Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
1998-06-17
2002-09-10
Brase, Sandra (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
Reexamination Certificate
active
06449442
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to developing apparatuses for developing an electrostatic latent image formed on an image bearing member. In particular, it relates to such a developing apparatus that is employed in image forming apparatuses, for example, copying machines or printers, which employ an electrophotographic recording system, an electrostatic recording system, or the like.
In an electrophotographic image forming apparatus or the like, an electrostatic latent image is formed on the image bearing member, and the latent image is developed with the use of a developing apparatus and developer.
A developing apparatus comprises a developer carrying member which delivers developer close to the peripheral surface of the image bearing member by carrying developer on its peripheral surface. The developer carried close to the peripheral surface of the image bearing member develops an electrostatic latent image on the image bearing member, or visualizes the latent image, as an alternating electric field is formed between the developer carrying member and the image bearing member. Generally, the image bearing member and the developer carrying member are constituted of a photosensitive drum and a development sleeve, respectively.
There are several methods for developing a latent image. One of the well known methods is the method which employs two component developer composed of carrier and toner. According to this method, a magnetic brush is formed of this developer by the magnet encased in a development sleeve, on the peripheral surface of the development sleeve which is disposed in such a manner that a microscopic gap is maintained between the peripheral surfaces of the development sleeve and the image bearing member. A latent image formed on the image bearing member is developed as the magnetic brush brushes, or virtually touches, the peripheral surface of the image bearing member. As for the alternating electric field formed between the development sleeve and the photosensitive drum, there are two types: an alternating electric field (Japanese Laid-Open Patent Application Nos. 34060/1980 and 165082/1984) and a DC electric field.
A development apparatus based on a magnetic brush formed of two component developer is generally structured as depicted in FIG.
4
. In the drawing, a referential
figure 105
designates a developer container of a developing apparatus which relies on a magnetic brush form of two component developer. The developer container
105
contains two component developer
103
, that is, a mixture of nonmagnetic toner and magnetic carrier. The developer container
105
has a wide opening which faces a photosensitive drum
100
. In this wide opening, a development sleeve
109
is disposed, and in the development sleeve, a magnetic roller is nonrotatively disposed. The positional relationship between the development sleeve
109
and photosensitive drum
100
is such that a predetermined gap is always maintained between the peripheral surfaces of the development sleeve
109
and the photosensitive drum
100
. Above the development sleeve
109
, a regulator blade
111
is attached to the developer container
105
. This blade
111
regulates the thickness of the developer layer formed on the peripheral surface of the development sleeve
109
. Approximately the bottom half of the internal space of the developer container
105
is partitioned into a developer space R
1
and a stirring space R
2
by a partition wall
113
. Above the stirring space R
2
, a toner storage space R
2
is located, which stores the replenishment toner
119
.
The development sleeve
109
is rotated in such a direction that the peripheral surfaces of the development sleeve
109
and the photosensitive drum
100
move in the same direction at the location where the two surfaces face each other. As the development sleeve
109
is rotated, the two component developer
103
in the developer container
105
is adhered to the peripheral surface of the development sleeve
109
by the effect of the magnetic roller
107
, and then, is carried to the location at which the peripheral surfaces of the development sleeve
109
and the photosensitive drum
100
face each other. As stated above, there is provided a gap
125
between the peripheral surfaces of the development sleeve
109
and the photosensitive drum
100
so that the developer on the development sleeve
109
develops the electrostatic latent image on the peripheral surface of the photosensitive drum
100
as the developer makes contact with the peripheral surface of the photosensitive drum
100
.
The toner density of the two component developer
103
within the developer container
105
, that is, the ratio (T/C ratio) of the amount of the toner relative to the amount of the carrier in the developer, is kept constant by allowing the toner in the toner storage space R
3
to free fall through a replenishment hole in the bottom wall of the toner storage space R
3
, by the same amount as the amount of toner consumed through development activity.
As for the method for detecting and/or maintaining the T/C ratio of the developer within the developer container
105
, various methods have been proposed, and some of them have been put to practical use. For example, according to one of the methods, an optical density sensor is disposed adjacent to the photosensitive drum
100
. In obtaining the T/C ratio, light is projected upon a toner image formed on the peripheral surface of the photosensitive drum
100
by developing the latent image formed on the peripheral surface of the photosensitive drum
100
, and the amount of the light which is transmitted through, or is reflected by, the tuner image is detected by the optical density sensor. Then, the T/C ratio is determined from the detected amount of the light. The amount of the toner allowed to free fall is adjusted according to the thus obtained T/C ratio, to keep the T/C ratio of the developer constant. According to another method, an optical density sensor is disposed on the development sleeve
109
. In obtaining the T/C ratio, light is projected upon the developer layer on the peripheral surface of the development sleeve
109
, and the T/C ratio is determined from the amount of the light reflected by the developer layer. Then, the amount of the toner to be added to the developer is adjusted according to the thus obtained T/C ratio of the developer.
However, the former method that maintains the T/C ratio of the developer in the developer container
105
on the basis of the toner density of the toner image suffers from the problem that it is very difficult to find a space for the sensor in a developing apparatus since the size of copying machines and image forming apparatuses has been continuously reduced in recent years. The latter method, that is, the method that maintains the T/C ratio in the developer container
105
on the basis of the detected T/C ratio of the toner layer on the development sleeve
109
, also suffers from a problem, that is, the problem that the sensor is contaminated due to the scattering of the toner particles, failing to accurately detect the T/C ratio of the developer layer on the peripheral surface of the development sleeve
109
.
Fortunately, there is another method for maintaining the T/C ratio of the developer in the developer container
105
. According to this third method, a sensor of a coil type is disposed as the toner density sensor in the developer container
105
, to obtain the apparent permeability of a specific volume of the developer; the inductance of the coil of the sensor is measured. Then, the amount of the toner to be added is adjusted on the basis of the thus obtained T/C ratio of the specific volume of the developer adjacent to the coil type sensor.
More specifically, according to this method that employs a toner density sensor of a coil type, the increase in the permeability of a specific volume of the developer means the decrease in the T/C ratio of the specific volume of the developer, that is, the decrease in the toner
Hibino Masaru
Kobayashi Yoshiaki
Ozawa Ichiro
Shida Masanori
Brase Sandra
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
Developing apparatus employing permeability sensor to detect... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Developing apparatus employing permeability sensor to detect..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developing apparatus employing permeability sensor to detect... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2831363