Abstract: An image forming device includes an image holding member and a charging unit. In a case in which an AC current, while being increased, is supplied to the charging unit in a state in which a DC voltage value and an AC voltage value applied to the charging unit are maintained, or a case in which a DC voltage, while being increased, is supplied to the charging unit in a state in which the AC voltage value applied to the charging unit is maintained, a current detection unit detects DC current values. An inflection point derivation unit derives an inflection point of a correlation line representing an correlation between the detected DC current values and the supply amounts. An execution unit executes pre-specified processing when a characteristic value of the derived inflection point reaches a pre-specified value.

Abstract: A charging device controller controls a charging device including a charging roller to charge a surface of an image carrying member carrying a toner image, a cleaning roller to come into contact with the charging roller to remove therefrom foreign substances including toner, and a contact-separation device to make the cleaning roller come into contact with and separate from the charging roller. The charging device controller includes a contact-separation device controller to cause the contact-separation device to make the cleaning roller come into contact with and separate from the charging roller during an image forming operation, which includes a latent image writing operation of writing a latent image on the image carrying member and a development operation of forming a toner image by supplying toner to the latent image, at an operation other than the latent image writing operation performed on the image carrying member.

Abstract: An image forming apparatus includes a photosensitive body to be developed by a conductive toner, a charger which charges a surface of the photosensitive body with a surface potential, a power supply which supplies one of a normal charging power to perform a normal charging operation and a compensation charging power, having a different absolute value than the normal charging power and having the same polarity as the normal charging power, to the charger, and a controller which controls the power supply to supply the normal charging power and the compensation charging power to the charger, respectively, before and after a charging time at which a rear end contact surface of the photosensitive body contacting a rear end of a printing medium is charged by the charger.

Abstract: A surface potential distribution measurement method and device including setting a sample having a surface with a surface potential distribution in a sample installation unit wherein both an electric field intensity formed on the sample surface and a potential bias component of the sample are variable, and scanning the sample surface in a one-dimensional or two-dimensional manner by irradiating a charged particle beam to the sample. The method also includes obtaining a detection signal from charged particles generated by the scanning, to measure the surface potential distribution of the sample by varying the electric field intensity and the potential bias component in order to control a quantity of the detection signal obtained from the charged particles.

Abstract: An image forming apparatus includes an image carrier configured to carry an image and a charger to which a direct current voltage overlapped with an AC voltage is applied as a charging bias to charge the image carrier. The charger is positioned in contact or contactlessly with the image carrier. A controller performs an adjustment to the AC voltage multiple times to gradually bring the AC voltage to a target value.

Abstract: In a charging device of the present invention, with reference to a state (movement speed of a charging receiving material, operating period of charging device) in which the charging device is used which state is obtained by an image formation controlling section, a voltage controlling section sets or changes an applied voltage to be applied between a discharge electrode and an inductive electrode. Accordingly, even in a case where discharge is hard to occur, a necessary amount of ions can be supplied stably.

Abstract: An image forming apparatus including: an image forming section for forming an image, the image forming section including a photoconductor, a charging unit, a developing unit, a toner supply unit which supplies a toner to said developing unit, and a developing bias power supply section which supplies a developing bias voltage to said developing unit; and a controller that activates said image forming section, determines a target value of a charging potential of said photoconductor and/or a developing bias voltage, for forming the image, and controls the charging unit and/or the developing bias power supply section in accordance with a determined result, wherein when an absolute value of the determined target value of the charging potential or an absolute value of the determined developing bias voltage is larger than a prescribed value, said controller controls replacement of a prescribed amount of a toner in the developing unit.

Abstract: The image forming apparatus includes image forming parts, a developing device and a cleaner to clean at least the intermediate transfer material or the transfer device, wherein at the image forming operation starting time, in each image forming part, after starting the charging, the application of the developing bias is started before the top end of the charging portion of the image bearing member surface reaches a developing area in which the image bearing member and the developer bearing member are set against each other, and from among the areas on the image bearing member in which the charging is not yet performed in each image forming part, in case each area having passed the developing area when the developing bias is applied is brought into contact with the intermediate transfer member, the contact area with each area in the intermediate transfer member is controlled without superposing on the intermediate transfer member.

Abstract: An image formation apparatus includes: a photoconductor that has a photoconductive layer having a surface on which an electrostatic latent image is formed; a charging roll to which a bias with an AC component superposed on a DC component is applied for charging the photoconductor at a predetermined potential; a film thickness detector that detects a film thickness of the photoconductive layer of the photoconductor without applying the AC component; an environment measuring section that measures at least one of ambient temperature and humidity; an AC component setting section that sets a value of the AC component of the bias based on detection results of the film thickness detector and the environment measuring section; and a charging controller that controls at least one of voltage and current applied to the charging roll based on the value of the AC component set by the AC component setting section.

Abstract: A corona generating device for charging a surface including, a housing; the housing including spaced generally parallel side panels; members for holding a corona generating electrode in an operable position within the housing; and system for adjusting the height spacing of the corona generating electrode relative to the surface the adjusting system includes a first bridge member adjacent to the inboard wire mount and a second bridge member adjacent to the outboard wire mount, the first bridge member and second bridge member contacts the wire to change the distance of the wire relative to the surface.

Abstract: An image forming apparatus includes: an image bearing body on which surface a solid lubricant is supplied, forming and bearing an image on the surface; a charging member to which a voltage is applied, being in contact with the image bearing body to impart a charge; a voltage applying section that applies the voltage to the charging member, capable of switching the voltage between superimposed voltage on which DC voltage and AC voltage are superimposed and non-superimposed voltage including only DC voltage; an image forming section that forms a toner image; a transfer device that transfers the formed toner image to a transferring body; a cleaning member that contacts the image bearing body to scrape unnecessary substance from the surface; and a voltage switching section that switches the voltage applied to the charging member between the superimposed voltage and the non-superimposed voltage according to an amount of the solid lubricant.

Abstract: An image formation apparatus that includes a photoconductor, a charging section that applies a bias voltage having an AC voltage superposed on a DC voltage and charges the photoconductor, a controller that controls at least one of the AC voltage and an AC current applied by the charging section, and a detector that detects an amount of discharge occurring between the photoconductor and the charging section. The controller controls at least one of the AC voltage and the AC current so that the amount of discharge detected by the detector falls within a predetermined range containing a singularity in change of the amount of discharge.

Abstract: A method of charging an imaging member having an outer surface with an imaging region and a seam region. A charge device is provided adjacent the imaging member. An electrical charge is provided to the imaging region of the imaging member using a voltage on the charge device. An other electrical charge is provided to the seam region of the imaging member using an other voltage on the charge device.

Abstract: An image forming apparatus is provided in which on-surface potential unevenness of an image carrier can be suppressed, and with which an output image having excellent on-surface uniformity of color or the like can be obtained. The image forming apparatus includes: a photoconductive image carrier; charger which charges the image carrier; image exposing unit which exposes an image on a surface of the image carrier after the charging to form a latent electrostatic image; developing unit which develops the latent electrostatic image by adhering toner to the latent electrostatic image to form a toner image; and transfer charger which transfers the obtained toner image to a final supporting member such as plain paper.

Abstract: A level determination circuit 60 determines whether a voltage level Vref of an output variable signal is a previously set reference level Vref?m or higher. According to this determination result, a constant voltage output circuit 70 and a constant current output circuit 80 selectively operate. The constant voltage output circuit 70 outputs a transfer voltage Vout of a level corresponding to the voltage level Vref of the output variable signal. The constant current output circuit 80 outputs a constant current Iout of a level corresponding to the voltage level Vref of the output variable signal.

Abstract: An image forming apparatus, performing a corresponding method of image forming, includes an image carrier, a writing unit, a developing unit, a charging member configured to rotate continuously with the image carrier at a portion contacting the image carrier and uniformly charge a surface of the image carrier while contacting a surface thereof with the surface of the image carrier, a charge bias applying unit configured to apply a charge bias to the charging member, and a controller configured to control of driving of the image carrier and the charging member and reduce at a charge nip at a given timing a linear velocity ratio of a travel speed of the surface of the charging member to a travel speed of the surface of the image carrier.

Abstract: The presently disclosed embodiments are directed to imaging members useful in electrostatography. More particularly, the embodiments pertain to an improved development systems for electrophotographic imaging and printing apparatuses and machines in which ghosting print defects are reduced, and more particularly, is directed to a method for reducing positive ghosting in such systems.

Abstract: An image forming apparatus includes a rotatable photosensitive member; a corona charger provided with an opening opposed to a surface of the photosensitive member; image forming means for forming a toner image on the photosensitive member; a shutter for opening and closing the opening relative to the photosensitive member; sliding means for sliding in contact with the photosensitive member; measuring means for measuring time elapsed from end of image formation; and control means for controlling the apparatus on the basis of an output of the measuring means such that shutter is closed and the photosensitive member is rotated in contact with the sliding means.

Abstract: In order to prolong life of a charger, there is provided an image forming device including a photosensitive member, a charger, an exposing unit, a developing unit and a control unit. The charger charges the photosensitive member at a charging position, and the exposing unit exposes the photosensitive member to light and forms an electrostatic latent image on the photosensitive member. The developing unit develops the electrostatic latent image formed on the photosensitive member at a developing position, the developing unit having a developing member that carries thereon developer charged to a polarity, the developing member having a surface potential.

Abstract: An ion generating device provided in an image forming apparatus of the present invention as a charging device for charging before a first transfer, a charging device for charging before a second transfer, or a charge device for charging an electrostatic latent image is arranged such that a discharge electrode can move with respect to a dielectric material and the relative positions of the discharge electrode and the dielectric material can be changed. This makes it possible to provide: a long-life ion generating device whose life has been extended by making effective use of a dielectric material; and an image forming apparatus including the ion generating device.

Abstract: This is a charging assembly that is useful in marking processes with an electrostatically charged surface. The assembly includes, besides the charger, a controller and an electric field probe. Charge and current flows can be detected by the probe and corrected immediately after detection of flaws by the probe and conveyed to the controller. If flaws in the charger are determined by the probe, corrections are made to the output by a controller; this is done before a final copy or print is made. The term flaws as used means any non-uniform appearing region in the printed image or any otherwise unacceptable defect. The probe is enabled to detect and indicate flaws and the controller which is in communication with the probe takes corrective action on the flaws. The probe used is a novel probe having two sensing elements surrounded by one or more reference electrodes.

Abstract: An image forming apparatus includes an image forming part for forming a toner image on an image bearing body based on an image signal, and a density detection part for detecting a density of the toner image on the image bearing body, such that it is determined whether a normal image formed by the image forming part has a density detection area which should be detected, and if it is determined that the density detection area is present, image forming conditions are controlled based on a detection result of the density detection area.

Abstract: Xerographic photoreceptor life is improved while maintaining output print quality by adjusting the AC charging actuator of a xerographic machine to a point at which photoconductor life is optimized while maintaining output print quality. Where the actuator is voltage, the actuator is set a predetermined amount above the knee voltage of the photoreceptor surface potential versus peak-to-peak voltage curve, which is determined during operation of the machine. Instead of determining the knee voltage, calibration sheets can be generated for various values of the actuator, the best sheet with the least possible actuator value is selected, and the AC charging actuator is set to the value corresponding to the best sheet. The sheets can be evaluated by a user, or an optical array sensor can be used to scan the sheets so that the controller can compare the sheets to stored criteria to automatically select the best sheet and set the actuator.

Abstract: An image forming apparatus includes a rotatable photosensitive member; a charging member for electrically charging the photosensitive member; applying means for applying to the charging member a charging bias in the form of a DC voltage biased with an AC voltage; toner image forming means for forming a toner image on the photosensitive member charged by the charging member; setting means for setting a frequency of a first charging bias at a first frequency in a first mode in which the photosensitive member is rotated at a first speed to effect image formation and for setting a frequency of a second charging bias at a second frequency, different from the first frequency, in a second mode in which the photosensitive member is rotated at a second speed lower than the first speed to effect image formation; detecting means for detecting a current passing between the charging member and the photosensitive member during application of a test bias to the charging member; and adjusting means for adjusting the second c

Abstract: An image forming apparatus includes a rotatable image bearing member on which an electrostatic latent image is formed; a charging member for being supplied with a charging voltage which is a DC voltage not having an AC voltage component and for contacting the bearing member to electrically charge a surface of the bearing member using an electric discharge; a transfer member for transferring onto a transfer material a toner image formed on the surface of the bearing member by developing the electrostatic latent image, at a transfer position; wherein the charging potential of the charging member is different between when the charging member provides a first region with a potential and when the charging member provides a second region with a potential, thus providing a predetermined potential difference between the first region and the second region, and wherein the transfer member is not supplied with a voltage when the second region is at the transfer position, where the first region is a region on the image b

Abstract: In an image forming apparatus in which a DC bias is applied to charge a photosensitive drum, when a charge eliminating device is in deterioration or failure, there are some cases where a proper charging is not made, and thus poor imaging occurs. A DC bias is applied to a charging member in the charge eliminating operation area of an image bearing member where the charge eliminating device makes charge eliminating operation; and based on the values of an electric current passing through the image bearing member on that occasion, a DC bias application is switched between by constant-current-control and by constant-voltage-control.

Abstract: An image forming method and apparatus is disclosed. The method may include charging a rotating latent image bearing member with a rotating charger selected from at least one of contact chargers and short range chargers; irradiating the rotating latent image bearing member with imagewise light to form an electrostatic latent image on the latent image bearing member; developing the electrostatic latent image with a developer including a toner having a charge to form a toner image on the latent image bearing member; transferring the toner image onto a receiving material; and forming an electric field between the charger and the latent image bearing member after the toner image transferring such that charged materials present on the surface of the charger fly toward the latent image bearing member.

Abstract: When image forming is performed by a photosensitive drum according to operating conditions corresponding to an image forming mode selected out of a predetermined plurality of candidates, an actual cumulative number of printed sheets Pi is corrected and recorded based on the image forming mode (monochrome mode or color mode; low-temperature and low humidity ambience mode or other ambience mode) selected at the time of each image forming (S7) and an adjustment volume (ko×Pia) of a charging applied voltage Ey is calculated and the charging applied voltage Ey is set based on a corrected cumulative number of printed sheets Pia (S5). As a result, the charging applied voltage Ey to a charging unit is changed according to a cumulative number of printed sheets and at the same time, a pace of change thereof is adjusted based on the image forming mode.

Abstract: In an image forming apparatus in which a DC bias is applied to charge a photosensitive drum, when a charge eliminating device is in deterioration or failure, there are some cases where a proper charging is not made, and thus poor imaging occurs. A DC bias is applied to a charging member in the charge eliminating operation area of an image bearing member where the charge eliminating device makes charge eliminating operation; and based on the values of an electric current passing through the image bearing member on that occasion, a DC bias application is switched between by constant-current-control and by constant-voltage-control.

Abstract: A system for adjusting selected operating parameters of an image forming device to improve color registration based on selected environmental conditions includes a first image forming station to print a first registration mark on a substrate, a second image forming station to at least partially erase the first registration mark to form a registration pattern in a reverse transfer process of the color registration, and a control mechanism to adjust voltage biases of charge and developer rolls of the second image forming station based on wet-bulb temperature values determined from measured dry-bulb temperature and relative humidity values and stored in a lookup table so as to maintain a predetermined potential difference between charged and uncharged areas of a PC drum of the second image forming station that avoids Paschen breakdown and the development of toner at charged areas of the PC drum during the reverse transfer process of the color registration.

Abstract: An image forming device includes plural electrostatic latent image holding bodies that hold, on surfaces thereof, electrostatic latent images to be developed with developers of multiple colors, respectively, plural electrification control units that face the electrostatic latent image holding bodies and charge or discharge the surfaces of the electrostatic latent image holding bodies, respectively, a current controller that controls electric currents, each of which is supplied between the electrostatic latent image holding body and the electrification control unit for a corresponding one of the multiple colors, to be a constant target current, a maximum voltage output unit that outputs a maximum voltage among voltages each of which is applied between the electrostatic latent image holding body and the electrification control unit for a corresponding one of the multiple colors, and a detector that detects malfunction of the electrification control units when the maximum voltage exceeds a predetermined value.

Abstract: An image formation device for forming an image on a print medium by an electrophotographic process comprises a photosensitive body on which a developer image to be transferred to the print medium is formed by the electrophotographic process including charging of the photosensitive body, a charging unit which includes a charging wire and a grid and thereby electrically charges the photosensitive body, a charging power unit which applies wire potential to the charging wire, a wire potential measuring unit which measures the wire potential, and a charging control unit which controls the amount of electric charge supplied from the charging unit to the photosensitive body by controlling the wire potential based on the wire potential measured by the wire potential measurement unit. The charging control unit includes a control range restricting unit which restricts a control range of the wire potential within a prescribed electric potential.

Abstract: A system for adjusting a selected operating parameter of an image forming device to control white vector based on selected environmental conditions includes an image forming station having a photoconductive surface with a latent image formed by discharged areas leaving non-discharged areas different from the discharged areas, a sensor mechanism for measuring selected environmental conditions of dry-bulb temperature and relative humidity, a control mechanism for reading the sensor mechanism to adjust the voltage bias of a charging unit by an offset applied to the charging unit based on a wet-bulb temperature value so as to minimize white vector without enabling onset of development of toner background on non-discharged areas, and a memory connected to and accessible by the control mechanism and storing a lookup table of a list of wet-bulb temperature values related to measured dry-bulb temperature and relative humidity values and correlated to a list of voltage bias offsets.

Abstract: A method and system for a color xerographic machine determines a lower bound for the ROS power levels so that color defects are not produced by light attenuation from one or more layers of toner particles on a latent image. The method computes a minimum ROS power level for the photoreceptor at its maximum and minimum charge levels. The minimum ROS power level is the level at which the discharge voltage does not drop beyond a maximum discharge voltage difference. The difference is related to a toner particle density that affects color reproduction. The minimum ROS power levels for the minimum and maximum photoreceptor charge levels are used to compute a functional relationship for minimum ROS power levels at other photoreceptor charge levels. Thereafter, the minimum ROS power level function may be used to compute minimum ROS power levels for other photoreceptor charge levels. The computed minimum ROS power levels may be used to control the power levels used during color reproduction performed by the machine.

Abstract: An image forming device. A direct voltage power supply is independently provided for each charging device for each color, and an alternating voltage power supply is commonly provided to the charging device for each color. A current detecting section detects current which flows between each image carrying body and each charging device. A control device judges that the image carrying body is damaged when a detected current value is not less than a preliminarily set specified value when a direct voltage is sequentially independently applied to the charging device for each color when leakage of charging voltage is generated.

Abstract: An image forming apparatus includes an image bearing member; a charging member for electrically charging the image bearing member through electric discharge by applying, to the charging member, a DC voltage biased with an AC voltage; and voltage condition determination means for determining a voltage condition during image formation on the basis of each of the values of AC currents obtained by applying a plurality of DC voltages biased with the AC voltages to said charging member.

Abstract: An image forming apparatus includes an image forming unit having image forming elements and a fixing unit. The image forming elements includes an image carrier, a charging unit, a developer carrier, and a developer supplier. The image forming apparatus further includes a post unoperated period image formation preparation processor operable to, when the unoperated period, which is a time period from an end of an image forming operation to a start of a subsequent image forming operation is equal to or greater than a threshold, perform an idling operation to rotate the image carrier while applying a post unoperated period image formation preparation voltage, which is different from a normal image formation voltage, to a given one or more of the image forming elements.

Abstract: A charging voltage control method of an image forming apparatus and an image forming apparatus thereof. The charging voltage control method of the image forming apparatus includes: applying a charging voltage amount determined by referring to a basic lookup table which determines the charging voltage based on a system load; and correcting the applied charging voltage by using a first correction value which is determined based on a first correction lookup table which determines the first correction value based on a difference between a target current corresponding to the lifespan of the charging roller and a charging current.

Abstract: An image forming apparatus includes an image bearing member and a charging roller rotatable in contact therewith. Before driving of the image bearing member starts, a bias having the same polarity as that of an image forming bias is applied between the charging roller and the image bearing member. The time of application of the bias varies with the accumulated time of rotation of the image bearing member or the time of making the driving of the image bearing member inactive.

Abstract: An image forming apparatus and an image forming method, which are capable of forming images at stable image quality by executing adjustment of operating conditions at appropriate timings, are provided. When a Vsync count corresponding to an integrated value of a rotation count of an intermediate transfer belt reaches a predetermined value V1 or V2, a charging current Iw is increased by one level and an adjusting operation of a developing bias is executed (at a time t4 or t5), to thereby stabilize an image density. Further, when remaining service life of a developer reaches a predetermined value (50%) (at a time t6), if the Vsync count at that moment suggests that the time to change the charging current Iw is drawing near, the change thereof is executed ahead of the schedule, whereby the adjusting operation of the developing bias, which should otherwise be executed at the time t7, is omitted.

Abstract: An image forming apparatus performs a control sequence in which an AC voltage having a peak-to-peak voltage is applied to a charging member so that a relationship between an absolute value of a surface potential of an image bearing member at a portion under a transfer residual toner remaining on the image bearing member which has been electrically charged by the charging member during non-image formation and an absolute value of a surface potential of a developer carrying member is reversed with respect to a relationship between these absolute values during image formation.

Abstract: An image forming method includes supplying a protective agent to an image carrier, and charging the image carrier by a plurality of charging units, wherein degrees of discharge deterioration of the surface of the image carrier in the plurality of charging units are different, and wherein, in the amounts of protective agent supplied to charging portions of the plurality of charging units, the amount of protective agent supplied to a charging portion, in which a degree of discharge deterioration of the surface of the image carrier is high, is large.

Abstract: A charging apparatus includes a charging device for electrically charging a photosensitive member; a bias applying device for applying to the charging member a charging bias voltage comprising a DC voltage component and a AC voltage component, wherein the bias applying device effect a constant voltage control with a constant AC component of the charging bias voltage; a AC detector for detecting a AC detected current when the charging member is supplied with a test bias voltage; a DC detector for detecting a DC detected current when the charging member is supplied with the test bias voltage; and a controller for controlling a charging bias voltage to be applied to the charging member; wherein the control means determines a peak-to-peak voltage Vo when a change rate of detected DC current provided by sequentially applying the test bias voltages having different peak-to-peak voltages in order of increasing or decreasing peak-to-peak voltage becomes not more than a predetermined level, and the control means sets

Abstract: The present invention is made to provide a pretransfer charging device, which allows (i) reduction of generation of discharge products such as ozone and nitroxide, (ii) excellent uniform charging, (iii) continuous stable charging for a long period of time, and (iv) restraint of distortion of a toner image. The pretransfer charging device includes (i) ion generation needles each provided face to face with an image carrier such as a photoconductor drum or an intermediating transfer belt, and (ii) a high-voltage power supply for applying a negative voltage to each of the ion generation needles. The voltage to be applied from the high-voltage power supply is not less than an ion production threshold voltage but is less than a corona discharge threshold voltage. With this, no corona discharge occurs but negative ions can be generated. This makes it possible to solve various problems caused due to the corona discharge.

Abstract: An image forming apparatus includes: a photoconductor; a charging unit configured to charge the photoconductor; an applying unit configured to produce a charging voltage; a current detecting unit configured to detect a charging current; an image forming unit configured to form an image on a recording medium; a conveying unit configured to convey the recording medium; and a control unit. The control unit is operable to: receive a current detecting signal; determine whether an abnormal discharge occurs during an image forming operation based on the current detecting signal; control the applying unit to reduce a value of the charging voltage if it is determined that the abnormal discharge occurs; determine whether the abnormal discharge stops by reducing the value of the charging voltage; and control the conveying unit to eject the recording medium during the image forming operation if it is determined that the abnormal discharge is stopped.

Abstract: An image forming apparatus charges the surface of a photosensitive member to a predetermined potential. A current detector detects a charging current when the charging bias is applied. A storage stores a target charging current value when the photosensitive member is charged to a required potential. A usage acquiring portion acquires information relating to usage of the charging roller. A bias corrector performs first and second corrections. The first correction compares a charging current value with a stored target charging current value and determines a new charging bias based on the comparison. The second correction determines whether usage of the charging roller is a predetermined first amount or a greater amount based on acquired usage information, and when the usage is the greater amount, changes the target charging current value in accordance with the usage amount and obtains a new charging bias based on the changed target charging current value.

Abstract: A bias corrector conducts a first bias correction calculation by performing first through third calculations. The first calculation compares a stored target charging current value to a first charging current value detected when a first charging bias was applied by a bias applying device. The second calculation is performed repeatedly to calculate a second charging bias based on the comparison result and then to compare the target charging current value to a second charging current value detected by the current detector when the second charging bias was applied by the bias applying device. The third charging bias is calculated based on the comparison result. A second bias correction calculation then is conducted to correct the charging bias obtained as a result of the first bias correction calculation based on photoconductor information detected by a photoconductor information detector.

Abstract: A charger includes: a charging brush which is rotatably provided and is brought into contact with an image carrier to charge the surface of the image carrier; a charging roller which is brought into contact with the image carrier at a portion on the downstream side relative to the charging brush in the rotational direction of the image carrier to charge the surface of the image carrier; and a controller which controls voltages applied to the charging brush and charging roller, wherein the controller controls voltages applied to the charging brush and charging roller such that one-fifth of the absolute value of a charging brush current flowing between the image carrier and charging brush is lower than the absolute value of a charging roller current flowing between the image carrier and charging roller.

Abstract: An image forming apparatus capable of suppressing occurrences of image defects and maintaining the image density constant while improving the development ability. The image forming apparatus includes a photosensitive drum on which an electrostatic latent image is carried, a developing sleeve on which developer is carried, an AC high-voltage drive circuit, an AC transformer, a DC high-voltage circuit, a p-p voltage detection circuit, and a CPU. The p-p voltage detection circuit converts a peak-to-peak voltage across a capacitor into a DC voltage which is taken out as a capacity detection signal. Based on the capacity detection signal output from the p-p voltage detection circuit, the CPU changes an image formation condition, e.g., a set value of a developing bias voltage.

Abstract: A charging device includes a charging member disposed so as to rotate in contact with a surface of an image carrier to charge the image carrier surface, a bias voltage applying unit that applies a bias voltage to the charging member, the bias voltage having an AC voltage superimposed on a DC voltage, a DC current detector that detects a DC current flowing between the image carrier and the charging member, a filter that extracts only a specific component from the DC current detected by the DC current detector, and a controller that controls at least one of an AC voltage and an AC current to be applied to the charging member in accordance with an amount of variation of the specific component extracted from the DC current by the filter.