Developing device having inductance sensor

A developing device comprising:

• a developer bearing member which bears developer including toner and carrier to develop an electrostatic latent image formed on an image bearing member;
• a developing container which accommodates the developer;
• a conveying screw which conveys the developer accommodated in the developing container;
• and
• an inductance sensor which includes a detecting portion which detects magnetic permeability of the developer accommodated in the developing container,
• wherein in a state the inductance sensor is not attached to the developing container and a predetermined magnetic material is disposed at a position in contact with the detection portion, an output value when the detecting portion detects magnetic permeability of the predetermined magnetic material is A, and
• in a state the inductance sensor is not attached to the developing container and the predetermined magnetic material is disposed 1 mm away from the detection portion in a vertical direction passing through the detection portion, an output value when the detecting portion detects magnetic permeability of the predetermined magnetic material is B, with B/A≥0.1 being satisfied,
• wherein the conveying screw includes:
• a first conveying portion which has a first rotary shaft portion and a first blade portion which is spirally formed on an outer circumferential surface of the first rotary shaft portion and which conveys the developer in a conveying direction of the conveying screw;
• and
• a second conveying portion which has a second rotary shaft portion and a second blade portion which is spirally formed on an outer circumferential surface of the second rotary shaft portion and which conveys the developer in the conveying direction of the conveying screw,
• wherein the first conveying portion is disposed opposite the detection portion with respect to the conveying direction of the conveying screw,
• wherein the second conveying portion is disposed within one pitch downstream of the first blade portion from a downstream end of the detection portion with respect to the conveying direction of the conveying screw, and
• wherein a shaft diameter of the second rotary shaft portion is greater than a shaft diameter of the first rotary shaft portion.