JPS61212871A - Transfer separating device - Google Patents

Abstract

PURPOSE:To separate easily without fail a transfer material by specifying a picture forming area and stopping at least the discharging of a transfer electrostatic charger until a blank area passes through the transfer/separation electrostatic charger, when the blank area lies on the tip of the transfer material. CONSTITUTION:After a photosensitive drum 1 rotating in the direction an an arrow A is uniformly charged by a primary electrostatic charger 2, by means of a blank exposing device 5 an electric charge in a non-picture forming area is removed by a blank exposure device 5 with the aid of an area specifying signal from a high voltage controller 9. Then an optical image 3 is projected in the prescribed part to form an electrostatic latent image, which is developed by a developing unit 4. Then the transfer material is supplied through a path 6. The transfer electrostatic charger 7 impresses an electrostatic charge of the polarity reverse to a toner to the transfer material and the toner image is transferred on the transfer material. Next, the reoparation electrostatic charger 8 executes AC discharging to the transfer material, or impresses the DC discharging of the same polarity as the toner, and the electrostatic attraction of the photosensitive drum 1 to the transfer material is released. However, until a picture non-forming area passes through the electrostatic chargers 7 and 8, the transfer electrostatic charger 7 will not discharge at least to eliminate the electrostatic attracting action of the drum 1 to the transfer material, thereby separating said material easily without fail.

Description

[Detailed Description of the Invention] (1) Purpose 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 or a printer, and in particular to a transfer material transfer separation device thereof. It is.

(Prior art and issues to be solved) After forming a transferable toner image on the surface of a moving image carrier, a transfer material is brought into close contact with this, the toner image is electrostatically transferred to the transfer material, and then this transfer 2. Description of the Related Art Image forming apparatuses that separate a material from an image carrier and fix and fix a carried toner image on a transfer material are conventionally 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 is present. The back surface of the transfer material is charged with a polarity opposite to that of the toner, so that the toner is forcibly transferred.

However, when the transfer material is electrically charged in this way, charges of opposite polarity to the charges on the transfer material are induced on the image carrier side, and the image carrier is strongly attracted to the image carrier, making it difficult to separate.
To avoid this, a separation charger is placed at the post-transfer position to apply an AC discharge to the transfer material or a DC discharge of the same polarity as the toner to neutralize the charge on the transfer material. This removes the adhesion force with the image carrier and improves the elasticity of the transfer material.

Means for separating the transfer material from the image carrier by utilizing the stiffness of the image bearing member are already widely used.

However, the charging characteristics of paper, which is widely used as a transfer material, change significantly depending on the environment, especially changes in humidity. Therefore, it is not easy to always sufficiently remove the adsorption effect that occurs between the image carrier and the image carrier. In particular, in this type of separation means, in areas where there is no toner between the image carrier and the transfer material, such as at the leading edge of the transfer material, the degree of adhesion between the two is high, so the electrostatic adsorption force acts strongly to separate them. It's difficult.

On the other hand, in recent years, among this type of image forming apparatuses, image forming apparatuses that are capable of area-directed copying in which an image of only a certain area of a part of a document is transferred have come into practical use. In such a device, especially when copying is performed where there is a large non-image forming area on the leading edge of the transfer material in the running direction, separation from the image carrier may be significant because the area where no toner exists becomes large. It becomes difficult.

The present invention has been made to deal with such a situation, and is designed to prevent separation defects from occurring even with the transfer material, such as the thick toner-free area at the tip as described above. The purpose of the present invention is to provide an image forming apparatus that can be used as an image forming apparatus.

(2) Structure of the invention (technical means for solving the problems and their effects) In order to achieve the above object, the present invention particularly focuses on image formation in which there is a non-image forming area at the leading end of the transfer material. In carrying out the work, the transfer charger and the separation charger are configured to discharge when the area passes through the transfer separation site of the image forming apparatus.

With this configuration, the area at the leading edge of the transfer paper where no toner is present is not charged at all, so strong electrostatic adsorption force does not act between it and the image carrier, and separation is prevented. There is no risk of causing defects.

(Description of the Embodiment) The accompanying drawing is a schematic side view of the main parts showing an embodiment in which the present invention is applied to a copying machine, and shows an image carrier (photosensitive material) formed in a cylindrical shape rotating in the direction of arrow A. Body) After the surface photoconductive layer is uniformly charged by the primary charger 2, a blank exposure device 5 irradiates a portion corresponding to a non-image forming area according to an area designation signal to remove the charge in the portion, resulting in a halo image. 3 is projected and an electrostatic latent image is formed only at a predetermined location.

This latent image becomes a toner image by the developing device 4, and then a transfer material (not shown) supplied through a passage 6 comes into close contact with the toner image at the position of the transfer charger 7, and the transfer material is attached to the transfer charger. 7, the photoreceptor is charged with a polarity opposite to that of the toner, and the toner image on the photoreceptor is transferred to the transfer material side.

Next, the separation charger 8 applies an AC discharge or a DC discharge of the same polarity as the toner to the transfer material to eliminate the charge on the transfer material and remove the electrostatic adhesion between the transfer material and the photoreceptor. It is assumed that the transfer material is separated from the photoreceptor due to the repulsive elasticity of the transfer material itself against the curved surface of the photoreceptor and is fed to a fixing site (not shown) by a conveying means]0.

In such a device, in the present invention, the blank exposure device 5 and the transfer charger 71 and the separation charger 8 are connected via the high voltage control device 9, and the leading edge of the transfer material, for example, a blank area of 20 wtb or more, is is formed by the image forming area designation operation, the blank area is not energized while it passes over the transfer 9 separation charger 7.8, and the discharge is turned off when the image area reaches the transfer site. Configure it to apply.

As a result, the blank area at the leading edge of the transfer material is not charged even more, so no electrostatic suction force acts between the transfer material and the photoreceptor, and the portion where no toner is present can be easily separated. This also makes it possible to avoid jamming.

In the above embodiments, if DC discharge is not performed in the separation charger, the charger has no function of charging the transfer material, so in this case, only the discharge timing of the transfer charger is controlled. A similar effect can be obtained by

(3) Effects of the Invention As described above, when an image forming area is designated and a blank area exists at the leading edge of the transfer material, the present invention does not apply electric discharge to the area by the transfer two-separation charger. Therefore, there is no electric charge in that part and there is no adsorption effect between it and the image carrier, so that the transfer material can always be easily separated.

[Brief explanation of the drawing]

The accompanying drawing is a schematic side view of the main parts of an embodiment in which the present invention is applied to a copying machine. 1...Photoreceptor, 2...-Charger, 4...Developer, 5
...Blank exposure device, 7...Transfer charger, 8...
Separation charger, 11...Cleaning device, 9...High pressure control device

Claims (1)

[Claims] When forming an image by commanding an image area, if the non-image forming area is on the leading edge side of the transfer material, at least the transfer charger of these chargers is used until the non-image forming area passes through each charger for transfer separation. A transfer separation device that stops the discharge of