Patent Publication Number: US-9423734-B2

Title: Fixing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2013-204743 filed on Sep. 30, 2013, which is incorporated herein by reference in its entirety. 
     FIELD OF DISCLOSURE 
     The disclosure relates to a fixing device configured to thermally fix a developing agent image transferred to a sheet. 
     BACKGROUND 
     A known fixing device includes a cylindrical fixing belt, a heating element disposed inside the fixing belt, a nip member disposed inside the fixing belt, and a pressure roller placing the fixing belt between the pressure roller and the nip member. More specifically, in the fixing device, each end of the heating element is supported by a member (e.g., a member different from the nip member) disposed at each end of the fixing belt. A certain distance is provided between the heating element and the nip member. 
     In the fixing device, air between the heating element and the nip member, and the member supporting the heating element take the heat from the heating element. Therefore, improvements are required to heat the nip member promptly. 
     SUMMARY 
     The disclosure relates to a fixing device in which a nip member may be heated promptly. 
     According to an aspect of the disclosure, a fixing device may include a heating element extending in a first direction and configured to generate heat, a nip member extending along the heating element in the first direction and configured to receive radiant heat from the heating element, an endless belt extending along the heating element in the first direction, and a backup member extending along the heating element in the first direction. The endless belt is configured to rotate. The endless belt surrounds the heating element and the nip member. The backup member nips the endless belt in cooperation with the nip member. The nip member includes a main portion facing in a second direction perpendicular to the first direction and a particular holding portion holding the heating element. 
     With this structure, heat from the heating element may be transmitted promptly to the particular holding portion of the nip member, and thus the nip member may be heated promptly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference now is made to the following description taken in connection with the accompanying drawings. 
         FIG. 1  is a schematic diagram of a laser printer comprising a fixing device in an illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 2  is a cross-sectional view of the fixing device. 
         FIG. 3  is an exploded perspective view of a heat unit of the fixing device. 
         FIG. 4  is a perspective view of a nip plate of the heating unit. 
         FIG. 5  is a perspective view of a cover member of the heating unit to which a halogen lamp of the heating unit is fixed. 
         FIG. 6  is a perspective view of a nip plate according to a first modification of the disclosure. 
         FIG. 7  is a perspective view of the nip plate according to the first modification to which the halogen lamp is attached. 
         FIG. 8  is a perspective view of a nip plate according to a second modification of the disclosure. 
         FIG. 9  is a perspective view of a nip plate according to a third modification of the disclosure. 
         FIG. 10A  is a perspective view of a nip plate according to a fourth modification of the disclosure. 
         FIG. 10B  is a cross-sectional view of the nip plate according to the fourth modification of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments will be described referring to the accompanying drawings. 
     In the following description, the expressions “front”, “rear”, “top or upper (up)”, “bottom or lower (down)”, “right”, and “left” are used to define the various parts when a laser printer  1  is disposed in an orientation in which it is intended to be used. 
     As depicted in  FIG. 1 , the laser printer  1  may comprise a housing  2 , in which a sheet feed unit  3  configured to feed a sheet S, an exposure device  4 , a process cartridge  5  configured to transfer a toner image to the sheet S, and a fixing device  100  configured to thermally fix the toner image on the sheet S may be disposed. 
     The sheet feed unit  3  may be disposed at a lower portion of the housing  2 . The sheet feed unit  3  may comprise a feed tray  31 , a sheet lifting plate  32 , and a sheet feeding mechanism  33 . The sheets S accommodated in the feed tray  31  may be raised by the sheet lifting plate  32  and may be supplied by the sheet feeding mechanism  33  toward the process cartridge  5  (e.g., between a photosensitive drum  61  and a transfer roller  63 ). 
     The exposure device  4  may be disposed at an upper portion of the housing  2 . The exposure unit  4  may comprise a laser light emitting unit (not shown), as well as a polygon minor, lenses, and reflecting mirrors, which are depicted without reference numerals. In the exposure device  4 , laser light (see the dash-dot line) emitted from the laser light emitting unit based on image data may scan at high speed across the surface of the photosensitive drum  61  to expose the surface of the photosensitive drum  61  to light. 
     The process cartridge  5  may be disposed below the exposure device  4 . The process cartridge  5  may be configured to be removably attached to the housing  2  through an opening exposed when a front cover  21  attached to the housing  2  is opened. The process cartridge  5  may comprise a drum unit  6  and a developing unit  7 . 
     The drum unit  6  may comprise the photosensitive drum  61 , a charger  62 , and the transfer roller  63 . The developing unit  7  may be configured to be removably attached to the drum unit  6 . The developing unit  7  may comprise a developing roller  71 , a supply roller  72 , a thickness-regulation blade  73 , and a toner storage  74  configure to store a developing agent, e.g., toner. 
     In the process cartridge  5 , the surface of the photosensitive drum  61  may be uniformly charged by the charger  62 . Thereafter, laser light from the exposure device  4  may scan at high speed across the surface of the photosensitive drum  61 , and the surface of the photosensitive drum  61  may be exposed to light. An electrostatic latent image based on image data may be formed on the photosensitive drum  61 . Toner in the toner storage  74  may be supplied through the supply roller  72  to the developing roller  71  and then may enter between the developing roller  71  and the blade  73 . The toner may be carried on the developing roller  71  as a thin layer having a uniform thickness. 
     The toner carried on the developing roller  71  may be supplied from the developing roller  71  to the electrostatic latent image formed on the photosensitive drum  61 . Thus, the electrostatic latent image may be visualized and a toner image may be formed on the photosensitive drum  61 . Then, as the sheet S is conveyed between the photosensitive drum  61  and the transfer roller  63 , the toner image on the photosensitive drum  61  may be transferred to the sheet S. 
     The fixing device  100  may be disposed behind the process cartridge  5 . The toner image transferred to the sheet S may be thermally fixed to the sheet S while the sheet S passes through the fixing device  100 . The sheet S on which the toner image has been thermally fixed may be discharged to a discharge tray  22  by feeding rollers  23  and  24 . 
     As depicted in  FIG. 2 , the fixing device  100  may comprise a rotatable, endless fixing belt  110 , a heating unit  200  disposed inside the fixing belt  110  and configured to heat the fixing belt  110 , and a backup member, e.g., a pressure roller  140 , that may nip the fixing belt  110  in cooperation with the heating unit  200 . 
     The fixing belt  110  may be configured to be heated by the heating unit  200 . The fixing belt  110  may have heat resistance and flexibility. The rotation of the fixing belt  110  may be guided by a guide member, which is depicted without a reference numeral. 
     The pressure roller  140  may be elastically deformable. The pressure roller  140  may be disposed below the fixing belt  110  and the heating unit  200 . A nip portion N may be formed when the pressure roller  140  is elastically deformed and nips the fixing belt  110  in cooperation with the heating unit  200  (particularly, a nip plate  220 ). In the illustrative embodiment, the heating unit  200  and the pressure roller  140  may be mutually brought into pressure contact with each other while one of them is urged toward the other. 
     The pressure roller  140  may be configured to rotate with drive force transmitted from a motor (not depicted) disposed in the housing  2 . As the pressure roller  140  rotates, the fixing belt  110  may be rotated by a frictional force exerted between the pressure roller  140  and the fixing belt  110  (or the sheet S). As the sheet S having the toner image transferred is conveyed rearward between the pressure roller  140  and the fixing belt  110  that has been heated, the toner image may be thermally fixed to the sheet S. 
     The heating unit  200  may be configured to apply heat to toner on the sheet S via the fixing belt  110 . The heating unit  200  may comprise a heating element, e.g., a halogen lamp  210 , a nip member, e.g., a nip plate  220 , a reflective member  230 , a stay  240 , and a cover member  250 . 
     As depicted in  FIGS. 2 and 3 , the halogen lamp  210  may be a heater configured to generate heat with the application of electricity. The halogen lamp  210  may comprise a glass tube  211 , a filament  212  provided in the glass tube  211 , two terminals  213  and  214 , each attached to a different end of the filament  212 . The glass tube  211  may comprise a cylindrical portion  211 A elongated along the left-right direction, and a sealed portion  211 B integrally formed with the cylindrical portion  211 A at each end of the cylindrical portion  211 A. The sealed portion  211 B may be formed in a flat plate shape. The sealed portion  211 B may be formed smaller or thinner in the top-bottom direction than the cylindrical portion  211 A, and greater or wider in the front-rear direction than the cylindrical portion  211 A. The dimension of the sealed portion  211 B in the top-bottom direction may be smaller than the dimension of the sealed portion  211 B in the front-rear direction and the dimension of the sealed portion  211 B in the left-right direction. The halogen lamp  210  may be held at the seal portions  211 B by holding portions  224  and  225  of the nip plate  220 , with the cylindrical portion  211 A contacting the nip plate  220  (refer to  FIG. 2 ). 
     The nip plate  220  may be a plate-shaped member configured to receive radiant heat from the halogen lamp  210 . The nip plate  220  may be disposed such that the lower surface of the nip plate  220  may contact the inner peripheral surface of the fixing belt  110 . The nip plate  220  may be formed by machining a material, e.g., an aluminum plate, having higher thermal conductivity than the steel stay  240  described later. 
     The reflective member  230  may be configured to reflect radiant heat (mainly emitted in the front-rear direction and in the upward direction) from the halogen lamp  210  toward the nip plate  220 . The reflective member  230  may be disposed with a predetermined distance from the halogen lamp  210  to cover the halogen lamp  210 . 
     As the reflective member  230  collects the radiant heat from the halogen lamp  210  to the nip plate  220 , the radiant heat from the halogen lamp  210  may be efficiently used, and the nip plate  220  and the fixing belt  110  may be promptly heated. 
     Specifically, the reflective member  230  may be formed by bending, in a substantially U-shape, a material, e.g., an aluminum plate, having high infrared and far-infrared reflectance, and higher thermal conductivity than the stay  240 . More specifically, the reflective member  230  may comprise a reflective portion  231  having a curved shape, e.g., a substantially U-shape in cross-sectional view, and a flange portion  232  extending outward in the front-rear direction from each lower end of the reflective portion  231 . The reflective member  230  may be formed thinner than the stay  240 . 
     The stay  240  may be configured to support each end of the nip plate  220  in the front-rear direction from a side opposite from the pressure roller  140 . The stay  240  may be configured to receive a force exerted from the pressure roller  140  on the nip plate  220 . The stay  240  may be formed by bending a metal plate, e.g., a steel plate, having relatively high stiffness, into a substantially U shape, in cross-sectional view, along the reflective member  230  (particularly, the reflective portion  231 ), so as to define an opening which is open toward the nip plate  220 , as depicted in  FIG. 2 . 
     More specifically, the stay  240  may comprise an upper wall  241  disposed above the halogen lamp  210 , as depicted in  FIG. 2 , and a front wall  242  and a rear wall  243  extending downward from the front and rear ends of the upper wall  241 , respectively. 
     The front wall  242  may be disposed upstream of the halogen lamp  210  in the feeding direction of the sheet S. The lower end of the front wall  242  may sandwich, in cooperation with the nip plate  220 , the flange portion  232  disposed on the front side of the reflective member  230 . The front wall  242  may support the front end of the nip plate  220  from above. 
     The rear wall  243  may be disposed downstream of the halogen lamp  210  in the feeding direction of the sheet S. The lower end of the rear wall  243  may sandwich, in cooperation with the nip plate  220 , the flange portion  232  disposed on the rear side of the reflective member  230 . The rear wall  243  may support the rear end of the nip plate  220  from above. 
     The cover member  250  may be disposed outward of the stay  240  to cover the stay  240 . The cover member  250  may have a substantially U-shape in cross-sectional view. 
     As depicted in  FIGS. 2-4 , the nip plate  220  may comprise a generally plate-shaped main portion  221  extending perpendicular to the top-bottom direction, a curve portion  222  extending forwardly and upwardly, while curving, from the front end of the main portion  221 , a bent portion  223  bent to protrude upward from the rear end of the main portion  221 , and a first holding portion  224  and a second holding portion  225  disposed at a different end of the main portion  221  in the left-right direction (e.g., a width direction of the fixing belt  110 ). The main portion  221 , the curve portion  222 , the bent portion  223 , the first holding portion  224  and the second holding portion  225  may be integrally formed. 
     The main portion  221  may be disposed below the halogen lamp  210  (e.g., the pressure roller  140  side). The main portion  221  may be formed longer than the glass tube  211  of the halogen lamp  210  in the left-right direction. More specifically, the main portion  221  may comprise a base portion  221 A having substantially the same length as the cylindrical portion  211 A of the glass tube  211 , a first extending portion  221 B extending leftward from the left end of the base portion  221 A, and a second extending portion  221 C extending rightward from the right end of the base portion  221 A. 
     The base portion  221 A may be formed such that a width thereof in the front-rear direction may be constant along the left-right direction. 
     The width of the first extending portion  221 B in the front-rear direction may be smaller than that of the base portion  221 A. The first holding portion  224  may be integrally formed with a right portion of the first extending portion  221 B. A pair of engagement portions  226  may be integrally formed with a left end portion of the first extending portion  221 B. The engagement portions  226  may be configured to engage with relevant hook portions  244  disposed on the left end portions of the stay  240 . 
     The first holding portion  224  may be a portion configured to hold an end portion of the halogen lamp  210 . More specifically the first holding portion  224  may be configured to hold the sealed portion  211 B disposed on an end of the glass tube  211 . The first holding portion  224  may comprise two first wall portions  224 A and two second wall portions  224 B. 
     The first holding portion  224  may be a portion to hold an end portion of the halogen lamp  210 . More specifically the first holding portion  224  may be configured to hold the sealed portion  211 B disposed on an end of the glass tube  211 . The first holding portion  224  may comprise two first wall portions  224 A and two second wall portions  224 B. 
     Each first wall portion  224 A may extend upward (e.g., opposite to the pressure roller  140 ) from a corresponding end of the first extending portion  221 B of the main portion  221  in the front-rear direction (or in the rotation direction of the fixing belt  110 ). Distance between the first wall portions  224 A may be substantially the same as the width of the sealed portion  211 B of the glass tube  211  in the front-rear direction. Thus, the sealed portion  211 B may be held between the first wall portions  224 A. 
     Each second wall portion  224 B may bend inwardly in the front-rear direction from a corresponding first wall portion  224 A. Each second wall portion  224 B may extend so as to come closer to each other. Each second wall portion  224 B may face the first extending portion  221 B of the main portion  221 . Each second wall portion  224 B may be configured to contact the sealed portion  211 B of the glass tube  211 , with the cylindrical portion  211 A of the glass tube  211  contacting the base portion  221 A of the main portion  221 . Thus, the halogen lamp  210  may be held between the second wall portions  224 B and the base portion  221 A of the main portion  221 . More specifically, the cylindrical portion  211 A of the halogen lamp  210  may be supported at the base portion  221 A. The upper surface of the sealed portion  211 B of the halogen lamp  210  may be held at the second wall portions  224 B. 
     The width of a left portion of the second extending portion  221 C in the front-rear direction may be smaller than that of the base portion  221 A. The width of a right portion of the second extending portion  221 C in the front-rear direction may be greater than that of the left portion of the second extending portion  221 C. The second holding portion  225  may be integrally formed with the left portion of the second extending portion  221 C in the left-right direction. The right portion of the second extending portion  221 C may have an engagement opening  227  configured to engage and hold an engagement protrusion  245  disposed at a right end portion of the stay  240 . 
     The second holding portion  225  may comprise two first wall portions  225 A similar to the first wall portions  224 A of the first holding portion  224 , and two second wall portions  225 B similar to the second wall portions  224 B of the of the first holding portion  224 . The second holding portion  225  may be configured to hold the sealed portion  211 B of the halogen lamp  210  between the first wall portions  225 A and to hold the halogen lamp  210  (e.g., the cylindrical portion  211 A and the sealed portion  211 B) between the second wall portions  225 B and the base portion  221 A of the main portion  221 . More specifically, the cylindrical portion  211 A of the halogen lamp  210  may be supported at the base portion  221 A. The upper surface the sealed portion  211 B of the halogen lamp  210  may be held at the second wall portions  225 B. 
     Further, a holding force between the first wall portions  225 A of the second holding portion  225  may be smaller than a holding force between the first wall portions  224 A of the first holding portion  224 . A holding force between the second wall portions  225 B of the second holding portion  225  and the base portion  221 A may be smaller than a holding force between the second wall portions  224 B of the first holding portion  224  and the base portion  221 A. 
     Thus, an end of the glass tube  211  of the halogen lamp  210  in the left-right direction may be held by the first holding portion  224 . The other end of the glass tube  211  of the halogen lamp  210  in the left-right direction may be held by the second holding portion  225  so as to allow the movement of the halogen lamp  210  in the left-right direction. 
     The halogen lamp  210  supported and held by the nip plate  220  with the holding portions  224  and  225  may be fixed to the cover member  250  by screws SC at each end of the halogen lamp  210  (specifically, at the terminals  213  and  214 ). More specifically, a hole for the screw SC formed on the left terminal  213  of the halogen lamp  210  may be round and may generally correspond to the diameter of the screw SC. Another hole for the screw SC formed on the right terminal  214  may be elongated in the left-right direction. 
     The following effects may be obtained in the illustrative embodiment. 
     The holding portions  224  and  225  configured to hold the halogen lamp  210  may be integrally formed with the nip plate  220 . Heat from the halogen lamp  210  may be directly transmitted to the holding portions  224  and  225  of the nip plate  220 . Therefore, the nip plate  220  may be heated promptly. As the cylindrical portion  211 A of the halogen lamp  210  (e.g., a central portion of the halogen lamp  210  in the left-right direction) is brought into contact with the main portion  221  of the nip plate  220 , heat from the halogen lamp  210  may be directly transmitted to the main portion  221  of the nip plate  220 . Accordingly, the nip plate  220  may be heated more promptly. Further, as the nip plate  220  holds the halogen lamp  210 , a member of the known fixing device configured to hold the heating element may be unnecessary. Thus, cost reduction may be achieved. 
     Each end of the halogen lamp  210  may be held by the holding portion  224  and  225 . Therefore, the halogen lamp  210  may be stably held by the holding portions  224  and  225 . Heat from the halogen lamp  210  may be transmitted to the main portion  221  of the nip plate  220  from the holding portions  224  and  225 . Therefore, as compared with a case in which, for example, one, holding portion is provided, the nip plate  220  may be heated more promptly. 
     One end of the halogen lamp  210  may be held by the first holding portion  224 . The other end of the halogen lamp  210  may be held by the second holding portion  225  so as to allow the movement of the halogen lamp  210  in the left-right direction. Therefore, thermal expansion of the halogen lamp  210  or the nip plate  220  in the left-right direction may be absorbed or relieved. 
     This disclosure is not limited to the above-described illustrative embodiment, but may be applied to, for example, the following modifications. Like reference numerals denote like corresponding parts and detailed description thereof with respect to the following modifications may be omitted herein. 
     In the above-described illustrative embodiment, the halogen lamp  210  may be held in the top-bottom direction between the second wall portions  224 B and  225 B and the base portion  221 A disposed at a different position from the second wall portions  224 B and  225 B in the left-right direction. However, the disclosure might not be limited thereto. For example, the halogen lamp  210  may be held in an upward direction between the second wall portions  224 B and  225 B and a portion of the main portion  221  of the nip plate  220  disposed at the same position as the second wall portions  224 B and  225 B in the left-right direction, as depicted in, for example,  FIG. 6 . 
     In the structure depicted in  FIG. 6 , the main portion  221  may comprise a base portion  221 A, and extension portions  221 D and  221 E bent upward from each end of the base portion  221 A in the left-right direction and then extending outward in the left-right direction. The extension portions  221 D and  221 E may be formed with the first holding portion  224  and the second holding portion  225 , respectively, similar to the above-described illustrative embodiment. 
     In such a structure, as depicted in  FIGS. 6 and 7 , the left sealed portion  211 B of the halogen lamp  210  may be held in the top-bottom direction between the left extension portion  221 D and the second wall portions  224 B opposing the left extension portion  221 D in the top-bottom direction. The right sealed portion  211 B of the halogen lamp  210  may be held in the top-bottom direction between the right extension portion  221 E and the second wall portions  225 B opposing the right extension portion  221 E in the top-bottom direction. 
     In the structure depicted in  FIG. 6 , the cylindrical portion  211 A of the glass tube  211  (e.g., a central portion of the halogen lamp  210  in its axial direction) and the main portion  221  of the nip plate  220  (e.g., the base portion  221 A) might not have to contact each other as in the above-described illustrative embodiment. A central portion of the halogen lamp  210  in its axial direction may be slightly separated from the nip plate  220 . In this case, the distance between the central portion of the halogen lamp  210  in its axial direction and the nip plate  220  may be preferably within 1 mm, more preferably within 0.5 mm. In other words, the halogen lamp  210  may be spaced apart from the nip plate  220  by at most 1 mm, more preferably at most 0.5 mm. 
     In the above-described illustrative embodiment, the nip plate  220  may be provided with the engagement portions  226  and the engagement opening  227  for engagement with the stay  240 . However, the disclosure might not be limited thereto. For example, as depicted in  FIG. 6 , the nip plate  220  might not have to be provided with a portion for engagement with the stay  240 , as in the above-described illustrative embodiment. 
     In the above-described illustrative embodiment and modification, each holding portion  224  and  225  may comprise two first wall portions  224 A and  225 A and two second wall portion  224 B and  225 B, respectively. However, the disclosure might not be limited thereto. For example, as depicted in  FIG. 8 , each holding portion  224  and  225  may comprise one first wall portion  224 A and  225 A, and one second wall portion  224 B and  225 B, respectively. The structure depicted in  FIG. 8  may be a modification of a portion of the structure depicted in  FIG. 6 . 
     More specifically, in the structure depicted in  FIG. 8 , the first wall portion  224 A of the first holding portion  224  may be disposed at the front end of the left extension portion  221 D (e.g., the upstream end in the rotation direction of the fixing belt  110 ). The second wall portion  224 B may protrude rearward (e.g., toward the downstream side in the rotation direction of the fixing belt  110 ) from the first wall portion  224 A. The first wall portion  225 A of the second holding portion  225  may be disposed at the rear end of the right extension portion  221 E (e.g., the downstream end in the rotation direction of the fixing belt  110 ). The second wall portion  225 B may protrude forward (e.g., toward the upstream side in the rotation direction of the fixing belt  110 ) from the first wall portion  225 A. 
     In this case also, each holding portion  224  and  225  may favorably hold the halogen lamp  210 . The positions of the first holding portion  224  and the second holding portion  225  in the left-right direction might not be limited to those depicted in  FIG. 8  but may be reversed. 
     As depicted in  FIG. 9 , each holding portion  224  and  225  may comprise two first wall portions  224 A and  225 A, respectively. The structure depicted in  FIG. 9  may be a modification of a portion of the structure depicted in  FIG. 6 . 
     More specifically, in the structure depicted in  FIG. 9 , each holding portion  224  and  225  may comprise a pair of the first wall portions  224 A and  225 A, respectively, extending upward from the front and rear ends of each extension portion  221 D and  221 E (e.g., the upstream end and the downstream end in the rotation direction of the fixing belt  110 , respectively). In this structure, the left and right sealed portions  211 B of the halogen lamp  210  may be held between the first wall portions  224 A and  225 A of the holding portions  224  and  225 , respectively. In this case also, each holding portion  224  and  225  may favorably hold the halogen lamp  210 . 
     In the above-described illustrative embodiment and modifications, the nip plate  220  may comprise two holding portions  224  and  225 . However, the disclosure might not be limited thereto. For example, as depicted in  FIGS. 10A and 10B , the nip plate  220  may comprise one holding portion  228  at a central portion thereof in the left-right direction. The structure of  FIGS. 10A and 10B  may be a modification of the structure of  FIG. 4 . 
     More specifically, the holding portion  228  may comprise two first wall portions  228 A similar to the first wall portions  224 A of the above-described illustrative embodiment and two second wall portions  228 B similar to the second wall portions  224 B of the above-described illustrative embodiment. In this structure, the width, in the front-rear direction, of the central portion of the base portion  221 A in the left-right direction may be smaller than that of the other portions of the base portion  221 A. 
     Each first wall portion  228 A may extend upward from the front and rear ends of the central portion of the base portion  221 A having a smaller width. The first wall portions  228 A may be configured to hold the cylindrical portion  211 A of the halogen lamp  210  in the front-rear direction. Each second wall portion  228 B may extend from the upper end of the corresponding first wall portion  228 A so as to come closer to each other. Each second wall portion  228 B may face the central portion of the base portion  221 A in the top-bottom direction. 
     The cylindrical portion  211 A of the halogen lamp  210  may be held between the second wall portions  228 B and the central portion of the base portion  221 A in the top-bottom direction. In such a structure, the holding portion  228  disposed at a central portion of the nip plate  220  may hold the halogen lamp  210  in a balanced manner. 
     In the structure of  FIGS. 10A and 10B , the holding portion  228  might not necessarily comprise the second wall portions  228 B but may comprise, for example, two first wall portions  228 A without the second wall portions  228 B. In this case also, the first wall portions  228 A may hold the halogen lamp  210 . 
     In the above-described illustrative embodiment and modifications, the halogen lamp  210  may be illustrated as an example of the heating element. However, the disclosure might not be limited thereto. For example, the heating element may comprise a carbon heater. 
     In the above-described illustrative embodiment and modifications, the nip plate  220  may be illustrated as an example of the nip member. However, the disclosure might not be limited thereto. The nip member may comprise, for example, a thick member that might not have a plate-like shape. 
     In the above-described illustrative embodiment, the pressure roller  140  may be illustrated as an example of the backup member. However, the disclosure might not be limited thereto. The backup member may comprise, for example, a belt-like pressing member. 
     While the disclosure has been described in detail referring to the specific embodiment thereof, this is merely an example, and various changes, arrangements and modifications may be applied therein without departing from the spirit and scope of the disclosure.