Electrophotography – Supplemental electrophotographic process – Exposure or charging
Reexamination Certificate
2000-02-02
2001-03-06
Beatty, Robert (Department: 2852)
Electrophotography
Supplemental electrophotographic process
Exposure or charging
Reexamination Certificate
active
06198892
ABSTRACT:
RELATED APPLICATION
This application is based on application No. H11-025391 field in Japan, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a laser beam printer, an electrostatic photocopier, or the like, and more particularly concerns an image forming apparatus which incorporates an improved light eraser for removing electric charges from a photoconductive member.
2. Description of the Related Art
In a typical image forming apparatus such as a laser beam printer and an electrostatic photocopier, an electrostatic latent image is formed on a photoconductive member overlying the outer peripheral surface of a rotating drum, which is then followed by (a) a toner development process in which particles of toner powder are adhered to the photoconductive member, (b) a transfer process in which a toner pattern on the photoconductive member is transferred onto a copy paper sheet, and (c) a fixing process in which the transferred toner pattern is affixed to the copy paper sheet. Thereafter, as preparations for the next image forming process, residual toner powder particles remaining on the photoconductive member are removed therefrom and the surface of the photoconductive member is illuminated with light rays from a light eraser located face to face with the photoconductive member so that residual electric charges remaining in the photoconductive member are optically removed.
A light eraser is required to illuminate light rays across the entire width of a photoconductive member. For the case of a full-color photocopier having a plurality of photoconductive members, it is necessary to illuminate light rays across the entire width of each of the plurality of photoconductive members.
a)
FIG. 4
shows a prior art technique (i.e., a light eraser
102
) for applying light rays across the entire width of a photoconductive member, wherein a plurality of light-emitting diodes (hereinafter called the LEDs)
104
or a plurality of incandescent electric lamps serving as light sources are mounted on a substrate
103
in a side by side fashion in the axial direction of a photoconductive member
101
. However, the problem with the light eraser
102
is that the LEDs
104
are likely to vary in performance, resulting in illuminating the photoconductive member
101
at different quantities of light. Therefore, the photoconductive member
101
cannot uniformly be discharged across its entire length. In order to avoid such a drawback, it has been proposed to employ a light receiving element
105
such as a photosensor for detecting the quantity of light. However, it is practically difficult to measure the quantity of light for each LED
104
because of some constraints such as limitations of space. Additionally, since the number of component parts increases, this will establish limits to improving durability as well as to reducing manufacturing costs.
b) In a full-color photocopier of a tandem type, a plurality of photoconductive members are each provided with a light eraser. Recently, with the downsizing of electrophotographic copiers, the size of photoconductive members is likewise reduced. Accordingly, it is necessary to reduce a space between devices (e.g., cleaners and chargers) mounted in the vicinity of a photoconductive member. It is therefore difficult to achieve the downsizing of photoconductive members when an LED unit as a light eraser is provided to each photoconductive member. The reason is that, when an LED unit is disposed around the periphery of a photoconductive member, space must be secured for the LEDs and a substrate.
Use of optical fibers may provide solutions to these problems with the prior art techniques. More specifically, in order to solve the problem a), a single light source
104
such as a lamp for electric charge removing is mounted and an optical fiber
201
is disposed such that it runs along specified portions of the photoconductive member
101
from the light source
104
as shown in FIG.
5
. Formed on the outer peripheral surface of the optical fiber
201
on the opposite side to the photoconductive member
101
are a diffusion area extending along the longitudinal direction of the optical fiber
201
and a reflection area exterior to the diffusion portion. In such an arrangement, rays of light (L) from the light source
104
are reflected or diffused in the radial direction of the optical fiber
201
so that the specified portions of the photoconductive member
101
are illuminated for optically removing residual electric charges (see S62-127786).
In such a configuration, the single light source
104
applies the light L to the photoconductive member
101
through the optical fiber
201
. The use of the configuration, however, increases component part costs to a great extent because optical fibers are relatively expensive. Moreover, since the optical fiber
201
, when used as it is, is unable to diverge the light L toward the specified portions, the configuration in point has the disadvantage of lacking in latitude with respect to the guiding of the light L of the light source
104
toward the specified portions.
Also, for the problem b), it may be considered that a simplified apparatus configuration is accomplished by making utilization of an optical fiber so as to guide light rays from a single LED unit toward a plurality of photoconductive members. However, such arrangement is difficult to make for the same reason as described previously, and is costly.
To solve both the problem a) and the problem b), a waveguide member capable of easily achieving divergence, refraction, and transmission of light rays is required. By the use of such a waveguide member, it becomes possible to reduce the number of light sources required and, further, as for the problem a), it is possible to evenly apply light rays across the entire width of a photoconductive member.
SUMMARY OF THE INVENTION
Accordingly, a general object of the present invention is to provide solutions to the above-described problems.
Another object of the present invention is to provide a waveguide member (a light propagation member) capable of easily achieving divergence and/or refraction of light rays.
Still another object of the present invention is to provide a simplified configuration to an image forming apparatus having a photoconductive member.
A further object of the present invention is to provide a waveguide member capable of evenly apply light rays across the entire width of a photoconductive member.
A still further object of the present invention is to provide a light charge-removing unit capable of reducing the number of light sources for illuminating photoconductive members.
Another object of the present invention is to provide a light-quantity control device capable of performing control so that the light quantity of a light source for illuminating a photoconductive member is set to a desired value.
These and other objects are attained by an image forming apparatus of the present invention, the image forming apparatus comprising:
a plurality of photoconductive members on which images are formed according to the principle of electrophotography technology;
a light source; and
a waveguide member including a body portion where rays of light from the light source enter and a divergence portion by which the light rays from the light source are made to branch off from the body portion and are guided to the plurality of photoconductive members.
Further, the object of the present invention is attained by a light charge-removing unit which is incorporated in an image forming apparatus having a plurality of photoconductive members and which is operable to remove electric charges from posterior-to-transfer/prior-to-charge areas of the plurality of photoconductive members by subjecting the plurality of photoconductive members to exposure to light, the light charge-removing unit comprising:
a light source common to all of the plurality of photoconductive members; and
a waveguide member
Beatty Robert
McDermott & Will & Emery
Minolta Co. , Ltd.
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