Electrophotography – Control of electrophotography process – Control of transfer
Reexamination Certificate
1999-12-03
2001-02-20
Braun, Fred L. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of transfer
C361S235000, C399S089000
Reexamination Certificate
active
06192204
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to transfer units for use with electrophotographic printers, and more particularly to a control over a transfer current which a transfer unit outputs. The present invention is suitable, for example, for a transfer unit in an electrophotographic printer. A printer according to the present invention is widely applicable not only to a single printer unit but also to those copiers, facsimile machines, computer systems and word processors, and combination machines thereof which have a print function.
An electrophotographic printer typically includes a photosensitive drum and transfer portion. A printing paper passes between the photosensitive drum and transfer portion. The photosensitive drum is charged by a pre-charger, exposed by a laser, and provided with a toner image on its surface by the development. The transfer portion typically utilizes a corona wire to apply a transfer current onto a printing paper using a corona discharge. The transfer portion attracts and attaches the toner image onto the printing paper using the transfer current, thereby completing a transfer of the toner image onto the printing paper.
A transfer current value should be adjusted according to a paper size (width), a printing-paper feed speed, a print environment (such as surrounding temperature and humidity), a printing-paper resistance (which differs according to different paper manufacturers and different paper types, e.g., thick and thin papers), print modes including single-sided (or anopisthographic) and double-sided (or duplex) prints. This is because an excessively small transfer current would insufficiently attract toner onto a printing paper for a desired transfer while an excessively large transfer current would deteriorate a printing quality by an unequal potential distribution.
Conventionally, n signal lines and 2
n
current control circuits have determined the transfer current. The current control circuit, as used herein, refers to a circuit that determines a target transfer current value and an essential part in the transfer circuit. Two signal lines, for instance, identify four states, such as, for example, [0, 0], [0, 1], [1,0] and [1,1] in response to digital signals 0 and 1. Information on these signal lines is eventually fed to current control circuits nos.
1
through
4
. The current control circuits nos.
1
through
4
respectively store different four types of transfer current values VT1 through VT4. For example, the current control circuit no.
1
corresponds to [
0
,
0
], and outputs VT1 as a transfer current for the signal [0,0].
However, there are many parameters necessary to control the transfer current as mentioned above, and a transfer current value to be changed differs every factor. Thus, four (i.e., VT1 through VT4) is insufficient for the number of transfer currents to be generated in the above example. Although it is conceivable to increase the number of signal lines and current control circuits by the number of desired transfer current values to supplement the insufficient number of producible transfer current values, such a configuration would result in the increased wiring number, the difficult packing and/or an expensive printer.
SUMMARY OF THE INVENTION
Accordingly, it is an exemplified general object of the present invention to provide a novel and useful transfer-current control method and circuit and a printer having such a control circuit in which the above disadvantages are eliminated.
Another exemplified and more specific object of the present invention is to provide a transfer-current control method and circuit and a printer having such a control circuit that may reduce the number of current control circuits and wires while maintaining the controllable number of currents.
In order to achieve the above objects, an output circuit of one aspect of the present invention which controls a current comprises a main controller module connected to a first signal line, an auxiliary controller module connected to a second signal line, an oscillator module connected to the main and auxiliary controller modules, and a transformer module connected to the main and auxiliary controller modules and oscillator module, wherein the main controller module includes a first current-switching circuit which receives a first signal through the first signal line, and a plurality of first current control circuits each of which is selected by the first current-switching circuit based on the first signal, and outputs a first value, the number of first current control circuits being 2
m
where the number of the first signal lines is m, wherein the auxiliary controller module includes a second current-switching circuit which receives a second signal through the second signal line, and a second current control circuit which is selected by the second current-switching circuit based on the second signal, and outputs a second value, and wherein where the number of first and second signal lines is n, the number of the second current control circuits is s, and s=n−m, the number of first and second current control circuits is (2
2 n-s
+s), the transformer module consequently being able to generate and output 2
n
currents using a combination of the first and second values.
A high-voltage power-supply unit of one aspect of the present invention comprises a transfer output circuit which controls a transfer current applied to a transfer unit in order to print a predetermined image on a printing paper, and a pre-charger output circuit which controls a pre-charger. The transfer output circuit comprises the above output circuit of the present invention. The pre-charger output circuit receives a signal indicative of a feed speed of the printing paper, and generates pre-charge voltage applied to the pre-charger. The second signal includes the signal indicative of the feed speed.
A printer of one aspect of the present invention includes a photosensitive body, a transfer unit that transfers onto a printing paper a toner image that has been formed on the photosensitive body, and the above transfer output circuit that controls transfer current applied to the transfer unit.
A control method of one aspect of the present invention comprises the steps of reading out, while referring to a set table, control value based on a control instruction including first and second parameters, the set table including the first and second parameters, the first parameter including 2
m
types of first elements, and the number of types of second parameter being s each of which includes two types of second elements, and identifying the first and second elements corresponding to the control value and set the first and second elements as first and second signals respectively, wherein the first signal is supplied to a main controller module including 2
m
first control circuits through m first signal lines, while the second signal is supplied to an auxiliary controller module including s second control circuits through s second signal lines.
A mechanical-part control circuit module of one aspect of the present invention comprises a memory which stores a set table including first and second parameters, the first parameter including 2
m
types of first elements, and the number of types of second parameter being s each of which includes two types of second elements, a processor which not only reads out a control value based on a control instruction including the first and second parameters while referring to the set table stored in the memory, but also identifies the first and second elements corresponding to the control value thereby setting the first and second elements as first and second signals respectively, wherein the mechanical-part control circuit module is connected to main and auxiliary controller modules, wherein the first signal is supplied to the main controller module including 2
m
first control circuits through m first signal lines, and the second signal is supplied to the a
Nakashima T.
Yagi Chiaki
Armstrong, Westerman Hattori, McLeland & Naughton
Braun Fred L.
Fujitsu Limited
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