JPS6275688A - Electrostatic separating device - Google Patents

Abstract

PURPOSE:To stabilize separation of transfer materials and to improve the stability of images by setting a ratio of intervals of front ends of destaticizing needles of a destaticizing needle array to the distance between front ends of destaticizing needles and an image carrier to a prescribed range. CONSTITUTION:Transfer paper P is sent onto a photosensitive body 1 by a paper feeding roll 9 and a resist roll 10 which is rotated at such timing that it resists an image on the photosensitive body 1, and the toner image on the photosensitive body 1 is transferred onto the transfer paper by a transfer charger 2. Thereafter, the transfer paper P is separated from the photosensitive body 1 by destaticizing needles 4 and is led to a fixing device 12 by a guide 11 and has the toner image fixed and is ejected onto a tray 14 by a paper eject roll 13. In this case, the pitch of front ends of destaticizing needles of the destaticizing needle array is set to <=1/4 and >=1/20 of the distance between front ends of destaticizing needles and the image carrier, thereby improving the stability of separation of the transfer material and the stability of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus, particularly an electrostatic transfer material S device for an electrostatic transfer type image forming apparatus.

2. Description of the Related Art Image forming apparatuses that are commonly used today uniformly charge a photoreceptor, then perform image forming lightning to create an electrostatic latent image, and deposit charged toner particles onto the photoreceptor.
After development, a transfer material (for example, paper) is brought into close contact with the photoreceptor, and a corona with a polarity opposite to that of the toner particles before transfer is irradiated from the back of the transfer material to transfer the toner particles on the photoreceptor to the transfer material. The configuration is such that the image is transferred, the transfer material is then separated from the photoreceptor, and the transfer material is sent to a fixing device.

In an image forming apparatus having the above configuration, in the process of irradiating corona from the back side of the transfer material and performing electrostatic transfer, electrostatic adhesion occurs between the transfer material and the photoreceptor.
The transfer material comes into close contact with the surface of the photoreceptor. Therefore, a separating means is required to separate the transfer material from the surface of the photoreceptor. Conventionally used separation means include mechanical methods,
There are separation claws, separation belts, etc. However, these methods have drawbacks such as the risk of missing a part of the image or damaging the photoreceptor. Other separation methods include blowing an air stream and suctioning the transfer material, but these methods require a large-scale installation and structure, and also have the disadvantage of causing toner scattering inside the machine. . Further, as another separating means, there is also a means for electrostatically separating the transfer material by providing a separation charger to eliminate static electricity from the transfer material from the back side of the transfer material. This method neutralizes the electrostatic attractive force between the photoreceptor surface and the paper, eliminates the adhesion force, and uses the transfer material's own weight and stiffness to allow the transfer material to separate naturally, making it possible to obtain satisfactory separation. It is. However, this method requires a high-voltage power source separate from the transfer source for separation, which is disadvantageous in terms of cost and volume, which is disadvantageous in terms of miniaturization and cost reduction of the device.

Furthermore, if the distance between the tips of the static eliminating needle rows is wide, there is a gap between the tips of the static eliminating needles and the photoreceptor, such as when the transfer material passes, so some parts are static neutralized and others are not, which stabilizes the separation of the transfer material. In addition, charge memory may occur in the photoreceptor depending on whether or not static electricity is removed, resulting in unevenness in one image. On the other hand, if the above-mentioned interval is narrow, discharge may be suppressed and the separation of the transfer material may lack stability.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the above-mentioned conventional examples and provides an electrostatic separation device that is small in size and has good transfer material conveyance.

The main components of the present invention capable of achieving the above object are h) an electrostatic separation device that develops an electrolytic layer image, electrostatically transfers the developed image onto a transfer material, and then removes the charge and separates the transfer material from the image carrier; In this electrostatic separation device, an array of static eliminating needles is provided in the forward direction of the transfer material traveling direction in the vicinity of the transfer charger, and an appropriate relationship between the array interval and the distance from the tips of the static eliminating needles to the image carrier is set.

Example The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a partial explanatory diagram of the separating device of the present invention, in which numeral 1 denotes an image carrier, and a transfer charger 2 is provided at a paper passing path with a gap.

Needle-shaped charge eliminating needles 4 are arranged in the generatrix direction of the image carrier 1 from the transfer charger to the front in the direction in which the transfer material moves, with an insulator 3 interposed therebetween. The application is to apply the polarity of the toner before transfer (■ in the figure) and the opposite polarity (C)) to the transfer corona wire, and apply the same polarity (■) as the toner to the static elimination needle. be.

If the distance between the tip of the static eliminating needle and the image carrier is a, and the pitch between the tips of the static eliminating needle is b, and b > 174 a, uneven static elimination will occur, resulting in a lack of stability in separation, and transfer corona will cause residual potential to increase over time. When using a photoconductor such as OPC that increases
Non-irradiated areas are affected. Figure 2 shows this phenomenon in terms of the surface (latent image) potential of the photoreceptor.As the photoreceptor, which has an initial VL value, progresses in image formation durability, the static-eliminating irradiated area becomes photosensitive with a VL value. The non-irradiated area has a photosensitive property showing a V''L value. Therefore, especially when an intermediate light amount r is applied, a latent image potential of ΔV is generated in the irradiated area and the non-irradiated area in the direction of movement of the photoreceptor, and a streak-like pattern is formed after development. This results in an uneven image.

Further, when b < 1/20 a, an interference state occurred in which discharge was suppressed between the tips of the static elimination needles, resulting in a lack of stability in separation due to insufficient static elimination.

From the above points, from the separation stability and image stability, a/20≦
It was found that b≦a/4 is appropriate.

FIG. 3 is an explanatory diagram of an image forming apparatus to which the separating device of the present invention is applied. Reference numeral 5 denotes a document mounting table made of a transparent member, which reciprocates in the horizontal direction. Reference numeral 6 denotes a short-focus small-diameter imaging element array, and an original image placed on an original table is slit-exposed onto the photoreceptor 1. Although the photoreceptor 1 is shown as a photoreceptor drum, it may also be an endlessly moving belt. A charger 7 charges the photoreceptor 1 uniformly. The uniformly charged photoreceptor 1 is exposed to an image by an element array to form an electrostatic image. Next, the image is visualized by the developing device 8.

On the other hand, the transfer paper P is fed onto the photoreceptor 1 by a paper feed roller 9 and a registration roller 10 that rotates in time to register the image on the photoreceptor 1, and then transferred onto the photoreceptor 1 by a transfer charger 2. toner image is transferred onto the transfer paper.

Thereafter, the transfer paper P is separated from the photoreceptor 1 by the static elimination needle 4, guided to the fixing device 12 by the guide 11, and after the toner image on the transfer paper P is fixed, the paper is discharged to the tray 14 by the paper discharge roller 13. . Here, photoreceptor 1. The charger 7, the developing device 8, and the cleaning device 15 may be integrated into a process kit that can be attached to and detached from the main body, and maintenance may be simplified by integral replacement.

In an example using the above image forming apparatus, the distance between the transfer wire and the 30φ photosensitive drum was set to 9 mm, and C) 5.5 KV was applied to the transfer wire. The shunt conditions at this time are ■3, OKV applied to the static elimination needle, a=7, 5mm, b=
l, Omm, when no transfer voltage is applied at room temperature and humidity, there is no discharge current from the static elimination needle, and when a transfer corona occurs, the surrounding impedance changes and the discharge current from the static elimination part is increased. Observed. In particular, a peak-like static elimination current was observed at the moment when the leading edge of the transfer material reached the static elimination section, and good separation and transferred images were obtained, with no image unevenness similar to photosensitive drum memory.

As described in detail, the present invention uses static eliminating needles as a static eliminating means, and arranges the static eliminating needles at an appropriate distance from the photoconductor, thereby achieving good separation of the transfer material and transfer image. It is possible to obtain the following properties and to obtain durability stability of the photosensitive drum.

[Brief explanation of drawings]

FIG. 1 is a diagram of a separating device of the present invention, FIG. 2 is a characteristic diagram of a photosensitive drum, and FIG. 3 is a sectional view of a copying machine to which the separating device of the present invention is applied. i--1 image carrier (photosensitive drum) 2--1 transfer charger 4--1 static elimination needle

Claims (1)

[Claims] In an electrostatic separation device that develops an electrostatic latent image, electrostatically transfers the developed image onto a transfer material, and then removes the charge and separates the transfer material from the image carrier, static electricity is removed in the forward direction of the transfer material near the transfer charger. An electrostatic separation device comprising a needle array, and an interval between the tips of the static eliminating needles of the static eliminating needle array is 1/4 or more and 1/20 or more of the distance between the static eliminating needle tips and the image carrier.