PATENT ABSTRACT
An image forming apparatus includes a cover that opens and closes an opening of an apparatus body, a unit removable from the apparatus body through the opening, a latch that is included in the unit and that is rotatable about a rotation fulcrum, the latch including a hook that is latched onto a latched portion of the apparatus body from downstream in a mounting direction of the unit to fix the unit onto the apparatus body and an operating portion that opposes the hook across the rotation fulcrum and that is operable through the opening, and a hindering portion that is included in the cover and that interferes, when the hook rotates in a separating direction in which the hook is separated from the latched portion in a state where the cover closes the opening, with the operating portion and hinders the hook from rotating in the separating direction.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-017959 filed Feb. 2, 2016. 
       BACKGROUND 
     Technical Field 
       [0002]    The present invention relates to an image forming apparatus. 
       SUMMARY 
       [0003]    According to an aspect of the invention, there is provided an image forming apparatus including a cover member that opens and closes an opening formed in an image forming apparatus body, a unit that is removable from the image forming apparatus body through the opening, a latch member that is included in the unit in such a manner as to be capable of rotating about a rotation fulcrum portion, the latch member including a hook that is to be latched onto a to-be-latched portion of the image forming apparatus body from a downstream side in a mounting direction of the unit and that fixes the unit onto the image forming apparatus body and an operating portion that is disposed so as to oppose the hook across the rotation fulcrum portion and that is capable of being operated through the opening, and a hindering portion that is included in the cover member and that interferes, when the hook rotates in a direction in which the hook is separated from the to-be-latched portion in a state where the cover member closes the opening, with the operating portion and hinders the hook from rotating in the direction in which the hook is separated from the to-be-latched portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein: 
           [0005]      FIG. 1  is a schematic side view illustrating the overall configuration of an image forming apparatus according to an exemplary embodiment of the present invention; 
           [0006]      FIG. 2  is a schematic perspective view of a fixing unit of the image forming apparatus according to the exemplary embodiment; 
           [0007]      FIG. 3  is a schematic side view of the fixing unit that is mounted in and fixed to the image forming apparatus according to the exemplary embodiment; 
           [0008]      FIG. 4  is a schematic enlarged side view of a mounting and unmounting mechanism included in the fixing unit of the image forming apparatus according to the exemplary embodiment; 
           [0009]      FIG. 5  is a schematic enlarged side view of a portion of a latch member included in the mounting and unmounting mechanism of the fixing unit of the image forming apparatus according to the exemplary embodiment, the portion being on the side on which a hook is present; 
           [0010]      FIG. 6  is a schematic side view illustrating a state where the hook of the latch member is not separated from a to-be-latched portion even though an external force has acted on the image forming apparatus according to the exemplary embodiment; and 
           [0011]      FIG. 7  is a schematic side view illustrating a state where a cover member is not closed when the fixing unit of the image forming apparatus according to the exemplary embodiment is not completely mounted in the image forming apparatus body. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    An exemplary embodiment of the present invention will be described in detail below with reference to the drawings. Note that, for convenience of description, arrow UP and arrow FR that are suitably illustrated in the drawings respectively indicate an upward direction and a forward direction of an image forming apparatus  10 . In addition, a direction toward the front side as viewed in  FIG. 1  is a left direction of the image forming apparatus  10 , and the term “when seen from the side” refers to the case of seeing from a left-right direction that is perpendicular to a mounting (inserting) direction of a fixing unit  70 , which will be described later. 
         [0013]    As illustrated in  FIG. 1 , an image processing unit  16  that performs image processing on image data, which is input, is disposed in the interior of an image forming apparatus body (hereinafter simply referred to as apparatus body)  12 , which serves as a housing of the image forming apparatus  10 . The image processing unit  16  processes image data, which has been input, into gradation data items of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and an exposure device  18  that receives the processed gradation data items and performs image exposure by using laser beams L is disposed in a central area inside the apparatus body  12 . 
         [0014]    Four image forming units  20 Y,  20 M,  20 C, and  20 K, which respectively correspond to the colors Y, M, C, and K, are disposed above the exposure device  18  in such a manner as to be spaced apart from one another in a direction inclined with respect to the horizontal direction and are removable from the apparatus body  12 . Note that, in the following description, when it is not necessary to describe the image forming units  20 Y,  20 M,  20 C, and  20 K in such a manner as to be distinguished in terms of color, the letters Y, M, C, and K will be omitted. 
         [0015]    The image forming units  20  are configured in a similar manner. Each of the image forming units  20  includes an image carrier  22  that has a columnar shape and that is driven so as to rotate at a predetermined speed, a charging member  24  for first charging that charges the outer circumferential surface of the corresponding image carrier  22 , a developing device  26  that develops, with a predetermined color toner, an electrostatic latent image, which has been formed on the charged outer circumferential surface of the image carrier  22  by image exposure performed by the exposure device  18 , so as to visualize the electrostatic latent image as a toner image, and a cleaning blade (not illustrated) that cleans the outer circumferential surface of the image carrier  22  after the toner image has been transferred. 
         [0016]    In addition, toner supply devices  14 Y,  14 M,  14 C, and  14 K that supply toners to the corresponding developing devices  26  are disposed in the interior of the apparatus body  12 . In the exposure device  18 , four semiconductor lasers (not illustrated) each having the same configuration are disposed in such a manner as to correspond to the four image forming units  20 Y,  20 M,  20 C, and  20 K, and the laser beams L are to be emitted from the semiconductor lasers in accordance with the gradation data items. 
         [0017]    Note that each of the laser beams L, which have been emitted from the semiconductor lasers, is radiated onto a polygon mirror (not illustrated), which is a rotating polygon mirror, via a cylindrical lens (not illustrated) and is caused to be deflected and scanned by the polygon mirror. Then, each of the laser beams L, which have been caused to be deflected and scanned by the polygon mirror, is radiated onto an exposure point on the corresponding image carrier  22  via an imaging lens (not illustrated) and plural mirrors (not illustrated) and is caused to scan and irradiate the image carrier  22 . 
         [0018]    Since there is a possibility of toners and the like falling onto the exposure device  18  from the developing devices  26  and the like, which are included in the four image forming units  20 Y,  20 M,  20 C, and  20 K disposed above the exposure device  18 , the periphery of the exposure device  18  is hermetically sealed by a frame  28  having a substantially rectangular parallelepiped shape. An upper portion of the frame  28  is provided with a window  29  that is made of transparent glass and that transmits the four laser beams L onto the corresponding image carriers  22 . 
         [0019]    Meanwhile, a first transfer unit  30  is disposed above the image forming units  20 . The first transfer unit  30  includes an endless intermediate transfer belt  32 , a driving roller  34  around which the intermediate transfer belt  32  is wound and which drives the intermediate transfer belt  32  so that the intermediate transfer belt  32  moves circularly in the direction of an arrow in  FIG. 1 , a tension-applying roller  36  around which the intermediate transfer belt  32  is wound and which exerts tension on the intermediate transfer belt  32 , a driven roller  38  that is disposed above the tension-applying roller  36  and that is driven so as to rotate by the intermediate transfer belt  32 , and first transfer rollers  40 Y,  40 M,  40 C, and  40 K each of which is positioned on the side opposite to the side on which a corresponding one of the image carriers  22  is disposed with the intermediate transfer belt  32  interposed therebetween. 
         [0020]    Toner images of the colors Y, M, C, and K, which have been sequentially formed on the image carriers  22  of the corresponding image forming units  20 Y,  20 M,  20 C, and  20 K, are transferred onto the intermediate transfer belt  32  in such a manner that the toner images are superposed with one another by the four transfer rollers  40 Y,  40 M,  40 C, and  40 K. Note that a cleaning blade  42  that cleans an outer peripheral surface of the intermediate transfer belt  32  is disposed so as to be positioned on the side opposite to the side on which the driving roller  34  is disposed with the intermediate transfer belt  32  interposed therebetween. 
         [0021]    A second transfer roller  44  is disposed so as to be positioned on the side opposite to the side on which the driven roller  38  is disposed with the intermediate transfer belt  32  interposed therebetween, and a portion where the intermediate transfer belt  32  and the second transfer roller  44  are in contact with each other serves as a second transfer position. Accordingly, the toner images of the colors Y, M, C, and K, which have been transferred to the intermediate transfer belt  32  in such a manner that the toner images are superposed with one another, are transported by the intermediate transfer belt  32  and are transferred in a second transfer process onto one of sheet members P, each of which is an example of a recording medium. 
         [0022]    The fixing unit  70  that fixes toner images that have been transferred to one of the sheet members P onto the sheet member P is disposed at a position downstream from the second transfer position in a transport direction of the sheet members P. Note that the term “in the transport direction of the sheet members P” will hereinafter be omitted when describing such a position downstream from something. The fixing unit  70  is an example of a unit that is removable from the apparatus body  12 , and details of mounting and unmounting mechanisms  80  (see  FIG. 2 ) of the fixing unit  70  that are used for mounting and unmounting the fixing unit  70  on and from the apparatus body  12  will be described later. 
         [0023]    The fixing unit  70  includes a heating roller  74  and a pressure roller  76 , and toner images are fixed onto one of the sheet members P as a result of the sheet member P passing through a portion where the pressure roller  76  and the heating roller  74  are in contact with each other (as a result of applying heat and pressure to the sheet member P). Ejection rollers  46  that eject the sheet member P, to which the toner images have been fixed, to an ejecting section  48  that is formed in an upper portion of the apparatus body  12  are each disposed at a position downstream from the fixing unit  70 . 
         [0024]    Meanwhile, a sheet-feeding member  50  in which the sheet members P are accommodated is disposed in a lower area of the apparatus body  12 . A sheet-feeding roller  52  that sends out the sheet members P, which are accommodated in the sheet-feeding member  50 , to a sheet-transport path is disposed at a position downstream from the sheet-feeding member  50 , and a pair of separation rollers  54  that transport the sheet members P by separating the sheet members P one by one and are each disposed at a position downstream from the sheet-feeding roller  52 . 
         [0025]    A pair of registration rollers  56  that adjust a transfer timing are each disposed at a position downstream from the separation rollers  54 . Consequently, as a result of rotation of the registration rollers  56 , one of the sheet members P that has supplied from the sheet-feeding member  50  is sent out, at a predetermined transfer timing, to the second transfer position where the intermediate transfer belt  32  and the second transfer roller  44  are in contact with each other. 
         [0026]    Transport rollers  58  that transport one of the sheet members P to the registration rollers  56  again in the case of printing an image on the two surfaces of the sheet member P are disposed in front of the ejection rollers  46 . The sheet member P is flipped over as a result of being transported along a transport path for two-sided printing by the transport rollers  58  and is transported to the registration rollers  56  again. 
         [0027]    An image forming process to be executed by the image forming apparatus  10  will now be briefly described. 
         [0028]    First, gradation data items of different colors are sequentially output from the image processing unit  16  to the exposure device  18 , and each of the laser beams L, which are emitted from the exposure device  18  in accordance with the gradation data items of the different colors, is caused to scan and irradiate the outer circumferential surface of the corresponding image carrier  22 , which has been charged by the corresponding charging member  24 . As a result, electrostatic latent images are formed on the outer circumferential surfaces of the image carriers  22 . 
         [0029]    The electrostatic latent images that have been formed on the image carriers  22  are visualized as toner images of the colors Y, M, C, and K, respectively, by the corresponding developing devices  26 . Then, by the transfer rollers  40 Y,  40 M,  40 C, and  40 K of the first transfer unit  30 , which is arranged above the image forming units  20 Y,  20 M,  20 C, and  20 K, the toner images of the colors Y, M, C, and K that have been formed on the corresponding image carriers  22  are transferred onto the intermediate transfer belt  32 , which moves circularly, in such a manner that the toner images are superposed with one another. 
         [0030]    Meanwhile, one of the sheet members P is transported to the sheet-transport path from the sheet-feeding member  50  by the sheet-feeding roller  52  and the separation rollers  54  and is transported to the second transfer position at a predetermined transfer timing by the registration rollers  56 . The toner images of the different colors that have been transferred to the intermediate transfer belt  32 , which moves circularly, in such a manner that the toner images are superposed with one another are transferred in a second transfer process onto the sheet member P at the second transfer position. 
         [0031]    The sheet member P to which the toner images have been transferred is transported to the fixing unit  70 , and the toner images, which have been transferred to the sheet member P, are fixed onto the sheet member P by the heating roller  74  and the pressure roller  76 . The sheet member P to which the toner images have been fixed is ejected to the ejecting section  48 , which is formed in an upper portion of the apparatus body  12 , by the ejection rollers  46 . 
         [0032]    Note that, in the case of printing an image on the two surfaces of one of the sheet members P, the sheet member P having toner images fixed to one surface thereof by the fixing unit  70  will not be ejected to the ejecting section  48  by the ejection rollers  46  and is transported to the transport path for two-sided printing by the transport rollers  58  as a result of the transport direction of the sheet member P being switched. 
         [0033]    The sheet member P that has been flipped over as a result of being transported along the transport path for two-sided printing is transported to the registration rollers  56  again, and toner images are transferred and fixed onto the other surface of the sheet member P. The sheet member P having the toner images fixed to the two surfaces thereof in the above manner is ejected to the ejecting section  48  by the ejection rollers  46 . 
         [0034]    The mounting and unmounting mechanisms  80  of the fixing unit  70  that are used for mounting and unmounting the fixing unit  70  on and from the apparatus body  12  will now be described in detail. 
         [0035]    As illustrated in  FIG. 1 , an opening  12 A is formed in the apparatus body  12  on the front side, and a cover member  60 , which is included in the apparatus body  12 , opens and closes the opening  12 A. A lower end portion (a portion positioned below protruding portions  64 , which will be described later) of the cover member  60  is rotatably supported by a support shaft  62 , which is an example of a rotary support portion having an axial direction parallel to the left-right direction, and accordingly, the cover member  60  is to be opened and closed in the direction of the other arrow in  FIG. 1 . 
         [0036]    As illustrated in  FIG. 3 , a pair of the protruding portions  64 , each of which is an example of a hindering portion, are integrally formed on the left and right sides of an intermediate portion of the inner surface of the cover member  60  in a height direction in such a manner as to protrude from the intermediate portion. When the cover member  60  closes the opening  12 A, each of the protruding portions  64  is inserted into a space between a lower surface  72 A of a housing  72  (described later) of the fixing unit  70  and an upper surface  86 A of a corresponding one of operating portions  86 . End surfaces of the protruding portions  64 , the end surfaces facing toward the rear side in a state where the cover member  60  closes the opening  12 A are flat or substantially flat surfaces  64 A (see  FIG. 4 ). 
         [0037]    As illustrated in  FIG. 2  and  FIG. 3 , the fixing unit  70  includes the housing  72  having a long length in the left-right direction, and the heating roller  74  and the pressure roller  76  (see  FIG. 1 ) are disposed in the housing  72 . The fixing unit  70  is removable from the apparatus body  12  by hand through the opening  12 A, which is formed as a result of the cover member  60  being opened, in a front-rear direction. 
         [0038]    A pair of left and right holding portions  78  that are to be pressed from above by thumbs of both hands are formed at the opposite upper ends of the housing  72  in the longitudinal direction of the housing  72 , the opposite upper ends being located on the side on which a surface of the housing  72  is present, the surface facing the front side and being exposed through the opening  12 A. Plural grooves  78 A each extending in the left-right direction are formed in upper surfaces of the holding portions  78  in order to prevent fingers from slipping. A pair of left and right latch members  82  that are to be pressed by index fingers of both hands are formed at the opposite lower ends of the housing  72  in the longitudinal direction, the opposite lower ends being located on the side on which the surface of the housing  72  is present, the surface facing the front side and being exposed through the opening  12 A. 
         [0039]    As illustrated in  FIG. 2  and  FIG. 4 , the longitudinal direction of the latch members  82 , which are included in the mounting and unmounting mechanisms  80  of the fixing unit  70 , is parallel to the front-rear direction, and a substantially central portion of each of the latch members  82  in the front-rear direction is a rotation fulcrum portion  84  having an axial direction parallel to the left-right direction. In other words, front side end portions (operating portions  86 , which will be described later) and rear side end portions (hooks  88 , which will be described later) of the latch members  82  rotate in a top-bottom direction about the corresponding rotation fulcrum portions  84 . 
         [0040]    The front side end portions (upstream side end portions in a mounting direction of the fixing unit  70 ) of the latch members  82  each have a reasonable width in the left-right direction and are the operating portions  86  that are to be pressed by index fingers from below (that are capable of being operated through the opening  12 A). Plural grooves  86 B each extending in the left-right direction are formed in lower surfaces of the operating portions  86  in order to prevent fingers from slipping. A surface of each of the operating portions  86 , the surface facing the front side, is an end surface  86 C. 
         [0041]    The operating portions  86  are urged downward by compression-coil springs  66 , each of which is an example of an urging member. In other words, upper ends of the compression-coil springs  66  are attached to the lower surface  72 A of the housing  72 , and lower ends of the compression-coil springs  66  are attached to the upper surfaces  86 A of the corresponding operating portions  86  in such a manner as to be located inside the upper surfaces  86 A in the left-right direction. 
         [0042]    Consequently, the operating portions  86  are constantly urged downward, and when the fixing unit  70  is mounted in (inserted into) the apparatus body  12 , each of the operating portions  86  is pressed upward against an urging force of the corresponding compression-coil spring  66  (is caused to rotate upward about the corresponding rotation fulcrum portions  84 ). 
         [0043]    Note that, as illustrated in  FIG. 2 , recesses  72 B, each of which is recessed upward, may be formed in the lower surface  72 A of the housing  72 , and upper portions of the compression-coil springs  66  may be accommodated in the recesses  72 B while the upper ends of the compression-coil springs  66  are attached to top surfaces of the recesses  72 B. 
         [0044]    On the other hand, the rear side end portions (downstream side end portions in the mounting direction of the fixing unit  70 ) of the latch members  82  are the hooks  88  that are latched onto to-be-latched portions  68 , which are included in the apparatus body  12 . As illustrated in  FIG. 5 , the to-be-latched portions  68  are fixed, in a so-called snap-fit manner, to support portions  13  that are included in the apparatus body  12  and each of which is substantially L-shaped when seen from the side by being inserted into the support portions  13  from the rear side. A rear end lower surface of each of the to-be-latched portions  68  is an arc-shaped or substantially arc-shaped surface  68 A that is an example of a contact surface formed so as to have an arc shape or a substantially arc shape when seen from the side. 
         [0045]    The hooks  88  protrude upward, and front lower portions of the hooks  88  are linear or substantially linear contact portions  88 A that are brought into contact with the arc-shaped or substantially arc-shaped surfaces  68 A of the corresponding to-be-latched portions  68  at a predetermined pressure (by the urging force of the corresponding compression-coil springs  66 ) from the rear side (the downstream side in the mounting direction of the fixing unit  70 ). With this configuration, the contact portions  88 A of the hooks  88  are secured to the arc-shaped or substantially arc-shaped surfaces  68 A of the corresponding to-be-latched portions  68 , and as a result, the fixing unit  70  is fixed to the apparatus body  12 . 
         [0046]    As illustrated in  FIG. 5 , in a state where the contact portion  88 A of each of the contact portions  88 A is secured to the arc-shaped or substantially arc-shaped surface  68 A of the corresponding to-be-latched portion  68 , an angle θ 1  formed by a contact-portion imaginary line K 1  extending from the center of rotation of the corresponding rotation fulcrum portion  84  to the contact portion  88 A through a center O of a circle formed of the arc-shaped or substantially arc-shaped surface  68 A of the to-be-latched portion  68  and an imaginary line K 3  indicating an extending direction of the contact portion  88 A is set to be 90 degrees or about 90 degrees or larger. 
         [0047]    Front upper portions of the hooks  88  (tip portions of the hooks  88  located above the corresponding contact portions  88 A) are barb portions  88 B each of which overlaps a rear end upper surface of the corresponding to-be-latched portion  68  from the rear side (in such a manner as to pass through the imaginary line K 3  in a securing direction). An angle θ 2  formed by a barb-portion imaginary line K 2  extending from the center of rotation of one of the rotation fulcrum portions  84  to the corresponding barb portion  88 B and an imaginary line K 4  indicating an extending direction of the barb portion  88 B is set to be 90 degrees or about 90 degrees or smaller. Note that each of the barb portions  88 B is formed in such a manner that the angle θ 2  is 90 degrees or about 90 degrees or smaller whichever portion of the barb portion  88 B the barb-portion imaginary line K 2  passes through. 
         [0048]    Rear portions of the hooks  88  are inclined portions  88 C each of which is inclined forward and upward (rearward and downward) when seen from the side as illustrated in  FIG. 5 . When, for example, the fixing unit  70  is mounted in the apparatus body  12  in a state where the operating portions  86  are not pressed upward, the inclined portions  88 C function as guide portions, which cause the corresponding hooks  88  to rotate downward about the corresponding rotation fulcrum portions  84 , by being brought into slidable contact with lower surfaces of the corresponding support portions  13 . 
         [0049]    Operation of the mounting and unmounting mechanisms  80  of the fixing unit  70 , which have the above-described configuration, will now be described. 
         [0050]    The cover member  60  opens the opening  12 A of the apparatus body  12  of the image forming apparatus  10  by rotating forward about the support shaft  62 . When mounting the fixing unit  70  in the apparatus body  12 , first, the holding portions  78 , which are formed in the upper portion of the housing  72 , and the operating portions  86  of the latch members  82 , which are formed in the lower portion of the housing  72 , are clamped by thumbs and index fingers. 
         [0051]    As a result, the operating portions  86  are pressed upward against the urging force of the corresponding compression-coil springs  66  and move (rotate) upward about the corresponding rotation fulcrum portions  84 . In other words, the hooks  88  move (rotate) downward about the corresponding rotation fulcrum portions  84 . In this state, the fixing unit  70  is inserted into (mounted in) the apparatus body  12  through the opening  12 A. 
         [0052]    The hooks  88  are moved downward as a result of moving the operating portions  86  upward about the rotation fulcrum portions  84 . Consequently, the hooks  88  are prevented from interfering with the corresponding support portions  13  through a process in which the fixing unit  70  is mounted in the apparatus body  12 . Note that, since each of the hooks  88  includes the inclined portion  88 C, even if the amount of downward movement of the hook  88  is not sufficient, the hook  88  moves downward while being guided by the lower surface of the corresponding support portion  13 . 
         [0053]    After the fixing unit  70  has been mounted in the apparatus body  12 , thumbs and index fingers are released from the holding portions  78  and the operating portions  86 . Then, the operating portions  86  are caused to move downward about the corresponding rotation fulcrum portions  84  by the urging force of the corresponding compression-coil springs  66 , and the contact portions  88 A of the hooks  88  are brought into contact with the arc-shaped or substantially arc-shaped surfaces  68 A of the corresponding to-be-latched portions  68  at a predetermined pressure (by the urging force of the compression-coil springs  66 ) from the rear side. As a result, the fixing unit  70  is fixed to the apparatus body  12 . 
         [0054]    Note that, in this case, the angle θ 1  formed by the contact-portion imaginary line K 1  extending from one of the rotation fulcrum portions  84  to the corresponding contact portion  88 A through the center O of the circle formed of the arc-shaped or substantially arc-shaped surface  68 A of the corresponding to-be-latched portion  68  and the imaginary line K 3  indicating the extending direction of the contact portion  88 A is set to be 90 degrees or about 90 degrees or larger (see  FIG. 5 ). 
         [0055]    After the fixing unit  70  has been fixed to the apparatus body  12  in the above manner, the cover member  60  is caused to rotate about the support shaft  62  in a direction opposite to the above-mentioned direction so as to close the opening  12 A. 
         [0056]    When the cover member  60  closes the opening  12 A, each of the protruding portions  64 , which are formed on the inner surface of the cover member  60  in such a manner as to protrude from the inner surface, is inserted between the lower surface  72 A of the housing  72  and an area outside the upper surface  86 A of the corresponding operating portion  86  in the left-right direction (see  FIG. 4 ). Here, in the case where an external force is applied to the fixing unit  70  in a direction in which the fixing unit  70  is separated from the apparatus body  12  (such as when, for example, the image forming apparatus  10  is dropped), the hooks  88  rotate in a direction in which the hooks  88  are separated from the corresponding to-be-latched portions  68  (see  FIG. 6 ). 
         [0057]    However, as illustrated in  FIG. 6 , since each of the protruding portions  64  is inserted between the lower surface  72 A of the housing  72  and the area outside the upper surface  86 A of the corresponding operating portion  86  in the left-right direction, when the hooks  88  rotate in the direction in which the hooks  88  are separated from the corresponding to-be-latched portions  68  in a state where the cover member  60  closes the opening  12 A, the operating portions  86  interfere with the corresponding protruding portions  64 , and the hooks  88  are hindered, by the protruding portions  64 , from rotating in the direction in which the hooks  88  are separated from the corresponding to-be-latched portions  68 . 
         [0058]    In other words, according to the mounting and unmounting mechanisms  80  of the fixing unit  70  of the present exemplary embodiment, the probability of the fixing unit  70 , which is removable from the apparatus body  12 , becoming separated from the apparatus body  12  due to an external force, such as vibration or a drop impact, is reduced, or the fixing unit  70  is prevented from becoming separated from the apparatus body  12  apparatus body  12  due to an external force, such as vibration or a drop impact, compared with the configuration in which the cover member  60  is not provided with the protruding portions  64  that hinder the corresponding hooks  88  from rotating in the direction in which the hooks  88  are separated from the corresponding to-be-latched portions  68 . 
         [0059]    In addition, since the angle θ 2  formed by the barb-portion imaginary line K 2  extending from one of the rotation fulcrum portions  84  to the corresponding barb portion  88 B and the imaginary line K 4  indicating the extending direction of the barb portion  88 B is set to be 90 degrees or about 90 degrees or smaller, each of the barb portions  88 B of the hooks  88  is less likely to be separated from the corresponding to-be-latched portion  68  compared with the configuration in which the angle θ 2  is larger than 90 degrees or about 90 degrees. 
         [0060]    As illustrated in  FIG. 7 , when performing an operation for closing the cover member  60  in a state where the hooks  88  are not latched to the corresponding to-be-latched portions  68 , the flat or substantially flat surfaces  64 A of the protruding portions  64  come into surface contact with the end surfaces  86 C of the corresponding operating portions  86 , and accordingly, it is difficult to close the cover member  60 . Therefore, the likelihood of failure of mounting the fixing unit  70  in the apparatus body  12  is reduced, or failure of mounting the fixing unit  70  in the apparatus body  12  is prevented from occurring compared with the configuration in which the protruding portions  64  do not have the flat or substantially flat surfaces  64 A, which hinder the cover member  60  from closing the opening  12 A. 
         [0061]    In other words, a probability of occurrence of a problem in that the cover member  60  is closed in a state where the fixing unit  70  is not mounted in the apparatus body  12  is reduced, or a problem in that the cover member  60  is closed in a state where the fixing unit  70  is not mounted in the apparatus body  12  is prevented from occurring. Note that, in this case, the fixing unit  70  is pushed into the apparatus body  12  by forcibly closing the cover member  60 , and the hooks  88  are latched onto the corresponding to-be-latched portions  68 . Therefore, the likelihood of the failure of mounting the fixing unit  70  in the apparatus body  12  is further reduced, or the failure of mounting the fixing unit  70  in the apparatus body  12  is further prevented from occurring. 
         [0062]    Although the image forming apparatus  10  according to the present exemplary embodiment has been described above with reference to the drawings, the image forming apparatus  10  according to the present exemplary embodiment is not limited to that illustrated in the drawings, and design changes may be suitably made within the gist of the present invention. For example, the mounting and unmounting mechanisms  80  according to the present exemplary embodiment are not limited to being included in the fixing unit  70  and may be included in a different unit, such as the first transfer unit  30 , that is removable from the apparatus body  12 . 
         [0063]    In addition, the to-be-latched portions  68  are not limited to having the shape illustrated in the drawings as long as the rear end lower surfaces of the to-be-latched portions  68 , with which the contact portions  88 A of the corresponding hooks  88  are brought into contact, are the arc-shaped or substantially arc-shaped surfaces  68 A each of which is formed so as to have an arc shape or a substantially arc shape when seen from the side. Therefore, each of the to-be-latched portions  68  may be, for example, a columnar shaft (not illustrated). 
         [0064]    The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.