JPH06103414B2 - 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 using an electrophotographic process such as an electrophotographic copying machine and a printer.

(Problems to be solved with conventional technology) After a transferable toner image is formed on the surface of a moving image carrier, a transfer material is brought into close contact with the surface of the image carrier to electrostatically transfer the toner image to the transfer material, and then the transfer image is transferred. An image forming apparatus that separates a material from an image carrier and fixes and fixes a carried toner image on a transfer material is well known.

In this type of image forming apparatus, in order to transfer the toner adhering to the image carrier by electrostatic attraction to the transfer material, the transfer material is brought into close contact with the surface of the image carrier at the position where the toner image exists. The rear surface of the transfer material is charged with a polarity opposite to that of the toner to forcibly transfer the toner.

However, when the transfer material is charged in this manner, a charge having a polarity opposite to that of the charge of the transfer material is induced on the side of the transfer material, and the transfer material is strongly adsorbed on the transfer material and becomes difficult to separate.
Since this may cause jams, a separating charger is placed at the position after transfer, which allows the transfer material to be subjected to an AC discharge or a DC discharge having the same polarity as the toner so that the charge on the transfer material is reduced. A means for removing the attraction force with the image carrier and separating the transfer material from the image carrier by utilizing the elasticity and elasticity of the transfer material has already been widely used.

However, since paper, which is widely used as a transfer material, has its charging characteristics remarkably changed depending on the environment such as a change in humidity, it is not easy to always guarantee the optimum charge removal by the separation charger. However, since the excess and deficiency of the static elimination occur, it is not easy to always sufficiently remove the adsorption action generated between the static electricity and the image bearing member. In particular, in this type of separation means, in a region where toner does not exist between the image carrier and the transfer material, such as the front end of the transfer material, the degree of adhesion between the two is high, so the electrostatic attraction force acts strongly to separate the two. It's hard to do.

On the other hand, recently, in this type of image forming apparatus, an image forming apparatus capable of performing an area command copy in which an image of only a certain area of a document is transferred has come into practical use. In such an apparatus, especially when performing a copy in which a large non-image forming area exists on the leading end side in the traveling direction of the transfer material, the area where the toner does not exist becomes large, so that the separation from the image carrier is remarkable. It will be difficult.

The present invention has been made to cope with such a situation, and does not cause a separation failure even with respect to a transfer material having a large toner-absent portion at the tip portion as described above. An object is to provide an image forming apparatus.

(2) Configuration of the Invention (Technical Means for Solving Problems and Actions Thereof) To achieve the above object, the present invention transfers an image carrier and a toner image formed on the image carrier onto a transfer material. An image forming apparatus having a transfer charger for performing a transfer, and a separation charger to which a voltage having a polarity opposite to the charge polarity of the transfer charger is applied to separate the transfer material from the image carrier after transfer, It has a charge eliminating means for eliminating charge before transfer of the non-image area of the image carrier corresponding to the front end side of the transfer material, and stops the charging operation of the transfer charger and the separation charger with respect to the non-image area. It is characterized by

With this configuration, since the area where no toner is present at the tip of the transfer paper is not charged by the eyelids, a strong electrostatic attraction force does not act between the image carrier and the image carrier. There is no risk of separation failure.

(Description of Embodiments) The accompanying drawings are schematic side views of the essential portions showing an embodiment in which the present invention is applied to a copying machine, in which a cylindrical image carrier (photoreceptor) rotating in the direction of arrow A is shown. ) After the surface photoconductive layer is uniformly charged by the temporary charger 2, a portion corresponding to the non-image forming area is illuminated by the blank exposure device 5 by the area designation signal and the image carrier is exposed. After removing the electric charge of a part, the light image 3 is projected and an electrostatic latent image is formed only on a predetermined part. This latent image becomes a toner visible image by the developing device 4, and then a copying material (not shown) supplied through the passage 6 comes into close contact with the toner visible image at the position of the transfer charger 7.
The transfer material is charged with a polarity opposite to that of the toner by the transfer charger 7, and the toner image on the photoconductor is transferred to the transfer material side.

Next, the separation charging device 8 applies an AC discharge or a DC discharge having the same polarity as that of the toner to the transfer material to gradually charge the transfer material to electrostatically adsorb the transfer material and the photoconductor. It is assumed that the transfer material is separated from the photoconductor by the repulsive elasticity of the transfer material itself against the curved surface of the photoconductor where the force is removed, and is fed to the fixing portion (not shown) by the conveying means 10.

In such a case, in the present invention, the blank exposure device 5 is connected to the transfer charger 7 and the separation charger 8 via a high-voltage control device 9, and the tip end of the transfer material, for example, 20
When a blank area of mm or more is formed by an image forming area designating operation, the blank area is not energized while passing over the transfer and separation chargers 7 and 8, and the image area is not transferred. It is configured to discharge when it reaches.

As a result, the blank portion at the front end of the transfer material is not charged, and as described above, there is no electric charge at the portion corresponding to the front end of the transfer material of the image carrier. The electrostatic suction force does not act between them, and the portion where toner does not exist can be easily separated, and the occurrence of jam can be avoided.

In the above embodiment, when the separate charger is not subjected to DC discharge, the charger does not have a function of charging the transfer material. In this case, therefore, only the discharge timing of the transfer charger should be controlled. The same effect can be obtained.

(3) Effect of the Invention As described above, the present invention provides a transfer material leading edge portion and a portion corresponding to that of the image bearing member when a blank portion is present at the transfer material leading edge by designating the image forming area. In each case, there is no charge and there is no adsorption action with the image carrier, so that the transfer material can always be easily separated.

[Brief description of drawings]

The accompanying drawings are schematic side views of essential parts of an embodiment in which the present invention is applied to a copying machine. 1 ... Photosensitive member, 2 ... Primary charger, 4 ... Developing device, 5 ...
... Blank exposure device, 7 ... Transfer charger, 8 ... Separation charger, 11 ... Cleaning device, 9 ... High voltage controller

Claims (1)

[Claims] 1. An image carrier, a transfer charger for transferring a toner image formed on the image carrier to a transfer material, and the transfer charging for separating the transfer material from the image carrier after transfer. In an image forming apparatus having a separation charging device to which a voltage having a polarity opposite to the charging polarity of the image carrier is applied, a charge removing means for removing charge from a non-image area of the image carrier corresponding to the leading end side of the transfer material is provided before transfer. An image forming apparatus, which has the charging operation of the transfer charger and the separation charger with respect to the non-image area.