Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-02-17
2001-06-12
Chen, Sophia S. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S066000, C399S149000, C399S296000, C399S343000
Reexamination Certificate
active
06246847
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from an application entitled Electronic Photograph Forming Apparatus And Method For Controlling The Same earlier filed in the Korean Industrial Property Office on the Feb. 19, 1999, and there duly assigned Serial No. 99-5522, a copy of which is annexed hereto.
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to an electronic photograph forming apparatus and a method for controlling the apparatus. More specifically, the present invention relates to an electronic photograph forming apparatus which is capable of entirely removing waste toner without using a waste toner removing unit and a method for controlling the same.
2. Related Art
A printer is an image formation device which receives data and then forms an image corresponding to the data on a recordable medium such as a sheet of paper.
In a laser printer, print data can be received from external equipment such as a host computer or a personal computer in order to develop the print data into printable image data. The developed image data are stored in a print image buffer. Then a laser beam, corresponding to image data of one raster read out from the print image buffer, is emitted from a laser diode to perform a main scanning operation, thereby forming an electrostatic latent image on a photosensitive drum for every dot line. Thereafter, toner is attached to the electrostatic latent image on the photosensitive drum and then transferred onto a recordable medium such as a sheet of paper. The toner on the recordable medium is heated by a fixing heater of a fixing device to fix the toner on the recordable medium, thereby completing a print process. Laser printers are also referred to as electrophotographic printers. The aforementioned photosensitive drum can correspond to a photoconductive drum or an organic photoconductive drum.
I have found that toner can often remain on various drums of a laser printer, which will contaminate those various drums. This contamination requires that a waste-toner removing unit be installed in the laser printer to prevent or reduce the contamination.
SUMMARY OF THE INVENTION
It is an object of the present invention to entirely remove waste toner without using a waste toner removing unit.
It is another object of the present invention to increase transferring efficiency and obtain a high quality image by varying the surface potential of the organic photoconductive drum before toner developed on the organic photoconductive drum enters a transferring portion.
It is another object of the present invention to increase transferring efficiency even though a small capacity of power supply is used by varying the voltage supplied to the transferring roller according to the resistance of the print paper.
It is still another object of the present invention to suppress waste toner generation and obtain a high quality image by using the space where the transferring roller and the organic photoconductive drum are raced as the space for cleaning the transferring roller and the organic photoconductive drum.
It is another object of the present invention to prevent toner from being attached to the organic photoconductive drum by the mechanical friction between the charging roller and the organic photoconductive drum.
It is another object of the present invention to efficiently collect the remaining toner by appropriately adjusting the potential difference between a charging voltage and a developing voltage.
According to an aspect of the present invention to achieve the objects and other objects, an electronic photograph forming apparatus including a supplying roller, a developing roller, a charging roller, a laser scanning unit (LSU), a transferring roller and a power supply is provided. An organic photoconductive drum is charged by the charging roller. By the laser scanning unit, an electrostatic latent image is formed. Then, toner is transferred from the developing roller to form a visible image on the organic photoconductive drum. At this time, the attached force of the toner is reduced to a predetermined level through a pre-transfer lamp. Then, the toner attached to the organic photoconductive drum is transferred onto a print paper by the transferring roller. Thereafter, the toner transferred paper is transferred to a fixing unit. On the other hand, in order to collect waste toner attached to the transferring roller onto the organic photoconductive drum before and behind an image printing space while the organic photoconductive drum and the transferring roller are raced, the voltage of the transferring roller is varied by a controller according to a predetermined standard, and toner having negative charges and existing in a non-image portion of the organic photoconductive drum is collected onto the developing roller by the potential difference.
Preferably, according to the predetermined standard, a lower voltage than the voltage supplied to the organic photoconductive drum is supplied to the transferring roller so that the toner attached to the transferring roller and having negative charges is transferred to the organic photoconductive drum, and a higher voltage than the voltage supplied to the organic photoconductive drum is supplied to the transferring roller so that the toner attached to the transferring roller and having positive charges is transferred to the organic photoconductive drum.
Preferably, the controller varies the voltage of the transferring roller according to the resistance of the print paper entering the transferring roller. According to the present invention, a blade for evenly spreading the toner supplied to the developing roller is further included. At this time, the voltages supplied to the blade and the supplying roller are the same, whereby an evenly coated toner layer can be obtained.
Preferably, the speeds of the charging roller and the organic photoconductive drum is structured in the ratio of one to one. Preferably, the toner is one of pulverization type toner and polymerization type toner.
According to the present invention, the pre-transfer lamp supplies the entire surface of the organic photoconductive drum with a light of a predetermined amplitude to make the surface potential of the organic photoconductive drum as 0 to −100 volts (V).
Preferably, the potential difference between the developing roller and the charged organic photoconductive drum is maintained as −500 volts (V). Preferably, the charging roller is supplied with a charging voltage of −1.4 kilovolts (kV) direct current (DC) so that the toner existing on the organic photoconductive drum and having positive charges is collected, negatively-charged, and transferred to the organic photoconductive drum again.
According to another aspect of the present invention, a method for controlling an electronic photograph forming apparatus including a supplying roller, a developing roller, a charging roller, an organic photoconductive drum, a laser scanning unit (LSU), a transferring roller and a power supply is provided. In the method, the organic photoconductive drum is charged by the charging roller. In order to remove waste toner attached to the transferring roller, the organic photoconductive drum and the transferring roller are raced. According to a predetermined standard, the voltage of the transferring roller is varied. The toner remaining on the organic photoconductive drum and having negative charges is collected onto the developing roller by a potential difference and an electrostatic latent image is formed on the charged organic photoconductive drum by the laser scanning unit. Then, the toner on the developing roller is transferred to the electrostatic latent image on the organic photoconductive drum to form a visible image. After the attached force of the toner to the organic photoconductive drum is reduced to a predetermined level, the visible image is transferred to a print paper.
Preferably, the method for controlling the electronic photogra
Jeong Su-Jong
Kim Sung-Gi
Kwon Tai-Eun
Bushnell , Esq. Robert E.
Chen Sophia S.
Samsung Electronics Co,. Ltd.
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