JP2007264099A - Electrophotographic image forming apparatus equipped with contact electrifying member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress such a failure as the main cause of a defective image that foreign substances stick to a contact electrifying means all over the life of a photoreceptor drum in a continuous mass printing process. <P>SOLUTION: The electrophotographic image forming apparatus includes: a cleaning means 13 for cleaning toner left on the photoreceptor drum 10 after the toner image is formed; the contact electrifying means 1 for uniformly electrifying the cleaned photoreceptor drum 10; a cleaning brush roller 2 that comes in contact with the contact electrifying means 1; and a first elastic member 3 arranged between the cleaning means 13 and the contact electrifying means 1 to clean particles slipping through the cleaning means 13. The first elastic member 3 is flexed and brought in press contact with the photoreceptor. The apparatus also includes a second elastic body 4 provided to press the first elastic member 3 against the photoreceptor drum 10, and the press contact force of the first elastic member 3 against the photoreceptor drum 10 is kept constant. Regarding the brush material for the cleaning brush roller, the single yarn fineness is 1 to 10T and the density is 40 to 300kF/inch<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus having a contact charging member, and in particular, between a cleaning unit that cleans toner remaining on a photoconductor after completion of image formation and a contact charging unit that uniformly charges the photoconductor. Furthermore, the present invention relates to an image forming apparatus in which an elastic member for cleaning is arranged.

  In an image forming apparatus equipped with a charging unit that uniformly charges the photoconductor in contact with the photoconductor, foreign matter such as paper dust or toner adhering to the contact charging unit becomes an image defect. ing.

For example, in the “contact charging device” disclosed in Patent Document 1, a cleaning member in which an elastic layer and a felt layer are laminated is attached to the contact charging unit, and toner, paper dust, or the like is attached to the contact surface between the contact charging unit and the photosensitive member. Prevent foreign material from entering. In addition, since the space surrounded by the contact charging means, the space between the photoconductor and the cleaning member is narrowly closed, it is possible to prevent adhesion of paper dust floating in the air.
JP-A-7-72709 (FIG. 1, paragraph 0033)

  Incidentally, foreign substances that contaminate the charging roller include a submicron-order toner external additive, toner aggregates of several tens to several hundreds of microns, and paper powder. The toner external additive constantly slips out of the cleaning blade and contaminates the charging roller, and fogging occurs particularly in a heavily contaminated portion due to a decrease in charging performance. On the other hand, toner agglomerates and paper powder slipping out are less frequent, but are especially likely to occur after changing the toner state at the blade edge, such as when the drum unit is detached from the machine, and strong at the nip between the drum and the charging roller. An image defect is caused by adhering to the charging roller.

  However, although cleaning with the blade method can remove toner aggregates and paper dust of the order of several tens to several hundreds of microns, it is difficult to remove the toner external additives of the order of submicrons. Uneven charging due to material contamination cannot be prevented.

  In particular, when an amorphous silicon (a-Si) drum is used, when toner aggregates are trapped by the method as in Patent Document 1, the surface of the drum is slightly shaved by the pressing force of the cleaning member. It has been found that the portion generates a gap between the drum and the cleaning blade, and a large amount of toner external additive slips through, causing the streaks of the charging roller to generate vertical streaks in the image.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to effectively suppress the adhesion of foreign matter to the contact charging means that causes image defects over the life of the photosensitive drum in an image forming apparatus equipped with the contact charging means. Moreover, it is suppressing the fall of the foreign material adhesion prevention effect in endurance conditions.

  In order to solve the above-described problems, first, in the image forming apparatus of the present invention, a cleaning unit that cleans toner remaining on the photoconductor after the toner image is formed, and a photoconductor after cleaning that comes into contact with the photoconductor. A first charging member that is disposed between the cleaning unit and the contact charging unit and that cleans particles that have passed through the cleaning unit; The elastic member is bent and pressed against the photoconductor. Furthermore, a second elastic body that presses the first elastic member against the photoconductor is provided, and the pressure contact force of the first elastic member to the photoconductor is kept constant.

In the present invention, secondly, the brush has a single yarn fineness of 1 dtex or more and 10 dtex or less, and a density of 40 kF / inch ² or more and 300 kF / inch ² or less.

  In the present invention, thirdly, the first elastic member is a urethane sheet, a polyethylene sheet, or a urethane foam sponge.

  In the present invention, fourthly, the second elastic member is a urethane foam sponge.

  Fifth, an image forming apparatus of the present invention exposes a photosensitive member to form an electrostatic latent image, developing means for developing the electrostatic latent image as a toner image, and transfers the toner image to a recording member. A transfer means for fixing, a fixing means for fixing the toner image on the recording medium, and a charge eliminating means for removing the residual potential of the photoconductor after the transfer.

  According to the present invention, first, the first elastic member and the brush reduce the scratches on the photosensitive member and the vertical lines of the contact charging means. Furthermore, even if the first elastic member undergoes permanent deformation, the second elastic member can surely press the photoconductor.

  According to the present invention, secondly, deterioration of charging performance can be suppressed by scattering and leveling the toner external additive material that has passed through the cleaning blade.

  According to the present invention, thirdly, the first elastic member can be bent in the rotation direction of the photosensitive drum.

  According to the present invention, fourthly, a second elastic member suitable for combination with the first elastic member is provided.

  According to the present invention, fifthly, it is possible to suppress a decrease in the effect of preventing foreign matter adhesion under the durability condition and to suppress the occurrence of image defects.

  As described above, according to the present invention, in a system having a charging roller and a cleaning blade on the upstream side thereof, a brush having a predetermined single yarn fineness range and density range is brought into contact with the charging roller, and is further bent toward the downstream side in the drum rotation direction. The first elastic member that contacts the drum is brought into contact with the cleaning blade and the charging roller, and the second elastic member is disposed on the opposite side of the first elastic member from the drum so as to contact the first elastic member. In addition, a decrease in pressure contact force to the drum due to the deformation of the first elastic member is suppressed.

  According to the present invention, in an image forming apparatus equipped with a contact charging unit, it is possible to suppress the adhesion of foreign matter to the contact charging unit, which causes image defects, over the life of the photosensitive drum, even under continuous large-scale printing.

  Embodiments of the present invention will be described below with reference to the drawings. However, even if there is a specific description in the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment, the present invention is not limited thereto.

  FIG. 1 is a conceptual diagram of an image forming apparatus according to this embodiment.

  Around the photosensitive member 10, a cleaning unit 13 such as a cleaning blade for cleaning the residual toner after the toner image is transferred to the paper P is disposed. On the downstream side, a static elimination unit 14 is arranged to remove the residual potential and prepare for the next image formation. Downstream thereof, the first elastic member 3 is bent and is in contact with the photosensitive drum 10, and further, the second elastic member 4 is pressed from the back surface of the first elastic member 3 to ensure a pressure contact force. A contact charging roller 1 and a brush roller 2 in contact with the contact charging roller 1 are disposed downstream thereof. On the downstream side, image exposure is performed by an exposure unit (not shown) to form an electrostatic latent image. On the downstream side, the electrostatic latent image is developed as a toner image by the developing device 11. The toner image is transferred to the paper P by the transfer means 12 downstream thereof. Finally, the paper P that has been detached from the photoreceptor 10 enters the nip between the heating roller 15 and the pressure roller 16, and the toner image is fixed on the paper P.

  Hereinafter, each part will be described according to the image forming process.

  As the latent image holding member on the surface of the photosensitive drum 10, various conventionally known organic or inorganic photosensitive members can be used. Among these, examples of the inorganic photosensitive member include those obtained by forming a photosensitive layer made of a thin film of an inorganic photoconductive material such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide on a conductive substrate. . Examples of the organic photoreceptor include those in which a single layer type or a laminate type organic photosensitive layer is formed on a conductive substrate. Among these, a single layer type photosensitive layer includes a charge generating agent, Examples thereof include those in which a charge transport agent or the like is dispersed in a binder resin. Examples of the laminated photosensitive layer include those in which a charge generation layer composed of a charge generation agent and a charge transport layer in which a charge transport agent is dispersed in a binder resin are laminated in this order or in the reverse order. .

  In order to hold the electrostatic latent image on the surface of the photosensitive member as a latent image holding member, a DC voltage or a DC superimposed AC voltage is applied to the charging roller 1 covered with an elastic member, and the photosensitive drum 10 is moved. It is necessary to charge to a predetermined polarity. The cleaning roller 2 prevents residual toner or paper dust that has passed through the cleaning means 7 from adhering to the charging roller, and is preferably a brush roller. However, not only the charging roller 26 but also a corotron / scorotron may be used.

  After uniform charging, an image of a reflection original is formed on the photosensitive member of the photosensitive drum 10 by an exposure unit (not shown), or a laser beam modulated by an image signal and scanned in the axial direction of the photosensitive drum 10 is formed. Thus, an electrostatic latent image is formed.

  In the developing means (developing roller) 11, for example, by a magnetic one-component jumping developing method, the photosensitive drum 1 holding an electrostatic latent image and a fixed magnet are rotated and a thin layer of magnetic toner is formed on the surface thereof. The magnetic toner is ejected from the thin layer onto the surface of the latent image holding member in a state where the developer carrying member is formed so that the thin layer and the latent image holding member are opposed to each other while holding the gap. Thus, the electrostatic latent image is visualized as a toner image.

  Thereafter, the formed toner image is transferred onto the surface of a printing material such as paper by the transfer unit 12 and fixed by the fixing unit (the heating roller 15 and the pressure roller 16). The heating roller 15 is made of, for example, aluminum whose outer periphery is coated with silicone rubber or the like, and has a heat source such as a resistance heater or a quartz lamp inside the cylinder. The pressure roller 16 is made of, for example, aluminum coated with silicone rubber or the like on the outer periphery of a nium cylinder.

  As the cleaning means 13 for removing the magnetic toner remaining on the surface of the photoconductor drum 10, it is preferable to use an elastic blade brought into pressure contact with the surface of the photoconductor. As the elastic blade, various known elastic blades such as rubber and soft resin can be employed. Specifically, for example, an elastic blade made of silicone rubber, fluorine rubber, urethane rubber, urethane resin or the like can be used. The elastic blade is preferably pressed at a linear pressure of 10 to 50 g / cm in consideration of cleaning and removing the toner satisfactorily and taking into consideration that no pressure contact mark or the like is generated on the surface of the photoreceptor.

  The static elimination lamp 14 is a white light source or the like, removes the residual potential after image formation, and prepares for the next image formation.

  Examples will be described below.

The contact charging means (charging roller) 1 has a single yarn fineness of 1 dtex (T) or more and 10 T or less, a density of 40,000 filaments / in ² (40 kF / inch ² ) or more and 300 kF / inch ² or less. A certain brush (brush roller) 2 is in contact therewith. The material is conductive nylon, which bites 0.5 mm into the charging roller 1 and rotates at a linear speed ratio of 85% with respect to the charging roller 1. The brush roller 2 can suppress deterioration of charging performance by scattering and leveling the toner external additive material that has passed through the cleaning blade. If the brush is out of the above specifications, the external additive adheres to the surface of the charging roller 1 and causes a deterioration in charging performance.

  The first elastic member 3 is disposed between the cleaning means (cleaning blade) 13 and the charging roller 1 for the purpose of trapping toner aggregates that cannot be removed by the cleaning brush roller 2 upstream of the charging roller 1. It is arranged and pressed against the photosensitive drum 10 in a bent form. The first elastic member 3 is pressed by the support 53. The first elastic member 3 is preferably a foamed sponge such as a urethane sheet, a polyethylene sheet, or urethane having a thickness of about 0.1 to 0.2 mm.

  Further, the second elastic member 4 is pressed against the back surface of the first elastic member 3. The second elastic member 4 is pressed by the support 54. A part of the second elastic member may directly contact the drum. The second elastic member 4 is preferably made of a foamed sponge such as urethane having a thickness of 1.5 mm or more, particularly a material having a low permanent strain such as poron, but is not limited thereto. Even if the first elastic member 3 is permanently deformed by supporting the first elastic member 3 from the side opposite to the photosensitive drum 10 by the second elastic member 4, the pressure contact force to the drum is reduced and the toner aggregate trap Prevent loss of ability.

  Using our printer at a paper feeding speed of 28 sheets / min, the occurrence of black spots on the images in the example and the comparative example was compared. In the example, black spots did not occur even after continuous printing of 300,000 sheets, whereas in the comparative example in which the second elastic member 4 was not attached, black spots occurred on 100,000 sheets. This is because without the second elastic member 4, the first elastic member 3 that has been permanently deformed cannot be brought into pressure contact with the photosensitive drum 10, and therefore, there is no toner aggregate trapping capability.

  The present invention is applicable to an electrophotographic image forming apparatus having a contact charging member.

Conceptual diagram of an electrophotographic image forming apparatus having a contact charging member of this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contact charging means 2 Brush 3 1st elastic member 4 2nd elastic member 5 Support member 10 Photosensitive drum 11 Developing means 12 Transfer means 13 Cleaning means 14 Static elimination means 15 Heating roller 16 Pressure means

Claims (5)

Cleaning means for cleaning toner remaining on the photoreceptor after toner image formation;
Contact charging means for contacting the photosensitive member and uniformly charging the cleaned photosensitive member;
A brush that contacts the contact charging means;
A first elastic member disposed between the cleaning means and the contact charging means for cleaning particles that have passed through the cleaning means;
A second elastic body that presses the first elastic member against the photoreceptor;
An image forming apparatus, wherein a pressing force of the first elastic member to the photosensitive member is kept constant. ^2. The image forming apparatus according to claim 1, wherein the brush has a single yarn fineness of 1 dtex or more and 10 dtex or less, and a density of 40 kF / inch ² or more and 300 kF / inch ² or less.   The image forming apparatus according to claim 1, wherein the first elastic member is a urethane sheet, a polyethylene sheet, or a urethane foam sponge.   The image forming apparatus according to claim 3, wherein the second elastic member is a urethane foam sponge. Exposure means for exposing the photoreceptor to form an electrostatic latent image;
Developing means for developing the electrostatic latent image as a toner image;
Transfer means for transferring the toner image to a recording medium;
Fixing means for fixing the toner image to the recording medium;
The image forming apparatus according to claim 1, further comprising a charge removing unit that removes a residual potential on the photoconductor after the transfer.

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