Developing device and image forming apparatus

An image forming apparatus comprising:

• an image carrier that holds an electrostatic latent image;
• and
• a developing device that develops the electrostatic latent image held on the image carrier,
• wherein the developing device includes
• a developing roller,
• a developing container that accommodates a developer to be supplied to the developing roller,
• an agitating and transport member that includes a rotation shaft and a helical blade formed in a helical shape in an axial direction with respect to the rotation shaft and that transports the developer in the developing container while agitating the developer,
• a transport path that accommodates the agitating and transport member and includes a high-speed transport region in which the developer is transported at a high speed and a low-speed transport region that is arranged on a downstream side of the high-speed transport region in a transport direction of the developer and in which the developer is transported at a lower speed than in the high-speed transport region, and
• a volume detection unit that is installed within a range set in advance from a switching portion that switches from the high-speed transport region to the low-speed transport region to an upstream side in the transport direction or in the low-speed transport region and that detects a volume of the developer in the transport path.