JPH0616961U - Scorotron charging device - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent abnormal discharge from occurring due to the toner adhering to the grid affecting the charging performance of the photosensitive drum. In a scorotron charging device 12 that has a grid 20 and charges the surface of the photoconductor drum 11 to a predetermined voltage, the linear portion 20a forming the grid 20 is insulated on the surface side facing the photoconductor drum 11. Layer 27 was formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the structure of a scorotron charging device used in an image forming apparatus such as a copying machine.

[0002]

[Prior art]

 Conventionally, in an image forming apparatus such as a copying machine, after the surface of the photoconductor drum is charged to a predetermined voltage by a charging device, an original image is guided to the photoconductor drum by scanning of an optical system and electrostatically formed on the surface of the photoconductor drum. A latent image is formed. The electrostatic latent image is developed by the developing device and then transferred to the transfer paper carried in by the transfer device. On the other hand, on the surface of the photoconductor drum, the residual toner is removed by the cleaning device and the charging device is charged again. As a charging device of an image forming apparatus having the above process, a device such as a corotron or a scorotron is generally known, but in recent years, a scorotron charging device capable of uniformly charging and preventing excessive charging is provided. It is widely used to meet high image quality needs. Therefore, various concrete structures of the scorotron charging device have been proposed as shown in JP-A-59-56381 and JP-A-62-269176.

[0003]

[Problems to be solved by the device]

 However, it is difficult to completely remove the residual toner on the surface of the photoconductor drum with a cleaning device. Therefore, the residual toner scatters and adheres to the surface of the grid constituting the scorotron charging device facing the photoconductor drum. The discharge voltage at the toner adhesion site may become abnormally high. In other words, there is a risk that the scorotron charging device may abnormally discharge, resulting in a failure to obtain a proper image. Therefore, in order to prevent the above problems, it is necessary to frequently clean the charging device, which is extremely complicated.

The present invention has been made to solve the above-mentioned problems, and the toner attached to the grid of the scorotron charging device affects the charging performance of the photoconductor drum to cause abnormal discharge. It is an object of the present invention to provide a scorotron charging device that can prevent this.

[0005]

[Means for Solving the Problems]

 The present invention is a scorotron charging device that has a control grid and charges the surface of a photoconductor drum to a predetermined voltage. Are formed (Claim 1).

Further, the insulating layer may extend to the side surface of the linear portion (claim 2).

Furthermore, the insulating layer according to claim 1 or 2 may be applied to both end portions of the control grid in the photosensitive drum axial direction (claim 3).

[0008]

[Action]

 According to the present invention as set forth in claim 1, since the toner attached to the control grid is attached to the insulating layer formed on the surface side of the linear portion forming the control grid, the surface facing the photoconductor drum, the toner directly adheres to the control grid. Since the toner does not adhere to the control grid, the charging performance of the photosensitive drum is not affected by the adhered toner.

According to the present invention as set forth in claim 2, not only the side of the linear portion facing the photoconductor drum but also the side of the linear portion has an influence on the charging performance by the toner adhering to the side surface of the linear portion. Will no longer receive.

According to the present invention as set forth in claim 3, the charging performance of the adhered toner is not affected at both axial end portions of the photosensitive drum of the control grid.

[0011]

【Example】

 FIG. 2 is a schematic configuration diagram showing an image forming apparatus to which the scorotron charging device according to the present invention is applied.

The image forming apparatus has a contact glass 1 and a document pressing member 2 on the upper surface thereof, and is provided with various components such as an optical system L, an image forming unit P, and a transfer paper conveying system inside. It

The optical system L is composed of an exposure lamp 3 and a reflection plate 4, and is a light source section that reciprocates to perform document scanning, and reflecting mirrors 6 and 7 that reflect light reflected from the document to form an optical path. , 8, a lens 10 for adjusting the magnification of the formed image, and a fixed mirror 9 for reflecting the reflected light toward a photosensitive drum 11 described later.

The image forming means P is a photosensitive drum 11 on which an electrostatic latent image is formed, a scorotron charging device 12 for charging the photosensitive drum 11 to a predetermined potential, which will be described in detail later, and a photosensitive drum. A blank lamp 13 for removing the electric charges of unnecessary portions on 11, a developing device 14 for adhering toner to the electrostatic latent image on the photosensitive drum 11 to develop it, a transfer device 15 for transferring the toner image to a transfer paper, It is composed of a separating device 16 for separating the transfer paper from the photosensitive drum 11, a cleaning device 17 for cleaning the toner remaining on the surface of the photosensitive drum 11 after the transfer, and the like.

On the other hand, as a transfer paper conveyance system, paper feed cassettes 28 and 29 that can store transfer papers of different sizes, paper feed rollers 30 and 31 that convey the transfer papers, and conveyance rollers are arranged in this order from the upstream side in the conveyance direction. A pair 32, 33 and a pair of registration rollers 34 are arranged. Further, on the downstream side of the transfer sheet after the transfer in the conveying direction, a conveyor belt 35 that conveys the transfer sheet, a fixing device 36 that fixes the toner image transferred onto the transfer sheet onto the transfer sheet, and a transfer sheet onto the discharge tray 38. A discharge roller 37 for discharging and the like are arranged.

In the image forming apparatus having the above-mentioned configuration, the light of the halogen lamp 3 is reflected by the original document, and the reflected image is passed through the reflecting mirrors 6, 7, 8 and the lens 10 and the fixed mirror 9 to the photosensitive drum 11 Be led to. The photosensitive drum 11 is charged in a predetermined voltage by the scorotron charging device 12 while being rotated in the direction of the arrow in FIG. 2, and is then exposed by being irradiated with the original image to form an electrostatic latent image. . The electrostatic latent image on the photoconductor drum 11 is developed by the developing device 14 and then transferred by the transfer device 15 to the transfer paper fed from the paper feed cassette 28 or 29. The transfer paper after the transfer is separated from the photoconductor drum 11 by the separating device 16 and is discharged onto the discharge tray 38 via the transport belt 36, the fixing device 36, and the discharge roller 37. On the other hand, the photoconductor drum 11 after the transfer is cleaned by the cleaning device 17 to remove the residual toner on the surface thereof, and is then charged again by the scorotron charging device 12.

Here, a specific configuration of the scorotron charging device 12 will be described.

As shown in FIG. 3, the scorotron charging device 12 has a shield case 18, a charging wire 19 as a corona discharge electrode, and a grid 20 attached to the shield case 18, and has a basic configuration. There is.

The shield case 18 is a long-sized member having a discharge opening 26 in which a stainless steel plate is bent in a U-shaped cross section, and is fitted and attached to the front housing 21 at one longitudinal end thereof. ing. A handle 22 is formed on the front housing 21 so that the handle 22 can be easily attached to and detached from the image forming apparatus. On the other hand, the other end of the shield case 18 is fitted and attached to the rear housing 23. A perforated portion 24 is formed on an end surface of the rear housing 23, and a banana chip 25 is screwed into the perforated portion 24. When the scorotron charging device 12 is mounted on the image forming apparatus, the banana chip 25 is connected to a high voltage power source (not shown).

A grid 20 is attached to the discharge opening 26 of the shield case 18, so that the discharge opening 26 is covered thereby. The grid 20 is, for example, a metal plate having a thickness of about 1 mm and provided with the linear portions 20 a, and faces the photoconductor drum 11 with the shield case 18 mounted on the image forming apparatus. As shown in FIG. 1, the surface (lower side surface in FIG. 3) is coated with an insulating layer 27.

In the shield case 18, a charging wire 19 such as a tungsten wire is stretched in the longitudinal direction of the shield case 18 from the front housing 21 to the rear housing 23. One end of the charging wire 19 is connected to a banana chip 25 screwed to the rear housing 23, so that a high voltage from a high voltage power source is applied to the charging wire 19 via the banana chip 25. And is configured to perform corona discharge.

Next, the operation of the scorotron charging device 12 will be described with reference to FIG.

As shown in the figure, the scorotron charging device 12 is attached to the image forming device so that the discharge opening 26 thereof faces the surface of the photosensitive drum 11. The grid 20 installed in the discharge opening 26 with the scorotron charging device 12 installed is interposed between the surface of the photosensitive drum 11 and the charging wire 19 to form the grid 20. The insulating layer 27 coated on the linear portion 20a is arranged to face the surface of the photosensitive drum 11.

The charging wire 19 of the scorotron charging device 12 causes corona discharge when a high voltage is applied from a high voltage power source (not shown), and charges the surface of the photosensitive drum 11 to a predetermined voltage. At this time, even if the toner that has not been completely removed by the cleaning device 17 is scattered and adheres to the grid 20 of the scorotron charging device 12, the linear portion 20a forming the grid 20 is not transferred to the photosensitive drum 11. Since the opposing surfaces are coated with the insulating layer 27, the discharge is performed without being affected by the adhered toner. As described above, since the toner does not directly adhere to the grid, the discharge voltage is not locally concentrated and abnormal discharge does not occur, and a stable image can be obtained. Further, it is also convenient in that the cleaning operation period of the scorotron charging device 12 can be extended.

In the above-described embodiment, the insulating layer 27 is coated only on the surface of the linear portion 20a forming the grid 20 facing the photosensitive drum 11 described above. As described above, in addition to the above-mentioned surface, the coating may be applied up to the side surface of the linear portion 20 a forming the grid 20. With such a configuration, since there is no influence of the toner advancing to the side surface and adhering thereto, it becomes possible to further prevent the abnormal discharge of the scorotron charging device 12.

Further, the insulating layer 27 may be coated only on both longitudinal end portions of the grid 20 (both axial front and rear end portions of the photosensitive drum when the image forming apparatus is mounted). This is based on the experimental result that the toner adhesion to the grid 20 is likely to occur at both end portions in the longitudinal direction. With the above configuration, the insulating layer 27 may be partially coated, which results in cost reduction. It is possible to effectively prevent abnormal discharge of the scorotron charging device 12 while achieving the above.

The linear portion 20a forming the grid 20 is not limited to a columnar shape or a plate shape, and may be formed by pressing a metal flat plate into a mesh shape. The means for forming the insulating layer 27 is not limited to coating, and may be formed by adhering an insulating layer.

Further, in the embodiment, the example in which the insulating layer is formed in the scorotron charging device has been described, but the present invention is also applicable to a transfer device, a blank lamp part and the like.

[0029]

[Effect of device]

 As described above, the present invention is a scorotron charging device that has a control grid and charges the surface of the photoconductor drum to a predetermined voltage. Since the insulating layer is formed on the surface of the photoconductor, even if toner adheres to the surface of the grid that faces the photoconductor drum, the charging performance on the photoconductor drum is affected by the toner because it passes through the insulating layer. It is possible to prevent abnormal discharge from being generated in response to this.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a scorotron charging device of the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus to which the scorotron charging device of the present invention is applied.

FIG. 3 is a schematic perspective view showing a scorotron charging device of the present invention.

FIG. 4 is a sectional view of a main part of a scorotron charging device of the present invention.

[Explanation of symbols]

 11 Photoconductor Drum 12 Scorotron Charging Device 18 Shield Case 19 Charging Wire 20 Grid 20a Linear Part 26 Discharge Opening 27 Insulating Layer

Claims (3)

[Scope of utility model registration request] 1. A scorotron charging device having a control grid for charging the surface of a photoconductor drum to a predetermined voltage, wherein the linear portion forming the control grid is insulated on the side facing the photoconductor drum. A scorotron charging device characterized in that a layer is formed. 2. The scorotron charging device according to claim 1, wherein the insulating layer extends to a side surface of the linear portion. 3. The scorotron charging device according to claim 1, wherein the insulating layer is provided on both end portions of the control grid in the axial direction of the photosensitive drum.