JP2004069814A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing an abnormal image such as a stripe-state void image caused by the sticking of silica to a photoreceptor by reducing the adhesive force of the silica to the photoreceptor. <P>SOLUTION: The image forming apparatus is equipped with a discharge device 10 and a potential sensor 11 between a transfer device 5 and a cleaning device 6. The discharge device 10 applies bias to the surface of the photoreceptor 1 to change the surface potential of the photoreceptor to 0±200V. Then, it is provided with a control mechanism for controlling the bias of the discharge device 10 according to a value from the sensor 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, such as a copying machine, a printer, and a facsimile, using silica as an additive of a toner.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile, an external additive such as silica or titanium oxide is added in order to secure the chargeability and fluidity of a toner used. In particular, since silica has a good function of enhancing transfer efficiency, the amount of silica added has been increasing due to recent demands for higher image quality.
However, as a drawback, the amount of silica floating in the toner increases, and as a result, silica partially adheres to the photoreceptor, resulting in an abnormal image having a short streak-like white spot in the circumferential direction. Further, such short streak-like white spots tend to occur more frequently in non-image areas where the charged potential of the photosensitive member after transfer is high.
[0003]
For example, Japanese Patent Application Laid-Open No. 6-19371 proposes a technique in which a charger is provided in front of a cleaning device, and electric charge is applied to a transfer residual toner on a photoconductor, thereby making cleaning easier. However, in this technique, although the cleaning property of the transfer residual toner is improved, the potential of the photosensitive member is increased, so that the adhesive force between the photosensitive member and the silica is increased, and the abnormal image may be lengthened.
Also, Japanese Patent Application Laid-Open No. 7-191590 proposes a technique in which a light irradiating means is provided in front of a cleaning device to attenuate the charging potential of a photoconductor to improve the cleaning property of transfer residual toner. However, in the light irradiating means, it is difficult to control the surface potential of the photoconductor by the charge erasing light, and the abnormal image may be increased depending on the attenuation of the charging potential.
On the other hand, for example, Japanese Patent Application Laid-Open No. 2001-201888 proposes a technique in which silica is prevented from aggregating and causing image defects such as white spots by defining a prescription for surface treatment of silica added to a toner. . However, this technique cannot completely prevent the silica from sticking to the photoconductor.
[0004]
[Problems to be solved by the invention]
In view of the above problems, the present invention reduces the adhesion between silica and a photoreceptor, improves not only the transfer residual toner, but also the cleaning efficiency of silica, and causes abnormalities such as streak-like white images due to the adhesion of silica. It is an object to provide an image forming apparatus in which an image is prevented.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention according to claim 1 includes a photoconductor, a charging device for charging the surface of the photoconductor, an exposure device for forming a latent image on the surface of the photoconductor, and a developing device for developing the latent image. An image forming apparatus including: a developing device that forms a toner image by transfer; a transfer device that transfers the toner image; and a cleaning device that collects toner and foreign matter remaining on the photoconductor. A discharge device is provided on the upstream side in the body rotation direction, and the discharge device is an image forming apparatus that changes the surface potential of the photoconductor.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the discharge device applies a bias to the surface of the photoconductor to change the surface potential of the photoconductor to 0 ± 200V. is there.
According to a third aspect of the present invention, in the image forming apparatus, the amount of silica added to the toner for developing the latent image is 0.5 to 5.0% by mass. Image forming apparatus.
[0006]
According to a fourth aspect of the present invention, in the image forming apparatus, a detecting device for detecting a photoconductor surface potential after applying a bias by a discharge device, and a control for maintaining a constant photoconductor surface potential after applying a bias by the discharge device. 4. The image forming apparatus according to claim 1, further comprising a mechanism.
According to a fifth aspect of the present invention, the control mechanism determines that a mechanical abnormality has occurred and issues an abnormality signal when the potential cannot be controlled even if the number of times of control exceeds a designated number of times. Image forming apparatus.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect, the control mechanism is capable of designating the number of discharge intervals according to the number of photoconductor prints.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an image forming area of the image forming apparatus of the present invention.
Reference numeral 1 denotes a photoreceptor that carries an electrostatic latent image. The photoreceptor is uniformly charged by a charging device 2 and forms an electrostatic latent image by exposure 3 from an exposure device. The electrostatic latent image is visualized by the toner charged in the developing device 4. After forming the visualized toner image on the photoreceptor 1, the transfer device 5 transfers the toner image to a transfer paper (not shown), and the fixing device (not shown) fixes the toner on the transfer paper to the transfer paper. Foreign matter such as toner and paper dust remaining on the photoreceptor 1 without being transferred is scraped off by the rubbing of a cleaning blade 7 provided in the cleaning device 6 and conveyed by a conveying screw 8. Thereafter, the surface of the photoconductor 1 is neutralized by the neutralization device 9.
[0008]
In the basic configuration described above, the present invention cleans the silica on the photoreceptor in order to prevent a streak-like white spot image due to the adhesion of the silica released from the toner and adhering to the photoreceptor.
As a feature of the present invention, a discharge device 10 is newly provided between the transfer device 5 and the cleaning device 6, and a bias is applied to the surface of the photoconductor 1 after the transfer, so that the surface potential of the photoconductor 1 is changed. Further, a potential sensor 11 for detecting the surface potential of the photoconductor 1 is provided downstream of the discharge device 10 in the rotation direction of the photoconductor 1, so that the surface potential of the photoconductor 1 after applying a bias by the discharge device 10 can be measured. .
[0009]
FIG. 2 is a graph showing the relationship between the amount of silica added and the number of foreign substances adhered on the photoconductor 1. As shown in FIG. 2, when the amount of silica added to the toner exceeds 0.5% by mass, the amount falls outside the allowable range, resulting in an abnormal image. However, in order to obtain good toner transfer efficiency, the amount of silica added is preferably 0.5% by mass or more.
FIG. 3 is a graph showing the relationship between the surface potential of the photoconductor 1 before cleaning and the number of adhered foreign substances on the photoconductor 1. As shown in FIG. 3, by lowering the surface potential of the photoconductor 1 by the discharge device 10, the number of adhered foreign substances is reduced. Even if the amount of silica added is 5%, the number of adhered particles can be reduced to the allowable number by setting the surface potential of the photoconductor 1 to -200V. Therefore, by setting the surface potential of the photoreceptor 1 to 0 ± 200 V and adding the silica in an amount of 0.5 to 5.0% by mass, the adhesion of the silica is reduced and the streak-like white image is prevented. Can be. Although only the negative electrode region is shown in FIG. 3, the same applies to the positive electrode side.
[0010]
In addition, the surface potential of the photoconductor 1 changes due to environmental changes, deterioration of the photoconductor 1, and the like. FIG. 4 is a graph showing a relationship between a temperature change and a surface potential of the photoconductor 1 as an example of an environmental change. As shown in FIG. 4, even when the applied bias is constant, the discharge characteristics change due to environmental changes, and the surface potential of the photoconductor 1 after the bias is applied changes.
FIG. 5 is a graph showing the relationship between the number of prints and the charged potential of the photoconductor 1 as an example of the fluctuation due to the deterioration of the photoconductor 1. As shown in FIG. 5, the charging potential of the photoconductor 1 changes over time, and the surface potential of the photoconductor 1 changes after application of the bias.
In order to cope with such changes in the discharge characteristics and the photosensitive member charging characteristics, the present invention includes a control mechanism that changes the bias of the discharge device 10 according to the value of the potential sensor 11. FIG. 6 is a flowchart showing a system of the control mechanism. By using this control mechanism, the surface potential of the photoconductor 1 can be controlled to the intended potential of 0 ± 200 V regardless of environmental fluctuations and deterioration of the photoconductor 1, and an effect can be stably obtained.
Further, when the control is not completed even if the number of times of the control is exceeded, it is preferable to provide a control mechanism for judging that the machine is abnormal and stopping the machine by an abnormal signal to prevent runaway or the like.
[0011]
FIG. 7 is a graph showing a relationship between the number of prints and the number of adhered foreign substances on the photoconductor 1. As shown in FIG. 7, the adhesion of foreign matter on the surface of the photoconductor 1 tends to occur relatively early, and tends to decrease over time.
Therefore, in addition to the system of FIG. 6, it is preferable to add a control mechanism capable of designating the number of bias application intervals of the discharge device 10 according to the number of prints. FIG. 8 shows a flowchart of the system. When the power is turned on, the control of CONT1 is performed, and the ratio of the number of times of bias application (the number of times of discharge / the number of prints) is designated. Over time, the number of times of bias application is reduced in accordance with the number of prints. And reduce power consumption.
As a result of an experiment conducted by the inventor, it was possible to prevent initial adhesion of foreign matters by controlling the discharge device 10 to apply a bias up to the number of prints of 10K and not to perform the bias after 10K.
[0012]
【The invention's effect】
As described above, according to the first aspect of the present invention, a discharge device is provided upstream of the cleaning device, and the surface potential of the photoconductor is changed to reduce the adhesive force with the silica. It is possible to provide an image forming apparatus in which the cleaning performance is improved and an abnormal image is prevented.
Further, according to the present invention as set forth in claims 2 and 3, by setting the surface potential of the photoreceptor to 0 ± 200 V and the addition amount of silica to 0.5 to 5.0% by mass, higher cleaning properties can be obtained. An image forming apparatus that can be obtained can be provided.
Further, according to the present invention, by providing a detection device for detecting a photoconductor surface potential after applying a bias by a discharge device, and a control mechanism for controlling a bias according to the value, the environment is improved. It is possible to provide an image forming apparatus that can always keep the surface potential of the photoconductor at a target potential in response to fluctuations, deterioration of the photoconductor, and the like.
Furthermore, according to the present invention described in claim 5, it is possible to provide an image forming apparatus that prevents a machine runaway by issuing a machine abnormality signal when it is determined that the control cannot be performed by the control mechanism of claim 3. it can.
Further, according to the present invention, there is provided an image forming apparatus in which the generation of ozone and the power consumption are reduced by reducing the number of unnecessary bias applications by the discharge device, and the environment is considered. Can be.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an image forming area of an image forming apparatus of the present invention.
FIG. 2 is a graph showing the relationship between the amount of silica added and the number of foreign particles adhered on a photoreceptor.
FIG. 3 is a graph showing a relationship between a photoconductor surface potential before cleaning and the number of adhered foreign substances on the photoconductor.
FIG. 4 is a graph showing a relationship between a temperature change and a photoconductor surface potential.
FIG. 5 is a graph showing the relationship between the number of prints and the charging potential of the photoconductor.
FIG. 6 is a flowchart illustrating a system of a control mechanism for changing a bias of the discharge device.
FIG. 7 is a graph showing a relationship between the number of prints and the number of adhered foreign substances on a photoconductor.
FIG. 8 is a flowchart showing a system of a control mechanism for specifying a bias application interval of the discharge device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Charging device 3 Exposure 4 Developing device 5 Transfer device 6 Cleaning device 7 Cleaning blade 8 Transport screw 9 Static elimination device 10 Discharge device 11 Potential sensor

Claims (6)

A photoconductor, a charging device that charges the photoconductor surface, an exposure device that forms a latent image on the photoconductor surface, a developing device that develops the latent image into a toner image, a transfer device that transfers the toner image, An image forming apparatus including a cleaning device that collects toner and foreign matter remaining on the photoconductor,
The image forming apparatus includes a discharge device on the upstream side of the cleaning device in the photoconductor rotation direction,
An image forming apparatus, wherein the discharge device changes a photoconductor surface potential. 2. The image forming apparatus according to claim 1, wherein the discharge device applies a bias to the surface of the photoconductor to change the surface potential of the photoconductor to 0 ± 200V. 3. The image forming apparatus according to claim 1, wherein the amount of silica added to the toner for developing the latent image is 0.5 to 5.0% by mass. The image forming apparatus includes: a detection device that detects a photoconductor surface potential after a bias is applied by a discharge device; and a control mechanism that keeps the photoconductor surface potential constant after a bias is applied by the discharge device. Item 4. The image forming apparatus according to any one of Items 1 to 3. The image forming apparatus according to claim 4, wherein the control mechanism determines that a mechanical abnormality has occurred and outputs an abnormality signal when the potential cannot be controlled even if the number of times of control exceeds a designated number of times. The image forming apparatus according to claim 4, wherein the control mechanism is capable of designating a discharge interval number according to a photoconductor print number.

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