Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2000-05-23
2002-11-05
Beatty, Robert (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
Reexamination Certificate
active
06477344
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to monochrome and color image forming apparatus applicable as, for example, a printer, a copying machine, a facsimile, or the like, and to a transfer belt unit, a cleaning device, and a cleaner unit, which are used for the image forming apparatus.
BACKGROUND OF THE INVENTION
A conventional image forming apparatus, in particular, an image forming apparatus having a cleaning mechanism for removing toner remaining on a transfer belt is disclosed, for example, in JP 9-80934 A.
The image forming apparatus disclosed in the above-mentioned publication includes a charging member for charging waste toner remaining on the transfer belt after secondary transfer, and a collecting member for collecting the waste toner charged by the application of voltage. The apparatus is designed so that the charge of the waste toner on the transfer belt is equalized by applying a voltage to the charging member, and then the waste toner with the equalized charge is collected by the collecting member to which the voltage having a polarity opposite to the charge is applied.
Furthermore, a configuration using a cleaner roller is known as another conventional cleaning device having a cleaner for removing waste toner on the intermediate transfer belt or transfer belt. In this configuration, the voltage having a polarity opposite to the charging polarity of toner is applied to the cleaner, whereby the toner on the belt is removed. For example, JP 6-161288 A discloses a configuration using a metal roller as the cleaner roller.
The following is an explanation of this configuration with reference to FIG.
12
. As shown in
FIG. 12
, a negatively charged toner image formed on a photosensitive member
201
is transferred onto a recording paper that is conveyed by the rotation of the transfer belt
202
. The transfer belt
202
is rotated in the arrow direction in FIG.
12
and conveys the recording paper supporting a toner image to a winding portion at the supporting axis
203
. The recording paper supporting a toner image is peeled off from the transfer belt
202
at the winding portion of the supporting axis
203
due to the stiffness of the recording paper, and then is conveyed to a fixing device (not shown) for further processing.
In this image forming process, besides the normal toner image, the toner of a residual image of a previous page, or toner fogging onto a region that is not in contact with the previous or subsequent recording pages is attached to the photosensitive member
201
. Such a toner may contaminate the rear surface of the recording paper. A cleaner
204
removes such a waste toner.
This cleaner
204
includes a first metal cleaner roller
205
and a second metal cleaner roller
206
that is provided downstream from the first cleaner roller
205
in the rotation direction of the transfer belt
202
. A voltage of −600V is applied to the first cleaner roller
205
, and a voltage of +1000V is applied to the second cleaner roller
206
. Then, the first cleaner roller
205
enhances the negative charge of the waste toner remaining on the transfer belt
202
, and the second cleaner roller
206
removes the negatively charged waste toner remaining on the transfer belt
202
. Moreover, the toner attached to the first and second cleaner rollers
206
and
206
is scraped off by a cleaning blade
207
.
Furthermore, JP 7-319356 A discloses a configuration in which a metal roller and an elastic roller are combined. As shown in
FIG. 13
, this configuration uses a first cleaner roller
221
that is a metal roller arranged facing the photosensitive member
220
via a small gap and a second cleaner roller
222
that is pressed onto the photosensitive member
220
downstream from the first cleaner roller
221
in the rotation direction of the photosensitive member
220
. The voltage having a polarity opposite to the charging polarity of the toner is applied to the first cleaner roller
221
, whereby the waste toner on the photosensitive member
220
is adsorbed by the first cleaner roller
221
. The second cleaner roller
222
removes the attached substances other than waste toner on the photosensitive member
220
by the force of the electric field and the mechanical shear force. The first and second cleaner rollers
221
and
222
are provided with a blade
224
for scraping off toner or attached substances on the surface of the cleaner rollers
221
and
222
.
Furthermore, JP 9-90840 A discloses a configuration using a fur brush roller as a cleaner roller.
Furthermore, as a cleaning device for removing off waste toner on an intermediate transfer belt and a transfer belt, one having a configuration in which a rubber cleaning blade is pressed onto the surface of the belt so as to scrape off the waste toner is well known.
However, the above-mentioned conventional image forming apparatus disclosed in JP 9-80934 A, etc. has the following problems. First, in order to equalize the charge of the toner, a power source for high voltage is required. Furthermore, the surface of the transfer belt is chemically deteriorated since toner on the transfer belt is charged by minute discharge. Furthermore, since the voltage is applied to the charging member, a large amount of toner having an opposite polarity is attached onto the charging member, thus disturbing the charging by the minute discharge.
In the cleaning device, it is required to improve the cleaning performance for completely removing waste toner on the surface of the transfer belt or the intermediate transfer belt. In the conventional configuration using a metal roller shown in
FIG. 12
, the second cleaner roller
206
provided at the downstream in the rotation direction of the transfer belt
202
so as to be pressed onto the transfer belt
202
, as well as the first cleaner roller
205
provided at the upper stream in the rotation direction of the transfer belt
202
, provides the waste toner remained on the transfer belt
202
with opposite charges. Therefore, the waste toner remaining on the transfer belt
202
has the same polarity as that of the second cleaner roller
206
, which makes it difficult to remove the waste toner remaining on the transfer belt
202
by the use of the second cleaner roller
206
.
Furthermore, in the conventional configuration shown in
FIG. 13
, since the first cleaner roller
221
is arranged facing the photosensitive member
220
via a gap, it is not possible to remove sufficiently the waste toner on the photosensitive member
220
. On the other hand, in the second cleaner roller
222
, which is an elastic roller, provided downstream in the rotation direction of the photosensitive member
220
so as to be pressed onto the photosensitive member
220
, the abrasion resistance is lower as compared with a metal roller, and the lifetime is short. Moreover, high accuracy cannot be secured, variation in the resistance due to the adsorbed moisture is large and furthermore the cost is high.
The conventional configuration in which a fur brush roller is used as a cleaner roller has the following problems: for example, the performance of removing toner is deteriorated because the fur lies flat after a long time of use; the resistance value is varied due to the absorbed moisture; the fur brush is clogged with toner; toner scatters by being blown away by the brush; toner is attached again onto the belt from the fur brush; and the like. Furthermore, a power source for a high voltage is required, and a fur brush itself is expensive, thus raising the cost as a whole.
Furthermore, in the configuration using a rubber cleaning blade, since the pressing power at the tip of the blade is large, the cleaning blade may damage the surface of the belt, and the cleaning blade may be deteriorated by abrasion. Furthermore, the load torque is increased by the friction force on a portion where the cleaning blade is in contact with and pressed onto the surface of the belt. When the cleaning blade is separated, toner accumulated at the tip of the blade scatters. When the cleaner unit is replaced wi
Asakura Kenji
Katakabe Noboru
Otsuka Masawo
Tamai Yasutaka
Yoshikawa Masanori
Beatty Robert
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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