Electrophotography – Image formation – Combined or plural functions by single component
Reexamination Certificate
2000-03-07
2001-08-07
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Combined or plural functions by single component
C399S283000, C399S357000
Reexamination Certificate
active
06272302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus for use in an electrophotographic apparatus, an electrostatic recording apparatus or the like.
2. Related Background Art
In an image forming apparatus utilizing the electrophotographic process, an electrostatic latent image is formed on an image bearing member such as a photosensitive drum, and this electrostatic latent image is developed and visualized by the use of a developer, and the thus obtained visible image (toner image) is transferred to a transfer material to thereby obtain an image.
As developing methods, there are generally a monocomponent developing method using a monocomponent developer comprising only a toner, and a two-component developing method using a two-component developer comprising a magnetic carrier (magnetic particles) and a toner, but the monocomponent developing method is simpler in the construction of a developing device and easier in maintenance and therefore, many developing devices based on the monocomponent developing method have been proposed.
Japanese Patent Application Laid-Open No. 58-116559 proposes a non-magnetic monocomponent developing method of effecting development by the use of not a magnetic toner but a non-magnetic toner, and according to this developing method, it is possible to obtain color images satisfying the recent requirement for the quality of image and moreover, a low-cost and compact developing device is realized.
FIG. 9
of the accompanying drawings shows a developing device using the non-magnetic monocomponent developing method which is installed in an image forming apparatus. This developing device E has a developing roller
1
rotatively driven in the direction of the arrow as a developer bearing member in the opening portion of a developer container
3
containing a non-magnetic toner (a non-magnetic monocomponent developer) therein, and a toner supplying and collecting roller
19
as a developer supplying and collecting member and a regulating blade
20
as a developer regulating member abut against the developing roller
1
.
The toner supplying and collecting roller
19
comprises a mandrel
19
a
of SUS or like material and an elastic member
19
b
of urethane foam or like material covering the outer peripheral surface of the mandrel
19
. The roller
19
elastically abuts against the surface of the developing roller
1
by the elastic member
19
b
and rotates to thereby supply a non-magnetic toner contained in the developer container
3
to the surface of the developing roller
1
, and also scrapes any unused toner returned to the developer container
3
with the rotation of the developing roller
1
without being used in development from the surface of the developing roller
1
.
The regulating blade
20
comprises a support member
20
a
formed of phosphor bronze or the like and an elastic member
20
b
of urethane rubber or like material adhesively secured to the support member
20
a
. The blade
20
acts to elastically abut against the surface of the developing roller
1
by the elastic member
20
b
and regulates the toner borne on the developing roller
1
to thereby form a thin layer of toner and impart charges to the toner.
An image forming apparatus using the above-described developing device E will now be described with reference to
FIG. 10
of the accompanying drawings. As shown in
FIG. 10
, the image forming apparatus has a photosensitive drum
11
as an image bearing member rotatively driven at a predetermined peripheral speed in the direction of the arrow, and a charging device
16
, an exposing device
15
, the developing device E and a cleaning device
18
are disposed around the photosensitive drum
11
.
To form an image, the photosensitive drum
11
is first rotated and in the rotation process thereof, the surface of the photosensitive drum
11
is uniformly charged to a desired polarity and potential by the charging device
16
, and then image exposure conforming to desired image data is effected by the exposing device
15
to thereby form an electrostatic latent image on the surface of the photosensitive drum
11
. Next, in a developing portion wherein the photosensitive drum
11
and the developing roller
1
of the developing device E are opposed to each other, the electrostatic latent image on the photosensitive drum
11
is developed by the non-magnetic toner on the developing roller
1
to thereby form on the photosensitive drum
11
a toner image conforming to the electrostatic latent image.
A transfer bias is then applied to a transfer roller
13
to thereby transfer this toner image to a transfer material P conveyed to a transfer portion in which the photosensitive drum
11
and the transfer roller
13
are opposed to each other. Thereafter, the transfer material P is introduced into a fixing device
14
, where the toner image is heated and fixed on the transfer material P, whereby an image is obtained on the transfer material P, thus completing a series of image forming steps.
After the transfer, the photosensitive drum
11
has any untransferred toner residual on its surface without being transferred removed and collected by the cleaning device
18
, and thereafter is used again for the image forming steps of charging, exposing, developing, etc. similar to those described above.
In recent years, the further downsizing and lower cost of the above-described image forming apparatus using the non-magnetic monocomponent developing method have been desired and the shortening of the image forming steps (including the omission of some of the steps) has been variously studied.
There has been proposed a cleanerless image forming apparatus in which of the above-described image forming steps, the cleaning step is omitted, but if the cleaning device
18
is simply omitted, there have been the following problems.
If the cleaning means for cleaning the surface of the photosensitive drum
1
is absent, untransferred toner, paper powder, etc. accumulate on the photosensitive drum and prevents uniform charging and image exposure for forming the electrostatic latent image and therefore, the unevenness of potential occurs to the electrostatic latent image and the unevenness of the density of an output image occurs.
Also, the developing device E effects the supply and collection of the toner to the developing roller
1
by the toner supplying and collecting roller
19
abutting against and frictionally rotating with the developing roller
1
, and effects the imparting of charges to the toner by the contact friction when the toner passes the regulating blade
13
and therefore, toner in the developer container
3
is very great in a mechanical load applied thereto until it is used for the development on the photosensitive drum
11
, and the damage to the toner is very great as compared with the other developing methods.
Further, depending on the disposed position and the direction of rotation of the toner supplying and collecting roller
19
, the toner which did not contribute to the development cannot be completely collected and in some cases, the toner has been remaining on the developing roller
1
. The toner residual on the developing roller
1
again passes the regulating blade
20
and is carried to a developing area, and if such a step is continuously repeated, an extraneous additive or the like controlling the charging amount and fluidity of the toner is buried into the interior of the toner by mechanical friction and the accumulation of heat, and it happens that the toner becomes a deteriorated toner of which the desired charging characteristic and fluidity cannot be obtained.
This deteriorated toner causes many problems during the image forming process. For example, when the deteriorated toner contributes to development, a proper developing characteristic is not obtained and therefore, bad development occurs or bad transfer such as a hollow image is sometimes caused. Further, the supply of fresh toner onto the developing roller
1
is hindered and the amount of toner coat (the applied amo
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Pendegrass Joan
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