Abstract: A developing device includes an image carrier, a developer carrier, a biasing unit disposed upstream of a developing area, and a controller configured to control the biasing unit, and a cleaning member disposed downstream of the developing area to remove the liquid developing agent remaining on the developer carrier. A latent image held on the image carrier may be developed with the liquid developing agent, including charged toner and a carrier liquid, at the developing area where the developer carrier faces the image carrier. The controller causes the biasing unit to apply a first bias voltage to the surface of the liquid developing agent held on the developer carrier during developing, or a second bias voltage thereto during cleaning.

Abstract: An image forming apparatus including: a developing device that develops an electrostatic latent image formed on an image bearing body into a visible image by using a charged developer, so as to form a developer image on the image bearing body; a developing-bias supplying device that supplies, to the developing device, a developing bias necessary for developing the electrostatic latent image into the visible image; a transfer device that transfers the developer image formed on the image bearing body onto a recording medium; a transfer-bias supplying device that supplies, to the transfer device, a transfer bias necessary for transferring the developer image onto the recording medium; and a controller that carries out at least one of (A) developing-bias-dependent transfer-bias control for controlling the transfer bias supplied by the transfer-bias supplying device to the transfer device, on the basis of the developing bias supplied by the developing-bias supplying device to the developing device, and (B) operati

Abstract: There is described an image forming apparatus, which prevents an occurrence of worm-shaped image irregularities even in the high-speed developing operation to form a high quality image. In the image forming apparatus, the contact developing employing a two components developer including toner and carrier is conducted in such a manner that the latent image bearing member and the developer bearing member move in directions being opposite relative to each other at a developing region where the latent image bearing member and the developer bearing member are opposed to each other. The frequency of the AC current component and a line velocity of the latent image bearing member fulfill a condition indicated as follow: vp/f?70condition 1 where vp (mm/sec) is the line velocity of the latent image bearing member and f (kHz) is the frequency of the AC current component.

Abstract: The invention provides an image forming apparatus and an image forming method, capable of providing an image with little deterioration, even in case the image contrast has to be adjusted not for the purpose of image adjustment, such as for reducing the toner consumption amount or for preventing the leak in the charging device.

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. The AC voltage applied to the charger in an adjustment of the AC voltage is not less than twice a charging start voltage Vth at which the image carrier starts to be charged.

Abstract: A development station in an electrostatographic imaging machine may be controlled to improve toner halftone dot development over a wide range of environmental conditions.

Abstract: An image forming apparatus includes an image bearing body and a developer bearing body. A transferring section transfers, onto a medium, a developer image formed on the image bearing body by development of the latent image. A voltage applying section alternately applies, to the developer bearing body, a first voltage for making the developer move from the developer bearing body toward the image bearing body in order to develop the latent image, and a second voltage for making the developer move from the image bearing body toward the developer bearing body. An image darkness adjusting section adjusts a darkness of the image to be formed on the medium by changing only the second voltage.

Abstract: An image forming apparatus including an image carrier configured to have a latent image formed thereon, a developer carrier configured to supply toner, and a conveying member configured to receive toner from the developer carrier and to convey the toner to the image carrier. The conveying member includes first and second electrodes disposed a predetermined distance from one another. A first voltage application unit is configured to apply a first voltage to the developer carrier. A second voltage application unit is configured to apply a second voltage to the conveying member such that a ratio of a potential difference between the conveying member and the developer carrier to a distance between the conveying member and the developer carrier is less than a ratio of the second voltage to the predetermined distance.

Abstract: An image forming apparatus includes: a plurality of development units having developing-agent carriers which are provided in correspondence to three or more developing agents, and developing electrostatic latent images on surfaces of image carriers to form developing-agent images on the image carriers; and a recovery unit that recovers the developing agent adhering to the developing-agent carrier during non-development operation. The recovery unit is provided for at least the development unit other than the development unit that transfers the developing-agent image first in sequence among the plurality of development units. When one of the plurality of development units performs development by the developing agent whose charge capability is higher than that of the developing agent of the development unit that transfers the developing-agent image later in sequence, the recovery unit starts recovery of the developing agent or performs recovery operation for improving recovery capability of the developing agent.

Abstract: An image forming apparatus is provided which can form an image without defective transfer even if a resistance value of a transfer device is so high that defective transfer tends to occur. Before starting operation of printing an image on a sheet, a transfer current is passed to a transfer roller so as to detect a voltage value V of a transfer voltage. When it is determined that the detected voltage value V does not exceed a reference voltage value Vr (resistance value of the transfer roller does not exceed a reference limiting value), an operation mode of the printing operation is set to a first printing mode. When it is determined that the detected voltage value V exceeds a reference voltage value Vr (resistance value of the transfer roller exceeds a reference limiting value), the operation mode of the printing operation is set to a second printing mode.

Abstract: An apparatus for and a method of controlling a high voltage in an image forming apparatus using the high voltage with a high alternating current voltage superimposed on a high direct current voltage. The apparatus includes: a high alternating current voltage output unit outputting the high alternating current voltage; a high direct current voltage output unit outputting the high direct current voltage; and a controlling unit controlling the high alternating current voltage output unit and the high direct current voltage output unit such that the high alternating current voltage is output before the high direct current voltage when the high voltage is required for printing.

Abstract: An amount of toner transfer on a reference pattern is calculated by using an optical detecting unit that detects both regular reflection light and diffuse reflection light from a detection target simultaneously, based on a relative ratio between a value obtained by subtracting a result of multiplying a “diffuse reflection output” by a “minimum value of a ratio between a regular reflection output and the diffuse reflection output” from the “regular reflection output” of the density detection reference pattern, and a value obtained by subtracting a result of multiplying the “diffuse reflection output” by a “minimum value of a ratio between the regular reflection output and the diffuse reflection output” from the “regular reflection output” in the background of a transfer belt or an intermediate transfer body.

Abstract: An image forming apparatus including a latent image bearing member; a developing device configured to develop a latent image on the image bearing member with a two-component developer; a development potential forming device configured to form a development potential; a toner replenishing device configured to supply the toner to the developing device; a toner concentration detecting device configured to detect and output the concentration of the toner in the developer; a toner concentration controlling device configured to compare the toner concentration output with a toner concentration target to control the toner concentration; an information detecting device configured to obtain information to determine the replacement amount of the toner in the developing device in a predetermined period of time; and a development potential correcting device configured to adjust the development potential on the basis of the information obtained by the information detecting device.

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 electrostatic latent image is formed by controlling the amount of light, the emission time, and the like, considering the spot diameters of a laser, without changing the charging bias, the developing bias, and the like so as to obtain a plurality of correlations between density patches and development contrasts faithfully representing the developing characteristics of an image forming apparatus in a short time.

Abstract: An image forming method includes measuring an electrical potential on a surface of a developer roller and adjusting a time varying component of a voltage applied to the developer roller using a measurement of the electrical potential.

Abstract: Provided is a method for adjusting a developing device including a magnetic roll (143) for holding a two-component developer (146) composed of a carrier and toner filled in a developing tank (142) in a brush state, and a developing roll (144) for developing an electrostatic latent image formed in an image carrier (110) by holding toner conveyed from the magnetic roll (143), having a bias voltage adjustment step for adjusting a conveyance amount of toner from the magnetic roll (143) to the developing roll (144) by an adjustment of bias voltages (Vdc3, Vdc4) applied to the magnetic roll (143) and the developing roll (144) respectively, and a mixing ratio adjustment step for adjusting a conveyance amount of the toner by an adjusting a mixing ratio of the two-component developer (146).

Abstract: A fixer configured to fix an image on an recording medium passing through a fixing nip includes a holder including an elastic layer, a fixing rotator including a heating layer, provided overlying the holder, and a pressurizer configured to pressurize the holder via the fixing rotator to form the fixing nip. A part of the pressurizer, which forms the fixing nip, has a length not less than a length of the heating layer in a width direction perpendicular to a conveyance direction of the recording medium.

Abstract: An oxidation catalyst unit for judging a life span of an oxidation catalyst and a wet-type electrophotographic image forming apparatus having the oxidation catalyst unit, and a method of judging the life span of the oxidation catalyst. The oxidation catalyst unit includes a duct unit, a fan motor, a heater, an oxidation catalyst filter, and a temperature sensing unit. The temperature sensing unit senses upper and lower atmospheric temperatures of the oxidation catalyst filter. A controller of the wet-type electrophotographic image forming apparatus having the oxidation catalyst unit then compares data on the upper and lower atmosphere temperatures sensed by the temperature sensing unit with input reference data to judge the life span of the oxidation catalyst.

Abstract: An image forming apparatus includes a developing contrast voltage controller to control a developing contrast voltage so as to obtain a desired image density, a transfer condition controller to control transfer conditions for transferring a toner image, an environment sensor to detect an environment, and a correcting coefficient setting unit to refer to a database for pre-registering correcting coefficients to correct the transfer conditions corresponding to the developing contrast voltage and environment and set the correcting coefficients on the basis of the developing contrast voltage controlled by the developing contrast voltage controller and the environment detected by the environment sensor.

Abstract: The residual potential and charging potential of the surface of a photosensitive drum 20, or the charging potential and exposure potential of the surface of the photosensitive drum 20 are detected by an exposure sensor 28. The lifetime of the photosensitive drum 20 is judged in accordance with the difference between the detected charging potential and residual potential, or the difference between the detected charging potential and exposure potential.

Abstract: A developing apparatus having: a first developer carrying member close to a developer regulating member for regulating an amount of developer; a second developer carrying member to which the developer is delivered from the first developer carrying member; and a mode for removing the toner on the surface of the second developer carrying member, in which mode, in a non-image-formation period, no toner transfer operation from the first developer carrying member to an image bearing member is substantially performed, but a toner transfer operation from the second developer carrying member to the image bearing member is performed.

Abstract: An image forming apparatus having an image bearing member on which an electrostatic image is formed, a first developer carrying member carrying a developer thereon, and a second developer carrying member disposed downstream of the first developer carrying member with respect to the direction of movement of the image bearing member, and designed such that one and the same electrostatic image on the image bearing member is developed with the developer carried on these developer carrying members, has a developer consumption mode in which during the other time than ordinary image formation, the developer borne on the first and second developer carrying members is shifted to the image bearing member, and during this developer consumption mode, control is effected so that the amount of developer consumed from the second developer carrying member to the image bearing member may be greater than the amount of developer consumed from the first developer carrying member to the image bearing member.

Abstract: An image forming method, includes a charging step of charging an image carrier; an image writing step of writing image data onto the image carrier; a developing step of developing a latent image area written by the image writing step on the image carrier; a transferring step of transferring a toner image developed by the developing step to a transferring member; an image writing position adjusting step of detecting a position of the image carrier where the image is written in a case where designated conditions are satisfied, and of adjusting an image writing position; and a voltage output control step of controlling voltages applied for charging, developing, and transferring in the charging step, the developing step, and the transferring step, respectively.

Abstract: An image forming apparatus that forms an image having proper density regardless of changes in a charged amount of developer per unit mass is provided. When image data is received in a laser printer, a main motor is driven to rotate a photosensitive drum, etc., and charging bias is applied to a charger to charge the photosensitive drum. Then, paper is fed. Predetermined current detection developing bias is applied to a developing roller for a predetermined period of time. A current value of a developing current during the application is detected. Developing bias applied to the developing roller is calculated so as to keep constant density in the printed image. Particularly, a charged amount of toner per unit mass (Q/M) is calculated from the detected current value. Based on the Q/M, the developing bias is calculated. A print process is performed by applying the developing bias to the developing roller.

Abstract: An image forming apparatus includes an image bearing member; a developer carrying member, disposed opposed to the image bearing member, for carrying a developer, wherein an electric field is formed between the developer carrying member and the image bearing member during a developing operation using the developer carrying member, and the electric field including an oscillating portion in which the electric field is an oscillating electric field, wherein a supply electric field of the oscillating electric field which is effective to supply the developer to the image bearing member from the developer carrying member is variably controllable in accordance with a peripheral speed of the image bearing member.

Abstract: An image forming apparatus includes a photosensitive member, a charging device, a developing device, a thickness detecting unit and a parameter setting unit. A photosensitive layer is formed on a surface of the photosensitive member. The charging device charges the photosensitive member. The developing device forms a toner image on the surface of the photosensitive member. The thickness detecting unit detects a thickness of the photosensitive layer on a basis of a value of a current supplied to the charging device. When the thickness detecting unit detects the thickness of the photosensitive layer, the parameter setting unit sets at least one of a charge parameter for the charging device and a development parameter to be different from that used in forming an image on a recording medium by transferring a toner image formed on the surface of the photosensitive member onto the recording medium.

Abstract: To correct a bias voltage of each roller upon estimating a toner potential precisely even where toner's characteristics change due to, e.g., changes of environmental condition, changes over time, supplements of the toner, replacement of an EP cartridge, or the like, on an image forming apparatus according to this invention, the toner potential is estimated upon measuring a DB current in a prescribed period from a time that a development starting point on the developing roller starts development to a time that the development starting point comes in contact with a toner supplying roller. Alternatively, where the measured DB current is equal to or less than a fixed amount, a period for a warming-up processing is extended. Alternatively, where the toner is judged as supplemented upon detection of the remaining toner amount, a prescribed warming-up processing is made before the measurement for the DB current.

Abstract: A developing device including a latent image supporter. Powder is adhered on the latent image supporter to develop a latent image on the latent image supporter and a transporting member is arranged opposite to the latent image supporter. A plurality of electrodes are formed in the transporting member for generating a traveling-wave electric field to move the powder, and n-phase voltages are applied to the electrodes of the transporting member to form an electric field in a first direction so that the powder moves towards the latent image supporter at an image portion of the latent image and in a second direction so that the powder moves in a direction opposite to the latent image supporter at a non-image portion of the latent image.

Abstract: An image forming apparatus includes an image bearing body which can bear an electrostatic image; a bias member to which a predetermined bias is applied from a bias applying device; and a surface potential detection device which detects a surface potential at the image bearing body. The surface potential detection device includes a detector portion which generates a signal corresponding to the surface potential at the image bearing body and a potential detection portion which detects the surface potential by the signal from the detector portion. In the image forming apparatus, the potential detection portion is also used for detection of a bias value which the bias applying device applies to the bias member, the bias applying device is controlled based on the detection result of the bias which the bias applying device applies, and the bias detection result is obtained by the potential detection unit.

Abstract: It is intended to provide a developing apparatus, an image forming apparatus and developing method capable of managing both decrease of load on apparatuses and improvement of image quality in case development of an image is made by applying contact developing and AC developing. For that intention, voltage at a portion between a development member and an image carrier is defined oscillating voltage, and in case negative polarity toner is used, relations of peak voltage V1 of oscillating voltage, background portion voltage VH (negative) and visible section voltage VL (negative, an absolute value of it is smaller than that of VH) are set as indicated below. ?500V?V1?VL??350V ?200V?V1?VH??50V On the above conditions, peak voltage V2 is set as indicated below. ?150V?VL?V2??70V V2?VH+500V.

Abstract: An image forming apparatus having: a transfer section which transfers a toner image onto an intermediate transfer body or a transfer material to form an image thereon; a selection section for selecting one mode among a plurality of modes including a first mode for forming the image by using a plurality of colors including a first color and a second mode for forming the image by using less number of colors including the first color than that of the colors in the first mode; and a control section for controlling the transfer section in order that a transfer rate of a toner image of the first color in the second mode is larger than that of a toner image of the first color in the first mode when toner images are transferred onto the intermediate transfer body or the transfer material by the transfer section.

Abstract: An image forming device includes a developer bearing member, a photosensitive member, a developing-bias applying portion, a pressing-force adjusting portion, and a density adjusting portion. The photosensitive member is disposed in contact with the developer bearing member. An electrostatic latent image is formed on the photosensitive member and developed by the developer supplied from the developer bearing member for forming a developer image. The developing-bias applying portion applies a developing bias to the developer bearing member. The pressing-force adjusting portion adjusts the pressing force between the developer bearing member and the photosensitive member.

Abstract: An image forming apparatus operates in such a way that when the conditions of toner changes due to changes in environmental conditions, changes with age, and replacement of an EP cartridge, the bias voltages for a charging roller, a developing roller, and a toner-supplying roller are set appropriately. An electrostatic latent image can be formed on a photoconductive body. The developing roller causes developer to adhere to the electrostatic latent image to develop the electrostatic latent image. The toner-supplying roller supplies the developer to the developing roller. The current measuring section measures a current flowing through at least one of the developing roller and the toner-supplying roller. An voltage-setting section sets at least one of the developing roller and the toner-supplying roller to a corresponding one of first voltages, the first voltages being set in timed relation with development of the electrostatic latent image.

Abstract: A developing device has a voltage application member which is in contact via a toner layer with a developing roller that rotates while holding the toner layer on its outer peripheral surface. A voltage that the voltage application member applies to the toner layer is switched between AC voltage and DC voltage based on humidity or drive cumulated time of the developing device.

Abstract: A developing apparatus includes a toner carrying member for carrying toner to a developing zone where the developing apparatus faces to an image bearing member; bias voltage applying means for applying to the toner carrying member a developing bias voltage for developing an electrostatic latent image formed on the image bearing member, wherein the developing bias voltage is in the form of a DC voltage biased with an AC voltage; wherein when a developing operation stops, rotation of the toner carrying member is stopped while rotating the image bearing member electrically charged, and then, the AC voltage is applied to the toner carrying member for a predetermined period, and thereafter, the AC voltage is stopped in a condition in which regular-charge toner is being urged from the toner carrying member toward the image bearing member.

Abstract: An image forming device having a developing unit for visualizing an electrostatic latent image formed on an image carrying body by utilizing a developing agent containing toners and carriers which transfers a toner image to a recording medium to obtain a record image. A patch sensor is provided for detecting the image density of the record image, and it controls toner density stabilization control and an adjustment value and bias voltage in the developing unit according to a value detected by the patch sensor and a value of current flowing in the image carrying body from the developing unit. Thereby, an image forming device is provided which performs stable image density control when a problem is caused during processing of a predetermined number of printing pages, even when a deterioration of the image due to an abnormal property change of a developing agent is caused.

Abstract: An electro-photographic image forming apparatus preventing toner from scattering during a printing operation and a control method of the same. The electro-photographic image forming apparatus includes a scattering preventive member being disposed downstream of the developing roller at a predetermined distance from the photosensitive medium, and a voltage being applied, and a controller controlling the voltage that is applied to the scattering preventive member so as to transport the toner attached on the scattering preventive member to the photosensitive medium.

Abstract: An image forming apparatus includes a plurality of developing devices each including a developer carrying member for carrying a developer to develop an electrostatic latent image formed on an image bearing member, and a developer regulating member for regulating the developer carried on the developer carrying member; a common voltage applying device for applying a common voltage to the plurality of the developer regulating member. When a first one of the developer carrying members is rotating, and when a second one of the developer carrying members is not rotating, a potential difference between a potential of the second developer carrying member and the common voltage is smaller than a potential difference between a potential of the first developer carrying member and the common voltage.

Abstract: A developing device having a developing gap detecting function includes a photosensitive medium, a developer conveyer, a DC power source, an AC power source, a current detecting unit and a controller. The current detecting unit detects a DC current flowing on the developer conveyer when toner from the developer conveyer is attached to a desired area of an electrostatic latent image on a photosensitive body by enhancing a voltage outputted from a power supply gradually at proper intervals. The controller obtains a developing gap between the photosensitive medium and the developer conveyer based on current values detected by the current detecting unit. In accordance with the developing device having the developing gap detecting function, the developing gap is sensed and developing voltage is easily and correctly calculated to control image forming conditions. As a result, an image quality improves.

Abstract: An image to be formed on paper (26) is held on the surface of photo-sensitive drum (1). This is a latent image of static electricity formed by an LED exposer (5). Then, the developing roller (7) puts toner on the surface of photo sensitive drum (1), so as to develop a toner image. Meanwhile, the toner conveying roller (9) supplies toner to the developing roller (7). In this occasion, the printer controller (17) calculates the image density of image data (18) with dot counter (13). And, it decides the first voltage impressed to developing roller (7) by developing bias source (8) as well as the second voltage impressed to toner conveying roller (9) by stretching bias source (10) according to the image density of original image.

Abstract: An image forming apparatus includes an image bearing member; a charging member for electrically charging the image bearing member; developing means for developing with a developer an electrostatic latent image formed on the image bearing member, the developing means having a developer carrying member for carrying the developer, wherein a gap is formed between the developer carrying member and the image bearing member; bias voltage applying means for applying a bias voltage to the developer carrying member, wherein the bias applying means applies an AC bias when the electrostatic latent image is developed, wherein the developing means is capable of collecting the developer fro the image bearing member, and an amplitude of an AC bias voltage applied to the developer carrying member by the bias applying means when the the developer is collected, is larger than that when the the electrostatic latent image is developed.

Abstract: A developing device including a latent image supporter. Powder is adhered on the latent image supporter to develop a latent image on the latent image supporter and a transporting member is arranged opposite to the latent image supporter. A plurality of electrodes are formed in the transporting member for generating a traveling-wave electric field to move the powder, and n-phase voltages are applied to the electrodes of the transporting member to form an electric field in a first direction so that the powder moves towards the latent image supporter at an image portion of the latent image and in a second direction so that the powder moves in a direction opposite to the latent image supporter at a non-image portion of the latent image.

Abstract: A printing device can determine a toner development control parameter. The printing device can receive a print job that describes an image to be printed. The printing device can determine if a band of image lines in the image satisfies pre-determined criteria. The printing device can determine a development control parameter value based, at least in part, on whether the band is determined to satisfy the pre-determined criteria.

Abstract: An image forming apparatus includes an image bearing member having a surface layer; an electrostatic image forming device for forming an electrostatic image on the surface layer; a developing device, containing at least toner and a carrier, for developing the electrostatic image; a density measuring device for measuring a density of the developed electrostatic image; a layer thickness measuring device for measuring a thickness of the surface layer; and an adjusting device for adjusting toner content in the developing device. The adjusting device adjusts the toner content on the basis of an output of the layer thickness measuring device.

Abstract: An apparatus for developing a latent image recorded on a movable imaging surface, including: a reservoir for storing a supply of developer material including toner particles, said reservoir including a transport member; a donor member being arranged to receive toner particles from said transport member and to deliver toner particles to the image surface at locations spaced apart from each other in the direction of movement of the imaging surface thereby to develop the latent image thereon; a power supply, connected to said donor member, for biasing said donor member to deliver toner to the image surface during a printing mode of operation; a second power supply, connected to the transport member, for maintaining a predefined voltage difference between the transport member and the donor member such that toner particles are attracted to the donor member from the transport member during a printing mode of operation; a controller for generating a donor member purge signal trigger based on sensed or calculated dev

Abstract: An image forming apparatus includes a plurality of developing devices, each of which includes a developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with a developer, and a developer regulating member for regulating the developer carried on the developer carrying member; a common voltage applying device for applying voltages to the developer regulating members, wherein the voltages are applied to the developer carrying members are variable independently from each other, and when at least one of the voltages varies, the voltage applied by the voltage applying device is capable of being changed.

Abstract: A developing device used with an electrophotographic image forming apparatus and developing method thereof includes a power supplying unit which applies a first electric field to a toner transfer body and a supplying member so that the toner is supplied to the toner transfer body when a development operation is performed, and applies a second electric field to the toner transfer body and the supplying member so that the toner is removed from the toner transfer body when the development operation is not performed, by varying a developing bias and a supplying bias.

Abstract: A method of forming an image includes the steps of providing a development bias having a DC component and an AC component superposed on one another and applying the development bias to a developer carrying member. The AC component is provided by superposing a waveform at a second frequency on a waveform at a first frequency in synchronism with each other. The second frequency is an odd multiple of the first frequency.

Abstract: An image forming device includes an image forming unit that includes a photoconductive drum which carries an electrostatic latent image, a developing roller which forms a developing nip by contacting the photoconductive drum and develops the latent image by using toner, and a transfer roller that forms a transferring nip by contacting the photoconductive drum and transfers a toner image onto a recording paper. A transferring voltage impressing circuit impresses to the transfer roller, a voltage of an opposite polarity to a polarity of a transfer process, for a prescribed period of time during a period when the recording paper is absent in the transferring nip. A developing voltage impressing circuit impresses to the developing roller, a voltage of a same polarity as a developing process and lower than the developing process when a field impressed with the voltage of the opposite polarity by the transferring voltage impressing circuit passes the developing nip.