A process for electric induction heating of large billets to a tapered cross sectional heating profile by inductively scan heating the axial circumference of the large billet with a single induction coil prior to hot working the large billet in an extrusion or forging process is provided.

A fixing rotating member that includes: a cylindrical base member comprising at least a resin; an electro-conductive layer on the base member; and a resinous layer on a surface of the electro-conductive layer, the surface being opposed to a surface facing the base member, the electro-conductive layer extending in a circumferential direction of an outer circumferential surface of the base member, the electro-conductive layer containing silver, the electro-conductive layer having a volume resistivity of 1.010.sup.8 to 8.010.sup.8 .Math.m, and the electroconductive layer having a compressive elastic modulus of 8 to 30 GPa, the elastic modulus being measured by contacting an indenter with a first surface of the electroconductive layer opposite to a surface facing the base member, and the elastic modulus being an average value of elastic moduli of a thickness region of 0.1 to 0.2 m from the first surface of the electroconductive layer.

The present invention is intended to adjust an amount of thermal expansion at a desired position in an axial direction of a roller body of an induction heated roll apparatus, regardless of an amount of load heat extracted from the roller body by a heating target object. The induction heated roll apparatus includes the roller body that is cylindrical and has a hollow space, a plurality of induction coils provided in an inside along the axial direction of the roller body, a power supply circuit that controls power supplied to each of the plurality of induction coils individually, and a cooling mechanism that cools the roller body by supplying a refrigerant to the roller body.

An embossing device and a method for embossing, employing an electromagnetic induction device such as to induce an eddy current prevalently on the outer surface of an embossing roller. The eddy currents are such as to prevalently heat the outer surface of the embossing roller.

A fixing unit includes a rotary member including a conductive layer and having a tubular shape extending in a longitudinal direction, a coil configured to generate an alternating magnetic field to generate heat in the conductive layer, and a core disposed inside the rotary member and configured to guide magnetic field lines of the alternating magnetic field. The core is constituted by a plurality of divided cores aligned along the longitudinal direction. At least one of the plurality of divided cores is formed in a columnar shape having an aspect ratio of 1:5 or less between a maximum width in a cross section orthogonal to the longitudinal direction and a length in the longitudinal direction, and is made of compacted magnetic core material disposed such that a hard-magnetization axis thereof is oriented in an intersection direction intersecting the longitudinal direction.

An image heating apparatus includes a tubular rotary member, a magnetic core, an exciting coil, an inverter, at least one temperature detecting portion configured to detect a temperature of the rotary member, and a storage configured to store a reference value of a variation amount per unit time of a detected temperature. The control portion is configured to change a driving frequency of the inverter. The control portion is configured to change a driving frequency of the inverter, acquire the variation amount per unit time of the detected temperature detected by the temperature detecting portion, correct the reference value based on the drive frequency of the inverter at the time when the variation amount is acquired, and stop heating of the rotary member in a case where the variation amount is smaller than the reference value being corrected.

An image heating device configured to heat an image formed on a recording material, includes a tubular rotary member, a magnetic core material, an excitation coil, an inverter, a control unit, and a power cutoff unit configured to cut off supply of power from the inverter to the excitation coil regardless of a control state of the inverter by the control unit in a case where the power input from the inverter to the excitation coil exceeds a threshold, the control unit is configured to change a driving frequency of the inverter. The power cutoff unit is configured to change a value of the threshold based on a value of the driving frequency of the inverter.

An embossing device and a method for embossing, employing an electromagnetic induction device such as to induce an eddy current prevalently on the outer surface of an embossing roller. The eddy currents are such as to prevalently heat the outer surface of the embossing roller.