JP2009122344A - Charging control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging control device designed to suppress meaningless wear of a body to be charged. <P>SOLUTION: The device comprises: a first alternate current determination part; a prohibition part; and a second alternate current determination part. The first alternate current determination part applies a dummy alternate current component to a charge body which gives charges to the body to be charged by superimposing and applying direct current and alternate current of current or voltage thereto at a plurality of intensities, directly or indirectly detects a direct current component of current carried from the charge body to the body to be charged, and determines an alternate current component value to be applied to the body to be charged based on the detection result of direct current component. When the detection result of current by the first alternate current determination part shows a predetermined detection result showing deterioration of the body to be charged, the prohibition part prohibits the determination of alternate current component value by the first alternate current determination part, and when the determination is prohibited by the prohibition part, the second alternate current determination part determines the alternate current component value based on information different from the detection result of direct current component instead of the first alternate current determination part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charge control device that controls a voltage applied to a charged body.

  2. Description of the Related Art Conventionally, in a charging device that charges the surface of a photoconductor, a DC voltage superimposed with an AC voltage is applied to uniformly charge the surface of the photoconductor.

  However, it is known that when the AC voltage superimposed on this DC voltage is large, the wear of the photoreceptor is intensified. Therefore, as a method for detecting an AC voltage value that can obtain sufficient charging while suppressing meaningless wear of the photoconductor, a dummy AC voltage is applied to the charging roll with multiple intensities to transfer from the charging roll to the photoconductor roll. A so-called 'shoulder detection' method has been proposed that detects the DC current value flowing in and determines the AC voltage value superimposed on the DC voltage based on the strength of the dummy AC voltage applied when the 'shoulder' appears. (For example, refer to Patent Document 1).

  FIG. 1 is a graph showing the state of 'shoulder detection'.

In FIG. 1, the horizontal axis represents the alternating current value Iac representing a dummy alternating voltage applied at a plurality of intensities, and the vertical axis represents the surface potential of the photosensitive member representing the direct current flowing from the charging roll to the photosensitive member roll. In this case, the surface potential of the photoconductor initially increases with respect to the increasing AC current value Iac, but after the AC current value Iac reaches the value A, the surface potential of the photoconductor becomes constant due to saturation. Thus, it is shown that a 'shoulder' appears in the part surrounded by the alternate long and short dash line on the graph.
JP 2006-276054 A

  However, since the wear of the photoconductor also progresses due to the above-mentioned “shoulder detection”, if the shoulder detection is frequently performed, the detection accuracy may be lowered instead, and the shoulder detection interval is lengthened. As a result, meaningless wear and insufficient charging of the photoreceptor cannot be avoided.

  Note that the above-mentioned wear or the like does not occur only on the photosensitive member having the photosensitive layer on the surface, but may similarly occur if the applied voltage composed of alternating current and direct current is applied by the charged body. It is.

  In view of the above circumstances, an object of the present invention is to provide a charge control device that is devised to suppress meaningless wear of an object to be charged.

In order to achieve the above object, a first charge control device of the present invention comprises:
Current and / or voltage direct current and alternating current are applied in a superimposed manner, and a dummy alternating current component is applied to a charged body that imparts a charge to the object to be charged with a plurality of intensities, and the current flows from the charged body to the object to be charged A first alternating current determination unit that directly or indirectly detects a direct current component of the first current component and determines an alternating current component value to be applied to the charged body based on a detection result of the direct current component;
Prohibition of prohibiting the determination of the AC component value by the first AC determining unit when the current detection result by the first AC determining unit indicates a predetermined detection result indicating the deterioration of the charged body. And
A second AC determination unit that determines the AC component value based on information different from the detection result of the DC component instead of the first AC determination unit when prohibited by the prohibition unit; It is characterized by.

  According to the first charge control device of the present invention, the charged object is not dependent on the first AC determining unit that does not improve the detection accuracy for exhausting the charged object when the charged object is deteriorated. By determining the AC component value by the second AC determining unit that does not cause fatigue, it is possible to suppress meaningless wear of the charged body.

  Here, when the cumulative increase in current over time in the detection result of the DC component for the same object to be charged reaches a predetermined upper limit, the prohibiting unit determines the AC component value by the first AC determining unit. Preferably, the determination is prohibited.

  Deterioration of the object to be charged appears in a current increase with time in the detection result of the DC component. Therefore, the AC component value is determined from the first AC determination unit to the second based on the accumulation of the current increase with time. By switching to the AC determining unit, it is possible to effectively suppress meaningless wear of the charged body.

  Alternatively, in a preferred aspect, the prohibiting unit prohibits the determination of the AC component value by the first AC determining unit when the stability of the detection result of the DC component reaches a predetermined lower limit. is there.

  Deterioration of the charged body often involves uneven wear, and the DC component detection result becomes unstable due to this uneven wear, so the AC component value is determined based on the stability of the DC component detection result. By switching from the first AC determining unit to the second AC determining unit, it is possible to effectively suppress meaningless wear of the charged body.

  Here, it is preferable that the second AC determination unit determines the AC component value based on a cumulative usage amount of the charged body, and the second AC determination unit It is also a preferable aspect that the AC component value is determined based on the cumulative usage amount of the charged body.

  Since the cumulative usage of the charged body and the cumulative usage of the charged body clearly indicate the deterioration of the charged body, the second AC determining unit determines the AC component value based on the cumulative usage of the charged body. As a result, the AC component can be determined with an accuracy that is not inferior to that of the first AC determining unit that does not improve the detection accuracy for exhausting the charged body when the charged body is deteriorated.

  Here, it is preferable that the second AC determining unit determines the AC component value based on at least one of temperature and humidity in an environment where the charged body exists.

  The discharge performance from the charged body to the charged body is affected by humidity, and the charging performance of the charged body is affected by temperature. When the second AC determining unit determines the AC component value based on at least one of temperature and humidity in the environment where the charged object exists, the deterioration of the charged object proceeds. The AC component can be determined with an accuracy not inferior to that of the first AC determining unit that does not improve the detection accuracy for exhausting the charged body.

In addition, the first alternating current determination unit detects the direct current component for each of a plurality of charged bodies that impart charge to each of the plurality of charged bodies, and determines the alternating current component value.
It is also a preferable aspect that the prohibiting unit prohibits the determination of the AC component value by the first AC determining unit individually for each of the plurality of charged bodies.

  In this way, if each of the plurality of charged bodies can be individually prohibited, compared to the case where the determination of the AC component value by the first AC determining unit can only be uniformly prohibited for the plurality of charged bodies, Insignificant wear can be suppressed more effectively.

  Here, the prohibiting unit prohibits the determination of the AC component value by the first AC determining unit for some of the plurality of charged members, and the first AC determining unit uses the one AC determining unit. While the dummy AC component is applied to the other charged bodies excluding the charged body of the part, the AC component in this part of the charged body is determined from the AC component value determined by the second AC determining unit. It is preferable to provide an alternating current limiting unit that keeps the power low.

  Among the plurality of charged bodies, when there is a charged body for which the determination of the AC component value by the first AC determining unit is prohibited, the charging for which the determination of the AC component value by the first AC determining unit is prohibited When the AC component value in the body is kept lower than the AC component value determined by the second AC determining unit during the determination of the AC component value by the first AC determining unit, the meaningless wear of the charged body is further increased. Can be suppressed.

Further, the charged body has a photosensitive film on the surface,
A dummy alternating current component is applied to the charged body with a plurality of intensities, and a direct current component of a current flowing from the charged body to the charged body is detected directly or indirectly, and the photosensitive film is based on a detection result of the direct current component. A film thickness measuring unit for measuring the film thickness of
The prohibiting unit prohibits determination of an AC component value by the first AC determining unit for a part of the plurality of charged bodies, and the first AC determining unit is configured to charge the partial charging unit. It is also a preferable aspect that the film thickness measuring unit includes a measurement control unit that measures the film thickness of the photosensitive film while applying a dummy AC component to the other charged body excluding the body. is there.

  When there is a charged body in which determination of the AC component value by the first AC determination unit is prohibited among the plurality of charged bodies, the first AC determination unit determines the first AC component value during the determination of the AC component value. When film thickness detection is performed on a charged body corresponding to a charged body that is prohibited from being determined by the alternating current determining section, the charged body corresponding to the charged body that is prohibited from being determined by the first alternating current determining section. It is possible to avoid a situation in which image formation must be waited because an opportunity for detecting the film thickness is provided separately.

In order to achieve the above object, the second charge control device of the present invention comprises:
A plurality of dummy alternating current components are applied to the charged body that contacts the charged body rotating at the set rotational speed and applies electric current and / or voltage with direct current and alternating current applied to the charged body. Applied with intensity, direct or indirect detection of the DC component of the current flowing from this charged body to this body to be charged is determined, and the AC component value to be applied to this charged body is determined based on the detection result of this DC component An exchange decision section to
A speed confirmation unit for confirming the setting of the rotational speed of the charged body;
And an AC determination timing control unit that executes determination of an AC component value by the AC determination unit when the setting of the rotational speed of the charged body is changed.

  Since the accuracy of the AC component value to be applied to the charged body increases as it is determined immediately before the operation switching of the charged body, the second charge control device of the present invention suggests the operation switching of the charged body. The AC component value is determined using a change in the rotational speed of the charged body as a trigger. Therefore, even the second charge control device of the present invention can suppress meaningless wear of the charged object.

Here, the charged body can set AC components of a plurality of frequencies for the same setting of the rotational speed of the charged body,
It is preferable that the AC determining unit applies a dummy AC component using a maximum frequency among frequencies that can be set with respect to the rotation speed setting confirmed by the speed confirmation unit.

  Even when the AC component value is determined by shoulder detection, it should be a value on the safe side that does not cause a charging failure, and the AC component value determined increases as the frequency of the dummy AC component increases. Therefore, it is possible to prevent the occurrence of charging failure by applying a dummy alternating current component having the maximum possible frequency, determining the alternating current component value, and placing the object to be charged in an overcharged state.

Further, the object to be charged is one on which an image is formed on the surface during a predetermined work period for forming a group of images.
It is also preferable that the AC determination timing control unit causes the AC determination value to be determined by the AC determination unit before the work period when the setting of the rotational speed of the charged body is changed. It is an aspect.

  Thus, by determining the AC component value before a predetermined work period (so-called job) for forming a group of images, for example, it should be applied to the charged body as compared with the case where it is performed after the work period. Since the accuracy of the AC component value is increased, it is possible to prevent the image quality from being deteriorated.

In order to achieve the above object, a third charge control device of the present invention is provided.
A contact is made with the object to be charged, and a direct current and an alternating current and voltage are applied in a superimposed manner to apply charge to the object to be charged. Apply AC component with multiple intensities, detect DC component of current flowing from this charged body to this body to be charged, directly or indirectly, and based on the detection result of this DC component, AC current to be applied to this charged body An AC determination unit for determining component values;
A frequency confirmation unit for confirming the setting of the frequency, and
And an AC determination timing control unit that executes determination of an AC component value by the AC determination unit when the frequency setting is changed.

  Since the AC component value to be applied to the charged body is more accurate as it is determined immediately before the operation of the charged body is switched, the third charge control device of the present invention suggests the switching of the operation of the charged body. The AC component is determined by using a change in the frequency setting of the AC component to be applied to the body as a trigger. Therefore, according to the third charge control device of the present invention, it is possible to suppress meaningless wear of the charged object.

Here, the charged body is in contact with a charged body rotating at a set rotational speed, and an alternating current component is applied at a set frequency corresponding to the rotational speed,
While the AC component value is determined by the AC determining unit, a speed setting unit that sets the rotation speed of the charged body to a maximum rotation speed corresponding to a frequency equal to or higher than the frequency confirmed by the frequency confirmation unit. It is preferable to have provided.

  In this way, when the frequency of the dummy alternating current component is reduced, the determined alternating current component value is also reduced, so that the maximum rotation that can be taken while avoiding the charged body becoming insufficiently charged due to a decrease in frequency is achieved. The time required to determine the AC component value can be minimized by determining the AC component value by the AC determining unit while rotating the member to be charged at a speed.

Further, the object to be charged is one on which an image is formed on the surface during a predetermined work period for forming a group of images.
It is also a preferable aspect that the AC determination timing control unit causes the AC determination value to be determined by the AC determination unit before the work period when the frequency setting is changed.

  In this way, by determining the AC component value before a predetermined work period for forming a group of images, for example, the AC component value to be applied to the charged body compared with the case where the AC component value is performed after the work period. Since the accuracy is increased, it is possible to prevent the image quality from being deteriorated.

In order to achieve the above object, a fourth charge control device of the present invention comprises:
Current and / or voltage direct current and alternating current are applied in a superimposed manner, and a dummy alternating current component is applied to a charged body that imparts a charge to the object to be charged with a plurality of intensities, and the current flows from the charged body to the object to be charged An AC determination unit that directly or indirectly detects a DC component of the AC component and determines an AC component value to be applied to the charged body based on a detection result of the DC component;
A change monitoring unit for monitoring a change with time in the detection result of the DC component;
When the change over time monitored by the change monitoring unit shows a change exceeding a predetermined level in a predetermined change mode, a value corresponding to the change mode is obtained for the AC component value determined by the AC determination unit. And an AC adjustment unit for increasing or decreasing the frequency.

  The change with time of the detection result of the DC component includes information to be added to the AC component value determined by the AC determination unit. In the fourth charging control device of the present invention, the change with time of the detection result of the DC component is included. When the change shows a change exceeding a predetermined level in a predetermined change mode, the value is increased or decreased according to the change mode with respect to the AC component value determined by the AC determination unit. Therefore, according to the fourth charging control device of the present invention, the AC component value determined by the AC determining unit can be adjusted to a value suitable for the situation, so that it is possible to suppress meaningless wear of the charged object.

  Here, it is preferable that the alternating-current adjusting unit increases the value with respect to the alternating-current component value when the slope of the change with time reaches a predetermined positive upper limit.

  Since the charged body becomes difficult to discharge at low humidity, the change over time has a positive slope.If the slope of the change over time reaches a predetermined positive upper limit, the value is increased with respect to the AC component value. Therefore, it is possible to secure the charge amount of the member to be charged.

  Moreover, it is also a preferable aspect that the AC adjusting unit is configured to reduce a value with respect to the AC component value when the slope of the temporal change reaches a predetermined negative lower limit.

  Since the charged body easily discharges when the humidity becomes high, the change with time has a negative slope, and when the slope of change with time reaches a predetermined negative lower limit, the value is reduced with respect to the AC component value. Thus, the object to be charged can be prevented from being exposed to a meaningless high voltage, and the meaningless wear of the object to be charged can be further suppressed.

  Here, it is preferable that the AC adjusting unit is configured to reduce a value with respect to the AC component value when the stability of the change with time reaches a predetermined lower limit.

  As the deterioration of the charged body progresses, uneven wear occurs, so the change over time becomes unstable, and abnormal discharge is likely to occur when the charged body is not deteriorated so much and the thickness is thick. Although the AC component value needs to be increased from the beginning, the deterioration with progress and thinning makes it difficult for abnormal discharge to occur even if the AC component value is small. If the value is reduced with respect to the AC component value when it is reached, the object to be charged is prevented from being exposed to meaningless high voltage, and the meaningless wear of the object to be charged can be further suppressed.

  It is also a preferred aspect that a direct current adjustment unit is provided that reduces the direct current component applied to the charged body when the stability of change with time reaches a predetermined lower limit.

  As the charged body deteriorates, the electrostatic capacity increases due to wear, and the charged amount of the charged body increases even when the same AC component value is applied to the charged body. In addition, as the deterioration of the charged body progresses, wear becomes intensified and uneven wear occurs and the change over time becomes unstable, so when the stability of change over time reaches a predetermined lower limit, it is applied to the charged body. By reducing the direct current component, it is possible to prevent the object to be charged from being meaninglessly highly charged and to prevent deterioration in image quality.

Further, the charged body is one on which an electrostatic latent image is formed on the surface,
A developing voltage adjusting unit is provided for reducing the developing voltage of the developing unit that develops the electrostatic latent image upon application of a DC developing voltage when the stability of the change with time reaches a predetermined lower limit. Is preferred.

  As deterioration of the charged body progresses, wear increases and uneven wear occurs, and the electrostatic capacity of the charged body increases, and even if the same AC component value is applied to the charged body, the charge amount of the charged body Since the change over time becomes unstable, the DC component applied to the charged body is reduced, and the development voltage is reduced when the stability of the change over time reaches a predetermined lower limit. It is possible to suppress deterioration in image quality due to the fact that the potential difference between the background potential of the member to be charged and the development voltage is too small.

  Further, by exposing the surface of the member to be charged, the amount of light of the exposure device that forms an electrostatic latent image on the surface of the member to be charged is increased when the stability of the change with time reaches a predetermined lower limit. It is also a preferable aspect that a light amount adjusting unit is provided.

  As the deterioration of the charged body progresses, the sensitivity of the charged body becomes dull, and the image density decreases even if the exposure light quantity does not change. In addition, as the deterioration of the charged body progresses, wear increases and uneven wear occurs and the change over time becomes unstable. Therefore, when the stability of change over time reaches a predetermined lower limit, the amount of exposure light is increased. As a result, it is possible to prevent image quality degradation due to image density degradation.

  ADVANTAGE OF THE INVENTION According to this invention, the charge control apparatus which suppresses meaningless abrasion of a to-be-charged body can be provided.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 2 is a schematic configuration diagram of a main part of the printer.

  The printer 1 shown in FIG. 2 includes four image forming units 10Y, 10M, 10C, and 10K. Each image forming unit includes photoreceptor rolls 11Y, 11M, 11C, and 11K, charging rolls 12Y, 12M, 12C, and 12K, exposure units 13Y, 13M, 13C, and 13K, developing units 14Y, 14M, 14C, and 14K, respectively. Primary transfer rolls 15Y, 15M, 15C, and 15K, charge control devices 16Y, 16M, 16C, and 16K, and static elimination lamps 17Y, 17M, 17C, and 17K are provided. The printer 1 is capable of full-color printing, and the symbols Y, M, C, and K added to the end of each of the above components are yellow, magenta, cyan, and black images, respectively. It is a component for formation.

  The printer 1 also includes an intermediate transfer belt 30, a secondary transfer roll 32, a fixing device 33, a tension roller 34, and a control unit 35.

  A color image forming operation in the printer 1 will be described.

  First, toner image formation by the yellow image forming unit 10Y is started, and the surface of the photoreceptor roll 11Y that rotates in the direction of arrow A is discharged by the charge eliminating lamp 17Y, and then rotates in contact with the rotating photoreceptor roll 11Y. A predetermined charge is applied by the charging roll 12Y. A predetermined voltage is applied to the charging roll 12Y by the charging control device 16Y.

  Next, exposure light corresponding to a yellow image is irradiated on the surface of the photoreceptor roll 11Y by the exposure unit 13Y to form a latent image. The latent image is developed with yellow toner by the developing unit 14Y, and a yellow toner image is formed on the photoreceptor roll 11Y. The toner image is transferred to the intermediate transfer belt 30 by the primary transfer roll 15Y. The intermediate transfer belt 30 circulates in the direction of arrow B, and the yellow toner image transferred onto the intermediate transfer belt 30 is subjected to primary transfer of the magenta image forming unit 10M on the downstream side in the movement direction of the intermediate transfer belt 30. The toner image is formed in the magenta image forming unit 10M so that the magenta toner image reaches the primary transfer roll 15M in accordance with the timing of reaching the roll 15M. The formed magenta toner image is transferred onto the yellow toner image on the intermediate transfer belt 30 by the primary transfer roll 15M.

  Subsequently, toner image formation by the cyan and black image forming units 10C and 10K is performed at the same timing as described above, and the yellow and magenta toner images on the intermediate transfer belt 30 are respectively formed by the primary transfer rolls 15C and 15K. The images are transferred one after the other.

  In this way, the multicolor toner image transferred onto the intermediate transfer belt 30 is secondarily transferred onto the paper 200 by the secondary transfer roll 32, conveyed along the paper 200 in the direction of arrow C, and onto the paper 200 by the fixing device 33. A color image is formed by fixing. The control unit 35 receives an instruction regarding the type of paper and a printing mode to be described later with respect to the printer 1 and instructs each image forming unit to operate individually according to the content of the instruction.

  FIG. 3 is a schematic configuration diagram of an image forming unit for yellow. Since the image forming units for colors other than yellow have the same configuration and the same function as the configuration shown in FIG. 3, the image forming unit 10Y for yellow is representatively taken below. I will give you a description.

  FIG. 3 shows each part of the image forming unit 10Y. The developing unit 14Y includes a developing roll 141Y to which a developing bias is applied and a housing that stores a developer. The developer includes toner and a magnetic carrier. The magnetic carrier is magnetic particles and charges the toner by friction with the toner. The charged toner adheres electrostatically to the magnetic carrier. Although not shown in the drawing, the developing roll 141Y has a hollow cylindrical sleeve that rotates in the direction of arrow C, and a plurality of magnets arranged in the circumferential direction of the sleeve, which is fixed inside the sleeve independently of the sleeve. The developer housed in the housing is adsorbed on the sleeve surface by the magnetic force from the magnet roll provided in the sleeve. Further, an alternating voltage and a developing bias are applied to the developing roll 141Y so that the toner in the developer adsorbed on the developing roll 141Y (sleeve surface) becomes the background of the electrostatic latent image. An electric field in a direction that prevents adhesion to the portion is generated between the developing roll 141Y and the background portion of the electrostatic latent image on the photoreceptor roll 11Y. Regarding the potential difference between them, the suppression of the flying of the reverse polarity toner to the background portion due to the potential difference being too large and the suppression of the flying of the low-charged toner to the background portion due to the potential difference being too small. Adjustments are made in points. On the other hand, the toner of the developer adsorbed on the surface of the developing roll 141Y is formed between the developing roll 141Y and the photosensitive roll 11Y by an electric field generated between the developing roll 141Y and the electrostatic latent image on the photosensitive roll 11Y. In the developed area, the toner image is formed by being electrostatically pulled toward the electrostatic latent image side of the photoreceptor roll 11Y and attached to the electrostatic latent image.

  FIG. 3 shows a detailed configuration of the charging control device 16Y provided in the yellow image forming unit 10Y.

  The charging control device 16Y includes a memory 161Y, a voltage determination unit 162Y, a voltage application unit 163Y, a direct current detection unit 164Y, and an environment sensor 165Y. The charge control device 16Y is a first embodiment of the charge control device of the present invention.

  The voltage application unit 163Y applies an applied voltage obtained by superimposing an AC voltage on a DC voltage having an intensity according to an instruction from the voltage determination unit 162Y to the charging roll 12Y, and the DC current detection unit 164Y receives light from the charging roll 12Y. A direct current flowing into the body roll 11Y is detected.

  The voltage determination unit 162Y sequentially increases the intensity of the dummy AC voltage applied to the charging roll 12Y while monitoring the DC current value detected by the DC current detection unit 164Y, and the surface potential of the rotating photoconductor roll 10Y is increased. The so-called 'shoulder detection' that detects the characteristic part called 'shoulder' in the process up to saturation is performed, and the alternating current value by the dummy AC voltage applied when this 'shoulder' is detected (this AC The current value is hereinafter referred to as a shoulder current value.) Is stored as a reference value, and the shoulder current value exceeding this reference value detected in the subsequent shoulder detection for the same photosensitive roll, Accumulate the difference from the reference value.

  The memory 161Y stores the temperature / humidity information detected by the environment sensor 165Y, the accumulated rotational speed of the currently used photoreceptor roll 10Y, and the accumulated discharge time of the currently used charging roll 12Y.

  In the image forming unit 10Y, charge is applied to the surface of the photoreceptor roll 10Y by applying an applied voltage in which an AC voltage and a DC voltage are superimposed on the charging roll 12Y. However, the alternating current generated by applying the alternating voltage promotes the wear of the photoreceptor roll 10Y. For this reason, it is desirable that the AC component of the applied voltage be set to the minimum necessary. For this reason, in this image forming unit 10Y, the above-described 'shoulder detection' is employed as a method for obtaining the necessary minimum applied AC voltage intensity (hereinafter referred to as a real AC voltage value).

  However, as described above, the wear of the photoreceptor roll is also advanced by the dummy AC voltage applied to detect the real AC voltage value applied to the charging roll. For this reason, if this ‘shoulder detection’ is frequently performed in an attempt to detect the real AC voltage value with high accuracy, wear may progress, and there may be a vicious circle in which the accuracy decreases.

  Therefore, in the image forming unit 10Y, the shoulder detection is set after changing the rotation speed in order to set the rotation speed according to the operation instruction from the control unit 35 and before starting the image forming operation. It is assumed that the rotation is performed at the maximum frequency that can be taken by the voltage application unit 163Y. Further, after the accumulation reaches the predetermined upper limit, the determination of the real AC voltage value by the shoulder detection is stopped, In addition, the temperature / humidity information detected by the environmental sensor 165Y, the accumulated rotational speed of the currently used photoreceptor roll 10Y, and the accumulated discharge time of the currently used charging roll 12Y are sequentially stored in the memory 161Y. Based on this, 'estimation detection' is performed to determine the real AC voltage value.

  As described above, the shoulder detection is performed after the rotation speed of the photoconductor roll 11Y is changed according to the operation instruction from the control unit 35. The rotation speed of the photoconductor roll 11Y is switched by the operation mode of the charging roll 12Y. This is because the accuracy increases as the real AC voltage value is determined immediately before the operation of the charging roll 12Y is switched. In addition, the determination of the real AC voltage value is performed before the image forming operation in a different mode from that before is started because the deterioration of the image quality can be prevented as compared with the case where it is performed after the image forming operation is completed. is there.

  In addition, the real AC voltage value is determined at the maximum frequency that can be taken by the voltage application unit 163Y for the set rotational speed. The real AC voltage value determined as the frequency of the dummy AC voltage is increased is This is because the photoconductor roll 11Y can be placed in an overcharged state, and in this way, it is possible to prevent the occurrence of charging failure and contribute to the suppression of deterioration in image quality.

  FIG. 4 is a diagram illustrating a case where shoulder detection is performed by changing the frequency of the dummy AC voltage.

  FIG. 4 shows the state of 'shoulder detection' performed by changing the intensity of the dummy AC voltage having different frequencies in the same manner. The vertical axis indicates the surface potential Vh of the photoreceptor roll 11Y, and the horizontal axis indicates. When the alternating current value Iac of the dummy alternating voltage is taken, the thick line represents shoulder detection by the dummy alternating voltage of the low frequency, and the thin line represents shoulder detection by the dummy alternating voltage of the high frequency.

  From FIG. 4, even when shoulder detection is performed by changing the intensity of the dummy AC voltage in the same manner, the detection is performed with the dummy AC voltage with a higher frequency than the shoulder current value a detected with the dummy AC voltage with a lower frequency. It can be read that the shoulder current value b is larger. A larger shoulder current value also increases a determined real AC voltage value, which is preferable when a charging failure is avoided and an image quality priority operation mode is instructed.

  FIG. 5 is a diagram showing the frequency of the real AC voltage value that is set corresponding to the combination of the rotation speed of the photoreceptor roll and the operation mode.

  In FIG. 5, the normal mode and the high image quality mode, which are operation modes prepared for this printer, and the rotation speed variations that can be set for the photoreceptor roll 11Y of the image forming unit 10Y are set. The frequency of the dummy AC voltage is shown. For example, even at the same rotation speed of 160 mm / sec, it is 800 Hz in the normal mode but 900 Hz in the high image quality mode. Further, the rotational speed of the photoconductor roll 11Y is suppressed, for example, as the thickness of the paper increases.

  In addition, after the accumulation of the difference between the shoulder current value exceeding the reference value and the reference value reaches a predetermined upper limit, the determination of the real AC voltage value by the shoulder detection is stopped. Since the deterioration of the roll 11Y appears in this accumulation, after the accumulation reaches the upper limit, the determination of the real AC voltage value is performed. When the deterioration of the photoreceptor roll 11Y progresses, the photoreceptor roll 11Y is exhausted. This is because meaningless wear of the photoreceptor roll 11Y can be suppressed by performing estimation detection instead of shoulder detection, which does not increase detection accuracy.

  In 'estimated detection', the photoreceptor roll is based on the temperature / humidity information, the cumulative rotation speed of the currently used photoreceptor roll, and the accumulated discharge time of the currently used charging roll, which are sequentially stored in the memory 161Y. The real AC voltage value can be determined without applying a voltage to 11Y and with an accuracy higher than the accuracy obtained by performing shoulder detection on the photoreceptor roll 11Y that has deteriorated.

  Here, determination of the real AC voltage value when shoulder detection is used will be described.

  In the voltage determining unit 162Y, a basic AC voltage value is determined by multiplying the dummy AC voltage value applied when the 'shoulder' is detected by a predetermined coefficient, and the basic AC voltage is determined to ensure image quality. The real AC voltage value is determined according to the situation.

  FIG. 6 is a graph showing the change in the shoulder current value and the corresponding AC current value of the real AC voltage value corresponding to the shoulder current value.

  The lower part of FIG. 6 plots a shoulder current value for each shoulder detection, and the upper part of FIG. 6 plots an alternating current value obtained by adding a predetermined margin to the shoulder current value, and this margin is added. The AC current value represents the AC current value of the real AC voltage value.

  In FIG. 6, as the shoulder current value within the range surrounded by the dotted line in the lower stage changes beyond the upper limit of the positive slope, the alternating current value increases stepwise as shown in the upper stage. The state of letting it be shown is shown.

  A large positive inclination as shown in the range surrounded by the dotted line in the lower part of FIG. 6 is detected when the periphery of the photoreceptor roll 11Y is low in temperature and humidity. That is, when the temperature is low, the shoulder current value increases because the resistance of the photoreceptor roll 10Y increases, and when the humidity is low, the shoulder current value increases because it is difficult to discharge.

  For the AC current value of the real AC voltage value as well, when the environment changes to low temperature and low humidity in this way, at the same margin as the previous margin α, a charging failure occurs in the photoreceptor roll 10Y, causing an image failure. Therefore, the margin is raised to margin β (β <α) as shown in the upper part of FIG.

  FIG. 7 is a graph showing the shoulder current value that changes beyond the lower limit of the negative slope and the AC current value of the real AC voltage value that changes correspondingly.

  The lower part of FIG. 6 shows the case where the shoulder current value changes beyond the upper limit of the positive slope, whereas the lower part of FIG. 7 shows the lower limit of the negative slope of the shoulder current value. The case of changing beyond is shown.

  A large negative inclination as shown in a range surrounded by a dotted line in the lower part of FIG. 7 is detected when the periphery of the photoreceptor roll 11Y is hot and humid. That is, since the resistance of the photoreceptor roll 11Y decreases at a high temperature, the surface potential of the photoreceptor roll 11Y can be saturated even if the upper limit of the dummy AC voltage value is further lowered, and the humidity is increased. Then, it becomes easy to discharge, and the same effect can be obtained even if the upper limit of the dummy AC voltage value applied in the shoulder detection is lower than before, and the shoulder current value also decreases accordingly.

  For the AC current value of the real AC voltage value as well, when the environment changes to high temperature and high humidity in this way, the photoreceptor roll 10Y is exposed to high AC current meaninglessly at the same margin as the previous margin α. As a result, the photoreceptor roll 11Y wears meaninglessly, so the margin is lowered to the margin γ (α <γ) as shown in the upper part of FIG.

  FIG. 8 is also a graph showing a shoulder current value in which a positive slope and a negative slope are alternately repeated, and a corresponding alternating current value of a real alternating voltage value.

  The lower part of FIG. 7 shows the case where the shoulder current value changes beyond the lower limit of the negative slope, whereas the lower part of FIG. 8 shows the positive and negative shoulder current values. It shows the case where the slope is alternately repeated and the stability exceeds the lower limit.

  The variation in shoulder current value as shown in the range surrounded by the dotted line in the lower part of FIG. 8 is detected because the wear of the photoreceptor roll 11Y advances and the thickness of the photosensitive layer is increased due to the occurrence of uneven wear. This is because variation occurs in the case. By the way, when the wear of the photoreceptor roll 10Y is not progressing and the film thickness of the photosensitive layer is thick, a “white spot” due to abnormal discharge is likely to occur in the photoreceptor roll 11Y, which causes deterioration in image quality. It is necessary to suppress this by increasing the voltage value. However, when the photoreceptor roll 11Y is worn and the film thickness is reduced, 'white spots' due to abnormal discharge are less likely to occur in the photoreceptor roll 11Y. Therefore, it is not necessary to increase the real AC voltage value. For this reason, as shown in the upper part of FIG. 8, the margin α is added before the variation in the shoulder current value is detected, but after the variation is detected, the photosensitive member roll 10Y is insignificantly high. Since there is no need to be exposed to alternating current, the margin is lowered to margin γ (γ <α).

  Here, when a variation in shoulder current value is detected, the voltage determination unit 162Y reduces the DC voltage value (hereinafter referred to as the real DC voltage value) together with the real AC voltage value.

  FIG. 9 is a graph showing changes in the real DC voltage value.

  The lower graph of FIG. 9 shows the same graph as shown in the lower graph of FIG. 8, that is, the case where the shoulder current value alternately repeats a positive slope and a negative slope. Shows a state in which the real DC voltage value applied to the charging roll 12Y has been lowered in accordance with the occurrence of variation within the range surrounded by the dotted line in the lower stage.

  When the photoreceptor roll 10Y is worn to the extent that the shoulder current value varies, the electrostatic capacity of the photoreceptor roll 10Y increases. As a result, even with a constant real DC voltage value, the amount of charge applied to the surface of the photoreceptor roll 11Y increases, and the potential difference between the developing bias and the surface potential of the photoreceptor roll 10Y increases. As a result, the development strength is increased, and a so-called “fogging” in which the toner is placed on the background portion where the toner is not originally placed is caused. Therefore, when the variation of the shoulder current value is detected, the voltage determination unit 162Y reduces the real DC voltage value and reduces the amount of charge applied to the surface of the photoreceptor roll 10Y. Thereby, 'fogging' is suppressed.

  In the image forming unit 10Y, the developing bias applied to the developing roll 141Y is also lowered in accordance with the reduction of the real DC voltage value by the voltage determining unit 162Y. As a result, it is possible to suppress the “fogging” caused by the low-charged toner flying to the background portion due to the too short potential difference between the developing roll 141Y and the photoreceptor roll 11Y.

  Further, in the image forming unit 10Y, the exposure light amount irradiated by the exposure unit 13Y is increased with the detection of the variation in the shoulder current value. This is because when the wear of the photoreceptor roll 11Y proceeds to the point where the variation in the shoulder current value is detected, the sensitivity of the photoreceptor roll 11Y decreases and the image density decreases even with a constant exposure light amount.

  Here, in the printer 1, in addition to the normal mode and the high image quality mode shown in FIG. 5, a monochrome image forming mode for instructing an image forming operation only to the K color image forming unit 10K, and all the four color image forming units. Two color image forming modes for instructing an image forming operation, and a photoconductor roll 11K of an image forming unit 10K for K color and a photoconductor roll of an image forming unit for other colors. In many cases, the degree of exhaustion is different. Accordingly, determination of the real AC voltage value by shoulder detection is prohibited only in, for example, the K color image forming unit 10K among the four image forming units, and the image forming units 10Y for the other Y, M, and C colors are prohibited. In 10M and 10C, it is also expected that the real AC voltage value will be determined by shoulder detection.

  FIG. 10 is a conceptual diagram showing how the real AC voltage value is determined in each image forming unit.

  FIG. 10 shows determination of real AC voltage values by shoulder detection in the image forming units 10Y, 10M, and 10C for Y color, M color, and C color except K color after an image formation instruction is issued. It is shown that image formation is performed with a real AC voltage value determined through a process (application of dummy AC voltages having different intensities shown in steps).

  Further, in FIG. 10, the use frequency is higher than other Y colors, M colors, and C colors, and the real AC voltage value is determined by estimation because the above-described accumulation exceeds a predetermined upper limit. In the image forming unit 10K for K color, the estimated real time until the real AC voltage value is determined by shoulder detection in the image forming units 10Y, 10M, and 10C for Y color, M color, and C color. It is shown that image formation is performed with a real AC voltage value determined by estimation after standby by an AC voltage value lower than the AC voltage value. In the image forming units 10Y, 10M, and 10C for Y, M, and C colors, when an image formation instruction according to a mode different from the previous one is issued and the rotation speed of the photoconductor roll changes, the shoulder detection is performed. Although the real AC voltage value is determined, the voltage applied to the charging roll 14K is estimated in the K-color image forming unit 10K that estimates the real AC voltage value until the real AC voltage value is determined. It is made lower than the real AC voltage value determined by. This is because, when the real AC voltage value determined by estimation is applied as it is to the charging roll 14K rotating in contact with the photosensitive roll 11K, the photosensitive roll 11K is caused by the alternating current from the charging roll 12K. It is because it is exhausted meaninglessly.

  Further, in the printer 1, the change in the shoulder current value is used for confirming whether or not the static elimination lamp has failed.

  FIG. 11 is a graph showing changes in the shoulder current value.

  In the range surrounded by the dotted line shown in FIG. 11, the case where the shoulder current value changes with a large negative slope is further shown than in the case shown in the lower part of FIG.

  Such a sudden decrease in the shoulder current value is considered to be a case where the function of the static elimination lamp 17Y is lowered and the potential of the photoreceptor roll 11Y remains high. This is because since a high potential has already been applied, the surface potential of the photoreceptor roll 11Y is saturated when the dummy AC voltage value in shoulder detection is low, and the shoulder current value also decreases accordingly.

  When the printer 1 detects such a sudden decrease in the shoulder current value, it displays on the display panel (not shown) that there is a possibility that the static elimination lamp has failed.

  Next, a printer provided with a charge control device having a control mode different from the charge control device 16Y shown in FIG. 3 will be described.

  The difference between this printer and the printer 1 shown in FIG. 2 is the function of the control unit that controls the entire printer and the function of the charge control device that controls the voltage application to the charging roll. 2 and FIG. 3, there is no difference from the member configuration, so illustration is omitted, and functions of these control unit and charging control device will be described in detail. This charge control device is a second embodiment of the charge control device of the present invention.

  In the charging control device 16Y shown in FIG. 3, when the predetermined accumulation related to the shoulder current value exceeds a predetermined upper limit value, the real AC voltage value is determined by estimation instead of shoulder detection. In the apparatus, when the wear of the photoreceptor roll is intensified as the variation in the shoulder current value is detected, the determination of the real AC voltage value is performed by estimation instead of the shoulder detection.

  Also in this printer, the frequency at which the real AC voltage value can be changed according to the rotational speed is as shown in FIG. 5, but the timing of shoulder detection in the image forming unit is the charge control device 16. The timing is different after the mode change between the normal mode and the high image quality mode and the frequency of the real AC voltage value is changed before the image forming operation is started. It is. The shoulder detection is performed by rotating the photoconductor roll at the maximum rotation speed that the photoconductor roll can take within a range in which the frequency does not become less than the changed frequency, and variations in the shoulder current value exceeding a predetermined limit are detected. After the detection, the determination of the real AC voltage value by the shoulder detection is stopped, and instead, the real AC voltage value is determined by the above-described estimation.

  As described above, the shoulder detection is performed after the frequency of the real AC voltage value is changed. The change in the setting of the frequency of the real AC voltage value applied to the charging roll suggests switching of the operation mode of the charging roll. This is because the accuracy increases as the real AC voltage value is determined immediately before the operation of the charging roll is switched. Further, the determination of the real AC voltage value is performed before the start of the image forming operation in a mode different from that before the start of the image forming operation after the end of the image forming operation. This is because deterioration in image quality can be prevented compared to the case.

  In addition, the maximum rotation speed that can be taken by the photoconductor roll within a range that does not become less than the changed frequency is the maximum rotation that the photoconductor roll can take while avoiding insufficient charging due to a decrease in frequency. This is because the time required to determine the real AC voltage value can be minimized by performing shoulder detection while rotating the photoconductor roll at a speed. By doing so, it is possible not to disturb the image forming operation.

  After the variation of the shoulder current value exceeding the predetermined limit is detected, the determination of the real AC voltage value by the shoulder detection is stopped because of the deterioration of the photoreceptor roll, the possibility of uneven wear. The occurrence of this uneven wear appears in the stability of the shoulder current value.According to the detection of the variation in the shoulder current value, the real AC voltage value is determined by switching from the shoulder detection to the estimation. The meaningless wear of the roll can be effectively suppressed.

  Also in this printer, the determination of the real AC voltage value by shoulder detection is prohibited only in, for example, the K color image forming unit among the four image forming units, and for other Y color, M color, and C color. It is expected that the image forming unit will continue to determine the real AC voltage value by shoulder detection.

  FIG. 12 is a timing chart showing the determination timing of the real AC voltage value.

  In the upper part of FIG. 12, every time the frequency of the real AC voltage value is changed, the K color image forming unit determines the real AC voltage value by estimation, and after that, C color, M color, and In the Y-color image forming unit, a case where a real AC voltage value is determined by shoulder detection is shown.

  In addition, in the upper part of FIG. 12, in addition to the determination timing of the real AC voltage value in each of the image forming units for each color, the film thickness detection for detecting the degree of wear of the photoconductor roll is performed. A case is shown in which the determination is performed at a predetermined interval from the determination timing.

  In the film thickness detection, similar to the shoulder detection, a dummy AC voltage is applied to the charging roll with a plurality of intensities, a direct current flowing from the charging roll to the photosensitive roll is detected, and the detection result is used to detect the photosensitive member. The film thickness of the roll is estimated.

  However, as shown in the upper part of FIG. 12, the thickness of the photoconductor roll for K color in which the photoconductor roll is heavily worn and the determination of the real AC voltage value is performed by estimation is performed separately. However, it does not necessarily interfere with the image forming operation.

  Therefore, in this printer, as shown in the lower part of FIG. 12, the shoulders in the C, M, and Y color image forming units after the determination of the real AC voltage value by the estimation in the K color image forming unit. Film thickness detection is performed using the timing of determination of the real AC voltage value by detection. In this way, an opportunity for film thickness detection can be obtained without interfering with the image forming operation.

It is a graph which shows the mode of 'shoulder detection'. FIG. 2 is a schematic configuration diagram of a main part of a printer. It is a schematic block diagram of the image forming part for yellow. It is a figure which shows the case where shoulder detection is performed by changing the frequency of a dummy alternating voltage. It is a figure which shows the frequency of the real alternating voltage value set corresponding to the combination of the rotational speed of a photoreceptor roll, and an operation mode. It is a graph which shows each change of the alternating current value of a shoulder current value and the real alternating voltage value corresponding to this. It is a graph which shows the shoulder current value which changes exceeding the lower limit of a negative inclination, and the alternating current value of the real alternating voltage value which changes corresponding to this. It is a graph which shows the shoulder current value which repeats a positive inclination and a negative inclination alternately, and the alternating current value of the real alternating voltage value corresponding to this. It is a graph which shows the change of a real DC voltage value. It is a conceptual diagram which shows the mode until the determination of the real alternating voltage value in each image formation part. It is a graph which shows the change of a shoulder current value. It is a timing chart showing the determination timing of a real alternating voltage value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 10Y Image formation part 11Y Photoconductor roll 12Y Charging roll 13Y Exposure part 14Y Development part 141Y Development roll 15Y Primary transfer roll 16Y Charge control apparatus 161Y Memory 162Y Voltage determination part 163Y Voltage application part 164Y DC current detection part 165Y Environmental sensor 17Y Electric discharge sensor lamp

Claims (22)

A current that flows from the charged body to the charged body by applying a plurality of dummy alternating current components to the charged body that gives a charge to the charged body by applying a direct current and an alternating current of the current and / or voltage. A first alternating current determination unit that directly or indirectly detects a direct current component of the first current component and determines an alternating current component value to be applied to the charged body based on a detection result of the direct current component;
Prohibition of prohibiting determination of an AC component value by the first AC determining unit when a current detection result by the first AC determining unit indicates a predetermined detection result indicating deterioration of the charged body And
A second AC determination unit that determines the AC component value based on information different from the detection result of the DC component instead of the first AC determination unit when prohibited by the prohibition unit; A charge control device characterized by the above.   The prohibition unit prohibits the determination of the AC component value by the first AC determination unit when the cumulative increase in current over time in the detection result of the DC component for the same charged body reaches a predetermined upper limit. The charge control device according to claim 1, wherein   The said prohibition part prohibits the determination of the alternating current component value by the first alternating current determination part when the stability of the detection result of the direct current component reaches a predetermined lower limit. 1. The charge control device according to 1.   The charging according to any one of claims 1 to 3, wherein the second AC determining unit determines the AC component value based on a cumulative usage amount of the charged body. Control device.   5. The charge control according to claim 1, wherein the second AC determining unit determines the AC component value based on a cumulative usage amount of the charged body. apparatus.   The said 2nd alternating current determination part determines the said alternating current component value based on at least one among temperature and humidity in the environment where the said to-be-charged body exists. 6. The charge control device according to any one of items 1 to 5. The first alternating current determination unit detects the direct current component for each of a plurality of charged bodies for applying a charge to each of the plurality of charged bodies, and determines the alternating current component value.
The said prohibition part prohibits the determination of the alternating current component value by the said 1st alternating current determination part separately about each of these some charged body, The any one of Claim 1 to 6 characterized by the above-mentioned. Charge control device.   The prohibiting unit prohibits determination of an AC component value by the first AC determining unit for a part of the plurality of charged bodies, and the first AC determining unit is configured to charge the partial charging unit. While the dummy AC component is applied to the other charged bodies excluding the body, the AC component in the charged body is kept lower than the AC component value determined by the second AC determining unit. The charging control device according to claim 7, further comprising an alternating current limiting unit. The charged body has a photoreceptor film on the surface,
A dummy alternating current component is applied to the charged body with a plurality of intensities, a direct current component of a current flowing from the charged body to the charged body is directly or indirectly detected, and the photosensitive film is based on a detection result of the direct current component A film thickness measuring unit for measuring the film thickness of
The prohibiting unit prohibits determination of an AC component value by the first AC determining unit for a part of the plurality of charged bodies, and the first AC determining unit is configured to charge the partial charging unit. And a measurement control unit that causes the film thickness measurement unit to measure the film thickness of the photosensitive film while applying a dummy AC component to the other charged body excluding the body. The charge control device according to claim 7. A plurality of dummy alternating current components are applied to the charged body that contacts the charged body rotating at the set rotational speed and applies a charge to the charged body by applying a direct current and an alternating current and voltage. Applying the intensity, directly or indirectly detecting the DC component of the current flowing from the charged body to the charged body, and determining the AC component value to be applied to the charged body based on the detection result of the DC component An exchange decision section to
A speed confirmation unit for confirming the setting of the rotational speed of the object to be charged;
A charging control apparatus comprising: an AC determination timing control unit configured to execute determination of an AC component value by the AC determination unit when setting of a rotation speed of the charged body is changed. The charged body is capable of setting AC components of a plurality of frequencies for the same setting of the rotational speed of the charged body,
The alternating current determination unit applies a dummy alternating current component using a maximum frequency among frequencies that can be set with respect to the rotation speed setting confirmed by the speed confirmation unit. The charging control device according to 10. An image is formed on the surface of the object to be charged during a predetermined work period for forming a group of images.
The AC determination timing control unit is configured to execute determination of an AC component value by the AC determination unit before the work period when the setting of the rotational speed of the charged body is changed. The charge control device according to claim 10 or 11. A charge is applied to the charged body by applying an alternating current component at a set frequency by applying a superimposed current and / or voltage direct current and alternating current to the charged body and applying an alternating current component at a set frequency. Applying alternating current components at multiple intensities, detecting direct or indirect direct current components flowing from the charged body to the charged body, and applying the alternating current to be applied to the charged body based on the detection results of the direct current components An AC determination unit for determining component values;
A frequency confirmation unit for confirming the setting of the frequency;
An electrification control device comprising: an AC determination timing control unit that executes determination of an AC component value by the AC determination unit when the setting of the frequency is changed. The charged body is in contact with a charged body rotating at a set rotational speed, and an AC component is applied at a set frequency according to the rotational speed,
While the determination of the AC component value by the AC determining unit is executed, the speed setting unit that sets the rotation speed of the charged body to the maximum rotation speed corresponding to the frequency equal to or higher than the frequency confirmed by the frequency confirmation unit. 14. The charge control device according to claim 13, further comprising: An image is formed on the surface of the object to be charged during a predetermined work period for forming a group of images.
14. The AC determination timing control unit, when the setting of the frequency is changed, causes the AC determination value to be determined by the AC determination unit before the work period. Or 15. The charge control device according to 14. A current that flows from the charged body to the charged body by applying a plurality of dummy alternating current components to the charged body that gives a charge to the charged body by applying a direct current and an alternating current of the current and / or voltage. An AC determining unit that directly or indirectly detects a DC component of the AC component and determines an AC component value to be applied to the charged body based on a detection result of the DC component;
A change monitoring unit for monitoring a change with time in the detection result of the DC component;
When the change over time monitored by the change monitoring unit indicates a change exceeding a predetermined level in a predetermined change mode, a value corresponding to the change mode is obtained for the AC component value determined by the AC determination unit. A charge control device comprising: an AC adjustment unit that increases or decreases the amount of charge.   17. The charge control device according to claim 16, wherein the AC adjusting unit increases a value with respect to the AC component value when a slope of the change with time reaches a predetermined positive upper limit.   18. The charge control according to claim 16, wherein the AC adjustment unit is configured to reduce a value with respect to the AC component value when a slope of the change with time reaches a predetermined negative lower limit. apparatus.   The said alternating current adjustment part reduces a value with respect to the said alternating current component value, when the stability of the said time-dependent change reaches a predetermined | prescribed lower limit, The any one of Claims 16-18 characterized by the above-mentioned. The charge control device according to item.   20. The DC adjustment unit according to claim 16, further comprising: a DC adjustment unit that reduces a DC component applied to the charged body when the stability of the change with time reaches a predetermined lower limit. The charging control device described. The object to be charged is one on which an electrostatic latent image is formed on the surface,
A developing voltage adjusting unit that reduces the developing voltage of the developing device that develops the electrostatic latent image in response to application of a DC developing voltage when the stability of the change with time reaches a predetermined lower limit; The charge control device according to claim 16, wherein the charge control device is a charge control device.   Light amount adjustment that increases the light amount of an exposure device that forms an electrostatic latent image on the surface of the charged body by exposing the surface of the charged body when the stability of the change with time reaches a predetermined lower limit. The charging control device according to claim 16, further comprising a unit.

Images