Abstract: An object of the present invention is to provide an image forming apparatus and a method for forming an image that are capable of controlling the consumption of opposite polarity particles and suppressing the reduction of toner charge amount due to the carrier deterioration and can form high quality images over a long period of time even in the case where large quantities of images with small image area ratio are printed. The image forming device includes a developer further including the opposite polarity particles, a developer carrying member, a toner carrying member, and a voltage applying section for applying bias voltage overlapped with alternating current between the toner carrying member and the image carrying member, wherein the bias voltage overlapped with alternating current is a vibrating waveform including a trapezoidal wave, or a vibrating waveform in which a blank is inserted during application of a reverse development side voltage component.

Abstract: An image forming apparatus includes: a photoconductive drum; a developing roller that is arranged opposite the photoconductive drum and that carries toner; a detecting portion that detects an occurrence of electrical discharge between the developing roller and the photoconductive drum; a control portion that controls the apparatus, that receives an output of the detecting portion and then recognizes the occurrence of the electrical discharge; a direct voltage applying portion that is connected to the developing roller; and an alternating voltage applying portion that, when an electrical discharge detection operation is performed in which the occurrence of the electrical discharge is detected by use of the detecting portion with the alternating voltage applied to the developing roller changed step by step, applies the alternating voltage having a duty ratio and a frequency different from the duty ratio and the frequency for an image forming operation so that the electrical discharge is made to occur simply in

Abstract: A developing device, process cartridge, and image forming apparatus that use ETH development, and are capable of forming good multi-color images with a simple construction, and are capable of preventing the dispersal of powder. The developing device is for developing latent images on a latent image carrying member by applying powder to the latent image carrying member, and comprises: a transport member disposed in opposition to the latent image carrying member and having a plurality of transport electrodes that generate a progressive wave electric field to move the powder; a voltage supply device for applying a multi-phase voltage to the transport electrodes; and a transport member surface potential determination device for determining the surface potential of the transport member.

Abstract: There is provided an image forming apparatus capable of realizing Improvement of an image density by improving dot reproducibility and reducing fog as well. An alternating voltage is applied to a development sleeve so that a first period during which a first peak-to-peak voltage Vpp(1) is applied and a second period during which a second peak-to-peak voltage Vpp(2) that is lower than the first peak-to-peak voltage is applied are repeated alternately. The alternating voltage to be applied is applied so that a development-side potential to move toner from the development sleeve to a photoreceptor and an opposite development-side potential to move toner from the photoreceptor to the development sleeve alternate with each other A frequency of the second period is lower than a frequency of the first period.

Abstract: The present invention provides a developing device that is provided with: a developer containing a toner and a carrier; a first transporting member placed at an opening portion of a developer vessel used for housing the developer; a second transporting member that faces the first transporting member with a first area interposed therebetween, and also faces an electrostatic latent image-supporting member with a second area interposed therebetween; a first electric-field-forming unit that forms a first electric field between the first transporting member and the second transporting member; and a second electric-field-forming unit that forms a second electric field between the second transporting member and the electrostatic latent image-supporting member, and in this structure, the first electric field, formed between the first transporting member and the second transporting member, includes at least an ac electric field, and the second transporting member has a surface that is charged to the same polarity as t

Abstract: There is provided an image forming apparatus capable of realizing improvement of an image density by improving dot reproducibility and reducing fog at the same time. An alternating voltage is applied to a development sleeve so that a first period during which a first peak-to-peak voltage Vpp(1) is applied and a second period during which a second peak-to-peak voltage Vpp(2) that is lower than the first peak-to-peak voltage is applied are repeated alternately. The alternating voltage to be applied is applied so that a development-side potential to move toner from the development sleeve to a photoreceptor and an opposite development-side potential to move toner from the photoreceptor to the development sleeve alternate with each other. The potential to be finally applied in the first period is preferably the development-side potential.

Abstract: An image forming apparatus uses a two-component developer containing a toner and a carrier. The apparatus has a latent image bearer for bearing an electrostatic latent image. A toner bearer bears the toner to be conveyed to a development region to develop the electrostatic latent image. A developer bearer bears the two-component developer and supplies the toner to the toner bearer. A regulator sets the thickness of a toner layer carried on the toner bearer to 6 ?m to 15 ?m and sets a difference between a half width of a first toner charge number distribution as a number distribution of the charge amount of the toner carried on the toner bearer and that of a second toner charge number distribution as a number distribution of the charge amount of the toner in the two-component developer carried on the developer bearer to 0.8 (10?10 C/m) or smaller.

Abstract: An image forming apparatus includes a rotatable image bearing member; a first rotatable developer carrying member for carrying a magnetic one component developer to a first developing position to develop a latent image on the image bearing member; a second rotatable developer carrying member, provided downstream of the first developer carrying member with respect to a rotational direction of the image bearing member, for carrying the magnetic one component developer to a second developing position to develop a latent image on the image bearing member. The second developer carrying member is rotatable in the same rotational direction as the first developer carrying member. The image forming apparatus further includes, a first magnetic member provided in the first developer carrying member and having a plurality of magnetic poles, and a second magnetic member provided in the second developer carrying member, also having a plurality of magnetic poles.

Abstract: A first bias Vslv is applied to a development roller 22 and a second bias Vmag is applied to a magnetic roller 23 to perform development; after completion of development, without changing the setting of Vslv, of the AC component Vpp2 of Vmag, the peak voltage value Vpp2 (max) at the side with the same polarity as toner is made lower than during a development period and development-residual toner on the development roller 22 is collected to prevent a lateral streak formed on photoconductor drums 1a to 1d during a non-development period.

Abstract: A development device in which abrasion of a developing roller can be reduced to expand the life of the device, and high-speed and high-quality images can be obtained stably over a long time. The developing roller is composed of an elastic body. An intermediate roller made of metal is disposed closely to the developing roller so as to face the developing roller. A magnetic roller is disposed closely to the intermediate roller so as to face the intermediate roller. A developer layer composed of a magnetic carrier and a toner is formed on the surface of the magnetic roller. The developer layer is carried to the intermediate roller side, and only the toner in the developer layer is transferred to the intermediate roller. A toner layer formed thus is transferred from the intermediate roller to the developing roller, and brought into contact with the surface of an image carrying member.

Abstract: A development station that improves toner halftone dot development over a wide range of environmental conditions includes a developer housing for retaining semi-conductive carrier particles and toner particles, a first magnetic roll having a stationary core with at least one magnet and a sleeve having longitudinal grooves that rotates about the stationary core of the first magnetic roll, a second magnetic roll having a stationary core with at least one magnet and a sleeve having longitudinal grooves that rotates about the stationary core of the second magnetic roll, an environmental sensor for generating an environmental condition signal, a variable voltage supply coupled to the first magnetic roll and the second magnetic roll, and a control circuit for adjusting an output level for the variable voltage supply.

Abstract: An image forming apparatus includes: an image carrying body; a latent image forming unit to form an electrostatic latent image on the image carrying body; a developing unit to develop the electrostatic latent image on the image carrying body to form a toner image, the developing unit including a developing agent carrying body to carry a developing agent in a development region, and a direct-current power supply and an alternating-current power supply, both applying a developing bias voltage to the developing agent carrying body, the developing bias voltage generated by superimposing a direct-current voltage to an alternating voltage; a printing rate detecting unit to detect a printing rate; and a control unit to control the alternating-current power supply, wherein the control unit controls an output of the alternating-current power supply based on a detection result of the printing rate detecting unit.

Abstract: An image forming apparatus and process cartridge which uses a two-component developer comprising a toner and a carrier. By using toner and carrier having a small-particle size, deterioration of the toner fluidity over time can be avoided, and further by maintaining stable toner charge even in a low-humidity environment, stable high-quality image formation can be achieved. The occurrence of adherence of carrier to the solid portions of the toner image is reduced in addition to the occurrence of adherence of carrier to the edge portions, and image abnormalities, toner scattering and the like are prevented.

Abstract: To provide a two-component developer and an image forming device which are excellent in stability of image density in formed images even when image formation is continued for a long time, by controlling non-electrostatic adhesion force between toner particle and a carrier or developing roll and maintaining the charge property of toner particle effectively. A two-component developer in which the surface of a toner particle and the surface of a carrier are each covered with a fluorine compound, wherein a ratio represented by (A2/A1) is adjusted to a value within a range of from 0.1 to 0.5 where the coverage with the fluorine compound on the surface of the toner particle is A1 and the coverage with the fluorine compound on the surface of the carrier is (A2).

Abstract: A two-component developer including toner and magnetic carriers is provided. The two-component developer is characterized in that when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 ?m thick layer of tetrafluoroethylene resin is provided to a conductive material, the number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member.

Abstract: The surface of a developing roller is coated with a phenol resin layer at a higher level in triboelectric series than a toner. A positively charged toner supplied from a magnetic roller onto the developing roller is negatively charged by friction with the phenol resin layer at the higher level in the triboelectric series. As a result, the positive charge of the toner is cancelled out, and the charge amount of toner per unit weight on the developing roller (Q/M)s decreases. Applying this principle, relationship between (Q/M)s and the charge amount of toner per unit weight on the magnetic roller (Q/M)m satisfies (Q/M)s<(Q/M)m.

Abstract: It is an object of the present invention to provide a process unit and an image forming apparatus in which generation of loss of image density due to flying off of developer and the edge effect occurring as a side-effect under developing conditions aimed at improving development performance can be reduced, even when a DC bias development system is adopted, and which can suppress developing density unevenness caused by impact occurring on contact of the teeth of gears in the drive system.

Abstract: An image forming apparatus and process cartridge which uses a two-component developer comprising a toner and a carrier. By using toner and carrier having a small-particle size, deterioration of the toner fluidity over time can be avoided, and further by maintaining stable toner charge even in a low-humidity environment, stable high-quality image formation can be achieved. The occurrence of adherence of carrier to the solid portions of the toner image is reduced in addition to the occurrence of adherence of carrier to the edge portions, and image abnormalities, toner scattering and the like are prevented.

Abstract: A developing apparatus having a developing sleeve provided with an elastic layer on its surface, and for developing an electrostatic image formed on an image bearing member with a mono-component magnetic toner having a mean degree of circularity of 0.965 or greater, a magnet provided in the developing sleeve, and a blade for regulating the amount of the developer carried on the developing sleeve satisfies the expressions |Br|/|B|?0.5 and Nsb/(Bs×R)?0.

Abstract: An image forming apparatus is provided with a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image formed on the photoconductive member by a first bias, and a magnetic roller for forming a magnetic brush thereon with a two-component developer and forming a thin toner layer on the developing roller by a second bias. If (D1) denotes the duty ratio of a first alternating-current bias included in the first bias and (D2) denotes the duty ratio of a second alternating-current bias included in the second bias, the duty ratios (D1, D2) satisfy the following relationship: D1>100?D2.

Abstract: An image forming apparatus has a photoconductive member on which a latent image is to be formed, a developing roller for developing the latent image on the photoconductive member by a first bias. A magnetic roller forms a magnetic brush thereon with a two-component developer and forms a thin toner layer on the developing roller by a second bias. The developing roller is aluminum with a surface treated for high resistance. The thickness (T) of the toner layer and the duty ratio (D1) of the first alternating-current bias satisfy relationships of the following equations for calculating the duty ratio (D1) using an application period of a voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: 7 ?m?T?13 ?m, and 35%?D1?70%.

Abstract: A developing device includes a developing housing which faces an image carrier on which an electrostatic latent image is carried and stores a developer which contains toner and magnetic carrier; a developer carrier that is disposed apart from the image carrier in the developing housing and carries and transports the developer; a developing bias applying unit that is disposed between the image carrier and the developer carrier and applies a developing bias comprising an AC component and a DC component which is superposed to a DC component; a volume resistivity detecting unit which detects a volume resistivity of the developer on the developer carrier; and a developing bias adjusting unit which sets the AC component of the developing bias to a reference value when the volume resistivity of the developer detected by the volume resistivity detecting unit falls within a given range, and corrects the AC component of the developing bias such that an image quality evaluation parameter falls within an allowable range

Abstract: A developing apparatus includes a developing roller for developing an image with a developer; a non-rotary magnet roll inside the roller; a blade; and an abutting member abutting against the roller, wherein the following expressions are satisfied: |Vs|>|Vdev|, |Br|/|B|?0.5, and L/(BH×R)?0.1, where |Vdev|: a DC component Vdev of a voltage applied to the roller, |Vs|: a DC component Vs of a voltage applied to the member, B(G): the magnetic flux density formed on the surface of the roller at the abutting position by the magnet roll, Br(G): the component of the magnetic flux density B(G) perpendicular to the surface of the roller, and L(mm): the abutting width between the roller and the member, BH(rad): the half value width of the component B?(G) horizontal to the surface of the roller, and R(mm): the radius of the roller.

Abstract: An image forming apparatus having a photosensitive drum bearing an electrostatic image, and a developing sleeve carrying a developer for developing the electrostatic image, the developing sleeve is in non-contact with the photosensitive drum, and is designed to be flexed so that the surface of the developing sleeve may go away from the surface of the photosensitive drum, and the rotation axis of the photosensitive drum and a straight line linking the centers of the cross-sections of the developing sleeve in a direction perpendicular to the developing sleeve at the both end portions may be in the skew relationship so that the value of the difference between the closest distance at the central portion of a maximum electrostatic image forming width and the closest distance at the both end portions thereof may be smaller than the value of the component of the flexure amount of the developing sleeve in the direction of the closest distance.

Abstract: A developing apparatus, a process cartridge and an image forming apparatus of which the image density can be maintained and the fogged image and the uneven density can be within an acceptable level even when the diameter of a developer carrying member is not more than 12 mm. The outer diameter of the developer carrying member 41 is not less than 8 mm and not more than 12 mm, and a magnetic mono-component developer 43 has a saturation magnetization of not less than 20 Am2/kg and not more than 37 Am2/kg when the magnetic field of 79.6 kA/m (1000 oersteds) is applied, the magnetization of not less than 70% and not more than 80% of the saturation magnetization when the magnetic field is lowered to 55.7 kA/m (700 oersteds), and the magnetization of not less than 50% and not more than 62% of the saturation magnetization when the magnetic field is lowered to 39.8 kA/m (500 oersteds).

Abstract: An image forming apparatus includes an image carrier that carries a latent image; a charging device that charges the image carrier with a charging voltage having an AC component; and a roller that carries a developer to be supplied to the image carrier in a developing position, with a surface of the roller provided with axially-formed grooves, the frequency of the AC component of the charging voltage and the number of the grooves provided on the roller being set so that non-uniformity in density of an output image becomes invisible, caused by interference between the frequency of the AC component of the charging voltage and the frequency at which the grooves pass the developing position.

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

Abstract: The invention relates to a method and devices for cleaning the surfaces of applicator rollers, photoconductor drums, transfer belts, and photoconductor belts using magnetic roller systems. The invention also relates to methods and systems for cleaning magnetic rollers to whose surfaces toner particles adhere. In a first embodiment, a squeegee/scraper is disposed at a distance to the surface of the roller. In another embodiment, a magnetic stator configuration with two spaced apart magnetic elements is used whose poles have substantially the same active direction.

Abstract: An image forming method, comprising the steps of: agitating a mixture of toner particles and carrier particles so as to electrically charge the toner particles; forming a charged toner layer on a toner conveying roller by extracting the charged toner particles from the mixture; forming an electrostatic latent image on an image carrying member; and conveying the charged toner layer by the toner conveying roller so as to develop the electrostatic latent image on the image carrying member with charged toner; wherein the carrier particles are carrier particles each formed by dispersing magnetic fine powder in a binder resin and have a shape coefficient SF-1 of 1.0 to 1.2, a shape coefficient SF-2 of 1.1 to 2.5, and a volume-based median size of 10 to 100 ?m.

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

Abstract: An image forming apparatus of includes a developing device bifunctioning as a cleaning device for collecting toner grains left on a photoconductive drum after the transfer of a toner image from the drum to a paper sheet or similar image transfer medium. In the event of toner collection, a DC voltage is applied that causes the residual toner to move from the drum toward a developing sleeve. A main-pole magnet generates, at a position where the developing sleeve faces the drum, a magnetic field of between 100 mT and 200 mT in a direction normal to the surface of the sleeve.

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

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

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

Abstract: A developing apparatus includes a developer carrying member for carrying a developer including one component magnetic toner to develop an electrostatic image formed on an image bearing member. The developer carrying member includes an elastic member contactable to the image bearing member; magnetic field generating means, for attracting the developer to the developer carrying member, and a regulating member for regulating an amount of the developer carried on the developer carrying member. The developer is regulated by the regulating member and applied on the developer carrying member at 5-16 g/mk2. At a position where the regulating member is contacted to the developer carrying member, a magnetic flux density B generated by the magnetic field generating means, and a component Br of the magnetic flux density B normal to a surface of the developer carrying member, satisfy, |Br|/|B|?0.5.

Abstract: An image forming apparatus includes an image bearing member; a charging device for electrically charging the image bearing member; a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on the image bearing member with the developer, the developer carrying member being supplied with a developing bias voltage including an AC voltage; non-rotatable magnetic field generating device, disposed inside the developer carrying member, for magnetically attracting the developer on the developer carrying member, wherein the developer carrying member has a surface elastic layer, and the developer carrying member is press-contacted to the image bearing member, and the developer is one component magnetic toner, and a maximum value of an absolute value of the developing bias voltage |V|max and a surface potential of the image bearing member charge by the charging device is Vd(V), satisfy, |V|max=|Vd|.

Abstract: A method of developing a latent image formed on a surface of an image carrier with toner grains, which constitute a developer together with magnetic carrier grains for supporting the toner grains, by depositing the developer on a developer carrier, which faces the image carrier and accommodates magnetic field forming mechanism, causing the developer carrier to convey the developer to a developing zone formed between the image carrier and the developer carrier, and forming, in the developing zone, a magnet brush including the magnetic carrier grains, which hold the toner grains and gather in a form of brush chains, and free toner grains to be released from the carrier grains, the brush chains of the magnetic carrier grains flow in the developing zone while forming the magnet brush, and, assuming that a potential of the image carrier is Vpc and that a DC component of a potential of the developer carrier is VDC, the free toner grains, parted from the magnetic carrier grains flowing, fly at a means flight velocit

Abstract: A thermal development apparatus for thermally developing a thermal developable recording material in a thermal development section, the thermal developable recording material having a latent image formed in advance, wherein the thermal development section has: a heating member made of a porous body having a gas permeability, the heating member having a heating surface that is disposed so as to face a surface of the thermal developable recording material; and an air feed unit for feeding heated air to the thermal developable recording material through the heating member.

Abstract: In an image forming system, an image-bearing member having a photoconductor layer comprising an Si-based non-single crystal material is charged at a relatively low potential of 250 to 600 volts by a contact charging member in the presence of electroconductive fine powder. An electrostatic latent image formed on the image-bearing member is developed with a magnetic toner which includes magnetic toner particles comprising at least a binder resin and a magnetic iron oxide, and inorganic fine powder and electroconductive fine powder present at the surface of the magnetic toner particles. The magnetic toner has a weight-average particle size of 3-10 ?m and an average circularity of 0.950 to 0.995, and contains 0.05 to 3.00% of isolated iron-containing particles.

Abstract: In a magnet brush type image 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: E ? ? ( A · ? T · d · R ) ( 3 ? B 1 2 · ? 0 · V SL ) ? where B is representative of Tc·D3·?c/(100?Tc)·d3·?T, A denotes a mean amount of charge (C/kg) deposited on the toner grains Tcdenotes the content of toner grains (wt %), d denotes the mean grain size (m) of the toner grains, D denotes the mean grain size (m) of the magnetic carrier grains, ?T denotes the specific weight (kg/m3) of the toner grains, ?c denotes the specific gravity (kg/m3) of the carrier grains, ?o is 8.854×10?12 (F/m), R denotes the diameter of the developer carrier, and VSL denotes the linear velocity of the developer carrier.

Abstract: A developing device configured such that an amount of weakly charged toner in a two-component developer passing through an opening in the device per unit time is not greater than 200 g·mm/min, wherein the amount of weakly charged toner is expressed by an equation, which is the ? ? amount ? ? of ? ? weakly ? ? charged ? ? toner ? [ g · mm ? / ? min ] = total ? ? amount of ? ? the ? ? two ? - ? component ? ? developer ? ? to ? ? be ? ? drawn ? [ g ? / ? min ] × length of ? ? the ? ? opening ? [ mm ] × a ? ? concentration ? ? of ? ? toner ? [ wt ? ? % ] × percentage ? ? of ? ? weakly ? ? charged ? ? toner ? [ % ] .

Abstract: A method is provided for developing a latent electrostatic image with marking particles through the process steps of: moving the surface of an image receiving member at a predetermined process speed; storing a supply of developer material comprising toner and carrier beads in a reservoirs said toner comprising electrically conductive core particles with an electrically insulating coating thereover; transporting marking particles onto an outer surface of a donor member to be delivered to a development zone adjacent the image receiving member; and inductive charging electrically conductive core particles of said toner onto said outer surface of said donor member prior to the development zone to a predefined charge level. Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings.

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 ?cm or more.

Abstract: A developing device having a plurality of sleeves is provided for high-speed development and the prevention of an abnormal image, for example, thinning of a 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 to an upstream-side sleeve, and a bias in the reverse direction is applied to a downstream-side sleeve. Alternatively, an AC bias with a low frequency is applied to the upstream-side sleeve and an AC bias with a high frequency is applied to the downstream-side sleeve. In addition, an AC bias with a large amplitude is applied to the upstream-side sleeve, and an AC bias with a small amplitude is applied to the downstream-side sleeve.

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. Assume that the potential of the image carrier is lowered to VL after exposure, that a development potential is |VB?VL|, that the maximum set value of the development potential for development is |VB?VL|max, and that the development potential varies in a range satisfying relations: |VB?VL|?|VB?VL|max+|VB?VL|max×0.2 |VB?VL|?|VB?VL|max?|VB?VL|max×0.2 |VB?VL|max?300 V Then image density varies by a width of 10% of image density corresponding to the maximum set value of the development potential or less.

Abstract: A developing apparatus includes a developer carrying member for carrying a developer; and a developer feeding member, disposed close to or in contact to the developer carrying member, for supplying a developer to the developer carrying member, the developer feeding member being in the form of a wire and is adapted to be supplied with a voltage which is effective to electrically charge the developer to a regular polarity and which is higher than a discharge starling voltage at which electric discharge starts between the developer carrying member and the developer feeding member.

Abstract: A developing method of the present invention uses a sleeve accommodating a stationary magnet roller formed with a plurality of magnetic poles and facing an image carrier. The sleeve is rotated to convey a developer, which is made up of toner grains and magnetic carrier grains and deposited on the sleeve, to a developing zone for thereby feeding the toner grains from a magnet brush formed by the developer to a latent image formed on the image carrier. When the developing zone is seen from the image carrier side, the ratio of the total area of voids present at the tips of the magnet brush to the total area of the developing zone is selected to be 25% or less.

Abstract: A method and apparatus for image forming includes a hybrid developing apparatus that supplies surly charged toner to a developing roll. The apparatus includes a developing roll that is electrically conductive at least on its surface. The image forming apparatus and the method have a constitution capable of applying an alternating current bias having a duty ratio in the range of 10 to 50% and a direct current bias superposed thereon. The developing roll is directly confronted with a latent image bearing body through an insulative toner thin layer at the nearest region of the developing roll and the latent image bearing body. An independent bias is applied to each of the developing roll and the magnetic roll, and the toner is refreshed by the varying duty ratio of the alternate current bias and the direct current bias after developing.

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: 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.