JP2007334089A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device disposed in an electrophotographic apparatus in order to transfer an image to paper, the device being designed so as to prevent toner from accumulating on a destaticizer, which prevents peeling discharge from arising when paper is peeled from a transfer belt, and sticking to paper with the result that print quality degrades. <P>SOLUTION: The grounded paper passage part of the case of the destaticizing device is provided with ribs. This prevents toner from accumulating on the paper passage part of the case of the destaticizing device and sticking to paper. Accordingly, stable print quality can be maintained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transfer device for transferring a toner image on a photoreceptor onto a sheet in an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic system.

  As a means for preventing toner from adhering to the paper discharge / conveying roller of the transfer paper, a technique has been proposed in which the outer peripheral surface of the driven roller is covered with a high-release resin (see, for example, Patent Document 1). In addition, a technique for providing a toner adhesion preventing power source for applying a bias voltage for preventing toner adhesion has been proposed (see, for example, Patent Document 2).

Japanese Patent Publication No. 2004-268294 Japanese Patent Publication No. 2004-21109

  Since the case of the static eliminator to which a high voltage is applied is usually made of a synthetic resin, it becomes easy to be charged by friction with the paper when the static eliminator has a paper guide function. For this reason, there is a problem that the toner floating and scattered in the environment around the static eliminator is electrostatically adsorbed and the adhered toner stains the paper, but the paper guide part of the static eliminator is grounded to discharge the frictional charge with the paper. Stable print quality can be maintained. However, in the above configuration, when the toner scattered in the environment around the static eliminator accumulates on the paper guide portion of the static eliminator due to natural fall or the like, it is not possible to avoid paper contamination due to the adhered toner.

  Further, when toner adheres due to physical contact, the outer peripheral surface is covered with a highly releasable resin to prevent adhesion, but when deposited due to natural fall or the like, toner adhesion cannot be prevented. In addition, a configuration for preventing toner adhesion by applying a bias voltage requires a toner adhesion preventing power supply, and is expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that eliminates the above-mentioned drawbacks of the prior art and performs stable and inexpensive toner adhesion prevention with a simple structure.

  In order to achieve the above object, the present invention has a transfer device for transferring a photosensitive toner image onto a sheet conveyed by a transfer belt, and discharges the sheet downstream from the transfer device in the sheet conveying direction of the transfer belt. In an electrophotographic image forming apparatus provided with a static eliminator having a discharge wire and a ground shield, a rib-shaped paper guide is provided on the surface of a paper passage portion of the static eliminator. The paper guide is made of a conductive material. The ribs of the paper guide have an inclination of 5 ° to 30 ° with respect to the paper running direction, and at least the ribs near the paper edge are inclined toward the outside of the paper running range in the downstream direction. Moreover, the width | variety of the front-end | tip of the said rib is 0.3 mm or less, It is characterized by the above-mentioned. The paper guide is disposed at a position that does not reach the paper edge passage position of the standard size paper.

According to the present invention, it is possible to easily prevent the toner deposited on the paper passage portion of the static eliminator from adhering to the paper without complicating the configuration of the apparatus, and to ensure stable print quality. it can.

  In the present invention, ribs are provided on the sheet conveying surface of the static eliminator, and the sheet shape and material are devised to prevent sheet contamination due to accumulated toner.

  An embodiment in which the present invention is applied to a laser beam printer using electrophotography will be described below with reference to the drawings. In FIG. 1, when a charged organic photoconductor (OPC) used in a copying machine, a printer, or the like is used, the surface of the photoreceptor 1 is charged to a polarity by a charger 2. In the reversal development method generally used in printers, a latent image is formed by an optical system 3 such as a semiconductor laser, and a negative polarity toner 5 having the same polarity as the potential of the surface of the photoreceptor 1 is developed by the developing machine 4. Adhere on. The sheet 6 conveyed by the sheet traveling member reaches the transfer belt 8 through the guide plate 7. The transfer belt 8 is supported at both ends by a driving roller 9 and a driven roller 10, and rotates in the direction of the arrow by the rotation of the driving roller 9. Since a high voltage is applied from the high voltage power supply 13 to the wire 12 of the transfer device 11 provided inside the transfer belt, a charge having a polarity opposite to that of the toner is generated on the surface of the transfer belt 8 by corona discharge. The transported paper 6 is attracted to and transported by the transfer belt 8 at the same time as the toner image is transferred by this charge. After the sheet 6 conveyed by the transfer belt 8 reaches the driving roller 9, the sheet 6 is neutralized by the static eliminator 14, peeled off from the belt, and then fixed by the fixing device 15. On the other hand, the toner remaining on the photoreceptor 1 after the transfer is cleaned by a cleaner 18 through a precharge 16 and an erase lamp 17.

  In the transfer belt method, when the paper 6 is peeled off from the transfer belt 8, the transfer toner 5 is scattered due to peeling discharge and the printing quality is deteriorated. Therefore, a static eliminator 14 is provided in the peeling area to prevent the toner 5 from scattering. Since the static eliminator 14 applies a high voltage, scattered toner in the surrounding environment is electrically sucked.

  When the static eliminator 14 also functions as a paper guide, the paper guide part of the static eliminator 14 is grounded to prevent the toner 5 adhering to the static resin case and the synthetic resin case of the static eliminator 14 from being frictionally charged. The accumulated toner 5 deposited on the paper guide portion of the static eliminator 14 due to a natural fall or the like adheres to the paper 6 and causes a decrease in print quality.

  FIG. 2 shows a specific structure of the static eliminator 14 of the present invention. As a main configuration, the static eliminator 14 includes a corotron wire 20 for applying a high voltage, a metal shield plate 21 and a resin case 22. FIG. 3 shows a structure in which a paper guide 23 made of a rib-like conductive sheet metal for preventing toner adhesion and accumulation is erected at the paper passage portion. FIG. 4 shows a view from the direction A of FIG.

  As shown in FIG. 4, the sheet guide 23 has an inclination of 5 ° to 30 ° with respect to the sheet traveling direction, so that the rib contact to the sheet specific portion is dispersed and the contamination is reduced. At least the ribs in the vicinity of the paper edge that are easily soiled are inclined toward the outside of the paper traveling range as going downstream, and the toner slightly adhered to the paper guide 23 is continuously wiped off at a specific portion of the paper and becomes dirty. Can be prevented.

  Further, by setting the rib-shaped tip width to 0.3 mm or less and the edge curvature to R 0.3 mm or less, the amount of toner adhering to the paper guide 23 is reduced to a level that does not substantially affect the paper. Can be reduced.

  Reduces the amount of adhering toner by not providing a paper guide that contacts the paper at the paper edge passing part of regular size paper such as A4, A3, B4, B5, Letter, Legal, Legal, etc. can do. The rib shape may be integrally molded or may be joined as a separate member by welding or the like.

  FIG. 5 shows a structure in which a paper guide 24 made of conductive resin ribs is combined with a paper passage portion. FIG. 6 shows the structure of a paper guide 25 in which an insulating resin is conductively coated on the paper passage portion.

  By adopting this structure, charging due to the friction of the paper is eliminated, the adhesion of the toner 5 scattered around the static eliminator 14 is prevented, and the adhesion of the toner 5 deposited on the paper passage portion of the static eliminator to the paper due to a natural fall or the like. Can be prevented, the structure is simple, and stable printing quality can be ensured at low cost.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 3 is a schematic diagram showing a structure of a static eliminator 14. FIG. FIG. 4 is a schematic diagram showing a structure in which a paper guide made of a rib-like conductive sheet metal for preventing toner adhesion and accumulation is erected at a paper passage portion. It is the schematic diagram seen from the A direction of FIG. It is a schematic diagram showing a structure in which a paper guide made of conductive resin ribs is combined with a paper passage portion. FIG. 4 is a schematic diagram illustrating a structure of a paper guide in which an insulating resin is conductively coated on a paper passage portion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Optical system, 3 ... Charger, 4 ... Developing machine, 5 ... Toner, 6 ... Paper, 7 ... Guide plate, 8 ... Transfer belt, 9 ... Drive roller, 10 ... Driven roller, 11 ... Transfer device, 12 ... wire, 13 ... high voltage power supply, 14 ... static discharger, 15 ... fixing device, 16 ... precharge, 17 ... erasing lamp, 18 ... cleaner, 20 ... corotron wire, 21 ... shield plate, 22 ... case 23 ... paper guide, 24 ... paper guide, 25 ... paper guide

Claims (5)

  A transfer unit that transfers a photosensitive toner image onto a sheet conveyed by a transfer belt is provided, and a discharger that has a discharge wire and a grounding shield for discharging the sheet when the sheet is peeled is provided downstream of the transfer unit in the sheet conveyance direction of the transfer belt. In the electrophotographic image forming apparatus, a rib-shaped paper guide is provided on the surface of the paper passage portion of the static eliminator.   The image forming apparatus according to claim 1, wherein the paper guide is formed of a conductive material.   The ribs of the paper guide are provided with an inclination of 5 ° to 30 ° with respect to the paper running direction, and at least the ribs near the paper edge are inclined toward the outside of the paper running range in the downstream direction. The image forming apparatus according to claim 1.   4. The image forming apparatus according to claim 1, wherein a width of a tip of the rib is 0.3 mm or less. 5. The image forming apparatus according to claim 1, wherein the sheet guide is disposed at a position that does not reach a sheet edge passing position of a standard size sheet.

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