Developing device including first and second developer carrying devices with insufficiently-charged developer control feature

A developing device comprising:

• a rotatable first developer carrying member for carrying a developer thereon to develop an electrostatic image formed on an image bearing member with the developer, said first developer carrying member being provided with a plurality of nonrotary magnetic poles therein;
• a rotatable second developer carrying member for carrying the developer thereon to develop said electrostatic image formed on said image bearing member with the developer, said second developer carrying member being provided upstream of said first developer carrying member in a direction of movement of said image bearing member, said second developer carrying member being provided with a regulation surface for regulating an amount of the developer carried on said first developer carrying member, and said developer carrying member being provided with a plurality of nonrotary magnetic poles therein, a direction of rotation of said second developer carrying member being the same direction as a direction of rotation of said first developer carrying member;
• and
• a developer regulating member for regulating an amount of the developer carried on said second developer carrying member,
• wherein positions of said plurality of magnetic poles within said first developer carrying member and said plurality of magnetic poles within said second developer carrying member are set so that a magnetic pole of a predetermined polarity among said plurality of magnetic poles within said first developer carrying member and a magnetic pole of an opposite polarity to said predetermined polarity among said plurality of magnetic poles within said second developer carrying member may not exist at a time at an opposite position whereat said first developer carrying member and said second developer carrying member are opposed to each other in an area formed between a tangent connecting a center of rotation of said second developer carrying member to a surface of said first developer carrying member on a side of said image bearing member and a line connecting a center of rotation of said first developer carrying member and the center of rotation of said second developer carrying member.