JPH0636116B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus utilizing an electrostatic transfer process such as an electrostatic copying machine and a printer.

(Problems to be Solved by Prior Art) A sheet-shaped transfer material, mainly paper, is brought into contact with a toner image formed of charged toner on the surface of an image carrier, and the transfer material is charged with a charge having a polarity opposite to that of the toner. In a well-known image forming apparatus in which a toner image is transferred onto a transfer material by electrostatic charge, it is electrostatically adsorbed to the image carrier after transfer by the charge obtained during transfer, so it is necessary to positively separate it. is there.

As a separating device for this, mechanical separating means,
A number of electrostatic separation means have been proposed, but with the recent miniaturization of the image forming apparatus, and accordingly, the diameter of the image carrier which is housed in the image forming apparatus and which is normally formed in the shape of a rotating cylinder, is reduced, the image carrier is reduced. From the viewpoint of demands for downsizing of image forming members arranged in the periphery, a wide range of devices in which a discharging needle is implanted in a supporting member made of an insulating material such as synthetic resin has been put into practical use.

This type is convenient because it is extremely small, but the charge of the opposite polarity is applied to the transfer material having a charge of a predetermined polarity to neutralize the charge of the transfer material, and then the transfer material itself loses its own weight and strain. Therefore, the separating action may be insufficient due to the environment such as humidity and the characteristics of the transfer material itself.

Further, as described above, since the separation device itself is small,
Inevitably, it will be close to the discharge wire of the adjacent transfer charger.In a high humidity environment, the resistance of the transfer material will decrease, and the separation current will reach the transfer site and interfere with the transfer action, resulting in image deterioration. It could happen.

The present invention has been made in order to cope with such a situation, and provides an image forming apparatus capable of stably obtaining a good charge eliminating action under any environment while maintaining the simplicity of the configuration itself. It is intended to be provided.

(2) Structure of the Invention (Technical Means for Solving the Problems) In order to achieve the above object, in the present invention, a transfer charger for transferring an image formed on an image carrier to a transfer material,
In an image forming apparatus having a charge eliminating electrode provided on the downstream side of the transfer charger in the transfer material moving direction for eliminating charge, the charge eliminating electrode is provided in the vicinity of a position facing the transfer material and is resistant to moisture absorption. Of the variable resistance member grounded, and the static elimination current by the static elimination electrode changes according to the moisture absorption state of the variable resistance member.

The transfer material can be stably discharged regardless of changes in the environment.

(Explanation of Embodiments) FIG. 1 is a side view of a main part of an implementation order showing a case where the present invention is applied to a copying machine having a rotating cylindrical photoreceptor 1. A transfer charger 3 is provided.

The transfer paper P travels in the direction of the arrow through the transport path 2 and contacts the toner image on the surface of the photoconductor at the transfer portion where the charger 3 is present to travel synchronously.

A high voltage is applied to the discharge wire arranged in the charger 3 by the high voltage power source 4, whereby charges having the opposite polarity to the toner are applied to the transfer paper P, and the toner image on the photoconductor is transferred to the transfer paper.

A separating device 5 including a supporting member 5a made of an insulating material and a discharging needle 5b integrally attached to the supporting member 5a is disposed downstream of the charger 3 in the running direction of the transfer paper.

The tip of the charge eliminating needle is located at a position close to the transfer sheet that projects outward and travels, and a high voltage having the same polarity as the toner is applied by the power source 6.

Therefore, the transfer paper that has completed the transfer and approaches the charge removal needle is given an electric charge of the opposite polarity to that at the time of transfer, and the attraction force of the transfer paper to the photoconductor is canceled to separate the transfer paper from the photoconductor. Will be transported to the next step.

In such a case, in the present embodiment, the resistance between the transfer charger 3 and the separating device 5 is the second depending on the humidity.
A variable resistance plate 7 that changes as shown in the drawing is arranged.

As the variable resistance plate, for example, polyethylene with 0.5 to 1.0 of dihydroxyethyllaurylamine as an activator is used.
What was kneaded with PHR can be used.

When the variable resistance plate has high resistance, that is, when the humidity is low, the separation state changes as shown in Table 1 depending on the paper type.

This table shows a paper with a width of 30 mm and a length of 100 mm at 15 ° C and 10%
RH, CLARK STIFFNESS TEST made by Kumagai Riki Kogyo Co., Ltd.
It is measured by ER, and the smaller the value is, the more difficult it is to separate.

Next, "Table-2" shows the relationship between the separability and the static elimination current when the paper was run in parallel to the skies.

From the above results, it is understood that a considerable amount of static elimination current is required to separate thin paper such as 40 g / m ² at low humidity. Further, there is a possibility that transfer defects may occur at high humidity (Table-
3).

This is because the static elimination current entered the transfer area through the transfer paper having the reduced resistance, and the transfer strength was substantially reduced.

In this embodiment, as described above, since the variable resistance plate is disposed adjacent to the separating device, it operates so as to promote the desired separating action as described above when the humidity is low, and the variable resistance plate is operated when the humidity is high. Since the variable resistance plate has a low resistance, the static elimination current does not dissipate to the plate and reach the transfer site, so that the transfer omission does not occur. That is, the static elimination current by the static elimination needle changes according to the moisture absorption state of the variable resistance plate.

The resistance value of the resistance plate can be set as appropriate, but as an example, the static elimination bias is 3.0 kv 125 μA,
When the discharge resistance is 2.4 × 10 ⁷ , the humidity is preferably set to 1 × 10 ⁷ Ω or less at a humidity of 80% or more.

Further, about 1.0 PHR of dihydraxyethyllaurylamine was kneaded into polyethylene so that the humidity was 10 ¹⁰ Ω at a humidity of 50% and 10 ¹³ Ω at a humidity of 25% to form a plate having a thickness of 1 mm.

That is, by determining the structure of the variable resistance plate so that the discharge resistance value becomes equal to or less than the above-mentioned discharge resistance value at high humidity, a stable separation function can be obtained at low humidity and a good quality transferred image can be obtained at high humidity.

FIG. 3 shows another embodiment, and parts corresponding to those of the above embodiment are designated by the same reference numerals.

In this case, the variable resistance plate 7 is sandwiched between the support member 5a made of an insulator and the shield case 3b of the charger, and these are fixed by the screw 8, and the charge elimination needle 5b is bonded to the support member 5a. It is fixed.

With this configuration, the same operation as that described above can be obtained, the structure is simplified, and the cost can be reduced.

The case where the present invention is applied to a copying machine has been described above.
Of course, the present invention is not limited to this, and can be applied to other image forming apparatuses.

(Advantages of the Invention) Since the present invention has the constitutional effect described above, a stable charge eliminating action is always obtained regardless of environmental changes, and a high-quality image is obtained without causing transfer defects. It is possible.

[Brief description of drawings]

FIG. 1 is a side view of an essential part showing an embodiment in which the present invention is applied to a copying machine, FIG. 2 is a graph showing characteristics of materials of a variable resistance plate used in the present invention, and FIG. 3 is another embodiment. FIG. 3 is a perspective view and a side view of a main part, respectively. 1 ... Photoreceptor, 3 ... Transfer charger, 5 ... Separator, 7
...... Variable resistance plate.

Claims (1)

[Claims] 1. A transfer charging device for transferring an image formed on an image bearing member onto a transfer material, and a charge eliminating electrode provided on the downstream side of the transfer charging device in the transfer material moving direction for discharging the transfer material. In the image forming apparatus, the static elimination electrode has a grounded variable resistance member which is provided in the vicinity of the position facing the transfer material and whose resistance changes depending on the moisture absorption state. The static elimination is performed according to the moisture absorption state of the variable resistance member. An image forming apparatus characterized in that the static elimination current by the electrodes changes.