Abstract: A charging apparatus includes plural charging devices including a first charging device and a second charging device, in which an absolute value of a current flowing from the second charging device to a member to be charged is 25% or less of an absolute value of a sum of currents respectively flowing from the plural charging devices to the member to be charged, thereby achieving uniform charging of the member to be charged.

Abstract: This invention provides an image forming apparatus where the useful life of the image carrier does not become significantly short. This system has a charging unit, a charge voltage loading unit, an exposure unit, a development unit, an image transfer unit and a control unit, wherein, when the transport interval of plural recording materials is shorter than a predetermined time the AC charge voltage applied to the image carrier during the transport interval is a first AC charge voltage, and when the transport interval is longer than the predetermined time the AC charge voltage applied to the image carrier during the transport interval being a second AC charge voltage, the control unit makes the current running in the charging unit when the second AC charge voltage is applied lower than the current running in the charging unit when the first AC charge voltage is applied.

Abstract: A charging apparatus includes a charging member, contactably provided to a member to be charged, for charging the member to be charged; a voltage application device for applying alternating voltages having different peak-to-peak voltages to the charging member; and a determination device for determining a peak-to-peak voltage to be applied to the charging member with respect to a second area of the member to be charged, on the basis of a peak-to-peak voltage corresponding to a minimum current which is not less than a predetermined current of alternating currents through the member to be charged when the alternating voltages having the different peak-to-peak voltages are applied to the charging member with respect to a first area of the member to be charged.

Abstract: An image forming system that can prevent the image carrier from wearing because of excessive discharge, even under property fluctuations in the charging unit and surrounding conditions, and can maintain stable, excellent image quality for a long time. The system lowers fluctuations in current detection by making the characteristic of the AC charge current detection circuit variable and switching the AC charge current detecting characteristics between the voltages lower than discharge threshold voltage and the voltages higher than that.

Abstract: A color image forming apparatus includes a controlling unit for controlling an exposure unit, developing devices, etc., so that an ordinary image of one color is formed within a period of time in which a carrier rotates once, and density detection pattern images of a plurality of colors are formed within the period of time in which the carrier rotates once.

Abstract: A charging apparatus has a movable image bearing member, a first charging member for charging the image bearing member, and a second charging member provided upstream of the first charging member with respect to the direction of movement of the image bearing member, the second charging member having an elastic rotary member rubbing against the image bearing member.

Abstract: An electrophotographic image forming apparatus having a photosensitive member 1, a charging roller 2 and a developing roller 31, and including an output variable power source 8 common to the charging and the developing rollers 2 and 31 for applying voltages to the charging and developing rollers 2 and 31, respectively, a power source output control portion 9, and a voltage changing device (Zener diode D1) interposed between the developing roller 31 and the power source 8, wherein, when the voltages applied to the charging and developing rollers 2 and 31 are raised to and lowered from voltages required for image formation, respectively, the control portion 9 controls an output of the power source 8 to perform the raising and lowering of the applied voltages for a predetermined time while keeping a potential difference for suppressing movement of developer onto the photosensitive member 1 between the voltages applied to the charging and developing rollers 2 and 31.

Abstract: A method of controlling a charging potential of an organic photoconductive cell (OPC) includes a first operation of applying two charging voltages Vc1 and Vc2 having respective duties D1 and D2 established in an engine controller unit (ECU) to a conductive roller via a high voltage power supply (HVPS) to charge the OPC, a second operation of measuring sensing voltages Vs1 and Vs2 through a sensing resistor Rs coupled to the conductive roller so that the ECU establishes a target charging current it and calculates a new charging voltage Vc3 and a new duty D3, a third operation of applying the new charging voltage Vc3 and the new duty D3 to the conductive roller via the HVPS to charge the OPC and measuring a charging current Ic3 of the conductive roller, and a fourth operation of comparing a difference between the charging current Ic3 of the conductive roller and the target charging current It with a tolerance value TOL to control the charging potential by using the target charging current when the difference is

Abstract: An image forming device includes an image forming unit that includes an image carrier which carries an electrostatic latent image, a developing unit which forms a developing nip by contacting with the image carrier and develops the latent image by using toner, a transfer unit which forms a transferring nip by contacting with the image carrier and transfers a toner image onto a recording paper, and a first driving unit which rotates the image carrier, the developing unit and the transfer unit. The image forming device also includes a laser scanner unit that includes a polygon mirror and a second driving unit which rotates the polygon mirror.

Abstract: An image forming apparatus includes a photoconductive drum, a charging roller to charge the photoconductive drum, a thermistor to detect an ambient temperature of the photoconductive drum. A ROM stores impedance characteristics data that is obtained in advance by experiments and that represent a relationship between the ambient temperature of the photoconductive drum and an impedance between the charging roller and the photoconductive drum. Current ambient temperature of the photoconductive drum detected, current impedance between the charging roller and the photoconductive drum is calculated from the current ambient temperature of the photoconductive drum and the impedance characteristics data, and a voltage applied to the charging roller is adjusted based on the current impedance.

Abstract: An image forming device is provided that is capable of easily preventing occurrence of stripe-like image noise that may be caused by intimate contact between a contact electrifying member and an image carrier even when an image forming operation is stopped for a while. In the image forming device having an electrifying roller in contact with a photoconductor, AC voltage is applied to the electrifying roller before the image carrier and the electrifying roller start rotating.

Abstract: An image forming apparatus includes a photosensitive member, a charger for electrically charging the photosensitive member at a charging position, an image forming system for forming an image on the photosensitive member charged by the charger, and an optical discharger for electrically discharging the photosensitive member. After a start of rotation of the photosensitive member, the optical discharger operates to discharge the photosensitive member and when a leading edge portion of a portion of the photosensitive member discharged by the optical discharger reaches the charging position the charger starts its charging operation.

Abstract: An image forming apparatus includes a rotating photoconductive drum, charging roller, exposing unit, developing unit, transfer roller, cleaning blade, and controller. The charging member charges the surface of the photoconductive drum. The exposing unit illuminates the surface charged by the charging roller to form an electrostatic latent image. The developing unit develops the electrostatic latent image into a toner image. The transfer roller transfers the toner image onto a recording medium. The cleaning blade removes residual toner that failed to be transferred onto the recording medium. Prior to the discharge of deteriorated toner in the developing unit, the charging member charges the photoconductive drum which in turn charges the transfer roller. The toner discharged from the developing unit remains on the photoconductive drum when an area on the photoconductive drum passes by the transfer roller as the photoconductive drum rotates.

Abstract: After an application of a first AC voltage for selecting a peak-to-peak voltage of a charging AC voltage for charging an image forming area of an image bearing member and before an application of a charging AC voltage, there is applied a second AC voltage having a peak-to-peak voltage larger than a peak-to-peak voltage of the first AC voltage.

Abstract: To provide an image forming apparatus improving discharging of a developer from charge providing member for providing charge to the developer remaining on an image bearing member to the image bearing member, the developer is charged from the charge providing member to the image bearing member. When a developer discharging region of the image bearing member is disposed at a charging position, charging member is applied with a voltage having a direct current component of an absolute value equal to or smaller than an absolute value of voltage applied to the charge providing member without an alternating current component.

Abstract: An electrophotographic printing method and apparatus in which a charge voltage is appropriately adjusted depending on the resolution selected for electrophotographic printing or the print mode are provided. The electrophotographic printing method and electrophotographic imaging apparatus provide for selecting a resolution for electrophotographic printing; charging an organic photoconductor (OPC) by applying to a charge roller an appropriate charge voltage depending on the selected resolution; forming an electrostatic latent image on the charged OPC by a laser scanning unit (LSU) and applying toner particles adhering to a developer roller to the electrostatic latent image to form a visible image; and transferring the visible image formed on the OPC to a sheet of print paper. By selecting the print resolution or print mode, the charge voltage can be adjusted depending on the print resolution or print mode, so that an image can be obtained with reduced image concentration variation.

Abstract: An AC voltage from a power generating circuit is applied to a charge roller. CPU controls the power generating circuit so as to flow a constant current according to a control value through a current path from the power generating circuit to the charge roller. CPU produces an information according to an peak value of the AC voltage applied to the charge roller. CPU produces an information according to the AC voltage applied to the charge roller when the AC voltage is in a predetermined phase.

Abstract: An image forming apparatus of an electrophotography system, in which 10<PS/|Hz1−Hz2| is satisfied where Hz1 indicates a frequency of charging bias, Hz2 indicates a frequency of developing bias, and PS indicates a peripheral speed of a photosensitive member, whereby preventing density unevenness in an image.

Abstract: An image forming apparatus includes an image bearing member; a rotatable charging member, forming a nip with the image bearing member, for electrically charging the image bearing member; developing structure for developing an electrostatic image formed on the image bearing member to form a toner image, the developing structure supplying electroconductive particles to the image bearing member, wherein the electroconductive particles are fed to the nip by the image bearing member; and transferring structure for transferring the toner image onto a recording material at a transfer position.

Abstract: An electrophotographic image-forming apparatus and a charging voltage control method therefor. The electrophotographic image-forming apparatus has a charging roller applying a predetermined voltage to a photosensitive medium, a developing roller for developing with a developing agent an electrostatic latent image formed on the photosensitive medium by a laser scanning unit, a transfer roller transferring onto a sheet of recording paper the image developed by the developing agent, and a high voltage power supply (HVPS) applying predefined voltages to the respective rollers.

Abstract: In an image forming apparatus employing a two-component developing system, there are provided printed-sheet number counting means; developing-device drive time integrating means for integrating time during which a developing device drives; and a toner replenishing motor drive time integrating means for integrating time during which a toner replenishing motor drives. Integrated drive time of the developing device and integrated drive time of the toner replenishing motor every fixed printed-sheet number, and the toner consuming quantity per drive time of the developing device is calculated from the extracted data. The toner charge quantity in a developer is predicted on the basis of the calculated data, and a developing bias voltage applied to the developing device is changed to thereby revise an image density.

Abstract: In an image forming apparatus employing a two-component developing system, there are provided print-sheet number counting means; developing-device drive time integrating means for integrating time during which a developing device drives; and a toner replenishing motor drive time integrated drive time integrating means for integrating time during which a toner replenishing motor drives. Integrated drive time of the developing device and integrated drive time of the motor toner replenishing motor every fixed printed-sheet number, and the toner consuming quantity per drive time of the developing device is calculated from the extracted data. The toner charge quantity in a developer is predicted on the basis of the calculated data, and a developing bias voltage applied to the developing device is changed to thereby revised an image density.

Abstract: A charging device includes a charging member for electrically charging a member to be charged which is adapted to form a nip with a member to be charged which has a surface layer having a volume resistivity of 1×109-1×1014 &OHgr;cm, said charging member having an elastic member and movable with a peripheral speed difference relative to the member to be charged; and electroconductive particles carried on said charging member to the nip, wherein a peripheral speed Vd (mm/sec) of said member to be charged, a peripheral speed Vc (mm/sec) of said charging member, a width N (mm) of the nip measured in a moving direction of said charging member, and a coverage ratio Rc of said electroconductive particles on said charging member, satisfy: N·Rc·|Vc−Vd|/Vd≧1.

Abstract: An image forming apparatus includes a charging unit for charging an image bearing member, an image forming unit for forming a toner image on the image bearing member that has been charged, and a cleaning unit for contacting the image bearing member to clean the surface of the image bearing member. In the apparatus, a ratio of a period wherein the image bearing member is moved without being charged to a period wherein the image bearing member is moved while being charged, is controlled to be a predetermined value or greater.

Abstract: An electrophotographic printer maintains a surface potential of a photosensitive drum at a constant value even when a photosensitive layer corresponding to a surface of the photosensitive drum wears down. The electrophotographic printer includes a charging power supply 3, a charging roller 1, a photosensitive drum 2, a discharge unit 11, a charging current detection unit 4, a transfer power supply 9, a transfer roller 8, a transfer current detection unit 14, an arithmetic and control unit 12, and a memory unit 13.

Abstract: During printing on a thick paper, a Scorotron charger disposed upstream of a developing roller in a drum rotational direction charges a photosensitive drum to about 1000 V. Then a transfer roller disposed downstream of the developing roller lowers the potential to about 80 V. The transfer bias is turned off at the end of printing at T1 and does not lower the surface potential after this. When the surface of the drum opposite the transfer roller reaches a position opposite the Scorotron charger at T2, a DC motor and a charging bias are turned off. The surface potential of the drum that passes opposite the developing roller remains at about 400 V and is higher than developing roller potential until the photosensitive drum comes to a complete stop after idling at T3. This prevents the developing agent from adhering to the photosensitive drum.

Abstract: A color image forming apparatus includes a plurality of image carriers for at least one color, a plurality of developing devices, each developing a toner image onto each image carrier, a plurality of charging devices, each charging the each image carrier, a first power source, connected to the developing devices in common, a second power source, connected to the charging devices in common, and a controller, changing a process control of at least one of the charging devices and the developing devices in accordance with a color image forming operation and a monochrome image forming operation.

Abstract: An image forming apparatus to which a process cartridge is detachably mountable,

Abstract: An image forming apparatus includes an image-forming unit having a charging section and a developing section that are rotated together with a photoconductor in an idling manner. The charging section and developing section receive voltages while rotating. The apparatus includes a toner sensor and a controller. The toner sensor outputs a detection signal indicating that the toner has been replenished in the image-forming unit. In accordance with the detection signal, the controller changes the voltages, a time length during which the photoconductor, charging section, and developing section are rotated, or speeds at which the photoconductor, charging section, and developing section are rotated. The time length is extended or speeds are increased when the image-forming unit has been replaced.

Abstract: A method for determining an altitude with a corona generating device having a grid and a coronode and a power supply for supply power to the grid and coronode, including: setting the grid at a predefined voltage with the power supply; applying a charge output voltage and a charged output current to the coronode with the power supply; monitoring the charged output voltage and the charge output current to the coronode from the power supply until a predefined charge output voltage is reached; correlating charged output current to an altitude when the predefined charge output voltage is reached.

Abstract: An apparatus for applying an electrical charge to a charge retentive surface, wherein a bias charge roll member is situated proximately to a surface to be charged such as, a photoreceptor. The bias contact roll member is supplied with an electrical bias including an oscillating voltage signal having, in one mode of operation, a clipped AC input voltage and in a second mode, an unclipped AC input voltage.

Abstract: A high image quality electrophotographic image forming apparatus is provided without increasing the size and cost, and reducing the life thereof. The potential difference (contrast potential) between a photoreceptor and a development roller for supplying toner to the photoreceptor by the use of a carrier is set to be smaller in the non-image area irrelevant to the printing operation, and set to be larger in the image area relevant to the printing operation. In this manner, the damage to the photoreceptor caused by the adhesion of the carrier is reduced in the non-image area irrelevant to the printing operation, and the fog is reduced in the image area relevant to the printing operation.

Abstract: An image forming apparatus which can prevent the electric discharge when the trailing edge of a recording material passes a transferring position, and yet can stabilize the surface potential of a photosensitive drum. A controller changes a transfer bias voltage Vt during the supply of paper to 0 V before the trailing edge of recording paper arrives at a transferring nip part, changes it to a transfer bias voltage V0 during the non-supply of paper after the trailing edge of the recording paper has passed the transferring nip part, and changes a charging bias voltage to a charging bias voltage smaller than a normal charging bias voltage when an area on the photosensitive drum to which 0 V has been applied passes a charging nip portion. The transfer bias voltage V0 during the non-supply of paper is smaller than the transfer bias voltage Vt during the supply of paper.

Abstract: In a printer with an electrically chargeable image drum, such as a laser or a LED printer, for imprinting a medium by transferring toner to the medium, including, arranged around the image drum, a charging unit, a writing unit and a toner unit, the toner unit is disposed at a predetermined angular distance from the charging unit and a sensor is disposed at essentially the same angular distance from the charging unit to determine the charge of the image unit at the toner location for adjusting the voltage of at least one of the charging unit and the toner unit depending on the charge voltage of the image drum as determined by the sensor.

Abstract: A high image quality electrophotographic image forming apparatus is provided without increasing the size and cost, and reducing the life thereof. The potential difference (contrast potential) between a photoreceptor and a development roller for supplying toner to the photoreceptor by the use of a carrier is set to be smaller in the non-image area irrelevant to the printing operation, and set to be larger in the image area relevant to the printing operation. In this manner, the damage to the photoreceptor caused by the adhesion of the carrier is reduced in the non-image area irrelevant to the printing operation, and the fog is reduced in the image area relevant to the printing operation.

Abstract: An electrophotographic print engine has a variable primary charger and toning bias which places the machine in abnormal reproduction modes in order to provide service and diagnostic information to troubleshoot subsystems involved in the electrophotographic process.

Abstract: A charger charges a body with a voltage in which an AC voltage is superimposed on a DC voltage. The charger and the body have a small gap therebetween. A sensor measures a humidity in the gap between the charger and the body. A magnitude of the AC voltage to be superimposed on the DC voltage is determined based on the humidity detected.

Abstract: A cartridge is provided in which an electrifying roller is driven in a counter direction to photosensitive member drum and which has a toner remaining amount detector and a memory, and the electrifying roller is driven by an electrifying roller drive motor. The electrifying roller optimum rotation speed stored in the memory in advance is accessed when the toner remaining amount reaches a predetermined value, and the electrifying roller rotation speed is changed in accordance with the electrifying roller optimum rotation speed. The accumulated distance by which the photosensitive member drum and the electrifying roller abrasively slide is written in the memory, and when the toner remaining amount reaches a predetermined value, the electrifying roller optimum rotation speed corresponding to the abrasive sliding distance is accessed. The electrifying roller rotation speed is changed in accordance with the electrifying roller optimum rotation speed.

Abstract: An image forming apparatus includes a photoconductive drum, a charging roller to charge the photoconductive drum, a thermistor to detect an ambient temperature of the photoconductive drum. A ROM stores impedance characteristics data that is obtained in advance by experiments and that represent a relationship between the ambient temperature of the photoconductive drum and an impedance between the charging roller and the photoconductive drum. Current ambient temperature of the photoconductive drum detected, current impedance between the charging roller and the photoconductive drum is calculated from the current ambient temperature of the photoconductive drum and the impedance characteristics data, and a voltage applied to the charging roller is adjusted based on the current impedance.

Abstract: An image forming apparatus includes an image bearing member, an electrifying member for electrifying the image bearing member; an image forming member for forming an image on the image bearing member electrified by the electrifying member; a conveying member for making a recording material, which has been conveyed from a recording material receiving portion held in waiting and waiting then conveying the image on the image bearing member to a transfer portion for transferring the image onto the recording material; and a control member controls a start timing of electrification by the electrifying member in accordance with a start timing of a conveyance of the recording material by the conveying member.

Abstract: A charging device includes a rotatable elastic charging roller, contactable to a member to be charged, for electrically charging the member to be charged. The charging device also includes a DC voltage source for applying a DC voltage to the charging roller. The voltage source is capable of controlling the width of a variation of the DC voltage, the variation being caused by passage of a deformed portion of the charging roller, resulting from contact between the member to be charged and the charging roller, by a charging region of the charging roller for the member to be charged, to be not more than 1%.

Abstract: A method of compensating for image quality controls a toner reproduction curve (TRC). The toner reproduction curve TRC &PHgr;(k) measured by a color toner density sensor is compared with a target TRC &PHgr;R to obtain a deviation &Dgr;&PHgr;. A variation &Dgr;VB of a developer bias VB is calculated from a Jacobian matrix (JB) of a measured developer bias VB to calculate a new developer bias VBN and determining a measured grid voltage VG as a new grid voltage VGN if the deviation (&Dgr;&PHgr;) is greater than a tolerance &Dgr;&PHgr;T. A backplating vector VBP is obtained from the grid voltage VGN and the developer bias VBN. The backplating vector VBP is compared with a critical value VT to set control parameters VGN and VBN and control the TRC &PHgr;. Thus, noise effects on the image quality are minimized to provide an output image closest to an input image quality so as to improve the image quality.

Abstract: An image forming system that can prevent the image carrier from wearing because of excessive discharge, even under property fluctuations in the charging unit and surrounding conditions, and can maintain stable, excellent image quality for a long time. The system lowers fluctuations in current detection by making the characteristic of the AC charge current detection circuit variable and switching the AC charge current detecting characteristics between the voltages lower than discharge threshold voltage and the voltages higher than that.

Abstract: Provided is an image forming apparatus including a unit for controlling each voltage value of peak-to-peak voltages of DC and AC voltages applied to a charging unit for charging an image bearing member, in which a residual charge eliminating unit conducts charge elimination on a surface of the image bearing member while at least the charging unit undergoes an application of the AC voltage including the peak-to-peak voltage that is, in the case of setting at Vth a discharge start voltage to the image bearing member when applying the DC voltage to the charging unit, twice or smaller than this discharge start voltage Vth.

Abstract: This invention provides an image forming apparatus where the useful life of the image carrier does not become significantly short. This system has a charging unit, a charge voltage loading unit, an exposure unit, a development unit, an image transfer unit and a control unit, wherein, when the transport interval of the plural recording materials is shorter than a predetermined time the AC charge voltage applied to the image carrier during the transport interval being a first AC charge voltage, and when the transport interval is longer than the predetermined time the ac charge voltage applied to the image carrier during the transport interval being a second AC charge voltage, the control unit makes the current running in the charging unit to which the second charge voltage is applied lower than the current running in the charging unit to which the first AC charge voltage is applied.

Abstract: A charging voltage controller of an image forming apparatus includes a charging roller charging a photoconductive drum with a predetermined charging voltage, a high voltage supply unit supplying the predetermined charging voltage to the charging roller, an electric current detecting unit detecting an electrical current flowing the charging roller, and a control unit supplying first and second test voltages of different degrees to the charging roller, determining a first reference voltage to be applied to the charging roller based on data from the electric]current detecting unit outputted in response to the first test voltage, calculating slope data based on the electrical current data detected from the electric current detecting unit in response to the first and second test voltages, and determining the charging voltage to be applied to the charging roller as a sum of the first reference voltage and a preset offset voltage that corresponds to the slope data.

Abstract: To provide an image forming apparatus improving discharging of a developer from charge providing means for providing charge to the developer remaining on an image bearing member to the image bearing member, the developer is charged from the charge providing means to the image bearing member. When a developer discharging region of the image bearing member is disposed at a charging position, charging means is applied with a voltage having a direct current component of an absolute value equal to or smaller than an absolute value of voltage applied to the charge providing means without an alternating current component.

Abstract: During the changeover of image resolution to 600 dpi and 1200 dpi, potential setting is controlled in conformity with the individual information of a process cartridge and the used amount of a photosensitive drum. The individual information is information regarding the manufacturing lots or the kinds of the process cartridge, a developer, the photosensitive drum, a charging roller for acting on the photosensitive drum, a developing apparatus, a cleaning apparatus, and a functional member of the charging roller.

Abstract: A charging device including: a first charger which charges a member to be charged, the first charger having conducting particles which come into contact with the member to be charged; a second charger which charges the member to be charged in a same polarity as charging polarity of the first charger on an upstream side of the first charger in a moving direction of the member to be charged; and a controller which controls application of a charging voltage to the first charger, in which the controller turns a charging voltage on or off in an area of the member to be charged which is not subjected to charging by the second charger.

Abstract: The image forming apparatus has charging device, developing device, transfer-charging device, and control device for controlling a charging bias applied to the charging device. In the image forming apparatus, the transferring material to which the developer image is transferred is separated from the photosensitive body by the transfer-charging device, and the control device reduces the charging bias such that a surface potential of the photosensitive body in the case where the developer image is formed on the transferring material having low rigidity is lower than the surface potential of the photosensitive body in the case where the developer image is formed on the transferring material having high rigidity.