Abstract: In a wet-type image forming apparatus, a plurality of patch images are successively transferred to a recording medium corresponding to a plurality of transfer biases obtained as bias value of the transfer bias is changed; density detecting unit measures image density of each of the plurality of patch images on the recording medium and detects a range of bias values of transfer bias in which the image density of patch image is substantially saturated; and the bias value of transfer bias when a normal image is formed on the recording medium is set to be within the range of bias values of transfer bias in which the image density of patch image is substantially saturated and to be not larger than absolute value of the bias value at which the image density of patch image is substantially saturated.

Abstract: An image forming apparatus includes an image bearing member, an image forming device for forming a toner image on the image bearing member, a recording material, a transfer device for transferring the toner image from the image bearing member to the recording material, a transfer belt for carrying the recording material, a first cleaning member, a second cleaning member, and a voltage control device. When continuously forming toner images on sheets of the recording material, a detection toner image is formed on the image bearing member between images to be formed on sheets of the recording material. The first cleaning member cleans the image bearing member. The second cleaning member cleans the transfer belt. The voltage control device controls the voltage applied to the transfer device so that the number of operations to clean the detection toner image is higher for the second cleaning member than the first cleaning member.

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: An image forming apparatus includes: a first image forming unit including a first transfer unit forming a first nip with a first photosensitive drum for black; a second image forming unit including a second transfer unit forming a second nip with a second photosensitive drum for a color; and a control device which, when a first sheet and a second sheet are continuously conveyed in corresponding order by the conveyance belt at the monochrome mode, is configured to supply a first transfer current for a first time period during which the first sheet or the second sheet pass through the second nip and supply a second transfer current, which is smaller than the first transfer current, for a second time period that is a sheet interval between the first sheet and the second sheet.

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.

Abstract: An image forming apparatus includes an image holding body on which a toner image is formed; a transfer unit that functions to transfer the toner image formed on the image holding body onto a recording medium; and an adjusting unit that adjusts a gap between the transfer unit and the image holding body based on the rigidity of the recording medium, the recording medium being conveyed through the gap with respect to the image holding body.

Abstract: A high voltage power source device includes piezoelectric transformers, each of the piezoelectric transformers being formed with a primary electrode and a secondary electrode on piezoelectric ceramics, receiving a primary voltage at the primary electrode, and generating a second voltage from the secondary electrode, switching elements, each of the switching elements driving a respective one of the piezoelectric transformers, and primary voltage supply devices, each of the primary voltage supply devices supplying the primary voltage to the primary electrode of the respective one of the piezoelectric transformers by driving the respective one of the switching elements when the secondary voltage is generated from the respective one of the second electrodes, wherein the respective one of the primary voltage supply devices supplies the primary voltage to the respective one of the primary electrodes by driving the respective one of the switching elements at the same frequency.

Abstract: An image forming apparatus includes plural image carriers, an intermediate transfer body, a contact and separation mechanism, a selection member, plural first transfer units, a second transfer unit, and an adjustment member. Each image carrier carries a toner image. The intermediate transfer body is disposed so as to be in contact with one or more image carriers. The contact and separation mechanism causes the intermediate transfer body to be in contact with or separated from the image carriers. The selection member selects a first contact state or a second contact state. Each first transfer unit forms a transfer electric field in a first transfer region to transfer a toner image onto the intermediate transfer body. The second transfer unit forms a transfer electric field in a second transfer region to transfer toner images onto a recording material. The adjustment member adjusts first transfer conditions.

Abstract: An image forming apparatus has an image forming section having a photoreceptor on which a toner image is formed, an endless belt that revolves with its outer surface facing the photoreceptor, a steering roller adapted to provide a tension to the belt and adjust the position of the belt in the width direction, a transfer roller that presses the belt toward the photoreceptor so as to form a transfer nip where the toner image is transferred, a transfer pressure adjusting mechanism adapted to adjust pressing force when the transfer roller presses the belt toward the photoreceptor, and a controller adapted to control the pressing force adjusted by the transfer pressure adjusting mechanism, according to the adjustment state of the steering roller.

Abstract: An image forming apparatus includes a nip forming member and a transfer bias output device that outputs a transfer bias to form a transfer electric field in a transfer nip between the nip forming member and an intermediate transfer member. Upon transfer of a composite toner image including a particular toner image onto a recording medium in the transfer nip, the transfer bias output device outputs the transfer bias including a first superimposed bias in which a direct current (DC) component is superimposed on an alternating current (AC) component. Upon transfer of the composite toner image without the particular toner image onto the recording medium in the transfer nip, the transfer bias output device outputs one of the transfer bias including a second superimposed bias having a peak-to-peak value of the AC component smaller than that of the first superimposed bias and the transfer bias including only the DC component.

Abstract: When a toner image formed on the surface of a photosensitive drum is transferred onto an intermediate transfer belt, a transfer bias is applied to a primary transfer portion. When a patch formed in an upstream image forming station and transferred onto the intermediate transfer belt and a patch formed on the surface of the photosensitive drum pass through the primary transfer portion, a passing bias different from the transfer bias is applied to the primary transfer portion. A control section controls a laser beam scanner as an exposure member not to expose the surface of the photosensitive drum to which the passing bias is applied.

Abstract: Provided is a transfer device including a transfer roll that interposes a sheet transported to a transfer unit to transfer the toner image to the sheet, a power supply that generates a voltage between the transfer roll and the image holding member, and a control unit that causes the power supply to generate a transfer voltage, a resistance detection voltage having a same polarity as a polarity of the transfer voltage, and a cleaning voltage having a polarity reverse to the polarity of the transfer voltage, wherein the control unit causes the power supply to generate the transfer voltage in a transfer interval, in a continuous traveling mode, and generates the resistance detection voltage and the cleaning voltage in a non-arriving interval while switching a single interval ratio which is a generation time ratio in the non-arriving interval between the resistance detection voltage and the cleaning voltage.

Abstract: An image forming apparatus includes a second transfer unit, and a control device. If a prescribed condition is satisfied, the control device sets a transfer current value for the second transfer unit so that an absolute value of a difference between the first current value and a second current value is greater than an absolute value of a difference between a third current value and a fourth current value. The first current value is set in a black-white mode, in which an image is formed by using black toner only, under the prescribed condition; the second current value is set if the prescribed condition is unsatisfied in the black-white mode; the third current value is set in a multi color mode, in which an multi-color image is formed, under the prescribed condition; and the fourth current value is set if the prescribe condition is unsatisfied in the multi color mode.

Abstract: An image forming apparatus includes image forming devices which each forms a developer image on a latent image carrier, transfers the developer image onto an intermediate transfer member, and cleans the latent image carrier by using a plate-shaped cleaning member, the intermediate transfer body, and a controller. The developer used in one of the image forming devices is a low-electrostatic-propensity developer having an electrification performance lower than those of the developers used in the other image forming devices. The controller has a control mode for executing a supply operation in which the low-electrostatic-propensity developer used in the one of the image forming devices is transferred onto the intermediate transfer body and at least a part of the low-electrostatic-propensity developer is reversely transferred onto the latent image carriers of the other image forming devices and caused to reach the respective plate-shaped cleaning members.

Abstract: An image forming apparatus includes an image bearing member which bears a toner image, an intermediate transfer member which bears the toner image transferred from the image bearing member, an endless recording material-conveying member which conveys a recording material, and a transfer portion which transfers the toner image to the recording material conveyed from the intermediate transfer member by the recording material-conveying member, wherein a perimeter of the intermediate transfer member is set to substantially an integral multiple of a perimeter of the recording material-conveying member.

Abstract: An image forming apparatus includes a first image bearing member (drum); a second drum; a belt; a first transfer unit; a second transfer unit; a first voltage applying unit; a second voltage applying unit; a detecting unit, connected to the first transfer unit, for detecting a value of a current passing through the first voltage applying unit; and a controller for controlling the first voltage applying unit and the second voltage applying unit. The controller controls the first voltage applying unit during image formation on the basis of a detection result of the value of the current detected by the detecting unit at timing before and after the voltage applied to the second voltage applying unit is changed plural times before the image formation.

Abstract: A system and method is provided for determining the location of one or more biased transfer rolls relative to associated photoreceptors in a printer. The one or more biased transfer rolls can be moved into contact with an intermediate transfer surface bringing the surface into contact with associated photoreceptors to form a closed biased transfer roll image transfer nip for transferring an image from the photoreceptor to the intermediate transfer surface. The open or closed condition of the biased transfer roll image transfer nip is determined by applying a constant current to the biased transfer roll and evaluating a voltage at the biased transfer roll. The open or closed condition of different image transfer nips can be determined in a similar manner. A plurality of biased transfer rolls can be ganged together for simultaneous movement with respect to associated photoreceptors to form a plurality of image transfer nips, the open and closed condition which can also be determined.

Abstract: An image forming device includes: a secondary transfer roller configured to secondarily transfer a toner image transferred to an intermediate transfer belt, to a transfer paper; separating plates; and a power supply circuit configured to apply bias voltages to the separating plates. The separating plates are configured to separate the transfer paper from the intermediate transfer belt when the bias voltages are applied to the separating plates. The separating plates include two or more separating plates installed along a direction perpendicular to the transfer paper conveying direction. The bias voltages are applied to the separating plates independently of each other depending on a toner amount distribution of the toner image transferred to the transfer paper, in the direction perpendicular to the transfer paper conveying direction.

Abstract: An electrophotographic image forming apparatus including a photoreceptor on which an electrostatic latent image is formed, a developing roller for forming a visual toner image by supplying toner onto the electrostatic latent image, a transfer unit for transferring the visual toner image onto a recording medium, and a cleaning member for removing residual toner remaining on the photoreceptor after the transfer of the visual toner image from the photoreceptor is described. The image forming apparatus operates in a printing mode, and a collecting mode in which the residual toner on the cleaning member is collected on the developing roller via the photoreceptor. A linear velocity of the developing roller in the collecting mode is faster than in the printing mode.

Abstract: A control unit is provided which controls at least one of a first power supply unit (a secondary transfer power supply connected to a secondary transfer roller) and a second power supply unit (high-voltage power supplies connected to a conductive brush and a conductive roller) so that a current supplied to a primary transfer region from a beginning of primary transfer until a beginning of secondary transfer has a magnitude larger than a magnitude of a current supplied to the primary transfer region from a beginning of image formation until the beginning of the primary transfer.

Abstract: An image formation device for forming an image by an electrophotographic process includes a charge voltage controller configured to control an application charge voltage to be applied to a charge member, a transfer voltage controller configured to control a transfer voltage to be applied to a transfer member, a charge current detector configured to detect a charge current flowing through the charge member, and a controller configured to determine the application charge voltage according to the application charge voltage and the detected charge current, both detected when the transfer voltage controller applies a predetermined transfer voltage.

Abstract: In an image forming apparatus including a power source for forming a secondary-transfer electric field at a secondary-transfer position and for forming a primary-transfer electric field at a primary-transfer position by applying a voltage to a transfer member to pass a current through a constant-voltage element, a potential of an image portion is controlled depending on a detection result of a detecting member.

Abstract: An image forming apparatus includes an apparatus main body, a power supply switch, a photoreceptor drum, a charging device, an exposure device, a developing device, a transfer roller, a cleaning device, and a toner-layer formation unit. The transfer roller contacts the circumferential surface of the photoreceptor drum at a downstream side with respect to the developing device in the rotation direction and is configured to transfer the toner image to a sheet. The cleaning device is cleaning device arranged opposed to the photoreceptor drum, downstream. The cleaning device is configured to clean the photoreceptor drum. The toner-layer formation unit is configured to form a toner layer on a surface of the transfer roller in an initial operation started after the apparatus main body is installed in a predetermined installation location and the power supply switch is switched on.

Abstract: A transfer device includes an intermediate transfer belt, a driving roller, an environment sensor, a resistance detecting sensor, and a speed ratio adjusting section. The toner images are transferred from the plurality of image carriers onto a surface of the intermediate transfer belt in a superimposed manner. The driving roller circumferentially and rotationally drives the intermediate transfer belt. The environment sensor detects a temperature or a humidity around the intermediate transfer belt. The resistance detecting section detects a change in a resistance value of the intermediate transfer belt. The speed ratio adjusting section controls a rotation speed of the driving roller according to results of detection by the environment sensor and the resistance detecting section, thereby adjusting a speed ratio Vb/Vd between a circumferential rotating speed Vb of the intermediate transfer belt and a rotation speed Vd of the image carrier.

Abstract: An image forming apparatus includes: a transfer unit, a reflectance sensor, a time-series data acquiring unit, and a transfer-unit rotation-time calculating unit. The time-series data acquiring unit is configured to acquire time-series data with respect to the image carrier background-portion reflectance, measured by the reflectance sensor, as reference data over a time period twice longer than a time period that by design the image carrier requires for one cycle, and as advance/delay data over a time period twice longer than a time period longer or shorter in multiples of a predetermined time interval than the by-design time period. The transfer-unit rotation-time calculating unit is configured to calculate a one-cycle-time calculation value that is the time actually required for one cycle of the image carrier, based on the reference data and the advance/delay data acquired by the time-series data acquiring unit.

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: Provided is a color image forming apparatus that includes: image carriers that form toner image of black and other colors; an intermediate transfer body that makes contact with the image carriers; and transfer units that transfer the toner images on the image carriers to the intermediate transfer body. A line velocity difference is set between the image carriers and the intermediate transfer body. An accelerated cohesion degree of toner is equal to or larger than 54%. A linear velocity difference X1 between the image carrier for black and the intermediate transfer body satisfies a relation of 0<X1?1.2 mm/sec. A linear velocity difference X2 between the image carriers for the colors and the intermediate transfer body satisfies a relation of 2.1?X2?4.0 mm/sec.

Abstract: An image forming apparatus includes a controller and a transfer device including a power source to output a superimposed bias in which an AC voltage is superimposed on a DC voltage, a first electrode, a second electrode disposed opposite the first electrode with an image bearing member interposed therebetween to form a transfer electric field to transfer a toner image on the image bearing member to a recording medium. The controller including a CPU adjusts the transfer electric field and a transfer speed. One of the first electrode and the second electrode is connected to the power source, and the other is grounded. The controller adjusts the transfer speed such that in a case in which an oscillating electric field of the transfer electric field is strong, a maximum transfer speed is slower than the maximum transfer speed in a case in which the oscillating electric field is weak.

Abstract: An image forming apparatus including a latent image bearing member, a charger, a latent image forming device, a developing device, and a transfer device is provided. The transfer device is adapted to transfer a toner image formed on the latent image bearing member onto an intermediate transfer member or a recording medium by action of a transfer elected field in a transfer position where the latent image bearing member faces the transfer device. When a non-charged portion of the latent image bearing member that has not been charged to a predetermined potential by the charger passes through the transfer position, a strength of the transfer electric field is lowered than that in transferring the toner image.

Abstract: An image forming apparatus includes an image forming unit, a sheet conveying unit, a TOD (Top of Data) control module for instructing the image forming unit to start generation of a toner image, a timing roller driving module for instructing the sheet conveying unit to start driving of the timing roller, an image synchronization module designed depending on the sheet conveying unit and the image forming unit, and a sheet information module for generating an image synchronization identifier for designating a pattern of image synchronization control related to printing of the toner image on the sheet, depending on a type of the sheet designated. The image synchronization module is activated when the formation of the toner image on the sheet has become possible, and activate each of the TOD control module and the timing roller driving module, with a relative time lag based on the image synchronization identifier.

Abstract: An image forming apparatus includes an inclining device for inclining the endless belt so as to keep the an endless belt in a normal range in a widthwise direction of the belt; a blade member for pressing against the belt at a pressing portion to clean it; a detecting portion for detecting deviation of the belt from a normal range in a widthwise direction thereof; and an executing portion for executing an operation in a mode in which a lubricant is supplied to the pressing portion, when the detecting portion detects that the belt is deviated from the normal range.

Abstract: Provided is an image forming apparatus which enables control to change a longitudinal magnification of an image transferred on a sheet in a sheet conveyance direction by changing a rotation speed of a second transfer section while prohibiting misalignment of transfer without requiring a changing time of the longitudinal magnification which causes the decreasing of productivity.

Abstract: A method for color registration includes determining if color registration is necessary, and if color registration is necessary, rotating an image forming medium and setting an optimum luminance of a registration sensor with respect to a rotating surface of the image forming medium, confirming an area with an undesirable surface condition on the image forming medium using luminance detected with respect to the rotating surface of the image forming medium during the setting of the optimum luminance, forming a preset mark for color registration adjustment excluding the area confirmed to have an undesirable surface condition, and carrying out color registration adjustment using the optimum luminance set with respect to the formed mark.

Abstract: An image forming apparatus includes a toner forced consumption control unit that performs toner forced consumption control in which toner in a developing unit is forcibly consumed when a certain condition to perform the toner forced consumption control is met. The certain condition to perform the toner forced consumption control includes a specific performance condition that a transfer bias switching condition to switch a transfer bias to a superimposed transfer bias in which an alternating current component is superimposed on a direct current component, from a direct current transfer bias is met. When the specific performance condition is met, the toner forced consumption control unit performs preliminary toner forced consumption control in which the toner forced consumption control is performed before an image forming operation using the superimposed transfer bias is started.

Abstract: An image forming apparatus includes a controller capable of performing a printing control and a cleaning control. In the printing control, developer images carried on the image carriers are transferred toward the opposing surface or a recording sheet by applying a transfer current between each of the image carriers and the transfer device. In the cleaning control, developer collected by the cleaning rollers is transferred toward the image carriers and the transfer device and collected by the cleaning device by applying a transfer current between each of the image carriers and the transfer device and switching an electric field established between the image carrier and the corresponding cleaning roller. The controller is configured to control the transfer current such that an average absolute value of the transfer current in the cleaning control is smaller than that in the printing control.

Abstract: An information forming apparatus includes an execution unit configured to execute a setting mode which sets a voltage to be applied to the transfer member during an image formation operation and a correction mode which corrects the voltage set by the setting mode and a storage unit configured to store in advance a correction current difference based on the environment that is a difference between a current when a predetermined voltage is applied to the transfer member during the first period and a current when a predetermined voltage is applied to the transfer member during the second period. The execution unit corrects the voltage set by the setting mode in accordance with the correction current difference based on a detection result from the first detection member and a detection result from the second detection member in a case that the correction mode is executed during the first period.

Abstract: In an image forming apparatus, one of a plurality of support members supporting an intermediate transfer belt is a guide member configured to regulate the rotational direction of the intermediate transfer belt while being held in sliding contact with the intermediate transfer belt at a position opposite the secondary transfer member across the intermediate transfer belt. This guide member is equipped with a first resistor portion in sliding contact with the intermediate transfer belt and a second resistor portion of a higher electrical resistance than the first resistor portion, with the second resistor portion provided upstream of the first resistor portion in the rotational direction of the intermediate transfer belt.

Abstract: An image forming apparatus includes an image bearer; a toner image forming unit, a transfer unit, a detector, and a controller. The toner image forming unit forms a plurality of types of density detection patterns on the surface of the image bearer in mutually-different positions in a surface-movement direction of the image bearer. The density detection patterns have mutually-different lengths in a direction orthogonal to the surface-movement direction of the image bearer. The transfer unit transfers the density detection patterns onto the surface of the transfer member. The detector detects image densities of the density detection patterns transferred on the surface of the transfer member. The controller calculates an image density difference between the density detection patterns on a basis of a detection result obtained by the detector, and corrects a transfer bias for transferring a toner image on a basis of a value of the image density difference.

Abstract: A protection member is arranged such that the distance from an opening plane of a reception guide to the center of the protection member is half of the distance from the opening plane of the reception guide to the surface of a reception vibration member. In other words, the arrangement position of the protection member is in the center between the opening plane of the reception guide and the surface of the reception vibration member. Accordingly, even if a protection member is arranged, a transmission coefficient is obtained that is equal to a transmission coefficient in the case where no protection member is present.

Abstract: Provided are an error detection circuit, a power source unit, and an image forming apparatus that are capable of detecting a short circuit state and an open circuit state of a power source output.

Abstract: An image forming apparatus includes image carrier carrying latent image, developer carrier supplying developer on the image carrier, transfer part transferring the developer on the image carrier, cleaning blade removing attachment that attaches to a surface of the image carrier, internal environment detection part detecting an internal environmental temperature in the apparatus, developer disposal control part controlling disposal of developer from the developer carrier to the image carrier, and voltage control part controlling an applied voltage to the transfer part. Wherein, the developer disposal control part determines an absolute value of the applied voltage larger, which is applied to the transfer part during disposing the developer, where the internal environment temperature is high, and the voltage control part controls the applied voltage to the transfer part based on the absolute value of the voltage decided by the developer disposal control part.

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: An image forming apparatus that transfers a developer image onto a sheet and forms the developer image on the sheet includes a developer image carrier, a first pressing member, a transfer member, a first voltage supply, and an adherence part. The developer image carrier holds the developer image and moves in a predetermined direction in which the sheet is being carried. The first pressing member presses against the developer image carrier from a side opposite to a side on which a developer image is held. The transfer member is arranged against the first pressing member through the developer image carrier, the first pressing member and the transfer member being responsive to a first voltage applied therebetween to transfer the developer image from the developer image carrier toward the transfer member. The adherence part adheres the sheet to the developer image carrier upstream the first pressing member in the predetermined direction.

Abstract: An image forming device has multiple image forming units that form developing agent images, an intermediate transfer member to which developing agent images are transferred from selected image forming units, and a transfer member for transferring the developing agent images from the intermediate transfer member to a recording medium, using a voltage supplied from a voltage supply unit. The voltage supply unit varies the voltage supplied to the transfer member, either before or after or both before and after the developing agent images are transferred from the intermediate transfer member to the recording medium, according to the number of selected image forming units or their disposition.

Abstract: In a constitution in which a power source exclusively for primary transfer is omitted and a predetermined voltage is generated in an intermediary transfer member by a constant-voltage element, a high power source voltage more than necessary is applied in order to avoid primary transfer defect, so that a transfer member is deteriorated by energization in some cases. By detecting a current flowing into the constant-voltage element, it becomes possible to obtain a minimum power source voltage at which the intermediary transfer member is capable of maintaining a predetermined voltage, so that it is possible to avoid the energization deterioration of the transfer member.

Abstract: A controller controls a voltage to be applied to the transfer member when there is a recording material having a predetermined largest width at a secondary-transfer position, so that a constant-voltage element maintains a predetermined voltage, whereby it is possible to prevent transfer defect due to short of a primary-transfer electric field at a primary-transfer portion when a toner image is secondary-transferred onto the recording material.

Abstract: In a constitution in which a power source exclusively for primary-transfer is omitted and a predetermined voltage is generated in an intermediary transfer member, in a test mode in which a test voltage is applied to a secondary-transfer member in advance in order to obtain a proper secondary transfer voltage, in the case where the test voltage is low, a proper secondary-transfer voltage cannot be obtained in some cases. In a period of the test mode, the power source is controlled in order to maintain a Zener breakdown voltage, so that the proper secondary-transfer voltage can be obtained.

Abstract: In a constitution of primary-transfer-high-voltage-less in which a power source dedicated to primary-transfer, in the case where voltage applications for determining primary-transfer and secondary-transfer voltages are carried out concurrently, there is a possibility of improper primary-transfer. The possibility is decreased by controlling a power source so that a voltage drop of a Zener diode maintains a Zener breakdown voltage.

Abstract: An image forming apparatus includes: a first image forming unit for a monochrome printing including a first photosensitive member for black, a first charging member and a first collection member; a second image forming unit for a multi-color printing including a second photosensitive member for a color, a second charging member and a second collection member; and a control device configured to, at the color printing mode, apply a first charging bias to the second charging member and apply a first bias having a reverse polarity to a charged polarity of developer to the first and second collection members, and at the monochrome printing mode, apply a second charging bias to the second charging member, apply a second bias having the reverse polarity to the first collection member and apply a third bias to the second collection member.

Abstract: A transfer device includes image bearing members, an intermediate transfer belt, transfer members, a transfer bias applying unit and a bias control unit. The transfer bias applying unit applies a transfer bias to the transfer. The bias control unit causes a transfer bias having a polarity opposite to that of the toner to be applied to a first transfer member during the transfer process in the first transfer nip and during an adjacent transfer process which is the non-transfer process in the first transfer nip and the transfer process in a second transfer nip adjacent to the first transfer nip. Further, the bias control unit causes a transfer bias having the same polarity as that of the toner to be applied to the first transfer member during an adjacent non-transfer process which is the non-transfer process in the first transfer nip and the non-transfer process in the second transfer nip.