JP2010102034A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that reduces deteriorated toner in developer. <P>SOLUTION: The image forming apparatus includes: a main charging part that charges the surface of an image holder except a predetermined end; and a sub-charging section that charges the end to a charging potential different from the potential to which the end is charged by the main charging section. The developing unit includes a developing roll that conveys developer to a developing area including a main area which is a developing area facing the image holder, that is, facing a part except the end and also including a sub-area facing the end; a first storing part in which while the stored developer is agitated, the developer is conveyed along the rotating shaft in a first direction toward the end from an area distant from the end; a second storing part in which while the developer and freshly supplied toner are agitated and mixed, they are conveyed in a second direction opposite the first direction; and a toner supply section that supplies toner to the second storage section through a toner supply port. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

In the developing device provided in the image forming apparatus, the storage tank is partitioned into a first storage chamber adjacent to the developing roll and a second storage chamber adjacent to the first storage chamber. There is one that moves the developer while stirring between the two storage chambers (see, for example, Patent Document 1).
JP-A-9-204105 (FIG. 5)

  An object of the present invention is to provide an image forming apparatus capable of reducing deteriorated toner in a developer.

An image forming apparatus according to claim 1 comprises:
An image carrier that forms an image on the surface and holds the image;
A charger for charging the surface of the image carrier;
An exposure unit that exposes the surface of the image carrier charged by the charger to form a latent image on the surface; and
A developing device containing a developer containing the toner to form a toner image by attaching a toner to the latent image formed on the surface of the image carrier;
The charger is
A main charging portion that charges the surface of the image carrier excluding a predetermined end; and
A sub-charging portion for charging the end portion to a charging potential different from the charging potential by the main charging portion;
The developer is
A developer region which is adjacent to the image carrier and holds the developer on the surface and rotates to cause the developer to face the image carrier and to face a portion excluding the end portion. A developing roll for transporting to a developing area including an area and a sub-area facing the end;
Adjacent to the developing roll and extending along the rotation axis of the developing roll, containing the developer inside and supplying the developer to the developing roll, stirring the contained developer on the rotating shaft Along the first storage portion for transporting in a first direction from the far side from the end portion toward the end portion,
Adjacent to the first housing part and extending side by side with the first housing part, both ends are provided with moving ports for moving the developer between the first housing part and containing the developer inside A second storage portion that is supplied with toner and conveys the developer and the toner in a second direction opposite to the first direction while stirring and mixing the developer;
And a toner supply unit for supplying toner to the second storage unit through a toner supply port.

  According to the image forming apparatus of the first aspect, it is possible to reduce the deteriorated toner in the developer.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a printer.

  A printer 1 shown in FIG. 1 includes a photoconductor 10, a charger 11 that applies a charge to the surface of the photoconductor 10, a laser exposure device 12 that generates laser light based on image data transmitted from the outside, and the like. A developer 13 containing a developer containing toner, a paper cassette 16 containing recording paper, a paper transport device 17 for pulling out and transporting the recording paper from the paper cassette 16, and a surface of the photoreceptor 10. A transfer roll 14 for transferring the toner image onto the recording paper conveyed in the direction of arrow B; a fixing device 15 for fixing the toner image on the recording paper by heating and pressurizing the toner image on the recording paper; And a cleaning device 20 for cleaning the surface of the photoconductor 10. The developing device 13 includes a developing roll 133 that conveys the developer to a region between the developing device 13 and the developing device 13 while rotating to face the photosensitive member 10. Further, the cleaning device 20 cleans the surface of the photoconductor 10 by bringing the cleaning member 21 into contact with the photoconductor 10. In addition to the toner, the developer contained in the developing unit 13 includes a magnetic carrier that is a charge-providing particle and a magnetic particle that frictionally charges the toner by friction with the toner.

  Here, the flow of the image forming operation in the printer 1 will be briefly described.

  In the printer 1 shown in FIG. 1, charge is applied to the surface of the photoconductor 10 rotating in the direction of arrow A by the charger 11, and image data transmitted from the outside to the surface of the photoconductor 10 to which the charge is applied. The laser exposure device 12 irradiates the laser beam based on the above to form an electrostatic latent image on this surface. The developer accommodated in the developing unit 13 is supplied to the surface of the developing roll 133 and is transported to a region between the developing roll 133 and the photoreceptor 10, and the photoreceptor 10 is transported by the toner in the transported developer. The electrostatic latent image on the surface is developed. The toner image obtained by this development is transferred onto the recording paper conveyed in the direction of arrow B by the transfer roll 14, and the toner image on the recording paper is melted by the fixing device 15 that heats and pressurizes the toner image. It is fixed on the recording paper. After that, the residue remaining on the portion of the photoconductor 10 where the transfer of the toner image is completed is downstream of the transfer roll 14 in the rotation in the direction of arrow A, upstream of the charger 11, and on the photoconductor 10. The cleaning member 21 whose tip is in contact with the entire width along the rotation axis is scraped off. The residue that has been removed is stored in a residue storage box 22. The printer 1 is an embodiment of the image forming apparatus of the present invention. The photoconductor 10 is an example of an image carrier according to the present invention in which an image is formed on the surface to hold the image. The laser exposure device 12 is an example of an exposure device according to the present invention that forms an electrostatic latent image on the surface of the image carrier charged by the charger so as to be exposed. The printer 1 is a monochrome image dedicated machine, but the present invention may be applied to a color image machine.

  2 is a perspective view from the exposure unit side of the developing unit shown in FIG.

  In FIG. 2, the developing device 13 includes a developing roll 133, a developer storage tank 132 that stores the developer, and a stirring transport member 131 that stirs and transports the developer inside the developer storage tank 132. It is shown.

  The developer storage tank 132 has a first storage chamber 132a adjacent to the development roll 133 and a second storage chamber adjacent to the first storage chamber 132a by a wall 1321 extending in parallel with the development roll 133. 132b.

  In each of the first storage chamber 132a and the second storage chamber 132b, one agitation transport member 131 is provided. Specifically, the agitation transport member 131 includes a spiral fin around the rod. It has a provided structure. As the agitating and conveying member 131 provided in each of the first accommodation chamber 132a and the second accommodation chamber 132b rotates in the opposite directions, the developer accommodated in the developer accommodating tank 132 is agitated around the wall 1321. Cycle counterclockwise. Inside the developer storage tank 132, the toner and the magnetic carrier are agitated by the agitating and conveying member 131, so that the toner is negatively charged and the magnetic carrier is positively charged. For this reason, the negatively charged toner adheres electrostatically to the magnetic carrier. As a result, the toner and the magnetic carrier are naturally integrated inside the developer storage tank 132.

  As shown in FIG. 2, the developer storage tank 132 is provided with a toner supply port 132 c for supplying new toner.

  Further, FIG. 2 shows a state in which the charger 11 includes a first charging unit 111 shown on the right side of FIG. 2 and a second charging unit 112 shown on the left side of FIG. . The first charging unit 111 is an example of a main charging unit that charges the surface of the image carrier except for a predetermined end, and the second charging unit 112 uses the main charging unit for the end. This is an example of a sub-charging unit that charges a charging potential different from the charging potential.

  In this printer 1, as will be described in detail later, an image forming unit 101 which is a portion on the right side of the dotted line shown in FIG. 2 of the photoconductor 10 is used for image formation, and a portion on the left side of the dotted line shown in FIG. A non-image forming portion 102 is used for adsorbing deteriorated toner.

  Hereinafter, the adsorption mechanism of the deteriorated toner by the non-image forming portion 102 of the photoreceptor 10 will be described.

  FIG. 3 is a sectional view of the developing device.

  Part (a) of FIG. 3 shows a case where the AA cross section of the developing device shown in FIG. 2 is viewed as an arrow, and part (b) of FIG. 3 shows the developing device shown in FIG. The case where the BB cross section is seen by the arrow is shown. Further, part (b) of FIG. 3 also shows a toner supply port 132 c provided for supplying new toner to the second storage chamber 132 b of the developer storage tank 132.

  The developing roll 133 shown in FIG. 3 includes a cylindrical member 1331 that rotates in the direction of arrow C, and a permanent magnet roll 1332 that is fixed inside the cylindrical member 1331 independently of the cylindrical member 1331. The permanent magnet roll 1332 has a plurality of magnetic poles arranged in the circumferential direction of the cylindrical member 1331 and has a magnetic force distribution that regulates adsorption and release of the developer.

  The rotating cylindrical member 1331 is supplied with the developer while passing through the developer storage tank due to the magnetic distribution of the permanent magnet roll 1332 inside, and the supplied developer is formed between the photosensitive member 10 and the developer. To the developed area.

  The photosensitive member 10 shown in part (a) of FIG. 3 is once charged to -720V by the charger 11, and the portion where the electrostatic latent image is formed by exposure by the exposure device 12 is about -300V. It becomes. On the other hand, the developing roll 133 of the developing device 13 is charged to −600V. Therefore, the toner that is electrically attached to the magnetic carrier held on the developing roll 133 and is conveyed to the first region 1301a between the image forming unit 101 of the photoreceptor 10 and the developing roll 133 is stored in the developer storage tank. Since it is charged with a negative polarity in 132, an electric field (potential difference is 300 V) from the electrostatic latent image portion of the image forming unit 101 of the photoconductor 10 toward the developing roll 133, and the magnetic carrier. The toner attracts the electrostatic attraction force and flies to the electrostatic latent image side to form a toner image. At this time, the magnetic carrier remains on the developing roll 133 while being attracted to the surface of the cylindrical member 1331 of the developing roll 133 by a magnetic force, and is collected into the developer containing tank 132.

  Here, in the printer 1, in a situation where image formation with low image density continues for a long time and new toner is not supplied much, it is applied to the toner surface by repeated friction between the existing toner and the magnetic carrier. In addition, the charge control member for controlling the chargeability of the toner is buried and the chargeability of the toner is deteriorated, so that a charge distribution in a wide range is supposed to be a narrow charge distribution. When such low image density image formation is continuously performed and then high image density image formation is performed, a large amount of new toner is supplied to the second storage chamber 132b of the developer storage tank 132 through the toner supply port 132c. To be supplied. In this case, the charge of the toner having a deteriorated charging property inside the developer storage tank 132 is quickly taken away by the newly supplied toner, and is newly supplied inside the developer storage tank 132. The toner is deprived of charge, and the charge amount rises slowly due to friction with the magnetic carrier due to deterioration. The extreme toner and the newly charged toner that is sufficiently charged are held on the developing roll 133. For this reason, the low-charged toner, whose electrostatic charge with the magnetic carrier is weakened due to insufficient charge, does not adhere to the electrostatic latent image even when it is separated from the magnetic carrier and becomes a cloud. In other words, the reverse polarity toner that has turned to the opposite polarity flies to the background area that is a part other than the part where the electrostatic latent image formed on the surface of the photoreceptor 10 is formed.

  Therefore, in the printer 1 of this embodiment, the deteriorated toner is adsorbed by the non-image forming portion 102 of the photoconductor 10 and collected by the cleaning device 20 as described below, so that the deteriorated toner is removed from the developer storage tank 132. Remove.

  As described above, when the toner is not replaced, and the same toner is repeatedly stirred and deteriorated with the magnetic carrier, the charge distribution that is originally in a narrow range gradually spreads over a wide range. When new uncharged toner is supplied, the charge of the overcharged toner in the charge distribution spread over a wide range is rapidly taken away by the new toner. Therefore, in the printer 1, the toner on the overcharge side of the deteriorated toner is removed before the toner supply port 132c to which new toner is supplied in the flow of the developer that is stirred and conveyed through the developer storage tank 132. Is done. This prevents the charge of the overcharged toner from rapidly moving to the newly supplied toner, thereby preventing the charge distribution of the developing toner from becoming extremely wide.

  Part (b) of FIG. 3 shows a state in which a second region 1302 a that is a developing region between the image non-forming portion 102 of the photoconductor 10 and the developing roll 133 is formed. The rotating cylindrical member 1331 of the developing roll 133 is supplied with the developer while passing through the developer storage tank due to the magnetic distribution of the permanent magnet roll 1332 inside, and transports the supplied developer to the second region 1302a. To do.

  Further, part (b) of FIG. 3 shows a state in which the transfer device 14 is not provided around the photosensitive member 10.

  The surface of the non-image forming portion 102 of the photoreceptor 10 is charged by the second charging portion 112 at any potential in the range of −200 V to 0 V, but the exposure by the exposure device 12 is not performed. For this reason, the surface potential of this region changes at the potential applied by the second charging unit 112.

  FIG. 4 is a schematic configuration diagram of the first charging unit and the second charging unit.

  FIG. 4 shows a state in which a negative power source 113 of −720V is connected to the first charging unit 111 and a variable power source 114 having a variable voltage between −200V and 0V is connected to the second charging unit 112. ing.

  Of the toner charged negatively in the developer storage tank 132, the toner that is overcharged due to deterioration is transferred from the electrostatic latent image portion of the image forming unit 101 of the photoconductor 10 to the developing roll 133. The electric field (potential difference is 400 V to 600 V) from the non-image forming portion 102 of the photoconductor 10 to the developing roll 133 is stronger than the electric field (potential difference is 300 V). It overcomes and flies to the non-image forming portion 102 of the photoconductor 10 and is transferred from the photoconductor 10 by the cleaning member 21 of the cleaning device 20 without being transferred because there is no transfer device 14, and is a residue storage box. 22 is accommodated. As a result, the overcharged toner of the deteriorated toner is removed from the developer before the toner supply port 132a, which is a new toner supply point in the transport direction of the developer transported inside the developer storage tank 132. .

  Further, in this printer 1, since the power supply for applying a voltage to the second charging unit 112 is variable, the electric field strength between the image non-forming unit 102 of the photoreceptor 10 and the developing roll 133 is low. Are automatically controlled according to the image density of image formation after successive image formations. For example, the higher the image density of image formation after continuous image formation at a low image density, the more toner is newly supplied to the developer storage tank 132. Therefore, the toner is overcharged before the toner supply port 132c. It is necessary to remove toner as much as possible. For this reason, the voltage applied to the second charging unit 112 is adjusted in the above-described range (−200 V to 0 V), so that the non-image forming unit 102 of the photoconductor 10 and the developing roll 133 (potential is −600 V). The amount of overcharged toner removed before the toner supply port 132c is adjusted by adjusting the electric field strength between them (potential difference is 400V to 600V).

  In the above embodiment, a printer has been described as an example of the image forming apparatus of the present invention. However, this may be a copying machine, and an example in which image formation is performed on recording paper has been described. Even when an image is formed on a transparent film, the effect obtained by the present invention is not changed.

1 is a schematic configuration diagram of a printer. FIG. 2 is a perspective view from the exposure device side of the developing device shown in FIG. 1. It is sectional drawing of a developing device. It is a schematic block diagram of a 1st charging part and a 2nd charging part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 10 Photoconductor 101 Image forming part 102 Image non-forming part 11 Charging part 111 1st charging part 112 2nd charging part 12 Laser exposure device 13 Developing device 1301a 1st area | region 1302a 2nd area | region 131 Stirring conveyance member 132 Developer accommodation Tank 133 Developing roll 1331 Cylindrical member 1332 Permanent magnet roll 14 Transfer roll 15 Fixing device 16 Paper cassette 17 Paper transport device 20 Cleaning device 21 Cleaning member 22 Residue storage box

Claims (1)

An image carrier that forms an image on the surface and holds the image;
A charger for charging the surface of the image carrier;
An exposure unit that forms a latent image on the surface by exposing the surface of the image carrier charged by the charger;
A developing unit containing a developer containing the toner, which forms a toner image by attaching toner to a latent image formed on the surface of the image carrier;
The charger is
A main charging unit that charges the surface of the image carrier excluding a predetermined end; and
A sub-charging unit that charges the end to a charging potential different from the charging potential of the main charging unit;
The developer is
A developer region that is adjacent to the image carrier and holds the developer on the surface and rotates to cause the developer to face the image carrier and to face a portion other than the end portion. A developing roll for transporting to a developing area including an area and a sub-area facing the end;
Adjacent to the developing roll and extending along the rotating shaft of the developing roll, containing the developer inside and supplying the developer to the developing roll, stirring the contained developer on the rotating shaft Along the first storage unit that conveys in a first direction from the side far from the end toward the end,
The developer is accommodated in the interior, provided with a moving port for moving the developer between the first accommodating portion and at both ends, which is adjacent to the first accommodating portion and extends side by side with the first accommodating portion. A second storage unit that is supplied with toner and conveys the developer and the toner in a second direction opposite to the first direction while stirring and mixing the developer;
An image forming apparatus comprising: a toner supply unit that supplies toner to the second storage unit through a toner supply port.

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