Electrophotography – Control of electrophotography process – Control of transfer
Reexamination Certificate
2002-07-22
2004-03-02
Ngo, Hoang (Department: 2852)
Electrophotography
Control of electrophotography process
Control of transfer
C399S045000
Reexamination Certificate
active
06701101
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2001-81151, filed Dec. 19, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transfer efficiency enhancement method and apparatus for use in electronic photograph development equipment, and more particularly, to a transfer efficiency enhancement method and apparatus for use in electronic photograph development equipment in which current trigger and paper sheet recognition are combined with an analog-to-digital converter (ADC) by using a high-impedance transfer roller.
2. Description of the Related Art
In general, electronic photograph development equipment is used in copy machines, laser printers, facsimile machines, etc., in which image data captured from a predetermined script or source is exposed to a photosensitive material to form an electrostatic latent image, a developer is deposited on the position where the electrostatic latent image has been formed, to form a visible image, and the visible image is transferred on a printing paper sheet and then fixed thereon to obtain a desired printed image.
The electronic photograph development equipment, which is used in equipment such as copy machines, laser printers, and facsimile machines, is the most widely used apparatus for printing high-resolution images. Although, the electronic photograph development equipment is still expensive, the electronic photograph development equipment is being widely distributed due to remarkable printing performance in areas such as high-speed printing, excellent printing state, and preservation.
According to the transfer characteristics of the electronic photograph development equipment, an appropriate voltage in the electronic photograph development equipment should be applied to a transfer roller so that an image may be transferred in an optimal state. Accordingly, a bad transfer does not occur. In the case that the transfer voltage is low (lower than the optimal state), an electrostatic force is weak and thus toner does not efficiently stick on a sheet of paper. Accordingly, a tremble occurs at the time of transferring. Further, in the case that the transfer voltage is high (higher than the optimal state), the toner on a photosensitive drum is counter-charged with a result that the toner does not stick on the sheet of paper, or an electrostatic force generated from the transfer roller is strong with a result that a toner is transferred on a sheet of printing paper before the printing paper approaches the photosensitive drum, thereby causing the image to be scattered. Thus, only if an appropriate transfer voltage is applied on the sheet of printing paper can a bad transfer be prevented and accordingly a transfer efficiency be enhanced.
Thus, the electronic photograph development equipment is provided with a transfer voltage recognition device which converts a load current flowing through a load of a transfer roller into a voltage, and adjusts a transfer voltage according to a voltage detected by applying a constant voltage of a predetermined level to the conversion voltage, which is obtained by converting the load current flowing through the load of the transfer roller into a voltage.
According to a general transfer environment recognition method, a current flowing through a load is feedback, the fedback current is converted into a voltage, and then the conversion voltage is read. Accordingly, a resistance value of the transfer load is recognized. Then, a final transfer voltage is determined with the resistance value of the recognized transfer load. Thus, a drawback of the contact-type transfer roller sensitive to variation of the transfer environment has been complemented so that a transfer efficiency is optimized.
Basically, two methods exist for sensing (or recognizing) a transfer voltage (or transfer current) and controlling the sensed voltage (or current). The first method is a current trigger method illustrated in
FIG. 1
, in which a transfer voltage is determined by detecting a voltage which causes a predetermined current to flow through the transfer roller. In this method, a voltage which causes a predetermined current to flow through the transfer roller is detected and then a transfer voltage is determined according to a previously prepared transfer voltage table illustrated in the following Table 1.
TABLE 1
Detected Voltage (V)
Final Transfer Voltage (V)
500
800
525
900
550
1000
.
.
.
.
.
.
FIG. 1
shows a transfer timing diagram of a current trigger transfer method, which implements a section obtaining a transfer voltage by increasing a voltage at an initial time until a predetermined current flows through a transfer roller, and another section transferring the determined transfer voltage on a sheet of paper.
The current trigger method has a problem that the transfer efficiency can vary by each sheet of paper because the transfer voltage is determined irrespective of the kind of the sheet of paper. Also, although the resistance of the transfer roller should be high in order to reduce paper sheet deviation, a high-impedance transfer roller may not be triggered in the case of a low-temperature, low-humidity environment.
The second method is a transfer method, which considers a paper sheet resistance as shown in
FIG. 2
, in which a fixed voltage is applied to a transfer roller to measure a resistance Rtr+Ropc between the transfer roller and developer, and another fixed voltage is applied to a section of a sheet of paper about several millimeters from a leading end of the sheet of paper immediately after the sheet of paper has been advanced in the same manner to measure a system resistance Rtr+Rpaper+Ropc between the transfer roller and the developer, to thereby determine a final transfer voltage. Rtr denotes a resistance of the transfer roller, Ropc denotes a resistance of the developer (OPC), and Rpaper denotes a resistance of the sheet of paper.
FIG. 2
shows a transfer timing diagram of the transfer method considering the resistance of a sheet of paper, which implements a transfer environment recognition section recognizing a resistance between a transfer roller and a developer at an initial time, a subsequent paper sheet recognition section recognizing a resistance of a sheet of paper, and a final section transferring a transfer voltage determined by using a system resistance to the sheet of paper.
The paper sheet recognition transfer method has the following problems. Since a trigger is triggered by only a fixed voltage when a system resistance is recognized only with a transfer roller and a developer before a sheet of paper has been advanced, an area where a trigger can be triggered is narrow. Also, since a deviation in resistance can be large according to a device peripheral environment, determining a fixed voltage can be difficult. Further, since an area where a trigger can be triggered varies according to a magnitude of the applied voltage in view of the circuitry features, determining a voltage at which a trigger can be triggered under all environments can be difficult.
Also, since the system resistance is small, a band may be generated at a halftone in case of a high set voltage under a high-temperature and high-humidity environment, and a positive (+) cleaning effect may be insignificant in case of a low set voltage under a low-temperature and low-humidity environment. Since a transfer voltage is determined by using a resistance recognized immediately after a sheet of paper has been advanced, the resistance of the paper sheet is not accurately recognized in the case that a skew of the paper sheet has occurred. As a result, a transfer efficiency may be sharply lowered. To prevent this phenomenon, the resistance of the transfer roller is made higher than that of the sheet of paper. However, in the case where a high-impedance transfer roller is used, a non-trigger phenomenon may occur under a l
Ngo Hoang
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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