JP6492995B2 - Image forming apparatus - Google Patents
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- JP6492995B2 JP6492995B2 JP2015119921A JP2015119921A JP6492995B2 JP 6492995 B2 JP6492995 B2 JP 6492995B2 JP 2015119921 A JP2015119921 A JP 2015119921A JP 2015119921 A JP2015119921 A JP 2015119921A JP 6492995 B2 JP6492995 B2 JP 6492995B2
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Description
本発明は、滑剤を外添したトナーで静電潜像を現像する画像形成装置に関するものである。 The present invention relates to an image forming apparatus that develops an electrostatic latent image with toner externally added with a lubricant.
感光体などの像担持体のクリーニング性の向上を目的として、ステアリン酸亜鉛などの滑剤を像担持体に供給し像担持体表面の付着力及び摩擦力を低下させる技術がこれまでから用いられている。また、像担持体に滑剤を供給する方式として、トナー表面に滑剤を添加して（以下、「外添」と記すことがある）像担持体に滑剤を供給する方式が広く採用されている。 For the purpose of improving the cleaning performance of an image carrier such as a photoconductor, a technique for reducing the adhesion and frictional force on the surface of the image carrier by supplying a lubricant such as zinc stearate to the image carrier has been used. Yes. As a method of supplying a lubricant to the image carrier, a method of adding a lubricant to the toner surface (hereinafter sometimes referred to as “external addition”) and supplying the lubricant to the image carrier is widely adopted.
しかしながら、滑剤が外添されたトナーが像担持体に１次された後、さらに像担持体から中間転写ベルト上に２次転写され、その後トナーから滑剤が離脱し中間転写ベルト上に滞留し固着することがあった。固着した滑剤は中間転写ベルトの抵抗や表面離型性を変化させるため、中間転写ベルトから用紙へのトナー像の２次転写が十分に行われず画像濃度ムラが発生することがあった。特に通紙方向の帯状画像あるような、回転軸方向に画像の有無がある画像が形成された場合には、画像の有無により中間転写ベルト上の滑剤量に大きな差がでるため画像濃度ムラの発生が顕著となる。 However, after the toner with externally added lubricant is primarily applied to the image carrier, the toner is further transferred to the intermediate transfer belt from the image carrier, and then the lubricant is detached from the toner and stays on the intermediate transfer belt to be fixed. There was something to do. Since the adhered lubricant changes the resistance and surface releasability of the intermediate transfer belt, secondary transfer of the toner image from the intermediate transfer belt to the paper is not sufficiently performed, and image density unevenness may occur. In particular, when an image having the presence or absence of an image in the rotation axis direction, such as a belt-like image in the paper passing direction, is formed, a large difference in the amount of lubricant on the intermediate transfer belt is caused by the presence or absence of the image. Occurrence becomes remarkable.
そこで、例えば特許文献１では、中間転写ベルトなどに供給する滑剤の量を軸方向に調整できる機構が提案されているが、この提案機構は、中間転写ベルトなどに滑剤を直接塗布する方式であって、滑剤塗布機構が必要であり装置の大型化を招いてしまう。 Thus, for example, Patent Document 1 proposes a mechanism that can adjust the amount of lubricant supplied to the intermediate transfer belt or the like in the axial direction. This proposed mechanism is a system that directly applies the lubricant to the intermediate transfer belt or the like. As a result, a lubricant application mechanism is required, resulting in an increase in the size of the apparatus.
また特許文献２には、中間転写ベルトと感光体との間に電位差を設けて中間転写ベルトから感光体に未転写トナーを回収する技術が提案されている。しかし、この提案技術では回転軸方向で電位差を調整することはできず、滑剤のみを回収することはできない。 Patent Document 2 proposes a technique for collecting a non-transferred toner from the intermediate transfer belt to the photosensitive member by providing a potential difference between the intermediate transfer belt and the photosensitive member. However, with this proposed technique, the potential difference cannot be adjusted in the direction of the rotation axis, and only the lubricant cannot be recovered.
また特許文献３にも、中間転写ベルトと感光体との間に電位差を設けて中間転写ベルトから感光体に未転写トナーを回収する技術が提案されている。また、特許文献３では感光体の露光によって中間転写ベルトと感光体との間の電位差を設けている。しかし、この提案技術でも滑剤のみを回収し滑剤を均一化ことはできない。 Patent Document 3 also proposes a technique for collecting untransferred toner from the intermediate transfer belt to the photosensitive member by providing a potential difference between the intermediate transfer belt and the photosensitive member. In Patent Document 3, a potential difference between the intermediate transfer belt and the photosensitive member is provided by exposure of the photosensitive member. However, even with this proposed technique, it is not possible to collect only the lubricant and make the lubricant uniform.
本発明の目的は、トナーに滑剤を外添して像担持体に滑剤を供給する方式の画像形成装置において、中間転写体上の滑剤量を回転軸方向で均一化し、画像濃度ムラの発生を抑制することにある。 An object of the present invention is to uniformize the amount of lubricant on the intermediate transfer member in the direction of the rotation axis in an image forming apparatus of a type in which a lubricant is externally added to a toner and the lubricant is supplied to an image bearing member, thereby generating uneven image density. It is to suppress.
前記目的を達成する本発明に係る画像形成装置は、回転自在の像担持体と、前記像担持体の表面を均一帯電させる帯電手段と、表面が均一帯電した前記像担持体に光を照射して静電潜像を形成する露光手段と、前記像担持体に形成された静電潜像を、滑剤を外添したトナーで現像する現像手段と、トナーの帯電極性と逆極性の電圧が印加され、前記現像手段により形成された前記像担持体上のトナー像を無端状で回転自在の中間転写体に転写する転写手段と、前記像担持体の表面をクリーニングするクリーニング部材と、前記中間転写体上に形成されたトナー像の回転方向の印字率を前記中間転写体の回転軸方向に所定間隔で分割した仮想領域ごとに算出して積算し、積算された印字率から前記仮想領域ごとの滑剤の付着量を推算し、当該推算結果に応じて、前記転写手段への印加電圧を画像形成時とは逆極性とするとともに、前記転写手段と前記像担持体との前記仮想領域ごとの電位差を制御して前記中間転写体上の滑剤を前記像担持体に回収する制御手段とを備えることを特徴とする。 The image forming apparatus according to the present invention that achieves the above object includes a rotatable image carrier, charging means for uniformly charging the surface of the image carrier, and irradiating the image carrier with a uniformly charged surface with light. An exposure means for forming an electrostatic latent image, a developing means for developing the electrostatic latent image formed on the image carrier with toner externally added with a lubricant, and a voltage having a polarity opposite to the charging polarity of the toner is applied. Transfer means for transferring the toner image on the image carrier formed by the developing means to an endless and rotatable intermediate transfer member, a cleaning member for cleaning the surface of the image carrier, and the intermediate transfer The printing rate in the rotation direction of the toner image formed on the body is calculated and integrated for each virtual region divided at a predetermined interval in the rotation axis direction of the intermediate transfer member, and the calculated printing rate is calculated for each virtual region. Estimate the amount of lubricant adhering to In accordance with the result, the voltage applied to the transfer unit is set to a polarity opposite to that at the time of image formation, and the potential difference between the transfer unit and the image carrier for each virtual region is controlled to control the voltage on the intermediate transfer unit. And a control means for collecting the lubricant on the image carrier.
上記構成においてより詳細には、前記中間転写体から前記像担持体に滑剤を回収する際、前記転写手段と前記像担持体との前記仮想領域ごとの電位差は、前記露光手段の露光量によって制御するのが好ましい。 More specifically, in the above configuration, when recovering the lubricant from the intermediate transfer member to the image carrier, the potential difference for each virtual region between the transfer unit and the image carrier is controlled by the exposure amount of the exposure unit. It is preferable to do this.
また上記構成においてより詳細には、前記制御手段は、前記積算された印字率が低いほど滑剤の付着量は多いと推算し、滑剤を前記像担持体に回収する際の前記転写手段と前記像担持体との電位差を大きくするのが好ましい。 More specifically, in the above configuration, the control means estimates that the lower the integrated printing rate is, the more the lubricant is attached, and the transfer means and the image when the lubricant is collected on the image carrier. It is preferable to increase the potential difference from the carrier.
また上記構成においてより詳細には、前記制御手段は、前記いずれかの仮想領域において所定期間トナー像の印字率の増分がゼロであった場合、前記中間転写体が少なくとも１回転する間、前記中間転写体上の滑剤を前記像担持体に回収する制御を行うのが好ましい。 More specifically, in the above configuration, when the increment of the printing rate of the toner image is zero for a predetermined period in any one of the virtual areas, the control unit performs the intermediate transfer for at least one rotation of the intermediate transfer member. It is preferable to perform control to collect the lubricant on the transfer member on the image carrier.
また上記構成においてより詳細には、前記制御手段は、前記いずれかの仮想領域において所定期間トナー像の印字率の増分がゼロであった場合、同一ジョブの実施中は印字間、同一ジョブの終了後は前記中間転写体が少なくとも１回転する間、前記中間転写体上の滑剤を前記像担持体に回収する制御を行うのが好ましい。 More specifically, in the above configuration, when the increment of the printing rate of the toner image is zero for a predetermined period in any one of the virtual areas, the control unit finishes the same job during printing during the same job. Thereafter, it is preferable to perform control to collect the lubricant on the intermediate transfer member on the image carrier while the intermediate transfer member rotates at least once.
また上記構成においてより詳細には、前記制御手段は、前記いずれかの仮想領域において所定期間トナー像の印字率の増分がゼロであった場合、複数の異なるジョブが連続して実施されているときは、前記複数の異なるジョブの終了後に前記回転軸方向に連続した帯状のベタ画像を形成するのが好ましい。 More specifically, in the above configuration, the control unit is configured to execute a plurality of different jobs in succession when the increment of the printing rate of the toner image is zero for a predetermined period in any one of the virtual areas. Preferably, after the plurality of different jobs, a continuous belt-like solid image is formed in the rotation axis direction.
また上記構成においてより詳細には、前記制御手段は、前記中間転写体の回転軸方向の全域にわたってベタ画像が形成された場合、積算された印字率をリセットするのが好ましい。 More specifically, in the above configuration, it is preferable that the control unit resets the integrated printing rate when a solid image is formed over the entire region of the intermediate transfer member in the rotation axis direction.
また上記構成においてより詳細には、前記現像手段が、補給用トナーを収容した交換可能なトナーボトルを備え、前記制御手段は、トナーボトルが交換された場合に、前記中間転写体上の滑剤を前記像担持体に回収する制御を行うのが好ましい。 More specifically, in the above configuration, the developing unit includes a replaceable toner bottle containing replenishing toner, and the control unit removes the lubricant on the intermediate transfer member when the toner bottle is replaced. It is preferable to perform control to collect on the image carrier.
本発明の画像形成装置では、中間転写体の回転軸方向に所定間隔で分割した仮想領域ごとに、中間転写体上から像担持体に回収する滑剤量を調整できるので、中間転写体上の滑剤量を回転軸方向で均一化でき画像濃度ムラの発生を抑制できる。 In the image forming apparatus of the present invention, the amount of lubricant recovered from the intermediate transfer member to the image carrier can be adjusted for each virtual region divided at predetermined intervals in the rotation axis direction of the intermediate transfer member. The amount can be made uniform in the direction of the rotation axis, and the occurrence of uneven image density can be suppressed.
また、本発明の画像形成装置では、像担持体及び中間転写体の使用劣化が抑制され長期間にわたって使用できる。 Further, in the image forming apparatus of the present invention, use deterioration of the image carrier and the intermediate transfer member is suppressed, and the image forming apparatus can be used for a long period of time.
そしてまた、本発明の画像形成装置では、滑剤の塗布及び回収の時間を必要としないので生産性の低下を防止できる。さらに、滑剤の塗布装置及び回収装置を新たに必要としないので装置の小型化や低コスト化が実現できる。また、無駄なトナーの使用も抑制できる。 In addition, the image forming apparatus of the present invention does not require the time for applying and collecting the lubricant, so that a reduction in productivity can be prevented. Furthermore, since a lubricant application device and a recovery device are not newly required, it is possible to reduce the size and cost of the device. In addition, useless toner can be suppressed.
本発明の実施形態について、各図面を参照しながら以下に説明する。但し本発明の内容は、当該実施形態に何ら限定されるものではない。 Embodiments of the present invention will be described below with reference to the drawings. However, the content of the present invention is not limited to the embodiment.
図１は、本発明の実施形態に係る画像形成装置の要部構成図である。なお、本図において、引用符のａ〜ｄは対応色の違い（ＹＭＣＫ）を示している。以下の説明にて各色のものを総称する場合には、ａ〜ｄの表記を省略する。例えば「画像形成ユニット１」は、画像形成ユニット１ａ〜１ｄを総称したものである。 FIG. 1 is a main part configuration diagram of an image forming apparatus according to an embodiment of the present invention. In the drawing, the reference signs a to d indicate the difference in corresponding colors (YMCK). In the following description, when all colors are collectively referred to, descriptions of a to d are omitted. For example, “image forming unit 1” is a generic term for the image forming units 1a to 1d.
本実施形態の画像形成装置は、中間転写体２０に複数の画像形成ユニット１を設けたタンデム型カラー画像形成装置である。画像形成ユニット１では、感光体（像担持体）１０の周りに、帯電装置１１、露光手段１２、現像器１３、１次転写ローラ１４、感光体清掃装置１５が配置されている。制御手段３０は、外部装置等から送られてきた画像情報データについて再現色別に位置ズレなどの補正処理を行い、制御手段３０内のメモリーに格納する。そして、画像形成ユニット１の動作制御を行って各色トナー像を感光体１０上に形成する。また、制御手段３０は、露光手段１２の露光制御などの画像形成ユニット１の動作制御の他、１次転写ローラ１４及び２次転写部２２の印加電圧制御なども行う。 The image forming apparatus of the present embodiment is a tandem type color image forming apparatus in which a plurality of image forming units 1 are provided on an intermediate transfer body 20. In the image forming unit 1, a charging device 11, an exposure unit 12, a developing device 13, a primary transfer roller 14, and a photoconductor cleaning device 15 are arranged around a photoconductor (image carrier) 10. The control unit 30 performs a correction process such as a positional shift for each reproduction color on the image information data sent from an external device or the like, and stores it in a memory in the control unit 30. Then, operation control of the image forming unit 1 is performed to form each color toner image on the photoreceptor 10. The control unit 30 also performs application voltage control of the primary transfer roller 14 and the secondary transfer unit 22 in addition to operation control of the image forming unit 1 such as exposure control of the exposure unit 12.
画像形成ユニット１によるトナー画像形成は、例えば図２に示すようにして行われる。まず感光体１０が帯電装置１１にて一様に（例えばＶ０＝−４００Ｖに）帯電される。その後、露光手段１２によって、ＹＭＣＫに色分解されたうちの対応色のデータが露光され、露光部分の感光体１０の表面電位が低下し（例えばＶｉ＝−７０Ｖ）、感光体１０上に対応色の静電潜像が形成される。さらに、対応色トナーを有する現像器１３において現像されトナー像が感光体１０上に形成される。 Toner image formation by the image forming unit 1 is performed, for example, as shown in FIG. First, the photosensitive member 10 is uniformly charged (for example, V0 = −400 V) by the charging device 11. After that, the exposure unit 12 exposes the data of the corresponding color among the color separated into YMCK, the surface potential of the exposed photoconductor 10 is lowered (for example, Vi = −70 V), and the corresponding color on the photoconductor 10. Electrostatic latent image is formed. Further, the toner image is developed in the developing unit 13 having the corresponding color toner, and a toner image is formed on the photoreceptor 10.
現像器１３としては、磁性を有するキャリアとトナーとを所定比率で混合させた現像剤を内蔵する２成分現像器が用いられる。現像器１３内の現像ローラには、Ｖｄｃ＝−３００ＶにＶｐｐ＝１．４ｋｖ（４．８ｋＨｚ）の交流が重畳された現像バイアスが印加されることにより、現像バイアスと感光体の表面電圧との電位差によってトナーが露光部分に移動し、感光体上にトナー像が形成される。 As the developing device 13, a two-component developing device containing a developer in which a magnetic carrier and toner are mixed at a predetermined ratio is used. A developing bias in which an alternating current of Vpp = 1.4 kv (4.8 kHz) is superimposed on Vdc = −300 V is applied to the developing roller in the developing unit 13, so that the developing bias and the surface voltage of the photoreceptor are changed. The toner moves to the exposed portion due to the potential difference, and a toner image is formed on the photoreceptor.
感光体１０上に形成されたトナー像は、１次転写部で、１次転写ローラ１４により押圧された中間転写体２０に接触し、１次転写ローラ１４に印加された１次転写バイアス（＋９００Ｖ）により形成される転写電界により、中間転写体２０上に転写される。その後、このトナー像と各画像形成ユニットの１次転写部で重なり合うよう同期を取って、各色トナー像が同様の構成を有する各画像形成ユニットで形成し、順次中間転写体２０上に写し重ね合わせられる。 The toner image formed on the photoreceptor 10 is in contact with the intermediate transfer body 20 pressed by the primary transfer roller 14 in the primary transfer portion, and the primary transfer bias (+900 V) applied to the primary transfer roller 14. ) Is transferred onto the intermediate transfer body 20 by the transfer electric field formed by (1). Thereafter, the toner image and the primary transfer portion of each image forming unit are synchronized so as to overlap each other, and each color toner image is formed by each image forming unit having the same configuration, and is sequentially copied onto the intermediate transfer member 20 and superimposed. It is done.
その後、２次転写部２２で被転写材に転写され、被転写材は図示しない定着装置で定着された後機外に排出される。一方、感光体１０は１次転写後に感光体清掃装置１５で、中間転写体２０は２次転写後に中間転写体清掃装置２１で、それぞれ転写後に残留したトナーが清掃され次の画像形成サイクルに備える。これらの清掃装置は常に圧接されている。 Thereafter, the toner image is transferred to a transfer material by the secondary transfer unit 22, and the transfer material is fixed by a fixing device (not shown) and then discharged outside the apparatus. On the other hand, the photosensitive member 10 is cleaned by the photosensitive member cleaning device 15 after the primary transfer, and the intermediate transfer member 20 is cleaned by the intermediate transfer member cleaning device 21 after the secondary transfer, and the toner remaining after the transfer is cleaned to prepare for the next image forming cycle. . These cleaning devices are always pressed against each other.
ここで、中間転写体２０の材料としては、ポリカーボネートやＰＴＦＥ、あるいはポリイミドを主原料としてカーボンを分散させた半導電性のものが用いられている。感光体１０としては、アルミニウム管の上に順次下引き層・電荷発生層・所定の厚みを有する電荷輸送層を積層した積層型感光体を用いる。 Here, as the material of the intermediate transfer member 20, a semiconductive material in which carbon is dispersed using polycarbonate, PTFE, or polyimide as a main raw material is used. As the photoreceptor 10, a laminated photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer having a predetermined thickness are sequentially laminated on an aluminum tube is used.
帯電装置１１としては、導電性ゴムローラを感光体１０に接触配置し、感光体１０の回転駆動に伴い従動回転する接触帯電ローラを用いる。感光体清掃装置１５は、ポリウレタンゴムによるクリーニングブレードが感光体１０に線圧３０Ｎ/ｍで当接される。転写後残留したトナーを回収する。 As the charging device 11, a contact charging roller is used in which a conductive rubber roller is disposed in contact with the photoconductor 10 and is driven to rotate as the photoconductor 10 is driven to rotate. In the photoconductor cleaning device 15, a cleaning blade made of polyurethane rubber is brought into contact with the photoconductor 10 at a linear pressure of 30 N / m. The toner remaining after the transfer is collected.
なお、現像器１３の現像槽内には、上述した現像ローラの他、現像ローラ上の現像剤搬送量を規制する規制部材と、現像ローラへ現像剤を供給しつつ長手方向へ現像剤を搬送する現像剤供給搬送経路と、現像剤供給搬送経路内に配置する搬送スクリューが設けられる。また更に当該現像槽内には、現像剤撹拌搬送経路（現像剤供給搬送経路に平行に配置され、現像剤搬送方向と反対方向へ撹拌を伴い、現像剤供給搬送経路の長手方向両端部で現像剤を受け渡す経路）と、現像剤撹拌搬送経路内に配置する現像剤撹拌搬送手段なども設けられる。 In addition to the developing roller described above, a regulating member that regulates the developer conveyance amount on the developing roller, and the developer is conveyed in the longitudinal direction while supplying the developer to the developing roller. And a developer supply / conveying path and a conveying screw disposed in the developer supply / conveying path. Further, in the developer tank, a developer stirring / conveying path (arranged in parallel with the developer supply / conveying path, accompanied by stirring in the direction opposite to the developer conveying direction, and developed at both ends in the longitudinal direction of the developer supply / conveying path). And a developer agitating / conveying means disposed in the developer agitating / conveying path.
撹拌供給路の一端にはトナー補給部が設けられ、現像にて減少したトナーが適宜供給される。トナーとキャリアから成る現像剤は、撹拌搬送路・供給搬送路を循環し、この循環経路中で混合撹拌されることで、キャリアとトナーの摩擦帯電により、トナー・キャリアの混合比に基づく所定帯電量にトナーは帯電される（本実施形態ではマイナスに帯電）。現像剤は供給搬送路にて、対向する現像ローラに磁気力で供給される。 At one end of the agitation supply path, a toner replenishing unit is provided, and the toner reduced by the development is appropriately supplied. The developer composed of toner and carrier circulates in the agitation conveyance path / supply conveyance path, and is mixed and agitated in this circulation path, so that a predetermined charge based on the mixing ratio of the toner and the carrier is generated by frictional charging of the carrier and toner. The amount of toner is charged (in this embodiment, it is negatively charged). The developer is supplied by a magnetic force to the opposing developing roller in the supply conveyance path.
現像ローラは、駆動回転されるスリーブローラと、スリーブローラ内に固定配置された磁石ローラとから構成される。磁石ローラは、スリーブローラの回転方向に沿って５つの磁極を有する。これらの磁極のうち、主磁極は、感光体１０と対向する位置に配置されており、また、スリーブローラ上の現像剤を剥離するための反発磁界を発生させる各同極部は、現像槽内部に対向した位置に配置されている。 The developing roller includes a sleeve roller that is driven to rotate and a magnet roller that is fixedly disposed in the sleeve roller. The magnet roller has five magnetic poles along the rotation direction of the sleeve roller. Of these magnetic poles, the main magnetic pole is disposed at a position facing the photoconductor 10, and each homopolar portion for generating a repulsive magnetic field for peeling off the developer on the sleeve roller is provided inside the developing tank. It is arrange | positioned in the position facing.
現像ローラのスリーブローラの回転方向は、感光体１０の回転方向と同じ（対向部において互いに反対方向）になるように設定されている。供給搬送路中の一部の現像剤は、現像ローラ上に磁気力により現像ローラに供給する。供給された現像剤については、規制部にて、現像ローラ上の現像剤の量が略一定に規制される。 The rotation direction of the sleeve roller of the developing roller is set to be the same as the rotation direction of the photosensitive member 10 (directions opposite to each other at the facing portion). A part of the developer in the supply conveyance path is supplied to the developing roller by a magnetic force on the developing roller. For the supplied developer, the amount of the developer on the developing roller is regulated to be substantially constant by the regulation unit.
この後、現像剤は感光体１０と対抗する領域に搬送され、現像ローラに印加された現像バイアスと感光体１０上の潜像との電位差により、所定量のトナーが感光体１０上の所定領域（潜像）に付着されて現像される。現像ニップを通過した現像剤は、同極部に達し現像ローラから剥離され、供給搬送路中に戻され、再び循環される。 Thereafter, the developer is conveyed to an area facing the photoconductor 10, and a predetermined amount of toner is applied to the predetermined area on the photoconductor 10 due to a potential difference between the developing bias applied to the developing roller and the latent image on the photoconductor 10. Attached to (latent image) and developed. The developer that has passed through the developing nip reaches the same pole portion, is peeled off from the developing roller, is returned to the supply conveyance path, and is circulated again.
以下に、本発明で使用可能な現像剤について説明する。本実施形態において、現像剤は、トナーとトナーを帯電するためのキャリアとを有する二成分系現像剤である。トナーとしては特に限定されず、一般に使用されている公知のトナーを使用することができ、バインダー樹脂中に着色剤や必要に応じて、荷電制御材や離型材等を含有させ、外添剤を処理したものを使用できる。トナー粒径としてはこれに限定されるものではないが、３〜１５μｍ程度が望ましい。 The developer that can be used in the present invention will be described below. In this embodiment, the developer is a two-component developer having a toner and a carrier for charging the toner. The toner is not particularly limited, and a commonly used known toner can be used. The binder resin contains a colorant or, if necessary, a charge control material or a release material, and an external additive is added. You can use the processed one. The toner particle size is not limited to this, but is preferably about 3 to 15 μm.
キャリアとしては特に限定されず、一般に使用されている公知のキャリアを使用することができ、コート型キャリアやバインダー型キャリアなどが使用できる。キャリア粒径としてはこれに限定されるものではないが、１５〜１００μｍが好ましい。 It does not specifically limit as a carrier, The well-known carrier generally used can be used, A coat type carrier, a binder type carrier, etc. can be used. Although it is not limited to this as a carrier particle size, 15-100 micrometers is preferable.
コート型キャリアは磁性体からなるキャリアコア粒子表面に樹脂コートがなされてなるキャリアである。コート型キャリアの極性等の帯電特性は、表面コート層の種類やキャリア表面に正または負帯電性の帯電性微粒子を固着させることにより制御することができる。 The coated carrier is a carrier in which a resin coat is formed on the surface of carrier core particles made of a magnetic material. The charging characteristics such as the polarity of the coat type carrier can be controlled by fixing positively or negatively chargeable fine particles to the type of the surface coat layer and the carrier surface.
表面コート樹脂としては、シリコーン樹脂、アクリル樹脂、エポキシ樹脂、フッ素系樹脂等が用いられる。帯電性微粒子としては、有機系では、ポリスチレン、スチレン系共重合物、アクリル樹脂、各種アクリル共重合物、ナイロン、ポリエチレン、ポリプロピレン、フッ素樹脂およびこれらの架橋物などの有機絶縁性微粒子を用いることができ、帯電レベルおよび極性については、素材、重合触媒、表面処理等により、希望するレベルの帯電及び極性を得ることができる。また、無機系としては、シリカ、二酸化チタン等の負帯電性の無機微粒子や、チタン酸ストロンチウム、アルミナ等の正帯電性の無機微粒子などが用いられる。 As the surface coat resin, silicone resin, acrylic resin, epoxy resin, fluorine resin, or the like is used. As the chargeable fine particles, organic insulating fine particles such as polystyrene, styrene copolymer, acrylic resin, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesin, and cross-linked products thereof may be used in the organic system. Regarding the charge level and polarity, a desired level of charge and polarity can be obtained by a material, a polymerization catalyst, a surface treatment, and the like. Further, as the inorganic type, negatively charged inorganic fine particles such as silica and titanium dioxide, and positively charged inorganic fine particles such as strontium titanate and alumina are used.
一方、バインダー型キャリアは、磁性体微粒子をバインダー樹脂中に分散させたものであり、キャリア表面に正または負帯電性の帯電性微粒子を固着させることや、表面コーティング層を設けることもできる。バインダー型キャリアの極性等の帯電特性は、バインダー樹脂の材質、帯電性微粒子、表面コーティング層の種類によって制御することができる。バインダー型キャリアに用いられるバインダー樹脂としては、コート型キャリアと同様の樹脂を用いることができる。 On the other hand, the binder type carrier is obtained by dispersing magnetic fine particles in a binder resin, and positive or negative chargeable fine particles can be fixed to the carrier surface, or a surface coating layer can be provided. Charging characteristics such as polarity of the binder type carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer. As the binder resin used for the binder type carrier, the same resin as that of the coat type carrier can be used.
トナーとキャリアの混合比は所望のトナー帯電量が得られるよう調整されれば良く、トナー比はトナーとキャリアの合計量に対して３〜１０重量％が適している。 The mixing ratio of the toner and the carrier may be adjusted so as to obtain a desired toner charge amount, and the toner ratio is suitably 3 to 10% by weight with respect to the total amount of the toner and the carrier.
２成分現像の場合、トナー濃度（トナー重量／現像剤重量）によりトナー帯電量が変化する。低いと帯電量が上昇し、甚だしい場合は画像濃度低下を引き起こす、一方で高い場合は帯電量の低下を引き起こし、甚だしい場合はかぶりや粉煙による機内汚染といった問題を引き起こす。このため、ある程度略一定のたとえば、４〜７重量％といったトナー濃度に収まるようにトナー補給制御を行っている。 In the case of two-component development, the toner charge amount varies depending on the toner concentration (toner weight / developer weight). If it is low, the charge amount will increase, and if it is severe, the image density will decrease. On the other hand, if it is high, it will cause a decrease in charge amount. For this reason, the toner replenishment control is performed so that the toner density falls within a substantially constant level, for example, 4 to 7% by weight.
ところで、感光体１０に滑剤被膜を形成することで、感光体１０への付着力を低下させたり、感光体１０とクリーニングブレードの負荷を落としたりして、画像ノイズを防止し感光体１０やクリーニングブレードの消耗を抑える方法が知られている。この滑剤被膜の形成のためトナーに滑剤を外添することで現像器１３より感光体１０へ滑剤を供給する方法は、特別な機構が不要であるため小型の機械でも用いることができ、塗布量も少量を安定して塗布できるという利点がある。 By forming a lubricant film on the photoconductor 10, the adhesion to the photoconductor 10 is reduced, or the load on the photoconductor 10 and the cleaning blade is reduced to prevent image noise and to clean the photoconductor 10 and the cleaning device. A method for suppressing blade wear is known. The method of supplying the lubricant from the developing unit 13 to the photosensitive member 10 by externally adding the lubricant to the toner for forming the lubricant film does not require a special mechanism and can be used even in a small machine. Has the advantage that a small amount can be stably applied.
滑剤とトナー及び滑剤と各部材とはファンデル・ワールス力及びクーロン力によって吸着する。滑剤とトナーとの間の吸着力は強いが、現像器１３における感光体１０と現像帆立ちの接触や、感光体清掃装置１５におけるクリーニングブレードによるせん断力などの力学的エネルギーが加えられることによって滑剤とトナーは分離する。トナーから分離した滑剤はクリーニングブレードによって均され感光体１０上の付着力を低減する。 The lubricant, the toner, the lubricant, and each member are adsorbed by van der Waals force and Coulomb force. Although the adsorbing force between the lubricant and the toner is strong, the lubricant is applied by applying mechanical energy such as contact between the photosensitive member 10 and the developing stool in the developing device 13 and shearing force by a cleaning blade in the photosensitive member cleaning device 15. And toner are separated. The lubricant separated from the toner is leveled by the cleaning blade to reduce the adhesion force on the photoreceptor 10.
滑剤としては、ステアリン酸金属塩やＰＴＦＥなどのフッ素樹脂が用いられる。特にステアリン酸亜鉛やステアリン酸カルシウムなどが望ましい。これらの滑剤は、前記の流動性や帯電性改善を目的とした外添剤とは異なり、トナーとは分離して感光体１０に供給され被膜として塗布される必要があるため、トナーとの付着力は小さく設計される。 As the lubricant, a fluororesin such as metal stearate or PTFE is used. In particular, zinc stearate and calcium stearate are desirable. Unlike the external additives for improving fluidity and chargeability described above, these lubricants need to be supplied to the photoconductor 10 separately from the toner and applied as a film, and therefore are attached to the toner. The wearing force is designed to be small.
二成分系現像方式では、現像領域において感光体１０と現像剤の帆立ちとが接触するので、白ベタ画像を印字しても力学的エネルギーが加えられることになり、結果として滑剤が感光体１０に移動する。一方、ベタ画像を印字した場合には、感光体１０に移動する滑剤の全体量は増えるが、感光体１０上に既にいる滑剤がトナーに再付着し現像剤へ移動する現象も発生する。この現象は、滑剤と感光体１０との間のファンデル・ワールス力よりも感光体１０とトナーとの間のファンデル・ワールス力の方が大きいため発生する。この結果、感光体１０表面の画像が形成されなかった部分の滑剤量は、画像が形成された部分よりも多くなる。 In the two-component development system, the photosensitive member 10 and the scallop of the developer are in contact with each other in the development region, so that mechanical energy is applied even when a solid white image is printed. As a result, the lubricant is transferred to the photosensitive member 10. Move to. On the other hand, when a solid image is printed, the total amount of the lubricant that moves to the photoconductor 10 increases, but there also occurs a phenomenon that the lubricant already on the photoconductor 10 reattaches to the toner and moves to the developer. This phenomenon occurs because the van der Waals force between the photoconductor 10 and the toner is larger than the van der Waals force between the lubricant and the photoconductor 10. As a result, the amount of the lubricant on the surface of the photoreceptor 10 where the image is not formed is larger than that on the portion where the image is formed.
この現象と同じことは感光体１０と中間転写体２０との間でも発生する。特に中間転写体２０の場合、ＹＭＣＫの４色が重なるため滑剤の供給に大きな差異が発生する。中間転写体２０上の滑剤量が異なると、トナーと中間転写体２０との間の吸着力に違いが生じる。滑剤が多い部分は２次転写しやすく、滑剤が少ない部分は２次転写しにくい現象が発生する。この結果、画像濃度ムラが生じて画像品質の低下を招いてしまう。 The same phenomenon occurs between the photosensitive member 10 and the intermediate transfer member 20. In particular, in the case of the intermediate transfer member 20, since four colors of YMCK are overlapped, a great difference occurs in the supply of the lubricant. If the amount of lubricant on the intermediate transfer member 20 is different, a difference occurs in the attractive force between the toner and the intermediate transfer member 20. A portion where the lubricant is large is easily subjected to secondary transfer, and a portion where the lubricant is small is difficult to perform secondary transfer. As a result, image density unevenness occurs, resulting in a decrease in image quality.
本発明者等は印字割合と中間転写体２０上の滑剤量との関係を調べるため、ベタ画像の印字割合の異なる図３に示すチャートを５枚連続して画像形成させた後、中間転写体２０上の滑剤量を測定した。このチャートは、領域Ａはベタ画像の印字割合が１００％、領域Ｂはベタ画像の印字割合が７５％、領域Ｃが印字割合が５０％、領域Ｄは印字割合が２５％、領域Ｅは印字割合が０％とされている。 In order to investigate the relationship between the printing ratio and the amount of lubricant on the intermediate transfer body 20, the present inventors formed five consecutive charts shown in FIG. 3 having different solid image printing ratios, and then formed the intermediate transfer body. The amount of lubricant on 20 was measured. In this chart, area A has a solid image printing ratio of 100%, area B has a solid image printing ratio of 75%, area C has a printing ratio of 50%, area D has a printing ratio of 25%, and area E has a printing ratio. The percentage is 0%.
表１に示すように、ベタ画像の印字割合が１００％である領域Ａを「１」とした場合、ベタ画像の印字割合が７５％の領域Ｂでは「１．２」、印字割合が５０％の領域Ｃでは「１．５」、印字割合が２５％の領域Ｄでは「２．２」、印字割合が０％の領域Ｅでは「５．２」と、印字割合が小さくなるにしたがって中間転写体２０上の滑剤量は多くなっていた。特に、通紙方向（副走査方向）の印字率の増分がゼロの状態が続く領域Ｅでは中間転写体２０上の滑剤量は著しく増加した。 As shown in Table 1, when the area A in which the solid image printing ratio is 100% is “1”, the area B in which the solid image printing ratio is 75% is “1.2” and the printing ratio is 50%. In the area C, “1.5”, in the area D where the printing ratio is 25%, “2.2”, and in the area E where the printing ratio is 0%, “5.2”, the intermediate transfer becomes smaller as the printing ratio becomes smaller. The amount of lubricant on the body 20 was increased. In particular, in the region E where the increment of the printing rate in the paper passing direction (sub-scanning direction) continues to be zero, the amount of lubricant on the intermediate transfer member 20 has increased remarkably.
そこで、本発明者等は、中間転写体２０上の滑剤量を均一するため、１次転写ローラ１４と感光体１０との間の電位差を用いて中間転写体２０上の滑剤を感光体１０に回収する方策を見出した。そして更に、中間転写体２０上に形成されたトナー像の副走査方向（回転方向）の印字率を中間転写体２０の回転軸方向に所定間隔で分割した仮想領域ごとに算出して積算し、積算された印字率から前記仮想領域ごとの滑剤の付着量を推算し、推算結果に応じて、１次転写ローラ１４への印加電圧を画像形成時とは逆極性とするとともに、１次転写ローラ１４と感光体１０との前記仮想領域ごとの電位差を制御して、中間転写体２０上から感光体１０に回収する前記仮想領域ごとの滑剤量を調整することした。これにより中間転写体２０上の滑剤量が均一となり画像濃度ムラの発生を低減できることを見出した。 Therefore, the present inventors use the potential difference between the primary transfer roller 14 and the photosensitive member 10 to make the lubricant on the intermediate transfer member 20 the photosensitive member 10 in order to make the amount of the lubricant on the intermediate transfer member 20 uniform. Found a strategy to recover. Further, the printing rate in the sub-scanning direction (rotation direction) of the toner image formed on the intermediate transfer member 20 is calculated and integrated for each virtual region divided at predetermined intervals in the rotation axis direction of the intermediate transfer member 20, The adhesion amount of the lubricant for each virtual area is estimated from the accumulated printing rate, and the voltage applied to the primary transfer roller 14 is set to have a polarity opposite to that at the time of image formation according to the estimation result. By controlling the potential difference between the virtual area 14 and the photoconductor 10 for each virtual area, the amount of lubricant for each virtual area collected from the intermediate transfer body 20 to the photoconductor 10 is adjusted. As a result, it has been found that the amount of lubricant on the intermediate transfer member 20 becomes uniform and the occurrence of uneven image density can be reduced.
なお、トナー像の印字率を積算する、中間転写体２０の回転軸方向に所定間隔で分割する仮想領域は、通常は数区分程度で足りるが、１ドットごとであってももちろん構わない。 It should be noted that the virtual area for integrating the toner image printing rate and divided at predetermined intervals in the direction of the rotation axis of the intermediate transfer member 20 is usually sufficient for several sections, but may of course be one dot at a time.
滑剤の回収制御では、まず、中間転写体２０の回転軸方向に所定間隔で分割された仮想領域ごとにトナー像の印字率を算出して積算する。具体的には、制御手段３０が、画像形成動作毎の画像情報（ドットカウント）に基づき仮想領域ごとのトナー像の印字率を算出して積算する。トナー像の印字率と中間転写体２０上の滑剤付着量との関係は、前記表１で例示したように、トナー像の印字率が低いほど中間転写体２０上の滑剤付着量は多くなる。このトナー像の印字率と中間転写体２０上の滑剤付着量との関係は装置の種類や現像条件などによって異なり、それぞれの装置毎に記憶手段に予め記憶されている。 In the lubricant recovery control, first, the printing rate of the toner image is calculated and integrated for each virtual region divided at a predetermined interval in the rotation axis direction of the intermediate transfer body 20. Specifically, the control unit 30 calculates and integrates the printing rate of the toner image for each virtual region based on the image information (dot count) for each image forming operation. As illustrated in Table 1 above, the relationship between the toner image printing rate and the lubricant adhesion amount on the intermediate transfer body 20 increases as the toner image printing rate decreases. The relationship between the toner image printing rate and the amount of lubricant adhering to the intermediate transfer member 20 varies depending on the type of device and development conditions, and is stored in advance in the storage means for each device.
そして、制御手段３０は、トナー印字率から推算される仮想領域毎の滑剤付着量に基づき、中間転写体２０上の滑剤量が均一となるように、１次転写ローラ１４と感光体１０との電位差を仮想領域毎に変えて、中間転写体２０上の滑剤を感光体１０に回収する。具体的には、制御手段３０は、１次転写ローラ１４の印加電圧を画像形成時とは逆極性にするとともに、推算された滑剤付着量に対応させて仮想領域ごとに露光量を制御し、１次転写ローラ１４と感光体１０との電位差を仮想領域毎に変える。露光手段１２による露光量を多くするほど感光体１０の表面電位がゼロに近づき、１次転写ローラ１４と感光体１０との電位差は大きくなって中間転写体２０上の滑剤は中間転写体２０から感光体１０に回収されやすくなる。 Then, the control unit 30 determines whether the primary transfer roller 14 and the photoconductor 10 are uniform so that the amount of lubricant on the intermediate transfer body 20 is uniform based on the lubricant adhesion amount for each virtual region estimated from the toner printing rate. The potential difference is changed for each virtual region, and the lubricant on the intermediate transfer member 20 is collected on the photosensitive member 10. Specifically, the control unit 30 sets the applied voltage of the primary transfer roller 14 to a polarity opposite to that at the time of image formation, and controls the exposure amount for each virtual region in accordance with the estimated lubricant adhesion amount, The potential difference between the primary transfer roller 14 and the photoreceptor 10 is changed for each virtual region. As the exposure amount by the exposure means 12 increases, the surface potential of the photosensitive member 10 approaches zero, and the potential difference between the primary transfer roller 14 and the photosensitive member 10 increases, and the lubricant on the intermediate transfer member 20 is transferred from the intermediate transfer member 20. The photoconductor 10 is easily collected.
中間転写体２０から感光体１０への滑剤の回収は、いずれの画像形成ユニット１で行ってもよいが、一つの画像形成ユニットで滑剤の回収を行うと、当該画像形成ユニットにおける感光体１０および感光体清掃装置１５の摩耗・劣化が他の画像形成ユニットよりも進むので、複数の画像形成ユニットで滑剤の回収を行うのが望ましい。 The recovery of the lubricant from the intermediate transfer member 20 to the photoconductor 10 may be performed by any of the image forming units 1. However, if the lubricant is recovered by one image forming unit, the photoconductor 10 and the photoconductor 10 in the image forming unit are collected. Since the wear and deterioration of the photoconductor cleaning device 15 proceeds more than other image forming units, it is desirable to collect the lubricant with a plurality of image forming units.
中間転写体２０から感光体１０に回収された滑剤は、画像形成ユニット１の感光体清掃装置１５で感光体１０から除去される。 The lubricant collected on the photoconductor 10 from the intermediate transfer body 20 is removed from the photoconductor 10 by the photoconductor cleaning device 15 of the image forming unit 1.
中間転写体２０から感光体１０への滑剤の回収制御は、いずれかの仮想領域において所定期間トナー像の印字率の増分がゼロであった場合、例えば用紙１ページ分（６００ｄｐｉの場合は４９６０ドット）以上トナー像の印字率の増分がゼロであった場合に、中間転写体２０が少なくとも１回転する間行うのが好ましい。 The lubricant recovery control from the intermediate transfer member 20 to the photosensitive member 10 is performed when the increment of the printing rate of the toner image is zero for a predetermined period in any virtual region, for example, for one page of paper (4960 dots in the case of 600 dpi). ) As described above, when the increment of the toner image printing rate is zero, it is preferably performed while the intermediate transfer member 20 rotates at least once.
ただし、同一ジョブの実施中に前記滑剤を回収する要件が満たされた場合は、画像形成効率の低下を抑えるため、滑剤回収制御は印字間において行い、同一ジョブの終了後に中間転写体２０が少なくとも１回転する間行うのが好ましい。 However, when the requirement for collecting the lubricant during the same job is satisfied, the lubricant collection control is performed between prints in order to suppress a decrease in image forming efficiency. It is preferable to carry out during one rotation.
また、複数の異なるジョブが連続して実施されているときに前記滑剤を回収する要件が満たされた場合は、複数の異なるジョブが終了した後に回転軸方向に連続した帯状のベタ画像を形成し、中間転写体２０上の滑剤量を均一化するのが好ましい。この帯状のベタ画像の回転方向の長さに特に限定はないが、通常、感光体１０の１／４周以上であるのが好ましい。 In addition, when the requirement for collecting the lubricant is satisfied when a plurality of different jobs are continuously performed, a continuous belt-shaped solid image is formed in the rotation axis direction after the plurality of different jobs are completed. The lubricant amount on the intermediate transfer member 20 is preferably made uniform. Although there is no particular limitation on the length of the strip-shaped solid image in the rotation direction, it is usually preferable that the length is 1/4 or more of the photoreceptor 10.
また、ジョブの実施中に中間転写体２０の回転軸方向の全域にわたってベタ画像が形成された場合は、積算された印字率をリセットするのが好ましい。これにより、滑剤回収制御の実施が抑えられる。 Further, when a solid image is formed over the entire area of the intermediate transfer member 20 in the rotation axis direction during execution of the job, it is preferable to reset the integrated printing rate. Thereby, implementation of lubricant recovery control is suppressed.
そしてまた、現像手段が、補給用トナーを収容した交換可能なトナーボトルを備える場合には、トナーボトルが交換されたときに、中間転写体２０上の滑剤を感光体１０に回収する制御を行うのが好ましい。 If the developing unit includes a replaceable toner bottle containing replenishing toner, control is performed to collect the lubricant on the intermediate transfer member 20 on the photosensitive member 10 when the toner bottle is replaced. Is preferred.
（第１実施例）
図４に、滑剤回収時の１次転写ローラ１４の印加電圧（回収電圧）と感光体１０の表面電位の一例を示す。これは、図３に示したチャートを５枚連続して画像形成した後、中間転写体２０上の滑剤を感光体１０に回収する処理を行う場合の電圧制御例である。１次転写ローラ１４の印加電圧を画像形成時と逆極性の−８００Ｖとする。そして、推算された中間転写体２０上の滑剤付着量に対応させて領域Ａ〜Ｅに露光量を変える。滑剤付着量の最も少ない領域Ａでは露光を行わず帯電装置１１による帯電電位（Ｖ０＝−４００Ｖ）を維持させ、１次転写ローラ１４と感光体１０との電位差ＰＡを−４００Ｖとする。領域Ｂでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−３００Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＢを−５００Ｖとする。領域Ｃでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−２８０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＣを−５２０Ｖとする。領域Ｄでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−２５０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＤを−５５０Ｖとする。領域Ｅでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−７０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＥを−７３０Ｖとする。マイナス帯電の滑剤は、１次転写ローラ１４と感光体１０との電位差が大きいほど中間転写体２０から感光体１０に移動するので、領域Ａから領域Ｅの順で中間転写体２０から感光体１０に回収される滑剤量は多くなる。これにより、中間転写体２０上の滑剤量は均一化される。
(First embodiment)
FIG. 4 shows an example of the applied voltage (collected voltage) of the primary transfer roller 14 and the surface potential of the photoconductor 10 when the lubricant is collected. This is an example of voltage control in the case where the process of recovering the lubricant on the intermediate transfer member 20 to the photosensitive member 10 is performed after the five charts shown in FIG. The voltage applied to the primary transfer roller 14 is set to −800 V having a polarity opposite to that at the time of image formation. Then, the exposure amount is changed to the areas A to E in accordance with the estimated lubricant adhesion amount on the intermediate transfer member 20. Without the least in the region A exposed lubricant adhesion amount to maintain the charging potential by the charging device 11 (V0 = -400V), the potential difference P A of the primary transfer roller 14 and the photoreceptor 10 and -400 V. In the region B, the surface potential Vi of the photoconductor 10 is set to −300 V by exposure by the exposure unit 12, and the potential difference P B between the primary transfer roller 14 and the photoconductor 10 is set to −500 V. In the region C, and the surface potential Vi of the photoreceptor 10 and -280V by exposure by the exposure means 12, the potential difference P C of the primary transfer roller 14 and the photoreceptor 10 with -520V. In the region D, and the surface potential Vi of the photoreceptor 10 and -250V by exposure by the exposure means 12, the potential difference P D of the primary transfer roller 14 and the photoreceptor 10 and -550 V. In the region E, the surface potential Vi of the photoreceptor 10 and -70V by exposure by the exposure means 12, the potential difference P E between the primary transfer roller 14 and the photoreceptor 10 with -730V. Since the negatively charged lubricant moves from the intermediate transfer member 20 to the photosensitive member 10 as the potential difference between the primary transfer roller 14 and the photosensitive member 10 increases, the intermediate transfer member 20 to the photosensitive member 10 in the order of region A to region E. The amount of lubricant recovered in this way increases. Thereby, the amount of lubricant on the intermediate transfer body 20 is made uniform.
図１に示した構成の画像形成装置を用いて、前記チャートの５枚連続形成を１ジョブとし、１ジョブごとに上記設定条件の滑剤回収制御を画像形成ユニット１ａにおいて中間転写体１回転分行い、これを１０００回繰り返した後、ブラックハーフトーン画像を印刷し画像濃度ムラを測定した。測定結果を表２に示す。 Using the image forming apparatus having the configuration shown in FIG. 1, the continuous formation of the five sheets of the chart is regarded as one job, and the lubricant recovery control under the above setting conditions is performed for one rotation of the intermediate transfer member in the image forming unit 1a for each job. After repeating this 1000 times, a black halftone image was printed and the image density unevenness was measured. The measurement results are shown in Table 2.
表２から明らかなように、滑剤回収制御を行わなかった場合には、領域Ａ〜領域Ｅにおける画像濃度が０．６〜０．８２の範囲となり画像濃度ムラが生じた。これに対し、滑剤回収制御を行った場合には、領域Ａ〜領域Ｅにおける画像濃度が０．６〜０．６４の範囲となり画像濃度ムラは生じなかった。 As is apparent from Table 2, when the lubricant recovery control was not performed, the image density in the areas A to E was in the range of 0.6 to 0.82, and image density unevenness occurred. On the other hand, when the lubricant recovery control was performed, the image density in the areas A to E was in the range of 0.6 to 0.64, and no image density unevenness occurred.
滑剤回収制御において、１次転写ローラ１４と感光体１０との電位差の制御は、感光体１０の露光量によって行う他、感光体１０の帯電制御や１次転写ローラ１４の印加電圧制御によって、あるいはこれらの組み合わせによって行ってもよい。 In the lubricant recovery control, the potential difference between the primary transfer roller 14 and the photoconductor 10 is controlled by the exposure amount of the photoconductor 10, the charging control of the photoconductor 10, the applied voltage control of the primary transfer roller 14, or You may carry out by the combination of these.
なお、滑剤がプラスに帯電している場合は、前記実施形態における１次転写ローラ１４の印加電圧及び感光体１０の表面電位を滑剤の帯電電極と同極性のプラスにする。 When the lubricant is positively charged, the applied voltage of the primary transfer roller 14 and the surface potential of the photosensitive member 10 in the above embodiment are made positive with the same polarity as the charging electrode of the lubricant.
（第２実施例）
図５に示す５枚のチャートを連続して画像形成させた後、中間転写体２０上の滑剤量を測定した。なお、領域Ａは５枚のチャート全部でベタ画像の印字割合が１００％である。領域Ｆは１枚目のベタ画像の印字割合が１００％で、２枚目〜５枚目のベタ画像は０％である。領域Ｄは５枚のチャート全部でベタ画像印字割合が２０％であり、それぞれのチャートの用紙搬送方向前側に１つのベタ画像が印字されている。領域Ｈは５枚のチャート全部でベタ画像印字割合が２０％であり、それぞれのチャートの用紙搬送方向に所定間隔で５％のベタ画像が４つ印字されている。領域Ｅは５枚のチャート全部で印字割合が０％とである。領域Ｆ、領域Ｄ、領域Ｈは５枚のチャートのベタ画像の印字割合の合計は同じであるが、ベタ画像の印字位置すなわち印字率の増分ゼロの状態が続く長さが異なっている。測定結果を表３に示す。
(Second embodiment)
After the five charts shown in FIG. 5 were continuously imaged, the amount of lubricant on the intermediate transfer member 20 was measured. In the area A, the printing ratio of the solid image is 100% in all the five charts. In the area F, the printing ratio of the first solid image is 100%, and the second to fifth solid images are 0%. In the area D, the solid image printing ratio is 20% for all the five charts, and one solid image is printed on the front side in the sheet conveyance direction of each chart. In the area H, the solid image printing ratio is 20% for all the five charts, and four solid images of 5% are printed at a predetermined interval in the sheet conveyance direction of each chart. In the area E, the printing ratio is 0% for all five charts. Area F, area D, and area H have the same total printing ratio of the solid images of the five charts, but are different in lengths in which the printing position of the solid images, that is, the state in which the printing rate increment is zero. Table 3 shows the measurement results.
表３によれば、５枚のチャート全部でベタ画像の印字割合が１００％である領域Ａを「１」とした場合、５枚のチャート全部で印字割合が０％である領域Ｅの滑剤量が「５．２０」と最も多かった。領域Ｆ、領域Ｄ、領域Ｈは５枚のチャートのベタ画像の印字割合の合計は同じであるが、印字率の増分ゼロの状態が最も長く続く領域Ｆでは滑剤量が「２．９８」と３つの領域の中で最も多かった。また、領域Ｄ及び領域Ｈでは、印字率の増分ゼロの状態が続く長さは違っていたが、中間転写体２０上の滑剤量は「２．２０」と「２．２１」と両者に大きな差は見られなかった。 According to Table 3, when the area A in which the printing ratio of the solid image is 100% in all the five charts is “1”, the amount of lubricant in the area E in which the printing ratio is 0% in all the five charts. Was “5.20”. The total print ratios of the solid images of the five charts are the same in the areas F, D, and H, but in the area F in which the print rate increment is zero for the longest, the lubricant amount is “2.98”. It was the most among the three areas. Further, in the region D and the region H, the length in which the print rate increment continues to be zero was different, but the amount of lubricant on the intermediate transfer member 20 was large in both “2.20” and “2.21”. There was no difference.
図１に示した構成の画像形成装置を用いて、図５に示す５枚のチャートの画像形成を１ジョブとし、１ジョブごとに下記設定条件の滑剤回収制御を画像形成ユニット１ａにおいて中間転写体１回転分行い、これを１０００回繰り返した後、ブラックハーフトーン画像を印刷し画像濃度ムラを測定した。測定結果を表４に示す。 Using the image forming apparatus having the configuration shown in FIG. 1, the image formation of the five charts shown in FIG. 5 is set as one job, and the lubricant recovery control under the following setting conditions is performed in the image forming unit 1a for each job. This was performed for one rotation, and this was repeated 1000 times, and then a black halftone image was printed to measure image density unevenness. Table 4 shows the measurement results.
１次転写ローラ１４の印加電圧を画像形成時と逆極性の−８００Ｖとする。そして、領域Ａでは露光を行わず帯電装置１１による帯電電位（Ｖ０＝−４００Ｖ）を維持させ、１次転写ローラ１４と感光体１０との電位差ＰＡを−４００Ｖとする。領域Ｆでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−３００Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＦを−５００Ｖとする。領域Ｄでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−２４０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＤを−５６０Ｖとする。領域Ｈでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−２４０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＨを−５６０Ｖとする。領域Ｅでは、露光手段１２による露光によって感光体１０の表面電位Ｖｉを−７０Ｖとし、１次転写ローラ１４と感光体１０との電位差ＰＥを−７３０Ｖとする。 The voltage applied to the primary transfer roller 14 is set to −800 V having a polarity opposite to that at the time of image formation. Then, to maintain the charge potential (V0 = -400 V) by the charging device 11 without exposure in the region A, the potential difference P A of the primary transfer roller 14 and the photoreceptor 10 and -400 V. In region F, the surface potential Vi of the photoreceptor 10 and -300V by exposure by the exposure means 12, the potential difference P F between the primary transfer roller 14 and the photoreceptor 10 and -500 V. In the region D, and the surface potential Vi of the photoreceptor 10 and -240V by exposure by the exposure means 12, the potential difference P D of the primary transfer roller 14 and the photoreceptor 10 with -560V. In the region H, the surface potential Vi of the photoreceptor 10 and -240V by exposure by the exposure means 12, the potential difference P H of the primary transfer roller 14 and the photoreceptor 10 with -560V. In the region E, the surface potential Vi of the photoreceptor 10 and -70V by exposure by the exposure means 12, the potential difference P E between the primary transfer roller 14 and the photoreceptor 10 with -730V.
表４から明らかなように、滑剤回収制御を行わなかった場合には、領域Ａ，Ｆ，Ｄ，Ｈ，Ｅにおける画像濃度が０．６〜０．８４の範囲となり画像濃度ムラが生じた。これに対し、滑剤回収制御を行った場合には、領域Ａ，Ｆ，Ｄ，Ｈ，Ｅにおける画像濃度が０．６〜０．６４の範囲となり画像濃度ムラは生じなかった。 As is apparent from Table 4, when the lubricant recovery control was not performed, the image density in the areas A, F, D, H, and E was in the range of 0.6 to 0.84, and image density unevenness occurred. On the other hand, when lubricant recovery control was performed, the image density in the regions A, F, D, H, and E was in the range of 0.6 to 0.64, and no image density unevenness occurred.
本実施形態に係る画像形成装置のように、中間転写体２０の回転軸方向に所定間隔で分割した仮想領域ごとに、中間転写体２０上から感光体１０に回収する滑剤量を調整することで、中間転写体２０上の滑剤量を回転軸方向で均一化でき画像濃度ムラの発生を抑制できる。また、従来装置に比べて、滑剤の塗布及び回収の時間を必要としないので生産性の低下を防止できる。さらに、滑剤の塗布装置及び回収装置を新たに必要としないので装置の小型化や低コスト化が実現できる。そしてまた、無駄なトナーの使用も抑制できる。 As in the image forming apparatus according to the present embodiment, the amount of lubricant recovered from the intermediate transfer member 20 to the photosensitive member 10 is adjusted for each virtual region divided at predetermined intervals in the rotation axis direction of the intermediate transfer member 20. Further, the amount of lubricant on the intermediate transfer member 20 can be made uniform in the direction of the rotation axis, and the occurrence of uneven image density can be suppressed. Further, compared with the conventional apparatus, the time for applying and recovering the lubricant is not required, so that a reduction in productivity can be prevented. Furthermore, since a lubricant application device and a recovery device are not newly required, it is possible to reduce the size and cost of the device. In addition, useless toner can be suppressed.
以上、本発明の実施形態について具体例を挙げて説明したが、本発明はその内容に限定されるものではない。本発明はその趣旨を逸脱しない範囲において、様々な具体的形態により実施され得る。 As mentioned above, although the specific example was given and demonstrated about embodiment of this invention, this invention is not limited to the content. The present invention can be implemented in various specific forms without departing from the spirit of the present invention.
本発明は、例えば複写機、ファクシミリ、或いは画像記録装置などに利用可能である。 The present invention can be used in, for example, a copying machine, a facsimile, or an image recording apparatus.
１ａ〜１ｄ 画像形成ユニット
１０ａ〜１０ｄ 感光体（像担持体）
１１ａ〜１１ｄ 帯電装置
１２ａ〜１２ｄ 露光手段
１３ａ〜１３ｄ 現像器
１４ａ〜１４ｄ １次転写ローラ
１５ａ〜１５ｄ 感光体清掃装置
１６ａ〜１６ｄ 除電装置
２０ 中間転写体
２１ 中間転写体清掃装置
２２ ２次転写部
３０ 制御手段
1a to 1d Image forming unit 10a to 10d Photoconductor (image carrier)
11a to 11d Charging device 12a to 12d Exposure unit 13a to 13d Developing device 14a to 14d Primary transfer roller 15a to 15d Photoconductor cleaning device 16a to 16d Charger 20 Intermediate transfer member 21 Intermediate transfer member cleaning device 22 Secondary transfer unit 30 Control means
Claims (8)
前記像担持体の表面を均一帯電させる帯電手段と、
表面が均一帯電した前記像担持体に光を照射して静電潜像を形成する露光手段と、
前記像担持体に形成された静電潜像を、滑剤を外添したトナーで現像する現像手段と、
トナーの帯電極性と逆極性の電圧が印加され、前記現像手段により形成された前記像担持体上のトナー像を無端状で回転自在の中間転写体に転写する転写手段と、
前記像担持体の表面をクリーニングするクリーニング部材と、
前記中間転写体上に形成されたトナー像の回転方向の印字率を前記中間転写体の回転軸方向に所定間隔で分割した仮想領域ごとに算出して積算し、積算された印字率から前記仮想領域ごとの滑剤の付着量を推算し、
当該推算結果に応じて、前記転写手段への印加電圧を画像形成時とは逆極性とするとともに、前記転写手段と前記像担持体との前記仮想領域ごとの電位差を制御して前記中間転写体上の滑剤を前記像担持体に回収する制御手段とを備える
ことを特徴とする画像形成装置。 A rotatable image carrier;
Charging means for uniformly charging the surface of the image carrier;
Exposure means for forming an electrostatic latent image by irradiating light onto the image carrier having a uniformly charged surface;
Developing means for developing the electrostatic latent image formed on the image carrier with a toner externally added with a lubricant;
A transfer means for transferring a toner image on the image carrier formed by the developing means to an endless and rotatable intermediate transfer body, to which a voltage having a polarity opposite to the charging polarity of the toner is applied;
A cleaning member for cleaning the surface of the image carrier;
The printing rate in the rotation direction of the toner image formed on the intermediate transfer member is calculated and integrated for each virtual region divided at predetermined intervals in the rotation axis direction of the intermediate transfer member, and the virtual printing rate is calculated from the integrated printing rate. Estimate the amount of lubricant attached to each area,
In accordance with the estimation result, the voltage applied to the transfer unit has a polarity opposite to that at the time of image formation, and the potential difference for each virtual region between the transfer unit and the image carrier is controlled to control the intermediate transfer member. An image forming apparatus comprising: control means for collecting the upper lubricant on the image carrier.
前記制御手段は、トナーボトルが交換された場合に、前記中間転写体上の滑剤を前記像担持体に回収する制御を行う請求項１〜７のいずれかに記載の画像形成装置。 The developing means comprises a replaceable toner bottle containing replenishing toner;
The image forming apparatus according to claim 1, wherein the control unit performs control to collect the lubricant on the intermediate transfer member on the image carrier when the toner bottle is replaced.
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