JPH0293571A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent turbulance in a toner powder body image on a transferring material by providing an electrode to impress voltage of a reverse polarity to the toner powder inside a sealed member of a transferring means in the carrying means which comes into contact with the transferring material after separation. CONSTITUTION:The electrode 15 to impress the voltage of the reverse polarity to the toner powder is provided inside the sealed member 19 of a transferring means C2 in the carrying means 9 which comes into contact with the transferring material P after separation. Then the carrying system 9, which comes into contact with the transferring paper P which retains an unfixed powder body image and can easily give electrostatic influence, is insulated from the other members, and when the voltage received by an electrode plate 15 is impressed to the carrying system 9, a negative electric charge is injected to the backside of the transferring paper after being transferred. Thus toner offsetting phenomenon can be prevented and an image of good quality can be obtained without causing turbulence to the toner image.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus having a method of transferring a powder image on an image carrier to a transfer material using an electric field generated by a transfer means.

[Prior Art] In conventional image forming apparatuses such as electrophotographic copying machines and electrophotographic printers, the transfer of a toner powder image formed on the surface of an image bearing member such as a photosensitive drum to a transfer paper is generally performed using the above-mentioned powder. The surface of the transfer paper is brought into close contact with the image carrier through the image, and at the same time, the back surface of the transfer paper is charged with charges of opposite polarity to those of the powder image, and the electrostatic force generated by the electric field formed by this charged charge causes The powder image is attracted to the surface of the transfer paper by its electric charge. Furthermore, in order to separate the transfer paper from the surface of the image carrier, the back surface of the transfer paper is charged with a charge having a polarity opposite to that of the transfer, and the transfer paper is electrostatically separated from the image carrier. Therefore,
The charge on the back side of the transfer paper charged during transfer is neutralized after separation, or the electrostatic force between the powder image and the transfer paper is weakened due to the polar charge received during separation.

[Problem that the invention seeks to solve] However,
When the transfer paper after transfer is sent to the fixing device through the conveyance system, some of the toner is pulled onto the fixing roller because the electrostatic force between the powder image and the transfer paper is weak. This causes a toner offset phenomenon and stains the transfer paper and fixing roller.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems, and it is possible to obtain good images by preventing the above-mentioned toner offset phenomenon and preventing disturbance of the toner powder image on the transfer material. An object of the present invention is to provide an image forming apparatus that can be obtained.

[Structure of the Invention] In order to achieve the above object, the present invention forms a powder image on the image carrier by developing an electrostatic latent image on the image carrier with charged toner powder. The powder image is transferred onto the transfer material by bringing the surface of the transfer material into contact with the image carrier through the image and at the same time applying an electric charge by a transfer means having a shield member. In an image forming apparatus that separates the image carrier from the image carrier, in which a charge having a polarity opposite to that of the transfer material is applied by a separating means to separate the transfer material from the carrier, the L/ner is applied to a conveying means that contacts the separated transfer material. The present invention is characterized in that an electrode for applying a voltage of opposite polarity to the powder is provided within the shield member of the transfer means.

[Example] The present invention will be described below with reference to the drawings.

FIG. 1 shows the main parts of a dry development type electronic copying machine to which the present invention is applied. That is, a charger CI that negatively charges the surface of the photoreceptor drum 1 surrounds the photoreceptor drum 1 as an image carrier, and an optical system that forms a document image on the charged surface of the photoreceptor drum 1 ( (represented by a lens)2
, a developer 3, which is powder charged toner made of a positively charged magnetic material, is magnetically applied to an electrostatic latent image formed by charging and exposing the surface of the photoreceptor l by a sleeve 4 containing a permanent magnet therein. a developing device 5 that holds the sleeve 4 and rotates the sleeve 4 in the direction of the arrow to apply toner powder to the photoreceptor drum 1; and a paper feed roller 7 that feeds the transfer paper P to the surface of the photoreceptor drum 1 at the transfer position. , the paper is passed through the transfer guide 14 to the transfer position, and the back surface of the transfer paper P, which is the transfer material that contacts the photosensitive drum 1 via the powder image, is negatively charged, and the powder image is transferred to the transfer paper P. A transfer charger C2 for transferring the powder image to the transfer paper P, a separation charger C3 for positively charging the back side of the transfer paper P to separate the transfer paper P on which the powder image has been transferred from the photoconductor surface, and a separation charger C3 for positively charging the back side of the transfer paper P to separate the transferred transfer paper P Belt 2 wrapped around the roller to the fixing position
3, a thermal fixing system 10 that thermally fixes the powder image on the withdrawn transfer paper P onto the transfer paper, and removes residual toner on the surface of the photoreceptor drum 1. A cleaning blade 11 and a lamp 12 for removing residual charges inside the photosensitive layer of the photosensitive drum 1 are provided.
As the photosensitive drum 1 rotates clockwise, these mechanisms operate in sequence to perform an image forming operation.

The heat fixing system 10 includes a heat roller 10a equipped with a heater inside.
and a pressure roller 10b, and while the transfer paper P is bitten and conveyed to the left in FIG. 1, the powder image is fixed on the transfer paper P by the heat of the heat roller 10a.

13 is a felt pad 13 for cleaning offset toner on the heat roller 10a.

Next, in FIG. 2, 2o is a transfer charger C which is a transfer means.
FIG. 2 is an enlarged view of a transfer separation charger 20 in which a transfer separation charger c3 and a separation charger c3 serving as a separation means are integrated to make handling convenient.

16 is a transfer wire electrode for performing corona discharge and forming an electric field in the transfer charger C2, and 19 is a transfer shield that is a shield member of the transfer means for directing the electric field formed by the transfer wire 16 toward the photosensitive drum 1. The plate 21 is an insulating plate attached to the side wall of the transfer shield plate 19 in order to prevent the electric fields formed by the separation charger and the transfer charger C2 from influencing each other, and the plate 15 is an insulating plate that is attached to the side wall of the transfer shield plate 19. This electrode plate is attached to the insulating plate 21 in the form of a sheet and having its end outside the image area on the transfer charger C2 in order to receive electric discharge. 17 is a separation wire for performing corona discharge and forming an electric field in the electric device C3, and 18 is a separation wire for directing the electric field formed by the separation wire 17 toward the photosensitive drum 1. It is a separation shield plate. Reference numeral 22 denotes a transport system 9 in which the potential received by the electrode plate 15 is electrically insulated from other members.
This is an electrode plate contact plate for flowing the flow to the electrode plate, and in this embodiment, it is in contact with a contact point 24 from a conveyance system 9 (not shown).

Figure 3 is to the left (in the direction of the arrow) from the transfer wire 16 in Figure 2.
FIG.

FIG. 4 is a perspective view of the conveyance system 9 and the transfer separation charger 2o.

Now, in this embodiment, as shown in FIG. 2, the transfer charger C2
A sheet-shaped electrode plate 15 affixed to the electrode plate 15 receives the discharge from the transfer wire 16 and transmits it to the electrode plate contact plate 22 . Next, it comes into contact with the transfer paper holding the unfixed powder image, insulates the conveying system 9, which is susceptible to electrostatic influences, from other members, and removes the voltage received by the electrode plate 15 from the contact point 24 (not shown). By applying a voltage to the transport system 9 (that is, by applying a voltage with a polarity opposite to that of the toner powder), a negative charge is injected into the back surface of the transfer paper after transfer.

Therefore, the electrostatic force of the toner powder on the paper becomes stronger, and electrostatic fixing offset is reduced.

In the above embodiment, as shown in FIG. 3, the electrode plate 15 is provided with a width larger than the maximum transfer width (maximum image area) in the generatrix direction of the image carrier, but as shown in FIG. A sheet-like electrode piece 24 may be pasted on the outside of the paper width (image area). Further, the position where the electrode plate is provided is not limited to the side wall within the shield plate, but may be the bottom plate within the shield plate.

However, in the above embodiment, when the sheet-shaped electrode plate 15 or electrode piece 24 is pasted inside the transfer shield plate 19, which is the side wall of the transfer charger C2, it is possible to suppress the staining of the electrodes due to toner scattering to a minimum level. . This has the effect of eliminating variations in the potential applied to the transport system 9 due to dirt on the electrodes.

Furthermore, since the end of the electrode is not placed within the image area of the transfer charger C2, the electric field for transfer that occurs within the image area due to the electrode being placed inside the transfer charger C2 will not become unstable. Therefore, uniform transfer can be performed within the image area.

By the way, in this embodiment in Figure 2, the electrodes are pasted on the side wall of the transfer charger on the back side in the figure, but even if an insulating plate is pasted on the front side wall and the electrodes are pasted on it, the effect will not be the same. are the same.

[Effects of the Invention] As explained above, according to the present invention, an electrode for applying a voltage having a polarity opposite to that of the toner image on the transfer material to the conveying means that contacts the transfer material after separation is provided in the shield member. By providing this, it was possible to prevent the toner offset phenomenon and obtain a good image without disturbing the toner image.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an image forming apparatus showing an embodiment of the present invention; FIG. 2 is an enlarged perspective view of a transfer separation charger; FIGS. 3 and 5 are sectional views of main parts of a transfer separation charger; FIG. 4 is an enlarged perspective view of the transfer separation charger and the conveyance system. 9 is a conveying system which is a transfer material conveying means, c2 is a transfer means, C3
15.24 is an electrode, and 19 is a transfer shield plate.

Claims (1)

[Scope of Claims] (1) A powder image is formed on the image carrier by developing an electrostatic latent image on the image carrier with charged toner powder, and the powder image is transferred to the surface of the transfer material via the powder image. is brought into contact with the image carrier, and at the same time, the powder image is transferred onto the transfer material by applying an electric charge by a transfer means having a shield member, and the transfer material is separated from the image carrier. In the image forming apparatus that separates the image carrier from the image carrier, the separation means applies a charge having a polarity opposite to that of the transfer material, and the image forming apparatus includes a method for applying a voltage having a polarity opposite to that of the toner powder to a conveying means that contacts the separated transfer material. An image forming apparatus characterized in that an electrode is provided within a shield member of the transfer means. (2) The image forming apparatus according to claim 1, wherein the electrode is provided on the inner wall of the shield member of the transfer means. (3) The image forming apparatus according to claim 1 or 2, wherein the electrode is sheet-shaped. (4) The image forming apparatus according to claim 1 or 2, wherein the electrode is arranged in a direction perpendicular to the moving direction of the image carrier. (5) The image forming apparatus according to any one of claims 1 to 4, wherein the electrode has an end portion located outside the image area of the powder image formed on the image carrier by the development.