An image heating apparatus includes a plurality of heat generating elements, a plurality of temperature detecting elements, and an energization controlling portion for selectively controlling, based on the temperature detected by each of the plurality of temperature detecting elements, electrical power to be supplied to the plurality of heat generating elements. The plurality of temperature detecting elements are arranged in each of the plurality of heat generating elements, and the energization controlling portion controls electrical power supply to the plurality of heat generating elements for the purpose of heating a non-sheet-passing heating region, through which a recording material does not pass, among the plurality of heating regions, based on a temperature detected by a temperature detecting element that is farthest from a conveyance reference position of the recording material, among the plurality of temperature detecting elements arranged in the non-sheet-passing heating region.

The image forming apparatus is characterized in that information about an input voltage detected on the primary side of a transformer is transmitted from a primary-side switching control unit to a secondary-side controller for controlling a heating device, and the controller controls the temperature of a heater of the heating device based on the transmitted information.

Provided is an image forming apparatus including a temperature sensing circuit to which a temperature sensing element is electrically connected, wherein a surface of a heater on a side where the temperature sensing element is provided is in contact with the inner surface of a film, a heating element is provided in a primary side circuit which is electrically connected to a commercial power supply, and the temperature sensing circuit is electrically insulated from both of the primary side circuit and a secondary side circuit which is electrically insulated from the primary side circuit.

A heater controller and heater control method is disclosed. The hater controller includes a detector, a determination circuit, a limiting circuit, a selection circuit, and a driving circuit. The detector detects a temperature of the heating object, which is heated by the heater. The determination circuit determines turn-on ratio for the heater for every control cycle of AC voltage, based on the surface temperature of the heating object and a target temperature of the heating object. The limiting circuit limits the turn-on ratio of current control cycle when the control method of previous control cycle is phase control. The selection circuit selects control pattern to control the heater, based on the turn-on ratio, and the driving circuit applies a heater driving signal to the heater.

A heater includes: a planar heat generator; a power supply circuit that controls supply of power to the planar heat generator; a plurality of temperature sensors that is provided on the planar heat generator and measures a temperature; and a hardware processor that controls the power supply circuit in a predetermined condition to maintain a temperature measured by at least one of the plurality of temperature sensors at a target value, wherein the planar heat generator includes: an insulator; and a heat generator disposed on the insulator, the heat generator includes each of a plurality of linear parts extending in parallel with each other at a predetermined interval P, and each of the plurality of temperature sensors is disposed along a direction orthogonal to an extending direction of each of the plurality of linear parts at a position mutually shifted by a predetermined distance D.

A heater includes a substrate, a heating resistor layer, and an electrode layer. The substrate has a substrate obverse surface and a substrate reverse surface. The heating resistor layer is formed on the substrate obverse surface. The electrode layer is formed on the substrate obverse surface and in contact with the heating resistor layer. The electrode layer includes a pair of strip portions extending in a longitudinal direction of the substrate and spaced apart from each other in the width direction of the substrate. The heating resistor layer includes a main heating member and a sub heating member each extending in the longitudinal direction of the substrate and located between the strip portions in the width direction. The sub heating member has a higher temperature coefficient of resistance than that of the main heating member.

Controlling power delivered to a heating device occurs using a phase control, wherein the phase control includes changing a cut-off phase of an alternating current electrical signal delivered to the heating device. The power delivered to the heating device is increased from zero to an operational level using the phase control. The level of the power delivered to the heating device is maintained at the operational level using both the phase control and an integral half cycle control. The integral half cycle includes selectively removing a plurality of half cycles from the alternating current electrical signal delivered to the heating device.

In a caser where a first current is supplied to a first heater, a controller gradually increases the first current in a first period, supplies the first current based on a first duty cycle in a second period, and gradually reduces the first current to stop supplying the first current in a third period. In a case where a second current is supplied to a second heater, the controller gradually increases the second current in a fourth period, supply the second current based on a second duty cycle in a fifth period, and gradually reduces the second current to stop supplying the second current in a sixth period. The controller controls the supply of the second current such that part of the fourth period overlaps with the third period.

A heating device includes a heating roller that includes a resistance heating layer, and a connection power feeder that is mounted on an end portion of the heating roller, is connected to the resistance heating layer, and feeds power to the resistance heating layer, in which the connection power feeder includes an annular frame that is disposed to be concentric with the heating roller and is conductively connected to the resistance heating layer, a power feed shaft of which a portion is disposed in the frame and which feeds power, plural rolling bodies that roll while being in conductive contact with an inner peripheral surface of the frame and an outer peripheral surface of the power feed shaft, and a non-conductive cover that holds and covers the frame and the rolling bodies in a state where a portion excluding the portion of the power feed shaft is exposed, and the connection power feeder excluding the power feed shaft is mounted on the heating roller so as to be integrally rotated with the heating roller.

An image heating apparatus includes an image heating portion including first, second, and third heat generating blocks divided in a direction orthogonal to a conveying direction of the recording material. The image heating apparatus also includes a first driving circuit, a second driving circuit, a first temperature detection member, and a second temperature detection member. A control portion controls the first and second driving circuits according to at least one of the temperatures detected by the first and second temperature detection members, and controls energization of the second heat generating block together with a heat generating block that is energized by a driving circuit connected to the second heat generating block. In addition, a connection switching portion selectively connects any one of the first and second driving circuits to the second heat generating block according to a switching instruction from the control portion.