Developing device and image forming apparatus

A developing device, comprising:

• a development container including
• a first conveyance chamber and a second conveyance chamber that are arranged parallel to each other,
• a first partition wall that separates the first conveyance chamber and the second conveyance chamber along a longitudinal direction of the first conveyance chamber and the second conveyance chamber,
• a communication portion that allows the first conveyance chamber and the second conveyance chamber to communicate with each other at opposite end-part sides of the first partition wall in a longitudinal direction thereof,
• a developer replenishment port through which a developer including a magnetic carrier and a toner is replenished, and
• a developer discharge port that is disposed at a downstream end part of the second conveyance chamber and through which an excess of the developer is discharged, the development container accommodating the developer;
• a first conveyance member that includes a first rotation shaft and a first conveyance blade formed on an outer circumferential surface of the first rotation shaft, and that conveys, while stirring, the developer in the first conveyance chamber in a first direction;
• a second conveyance member that includes a second rotation shaft and a second conveyance blade formed on an outer circumferential surface of the second rotation shaft, and that conveys, while stirring, the developer in the second conveyance chamber in a second direction that is opposite to the first direction;
• and
• a developer carrier that is rotatably supported in the development container so as to face an image carrier, and that supplies the toner inside the second conveyance chamber to the image carrier,
• wherein
• the second conveyance member includes
• a regulation blade that is formed downstream of the second conveyance blade with respect to the second direction, and that conveys the developer in a direction opposite to the second conveyance blade, and
• a discharge blade that is formed downstream of the regulation blade with respect to the second direction, and that conveys the developer in a same direction as the second conveyance blade to discharge the developer through the developer discharge port,
• the developer replenishment port is an opening formed in an upper surface of the development container, and at least part of an opening length thereof in the second direction is included in a regulation area which is an area inside the second conveyance chamber where the regulation blade is disposed,
• at least part of the developer replenished through the developer replenishment port falls into both the first conveyance chamber and the regulation area,
• the communication portion includes
• a first communication portion that delivers the developer, at a downstream side in the first direction, from the first conveyance chamber to the second conveyance chamber, and
• a second communication portion that delivers the developer, at a downstream side in the second direction, from the second conveyance chamber to the first conveyance chamber,
• the development container includes a second partition wall that is disposed downstream of the second communication portion with respect to the second direction so as to be adjacent to the regulation area, and that separates the first conveyance chamber and the regulation area,
• the developer replenishment port is disposed above the second partition wall,
• a falling area into which the developer replenished through the developer replenishment port falls is partitioned by the second partition wall into the first conveyance chamber and the regulation area, and
• the opening length of the developer replenishment port in the second direction is entirely located downstream of the second communication portion with respect to the second direction.