Abstract: A housing of a developing apparatus is provided with a conveying member and two agitating members. A guide is provided in an inner bottom surface of the housing between two agitating members. A guide is formed into a mountain shape with wide foot portion in a cross sectional shape which is orthogonal to an axial direction of rotating shafts of the agitating members. The guide is arranged in such a manner that a gap between respective outermost portions of two agitating members, and an inner bottom surface of the housing and the guide becomes equal to or more than 1.5 mm and less than 3 mm. Further, each of two agitating members rotates in a direction from the below to the above at a position of the guide.

Abstract: A powder supply unit is disclosed, which includes a housing accommodating powder, a rotating member rotatably provided in the housing, a sheet-like transporting member fixed to the rotating member and having a free end at a side different from the fixed portion side and slidingly moved on an inner wall of the housing by the rotation of the rotating member to transport the powder in the axial direction of the rotating member, and a powder supplying hole provided on the downstream side in the transporting direction of the powder in the housing. The powder supply unit is constructed such that the transporting member, when not in use, is in a hold state in which the free end side thereof is bent in a direction opposite to the direction of bending when in use.

Abstract: A developing device using a two-component developing agent including a toner and a carrier. The developing device includes a toner concentration sensor which detects a concentration of a toner contained in the developing agent within the accommodation unit by using electrostatic capacity. The toner concentration sensor includes a frame combined with a housing that forms the accommodation unit, a measuring groove formed in the frame to be concave with respect to an inner surface of the housing so that the developing agent conveyed by the agitator is flowed into the measuring groove, and a pair of opposite electrodes disposed on the measuring groove.

Abstract: The present invention provides a developing device and an image forming apparatus capable of preventing a developer from being discharged excessively using simple configurations in the case that a trickle developing device that uses a two-component developer is in a tilted state.

Abstract: This is an auger shaft seal used in an electrophotographic marking system. The seal is made up of alternating raised and depressed pie-shaped sections, each having edges that force developer away from auger bearings. The seal of this invention can be used on bi-directional augers and will protect the bearing when the auger moves in a clockwise or counter-clockwise direction. The seal is used with a magnetic seal to add additional protection for the bearings.

Abstract: A developing device includes a developer tank and a developing roller. An internal space of the developer tank is divided into an upper conveying path, a lower conveying path, a communication path, a main pumping conveying path section, and a developer supply path, by a partition wall. A developer pumping conveying section conveys a developer inside the main pumping conveying path section in a conveyance direction Z, and includes an inner spiral blade, a rotational tube, a first outer spiral blade, a second outer spiral blade, a pumping rotation shaft member, and a pumping gear. An attracting magnet is located in a position horizontally spaced from the rotational tube.

Abstract: Developing devices, process cartridges and image-forming apparatuses, having a chamber for conveying recovered developer on the top of another chamber for conveying supplying developer, where the developer is conveyed by screws inside the chambers respectively, when mixing and conveying the developing agent, a shielding member which separates the chambers, a guide section is provided in the shielding member to guide a developing agent which has left a developing roller toward the screw in the upper chamber, and a third communication section is provided next to the guide section, at the back of where the guided developer contacts the screw wings in the upper chamber, and the third communication section communicates the chambers with each other, and the third communication section is provided from center to downstream in the conveyance direction of the developer by the screw upper.

Abstract: In a developing device including a developer tank and a developing roller, an internal space of the developer tank is divided by a partition wall into a first conveying path, a second conveying path, a communication path and a pumping path. In the pumping path, there is disposed a developer pumping section including a pumping spiral blade, a pumping rotation shaft member, and a pumping gear. A developer in the pumping path is pumped up by the developer pumping section, so that a part of the developer is moved to a side of the first conveying path while another part of the developer is moved to a side of the second conveying path.

Abstract: A developing device includes a conveyance path, a conveyance member, a return path, and a pre-agitation region. The conveyance path conveys a toner while agitating the toner. The conveyance member has a rotational shaft, which is rotatably disposed along an upstream end to a downstream end of the conveyance path, and conveys the toner toward the downstream end due to rotation of the rotational shaft. The return path communicates with the downstream end and an intermediate portion of the conveyance path, thereby forming a circulation path, and returns the toner from the downstream end to the intermediate portion. The pre-agitation region is formed at the upstream end side, extending from the intermediate portion and outside the circulation path, and pre-agitates the toner to be conveyed to the circulation path.

Abstract: A developer holding apparatus holds developer therein. The developer is discharged through a discharging opening. An agitator includes shaft portions and an agitating portion. A bearing member includes a bearing hole formed therein. One of the shaft portions is rotatably received in the bearing hole. The bearing hole has a larger diameter than the shaft portions. A hollow body is rotatable in the developer holding apparatus and the agitator rotates in the hollow body.

Abstract: An image forming apparatus that may securely mix a toner and a carrier in a minimum space when high-speed printing is performed. The image forming apparatus including: a photosensitive drum; a developing roller; and a developing unit, wherein the developing unit includes: a receiving or transferring unit for receiving or transferring a two-component developing agent in an axial direction of a developing roller; and a preparatory agitation unit disposed on an end part of the receiving or transferring unit and including an agitation screw that has a large diameter and for mixing the newly-supplied toner and the carrier.

Abstract: An image forming apparatus includes plural developing devices arranged at a fixed interval, plural toner cartridges arranged at an interval smaller than the interval among the developing devices, and plural sub-hoppers that receive toners stored in the toner cartridges and feed the toners to plural developing devices. The plural sub-hoppers respectively have toner receiving ports formed in positions opposed to toner discharging ports of the toner cartridges and have toner supply ports for feeding toners to the developing devices. The plural sub-hoppers are arranged at an interval same as an arrangement pitch of the developing devices.

Abstract: In one embodiment, in a development apparatus in which at least a first screw conveyor has been provided in a case, a developer affixing prevention member that prevents a developer from affixing to the first screw conveyor is disposed in the vicinity of a toner resupply port provided in the case. More specifically, the developer affixing prevention member is formed with a torsion coil spring formed from the wire rod whose middle has been wound in a coil-like shape, and in a state with the wound portion of this torsion coil spring supported by a support plate of the case, one arm portion is fixed to the support plate, and another arm portion is extended so as to contact a fin and a rotating shaft of the first screw conveyor.

Abstract: In an embodiment, a reducing plate that dams up a part of a developer scraped up by a blade is provided. The reducing plate suppresses swell of the developer held up by a discharge mixer from fluctuating according to the rotation of the blade. Fluctuation in an excess developer discharged from a discharge port is suppressed and replace a deteriorated carrier in a development container with a new carrier little by little.

Abstract: A housing of a developing apparatus is provided with a conveying member and first and second agitating members. A guide is provided in an inner bottom surface of the housing between the first and second agitating members. The guide has a mountain shape with a wide foot portion in a cross sectional shape which is orthogonal to an axial direction of rotating shafts of the first and second agitating members. The first and second agitating are arranged in such a manner that gaps between respective outermost portions thereof and the inner bottom surface of the housing and the guide become equal to or more than 1.5 mm and less than 3 mm. A discharge portion is provided on a downstream side of a developer agitating portion in a developer conveying direction of the first and second agitating members.

Abstract: A technique that makes it possible to switch high-torque power transmission with a compact and simple configuration is provided. A driving force transmitting device that transmits driving force received by one of a first rotating body and a second rotating body to the other includes: the first rotating body; a first engaging section that is provided in the first rotating body; the second rotating body that rotates around a rotating shaft the same as that of the first rotating body; elastically deforming sections that are arranged in the second rotating body; and a second engaging section that is provided in the second rotating body and elastically supported by the elastically deforming sections to engage with the first engaging section and is disengaged from the first engaging section by centrifugal force involved in the rotation of the second rotating body.

Abstract: A developing device includes a developing unit, a developer agitating unit, a developer conveying unit, and a toner supplementing unit. The developing unit develops an electrostatic latent image on an image carrier with a developer containing toner and carrier. The developer agitating unit agitates the developer. The developer conveying unit connects the developing unit and the developer agitating unit, and conveys the developer from the developing unit to the developer agitating unit. The toner supplementing unit is connected to the developer conveying unit, and supplements toner to the developer conveyed from the developing unit to the developer agitating unit.

Abstract: A developer container for an image forming apparatus includes a developer accommodating chamber, provided with an opening, for accommodating a developer to be supplied to the opening; a feeding member, provided in the developer accommodating chamber and having an elasticity, for feeding the developer by rotation thereof; a deforming portion, provided in the developer accommodating chamber and contactable to the feeding member, for deforming the feeding member against the elasticity with the rotation of the feeding member; and a restoration portion for permitting the feeding member deformed by the deformed portion to restore elastically, thereby to throw the developer toward the opening, wherein a boundary portion between the deformed portion the restoration portion is disposed below a lower end of the opening.

Abstract: An image forming apparatus includes: a photosensitive drum; a toner cartridge; and a developing unit that forms a toner image by visualizing a latent image formed on the photosensitive drum. The developing unit includes a feed opening through which toner is supplied from the toner cartridge, and a paddle that agitates toner supplied through the feed opening and feeds the toner in a direction of the photosensitive drum. The feed opening has an opening length shorter than a length in a direction of a rotary axis of the paddle, and the paddle includes a toner guide that diffuses the toner in the direction of the rotary axis of the paddle.

Abstract: A toner cartridge having a magnetically coupled drive apparatus is provided. The cartridge provides a first toner holding member that houses toner and a second toner holding member adjacent to the first member that houses toner. A dividing wall separates the first toner holding member from the second toner holding member. A toner shifting component shifts the waste toner housed in the first toner holding member and a toner stirring component stirs the fresh toner housed in the second toner holding member. The toner shifting component and toner stirring component are magnetically coupled through the dividing wall so that when the toner stirring component rotates the toner shifting component rotates. The magnetic coupling disposed between the toner shifting component and toner stirring component engages without an opening through the dividing wall. As a result, waste toner cannot pass through the dividing wall into the fresh toner housing and vice versa.

Abstract: An image forming apparatus and method for developing a latent image on an image bearing member includes the image bearing member, an air flow generator, and an air intake device. The image bearing member is configured to bear the latent image on the surface thereof. The airflow generator is configured to generate airflow to transport a developer. The air intake device is configured to connect outside the image forming apparatus with the airflow generator to draw air from outside the image forming apparatus to supply the air to the airflow generator.

Abstract: A housing of a developing apparatus is provided with a conveying member in a developer supplying and recovering portion, and with first and second agitating members rotating from the below to the above in portions opposed to each other in a developer agitating portion. A guide is provided in an inner bottom surface of the housing between the first and second agitating members. A discharge portion provided with a developer discharge port is provided on a downstream side of the developer agitating portion in a developer conveying direction of the first agitating member. A suitable amount of developer can be circulated while conveying a part of an excess amount of developer in a circulating conveying path to the discharge portion and discharging from the developer discharge port. Packing and leaking of the developer within the developing apparatus and breakage of the developing apparatus can be prevented and also a good image can be obtained even if high printing images are continuously provided.

Abstract: A developing unit includes: a developing roller; a first conveying member provided in a first container, having a first shaft and a spiral blade, that agitates and conveys developer; a second conveying member provided in a second container connected to the first container via a hole, having a second shaft and a spiral blade, that agitates and conveys the developer; and a supplying member having a third shaft and a paddle blade, that supplies the developer conveyed by the first or the second conveying member to a developing roller, wherein: at least one of the first and second shafts includes a first portion that faces the hole and a second portion that does not face the hole; and a diameter of the at least one of the first and second shafts in at least a part of the first portion is smaller than a diameter in the second portion.

Abstract: A developing device comprising a developer carrying member for carrying the developer containing non-magnetic toner and magnetic carrier to a position where said developer carrying member is opposed to an image bearing member; a developing container including a first chamber for accommodating a developer to be supplied to said developer carrying member, a second chamber provided below said first chamber, and a pair of transferring portions for circulating the developer between said first chamber and said second chamber; a first feeding member and a second feeding member, rotatably provided, in said first chamber and said second chamber, respectively, for stirring and feeding the developer; and a magnetic member provided at least on said first feeding member, wherein said magnetic member is provided in a region opposing at least one of said transferring portions where the developer is scooped from said second chamber into said first chamber.

Abstract: A image forming unit includes an image forming unit including an image bearing body that bears a latent image, a developer bearing body that develops the latent image, a developer supplying portion that supplies the developer to the developer bearing body, an agitating portion provided in the vicinity of the developer supplying portion and including a plate member for agitating the developer in the vicinity of the developer supplying portion and a rotation shaft that holds the plate member, and a driving mechanism that causes the plate member of the agitating portion to reciprocatingly swing about the rotation shaft.

Abstract: A developing device for developing an electrostatic latent image formed on an photoreceptor drum with a dual-component developer, includes: a developing hopper for storing the developer; an agitation roller for conveying the developer while agitating; a developing roller which supplies the developer to a developing area located opposing the photoreceptor drum; a layer thickness-regulating member for regulating the layer thickness of the developer being conveyed by the developing roller; a flow-guide plate for flowing down the surplus developer that was rejected to a position away from the layer thickness-regulating member; a multiple number of partitioning ribs arranged upright on the flow-guided plate for flowing down the surplus developer in a predetermined direction while diffusing the developer with respect to the longitudinal direction of the developer roller; and a downflow direction control mechanism for controlling the downflow direction of the surplus developer regulated by the partitioning ribs.

Abstract: A developing device includes a first conveying unit provided within a developing agent storage chamber and configured to convey developing agent from one end of the storage chamber to another end in a longitudinal direction of a developing agent carrier disposed within a developing chamber and to supply the developing agent from the storage chamber to the developing chamber. The device may include a second conveying unit provided within the developing chamber and configured to convey the developing agent from the other end of the developing chamber to the one end in the longitudinal direction and to supply the developing agent toward a developing agent carrier, and a third conveying unit provided between the one end of the storage chamber and the one end of the developing chamber and configured to convey the developing agent from the one end of the developing chamber to the one end of the storage chamber.

Abstract: A developing apparatus for an image forming apparatus. In order to suppress toner scattering that may occur after a development operation has been halted for a long time, the developer is transferred to a developer storage unit on the exterior of the developing machine when the development operation ends. A range in which an angle of a restricting member upstream side central angle ?, which is a central angle of the surface of a developing roller on the upstream side of a restricting member opposing position opposing a developer amount restricting member in a surface motion direction of the developing roller, is not less than 0° and not more than 60° is set as a low magnetic flux density area ? in which the maximum value of a normal direction magnetic flux density on the surface of the developing roller is not more than 30 mT.

Abstract: Developing device supplying developer to developing roller, while causing developer to circulate in passage including first and second conveying passages in parallel, and while ejecting part of developer to outside via ejection passage formed as extension of first conveying passage on downstream side in developer conveying direction, developing roller being provided along first conveying passage.

Abstract: A developing apparatus using a two-component developer constituted by a magnetic carrier and a toner, and an image forming apparatus comprising the developing apparatus. A developing unit and a stirring unit are provided, and in order to suppress toner scattering that may occur after a development operation has been halted for a long time, and thereby suppress contamination of the apparatus interior, the developer in a developing machine is transferred to a stirrer serving as a developer storage unit on the exterior of the developing machine when the development operation ends.

Abstract: A developing device that is capable of securing an amount of developer that can be stored in a developer tank while suppressing the bending of a developer conveying section, as well as an image forming apparatus are provided. In a developer tank of a developing device, there is provided a first developer conveying section that includes a first rotation shaft member having a columnar shape in which grooves extending in an axial line direction are formed, and a first spiral blade that is spirally wound around the first rotation shaft member and conveys the developer by rotation around the axial line of the first rotation shaft member.

Abstract: There is provided a development apparatus including: a first developer storage container and a second developer storage container that store developer, having a first a and second openings, respectively; a first transport member provided within the first developer storage container, and that causes the developer to move to the second developer storage container via the first opening; a second transport member provided within the second developer storage container, and that causes the developer to move to the first developer storage container via the second opening; a developer holding member that performs development by causing the developer to move to a position facing an image holding body on which a latent image is formed; and a moving member provided so as to fit between an inner wall face of the second developer storage container and an outer edge of the second transport member.

Abstract: A developing unit includes a developer carrying member, a supplying compartment, a recovery compartment, and an agitation compartment. The developer carrying member develops a latent image formed on an image carrier with a two-component developer. The supplying compartment has a developer supplying transporter to supply the two-component developer to the developer carrying member while transporting the two-component developer. The recovery compartment has a developer recovery transporter to transport the two-component developer recovered from the developer carrying member. The agitation compartment has a developer agitation transporter to agitatingly transports developer. The developer agitation transporter includes a first screw having a screw pitch to transport developer to an upstream end of the supplying compartment from a downstream end of the agitation compartment.

Abstract: A developing device includes a developing tank, a developing roller, a supply toner carrying path, and a supply toner diffusion screw. A partition board provided parallel to the developing roller in the developing tank has, in an axial direction of the supply toner diffusion screw, a first region and a second region lower than the first region. The first region is located so as to face a region perpendicularly below a toner supply opening, and the second region is located so as not to face the region perpendicularly below the toner supply opening.

Abstract: A development device includes a development portion, to develop a latent image formed on a latent image carrier with developer, disposed close to the latent image carrier; a developer agitation container to agitate the developer, provided separately from the development portion; a transport system connecting the development portion and the developer agitation container, through which the developer is transported from the developer agitation container to the development portion by air; and a developer retainer to temporarily retain the developer, disposed downstream from the transport system, to which the developer remaining in the transport system escapes.

Abstract: In an embodiment, a contact pivoting plate, which comes into contact with a developer swelled by a discharge mixer, is provided in a case. The contact pivoting plate is pivoted according to a detection result of a temperature and humidity sensor to change the magnitude of resistance by the contact pivoting plate with respect to a flow of the developer. The height of the swell of the developer is suppressed from fluctuating according to an environmental change. The fluctuation in an amount of an excess developer discharged from a discharge port is suppressed to replace a deteriorated carrier in a development container with a new carrier little by little.

Abstract: A developing device in the embodiment includes: a developer carrier that carries a two-component developer, moves the surface, and supplies the toner to a latent image on a surface of a latent image carrier; a first conveying member that conveys the developer in a first conveying path; a second conveying member that conveys the developer in a second conveying path; and a developer passing unit that conveys upward the developer which has reached at a conveying-direction posterior end of the second conveying path and passes the developer to the first conveying path. The developer passing unit includes a plurality of pushing members that push up the developer. The developer can pass through from upper surfaces of the pushing members to lower surfaces of the pushing members.

Abstract: A development device includes a development portion, having a developer spout, to develop a latent image formed on a latent image carrier with developer including toner and carrier particles; a circulation unit to convey developer collected from the development portion to the developer spout in the development portion; a developer container, provided in the circulation unit, to contain the developer at a position upstream from the development portion in a developer circular direction, the developer container having a cylindrical upper portion and a funnel-shaped lower portion continuous with the cylindrical upper portion through a joint so that a level of the developer contained in the developer container at rest is positioned near the joint between the cylindrical upper portion and the funnel-shaped lower portion; and an agitator, provided inside the developer container, to agitate and mix the collected developer and fresh toner supplied to the developer container.

Abstract: A development device includes a developer bearer to carry by rotation two-component developer to a development range to develop a latent image formed on a latent image bearer, a magnetic field generator disposed inside the developer bearer, a developer regulator for adjusting an amount of the developer on the developer bearer, positioned upstream from the development range in a rotational direction of the developer bearer and facing the developer bearer across a regulation gap, a supply compartment from which the developer is supplied by a developer agitator to the developer bearer, a collection compartment, a pre-regulation portion adjacent to and upstream from the developer regulator in the rotational direction of the developer bearer, and a developer mobility adjuster that makes mobility of the developer in the pre-regulation portion higher on an upstream side in a developer conveyance direction in the supply compartment.

Abstract: In a developing device including a developer tank and a developing roller, an internal space of the developer tank is partitioned by a partition into a first conveying path, a second conveying path, a first communication path, and a second communication path. A first developer conveying section that conveys the developer in the developer tank in a first conveying direction X is disposed in the first conveying path. A second developer conveying section that conveys the developer in the developer tank in a second conveying direction Y is disposed in the second conveying path. The first developer conveying section includes a first spiral blade, and a rotation tube.

Abstract: Disclosed are a developing unit, in which a developing agent storing part is closed by an agitating member, and an image forming apparatus having the same. The developing unit includes a developing agent storing part to store a developing agent, a developing part connected to the developing agent storing part, and an agitating member rotatably provided in a channel between the developing agent storing part and the developing part to transfer the developing agent stored in the developing agent storing part to the developing part, wherein the channel is closed by the agitating member.

Abstract: A developing device includes: a developing vessel for storing a developer D containing a toner and a magnetic carrier; a first conveying passage for conveying the developer; a first conveying member provided in the first conveying passage for agitating and conveying the developer in a predetermined direction; a developing roller; a toner supply port for supplying toner to the first conveying passage; and an electromagnet arranged at the outer periphery of the toner supply port, and is constructed such that the toner supply port is formed over the first conveying member and the electromagnet intermittently attracts the developer residing under the toner supply port.

Abstract: A development device mounted on an electrophotographic image forming apparatus including a photoconductive drum in which an electrostatic latent image is formed on a surface thereof, the development device comprising: a developer tank; a development roller that is provided in the developer tank; first and second developer conveying paths; and first and second developer conveying spiral members that conveying the developer in the circulating manner in the first and second developer conveying paths, wherein at least one of the first and second developer conveying spiral members further includes an end blade that is provided at one end of the rotary shaft, the end blade includes: a spiral blade portion that is fixed to the circumferential surface of the rotary shaft; and a circumferential agitating plate portion that is fixed to a circumferential portion of the spiral blade portion.

Abstract: A developing apparatus includes a developing roller and a feed roller accommodated in a developing chamber of a developing frame, a first agitating member accommodated in a storing chamber of the developing frame for agitating the developer by rotating in a prescribed rotational direction while moving the developer in the rotational direction, a second agitating member accommodated in a developer accommodation chamber of a developer cartridge, a wall portion provided between the storing chamber and the developer accommodation chamber and formed with an opening for circulating the developer between the storing chamber and the developer accommodation chamber to face the storing chamber on a position above the upper end portion of the feed roller, and a conveyance member arranged between the opening of the wall portion and the developer accommodation chamber for conveying the developer in an axial direction of the developing roller.

Abstract: A developer stirring unit, a developing device containing the developer stirring unit and an image forming apparatus comprising the developing device are supplied capable of correctly judging a remainder amount of developer in accommodating tank. In the developer stirring unit, a accommodating tank accommodates developer; a stirring member has at least one shaft portion and is used to stir the developer accommodated in the accommodating tank; a bearing member couples with the shaft portion and supports the stirring member to possibly rotate around the shaft portion serving as rotation axis and to possibly move along a axis direction of the rotation axis; a driving section drives the stirring member to rotate; and a judging section judges a remainder amount of the developer in the accommodating tank, wherein the stirring member is controlled to move along an axis direction of the rotation axis together with rotating along a rotation direction of the rotation axis.

Abstract: An image forming apparatus, which has a plurality of image forming units, comprises a plurality of cartridges adapted to supply developer; a plurality of supply members adapted to supply developer to the image forming units from a plurality of the cartridges; a drive unit adapted to drive a plurality of the supply members; and a control unit adapted to supply developer from a plurality of the cartridges by selectively operating a plurality of the supply members based on the amount of developer accommodated in the cartridges.

Abstract: There are provided a developing unit and a developer stirring and transporting method in which the amount of developer in the developing unit can always be kept at a specified amount without being influenced by a use environment. A developing unit 10 includes a developing roller 12, a containing unit 16 to contain the developer and having a discharge port 14 to discharge the overflown developer in its side wall, a stirring and transporting member 20 to stir and transport the developer along a passage 18 formed in the containing unit 16, and a guide unit 22 provided in the passage 18 correspondingly to the discharge port 14 of the containing unit 16 and to guide the developer transported in the passage 18 by the stirring and transporting member 20 to the discharge port 14 side.

Abstract: A development agent circulation unit includes a development unit, an agitation unit, and a rotary feeder. The development unit develops a latent image on an image carrier using a developing agent. The agitation unit agitates developing agent recovered from the development unit. The rotary feeder receives the developing agent from the agitation unit and discharges the developing agent in predetermined discrete amounts. The discharged developing agent is transported to the development unit using a gas stream. The rotary feeder includes a rotor and a stator having a clearance “t” between the rotor and the stator. The clearance “t” satisfies a relation “t<2D” where D denotes a developing agent particle diameter, and a toner particle diameter dt of a toner particle of the developing agent and a carrier particle diameter dc of a carrier particle of the developing agent satisfy a relation D=dc+2dt.

Abstract: An image forming apparatus includes a two-component developing devices for each of a plurality of photoreceptors and a motor for the developing device. A transmission can assume a coupled state where the transmission transmits driving force of the motor to the developing device and a separated state where the transmission does not transmit the driving force of the motor to the developing device. A toner agitating mechanism stirs toner inside the developing device. A permeability sensor detects permeability inside the developing device and outputs a signal according to a ratio of the toner to the carrier. A coupling judging section judges that the coupling state exists when a variation of a signal value outputted by the permeability sensor equals or exceeds a predetermined value and judges that the separated state exists when the variation of the signal value outputted by the permeability sensor is lower than the predetermined value.

Abstract: An image forming apparatus includes: at least one retaining member configured to temporarily retain remaining developer remaining on a photosensitive member; a belt arranged opposite to a plurality of photosensitive members; a cleaning device collecting developer on the belt; a remaining developer collecting unit configured to cause the remaining developer retained by the retaining member to be transferred onto the belt via the photosensitive member and thereafter collected by the cleaning device; a circulation mechanism configured to circulate developer between the development chamber and the developer storage chamber; a detector detecting the amount of developer in the developer storage chamber; a determination unit configured to determine if the amount of developer in the developer storage chamber is less than a predetermined amount; and a notifying unit notifying to replace a developer receptacle when the amount of developer stored in the developer storage chamber becomes less than the predetermined amoun