JP2004109538A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove ozone produced by corona discharge from nearby an electrostatic charging device and a photoreceptor drum and to maintain excellent electrostatic charging characteristics even when the electrostatic charging device is used for a long period. <P>SOLUTION: This image forming apparatus is provided with a fan 15 and a duct 16 which blow air to nearby the electrostatic charging device 2 and a fan 17 and a duct 18 for removing remaining air near them. The fans 15 and 17 are stopped when the electrostatic charging device 2 is driven, so the amount of air coming into contact with a grid 2c of the electrostatic charging device during corona discharge is small. Thus, a layer of oxide is deterred from being formed on the surface of the grid to maintain electrostatic charging performance. Then the fans 15 and 17 are driven strongly for a given time right after the electrostatic discharging device 2 stops to remove the ozone produced during the corona discharge, nitrogen oxide and a toner suspended in a development area from nearby the photoreceptor drum. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that transfers a toner to a latent image due to a difference in electrostatic potential to form a visible image, such as an electrophotographic method, an electrostatic recording method, and ionography. The present invention relates to an image forming apparatus having a charging device for uniformly charging a body surface by corona discharge.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus that forms a visible image using a powdery toner such as an electrophotographic type or an electrostatic recording type is widely used as a copying machine, a facsimile, a printer, and the like. In such an image forming apparatus, the surface of the image carrier is uniformly charged by the charging device, and the latent image is formed by irradiating the image light with a difference in electrostatic potential. Then, the toner is transferred to the latent image to form a toner image, which is directly or primarily transferred to an intermediate transfer member, and then transferred to a recording medium.
[0003]
As the charging device, a roll made of a conductive metal is brought into contact with the image carrier, and a predetermined voltage is applied to the roll to charge the roll. There is known a corona discharger which generates a corona discharge between the electrodes and charges the corona discharge. In a charging device using corona discharge, ozone and nitrogen oxides are generated during corona discharge, and if these accumulate near the surface of the image carrier, the photosensitive layer on the surface of the image carrier may be deteriorated. This causes image deterioration such as uneven image density.
[0004]
For this reason, conventionally, there has been known a method of circulating air in a device or blowing clean air around a corona discharger to eliminate or diffuse ozone and nitrogen oxides. The image forming apparatus described in Patent Document 1 is provided with a blowing mechanism at one end in the longitudinal direction of the charging device, that is, one end in the width direction of the image forming area, and a suction mechanism at the other end. In this image forming apparatus, when the charging device is driven, clean air is sent to the periphery thereof, and this air is sucked and discharged to the outside. As a result, toner and the like floating with the ozone and nitrogen oxide generated from the charging device can be discharged to the outside. The image forming apparatus described in Patent Document 2 includes a fan that discharges air around the charging device to the outside, and a plate-shaped member that adjusts an air flow rate by the fan. This fan is always driven when the main motor and the charging device are driven, and the air flow is adjusted by the plate member to prevent foreign matter from entering the charging device.
[0005]
[Patent Document 1]
JP-A-7-301977 [Patent Document 2]
JP-A-10-123889
[Problems to be solved by the invention]
However, the image forming apparatus has the following problems.
Some charging devices using corona discharge include a grid made of a thin metal plate or a metal mesh provided with perforations in order to charge the image carrier to a predetermined potential. When this grid comes into contact with excess air during corona discharge, a layer of an oxide such as silicon is formed on the surface. When an oxide layer is formed on the surface of the grid, the electric resistance value changes, and the charging polarity also changes. Further, the grid may be insulated.
[0007]
In the conventional image forming apparatus as described above, an air flow is formed while the charging device is being driven and is blown near the charging device, so that the grid excessively contacts the air during corona discharge. For this reason, the oxide easily adheres to the grid, and the electric resistance value of the grid may fluctuate. When the electric resistance value of the grid fluctuates in this way, the charging potential of the image carrier becomes uneven, or a predetermined charging potential cannot be obtained.
[0008]
Such a phenomenon was not known before the filing of the present application, but it has also been found that the above-mentioned phenomenon is unlikely to occur when the amount of air contacting the grid during corona discharge is reduced. Was issued.
[0009]
The present invention has been made based on the above-described circumstances, and an object of the present invention is to eliminate ozone and nitrogen oxides generated by corona discharge from the vicinity of the charging device and the photosensitive drum and to extend the charging device for a long time. It is to maintain good charging performance even when used.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is an image carrier on which a latent image is formed by a difference in electrostatic potential, and a charging device for uniformly charging the surface of the image carrier by corona discharge. An exposure device for irradiating the image carrier with image light to form a latent image on the surface; a developing device for visualizing the latent image on the image carrier by selective adhesion of toner; and a vicinity of the charging device A fan that forms an airflow in the charging device, wherein the fan is driven so that the charging device stops or forms a gentle airflow when driven, and the charging device is stopped for a predetermined time immediately after the charging device stops. An image forming apparatus is provided that is driven to form a strong airflow that excludes nearby stagnant air.
[0011]
Since the fan stops or forms a gentle airflow during the operation of the charging device, the flow rate of air passing near the charging device during the operation of the charging device decreases. For this reason, when the charging device has a grid made of metal, the air that the grid contacts during corona discharge is reduced. Thereby, formation of an oxide layer on the surface of the grid can be suppressed, and the image carrier can be favorably charged. Then, immediately after the charging device stops, ozone and nitrogen oxides generated by the corona discharge are removed from the vicinity of the charging device by the airflow formed by the fan. For this reason, it is possible to prevent ozone and nitrogen oxide from coming into contact with the surface of the image bearing member and deteriorating the photosensitive layer on the surface.
[0012]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the image forming apparatus forms a plurality of toner images continuously, the charging is performed every time a predetermined number of toner images are formed. It is assumed that the driving of the apparatus is set to stop for the predetermined time or more.
[0013]
The charging device is stopped every time the image forming apparatus forms a predetermined number of toner images, and immediately thereafter, the stagnant air near the charging device is removed by the airflow formed by the fan. For this reason, even when a plurality of toner images are continuously formed, ozone and nitrogen oxide do not stay for a long time near the charging device. Since the time during which the charging device is stopped is set to be equal to or longer than the time during which the fan is driven for a predetermined time, when the charging device restarts driving, the fan stops or forms a gentle airflow. For this reason, the flow rate of air passing near the charging device during corona discharge is reduced, and formation of an oxide layer on the grid of the charging device can be prevented.
[0014]
The invention according to claim 3 is an image carrier on which a latent image is formed by a difference in electrostatic potential, a charging device for uniformly charging the surface of the image carrier by corona discharge, and an image light on the image carrier. An exposure device that forms a latent image on the surface by irradiating the toner, a developing device that visualizes the latent image on the image carrier by selective adhesion of toner, and a fan that forms an air flow near the charging device. An image forming apparatus, wherein the fan is driven to stop or form a gradual air flow when the driving of the charging device is started, and when the image forming device continuously forms a plurality of toner images, Each time a predetermined number of toner images are formed, the charging device is driven for a predetermined time so as to form a strong airflow so as to eliminate the staying air near the charging device while driving the charging device is continued. The drive of the device The immediately after it sealed, to provide an image forming apparatus, wherein the at stronger driven a predetermined time so as to form an air flow.
[0015]
The fan forms a strong airflow immediately after the charging device is stopped and each time the image forming apparatus forms a predetermined number of toner images while the charging device is driven. Therefore, even when a plurality of toner images are continuously formed, ozone and nitrogen oxide can be removed from the vicinity of the charging device while maintaining the image forming speed. Then, it is possible to prevent the image carrier from deteriorating. At this time, by appropriately setting the predetermined time during which the fan is driven, it is possible to prevent the grid of the charging device from excessively contacting the air. In addition, since the fan is stopped or forms a gentle air flow except when it is driven for a predetermined time, the grid may come into contact with excess air during corona discharge, and an oxide layer may be formed. Can be suppressed.
[0016]
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the airflow formed by the fan is moved from the back side of the charging device to the image carrier side. It shall have a duct to guide it to blow.
[0017]
The air flow formed by the fan passes through the duct and is blown from the back of the charging device to the image carrier, so that the staying air near the charging device is removed to the image carrier. For this reason, when removing ozone and nitrogen oxides, it is possible to prevent toner or fine dust floating near the charging device from entering the charging device and adhering to the grid, electrode wires, and the like. . Thereby, good corona discharge always occurs between the electrode wire and the image carrier, and the image carrier can be charged to a predetermined potential.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention according to the present application will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
The image forming apparatus includes a cylindrical photosensitive drum 1 having a surface on which a latent image is formed by a difference in electrostatic potential by irradiating image light after uniform charging. A charging device 2 for uniformly charging the surface of the photosensitive drum 1 by corona discharge; an exposure device 3 for irradiating the photosensitive drum 1 with image light to form a latent image on the surface; A developing unit 4 for selectively transferring toner to a latent image to form a toner image; a pre-transfer corotron 6 for applying a charge to the visualized toner image; and a toner image on the photosensitive drum to an intermediate transfer belt 5 A primary transfer roll 10 for transferring, a pre-cleaning corotron 7 for removing static electricity from the toner remaining on the photosensitive drum after the transfer of the toner image, a cleaning device 8 for removing residual toner on the photosensitive drum 1, And a discharging exposure device 9 which neutralizes the surface of the body drum 1.
[0019]
The primary transfer roll 10 is in contact with the inner peripheral surface of an endless intermediate transfer belt 5 whose peripheral surface is rotatably supported, and presses the intermediate transfer belt 5 against the photosensitive drum 1. . The intermediate transfer belt 5 is stretched around three support rolls 11a, 11b, 11c and a transfer opposing roll 12 for performing secondary transfer, and is driven to rotate.
[0020]
A secondary transfer roll 13 for transferring the toner image on the intermediate transfer member to a recording material is disposed at a position facing the transfer opposing roll 12, and is pressed by the transfer opposing roll 12 via the intermediate transfer belt 5. ing. A transfer bias voltage is applied between the secondary transfer roll 13 and the transfer opposing roll 12, and a recording material that is conveyed from a paper tray (not shown) and passes between both rolls is applied to a recording material on the intermediate transfer belt. The toner image is secondarily transferred. Further, a fixing device 14 for heating and melting the toner image on the recording material and pressing the toner image on the recording material is provided downstream of a portion where the secondary transfer roll 13 and the transfer opposing roll 12 face each other.
[0021]
The charging device 2 is a corona discharger, and includes a metal shield case 2a, an electrode wire 2b, a thin metal plate having a hole, and a grid 2c for charging the photosensitive drum to a predetermined potential. Have been. A high voltage is applied to the electrode wire 2b to generate corona discharge between the electrode wire 2b and the photosensitive drum 1, whereby the photosensitive drum 1 is uniformly charged. Then, the exposure device 3 forms an electrostatic latent image on the photosensitive drum. At this time, ozone and nitrogen oxides are generated by corona discharge of the charging device 2. If these accumulate near the surface of the photoconductor drum 1, the photoconductor may be deteriorated. In order to eliminate these, a fan 15 and a duct 16 for blowing air near the charging device are provided.
[0022]
Further, the toner is transferred to the electrostatic latent image formed on the photosensitive drum by a developing device provided in the developing unit 4, and is visualized as a toner image. At this time, a part of the toner is clouded and floats near the development area. A fan 17 and a duct 18 are provided for sucking and removing these, and for removing ozone, nitrogen oxides, and the like generated by the charging device 2. The fan 17 also sucks and removes ozone and nitrogen oxides generated by the pre-transfer corotron 6 and the pre-cleaning corotron 7. The air removed by the fan 17 passes through the filter 19 in the duct 18 to remove floating toner and ozone / nitrogen oxide contained in the sucked air.
[0023]
The toner image formed on the photosensitive drum is transferred onto the intermediate transfer belt 5 by the primary transfer roll 10, and four color toner images are sequentially superimposed on the intermediate transfer belt. Then, the toner image on the intermediate transfer belt 5 is secondarily transferred onto the recording material 20 at a position where the secondary transfer roll 13 and the transfer opposing roll 12 are pressed, and is conveyed to the fixing device 14. In the fixing device 14, the toner image on the recording material is heated by a fixing roll heated to a predetermined temperature, and is pressed between the recording material and a pressing roll. As a result, the toner image is melt-pressed on the recording material 20.
[0024]
Next, the operation of the charging device 2 and the fans 15 and 17 during image formation will be described based on the timing chart shown in FIG.
When image formation is started, as shown in FIG. 2A, the charging device 2 starts driving, and a high voltage is applied to the electrode wire 2a. Then, a corona discharge is generated between the charging device 2 and the photosensitive drum 1, and the surface of the photosensitive drum 1 is uniformly charged. During this time, the fan 15 is stopped. The charging device 2 stops after charging the area corresponding to the four-color toner image on the photosensitive drum 1. Immediately thereafter, the fan 15 is driven to form a strong airflow for a predetermined time, and the airflow passes through the duct 16. After passing through, it is sent to the back side of the charging device 2. Then, the air flow passes through a slit provided in the shield case 2a of the charging device 2 and is blown into the vicinity of a charging area where the charging device 2 and the photosensitive drum 1 face each other, and contains ozone and nitrogen oxides in the vicinity. Stagnant air is eliminated.
[0025]
The fan 17 operates in conjunction with the fan 15, and is driven at the same time as the fan 15 is driven. The air removed from the charged area by the fan 15 is sucked by the fan 17 and is discharged to the outside through the duct 18. At the same time, the toner floating in the vicinity of the developing area and the ozone and nitrogen oxides generated by the pre-transfer corotron 6 and the pre-cleaning corotron 7 are sucked by the fan 16 and adsorbed on the filter 19.
[0026]
On the other hand, as shown in FIG. 2B, when a plurality of toner images are continuously formed, the charging device 2 is driven while the fans 15 and 17 are stopped, and the charging device 2 is placed on the photosensitive drum. A predetermined number of toner images are continuously formed. The charging device 2 stops after charging a region corresponding to a predetermined number of toner images on the photosensitive drum 1, and immediately thereafter, the fan 15 is driven for a predetermined time so that a strong air flow is formed. Driven. As a result, air containing ozone and nitrogen oxides in the charging area is flushed from the back side of the charging device 2 to the photosensitive drum 1 side, is sucked into the duct 18, and is discharged to the outside. Further, the toner 17 and the air containing ozone and nitrogen oxide near the pre-transfer corotron 6 and the pre-cleaning corotron 7 are also removed to the outside by the fan 17. Then, after the fans 15 and 17 are stopped, the charging device 2 is driven again, and the formation of the toner image is restarted. Immediately after the image forming is completed and the charging device 2 is stopped, the fans 15 and 17 are driven for a predetermined time to remove ozone and nitrogen oxides in the charged area.
[0027]
Since the fan 15 and the fan 17 are stopped while the charging device 2 is driven, the flow rate of air passing through the charging region during corona discharge can be suppressed. For this reason, it can suppress that the grid 2c which the charging device 2 has contacts with air excessively, and an oxide layer is formed on the surface. Ozone and nitrogen oxides generated during the operation of the charging device 2 are removed by the fans 15 and 17 before staying for a long time, so that the photosensitive drum 1 is hardly deteriorated. Further, the staying air in the charging area is pushed to the photosensitive drum 1 side by the airflow sent from the back surface of the charging device 2 through the slit 2 d and is sucked into the duct 17. Therefore, it is possible to prevent the toner and the like floating in the developing area from entering the case 2a of the charging device 2 and adhering to the electrode wires 2b and the grid 2c.
[0028]
In the above-described driving example, the driving of the fans 15 and 17 is stopped while the charging device 2 is driven. However, the fans 15 and 17 are assumed to be capable of adjusting the amount of air blow during driving. As shown by the broken line, the charging device 2 may be driven weakly during driving to form a gentle air flow. Also in this case, the amount of air with which the grid 2c contacts when corona discharge is occurring is suppressed, and the same effect can be obtained.
[0029]
Next, another driving example of the charging device 2 and the fans 15 and 17 when a plurality of toner images are continuously formed in the image forming apparatus will be described.
As shown in FIG. 2C, the charging device 2 is driven while the fans 15 and 17 are stopped, and the charging device 2 charges an area of the photoconductor drum 1 corresponding to a predetermined number of toner images. Each time, the fan 15 is driven to form a strong airflow for a predetermined time. At the same time, the fan 17 is driven. At this time, the staying air in the charging area is removed by the airflow sent from the back surface of the charging device 2, and is sucked into the duct 18. When the image formation is completed, the charging device 2 is stopped. Immediately thereafter, the fans 15 and 17 are driven for a predetermined time to remove ozone and nitrogen oxides in the charged area.
[0030]
By driving the fan 15 and the fan 17 at predetermined intervals while the charging device 2 is driven in this way, even when a plurality of toner images are continuously formed, the image forming speed is maintained, and the charging area is maintained. Ozone and nitrogen oxides can be eliminated. And since the fan 15 and the fan 17 are stopped except when driven for a predetermined time, it is possible to suppress the grid from being in contact with excess air and being oxidized during corona discharge.
In this case as well, the fan 15 and the fan 17 may be weakly driven when the charging device 2 is driven, as indicated by a broken line in FIG. 2C.
[0031]
【The invention's effect】
As described above, according to the invention of the present application, in an image forming apparatus having a charging device that uniformly charges the surface of an image carrier by corona discharge, a fan that feeds an airflow to a charging area while the charging device is driven is provided. Stops or forms a slow air flow. Therefore, the amount of air contacting the grid of the charging device during corona discharge is reduced, and formation of an oxide layer on the surface of the grid can be suppressed. Further, the fan is driven immediately after the charging device is stopped, and ozone and nitrogen oxides generated by corona discharge are eliminated. For this reason, it is possible to prevent ozone and nitrogen oxide from coming into contact with the surface of the image bearing member and deteriorating the photosensitive layer on the surface.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a time chart showing operations of a charging device and a fan of the image forming apparatus shown in FIG.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 photosensitive drum 2 charging device 3 exposure device 4 developing unit 5 intermediate transfer belt 6 pre-transfer corotron 7 pre-cleaning corotron 8 cleaning device 9 static elimination exposure device 10 primary transfer roll 11 support roll 12 transfer facing roll 13 secondary transfer roll 14 fixing Equipment 15, 17 Fan 16, 18 Duct 19 Filter

Claims (4)

An image carrier on which a latent image is formed due to a difference in electrostatic potential;
A charging device for uniformly charging the surface of the image carrier by corona discharge,
An exposure apparatus that forms a latent image on the surface by irradiating the image carrier with image light,
A developing device for visualizing the latent image on the image carrier by selective adhesion of toner,
A fan that forms an air flow near the charging device,
The fan is driven so that the charging device is stopped or forms a gentle air flow when the charging device is driven, and forms a strong air flow that eliminates stagnant air near the charging device for a predetermined time immediately after the charging device stops. An image forming apparatus characterized in that the image forming apparatus is driven. When the image forming apparatus continuously forms a plurality of toner images, the drive of the charging device is set to be stopped for the predetermined time or more every time a predetermined number of toner images are formed. The image forming apparatus according to claim 1. An image carrier on which a latent image is formed due to a difference in electrostatic potential;
A charging device for uniformly charging the surface of the image carrier by corona discharge,
An exposure apparatus that forms a latent image on the surface by irradiating the image carrier with image light,
A developing device for visualizing the latent image on the image carrier by selective adhesion of toner,
An image forming apparatus having a fan that forms an airflow near the charging device,
The fan,
At the start of driving of the charging device, the charging device is driven to stop or form a gentle air flow,
When the image forming apparatus continuously forms a plurality of toner images, every time a predetermined number of toner images are formed, the air remaining near the charging device is removed while the driving of the charging device is continued. Is driven for a predetermined time so as to form a strong air flow,
The image forming apparatus is driven for a predetermined time so as to form the strong air flow immediately after the driving of the charging device is stopped. 4. The image forming apparatus according to claim 1, further comprising a duct configured to guide an air flow formed by the fan from a back side of the charging device toward the image carrier. 5. Image forming device.

Images