Abstract: A developing apparatus includes a developer carrying member configured to carry a developer including a toner and a carrier, a supply chamber provided opposite to a peripheral surface of the developer carrying member, and a collection chamber provided opposite to the peripheral surface of the developer carrying member. In addition, a first conveyance member is provided in the supply chamber, a second conveyance member is provided in the collection chamber, and a third conveyance member is provided opposite to the second conveyance member. The third conveyance member and the second conveyance member are directly opposed to each other in a predetermined position which overlaps with a developer carrying area of the developer carrying member, and the third conveyance member conveys a part of the developer conveyed by the second conveyance member in the predetermined position in the direction opposite to the second conveyance member.

Abstract: A developing device includes a developing container, a feeding member including a blade, and a discharge opening for permitting discharge of an excessive developer, with supply of the developer, from the developing container. The blade is rotatable such that the blade moves downwardly at a side opposing to the discharge opening. A winding direction of the blade is such as to ascend toward the downstream with respect to the developer feeding direction, at the opposing side. A bottom end of the downstream edge of the discharge opening in a first cross-section taken perpendicularly to the rotation shaft is at a higher level than in a second cross-section at an upstream of the first cross-section with respect to the developer feeding direction.

Abstract: A developing apparatus includes a rotatable developer carrying that carries developer on its surface. A first screw conveys the developer in a developing chamber, a second screw conveys the developer in a collection chamber in a direction opposite to the first screw, and a third screw conveys the developer in the collection chamber in a direction opposite to the second screw. A rotation center of the third screw is disposed opposite to a rotation center of the second screw and in a projection area on which an area of the surface of the developer carrying member downstream of a first position in the rotation direction of the developer carrying member and upstream of a second position in the rotation direction of the developer carrying member is projected downward in a gravity direction in a cross section orthogonal to a rotation axis of the third screw.

Abstract: A developing apparatus includes a developer carrying member configured to carry a developer, and a magnet member disposed inside the developer carrying member. The magnet member includes one or more first magnet portions having a first magnetic polarity at an outer surface thereof opposing an inner surface of the developer carrying member, and one or more second magnet portions having a second magnetic polarity at an outer surface thereof opposing the inner surface. In a cross-section perpendicular to a longitudinal direction of the magnet member at a longitudinally central portion thereof, a number of the first magnet portions is larger than a number of the second magnet portions, and a ratio of a total area of the first magnet portions in the cross-section is smaller at a longitudinally end portion of the magnet member than at the longitudinally central portion.

Abstract: A magnet roller includes a plurality of magnet pieces disposed along a circumferential direction of the magnet roller. The magnetic pieces include one or more first magnet pieces having a first magnetic polarity at a surface opposing an inner surface of the magnet roller, and one or more second magnet pieces having a second magnetic polarity, which is opposite of the first magnetic polarity, at a surface opposing the inner surface of the magnet roller. In a longitudinally central portion of the magnet roller, a ratio of a total sum of volumes occupied by the one or more first magnet pieces per unit length is larger than a ratio of a total sum of volumes occupied by the one or more second magnet pieces per unit length, and the ratio of the total sum of the volumes occupied by the one or more first magnet pieces per unit length in a longitudinally end portion is smaller than that in the longitudinally central portion.

Abstract: An image forming apparatus comprising: a replenishment toner container which houses toner; and a development device which forms an image by using the toner supplied from the replenishment toner container, wherein at least two types of external additives are added to the toner, wherein, of the two types of external additives, when an added amount of a first external additive is Wh (volume % with respect to the toner) and an added amount of a second external additive is Wl (volume % with respect to the toner), a value of Wh+Wl in initial toner of a developer housed in the development device in advance is larger than a value of Wh+Wl in replenishment toner of a developer housed in the replenishment toner container; and wherein the fluidity of the replenishment toner is higher than the fluidity of the initial toner.

Abstract: A developing apparatus includes a developing sleeve, a regulating member configured to regulate a developer, and first and second chambers forming a circulation route of the developer. A magnet is fixed in the developing sleeve and includes a first magnetic pole, a second magnetic pole having the same polarity as the first magnetic pole, and a third magnetic pole having a different polarity from the second magnetic pole. The second magnetic pole is arranged upstream of an intersection at which a vertical line passing through a rotation center of a first conveying member in the first chamber arranged below the rotation center of the developing sleeve intersects with a lower surface of the developing sleeve.

Abstract: A developing device, comprising: a first developer bearing member which includes a first magnetic field generating member having a plurality of magnetic poles for bearing and conveying developer including magnetic particles; and a second developer bearing member which includes a second magnetic field generating member having a plurality of magnetic poles for bearing and conveying the developer delivered from the first developer bearing member, wherein the first magnetic field generating member and the second magnetic field generating member respectively have a first low magnetic field region and a second low magnetic field region formed by adjacent magnetic poles having a same polarity among respective plurality of magnetic poles, and wherein two or more minimal points are formed in magnetic flux density of a normal component of a surface of the second developer bearing member in the second low magnetic field region.

Abstract: In a developing device, the conveying ability of a second screw in a first area that includes an area, which is superposed with, in an axial direction of a developing sleeve, a developer carrying area of the developing sleeve and a downstream communicating portion through which a developer is conveyed from a developing chamber to a collecting chamber, is lower than the conveying ability of the second screw in a second area, which is positioned further downstream than the first area in a direction in which the developer is conveyed and which is superposed with the developer carrying area of the developing sleeve.

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

Abstract: A developing apparatus, including: a developing sleeve; a regulating member configured to regulate a developer; a first chamber; a second chamber communicating with the first chamber to form a circulation route of the developer; and a magnet fixed in the developing sleeve and including a first magnetic pole, a second magnetic pole having the same polarity as the first magnetic pole and being arranged adjacently to and downstream of the first magnetic pole, and a third magnetic pole having a different polarity from the second magnetic pole and being arranged adjacently to and downstream of the second magnetic pole, the second magnetic pole being arranged upstream of an intersection at which a vertical line passing through a rotation center of a first conveying member in the first chamber arranged below the rotation center of the developing sleeve intersects with a lower surface of the developing sleeve.

Abstract: A developing apparatus includes a developer carrying member; and a magnetic member provided inside the carrying member and having magnetic poles arranged circumferentially, wherein on a center axis of the carrying member outside an end of the magnetic member, there is a region in which a magnetic flux density of a first magnetic polarity converges toward zero; and wherein a ratio of a volume, per unit length, of a portion of the magnetic member which has a surface magnetic pole of a second magnetic polarity which is different from the first magnetic polarity in a longitudinal end portion to that in a longitudinally central portion is smaller than a ratio of a volume of a portion of the magnetic member which has a surface magnetic pole of the first magnetic polarity in a longitudinal end portion to that in a longitudinally central portion.

Abstract: A developing apparatus includes a sleeve for carrying a developer including toner and magnetic carrier, the sleeve having a plurality of grooves extending in a longitudinal direction; a magnet provided inside the sleeve, a non-magnetic regulating member, provided spaced from the sleeve, wherein an amount M/S (mg/mm2) of the developer carried on a unit area of the sleeve after passing by the regulating member, a gap SB (mm) between a free end of the regulating member and the sleeve, a density G (mg/mm3) of the developer, and a groove ratio ? which is a ratio of the grooves in the surface of the sleeve satisfy, 0.1?M/S(mg/mm2)?0.5 0.2?SB(mm), and m/S(mg/mm2)×1/4??×{SB(mm)+D(mm)}×G(mg/mm3)<M/S(mg/mm2).

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

Abstract: A developing apparatus includes a developer carrying member for carrying a developer; and a magnetic member including a plurality of magnet pieces disposed inside the developer carrying member along a circumferential direction of the developer carrying member. The magnetic member includes one or more first magnet pieces having the same magnetic polarity at a surface opposing an inner surface of the developer carrying member, and one or more second magnet pieces having the other magnetic polarity opposing the inner surface of the developer carrying member. A total sum of the first magnet pieces is larger than a total sum of the second magnet pieces, and a ratio of the total sum of a volume of the first magnet pieces to a space occupied by the magnetic member is smaller at an end portion than in a central portion with respect to a longitudinal direction of the magnetic member.

Abstract: A developing apparatus is provided in which, with reference to a middle position in a developer conveyance direction, an average friction coefficient between an inner wall of the developing chamber and the developer, is smaller at an upstream side than at a downstream side in the developer conveyance direction.

Abstract: A developing apparatus, including: a developing sleeve; a magnet configured to cause the sleeve to carry the developer and including a first magnetic pole and a second magnetic pole; a supply chamber configured to supply the developer to the sleeve; a collection chamber configured to collect the developer used for development; a first conveyance member and a second conveyance member provided in the supply chamber and the collection chamber, respectively; and a third conveyance member configured to convey the developer collected in the collection chamber in a direction opposite to a developer conveying direction in the collection chamber, wherein a center of the third conveyance member is arranged below a zone and overlaps the zone, which is defined on a surface of the sleeve between a local maximal peak of a magnetic flux density of the first magnetic pole and a local minimal peak of the magnetic flux density.

Abstract: A repulsive magnetic field is formed in a section immediately upstream of a regulating blade, so that generation of a developing-agent stationary layer is suppressed or eliminated. Accordingly, a developing apparatus capable of stably maintaining the layer thickness of developing agent conveyed to a developing area for a long time is provided.

Abstract: In a development apparatus including conveying screws which circulates and conveys developer in a developer container as being rotated, a developing sleeve which bears and conveys developer in the developer container as being rotated, and a restriction blade which restricts developer quantity at the developing sleeve, the developer container includes a supply chamber to supply developer to the developing sleeve and a retrieval chamber to retrieve developer from the developing sleeve, and rotation speed of the conveying screws or rotation speed of the developing sleeve is changed so that Vsc/Vsl during image forming is not performed is to be smaller than that during image forming is performed, as Vsc denotes the rotation speed of the conveying screws and Vsl denotes the rotation speed of the developing sleeve.

Abstract: A developing apparatus is provided in which, with reference to a middle position in a developer conveyance direction, an average friction coefficient between an inner wall of the developing chamber and the developer, is smaller at an upstream side than at a downstream side in the developer conveyance direction.