An image forming apparatus includes: toner supply amount detecting means for detecting a toner supply amount to a developer tank; detecting means for detecting a signal value of each pixel of an image; and toner consumption amount estimating means for estimating a toner consumption amount, based on the signal value. The sheet feeding drum includes a liquid container receiving chamber receiving the liquid container and the liquid container receiving chamber communicates with the supply passage. The igniter also includes a shell bore extending from the tip surface to the cavity and a pin embedded into the tip surface extending substantially tangentially with respect to the bore.