JPH08292623A - Color eleectrophotographic device - Google Patents

Abstract

PURPOSE: To provide a high-performance cleaning device completely removing toner remaining on an intermediate transfer body in accordance with the use environment of a color electrophotographic device, and to obtain high-quality image output without an afterimage or faulty cleaning. CONSTITUTION: This device is provided with a cleaning means 2 for removing the toner remaining on the intermediate transfer body, a toner recovering means 8 recovering the toner adhering to the cleaning means 2, and a bias setting means 5 setting bias required for cleaning. It is also equipped with a bias control means 7 variably controling the bias and an environment detection means 3 detecting the environmental state, and the cleaning bias is variably controlled by the control means 7 based on the detected result by the detection means 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus using an intermediate transfer member, and more particularly to a cleaning device for removing toner remaining on the intermediate transfer member after transfer to a recording medium. .

[0002]

2. Description of the Related Art A conventional color electrophotographic apparatus forms a color image by using toners of four colors of three primary colors of yellow, magenta, cyan and black. In forming a color image, a latent image for each color is formed on a photoconductor based on the color-coded print data, the latent image is developed by a developing device having toner for each color, and the latent image is formed on an intermediate transfer body or a recording medium. Overlap with. In many color electrophotographic apparatuses, in particular, toner images of respective colors are superposed on an intermediate transfer member. In the case of using an intermediate transfer member, the four color toner images are superposed on each other on the intermediate transfer member, transferred to a recording medium at once, and then heat-fixed by a fixing device to form a color image. In the above process, the toner image formed on the intermediate transfer body is not all transferred onto the recording medium, and residual toner remains on the intermediate transfer body after the transfer. In order to clean the toner remaining on the intermediate transfer member, a cleaning device is provided as disclosed in Japanese Patent Laid-Open No. 4-115772. The cleaning device generally provides a brush having a potential difference with the intermediate transfer member to clean the toner on the intermediate transfer member with a conductive brush. The toner attached to the conductive brush is collected by a collecting roller provided with a constant potential difference from the conductive brush. Further, the toner attached on the collecting roller is scraped off by the blade. Thus, the toner remaining on the intermediate transfer member is cleaned by using the conductive brush, the collecting roller and the blade.

[0003]

However, in the cleaning device for the intermediate transfer member utilizing the potential difference as described above, its cleaning ability is determined by the charge amount of the toner. The charge amount of toner largely depends on the environment in which the color electrophotographic apparatus is placed.In general, the charge amount of toner is high in a low temperature and low humidity environment and low in a high temperature and high humidity environment. I will end up. Therefore, when the charge amount of the toner is high, the cleaning ability is deteriorated. When the cleaning ability is lowered, the toner remains on the intermediate transfer member, so that there is a problem that an afterimage appears in the next image when continuous printing is performed.

The cleaning ability is also affected by the environmental dependency of the impedance of the semiconductor material used for the intermediate transfer member and the impedance of the conductive brush used for the cleaning means.

The present invention provides a high-performance cleaning device capable of sufficiently cleaning the toner remaining on the intermediate transfer member irrespective of the environment in which the color electrophotographic device is used, and provides a high-quality image having no afterimage or cleaning failure. It is intended to get the output.

[0006]

In order to solve the above problems, a cleaning means for cleaning the toner remaining on the intermediate transfer member, a toner collecting means for collecting the toner adhering to the cleaning means, and a cleaning means are necessary. Bias setting means for setting a different bias, bias control means for variably controlling the bias, and environment detecting means for detecting the environmental condition of the apparatus are provided.

As a first method, the bias means is provided with a recovery bias setting means for applying to the toner recovery means, and the recovery bias is set between the toner recovery means, the cleaning means, and the intermediate transfer member arranged in series. Only one bias of the means is applied. The impedance of the semiconductor material of the intermediate transfer member and the impedance of the conductive brush of the cleaning means are selected so that a potential difference of a predetermined value or more between the toner recovery means and the cleaning means is generated when the recovery bias is applied. Configured. Further, a voltage detecting means for detecting the shared voltage in the cleaning means portion when the recovery bias is applied is provided. In such a configuration, the bias of the bias setting means is variably controlled by the bias control means based on the detection result of the environment detecting means.

Next, as a second method, the bias setting means is provided with two collecting bias setting means applied to the toner collecting means and cleaning bias setting means applied to the cleaning means, and the cleaning means-intermediate A cleaning bias is applied between the transfer bodies, the recovery bias setting means is overlaid on the cleaning bias setting means, and the recovery bias is applied between the toner recovery means and the cleaning means. In such a configuration, the bias of the bias setting means is variably controlled by the bias control means based on the detection result of the environment detecting means.

[0009]

In the first method, the semiconductor material of the intermediate transfer member and the impedance of the conductive brush of the cleaning means are selected so that only one bias of the recovery bias setting means is applied. It acts to ensure a potential difference between the means. Since only one bias setting means is required, the cost of the device can be reduced. Further, by variably controlling the bias based on the detection result of the environment detecting means, it is possible to always perform a stable cleaning operation of the intermediate transfer member in all environments where the color electrophotographic apparatus can be used.

In the second method, the cleaning bias and the recovery bias are superposed, so that the impedances of the intermediate transfer member and the cleaning means are not strictly defined unlike the first means. A potential difference can be provided between the cleaning unit and the toner collecting unit. Further, when the cleaning bias is variably controlled, it is not necessary to care about the balance with the recovery bias, and only one bias is variably controlled, which simplifies the control method. By the way, the recovery bias does not have to be a constant value.

With the above-mentioned structure, the bias structure of the cleaning device and the control method thereof are simplified. Further, it is possible to obtain a cleaning capability higher than the conventional one, and it is possible to obtain a high-quality image output without an afterimage.

[0012]

Embodiments of the present invention will be described with reference to FIGS.

First, the outline of the color electrophotographic apparatus will be described with reference to the schematic view of FIG. Organic photoconductive material (OP
The photoreceptor belt 11 coated with C) is
It is rotationally driven in the direction of the arrow in the figure. Belt cleaner 24
Cleans the toner remaining on the photoreceptor belt 11 after the image formation for each color is completed. The charger 17 charges the surface of the photoreceptor belt 11 with electric charges necessary to form an electrostatic latent image. The laser beam 23 exposes the charged surface of the photoreceptor belt 11 to form an electrostatic latent image. The developing device 12 (Y, M, C, K) transfers the electrostatic latent image formed on the surface of the photoreceptor belt 11 to the first yellow, the second magenta,
Develop with each developer in the order of third cyan and fourth black. The intermediate transfer body 1 is rotated by contact with the photosensitive belt 11, and the toner images formed on the surface of the photosensitive belt 11 are transferred onto the intermediate transfer body 1 in the order of yellow, magenta, cyan, and black (first Transfer) and superposition to form a color image. The transfer device 26 transfers the color image formed on the intermediate transfer member 1 to a recording medium 27.
The toner is transferred onto the recording medium by applying an electric field having a polarity opposite to that of the toner charging from the back side of the toner (second transfer). Fixing device 25
Heats the toner transferred onto the recording medium. The intermediate transfer member cleaning device 22 cleans the toner remaining on the intermediate transfer member after the color image is transferred onto the recording medium.

Next, the intermediate transfer member cleaning device 2
The structure of No. 2 will be described with reference to FIG. First, the intermediate transfer member cleaning device 22 is large, and includes a cleaning unit 2 that cleans residual toner from the surface of the intermediate transfer member 1.
The cleaning unit 2 includes a toner collecting unit 3 for collecting the toner attached to the cleaning unit 2 and a blade 21 for scraping off the collected toner. The intermediate transfer member 1 is indicated by an arrow a in the figure.
Is rotating in the direction of. Intermediate transfer member cleaning device 2
Reference numeral 2 makes contact with or separates from the intermediate transfer body 1 about the axis of the toner collecting means 3. As a matter of course, during the cleaning operation, they are in contact with each other, and the cleaning means 2 and the toner collecting means 3 are rotationally driven by motors (not shown) in the directions of arrows bc in the figure. In the cleaning means 2, the central core material serves as an electrode, and a conductive fiber brush is applied to the surface. The impedance characteristic of the fiber brush has a dependency on humidity as shown in FIG. 3, and it is necessary to select the characteristic according to the performance. In terms of cleaning performance, it can be said that which type of fiber brush is selected in consideration of compatibility with the intermediate transfer body 1 and environmental changes is the design power. The toner collecting means 3 is a metal cylinder whose surface is well polished. Similar to the cleaning means 2, electrodes are provided.

Next, the overall structure of the high voltage system of the color electrophotographic apparatus will be described with reference to FIG. First, the reference of the entire high-voltage system is the intermediate transfer body 1, and the aluminum tube forming the drum is grounded. This high-voltage system is a high-voltage system overall control means 2
Each part is controlled by a control command from 0. The intermediate transfer member 1 has a surface of an aluminum tube covered with a rubber material (urethane rubber or the like), and the surface thereof is coated. A negative bias is applied by the belt bias setting means 15 to the photoconductor belt 11 in contact with the intermediate transfer body 1 in order to provide a potential difference from the reference. With this belt bias, the toner image formed on the photoconductor belt 11 can be transferred to the intermediate transfer body 1. The charging bias setting means 16 superposed on the belt bias setting means 15 comprises:
A bias for charging the surface of the photoconductor belt 11 is applied. Further, the other developing bias setting means 13 superposed on the belt bias setting means 15 is the developing device 1
A developing bias is applied to 2Y, 12M, 12C and 12K. The transfer bias setting unit 10 applies a positive bias to the reference, and transfers the color image formed on the intermediate transfer body 1 onto a recording medium. The AC high voltage power supply 18 is an AC
By applying an AC bias to the static eliminator 19, the charge on the recording medium and the intermediate transfer body 1 is removed, and the releasability of the recording medium from the intermediate transfer body 1 is improved. The cleaning bias setting means 5 gives a cleaning bias to the cleaning means 2. The collection bias setting unit 4 gives the toner collection unit 3 a collection bias. In the conventional control, the recovery bias setting means 4 is variably controlled according to the detection result of the transfer environment detecting means 8. In the middle of the system, control may be performed according to the detection result of the device environment detection means 14.

When an environmental test was conducted on the color electrophotographic apparatus, which is the intermediate transfer member cleaning device 22 having the above-mentioned structure, a problem that an afterimage was generated in a low temperature and low humidity environment occurred. The afterimage is that the previous image appears in the next image output due to insufficient cleaning of the intermediate transfer member 1. As a result of further study on the countermeasure of this case, it was found that increasing the cleaning bias is effective for cleaning the residual toner from the intermediate transfer body 1. Further, it has been found that it is sufficient to collect the toner from the cleaning means if a predetermined potential difference is secured. However, increasing the cleaning bias at high temperature and high humidity negatively affects the afterimage in the reversal mode. The afterimage in the reversal mode is a mode in which toner that has been positively charged during transfer onto a recording medium remains as an afterimage. As a result of further study, as shown in FIG. 1, when a bias is applied only to the toner collecting means 3, a voltage sharing occurs in the cleaning means 2, and a potential difference is secured between the cleaning means 2 and the toner collecting means 3. I was able to obtain the knowledge that it will be done. Furthermore, if the semiconductor material (urethane rubber) of the intermediate transfer member 1 and the conductive fiber brush of the cleaning means have the same environmental dependency, it is also found that the voltage sharing ratio does not change in each environment. I was able to get it. Further, as shown in FIG. 4, if the conductive fiber brush having a negative characteristic with respect to the applied voltage is selected,
It was also found that even when the applied voltage was lowered, the operation was performed such that the potential difference was automatically secured between the toner collecting means 3 and the cleaning means 2.

Based on the above findings, the bias structure of the intermediate transfer member cleaning device 22 is as shown in FIG. The bias control unit 7 determines, based on the detection result of the transfer environment detection unit 8,
The recovery bias setting means 4 is variably controlled. The transfer environment detecting means 8 applies a bias from the transfer bias setting means 10 and determines the environment from the impedance of the intermediate transfer body 1 at that time. Further, the cleaning means 2
By providing the voltage detection means 6 for detecting the shared voltage in the part, the voltage value desired to be set in each environment can be fed back and controlled, and therefore, the intermediate transfer member 1 can be controlled.
It is possible to control the fluctuation of the voltage value even with respect to the dispersion of the conductive fiber brush. According to the present invention, the bias structure can be made very simple, while the cleaning ability is improved.

FIG. 2 shows a second bias configuration that can be considered from the above findings. This configuration takes into consideration the case where a sufficient potential difference cannot be ensured between the toner collecting unit and the cleaning unit. Bias setting means is 2
However, the configuration is simple in terms of control.

By adopting the intermediate transfer member cleaning device of the present invention as described above, the optimum cleaning conditions can be set in each environment, so that a high-quality image output without an afterimage can be obtained.

[0020]

According to the present invention, the bias structure of the intermediate transfer member cleaning device and the control method thereof can be simplified, the cost can be reduced, and further, the cleaning performance can be higher than the conventional one. Therefore, there is an effect that a high-quality image output with no afterimage can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first means of the present invention.

FIG. 2 is a diagram illustrating a second means of the present invention.

FIG. 3 is a diagram showing humidity dependence of impedance of a conductive fiber brush.

FIG. 4 is a diagram showing an applied voltage dependency of impedance of a conductive fiber brush.

FIG. 5 is an overall configuration diagram of a high-voltage system in a conventional color electrophotographic apparatus.

FIG. 6 is a side sectional view showing a structure of an intermediate transfer member cleaning device.

FIG. 7 is a schematic diagram illustrating the structure of a color electrophotographic apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer body, 2 ... Cleaning means, 3 ... Toner collection means, 4 ... Collection bias setting means, 5 ... Cleaning bias setting means, 6 ... Voltage detection means, 7 ... Bias control means, 8 ... Transfer environment detection means, 9 ... Transfer means, 10 ...
Transfer bias setting means, 11 ... Photosensitive belt, 12
(Y, M, C, K) ... Developing device, 13 ... Developing bias setting means, 14 ... Device environment detecting means, 15 ... Belt bias setting means, 16 ... Charging bias setting means, 17 ... Charging device, 18 ... AC high voltage Power source, 19 ... AC static eliminator, 20 ... High-voltage system overall control means, 21 ... Blade, 22 ... Intermediate transfer member cleaning device, 23 ... Laser, 24 ... Belt cleaner, 25 ... Fixing device, 26 ... Transfer device, 27 ... Recording Medium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masashi Yamamoto 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (7)

[Claims] 1. A photoreceptor for irradiating a laser on the basis of color-coded print data to form a latent image for each color, and a development for developing the latent image for each color formed on the photoreceptor with toner for each color. A container, an intermediate transfer member that transfers and superimposes toner images formed for each color to form a color image, and a unit that transfers and fixes the color image formed on the intermediate transfer member onto a recording medium, After the color image is transferred onto the recording medium, a cleaning means for cleaning the toner remaining on the intermediate transfer body, a toner collecting means for collecting the toner adhering to the cleaning means, and a bias setting for setting a bias necessary for cleaning In the color electrophotographic apparatus provided with the means, the bias setting means is provided with only one collecting bias setting means to be applied to the toner collecting means and arranged in series. A color electrophotographic apparatus characterized in that only one bias of the recovery bias setting means is applied between the toner recovery means, the cleaning means and the intermediate transfer member. 2. A semiconductor material is used for the intermediate transfer member, a conductive fiber brush is used for the cleaning means, and a cleaning means and a toner recovery means are used when the recovery bias is applied. A color electrophotographic apparatus, wherein impedances of the intermediate transfer member and the cleaning unit are selected so that a potential difference of a predetermined value or more is generated therebetween. 3. The conductive fiber brush according to claim 2, wherein the semiconductor material of the intermediate transfer member and the conductive fiber brush of the cleaning means have environmental impedances having substantially the same impedance. Is a color electrophotographic device characterized in that its impedance has a negative characteristic with respect to the applied voltage. 4. An environment detecting means for detecting an environmental condition of a color electrophotographic apparatus, and a bias control means for variably controlling the bias setting means, wherein the bias is based on a detection result of the environment detecting means. A color electrophotographic apparatus characterized in that setting means is variably controlled. 5. The environment detecting means for detecting the environmental condition of the color electrophotographic apparatus, the bias controlling means for variably controlling the bias setting means, and the cleaning means for cleaning the bias applied by the bias setting means. The bias setting means is variably controlled so that the shared voltage in the cleaning means portion has a predetermined voltage value, based on the detection result of the environment detecting means. Characteristic color electrophotographic device. 6. A photoconductor for forming a latent image for each color by irradiating a laser with color-coded print data, and a developing device for developing the latent image for each color formed on the photoconductor with toner for each color. An intermediate transfer member that transfers the toner images formed for each color and forms a color image by superimposing them, a unit that transfers and fixes the color image formed on the intermediate transfer member onto a recording medium, After transferring the color image onto the recording medium, a cleaning means for cleaning the toner remaining on the intermediate transfer body, a toner collecting means for collecting the toner adhering to the cleaning means, and a bias setting means for setting a bias necessary for the cleaning. In the color electrophotographic apparatus, the bias setting unit applies the recovery bias setting unit applied to the toner collecting unit and the cleaning unit. Two cleaning bias setting means are provided, a cleaning bias is applied between the cleaning means and the intermediate transfer member, and further, the recovery bias setting means is superposed on the cleaning bias setting means, so that the toner recovery means-cleaning means. A color electrophotographic apparatus having a configuration in which a recovery bias is applied to the color electrophotographic apparatus. 7. The setting bias of claim 6, wherein the environment detecting means for detecting the environmental condition of the color electrophotographic apparatus, both the cleaning bias setting means and the recovery bias setting means, or one of the cleaning bias setting means. A color electrophotographic apparatus, comprising bias control means (cleaning bias control means, recovery bias control means) for controlling, and variably controlling the bias setting means based on a detection result of the environment detecting means.