Abstract: An image forming apparatus including: a developing bias application portion that applies a developing bias in which an AC voltage and a DC voltage are superimposed on the developer bearing member in order to develop an electrostatic latent image formed on the image bearing member by the developer carried on the developer bearing member; a toner replenishment container that accommodates a toner to be supplied to the developing container; an acquisition portion that acquires information on a coverage of an external additive carried on a surface of the toner accommodated in the toner replenishment container; and a controller that controls the developing bias application portion based on the information on the coverage acquired by the acquisition portion.

Abstract: An image forming apparatus includes an image bearing member, a charging portion, a latent image forming portion, a developer bearing member for bearing and feeding a developer including toner and an external additive having the same polarity as a charging polarity of the toner, and a developing bias application portion for applying a developing bias in which a DC voltage is superposed with an AC voltage to the developer bearing member. In a continuous image forming job, the developing bias application portion applies the developing bias to the developer bearing member so that an absolute value of a difference between a predetermined charging potential and the DC voltage in a non-developing period is larger than an absolute value of that in a developing period and a peak-to-peak voltage of the AC voltage in the non-developing period is larger than that in the developing period.

Abstract: An image forming apparatus includes an image bearing member, a developing apparatus, a driving device, an airflow space portion, a duct, and, a drawing fan. A driving-force transmission member, the driving device and the airflow space portion are disposed on a side on which a developer container faces the image bearing member. The driving-force transmission member, the driving device, the duct and the drawing fan are disposed on one end side of a developing rotary member in a rotation-axis direction of the developing rotary member. The duct is disposed underneath the developer container, formed from the side on which the developer container faces the image bearing member to a side opposite to the side on which the developer container faces the image bearing member. The drawing fan is disposed on the side opposite to the side on which the developer container faces the image bearing member.

Abstract: An image forming apparatus includes an image bearing member, a developing apparatus, a driving device, an airflow space portion, a duct, and, a drawing fan. A driving-force transmission member, the driving device and the airflow space portion are disposed on a side on which a developer container faces the image bearing member. The driving-force transmission member, the driving device, the duct and the drawing fan are disposed on one end side of a developing rotary member in a rotation-axis direction of the developing rotary member. The duct is disposed underneath the developer container, formed from the side on which the developer container faces the image bearing member to a side opposite to the side on which the developer container faces the image bearing member. The drawing fan is disposed on the side opposite to the side on which the developer container faces the image bearing member.

Abstract: An image forming apparatus includes a developing apparatus including a housing having a supply opening to receive developer supplied by a pump unit, a developing device screw disposed in a discharge path of the housing to supply and discharge the developer through a discharge opening to an image bearing member, and a developer bearing portion having a magnetic body that generates a magnetic force and is configured to bear the developer with a carrying force working in a substantially perpendicular direction to the magnetic force. In addition, a developer accommodation portion within the housing accommodates the developer supplied from a supply opening and has no opening other than the supply opening and the discharge opening, with the developer accommodation portion having a space volume capable of suppressing a spouting force caused by an inner pressure increase due to operation of the pump unit.

Abstract: A developing apparatus includes: a supply path configured to supply a developer; a discharge path configured to discharge the developer supplied from the supply path and perform developing; a developer holding portion configured to exert a predetermined force for holding the developer at the discharge path; and a developer accommodation portion accommodating the developer which is supplied from the supply path, and having a space volume so that the developer does not spout out from the discharge path on which the predetermined force is exerted by the developer holding portion according to an increase in an internal pressure of the developer accommodation portion when the developer is supplied from the supply path in a state where a predetermined amount of the developer is accommodated.