Abstract:
An image heating apparatus to which a lubricant application container is dismountably mountable, the image heating apparatus including: an endless belt configured to heat, in a nip, a toner image on a sheet; a rotatable member cooperative with the belt to form the nip; an urging member extending in a widthwise direction of the belt and configured and positioned to urge the belt toward the rotatable member; and a guide portion configured and positioned to guide a sliding movement of the lubricant application container while substantially preventing dismounting of the lubricant application container during the sliding movement. The lubricant application container applies a lubricant to a sliding surface of the urging member relative to the belt along a longitudinal direction, when the belt is dismounted from the image heating apparatus.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an image heating apparatus, a lubricant application system, a lubricant applying method, and a lubricant container-applicator. 
     There have been known various image forming apparatuses, for example, a printer, a copying machine, a facsimile machine, and a multifunction machine capable of performing two or more functions of the preceding machines and apparatuses. The image formation processes used by these image forming apparatuses are an electrophotographic image formation process, an electrostatic recording process, an electromagnetic recording process, and the like. 
     These image forming apparatuses, which form an unfixed image on a sheet of recording medium through a process in which an image is formed on an image bearing member, based on the information of the image to be formed, and then, is transferred onto a sheet of recording medium, or a process in which an unfixed image is directly formed on a sheet of recording medium, based on the information of the image to be formed. Further, some of them have been known to be equipped with a fixing apparatus (device), which is an image heating apparatus (device) for fixing an unfixed image (unfixed toner image) on a sheet of recording medium by applying heat and pressure to the sheet of recording medium and the unfixed toner image thereon. Recording media which can be listed as the medium usable by these image forming apparatuses are transfer paper, electro-facsimile paper, electrostatic recording paper, OHP film, printing paper, formatted paper, and the like. 
     In recent years, from the standpoint of faster startup, energy conservation, etc., fixing devices of the so-called belt heating type have been put to practical use. They employ a fixation belt (endless belt), which is high in thermal conductivity. More concretely, they employ a ceramic heater (pressing member), a pressure roller, and a fixation belt, for example. They are structured so that the fixation belt is sandwiched between the ceramic heater and pressure roller to form a fixation nip. In operation, a sheet of recording medium, on which an unfixed toner image is present, is conveyed through the fixation nip, that is, the interface between the fixation belt and pressure roller, to fix the unfixed toner image to the sheet of recording medium. 
     Also in recent years, there have been proposed image forming apparatuses equipped with a fixing device, the fixation belt of which is replaceable (Japanese Laid-open Patent Application H10-171276). These fixing devices are structured so that their fixation belt, which is relatively short in service life compared to the other components of the fixing devices, is replaceable. Therefore, the components of the fixing devices, which have not reached the end of their service lives can be used as they are. That is, this structural arrangement for a fixing device made it possible to reduce a fixing device in component cost. Further, from the standpoint of resource conservation, this structural arrangement made it possible to use a fixing device more efficiently than the conventional structural arrangement for a fixing device. 
     In the case of the fixing devices described above, however, in order to minimize the friction between the fixation belt, and the component on which the fixation belt slides, grease (lubricant) has to be applied to the surface of the component, on which the fixation belt slides, before the fixation belt is attached to the rest of the fixing device during the manufacture of the fixing device, or when the fixation belt is replaced. Thus, it is desired to find a method which can make it easier for a person, who has to replace the fixation belt, to apply grease (lubricant) to the surface of the component, on which the fixation belt slides, in the direction parallel to the lengthwise direction of the component. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided an image heating apparatus to which a lubricant application container is dismountably mountable, said image heating apparatus comprising an endless belt configured to heat, in a nip, a toner image on a sheet; a rotatable member cooperative with said endless belt to form said nip; an urging member extending in a widthwise direction of said endless belt and configured and positioned to urge said endless belt toward said rotatable member; and a guide portion configured and positioned to guide a sliding movement of the lubricant application container while substantially preventing dismounting of the lubricant application container during the sliding movement, wherein the lubricant application container is effective to apply a lubricant to a sliding surface of said urging member relative to said endless belt along a longitudinal direction, in a state that said endless belt is dismounted from said image heating apparatus. 
     According to another aspect of the present invention, there is provided a lubricant application system including a lubricant application container and an image heating apparatus to which the lubricant application container is dismountably mountable, said lubricant application system comprising (i) said image heating apparatus comprising (i-i) an endless belt configured to heat, in a nip, a toner image on a sheet, (i-ii) a rotatable member cooperative with said endless belt to form said nip, and (i-iii) an urging member extending in a widthwise direction of said endless belt and configured and positioned to urge said endless belt toward said rotatable member; a guide portion configured and positioned to guide a sliding movement of the lubricant application container while substantially preventing dismounting of the lubricant application container during the sliding movement, wherein the lubricant application container is effective to apply a lubricant to a sliding surface of said urging member relative to said endless belt along a longitudinal direction, in a state that endless belt is dismounted from said image heating apparatus; (ii) said lubricant application container comprising, (ii-i) an accommodating portion configured to accommodate the lubricant, and (ii-ii) an engaging portion engageable with said guide. 
     According to a further aspect of the present invention, there is provided a lubricant application container for applying a lubricant to an urging member of an image heating apparatus, said image forming apparatus including an endless belt configured to heat, in a nip, a toner image on a sheet, a rotatable member cooperative with said endless belt to form said nip, and an urging member extending in a widthwise direction of said endless belt and configured and positioned to urge said endless belt toward said rotatable member, said lubricant application container comprising an accommodating portion configured to accommodate the lubricant; a discharge opening configured and positioned to permit the lubricant to discharge from said accommodating portion; and an engaging portion engaged with the image heating apparatus and configured to be guided by the image heating apparatus and to substantially prevent dismounting of said lubricant application container from the image heating apparatus when said lubricant application container is slid relative to the image heating apparatus. 
     According to a further aspect of the present invention, there is provided an endless belt exchanging method for an image heating apparatus, said image heating apparatus including an endless belt configured to heat, in a nip, a toner image on a sheet, a rotatable member cooperative with said endless belt to form said nip, and an urging member extending in a widthwise direction of said endless belt and configured and positioned to urge said endless belt toward said rotatable member, said endless belt exchanging method comprising the steps of dismounting said endless belt from said image heating apparatus; engaging said lubricant application container with said image heating apparatus; applying the lubricant to said urging member while sliding said lubricant application container along a longitudinal direction of said urging member; dismounting said lubricant application container from said image heating apparatus; and mounting a fresh endless belt to said image heating apparatus. 
     According to a further aspect of the present invention, there is provided a lubricant application container comprising an accommodating portion configured to accommodate the lubricant; a discharge opening configured and positioned to permit the lubricant to discharge from said accommodating portion; and a projected portion provided in at a position more away from said discharge opening than said accommodating portion, said projected portion having a root portion which is thinner than a free end portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of the fixing device in the first embodiment of the present invention. 
         FIG. 2(   a ) is a sectional view of the film guide at a plane A-A in  FIG. 4 , and  FIG. 2(   b ) is a side view of the fixing device. 
         FIG. 3  is a perspective view of the film unit, minus the fixation film and one of the flanges attached to the lengthwise ends of the film unit, one for one. It shows the state of the film unit after the removal of the fixation belt and flange. 
         FIG. 4(   a ) is a sectional view of the grease container-applicator, at a plane perpendicular to the lengthwise direction of the ceramic heater and film guide, and  FIG. 4(   b ) is an enlarged sectional view of one of the grooves of the film guide, and the corresponding protrusive guide of the grease container-applicator. 
         FIG. 5(   a ) is a front view of the grease container-applicator, and  FIG. 5(   b ) is an enlarged schematic sectional view of the grease container-applicator, minus the cap of the grease container-applicator. 
         FIGS. 6(   a )- 6 ( c ) are side views of the fixing device, which show the fixation film replacement procedure. 
         FIGS. 7(   a )- 7 ( c ) are side views of the fixing device, which show the fixation film replacement procedure. 
         FIG. 8  is a perspective view of the combination of the fixing device (minus fixation film and one of film unit flanges), and grease container-applicator, during the grease application. 
         FIG. 9  is a schematic sectional view of a typical image forming apparatus, to the fixing device of which the present invention is applicable. It shows the general structure of the apparatus. 
         FIG. 10(   a ) is a sectional view of the grease container-applicator in the second embodiment of the present invention, and  FIG. 10(   b ) is a sectional view of the film guide at a plane B-B in  FIG. 10(   a ). 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Hereinafter, embodiments of the present invention are described in detail with reference to the appended drawings. The image heating devices in the following embodiments of the present invention are described as a fixing device for fixing an unfixed toner image to a sheet of recording medium. However, these image heating devices can also be used as a heating device for applying heat and pressure to a fixed image or incompletely fixed image on a sheet of recording medium to alter the image in surface properties. 
     First, referring to  FIG. 9 , an image forming apparatus  1 , which is compatible with the present invention, is described.  FIG. 9  is a schematic sectional view of the image forming apparatus  1 , equipped with a fixing device  40  which functions as an image heating device, at a vertical plane parallel to the recording medium conveyance direction of the image forming apparatus  1 . It shows the general structure of the apparatus  1 . This image forming apparatus  1  is a full-color laser printer (electrophotographic color printer) of the so-called tandem type. That is, it has first, second, third, and fourth image formation stations Pa, Pb, Pc and Pd, and an intermediary transfer belt  31  along which the four image formation stations are aligned in parallel. 
     [Image Forming Apparatus] 
     Referring to  FIG. 9 , the first, second, third, and fourth image formation stations Pa, Pb, Pc and Pd of the image forming apparatus  1  are aligned in parallel in the main assembly  1   a  of the image forming apparatus  1 . They are the same in structure although they are different in the color of the toner (developer) they use. They form four monochromatic toner images, different in color, one for one. Each image formation station has its own electrophotographic photosensitive member (photosensitive drum  11 , in this embodiment), on which it forms a monochromatic toner image. 
     The image forming apparatus  1  is structured so that the intermediary transfer belt  31  remains in contact with each photosensitive drum  11 . In operation, the four toner images, different in color, are formed on the four photosensitive drums  11 , one for one, and are transferred (primary transfer) onto the intermediary transfer belt  31 , and then, are transferred (secondary transfer) onto a sheet P of recording medium, in the secondary transfer station  33 . After the transfer of the toner images onto the sheet P, the sheet P is subjected to heat and pressure by the fixing device  40  so that the toner images are fixed to the sheet P. Then, the sheet P is discharged, as a finished print, from the image forming apparatus  1 . 
     The image formation stations Pa-Pd, and intermediary transfer belt  31 , make up an image forming portion, which forms toner images on a sheet P of recording. The fixing device  40  fixes the toner images on a sheet of recording medium to the sheet P, after the formation of the toner images on the sheet P by the image formation portion. As for the examples of recording medium, ordinary paper, resinous paper, cardstock, overhead projector film, and the like can be listed. 
     There are a charging device  12 , a developing device  14 , a primary transfer belt  17 , and a cleaning device  15  in the adjacencies of each photosensitive drum  11 , being arranged in the listed order. There is also disposed a laser scanner  13 , which is an exposing means, in the top portion of the image forming apparatus  1 . 
     The laser scanner  13  has an unshown light source, an f-θ lens (unshown), etc. It writes an electrostatic latent image, which is in accordance with the image formation signals, on the charged area of the peripheral surface of the photosensitive drum  11 , by scanning (exposing) the peripheral surface of the photosensitive drum  11  with the beam of laser light emitted from the unshown light source; the flux of laser light emitted from the light source is deflected, and focused on the generatrix of the photosensitive drum  11  through the f-θ lens. 
     The developing devices  14  are filled with a preset amount of Y (yellow), M (magenta), C (cyan) and Bk (black) toners as developers, by unshown toner (developer) supplying devices, one for one. They develop the latent images on the photosensitive drums  11 , into visible images, that is, yellow, magenta, cyan and black toner images, respectively. 
     The intermediary transfer belt  31  is circularly driven at the same velocity as the peripheral velocity of the photosensitive drum  11  in the direction indicated by an arrow mark E in  FIG. 9 . A toner image of yellow color, or the first color, formed on the photosensitive drum  11  is transferred onto the outward surface of the intermediary transfer belt  31 , by the electric field generated by the primary transfer bias applied to the intermediary transfer belt  31 , and the pressure, while the toner image is conveyed through the nip between the photosensitive drum  11  and intermediary transfer belt  31 . 
     Similarly, the toner images of the magenta, cyan and black colors, that is, the second, third, and fourth colors, respectively, are sequentially transferred onto the intermediary transfer belt  31  in such a manner that they are layered upon the preceding toner images. Consequently, a synthetic full-color toner image, which reflects the original image, is effected on the intermediary transfer belt  31 . Then, the synthetic full-color toner image is transferred onto a sheet P of recording medium in such a manner that preset margins are provided between the transferred full-color image and the four edges of the sheet P, respectively. 
     After the completion of the primary transfer, the photosensitive drum  11  is cleaned by the cleaning device  15 . That is, the toner remaining on the peripheral surface of the photosensitive drum  11  is removed by the cleaning device  15  to prepare the photosensitive drum  11  for the following image formation process. The toner particles, and the like contaminants, remaining on the intermediary transfer belt  31  after the transfer of the synthetic full-color toner image from the intermediary transfer belt  31  are wiped away by an unshown piece of cleaning web (unwoven fabric) placed in contact with the surface of the intermediary transfer belt  31 . 
     A referential numeral  38  stands for the secondary transfer roller, which is supported by a pair of bearings, in parallel to the widthwise direction of the intermediary transfer belt  31 , and also, in contact with the downwardly facing portion of the outward surface of the intermediary transfer belt  31 . The intermediary transfer belt  31  is suspended and kept stretched by three rollers  32 ,  34  and  35 . The secondary transfer roller  38  is kept pressed against a roller  34 , with the placement of the intermediary transfer belt  31  between itself and the roller  34 , forming the second transfer nip between itself and intermediary transfer belt  31 . To the secondary transfer roller  38 , a preset secondary transfer bias is applied by a secondary transfer bias source. 
     The synthetic full-color toner image on the intermediary transfer belt  31 , that is, the combination of four monochromatic toner images, different color, transferred onto the intermediary transfer belt  31 , is transferred onto a sheet P of recording medium in the following manner. That is, a sheet P of recording medium is moved out of one of the pair of sheet feeder cassettes  20 , or a manual sheet feeder tray  25 , and into the main assembly  1   a  of the image forming apparatus  1 . Then, the sheet P is sent to a pair of registration rollers  23 , which catch the sheet P, and temporarily hold the sheet P. It a case where the sheet P is sent askew, the registration rollers  23  correct the sheet P in attitude. 
     Then, the registration rollers  23  send the sheet P of recording medium with such a timing that the sheet P enters the secondary transfer nip, following a pre-transfer guide  36 , at the same time as the toner image on the intermediary transfer belt  31 . At the same time as the sheet P enters the secondary transfer nip, the secondary transfer bias begins to be applied from the secondary transfer bias source. Thus, the synthetic full-color toner image on the intermediary transfer belt  31  is transferred from the intermediary transfer belt  31  onto the sheet P. After the sheet P received the full-color toner image, it is introduced into the fixing device  40  through the pre-fixation guide  2 . In the fixing device  40 , heat and pressure are applied to the sheet P and the toner image thereon. Consequently, the toner image becomes fixed to the sheet P. 
     In a case where a toner image is to be formed on only one of the two surfaces of a sheet P of recording medium, a flapper  61  is switched in position. Then, after a toner image is fixed to one of the two surface of the sheet P, the sheet P is discharged into a delivery tray  64 , which is attached to one of the lateral walls of the main assembly  1   a  of the image forming apparatus  1 , by way of a pair of discharge rollers  63 , or a delivery tray  65  which is a part of the top wall of the main assembly  1   a . Depending on the positioning of the flapper  61 , the sheet P is discharged into the delivery tray  64 , with its image bearing surface facing upward, or in the delivery tray  65  with its image bearing surface facing downward. 
     An image forming operation in which a toner image is to be formed on both of the two surfaces of the sheet P of recording medium is as follows. After a toner image is fixed to one of the two surfaces of the sheet P by the fixing device  40 , the sheet P is guided upward by the flapper  61 , which was switched in attitude. Then, as the trailing edge of the sheet P reaches the reversing point R, the sheet P is reversed in direction, and conveyed into the recording medium conveyance passage  73 , being therefore put upside-down. Then, the sheet P is conveyed through a two-sided print passage  70 . Then, a toner image is formed on the other (second) surface of the sheet P through an image formation process which is similar to the process in which a toner image was formed on the first surface. Then, the sheet P is discharged into the delivery tray  64  or  65 . The portion of the image forming apparatus  1 , which is made up of the flapper  61 , recording medium conveyance passage  73 , and the like structural components, is an example of the means for placing a sheet P of recording medium upside-down. 
     [Fixing Device] 
     Next, referring to the drawings, the fixing device  40 , which functions as an image heating device, is described in detail about it structure. As described above, the image forming apparatus  1  is equipped with the fixing device  40 , which is an image heating device in accordance with the present invention. This fixing device  40  is of the so-called film heating type. It has a fixation film (belt)  101 , and a pressure roller  106 . The fixation film  101  has a cylindrical thin substrative layer formed of a metallic substance, and an elastic layer formed on the substrative layer. The fixing device  40  is structured so that the pressure roller  106  is driven. 
     First, referring to  FIGS. 1 ,  2 ( a ),  2 ( b ) and  3 , the structure of the fixing device  40  is described.  FIG. 1  is a schematic sectional view of the fixing device  40  in this embodiment. It shows the general structure of the fixing device  40 .  FIG. 2(   a ) is a sectional view of the film guide  103  of fixing device  40 , at a plane A-A in  FIG. 4(   a ).  FIG. 2(   b ) is a side view of the fixing device  40  as seen at a plane C-C in  FIG. 9 .  FIG. 3  is a perspective view of the film unit  111 , minus the fixation film  101  and one of the flanges  104  of the film unit  111 . 
     Referring to  FIG. 1 , the fixing device  40  heats an unfixed toner image on a sheet P of recording medium, with its fixation film  101  (circularly movable endless belt), while the sheet P is moved through the fixation nip N (remaining pinched between fixation film  101  and pressure roller). This fixing device  40  is also provided with an unshown casing in which the fixation film  101 , pressure roller  106 , etc., are held. 
     The pressure roller  106  forms the fixation nip N by being pressed upon the fixation film  101 . It is a pressure applying rotatable member. The pressure roller  106  circularly moves the fixation film  101  by being placed in contact with the outward surface of the fixation film  101 . That is, not only does it form the fixation nip N between itself and fixation film  101 , but also, circularly drives the fixation film  101 . 
     Next, referring to  FIGS. 1 ,  2  and  3 , the fixing device  40  has: the pressure roller  106 , a ceramic heater  110  as a pressing member, the fixation film  101  (endless belt), and the pair of flanges  104 . The flanges  104  are positioned at the edges of the film  101 , one for one, in terms of the direction parallel to the axial line of the film  101 , to regulate the movement of the film  101  in the widthwise direction (indicated by arrow mark X in  FIG. 2(   a )). The ceramic heater (pressing member)  110  is a heating member which is disposed in the hollow of the fixation film  101  to heat the fixation film  101  from within the loop which the film  101  forms. 
     Further, the fixing device  40  has: the film guide  103  which forms the fixation nip N between itself and the pressure roller  106 , with the presence of the fixation film  101  between itself and the pressure roller  106 , and circularly moves the fixation film  101 ; and a stay  102  which is placed on the inward side of the fixation film  101  to reinforce the film guide  101  in terms of stiffness. The ceramic heater  110  extends in the widthwise direction of the fixation film  101  (that is, direction parallel to fixation film  101  as rotational member), and presses the fixing film  101  toward the pressure roller  106 . The fixation film  101  is fitted around the combination of the film guide  103  and ceramic heater  110 , in such a manner that it is sandwiched between the combination of the film guide  103  and ceramic heater  110 , and the pressure roller  106  (rotational driving member). Thus, as the pressure roller  106  is driven, the inward surface of the fixation film  110  slides on the film guide  103  and ceramic heater  110 . 
     The ceramic heater  110  and film guide  103  are in contact with the inward surface of the fixation film  101 . The ceramic heater  110  has the function of heating the fixation film  101  from within the inward side of the loop which the cylindrical fixation film  101  forms. It makes the fixation film  101  form the fixation nip N between the fixation film  101  and pressure roller  106 . The fixation film  101 , ceramic heater  110 , film guide  103 , stay  102 , and flanges  104  make up the film unit  111 . 
     Referring to  FIG. 1 , the pressure roller  106  is made up of a metallic core  106   a , and an elastic layer  106   b  concentrically formed around the peripheral surface of the metallic core  106   a , of heat resistant material such as silicone rubber, fluorinated rubber, fluorinated resin, etc. The pressure roller  106  has also a surface layer as a parting layer  106   c , which is formed of such a substance as fluorinated resin, silicone resin, fluorosilicone rubber, fluorinated resin, silicone rubber, PFA, PTFE, FEP, etc., that is excellent in parting properties and heat resistance. 
     Referring to  FIG. 2(   b ), the lengthwise ends of the metallic core  106   a  are fitted with a pair of bearings  113 , one for one, formed of heat resistant resin such as PEEK, PPS, liquid polymer, or the like. The metallic core  106   a  is rotatably supported by the lateral plates of the fixing device frame  112 , with the placement of the pair of bearings  113  between itself and lateral plates, one for one. Further, one of the lengthwise ends of the metallic core  106   a  is fitted with an input gear  39  which receives the rotational driving force from a driving mechanism M. 
     Referring to  FIG. 1 , the fixation film (endless belt)  101  is a cylindrical heat resistant film (belt) which is for transferring heat to a sheet P of recording medium. It is loosely fitted around the film guide  103 . In order to ensure that the fixing device  40  quickly starts up, the fixation film  101  is required to be small in thermal capacity. Thus, it is formed as single or two-layer film. 
     In a case where the fixation film  101  is formed as single-layer film, it is desired to be no more than 100 μm, preferably, no more than 50 μm and no less than 20 μm, in thickness. As the material for the single-layer fixation film  101 , heat resistance substance such as PTFE, PFA, FEP, and the like can be listed. In a case where the fixation film  101  is formed as two-layer film, the outward surface of cylindrical film formed of polyimide, polyamide-imide, PEEK, PES, PPS, or the like, is coated with PTFE, PFA, FEP, or the like. Further, the fixation film  101  may be formed of a metallic substance, instead of a resinous substance such as those listed above. 
     The fixation film  101  is rotated by the rotation of the pressure roller  106  which is in contact with the fixation film  101 . As the pressure roller  106  is rotated, the fixation film  101  is circularly moved by the rotation of the pressure roller  106 , sliding on the heating surface of the film guide  103  fitted with the ceramic heater  110 , and remaining in contact with the heating surface of the film guide  103 , at roughly the same speed as the speed at which a sheet P of recording medium is conveyed. 
     As the film guide  103 , a heat resistant and thermally insulating component which is roughly semicircular in cross-section, and the length of which is roughly the same as the width of the fixation film  101 , may be employed (it is to be positioned in such an attitude that its lengthwise direction becomes perpendicular to the recording medium conveyance direction). As the material for the film guide  103 , such a substance as phenol resin, polyimide resin, polyamide resin, polyamide-imide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, LCP resin, etc., that is excellent in electrically insulating properties and heat resistance, can be listed. The film guide  103  plays the role of backing up the fixation film  101 . It plays also the role of keeping the fixing device  40  stable in the internal pressure of the fixation nip N, which it forms by being pressed against the pressure roller  106 , and also, in the circular movement of the fixation film  101  as the fixation film  101  is circularly moved. 
     The pressure roller  106  is rotationally driven, in contact with the fixation film  101 , by the driving mechanism M, which includes a motor, gears, etc., at a preset peripheral velocity, in the same direction as the direction, indicated by an arrow mark D in  FIG. 1 , in which a sheet P of recording medium is conveyed. As the pressure roller  106  is rotated, the fixation film  101  is given a rotational force which acts in the direction indicated by an arrow mark E in  FIG. 1 , by the friction which occurs between the pressure roller  106  and fixation film  101  in the fixation nip N as the pressure roller  6  is driven. Thus, the fixation film  101  circularly moves around the film guide  103  in the direction indicated by the arrow mark E, with its inward surface sliding on, and remaining in contact with, the downwardly facing surface of the ceramic heater  110 , in the fixation nip N. 
     As the pressure roller  106  is rotated, the fixation film  101  is rotated by the rotation of the pressure roller  106 . As the ceramic heater is supplied with electric power, its temperature rises to a preset target level, and is kept at the target level. Then, a sheet P of recording medium is introduced into the fixation nip N. As the sheet P, on which an unfixed toner image is present, is introduced into the fixation nip N between the fixation film  101  and pressure roller  106 , the surface of the sheet P, on which the unfixed toner image is present, comes into contact with the outward surface of the fixation film  101 , and the sheet P is moved through the fixation nip N, along with the fixation film  101 . While the sheet P is conveyed through the fixation nip N, the heat from the ceramic heater  110  is given to the sheet P through the fixation film  101 . Thus, the unfixed toner image on the sheet P becomes fixed to the surface of the sheet P. After being moved through the fixation nip N, the sheet P is separated from the outward surface of the fixation film  101  by the curvature of the fixation film  101  (film guide  103 ), and then, is conveyed further to be discharged. 
     Next, referring to  FIGS. 1 and 3 , the film guide  103  is formed of relatively soft resin. Thus, the stay  102  is placed in contact with the back surface of the film guide  103  to reinforce the film guide  103 , more specifically, to prevent the film guide  103  from bending in the direction perpendicular to the lengthwise direction of the film guide  103 , and also, to keep the film guide  103  correct in shape and attitude. 
     Referring to  FIGS. 2(   a ) and  3 , there are disposed the pair of flanges  104  at the edges of the fixation film  101 , one for one. These flanges  104  are fitted around the lengthwise ends, one for one, of the combination of the film guide  103  and stay  102 . They guide the fixation film  101  as the fill  101  circularly moves. Further, they prevent the fixation film  101  from disengaging from the combination in the lengthwise direction of the combination. 
     Referring to  FIGS. 1 ,  2 ( a ) and  3 , the film guide  103  is provided with a groove  103   c , the bottom surface  103   g  of which is flat, and in which the ceramic heater (pressing member)  110 , which is long and narrow, is to be embedded. The groove  103   c  extends in the lengthwise direction of the film guide  103 . The ceramic heater  110  has a ceramic substrate, which is thin, long, and narrow, and a layer of heat generating resistor formed on the surface of the ceramic substrate. The ceramic heater  110  structured as described above is such a heater that is low in thermal capacity, being therefore characterized in that as electric current is flowed through it, it can very quickly increase in temperature. It is supported by the film guide  103 , by being embedded in the above described groove  103   c  in the downwardly facing surface of the film guide  103 . 
     Referring to  FIGS. 1 and 3 , the film guide  103  has a grease application guide G, which guides a grease container-applicator  200  (lubricant container-applicator), while making it virtually impossible for the grease container-applicator  200  to disengage from the film guide  103 , in the direction indicated by an arrow mark Z ( FIG. 2(   a )), when grease is applied to the ceramic heater  110  (and part of film guide  103 ). The grease application guide G has a pair of grooves  103   a  and  103   b  which extend in the lengthwise direction of the film guide  103 . The grooves  103   a  and  103   b  guide the grease container-applicator  200  when the surface  110   a  ( FIG. 4(   a )) of the ceramic heater  110 , on which the fixation film  101  slides, is coated with grease (lubricant) after the removal of the fixation film  101 . The film guide  103  is structured so that the grooves  103   a  and  103   b  extend in the same direction as the surface  110   a  (to be coated with lubricant) of the ceramic heater  110 , which is to be coated with the lubricant. 
     The grooves  103   a  and  103   b  are positioned so that they do not come into contact with the fixation film  101  when the fixing device  40  is in use. They guide the grease container-applicator  200  by the pair of protrusive guides  203   a  and  203   b , with which the grease container-applicator  200  is provided, in such a manner that the protrusive guides  203   a  and  203   b  slide in the grooves  103   a  and  103   b , respectively. The grease container-applicator  200  is used to coat the ceramic heater  110  with grease after the removal of the fixation film  101  from the film unit  111 . 
       FIG. 4(   a ) is a sectional view of the combination of the grease container-applicator  200 , ceramic heater  110 , and film guide  103 , as seen from the direction parallel to the lengthwise direction of the combination, when the ceramic heater  110  is being coated with grease.  FIG. 4(   b ) is an enlarged sectional view of the engaged combination of the groove  103   a  ( 103   b ) and protrusive guides  203   a  ( 203   b ). As will be evident from these drawings, in terms of the direction (indicated by arrow mark P in  FIG. 4(   b )) in which the protrusive guide  203   a  ( 203   b ) protrudes from the main portion  200   a  of the grease container-applicator  200 , the base portion of the protrusive guide  203   a  ( 203   b ) is narrower than the center portion of the protrusive guide  203   a  ( 203   b ). That is, the combination of the grease container-applicator  200  and film guide  103  is structured so that when the grease container-applicator  200  is slid along the film guide  103 , it is virtually impossible for the grease container-applicator  200  to disengage from the film guide  103 . 
       FIG. 4(   a ) is drawn as if the grooves  103   a  and  103   b  in this embodiment are simply open upward. In reality, however, the grooves  103   a  and  103   b  are structured as shown in  FIG. 4(   b ). That is, they are shaped so that they clamp the base portions of the protrusive guides  203   a  and  203   b , respectively. The protrusive guides  203   a  and  203   b  of the grease container-applicator  200  are shaped so that at least a part of their middle to end portions are greater in dimension, in terms of their widthwise direction (left-right direction of  FIG. 4) , than their base portion. The protrusive guides  203   a  and  203   b , that is, the protruding portions of the main portion  200   a  of the grease container-applicator  200 , and the grooves  103   a  and  103   b  of the film guide  103 , that is, the recessed portions of the main portion  200   a , engage with each other in such a manner that the latter embrace the former. That is, in terms of their cross-section, the grooves  103   a  and  103   b  are recessed in such a shape that their contour matches that of the protrusive guides  203   a  and  203   b , respectively. Therefore, it is virtually impossible for the grease container-applicator  200  to become disengaged upward from the film guide  103  while it is moved for grease application. 
     Incidentally, the relationship between the groove  103   a  ( 103   b ) and protrusive guide  203   a  ( 203   b ) in terms of their shape (recessive or protrusive) may be opposite from the one in this embodiment. That is, the main portion  200   a  of the grease container-applicator  200  may be provided with a pair of grooves  103   a  and  103   b  (grooves), and the film guide  103  may be provided with a corresponding pair of protrusive guides  203   a  and  203   b . The effects of such structural arrangement are the same as the effects of this embodiment. 
     The operation for applying grease to the ceramic heater  110  is as follows. Referring to  FIG. 3 , one of the flanges  104 , that is, the removable one (left one in  FIG. 3 ), is to be removed from the film guide  103 . Then, the film guide  103  is to be fitted with the grease container-applicator  200  from the left side of the film guide  103  in such a manner that protrusive guides  203   a  and  203   b  fit into the grooves  103   a  and  103   b , respectively. With the protrusive guides  203   a  and  203   b , which also are shaped as described, being fitted in the grooves  103   a  and  103   b , respectively, which also shaped as described above, it is virtually impossible for the grease container-applicator  200  to become disengaged from the film guide  103 . Thus, the grease container-applicator  200  can be smoothly guided along the film guide  103  in the lengthwise direction of the film guide  103 . 
     Each of the lengthwise ends of the groove  103   a  ( 103   b ) is provided with a surface  103   f  which prevents (regulates) the protrusive guides  203   a  ( 203   b ), that is, the grease container-applicator  200 , from moving outward of the film unit  111 , beyond the surface  103   f . That is, as the grease container-applicator  200  is slid along the film guide  103 , its protrusive guide  203   a  ( 203   b ) comes into contact with the regulating surface  103   f . In other words, the regulating surface  103   f  determines the length (L3 in  FIG. 2(   a )) of the range, in terms of the lengthwise direction of the film guide  103 , in which the grease is applied to the ceramic heater  110 . That is, because of the presence of the regulating surface  103   f  at the lengthwise ends of the grooves  103   a  ( 103   b ), only the preset range of the ceramic heater  110  can be coated with grease, in terms of the lengthwise direction of the heater  110 . In other words, it is prevented that grease is applied to the portions of the ceramic heater  110 , which are on the outward side of the regulating surface  103   f  in terms of the lengthwise direction of the ceramic heater  110 . 
     [Structural Details of Grease Container-Applicator] 
     Next, referring to  FIGS. 4(   a ),  4 ( b ),  5 ( a ) and  5 ( b ), the structure of the grease container-applicator  200 , which is used during the replacement of the fixation film  101  of the fixing device  40 , is described in detail.  FIG. 5(   a ) is a front view of the grease container-applicator  200  in this embodiment, and  FIG. 5(   b ) is a schematic sectional view of the grease container-applicator  200  after the removal of the cap  204  of the grease container-applicator  200 . 
     The grease container-applicator  200  is a container-applicator for applying grease to the ceramic heater (pressing member)  110  (object to be coated with grease). Referring to  FIGS. 4(   a ),  4 ( b ),  5 ( a ) and  5 ( b ), the grease container-applicator  200  has a grease storing member  201 , which is roughly in the form of a rectangular parallelepiped, and the pair of protrusive guides  203   a  and  203   b . As the guides  203   a  and  203   b  are pressed upon the film guide  103 , they fit into the grooves  103   a  and  103   b  of the film guide  103 , in such a manner that they slide in the grooves  103   a  and  103   b , respectively. The grease storing member  201  has a grease storage  201   a.    
     Further, the grease container-applicator  200  has a grease outlet  201   b , and the cap  204  with which the grease storage portion  201  is fitted to prevent the grease in the grease storage  201   a  from leaking. This cap  204  is removably attachable to the grease storage (lubricant storage)  201   a  to seal the grease outlet (lubricant outlet)  201   b.    
     The removal of the cap  204  from the grease storing member  201  enables the grease outlet  201   b  to discharge outward the grease stored in the storing portion  201   a . The grease outlet  201   b  is the lubricant outlet which enables the grease in the grease storage member  201  to be applied to the ceramic heater  110  while the protrusive guides  203   a  and  203   b  are slid in the grooves  103   a  and  103   b.    
     In this embodiment, the grease storage  201   a  of the grease storing member  201 , contains roughly 2 g of grease, in practical terms. The 2 g of grease is the right amount of grease for coating the ceramic heater  110  only once, by moving the grease storing member  201  of the grease container-applicator  200  along the ceramic heater  110  in the direction indicted by an arrow mark T. 
     As for the material for the grease storing member  201  and cap  204  of the grease container-applicator  200 , it is desired to be such a substance as polypropylene, for example, that is excellent in terms of oil resistance and water resistance. As for the grease, heat resistant lubricant (heat resistant grease) made up of perfluoropolyether (as base), polytetrafluoro-ethylene (PTFE as density-increaser), etc., for example, is usable. 
     Referring to  FIGS. 5(   a ) and  5 ( b ), as the cap  204  is removed from the grease storing member  201 , the protrusive guides  203   a  and  203   b  become exposed, and therefore, it becomes possible for the protrusive guides  203   a  and  203   b  to be pressed into the grooves  103   a  and  103   b , respectively. The grease container-applicator  200  and film guide  103  are structured so that when the protrusive guides  203   a  and  203   b  are in engagement with the grooves  103   a  and  103   b , respectively, the width (L1 in  FIG. 4)  of the grease outlet  201   b  is equal to the width (dimension) (L2 in  FIG. 4 ) of the surface of the film guide  103 , which is to be coated with the grease, in terms of the direction perpendicular to the lengthwise direction of the film guide  103 . 
     Referring to  FIG. 4(   a ), the gap Δt1 between the grease outlet  201   b , and the surface  110   a  of the ceramic heater  110 , on which the fixation film  101  slides, is set to satisfy the following requirement. In  FIG. 4(   a ), M1 stands for the total amount of grease to be applied to the ceramic heater  110  (and part of film guide  103 ), and S1 stands for the surface area of the ceramic heater  110  (and part of film guide  103 ). The grease container-applicator  200  and film unit  111  are structured to satisfy the following equation:
 
Δ t 1= M 1/ S 1.
 
     Next, referring to  FIGS. 3 ,  6 ( a )- 6 ( c ), and  7 ( a )- 7 ( c ), the procedure for replacing the fixation film  101  of the fixing device  40  is described in steps.  FIGS. 6(   a )- 6 ( c ), and  7 ( a )- 7 ( c ) are side views of the fixing device  40 , which show the steps through which the fixation film  101  of the fixing device  40  is to be replaced. For the sake of convenience,  FIGS. 6(   a )- 6 ( c ) were dawn to make the flanges  104  appear smaller than those in  FIG. 3 . However, the flanges  104  in  FIGS. 7(   a )- 7 ( b ) are the same in function as those in  FIGS. 6(   a )- 6 ( c ). 
     The lubricant applying method for applying grease to the ceramic heater (pressing member; object to be coated with grease)  110  of the fixing device  40  in this embodiment roughly comprises the following steps. 
     First, the fixation film  101  is to be slipped away from the film guide  103  (first step). Then, the protrusive guides  203   a  and  203   b  of the grease container-applicator  200  is to be fitted into the grooves  103   a  and  103   b , respectively, of the film guide  103 , while the grease container-applicator  200  is held in such an attitude that the grease outlet  201   b  faces the film guide  103 . Then, the grease container-applicator  200  (grease storing member  201 ) is to be moved along the film guide  103  (second step) to coat the ceramic heater  110  with the grease. Finally, a replacement (brand-new) fixation film  101  is to be fitted around the combination of the film guide  103  and the ceramic heater coated with a fresh supply of grease (third step). 
     Next, the above-described method for applying grease to the ceramic heater  110  (and part of film guide  103 ) is concretely described in further detail. 
     First, the film unit  111  supported by the fixing device frame  112  is to be lifted away ( FIG. 6(   b )) from the frame  112 , by which the film unit  111  and pressure roller  106  are held ( FIG. 6(   a )). 
     Next, referring to  FIG. 6(   c ), the operator is to pull the flange  104  attached to one of the lengthwise ends of the film unit  110 , away from the film unit  111  in the direction indicated by an arrow mark H while holding the film unit  111  away from the frame  112 . 
     Then, referring to  FIG. 7(   a ), after the operator removed the flange  104  from one of the lengthwise ends of the film unit  110 , the operator is to pull the fixation film  101  away from the film unit  111  in the direction indicated by an arrow mark I. After the removal of the fixation film  101 , the fixing device  40  appears as shown in  FIG. 3 . It sometimes occurs that when the fixing device  40  is in the state shown in  FIG. 3 , there remains a certain amount of used grease adhering to an area Q (contoured by broken line in  FIG. 3) , that is, the area of contact between the ceramic heater  110  (and part of film guide  103 ) and fixation film  101 . Thus, in order to clean the area Q, the area Q is to be wiped with alcohol or the like cleaning agent as necessary. 
     Next, the operator is to apply a fresh supply of grease to the cleaned ceramic heater  110  (and part of film guide  103 ). After the application of the grease, the operator is to fit the fixation film  101  around the combination of the film guide  103  and ceramic heater  110  in the direction indicated by an arrow mark J, from the side from which the fixation film  101  was removed in  FIG. 7(   a ). Next, referring to  FIG. 7(   b ), the operator is to attach the flange  104  removed ( FIG. 6(   a )) from one of the lengthwise ends of the film unit  111 , to the corresponding end of the film unit  111  in the direction indicated by the arrow mark J. 
     Lastly, referring to  FIG. 7(   c ), the operator is to lower the reassembled film unit  111  (which is in the state shown in  FIG. 6(   b )) to the frame  112 , and press the film unit  111  upon the frame  112 , to put the film unit  111  back into the state shown in  FIG. 6(   a ), ending thereby the operation to replace the film unit  111 . 
     At this point in time, referring to  FIGS. 4(   a ),  4 ( b ),  5 ( a ),  5 ( b ) and  8 , the lubricant applying method for applying grease to the ceramic heater  110  (and part of film guide  103 ) with the use of the grease container-applicator  200  when the film unit  111  is in the state shown in  FIG. 7(   a ) is described.  FIG. 8  is a perspective view of the combination of the grease container-applicator  200 , film guide  103 , and ceramic heater  110 , during the grease application. 
     First, the operator is to remove the cap  204  from the grease container-applicator  200  shown in  FIG. 5(   a ), to make the grease container-applicator  200  appear as shown in  FIG. 5(   b ). Then, the operator is to align the protrusive guides  203   a  and  203   b  of the grease storing member  201  with the grooves  103   a  and  103   b  of the film guide  103 , respectively, and to press the grease storing member  201   a . As the grease storing member  201  is pressed by the operator in the manner described above, the protrusive guides  203   a  and  203   b  engage into the grooves  103   a  and  103   b , at the lengthwise end (left end in  FIG. 8)  of the film unit  111  (film guide  103 ), from which the flange  104  was removed, as shown in  FIG. 8 , because both the material for the protrusive guides  203   a  and  203   b  (grease container-applicator  200 ), and the material for the film guide  103  (grooves  103   a  and  103   b ), are elastic. 
     As described above, the dimension (L1) of the grease outlet  201   b  is equal to the dimension (L2) of the surface of the film guide  103 , which is to be coated with grease, in terms of the widthwise direction of the film guide  103 . Therefore, it is possible for the operator to slide the grease storing member  201  in the direction indicated by an arrow mark T, that is, the lengthwise direction (indicated by arrow mark X) of the film guide  103 , while continuously discharging the grease in the grease storing member  201  through the grease outlet  201   b , and also, keeping the grease storing member  201  pressed on the film guide  103 . Therefore, it is possible to uniformly apply grease to the ceramic heater  110  (and part of film guide  103 ), to a preset thickness, while insuring that the grease storing member  201  slides in the direction indicated by the arrow mark X without dislodging from the film guide  103  in the direction indicated by the arrow mark Y, that is, the direction perpendicular to the lengthwise direction of the film guide  103 . 
     Since the film unit  111  and grease container-applicator  200  are designed so that the gap Δt1 between the grease outlet  201   b  and ceramic heater  110  satisfies: Δt1=M1/S1, the grease in the grease storing member  201   a  is used up virtually at the same time as the grease storing member  201  reaches the end of its movement in the direction indicated by the arrow mark T in  FIG. 8 . 
     As will be evident from the foregoing description of this embodiment, this embodiment makes it possible for an operator of the image forming apparatus  1  to accurately apply a preset amount of grease to the ceramic heater  110  in the lengthwise direction of the ceramic heater  110  during the replacement of the fixation film  101 . That is, this embodiment makes it possible for the operator to extremely efficiently replace the fixation film  101 . 
     In this embodiment, the pressing member embedded in the film guide  103  was the ceramic heater  110 . However, this embodiment is not intended to limit the present invention in terms of the pressing member to be embedded in the film guide  103 . For example, the pressing member to be embedded in the film guide  103  may be a pressure pad, or the like, which is formed of SUS and does not have a heating function. In such a case, the fixing device has only to be equipped with a separate means for heating the fixation film  101 . Also in such a case, the pressure pad (as pressing member) is to press the fixation film  101  toward the pressure roller  106  from within the fixation film loop, to form a nip between the fixation film and pressure roller  106 . That is, the present invention is also applicable to a fixing device, the film guide of which holds a pressure pad as a film pressing member. 
     Embodiment 2 
     Next, referring to  FIGS. 10(   a ) and  10 ( b ), the second embodiment of the present invention is described.  FIG. 10(   a ) is a sectional view of the grease container-applicator, etc., in this embodiment.  FIG. 10(   b ) is a sectional view of the film guide  103  in this embodiment, at a plane B-B in  FIG. 10(   a ). 
     In the case of the fixing device in the first embodiment, grease was uniformly applied to the ceramic heater  110  (and part of film guide  103 ), to a preset thickness. In comparison, the fixing device in this embodiment is structured so that the amount by which the lengthwise end portions of the ceramic heater  110  (and part of film guide  103 ) are coated with grease, per unit area, is greater than the amount by which the lengthwise center portion of the ceramic heater  110  (and part of film guide  103 ) is coated with grease, per unit area. 
     For example, in a case of a fixing device structured so that the lengthwise center portion of the nip (fixation nip) between the film guide  103  and pressure roller  106  is higher in internal pressure than the lengthwise end portions of the nip, the grease applied to the lengthwise center portion of the ceramic heater  110  is likely to move outward of the lengthwise center portion of the nip between the film guide  103  and pressure roller  106 . As the grease moves outward of the lengthwise center portion of the nip, the layer of the grease applied to the ceramic heater  110  (and part of film guide  103 ) becomes nonuniform in thickness in terms of the lengthwise direction of the ceramic heater  110 . This is problematic in that it possibly reduces the image forming apparatus  1  (fixing device  40 ) in image quality during the initial period of usage of the fixing device  40 . 
     This problem can be solved by applying grease to the ceramic heater  110  (and part of film guide  103 ) in such a manner that the lengthwise end portions of the ceramic heater  110  becomes greater in the amount of grease, per unit area, than the lengthwise center portion of the ceramic heater  110 . This embodiment is the same as the first embodiment, except that the grooves  103   a  and  103   b  of the film guide  103  in this embodiment are different in shape from the counterparts in the first embodiment. Thus, the components of the fixing device in this embodiment other than the grooves  103   a  and  103   b  are not described here. 
     That is, like the film guide  103  in the first embodiment, the film guide  103  in this embodiment has a groove  103   c , the bottom surface  103   g  of which is flat, and in which the ceramic heater (pressing member)  110 , which is long and narrow, is to be embedded. The groove  103   c  extends in the lengthwise direction of the film guide  103 . The ceramic heater  110  is embedded in this groove  103   c  of the film guide  103 . The grooves  103   a  and  103   b  are shaped so that their distance from the surface  110   a  ( FIG. 10(   a )) of the ceramic heater  110  (in the groove  103   c  of the film guide  103 ), which is facing the inward surface of the fixation film  101 , and on which the fixation film  101  slides, is greater across their center portion than their lengthwise end portions in terms of their lengthwise direction. 
     In other words, the grooves  103   a  and  103   b  are shaped like a crown, as seen from the direction perpendicular to the lengthwise direction of the film guide  103 . “Shaped like a crown” means that the external diameter of the lengthwise center portion is greater than the external diameter of the lengthwise end portions. The reason why the grooves  103   a  and  103   b  were said to be shaped like a crown is that in terms of the lengthwise direction of the grooves  103   a  ( 103   b ) in  FIG. 10(   b ), they look as if the external diameter of the lengthwise center portion is greater in diameter than the external diameter of the lengthwise end portions. 
     The protrusive guides  203   a  and  203   b  of the grease container-applicator  200  are guided by the grooves  103   a  and  103   b  of the film guide  103 , which are bent in a slight curvature in the form of an arc, as the grease container-applicator  200  is moved along the film guide  103 . Therefore, the distance between the grease application surface (L2 in  FIG. 10(   a )) of the film guide  103  and the grease outlet  201   b , in terms of the direction indicated by the arrow mark Z, gradually increases from the lengthwise center toward the lengthwise ends. Therefore, the gap Δt1 between the grease application surface of the ceramic heater  110  and grease outlet  201   b  gradually increases from the lengthwise center toward the lengthwise ends. 
     Also in the case of this embodiment, the lengthwise ends of each of the grooves  103   a  and  103   b  are provided with a regulating surface  103   f , which determines in dimension, the range (L3 in  FIG. 10(   b )), in terms of the lengthwise direction of the film guide  103 , across which the ceramic heater  110  (and part of film guide  103 ) is to be coated with the grease. 
     The film unit  111  is designed so that the curvature of each of the grooves  103   a  and  103   b  of the film guide  103  satisfies the following mathematical formula: 
     
       
         
           
             
               
                 
                   
                     M 
                     1 
                   
                   = 
                   
                     
                       ∫ 
                       0 
                       
                         L 
                         3 
                       
                     
                     ⁢ 
                     
                       Δ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         t 
                         1 
                       
                       ⁢ 
                       
                         ⅆ 
                         x 
                       
                       × 
                       
                         L 
                         2 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     On the other hand, a structural arrangement for applying grease to the ceramic heater  110  in such a manner that the lengthwise center portion of the ceramic heater  110  becomes greater in the amount of grease than the lengthwise end portions, unlike the structural arrangement in the first embodiment, is described. 
     For example, in a case where the pressure between the lengthwise center portion of the film guide  103  and the lengthwise center portion of pressure roller  106  in terms of the their lengthwise direction is higher than that between the lengthwise end portions of the film guide  103  and corresponding portions of the film guide  103 , the grease applied to the lengthwise center portion of the ceramic heater  110  is likely to migrate from the lengthwise center portion toward the lengthwise end portions. As the grease migrates from the lengthwise center portion toward the lengthwise end portions, the layer of the applied grease on the ceramic heater  110  (and part of film guide  103 ) becomes nonuniform in thickness, and therefore, it is possible that the image forming apparatus  1  (fixing device  40 ) will reduces in image quality as described previously regarding the first embodiment. 
     In the case of this structural arrangement, therefore, the problem can be solved by applying the grease in such a manner that the lengthwise center portion of the ceramic heater  110  becomes greater in the amount of the applied grease than the lengthwise end portions of the ceramic heater  110 . In this case, the grooves  103   a  and  103   b  are to be gently bent in the curvature in the form of an arc, in the opposite direction from the above-described direction. This structural arrangement can make the amount by which the grease is applied to the lengthwise center portion of the ceramic heater  110 , greater than the amount by which the grease is applied to the lengthwise end portions of the ceramic heater  110 . 
     That is, in the case of this example of structural arrangement, the film guide  103  has the groove  103   c  which is flat at the bottom, and in which the ceramic heater  110  is to be embedded. Further, the groove  103   a  and  103   b  are shaped so that the distance from them to the surface  110   a  of the ceramic heater  110  (embedded in groove  103   c ), on which the fixation film  101  slides, is greater across the lengthwise end portions of the film guide  103  than the lengthwise center end portions. 
     As described above, this embodiment can provide the same effects as the first embodiment. Further, even if the pressure between the film guide  103  and pressure roller  106  is nonuniform in terms of the lengthwise direction of the film guide  103  (pressure roller  106 ), it is possible to prevent the ceramic heater  110  from becoming nonuniform in the amount of the grease, per unit area, in the lengthwise direction of ceramic heater. Therefore, this embodiment can solve the problem that the image forming apparatus  1  (fixing device  40 ) reduces in image quality during the initial period of usage of the fixing device  40 . 
     Further, it is feasible to structure the film unit  111  so that instead of providing the film guide  103  with the grooves  103   a  and  103   b  and protrusive guides  203   a  and  203   b , the portion of the grease storing member  201 , which extend downward from the edges of the grease outlet  201   b , accommodate the protrusive curvature of the film guide  103 , so that the grease storing member  201  slides on the film guide  103  in the lengthwise direction of the film guide  103 . 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims priority from Japanese Patent Application No. 036758/2013 filed Feb. 27, 2013, which is hereby incorporated by reference.