JPH0740158B2 - Electrostatic separator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an electrostatic separation apparatus for a transfer material of an electrostatic transfer type image forming apparatus.

2. Description of the Related Art Today's widely-used image forming apparatus uniformly charges a photoconductor, then forms an electrostatic latent image by performing image forming lightning, and attaches charged toner particles onto the photoconductor.
After the development, a transfer material (such as paper) is brought into close contact with the photoconductor, and a corona having a polarity opposite to that of the toner particles before the transfer is irradiated from the back surface of the transfer material to expose the toner particles on the photoconductor to the transfer material. The transfer material is transferred, then the transfer material is separated from the photoreceptor, and the transfer material is sent to the fixing device.

In the image forming apparatus having the above configuration, in the process of irradiating the corona from the back surface of the transfer material and electrostatically transferring, electrostatic attraction occurs between the transfer material and the photoconductor,
The transfer material adheres to the surface of the photoconductor. Therefore, a separating means for separating the transfer material from the surface of the photoconductor is required. As a separation method that has been conventionally used, as a mechanical method,
There are separation claws and separation belts. However, these means have drawbacks such as a lack of a part of the image and a risk of damaging the photoreceptor. Further, as another separating means, there are a method of blowing an air flow, a method of sucking a transfer material, and the like, but there are drawbacks that the apparatus configuration becomes large and scattering of toner and the like occurs in the apparatus. Also,
As another separating means, there is also a means for electrostatically separating the transfer material by providing a separation charger and removing the charge from the back surface of the transfer material. This method neutralizes the electrostatic attraction between the surface of the photoconductor and the paper, eliminates the attraction, and naturally separates using the transfer material's own weight and waist, and it is possible to obtain satisfactory separation. Is. However, a separate high-voltage power supply is required for the separation, which is disadvantageous in terms of cost and volume, which is inconvenient in terms of downsizing and cost reduction of the device.

In addition, if the distance between the tips of the charge eliminating needles is widened, there is a gap between the charge eliminating needle tips and the photoconductor to allow the transfer material to pass therethrough. There is a case where the image has unevenness and an image unevenness occurs due to the presence or absence of charge removal in the photosensitive member due to the presence or absence of charge removal. On the contrary, if the interval is narrow, the discharge may be suppressed and the separation of the transfer material may not be stable.

SUMMARY OF THE INVENTION The present invention eliminates the above-mentioned drawbacks of the prior art and provides a small-sized electrostatic separation device which is excellent in transfer material transfer.

The main constitution of the present invention which can achieve the above object is an electrostatic separation device for transferring an image formed on a photoconductor to a transfer material and then removing the charge from the transfer material to separate the transfer material from the photoconductor. The static elimination member includes a plurality of discharge tips that face the body and extend in a direction intersecting the transfer material transport direction, and the static elimination member is applied with a voltage, and the gap between adjacent discharge tips of the plurality of discharge tips. There is an electrostatic separation device, wherein the at discharge tip and the distance between the photoconductor _^1/4 or less _^1/20 or more.

Examples Hereinafter, details of the present invention will be described with reference to the drawings.

FIG. 1 is a partial explanatory view of a separating device of the present invention, in which an image carrier 1 has a transfer charger 2 having a gap in a sheet passing path.
Needle-shaped charge elimination needles 4 are arranged in the generatrix direction of the image carrier 1 from the transfer charger to the front in the traveling direction of the transfer material via the insulator 3. The applied bias applies the polarity () opposite to the polarity (in the figure) of the visible image toner before transfer to the transfer corona wire,
The same polarity () as that of the toner is applied to the charge elimination needle.

If the distance between the tip of the charge eliminating needle and the image carrier is a, and the pitch of the tip of the charge eliminating needle is b and b> 1 / 4a, unevenness of the charge eliminating needle may occur, resulting in lack of stability of separation, or residual potential due to transfer corona. When a photoconductor such as OPC which increases with durability is used, the irradiation corona of the charge removal is less affected by the transfer corona, and the non-irradiation part is affected. This phenomenon is shown by the surface (latent image) potential of the photoconductor in FIG. 2. As the photoconductor having the initial V _L value progresses in image forming durability, the static elimination irradiation unit exhibits the V ′ _L value. As a result, the non-irradiated portion has a photosensitive characteristic showing a V ″ _L value. Therefore, when an intermediate light amount E ′ is applied, a latent image potential difference ΔV between the irradiated portion and the non-irradiated portion is generated in the direction perpendicular to the photosensitive member moving direction. However, a streaky uneven image is formed after development.

Further, when b <1 / 20a, the discharging needles suppress the discharge between the tips of the discharging needles, but an interference state occurs, and the separation is unstable due to insufficient discharging. From the above points, it was found that a / 20 ≦ b ≦ a / 4 is appropriate from the viewpoint of separation stability and image stability.

FIG. 3 is an explanatory view of an image forming apparatus to which the separating apparatus of the present invention is applied, and 5 is an original placing table made of a transparent member, which reciprocates in the horizontal direction. Reference numeral 6 denotes a short-focus small-diameter image-forming element array, and an original image placed on the original placing table is slit-exposed on the photoconductor 1. Although the photoreceptor 1 is shown as a photosensitive drum, it may be a belt that moves endlessly. A charger 7 uniformly charges the photosensitive member 1. An image of the uniformly charged photoconductor 1 is exposed by an element array to form an electrostatic image. Next, it is visualized by the developing device 8.
On the other hand, the transfer paper P is fed onto the photoconductor 1 by the paper feed roller 9 and the registration roller 10 which rotates at a timing such that the image on the photoconductor 1 is registered, and is then transferred onto the photoconductor 1 by the transfer charger 2. The toner image is transferred onto the transfer paper. After that, the transfer paper P is separated from the photoconductor 1 by the charge elimination needle 4, guided to the fixing device 12 by the guide 11, and after the toner image of the transfer paper P is fixed, it is discharged to the tray 14 by the paper discharge roller 13. . Here, the photoconductor 1, the charger 7,
The developing device 8 and the cleaning device 15 may integrally form a process kit that can be attached to and detached from the main body, and the maintenance may be simplified by integral replacement.

As an example of the image forming apparatus, the distance between the transfer wire and the photosensitive drum of 30φ is set to 9 mm, and the transfer wire is set to 5.5 mm.
KV was applied. When the separation conditions at this time were 3.0 KV applied to the static elimination needle, and a = 7.5 mm and b = 1.0 mm, the discharge current from the static elimination needle was smooth when the transfer voltage was not applied at room temperature and normal humidity. When transfer corona occurs, the surrounding impedance fluctuates and the discharge current is observed from the static elimination needle. In particular, at the moment when the leading edge of the transfer material reached the charge eliminating portion, a peak charge eliminating current was observed, good separability and a transferred image were obtained, and image unevenness like a photosensitive drum memory did not occur.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is preferable to use a charge eliminating member having a plurality of discharge tips as the charge eliminating means, and to arrange the discharge tips adjacent to the image carrier at an appropriate distance with proper intervals. The separation property of the transfer material and the transferred image can be obtained, and the durability stability of the photosensitive drum can be obtained.

[Brief description 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. 1 ... Image carrier (photosensitive drum) 2 ... Transfer charger 4 ... Charge elimination needle

Claims (1)

[Claims] 1. An electrostatic separator for transferring an image formed on a photoconductor onto a transfer material, and then removing the charge from the transfer material to separate the transfer material from the photoconductor. A discharge member having a plurality of discharge tips extending in a direction intersecting the direction, and a voltage is applied to the discharge member, and a distance between adjacent discharge tips of the plurality of discharge tips is the discharge tip and the photoconductor. An electrostatic separation device characterized in that it is 1/4 or less and 1/20 or more of the distance from.