JPH0116102Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] This invention relates to an improvement in a corona ion discharge device for charging or neutralizing a photoreceptor or transferring an image in, for example, an electrophotographic device. [Technical background of the invention and its problems] In the case of electrophotographic devices, etc., in order to charge the photoreceptor, transfer the image, and further remove the static electricity, it is generally necessary to use a grounded metal casing and a metal casing attached to the casing. A corona ion generator is used, which is made of a metal wire that generates corona ions by applying a high DC voltage or an AC high voltage. Furthermore, with the diversification of electrophotographic devices in recent years, devices with image enlargement or reduction functions have been developed. In order to reduce the burden on the printer and the dirt inside the machine, it is necessary to prevent latent images from being formed in the non-image areas at both ends of the photoreceptor drum. For this reason, conventionally, a device has been used in which a lamp is installed before development to irradiate the surface of the non-image area to erase unnecessary latent images. A new lamp must be provided for this purpose, which increases costs and requires installation space, which impedes miniaturization. In order to solve the above-mentioned problems, a device as shown in FIG. 1 is also used. That is, in order to charge the photoreceptor drum, a corona ion generator 10 and a shielding member 11 slidably provided in front of the corona ion generator 10 are provided.
This uses a corona ion discharger consisting of: Accordingly, during reduction, the charging width on the photosensitive drum can be limited in advance by the shielding member 11, so that a latent image is not formed in a non-image area. However, in general, charging devices use a constant current power source, which has better surface potential characteristics than constant voltage characteristics, in order to stabilize the surface potential characteristics due to temperature changes of the photoreceptor drum. Depending on the material of the shielding member 11, corona ions may leak and the surface potential of the photoreceptor drum becomes insufficient, or corona ions are deposited and the surface potential increases, causing a serious adverse effect on image quality. In some cases, electric charges are induced under the shielding member 11, and the photoreceptor drum is charged by the electric charges, and even though the charging width is limited, the charging width is expanded, and the electric charge is not applied to that part. Well,
Another problem is that an image similar to a solid black image is formed on the photoreceptor drum. [Purpose of the invention] This invention was made based on the above circumstances, and although it has a relatively simple configuration, it is possible to limit the discharge width of corona ions by a shielding member, even though a constant current power source is used. Even when charging, the surface potential of the photoreceptor drum can be kept constant without decreasing, and a high-quality image can be obtained.Moreover, no charge is induced in the shielding member at the end of the shielding member, and the shielding member allows the photosensitive drum to be exposed to light. To provide a highly reliable corona ion discharger capable of limiting the charging width on a body drum to a sharp one. [Summary of the invention] In this invention, the shielding member is formed of a flat plate-like conductive material with a portion of an insulating material, and the surface potential of the photoreceptor drum is reduced by making the area ratio of the two approximately 1:1. Furthermore, by providing an insulating material at the end of the shielding member, the charging width on the photoreceptor drum is limited to a sharp range, thereby improving reliability. [Embodiment of the invention] Next, in describing an embodiment of the invention, in order to explain the principle thereof, a measuring device for examining the shielding characteristics of each material of the shielding member and its measurement results will be described. First, the first experiment will be explained with reference to FIGS. 2 to 5. First experimental device 1
2, the total length of the discharge applied by the power source 13 is approximately
To the aluminum plate 17 provided in front of the corona ion generator 14 when a movable shielding member 16 is provided at both front ends of the 277 [mm] corona ion generator 14 and the shielding member 16 is moved to change the discharge length. The inflow current is measured by an ammeter 18.
As the power supply 13, two types of power supplies are used: a 140 [μA] constant current power supply and a +0.5 [KV] constant voltage power supply.
Changes in inflow current due to differences in power sources were measured, and changes in inflow current due to differences in materials were also measured using two types of shielding members 16, a grounded aluminum plate and an insulating tape. Shown below [Table-
1] and [Table 2] show the results.

【table】

[Effect of idea]

As explained above, according to this invention, even when a constant current power source is used as the power source for the corona ion generator, an insulating material is provided as a part of the conductive material as a shielding member, and the area ratio of the two is almost the same. evenly 1
By using a photoconductor that is formed to have a one-to-one ratio, the corona ion generator will not be adversely affected by the shielding member even during reduction copying, and the surface potential of the photoreceptor will be increased or insufficient compared to when copying at full size. Since the photoreceptor can be charged in the same way as during full-size copying, clear and high-quality copied images can be obtained even during reduced-size copying. In addition, since an insulating material is provided at the end of the shielding member, the charging length of the photoreceptor is limited to a sharp end, and unlike conventional methods, a part of the non-image area is not charged. There is no toner attached to non-image areas during development, which prevents excess toner consumption, reduces the burden on the cleaner, reduces maintenance, extends its life, and prevents dirt inside the machine. This reduces the negative effect on the copied image due to staining. It should be noted that if the structure of the embodiment is adopted, the shielding member can be easily formed by simply covering the conductive material with an insulating tape, and the manufacturing time can be shortened.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing a conventional device, and Figures 2 to 5 are first diagrams explaining the principle of this device.
Fig. 2 is a schematic cross-sectional view of the experimental equipment, Fig. 3 is a graph of the experimental results, Fig. 4 is a graph of the experimental results using the shielding member used in the experiment, and Fig. 5 is a graph of the experimental results. Graphs of experimental results using the shielding member shown in Figures 6 to 8 show the second experiment to explain the principle of this invention. A partially omitted top view of the device, and Figure 8 is a graph of the experimental results.
9 and 10 show an embodiment of this invention, FIG. 9 is a perspective view thereof, and FIG. 10 is a partially omitted sectional view of the shielding plate. 12...First experimental device, 13...Power supply, 14
... Corona ion generator, 16 ... Shielding member,
17... Aluminum plate, 18... Ammeter, 20... Aluminum plate, 21... Insulating tape, 22... Second experimental device, 23... Power supply, 24... Corona ion generator, 26... Shielding Member, 27...Corona ion distribution measurement plate, 28...Ammeter, 30...
Corona ion generator, 31... first shielding plate,
32... Second shielding plate, 33a, 33b... Mylar film, 36... Motor, 37... Pinion.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In an image forming apparatus capable of converting magnification, a corona ion generator that generates corona ions;
A flat shielding member made of a conductive material and an insulating material, which is movable in the longitudinal direction of the front surface of the corona ion generator, and arranged so that the area ratio in the longitudinal direction is approximately 1:1; A corona ion discharger comprising: a drive device that moves the shielding member in parallel in the longitudinal direction according to the magnification of the image, and changing the region in which corona ions are generated by the corona ion generator at the end in the longitudinal direction. . (2) The power source of the corona ion generator is a constant current power source, and the shielding member consists of a grounded conductive flat plate and an insulating material covering a part of this conductive flat plate in parallel with the longitudinal direction. A corona ion discharger according to claim 1, which is characterized by: (3) The corona ion discharger according to claim 1 or 2, wherein the shielding edge of the shielding member is coated with an insulating material.