Abstract: In an apparatus which cannot detect a size of recording sheet before the recording sheet is fed, the first recording sheet is regarded as having the maximum size and paper feeding is controlled on this basis and the size of the sheet is measured during the conveyance of the recording sheet. For the second or third and subsequent recording sheets, paper feeding control is executed at a paper feeding interval at which a maximum throughput is obtained in accordance with the measured size.

Abstract: A heat fixing apparatus includes a heater; a temperature sensor for sensing a temperature of the heater; a bias wave number determining limit for determining the number of bias waves corresponding to a predetermined image fixing temperature in accordance with utility voltage source voltage; a bias wave number changing unit for changing a bias wave number in accordance with temperature changing rate of the heater; and a supply wave number control unit for controlling the number of waves supplied to the heater in accordance with an output of the temperature sensor and bias wave number. The unit includes a PID controller.

Abstract: An image heating apparatus includes a heater; temperature detector for detecting a temperature of the heater; electric power supply controller for controlling electric power supply to the heater during image heating, so that the temperature detector detects a predetermined set temperature; and a temperature determining device for determining the set temperature on the basis of a change of the temperature detected by the temperature detector when electric power supply to the heater is stopped.

Abstract: An image forming apparatus includes a detecting unit that detects the size of a recording medium and a designating unit that designates the size of a recording medium onto which an image is to be recorded. The comparing unit compares the detected size with the designated size to determine which size is larger and a control unit controls the apparatus to perform operations such that an operation when the detected size is larger than the designated size is different from that when the detected size is smaller than the designated size.