Abstract: In a method or system for generation of a toner image layer with a preset layer thickness on a surface of a photoconductor, the two-component mixture of electrically charged toner particles and carrier particles is directed on an auto-surface of a roller adjacent a surface of an applicator element to be inked. At least a portion of the toner particles is transferred onto the surface of the applicator element. An electrical field is generated that exerts at least one force on a portion of the electrically charged toner particles between the roller and the applicator element. A strength of the electrical field is varied to adjust a layer thickness of a layer of the toner particles transferred onto the surface of the applicator element and thus to adjust a thickness of the toner image layer on the photoconductor. A measurement arrangement detects a thickness of at least one region of the toner image layer inked on the surface of the photoconductor as a real value.

Abstract: Provided is a developing device employing a two-component developer where a good image can be obtained by preventing the influence of scratching caused by a magnetic brush.

Abstract: An image forming apparatus that includes: an image carrier; a developing cartridge detachably mountable with respect to the image carrier; a processing device to which voltage acting between the image carrier and the processing device is applied; and a first electrode, wherein the developing cartridge further includes: a developing roller on which toner is capable of being held; and a second electrode capable of being electrically connected with the first electrode when the developing cartridge is mounted with respect to the image carrier, the processing device further includes: a third electrode capable of being electrically connected with the second electrode when the developing cartridge is mounted with respect to the image carrier, wherein the second electrode positions the developing cartridge in an axial direction of the developing roller.

Abstract: Disclosed is an image forming apparatus, which makes it possible to remove the resistance reduced carriers included in the developer without abandoning normal carriers whose resistances have not reduced, even in mid-course of implementing the image forming operation. The image forming apparatus includes: a carrier adhering roller to make at least a part of carriers, included in the developer, shift and adhere onto a carrier adhering roller in response to an electric field generated between the developer conveyance member and the carrier adhering roller, a recollection roller, rotatably disposed in such a manner that the recollection roller and the carrier adhering roller oppose to each other with a gap between them, to attract carriers, currently adhered onto the carrier adhering roller, onto a circumferential surface of the recollection roller; and a scraping member, contacting the recollection roller, to scrape the adhered carriers off the circumferential surface of the recollection roller.

Abstract: A developing device is provided with a developer transporting member for transporting a developer containing a toner and a carrier; a toner transporting member opposite to the developer transporting member and opposite to an electrostatic latent image carrying member; a first electric field forming device, which is composed of a power source for the developer transporting member and a power source for the toner transporting member, for shifting the toner in the developer held onto the developer transporting member to the toner transporting member; and a second electric field forming device for shifting the toner held onto the toner transporting member to an electrostatic latent image on the carrying member. Operation of the first electric field forming device is controlled based on an electric current flowing in the developer transporting member power source, which is detected by a detecting block.

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: A developing device is provided with a first transporting member for transporting a developer containing a toner and a carrier; a second transporting member opposite to the first transporting member to interpose a first spatial region therebetween and opposite to an electrostatic latent image carrying member to interpose a second spatial region therebetween; a first electric field forming device, composed of first and second power sources, for shifting the toner in the developer held onto the first transporting member to the second transporting member; and a second electric field forming device, composed of the second power source, for shifting the toner held onto the second transporting member to an electrostatic latent image on the carrying member. The operation of the second electric field forming device is controlled based on electric currents flowing in the first and second power sources, which are detected by first and second detecting blocks, respectively.

Abstract: An image forming apparatus includes first and second image supporting members; first and second developer supporting members for forming a first developer image in a first color and a second developer image in a second color, respectively; first and second transfer members for transferring the first developer image and the second developer image to a medium, respectively; a voltage applying unit for applying a first voltage to one of the first image supporting member and the first transfer member and a second voltage to one of the second image supporting member and the second transfer member. The voltage applying unit is arranged to apply the second voltage greater than the first voltage to one of the second image supporting member and the second transfer member when a printing operation is performed to form an image only in the first color.

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: A typical configuration of a development device and an image forming apparatus according to the invention includes: a development sleeve and an electrode portion. In the development device, a pre-bias is applied between the electrode portion and the photosensitive drum, a DC voltage is applied to the development sleeve, a development bias is applied between the development sleeve and the photosensitive drum, the toner in the developer on the development sleeve is moved to the photosensitive drum, and an electrostatic latent image is developed on the photosensitive drum. In the development device, electric field intensity between the electrode portion and the development sleeve by the pre-bias is larger than electric field intensity between the image bearing member and the development sleeve by the development bias.

Abstract: A duty ratio Du (%), denoted by (T2/(T1+T2))×100, is in the range of 60?Du?80; a magnetic carrier has a resistivity ? which decreases in accordance with an increasing electric field strength, and a relative dielectric constant ? which increases in accordance with an increasing electric field strength; a product of a time constant ?0??(s) of electric charge decay in an electric field strength E2D decided by a second peak voltage V2 and a dark potential VD, and an electric field strength E2D satisfies a relation of 20??0?? E2D (s·V/cm); and a time constant ?0??(s) and a relative dielectric constant ? in an electric field strength E1L, which is decided by a first peak voltage V1 and a bright potential VL, satisfy the following relations: ?0??(s)?6.0×10?4, and 30??.

Abstract: A developing device having: a plurality of toner support members for supporting toner on their peripheral surfaces, the plurality of toner support members being arranged in a direction of rotation of an image support member out of contact with the image support member; and a developer support member for supporting a developer containing toner and carriers and supplying the toner to the plurality of toner support members; wherein the plurality of toner support members have dielectric layers on their surfaces, the dielectric layers satisfying a condition d1/?1>d2/?2; and wherein the first toner support member and the second toner support member are connected to a single power source.

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: 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: An image forming apparatus includes: a developing device that allows a developer to be retained on a developer carrier having a magnet member equipped with a plurality of magnetic poles mounted on an inner periphery thereof and rotates the developer carrier to deliver the developer to an image carrier and that forms a toner image by supplying the toner of the developer to the image carrier by applying a developing bias voltage from a bias voltage source between the developer carrier and the image carrier; a transfer device for transferring the toner image formed on the image carrier to a transfer receiving material; a toner recovery device for recovering the toner remaining on the surface of the image carrier after the transfer of the toner image; and a toner return device for returning to the developing device the toner recovered by the toner recovery device.

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: Provided are a developing device and an image forming apparatus which employ a hybrid development method, have a toner-collecting developer supporting member and keep toner collecting ability stable for a long period of time to form high-quality images without development hysteresis (ghost) over a long period of time. A toner separation member abutting the toner-collecting developer supporting member through a toner-collecting developer layer is provided, and the toner separation member is applied with a bias voltage to form an electric field in such a direction as to pull toner away from the toner-collecting developer supporting member to prevent the toner from accumulating on the surface of the toner-collecting developer supporting member.

Abstract: An image forming apparatus includes: a photoconductive drum; a developing roller carrying toner; a DC voltage application portion outputting a DC voltage to be applied to the developing roller, and receiving a feedback voltage; an AC voltage application portion applying an AC voltage to be applied to the developing roller; a detection portion detecting occurrence of electric discharge; a first resistor portion generating a feedback voltage that is fed to the DC voltage application portion; a second resistor portion connected between the DC voltage application portion and the AC voltage application portion, and having a switching portion with which conducting on and off are switchable; and a control portion controlling the switching portion, at the time of printing, to bring the second resistor portion into a conducting state and, at the time of electric discharge detection, to bring the second resistor portion into a non-conducting state.

Abstract: A developing device and image forming apparatus are provided, wherein high quality images, in which generation of development hysteresis (ghost image) is alleviated, are obtained over a long period using a hybrid development method including a toner-supplying developer supporting member and a toner-collecting developer supporting member. Bias voltage is applied in the direction in which the toner is supplied to the toner supporting member in the toner supply region and the toner collection region of the toner-supplying developer supporting member and the toner-collecting developer supporting member respectively so that the toner collecting capability in the toner collection region is higher than the toner collecting capability in the toner supply region.

Abstract: An image forming apparatus including: an image bearing member; and a developer bearing member bearing a developer including a toner and a carrier, the developer bearing member developing an electrostatic image formed on the image bearing member with the developer, and the developer bearing member being applied with an alternate voltage in order to form an alternate electric field between the developer bearing member and the image bearing member, wherein assuming that electric field intensities Eb and Ed be Eb=|(Vp1?VL)/D| and Ed=|(Vp2?VL)/D|, a relationship, 0?K1>K2, is satisfied, where K1: a gradient at Ed, and K2: a gradient at Eb, and wherein a resistivity ?b of the carrier at the electric field intensity Eb satisfies 1.1×106×en<?b<6.0×107 [?·m] (where: e is the base of natural logarithms; and n=4×Eb×10?7).

Abstract: A developing device includes: 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. An image-forming apparatus includes the above-mentioned developing device.

Abstract: An image forming apparatus has a pair of spacedly opposed first and second bearing members, in which a powder developer material is moved from the first bearing member to the second bearing member. The apparatus also has an electric field generator. The generator forms an electric field between the first and second bearing members and outputs a first voltage and a second voltage alternately. The first voltage generates, between the first and second bearing members, a first electric field electrically forcing the developer material from the first bearing member toward the second bearing member. The second voltage generates between the first and second bearing members a second electric field electrically forcing the developer material from the second bearing member toward the first bearing member.

Abstract: An image forming apparatus that 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 is disclosed herein.

Abstract: The purpose is to provide, in a development apparatus using a two-component developer, a compact development apparatus, image forming apparatus and development method that prevents carrier deterioration and that can carry out good image formation over a long time period. In a development apparatus using a developer in which are mixed a toner, a carrier, and opposite polarity particles that are charged to a polarity opposite to the charging polarity of the toner, the surface charge density of the opposite polarity particles should be in the range of 0.5 to 3.0 times the surface charge density of the carrier.

Abstract: An image forming apparatus having an image carrier for forming an electrostatic latent image and a developing unit for developing the electrostatic latent image with a two-component developing agent, the developing unit includes: a developing agent carrier for developing the electrostatic latent image to form a visible image, having inside thereof a development main magnetic pole for forming a bristle of a magnetic brush; and a plurality of magnetic poles for conveying the developing agent, wherein the developing unit performs a counter type contact developing method, and wherein, a development area is formed so that, a contact width of the bristle of the magnetic brush is 70% or less with respect to a development width, and a center position of the contact width is positioned on an upstream side with respect to a center position of the development width in a rotation direction of the image carrier.

Abstract: In an embodiment in which an electrostatic latent image formed on the surface of a photoreceptor is developed with a toner by applying an oscillating bias voltage in which a development-side electrical potential and an opposite development-side electrical potential alternate with each other, between a development sleeve of a development roller and the photoreceptor, the development-side electrical potential is applied in two stages, and, in the two-staged development-side electrical potential, the absolute value of a first electrical potential V1 that is initially applied is larger than the absolute value of a second electrical potential V2 that is subsequently applied.

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: Disclosed is an image forming apparatus, which makes it possible to remove the resistance reduced carriers included in the developer without abandoning normal carriers whose resistances have not reduced, even in mid-course of implementing the image forming operation. The image forming apparatus includes: a carrier adhering roller to make at least a part of carriers, included in the developer, shift and adhere onto a carrier adhering roller in response to an electric field generated between the developer conveyance member and the carrier adhering roller, a recollection roller, rotatably disposed in such a manner that the recollection roller and the carrier adhering roller oppose to each other with a gap between them, to attract carriers, currently adhered onto the carrier adhering roller, onto a circumferential surface of the recollection roller; and a scraping member, contacting the recollection roller, to scrape the adhered carriers off the circumferential surface of the recollection roller.

Abstract: Provided is a developing device employing a two-component developer where a good image can be obtained by preventing the influence of scratching caused by a magnetic brush.

Abstract: The first direct-current bias power supply applying the first direct-current bias Vdc1 and the first alternating-current bias power supply applying the first alternating-current bias Vac1 are connected to a development roller. The second direct-current bias power supply applying the second direct-current bias Vdc2 and the second alternating-current bias power supply applying the second alternating-current bias Vac2 are connected to a magnetic roller. The peak-to-peak value Vpp of the first alternating-current bias Vac1 applied to the development roller remains the same, and the second alternating-current bias Vac2 that is in phase with the first alternating-current bias Vac1 and that has a peak-to-peak value of a predetermined value or above is applied to the magnetic roller. Thus, the potential difference between the peak voltage of the development bias on the opposite polarity side to the polarity of the toner and the peak voltage of a supply bias is set at a predetermined value or below.

Abstract: A developing device includes: an electric field generating unit that generates an electric field; and a cylindrical developer holder, to which a voltage is applied, that surrounds the electric 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 electric field generated by the electric 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 developing device for a toner powder cloud development system, which can achieve high image quality and can be made compact. The developing device has a two-component development unit, a toner carrier, and an alternating current power source. The toner carrier, which is arranged opposing a latent image carrier, has a plurality of electrodes disposed in a line in a prescribed direction on the surface thereof, and mutually insulated. The alternating current power source supplies a voltage such that an electric field across the plurality of electrodes is temporally switched. The inter-electrode electric field causes the toner being carried on the surface of the toner carrier to carry out hopping, thereby forming a toner powder cloud and carrying out development. The movement speed of the latent image carrier and the linear velocity of the toner carrier are set at approximately equivalent speeds.

Abstract: An image forming apparatus including a first developing device including a first developer carrying member for carrying a developer containing toner, wherein a developing voltage including an AC component is applicable to the first developer carrying member to develop an electrostatic image; a second developing device including a second developer carrying member for carrying a developer containing toner, wherein a developing voltage including an AC component is applicable to the second developer carrying member to develop an electrostatic image; a transferring device for transferring a toner image formed by the first developing device to a moving transfer medium and then transferring a toner image formed by the second developing device onto the transfer medium; a controller for selectively executing an operation in a first mode wherein the image is formed by both of the first developing device and the second developing device or in a second mode wherein the image is formed by only the second developing device

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: A method (400) and apparatus (100) that detects carrier particles (130) in an electrophotographic device is disclosed. The apparatus may include an image carrying member (110). The image carrying member may have a first side (111) and have a second side (112) opposite from the first side. The image carrying member may be configured to operate in a direction of motion (115). The image carrying member may also be configured to transport an image on the first side. The apparatus may also include a magnet (120) coupled to the second side of the image carrying member. The magnet may have a length (122). The length of the magnet may be at an angle (124) of greater than zero and less than 90 degrees to the direction of motion of the image carrying member. The magnet may be configured to attract toner carrier particles transported on the image carrying member. The apparatus may also include a first sensor (140) coupled in proximity to the first side of the image carrying member and coupled in proximity to the magnet.

Abstract: A developing apparatus for visualizing an electrostatic latent image on an electrostatic latent image bearing member by using a developer including toner and carrier particles, has a developer including toner and carrier particles, a first transport member, a second transport member positioned to oppose to the first transport member across a first region and to the electrostatic latent image bearing member across a second region. A first electric field forming unit forms a first electric field between the first and second transport members to move the toner particles from the first transport member to the second transport member. A second electric field forming unit forms a second electric field between the second transport member and the electrostatic latent image bearing member to move the toner particles from the second transport member to the electrostatic latent image bearing member and thereby to visualize an electrostatic latent image on the image into a visible image.

Abstract: An image forming apparatus has a photoconductive member, and a developing roller develops a latent image on the photoconductive member by a first alternating-current bias in the form of a rectangular wave. The following relationships are satisfied in calculating the duty ratio (D1) of the first alternating-current bias using an application period of voltage in a direction to transfer the toner from the developing roller towards the photoconductive member as a positive period: a CV value in the number particle size distribution of the toner is ?25%, 4 ?m?Dt?7 ?m, 105 ?·cm?pv?109 ?·cm, 0.4 ?m?Ra?1.5 ?m, and 35%?D1?75%. where Dt denotes the volume average particle diameter of the toner, pv denotes the intrinsic resistance value of a developing roller surface, Ra denotes the arithmetic average roughness of the developing roller surface.

Abstract: An image forming apparatus includes a photosensitive drum to which an electrostatic image is formed and a developing sleeve carrying a developer including toner carrier. An alternating voltage is applied to the sleeve to form an alternating electric field between the sleeve and the drum to develop the electrostatic image with the developer. A relation |K1|<|K2| is satisfied, where K1: a slope at an electric field intensity Ed=|(Vp2?VL)/D|, K2: a slope at an electric field intensity Eb=|(Vp1?VL)/D|, VL: a potential [V] of the electrostatic image at which a maximum density is obtained, Vp1: a peak potential [V] that provides a potential difference to move the toner toward the drum, Vp2: a peak potential [V] that provides a potential difference to move the toner toward the sleeve, and D: a closest distance [m] between the drum and the sleeve.

Abstract: An image forming apparatus that includes: an image carrier; a developing cartridge detachably mountable with respect to the image carrier; a processing device to which voltage acting between the image carrier and the processing device is applied; and a first electrode, wherein the developing cartridge further includes: a developing roller on which toner is capable of being held; and a second electrode capable of being electrically connected with the first electrode when the developing cartridge is mounted with respect to the image carrier, the processing device further includes: a third electrode capable of being electrically connected with the second electrode when the developing cartridge is mounted with respect to the image carrier, wherein the second electrode positions the developing cartridge in an axial direction of the developing roller.

Abstract: A duty ratio Du (%), denoted by (T2/(T1+T2))×100, is in the range of 60?Du?80; a magnetic carrier has a resistivity ? which decreases in accordance with an increasing electric field strength, and a relative dielectric constant ? which increases in accordance with an increasing electric field strength; a product of a time constant ?0??(s) of electric charge decay in an electric field strength E2D decided by a second peak voltage V2 and a dark potential VD, and an electric field strength E2D satisfies a relation of 20??0?? E2D (s·V/cm); and a time constant ?0??(s) and a relative dielectric constant ? in an electric field strength E1L, which is decided by a first peak voltage V1 and a bright potential VL, satisfy the following relations: ?0??(s)?6.0×10?4, and 30??.

Abstract: An image forming apparatus including: an image bearing member; and a developer bearing member bearing a developer including a toner and a carrier, the developer bearing member developing an electrostatic image formed on the image bearing member with the developer, and the developer bearing member being applied with an alternate voltage in order to form an alternate electric field between the developer bearing member and the image bearing member, wherein assuming that electric field intensities Eb and Ed be Eb=|(Vp1?VL)/D| and Ed=|(Vp2?VL)/D|, a relationship, 0?K1>K2, is satisfied, where K1: a gradient at Ed, and K2: a gradient at Eb, and wherein a resistivity ?b of the carrier at the electric field intensity Eb satisfies 1.1×106×en<?b<6.0×107 [?·m] (where: e is the base of natural logarithms; and n=4×Eb×10?7).

Abstract: The present invention provides a developing apparatus using a two-component developer, an image forming apparatus, and a method of forming an image capable of forming a high quality image characterized by stable suppression of carrier deterioration and absence of a residual image (memory effect) for a long period of time. The voltage formed by overlapping AD voltage to DC voltage is applied separately to each of the developer carrying member and the toner carrying member. The toner separation field made up of AC field is formed between the developer carrying member and the toner carrying member, and the development electric field made up AC field is formed between the toner carrying member and the image carrying member.

Abstract: A developing unit using a two-component developer intended to provide an image forming apparatus capable of forming a high-quality image for a long period of time. A developing unit using a developer contains toner, carrier and opposite polarity particles having a polarity opposite to the charging polarity of toner includes separation means for separating the toner or opposite polarity particles, and control mechanism for controlling opposite polarity particle separation ratio in response to the image area ratio and the number of prints.

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 development apparatus and an image forming apparatus capable of minimizing deterioration of a carrier for a long time, even in a case of continuous formation of images of a smaller image area ratio. The charging of toner is assisted by using a developer composed of a mixture of toner and the carrier, to the surface of which is added a reverse polarity particle having a polarity reverse to that of a charged toner. Separation of the toner or reverse polarity particle of the developer prior to a process of development prevents the reverse polarity particle from being consumed in a developing area, whereby an effect thereof is maintained for a long time.

Abstract: An apparatus includes an upstream transport surface TSa which, while facing a circumferential surface DS of a developing roller 33, is disposed upstream of an area (developing area) in the vicinity of a latent image forming surface LS, and a downstream transport surface TSb which, while facing the circumferential surface, is disposed downstream of the developing area. The apparatus forms electric fields on the upstream and downstream transport surfaces for moving a charged developer T from an upstream side toward a downstream side. In the apparatus, the transport speed of developer on the upstream transport surface is higher than that on the downstream transport surface. As a result, there can be lowered a speed at which the developer which has not adhered to the circumferential surface and has reached a downstream end portion of the upstream transport surface flies out toward the vicinity of the developing area.

Abstract: A developing device 2a, which is provided with: a developer tank 16 that houses a developer 24 containing a toner, a carrier for charging the toner and reverse polarity particles that are charged with a polarity reversed to the electrostatic charge polarity of the toner by the carrier; a developer-supporting member 11 that supports the developer supplied from the developer tank on the surface thereof, and transports the developer; and a separating mechanism 22 that separates the toner or the reverse polarity particles from the developer supported on the developer-supporting member, and the reverse polarity particles are collected into the developer tank, is provided, and an image-forming apparatus having such a developing device and an image-forming method applied thereto are also provided.

Abstract: An image forming apparatus includes a photosensitive drum to which an electrostatic image is formed and a developing sleeve carrying a developer including toner carrier. An alternating voltage is applied to the sleeve to form an alternating electric field between the sleeve and the drum to develop the electrostatic image with the developer. A relation |K1|<|K2| is satisfied, where K1: a slope at an electric field intensity Ed=|(Vp2?VL)/D|, K2: a slope at an electric field intensity Eb=|(Vp1?VL)/D|, VL: a potential [V] of the electrostatic image at which a maximum density is obtained, Vp1: a peak potential [V] that provides a potential difference to move the toner toward the drum, Vp2: a peak potential [V] that provides a potential difference to move the toner toward the sleeve, and D: a closest distance [m] between the drum and the sleeve.

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: 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.