JP4669677B2 - Compensation method for photoreceptor drum surface potential drop in image forming apparatus - Google Patents

Description

  The present invention relates to a method for compensating for a decrease in surface potential of a photosensitive drum in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and in particular, a corona charger is used for charging a photosensitive member. The present invention relates to a method for compensating for a decrease in surface potential of a photosensitive drum in the used image forming apparatus.

  In image forming apparatuses such as copiers, printers, facsimiles, and multi-function printers that use electrophotography, the demands for miniaturization, personalization, and price reductions have taken into account their use at home. There is a demand for lowering the charging voltage of the photosensitive drum. For example, Japanese Patent Application Laid-Open No. H10-260260 discloses that the position of the photosensitive drum is regulated both in the circumferential direction and in the height direction so that the photosensitive drum is uniformly charged. It has been shown that a certain distance can be maintained.

  However, in an image forming apparatus using an OPC (organic photoconductor) as a photoconductor, the surface potential decreases due to wear of the photoconductive layer on the photoconductor drum as the number of sheets used increases. When performed with voltage, there is not much room for fluctuations in the surface potential, and problems such as fogging occur as the surface potential decreases. Therefore, for example, Patent Document 2 shows that the dark potential and the light potential of the photosensitive drum are measured and the main charging potential is increased so that the difference falls within a certain range.

Japanese Patent No. 3256385 JP 2003-295528 A

  However, the technique disclosed in Patent Document 1 is a method in which the charging wire of the corona charger and the photosensitive drum are always kept at a constant distance in order to uniformly charge the photosensitive drum. A method for coping with the decrease is not shown, and the technique disclosed in Patent Document 2 applies a means for measuring the surface potential of the photosensitive drum and an output voltage according to a correction signal to a high voltage circuit that generates a corona voltage. There is a problem that the means for changing must be provided, the configuration is complicated, and the cost is increased.

  Therefore, an object of the present invention is to provide a method for compensating for a decrease in the surface potential of a photosensitive drum in an image forming apparatus that can compensate for a decrease in the surface potential due to wear of the photosensitive layer of the photosensitive drum with a simple configuration.

In order to solve the above problems, a method for compensating for a decrease in surface potential of the photosensitive drum in the image forming apparatus according to the present invention is as follows.
A compensation method for compensating for a decrease in surface potential caused by wear on the surface of the photosensitive drum in an image forming apparatus having a photosensitive drum for forming a toner image by an electrophotographic method and a corona charger for charging the photosensitive drum. There,
The corona charger, dissipate regulate the distance between the corona wire and the photoconductor drum in the corona charger a supporting bearing member provided at both end portions thereof in contact with the photosensitive drum, at least a portion of the support Is composed of a material that wears in accordance with the usage frequency of the photosensitive drum to reduce the distance between the corona wire and the photosensitive drum ,
A support provided in the corona charger includes a roller that is provided on the corona charger and rotates in contact with the photosensitive drum, and a holder that holds the roller and wears in contact with the shaft of the roller. characterized in that the configuration was.
The reduction in the surface potential of the photosensitive drum is compensated by increasing the amount of charge to the photosensitive drum by reducing the distance between the corona wire and the photosensitive drum caused by wear on at least a part of the support. It is characterized by that.

  In this way, the support provided at both ends of the corona charger is brought into contact with the photosensitive drum, and at least a part of the support is worn to reduce the distance between the corona wire and the photosensitive drum, whereby the corona wire and the photosensitive drum are reduced. The amount of wear on the surface of the photoconductor drum and the amount of decrease in the surface potential are compensated by compensating for the decrease in surface potential of the photoconductor drum by approaching the photoconductor drum and thereby increasing the amount of charge on the photoconductor drum. The relationship between the corona charger and the distance between the surface of the photosensitive drum and the amount of charge on the surface of the photosensitive drum is investigated, and at least a part of the support is subjected to the amount of wear of the support according to the usage frequency of the photosensitive drum. It is only necessary to use a material that can compensate for the amount of decrease in the surface potential of the photosensitive drum (that is, the amount of decrease in the distance between the corona wire and the photosensitive drum). Can compensate for the reduction of the surface potential of the photosensitive drum, the compensation method of the photosensitive drum surface potential drop in the image forming apparatus can be provided.

  As described above, according to the present invention, it is possible to provide a method for compensating for a decrease in the surface potential of a photosensitive drum in an image forming apparatus that can compensate for a decrease in the surface potential due to wear of the photosensitive layer of the photosensitive drum with a very simple configuration. it can.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a diagram showing a first embodiment of a schematic configuration of a photosensitive drum and a corona charger for performing a compensation method for a decrease in surface potential of the photosensitive drum in an image forming apparatus according to the present invention. FIG. 3 is a schematic perspective view of the support of the corona charger in the example, FIG. 3 is a table showing the transition of the surface potential of the photosensitive drum when the first embodiment is not applied, and FIG. FIG. 5 is a diagram showing a second embodiment of a schematic configuration of a photoconductor drum and a corona charger for carrying out a method for compensating for a decrease in surface potential of the photoconductor drum in the image forming apparatus according to the invention. FIG. 5 is a second embodiment of the present invention. FIG. 6 is a graph showing the relationship between the number of printed sheets and the photosensitive drum surface potential, and FIG. 7 is a diagram showing the relationship between the corona charger and the photosensitive member. Between the distance to the drum and the surface potential. Graph showing the engagement, Figure 8 is a schematic diagram of an example of an image forming apparatus according to the present invention.

  First, a schematic configuration of an example of an image forming apparatus to which the present invention is applied will be described with reference to FIG. 8. The charging unit 2 is disposed around the photosensitive drum 1 rotatably provided along the rotation direction. The exposure device 3, the developing device 4, the transfer device 5, the cleaning device 6 and the charge eliminating lamp 7 are arranged, and a transfer sheet 9 such as predetermined paper is conveyed between the transfer device 5 and the photosensitive drum 2, A toner image is transferred onto the surface of the transfer sheet 9. Although omitted in FIG. 8, a fixing device composed of a heat roller or the like is disposed on the discharge side of the transfer sheet 9.

  When an image forming instruction is received from a control device (not shown), the entire surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by the charging unit 2 and the surface of the photosensitive drum 1 charged by the exposure device 3 is charged. Then, exposure based on predetermined image information is performed to form an electrostatic latent image. The electrostatic latent image is developed by the developing unit 4 to form a toner image on the surface of the photosensitive drum 1, transferred to the transfer sheet 9 by the transfer unit 5, and heat and pressure by a fixing device (not shown). Is added to fix the toner image on the surface of the transfer sheet 9.

  On the other hand, the photosensitive drum 1 on which the toner image has been transferred to the transfer sheet 9 has the removal of the toner remaining on the surface by the cleaning device 6 and the removal of the charge remaining on the surface of the photosensitive drum 1 by the light irradiation by the charge eliminating lamp 7. As a result, one step of the image forming cycle is completed and the next image forming cycle is performed.

  Among these, the photosensitive drum 1 of the image forming apparatus embodying the present invention is an organic single-layer photosensitive drum in which an organic (OPC) photosensitive layer is formed on a conductive element tube such as aluminum, and charging means. Reference numeral 2 denotes a corona charger such as a corotron charger or a scorotron charger that applies a high voltage to a corona wire accommodated in a shield case to cause corona discharge to charge the photosensitive drum 1.

  The method for compensating for the decrease in the surface potential of the photosensitive drum according to the present invention is provided with supports for contacting the photosensitive drum 1 at both ends of the charging means 2 such as a corona charger, and the corona charger is charged by the support. The distance between the corona wire and the photosensitive drum 1 in the means 2 is regulated, and at least a part of the support is worn according to the frequency of use of the photosensitive drum 1 to cause the distance between the corona wire and the photosensitive drum 1. The material is made of a material capable of reducing the distance, and the reduction in the surface potential of the photosensitive drum 1 is compensated by increasing the amount of charge to the photosensitive drum 1 by reducing the distance.

  That is, in the organic photoreceptor (OPC), as described above and as shown in FIG. 6, as the number of images formed increases, the photosensitive layer wears down and the surface potential decreases. FIG. 6 is a graph showing the relationship between the number of formed images (number of printed sheets) and the surface potential of the photosensitive drum 1. The horizontal axis represents the number of printed sheets and the vertical axis represents the surface potential. As apparent from FIG. 6, the surface potential, which was 400 V in the initial stage, is reduced by almost 40 V due to the printing of 100,000 sheets.

  Further, FIG. 7 is a graph in which the relationship between the distance between the grid of the charging means 2 and the photosensitive drum 1 and the surface potential on the photosensitive drum 1 is examined, and the horizontal axis represents the charging means 2 and the photosensitive drum 1. The vertical axis indicates the surface potential. As can be seen from FIG. 7, when the distance between the charging means 2 and the photosensitive drum 1 is about 1 mm, the surface potential changes by about 10 V when the distance changes by 0.1 mm. That is, as shown in FIG. 6, when 100,000 sheets are printed and the surface potential decreases by about 40 V, if the distance between the charging unit 2 and the photosensitive drum 1 is reduced by about 0.4 mm, the photosensitive drum 1 is started to be used. The same surface potential as that at that time can be obtained.

  FIG. 1 shows a first embodiment of the configuration of the photosensitive drum 1 and the charging means 2 that implements the compensation method for the decrease in surface potential of the photosensitive drum 1 based on such a concept. In the first embodiment, the shield case 20 in the charging means 2 such as a corona charger has a portion 23 in contact with the shaft 22 of the roller 21 as shown in a perspective view in FIG. 24 is attached, and the charging means 2 is pressed toward the photosensitive drum 1 by a pressing spring 25 provided on the image forming apparatus main body side, so that the roller 21 of the holder 24 is pressed against the photosensitive drum 1. In this way, the distance between the corona wire and the photosensitive drum 1 in the charging unit 2 is kept constant, and the roller 21 rotates in contact with the photosensitive drum 1 at a portion 23 in contact with the shaft 22 of the roller 21. In this case, the wear is made of a member that wears, the distance between the corona wire and the photosensitive drum 1 is reduced by this wear, and the charge amount to the photosensitive drum 1 is increased to compensate for the surface potential drop. .

  FIG. 3 is a table in which the configuration for implementing the surface potential drop compensation method according to the first embodiment shown in FIGS. 1 and 2 is applied to an actual image forming apparatus and the state of the surface potential is examined. An FS-1010 printer manufactured by Kyocera is used as an image forming apparatus. “Applying the present invention” uses polyacetal as the material of the roller 21 and polycarbonate as the material of the portion 23 in contact with the shaft 22 of the roller 21 in the holder 24. The distance between the drum 1 and the corona wire in the charging unit 2 is 1 mm, the pressing force of the charging unit 2 against the photosensitive drum 1 is 5 N, and “not applying the present invention” means that the shaft 22 of the roller 21 in the holder 24 is not applied. As the material of the portion 23 in contact with the surface, ultrahigh molecular weight polyethylene with a small amount of wear is used, and the distance between the photosensitive drum 1 and the corona wire in the charging means 2 is kept at 1 mm. As Mom, it is those that were investigated for the occurrence of the transition and the fog of the surface potential by repeating the printing of 100,000 copies each.

  As can be seen from the table of FIG. 3, a large difference is not seen up to about 10,000 sheets, but the surface potential decreases when the present invention is not applied from about 30,000 sheets. At 100,000 sheets, the image quality was impaired by fogging. On the other hand, those who applied the present invention had a slight decrease in surface potential even with 100,000 sheets, and no fogging occurred.

  FIG. 4 shows a second embodiment of the configuration of the photosensitive drum 1 and the charging means 2 for carrying out the compensation method for the surface potential drop of the photosensitive drum 1. In the second embodiment, the portions 41 where the photosensitive material is not applied are provided at both ends of the portion 40 where the photosensitive material of the photosensitive drum 1 is applied, and the shield case in the charging means 2 such as a corona charger is provided. 42 is provided with a support member 43 that contacts the portion 41 of the photosensitive drum 1 where the photosensitive material is not applied and keeps the distance between the corona wire and the photosensitive drum 1 in the charging means 2 constant. The charging means 2 is pressed in the direction of the photosensitive drum 1 by a pressing spring 44 provided on the forming apparatus main body side.

  The surface roughness of the photosensitive drum 1 where the photosensitive material is not applied 41 is set in a range of Rz 0.20 μm to 1.00 μm, and the support is in contact with the photosensitive material drum 41 where the photosensitive material is not applied. The member 43 is made of a material that is worn by the surface roughness of the portion 41. Due to this wear, the distance between the corona wire and the photosensitive drum 1 is reduced, and the amount of charge on the photosensitive drum 1 is increased. Thus, a decrease in surface potential is compensated.

  The material of the support member 43 is preferably a polyacetal-based material. If polycarbonate or ABS material is used, the amount of friction is so great that the correction works more than the reduction in surface potential due to wear of the photosensitive layer 40 on the photosensitive drum 1. bad. On the other hand, if a highly slidable material such as PBT or ultra-high molecular weight polyethylene is used, the amount of friction is too small to compensate.

  FIG. 5 is a table in which the surface potential state is examined by applying the configuration for implementing the surface potential drop compensation method of the second embodiment shown in FIG. 4 to an actual image forming apparatus. This uses a Kyocera FS-1010 printer as an image forming apparatus. First, “Apply the present invention” sets the surface roughness of the photosensitive drum 1 where the photosensitive material is not applied to Rz 0.55 μm. The support member 43 is made of polyacetal LA-541 and the distance between the photosensitive drum 1 and the corona wire in the charging means 2 is set to 1 mm, and the pressing force of the charging means 2 against the photosensitive drum 1 is set to 5N. . In the case of “not applying the present invention”, ultrahigh molecular weight polyethylene having a small amount of wear is used as the material of the support member 43, and the distance between the photosensitive drum 1 and the corona wire in the charging means 2 is kept at 1 mm. In each of these, 100,000 sheets of printing were repeated to investigate changes in surface potential and occurrence of fog.

  As can be seen from the table of FIG. 5, a large difference is not seen up to about 10,000 sheets, but the surface potential decreases when the present invention is not applied from about 30,000 sheets. At 100,000 sheets, the image quality was impaired by fogging. On the other hand, those who applied the present invention had a slight decrease in surface potential even with 100,000 sheets, and no fogging occurred.

  As described above, according to the present invention, the support provided at both ends of the corona charger is brought into contact with the photosensitive drum, and the distance between the corona wire and the photosensitive drum is caused by at least partial wear of the support. The decrease in surface potential of the photosensitive drum is compensated by the method of increasing the charge amount to the photosensitive drum by reducing the amount of the toner, the relationship between the wear amount on the surface of the photosensitive drum and the decrease in the surface potential, and the corona Investigate the relationship between the distance between the charger and the surface of the photosensitive drum and the amount of charge on the surface of the photosensitive drum, and the amount of wear of the support (that is, the decrease in the distance between the corona wire and the photosensitive drum) Since at least a part of the support only needs to be made of a material that can compensate for the amount of decrease, the photosensitive drum in the image forming apparatus can compensate for the decrease in the surface potential of the photosensitive drum with a very simple configuration. It is possible to provide a compensation method of the drum surface potential drop.

  According to the present invention, it is possible to provide an image forming apparatus that can compensate for a decrease in surface potential due to abrasion of the photosensitive drum photosensitive layer with a very simple configuration and can form an image free from fogging.

FIG. 2 is a diagram illustrating a first embodiment of a schematic configuration of a photosensitive drum and a corona charger that performs a method for compensating for a decrease in surface potential of the photosensitive drum in the image forming apparatus according to the present invention. It is a schematic perspective view of the support body of the corona charger in the first embodiment. 6 is a table showing changes in the surface potential of the photosensitive drum when the first embodiment of the present invention is applied and when it is not applied. FIG. 7 is a diagram illustrating a second embodiment of a schematic configuration of a photosensitive drum and a corona charger, which performs a method for compensating for a decrease in surface potential of the photosensitive drum in the image forming apparatus according to the present invention. 6 is a table showing changes in the surface potential of the photosensitive drum when the second embodiment of the present invention is applied and when it is not applied. 6 is a graph showing the relationship between the number of printed sheets and the surface potential of the photosensitive drum. 6 is a graph showing the relationship between the distance between the corona charger and the photosensitive drum and the surface potential. 1 is a schematic configuration diagram of an example of an image forming apparatus to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging means 3 Exposure apparatus 4 Developing means 5 Transfer means 6 Cleaning apparatus 7 Static elimination lamp 9 Transfer sheet 20 Shield case 21 Roller 22 Shaft 23 Axis contact 24 Holder 25 Press spring

Claims (2)

A compensation method for compensating for a decrease in surface potential caused by wear on the surface of the photosensitive drum in an image forming apparatus having a photosensitive drum for forming a toner image by an electrophotographic method and a corona charger for charging the photosensitive drum. There,
The corona charger, dissipate regulate the distance between the corona wire and the photoconductor drum in the corona charger a supporting bearing member provided at both end portions thereof in contact with the photosensitive drum, at least a portion of the support Is composed of a material that wears in accordance with the usage frequency of the photosensitive drum to reduce the distance between the corona wire and the photosensitive drum ,
A support provided in the corona charger includes a roller that is provided on the corona charger and rotates in contact with the photosensitive drum, and a holder that holds the roller and wears in contact with the shaft of the roller. A method of compensating for a decrease in surface potential of a photosensitive drum in an image forming apparatus.   Compensation for the decrease in surface potential of the photosensitive drum is performed by increasing the amount of charge to the photosensitive drum by reducing the distance between the corona wire and the photosensitive drum caused by wear on at least a part of the support. The method for compensating for a decrease in surface potential of the photosensitive drum in the image forming apparatus according to claim 1.

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