Electrophotography – Image formation – Combined or plural functions by single component
Reexamination Certificate
2000-02-14
2001-10-16
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Combined or plural functions by single component
C399S270000
Reexamination Certificate
active
06304738
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrophotographic system image forming apparatuses such as a copying machine and a printer in which an electrostatic latent image formed on an image bearing member is developed by toner to obtain an image.
2. Related Background Art
An image forming process by an image forming apparatus will be described with reference to FIG.
4
.
First, by setting an original G with a surface to be copied facing downward onto an original stand
10
, and pressing a copy button, copying is started. When a unit
9
integrally formed of an original irradiation lamp, short focus lens array and CCD sensor irradiates and scans the original, and the lighting scan light reflected by the original surface is formed into an image by the short focus lens array, and is incident upon the CCD sensor.
The CCD sensor is constituted of a light receiving section, transfer section and output section. A light signal is converted to an electric signal in the CCD light receiving section, and successively transferred to the output section in the transfer section in synchronization with a clock pulse, and the charge signal is converted to a voltage signal, and subjected to amplification and low impedance treatment in the output section to emit an output. The analog signal obtained in this manner is subjected to a known image processing, converted to a digital signal and transmitted to an image forming section.
In the image forming section, the above-described image signal is received, and an electrostatic latent image is formed as follows. A photosensitive drum
1
is rotatively driven centering on a central spindle at a predetermined peripheral speed, and uniformly charged to provide a positive or negative polarity by a charger
3
in the process of the rotation. The light of a solid laser element
102
(
FIG. 5
) turned on/off in response to the image signal and emitted to the uniformly charged surface is scanned by a rotary polygonal mirror
104
(
FIG. 5
) rotating at a high rate, and the electrostatic latent image is successively formed on the surface of the photosensitive drum
1
.
FIG. 5
schematically shows the constitution of a laser scan section
100
for scanning the laser beam in the above-described device. When the laser beam is scanned by the laser scan section
100
, the solid laser element
102
is flickered at a predetermined timing by a light emitting signal generating device
101
based on the inputted image signal. Subsequently, the laser beam radiated from the solid laser element
102
is converted to a substantially parallel light flux by a collimator lens system
103
, further scanned in the direction of arrow C by the rotary polygonal mirror
104
rotating in the direction of arrow B, and formed into a spot-like image on a scanned surface
106
of a photosensitive drum or the like by the group of f&thgr; lenses
105
a,
105
b,
105
c.
By the scanning of the laser beam, an exposure distribution is formed on the scanned surface
106
for one image scanning. Furthermore, when the scanned surface
106
is scrolled by a predetermined amount vertically to the scanning direction for every scanning, the exposure distribution is obtained on the scanned surface
106
in response to the image signal.
A developing process will next be described. Generally, developing methods are roughly classified into four types: a method comprising coating a sleeve with nonmagnetic toner with a blade or the like, or coating the sleeve with magnetic toner using a magnetic force, carrying the toner, and developing the image on the photosensitive drum in a non-contact state (mono-component non-contact development); a method of developing the image of the toner coated as described above in a contact state (mono-component contact development); a method comprising using a mixture of toner particles and a magnetic carrier as a developer, carrying the developer by the magnetic force, and developing the image on the photosensitive drum in the contact state (two-component contact development); and a method of developing the image of the above-described two-component developer in the non-contact state (two-component non-contact development). In respect of the high image quality and high stability of the image, the two-component contact development method is frequently used.
As shown in
FIG. 3
, a developing device
4
is provided with a developer container
16
, the inside of the developer container
16
is divided into a development chamber (first chamber) R
1
and an agitation chamber (second chamber) R
2
by a partition wall
17
, and replenishing toner (nonmagnetic toner)
18
is contained in a toner storage chamber R
3
. Additionally, the partition wall
17
is provided with a replenishing port (not shown), and the amount of the replenishing toner
18
corresponding to the amount of the consumed toner drops for replenishment in the agitation chamber R
2
via the replenishing port.
On the other hand, a developer
19
is contained in the development chamber R
1
and the agitation chamber R
2
. The developer
19
is a two-component developer containing the nonmagnetic toner and magnetic particles (carrier), and the mixture ratio is set so that about 4 to 10% by weight of the nonmagnetic toner is mixed. Here, the nonmagnetic toner has a volume average particle diameter of about 5 to 15 &mgr;m. Moreover, the magnetic particles contain ferrite particles coated with a resin, or resin particles with magnetic materials dispersed therein, the weight average particle diameter is in a range of 25 to 60 &mgr;m, and a volume resistance is in a range of 10
6
to 10
12
&OHgr;·cm. Furthermore, the permeability of the magnetic particles is in a range of 2.5 to 5.0.
The developer container
16
has an opening in the vicinity of the photosensitive drum
1
, and a development sleeve
11
protrudes to the outside via the opening. The development sleeve
11
is rotatably incorporated in the developer container
16
. The development sleeve
11
has an outer diameter of 32 mm, and a peripheral speed of 280 mm/sec, and rotates in a direction shown by an arrow in FIG.
3
. The development sleeve
11
is disposed so that an interval from the photosensitive drum
1
is about 500 &mgr;m. The development sleeve
11
is formed of a nonmagnetic material, and a magnet
12
is fixed inside as magnetic field generating means.
The magnet
12
has a development pole S
1
, a magnetic pole N
3
positioned on the downstream, and magnetic poles N
2
, S
2
, N
1
for carrying the developer
19
. The magnet
12
is disposed in the development sleeve
11
so that the development pole S
1
is substantially opposite to the photosensitive drum
1
. The development pole S
1
forms a magnetic field in the vicinity of the development section between the development sleeve
11
and the photosensitive drum
1
, and a magnetic brush is formed by the magnetic field.
A blade
15
is disposed above the development sleeve
11
and at a predetermined interval from the development sleeve
11
. An interval between the development sleeve
11
and the blade
15
is about 800 &mgr;m. The blade
15
is fixed to the developer container
16
. The blade
15
is formed of nonmagnetic materials such as aluminum and SUS316, and regulates the layer thickness of the developer
19
on the development sleeve
11
. A carrying screw
13
is contained in the development chamber R
1
. The carrying screw
13
is rotated in a direction shown by an arrow of
FIG. 3
, and the developer
19
in the development chamber R
1
is carried in the longitudinal direction of the development sleeve
11
by rotatively driving the carrying screw
13
.
A carrying screw
14
is contained in the agitation chamber R
2
. The carrying screw
14
carries the toner along the longitudinal direction of the development sleeve
11
by its rotation. The toner freely drops into the agitation chamber R
2
from a replenishing port
20
of the storage chamber R
3
.
The development sleeve
11
bears the developer in the vicinity of the magnetic pol
Hibino Masaru
Kobayashi Yoshiaki
Ozawa Ichiro
Shida Masanori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grimley Arthur T.
Tran Hoan
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