JPS6115161A - Image forming device - Google Patents

Abstract

PURPOSE:To dissolve an uneven image caused by a residual toner without executing special cleaning by placing a corona ion flow control screen in am opening part for irradiating corona ions or its vicinity of an electrifying device serving as a corona discharger. CONSTITUTION:As for a toner which is not transferred by a transfer device 5 but left on a photosensitive surface 12, its surface charge is eliminated by a destaticizing lamp 6, and it is sent to an electrifying device 2 again in a state that the residual toner remains adhering. A high voltage is applied to a corona wire 9 of the electrifying device 2 from a power source 10 and a wire side of a corona ion flow control screen 13 is electrified to positive by generated corona ions. In this case, a line of electric force as indicated with an arrow of a dotted line is generated in a gap part of the screen 13, and the corona ions generated from the wire 9 are accelerated along the line of electric force and goes toward the photosensitive surface 12. Accordingly, a high potential is applied from an area in which no residual toner exists, the residual toner is removed after passing through a developing and cleaning device 4, the potentials of all areas become the same level, and an uneven density of an image can be eliminated.

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to image formation in electronic copying devices and the like.

In particular, the present invention relates to an image forming apparatus that performs cleaning at the same time as development using a developing/cleaning device.

[Prior art]

In an image forming apparatus that has a developing and cleaning device, when copying onto transfer paper that is longer than the circumference of the photoreceptor 1-ram, it is necessary to rotate the photoreceptor 1 ram two or more times for - sheets of transfer paper. . Therefore, the 1-toner on the photosensitive surface that was not completely transferred by the transfer device during the first rotation of the ram remains in area B as shown in FIG. The region W where there is no charge has a slight potential V+ even after the charge is removed by the charge removal lamp. However, the FF4 region B has an additional voltage ■2 due to the discharge that fills the transfer device. Figure (b) shows this at this time. In this state, as shown in fcl in the same figure, if a positively charged corona discharge is performed by the charger 1, the corona ions have the same polarity as the residual potential, so the area where the lines of electric force are weak is shown. As shown in fdl in the figure, both regions B and W have approximately the same potential (3), and in particular, the edge portion has a lower potential than (2).

Furthermore, when the residual toner is removed using the developing/cleaning device J and 1, the potential distribution becomes as shown in the figure (e), and the image transferred to the transfer paper by the transfer device has an image density as shown in the figure (fl). Therefore, the influence of residual toner from the first rotation of one ram of five photoreceptors appears as density unevenness in the copied image during the second rotation.

Conventionally, in order to solve this problem, the initial surface potential of the photosensitive surface is set higher than the saturated image density potential in consideration of the potential drop due to residual toner.

That is, as shown in FIG. 2, the initial surface potential of the photosensitive surface is set to 4, and the potential 5 when the residual toner is removed becomes the saturated image density potential V[, which becomes 1゛6. This is intended to prevent the effects of image unevenness due to residual toner on the transfer paper.

[Problems with conventional technology]

The conventional method of trying to solve the potential unevenness caused by residual toner by increasing the initial surface potential is initially possible, but as the copying operation continues, the developing ability decreases and the saturated image density potential v6 increases. , If the potential exceeds 5, image unevenness will appear.

Also, if you require halftone as a copy image,
Traditional methods provide no solution.

[Purpose of the invention]

The present invention has been developed in view of the above-mentioned conventional drawbacks! It is an object of the present invention to provide an image forming apparatus that prevents a decrease in surface potential due to residual l/ner without increasing the initial surface potential of three optical surfaces, and prevents density unevenness in a copied image.

[Key points of the invention]

In order to achieve the above object, the present invention uses an image carrier having a circumference shorter than the maximum transfer paper used, and includes at least a charging device and an exposure device around the image carrier.

In an image forming apparatus including a developing/cleaning device and a transfer device, the charging device is a JRO! The device is characterized by a small ion flow control screen disposed at or near the opening for irradiation with ions.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a schematic diagram of the periphery of the photoreceptor 1 ram of the image forming apparatus of the present invention.

In the same figure, 2 parts of the main part of the present invention, 1
liX:' 2 is provided near the photosensitive drum 3,
Furthermore, the cursed image and cleaning device 4. Transfer device5. A non-static charge remover is also provided near the photoreceptor drum. Further, a fixing device 8 is provided in the conveyance path 7 of the transfer paper (shown in the figure-1).

FIG. 4 is a detailed diagram of the charger 2, where the :lll:JNaraiya 9 is connected to the corona generation power supply 10, and the voltage required for discharge is 1+1:I from the corona generation power supplies 10 to 211:
It is applied to the Ina wire 9. Further, a seal 1-case 11 is provided surrounding the corona wire 9.
1 is grounded. Further: I T:j Nawa Iya 9
A corona ion flow control screen 13 is located between the photosensitive surface 12 and the photosensitive surface 12.
The corona ion flow control screen 13 is connected to the bias power supply 14, and the constant voltage is connected to the bias power supply 1.
4 is applied.

The image forming operation of the image forming apparatus configured as described above will be described below.

An electrostatic latent image is formed on the uniformly charged photosensitive surface 12 of the photosensitive tram 3 by exposure 17 containing information of the document. By rotating the photoreceptor 1 and 3 in the direction of the arrow, the electrostatic latent image is visualized as a toner image by the 1 and 1 in the developing and cleaning device 4. The toner image is transferred to a transfer paper by a transfer device 5, and the toner image on the paper is thermally fixed by a fixing device 8, and is then sent out of the machine.

On the other hand, 1-1 remaining on the photosensitive surface 12 without being transferred by the transfer device 5
The surface charge of the toner is uniformly removed by the static eliminating lamp 6, and the toner is sent to the charger 2 again with the residual l·tonner still attached.

The corona wire 9 of the charger 2 is connected to the power source 10.
A high voltage of, for example, about 500 V to 6000 V is applied, and the corona wire 9 of the corona ion flow control screen 13 is caused by the generated ions 19'.
side is positively charged. FIG. 5 shows that the IJ + naso I3 is made up of a circular conductive member 15 and an insulating member 1G, and shows that a positive charge is generated in the insulating part +A] 6 o) -1-. This 11-2. The conductive member of the flow control screen 13 is connected to the bias power supply 14.
Since it is grounded through the corona ion flow control screen 13, lines of electric force are generated in the gap between the corona ion flow control screen 13 as shown by dotted arrows in the figure. Therefore, the corona ions emitted from the corona wire 9 are accelerated along the direction of the electric lines of force as shown in FIG. 6, and advance towards the photosensitive surface 12 from the normal direction of the photosensitive surface 12 at high speed.

Therefore, irrespective of the level of the surface potential existing on the photosensitive surface 12, and almost unaffected by the strength of the electric lines of force, the corona ions proceed straight, even in the residual toner region B shown in FIG. 7, for example.

As shown in FIG.

As shown in the figure ([]), a higher potential is applied to the region W where there is no residual l-toner, and after passing through the developing/cleaning device 4, the residual l-toner is removed, and as shown in tdl in the figure. The potentials in regions B and W are at the same level, and the image transferred to the transfer paper by the transfer device 5 becomes an image without density unevenness.

As described above, according to this embodiment, there is no need to clean the toner remaining on the photosensitive surface 12 using a special cleaning device, and there is no possibility that the toner remaining on the photosensitive surface 12 will cause unevenness in the image.

The embodiment of the present invention is not limited to the above, and the conductive member 15 of the ion current screen 13 is grounded via the bias power supply 17, but instead of using a high-frequency power supply, an impedance such as a resistor or a Harris It can be implemented in the same way even if it is grounded through the element.

〔Effect of the invention〕

As described in detail above, according to the present invention, in an image forming apparatus using a developing/cleaning device, a decrease in the surface potential of the photosensitive surface due to residual toner is prevented, and density unevenness due to the influence of residual toner is prevented from occurring in a copied image. This can be prevented.

[Brief explanation of drawings]

Fig. 1 is a diagram of the 11 process using the developing/cleaning device 7i, and Fig. 2 is an image II'ba<degree 1 for surface potential.
! 1 and 3 are I-line diagrams of the image forming apparatus of the present invention (
^1 diagram, Figure 4 is a configuration diagram of the charger and the power supply connected to it, Figure 5 is a configuration diagram of the corona ion flow control screen, Figure 6 is a configuration diagram showing the flow of corona ions, and Figure 7 The figure is a process diagram for copying using the image forming apparatus of the present invention. 2... Charger, 3... Photoconductor tram. 4...Developing and cleaning device, 9...Corona wire, 10...Corona generation power supply,
11... Shield case. 12... Photosensitive surface, 13... -11-1 Nion flow control screen, 14... Bias power supply, 15... Conductive member. 16...Insulating member. Patent Applicant Casio 81 Computer Co., Ltd. Same as above
ID Co., Ltd. Patent Attorney Yoshiyuki Osuga Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 7

Claims (4)

[Claims] (1) In an image forming apparatus using an image bearing member having a circumference shorter than the maximum transfer paper used, at least a charging device, an exposure device, a developing/cleaning device, and a transfer device are arranged around the image bearing member, An image forming apparatus characterized in that the charging device is a corona discharger in which a corona ion flow control screen is arranged at or near an opening for irradiating corona ions. (2) The corona ion flow control screen has a conductive member and an insulating member, and the insulating member is provided on the corona ion flow input surface of the conductive member. The image forming apparatus according to scope 1. (3) The image forming apparatus according to claim 1 or 2, wherein the corona ion flow control screen is grounded via a bias power source. (4) The image forming apparatus according to claim 1 or 2, wherein the corona ion flow control screen is grounded via an impedance element.