JP3570700B2 - Contact charging method and device - Google Patents

Description

上記の結果から、従動回転体４を設けたことにより、炭酸ガスの使用量を大幅に削減しつつ、帯電ローラ２から感光体ドラム１へ安定にコロナ放電を発生させて、良好な画像形成を長期行えることが判る。
なお、上記形態例では帯電部材を主な例として説明したが、本発明は、転写装置、除電装置等にも適用が可能である。
【００１５】
【発明の効果】
以上説明したように、本発明は以下のような優れた効果を奏する。
請求項１に記載の発明では、互いに平行且つ水平に配置された被帯電部材と帯電部材とを互いに接触させて回転させ、前記被帯電部材の表面と前記帯電部材の表面との間の微小空間中に発生する放電により前記被帯電部材の表面に電荷を供給し帯電させる接触帯電方法において、前記被帯電部材と前記帯電部材とが接触することにより形成される溝状の隘狭部に空気よりも比重の大きいオゾン非発生ガスを滞留させるとともに、当該隘狭部の上方に前記帯電部材に接して連れ回りする従動回転体を設けて当該隘狭部からのオゾン非発生ガスの漏れを抑制しつつ前記放電を発生させるようにしたことにより、コロナ放電発生箇所からオゾン非発生ガスが逃げ出さないようにするために装置構成をさほど複雑化することなく、コロナ放電発生箇所にオゾン非発生ガスを供給して、コロナ放電によるオゾンやＮＯｘの発生を防止しつつ被帯電部材を帯電させることができる。
また、請求項２に記載の発明では、請求項１に記載の方法において、前記従動回転体の電位を前記帯電部材の帯電部の電位と同電位にしたことにより、従動回転体と帯電部材との間で放電が発生するのを防止できるので、帯電部材から被帯電部材への放電が安定して起こり、被帯電部材を安定して帯電させることができる。
【００１６】
また、請求項３に記載の発明では、請求項２に記載の方法において、前記オゾン非発生ガスとして炭酸ガスを使用するとともに、前記従動回転体の表面と前記被帯電部材との間の最短距離を０．００７ｍｍ以上としたことにより、従動回転体から被帯電部材への放電を起こりにくし、被帯電部材をより安定して帯電させることができる。
また、請求項４に記載の発明では、請求項２に記載の方法において、前記従動回転体の表面と前記被帯電部材との間の最短距離ｄ、気圧Ｐ、及び放電開始極小電圧Ｖにパッシェンの法則を適用したとき、前記最短距離ｄが前記気圧Ｐが１気圧のときにおける最短距離ｄ０ よりも大きくなるようにしたことにより、前記オゾン非発生ガスとして炭酸ガス以外のガスを使用した場合でも、従動回転体の表面と被帯電部材との間の最短距離ｄをどの程度以上とすれば良いかをパッシェンの法則に基づいて決定できるので、従動回転体から被帯電部材への放電を起こりにくくして、被帯電部材をより安定して帯電させることができる。
また、請求項５に記載の発明では、装置構成をさほど複雑化することなく、コロナ放電発生箇所に不活性ガスを供給して、コロナ放電によるオゾンやＮＯｘの発生を防止しつつ被帯電部材を帯電させることができる。
【図面の簡単な説明】
【図１】本発明の接触帯電方法の実施の形態の一例を示す画像形成装置の要部の構成を示した概略側面図である。
【図２】図１に示した画像形成装置の要部を矢印Ａ方向から見た正面図である。
【符号の説明】
１ 感光体ドラム（被帯電部材）、２ 帯電ローラ（帯電部材）、３ 隘狭部、４ 従動回転体、Ｇ オゾン非発生ガス、Ｏ１ 回転中心、 Ｒ 感光体ドラム１の半径、ｒ 帯電ローラの半径、ｄ 最短距離。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for charging a member to be charged such as a photoreceptor in an electrophotographic image forming apparatus, and more particularly to a contact charging method.
[0002]
[Prior art]
Image forming apparatuses such as copiers, printers, and facsimile machines uniformly charge the surface of a photoconductor whose resistance changes depending on the degree of light irradiation, and irradiate the surface of the photoconductor with a laser beam or the like to output an image. After the electrostatic latent image is formed in accordance with the toner image, a charged charge carrier (toner) is attached to the electrostatic latent image and developed, and the toner image is transferred to a charged transfer body such as paper. There is a method in which an image is formed by a series of so-called electrophotographic processes in which a toner image on a transfer member is fixed by heat and pressure after the toner image is removed from the photoreceptor by removing static electricity. After the above series of processes, the toner remaining on the surface of the photoconductor is removed. Then, the surface of the photoreceptor is once charged and then uniformly charged for the next image formation.
The electrophotographic method utilizes the movement of electric charges in each process of charging, development, transfer, and static elimination. As methods for generating electric charges, there are corona discharge method, contact friction charging method, contact charge injection method, and the like. Has been used. Among them, the most common method is a corona discharge method.
[0003]
In the corona discharge method, a corona discharge is generated between electrodes by applying a strong electric field between an electrode using a fine wire or a needle and an opposing electrode, and ions generated by the discharge are applied to a charged member such as a photoconductor. This is a method in which charge is supplied by attaching. This method has a simple principle and a very simple apparatus configuration for implementing the method. However, since corona discharge is performed in the air, oxygen occupying 20% of the air component is ionized and ozone (O ₃ ) occurs. Ozone is a molecule required in the air above the atmosphere to suppress the amount of ultraviolet rays and the like incident from the sun to the ground, but it is a harmful substance in the office environment and its generation must be suppressed.
The contact frictional charging method and the contact charge injection method are applied to a developing roller and a charging roller.However, since the developing roller and the charging roller come into contact with the surface of the photoreceptor which is a member to be charged when the roller is stopped, the rubber layer of the roller is The low molecular weight component contained in the photoreceptor precipitates and migrates to the photoreceptor, thereby causing contamination of the photoreceptor and eventually causing an abnormality in an image.
Therefore, recently, the surface of the charging member is made to have a high resistance, and the charging portion of the charging member is sequentially brought into contact with the surface of the member to be charged such as a photoconductor, and before and after the contact between the surface of the charging member and the charging portion of the charging member. A contact charging method has been employed in which a corona discharge is generated in a minute space to uniformly charge the entire surface of the member to be charged.
[0004]
[Problems to be solved by the invention]
However, in the case of the contact charging method as well, since corona discharge is used, oxygen in the air is ionized and inevitably generates ozone and knock (NOx). The knock component has a hygroscopic property, and if this component adheres to the photoreceptor, an abnormal image called image deletion occurs, and it adheres to the photoreceptor and the charging roller, and when the two come into contact with each other, the low-molecular component from the charging roller is transferred to the photoreceptor It has been found that the movement and adhesion cause white spots after the stop and restart.
Therefore, development of a discharge atmosphere gas that does not generate ozone has been desired. As one example, Japanese Patent Application Laid-Open No. Sho 60-95459 proposes a method using a gas having a lower oxygen concentration than air. However, although simply reducing the oxygen concentration has the effect of reducing the amount of ozone generated, it does not completely prevent ozone generation, and the amount of corona discharge current varies depending on the type of gas. The potential fluctuates and the image density varies. For this reason, there is a problem that the device configuration is complicated, for example, it is necessary to attach a gas separation filter.
Therefore, it is necessary to create a discharge atmosphere that does not contain oxygen at all or that does not generate O ₃ by corona discharge even if it contains oxygen.
[0005]
Nitrogen (N ₂ ) gas, which is a main component of air, can be considered as a gas that can be easily used around us. However, since nitrogen has a gas density close to oxygen, nitrogen diffuses into air immediately and dissipates. Therefore, in order to constantly maintain a pure nitrogen atmosphere, a special device and a nitrogen supply device are required. Further, as also described in JP-A-60-95459, NO _X is produced by corona discharge nitrogen, cause the equal, significantly degrade the chargeability of the photosensitive member hygroscopicity is increased Therefore, the charging method to generate the NO _X should be avoided.
Other familiar gases include steam (H ₂ O), hydrogen (H ₂ ), helium (He), neon (Ne), propane (C ₃ H ₈ ), methane (CH ₄ ), and the like. Dangerous substances cannot be used, and those that are not gaseous at normal temperature cannot be used stably.
In addition, if a gas that is lighter than air is used even if it is a gas that does not generate ozone, take measures such as installing an umbrella-shaped container so that the gas does not escape from the location where corona discharge occurs, or supplying gas constantly to the location where corona discharge occurs. Need to be taken.
The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent ozone non-evolved gas from escaping from a corona discharge generation location without significantly complicating the device configuration, and to achieve ozone generation by corona discharge. It is an object of the present invention to provide a contact charging method capable of charging a member to be charged while preventing generation of NOx and NOx.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is an image forming method in which at least one of charging, transfer, and charge elimination processes, which are each of the electrophotographic image forming processes, is performed using corona discharge. In the apparatus, a member to be charged and a charging roller which are arranged in parallel and horizontally to each other are rotated while being in contact with each other, and a discharge generated in a minute space between the surface of the member to be charged and the surface of the charging roller is performed. In the contact charging method of supplying a charge to the surface of the member to be charged and charging the member, the ozone non-uniform having a larger specific gravity than air is formed in a narrow narrow groove formed by contact between the member to be charged and the charging roller. It causes the retention of the generated gas, suppress the leakage of non-ozone gas generated from the隘狭portion provided driven rotor to rotate together in contact with the charging roller above the隘狭portion And so as to generate said discharge while.
Since the gas having a higher specific gravity than air naturally flows to a lower portion, a non-ozone-generating gas having a higher specific gravity than air is used as described above, and the charged member and the charging member come into contact with each other. And the outflow of non-ozone-generating gas from the narrow portion, in particular, the dissipation of gas upward, and the outflow due to diffusion, are supplied to the narrow portion above the narrow portion. By preventing the non-ozone-generating gas from staying in the narrow portion by preventing the rotation by the driven rotating member provided in contact with the charging member. Therefore, according to the contact charging method of the first aspect, a non-ozone-generating gas is supplied to a location where corona discharge is generated without significantly complicating the apparatus configuration, thereby preventing ozone and NOx from being generated by corona discharge. The member to be charged can be charged while being charged.
[0007]
According to a second aspect of the present invention, based on the contact charging method according to the first aspect, the potential of the driven rotator is set to the same potential as the potential of the charging portion of the charging member. According to the contact charging method of the second aspect, since no discharge occurs between the driven rotary member and the charging member, the discharge from the charging member to the member to be charged occurs stably, and Can be stably charged.
According to a third aspect of the present invention, on the premise of the contact charging method according to the second aspect, a carbon dioxide gas is used as the non-ozone-generating gas, and the surface of the driven rotor and the member to be charged are Is set to 0.007 mm or more. At the normal corona discharge generation voltage used in the electrophotographic process, it is known from Paschen's law that the shortest starting distance between members in carbon dioxide gas at 1 atm is 0.0066 mm. As described in Item 3, when the shortest distance between the surface of the driven rotating body and the member to be charged is set to about 0.007 mm or more, discharge from the driven rotating body to the member to be charged hardly occurs, and The charging member can be more stably charged.
According to a fourth aspect of the present invention, based on the contact charging method of the second aspect, the shortest distance d between the surface of the driven rotary member and the member to be charged, the atmospheric pressure P, and the start of discharge when applying Paschen's law on the minimum voltage V, the shortest distance d is set to be larger than the shortest distance d ₀ at the time of the air pressure P is 1 atm. According to the invention described in claim 4, even when a gas other than carbon dioxide gas is used as the non-ozone-generating gas, the minimum distance d between the surface of the driven rotary member and the member to be charged should be set to any value. Since it suffices to determine based on Paschen's law, discharge from the driven rotor to the member to be charged hardly occurs, and the member to be charged can be charged more stably.
The invention of claim 5 includes a charging roller which rotates in contact with the photosensitive member to form an electrostatic latent image, the photosensitive body contact Ru contacting charging performed corona discharge charged by applying a voltage to the charging roller The apparatus further comprises a driven rotating member that is in contact with the charging roller and that is arranged with a gap between the charging roller and the photoconductor surface, and inactive gas is supplied from the driven rotating member side to the charging roller, the photosensitive member, and the driven rotation member. A configuration is provided in which contact charging is performed while supplying and staying in a space formed by the body . According to the invention as set forth in claim 5, an inert gas is supplied to a location where corona discharge is generated without significantly complicating the device configuration, and the member to be charged is supplied while preventing generation of ozone and NOx due to corona discharge. Can be charged.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic side view showing the configuration of the main part of an example of an image forming apparatus to which the contact charging method (contact charging device) of the present invention is applied, and FIG. 2 is an arrow showing the main part of the image forming apparatus shown in FIG. FIG. 1 is a front view as viewed from a direction A, in which 1 denotes a photosensitive drum as a member to be charged, and 2 denotes a charging roller as a charging member. In this apparatus, a charged charging roller 2 is rotated while being in contact with the surface of a photosensitive drum 1 rotating at a constant speed in a fixed direction, so that the surface of the photosensitive drum 1 and the surface (charging portion) of the charging roller 2 are rotated. By generating a corona discharge in the minute space between them, a charge is supplied to the surface of the photosensitive drum 1 to be charged. At this time, carbon dioxide gas (CO ₂ ) is retained as a non- ozone - generating gas G having a specific gravity larger than that of air in a narrow portion 3 formed by the contact between the photosensitive drum 1 and the charging roller 2 to generate no ozone. A corona discharge is generated in a gas atmosphere. The non- ozone generating gas G is supplied into the narrow portion 3 through a gas supply pipe (not shown).
The contact charging device of the present invention is arranged with a gap between a charging roller 2 that rotates in contact with a photosensitive drum 1 that forms an electrostatic latent image and a surface of the photosensitive member that rotates while contacting the charging roller 2. And a driven rotator 4 for applying a voltage to the charging roller 2 to perform corona discharge on the photoconductor to charge the photoconductor in contact.
[0009]
The photosensitive drum 1 and the charging roller 2 are members that are fixed to respective shaft cores 6 and 7 that extend in parallel and horizontally with each other and that rotate respectively. The length of the photosensitive drum 1 and the length of the charging roller 2 are the same, and a disc-shaped shielding member 5 (at both ends of the charging roller 2) for preventing the non-ozone generating gas G from flowing out from both sides of the narrow portion 3. 2 is fixed concentrically with the charging roller 2.
Above the narrow portion 3, there is provided a driven rotator 4 that rotates in contact with the charging roller 2. The driven rotator 4 has the same length as the charging roller 2, and the radius r ′ is set to be smaller than the radius r of the charging roller 2. The shortest distance d between the surface of the driven rotary member 4 and the surface of the photosensitive drum 1 is set to 0.007 mm. This shortest distance is not set to less than 0.007 mm.
[0010]
Since the driven rotary member 4 is provided as described above, the upper portion of the narrow portion 3 is almost completely closed except for a small gap s between the driven rotary member 4 and the photosensitive drum 1. It is possible to suppress the outflow of the non-ozone-generating gas from the narrow portion 3, particularly the outflow due to the dissipation and diffusion of the gas upward, and to increase the use efficiency of the non-ozone-generating gas G. Further, since the driven rotary member 4 comes into contact with the charging roller 2 and rotates, no new driving unit is required. When the non-ozone-generating gas G stays in the narrow portion 3, the non- ozone - generating gas G naturally flows down through the gap s between the driven rotary member 4 and the photoconductor drum 1, thereby allowing the non- ozone - generating gas G to flow inside the narrow portion 3. Can be filled with the non- ozone generating gas G. Further, Kitara discharge conditions is changed by dissipation or dilution of non-ozone generated gas G, which supplies ozone non-generation gas G on the outer peripheral surface of the charging roller 2 as a charging member. The method is simple, and it suffices to supply the non- ozone - generating gas G excessively from the gas supply pipe into the narrow portion 3 to cause a slight overflow.
[0011]
The driven rotator 4 and the charging roller 2 are at the same potential because they are in contact with each other. Therefore, no discharge is generated between the driven rotary member 4 and the charging roller 2, so that the discharging from the charging roller 2 to the photosensitive drum 1 occurs stably, and the photosensitive drum 1 is stably charged. be able to. Further, since carbon dioxide gas is used as the non- ozone generating gas G and the shortest distance between the surface of the driven rotary member 4 and the photosensitive drum 1 is set to 0.007 mm or more, the photosensitive drum from the driven rotary member 4 Discharge to the body drum 1 hardly occurs. Also in this case, the discharge from the charging roller 2 to the photosensitive drum 1 can be stably generated, and the photosensitive drum 1 can be stably charged.
[0012]
As described above, according to the present embodiment, it is possible to satisfactorily generate corona discharge and charge the photosensitive drum 1 while suppressing generation of ozone harmful to the office environment. A photoreceptor made of an organic material such as OPC is greatly deteriorated by ozone. However, since the generation of ozone is suppressed, the photoreceptor can be prevented from being deteriorated and the durability life can be extended. Further, since the generation of NOx can be prevented by using carbon dioxide as the non- ozone generating gas G, it is possible to prevent the occurrence of an abnormal image or the like due to the NOx component adhering to the photoconductor. Further, carbon dioxide gas is a gas which is present in the air in a large amount and can be collected relatively easily, and is inexpensive, so that the operation cost can be reduced as compared with the case where other gases are used. In addition, since carbon dioxide gas is not generated secondary by corona discharge, the influence on the global environment such as global warming is small.
[0013]
【Example】
EXAMPLE In the apparatus configuration of the above-described embodiment, a photosensitive drum 1 having a diameter of 40 mm, a charging roller 2 having a diameter of 15 mm, and a driven rotary member 4 having a diameter of 10 mm are used, and the rotation center O ₁ of the photosensitive drum 1 is used. installing a linear l ₁ and the angle θ is the charging roller 2 to the position where the 60 ° linearly l ₂ passes through the rotation center O ₁ of the photosensitive drum 1 in a vertical direction connecting the rotation center O ₂ of the charging roller 2 and The driven rotator 4 was placed at a position where the driven rotator 4 was in contact with the charging roller 2 and the distance from the photosensitive drum 1 was 0.01 mm. A voltage is applied to the photosensitive drum 1 and the charging roller 2 in a state where the carbon dioxide gas is retained in the narrow portion 3 formed by the photosensitive drum 1 and the charging roller 2 to generate corona discharge. After charging the body drum 1, a series of image forming steps of exposure, development, transfer, and fixing were performed to form an image.
Comparative Example An image was formed in the same manner as described above except that only the driven rotor 4 was removed.
As a result, the results shown in Table 1 below were obtained.
[0014]
[Table 1]

From the above results, the provision of the driven rotary member 4 enables corona discharge to be stably generated from the charging roller 2 to the photosensitive drum 1 while greatly reducing the amount of carbon dioxide gas used, thereby achieving good image formation. You can see that it can be done for a long time.
In the above embodiment, the charging member is described as a main example, but the present invention is also applicable to a transfer device, a charge removing device, and the like.
[0015]
【The invention's effect】
As described above, the present invention has the following excellent effects.
According to the first aspect of the present invention, the charged member and the charging member arranged in parallel and horizontally to each other are rotated by contacting each other, and a minute space between the surface of the charged member and the surface of the charging member is rotated. In a contact charging method of supplying a charge to the surface of the charged member by discharging generated therein and charging the charged member, air is supplied to a narrow groove-shaped portion formed by contact between the charged member and the charging member. Also, a non-ozone-generating gas having a large specific gravity is retained, and a driven rotator that contacts and rotates with the charging member is provided above the narrow portion to suppress leakage of the ozone non-generating gas from the narrow portion. In addition, by causing the discharge, the ozone non-generating gas is prevented from escaping from the corona discharge generating position, without complicating the apparatus configuration so much, the corona discharge generating position The non-ozone generating gas is supplied, while preventing the generation of ozone and NOx by corona discharge can be charged member to be charged.
According to a second aspect of the present invention, in the method according to the first aspect, the potential of the driven rotating body is set to the same potential as the potential of the charging portion of the charging member. The discharge from the charging member to the member to be charged occurs stably, and the member to be charged can be charged stably.
[0016]
According to a third aspect of the present invention, in the method according to the second aspect, carbon dioxide is used as the non-ozone-generating gas, and a shortest distance between the surface of the driven rotating body and the member to be charged is provided. Is set to 0.007 mm or more, discharge from the driven rotating body to the member to be charged hardly occurs, and the member to be charged can be charged more stably.
According to a fourth aspect of the present invention, in the method according to the second aspect, the shortest distance d between the surface of the driven rotary member and the member to be charged, the atmospheric pressure P, and the discharge starting minimal voltage V are adjusted to the minimum value. When the law of is applied, the shortest distance d is set to be larger than the shortest distance d0 when the atmospheric pressure P is 1 atm, so that even when a gas other than carbon dioxide gas is used as the ozone non-generating gas, Since the minimum distance d between the surface of the driven rotor and the member to be charged can be determined based on Paschen's law, discharge from the driven rotor to the member to be charged hardly occurs. Thus, the member to be charged can be charged more stably.
Further, in the invention according to claim 5, an inert gas is supplied to a location where corona discharge is generated without significantly complicating the device configuration, and the member to be charged is supplied while preventing generation of ozone and NOx due to corona discharge. Can be charged.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing a configuration of a main part of an image forming apparatus showing an example of an embodiment of a contact charging method of the present invention.
FIG. 2 is a front view of a main part of the image forming apparatus shown in FIG.
[Explanation of symbols]
Reference Signs List 1 photosensitive drum (charged member), 2 charging roller (charging member), 3 narrow part, 4 driven rotating body, G non-ozone generating gas, O1 rotation center, R radius of photosensitive drum 1, radius of r charging roller Radius, d the shortest distance.

Claims (5)

In an image forming apparatus that performs at least one of charging, transfer, and charge elimination processes, each of electrophotographic image forming processes, using a corona discharge, a member to be charged and a charging roller that are arranged parallel and horizontally to each other And contacting each other and rotating them, and supplying a charge to the surface of the member to be charged by discharging generated in a minute space between the surface of the member to be charged and the surface of the charging roller . , the charging roller the causes retained a large non-ozone generated gas specific gravity than air隘狭portion groove-like formed by said charging roller and the charging member is in contact, over the said隘狭portion A driven rotating member that rotates in contact with and is provided so as to generate the discharge while suppressing leakage of non-ozone-generating gas from the narrow portion. That contact charging method. 2. The contact charging method according to claim 1, wherein the potential of the driven rotator is the same as the potential of the charging section of the charging roller . The contact charging according to claim 2, wherein carbon dioxide gas is used as the non-ozone generating gas, and a shortest distance between a surface of the driven rotating body and the member to be charged is 0.007 mm or more. Method. When Paschen's law is applied to the shortest distance d between the surface of the driven rotating body and the member to be charged, the pressure P, and the minimum discharge start voltage V, the shortest distance d is 1 atm. contact charging method according to claim 2, wherein greater than the shortest distance d ₀ in. Includes a charging roller which rotates in contact with the photosensitive member to form an electrostatic latent image, in a contact charging device Ru contacting charging performed corona discharge to the photosensitive member by applying a voltage to the charging roller,
A driven rotator that rotates while being in contact with the charging roller and with a gap between the photoreceptor surface,
A contact charging device comprising a configuration in which an inert gas is supplied from a side of the driven rotator to a space formed by a charging roller, a photoreceptor, and a driven rotator and is contact-charged while being retained.

Images