer may not be peeled off from the image carrier or the like due to insufficient static elimination, or the toner of the image transferred to the recording medium may scatter. A malfunction will occur.
[0005]
In order to avoid such problems, conventionally, for example, means for adjusting the voltage for static elimination (JP-A-9-114337, JP-A-9-40225), recording medium material, thickness, etc., according to environmental conditions. Means for adjusting the static elimination voltage according to the size and the like (Japanese Patent Laid-Open No. 10-39641) have been proposed. In order to cope with differences in environmental conditions and recording medium conditions at the time of actual image formation, all of these attempts to stabilize the neutralization performance mainly by focusing on the voltage for neutralization applied to the electrode members. Yes.
[0006]
However, even when the static elimination voltage is appropriately adjusted in this way, the electrode member is gradually contaminated by the adhesion of the developer and the discharge product and the discharge characteristics are lowered, so that sufficient static elimination performance is finally obtained. In some cases, this results in insufficient static elimination and causes the above-described problems such as poor recording medium peeling and toner scattering.
[0007]
For this reason, for example, in the above-mentioned Japanese Patent Application Laid-Open No. 9-40225, a detection means (separation detection sensor) for detecting a separation failure of the recording medium from the image carrier after transfer is provided, and a detection result from this detection means. In response to this, it has been proposed to be configured to issue an alarm for prompting replacement of the static elimination needle.
[0008]
[Problems to be solved by the invention]
However, the solution means for issuing an alarm according to the detection result of the detection means has the following problems.
[0009]
First, an alarm is not issued unless a recording medium separation (separation) defect actually occurs, and the occurrence of such a separation defect or toner scattering cannot be prevented. In addition, when a recording medium separation failure occurs due to a factor other than the deterioration of the performance of the static elimination needle, an alarm will be issued and the static elimination needle will be replaced. It must be exchanged, forcing improper exchange.
[0010]
The present invention has been made in view of these circumstances, and the main object of the present invention is a recording medium caused by a shortage of charge removal due to fluctuations in the performance of the electrode member for charge removal (discharge performance and hence charge removal performance). It is an object of the present invention to provide an image forming apparatus capable of preventing the occurrence of poor peeling and toner scattering.
[0011]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes an image carrier that carries an image composed of a developer, a transfer unit that transfers an image on the image carrier to a recording medium, and a proximity of the recording medium in the vicinity of the transfer unit. In an image forming apparatus comprising a static elimination electrode member disposed so as to be opposed to each other and a voltage application means for applying a static elimination voltage to the electrode member, discharge start in an unused stage of the electrode member Control means is provided for measuring a voltage and a discharge start voltage at a predetermined stage after use, and displaying a warning regarding the electrode member based on a difference between the two discharge start voltages.
[0012]
Here, the predetermined stage after use refers to a stage where a predetermined time or period has passed since the electrode member actually started to be used. The difference between the two discharge start voltages can be arbitrarily set. For example, after examining in advance the correlation between the magnitude of the difference and the presence or absence of occurrence of separation failure of the recording medium or toner scattering. It is good to set as appropriate. The warning display can be performed by display means such as a liquid crystal panel capable of displaying a warning message on the screen, but may be performed by other display means such as a lamp and a voice guide. The warning display regarding an electrode member is a warning notifying the advance action which should be taken about the electrode member with respect to the discharge performance of that electrode member, and the fall of static elimination performance.
[0013]
The image carrier is a photoreceptor, an intermediate transfer member, or the like. The transfer means is preferably a contact-type transfer device in which a transfer member is brought into contact with the image carrier, but other transfer systems may be used. The developer develops the latent image and is, for example, a dry toner. Further, the recording medium can record and form an image made of a developer, such as various recording papers, OHP sheets, thin paper, postcards, envelopes, and the like.
[0014]
According to such an image forming apparatus, the warning display regarding the electrode member is performed based on the difference between the measurement results of the discharge start voltage at the unused stage of the electrode member and the discharge start voltage at the predetermined stage after the use. As a result, a warning is given based on information indicating that the actual discharge performance of the electrode member has deteriorated, so that appropriate measures can be taken before discharge shortage due to fluctuations in the discharge performance of the electrode member and thus the charge removal performance occurs.
[0015]
As the warning display, it is preferable to perform either or both of a display prompting cleaning of the electrode member and a display prompting replacement of the electrode member. In the case of a warning message for prompting cleaning, it is possible to prevent the occurrence of problems by recovering the performance recovery by cleaning work without having to replace the electrode member, and the electrode member can be effectively used. For example, when performing a warning display for prompting cleaning and a warning display for prompting replacement, for example, the difference value (threshold) serving as a criterion for warning display for prompting cleaning is set to a value smaller than that of the warning display for prompting replacement. It may be configured so that the cleaning display is performed while the difference value is relatively small, and the replacement display is performed when the difference value becomes large.
[0016]
And about the control means in this image forming apparatus, while setting the reference value of the voltage for static elimination applied from the said voltage application means based on the measurement result of the discharge start voltage in the unused stage of the said electrode member, the said electrode The reference value of the voltage for discharging may be reset based on the measurement result of the discharge start voltage at a predetermined stage after use of the member.
[0017]
In this case, setting the reference value of the static elimination voltage based on the discharge start voltage means that the discharge start voltage is used as it is as a reference value or is measured with a reference value at the time of initial setting prepared in advance. This is the case where the initial setting reference value is replaced with the discharge start voltage when the difference with the discharge start voltage is compared to a predetermined value or more. In addition, resetting the reference value for the static elimination voltage based on the discharge start voltage means that the discharge start voltage is used as a new reference value as it is, or the previous reference value and the newly measured discharge start voltage are When the difference at that time is equal to or greater than a predetermined value, the immediately preceding reference value is replaced with a new discharge start voltage.
[0018]
When configured in this way, even if there are variations in the size and shape of the electrode member, the mounting state, etc. between the devices in the unused stage (when new or before first use), the electrode member Since the reference value of the neutralization voltage based on the actual (unique) discharge characteristics is set, the desired discharge expected by applying the neutralization voltage based on the set standard value to the electrode member It is possible to obtain the characteristic ability and the charge eliminating performance. In addition, even if the electrode member may become contaminated due to adhesion of developer, discharge products, etc. after the start of use, it is used for static elimination based on the actual (inherent) discharge characteristics of the electrode member at the predetermined stage. Since the reference value of the voltage is reviewed and reset, by applying a voltage for static elimination based on the reset reference value to the electrode member, the desired discharge characteristic ability comparable to the initial stage It is possible to obtain static elimination performance.
[0019]
As a result, the discharge characteristics of the electrode member can be optimized and stabilized, and as a result, good static elimination performance can be obtained. In addition to this, the usable period of the electrode member can be extended to some extent despite the fact that performance deterioration has started to occur, and the value of the difference serving as a judgment criterion for performing the warning display is set to a larger value. Thus, it is possible to effectively use the electrode member by artificially extending the life of the electrode member.
[0020]
Regarding the measurement of each discharge start voltage, it is possible to configure the actual discharge start voltage at each stage of the electrode member with high accuracy, but the viewpoint that simple and efficient measurement is possible. From the above, when a voltage for measurement is applied to the electrode member, and the voltage value when the current value accompanying the voltage application reaches a current value that is regarded as the discharge start specified in advance is measured as the discharge start voltage. Good.
[0021]
In this case, the voltage for measurement is usually applied by the voltage application means of the static eliminator, but may be configured to be applied by other voltage application means. The measurement voltage may be applied while increasing the voltage value from zero at a constant rate. However, from the viewpoint of shortening the measurement time, the voltage for measurement starts to be applied from a certain voltage value. It is good to apply so that it may increase at the rate.
[0022]
In addition, the measurement of each discharge start voltage can be performed at any time, but from the standpoint that proper measurement is possible by eliminating errors in the measurement results in the presence of the recording medium. It may be set to be performed when the recording medium is not passed. In this case, the non-passing time may be any time when the recording medium does not exist in the vicinity of the electrode member at the time of measurement. Preferably, for example, when the power is turned on, the replacement consumable part is replaced, or the preset number of times of image formation This is the non-image formation time at the time of the next image formation opening operation (job) after reaching the above. In addition, since the discharge performance over time of the electrode member tends to gradually decrease rather than suddenly decrease, the measurement of the discharge start voltage at the predetermined time after use is necessary for each job. However, it is sufficient to perform it at a relatively long cycle such as once a day or every time when replacement consumable parts are replaced.
[0023]
In addition, the measurement of the discharge start voltage in the aging stage after the use of the electrode member is preferably performed under the same environmental conditions as the measurement of the discharge start voltage in the unused stage of the electrode member. However, the environmental conditions when measuring the discharge start voltage in the aging stage after use are not the same as the environmental conditions when measuring the discharge start voltage in the unused stage, and the measurement cannot be performed at a desired time. From the viewpoint of solving the problem, the following configuration is preferable.
[0024]
That is, a correction coefficient for measuring the discharge start voltage according to the difference in environmental conditions is prepared in advance, and the correction coefficient according to the environmental condition when measuring the discharge start voltage at a predetermined stage after use of the electrode member The discharge start voltage is selected based on the difference from the environmental conditions at the time of measurement of the discharge start voltage in the unused stage, and is corrected by multiplying the discharge start voltage measured in the predetermined stage by the selected correction coefficient.
[0025]
In this case, the environmental conditions are the conditions of the usage environment governed by temperature and humidity. This environmental condition may be measured directly using a detection means such as a humidity sensor or a temperature sensor, or may be a physical quantity that changes with an environmental change such as humidity or temperature (for example, the resistance of the transfer member of the transfer means). Value) may be measured directly or indirectly. The correction coefficient for measuring the discharge start voltage is, for example, the measurement of the discharge start voltage of the electrode member in the unused period in advance under various environmental conditions, and the measurement results under each environmental condition are measured under different environmental conditions. The coefficient values for correction necessary for making the values equal to the values of (1) may be prepared in a (contrast) table.
[0026]
Further, in the image forming apparatus as described above, the electrode member holds an electrode body having a sharp tip on the side facing the recording medium, and the electrode body from the outside to the tip. It is preferable to apply an electrode holding member in a form in which a protective protrusion for preventing contact is formed, and the electrode body and the electrode holding member can be removed integrally.
[0027]
In this case, a sharp corner is formed by the recording medium passing through the protective protrusion of the electrode holding member over a long period of time and wearing, and abnormal discharge occurs when the corner contacts the recording medium. Toner splattering may occur, but the electrode member may be cleaned or replaced by a warning display, so check the state of the protective protrusion at that time, and if necessary, only the electrode holding member or It can be exchanged together with the electrode body. As a result, the occurrence of toner scattering and the like due to the formation of the sharp angle is avoided.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
FIG. 1 shows a printer according to Embodiment 1 of the present invention.
[0029]
<Configuration of the entire printer>
This printer has a main body 1 composed of a support frame, an exterior cover, and the like, and an image forming unit 2, a paper feeding unit 3, a fixing unit 4 and a paper conveyance path 5 arranged and formed inside the main body 1, and the main parts thereof are It is configured.
[0030]
The image forming unit 2 includes a photosensitive drum 11, a roll charging device 12, a latent image forming device 13, a developing device 14, a roll transfer device 15, a cleaning device 16, and the like. In particular, in this image forming unit 2, as shown in FIGS. 2 and 3, etc., the photosensitive drum 11, the charging device 12, the developing device 14, and the cleaning device 16 are integrated and detachably attached to the main body 1. The process cartridge 10 is configured to be replaced with a new process cartridge based on reference information such as the deterioration time of the photosensitive drum 11 and the developer consumption time of the developing device 14.
[0031]
In the image forming unit 2, a photosensitive layer made of an organic photoconductive material or the like is formed on the peripheral surface of a cylindrical rotary support, and the photosensitive layer is rotated in a direction indicated by an arrow A by a driving force of a driving motor (not shown). The peripheral surface (photosensitive layer) of the photosensitive drum 11 is uniformly charged by the charging device 12. The charging device 12 performs charging by applying a charging voltage (charging bias) to a charging roll that rotates in contact with the peripheral surface of the photosensitive drum 11. In the charging device 12, since the photosensitive layer of the photosensitive drum 11 is negatively charged, charging is performed by applying a charging bias in which alternating current is superimposed on negative direct current to the charging roll.
[0032]
An electrostatic latent image corresponding to the image information is formed on the circumferential surface of the uniformly charged photosensitive drum 11 by the latent image forming device 13. The latent image forming device 13 emits light (light beam) Bm emitted from a light emitting source such as a semiconductor laser based on an image signal obtained by performing predetermined image processing on image information input from a document reading device or an externally connected device. A latent image is formed by being guided to the peripheral surface of the photosensitive drum 11 through predetermined optical system parts (lenses, reflecting mirrors, rotating polygon mirrors, etc.) and scanning exposure. The light Bm is irradiated on the photosensitive drum 11 through a gap 10a formed between the charging device 12 and the developing device 14 of the process cartridge 10.
[0033]
The electrostatic latent image formed on the photosensitive drum 11 is developed by the developing device 14 to be visualized. The developing device 14 is a one-component developing device that uses a one-component developer made of toner (T), and is stirred by a stirring and conveying member 21 such as an agitator that rotates inside a main body 20 that contains the one-component developer. After the developer to be conveyed is supplied to the developing roll 22 that rotates at a position facing the photosensitive drum 11, the developer is frictionally charged on the developing roll 22 by the contact blade 23 that comes into contact with the peripheral surface of the developing roll 22. After being regulated to be held in a thin layer, it is transported to a development area facing the photosensitive drum 11. A developing bias (voltage in which alternating current is superimposed on direct current) is applied to the developing roll 21. Then, the developer is electrostatically attached only to the latent image portion of the photosensitive drum 11, thereby forming a toner image made of a one-component developer on the photosensitive drum. Incidentally, the lower surface portion 20a from the arrangement position of the developing roll 22 of the main body 20 to the position facing the registration roll 50 functions as a conveyance guide for the sheet conveyance path 5a for paper supply.
[0034]
The toner image formed on the photosensitive drum 11 in this manner is electrostatically transferred by the transfer device 15 to the recording paper P conveyed and supplied from the paper feeding unit 3. The transfer device 15 has a charging voltage having a polarity opposite to the charging polarity (negative polarity in this example) (positive polarity in this example) of the toner on the transfer roll (15a) rotating in contact with the peripheral surface of the photosensitive drum 11. The toner image is electrostatically transferred onto the recording paper P by inserting the recording paper P between the transfer roll and the photosensitive drum 11 (nip portion) in a state where the toner image is applied. The peripheral surface of the photosensitive drum 11 after the transfer is cleaned by removing residual toner and the like by the cleaning blade 16a of the cleaning device 16.
[0035]
The paper feeding unit 3 stacks and stores a plurality of recording papers P on the trays 31 of the paper cassettes 30a and 30b that are detachably attached to the main body 1 (also detachable), and sends out the recording papers P. A roll 31 and a rolling member (for example, a retard pad arm) 32 are sequentially fed out one by one from the uppermost side. The recording paper P sent out from the paper cassette 30 is disposed in a paper feed path 5a for feeding between the paper feed section 3 and the image forming section 2 (transfer site) (rotation register roll ( After being stopped once by the pair 50, the sheet is fed in accordance with the transfer timing, and is fed between the photosensitive drum 11 and the transfer roll while being guided by the conveyance guide member 51 constituting the sheet conveyance path 5a.
[0036]
The recording paper P onto which the toner image has been transferred at the transfer site of the image forming unit 2 (nip portion between the photosensitive drum and the transfer roll) is placed in a relay paper transport path 5b that connects the image forming unit 2 and the fixing unit 4. After being removed from the photosensitive drum 11 while being neutralized by the static eliminator 6 disposed, it is fed into the fixing unit 4 while being guided by the conveyance guide member 52 constituting the sheet conveyance path 5b.
[0037]
The fixing unit 4 passes the recording paper P between a heating roll 41 and a pressure roll 42 (nip part) arranged to rotate while being pressed against the inside of the housing 40, thereby transferring the toner image to the recording paper P. It is designed to be heat-fixed. The recording paper P fixed by the fixing unit 4 is a conveyance guide member that constitutes a paper conveyance path 5c for paper discharge that connects the fixing unit 4 and a paper discharge tray unit 1a formed on the upper surface side of the main body 1. While being guided by the sheet 53, the sheet is discharged onto the sheet discharge tray portion 1a through the discharge port 1b by a discharge roll (pair) 54 disposed and rotated in the middle of the sheet conveyance path 5c. Through the above process, image formation (printing) is performed on one recording sheet P.
[0038]
<Configuration of static eliminator>
The static eliminator 6 in this printer is a static eliminator 60 disposed in the vicinity of the transfer roll 15a on the downstream side in the paper feed direction (the direction of the dotted line arrow in FIG. Power supply device 65 (FIG. 5).
[0039]
As shown in FIG. 4, the static elimination needle 60 includes a needle-like electrode plate 61 made of a conductive material (metal or the like) having a tip portion 61 a formed in a saw blade shape, and a needle electrode plate 61 for holding the needle-like electrode plate 61. It is formed of an electrode holder plate 62 made of an insulating resin and is detachably screwed and fixed at a position corresponding to a transfer portion of the conveyance guide members 51 and 52 constituting the sheet conveyance paths 5a and 5b. (Fig. 3). At this time, the static elimination needle 60 is attached so that the distal end portion 61a of the needle electrode plate 61 is kept in a positional relationship facing the peripheral surface of the photosensitive drum 11 with a predetermined (shortest) separation distance d. Further, the electrode holder plate 62 is located between the adjacent tip portions 61a and protrudes from the tip portion 61a in order to prevent direct contact with the sharp tip portion 61a of the needle electrode plate 61. A plurality of protective protrusions 62a formed in the state are formed. Reference numeral 63 in FIG. 3 denotes a mounting screw, and reference numeral 62 b in FIG. 4 a denotes a screw through hole of the mounting screw 63.
[0040]
As shown in FIG. 5, the power supply device 65 is connected to the needle electrode plate 61 of the static elimination needle 60. In this example, the power supply device 65 is constituted by a DC power source capable of applying a negative DC voltage. Further, the power supply device 65 has a transformation function capable of adjusting the value of the DC voltage to be applied, and has a current measurement function (ammeter) capable of measuring a current flowing through the electrode plate 61 when the voltage is applied. Yes. A reference numeral 15 b in FIG. 5 is a power supply device for transfer for applying a transfer bias to the transfer roll 15 a of the transfer device 15. The transfer power supply device 15b is also composed of a DC power supply, as well as the static elimination power supply device 65, and has a transformation function and a current measurement function. Reference numeral 18 denotes an environment detection sensor for detecting the temperature and humidity in the main body 1, and 19 denotes an exchange detection means for detecting the replacement of the new process cartridge 10. As the exchange detection means 19, for example, a non-volatile memory attached to the process cartridge 10 side, and new identification information stored in the memory connected to the memory when the cartridge is attached are transferred to the control device 7 on the printer main body side, etc. What is comprised with the input-output terminal part for inputting into is applied. Reference numeral 8 denotes a liquid crystal panel type display device capable of displaying various messages on the screen.
[0041]
The power supply device 65 for neutralization and the power supply device 15b for transfer are controlled by the control device 7 composed of a microcomputer or the like for the output timing, voltage value, etc. of the power supply devices 65 and 15b. ing.
[0042]
The application of the neutralizing voltage (Ve) from the power supply device 65 is basically performed continuously during image formation (printing), and at this time, a voltage based on a certain reference value is applied. In this example, as a voltage for static elimination (Ve), a certain reference value (V _std ) Multiplied by a predetermined correction coefficient k (for example, k = 0.6) (k · V _std ) Is actually applied. In this example, the reference value (V _std ) Is used as a predetermined value. The application of the transfer voltage from the power supply device 15b is also performed substantially in the same manner during image formation (printing), and at this time, a voltage based on a certain reference value is applied. If necessary, the neutralization voltage or transfer voltage is applied at a specific time during printing such as when the recording paper P passes through the neutralization needle 60 or the transfer roll 15a. Also good.
[0043]
At this time, with respect to the neutralizing voltage and the transfer bias to be applied, if necessary, in order to realize transfer and neutralization suitable for the environmental conditions at the time of actual printing, detection information (temperature and humidity) is detected from the environmental detection sensor 19. It is also possible to apply a product obtained by further multiplying a predetermined use environment correction coefficient. For example, a standard environment (normal temperature and normal humidity environment: 22 ° C./55% RH, hereinafter also referred to as “N / N environment”) is used as a standard (correction coefficient du = 1.0), and correction necessary at high temperature and high humidity or low temperature and low humidity. Adjust the neutralization voltage to be applied by applying the coefficient. Specifically, if the detection information is a high-temperature and high-humidity environment (28 ° C./85% RH, hereinafter also referred to as “H / H environment”), the value is smaller than 1.0 because it is easier to discharge than the standard environment. For example, 0.9 is applied as the correction coefficient du for adjustment. Further, if the detection information is a low temperature and low humidity environment (10 ° C./15% RH, hereinafter also referred to as “L / L environment”), it is less likely to discharge than the standard environment, so a value larger than 1.0, for example, 1. Adjustment is performed by applying 1 or the like as the correction coefficient du. In addition, when performing single-sided printing for printing on one side of the recording paper P and double-sided printing for printing on both sides of the recording paper P, the neutralization voltage to be applied is further multiplied by a correction coefficient determined in advance according to the printing surface. It is also possible to adjust. It is also possible to perform correction by multiplying a predetermined correction coefficient according to conditions such as the thickness of the recording paper P by the reference value of the static elimination voltage.
[0044]
By the way, in such a static elimination apparatus 6, as shown in FIG. 14, the separation distance d of the front-end | tip part of the electrode plate 61 and the photosensitive drum 11 is 4.5 mm, for example by the attachment error of the static elimination needle 60, 5 If the difference is 0.0 mm, the voltage-current characteristic is different. That is, as is apparent from the results of this figure, when the applied voltage exceeds a certain amount, the current increases greatly and discharge starts, but when the separation distance d is different, the discharge starts. The value of the applied voltage is different. That is, it can be seen that even with the same electrode plate 61, the discharge characteristics are different if the distance d from the photosensitive drum 11 is different. Thus, when the discharge characteristics in the initial stage of the electrode plate 61 differ, even if the same voltage for static elimination is applied, the static elimination performance by each electrode plate 61 will differ.
[0045]
Further, when the voltage-current characteristics of the electrode plates 61 having different separation distances d when they are new and after printing 10,000 sheets (10k sheets) are obtained, the results shown in FIGS. 15 and 16 are obtained. From this result, it can be seen that the discharge characteristics of any electrode plate 61 deteriorate with time. It can also be seen that the method of reducing the discharge characteristics is slightly different between the electrode plates 61. As described above, even when the discharge characteristics of the electrode plates 61 with time are different, even if the same voltage for discharging is applied, the discharging performance of each electrode plate 61 is different.
[0046]
For this reason, in this printer, the control device 7 causes the discharge start voltage (Vh1) when the needle electrode plate 61 of the static elimination needle 60 is not used and the discharge start voltage (Vh2) at a predetermined stage after the use. And the warning display regarding the electrode plate 61 is set based on the difference between the discharge start voltages (Vh1, Vh2) (FIG. 6).
[0047]
First, as shown in FIG. 7, the measurement of the discharge start voltage (Vh1) when not in use is performed prior to the start of a print job when the power is turned on for the first time after a new product is installed.
[0048]
That is, as shown in FIG. 7, when power is turned on for the first time in a new printer (step S10), a measurement voltage (denoted as “DTS”) is applied from the power source device 65 for static elimination to the needle electrode plate 61 (also referred to as “DTS”). Vn) is applied (S11), and the current value (In) flowing to the needle electrode plate 61 side with the application of the voltage Vn is monitored by the current measuring function of the power supply device 65 (S12). It is determined whether or not the value reaches the absolute value of the current value (Ix) regarded as the discharge start specified in advance (S13).
[0049]
In this example, when the initial value “−1600 V” is applied as the measurement voltage Vn and the current value In has not reached the current value Ix, it is considered that the discharge on the needle electrode plate 61 has not started. 50 msec later, a measurement voltage Vn to which an increased voltage ΔV (for example, −200 V) is added is newly applied (S14), and monitoring and determination of the current value In are repeated. The current value Ix may be appropriately set to a value that can efficiently measure the assumed voltage at which discharge starts, and for example, −5 mμA is adopted.
[0050]
When the current value In reaches the threshold current value Ix, the measurement voltage Vn applied to the needle electrode plate 61 is measured (S15), and the measured voltage is determined as the discharge start voltage Vh1 when not in use (S15). S16). The determined discharge start voltage Vh1 is stored and held in the storage unit of the control device 7.
[0051]
As a result, even if there is an error in the shape of the needle electrode plate 61 or an error in the mounting state that may exist in units of the printer (static elimination device 6), the actual discharge of the needle electrode plate 61 in the initial stage. The starting voltage characteristic becomes clear.
[0052]
As shown in FIG. 9, the measurement of the discharge start voltage Vh1 is performed only by the operation in which the photosensitive drum 11 is rotated by the drive motor when the power is turned on (power ON), and the photosensitive drum 11 is charged by the charging device 12. It is performed under the executed condition, and operations such as the application of the developing bias to the developing roll 22 and the application of the transfer bias to the transfer roll 15a are not performed. Therefore, the measurement of the discharge start voltage is performed in a non-sheet passing state in which the recording paper P does not pass over the needle electrode plate 61. As a result, it is possible to avoid that the measurement voltage applied to the needle electrode plate 61 flows to other components via the recording paper P and cannot be accurately measured.
[0053]
The measurement of the discharge start voltage Vh1 ends when the monitored current value In reaches the threshold current value Ix. When the measurement of the discharge start voltage is finished, the cleaning cycle of the transfer roll 15a is started. For example, as shown in FIG. 9, in the cleaning cycle, a voltage having a polarity opposite to the transfer bias (negative polarity in this example) is first applied as a first cleaning voltage from the power supply device 15b to the transfer roll 15a for a predetermined time. Thereafter, a voltage having the same polarity as the transfer bias is applied as a second cleaning voltage from the power supply device 15b to the transfer roll 15a for a predetermined time. As a result, both the negatively charged toner adhering to the transfer roll 15a and the toner charged to the opposite polarity (positive polarity) are electrostatically transferred (returned) to the photosensitive drum 11 side and removed. When such a cleaning cycle is completed, the rotation operation of the photosensitive drum 11 and the charging operation of the charging device 12 are also completed, and the printer enters a standby state in which printing can be performed. The measurement of the discharge start voltage Vh1 may be performed after this cleaning cycle, or may be performed independently regardless of other operations such as this cleaning cycle.
[0054]
On the other hand, when the process cartridge 10 is replaced with a new one as shown in FIG. 8, the measurement of the discharge start voltage (Vh2) at a predetermined stage after use is performed immediately after the replacement operation is completed.
[0055]
In addition, in order to measure the discharge start voltage Vh2 at the time of cartridge replacement, a correction coefficient (dm) for measuring the discharge start voltage corresponding to the difference in environmental conditions is prepared in advance. As shown in FIG. 17, this corresponds to the fact that the voltage-current characteristic varies depending on the environmental conditions at the time of measurement. The correction coefficient dm is based on various environmental conditions (at least in a standard environment, a high temperature and high humidity environment, a low temperature and low humidity environment, etc.) in advance with respect to the discharge start voltage Vh1 of the electrode plate 61 when not in use by experiments before manufacturing. , And a table of coefficient values necessary for aligning (correcting) the measurement results under the respective environmental conditions with the measurement values under the other environment is used. The selection of the correction coefficient dm is performed based on the difference between the environmental condition when measuring the discharge start voltage Vh2 at the time of cartridge replacement and the environmental condition when measuring the discharge start voltage Vh1 when not in use.
[0056]
As shown in FIG. 8, it is first determined whether or not the process cartridge 10 has been replaced with a new one (S20). Whether the cartridge 10 has been replaced with a new one is determined by the detection information of the replacement detection means 19.
[0057]
When the cartridge is replaced with a new cartridge 10, the environmental condition at the time of replacement is detected by the environment detection sensor 18 (S21), and a correction coefficient dm for measuring the discharge start voltage is selected (S22). The selection of the correction coefficient dm is performed based on the difference between the environmental condition at the time of replacement and the environmental condition at the time of measurement of the discharge start voltage Vh1 (detection information is stored and held at the time of measurement).
[0058]
Subsequently, as in the case of the measurement of the discharge start voltage Vh1 when not in use, the measurement voltage Vn is applied to the needle electrode plate 61 from the power removal device 65 (S23), and the current at that time The value In is monitored (S24), and it is determined whether or not the absolute value of the current value In reaches the absolute value of the current value Ix regarded as the discharge start specified in advance (S25). At the stage where the current value Ix has not been reached, the measurement voltage Vn to which the increased voltage ΔV is added is newly applied (S16), and the above monitoring and determination are repeated.
[0059]
When the current value In reaches the threshold current value Ix, the measurement voltage Vn applied at that time is regarded as the discharge start voltage Vh2 when the cartridge is replaced (S27). Then, the discharge start voltage Vh2 is multiplied by the selected correction coefficient dm to correct the environmental condition difference (S28), and the corrected voltage value (dm · Vh2) is used as the discharge start voltage at the time of cartridge replacement. It is determined as Vh2 (S29). The determined discharge start voltage Vh2 is stored and held in the storage unit of the control device 7 if necessary. Thereby, the actual discharge start voltage characteristic of the needle electrode plate 61 at the time of cartridge replacement is clarified.
[0060]
In the measurement of the discharge start voltage Vh2 at the time of cartridge replacement, the voltage value obtained by measuring according to the difference between the environmental condition at the time of measurement and the environmental condition at the time of measurement of the initial discharge start voltage Vh1 is discharged. Since the correction is made by multiplying the correction coefficient dm for starting voltage measurement, the discharge starting voltage Vh2 can be measured efficiently and accurately without waiting until the environmental conditions at the time of initial discharge starting voltage measurement come again. it can.
[0061]
Then, when it is detected that the process cartridge 10 has been replaced with a new one as shown in FIG. 6 (S30), the control device 7 starts the discharge start voltage Vh1 when not in use and the discharge when replacing the cartridge. After the voltage Vh2 is read (S31), a difference (= | Vh2 | − | Vh1 |) between the discharge start voltages Vh1 and Vh2 is obtained, and it is determined whether or not the difference is greater than a preset threshold value M. (S32).
[0062]
At this time, if it is determined that the difference is larger than the threshold value M, it is considered that the discharge performance (and consequently the charge removal performance) of the needle electrode plate 61 has been lowered, and a necessary warning is displayed via the display device 8 (S33). ). In the warning display, a warning message (for example, “clean the static elimination needle”) for prompting cleaning of the static elimination needle 60 or a warning message for prompting replacement of the static elimination needle 60 (for example, “Please replace the static elimination needle”) is displayed. The The threshold value M is set to “800 (V)” when, for example, a replacement warning is displayed, and is set to “500 (V)” when a cleaning warning is displayed.
[0063]
When the replacement warning is displayed, the old static elimination needle 60 is removed, and then the new static elimination needle 60 is attached and exchanged. On the other hand, when the warning for cleaning is displayed, the toner adhering to the static elimination needle 60 is removed and cleaned. This cleaning is performed with the static elimination needle 60 attached or removed.
[0064]
If this warning is displayed, the mounting state of the charge eliminating needle 60 may be changed. Therefore, when the power supply is turned on for the first time after the action for the warning display is completed, the above-mentioned unrenewed state is not obtained. The discharge start voltage Vh1 at the time of use is measured, and the value is determined and held as the latest discharge start voltage Vh1.
[0065]
Table 1 shows the measurement results of experiments conducted on the performance transition state of the static eliminator 6 in this printer.
[0066]
In the experiment, test printing was performed while measuring the discharge start voltage Vh2 for every 50k printed sheets, and the degree of occurrence of toner scattering and thin paper peeling failure at that time was examined. All experiments were conducted under a standard environment (N / N environment). As the needle-like electrode plate 61, a stainless steel plate having a thickness of 0.1 mm having a tip portion formed in a saw blade shape with a pitch of 3 mm was used. The distance d from the photosensitive drum 11 was 4.5 mm. In the test print, a test toner image having a predetermined density was formed, and about +500 V was applied as an appropriate transfer bias suitable for the resistance value of the transfer roll 15A. As recording paper P, A4 size paper (basis weight: 56 g / m) ² )It was used.
[0067]
Regarding toner scattering, a sample obtained by printing a halftone image on the entire surface of the paper is visually inspected for the occurrence of toner scattering. evaluated. In addition, regarding the thin paper peeling failure, the peeling posture of the paper from the photosensitive drum when 100 sheets were transported and the occurrence of the peeling failure were investigated. Evaluation was made based on the criteria “Δ: no peeling failure occurred and peeling posture was unstable, x: peeling failure occurred”. The discharge start voltage in the table is a measured value. Further, the DTS current is a current value when the discharge start voltage is measured, and the DTS applied voltage is a constant charge eliminating voltage applied to the electrode plate 61.
[0068]
[Table 1]

[0069]
As is apparent from Table 1, the discharge start voltage gradually fluctuates (increases) as the number of prints increases with respect to the discharge start voltage (−2500 V) when not in use, and when the number of prints exceeds 200k. As a result, defective peeling and toner scattering occur.
[0070]
Therefore, in view of such characteristics, the threshold value M, which is a criterion for performing the warning display, is set to “800 (V)” in order to display a replacement warning, and for cleaning. Is set to “500 (V)”. Each of the threshold values M is such a value that a warning is displayed before the difference between the discharge start voltages exceeds the number of printed sheets reaching 150k, and therefore, when the separation failure or toner scattering occurs (printing) It is possible to clean or replace the static elimination needle 60 before the number of sheets exceeds 200k).
[0071]
[Embodiment 2]
10 to 12 show the main configuration of the printer according to the second embodiment. The printer according to this embodiment has the same configuration as that of the printer according to the first embodiment except that a part of the control content related to the warning display of the static elimination device 6 is changed.
[0072]
That is, in this printer, the control device 7 determines whether or not to display a warning message for prompting cleaning or replacement of the static elimination needle 60 in the static elimination device 6 in the same manner as in the first embodiment. Based on the measurement result of the discharge start voltage Vh1 when the electrode plate 61 is not used, the reference value (V _std 1) and a reference value (V for the static elimination voltage Ve based on the measurement result of the discharge start voltage Vh2 when the process cartridge of the electrode plate 61 is replaced. _std 2) is reset and both reference values (V _std 1, V _std Based on the difference of 2), the warning display regarding the electrode plate 61 is set (FIG. 10).
[0073]
First, the reference value (V of the static elimination voltage Ve when the electrode plate 61 is not used). _std In the setting of 1), as shown in steps S10 to S16 in FIG. 11, the measurement of the discharge start voltage Vh1 when not in use is performed in the same manner as in the first embodiment (steps S10 to S16 in FIG. 7). The discharge start voltage Vh1 is set to the reference value V at the initial stage of the charge removal voltage Ve. _std 1 is set (S50). This set reference value V _std 1 is stored and held in the storage unit of the control device 7.
[0074]
As a result, even if there is an error in the shape of the acicular electrode plate 61 or an error in the mounting state that may exist in units of the printer (static elimination device 6), the discharge start voltage Vh1 in the initial stage is measured and the printer is measured. (Staticizer 6) Reference value V of the neutralizing voltage Ve _std By determining the above, it becomes possible to obtain the expected discharge characteristics and consequently the static elimination performance without being influenced by the initial error. Incidentally, in this printer, the set reference value V is used until the next cartridge replacement. _std A voltage obtained by multiplying 1 by a predetermined coefficient k (for example, k = 0.6), that is, 0.6 · V _std 1 is actually applied as the static elimination voltage Ve.
[0075]
On the other hand, the reference value (V _std In the setting of 2), as shown in steps S20 to S29 in FIG. 12, the measurement of the discharge start voltage Vh2 at the time of cartridge replacement is performed in the same manner as in the first embodiment (steps S20 to S29 in FIG. 8). The discharge start voltage Vh2 (multiplied by the correction coefficient dm) is the reference value V at the time of cartridge replacement of the static elimination voltage Ve. _std 2 is set (S60). This reset reference value V _std 2 is stored and held in the storage unit of the control device 7 in place of the reference value at the initial stage.
[0076]
As a result, even if the needle-like electrode plate 61 is contaminated over time due to adhesion of toner or the like, the discharge start voltage Vh2 at the time of replacement of the process cartridge 10 is actually measured to be used peculiar to the printer (static eliminating device 6). Later, the reference value V of the static elimination voltage Ve at a predetermined time _std By determining 2 (= dm · Vh2), it is possible to obtain the expected discharge characteristics and, as a result, the charge removal performance without being affected by the variation with time. By the way, after this cartridge replacement, the reset reference value V _std A voltage obtained by multiplying 2 by a predetermined coefficient k (for example, k = 0.6), that is, 0.6 · V _std 2 is actually applied as the neutralizing voltage Ve.
[0077]
Then, in the control device 7, as shown in FIG. 10, when it is detected that the process cartridge 10 has been replaced with a new one (S40), the reference value V of the static elimination voltage Ve when not in use. _std 1 and the reference value V of the static elimination voltage Ve when replacing the cartridge _std After reading 2 (S41), the reference value V _std 1, V _std Difference of 2 (= | V _std 2 |-| V _std 1 |) is determined, and it is determined whether or not the difference is greater than a preset threshold value M (S42).
[0078]
At this time, if it is determined that the difference is larger than the threshold value M, it is considered that the discharge performance (and consequently the charge removal performance) of the needle-like electrode plate 61 has deteriorated, and a necessary warning is displayed via the display device 8 (S43). ). In the warning display, a warning message (for example, “clean the static elimination needle”) for prompting cleaning of the static elimination needle 60 or a warning message for prompting replacement of the static elimination needle 60 (for example, “Please replace the static elimination needle”) is displayed. The For example, the threshold value M is set to “1500 (V)” when a warning display for replacement is performed, and is set to “1000 (V)” when a warning display for cleaning is performed.
[0079]
Table 2 shows the measurement results of experiments conducted on the performance transition state of the static eliminator 6 in this printer.
[0080]
In this experiment, a coefficient k is applied to each reference value (= discharge start voltage) set (re-) based on the discharge start voltage measured for every 50k printed sheets as the voltage Neu for discharging applied to the charge eliminating needle (DTS) 60. The experiment was performed under the same conditions as in the experiment in Embodiment 1 except that a voltage multiplied by 0.6 was applied.
[0081]
[Table 2]

[0082]
As is apparent from Table 2, the discharge start voltage gradually fluctuates (increases) as the number of printed sheets increases with respect to the discharge start voltage (−2500 V) when not in use, but the reference for resetting as the neutralization voltage Ve Since the voltage based on the value is applied, when the number of printed sheets exceeds 300k, peeling failure and toner scattering start to occur. In this respect, compared with the experimental result (Table 1) in the first embodiment, where the defect of peeling started to occur when the number of printed sheets exceeded 200 k, the generation timing of the defect of peeling can be delayed. It has been confirmed that the usable period of the static elimination needle 60 can be extended to some extent despite the fact that its performance degradation has begun to occur.
[0083]
In view of such characteristics, the threshold value M, which is a criterion for performing the warning display, is set to “1500 (V)” in order to display a replacement warning, and for cleaning. Is set to “1000 (V)”. In particular, regarding the threshold value M for the criterion for performing each warning display, the usable period of the static elimination needle 60 can be extended to some extent by resetting the reference value as compared with the threshold value in the first embodiment. Thus, it was confirmed that the difference value, which is a criterion for performing the warning display, is set to be large so that the life of the electrode member can be artificially extended and effectively used.
[0084]
Here, as shown in Table 2, the discharge start voltage remains “−4000 V” when the number of printed sheets is 300k and 350k, and is the same as the discharge start voltage when the number of printed sheets is 250k. This is because the maximum value of the power capacity of the power source device 65 for static elimination is −4000 V, and a higher voltage than this cannot be applied. Therefore, the discharge start voltage at this time is the one before reaching the current value (Ix) “−5 μA” regarded as the start of discharge, and therefore, the neutralizing voltage Ve applied at that time is smaller than the voltage to be originally applied. The voltage is
[0085]
In the second embodiment, the neutralization voltage reference value is corrected by resetting, and the performance deterioration due to contamination of the static elimination needle 60 is compensated to delay the timing of occurrence of defects such as peeling failure, so that the static elimination needle 60 can be used. However, on the other hand, the maximum value of the power capacity (V _MAX ), The measurement of the discharge start voltage at the time of cartridge replacement or the like depends on the initial value of the discharge start voltage (which also corresponds to the reference value) and the setting value of the threshold value M, which is a criterion for warning display. Sometimes the measurement voltage to be applied is not sufficient for the maximum value of the power supply capacity, so that accurate measurement cannot be performed. As a result, there are no scenes where the threshold value M is exceeded, and warning display may not be possible.
[0086]
Therefore, from the viewpoint of determining whether or not to perform warning display in consideration of the power supply capacity of such a static elimination power supply device 65, as shown in FIG. 13, measurement is performed when the reference value of the static elimination applied voltage is set. The value of the discharge start voltage is the maximum value of the power supply capacity (V _MAX ) Or not (S70), and if it is equal to or greater than the maximum value, it is further determined whether or not the current value In at the time of measuring the discharge start voltage is less than the current value Ix regarded as the start of discharge. However, when it is determined that the current value is less than the current value Ix, each warning display described above may be configured to be given priority over the determination result as to whether or not the threshold value M is exceeded. Such warning display determination is configured, for example, to perform parallel processing using data of the discharge start voltage measured in the process of resetting the reference value at the time of cartridge replacement (step S27 in FIG. 12).
[0087]
Incidentally, in the first and second embodiments, the static elimination needle 60 employs a structure in which the needle electrode plate 61 and the electrode holder plate 62 are integrally removable as shown in FIG. When the static elimination needle 60 is replaced, the electrode holder plate 62 is also replaced at the same time.
[0088]
As a result, in the case of a path form curved in an arc shape (C-shaped path), such as a relay paper transport path 5b connecting the transfer site and the transfer unit 4 in this printer, the transfer is particularly important. The rear end portion of the recording paper P that has been discharged from the portion moves in a state of touching the static elimination needle 60 immediately after the transfer portion is discharged due to the reaction of being conveyed in a curved state, and the protective protrusion 62a of the electrode holder 62 The contact portion of the protective projection 62a is gradually worn out by repeating this contact passage over a long period of time, and the upper side of the two-dot chain line C shown in FIG. A sharp corner 62c is formed at the upper end of 62a. The electrode holder 62 having the corner 62c is also replaced with a new one at the same time as the replacement of the static elimination needle 60. As a result, it is possible to avoid a problem that abnormal discharge occurs at the time of contact between the corner portion 62c and the recording paper P and toner scattering occurs.
[0089]
In the first embodiment, the environmental detection sensor 18 detects the environmental condition. However, instead of the detection sensor 18, the resistance value of the transfer roll 15a that changes in accordance with environmental changes such as humidity and temperature. Detection may be performed using the result of indirectly measuring. FIG. 18 shows voltage-current characteristics when the current value when a voltage is applied from the transfer power supply device 15b to the transfer roll 15a is examined. As shown in this figure, since the voltage-current characteristic varies depending on each environmental condition, the environmental condition can be determined by measuring the current value when a constant measurement voltage is applied from the power supply device 15b.
[0090]
In the first embodiment, the measurement of the discharge start voltage Vh2 over time of the electrode plate 61 of the static elimination needle is performed when the process cartridge is replaced. However, it can be set to be performed at other times. Yes, for example, it may be set to be executed every time the power is turned on.
[0091]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the warning display regarding the electrode member is made based on the measurement result of the discharge start voltage performance in the unused stage and the predetermined elapsed stage of the electrode member for static elimination. Thus, it is possible to prevent the occurrence of discharge failure of the recording medium and toner scattering of the developer (toner) due to insufficient discharge due to fluctuations in the discharge performance of the electrode member.
[0092]
Therefore, in such an image forming apparatus, it is possible to reliably prevent the occurrence of defects such as recording medium peeling failure and developer scattering due to insufficient static elimination, and to perform good image formation without such defects. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a printer according to a first embodiment.
FIG. 2 is an enlarged cross-sectional view showing a main part of the printer of FIG.
3 is a cross-sectional view showing a portion including a static eliminator after the process cartridge is removed in FIG. 2;
4A and 4B show a configuration of a static elimination needle of a static elimination device, in which FIG. 4A is a front view showing a positional relationship with the photosensitive drum, and FIG. 4B is a sectional view taken along line BB in FIG.
FIG. 5 is an explanatory diagram showing a configuration of a control system such as a static eliminator.
FIG. 6 is a flowchart showing details of control for displaying a warning based on a difference in discharge start voltage.
FIG. 7 is a flowchart showing control details for measuring a discharge start voltage when the electrode plate is not used.
FIG. 8 is a flowchart showing the contents of control for measuring a discharge start voltage in an elapsed stage (at the time of cartridge replacement).
FIG. 9 is a timing chart showing each operation when measuring a discharge start voltage when not in use.
FIG. 10 is a flowchart showing details of control for displaying a warning based on a difference between the reference values of the static elimination voltage.
FIG. 11 is a flowchart showing the contents of control for setting a reference value of a static elimination voltage based on an initial stage discharge start voltage.
FIG. 12 is a flowchart showing the control contents for resetting the reference value of the static elimination voltage based on the discharge start voltage at the elapsed stage (at the time of cartridge replacement).
FIG. 13 is a flowchart showing control contents for performing warning display in consideration of the power supply capacity of the power supply device;
FIG. 14 is a graph showing measurement results of voltage-current characteristics regarding the electrode member of the static elimination needle when the separation distance from the photosensitive drum is different;
FIG. 15 is a graph showing measurement results of voltage-current characteristics regarding the electrode member (d = 4.5 mm) of the static elimination needle when new and after constant use.
FIG. 16 is a graph showing measurement results of voltage-current characteristics regarding the electrode member (d = 5.0 mm) of the static elimination needle when new and after constant use.
FIG. 17 is a graph showing measurement results of voltage-current characteristics regarding the electrode member of the static elimination needle when environmental conditions at the time of measurement are different.
FIG. 18 is a graph showing measurement results of voltage-current characteristics related to a transfer roll when environmental conditions at the time of measurement are different.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 7 ... Control apparatus (control means), 8 ... Display apparatus, 11 ... Photosensitive drum (image carrier), 15 ... Transfer apparatus (transfer means), 60 ... Static elimination needle (electrode member), 61 ... Needle-shaped electrode plate (electrode) Main body), 62 ... Electrode holder (electrode holding member), 62a ... Protection projection, 65 ... Static elimination power supply device (voltage applying means), Vh1 ... Discharge start voltage when not in use, Vh2 ... When cartridge is replaced (after use) Discharge start voltage at a predetermined stage), P... Recording paper (recording medium).

Claims (5)

An image carrier that carries an image made of a developer, a transfer unit that transfers an image on the image carrier to a recording medium, and a unit that is disposed in the vicinity of the transfer unit so as to be close to and opposed to the recording medium. In an image forming apparatus comprising: a charge removing electrode member; and a voltage applying means for applying a charge removing voltage to the electrode member.
Control means for measuring a discharge start voltage at an unused stage of the electrode member and a discharge start voltage at a predetermined stage after use of the electrode member, and displaying a warning regarding the electrode member based on a difference between the two discharge start voltages Provided ,
The electrode member has a plurality of sharp tip portions on the side facing the recording medium, and a protection for holding the electrode body and preventing external contact with the tip portion The electrode main body and the electrode holding member are integrally removable, and the protective protrusion is adjacent to the electrode main body with the sharp tip. An image forming apparatus, characterized in that the image forming apparatus is located between the portions and protrudes from the tip portion .   The control means sets a reference value for the charge removal voltage applied from the voltage application means based on the measurement result of the discharge start voltage in the unused stage of the electrode member, and a predetermined stage after use of the electrode member The image forming apparatus according to claim 1, wherein the reference value of the static elimination voltage is reset based on the measurement result of the discharge start voltage at.   The said control means applies the voltage for a measurement to the said electrode member, and measures the voltage value when the electric current value accompanying the voltage application reaches the electric current value specified beforehand as a discharge start voltage. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit measures the discharge start voltage when the recording medium is not passed.   The image forming apparatus according to claim 1, wherein the control unit performs one or both of a display for prompting cleaning of the electrode member and a display for prompting replacement of the electrode member as the warning display.

Images