Abstract: A toner fusing system for fixing toner to paper. This system includes a fuser member for contacting and heating the toner in the fusing process. The fuser member has a fuser base, a fluoroelastomer fusing surface layer at least 38 microns thick, and a cushion layer between the fuser base and the fusing surface layer. This system utilizes external heating as the primary source of heat energy for the fusing process.

Abstract: The circumferential edge portion of a ductile rotating body containing abrasive grains is used to polish the surface of a ceramic substrate. The angle &thgr; formed between the polished direction D0 of the ceramic substrate and the rotating direction D1 of the rotating body is set in the range from 10° to 80° for the polishing step. Alternatively, the polishing process is divided into at least two steps, and the average grain size of abrasive grains is reduced stepwise in the successive steps of the polishing process. According to this method, the surface of a large-area and thin ceramic substrate can be polished without damage, and a smooth polished ceramic surface can be provided. This method is particularly suitable for polishing a ceramic substrate having a thickness of at most 2.0 mm, and the resulting polished ceramic substrate is suitable for a ceramic heater in a thermal fixation device for fixing a toner image.

Abstract: An image forming toner is provided, including at least:

Abstract: A fixing device having a heat roller which is adapted to be moved at the same velocity as the transferring speed of a paper with an image thereon and is adapted to be contacted with the paper to thereby enable the image on the paper to be thermally fixed, and an induction heating mechanism for performing an induction heating of the heat roller. The induction heating mechanism having a coil, and a supporter for supporting the coil, and the coil is constituted by a plurality of litz wir which are designed to be altered in the manner of combination or of connection thereof, thereby enabling a plurality of different electric voltages to be applicable.

Abstract: An implementation of a technology, described herein, for fusing portions of a print medium as it passes through a fuser assembly of an electrophotographic device, such as a laser printer. An implementation, described herein, of the claimed invention includes a fuser assembly of an electrophotographic device that can selectively fuse portions of a print medium passing there through. This abstract itself is not intended to limit the scope of this patent. The scope of the present invention is pointed out in the appending claims.

Abstract: Fuser members having improved thermal conductivity include an outer layer composed of elastomers and filler materials. The filler materials are oriented in the outer layer to provide directional thermal conductivity. Processes for forming the fuser members apply a liquid coating over a substrate and apply a magnetic field to the coating to orient the filler material. The coating is cured to retain the orientation of the filler material in the outer layer.

Abstract: A ceramic heater that is used in a toner-fixing system comprising a ceramic heater and a heat-resistant film, that reduces the degree of deformation of the heat-resistant film, that lightens the load applied to the film at the time of revolution, that prevents the fracture of the film, and that enables fixing at a high rate exceeding 24 ppm. A ceramic base material 11 of the ceramic heater attached to a heating cylinder comprises aluminum nitride or silicon nitride. A heating element 12 and current-feeding electrodes are made of silver or silver alloy and are formed on the ceramic base material. In the ceramic heater, at least one part of the face (the fixing face) that contacts the heat-resistant film is curved when viewed from a direction perpendicular to the feeding direction of a copying sheet.

Abstract: A ceramic heater that is used in a toner-fixing system comprising a ceramic heater and a heat-resistant film, that reduces the degree of deformation of the heat-resistant film, that lightens the load applied to the film at the time of revolution, that prevents the fracture of the film, and that enables fixing at a high rate exceeding 24 ppm. A ceramic base material 11 of the ceramic heater attached to a heating cylinder comprises aluminum nitride or silicon nitride. A heating element 12 and current-feeding electrodes are made of heat-resistant metal such as tungsten and molybdenum or heat resistant alloy and are formed on the ceramic base material. In the ceramic heater, at least one part of the face (the fixing face) that contacts the heat-resistant film is curved when viewed from a direction perpendicular to the feeding direction of a copying sheet.

Abstract: A device of this invention has a hollow heat roller (1), the surface of which has a coat of a metal layer, an excitation coil which is arranged in the heat roller (1) and generates a magnetic flux in the heat roller (1) to heat it by induction, and a press roller (2) which is in contact with the heat roller (1) under a predetermined pressure. The excitation coil has at least two maximal heating portions (42, 43) in the circumferential direction of the heat roller (1). The excitation coil is located to form one maximal heating portion (42) within the range of ±30° along the circumferential direction from the position of a nip (41) where the heat roller (1) contacts the press roller (2). With this structure, since heat accumulates in the heat roller (1) to keep it warm, the warm-up time can be shortened.

Abstract: A developing agent comprising a toner particle containing a binder resin having an acid value of 1 to 30, a glass transition temperature of 40 to 65° C. and a softening point of 80 to 140° C., an azo-based iron complex, and a colorant and/or a first magnetic particle. This developing agent is suited for use in a fixing device of electromagnetic induction heating system.

Abstract: An induction heating fixing device transports a sheet sandwiched between a fixing belt and a pressing roller pressed thereagainst, heats the sheet, and thereby fixes a toner image onto the sheet. The fixing belt is composed of a conductive member, a core, and an induction coil which have been formed into thin films and stacked in layers so that the size and weight of the fixing device are reduced.

Abstract: A member for use is a copying device includes at least a substrate and thereon a surface layer comprised of a nitrile-silicone rubber or elastomer. The nitrile-silicone rubber or elastomer provides superior resistance to swelling from solvents such as hydrocarbons found in many developer compositions. The member may have any form, including a belt, plate or drum configuration. The member may be used in the copying device as a fuser member, a pressure member, a transfer member or a transfix member.

Abstract: A control system for delivering a constant fuser temperature despite variations in the line voltage is effected by a control circuit which employs closed loop feedback control to control the rms voltage across the load. This is accomplished by a circuit and method which functionally provides a continuous solution to the equation which describes the relationship between the temperature of the fuser and the temperature of a desired control setpoint. Briefly, the solution of this equation is obtained by monitoring, i.e. sampling, the temperature of the fuser, subtracting the desired control temperature, and then integrating the difference over time. The resultant time integral is used to control the operating point of a pulse width modulated power controller. The integrator has a time constant sufficiently long and the power controller operates at a frequency sufficiently high so as to render lighting flicker imperceptible.

Abstract: A photoreceptor web for an image forming apparatus includes a base layer, a conductive ground layer formed on the base layer, and a photosensitive layer formed on the ground layer, where an electrostatic latent image is formed by scanned light. A first protective layer is formed on the photosensitive layer for protecting the photosensitive layer, and a heating layer is formed on a rear surface of the base layer in a predetermined pattern for receiving electric power and generating resistance heat. The photoreceptor web is maintained at a constant temperature by the resistance heat generated by the heating layer.

Abstract: A fixing device for an image forming apparatus includes an inverter circuit for induction heating. In the inverter circuit, a main switch Q1 drives one end of a work coil L1 whose other end is connected to a power source. A serial connection of a capacitor Cs and a subswitch Q2 is connected to opposite ends of the coil L1 in parallel such that one end of the capacitor Cs is connected to the power source E. A second capacitor C1 is connected to the subswitch Q2 in parallel. For a capacitance of 0.1 &mgr;F of the capacitor C1, the factor of the coil L1 and that of the capacitor Cs are selected to be between 70 &mgr;H and 100 &mgr;H and between 1.8 &mgr;F and 5 &mgr;F, respectively. The inverter circuit is operable with optimal efficiency in the event of PWM (Pulse Width Modulation) control using a fixed frequency.

Abstract: A ceramic heater that is used in a toner-fixing system comprising a ceramic heater and a heat-resistant film, that reduces the degree of deformation of the heat-resistant film, that lightens the load applied to the film at the time of revolution, that prevents the fracture of the film, and that enables fixing at a high rate exceeding 24 ppm. A ceramic base material 11 of the ceramic heater attached to a heating cylinder comprises aluminum nitride or silicon nitride. A heating element 12 and current-feeding electrodes are made of silver or silver alloy and are formed on the ceramic base material. In the ceramic heater, at least one part of the face (the fixing face) that contacts the heat-resistant film is curved when viewed from a direction perpendicular to the feeding direction of a copying sheet.

Abstract: A ceramic heater that is used in a toner-fixing system comprising a ceramic heater and a heat-resistant film, that reduces the degree of deformation of the heat-resistant film, that lightens the load applied to the film at the time of revolution, that prevents the fracture of the film, and that enables fixing at a high rate exceeding 24 ppm. A ceramic base material 11 of the ceramic heater attached to a heating cylinder comprises aluminum nitride or silicon nitride. A heating element 12 and current-feeding electrodes are made of heat-resistant metal such as tungsten and molybdenum or heat resistant alloy and are formed on the ceramic base material. In the ceramic heater, at least one part of the face (the fixing face) that contacts the heat-resistant film is curved when viewed from a direction perpendicular to the feeding direction of a copying sheet.

Abstract: A heating apparatus which forms an image by heating a sheet-form material carrying image data. The heating apparatus comprises a heater, which is disposed at an axial center portion of the sheet-form material, for directly heating the sheet-form material to a temperature suitable for heat developing processing, and rings or a cylinder for rotating and allowing the sheet-form material to be exposed to the heater. The sheet-form material can be rotated on either an inner or outer surface of the rings or an inner surface of the cylinder. In addition, a plurality of rings can be used which correspond to differing widths of sheet-form material.

Abstract: Apparatus for forming an ink image with improved image properties on a receiver in response to a digital image includes an ink jet print head for delivering ink to a receiver to form an image. Relative movement is provided between the receiver and the print head and the ink jet print head is actuated in accordance with the digital image so that the print head transfers ink to the receiver to form the ink image corresponding to the digital image. Replaceable receiver treatment device treats the receiver or the ink image to improve selective aspects of image properties.

Abstract: The present invention has an object to provide an induction-heating fusion device which is capable of stabilizing the fusing temperature over the entire width of a sheet therethrough by inhibiting an excessive temperature rise in a sheet-nonpassing zone defined when a small-size sheet is subjected to fusion. The induction-heating fusion device according to the present invention includes an iron core 17 forming a closed magnetic circuit, a main induction coil 14a wound around the iron core 17 for generating a magnetic flux which causes an electrically conductive member to generate an induction current circumferentially thereof, and at least one induction sub-coil 14b provided on an end portion of the main coil for generating a magnetic flux which causes the electrically conductive member to generate an induction current circumferentially thereof.

Abstract: A cooling section 400 for cooling a recording material A, which is a recording material, is disposed in a downstream portion of a heat development section 18. The cooling section 400 has a pair structure consisting of a metal roller 404 and a roller 402 made of an elastic material. The metal roller 404 having excellent heat conductivity is brought into contact with an image forming surface of the recording material A. As a result of the foregoing structure, the recording material A subjected to the heat development can uniformly be cooled to a temperature not higher than a development interruption temperature during conveyance in the cooling section 400. The metal roller may be modified variously. For example, the metal roller is cooled by a cooling mechanism or replaced by a belt.

Abstract: A fixing device using induction heating for an electrophotographic image forming apparatus includes a heat roller and a press roller for fixing a toner image on a recording medium while conveying the recording medium. A coil unit is located outside of the heat roller and upstream of a nip between the heat roller and the press roller in the direction of rotation of the heat roller for generating an induced magnetic flux. The coil unit concentratedly heats the heat roller and thereby efficiently feeds heat to the recording medium.

Abstract: A sheet treating apparatus has a container containing a plurality of sheets therein, a recorder for effecting recording on the sheets, a substantially straight path for conveying the recorded sheets and a heat-developer for heat-developing the sheets in the path. The container and/or the recorder are disposed under the heat-developer, are vertically overlapped with one another, and may be vertically overlapped with the heat-developer. The container and the straight path are disposed so that the straight path and the sheets in the container may be substantially parallel or substantially orthogonal to one another.

Abstract: To provide a temperature control wherein a controller provided at a secondary side of a transformer can control a temperature of a heat roller which includes a heat generating sheet. An operational amplifier 161 compares a potential V with a reference potential Vr, and outputs a comparison result. The potential V corresponds to temperature of the heat roller which is detected by a thermistor 171. The reference potential Vr corresponds to a control signal received from a CPU 71 through photo-transistor-couplers PC1 to PCn. The comparison result is input to the CPU 71 through a photo-transistor-coupler 171. The CPU 71 controls ON/OFF of a fixing heater 15a through a photo-TRIAC-coupler 93. Because the photo-transistor-couplers and the photo-TRIAC-coupler can transmit signals without relying on electrical conductivity, the above temperature control can be performed while the fixing heater 15a, a TRIAC 95, and the thermistor are provided at a primary side of a transformer 121, and the CPU 71 at a secondary side.

Abstract: A device configured to be heated to a temperature sufficient to fuse an image forming substance to a sheet includes a hollow roller made of a conductive material and a coil arranged in a hollow portion of the hollow roller. The coil is configured to carry an electrical current that induces a current in the conductive material of the hollow roller such that the hollow roller becomes heated so as to fuse toner to a sheet. The coil is mounted on a member that is disposed in the hollow portion of the roller. The member includes various combinations of features that permit a reliable and safe operation of the induction heating apparatus such as recess and projections formed in the member to separate respective turns in the coil, a hollow center of the member that can be ventilated with a ventilation fan, and predefined gaps being maintained between the inside surface of the hollow roller and an outer surface of the coil.

Abstract: A fixing device for an electrophotography system, which is capable of efficiently and uniformly heating an object to be heated, which has a coil capable of being easily produced and which is capable of being stably fixing a fixed material, is provided by preventing the distance between the going and returning portions of a certain turn of the coil from being too close to each other, by preventing the diameter of the coil from changing when the coil is wound, by providing a uniform gap between the coil and the inside surface of the heating roller over the whole length, by preventing the fixing performed by the heating roller to be affected by the turning ON/OFF of a power supply, by preventing noises from being generated from the coil ejecting portion, and by devising the procedure for efficiently winding the coil.

Abstract: A localized heating device includes a laminate structure of a heat insulating substrate, a heating region made by sandwiching a heating layer between a pattern electrode layer and a conductive layer and a low surface energy layer. In another aspect of the invention, a localized heating apparatus includes a localized heating device and a power supply system that supplies a current selectively and stably to the heating layer between the pattern electrode layer and the conductive layer from the current supply portion formed at one or both end portions of the heating region.

Abstract: In a heat developing section, heater boxes heated by sheet-like heaters are disposed vertically in pairs between an insertion roller pair and a discharging roller pair. When a heat developing photosensitive material is fed between the heater boxes by the insertion roller pair with a photosensitive layer of the heat developing photosensitive layer facing upward, it is guided by a guide plate of a lower heater box and is conveyed with an air layer being constantly formed between an upper heater box and the heat developing photosensitive material. As a result, the heat developing photosensitive material is heated without the photosensitive layer thereof being pressed. Accordingly, the heat developing photosensitive material is uniformly heated with no wrinkles generated therein, and an image of high finished quality is formed.

Abstract: An image reading apparatus having a partition module between an image sensor module and a heat source (e.g., a laser-beam printer) includes a partition module disposed between the image sensor module and the heat source. The partition module has two walls with a gap therebetween for thermally insulating the image reading module from the heat source. Preferably, the partition module has an air intake port, and an air exhaust port, and a fan for circulating cooling air.

Abstract: For use in a copying apparatus or the like, there is provided an image heating apparatus having a first heater, a second heater, and a power supply control device for controlling the power supply to the first and second heaters, wherein the power supply control unit is adapted, in case of power supply to both of the first and second heaters, to at first start power supply to the first heater and then to the second heater, and, in case of power supply again to both of the first and second heaters, to at first start power supply to the second heater and then to the first heater.

Abstract: A fixing station for fixing toner images on a carrier material is provided in a printer or copier. A flap or shutter mechanism having a plurality of flaps or shutters that are pivotable into an open and into a closed position are arranged between a heat radiation source and the carrier material for controlling fixing of the toner to the carrier material.

Abstract: A method for fixing a toner image contact-free on a substrate, which includes exposing the toner image to a hot gas containing a significant component of steam; and a device for performing the method.

Abstract: An image formation apparatus includes an image fixing roller for performing thermal image fixing, which image fixing roller includes an exothermic phase transition layer capable of performing reversible phase transition from an amorphous state to a crystalline state and vice versa, with liberation of crystallization heat at the phase transition from the amorphous state to the crystalline state, and the crystallization heat is used for increasing the temperature elevation rate for the image fixing roller.

Abstract: A fixing device includes a fusing roller, a backing roller and an adjustable heater for selectively heating the fusing roller and the backing roller. The adjustable heater includes a heating element and a reflector. The reflector can be positioned to direct heat from the heating element upon the fusing roller or the backing roller. The reflector is coupled to the shaft of a solenoid. Positioning of the reflector is controlled by alternately energizing or de-energizing the solenoid. During the time period between the passing of successive units of the media through the fixing device, the reflector is positioned to heat the backing roller. Heating the backing roller melts toner accumulated on its surface. When the next unit of the media passes between the fusing roller and the backing roller, toner accumulated on the surface of the backing roller is moved onto to the media.

Abstract: A support member has a plurality of through-holes for supporting printing paper to which a fusible toner is adhered. Hot air is blown toward the printing paper. By releasing a considerable amount of hot air blown toward the support member downward through the through-holes, the amount of hot air bouncing on the surface of the support member is decreased. Thus, floating or fluttering of the leading end of the printing paper is prevented when the leading end of the printing paper rushes into the fixing apparatus.

Abstract: An image heating device comprises a cylindrical heating roller with a Curie temperature of 210.degree. C., a magnetization coil for magnetizing the heating roller with an alternating magnetic field, which is arranged inside the heating roller, and a nip portion for heating a recording material that carries a toner image with heat from the heating roller, while the recording material is being conveyed along said nip portion. The ratio between the amount of heat generated in said heat-generating member at Curie temperature or higher to the amount of heat generated at room temperature in said heat-generating member is not more than 1/2. With this configuration, the heating roller can regulate its own temperature to stabilize at a temperature that is suitable for fixing, and the problems of partial overheating or underheating, unstable heat generation, or damage of the device can be eliminated.

Abstract: When the media enters the fuser, the added thermal load causes the fuser temperature to dip. Eventually, the control system compensates for the thermal load and stabilizes the fuser temperature at the desired temperature. Depending on several factors, the dip in fusing temperature may cause a degradation in the fusing process. An improved temperature profile can be achieved by increasing the amount of power supplied to the fusing system a predetermined amount of time before the thermal load enters the fusing system. Similarly, the amount of power supplied to the fusing system is decreased a predetermined amount of time before the thermal load exits the fusing system. The Desired Temperature input to the fuser temperature control system is modified to anticipate changes in thermal loads thereby changing the amount of power supplied to the fusing system.

Abstract: A heater of a fixing unit of a recording apparatus is constructed by a main heater and a sub heater. When the apparatus is in a standby mode, each heater is first turned off. When a temperature of the fixing unit is equal to or lower than a heating start temperature of the sub heater, the sub heater is turned on. After that, when the temperature of the fixing unit reaches a heating stop temperature of the sub heater, the sub heater is turned off. After that, when the temperature of the fixing unit is equal to or lower than the heating start temperature, the main heater is turned on. After that, when it reaches the heating stop temperature of the main heater, the main heater is turned off. The above operations are repeated. In the recording mode, the order of the on/off periods in a control unit time of each heater is switched every period and the temperature control is executed, thereby reducing a flickering.

Abstract: An image fixing apparatus for thermally fixing images on an image receiving material at a predetermined image fixing temperature, comprising an image fixing device comprising a core member, and an exothermic phase transition layer provided on said core member, comprising an exothermic phase transition material which is capable of performing reversible phase transition from an amorphous solid state to a crystalline state with liberation of crystallization heat therefrom, and vice versa, and has a melting point higher than said predetermined image fixing temperature, a heating device which maintains the temperature of at least an outer surface of said image fixing device at said predetermined image fixing temperature, a first phase transition device which heats said exothermic phase transition layer, thereby having said exothermic phase transition material perform phase transition from said amorphous state to said crystalline state for liberation of crystallization heat therefrom, a second phase transition devi

Abstract: A fusing station of an electrographic apparatus fixes in a single pass a duplex resinous powder color image to a support material as the support material is moved over a predetermined path through the fusing station. The fusing station employs a symmetrical fixing operation on both sides of the support material. The fusing station applies hot air to both sides of the support material in substantially equal flows. The hot air is heated by heating sources with substantially identical operational characteristics such that the flows of hot air are heated to substantially equal temperatures on both sides of the support material.

Abstract: A substrate carrying an unfixed toner image is fed through a contact zone which extends continuously from an entrance to an exit (18; 78). The zone is defined by an endless surface such as a first belt and a reaction surface such as a second belt in face-to-face pressure contact therewith. The first belt adjacent the entrance is heated to a temperature sufficient to reduce the viscosity of the toner to less than 50 Pa s. The first belt is forcibly cooled intermediate the entrance and the exit to a temperature below the glass transition point T.sub.g of the toner. Thereby un-fixed toner images can be fixed to the substrate and provided with a desirable level of gloss in one single device, while widening the range of operating conditions without risk of offset occurring.

Abstract: An image formation apparatus includes an image fixing roller for performing thermal image fixing, which image fixing roller includes an exothermic phase transition layer capable of performing reversible phase transition from an amorphous state to a crystalline state and vice versa, with liberation of crystallization heat at the phase transition from the amorphous state to the crystalline state, and the crystallization heat is used for increasing the temperature elevation rate for the image fixing roller.

Abstract: A toner fixation film has an exothermic layer within which an eddy current is induced with application of a magnetic field and then heat is generated. The exothermic layer is a composite layer in which an exothermic part and resin part coexist. The toner fixation film can offer a sufficient heat generation necessary for toner fixation, and has enough flexiblity to permit curvature separation. A toner fixation apparatus comprises the toner fixation film and at least one coil for producing an alternating magnetic field for eddy current induction.

Abstract: An rapid wake up fuser system member for use in an electrophotographic apparatus for fusing toner images to a copy substrate, the fuser member having a substrate, a heat transmissive layer having a silicone material and a Q-resin provided on the substrate layer, and a polymer-containing toner release layer provided on the heat transmissive layer.

Abstract: According to a first aspect of the invention, when a printer runs out of printing media while printing data supplied by a host computer on a series of pages, after being resupplied with printing media, the printer waits for the host computer to resume the sending of data before printing is resumed. According to a second aspect of the invention, before starting to prepare the data for the first page, the host computer sends the printer a warm-up command, causing the printer to commence preparations for printing.

Abstract: In an image heating apparatus, a film has one face in sliding contact with a heater having a heat generating portion on a substrate. The other face of the film contacts a recording material bearing an image. The film moves with the recording material and the image on the recording material is heated by heat generated by the heater which is transmitted through the film. A temperature detecting element detects the temperature of the heater. The heat generating portion of the heater has a first heat generating portion and a second heat generating portion on the downstream side of the first heat generating portion with respect to the moving direction of the film. The middle of the temperature detecting element is positioned at the upstream side of the middle between the first and second heat generating portions with respect to the moving direction of the film.

Abstract: An image heating apparatus is provided with:a moving member having an electrically conductive layer and arranged to move together with a recording medium, an exciting coil for generating a magnetic flux, wherein the magnetic flux generated by the exciting coil generates eddy currents in the moving member and the eddy currents make the moving member generate heat, wherein the heat of the moving member heats an image on the recording medium, a magnetic member for guiding the magnetic flux generated by the exciting coil, wherein the moving member and the magnetic member form a substantially closed magnetic circuit, wherein an angle .theta. ?rad! formed between a principal line of magnetic force directed from the magnetic member to the moving member and a principal line of magnetic force directed from the moving member to the magnetic member is determined to be 0<.theta.<.pi..

Abstract: An apparatus for security printing of a document on a substrate, having a first and second side, comprising:i) means for feeding variable data in a predetermined digital format to printing stations,ii) at least two printing stations, for image-wise depositing, in accordance to the predetermined format of the variable data, toner particles on the substrate,iii) means for fusing the toner particles to the substrate, to form a fused toner image, characterized in thata) the apparatus comprises means for introducing security features in the document andb) the means for fusing the toner particles to the substrate comprise means for heating and melting the toner particles such that between the melting toner particles and the substrate a contact angle of at most 90.degree. is formed and leave at most 25 mg/m.sup.2 of an external releasing agent on the fused toner image.

Abstract: A fixing device for heating and fixing an unfixed image to a record medium bearing the unfixed image, includes a heating roller provided with a core roller and at least two resistance heating members arranged at the core roller and controlled to be electrically powered independently of each other, the resistance heating members provide different heat distributions in a direction of a rotation axis of the heating roller.

Abstract: An image heating apparatus is constructed by a heat generating member having a conductive layer and a magnetic field generating apparatus for generating a magnetic field. The magnetic field generating apparatus has an exciting coil and an electric power is supplied from a power source to the exciting coil by a switching circuit. An eddy current is generated in the heating member by the magnetic field generated by the magnetic field generating apparatus, the heat generating member generates a heat by the eddy current, and an image on a recording material is heated by the heat. The exciting coil has a first coil portion and a second coil portion for matching the impedances of the first coil portion and the heat generating member. The first coil portion and the second coil portion are neighboring. The magnetic coupling between the second coil portion and the heat generating member is weaker than that between the first coil portion and the heat generating member.