JP3788251B2 - Image forming apparatus and cleaning apparatus - Google Patents

Description

【００５２】
以上のように、実施例１に係る本発明の画像形成装置によれば、クリーニング不良や機内汚れが発生することがなく、長期にわたって画質の高い画像を得ることができることが確認された。これに対して、比較例１〜比較例３に係る画像形成装置においては、いずれも機内汚れが発生しており、さらに比較例１および比較例２については、帯状のクリーニング不良が発生しており、実用的ではないことが確認された。
【００５３】
＜実施例２＞
帯電装置（１１）の有効帯電領域Ｗ３に対応する導電性部分（３１）の両外端より外方に突出する絶縁性部分（３２）が１０ｍｍずつ形成されてなるクリーニングローラ（３０）を用い、帯電装置（１１）による有効帯電領域Ｗ３を３０２ｍｍに設定したことの他は実施例１と同様の画像形成装置を構成し、下記に示す条件で２０万枚印字する実写テストを実施して、機内汚れの発生およびクリーニング不良の発生の有無について評価を行ったところ、機内汚れおよびクリーニング不良が発生することなく、長期にわたって画質の高い画像が形成されることが確認された。
【００５４】
実写テストは、０〜１０万枚までを常温常湿環境（温度２０℃、相対湿度５０％）下で、１０万枚〜１５万枚までを低温低湿環境（温度１０℃、相対湿度２０％）下で、１５万枚〜２０万枚までを高温高湿環境（温度３０℃、相対湿度８０％）下で行った。
【００５５】
以上、本発明の実施の形態について説明したが、本発明は上記の態様に限定されるものではない。
（１）帯電装置は、非接触型および接触型のいずれのものであってもよく、例えば電圧が印加可能とされたローラ等により構成することもでき、この場合には、有効帯電領域は、実際に感光体の表面に接触している幅である。
（２）クリーニング装置におけるクリーニングブレードの支持方式は、感光体の回転軸と平行な軸周りに回動可能とされ、バネまたは重力による加重によってクリーニングブレードに一定の圧接力を与える回動式のブレードホルダーを用いることも可能である。
（３）クリーニングローラに転移したトナー等を除去するには、スクレーパの他に、ローラやブラシを用いることも可能である。
（４）本発明において用いられるトナーは、一成分現像剤および二成分現像剤のいずれにも用いることができ、また、磁性トナーおよび非磁性トナーのいずれのトナーとしても用いることができる。
また、潜像の現像方式は、反転現像法に限定されるものではない。
（５）クリーニングローラにおける絶縁性部分は、種々の構成とすることが可能であり、例えばローラ全体を同一の導電性/ 半導電性材料で構成し、帯電装置による有効帯電領域に相当する部分の両外端より外方に位置する部分に、絶縁性のコーティングやチューブが被覆された構成とすることもできる。
【００５６】
【発明の効果】
本発明のクリーニング装置によれば、クリーニングローラの幅方向において、潜像担持体の帯電領域に相当する部分の両外端より外方に位置する部分が絶縁性とされていることにより、クリーニングローラによって潜像担持体の有効帯電領域を超えて帯電されることがないので、トナー付着による機内汚れや潜像担持体の絶縁破壊によるクリーニング不良が発生することがなく、長期にわたって安定的にクリーニング効果を発揮することができる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の一例における概略的な構成を示す説明図である。
【図２】図１におけるクリーニング装置の構成を拡大して示す説明図である。
【図３】クリーニングローラによる有効クリーニング領域、転写装置による有効転写領域、および帯電装置による有効帯電領域の３者の関係の一例を示す説明用斜視図である。
【図４】クリーニングローラの他の構成例を示す説明図である。
【符号の説明】
１０ 感光体
１１ 帯電装置
１２ 露光装置
１３ 現像装置
１３Ａ 現像スリーブ
１４ 転写装置
１５ 分離装置
１６ 定着装置
２０ クリーニング装置
２１ クリーニングブレード
２２ クリーニングローラ
２３ バイアス電圧印加手段
２４ スクレーパ
２５ 回収ローラ
２６ ブレードホルダー
２７ 制御手段
３０ クリーニングローラ
３１ 導電性部分
３２ 絶縁性部分
３３ 緩衝部材
Ｗ１ 有効クリーニング領域
Ｗ２ 有効転写領域
Ｗ３ 有効帯電領域
Ｗ４ 逆帯電領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus and a cleaning device mounted on the image forming apparatus.
[0002]
[Prior art]
As a cleaning method in an electrophotographic process, for example, a blade cleaning method in which a blade made of an elastic body is brought into contact with the surface of a latent image carrier to remove residual toner such as untransferred toner and transfer residual toner on the latent image carrier Is being used.
In recent years, in an electrophotographic image forming apparatus, there has been a demand for reducing the particle size of toner particles from the viewpoint of high image quality. Examples of methods for obtaining such toner particles include an emulsion polymerization method and a suspension polymerization method. The polymerization method is preferably used.
[0003]
Thus, as the toner particles become smaller in size, the adhesion between the toner particles and the latent image carrier increases, so that it becomes difficult to remove the residual toner on the latent image carrier. In particular, when a so-called polymerized toner manufactured by a polymerization method is used, the shape of the toner particles is close to a sphere, so that the toner particles roll on the latent image carrier and pass through a cleaning blade. There is a problem that a cleaning defect called “suri-nuke” is likely to occur, and it is further difficult to remove the residual toner on the latent image carrier.
[0004]
In order to prevent the occurrence of such a cleaning failure, a cleaning method using both mechanical cleaning by a cleaning blade and electrostatic cleaning is disclosed in, for example, Japanese Patent Laid-Open No. 3-179675.
Specifically, a brush roller made of a conductive material capable of applying a voltage is installed at a position upstream of the cleaning blade with respect to the moving direction of the latent image carrier. An appropriate bias voltage having a polarity opposite to that of the residual toner is applied, and the cleaning performance is improved by the mechanical cleaning effect by the cleaning blade and the electrostatic cleaning effect by the brush roller. .
[0005]
However, the toner used to visualize the latent image formed on the latent image carrier adheres over a wider area than the image forming area of the latent image carrier due to scattering from the developing device. Even in such a cleaning system, it is actually difficult to remove the toner on the latent image carrier scattered over a wide range.
To solve this problem, simply increasing the width of the brush roller to simply increase the cleaning area in the axial direction of the latent image carrier, the polarity of the residual toner on the latent image carrier is opposite to the polarity of the residual toner. In the reversely charged region that is charged by the brush roller and is not recharged by the charging device, contamination due to toner adhesion or dielectric breakdown of the photosensitive layer of the latent image carrier occurs. As a result, in-machine contamination and poor cleaning are likely to occur.
Such a problem remarkably appears when the reversal development method which is mainstream in current digital machines and the like is used.
[0006]
[Problems to be solved by the invention]
  The present invention has been made based on the above circumstances, and its purpose is as follows.An object of the present invention is to provide a cleaning device that has high cleaning performance and that does not cause in-machine dirt on the mounted image forming apparatus, and an image forming apparatus including the cleaning device.
[0007]
[Means for Solving the Problems]
  Of the present inventionCleaning deviceIsA cleaning blade that contacts the surface of the latent image carrier that is driven to rotate, and a surface that contacts the surface of the latent image carrier at a position upstream from the cleaning blade in the moving direction of the latent image carrier. A cleaning roller arranged to extend in the axial direction of the carrier, and a bias voltage applying means for applying a bias voltage to the cleaning roller,
  The cleaning roller has a conductive portion in the width direction corresponding to an effective charging area where the surface of the latent image carrier is charged by a charging device, and from both outer ends of the portion corresponding to the effective charging area. The part located outside is insulativeIt is characterized by that.
  In addition, an image forming apparatus of the present invention includes the above-described cleaning device.
[0013]
[Action]
  Of the present inventionAccording to the cleaning device, in the width direction of the cleaning roller, the portions positioned outward from both outer ends of the portion corresponding to the charged region of the latent image carrier are made insulating, so that the latent image is removed by the cleaning roller. Since it is not charged beyond the effective charging area of the carrier, there is no in-machine contamination due to toner adhesion or cleaning failure due to dielectric breakdown of the latent image carrier, and the cleaning effect is stably demonstrated over a long period of time. The
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing an outline of the configuration of an example of the image forming apparatus of the present invention, and FIG. 2 is an explanatory diagram showing the cleaning device in FIG. 1 in an enlarged manner.
In this image forming apparatus, a drum-shaped photoconductor 10 which is a latent image carrier to be rotated, a charging device 11 for uniformly charging the surface of the photoconductor 10, and the charging device 11 is charged. An exposure device 12 that exposes the surface of the photoreceptor 10 to form an electrostatic latent image, and a developing device that visualizes the electrostatic latent image formed by the exposure device 12 using a developer containing toner. 13, a transfer device 14 that transfers a toner image formed on the photoconductor 10 to a recording material in a transfer region, a separation device 15 that separates a recording material that is in close contact with the photoconductor 10, and a photoconductor that has passed through the transfer region. 10 and a cleaning device 20 for removing the toner on the surface. In FIG. 1, reference numeral 16 denotes a fixing device for fixing the toner image transferred to the recording material.
[0016]
The photoconductor 10 is made of an organic photoconductor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate, and the width direction of the recording material to be conveyed (in FIG. 1). , Extending in a direction perpendicular to the paper surface).
[0017]
The charging device 11 includes, for example, a scorotron charger having a control grid and a discharge electrode, and is disposed so as to face the photosensitive member 10 and extend in the axial direction (a direction perpendicular to the paper surface in FIG. 1). .
[0018]
The developing device 13 includes a developing sleeve 13A disposed so as to face the photoconductor 10 with a developing region interposed therebetween, and a DC developing bias or an alternating current having the same polarity as the charging polarity of the charging device 11 is provided on the developing sleeve 13A. A developing bias in which a direct current voltage having the same polarity as the charging polarity of the charging device 11 is superimposed on the voltage is applied, whereby reversal development is performed by the exposure device 12 to attach toner to an exposure region.
[0019]
The transfer device 14 includes, for example, a corona charger, and is disposed so as to face the photoconductor 10 and extend in the axial direction thereof.
[0020]
The cleaning device 20 is made of, for example, an elastic body such as urethane rubber. A cleaning roller 22 that is in contact with the surface of the photoconductor 10 at a position upstream of the moving direction of the photoconductor 10 and extends in the axial direction thereof, and a bias voltage application that applies a bias voltage to the cleaning roller 22 Means 23.
In FIG. 2, reference numeral 24 denotes a scraper provided on the cleaning roller 22, whereby the toner on the cleaning roller 22 is collected, and the developing device 13 is disposed by a collection roller 25 disposed so as to extend opposite the cleaning roller 22. Sent to.
[0021]
The cleaning blade 21 is held at its base end portion by a fixed blade holder 26, for example, and is pressed against the photoconductor 10 with a substantially constant load over the entire area in the axial direction by the elasticity of the cleaning blade 21 itself. It is supposed to be in a state to do.
[0022]
The contact load of the cleaning blade 21 with respect to the photoconductor 10 is preferably 0.1 to 30 g / cm, and more preferably 1 to 25 g / cm. When the contact load is less than 0.1 g / cm, the cleaning power is insufficient and image smearing is likely to occur. On the other hand, when the contact load is larger than 30 g / cm, the wear of the photoconductor 10 is increased, and image fading is likely to occur.
The contact load is measured by pressing the tip edge of the cleaning blade 21 against the balance, or by placing a sensor such as a load cell at the contact position between the photosensitive member 10 and the tip edge of the cleaning blade 21. For example, a measuring method is used.
[0023]
The contact angle θ of the cleaning blade 21 with respect to the photoconductor 10 is preferably 0 to 40 °, and particularly preferably 0 to 25 °. When the contact angle θ is smaller than 0 °, the cleaning power is reduced, and image smearing is likely to occur. On the other hand, when the contact angle θ is larger than 40 °, so-called “blade turning” is easily generated in which the leading edge of the cleaning blade 21 is reversed following the photoreceptor 10.
Here, “the contact angle θ with respect to the photoconductor 10” refers to the tangent plane N 1 of the cleaning blade 21 and the tangential plane N 2 of the photoconductor 10 at a position P where the leading edge of the cleaning blade 21 and the photoconductor 10 abut. Is the angle formed by
[0024]
The JIS A hardness of the cleaning blade 21 is preferably 20 to 90 °, and particularly preferably 60 to 80 °. When the JIS A hardness is less than 20 °, the cleaning blade 21 is too soft and the blade is likely to be turned over. On the other hand, when the JIS A hardness is greater than 90 °, it becomes difficult to follow the slight irregularities and foreign matter of the photoreceptor 10 and toner particles are liable to “slip”.
Here, JIS A hardness is measured on the basis of JIS K-6253.
[0025]
The thickness and free length of the cleaning blade 21 are not particularly limited as long as the contact load and the contact angle θ of the cleaning blade 21 are within the above ranges, but the controllability of the contact load and the occurrence of blade turning are not limited. From the viewpoint of prevention, the thickness of the cleaning blade 21 is preferably 1 to 3 mm, more preferably 1.5 to 2.5 mm, and the free length is preferably 2 to 20 mm. Preferably it is 3-15 mm. The “free length” is the length of the portion not restrained by the blade holder 26, that is, the length of the portion from the lower end surface of the blade holder 26 to the tip of the blade 21.
The width dimension of the cleaning blade 21 is preferably basically the same as the width dimension of the cleaning roller 22 to be described later, but even if there is a difference of about 5 mm at both ends due to mechanical design conditions. There is no practical problem.
[0026]
The cleaning roller 22 is made of an elastic body from the viewpoint of obtaining a good contact state with the photoreceptor 10, and as the material of the elastic body, a conventionally known rubber material such as silicone rubber or polyurethane, foaming, etc. A body or foam coated with a resin or the like can be used.
The cleaning roller 22 is conductive or semiconductive and has a surface resistance of 10²-10^TenIt is preferably Ωcm. Surface resistance is 10²When it is smaller than Ωcm, banding or the like due to discharge is likely to occur. Meanwhile, 10^TenIf it is larger than Ωcm, the potential difference required to remove the toner cannot be obtained, and cleaning failure tends to occur.
Here, the surface resistance is determined by adding a conductive material such as carbon, metal, or conductive polymer to the elastic material constituting the cleaning roller 22, or adding a polar group to the rubbery polymer constituting the elastic material. It can be adjusted by introducing it.
[0027]
The cleaning roller 22 preferably rotates so that the contact portion with the photosensitive member 10 moves in the same direction as the moving direction of the photosensitive member 10. When the contact portion with the photoconductor 10 is rotated so as to move in the opposite direction, if excessive toner is present on the surface of the photoconductor 10, the toner removed by the cleaning roller 22 is spilled and the recording material. And may contaminate the equipment.
The linear velocity ratio (Vr / Vp) between the linear velocity (Vr) of the cleaning roller 22 and the linear velocity (Vp) of the photosensitive member 10 is preferably 0.5-2. When the linear velocity ratio is less than 0.5, the cleaning power is reduced and image smearing is likely to occur. On the other hand, if the linear velocity ratio is greater than 2, scratches or the like are likely to occur on the surface of the photoconductor 10 when a foreign object or the like is inserted.
[0028]
As described above, the bias voltage applying means 23 is connected to the cleaning roller 22, and a bias voltage having a polarity opposite to that of the toner used for visualizing the electrostatic latent image on the photoreceptor 10, for example, toner. Is negatively charged, a current controlled by the control means 27 is applied to the cleaning roller 22 so that a positive bias voltage is applied. As a result, the toner is electrostatically attracted to the cleaning roller 22 and removed from the photoreceptor 10.
The bias voltage applying means 23 is preferably a constant current power source.
[0029]
The current value applied to the cleaning roller 22 by the bias voltage applying means 23 varies depending on the thickness of the photosensitive layer of the photoreceptor 10 and the surface resistance of the cleaning roller 22, but is preferably 1 to 50 μA in absolute value. When the current value is smaller than 1 μA, it is difficult to perform sufficient cleaning. On the other hand, when the current value is larger than 50 μA, discharge or the like is likely to occur.
For example, the thickness of the photosensitive layer of the photoreceptor 10 is 15 to 30 μm, and the surface resistance of the cleaning roller 22 is 10²-10^TenIn the case of Ωcm, the current value applied to the cleaning roller 22 is preferably 5 to 40 μA in absolute value.
[0030]
In the image forming apparatus of the present invention, as shown in FIG. 3, in the axial direction (width direction) of the photoreceptor 10, the effective cleaning area by the cleaning roller 22 is W1, and the effective transfer area by the transfer device 14 is W2. The effective cleaning area W1 is set to be larger than the effective transfer area W2. As a result, the toner scattered to the outside of the effective transfer area W2 and adhering to the photoconductor 10 can also be reliably removed by the cleaning roller 22.
Here, the “effective cleaning region W1” refers to a width in which a removal electric field formed between the photoconductor 10 and the cleaning roller 22 acts effectively in the width direction of the photoconductor 10, and “effective transfer region W2”. "Means a width in which discharge by the transfer device 14 effectively acts in the width direction of the photoconductor 10. When the transfer device 14 is of a contact type, the width of the transfer device that is actually in contact with the surface of the photoconductor 10 is the effective transfer region W2.
[0031]
The effective cleaning area W1 is preferably larger than the effective transfer area W2 by at least 3 mm, preferably 7 mm or more at each of both ends thereof. Thereby, toner scattered over a wide range in the width direction of the photoconductor 10 can be removed. On the other hand, when the effective transfer area W2 is equal to or greater than the effective cleaning area W1, the toner scattered outside the effective transfer area W2 and adhering to the photoconductor 10 cannot be removed, and contamination of the belt electrode and the optical system is prevented. This causes image defects such as fogging and white streaks.
[0032]
In the width direction of the photoconductor 10, when the effective charging area by the charging device 11 is W3, the absolute value | W3−W1 | ≦ 30 of the difference between the effective charging area W3 and the effective cleaning area W1 is set. As a result, a predetermined region can be reliably recharged by the charging device 11, and it is possible to reliably prevent cleaning failure due to dielectric breakdown of the photosensitive layer of the photoreceptor 10 and occurrence of internal contamination due to toner adhesion.
Here, the “effective charging area W <b> 3” refers to a width in which discharge by the charging device 11 in the width direction of the photoreceptor 10 acts effectively. When the charging device 11 is a contact type, the width of the charging device that actually contacts the surface of the photoconductor 10 is the effective charging region W3.
[0033]
For example, when the effective transfer area W2 by the transfer device 14 is 300 mm, the effective cleaning area W1 is at least at both ends of the effective transfer area W2. When the effective cleaning area W1 is set to 306 mm and the effective cleaning area W1 is set to 306 mm or more, which is 3 mm or more, the effective charging area W3 by the charging device 11 is set to 276 to 336 mm. In practice, the effective charging area W3 is an effective cleaning area in order to make the reverse charging area (W4 in FIG. 3) that is charged by the cleaning roller 22 and not recharged by the charging device 11 extremely small. It is preferable to set the size very close to W1 or more than the effective cleaning area W1.
[0034]
The operation of the image forming apparatus will be described.
The surface of the photoconductor 10 that is driven to rotate is sequentially charged to a predetermined polarity (for example, negative polarity) by the charging device 11, and the surface of the photoconductor 10 is irradiated with light selectively by the exposure device 12. The potential of the portion (exposure region) is lowered, and an electrostatic latent image corresponding to the original image is formed. Further, the surface of the developing sleeve 13A constituting the developing device 13 is also charged with the same polarity (for example, negative polarity) as the surface potential of the photosensitive member 10 by a developing bias applied from a power source (not shown), and the surface potential of the developing sleeve 13A. A developer containing toner charged to the same polarity (for example, negative polarity) is conveyed to the development area.
The surface potential [Vh] in the non-exposed area of the photoconductor 10, the surface potential [Vl] in the exposed area of the photoconductor 10, and the surface potential [Vd] of the developing sleeve 13A have the same polarity and are absolute The value is [Vh]> [Vd]> [Vl]. Therefore, in the developing area, the toner on the developing sleeve 13A adheres to the exposed area of the photoconductor 10 and reversal development is performed. The toner image formed on the photoconductor 10 is transferred to a recording material by the transfer device 14, and the recording material on which the toner image is transferred is separated from the surface of the photoconductor 10 by the separation device 15, and then is fixed in the fixing device 16. A fixing process is performed.
[0035]
On the other hand, a bias voltage corresponding to the magnitude of the current controlled by the control device 27 is applied to the cleaning roller 22 constituting the cleaning device 20 by the bias voltage applying means, whereby the photosensitive roller 10 that has passed through the transfer region is applied. The remaining toner is charged to a polarity opposite to the polarity of the remaining toner (for example, positive polarity), and most of the remaining toner on the photoreceptor 10 is electrostatically removed. Then, after the residual toner that has passed through the cleaning roller 22 is mechanically removed by the cleaning blade 21, the photosensitive member 10 is recharged by the charging device 11, and the above operation is repeated as necessary.
The collected residual toner is sent to the developing device 13 by the collecting roller 25 and used again.
[0036]
Thus, according to the above-described image forming apparatus, in addition to mechanical cleaning by the cleaning blade 21, electrostatic cleaning is performed by the cleaning roller 22, so that basically a high cleaning effect is exhibited. In addition to being able to reliably remove the residual toner on the photoconductor 10, the effective cleaning area W1 of the cleaning roller 22 is set to a specific range, so that it is formed between the photoconductor 10 and the cleaning roller 22. As a result of the applied removal electric field acting on a predetermined region in the width direction of the photoconductor 10, it is ensured that internal contamination due to toner adhesion and cleaning failure due to dielectric breakdown of the photoconductive layer of the photoconductor 10 occur. Can be prevented.
[0037]
Specifically, since the effective cleaning area W1 is larger than the effective transfer area W2 by the transfer device 14, the removal electric field is applied to the toner scattered and adhered to the outside of the effective transfer area W2 in the width direction of the photoconductor 10. As a result, the toner can be surely removed, and the effective cleaning area W1 is | W3-W1 | ≦ 30 with respect to the effective charging area W3 by the charging device 11. As a result of being able to make the area charged by the cleaning roller 22 in the body 10 and not recharged by the charging device 11, that is, the reverse charged area charged to a polarity opposite to that of the toner, an extremely small state. It is possible to prevent toner from adhering to and accumulating in the area, or causing the dielectric breakdown of the photosensitive layer of the photoreceptor 10, Les by, is a high cleaning performance for a long time to maintain, it is possible to form a high quality image.
[0038]
When the bias voltage applying means 23 in the cleaning device 20 is a constant current power source, a potential difference is always generated between the surface of the cleaning roller 22 and the surface of the photoconductor 10 so that a constant current always flows. Since this potential difference occurs in a state that is always constant according to the surface potential of the photoconductor 10, unevenness due to the potential level and polarity of the photoconductor 10 and the occurrence of poor cleaning are generated as compared with the case where a constant voltage power supply is used. Can be reliably prevented.
[0039]
In the image forming apparatus according to the present invention, as shown in FIG. 4, the cleaning roller 30 constituting the cleaning device 20 has a conductive portion 31 and an outer side of both outer ends of the conductive portion 31 in the width direction. It is preferable that it is comprised by the insulating part 32 located in this.
Specifically, the cleaning roller 30 is configured such that a portion corresponding to the effective charging region W3 by the charging device 11 is made of a conductive or semiconductive material, and is further outward than a portion corresponding to the effective charging region W3. The extending portions are made of an insulating material, and the cleaning roller constituent materials having different surface resistances are bonded to each other through, for example, an insulating buffer member 33 in order to prevent discharge from the conductive portion 31.
[0040]
The surface resistance of the insulating portion 32 is 10¹¹It is preferably Ωcm or more, more preferably 10¹³Ωcm or more. As a result, it is possible to reliably prevent discharge due to the current applied to the cleaning roller 30 and accumulation of charges on the photoconductor 10.
The surface resistance is obtained by installing a cleaning roller 30 on a conductive flat plate and applying a constant voltage (V) to the cleaning roller 30 to obtain a current value (I) obtained from the flat plate. And (V / IW) from the contact width (W) between the flat plate and the cleaning roller 30.
[0041]
The length of the insulating portion 32 is preferably 2 to 80 mm, and this can reliably prevent the toner once collected from blowing out toward the photoconductor 10 and adhering to the photoconductor 10 again. it can.
[0042]
According to the above-described image forming apparatus, in the width direction of the cleaning roller 30, the portions located outside the both outer ends of the conductive portion 31 corresponding to the effective charging area W <b> 3 are insulative, so that the photoconductor 10. In this surface, a reversely charged region that is charged by the cleaning roller 30 and not recharged by the charging device 11 is not formed. That is, since the surface of the photoconductor 10 is reliably recharged by the charging device 11, there is no occurrence of in-machine contamination due to toner adhesion or cleaning failure due to dielectric breakdown of the photosensitive layer, and therefore high cleaning performance is maintained over a long period of time. High-quality images can be formed.
Further, since the insulating portion 32 is formed on the cleaning roller 30, it is possible to prevent the toner once collected from being blown again toward the photoconductor 10 and attached to the photoconductor 10.
[0043]
As described above, according to the image forming apparatus of the present invention, in addition to the mechanical cleaning by the cleaning blade 21, electrostatic cleaning by the cleaning roller 30 is executed. Without increasing the contact load, high cleaning performance can be stably exhibited over a long period of time. Therefore, with a conventional cleaning device, the contact load of the cleaning blade 21 cannot be increased over a long period of time. This is extremely effective when an organic photoconductor that has been difficult to stably exhibit cleaning performance is used as a latent image carrier.
[0044]
In addition, according to the present invention, it is extremely effective when using a toner having a small particle diameter such as “suriuke”, which is liable to cause poor cleaning, and a polymer toner produced by a polymerization method and having a nearly spherical shape. is there. Specifically, those composed of toner particles having a volume average particle diameter of 8.5 μm or less, and further 6.5 μm or less, a polymerized toner having a nearly spherical shape, or a volume average particle diameter in the range of 2 to 32 μm. Even when toner having a CV value of 20% or less for certain toner particles is used, an appropriate removal electric field is applied to these toners by the cleaning roller 30, so that the toner 10 can be reliably applied from above the photoreceptor 10. Can be removed. Here, the “CV value” indicates the sharpness of the particle size distribution of the toner particles, and is obtained by the following formula.
[0045]
[Equation 3]
CV value = (standard deviation of particle diameter / arithmetic diameter) × 100 [%]
[0046]
【Example】
Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.
<Example 1>
According to the configuration of the image forming apparatus shown in FIG. 1, the photosensitive member, the developing device, the toner, the cleaning roller, the cleaning blade, and the like were set as follows.
[0047]
(1) Photoconductor
As the photoconductor (10), a drum-shaped organic photoconductor was used in which a photosensitive layer having a thickness of 25 μm made of polycarbonate containing a phthalocyanine pigment was formed on the outer peripheral surface of a drum-shaped metal substrate made of aluminum.
(2) Charging device
As the charging device (11), a scorotron charger was used. The effective charging area (W3) of the charging device (11) is 318 mm.
(3) Developing device
The developing device (13) includes a developing sleeve (13A) that is rotationally driven at a linear velocity of 370 mm / min. A bias voltage having the same polarity as the surface potential of the photoconductor (10) is applied to the developing sleeve (13A). In this case, a reversible developer is used with a two-component developer.
The toner constituting the two-component developer is made of toner particles having a volume average particle diameter of 6.5 μm produced by an emulsion polymerization method, and has negative chargeability.
(4) Cleaning roller
The cleaning roller (22) has a surface resistance of 10 made of conductive foamed urethane.^FourThe thing of Ωcm was used. The effective cleaning area (W1) of the cleaning roller (22) is 320 mm.
The cleaning roller (22) is rotationally driven so that the contact portion with the photosensitive member (10) moves in the same direction as the moving direction of the photosensitive member (10), and the linear velocity (Vr) of the cleaning roller 22 and the photosensitive member 10 are driven. The linear velocity ratio (Vr / Vp) to the linear velocity (Vp) was set to 1.1.
(5) Cleaning blade
The cleaning blade (21) was made of urethane rubber having a JIS A hardness of 70 °, a thickness of 2.00 mm, and a free length of 10 mm.
The contact angle (θ) with respect to the photoreceptor (10) was set to 10 °, and the contact load was set to 20 g / cm.
(6) Other
As the transfer device (14), a corona charger having an effective transfer area (W2) of 300 mm was used.
[0048]
In the above, the surface potential [Vh] of the photoreceptor (10) in the non-exposed area is set to −750V, the surface potential [Vl] of the photoreceptor (10) in the exposed area is set to −100V, and −600V is applied to the developing sleeve (13A). A development bias of.
Further, the surface potential was charged to +600 V by applying +20 μA to the cleaning roller (22) by the bias voltage applying means (23) comprising a constant current power source.
[0049]
Using the image forming apparatus as described above, an actual photograph test for printing 200,000 sheets was performed to evaluate the occurrence of in-machine contamination and the occurrence of poor cleaning. The live-action test is performed at 0 to 100,000 sheets in a normal temperature and normal humidity environment (temperature 20 ° C., relative humidity 50%) and 100,000 to 200,000 sheets at high temperature and high humidity environment (temperature 30 ° C., relative humidity 80 %) Under. The results are shown in Table 1.
[0050]
<Comparative Examples 1 to 3>
According to Table 1, a live-action test was performed in the same manner as in Example 1 except that W1, W2, and W3 were changed. The results are shown in Table 1.
[0051]
[Table 1]

[0052]
As described above, according to the image forming apparatus of the present invention related to Example 1, it has been confirmed that an image with high image quality can be obtained over a long period of time without causing defective cleaning and in-machine contamination. On the other hand, in the image forming apparatuses according to Comparative Examples 1 to 3, all of the in-machine stains occurred, and in Comparative Examples 1 and 2, a belt-like cleaning defect occurred. Confirmed to be impractical.
[0053]
<Example 2>
Using a cleaning roller (30) in which insulating portions (32) protruding outward from both outer ends of the conductive portion (31) corresponding to the effective charging region W3 of the charging device (11) are formed by 10 mm each, Except that the effective charging area W3 by the charging device (11) was set to 302 mm, an image forming apparatus similar to that of Example 1 was configured, and a live-action test for printing 200,000 sheets under the following conditions was performed. As a result of evaluating the occurrence of contamination and the occurrence of poor cleaning, it was confirmed that an image with high image quality was formed over a long period of time without occurrence of internal contamination and defective cleaning.
[0054]
In the live-action test, 0 to 100,000 sheets are in a normal temperature and humidity environment (temperature 20 ° C., relative humidity 50%), and 100,000 to 150,000 sheets are in a low temperature and low humidity environment (temperature 10 ° C., relative humidity 20%). Below, 150,000 to 200,000 sheets were performed under a high-temperature and high-humidity environment (temperature 30 ° C., relative humidity 80%).
[0055]
As mentioned above, although embodiment of this invention was described, this invention is not limited to said aspect.
(1) The charging device may be either a non-contact type or a contact type, and may be constituted by, for example, a roller to which a voltage can be applied. In this case, the effective charging area is The width is actually in contact with the surface of the photoreceptor.
(2) The cleaning blade support system in the cleaning device is a rotating blade that can rotate about an axis parallel to the rotation axis of the photosensitive member and applies a constant pressure contact force to the cleaning blade by a load applied by a spring or gravity. It is also possible to use a holder.
(3) In order to remove the toner transferred to the cleaning roller, a roller or a brush can be used in addition to the scraper.
(4) The toner used in the present invention can be used as either a one-component developer or a two-component developer, and can be used as either a magnetic toner or a non-magnetic toner.
Further, the latent image developing method is not limited to the reversal developing method.
(5) The insulating portion of the cleaning roller can have various configurations. For example, the entire roller is made of the same conductive / semiconductive material, and the portion corresponding to the effective charging area by the charging device It can also be set as the structure which coat | covered the insulating coating and the tube in the part located outside from both outer ends.
[0056]
【The invention's effect】
  Of the present inventionAccording to the cleaning device, in the width direction of the cleaning roller, the portions positioned outward from both outer ends of the portion corresponding to the charged region of the latent image carrier are made insulating, so that the latent image is removed by the cleaning roller. Since it is not charged beyond the effective charging area of the carrier, it does not cause in-machine contamination due to toner adhesion or cleaning failure due to dielectric breakdown of the latent image carrier, and exhibits a stable cleaning effect over a long period of time. be able to.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration in an example of an image forming apparatus of the present invention.
FIG. 2 is an explanatory view showing an enlarged configuration of the cleaning device in FIG. 1;
FIG. 3 is an explanatory perspective view showing an example of the relationship between an effective cleaning area by a cleaning roller, an effective transfer area by a transfer device, and an effective charging area by a charging device.
FIG. 4 is an explanatory diagram showing another configuration example of the cleaning roller.
[Explanation of symbols]
10 photoconductor
11 Charging device
12 Exposure equipment
13 Development device
13A Development sleeve
14 Transfer device
15 Separation device
16 Fixing device
20 Cleaning device
21 Cleaning blade
22 Cleaning roller
23 Bias voltage application means
24 Scraper
25 Collection roller
26 Blade holder
27 Control means
30 Cleaning roller
31 Conductive part
32 Insulating part
33 cushioning member
W1 Effective cleaning area
W2 Effective transfer area
W3 Effective charging area
W4 Reverse charging area

Claims (3)

A cleaning blade that contacts the surface of the latent image carrier that is driven to rotate, and a surface that contacts the surface of the latent image carrier at a position upstream from the cleaning blade in the moving direction of the latent image carrier. A cleaning roller arranged to extend in the axial direction of the carrier, and a bias voltage applying means for applying a bias voltage to the cleaning roller,
The cleaning roller has a conductive portion in the width direction corresponding to an effective charging area where the surface of the latent image carrier is charged by a charging device, and from both outer ends of the portion corresponding to the effective charging area. A cleaning device characterized in that an outer portion is insulative. The cleaning apparatus according to claim 1, wherein the cleaning roller is configured by bonding an insulating material to an outer end of the conductive portion via an insulating buffer member. An image forming apparatus comprising the cleaning device according to claim 1 .

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