Developing device

A developing device comprising:

• a rotatable developing member configured to carry and feed a developer containing toner and a carrier to a position where an electrostatic latent image formed on an image bearing member is developed;
• a developing container including a first chamber in which the rotatable developing member is provided and in which the developer is supplied to the rotatable developing member and a second chamber which is partitioned from the first chamber by a partition wall and in which the developer is circulated between itself and the first chamber;
• a first communication opening configured to permit communication of the developer from the first chamber to the second chamber;
• a second communication opening configured to permit communication of the developer from the second chamber to the first chamber;
• a first feeding screw provided in the first chamber and including:
• a first rotation shaft;
• a first blade portion provided upstream of a downstream end of the first communication opening with respect to a first direction from the second communication opening toward the first communication opening and formed in a helical shape on an outer peripheral surface of the first rotation shaft so as to feed the developer in the first direction;
• a second blade portion provided downstream of an upstream end of the first communication opening and the first blade portion with respect to the first direction and formed in a helical shape on the outer peripheral surface of the first rotation shaft so as to feed the developer in the first direction;
• and
• a third blade portion provided downstream the first blade portion and upstream of the second blade portion with respect to the first direction and formed in a helical shape on the outer peripheral surface of the first rotation shaft so as to feed the developer in a second direction opposite to the first direction;
• a second feeding screw provided in the second chamber and including:
• a second rotation shaft;
• a fourth blade portion provided downstream of an upstream end of the first communication opening with respect to the second direction and formed in a helical shape on an outer peripheral surface of the second rotation shaft so as to feed the developer in the second direction;
• and
• a fifth blade portion provided upstream of a downstream end of the first communication opening and the fourth blade portion with respect to the second direction and formed in a helical shape on the outer peripheral surface of the second rotation shaft so as to feed the developer in the second direction;
• a developer discharge opening provided in the first chamber and disposed downstream of the downstream end of the first communication opening with respect to the first direction so as to discharge the developer from the developing container;
• and
• a third communication opening provided downstream of the downstream end of the first communication opening with respect to the first direction so as to permit communication of airflow between the first chamber and the second chamber,
• wherein with respect to the first direction, the third communication opening overlaps with the second blade portion,
• wherein with respect to the second direction, the third communication opening overlaps with the fifth blade portion, and
• wherein with respect to the first direction, an upstream end of the third communication opening is positioned upstream of an upstream end of the developer discharge opening.

A developing device comprising:

• a rotatable developing member configured to carry and feed a developer containing toner and a carrier to a position where an electrostatic latent image formed on an image bearing member is developed;
• a developing container including a first chamber in which the rotatable developing member is provided and in which the developer is supplied to the rotatable developing member and a second chamber which is partitioned from the first chamber by a partition wall and in which the developer is circulated between itself and the first chamber;
• a first communication opening configured to permit communication of the developer from the first chamber to the second chamber;
• a second communication opening configured to permit communication of the developer from the second chamber to the first chamber;
• a first feeding screw provided in the first chamber and including:
• a first rotation shaft;
• a first blade portion provided downstream of an upstream end of the second communication opening with respect to a first direction from the second communication opening toward the first communication opening and formed in a helical shape on an outer peripheral surface of the first rotation shaft so as to feed the developer in the first direction;
• and
• a second blade portion provided upstream of a downstream end of the second communication opening and the first blade portion with respect to the first direction and formed in a helical shape on the outer peripheral surface of the first rotation shaft so as to feed the developer in the first direction;
• a second feeding screw provided in the second chamber and including:
• a second rotation shaft;
• a third blade portion provided upstream of a downstream end of the second communication opening with respect to the second direction and formed in a helical shape on an outer peripheral surface of the second rotation shaft so as to feed the developer in a second direction opposite to the first direction;
• a fourth blade portion provided downstream of an upstream end of the second communication opening and the third blade portion with respect to the second direction and formed in a helical shape on the outer peripheral surface of the second rotation shaft so as to feed the developer in the second direction;
• and
• a fifth blade portion provided downstream of the third blade portion and upstream of the fourth blade portion with respect to the second direction and formed in the helical shape on the outer peripheral surface of the second rotation shaft so as to feed the developer in the first direction;
• a developer discharge opening provided in the second chamber and disposed downstream of the downstream end of the second communication opening with respect to the second direction so as to discharge the developer from the developing container;
• and
• a third communication opening provided downstream of the downstream end of the second communication opening with respect to the second direction so as to permit communication of airflow between the first chamber and the second chamber,
• wherein with respect to the second direction, the third communication opening overlaps with the fourth blade portion,
• wherein with respect to the first direction, the third communication opening overlaps with the second blade portion, and
• wherein with respect to the second direction, an upstream end of the third communication opening is positioned upstream of an upstream end of the developer discharge opening.