JPH09101656A - Controlling method for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of interference fringes to a developed image caused by interference made by the frequency of electrifying bias and the frequency of developing bias in the case that the frequency of the electrifying bias is controlled in accordance with the change of the film thickness of a body to be electrified. SOLUTION: As for an image forming device executing image-forming applying an image-forming process including a process where electrifying processing is performed to the body to be electrified 1 as an image carrier by an AC electrifying system contact electrifying device 2 and the process where an electrostatic latent image formed on the surface of the body to be electrified is developed as the developed image by sticking developer by a developing device 11 using an AC electric field; when an electrifying member 2 corresponds to the non-image-forming area of the body 1, current/voltage characteristics in accordance with capacitance for the layer thickness of the body 1 of the member 2 are detected, and when the member 2 corresponds to the image- forming area of the body 1, the frequency of the electrifying bias for the member 2 in accordance with the current/voltage characteristics detected is controlled, so that the developing bias condition of the developing device 11 is changed in accordance with the change of the frequency of the electrifying bias controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image carrier (electrophotographic photosensitive member) as a member to be charged, such as an image forming apparatus such as an electrophotographic apparatus (copier, optical printer, etc.) or electrostatic recording apparatus. The present invention relates to a control method of an image forming apparatus that executes image formation by applying a transfer (indirect) or direct image forming process including a step of charging a surface of an electrostatic recording dielectric or the like.

More specifically, as a charging processing means for a member to be charged, a contact charging device for charging a surface of the member to be charged by bringing a charging member to which a voltage is applied into contact with the member to be charged is used. A developing bias containing at least an AC component as a developing means for forming an electrostatic latent image by means such as irradiating an optical image containing image information on the The present invention relates to a method for controlling an image forming apparatus using a developing device (developing device using an alternating electric field) having a developer carrier to which is applied.

[0003]

2. Description of the Related Art In the image forming apparatus as described above, a corona discharge device has been widely used as a device for charging the surface of an image bearing member as a member to be charged.
This is a device in which a corona discharge device is placed in a non-contact manner with its discharge opening facing the body to be charged, and the surface of the non-charged body is exposed to the corona current from the discharge opening to perform charging processing to a predetermined polarity and potential. Is.

The corona discharge device is effective as a means for uniformly charging the surface of an object to be charged such as an image carrier to a predetermined potential. However, there is a problem that a high voltage power source is required and undesirable ozone is generated due to corona discharge.

In contrast to such a corona discharge device, the contact type charging device for charging the surface of the body to be charged by bringing the charging member to which a voltage is applied into contact with the surface of the body to be charged as described above does not reduce the power supply voltage. Since it has advantages such as a small amount of generated ozone, for example, in an image forming apparatus, instead of a corona discharge device, an image carrier such as a photoconductor or a dielectric is charged, and other charged surfaces are charged. Attention has been paid as a processing means, and researches for its practical use have been advanced.

[0006] contact with the charging device, the charging member, was applied only DC voltage V _DC as the charging bias and the "DC charging method" for charging handle member to be charged, the AC voltage V _AC to a DC voltage V _DC There is an "AC charging method" in which the charge is applied to the charged body by superimposing and applying.

In any case, the surface of the body to be charged is charged to a predetermined polarity and potential by the contact charging member to which the charging bias voltage is applied.

Regarding the AC charging method, the applicant's earlier proposal (Japanese Patent Publication No. 3-52058 (= Japanese Patent Laid-Open No. 63-149).
No. 668), the charging member has a contact area that contacts the charged body and a separation surface area where the distance from the charged body surface increases downstream of the contact area in the moving direction of the charged body. A voltage having a DC voltage component and a peak-to-peak voltage component that is at least twice the voltage value applied to the charging member when a DC voltage is applied to the charging member to start charging the member to be charged. The contact charging method or apparatus is characterized in that an oscillating electric field is formed between the surface of the body to be charged and the separated surface area of the charging member by applying it between the charging member and the charging member. In addition, since it is converged to a predetermined potential by the DC component, it is effective and effective in that it can be uniformly and stably charged without causing uneven charging, and has been widely used in recent years.

Further, by using a charging member having a high resistance layer as a surface layer, it is possible to achieve uniform charging of the charged body and prevention of leakage due to pinholes and scratches on the surface of the charged body such as a photoconductor. It is possible (Japanese Patent Publication No. 5-16033).

Further, a conductive member (conductive potential maintaining member) such as a conductive fiber brush or a conductive elastic roller as a charging member is brought into contact with the member to be charged, and a DC voltage is applied from the outside to the member to be charged. There is also one in which electric charge is directly injected into the surface to charge the surface of the body to be charged to a predetermined potential.

[0011]

By the way, in an image forming apparatus in which an image bearing member as a member to be charged is cleaned and used repeatedly in each image forming cycle, the outer periphery of the member to be charged is increased as the number of times of image formation is increased. The surface is scraped by a cleaning blade of a cleaning means, a developer or the like. Then, the charging characteristic changes due to a change in equivalent capacity due to a decrease in the thickness (layer thickness, film thickness) of the member to be charged.

As a coping means therefor, when the charging processing means for the member to be charged is a contact charging device, a current-voltage characteristic corresponding to the capacity of the charging member with respect to the layer thickness of the member to be charged is detected, and the detected current- By optimally correcting and controlling the charging bias condition for the charging member according to the voltage characteristics,
It is possible to maintain and execute the charging process and the image formation in the optimum state regardless of the reduction in the thickness of the body to be charged.

However, in this case, the charging processing means of the member to be charged has a voltage (V _DC) obtained by multiplying DC by AC as a charging bias.
+ V _AC ) is a contact charging device of an AC charging type in which a charging member applied with a + V _AC ) is brought into contact with an object to be charged to charge the surface of the object to be charged, and an electrostatic latent image formed on the surface of the object is charged with a developer. When the developing means for adhering and developing a visible image has a developer carrying body to which a developing bias containing at least an AC component is applied, and the charging member corresponds to the non-image forming area of the body to be charged. , Detecting the current-voltage characteristic corresponding to the capacity of the charging member with respect to the layer thickness of the member to be charged, and charging when the charging member corresponds to the image forming area of the member to be charged, according to the detected current-voltage characteristic. In the image forming apparatus in which the charging bias condition for the charging member is optimally corrected and controlled by controlling the frequency of the charging bias of the member, the control charging bias frequency for the charging member and the developer carrier of the developing device are set. Due to the interference with the applied developing bias frequency, an interference fringe appears in the developed visible image.

It is an object of the present invention to solve the problem of the occurrence of interference fringes on an image due to the interference between the charging bias frequency and the developing bias frequency in the image forming apparatus as described above.

[0015]

The present invention is a control method for an image forming apparatus characterized by the following control configuration.

(1) A step of charging the surface of the body to be charged with a charge, and a step of developing the electrostatic latent image formed on the surface of the body to be developed into a visible image by attaching a developer thereto. An image forming process is applied to form an image, and the charging processing means of the charged body applies a voltage obtained by multiplying the direct current by the alternating current as a charging bias to the charging member to contact the charged body to charge the surface of the charged body. In the image forming apparatus in which the developing unit is a developing unit that uses an AC electric field, when the charging member corresponds to the non-image forming area of the member to be charged, Detecting the current-voltage characteristics according to the capacity, when the charging member corresponds to the image forming area of the member to be charged, controlling the frequency of the charging bias for the charging member according to the detected current-voltage characteristics, The controlled charging bias Method of controlling an image forming apparatus characterized by changing the developing bias conditions of the developing device in accordance with a change in frequency.

(2) The bias component applied to the charging member in order to detect the current-voltage characteristics corresponding to the capacity of the charging member with respect to the thickness of the layer to be charged is a direct current or an alternating current, or a direct current superimposed on an alternating current. The method of controlling an image forming apparatus according to (1), characterized in that it is controlled with a constant current or a constant voltage.

(3) The developing means is a developing device having a developer carrier to which a developing bias containing at least an AC component is applied, and the frequency of the developing bias is changed according to the change of the frequency of the charging bias controlled as described above. The method of controlling an image forming apparatus according to (1) or (2), characterized in that.

(4) The developing device is a developing device having a developer carrier to which a developing bias containing at least an AC component is applied, and the frequency of the developing bias is changed according to the change of the frequency of the controlled charging bias. Further, the alternating voltage of the developing bias is changed (1)
Alternatively, the control method of the image forming apparatus according to (2).

(5) A developing device in which the developing means has a developer carrying member to which a developing bias containing at least an AC component is applied, and the developing bias has a duty in accordance with a change in the frequency of the controlled charging bias. The method of controlling an image forming apparatus according to claim 1, wherein the ratio is changed.

(6) A developing device in which the developing means has a developer carrier to which a developing bias containing at least an AC component is applied, and the duty ratio of the developing bias is changed according to the change in the frequency of the controlled charging bias. The control method of the image forming apparatus according to (1) or (2) is characterized in that the alternating voltage of the developing bias is changed.

That is, even if there is a change in the capacity of the member to be charged due to a decrease in the layer thickness of the member to be charged as the image bearing member due to an increase in the number of image formations, the capacity of the charging member relative to the layer thickness of the member to be charged is A current-voltage characteristic is detected according to the detected current-voltage characteristic, and the charging bias condition applied to the charging member is optimally corrected and controlled according to the detected current-voltage characteristic. And maintain image formation
It can be executed.

More specifically, when the charging member corresponds to the non-image forming area of the member to be charged, the voltage of the charging member is detected in the constant current control, and the current amount is detected in the constant voltage control. When the charging member corresponds to the image forming area of the member to be charged, the applied charging bias condition for the charging member is corrected and controlled according to the detection value, so that the number of times of image formation is increased and the charging target is increased. Even if the thickness of the body is reduced, it is possible to apply the optimum voltage or current according to the capacitance with respect to the thickness of the body to be charged each time. That is, the detected current amount or voltage when a predetermined voltage or current is applied to the charging member when the charging member corresponds to the non-image forming area of the charged member is dependent on the capacitance due to the film thickness of the charged member. The charging process of the charged object is always in the optimum state by correcting the applied voltage or current to the charging member when the charging member corresponds to the image forming area of the charged object according to the change amount. And image formation is executed.

Further, even when the resistance value changes due to environmental humidity fluctuations and durability fluctuations of the resistance layer of the charging member, the voltage-current characteristics are detected in the same manner as when the film thickness of the member to be charged changes.
It is possible to optimize the voltage or current applied to the charging member when the charging member corresponds to the image forming area of the member to be charged, and perform uniform and necessary and sufficient charging processing and image formation of the member to be charged.

The bias component applied to the charging member in order to detect the current-voltage characteristic corresponding to the capacity of the charging member with respect to the thickness of the layer to be charged is a direct current or an alternating current, or a direct current superposed with an alternating current. Current or constant voltage control is performed. The voltage is detected in the constant current control, and the current amount is detected in the constant voltage control.

In the present invention, when the charging member corresponds to the non-image forming area of the member to be charged, the current-voltage characteristic corresponding to the capacity of the charging member with respect to the thickness of the member to be charged is detected,
When the charging member corresponds to the image forming area of the member to be charged, by controlling the frequency of the charging bias to the charging member according to the detected current-voltage characteristics, it is optimal regardless of the decrease in the thickness of the member to be charged. Maintain and execute the charging process and image formation in the state.

In this case, the developing bias condition of the developing device, specifically, the frequency or duty ratio of the developing bias is changed according to the change in the frequency of the controlled charging bias.

That is, the frequency of the developing bias is changed to the direction in which the interference fringes in the image are the most inconspicuous according to the amount of change in the frequency of the charging bias to prevent the reproduction of the interference fringes. Normally, the frequency of the developing bias is controlled to change at the same rate as the rate of change of the frequency of the charging bias.

Alternatively, the duty ratio of the developing bias is changed to the direction in which the interference fringes in the image are the most inconspicuous according to the amount of change in the frequency of the charging bias to prevent the interference fringes from being reproduced. For example, the duty ratio of the developing bias is changed at the same ratio as the rate of change of the AC bias cycle that changes with the amount of change of the charging bias frequency.

As described above, when the frequency of the charging bias is changed and the frequency of the developing bias or the duty ratio is correspondingly changed, the density gradient of the output image may change. The AC voltage adjustment control can correct the output image density gradient.

Thus, according to the present invention, when the frequency of the charging bias is controlled corresponding to the change in the film thickness of the member to be charged, the interference fringes on the visible image due to the interference between the frequency of the charging bias and the developing bias frequency. It is possible to prevent the occurrence and to obtain a uniform density image. Regardless of the change in the film thickness of the member to be charged due to the durability, the change in the durability of the charging member, and the environmental change of the resistance layer of the charging member, there is no insufficient charging, and a sufficient image density and image quality can always be maintained.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

 <Embodiment 1> (FIGS. 1 to 5) (1) Example of image forming apparatus FIG. 1 shows a schematic configuration of an example of an image forming apparatus.

Reference numeral 1 denotes an image bearing member as a member to be charged, and this embodiment is of a drum type having a conductive base layer 1b made of aluminum or the like and a photoconductive layer 1a formed on the outer peripheral surface thereof as a basic constituent layer. It is an electrophotographic photoreceptor. It is driven to rotate around the support shaft 1d clockwise in the drawing at a predetermined peripheral speed (process speed).

Reference numeral 2 denotes a contact charging member which is in contact with the surface of the photosensitive member 1 and uniformly performs a primary charging process on the surface of the photosensitive member so as to have a predetermined polarity and potential. This example is a roller type (charging roller). The charging roller 2 is composed of a central core metal 2c, a conductive layer 2b formed on the outer periphery thereof, and two resistance layers 2a ₁ and 2a ₂ sequentially formed on the outer periphery thereof, and both ends of the core metal 2c are not shown. The bearing member is rotatably rotatably arranged in parallel with the drum type photoconductor 1 and is pressed against the surface of the photoconductor 1 by a pressing means (not shown) with a predetermined pressing force to rotate the photoconductor 1. Along with the rotation.

Then, a predetermined charging bias is applied to the core metal 2c from the charging bias power source 3 through the sliding contact 3a, so that the peripheral surface of the rotary photosensitive member 1 is contact-charged to a predetermined polarity and potential ( (Primarily charged).

In this example, a voltage (V _DC + V _AC ) obtained by multiplying _{DC with AC} is applied to the charging roller 2 from the charging bias power source 3 to contact-charge the photosensitive member 1 by the AC charging method.

The surface of the photosensitive member 1 which has been uniformly charged by the charging member 2 is then subjected to the exposure L of the target image information (exposure slit exposure of the original image, laser beam scanning exposure, etc.) by the exposure means 10. An electrostatic latent image corresponding to the target image information is formed on the peripheral surface.

The exposure means 10 in the apparatus of this embodiment is a fixed document platen-optical system movable type document image forming slit exposure means. In the exposure means 10, 20 is a fixed original platen glass, O is an original document placed and set on the original platen glass with the image surface facing downward, 21 is an original pressing plate, 22 is an original illumination lamp (exposure lamp), Reference numeral 23 is a slit plate, 24-26 are movable first to third mirrors, 27 is an imaging lens, and 28 is a fixed mirror. The lamp 22, the slit plate 23, and the moving first mirror 24 move the lower surface of the original platen glass 20 from one end side to the other end side at a predetermined speed V, and also move the second and third mirrors 25.
6 is driven to move at a speed of V / 2, the downward document surface on the document table glass 20 is scanned from one end side to the other end side, and the document image is image-formed slit exposure L on the surface of the rotary photosensitive member 1. .

The latent image formed on the surface of the photosensitive member 1 is then developed by the developing means 1.
By 1, the toner images are sequentially visualized.

The developing means 11 is a developing device using an AC electric field, 11a is a rotary developing roller (or sleeve) as a developer (toner) carrier, and 4 is a developing bias power source for the developer carrier 11a. . The developer bearing member 11a faces the photoconductor 1, and a development bias including at least an AC component is applied from the development bias power source 4 to the electrostatic latent image formed on the surface of the photoconductor 1 with the developer (toner). ) Is attached and is visualized as a toner image.

This toner image is then transferred to the transfer means 12.
By the above, on the surface of the transfer material 14 as a recording medium which is synchronized with the rotation of the photoconductor 1 from an unillustrated paper feeding unit and is conveyed to the transfer unit between the photoconductor 1 and the transfer unit 12 at an appropriate timing. Transferred in sequence.

The transfer means 12 of this example is a transfer roller,
A transfer bias is applied from the transfer bias power source 5 and the back surface of the transfer material 14 is charged with a polarity opposite to that of the toner, so that the toner image on the surface of the photoconductor 1 is transferred to the surface of the transfer material 14.

The transfer material 14 to which the toner image has been transferred is separated from the surface of the photosensitive member 1 and conveyed to an image fixing means (not shown) to be subjected to image fixing and output as an image-formed product. Alternatively, in the case of forming an image on the back surface, the sheet is conveyed to a re-conveying unit to the transfer unit.

After the image transfer, the surface of the photosensitive member 1 is cleaned by the cleaning means 13 to remove the transfer residual toner and other adhering contaminants, and is then discharged by the discharging exposure device 15.
It is repeatedly provided for image formation.

A main control circuit unit 100 controls the image forming apparatus in a predetermined image forming operation sequence. The charging bias power source 3, the developing bias power source 4, the transfer bias power source 5 and the like are also controlled by the main control circuit unit 100 in a predetermined manner.

(2) Various Embodiments of Charging Member 2 The charging member 2 is a conductive charging member having at least a high resistance layer on the surface layer, so that pinholes and
Leakage due to scratches and the like can be prevented.

The charging roller 2 as the contact charging member in the above-mentioned example may be rotated or driven by the photosensitive member 1 as the member to be charged which is surface-moved and driven, or may not be rotated.
It is also possible to positively rotate the photosensitive member 1 in the forward or reverse direction of the surface movement direction at a predetermined peripheral speed.
The layer structure of the roller 2 is the same as the layer structure 2c, 2b, 2a described above.
The present invention is not limited to ₁ · 2a _2.

The contact charging member 2 is not limited to the roller type,
It can be configured in a blade type, a block type, a rod type, a belt type, and the like.

FIG. 2A shows a schematic cross-sectional view of an example of the blade type. In this case, the direction of the blade-shaped charging member 2 contacting the surface of the photoconductor 1 may be either forward or reverse to the surface movement direction of the surface of the photoconductor 1.

FIG. 2B shows a schematic cross-sectional view of an example of a block or rod shape.

In each type of charging member 2, 2c is a conductive core metal member, 2b is a conductive layer, and 2a is a resistance layer.

The block-shaped or rod-shaped one is a roller type of rotatable type, and the core metal is provided without the power supply sliding contact 3a necessary for applying a bias voltage to the core metal member 2c. The lead wire leading to the power source 3 can be directly connected to the member 2c, and the electric noise that may be generated from the power feeding sliding contact 3a can be eliminated, and the space can be saved. It is also possible to adopt a configuration in which the cleaning blade of 1 is also used.

(3) Sequence FIG. 3 shows an example of an operation sequence of the apparatus shown in FIG. This example is 2
The case of continuous printing on one sheet is shown.

[0054] Based on the print (copy) start signal, the rotation drive of the photosensitive member 1 (hereinafter, referred to as a drum) of the apparatus which has been in the standby state until then is started to start the pre-rotation period. At the same time when the rotation of the drum 1 is started, the static elimination exposure 15 is turned on, and static electricity is discharged from one peripheral surface or more of the drum 1 in the section A1.

[0055] Next, the charging roller 2 which is a contact charging member
The primary charging bias (V _DC + V _AC ) is turned on.

[0056] With respect to the primary charging bias, first, the current-voltage characteristic of the charging roller is detected in the section B1, and then the charging roller frequency control corresponding to the detected current-voltage characteristic is performed. The developing bias condition can be changed accordingly.

The period before the image formation starts is the pre-rotation period of the drum 1, and the surface of the drum 1 during that period is the non-image forming area surface. Therefore, the charging roller 2 corresponds to the non-image forming area surface of the drum 1. The charging bias control is performed in the section B1 of the pre-rotation period, and the current-voltage characteristics at this time are detected, the primary frequency is corrected (the primary charging bias frequency is corrected with respect to the charging roller 2), and the developing bias is corrected (the developer carrier 11a is applied). The frequency of the developing bias, the duty ratio, and the voltage correction) are performed.

[0058] When the frequency control of the charging bias starts with the primary correction voltage, the first image formation is performed by image exposure (image forming slit exposure of the original image). The charging roller 2 corresponds to the image forming area surface of the drum 1. The surface of the drum 1 is charged under the frequency control condition, and the electrostatic latent image on the drum 1 is developed by the developing bias corrected. A visible image is formed in the vicinity of the surface facing the carrier 11a.

[0059] The so-called drum surface between sheets until the image formation for the first print is completed and the image formation for the next second print is started is the non-image formation area surface. In the example, detection of the current-voltage characteristic of the charging roller 2 and bias control of charging and developing are executed again during this sheet interval.

That is, when the printing of the first sheet is completed, the primary charging bias is again detected in the interval B2 between the sheets to detect the current-voltage characteristic of the charging roller 2, and then the frequency of the charging bias corresponding to the detected characteristic. The latent image is visualized by executing the control to form the image for the second print and the developing bias control according to the charging bias control.

Similarly, in continuous printing of three or more sheets, the current-voltage characteristics of the charging roller 2 are similarly detected between each sheet.
A sequence of charging bias control and developing bias control is performed.

[0062] When the image formation of the final print is completed, the drum 1 enters the post-rotation period, and in the section A2 of the post-rotation period, the static elimination exposure 15 on one circumferential surface or more of the drum 1 is performed.
Is removed and the charge is removed, and the rotation of the drum 1 and the charge removal exposure are OF
The status becomes F, and the apparatus enters the standby state until the next print start signal is input.

(4) Charging Bias Frequency Control Method As the photosensitive member (drum) 1, a negative polarity OPC photosensitive drum was used. Specifically, as a photoconductor layer, an azo pigment is CG
As an L layer (carrier generation layer), a mixture of hydrazone and a resin thereon is laminated as a CTL layer (carrier transport layer) to form a negative polarity organic semiconductor layer (OPC layer).
The PC photoconductor 1 is rotationally driven, and the charging roller 2 is attached to the surface thereof.
Contacting a, O and shall carry out the charging of the OPC photosensitive member 1 in the dark by applying a voltage V _DC + V _AC multiplied by alternating to direct current to the charging roller 2, which is charged after charging roller 2 passes
The relationship between the applied current I _PRM (charging bias alternating current, mA) required for the charging roller 2 to _bring the surface potential of the PC photoconductor 1 to a certain value V _D and the OPC layer thickness D _OPC (μm) were measured.

FIG. 4 shows the measurement result.
It was found that the applied current I _PRM to the charging roller 2 required to bring the surface potential of the OPC photosensitive member 1 to a certain value V _D increases as the OPC layer thickness D _OPC decreases.

Next, the relationship between the frequency f (kHz) of the AC bias V _AC of the charging bias applied to the charging roller 2 and the current I _PRM flowing at that time was measured.

FIG. 5 shows the result of the measurement, and it was found that the higher the AC bias frequency f, the more the current I _PRM flows.

From the above two relationships, a certain OPC layer thickness D
_If the current-voltage characteristic of the OPC photosensitive drum of OPC is detected, the OPC layer thickness D _OPC is predicted, and the OPC of that layer thickness is predicted.
The current I _PRM necessary for optimum charging of the photosensitive drum is known, and the charging AC bias frequency f to be applied
Is determined, which allows the charging frequency to be controlled.

(5) Charging Bias-Development Bias Tuning Control Method As described in (4) above, the charging bias V is applied in order to optimally charge the surface of the OPC photosensitive member 1 according to the OPC layer thickness D _OPC.
When controlled to vary the _DC + V _AC frequency f (charging bias frequency), the image-forming by the difference between the frequency (the developing bias frequency) of the developing AC bias is applied to the developer carrying member 11a of the developing device 11 Interference fringes appear in the captured image.

Normally, the charging bias frequency and the developing bias frequency are set at a ratio at which the interference fringes in the image are the most inconspicuous. However, when the charging bias frequency is changed by the charging bias frequency control as described above, the interference fringes are changed. Will be reproduced.

Therefore, the frequency of the developing bias is changed to a ratio in which the interference fringes in the image are the most inconspicuous according to the amount of change in the charging bias frequency to prevent the reproduction of the interference fringes.

Normally, the frequency of the developing bias is controlled to be changed at the same rate as the rate of change of the frequency of the charging bias. Alternatively, a correspondence table of both frequency change amounts may be used.

<Embodiment 2> After the control of (4) and (5) of Embodiment 1 described above, the density gradient of the output image changes the frequency of the charging bias and the frequency of the developing bias. When it changes before and after, the AC voltage of the developing bias is adjusted so that an appropriate output image density gradient can be obtained.

<Embodiment 3> This embodiment is another charging bias-development bias synchronization control method.

That is, the duty ratio of the developing bias is changed according to the change amount of the frequency of the charging bias by the control of (4) of the first embodiment to prevent the interference fringes from being reproduced.

For example, the duty ratio of the developing bias is changed at the same ratio as the rate of change of the AC bias cycle which changes with the amount of change of the charging bias frequency. However, the duty ratio may be such that interference fringes do not appear most even if the ratios are not matched at all. Alternatively, the correspondence table may be prepared in advance and used.

<Embodiment 4> After the charging bias-development bias synchronization control of Embodiment 3 described above is performed, the density gradient of the output image changes the frequency of the charging bias and the duty ratio of the developing bias. When it changes before and after, the AC voltage of the developing bias is adjusted so that an appropriate output image density gradient can be obtained.

<Others> The control method of the image forming apparatus according to the present invention is not limited to the case where the image forming apparatus is the electrophotographic apparatus as in the embodiment, but in addition, for example, a dielectric is used as a charged body (image carrier). ) Can be effectively applied to the electrostatic recording device.

In the image forming apparatus of the present invention, the image portion formed on the surface of the body to be charged is positioned at the display portion for reading, and thereafter the image is transferred to the recording medium without transfer. The surface of the charged body is removed by cleaning, and the body to be charged includes a device such as an image forming display device which is repeatedly used for forming a display image, and the control method of the present invention can be effectively applied to such a device.

In the present invention, the image forming apparatus includes a direct type image forming apparatus, that is, an image forming process including a charging step and a developing step on a member to be charged such as photosensitive paper (electrofax sheet) or electrostatic recording paper. A device for applying and forming a toner image corresponding to target image information, fixing the toner image on the surface of the recording medium without transferring the toner image to another recording medium, and printing out is also included. Also, the control method of the present invention can be effectively applied. That is,
It is possible to execute the charging process and the image formation in an optimum state regardless of variations in the thickness of the photosensitive layer of the photosensitive paper or the thickness of the dielectric layer of the electrostatic recording paper.

In short, according to the present invention, a charged member as an image bearing member is subjected to a charging process by a contact charging device of an AC charging system, and an electrostatic latent image formed on the surface of the charged member is subjected to an AC electric field. This is effective as a control method of an image forming apparatus that executes image formation by applying an image forming process including a step of developing a visible image by applying a developer by a developing device.

[0081]

As described above, according to the present invention, a process of charging a charged member as an image bearing member with a contact charging device of an AC charging system, and an electrostatic latent image formed on the surface of the charged member. In an image forming apparatus that executes image formation by applying an image forming process that includes a step of developing a developed image by applying a developer using a developing device that uses an AC electric field, it is possible to cope with a change in film thickness of a member to be charged. It is possible to prevent the occurrence of interference fringes on the visible image due to the interference between the charging bias frequency and the developing bias frequency when the charging bias frequency is controlled, and it is possible to obtain a uniform density image. Regardless of the change in the film thickness of the member to be charged due to the durability, the change in the durability of the charging member, and the environmental change of the resistance layer of the charging member, there is no insufficient charging, and a sufficient image density and image quality can always be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

2A and 2B are schematic cross-sectional views of a contact charging member of a type other than a roller type, respectively.

FIG. 3 is an operation sequence diagram of the device.

FIG. 4 is a graph showing the relationship between the OPC layer thickness of the OPC photosensitive drum and the amount of current required for proper charging.

FIG. 5 is a graph showing the relationship between the charging bias frequency and the amount of current flowing therewith.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged object (photoreceptor) 2 Charging roller 3 Charging bias applying power source 10 Image exposing means 11 Developing means 11a Developer material carrying member (developing roller) 4 Developing bias applying power source 12 Transfer means (transfer roller) 5 Transfer bias applying power source 13 Cleaning means 14 Transfer material (recording medium) 100 Main control circuit section

Claims (6)

[Claims] 1. A process including a step of charging a surface of a body to be charged with an electrostatic charge, and a step of developing an electrostatic latent image formed on the surface of the body to be developed into a visible image by attaching a developer thereto. An image is formed by applying an image process, and the charging processing means of the member to be charged charges the surface of the member to be charged by bringing the charging member, to which a voltage obtained by multiplying direct current by alternating current is applied as a charging bias, into contact with the member to be charged. In the image forming apparatus, which is the contact charging device and the developing means uses the AC electric field, when the charging member corresponds to the non-image forming area of the charged body, the capacity of the charging member with respect to the thickness of the charged body layer Detecting the current-voltage characteristic according to, and when the charging member corresponds to the image forming area of the body to be charged, the frequency of the charging bias for the charging member is controlled according to the detected current-voltage characteristic, Controlled charging bias perimeter A method for controlling an image forming apparatus, wherein a developing bias condition of the developing device is changed according to a change in wave number. 2. A bias component applied to the charging member in order to detect the current-voltage characteristic corresponding to the capacity of the charging member with respect to the thickness of the layer to be charged is a direct current or an alternating current, or a direct current superimposed on an alternating current. The control method of the image forming apparatus according to claim 1, wherein the constant current or constant voltage is controlled. 3. A developing device in which the developing means has a developer carrier to which a developing bias containing at least an AC component is applied, and the frequency of the developing bias is changed according to the change in the frequency of the controlled charging bias. The method for controlling an image forming apparatus according to claim 1 or 2, characterized in that. 4. A developing device in which the developing means has a developer carrier to which a developing bias containing at least an AC component is applied, and the frequency of the developing bias is changed according to the change in the frequency of the controlled charging bias. The method of controlling an image forming apparatus according to claim 1, further comprising changing an AC voltage of the developing bias. 5. A developing device in which the developing means has a developer carrier to which a developing bias containing at least an AC component is applied, and a duty ratio of the developing bias in accordance with a change in the frequency of the controlled charging bias. The method for controlling an image forming apparatus according to claim 1, wherein the control method is changed. 6. A developing device in which the developing means has a developer carrier to which a developing bias containing at least an AC component is applied, and the duty ratio of the developing bias is changed according to the change in the frequency of the controlled charging bias. 3. The method of controlling an image forming apparatus according to claim 1, further comprising changing the AC voltage of the developing bias.