JPH0255785B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a corona discharge device.

Corona discharge devices are utilized as important components in devices that utilize static electricity, such as electrophotographic copying machines and electrostatic printing machines.

FIG. 1 shows a very schematic configuration of an example of an electrophotographic copying machine, in which a number of corona discharge devices are incorporated as important process execution equipment.

That is, the copying machine of this example is a transfer type copying machine that follows the electrophotographic process disclosed in Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748.
A drum-shaped photoreceptor that basically consists of three layers: a photoconductive layer and a surface insulating layer, and is driven to rotate in the direction of the arrow.

The following processes are sequentially applied to one side of the photoreceptor to obtain a copy.

(1) Pre-exposure static elimination using AC corona discharge device C1 and full surface exposure device 2. This removes the photoreceptor's electrical memory remaining from the previous copying process.

(2) Uniform positive or negative primary charging by DC corona discharge device C2.

(3) Simultaneously with the exposure of the original light image L, AC static elimination or secondary charging with the opposite polarity to the primary charging is performed by the AC or DC corona discharge device C3.

(4) Full-surface exposure using full-surface exposure unit 3. This entire surface exposure increases the potential contrast of the electrostatic latent image on the photoreceptor surface formed in step (3) above.

(5) Toner development of the electrostatic latent image by the developing device 4.

(6) Corona discharge (post charge) by AC or DC corona discharge device C4. The electrostatic bonding force between the toner developed image and the photoreceptor surface is weakened, increasing the image transfer rate in the next transfer step.

(7) Transfer of the toner developed image to the copy material P side by the DC corona discharge device C5. The copy material P is then separated from the photoreceptor surface, passes through the fixing device 5, and is discharged outside the machine as a copy.

(8) Elimination of static electricity on the photoreceptor surface after copy material separation using AC or DC corona discharge device C6. The bonding force of the transferred residual toner developed image with the photoreceptor surface is extremely weakened,
The cleaning efficiency in the next photoreceptor surface cleaning process is increased.

(9) Cleaning of the photoreceptor surface by the cleaning device 6 (removal of transferred residual toner image).

The structure of the discharge device C generally includes a conductive gutter-shaped shield member 1 having a substantially U-shaped cross section as shown in FIGS.
0, an insulator block 11 arranged at both ends of the shield member, and a corona wire (discharge electrode) 12 positioned in the groove of the shield member and stretched between the insulator blocks at both ends. .

Reference numeral 13 denotes a power supply terminal buried in one insulator block 11 with both ends exposed on the inner and outer end surfaces of the block during _molding . The end of the corona wire 12 on the block side is locked. 14
is a small insulating cover that is integrally attached to the top surface of the block 11 so as to hide the insulator block locking portion of the corona wire 12.

Therefore, when one output end of the DC or AC high voltage power supply 15 and the exposed end 13 ₂ of the power supply terminal 13 on the block outer end surface side are connected, and the other output end and the shield member 10 are connected, high voltage is applied. When the power source 15 is activated, a high voltage is applied to the corona wire 12 and the shield member 10, and the gas (air) around the corona wire 12 becomes ionized. Then, the ionized charged particles move toward the opening 16 of the shield member 10, and at this time, give kinetic energy to other gas molecules to generate an ion wind blowing out at the opening of the shield member, and this ion wind causes photosensitive Charged areas of the object M, such as the back surface of the body 1 and the copy material P, are neutralized.

Figure 1. Examples of Figures 7 to 9 in the case of a type that allows light to pass through the device, such as the corona discharge device C1 for pre-exposure static neutralization in a copying machine and the corona discharge device C3 for charging simultaneously with light image exposure of the original. Shield member 10 as in
A light guiding elongated window hole 17 is formed along the length of the bottom wall. Reference numeral 18 denotes an insulating coating layer applied to approximately the lower half of the inner surface of the bottom wall and the inner surfaces of both side walls in which the shield member 10 forms the window hole in order to prevent the ion wind from blowing out from the window hole 17. There is also one in which the window hole 17 is covered with a transparent plate such as glass. Shield member 10
Some have the bottom wall completely open as a window hole 17.

The discharge electrode 12 may be an array of discharge needles.

By the way, in these discharge devices, since the interior of the shield member 10 becomes negative pressure as the ion wind is blown out, outside air enters the interior of the shield member from the shield member opening 16 to replace the ion wind. In this case, the inflow of the outside air into the space inside the shield member is not carried out in a substantially uniformly distributed manner at each part along the length of the shield member opening 16, but because both ends of the shield member 10 are insulator blocks 11. The ion wind blowing pressure at the shield member opening A (FIG. 3) near the insulator block 11 is weak, so that in reality, the outside air flows into the interior of the shield member only near the insulator block 11 on both ends of the shield member. from the above-mentioned pinch opening part A to the arrow a
It is done as follows. And the sucked air a
The flow velocity becomes quite strong in order to compensate for the negative pressure throughout the interior of the shield member.

As a result, the rate at which foreign matter floating in the outside air is drawn into the inner space of the shield member 10 increases due to the strong blown air flow a, and the rate of contamination of the discharge electrode 12 and the inner wall surface of the shield increases. In the case of a copying machine like the example in Figure 1, the strong suction air flow a at both ends of the discharge device causes floating dust and floating toner inside the machine.
A portion of the toner adhering to the surface of the photoreceptor 1 and a portion of the paper fibers of the copying material P are forcibly absorbed and enter the shield member 10, and the discharge electrode 12 and the inner wall surface of the shield become dirty at an early stage. Foreign matter contamination on the discharge electrode 12 and the inner wall surface of the shield is a major cause of uneven discharge, and in the case of copies, it has a great negative effect on the image quality, so it is necessary to frequently clean it and keep it free from contamination.

In view of the above, the present invention distributes the replacement flow of outside air into the interior of the shield member 10 due to the blowing of ionized wind almost uniformly at each part along the length of the opening 16, including both ends of the shield member 10. By doing so, we have created a discharge device that has been devised to suppress the localized strong outside air suction phenomenon where the rate of foreign matter introduction is high as described above, thereby slowing down the rate of contamination and therefore significantly reducing the frequency of cleaning. The purpose is to provide.

That is, this type of discharge device is characterized in that a grounded conductive member 19 is provided on each of the end insulator blocks 11 on the top surface of the block so as to face the corona discharge electrode.

In the example shown in FIG. 4, the overhanging small cover 14 that hides the insulator block locking part of the corona wire 12 in the discharge device shown in FIG. An embodiment in which the sexual member 19 is also used. Figure 5 is the third
An embodiment in which the insulating small cover 14 shown in the figure has a relatively short overhang, and a grounded conductive member 19 is provided over the end surface and upper surface of the overhang side edge of the cover 14. FIG. 6 shows an embodiment in which a conductive member 19 is attached in a bead shape to the end surface of the protruding edge of the cover 14, and this member is grounded. A conductive member 19 that is grounded across the end surface and top surface of the protruding edge of the insulating cover 14 with the same length as
Embodiments in which these are provided are shown below.

That is, in any of the above cases, due to the presence of the grounded conductive member 19, the insulator blocks 1 at both ends of the device
The ion wind blowout at the shield member opening A (Fig. 3) closer to 1 is promoted, and the ion wind blows out from each part along the length of the shield member opening, including the opening part A, as shown in Fig. 4. It will now be done almost equally. As a result, the flow a of the outside air into the interior of the shield member 10 due to the ion wind being blown out is distributed approximately uniformly at each portion along the length of the shield member opening, as shown by the chain line in FIG. The flow of outside air into each part is gradual. Therefore, the rate at which foreign matter is taken into the shield member is significantly reduced, and the rate of contamination of the discharge electrode 12 and the inner wall surface of the shield by foreign matter is slowed down, and the discharge performance of the device can be maintained well over a long period of time. The intended purpose is well achieved with a simple configuration.

In addition, when the shield member 10 has a through hole 17 on the bottom surface as shown in FIGS. 7 to 9, clean air can be actively sent into the shield member 10 from the hole 17 by using the hole 17. As a result, the discharge side opening 16 of the shield member 10 becomes a blow-out system as a whole, and contamination caused by foreign matter getting into the shield member 10 is almost completely prevented.

Also, the inner surface of the bottom of the shield member of the discharge device is insulated 1
8, no current flows through the bottom of the shield member, and no ion wind is generated toward the bottom. As a result, the bottom becomes in a negative pressure state, and the hole 1 in the bottom becomes
Clean air naturally flows into the shield member 10 from 7, and since the discharge side opening 16 is a blow-out system as a whole, contamination caused by getting mixed up with foreign objects in the shield member 10 is almost completely and naturally prevented. This results in a more effective discharge device.

[Brief explanation of drawings]

FIG. 1 is a very schematic configuration diagram of an example of an electrophotographic copying machine, and FIG. 2 is a cross-sectional view of an example of a conventional discharge device.
3 is a longitudinal sectional side view of one end of the device, FIGS. 4 to 6 are longitudinal sectional side views of one end of the apparatus according to the embodiment of the present invention, and FIG. 7 is a light guide window on the bottom wall of the shield member. FIG. 8 is a plan view of the same end, and FIG. 9 is a cross-sectional view of the same end. 10 is a shield member, 11 is an insulator block at the end of the shield member, 12 is a corona wire, and 19 is a conductive member.

Claims (1)

[Claims] 1. A corona characterized in that a grounded conductive member is disposed on the top surface side of an insulator block that is provided at both ends of the shield member and supports a corona discharge electrode, so as to face the corona discharge electrode. Discharge device.