Abstract: A developing device includes first and second chambers, a partition wall, first and second feeding screws, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including second to fourth magnetic poles, and a guiding portion. With respect to a supplying roller rotational direction, in a position downstream of the third magnetic pole, a magnetic flux density of the fourth magnetic pole in a normal direction is 20% of a maximum value thereof is a first position positioned downstream of a second position where a line connecting a lowermost end of the guiding portion and a supplying roller center crosses an outer peripheral surface of the supplying roller, and upstream of a third position where a line connecting an uppermost end of the first feeding screw and the supplying roller center crosses the outer peripheral surface of the supplying roller.

Abstract: A developing device includes a rotatable developing member, a developing container, a first communication opening, a second communication opening, a first feeding screw including a first rotation shaft, first and second blade portions, a second feeding screw including a second rotation shaft, third and fourth blade portions, a developer discharge opening provided upstream of an upstream end of the second communication opening in a first direction, and a third communication opening provided upstream of the upstream end of the second communication opening in the first direction. In a second direction opposite to the first direction, the third communication opening overlaps with the second blade portion. In the first direction, the third communication opening overlaps with the fourth blade portion. In the first direction, a downstream end of the third communication opening is positioned downstream of a downstream end of the developer discharge opening.

Abstract: A developing device includes first and second chambers, a partition wall, first and second feeding screws, a developing roller, a supplying roller, a first magnet including a first magnetic pole, a second magnet including second to fourth magnetic poles, and a guiding portion. With respect to a supplying roller rotational direction, in a position downstream of the third magnetic pole, a magnetic flux density of the fourth magnetic pole in a normal direction is 20 % of a maximum value thereof is a first position positioned downstream of a second position where a line connecting a lowermost end of the guiding portion and a supplying roller center crosses an outer peripheral surface of the supplying roller, and upstream of a third position where a line connecting an uppermost end of the first feeding screw and the supplying roller center rosses the outer peripheral surface of the supplying roller.

Abstract: A developing device includes a rotatable developing member, a developing container, a first communication opening, a second communication opening, a first feeding screw including a first rotation shaft, first and second blade portions, a second feeding screw including a second rotation shaft, third and fourth blade portions, a developer discharge opening provided upstream of an upstream end of the second communication opening in a first direction, and a third communication opening provided upstream of the upstream end of the second communication opening in the first direction. In a second direction opposite to the first direction, the third communication opening overlaps with the second blade portion. In the first direction, the third communication opening overlaps with the fourth blade portion. In the first direction, a downstream end of the third communication opening is positioned downstream of a downstream end of the developer discharge opening.

Abstract: A developing device includes a developer container configured to contain a developer, a developing carrying member configured to carry and feed the developer to a developing position, and a regulating member configured to regulate an amount of the developer carried by the developer carrying member, wherein the developer carrying member includes a magnet provided non-rotatably and stationarily inside the developer carrying member, and wherein the developer carrying member is provided with information regarding magnetic flux density of the magnet.

Abstract: An image formation apparatus includes an image-bearing member, an exposure device, an electro-conductive member, a bias application unit and a development device having a development roller and a toner supply roller. The bias application unit configured to apply biases to the toner supply roller, the development roller, and the electro-conductive member during image formation so that a first potential difference between the toner supply roller and the development roller and a second potential difference between the electro-conductive member and the development roller cause normally charged toner to travel respectively from the toner supply roller and the electro-conductive member to the development roller, and a third potential difference between the electro-conductive member and the toner supply roller causes normally charged toner to travel from the electro-conductive member to the toner supply roller.

Abstract: An image formation apparatus includes an image-bearing member, an exposure device, an electro-conductive member, a bias application unit and a development device having a development roller and a toner supply roller. The bias application unit configured to apply biases to the toner supply roller, the development roller, and the electro-conductive member during image formation so that a first potential difference between the toner supply roller and the development roller and a second potential difference between the electro-conductive member and the development roller cause normally charged toner to travel respectively from the toner supply roller and the electro-conductive member to the development roller, and a third potential difference between the electro-conductive member and the toner supply roller causes normally charged toner to travel from the electro-conductive member to the toner supply roller.

Abstract: A target value for a gap between a developer bearing member supported by a developing frame member and a regulating blade that is fixed to the developing frame member is determined based on input information about a local maximum peak value of magnetic flux density of a predetermined magnetic pole which is located closest to the regulating blade when the regulating blade is fixed to the developing frame member among a plurality of magnetic poles included in a magnet fixedly located inside the developer bearing member and configured to generate a magnetic field for causing a developer to be borne by the developer bearing member.

Abstract: According to a first aspect of the present invention, a developing apparatus includes a developer container, a conveyance screw, and an inductance sensor. The conveyance screw further comprises a rib, protruding in a radial direction from the shaft portion, provided at a position opposed to the inductance sensor, and a second blade portion provided continuously to an upstream end portion of the rib with respect to the conveyance direction and configured to convey the developer to the conveyance direction by rotation. The second blade portion is formed to extend not more than one-third of a turn from the upstream end portion of the rib downstream in a direction of rotation of the conveyance screw when viewed in an axial direction of the conveyance screw.

Abstract: A target value for a gap between a developer bearing member supported by a developing frame member and a regulating blade that is fixed to the developing frame member is determined based on input information about a local maximum peak value of magnetic flux density of a predetermined magnetic pole which is located closest to the regulating blade when the regulating blade is fixed to the developing frame member among a plurality of magnetic poles included in a magnet fixedly located inside the developer bearing member and configured to generate a magnetic field for causing a developer to be borne by the developer bearing member.

Abstract: A conveyance screw includes a shaft member, a first blade and a second blade each formed helically on a circumference of the shaft member. The first blade includes a first wide portion and a first narrow portion both located within an area in the axial direction where both of the first blade and the second blade are provided. The first wide portion is protruded radially outward from the shaft member to a first outer diameter. The first narrow portion is formed continuously with the first wide portion in a winding direction of the first blade around the shaft member, and is protruded radially outward from the shaft member to a second outer diameter that is smaller than the first outer diameter.

Abstract: A feeding screw for feeding a developer includes a rotation shaft, a first blade portion helically formed on an outer peripheral surface of the rotation shaft to feed the developer in one direction, a second blade portion helically formed on the outer peripheral surface to feed the developer in the one direction, and a third blade portion helically formed on the outer peripheral surface to feed the developer in the one direction. The first blade portion and the second blade portion overlap with each other with respect to a rotational axis direction of the feeding screw, the second blade portion and the third blade portion do not overlap with each other with respect to the rotational axis direction, and the third blade portion and the first blade portion overlap with each other with respect to the rotational axis direction.

Abstract: According to a first aspect of the present invention, a developing apparatus includes a developer container, a conveyance screw, and an inductance sensor. The conveyance screw further comprises a rib, protruding in a radial direction from the shaft portion, provided at a position opposed to the inductance sensor, and a second blade portion provided continuously to an upstream end portion of the rib with respect to the conveyance direction and configured to convey the developer to the conveyance direction by rotation. The second blade portion is formed to extend not more than one-third of a turn from the upstream end portion of the rib downstream in a direction of rotation of the conveyance screw when viewed in an axial direction of the conveyance screw.

Abstract: A developing device includes a developer carrying member, a first chamber, a second chamber, a first communicating portion, a second communicating portion, and a feeding screw, provided in the second chamber, including a feeding portion having a first helical blade and including a returning portion having a second helical blade in the form of a plurality of threads, the feeding portion and the returning portion being provided so that a boundary portion therebetween opposes the second communicating portion. The first helical blade and the second helical blade satisfy the following relationship: P2?P1, where P1 is a pitch, or lead, of the first helical blade and P2 is a lead of the second helical blade.

Abstract: A conveyance screw includes a shaft member, a first blade and a second blade each formed helically on a circumference of the shaft member. The first blade includes a first wide portion and a first narrow portion both located within an area in the axial direction where both of the first blade and the second blade are provided. The first wide portion is protruded radially outward from the shaft member to a first outer diameter. The first narrow portion is formed continuously with the first wide portion in a winding direction of the first blade around the shaft member, and is protruded radially outward from the shaft member to a second outer diameter that is smaller than the first outer diameter.

Abstract: A feeding screw for feeding a developer includes a rotation shaft, and first, second, and third blade portions helically formed on the outer peripheral surface of the rotation shaft to feed the developer in one direction. The first blade portion and the second blade portion overlap with each other, the second blade portion and the third blade portion do not overlap with each other, and the third blade portion and the first blade portion overlap with each other, all with respect to the rotational axis direction of the feeding screw. A gap is provided between a downstream end of the second blade and an upstream end of the third blade portion in the one direction, and the gap is disposed within a region where the first blade portion is formed with respect to the rotational axis direction of the feeding screw.

Abstract: A feeding screw for feeding a developer includes a rotation shaft, a first blade portion helically formed on an outer peripheral surface of the rotation shaft to feed the developer in one direction, a second blade portion helically formed on the outer peripheral surface to feed the developer in the one direction, and a third blade portion helically formed on the outer peripheral surface to feed the developer in the one direction. The first blade portion and the second blade portion overlap with each other with respect to a rotational axis direction of the feeding screw, the second blade portion and the third blade portion do not overlap with each other with respect to the rotational axis direction, and the third blade portion and the first blade portion overlap with each other with respect to the rotational axis direction.

Abstract: A target value for a gap between a developer bearing member supported by a developing frame member and a regulating blade that is fixed to the developing frame member is determined based on input information about a local maximum peak value of magnetic flux density of a predetermined magnetic pole which is located closest to the regulating blade when the regulating blade is fixed to the developing frame member among a plurality of magnetic poles included in a magnet fixedly located inside the developer bearing member and configured to generate a magnetic field for causing a developer to be borne by the developer bearing member.

Abstract: A developing apparatus includes a developer bearing member, a first chamber to supply developer to the developer bearing member, and a second chamber to collect the developer conveyed from the developer bearing member. A first screw is disposed within the first chamber and conveys the developer in a first direction, and a second screw is disposed within the second chamber and includes a first conveyance portion to convey the developer in an opposite second direction and a return portion provided downstream of the first communication port in the second direction. The return portion conveys the developer in the first direction. A discharge portion is provided in the second chamber and downstream of the return portion in the second direction to discharge the developer out of the second chamber. The first communication port is disposed outside a developer bearing area on the developer bearing member in the second direction.

Abstract: A developing device includes a first communication portion defining a communication path through which developer in a second chamber is communicated to a first chamber. The communication path has a first area and a second area. The first area is positioned within a range corresponding to a developer coating area of a developer bearing member in a conveyance direction of developer in the collection chamber, while the second area is positioned downstream of the developer coating area in the conveyance direction. A first length of the first area is shorter than a second length of the second area. The first length is a maximum length from a bottom surface portion of the communication path to an upper portion of the first area, and the second length is a maximum length from the bottom surface portion of the communication path to an upper portion of the second area.