Image forming apparatus configured to set a start of a feeding operation based on a value related to a rate of temperature rise for a fixing portion

An image forming apparatus comprising:

• an image forming portion configured to form a toner image on a recording material;
• a fixing portion including a heater and configured to fix the toner image on the recording material by heating the toner image formed on the recording material;
• a temperature detecting portion configured to detect a temperature of said fixing portion;
• a measuring portion configured to measure, with said temperature detecting portion, a temperature rising rate of said fixing portion when the temperature of said fixing portion rises, upon receipt of a print instruction, to a predetermined temperature at which the toner image is fixable;
• a storing portion configured to store a value related to the temperature rising rate measured by said measuring portion the value relating to the temperature rising rate for an (N−1)-th print instruction being stored in said storing portion;
• and
• a controller configured to control feeding start timing of the recording material, wherein said controller is capable of setting (i) a case in which a start of feeding of the recording material is permitted after a lapse of a predetermined time from a start of supply of electrical power to said heater in response to a print instruction and (ii) a case in which that the start of feeding of the recording material is permitted, depending on the value stored in said storing portion, at a timing before the lapse of the predetermined time, and wherein, when the value for the (N−1)-th print instruction is less than a value relating to the predetermined time, said controller sets timing of permission of a start of feeding of the recording material for an N-th print instruction at timing before a lapse of the predetermined time and depending on the value stored in said storing portion.