Developing device, image forming apparatus, coil attaching method to developing device

A method of attaching a coil of a developing device, the method comprising:

• storing developer containing carrier and toner in a developer container;
• stirring and feeding the developer along a longitudinal direction of the developer container by a first feeding member disposed in a first compartment that is one of compartments disposed in the developer container;
• stirring and feeding the developer in the developer container in the opposite direction to the first feeding member by a second feeding member disposed in a second compartment that is the other of the compartments disposed in the developer container;
• carrying the developer on a surface of the developing roller disposed in an upper part of the developer container so as to face an image carrier on which an electrostatic latent image is formed, the developing roller being supported by the developer container in a rotatable manner;
• allowing the toner density sensor including a coil to detect toner density in the developer;
• connecting an end of the first compartment to an end of the second compartment via a pair of communication portion disposed on both ends in the longitudinal direction of the first compartment and the second compartment;
• forming a gap between the first compartment and the second compartment inside the pair of communication portion in the longitudinal direction, so as to use a part of the first compartment adjacent to the gap as a cylindrical portion through which the first feeding member and the developer pass;
• using a flat cable as the coil;
• and
• making the flat cable pass through the gap and be wound around the cylindrical portion so as to form a winding by overlapping both end portions of the flat cable in a state where terminals of wires are shifted by one pitch.