Image forming apparatus

An image forming apparatus comprising:

• a developing device including
• a developing container which includes
• a first conveyance chamber,
• a second conveyance chamber disposed above the first conveyance chamber,
• a first communication portion which allows the first conveyance chamber and the second conveyance chamber to communicate with each other at end portions thereof on a downstream side in a first direction,
• a second communication portion which allows the first conveyance chamber and the second conveyance chamber to communicate with each other at end portions thereof on a downstream side in a second direction, the second direction being a direction opposite to the first direction, and
• a toner replenishing port which is disposed at an end portion of the first conveyance chamber on the downstream side in the second direction for toner replenishment to the developing container,
• the developing container holding therein a two-component developer including a carrier and a toner,
• a first stirring-conveyance member which is rotatably supported inside the first conveyance chamber, and conveys the developer in the first conveyance chamber in the first direction, while stirring the developer,
• a second stirring-conveyance member which is rotatably supported in the second conveyance chamber, and conveys the developer in the second conveyance chamber in the second direction, while stirring the developer, and
• a developer carrier which is rotatably supported in the developing container, and carries on a surface thereof the developer in the second conveyance chamber;
• a toner reservoir which holds therein the toner to be replenished to the developing device;
• a toner replenishing device which replenishes the toner from the toner reservoir to the developing device;
• a development driving device which drives the first stirring-conveyance member and the second stirring-conveyance member;
• a controller which controls driving of the toner replenishing device and driving of the development driving device;
• and
• a developer amount detecting sensor which detects an amount of developer conveyed from the second conveyance chamber, through the second communication portion, to fall to vicinity of the toner replenishing port in the first conveyance chamber,
• wherein
• the controller controls the driving of the toner replenishing device or the driving of the development driving device based on a result of detection performed by the developer amount detecting sensor, and thereby keeps a ratio of toner with respect to the developer substantially constant in a vicinity of the toner replenishing port, the toner being replenished through the toner replenishing port, developer being conveyed from the second conveyance chamber, through the second communication portion, to fall to the vicinity of the toner replenishing port in the first conveyance chamber.