JPH0458277A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a stable image without the unevenness of density by providing an electrified substance capturing means having the same discharge polarity as an electrifying means in an area between the electrifying means and a developing means. CONSTITUTION:When an image forming device 1 is actuated, a part of toner TN in developer D on a magnetic roller 5A starts to scatter to the outside of a developing means 5. A part of Si which is exteriorly added to the toner TN also starts to scatter to the outside of the means 5. the discharged toner TN and the Si initially suspend on the periphery of the means 5 and electrostatically attracted by the (-) potential of a conductive member 13 positioned near the means 5, start to move toward the member 13 and adhere to the member 13 soon. Since the toner TN and the Si are mostly captured by the member 13 in such a way, they do not adhere to the electrifying means 3. As a result, the irregularity of the electric discharge in the means 3 is eliminated and the unevenness of image density at the time of forming the image, furthermore, is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrophotographic method.

(Prior Art) As shown in FIG. 3, an image forming apparatus using an electrophotographic method includes charging means 3. Exposure means 4. A developing means 5 is disposed, and although not shown, a transfer means, a peeling means, a cleaning means, a static elimination lamp, etc. are also disposed, and a toner image (electrostatic latent) formed on the circumferential surface of the photoreceptor 2 by charging and image exposure is disposed. image) is converted into a visible image by the developer in the developing means 5, and then the toner image on the circumferential surface of the photoreceptor 2 is transferred to a transfer paper by the discharge charge from the transfer means, and then the toner image on the transfer paper is converted into a visible image. is fixed by heat or pressure to obtain a desired image on transfer paper.

Here, the charging means 3 charges (+) according to the charging polarity of the photoreceptor 2.
) or (-) discharge charges are generated.

Particularly in the case of an electrophotographic copying machine or the like in which the photoreceptor 2 has (-) charging polarity, a scorotron system using a grid 7 as the charging means 3 is generally used. The scorotron method is a method that controls the discharge current from the charging wire 10 to a constant level by giving the grid 7 a potential of the same polarity as the charging polarity of the photoreceptor 2, thereby realizing stable and uniform discharge at all times. be. The magnitude of the potential applied to the grid 7 is the surface potential V of the photoreceptor 2. It is almost the same size as .

In the arrangement of each process unit around the photoreceptor 2,
In a region intermediate between the charging means 3 and the developing means 5, an exposure means 4 is usually provided which exposes the photoreceptor 2 to a light image formed through an exposure optical system.

Furthermore, in some image forming apparatuses, a lamp unit (usually using an LED array) for canceling the electrical charges in the non-image area on the photoreceptor 2 is installed after the charging means 3 (on the downstream side). In some cases, it is provided before (upstream side) the exposure means-4.

Currently, there are no examples of conventional image forming apparatuses in which any other unit is provided between the charging means 3 and the developing means 5.

Generally, around the developing means 5 around the photoreceptor 2, toner TN and the like in the developer from the developing means 5 scatters and floats in a large amount. Charged objects (insulators) such as toner TN
If it flows into the charging means 3, the case 12
．． If it adheres to the wire 10 or the grid 7, the discharge conditions of the attached part will be different from those of other parts, resulting in uneven charging of the photoreceptor 2 (VO unevenness), and as a result, for example, partial unevenness in halftone images, etc. Density unevenness occurs.

Particularly in the case of the scorotron method, if some kind of insulator adheres to the grid 7, the resistance of the attached part on the grid 7 increases, causing the potential of the grid 7 to locally become higher than the set value (potential unevenness on the grid 7). Occur). This causes uneven charging of the photoreceptor 2 (V O unevenness), and as a result, it has been confirmed that the density of the image is not higher at the position corresponding to the portion to which the charged object is attached than at other parts.

The adhesion of charged substances such as toner TN may be caused by scattering and floating substances during the five rotations of the developing means, which may move to the periphery of the charging means 3 due to the movement of the air current (wind flow) within the image forming apparatus and become physically attached. many. However, apart from this, for example, toner T
Let us consider a case where N or the like is scattered or floating in a state with a certain polarity. Since the toner TN is generally charged with a polarity opposite to the discharge polarity of the charging means, the toner TN scattered and floating around the developing means 5 is not only caused by the movement of airflow but also by electrostatic force to the surrounding area of the charging means 3. It may move up to. In particular, when the grid 7 is used in the scorotron method, the grid 7 has a potential of opposite polarity to the toner TN and is arranged over a wide area, so the toner TN with polarity (charged) The attracting force becomes very strong, and the probability of toner adhesion to the grid 7 becomes very high.

The toner Ts is not the only floating charged object having a polarity opposite to that of the grid 7 and the wire 10. That is, in order to improve the fluidity of toner TN, St, which is generally externally added to toner TN, also has strong polarity. St, which is usually added externally, is
Use one that has the same charged polarity as the toner TN (
For example, (+) toner TN has (+) polarity Si), so like toner TN, Si is also electrostatically drawn around the charging means 3 and adheres to the grid 7, wire 10, etc. Since the previously used Si may be physically liberated from the toner matrix, Si alone may float around the developing means 5).

(Problem to be Solved by the Invention) As mentioned above, in the conventional method, charged substances such as toner and Si move and adhere to the charging means, which causes uneven discharge of the charging means and causes uniform image density. There's a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming apparatus that can achieve uniform discharge of a charging means and uniform image density by improving the configuration around an image carrier. .

[Structure of the Invention (Means for Solving the Problems) The present invention provides an image forming apparatus including a charging means and a developing means around an image bearing member carrying an electrostatic latent image to be used for image formation. A charged object capturing means having the same discharge polarity as the charging means is provided in a region between the means and the developing means.

(Function) According to the image forming apparatus configured as described above, charged objects scattered or floating around the developing means are captured by the charged object capturing means having the same discharge polarity as the charging means, so that the charged objects are not affected by the charging means. Adhesion of charged objects is avoided.

(Example) Examples of the present invention will be described in detail below.

The image forming apparatus 1 shown in FIG.
．． The developing means 5 are sequentially arranged at predetermined intervals.

The charging means 3 is a scorotron type, and includes a grid 7,
Discharge wire 10. A case 12 is provided, a high voltage power supply 9 is connected to the wire 10, and a negative (-) is connected to the wire 10.
) is designed to discharge the electric charge. Furthermore, the grid 7 is grounded via a Zener diode 8.

Therefore, a (-) potential is generated on the grid 7 due to the (-) charge from the wire 10.

There is a space between the exposing means 3 and the developing means 5 as shown in FIG.

Charged object capturing means 11 as shown in FIG. 2 is arranged.

This charged object capturing means 11 includes a plate-shaped insulating support 6 disposed along the axial direction of the photoreceptor 2, and a conductive member 13 having the same structure as the grid 7 supported by the support 6. The conductive member 13 is connected to one end of the grid 7 by a lead wire 14. That is, the conductive member 13 is electrically ungrounded because the support body 6 is made of an insulator, and is at a negative potential (-) similar to that of the grid 7.
are kept at the same potential).

Next, the operation of the image forming apparatus 1 will be explained.

When the image forming apparatus 1 is operated, the magnetic roller 5A in the developing means 5 starts rotating, and a part of the toner TN in the developer on the magnetic roller 5A begins to scatter to the outside of the developing means 5. Further, a part of the Si externally added to the toner TN is released from the toner TN matrix, and this also begins to scatter to the outside of the developing means 5. Toner TN and Si are charged by charging means 3.
Since the toner TN and Si are charged to the opposite polarity (+) to the discharge polarity, the toner TN and Si that are scattered and discharged to the outside of the developing means 5 also have a weak polarity (in this case, (+) polarity).

The discharged toners TN and Si are initially floating around the developing means 5, but are electrostatically attracted by the (-) potential of the conductive member 13 located near the developing means 5 and move in that direction. At first, it eventually adheres to the conductive member 13. This state is shown in FIG. In this way, most of the toner TN and Si are captured by the conductive member 13, so that the toner TN and Si do not adhere to the charging means 3, and as a result, uneven discharge of the charging means 3 is eliminated. Also, unevenness in image density during image formation is eliminated.

In the embodiment described above, the common high-voltage power supply 9 is used for the conductive member 13 and the grid 7, so a dedicated power supply for the conductive member 13 is not required.

In addition to the embodiments described above, the present invention can be modified in various ways within the scope of the gist thereof. It is possible to provide an image forming apparatus that can perform stable image formation without uneven charging of the device and uneven density of the image.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an apparatus according to an embodiment of the present invention, FIG. 2 is a cutaway perspective view of a charged object capturing means of the same apparatus, and FIG. 3 is a schematic sectional view of a conventional apparatus.

Claims (1)

[Claims] An image forming apparatus including a charging means and a developing means around an image bearing member carrying an electrostatic latent image to be used for image formation,
An image forming apparatus characterized in that a charged object capturing means having the same discharge polarity as the charging means is provided in a region between the charging means and the developing means.