Abstract:
An image fixing apparatus for heating and fixing an unfixed image formed on a recording material, comprising a heater including a substrate, a first electrode provided on one side of the substrate and a second electrode provided on the other side of the substrate; and a connector, connected with the heater, for receiving electric power, the connector including an electrically insulative housing, and a contact terminal provided inside the housing and having first spring contact contacted to the first electrode and a second spring contact contacted to the second electrode, wherein the contact terminal is swingable relative to the housing.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to a fixing apparatus (device) for an image forming apparatus, and a connector for supplying the fixing apparatus (device) with electric power. 
         [0002]    An apparatus having a combination of an endless belt and a ceramic heater which is in contact with the inward surface of the endless belt has been put to practical use as a fixing apparatus for thermally fixing a toner image formed on a sheet of recording medium, to the sheet of recording medium. A ceramic heater used by such an apparatus has a ceramic substrate, a heat generating member, and electrodes which are in electrical connection with the heat generating member. The heater is held by a heater holder made of resin. It is to the electrode(s) of the heater that a connector for supplying the heater with electric power is connected. 
         [0003]    The connector is provided with a terminal (or terminals), which is within the connector. In order to ensure that the terminal of the power supply connector remain satisfactorily connected with the electrodes of the heater, it is necessary for a preset amount of contact pressure to be maintained between the terminal of the power supply connector and the heater electrodes. 
         [0004]    The connector disclosed in Japanese Patent No. 4585668 has a terminal having a pair of spring contacts which sandwich a heater as the connector is engaged with the electrodes of the heater. One of the spring contacts plays the role of an electrical contact which contacts the electrode of the heater, whereas the other (support spring) plays the role of keeping the heater pressed toward the heater holder, with the presence of a spacer between itself and the heater. 
         [0005]    The connector is structured so that the contact pressure between the spring support and the heater (spacer) becomes greater than the contact pressure between the spring contact (as electrical contact) and the electrode. Thus, it does not occur that the heater separates from the heater supporting surface of the heater holder. Therefore, the connector disclosed in the abovementioned Japanese Patent is higher in the level of accuracy, than a conventional connector, in terms of the positional relationship between the electrodes of the heater and the terminal of the connector, which in turn can keep the spring contacts of the connector stable in the amount by which the points of contact of the spring contacts are displaced, or the angle by which they are bent. With the spring contacts being kept stable in the amount by which the points of contact are displaced, or the angle by which the spring contacts are bent, the contact pressure between the spring contacts of the connector, and the electrodes, one for one, of the heater, remain stable at a preset, desired, level. Thus, this connector is suitable as a connector for a fixing device, the heater of which is attached to the heater holding surface of the heater holder so that the heat generating member of the heater faces the heater holding surface. 
         [0006]    However, in a case where the connector disclosed in Japanese Patent No. 4585668 is used as the connector for a heater having a heater or heaters, on both of the primary surfaces of its ceramic substrate (this heater will be referred to as “two-sided heater”, hereafter), it is possible that the contact pressure between one of the spring contacts of the connector terminal and the electrode of the heater on the top surface, for example, of the two-sided heater will become different from the contact pressure between the other spring contact of the connector terminal and the corresponding electrode of the heater. If the contact pressure between one of the spring contacts of the connector terminal and the electrode of the heater on the top surface of the two-sided heater is substantially different from the contact pressure between the other spring contact of the connector terminal and the corresponding electrode, the two-sided heater is subjected to a substantial amount of stress. Thus, in order to prevent the ceramic substrate of the two-sided heater from being broken by the stress, the connector is designed so that it is as small as possible in the amount of the stress which it imparts to the ceramic substrate of the heater. 
         [0007]    Therefore, the two sides of a two-sided heater have to be made the same in the amount of contact pressure between the electrode of the heater and the spring contact of the terminal of the connector for the heater. Further, a connector for a two-sided heater is structured so that when it is engaged with a two-sided heater, its two spring contacts come into contact with the electrodes of the heater, in such a manner that they oppose each other with the presence of the electrode of the two-sided heater between them. Thus, the amount by which the point of contact of each spring contact is displaced when the connector is engaged with the two-sided heater is affected by the thickness of the substrate of the heater. For example, if the substrate of the two-sided heater is reduced in thickness, the amount by which the point of contact of the spring contact of the connector is displaced also reduces. 
         [0008]    Further, if a two-sided heater, the substrate of which is very thin, deviates in position because of the tolerance for heater components, and/or the components related to the heater, the point of contact of the spring contact of the connector sometimes separates from the heater, resulting in unsatisfactory fixation attributable to the interruption of the electric power supply to the heater. In order to prevent the occurrence of this problem, the components related to a heater (two-sided heater in particular) are required to have a high level of accuracy in measurement, which possibly reduces in yield the mass-production of the aforementioned components. 
       SUMMARY OF THE INVENTION 
       [0009]    Thus, the primary object of the present invention, which was made in consideration of the above described issue, is to provide a connector which can engage with the electrode of a heater in such a manner that as the connector is engaged with the electrode of the heater, a preset (proper) amount of contact pressure is generated and maintained between the electrode of a heater and the spring contact of the connector, and also, to provide a fixing apparatus (device) which has such a connector. 
         [0010]    According to an aspect of the present invention, there is provided an image fixing apparatus for heating and fixing an unfixed image formed on a recording material, comprising a heater including a substrate, a first electrode provided on one side of said substrate and a second electrode provided on the other side of the substrate; and a connector, connected with said heater, for receiving electric power, said connector including an electrically insulative housing, and a contact terminal provided inside said housing and having first spring contact contacted to said first electrode and a second spring contact contacted to said second electrode, wherein said contact terminal is swingable relative to said housing. 
         [0011]    According to another aspect of the present invention, there is provided an electrical connector for electric power supply, said connector comprising electrically insulative housing; and a contact terminal provided inside said housing and including a first spring contact for contacting to a first electrode provided on one side of a heater substrate and a second spring contact for contacting to a second electrode provided on the other side of the substrate, wherein said contact terminal is swingable relative to said housing. 
         [0012]    According to a further aspect of the present invention, there is provided an image fixing apparatus for heating and fixing an unfixed image formed on a recording material, comprising a heater including a substrate, and an electrode provided on said substrate; a connector, connected with said heater, for receiving electric power, said connector including an electrically insulative housing, and a contact terminal provided inside said housing and having spring contact contacted to said electrode, a holder holding said heater; wherein said contact terminal is provided, at a position opposing said spring contact, with a projection cooperating with said spring contact to nip said holder, and said contact terminal is swingable with a fulcrum at said projection. 
         [0013]    According to a further aspect of the present invention, there is provided an electrical connector for electric power supply, said connector comprising electrically insulative housing; and a contact terminal provided inside said housing and including a spring contact for contacting to an electrode provided on heater; wherein said contact terminal is provided, at a position opposing said spring contact, with a projection cooperating with said spring contact to nip a holder for holding the heater, and said contact terminal is swingable with a fulcrum at said projection. 
         [0014]    According to a further aspect of the present invention, there is provided an image fixing apparatus for heating and fixing an unfixed image formed on a recording material, comprising a heater including a substrate, and an electrode provided on said substrate; a connector, connected with said heater, for receiving electric power, said connector including an electrically insulative housing, and a contact terminal provided inside said housing and having spring contact contacted to said electrode, wherein a hook shaped portion is provided by two surfaces perpendicular to each other, between the fulcrum of swing and a contact portion of the spring contact contacting to said electrode. 
         [0015]    According to a further aspect of the present invention, there is provided an electrical connector for electric power supply, said connector comprising electrically insulative housing; and a contact terminal provided inside said housing and including a spring contact for contacting to an electrode of a heater; wherein a hook shaped portion is provided by two surfaces perpendicular to each other, between the fulcrum of swing and a contact portion of the spring contact contacting to said electrode. 
         [0016]    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 
         [0017]      FIG. 1  is a schematic sectional view of a typical fixing apparatus to which the present invention is applicable. It shows the general structure of the fixing apparatus. 
           [0018]      FIG. 2  is a perspective view of the heater and heater supporting member, and shows how the heater is supported by the heater supporting member. 
           [0019]      FIG. 3  is a drawing for showing the structure of the heater. 
           [0020]      FIG. 4  is a schematic perspective view of the combination of the heater, heater supporting member, and endless film. It shows how the connector is attached to the combination. 
           [0021]      FIG. 5  is a perspective view of the terminal of the connector in the first embodiment, and shows the structure of the terminal. 
           [0022]      FIG. 6  is a sectional view of the connector, and shows the structure of the connector. 
           [0023]      FIG. 7  is a sectional view of the combination of the connector, heater, and heater supporting member, when the connector is in engagement with the heater and heater supporting member. 
           [0024]      FIG. 8  is a sectional view of the combination of the connector, heater, and heater supporting member (which is different in thickness from the one in  FIG. 7 ) when the connector is in engagement with the heater and heater supporting member. 
           [0025]      FIG. 9  is a schematic sectional view of a typical image forming apparatus which is compatible with the present invention. It shows the structure of the apparatus. 
           [0026]      FIG. 10  is a schematic drawing of the connector in the second embodiment of the present invention, and shows the structure of the connector. 
           [0027]      FIG. 11  is a drawing of the combination of the connector (shown in  FIG. 10 ), heater, and supporting member, when the connector is in engagement with the heater and heater supporting member. 
           [0028]      FIG. 12  is a sectional view of the combination of the connector (shown in  FIG. 10 ), heater, and supporting member, when the connector terminal is tilted relative to the connector housing while being in engagement with the heater and heater supporting member. 
           [0029]      FIG. 13  is a drawing of the combination of the heater and heater supporting member in the third embodiment of the present invention, and shows the structure of the combination. 
           [0030]      FIG. 14  is a sectional view of the combination of the connector, heater, and heater supporting member in the third embodiment the present invention, when the connector is in engagement with the heater and heater supporting member. 
           [0031]      FIG. 15  is a sectional view of the connector in the fourth embodiment of the present invention, and shows the structure of the connector. 
           [0032]      FIG. 16  is a combination of drawings of the heater and heater supporting member, which shows the overall structure of the heater and heater supporting member. 
           [0033]      FIG. 17  is a sectional view of the connector in the fourth embodiment, and shows the structure of the connector. 
           [0034]      FIG. 18  is a sectional view of the combination of the connector, heater, and heater supporting member, in the fourth embodiment, before the terminal of the connector was allowed to come into contact with the electrode of the heater. 
           [0035]      FIG. 19  is a sectional view of the combination of the connector, heater, and heater supporting member, in the fourth embodiment, after the terminal of the connector came into contact with the electrode of the heater. 
           [0036]      FIG. 20  is a sectional view of the connector in the fifth embodiment of the present invention, and shows the structure of the connector. 
           [0037]      FIG. 21  is a sectional view of the connector in the fifth embodiment, when the connector is ready to be engaged with the heater and heater supporting member. It shows the structure of the connector. 
           [0038]      FIG. 22  is a sectional view of the combination of the connector, heater, and heater supporting member, in the fifth embodiment, when the connector is in engagement with the heater and heater supporting member, but the connector terminal is yet to be allowed to come into contact with the heater electrode. It shows the structure of the connector. 
           [0039]      FIG. 23  is a sectional view of the combination of the connector, heater, and heater supporting member, in the fifth embodiment of the present invention, when the connector terminal is in full engagement with the heater electrode. It shows the structure of the connector. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
       [0040]    First, a connector in accordance with the present invention, and a fixing apparatus (device) having this connector, in this embodiment, are concretely described. 
       &lt;Image Forming Apparatus&gt; 
       [0041]    This embodiment is described with reference to an electrophotographic color image forming apparatus having four photosensitive drums.  FIG. 9  is a vertical sectional view of a full-color laser beam printer  22  (which hereafter will be referred to simply as “printer”). It shows the general structure of the printer  22 . 
         [0042]    Referring to  FIG. 9 , the printer  22  is provided with a recording medium feeder cassette  23 , which is removably stored in the bottom portion of the printer  22 . It is also provided with a manual feed tray  24  for manually feeding recording medium into the printer  22 . The tray  24  is on the right side (in  FIG. 9 ) of the printer  22 . The printer  22  is structured so that multiple sheets of recording medium, placed in layers in the recording medium feeder cassette  23 , or on the manual feed tray  22 , are fed one by one into the main assembly of the printer  22  while being separated from the rest. The printer  22  is designed to employ four means for forming a toner image on a sheet of recording medium, more specifically, four cartridges  25   y ,  25   m ,  25   c  and  25   k  for forming yellow, magenta, cyan, and black toner images, respectively. 
         [0043]    The cartridges  25   y ,  25   m ,  25   c  and  25   k  are provided with photosensitive drums  26   y ,  26   m ,  26   c  and  26   k  (as image bearing member), and charging apparatuses (devices)  27   y ,  27   m ,  27   c  and  27   k  for uniformly and negatively charging the photosensitive drums  26   y ,  26   m ,  26   c  and  26   k , respectively. They are also provided with development rollers  28   y ,  28   m ,  28   c  and  28   k , respectively, for adhering toner to an electrostatic latent image to develop the latent image into a toner image, that is, a visible image formed of toner. They are also provided with cleaning blades  29   y ,  29   m ,  29   c  and  29   k  for removing the toner remaining on the peripheral surface of the photosensitive drums  26   y ,  26   m ,  26   c  and  26   k , respectively. 
         [0044]    The printer  22  is also provided with a scanner  30  (scanning unit) and an intermediary transfer unit  31 , which are in the adjacencies of the four cartridges. The scanner  20  forms an electrostatic latent image on the peripheral surface of each photosensitive drum  26  by projecting a beam of laser light upon the peripheral surface of the photosensitive drum  26 , while modulating the beam according to the information of the image to be formed. 
         [0045]    The intermediary transfer unit  31  has four primary transfer rollers  32   y ,  32   m ,  32   c  and  32   k , an intermediary transfer belt  33 , a driver roller  34 , and an idler roller  35 . It forms a unit by being combined with a cleaning device  36  for removing the transfer residual toner remaining on the intermediary transfer belt  33 . The intermediary transfer belt  33  is an endless (cylindrical) belt, and is suspended by the driver roller  34  and idler roller  35 . The idler roller  35  is grounded. It is kept pressured by an unshown pressure applying means in the direction indicated by an arrow mark d in  FIG. 9 , providing thereby the intermediary transfer belt  33  with a preset amount of tension. 
         [0046]    As the driver roller  34  is rotationally driven by an unshown motor or the like, the intermediary transfer belt  33  is circularly moved in the direction indicated by an arrow mark e in  FIG. 9 , at a preset speed. As for the primary transfer, positive voltage (bias) is applied to the primary transfer rollers  32   y ,  32   m ,  32   c  and  32   k  to use the difference in potential level between the positive voltage applied to the primary transfer rollers and the negatively charged peripheral surface of the photosensitive drums  26   y ,  26   m ,  26   c  and  26   k.    
         [0047]    After the transfer (primary transfer) of the toner images from the photosensitive drums  26  onto the intermediary transfer belt  33 , in the nips formed between the primary transfer roller  32  and photosensitive drums  26 , the toner images on the intermediary transfer belt  33  are transferred onto a sheet of recording medium, in the secondary transfer station  37 . Then, the sheet of recording medium, on which the toner images have just been borne, is processed by the fixing device  1 ; the toner images are fixed to the sheet of recording medium. Designated by a referential code  28  is a flapper for switching the direction in which a sheet of recording medium is to be conveyed after the fixation of the toner images on the sheet of recording medium. More specifically, the flapper  38  guides the sheet of recording medium toward a pair of discharge rollers  39 , or to a switchback roller  40 . As the sheet S of recording medium is guided toward the switchback roller  40 , it is conveyed backward by the switchback roller  40 , being thereby conveyed through the secondary transfer station  37  and fixing device  1 , and then, is guided toward the discharge rollers  39 . Then, it is discharged into a delivery tray  41  by the discharge rollers  39  (through nip between two rollers  39 ). 
       &lt;Fixing Apparatus (Device)&gt; 
       [0048]    Next, referring to  FIG. 1 , the fixing device  1  which is employed by an image forming apparatus such as a laser beam printer is described regarding its structure.  FIG. 1  is a sectional view of the fixing device  1  in this embodiment. The fixing device  1  has a heating unit  2 , a pressure roller  3 , a sheet conveyance roller  4 , a sheet guide  18 , a housing  19 , etc. There is a fixation nip  20  between the heating unit  2  and pressure roller  3 . After the transfer of the toner images onto a sheet of recording medium, the sheet S is conveyed through the fixation nip  20  while remaining pinched between the heating unit  2  and pressure roller  3 . 
         [0049]    The heating unit  2  has a cylindrical film (endless belt), a heater  5 , and a heater supporting member  6  (heater holder) which supports the heater  5 . Referring to  FIG. 3 , the heater  5  has a pair of heat generating members  8   a  and  8   b , which are provided on the front and rear surfaces, one for one, of the dielectric substrate  9 . The heating unit  2  has also a pair of electrodes  10   a ,  10   b , which are positioned at the lengthwise end portions ( FIG. 3(   b ) of one of the primary surfaces of the substrate  9 , one for one, and a pair of electrodes  10   c  and  10   d , which are positioned at the lengthwise end portions ( FIG. 3(   c )) of the other primary surface of the substrate  9 , one for one. 
         [0050]    The heat generating members  8   a  and  8   b , which are on the front and rear surfaces, one for one, of the substrate  9 , are different in dimension in terms of the lengthwise direction (left and right directions in  FIGS. 3(   b ) and  3  ( c )). The length of each of the heat generating members  8   a  and  8   b  is set according to the size (width) of a sheet S of recording medium to be conveyed through the fixation nip  20  of the fixing device  1 . 
         [0051]    The layout of the electrodes  10   a - 10   d  is as follows. 
         [0052]    The electrodes  10   b  and  10   d  provided on the front and rear surfaces, one for one, at the same lengthwise end portions (right end portion in  FIGS. 3(   b ) and  3 ( c )) of the substrate  9 , are positioned so that they overlap with each other in terms of the lengthwise direction of the substrate  9  (as seen from direction perpendicular to substrate  9 ). Further, the electrodes  10   a  and  10   c  which are provided on the front and rear surfaces, one for one, at the same lengthwise end portions (left end portion in  FIGS. 3(   b ) and  3 ( c )) of the substrate  9 , and through which the heat generating members are supplied with electric power, are positioned so that they do not overlap with each other in terms of the lengthwise direction of the substrate  9  (as seen from direction perpendicular to substrate  9 ). 
         [0053]    It is to the electrodes of the heater  5  that the connector for supplying the heater with electric power is connected. More specifically, it is to the electrodes  10   b  and  10   d  that the connector  13  having two spring contacts, which correspond to electrodes  10   b  and  10   d , one for one, is connected.  FIGS. 4-8  are drawings for showing the structure of this connector  13 . It is also to the electrodes  10   a  and  10   c  that the connector  13  is connected. That is, in this embodiment, three connectors  13  are used. One of the two spring contacts in the connector to be connected to the electrode  10   a  contacts the portion of the heater substrate  9 , which does not have an electrode. Therefore, it does not play a role of supplying the heater  5  with electric power. This is true with the connector that is to be connected to the electrode  10   c . A connector, both of the two spring contacts of which contact the electrode of the heater  5 , is the connector  13  having the two spring contacts which contact the electrodes  10   b  and  10   d , one for one, of the heater  5 . Next, the structure of the connector  13  is described with reference to the connector  13 , which is to be connected to the electrodes  10   b  and  10   d.    
         [0054]    The connector  13  is made up of a dielectric housing  15 , and a terminal  14  (shown in  FIGS. 5-8 ) fitted in the housing  15 . Referring to  FIG. 7 , as the connector  13  is attached to the combination of the heater  5  and heater supporting member, a pair of spring contacts  16   a  and  16   b  of the terminal  14  come into contact with, and press on, the electrodes  10   b  and  10   d , respectively, generating thereby a preset amount of contact pressure between the spring contacts  16  and  16   b  and the electrodes  10   b , and  10   d , respectively. Consequently, electrical connection is established between the electric power source and the heat generating members. Then, as the connector terminal  14  is provided with electric power through a lead  21 , from the unshown electric power source, both, or one of, the two heat generating member  8   a  and  8   b  generates heat. That is, the fixing device  1  in this embodiment is structured so that the heat generating members  8   a  and  8   b  can be independently driven from each other. Therefore, such a control as adjusting the heat generation amount distribution of the heater  5  according to recording medium sheet size can be carried out. 
         [0055]    The heating unit  2  is kept pressed against the pressure roller  3  by an unshown pressure applying means, whereby the film  7  and pressure roller  3  are kept pressed upon each other. The pressure roller  3  rotates by being driven by an unshown external mechanical power source. The film  7  is rotated by the rotation of the pressure roller  3 . 
         [0056]    A sheet S of recording medium by which an unfixed toner image formed in the unshown image formation station of the image forming apparatus is conveyed to, and then through, the fixation nip  20 , which is the area of contact between the heating unit  2  and pressure roller  3 . As the sheet S is conveyed through the fixation nip  20 , the toner in the unfixed toner image is fixed (permanently adhered) to the sheet S by the heat and pressure in the fixation nip  20 . Thereafter, the sheet S which is bearing the fixed toner image is discharged into an unshown delivery area by a pair of sheet conveyance rollers  4 . 
       &lt;Heating Unit&gt; 
       [0057]    Next, referring to  FIGS. 1-4 , the heating unit  2  in this embodiment is described regarding its structure. 
         [0058]    First, referring to  FIG. 3 , the structure of the heater  5  is described.  FIG. 3(   a ) is a sectional view of the heater  5 .  FIG. 3(   b ) is a plan view of the heater  5  as seen from the direction indicated by an arrow mark b in  FIG. 3(   a ). It shows the surface of the heater  5 , on which the heat generating member  8   a  is present.  FIG. 3(   c ) is a plan view of the heater  5  as seen from the direction indicated by an arrow mark c in  FIG. 3(   a ). It shows the surface of the heater  5 , on which the heat generating member  8   b  is present. 
         [0059]    The heater  5  has the dielectric substrate  9  made of ceramic material. It has also the heat generating members  8   a  and  8   b , which are on the front and rear surfaces, respectively, of the substrate  9 . Further, it has electrodes  10   a - 10   d  which the pair of spring contacts  16   a  and  16   b  of the connector terminal  14  contact, as shown in  FIG. 7 . It has also leads  11  which provide electrical connection between the electrodes  10   a - 10   d  and the pair of heat generating members  8   a  and  8   b . Further, it has a protective layer  12  for protecting the heat generating members  8   a  and  8   b  and the leads  11 . The protective layer  12  is formed of glass or the like substance, and is placed on both of the front and rear surfaces of the substrate  9  to cover the heat generating members  8   a  and  8   b  and the leads  11 , except for the electrodes  10   a - 10   d ; the electrodes  10   a - 10   d  are exposed. 
         [0060]    The heat generating members  8   a  and  8   b  are made different in dimension in terms of the lengthwise direction (left and right directions in  FIGS. 3(   a ) and  3 ( b )), in order to enable the fixing device  1  to accommodate various sheets of recording medium which are different in size. 
         [0061]    Next, referring to  FIGS. 4-7 , electric power is supplied to the power reception terminal  14   a  of the terminal  14  of the connector  13  through a cable  21  which is in connection to the power reception terminal  14   a . As the electric power is supplied, electric current flows through the heat generating members  8   a  and  8   b  through the pair of spring contacts  16   a  and  16   b  of the terminal  14 , electrodes  10   a - 10   d , and leads  11 . Thus, heat is generated in the heat generating members  8   a  and  8   b  (Joule&#39;s law). 
         [0062]    That is, the heat generating members  8   a  and  8   b  generate heat by the amounts proportional to the supplied amount of electric power. Thus, the amount by which heat is generated by the heater  5  can be controlled by deciding whether both or only one of the two heat generating members  8   a  and  8   b  is to be supplied with electric power. 
       &lt;Attachment of Connector&gt; 
       [0063]    Next, referring to  FIGS. 2 and 4 , how the connector  13  is attached to the heating unit  2  is described.  FIG. 2  shows how the heater  5  is supported by the heater supporting member  6  (heater holder).  FIG. 2(   b ) shows the overall structure of the combination of the heater  5  and heater supporting member  6 .  FIG. 2(   b ) is a perspective view of one of the lengthwise end portions of the combination, as seen from the side on which the heater  5  contacts the film  7 .  FIG. 2(   c ) is a perspective view of the same portion of the combination, as seen from the opposite side from the side on which the heater  5  contacts the film  7 . 
         [0064]    The heater supporting member  6  is provided with a groove  6   a  which extends in the lengthwise direction (left and right directions in  FIG. 2(   a )) of the heater supporting member  6 , and in which the heater  5  is held. It supports the cylindrical film  7  (shown in  FIG. 1) , in such a manner that the film  7  can be circularly moved while sliding on the film supporting surface of the heater supporting member  6 . In other words, the heater supporting member  6  controls the film  7  in position in the fixation nip  20 . 
         [0065]    Referring to  FIGS. 2(   a )- 2 ( c ), the heater supporting member  6  has a slot  6   b , through which the electrodes  10   a  and  10   c  are exposed.  FIG. 4  shows how the connector  13  is to be connected to the heater  5 . The connector  13  is attached to the heater supporting member  6  by being moved to one of the lengthwise end portions of the heater supporting member  6 , which is on the outward side of the film  7  in terms of the widthwise direction of the film  7 , in the direction indicated by an arrow mark a in  FIG. 4 . 
       &lt;Structure of Connector&gt; 
       [0066]    Next, referring to  FIGS. 5 and 6 , the structure of the connector  13  is described.  FIG. 5  is a perspective view of the terminal  14  of the connector  13 . It shows the structure of the terminal  14 .  FIG. 6  is a sectional view of the connector  13  made up of the housing  15  and the terminal  14  inserted in the housing  15  in such a manner that it is allowed to move in the direction perpendicular to the front and rear surfaces of the heater  5  (vertical direction in  FIG. 6 ). It also shows the structure of the connector  13 . 
         [0067]    Referring to  FIG. 6 , the connector  13  is made up of the housing  15  which is roughly U-shaped in cross section, as seen from the direction perpendicular to the direction in which the connector  13  is attached to the heater  5  (heater supporting member  6 ), and the terminal  14  which also is roughly U-shaped in cross section. More specifically, the lateral walls of the housing  15 , and the lateral walls of the terminal  14 , in terms of the direction in which the connector  13  is attached to the heater supporting member  6 , are provided with a slot of a preset size. The terminal  14  is positioned in the housing  15  in such a manner that it is allowed to move within the housing  15 . The terminal  14  is made of an electrically conductive substance such as stainless steel or titanium alloy, and is plated. The housing  15  is made of dielectric substance such as resin. 
         [0068]    The connector terminal  14  is provided with the pair of spring contacts  16   a  and  16   b , which press on the pair of electrodes on the front and rear surfaces, one for one, of the heater  5 , so that a preset amount of contact pressure is generated, and maintained, between the spring contacts  16   a  and  16   b  and the corresponding electrodes of the heater  5 . The two spring contacts  16   a  and  16   b  are the same in shape, and are symmetrically positioned with reference to a plane which is parallel to the front and rear surfaces of the housing  15  and coincides with the center of the housing  15  in terms of the direction perpendicular to the front and rear surfaces of the housing  15 . Referring again to  FIG. 6 , the connector  13  (terminal  14 ) is structured so that when the electrode portion of the heater  5  is not in the space of the connector terminal  14 , which corresponds in position to the aforementioned slot of the lateral wall of the terminal  14 , there is a preset amount of gap  16   c  between the pair of spring contacts  16   a  and  16   b  of the connector terminal  14 . 
         [0069]    The housing  15  of the connector  13  is structured so that there is a space  15   b , which is U-shaped in cross section and allows the connector terminal  14  to perpendicularly (vertical direction in  FIG. 6 ) move relative to the front and rear surfaces of the housing  15 . 
         [0070]    The connector terminal  14  is fitted into the housing  15  by being inserted into the housing  15  from an unshown opening of the housing  15 , which is on the opposite side (right side in  FIG. 6 ) of the housing  15  from the space  15   b . The inward surface of the housing  15  is provided with a pair of projections  17  for preventing the connector terminal  14  from becoming disengaged from the housing  15 . Thus, as the connector terminal  14  is inserted into the housing  15  to a preset position, the vertical portion  14   c  (in  FIG. 6 ) of the connector terminal  14  engages with the projections  17 , preventing thereby the terminal  14  from coming out of the housing  15 . The projections  17  also play a role of controlling the connector terminal  14  in position relative to the housing  15  after the connector  13  is properly attached to the heater supporting member  6 . 
         [0071]    Referring to  FIG. 6 , the housing  15  and terminal  14  of the connector  13  are structured so that after the insertion of the terminal  14  into the housing  15 , there are clearances A between the top portion of the housing  15  and top portion of the connector terminal  14 , and also, between the bottom portion of the housing  15  and bottom portion of the connector terminal  14 , in terms of the direction (vertical direction in  FIG. 6 ) perpendicular to the front and rear surfaces of the heater  5 . In this embodiment, the inward surface of the housing  15  has two projections  17 , which are different in position. Thus, the terminal  14  is retained in the housing  15  in such a manner that the vertical portion  14   c  of the terminal  14  is regulated in position, in terms of the direction in which the connector  13  is moved to be engaged with the heater supporting member  6 , by the bottom wall  15   c  of the recess  15   a  (vertical portion of edge of recess  15   a  in  FIG. 6 ), and the projections  17 , while being allowed to move in the vertical direction in  FIGS. 6-8 . 
         [0072]    The connector  13  and its terminal  14  are structured so that as the terminal  14  is inserted into the housing  15  of the connector  13 , the spring contacts  16   a  and  16   b  oppose each other in the vertical direction in  FIGS. 6-8 . Further, they are structured so that when the connector  13  is not in engagement with the heater  5 , a preset amount of gap  16   c  is provided between the spring contacts  16   a  and  16   b , as shown in  FIG. 6 , in order to prevent the surface plating of the spring contacts  16   a  and  16   b  from being peeled away. 
         [0073]      FIGS. 7 and 8  are sectional views of the connector  13  when the connector  13  is in connection to the heater  5 . They are different in the thickness of the heater seat portion of the heater supporting member  6 , which is attributable to the dimensional tolerance for the heater supporting member  6  (thickness in  FIG. 7  is B 1 , whereas thickness in  FIG. 8  is B 2 ). 
         [0074]    As the connector  13  is connected to the heater  5 , the housing  15  of the connector  13  sandwiches the heater supporting member  6 , whereas the pair of spring contacts  16   a  and  16   b  of the connector terminal  14  come into contact with the electrodes  10   d  and  10   b , respectively, of the heater  5 , in the housing  15 , so that the heat generating members  8   a  and  8   b  can be supplied with electric power. 
         [0075]    That is, as the connector  13  engages with the heater supporting member  6  on which the heater  5  is held, the housing  15  engages with the heater supporting member  6 . The spring contacts  16   a  and  16   b  come into contact with the electrodes  10   d  and  10   b  on the front and rear surfaces, one for one, of the heater  5 , in such a manner that a preset amount of contact pressure is generated and maintained between the spring contacts  16   a  and  16   b , and the electrodes  10   d  and  10   c , respectively. 
         [0076]    Next, referring to  FIG. 8 , it is assumed here that because of the dimensional tolerance for the components of the heating unit  2  and connectors  13 , the components are not perfectly accurate in dimension. For example, it is assumed that because of the errors in the dimension of the abovementioned components, the gap B 2 , between the bottom surface of the groove  6   a , and the actual heater supporting portion  6   c  of the heater supporting member  6 , shown in  FIG. 8 , is larger than the gap B 1  between the bottom surface of the groove  6   a , and the actual heater supporting portion  6   c  of the heater supporting member  6 , shown in  FIG. 7 . 
         [0077]    In such a case, the position of the heater  5  relative to the housing  15  in terms of the vertical direction in  FIG. 8  is different from that in  FIG. 7 . If the heater position relative to the housing  15  of the connector  13  is different from the position in the specification, the contact pressure between the heater electrode and the spring contact becomes different from that in the specification. In this embodiment, however, the connector  13  is structured so that its terminal  14  is allowed to freely move in the vertical direction in  FIG. 8 , within the internal space of the housing  15 , and also, that the pair of spring contacts  16   a  and  16   b  of the connector terminal  14  are the same in shape and are symmetrically positioned relative to each other. 
         [0078]    Therefore, the connector terminal  14  moves in the vertical direction in  FIG. 8  according to the vertical dimension of the heater  5  in  FIG. 8 . In  FIG. 7 , the clearance between the housing  15  and terminal  14  is A, which is in a range of 0.3 mm-1.5 mm (0.3 mm≦A≦1.5 mm), whereas in  FIG. 8 , the clearances between the housing  15  and terminal  14  are A 1  or A 2 , indicating that the connector terminal  14  has moved. Therefore, the contact pressure between the pair of spring contacts  16   a  and  16   b , and the electrodes  10   b  and  10   d , respectively, in  FIG. 8  remains roughly the same as that in  FIG. 7 , despite the deviation in the component dimension. Therefore, the heater  5  is not subjected to an excessive amount of stress. In other words, this embodiment ensures that as the connector  13  is engaged with the heater supporting member  6 , the spring contacts  16   a  and  16   b  come into, and remain in, contact with the electrodes  10   d  and  10   b , in such a manner that a preset amount (proper amount) of contact pressure is generated and maintained between the spring contacts of the terminal  14  and the electrodes of the heater  5 , one for one, without requiring that the components of the heater  5 , heater supporting member  6 , and connector  13  are highly accurate in measurement. 
         [0079]    Next, the connector in the second embodiment, and the connector in the third embodiment, are described. The only difference in the second and third embodiments from the first embodiment is in the shape of the connectors. Therefore, the second and third embodiments are described regarding the difference of their connectors from the connector  13  in the first embodiment. In the following description of the second and third embodiment, the heater, heater holder, and electrodes (on both surfaces of heater substrate, one for one), are referred to as heater  100 , heater holder  106 , and electrodes  103   d  and  103   e.    
       Embodiment 2 
       [0080]      FIG. 10(   a ) is a side view of the terminal  120  of the connector  110 , and shows the structure of the terminal  120 .  FIG. 10(   b ) is a sectional view of the connector terminal  120 .  FIG. 10(   c ) is a perspective view of the connector terminal  120 , and shows the structure of the terminal  120 .  FIG. 10(   d ) is a sectional view of the connector  110 , and shows the structure of the connector  110 . Referring to  FIG. 10(   d ), the connector  110  is provided with a housing  111 , and a terminal  120  having a pair of spring contacts  121  and a pair of protrusions  122 . 
         [0081]    Referring to  FIGS. 10(   a )- 10 ( d ), the housing  111  is structured so that it appears roughly U-shaped in cross section. It has an opening  111 X, which may be referred to as the “first opening”, hereafter. The connector terminal  120  also is structured so that it appears roughly U-shaped in cross section; it has a pair of roughly U-shaped lateral walls having a slot  120 X which may be referred to as the “second opening”, hereafter. The connector  110  is structured so that the connector terminal  120  is allowed to change in attitude even after the insertion of the connector terminal  120  into the housing  111 . Further, the connector terminal  120  is provided with a pair of spring contacts  121 , and a pair of protrusions  122 . Further, the connector  110  and its terminal  120  are structured so that when the connector terminal  120  is properly situated in the housing  111 , the openings  120 X and  111 X are in alignment with each other in terms of the direction in which the connector terminal  120  is inserted into the housing  111 . 
         [0082]    The pair of spring contacts  121  extend toward each other from the top and bottom sides of the slot  120 X. That is, the first spring contact  121  (top spring contact in  FIG. 11 ), which is one of the pair of spring contacts  121 , extends diagonally downward from the top side of the slot  120 X, whereas the second spring contact (bottom spring contact in  FIG. 11 ), which is the other of the pair of spring contacts  121 , extends diagonally upward from the bottom side of the slot  120 X. The pair of spring contacts  121  are springy. Thus, as the spring contacts  121  are subjected to load, they resiliently bend. The point  125  of contact of one of the spring contacts  121 , and the point  125  of contact of the other of the spring contacts  121 , come into contact with the electrodes  103   e  and  103   d , respectively, of the heater  100 . The portion of each spring contact  121 , by which the spring contact  121  contacts the corresponding electrode  103  is shaped so that it appears semicircular in cross section. This semicircularly curved portion of the spring contact  121   c  serves as the actual point  125  of contact. 
         [0083]    The pair of protrusions  122  protrude toward each other from the top and bottom edges of each slot  120 X of the connector terminal  120 , so that each protrusion  122  coincides in position with the point  125  of contact of the corresponding spring contact  121 . More specifically, the first protrusion  122  (bottom protrusion in  FIGS. 11(   a ) and  11 ( b )), which is one of the pair of protrusions  122 , coincides in position with the point  125  of contact of the first spring contact  121 . It is shaped so that it protrudes upward from the bottom edge of the slot  120 X, whereas the second protrusion  122  (top protrusion in  FIGS. 11(   a ) and  11 ( b )) coincides in position with the point  125  of contact of the second spring contact  121 , and is shaped so that it protrudes downward from the top edge of the slot  120 X. Unlike the spring contacts  121 , the protrusions  122  are not elastic. Further, each protrusion  121  is shaped so that its area of contact is semicircular in cross section. As described above, the bottom protrusion  122  (top protrusion  122 ) which supports (backs up) the object (heater) to be supported (backed up), is on the bottom edge of the slot  120 X of each of the lateral walls of the connector terminal  120 . It coincides in position with the point  125  of contact of the top (bottom) spring contact  120 . 
         [0084]    The connector terminal  120  is roughly U-shaped in cross section. It is made of stainless steel, titanium alloy, or the like substance, and is plated. It is provided with the pair of spring contacts  121 , which are on the top and bottom sides, one for one, of the slot  120 X. Each spring contact  121  has the point  125  of contact, which is the actual portion of the spring contact  121 , by which the spring contact  121  presses upon one of the electrodes of the heater  100 . The connector terminal  120  is provided with four protrusions  122  (which contact heater  100 ), which coincide with a vertical plane P (in  FIG. 10 ) which coincides with the point  125  of contact of the top spring contact  121  and the point  125  of contact of the bottom spring contact  121 . Therefore, the distance from the entrance of the slot  120 X (right end in  FIG. 10(   a )) to the top protrusion  122  (top protrusion  122 ) is roughly the same as the distance from the entrance of the slot  120 X to the point  125  of contact of the top spring contact  121  (point  125  of contact of bottom spring contact  121 ). 
         [0085]    Further, the end portion of the connector terminal  120 , which is on the opposite side of the connector terminal  120  from the slot  120 X, is connected to a bundle  123  of fine wires, so that voltage can be applied to the connector terminal  120  through the bundle  123  of fine wires. As described above, the connector  110  is made up of the housing  111 , and the connector terminal  120  fitted in the housing  111 . The housing  111  is roughly U-shaped in cross section like the lateral walls of the connector terminal  120  of the connector  110 . The housing  111  is provided with a pair of retainers  112 , which prevent the connector terminal  120  from coming out of the housing  111  after the insertion of the terminal  120  into the housing  111  from the opposite side of the housing  111  from the opening  111 X of the housing  111 . Further, the connector  110  is structured so that after the proper insertion of the connector terminal  120  into the housing  111 , there is a clearance A between the connector terminal  120  and housing  111 . 
         [0086]      FIG. 11(   a ) is a sectional view of the combination of the connector  110  and heater  100  after the connection of the connector  110  to the heater  100 .  FIG. 11(   b ) is a sectional view of the combination of the connector  110  and heater  100 , at the plane P-P in  FIG. 11(   a ), after the connection of the connector  110  to the heater  100 .  FIG. 11(   c ) is a side view of the connector  110  after its engagement with the heater supporting member  106 . It shows the structure of the connector  110 . Referring to  FIG. 11(   a ), when the connector  110  is in connection with the heater  100 , the supporting member  106  which supports the heater  100  is in contact with the edges of the slot  120 X of the connector terminal  120 . 
         [0087]    As the connector  110  is engaged with the supporting member  106  which is supporting the heater  100 , the supporting member  106  comes into contact with the vertical edge  124  (in  FIG. 11 ) of the slot  120 X of the terminal  120  of the connector  110 . Further, the point  125  of contact of the top spring contact  121 , and the point  125  of contact of the bottom spring contact  121  come into contact with the top and bottom electrodes  103   e  and  103   d  of the heater  100 , generating a preset amount of contact pressure between themselves and the corresponding electrodes  103   e  and  103   d , respectively. Further, the top and bottom protrusions  122  of the connector terminal  120  come into contact with the heater supporting member  106 , at the plane P which coincides in position with the top and bottom points  125  of contact. 
         [0088]    More specifically, as the connector  110  is engaged with the supporting member  106  on which the heater  100  is present, each protrusion  122  comes into contact with the supporting member  106  at the same time as the corresponding point  125  of contact of the spring contact  121  comes into contact with the electrode of the heater  100 . 
         [0089]    In this case, the first spring contact  121  presses on the first electrode  103   e  from the top side of the heater  100 , and the first protrusion  122  comes into contact with the supporting member  106  from the bottom side of the supporting member  106 . Further, the second spring contact  121  presses on the second electrode  103   d  from the bottom side of the second electrode  103   d , and the second protrusion  122  comes into contact with the supporting member  106  from the top side of the supporting member  106 . Consequently, the supporting member  106  is sandwiched by the first and section protrusions  122 . 
         [0090]      FIG. 12  is a sectional view of the combination of the connector  110  and heater  100  after the connector terminal  120  has tilted in the housing  111 . As is evident from  FIG. 12 , in a case where the connector terminal  120  is subjected to an external force F (downward force in  FIG. 12 ), such as the reactive force which generates as the bundle  123  of fine wires attached to the aforementioned end of the connector terminal  120  is moved, the connector terminal  120  is allowed to pivotally move about the point of contact of the protrusion  122  in an oscillatory manner, within the housing  111 . However, the point of contact between the connector terminal  120  and the supporting member  016 , on which the heater  106  is held, coincides with the plane P which coincides with the point  125  of contact of the spring contact  121 . Therefore, the connector terminal  120  is allowed to pivotally move about the adjacencies of the point  125  of contact, without being twisted and/or bent. 
         [0091]    Therefore, there is virtually no change in the position of the point  125  of contact of the spring contact  121 . Therefore, there occurs no change in the amount of the contact pressure between the point  125  of contact of the spring contact  121  and the corresponding electrode of the heater  100 . Therefore, it does not occur that as the connector terminal  120  becomes tilted, the point  125  of contact of the spring contact  121  becomes separated from the electrode of the heater  100 . Incidentally, even if the connector  110  is structured so that the protrusion  122  directly contacts the heater  100 , instead of the supporting member  106 , in the plane P which coincides with the point  125  of contact, the effect of the present invention is the same as the above described one. 
       Embodiment 3 
       [0092]      FIG. 13(   a ) is a perspective view of the combination of the heater  140  to which the connector  210  is attached, and the supporting member  106  for supporting the heater  140 , in the third embodiment. It shows the structure of the combination.  FIG. 13(   b ) is a perspective view of one of the lengthwise end portions of the combination of the heater  140  and supporting member  106 , as seen from the side on which the supporting member  106  contacts the film  33 . It shows the structure of the lengthwise end.  FIG. 13(   c ) is a perspective view of one of the lengthwise end portions of the supporting member  106 , as seen from the side on which the supporting member  106  is supported. It shows the structure of the lengthwise end portion. The components of the connector  210 , heater  140 , and heater supporting member  106 , which are the same in structure and effect as the counterparts in the second embodiment, are given the same referential codes as those given to their counterparts in the second embodiment, and are not described here. The difference between the third embodiment and second embodiment of the present invention, in terms of the structure of the connector, heater, and heater supporting member, is as follows: 
         [0093]    The connector in the second embodiment was for a two-sided heater, that is, a heater having a heat generating member on both the top and bottom surface of its substrate. In comparison, the connector in this embodiment is for a one-sided heater  140 , that is, a heater having a heat generating member  102  and an electrode  103  for the heat generating member  102 , on only one of the top and bottom surfaces of its substrate. First, how the one-sided heater  140  is supported by the supporting member  106  is described with reference to  FIG. 13 . 
         [0094]    Referring to  FIG. 13(   a ), the supporting member  106  supports the one-sided heater  140 . Next, referring to  FIG. 13(   b ), the supporting member  106  is provided with a groove  106 A which extends in the lengthwise direction of the supporting member  106 . The one-sided heater  140  is held in this groove  106 A. The supporting member  106  regulates the film  33  in position as the film  33  is circularly moved. The supporting member  106  is provided with a spacer  132 , which is placed on the same surface of the supporting member  106  as the one which the heat generating member  106  is placed. Referring to  FIG. 13(   c ), the supporting member  106  is provided with a hole  107 , through which the electrode  103  is exposed. However, the heating unit may be structured so that both the heat generating member  102  and electrode  103  are on one of the primary surfaces of the supporting member  106 , and the spacer  132  is on the other primary surface, that is, the opposite surface from the surface on which the heat generating member  102  and electrode  103  are placed. 
         [0095]      FIG. 14(   a ) is a sectional view of the combination of the connector  210  and the one-sided heater  140  after the engagement of the connector  210  with the heater  140 . 
         [0096]    The spring contact  121  extends diagonally downward from the top side of the slot  220 X. To describe in detail, the base portion of the spring contact  121  is a part of the top wall of the connector terminal  220 , and extends diagonally downward into the space of the terminal  220 , which corresponds in position to the slot  220 X so that the point  125  of contact of the terminal  220  coincides in position with the slot  220 X. Thus, as the connector  210  is attached to the heating unit, the point  125  of contact of the spring contact  121  comes into contact with the electrode  103  of the one-sided heater  140 . 
         [0097]    One of the protrusions  122  protrudes upward from the bottom edge of the slot  220 X, toward the point  125  of contact of the spring contact  121 . Thus, as the connector  210  is engaged with the heating unit, the protrusion  122  comes into contact with the spacer  132  attached to the supporting member  106 , and the spring contact  121  comes into contact, from above, with the electrode  103  exposed through the hole  107 , and presses on the electrode  103  so that a preset amount of contact pressure is generated and maintained between the point  125  of the spring contact  121  and electrode  103 . 
         [0098]    Since the connector  210  and heating unit in this embodiment are structured as described above, the contact pressure between the point  125  of contact (which opposes bottom protrusion  122 ) and electrode  103  of the heater  140  does not reduce from the initial amount (preset amount), even if the connector  120  is subjected to an external force. Further, even if the terminal  220  is moved by an external force in the opposite direction, all that happens is that the connector terminal  120  pivotally moves about the adjacencies of the protrusion  122  in an oscillatory manner. Therefore, the contact pressure between the point  125  of contact and the electrode  103  does not change. 
         [0099]      FIG. 14(   b ) is a sectional view of one of the modified versions of the connector  210  in the third embodiment of the present invention. Referring to  FIG. 14(   b ), the connector terminal  320 , or the modified version of the terminal  220  of the connector  210  in the third embodiment, is structured so that it appears roughly U-shaped in cross section. It has a pair of protrusions  122  which protrude from the top and bottom edges of the slot  320 X, one for one, and which contact the supporting member  106  from the top and bottom sides, respectively. 
         [0100]    To describe in detail, the connector terminal  320  is provided with not only the protrusion  122  which protrudes upward from the bottom edge of the slot  320 X, but also, the protrusion  122  which protrudes downward from the top edge of the slot  320 X. The connector terminal  320  is structured so that the two protrusions  122  squarely oppose each other. Further, the connector terminal  320  is provided with a spring contact  121  having a point  125  of contact. The point  125  of contact comes into contact with the electrode  103  of the one-sided heater  140  in such a manner that a preset amount of contact pressure is generated and maintained between itself and the electrode  103 , as the connector  310  is engaged with the heater  140 . The position of the point  125  of contact coincides with the plane P which coincides in position with the top and bottom protrusions  122 . Thus, as the connector  310  is engaged with the heater  140 , the supporting member  106  by which the one-sided heater  140  is supported comes into contact with the bottom edge  124  of the slot  320 X, and the point  125  of contact of the spring contact  121  comes into contact with the electrode  103 , generating a preset amount of contact pressure between itself and the electrode  103 . Further, the protrusions  122  come into contact with the supporting member  106 . 
         [0101]    Since the modified version  310  of the connector terminal  320  in the third embodiment is structured as described above, if the connector terminal  320  is subjected to an external force such as the reactive force which occurs as the bundle  123  of fine wires attached to the connector terminal  320  is moved, all that occurs is that the connector terminal  320  pivotally moves about the adjacencies of the protrusions  122 , within the housing  111 . Therefore, the contact pressure between the point  125  of contact (which coincides with plane P which coincide with protrusion  122 ) and the electrode  103  does not change. 
         [0102]    The combinations of connector, heater, and supporting member in the first and second embodiment, and the modified version of the combination in the third embodiment, are structured as described above. Therefore, even if the contact terminals are changed in attitude in the housing by an external force, a preset amount (proper amount) of contact pressure is maintained between the spring contact and heater electrode. That is, even if the connector terminal is forced to change in attitude in the housing, by an external force, the terminal pivotally moves about the protrusion, within the housing in an oscillatory manner. Therefore, it is ensured that the preset amount (proper amount) of contact pressure is maintained between the spring contact and heater electrode. 
         [0103]    Next, the fourth and fifth embodiments of the present invention are described regarding the connector. The fourth and fifth embodiments are different from the preceding embodiments only in the shape of the connector. Therefore, their description will concentrate on the difference between the connectors in the fourth and fifth embodiments, and the connectors in the preceding embodiments. 
       Embodiment 4 
       [0104]    The connector in this embodiment is suitable for supplying electric power to a heater having an electrode on only one of its primary surfaces. 
         [0105]      FIG. 15  is a sectional view of the connector  313  in this embodiment, and shows the structure of the connector  313 . The connector  313  has a housing  315  and a terminal  314 . The lateral walls of the housing  315  have a pair of slots  315 X, one for one, into which a heater  305  shown in  FIG. 16  fits. The terminal  314  is supported by the housing  315  in such a manner that it is allowed to move in an oscillatory manner. The housing  315  is roughly U-shaped in cross section; each of the lateral walls of the housing  315  is provided with the slot  315 X. The bottom wall of the slot  315 X is provided with a hole  315 Y, through which a part of the terminal  314  is allowed to protrude into, or retract from, the slot  315 X. Further, the housing  315  is provided with a catch (seat)  346  by which the tip  345  of the terminal  314  is caught. One side of the hole  315 Y is the edge of the catch  345 , and the other side of the hole  315 Y is the edge of the pressing portion  371  of a regulating member  317  (which will be described later). 
         [0106]    The connector  313  has the regulating member  317  which is within the housing  315 . The regulating member  317  can be kept in a regulatory position (shown in  FIG. 17 ) in which it keeps the terminal  314  retracted from the slot  315 X, and a home position (shown in  FIG. 15 ), into which the regulating member  317  is retracted, and in which the regulating member  317  does not regulate the terminal  314 . The direction in which the regulating member  317  is movable is parallel to the direction (indicated by arrow mark X 1  in  FIG. 15 , and arrow mark X 2  in  FIG. 19 ) in which the heater enters the slot  315 X when the connector  313  is engaged with the heater. The connector  313  is also provided with a controller  318  which is for moving the regulating member  317 , or keeping the regulating member  317  locked in a specific position. The controller  318  is attached to the bottom surface of the housing  315 . It is movable between the position shown in  FIG. 15  and the position shown in  FIG. 17 , and can be placed in the position shown in  FIG. 15 , or the position shown in  FIG. 17 . The controller  318  is provided with a protrusion  315   a , which is to fit into the recess  315   a  or  351   b , with which the bottom surface of the housing  315  is provided, to regulate the controller  318  in position in order to regulate thereby the regulating member  317  in position. 
         [0107]    The terminal  314  has a base portion  341 , a flexible portion  342 , a catch portion  343  (hook-shaped portion), a point  344  of contact, and the tip portion  345 , listing from the side at which the terminal  314  is anchored to the bottom wall of the terminal  314 . The terminal  314  is such a terminal that establishes electrical connection between itself and the heater electrode  310  by being allowed to be moved into the slot  315 X by its own resiliency. As the terminal  314  is allowed to move into the slot  315 X, its point  344  of contact comes into contact with the electrode  310  of the heater  305 . The point between the base portion  341  and flexible portion  342  functions as the pivot for the flexing of the terminal  314  (flexible portion  342 ). Referring to  FIG. 15 , the terminal  314  has the catch portion  343  (hook-shaped portion), which is on the downstream side of the point  344  of contact, in terms of the direction in which the heater (object to be supplied with electric power) enters the slot  315 X ( FIG. 19 ). The catch portion  343  (hook-shaped portion) is between the point  344  of contact and the aforementioned pivot. The catch portion  343  is stair-like, having a roughly horizontal portion  343   a  and a roughly vertical portion  343   b . The roughly horizontal portion  343   a  is roughly parallel to the direction indicated by the arrow mark X 2  in  FIG. 19 , that is, the direction in which the heater  205  enters the slot  315 X. The roughly vertical portion  343   b  is roughly vertical relative to the roughly horizontal portion  343   a . The base portion  341  is the portion of the terminal  314 , by which the terminal  314  is attached to the bottom wall of the terminal  314 . The flexible portion  342  extends at a preset angle relative to the base portion  341 . The terminal  314  is springy. Therefore, if it is subjected to a force which acts in the direction to cause the base portion  341  and flexible portion to form a straight line, it generates a reactive force in itself. 
         [0108]    The point  344  of contact is curved. It establishes electrical connection between itself and the electrode  310  of the heater  305  by coming into contact with the electrode  310  as the connector  313  is engaged with the heater  305 . It is kept pressed upon the electrode  310  by the resiliency of the above described flexible portion  342 . The tip portion  345  is a portion of the terminal  314 , which prevents the terminal  314  from shifting, by being caught by the catch portion  346  of the housing  315 . 
         [0109]    The material for the connector terminal  314  is stainless steel or titanium alloy. The surface of the terminal  314  is plated with gold or the like substance, which is low in electrical resistance. 
         [0110]    The regulating member  317  is in the housing  315 . It has the terminal pressing portion  371  which extends in the direction indicated by the arrow mark X 1  in  FIG. 17 , that is, the direction in which the regulating member  317  is to be moved to regulate the terminal  314 . As the regulating member  317  is pressed in the terminal regulating direction X 1 , it moves in the terminal regulating direction X 1  while pressing downward the flexible portion  342  of the terminal  314 , with the terminal pressing portion  371 , until it reaches the hook-shaped catch portion  342 . As soon as the pressing portion  371  of the regulating member  317  reaches the hook-shaped catch portion  343  (regulating position), the parallel portion  343   a  of the terminal  314  is pressed downward by the pressing portion  371  of the regulating member  317 . Therefore, the terminal  314  is kept downwardly bent by the regulating member  317 . 
         [0111]    The regulating member  317  is solidly attached to the controller  318 . The controller  318  is for moving the regulating member  317  in the regulating direction X 1  or releasing direction X 2 . The controller  318 , or the terminal controlling member, is provided with the protrusion  318   a  which fits in the recess  315   a  or  315   b  of the housing  315 . As the controlling member  318  is moved in the releasing direction X 2  as far as it is allowed to move, the protrusion  318   a  fits into the recess  315   b , allowing thereby the terminal  314  to protrude into the slot  315 X so that as the connector  313  is engaged with the heater  305 , the heater  105  enters the slot  315 X and electrical connection is established between the terminal  314  and the electrode  310  of the heater  305 . On the other hand, as the controlling member  318  is moved in the regulating direction X 1 , its protrusion  318   a  fits into the recess  315   a . When the protrusion  318   a  is in the recess  315   a , the terminal  314  is outside the slot  315 X ( FIG. 17 ). 
         [0112]      FIG. 16(   a ) is a perspective view of the combination of the heater  305  and supporting member  306 , and shows the overall structure of the combination.  FIG. 16(   b ) is an enlarged perspective view of one of the lengthwise end portions of the combination of the heater  305  and supporting member  306 , as seen from the side on which the supporting member  306  (heater  305 ) contacts the film (endless belt). It shows the structure of the lengthwise end portion.  FIG. 16(   c ) is an enlarged perspective view of one of the lengthwise end portion of the supporting member  306 , and shows the structure of the end portion. Referring to  FIGS. 16(   a ) and  16 ( b ), the supporting member  306  is provided with a groove  306 A which extends in the lengthwise direction of the supporting member  306 , and in which the heater  305  is supported. The supporting member  306  plays the role of regulating the film  7  in position while the film  7  is circularly moved. 
         [0113]    Next, referring to  FIGS. 17 ,  18 , and  19 , how the connector  313  is to be engaged with the supporting member  306  (heater  305 ) is described. 
         [0114]      FIG. 17  is a sectional view of the connector  313 , and shows the structure of the connector  313 . Before a user of the image forming apparatus engages the connector  313  with the supporting member  306  which is supporting the heater  305 , the user is to move the regulating member  317  from its position shown in  FIG. 15  to the position shown in  FIG. 17 , by manipulating the controller  318 . As the controller  318  is manipulated as described above, the regulating member  317  moves toward the slot  315 X of the housing  315 , in the direction X 1 . 
         [0115]    While the regulating member  317  is moved into the slot  315 X, the pressing portion  371  of the regulating member  317  comes into contact with the flexible portion  342  of the terminal  314  and continues to press the flexible portion  342  downward, bending thereby the terminal  314  downward. As the regulating member  317  is moved further in the direction X 1 , the pressing portion  371  comes into contact with the catch portion  343  (hook-shaped portion). Meanwhile, the pressing portion  371  is remaining in contact with the parallel portion  343   a . Then, as the controller  318  is moved as far as it can be moved in the direction X 1 , that is, until the front surface  318 A of the controller  318  ( FIG. 15 ) in terms of the direction X 1  comes into contact with the deepest end  315 A (vertical edge in  FIG. 4 ) of the slot  315 X of the housing  315 , the pressing portion  371  of the regulating member  317  is caught by the catch portion  343  of the terminal  314 . 
         [0116]    The connector  313  and its terminal  314  are structured so that while the pressing portion  371  is in contact with the horizontal portion  343   a , the horizontal portion  343   a  remains roughly parallel to the direction X 1  in which the pressing portion  371  is moved to regulate the terminal  314 . Therefore, the regulating member  317  can be smoothly moved, that is, without being hung up by the terminal  314 . As described above, the catch portion  343  has not only the horizontal portion  343   a , but also, the vertical portion  343   b  which is between the horizontal portion  343   a  and the point  344  of contact. The vertical portion  343   b  plays also a role of preventing the point  344  of contact from coming into contact with the pressing portion  371 . 
         [0117]      FIG. 18  is a sectional view of the combination of the connector  313 , heater  305 , and supporting member  306  before the release of the terminal  314  by the regulating member  317  after the engagement of the connector  313  with the supporting member  306  (heater  305 ). It shows the structure of the connector  313  and supporting member  306 . The connector  313  is attached to the supporting member  306  which is supporting the heater  305 , as shown in  FIG. 18 , with the terminal  314  being kept pressed downward so that the terminal  314  remains in the state shown in  FIG. 17 . That is, before the connector  313  is attached to the supporting member  306 , the terminal  314  is bent downward by the regulating member  317  in such a manner that it remains downwardly bent while the connector  313  is attached to the supporting member  306 . Therefore, the catch portion  343  and point  344  of contact of the terminal  314  do not come into contact with the heater  305  (more specifically, electrode  310 ). 
         [0118]      FIG. 19  is a sectional view of the combination of the connector  313 , heater  305 , and supporting member  306  after the release of the terminal  314  by the regulating member  317  after the engagement of the connector  313  with the supporting member  306  (heater  305 ). It shows the structure of the connector  131  and supporting member  306 . After the connector  313  is engaged with the supporting member  306  which is supporting the heater  305 , as shown in  FIG. 18 , the controller  318  is to be operated so that the regulating member  317  is moved in the terminal releasing direction X 2 , that is, the opposite direction from the direction in which the regulating member  318  is moved toward the slot  315 X of the housing  315 , as shown in  FIG. 19 . As the controller  318  is moved in the above described direction, the catch portion  343  of the terminal  314  which was kept downwardly pressed by the pressing portion  371  of the regulating member  317  is released by the pressing portion  371 , allowing thereby the point  344  of contact to virtually vertically move upward and come into contact with the electrode  310  of the heater  305 . After the point  344  of contact came into contact with the electrode  310 , there are a gap (encircled with dotted line in  FIG. 9 ) between the flexible portion  342  of the terminal  314  and the pressing portion  371  of the regulating member, and a gap (encircled by dotted line in  FIG. 19 ) between the tip portion  345  of the terminal  314  and the catch portion  346  of the housing  315 . Thus, the point  344  of contact is allowed to remain in contact with the electrode  310  while maintaining a preset amount of contact pressure between itself and the electrode  310 . 
         [0119]    In this embodiment, the terminal  314  is pressed downward, and kept downwardly bent, by the regulating member  317 . However, the connector  314  may be structured so that the terminal  314  can be pressed down, and kept downwardly bent, by a special tool; it does not need to have the regulating member  317  and controller  318 . In such a case, all that is necessary is to press downward the horizontal portion  343   a  of the terminal  314  with the special tool. More specifically, in a case where the connector is structured so that a special tool is used to downwardly bend the contact terminal, the housing  315  is provided with the second opening which allows the special tool to be inserted into the slot  315 X, from the opposite direction from the direction in which the heater  305  enters the slot  315 X. With the provision of the second opening, the special tool can be insert into the slot  315 X to downwardly press the horizontal portion  343   a  of the catch portion  343  (hook-shaped portion) to bend the terminal  314  downward in order to move the point  344  of contact out of the slot  315 X. 
         [0120]    In this embodiment, the connector  313  is engaged with the supporting member  306  which is supporting the heater  305 , while the terminal  314  is kept downwardly bent by the pressing portion  371  of the regulating member  317  (or special tool), which presses downward the horizontal portion  343   a  of the catch portion  343  of the terminal  314 . Therefore, while the connector  313  is engaged with the supporting member  306 , a gap is present between the point  344  of contact and the heater  305 , and therefore, the point  344  of contact and heater  305  do not rub against each other. Therefore, the heater electrode  310  and/or the point  344  of contact of the terminal  314  of the connector  313  is not frictionally worn during the engagement or disengagement of the connector  313 . Therefore, the unsatisfactory electrical connection between the connector  313  and heater electrode  310 , which is attributable to repeated engagement or disengagement of the connector  313 , is unlikely to occur. 
         [0121]    Further, the connector terminal  314  is provided with the hook-shaped portion (catch portion). Therefore, the amount by which the terminal  314  is bent downward by the regulating member  317  or special tool remains accurate. Therefore, it is ensured that the point  344  of contact of the terminal  314  of the connector  313  is not frictionally worn when the connector  313  is engaged with the heater  305 . 
       Embodiment 5 
       [0122]    The connector in this embodiment is suitable for supplying electric power to a two-sided heater, that is, a heater which has a heater (or heaters) and electrodes, on both surfaces of its ceramic substrate. 
         [0123]    Referring to  FIG. 20 , the connector  222  in this embodiment is provided with a pair of terminals  224 , which are positioned in the housing  223  of the connector  222 , in such a manner that the two points  224  of contact, one for one, of the pair of terminals  224  oppose each other in the slot  223 X. As the supporting member  221  which is supporting the heater  220  ( FIG. 20 ) enters the slot  223 X, one of the pair of terminals  223  comes into contact with the electrode on one of the two primary surfaces of the ceramic substrate of the heater  220 , and the other terminal  223  comes into contact with the electrode on the other primary surface. The detail of the engagement between the connector  222  and the supporting member  221  of the heating unit is as follows. 
         [0124]      FIG. 20  is a sectional view of the connector  222 , and shows the structure of the connector  222 . The connector  222  has a housing  223 , a pair of terminals  224 , a regulating member  225 , and a controller  218 . The housing  223  has a slot  223 X, between its roughly U-shaped lateral walls. 
         [0125]    The connector terminal  224  has: a base portion  241  by which the terminal  224  is held to the housing  223 ; a flexible portion  242  for providing the terminal  224  with resiliency; a catch portion  243  (hook-shaped portion); a point  344  of contact with curvature, and the tip portion  345 , listing from the side at which the terminal is held to the housing  223 . The housing  223  is provided with a catch  246 , by which the tip portion  245  is caught. The catch portion  243  has a horizontal portion  243   a  and a vertical portion  243   b . These portions of the contact terminal  224  are the same in function as the counterparts of the contact terminal  314  in the above described fourth embodiment. 
         [0126]    The connector  222  in this embodiment is also structured so that the point  244  of contact of one of the spring contacts of the terminal  224  opposes the other of the spring contacts. Thus, it is desired to prevent the problem that the plating of the point  224  of contact is changed in condition by the contact between the opposing two points  224  of contact. Therefore, the connector  222  is structured so that when the connector  222  is not in engagement with the heater  220  (as shown in  FIG. 20 ), a gap is maintained between the two points  224  of contact. 
         [0127]    The regulating member  225  has two pressing portions  251 , that is, the top and bottom pressing portions. The top pressing portion  251  presses the top terminal  224 , and the bottom pressing portion  251  presses the bottom terminal  224 . 
         [0128]      FIG. 21  is a sectional view of the connector  222  when the connector  222  is ready to be engaged with the heater  220 . It also shows the structure of the connector  222 . Referring to  FIG. 21 , before a user of the image forming apparatus engages the connector  222  with the supporting member  221  which is supporting the heater  220 , the user is to move the regulating member  225  from its position shown in  FIG. 20  to the position shown in  FIG. 21 , by manipulating the controller  218 . As the controller  218  is manipulated as described above, the regulating member  225  moves toward the slot  223 X between the U-shaped lateral walls of the housing  223 . While the regulating member  225  is moved into the slot  223 X between the U-shaped lateral portions of the housing  223 , the top and bottom pressing portions  251  come into contact with the flexible portion  242  of the top terminal and that of the bottom terminal, respectively, and continue to press the flexible portions  242 , bending thereby the terminals upward and downward, respectively. As the regulating member  225  is moved further, the top and bottom pressing portions  251  come into contact with the catch portions  243  (hook-shaped portion) of the top and bottom terminals  224 . Then, as the controller  218  is moved as far as it can be moved, that is, until the front surface  218 A of the controller  218  comes into contact with the vertical edge  223 A (encircled by dotted line in  FIG. 21 ) of the slot  223 X of the housing  223 , the pressing portion  251  of the regulating member  225  is caught by the catch portion  243  of the terminal  224 , whereby the regulating member  225  is stopped. 
         [0129]      FIG. 22  is a sectional view of the combination of the connector  222 , heater  220 , and supporting member  221  before the controller  218  is returned to its home position. It shows the structure of the combination. Referring to  FIG. 22 , the connector  222  is engaged with the supporting member  221  which is supporting the heater  220 . Immediately after the engagement of the connector  222 , there still remains a preset amount of gap between the point  224  of contact of the terminal  224  and the corresponding electrode of the heater  220 . 
         [0130]      FIG. 23  is a sectional view of the combination of the connector  222 , heater  220 , and supporting member  221  after the completion of the process of engaging the connector  222  with the supporting member  221 . Referring to  FIG. 23 , the regulating member  225  is to be moved in the release direction X 2  by the manipulation of the controller  218 . As the regulating member  225  is moved in the release direction X 2 , the top and bottom pressing portions  251  of the regulating member  225  disengage from the catch portion  243  of the top and bottom terminals  224 , allowing thereby the point  224  of contact of the top terminal  224  and the point  224  of contact of the bottom terminal  224  to come into contact with the top and bottom electrodes of the heater  220 , respectively, in the direction which is roughly perpendicular to the heaters  220 . 
         [0131]    In this embodiment, the connector  222  is engaged with the supporting member  221  which is supporting the heater  220 , while the top and bottom terminals  224  are kept downwardly and upwardly bent by the top and bottom pressing portions  251 , respectively, of the regulating member  225 . Therefore, while the connector is engaged with the supporting member  221 , a gap is present between the point  244  of contact and the electrode of the heater  220 , and therefore, the point  244  of contact and the electrode of the heater  220  do not rub against each other. Therefore, the point  224  of contact is not frictionally worn. Therefore, the unsatisfactory electrical connection between the connector  222  and the heater electrode  220 , which is attributable to the frictional wear of the point  224  of contact does not occur. 
         [0132]    In the fourth and fifth embodiments, the connectors  313  and  222 , respectively, are structured so that before the connectors  313  and  222  are engaged with the heater  305  and  220 , the terminals  314  and  224  can be regulated by the regulating member or special tool. Therefore, it does not occur that the points  344  and  244  of contact of the terminals  314  and  224  come into contact with the supporting members  306  and  221 , respectively. Therefore, the phenomenon that the terminals  314  and  224  are permanently deformed by a substantial amount of load to which the points  344  and  244  of contact of the terminals  314  and  224  are subjected when the terminals  314  and  224  are engaged with the supporting members  306  and  221 , respectively, and/or the phenomenon that the points  334  and  244  of contact are frictionally worn when the terminals  314  and  224  are engaged with the supporting members  306  and  221 , respectively, does not occur. Therefore, a proper amount of contact pressure is generated and maintained between the points  334  and  244  of contact and the electrodes of the heaters  305  and  220 , respectively. 
         [0133]    Further, the terminals  314  and  224  are provided with a hook-shaped portion. Therefore, the amount by which they are resiliently bent by the regulating member or special tool is accurate. Therefore, it is ensured that the point of contact is not frictionally worn when the connector is engage with the heater. 
         [0134]    Further, because the connectors in the fourth and fifth embodiments are structured as described above, a disassembler of the heating unit can disengage the connectors  313  and  222  without allowing the points  344  and  244  of contact rub against the electrodes when the disassembler disassembles or reassemble the heating unit. Therefore, a reassembled connector is virtually the same in condition in terms of electrical connection as it was before it was disassembled. That is, the connectors do not need to be adjusted in the state of electrical connection related to the performance of a fixing device, and therefore, are easier to maintain than a conventional connector. 
         [0135]    While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
         [0136]    This application claims priority from Japanese Patent Applications Nos. 109321/2012, 109322/2012 and 265482/2012 filed May 11, 2012, May 11, 2012 and Dec. 4, 2012, respectively, which are hereby incorporated by reference.