Electrophotography – Image formation – Development
Reexamination Certificate
2002-12-24
2004-11-09
Grimley, Arthur T. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06816694
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a developer apparatus and to an image forming apparatus wherein developer material is transported by a traveling-wave electric field and a latent electrostatic image is developed by means of this developer material.
2. Conventional Art
In the field of copiers, printers, and other such image forming apparatuses where electrophotography is employed, developer apparatuses utilizing noncontact methods in which developer material is transported to the vicinity of an image carrier and developer material is cast onto a latent electrostatic image on the image carrier to develop this latent electrostatic image have drawn attention. Such noncontact methods include the powder cloud method, the jumping method, and methods employing an electric field curtain (traveling-wave electric field).
Methods employing traveling-wave electric fields are described, for example, at Japanese Patent Application Publication Kokoku No. H5-31146 (1993), Japanese Patent Application Publication Kokoku No. H5-31147 (1993), and elsewhere. In such descriptions, a multiplicity of electrodes are embedded in a developer material transport path, polyphase AC voltage(s) is or are applied to these electrodes to form a traveling-wave electric field, and developer material in the transport path is transported to an image carrier by means of this traveling-wave electric field. Developer material transported to the vicinity of the image carrier and cast onto a latent electrostatic image on the image carrier adheres to the latent electrostatic image. As a result, the latent electrostatic image on the image carrier is developed.
Furthermore, at Japanese Patent Application Publication Kokai No. H3-21967 (1991), not only is developer material in a transport path transported by a traveling-wave electric field, but art is also disclosed in which a precharge roller made of urethane foam and a blade that contacts the precharge roller are provided, friction between the precharge roller and the transport path causing precharging of developer material while developer material layer thickness is at the same time restricted, as a result of which uniform and appropriate charging, as well as stable transport, of developer material are achieved, while scattering of developer material and fogging of the image are prevented.
However, as a result of intensive research on the part of the inventors of the present invention, it has been found that the foregoing conventional developer apparatuses have problems such as the following.
The traveling-wave electric field for transport of developer material is formed due to differences in electric potential between the respective electrodes of the transport path and the developer material supply member which supplies the developer material to the transport path. For this reason, it is necessary to not only apply AC voltage(s) Vac to the electrodes of the transport path but to also apply prescribed DC bias voltage(s) Vd to the developer material supply member, as shown at FIG.
15
(
a
). Furthermore, where the developer material supply member is additionally outfitted with restricting members for restricting developer material layer thickness, supplemental supply members for smooth supply of developer material, and so forth, it will be necessary to apply DC voltage(s) to the restricting members, supplemental supply members, and so forth so as to respectively bias these relative to the DC bias voltage Vd at the developer material supply member.
Now, the developer material becomes charged through ionic irradiation by a corona discharge device, immersion in an electric field, triboelectric action, or the like. However, the amount of charge acquired will vary depending upon ambient conditions and will vary as a function of time. Similarly, developer material layer thickness (the amount of developer material adhering to media) will also vary. Such variations in developer material contribute to variation in the amount of developer material supplied from the developer material supply member to the transport path, and therefore to variation in the amount of developer material supplied from the transport path to the image carrier, causing development nonuniformity and interfering with stable image formation.
One proposal for increasing stability of the amount of developer material which is supplied is a method wherein the traveling-wave electric field for transport of developer material is varied. For example, if there is a decrease in the amount of developer material being supplied, the difference in electric potential between AC voltage Vac and the DC bias voltage Vd at the developer material supply member might be increased by raising DC bias voltage Vd as shown in FIG.
15
(
b
) and/or lowering AC voltage Vac as shown in FIG.
15
(
c
), thereby increasing the intensity of the traveling-wave electric field and causing the amount of developer material being supplied to increase.
Where AC voltage Vac is varied as shown in FIG.
15
(
c
), however, the fact that it will be necessary to uniformly vary at least three or four phases of high-voltage AC voltage makes for complicated voltage supply circuitry for supply of the high-voltage AC voltage(s), which leads to increased cost. And if a relative shift were to develop among the respective high-voltage AC voltages, transport of developer material would become destabilized and the amount of developer material being supplied would likewise become destabilized. Accordingly, in addition to the fact that voltage supply circuitry is made complicated by additional equipment in the form of a mechanism for varying the respective high-voltage AC voltages, as stable operation of the voltage supply circuitry must be maintained and as it will be necessary to simultaneously achieve both stable operation as well as a mechanism for varying respective high-voltage AC voltages, increases in cost will be unavoidable.
Furthermore, where the DC bias voltage Vd at the developer material supply member is varied as shown in FIG.
15
(
b
), as it will also be necessary, in conjunction with variation of the DC bias voltage Vd, to vary the respective DC bias voltages at the aforementioned restricting members for restricting developer material layer thickness, supplemental supply members for smooth supply of developer material, and so forth, here again this will complicate the voltage supply circuitry for supply of respective DC bias voltages, increasing cost. Furthermore, because variation of the respective DC bias voltages at such members will result in variation in the electric field distribution in the vicinity of the developer material transport path, it is entirely possible that this will produce unexpected behavior in the development process or affect transport of developer material.
SUMMARY OF INVENTION
It is therefore an object of the present invention to provide a developer apparatus and an image forming apparatus conceived in light of the foregoing problems in the conventional art and permitting adjustment in the amount of developer material supplied through a simple constitution to achieve improved stability in image formation while holding increases in cost to a minimum.
In order to solve the foregoing problems, the present invention, in the context of a developer apparatus equipped with one or more transport path or paths wherein a plurality of electrodes are arranged in a row or rows so as to be mutually separated by a prescribed spacing or spacings and with one or more developer material supply means arranged at the front side of at least one of the transport path or paths, developer material being supplied from at least one of the developer material supply means to the front of at least one of the transport path or paths, a polyphase alternating current voltage or voltages being applied to respective electrodes of at least one of the transport path or paths, a traveling-wave electric field or fields being formed, at least one of the traveling-wave electric field or fields causing at least a port
Adachi Katsumi
Sakuma Masamitsu
Gleitz Ryan
Grimley Arthur T.
LandOfFree
Developer apparatus and image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Developer apparatus and image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developer apparatus and image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3284989