Abstract: The invention provides an electronic photographing apparatus using a two-component developer as a mixture of a toner and a carrier as well as a development unit including a developer roll having magnetic poles therein. The electronic photographing apparatus includes a development bias power source for applying to the developer roll a development bias voltage where an AC voltage is superimposed on a DC voltage. The electronic photographing apparatus develops a latent image on a photosensitive body by using toner to form an image, characterized in that the ratio of the volume of the carrier to a space sandwiched between the developer roll and the photosensitive body is set within a range from 32 percent to 46 percent and that that the resistivity of the carrier under a field strength of 2000 V/cm is set to 3×1010 &OHgr;cm or more.

Abstract: In a magnet brush type developing method of the present invention, at least one position where brush chains formed by magnetic carrier grains rise exists in a portion where an electric field formed between a facing zone where an image carrier and a developer carrier face each other has a strength E (V/m) expressed as:

Abstract: An image forming apparatus in which the flux density of a main magnetic pole for development has an attenuation ratio of 40% or above in the normal direction is disclosed. Assume that a period of time of T1 is necessary for a photoconductive element to move by a single dot at a nip for development. Also, assume that, in a single period of an alternating electric field applied to a developing sleeve as a bias, the duration of an electric field causing toner to move toward the photoconductive element is T2. Further, assume that the duration of an electric field causing the toner to move toward the sleeve is T3. Then, a relation of T1>T2>0 or a relation of T1>T3>0 holds.

Abstract: An image forming apparatus of the present invention includes a bias power supply for applying a bias VB to a developer carrier on which a developer is deposited. A charge potential deposited on an image carrier, which faces the developer carrier for forming a latent image thereon, is 400 V or below in absolute value.

Abstract: An image forming apparatus of the present invention includes a developing device including a rotatable, nonmagnetic developer carrier and a magnetic field forming device. In a developing region where the developer carrier faces an image carrier, the magnetic field forming device causes a developer made up of toner and magnetic grains to rise on the developer carrier in the form of a magnet brush. In the developing region, the magnet brush on the developer carrier is caused to move at a higher speed than the surface of the image carrier in the same direction as and in contact with the surface of the image carrier, thereby developing the latent image. The toner of the developer is magnetic toner. Flux density set up in the developing region outside of the surface of the developer carrier in a normal direction has an attenuation ratio of 50% or above.

Abstract: A method of developing a latent electrostatic image using a two-component developer system, having a ratio (Vr/Vp) ranges 1.2<(Vr/Vp)<3 where the (Vp) is a linear speed (Vp)[m/sec] of a photosensitive member and the (Vr) is a linear speed (Vr) [m/sec] of a developing sleeve, and applying a biased direct-current (VB) [by volt] wherein; a developing gap(Gp)[cm] as a distance at the nearest point between a photosensitive member and a developing sleeve is less than or equal to 0.6 mm, a ratio(&rgr;p/&rgr;a) satisfies an expression (&rgr;p/&rgr;a)<0.

Abstract: To avoid developing ghost and selective developing without complicating a developing apparatus and to supply surly charged toner to a developing roll while unevenness of images is not generated to obtain stable images for a long time even when continuous printing, a method for developing in a hybrid developing apparatus is provided, which is characterized in that a data amount of each image, which an image forming apparatus prints and a number of paper sheets passed are detected and that an interval of the action of recovering and exchanging a toner layer on the developing roll to the magnetic roll after printing (between paper sheets) is variably set in accordance with a printing coefficient determined by the data amount and the number of paper sheets passed and further, a method for developing in a color tandem-type image forming apparatus provided with a plurality of the hybrid developing apparatuses for all different colors of toner, which are disposed along the moving direction of a transfer medium of im

Abstract: An image transfer apparatus with the capacity to reduce or clean wire history. The cleaning is performed by supplying a voltage burst to shift, relative to nominal, the D.C. component of the electrode bias relative to the electrical bias of the donor member during the movement of the inter-imaging region through the development zone. A voltage shift may also be applied to electrically bias the donor member relative to the photoreceptor belt during the movement of the inter-imaging region through the development zone. These voltage shifts may be conducted individually or simultaneously.

Abstract: In an image forming apparatus including a developing device, an inequality of 1≦(&agr;/100)×Vr×Hr1/3<3.5 is satisfied, wherein Vr denotes the peripheral speed ratio of an outer circumferential surface of a developer carrying member to the outer circumferential surface of an image carrying member, Hd denotes a spacing of the outer circumferential surface of the developer carrying member to the outer circumferential surface of the image carrying member, Hh denotes an average value of a height of a magnetic brush layer, Hr denotes a ratio of an average value of the height Hh to the spacing Hd, and &agr; (%) denotes a coverage ratio of an area of the magnetic brush layer to cover the outer circumferential surface of the developer carrying member to the outer circumferential surface of the developer carrying member.

Abstract: A developing device having a plurality of sleeves is provided to be able to perform a high-speed development. The developing device is provided to be able to prevent the abnormal image, for example, blur at the rear end of a solid image or a thinning of the line image. An AC bias is effectively applied, so that the base contamination is suppressed to obtain a smooth image without obvious grains. Among the plural sleeves, a bias towards the photoreceptor side is applied on an upstream-side sleeve, and a bias in the reverse direction (towards the sleeve side) is applied to the downstream-side sleeve. Alternatively, a bias with a low frequency is applied to the upstream-side sleeve and a bias with a high frequency is applied to the downstream-side sleeve. In addition, a bias with a large frequency amplitude is applied to the upstream-side sleeve, and a bias with a small frequency amplitude is applied to the down stream-side sleeve.

Abstract: A developing device of the present invention includes a developing roller provided with a plurality of magnetic poles. The magnetic poles include a main pole and two auxiliary poles positioned at both sides of the main pole for helping the main pole form a magnetic force. The auxiliary poles reduce the half width of the main pole. An AC-biased DC bias for development is applied to the developing roller and disturbs carrier grains close to the developing roller. Images free from various defects including granularity and local omission are achievable with the developing device.

Abstract: A method of developing a latent electrostatic image using a two-component developer system, having a ratio (VrNVp) ranges 1.2<(Vr/Vp)<3 where the (Vp) is a linear speed (Vp) [m/sec] of a photosensitive member and the (Vr) is a linear speed (Vr) [m/sec] of a developing sleeve, and applying a biased direct-current (VB) [by volt] wherein; a developing gap(Gp)[cm] as a distance at the nearest point between a photosensitive member and a developing sleeve is less than or equal to 0.6 mm, a ratio(&rgr;p/&rgr;a) satisfies an expression (&rgr;p/&rgr;a)<0.

Abstract: The development is performed under a condition that |Q2|−|Q1|/|Q1≦±0.45. Here, Q1 denotes an average amount of charge on toner held on a development roller and carried toward a development region immediately before development. Q2 denotes an average amount of charge on toner immediately before development held and carried toward the development region in the state immediately after development of an electrostatic latent image on a development drum. This is effective to allow the amount of charge q/m on toner held on the development roller to have a variation rate of 45% or below and an afterimage rate R within 2%.

Abstract: When image formation is performed by an apparatus comprising: a magnetic roll for generating a magnetic brush by carrier having toner adhering triboelectrically thereto, a developer roll on the surface of which a thin layer of the toner supplied by the magnetic brush is formed, and a photoreceptor onto which the toner of thin layer jumps selectively in accordance with the latent image thereon; positively chargeable toner of which charge amount is controlled in 5˜20 &mgr;C/g is used, the surface potential of the photoreceptor is set to a range above 0 to 250 V, and the after exposure potential which is the potential right after the photoreceptor is exposed is in a range of 0˜ to 100 V.

Abstract: An image forming apparatus includes a developing device including plural developer supporters provided opposite to a photoconductor, a development bias applying unit for applying a development bias voltage generated by superimposing an AC voltage on a DC voltage to each of the developer supporters, and a phase shifter for shifting a phase of the AC voltage in the development bias voltage in each of the developer supporters.

Abstract: In an image forming apparatus having a reverse development system and using a two-component developer, respective potentials applied when charging an image bearing member and when applying a development bias to a developer bearing member are attenuated when the image bearing member is driven for an operation other than an image forming operation, compared to respective level of potentials applied when the image bearing member is driven for the image forming operation. Thus, an occurrence of an adhesion of a carrier to an image bearing member is reduced to produce a high quality image, when a power switch of the apparatus is turned off or when a door of the apparatus is opened while the image bearing member is driven for an operation other than the image forming operation, or when the apparatus is activated again after the power switch is turned off.

Abstract: An image forming apparatus of the present invention includes an image carrier made up of a conductive base and photoconductive layer and a toner carrier to which a bias for development is applied. The toner carrier conveys toner deposited thereon to a developing position where the toner carrier faces the image carrier, thereby developing a latent image formed on the image carrier. The apparatus effects low-voltage development that protects the image carrier from electrostatic fatigue, obviates background contamination, and realizes image density as high as 0.5 ×10−3 g/cm2 or above in terms of the amount of toner deposition. Further, the apparatus implements faithful development of the latent image by reducing the edge effect. An image forming process unit removable from the apparatus is also disclosed.

Abstract: In an image forming apparatus for charging a photosensitive body, changing the light exposure amount in at least three levels at exposure to light, thereby forming an electrostatic image made up of a high-potential part, a low-potential part, and an intermediate-potential part therebetween on the photosensitive body, and normally developing and inversely developing the electrostatic image using toners different in charge polarity for forming two types of toner images on the photosensitive body, a first developer used with a first toner image developing unit has electric resistance changed within 10% in the change range of applied voltage to the developer as the difference between a surface potential of the photosensitive body and a developing bias voltage.

Abstract: A developing device includes a rotatable developer carrying member for carring a developer; a magnet roller provided in the developer carrying member; a first electrode portion connected electrically with the developer carrying member, the first electrode portion being rotatable with the developer carrying member; a second electrode portion provided with a contact portion in sliding contact with the first electrode portion, the contact portion being disposed outside a longitudinal end portion of the magnet roller substantially at a center of rotation of the developer carrying member.

Abstract: A developing device for an image forming apparatus includes a developing roller for conveying toner deposited thereon to a developing region where it faces a photoconductive element. A magnet brush roller conveys a two-ingredient type developer, which consists of toner and magnetic particles, deposited thereto to a toner supplying region where it faces the developing roller. In the toner supplying region, only the toner is supplied from the magnet brush roller to the developing roller. The distribution of the number of toner particles for an amount of charge differs from the developing roller to the magnet brush roller.

Abstract: A developing apparatus has a developer carrying body provided to face an image bearing body. The developer carrying body carries and conveys a developer having toner and carrier to a developing region. A bias applying device applies a developing bias to the developer carrying body, wherein the bias applying device applies to the developer carrying body the developing bias having periodically a voltage portion having alternately a first voltage to generate an electric field to direct toner from the developer carrying body to the image bearing body and a second voltage to generate an electric field to direct the toner from the image bearing body to the developer carrying body and a pause portion to pause applying the alternate voltage, wherein T1 and T2 have a relationship of T1>T2, where T1 is as an applying time period of the first voltage and T2 is an applying time period of the second voltage.

Abstract: An image forming apparatus in which the flux density of a main magnetic pole for development has an attenuation ratio of 40% or above in the normal direction is disclosed. Assume that a period of time of T1 is necessary for a photoconductive element to move by a single dot at a nip for development. Also, assume that, in a single period of an alternating electric field applied to a developing sleeve as a bias, the duration of an electric field causing toner to move toward the photoconductive element is T2. Further, assume that the duration of an electric field causing the toner to move toward the sleeve is T3. Then, a relation of T1>T2>0 or a relation of T1>T3>0 holds.

Abstract: An image forming apparatus of the present invention includes a developing device including a rotatable, nonmagnetic developer carrier and a magnetic field forming device. In a developing region where the developer carrier faces an image carrier, the magnetic field forming device causes a developer made up of toner and magnetic grains to rise on the developer carrier in the form of a magnet brush. In the developing region, the magnet brush on the developer carrier is caused to move at a higher speed than the surface of the image carrier in the same direction as and in contact with the surface of the image carrier, thereby developing the latent image. The toner of the developer is magnetic toner. Flux density set up in the developing region outside of the surface of the developer carrier in a normal direction has an attenuation ratio of 50% or above.

Abstract: In an image forming apparatus for charging a photosensitive body, changing the light exposure amount in at least three levels at exposure to light, thereby forming an electrostatic image made up of a high-potential part, a low-potential part, and an intermediate-potential part therebetween on the photosensitive body, and normally developing and inversely developing the electrostatic image using toners different in charge polarity for forming two types of toner images on the photosensitive body, a first developer used with a first toner image developing unit has electric resistance changed within 10% in the change range of applied voltage to the developer as the difference between a surface potential of the photosensitive body and a developing bias voltage.

Abstract: When image formation is performed by an apparatus comprising: a magnetic roll for generating a magnetic brush by carrier having toner adhering triboelectrically thereto, a developer roll on the surface of which a thin layer of the toner supplied by the magnetic brush is formed, and a photoreceptor onto which the toner of thin layer jumps selectively in accordance with the latent image thereon; positively chargeable toner of which charge amount is controlled in 5˜20 &mgr;C/g is used, the surface potential of the photoreceptor is set to a range above 0 to 250 V, and the after exposure potential which is the potential right after the photoreceptor is exposed is in a range of 0˜ to 100 V.

Abstract: An image forming apparatus develops a latent image formed on an image carrier with a developer that forms a magnet brush on a developer carrier. The developer carrier is made up of a sleeve and a stationary magnet roller accommodated in the sleeve. The magnet roller includes a main pole for causing the developer to form the magnet brush and auxiliary poles for helping the main pole exert a magnetic force. An electric field including an oscillation component is formed between the image carrier and the developer carrier. A particular ratio is set up between a distance between the image carrier and the developer carrier, as measured at the boundary of a nip, and the shortest distance between them, between the above shortest distance and the shortest distance between the developer carrier and a metering member, or between the shortest distance between the image carrier and the developer carrier and the amount of developer scooped up to the image carrier.

Abstract: An image forming apparatus includes a developing device including plural developer supporters provided opposite to a photoconductor, a development bias applying unit for applying a development bias voltage generated by superimposing an AC voltage on a DC voltage to each the developer supporter, and a phase shifter for shifting a phase of the AC voltage in the development bias voltage in each the developer supporter.

Abstract: A developing device includes a frame; a developer carrying member including a first cylindrical portion and a second cylindrical portion provided at an end of the first cylindrical portion; and a magnet provided in the developer carrying member, extending from inside of the developer carrying member to outside thereof. A first electroconductive portion is supported on the magnet; and a second electroconductive portion is electrically connected with an inner surface of the first cylindrical portion and in slidable contact with the first electroconductive portion. A third electroconductive portion includes a first contact portion electrically connected with the first electroconductive portion and a second contact portion. The third electroconductive portion is electrically connected with an electrical contact of a main assembly of an image forming apparatus so that a developing bias is applied to the developer carrying member.

Abstract: An image forming apparatus uses a toner wherein when a weight average diameter of the initial toner in a developing device is set to D1, and a weight average diameter of a toner forming an initial toner image on an image bearing member is D2, such that D1≧D2 is satisfied.

Abstract: An object of the present invention is to provide a compact developing device. The present invention provide a developing device detachably attachable to an image forming apparatus, which has a developer carrying member, a developer regulating member, a conductive support member, a driving gear, a first electrode member which is provided at a driving side of the developer carrying member and to which developing voltage is applied and which is electrically communicated with the conductive support member, and a second electrode member for electrically communicating between the conductive support member and a non-driving side of the developer carrying member.

Abstract: A developing device includes a rotatable developer carrying member for carring a developer; a magnet roller provided in the developer carrying member; a first electrode portion connected electrically with the developer carrying member, the first electrode portion being rotatable with the developer carrying member; a second electrode portion provided with a contact portion in sliding contact with the first electrode portion, the contact portion being disposed outside a longitudinal end portion of the magnet roller substantially at a center of rotation of the developer carrying member.

Abstract: An image forming apparatus includes an image bearing member for carrying an electrostatic image, a contact charger for electrically charging the image bearing member while contacting to a surface of the image bearing member, the contact charger forming an oscillating electric field having a frequency of 100-600 Hz; a developer for developing the electrostatic image on the image bearing member with a developer comprising toner and a carrier having a volume resistivity value of 106-1010 &OHgr;.

Abstract: An image forming method includes (i) a charging step of using a charging device including conductive magnetic particles, a rotatable conductive-magnetic-particle carrying member for carrying and conveying the conductive magnetic particles, and a plurality of magnetic-field generation means provided within the conductive-magnetic-particle carrying member, and charging a surface of an image bearing member by applying a voltage to the conductive-magnetic-particle carrying member and causing the conductive magnetic particles to contact the image bearing member, (ii) a latent-image forming step of forming an electrostatic latent image on the charged surface of the image bearing member, and (iii) a developing step of using a developing device facing the image bearing member and including a two-component developer including a toner and magnetic carrier particles, a developer carrying member for carrying the two-component developer, and a plurality of magnetic-field generation means provided within the developer carr

Abstract: An image forming apparatus, including: a charger, arranged around an image carrier, for charging a surface of the image carrier; an exposure device, arranged around the image carrier, for exposing the surface of the image carrier, after it is charged by the charger, and for forming an electrostatic latent image on the surface of the image carrier; a developer device, having a developer carrier and arranged around the image carrier, for carrying developer with which the electrostatic latent image is developed so as to obtain a developed image; and a transfer device, arranged around the image carrier, for transferring the developed image onto a transfer material.

Abstract: A developing apparatus in which a voltage application means which applies a voltage varying with a cycle T between a first voltage value and a second voltage value, and a transition time T1 from the first voltage value to the second voltage value and a transition time T2 from the second voltage value to the first voltage value satisfy: 0.3T<T1<0.5T and T2<0.1T.

Abstract: A developing apparatus includes a developer bearing member for bearing and carrying developer to a developing area. A developer is borne on the developer bearing member, wherein the developer has a weight average particle size not exceeding 6.5 &mgr;m and contains an external additive of a charging polarity opposite to that of the developer. A voltage application device applies a voltage to the developer bearing member, wherein the voltage including at least a first voltage V1 for acting on the developer in a direction from the developer bearing member toward an image bearing member and a second voltage V2 for acting on the developer in a direction from an image bearing member toward said developer bearing member, and a charged potential VL of the image bearing member, a latent image potential VD a distance H between the developer bearing member and an image bearing member, and wherein the voltages V1 and V2 satisfy a following relationships: |V1−VL|/H≦3.

Abstract: An apparatus for non-interactive, dry powder development of electrostatic Images composed of solid areas and fine lines areas on an imageable surface including a housing containing developer material; a first magnetic roll, spaced a first predefined distance from the image, for transporting the developer material from the housing to develop solid areas of the image, the magnetic roll including an magnetic core and a cylindrical sleeve enclosing and rotating about the magnetic core; and a second magnetic roll, spaced a second predefined distance from the image, for transporting the developer material from the housing to develop fine line areas of the image, the magnetic roll including an magnetic core and a cylindrical sleeve enclosing and rotating about the magnetic core.

Abstract: The present invention relates to a development density adjusting method in which development density is adjusted by varying ratio of application time of a voltage having the first voltage value to application time of a voltage having the second voltage value in one period, and difference between a potential of the developer bearing member and a potential of the electrostatic latent image, when the voltage having the first voltage value is applied to the developer bearing member.

Abstract: An image forming apparatus includes an image bearing member for bearing an electrostatic image; a developer carrying member for carrying a developer and for forming a developing zone with the image bearing member, wherein the developer is externally added with additive having a charging polarity opposite from that of the developer; a voltage applying device for applying a developing voltage to the developer carrying member; voltage a control device for controlling the developing voltage so as to change force for directing the additive toward a non-image portion of the image bearing member in accordance with a number of image forming operations.

Abstract: The invention relates to an image forming device and method therefor solving the subject matter that, if the linear speed of the developing solution carrier for that of the latent image carrier is lowered in order to secure the development capacity, the line image is deteriorated and there occurs a troublesome matter such as the blanking at the halftone rear edge. Such image forming device of the present invention is provided with a two-component magnetic brush type developing apparatus in which the developing bias composed of the DC bias and the AC bias superposed thereon is applied to the developing apparatus, and the latent image formed on the latent image carrier is developed with the two-component developing solution including the magnetic toner and the magnetic carrier. In the image forming device, the magnetic substance including percentage of the magnetic toner is set to 5 wt %.about.35 wt %.

Abstract: A developing apparatus according to the present invention for developing an electrostatic latent image formed on an image carrying member has a developer carrying member arranged opposite to an image carrying member and holding a developer, and a voltage applying device applying an AC voltage to the developer carrying member, wherein the AC voltage has a first peak potential and a second peak potential, the first peak potential being a peak potential on the side of development for supplying the developer to the image carrying member, the second peak potential being a peak potential on the side of recovery for returning the developer to the developer carrying member, and a voltage waveform of the AC voltage always has two straight line portions which differ in slopes while changing from the first peak potential to the second peak potential and/or from the second peak potential to the first peak potential.

Abstract: In a developing device and a developing method in which a developer containing toners and carriers is conveyed to a developing area opposite to an image carrying member with it being held on the surface of a developer carrying member, and the toners in the developer are supplied to the electrostatic latent image formed on the image carrying member upon exerting an electric field between the developer carrying member and the image carrying member, to perform development, an impedance Zs (.OMEGA./cm.sup.2) per unit area of the surface of said developer carrying member and an impedance Zc (.OMEGA./cm.sup.2) of said carriers satisfy the condition of 1.8.times.10.sup.5 .ltoreq.Zs.multidot.Zc.ltoreq.2.1.times.10.sup.9.

Abstract: An image forming method for operating a moving image-bearing member bearing an electrostatic latent image and a plurality of developing units disposed near the image-bearing member and being selectively operable is described.

Abstract: In image forming method comprising an exposure step of forming an electrostatic latent image and a developing step of developing the electrostatic latent image, a developer comprises a magnetic carrier and a toner; a developing curve of the developer at the time when the developer is used has a saturated characteristic, the developing curve being as expression of the relation between the amount of toner transferred to the latent image support member and contrast potential, the contrast potential being determined by the developing bias potential applied to the developer support member and the potential of an exposed portion of the latent image support member; a proportion of the toner in the developer is in a range from 5 to 10% by weight; a time constant of the developer is less than or equal to 40 msec; and the developing step comprises applying developing bias voltage to the developer support member such that an amount of the toner transferred to the latent image support member reaches a saturated range.

Abstract: A developing apparatus has a developer bearing member disposed in opposed relationship with an image bearing member bearing an electrostatic image thereon with a gap of 6.times.10.sup.-4 m or less with respect to the image bearing member, and bearing and conveying a developer thereon. The developer bearing member is moved in a direction opposite to the direction of movement of the image bearing member in the portion opposed to the image bearing member, and the developer has a non-magnetic toner and a carrier of which the magnetization rate in a magnetic field of 1000 gauss is equal to or greater than 30 emu/cm.sup.3 and equal to or less than 200 emu/cm.sup.3 and the specific resistance at electric field intensity of 5.times.10.sup.4 V/m is 10.sup.12 .OMEGA.cm or greater. The developing apparatus further has applying means for applying a bias voltage having a vibration component to the developer bearing member.

Abstract: A plurality of electrostatic images are formed on a moving tensioned belt formed with an electrically conductive base having a non-conductive image-carrying surface layer. The images are developed by passing the belt through toner development stations, each of which includes a development unit including a magnetic roller and a backing member, in opposed position to the magnetic roller, over which the belt passes. Under non-ideal conditions, the image quality in terms of image density and uniformity of image density and rendition of sharp image transitions, is substantially improved by applying an alternating electrical field between the magnetic roller and the belt, with a peak-to-peak voltage greater than 800 volts.

Abstract: An image forming apparatus including, an image bearing member capable of having a latent image formed thereon, and a developer bearing member that bears a developer comprising a toner and a carrier, wherein a latent image formed on the image bearing member is developed by a non-contacting method under application of a vibrating electric field, so that the toner is transferred from the developer bearing member toward the image bearing member, and wherein the following relation holds:1.0.times.10.sup.-4 <t.sub.1.sup.2 /L.sub.T <1.0.times.10.sup.-3 (sec.sup.2 /m),where t.sub.1 represents a phase period during which a toner particle of the toner is transferred from the toner bearing member to the latent image during application of the vibrating electric field and L.sub.T represents a weight average particle diameter of the toner particles.

Abstract: An image forming apparatus includes an image bearing member for bearing an electrostatic latent image; a first developing device for developing the electrostatic latent image on the image bearing member; a second developing device, faced to the image bearing member and having a movable developer carrying member for carrying toner and carrier, for effecting development after a first developed image provided by the first developing device passes through a position where the developer carrying member is faced to the image bearing member; and a preventing device for forming an alternating electric field between the developer carrying member and the image bearing member, while the second developing device is at reset to prevent the carrier of the second developing device from rubbing the first developed image.

Abstract: A developing device capable of producing images having excellent image density and texture without density irregularities, which includes a developer carrier disposed opposite the image carrier and transporting a developer hell on its surface to a developing region and a voltage supplying unit which applies an alternating current voltage to the developer carrier, the alternating current voltage having a first frequency during a first action period and a second frequency during a second action period, the first action period and the second action period being alternately repeated, the second frequency being higher than the first frequency.

Abstract: An image forming apparatus includes an image support which supports an electrostatic latent image on a surface of the image support. A developing unit has a developing agent support which retains a developing agent, including a toner and carriers, contained in the developing unit. The developing unit converts the latent image on the image support into a toner image by causing the toner to adhere to the surface of the image support. A developing bias supplying unit supplies a developing bias voltage to the developing agent support of the developing unit, the developing bias voltage being one of a DC bias voltage and an AC bias voltage. A timer measures a non-driven period of the developing agent in the developing unit.