Image forming apparatus

An image forming apparatus comprising:

• an image carrier for electrostatically forming a latent image thereon;
• a developer carrier for conveying a developer consisting of toner and carrier while retaining the developer thereon, and causing the toner to deposit on the latent image formed on said image carrier;
• and
• means for forming an oscillation electric field between said image carrier and said developer carrier for causing the toner to move;
• wherein the carrier has a volume resistivity of lower than 10.sup.10 .OMEGA.cm inclusive, and wherein a period of time assigned to a phase for causing the toner to move toward the latent image is t.sub.1, a period of said oscillation electric field is T, a mass-average particle size of toner is L.sub.t, and a mass-average particle size of the carrier is L.sub.c, and the following conditions are satisfied:
• 1.0.times.10.sup.-4 <t.sub.1.sup.2 /L.sub.t <5.0.times.10.sup.-4 (sec.sup.2 /m)
• T.sup.2 /L.sub.c <0.002(sec.sup.2 /m).

An image forming apparatus comprising:

• an image carrier for electrostatically forming a latent image thereon;
• a developer carrier for conveying a developer consisting of toner and carrier while retaining the developer thereon, and causing the toner to deposit on the latent image formed on said image carrier;
• and
• control means for forming, with an AC voltage and a DC voltage, an oscillation electric field for causing the toner to move between said image carrier and said developer carrier, and varying a duty ratio of the AC voltage and the DC voltage in accordance with a change in a developing condition.

An image forming apparatus comprising:

• an image carrier for electrostatically forming a latent image thereon;
• a developer carrier for conveying a developer consisting of toner and carrier while retaining the developer thereon, and causing the toner to deposit on the latent image formed on said image carrier;
• control means for forming, with an AC voltage and a DC voltage, an oscillation electric field for causing the toner to move between said image carrier and said developer carrier, and varying a duty ratio of the AC voltage and the DC voltage based on a characteristic of the developer carrier;
• and
• varying means for varying the duty ratio of the AC voltage and the DC voltage in accordance with humidity in or around a developing device accommodating said developer carrier.

An image forming apparatus comprising:

• an image carrier for electrostatically forming a latent image thereon;
• a developer carrier for conveying a developer consisting of toner and carrier while retaining the developer thereon, and causing the toner to deposit on the latent image formed on said image carrier;
• and
• control means for forming, with an AC voltage and a DC voltage, an oscillation electric field for causing the toner to move between said image carrier and said developer carrier, and varying a duty ratio of the AC voltage and the DC voltage based on a characteristic of the developer carrier.