IMAGE FORMING APPARATUS THAT CALCULATES INCLINATION OF APPROXIMATE STRAIGHT LINE, APPROXIMATING RELATION BETWEEN TONER DENSITY AND DEVELOPING CURRENT, USING DIFFERENT MATHEMATICAL EXPRESSIONS DEPENDING ON WHETHER THREE TONER PATCHES OR FOUR OR MORE TONER PATCHES ARE PROVIDED

摘要

An image forming apparatus includes a developing roller, a photoconductor drum, a density detector, a current detector, and a controller. The developing roller carries a toner. The photoconductor drum carries a toner patch. The density detector detects toner density of the toner patch. The current detector detects developing current flowing to the toner patch. The controller calculates an inclination of an approximate straight line approximating a relation between the toner density and the developing current. The developing roller develops three or more toner patches, different in toner density and different in developing current from one another, on the photoconductor drum. The controller calculates the inclination, using different mathematical expressions depending on whether three toner patches or four toner patches are provided.