Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
2001-12-17
2003-05-13
Tran, Hoan (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
C399S012000, C399S013000, C399S055000
Reexamination Certificate
active
06564024
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image formation apparatus such as a copier or a printer and in particular to an improvement in an image formation apparatus of the type comprising a charger having a charging member in contact with or brought close to the top of a photoreceptor.
2. Description of the Related Art
In recent years, demands for miniaturizing a color image formation apparatus and devises thereof have been made as the demands of the market.
For example, a tandem image formation apparatus comprises a plurality of photoreceptors such as photoconductor drums and devices such as a charger and a developing device disposed on each of the photoreceptors. As the apparatus itself is miniaturized, a so-called cleanerless system wherein a cleaning device and a remaining toner collection device are not provided for each of photoreceptors is often adopted.
However, in this kind of cleanerless system, after transfer, remaining toner exists on a surface of the photoreceptor although a trace quantity of toner remains, and the remaining toner becomes “memory” at a next image formation time, to affect the image quality adversely.
Thus, in a related art, for example, an art has been proposed wherein a memory removal member (for example, a brush roll) is placed in an upstream of a charger member (for example, a charge brush) as a charger to disturb the remaining toner (for example, refer to JP-A-Hei.4-371975).
However, in this kind of image formation apparatus, for example, using a charger of a charging roll type, as shown in
FIG. 11
, a phenomenon in which random spots are produced at arbitrary points on paper or continuous points, for example, which are spots in correspondence with every rotation period of a charging roll or a photoconductor drum (P/R), are produced is observed. The spots are roughly classified into background spots (BKG spots) occurring in a background and image part spots occurring in an image part (for example, a halftone image).
Particularly, it is acknowledged that such a spot phenomenon appears noticeably at the initial use stage of first using an image formation apparatus.
Next, the production principle of such spots is estimated. For example, as shown in
FIG. 12
, when a foreign substance
502
such as an aggregate of a developer is deposited on a photoconductor drum
510
and enters a nip area between a charging roll
511
and the photoconductor drum
510
, the foreign substance
502
portion shields an electric field and a tenting part is formed on a surface layer film portion of the charging roll
511
in which the foreign substance
502
intervenes to cause a charge failure to occur in the part corresponding to the photoconductor drum
510
portion.
At this time, if the charge failure part caused by the foreign substance
502
moves to downstream of the photoconductor drum
510
and an electrostatic latent image is formed in the charge failure part and is developed, a spot having a comparatively large diameter is produced.
On the other hand, if the foreign substance
502
is deposited, for example, on the charging roll
511
side, a continuous point is produced every rotation period of the charging roll
511
.
Pursuing the production cause of such a spot phenomenon, the inventors have estimated that the main cause of producing a spot is the fact that since the developer in a developing device often coagulates particularly at the initial use stage of an image formation apparatus, the aggregate of the developer is easily deposited on a charging roll.
If the developing device is immediately used at the initial use stage of the image formation apparatus, shortage of the charge amount of the developer is prone to occur and accordingly foreign substances of an external additive, a coating agent, etc., of the developer are parted to be easily transferred to the photoreceptor side; it is estimated that this factor also becomes the cause of producing a spot.
SUMMARY OF THE INVENTION
The invention is intended for solving the above-described technical problems and it is an object of the invention to provide an image formation apparatus intended for effectively avoiding a spot phenomenon at the initial use time.
According to the invention, there is provided an image formation apparatus comprising: a photoreceptor; a charger having a charging member placed in contact with or close to the photoreceptor, the charger for charging the photoreceptor; a latent image write unit for writing an electrostatic latent image onto the photoreceptor charged by the charger; a developing device having an agitating and charging element of a developer, the developing device for rendering visible the electrostatic latent image written onto the photoreceptor with the developer; and a performance maintaining controller for executing a performance maintaining initial sequence for agitating and charging the developer uniformly to such a degree that aggregating of the developer in the developing device is at least eliminated under a condition that the image formation apparatus is first used, wherein in the performance maintaining initial sequence, a unit sequence is executed a predetermined number of times, the unit sequence comprising a charge-up mode for agitating and charging the developer in the developing device to raise the charge amount of the developer and a cleaning cycle for cleaning a foreign material of the developer transferred to the photoreceptor.
DESCRIPTION OF THE INVENTION
According to the invention, as shown in
FIG. 1
, there is provided an image formation apparatus comprising a photoreceptor
1
, a charger
2
having a charging member
2
a
placed in contact with or close to the photoreceptor
1
, the charger
2
for charging the photoreceptor
1
, a latent image write unit
3
for writing an electrostatic latent image onto the photoreceptor
1
charged by the charger
2
, a developing device
4
having an agitating and charging element
4
a
of a developer G to render visible the electrostatic latent image written onto the photoreceptor
1
with the developer G, and a performance maintaining controller
5
for executing a performance maintaining initial sequence A for agitating and charging the developer G uniformly to such a degree that aggregating of the developer G in the developing device
4
is at least eliminated under a condition that the image formation apparatus is first used.
In such technical means, the invention includes not only a form in which a single photoreceptor
1
is provided, of course, but also a tandem form in which a plurality of photoreceptors
1
are arranged and further includes various forms such as a form in which a record material transport body and an intermediate transfer body are placed to face the photoreceptor
1
.
The charger
2
is required to have the charging member
2
a
placed in contact with or close to the photoreceptor
1
.
Since it is taken into consideration that it is possible to charge by minute space discharge even in the form in which the charging member
2
a
is placed close to the photoreceptor
1
, the form in which the charging member
2
a
is placed not to contact with the photoreceptor
1
is also included.
However, preferably the charging member
2
a
is placed in contact with the photoreceptor
1
because it is facilitated to position the charging member
2
a
relative to the photoreceptor
1
and the dimension accuracy of the charging member
2
a
need not be high.
Further, the charger
2
may basically comprise the charging member
2
a
, but is not necessarily be limited to this. For example, the charger
2
maybe provided with a removal member disposed in contact with the photoreceptor
1
in upstream of the charging member
2
a
, the removal member for removing the deposit on the photoreceptor
1
.
The removal member may be of contact type for removing the deposit on the photoreceptor
1
or may temporarily remove the deposit on the photoreceptor
1
; the removal member may serve as a functional member for eliminating a situation in which the deposit on the p
Asano Kazuo
Masubuchi Toshio
Muraki Keiji
Ono Akinori
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Tran Hoan
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