JP3166940B2 - Image forming operation method and image forming apparatus of reversal development system - Google Patents

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明は、反転現像方式の画像形
成運転方法と画像形成装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversal developing type image forming operation method and an image forming apparatus.

【０００２】[0002]

【従来の技術】図７において、感光体１０，帯電器３
０，現像ローラ２０を含む現像器，転写器（図示省
略），ブレード４６を含む廃トナー回収装置４５，除電
ランプ５０等からなる反転現像方式の画像形成装置が知
られている。感光体１０は、ドラム形状の基体部１１と
その周面に形成された感光層１２とからなり、所定方向
に回動可能である。帯電器３０は、グリッド３３と電気
的に同電位なシールドケース３２と、このケース内に張
設された放電ワイヤー３１とからなり、放電ワイヤー３
１には帯電用電源装置３５が接続されている。また、設
定帯電電位Ｖｃを安定化するために、グリッド３３（３
２）は定電圧素子４０を介して接地される。2. Description of the Related Art In FIG.
There is known an image forming apparatus of a reversal developing type including a developing unit including a developing roller 20, a transfer unit (not shown), a waste toner collecting unit 45 including a blade 46, a static elimination lamp 50, and the like. The photoconductor 10 includes a drum-shaped base portion 11 and a photosensitive layer 12 formed on a peripheral surface thereof, and is rotatable in a predetermined direction. The charger 30 includes a shield case 32 having the same electric potential as the grid 33 and a discharge wire 31 stretched in the case.
1 is connected to a charging power supply device 35. Further, in order to stabilize the set charging potential Vc, the grid 33 (3
2) is grounded via the constant voltage element 40.

【０００３】現像ローラ２０は、基体部２１とこれに被
覆された弾性層２２とからなり、この弾性層２２の一部
周面は感光体１０（１２）の一部周面と接触され、現像
箇所Ｐ２を形成する。つまり、１成分トナーを用いた反
転現像方式を形成する。この現像ローラ２０の現像バイ
アス電位Ｖｂは、その電源装置２５から印加される。[0003] The developing roller 20 comprises a base portion 21 and an elastic layer 22 coated thereon. A part of the peripheral surface of the elastic layer 22 is brought into contact with a part of the peripheral surface of the photoreceptor 10 (12). A location P2 is formed. That is, a reversal development method using one-component toner is formed. The developing bias potential Vb of the developing roller 20 is applied from the power supply device 25.

【０００４】なお、図７中の２７はバイアス電源装置２
５のＯＮ／ＯＦＦ信号発生手段で、３７は帯電用電源装
置３５のＯＮ／ＯＦＦ信号発生手段である。また、１５
は詳細後記の感光体バイアス電位Ｖｄを印加する感光体
バイアス電源装置で、１７はそのＯＮ／ＯＦＦ信号発生
手段である。[0004] Incidentally, reference numeral 27 in FIG.
Reference numeral 5 denotes an ON / OFF signal generator, and reference numeral 37 denotes an ON / OFF signal generator of the charging power supply unit 35. Also, 15
Reference numeral 17 denotes a photoreceptor bias power supply for applying a photoreceptor bias potential Vd described later. Reference numeral 17 denotes an ON / OFF signal generation unit.

【０００５】かかる構成の画像形成装置では、メインモ
ータによって感光体１０を所定方向に所定速度で回動さ
せつつ帯電用電源装置３５をＯＮする。すると、放電ワ
イヤー３１からのコロナ放電作用によって帯電箇所Ｐ１
を通過する感光体１０の周面の電位Ｖｓ１を設定帯電電
位Ｖｃ（例えば、−６００Ｖ）の値に一様に帯電する。
このように帯電された周面に露光手段（図示省略）を用
いて光照射し露光部（静電潜像部）と未露光部を形成す
る。露光部は例えば−５０Ｖとされるが、未露光部は−
６００Ｖのままである。In the image forming apparatus having such a configuration, the charging power supply unit 35 is turned on while rotating the photosensitive member 10 in a predetermined direction at a predetermined speed by a main motor. Then, the charged portion P1 is generated by the corona discharge action from the discharge wire 31.
Is uniformly charged to the value of the set charging potential Vc (for example, -600 V).
The charged peripheral surface is irradiated with light using exposure means (not shown) to form an exposed portion (electrostatic latent image portion) and an unexposed portion. The exposed portion is, for example, -50 V, while the unexposed portion is-
It remains at 600V.

【０００６】現像箇所Ｐ２に至ると、現像ローラ２０側
の電位は現像バイアス電位Ｖｂに等しい例えば−３００
Ｖであるところ露光部はその電位が−５０Ｖであるか
ら、その電位差（−２５０Ｖ）によって現像ローラ２０
側からトナーが供給され露光部に１成分トナー像が形成
される。一方、未露光部は−６００Ｖでありかつ現像ロ
ーラ２０側は−３００Ｖであるから、−３００Ｖの電位
差が生じる。したがって、未露光部には現像ローラ２０
側からトナーが供給されない。つまり、無駄なトナーを
消費することはない。その後トナー像は、転写器を通過
するときに、用紙上へ転写される。感光体１０（１２）
の周面は、除電箇所Ｐ３にある除電ランプ５０を通過す
るとき、初期電位に一様に戻される。感光体１０上に残
ったトナーは廃トナー回収装置４５（４６）でクリーニ
ングされる。When reaching the developing point P2, the potential on the developing roller 20 side becomes equal to the developing bias potential Vb, for example, -300.
In the case of V, the exposed portion has a potential of −50 V, and the potential difference (−250 V) causes the developing roller 20
The toner is supplied from the side, and a one-component toner image is formed on the exposed portion. On the other hand, since the unexposed portion is at -600 V and the developing roller 20 side is at -300 V, a potential difference of -300 V is generated. Therefore, the developing roller 20
No toner is supplied from the side. That is, useless toner is not consumed. Thereafter, the toner image is transferred onto the paper when passing through the transfer device. Photoconductor 10 (12)
When passing through the static elimination lamp 50 at the static elimination point P3, the peripheral surface of is uniformly returned to the initial potential. The toner remaining on the photoconductor 10 is cleaned by the waste toner collecting device 45 (46).

【０００７】ところで、運転開始時に図７に示す帯電箇
所Ｐ１と現像箇所Ｐ２との間に所在する感光体１０（１
２）の初期周面部位Ｆ１は、１回目に現像箇所Ｐ２を通
過する際には未だ設定帯電電位Ｖｃ（−６００Ｖ）に帯
電されていない。現像ローラ２０にもバイアス電位Ｖｂ
（−３００Ｖ）が印加されていない。したがって、現像
箇所Ｐ２における感光体側電位Ｖｓ２と現像ローラ２０
側の電位Ｖｂ（グランド）との間に電位差がないので、
現像ローラ２０側から初期周面部位Ｆ１に無駄なトナー
が付着してしまう。By the way, at the start of operation, the photosensitive member 10 (1) located between the charging point P1 and the developing point P2 shown in FIG.
The initial peripheral surface portion F1 of 2) has not yet been charged to the set charging potential Vc (−600 V) when passing through the developing portion P2 for the first time. The bias potential Vb is also applied to the developing roller 20.
(-300V) is not applied. Therefore, the photoconductor-side potential Vs2 at the developing location P2 and the developing roller 20
Since there is no potential difference with the potential Vb (ground) on the
Unnecessary toner adheres to the initial peripheral surface portion F1 from the developing roller 20 side.

【０００８】かくして、従来は、図８に示す如く、帯電
器３０をＯＮして帯電箇所Ｐ１を通過する感光体１０
（１２）の周面電位Ｖｓ１を例えば−６００Ｖの設定帯
電電位（Ｖｃ）に帯電開始させると同時に、感光体バイ
アス電源装置１５をＯＮさせて感光体１０（１２）の全
体に感光体バイアス電位Ｖｄ（例えば−２００Ｖ）を印
加している。この感光体バイアス電位Ｖｄを印加する期
間は、運転開始時に帯電箇所Ｐ１と現像箇所Ｐ２との間
にあった感光体１０の初期周面部位Ｆ１の全てが現像箇
所Ｐ２を通過してしまうまでの時間Ｔ１である。Thus, conventionally, as shown in FIG. 8, the charging device 30 is turned on to charge the photosensitive member 10 passing through the charging portion P1.
At the same time, the peripheral surface potential Vs1 of (12) is started to be charged to a set charging potential (Vc) of, for example, −600 V, and at the same time, the photoconductor bias power supply device 15 is turned on to apply the photoconductor bias potential Vd to the entire photoconductor 10 (12). (For example, -200 V). The period during which the photoconductor bias potential Vd is applied is a time T1 until all of the initial peripheral surface portion F1 of the photoconductor 10 between the charging portion P1 and the developing portion P2 at the start of operation passes through the developing portion P2. It is.

【０００９】したがって、上記初期周面部位Ｆ１が現像
箇所Ｐ２を通過する際の感光体側電位Ｖｓ２は、図９に
示すように感光体バイアス電位Ｖｄに等しい−２００Ｖ
となっている。これに対し、現像バイアス電位Ｖｂは時
間Ｔ１が経過するまで印加されていないので、感光体側
電位Ｖｓ２と現像ローラ側電位Ｖｂ（＝０）との間に
は、−２００Ｖの電位差を生じさせることができる。す
なわち、現像ローラ２０側から初期周面部位Ｆ１上への
トナーの付着を防止できる。そして、未露光部（−６０
０Ｖ）と、例えば−５０Ｖとされた露光部（静電潜像）
とが形成されている次周面部位Ｆ２が、現像箇所Ｐ２に
到達しかつ通過する。すなわち、時間Ｔ１の経過後に本
来現像を開始するために、現像バイアス電源装置２５を
ＯＮして現像バイアス電位Ｖｂ（−３００Ｖ）を印加す
る。なお、上記次周面部位Ｆ２とは、上記初期周面部位
Ｆ１と同じ周長である。つまり、運転開始時に、図７に
示す帯電箇所Ｐ１の上流側（除電箇所Ｐ３側）に所在し
ていた部分である。Therefore, the photoconductor-side potential Vs2 when the initial peripheral surface portion F1 passes through the development site P2 is -200 V equal to the photoconductor bias potential Vd as shown in FIG.
It has become. On the other hand, since the developing bias potential Vb is not applied until the time T1 has elapsed, a potential difference of -200 V may occur between the photoconductor-side potential Vs2 and the developing roller-side potential Vb (= 0). it can. That is, it is possible to prevent toner from adhering from the developing roller 20 side to the initial peripheral surface portion F1. Then, the unexposed portion (−60)
0 V) and an exposed portion (electrostatic latent image), for example, -50 V
The next peripheral surface portion F2 where is formed reaches and passes through the development location P2. That is, the developing bias power supply device 25 is turned on to apply the developing bias potential Vb (-300 V) in order to start the development after the elapse of the time T1. The next peripheral surface portion F2 has the same peripheral length as the initial peripheral surface portion F1. That is, at the start of the operation, the portion is located on the upstream side of the charged portion P1 shown in FIG.

【００１０】[0010]

【発明が解決しようとする課題】ところで、次周面部位
Ｆ２は１回目から帯電箇所Ｐ１を通過する際に帯電器３
０によって設定帯電電位Ｖｃ（−６００Ｖ）に帯電され
るが、これと同時に感光体１０全体として図９に示す感
光体バイアス電位Ｖｄ（−２００Ｖ）も印加されてい
る。したがって、かかる次周面部位Ｆ２の実効帯電電位
は−４００Ｖとなる。すなわち、最初の時間Ｔ１経過後
から現像箇所Ｐ２を通過することになる次周面部位Ｆ２
の電位つまり感光体側電位Ｖｓ２は、図９に示す通り−
４００Ｖである。しかるに、現像ローラ側電位Ｖｂは−
３００Ｖである。したがって、初期周面部位Ｆ１が通過
する際の電位差（｜Ｖｂ｜−｜Ｖｓ２｜）＝（｜０Ｖ｜
−｜２００Ｖ｜）が−２００Ｖであったのに対して、次
周面部位Ｆ２の電位差（｜Ｖｂ｜−｜Ｖｓ２｜）＝（｜
３００Ｖ｜−｜４００Ｖ｜）は−１００Ｖに低下してし
まう。By the way, when the next peripheral surface portion F2 passes through the charging portion P1 from the first time, the charging device 3
At 0, the photoconductor 10 is charged to the set charging potential Vc (−600 V). At the same time, the photoconductor bias potential Vd (−200 V) shown in FIG. Therefore, the effective charging potential of the next peripheral surface portion F2 is -400V. That is, after the first time T1 has elapsed, the next peripheral surface portion F2 that passes through the development location P2
, That is, the photoconductor-side potential Vs2, as shown in FIG.
400V. However, the developing roller side potential Vb is −
300V. Therefore, the potential difference ( | Vb |-| Vs2 | ) = ( | 0V | ) when the initial peripheral surface portion F1 passes.
− | 200V | ) was −200 V, whereas the potential difference ( | Vb | − | Vs2 | ) = ( |
300V |-| 400V | ) drops to -100V.

【００１１】したがって、感光体バイアス電位Ｖｄ（−
２００Ｖ）を印加して初期周面部位Ｆ１について現像ロ
ーラ２０側からトナーが付着しないように形成しても、
本来現像が開始可能となる次周面部位Ｆ２については現
像ローラ２０側からトナーが付着してしまう。つまり、
無駄なトナーを消費する。Therefore, the photosensitive member bias potential Vd (-
200V) to prevent toner from adhering to the initial peripheral surface portion F1 from the developing roller 20 side.
At the next peripheral surface portion F2 at which development can be started, toner adheres from the developing roller 20 side. That is,
Wastes toner.

【００１２】なお、帯電器３０をＯＦＦした後に、感光
体バイアス電位Ｖｂを図８，図９に示す時間Ｔ２だけ印
加する場合は問題がない。以上の問題は、帯電器３０が
図１０に示す帯電ローラ（基体部３１Ｂと弾性層３２
Ｂ）から形成されている場合にも同様に生ずる。There is no problem when the photoconductor bias potential Vb is applied for the time T2 shown in FIGS. 8 and 9 after the charger 30 is turned off. The above-described problem is caused by the fact that the charger 30 uses the charging roller (the base portion 31B and the elastic layer 32) shown in FIG.
The same applies to the case of forming from B).

【００１３】本発明の目的は、運転開始時における無駄
なトナー消費を一掃することのできる反転現像方式の画
像形成運転方法と画像形成装置とを提供することにあ
る。An object of the present invention is to provide a reversal developing type image forming operation method and an image forming apparatus which can eliminate wasteful toner consumption at the start of operation.

【００１４】[0014]

【課題を解決するための手段】例えば図４に示すよう
に、画像形成装置の構成が特定されかつ粒径等のトナー
性状等が決まれば、現像箇所Ｐ２での感光体側電位Ｖｓ
２と現像ローラ側電位Ｖｂとの電位差によって、現像ロ
ーラ側から感光体へのトナー付着量が変化する。換言す
れば、未露光部へのトナー付着を防止しつつ最も効率よ
く現像するための設定電位差（｜Ｖｂ｜−｜Ｖｓ２｜）
が決まる。したがって、本発明は、連続運転中に現像を
行う際の電位差は、上記設定電位差となるように構築さ
れかつ運転されていることに着目し、従来の感光体バイ
アス電位Ｖｄの印加による初期周面部位Ｆ１への無駄な
トナー消費を防止する方法を取り入れつつ、感光体バイ
アス電位Ｖｄの印加に伴う不都合つまり次周面部位Ｆ２
について無駄なトナーが付着してしまうことを防止でき
る画像形成運転方法とその装置である。For example, as shown in FIG. 4, when the configuration of the image forming apparatus is specified and the toner properties such as the particle size are determined, the photoconductor-side potential Vs at the developing site P2 is determined.
The amount of toner adhering from the developing roller side to the photoreceptor changes due to the potential difference between 2 and the developing roller side potential Vb. In other words, the set potential difference ( | Vb |-| Vs2 | ) for the most efficient development while preventing the toner from adhering to the unexposed area.
Is determined. Therefore, the present invention focuses on the fact that the potential difference at the time of developing during the continuous operation is constructed and operated so as to become the above-mentioned set potential difference, and the conventional initial peripheral surface by applying the photosensitive member bias potential Vd is used. The disadvantage associated with the application of the photoconductor bias potential Vd, that is, the next peripheral surface portion F2, while adopting a method of preventing wasteful toner consumption to the portion F1.
An image forming operation method and an apparatus therefor which can prevent wasteful toner from adhering.

【００１５】すなわち、請求項１の発明に係る反転現像
方式の画像形成運転方法は、帯電器を通過した感光体の
周面に光照射して露光部と未露光部とを形成し、感光体
側と現像ローラ側との設定電位差を利用して露光部へ現
像ローラ側から１成分トナーを供給して現像するととも
に、運転開始時に帯電箇所と現像箇所との間にあった感
光体の初期周面部位の全てが現像箇所を通過してしまう
までの期間中に感光体に設定帯電電位と同極性で絶対値
の小さい感光体バイアス電位を印加して運転を開始する
反転現像方式の画像形成運転方法であって、前記初期周
面部位の全てが前記現像箇所を通過してしまうまでの運
転開始期間中に前記帯電箇所を通過する前記感光体の次
周面部位が前記現像箇所を通過する際に該次周面部位側
と前記現像ローラ側との電位差が前記設定電位差と等し
い電位差となるように、該次周面部位が前記帯電箇所を
通過する期間中だけその帯電電位を前記設定帯電電位よ
りも強制的に高めて運転することを特徴とする。That is, in the image forming operation method of the reversal developing method according to the first aspect of the present invention, the exposed surface and the unexposed portion are formed by irradiating the peripheral surface of the photoreceptor that has passed through the charger with light. A one-component toner is supplied from the developing roller side to the exposure section using the set potential difference between the developing roller side and the developing roller side to perform development. This is a reversal developing type image forming operation method in which a photosensitive member bias potential having the same polarity as the set charging potential and having a small absolute value is applied to the photosensitive member and the operation is started during a period until all the toner passes through the developing portion. When the next peripheral surface portion of the photoreceptor that passes through the charged portion during the operation start period until all of the initial peripheral surface portion passes through the developing portion, the next peripheral portion passes through the developing portion. Peripheral surface side and the developing roller The operation is performed by forcibly increasing the charged potential of the next peripheral surface portion to be higher than the set charging potential only during a period in which the next peripheral surface portion passes through the charging portion so that the potential difference between the charging portion and the second charging portion becomes equal to the potential difference. And

【００１６】[0016]

【００１７】また、請求項２の発明に係る反転現像方式
の画像形成装置は、帯電器を通過した感光体の周面に光
照射して露光部と未露光部とを形成し、感光体側と現像
ローラ側との設定電位差を利用して露光部へ現像ローラ
側から１成分トナーを供給して現像するとともに、運転
開始時に帯電箇所と現像箇所との間にあった感光体の初
期周面部位の全てが現像箇所を通過してしまうまでの期
間中に感光体に設定帯電電位と同極性で絶対値の小さい
感光体バイアス電位を印加して運転を開始する反転現像
方式の画像形成装置において、前記帯電器を前記感光体
の周面に摺接する帯電ローラから形成するとともに、こ
の帯電ローラに帯電電圧を印加する帯電用電源装置を設
定電圧とこれより高い高圧電圧とのいずれかに切替出力
可能に形成し、前記感光体バイアス電位を印加している
間だけ該帯電用電源装置の出力を高圧電圧に切替える電
圧切替手段を設けたことを特徴とする。 Further, the image forming apparatus of reversal development system according to the invention of claim 2, the charger and the light irradiated on the peripheral surface of the photoreceptor which has passed through the forming the exposed portion and the unexposed portion, and the photoconductor side A one-component toner is supplied from the developing roller side to the exposure part using the set potential difference from the developing roller side to perform development, and all of the initial peripheral surface portion of the photoconductor between the charged part and the developed part at the start of operation. In a reversal developing type image forming apparatus, a photosensitive member bias potential having the same polarity as the set charging potential and having a small absolute value is applied to the photosensitive member and the operation is started during a period until the photosensitive member has passed the developing portion. The charging device is formed of a charging roller that is in sliding contact with the peripheral surface of the photoreceptor, and a charging power supply device that applies a charging voltage to the charging roller is formed so as to be switchable between a set voltage and a higher voltage higher than the set voltage. And before The output of the charging power source device only during the application of the photosensitive member bias potential, characterized in that a voltage switching means for switching the high voltage.

【００１８】[0018]

【作用】上記運転方法による請求項１の発明によれば、
運転開始に際して帯電器と感光体バイアス電源装置とを
同時にＯＮさせかつ感光体を所定方向に回動させる。す
ると、運転開始時に帯電箇所と現像箇所との間にあった
感光体の初期周面部位は感光体バイアス電位（例えば−
２００Ｖ）と同電位となり、それに引続く次周面部位は
帯電箇所を通過するときに設定帯電電位（例えば−６０
０Ｖ）に帯電されるが感光体バイアス電位（−２００
Ｖ）が一様に印加されているので実際電位は（−４００
Ｖ）となる。According to the first aspect of the present invention, there is provided the following operation method.
At the start of operation, the charger and the photoconductor bias power supply are turned on simultaneously and the photoconductor is rotated in a predetermined direction. Then, the initial peripheral surface portion of the photoconductor between the charged portion and the developed portion at the start of the operation has a photoconductor bias potential (for example,-).
200 V), and the subsequent peripheral portion following the charged portion has a set charging potential (for example, −60) when passing through a charged portion.
0V), but the photosensitive member bias potential (-200
V) is applied uniformly, so that the actual potential is (−400).
V).

【００１９】ここに、次周面部位が帯電箇所を通過する
ときだけ、例えば帯電電位を設定値（−６００Ｖ）より
高い所定値（−８００Ｖ）とすれば、次周面部位の実質
帯電電位を感光体バイアス電位に影響されずに設定帯電
電位（−６００Ｖ）と同じ電位（−６００Ｖ）にするこ
とができる。Here, when the charging potential is set to a predetermined value (-800 V) higher than the set value (-600 V) only when the next peripheral portion passes through the charged portion, the substantial charging potential of the next peripheral portion is changed. The same potential (-600 V) as the set charging potential (-600 V) can be used without being affected by the photoconductor bias potential.

【００２０】かくして、感光体バイアス電位（−２００
Ｖ）が印加された初期周面部位の全てが現像箇所を通過
するときは、現像バイアス電位は印加されていないの
で、感光体側電位（−２００Ｖ）と現像ローラ側電位
（０Ｖ）との電位差（−２００Ｖ）によって現像ローラ
側から感光体上へのトナー付着を防止できる。また、実
質帯電電位が設定帯電電位（−６００Ｖ）と等しい値
（−６００Ｖ）とされた次周面部位が現像箇所を通過す
る際は、現像バイアス電位（例えば−３００Ｖ）が印加
されているので、感光体側電位（−６００Ｖ）と現像ロ
ーラ側電位（−３００Ｖ）との間には、連続運転時にお
ける設定電位差（−３００Ｖ）と等しい値（−３００
Ｖ）の電位差を発生できる。したがって、次周面部位を
連続運転中と同じ最良的な設定電位差（−３００Ｖ）で
効率良く運転できるとともに現像ローラ側から感光体上
への無駄なトナー付着を防止することができる。Thus, the photosensitive member bias potential (-200
When all of the initial peripheral surface portions to which V) is applied pass through the developing portion, the developing bias potential is not applied, and therefore, the potential difference (−200 V) between the photoconductor-side potential (−200 V) and the developing roller-side potential (0 V). −200 V) can prevent toner from adhering to the photosensitive member from the developing roller side. Further, when the next peripheral surface portion having the substantially charged potential (-600 V) equal to the set charging potential (-600 V) passes through the developing portion, the developing bias potential (for example, -300 V) is applied. , A value (−300 V) equal to the set potential difference (−300 V) during continuous operation between the photoconductor side potential (−600 V) and the developing roller side potential (−300 V).
V). Therefore, the next peripheral surface portion can be efficiently operated with the same best potential difference (-300 V) as that during the continuous operation, and wasteful toner adhesion from the developing roller side to the photoconductor can be prevented.

【００２１】[0021]

【００２２】また、請求項２の発明によれば、帯電用電
源装置の出力を設定電圧とした場合に、帯電ローラが摺
接する箇所（帯電箇所）に位置する感光体周面を設定帯
電電位（−６００Ｖ）に帯電できるが、感光体バイアス
電位（−２００Ｖ）を印加している間は電圧切替手段が
その出力を高圧電圧に切替える。したがって、この高圧
電圧を設定電圧よりも感光体バイアス電位（−２００
Ｖ）による感光体への帯電作用と同じ作用を発揮するこ
とのできる値としておけば、次周面部位を設定帯電電位
（−６００Ｖ）と同じ値（−６００Ｖ）に帯電できる。
よって、請求項１の発明と同様に無駄なトナー消費を防
止することができる。 Further, according to the second aspect of the invention, when the set voltage output of the charging power source device, set the photoreceptor peripheral surface charging roller located sliding contact portion (charging portion) charging potential ( -600 V), but the voltage switching means switches the output to a high voltage while the photoconductor bias potential (-200 V) is applied. Therefore, this high voltage is set to a photoconductor bias potential (−200) higher than the set voltage.
If the value that can exert the same action as the charging action on the photoreceptor by V) can be applied, the next peripheral surface portion can be charged to the same value (-600 V) as the set charging potential (-600 V).
Thus, wasteful consumption of toner can be prevented as in the first aspect of the present invention.

【００２３】[0023]

【実施例】以下、本発明の実施例を図面を参照して説明
する。 （第１実施例） 本画像形成運転方法を実施するための画像形成装置は，
図１に示す如く、基本構成（１０，２０，３０等）が従
来例（図７）と同じとされ、かつ帯電器３０〔グリッド
３２（３３）〕と感光体バイアス電源装置１５とを定電
圧素子４０を介して接続し、次周面部位Ｆ２が帯電箇所
Ｐ１を通過する期間中だけ帯電器３０による帯電電位を
設定帯電電位Ｖｃ（−６００Ｖ）よりも強制的に高めた
帯電電位（−８００Ｖ）として本反転現像方式の画像形
成運転を能率よくかつ円滑に実施しつつ無駄なトナー消
費を防止することができるように構築されている。Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) An image forming apparatus for performing the present image forming operation method includes:
As shown in FIG. 1, is constituted basically (10, 20, 30, etc.) is the same as the conventional example (FIG. 7), and a charger 30 [grid 32 (33)] and the constant collector and a photosensitive member bias power supply 15 <br/> Connected via the pressure element 40 , the next peripheral surface portion F2 is charged
Only during the period of passing through P1, the charging potential of the charger 30 is changed.
Forced higher than the set charging potential Vc (-600 V)
The image forming apparatus is constructed so that the image forming operation of the present reversal developing method can be efficiently and smoothly performed with the charged potential (−800 V) while preventing wasteful toner consumption.

【００２４】したがって、従来例（図７）の場合と同一
または共通する部分については同一の符号を付しその説
明を簡略または省略する。Therefore, the same or common parts as in the conventional example (FIG. 7) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

【００２５】まず、図１に示す帯電器３０の設定帯電電
位Ｖｃを−６００Ｖ、感光体１０に形成される露光部
（静電潜像）の電位を−５０Ｖと決めてある。また、現
像箇所Ｐ２における感光体側電位Ｖｓ２と現像ローラ２
０（２２）側電位Ｖｂとの電位差が、図４に示す如く、
−３００Ｖ〜−２００Ｖの間で現像ローラ２０側から感
光体１０上に付着されるトナー量が最小となる実機デー
タに基づき、現像バイアス電位Ｖｂを−３００Ｖと選定
している。First, the set charging potential Vc of the charger 30 shown in FIG. 1 is determined to be -600 V, and the potential of the exposed portion (electrostatic latent image) formed on the photosensitive member 10 is determined to be -50 V. Also, the photoconductor-side potential Vs2 at the developing location P2 and the developing roller 2
The potential difference from the 0 (22) side potential Vb is, as shown in FIG.
The developing bias potential Vb is selected to be -300 V based on actual machine data in which the amount of toner adhered onto the photoreceptor 10 from the developing roller 20 side becomes minimum between -300 V and -200 V.

【００２６】したがって、連続運転中の未露光部の電位
を、設定帯電電位Ｖｃ（Ｖｓ１）と等しい−６００Ｖに
することができるから、現像箇所Ｐ２における感光体側
電位Ｖｓ２と現像ローラ側電位Ｖｂとの電位差つまり設
定電位差は、感光体側の絶対値が大きい−３００Ｖとな
る。一方、露光部の電位は上記値（−５０Ｖ）とされて
いるから、現像箇所Ｐ２の現像用設定電位差は、感光体
側の絶対値が小さい−２５０Ｖとなる。Therefore, the potential of the unexposed portion during the continuous operation can be set at -600 V, which is equal to the set charging potential Vc (Vs1). Therefore, the potential difference between the photoconductor-side potential Vs2 and the developing roller-side potential Vb at the developing point P2 is obtained. The potential difference, that is, the set potential difference is −300 V, where the absolute value on the photoconductor side is large. On the other hand, since the potential of the exposed portion is set to the above value (−50 V), the set potential difference for development at the development site P2 is −250 V, where the absolute value on the photoconductor side is small.

【００２７】かくして、初期周面部位Ｆ１に印加する感
光体バイアス電位Ｖｄは、上記各電位Ｖｃ，Ｖｂ等の電
位、電位差並びに図４に示すトナー付着特性を比較考量
して−２００Ｖに決定している。この感光体バイアス電
位Ｖｄを出力する電源装置１５は、運転開始時、ＯＮ／
ＯＦＦ信号発生手段１７によって図２，図３に示すよう
に帯電用電源装置３５と同時にＯＮされ、時間Ｔ１の経
過後にＯＦＦされる。この時間Ｔ１は、初期周面部位Ｆ
１の全てが現像箇所Ｐ２を通過してしまうに必要とする
時間である。Thus, the photosensitive member bias potential Vd applied to the initial peripheral surface portion F1 is determined to be -200V by comparing the potentials such as the potentials Vc and Vb, the potential difference, and the toner adhesion characteristics shown in FIG. I have. The power supply device 15 that outputs the photoconductor bias potential Vd is turned ON / OFF at the start of operation.
As shown in FIGS. 2 and 3, the OFF signal generating means 17 turns on the charging power supply 35 at the same time as the charging power supply 35, and turns off after the lapse of time T1. This time T1 corresponds to the initial peripheral surface portion F
1 is the time required for all of 1 to pass through the development site P2.

【００２８】なお、運転終了時には、帯電器３０がＯＦ
Ｆとされたときに、帯電箇所Ｐ１と現像箇所Ｐ２との間
に位置した感光体１０の周面（この周長は初期周面部位
Ｆ１の周長と等しい）の全てが現像箇所Ｐ２を通過して
しまうまでに要する時間Ｔ１の経過後に、感光体バイア
ス電源装置１５は再びＯＮされる。そのＯＮ時間Ｔ２は
適宜に設定すればよい。感光体が１周以上回動できるよ
うに設定するのが望ましい。At the end of the operation, the charger 30 is turned off.
When set to F, the entire peripheral surface of the photoreceptor 10 located between the charged portion P1 and the developed portion P2 (this peripheral length is equal to the peripheral length of the initial peripheral portion F1) passes through the developed portion P2. After a lapse of the time T1 required to complete the operation, the photoconductor bias power supply device 15 is turned on again. The ON time T2 may be set appropriately. It is desirable to set the photoconductor so that it can rotate one or more turns.

【００２９】ここに、設定帯電電位Ｖｃ（Ｖｓ１）を安
定化するための定電圧素子（例えば、ツェナーダイオー
ドやバリスタ）は、帯電器３０すなわちグリッド３３と
等電位のシールドケース３２と感光体バイアス電源装置
１５との間に介装され、帯電電位Ｖｃ（Ｖｓ１）に感光
体バイアス電位Ｖｄを重畳できるように接続されてい
る。一方、現像バイアス電源装置２５は、図３に示す時
間Ｔ１の経過後にＯＮされ、帯電器３０がＯＦＦされて
から時間Ｔ１の経過後にＯＦＦされる。Here, a constant voltage element (for example, a Zener diode or a varistor) for stabilizing the set charging potential Vc (Vs1) includes a charging device 30, that is, a grid 33, a shield case 32 having the same potential as the grid 33, and a photosensitive member bias power source. The photosensitive drum bias potential Vd is interposed between the device 15 and the charging potential Vc (Vs1). On the other hand, the developing bias power supply device 25 is turned on after the time T1 shown in FIG. 3 has elapsed, and is turned off after the time T1 has elapsed since the charger 30 was turned off.

【００３０】次に、本発明の実施例を用いての画像形成
運転方法を説明する。運転開始に際しては、図１に示す
帯電用電源装置３５と感光体バイアス電源装置１５と
を、図２，図３に示すように、同時にＯＮさせる。感光
体１０は所定方向に回動を始める。Next, an image forming operation method using an embodiment of the present invention will be described. When starting the operation, the charging power supply device 35 and the photoconductor bias power supply device 15 shown in FIG. 1 are simultaneously turned on as shown in FIGS. The photoconductor 10 starts rotating in a predetermined direction.

【００３１】すると、感光体１０には全体的に感光体バ
イアス電位Ｖｄ（−２００Ｖ）が印加されるから、初期
周面部位Ｆ１の電位は−２００Ｖとなる。一方、帯電箇
所Ｐ１を通過する感光体１０の周面の電位Ｖｓは設定帯
電電位Ｖｃ（−６００Ｖ）と同じ電位Ｖｓ１に帯電され
るが、定電圧素子４０を介して感光体バイアス電位Ｖｄ
（−２００Ｖ）と同電位（−２００Ｖ）が重畳されるの
で、次周面部位Ｆ２は図２に示す電位Ｖｓ（−８００
Ｖ）に帯電される。しかし、感光体１０の全体に感光体
バイアスＶｄ（−２００Ｖ）が印加されているので、次
周面部位Ｆ２の電位Ｖｓ１は実質的に−６００Ｖとな
る。Then, since the photosensitive member bias potential Vd (-200 V) is applied to the entire photosensitive member 10, the potential of the initial peripheral surface portion F1 becomes -200V. On the other hand, the potential Vs of the peripheral surface of the photoconductor 10 passing through the charging point P1 is charged to the same potential Vs1 as the set charging potential Vc (−600 V), but the photoconductor bias potential Vd via the constant voltage element 40.
Since the same potential (−200 V) is superimposed on (−200 V), the next peripheral surface portion F2 has the potential Vs (−800 V) shown in FIG.
V). However, since the photoconductor bias Vd (−200 V) is applied to the entire photoconductor 10, the potential Vs1 of the next peripheral surface portion F2 becomes substantially −600 V.

【００３２】したがって、初期周面部位Ｆ１の全てが現
像箇所Ｐ２を通過してしまうまでに必要とする時間Ｔ１
内における現像箇所Ｐ２での感光体側電位Ｖｓ２は−２
００Ｖであり、かつ現像ローラ側電位（Ｖｂ）は未だ現
像バイアス電位Ｖｂ（−３００Ｖ）が印加されていない
ので零（０）Ｖである。したがって、図３に示すよう
に、実線で示す電位Ｖｓ２と点線で示す電位Ｖｂとの間
に−２００Ｖの電位差が発生するから、現像ローラ２０
側から初期周面部位Ｆ１にトナーが付着してしまうこと
を防止できる。連続運転中の設定電位差（−３００Ｖ）
より絶対値は小さいが、図４に示す特性から、連続運転
中と遜色なく無駄なトナー消費を一掃できる。Therefore, the time T1 required until all of the initial peripheral surface portion F1 passes through the development site P2.
The photoconductor-side potential Vs2 at the developing point P2 in the inside is within -2.
00 V, and the developing roller side potential (Vb) is zero (0) V because the developing bias potential Vb (-300 V) has not yet been applied. Therefore, as shown in FIG. 3, a potential difference of -200 V occurs between the potential Vs2 shown by the solid line and the potential Vb shown by the dotted line.
The toner can be prevented from adhering to the initial peripheral surface portion F1 from the side. Set potential difference during continuous operation (-300V)
Although the absolute value is smaller, the characteristic shown in FIG. 4 can eliminate wasteful toner consumption as in continuous operation.

【００３３】引続き、時間Ｔ１の経過後に次周面部位Ｆ
２が現像箇所Ｐ２に到達し、かつその全てが通過してし
まうまでの間における感光体側電位Ｖｓ２が−６００Ｖ
であるのに対して、現像ローラ側電位Ｖｂは図３に示す
ように時間Ｔ１の経過後に現像バイアス電源装置２５が
ＯＮされているので現像バイアス電位Ｖｂと同じ−３０
０Ｖである。したがって、電位差〔｜Ｖｂ｜−｜Ｖｓ２
｜〕が−３００Ｖとなるから、連続運転中と同じ設定電
位差（−３００Ｖ）と同じ状態とすることができるか
ら、この場合も無駄なトナー消費を一掃できる。Subsequently, after the lapse of time T1, the next peripheral surface portion F
2 reaches the developing point P2, and the photosensitive member side potential Vs2 is -600V until all of the photosensitive member P2 passes through the developing point P2.
On the other hand, since the developing bias power supply device 25 is turned on after the elapse of the time T1 as shown in FIG. 3, the developing roller side potential Vb is the same as the developing bias potential Vb.
0V. Therefore, the potential difference [ | Vb |-| Vs2
| Because] becomes -300 V, since it can be in the same state as the same set potential difference as in continuous operation (-300 V), this case may wipe out wasteful toner consumption.

【００３４】と同時的に、次周面部位Ｆ２に露光された
静電潜像（−５０Ｖの露光部）があるときは、現像用箇
所Ｐ２における感光体側電位Ｖｓ２（−５０Ｖ）と現像
ローラ側電位Ｖｂ（−３００Ｖ）との電位差（−２５０
Ｖ）によって現像ローラ２０側から感光体１０側にトナ
ーが供給され現像される。At the same time, when there is an exposed electrostatic latent image (−50 V exposed portion) on the next peripheral surface portion F 2, the photosensitive member side potential Vs 2 (−50 V) at the developing point P 2 and the developing roller side Potential difference from potential Vb (−300 V) (−250 V)
By V), toner is supplied from the developing roller 20 side to the photoreceptor 10 side and is developed.

【００３５】なお、次周面部位Ｆ２に引続く感光体１０
の周面が帯電箇所Ｐ１を通過する際は、時間Ｔ１が経過
しているので感光体バイアス電源装置１５はＯＦＦとさ
れ感光体バイアス電位Ｖｄ（−２００Ｖ）が印加されて
いない。また、帯電器３０にも感光体バイアス電位Ｖｄ
が重畳されていない。したがって、設定帯電電位Ｖｃ
（Ｖｓ１）と同値の−６００Ｖに帯電される。よって、
感光体側の絶対値が高い設定電位差（−３００Ｖ）によ
って無駄なトナー消費が防止され、かつ感光体側の絶対
値が低い現像用設定電位差（−２５０Ｖ）によって、現
像が行われる。現像されたトナー像は、転写器を通ると
きに用紙上へ転写され、所定の画像を形成する。The photoconductor 10 following the next peripheral portion F2
When the peripheral surface passes through the charged portion P1, the photoconductor bias power supply device 15 is turned off and the photoconductor bias potential Vd (−200 V) is not applied since the time T1 has elapsed. Also, the photoconductor bias potential Vd is applied to the charger 30.
Are not superimposed. Therefore, the set charging potential Vc
It is charged to -600 V of the same value as (Vs1). Therefore,
Useless toner consumption is prevented by the set potential difference (-300 V) having a high absolute value on the photoconductor side, and development is performed by the set potential difference for development (-250 V) having a low absolute value on the photoconductor side. The developed toner image is transferred onto a sheet when passing through a transfer device, and forms a predetermined image.

【００３６】運転終了時に備え帯電器３０をＯＦＦする
と、初期周面部位相当の周面の全てが現像箇所Ｐ２を通
過してしまうに要する時間Ｔ１の経過後に、現像バイア
ス電源２５がＯＦＦされかつ感光体バイアス電源装置１
５が再びＯＮされる。このＯＮ時間Ｔ２は、感光体１０
を１周以上回転させることのできる時間長とされる。When the charger 30 is turned off in preparation for the end of the operation, the developing bias power supply 25 is turned off and the photosensitive drum is turned off after a lapse of a time T1 required for the entire peripheral surface corresponding to the initial peripheral surface portion to pass through the developing point P2. Body bias power supply 1
5 is turned on again. This ON time T2 corresponds to the photoconductor 10
Is a time length that can be rotated one or more turns.

【００３７】しかして、この実施例によれば、初期周面
部位Ｆ１の全てが現像箇所Ｐ２を通過してしまうまでの
運転開始期間中に帯電箇所Ｐ１を通過する感光体１０の
次周面部位Ｆ２が現像箇所Ｐ２を通過する際に、次周面
部位側電位Ｖｓ２と現像ローラ側電位Ｖｂとの電位差が
連続運転中の設定電位差（−３００Ｖ）と等しい電位差
となるように、次周面部位Ｆ２が帯電箇所Ｐ１を通過す
る期間中だけ帯電器３０による帯電電位を設定帯電電位
Ｖｃ（−６００Ｖ）よりも強制的に高めた帯電電位（−
８００Ｖ）として運転する方法であるから、感光体バイ
アス電位Ｖｄ（−２００Ｖ）の印加による初期周面部位
Ｆ１へのトナー付着防止を保障しながら、これに引続く
次周面部位Ｆ２の場合も最良的な設定電位差（−３００
Ｖ）で行え、全体として無駄なトナー消費量を一掃でき
る。Thus, according to this embodiment, the next peripheral portion of the photoconductor 10 that passes through the charging portion P1 during the operation start period until all of the initial peripheral portion F1 passes through the developing portion P2. When F2 passes through the developing portion P2, the potential difference between the next peripheral surface portion side potential Vs2 and the developing roller side potential Vb becomes the same as the set potential difference (−300 V) during the continuous operation. Only during the period when F2 passes through the charging portion P1, the charging potential of the charger 30 is forcibly increased from the set charging potential Vc (−600 V) (−600 V).
800 V), the toner is prevented from adhering to the initial peripheral portion F1 by applying the photoreceptor bias potential Vd (−200 V), and the subsequent peripheral portion F2 is also best. Set potential difference (-300
V), so that wasteful toner consumption can be eliminated as a whole.

【００３８】また、画像形成装置が、放電型帯電器３０
のグリッド３３（３２）と感光体バイアス電源装置１５
とを定電圧素子４０を介して接続し、次周面部位Ｆ２が
帯電箇所Ｐ１を通過する期間中だけ設定帯電電位Ｖｃ
（−６００Ｖ）に感光体バイアス電位Ｖｂ（−２００
Ｖ）相当分を重畳させた高圧電圧（−８００Ｖ）とする
構成とされているので、設定帯電電位Ｖｃ（−６００
Ｖ）を安定化するための定電圧素子４０を利用しかつそ
の接続を変るだけで上記本画像形成運転を行える。した
がって、設備的負担がなく経済的である。The image forming apparatus is provided with a discharge type charger 30.
Grid 33 (32) and photoconductor bias power supply 15
Are connected via a constant voltage element 40, and the set charging potential Vc is set only during the period when the next peripheral surface portion F2 passes through the charging portion P1.
(−600 V) at the photoconductor bias potential Vb (−200 V).
V) is set to a high voltage (−800 V) in which an equivalent amount is superimposed, so that the set charging potential Vc (−600 V) is set.
The main image forming operation can be performed only by using the constant voltage element 40 for stabilizing V) and changing the connection. Therefore, there is no equipment burden and it is economical.

【００３９】（第２実施例）この第２実施例の画像形成
装置は、図５に示す如く、基本構成（１０，２０等）が
第１実施例（図１）の場合と同様であるが、帯電器３０
を従来例（図１０）と同じ帯電ローラ（３１Ｂ，３２
Ｂ）から形成し、かつ帯電用電源装置３５Ｈの出力電圧
ＶｃＳを設定電圧と高圧電圧との２段階に切替可能に形
成するとともに電圧切替手段を設け、運転開始時に感光
体バイアス電源装置１５をＯＮさせている間だけ帯電用
電源装置３５Ｈの出力電圧ＶｃＳを高圧電圧に自動的に
切替えるものと形成している。(Second Embodiment) As shown in FIG. 5, the image forming apparatus of the second embodiment has the same basic configuration (10, 20, etc.) as that of the first embodiment (FIG. 1). , Charger 30
Is the same as the charging roller (31B, 32) of the conventional example (FIG. 10).
B), and the output voltage VcS of the charging power supply 35H can be switched between a set voltage and a high voltage, and a voltage switching means is provided, and the photoconductor bias power supply 15 is turned on at the start of operation. The output voltage VcS of the charging power supply device 35H is automatically switched to the high voltage only during the operation.

【００４０】ここに、帯電用電源装置３５Ｈの設定電圧
は、図６に示すように、帯電箇所Ｐ１を通過する感光体
１０の周面電位Ｖｓ１を設定帯電電位（−６００Ｖ）と
等しい電位に帯電させることができる−１．１ｋＶであ
る。一方、高圧電圧は、その周面電位Ｖｓ１を図２に示
す−８００Ｖに帯電させることのできる−１．３ｋＶと
されている。Here, as shown in FIG. 6, the set voltage of the charging power supply unit 35H is such that the peripheral surface potential Vs1 of the photoconductor 10 passing through the charging portion P1 is charged to a potential equal to the set charging potential (-600 V). -1.1 kV. On the other hand, the high voltage is -1.3 kV which can charge the peripheral surface potential Vs1 to -800V shown in FIG.

【００４１】次に、電圧切替手段は、感光体バイアス電
位Ｖｄ（−２００Ｖ）を感光体１０に印加している間だ
け帯電用電源装置３５Ｈの出力電圧ＶｃＳを高圧電圧
（１．３ｋＶ）に切替えるものであるから、この実施例
ではそのＯＮ／ＯＦＦ信号発生手段３７Ｈを利用して構
築している。また、そのタイミング信号は、感光体バイ
アス電源装置１５用のＯＮ／ＯＦＦ信号発生手段１７か
ら入力される。Next, the voltage switching means switches the output voltage VcS of the charging power supply unit 35H to the high voltage (1.3 kV) only while the photoconductor bias potential Vd (-200 V) is applied to the photoconductor 10. Therefore, in this embodiment, the ON / OFF signal generating means 37H is used for construction. The timing signal is input from the ON / OFF signal generating means 17 for the photoconductor bias power supply device 15.

【００４２】しかして、この第２実施例の場合にも、第
１実施例の場合と同様に次周面部位Ｆ２の全てが現像箇
所Ｐ２を通過するまでの期間中だけ連続運転時と同じ設
定電位差（−３００Ｖ）として運転できるから、無駄な
トナー消費を一掃できる。Thus, in the case of the second embodiment, as in the case of the first embodiment, the same setting as in the continuous operation is performed only during the period until all of the next peripheral surface portion F2 passes through the developing point P2. Since the operation can be performed with the potential difference (−300 V), wasteful toner consumption can be eliminated.

【００４３】[0043]

【発明の効果】請求項１の発明によれば、初期周面部位
の全てが現像箇所を通過してしまうまでの運転開始期間
中に帯電箇所を通過する感光体の次周面部位が現像箇所
を通過する際に次周面部位側電位と現像ローラ側電位と
の電位差が連続運転時の設定電位差と等しい電位差とな
るように、次周面部位が帯電箇所を通過する期間中だけ
帯電器による帯電電位を設定帯電電位よりも強制的に高
めた帯電電位として運転する方法であるから、感光体バ
イアス電位の印加による初期周面部位へのトナー付着防
止効果を保障しながら、これに引続く次周面部位へのト
ナー付着も防止できる。よって、全体として無駄なトナ
ー消費を一掃できる。According to the first aspect of the present invention, the next peripheral portion of the photoconductor passing through the charged portion during the operation start period until all of the initial peripheral portion passes through the developing portion is the developing portion. So that the potential difference between the next circumferential surface portion side potential and the developing roller side potential becomes equal to the potential difference set during continuous operation when passing through the charging portion only during the period when the next circumferential surface portion passes through the charging portion. Since the charging potential is set to a charging potential that is forcibly increased from the set charging potential, the effect of preventing the toner from adhering to the initial peripheral surface portion by applying the photoconductor bias potential is ensured. It is also possible to prevent toner from adhering to the peripheral portion. Thus, wasteful toner consumption can be eliminated as a whole.

【００４４】[0044]

【００４５】また、請求項２の発明によれば、画像形成
装置が、帯電ローラに帯電電圧を印加する帯電用電源装
置を設定電圧と高圧電圧との２段階に切替可能に形成す
るとともに電圧切替手段を設け、運転開始時に感光体バ
イアス電源装置をＯＮさせている間だけ、帯電用電源装
置の出力電圧を高圧電圧に自動切替えすることのできる
構成とされているので、請求項１の画像形成運転を円滑
に行える。 Further, according to the second aspect of the invention, an image forming apparatus, the voltage switching with switchably formed in two stages between the setting voltage and the high voltage charging power supply device for applying a charging voltage to the charging roller means provided, only while is oN the photoreceptor bias power supply at the start of operation, since the output voltage of the charging power supply device has a configuration that can be switched automatically to high voltage, the 請 Motomeko 1 image The forming operation can be performed smoothly.

【図面の簡単な説明】[Brief description of the drawings]

【図１】本発明の第１実施例を説明するための全体構成
図である。FIG. 1 is an overall configuration diagram for explaining a first embodiment of the present invention.

【図２】同じく、帯電用電源装置と感光体バイアス電源
装置とのＯＮ−ＯＦＦタイミングと次周面部位を帯電さ
せる場合の帯電電位との関係を説明するための図であ
る。FIG. 2 is a diagram for explaining a relationship between ON / OFF timings of a charging power supply device and a photoreceptor bias power supply device and a charging potential when a next circumferential portion is charged.

【図３】同じく、現像箇所における感光体側電位と現像
ローラ側電位との関係を説明するための図である。FIG. 3 is a diagram for explaining a relationship between a photoconductor-side potential and a developing roller-side potential at a development location.

【図４】同じく、電位差とトナー付着量との特性関係を
説明するための図である。FIG. 4 is a view for explaining a characteristic relationship between a potential difference and a toner adhesion amount.

【図５】本第２実施例の説明をするための全体構成図で
ある。FIG. 5 is an overall configuration diagram for explaining the second embodiment.

【図６】同じく、帯電用電源装置の出力電圧と感光体の
帯電電圧との関係を説明するための図である。FIG. 6 is a diagram for explaining the relationship between the output voltage of the charging power supply device and the charging voltage of the photosensitive member.

【図７】従来例（１）を説明するための全体構成図であ
る。FIG. 7 is an overall configuration diagram for explaining a conventional example (1).

【図８】同じく、帯電用電源装置と感光体バイアス電源
装置とのＯＮ−ＯＦＦタイミングと次周面部位を帯電さ
せる場合の帯電電位との関係を説明するための図であ
る。FIG. 8 is a diagram for explaining a relationship between ON-OFF timings of the charging power supply device and the photoconductor bias power supply device and a charging potential when the next peripheral surface portion is charged.

【図９】同じく、現像箇所における感光体側電位と現像
ローラ側電位との関係を説明するための図である。FIG. 9 is a view for explaining a relationship between a photoconductor-side potential and a developing roller-side potential at a development location.

【図１０】従来例（２）を説明するための全体構成図で
ある。FIG. 10 is an overall configuration diagram for explaining a conventional example (2).

【符号の説明】[Explanation of symbols]

１０ 感光体 １５ 感光体バイアス電源装置 １７ ＯＮ／ＯＦＦ信号発生手段 ２０ 現像ローラ ２５ 現像バイアス電源装置 ２７ ＯＮ／ＯＦＦ信号発生手段 ３０ 帯電器 ３１ 放電ワイヤー ３１Ｂ 基体部（帯電ローラ） ３２ シールドケース（グリッド） ３２Ｂ 弾性層（帯電ローラ） ３３ グリッド ３５ 帯電用電源装置 ３５Ａ 電圧切替型帯電用電源装置 ３７ ＯＮ／ＯＦＦ信号発生手段 ３７Ｈ ＯＮ／ＯＦＦ信号発生手段（電圧切替手段） ４０ 定電圧素子 ４５ 廃トナー回収装置 ４６ ブレード ５０ 除電ランプ Ｆ１ 初期周面部位 Ｆ２ 次周面部位 Ｖｂ 現像バイアス電位 Ｖｄ 感光体バイアス電位 REFERENCE SIGNS LIST 10 photoconductor 15 photoconductor bias power supply 17 ON / OFF signal generating means 20 developing roller 25 developing bias power supply 27 ON / OFF signal generating means 30 charger 31 discharge wire 31B base unit (charging roller) 32 shield case (grid) 32B elastic layer (charging roller) 33 grid 35 charging power supply device 35A voltage switching type charging power supply device 37 ON / OFF signal generating means 37H ON / OFF signal generating means (voltage switching means) 40 constant voltage element 45 waste toner collecting device 46 Blade 50 Static elimination lamp F1 Initial peripheral surface part F2 Secondary peripheral surface part Vb Development bias potential Vd Photoconductor bias potential

───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.⁷，ＤＢ名) G03G 15/00 303 G03G 15/02 G03G 15/06 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 15/02 G03G 15/06

Claims (2)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 帯電器を通過した感光体の周面に光照射
して露光部と未露光部とを形成し、感光体側と現像ロー
ラ側との設定電位差を利用して露光部へ現像ローラ側か
ら１成分トナーを供給して現像するとともに、運転開始
時に帯電箇所と現像箇所との間にあった感光体の初期周
面部位の全てが現像箇所を通過してしまうまでの期間中
に感光体に設定帯電電位と同極性で絶対値の小さい感光
体バイアス電位を印加して運転を開始する反転現像方式
の画像形成運転方法であって、 前記初期周面部位の全てが前記現像箇所を通過してしま
うまでの運転開始期間中に前記帯電箇所を通過する前記
感光体の次周面部位が前記現像箇所を通過する際に該次
周面部位側と前記現像ローラ側との電位差が前記設定電
位差と等しい電位差となるように、該次周面部位が前記
帯電箇所を通過する期間中だけその帯電電位を前記設定
帯電電位よりも強制的に高めて運転することを特徴とす
る反転現像方式の画像形成運転方法。1. A method of irradiating a peripheral surface of a photoreceptor having passed a charger with light to form an exposed portion and an unexposed portion, and using a set potential difference between a photoreceptor side and a developing roller side to a developing roller While supplying the one-component toner from the side to develop, the photosensitive member is charged to the photosensitive member during a period until all of the initial peripheral surface portion of the photosensitive member between the charged portion and the developed portion at the start of operation passes through the developed portion. An image forming operation method of a reversal development method in which a photosensitive member bias potential having the same polarity as the set charging potential and having a small absolute value is applied and operation is started, wherein all of the initial peripheral surface portion passes through the development site. When the next peripheral surface portion of the photoreceptor that passes through the charged portion during the operation start period until the end passes through the developing portion, the potential difference between the next peripheral surface portion side and the developing roller side is equal to the set potential difference. The next round so that the potential difference becomes equal. The image forming method of operating a reverse developing method, wherein a site is operated by increasing forces than the set charging voltage the charge potential only during passing through the charging portion. 【請求項２】 帯電器を通過した感光体の周面に光照射
して露光部と未露光部とを形成し、感光体側と現像ロー
ラ側との設定電位差を利用して露光部へ現像ローラ側か
ら１成分トナーを供給して現像するとともに、運転開始
時に帯電箇所と現像箇所との間にあった感光体の初期周
面部位の全てが現像箇所を通過してしまうまでの期間中
に感光体に設定帯電電位と同極性で絶対値の小さい感光
体バイアス電位を印加して運転を開始する反転現像方式
の画像形成装置において、 前記帯電器を前記感光体の周面に摺接する帯電ローラか
ら形成するとともに、この帯電ローラに帯電電圧を印加
する帯電用電源装置を設定電圧とこれより高い高圧電圧
とのいずれかに切替出力可能に形成し、前記感光体バイ
アス電位を印加している間だけ該帯電用電源装置の出力
を高圧電圧に切替える電圧切替手段を設けたことを特徴
とする反転現像方式の画像形成装置。2. A method of irradiating a peripheral surface of a photoreceptor that has passed through a charger to form an exposed portion and an unexposed portion, and using a set potential difference between the photoreceptor side and the developing roller side to a developing roller While supplying the one-component toner from the side to develop, the photosensitive member is charged to the photosensitive member during a period until all of the initial peripheral surface portion of the photosensitive member between the charged portion and the developed portion at the start of operation passes through the developed portion. In a reversal developing type image forming apparatus which starts operation by applying a photosensitive member bias potential having the same polarity as the set charging potential and a small absolute value, the charger is formed from a charging roller which is in sliding contact with the peripheral surface of the photosensitive member. In addition, a charging power supply for applying a charging voltage to the charging roller is formed so as to be switchable between a set voltage and a higher voltage higher than the set voltage, and the charging is performed only while the photoconductor bias potential is applied. Power supply The image forming apparatus of the reversal developing system the output, characterized in that a voltage switching means for switching the high voltage.