Developing device

A developing device comprising:

• a developing container configured to accommodate a developer including toner and a carrier;
• a rotatable developing member configured to carry and feed the developer to a developing position where an electrostatic latent image formed on an image bearing member is developed;
• a supplying screw configured to supply the developer to the rotatable developing member while stirring and feeding the developer;
• a regulating portion configured to regulate an amount of the developer carried on an outer peripheral surface of the rotatable developing member, the regulating portion being positioned below a rotation center of the rotatable developing member with respect to a vertical direction and upstream of a lowest point of the rotatable developing member with respect to a rotational direction of the rotatable developing member;
• a magnet provided non-rotatably and stationarily inside the rotatable developing member, the magnet including
• a regulating pole provided opposed to the regulating portion,
• an upstream pole provided upstream of the regulating pole and adjacent to the regulating pole, with respect to the rotational direction of the rotatable developing member, and having a polarity different from that of the regulating pole, and
• a downstream pole provided downstream of the regulating pole and adjacent to the regulating pole, with respect to the rotational direction of the rotatable developing member, and having a plurality different from that of the regulating pole;
• and
• an inclined portion inclined downward in a vertical direction toward the regulating portion, wherein
• a starting point of inclination of the inclined portion downward in the vertical direction is positioned below, in the vertical direction, a point on the outer peripheral surface of the rotatable developing member where an absolute value of magnetic flux density of the upstream pole in a normal direction to the outer peripheral surface of the rotatable developing member becomes a maximum value, and above the regulating portion in the vertical direction, and
• the starting point of inclination of the inclined portion downstream in the vertical direction is positioned between the supplying screw and the rotatable developing member with respect to a horizontal direction,
• wherein in a case where
• of a magnetic force acting on the carrier on the outer peripheral surface of the rotatable developing member, the magnetic force in a tangential direction to the outer peripheral surface of the rotatable developing member is defined as Fθ,
• a sign of Fθ when a direction of Fθ is the same direction as the rotational direction of the rotatable developing member is defined as a positive, and
• a sign of Fθ when the direction of Fθ is a direction opposite to the rotational direction of the rotatable developing member is defined as a negative,
• with respect to the rotational direction of the rotatable developing member, Fθ>0 is satisfied over a range from a point where a line connecting the rotation center of the rotatable developing member and the starting point of inclination of the inclined portion downward in the vertical direction crosses the outer peripheral surface of the rotatable developing member to a point where a line connecting the rotation center of the rotatable developing member and the regulating portion crosses the outer peripheral surface of the rotatable developing member.