Patent Publication Number: US-2023134207-A1

Title: Fixing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-178661, filed Nov. 1, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a fixing device for printer devices and the like. 
     BACKGROUND 
     An image forming device for forming an image on a sheet is known. Certain types of such image forming devices include a fixing device. The fixing device heats and presses a toner image on a sheet to fix the toner image to the sheet. However, a fixing device capable of reducing unevenness in the fixed image is required for improving printed image quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts an image processing device. 
         FIG.  2    is a cross-sectional view of a fixing device. 
         FIG.  3    is a cross-sectional view of a heater unit. 
         FIG.  4    is a bottom view of a heater unit. 
         FIG.  5    is another cross-sectional view of a fixing device. 
         FIG.  6    is a perspective view of a guide member. 
         FIG.  7    is a plan view of a guide member according to a first embodiment. 
         FIG.  8    is a cross-sectional view of a guide member. 
         FIG.  9    is a plan view of a guide member according to a second embodiment. 
         FIG.  10    is a plan view of a guide member according to a third embodiment. 
         FIG.  11    is a cross-sectional view of a guide member according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a fixing device capable of reducing unevenness of an image is provided. 
     According to an embodiment, a fixing device includes a tubular body, a heater unit contacting an inner surface of the tubular body, a frame configured to support the heater unit inside the tubular body, and a guide member contacting the frame on a side opposite the heater unit. The guide member has a plurality of contact portions which are spaced from each other in a longitudinal direction of the guide member that parallels an axial direction of the tubular body. The contact portions are configured to contact the inner surface of the tubular body. A first contact portion of the plurality of contact portions is located in an end portion of the guide member in the longitudinal direction. A second contact portion of the plurality of contact portions is located in a central portion of the guide member in the longitudinal direction. The second contact portion has an effective heat transfer coefficient with respect to the tubular body that is less than an effective heat transfer coefficient of the first contact portion with respect to the tubular body. In this context, an effective heat transfer coefficient relates to the ability of the portion to receive heat from the tubular body, such that transfer rates, for example, differ for different effective heat transfer coefficients. 
     Hereinafter, a fixing device according to certain example embodiments will be described with reference to the drawings. 
       FIG.  1    provides a schematic configuration diagram of an image forming device  1 . 
     An image forming device  1  performs a process of forming an image on a sheet S. The sheet S may be paper. The image forming device  1  includes a housing  10 , a scanner  2 , an image forming unit  3 , a sheet supply unit  4 , a conveyance unit  5 , an inversion unit  9 , a tray  7 , a control panel  8 , and a control unit  6 . 
     The housing  10  forms the outer shape of the image forming device  1 . 
     The scanner  2  reads image information of an object to be copied based on brightness and darkness of light, and generates an image signal. The scanner  2  outputs the generated image signal to the image forming unit  3 . 
     The image forming unit  3  forms a toner image based on the image signal from the scanner  2  or an outside source (external source). The toner image is an image made of toner or other similar material. The image forming unit  3  transfers the toner image onto a surface of the sheet S. The image forming unit  3  heats and presses the toner image on the surface of the sheet S to fix the toner image to the sheet S. 
     The sheet supply unit  4  supplies the sheets S one by one to the conveyance unit  5  for the image forming unit  3  to form toner images on each. The sheet supply unit  4  includes a sheet housing portion  20  and a pickup roller  21 . 
     The sheet housing portion  20  houses the sheet S on which printing has not yet been performed. In general, the sheet housing portion  20  stores individual sheets S of a known size and type. 
     The pickup roller  21  takes out the sheets S one by one from the sheet housing portion  20 . The pickup roller  21  supplies the taken-out sheet S to the conveyance unit  5 . 
     The conveyance unit  5  conveys the sheet S from the sheet supply unit  4  to the image forming unit  3 . The conveyance unit  5  includes conveyance rollers  23  and registration rollers  24 . 
     The conveyance rollers  23  convey the sheet S from the pickup roller  21  to the registration rollers  24 . The conveyance rollers  23  work to abut a tip (leading edge) of the sheet S in a conveyance direction against nip RN formed by the registration rollers  24 . 
     The registration rollers  24  adjust a position of the tip of the sheet S along the conveyance direction by pressing the sheet S against the nip RN. The registration rollers  24  convey the sheet S onward at a timing corresponding to that necessary for the image forming unit  3  to appropriately transfer the toner image to the sheet S at the correct position. 
     The image forming unit  3  includes a plurality of image forming portions F, a laser scanning unit  26 , an intermediate transfer belt  27 , a transfer portion  28 , and a fixing device  30 . 
     The image forming portions F include a photoreceptor drum D. The image forming portions F form, on the photoreceptor drum D, the toner image corresponding to the image signal. The plurality of image forming portions FY, FM, FC, and FK form toner images with yellow, magenta, cyan, and black toners, respectively. 
     A charger electrostatically charges a surface of the photoreceptor drum D. A developing device houses developers containing the yellow, magenta, cyan, and black toners. The developing device provides developer/toner to develop an electrostatic latent image that has been formed on the photoreceptor drum D in correspondence with the image signal to be printed. In this example, each image forming portion F forms a separate color toner image on a respective photoreceptor drum D and these separate color toner images are transferred one after the other to the intermediate transfer belt  27 . 
     The laser scanning unit  26  scans each charged photoreceptor drum D with a laser beam L to selectively expose the photoreceptor drum D in correspondence with the image signal to be printed. In order to form the electrostatic latent images on the photoconductor drums D of the image forming portions FY, FM, FC, and FK of the respective colors, the photoreceptor drums D are exposed with different laser beams LY, LM, LC, and LK by the laser scanning unit  26 , respectively. 
     The intermediate transfer belt  27  receives the toner image from the surface of the photoreceptor drums D. The transfer from photoreceptor drum D to the intermediate transfer belt  27  is sometimes referred to as a primary transfer. 
     Then, at the transfer portion  28 , the toner image(s) are transferred onto the surface of the sheet S from the intermediate transfer belt  27  at what is called a secondary transfer position. The transfer from the intermediate transfer belt to the sheet S is sometimes referred to as a secondary transfer. 
     The fixing device  30  heats and presses the toner image on the sheet S to fix the toner image to the sheet S. 
     The inversion unit  9  (reversing unit) can invert the sheet S so an image can be formed on a back surface of the sheet S (e.g., double-sided printing). The inversion unit  9  reverses a sheet S that has been discharged from the fixing device  30  by use of a switchback. The inversion unit  9  conveys the inverted sheet S back toward the registration rollers  24 . 
     The tray  7  can receive a discharged sheet S on which an image has been formed. 
     The control panel  8  is a part of an input unit by which information can be input by an operator to operate the image forming device  1 . The control panel  8  includes a touch panel and various hard keys, buttons, switches, or the like. 
     The control unit  6  controls an operation of each sub-unit of the image forming device  1 . 
       FIG.  2    is a cross-sectional view of the fixing device  30 . The fixing device  30  includes a pressure roller  31  and a heating roller  34 . A nip N is formed between the pressure roller  31  and the heating roller  34 . 
     In the present application, a z direction, an x direction, and a y direction are defined as follows for purposes of descriptive convenience. The z direction is a thickness direction of a substrate  41 . The z direction is also the direction in which the heating roller  34  and the pressure roller  31  are arranged adjacent to each other. The +z direction is a direction from the heating roller  34  toward the pressure roller  31 . The x direction is a lateral direction of the substrate  41  and also the conveyance direction of the sheet S through the nip N. The +x direction is the downstream side of the sheet S along the conveyance direction. The y direction is a longitudinal direction of the substrate  41  and also the axial direction of tubular film  35  of the heating roller  34 . 
     The pressure roller  31  presses the toner image on the sheet S in the nip N. The pressure roller  31  includes a metal core  32  and an elastic layer  33 . The configuration of the pressure roller  31  is not limited to the above, and various configurations are possible. 
     The metal core  32  is formed in a columnar shape by a metal material such as stainless steel. The elastic layer  33  is made of an elastic material such as silicone rubber. The elastic layer  33  is formed on an outer surface of the metal core  32  with a constant thickness. A release layer made of a resin material such as a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) may be formed on an outer surface of the elastic layer  33 . 
     The pressure roller  31  is driven by a motor to rotate. When the pressure roller  31  rotates in a state where the nip N is formed (that is, the pressure roller  31  can contact the heating roller  34 ), the tubular film  35  of the heating roller  34  is driven to rotate. The pressure roller  31  rotates to convey the sheet S in a conveyance direction W through (past) the nip N. 
     The heating roller  34  heats the toner image on the sheet S in the nip N. The heating roller  34  includes the tubular film  35 , a heater unit  40 , a heat transfer member  48 , a support member  50 , a frame  36 , and temperature sensitive elements ( 37 ,  38 ,  39 ). A configuration of the heating roller  34  is not limited to the above, and various configurations are possible. 
     The tubular film  35  has a tubular shape and may be more generally referred to as a tubular body, a cylinder, or a cylindrical body. The tubular film  35  includes a base layer, an elastic layer, and the release layer stacked in this order from an inner peripheral side. The base layer can be made of a resin material such as PI (polyimide) with a low heat capacity. The elastic layer is made of an elastic material such as silicone rubber. The release layer is made of a material such as PFA resin. 
     The heater unit  40  is inside the tubular film  35 . A surface of the heater unit  40  facing in the +z direction is in contact with an inner surface of the tubular film  35  via a grease or the like. 
       FIG.  3    is a cross-sectional view of the heater unit  40  taken along a line III-III in  FIG.  4   .  FIG.  4    is a bottom view (viewed from the +z direction) of the heater unit  40 . The heater unit  40  includes the substrate  41 , a heating element  45 , and a wiring  46 . 
     The substrate  41  is made of a metal material such as stainless steel or a ceramic material such as aluminum nitride. As illustrated in  FIG.  4   , the substrate  41  has a rectangular plate shape. The axial direction of the tubular film  35  corresponds to the longitudinal direction of the substrate  41 . As illustrated in  FIG.  3   , an insulating layer  42  is on a surface of the substrate  41  facing in the +z direction. The insulating layer  42  may be a glass or glass-like material in some examples. Another insulating layer, similar to the insulating layer  42 , may be formed on the −z direction side of the substrate  41  in some examples. 
     The heating element  45  is made of a silver-palladium alloy or the like. The heating element  45  generates heat when energized (e.g., supplied with electric current). The heating element  45  and the wiring  46  are disposed on the +z direction surface of the substrate  41  via the insulating layer  42 . A protective layer  43  made of a glass material or the like covers the heating element  45  and the wiring  46 . A protective layer similar to the protective layer  43  may be formed in the −z direction side of the substrate  41  in some examples. 
     As illustrated in  FIG.  4   , the heating element  45  includes a central heating element and a pair of end heating elements. The central heating element is disposed at a middle portion along the y direction. The pair of end heating elements are located at both ends of the central heating element in the y direction. The central heating element and the pair of end heating elements can be separately controlled to generate heat independently of each other. In this example, the pair of end heating elements are controlled together for heat generation, though in other examples the pair may be independent of one another. 
     The heat transfer member  48  (illustrated in  FIG.  2   ) is made of a metal material having high thermal conductivity such as copper. An outer shape of the heat transfer member  48  is generally the same as that of the substrate  41  of the heater unit  40 . The heat transfer member  48  is arranged in the −z direction from the substrate  41  and is in contact with the substrate  41 . 
     The support member  50  is made of a resin material such as a liquid crystal polymer. The support member  50  covers both edges of the heater unit  40  in the x direction and also covers a portion of the heater unit  40  from the −z direction. The support member  50  supports the heater unit  40  via the heat transfer member  48  from the −z direction. The support member  50  also provides support (e.g., contacts) to an inner surface of the tubular film  35  on both sides of the heater unit  40  in the x direction. 
     The support member  50  includes an upstream rib  51  and a downstream rib  52 . These rib components may be referred to as a pair of ribs in some instances. The upstream rib  51  extends upstream along a rotational direction of the tubular film  35 . The downstream rib  52  extends downstream along the rotational direction of the tubular film  35 . The ribs  51  and  52  can abut on an inner surface of the tubular film  35 . The ribs  51  and  52  hold the tubular film  35  in a defined shape. The ribs  51  and  52  have a plate shape with the y direction as a plate thickness direction. In this example, there is a plurality of upstream ribs  51  and a plurality of downstream ribs  52  arranged in the y direction. The upstream ribs  51  may be located at different positions along the y direction from the downstream ribs  52 . That is, the upstream ribs  51  may be offset in the y direction from the downstream ribs  52 . Accordingly, by such an arrangement, temperature unevenness of the fixing device  30  can be reduced. 
     The frame  36  is made of a steel plate material or the like. The frame  36  is inside the tubular film  35 . A cross section of the frame  36  perpendicular to the y direction is a U shape. The frame  36  is mounted on a −z direction side of the support member  50  such that the U-shaped opening of the frame is closed with the support member  50 . The frame  36  extends in the y direction. Both ends of the frame  36  in the y direction can be fixed to the housing  10  of the image forming device  1 . The frame  36  physically supports the heater unit  40  via the support member  50  and the heat transfer member  48 . 
     The temperature sensitive elements ( 37 ,  38 ,  39 ) are a heater thermometer  37 , a thermostat  38 , and a film thermometer  39 . The heater thermometer  37  and the thermostat  38  are located on the −z direction side of the heater unit  40  with the heat transfer member  48  interposed therebetween. The heater thermometer  37  measures a temperature of the heater unit  40  via the heat transfer member  48 . The thermostat  38  cuts off power to the heating element  45  when the temperature of the heater unit  40  (as detected via the heat transfer member  48 ) exceeds a predetermined temperature (threshold temperature). The film thermometer  39  is in contact with the inner surface of the tubular film  35  and measures a temperature of the tubular film  35 . The film thermometer  39  measures the temperature of the tubular film  35  at positions corresponding to the central heating element and the end heating elements of the heater unit  40 . 
     A guide member  60  is made of a resin material such as a liquid crystal polymer. The guide member  60  is inside the tubular film  35 . The guide member  60  is on a side opposite the heater unit  40  with the frame  36  interposed therebetween. The guide member  60  covers about half of a +x direction surface of the frame  36  and an entire surface of the frame  36  in the −z direction. The guide member  60  includes a base portion  61  and ribs  62 . 
     The base portion  61  is in the +x direction and the −z direction of the frame  36 . The base portion  61  is fixed to the frame  36 . The base portion  61  is long in the y direction. 
     The ribs  62  contact the tubular film  35 . Each rib  62  projects from the base portion  61  in a radial direction of the tubular film  35 . The ribs  62  extends around the circumferential direction of the tubular film  35 . Since the ribs  62  are in contact with the tubular film  35 , the tubular film  35  is supported by the ribs  62 . Thus, even when the tubular film  35  is formed of a thin, low-rigidity (flexible) resin material, the rotational trajectory and shape of the tubular film  35  is secured. 
       FIG.  6    is a perspective view of a guide member  60 . A rib  62  has a plate-like shape with the y direction as the plate thickness direction. The plurality of ribs  62  are arranged in the y direction. The plurality of ribs  62  may be located at different positions along the y direction from the upstream ribs  51  and the downstream ribs  52  of the support member  50  (illustrated in  FIG.  2   ). Accordingly, the temperature unevenness of the fixing device  30  is reduced. 
     As illustrated in  FIG.  6   , the base portion  61  has recesses  63 . A recess  63  is located at a central portion of the base portion  61  and another is located and at a +y direction end of the base portion  61 . The recesses  63  are recessed in the −x direction of the base portion  61 .  FIG.  2    corresponds to a cross-sectional view of the fixing device  30  taken along a line II-II in  FIG.  6   . A film thermometer  39  (see  FIG.  2   ) is disposed inside the recess  63  located at the line II-II. Another film thermometer  39  or the like may be disposed inside the centrally located recess  63 . As illustrated in  FIG.  6   , the plurality of ribs  62  includes pairs of recess ribs  64 . The recess ribs  64  are located on both sides of each recess  63  in the y direction. When the recess ribs  64  are in contact with the tubular film  35 , the posture of the tubular film  35  is stabilized around a position of the film thermometer  39  disposed in the corresponding recess  63 . Accordingly, accuracy of the temperature measurement by the film thermometer  39  is improved. 
       FIG.  5    is a cross-sectional view of the fixing device taken along a line V-V in  FIG.  2   . As depicted, the pressure roller  31  is narrower in the middle and thicker at the ends. That is, a diameter of the central portion (along the y direction) of the pressure roller  31  is less than the diameter of the y-direction ends. Accordingly, wrinkling of a sheet S passing through the nip N of the fixing device  30  can be reduced. 
     The support member  50  of the heating roller  34  has a correspondingly outwardly bowed shape. That is, a thickness of the support member  50  at a middle portion of the support member  50  is greater than at the thickness of the support member at both y direction ends. The width in the x direction of the nip N formed between the pressure roller  31  and the heating roller  34  is substantially uniform along the y direction. Accordingly, fixing performance of the fixing device  30  is substantially uniform along the y direction. 
     The frame  36  is connected to the support member  50  via a positioning member  55 . The positioning member  55  is mounted at a central portion of the frame  36  along the y direction. A locking claw  56  of the support member  50  is inserted into a locking hole of the positioning member  55 . The frame  36  is curved (or bent) in the −z direction. More particularly, the frame  36  is curved such that the central portion thereof is convex in the −z direction. On the other hand, side of the tubular film  35  on the −z direction side of the frame  36  is substantially parallel along the y direction since this side of the tubular film  35  is not constrained by other members. 
     The guide member  60  is curved in the same manner as the frame  36 . The guide member  60  is curved such that a central portion thereof is convex in the −z direction. It is assumed in the present example that shapes of the ribs  62  are all the same. In this case, a tip of a second rib  66 , which is one of the ribs  62  near the middle of the guide member  60  along the y direction, will be closer to the tubular film  35  in the −z direction than will be a tip of a first rib  65 , which is one of the ribs at an end in the y direction of the guide member  60 . That is, the distance along the z direction between the tip of the first rib  65  and the tubular film  35  is less than the distance along the z direction between the tip of the second rib  66  and the tubular film  35 . The second rib  66  is thus more likely to come into contact with the tubular film  35  than the first rib  65 . Heat of the tubular film  35  is transferred to the plurality of ribs  62  by physical contact between the tubular film  35  and a rib  62 . A temperature at a central portion of the tubular film  35  is thus generally lower than the temperature at the of ends since centrally located ribs  62  are more often in contact with the tubular film  35  than the ribs  62  located at the ends of the tubular film  35 . Thus, a temperature unevenness of the fixing device  30  occurs, and/or gloss unevenness occurs in the image formed on a sheet. 
     First Embodiment 
       FIG.  7    is a plan view of the guide member  60  according to a first embodiment. The guide member  60  includes the first ribs  65  and the second ribs  66  as members of the plurality of ribs  62 . Three first ribs  65  are disposed at each of the ends of the guide member  60  in the y direction. Nine second ribs  66  are disposed in the central portion of the guide member  60 . The numbers of the first ribs  65  and the second ribs  66  are not limited thereto. 
     Widths of each first rib  65  and each second rib  66  in the y direction are the same as one another. 
       FIG.  8    is a cross-sectional view taken along a line VIII-VIII in  FIG.  7   . Heights of the first ribs  65  and the second ribs  66  in the radial direction of the tubular film  35  are the same. However, lengths of the second ribs  66  in the circumferential direction of the tubular film  35  are shorter than those of the first ribs  65 . The lengths of the ribs  65  and  66  in the circumferential direction are the lengths of outer circumferences of the ribs  65  and  66 . The lengths of the second ribs  66  are about half the lengths of the first ribs  65 . Thud, the contact areas between the second ribs  66  and the tubular film  35  are less than the contact areas between the first ribs  65  and the tubular film  35 . An effective heat transfer coefficient between the second ribs  66  and the tubular film  35  is thus smaller than an effective heat transfer coefficient between the first ribs  65  and the tubular film  35 . 
     As detailed above, the fixing device  30  according to the first embodiment includes the tubular film  35 , the heater unit  40 , the frame  36 , the guide member  60 , the first ribs  65 , and the second ribs  66 . The heater unit  40  is inside the tubular film  35  and is in contact with the tubular film  35 . The frame  36  is inside the tubular film  35  and supports the heater unit  40 . The guide member  60  is inside the tubular film  35  and is on the side opposite the heater unit  40  with the frame  36  interposed therebetween. The guide member  60  includes the plurality of ribs  62  which can contact the tubular film  35 . The first ribs  65  are located at ends in the y direction among the plurality of ribs  62 . The second ribs  66  are located at the central portion in the y direction among the plurality of ribs  62 . The heat transfer between the second ribs  66  and the tubular film  35  is less than the heat transfer between the first ribs  65  and the tubular film  35  due to the differences in rib length (outer circumference). 
     As described above, the guide member  60  is curved such that the central portion thereof is convex in the −z direction. The heat transfer between the second ribs  66  and the tubular film  35  is less than the heat transfer between the first ribs  65  and the tubular film  35 . Heat transfer from the tubular film  35  to the plurality of ribs  62  is thus more uniform along the y direction. The temperature unevenness of the fixing device  30  is reduced, and unevenness of an image is reduced. 
     The contact areas between the second ribs  66  and the tubular film  35  are smaller than the contact areas between the first ribs  65  and the tubular film  35 . 
     Accordingly, the effective heat transfer coefficient between the second ribs  66  and the tubular film  35  is less than the effective heat transfer coefficient between the first ribs  65  and the tubular film  35 . 
     In the guide member  60  according to a first embodiment, the lengths of the second ribs  66  in the circumferential direction are shorter than the lengths of the first ribs  65  in the circumferential direction. 
     Accordingly, the contact areas between the second ribs  66  and the tubular film  35  are smaller than the contact areas between the first ribs  65  and the tubular film  35 . 
     Second Embodiment 
       FIG.  9    is a plan view of a guide member  60  according to a second embodiment. The guide member  60  according to the second embodiment is different from the first embodiment in that widths in the y direction of the first ribs  65  and second ribs  67  are different from one another. The description of the second embodiment may omit those aspects shared with the first embodiment. 
     Heights of the first ribs  65  and the second ribs  67  in the radial direction of the tubular film  35  are the same in the second embodiment. Lengths of the first ribs  65  and the second ribs  67  in the circumferential direction of the tubular film  35  are also the same in this embodiment. However, widths of the second ribs  67  in the y direction are less than those of the first ribs  65 . In the present example, the width of each of the second ribs  67  is about half the width of each of the first ribs  65 . Contact area between the second ribs  67  and the tubular film  35  are thus less than contact area between the first ribs  65  and the tubular film  35 . An effective heat transfer coefficient between the second ribs  67  and the tubular film  35  is less than the effective heat transfer coefficient between the first ribs  65  and the tubular film  35 . 
     In the second embodiment, the widths of the second ribs  67  in the y direction are less than the widths of the first ribs  65  in the y direction. Heat transfer from the tubular film  35  to the plurality of ribs  62  is thus more uniform along the y direction. Temperature unevenness of the fixing device  30  is reduced, and unevenness of an image is reduced. 
     Third Embodiment 
       FIG.  10    is a plan view of a guide member  60  according to a third embodiment. The guide member  60  according to the third embodiment is different from that according to the first embodiment in that heights of the first ribs  65  and second ribs  68  in the radial direction of the tubular film  35  are different. The description of the third embodiment may omit those aspects shared with the first embodiment. 
     Widths of the first ribs  65  and the second ribs  68  in the y direction are the same in the third embodiment. 
       FIG.  11    is a cross-sectional view taken along a line XI-XI in  FIG.  10   . Lengths of the first ribs  65  and the second ribs  68  in the circumferential direction of the tubular film  35  are the same in this third embodiment. Heights of the second ribs  68  in the radial direction of the tubular film  35  are less than that of the first ribs  65 . The heights of the ribs  65  and  68  in the radial direction of the tubular film  35  are taken in this context as distances from a central axis of the tubular film  35  to outermost surface of the ribs  65  and  68 . The heights of the ribs  65  and  68  in this context are those compared at the same phase position along the circumferential direction of the tubular film  35 . Contact areas between the second ribs  68  and the tubular film  35  are less than contact areas between the first ribs  65  and the tubular film  35 . An effective heat transfer coefficient between the second ribs  68  and the tubular film  35  is less than the heat transfer coefficient between the first ribs  65  and the tubular film  35 . 
     As described above, the heights of the second ribs  68  in the radial direction of the tubular film  35  are less than the heights of the first ribs  65  in the radial direction of the tubular film  35 . Heat transfer from the tubular film  35  to the plurality of ribs  62  is thus more uniform along the y direction. Temperature unevenness of the fixing device  30  is reduced, and unevenness of an image is reduced. 
     Fourth Embodiment 
     The guide member  60  according a fourth embodiment is different from that according to the first embodiment in that materials of the first ribs  65  and second ribs  69  are different from one another. The description of the fourth embodiment may omit those aspects shared with the first embodiment. 
     Shapes of the first ribs  65  and the second ribs  69  are the same. Contact area between the second ribs  69  and the tubular film  35  are equal to the contact area between the first ribs  65  and the tubular film  35 . 
     The base portion  61  and the first ribs  65  of the guide member  60  are integrally made of a resin material such as a liquid crystal polymer. The second ribs  69  are formed separately from the base portion  61  in this example. The second ribs  69  are made of a material having lower thermal conductivity than the material from which the first ribs  65  are formed. For example, the second ribs  69  are made of a resin material such as a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). A heat transfer coefficient of the material of second ribs  69  is less than the heat transfer coefficient of the material of the first ribs  65 . 
     For fabricating the fourth embodiment, in one example, mounting pins can be formed on the second ribs  69  and mounting holes can be formed on the base portion  61 . The mounting pins of the second ribs  69  can then be inserted into the mounting holes formed in the base portion  61 , and the second ribs  69  thus can be fixed to the base portion  61 . The method for mounting the second ribs  69  to the base portion  61  is not limited thereto. 
     As described above, the thermal conductivity of the material of the second ribs  69  is lower than the thermal conductivity of the material of the first ribs  65 . Heat transfer from the tubular film  35  to the plurality of ribs  62  is thus more uniform along the y direction. Temperature unevenness of the fixing device  30  is reduced, and unevenness of an image is reduced. 
     In the fourth embodiment, the entire material of the second ribs  69  is different from that of the first ribs  65 . However, in some examples, just the material at the outer surfaces of the second ribs  69  that contact with the tubular film  35  may be formed of a material different from the outer surfaces of the first ribs  65 . For example, the outer surfaces of the second ribs  69  may be coated with a material having a low thermal conductivity such as PFA resin. In this case, the entire guide member  60  including the second ribs  69  can be integrally made of the same resin material, such as a liquid crystal polymer with just a different surface coating on certain portions. 
     The second ribs ( 66 ,  67 ,  68 ,  69 ) in the various example embodiments are different from the first ribs  65  in some manner or characteristic according to the first to fourth embodiments. In some examples, a second rib that combines aspects of the differences in two or more of the first to fourth embodiments may be adopted. 
     The guide member  60  according to certain embodiments includes as a plurality of ribs  62 , the described first ribs  65  and at least one of the types of second ribs ( 66 ,  67 ,  68 ,  69 ). Thus, the plurality of ribs  62  includes ribs with at least two different effective heat transfer coefficients (or heat transfer rates) and thus transfer heat to the tubular film  35  in a dissimilar manner. In some examples, the guide member  60  may include ribs of three or more types with different effective heat transfer coefficients with respect to heat transfer to the tubular film  35 . In some examples, the guide member  60  or the like may include ribs in which the heat transfer coefficient difference between adjacent ribs changes stepwise along the y direction. 
     The guide member  60  according to certain embodiments includes the first ribs  65  as first contact portions and at least one of the second ribs  66 ,  67 ,  68 ,  69  as a second contact portion. On the other hand, a guide member  60  or the like may instead have a first contact surface as the first contact portion and a second contact surface as the second contact portion. For example, the first contact surface and the second contact surface may be partitioned from one another by a groove or the like. 
     The image forming device is one example of an image processing device, and the fixing device  30  is one example of a heating device. In other examples, the image processing device  1  may be a decoloring device, and the fixing device  30  may be utilized as a heating device that functions as a decoloring unit. A decoloring device performs a process of decoloring (erasing) an image formed on a sheet in a decoloring or decolorable toner that changes color in response to heat or the like. The decoloring unit heats and decolors a decoloring toner image that has been formed on a sheet passed through a nip N or the like. 
     According to one or more embodiments described above, the guide member  60  includes the second ribs ( 66 ,  67 ,  68 , or  69 ) for which the effective heat transfer to the tubular film  35  is less than the effective heat transfer of the first ribs  65  to the tubular film  35 . Accordingly, unevenness in the printed image can be reduced and print quality can be improved. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of invention. These embodiments may be embodied in a variety of other forms; various omissions, substitutions, and changes may be made without departing from the spirit of the invention. The accompanying claims and these equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.