Developing device including toner concentration sensor that detects toner concentration in developer and image forming apparatus

A developing device, comprising:

• a development container that includes a first conveyance chamber and a second conveyance chamber arranged parallel to each other and mutually communicating at opposite end parts thereof in a longitudinal direction of the development container, the development container containing a developer that includes a toner to be supplied to an image carrier;
• a first conveyance member and a second conveyance member that are rotatably supported in the first conveyance chamber and the second conveyance chamber, respectively, and that convey the developer, while stirring the developer, in mutually opposite directions along the longitudinal direction of the development container;
• a developer carrier that is rotatably supported in the development container so as to face the image carrier, and that supplies the toner in the second conveyance chamber to the image carrier;
• and
• a toner concentration sensor that is disposed, on a wall of the development container along the longitudinal direction thereof, so as to face the first conveyance member or the second conveyance member, and that detects toner concentration in the developer,
• wherein
• the first conveyance member and the second conveyance member each include a rotation shaft extending along the longitudinal direction of the development container, and a conveyance blade helically formed on an outer circumferential part of the rotation shaft, and
• the conveyance blade includes a cutout portion that is formed by removing part of the conveyance blade in a facing region with respect to the toner concentration sensor,
• the developing device further comprising:
• a scraper that is secured to the rotation shaft in the cutoff portion, and that moves the developer facing the toner concentration sensor;
• and
• a holding portion that is formed on the rotation shaft in the cutoff portion, and that holds the scraper, and
• the holding portion has a peripheral end surface that extends in a radial direction of the rotation shaft at opposite ends of the rotation shaft in a circumferential direction thereof, and that is disposed at an edge of the cutout portion in a circumferential direction thereof.