JPH07295384A - Image-forming device - Google Patents

Abstract

PURPOSE:To provide an image-forming device equipped with a magnetic brush cleaner which is simple in mechanism and small in size. CONSTITUTION:The image-forming device equipped with the magnetic brush cleaner 4 arranged opposite to an image carrier so that its magnetic brush abuts on the image carrier is further equipped with one magnetic brush hold means for holding the magnetic brush. a toner concentration adjustment means for adjusting the toner concentration of the magnetic brush in a developing process and in a cleaning process, a bias switch means 11 for switching a bias, which is applied to the magnetic brush hold means, in the developing process and in the cleaning process, and a cleaning pre-process means for performing a cleaning pre-process each time the developing process on a prescribed number of sheets is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention serves to clean a magnetic brush in the same magnetic brush developing device, and the same photosensitive member is
The present invention relates to an image forming apparatus that rotates to end one printing process.

[0002]

2. Description of the Related Art In an image forming apparatus having a magnetic brush cleaning device, the magnetic brush of the magnetic brush cleaning device contacts an image carrier to remove residual toner on the image carrier. Toner newly cleaned or cleaned around, that is,
Since the waste toner box for storing the waste toner is not required, it is easy to downsize and simplify the apparatus. Japanese Unexamined Patent Publication No. 56-137380 proposed as such an image forming apparatus has one magnetic brush holding means for forming a magnetic brush, and the magnetic brush holding means serves as a developing means for the first rotation of the image carrying body. The second rotation functions as a cleaning unit, and the image carrier rotates twice to complete one printing step, that is, a two-rotation process. Similarly, 2
Japanese Patent Laid-Open No. 62-983 discloses a rotating process. On the other hand, there is also a proposal of a one-rotation process method, which is disclosed in JP-A-58
In Japanese Patent Laid-Open No. 46373 and Japanese Patent Laid-Open No. 60-26372, two magnetic brush holding means are provided and one is used for cleaning and the other is used for development. The process ends.

[0003]

In the above-mentioned prior art, in the two-rotation process, the height and the moving direction of the magnetic brush are changed during development and during cleaning in order to improve cleaning efficiency and prevent scattering. Becomes complicated. On the other hand, the one-rotation process requires two magnetic brush holding means, so that the magnetic brush cleaning device becomes large.

An object of the present invention is to provide an image forming apparatus having a simple mechanism and a small magnetic brush cleaning device.

[0005]

In order to achieve the above object, the present invention provides an image forming apparatus having a magnetic brush cleaning device which is arranged so as to face the image carrier so that the magnetic brush is provided with a magnetic brush. One magnetic brush carrying means for carrying, toner concentration adjusting means for adjusting the toner density of the magnetic brush between the developing step and the cleaning step, and the bias to the magnetic brush carrying means is switched between the developing step and the cleaning step. Bias switching means and cleaning pretreatment means for performing cleaning pretreatment each time the desired number of developing processes are completed are included.

[0006]

The cleaning pretreatment means performs the cleaning pretreatment every time the desired number of printing steps are completed, and the toner density adjusting means reduces the toner density of the magnetic brush carried by the magnetic brush carrying means during the cleaning step to less than that during the developing step. In addition, the bias switching means switches the bias applied to the magnetic brush carrying means to clean the residual toner on the image carrying body.

As a result, it is possible to perform development on the image bearing member and cleaning of residual toner on the image bearing member with one magnetic brush bearing means for bearing the magnetic brush.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of an image forming apparatus for explaining an embodiment of the present invention. The image forming apparatus shown in FIG. 1 includes a charging device 2, an exposure device 3, a magnetic brush cleaning device 4, a transfer device 5, a fixing device 15 and the like around a photosensitive drum 1 which is an image carrier.

The magnetic brush cleaning device 4 includes a developing roller 6 and a toner suction roller 1 which are magnetic brush holding means.
3, bias applying means 12 and bias applying means 14. The bias applying unit 12 includes a developing bias 9, a developing bias 10, and a bias changeover switch 11, and the bias applying unit 14 includes a bias changeover switch 16.

The magnetic brush cleaning device 4 serves as both a cleaning device and a developing device, and operates by the printing process control 8 so as to form one image while the photosensitive drum 1 rotates twice. The magnetic brush cleaning device 4
As described above, the cleaning device and the developing device also serve as the magnetic brush holding means, and the magnetic brush formed on the developing roll 6, which is the magnetic brush holding means, is composed of two components, carrier and toner, During the process, the toner is attached to the photoconductor drum 1 for development, and during the cleaning process, the toner is removed from the photoconductor drum 1 for cleaning.

The operation of the image forming apparatus shown in FIG. 1 will be described with reference to the operation sequence shown in FIGS. When the power of the image forming apparatus is turned on, the cleaning process is started, and the cleaning process in the normal printing process is performed twice on the photosensitive drum 1. In this cleaning step, a cleaning pretreatment step is performed, and the residual toner on the photosensitive drum 1 is precharged by the charger 2 before cleaning, that is, when the charging polarity of the toner is negative, the toner is negatively charged. Further, the charge remaining on the photosensitive drum 1 is removed by the exposing device 3 (overall exposure) to facilitate removal of the residual toner on the photosensitive pair 1. When this cleaning process ends, the photosensitive drum 1 stops.

Next, when a print command is input to the image forming apparatus shown in FIG. 1 from a personal computer, a word processor, or the like (not shown), the process control unit 8 controls each unit to perform a printing operation and prints (1 ) The process begins. In the printing process, one image is formed while the photosensitive drum 1 rotates twice. Specifically, the developing operation is performed on the first rotation (third rotation in FIG. 2) of the photosensitive drum 1, and the cleaning operation is performed on the second rotation (fourth rotation in FIG. 2). That is, in the first rotation of the photoconductor drum 1, uniform charging by the charger 2, image exposure by the exposure device 3, development by the magnetic brush cleaning device 4 operating as a developing device, transfer to the paper 7 by the transfer device 5, An image is formed on the sheet 7 by sequentially performing steps such as fixing by the fixing device 15.
On the other hand, the photosensitive drum 1 ends the operation of the first rotation with the toner (residual toner) that has not been transferred to the paper 7 being attached. When the photoconductor drum 1 enters the second rotation, the residual toner on the photoconductor drum 1 is subjected to pre-cleaning charging by the charging device 2 and the entire surface exposure by the exposure device 3, and then the photoconductor drum 1 is rotated. The residual toner is rubbed by the magnetic brush of the magnetic brush cleaning device 4 which operates as a cleaning device. When being rubbed by the magnetic brush, the residual toner is sucked by the magnetic brush and removed from the photosensitive drum 1. After the photoconductor drum 1 is cleaned by the magnetic brush as described above, 2
The rotation operation is finished, and the printing (1) step is finished. Then, thereafter, the printing (2) step and the printing (3) step are similarly performed, and the developing operation and the cleaning operation are repeated.

When the printing (N) step is completed, the cleaning step is performed twice as in the case of turning on the power source, and the image quality is deteriorated even in the cleaning step performed in the normal printing step even if the residual toner cannot be removed. Will not occur. The cleaning process is performed when printing of the desired number of sheets is completed. When the cleaning process is complete,
The photosensitive drum 1 is stopped and waits for the next print command.

The operation of the magnetic brush cleaning device 4 which performs both the developing operation and the cleaning operation will be described in detail with reference to FIG. FIG. 4 is an enlarged view of the periphery of the developing roll 6 of the image forming apparatus of FIG. Reference numeral 17 is a blade. Here, the charging polarity of the toner is negative. When performing the developing operation, the bias applying unit 12 sets the bias changeover switch 11 so as to supply the developing bias 9 to the developing roll 6 which is the magnetic brush holding unit which holds the magnetic brush, and the bias applying unit. Reference numeral 14 sets the bias changeover switch 16 so that the bias to the toner suction roll 13 installed near the developing roll 6 becomes the developing bias 9. Then, the toner density of the magnetic brush carried by the developing roller 6 contacts the photosensitive drum 1 in a state where the toner density is set to a desired value, so that a toner image having an appropriate density is formed on the photosensitive drum 1. . On the other hand, when performing the cleaning operation, first, the bias applying unit 12
The bias application unit 14 is set so that the bias applied to the toner suction roll 13 becomes the suction bias (0 V) without switching the bias changeover switch 11 of. Then, since the toner of the magnetic brush of the developing roll 6 is adsorbed to the toner adsorbing roll 13, the toner concentration of the magnetic brush of the B portion is lower than that of the A portion, and becomes carrier rich. The toner (C portion) adsorbed on the adsorbing roll 17 is scraped off by the blade 17. In this state, the developing roll 6
The bias changeover switch 11 is set so that the developing bias 10 is supplied to. The residual toner adhering to the photosensitive member 1 is charged before cleaning by the charger 2 and the exposure device 3, which also operate as cleaning pretreatment means.
Since the pre-cleaning process of the entire surface exposure is performed, when the carrier-rich magnetic brush carried on the developing roll 6 is rubbed, the electrostatic force and the magnetic force for attracting the residual toner toward the magnetic brush are applied. Acts and is easily removed.

[0015]

According to the present invention, it is possible to perform development on an image carrier and cleaning of residual toner on the image carrier with a single magnetic brush carrying means for carrying a magnetic brush, which is a simple mechanism. It is possible to provide a small-sized magnetic brush cleaning device.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an operation of the image forming apparatus in FIG.

3 is an explanatory diagram of an operation of the image forming apparatus of FIG.

FIG. 4 is an explanatory diagram around a developing roll of the image forming apparatus in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging device, 3 ... Exposure device, 4 ... Magnetic brush cleaning device, 5 ... Transfer device, 6 ... Development roll, 7 ... Paper, 8 ... Process control, 9, 10 ... Development bias, 11 , 16 ... Bias select switch, 12,
14 ... Bias applying means, 13 ... Toner suction roll, 1
5 ... Fixer

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Claims (6)

[Claims] 1. An image forming apparatus including a magnetic brush cleaning device arranged so that a magnetic brush is in contact with an image carrier, the magnetic brush carrying unit carrying the magnetic brush, at the time of development and cleaning. A toner concentration adjusting means for adjusting the toner concentration of the magnetic brush with
An image forming apparatus comprising: a bias switching means for switching a bias to the magnetic brush holding means during development and cleaning; and a cleaning pretreatment means for performing cleaning pretreatment every time a desired number of developing processes are completed. . 2. An image forming apparatus in which the magnetic brush cleaning device according to claim 1 also functions as a developing device. 3. An image forming apparatus in which the developer forming the magnetic brush according to claim 1 is a two-component developer including a carrier and a toner. 4. The image forming apparatus according to claim 1, wherein the toner density adjusting means comprises a toner attracting means arranged near the magnetic brush carrying means, and a bias switching means for switching a bias to the toner attracting means. 5. The image forming apparatus according to claim 1, wherein the toner concentration of the magnetic brush contacting the image carrier is smaller during the cleaning process. 6. The image forming apparatus according to claim 1, wherein the cleaning pretreatment means comprises a charging means for precharging the residual toner on the image carrier and an exposing means for erasing the electric charge of the image carrier.