Patent Publication Number: US-7725065-B2

Title: Fixing device, and image forming device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based on and claims priority under 35 USC 119 from Japanese Patent Applications Nos. 2006-328144 filed on Dec. 5, 2006. 
   BACKGROUND 
   1. Technical Field 
   The invention relates to a fixing device, and an image forming device. 
   2. Related Art 
   As a fixing device for image forming devices, suggested is a fixing device wherein an electromagnetic induction heating mode is adopted. 
   SUMMARY 
   According to an aspect of the invention, there is provided a fixing device comprising: 
   a first rotary body having a thermosensitive magnetic metal layer, the thermosensitive magnetic layer including a thermosensitive magnetic metal material having a Curie point; 
   a second rotary body contacting the first rotary body; and 
   a magnetic field generating unit for generating a magnetic field, the unit being arranged to have a predetermined interval with respect to the inner circumferential face or the outer circumferential face of the first rotary body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will be described in detail based on the following figures, wherein: 
       FIG. 1  is a schematic structural view illustrating an image forming device according to an embodiment; 
       FIG. 2  is a schematic sectional view illustrating a fixing device according to the embodiment; 
       FIG. 3  is a schematic sectional view illustrating the fixing device according to the embodiment; 
       FIG. 4  is a schematic sectional view illustrating a situation that in the fixing device according to the embodiment, a fixing belt and a pressing roll are separated from each other. 
       FIG. 5A  is a schematic sectional view schematically illustrating main magnetic fluxes which penetrate the fixing belt in the fixing device according to the embodiment. 
       FIG. 5B  is a schematic sectional view schematically illustrating main magnetic fluxes which penetrate the fixing belt in the fixing device according to the embodiment. 
   

   DETAILED DESCRIPTION 
   Embodiments according to the invention will be described hereinafter with reference to the attached drawings. In all of the figures, the same reference numbers are attached to members having substantially the same function, and repeated description thereof may be omitted. 
   A Curie point may also be referred to as a Curie temperature. When the temperature of a magnetic material reaches this temperature or higher, the magnetism thereof is lost so that the material turns into a nonmagnetic body (paramagnetic material). A thermosensitive magnetic material is a magnetic material having magnetic properties varied by a change in the temperature of the magnetic material. 
   Setup temperature of the first rotary body means a surface temperature of the first rotary body at the beginning of the fixing operation. The heat resistant temperature means a temperature where constituent material deteriorates and loses its function and deformation occurs during continuous use. 
     FIG. 1  is a schematic structural view illustrating an image forming device according to an embodiment.  FIG. 2  is a schematic sectional view illustrating a fixing device according to the embodiment.  FIG. 3  is another schematic sectional view illustrating the fixing device according to the embodiment.  FIG. 2  illustrates a cross section viewed along the axial direction of the fixing device, and  FIG. 3  illustrates a cross section taken on line  2 - 2  in  FIG. 2  and viewed along a direction perpendicular to the axial direction of the fixing device. 
   As illustrated in  FIG. 1 , an image forming device  100 , which is the image forming device according to the present embodiment, has a cylindrical photoreceptor drum  10  rotatable into a single direction (a direction of an arrow A in  FIG. 1 ). Around this photoreceptor drum  10 , the following are successively arranged from an upstream side of the drum  10  in the rotating direction thereof toward a downstream side thereof: an charging device  12  for charging the surface of the photoreceptor drum  10 ; an exposure device  14  for radiating light L imagewise onto the photoreceptor drum  10  to form a latent image on the surface; a developing device  16  for transferring a toner selectively onto the surface of the photoreceptor drum  10  to form a toner image, this device being composed of developing units  16 A to  16 D; an intermediate transferring body  18 , in an endless belt form, which is supported oppositely to the photoreceptor drum  10  and has a rotatable circumferential face; a cleaning device  20  for removing the toner remaining on the photoreceptor drum  10  after the toner image is transferred; and a discharging exposure device  22  for discharging the surface of the photoreceptor drum  10 . 
   Furthermore, inside the intermediate transferring body  18  are arranged a transferring device  24  for transferring the toner image formed on the surface of the photoreceptor drum  10  primarily onto the intermediate transferring body  18 , two supporting rolls  26 A and  26 B, and a transferring opposite roll  28  for attaining secondary transfer. By these members, the intermediate transferring body  18  is strained so as to be rotatable into a single direction (a direction of an arrow B in  FIG. 1 ). At a position opposite to the transferring opposite roll  28 , a transferring roll  30  is arranged with the intermediate transferring body  18  interposed between the rolls  28  and  30 . The transferring roll  30  is a roll for transferring, onto a recording paper (recording medium) P secondarily, the toner image primarily transferred on the outer circumferential face of the intermediate transferring body  18 . The recording paper P is fed to a portion in a direction of an arrow C where the transferring opposite roll  28  and the transferring roll  30  contact each other so as to be pressed against each other. In this press-contact portion, the recording paper P on the surface of which the toner image is secondarily transferred is carried, as it is, in a direction of an arrow C. 
   At a downstream position of the carrier direction (the arrow C direction) of the recording paper P, a fixing device  32  is arranged for heating the toner image on the surface of the recording paper P so as to be melted, and then fixing the melted image onto the recording paper P. The recording paper P is fed in the fixing device  32  through the carrier guide  36 . At a downstream side of the intermediate transferring body  18  along the rotating direction of the body  18  (the arrow B direction), a cleaning device  34  is arranged for removing the toner remaining on the surface of the intermediate transferring body  18 . 
   The following will describe the fixing device according to the present embodiment. 
   As illustrated in  FIGS. 2 and 3 , the fixing device  32  according to the present embodiment has an endless-belt-form fixing belt  38  (a first rotary body) rotatable in a single direction (a direction of an arrow D), a pressing roll  40  (a second rotary body) rotatable in a single direction (a direction of an arrow E) and contacting the circumferential face of the fixing belt  38  so as to be pressed against the face, and a magnetic field generating device  42  (magnetic field generating unit) arranged oppositely to the outer circumferential face of the belt  38  reverse to the press-contact face of the belt  38 , which contacts the pressing roll  40 , and separately from the outer circumferential face. 
   At the side of the inner circumferential face of the fixing belt  38  are arranged a fastening pad  44  for forming a contact region together with the pressing roll  40 , and a supporting member  48 . The member  48  supports the fastening pad  44 , and is arranged oppositely to the magnetic field generating device  42  so as to interpose the fixing belt  38  between the member  48  and the device  42 , and separately from the inner circumferential face of the fixing belt  38 . In order to drive and rotate the fixing belt  38 , driving force transmitting members  50  for transmitting rotary driving force for the belt  38  are fitted to both ends of the belt  38 . 
   At a downstream side of the contact region between the fixing belt  38  and the pressing roll  40  along the carrier direction of the recording paper P (the direction of an arrow F), a peeling member  52  is set up. The peeling member  52  is composed of a supporting section  52 A, an end of which is supported to be fixed, and a peeling sheet  52 B supported by the section  52  A. The peeling member  52  is arranged to cause a front end of the peeling sheet  52 B to approach or contact the fixing belt  38 . 
   First, the fixing belt  38  will be described hereinafter. The fixing belt  38  has, for example, a structure wherein a heat generating layer  38 A which also functions as a substrate is arranged and further an elastic layer  38 B and a surface releasing layer  38 C are successively laminated onto the outer circumferential face of the layer  38 A. The elastic layer  38 B and the surface releasing layer  38 C are optional layers, which are formed if necessary. 
   The heat generating layer  38 A, which also functions as a substrate, may be a thermosensitive magnetic metal layer. The thermosensitive magnetic metal layer is a heat generator which contains a thermosensitive magnetic metal material having a Curie point and causes electromagnetic induction by action of a magnetic field, so as to generate heat. 
   When the temperature of the thermosensitive magnetic metal material rises near the Curie point of this material, the material is non-magnetized. When a magnetic material having a relative magnetic permeability of several hundreds or more is non-magnetized (i.e., gets into a paramagnetic or diamagnetic state), the relative magnetic permeability gets close to 1 so that the magnetic flux density changes (i.e., the magnetic field becomes strong or weak). Thus, by the non-magnetization of the thermosensitive magnetic metal material, the magnetic flux density thereof is made weak so that this material can be changed into a material which does not generate heat with ease. 
   Generally, the skin depth of any electric conductor made of metal is represented by a formula 1 described below. When the skin depth of a conductor is set to the thickness of the thermosensitive magnetic metal layer or less, the conductor is thermally treated, thereby making the magnetic permeability thereof high, or the frequency of the magnetic field generating device  42  is made high. Alternatively, the setting can be realized by selecting a material having a small intrinsic resistivity value. In the present embodiment, it is unessential that the skin depth is the thickness of the thermosensitive magnetic metal layer or less. It is desired to set the skin depth into the thickness of the thermosensitive magnetic metal layer or less since the advantageous effect is increased. 
                 δ   =     503   ⁢       ρ     f   ·     μ   r                     [     Formula   ⁢           ⁢   1     ]               
wherein δ: the skin depth (m), ρ: the intrinsic resistivity value (Ωm), f: the frequency (Hz), and μ: the relative magnetic permeability.
 
   Preferably, this Curie point is equal to or higher than a setup temperature of the fixing belt  38 , and is equal to or lower than the heat resistant temperature of the fixing belt  38 . Specifically, the Curie point is desirably from, e.g., 140 to 240° C., more desirably from, e.g., 150 to 230° C. 
   The thermosensitive magnetic metal material may be, for example, a metal material which is inexpensive, can easily be molded into a thin form, and has good workability, flexibility and a high thermal conductivity. Examples of the metal material include magnetism-adjusted steel of amorphous alloy, and amorphous alloy. In other words, it is desired to use a metal soft magnetic material containing Fe, Ni, Si, B, Nb, Cu, Zr, Co, Mo, V, Mn or the like, for example, binary magnetism-adjusted steel made of Fe and Ni, or ternary magnetism-adjusted steel made of Fe, Ni and Cr. 
   When the relative magnetic permeability of the thermosensitive magnetic metal material is at least about 400 or more, the advantageous effect can be obtained. 
   The thickness of the heat generating layer  38 A, which is a thermosensitive magnetic metal layer, is, for example, from 20 to 200 μm, desirably from 50 to 150 μm. 
   The surface releasing layer  38 C may be, for example, a fluorine-contained resin layer (for example, a PFA layer: a layer made of copolymer PFA (i.e., copolymer made from tetrafluoroethylene and perfluoroalkyl vinyl ether) having a thickness of 1 to 30 μm. 
   The elastic layer  38 B may be, for example, a layer containing an elastic material (such as silicone rubber, fluorine-contained rubber or fluorosilicone rubber) having a thickness of 100 to 600 μm (desirably, 200 to 400 μm). 
   The fixing belt  38  may have a structure wherein the heat generating layer  38 A, the elastic layer  38 B and the surface releasing layer  38 C are successively laminated onto the outer circumferential face of a substrate. In this case, the thickness of the thermosensitive magnetic metal layer, which is the heat generating layer  38 A, can be set into the range of, e.g., 20 to 200 μm (desirably, 50 to 150 μm). 
   The substrate is appropriately selected from one made of a material which has heat resistance and which transmits a magnetic field (magnetic fluxes) but does not generate heat with ease or does not generate any heat by action of the magnetic field. The substrate may be, for example, the following: a metal belt (made of a nonmagnetic metal, such as nonmagnetic stainless steel, or made of a soft magnetic material or hard magnetic material, such as Fe, Ni, Cr, or an alloy thereof such as Ni—Fe alloy or Ni—Cr—Fe alloy) having a thickness of 30 to 200 μm (desirably, 50 to 150 μm, more desirably 100 to 150 μm); or a resin belt (such as a polyimide belt) having a thickness of 60 to 200 μm. 
   The fixing belt  38  is preferably formed to have a structure having a small thermal capacity (for example, a thermal capacity of 5 to 60 J/k, desirably 30 J/K or less), for example, by making the thickness thereof small or selecting the constituting material(s) thereof. 
   The diameter of the fixing belt  38  may be, for example, from 20 to 50 mm. It is allowable to form, on the inner circumferential face of the fixing belt  38 , a sliding sheet covered with a fluorine-contained resin (for example, set such a sliding sheet only onto the fastening pad  44 ), or to coat the inner circumferential face with a fluorine-contained resin or the like or paint a lubricant (such as silicone oil) onto the inner circumferential face. 
   The following will describe the pressing roll  40  hereinafter. The pressing roll  40  is set up to press both ends thereof onto the fastening pad  44  at a total load of, e.g., 294 N (30 kgf) by means of spring members (not illustrated) so as to interpose the fixing belt  38  between both of the ends and the fastening pad  44 . When the pressing roll  40  is pre-heated (warmed up), the pressing roll  40  is shifted so as to be separated from the fixing belt  38  (see  FIG. 4 ). 
   The pressing roll  40  may be, for example, a roll having a cylindrical core member  40 A made of a metal, and an elastic layer  40 B (such as a silicone rubber layer or a fluorine-contained rubber layer) formed on the surface of the core member  40 A. If necessary, the pressing roll  40  may have, on the outermost surface thereof, a surface releasing layer (such as a fluorine-contained resin layer). 
   The following will describe the fastening pad  44  hereinafter. The fastening pad  44  is, for example, a rodlike member having an axial line in the axial direction (the width direction) of the fixing belt  38 . The pad  44  is a member for resisting pressing force acting from the pressing roll  40 . When the pressing roll  40  is pressed across the fixing belt  38  against the fastening pad  44 , the fixing belt  38  is deformed toward the side of the inner circumferential face thereof. When a curvature is given to the fixing belt  38  at the downstream side of the contact region in the pressing roll  40  and the fastening member  44  along the carrier direction of the sheet as described above, the sheet is peeled from the fixing belt. 
   In order to gain the peelable performance of the sheet, the fixing belt is selected or decided, considering “whether or not the fixing belt  38  can be deformed toward the side of the inner circumferential face thereof when the pressing roll  40  is pressed across the fixing belt  38  against the fastening pad  44 ”. However, in the fixing belt  38  in the present embodiment, the metal material is used; therefore, the flexibility is decided by the metal layer for deciding the rigidity of the fixing belt  38 , that is, the thickness of the thermosensitive magnetic metal layer. 
   It can be examined by use of a hard material (trade name: MS-220) manufactured by Neomax Material whether or not the fixing belt  38  warps or bends toward the inside thereof inside its elastic deformation region. When a pressing force equal to or more than the load imposed onto the fixing belt at least at the time of the fixation of an image is given thereto, the warp amount thereof is evaluated. As a result, when the thickness of the hard material is 250 μm, the material hardly warps. When the thickness is 200 μm, the generation of a slight warp begins. When the thickness is 150 μm, 125 μm, 100 μm, and 75 μm, a sufficient warp is generated. Accordingly, the metal material layer of the fixing belt  38  is desirably 200 μm or less. 
   The material of the fastening pad  44  is not particularly limited as long as the material is a material which gives a warp amount in an allowable level range or less (specifically, for example, a warp amount of 0.5 mm or less) when the material receives pressing force from the pressing roll  40 . Aluminum is most suitable. Besides aluminum, for example, a heat resistant resin may be used, examples thereof including glass fiber reinforced PPS (polyphenylenesulfide), phenol, polyimide, and liquid crystal polymer. 
   The following will describe the supporting member  48  hereinafter. In the supporting member  48 , its surface opposing to the magnetic field generating device  42  so as to interpose the fixing belt  38  between the surface and the device  42  is formed into a curved form following the inner circumferential face of the fixing belt  38 . At the side of the member  40  reverse thereto, the member  48  supports the fastening pad  44 . The supporting member  48  is formed to include, at least at the side opposing to the magnetic field generating device  42 , a nonmagnetic member containing a nonmagnetic metal material (such as copper, aluminum or silver). In the supporting member  48 , shafts  48 A are set up to both ends of the member  48  along the longitudinal direction thereof. In the case that the shafts  48 A are largely warped by load imposed onto the shafts  48 A so that a problem is caused about the rigidity of the shafts  48 A, the supporting member may be a structural body composed of a member made of a material having such a Young&#39;s modulus that a small warp is given and a nonmagnetic metal layer. In this case, the thickness of the nonmagnetic layer should be made equal to or more than the skin depth represented by the formula 1. 
   The following will describe the driving force transmitting members  50 . The driving force transmitting members  50  are each a member for transmitting driving force for rotating the fixing belt  38  around its rotary center. The members  50  are each composed of, for example, a flange section  50 A fitted to the inside of one of ends of the fixing belt  38  and a cylindrical gear section  50 B having, in its outer circumferential face, irregularities. The driving force transmitting members  50  are made of, for example, a metal material, or a resin material. 
   The driving force transmitting members  50  are supported by the ends of the fixing belt  38  by inserting the flange sections  50 A to the insides of the ends of the fixing belt  38 . The gear sections  50 B of the driving force transmitting members  50  are driven to be rotated by a motor or the like, which is not illustrated. Furthermore, the rotary driving force is transmitted to the fixing belt  38  so that the belt  38  is rotated around its rotary center. 
   The driving force transmitting members  50  are fitted to both the ends of the fixing belt  38  in its axial direction; however, the invention is not limited to this form. A driving force transmitting member may be fitted only to one end of the fixing belt  38  in its axial direction. The driving force transmitting members  50  are supported at the ends of the fixing belt  38  by fitting the flange sections  50 A to the insides of the ends of the fixing belt  38 ; however, the invention is not limited to this form. The driving force transmitting members  50  may be supported at the ends of the fixing belt  38  by fitting ends of the fixing belt  38  to the insides of the flange sections  50 A. 
   The following will describe the magnetic field generating device  42  hereinafter. The magnetic field generating device  42  is formed to have a shape following the outer circumferential face of the fixing belt  38 . The device  42  is arranged oppositely to a heat generation controlling member  46  to interpose the fixing belt  38  between the device  42  and the member  46 , and separately from the outer circumferential face of the fixing belt  38  to have an interval of, e.g., 1 to 3 mm. In the magnetic field generating device  42 , an exciting coil (magnetic field generating unit)  42 A wound into plural circles is arranged along the axial direction of the fixing belt  38 . 
   To this exciting coil  42 A is connected an exciting circuit (not illustrated) for supplying an alternating current to the exciting coil  42 A. Moreover, a magnetic substance member  42 B is arranged to extend along the length direction of the exciting coil  42 A (the axial direction of the fixing belt  38 ) on the surface of the coil  42 A. 
   The power of the magnetic field generating device  42  is set within a scope described as follows: for example, the magnetic fluxes (magnetic field) of the heat generating layer  38  (the thermosensitive magnetic metal layer), has magnetism at a temperature lower than the Curie point; and the layer  38 A is non-magnetized (turns into a paramagnetic state) at the Curie point or higher to cause magnetic fluxes to penetrate the layer  38 A with ease and further cause the layer  38  to undergo electromagnetic induction to generate heat. Specifically, the scope is, for example, from 50 to 200 μm. 
   The magnetic field generating device  42  is arranged at the side of the inner circumferential face of the fixing belt  38  to have a predetermined interval from the face. 
   The following will describe the action of the image forming device  100  according to the present embodiment. 
   First, the surface of the photoreceptor drum  10  is charged by the charging device  12 . Next, from the exposure device  14 , the light L is imagewise radiated to the surface of the photoreceptor drum  10  so that a latent image is formed on the surface by a difference between electrostatic potentials on the surface. The photoreceptor drum  10  is rotated in the direction of the arrow A so that the latent image is shifted to a position opposite to one (the unit  16 A) out of the developing units of the developing device  16 . A first color toner is then shifted from the developing unit  16 A onto the latent image so that a toner image is formed on the surface of the photoreceptor drum  10 . By the rotation of the photoreceptor drum  10  in the direction of the arrow A, this toner image is transported to a position opposite to the intermediate transferring body  18 , and then the image is electrostatically transferred primarily onto the surface of the intermediate transferring body  18  by the transferring device  24 . 
   After the primary transfer, the toner remaining on the surface of the photoreceptor drum  10  is removed by the cleaning device  20 . The surface of the photoreceptor drum  10  subjected to the cleaning is potentially initialized by the discharging exposure device  22 , and again shifted to the position opposite to the charging device  12 . 
   Thereafter, three (the units  16 B,  16 C and  16 D) out of the developing units of the developing device  16  are successively shifted to the position opposite to the photoreceptor drum  10 . Second, third and fourth color toner images are successively formed in the same manner, so that the four color toner images are unified. The unified toner images are transferred onto the surface of the intermediate transferring body  18  at a time. 
   The toner images unified on the intermediate transferring body  18  are carried onto a position where the transferring roll  30  and the transferring opposite roll  28  face each other by a rotary shift of the intermediate transferring body  18  in the direction of the arrow B, so that the toner images are brought into contact with the fed recording paper P. A transferring bias voltage is being applied to the transferring roll  30  and the intermediate transferring body  18  across these members  30  and  18 , so that the toner images are transferred secondarily onto the surface of the recording paper P. 
   The recording paper P holding the toner images, which have not yet been fixed, is carried via a carrier guide  36  to the fixing device  32 . 
   The following will describe the action of the fixing device  32  according to the present embodiment hereinafter. 
   For example, at the same time (Of course, it is unnecessary that the two actions are strictly simultaneously carried out. This matter is applied, in the same manner, to the following.) when the toner image forming action is started in the image forming device  100 , the following action is first carried out in the fixing device  32 : in the state that the fixing belt  38  and the pressing roll  40  are separated from each other (see  FIG. 4 ), the driving force transmitting member  50  is driven by the motor (not illustrated), so as to be rotated, and the fixing belt  38  is driven to be rotated accordingly in the direction of the arrow D at a circumferential speed of, e.g., 170 mm/sec. 
   Together with the rotary driving of the fixing belt  38 , an alternating current is supplied from the exciting circuit (not illustrated) to the exciting coil  42 A included in the magnetic field generating device  42 . When the alternating current is supplied to the exciting coil  42 A, magnetic fluxes are generated or extinguished around the exciting coil  42 A. The generation and the extinction are repeated. When the magnetic fluxes (the magnetic field) cross the heat generating layer  38 A of the fixing belt  38 , an eddy current is generated in the heat generating layer  38 A to generate a magnetic field for inhibiting the change in the former magnetic field. As a result, heat is generated in proportion to the skin resistance of the heat generating layer  38 A and the square of the current flowing into the heat generating layer  38 A (see  FIG. 5A ). In  FIG. 5 , alternate long and two short dashes lines each represent main magnetic fluxes. 
   By this heat generated in the heat generating layer  38 A, the fixing belt  38  is heated to the setup temperature (for example, 150° C.) in, for example, about 10 seconds. 
   Next, in the state that the pressing roll  40  is pressed against the fixing belt  38 , the recording paper P fed to the fixing device is sent into the contact region between the fixing belt  38  and the pressing roll  40 , and then heated and pressed by means of the fixing belt  38  heated by the heat generator and the pressing roll  40  to melt the toner image and compress the image onto the surface of the recording paper P. As a result, the toner image is fixed on the surface of the recording paper P. 
   When images are continuously fixed on recording papers P each having a smaller size than the fixing region width (i.e., the length in the axial direction) of the fixing belt  38  in image-fixation by the fixing belt  38  and the pressing roll  40 , heat is consumed in a paper-passing region in the fixing belt  38  while heat is not consumed in regions other than the paper-passing region. For this reason, in the regions other than the paper-passing region in the fixing belt  38 , temperature rises. 
   When the temperature of the regions other than the paper-passing region in the fixing belt  38  gets close to the Curie point of the thermosensitive magnetic metal material which constitutes the heat generating layer  38 A, a region in the heat generating layer  38 A which lies on the regions other than the paper-passing region in the fixing belt  38  (i.e., which contacts the regions) is non-magnetized. In this way, a difference in magnetic fluxes (i.e., strength and weakness of the magnetic field) is generated between the paper-passing region, where magnetism is maintained, and the regions other than the paper-passing region, which are being non-magnetized (i.e., is in a paramagnetic state). As a result, in the heat generating layer, heat is less generated in the regions other than the paper-passing region than in the paper-passing region. In this way, the generation of heat in the heat generating layer of the fixing belt  38  is controlled by the heat generating layer  38 A. 
   As is understood from the formula 1, when the heat generation controlling member is non-magnetized (i.e., the relative magnetic permeability thereof gets close to one), the magnetic fluxes (the magnetic field) penetrate it with ease. As illustrated in  FIG. 5B , in the case that at this time the supporting member body  48 A is present which is made of a nonmagnetic metal material having a low intrinsic resistivity value (such as silver, copper or aluminum) (i.e., which has a larger thickness than the skin depth), the magnetic fluxes (the magnetic field) flow mainly as an eddy current into the supporting member body  48 A so as to restrain further heat generated by loss based on an eddy current flowing in the heat generating layer of the fixing belt  38 . The magnetic fluxes (the magnetic field) penetrating the heat generation controlling member  46  reach the supporting member body  48 A, which is made of a nonmagnetic metal material, so as to return to the magnetic field generating device  42 . Additionally, the supporting member body  48 A is arranged neither to contact the fixing belt  38  nor the heat generation controlling member  46  so that the body  48 A does not take thermal energy away from the fixing belt  38 . 
   When the recording paper P is fed out from the contact region between the fixing belt  38  and the pressing roll  40 , the paper P willingly advances straightly, in the direction along which the paper P is fed out, by the rigidity thereof. The pressing roll  40  is then pressed against the fastening pad  44  across the fixing belt  38 , whereby the front end of the paper P is peeled from the fixing belt  38  deformed to the side of its inner circumferential face so as to be wound. The peeling member  52  (the peeling sheet  52 B) is then put into a gap between the front end of the recording paper P and the fixing belt  38 , so that the recording paper P is peeled from the surface of the fixing belt  38 . 
   As described above, the toner image is formed on the recording paper P and then fixed thereon. 
   EXAMPLES 
   Test Example 
   The following will describe a test example of a fixing device according to the above-mentioned exemplary embodiment. 
   Test Example 1 
   First, the fixing device (see  FIGS. 1 and 2 ) according to the above-mentioned embodiment is used to make an evaluation described below. Members used in the device are as follows: 
   Fixing belt: a belt which has a diameter of 30 mm, a width of 370 mm and a thickness of 120 μm and is formed by laminating a silicon rubber layer having a thickness of 250 μm and a PFA layer (PFA: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) having a thickness of 30 μm successively onto the outer circumferential face of a thermosensitive magnetic metal layer (i.e., a heat generating layer which also functions as a substrate) which is made of MA-220 manufactured by Neomax Material, and has a Curie point of 230° C. (heat resistant temperature: about 230° C.)
 
Pressing roll: a roll which has an outer diameter of 28 mm and a length of 355 mm and is formed by laminating a sponge elastic layer having a thickness of 5 mm and a PFA layer having a thickness of 30 μm as a surface releasing layer successively onto a core metal axis, 18 mm in diameter, made of stainless steel
 
Supporting Member: a Support Made of Aluminum
 
   Evaluation 
   The power of the magnetic field generating device is controlled into the range of 500 to 1200 W. Under that conditions that the setup temperature is from 160 to 170° C. and the process speed is 170 mm/s, recording papers (trade name: JD PAPER, manufactured by Fuji Xerox Co., Ltd., and each having a size B5, weight per unit area: 98 g/m 2 ) are used. The papers are each fed into the device so as to direct one out of short sides thereof ahead. Image fixation is continuously carried out onto the papers, the number of which is 500. The temperature of the paper-passing region in the fixing belt and that of regions other than the paper-passing region are then each measured. 
   As a result, the temperature of the paper-passing region in the fixing belt is from 160 to 170° C. while that of the regions other than the paper-passing region is controlled into 230° C. or less. 
   Comparative Example 1 
   The same evaluation is made in the same way as in Test Example 1 except that instead of the thermosensitive magnetic metal layer, a fixing belt having nonmagnetic stainless steel (SUS 304) layers having a thickness of 50 μm and that of 120 μm, respectively, is used. 
   As a result, before image fixation is continuously carried out onto the same papers as described above, the number of which is 100, the temperature of the regions other than the paper-passing region exceeds 230° C., which is the heat resistant temperature of the fixing belt. 
   Thus, a structural body including a heat pipe having a diameter of 12.7 mm is arranged, as a temperature uniformalizing unit for restraining a rise in the temperature of the regions other than the paper-passing region, to contact the pressing roll. The same evaluation as described above is made. As a result, when image fixation is continuously carried out onto the same papers the number of which is from about 300 to 400, the temperature of the regions other than the paper-passing region reaches 232° C., which is the heat resistant temperature of the fixing belt. 
   It is understood from the results of the above-mentioned test examples that even if recording media having various sizes various, for example, a small size are used in the invention (such as Test Example 1), a rise in the temperature of regions other than a paper-passing region in a fixing belt is made lower so as to prevent overheating further than in the prior art (such as Comparative Example 1). 
   The foregoing description of the embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.