JP2000162934A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing image flowing in the case of using a scorotron electrifier. SOLUTION: A casing 63 having an aperture on the extension in the axial direction of a photoreceptor drum 1 is provided to be opposed to a gap between the grid of the scorotron electrifier 2 and the drum 1. An axial fan 62 is attached to the casing 63 so as to consecutively or intermittently exhaust air in the gap while image forming operation is executed and also after the image forming operation is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer and an electrostatic recording device.

[0002]

2. Description of the Related Art FIG. 6 is a schematic configuration diagram showing a conventional example of an image forming apparatus. A photoconductor (photosensitive drum) 1 as an image carrier has a photoconductive layer provided on a cylindrical conductive substrate, and is rotatably supported in a direction of an arrow R1 in the drawing.
A scorotron charger 2 for charging the surface of the photosensitive drum 1 is read around the photosensitive drum 1 in order along the rotation direction, a document is read, and the photosensitive drum 1 is exposed based on an image signal. An exposure device for forming a latent image; a developing device 4 for forming a toner image by attaching toner to the electrostatic latent image; a surface potential sensor 41 for detecting a surface potential of the photosensitive drum near a developing position; Transfer charger (transfer charger) 8 for transferring the image formed on the transfer paper P as a transfer material, and an electrostatic separation charger (separator) for separating the transfer paper P on which the image has been transferred from the photosensitive drum 1 Charger)
9. A cleaning device 13 for removing residual toner on the photosensitive drum 1 after transferring an image, a pre-exposure device (lamp) 30 for removing residual charges on the photosensitive drum 1, and the like are provided.

The transfer paper P on which the image has been transferred is transported to a fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed to form an image. It is discharged outside the device body.

On the other hand, an image scanner unit 18 illuminates the original 15 placed on the original glass table 14 with the illumination lamp 1.
6 for scanning and reading, and converting the image information into an electric signal by the photoelectric conversion element 19.
The reflected light from the original 15 scanned by the
The light is guided to a, 17b, and 17c and is imaged on the photoelectric conversion element 19 by the lens 17d.

[0005] After the electric signal is digitized by the A / D converter 21 by the photoelectric conversion element 19,
The image processing circuit 22 sets 0 (00h) proportional to the image density.
ex) to an image signal of 256 gradations from 255 (FFhex). The image signal converted by the image processing circuit 22 is sent to a laser driver 24 as a signal generator, and a laser (laser oscillator) 20
Modulates light emission from The laser light modulated according to the image signal writes an electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirror 17e as image information.

[0006]

However, particularly when amorphous silicon is used as the photoreceptor, after an image is formed in a high-humidity environment, an image defect called image deletion occurs when the image is formed after being left for a certain period of time. I got up. The occurrence of this phenomenon will be described in detail in an embodiment of the invention described later.

An object of the present invention is to provide an image forming apparatus capable of preventing occurrence of image deletion.

[0008]

A first configuration for realizing the object of the present invention according to the present application is to charge an image bearing member by a scorotron charging means, expose, develop, and develop a developed image on a transfer material. In the image forming apparatus, the air in a gap formed between the grid of the scorotron charging means and the image carrier is exhausted by an exhaust means.

In a second configuration for realizing the object of the invention according to the present application, in the above-mentioned first configuration, the exhaust unit is provided in a gap formed between the grid of the scorotron charging unit and the image carrier. It comprises a casing having an opening facing the image carrier in the axial direction and a fan attached to the casing.

A third configuration for realizing the object of the present invention according to the present application is the above-described first or second configuration, wherein the exhaust unit performs an exhaust operation at least during an image forming operation. is there.

A fourth configuration for realizing the object of the invention according to the present application is the above-mentioned first or second configuration, wherein the exhaust unit performs an exhaust operation even after the end of the image forming operation. It is.

A fifth configuration for realizing the object of the invention according to the present application is the fifth configuration according to the first, second or fourth configuration described above.
The evacuation unit intermittently performs an evacuation operation after the end of the image forming operation.

According to a sixth aspect of the invention for achieving the object of the invention of the present application, in any one of the above-described configurations, the apparatus further comprises a moisture content detecting means for detecting the moisture content in the machine, The operation time of the exhaust means is controlled based on the information.

A seventh configuration for realizing the object of the invention according to the present application is the above-mentioned one of the first to fifth configurations, further comprising a water content detecting means for detecting a water content in the machine. The exhaust amount of the exhaust unit is controlled based on the detection information of the moisture amount detecting unit.

An eighth configuration for realizing the object of the invention according to the present application is the above-mentioned one of the first to fifth configurations, further comprising a water content detecting means for detecting a water content in the machine. The operating time and the exhaust amount of the exhaust unit are controlled based on the detection information of the moisture amount detecting unit.

According to a ninth configuration for realizing the object of the invention according to the present application, in any one of the first to fifth configurations described above, the operation time of the exhaust unit is controlled based on the number of formed images. It was made.

A tenth embodiment for realizing the object of the invention according to the present application is:
According to the configuration described in any one of the first to fifth configurations, the exhaust amount of the exhaust unit is controlled based on the number of formed images.

An eleventh embodiment for realizing the object of the invention according to the present application is as follows.
Is a configuration in which, in any one of the above-described first to fifth configurations, the operation time and the exhaust amount of the exhaust unit are controlled based on the number of formed images.

A twelfth embodiment for realizing the object of the present invention according to the present application.
The image carrier according to any one of the first to eleventh embodiments, wherein the image carrier uses amorphous silicon.

[0020]

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

<First Embodiment> FIG. 3 is a schematic configuration diagram showing a first embodiment of an image forming apparatus according to the present invention.

Photoconductor (Photosensitive Drum) 1 as Image Carrier
Is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. A scorotron charger 2 for charging the surface of the photosensitive drum 1 is read around the photosensitive drum 1 in order along the rotation direction, a document is read, and the photosensitive drum 1 is exposed based on an image signal. An exposure device for forming a latent image; a developing device 4 for forming a toner image by attaching toner to the electrostatic latent image; a surface potential sensor 41 for detecting a surface potential of the photosensitive drum near a developing position; Transfer charger (transfer charger) 8 for transferring the image formed on the transfer paper P as a transfer material, and an electrostatic separation charger (separator) for separating the transfer paper P on which the image has been transferred from the photosensitive drum 1 Charger) 9,
A cleaning device 13 for removing residual toner on the photosensitive drum 1 after transferring an image, a pre-exposure device (lamp) 30 for removing residual charges on the photosensitive drum 1, and the like are provided.

The transfer paper P on which the image has been transferred is conveyed to a fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed to form an image. It is discharged outside the device body.

The image scanner unit 18 scans the original 15 placed on the original glass table 14 by scanning with an illumination lamp 16 and converts image information into an electric signal by a photoelectric conversion element 19. The reflected light from the original 15 scanned by the mirror 16 is reflected by mirrors 17a and 17a.
The light is guided to 7b and 17c and is imaged on the photoelectric conversion element 19 by the lens 17d.

After the electric signal is digitized by the A / D converter 21 by the photoelectric conversion element 19,
The image processing circuit 22 sets 0 (00h) proportional to the image density.
ex) to an image signal of 256 gradations from 255 (FFhex). The image signal converted by the image processing circuit 22 is sent to a laser driver 24 as a signal generator, and a laser (laser oscillator) 20
Modulates light emission from The laser light modulated according to the image signal writes an electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirror 17e as image information.

In the present embodiment, an amorphous silicon drum is used as the photosensitive drum 1. When an amorphous silicon drum is used, high durability, long life, and high image quality can be obtained.

However, particularly in an image forming apparatus using an amorphous silicon photosensitive drum, a corona product generated due to the presence of a charger in the apparatus and moisture present in the air, etc., on the surface of the photosensitive drum. It is known that the surface resistance of the photosensitive drum decreases due to adsorption or the like, and a phenomenon called image deletion that causes image deterioration is caused.

When this phenomenon was examined in detail, it was found that the following process was performed.

1. Ozone is generated by charging during the image forming operation.

2. Ozone reacts with nitrogen and the like in the air to form nitrogen oxides.

3. Nitrogen oxides adsorb to the charger shield and grid.

4. Adsorbed nitrogen oxides are released from the charger shield and grid. 5. The released nitrogen oxides are adsorbed on the photoreceptor.

6. Particularly in a high humidity state, nitrogen oxides and the like on the photoreceptor react with water to form nitric acid compounds.

7. Thereafter, when an image forming operation is performed, the latent image on the photoconductor whose surface resistance has been lowered by the nitric acid compound is disturbed, resulting in image deletion.

It has been found that when a scorotron charger having a grid is used as the charger, image flow after completion of image formation occurs earlier than when a corotron charger without a grid is used. FIG. 2 is a table showing experimental results showing the relationship between the pause time after completion of image formation and the occurrence of image deletion in the scorotron charger and the corotron charger.

This is presumably because nitrogen oxides adsorbed to and released from the grid in steps 3 and 4 are caused by step 5 in a short time because the grid is close to the photoreceptor. In evidence, when a part of the grid of the scorotron charger was removed, image deletion occurred in a part of the grid, but no image deletion occurred in the part where the grid was removed.

That is, in order to suppress the occurrence of image deletion when a scorotron charger is used, it is effective to discharge nitrogen oxides released from the grid to the outside of the apparatus before adsorbing to the photoreceptor. It is.

Therefore, in this embodiment, as shown in FIG. 1, a casing 63 having an opening 61 opposed to the gap between the grid of the scorotron charger 2 and the photosensitive member 1 is extended in the axial direction of the photosensitive member 1. And an axial fan 62 is attached to the casing 63 so that air can be sucked into the casing 63 from the opening 61 through the gap.

In this embodiment, the axial fan 6
The operation 2 is performed not only during the image forming operation but also after the completion of the image forming operation by exhausting the air with the axial fan 62, thereby effectively discharging the nitrogen oxides released particularly from the grid in the above step 4 to the outside of the machine. Therefore, the occurrence of image deletion can be prevented.

On the other hand, the amount of ozone generation increases or decreases according to the number of formed images, that is, the charging time. That is, the types of nitrogen oxides to be discharged also increase or decrease. Therefore, the exhaust capacity of the axial fan 62 may be controlled by changing the number of rotations of the fan according to the number of images formed.

<Second Embodiment> In this embodiment, the image flow is eliminated while saving the operation of the axial fan, and the same parts as those in the first embodiment are omitted and only different parts are described. explain.

Step 4 described in the first embodiment,
5 is performed over a relatively long time. There is some time between release of the nitrogen oxides from the grid and adsorption to the photoreceptor.

Therefore, it is effective for the image deletion even if the exhaust operation in the first embodiment is performed only from the release of the nitrogen oxides from the grid to the adsorption to the photosensitive member.

According to the experiment, the operation of the axial fan 62 was
It was found that the gas in the vicinity of the grid and the photoreceptor could be almost completely exhausted outside the apparatus when the operation was performed for one minute. Therefore, an experimental result showing the relationship between the evacuation operation stop time and the image flow when the evacuation operation is performed for 5 minutes after the image formation, the evacuation operation is stopped for a certain period of time, and the evacuation operation is repeated for 5 minutes and the evacuation operation is stopped for a certain period of time. Is shown in FIG.

Therefore, in the present embodiment, based on the experimental results shown in FIG. 4, an algorithm is provided for repeating the evacuation operation for 5 minutes after the image formation is completed and the stoppage of the evacuation operation for 1 hour. It was found that the image flow can be eliminated even by the intermittent exhaust operation by this control.

As in the present embodiment, the operation of the axial fan 62 is controlled to be performed intermittently to prevent image flow, and to reduce the power consumption by not operating the axial fan when unnecessary. Waste and fan noise were also reduced.

The amount of ozone generation increases or decreases according to the number of formed images, that is, the charging time. Therefore, the types of nitrogen oxides to be discharged increase or decrease. Therefore, the operation time of the axial fan, the operation power, that is, the number of rotations of the fan, or the exhaust operation stop time may be controlled according to the number of formed images.

<Third Embodiment> This embodiment is characterized in that the operation of the axial fan 62 is controlled in accordance with the amount of water in the machine, and is similar to that of the first embodiment. Portions are omitted, and only different portions will be described.

The image deletion phenomenon occurs due to the reaction between nitrogen oxides and water as shown in step 6 of the first embodiment. Therefore, it can be said that the evacuation operation shown in the first embodiment is necessary when the amount of moisture is large, but unnecessary when the amount of moisture is sufficiently small. FIG. 5 shows a table summarizing the experimental results showing the relationship between the water content and the occurrence of image deletion.

Therefore, in this embodiment, a moisture detection sensor 63 (not shown) for detecting the absolute moisture content in the machine is provided in the machine, and the operation of the axial fan 62 is controlled based on the value. In the present embodiment, based on the experimental results shown in FIG. 5, when the water content is 15 g or more, the axial fan 62 is operated after the completion of the image formation, and is not operated when the water content is less than 15 g.

A moisture detecting means is provided as in the present embodiment, and the operation of the axial fan 62 is controlled in accordance with the value to prevent image deletion, and the operation of the axial fan is performed when unnecessary. The absence of electricity also reduced power waste and fan noise.

[0052]

As described above, according to the present invention,
Charge the image carrier by scorotron charging means,
In an image forming apparatus that transfers a developed image onto a transfer material through exposure and development, an air flow in a gap formed between the grid of the scorotron charging unit and the image carrier is exhausted by an exhaust unit, so that an image flow is performed. Was effectively eliminated.

It is also effective to operate the exhaust unit after the image forming operation is completed, and it is also effective to intermittently operate the exhaust unit after the image forming operation is completed.

It is also effective to have a moisture detecting means, and control the operating time of the exhaust means, the operating force of the exhaust means, or both in accordance with the value.

It is also effective to control the operation time of the exhaust means and / or the operating force of the exhaust means in accordance with the number of formed images.

Further, it is particularly effective when amorphous silicon is used as the image carrier.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a charger and an axial fan in an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a table showing experimental results of a relationship between a pause time and occurrence of image deletion after image formation is completed.

FIG. 3 is a schematic configuration diagram showing a first embodiment of the image forming apparatus according to the present invention;

FIG. 4 is a table showing an experimental result of a relationship between an exhaust operation stop time and occurrence of image deletion.

FIG. 5 is a table showing experimental results of a relationship between a water content and occurrence of image deletion.

FIG. 6 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoconductor (photosensitive drum) 2 ... Scorotron charger 4 ... Developing device 61 ... Grid part opening 62 ... Axial flow fan

Claims (12)

[Claims] 1. An image forming apparatus which charges an image bearing member by a scorotron charging means, and transfers a developed image onto a transfer material through exposure and development, wherein a gap between the grid of the scorotron charging means and the image bearing member is provided. An image forming apparatus, wherein air in a gap formed in the image forming apparatus is exhausted by exhaust means. 2. A casing having an opening extending in the axial direction of the image carrier opposite to a gap formed between the grid of the scorotron charging device and the image carrier, the exhaust device being attached to the casing. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a fan. 3. The image forming apparatus according to claim 1, wherein the exhaust unit performs an exhaust operation at least during an image forming operation. 4. The image forming apparatus according to claim 1, wherein the exhaust unit performs an exhaust operation even after the end of the image forming operation. 5. The image forming apparatus according to claim 1, wherein the exhaust unit intermittently performs an exhaust operation after the end of the image forming operation. 6. The apparatus according to claim 1, further comprising a water content detecting means for detecting a water content in the machine, wherein an operation time of said exhaust means is controlled based on detection information of said water content detecting device. The image forming apparatus according to any one of the above. 7. The apparatus according to claim 1, further comprising a water content detecting means for detecting a water content in the machine, and controlling an exhaust amount of said exhaust means based on detection information of said water content detecting means.
6. The image forming apparatus according to any one of claims 1 to 5, 8. The apparatus according to claim 1, further comprising a water content detecting means for detecting a water content in the machine, and controlling an operation time and an exhaust gas amount of said exhaust means based on detection information of said water content detecting means. 6. The image forming apparatus according to any one of 1 to 5, 9. The image forming apparatus according to claim 1, wherein the operation time of the exhaust unit is controlled based on the number of formed images. 10. The image forming apparatus according to claim 1, wherein an exhaust amount of the exhaust unit is controlled based on the number of formed images. 11. The operation time and exhaust amount of the exhaust unit are controlled based on the number of formed images.
6. The image forming apparatus according to any one of claims 1 to 5, 12. The image forming apparatus according to claim 1, wherein the image carrier uses amorphous silicon.