Electrophotography – Image formation – Development
Reexamination Certificate
2000-06-23
2002-03-12
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Development
C015S256500, C399S251000, C399S274000
Reexamination Certificate
active
06356730
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus and a cleaning apparatus suitable for use in an image forming apparatus such as a printer, a copying machine, a facsimile or the like.
2. Description of the Related Art
One example of a conventional process cartridge detachable from an image forming apparatus will hereinafter be described with reference to
FIGS. 13
to
16
. In FIG.
13
and
FIG. 14
, numeral
101
refers to a developing roller as a developing agent carrier, and a developing blade
102
as a developing agent layer thickness regulating member, disposed in parallel with a longitudinal direction of the developing roller
101
, is disposed in direct contact with a surface of the developing roller
101
. Both ends of the developing blade
102
are secured by screws to seat surfaces
104
a
of a developing container
104
.
As shown in
FIG. 14
, a pressingly contacting force between the developing blade
102
and the developing roller
101
is controlled by a flexure angle &thgr;
1
of an elastic portion
102
a.
In
FIG. 16
, numeral
105
is a photosensitive drum, and a cleaning blade
106
as a cleaning member, disposed in parallel with a longitudinal direction of the photosensitive drum
105
, is disposed in direct contact with a surface of the photosensitive drum
105
. Similarly, the cleaning blade
106
is secured by screws
103
to seat surfaces
107
a
of a cleaning frame
107
.
As shown in
FIG. 16
, a pressingly contacting force between the cleaning blade
106
and the photosensitive drum
105
is controlled by a spacing distance (intrusion amount) Q between a virtual position of a tip of an elastic portion
106
a
of the cleaning blade
106
without the photosensitive drum
105
and a directly contacting point Y of the elastic portion
106
a
with the photosensitive drum
105
, and also by a flexure angle &thgr;
2
of the elastic portion
106
a.
In the aforementioned conventional example, however, internal temperature of the image forming apparatus changes due to influences such as installation environment or fixing device temperature, and accompanied by this change, temperatures of respective parts inside the process cartridge change, too. When the temperature inside the apparatus rises, the developing container
104
and the developing blade
102
are elongated in right and left directions in
FIG. 15
(in an arrow a direction) according to respective coefficients of thermal expansion.
At this time, as for the developing container
104
made of resin and a sheet metal portion
102
b,
made of metal, of the developing blade
102
, the developing container
104
made of resin has a larger coefficient of liner thermal expansion (a typical resin has a coefficient of liner thermal expansion of 7×10
−5
; iron has a coefficient of liner thermal expansion 1.12×10
−5
) and a larger elongation than those of the sheet metal portion
102
b,
thereby deforming the sheet metal portion in a downward direction in
FIG. 15
(in an arrow b direction) based on screws
103
as base points provided in two spots, and therefore, the flexure angle &thgr;
1
at a center portion in a longitudinal direction of the developing blade
102
shown in
FIG. 14
becomes smaller, with the result that a pressingly contacting force of the developing blade
102
with respect to the developing roller
101
becomes lower at the center portion in the longitudinal direction.
When a pressingly contacting force of the developing blade
102
becomes lower at the center portion of the longitudinal direction, a thickness of a toner coat and a frictionally sliding charging amount on the developing roller
101
become reduced, and therefore an image density at the center portion in the longitudinal direction becomes lowered, which might cause image unevenness.
For example, it has experimentally proved that, provided that a length of the securing portions (a spacing distance between holes for the screws
103
of the end portions) of the sheet metal portion
102
b
of the developing blade
102
is 211 mm and the temperature is changed to 30° C., a changing amount in a downward direction (in a arrow b direction) was approximately 0.4 mm at the center portion in the longitudinal direction of the developing blade
102
.
When temperature is lowered, on the other hand, the deforming direction becomes in an upward direction in
FIG. 15
(in an arrow c direction) which is an opposite direction when the temperature becomes higher, and therefore, a pressingly contacting force of the developing blade
102
becomes increased at the center portion in the longitudinal direction. Due to this, the thickness of the toner coat and the sliding-rubbing charging amount on the developing roller
101
become increased, and then an image density at the center portion in the longitudinal direction becomes higher, which might cause image unevenness.
Also, when the temperature inside the image forming apparatus rises, the cleaning frame
107
and the cleaning blade
106
shown in
FIG. 16
becomes elongated in the right and left directions in
FIG. 15
(in an arrow a direction) according to respective coefficients of thermal expansion, in the same way as that of the aforementioned developing container
104
and the developing blade
102
shown in FIG.
15
.
At this time, as for the cleaning frame
107
made of resin and a sheet metal portion
106
b,
made of metal, of the cleaning blade
106
, the cleaning frame
107
made of resin has a larger coefficient of liner thermal expansion and a larger elongation than those of the sheet metal portion
106
b,
thereby deforming the sheet metal portion in a downward direction in
FIG. 15
(in an arrow b direction) based on the screws
103
as base points provided in the two spots, and therefore, the flexure angle &thgr;
2
at a center portion in a longitudinal direction of the cleaning blade
106
shown in
FIG. 16
becomes smaller, with the result that a pressingly contacting force of the cleaning blade
106
with respect to the photosensitive drum
105
becomes decreased at the center portion in the longitudinal direction and the intrusion amount Q with respect to the photosensitive drum
105
also becomes decreased, thus to cause problems such as a cleaning insufficiency or the like.
When temperature is lowered, on the other hand, the deforming direction becomes in an upward direction in
FIG. 15
(in an arrow c direction) which is an opposite direction when the temperature becomes higher, and therefore, a pressingly contacting force of the cleaning blade
106
becomes increased at the center portion in the longitudinal direction, and the intrusion amount Q with respect to the photosensitive drum
105
becomes in excess. Thus, when an inappropriate portion of the elastic portion
106
a
of the cleaning blade
106
, instead of the tip of the elastic portion
106
a
which is originally designed to be contacted with a surface of the photosensitive drum
105
, is contacted with the surface of the photosensitive drum
105
, cleaning insufficiency occurs; for example, residual developing agent, which is supposed to be scraped off, on the surface of the photosensitive drum
105
goes by to remain thereon. In addition, the photosensitive drum has been rubbed for a long time, which then causes problems such as a shorter lifetime of the photosensitive drum
105
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a developing apparatus which absorbs a difference between elongation and contraction of a regulating member and elongation and contraction of a main body of the developing apparatus.
An another object of the present invention is to provide a cleaning apparatus which absorbs a difference between elongation and contraction of a cleaning member and elongation and contraction of a main body of the cleaning apparatus.
A still another object of the present invention is to provide a developing apparatus in which a positional relation between the regulating member and a developing age
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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