JP2007271879A - Image-forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-forming device which uses a conductive brush, which contacts an intermediate transfer body, so as to scratch off an untransferred toner sticking to the intermediate transfer body and adequately controls a bias voltage applied to the conductive brush independently of an environmental variation so that the voltage may be kept constant. <P>SOLUTION: The image-forming device includes a bias voltage-controlling means which controls a bias voltage applied to a conductive brush from electric resistance of the whole system from the conductive brush to the intermediate transfer body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning mechanism in an image forming apparatus using electrophotographic technology, and more particularly to an image forming apparatus capable of appropriately controlling a bias voltage applied to a cleaning conductive brush.

In an image forming apparatus using an electrophotographic system, a toner image is electrostatically formed on an image carrier. In the image forming apparatus provided with the intermediate transfer member, the formed toner image is primarily transferred from the image carrier to the intermediate transfer member by the transfer unit. Further, the toner image formed on the intermediate transfer member is secondarily transferred onto the transfer material, and a toner image is formed on the transfer material. When forming a color image, a toner image of each color is formed on the image carrier by developing means, and primary transfer is performed on each intermediate transfer member, and the colors are superimposed on the intermediate transfer member. Form an image.
When secondary transfer is performed from the intermediate transfer member onto the transfer material, the toner remaining on the intermediate transfer member is removed by a cleaning device provided in contact with the intermediate transfer member after separation of the transfer material.

Although there are various cleaning methods, a case where the surface is electrostatically peeled off from the intermediate transfer member using a fur brush (an example of a conductive brush) to which a bias is applied will be described below. The toner that has been peeled off is transferred from the fur brush to a metal recovery roller that contacts the fur brush, and then scraped off and recovered by a blade that contacts the metal recovery roller.
A predetermined bias voltage needs to be applied to the fur brush that scrapes off the toner from the intermediate transfer member. This is because if the bias voltage is not applied, the toner transferred to the fur brush returns to the intermediate transfer member and causes image smearing. The intermediate transfer member includes a belt-shaped member, a drum-shaped member, and various other members. Here, the drum-shaped intermediate member is described as an example.

When the fur brush and the intermediate transfer member are separated, it is necessary to apply a bias at the time of separation in order to prevent the toner from transferring to the intermediate transfer member. Since the electrical resistance becomes infinite at the time of this separation, the maximum voltage of the transformer capacity is applied. If the fur brush is detached and attached in this state, there are problems such as damage to the brush and generation of electrostatic noise. In order to prevent this, the applied bias needs to be controlled at a constant voltage.
However, the environmental variation of the resistance value of the fur brush is quite large, and the resistance is lowered in a high temperature and high humidity environment. Therefore, when the constant voltage control as described above is performed, the current becomes remarkably large and the cleaning performance is deteriorated. On the other hand, in a low temperature and low humidity environment, the resistance increases and the current required for cleaning does not flow.

Unlike the present invention, Patent Document 1 directed to an image forming apparatus provided with a conductive brush for cleaning a photoconductor detects the resistance of the conductive brush itself in order to solve the above problem. Based on the result, control is performed so that the voltage at the portion of the conductive brush in contact with the image carrier is constant.
JP-A-4-174488

However, this method considers the case where a photoconductor is used as the image carrier, and the effect of resistance fluctuation is much larger in the intermediate transfer body than in the photoconductor, so the part where the fur brush contacts the intermediate transfer body. Even if the voltage is kept constant, the current required for cleaning cannot be obtained.
Therefore, in the present invention, the conventional intermediate transfer member as described above is provided, and the conductive brush that contacts the intermediate transfer member is used to scrape off the untransferred toner adhered to the intermediate transfer member. An object of the present invention is to provide an image forming apparatus that can appropriately control the bias voltage applied to the voltage regardless of environmental changes.

As described above, in order to control the voltage applied to a conductive brush such as a fur brush in contact with the intermediate transfer member to a constant voltage, in the case of the intermediate transfer member, simply measuring the electric resistance of the conductive brush. , Accurate constant voltage control cannot be performed. Therefore, in the present invention, the bias voltage applied to the conductive brush is controlled based on the electrical resistance of the entire system from the conductive brush to the intermediate transfer member.
As a result, even in an intermediate transfer body whose resistance is greatly influenced by the environmental change, the bias voltage to the intermediate transfer body can be appropriately controlled without being affected by the environmental change.
As a modification of the present invention, a toner recovery roller is in contact with the conductive brush, and the bias voltage control means is based on the electrical resistance of the system between the toner recovery roller and the conductive brush intermediate transfer member. A case where the bias voltage is controlled can be considered. Actually, the toner collecting roller as described above is often used. If such a toner collecting roller is made of metal, for example, a practical voltage detection circuit can be achieved because of good electrical conductivity.

  As described above, the present invention includes an image carrier that carries an image, a charging unit that charges the image carrier, an exposure unit that forms an electrostatic latent image on the image carrier, and the image carrier. Developing means for developing a toner image on the electrostatic latent image formed thereon, an intermediate transfer member for primary transfer of the developed toner image, and a toner image formed on the intermediate transfer member as a transfer material In an image forming apparatus comprising a secondary transfer means for performing secondary transfer upward and a conductive brush provided close to the surface of the intermediate transfer body and applied with a bias voltage, the image applied to the conductive brush Since the image forming apparatus includes bias voltage control means for controlling the bias voltage based on the electrical resistance of the entire system from the conductive brush to the intermediate transfer member, Brush and inside If the resistance of the transfer member varies also, can be a current flowing from the fur brush to the intermediate transfer member at a constant, it is possible to obtain an optimum cleaning current.

Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. It should be noted that the following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention.
Here, FIG. 1 is a schematic diagram of the entire image forming apparatus showing the background art of the present invention, FIG. 2 is a conceptual diagram for explaining the outline of a low voltage control unit such as a conductive brush in the image forming apparatus, and FIG. FIG. 3 is a flowchart showing a voltage control procedure by a control unit.

First, an image forming apparatus to which the present invention can be applied will be described with reference to a schematic sectional view of the electrophotographic image forming apparatus shown in FIG.
In this image forming apparatus A, an exposure unit 2, a developing unit 3, a drum cleaning unit 4, a static eliminator 5, and a charger 6 are provided around an amorphous silicon photosensitive drum 1. The charger 6 forms a latent image on the uniformly charged amorphous silicon photosensitive drum 1 by the exposure means 2, and the developer 3 forms an image visualized for each color by toner. The formed color image images are primarily transferred onto the drum-shaped intermediate transfer body 7, and the toner images of the respective colors are superimposed on the intermediate transfer body 7 to form a color image. As described above, the toner remaining on the amorphous silicon photosensitive drum 1 by the primary transfer is removed by the drum cleaning means 4. Thereafter, the surface of the amorphous silicon photosensitive drum 1 is neutralized by the neutralizer 5.

The toner image on the intermediate transfer member 7 is transferred to the transfer material 13 fed out by the registration roller 8 at the timing when the toner image on the intermediate transfer member 7 passes between the secondary transfer belt 9 and the intermediate transfer member 7. Transcribed. The transfer material 13 that has been secondarily transferred is sent to the fixing device 12 by the conveying belt 13, and the toner image on the transfer material 13 is fixed.
The secondary transfer residual toner on the intermediate transfer member 7 that has not been transferred to the transfer material 13 at the time of the secondary transfer is removed from the intermediate transfer member 7 by the intermediate transfer cleaning unit 11. As shown in FIG. 2, the intermediate transfer cleaning unit 11 uses a fur brush as an example of a conductive brush.

Details of the intermediate transfer cleaning unit 11 will be described with reference to FIG.
The intermediate transfer cleaning means 11 includes a fur brush 15 provided in contact with the outer periphery of the intermediate transfer body 7 provided with an aluminum tube 18 inside, a metal recovery roller 16 that rotates in contact with the fur brush 15, The cleaning roller 17 scrapes the toner adhering to the collecting roller 16 in contact with the collecting roller 16 from the collecting roller 16. The fur brush 15 rotates in the opposite direction with respect to the intermediate transfer member 7, and the recovery roller 16 rotates in the same direction with respect to the fur brush 15.

Accordingly, the toner on the collection roller 16 is scraped off by the cleaning blade 17 and accumulated in the toner discard box 19 below.
A voltage is applied to the collection roller 16 by a power source 20. The aluminum element tube 18 of the intermediate transfer member 7 is grounded. As a result, the collection roller 16, the fur brush 15, and the intermediate transfer body 7 constitute a series of conductive systems, and a voltage difference is generated between the fur brush 15 and the collection roller 16, and between the fur brush 15 and the intermediate transfer body 7. Thus, the toner is electrically attracted from the intermediate transfer member 7 to the fur brush 15 and further to the collection roller 16.
On the other hand, a bias voltage is applied to the collecting roller 16 as described above, and a current flows to the fur brush 15 and the intermediate transfer member 7, and an ammeter 21 for detecting the current is connected in series to the power source 20. The detection information of the ammeter 21 is sent to CPUs connected in parallel. The CPU measures the current flowing through the entire conductive system measured by the ammeter 21 and controls the power source 20 based on this current, that is, based on the electrical resistance obtained from this current, and the constant voltage Is applied to the conductive system.

Next, a method for detecting the electrical resistance and a method for controlling the bias voltage will be described with reference to the flowchart of FIG. Here, S1, S2,... Indicate processing procedure numbers.
At the start of printing, a low predetermined voltage V1 (for example, 800 V) is applied to one turn of the intermediate transfer member 7 during stable driving (S1) during the first preliminary driving before printing (S2), The current I1 "from the brush 15 to the intermediate transfer member 7 is detected (S3) and stored (S7). Further, a predetermined high voltage V2 (for example, 1300 V) is applied for the next round (S4), and “current I2 from the fur brush 15 to the intermediate transfer member 7” is measured under the high voltage (S5). Store (S8). The resistance of the fur brush 15 and the intermediate transfer member 7 has voltage dependency, and the value changes depending on the applied voltage. In this way, the impedance at the low voltage and the impedance at the high voltage are measured by changing the applied voltage when cleaning the toner after transfer and when cleaning the untransferred toner. It is for measuring.
Thereafter, from the two current values I1 and I2, a voltage V01 to be applied after transfer and a voltage V02 at the time of non-transfer are obtained according to the following equations (S9).
V01 = Idef × V1 / I1
V02 = Idef × V2 / I2
Here, Idef is a current value at the time of design.

  After the printing operation is completed, the fur brush 15 is brought into contact with the intermediate transfer body 7 in order to clean the intermediate transfer body 7. When contacting, a constant voltage V01 is applied so that an optimum current flows in the contacted state based on the impedance measured by the above method before the operation. Further, the voltage at the time of non-transfer is set to V02 and applied to the fur brush 15 at each time. When this method is used, even when the resistance of the fur brush 15 and the intermediate transfer body 7 fluctuates due to changes over time or due to environmental changes, the current can be made constant by measuring impedance, and an optimum cleaning current can be obtained. be able to.

1 is a schematic view of an entire image forming apparatus showing a background art of the present invention. FIG. 2 is a conceptual diagram illustrating an outline of a low voltage control unit such as a conductive brush in the image forming apparatus. The flowchart which shows the control procedure of the voltage by a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 2 ... Exposure device 3 ... Developing device 4 ... Drum cleaning means 5 ... Static eliminator 7 ... Intermediate transfer body 9 ... Secondary transfer belt 13 ... Transfer material 15 ... Fur brush 16 ... Collection roller 17 ... Cleaning blade 18 ... Aluminum tube 19 ... Disposal box 20 ... Power supply 21 ... Ammeter

Claims (2)

An image carrier that carries an image; a charging unit that charges the image carrier; an exposure unit that forms an electrostatic latent image on the image carrier; and the electrostatic latent image formed on the image carrier. Developing means for developing a toner image on the image, an intermediate transfer body for primary transfer of the developed toner image, and secondary transfer for secondary transfer of the toner image formed on the intermediate transfer body onto a transfer material And an image forming apparatus comprising a conductive brush provided close to the surface of the intermediate transfer member and applied with a bias voltage.
An image forming apparatus comprising bias voltage control means for controlling the bias voltage applied to the conductive brush based on an electrical resistance of the entire system extending from the conductive brush to the intermediate transfer member.   2. A toner recovery roller is in contact with the conductive brush, and the bias voltage control means controls the bias voltage based on an electrical resistance between the toner recovery roller and the conductive brush intermediate transfer member. The image forming apparatus described in 1.

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