JP2005084213A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem on the occurrence of a drum wrap phenomenon that paper can not be separated from a photoreceptor and is stuck to the photoreceptor in a high-speed machine having the large diameter of the photoreceptor in a transfer belt system. <P>SOLUTION: An electrostatic charge eliminating member for eliminating electrostatic charge in a non-contact state is attached to a guide member for guiding paper to a transfer belt, and removes excess charge generated by triboelectrification by an elastic roller provided in a paper carrying path, whereby the paper is prevented from being electrostatically attracted to the photoreceptor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser printer using electrophotography.

  In the transfer device of cut paper laser printers and copiers that use electrophotography, there is a transfer belt system that uses a dielectric belt for the purpose of transporting and transferring the paper that is the recording material, inducing charges on the surface of the transfer belt. Thus, the sheet is sucked and conveyed by this charge, and the image formed on the photoconductor serving as an image carrier is transferred to the sheet.

  Compared with the conventional corotron transfer method and the transfer roller method that has been frequently used in recent years, it can transfer uniformly from the leading edge to the trailing edge of the paper regardless of the paper type, and also has the function of conveying the paper after transfer This also has the advantage of eliminating the need for a mechanism that separates from the photoreceptor and transports it to fixing.

  However, in this method, the toner image on the photoconductor is transferred with the paper adsorbed to the transfer belt. Therefore, in a high-speed machine having a large photoconductor diameter, the paper cannot be separated from the photoconductor and sticks to the photoconductor. Drum wrap phenomenon may occur.

  This drum wrap phenomenon involves various factors such as physical properties of the transfer belt and transfer conditions, but it often occurs depending on the state of the paper, and in particular, the paper is not well cut and the edges are deformed. It is known that it is likely to be generated by a material that is deformed by moisture absorption.

  In recent years, recycled paper that is friendly to the global environment has been used in place of fine paper, but recycled paper uses waste paper pulp, so it is easily deformed by cutting and moisture absorption. It tends to occur easily.

  In order to prevent drum wrapping, a method has been proposed in which a special solution is applied to the surface of the transfer belt to improve the sheet separation performance of the transfer belt (see Patent Document 1).

Japanese Patent Laid-Open No. 11-161036

  However, the method of performing the surface treatment on the transfer belt has a drawback that not only the special equipment is required but also the cost of the parts becomes high. Since the transfer belt has characteristic values of the transfer belt that fluctuate and deteriorate due to ozone generated in the apparatus and friction with the paper, the transfer belt is usually replaced with several hundred thousand to million pages. For this reason, an increase in the cost of parts leads to an increase in the cost for maintaining the apparatus. In particular, when the life of the transfer belt is short, the replacement period is shortened, which is a heavy burden on the user who uses it. .

  As described above, the drum wrap has various factors, but one of the factors is that the sheet is charged until it reaches the transfer belt. The paper transported from the paper supply unit to the transfer belt is electrostatically attracted by the charge of the transfer belt to transfer the toner on the photoconductor. It is conveyed by an elastic roller provided on the surface. For this reason, the sheet is triboelectrically charged with the elastic roller, and depending on the charging polarity, it may be easily electrostatically adsorbed to the photosensitive member instead of the transfer belt.

  Therefore, when the paper is excessively charged before transfer and the electrostatic adsorption force with the photosensitive member becomes the dominant factor, the method of performing the surface treatment of the transfer belt not only increases the component cost but also the effect. Will not be obtained.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent the occurrence of electrostatic drum wrap with a simple configuration without increasing the cost of a transfer belt.

  In order to achieve the above object, in claim 1 of the present invention, a static elimination member for neutralizing electricity is attached to the transfer belt in a non-contact manner on a guide member for guiding the paper, so that an elastic roller provided in the paper conveyance path is used. When transported, excess charge accumulated on the frictionally charged paper is removed to prevent electrostatic adsorption with the photoreceptor.

  According to a second aspect of the present invention, the static elimination member is made of a brush-like fiber attached to a metal plate, and an angle formed by the paper transported from the paper travel mechanism is 50 to 80 °. By setting the distance from the brush fiber to 1 to 2 mm, paper damage is prevented without impairing the effect of static elimination, and paper dust is prevented from adhering to the static elimination brush.

  According to a fourth aspect of the present invention, the guide member serves as both a neutralizing brush attachment and a paper regulation with the same component by forming a substantially square shape that also functions to attach the static elimination brush and to regulate the angle of the paper conveyed to the transfer belt. Therefore, it is possible to reduce the number of parts and prevent dirt and broken ears.

  As described above, according to the present invention, drum wrap can be prevented without complicating the parts cost of the transfer belt and the configuration of the apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  An embodiment in which the present invention is applied to a laser printer using electrophotography will be described below with reference to FIG. In the case of an organic photoconductor (OPC) used in a copying machine, a laser printer or the like, the surface of the photoreceptor 1 is negatively charged by corona discharge of the charger 2. In the reversal development method often used in laser printers, a latent image is formed by an optical system 3 such as a semiconductor laser, and toner 5 having the same polarity as the potential of the surface of the photoreceptor 1 is applied onto the photoreceptor 1 by the developing machine 4. Adhere. Although details are omitted, the sheet 6 conveyed by the sheet traveling mechanism is guided to a guide member 8 that serves both as a guide for the sheet 6 and to attach the neutralizing brush 7, and then reaches the transfer belt 9. The transfer belt 9 is supported at both ends by a driving roller 10 and a driven roller 11, and rotates in the arrow direction when the driving roller 10 rotates. By the corona discharge generated from the transfer device 12 inside the transfer belt 9, a reverse polarity, that is, a positive charge is generated on the surface of the transfer belt 9, and the sheet 6 is attracted to the transfer belt 9 by this positive charge, and the toner 5 is transferred. Thereafter, the transferred sheet reaches the driving roller 10, is neutralized by the static eliminator 13, is separated by the transfer belt 9, and is fixed by the fixing device 14. On the other hand, the toner 5 on the photosensitive member 1 remaining after the transfer is cleaned by a cleaning device 17 through a precharge 15 and an erase lamp 16.

Next, the effect of the present invention will be described in detail with reference to FIG.
As shown in FIG. 2, the neutralizing brush has a fibrous brush 19 made of stainless steel or carbon fiber attached to a metal plate 18, and the metal plate 18 of the neutralizing brush 7 is screwed to the guide member 8. When the paper 6 holding the positive charge 20 approaches the brush 19, the negative charge 21 having the opposite polarity due to electrostatic induction gathers at the tip of the brush 19, and the collected negative charge 21 exceeds a certain amount of charge. Corona discharge occurs in the gap d22. The negative charge 21 generated at this time has a polarity opposite to that of the paper 6 and attracts the positive charge 20 on the surface of the paper 6 to eliminate the charge. Is.

  Although not shown, the paper 6 is conveyed by the elastic roller provided in the paper conveyance path until it reaches the transfer belt 9 as described above, so that it is frictionally charged. This polarity varies depending on the material constituting the elastic roller and the charging series of the paper 6. If the elastic roller is urethane rubber, the paper 6 is considered to be easily charged to the positive side. In particular, when the temperature is low and humidity is low, the resistance of the paper 6 itself increases, so that the generated charges are held without escaping, and this phenomenon becomes remarkable. On the other hand, since the charging polarity of the photosensitive member 1 is negative, when the sheet 6 is positively charged, a positive charge is further transferred from the transfer device 12 when attracted to the transfer belt 9 and transferred. As a result, the toner is charged to the positive side and is easily attracted electrostatically to the photosensitive member 1, and drum wrapping occurs.

  In the present invention, in order to remove excess electric charge accumulated on the paper 6 before reaching the transfer belt 9, as shown in FIG. 3, the neutralization brush 7 is provided on the guide member 8 at the entrance of the transfer belt 9, and the neutralization brush The attachment angle θ formed by 7 and the paper transport direction is attached at an angle of about 60 °. This attachment angle θ is important in removing and transporting the paper 6. When the mounting angle θ is as small as 30 ° with respect to the paper conveyance direction as shown in FIG. The effect will not be obtained sufficiently. When the potential of the paper 6 was measured with a non-contact electrometer, the attachment angle θ was effective at 50 ° or more.

  On the other hand, when the mounting angle θ exceeds 90 ° as shown in FIG. 5, the sheet 6 may be caught by the static elimination brush tip 23, or the sheet 6 may hit the bent portion 24 of the guide member 8 and damage the tip. . For this reason, the static elimination brush 7 attachment angle (theta) was made into the range of 50-80 degrees with respect to a paper conveyance direction.

  Further, when the trajectory on which the paper 6 travels from the paper transport mechanism to the guide member 8 is verified, it is as shown in FIG.

  If the paper is always brought into contact with the tip 23 of the static elimination brush, the effect of neutralizing the paper 6 is enhanced. However, it is considered that paper dust adheres or the brush 19 comes off from the metal plate 18. If paper dust adheres to the brush 19 and accumulates a certain amount, it may fall on the paper and cause printing stains, or if the brush 19 comes off and enters the transfer belt 9, it may cause high-pressure failure. Therefore, it is desirable that the static eliminating brush 7 and the paper 6 are not in contact with each other. On the other hand, if the interval d22 is widened, the effect of eliminating the charge of the paper 6 cannot be obtained sufficiently. For this reason, in this invention, the space | interval d22 of the paper 6 and the static elimination brush 7 front-end | tip is set to 1-2 mm.

  Further, the guide member 8 has an inverted character shape, and also serves to restrict the position of the sheet 6 conveyed to the transfer belt 9 and the attachment of the neutralizing brush 7. The trajectory of the paper 6 is not always constant, and the travel timing of the paper 6 also varies. When double-sided printing is performed, the trajectory of the paper 6 slightly varies depending on the moisture content of the paper 6. As shown in FIG. 7, when the position of the sheet 6 is not sufficiently regulated and the sheet travels into the transfer belt 9 at a position higher than normal, contact between the photosensitive member 1 and the sheet 6 is not uniform in the axial direction. In this case, it may cause broken ears and print stains.

  For this reason, at the tip of the guide member 8, the position of the sheet 6 can be controlled even if the sheet 6 fluctuates to an upper position, which can also prevent the stains and the folding of the ears. .

  In the present invention, an example of the transfer belt system is shown, but the present invention is also effective in other transfer systems such as corotron transfer and transfer roller system.

1 is a configuration of a laser printer representing an embodiment of the present invention. The figure showing the structure and principle of the static elimination brush. The figure showing the effect of the static elimination brush. The figure showing the attachment state of the static elimination brush. The figure showing the attachment state of the static elimination brush. FIG. 6 is a diagram illustrating a restriction position of a guide member according to a paper traveling position. FIG. 6 is a diagram illustrating a restriction position of a guide member according to a paper traveling position.

Explanation of symbols

1: Photoconductor, 2: Charger, 3: Optical system, 4: Developer, 5: Toner, 6: Paper, 7: Static elimination brush, 8: Guide member, 9: Transfer belt, 10: Drive roller, 11: Followed roller, 12: transfer device, 13: static eliminator, 14: fixing device, 15: precharge, 16: erase lamp, 17: cleaning machine, 18: metal plate, 19: brush, 20: positive charge, 21: negative Electric charge, 22: gap d, 23: tip of static elimination brush, 24: bent portion of guide member

Claims (4)

  A transfer device that sucks and conveys the recording material by applying a charge having a polarity opposite to that of the toner to the back surface of the transfer belt, and transfers the toner image formed on the image carrier to the recording material, and a recording material on the transfer belt. An image forming apparatus comprising a guide member for guiding, wherein a charge eliminating member for neutralizing a recording material in a non-contact manner is attached to the guide member, and the conveyed recording material is neutralized.   2. The neutralizing member comprises a brush-like fiber attached to a metal plate, and an angle formed with a recording material conveyed from a recording material traveling mechanism is defined as 50 to 80 degrees. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the neutralizing member defines an interval between the recording material and the brush fiber to be 1 to 2 mm. The image forming apparatus according to claim 1, wherein the guide member has a substantially U-shape that has both a function of attaching a static elimination brush and regulating a position of the recording material conveyed to the transfer belt.

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