Electrophotography – Control of electrophotography process – Control of transfer
Reexamination Certificate
1998-05-11
2001-02-06
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of transfer
C399S019000, C399S046000, C399S076000, C399S100000, C399S101000, C399S149000
Reexamination Certificate
active
06185387
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to image forming apparatuses such as electrophotographic recording apparatuses, electrostatic recording apparatuses, or the like, which employ an electrophotographic method. In particular, it relates to image forming apparatuses which employ a cleanerless system. In cleanerless type image forming apparatuses, the toner particles remaining on a photosensitive member are recovered during a developing step, and therefore, the toner particles remaining on the photosensitive member can be efficiently recovered even when an operational error such as a paper jam occurs during an image forming operation.
There are various image forming apparatuses which employ an electrophotographic method. For example, to begin with, there are copying machines, and also, there are page printers such as laser beam printers; and plain paper facsimile machines which employ laser beam printers or the like. In recent years, these image forming apparatuses have suddenly become very popular.
Lately, cleanerless type image forming apparatuses have become more popular than the others. In these apparatuses, the cleaning apparatus, which is one of the essential components of a conventional electrophotographic image forming apparatus, has been eliminated to reduce the size and cost of the apparatus.
In these cleanerless type image forming apparatuses, a developing apparatus carries out the cleaning process for removing the toner particles remaining on a photosensitive drum after image transfer, in addition to its principal duty, that is, the developing process. In the past, in order to improve the cleaning efficiency of the developing apparatus, and also in order to prevent the production of substandard images traceable to exposure problems caused by the residual toner particles, a member such as an electrically conductive brush or an electrically conductive roller has been placed in contact with the peripheral surface of a photosensitive drum. For example, Japanese Laid-Open Patent Application Nos. 5-2289 and 5-313431, respectively and the like disclose such an arrangement, in which an electrically conductive brush is placed in contact with the peripheral surface of a photosensitive drum, on the area between the transferring means and the primary charging means. Thus, the actual structure of a typical conventional cleanerless system will be described below, with reference to these arrangements.
The image forming apparatus in
FIG. 9
comprises: a photosensitive drum
100
which is rotated in the direction indicated by an arrow mark X; a charging device
101
for uniformly charging the peripheral surface of the photosensitive drum
100
; an exposing device
102
for exposing the charged peripheral surface of the photosensitive drum
100
so that image data are written in the form of an electrostatic latent image; a developing device
103
for developing the electrostatic latent image into a toner image (visible image) by applying toner to the electrostatic latent image; a charging device
104
for transferring the toner image onto transfer medium; a lamp
105
for discharging the peripheral surface of the photosensitive drum
100
by exposing it, after toner image transfer; and an electrically conductive brush
106
which gently scratches the peripheral surface of the photosensitive drum
100
so that the toner particles remaining, unaffected by the transfer process, on the peripheral surface of the photosensitive drum
100
are dispersed. The developing device
103
carries out a cleaning process, in addition to a developing process, that is, the principal process. In this cleaning process, the toner particles dispersed on the peripheral surface of the photosensitive drum
100
are recovered by the electrically conductive brush
106
.
A switch
107
makes it possible to choose between applying positive voltage to the electrically conductive brush
106
and grounding the electrically conductive brush
106
. A switch
108
makes it possible to choose between applying positive voltage to the transfer charger
104
and grounding the transfer charger
104
. These switches
107
and
108
are connected to a CPU
110
through an I/O port
109
, and are controlled by the CPU
110
which carries out the programs stored in a ROM
111
. At a proper time, the CPU
110
applies positive voltage of a predetermined magnitude to the transfer charger
104
by controlling the switch
108
, so that the peripheral surface of the photosensitive drum
100
is charged to positive polarity. At the same time, it controls the switch
107
to ground the electrically conductive brush
106
, so that the toner particles accumulated in the electrically conductive brush
106
are discharged onto the photosensitive drum
100
.
The above described structure of the conventional cleanerless system is effective from the standpoint of assuring that the residual toner particles are temporarily recovered by the electrically conductive brush
106
.
However, it absolute terms, the electrically conductive brush
106
is a component unnecessary for an image forming operation, as is disclosed in Japanese Laid-Open Patent Application No. 8-254899. More specifically speaking, lately, toners composed of spherical toner particles, which are produced by polymerization, have been commercialized, being available in some areas, and the transfer efficiency for this type of toner is extremely high (98% or higher) compared to the transfer efficiency for the conventional toners produced by pulverization; the residual toner particles are virtually nonexistent. In this kind of environment, providing an image forming apparatus with the electrically conductive brush
106
, the discharger lamp
105
, and the like contribute very little to the improvement of the apparatus, but it does increase apparatus cost, canceling the beneficial effects, such as cost reduction or size reduction, of the cleanerless system. In other words, the conventional cleanerless systems are effective in terms of environmental concerns (they do not produce waste toner), but in terms of other concerns, they have little merit. The only virtue of these conventional cleanerless systems (electrically conductive brush
106
and the like) is that they are very effective when an operational error such as a paper jam occurs during an image forming operation.
Further, the technology disclosed in Japanese Laid-Open Patent Application No. 8-254899 is compatible only with the systems which employ a noncontact type primary charger and a noncontact type transfer charger (charger with the structure depicted in FIG.
9
), that is, the corona based charger. In other words, they are not compatible with the systems which employ a contact type primary charger and a contact type transfer charger, that is, the systems which have been becoming popular lately. This is due to the following reason. In the case of a primary charger or a transfer charger of the contact type, the charging member is placed in contact with the peripheral surface of a photosensitive drum, and therefore, the charging member becomes contaminated with toner before an exposing process, and as the charging member is contaminated, the photosensitive drum cannot be uniformly charged to a predetermined potential level, which contributes to further contamination of the peripheral surface of the photosensitive drum by toner; the contamination of the photosensitive drum by toner becomes extreme.
As is evident from the above description, the technologies prior to the present invention have failed to take advantage of the primary merits (size reduction, cost reduction, and environmental superiority) of the cleanerless system.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a cleanerless image forming apparatus, that is, an image forming apparatus which does not employ a cleaning assisting member such as an electrically conductive brush, and therefore, is compatible with a primary charger and a transfer charger which are based on a contact type charging system.
Acco
Ohzeki Yukihiro
Sakaizawa Katsuhiro
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561954