JPS6114660A - Corona discharge device - Google Patents

Abstract

PURPOSE:To prevent an accumulation of an adhering toner to a corona discharge device, and to execute a uniform and stable electrostatic charge by providing a toner collecting means for surrounding a shielding case and a corona ion flow control screen except an opening part, and consisting of a conductive part in which a bias is impressed to the vicinity of the opening part, so that it is insulated from the shielding case. CONSTITUTION:A corona discharge device 6 is provided with a toner collecting plate 10 for surrounding a shielding case, a corona wire 8 and a corona ion flow control screen 9, and a large voltage of the same polarity as that of a voltage impressed to the screen 9 is impressed to said plate by a bias power source 13. A residual toner of a very small quantity on a photosensitive body is absorbed electrically to the collecting plate 10, and an accumulation of an adhering toner to the screen 9 and the corona wire 8 is prevented. Accordingly, a uniform and stable electrification is executed extending over many hours.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to preventing toner from adhering to a corona discharge wire of a discharge device in an image forming apparatus or the like.

[Prior art]

Conventional 1 For example, a bipolar photoreceptor is primarily charged with a predetermined polarity, and a first electrostatic latent image or a first developed image is formed by imagewise exposure, development, etc., and this first electrostatic latent image or first I -F4
A two-color method using a corona discharger with a corona ion flow control screen placed at or near the opening for irradiating corona ions to perform secondary charging of the opposite polarity to the primary charging on the photoreceptor with an image formed thereon. Image forming apparatuses have been proposed.

FIG. 1 is a block diagram of a corona discharger equipped with a corona ion flow control screen.

The corona ion flow control screen 2 is a lattice-like screen having a large number of fine openings, and has an insulator portion and a lattice-like structure.

It has a laminated structure of conductor parts. Further, a voltage having the same polarity as the voltage applied to the two-way na wire 5 by the power source 4 is applied to the conductor portion of the corona ion flow control screen 2 by the power source 3. With this configuration, an electric field is formed in the screen opening hole of the corona ion flow control screen 2,
Corona ions generated from the vicinity of the corona wire 5 are accelerated by the action of the generated electric field, and the screen opens [1 hole,
The straightness of corona ions that have passed through 1ffi increases. Therefore,
High potential part of the latent image part on the photoreceptor] For example, edge 813
This will prevent corona ions from flowing into the area.

Uniform charging is performed.

[Problems with conventional technology]

However, even after passing through the cleaning section, a trace amount of toner still remains on the photoreceptor, and is charged with the polarity opposite to the bias applied to the screen during secondary charging due to primary charging. Among the toner scattered inside the machine, toner particles that are charged to the opposite polarity to the bias applied to the screen.
``While F2 was performing two consecutive bees, it gradually accumulated on the corona ion flow control screen 2, clogging the 11 holes of the screen, and furthermore, it also adhered to the corona wire 5. ζ, which prevents uniform charging.Thus, good image quality can be obtained initially, but as you continue to copy hundreds to dozens of copies, vertical streaks and fog appear in the images. This results in an unclear image.

(Object of the Invention) In view of the above-mentioned conventional drawbacks, the present invention provides a corona discharge device that prevents toner from adhering and accumulating on a corona ion flow control screen or corona wire, and can perform uniform and stable charging over a long period of time. The purpose is to provide.

C. Summary of the Invention] In order to achieve the above object, the present invention surrounds the corona discharge wire with a shield case having an opening on the side opposite to the surface to be charged, and applies a bias to the opening or the vicinity thereof. In the corona discharge device in which a corona ion flow control screen is arranged, the shield case and the corona ion flow control screen are surrounded except for the opening, and an extension part facing the charged surface is further provided near the opening. I have it.

The present invention is characterized in that the toner trapping means, which is a conductive portion made up of a conductive phase 11 to which a bias is applied, is provided electrically insulated from the shield case.

[Embodiments of the invention]

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

FIG. 2 is a configuration diagram of a corona discharge device showing an embodiment of the present invention, and FIG. 3 is a perspective view thereof.

The corona discharge device 6 includes a conductive shield case 7 and a corona wire 8. Corona ion flow control screen9. Conductive toner collection plate 10. Insulating heat 11. Corona generation power supply 12, 1-ner collection plate 10 river bias power supply 13
and a bias voltage lf!1114 for the ion flow control screen 9.

The opening 11 of the shield case 7 has a width of about 20 to 30,110 mm, and the corona wire 8 is made of a tungsten wire or a gold-plated tungsten wire with a wire diameter of 50 to 80 μm. Further, a predetermined voltage is applied to the corona wire 8 from a power source 12 for generating corona.

The corona ion flow control screen 9 is disposed at or near the opening of the shield case 7, and is designed to cover the conductor portion 9a having a large number of fine openings 11 parallel to the corona wire 8 and the corona wire 8 side of the conductor portion 9a. and an insulator portion 9b coupled to the insulator portion 9b.

The conductor portion 9a is connected to a bias power supply 14.

The toner collecting plate 10 is arranged adjacent to the left and right sides of the shield case 7 while being electrically insulated by a distance p, and is connected to a bias power source 13.

The insulating heath 11 connects the ends of the left and right toner collection plates 10,
Along with the connection, it is provided so as to circumscribe the bottom of the shield case. Therefore, the toner collecting plate 10 and the heath 1
1 covers the shield case 7, corona wire 8, and corona ion flow control screen 9 with the photoreceptor 1 side open.

Further, the end portion of the toner collecting plate 1O on the side of the photoreceptor 1 forms an extended portion that faces the surface of the photoreceptor 1, and this extended portion is formed on the photoreceptor 1 side.
It is located at the same distance from the corona ion flow control screen 9 or closer to the photoreceptor l side with respect to the surface.

In this embodiment, the distance between the extended portion of the toner collection plate 10 and the photoreceptor 1 is 1 mm, the distance between the shield case 7 and the photoreceptor 1 is 3 va, and the distance between the corona ion flow control screen 9 and the photoreceptor 1 is 1 mm. 2 as, the distance between the Ninorona Tsuya 8 and the photoreceptor is 9 mm, the distance 1111 between the lner collecting plate lO and the shield case 7 is 7 mm, and the distance of the extended portion of the lner collecting plate 10 facing the photoreceptor 1 is The length is 1O2 on each side.

Next, a case where the corona discharge device of the present invention having the above structure is applied to a corona discharge device for secondary charging in a two-color image forming apparatus will be described.

FIG. 4 shows an example of the configuration of a two-color image forming apparatus that is compatible with the present invention.
FIG. 5 is a diagram showing changes in photoreceptor surface potential in a two-color image forming process. The photoreceptor 1 has a bipolar photoconductor layer formed on a cylindrical aluminum substrate, and is supported rotatably in the direction of the arrow 2 shown in the figure.

First, the surface of the photoreceptor 1 is uniformly charged to a negative polarity by a corona discharge device 15 for primary charging (FIG. 5(a)).

Next, there is a document table 23 on which a two-color original f1%O having a red part R and a black part B is placed on a white background part W.

The light source 24 for first exposure is moved in the direction of the arrow shown in the figure.
The light is reflected by the original IKo, passes through a mirror lens 25 and a red filter 26, and is subjected to a first exposure 27 onto the photoreceptor 1.

Then, the light attenuates significantly in the red-corresponding portion and the white-corresponding portion on the photoreceptor 1, and a first electrostatic latent image is formed in such a manner that charges remain only in the black-corresponding portion.

(Figure 5(b)).

Next, when secondary charging is applied to the photoreceptor 1 by setting an appropriate voltage using the corona discharge device 6 for secondary charging, which is applicable to the present invention, as shown in FIG. The polarity of the black area is reversed and the area is charged to a positive polarity, but since the black corresponding area is originally at a high potential with a negative polarity, the surface potential decreases due to the positive electrification and reaches approximately A of the initial level of al. By the way, when a voltage of, for example, about 5 to 6 KV is applied to the corona wire 8 from the corona generation power source 12, the surface of the insulator portion 9b of the corona ion flow control screen 9 is positively charged by the corona ions generated thereby. At this time, since the conductor portion 9a of the corona ion flow control screen 9 is grounded via a bias power source 14 of, for example, about 1 to 3 KV, the screen opening hole is indicated by the broken line arrow in FIG. 6 (8). Lines of electric force are generated.The subsequent corona ions 33 are accelerated along the direction of the generated lines of electric force, and as shown in FIG. Therefore, the electric field contrast with the periphery of the first electrostatic latent image already formed on the photoreceptor 1 does not concentrate and flow in. Corona ions are uniform regardless of the magnitude of the surface potential of the photoreceptor 11. The whole can be shifted uniformly and regularly while maintaining the potential contrast formed by the first electrostatic latent image.

After the secondary charging is completed, the second exposure 30 of the image of the document 0 is performed again through the scene filter 29 that blocks the red light component, while keeping the gate open from the time of forming the first electrostatic latent image.
Either the potential of the white background-corresponding part at the top undergoes a large optical attenuation, or the red-corresponding part maintains the level of optical attenuation (4)), so the second static potential is generated in the form of a positive charge only in the red-corresponding part. An electrostatic latent image is formed (FIG. 5(d)).

Subsequently, the black developing device 16 and the red developing device 17 develop the negative latent image corresponding to the black portion on the photoreceptor 1 with the positively charged black toner BT, and the pressure latent image corresponding to the red portion with the negatively charged red toner RT. A two-color toner image is formed thereon (FIG. 5(e)).

Next, the polarities of the two color toner images having different polarities are aligned to one polarity by the polarity alignment discharger 18.

The transfer discharge device 19 transfers the images all at once onto the transfer paper 32 fed from the paper feed roll 3I, and then the separation discharge device 20 separates the transfer paper 32 from the photoreceptor I. 1
A final two-color image is obtained from the 111 feeding device 28 through a fixing device (not shown). Note that toner and charges remaining on the photoreceptor 1 are removed by a cleaner 21 and an eraser lamp 22, respectively.

Further, the toner collection plate 10 of the corona discharge device 6 for secondary charging that is applicable to the present invention has the same polarity as that applied to the corona ion flow control screen 9, and a voltage value larger than this. Since a voltage of a predetermined magnitude is applied from the bias power source 3, the corona ion flow control screen 9 and the corona wire 8 were conventionally attached.

Bias power supply 14 for corona ion flow control screen 9
The red l-ner 3 floating inside the aircraft is charged with the opposite polarity to that of
A small amount of red and black l-toner 35.36 remaining on the photoconductor 1-11, which is intensely charged to the polarity opposite to that of the bias power supply 14 due to primary charging, is electrically pulled to the toner collection plate 10. (see Figure 7), the corona ion flow control screen 9 or the corona 4
・Prevent toner from -1- from adhering to 8. The corona ion flow control screen 9 and the corona wire 8 are not contaminated with toner by providing the toner collecting plate 10 to which a bias is applied and allowing floating toner to adhere thereto, so that tens to tens of thousands of sheets can be copied. Good, stable and uniform charging can be achieved even if the process is continued.

It should be noted that the entire toner collection plate 10 does not need to be made of a conductive material, as long as at least the portion facing the photoreceptor 1 is made of a conductive material to which a bias is applied.

In addition, in this embodiment, the bias power supply 14 applied to the conductor portion 9a of the corona ion flow control screen 9 and the toner collection plate 1
Although a bias power supply 13 for applying 0 is provided separately, these bias power supplies may be shared and the same voltage may be applied.

Although the case where the corona discharge device of the present invention is applied to a two-color image forming apparatus has been described above, the present invention is not limited to this and can of course be applied to a corona discharge device in a monochrome image forming apparatus.

〔Effect of the invention〕

As explained in detail above, the corona discharge device of the present invention includes:
It prevents toner from adhering to and accumulating on the corona ion flow control screen and corona wire, and enables uniform and stable charging over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional corona discharge device, FIG. 2 is a configuration diagram of a corona discharge device showing an embodiment of the present invention, FIG. 3 is a perspective view of an embodiment of the present invention, and FIG. 4 is a diagram of the present invention. The invention passed 2
FIG. 1 is a configuration diagram of a color image forming apparatus. FIG. 5 is a diagram of photoreceptor surface potential changes in the two-color image forming process, FIG. 6 is an enlarged view of the vicinity of the corona ion flow control screen, and FIG. 7 is a configuration diagram showing an embodiment of the present invention. . 1... Photoreceptor, 6... Corona discharge device,
7... Shield case, 8... Corona wire, 9... Corona ion flow control screen, 10... Toner collection plate, 11
...Base, 12.13゜14...Power supply.

Claims (5)

[Claims] (1) In a corona discharge device in which a corona discharge wire is surrounded by a shield case having an opening on the side facing the surface to be charged, and a corona ion flow control screen to which a bias is applied at or near the opening is disposed, the opening an extending portion surrounding the shield case and the corona ion flow control screen except for a portion thereof, and further having an extending portion facing the charged surface near the opening, at least a portion of which is made of a conductive material to which a bias is applied. A corona discharge device characterized in that a toner collecting means, which is a conductive portion, is provided electrically insulated from the shield case. (2) The corona discharge device according to claim 1, wherein at least the extending portion is a conductive portion. (3) The extended portion is located at the same distance from the charged surface as the corona ion flow control screen or closer than the corona ion flow control screen. Or the corona discharge device according to item 2. (4) Claims characterized in that the bias applied to the conductive portion is equal to or greater than the bias applied to the corona ion flow control screen. Corona discharge device according to any one of items 1 to 3. (5) The corona discharge device according to any one of claims 1 to 4, characterized in that the bias applied to the conductive portion and the bias applied to the corona ion flow control screen are shared. .