JP3357099B2 - Electrophotographic printing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printing apparatus, and more particularly, to an electrophotographic printing apparatus which performs charging by applying a voltage having an AC component.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic printing apparatus includes a step of uniformly charging a photosensitive member surface to a predetermined potential, as is well known. As the charging means, a corona discharger having a wire electrode and a shield electrode as main components is mainly used. However, the charging system using the corona discharger has the following problems.

1) Application of high voltage In order to obtain a surface potential of 700 to 800 V on the photoreceptor,
A high voltage such as ８8 kV must be applied.

2) Low charging efficiency Most of the discharge from the wire flows to the shield electrode, and the current flowing to the photoreceptor is only a few% of the total discharge current.

3) Generation of corona discharge products Ozone and the like are generated by the corona discharge, and it is necessary to consider the deterioration of images and the effect on human bodies.

[0006] 4) Dirt on the Wire The high electric field formed on the surface of the wire collects minute dust in the device, and the surface of the wire becomes dirty. The wire contamination tends to cause uneven discharge, which causes image unevenness.

Therefore, recently, the use of contact charging means without using the corona discharger having many problems as described above has been studied.

More specifically, a charge is directly injected into the surface of the photoreceptor by bringing a conductive member such as a conductive elastic roller to which a DC voltage of about 1 kV is applied from the outside into contact with the surface of the photoreceptor to be charged. To charge the surface of the photosensitive member to a predetermined potential. However, actually, since the surface of the conductive member to which the voltage is applied and the surface of the photoreceptor in contact therewith have microscopic irregularities, spot-like unevenness occurs on the photoreceptor surface.

As means for solving this problem, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Unexamined Patent Publication No. 3-149669, an oscillating electric field obtained by superimposing an alternating current having a peak voltage twice or more of a charging start voltage when a direct current voltage is applied to the charging member on the direct current voltage is applied to the charging member and the member to be charged. A method of performing charging by forming between them has been proposed and put to practical use.

An electrophotographic printing apparatus using roller charging will be described as an example. As shown in FIG. 1, the charging member 4 and the member to be charged 3 are cylindrical rollers, respectively. The charging is performed in the vicinity of the contact with. Since charging is performed by applying to the charging member 4 a voltage in which an AC component is superimposed on a DC component, the surface potential of the member to be charged fluctuates in the same cycle as the cycle of the AC component. At this time, since the charged body 3 is charged while rotating, a charged surface of the charged body 3 has a stripe-shaped surface potential distribution that periodically fluctuates in the circumferential direction of the drum. Assuming that the frequency of the AC component to be applied is f and the speed of the surface of the member to be charged is v, the spatial frequency of the surface potential variation generated on the surface of the member to be charged 3 is (f
/ V).

When such a surface potential that fluctuates periodically in the circumferential direction of the photoconductor is formed, the periodic fluctuation is reflected on an output image after the subsequent image forming process. For example, when an image is formed such that the entire surface becomes black, the output image has light and dark stripes corresponding to the periodic fluctuation of the surface potential of the photoconductor.

However, such a light and shade stripe cannot be recognized by human eyes if the spatial frequency is sufficiently high, so that the output does not become a factor of deteriorating the image quality. For example, f = 5
At 00 Hz and v = 50 mm / S, the spatial frequency is 10 lines /
mm, so that it is usually difficult for the human eyes to determine the image, and no shading is observed in the image.

By setting the spatial frequency to a sufficiently high value as described above, the density of an image caused by the periodic fluctuation of the surface potential does not normally become a problem. In the case where printing is performed using the aggregate of (1), a periodic density difference may occur due to the relationship between the printing pattern and the above spatial frequency. For example, in a laser printer, in the case of a printing pattern in which a line in the main scanning direction is repeatedly drawn every other line, paying attention to that one line, it is determined whether the edge of the exposed line has a high or low surface potential. The line width to be developed slightly changes.

That is, when the spatial frequency of the latent image formed by such repetitive writing is very close to the spatial frequency of the surface potential due to charging or an integer multiple thereof, the adjacent frequency is determined by the difference between the frequency and the integer multiple of the frequency. The width / thickness of the line width changes slightly. Such repeated printing pattern drawing and low-period interference unevenness caused by the difference in the spatial frequency of the surface potential are generally called moiré.

In order to prevent the occurrence of moire, the spatial frequency of the fluctuation of the surface potential is set to be clearly higher than the spatial frequency of the drawing, or when a lower frequency is used, the moire does not occur. In addition, every other line, every other line, every third line, every fourth line, and the spatial frequency of the drawing when all the repetitive printing patterns are drawn , The spatial frequency of the surface potential is set.

[0016]

However, the conventional method has the following problems.

That is, in printing with an electrophotographic printing apparatus, when printing on paper such as postcards, envelopes, and thick papers having a large mass per unit area and a large heat capacity as compared with thin papers which are usually used, paper absorption is not possible. Due to the large amount of heat, the fixability may be inferior to thin paper in some cases. In order to solve this problem, there is a method of giving a large amount of heat to the paper by simply reducing the length of the paper on which printing is performed per unit time, that is, the process speed, and lengthening the time the paper passes through the fixing device. Conceivable. However, as described above, the charging AC bias of the roller charging system must have a very limited AC charging bias frequency which is regulated by its printing resolution and process speed.

For this reason, in an electrophotographic printing apparatus which performs charging by a power supply having a specific AC charging bias frequency,
If the overall printing process speed is reduced in order to increase the paper transit time of the fixing device, that is, if the rotation speed of the photosensitive drum is changed, the spatial frequency of the photosensitive drum surface potential is also changed, and the above-described limited spatial frequency and And moire may occur depending on the repetitive printing pattern. Therefore, in the electrophotographic printing apparatus of the contact charging type, there is a problem that it is difficult to change the printing process speed in the same apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its object is to provide a photo-sensitive device in the same apparatus.
Even if the body rotation speed is changed, the spatial frequency of the surface potential changes.
An object of the present invention is to provide an electrophotographic printing apparatus capable of obtaining a clear image without moiré by making the same as before the change of the rotation speed .

[0020]

In order to achieve this object, an electrophotographic printing apparatus according to claim 1 of the present invention is a charged AC oscillating device which oscillates two or more different charged AC frequencies. When a charging AC frequency selection means for selecting one of the charging AC frequency of the charging AC oscillating device, the band selected
Comprising a charging device which performs charging the photosensitive member by applying an AC charging bias by the charging AC frequency of the electric alternating current oscillator, and changing means for changing the rotational speed of the photosensitive member, the change hands
According to the rotation speed of the photoconductor changed by the step ,
Charged AC frequency after change to charged AC frequency before change
The ratio of the number, after changes to the rotational speed of the photosensitive member before the change
So that the ratio is the same as the rotation speed ratio of the photoconductor.
The charging AC frequency selecting means changes the charging AC frequency.

According to a second aspect of the present invention, in the electrophotographic printing apparatus according to the first aspect of the present invention, the photoconductor comprises:
Rotated by drive means that drives the transport means that transports the paper
Being driven, and the changing unit is configured to control the feeling by the driving unit.
The configuration is such that the rotation speed of the optical body and the paper conveyance speed are changed .

According to a third aspect of the present invention, there is provided the electrophotographic printing apparatus according to the first or second aspect.
A developing AC oscillating device that oscillates two or more developing AC frequencies;
Further comprising: a developing AC frequency selecting unit for selecting one of the developing AC frequencies ; and a developing device to which an AC developing bias is applied by a selected developing AC frequency of the developing AC oscillating device.
Before corresponding to the rotational speed of the photosensitive member is changed by the step
The developing AC frequency selecting means changes the developing AC frequency .

[0023]

In the electrophotographic printing apparatus according to the first aspect of the present invention having the above-described structure, the rotating speed of the photosensitive member is changed by the changing means, and the charging AC frequency is selected in accordance with the change. The means selects the charging AC frequency to be supplied to the charging device. The selected charging AC frequency is the charging AC frequency before the change.
The ratio of the charged AC frequency to the wave number after the change is
Photoconductor rotation speed after changing the photoconductor rotation speed
Is set to be the same as the ratio of That
Therefore, even if the rotation speed of the photoconductor is changed,
A surface potential having the same spatial frequency as the spatial frequency at which no moire occurs is formed on the photoreceptor .

Further, the electrophotographic printing apparatus of the present invention according to claim 2, provides the same effect as claim 1, further photoreceptor and the sheet conveying means is driven to the drive means, the rotational speed of the photosensitive member And the paper conveyance speed is changed by the change unit, and the charging AC frequency selection unit selects the charging AC frequency to be supplied to the charging device in response to the change. Moiré departure
A surface potential having the same spatial frequency as the non- generated spatial frequency is formed on the photoconductor .

Further, the electrophotographic printing apparatus according to the third aspect of the present invention has the same function as the first or second aspect.
However, the rotation speed of the photoconductor is changed by the changing means,
In response to the change, the charging AC frequency selection means for selecting a charging AC frequency supplied to the charging device, a developing exchange
The flow frequency selecting means selects a developing AC frequency to be supplied to the developing device. Selected charging AC frequency and developing AC frequency
Since the wave number is set in a region where moiré does not occur in accordance with the rotation speed of the photoreceptor, a surface potential having an appropriate spatial frequency at which moiré does not occur is formed on the photoreceptor.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an electrophotographic printing apparatus to which the charging device of the present invention can be applied. In this embodiment, an electrophotographic printing apparatus in which a sheet feeding section A and a laser beam printing section B are combined is used. 1 shows a photo printing device.

The printer of this embodiment has the front end on the right end side in the drawing, and the exterior of the printer B of this embodiment comprises a printer exterior housing 1 and a printer front plate 1A. Printer front panel 1A
Can be opened and closed as shown by the two-dot chain line with respect to the hinge shaft 1B on the lower side with respect to the printer exterior housing 1, and can be raised and closed as shown by the solid line. The operation of attaching and detaching the process cartridge 2 to and from the inside of the printer, and checking and maintaining the inside of the printer are performed by opening the front plate 1A to open the inside of the printer.

The process cartridge 2 includes a cartridge housing 2a in which four image forming process devices including a photosensitive drum 3, a charging roller 4, a developing unit 5, and a cleaner 6 are included. A printer front plate 1A is indicated by a two-dot chain line. And can be freely attached to and detached from a predetermined storage section in the printer exterior housing 1 as shown in FIG. When the process cartridge 2 is properly mounted in the printer, the mechanical drive system and the electric circuit system on both the cartridge side and the printer side are connected via a mutual coupling member (not shown) to provide mechanical and Electrically integrated.

In this embodiment, the photosensitive drum 3, the charging roller 4, the developing device 5, and the cleaner 6 are integrally provided in the process cartridge 2. However, the present invention is not limited to this.
It is sufficient that at least the photosensitive drum 3 and the charging roller 4 are integrally supported and can be detached from the main unit.

The laser beam scanner unit 7 is disposed on the back side inside the printer exterior housing 1 and includes a semiconductor laser, a scanner motor 7a, a polygon mirror 7b, a lens system 7c, and the like. Laser beam L enters the housing 2a substantially horizontally from the exposure window 2b of the cartridge housing 2a mounted in the printer, and the space between the cleaner 6 and the developing unit 5 disposed vertically in the housing is provided. The light enters the exposure unit 3a on the left side of the photosensitive drum 3 through the passage, and the surface of the photosensitive drum 3 is scanned and exposed in the generatrix direction.

When an image formation start signal is input to the printer control system, the photosensitive drum 3 is driven to rotate at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow, and the peripheral surface thereof is positive or negative by a charging roller 4. It is uniformly charged to a predetermined polarity. The charging roller 4 is a conductive member to which a bias is applied by superimposing an alternating current whose current is controlled by a predetermined DC voltage and a sine wave AC voltage having a predetermined frequency, and the photosensitive drum 3 is contacted by the roller ( Alternatively, the charging process is performed directly. The charging roller 4 may be driven to rotate by the photosensitive drum 3, may be rotated in the opposite direction, or may not rotate.

Next, on the uniformly charged surface of the rotating photoreceptor drum 3, the laser beam scanner 7
The pixel laser light L corresponding to the time-series electrical image signal of the image information output from the printer is incident, and the surface of the photosensitive drum 3 is sequentially subjected to main scanning by the laser light L in the drum generatrix direction. Electrostatic latent images of image information are formed on three surfaces.

A DC voltage of -500 V and a peak-to-peak voltage of 16
The electrostatic latent image formed on the photosensitive drum 3 is applied between the sleeve 5 a and the photosensitive drum 3 by applying a bias in which a rectangular wave alternating current of 00 V and a frequency of 2 kHz is superimposed on the sleeve 5 a. The roller is sequentially developed with the toner carried on the roller (roller) and is visualized.

On the other hand, the uppermost sheet material among the sheet materials (transfer sheets) S set on the multi-feed tray 8 is drawn into the printer from the feed roller 10 rotated and driven in the direction of the arrow, and subsequently fed. The photosensitive drum 3 is fed between the roller 10 and the transport roller 12 toward a contact portion (transfer portion) between the photosensitive drum 3 and the transfer roller 13 at a constant speed equal to the rotational peripheral speed of the photosensitive drum 3.

The sheet material fed to the transfer section sequentially passes between the photosensitive drum 3 and the transfer roller 13 and a voltage (a voltage having a polarity opposite to that of the toner) applied to the transfer roller 13. The transfer of the toner image on the surface of the photosensitive drum 3 is sequentially performed by the pressing force of the transfer roller against the photosensitive drum 3. The voltage application to the transfer roller 13 is performed when the leading edge of the fed sheet material reaches a contact portion (transfer portion) between the photosensitive drum 3 and the transfer roller 13.

The sheet material that has passed through the transfer section is separated from the surface of the photosensitive drum 3, guided by the guide plate 14, and introduced into the pair of fixing rollers 15a and 15b. Fixing roller pair 15a
Of the rollers 15b, the roller 15a on the side contacting the image transfer surface of the sheet material is a heating roller having a built-in halogen heater, and the roller 15b on the side contacting the back side of the sheet material is a pressure roller made of an elastic material. is there. In the sheet material to which the toner image has been transferred, the toner transferred in the process of passing through the pair of rollers 15a and 15b is fixed to the surface of the sheet material by heat and pressure. It is discharged as an object (print).

This series of image forming steps is called a process, and the length of a sheet processed per unit time is called a process speed. What determines the process speed is the number of rotations of the paper feed roller 10, the transport roller 12, the photosensitive drum 3, the transfer roller 13, the fixing roller pair 15a and 15b, etc. And is driven by one main motor 42 (not shown). In the case of the present embodiment, the main motor 42 normally rotates at 500 rpm, and the rotation coupling mechanism is configured so that the process speed (the peripheral speed of the photosensitive drum 3) in this case is 50 mm / S. In addition, since the variation in the process speed has a significant effect on the print quality, the main motor 42 must rotate accurately.
For this reason, the rotation speed of the main motor 42 is controlled in synchronism with the oscillation frequency of the reference oscillator F4 whose crystal oscillation is guaranteed to be accurate. In this embodiment, the reference oscillation frequency is 1.5 M
A rotation of 500 rpm is obtained at Hz.

After the transfer of the toner image, the surface of the photosensitive drum 3 is cleaned and cleaned by the cleaning blade 6a of the cleaner 6 to remove the residual toner and other contaminants, and is repeatedly used for image formation.

When the sheet is fed from the cassette 100 of the sheet feeding apparatus A instead of using the multi-feed tray 8, the uppermost sheet among the sheets S stacked on the cassette 100 is picked up by the pickup roller 26. The sheet material is sent to the registration rollers 28 and 55 and proceeds in the direction of the arrow, and the sheet material is fed between the feed roller 10 and the transport roller 12 as described above.

Next, the charging method in this embodiment will be described. FIG. 2 is a simplified view of the configuration of the main part of this embodiment in FIG. The charging bias power supply E4 includes a DC power supply E4b and an AC power supply E4a.
A bias voltage in which an AC component is superimposed on a DC is supplied to the charging roller 4 from the charging bias power supply E4. Further, the AC power supply E4a includes AC oscillators E4a1 and E4a2 having different frequencies, an analog switch E4a3,
It comprises a power amplifier circuit E4a4 and a step-up transformer E4a5.

A main motor 42 for determining the length of paper on which printing is performed per unit time, that is, the process speed, and obtaining a rotational force for transporting the paper is driven by a motor drive circuit 43. AC oscillator F4
Are accurately defined according to the reference frequency at which AC oscillator F4 also includes AC oscillators F4a and F4b having different frequencies, and an analog switch F4c.
It is composed of The oscillation frequencies of the AC oscillators F4a and F4b are accurately calibrated by quartz. The rotational movement of the main motor 42 and the photosensitive drum 3 is mechanically connected by a drive transmission mechanism 41.

The paper type changeover switch G1 is provided on the front of the printer B, and can be switched according to the paper type used by the operator. Further, the paper type changeover switch G1 is electrically linked with the analog switches E4a3 and F4c. When the paper type changeover switch G1 is set to the X side, the analog switches E4a3 and F4c are also set to the X side and the paper type changeover switch G1 is set to the Y side. Then, the analog switches E4a3 and F4c are also selected on the Y side.

When using the present electrophotographic printing apparatus, the operator normally selects and uses the paper type changeover switch G1 on the X side. At this time, the analog switches E4a3, F4c
Also, the X side is selected according to the paper type changeover switch G1, so that the rotation speed of the main motor 42 is 500 rpm.
And the process speed (the peripheral speed of the photosensitive drum 3) is 50
mm / S. When the resolution is 400 dpi at a process speed of 50 mm / S and the oscillation frequency of the AC oscillator E4a1 is set to a charging frequency of 600 Hz at which moire is unlikely to occur, an optimal charging AC bias frequency is applied to the photosensitive drum 3. Is done. The photoconductor driver at this time
Spatial frequency of the surface potential generated on the arm 3 surface is 600 /
50 = 12 lines / mm, the spatial frequency of this surface potential
12 lines / mm, as shown in the column of the prior art,
The light and dark stripes in an image due to spatial frequencies
Meet the point that cannot be identified
Spatial frequency and spatial frequency of repeated print pattern drawing
Satisfies the point that no moiré is generated from the difference from the number
Value.

On the other hand, when printing on a large heat capacity paper such as a postcard, an envelope, or a thick paper, the operator selects the paper type changeover switch G1 to the Y side. When the paper type changeover switch G1 is selected to the Y side, the analog switch F4c is also selected to the Y side, and the rotation frequency of the main motor 42 has a reference frequency of 2/3. Both process speeds are 2/3. At this time, if the resolution in the sub-scanning direction is not changed, the spatial frequency in the case of repeatedly printing the drawing pattern does not change. However, if the frequency of the charging AC bias is the same, the spatial frequency of the surface potential fluctuation is 2/3 because the rotation speed of the photosensitive drum 3 is 2/3, and there is a possibility that moire may occur. I do. Therefore, the AC oscillator E4a2 that can obtain 400 Hz is selected so that the optimum spatial frequency of the surface potential fluctuation can be obtained even when the rotation speed of the photosensitive drum 3 is changed by 2/3. In other words, the photoconductor before the change
Of the photosensitive drum 3 after the change to the rotation speed of the drum 3
Since the rotation speed ratio is 2/3, the charging frequency before the change
The ratio of the charging frequency after the change to the number becomes 2/3
Change the charging frequency from 600Hz to 400Hz
Is done. The surface voltage generated on the surface of the photosensitive drum 3 at this time is
The spatial frequency of the order is 400 / (50 × 2/3) = 12
/ Mm after the rotation speed of the photosensitive drum 3 is changed.
The spatial frequency of the surface potential varies with the rotation speed of the photosensitive drum 3.
It is the same as the spatial frequency of the previous surface potential,
Spatial frequency of surface potential after changing the rotation speed of the optical drum 3
Is the image streaks usually caused by the spatial frequency of the surface potential
Satisfies the requirement that
Drawing of spatial frequency of surface potential and repetitive printing pattern
No moiré due to the difference with the spatial frequency of
It is the value that satisfied the point.

Therefore, when printing on a paper having a large heat capacity such as a postcard, an envelope, or a cardboard, printing without moire can be performed even if the process speed becomes slow.

In the above embodiment, the AC bias frequency is changed depending on the process speed or the paper transport speed. However, if the AC bias is used also in the development of the image forming process, the present invention is applied. 4-95618
As described in the specification and the drawings, the developing AC bias frequency must be changed in order to obtain a clearer image.

FIG. 3 shows another embodiment of the present invention in which not only the charging AC bias frequency but also the developing AC frequency are changed according to the process speed and the paper transport speed.
Note that the same members as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The developing bias power source H4 has a configuration substantially the same as the charging bias power source E4.
b and an AC power supply H4a. From the developing bias power supply H4, a bias voltage in which an AC component is superimposed on a DC is supplied to the sleeve 5a. The AC power supply H4a has AC oscillators H4a1 and H4a2 having different frequencies, and an analog switch H4, similarly to the charging AC power supply E4a.
a3, a power amplifier circuit H4a4, and a step-up transformer H4a5.

The charging AC oscillator according to claim 1 corresponds to the AC oscillators E4a1 and E4a2 of the above embodiment. The charging AC frequency selecting means of claim 1 corresponds to the analog switch E4a3 of the above embodiment. Claim 1
The charging device corresponds to the charging roller 4 of the above embodiment. The changing means of claim 1 is the AC oscillator F4 of the above embodiment.
a, F4b and analog switch F4c are supported. The driving means according to claim 2 is the main motor 4 of the above embodiment.
2 is supported. The conveying means according to claim 2 is a fixing roller.
It corresponds to pairs 15a and 15b. A developing AC oscillator according to claim 3 is the AC oscillator H4a1, H4a of the above embodiment.
2 is supported. The developing AC frequency selecting means of claim 3 corresponds to the analog switch H4a3 of the above embodiment. The developing device according to claim 3, wherein the sleeve 5 of the above embodiment is used.
It corresponds to a.

The charging member described above is not limited to the roller,
It may be a blade, a brush, or a belt.

The switching of the process speed may be performed automatically based on a signal detected by a paper thickness sensor or the like without operating by an operator.

To determine the oscillation frequency of the AC bias,
The one or more AC oscillators and the selecting means may be realized by using one AC oscillator and a frequency dividing circuit.

Further, two or more AC oscillators for determining the oscillation frequency of the AC bias may share a part of the circuit.

The change of the process speed may be realized not by switching the reference frequency but also by a mechanical or other electrical method.

[0056]

As is apparent from the above description, the electrophotographic printing apparatus according to the present invention can be applied to the photoconductor in the same apparatus.
Even if the rotation speed is changed, the charging AC frequency before the change
The ratio of the charging AC frequency after the change
Same as the ratio of the rotation speed of the photoconductor after the change to the rotation speed
The charging AC frequency selection means sets the charging
Due to spatial frequency of surface potential to change flow frequency
The dark and light stripes in an image are usually indistinguishable to the human eye
And the spatial frequency of the surface potential
Moiré is calculated from the difference from the spatial frequency of the
Spatial frequency before change that satisfies the point where it did not occur
A surface potential with the same spatial frequency as
Therefore , a clear image without moire can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electrophotographic printing apparatus.

FIG. 2 is a block diagram illustrating a main configuration of an electrophotographic printing apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating a main configuration of an electrophotographic printing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 3 Charged member (photosensitive drum) 4 Charging member (charging roller) 42 Main motor E4 Power supply for charging bias F4 Main motor rotation reference oscillator G1 Paper type switch H4 Power supply for developing bias

Claims (3)

(57) [Claims] 1. Oscillation of two or more different charging AC frequencies
A charging AC oscillating device, the charging AC and charging AC frequency selection means for selecting one of the charging AC frequency of the oscillation device, by applying an AC charging bias by the charging AC frequency of said selected charging AC oscillator photosensitive to a charging device which performs charging to the body, said a changing means for changing the rotational speed of the photosensitive member, in response to the rotational speed of the photosensitive member is changed by the changing means changes to the charging AC frequency before changing Later belt
The ratio of the AC frequency to the rotation speed of the photoconductor before the change
The same ratio as the ratio of the rotation speed of the photoconductor after the change
As described above, the charging AC frequency selection means changes the charging AC frequency, and the electrophotographic printing apparatus is characterized in that the charging AC frequency selecting means changes the charging AC frequency. 2. A transport means for transporting a sheet, wherein the photosensitive member transports a sheet.
Is driven by a driving unit that drives the photoconductor, and the changing unit is configured to rotate the photoconductor by the driving unit.
A contractor characterized by changing the speed and paper transport speed.
The electrophotographic printing device according to claim 1. 3. Oscillation of two or more different development AC frequencies
A developing AC oscillation device, a developing AC frequency selecting means for selecting one of the developing AC frequencies of the developing AC electric oscillating device, and a developing device in which an AC developing bias is applied by the selected developing AC frequency of the developing AC oscillating device. Further equipment
The developing AC frequency selecting means may select the developing AC frequency corresponding to the rotation speed of the photoconductor changed by the changing means.
3. The method according to claim 1 or 2, wherein
Mounting an electrophotographic printing device.