Patent Publication Number: US-9409429-B2

Title: Belt unit, image forming apparatus and belt member exchanging method

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a belt unit of an image forming apparatus, the image forming apparatus and a belt member exchanging method. 
     In Japanese Laid-Open Patent Application (JP-A) 2011-13305, a so-called tandem type image forming apparatus in which toner images independently formed at a plurality of image forming portions are superposed by being transferred onto a recording material by using a belt member (intermediary transfer belt or recording material conveying belt) has been widely used. In the image forming apparatus using the belt member, a belt rotating unit in which the belt member is stretched by a plurality of rotatable supporting members supported by a pair of side members is provided so as to be pullable out from a casing of the image forming apparatus. 
     In JP-A 2010-204250, an image forming apparatus in which a belt unit prepared by integrally assembling such a belt rotating unit with a cleaning unit for cleaning a belt member is provided so as to be pullable out from a casing of the image forming apparatus is shown. 
     With respect to the belt rotating unit, a durable lifetime of the belt member is short compared with the pair of side members, the rotatable side members and other mechanism parts (components), and therefore the belt rotating unit is required to be reused again and again by exchanging only the belt member. In that case, if the belt rotating unit can be kept in a standing state such that one of the side members is landed (put down) and the other side member is directed upward, the belt member can be pulled out toward above along the rotatable side members, so that operativity is good. 
     However, the belt rotating unit has an outer appearance in a thin plate-like shape as a whole, and therefore there is no self-standing property in a standing state, so that the belt rotating unit is liable to fall in a front-rear direction with respect to a thickness direction thereof. For that reason, there is no other choice but to support the belt rotating unit in the standing state by an operator and to pull out the belt member, by another operator, from the rotatable belt members supported in the standing state, so that an operating cost corresponding to the two operators was entailed. Further, during an exchanging operation of the belt member, the belt rotating unit fallen or inclined to contact surrounding members, so that there was also a possibility that an exchanged belt member was damaged. 
     Therefore, preparation of a dedicated jig (tool), for holding the belt rotating unit in the standing state during the operation of the belt member, in the casing of the image forming apparatus was proposed. However, in the image forming apparatuses in recent years, there are no preparation cost and storing space of the dedicated jig which is seldom used. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided a belt unit comprising: a belt member; a belt supporting unit including a plurality of supporting rollers for supporting the belt member, and a pair of side units for supporting end portions of each of the plurality of supporting rollers; and a cleaning unit, including a cleaning blade for cleaning the belt member, detachably mountable to the belt supporting unit, wherein the cleaning unit includes a connecting portion connectable to one of the side units so that the belt supporting unit from which the cleaning unit is demounted is placed in a standing state such that the one of the side units is directed downward and the other side unit is directed upward. 
     These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a general structure of an image forming apparatus. 
       Parts (a) and (b) of  FIG. 2  are schematic views for illustrating mounting and demounting of an intermediary transfer unit with respect to the image forming apparatus. 
         FIG. 3  is an illustration of a structure of the intermediary transfer unit. 
       Parts (a) and (b) of  FIG. 4  are illustrations of connection between a belt rotating unit and a cleaning unit. 
         FIG. 5  is a perspective view of the belt rotating unit in a state in which an intermediary transfer belt  61  is removed. 
         FIG. 6  is an illustration of a cross-sectional structure of the cleaning unit. 
         FIG. 7  is a perspective view of the cleaning unit as seen from above. 
         FIG. 8  is a perspective view of the cleaning unit as seen from below. 
         FIG. 9  is a perspective view of the belt rotating unit and the cleaning unit before the connection. 
         FIG. 10  is a side view of the belt rotating unit and the cleaning unit before the connection. 
         FIG. 11  is a perspective view of the belt rotating unit and the cleaning unit after the connection. 
         FIG. 12  is a side view of the belt rotating unit and the cleaning unit after the connection. 
         FIG. 13  is a perspective view of the belt rotating unit and the cleaning unit after the connection as seen at a different angle. 
         FIG. 14  is a front view of the belt rotating unit and the cleaning unit after the connection. 
         FIG. 15  is an illustration of a tilt angle of the belt rotating unit. 
         FIG. 16  is a perspective view of the belt rotating unit and the cleaning unit during exchange of the intermediary transfer belt. 
       Parts (a), (b) and (c) of  FIG. 17  are illustrations of demounting of a tension roller bearing. 
       Parts (a) and (b) of  FIG. 18  are illustrations of a tension releasing operation of a tension roller. 
         FIG. 19  is an illustration of a tension roller demounting position. 
         FIG. 20  is an illustration of a pulling-out operation of the intermediary transfer belt. 
         FIG. 21  is an illustration of a disconnecting operation of a cleaning blade. 
         FIG. 22  is an illustration of a demounting operation of the cleaning blade. 
         FIG. 23  is an illustration of a connecting portion in Embodiment 4. 
         FIG. 24  is an illustration of a connecting portion in Embodiment 5. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described specifically with reference to the drawings. 
     Embodiment 1 
     (Image Forming Apparatus) 
       FIG. 1  is an illustration of a general structure of an image forming apparatus  1 . As shown in  FIG. 1 , the image forming apparatus  1  is an intermediary transfer type full color printer of a tandem type in which image forming portions  10 Y,  10 M,  10 C and  10 K for yellow, magenta, cyan and black, respectively, are arranged along an intermediary transfer belt  61 . 
     At the image forming portion  10 Y, a yellow toner image is formed on a photosensitive drum  11 (Y) and then is transferred onto the intermediary transfer belt  61 . At the image forming portion  10 M, a magenta toner image is formed on a photosensitive drum  11 (M) and then is transferred onto the intermediary transfer belt  61 . At the image forming portions  10 C and  10 K, cyan and black toner images are formed on photosensitive drums  11 (C) and  11 (K), respectively, and then are transferred onto the intermediary transfer belt  61 . 
     A recording material P is pulled from a recording material cassette  20  and then is separated one by one by a separating roller  21 . Then, the recording material P is in a stand-by state at a registration roller pair  23 , and then is sent into a secondary transfer portion T 2  by the registration roller pair  23 . The four color toner images transferred on the intermediary transfer belt  61  are transferred onto the recording material P conveyed through the secondary transfer portion T 2 . The recording material P on which the toner images are transferred is pressed and heated by a fixing device  40 , and then is, after being subjected to fixing of the toner images thereon, discharged onto a tray  50  by a discharging roller pair  41 . 
     (Image Forming Portion) 
     The image forming portions  10 Y,  10 M,  10 C and  10 K have the same constitution except that colors of toners used in developing devices are different from each other. In the following, the image forming portion  10 Y is described, and redundant explanation about the image forming portions  10 M,  10 C and  10 K will be omitted. 
     The image forming portion  10 Y includes, at a periphery of the photosensitive drum  11 , a charging roller  12 , an exposure device  13 , a developing device  14 , a primary transfer roller  17  and drum cleaning device  15 . The photosensitive drum  11  includes an OPC photosensitive layer. The charging roller  12  electrically charges a surface of the photosensitive drum  11  to a negative potential uniformly. The exposure device  13  scans the surface of the photosensitive drum  11  with a laser beam through a rotating mirror, so that an electrostatic image is written (formed) on the photosensitive drum  11 . The developing device  14  develops the electrostatic image with a two-component developer, so that the toner image is formed on the surface of the photosensitive drum  11 . A toner cartridge  19  supplies the toner to the developing device  14 . 
     The primary transfer roller  17  presses an inner surface of the intermediary transfer belt  61  to form a primary transfer portion between the photosensitive drum  11  and the intermediary transfer belt  61 . By applying a positive DC voltage to the primary transfer roller  17 , the toner image on the photosensitive drum  11  is primary-transferred onto the intermediary transfer belt  61 . 
     The drum cleaning device  15  rubs the photosensitive drum  11  with a cleaning blade to collect a transfer residual toner remaining on the photosensitive drum  11  without being transferred onto the intermediary transfer belt  61 . A belt cleaning device  70  rubs the intermediary transfer belt  61  with a cleaning blade  71  ( FIG. 6 ) to collect a transfer residual toner from the intermediary transfer belt  61  having passed through the secondary transfer portion T 2 . 
     (Mounting and Demounting of Intermediary Transfer Unit) 
     Parts (a) and (b) of  FIG. 2  are sectional views for illustrating mounting and demounting of an intermediary transfer unit with respect to the image forming apparatus. 
     As shown in  FIG. 1 , an intermediary transfer unit  80  is mounted detachably by being pulled out from a casing  1 A of the image forming apparatus  1  in a right direction. At a right side surface of the image forming apparatus  1 , an openable door  92  capable of opening the casing  1 A rightward is provided. The openable door  92  is shaft-supported by a lower-side rotation shaft  92   a  and is locked to the image forming apparatus  1  by an upper-side door-locking portion  92   b.    
     As shown in (a) of  FIG. 2 , when lock of the door-locking portion  92   b  is released and then the openable door  92  is rotated about the rotation shaft  92   a , the openable door  92  is opened. As shown in (b) of  FIG. 2 , the openable door  92  is opened and then the intermediary transfer unit  80  is pulled out in an arrow B direction, so that the intermediary transfer unit  80  can be demounted from the casing  1 A of the image forming apparatus  1 . 
     (Intermediary Transfer Unit) 
       FIG. 3  is an illustration of a structure of the intermediary transfer unit. Parts (a) and (b) of  FIG. 4  are schematic views for illustrating connection between a belt rotating unit and a cleaning unit, wherein (a) shows a front side and (b) shows a rear side. 
     As shown in  FIG. 3 , the intermediary transfer belt  80  is an exchanging unit prepared by integrally connecting a belt rotating unit  6  and a cleaning unit  70 . Grip portions  65   a  and  65   b  are gripped in the fingers to pull out the intermediary transfer unit  80  in the arrow B direction, so that the intermediary transfer unit  80  is demounted from the image forming apparatus  1  as shown in (b) of  FIG. 2 . 
     As shown in (a) of  FIG. 4 , in the rear side of the intermediary transfer unit  80 , a tension roller bearing  66  ( 66   a ) of the belt rotating unit  6  and a collected toner accommodating portion  74  of the cleaning unit  7  are engaged by developing portions  83  and then are fixed with a screw  82 . The screw  82  is disconnected and then the cleaning unit  70  is slid toward the rear side with respect to a rotational axis direction, so that engagement of the positioning portions  83  is eliminated to separate the cleaning unit  70  from the belt rotating unit  6 . 
     As shown in (b) of  FIG. 4 , in the front side of the intermediary transfer unit  80 , a tension roller bearing  66  ( 66   b ) of the belt rotating unit  6  and the collected toner accommodating portion  74  of the cleaning unit  7  are fastened by screws  82  via a fastening member  81 . The screws  82  are disconnected and then the fastening member  81  is removed, so that the cleaning unit  70  can be moved toward the rear side with respect to the rotational axis direction. 
     (Belt Rotating Unit) 
       FIG. 5  is a perspective view of the belt rotating unit in a state in which the intermediary transfer belt  61  is removed. 
     As shown in  FIG. 1 , in the belt rotating unit  6 , the intermediary transfer belt  61  is stretched by the four primary transfer rollers  17 , a driving roller  62 , a follower roller  63  and a tension roller  64 . A rotational driving force is transmitted from the driving roller  62  to the intermediary transfer belt  61 . 
     The intermediary transfer belt  71  is formed with a polyether ether ketone (PEEK) resin material in view of resistance to fatigue from flexing. 
     As shown in  FIG. 5 , a transfer frame  65  constitutes a framework for supporting a whole of the belt rotating unit  6 . At a longitudinal end portion of the transfer frame  65 , the grip portions  65   a  and  65   b  for pulling out the belt rotating unit  6  (intermediary transfer unit  80 ) from the image forming apparatus  1  ( FIG. 1 ) are disposed. 
     At end portions of each of the four primary transfer rollers  17 , the driving roller  62  and the follower roller  63 , these rollers are rotatably supported via bearings by side members provided in front and rear sides of the transfer frame  65 . The tension roller  64  is rotatably supported at end portions thereof via bearings by tension roller bearing members  66  ( 66   a ,  66   b ). The tension roller  64  is urged at the end portions thereof toward a longitudinal outside thereof by a tension spring  67  provided on the transfer frame  65  as a bearing surface. 
     The primary transfer roller  17  is prepared by coating an electroconductive elastic layer on a surface of a shaft formed of metal (e.g., stainless steel) in a diameter of 8 mm. The electroconductive elastic layer uniformly applies a high voltage to the intermediary transfer belt  61  sandwiched between itself and the photosensitive drum  11  ( FIG. 1 ). As a material for the electroconductive elastic layer, it is possible to use EPDM (ethylene-propylene copolymer rubber), foamed urethane, and the like. 
     (Cleaning Unit) 
       FIG. 6  is an illustration of a cross-sectional structure of the cleaning unit.  FIG. 7  is a perspective view of the cleaning unit as seen from above.  FIG. 8  is a perspective view of the cleaning unit as seen from below. 
     As shown in  FIG. 6 , the cleaning unit  70  rubs the intermediary transfer belt  61  with the cleaning blade  71  to remove and collect, in the collected toner accommodating portion  74 , the transfer residual toner remaining on the intermediary transfer belt  61 . The cleaning blade  71  is formed in a thickness of 2 mm by an urethane rubber having an Asker hardness of 70 degrees according to JIS. The collected toner accommodating portion  74  is formed with a rigid resin member. 
     The cleaning blade  71  is supported by a metal plate portion  72 . A fixing shaft  79  rotatably mounts the metal plate portion  72  to the collected toner accommodating portion  74 . A spring  707  pressed a pressing bearing surface member  72   a  fixed to the metal plate portion  72 , thus elastically urge the cleaning blade  71  toward the intermediary transfer belt  61 . 
     As shown in  FIG. 7 , a collected toner feeding screw  75  is rotationally supported by the collected toner accommodating portion  74 . A gear  76  receives a driving force from a gear fixed to the tension roller  64  of the belt rotating unit  6 , thus rotationally driving the collected toner feeding screw  75 . 
     As shown in  FIG. 8 , a collected toner discharging port  71  delivers the collected toner, fed by the collected toner feeding screw  75 , to a collected toner passage formed in the main assembly of the image forming apparatus  1  ( FIG. 1 ). A shutter  78  is urged by an unshown spring in a direction in which the collected toner discharging port  77  is blocked. When the intermediary transfer unit  80  is demounted from the image forming apparatus  1  ( FIG. 1 ), the shutter  78  automatically blocks the collected toner discharging port  77  to prevent the collected toner from leaking out of the cleaning unit  70 . 
     (Problem of Operativity) 
     With respect to the image forming apparatus  1 , the intermediary transfer belt  80  which has already been used can also be collectively exchanged (replaced) with a new one. However, in recent years, there is an increasing need to re-use the transfer frame  65  and the rollers of the belt rotating unit  6  by exchanging only the intermediary transfer belt  61  of an expensive intermediary transfer unit  80 . 
     When the intermediary transfer belt  61  is demounted from and mounted to the intermediary transfer unit  80 , in order to prevent the intermediary transfer belt  61  and another member from generating scars or a dent, there is a need to carefully operate (handle) the intermediary transfer belt  61  with hands of an operator. For that reason, in a conventional constitution, a dedicated tool or an auxiliary stand jig was prepared for ensuring operativity, and the belt rotating unit  6  was held to stand vertically. 
     Further, the operator is required to stand the cleaning unit  70  in an unused work space in a state in which a toner opening is directed upward in order to prevent the collected toner, collected in the cleaning unit  70  demounted from the belt rotating unit  6 , from scattering over the outside. 
     However, during the exchanging position of the intermediary transfer belt  61 , there was the case where the operator accidentally touches the cleaning unit  70  to cause the cleaning unit  70  to fall down to scatter the collected toner over a floor. 
     Therefore, in Embodiment 1, a constitution in which the belt rotating unit  6  and the cleaning unit  70  was connected with each other in a T-character shape to stand at the same was employed. 
     Characteristic Portion of Embodiment 1 
     As shown in  FIG. 1 , the plurality of image forming portions  10 Y,  10 M,  10 C and  10 K are arranged and disposed in a conveyance direction of the intermediary transfer belt  61  as an example of the belt member, and the photosensitive drum  17  as an example of an individual image bearing member, the toner image is formed and then is transferable onto the intermediary transfer belt member. The intermediary transfer unit  80  as an example of the belt unit is demountable from the casing  1 A by being moved in an arrangement direction of the plurality of image forming portions  10 Y,  10 M,  10 C and  10 K. 
     In the belt rotating unit  6 , the intermediary transfer belt  61  as the example of the belt member is stretched by, as examples of a plurality of rotatable supporting members, the four primary transfer rollers  17 , the driving roller  62 , the follower roller  63  and the tension roller  64 . The cleaning unit  70  is assembled demountably from the belt rotating unit  6  to collect the toner from the intermediary transfer belt  61  in a rotation state. 
     As shown in  FIG. 5 , the grip portion  65   a  as an example of a grip portion is disposed at a longitudinal end portion of a side member  65 F, and is used when the intermediary transfer unit  80  is pulled out from the image forming apparatus  1 . The primary transfer rollers  17 , the driving roller  62 , the follower roller  63  and the tension roller  64  are supported by a pair of side members  65 F and  65 R. 
     As shown in  FIG. 9 , a connecting portion  100  as an example of a connecting means is capable of connecting the cleaning unit  70 , demounted from the belt rotating unit  6 , to the side member  65 F by positioning the cleaning unit  70  with respect to a direction crossing the longitudinal direction of the side member  65 F. With respect to the intermediary transfer unit  80 , in a state in which the side member  65 F and the cleaning unit  70  which are connected with each other are directed downward and the other side member  65 R is directed upward, the belt rotating unit  6  can be held in a standing state. 
     As shown in  FIG. 20 , in the standing state, the side member  65 R positioned in an upper side of the belt rotating unit  6  is constituted so that the intermediary transfer belt  61  is capable of being pulled out upward. The side member  65 F positioned in a lower side of the belt rotating unit  6  has a bearing surface  65   d  as an example of a projected portion, for landing, projected in the rotation axis direction of the primary transfer roller  17 . The cleaning unit  70  includes bearing surfaces  70   a  and  70   b , as an example of a projected portion capable of landing, provided at end portions in a side opposite from a side where the cleaning unit  70  opposes the intermediary transfer belt  61  in a state in which the cleaning unit  70  is assembled with the belt rotating unit  6  to collect the toner. 
     The connecting portion  100  connects the side member  65 F to the cleaning unit  70  in a position outside the intermediary transfer belt  61  with respect to the conveyance direction of the intermediary transfer belt  61 . As a result, the intermediary transfer belt  61  is prevented from entering above the cleaning unit  70 . The connecting portion  100  connects the side member  65 F in a position lower than a toner collecting mechanism of the cleaning unit  70  in a state in which a surface opposing the intermediary transfer belt  61  in a toner collecting state is directed upward. As a result, the belt rotating unit  6  can be compactly connected while crossing the toner collecting mechanism. 
     As shown in  FIG. 9 , the grip portion  65   b  and a positioning projection  65   e  which are examples of a plurality of projected portions are provided on the belt rotating unit  6 . Holes  101   a  and  101   c  which are examples of openings are provided in the cleaning unit  70 . The connecting portion  100  has a structure in which the grip portion  65   b  and the positioning projection  65   e  are inserted into the holes  101   a  and  101   c , respectively. As a result, a load of the hole  101   a  in the case where a torsional force acts on the belt rotating unit  6  relative to the cleaning unit  70  is alleviated. 
     As shown in  FIG. 9 , the hole  101   a  as the example of the opening is provided in the cleaning unit  70  so that the grip portion  65   b  is insertable into the hole  101   a . As shown in  FIG. 10 , a snap-fit portion  101   b  positions and fixes the cleaning unit  70 , moved by inserting the grip portion  65   b  into the hole  101   a , relative to the grip portion  65   b  in a predetermined position with respect to an insertion direction. 
     (Connecting Portion) 
       FIG. 9  is a perspective view of the belt rotating unit and the cleaning unit before the connection.  FIG. 10  is a side view of the belt rotating unit and the cleaning unit before the connection.  FIG. 11  is a perspective view of the belt rotating unit and the cleaning unit after the connection.  FIG. 12  is a side view of the belt rotating unit and the cleaning unit after the connection. 
     As shown in  FIG. 9 , in order to connect the belt rotating unit  6  and the cleaning unit  70 , the belt rotating unit  6  uses the grip portion  65   b  and the positioning projection  65   e  which are formed on the transfer frame  65 . The cleaning unit  70  is provided with the holes  101   a  and  101   c , a longitudinal central portion of the collected toner accommodating portion  74 . The grip portion  65   b  of the belt rotating unit  6  is inserted into the hole  101   a  of the cleaning unit  70 . The positioning projection  65   e  of the belt rotating unit  6  is inserted into the hole  101   c  of the cleaning unit  70 . As shown in  FIG. 11 , when the belt rotating unit  6  and the cleaning unit  70  are connected, the grip portion  65   b  and the positioning projection  65   e  are engaged into the holes  101   a  and  101   c , respectively, so that positioning and fixing between the belt rotating unit  6  and the cleaning unit  70  with respect to Y direction and Z direction are realized. The positioning projection  65   e  takes charge of positioning a rotation center of the cleaning unit  70  in a YZ plane, and the grip portion  65   b  takes change of limiting tilting of the cleaning unit  70  in the YZ plane. 
     As shown in  FIG. 10 , the grip portion  65   b  of the belt rotating unit  6  is provided with a hole  65   g . The cleaning unit  70  is provided with the snap-fit portion  101   b  for being engaged with the hole  65   g . As shown in  FIG. 12 , when the belt rotating unit  6  and the cleaning unit  70  are connected with each other, the snap-fit portion  101   b  is engaged in the hole  65   g , so that the positioning and fixing between the belt rotating unit  6  and the cleaning unit  70  with respect to the insertion direction (X direction). For this reason, through an exchanging operation procedure of the intermediary transfer belt  61 , there is no fear that the connection between the belt rotating unit  6  and the cleaning unit  70  is eliminated (released). 
     As shown in  FIG. 11 , in the state in which the belt rotating unit  6  and the cleaning unit  70  are connected with each other, a surface  65   k  of the transfer frame  65  and a surface  70   k  of the cleaning unit  70  abut against each other to limit further movement in the insertion direction (X direction). For this reason, through the exchanging operation procedure of the intermediary transfer belt  61 , there is no fear that the intermediary transfer belt  61  contacts the cleaning unit  70  to be damaged. 
     Incidentally, the positioning projection  65   e  of the transfer frame  65  is not a dedicated structure for the connection but is a structure for positioning a secondary transfer unit  36  including a secondary transfer outer roller  35  provided in the right-side door unit  92  shown in  FIG. 1 . The secondary transfer unit  36  is mounted to the right-side door unit  92  so as to be translatable and rotationally movable by an unshown spring in a plane including the secondary transfer portion T 2 . The positioning projection  65   e  is engaged in an unshown opening provided in a side of the opposing secondary transfer unit  36 , thus positioning the driving roller  62  and the secondary transfer outer roller  35  in parallel. 
     In Embodiment 1, at the connecting portion  100  between the belt rotating unit  6  and the cleaning unit  70 , the cleaning unit  70  is provided with the snap-fit portion  101   b , and therefore there is no need to provide a dedicated connecting member such as a screw. Accordingly, a connecting structure can be simply constituted without being complicated. 
     In this embodiment, the structure for the connection in the belt rotating unit  6  side includes the positioning projection  65   e  and the grip portion  65   b  which have already been provided, and therefore, there is no need to provide a dedicated connecting structure. For that reason, it is possible to realize a whole structure of the belt rotating unit in a small and compact manner. 
     (Self-Standing State) 
       FIG. 13  is a perspective view of the belt rotating unit and the cleaning unit after the connection as seen at a different angle.  FIG. 14  is a front view of the belt rotating unit and the cleaning unit after the connection.  FIG. 15  is an illustration of a tilt angle of the belt rotating unit. 
     As shown in  FIG. 5 , the side member of the transfer frame  65  in the front side is provided with the bearing surface  65   d  which lands when the belt rotating unit  6  is placed in a standing state. The bearing surface  65   d  is disposed with respect to a direction opposite to a pulling-out direction of the intermediary transfer belt  61 . As shown in  FIG. 8 , the cleaning unit  70  is provided with the bearing surfaces  70   a  and  70   b  at longitudinal end portions, and is provided with a connecting portion bearing surface  102  at a longitudinal central portion. 
     As shown in  FIG. 13 , the connecting portion  100  connects the belt rotating unit  6  and the cleaning unit  70  outside the image forming apparatus  1  ( FIG. 1 ). By the connection, simultaneously with self-standing of the belt rotating unit  6  in the vertical direction, an opening through which the collected toner is accommodated in the cleaning unit  70  is held upward with respect to the vertical direction, so that the cleaning unit  70  stands by itself so that the collected toner is not leaked out to the outside thereof. 
     In this embodiment, in the self-standing state, the opening through which the collected toner is accommodated in the cleaning unit  70  is positioned at an end of the cleaning blade  71 , and therefore the operator can also check a damage state of the end of the cleaning blade  71 . 
     As shown in  FIG. 12 , in the self-standing state of the belt rotating unit  6  and the cleaning unit  70  connected by the connecting portion  100 , the bearing surface  65   d  formed on the transfer frame  65  in the belt rotating unit  6  side and the connecting portion bearing surface  102  of the cleaning unit  70  land. The connecting portion bearing surface  102  and the bearing surface  65   d  establish a substantially horizontal positional relationship with respect to the Z direction. 
     As a result, the belt rotating unit  6  and the cleaning unit  70  which are connected with each other can be kept in a stable state as seen in an XZ plane. Accordingly, the cleaning unit  70  is supported with respect to a falling direction (in which the cleaning unit  70  is rotated in the XZ plane), so that the self-standing state of the cleaning unit  70  can be maintained. 
     As shown in  FIG. 14 , the cleaning unit  70  includes the bearing surfaces  70   a  and  70   b  at the longitudinal end portions. When the belt rotating unit  6  and the cleaning unit  70  which are connected with each other are stood so that the belt rotating unit  6  is parallel to a Z axis, the bearing surfaces  70   a  and  70   b  are kept in a slightly floating state from an installation surface relative to the connecting portion bearing surface  102 . As a result, the belt rotating unit  6  can be obliquely supported when the belt rotating unit  6  is viewed from the YZ plane by the operator. 
     As shown in  FIG. 15 , the belt rotating unit  6  and the cleaning unit  70  which are placed in a connected state can be tilted by an angle θ in the YZ plane. For example, in  FIG. 15 , when these units are tilted in a clockwise direction, the belt rotating unit  6  is rotated in an arrow D direction with the connecting portion bearing surface  102  as a supporting point, so that the bearing surface  70   a  lands. A tilt angle at this time is the angle θ. 
     In a state in which the belt rotating unit  6  is tilted by the angle θ in the clockwise direction, rotation movement M, about the bearing surface  70   a , generated by a force F exerted on a position G of gravitation is always generated with respect to a counterclockwise direction and thus acts in a direction in which the cleaning unit  70  is not caused to fall down. In this way, the position of the bearing surface  70   a  is designed. Also the case where the belt rotating unit  6  is tilted toward the bearing surface  70   b  side in the counterclockwise direction is similar to the above case. 
     On the other hand, in the case where the position of the bearing surface  70   a  is close to the connecting portion bearing surface  102  and in the case where the position of the bearing surface  70   a  is designed as a position considerably higher than the connecting portion bearing surface  102 , a tiltable angle θ becomes large. In this case, when the belt rotating unit  6  is largely tilted until the rotation M acts clockwise, the belt rotating unit  6  is rotated about the bearing surface  70   a  to fall down. 
     In this way, by tilting the belt rotating unit  6  in a direction (arrow D direction) of the operator himself (herself), the intermediary transfer belt  61  can be pulled out toward the direction of the operator. It becomes also possible to tilt the belt rotating unit  6  in both of left and right directions. For this reason, even when the operator is positioned in either side, exchanging operativity becomes easy. 
     (Exchange Constitution of Intermediary Transfer Belt) 
       FIG. 16  is a perspective view of the belt rotating unit and the cleaning unit during exchange of the intermediary transfer belt. Parts (a), (b) and (c) of  FIG. 17  are illustrations of demounting of a tension roller bearing. Parts (a) and (b) of  FIG. 18  are illustrations of a tension releasing operation of a tension roller.  FIG. 19  is an illustration of a tension roller demounting position.  FIG. 20  is an illustration of a pulling-out operation of the intermediary transfer belt. 
     As shown in  FIG. 5 , in order to pull out the intermediary transfer belt  61  ( FIG. 3 ) from the belt rotating unit  6  toward the rear side, there is a need to not only remove an obstacle (interference member) from a pulling-out passage of the intermediary transfer belt  61  ( FIG. 3 ) but also release tension pressure of the tension spring  67 . The obstacle includes the rear-side grip portion  65   a  and the rear-side tension roller bearing  66   a.    
     The front-side grip portion  65   b  is integrally formed with the transfer frame  65  but the rear-side grip portion  65   a  is detachably mountable to the transfer frame  65 . For that reason, in a state in which the transfer frame  65  is directed downward in the front side to stand the belt rotating unit  6  (vertical disposition), the upper grip portion  65   a  is demounted from the rear side of the transfer frame  65 , so that it becomes possible to pull out the intermediary transfer belt  61  in a rear side direction of the transfer frame  65 . 
     As shown in  FIG. 16 , the belt rotating unit  6  and the cleaning unit  70  are connected to stand. The upper grip portion  65   a  is disconnected from the transfer frame  65  by disconnecting a lock portion  65   r.    
     As shown in (a) of  FIG. 17 , the tension roller bearing  66   a  is supported by a guide portion  65   p  of the transfer frame  65 . As shown in (b) of  FIG. 17 , when the tension roller bearing  66   a  is moved in an arrow D direction opposite to a direction in which tension is applied, the tension roller bearing  66   a  is disconnected from the guide portion  65   p  of the transfer frame  65 . As a result, as shown in (c) of  FIG. 17 , the tension roller bearing  66   a  is demountable in an arrow E direction. The tension spring  67  is lightly press-fitted into the tension roller bearing  66   a , and therefore also the tension spring  67  is disconnected simultaneously with the demounting of the tension roller bearing  66   a.    
     As shown in (b) of  FIG. 18 , tension pressure applied to the lower tension roller bearing  66   b  in the self-standing state is released in a state in which the tension roller bearing  66   b  is still mounted to the transfer frame  65 . As shown in (b) of  FIG. 18 , when the tension roller bearing  66   b  is moved in an arrow S side, the tension roller bearing  66   b  is locked at a lock portion  65   s  of the transfer frame  65  by a snap-fit portion  66   s  in a state in which the tension spring  67  is compressed. As a result, the intermediary transfer belt  61  is placed in a pressure-released state. 
     As shown in  FIG. 19 , before demounting the intermediary transfer belt  61 , the tension roller  64  is pulled out from above. This is because in the case where only the tension pressure of the tension roller bearing  66   b  is released by disconnecting the grip portion  65   a  and the tension roller bearing  66   b , at the instant when the intermediary transfer belt  61  is pulled out upward, the tension roller  64  which has lost its support falls down. 
     As shown in  FIG. 20 , the intermediary transfer belt  61  is then moved upward to be pulled out from the belt rotating unit  6 . 
     According to Embodiment 1, when the intermediary transfer belt  61  is exchanged, the operator can use both hands throughout the operation, so that the operator can carefully perform the exchange of the intermediary transfer belt  61  from the belt rotating unit with both hands. 
     According to this embodiment, the belt rotating unit  6  and the cleaning unit  70  can be held in the standing state by being connected with each other, and therefore the belt rotating unit  6  can be kept in the self-standing state without using a dedicated tool or part. 
     According to this embodiment, a single serviceperson can perform the exchanging operation with both hands with no fear that the cleaning unit  70  containing the collected toner falls down, and therefore the exchanging operativity is improved. Accordingly, a service cost can be reduced. 
     Embodiment 2 
     In Embodiment 2, an exchanging procedure of the intermediary transfer belt  61  in the intermediary transfer unit  80  in Embodiment 1 will be described. 
     (1) As shown in  FIG. 2 , the intermediary transfer unit  80  is demounted from the image forming apparatus  1 . Then, as shown in  FIG. 3 , the intermediary transfer unit  80  is mounted on a work-bench (working table). 
     (2) As shown in  FIG. 4 , the fastening member  81  is demounted, and then the cleaning unit  70  is separated from the belt rotating unit  6 . 
     (3) As shown in  FIG. 9 , the belt rotating unit  6  is stood, and then is connected with the cleaning unit  70  by the connecting portion  100 . Thus, as shown in  FIG. 13 , after the connection, the belt rotating unit  6  and the cleaning unit  70  self-stand even when the operator removes the both hands from these units. 
     (4) As shown in  FIG. 16 , the grip portion  65   a  and the tension roller bearing  66   a  are demounted form the transfer frame  65 . 
     (5) As shown in  FIG. 18 , the lower tension roller bearing  66   b  is locked to place the intermediary transfer belt  61  in the pressure-released state. 
     (6) As shown in  FIG. 19 , the tension roller  64  is demounted. 
     (7) As shown in  FIG. 20 , the intermediary transfer belt  61  is demounted from the belt rotating unit  6 . 
     Thereafter, a new intermediary transfer belt  61  is inserted into the belt rotating unit  6  and then is assembled as it was. 
     (1) As shown in  FIG. 20 , the new intermediary transfer belt  61  is inserted into the belt rotating unit  6 . 
     (2) As shown in  FIG. 19 , the tension roller  64  is mounted. 
     (3) As shown in  FIG. 18 , the lock of the lower tension roller bearing  66   b  is released to restore the intermediary transfer belt  61  to the pressed state. 
     (4) As shown in  FIG. 16 , the grip portion  65   a  and the tension roller bearing  66   a  are mounted to the transfer frame  65 . 
     (5) As shown in  FIG. 9 , the belt rotating unit  6  is pulled out from the cleaning unit  70  to eliminate (remove) the connection between the belt rotating unit  6  and the cleaning unit  70  by the connecting portion  100 . 
     (6) As shown in  FIG. 4 , the cleaning unit  70  is positioned at the end portion of the belt rotating unit  6  and then the fastening member  81  is attached, thus being assembled into the intermediary transfer unit  80 . 
     (7) As shown in  FIG. 2 , the intermediary transfer unit  80  is inserted into the image forming apparatus  1 . 
     Embodiment 3 
       FIG. 21  is an illustration of a disconnecting operation of the cleaning blade. FIG.  22  is an illustration of a demounting operation of the cleaning blade. 
     In Embodiment 3, an exchanging procedure of the cleaning blade  71  in the intermediary transfer unit  80  in Embodiment 1 will be described. 
     (1) As shown in  FIG. 2 , the intermediary transfer unit  80  is demounted from the image forming apparatus  1 . Then, as shown in  FIG. 3 , the intermediary transfer unit  80  is mounted on a work-bench (working table). 
     (2) As shown in  FIG. 4 , the fastening member  81  is demounted, and then the cleaning unit  70  is separated from the belt rotating unit  6 . 
     (3) As shown in  FIG. 9 , the belt rotating unit  6  is stood, and then is connected with the cleaning unit  70  by the connecting portion  100 . Thus, as shown in  FIG. 13 , after the connection, the belt rotating unit  6  and the cleaning unit  70  self-stand even when the operator removes the both hands from these units. 
     As shown in  FIG. 13 , in a state in which the belt rotating unit  6  and the cleaning unit  70  are connected with each other to self-stand, the cleaning blade  71  of the cleaning unit  70  is exchanged. 
     Before exchanging the cleaning blade  71  from the cleaning unit  70 , in order to prevent the collected toner from scattering over the outside, the cleaning blade  71  and the neighborhood thereof are wiped with a non-woven fabric to clean the cleaning blade  71 . 
     As shown in  FIG. 21 , the fixing shaft  79  rotatably supporting the metal plate portion  72  of the cleaning blade  71  is demounted from the collected toner accommodating portion  74 . Thus, as shown in  FIG. 6 , by demounting the fixing shaft  79 , a cleaning blade unit into which the cleaning blade  71  and the metal plate portion  72  are integrally assembled is separable from the collected toner accommodating portion  74 . 
     As shown in  FIG. 22 , the operator demounts the cleaning blade  71  and the metal plate portion  72 , as a unit, from the cleaning unit  70 . Thereafter, the operator demounts the old cleaning blade  71  from the metal plate portion  72  and then mounts a new cleaning blade  71  to the metal plate portion  72 . After the exchange of the cleaning blade  71 , the operator mounts the new cleaning blade  71  and the metal plate portion  72 , as a unit, to the cleaning unit  70 . 
     As shown in  FIG. 21 , the fixing shaft  79  is mounted to the collected toner accommodating portion  74 . As shown in  FIG. 6 , when the fixing shaft  79  is mounted, the metal plate portion  72  of the cleaning blade  71  is rotatably supported by the collected toner accommodating portion  74 . In this state, a lubricant is applied onto the cleaning blade  71 . 
     (1) As shown in  FIG. 9 , the belt rotating unit  6  is pulled out from the cleaning unit  70  to eliminate (remove) the connection between the belt rotating unit  6  and the cleaning unit  70  by the connecting portion  100 . 
     (2) As shown in  FIG. 4 , the cleaning unit  70  is positioned at the end portion of the belt rotating unit  6  and then the fastening member  81  is attached, thus being assembled into the intermediary transfer unit  80 . 
     (3) As shown in  FIG. 2 , the intermediary transfer unit  80  is inserted into the image forming apparatus  1 . 
     According to Embodiment 3, the operator can perform the exchanging operation easily with both hands throughout the operation without causing the falling-down of the cleaning unit  70  in which the collected toner is accommodated. 
     Embodiments 4 and 5 
       FIG. 23  is an illustration of a connecting portion in Embodiment 4.  FIG. 24  is an illustration of a connecting portion in Embodiment 5. Embodiments 4 and 5 are different from Embodiment 1 only in constitution of the connecting portion, and other constitutions thereof are the same as those in Embodiment 1. Therefore, redundant description about constituent elements (portions) other than the connecting portion will be omitted. 
     As shown in  FIG. 23 , a connecting portion  100 A in Embodiment 4 connects the belt rotating unit  6  and the cleaning unit  70  by being fastened with a dedicated screw  120 . 
     As shown in  FIG. 24 , a connecting portion  100 B in Embodiment 5 connects the belt rotating unit  6  and the cleaning unit  70  by including a dedicated connecting part  121 . 
     The above-described embodiments can also be carried out in the embodiments in which a part or all of constituent elements are replaced with their alternative constituent elements so long as the belt rotating unit is caused to self-stand by being connected with the cleaning unit. 
     Therefore, the belt member is not limited to the intermediary transfer belt but may also be a recording material conveying belt, a transfer belt and the like. The present invention can be carried out irrespective of one drum type/tandem type and intermediary transfer type/recording material conveying member type if the image forming apparatus is an image forming apparatus using the belt member. The present invention can also be carried out irrespective of the number of the image bearing members, a charging type of the image bearing members, a type of formation of the electrostatic image, the developer and a developing type, a transfer type, and the like. 
     Further, in the above-described embodiments, only a principal portion relating to formation/transfer of the toner image was described, but by adding necessary devices, equipment and casing structures and the like, the present invention can be carried out in image forming apparatuses of various uses, such as printers, various printing machines, copying machines, facsimile machines, and multi-function machines. 
     In the belt unit in the present invention, the cleaning unit demounted from the belt unit is connected with the belt rotating unit by the connecting means, so that the belt rotating unit is kept in the standing state. Therefore, without preparing the dedicated jig, the belt rotating unit of the belt unit is stably held in the standing state, so that the operativity of the exchange of the belt member can be enhanced. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 281067/2012 filed Dec. 25, 2012, which is hereby incorporated by reference.