JP2005285657A - Induction heating roller device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating roller device in which heat absorbed into an induction coil is reduced by making a heat capacity smaller, and heating efficiency is enhanced by the amount of the reduction, and provide an image forming device provided with it. <P>SOLUTION: The induction heating roller device is provided with a heating roller HR which generates heat by an induction current, an induction coil IC which is formed into a sheet form including an insulation sheet f and a sheet state coil c attached to the insulation sheet f, and a high frequency power supply HFG which supplies high frequency electric power to the induction coil IC. The magnetic coupling of the induction coil IC to the heating roller HR may be performed by either of an air-core transformer connection method or an eddy current loss method. In the former case, the induction coil is arranged concentrically with the heating roller as is shown in the figure. In the latter case, it may be arranged either inside or outside the heating roller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an induction heating roller device and an image forming apparatus including the induction heating roller device.

  Conventionally, a heating roller using a halogen light bulb as a heat source has been used for heat-fixing a toner image, but there is a problem in that the efficiency is low and a large amount of power is required. Therefore, development has been carried out to solve this problem by introducing an induction heating method. As an induction heating method for this kind of purpose, there are an eddy current loss method (for example, refer to Patent Document 1) and a transformer method (for example, refer to Patent Document 2).

  The eddy current loss method has the same operation principle as that in practical use in IH jars. In addition, the frequency of the high frequency used in the eddy current loss method is about 20 to 100 kHz. On the other hand, the transformer system has higher steady-state efficiency due to stronger magnetic coupling than the eddy current loss method, and the entire heating roller can be heated, so the structure of the fixing device is simpler than the eddy current loss method. There is an advantage of becoming. In addition, by increasing the operating frequency to 20 kHz or higher, preferably 1 MHz or higher, the Q of the induction coil can be increased and the power transmission efficiency can be increased. For this reason, the overall efficiency of heating is increased and power saving can be achieved. In addition, there is an advantage that the structure of the fixing device is simplified as compared with the eddy current loss method. Furthermore, the heat capacity can be made considerably smaller than that of the eddy current loss type heating roller. Therefore, the transformer method is suitable for speeding up heat fixing.

  Furthermore, as an improved version of the transformer system, by forming the secondary side resistance value of the heating roller having a hollow structure rotatably supported by the air core transformer coupled to the induction coil in a closed circuit substantially equal to the secondary reactance, The present inventor has made an air-core transformer coupling method in which the power transfer efficiency from the induction coil to the heating roller is high and the heating roller can be efficiently heated, and a patent application has been filed by the present applicant (patent) Reference 3). According to the present invention, it is possible to save power in induction heating of the heating roller and to easily increase the speed of thermal fixing.

The heating roller device for fixing by induction heating described above uses an induction coil that is magnetically coupled to the heating roller, regardless of whether it is an eddy current method or a transformer method, and the induction coil uses a winding as a coil bobbin. It is common to form by winding.
JP 2000-215974 A JP 59-33787 JP 2002-222688

  However, the coil bobbin generally has a large heat capacity and absorbs heat generated in the heating roller. For this reason, the heating efficiency of the heating roller is reduced.

  It is an object of the present invention to provide an induction heating roller device and an image forming apparatus including the induction heating roller device in which the heat capacity is reduced to reduce the heat absorbed by the induction coil and its supporting member, and the heat efficiency of the heating roller is increased accordingly. Objective.

    An induction heating roller device according to a first aspect of the present invention includes a heating roller that generates heat by an induction current; and includes an insulating sheet and a sheet-like coil attached to the insulating sheet to form a sheet and is magnetically coupled to the heating roller. An induction coil; and a high-frequency power source that supplies high-frequency power to the induction coil device.

  In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

  <Regarding Heating Roller> The heating roller is magnetically coupled to an induction coil described later and generates heat by an induced current. Heat generation by the induction coil may be either an eddy current loss method or a transformer method. What is common to both heating systems is that a conductor having an appropriate resistance value, that is, a heat generating layer, is disposed in a cylindrical shape on the peripheral surface of the heating roller. In the case of the transformer system, the heating roller includes a secondary coil that forms a closed circuit in the circulation direction, that is, a heat generation layer, and the secondary coil is magnetically coupled to the induction coil, for example, an air-core transformer. In the case of air core transformer coupling, the secondary side resistance value of the closed circuit has a value substantially equal to the secondary reactance of the secondary coil. The secondary resistance value and the secondary reactance are “substantially equal” means that when the secondary resistance value is Ra, the secondary reactance is Xa, and α = Ra / Xa, Equation 1 The range is satisfactory. The reason for defining the mathematical condition is disclosed in Patent Document 3. Further, the secondary resistance value can be obtained by measurement. The secondary reactance can be obtained by calculation. Furthermore, α is preferably in the range of 0.25 to 4 times, and most preferably in the range of 0.5 to 2 times.

[Equation 1]
0.1 <α <10
Moreover, the heating roller can arrange | position single or multiple secondary coils. When providing a plurality of secondary coils, it is desirable to disperse them in the axial direction of the heating roller. In order to support the secondary coil, a roller base made of an insulating material or a metal having appropriate conductivity can be used. A secondary coil, that is, a heat generation layer can be disposed on the outer surface, the inner surface, or the roller substrate.

  Furthermore, the heating roller is divided into a plurality of heating regions along the axial direction in accordance with the size of the object to be heated. That is, when a heating roller is used for the purpose of heating the heated object such as fixing of a recording medium on which a toner image is formed, an appropriate heating area can be selected according to the width size of the heated object. These heating regions may not be apparently discernible, but the heating is divided by cooperation with an induction coil described later. The heating region will be described by taking the case of toner image fixing as an example. For example, when fixing a fixed body made of an A4 size recording medium on which a toner image is formed, the length of the heating region required is fixed depending on whether the fixed body is fixed vertically or horizontally. Is different. Further, for example, the required heating area width is different when fixing an A4 size recording medium and when fixing a B4 size fixing body. On the other hand, it is wasteful to generate heat uniformly in areas other than the heating area necessary for fixing, and, as described above, the temperature distribution in the axial direction of the heating roller becomes non-uniform and must be avoided. . On the other hand, heat generation that is as uniform as possible is necessary in the necessary heating region. Further, even in two different heating regions, there can be a common heating region that contributes in common to any region and a single heating region that contributes only to each heating region. Furthermore, the mode of arrangement of the common heating site and the single heating site is a mode in which the common heating site is shifted to either the left or right side and the single heating site is moved to the other side, and the common heating site is centered. However, in the present invention, it is allowed to accommodate any one or all of the above.

Furthermore, in the case of the transformer system, the secondary coil, that is, the heat generation layer, can be formed of a conductor such as a conductor layer, a conductive wire, or a conductive plate. In order to obtain a desired secondary resistance value, the conductor layer can employ the following materials and manufacturing methods. In the case of forming by a thick film forming method (application of conductive paste + firing), a material selected from the group consisting of Ag, Ag + Pd, Au, Pt, RuO ₂ and C is preferably used. As a coating method, a screen printing method, a roll coater method, a spray method, or the like can be used. On the other hand, in the case of forming by plating, vapor deposition or sputtering, it is preferable to use a material selected from the group of Au, Ag, Ni and Cu + (Au, Ag). For the conductive wire and the conductive plate, Cu, Al, or the like can be used. In the case of Cu and Al, in order to prevent oxidation, it is preferable to form a rust preventive film on the surface. Further, when the roller base is made of Fe or SUS (stainless steel), the surface layer of the roller base acts as a secondary coil, that is, a heat generation layer due to a high-frequency skin effect. Therefore, it is not necessary to provide a special heat generation layer as described above. However, even in this case, if necessary, a heat generating layer can be provided separately from the roller base. Note that a rust preventive film such as a zinc film can be formed on the surface of a roller base made of Fe or SUS.

  On the other hand, in the case of the eddy current loss method, the heat generating layer can be made of a metal such as Fe, SUS, Ni, or Cu.

  Next, in order to obtain a more practical heating roller, it is allowed to add the following configuration as necessary.

  1. (Regarding Roller Base) In order to support the heat generating layer, a roller base made of an insulating material can be used. In this case, the heat generating layer can be disposed on the outer surface, the inner surface, or the inside of the roller base. The insulating roller base can be formed using ceramics or glass. In consideration of the heat resistance, strong impact and mechanical strength of the roller base, for example, the following materials can be used. Examples of the ceramic include alumina, mullite, aluminum nitride, and silicon nitride. Examples of the glass include crystallized glass, quartz glass, and Pyrex (registered trademark).

  2. (Regarding Thermal Diffusion Layer) The thermal diffusion layer can be disposed on the upper side of the heat generating layer as necessary as means for improving the temperature uniformity in the axial direction of the heating roller. For this reason, it is preferable to use a material having good heat conduction in the axial direction of the heating roller for the heat diffusion layer. Substances with high thermal conductivity are often found in metals with high conductivity such as Cu, Al, Au, Ag and Pt. However, the thermal diffusion layer only needs to have a thermal conductivity equal to or higher than that of the material of the heat generating layer. Therefore, the heat diffusion layer may be made of the same material as the heat generation layer.

  Further, when the heat diffusion layer is made of a conductive material, it may be in conductive contact with the heat generating layer. However, by providing the heat diffusion layer through an insulating film, it also has an effect of blocking radiation noise. Since the high frequency magnetic field does not act up to the heat diffusion layer, a secondary current that contributes to heat generation is not induced in the heat diffusion layer.

  3. (Regarding Protective Layer) The protective layer can be disposed as necessary for mechanical protection and electrical insulation of the heating roller, or for improving elastic contact property or toner separation property. As the constituent material of the protective layer for the former, glass can be used, and as the constituent material of the protective layer for the latter, synthetic resin can be used. The glass can be selected from the group consisting of zinc borosilicate glass, lead borosilicate glass, borosilicate glass, and aluminosilicate glass. The latter can be selected from the group consisting of silicone resin, fluororesin, polyimide resin + fluororesin and polyamide + fluororesin. In the case of polyimide resin + fluororesin and polyamide + fluororesin, the fluororesin is disposed on the outside.

  4). (Regarding the shape of the heating roller) If desired, a crown can be formed on the heating roller. The crown may be either a drum shape or a barrel shape.

  5). (Regarding Rotation Mechanism of Heating Roller) As a mechanism for rotating the heating roller, a known configuration can be appropriately selected and employed. When the toner image is heat-fixed, a pressure roller is disposed in front of the heating roller, and the toner is heated when the recording medium on which the toner image is formed passes between the two rollers. It can be configured to be fused to a recording medium.

  <Induction coil> When an induction coil is excited by a high-frequency power source, which will be described later, the magnetic flux generated there is linked to the heating roller to induce eddy current or secondary current in the heating roller to generate resistance heat. This is high frequency power transmission means for heating the heating roller as required. In the present invention, the induction coil has a sheet shape. That is, it is comprised including the sheet-like coil stuck on the insulating sheet and the insulating sheet. The insulating sheet is made of plastics excellent in heat resistance and electrical insulation, such as polyimide. The sheet-like coil is flat and is attached to the insulating sheet using an appropriate means such as a printed wiring technique. Therefore, in order to obtain an induction coil with the desired number of turns, the desired number of unit coils made of an insulating sheet with a sheet coil attached in advance are stacked in multiple layers, and the sheet coils are connected in series with each other. do it. The sheet coil is preferably sandwiched between two insulating sheets so as not to be exposed to the outside. However, if desired, an insulating material can be applied to the surface of the sheet-like coil. In addition, when laminating so that the insulating sheet with the sheet-like coil attached in advance becomes a plurality of layers, the back surface of the insulating sheet with the sheet-like coil attached to the surface is covered with the surface of the adjacent sheet-like coil. It can comprise so that it may act as an insulating sheet for pinching.

  Further, the arrangement position of the induction coil with respect to the heating roller may be either inside or outside the heating roller. That is, when heating by the eddy current loss method is performed, the heating roller can be disposed close to a specific position on the outer periphery or inner periphery of the heating roller so as to be intensively heated at a desired rotational position. In this case, it arrange | positions so that the axis | shaft of an induction coil may be substantially orthogonal with respect to the surface of a heating roller. The induction coil is disposed at a position relatively stationary with respect to the heating roller.

  On the other hand, when performing the heating by a transformer system, the induction coil is disposed inside the heating roller. Then, the induction coil is arranged so that the induction coil faces the entire inner periphery of the heating roller and the axis of the coil is coaxial with the heating roller. If desired, the induction coil can be arranged eccentrically with respect to the heating roller so as to approach the inner peripheral surface of the heating roller at a specific rotational position and relatively away from other positions. In addition, the induction coil is energized, that is, excited directly from a high frequency generation circuit of a high frequency power supply or via a load circuit, a matching circuit or / and an output circuit as described later, and further via a power supply lead wire. It may be stationary with respect to the rotating heating roller, or may rotate together with or separately from the heating roller. When the induction coil rotates together with the heating roller, the induction coil is composed of a sheet-like insulating substrate and a sheet coil, so that it is easy to dispose the induction coil so as to be in close contact with the inner peripheral surface of the heating roller. Then, since the distance between the induction coil and the heating roller can be reduced, the magnetic coupling is remarkably increased, and as a result, the high-frequency power transmission efficiency can be further increased. When rotating, a rotating current collecting mechanism may be interposed between the high frequency power source and the induction coil.

  Furthermore, the induction coil may be either single or plural. When there are a plurality of induction coils, they are distributed in the axial direction of the heating roller so as to be opposed to a plurality of heating regions divided in the axial direction of the heating roller. When a plurality of induction coils are provided, they can be connected in parallel to a common high-frequency power source. However, if necessary, a plurality of induction coils may be connected in series. Further, the induction coils may be individually or grouped and connected to individual high frequency power sources.

  Furthermore, the induction coil is allowed to have a core if desired. In particular, in the case of the eddy current loss method, a relatively high magnetic coupling can be obtained by providing the core.

  When the induction coil is a transformer system, the power supply lead wire for supplying high-frequency power from the high-frequency power source to the induction coil is arranged at a position close to the inner surface or the outer surface of the induction coil, regardless of which of the above modes. It is good to do. When passing the power supply lead wire inside the induction coil, if the power supply lead wire is close to the central axis of the induction coil, the amount of magnetic flux interlinking with the power supply lead wire increases. Since efficiency falls, it is not preferable. On the other hand, by configuring as described above, the magnetic flux interlinking with the power supply lead wire is reduced, so that a reduction in power transmission efficiency is relatively suppressed.

  <About a high frequency power supply> A high frequency power supply is a high frequency electric power generation means for supplying high frequency electric power to a heating roller via an induction coil, and heating a heating roller required. For this purpose, the output frequency (or range) of the high frequency power supply is not basically limited. However, in the case of the transformer system, it is effective to be configured to output a high frequency of 20 kHz or more. This is because by increasing the frequency to 20 kHz or higher, it is possible to increase the Q of the induction coil and further increase the power transmission efficiency. When the power transmission efficiency is increased, the overall efficiency of heating is increased and power saving can be achieved. However, in practice, by setting the frequency to 15 MHz or less, the problem of radiation noise can be avoided as easily as possible. In addition, from the viewpoint of the economic efficiency of a suitable active element (for example, a MOSFET can be used as described later) and the ease of suppressing high-frequency noise, the frequency is preferably 20 kHz to 4 MHz. Furthermore, the present invention may be an eddy current loss method as described above, but in this case, a frequency in the range of 20 to 100 kHz is suitable.

  Further, the output frequency of the high frequency power supply may be constant or variable. For example, when the induction heating roller device includes a plurality of induction coils and induction coil selection means for selecting an induction coil, and the induction coil selection means includes a filter means or a resonance circuit, the output frequency of the high frequency power supply Must be variable. In order to make the output frequency of the high-frequency power source variable, for example, known frequency variable means such as making the oscillation frequency of the excitation circuit variable can be used. In addition, if necessary, for example, it is possible to perform rapid heating by making the input power at the time of startup larger than that at the time of normal operation.

  In order to generate a high frequency, it is practical to directly or indirectly convert direct current or low frequency alternating current into a high frequency using an active element such as a semiconductor switch element. In order to obtain high-frequency power from low-frequency alternating current, it is preferable to convert the low-frequency alternating current into direct current using a rectifier. The direct current may be a smoothed direct current formed using a smoothing circuit or a non-smooth direct current. In order to convert direct current into high frequency, circuit elements such as an amplifier or an inverter can be used. As the amplifier, for example, a class E amplifier with high power conversion efficiency can be used. A half-bridge inverter or the like can also be used. Further, as the active element, a MOSFET having excellent high frequency characteristics is suitable. A plurality of high-frequency power supply circuits can be connected in parallel so that the high-frequency outputs of the respective high-frequency power supply circuits are combined and then applied to the induction coil. As a result, since the output of each high-frequency power supply circuit can be reduced while maintaining the desired power, a high-frequency can be efficiently generated at low cost by using a MOSFET as an active element.

  In addition, the high frequency power supply can be configured to be disposed in common with respect to the plurality of induction coils. However, if necessary, it is allowed to arrange a plurality of high-frequency power sources individually or in groups with respect to the plurality of induction coils.

  Further, the high-frequency power source can be provided with a rectified DC power source that rectifies an AC voltage such as a commercial AC power source, and can obtain a DC voltage for conversion into a high-frequency voltage. Further, when the DC voltage for converting to a high frequency voltage is excessive or insufficient with respect to a desired value, a DC switching regulator such as a step-up chopper or a step-down chopper is interposed between the rectified DC power supply and the high frequency generation circuit. be able to.

  Furthermore, the high frequency power supply can take out the high frequency output from the high frequency generation circuit via the load circuit. The load circuit may include a resonance circuit that resonates in series with the high-frequency voltage. Further, the high frequency power supply can include a matching circuit. The matching circuit is a means for efficiently transmitting high-frequency power to the induction coil by suppressing reflection of high-frequency power between the high-frequency power source HFS and the induction coil. Further, the high frequency power supply can include an output circuit. The output circuit exhibits substantially the same impedance and phase difference by performing impedance conversion at different frequencies as a load for the high frequency power supply HFS in order to operate the high frequency power supply HFS in a state of high efficiency at each of different output frequencies. This is a means for efficiently outputting high frequency power.

  <About the effect | action of this invention> In this invention, since the induction coil comprises the sheet | seat shape including the insulation sheet and the sheet coil, its own heat capacity becomes small. Moreover, it can arrange | position in a predetermined position, without using the coil support means which becomes large in heat capacity like a coil bobbin. Furthermore, the surface of the induction coil can be smoothed.

  Since the induction coil has a sheet shape as described above, the induction coil can be disposed closer to the heating roller. For this reason, the magnetic coupling between the induction coil and the heating roller can be further strengthened, and the high-frequency power transmission efficiency and thus the heating efficiency can be improved. This reduces power consumption when the induction heating roller device is operated continuously. Therefore, the fixing device incorporating the induction heating roller device of the present invention, and thus energy saving as an image forming apparatus equipped with this fixing device. Also contribute to. Further, since the heat capacity of the induction coil is small, it is effective not only for induction heating but also for quicker heat-up.

<About other configurations>
Although not an essential component of the present invention, a more effective induction heating roller device can be obtained by selectively adding the following components as desired.

  1. (Warm-up control) During the warm-up period after the start-up, that is, the start of power supply, the heating roller can be controlled to rotate at a lower rotational speed than during normal operation.

  2. (Regarding Temperature Control of Heating Roller) In order to keep the temperature of the heating roller constant within a predetermined range, for example, 200 ° C., the heat sensitive element can be brought into thermal contact with the surface of the heating roller. Then, the thermal element is connected to the temperature control circuit. As the thermal element, a thermistor having a negative temperature characteristic or a non-linear resistance element having a positive temperature characteristic can be used.

  3. (Conveying sheet) When a sheet-shaped recording medium is heated using a heating roller, the heating roller can be configured to directly contact the heated object. It can be configured to intervene. In this case, the conveyance sheet is allowed to take an endless or roll shape. By using the conveyance sheet, it becomes possible to smoothly heat and convey the heated object.

    According to a second aspect of the present invention, there is provided an image forming apparatus main body including an image forming means for forming an image on a recording medium; a fixing apparatus main body including a pressure roller; The induction heating roller device according to claim 1, wherein the induction heating roller device is arranged so as to fix the image while fixing the image while conveying the recording medium on which the image is formed between both rollers. And a fixing device that is disposed in the apparatus main body and fixes an image on a recording medium.

  The image forming apparatus main body is a remaining part of the image forming apparatus except for the fixing device, and includes an image forming unit. The image forming means is a means for forming an image for forming image information on a recording medium by an indirect method or a direct method. The “indirect method” is a method of forming an image by transfer. Examples of the image forming apparatus include an electrophotographic copying machine, a printer, and a facsimile. Examples of the recording medium include a transfer material sheet, printing paper, electrofax sheet, and electrostatic recording sheet.

  The fixing device includes a fixing device main body having a pressure roller, and a recording medium on which an image, for example, a toner image is formed between the two rollers, and a heating roller is provided in pressure contact with the pressure roller of the fixing device main body. The induction heating roller device according to claim 1, which is disposed so as to fix an image while being nipped and conveyed. Here, the “fixing device main body” refers to the remaining portion of the fixing device excluding the induction heating roller device. The pressure roller and the heating roller may be in direct pressure contact, but may be indirectly in pressure contact with each other via a conveyance sheet, if necessary. Note that the transport sheet may be endless or roll-shaped. In the present invention, the recording medium corresponds to the heated body in the invention of claim 1.

  Since the induction coil is closer to a specific part of the heating roller than the heating roller, when the specific part is arranged to be heated more, the above-mentioned closest part is aligned with the pressure roller. If it is made to face, or if it is made to face right in front of the rotation direction of a heating roller, a to-be-heated body can be heated effectively using the high heat which generate | occur | produces in the closest part. The forward position is an effective range in which a high temperature can be obtained. Specifically, although it depends on design conditions such as the rotational speed on the peripheral surface of the heating roller, it generally exceeds 0 °. It should just be in the range of -90 degrees. However, it is preferably in the range of 5-60 °.

  Thus, in the present invention, the image forming apparatus has the same effect as in the first aspect.

    According to the first aspect, since the induction coil has a sheet shape, it is possible to provide an induction heating roller device that can reduce the heat capacity of the induction coil, improve the heating efficiency, and save energy during continuous operation. .

    According to the second aspect, the same effect as in the first aspect can be obtained, and the warm-up can be accelerated by induction heating, so that the image forming apparatus suitable for the high-speed type can be obtained.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

    1 to 4 show a first embodiment for implementing the induction heating roller device of the present invention, FIG. 1 is a circuit block diagram showing an outline of the entire device, and FIG. 2 is a conceptual diagram of an induction coil and a heating roller. FIG. 3 is an exploded perspective view of the induction coil, and FIG. 4 is a circuit diagram of the high-frequency power source. In this embodiment, the induction heating roller device includes a heating roller HR, an induction coil IC, and a high frequency power source HFS, and is configured to perform eddy current loss type induction heating. Hereafter, the structure is demonstrated in detail for every said component.

  The heating roller HR includes a roller base, a heat generating layer, and a protective layer, and is driven to rotate by a rotation mechanism that is not shown. The roller base is made of, for example, a cylindrical body made of alumina ceramics, and has a length corresponding to the size of the heated object. In the heat generating layer, a conductive metal such as iron or copper forms a film-like cylinder. And it is arrange | positioned in the outer surface of a roller base | substrate over substantially the whole effective length of an axial direction. The protective layer is made of a fluororesin and is formed so as to cover the outer surface of the heat generating layer.

  The induction coil IC is in the form of a sheet, and is arranged inside the heating roller HR as shown by attaching the symbol A to the right side of the heating roller HR in FIG. 2, or on the left side of the heating roller HR in FIG. As indicated by the reference numeral B, it is disposed outside the heating roller HR and is held stationary. In any of the above-described aspects, the induction coil IC and the heating roller HR are common in that eddy current loss type magnetic coupling is performed. That is, the magnetic flux generated by the induction coil IC is linked so as to penetrate the heat generating layer of the heating roller HR. As a result, an eddy current is induced around the magnetic flux penetrating the heat generating layer, an eddy current loss occurs due to the resistance of the heat generating layer, and the heating roller HR generates heat.

  In addition, as shown in FIG. 3, the induction coil IC is formed by laminating a required number of unit coils UC composed of an insulating sheet f1 and a sheet-like coil c and connecting them in series, and exhibits a sheet shape as a whole. ing. The insulating sheet f1 is made of plastics having excellent insulating properties and heat resistance, such as polyimide resin. The sheet-like coil c is formed in a ring shape such as a quadrangular or circular shape in which a conductive metal such as copper foil is formed into a thin plate and partially opened, and is printed on one or both sides of the insulating sheet f by a printing method or the like. It is attached. In addition, a known connection means can be used for the connection between the plurality of unit coils UC.

  The high-frequency power supply HFS is schematically shown in FIG. 1 and is composed of a rectified DC power supply RDC, a high-frequency generation circuit HFI, a load circuit LC, and a matching circuit MC as shown in detail in FIG. Connected to the power supply AS. The low frequency AC power supply AS is composed of, for example, a 100V commercial AC power supply.

  The rectified DC power supply RDC is a full-wave rectifier circuit. The AC input terminal is connected to the low-frequency AC power supply AS, converts the low-frequency AC voltage into a non-smooth DC voltage, and outputs a rectified DC voltage from the DC output terminal.

  The high frequency generation circuit HFI includes a high frequency filter HFF, a half-bridge inverter main circuit HBI, and a drive circuit DC. The high frequency filter HFF includes a pair of inductors L1 and L2 connected in series to both lines connected to the output terminal of the rectified DC power supply RDC, and a pair of capacitors C1 connected between the lines before and after the pair of inductors L1 and L2. C2 is interposed between the DC power supply RDC and a half-bridge inverter main circuit HBI described later to prevent high frequency from flowing out to the low frequency AC power supply AS side.

  The half-bridge inverter main circuit HBI is connected in series between the output terminals of the DC power supply RDC and is connected in parallel to a pair of MOSFETs Q1 and Q2 and a pair of MOSFETs Q1 and Q2 that are alternately switched by being excited by a drive signal of the drive circuit DC. Consists of capacitors C3 and C4. Capacitors C3 and C4 perform a high frequency bypass action during inverter operation.

  The drive circuit DC includes a drive signal generation circuit DSG and a drive transformer DT. The drive signal generation circuit DSG generates gate drive signals for the pair of MOSFETs Q1 and Q2. Note that the oscillation frequency of the gate drive signal can be changed as desired. The drive transformer DT makes the gate drive signal applied to the pair of MOSFETs Q1 and Q2 have an antiphase relationship.

  The load circuit LC includes a series circuit of a DC cut capacitor C5, an inductor L3, and a matching circuit MC, which will be described later, and is connected in parallel to the high frequency output terminal of the high frequency generation circuit HFI, that is, the MOSFET Q2 of the half bridge inverter main circuit HBI. Then, it resonates with the high frequency voltage and is shaped into a sine wave.

  The matching circuit MC includes a pair of capacitors C6 and C7. The capacitor C6 is connected in series between the load circuit LC and the power feed lead l1. The capacitor C7 is connected in series to the load circuit LC.

  The power feed leads l1 and l2 constitute a transmission path for supplying high frequency power to the induction coil. Further, the base end of the power supply lead l2 is connected to the connection of the source of the MOSFET Q2 and the capacitor C7.

  Thus, the high frequency output generated in the high frequency power supply HFS is supplied to the induction coil IC via the load circuit LC and the matching circuit MC.

  Hereinafter, second to fifth embodiments for carrying out the induction heating roller device of the present invention will be described with reference to FIGS. The same parts as those in FIG. 1 to FIG.

    FIG. 5 is an exploded perspective view of an induction coil showing a second mode for carrying out the induction heating roller device of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that the sheet coil c of the induction coil IC is sandwiched between a pair of insulating sheets f1 and f2. That is, the sheet coil c is formed on one surface of the insulating sheet f1, and the insulating sheet f2 is laminated in the arrow direction from above.

  Thus, in this embodiment, since the sheet coil is covered with the insulating sheets f1 and f2, the insulation of the induction coil IC is improved. Further, in the first embodiment shown in FIG. 4, by adopting the configuration of this embodiment for the uppermost sheet coil c, it is possible to provide good insulation.

    FIG. 6 is a conceptual perspective view showing a third mode for carrying out the induction heating roller device of the present invention. In this embodiment, the induction heating roller device is configured to perform transformer type induction heating.

  The heating roller HR has a heat generating layer in the form of a film made of a deposited film of a conductive metal such as copper, and constitutes a secondary coil made up of a cylindrical one-turn coil. The thickness of the heat generating layer is set so that the value of the secondary resistance R in the circumferential direction of the heating roller HR is 1Ω, which is substantially the same value as the secondary reactance.

  The induction coil IC is concentric with the heating roller HR, has an outer diameter slightly smaller than the inner diameter of the heating roller HR, is held stationary, and is connected to the heating roller HR with an air-core transformer. Do. The induction coil IC is formed in a cylindrical shape by integrating the insulating sheet f and the sheet coil c. For example, a plurality of conductive strips are formed on one surface of the flat insulating sheet f obliquely and at equal intervals so as to have a desired coil pitch, and then the insulating sheet f is curved and formed into a cylindrical shape. At the same time, by connecting one end of the plurality of conductive strips to the other end of the adjacent conductive strip, each of the plurality of conductive strips forms one turn of the coil, so that the cylindrical sheet coil c having a plurality of turns is formed. Can be formed.

  Thus, the induction coil IC performs a magnetic coupling of the heating layer of the heating roller HR and the air-core transformer coupling, so that the magnetic flux generated by the induction coil IC is distributed so as to wrap the heating layer along the axial direction of the heating roller HR. And interlink with the heating layer. Therefore, a secondary current is induced in the heat generation layer so as to surround the magnetic flux distributed along the central axis of the heating roller HR and the induction coil IVC. As a result, the secondary current flows in the circulation direction of the heat generating layer, and at that time, the heat generating layer is Joule-heated, so that the heating roller HR is heated at an increased temperature.

    FIG. 7 is a conceptual cross-sectional view of a heating roller and an induction coil showing a fourth mode for carrying out the induction heating roller device of the present invention. In this embodiment, the transformer type induction heating is performed in the same manner as in the third embodiment shown in FIG. 6, but the induction coil IC is integrated with the heating roller HR so that the magnetic coupling between the two is particularly increased. Is different.

  That is, the induction coil IC is fixed while being in contact with the inner surface of the heating roller HR and integrated with the heating roller HR. The induction coil IC and the heating roller HR can be fixed by, for example, adhesion. Therefore, the induction coil IC rotates together with the heating roller HR. Therefore, in order to supply high frequency power to the induction coil IC, it is preferable to interpose a rotating current collecting mechanism between the induction coil IC and the high frequency power source. It should be noted that since a known rotary current collecting mechanism may be adopted as appropriate, the illustration is omitted. As an example, a current collecting ring can be connected to both ends of the induction coil IC, and a current collecting which is in sliding contact with the current collecting ring can be disposed on the high frequency power supply side. In this case, the current collecting ring can be formed on the insulating sheet f by the same means as the sheet coil c. Note that the arrangement of the last power ring and the current collector may be the reverse of the above.

    FIG. 8 is a conceptual cross-sectional view showing a fifth embodiment for carrying out the induction heating roller device of the present invention. In this embodiment, the transformer type induction coil is integrated with the heating roller as in the third embodiment, but the heat generation layer h of the induction coil IC and the heating roller HR is laminated without the base b. It is different.

  That is, the induction coil IC has a sheet shape and is disposed in close contact with the outer surface of the base b of the heating roller HR, and further, the heat generation layer h is adhered and laminated thereon. As the rotating current collecting mechanism, for example, a power receiving terminal of an induction coil is led out on an insulating sheet that is in close contact with the outer surface of the base, and the power receiving terminal is connected to a current collecting ring disposed on the outer surface of the base. A current collector connected to the high-frequency power source can be disposed opposite the electric ring.

  Moreover, in order to insulate between the induction coil IC and the heat generating layer h, the front and back of the induction coil can be sandwiched between insulating sheets. The heat generating layer h can be formed on the insulating sheet as a metal evaporation layer, or a conductive metal foil can be attached, and the insulating sheet on the back side can also be used as the insulating sheet on the surface side of the induction coil. The heating roller HR includes a base b, a heat generating layer h, and a protective layer p.

  Thus, in the present embodiment, the induction coil IC and the heat generating layer h of the heating roller HR are directly laminated, so that even higher magnetic coupling can be obtained.

    9 and 10 show a copying machine as an embodiment for carrying out the image forming apparatus of the present invention. FIG. 9 is a conceptual sectional view, and FIG. 10 is a sectional view of a fixing device. In each figure, 31 is a reading device, 32 is an image forming means, 33 is a fixing device, and 34 is an image forming device case.

  The reading device 31 optically reads a base paper to form an image signal.

  The image forming means 32 forms an electrostatic latent image on the photosensitive drum 32a based on the image signal, attaches toner to the electrostatic latent image to form a reverse image, and transfers this to a recording medium such as paper. To form an image.

  As shown in FIG. 10, the fixing device 33 heat-melts the toner adhering to the recording medium and heat-fixes it. The fixing device 33 includes an induction heating roller device 21, a pressure roller 22, and a mount 25. In the figure, reference numeral 23 denotes a recording medium, and 24 denotes toner. The pressure roller 22 is disposed so as to be in pressure contact with the heating roller HR of the induction heating roller device 21 and conveys the recording medium 23 while narrowly pressing between them. The recording medium 23 forms an image by the toner 24 adhering to the surface thereof. The recording medium 23 has a toner image formed thereon and corresponds to a heated body. The gantry 25 mounts the above constituent elements (excluding the recording medium 23) in a predetermined positional relationship.

  In the fixing device 33, the recording medium 23 on which the toner 24 adheres and forms an image is inserted between the heating roller HR and the pressure roller 22 of the induction heating roller device 21 and conveyed. The toner 24 is heated and melted by receiving heat from the heating roller HR, and heat fixing is performed.

  The image forming apparatus case 34 accommodates the above-described devices and means 31 to 33, and includes a transport device, a power supply device, a control device, and the like.

The circuit block diagram which shows the outline | summary of the whole apparatus which shows the 1st form for implementing the induction heating roller apparatus of this invention Also conceptual cross-sectional view of induction coil and heating roller Similarly induction coil exploded perspective view Similarly high-frequency power supply circuit diagram The disassembled perspective view which shows the 2nd form for implementing the induction heating roller apparatus of this invention The conceptual perspective view of the induction coil which shows the 3rd form for implementing the induction heating roller apparatus of this invention The conceptual cross-sectional view of the heating roller and induction coil which shows the 4th form for implementing the induction heating roller apparatus of this invention The conceptual cross-sectional view which shows the 5th form for implementing the induction heating roller apparatus of this invention 1 is a conceptual cross-sectional view showing a copying machine as an embodiment for carrying out an image forming apparatus of the present invention. Cross-sectional view of the fixing device

Explanation of symbols

  A ... Induction coil internal arrangement, B ... Induction coil external arrangement, c ... Sheet coil, f ... Insulating sheet, HR ... Heating roller, IC ... Induction coil

Claims (2)

A heating roller that generates heat by an induced current;
An induction coil that is in the form of a sheet including an insulating sheet and a sheet-like coil attached to the insulating sheet and is magnetically coupled to the heating roller;
A high frequency power supply for supplying high frequency power to the induction coil device;
An induction heating roller device comprising: An image forming apparatus main body provided with an image forming means for forming an image on a recording medium;
A fixing device body provided with a pressure roller, and a heating roller in a pressure contact relationship with the pressure roller of the fixing device body, and fixing the image while conveying a recording medium on which an image is formed between both rollers. A fixing device comprising the induction heating roller device according to claim 1 arranged in such a manner;
An image forming apparatus comprising:

Images