JPS6180277A - Corona discharger - Google Patents

Abstract

PURPOSE:To prevent the inside of a device from inflow of external air and to reduce contamination due to foreign substances by arranging an air blowing means adjacently to a shielding plate. CONSTITUTION:The device is constituted with an air blowing fan 19, a filter 20, an insulating supporting member 21, a discharging wire 22, a shielding plate 23, etc. Air flows from the fan 19 setting side to the opposite side having no air blowing means so as to cross the side plate 23 of an electrifier obliquely. Side plates for holding the electrifier are arranged so that air flows out easily through many holes formed on the side plate of the front side, but the outflow of air is difficult on the depth side. In this case, air flow having an optional air speed more than a fixed value is obtained over the whole area of the longitudinal direction of the electrifier without pressure loss by arranging a fan 19 on the slow air speed side and sending air to the high air speed side. Thus, stable discharging characteristics can be maintained.

Description

Detailed Description of the Invention (Technical Part!+?) The present invention relates to a corona discharge device used in electrophotographic devices, electrostatic recording devices, etc. The present invention relates to a corona discharge device capable of imparting.

(Background Art) A corona discharge device is a corotron device consisting of a corona discharge electrode connected to a high-voltage power source and a shield plate surrounding the corona discharge electrode, or a corotron device equipped with a discharge control member (hereinafter referred to as a grid). , S.) Scorotron devices are known.

Since these devices use corona discharge by applying high voltage, the dust collection effect is unavoidable, and dirt due to foreign matter adhering to the corona discharge electrode, shield plate, and grid shade, that is, developer,
Oxide due to discharge,? :C 1/I in air (contamination due to dust, etc. is likely to occur, which causes uneven charging and neutralization. This has the disadvantage of maintaining stable charging and static neutralization characteristics. In order to do this, it was necessary to carry out cleaning work at regular intervals.In particular, since the discharge is weak near the insulating support member that supports the corona discharge electrode, the wind pressure of the ion wind is weak, and the When the ionized wind blows out of the corona discharge device, outside air flows in from the end of the insulating support member where the wind pressure of the ionized wind is lower than elsewhere so as to maintain the balance of the atmospheric pressure inside the corona discharge device.As a result, Foreign matter contained in the outside air enters the corona discharge device and causes contamination.

Therefore, as shown in Japanese Utility Model Application Publication No. 57-93942, it is known to provide an air inflow prevention means at the end of the corona discharge device, but the inflow of outside air into the corona discharge device is prevented. It was unavoidable and had little effect. Furthermore, as shown in Japanese Patent Application Laid-Open No. 57-188062, a conductive member is disposed on the top surface of the insulating support member to increase the amount of discharge at the end of the corona discharge device, and to Increasing the discharge capacity has some effect, but unnecessarily increasing the amount of discharge may have practical problems, such as increased ozone generation and the need for a high-capacity, high-voltage power source.

Furthermore, as shown in Japanese Patent Publication No. 40-17229, by blowing a dedusted and dehumidified air stream onto an insulating support member or a corona discharge electrode, an air curtain is created and the insulating support member is There are methods to prevent foreign matter from accumulating on the corona discharge electrode. This method has a great effect on preventing contamination, but there are other reasons such as the need to form an air curtain over the entire corona discharge device, and the fact that the airflow is blown through the duct I (-1), so the pressure drop of the air is large. Therefore, a blower with a considerably large capacity is required, and in that case, the noise becomes louder, the power consumption increases, and there is a risk that the device will become larger and more expensive.

(Object of the Invention) The present invention has been made in view of the points mentioned in -1-. An object of the present invention is to provide a corona discharge device with excellent durability that can maintain stable discharge characteristics over a long period of time by suppressing the discharge characteristics.

(Summary of the Invention) The present invention provides a corona discharge device having a corona discharge electrode, a shield plate surrounding the corona discharge electrode, and an insulating +1 support member supporting the corona discharge electrode.
In addition to the discharge capacity 11, a part of the corona discharge device is provided with an opening [1], and an airflow is blown directly into the interior of the corona discharge device with the air blowing direction forming an arbitrary angle with the shield plate with respect to this opening. The means is provided close to the shield plate.

(Example) Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a schematic diagram for explaining an electrophotographic apparatus to which the corona discharge apparatus of the present invention is applicable.

Reference numeral 1 denotes a photoreceptor drum in which a photoreceptor having a photoconductive layer as a basic constituent is formed in the form of a drum on a conductive support, and is rotatably supported by a shaft 2 on a machine frame (not shown) in the direction of the arrow. ing. Around this photosensitive drum, a charger 12, a light image exposure 13 when an original (not shown) is exposed and scanned, a developer 14,
Transfer charger 15, separation charger 16, cleaning device t
17, a pre-exposure lamp 18, and other electrophotographic process components are arranged. 3' is a cassette for supplying the transfer material, 3 is the transfer material, 4 is a supply roller for sending out the transfer material, and 5 is the transfer material 3 via the guide plate 6 between the photosensitive drum l and the transfer charger 15. Register roller to feed into, 1
6 is a separation charger for separating the transfer material 3 from the photoreceptor drum l; 7 is a transfer material 3 separated from the photoreceptor drum l;
This is the conveyance system that conveys the image to the fixing device, and the conveyor belt is stretched. 8 is a fixing device for fixing the developer (toner) transferred to the transfer material 2 to the transfer material. Note that 9 is a pre-transfer charger, and 10 is a pre-transfer exposure light source.

Conventionally, a corona discharge device used as a charger in an electrophotographic device as described in 1. This adhesion can cause a decrease in the amount of discharge or stoppage of discharge. Further, dirt on the discharge wire causes non-uniformity in the corona discharge current density, which adversely affects the quality of the final image. In other words, the difference W in current density caused by activation of toner etc. on the discharge wire appears as a difference in drum surface potential during development, and even if the same development is performed, a constant density cannot be obtained. This causes uneven shading in the image.

The sources of scattered toner that adheres to the discharge wire are mainly the developing device 14 and the cleaning device 17.
In particular, it is technically difficult to completely prevent toner scattering from the ends of the cleaning device 17 and the developing device 14.
The atmosphere in the vicinity of the corona discharge device 12 contains a considerable amount of toner fine powder. On the other hand, in the charger, charges flow from the discharge wire toward the shield plate and the photosensitive drum due to corona discharge, and this movement of charges generates a wind called ion wind in the direction in which the charges flow. This ion wind is strong in the center, and weaker near the insulating blocks at the ends because there is less current flow. When the space on the opposite side of the photosensitive drum with respect to the discharge wire becomes negative pressure, air flows into the charger from the end. This air contains foreign matter such as dust and developer powder, and these foreign matter adhere to the discharge wire, causing uneven discharge.
As a result, the image becomes uneven. In particular, suction is noticeable at the end of the charger, which tends to cause image unevenness. In addition, air containing foreign matter flows into the charger not only at the edges, but also in a thin layer of air about 1 mm thick from the drum surface, which flows along the photosensitive drum l shown in Figure 2, and acts as an ion wind. There are t people who interfere.

The present invention has been developed in view of the above points, and is
Figure C shows an embodiment of the present invention. In the figure, 22 is an insulating block that supports the discharge wire 21, and 23 is an insulating block that surrounds the discharge wire and is an opening r123 for the discharge wire.
It is a shielding plate having b. The rear shield plate of the shield plate 1, 23, which is opposite to the discharge closing/opening II 23b when viewed from the discharge wire 22, is provided with an opening 23a through which airflow flows (
Figure 1C). Further, a blower stage 19 such as a fan is provided adjacent to the rear shield plate 1· so that the air blowing direction forms a constant angle θ with the rear shield plate 1·. The airflow is blown through a dust removal filter 20.

Reference numeral 24 denotes a chamber, which is provided so as to be able to blow air at a certain wind speed or higher over the longitudinal direction of the charger. The above angle O depends on the installation position of the first stage of air blower 19 in the longitudinal direction of the charger, but the opening Ill between the insulating blocks is 320 mm, and the air is blown at a position 3'5 mm from the end face of the insulating block. If the center is located, the angle θ is 10° to 60°, preferably 25° to 32°.
It is better to set the charger to 50° so that the static pressure does not decrease and the airflow flows over the entire length of the charger. The airflow flows diagonally across the side shield plate of the charger from the side where the blower is installed toward the side without the blower. Also, usually the first
An image forming apparatus such as an electrophotographic apparatus shown in the figure is provided with side plates for holding a charger, but the ease of airflow varies depending on these side plates. In other words, the front side plate has a number of holes to make it easier to pull out the drum and other units, or to remove the transfer material when it jams, but the back side plate is especially Since a drive source or transmission device is attached without the need for it, it must be strong and have no unnecessary holes. Therefore, when QiQ flows, the airflow easily flows on the front side due to the large number of holes in the side plate, but it is difficult to flow on the back side. In such a case, placing the blower on the side where the airflow is difficult and blowing the air towards the side where the airflow is easy will reduce pressure loss and ensure that the airflow exceeds a given wind speed over the entire length of the charger in one direction. is obtained.

FIG. 3 shows an example of the wind speed distribution. The wind speed is maximum at the position where the blower is installed, but when the charger faces the image carrier, this distribution is relaxed and smoothed.

As a result, as a certain amount of airflow with a wind speed of 2 flows outside the shield plate in the longitudinal direction of the charger, a flow containing foreign matter such as dust and toner along the photoreceptor drum enters the charger. By suppressing this as much as possible, contamination of the corona discharge electrode by foreign matter is prevented, and even and stable discharge is maintained for a long period of time.

In addition, the ion wind blows out particularly weakly at the ends of the charger, and it is necessary to flow an air current at a faster wind speed to this part than to the central part. Therefore, it is also possible to widen the opening end on the back surface of the shield plate. According to the experimental results, 2 at the center of the charger.
m/SeC or more, preferably 3 m/SeC at the end of the charger
By flowing airflow at a wind speed of sec or higher, it is possible to prevent dirty airflow from entering the charger.

4A and 4B show another embodiment of the present invention, in which the blowing means is provided close to the side shield plate of the charger. In the embodiment, the air blowing means is installed at an angle of θ1=to with respect to the charger longitudinal opening width fL1=330 mm.
-16°, preferably 25 to 32°. Also, the angle θ
2 is for charging width 12 = 30 mm and charger height 13 = 30 mm, so that the airflow flows outside the shield plate at an angle of 30° to 80°, preferably 60° to 70°, although it is not particularly limited. You can set it to . The side shield plate to which the air blowing means is attached may be placed on either side of the shield plate I, but if the photoreceptor drum moves, it should be provided close to the side shield plate on the downstream side in the direction of movement. Preferably, air flow along the drum entering the drum is blocked.

Next, in the electrophotographic apparatus as shown in FIG.
The effects of using the corona discharge device of the present invention as shown in Figure c will be explained based on Table 1 below. (In addition, the blower fans A and B in the table were those shown in Table 2.

) By blowing airflow into the corona discharge device using a small-capacity blowing means as shown in L, the inflow of harmful outside air containing foreign matter such as dust and toner from the discharge opening can be prevented. By suppressing the entry of foreign matter adhering to each part, it is possible to eliminate abnormal discharge due to foreign matter adhesion, and to maintain uniform and stable discharge for a long period of time.

Furthermore, by providing one stage of small-capacity air blowing directly near the shield plate 1, there is no need for complicated ducts, there is little pressure loss in the airflow, and a small space can be used effectively. Further, since the air blowing means has a small capacity, noise can also be reduced.

By the way, when the electrophotographic apparatus shown in FIG. 2 is used for a long period of time, corona dischargers 9.12, 15.1
The corona products generated by the corona discharge of 6 etc. are
When the transfer material 3 comes into direct contact with the photoreceptor drum 1 and is transferred from the back side of the transfer material, a part of the material, such as paper powder, is transferred by being charged with a corona charge from the charger 15. Foreign matter may adhere to the photoreceptor drum. When an electrophotographic device is used at high temperatures, water molecules adsorb to the deposits mentioned above.
The surface resistance of the photoreceptor drum may become low, causing electrostatic latent images to flow and contrast to decrease.

In order to solve this problem, in the corona discharge device of the present invention, water molecules attached to the photoreceptor drum are removed by blowing airflow heated by a heat source into the corona discharge device, and the water molecules attached to the photoreceptor drum are removed. However, it is possible to form a stable latent image. As the heat generation source, for example, an exposure source of an optical system can be used. Conventionally, in order to prevent the flow of electrostatic latent images and the decrease in contrast, a heater was built into the photoreceptor drum, and the water molecules adsorbed on the photoreceptor drum were removed using the heat. It is also possible to reduce the power consumption of the drum heater by using the heat of the drum heater.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent outside air from flowing into the corona discharge device by using a small-capacity blowing means, and the corona discharge device is provided.

4. Contamination by foreign matter inside 4 can be significantly reduced.

Therefore, stable discharge characteristics can be maintained over a long period of time.

[Brief explanation of the drawing]

FIG. 1A is a longitudinal cross-sectional view of a corona discharge device showing an embodiment of the present invention, FIG. 1B is a cross-sectional view thereof, FIG. 1C is a plan view showing an opening in a rear shield plate, and FIG. 2 is a corona discharge device according to the present invention. A schematic diagram of an electrophotographic device to which the device can be applied, FIG. 3 is a graph showing the wind speed distribution of the corona discharge device of the present invention, and FIG. 4A is a view from the discharge opening side of the corona discharge device showing another embodiment of the present invention. The view shown in FIG. 4B is a cross-sectional view of the same. l...Photosensitive drum 19...Blower fan 20...
・Filter 21... Insulating support member 22...
Discharge wire 23... Shield plate 24...
Chan 8

Claims (5)

[Claims] (1) In a corona discharge device having a corona discharge electrode, a shield plate surrounding the corona discharge electrode, and an insulating support member supporting the corona discharge electrode, in a part of the shield plate, apart from the discharge opening, In addition to providing an opening, a blowing means is provided in close proximity to the shield plate to blow air directly into the corona discharge device so that the blowing direction forms an arbitrary angle with respect to the shield plate. corona discharge device. (2) A patent characterized in that the above-mentioned air blowing means is provided in the longitudinal direction of the corona discharge device on the side where the airflow is difficult to blow out through the corona discharge device, and blows air in the direction where the airflow is easy to blow out. A corona discharge device according to claim 1. (3) Claim 1, wherein the air blowing means blows air through a filter for removing dust.
Corona discharge device according to item 1 or 2. (4) The corona discharge device according to any one of claims 1 to 3, wherein the airflow from the blowing means is an airflow heated by a heat generating source. (5) The corona discharge device according to claim 4, wherein the heat generation source is an exposure source.