Patent Publication Number: US-11397403-B2

Title: Image formation apparatus including fixation device with handle

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. 2020-179104 filed on Oct. 26, 2020, entitled “IMAGE FORMATION APPARATUS”, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The disclosure may relate to an image formation apparatus. 
     An electrophotographic image formation apparatus, such as a photocopier, a printer, and a fax machine, is configured to form a developer image by electrophotography, and transfer the developer image to a medium, and then fixes the developer image transferred to the medium to the medium by a fixation device. 
     In a related art, such an image formation apparatus is provided with: an apparatus housing having, at an outer periphery thereof, a stacker to which a medium having a fixed image is discharged; and a fixation device that can be removably attached to the apparatus housing through an opening provided at the stacker, wherein when the fixation device is attached to the apparatus housing, a portion of the fixation device is exposed from the opening of the stacker so as to form a portion of the stacker (see, for example, Patent Document 1).
     Patent Document 1: Japanese Patent Application Publication No. 2020-38342   

     SUMMARY 
     In the image formation apparatus described above, the fixation device can be directly attached to and removed from the apparatus housing without opening the cover of the apparatus housing, which facilitates the attachment and removal of the fixation device. However, there may be a problem that if, when the fixation device is inserted through the opening of the apparatus housing, the force of the insertion is insufficient, a connector of the fixation device fails to be mated to a connector of the apparatus housing, so that the attachment of the fixation device is incomplete. 
     An object of an embodiment of the disclosure may be to provide an image formation apparatus that allows reliable attachment of a fixation device. 
     An aspect of the disclosure may be an image formation apparatus that may include: an apparatus housing that includes, at an outer peripheral portion thereof, a stacker, an opening being provided at the stacker; an image formation unit that is provided in the apparatus housing and configured to form an image on a medium; and a fixation device that is removably attached to the apparatus housing through the opening, and is configured to fix the image formed on the medium by the image formation unit to the medium. In a state where the fixation device is attached to the apparatus housing, a portion of the fixation device that is exposed from the opening provided at the stacker forms a portion of the stacker, and a connector of the fixation device is mated to a connector of the apparatus housing. The fixation device includes, at the exposed portion thereof exposed from the opening, a handle that is allowed to transition between an upright position in which the handle stands with respect to the exposed portion and a laid-flat position in which the handle is laid flat with respect to the exposed portion. The image formation apparatus may further include a laid-flat position-keeping detent mechanism that, when at least a predetermined force is applied to the handle in order to transition the handle from the upright position to the laid-flat position, allows the handle to transition to the laid-flat position and keeps the handle in the laid-flat position. 
     According to the aspect described above, for example, after the handle of the fixation device is grasped in the upright position and the fixation device is inserted through the opening, at least a predetermined force set for the laid-flat position-keeping detent mechanism is applied to the handle in order to cause the handle to transition from the upright position to the laid-flat position. By this force, the connector of the fixation device can be reliably mated to the connector of the apparatus housing. 
     Thus, according to the aspect described above, an image formation apparatus can be implemented in which a fixation device can be reliably attached thereto. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an appearance or external configuration of an image formation apparatus; 
         FIG. 2  is a side cross-sectional view illustrating an internal configuration of the image formation apparatus; 
         FIG. 3  is a perspective view illustrating an appearance or external configuration of the image formation apparatus with an apparatus cover open; 
         FIG. 4  is a perspective view illustrating an appearance or external configuration of the image formation apparatus with a fixation device removed; 
         FIG. 5  is an enlarged cross-sectional view of configurations of the fixation device and surrounding parts; 
         FIGS. 6A and 6B  are perspective views illustrating an appearance or external configuration of the fixation device as viewed from the front; 
         FIGS. 7A and 7B  are front perspective views illustrating an appearance or external configuration of the fixation device as viewed obliquely from above; 
         FIGS. 8A and 8B  are enlarged perspective views illustrating an appearance or external configuration of a left handle and surrounding parts; 
         FIGS. 9A and 9B  are enlarged perspective views illustrating an internal configuration of the left handle and surrounding parts; 
         FIGS. 10A and 10B  are cross-sectional views taken along line A-A of  FIG. 9A ; 
         FIGS. 11A and 11B  are cross-sectional views taken along line B-B of  FIG. 9B ; 
         FIGS. 12A and 12B  are enlarged perspective views illustrating a left portion of a fixation device housing as it is contained in a fixation device compartment; 
         FIGS. 13A to 13C  are partial cross-sectional views illustrating a configuration of a linking member; and 
         FIG. 14  is a cross-sectional view illustrating a handle as it is immediately before the handle is transitioned to a laid-flat position. 
     
    
    
     DETAILED DESCRIPTION 
     Descriptions are provided hereinbelow for embodiments based on the drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted. All of the drawings are provided to illustrate the respective examples only. 
     1. Configuration of Image Formation Apparatus 
       FIG. 1  and  FIG. 2  illustrate a configuration of an image formation apparatus  1  according to an embodiment. The image formation apparatus  1  is a color printer that forms (i.e., prints) an image on paper by electrophotography.  FIG. 1  is a perspective view illustrating an appearance or external configuration of the image formation apparatus  1 .  FIG. 2  is a side cross-sectional view illustrating an internal configuration of the image formation apparatus  1 . 
     Firstly, an appearance or external configuration of the image formation apparatus  1  is described. As illustrated in  FIG. 1 , the image formation apparatus  1  has, as a cover, an apparatus housing  2  generally in the shape of a rectangular parallelepiped. A backward direction is herein defined as a direction from a front surface  2   f  to a rear surface  2   b  of the apparatus housing  2 . A forward direction is herein defined as a direction from the rear surface  2   b  to the front surface  2   f . An upward direction is herein defined as a direction from the bottom to top of the apparatus housing  2 . A downward direction is herein defined as a direction from the top to bottom of the apparatus housing  2 . A leftward direction is herein defined as a direction from the right to left of the apparatus housing  2 . A rightward direction is herein defined as a direction from the left to right of the apparatus housing  2 . 
     The apparatus housing  2  includes a housing body  2   m  that is generally in the shape of a box whose upper side (opening  3 ) is open (see a perspective view illustrated in  FIG. 3 ), and an apparatus cover  2   c  that forms an upper surface of the apparatus housing  2  and is in the shape of a lid covering the opening (hereinafter referred to as a “body opening”)  3  of the housing body  2   m . As illustrated in  FIG. 2 , the apparatus cover  2   c  has an apparatus cover rotating shaft  4  that is provided at a rear end thereof, extending in the leftward/rightward direction, and is rotatably supported by a bearing (not illustrated) provided at an upper end of a rear end portion of the housing body  2   m . As illustrated in  FIG. 3 , this allows the apparatus cover  2   c  to be opened when the front side of the apparatus cover  2   c  is rotated about the apparatus cover rotating shaft  4  (not illustrated in  FIG. 3 ) in a direction away from the housing body  2   m , and to be closed when the front side is rotated in a direction toward the housing body  2   m . The image formation apparatus  1  is thus configured such that, when the apparatus cover  2   c  is open, the inside of the image formation apparatus  1  is exposed from the body opening  3  of the housing body  2   m  and can therefore be accessed. 
     A state of the apparatus cover  2   c  in which the body opening  3  is covered and completely closed by the apparatus cover  2   c  as illustrated in  FIG. 1  is hereinafter referred to as a “closed state,” and a state of the apparatus cover  2   c  in which the body opening  3  is fully open so that the inside of the image formation apparatus  1  is exposed as illustrated in  FIG. 3  is hereinafter referred to as an “open state.” 
     As illustrated in  FIGS. 1 and 2 , a portion of the upper surface of the apparatus cover  2   c  is recessed, and this recessed portion forms a stacker  5  on which sheets of paper are stacked (collected). In other words, the apparatus cover  2   c  has the stacker  5  at the upper surface, which is an outer peripheral portion of the apparatus cover  2   c . The stacker  5  has a stack surface (i.e., a bottom surface)  5   s  on which sheets of paper are stacked. The stack surface  5   s  is sloped upward from the rear end to the front end. The image formation apparatus  1  is thus configured such that sheets of paper discharged forward from a paper discharge opening  6  provided at a rear wall surface  5   b  of the stacker  5  are stacked on the stack surface  5   s  of the stacker  5 . 
     The apparatus cover  2   c  is also provided with a cover opening  7  at a rear portion of the stacker  5 . The cover opening  7  is a hole that is elongated in the leftward/rightward direction and opens the rear portion of the stacker  5  and portions (hereinafter referred to as “left and right outer portions flanking the stacker  5 ”) of the apparatus cover  2   c  that are located on both left and right sides of (i.e., outward of) the rear portion of the stacker  5 . 
     In the image formation apparatus  1 , when a fixation device  8  is removably attached to the housing body  2   m , an upper surface of the fixation device  8  is exposed to the outside from the cover opening  7 . The fixation device  8  is described in detail later. The upper surface of the fixation device  8  is shaped so as to block the cover opening  7 , and to form the rear portion of the stacker  5  (i.e., a rear portion of the stack surface  5   s  of the stacker  5  and rear portions of a left and a right side wall surface  5   w  of the stacker  5 ) and the left and right outer portions flanking the stacker  5 . The rear wall surface  5   b  of the stacker  5  is a portion of the housing body  2   m . Thus, the stack surface  5   s  and the side wall surfaces  5   w  of the stacker  5  are formed by the apparatus cover  2   c  and the fixation device  8 , and the rear wall surface  5   b  of the stacker  5  is formed by the housing body  2   m.    
     Furthermore, handles  9  are provided on the upper surface of the fixation device  8  at the left and right outer portions flanking the stacker  5 . As illustrated in a perspective view of  FIG. 4 , the image formation apparatus  1  is configured such that while the apparatus cover  2   c  remains in the closed state, the fixation device  8 , which has been attached to the housing body  2   m , can be removed from the housing body  2   m  through the cover opening  7  of the apparatus cover  2   c  by holding and pulling upward the handles  9 , which are exposed from the cover opening  7  of the apparatus cover  2   c . The image formation apparatus  1  is also configured such that the fixation device  8  is lifted up with the handles  9  grasped, and is inserted through the cover opening  7  of the apparatus cover  2   c , whereby the fixation device  8  can be attached to the housing body  2   m  through the cover opening  7  of the apparatus cover  2   c.    
     A control unit  10  that controls the entire image formation apparatus  1  is also provided at a predetermined position in the housing body  2   m . Although not illustrated in  FIG. 1 , a display panel that can be controlled by a touch operation and displays various kinds of information, various operation buttons, and the like are provided at predetermined sites of the housing body  2   m  or the apparatus cover  2   c.    
     Next, an internal configuration of the image formation apparatus  1  is described. As illustrated in  FIG. 2 , parts are arranged in the apparatus housing  2  along a conveyance path R along which paper M is conveyed. Specifically, in the apparatus housing  2 , four image formation units  20  ( 20 K,  20 Y,  20 M,  20 C) corresponding to a plurality of color developers (e.g., four color toners of black (K), yellow (Y), magenta (M), and cyan ( 0 )) that are used in the image formation apparatus  1  are provided at almost the middle in the upward/downward direction, and are arranged side by side along the conveyance path R in the forward/backward direction. 
     Each image formation unit  20  ( 20 K,  20 Y,  20 M,  20 C) includes an LED head  21  ( 21 K,  21 Y,  21 M,  21 C), a photosensitive drum  22  ( 22 K,  22 Y,  22 M,  22 C), and a toner container  23  ( 23 K,  23 Y,  23 M,  23 C). Each image formation unit  20  is a hardware device in which a surface of the photosensitive drum  22  is exposed to light emitted by the LED head  21  so that an electrostatic latent image is formed on the surface of the photosensitive drum  22 , and thereafter, toner supplied from the toner container  23  is caused to adhere to the electrostatic latent image, whereby a toner image is formed on the surface of the photosensitive drum  22 . 
     In the apparatus housing  2 , a transfer unit  24  is also provided below the four image formation units  20 . The transfer unit  24  has a loop of conveyance belt  25  that is movable along the conveyance path R in the forward/backward direction, and transfer rollers  26  ( 26 K,  26 Y,  26 M,  26 C) that are provided below the photosensitive drums  22  ( 22 K,  22 Y,  22 M,  22 C), facing the photosensitive drums  22  ( 22 K,  22 Y,  22 M,  22 C) with the conveyance belt  25  interposed therebetween. 
     Each transfer roller  26  is a member that electrostatically charges paper M to the polarity opposite to that of the toner while the paper M is being passed between the photosensitive drum  22  and the conveyance belt  25  so that a toner image of the corresponding color formed on the photosensitive drum  22  is transferred to the paper M. 
     In the apparatus housing  2 , a paper tray  27  that contains paper M is also provided below the transfer unit  24  (i.e., at a lower portion of the apparatus housing  2 ). In the apparatus housing  2 , a pair of transfer rollers that convey paper M, and the like, are also provided on the conveyance path R between the paper tray  27  and the transfer unit  24 . 
     In the apparatus housing  2 , the fixation device  8  is also provided downstream of (i.e., at the back of) the transfer unit  24  in a paper conveyance direction. The fixation device  8  includes a hot roller  28 , and a backup roller  29  that is provided below the hot roller  28 , facing the hot roller  28  with the conveyance path R interposed therebetween. The fixation device  8  fixes a toner image transferred to paper M by the transfer unit  24  to the paper M by heating and pressurization using the hot roller  28  and the backup roller  29 . 
     In the apparatus housing  2 , a pair of discharge rollers that discharges paper M to the stacker  5  through the paper discharge opening  6  is provided on the conveyance path R between the fixation device  8  and the paper discharge opening  6 . The image formation apparatus  1  has the internal configuration described above. 
     As illustrated in  FIG. 2 , parts other than the paper tray  27  of the image formation apparatus  1  are tilted with respect to a bottom surface of the apparatus housing  2 . For example, the four image formation units  20  and the fixation device  8  are each tilted with respect to the bottom surface of the apparatus housing  2  toward the front of the apparatus housing  2 , and therefore; are located at different positions or heights in the upward/downward direction. The image formation apparatus  1  is thus configured such that a length in the forward/backward direction of the apparatus housing  2  can be reduced compared to the case where parts other than the paper tray  27  are arranged in parallel to the bottom surface of the apparatus housing  2 . 
     2. Configurations of Fixation Device and Surrounding Parts 
     Next, configurations of the fixation device  8  and surrounding parts are described in greater detail. Here, of the configurations of the fixation device  8  and surrounding parts, only configurations of parts involved in attachment and removal of the fixation device  8  are described. 
       FIG. 5  illustrates configurations of the fixation device  8  and surrounding parts,  FIG. 5  is an enlarged cross-sectional view illustrating configurations of the fixation device  8  and surrounding parts with the apparatus cover  2   c  in the closed state and the fixation device  8  attached to the housing body  2   m.    
     As illustrated in  FIG. 5 , in the housing body  2   m , a fixation device compartment  30  in which the fixation device  8  is removably contained is provided below the cover opening  7  of the apparatus cover  2   c  as it is in the closed state. 
     As illustrated in  FIG. 4  in addition to  FIG. 5 , the fixation device  8  has, as a cover, a fixation device housing  40  that is generally in the shape of a rectangular parallelepiped and is elongated in the leftward/rightward direction. The fixation device housing  40  is configured to be contained in the fixation device compartment  30  of the housing body  2   m  with an upper surface thereof exposed to the outside from the cover opening  7 . Note that the fixation device compartment  30  is configured to contain the fixation device housing  40  with the fixation device housing  40  tilted forward. Due to this, the fixation device housing  40  is configured to be pulled forward and diagonally upward in order to remove the fixation device  8  from the image formation apparatus  1 , and is configured to be inserted backward and diagonally downward in order to attach the fixation device  8  to the image formation apparatus  1 . 
     The fixation device housing  40  has an upper surface that is elongated in the leftward/rightward direction and serves as an exposed portion. The upper surface is formed by a fixation device cover  40   c . The fixation device cover  40   c  is recessed at a middle portion thereof in the leftward/rightward direction. This recessed portion forms a rear portion of the stacker  5  (i.e., rear portions of the stack surface  5   s  and the left and right side wall surfaces  5   w ). 
     A portion  40   s  of the entire fixation device cover  40   c  that forms the stack surface  5   s  of the stacker  5  is herein referred to as a “stack surface formation portion  40   s ,” and portions  40   w  of the entire fixation device cover  40   c  that form the side wall surfaces  5   w  are herein referred to as “side wall surface formation portions  40   w .” Meanwhile, a portion  50   s  of the entire apparatus cover  2   c  that forms a front portion of the stack surface  5   s  of the stacker  5  is referred to as a “stack surface formation portion  50   s ,” and portions  50   w  of the entire apparatus cover  2   c  that form front portions of the left and right side wall surfaces  5   w  of the stacker  5  are referred to as “side wall surface formation portions  50   w.”   
     The stack surface formation portion  40   s  and the side wall surface formation portions  40   w  of the fixation device cover  40   c  are flush with the stack surface formation portion  50   s  and the side wall surface formation portions  50   w , respectively, of the apparatus cover  2   c . The stack surface formation portion  40   s  and the side wall surface formation portions  40   w  of the fixation device cover  40   c , and the stack surface formation portion  50   s  and the side wall surface formation portions  50   w  of the apparatus cover  2   c , form the stacker  5 . 
     Furthermore, the fixation device cover  40   c  is provided with the handle  9  ( FIG. 1 ) at each of the left and right outer portions franking the stacker  5 . As illustrated in  FIG. 4 , the left and right handles  9  can be rotated and transitioned between an upright position in which the handle  9  stands and protrudes upward from the fixation device cover  40   c , and a laid-flat position in which the handle  9  is tilted toward the middle in the leftward/rightward direction (inward in a longitudinal direction of the upper surface of the fixation device housing  40 ) until it is laid flat so as to be contained in the fixation device cover  40   c  as illustrated in  FIG. 1 . The user, when attaching and removing the fixation device  8 , can turn the left and right handles  9  into the upright position, and then grasp the left and right handles  9 . Configurations of the handle  9  and surrounding parts are described in greater detail later. 
     In addition to the fixation device cover  40   c , a sub-cover  41  is attached to the upper surface of the fixation device housing  40 . The sub-cover  41  is configured to cover a gap Sp 1  between a front end of the stack surface formation portion  40   s  of the fixation device housing  40  as it is contained in the fixation device compartment  30 , and a rear end of the stack surface formation portion  50   s  of the apparatus cover  2   c  as it is in the closed state. The sub-cover  41  is attached to the fixation device cover  40   c , covering a front portion of the fixation device cover  40   c . That is, a front portion of the upper surface of the fixation device housing  40  has a double structure including the fixation device cover  40   c  and the sub-cover  41 . The fixation device cover  40   c  and the sub-cover  41  form a rear portion of the stacker  5 . A portion  41   s  of the entire sub-cover  41  that forms the stack surface  5   s  of the stacker  5  is herein referred to as a “stack surface formation portion  41   s ,” and portions  41   w  of the entire sub-cover  41  that form the side wall surfaces  5   w  are herein referred to as “side wall surface formation portions  41   w.”   
     The sub-cover  41  has a sub-cover rotating shaft  42  that is provided at rear ends of the left and right side wall surface formation portions  41   w , extending in the leftward/rightward direction. The sub-cover rotating shaft  42  is rotatably supported by bearing parts (not illustrated) provided at rear portions of the side wall surface formation portions  40   w  of the fixation device cover  40   c . This allows the sub-cover  41  to be opened by rotation about the sub-cover rotating shaft  42  in a direction (anticlockwise direction in  FIG. 5 ) that causes the stack surface formation portion  41   s  of the sub-cover  41  to move away from the stack surface formation portion  40   s  of the fixation device cover  40   c , and to be closed by rotation in a direction (clockwise direction in  FIG. 5 ) that causes the stack surface formation portion  41   s  of the sub-cover  41  to move toward the stack surface formation portion  40   s  of the fixation device cover  40   c.    
     Furthermore, the sub-cover  41  is pressed by a pressing member (not illustrated) in a direction that causes the stack surface formation portion  41   s  of the sub-cover  41  to move toward the stack surface formation portion  40   s  of the fixation device cover  40   c  (i.e., in a direction that causes the sub-cover  41  to be closed). 
     The sub-cover  41  is also configured such that a front end portion of the stack surface formation portion  41   s  overlays the stack surface formation portion  50   s  of the apparatus cover  2   c , and therefore, when the apparatus cover  2   c  is opened, the stack surface formation portion  41   s  of the sub-cover  41  is pressed upward by the stack surface formation portion  50   s  of the apparatus cover  2   c , so that the sub-cover  41  is opened together with the apparatus cover  2   c . When the apparatus cover  2   c  is closed, the sub-cover  41  is closed together with the apparatus cover  2   c  due to a pressing force of the pressing member. Thus, the sub-cover  41  is configured to cover the gap Sp 1  and to be opened and closed together with the apparatus cover  2   c  when the apparatus cover  2   c  is opened and closed. 
     As illustrated in  FIG. 6A , which is a perspective view illustrating an appearance of the fixation device  8  as viewed from the front, a connector  43  is provided at one end (e.g., a left end) in the longitudinal direction (leftward/rightward direction) of a lower end portion of the fixation device housing  40 , protruding downward. A gear part  44  is provided at the other end (e.g., a right end) in the longitudinal direction of the lower end portion of the fixation device housing  40 , protruding downward. 
     As illustrated in  FIG. 6B , when the fixation device housing  40  is contained in the fixation device compartment  30 , the connector  43  of the fixation device housing  40  is mated to a connector  31  provided at a bottom portion of the fixation device compartment  30  from above. When the connector  43  is mated to the connector  31 , the fixation device  8  can be supplied with power from the image formation apparatus  1 , and can exchange various signals with the image formation apparatus  1 . When the fixation device housing  40  is contained in the fixation device compartment  30 , the gear part  44  of the fixation device housing  40  is engaged with a gear part  32  provided at a bottom portion of the fixation device compartment  30  from above. When the gear part  44  is mated to the gear part  32 , the fixation device  8  can be supplied with a drive force from the image formation apparatus  1 . 
     3. Configurations of Handle and Surrounding Parts 
     Next, the handle  9  and surrounding parts of the fixation device  8  are described in greater detail. As illustrated in  FIGS. 7A and 7B , which are front perspective views of an appearance of the fixation device  8  as viewed obliquely from above, one handle  9  is provided at each of a left and a right side portion of the fixation device cover  40   c  (i.e., a left and a right portions of an upper end portion of the fixation device housing  40 ). In  FIG. 7A , the handle  9  is in an upright position. In  FIG. 7B , the handle  9  is in a laid-flat position. The left and right handles  9  are laterally symmetrical, and have the same basic configuration, and therefore, the left handle  9  is here mainly described. 
     Here,  FIGS. 8A and 8B  illustrate an appearance or external configuration of the handle  9 , and an appearance or external configuration of surrounding parts.  FIGS. 9A and 9B  illustrate an appearance or external configuration of the handle  9 , and an internal configuration of surrounding parts. In  FIGS. 8A and 9A , the handle  9  is in the upright position. In  FIGS. 8B and 9B , the handle  9  is in the laid-flat position. 
     As illustrated in  FIGS. 8A, 8B, 9A, and 9B , the handle  9  includes a grasp section  60  that is generally in the shape of a squared C and configured to be grasped by the user, and an attachment section  61  that extends from one end of the squared-C shape of the grasp section  60  to the other end and configured to be attached to the fixation device housing  40 . The handle  9  is generally in the shape of D as a whole, and therefore, has an annular shape. The handle  9  is also provided with a rotating shaft  62  at the attachment section  61 . The rotating shaft  62  extends in a direction in which the attachment section  61  extends. The rotating shaft  62  protrudes from both ends in the extending direction of the attachment section  61 . 
     As illustrated in  FIGS. 8A and 8B , the attachment section  61  of the handle  9  is attached to a left end of a recessed section  70  that has almost the same size as that of the handle  9  and is provided at a left portion of an upper end portion of the fixation device housing  40  with the rotating shaft  62  (see  FIGS. 9A and 9B ) oriented in the forward/backward direction. Here, as illustrated in  FIGS. 9A and 9B , the rotating shaft  62 , which protrudes from the front and rear ends of the attachment section  61 , is inserted through respective shaft holes  71   h  that are provided at a frame  71  of the fixation device housing  40  and are located on a front and a rear side of the recessed section  70 . Thus, the attachment section  61  of the handle  9  is supported by the frame  71  of the fixation device housing  40  in a manner that allows the attachment section  61  to rotate about the rotating shaft  62 , which extends in the forward/backward direction. 
     The handle  9 , which rotates about the rotating shaft  62 , can be transitioned between the upright position and the laid-flat position. Here, as illustrated in  FIG. 8A , the upright position with respect to the handle  9  means that the handle  9  stands in substantially a vertical position with respect to a bottom surface  70   b  of the recessed section  70  (i.e., the upper surface of the fixation device housing  40 ) with the grasp section  60  located above the attachment section  61 . As illustrated in  FIG. 8B , the laid-flat position with respect to the handle  9  means that the handle  9  is laid flat to be substantially parallel to the bottom surface  70   b  of the recessed section  70  with the grasp section  60  located on the right side of the attachment section  61 , and the handle  9  is substantially entirely contained in the recessed section  70 . 
     As illustrated in  FIG. 9B , the handle  9  and the frame  71  of the fixation device housing  40  also have a detent mechanism (hereinafter referred to as an “upright position-keeping detent mechanism”)  80  for keeping the handle  9  in the upright position, and a detent mechanism (hereinafter referred to as a “laid-flat position-keeping detent mechanism”)  90  for keeping the handle  9  in the laid-flat position. Here, the upright position-keeping detent mechanism  80  and the laid-flat position-keeping detent mechanism  90  are described in sequence. 
     As illustrated in  FIG. 9B , and in addition,  FIG. 10A , which is a cross-sectional view of the handle  9  and the frame  71  taken along line A-A of  FIG. 9A , the upright position-keeping detent mechanism  80  includes an upright position-keeping arm  81  that is provided at the attachment section  61  of the handle  9 , and an upright position-keeping arm engagement section  82  that is provided at the frame  71  of the fixation device housing  40 . 
     There are two of the upright position-keeping arms  81  that are located at a middle portion in an axial direction of the attachment section  61  with a space therebetween in the axial direction. The two upright position-keeping arms  81  are a cantilever plate spring that, when the handle  9  is in the upright position, is located at a lower end (below the rotating shaft  62 ) of the attachment section  61 , extending from a left end toward a right end of the lower end of the attachment section  61  (from the outside toward the inside in the longitudinal direction of the fixation device housing  40  ( FIG. 7 )). 
     In other words, the two upright position-keeping arms  81  are a cantilever plate spring member that, when the handle  9  is in the upright position, is located at the lower end of the attachment section  61 , extending from the left end of the lower end of the attachment section  61  in a direction opposite to the direction of rotation of the handle  9  that occurs when the handle  9  is rotated and transitioned from the upright position to the laid-flat position (clockwise direction indicated by an arrow Ar 1  in  FIG. 10A ). 
     A tip of the upright position-keeping arm  81  is located rightward of a center P of the rotating shaft  62  (further inside in the longitudinal direction of the upper surface of the fixation device housing  40  than is the center P). The tip of the upright position-keeping arm  81  is provided with a protrusion  81   p  protruding downward. 
     Meanwhile, there are two of the upright position-keeping arm engagement sections  82  that are located below a middle portion in the axial direction of the attachment section  61  with a space therebetween in the axial direction. The two upright position-keeping arm engagement sections  82  are flat sections that, when the handle  9  is in the upright position, are located below the two upright position-keeping arms  81 , and form a portion of the bottom surface  70   b  of the recessed section  70 . 
     As illustrated in  FIG. 10A , the upright position-keeping arm  81  is configured such that, when the handle  9  is in the upright position, the protrusion  81   p  is in contact with the upright position-keeping arm engagement section  82  to keep the handle  9  in the upright position. Specifically, at this time, the handle  9  is restrained from rotating in the clockwise direction indicated by the arrow Ar 1  in  FIG. 10A , by the upright position-keeping arm engagement section  82  being located inside a movement path (closer to the rotating shaft  62 ) of the protrusion  81   p  indicated by a dashed line in  FIG. 10A , and is thereby kept in the upright position. 
     Here, for example, when the user applies at least a predetermined force to the handle  9  in a tilting direction indicated by an arrow Ar 2  in order to rotate and transition the handle  9  from the upright position to the laid-flat position (a first predetermined force), the upright position-keeping arm  81  is bent in a direction that causes the tip thereof to move toward the rotating shaft  62  as illustrated in  FIG. 198 . As a result, the upright position-keeping arm engagement section  82  is located outside the movement path of the protrusion  81   p , which allows the handle  9  to rotate clockwise as illustrated in  FIG. 10B  with the protrusion  81   p  being slid on the upright position-keeping arm engagement section  82 . At this time, the protrusion  81   p  is pressed against the underlying upright position-keeping arm engagement section  82  by the elastic force of the upright position-keeping arm  81 , and therefore, a downward pressing force indicated by an arrow Ar 3  is applied to the upright position-keeping arm engagement section  82 . 
     When the protrusion  81   p  of the upright position-keeping arm  81  is moved to a position located leftward of the center P of the rotating shaft  62 , past the upright position-keeping arm engagement section  82 , the handle  9  is no longer kept in the upright position, and continues to be moved in the clockwise direction indicated in  FIG. 10B , Specifically, the keeping of the handle  9  in the upright position ends when the handle  9  has been rotated from the upright position by about 10 degrees in the clockwise direction indicated in  FIG. 10B . 
     Thus, the upright position-keeping detent mechanism  80  can keep the handle  9  in the upright position, and when at least the predetermined force (i.e., a force that can move the protrusion  81   p  to a position leftward of the rotating shaft  62 ) is applied to the handle  9  in a direction that causes the handle  9  to tilt, can end the keeping of the handle  9  in the upright position, and allow the handle  9  to rotate and transition to the laid-flat position. 
     When the handle  9  is transitioned from the laid-flat position to the upright position, the upright position-keeping detent mechanism  80  operates in an opposite manner to that in the transition from the upright position to the laid-flat position. Specifically, when the handle  9  is rotated in the direction that causes the handle  9  to stand up until the handle  9  is very close to the upright position, the upright position-keeping arm  81  is in contact with the upright position-keeping arm engagement section  82 . In this situation, if the user applies at least a predetermined force to the handle  9  in the direction that causes the handle  9  to stand up (a second predetermined force), the upright position-keeping arm  81  is bent in the direction that causes the tip to move toward the rotating shaft  62 . As a result, the upright position-keeping arm engagement section  82  is located outside the movement path of the protrusion  81   p , which allows the handle  9  to rotate with the protrusion  81   p  being slid on the upright position-keeping arm engagement section  82 . At this time, the protrusion  81   p  is also pressed against the underlying upright position-keeping arm engagement section  82  by the elastic force of the upright position-keeping arm  81 , and therefore, the downward pressing force indicated by the arrow Ar 3  is applied to the upright position-keeping arm engagement section  82 . 
     When the protrusion  81   p  of the upright position-keeping arm  81  is moved to a position rightward of the center P of the rotating shaft  62 , so that the handle  9  is transitioned to the upright position, the upright position-keeping arm  81  is moved past the upright position-keeping arm engagement section  82  to return to an original shape thereof, so that the handle  9  is kept in the upright position. 
     Thus, if, when the handle  9  is very close to the upright position, at least the predetermined force (i.e., a force that can cause the protrusion  81   p  to move to a position rightward of the rotating shaft  62 ) is applied to the upright position-keeping detent mechanism  80  in the direction that causes the handle  9  to stand up, the handle  9  is rotated and transitioned to the upright position, and is then kept in the upright position. 
     Next, the laid-flat position-keeping detent mechanism  90  is described. As illustrated in  FIG. 9B , and in addition,  FIG. 11A , which is a cross-sectional view of the handle  9  and the frame  71  taken along line B-B of  FIG. 9B , the laid-flat position-keeping detent mechanism  90  includes a laid-flat position-keeping arm  91  provided at the attachment section  61  of the handle  9 , and a laid-flat position-keeping arm engagement section  92  provided at the frame  71  of the fixation device housing  40 . 
     There are two of the laid-flat position-keeping arms  91  that are provided at both ends in the axial direction of the attachment section  61  (i.e., axially outward of the upright position-keeping arms  81 ). The two laid-flat position-keeping arms  91  are a cantilever plate spring that, when the handle  9  is in the laid-flat position, is located at the lower end (below the rotating shaft  62 ) of the attachment section  61 , extending from a right end toward a left end of the lower end of the attachment section  61  (from the inside toward the outside in the longitudinal direction of the fixation device housing  40 ). 
     In other words, the two laid-flat position-keeping arms  91  are a cantilever plate spring member that, when the handle  9  is in the laid-flat position, is located at the lower end of the attachment section  61 , and extends from a right end of the lower end of the attachment section  61  in the direction opposite to the direction of rotation of the handle  9  that occurs when the handle  9  is transitioned from the laid-flat position to the upright position (anticlockwise direction indicated by an arrow Ar 4  of  FIG. 11A ). 
     A tip of the laid-flat position-keeping arm  91  is located leftward of the center P of the rotating shaft  62  (outward of the center P in the longitudinal direction of the upper surface of the fixation device housing  40 ). The Up of the laid-flat position-keeping arm  91  is provided with a protrusion  91   p  protruding downward. 
     Meanwhile, there are two of the laid-flat position-keeping arm engagement sections  92  below both ends in the axial direction of the attachment section  61 . When the handle  9  is in the laid-flat position, the two laid-flat position-keeping arm engagement sections  92  are located below the two laid-flat position-keeping arms  91 . The two laid-flat position-keeping arm engagement sections  92  include a flat section  92   s  that forms a portion of the bottom surface  70   b  of the recessed section  70  (see  FIG. 8B ), and a recessed section  92   c  that is formed in the flat section  92   s.    
     As illustrated in  FIG. 11A , when the handle  9  is in the laid-flat position, the protrusion  91   p  of the laid-flat position-keeping arm  91  is inserted in the recessed section  92   c  of the laid-flat position-keeping arm engagement section  92 , whereby the laid-flat position is kept, Specifically, at this time, a wall at a right end of the recessed section  92   c  of the laid-flat position-keeping arm engagement section  92  is located inside a movement path (closer to the rotating shaft  62 ) (indicated by a dashed line in  FIG. 11A ) of the protrusion  91   p , As a result, the handle  9  is restrained from rotating in the anticlockwise direction indicated by the arrow Ar 4  in  FIG. 11A , and is thereby kept in the laid-flat position. 
     Here, for example, when the user applies at least the predetermined force to the handle  9  in the direction indicated by an arrow Ar 5  that causes the handle  9  to stand up in order to rotate and transition the handle  9  from the laid-flat position to the upright position, the laid-flat position-keeping arm  91  is bent in the direction that causes the tip thereof to move toward the rotating shaft  62  as illustrated in  FIG. 11B . When the handle  9  is further rotated until the protrusion  91   p  of the laid-flat position-keeping arm  91  moves past the wall at the right end of the recessed section  92   c  of the laid-flat position-keeping arm engagement section  92 , the handle  9  is no longer kept in the laid-flat position, and continues to be moved in the anticlockwise direction indicated in  FIG. 11B . Specifically, the keeping of the handle  9  in the laid-flat position ends when the handle  9  has been rotated from the laid-flat position by about 10 degrees in the anticlockwise direction indicated in  FIG. 11B . At this time, the protrusion  91   p  is pressed against the underlying laid-flat position-keeping arm engagement section  92  by the elastic force of the laid-flat position-keeping arm  91 , and therefore, a downward pressing force indicated by an arrow Ar 6  is applied to the laid-flat position-keeping arm engagement section  92 . 
     Thus, the laid-flat position-keeping detent mechanism  90  keeps the handle  9  in the laid-flat position, and when at least the predetermined force (La, a force that can dislodge the protrusion  91   p  from the recessed section  92   c ) is applied to the handle  9 , ends the keeping of the handle gin the laid-flat position, which allows the handle  9  to rotate and transition to the upright position. 
     When the handle  9  is transitioned from the upright position to the laid-flat position, the laid-flat position-keeping detent mechanism  90  operates in an opposite manner to that in the transition from the laid-flat position to the upright position. Specifically, when the handle  9  is rotated in the direction that causes the handle  9  to tilt until the handle  9  is very close to the laid-flat position, the laid-flat position-keeping arm  91  is in contact with the flat section  92   s  of the laid-flat position-keeping arm engagement section  92 . In this situation, when the user applies at least the predetermined force to the handle  9  in the direction that causes the handle  9  to tilt, the handle  9  is further rotated with the laid-flat position-keeping arm  91  bent in the direction that causes the tip thereof to move toward the rotating shaft  62 . At this time, the protrusion  91   p  is also pressed against the underlying laid-flat position-keeping arm engagement section  92  by the elastic force of the laid-flat position-keeping arm  91 . Therefore, the downward pressing force indicated by the arrow Ar 6  is applied to the laid-flat position-keeping arm engagement section  92 . When the handle  9  is completely transitioned to the laid-flat position, the protrusion  91   p  is moved past the flat section  92   s  of the laid-flat position-keeping arm engagement section  92  to be inserted into the recessed section  92   c , so that the laid-flat position-keeping arm  91  returns to an original shape thereof, which allows the handle  9  to be kept in the laid-flat position. 
     Thus, if, when the handle  9  is very close to the laid-flat position, at least the predetermined force (i.e., a force that can cause the protrusion  91   p  to be inserted into the recessed section  92   c ) is applied to the handle  9  in the direction that causes the handle  9  to tilt, the laid-flat position-keeping detent mechanism  90  allows the handle  9  to rotate and transition to the laid-flat position, and keeps the handle  9  in the laid-flat position. 
     As illustrated in  FIGS. 8A and 8B , the fixation device housing  40  is further provided with a lever  100  that is configured to, when the left handle  9  is in the upright position, protrude through an opening  40   h  provided at a left side surface  40 L of the fixation device housing  40 . The lever  100  is configured to be moved in association with the rotation of the handle  9 , and when the handle  9  is transitioned from the upright position to the laid-flat position, protrude through the opening  40   h.    
     Here,  FIGS. 12A and 12B  illustrate a left portion of the fixation device housing  40  as it is contained in the fixation device compartment  30 . Note that the handle  9  is in the upright position in  FIG. 12A , and in the laid-flat position in  FIG. 12B . 
     The fixation device compartment  30  is provided with a lever fitting hole  30   h  at a position that is opposite the opening  40   h  provided at the left side surface  40 L of the fixation device housing  40  when the fixation device housing  40  is contained in the fixation device compartment  30 . If, when the fixation device housing  40  is contained in the fixation device compartment  30 , the handle  9  is transitioned from the upright position to the laid-flat position, the lever  100  protrudes through the opening  40   h  of the fixation device housing  40 , and is fitted into the lever fitting hole  30   h . Although not illustrated, a lever that protrudes through an opening when the right handle  9  is in the upright position is also provided at a right side surface of the fixation device housing  40 . That lever is fitted into a lever fitting hole of the fixation device compartment  30 . 
     Thus, if, when the fixation device housing  40  is contained in the fixation device compartment  30 , the handle  9  is transitioned from the upright position to the laid-flat position, the lever  100  protrudes from the fixation device housing  40 , and is fitted into the lever fitting hole  30   h  of the fixation device compartment  30 , whereby the fixation device housing  40  is fixed to the fixation device compartment  30 . 
     In the course of the rotation and transition of the handle  9  from the upright position to the laid-flat position (rotational zone), the lever  100  does not protrudes from the fixation device housing  40  while the handle  9  is kept in the upright position by the upright position-keeping detent mechanism  80  (i.e., until the handle  9  has been rotated by about 10 degrees with respect to the upright position (upright zone)), and protrudes from the fixation device housing  40  after the handle  9  has been rotated past the upright zone. In other words, unless the handle  9  is in the upright position, the fixation device  8  cannot be removed from the image formation apparatus  1 . 
     As illustrated in  FIGS. 12A and 12B , the fixation device compartment  30  is provided with a lock switch  101  that, when the lever  100  is fitted into the lever fitting hole  30   h , is turned on by being pressed by a tip of the lever  100 . Although not illustrated, a similar lock switch is provided on the right side of the fixation device compartment  30 . The image formation apparatus  1  is configured such that, when the left and right lock switches  101  are on, the control unit  10  recognizes that the fixation device  8  is completely attached. If at least one of the left and right lock switches  101  is turned off during printing, the control unit  10  recognizes that the fixation device  8  has been removed, and stops printing. 
     Next, a linking member  102  that allows the handle  9  and the lever  100  to move in associated with each other is briefly described with reference to  FIGS. 9A, 9B, and 13A to 13C .  FIGS. 13A to 13C  are each an elevation view as viewed from the front, including a cross-sectional view of the handle  9 . 
     The linking member  102  is a bar-shaped member that is elongated in the upward/downward direction, and is located between a middle portion in the axial direction (forward/backward direction) of the attachment section  61  of the handle  9 , and the lever  100 , which is located below the middle portion, extending in the leftward/rightward direction. A lower end of the linking member  102  is linked to the lever  100 , and an upper end of the linking member  102  is supported by the attachment section  61  of the handle  9  in a manner that allows the linking member  102  to rotate about the rotating shaft  62 . Specifically, the rotation of the linking member  102  about the rotating shaft  62  can move the lever  100  in the direction that causes the lever  100  to protrude from the fixation device housing  40  and in the direction that causes the lever  100  to be put into the fixation device housing  40 . 
     The attachment section  61  of the handle  9  is provided with a lever contact part  63  that is located at a middle in the axial direction (between the two upright position-keeping arms  81 ) and is configured to be brought into contact with an upper end of the linking member  102 . The lever contact part  63  is brought into contact with the upper end of the linking member  102  (a portion below the rotating shaft  62 ) immediately before the handle  9  is transitioned to the upright position. In this state, while the handle  9  is being rotated until the handle  9  is transitioned to the upright position, the lever contact part  63  presses the linking member  102 , which is in turn rotated in the same direction in which the handle  9  is rotated. 
     The lever  100  is also pressed by a pressing member  103  such as a spring in the direction that causes the lever  100  to protrude from the fixation device housing  40 . 
     Here, movements of the handle  9 , the lever  100 , and the linking member  102  are briefly described with reference to  FIGS. 13A to 13C . As illustrated in  FIG. 13A , when the handle  9  is in the laid-flat position, the lever contact part  63  of the handle  9  is separated from the upper end of the linking member  102 . In this state, the lever  100  protrudes from the fixation device housing  40  due to a pressing force of the pressing member  103  as indicated by a dashed line in  FIG. 13A . 
     During the transition of the handle  9  from this state to the upright position, the lever contact part  63  of the handle  9  is brought into contact with the upper end of the linking member  102  immediately before the handle  9  is transitioned to the upright position as illustrated in  FIG. 13B . At this time, the lever  100  still protrudes from the fixation device housing  40 . 
     In this state, when the handle  9  is further moved toward the upright position, the linking member  102  is rotated about the rotating shaft  62  in an anticlockwise direction indicated by an arrow Ar 7  by the lever contact part  63  of the handle  9  pressing the upper end of the linking member  102  rightward (inward in the longitudinal direction of the fixation device housing  40 ) as illustrated in  FIG. 13C . At this time, the lower end of the linking member  102  is moved in a rightward direction that causes the lever  100  to be put into the fixation device housing  40 . As a result, the lever  100 , which is linked to the lower end of the linking member  102 , is moved rightward against the pressing force to be put into the fixation device housing  40 . 
     Thus, the linking member  102  is configured to, when the handle  9  is transitioned to the upright position, cause the lever  100  to be put into the fixation device housing  40 . Conversely, when the handle  9  is transitioned from the upright position to the laid-flat position, the linking member  102  causes the lever  100  to protrude from the fixation device housing  40 . Configurations of the handle  9  and surrounding parts have been described. 
     4. Operation of Attaching Fixation Device 
     Next, an operation of attaching the fixation device  8  to the image formation apparatus  1  is described. As described above, the fixation device  8  is attached to the image formation apparatus  1  by the following procedure: the user grasps the handle  9  as it is in the upright position, lifts up the fixation device  8 , and inserts the fixation device  8  into the image formation apparatus  1  through the cover opening  7  of the apparatus cover  2   c ; and the user pushes the fixation device  8  until the fixation device  8  is completely contained in the apparatus housing  2  of the image formation apparatus  1 . 
     As a result, the fixation device  8  is contained in the fixation device compartment  30 , which is provided in the apparatus housing  2 , and the connector  43  of the fixation device  8  is mated to the connector  31  of the fixation device compartment  30 , and the gear part  44  of the fixation device  8  is engaged with the gear part  32  of the fixation device compartment  30 . 
     Incidentally, in order to reliably mate the connector  43  of the fixation device  8  to the connector  31  of the fixation device compartment  30 , a force set to a specific value for the connectors  43  and  31  is required. For the image formation apparatus  1  according to an embodiment, the specific value is set to 2 kgf. Thus, it is necessary to exert a force of at least 2 kgf in order to reliably mate the connector  43  to the connector  31 . 
     Meanwhile, for the image formation apparatus  1  according to an embodiment, the weight of the fixation device  8  itself is 1.5 kgf. Therefore, when the fixation device  8  is inserted through the cover opening  7  and is caused to move downward only due to its own weight, the force (1.5 kgf) exerted by the weight of the fixation device  8  itself is smaller than the force (2 kgf) necessary to reliably mate the connector  43  to the connector  31 . Therefore, the connector  43  of the fixation device  8  cannot be reliably mated to the connector  31  of the fixation device compartment  30 . 
     In other words, when the fixation device  8  is inserted through the cover opening  7  and then attached to the image formation apparatus  1 , then if the force exerted during the insertion is too weak, the connector  43  of the fixation device  8  fails to be reliably mated to the connector  31  of the fixation device compartment  30 , and therefore, the fixation device  8  fails to be reliably attached to the image formation apparatus  1 . 
     Under the circumstances described above, for the image formation apparatus  1  according to an embodiment, the fixation device  8  is provided with the laid-flat position-keeping detent mechanism  90  for keeping the handle  9  in the laid-flat position, and the user is required to apply at least the predetermined force set for the laid-flat position-keeping detent mechanism  90  to the handle  9  in order to transition the handle  9  to the laid-flat position. This force is used to reliably mate the connector  43  of the fixation device  8  to the connector  31  of the fixation device compartment  30 . 
     Specifically, the user grasps the handle  9  as it is in the upright position, lifts up the fixation device  8 , and inserts the fixation device  8  into the image formation apparatus  1  through the cover opening  7  of the apparatus cover  2   c . Thereafter, the user moves the fixation device  8  downward until the fixation device  8  is completely contained in the apparatus housing  2 . 
     After the fixation device  8  is completely inserted, the user lays the handle  9  flat, i.e., transitions the handle  9  from the upright position to the laid-flat position. At this time, the user rotates and transitions the handle  9  from the upright position to a position that is very close to the laid-flat position, and then applies at least the predetermined force set for the laid-flat position-keeping detent mechanism  90  to the handle  9  so as to rotate and transition the handle  9  to the laid-flat position. 
     At this time, as illustrated in  FIG. 14 , the protrusion  91   p  is pressed against the underlying laid-flat position-keeping arm engagement section  92  due to the elastic force of the laid-flat position-keeping arm  91 . Therefore, the laid-flat position-keeping arm  91  applies the downward pressing force indicated by the arrow Ar 6  to the laid-flat position-keeping arm engagement section  92 . The force by which the laid-flat position-keeping arm  91  presses the laid-flat position-keeping arm engagement section  92  downward is used to mate the connector  43  of the fixation device  8  to the underlying connector  31  of the fixation device compartment  30 . 
     Specifically, if Fa+Ff&gt;Fc, the connector  43  can be reliably mated to the underlying connector  31 , where Fa represents the force by which the laid-flat position-keeping arm  91  presses the laid-flat position-keeping arm engagement section  92  downward, Fc represents the force (2 kgf) necessary to reliably mate the connector  43  to the underlying connector  31 , and Ff represents the weight (1.5 kgf) of the fixation device  8  itself. 
     In this case, if the force (Fa) by which the laid-flat position-keeping arm  91  presses the laid-flat position-keeping arm engagement section  92  downward is greater than the difference (0.5 kgf) between Fc (2 kgf) minus Ff (1.5 kgf), the connector  43  can be reliably mated to the underlying connector  31 . 
     Therefore, for the laid-flat position-keeping detent mechanism  90 , the amount of displacement of the tip of the laid-flat position-keeping arm  91  that occurs when the laid-flat position-keeping arm  91  is bent, the thickness of the laid-flat position-keeping arm  91 , or the like, is appropriately selected so as to establish Fa&gt;0.5 kgf. 
     Actually, when the fixation device  8  is put into the fixation device compartment  30 , the fixation device  8  receives a predetermined reaction force from the fixation device compartment  30  due to, for example, contact with the fixation device compartment  30 . Therefore, it is desirable to take such a reaction force into consideration in setting the force (Fa) by which the laid-flat position-keeping arm  91  presses the laid-flat position-keeping arm engagement section  92  downward. 
     Specifically, if Fa+Ff&gt;Fc+Fo, the connector  43  can be reliably mated to the underlying connector  31 , where Fo represents the maximum value of a reaction force that the fixation device  8  receives from the fixation device compartment  30 . 
     In this case, if the force (Fa) by which the laid-flat position-keeping arm  91  presses the laid-flat position-keeping arm engagement section  92  downward is greater than the difference (0.74 kgf) between the sum of Fc (2 kgf) and Fo (e.g., 0.24 kgf) minus Ff (1.5 kgf), the connector  43  can be reliably mated to the underlying connector  31 . 
     Therefore, for the laid-flat position-keeping detent mechanism  90  according to an embodiment, the amount of displacement of the tip of the laid-flat position-keeping arm  91  that occurs when the laid-flat position-keeping arm  91  is bent, the thickness of the laid-flat position-keeping arm  91 , or the like, is appropriately selected so as to establish Fa&gt;0.74 kgf. Specifically, the displacement amount is set to 0.6 mm±0.2 mm, and the thickness is set to 2.5 mm. 
     With the configuration described above of the image formation apparatus  1  according to an embodiment, when the fixation device  8  is attached to the image formation apparatus  1 , the connector  43  of the fixation device  8  can be reliably mated to the connector  31  of the fixation device compartment  30 . Thus, the fixation device  8  can be reliably attached to the image formation apparatus  1 . The operation of attaching the fixation device  8  to the image formation apparatus  1  is as described above. 
     5. Effects 
     As described above, the image formation apparatus  1  according to an embodiment includes: the apparatus housing  2  having, at an outer peripheral portion thereof, the stacker  5  on which paper M (medium) is stacked, the cover opening  7  being provided at the stacker  5 ; the image formation units  20  (image formation unit) that are provided in the apparatus housing  2  and form an image on paper M; and the fixation device  8  that is removably attached to the apparatus housing  2 , is removably attached to the apparatus housing  2  through the cover opening  7  (opening), and fixes, to the paper M, the image formed on the paper M by the image formation units  20 . When the fixation device  8  is attached to the apparatus housing  2 , a portion (upper end) of the fixation device  8  is exposed from the cover opening  7  provided at the stacker  5  to form a portion of the stacker  5 , and the connector  43  of the fixation device  8  is mated to the connector  31  of the apparatus housing  2 . 
     The fixation device  8  includes, at an exposed portion (upper end) thereof exposed from the cover opening  7 , the handle  9  that is allowed to transition between the upright position in which the handle  9  stands with respect to the exposed portion and the laid-flat position in which the handle  9  is laid flat with respect to the exposed portion. 
     The image formation apparatus  1  includes the laid-flat position-keeping detent mechanism  90  that, when at least the predetermined force is applied to the handle  9  in order to transition the handle  9  to the laid-flat position, allows the handle  9  to transition to the laid-flat position and keeps the handle  9  in the laid-flat position. 
     More specifically; the laid-flat position-keeping detent mechanism  90  includes the laid-flat position-keeping arm  91  (laid-flat position-keeping elastic member), and the laid-flat position-keeping arm engagement section  92  (laid-flat position-keeping contact member). During the rotation and transition of the handle  9  from the upright position to the laid-flat position, the protrusion  91   p  of the laid-flat position-keeping arm  91  is brought into contact with the flat section  92   s  of the laid-flat position-keeping arm engagement section  92  immediately before the handle  9  is transitioned to the laid-flat position. Here, when at least the predetermined force is applied to the handle  9  in the direction that causes the handle  9  to transition to the laid-flat position, the handle  9  is rotated with the laid-flat position-keeping arm  91  in contact with and bent by the laid-flat position-keeping arm engagement section  92 , and when the handle  9  is transitioned to the laid-flat position, the protrusion  91   p  of the laid-flat position-keeping arm  91  is moved past the flat section  92   s  of the laid-flat position-keeping arm engagement section  92  and is put into the recessed section  92   c , so that the laid-flat position-keeping arm  91  returns to an original shape thereof, which allows the handle  9  to be kept in the laid-flat position. In addition, while the handle  9  is being rotated with the laid-flat position-keeping arm  91  in contact with and bent by the laid-flat position-keeping arm engagement section  92 , the fixation device  8  is pressed by the elastic force of the laid-flat position-keeping arm  91  in the direction that causes the connector  43  of the fixation device  8  to be mated to the connector  31  of the apparatus housing  2 . 
     Thus; for example, after the user grasps the handle  9  as it is in the upright position and inserts the fixation device  8  into the image formation apparatus  1  through the cover opening  7 , at least the predetermined force set for the laid-flat position-keeping detent mechanism  90  is applied to the handle  9  in order to cause the handle  9  to transition from the upright position to the laid-flat position. This force can be used to reliably mate the connector  43  of the fixation device  8  to the connector  31  of the apparatus housing  2 . Thus, in the image formation apparatus  1 , the fixation device  8  can be reliably attached to the apparatus housing  2 . 
     The image formation apparatus  1  further includes the upright position-keeping detent mechanism  80  (detent mechanism) that, when at least the predetermined force is applied to the handle  9  in order to cause the handle  9  to transition to the upright position, causes the handle  9  to transition to the upright position, and keeps the handle  9  in the upright position. 
     More specifically, the upright position-keeping detent mechanism  80  includes the upright position-keeping arm  81  (upright position-keeping elastic member), and the upright position-keeping arm engagement section  82  (upright position-keeping contact member). During the rotation and transition of the handle  9  from the laid-flat position to the upright position, the protrusion  81   p  of the upright position-keeping arm  81  is brought into contact with the upright position-keeping arm engagement section  82  immediately before the handle  9  is transitioned to the upright position. Here, when at least the predetermined force is applied to the handle  9  in the direction that causes the handle  9  to rotate and transition to the upright position, the handle  9  is rotated with the upright position-keeping arm  81  in contact with and bent by the upright position-keeping arm engagement section  82 , and when the handle  9  is transitioned to the upright position, the protrusion  81   p  of the upright position-keeping arm  81  is moved past the upright position-keeping arm engagement section  82 , so that the upright position-keeping arm  81  returns to an original shape thereof, which allows the handle  9  to be kept in the upright position. 
     Thus, for example, the handle  9  can be kept in the upright position during an operation of attaching or removing the fixation device  8  to or from the apparatus housing  2 . Therefore, the user can easily attach or remove the fixation device  8  while grasping the handle  9 . 
     The image formation apparatus  1  further includes the levers  100  that, when the handle  9  is kept in the upright position by the upright position-keeping detent mechanism  80 , are put in the fixation device housing  40  of the fixation device  8 , and otherwise, protrude from the left and right side surfaces of the fixation device housing  40  (an accommodation section where the fixation device  8  is accommodated in the apparatus housing  2 ). The levers  100 , when protrude from the fixation device housing  40 , are fitted into the fixation device compartment  30  of the apparatus housing  2 , whereby the fixation device housing  40  is fixed to the fixation device compartment  30 . 
     The image formation apparatus  1  further includes the lock switch  101  (detector) that detects the protrusion of the lever  100  from the fixation device housing  40  that occurs when the fixation device housing  40  is contained in the fixation device compartment  30 . When the lock switch  101  detects the protrusion of the lever  100 , the control unit  10  determines that the fixation device  8  is attached to the apparatus housing  2 . 
     Thus, in the image formation apparatus  1 , for example, even if, after the fixation device  8  is attached to the apparatus housing  2 , a hand or the like of a user who is trying to pick up paper M discharged to the stacker  5  merely hits the handle  9 , the handle  9  is not transitioned from the laid-flat position to the upright position. Therefore, it is possible to avoid situations in which the user accidentally causes the handle  9  to transition to the upright position and thereby ends fixation of the fixation device  8 , and the control unit  10  determines that the fixation device  8  has been removed from the apparatus housing  2  and ends printing. 
     In addition, in the image formation apparatus  1 , when the handle  9  is kept in the upright position by the upright position-keeping detent mechanism  80 , the lever  100  is put in the fixation device housing  40 . Therefore, by causing the handle  9  to be in the upright position, the lever  100  can be kept in the state in which the lever  100  does not protrude from the fixation device housing  40 . As a result, it is possible to avoid, for example, a situation that during an operation of attaching the fixation device  8  to the apparatus housing  2 , the lever  100  protrudes from the fixation device housing  40  and hits and breaks the apparatus housing  2 . 
     6. Other Embodiments 
     6-1. First Alternative Embodiment 
     In one or more embodiments described above, the case has been described in which the upright position-keeping arm  81 , which includes a plate spring member, and the upright position-keeping arm engagement section  82 , which is a flat section that is engaged (contact) with the upright position-keeping arm  81 , constitute the upright position-keeping detent mechanism  80 . Here, for example, the upright position-keeping arm  81  may be provided at the fixation device housing  40 , and the upright position-keeping arm engagement section  82  may be provided at the handle  9 . Alternatively, another detent mechanism may be employed instead of the upright position-keeping detent mechanism  80  as long as that mechanism can cause the handle  9  to transition to the upright position when at least the predetermined force is applied to the handle  9  in order to cause the handle  9  to transition to the upright position, and keep the handle  9  in the upright position. For example, a detent mechanism having a latch structure may be employed, or a detent mechanism having a rotation prevention structure including an elastic member such as a spring may be employed. 
     Likewise, the laid-flat position-keeping detent mechanism  90  may, for example, be configured such that the laid-flat position-keeping arm  91  is provided at the fixation device housing  40 , and the laid-flat position-keeping arm engagement section  92  is provided at the handle  9 . Alternatively, another detent mechanism may be employed as long as that mechanism can cause the handle  9  to transition to the laid-flat position when at least the predetermined force is applied to the handle  9  in order to cause the handle  9  to transition to the laid-flat position, and keep the handle  9  in the laid-flat position. 
     6-2. Second Alternative Embodiment 
     In one or more embodiments described above, the case has been described in which the fixation device  8  is provided with the upright position-keeping detent mechanism  80  that keeps the handle  9  in the upright position, and the laid-flat position-keeping detent mechanism  90  that keeps the handle  9  in the laid-flat position. Alternatively, for example, the upright position-keeping detent mechanism  80  may be removed, and only the laid-flat position-keeping detent mechanism  90  may be provided. 
     6-3. Third Alternative Embodiment 
     In one or more embodiments described above, the case has been described in which, when the handle  9  is kept in the upright position by the upright position-keeping detent mechanism  80 , the lever  100  is put in the fixation device housing  40  of the fixation device  8 , and otherwise, the lever  100  protrudes from the fixation device housing  40 . Alternatively, for example, the lever  100  may protrude from the fixation device housing  40  only when the handle  9  is kept in the laid-flat position by the laid-flat position-keeping detent mechanism  90 . 
     6-4. Fourth Alternative Embodiment 
     In one or more embodiments described above, the case has been described in which the lock switches  101  for detecting the protrusion of the levers  100  from the left and right side surfaces of the fixation device housing  40  are provided on both of the left and right sides of the fixation device compartment  30 . Alternatively, the lock switch  101  may be provided on only one of the left and right sides of the fixation device compartment  30 . 
     6-5. Fifth Alternative Embodiment 
     In one or more embodiments described above, the case has been described in which the fixation device  8  is provided with the sub-cover  41 . Alternatively, the sub-cover  41  may be removed. 
     6-6. Sixth Alternative Embodiment 
     In one or more embodiments described above, the disclosure is applied to the image formation apparatus  1  that is an electrophotographic color printer. Alternatively, the disclosure can be applied to image formation apparatuses having configurations different from that of the image formation apparatus  1  as long as those image formation apparatuses include a fixation device. For example, the disclosure may be applied to an image formation apparatus that is configured such that a toner image formed by an image formation unit is transferred to an intermediate transfer belt before being transferred to a medium. The disclosure may also be applied to a monochromatic image formation apparatus having a single image formation unit, or a color image formation apparatus having four or more image formation units. The disclosure may also be applied to an image formation apparatus that forms an image on a medium other than paper. The disclosure may also be applied to image formation apparatuses such as an electrophotographic photocopier, fax machine, and multifunction peripheral. 
     6-7. Seventh Alternative Embodiment 
     Furthermore, the disclosure is not limited to one or more embodiments described above. Specifically, the disclosure encompasses embodiments obtained by combining all or a portion of one or more embodiments described above, or embodiments obtained by extracting a portion of one or more embodiments described above. 
     The disclosure is widely applicable to, for example, image formation apparatuses such as an electrophotographic printer, photocopier, fax machine, and multifunction peripheral that include a fixation device. 
     The invention includes other embodiments or modifications in addition to one or more embodiments described above without departing from the spirit of the invention. One or more embodiments described above are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.