Abstract: An image forming apparatus includes an image carrier, a charging device, a developing device, a transfer device, a development power supply, a current measurement device, and a processor. The development power supply applies a predetermined bias voltage to the developing device. The processor functions as a calculator and a controller. The calculator calculates a surface potential of the image carrier based on the development current measured by the current measurement device. The controller controls the charging device, the developing device, the transfer device, and the development power supply. The controller sets a tentative transfer current to be flowed through the transfer device while the calculator calculates the surface potential.

Abstract: An image forming apparatus includes: a development device that develops an electrostatic latent image formed on a photosensitive drum into a toner image; a charger that charges the photosensitive drum; a development power supply that applies a prescribed bias voltage to the development device; an electric current measuring section that measures a development current flowing in the development device; and a calculating section that calculates a surface potential of the photosensitive drum based on the development current. The development device sequentially forms a plurality of image formation toner images on respective sheets of a recording medium. The image formation toner images each are a toner image for image formation. The electric current measuring section measures the development current in a period during which the image formation toner images are not formed.

Abstract: Provided is an image forming apparatus capable of suppressing the occurrence of image defects in response to a difference in carrier resistance and obtaining high image quality. A developing unit has a developing roller that carries toner in a two-component developer that includes a toner and a magnetic carrier on the surface thereof, and forms a toner image on the surface of a photosensitive drum. A current detecting unit detects developing current flowing between the developing roller and the photosensitive drum when a developing voltage is applied to the developing roller by a developing power supply. When the developing voltage is applied to the photosensitive drum, a control unit derives a carrier resistance based on the developing current detected by a current detecting unit, and controls an AC amplitude of an AC voltage of the developing voltage based on the carrier resistance.

Abstract: According to one embodiment, a charger charges a surface of an image carrier by discharge in a wide-angle. A charging bias voltage application section applies a charging bias voltage to the charger. An exposing device forms an electrostatic latent image in a charged image carrier. A toner carrier causes toner to adhere to the electrostatic latent image formed in the image carrier. A developing bias voltage application section applies the developing bias voltage to the toner carrier. In addition, the developing bias voltage application section changes the charging bias voltage in one step and changes the developing bias voltage applied to the toner carrier in multiple steps.

Abstract: A development device includes a developer bearing member and a magnet which is fixed inside of the developer bearing member. The magnet includes a first magnetic pole for developing a latent image, a second magnetic pole adjacent to the first magnetic pole and being an opposite pole to the first magnetic pole, and a third magnetic pole adjacent to both the first and second magnetic poles and having an opposite pole to the first magnetic pole. A developer regulation portion is disposed such that when a maximum peak amount of a magnetic flux density of the first magnetic pole in a normal direction of the developer bearing member is defined as positive, the magnetic flux density of the first magnetic pole becomes positive in an entire region from a downstream side of the regulating member in a rotary direction of the developer bearing member and through a developing area.

Abstract: A semiconductive roller is provided, which has a toner transport amount and a toner charge amount properly controlled, particularly, when being used as a developing roller, and is substantially free from imaging failure such as fogging and background smudging. The semiconductive roller is formed from a semiconductive rubber composition, and has an outer peripheral surface having a surface roughness defined by a roughness profile such that an arithmetic average roughness is not greater than 0.7 ?m and a difference R?c between vertical section levels at two different load length percentages (at a load length percentage Rmr1 of 25% and a load length percentage Rmr2 of 75%) is not greater than 1.2 ?m.

Abstract: There are provided a developing device including a developing roller to develop an image carrier by use of a two-component developer and a developing bias power source, and an image forming apparatus using the developing device. The developing device further includes a variable resistance unit provided on a bias apply path to apply a bias from the developing power source to the developing roller, and a resistance controller to control a resistance value of the variable resistance unit based on a charge amount signal indicating a toner's charge amount in a developer layer on the developing roller. The resistance controller provides a low mode to lower the resistance of the variable resistance unit and a high mode to enhance the resistance. The low mode is set if the toner charge amount is low, and the high mode is set if the toner charge amount is high.

Abstract: A developing unit includes a developing container, a developing sleeve, a developer regulating member, and a magnetic field generating portion. The magnetic field generating portion includes a drawing-up pole and a cut pole. In addition, in a peak-to-peak area, the magnetic field generating portion includes at least one of an Fr flat area in which Fr is substantially constant and an Fr attenuation area in which Fr attenuates toward the cut pole side from the drawing-up pole side, and is configured that F? is oriented toward the same direction as a direction of rotation of the developing sleeve in the entire peak-to-peak area.

Abstract: An image forming apparatus includes an image carrier, a developing part that develops an electrostatic latent image formed on the image carrier by using toner, a supply part that supplies a developing bias between the image carrier and the developing part, the developing bias having an AC component superimposed on a DC component, and a setting part that sets a peak-to-peak value of the AC component of the developing bias to vary between a reference value that is determined in advance and a special value smaller than the reference value when an image region on the image carrier passes through a developing region, the image region being a region on the image carrier in which an image is to be formed, the developing region being a region in which the image carrier is opposed to the developing part.

Abstract: A developing device includes a developing container, a toner carrier, and a plurality of air outlet ports. The plurality of air outlet ports are formed in such part of a wall of the developing container as faces the toner carrier, along a longitudinal direction of the developing container, the air outlet ports communicating with a duct next to the developing container. The toner carrier includes a coat layer on the outer circumferential surface thereof. The coat layer is formed by dripping the toner carrier into a resin coating liquid with one end in the longitudinal direction thereof first, the one end being a lower end of during the dipping, and then lifting the toner carrier out of the resin coating liquid. The toner carrier is arranged such that the lower end of during the dipping is disposed on an upstream side with respect to an airflow direction in the duct.

Abstract: A developing device of the present disclosure includes a magnetic roller and a developing roller arranged so as to oppose the magnetic roller. Inside the magnetic roller, a regulation pole and a conveyance pole are provided. The regulation pole is turned toward an opposing surface side of an end portion of a regulation blade provided in a developer container. The regulation pole and the conveyance pole are arranged such that in magnetic fields formed by these magnetic poles, a point where no magnetic pole perpendicular to a surface of the magnetic roller is generated is located in a gap between the surface of the magnetic roller and the regulation blade.

Abstract: A developing device includes a developer bearer to carry, by rotation, developer including toner and magnetic carrier to a development range facing a latent image bearer to bear a latent image. The developer bearer includes a magnetic field generator having multiple magnetic poles and a cylindrical developing sleeve to rotate and bear developer on an outer circumferential surface thereof with magnetic force of the magnetic field generator disposed inside the developing sleeve. The developing sleeve receives development voltage including an AC component having a frequency of 2.0 kHz or lower, and a duty ratio of a component having a polarity opposite a toner normal charge polarity of the AC component is within a range from 4% to 20%.

Abstract: An image forming apparatus includes a power source and a controller. A time-averaged value (Vave) of a voltage output from the power source has a polarity in a transfer direction, and an absolute value of Vave is greater than a midpoint value (Voff) of the voltage intermediate between a maximum value and a minimum value of the voltage. With an increase in a difference (Vpp) between the maximum value and the minimum value of the voltage, the controller controls the power source to increase a duty ratio (Duty) expressed by A/(A+B), where A is an application time in one cycle at a return direction side opposite a transfer direction side relative to Voff and B is an application time at the transfer direction side relative to Voff, and with a decrease in (Vpp), the controller controls the power source to reduce Duty.

Abstract: An image forming apparatus includes an exposure device having an adjustment period for adjusting an output while exposing a photosensitive drum to light prior to image formation and a developing device. The developing device is configured to change between a contact state where the photosensitive drum and a developing roller are in contact with each other and a separation state where they are separated from each other. The developing device changes from the separation state to the contact state when a portion on the photosensitive drum exposed to light in the adjustment period of the exposure device is at a developing position.

Abstract: A developing device includes a development housing, a developer carrier, a toner carrier, a bias applying unit, a leakage detecting unit, a bias control unit and a leakage detection control unit. The developer carrier carries a developer layer. The toner carrier receives the toner from the developer layer and supplies the toner to an image carrier. The bias applying unit includes one transformer and applies direct-current voltages and alternating-current voltages to the developer carrier and the toner carrier. The leakage detecting unit detects leakage occurring between the image carrier and the toner carrier or between the toner carrier and the developer carrier. The leakage detection control unit detects a value of an inter-peak voltage at which the leakage occurs and determines whether the leakage occurs between the image carrier and the toner carrier or between the toner carrier and the developer carrier.

Abstract: An image forming apparatus includes an image bearing member which bears an electrostatic latent image; a developing device including a developing container which contains a developer, a developer carrying member which carries the developer to develop the electrostatic latent image, and an electrode member provided in the developing container; a voltage applying device which applies an alternate-current voltage to the developer carrying member; and a detecting device which detects information on a capacitance between the developer carrying member and the electrode member when the voltage applying device applies the alternate-current voltage to the developer carrying member in forming an image.

Abstract: According to one embodiment, an image forming apparatus includes an image bearing member on which an electrostatic latent image is formed by exposure, an exposing device including a plurality of light sources and a plurality of lenses, which are provided along a longitudinal direction of the image bearing member, and configured to radiate light on the image bearing member, and a developing device arranged at a fixed distance apart from the image bearing member and configured to develop, according to application of a direct-current bias, the electrostatic latent image formed on the image bearing member into a visible image using a two-component developer.

Abstract: A developing device includes a developing roller, a magnetic roller, a capacitor, a transformer, and a control signal generating unit. The developing roller carries toner. The magnetic roller performs supply of toner to the developing roller and removal of toner from the developing roller. The transformer includes a primary side to which a capacitor is connected and a secondary side from which an AC voltage is output and applied to the developing roller. The control signal generating unit inputs a control signal to the capacitor and adjusts a DC bias value of the control signal so that a DC component of the control signal is the same before and after the change of the duty ratio of the control signal.

Abstract: An image forming apparatus includes an image carrier, a developing device, a bias applying unit, a leak detecting unit, a bias controller and a leak detection controller. The developing device includes a magnetic roller and a developer layer. The bias applying unit applies development biases to the magnetic roller and the developing roller. The leak detecting unit detects a leak generated between the image carrier and the developing roller or a leak generated between the developing roller and the magnetic roller. The leak detection controller performs a leak detecting operation for detecting the value of an inter-peak voltage of the alternating current voltage of the development bias applied to the developing roller, at which the leak is generated, while changing the inter-peak voltage at a time different from that during the developing operation.

Abstract: A developing device includes a developer bearer to carry, by rotation, developer including toner and magnetic carrier to a development range facing a latent image bearer, and the developer bearer includes a magnetic field generator having multiple magnetic poles and a cylindrical developing sleeve to rotate and bear developer on an outer circumferential face thereof with magnetic force of the magnetic field generator provided inside the developing sleeve. The developing sleeve receives developing bias voltage including an AC component, and includes a base to maintain a cylindrical shape of the developing sleeve and a low friction surface layer including a material lower in friction coefficient with toner than a material of the base.

Abstract: A developing apparatus includes a developer carrying sleeve for carrying a developer to a position opposing an image bearing drum, wherein said sleeve is provided with a plurality of groove portions extending in an axial direction of said sleeve; and a developing bias voltage applying device for applying a developing bias voltage to said sleeve, wherein said bias voltage applying device is capable of outputting, as the bias voltage, a voltage of a waveform having a cyclic period including an AC bias portion comprising an AC component and a DC component superimposed thereto, and a blank portion following the AC bias portion and consisting of a DC component, wherein a width L (m) of the groove, a peripheral speed Vs (m/s) of said sleeve, and a duration t1 (s) of the blank portion in one cyclic period of the bias voltage satisfy L/Vs<t1.

Abstract: A two-component developer includes toner and a magnetic carrier. The two-component developer is used in a developing device including a circular cylindrical developer transporting member that is disposed so as to be separated by 125 ?m to 250 ?m from a latent image carrier that rotates. The two-component developer is used so as to satisfy a condition in which a width of a region where a magnetic brush contacts a surface of the latent image carrier is in a range of from 1.0 mm to 2.25 mm, and a condition in which a developer density of the region where the magnetic brush contacts the surface of the latent image carrier is in a range of from 0.75×10?6 to 1.50×10?6 g/m3.

Abstract: A developing device includes a developing roller, a magnetic roller, a capacitor, a transformer, a switching section, a control section, a temperature detecting section, and a storage section. When changing the duty ratio of a control signal in multiple sequential steps, the control section determines the resonance period based on the temperature and temperature characteristic data and changes the duty ratio of the control signal to the next step during a changing time slot which is one of the first and second halves of a period of voltage fluctuation of the capacitor based on the determined resonance period, the one half in which the current flowing through the switching section is smaller than in the other half of the period.

Abstract: An image forming apparatus can perform a toner collection mode that includes a first positive rotation step in which at the time of no image formation, in a state where the second bias applied to a toner carrying member is set at a higher voltage on the same polarity side as a toner than a first bias, a developer carrying member and the toner carrying member are rotated in the same direction as a direction at the time of image formation and a reverse rotation step in which after the first positive rotation step is performed, in a state where the first bias is set at a higher voltage on the same polarity side as the toner than the second bias, the developer carrying member and the toner carrying member are rotated in a reverse direction to the direction at the time of image formation.

Abstract: A power supply apparatus outputs a developing voltage in which a pulse wave shape at a time of positive amplitude is different from a pulse wave shape at a time of negative amplitude. Voltages are supplied from two switching regulators respectively to a bridge circuit for driving a transformer. Here, an absolute value of a difference between a drive frequency of a first switching regulator and a drive frequency of a second switching regulator is configured to be not less than an invisible frequency at which a banding cannot be recognized by humans.

Abstract: A developing device includes a developing roller, a magnetic roller opposed to the developing roller so as to form a magnetic blush, a high voltage power supply including a transformer having secondary side outputs one of which is connected to the developing roller while the other output is connected to the magnetic roller, so as to apply AC voltages to the developing roller and the magnetic roller, a detection portion for detecting occurrence of discharge between the developing roller and the photoreceptor drum, a restriction portion for restricting movement of toner from the magnetic roller to the developing roller, and a moving portion configured to move the restriction portion in discharge start voltage detection mode so as to restrict toner movement to the developing roller.

Abstract: A developing device includes a development roller, a magnetic roller, a transformer, a switching portion, output control portion and a capacitor. The development roller is opposite a photoconductor drum. The magnetic roller performs, with a magnetic brush, the supply of a toner to the development roller and the removal of the toner. The transformer generates an alternating-current voltage applied to the development roller. The switching portion passes and interrupts a current to the transformer. The output control portion stepwise changes, when a duty ratio in switching is changed, the duty ratio a plurality of times from a first duty ratio to a second duty ratio. The capacitor has one end connected to the transformer and the other end connected to the switching portion.

Abstract: The image forming apparatus includes an image carrier, a developer carrier, a magnetic field generation unit that is fixedly disposed in a hollow part of the developer carrier and includes a plurality of magnetic poles disposed in a circumferential direction of the developer carrier, a conductive member disposed so as to oppose a predetermined magnetic pole, of the plurality of magnetic poles, which is located odd-number pole upstream of a magnetic pole corresponding to a developing area D in a rotational direction of the developer carrier, a power source that can apply a voltage to the conductive member, a potential detection unit configured to detect pre-development and post-development potentials of a predetermined image formed on the image carrier, and a changing unit configured to change the voltage to be applied from the power source to the conductive member based on a detection result obtained by the potential detection unit.

Abstract: The developing device includes a toner layer formation control unit instructing a voltage control unit to set a first voltage difference to form a toner layer on a surface of a toner supporting rotator, a stripping control unit that instructs the voltage control unit to, in a toner layer stripping mode, set a second voltage difference that moves substantially an entire amount of toner composing the toner layer to a developer supporting rotator, and a density detection unit detecting the toner density on a transfer member onto which a toner image is primarily transferred. When the toner remains on a surface of the toner supporting rotator, the stripping control unit causes the toner to fly to the surface of the image carrier, while outputting an instruction adjusting the second voltage difference to the voltage control unit in order to reduce the toner density detected by the toner density detection unit.

Abstract: An image forming apparatus, wherein the packing density at a closest point where the first peripheral surface and the second peripheral surface are the closest to each other is within a range from 0.3 to 0.4; wherein a maximum magnetic flux density of a principal magnetic pole for generating the magnetic field for development is located in an upstream side from the closest point with respect to the specified direction and at a point where the packing density is equal to or greater than 0.2; and wherein a magnetic flux density of the principal magnetic pole at a point where the packing density is 0.2 in a downstream side from the closest point with respect to the specified direction is equal to or less than ½ of a magnetic flux density of the principal magnetic pole at a point where the packing density is 0.2 in the upstream side.

Abstract: Printers are provided in which a charge pattern is formed with a second area having a surface potential that is at least 30 percent less than a surface potential of an adjacent first area that creates an inter-area field between the first area and second area that extends into a portion of the first area that is proximate to the second area. A development station applies a first development field and a first toner is partially developed in the first area based upon the influence of the inter-area and first development fields. The charge pattern and first toner are further developed with a different second toner. The surface charge, the first toner and second toner have the same polarity.

Abstract: A developing device includes: a first developer carrier that is moved in a same direction as a moving direction of a latent image carrier at a faster linear speed than the latent image carrier; a second developer carrier that further develops the obtained toner image and that is moved in a same direction at a faster linear speed than the latent image carrier; and a bias output unit that outputs a developing bias to be applied to the second developer carrier. The developing bias includes a direct-current component and a non-rectangular alternating-current component whose waveform has a gentle edge at which a direction of an electric field between the second developer carrier and a background portion of the latent image carrier is changed to a direction in which the toner is moved from the background portion toward the second developer carrier.

Abstract: An image forming apparatus includes a rotating image carrier, a charging device, a latent image forming device, a developing device having a developer holder and developing a latent image as a visible image, a voltage application unit that generates a potential difference between the image carrier and the developer holder to form an electric field, by which toner is directed toward the latent image, in a developing region, and a transfer device that transfers the visible image of the image carrier to a medium, wherein the developer holder having a concavo-convex portion having a convex portion and a concave portion is provided in an outer surface thereof and formed such that the volume resistivity of a portion corresponding to the convex portion is set to be larger than the volume resistivity of a portion corresponding to the concave portion.

Abstract: An electronic development compensation method which is broadly applicable to SCMB development includes controlling image banding by actively correcting for mechanical development errors by modulating DC bias to a magnetic brush.

Abstract: A developing unit develops a latent image with a developing agent. A supply unit supplies, to the developing unit, a developing alternating current bias voltage with a waveform having a pulse period during which a rectangular wave is output and a blank period during which no rectangular wave is output. An input signal generation unit generates, as an input signal be supplied to a primary side of a transforming unit that forms the developing alternating current bias voltage, an input signal obtained by adding an additional pulse smaller in width than the rectangular wave in the pulse period at a timing to transit from the pulse period to the blank period.

Abstract: A developing device, includes a developer agitating member, an upstream side developing roller, and a downstream side developing roller; wherein a toner in a developer handed over from the upstream side developing roller to the downstream side developing roller has a volume average particle size larger than a volume average particle size of the toner in the developer conveyed by the upstream side developing roller to the facing position between the upstream side developing roller and a photoreceptor drum.

Abstract: A developing device includes a non-magnetic rotatable sleeve of a developer bearer to bear developer and a development electric field generator to generate a development electric field between the image bearer and the developer bearer by applying a development bias to the developer bearer. The developing bias is an AC bias generating an AC electric field therebetween. The magnetic carrier includes a plurality of fine particles each covered by a covering layer made of prescribed material having a volume resistivity equal to or more than 1012 [?·cm] having a prescribed particle diameter equal to or less than 100 [nm]. Each of the a plurality of fine particles has a total volume resistivity equal to or less than 105 [?·cm]. The magnetic carrier has a total volume resistivity equal to or more than 1012 [?·cm].

Abstract: An image forming apparatus of a representative configuration of the present invention includes a photosensitive drum, which carries an electrostatic latent image, and a developing sleeve, which carries a two-component developer and develops the electrostatic latent image on the photosensitive drum into a toner image. Moving directions of the photosensitive drum and the developing sleeve are opposite at an opposing portion in a developing device having a speed changing portion, which changes the driving speed of the developing sleeve, and a controller, which switches a target speed of the developing sleeve so that it is driven at a second velocity, before it is driven at the first velocity set in a lower speed mode, when the lower speed mode is executed in which the photosensitive drum is driven at a lower speed than in the normal image forming.

Abstract: A developing device includes a developing roller, a magnetic roller, a capacitor, a transformer, a switching section, a control section, a temperature detecting section, and a storage section. When changing the duty ratio of a control signal in multiple sequential steps, the control section determines the resonance period based on the temperature and temperature characteristic data and changes the duty ratio of the control signal to the next step during a changing time slot which is one of the first and second halves of a period of voltage fluctuation of the capacitor based on the determined resonance period, the one half in which the current flowing through the switching section is smaller than in the other half of the period.

Abstract: According to one embodiment, an image forming apparatus includes an image bearing member on which an electrostatic latent image is formed by exposure, an exposing device including a plurality of light sources and a plurality of lenses, which are provided along a longitudinal direction of the image bearing member, and configured to radiate light on the image bearing member, and a developing device arranged at a fixed distance apart from the image bearing member and configured to develop, according to application of a direct-current bias, the electrostatic latent image formed on the image bearing member into a visible image using a two-component developer.

Abstract: A developing device includes: an magnetic field generating unit that generates an magnetic field; and a cylindrical developer holder, to which a voltage is applied, that surrounds the magnetic field generating unit and rotates, the cylindrical developer holder: having an outer circumferential surface having a plurality of grooves that extend in a direction of a rotational axis, the outer circumferential surface being capable of holding developer including a magnetic substance by using the magnetic field generated by the magnetic field generation unit, an electrical resistance of an inner wall surface of each of the grooves being higher than an electrical resistance of the magnetic substance included in the developer; and supplying the developer to an image holder that holds an electrostatic latent image.

Abstract: A longitudinal end portion of an opposing magnetic member of a developer supporting rotator is positioned more longitudinally outside than a longitudinal end portion of a toner supporting side magnetic member. With respect to the opposing magnetic member facing the toner supporting side magnetic member and a downstream magnetic member disposed more downstream than the opposing magnetic member in a rotational direction, a magnetic force generated in a vicinity of both longitudinally end portions thereof is greater than a magnetic force generated longitudinally inside thereof. A housing includes a sealing portion that projects from a position facing a face at a longitudinal end portion of the developer supporting rotator toward the face, such that the sealing portion prevents the toner in a space between the face and an inner face of the housing from scattering outside.

Abstract: A developing device includes a developer supporting rotator, toner supporting rotator and voltage application unit. The toner supporting rotator is arranged opposite to a developer supporting rotator, supports toner supplied from the developer supporting rotator, and forms a toner layer by a magnetic brush. The voltage application unit causes the toner supported by the toner supporting rotator to an electrostatic latent image on a surface of an image carrier to develop it into a toner image. A longitudinal end portion of the toner supporting side magnetic member is positioned longitudinally more outside than a longitudinal end portion of the developer supporting side magnetic member. A surface of the second rotating sleeve positioned more outside than the end of the developer supporting side magnetic member is composed of a surface of low adherence with lower toner adherence and a higher dielectric constant than those of a surface positioned inside thereof.

Abstract: The developing device includes a toner layer formation control unit instructing a voltage control unit to set a first voltage difference to form a toner layer on a surface of a toner supporting rotator, a stripping control unit that instructs the voltage control unit to, in a toner layer stripping mode, set a second voltage difference that moves substantially an entire amount of toner composing the toner layer to a developer supporting rotator, and a density detection unit detecting the toner density on a transfer member onto which a toner image is primarily transferred. When the toner remains on a surface of the toner supporting rotator, the stripping control unit causes the toner to fly to the surface of the image carrier, while outputting an instruction adjusting the second voltage difference to the voltage control unit in order to reduce the toner density detected by the toner density detection unit.

Abstract: An image forming apparatus includes: an image bearing member; an electrostatic image forming device; and a developer carrying member. The developer carrying member is provided so as to be rotated in a direction opposite to a rotational direction of the image bearing member at a peripheral speed higher than that of the image bearing member. When the peripheral speed of the image bearing member is Vp (m/sec), the peripheral speed of the developer carrying member is Vs (m/sec), and a time, of movement of the developer from the surface of the developer carrying member to the image bearing member, actually measured in a gap between the image bearing member and the developer carrying member is Tsd (sec), the peripheral speeds Vp and Vs and the time Tsd satisfy the following relationship: (Vs?Vp)×Tsd<3×105 (m).

Abstract: An image forming apparatus has a first voltage application section for applying a first bias to a magnetic roller, a second voltage application section for applying a second bias to a developing roller, and a controller for controlling the voltages of the first and second voltage application sections and the driving/rotating of the magnetic roller and the developing roller. When no image formation is taking place, the controller can execute a toner collection mode in which, with the first and second biases set at the same potential and the second bias set lower than the voltage applied to an image carrying member, the magnetic roller is rotated in the direction reverse to that in which it is rotated during image formation.

Abstract: A developing device includes a developing roller, a magnetic roller, a capacitor, a transformer, and a switching portion. The magnetic roller supplies toner to the developing roller or takes off the toner from the same. The capacitor is connected to a primary of the transformer, and the developing roller is connected to a secondary of the same. During a period while the voltage between electrodes of the capacitor is changing, the switching portion changes the duty ratio in a predetermined second time slot in which current flowing in the switching portion is smaller than that flowing in a first time slot.

Abstract: An image forming apparatus has: a photoconductive drum that rotates; a developing roller that carries toner to be charged and to which a first voltage application portion outputting an AC voltage is connected; a contact member that makes contact with the photoconductive drum to remove residual toner; a detection portion for detecting occurrence of electric discharge between the developing roller and the photoconductive drum; and a developing unit that feeds toner to the developing roller, that supports the developing roller opposite the photoconductive drum with a gap secured in between, and that feeds toner to the developing roller with prescribed timing and for a prescribed time during electric discharge detection.

Abstract: A hybrid developing carrier, comprising a resin layer formed on an outermost surface, wherein the surface of said resin layer is provided with sites formed of an inorganic compound having basic points or acidic points and sites where the resin forming the resin layer is exposed, a hybrid developing device equipped with the hybrid developing carrier, and an image-forming apparatus equipped with the hybrid developing device.

Abstract: A developing device includes a development roller, a magnetic roller, a transformer, a switching portion, output control portion and a capacitor. The development roller is opposite a photoconductor drum. The magnetic roller performs, with a magnetic brush, the supply of a toner to the development roller and the removal of the toner. The transformer generates an alternating-current voltage applied to the development roller. The switching portion passes and interrupts a current to the transformer. The output control portion stepwise changes, when a duty ratio in switching is changed, the duty ratio a plurality of times from a first duty ratio to a second duty ratio. The capacitor has one end connected to the transformer and the other end connected to the switching portion.