Abstract:
An image forming apparatus includes: a main body; an opening and closing unit disposed so as to be openable and closable for the main body; a fixing unit fixing the opening and closing unit to the main body; a structure including a component for realizing an image forming function and/or a transfer medium-conveying function, the structure being supported movably for the main body; a bias unit disposed between the opening and closing unit and the structure, the bias unit biasing the structure so as to be pushed to a member mounted within the main body; a constraining unit constraining the opening and closing unit and the structure against a bias force of the biasing unit when the fixing unit does not fix the opening and closing unit; and a releasing unit releasing the opening and closing unit and the structure from being constrained when the fixing unit fixes the opening and closing unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims priority under 35 USC §119 from Japanese Patent Application No. 2007-92036 filed Mar. 30, 2007. 
       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 comprising: 
         [0004]    a main body; 
         [0005]    an opening and closing unit disposed so as to be openable and closable with respect to the main body; 
         [0006]    a fixing unit that fixes the opening and closing unit to the main body; 
         [0007]    a structure comprising a component for realizing at least one of an image forming function and a transfer medium-conveying function, the structure being supported movably with respect to the main body; 
         [0008]    a bias unit disposed between the opening and closing unit and the structure, the bias unit biasing the structure so as to push the structure to at least one member mounted within the main body; 
         [0009]    a constraining unit that constrains the opening and closing unit and the structure against a bias force of the biasing unit when the fixing unit does not fix the opening and closing unit; and 
         [0010]    a releasing unit that releases the opening and closing unit and the structure from being constrained when the fixing unit fixes the opening and closing unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Embodiments of the present invention will be described in detail based on the following figures, wherein: 
           [0012]      FIG. 1  is a side view showing a schematic structure of an image forming apparatus according to a first exemplary embodiment of the invention; 
           [0013]      FIG. 2  is a side view showing a state in which a front cover and a transfer unit used for the first embodiment are assembled in a main body of the image forming apparatus; 
           [0014]      FIG. 3  is a side view showing a structure of the front cover used for the first embodiment; 
           [0015]      FIG. 4  is a side view showing a structure of the transfer unit used for the first embodiment; 
           [0016]      FIG. 5  is a perspective view showing a state in which the front cover and the transfer unit used for the first embodiment are assembled in the main body of the image forming apparatus; 
           [0017]      FIG. 6  is a first explanatory view for explaining an operation of the image forming apparatus according to the first embodiment; 
           [0018]      FIG. 7  is a second explanatory view for explaining an operation of the image forming apparatus according to the first embodiment; 
           [0019]      FIG. 8  is a third explanatory view for explaining an operation of the image forming apparatus according to the first embodiment; 
           [0020]      FIG. 9  is a fourth explanatory view for explaining an operation of the image forming apparatus according to the first embodiment; 
           [0021]      FIG. 10  is a side view showing a structure of the front cover used for a second exemplary embodiment of the present invention; 
           [0022]      FIG. 11  is a side view showing a state in which a front cover and a transfer unit used for the second embodiment are assembled in a main body of the image forming apparatus; 
           [0023]      FIG. 12  is a first explanatory view for explaining an operation of the image forming apparatus according to the second embodiment; 
           [0024]      FIG. 13  is a second explanatory view for explaining an operation of the image forming apparatus according to the second embodiment; 
           [0025]      FIG. 14  is a third explanatory view for explaining an operation of the image forming apparatus according to the second embodiment; 
           [0026]      FIG. 15  is a forth explanatory view for explaining an operation of the image forming apparatus according to the second embodiment; 
           [0027]      FIG. 16  is a side view showing a structure of the front cover and the transfer unit used for a third exemplary embodiment; 
           [0028]      FIG. 17  is a first explanatory view for explaining an operation of the image forming apparatus according to the third embodiment; 
           [0029]      FIG. 18  is a second explanatory view for explaining an operation of the image forming apparatus according to the third embodiment; and 
           [0030]      FIG. 19  is a third explanatory view for explaining an operation of the image forming apparatus according to the third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Next, exemplary embodiments according to the invention will be described with reference to the drawings. 
         [0032]      FIG. 1  shows an image forming apparatus  10  according to a first exemplary embodiment of the invention. This image forming apparatus  10  has a main body  12  of the image forming apparatus, a paper feeding apparatus  14  disposed on the lower part of the main body  12 , and a paper discharge unit  16  formed on the upper part of the main body  12 . 
         [0033]    The paper feeding apparatus  14  has a sheet tray  18  and sheets to be used as a transfer medium are stacked on the sheet tray. A feed roll  20  is disposed on an upper part of one end of the sheet tray  18 , and a retard roll  22  is disposed being opposed to the feed roll  20 . The sheet positioned at the highest position of the sheet tray  18  is picked up by the feed roll  20  and then, the sheet is brushed and conveyed in combination with the feed roll  20  and the retard roll  22 . 
         [0034]    The sheet conveyed from the sheet tray  18  is temporarily stopped by a resist roll  24 , and at a timing, the sheet goes through between a photoconductor unit  26  and a transfer unit  28  and through a fixing apparatus  30 , and is discharged to the paper discharge unit  16  to be described later by a paper discharge roll  32 . 
         [0035]    On the front side of the image forming apparatus main body  12  (namely, the right side in  FIG. 1 ), a front cover  11  as a first opening and closing unit is disposed. The front cover  11  is mounted rotatably (movably) by an axis  15  as a support unit with respect to the image forming apparatus main body  12  and the front cover  11  is rotated around the axis  15  so as to be opened to the front side of the image forming apparatus main body  12 . In addition, on the upper side of the image forming apparatus main body  12 , an upper cover  13  as a second opening and closing unit is disposed. The upper cover  13  is rotated by an axis  17  as a support unit with respect to for the image forming apparatus main body  12  so as to be opened to the upper side of the image forming apparatus main body  12 . 
         [0036]    The upper cover  13  is closed so as to overlap the front cover  11  in a closed state, from the front side. In other words, the upper cover  13  as being closed may interfere with the front cover  11  being opening or closing. Therefore, unless the upper cover  13  is opened, the front cover  11  cannot be opened. In addition, after closing the front cover  11 , the upper cover  13  is closed. 
         [0037]    In the interior part of the image forming apparatus main body  12 , the photoconductor unit  26 , the transfer unit  28 , a power source unit  34 , and a control unit  36  are disposed. The photoconductor unit  26  is used as a mounted member detachably mounted in the interior part of the image forming apparatus main body  12  and includes a photoconductor unit main body  38 . For example, four sub units  50  are supported by the photoconductor unit main body  38 . Each of sub units  50  has a photoconductor  40 . A charging apparatus  42  used as a charging unit provided with a charging roll for uniformly charging the photoconductor  40 , a developing apparatus  44  used as a developing unit for developing a latent image formed on the photoconductor  40  with a development agent image (a toner), a charge removal apparatus  46  used as a charge removing unit for removing electricity from the photoconductor  40  by irradiating a light to the transcribed photoconductor  40 , and a cleaning apparatus  48  as a development agent removing unit for removing the development agent remaining in the photoconductor  40  after transfer is made are provided around the photoconductor  40 . 
         [0038]    Four sub units  50  may include one for forming a yellow toner image, one for forming a magenta toner image, one for forming a cyan toner image, and one for forming a black toner image, from an upstream in a sheet conveying direction, which is the lower side in the gravity direction, and a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the surfaces of respective photoconductors  40 . Each of four sub units  50  can be attached and detached in the interior part of the photoconductor unit main body  38 . 
         [0039]    Each of optical writing apparatuses  56  includes a laser exposure apparatus and they are arranged on the positions corresponding to respective photoconductors  40  on the rear face side of the photoconductor unit  26  so as to form a latent image by irradiating a laser to the uniformly charged photoconductor  40 . 
         [0040]    The transfer unit  28  is used as a structure and is arranged in a longitudinal direction being opposed to the photoconductor unit  26  on the front side of the photoconductor unit  26 . The transfer unit  28  has a transfer unit main body  29 . In the interior part of the transfer unit main body  29 , two support rolls  58  are mounted in a vertical direction and a conveying belt  60  is hanged on the two support rolls  58 . In addition, in the interior part of the transfer unit main body  29 , a transfer roll  62  is mounted so as to be opposed to each photoconductor  40  across the conveying belt  60 . 
         [0041]    The conveying belt  60  is a member for conveying the sheet and serves to realize a conveying function of the sheet (the transfer medium). In addition, the transfer roll  62  is a member used for transfer, which is a part of an image forming function. In this way, the transfer unit  28  has at least one member for realizing at least one of the image forming function and the transfer medium conveying function. 
         [0042]    In the image forming apparatus  10  that is constructed as described above, the photoconductor  40  is uniformly charged by the charging apparatus  42 , a latent image is formed by the optical writing apparatuses  56 , and the latent image is developed by the developing apparatus  44  so as to form a development agent image (a toner image). The development agent images formed on the photoconductor  40  are transferred on the sheet conveyed by the conveying belt  60  in the order from the lower one by using the transfer roll  62  of the transfer unit  28  to be fixed on the sheet by the fixing apparatus  30 . 
         [0043]      FIG. 2  shows the front cover  11  and the transfer unit  28 ,  FIG. 3  shows the front cover  11 , and  FIG. 4  shows the transfer unit  28 . 
         [0044]    As shown in  FIGS. 2 and 4 , the transfer unit  28  is disposed on the side of the image forming apparatus main body  12  and by using an axis  94  used as a support unit, the transfer unit  28  is mounted so as to be capable of rotating with respect to the image forming apparatus main body  12  as shown by an arrow direction in the drawing. 
         [0045]    In addition, as shown in  FIGS. 2 and 3 , as described above, the front cover  11  is mounted on the image forming apparatus main body  12  by using the axis  15 , and as shown by an arrow in the drawing, the front cover  11  is rotatably opened and closed with respect to the image forming apparatus main body  12 . In  FIGS. 2 and 3 , the front cover  11  as being closed for the image forming apparatus main body  12  is illustrated. 
         [0046]    The image forming apparatus  10  according to the first embodiment has a fixing mechanism  130  used as a fixing unit, which is used for fixing the front cover  11  at a closed position. The fixing mechanism  130  has a fixing member  132  and the fixing member  132  is rotatably mounted in the image forming apparatus main body  12  around an axis  134 . In addition, the fixing member  132  has an operation unit (not illustrated) that is used for the operation by an operator and a contact unit  140  contacting a protrusion  138  for fixing, which is used for fixing the front cover  11 . 
         [0047]    In addition, the fixing mechanism  130  has a bias member  146 , for example, made of a coil spring, and the bias member  146  biases the fixing member  132  so as to be rotated around the axis  134  in a clockwise direction around the axis  134 . Although the fixing mechanism  130  is disposed on the both sides, the right and left sides of the front cover  11  one by one, namely, two in total,  FIG. 2  shows the fixing mechanism  130  located on the left side. 
         [0048]    A constraining member  70  is mounted on the both sides, namely, the right and left sides of the front cover  11 . The constraining member  70  is used for constraining the front cover  11  and the transfer unit  28  and configures a constraining unit. The constraining member  70  is mounted on the front cover  11  by using the axis  72  to be supported around the axis  72  so as to be capable of rotating for the front cover  11 . 
         [0049]    In the constraining member  70 , a groove  74  is formed, into which a protrusion  80  of a transfer unit main body, formed on the transfer unit main body  29  as a protrusion portion, can be inserted, and a pressing face  76  for pressing the transfer unit main body&#39;s protrusion  80  is formed. In addition, in a constraining member  70 , for example, a bias member  78  made of an elastic body such as a coil spring is mounted, and the bias member  70  is biased in a direction rotating in an anticlockwise direction around the axis  72  by the bias member  78 . 
         [0050]    On the both sides, namely, the right and left sides of the front cover  11 , a sliding member  82  is mounted so as to be capable of sliding with respect to the front cover  11 . A guide hole  83  is formed on the sliding member  82  and a protrusion  85  for mounting, formed on the side of the front cover  11 , is inserted into the guide hole  83 . On the protrusion  85  for mounting, for example, one end portion of a bias member  84  made of an elastic body such as a coil spring is mounted, and being pressed by other end portion of the bias member  84 , the sliding member  82  is biased in an inverse direction to the protrusion  85  for mounting (the upper direction in  FIG. 2 ). 
         [0051]    In addition, on the both sides, namely, the right and left sides of the front cover  11 , a notch  86  is formed so as to be capable of inserting the transfer unit main body&#39;s protrusion  80  disposed on the transfer unit main body  29 . On the lower side of the notch  86  in  FIG. 2 , a guide face  88  for guiding a movement of the transfer unit main body&#39;s protrusion  80  is formed. In addition, one end portion of the bias member  98 , for example, made of an elastic member such as a coil spring is fixed to the side face in the inside of the front cover  11  via a fixing portion  90 . 
         [0052]    The bias member  98  has other end portion contacting the transfer unit main body  29 . Therefore, the bias member  98  may press the transfer unit  28  to a main body frame  12   a  forming a part of the image forming apparatus main body  12  so as to be rotated around the axis  94  in an anticlockwise direction. Therefore, being biased by the bias member  98 , the transfer unit  28  is positioned and fixed to a usage position shown in  FIG. 2  where the transfer unit  28  is used for forming an image. 
         [0053]    Due to the bias member  98 , an appropriate figuration other than a configuration that the transfer unit  28  is positioned being pressed to the main body frame  12   a  can be selected, for example, a configuration that the transfer unit  28  is pressed to the photoconductor  40  of the photoconductor unit  26  and a configuration that the transfer unit  28  is positioned being pressed to the both of the main body frame  12   a  and the photoconductor unit  26  or the like. In other words, the bias member  98  may bias the transfer unit  28  so as to be pressed to at least any of the image forming apparatus main body  12  and a mounted member such as the photoconductor  40  and the photoconductor unit  26 , mounted in the interior part of the image forming apparatus main body  12 . 
         [0054]    In this way, the bias member  98  is disposed between the front cover  11  and the transfer unit  28  and is used as a bias unit for biasing the transfer unit  28  to the image forming apparatus main body  12  or the like. Further, in  FIG. 2 , the constraining member  70 , the bias member  78 , the sliding member  82 , the bias member  84 , and the notch  86  or the like disposed only on the left side are illustrated, however, as described above, they are disposed on the both sides, namely, the right and left sides one by one. 
         [0055]      FIG. 5  shows a state in which the front cover  11  and the transfer unit  28  are assembled in the image forming apparatus main body  12 . Further, in  FIG. 5 , the illustration of the constraining member  70  is omitted. 
         [0056]    As shown in  FIG. 5  and the above-described  FIG. 2 , the transfer unit main body  29  is assembled in the front cover  11  so that the transfer unit main body&#39;s protrusion  80  as a protrusion portion of the transfer unit main body  29  is inserted from the inside into the notch  86  shaped in a reversed L as the notch portion of the front cover  11 . The transfer unit main body&#39;s protrusion  80  contacts the sliding members  82  disposed on the both sides of the front cover  11  via the front cover  11  provided with the notch  86 . In addition, the upper part of the constraining member  70  contacts the upper cover  13  in the closed state as shown in  FIG. 2 . Then, the contact unit  140  of the fixing member  132  of the fixing mechanism  130  may contact the protrusion for contact  138 , and the front cover  11  is fixed to the image forming apparatus main body  12 . The notches  86  are disposed on the both sides of the front cover  11  in a condition of a reversed L (namely, shaped in a reversed L) as described above, and the transfer unit main body&#39;s protrusion  80  disposed in the transfer unit  28  is located at the positions shown in  FIG. 2  and  FIG. 5  so as to be released from constraint of the constraining member  70 , namely, is located at a constraining released position. 
         [0057]    With reference to  FIGS. 6 to 9 , the opening and closing operation of the front cover  11  and the upper cover  13  and the moving operation of the transfer unit  28  will be described below. In  FIGS. 6 to 9 , the illustration of the fixing mechanism  130  is omitted. In order to open the front cover  11  and the upper cover  13  from a state in which they are closed, as shown in  FIG. 6 , the operation to open the upper cover  13  is carried out by the operator. By opening the upper cover  13 , the front cover  11  can be opened moving from the position interfering with a locus of opening and closing of the front cover  11 . Then, when the operator operates an operation unit (not illustrated) of the front cover  11 , the fixing mechanism  130  is released, and the operation for opening the front cover  11  is carried out. In this time, the transfer unit main body&#39;s protrusion  80  is located at a constraint release position. Then, if the front cover  11  is rotated in a clockwise direction around the axis  15 , the transfer unit main body&#39;s protrusion  80  disposed on the transfer unit main body  29  may press down the sliding member  82  that is biased upward ( FIG. 7 ), and when the front cover  11  is further rotated, the transfer unit main body&#39;s protrusion  80  may move to the position of the guide face  88  in the notch  86  over the sliding member  82  ( FIG. 8 ). 
         [0058]    Describing this further in detail,  FIG. 8  shows the front cover  11  and the transfer unit  28  when the front cover  11  is opening. Here, since the front cover  11  and the transfer unit main body  29  are supported by the support portions (the axis  15 , the axis  94 ), which are disposed on different positions (the position displaced horizontally or vertically from the main body of the image forming apparatus) of the image forming apparatus main body  12 , a relative position with respect to the front cover of the transfer unit main body&#39;s protrusion  80  may move in a vertical direction of the image forming apparatus main body  12  in accordance with opening and closing of the front cover  11 . Therefore, in combination with opening of the front cover  11 , the transfer unit main body&#39;s protrusion  80  may press down the sliding member  82  to overleap the sliding member  82  at an opening and closing position. 
         [0059]    Then, when the transfer unit main body&#39;s protrusion  80  moves to the guide face  88 , the transfer unit main body&#39;s protrusion  80  is guided into the guide face  88  and this allows the front cover  11  to open. In accordance with this, the transfer unit  28  may move so as to be rotated in the clockwise direction around the axis  94 . Then, the front cover  11  and the transfer unit  28  are continuously rotated in the clockwise direction up to the position where the transfer unit main body&#39;s protrusion  80  contacts a lower end portion  104  of the notch  86 , and then, the front cover  11  and the transfer unit  28  are in the state to be opened with respect to the image forming apparatus main body  12 . 
         [0060]      FIG. 9  shows a state in progress since the front cover  11  and the transfer unit  28  are opened with respect to the image forming apparatus main body  12  (not illustrated) till the front cover  11  shown in the above-described  FIG. 4  is closed to be arranged on the position where the transfer unit  28  is used for forming an image. In order to shift a state in which the front cover  11  and the transfer unit  28  are opened with respect the image forming apparatus main body  12  into a state in which the front cover  11  is closed to be arranged on the position where the transfer unit  28  is used for forming an image, the operation by the operator for closing the front cover  11 , namely, the operation for rotating the front cover  11  in an anticlockwise direction around the axis  15  will be carried out. 
         [0061]    When the front cover  11  moves so as to be rotated around the axis  15  in the anticlockwise direction due to the operation by the operator, the transfer unit main body&#39;s protrusion  80  may move so as to be separated from the lower end portion  104  within the notch  86  as being guided by the guide face  88  of the notch  86 . Then, in combination with closing of the front cover  11 , the transfer unit  28  may move in the anticlockwise direction around the axis  94 . When the transfer unit  28  moves in the anticlockwise direction, as shown in  FIG. 9 , the transfer unit main body&#39;s protrusion  80  is in a state to be fitted in the groove  74  of the constraining member  70 . In other words, the transfer unit main body&#39;s protrusion  80  is in a state in which the front cover  11  is constrained with the transfer unit  28  each other, namely, a constrained state. 
         [0062]    In this case, before the transfer unit main body&#39;s protrusion  80  is fitted in the groove  74 , the transfer unit main body&#39;s protrusion  80  may press the face continued to the guide face  88  of the sliding member  82  in a substantially vertical direction. However, since the sliding member  82  is disposed so as to move only in a direction in parallel with the guide face  88 , it is not feared that the transfer unit main body&#39;s protrusion  80  is deviated from the guiding direction of the guide face  88  before the transfer unit main body&#39;s protrusion  80  is fitted in the groove  74 , and the transfer unit main body&#39;s protrusion  80  fails to be fitted in the groove  74 . In this way, the constraining member  70  and the transfer unit main body&#39;s protrusion  80  are used as a constraining unit for constraining the front cover  11  and the transfer unit  28 . Here, in order to prevent the constraining member  70  from being released upon receipt of a moment in the clockwise direction due to the force that the transfer unit main body&#39;s protrusion  80  receives from the bias member  98 , it is desirable that the rotational axis  72  is arranged so that the direction of the force that the constraining member  70  receives from the transfer unit main body&#39;s protrusion  80  by means of the bias member  98  and a virtual line connecting the transfer unit main body&#39;s protrusion  80  and the rotational axis  72  substantially coincide with each other. 
         [0063]    With the front cover  11  and the transfer unit  28  shown in  FIG. 9  constrained, the left end portion of the bias member  98  contacts the transfer unit main body  29 . Therefore, the front cover  11  and the transfer unit  28  are in a state in which one member presses the other member with each other. In addition, in the state shown in  FIG. 9 , the transfer unit main body  29  is separated from the main body frame  12   a  without contacting the main body frame  12   a . In this way, since the front cover  11  and the transfer unit  28  are constrained and the transfer unit main body  29  is separated from the main body frame  12   a , when closing the front cover  11 , the front cover  11  never receive a force in a direction opened to the image forming apparatus main body  12  due to the bias member  98 . In addition, even in the case that the transfer unit main body  29  contacts the main body frame  12   a , a reaction force that the front cover  11  receives is decreased because the front cover  11  and the transfer unit  28  are constrained. 
         [0064]    The operator carries out the operation that the operator opens the upper cover  13  from the state shown in  FIG. 9  in which the front cover  11  is closed. During closing of the upper cover  13 , the upper cover  13  may contact the constraining member  70  so as to press the constraining member  70  and rotate the constraining member  70  against a bias force of the bias member  78  in the clockwise direction around the axis  72 . Then, when the constraining member  70  is rotated in the clockwise direction, the transfer unit main body&#39;s protrusion  80  fitted in the groove  74  is detached from the groove  74 . Then, since the transfer unit main body&#39;s protrusion  80  is detached from the groove  74 , constraint between the front cover  11  and the transfer unit  28  is released. Since constraint between the front cover  11  and the transfer unit  28  is released, the transfer unit  28  is biased in a direction so that the transfer unit  28  is rotated around the axis  94  in the anticlockwise direction by means of the bias member  98  and the transfer unit main body  29  is pressed by the main body frame  12   a . Then, as shown in the above-described  FIG. 4 , the transfer unit  28  is positioned and fixed to a usage position where the transfer unit  28  is used for forming an image or the like. 
         [0065]      FIG. 10  shows the front cover  11  that is used for a second exemplary embodiment of the invention. 
         [0066]    Although the front cover  11  used for the above-described first embodiment is provided with the sliding member  82 , in this second embodiment, the front cover  11  is not provided with the sliding member  82 . In addition, according to this embodiment, a connection mechanism  110  used as a connecting unit for connecting the image forming apparatus main body  12  to the front cover  11  is mounted on the front cover  11 . 
         [0067]    The connection mechanism  110  has a first connection member  112  and a second connection member  114 . The first connection member  112  and the second connection member  114  are connected so that they can rotate with each other by using an axis  116 . On other end side of the axis  116  of the first connection member  112 , a protrusion  118  is formed toward the side of the front cover  11 , and the protrusion  118  is guided to a guide groove  120  formed on the front cover  11 . In addition, on the other end side of the axis  116  of the first connection member  112 , a press face  113  is formed. The second connection member  114  is mounted rotatably in the image forming apparatus main body  12  by using an axis  122 . 
         [0068]    In addition, according to this second embodiment, a support unit  124  is disposed on the front cover  11  so as to be protruded toward the inside of the image forming apparatus main body  12 . Although the connection mechanism  110  and the support unit  124  are disposed on the both side, the right and left sides of the front cover  11  one by one, namely, two in total,  FIG. 10  only shows the connection mechanism  110  and the support unit  124 , which are located on the left side. In addition, the image forming apparatus  10  according to this second embodiment has the fixing mechanism  130  used as a fixing unit, which is used for fixing the front cover  11  at a position where the front cover  11  is closed, as in the first embodiment 
         [0069]      FIG. 11  shows a state in which the front cover  11  and the transfer unit  28  are assembled in the image forming apparatus main body  12 .  FIG. 11  shows such a state that the transfer unit  28  is arranged at a usage position where it is used for forming an image or the like, and the front cover  11  and the upper cover  13  are closed to the image forming apparatus main body  12 . According to the above-described first embodiment, the transfer unit  28  is attached so as to be capable of rotating for the image forming apparatus main body  12  by using the axis  94 . On the contrary, according to this second embodiment, the transfer unit  28  is disposed to the support unit  124  of the front cover  11  so as to be capable of rotating by using the axis  94 . Further, the same parts as the first embodiment are given the same reference numerals and the detailed explanation is herein omitted. 
         [0070]    With reference to  FIGS. 12 to 15 , the opening and closing operations of the front cover  11  and the upper cover  13  and the moving operation of the transfer unit  28  according to the second embodiment will be described. Further, in  FIGS. 12 to 15 , the illustration of the fixing mechanism  130  is omitted. In order to open the front cover  11  and the upper cover  13  from a state in which they are closed, the operation to open the upper cover  13  is carried out by the operator as shown in  FIG. 12 , as in the above-described first embodiment. By opening the upper cover  13 , the upper cover  13  is separated from the constraining member  70  and the front cover  11  can be opened moving from the position interfering with a locus of opening and closing of the front cover  11 . Then, when the operator operates an operation unit (not illustrated) of the front cover  11 , the fixing mechanism  132  is released, and as shown by an arrow in  FIG. 12 , the front cover  11  will start to rotate around the axis  15  in the clockwise direction. 
         [0071]    When the front cover  11  starts to rotate, in combination with this, the protrusion  118  is guided to the guide groove  120  and the first connection member  112  starts to rotate around the axis  116  in the clockwise direction. Then, since the first connection member  112  starts to rotate, the transfer unit main body&#39;s protrusion  80   29  is pressed in a right direction by the press face  113 . Then, since the transfer unit main body&#39;s protrusion  80   29  is pressed in the right direction, the transfer unit  28  starts to move so as to rotate around the axis  94  in the clockwise direction in combination with the front cover  11 . 
         [0072]      FIG. 13  shows the front cover  11  that moves from the state shown in  FIG. 12  so as to be rotated around the axis  15  in the clockwise direction being biased by the bias member  98  and the transfer unit  28  that rotationally moves around the axis  94  in the clockwise direction in combination with movement of the front cover  11 . In this state, being pressed to the press face  113  of the first connection member  112 , the transfer unit main body&#39;s protrusion  80  moves to the right side within the notch  86 . Then, the transfer unit main body&#39;s protrusion  80  moves to be fitted in the groove  74  of the constraining member  70  so as to be in the state such that the front cover  11  and the transfer unit  28  are constrained each other. In other words, in combination with opening of the front cover  11 , the front cover  11  and the transfer unit  28  are constrained each other. 
         [0073]      FIG. 14  shows the state that the front cover  11  is further opened from the state shown in  FIG. 13 , for example, when the operator carries out the operation for opening the front cover  11  and the front cover  11  moves due to an effect by gravity. In this state, the front cover  11  may rest for the image forming apparatus main body  12  so that the protrusion  118  contacts the lower end portion of the guide groove  120  and the front cover  11  is opened to the maximum for the image forming apparatus main body  12 . 
         [0074]      FIG. 15  shows the state in progress since the front cover  11  and the transfer unit  28  are opened for the image forming apparatus main body  12  (refer to  FIG. 14 ) till the front cover  11  shown in the above-described  FIG. 11  is closed to be arranged on the position where the transfer unit  28  is used for forming an image. In order to shift a state in which the front cover  11  and the transfer unit  28  are opened with respect to the image forming apparatus main body  12  into a state in which the front cover  11  is closed to be arranged on the position where the transfer unit  28  is used for forming an image, the operation by the operator for closing the front cover  11 , namely, the operation for rotating the front cover  11  in an anticlockwise direction around the axis  15  will be carried out. 
         [0075]    In the state shown in  FIG. 15 , the front cover  11  and the transfer unit  28  are constrained each other and the left end portion of the bias member  98  contacts the transfer unit main body  29 . Therefore, the front cover  11  and the transfer unit  28  are in the state that one presses other each other. In addition, in the state shown in  FIG. 15 , the transfer unit main body  29  is separated from the main body frame  12   a . In this way, since the front cover  11  and the transfer unit  28  are constrained and the transfer unit main body  29  is separated from the main body frame  12   a , when the transfer unit  28  is arranged on a usage position where the transfer unit  28  is used for forming an image or the like, the front cover  11  does not receive a force in a direction of being opened to the image forming apparatus main body  12  from the bias member  98  in the case of closing the front cover  11 , as in the first embodiment. 
         [0076]    The operator carries out the operation to close the upper cover  13  from the state in which the front cover  11  is closed shown in  FIG. 15 . In the progress of closing the upper cover  13 , the upper cover  13  contacts the constraining member  70  so as to press the constraining member  70  and rotate the constraining member  70  around an axis  72  in the clockwise direction against a bias force of a bias member  78 . Then, when the constraining member  70  is rotated in the anticlockwise direction, the transfer unit main body&#39;s protrusion  80  fitted in the groove  74  is detached from the groove  74 . Then, since the transfer unit main body&#39;s protrusion  80  fitted in the groove  74  is detached from the groove  74 , constraint between the front cover  11  and the transfer unit  28  is released, the transfer unit  28  is biased in a direction so that the transfer unit  28  is rotated around the axis  94  in the anticlockwise direction, and the transfer unit main body  29  is pressed by the main body frame  12   a . Then, as shown in the above-described  FIG. 11 , the transfer unit  28  is positioned and fixed to the usage position where the transfer unit  28  is used for forming an image or the like. 
         [0077]      FIG. 16  shows the front cover  11  and the transfer unit  28  that are used for a third exemplary embodiment according to the invention. According to the above-described first and second embodiments, the image forming apparatus  10  has the front cover  11  and the upper cover  13 . On the contrary, in this third embodiment, the upper cover  13  is not disposed but the front cover  11  is only disposed. In addition, the image forming apparatus  10  according to this third embodiment has a fixing mechanism  130  as a fixing unit, which is used for fixing the front cover  11 , as in the first and second embodiments and 
         [0078]    In addition, according to this third embodiment, the transfer unit  28  is mounted so as to be capable of being rotated for the image forming apparatus main body  12  by using the axis  94 , as in the above-described first embodiment. In addition, according to this third embodiment, a protrusion portion  71  is disposed so as to be protruded in a direction of a paper face, and in the state shown in  FIG. 16 , the downward face of an operation unit  136  contacts the protrusion portion  71 . In order to open the front cover  11  from the closed state, the operator may carry out the operation of the fixing member  132 . In other words, the operator may pull the operation unit  136  of the fixing member  132  upward. When the operation unit  136  is pulled upward, the fixing member  132  is rotated around the axis  134  in the anticlockwise direction against the bias force of a bias member  146 . Then, since the fixing member  132  is rotated, the contact unit  140  is separated from the protrusion for fixing  138  to be in a state so that the front cover  11  can be opened. The front cover  11  and the transfer unit  28  are continuously rotated in the clockwise direction up to the position where the transfer unit main body&#39;s protrusion  80  is in the state of contacting the lower end portion  104  of the notch  86 , and the front cover  11  and the transfer unit  28  are in the state of being opened to the image forming apparatus main body  12 . Further, the same parts as the first embodiment are given the same reference numerals and the explanation thereof is herein omitted. 
         [0079]      FIGS. 17 to 19  illustrate the operation till the front cover  11  is closed and the moving operation of the transfer unit  28 .  FIG. 17  shows the state in progress since the front cover  11  is opened for the image forming apparatus main body  12  till the front cover  11  shown in the above-described  FIG. 16  is closed to be arranged on the position where the transfer unit  28  is used for forming an image. In order to shift a state in which the front cover  11  and the transfer unit  28  are opened for the image forming apparatus main body  12  into a state in which the front cover  11  is closed to be arranged on the position where the transfer unit  28  is used for forming an image, the operation by the operator for closing the front cover  11 , namely, the operation for rotating the front cover  11  in the anticlockwise direction around the axis  15  will be carried out. 
         [0080]    In the operation by the operator, if the front cover  11  is moved so as to be rotated around the axis  15  in the anticlockwise direction, the transfer unit main body&#39;s protrusion  80  is guided into the guide face  88  and this allows the transfer unit main body&#39;s protrusion  80  to move within the notch  86  so as to be separated from the lower end portion  104 . Then, in combination with closing of the front cover  11 , the transfer unit  28  is moved in the anticlockwise direction in the anticlockwise direction around the axis  94 . In addition, when the transfer unit main body&#39;s protrusion  80  is moved from the state shown in  FIG. 18 , the transfer unit main body&#39;s protrusion  80  is fitted in the groove  74  of the constraining member  70 . Then, when the transfer unit main body&#39;s protrusion  80  is fitted in the groove  74  of the constraining member  70 , the front cover  11  and the transfer unit  28  are constrained each other. In this way, the constraining member  70  and the transfer unit main body&#39;s protrusion  80  are used as a constraining mechanism for constraining the front cover  11  and the transfer unit  28  in combination with the operation for closing the front cover  11 . 
         [0081]    With the transfer unit main body&#39;s protrusion  80  fitted in the groove  74  and the front cover  11  and the transfer unit  28  constrained, the left end portion of the bias member  98  contacts the transfer unit main body  29 . Therefore, the front cover  11  and the transfer unit  28  are in a state in which one member presses the other member with each other. In addition, in this state, the transfer unit main body  29  is separated from the main body frame  12   a  without contacting the main body frame  12   a . In this way, since the front cover  11  and the transfer unit  28  are constrained and the transfer unit main body  29  is separated from the main body frame  12   a , when the transfer unit  28  is arranged on the usage position where the transfer unit  28  is used for forming an image or the like, also in this third embodiment, upon closing of the front cover  11 , the front cover  11  does not receive a force in a direction of being opened to the image forming apparatus main body  12  from the bias member  98 . Further, although it is preferable that the front cover  11  does not receive the bias force from the bias member  98  in the case of closing the front cover in any embodiment, there is no problem if the bias force is given to an extent such that the operability of the opening and closing unit is not damaged. 
         [0082]    From the state shown in  FIG. 18 , the operator will carry out the operation of the front cover  11 . In other words, the front cover  11  is moved so as to be rotated in the anticlockwise direction around the axis  15 . Then, due to the above-described operation, the protrusion for fixing  138  formed in the front cover  11  is moved from the side of a press face  142  to the side of the contact unit  140 . When the protrusion for fixing  138  is detached from the press face  142 , the fixing member  132  is biased by the bias member  146  to be rotated around the axes  134  in the clockwise direction. 
         [0083]    Then, as shown in  FIG. 19 , by rotating the fixing member  132 , the protrusion for fixing  138  is fitted in the contact unit  140 , the fixing member  132  contacts the constraining member  70 , and then, pressing the constraining member  70 , the constraining member  70  is rotated in the anticlockwise direction around the axis  72  against the bias force of the bias member  78 . Then, if the constraining member  70  is rotated in the anticlockwise direction, the transfer unit main body&#39;s protrusion  80  fitted in the groove  74  is detached from the groove  74 . Then, since the transfer unit main body&#39;s protrusion  80  is detached from the groove  74 , constraint between the front cover  11  and the transfer unit  28  is released. Since constraint between the front cover  11  and the transfer unit  28  is released, the transfer unit  28  is biased in a direction so that the transfer unit  28  is rotated around the axis  94  in the anticlockwise direction by means of the bias member  98  and the transfer unit main body  29  is pressed by the main body frame  12   a . Then, as shown in the above-described  FIG. 16 , the transfer unit  28  is positioned and fixed to the usage position where the transfer unit  28  is used for forming an image or the like. 
         [0084]    As described above, the invention can be applied to an image forming apparatus such as a copying machine, a facsimile, and a printer having an opening and closing unit and a structure, for example, a transfer unit.