JPH0667500A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent filming of silica, etc., produced on the surface of a photosensitive drum and to prevent the deterioration of the surface caused by the exposure of the drum surface to an oxidizing atmosphere produced by the operation of a discharger. CONSTITUTION:When the device detects by the number of counts of a sheet-feed counter that the number of transfer sheets has reached a prescribed number, the surface of the drum 1 is electrified with no sheet fed. In the specific area on the surface of the drum 1, a solid image is developed by the sticking of toner, and the image developed with toner is scraped off by a cleaning blade 12 without being transferred to a sheet. In the removal process, the surface of the drum 1 is ground by abrasive function which toner itself has.

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 an electronic copying machine or a printer, and more particularly to filming of silica or the like as a toner external additive generated on the surface of a photoconductor or deterioration of the surface of the photoconductor. The present invention relates to prevention of defective printing.

[0002]

2. Description of the Related Art As is well known, in this type of image forming apparatus, the surface of a photosensitive drum that rotates at a constant speed in one direction is charged by a discharger, and the charged photosensitive drum surface, that is, the photosensitive surface is charged. A latent image is formed by exposing using a halogen lamp, an LED array, a laser beam, etc., toner is electrically attracted and adhered to the electrostatic latent image for development, and the visible image obtained by the development is After the transfer from the photosensitive surface of the drum to the paper surface, the toner remaining on the surface of the drum is scraped off by a cleaning device.

By the way, in recent years, a one-component magnetic toner in which a magnetic material is contained in the toner itself is used, and the toner is made to adhere to the latent image on the surface of the organic photoconductor charged with opposite polarity. Although a model equipped with a so-called one-component magnetic flying developing device has been put into practical use, a one-component magnetic toner has a toner surface modification compared to a non-magnetic one-component developer or a two-component developer which has been widely used in the past. It is characterized in that the amount of silica used as an external additive for quality is relatively large. However, since the silica contained in the one-component magnetic toner has a very small particle size of about 5 nm, even if the toner remaining on the surface of the photoconductor drum is scraped off with a cleaning blade, the toner does not adhere. It is difficult to remove the unfilled area. Therefore, depending on the ratio of the toner amount in the paper, a so-called filming, in which a silica layer is locally formed on the surface of the photoconductor drum when the number of printed sheets reaches several tens to several hundreds. There was a problem that it occurred.

[0004]

When this filming occurs on the surface of the photosensitive drum, the charged potential of the drum decreases (sometimes rises), and the normal potential is not maintained. Other than the above, the area of the paper that should be a white background will be printed in black. Problems such as filming occur frequently on both sides of the paper on which characters are not printed or on blank spaces between lines when printing a standard document continuously, and are compatible with large-sized paper. When printing on a large-sized paper surface occasionally using a model that is unevenly printed on the small-sized paper surface, it is likely to occur in the paper surface area other than the portion corresponding to the small-sized paper surface.

In order to suppress the occurrence of such silica filming, conventionally, a cleaning blade having a hardness adapted to a one-component magnetic toner is selected, and the pressing force of the blade with respect to the surface of the photosensitive drum is adjusted. Alternatively, although measures have been taken such as using a type of silica that is less likely to cause filming, at present, no remarkable suppression effect has been obtained.

In addition to the silica filming described above, the surface of the photosensitive drum is conventionally exposed to an oxidizing atmosphere such as ozone (O ₃ ) or nitrogen oxide (NO _x ) generated when the discharger operates. There was a problem. That is, it is known that ozone, nitrogen oxides, etc. are generated in the machine by corona discharge generated at the time of transfer from the drum to the paper surface, but when exposed to such an oxidizing atmosphere, the surface of the organic photosensitive drum deteriorates. Is promoted and the printing quality is significantly deteriorated.

To prevent this, conventionally, the exhaust efficiency in the machine in which the photosensitive drum is housed is increased, or the drum is rotated and released so that the same portion of the drum is not repeatedly exposed to the oxidizing atmosphere. I was adjusting the operation timing with the electric appliances.

[0008] However, the former measure for improving the exhaust efficiency has a technical difficulty because it is necessary to add an exhaust fan to be installed inside the machine and solve a design problem related to the distribution of the air flow inside the machine. Also, the latter measure of adjusting the operation timing of the discharger is effective in suppressing the deterioration of the drum surface, but even if any of the measures can delay the deterioration of the drum surface, It is impossible to lose. Therefore, it is difficult to maintain the print quality over many sheets in any case.

The above-mentioned various problems are particularly remarkable when the one-component magnetic toner is used as the developer, but also when the one-component non-magnetic toner or the two-component developer is used. It occurs to a similar extent to varying degrees.

The present invention has been made in order to solve the above problems, and prevents the filming of silica or the like generated on the surface of the photosensitive member by a relatively simple means and also causes it by the operation of the discharger. The purpose is to prevent the deterioration of the surface of the photoconductor due to exposure to the oxidizing atmosphere.

[0011]

In order to achieve the above object, the present invention provides an image forming apparatus in which a charging section, an exposing section, a developing section, a transferring section and a cleaning section are arranged along the traveling direction of a photoreceptor. A paper feed detecting means for detecting a non-paper feed state, a charging means for receiving a detection signal from the paper feed detecting means to operate the charging section to charge the surface of the photoconductor, the exposing section, the developing section or the developing section. And a means for adhering the toner to a specific area on the surface of the photoconductor that is charged by operating only the image forming section, and a means for turning off the transfer section while at least the toner adhesion specific area on the surface of the photoconductor passes through the transfer section. The toner attached to the specific region is scraped and collected by the cleaning unit when the specific region passes through the cleaning unit.

The toner adhering means may be provided with means for creating image information to be imaged in a specific area on the surface of the photoconductor by the exposing section. In the case of using a one-component magnetic toner, a high-frequency AC bias is applied to the developing device to cause the toner prepared in the developing device to fly and adhere to a specific area on the surface of the photoconductor. Further, preferably, the specific area on the surface of the photoconductor is set to an area having no image information for transfer on the surface.

[0013]

According to the above structure, the time gap in the non-feeding state such as the paper feed standby gap in continuous paper feeding is used to charge the photoconductor in the same manner as in normal printing, and the toner is applied to a specific area on the photoconductor surface. After the toner is adhered, the cleaning is performed by scraping and collecting the visible image due to the toner adhesion, and in the scraping process, the specific region and the corresponding photoconductor surface region along the traveling direction of the photoconductor. The filming layer typified by silica is ground and removed by the polishing function of the toner itself, so that the surface of the photoconductor is refined and local stains on the paper surface due to contamination with silica etc. are ensured. It can be lost. Further, by regularly repeating the refining by appropriately scraping the surface of the photoconductor, the deteriorated portion of the surface of the photoconductor due to the oxidizing atmosphere generated at the time of discharge is removed by grinding each time, so it is constantly updated. Original high-quality printing is maintained by the photoconductor.

[0014]

FIG. 1 schematically shows the structure of an image forming apparatus embodying the present invention, in which 1 is a photosensitive drum which rotates in one direction at a constant speed, and this drum 1 is the surface of a drum substrate. Is formed by vapor deposition of a photosensitive material. Around the drum 1, a charging unit 2, an exposing unit 3, a developing unit 4, a transferring unit 5, a separating unit 6, a cleaning unit 7, and a charge eliminating unit 8 are provided in this order along the traveling direction, that is, the rotating direction. ing.

The charging section 2 has a charge wire 2b arranged in a U-shaped case 2a in proximity to the surface of the photosensitive drum 1 along the drum axis direction. A high voltage is applied to the charge wire 2b, and the surface of the photosensitive drum 1 is normally charged to about 700V by the voltage. When this charged portion is exposed by the next exposure unit 3, the exposed portion is positively charged, whereby an electrostatic latent image is formed.

The developing section 4 is composed of a one-component magnetic flying developing device. That is, the developing unit 4 is provided with an agitator 9 in the containing unit 4a for the one-component magnetic toner, and a sleeve 10 that is closely opposed to the photosensitive drum 1 and rotates at the same speed as the drum 1. . The toner stirred by the agitator 9 is sent to the sleeve 10,
It is negatively charged by friction with the surface of the sleeve 10. When a high-frequency AC bias is applied to the sleeve 10, the surface polarities are positively and negatively alternated and vibrated, so that the toner floats from the surface of the sleeve 10 and flies toward the surface of the drum 1. . Since the exposed area on the surface of the drum 1 is positively charged, toner having a negative charge is attached, and the unexposed area has a negative polarity, so the toner repels. As a result, the toner adheres to the latent image formed on the surface of the drum by the exposure, and a visible image appears.

The toner on which this visible image is formed is fed by the paper feed roller 1.
It is transferred at the transfer unit 5 to the paper fed through 1. The separating unit 6 serves to separate the transferred sheet from the drum 1 by releasing the suction state between the drum 1 and the sheet by applying an AC electric field to the drum surface. Thereafter, the toner remaining on the drum surface is subjected to the toner wiping action by the blade 12 made of a rubber material in the cleaning unit 7, and the charge removing unit 8 removes the charge on the drum surface.
Ready for the next print.

In the image forming apparatus having the above-described basic structure, in this embodiment, a specific portion of the surface of the photoconductor drum is ground by the toner so that the surface of the photoconductor is not contaminated by a component such as silica contained in the toner. It is significantly different from the conventional one in that the configuration is added. That is, in FIG. 2, 13 is a paper feed detecting means for detecting whether or not a paper is fed to the transfer portion 5, and 14 is a paper feed detecting means 13 which has not fed a paper such as a standby gap for continuous paper feeding at present. A charging unit that operates the charging unit 2 when a signal notifying that it is in a state is output, and 15 is an exposure unit for exposing image information of a predetermined shape and size on a specific area set in advance on the charged drum surface. An exposure unit for operating the unit 3, and a developing unit 16 for operating the developing unit 4 so that toner is attached onto the electrostatic latent image of the image information obtained by the exposure and the image of the image information is exposed on the drum surface. A means 17 is a transfer-off means for turning off the transfer portion 5 while the specific region where the development is exposed passes through the transfer portion 5.
All of 3 to 17 are controlled by a central control unit 18 of a microcomputer incorporated in the device. Reference numeral 19 is a paper feed counter provided in the central controller 18. In addition, generally, in the sheet feeding gap in continuous sheet feeding, the transfer unit 5 is used.
Is turned off, the configuration may be operated as the transfer off means 17.

In such a construction, when it is detected by the count number of the paper feed counter 19 that the number of transferred sheets of paper until silica filming becomes remarkable is detected by the paper feed counter 19, the paper feed detection means 13 operates. , And outputs a signal notifying that the sheet is not fed, such as the start time of the standby gap for continuous feeding. About 10 to 100 sheets are suitable for the number of transferred sheets. In response to the signal output from the paper feed detection means 13, the charging means 14 operates the charging section 2 to charge the surface of the photosensitive drum. When the drum surface is charged, the exposure means 1
5 operates the exposure unit 3 to expose the above-mentioned image information to a specific area on the drum surface.

FIG. 3 shows the surface of the photosensitive drum 1 unfolded,
3 schematically shows an example of a specific area in which the image information is imprinted. In the figure, 20 is a drum surface, and 21 is a paper area corresponding to the transfer paper on the drum surface. In the case of a normal fixed-size document, the print area 22
Is placed in the central area of the paper area 21, so that the printing area 2
Surrounding 2 is a frame-shaped blank area 23 with a width of several centimeters.
Is formed. The above-mentioned specific area 24 is set in this blank area 23.

The image information to be imprinted in the specific area 24 is, as shown in FIG. 3 in the form of overlapping on the specific area 24, a straight line having a width of 2 to 3 mm and a length across the blank area 23. A so-called black solid image can sufficiently perform the grinding action of the drum surface. In a digital type image forming apparatus, this solid black image information is given by an exposure lamp 25 (see FIG. 1) formed of an LED array or the like arranged along the axial direction of the photosensitive drum 1 or a laser beam. It can be easily created by controlling the optical information provided. Further, in the analog type image forming apparatus, as shown by the chain double-dashed line in FIG. 1, a shield 27 that shields a part of the optical axis 26 of the transfer image through which the optical axis 26 of the halogen light or the like passes. It can be created by facing.
Further, in the standard document as described above, a blank space between lines is formed even in the print area 22, and therefore, in the blank area 23 which is the upper end in the figure of the paper area 21 corresponding to this blank space between lines in the drum running direction. The specific region 24 'may be formed as shown by the broken line.

In this way, when the image information is exposed on the specific area of the drum surface to form a latent image of the image information,
The developing unit 4 operates in response to a signal from the developing unit 16, and the toner supplied from the developing unit 4 adheres to the latent image to form a visible image of image information on the drum. Then, at the same time when the drum 1 is rotated, the transfer unit 5 is operated by the operation of the transfer off means 17.
Is turned off. Therefore, the toner forming the visible image on the drum surface reaches the cleaning unit 7 by the rotation of the drum 1 without being transferred, and is scraped and collected by the blade 12 of the cleaning unit 7.

In the process in which toner is scraped off the surface of the drum by the blade 12 of the cleaning section 7, the blade 12 has blank areas on both sides of the print area 22 corresponding to the specific area 24 in the traveling direction of the drum 1 (shaded lines in FIG. 3). The toner adhering to the specific area 24 is pressed against 23a, 23a (shown by a portion) with a strong force by the sliding action of the blade 12, whereby the blank area 23a,
The silica filming layer formed on 23a is effectively scraped off by the polishing function of the toner itself, and a new drum photosensitive surface is generated. After the operation of the cleaning unit 7, the charge removing unit 8 removes the charge on the drum surface, and the normal printing mode is restored.

The shaving of the drum surface with the toner as described above is the most effective because the one-component magnetic toner has a better polishing ability than the other toners, but has a drawback that filming is likely to occur. It can be said that the drum surface can be carved out by utilizing the toner polishing function even in the other models using the two-component developer.

In the above embodiment, the toner adhering means operates the exposing portion and the developing portion to form a latent image on a specific area on the surface of the photoconductor drum, and then the toner is attached onto the latent image. However, in the case of using a one-component magnetic flying developing device, a black solid image is formed by a so-called bias developing method in which a high-frequency AC bias is applied to the developing device for a short period of time to cause toner to fly and adhere to the surface of a charged photoreceptor. The image may be formed in a specific area. Further, the present invention can be applied to any apparatus of the reversal recording method in which the toner is attached to the exposed portion as in the present embodiment and the ordinary recording method in which the toner is attached to the unexposed portion.

[0026]

As described above, according to the present invention, the toner is adhered to a specific area on the surface of the photoconductor in the time gap in which the paper is not fed, and the toner is scraped by the cleaning unit without transferring the toner to the paper. At the time of collecting and collecting the toner, since the surface of the photoconductor is ground by the polishing function of the toner itself, a specific region on the surface of the photoconductor, in which foreign matter typified by silica filming adheres, that is, a large number of sheets A region where a visible image due to toner adhesion is not formed and the above-described filming is likely to occur can be refined. Therefore, to prevent deterioration of the surface of the photoconductor due to exposure of the surface of the photoconductor to an oxidizing atmosphere containing ozone, nitrogen oxides, etc. generated by the adhesion of foreign matter to the surface of the photoconductor or the discharge of the transfer portion. It is possible to eliminate image defects such as black streaks, white streaks, image blurring, and cleaning defects that appear on the sheet transferred due to the deterioration of the other surface of the photosensitive material.

[Brief description of drawings]

FIG. 1 is a front view schematically showing the configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a main part thereof.

FIG. 3 is a diagram schematically showing an example of developing a surface of a photosensitive drum and allocating various areas on the surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging part 3 Exposure part 4 Developing part 5 Transfer part 7 Cleaning part 12 Blade 13 Paper feed detecting means 14 Charging means 15 Exposure means 16 Developing means 17 Transfer off means 24 Specific area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Tsuji 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (4)

[Claims] 1. An image forming apparatus in which a charging section, an exposing section, a developing section, a transfer section and a cleaning section are arranged along a traveling direction of a photoconductor, and a paper feed detecting means for detecting a non-feed state, A charging unit that operates the charging unit to charge the surface of the photoconductor in response to a detection signal from the paper feeding detection unit, and a specific region on the surface of the photoconductor charged by operating only the exposure unit and the developing unit or the developing unit. A means for adhering toner and a means for turning off the transfer portion while at least the toner adhering specific area on the surface of the photoconductor passes through the transfer portion, and the toner adhering to the specific area is stored in the specific area An image forming apparatus characterized in that it is scraped and collected by the cleaning unit when passing through the cleaning unit. 2. The image forming apparatus according to claim 1, wherein the toner adhering means includes means for creating image information to be imaged in a specific area on the surface of the photoconductor by the exposure section. 3. The toner adhering means applies a high-frequency AC bias to the developing device to fly-adhere the one-component magnetic toner prepared in the developing device to a specific region on the surface of the photoconductor. Image forming apparatus. 4. The image forming apparatus according to claim 1, wherein the specific area on the surface of the photoconductor is set to an area having no image information for transfer on the surface of the photoconductor.