Developing apparatus featuring first and second developing systems

A developing apparatus comprising:

• first developing means for developing a latent image formed on an image bearing member with a first developer comprising a magnetic toner, said first developing means including a first developer carrying member for carrying and feeding the first developer to the image bearing member and first magnetic field generating means disposed in said first developer carrying member;
• and
• second developing means for developing a latent image formed on the image bearing member with a second developer comprising a magnetic carrier and a non-magnetic toner while the second developer contacts the image bearing member, said second developing means including a second developer carrying member for carrying and feeding the second developer to the image bearing member and second magnetic field generating means disposed in said second developer carrying member;
• wherein a magnetization intensity Mσ′ (Am2/kg) of the magnetic toner in an external magnetic field, which is a development magnetic field provided by said first magnetic field generating means and a magnetization intensity Cσ′ (Am2/kg) of the magnetic carrier in an external magnetic field which is a development magnetic field provided by said second magnetic field generating means, satisfy the following inequalities:
• 30<Cσ′(Am2/kg)<Mσ′(Am2/kg)×1.8.

A developing apparatus comprising:

• first developing means for developing a latent image formed on an image bearing member with a first developer comprising a magnetic toner, said first developing means including a first developer carrying member for carrying and feeding the first developer to the image bearing member and first magnetic field generating means disposed in said first developer carrying member;
• and
• second developing means for developing a latent image formed on the image bearing member with a second developer comprising a magnetic carrier and a non-magnetic toner while the second developer contacts the image bearing member, said second developing means including a second developer carrying member for carrying and feeding the second developer to the image bearing member and second magnetic field generating means disposed in said second developer carrying member,
• wherein a magnetization intensity Mσ (Am2/kg) of the magnetic toner in an external magnetic field of 795.8 (kA/m) and a magnetization intensity Cσ (Am2/kg) of the magnetic carrier in the same external magnetic field, satisfy the following inequality:
• Cσ(Am2/kg)<Mσ(Am2/kg)×1.7.

A developing apparatus comprising:

• first developing means for developing a latent image formed on an image bearing member with a first developer comprising a magnetic toner, said first developing means including a first developer carrying member for carrying and feeding the first developer to the image bearing member and first magnetic field generating means disposed in said first developer carrying member;
• and
• second developing means for developing a latent image formed on the image bearing member with a second developer comprising a magnetic carrier and a non-magnetic toner while the second developer contacts the image bearing member, said second developing means including a second developer carrying member for carrying and feeding the second developer to the image bearing member and second magnetic field generating means disposed in said second developer carrying member,
• wherein a magnetization intensity Mσ′(Am2/kg) of the magnetic toner in an external magnetic field, which is a development magnetic field provided by said first magnetic field generating means and a magnetization intensity Cσ′(Am2/kg) of the magnetic carrier in an external magnetic field, which is a development magnetic field provided by said second magnetic field generating means, satisfy the following inequality:
• Cσ′(Am2/kg)<Mσ′(Am2/kg)×1.8.