JPH063970A - Transferring device for electronic copying machine - Google Patents

Abstract

PURPOSE:To prevent a photosensitive body from being locally and electrostatically charged at the edge of a paper. CONSTITUTION:The photosensitive body 1 and a transferring corotron 2 are arranged through a dielectric sheet 3, and the paper 4 is electrostatically attracted on the dielectric sheet and is carried. A toner image 6 on the photosensitive body is directly transferred on the paper. An electrode board 5 for preventing peeling and discharging which comes close to the dielectric sheet and extends in the axial direction of the photosensitive body is arranged on the non-paper surface side of the dielectric sheet 3 in the vicinity of a peeling point where the leading edge and the trailing edge of the paper are separated from the photosensitive body, and a voltage whose polarity is reverse to the transferring corotron 2 is impressed on the electrode board. When the voltage is impressed on the electrode board in a timing that the leading and trailing edges of the paper pass through the peeling point, spark discharge between the photosensitive body and the edge parts of the paper is restrained from being generated so that a line on a copy caused by electrostatically charging history is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device of an electronic copying machine for directly transferring a toner image on a photoconductor onto a sheet through a dielectric sheet, and particularly to a partial photosensitivity at the front and rear edges of the sheet. The present invention relates to a transfer device suitable for eliminating deterioration of copy quality due to body charge history.

[0002]

2. Description of the Related Art In a copying machine which obtains a color copy by repeatedly transferring toner images of a plurality of colors on the same paper, a dielectric sheet is formed in a drum shape or a belt shape in order to accurately convey the paper. It is driving.
Paper is electrostatically adsorbed on the dielectric sheet by means of a corotron and a metal roll or the like. The surface of the dielectric sheet on the side opposite to the paper is charged with the opposite polarity to the toner polarity by means such as corona discharge or transfer roll, and the toner image on the photoconductor is transferred onto the paper. .

In such a conventional transfer device, voids are generated between the dielectric sheet and the photoconductor at the front and rear edges of the paper, and the spark discharge of Paschen causes the photoconductor to be charged with the same polarity as the transfer. Be seen. Due to this partial charging history of the photoconductor, there is a problem that a line is formed on a copy of a subsequent sheet. In order to improve this problem, various measures have been taken, such as using a static elimination corotron on the downstream side of the transfer area of the photoconductor and limiting the transfer current to a low value at the edge of the paper.

[0004]

However, in the method of limiting the transfer current to a low value at the edge of the paper, if the transfer current is controlled immediately before the trailing edge of the paper, the transfer is not performed at the edge of the paper, and conversely. If it is too far from the trailing edge of the paper, the problem such as the ineffectiveness occurs. If the paper interval is made narrower to further improve the productivity, the transfer current control becomes difficult due to the response characteristics of the transfer corotron. In addition, when a system for creating a density control patch between the images on the photoconductor, measuring the reflection or transmission density of the transferred toner, and controlling the toner supply amount is used, Since the inter-image toner image formed in the copy area must be transferred under the same conditions as when copying, it was not possible to change and limit the transfer current even in the non-paper area, and new measures were needed. . It is an object of the present invention to provide a transfer device of an electronic copying machine capable of preventing local charging of the photoconductor at the edge of the paper.

[0005]

In order to achieve the above object, the present invention relates to a transfer device of an electronic copying machine for directly transferring a toner image on a photoconductor onto a sheet through a dielectric sheet,
On the non-paper surface side of the dielectric sheet facing the peeling point of the photoconductor and the paper, a peeling discharge prevention electrode extending in the axial direction of the photoconductor is provided with a constant gap between the dielectric sheet and the peeling discharge prevention electrode. A voltage having a polarity opposite to that of the transfer corotron is applied at the timing when the leading edge and the trailing edge of the sheet pass.

[0006]

[Function] When a voltage having a polarity opposite to that of the transfer corotron is applied to the peeling discharge prevention electrode at the timing when the leading edge and the trailing edge of the sheet pass the peeling point, spark discharge is generated at the photoreceptor and the leading edge and the trailing edge of the sheet. It can be suppressed, and lines will not appear on the copy due to the charging history. Since it is not necessary to change the transfer current between the paper part and non-paper part in order to suppress the occurrence of spark discharge at the paper edge part, the inter-image toner image is transferred onto the dielectric sheet of the non-paper part, It can be applied to a method of controlling the toner supply amount based on the toner density.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a main part of a transfer device of an electronic copying machine according to the present invention. In the transfer device, a photoconductor 1 and a transfer corotron 2 are arranged via a dielectric sheet 3,
The sheet 4 is electrostatically adsorbed and conveyed to the side of the dielectric sheet 3 on the photoconductor 1, and the toner image 6 on the photoconductor 1 is directly transferred to the paper 4. On the non-paper surface side of the dielectric sheet 3 near the peeling point where the front edge and the rear edge of the sheet 4 separate from the photoconductor 1, a peeling discharge prevention electrode 5 that is close to the dielectric sheet and extends in the axial direction of the photoconductor 1 is provided. Has been deployed,
A voltage having a polarity opposite to that of the transfer corotron 2 is applied to the peeling discharge prevention electrode 5.

The distance between the electrode 5 and the peeling point of the paper 4 is
The applied voltage may be low if they are brought close to each other, which is preferable as a peeling discharge prevention electrode, but 0.5 to 5 m is required because a clearance is required for the transfer belt as a dielectric sheet.
A spacing of m is suitable. The structure of the peeling discharge prevention electrode 5 is
The plate member shown in FIG. 2 is formed, and its shape is such that the surface facing the dielectric sheet 3 is formed linearly as shown in FIG. 2A, or as shown in FIG. 2B. The facing surface is formed in a sawtooth shape. As another structure, a comb-shaped or needle-shaped structure can be naturally applied.

Next, the operation of the above embodiment will be described. The sheet 4 is conveyed onto the dielectric sheet 3 by the conveying system, and the toner image 6 on the photoconductor is transferred at the transfer section. In the process of processing up to this point, the leading edge of the sheet is determined by the sheet transport time between the register and the transfer separation point, and the trailing edge of the sheet is determined based on the sheet size, based on the register signal output when the sheet passes through the register. Therefore, when the leading edge of the transferred paper reaches the peeling point, a voltage having a polarity opposite to that of the transfer corotron 2 is applied to the peeling discharge prevention electrode 5, and then when the trailing edge of the paper passes through the peeling point, the peeling discharge preventing electrode 5 is again reset. Similarly, a voltage is applied.

For example, as a condition of an application example to a digital color copying machine using a photosensitive member having a process speed of 160 mm, a photosensitive member outer diameter of φ84 mm, and negative sensitivity and infrared sensitivity, the peeling discharge prevention electrode 5 has a thickness of 1 mm of aluminum. An electrode plate was used and the shape shown in FIG. 2B was used. The electrode plate was provided at a separation portion between the photoconductor and the paper, with a distance of 1 mm from the dielectric sheet. The toner was a negative polarity toner, and the transfer corotron was a positive polarity toner.

The required applied voltage naturally changes depending on the gap between the sheet and the dielectric sheet, but in the present embodiment, -2 KV is applied to the peeling discharge prevention electrode 5 at the timing when the leading edge and the trailing edge of the sheet pass the peeling point of the sheet. Applied. It was confirmed that the electric field at this time could prevent the generation of lines due to peeling. In this example, the distance between the electrode plate and the dielectric sheet is set to 1 mm so as not to be affected by the fluttering of the belt. However, if the belt drive is stabilized, the applied voltage can be reduced.
It is preferably 1 mm or less. As an embodiment of the present invention,
The discharge at the leading edge is weaker than that at the trailing edge and is less likely to affect the copy. Therefore, if the voltage is applied only to the trailing edge, the software can be simplified.

[0012]

As described above, according to the present invention, a plate-shaped peeling discharge preventing electrode extending in the axial direction of the photoconductor is provided at the peeling point between the photoconductor and the paper, and the electrode is provided at the front and rear of the paper. By applying a voltage having a reverse polarity to the polarity at the time of transfer to the end, it is possible to prevent a line from entering the copy due to the charging history of the photoconductor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a transfer device of an electronic copying machine of the present invention.

FIG. 2 shows a peeling discharge prevention electrode, FIG. 2A is a perspective view of a first embodiment, and FIG. 2B is a perspective view of a second embodiment.

[Explanation of symbols]

1 photoconductor, 2 transfer corotron, 3 dielectric sheet,
4 paper, 5 peeling discharge prevention electrode

Claims (1)

[Claims] 1. In a transfer device of an electronic copying machine for directly transferring a toner image on a photoconductor onto a sheet through a dielectric sheet, the non-sheet surface side of the dielectric sheet facing a separation point between the photoconductor and the sheet. , A peeling discharge prevention electrode extending in the axial direction of the photoconductor with a constant gap between the dielectric sheet and a voltage having a polarity opposite to that of the transfer corotron at the timing when the leading and trailing edges of the paper pass through the peeling discharge prevention electrode. A transfer device for an electronic copying machine, which is characterized by applying a voltage.