JP2004347662A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical image forming apparatus which reduces toner consumption according to environmental conditions such as temperature and humidity, with respect to an image forming apparatus using no drum heater and applying a refreshing mode by which the surface of an amorphous silicon photoreceptor is rubbed and polished. <P>SOLUTION: In the image forming apparatus applying a refreshing mode by which the surface of an amorphous silicon photoreceptor is rubbed and polished with an abrasive material contained in a toner, cleaning is carried out after the amount of the toner for rubbing and polishing is set by varying the formative pattern of a toner image formed on the surface of the photoreceptor. The image forming apparatus has a temperature and humidity sensing means and cleaning is carried out after the amount of the toner for rubbing and polishing is set by varying the formative pattern of a toner image on the basis of signals of temperature and humidity sensed by the temperature and humidity sensing means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an amorphous silicon (a-Si) photoconductor, and more particularly to an image forming apparatus using an a-Si photoconductor capable of suppressing image deletion. It is.
[0002]
[Prior art]
In an image forming apparatus, ozone is generated by discharge when charging is performed by a charger, and the ozone decomposes moisture in the air to generate ion products such as nitrogen oxides and ammonium salts. Since the ion product is water-soluble, it adheres to an image carrier such as a photoreceptor drum, and takes in moisture in the air, particularly in an environment of high temperature and high humidity, and the resistance of the surface of the image carrier decreases. As a result, a lateral flow of potential occurs at the edge of the electrostatic latent image formed on the surface of the image carrier, and as a result, an image deletion phenomenon occurs.
[0003]
An image carrier having an a-Si photoreceptor is used to improve the durability and free maintenance of the image carrier. However, a-Si has higher hygroscopicity than an organic photoreceptor. Such image deletion is likely to occur in an image forming apparatus using an a-Si photosensitive member.
[0004]
In order to prevent such a lateral flow phenomenon, it is necessary to remove the water which lowers the surface resistance of the image carrier.Therefore, in the past, a drum heater was put on the inner surface of the image carrier and heated to remove ion products. It has been practiced to evaporate the taken-in water to suppress a decrease in resistance of the surface of the image carrier in a high-humidity environment.
[0005]
However, a system using such a heater requires heat control means and the like, which complicates the configuration, and poses a problem such as durability with respect to abrasion of a sliding contact for supplying power to the heater. In addition, the power supply capacity increases, leading to an increase in cost. Furthermore, it takes time for the surface of the image carrier to rise to a certain temperature, which increases the time required for printing and increases power consumption.
[0006]
Therefore, as disclosed in Japanese Patent Application Laid-Open No. H11-3014, the inventor of the present application performed a solid image forming operation in which a developing operation is performed on an image carrier separately from a normal printing mode to attach a large amount of toner containing an abrasive. An image forming apparatus which does not use a heater by providing a mode for refreshing the toner by rubbing the surface of the image carrier with the toner is proposed.
[0007]
Specifically, for example, as shown in FIG. 2, before the cleaning blade 16, an elastic roller (cleaning roller 15) that rubs and polishes the surface of the image carrier 1 with a toner abrasive supplied as a solid image is provided. It is installed, and the component itself that causes a decrease in the resistance of the surface of the image carrier 1 is removed.
[0008]
[Problems to be solved by the invention]
However, the amount of moisture absorbed by the ion product that causes the reduction in the resistance of the surface of the image bearing member varies greatly depending on environmental conditions such as temperature and humidity, but is shown in JP-A-11-3014. In this method, a constant amount of toner is constantly developed and the rubbing operation is performed in accordance with the worst conditions regardless of such environmental conditions, so that the toner is unnecessarily consumed and is uneconomical.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to provide an image forming apparatus having a refresh mode for rubbing and polishing the surface of an amorphous silicon photoreceptor without using a drum heater, in accordance with environmental conditions such as temperature and humidity. An object of the present invention is to provide an economical image forming apparatus in which toner consumption is suppressed.
[0010]
[Patent Document 1]
JP-A-11-3014
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an image forming apparatus according to the present invention includes an image forming step of transferring a toner image formed by developing toner by a developing unit to an electrostatic latent image formed on an amorphous silicon photoreceptor onto a transfer material. When the image forming step is not performed, a toner image is formed on the surface of the photoconductor by a developing unit, and the toner image is cleaned, so that the surface of the photoconductor is rubbed with an abrasive contained in the toner. An image forming apparatus having a refresh mode for rubbing is characterized in that cleaning is performed by setting the amount of toner for rubbing by changing the toner image formation pattern.
[0012]
Preferably, the image forming apparatus has a temperature and humidity detecting unit, and based on a signal of the temperature and humidity detected by the temperature and humidity detecting unit, changes a formation pattern of the toner image to perform rubbing and polishing. The cleaning is performed by setting the toner amount.
[0013]
[Operation of the present invention]
According to the first aspect of the present invention, in an image forming apparatus provided with a refresh mode using an amorphous silicon photoreceptor, the amount of toner for rubbing and polishing is changed by changing a formation pattern of a toner image developed in the refresh mode. Is set, it is possible to suppress unnecessary toner consumption instead of always using a fixed amount of toner as in the related art.
[0014]
According to the second aspect of the present invention, the amount of toner for rubbing and polishing is changed by changing the formation pattern of the toner image based on the temperature and humidity signal detected by the temperature and humidity detection means provided in the image forming apparatus. Therefore, unnecessary toner consumption can be suppressed, and polishing suitable for the amount of water absorbed by the ion product that changes with temperature and humidity can be performed.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.
[0016]
The configuration and image forming process of the image forming apparatus of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing one embodiment of the color image forming apparatus of the present invention. The present invention is applicable not only to a color image forming apparatus but also to a monochrome image forming apparatus.
[0017]
Reference numeral 1 denotes an image carrier formed of an a-Si photosensitive drum, 2 denotes an exposure unit, 3 denotes a charger of the image carrier 1, and 4 to 7 denote, for example, yellow (Y), magenta (M), and cyan (C). , A developing device including a developer container of each color of black (K), 8 is a transfer material such as paper, 9 is a conveying device using an endless belt, 10 is a cleaning device for an image carrier, and slides the image carrier. It has a cleaning roller 15 for rubbing and a cleaning blade 16 for scraping off toner on the image carrier. Reference numeral 12 denotes an intermediate transfer member, 11 denotes a cleaning device for the intermediate transfer member, 13 denotes a secondary transfer device including a secondary transfer roller, and 14 denotes a fixing device.
[0018]
In the image carrier 1, when the surface layer is represented by an element ratio composition formula (a-Si _1-x C _x : H), x is 0.95 ≦ x <1, and dynamic indentation of the outermost surface is performed. The hardness is 2.94 × 10 ⁹ N / m ² or less, and the hardness on the back side of the photoconductive layer side is larger than that on the outermost surface side, and preferably, the hardness gradually increases toward the back side. With this configuration, not only the ion product but also the outermost surface layer is shaved, and the shaving amount is gradually reduced, so that a long life and high durability can be maintained. The rotation direction of the cleaning roller 15 is opposite to the rotation direction of the image carrier 1, and the rotation speed is about 1.2 when the speed of the image carrier 1 is 1. Further, it is preferable that the developer is added with 1 to 3% by weight of an abrasive having a particle diameter of 0.1 to 2.0 μm and an electric resistance of 1 × 10 ⁵ to 1 × 10 ¹⁰ Ωcm.
[0019]
In the normal image forming process in the image forming apparatus configured as described above, first, the retracting device (not shown) retracts the intermediate transfer body cleaning device 11 and the secondary transfer device 13, and is illustrated on the image carrier 1. A voltage of, for example, +300 V is supplied from a high voltage power supply for the image carrier, and the intermediate transfer body 12 is grounded. When the surface of the image carrier 1 is charged to about +800 V by the charger 3 and the image corresponding to each color is exposed from the exposure unit 2, the light-irradiated portion (exposure portion) becomes +300 V and the light non-irradiation portion ( The unexposed portion remains at + 800V.
[0020]
For this reason, when a developing bias is applied from a developing device bias power source (not shown) to a toner carrier of a developing device of a corresponding color among the developing devices 4 to 7 to develop the toner, the toner adheres to an exposed portion and a toner image is formed. It is formed. Then, the toner image moves from the image carrier 1 to the side of the intermediate transfer body 12 at the ground potential at the nip portion where the image carrier 1 and the intermediate transfer body 12 are in contact with each other, and the primary transfer is performed. When the toner images of all colors are primary-transferred to the intermediate transfer member 12, the intermediate transfer member cleaning device 11 and the secondary transfer device 13 are brought into contact with the intermediate transfer member by a retraction device (not shown), and the secondary transfer is performed. When a transfer voltage is applied to the apparatus 13 and the transfer material 8 is conveyed from a paper cassette (not shown) and brought into contact with the intermediate transfer body 12, the toner image on the intermediate transfer body 12 is secondarily transferred to the transfer material 8. Then, the sheet is heated and fixed by the fixing device 14 and discharged.
[0021]
During this time, the image carrier cleaning device 10 rubs and polishes the surface of the image carrier 1 with the cleaning roller 15 using the toner remaining without being transferred from the image carrier 1 to the intermediate transfer member 12, and furthermore, the cleaning blade At 16, the toner is scraped off the surface of the image carrier 1 to clean the image carrier 1 and prepare for the next image formation. On the other hand, the toner remaining on the intermediate transfer body 12 without being transferred to the transfer material 8 is cleaned by the intermediate transfer body cleaning device 11.
[0022]
The above is the ordinary image forming process. Next, the image carrier refresh mode, which is a component of the present invention, will be described with reference to FIGS. FIG. 2 is a diagram showing a control block of one embodiment of the image forming apparatus of the present invention, and FIG. 3 is a schematic diagram showing an example of a pattern for forming an electrostatic latent image (or toner image) in the refresh mode of the present invention. FIG.
[0023]
As described above, in an image carrier using an a-Si photoreceptor, in a high-temperature, high-humidity environment, moisture in the atmosphere is reduced due to the absorption of ion products and the high hygroscopicity of the a-Si photoreceptor itself. Incorporation reduces the surface resistance. The temperature and humidity in the image forming apparatus that have not been used for a certain period of time are considered to be equivalent to the temperature and humidity of the environment in which the image forming apparatus is installed, and image flow easily occurs in a high-temperature and high-humidity environment.
[0024]
For this reason, the cleaning operation of the image carrier is performed in a manner other than the normal image forming process described above, for example, when the power of the apparatus is turned on, when the apparatus returns from the energy saving mode, or when image flow occurs for some reason. It is preferable to carry out the test whenever necessary.
[0025]
When the power of the image forming apparatus is turned on as an example, each unit enters a preparatory operation when the power of the image forming apparatus is turned on, and the image carrier 1 and the cleaning roller 15 are driven. , The heater of the fixing device 14 is heated, the intermediate transfer body 12 is driven, and the image carrier refresh operation is performed. At the same time, the signal from the temperature / humidity sensor 17 installed in the image forming apparatus is subjected to analog / digital exchange by the A / D converter 27 (FIG. 2), and the exposure controller 25 (FIG. 2) is passed through the controller 26 (FIG. 2). Sent to 2). Then, the exposure control unit 25 (FIG. 2) previously stores the relationship between the absolute humidity calculated from the environmental temperature and humidity and the formation patterns (exposure patterns) of several types of electrostatic latent images as a table. An optimum pattern for forming an electrostatic latent image is selected based on a signal from 17.
[0026]
The formation pattern (exposure pattern) of the electrostatic latent image is formed, for example, as a pattern shown in FIG. 3, in a six-stage pattern in which the dot area ratio per unit area is changed.
[0027]
And as an example, the dot area rate when the absolute humidity calculated from the environmental temperature and humidity of 1 g / ^{m 3} or less and 0/64, the absolute humidity is the dot area rate in the case of 1 to 5 g / ^{m 3} 4/64, the absolute humidity dot area rate in the case of 5~10g / ^{m 3} 8/64, absolute humidity 16/64 dot area rate in the case of 10 to 20 g / ^{m 3,} the absolute humidity of 20 to 30 g / ^{m 3} In this case, the dot area ratio was set to 32/64, and when the absolute humidity was 30 g / m ³ or more, the dot area ratio was set to 64/64. In FIG. 3, a solid black portion is a one-dot electrostatic latent image formed by exposure, where a toner image is formed by development.
[0028]
Regarding the relationship between the absolute humidity calculated from the environmental temperature and humidity stored in the exposure controller 25 and the pattern of forming the electrostatic latent image (exposure pattern), the lower the absolute humidity is, the more the ion generation formed on the surface of the image carrier is reduced. Since the amount of moisture absorbed by the object is small, as described above, the number of dots of the electrostatic latent image per unit area is reduced, thereby reducing the amount of developed toner and the amount of toner supplied to the rubbing roller 15. Let it do.
[0029]
Conversely, the higher the absolute humidity, the greater the amount of water that the ion product absorbs. As described above, by increasing the number of dots of the electrostatic latent image per unit area, the amount of developing toner is increased, and The amount of toner supplied to the polishing roller 15 is increased.
[0030]
The portion where such an electrostatic latent image is formed may be the entire portion of the photosensitive drum or a portion thereof. Also, the size of the area where dots are formed can be set appropriately.
[0031]
Then, the refresh mode of the image carrier is started. In the refresh mode of the image carrier, first, a voltage of −300 V is supplied to the image carrier 1 from the high voltage power supply for the image carrier. This is to make it difficult for the toner formed on the image carrier 1 to be transferred to the intermediate transfer body 12. Next, a charging bias is applied to the charger 3. Thereafter, the exposure unit 2 performs pattern exposure so that the electrostatic latent image on the image carrier 1 has a dot pattern that is optimally selected as described above. Finally, a developing bias is applied to the black developing device 7 to form a dot pattern image of the toner corresponding to the electrostatic latent image on the image carrier 1.
[0032]
As described above, a required amount of toner is supplied to the rubbing and polishing roller 15, and the surface of the image carrier 1 is rubbed and polished with the abrasive contained in the toner, so that the ion generation on the entire peripheral surface of the image carrier 1 is generated. The object and other deposits are removed, and the refresh operation ends.
[0033]
In the above embodiment, the toner image formation pattern is changed by the environmental temperature and humidity to control unnecessary toner consumption. However, for example, the elapsed time from the last image formation is measured. The longer the elapsed time, the more the number of dots of the electrostatic latent image per unit area may be increased so that the amount of toner development may be controlled. It is also possible to change the image formation pattern.
[0034]
In addition, the description has been given of removing the ion product by adding a polishing agent having a polishing effect to the black toner of the developing device 7 located at the most downstream side. An abrasive may be added, or an abrasive may be added to all colors.
[0035]
【The invention's effect】
As described above, in the present invention, in the image forming apparatus having the refresh mode using the amorphous silicon photoreceptor, the amount of the toner for rubbing and polishing is changed by changing the formation pattern of the toner image developed in the refresh mode. Instead of always using a fixed amount of toner for setting, an economical image forming apparatus is provided in which toner consumption is suppressed according to environmental conditions such as temperature and humidity. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing one embodiment of a color image forming apparatus of the present invention.
FIG. 2 is a diagram showing an embodiment control block of the image forming apparatus of the present invention.
FIG. 3 is a diagram schematically showing an example of a formation pattern of an electrostatic latent image (or toner image) in a refresh mode of the present invention.
[Explanation of symbols]
Reference Signs List 1 a-Si image carrier 2 exposure unit 3 charger 4 yellow developing device 5 magenta developing device 6 cyan developing device 7 black developing device 8 transfer material 9 transfer device 10 cleaning device for image carrier 11 cleaning device for intermediate transfer member 12 Intermediate transfer member 13 Secondary transfer device 14 Fixing device 15 Rubbing and polishing roller 16 Cleaning blade 17 Temperature and humidity sensor

Claims (2)

An image forming step of transferring a toner image formed by developing toner by a developing unit to an electrostatic latent image formed on the amorphous silicon photoreceptor to a transfer material,
When the image forming step is not performed, a toner image is formed on the surface of the photoreceptor by a developing unit, and the toner image is cleaned, so that the surface of the photoreceptor is rubbed and polished with an abrasive contained in the toner. In an image forming apparatus having a mode,
An image forming apparatus, wherein the cleaning is performed by setting the amount of toner for rubbing by changing the formation pattern of the toner image. The image forming apparatus has a temperature and humidity detecting unit, and sets a toner amount for rubbing by changing a toner image forming pattern based on a temperature and humidity signal detected by the temperature and humidity detecting unit. 2. The image forming apparatus according to claim 1, wherein cleaning is performed by performing the cleaning.

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