JPH0980907A - Electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate waste toner without using a cleaning mechanism and a scattering roller. SOLUTION: Only DC voltage of -1200V is applied to a charging brush roller 2 at cleaning processing, so that a photosensitive drum 1 is charged at -600V and toner stuck on the charging brush roller 2 is stuck on the photosensitive drum 1. Voltage of +320V is applied to a developing roller 3, and the voltage of +420V is applied to a supply roller 4, so that the toner stuck on the photosensitive drum 1 is stuck on the developing roller 3 and the toner stuck on the developing roller 3 is stuck on the supply roller 4. The voltage of -1000V is applied to a transfer roller 5, so that the toner stuck on the photosensitive drum 1 is prevented from sticking on the transfer roller 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer device, and more particularly, to an electrophotographic printer device which prevents waste toner from being generated without using a toner cleaner mechanism and a flyer roller.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional technique and shows an example of a conventional electrophotographic printer device. In the conventional electrophotographic printer device shown in FIG. 4A, printing is performed as follows. The example shown in FIG. 4 is an example in which the toner is negatively charged.

First, the surface of the photosensitive drum 101 is charged to about -600 V by the charging brush roller 102 (charging process). Therefore, the charging brush roller 102 is applied with a voltage obtained by superimposing a DC voltage of about -600V and an AC voltage of about 1200Vp-p.

The surface of the photosensitive drum 101 is partially exposed (image exposure) by rotating the charged photosensitive drum 101 in the direction of the arrow and irradiating the laser beam A, and the surface of the photosensitive drum 101 is statically exposed. Form a latent image (exposure process). The potential of the latent image portion is about -100V to -50V, which is a potential relatively higher than the surrounding potential of -600V.

Next, the photosensitive drum 101 is rotated in the direction of the arrow shown in the drawing, toner is supplied to the surface of the photosensitive drum 101 by the developing roller 103 and the supply roller 104, and a visible image is formed by adhering only to the exposed portion. (Development process). The potentials of the developing roller 103 and the supply roller 104 are about −320V and about −420V, respectively. The negatively charged toner adheres only to the latent image portion (−100 V to −50 V) having a potential higher than that of the developing roller 103, while the toner having a potential lower than that of the developing roller 103 (−) around the latent image portion is used. It does not adhere to 600V).

Next, the photosensitive drum 101 is rotated in the direction of the arrow in the figure, and the conductive transfer roller 105 is used to feed the paper 10.
9 is charged, and the visible image formed on the surface of the photosensitive drum 101 is transferred to the paper 109 (transfer process). The electric potential of the transfer roller 105 is about + 2000V. The toner having a negative potential existing only in the latent image portion is the photosensitive drum 101.
It adheres to the paper 109 of higher potential.

After this, although not shown in the drawing, the paper 109
Is discharged from between the photosensitive drum 101 and the transfer roller 105 and supplied between the heat fixing roller and the fixing roller, and the visible image formed on the paper 109 is heat fixed by the heat fixing roller and the fixing roller (fixing process). . The heat fixing roller is heated to a high temperature.

By the way, even after the visible image is transferred to the sheet 109 in the transfer process, a small amount of toner remains on the surface of the photosensitive drum 101 in the shape of the visible image. For example,
About 90% of the toner adhered to the photosensitive drum 101
Toner is transferred to the paper 109, and about 10% of the toner remains on the photosensitive drum 101. Most of the residual toner adheres to the charging brush roller 102. As the amount of the residual toner attached to the charging brush roller 102 increases, the charging current decreases and the electrostatic latent image is not formed clearly. Further, the residual toner adhered to the charging brush roller 102 causes the sheet 109 of the paper 109 to be formed. Increased contamination of non-image areas. Therefore, the print quality is deteriorated. Therefore, the photosensitive drum 1 is prevented so that the residual toner does not adhere to the charging brush roller 102.
01 need to be removed from the surface.

Therefore, a toner cleaner mechanism 106 is provided upstream of the charging brush roller 102. A rubber blade, for example, is provided on the contact surface of the cleaner mechanism 106 with the photosensitive drum 101 so as not to damage the photosensitive drum 101. After discharging the paper 109, the photosensitive drum 10
1 is rotated in the direction of the arrow in the figure, and the blade of the cleaner mechanism 106 rubs the surface of the photosensitive drum 101 to collect the toner remaining on the surface of the photosensitive drum 101. The collected toner is discarded as unusable toner (waste toner).

However, according to this method, when normal printing is performed, about 10% of all toners (about 20% when there are many toners) are used.
Are discarded without being used for printing, which increases running costs. Further, by providing the cleaner mechanism 106, the electrophotographic printer device becomes complicated, large-sized, and costly.

Against this background, in recent years, a cleanerless electrophotographic printer device as shown in FIG. 4B has been proposed. In this electrophotographic printer device, the cleaner mechanism 106 is omitted, and the residual toner on the photosensitive drum 101 is left up to the developing process of the next process and is collected while printing. That is, in the developing process, the residual toner is collected by a method of removing a portion unnecessary for forming a visible image from the photosensitive drum 101. Specifically, the residual toner existing other than the latent image portion in the next process moves to the developing roller 103 having a relatively high potential because the potential of that portion is about −600V.

[0012]

The above-mentioned conventional FIG.
According to the electrophotographic printer device shown in (B), the discarded toner can be eliminated and the cleaner mechanism 106 can be eliminated.

However, in order to leave the residual toner of the pre-printing process until the developing process of the next printing process, it is a condition that the residual toner is in an amount that does not affect the charging process and the exposure process of the next printing process. Become. Further, in order to maintain the print quality, it is also a condition that the residual toner of the pre-printing process can be completely collected in the developing process. In order to realize the above conditions, it is possible to preliminarily scatter the residual toner remaining in a lump (locally deposited) around the upstream of the charging process (to partially reduce the toner density). It becomes indispensable.

Therefore, actually, as shown in FIG. 4B, a new flyer roller (or flyer brush) 107 is required at the upstream position of the charging mechanism 108. That is, the residual toner locally deposited on the surface of the photosensitive drum 101 by the spilling roller 107 is spilled by a mechanical or electrostatic force to reduce the toner density. For this reason, as a result, even if the cleaner mechanism 106 is omitted, the flyer roller 107 is required, and there is a problem that the electrophotographic printer device cannot be complicated, large, and costly.

Further, since the residual toner of the pretreatment is left until the developing process of the next printing treatment, there is a problem that the use of the charging brush roller 102 is restricted. That is, since the residual toner of the pre-printing process exists during the charging process, when the charging brush roller 102 is used as the charging unit, the residual toner is contaminated with the residual toner. Therefore, after repeating the process a certain number of times, it is necessary to remove the charging brush roller 102 and clean it, which is troublesome. Therefore, in most cases, the charging mechanism 108 using corona discharge shown in FIG. 4B is used, and the use of the charging brush roller 102 is restricted.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic printer device which eliminates waste toner without using a cleaner mechanism and a flyer roller. Also, the present invention
An object of the present invention is to provide an electrophotographic printer device that prevents deterioration of print quality without using a cleaner mechanism and a flyer roller.

It is another object of the present invention to provide an electrophotographic printer device in which waste toner is eliminated while preventing deterioration of print quality.

[0018]

An electrophotographic printer apparatus according to the present invention comprises a charging brush roller for charging the surface of a photosensitive drum and an electrostatic latent image on the surface charged by the charging brush roller by a predetermined means. A photosensitive drum that forms a visible image, a developing roller that supplies toner to the photosensitive drum having an electrostatic latent image formed thereon to form a visible image, a supply roller that supplies toner to the developing roller, and a photosensitive drum And a transfer roller that transfers the visible image formed on the surface of the sheet to a sheet.

This electrophotographic printer device performs a cleaning process by rotating the charging brush roller, the photosensitive drum, the developing roller, the supply roller and the transfer roller in a predetermined direction at a predetermined timing. In this cleaning process, by applying only the DC high voltage (for example, about -1200V) which is the first potential to the charging brush roller,
The surface of the photosensitive drum has a second potential (for example, about -600V).
To charge. The first and second potentials have the same sign (first
And the absolute value of the second potential is smaller than that of the first potential. Further, only the DC voltage having the third potential (for example, about + 320V) is applied to the developing roller, and only the DC voltage having the fourth potential (for example, about + 420V) is applied to the supply roller. The third and fourth potentials have a sign opposite to the first sign (second sign), and the fourth potential has an absolute value larger than that of the third potential. Further, only the DC voltage (for example, about -1000V) which is the fifth potential is applied to the transfer roller. The fifth potential has the first sign and its absolute value is larger than that of the second potential.

Therefore, according to the electrophotographic printer device of the present invention, the toner adhered to the charging brush roller and the photosensitive drum can be recovered by utilizing the Coulomb attractive force by the above-mentioned cleaning process.

For simplicity of explanation, it is assumed that the toner is negatively charged. In this case, the signs (first signs) of the first, second, and fifth potentials are negative, and the signs of the third and fourth potentials (second sign) are positive.

First, since the toner adhered to the charging brush roller is negatively charged, it moves and adheres to the photosensitive drum having a higher electric potential. Next, on the downstream side in the rotation direction of the photosensitive drum, the toner attached to the photosensitive drum (the one originally attached to the photosensitive drum and the one moved from the charging brush roller) moves to the developing roller having a higher potential. Then, it moves to a supply roller having a higher potential. This makes it possible to collect the entire amount of the toner attached to the charging brush roller and the photosensitive drum. Furthermore, since the electric potential of the transfer roller is lower than the electric potential of the photosensitive drum, it is possible to prevent the negatively charged toner from moving from the surface of the photosensitive drum to the transfer roller. Even if toner adheres to the transfer roller, this toner moves to the photosensitive drum and is finally collected as described above.

The above is the same when the toner is positively charged. In this case, the signs of the first, second, and fifth potentials are positive, and the signs of the third and fourth potentials are negative. That is, the same effect can be obtained by reversing the sign of the potential applied to the charging brush roller or the like.

Therefore, according to the present invention, it is possible to collect all the remaining toner except the toner used for printing (transferred to the paper), so that the waste toner can be eliminated and the printing cost can be reduced. It is possible to reduce the print quality and prevent deterioration of print quality. Further, since the toner is all collected by utilizing the Coulomb attractive force, the cleaner mechanism 106 and the flyer roller 111, which have been conventionally used, are used.
Can be eliminated, the electrophotographic printer device can be prevented from becoming complicated, large-sized, and cost increased, and deterioration of print quality can be prevented.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an electrophotographic printer device, showing the configuration of the essential parts of the electrophotographic printer device.
This electrophotographic printer device includes an image printing unit 8 including a photosensitive drum 1, a charging brush roller 2, a developing roller 3, a supply roller 4, a transfer roller 5, a heat fixing roller 6, and a fixing roller 7, and a print control unit 9. The print control unit 9 includes a cleaning control unit 91. The electrophotographic printer device performs a printing process for performing normal printing (electrophotographic printing) on the paper 12 and a cleaning process for cleaning the photosensitive drum 1 and the charging brush roller 2 and collecting toner in the toner box 10. . The print control unit 9 and the cleaning control unit 91 respectively control the image printing unit 8 to execute the printing process and the cleaning process.

The photosensitive drum 1 is used for electrophotographic printing.
For example, it has a known structure including an aluminum drum and an electrophotographic photosensitive member on the surface (outer periphery) thereof. As the electrophotographic photosensitive member, for example, an organic photoconductor (OPC) is used. In the printing process, an electrostatic latent image is formed on the surface of the charged photosensitive drum 1, and the latent image is used to form a visible image (toner image) with toner.
Transfer to 2. That is, image printing is performed.

The toner (residual toner) remaining on the photosensitive drum 1 in the printing process becomes an obstacle to image printing in the next printing process. Therefore, the photosensitive drum 1 is targeted for cleaning in the cleaning process.

In the printing process and the cleaning process,
Under the control of the print control unit 9 and the cleaning control unit 91, the photosensitive drum 1 is rotated by being given a rotational driving force in the direction of the arrow in the figure by a driving unit (not shown) such as a motor.

The charging brush roller 2 charges the surface of the photosensitive drum 1 in the printing process and the cleaning process. The charging brush roller 2 is mainly, for example, 10 ⁹ to 10
Consists of conductive fibers with a resistance of about ¹² Ω. This fiber has a fiber thickness of, for example, 6 denier / F, and is 100
Implanted at a density of 000 F / inch ² is used. The charging brush roller 2 is in contact with the photosensitive drum 1 at the position shown (actually, it faces with a very small gap).
Then, the photosensitive drum 1 is charged to a predetermined potential.

The residual toner on the photosensitive drum 1 tends to adhere to the charging brush roller 2. That is, due to the influence of an oscillating electric field due to an AC bias (described later) applied to the charging brush roller 2 and the mechanical force of the fiber of the charging brush roller 2,
The residual toner on the photosensitive drum 1 is scattered around the contact position with the charging brush roller 2 on the photosensitive drum 1, and most of the toner adheres to the fibers of the charging brush roller 2. As a result,
Since the amount of the residual toner on the photosensitive drum 1 is small, the influence of the next printing process on the exposure is small, and the amount of the residual toner can be collected by the developing roller 3.

However, as the amount of residual toner deposited on the charging brush roller 2 cumulatively increases, the charging current decreases. Therefore, the electrostatic latent image is not clearly formed. Further, the toner attached to the charging brush roller 2 contaminates the non-image portion of the paper 12 (the portion that should remain a white background). Therefore, the print quality is degraded. Therefore, the charging brush roller 2 is targeted for cleaning in the cleaning process.

The rotating shaft of the charging brush roller 2 is rotated in a direction indicated by an arrow by a driving device (not shown) such as a motor under the control of the printing control unit 9 and the cleaning control unit 91 in the printing process and the cleaning process. Driving force is given. That is, the charging brush roller 2 is the photosensitive drum 1
It rotates in the same direction as the rotation direction of. Therefore, the charging brush roller 2 runs in the direction opposite to the photosensitive drum 1 at the contact portion with the photosensitive drum 1.

The charged photosensitive drum 1 is exposed by a predetermined exposure means, for example, a laser beam, in a printing process to form an electrostatic latent image. Therefore, this electrophotographic printer device is a laser beam printer. The exposure means is not limited to the laser beam, and may be, for example, reflected light obtained by irradiating the paper 12 with a halogen lamp. Therefore, the present invention can be applied to a copying machine.

For example, as shown in the figure, under the control of the print control unit 9, a laser beam (shown by a dotted line) is irradiated onto the surface of the photosensitive drum 1 by an exposing means (not shown) to rotate the photosensitive drum 1. A desired image is drawn synchronously. The potential of the portion irradiated with the laser beam changes from the charging potential given by the charging brush roller 2 to a higher or lower potential. As a result, an electrostatic latent image is formed. No exposure is performed in the cleaning process.

In the printing process, the developing roller 3 supplies toner to the photosensitive drum 1 having an electrostatic latent image formed on its surface to form a visible image. For this reason, the developing roller 3 is made of conductive rubber and rotates in the direction of the arrow in the figure while being in contact with the photosensitive drum 1. The toner is supplied to the developing roller 3 from around the supply roller 4. By rotating the developing roller 3 in contact with the photosensitive drum 1,
The amount of toner above is controlled and stabilized, and as a result, the amount of toner supplied to the photosensitive drum 1 is made uniform.

In the cleaning process, the developing roller 3
Is used for cleaning the photosensitive drum 1 (and the charging brush roller 2) and collecting the toner. Also in this case, the rotation direction of the developing roller 3 is the same as in the printing process.

Therefore, in the printing process and the cleaning process, the rotary shaft of the developing roller 3 is moved in the direction of the arrow in the figure by a driving means (not shown) such as a motor under the control of the printing control unit 9 and the cleaning control unit 91. Rotational driving force is given and it is made to rotate.

The supply roller 4 supplies toner to the developing roller 3 and collects excess toner existing on the developing roller 3. For this reason, the supply roller 4 is made of conductive rubber and rotates in the direction of the arrow in the drawing while contacting the developing roller 3. The toner supplied to the developing roller 3 is charged to a negative potential due to contact friction with the supply roller 4 rotating in the opposite direction. In addition, excess toner on the developing roller 3 (including toner that has not adhered to the surface of the photosensitive drum 1 in the preprinting process) is collected by the supply roller 4 in the toner box 10.

In the cleaning process, the supply roller 4
Is used for cleaning the photosensitive drum 1 (and the charging brush roller 2) together with the developing roller 3 and collecting the toner.

Therefore, in the printing process and the cleaning process, the rotary shaft of the supply roller 4 is moved in the direction of the arrow shown by a driving means (not shown) such as a motor under the control of the printing control unit 9 and the cleaning control unit 91. Rotational driving force is given and it is made to rotate.

The toner supplied to the photosensitive drum 1 by the developing roller 3 adheres only to the portion of the electrostatic latent image formed on the surface thereof, and does not adhere to the peripheral portion thereof.
This is due to the potential difference caused by the exposure. As a result, a visible image (toner image) represented by the adhered toner is formed on the surface of the photosensitive drum 1.

The developing roller 3 and the supply roller 4 are
As shown, the toner box 10 is provided. The toner box 10 is a toner supply source, and the toner is sealed inside the toner box 10. A doctor blade 11 is provided in the toner box 10. Doctor blade 1
1 is made of metal and contacts the developing roller 3 as shown. The toner supplied onto the developing roller 3 is rubbed by the doctor blade 11 to form a uniform thin layer, and is negatively charged by friction with the doctor blade 11.

The transfer roller 5 transfers the toner image formed on the surface of the photosensitive drum 1 to the paper 12 in the printing process. The transfer roller 5 is made of conductive rubber, and rotates in the direction of the arrow in the figure while being in contact with the photosensitive drum 1. In the printing process, the paper 12 is supplied between the transfer roller 5 and the photosensitive drum 1. The sheet 12 is sandwiched between the transfer roller 5 and the photosensitive drum 1, and moves in the direction of the arrow shown. The paper 12 is supplied and moved by a paper supply unit (not shown).

In the cleaning process, the transfer roller 5
The residual toner is prevented from adhering from the photosensitive drum 1. Further, when the toner adheres to the transfer roller 5, it is targeted for cleaning. In the cleaning process, the rotation direction of the fixing roller 5 is the same as in the printing process.

Therefore, in the printing process and the cleaning process, the rotary shaft of the transfer roller 5 is moved in the direction of the arrow shown by a driving means (not shown) such as a motor under the control of the printing control unit 9 and the cleaning control unit 91. Rotational driving force is given and it is made to rotate.

In the printing process, the paper 12 to which the toner image is transferred is sent in the direction of the arrow shown in the figure, and the toner image is fixed. The paper 12 is supplied between the heat fixing roller 6 and the fixing roller 7. The heat fixing roller 6 and the fixing roller 7 each rotate in the direction of the arrow shown. Therefore,
In the printing process, the rotary shafts of the heating and fixing roller 6 and the fixing roller 7 are each given a rotational driving force in the direction of the arrow in the drawing by a driving unit (not shown) such as a motor under the control of the printing control unit 9. . In the cleaning process, the heat fixing roller 6 and the fixing roller 7 do not operate.

The heating and fixing roller 6 and the fixing roller 7 heat and press the toner image transferred onto the paper 12 to
The paper 12 is fixed. For this reason, although not shown in particular, the heat fixing roller 6 has a heater, for example, a halogen lamp therein, and heats the paper 12 to a predetermined temperature. The fixing roller 7 pressurizes the paper 12 together with the heating fixing roller 6 and heats the paper 12 to melt the toner.
Promote the establishment of The surfaces of the heat fixing roller 6 and the fixing roller 7 are covered with, for example, Teflon rubber so that the toner is not reattached from the paper 12.

The print control unit 9 controls the image printing unit 8, the paper supply unit, the exposure unit, the driving unit, and the power supply unit to supply the paper to the image printing unit 8 and print the image. The print control unit 9 includes a CPU, a memory, and a print control program on the memory. The print control unit 9 includes a cleaning control unit 91. The cleaning control unit 91 includes a cleaning control subroutine.

Regarding the print processing performed by the print control unit 2
This will be described with reference to the drawings. The print control unit 9 rotates the photosensitive drum 1 and the like in the direction of the arrow in the drawing in the printing process.
By this rotation, the charging process, the exposing process, the developing process,
The transfer process takes place. That is, the charging process side is upstream. Further, after this, a fixing process is further performed.

In the printing process, the print control section 9 controls a power supply means (not shown) to apply a predetermined potential to the charging brush roller 2 and the like. In the following description, the toner is assumed to be negatively charged. Therefore, in the printing process, the photosensitive drum 1, the charging brush roller 2, the developing roller 3, and the supply roller 4 are set to a negative potential, and the transfer roller 5 is set to a positive potential.

The potential of the toner to be charged is not limited to negative, and the present invention can be applied to an electrophotographic printer device using a toner that is positively charged. In this case, the potentials applied to the photosensitive drum 1 and the like may have the opposite signs only, and the absolute value of the potential may be left unchanged. The same applies to the cleaning process described later.

As shown in FIG. 2, the print controller 9 sets the potential of the charging brush roller 2 to a negative DC high voltage (for example, -60).
0 V) and AC high voltage (1200 Vp-p) are superimposed, the potential of the developing roller 3 is set to a negative potential (eg, -320 V) higher than the surface potential of the photosensitive drum 1, and the potential of the supply roller 4 is set to the developing roller 3. Is set to a negative potential (e.g., -420V) lower than the surface potential of the photosensitive drum 1 and the potential of the transfer roller is set to a positive DC high voltage (e.g., + 20V).
00V).

First, the charging brush roller 2 has -600
A voltage obtained by superimposing a negative DC high voltage of V and an AC high voltage of 1200 Vp-p is applied. That is, -1200V to 0
An alternating voltage with an amplitude of 1200 V is applied in the range of V. As a result, the photosensitive drum 1 that contacts the charging brush roller 2
Is charged to a negative potential of, for example, -600V. That is,
The voltage of −600 V applied to the charging brush roller 2 corresponds to the charging voltage of the photosensitive drum 1. The surface of the photosensitive drum 1 is sequentially charged by the rotation of the photosensitive drum 1 (charging process).

In the printing process, it is indispensable that the potential of the charging brush roller 2 is a DC high voltage superposed with an AC high voltage of 1200 Vp-p. That is, due to this AC bias, the discharge from the charging brush roller 2 to the photosensitive drum 1 and the discharge in the opposite direction are repeated in the minute gap between the photosensitive drum 1 and the charging brush roller 2. As a result, the charging potential of the surface of the photosensitive drum 1 becomes uniform at the DC potential of the charging brush roller 2 of -600V. Without this AC bias, the charging potential on the surface of the photosensitive drum 1 becomes non-uniform, which hinders the formation of an electrostatic latent image.

Regarding the voltage applied to the charging brush roller 2, the negative DC high voltage may be about -500V to -800V, and the AC high voltage is 1000V to 1300.
What has an amplitude of about V may be used.

In the exposure process, the surface of the photosensitive drum 1 is irradiated with the laser beam A by a predetermined exposure means. As a result, the potential of the portion irradiated with the laser beam A changes, for example, from -50V to -100V. Therefore, an electrostatic latent image is formed due to the relative potential difference between it and the surrounding potential of -600V.

To the developing roller 3, a negative potential of -320V, which is higher than the potential of -600V on the surface of the photosensitive drum 1, is applied.
The supply roller 4 is applied with a negative potential of -420V which is lower than the potential -320V of the developing roller 3 and higher than the potential -600V of the surface of the photosensitive drum 1.

The toner is filled with a charge control agent so that the toner itself becomes negatively charged. Therefore, by setting the bias voltage of the supply roller 4 to a potential (minus potential) slightly lower (about 100 V to 300 V, 100 V in this example) than that of the developing roller 3, the toner box 1
The toner in the vicinity of the supply roller 4 within
Move to the side. As a result, a sufficient amount of toner is supplied onto the developing roller 3 to obtain a desired print density, and a toner layer having a sufficient thickness is formed.

-50V potential of the latent image portion on the photosensitive drum 1.
Since −100V is higher than the potential −320V of the developing roller 3, the toner on the developing roller 3 that opposes the latent image portion moves to and adheres to the latent image portion on the photosensitive drum 1. As a result, a visible image (toner image) of toner is formed on the photosensitive drum 1 (developing process). On the other hand, the potential of -600V other than the latent image portion on the photosensitive drum 1 is applied to the developing roller 3
Since the potential of the developing roller 3 is lower than the potential of −320V, the toner on the developing roller 3 that opposes the portion does not move onto the photosensitive drum 1.

The transfer roller 5 has a positive DC high voltage of +200
0 V is applied. As a result, the paper 12 is charged to a predetermined potential. The potential of the transfer roller 5 +2000 V and the potential of the paper 12 are the potential of the toner image portion on the photosensitive drum 1 −.
Since the voltage is higher than 50V to -100V, the toner of the toner image portion on the developing roller 3 moves and adheres to the transfer roller 5 side, that is, the surface of the paper 12. The proportion of toner that moves is, for example, about 90%. As a result, the visible image formed on the surface of the photosensitive drum 1 is transferred to the paper (transfer process).

As described above, in the printing process, the toner (residual toner) not transferred to the paper 12 remains on the photosensitive drum 1, and the residual toner on the photosensitive drum 1 easily adheres to the charging brush roller 2. Therefore, in order to clean the photosensitive drum 1 and the charging brush roller 2 and collect all the residual toner, a cleaning process using the Coulomb attractive force is executed.

The print controller 9 calls the cleaning controller 91, which is a cleaning control subroutine, by a subroutine call at a predetermined timing. Then, the print control unit 9 transfers control to the called cleaning control unit 91 to execute the cleaning process.

The cleaning controller 91 rotates the photosensitive drum 1 and the like in the direction of the arrow in the drawing in the cleaning process. This rotation direction is the same as the printing process. By this rotation, cleaning is sequentially performed on an arbitrary portion of the surface of the photosensitive drum 1. Therefore, the cleaning process is performed by rotating the photosensitive drum 1 at least once. As a result, the entire surface of the electrophotographic photosensitive member of the photosensitive drum 1 is cleaned.

In the actual cleaning process,
The cleaning controller 91 rotates the photosensitive drum 1 four to five times for each cleaning. Thereby, even if the amount of toner attached to the charging brush roller 2 is considerably large, the cleaning can be sufficiently performed. Rotate photosensitive drum 1 4-5 times
Since it takes 1 to 2 seconds to rotate,
The user of the electrophotographic printer device hardly feels inconvenience that the printing is delayed due to the cleaning in the actual use.

Further, in the actual cleaning process, the cleaning control section 91 performs one cleaning every time 10 to 20 sheets of paper 12 are printed. That is,
The photosensitive drum 1 is rotated 4 to 5 times to perform a cleaning process for 1 to 2 seconds. As a result, even when the number of continuous prints is considerably large, the charging brush roller 2 and the like can be sufficiently cleaned.

Further, in the actual cleaning process,
The timing when the cleaning process is executed, that is, the timing when the cleaning control unit 91 is called, is the potential applied to the charging brush roller 2 and the like in the printing process and the cleaning process, the type of toner, the type of the paper 12 (especially the photosensitive drum 1). The width of the sheet 12 with respect to the width of the sheet), environmental conditions (temperature, humidity), and other various conditions are taken into consideration. Actually, it is empirically determined from the performance of the electrophotographic printer device.

The cleaning process executed by the cleaning controller 91 will be described with reference to FIG. In the cleaning process, the cleaning control unit 91 controls a power supply unit (not shown) to apply a predetermined potential to the charging brush roller 2 and the like. Since the toner is negatively charged, the charging brush roller 2, the photosensitive drum 1 and the transfer roller 5 are set to a negative potential and the developing roller 3 and the supply roller 4 are set to a positive potential in the cleaning process.

As shown in FIG. 3, the cleaning controller 9
In No. 1, the potential of the charging brush roller 2 is only a negative DC high voltage (for example, -1200V), and the potential of the developing roller 3 is a positive potential (for example, +32) higher than the potential of the surface of the photosensitive drum 1.
0 V), the potential of the supply roller 4 is a positive potential higher than the potential of the developing roller 3 (for example, +420 V), and the potential of the transfer roller 5 is a negative potential (for example, -1000 V) lower than the surface potential of the photosensitive drum 1.

Only a negative DC high voltage of -1200V, which is the first potential, is applied to the charging brush roller 2. As a result, the surface of the photosensitive drum 1, which is in contact with the charging brush roller 2 (actually, it opposes with a minute gap), is charged to the second potential. The second potential is a negative potential, for example -600V. That is, the surface of the photosensitive drum is the second potential higher than the first potential.
It is charged to a negative potential, which is the potential of. The voltage of -1200V applied to the charging brush roller 2 is a potential for making the charging voltage of the photosensitive drum 1 a negative potential of -600V in consideration of the dielectric breakdown voltage (discharge starting voltage) of the surrounding atmosphere (air). Is. The surface of the photosensitive drum 1 is sequentially charged by the rotation of the photosensitive drum 1.

Here, considering that the surface of the photosensitive drum 1 is charged to −600 V in the printing process, the surface of the photosensitive drum 1 is charged to the same potential also in the cleaning process. Therefore, the potential applied to the charging brush roller 2 is -1200V.

The first potential applied to the charging brush roller 2 may be about -1000V to -1300V. In this case, the surface potential (second potential) of the photosensitive drum 1 is about -500V to -800V.

Along with this charging, the toner attached to the charging brush roller 2 moves (is discharged) to the surface of the photosensitive drum 1 and is attached. As a result, first, the charging brush roller 2 is cleaned.

Such cleaning of the charging brush roller 2 can be performed by not applying an AC bias to the charging brush roller 2 unlike the printing process. The reason for this is considered as follows according to the knowledge of the present inventor.

That is, as in print processing, 1200 Vp-p
When the AC bias of is applied to the charging brush roller 2,
The oscillating electric field generated by this causes the residual toner on the negatively charged photosensitive drum 1 to vibrate near the contact portion between the charging brush roller 2 and the photosensitive drum 1. It is considered that the force acting on the toner by the oscillating electric field is relatively large. Further, the charging brush roller 2 runs in the opposite direction to the photosensitive drum 1 on the contact surface with the photosensitive drum 1. Therefore, the residual toner on the photosensitive drum 1 is caused by this vibration and the charging brush roller 2
By the cooperation with the rotation of the charging drum, the toner is easily scraped from the photosensitive drum 1 to the charging brush roller 2 side, and finally is scraped (moves) toward the relatively center of the brush material of the charging brush roller 2. With respect to such toner, the action force of the electric field due to the potential difference between the surface of the photosensitive drum 1 and the brush material (the force to move the toner to the photosensitive drum 1 side) is relative to the amount of vibration. Just smaller.
As a result, the adhesive force (the force that the toner tries to attach to the brush material) due to the charged charge of the toner itself exceeds the force that moves the toner to the photosensitive drum 1 side, and the toner causes the brush material of the charging brush roller 2 to move. Adhere to. By such a principle, toner adheres to the charging brush roller 2 in the printing process.

On the other hand, in the cleaning process, the AC bias is cut off and only the DC bias is applied. Therefore, there is no oscillating electric field near the contact portion between the charging brush roller 2 and the photosensitive drum 1. Therefore, the acting force of the electric field due to the potential difference between the surface of the photosensitive drum 1 and the brush material exceeds the adhesive force due to the charge of the toner itself.
Further, the rotational centrifugal force of the charging brush roller 2 and the mechanical squeezing force or scraping force of the charging brush roller 2 also promote the separation of the toner from the charging brush roller 2. That is, the rotation of the charging brush roller 2 acts to scrape up the toner on the photosensitive drum 1 and move it to the charging brush roller 2 side, and to the toner attached to the charging brush roller 2. It is considered that this acts to scrape it off and move it toward the photosensitive drum 1. Therefore, the attraction force between the toner and the charging brush roller 2 is weakened. With the above operation, the toner separates from the charging brush roller 2 and moves and adheres onto the photosensitive drum 1.

At this time, the toner is considered to be relatively strongly negatively charged. This is because the toner itself is negatively charged, and the toner is negatively discharged from the charging brush roller 2 when the toner is attached to the charging brush roller 2. Therefore, when only a negative DC bias is applied to the charging brush roller 2, the toner easily moves to the photosensitive drum 1 side by the action force of the electric field due to the potential difference between the surface of the photosensitive drum 1 and the brush material. Conceivable.

On the other hand, in the cleaning process, there is no problem in the cleaning even if the AC bias is not applied. That is, by applying a sufficiently high DC voltage in consideration of the dielectric breakdown voltage of air to the charging brush roller 2, the photosensitive drum 1 can be charged to a predetermined potential. Since the potential difference between the charging brush roller 2 and the photosensitive drum 1 is determined by the dielectric breakdown voltage of air, it is as large as 600V. This is a potential difference sufficient to move the toner attached to the charging brush roller 2 to the photosensitive drum 1. In addition to this, by making the sign of the voltage applied to the charging brush roller 2 opposite to the sign of the voltage applied to the developing roller 3, the potential difference between the photosensitive drum 1 and the developing roller 3 is as large as 920V. Can be This is also a potential difference sufficient to move the toner adhering to the photosensitive drum 1 to the developing roller 3.

A third potential is applied to the developing roller 3. The third potential is -600V on the surface of the photosensitive drum 1.
The higher positive potential is + 320V. A fourth potential is applied to the supply roller 4. The fourth potential is a positive potential + 420V which is higher than the potential + 320V of the developing roller 3.

The potential −600V of the photosensitive drum 1 is lower than the potential + 320V of the developing roller 3, and the toner itself is negatively charged. Therefore, the toner on the photosensitive drum 1 moves and adheres to the developing roller 3. Since the potential difference between the photosensitive drum 1 and the developing roller 3 is sufficiently large as 920 V, the toner on the photosensitive drum 1 can be almost completely adsorbed to the developing roller 3. Due to the rotation of the photosensitive drum 1, the residual toner on the photosensitive drum 1 (the residual toner originally remaining on the photosensitive drum 1 and the toner moved from the charging brush roller 2 as described above).
Moves to the developing roller 3. As a result, the surface of the photosensitive drum 1 is cleaned. In addition, the bias voltage of the supply roller 4 is slightly lower than that of the developing roller 3 (about 100
By setting a high potential (plus potential) to V to 300 V, 100 V in this example, the toner near the developing roller 3 moves to the supply roller 4 side in the toner box 10 which is the toner supply source. As a result, the amount of toner on the developing roller 3 is always kept very small, and the toner is easily collected from the photosensitive drum 1.

The potential applied to the developing roller 3 is 0V.
It may be about + 300V. Even in this case, the voltage applied to the supply roller 4 is set to a potential higher than the potential of the developing roller 3 by about 100V to 300V.

Here, the peripheral speed ratio between the developing roller 3 and the photosensitive drum 1 in the cleaning process is made higher than the peripheral speed ratio between the developing roller 3 and the photosensitive drum 1 in the printing process under the control of the cleaning controller 91. It

The peripheral speed is different from each speed and is a speed at which a certain point on the outer circumference of the photosensitive drum 1 and the developing roller 3 moves. The peripheral speed ratio is the peripheral speed of the developing roller 3 and the photosensitive drum 1.
It is the value divided by the peripheral speed. Specifically, the peripheral speed ratio between the developing roller 3 and the photosensitive drum 1 in the printing process is 1.3.
The peripheral speed ratio between the developing roller 3 and the photosensitive drum 1 in the cleaning process is about 2.0. Since the rotation speed of the photosensitive drum 1 is the same in the printing process and the cleaning process, the peripheral speed of the developing roller 3 is 1.3 times the peripheral speed of the photosensitive drum 1 in the printing process, and the peripheral speed of the photosensitive drum 1 in the cleaning process. Is 2.0 times.

The rotation speed (and therefore the peripheral speed) of the photosensitive drum 1 in the cleaning process may be higher than that in the printing process in order to finish the cleaning process in a short time. In this case, the rotation speed of the developing roller 3 in the cleaning process is made extremely higher than that in the printing process in order to achieve the above-described peripheral speed ratio.

As a result, more residual toner can be collected from the photosensitive drum 1. This is for the following reason. That is, by increasing the relative speed of the developing roller 3 with respect to the photosensitive drum 1, the contact area of the developing roller 3 per unit time at one point on the surface of the photosensitive drum 1 increases. The amount of toner transfer from the photosensitive drum 1 to the developing roller 3 is the developing roller 3 if the other conditions are the same.
It is considered to depend on the contact area of. Therefore, by increasing the rotation speed of the developing roller 3, it is possible to further improve the toner collection efficiency.

A fifth potential is applied to the transfer roller 5. The fifth potential is a negative DC high voltage of -1000V, which is lower than the potential of the photosensitive drum 1 of -600V. Therefore, the potential of the transfer roller 5 of −1000 V is equal to the potential of the photosensitive drum 1 of −60 V.
Since it is lower than 0V, the toner on the photosensitive drum 1 does not move to the transfer roller 5 side. Accordingly, it is possible to prevent the toner attached to the surface of the photosensitive drum 1 from attaching to the transfer roller 5 in the cleaning process. The fifth potential applied to the transfer roller 5 is −
It may be about 2000V to -500V.

If toner is attached to the transfer roller 5 for some reason, the toner can be moved and attached to the photosensitive drum 1 side. That is, the negatively charged toner moves from the transfer roller 5 having the potential of −1000V to the photosensitive drum 1 side having the higher potential of −600V. As a result, the transfer roller 5 can be cleaned. Finally, this toner can be collected on the developing roller 3 side as described above.

The cleaning process is executed so as not to hinder the printing process. Therefore, the cleaning process
It is performed after the electrophotographic printer device is started and before the printing process is started, after the printing process is finished, and at any or all of three timings for each predetermined number of prints during the printing process for performing continuous printing.

For example, after the electrophotographic printer device is started for printing, cleaning processing is performed before actual printing. The cleaning process before the start of printing can be performed by using the pre-rotation process performed in the electrophotographic printer device. The pre-rotation process is performed after the electrophotographic printer device is started and before printing is started. In the pre-rotation process, the photosensitive drum 1 and the like are rotated.
Therefore, the cleaning process can be completed by utilizing this pre-rotation process and applying the potential to the photosensitive drum 1 or the like to rotate the photosensitive drum 1 as described above. By using the pre-rotation process, the start of printing is not delayed and the user does not feel inconvenience. This cleaning process can improve the quality of printing performed immediately after.

Further, for example, the cleaning process is performed after the electrophotographic printer device finishes the actual printing. The cleaning process after the completion of printing can be executed by utilizing the post-rotation process performed in the electrophotographic printer device. The post-rotation process is performed after the electrophotographic printer device finishes the actual printing and before the device is stopped. In the post-rotation processing, the photosensitive drum 1 and the like are rotated in the same manner as in normal printing. Therefore, the cleaning process can be completed by applying the potential to the photosensitive drum 1 or the like and rotating the photosensitive drum 1 by utilizing the post-rotation process. By using the post-rotation process, the user does not need to be aware of the cleaning process. This cleaning process can improve the print quality in the next print process.

In the case of continuous printing in which a plurality of sheets 12 are continuously printed, the cleaning process is periodically executed during the printing. The cleaning process during the continuous printing can be completed by stopping the supply of the paper 12 and applying the potential to the photosensitive drum 1 or the like as described above to rotate the photosensitive drum 1.

The printing control unit 9 causes the cleaning control unit 91 to periodically perform the cleaning process every predetermined number of times during the repetition of the printing process. Therefore, the print control unit 9 counts the actual number of printed sheets, and when the count value reaches a predetermined value, causes the cleaning control unit 91 to perform the cleaning process. The predetermined value is given to the print controller 9 in advance. This predetermined value can be empirically determined as an appropriate value. Since the cleaning process is automatically performed, the user does not need to be aware of the cleaning process. Further, it is possible to prevent the print quality from deteriorating even in continuous printing.

[0092]

【Example】

(Experiment 1) The following experiment was conducted in order to verify whether or not the toner movement as described above is performed in the printing process and the cleaning process.

As an experimental method, the amount of adhered toner at each point on the photosensitive drum 1 during printing and cleaning was measured. As a measuring method, printing is forcibly stopped by turning off the power during the printing operation, and the photosensitive drum 1
The toner adhering at each of the measurement points in 1 was sampled with a transparent adhesive tape, which was attached to a white paper to measure its density. A commercially available optical densitometer was used to measure the concentration. Nine measurement points were randomly set. The measured optical density value includes the density (reflectance) of the used paper and the transparent adhesive tape. The optical density value when the transparent adhesive tape was attached to the paper was 0.10 to 0.11.

(Measurement 1) First, when an electric potential as in the above-mentioned printing process is applied to the charging brush roller 2 or the like, that is, the amount of adhered toner in the normal printing process is measured. Table 1 shows the measurement results.

[0095]

[Table 1]

At a measurement point existing between development and transfer (between the developing roller 3 and the transfer roller 5 in the rotation direction of the photosensitive drum 1), the amount of adhered toner is large because it is immediately after development. Therefore, all the toner cannot be collected completely by collecting the toner with the transparent adhesive tape once, and the toner is collected twice. These values cannot be simply added to obtain an optical density value, but it can be seen that the amount of toner is very large. At the measurement points existing between the transfer and the charging (between the transfer roller 5 and the charging brush roller 2 in the rotation direction of the photosensitive drum 1), most of the toner is on the paper because the amount of the adhered toner is considerably reduced. After transfer to No. 12, it can be seen that only a small amount of residual toner is present. At the measurement points existing between the charging and the developing (between the charging brush roller 2 and the developing roller 3 in the rotating direction of the photosensitive drum 1), the amount of the adhered toner is further reduced, so that the residual toner after the transfer is reduced. It can be seen that the toner was scraped off by the charging brush roller 2.

This state shows the case of normal printing, and shows that the transfer efficiency is quite good. That is, the amount of residual toner on the photosensitive drum 1 is considerably small. (Measurement 2) Next, the state of scraping off the residual toner by the charging brush roller 2 is verified. For this reason, the transfer conditions were set so that transfer efficiency was intentionally lowered (the amount of residual toner increased), and the amount of adhered toner was measured. Specifically, the transfer efficiency was deteriorated by setting the voltage applied to the transfer roller 5 to +500 V (1/4 of the normal printing process) and lowering the effective current value. The measurement results are shown in Table 2.

[0098]

[Table 2]

At the measurement points existing between development and transfer, the toner was sampled twice as in the above. At the measurement points existing between the transfer and the charging, the amount of the adhered toner is considerably increased as compared with that in Table 1, and it can be seen that the residual toner is considerably increased. At the measurement points existing between charging and development, the amount of adhered toner has dropped to a value almost equal to that in Table 1. Therefore, even if the amount of residual toner increases, most of the residual toner is due to the charging brush roller 2. You can see that it was scraped.

From this, it was proved that the movement pattern of the toner in the normal printing process, in particular, the residual toner after transfer was scraped off by the charging brush roller 2 and absorbed and held by the charging brush roller 2.

(Measurement 3) Next, it will be verified that the residual toner absorbed and held by the charging brush roller 2 is discharged to the photosensitive drum 1 and further collected by the developing roller 3 by the cleaning process. Therefore, when an electric potential is applied to the charging brush roller 2 or the like as in the cleaning process described above, that is, the amount of adhered toner in the cleaning process is measured. The measurement results are shown in Table 3.

[0102]

[Table 3]

At the measuring points existing between transfer and charging, the amount of adhered toner is considerably low. On the other hand, at the measurement points existing between the charging and the developing, the amount of the adhered toner increases, so that the residual toner absorbed and held by the charging brush roller 2 is discharged to the photosensitive drum 1. I understand. At the measurement points existing between development and transfer,
Again, since the amount of adhered toner has dropped considerably,
The residual toner discharged onto the photosensitive drum 1 is the developing roller 3
It can be seen that they have been collected.

As described above, from the measurement 1 to the measurement 3 of the experiment 1, the toner movement pattern in the printing process and the cleaning process was verified. In particular, by applying an AC bias to the charging brush roller 2 in the printing process, the residual toner on the photosensitive drum 1 can be scraped off and absorbed by the charging brush roller 2, and the AC bias is applied in the cleaning process. It was proved that the toner absorbed by the charging brush roller 2 can be discharged onto the photosensitive drum 1 by shutting off and using only the DC bias. It was also proved that the toner discharged onto the photosensitive drum 1 can be collected in the toner box 10 via the developing roller 3.

(Experiment 2) Next, the following experiment was conducted in order to verify the cleaning effect by the above-described cleaning treatment from the viewpoint of the actual image printing quality.

As an experimental method, the degree of deterioration of the image (increase of fog density) in the case of continuous printing without the cleaning process and the degree of recovery of the image quality after the cleaning process is carried out from this deteriorated state ( (Lower fog density)
And compared. The "fog" means stains on a non-image portion, that is, a white background portion on the paper 12, and the "fog density" means the density of the stain. As the measuring method, the optical density of the non-image portion, that is, the white background portion on the paper 12 was measured by the optical densitometer in the same manner as in Experiment 1 after the printing process was completed. The measurement conditions are as follows: room temperature environment, paper is 55 Kg / ream A
Four sheets were used and the printing rate (white / black rate) was 50%. Table 4 shows the measurement results.

[0107]

[Table 4]

From the results shown in Table 4, it can be seen that the "fog density" increases as the continuous printing proceeds, and the charging brush roller 2 and the photosensitive drum 1 are contaminated by the remaining toner. Then, it is understood that the "fog density" is restored to the level at the time of printing the first sheet by performing the cleaning process after printing the 30th sheet. The cleaning time at this time was 4 to 5 seconds.

This experiment 2 is for verifying the effect of the cleaning process, and does not determine the print allowable number of sheets after one cleaning. That is, Experiment 2
In the above, as the cleaning conditions, the type of paper 12 (in particular, the width of the paper 12 with respect to the width of the photosensitive drum 1)
Environmental conditions (temperature, humidity) etc. are not taken into consideration. These influence the charging state of the paper 12 at the time of transfer, that is, the ratio of the toner on the photosensitive drum 1 to the paper 12. Therefore, the number of sheets of paper 12 on which the cleaning process is executed is determined in consideration of the various conditions described above, and is actually empirically determined from the performance of the electrophotographic printer. .

However, since the printing rate (50%) of this experiment 2 is such a high duty that it does not exist in reality, when the normal printing (printing of a document appropriately including a figure) is performed, By performing the cleaning process for 1 to 2 seconds (4 to 5 rotations of the photosensitive drum 1) every time 10 to 20 sheets are printed, the "fog density" can be sufficiently maintained at the initial level.

[0111]

As described above, according to the present invention,
In an electrophotographic printer, cleaning is performed by setting the potentials of a charging brush roller, a photosensitive drum, a developing roller, and a supply roller to a predetermined relationship so that the toner adhering to the surface of the photosensitive drum can be removed by utilizing Coulomb attractive force. Since it can be collected via the supply roller and the supply roller, all the remaining toner except the toner used for printing (transferred to the paper) can be collected, and as a result, the waste toner is eliminated and printing is performed. The cost can be reduced. Further, since the toner is all collected by utilizing the Coulomb attractive force, the cleaner mechanism and the flyer roller can be eliminated, and the electrophotographic printer device can be prevented from becoming complicated, large-sized, and costly.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic printer device.

FIG. 2 is an explanatory diagram of print processing.

FIG. 3 is an explanatory diagram of a cleaning process.

FIG. 4 is an explanatory view of a conventional technique.

[Explanation of symbols]

 1 Photosensitive Drum 2 Charging Brush Roller 3 Developing Roller 4 Supply Roller 5 Transfer Roller 6 Heat Fixing Roller 7 Fixing Roller 8 Image Printing Section 9 Printing Control Section 10 Toner Box 11 Doctor Blade 91 Cleaning Control Section

Claims (7)

[Claims] 1. A charging brush roller for charging the surface of a photosensitive drum, a photosensitive drum for forming an electrostatic latent image on the surface charged by the charging brush roller by a predetermined means, and an electrostatic drum for the surface. Developing roller that supplies toner to the photosensitive drum on which a latent image is formed to form a visible image, a supply roller that supplies toner to the developing roller, and a visible image formed on the surface of the photosensitive drum And a transfer roller configured to transfer the sheet onto a sheet of paper, wherein the charging brush roller and the photosensitive drum are rotated in a predetermined direction at a predetermined timing to perform a cleaning process. By applying only the DC voltage, which is the first potential, to the roller, the surface of the photosensitive drum is charged to the second potential, and The potential has a first code is the same code, the second potential is an electrophotographic printer apparatus characterized by its absolute value than the first potential is small. 2. The cleaning process is performed by further rotating the developing roller and the supply roller in a predetermined direction at a predetermined timing, and in the cleaning process, only a DC voltage having a third potential is applied to the developing roller. , Fourth to the supply roller
Applied only a DC voltage that is the potential of the third potential, the third and fourth potentials have a second sign that is the opposite sign of the first sign, and the fourth potential has the absolute value of the third potential. The electrophotographic printer device according to claim 1, wherein the electrophotographic printer device is larger than the above. 3. A cleaning process is further performed by rotating the transfer roller in a predetermined direction at a predetermined timing, and in the cleaning process, only a negative DC voltage, which is a fifth potential, is applied to the transfer roller. The electrophotographic printer device according to claim 3, wherein the fifth potential has a first sign and is larger in absolute value than the second potential. 4. In the printing process, a voltage obtained by superimposing a DC high voltage and an AC high voltage of a first code is applied to the charging brush roller to charge the surface of the photosensitive drum to a potential of the first code, An electrostatic latent image is formed on this surface, and a potential having a first sign, which is smaller in absolute value than the potential on the surface of the photosensitive drum, is applied to the developing roller, and the first potential is applied to the supply roller. A potential having a larger absolute value than the potential of the developing roller is applied, toner is supplied to the surface of the photosensitive drum by the developing roller and the supply roller to form a visible image, and the transfer roller 4. The electrophotographic printer apparatus according to claim 3, wherein the visible image formed on the surface of the photosensitive drum is transferred to a sheet by applying a DC high voltage of the second code to the sheet. 5. The absolute value of the first potential is 1000 V to 13 V.
00V, and the absolute value of the second potential is 500V to 800V.
V, the absolute value of the third potential is 0V to 300V, and the absolute value of the fourth potential is 10 from the absolute value of the third potential.
0V to 300V larger, the absolute value of the fifth potential is 500V
The electrophotographic printer device according to claim 3, wherein the electrophotographic printer device has a voltage of about 2000V. 6. The method according to claim 1, wherein a peripheral speed ratio between the developing roller and the photosensitive drum in the cleaning process is set to be higher than a peripheral speed ratio between the developing roller and the photosensitive drum in the printing process. The electrophotographic printer device according to any one of claims. 7. The cleaning process is performed at any one of three timings after the electrophotographic printer device is started up, before the printing process, after the printing process is completed, and during a printing process in which continuous printing is performed for each predetermined number of printed sheets, or The electrophotographic printer device according to claim 1, wherein the electrophotographic printer device is performed in all cases.