Developing device

A developing device comprising:

• a developing container configured to accommodate a developer including toner and a carrier;
• a first rotatable member to which the developer accommodated in the developing container is supplied and which carries and feeds the developer to a first developing position where an electrostatic latent image formed on an image bearing member is developed;
• a first magnet provided non-rotatably and stationarily inside the first rotatable member, wherein the first magnet includes a first developing pole provided opposed to the image bearing member in the first developing position, a delivering pole provided downstream of the first developing pole with respect to a rotational direction of the first rotatable member, and a first feeding pole provided upstream of the delivering pole and adjacent to the delivering pole, with respect to the rotational direction of the first rotatable member, and having a magnetic polarity different from the delivering pole;
• a second rotatable member provided opposed to the first rotatable member and to which the developer is delivered from the first rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position where the electrostatic latent image is developed, and wherein a rotational direction of the second rotatable member in a position where on an outer peripheral surface of the second rotatable member, the second rotatable member is closest to the first rotatable member is opposite to the rotational direction of the first rotatable member in a position where on an outer peripheral surface of the first rotatable member, the first rotatable member is closest to the second rotatable member;
• and
• a second magnet provided non-rotatably and stationarily inside the second rotatable member, wherein the second magnet includes a plurality of magnetic poles including a second developing pole provided opposed to the image bearing member in the second developing position, a receiving pole provided upstream of the second developing pole with respect to the rotational direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole provided downstream of the receiving pole and adjacent to the receiving pole, with respect to the rotational direction of the second rotatable member, and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole, of the plurality of magnetic poles, provided closest to the delivering pole,
• wherein a position where on the outer peripheral surface of the second rotatable member, a magnetic flux density of the receiving pole in a normal direction relative to the outer peripheral surface of the second rotatable member is maximum is a point T,
• of positions each where on the outer peripheral surface of the second rotatable member, the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a half value of the maximum, the position on an upstream side with respect to the rotational direction of the second rotatable member is a point Hu, and
• of the positions each where on the outer peripheral surface of the second rotatable member, the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is the half value of the maximum, the position on a downstream side with respect to the rotational direction of the second rotatable member is a point Hd, and
• wherein in a graph in which an ordinate represents the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member and an abscissa represents an angle of the second rotatable member with respect to the rotational direction of the first rotatable member,
• in a case where
• a rectilinear line passing through the point T and parallel to the abscissa is a rectilinear line HLt,
• a rectilinear line passing through the points Hu and Hd and parallel to the abscissa is HLh,
• a rectilinear line passing through the point Hu and parallel to the ordinate is VL21,
• a rectilinear line passing through the point Hd and parallel to the ordinate is VL22,
• an area of a rectangle enclosed by the rectilinear lines VL21, VL22, HLt, and HLh is an area S, and
• in a region of the rectangle, an area obtained by integrating the magnetic flux density of the receiving pole, in the normal direction relative to the outer peripheral surface of the second rotatable member, from the rectilinear line VL21 to the rectilinear line VL22 in terms of the angle of the second rotatable member with respect to the rotational direction of the second rotatable member is an area Sa,
• the following relationship is satisfied:
• Sa
• /
• S
• ≥
• 75
• ⁢
• %
• .

A developing device comprising:

• a developing container configured to accommodate a developer including toner and a carrier;
• a first rotatable member to which the developer accommodated in the developing container is supplied and which carries and feeds the developer to a first developing position where an electrostatic latent image formed on an image bearing member is developed;
• a first magnet provided non-rotatably and stationarily inside the first rotatable member, wherein the first magnet includes a first developing pole provided opposed to the image bearing member in the first developing position, a delivering pole provided downstream of the first developing pole with respect to a rotational direction of the first rotatable member, and a first feeding pole provided upstream of the delivering pole and adjacent to the delivering pole, with respect to the rotational direction of the first rotatable member, and having a magnetic polarity different from the delivering pole;
• a second rotatable member provided opposed to the first rotatable member and to which the developer is delivered from the first rotatable member by a magnetic field generated by the first magnet, wherein the second rotatable member carries and feeds the developer to a second developing position where the electrostatic latent image is developed, and wherein a rotational direction of the second rotatable member in a position where on an outer peripheral surface of the second rotatable member, the second rotatable member is closest to the first rotatable member is opposite to the rotational direction of the first rotatable member in a position where on an outer peripheral surface of the first rotatable member, the first rotatable member is closest to the second rotatable member;
• and
• a second magnet provided non-rotatably and stationarily inside the second rotatable member, wherein the second magnet includes a plurality of magnetic poles including a second developing pole provided opposed to the image bearing member in the second developing position, a receiving pole provided upstream of the second developing pole with respect to the rotational direction of the second rotatable member and having a magnetic polarity different from that of the delivering pole, and a second feeding pole provided downstream of the receiving pole and adjacent to the receiving pole, with respect to the rotational direction of the second rotatable member, and having a magnetic polarity different from that of the receiving pole, the receiving pole being a magnetic pole, of the plurality of magnetic poles, provided closest to the delivering pole,
• wherein a position where on the outer peripheral surface of the second rotatable member, a magnetic flux density of the receiving pole in a normal direction relative to the outer peripheral surface of the second rotatable member is maximum is a point T,
• of positions each where on the outer peripheral surface of the second rotatable member, the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a half value of the maximum, the position on an upstream side with respect to the rotational direction of the second rotatable member is a point Hu, and
• of the positions each where on the outer peripheral surface of the second rotatable member, the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is the half value of the maximum, the position on a downstream side with respect to the rotational direction of the second rotatable member is a point Hd, and
• wherein in a graph in which an ordinate represents the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member and an abscissa represents an angle of the second rotatable member with respect to the rotational direction of the second rotatable member,
• in a case where
• of positions each where the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a value which is 10% of the maximum of the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member, the position on an upstream side with respect to the rotational direction of the second rotatable member is a point Cu,
• of positions each where the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a value which is 10% of the maximum of the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member, the position on a downstream side with respect to the rotational direction of the second rotatable member is a point Cd,
• of positions each where the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a value which is 90% of the maximum of the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member, the position on an upstream side with respect to the rotational direction of the second rotatable member is a point Du,
• of positions each where the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member is a value which is 90% of the maximum of the magnetic flux density of the receiving pole in the normal direction relative to the outer peripheral surface of the second rotatable member, the position on a downstream side with respect to the rotational direction of the second rotatable member is a point Dd,
• an angle formed by a rectilinear line L21C connecting the rotation center R2 and the point Cu and a rectilinear line L22C connecting the rotation center R2 and the point Cd is Wc, and
• an angle formed by a rectilinear line L21D connecting the rotation center R2 and the point Du and a rectilinear line L22D connecting the rotation center R2 and the point Dd is Wd, and
• the following relationship is satisfied:
• Wd
• /
• Wc
• ≥
• 40
• ⁢
• %
• .