JP4862791B2 - Electrophotographic equipment - Google Patents

Description

  The present invention relates to an electrophotographic apparatus capable of cleaning the inside of a charger.

  In an electrophotographic apparatus in which an electrostatic latent image is formed by charging the photosensitive member and exposing it to a charged surface and visualized with the toner, when the photosensitive member is charged by a charger, generally an air discharge (corona discharge) is performed. In many cases, a discharge product is generated by this air discharge, and examples of the discharge product include nitride oxide.

  Although the discharge product is not restricted from being discharged out of the machine like ozone, it has various effects on members inside the electrophotographic apparatus. For example, when the discharge product is a nitrided oxide, nitric acid is produced by reacting with moisture in the air, and metal nitrate is produced when the nitric acid reacts with the metal. Moreover, although the said nitric acid and nitrate are high resistance in a low-humidity environment, they react with the water in air and become low resistance in a high-humidity environment. Therefore, when a film made of nitric acid or nitrate is formed on the surface of the photoconductor, nitric acid or nitrate absorbs moisture, the film portion becomes low resistance, the electrostatic latent image on the surface of the photoconductor collapses, and the abnormal image appears to flow. Is formed (so-called image generation).

  The discharge products described above are difficult to accumulate inside the charger due to, for example, ion wind during corona charging, but easily accumulate inside the charger when the charger is paused or stopped, and accumulate inside the charger without further decomposition. Highly oxidizing gas is generated from the discharged product. On the other hand, in general electrophotographic apparatuses, a charger is often disposed above the photosensitive member from the viewpoint of conveying a recording medium. Therefore, if the discharge product or highly oxidizing gas accumulated or staying in the charger falls and adheres to the surface of the photoconductor, the chargeability of the photoconductor surface may be changed. In addition, for example, when the electrophotographic apparatus is stopped or stopped, if the discharge product or highly oxidizing gas accumulated or stays in the charger falls and adheres to the surface of the photosensitive member, the discharge product or highly oxidizing The gas penetrates from the surface of the photoreceptor to the inside, and there is a possibility that deterioration of the photoreceptor is promoted.

  In Patent Document 1, a cover member made of a porous or activated carbon material is provided in the opening of the charger in order to shield the opening of the charger of the corona discharge system facing the photoconductor when the image forming apparatus is stopped. A proposed image forming apparatus has been proposed.

  Further, Patent Document 2 discloses that a corona discharge type charger is arranged in a predetermined range vertically below and below the photoreceptor, and discharge products fall from the opening of the charger to the surface of the photoreceptor due to gravity. An electrophotographic apparatus for preventing it has been proposed. However, although the gravity drop of the discharge product accumulated in the charger can be suppressed, there is a possibility that the highly oxidizing gas derived from the discharge product accumulated in the charger rises on the surface of the photoreceptor and deteriorates the surface of the photoreceptor.

  Patent Document 3 proposes a corona charger in which one of the shield side surfaces of the shield case of the corona charger has a mesh shape, and an electrode plate is provided outside the mesh shield side surface. In this corona charger, the mesh shield side face and electrode plate and the grid electrode of the corona charger are equipotential during image formation, while the mesh shield side face and electrode plate are switched to ground when image formation is completed. As a result, the ion wind of positive ions generated during image formation passes through the side of the mesh-shaped seal while carrying ozone and discharge products, and as a result, ozone and discharge products are released out of the charger together with the ion wind.

  Patent Document 4 proposes an image forming apparatus that performs forced exhaust by flowing air into a charger when the corona charger is stopped.

JP 2001-267039 A JP 2001-290338 A JP 2003-270912 A Japanese Patent Laid-Open No. 10-123889

  A device configuration that suppresses oxidation or degeneration of the surface of the photoconductor by the discharge product or highly oxidizing gas falling on the surface of the photoconductor with a simple device configuration without changing the positional relationship between the conventional charger and the photoconductor. Is desired.

  The electrophotographic apparatus of the present invention has the following features.

(1) a charging unit having an electrophotographic photoreceptor charger for charging the arrangement electrophotographic photoconductor above, an exposure means for exposing said electrophotographic photosensitive member to be charged by the charging unit, the exposing unit A developing means for developing the exposed portion by the developing means, a transfer means for transferring the image developed on the electrophotographic photosensitive member by the developing means, and a rotation provided at one end portion forming the opening of the charger. A charging unit separation holding unit that includes a shaft and holds the opening of the charging unit at a position not facing the surface of the photosensitive member; and controls an electrophotographic process by at least the charging unit, the exposure unit, the developing unit, and the transfer unit. and and holding the charger to the opening of the central rotary shaft provided on the charger spaced holding means rotates the charger charger faces the air flow position when the non-image formation is separated from the photosensitive member A control means for returning the charger high oxidizing gas residence and discharge products accumulated inside when removed and the image formed from the opening of the charging device in an electrophotographic process execution position, was perforated, the charger The distance holding position of the charger by the distance holding means is an electrophotographic apparatus having a range of 90 ° ± θ with respect to the angle θ based on the following formula with respect to the position of the charger during the electrophotographic process .
(Equation 1)
θ = Sin ⁻¹ (G / H)
(Where G is the gap length from the surface of the photoreceptor to the opening of the charger, H is the height of the charger, θ is the separation inclination angle θ ₀ of the charger , and θ = | θ ₀ −90 ° |)

( 2 ) In the electrophotographic apparatus according to the above (1 ), an inactive film on which discharge products are difficult to adhere is formed at least on the inner surface of the charger and the surface of the grid electrode for controlling the photoreceptor potential inside the charger. An electrophotographic apparatus.

( 3 ) In the electrophotographic apparatus according to ( 1 ), the airflow is caused by an operation of an exhaust fan that suppresses a temperature increase in the electrophotographic apparatus or accompanying rotation of a photoconductor during execution of an electrophotographic process. This is an electrophotographic apparatus that generates airflow.

( 4 ) The electrophotographic apparatus according to ( 2 ), wherein the inert film is an electrophotographic apparatus made of tetrahedral amorphous carbon.

  According to the electrophotographic apparatus of the present invention, the discharge product and the highly oxidizing gas fall on the surface of the photoconductor with a simple apparatus configuration without changing the positional relationship between the conventional charger and the photoconductor, and the photoconductor. Inhibits surface oxidation or alteration.

  FIG. 1 is a schematic diagram of an electrophotographic apparatus according to the present embodiment. It is sectional drawing which shows schematically the basic composition of suitable one Embodiment of the subphotograph apparatus shown in FIG. An electrophotographic apparatus 200 shown in FIG. 1 includes an electrophotographic photoreceptor 7, a charger 8 such as a corotron or a scorotron that charges the electrophotographic photoreceptor 7 by a corona discharge method, a power source 9 connected to the charger 8, An exposure means 10 for exposing the electrophotographic photosensitive member 7 charged by the charger 8, a developing means 11 for developing a portion exposed by the exposure means 10, and an image developed on the electrophotographic photosensitive member 7 by the developing means 11. Transfer means 12 for transferring the toner, a cleaning device 13, a static eliminator 14, and a fixing device 15.

  Further, as shown in FIG. 2, the electrophotographic apparatus in the present embodiment includes a charger separation holding unit that holds and separates the opening 30 of the charger 8 at a position not facing the surface of the electrophotographic photosensitive member 7; Controls at least the electrophotographic process by the charger 8, the exposure means 10, the developing means 11, and the transfer means 12, and controls the internal cleaning of the charger 8 by the charger separating and holding means, and makes the charger 8 an electrophotographic process execution position. And a control means for returning to.

  The charger 8 is further provided with a charging wire 34 for performing corona discharge under constant current control by a power source 9 (FIG. 1), and a grid electrode 26 to which a voltage is applied by the power source 9. As a result, the cations generated around the corona-discharged charged wire 34 pass through the grid electrode 26 and flow toward the electrophotographic photosensitive member 7 held at the ground potential, and the electrophotographic photosensitive member 7 is charged with positive ions. . The discharge product 40 gradually accumulates in the charger 8 due to the corona discharge, and a highly oxidizing gas 42 derived from the discharge product 40 is generated and stays there.

  Further, the charger separation holding means of the charger 8 is a rotating shaft provided on at least one side end portion of the side end portions 22 and 24 forming the opening 30 of the charger 8, in FIG. 20 By rotating the rotating shaft 20 by a control means described later, the opening 30 of the charger 8 is separated and held at a position not facing the surface of the electrophotographic photosensitive member 7 as shown in FIG. Thereby, it is possible to suppress the discharge product 40 and the highly oxidizing gas 42 accumulated inside the charger 8 during non-image formation from dropping on the surface of the electrophotographic photoreceptor 7.

  Further, as shown in FIG. 3, the charger separation holding means of the charger 8 holds the charger 8 at a position where the opening 30 of the charger 8 faces the airflow flowing around the charger 8. Thereby, the discharge product and highly oxidizing gas accumulated in the charger 8 are removed by the airflow. When the flow velocity of the airflow is high, it may be separated from the electrophotographic photoreceptor 7 so that the opening 30 of the charger 8 faces in the direction opposite to the airflow direction.

  Further, as shown in FIG. 3, the charger separation / holding means of the present embodiment has the position of the charger during the electrophotographic process (that is, the electrophotographic photosensitive member 7 is moved with respect to the angle θ based on the following equation: The charger 8 is held at a distance within a range of 90 ° ± θ with respect to the position where charging is possible.

(Equation 2)
θ = Sin ⁻¹ (G / H)
(Where G is the gap length from the surface of the photoreceptor to the opening of the charger, H is the height of the charger, θ is the separation inclination angle θ ₀ of the charger, and θ = | θ ₀ −90 ° |)

The separation oblique angle θ ₀ is parallel to the bottom surface of the charger 8 at the position of the charger 8 at the time of performing the standard electrophotographic process, that is, the position where the electrophotographic photosensitive member 7 can be charged, and A reference horizontal plane extending from the position (“chargeable position” in FIG. 3) and a retracting surface extending from the position of the rotating shaft 20 parallel to the bottom surface of the charger 8 retracted from the surface of the electrophotographic photosensitive member 7. The angle to be done. Therefore, for example, in the case of the charger 8A of FIG. 3, the separation oblique angle θ ₀ is parallel to the reference horizontal plane (“chargeable position” in FIG. 3) and the bottom surface of the charger 8A and It is an angle formed by the retreating surface extending from the position, and in this case, θ ₀ = 90 ° −θ. On the other hand, in the case of the charger 8B of FIG. 3, the separation oblique angle θ ₀ is parallel to the reference horizontal plane (“chargeable position” in FIG. 3) and the bottom surface of the charger 8B and the position of the rotating shaft 20. In this case, θ ₀ = 90 ° + θ.

  As described above, by holding the charger 8 at the separation holding position, it is possible to prevent the discharge products and highly oxidizing gas accumulated in the charger 8 from falling on the surface of the electrophotographic photoreceptor 7. In addition, discharge products and the like can be removed by the air current, and there is no possibility of contacting the surface of the electrophotographic photoreceptor 7. In consideration of the size of the general charger 8 and the gap length from the normal electrophotographic photosensitive member 7 to the opening 30 of the charger 8, the angle θ may be set to 15 °.

  If the charger 8 is rotated beyond [90 ° + θ] and separated, the side surface of the photoreceptor shield may come into contact with the surface of the electrophotographic photoreceptor 7, while the charger 8 is moved to [90 ° −θ]. If the rotation is less than the distance, the discharge product accumulated in the inside of the charger 8 by the air current is insufficiently removed or needs to be removed by the air current for a long time.

  Further, as shown in FIG. 3, in order to hold the charger 8 away from the surface of the electrophotographic photosensitive member 7 and hold it at a predetermined position, a stop rod 58 is provided on an inner wall (not shown) around the charger 8 of the electrophotographic apparatus. And the rotation of the charger 8 may be controlled by the rotating shaft 20.

  Next, an example of the charger separation holding unit and the control unit of the present embodiment is shown in FIG. The rotating shaft 20 is connected to one side of the opening of the charger 8 by a support 32 provided at one end of the charger 8. Further, one end of the rotating shaft 20 is connected to a motor 50 that is a drive source via a coupling 52, and a claw portion 56 is formed at the other end of the rotating shaft 20.

  The motor 50 is driven via the control unit 54 that is the control means described above, and the torque transmission is controlled by the coupling 52 for the rotation of the motor 50, whereby the charger 8 is moved to the above-described separation holding position. Rotate and hold. Here, as the coupling 52, for example, a gear coupling having a gear structure may be used. Further, the claw portion 56 may be brought into contact with a pin provided on the inner wall around the charger 8 of the electrophotographic apparatus (not shown) to control the rotation of the charger 8.

In addition, as the above-described airflow, for example, an airflow caused by the operation of an exhaust fan that suppresses a temperature increase in the electrophotographic apparatus or an airflow generated with the rotation of the photoconductor during the electrophotographic process is used. The controller 54, which is the above-described control means, may control the flow rate of the air flow by the exhaust fan for a certain period of time during which the charger 8 is held away. Further, the flow velocity of the air flow by the exhaust fan in the conventional electrophotographic apparatus, a 0.2 m ³ / min from 0.1 m ³ / min, in the charger 8 of the internal volume of about 147cm ^3, above the flow velocity, at least The above-mentioned discharge products and the like can be removed by flowing the airflow at the above flow rate for 5 seconds or more, preferably 10 to 60 seconds.

  Further, as shown in FIG. 5, an inactive film 60 on which the discharge product hardly adheres is formed on the inner wall surface of the charger 8 a and the surface of the grid electrode 26 for controlling the photoreceptor potential inside the charger 8. . The inert film 60 is made of, for example, tetrahedral amorphous carbon. By forming the inactive film 60 on the inner wall surface of the charger 8a and the grid electrode 26, the inactive film 60 can be removed more easily by the air current than when the inactive film 60 is not formed, and the removal time by the air current is also increased. It can be shortened.

  Next, an example of the cleaning operation in the charger in the electrophotographic apparatus of this embodiment will be described with reference to FIG. The operation shown in FIG. 6 is controlled by the control unit 54 (FIG. 4) which is a control means.

  First, considering the state of the charger 8, the exposure means 10, the developing means 11, and the transfer means 12 shown in FIG. 1, is the electrophotographic apparatus stopped, the end of the print job, or the total number of sheets (for example, 10,000 sheets) or more? (S100), if the electrophotographic apparatus is stopped or the print job is completed or the total number of sheets is equal to or greater than the predetermined number, the charger 8 is separated from the electrophotographic photosensitive member 7 (also referred to as “photosensitive member 7”). Then, the rotary shaft 20 provided at one end of the charger 8 is rotated around a fulcrum so that the opening 30 (FIG. 3) of the charger 8 faces the airflow (S102), and then a predetermined time (for example, 10). Second to 60 seconds, the charger 8 is held at the separation holding position (the above-mentioned rotation state) (S104), and after holding for a predetermined time, the charger 8 is returned to the position where the photosensitive member 7 is charged (S106). To complete the cleaning operation .

  Hereinafter, the contents of the electrophotographic apparatus of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The corona discharge-type charger 8 used in the examples and comparative examples has an internal volume of 147 cm ³ , a constant current control of (700 μA) at 4.5 to 5.5 kV on the discharge wire, and a total of 10,000 printed sheets At that time, the charger was held away from the electrophotographic photosensitive member by using the charger separation holding means and the control means shown in FIGS. The flow rate of the exhaust fan was 0.15 m ³ / min.

The height H of the charger is 1.5 cm, and the gap length G from the surface of the photoreceptor to the opening of the charger is 0.2 cm. Based on the above-described formula, the charging device separation inclination angle θ _0. Θ = | θ ₀ −90 ° | = 8 °.

Example 1.
After printing the total number of printed sheets 10,000, as shown in FIG. 4, the charger 8 is separated by 90 ° + 10 ° from the position where the surface of the photoconductor 7 can be charged so that the opening 30 of the charger 8 faces the air flow. Then, the separated state was held for 10 seconds, and the inside of the charger 8 was cleaned by an air stream. After that, the surface of the photoconductor 7 was returned again to the position where the surface of the photoconductor 7 can be charged. After this, when the printing process was performed, no image flow was confirmed.

Example 2
The charging device 8 is held in the separated state for 10 seconds in the same manner as in Example 1 except that the charging device 8 is separated by 90 ° + 10 ° from the position where the surface of the photoconductor 7 can be charged in the direction opposite to the airflow. The inside of the charger 8 was cleaned with an air flow, and then returned to the position where the surface of the photoconductor 7 can be charged again, and left in this fixed position for 2 hours. After this, when the printing process was performed, no image flow was confirmed.

Example 3
The charger 8 is held for 10 seconds in the separated state in the same manner as in Example 1 except that the charger 8 is separated from the surface chargeable position of the photoreceptor 7 by 90 ° -10 ° so that the opening 30 of the charger 8 faces the airflow. Then, the inside of the charger 8 was cleaned with an air flow, and then returned to the position where the surface of the photoconductor 7 can be charged again, and left in this fixed position for 2 hours. After that, when a printing process was performed, an image flow occurred very slightly although there was no problem as an image.

Example 4 :
Except that the charger 8 is separated from the surface chargeable position of the photoreceptor 7 by 90 ° so that the opening 30 of the charger 8 is opposed to the airflow, the airflow is maintained for 10 seconds in the separated state according to Example 1. Then, the inside of the charger 8 was cleaned, and then returned to the position where the surface of the photoconductor 7 can be charged again, and left in this fixed position for 2 hours. After this, when the printing process was performed, no image flow was confirmed.

Comparative Example 1
Except that the charger 8 was not held apart in Example 1, it was left for 2 hours at a fixed position where the photoconductor 7 can be charged in accordance with Example 1. After that, when a printing process was performed, it was confirmed that a strong image flow occurred on the surface portion of the photoreceptor 7 facing the opening 30 of the charger 8.

Example 5 FIG.
As shown in FIG. 5, an inert film 60 is formed by depositing 50 nm of tetrahedral amorphous carbon on the inner wall surface of the charger 8 a and the grid electrode 26 by plasma CVD, and the charger 8 a treated with the inert film 60. The charger 8a is spaced 90 ° + 10 ° and 90 ° −10 ° from the position where the surface of the photoconductor 7 can be charged in a direction against the airflow through the opening 30 of the charger 8, according to Example 1, The inside of the charger 8 was cleaned by airflow while being held in the separated state for 10 seconds, and then returned to the position where the surface of the photoconductor 7 can be charged again, and left in this fixed position for 2 hours. After this, when the printing process was performed, no image flow was confirmed. Further, corrosion of the inner wall surface of the shield of the charger 8a and the grid electrode 26 did not occur even when the operation exceeded the cumulative 500 KPV.

Comparative Example 2
The corona charger is not rotated away from the photosensitive member 7, and the opening of the charger is covered with a shielding plate with activated carbon attached to shield the opening for 2 hours, and then the shielding plate is removed from the opening for printing. As a result, although the image flow could be prevented, density unevenness occurred in the image in the process direction.

  As an application example of the present invention, there is application to an image forming apparatus such as a copying machine or a printer using an electrophotographic system.

It is a schematic block diagram explaining the structure of an example of the electrophotographic apparatus in this Embodiment. It is a schematic sectional drawing explaining an example of the charger separation holding | maintenance means in the electrophotographic apparatus of this Embodiment. It is the schematic explaining the separation holding position of an example of the charger separation holding means in the electrophotographic apparatus of the present embodiment. FIG. 3 is a schematic configuration diagram illustrating a separation position holding structure as an example of a charger separation holding unit in the electrophotographic apparatus of the present embodiment. It is a schematic sectional drawing explaining the other charger of this Embodiment in which the inactive film was formed. 6 is a flowchart for explaining an example of a separation holding operation with respect to a photoreceptor of a charger in the present embodiment.

Explanation of symbols

  7 Electrophotographic photosensitive member, 8, 8a charger, 9 power source, 10 exposure means, 11 developing means, 12 transfer means, 13 cleaning device, 14 static eliminator, 20 rotating shaft, 22, 24 edge, 26 grid electrode, 28 Inside, 30 Opening, 32 Support, 34 Charged wire, 40 Discharge product, 42 High oxidizing gas, 50 Motor, 52 Coupling, 54 Control part, 56 Claw part, 58 Stop rod, 60 Inert coating, 200 Electrophotographic apparatus.

Claims (4)

A charging means having a charger for charging the electrophotographic photosensitive member disposed above the electrophotographic photosensitive member;
Exposure means for exposing the electrophotographic photosensitive member charged by the charging means;
Developing means for developing a portion exposed by the exposure means;
Transfer means for transferring the image developed on the electrophotographic photosensitive member by the developing means;
A charger separation holding unit that includes a rotation shaft provided at one side end portion that forms the opening of the charger, and separates and holds the opening of the charger at a position not facing the surface of the photoreceptor;
At least the charging unit, the exposure unit, the developing unit, and the transfer unit control the electrophotographic process and rotate the charging unit around the rotation axis provided in the charging unit separation and holding unit during non-image formation to open the opening of the charging unit Holds the charger away from the photoconductor at a position facing the air flow, removes the accumulated discharge products and the highly oxidizing gas from the opening of the charger, and removes the charger during image formation. possess a control means for returning the electrophotographic process execution position, the,
The charger separation holding position by the charger separation holding means is in the range of 90 ° ± θ with respect to the angle θ based on the following formula, with reference to the position of the charger during the electrophotographic process. An electrophotographic apparatus.
(Equation 1)
θ = Sin ⁻¹ (G / H)
(Where G is the gap length from the surface of the photoreceptor to the opening of the charger, H is the height of the charger, θ is the separation inclination angle θ ₀ of the charger , and θ = | θ ₀ −90 ° |) The electrophotographic apparatus according to claim 1 ,
An electrophotographic apparatus, wherein an inert film is formed at least on the inner surface of the charger and on the surface of the grid electrode for controlling the photoreceptor potential inside the charger. The electrophotographic apparatus according to claim 1 ,
The electrophotographic apparatus according to claim 1, wherein the airflow is an airflow caused by an operation of an exhaust device that suppresses a temperature rise in the electrophotographic apparatus or an airflow generated along with rotation of a photosensitive member during an electrophotographic process. The electrophotographic apparatus according to claim 2 .
2. The electrophotographic apparatus according to claim 1, wherein the inert film is made of tetrahedral amorphous carbon.

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