JP2007155888A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which secures effective resolution of ozone and NOx as a discharge product caused when a photoreceptor is electrified, and electrification stability. <P>SOLUTION: The image forming apparatus is provided with: a photocatalytic material 103 in a surface opposite to a discharge wire 101 inside a primary electrifier 7 electrifying a photoreceptor 1; and photocatalytic openings 105 at a fixed interval so as not to make the discharge of the primary electrifier 7 unstable, or configured so that the arrangement area of the photocatalytic material 103 is provided outside an image forming area, to blow the discharge product caused in the primary electrifier 7 by a fan 301, etc. and send the discharge product into the arrangement area of the photocatalytic material 103. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus capable of decomposing a discharge product generated in an image forming process.

  In an image forming apparatus using an electrophotographic process, such as an electrophotographic copying machine, an electrostatic printer, or a facsimile, first, a photosensitive member is uniformly charged (primary charging), and then a laser beam or the like is imaged on the surface of the photosensitive member. Irradiation is performed according to information to form an electrostatic latent image, and toner is supplied to form a toner image.

  Further, the toner image is transferred to an image forming member and then fixed by heat or the like to obtain a final image. At this time, the image forming apparatus includes a charging unit, a transfer unit, and a charge removing unit for removing toner remaining on the photoconductor after the image transfer. For each of these parts, a corona discharge method is often used in which a high voltage is applied to a discharge wire placed in a longitudinal direction perpendicular to the rotation direction of the photoconductor in order to apply a constant electrostatic charge to the photoconductor or image forming member. ing.

  However, this corona discharge generates discharge products such as ozone and NOx.

  If ozone accumulates in the image forming apparatus at a high concentration, the deterioration of the photoconductor and the like is promoted, and if ozone at a high concentration is discharged into the image forming apparatus, adverse effects on the human body such as odor and allergies may be considered.

  On the other hand, when NOx adheres to a discharge wire or the like, the discharge becomes unstable, charging unevenness occurs, and image deterioration can be considered. Furthermore, after adhering to the surface of the photoconductor, when it is combined with moisture in the air, the resistance value is lowered, so that a phenomenon (image flow) that disturbs the electrostatic image occurs and the image is deteriorated.

  For this reason, in the conventional image forming apparatus, after the air around the photosensitive member is sucked by a large capacity fan, the ozone treatment is performed by discharging the air through the ozone filter.

  For NOx, the deposit on the discharge wire is cleaned and removed at regular intervals by applying a wire cleaning member. Measures are taken such as NOx adhering to the photoconductor is scraped little by little during cleaning, or the photoconductor is kept at a certain temperature or higher by a heater or the like to make it difficult to combine with moisture.

  However, all of the above methods still have problems such as an increase in cost, deterioration of filters and photoconductors, and increase in energy consumption due to large capacity fans and heaters.

  On the other hand, in recent years, development of photocatalytic materials having an action of adsorbing and decomposing ozone and NOx has been accelerated.

In such a technique, a photocatalytic substance such as titanium oxide is added to the inside of a charger casing or the like to decompose ozone and discharge generation substances such as NOx to reduce the concentration (for example, Patent Documents). 1).
JP 2001-75338 A

  In the conventional image forming apparatus, a stable charged state of the photosensitive member is maintained by flowing a constant discharge current (shield current) from the discharge wire to the shield casing. However, in the arrangement method of the photocatalytic material, the resistance value of the shield casing surface is changed by applying a semiconductor material such as titanium oxide to the surface facing the wire, so that a stable shield current cannot be maintained, and the charging of the photoconductor is not possible. Can also become unstable.

  In order to prevent this, a means for allowing a larger current to flow and stabilizing the discharge current can be considered, but for this purpose, an increase in the size and cost of the high-voltage power source cannot be avoided.

  In addition, a means for reducing the area to which the photocatalytic substance is added and providing a portion where the shield casing and the discharge wire are directly opposed to each other and allowing a discharge current to flow through the directly opposed portion can be considered. However, in this case, the discharge state cannot be stabilized with respect to the configuration using the conventional high-voltage power supply unless the shield casing portion is exposed except for the photocatalytic substance over a certain area.

  In an experiment in our copier, stable discharge conditions as before could not be maintained unless the photocatalyst material arrangement area was reduced to 50% or less of the discharge area in the length direction.

That is, it is assumed that the photocatalytic substance 103 is disposed only in the longitudinal part 501 (= length L1) of the charger as shown in FIG. At this time, the portion 502 (= length L2) where the photocatalyst is not disposed is
L1 ≦ L2
Therefore, it is impossible to decompose ozone and NOx generated in this region.

  In addition, since partial discharge abnormality occurs in the photocatalyst material arrangement region 501, there is a possibility that partial abnormality (such as image blanking) of an image formed by the portion 501 may occur.

  Accordingly, an object of the present invention is to provide an image forming apparatus that efficiently decomposes ozone and NOx at a discharge location by a photocatalyst and stably discharges the photosensitive member at the discharge location. To do.

  The first aspect of the present invention is to provide an opening through which the shield casing surface is exposed at predetermined intervals when the photocatalytic substance is formed on the inner surface of the charger casing.

  According to a second embodiment of the present invention, a photocatalytic substance is provided in a non-image forming region on the inner surface of a charger casing, and air is blown to a position opposite to the longitudinal direction so that air in the casing is blown to the photocatalyst. The fan is arranged.

  That is, the technical contents of the present invention can solve the above-described problems by including the following configuration.

  (1) Provided with a charging means in which a discharge wire is housed in a predetermined casing and a photocatalytic substance for decomposing a discharge product is disposed, and is input from the outside onto a moving photoreceptor uniformly charged by the charging means. An electrostatic latent image is formed by sequentially irradiating laser light modulated based on the source image data, and then a toner image is formed on the photosensitive member by supplying heat-meltable toner to the electrostatic latent image. In the image forming apparatus for forming an image, the photocatalytic substance is disposed within a range in which the charged state of the photoconductor can be stably maintained.

  According to the present invention, since the photocatalytic substance for decomposing the discharge generation substance is arranged so as not to disturb the discharge state, the discharge generation substance such as ozone and NOx can be efficiently decomposed and the photosensitive member or the image forming member. Can be stably charged.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  First, FIG. 4 is a block diagram of the main part of a full-color printer which is an example of an image forming apparatus according to the present invention. A photosensitive drum (hereinafter simply referred to as “photosensitive member”) 1 as an image carrier is provided so as to be rotated in the direction of arrow A by a motor (not shown). Around the photoreceptor 1, a primary charger 7 (corresponding to a charging means), an exposure device 8, a developing unit 13, a transfer charger 10, and a cleaner device 12 are arranged. A cleaning charger 11 is disposed in front of the cleaner device 12.

  The photosensitive member 1 uses amorphous silicon as a material.

  The developing unit 13 comprises three color developing devices 13Y, 13M, 13C for full color development and a black developing device 13K. The developing devices 13Y, 13M, 13C, and 13K develop the latent images on the photoreceptor 1 with Y, M, C, and K toners, respectively. When developing each color of Y, M, and C, the developing unit 13 is rotated in the direction of arrow R by a motor (not shown), and the developing device of the corresponding color is aligned so as to contact the photoreceptor 1. In the black developing device 13K, the developing roller is always in contact with the photosensitive member. When developing each color other than black, the high-voltage bias of the black developing device is controlled so that the black toner is not developed. Sometimes black toner is developed by switching to a high-voltage bias at which the toner develops.

  The toner images of the respective colors developed on the photosensitive member 1 are sequentially transferred to the belt 2 as an intermediate transfer member by the transfer charger 10, and the four color toner images are superimposed. The belt 2 is stretched around rollers 17, 18, 19, and 20. Among these, the roller 17 is coupled to a driving source (not shown) and functions as a driving roller that drives the belt 2, and the roller 18 and the roller 20 function as tension rollers that adjust the tension of the belt 2. The roller 19 functions as a backup roller for the transfer roller 21 as a secondary transfer device.

  A belt cleaner 22 is provided at a position facing the roller 17 with the belt 2 interposed therebetween, and residual toner on the belt 2 is scraped off by a blade.

  The recording paper drawn from the recording paper cassette 23 to the conveyance path by the pickup roller 24 is fed to a nip portion, that is, a contact portion between the transfer roller 21 and the belt 2 by a pair of rollers 25 and 26. The toner image formed on the belt 2 is transferred onto the recording paper at the nip portion, thermally fixed by the fixing device 5 and discharged outside the device.

  In the color printer configured as described above, an image is formed as follows. First, a voltage is applied to the primary charger 7 to negatively charge the surface of the photoreceptor 1 uniformly at a predetermined charged portion potential. Subsequently, exposure is performed by an exposure device 8 formed of a laser scanner so that a charged image portion on the photosensitive member 1 has a predetermined exposure portion potential, thereby forming a latent image.

  The exposure device 8 is turned on / off based on the image signal to form a latent image corresponding to the image.

  A developing bias set in advance for each color is applied to the developing roller of the developing device 13Y and the like, and the latent image is developed with toner when passing through the position of the developing roller and visualized as a toner image. The toner image is transferred to the belt 2 by the transfer charger 10, further transferred to the recording paper by the transfer roller 21, and then fed to the fixing device 5.

  In full-color printing, toners of four colors are superimposed on the belt and then transferred onto the recording paper. The toner remaining on the photosensitive member 1 is made easy to clean with a preliminary cleaning device, and is removed and collected by the cleaner device 12. Finally, the photosensitive member 1 is uniformly removed by a static eliminator (not shown). The charge is removed to near 0 volts to prepare for the next image forming cycle.

  FIG. 1 is a schematic view of a primary charger 7 showing an embodiment of the present invention.

  FIG. 1A is an overall view of the charger in the longitudinal direction of the photoconductor, 101 is a discharge wire, and 102 is a shield casing.

  FIG. 1B is a cross-sectional view taken along the line bb ′ of FIG. 1A. The shield casing 102 has an opening on the surface facing the photoconductor, and is applied to the photoconductor by applying a high voltage from the high-voltage power source 104. Discharge and apply a constant potential to the surface.

  Also, a photocatalytic substance 103 is disposed on the inner discharge wire facing surface, so that ozone and NOx generated at the time of discharge are not discharged out of the image forming apparatus and before being adsorbed to the photoreceptor 1 and the discharge wire 101 efficiently. Image degradation and the like can be prevented by performing adsorption decomposition.

  FIG. 1C is a detailed schematic view of the inner surface of the casing in the longitudinal direction. The photocatalyst material 103 arranged in a planar shape has a photocatalyst opening so that the surface of the shield casing 102 directly faces the discharge wire 101 at a predetermined interval. 105 is provided. The photocatalyst opening 105 stably secures a shield current to the shield casing 102, so that the photosensitive member is also stably charged.

However, as described in the section of the problem here, the total area S1 and the opening S2 of the photocatalytic substance are approximately S1 ≦ S2
Set to

  Further, the opening width W1 and the distance between the openings, that is, the photocatalyst width W2, are determined as appropriate so as not to cause a problem on an image in which discharge instability is generated at a minute portion.

  As described above, it is possible to prevent the deterioration of the image by effectively decomposing the discharge generating substance that causes the image deterioration and stably charging the photosensitive member.

  FIG. 2 is a schematic diagram of the arrangement of the photocatalytic substance in the primary charger 7 showing another embodiment of the present invention.

  As long as the discharge (shield current) to the shield casing 102 flows stably for a predetermined amount and the charge to the photosensitive member 1 is stably secured, the present invention is not limited to the first embodiment. As described above, the shape and arrangement of the photocatalyst opening 105 ′ are arbitrary.

  Alternatively, the same effect can be obtained even if the photocatalytic substance 103 is not disposed only within a certain spatial distance from the discharge wire 101 as shown in FIG.

However, even in this case, as in Example 1, the total area S1 and the opening S2 of the photocatalytic substance are approximately S1 ≦ S2.
Set to

  FIG. 3 is a schematic view of the arrangement of the photocatalytic substance in the primary charger 7 showing still another embodiment of the present invention.

  Constituent materials equivalent to those in FIG.

  The photocatalytic substance is disposed in the shield casing 102 outside the image forming region at one end in the longitudinal direction of the charger (the cross section is FIG. 3B).

  Therefore, since the discharge wire 101 and the shield casing 102 are directly opposed in the image forming region, the discharge is stably performed as predetermined.

  At the other end of the shield casing 102 of the charger, a fan 301 (corresponding to a moving means) for blowing outside air into the case is provided.

  When the fan 301 is activated during image formation, air is blown in the direction of the arrow in FIG.

  Therefore, generated substances such as ozone and NOx generated during the discharge of the discharge wire 101 are also transported in the direction of the arrow in the shield casing 102 and eventually reach a place where the photocatalytic substance 103 is provided.

  Here, generation of an image stream or the like can be prevented by decomposing ozone and NOx by the photocatalytic action 103.

  In the above embodiment, an example in which the present invention is applied to the primary charger 7 has been described in detail. However, as in the prior art, a charger having the same structure is used in the image forming apparatus as follows.

Transfer of toner image from photoconductor to image forming member and separation of image forming member after transfer
(Charging of the image forming member)
And charge removal of residual toner on the photoconductor after image transfer (charging of photoconductor)

  It is obvious that a similar structure can be constructed where a discharge product harmful to these other chargers is generated.

(A) is a side view of the charger in Example 1, (b) is an enlarged cross-sectional view taken along line bb ′ of (a), and (c) is a right side surface of a portion surrounded by an ellipse in (b). Some enlarged views FIG. 5 is a diagram illustrating the arrangement of the photocatalytic substance in the charger in Example 2, where (a) is a diagram when the opening is rectangular, (b) is a diagram when the opening is circular, and (c) is an aperture. When the part is at a certain spatial distance to the discharge wire (A) is a side view of the charger in Example 3, and (b) is an enlarged sectional view taken along line c-c ′ in (a). Schematic schematic diagram of an image forming apparatus to which the present invention is applied Side view showing arrangement of photocatalytic substance in charger in conventional example

Explanation of symbols

1 Photoconductor 7 Primary charger (corresponding to charging means)
101 discharge wire 102 shield casing 103 photocatalytic substance 104 high voltage power source 105 photocatalyst opening 301 fan (corresponding to moving means)

Claims (5)

A charging unit in which a discharge wire is housed in a predetermined casing and a photocatalytic substance for decomposing a discharge product is disposed. A source input from the outside on a moving photoreceptor uniformly charged by the charging unit An electrostatic latent image is formed by sequentially irradiating laser light modulated based on image data, and then a toner image is formed on the photoreceptor by supplying heat-meltable toner to the electrostatic latent image. In the image forming apparatus,
The image forming apparatus, wherein the photocatalytic substance is disposed within a range in which the charged state of the photoconductor can be stably maintained.   2. The photocatalytic substance is disposed on a surface facing the discharge wire inside the casing of the charging means, and has a plurality of openings that expose casing members having a predetermined size at regular intervals. The image forming apparatus described.   The charging means includes a photocatalyst substance in one end of the charging means in the longitudinal direction orthogonal to the photoconductor rotation direction and inside the casing outside the image forming area, and in the arrangement area of the photocatalytic substance in the charging means. The image forming apparatus according to claim 1, further comprising a moving unit that collects the generated discharge products.   The image according to claim 3, wherein the moving unit is a blowing unit that is arranged at a longitudinal end portion of the charging unit and blows air into a casing of the charging unit toward a region where the photocatalytic substance is disposed. Forming equipment.   The image forming apparatus according to claim 4, wherein the blowing unit is a fan.

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