Abstract: An image forming apparatus forms an image on a recording medium and includes a rotatable image bearing member, and a rotatable developer carrying member that carries a developer, forms a developing portion by contacting the image bearing member, and forms a developer image on a surface of the image bearing member by supplying the developer to an electrostatic latent image formed on the surface of the image bearing member in the developing portion. After performing an image forming operation, a controller controls driving of the image bearing member and the developer carrying member to perform a rotation operation for rotating the image bearing member with rotation of the developer carrying member stopped in a state where an amount of carried developer in the developing portion during the rotation operation is smaller than the amount of carried developer in the developing portion during the image forming operation.

Abstract: An image forming apparatus includes an image bearer, a power source to generate a voltage, a voltage applying device facing the image bearer, the voltage applying device being applied with the voltage, and circuitry to control the voltage of the power source. The circuitry switches the voltage between a first direct current (DC) bias and a second DC bias different from the first DC bias, and changes the first DC bias in accordance with a speed of the image bearer, based on a DC component of a current flowing between the power source and the image bearer during application of the second DC bias.

Abstract: An image forming apparatus includes a transport unit, a transfer unit and a support unit. The transport unit transports a recording medium. The transfer unit transfers an image formed with particles onto an image formation surface of the recording medium transported by the transport unit by an electric field formed between the transfer unit and the image formation surface by making contact with the image formation surface. The support unit supports the recording medium, is transported to the transfer unit together with the recording medium by the transport unit, and is not directly conductive with the transfer unit.

Abstract: An image forming apparatus includes an image forming portion, a transfer portion, a power source, a reading portion, and a controller. The controller executes an output operation so that first test images do not overlap with second test images, respectively, on a first side and a second side of a recording material. On the basis of information on a second test voltage for transfer of the second test image, of the plurality of second test images, of which information on a density read by the reading portion coincides with a preset condition, the controller sets a transfer voltage for image transfer onto the second side in double side image formation so that an absolute value of the transfer voltage set for the image transfer onto the second side in double side image formation is greater than an absolute value of the second test voltage that coincides with the preset condition.

Abstract: An image forming apparatus includes an image bearing member, a transfer member, a moving portion, a driving portion, a voltage applying portion, a first detecting portion, and a second detecting portion. On the basis of a detection result of the first detecting portion when a first test voltage is applied to the transfer member by the voltage applying portion, the second detecting portion sets a second test voltage. The second detecting portion detects a position of the transfer member on the basis of a detection result of a current value by the first detecting portion acquired when the second test voltage is applied to the transfer member by the voltage applying portion.

Abstract: A recording-medium transport device includes: a rotating first and second member, the first and second member forming a nip area therebetween and transporting a recording medium while nipping; a gripping member that grips the recording medium; a separating member that separates the recording medium passing through the nip area from the first or second member; and a control mechanism that controls contact and separation between the first and second member and opening and closing the gripping member where, in a first section, the gripping member passes between the first and second member, the first and second member are separated, and the gripping member is opened to release the recording medium until the first and second member come into contact with each other and, in a second section subsequent to the first section and before the recording medium reaches the separating member, the gripping member opens wider than the first section.

Abstract: A power supply includes a first control circuit configured to control an output voltage of the power supply, a second control circuit configured to control an output current of the power supply, a switching circuit configured to switch control of the power supply from the first control circuit to the second control circuit based on the output current of the power supply while the first control circuit controls the output voltage of the power supply, and a power supply control circuit configured to output status information indicating a failure of the power supply acquired based on the output voltage of the power supply while the second control circuit controls the output current of the power supply.

Abstract: An image forming apparatus includes an image bearing member, a transfer member, a voltage source, a current detecting portion, a controller, and a receiving portion. During the recording material passing through the transfer portion, the controller controls a voltage applied to a transfer member on the basis of a detection result of the current detecting portion so that a current flowing through the transfer member falls within a predetermined range. The controller sets at least one of an upper limit and a lower limit of the predetermined range on the basis of a predetermined voltage changing instruction received by the receiving portion.

Abstract: An image forming apparatus includes an image bearing member, a transfer roller, an electric energy supply member, a voltage source, a detector, and a controller for adjusting a transfer voltage. A circumferential length 2K of the transfer roller and a distance k measured along an outer periphery of the transfer roller from the electric energy supplying member to the transfer roller satisfy 0.8K?k?1.2K. The controller controls the voltage source so as to satisfy 0.7T?t?1.3T, where 2T is time required for one full rotation of the transfer roller, and t is time during which the voltage source supplies the test current or the test voltage per one level in the operation of a setting mode.

Abstract: An image forming apparatus including an image bearer; a nip forming member, a nip width changing device, a power source; and a controller. The controller switches between a first mode and a second mode according to a predetermined condition. In the first mode, a duty of the transfer bias is a first duty and a width of a transfer nip is a first width. In the second mode, the duty of the transfer bias is a second duty lower than the first duty and the width of the transfer nip is a second width greater than the first width. The duty is (T?Tt)/T×100% where T denotes one cycle of the transfer bias, and Tt denotes a time period, in which the transfer bias is on a transfer-directional side relative to a time-averaged value of the transfer bias, in the one cycle.

Abstract: Certain embodiments provide a transfer apparatus, which including: an conductive intermediate transfer member; a transfer section configured to secondarily transfer a toner image onto an image receiving medium in a constant current system; a conveyance section configured to convey the image receiving medium; and a high voltage transformer configured to apply a bias to the transfer member, wherein the sum of the products of the volume resistivities [?·cm] and the thicknesses [cm] of the intermediate transfer member and the transfer member is equal to or greater than 3.6×108 ?·cm2, and the conveyance speed V[mm/s] of the image receiving medium={the output upper limit value A[V] of the absolute value of the voltage output from the transfer polarity side of the high voltage transformer}×0.009.

Abstract: An image forming apparatus includes a movable endless belt, an image forming unit, a plurality of rollers including a first roller and a second roller, and an urging member. The urging member is provided on an inner peripheral surface side at a position which is adjacent to and upstream of the first roller and which is downstream of the second roller with respect to a movement direction of the belt. The urging member is supported at an upstream end portion thereof with respect to the movement direction of the belt and includes a first urging portion and a second urging portion at two different positions with respect to the movement direction of the belt. The first urging portion and the second urging portion urge the belt along a widthwise direction crossing the movement direction of the belt.

Abstract: Provided is a belt driving roller for a belt driving device configured to drive and rotate an endless belt with at least one driving roller of a plurality of rollers over which the belt is hung by its internal surface, wherein the belt driving roller includes an electroviscosity retaining member of which surface viscosity force reversibly changes under an effect of an electric field.

Abstract: An image forming apparatus according to the present invention includes: an opposite roller switching mechanism which switches an opposite roller forming a transfer nip to a second opposite roller of which the outer diameter is different from the outer diameter of a first opposite roller; a paper type information acquirer which acquires the type information of a recording medium used; and a controller which controls the opposite roller switching mechanism based on the type information acquired from the paper type information acquirer.

Abstract: An image forming apparatus includes an image bearer; a charger to charge a surface of the image bear; a developing device to develop a toner image on the surface of the image bearer; an image bearer cleaner to remove residual toner remaining on the surface of the image bearer after a transfer process; and a controller to cause the image forming apparatus to perform, before a start of printing operation, a corona products removal mode. In the image forming apparatus further including a temperature and humidity sensor to measure temperature and humidity of an ambient environment of the image bearer, the controller to cause the image forming apparatus to perform, before a start of an image forming operation, a corona products removal mode based on an absolute humidity obtained by the temperature and humidity detected by the temperature and humidity sensor.

Abstract: The present invention relates to an image forming apparatus that forms an image by consecutively superposing toner images that have been formed on a plurality of photosensitive drums, on an intermediate transfer member or a transfer medium. The image forming apparatus is made compact and operates at a low cost. Since a current supply member supplies a current in a rotational direction of an intermediate transfer belt, multiple first transfer portions do not need corresponding voltage sources. Even in the case where a charging member supplies a current, the potential of the intermediate transfer belt is maintained at a predetermined potential by a constant-voltage element connected to support rollers.

Abstract: An image forming apparatus includes an image bearer to bear a toner image on a surface thereof, a transfer device to contact the image bearer to form a transfer nip, and a power source to output a voltage to transfer the toner image from the image bearer onto a recording medium interposed at the transfer nip. The voltage including a first voltage in a transfer direction in which the toner image is transferred from the image bearer to the recording medium and a second voltage having a polarity opposite that of the first voltage. The first voltage and the second voltage alternate upon transfer of the toner image from the image bearer to the recording medium. The power source is configured to output the voltage that is superimposed a plurality of the alternating current voltage having a basic waveform, and a waveform of the voltage is biased in the transferring direction.

Abstract: An image forming apparatus includes an image forming unit, an image carrier carrying on a surface thereof a developer image formed by the image forming unit, a transfer unit for transferring the developer image carried on the image carrier to a recording medium, a voltage supplying unit for supplying a transfer voltage to the transfer unit, a transfer current measuring unit for measuring a transfer current value at a time that a prescribed voltage is applied from the voltage supplying unit to the transfer unit in a state that no recording medium exists in the transfer unit, a resistor serially coupled between the transfer current measuring unit and the transfer unit, a memory unit for memorizing electrical character information of the recording medium, and a controller for controlling the transfer voltage supplied from the voltage supplying unit to the transfer unit where the developer is transferred to the recording medium, based on a consequence measured by the transfer current measuring unit, a recording m

Abstract: A transfer device includes a direct-current (DC) power supply configured to output a DC voltage; an alternating-current (AC) power supply configured to selectively output a superimposed voltage in which an AC voltage is superimposed on the DC voltage output from the DC power supply or the DC voltage output from the DC power supply; and a transfer unit configured to transfer a developer to a sheet using the voltage output from the AC power supply.

Abstract: A transfer device comprising: a load including a transferring unit, the transferring unit being configured to transfer an image on a transferable material; a direct current source connected to the load and configured to apply a direct voltage to the load; and an alternating current source connected between the load and the direct current source in attachable and detachable manner, the alternating current source being configured to selectively apply to the load an overlapping voltage that is formed by overlapping an alternating voltage and the direct voltage.

Abstract: A Zener diode contacts an inner periphery surface of an intermediate transfer belt, and an opposing roller which opposes a detecting member is electrically insulated, in a configuration where transfer is performed at multiple photosensitive drums while an electrical current is applied in a peripheral direction of the intermediate transfer belt.

Abstract: An image forming apparatus including an image forming device, a transfer device, a fixing device, an inverting device, and a processor. The transfer device includes an intermediate transfer member, a nip forming member, and an electric potential difference generator to generate an electric potential difference between the intermediate transfer member and the nip forming member. The processor causes the electric potential difference generator to generate a first electric potential difference containing only a DC component when a toner image is transferred onto a first side of a recording sheet, and to generate a second electric potential difference containing a DC component and a superimposed AC component when the toner image is transferred onto a second side of the recording sheet. The second electric potential difference has an averaged absolute value per unit of time smaller than an absolute value of the first electric potential difference.

Abstract: A transfer device includes a transfer roller that has a characteristic in which an electrical resistance is changed in accordance with a rotation speed, contacts a transferred body that moves in synchronization with movement of an image holding body holding a toner image, and transfers the toner image held by the image holding body on the transferred body by applying a transfer voltage to the transferred body; and a regulator that regulates the rotation speed of the transfer roller independently from the movement of the image holding body and the transferred body.

Abstract: A transfer device includes a first-transfer power supply that includes a direct-current power supply and an alternating-current power supply, and a first-transfer member that transfers a toner image formed on an outer peripheral surface of an image carrier to a receiving member from which the toner image is transferred to a medium. The first-transfer member transfers the toner image by receiving a voltage from the first-transfer power supply.

Abstract: A transfer device includes a transfer portion that transfers a toner image formed with a toner containing flat pigment particles to a recording medium; a DC voltage applying portion that applies a DC voltage to the transfer portion; and an AC voltage applying portion that applies an AC voltage to the transfer portion.

Abstract: A transfer device comprises a freely rotatable transferring member contacting an image bearing member to form a transfer nip therebetween; a transfer bias applying member to apply a first bias created by superimposing an alternating current component on a direct current component to the transferring member to transfer a toner image borne on the image bearing member to a recording medium in the transfer nip; and an applicator to apply a protective agent to a surface of the transferring member.

Abstract: An image forming apparatus includes a transfer unit configured to transfer a toner image onto a recording medium; a power supply unit configured to apply one of a superimposed voltage in which an alternating-current voltage and a first direct-current voltage are superimposed and a second direct-current voltage to the transfer unit; and a power supply control configured to, when the power supply unit outputs the superimposed voltage, instruct the power supply unit to output the first direct-current voltage at a first timing, and, when the power-supply unit outputs the second direct-current voltage, instruct the power-supply unit to output the second direct-current voltage at a second timing which is later than the first timing.

Abstract: An image forming apparatus includes: a first image bearing member (drum); a second drum; a transfer belt; a first transfer member provided correspondingly to the first drum via the transfer belt; a second transfer member provided correspondingly to the second drum via the transfer belt; a high-voltage power source; and a controller. After an image is continuously formed on transfer materials by applying, to the first transfer member, a voltage of a predetermined polarity from the power source in a state that the first transfer member contacts the transfer belt and the second transfer member is spaced from the transfer belt, the controller executes an adjusting operation in which a voltage of a polarity opposite to the predetermined polarity is applied from the power source to the first transfer member in a state that the second transfer member is spaced from the transfer belt.

Abstract: An image forming apparatus having: a toner image carrier; a transfer member; a transfer voltage applying device which applies a bias voltage to the transfer member; a voltage controller which performs constant voltage control on the transfer voltage applying device; a transfer contribution current detecting device; an antistatic member for removing static electricity from the record medium after transfer of a toner image; and an antistatic voltage applying device which applies an AC voltage to the antistatic member. The transfer contribution current detecting device measures current values during a current detection time, which corresponds to an integral multiple of a period of the AC voltage applied to the antistatic member, and detects a transfer contribution current value from the measured values, and the voltage controller controls the bias voltage applied to the transfer member based on the transfer contribution current value.

Abstract: An image forming apparatus includes a transfer unit configured to transfer a toner image onto a recording medium; a power supply unit configured to output one of an alternating-current-based voltage including at least an alternating-current voltage and a direct-current voltage to the transfer unit; and a power supply control unit configured to cause the power supply unit to start switching to the alternating-current-based voltage a first time after the power supply unit stops outputting the direct-current voltage in the case that output of the power supply unit is switched to the alternating-current-based voltage, and cause the power supply unit to start switching to the direct-current voltage a second time after the power supply unit stops outputting the alternating-current-based voltage in the case that output of the power supply unit is switched to the direct-current voltage. The second time is longer than the first time.

Abstract: A transfer device comprises a freely rotatable transferring member contacting an image bearing member to form a transfer nip therebetween; a transfer bias applying member to apply a first bias created by superimposing an alternating current component on a direct current component to the transferring member to transfer a toner image borne on the image bearing member to a recording medium in the transfer nip; and an applicator to apply a protective agent to a surface of the transferring member.

Abstract: An image forming apparatus includes a main body, a sheet stack unit, an endless intermediate transfer member, a first transfer member for transferring a toner image onto the sheets conveyed from the sheet stack unit, at a nip formed between the intermediate transfer member and the first transfer member, and a second transfer member. In addition, a first voltage applying device applies a voltage to the first transfer member, a second voltage applying device applies a voltage having an opposite polarity to the second transfer member, and a controller controls the first and second voltage applying devices.

Abstract: The present invention relates to an image forming apparatus that forms an image by consecutively superposing toner images that have been formed on a plurality of photosensitive drums, on an intermediate transfer member or a transfer medium. The image forming apparatus is made compact and operates at a low cost. Since a current supply member supplies a current in a rotational direction of an intermediate transfer belt, multiple first transfer portions do not need corresponding voltage sources. Even in the case where a charging member supplies a current, the potential of the intermediate transfer belt is maintained at a predetermined potential by a constant-voltage element connected to support rollers.

Abstract: A transfer device includes a transfer member and a bias applicator. The transfer member contacts a surface, on which a toner image is borne, of an image bearing body, to form a transfer nip. The bias applicator applies a DC voltage and an AC voltage as transfer bias to transfer the toner image on the image bearing body to a recording sheet in the transfer nip. The bias applicator applies a DC voltage having a same polarity as the DC voltage of the transfer bias and an AC voltage having an amplitude smaller than the AC voltage of the transfer bias or applies the DC voltage having the same polarity as the DC voltage of the transfer bias without applying an AC voltage, when an inter-sheet area that exists on the image bearing body passes through the transfer nip during a continuous image formation period.

Abstract: An electrophotographic apparatus and method that can effect favorable transfer of a toner image onto a medium under a nip pressure between a transfer roller and a backup roller and a potential difference between the transfer and backup rollers even if the medium has a high insulating property, such as due to its being thick.

Abstract: An aspect of the present invention provides an image forming apparatus including: a photosensitive element where a latent image is formed and developed into a toner image; an image carrier; an intermediate transfer driving roller that drives the image carrier; a primary transfer roller for transferring the toner image from the photosensitive element to the image carrier; a secondary transfer roller for secondary transfer of the toner image from the image carrier to a medium; a bias applying unit that applies, as a secondary transfer bias, a first bias and a second bias to the intermediate transfer driving roller and the secondary transfer roller, respectively; and a fixing unit that fixes the toner image onto the medium. The first bias is lower than a minimum voltage at which discharge to the primary transfer roller can occur. The second bias depends on the first bias and is opposite in polarity therefrom.

Abstract: A device and method for determining and applying a transfer voltage in an imaging apparatus is provided. A servo voltage is determined based in part upon a change in an environmental condition. A determination is made whether or not to perform a new transfer servo operation based upon at least one of an amount of time passing since the last transfer servo operation was performed and a comparison of the determined servo voltage and a servo voltage used in a prior transfer servo operation. A transfer servo operation includes charging a photoconductive drum to a charge corresponding to a printing voltage.

Abstract: An image forming apparatus includes a rotatable image bearing member, a nip forming member, and a power source. The rotatable image bearing member bears a toner image on a surface thereof and rotates. The nip forming member contacts the surface of the image bearing member to form a transfer nip therebetween. The power source applies a transfer bias to the transfer nip to transfer the toner image from the image bearing member onto a recording medium interposed in the transfer nip. The transfer bias includes a superimposed transfer bias in which an alternating current (AC) component is superimposed on a direct current (DC) component and a polarity of the superimposed transfer bias changes with time. A phase difference between an AC voltage and an AC current output from the power source is equal to or less than 0.47 cycles.

Abstract: Described herein is a transfer device that transfers a visualized image formed on an image carrier onto a recording medium. The transfer device includes an image carrier that carries a toner image, a contacting member that contacts the image carrier via a recording medium and a power source that outputs a transfer bias to transfer the toner image from the image carrier onto the recording medium at a transfer nip formed between the image carrier and the contacting member. The transfer bias has a direct current component and an alternating current (AC) component superimposed on the direct current component. The transfer device also includes a controller that controls the power source such that the controller controls a level of the direct current component output from the power source by a constant current control.

Abstract: An image forming apparatus includes an image bearing member for bearing a toner image, a movable endless transfer belt for transferring the toner image from the image bearing member onto a transfer material, and a transfer device for transferring the toner image from the image bearing member toward the transfer belt. The transfer device includes a transfer member for sliding on an inner surface of the transfer belt in contact with the inner surface, a supporting member for supporting the transfer member, and an urging member for urging the supporting member toward the transfer belt, wherein the transfer member contacts the inner surface of the transfer belt at a contact surface thereof without rotation relative to the supporting member during movement of the transfer belt. The supporting member is rotatable about a center axis during movement of the transfer belt, and the contact surface is convex with predetermined curvature toward the transfer belt.

Abstract: A method for producing a printed material, a method for producing a dye-printed material, a printing apparatus, and a dye-printing system have a good transfer property when a dry toner including a dye is electrostatically transferred to a base material, such as a fabric, based on an electrophotographic system or the like. The methods include a step of providing at least one type of dry toner containing a dye component and a binder resin to a charged body, a step of transferring the dry toner from the charged body to a base material, and a step of fixing the dry toner on the base material. In the transfer step, an electric field is applied between the charged body and the base material to fly the dry toner on the charged body from the charged body to the base material.

Abstract: An image forming apparatus includes an image carrier, a transfer unit, an applying unit, a detector, an acquisition unit, and an adjusting unit. The image carrier carries a toner image obtained by developing an electrostatic latent image using toner. The transfer unit transfers the toner image from the image carrier to a recording medium. The applying unit applies a voltage to the transfer unit. The detector detects a current being made to flow in the transfer unit. The acquisition unit acquires the image density of the toner image to be transferred in the transfer unit. The adjusting unit adjusts a voltage to be applied to the applying unit on the basis of a change in the relationship between the current detected by the detector and the image density acquired by the acquisition unit.

Abstract: In a high voltage power supplying apparatus, a pulse generation unit generates a pulse signal with a predetermined frequency. A piezoelectric transformer outputs a voltage in accordance with the frequency of the pulse signal. A detection unit detects an output voltage of the piezoelectric transformer. A control unit controls the pulse generation unit to change the frequency of the pulse signal by a predetermined value towards a frequency corresponding to a target voltage until the output voltage becomes equal to the target voltage. A storage unit stores data indicating the frequency when the output voltage reaches the target voltage. The control unit controls the output voltage to be equal to the target voltage by variably controlling the frequency of the pulse signal by a value smaller than the predetermined frequency from the frequency corresponding to the data stored in the storage unit.

Abstract: An image forming apparatus includes a bias controller that controls a first application unit that applies a bias to a transfer member. The bias controller applies a reverse bias to the transfer member when a first region passes through a nip part. Then, when a second region passes through the nip part, the bias controller applies a fixed first forward bias to the transfer member. When a third region passes through the nip part, in order to implement the control the bias controller applies a variable second forward bias to the transfer member. The first forward bias is set at a predetermined value or above and increases a potential of the transfer member 46 to a level at which a toner image is transferred in the second region when the second region passes through the nip part.

Abstract: A transfer device comprising: a load including a transferring unit, the transferring unit being configured to transfer an image on a transferable material; a direct current source connected to the load and configured to apply a direct voltage to the load; and an alternating current source connected between the load and the direct current source in attachable and detachable manner, the alternating current source being configured to selectively apply to the load an overlapping voltage that is formed by overlapping an alternating voltage and the direct voltage.

Abstract: A transfer device includes a power supply control unit, a direct-current (DC) power supply, an alternating-current (AC) power supply, and a transfer unit. The power supply control unit controls a first control signal for controlling a DC voltage and a second control signal for controlling an AC voltage based on a condition relating to image formation. The DC power supply outputs the DC voltage based on the first control signal. The AC power supply selectively outputs, with a particular waveform, either of the DC voltage output from the DC power supply or a superimposed voltage obtained by superimposing the AC voltage determined based on the second control signal on the DC voltage output from the DC power supply. The transfer unit transfers a developer onto a sheet using a voltage output from the AC power supply.

Abstract: An image forming apparatus includes an image carrier that carries a toner image; a transfer member that transfers the toner image to an object to be transferred at a transfer position that faces the image carrier; an endless transfer belt that is wound around the transfer member, and rotates circumferentially as the transfer member rotates; a facing member that is arranged to face the transfer member so as to nip the transfer belt at the transfer position; a transfer voltage application member that applies a voltage at the transfer position such that a transfer current flows between the transfer member and the facing member; and a conductive member to which a voltage is applied between the conductive member and a target member at a position different from the transfer position such that a current in a direction opposite to the transfer current flows to the transfer belt.

Abstract: A transfer bias voltage supplier supplies, to a transfer member, a transfer bias voltage of a polarity opposite to the polarity of toner. The absolute value of transfer bias voltage to be supplied to the transfer member when a leading/trailing end of the sheet is passed through the nip portion is set smaller than when a toner image transfer region of the sheet is passed through the nip portion. A separation bias voltage supplier supplies, to a discharging electrode member, a separation bias voltage of a polarity opposite to the polarity of transfer bias voltage. The absolute value of separation bias voltage to be supplied to the discharging electrode member when the leading/trailing end of the sheet is passed through a discharging gap is set smaller than when the transfer region is passed through the discharging gap.

Abstract: A novel image forming apparatus includes a photoreceptor to bear an electrostatic latent image on a surface thereof, a developing device to develop the electrostatic latent image into a toner image, an intermediate transfer member onto which the electrostatic latent image is transferred, a primary transfer member to apply a primary transfer bias to the intermediate transfer member to transfer the toner image thereto, a secondary transfer member supplied with a secondary transfer bias to transfer the toner image from the intermediate transfer member onto a recording medium, and a transfer bias power source to selectively apply to the secondary transfer member one of a secondary transfer bias consisting of a direct current (DC) voltage in a DC transfer mode and a secondary transfer bias consisting of a superimposed bias in which an alternating voltage is superimposed on a DC voltage.

Abstract: An image forming apparatus includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The transfer unit includes a bias power supply and transfers a developed image onto a transfer body. The bias power supply includes a first power supply unit, a second power supply unit, a threshold setting unit, a detector, and an output controller. The first power supply unit generates a transfer electric field. The second power supply unit generates a non-transfer electric field. The threshold setting unit has a first threshold and a second threshold, and performs a change from the first threshold to the second threshold when switching from the non-transfer electric field to the transfer electric field is performed. The detector detects the current which is caused to flow by the first power supply unit. The output controller controls the first power supply unit.