JPH0252380A - Transfer separating electrostatic charger for image forming device - Google Patents

Abstract

PURPOSE:To obtain an image of good quality by simple constitution without any unevenness in electrostatic charging by arranging guide members so that the entire surface of a transfer material passes on a surface of one of the guide members. CONSTITUTION:Two discharging wires 4 and 4 are extended in a shield case 1 and the several guide members 51...54... are arranged in an opening surface facing an image carrier. Then the respective guide members are so arranged that an upstream-side end part of one guide member which is fitted to the shield case is nearly aligned with a downstream-side end part of an adjacent guide member. The discharging current from an electrostatic charging line is therefore affected uniformly by the guide members to the overall length of the discharging line, so the nearly uniform current is supplied to the transfer material. Consequently, the generation of an image unevenness due to a local deficiency in electrostatic charging is evaded and the image of good quality is obtained.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine or a printer, and particularly to an image forming apparatus for transferring and separating the image forming apparatus. This relates to a charger.

(Prior art and issues to be solved) A sheet-like transfer material such as paper is brought into contact with the transferable toner image formed on the surface of a moving image carrier, and at this position, a transfer charger applies an electric charge to the transfer material at I4. The I/toner image is electrostatically transferred to a transfer material, and then a separate charger applies a charge of opposite polarity to that at the time of transfer to the transfer material, and the transfer material is transferred to an image carrier. Image forming apparatuses configured to be separated from each other are conventionally well known.

In such an apparatus, the transfer material passes through a small gap formed between the surface of the image carrier and the transfer and separation charger at the transfer and separation portion described above.
Each charger usually has an opening that opens in the direction of the gap, so when a weak transfer material or a strongly curled transfer material passes through this transfer/separation area,
There is a risk that the charger may enter the charger through the opening of each charger and damage the charger or cause a jam.

In order to avoid such a situation, a structure has been proposed in which a nylon thread or a bar-shaped member is suspended in the opening of the charger to prevent the transfer material from entering.

FIG. 4 schematically shows an example of such a device.
The transfer charger and the separation charger are integrally formed by dividing the transfer charger into two parts by 2, and extending a discharge wire 13 for transfer and a discharge wire 14 for separation into each part.

A transfer material is supplied in the direction of the white arrow A between an image carrier (not shown) disposed opposite to the opening on the side of the 11-plane, and an appropriate number of transfer materials are supplied to the opening on the side of the separation charger. The bar-shaped guide members 15, 15, . . . are attached.

These members 15 divide the charger into two parts at the center in the longitudinal direction, and the members 15 of each part are arranged so as to be inclined outward at an appropriate angle θ, so that the transfer material passing through the charger is divided into two parts. I am formed so that I may not be formed.

This configuration can be expected to have a certain effect in preventing the transfer material from entering the charger, but on the other hand,
Since these members 15 are normally made of an insulating material such as synthetic resin, charges are accumulated on them by the operation of the charger and the polarity becomes the same as that of the discharge wire, so that the width W in which the guide member 15 exists is In the part, the discharge wire 14
This prevents the discharge current from flowing in the direction of the transfer material, and as a result, the portion of the transfer material that passes through the W portion becomes undercharged.
The problem was that white or black streaks appeared on the image.

FIG. 2A and FIG. 2B illustrate the influence of the above-mentioned guide member on the discharge current, and FIG. 2A shows the current change in the longitudinal direction in the charger without the guide member, and Δi The ripple rate R defined as /I p Here, Δi represents the ripple width, and Ip represents the absolute value of the current (peak-to-peak current value).

FIG. 2B shows a change in current when a guide member as shown in FIG. 4 is provided in such a 4JK electric appliance.

As can be seen from the figure, in this case, the current changes significantly locally, and the ripple rate measured in the same way as above is
R=28.6%, and especially in the case of halftone originals, image unevenness occurred depending on the presence or absence of the guide member.

In order to avoid such a situation, there are methods or means such as increasing the voltage applied to the charger or making the guide member conductive by appropriate means to avoid accumulation of charge on the guide member. However, with the former method, other parts become overcharged, which may cause retransfer and image deterioration, while with the latter method, current leakage is likely to occur. Neither method has yielded satisfactory results.

The present invention has been made in view of the current situation, and provides a transfer square charger that does not require any special accessory mechanism, has an extremely simple configuration, and is free from uneven charging and contributes to obtaining high-quality images. It is intended to be provided.

(2) Structure of the invention (technical means for solving the problem, its operation)] - In order to achieve the above object, the present invention provides a transferable toner image formed on the surface of a moving image carrier, which runs in synchronization with the transferable toner image formed on the surface of a moving image carrier. The toner image is transferred to the transfer material by the action of a transfer charger placed close to the image carrier, and then the transfer material is separated from the image carrier by a separation charger. In the forming apparatus, a plurality of guide members are disposed in the open portion of at least one of the transfer and separation chargers, and a plurality of guide members are provided in the open portion of the charger from the upstream side to the downstream side of the open portion of the charger when viewed in the traveling direction of the transfer material. The guide members are arranged so that the entire surface of the transfer material passes through the surface of one of the guide members between the guide members.

With this configuration, in an image forming apparatus configured to electrostatically transfer a transferable toner image on the surface of an image carrier to a transfer material, and further electrostatically separate the transfer material from the image carrier, When the transfer material passes through the transfer/separation charger, a discharge like - can be applied to the entire surface of the transfer material to the extent possible, thereby preventing image deterioration from occurring.

(Description of Examples) Hereinafter, examples in which the present invention is applied to a separation charger will be described.

1A, 1B, and 1C are plan views of the separation charger according to the present invention, in which two discharge wires 4, 4 are stretched inside the shield case 1, On the opening surface facing the image carrier (front side of the paper), there are several guide members 51, 52, 53, 54, etc., similar to the known ones described above.
The fist is arranged.

In the case shown in FIG. 1A, the end of one guide member attached to the shield case on the upstream side is on the downstream side of the adjacent guide member when seen in the traveling direction of the transfer material. Each guide member is arranged so as to substantially match the end of the guide member.

With this structure, the discharge current from the charging wire is influenced by the guide member over the entire length of the discharge wire, making it impossible for a substantially uniform current to reach the transfer material. can.

FIG. 1B shows a point 6 where the charging wire and the guide member spatially intersect.
are arranged on the same line as each other's guide members, so that the same effect as in the previous embodiment can be achieved.

In FIG. 1C, the intersection 6 is divided into smaller parts to further reduce the ripple of the current.

FIG. 2C shows the state of change in the discharge current of the above-mentioned separation charger according to the present invention as seen in the direction of the charging line. The results were obtained. Ripple rate R in this case
was 11.1%, which is close to the value shown in FIG. 2A without the guide member, and it was confirmed that a good image without image unevenness could be obtained in practical use.

Figures 3A and 3B show an embodiment in which a guide member attached to the shield case of the charger is integrally configured.
As shown in the diagram, an appropriate number of holes 7Φ are provided on the side of the shield case.
... is formed, and the guide member 5 is integrated as a whole by attaching its respective ends to a pair of frames 5a and 5b, each of which has projections 8... corresponding to each hole in 1. It is composed of:

Therefore, by engaging the protrusions 8 with the respective holes 7, the guide member can be easily attached to and detached from the charger.

With this configuration, it becomes easy to replace and clean the charging wires, guide members, etc., and it also becomes easy to secure the relative positions of each guide member as described above.

Although the present invention has been described above with respect to a separation charger, it is easy to understand that the present invention is not limited to this and can be applied to a transfer charger as necessary.

(3) Effect of Invention 1 As explained above, according to the present invention, in an image forming apparatus using a transfer/separation charger, the discharge current flowing in the direction of the image carrier is Since it is possible to make the image as uniform as possible over the area, it is possible to avoid image unevenness, poor separation, and retransfer due to local insufficient charging, which contributes to stable operation of the image forming apparatus and obtaining high-quality images. It's large.

[Brief explanation of the drawing]

Figures 1A to 1C are partial plan views showing an embodiment in which the present invention is applied to a separation charger, and Figure 2A shows a current distribution in the longitudinal direction of a charging wire in a charger without a guide member. Figures 2B and 2B are diagrams showing current distribution when a known guide member is installed, Figure 2C is a diagram showing current distribution when a guide member according to the present invention is installed, Figure 3A, and Figure 3B. The figure is a perspective view of a shield case and a guide member of a charger configured so that a plurality of guide members integrally formed are attached to the shield case. FIG. 4 explains the structure and operation of a known charger. It is a slope view of a part of Sudame. 1... Φ shield case, 4... charging wire, 5... guide member, 6... intersection.

Claims (1)

[Claims] A transferable toner image formed on the surface of a moving image carrier is brought into contact with a transfer material traveling in synchronization with the transferable toner image, and the toner image is transferred to the transfer material by the action of a transfer charger disposed close to the image carrier. In the image forming apparatus, a plurality of guide members are disposed in an open portion of at least one of the transfer and separation chargers. At the same time, the guide member is arranged so that the entire surface of the transfer material passes through the surface of one of the guide members between the upstream side and the downstream side of the open part of the charger when viewed in the traveling direction of the transfer material. A charger that does this.