Patent Publication Number: US-11022915-B2

Title: Image forming apparatus with belt unit having cleaning unit

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an image forming apparatus, such as a copying machine, a printer or a facsimile machine, using an electrophotographic type or an electrostatic recording type. 
     Conventionally, in the image forming apparatus of an electrophotographic type or an electrostatic recording type, the belt feeding device including the endless belt stretched by the plurality of stretching rollers is used. The belt is used as a feeding member for carrying and feeding a toner image or carrying and feeding a recording material on which the toner image is formed. As the feeding member for carrying and feeding the toner image, an intermediary transfer member (intermediary transfer belt) for carrying and feeding the toner image in order to transfer the toner image from the photosensitive member onto the recording material, a belt-shaped electrophotographic photosensitive member (photosensitive belt), a belt-shaped electrostatic recording dielectric member, and the like member are used. Further, as the feeding member for carrying and feeding the recording material on which the toner image is formed, a recording material feeding member (recording material feeding belt) for carrying and feeding the recording material onto which the toner image is transferred from the photosensitive member is used. 
     In such a belt feeding device, a “belt shift” such that the belt shifts toward an end portion side of either of stretching rollers with respect to a rotational axis direction during feeding (traveling) of the belt due to accuracy of outer diameters of the stretching rollers, accuracy of relative alignment between the respective stretching rollers, and the like occurs. For that reason, a steering mechanism in which a force for swinging (tilting) the steering belt by a slidable member slidable with an inner peripheral surface of a rotating belt at each of end portions with respect to a widthwise direction of the belt is imparted to the steering roller, and center alignment (adjustment of a belt feeding position with respect to a widthwise direction) of the belt is carried out, is provided in some instances. In this steering mechanism, the steering roller is capable of automatically carrying out the center alignment of the belt by a balance of a frictional force “automatic belt center alignment”). Further, a steering mechanism, in which an end portion position of a belt with respect to a widthwise direction is detected by a sensor and a steering roller is swung by an actuator depending on a detection result thereof, has also been known. 
     Further, the belt feeding device is provided with a cleaning device for removing toner from the belt by a cleaning blade or the like in some instances. The toner accommodated in the cleaning device is fed and collected in a collecting portion such as a collecting container or the like provided in an apparatus main assembly of the image forming apparatus. Incidentally, deposited matter on the belt removed from the belt by the cleaning device includes paper powder or the like in addition to the toner in some instances, but herein the toner as principal deposited matter will be representatively described. 
     Japanese Laid-Open Patent Application (JP-A) 2015-64503 discloses a constitution of a delivering portion of toner from a cleaning device toward a collecting portion provided in an apparatus main assembly in an image forming apparatus in which an automatic belt center alignment is employed and the cleaning device is swingable together with a steering roller. In the constitution of JP-A 2015-64503, a path member which is connected and integrally swingable with the cleaning device and configured to communicate a toner discharge opening of the cleaning device and an opening of a collecting container provided in the apparatus main assembly with each other is provided. The path member includes a nozzle portion communicating with the toner discharge opening. Further, the path member includes a cylindrical portion inserted so that the nozzle portion overlaps with the toner discharge opening through the opening with respect to a height direction in a non-contact state. As a result, the path member is not only swingable together with a steering unit but also intended so as not to prevent swing of the steering unit. 
     However, in the constitution of JP-A 2015-64503, the path member is a rigid member. In this case, in consideration of a movable region of the path member swingable together with the steering unit, in order to prevent the path member from disconnecting from the collecting container provided in the apparatus main assembly through the opening, there is a need that the path member be provided with an extended portion where a length of the path member is extended. Further, there is a need that a receiving member, in which the extended portion is accommodatable, be provided below the opening of the collecting container provided in the apparatus main assembly. For that reason, the constitution of the toner delivering portion from the cleaning device toward the collecting portion provided in the apparatus main assembly is upsized, so that there is possibility that the upsized toner delivering portion leads to upsizing of the image forming apparatus. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide an image forming apparatus capable of realizing downsizing of a constitution of a toner delivering portion from a cleaning device swingable together with a steering roller toward a collecting portion provided at a predetermined position. 
     According to an aspect of the present invention, there is provided an image forming apparatus comprising: a belt unit including an endless belt on which a toner image is formed, wherein the belt unit includes a supporting unit configured to rotatably support a first roller for stretching the belt and includes a steering unit which includes a second roller for stretching the belt and which is configured to rotatably support the second roller and to swingably support the second roller so that an angle of a rotational axis of the second roller relative to a rotational axis of the first roller is changeable, a cleaning unit provided in the steering unit and configured to remove toner remaining on the belt, the cleaning unit being provided with a discharge opening through which collected toner is discharged to an outside of the cleaning unit; a receiving opening through which the toner discharged through the discharge opening is received; and a communicating portion configured to establish communication between the discharge opening and the receiving opening, wherein the communicating portion includes a tube-shaped portion constituted by a bellows-shaped elastic member capable of expansion and contraction with movement of the steering unit. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of an image forming apparatus. 
         FIG. 2  is a perspective view of a steering unit and a neighborhood of the steering unit. 
         FIG. 3  is a partially cut-away perspective view showing neighborhood of a swing center of the steering unit. 
       Parts (a) and (b) of  FIG. 4  show examples of a sliding ring. 
       Parts (a) and (b) of  FIG. 5  are schematic views for illustrating a bearing width between an intermediary transfer belt and the sliding rings. 
         FIG. 6  is a perspective view of a belt unit and a neighborhood of the belt unit. 
         FIG. 7  is an exploded perspective view of a belt cleaning device and a peripheral portion thereof. 
         FIG. 8  is a schematic sectional view of a communicating member and a neighborhood thereof. 
         FIG. 9  is a perspective view showing a state in which the steering unit is swung and the communicating member is expanded. 
         FIG. 10  is a perspective view showing a state in which the steering unit is swung and the communicating member is contracted. 
         FIG. 11  is a perspective view of a belt unit in another embodiment and a neighborhood of the belt unit. 
       Parts (a) and (b) of  FIG. 12  are schematic structural views for illustrating a sensor unit and a steering driving portion. 
         FIG. 13  is a sectional view of a communicating member in another embodiment described above and a neighborhood of the communicating member. 
         FIG. 14  is a perspective view of a belt cleaning device in another embodiment described above and a neighborhood of the belt cleaning device. 
         FIG. 15  is an illustration of an image forming apparatus. 
       Parts (a), (b) and (c) of  FIG. 16  are illustrations of an intermediary transfer unit. 
         FIG. 17  is a perspective view of a steering mechanism. 
       Parts (a), (b) and (c) of  FIG. 18  are illustrations of an opening of the steering mechanism. 
         FIG. 19  is an illustration of a mounting state of an intermediary transfer belt cleaner unit. 
         FIG. 20  is a sectional view of the intermediary transfer belt cleaner unit and a supporting portion. 
         FIG. 21  is a perspective view of the intermediary transfer unit in a state in which the intermediary transfer unit is mounted in the image forming apparatus. 
         FIG. 22  is a perspective view of an intermediary feeding unit. 
         FIG. 23  is an illustration of the image forming apparatus from which the intermediary transfer unit is pulled out through an opening of the image forming apparatus. 
         FIG. 24  is an illustration of a structure of side plates of the image forming apparatus. 
         FIG. 25  is a perspective view showing a state in which the intermediary transfer unit is mounted in guiding rails. 
         FIG. 26  is an illustration of the guiding rails. 
         FIG. 27  is an illustration of a position in a connecting process. 
         FIG. 28  is an illustration of another position in the connecting process. 
         FIG. 29  is an illustration of a position of completion of mounting. 
       Parts (a) and (b) of  FIG. 30  are illustrations of the guiding rails on a rear side and a front side, respectively, of an apparatus main assembly of the image forming apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An image forming apparatus according to the present invention will be described with reference to the drawings. 
     Embodiment 1 
     1. General Structure and Operation of Image Forming Apparatus 
       FIG. 1  is a schematic sectional view of an image forming apparatus  100  in this embodiment. 
     The image forming apparatus  100  in this embodiment is a tandem-type multi-function machine which is capable of forming a full-color image using an electrophotographic method and which employs an intermediary transfer method, and which has functions of a copying machine, a printer and a facsimile machine. The image forming apparatus  100  is capable of forming and outputting an image on a sheet-like recording material P in accordance with an image signal sent from an image reading device (not shown), a personal computer or the like. 
     The image forming apparatus  100  includes, as a plurality of image forming portions (image forming units), first to fourth image forming portions UY, UM, UPC and UK for forming images of color of yellow (Y), magenta (M), cyan (C) and black (K), respectively. As regards elements having the same or corresponding functions or constitutions in the respective image forming portions UY, UM, UC and UK, suffixes Y, M, C and K for representing the elements for associated colors, respectively, are omitted, and the elements will be collectively described in some cases. Each image forming portion U is constituted by including a photosensitive drum  101 , a charging roller  102 , an exposure device  103 , a developing device  104 , a primary transfer roller  16  and a drum cleaning device  105 , which are described below. 
     The image forming portion U includes, as an image bearing member, the photosensitive drum  101  which is a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member). The photosensitive drum  101  is rotationally driven at a predetermined peripheral speed in an arrow R 1  direction (clockwise direction) in  FIG. 1 . A surface of the rotating photosensitive drum  101  is electrically charged uniformly to a predetermined polarity (negative in this embodiment) and a predetermined potential by the charging roller  102  which is a roller-shaped charging member as a charging means. The charged surface of the photosensitive drum  101  is subjected to scanning exposure by the exposure device (laser scanner)  103  as an exposure means, so that an electrostatic image (electrostatic latent image) is formed on the surface of the photosensitive drum  101 . In this embodiment, the exposure device  103  is constituted as a single unit for exposing the respective photosensitive drums  101  to light. The exposure device  103  projects (emits) laser light on the respective photosensitive drums  101  on the basis of pieces of image information (image signals) of the respective colors. The electrostatic image formed on the photosensitive drum  101  is developed (visualized) by being supplied with toner by the developing device  104  as a developing means, so that a toner image (developer image) is formed on the photosensitive drum  101 . In this embodiment, on an exposed portion (image portion) of the photosensitive drum  101  where an absolute value of the potential is lowered by the exposure to light after the uniform charging of the photosensitive drum surface, the toner charged to the same polarity as the charge polarity (negative in this embodiment) of the photosensitive drum  101  is deposited. 
     An intermediary transfer belt  11 , which is a rotatable intermediary transfer member constituted by an endless belt, is provided so as to oppose the four photosensitive drums  101 . The intermediary transfer belt  1  is extended around and stretched by, as a plurality of stretching rollers, a secondary transfer opposite roller  12 , a steering roller  13 , and idler rollers  14  and  15 . In this embodiment, the secondary transfer opposite roller  12  also functions as a driving roller. That is, the secondary transfer opposite roller  12  not only rotates (circulates and moves) the intermediary transfer belt  11  by being driven by a driving source (not shown), but also functions as an opposing member (opposite electrode) to a secondary transfer roller  108  (described later). The intermediary transfer belt  11  is rotated at a predetermined peripheral speed (surface movement speed) in an arrow R 2  direction (counterclockwise direction) in  FIG. 1  by transmission of a driving force thereto by the secondary transfer opposite roller  12 . The peripheral speed of the intermediary transfer belt  11  is set at the substantially same peripheral speed (process speed) of the photosensitive drums  101 . In this embodiment, the steering roller  13  also functions as a tension roller. That is, the steering roller  13  not only constitutes a steering unit  1  described specifically later and adjusts a feeding position of the intermediary transfer belt  11 , but also imparts a predetermined tension to the intermediary transfer belt  11 . The first and second idler rollers  14  and  15  support the intermediary transfer belt  11  extending along an arrangement direction of the photosensitive drums  101 . Incidentally, the number of the plurality of steering rollers steering the intermediary transfer belt  11  is not limited to four, but may also be less than or more than four. 
     In an inner peripheral surface side of the intermediary transfer belt  11 , primary transfer rollers  16  which are roller-shaped primary transfer members as primary transfer means are provided correspondingly to the photosensitive drums  101 . Each of the primary transfer rollers  16  is urged (pressed) against the intermediary transfer belt  1  toward the associated photosensitive drum  101 , so that a primary transfer portion (primary transfer nip) T 1  where the photosensitive drum  101  and the intermediary transfer belt  11  are in contact with each other is formed. The toner images formed on the photosensitive drums  101  as described above are primary-transferred onto the rotating intermediary transfer belt  1  at the primary transfer portions T 1  by a predetermined pressure and an electrostatic load bias which are imparted by the primary transfer rollers  16 . During the primary transfer step, to the primary transfer rollers  16 , a primary transfer voltage (primary transfer bias) of an opposite polarity (positive in this embodiment) to the normal charge polarity (the charge polarity during development) of the toner is applied by a primary transfer voltage source (high voltage source circuit). For example, during full-color image formation, the toner images of the respective colors of Y, M, C and K formed on the respective photosensitive drums  101  are successively primary-transferred superposedly onto the intermediary transfer belt  11  at the primary transfer portions T 1 . 
     In an outer peripheral surface side of the intermediary transfer belt  11 , at a position opposing the secondary transfer opposite roller  12 , the secondary transfer roller  108  which is a roller-shaped secondary transfer member as a secondary transfer means is provided. The secondary transfer roller  108  is urged (pressed) against the intermediary transfer belt  11  toward the secondary transfer opposite roller  12 , and forms a secondary transfer portion (secondary transfer nip) T 2  where the intermediary transfer belt  11  and the secondary transfer roller  108  are in contact with each other. 
     The toner images formed on the intermediary transfer belt  11  as described above are secondary-transferred at the secondary transfer portion T 2  onto a recording material (recording medium, sheet) P by a predetermined pressure and an electrostatic load bias which are imparted by the secondary transfer roller  108 . At the secondary transfer portion T 2 , the recording material P is nipped and fed by the intermediary transfer belt  1  and the secondary transfer roller  108 . During a secondary transfer step, to the secondary transfer roller  108 , a secondary transfer voltage (secondary transfer bias) of an opposite polarity (positive in this embodiment) to the normal charge polarity of the toner is applied by a secondary transfer voltage source (high-voltage source circuit). The recording material P is fed one by one from a recording material accommodating portion  106  by a pick-up roller or the like and is conveyed to a registration roller pair  107 . This recording material P is conveyed toward the secondary transfer portion T 2  by the registration roller pair  107  while being timed to the toner images on the intermediary transfer belt  11 . 
     The recording material P on which the toner images are transferred is conveyed to a fixing device  109  as a fixing means. The fixing device  109  fixes (melts) the toner images on the recording material P by heating and pressing the recording material P carrying thereon unfixed toner images. The recording material S on which the toner images are transferred is discharged (outputted) toward an outside of an apparatus main assembly  110  of the image forming apparatus  100 . 
     Further, toner (primary transfer residual toner) remaining on the surface of each of the photosensitive drums  101  without being transferred onto the intermediary transfer belt  11  during the primary transfer is removed and collected from the photosensitive drum  101  by the drum cleaning device  105  as a photosensitive member cleaning means. Further, on the outer peripheral surface side of the intermediary transfer belt  11 , at a position opposing the steering roller  13 , a belt cleaning device  30  as an intermediary transfer member cleaning means is provided. Toner (secondary transfer residual toner) remaining on the intermediary transfer belt  11  without being transferred onto the recording material P during the secondary transfer is removed and collected from the intermediary transfer belt  11  by the belt cleaning device  30 . The belt cleaning device  30  will be further described later specifically. 
     Incidentally, in this embodiment, the image forming apparatus  100  includes the four image forming portions U for the four colors, but the number of the image forming portions U is not limited to four, and an order of arrangement of the image forming portions for forming the images of the respective colors is also not limited to the arrangement order in this embodiment. 
     2. Belt Unit 
     In this embodiment, the intermediary transfer belt  11 , the stretching rollers  12  to  15  thereof, the respective primary transfer rollers  16 , the belt cleaning device  30  and the like constitutes a belt unit (intermediary transfer belt unit)  10  as a belt feeding device. In this embodiment, the belt unit  10  is mountable to and dismountable from the apparatus main assembly  110 . 
     The belt unit  10  includes a unit frame (casing)  2  ( FIG. 2 ) as a first supporting member and a supporting table  8  ( FIG. 2 ) as a second supporting member. The unit frame  2  rotatably supports the secondary transfer roller  12  and the first and second idler rollers  14  and  15  of the plurality of stretching rollers, and the respective primary transfer rollers  16 . The supporting table  8  rotatably supports the steering roller  13  of the plurality of stretching rollers. The supporting table  8  is swingably (rotatably or pivotably) supported by the unit frame  2 . As a result, alignment of the steering roller  13  relative to the secondary transfer opposite roller  12  can be changed. That is, the supporting table  8  rotatably supports the steering roller  13  and is swingable so as to change an angle of a rotational axis of the steering roller  13  relative to a rotational axis of the secondary transfer opposite roller  12 . As described later, the steering roller  13 , the supporting table  8  and the like constitute a steering unit  1  as a steering mechanism for controlling a feeding position of the intermediary transfer belt  11  with respect to a widthwise direction (rotational axis direction of the steering roller  13 ) substantially perpendicular to a circumferential direction (surface movement direction) of the intermediary transfer belt  11 . 
     3. Steering Unit 
     Next, the steering unit  1  as a steering mechanism (automatic belt center alignment mechanism) in this embodiment will be described.  FIG. 2  is a perspective view of the steering unit  1  as the steering mechanism in this embodiment and the neighborhood of the steering unit  1 . 
     The steering roller  13  as a steering member is rotatably supported by the supporting table  8 . The supporting table  8  is constituted by including a swingable plate  7  and a side supporting member  6 . The swingable plate  7  is supported by the unit frame  2  so as to be swingable about a steering axis (swing axis) J substantially at a central portion thereof with respect to a rotational axis D direction of the steering roller  13 . The rotational axis D of the steering roller  13  and the steering axis J are substantially perpendicular to each other. The side supporting member  6  is fixed to each of opposing end portions of the swingable plate  7  with respect to a longitudinal direction (rotational axis D direction of the steering roller  13 ) of the swingable plate  7 . Each of the side supporting members  6  is provided with a slide groove  6   a . With each of the slide grooves  6   a , a slide bearing member  4  is slidably engaged. Each of the slide bearing members  4  is urged in an arrow P T  direction (direction from an inner peripheral surface side toward an outer peripheral surface side) in  FIG. 2  by a tension spring (compression spring)  5  which is an elastic member as an urging means. 
     The steering roller  13  is supported by a steering roller shaft  13   a  (part (a) of  FIG. 4 ) in a rotatable state about the steering roller shaft  13   a  by bearings or the like incorporated therein. Opposite end portions of the steering roller shaft  13   a  with respect to the axial direction have a D-cut shape, and are supported by the slide bearing members  4  in a non-rotatable state about the slide bearing members  4 . As a result, the steering roller  13  is rotated by the intermediary transfer belt  11  while imparting tension to the intermediary transfer belt  11  in a state in which the steering roller  13  is swingably supported by the supporting table  8 . 
     Further, at the end portions of the steering roller  13  with respect to the rotational axis D direction, sliding rings  3  which have a larger frictional resistance against the intermediary transfer belt  11  than the steering roller  13  and which are used as slidable members are provided. Each of the sliding rings  3  is supported with a parallel pin or the like by the steering roller shaft  13   a  in a non-rotatable state about the steering roller shaft  13   a  (part (a) of  FIG. 4 ) so as not to be rotated by the intermediary transfer belt  11 . Accordingly, when the intermediary transfer belt  11  is rotated, the steering roller  13  does not slide on the inner peripheral surface of the intermediary transfer belt  11 , but the sliding rings  3  slide on the inner peripheral surface of the intermediary transfer belt  11 . 
     Thus, the supporting table  8  supports the steering roller  13  and the sliding rings  3  so as to be swingable about the steering axis J extending in a direction crossing (in this embodiment, substantially perpendicular to) the rotational axis D of the steering roller  13 . Further, the steering roller  13  which is a rotatable member provided at a central portion with respect to the rotational axis D direction of the steering roller  13  and the sliding rings  3  which are slidable portions provided at the end portions of the steering roller  13  with respect to the rotational axis D direction are connected coaxially with each other. 
     A frame stay  2   a  which is a member constituting the unit frame  3  is extended and provided between side plates  2   b  on opposite sides of the unit frame  2 . At each of opposite end portions of the frame stay  2   a  with respect to a longitudinal direction (rotational axis D direction of the secondary transfer opposite roller  12 ), two slidable rollers  9  are provided. The slidable rollers  9  are rotatably supported by the frame stay  2   a . The swingable plate  7  is disposed so as to opposite the frame stay  2   a . The swingable plate  7  is supported by the frame stay  2   a  so as to be swingable about the steering axis J in an arrow S direction in  FIG. 2 . The slidable rollers  9  have a function of reducing a resistance (rotational resistance) against the frame stay  2   a  when the swingable plate  7  is swung. 
       FIG. 3  is a partially cut-away perspective view showing a structure of a swing center portion of the supporting table  8 . At a central portion (center portion) of the swingable plate  7  with respect to the longitudinal direction, a steering shaft  21  which is a swing shaft (rotation shaft) is fixed. The steering shaft  21  is provided with a key-shaped portion  21 D cut at two portions on one end side with respect to an axial direction thereof (i.e., cut along two planes of a part of a cylindrical outer peripheral surface of the steering shaft  21 ), and is integrally fastened to the swingable plate  7  with a screw  24  in an engaged state with the swingable plate  7 . This steering shaft  21  is inserted in a bearing (shaft-supporting portion)  23  such as a bearing provided on the frame stay  2   a  and is rotatably supported by the frame stay  2   a  via the bearing  23 . At the other end portion of the steering shaft  21  with respect to the axial direction, a thrust retaining member  26  is fixed via a fixing member  20 , so that retention of the steering shaft  21  is realized. Further, a supporting plate  25  is interposed between the frame stay  2   a  and the fixing member  20  in a state in which the steering shaft  21  is penetrated through the supporting plate  25 , and is fixed to the frame stay  2   a  with screws  25   a . An axis of the steering shaft  21  constitutes the steering axis J. 
     In this embodiment, the steering unit  1  as a steering mechanism is constituted by the supporting plate  8 , the steering roller  13 , the sliding rings  3 , the steering roller shaft  13   a , the steering shaft  21  and the like which are described above. 
     4. Automatic Belt Center Alignment 
     Next, automatic belt center alignment by the steering unit  1  will be described. Parts (a) and (b) of  FIG. 4  are perspective views showing examples of the sliding rings  3 . Parts (a) and (b) of  FIG. 5  are schematic views for illustrating a relationship in bearing width between the intermediary transfer belt  11  and the sliding rings  3 . 
     In part (a) of  FIG. 4 , as an example of the sliding rings  3 , a sliding ring  3   a  of a straight type in which an outer diameter of the steering roller is substantially the same with respect to the axial direction (rotational axis direction of the steering roller  13 ) is shown. In part (b) of  FIG. 4 , as another example of the sliding rings  3 , a sliding ring  3   b  of a taper type in which the outer diameter of the steering roller  13  continuously increases toward an outside (a side opposite from the steering axis J side) with respect to the axial direction (rotational axis direction of the steering roller  13 ) is shown. 
     As described above, the steering roller  13  is supported by the steering roller shaft  13   a  in the rotatable state about the non-rotatable steering roller shaft  13   a . On the other hand, the sliding rings  3  ( 3   a ,  3   b ) provided at the opposite end portions of the steering roller  13  with respect to the rotational axis direction of the steering roller  13  are supported by the steering roller shaft  13   a  in the non-rotatable state about the non-rotatable steering roller shaft  13   a . Accordingly, when the intermediary transfer belt  11  is rotated, the steering roller  13  does not slide on the inner peripheral surface of the intermediary transfer belt  11 , but the sliding rings  3  ( 3   a ,  3   b ) slides on the inner peripheral surface of the intermediary transfer belt  11 . By such a constitution, automatic belt center alignment is enabled. That is, when a receiving where the sliding rings  3  ( 3   a ,  3   b ) and the intermediary transfer belt  11  are in contact with each other in a predetermined amount or more, the steering unit  1  starts steering. 
     Incidentally, a constitution in which the sliding rings  3  ( 3   a ,  3   b ) are rotatably supported may also be employed. However, in that case, there is a need that a torque required for rotating the sliding rings  3  in the rotational direction of the intermediary transfer belt  11  is large them a torque required for rotating the steering roller  13  in the same direction. As a result, the steering is enabled. 
     In this embodiment, a width (a length with respect to a direction substantially perpendicular to a surface movement direction) of the intermediary transfer belt  11  is broader than a width (a length with respect to the rotational axis direction) of the steering roller  13  and is narrower than a total width including the width of the steering roller  13  are widths of the sliding rings  3  at the opposite end portions of the steering roller  13 . For that reason, in this embodiment, when the intermediary transfer belt  11  is in an ideal steady center alignment state, the relationship in bearing width between the intermediary transfer belt  11  and the sliding rings  3  is as shown in part (a) of  FIG. 5 . That is, bearing widths w (hatched portions in the figure) are substantially equal to each other at the opposite end portions of the intermediary transfer belt  11  with respect to a widthwise direction of the intermediary transfer belt  11 . In the case of such a bearing width relationship, even when a belt shift occurs during rotation of the intermediary transfer belt  11 , the intermediary transfer belt  11  always slides with at least one of the sliding rings  3 . On the other hand, in the case where the width of the intermediary transfer belt  11  is narrower than the width of the steering roller  13 , the bearing width relationship between the intermediary transfer belt  11  and the sliding rings  3  is as shown in part (b) of  FIG. 5 . In this case, even when the belt shift occurs during the rotation of the intermediary transfer belt  11 , the steering unit  1  is not swung until the bearing width between the intermediary transfer belt  1  and the sliding ring  3  generates. For that reason, an abrupt center alignment opening is liable to occur. In principle, even in the bearing width relationship as shown in part (b) of  FIG. 5 , the automatic belt center alignment using a balance of the frictional force can be carried out. However, the bearing width relationship as shown in part (a) of  FIG. 5  in which the balance of the frictional force can always be detected enables finer center alignment opening, and therefore, has an advantage such that a large fluctuation in timewise change of a rubber angle does not occur. 
     Thus, in this embodiment, slidable members  3  for generating a force for swinging the supporting plate  8  by sliding with the intermediary transfer belt  11  through rotation of the intermediary transfer belt  11  are provided at the opposite end portions of the steering roller  13  with respect to the rotational axis direction of the steering roller  13 . Further, the position of the intermediary transfer belt  11  is automatically adjusted by the rotation of the intermediary transfer belt  11 . 
     5. Belt Cleaning Device 
     The belt cleaning device  30  in this embodiment will be described. Incidentally, as regards the image forming apparatus  100  and elements thereof, a front side of the drawing sheet of  FIG. 1  is a front (surface) side, and a rear side of the drawing sheet of  FIG. 1  is a rear (surface) side. A direction perpendicular to the drawing sheet of  FIG. 1  connecting the front side and the rear side is substantially parallel to the rotational axis direction of the photosensitive drum  1  or the widthwise direction of the intermediary transfer belt  11 . Further, as regards the image forming apparatus  100  and the elements thereof, a vertical (up-down) direction refers to a vertical direction with respect to a direction of gravitation. 
     As shown in  FIG. 1 , the cleaning device  30  includes a cleaning container  31 , a cleaning blade  32  as a cleaning member, a fixing metal plate  33  as a blade fixing member, and a feeding screw  34  as a feeding member. The cleaning blade  32  is bonded and fixed to the fixing metal plate  33  and this fixing metal plate  33  is fixed to the cleaning container  31 . The feeding screw  34  is rotatably supported by the cleaning container  31 . 
     The cleaning blade  32  is disposed at a position opposing the steering roller  13  through the intermediary transfer belt  11  and contacts the intermediary transfer belt  11  toward the steering roller  13 . That is, the cleaning blade  32  applies an external force to the steering roller  13  through the intermediary transfer belt  11 . In this embodiment, the cleaning blade  32  is formed of a urethane rubber as an elastic material. The cleaning blade  32  is a plate-like member which has lengths with respect to a longitudinal direction disposed substantially in parallel to the widthwise direction (the rotational axis direction of the steering roller  13 ) of the intermediary transfer belt  11  and with respect to a widthwise (short side) direction substantially perpendicular to the longitudinal direction and which has a predetermined thickness. The cleaning blade  32  is contacted to the intermediary transfer belt  11  with an angle at which the cleaning blade  32  extends in a counterdirection to the rotational direction of the intermediary transfer belt  11 . Further, in this embodiment, the width of the cleaning blade  32  with respect to the longitudinal direction is shorter than the width (the length with respect to the rotational axis direction) of the steering roller  13 . 
     The toner on the intermediary transfer belt  11  is scraped off of the rotating intermediary transfer belt  11  by the cleaning blade  32  and is accommodated inside the cleaning container  31 . The toner accommodated inside the cleaning container  31  is fed by the feeding screw  34  toward the front side along the longitudinal direction (rotational axis direction of the steering roller  13 ) of the cleaning device  30 . Further, as specifically described later, the toner fed by the feeding screw  34  is sent toward and collected in a collecting container  51  provided inside the apparatus main assembly  110  on the front side of the apparatus main assembly  110 . 
       FIG. 6  is a perspective view of the belt unit  10  in this embodiment and a neighborhood of the belt unit  10 .  FIG. 7  is an exploded perspective view of the cleaning device  30  and a periphery thereof.  FIG. 8  is a schematic sectional view of a communicating member  40  (described later) and a neighborhood of the communicating member  40 . The cleaning device  30  is held by the belt unit  10 . In this embodiment, the cleaning device  30  is held (positioned) by the supporting table  8  of the steering unit  1  via a holding mechanism such as a holding portion  31   a  provided on the cleaning container  31 . As a result, the cleaning device  30  is swingable integrally with the steering unit  1  (steering roller  13 ). The cleaning blade  32  is capable of collecting the toner from the intermediary transfer belt  11  in a state in which a contact state with the intermediary transfer belt  11  is maintained even in the case where the steering unit  1  is inclined in any direction about the steering axis J. Further, in this embodiment, in a state in which the belt unit  10  is mounted in the apparatus main assembly  110 , the cleaning device  30  is supported by a cleaning device supporting member  61  provided in the apparatus main assembly  110 . The cleaning device supporting member  61  supports a lower portion of the cleaning container  31  from an outside of the cleaning container  31  at a substantially central portion of the cleaning container  31  with respect to the longitudinal direction (rotational axis direction of the steering roller  13 ) of the cleaning container  31 , i.e., at a position corresponding to the steering axis J. As a result, the cleaning device supporting member  61  does not prevent the steering unit  1  from swinging. 
     The cleaning device  30  is provided with a discharging portion  35  provided with a discharge opening  35   a  for permitting discharge of the toner in the cleaning container  31  toward the outside of the cleaning container  31  through the discharge opening  35   a . In this embodiment, the discharging portion  35  is provided integrally with the cleaning container  31  at a front-side end portion of the cleaning container  31  with respect to the longitudinal direction of the cleaning container  31 . In this embodiment, the discharge opening  35   a  is open downward. That is, in this embodiment, the discharging portion  35  is disposed on one end portion side (on the front-side end portion side in this embodiment) of the cleaning device  30  than the steering axis J is with respect to the rotational axis direction of the steering roller  13 . On the other hand, the apparatus main assembly  110  is provided with a collecting portion  50  which is configured to collect the toner discharged from the cleaning container  31  and which is disposed at a predetermined position is provided. In this embodiment, the collecting portion  50  is constituted by including a collecting container  51  and a feeding portion  52  as a receiving portion. The feeding portion  52  is provided with a receiving opening  50   a  for receiving the toner from an outside toward an inside of the collecting portion  5   a . The feeding portion  52  is provided with a feeding member  52   a  for feeding the toner, toward the collecting container  51 , received inside the collecting portion  50  through the receiving opening  50   a . The feeding member  52  is constituted by a screw and the like. The image forming apparatus  100  includes the communicating member  40  for communicating the discharge opening  35   a  of the cleaning device  30  and the receiving opening  50   a  of the collecting portion  50  with each other. That is, in this embodiment, in the state in which the belt unit  10  is mounted in the apparatus main assembly  110 , the communicating member  40  causes the discharge opening  35   a  on the belt unit  10  side and the receiving opening  50   a  on the apparatus main assembly  110  side to communicate with each other. 
     The communicating member  40  is constituted by including an upper engaging portion  41  as a first engaging portion, a lower engaging portion  42  as a second engaging portion, and a tube-shaped portion  43  connected with the upper engaging portion  41  and the lower engaging portion  42 . The upper engaging portion  41  is provided with an upper opening  41   a  as a first opening communicating with the discharge opening  35   a  of the cleaning device  30 . The upper engaging portion  41  engages with the discharging portion  35  of the cleaning device  30  and is movable with the swing of the steering unit  1 . The lower engaging portion  42  is provided with a lower opening  42   a  as a second opening communicating with the receiving opening  50   a  of the collecting portion  50 . The lower engaging portion  42  engages with the feeding portion  52  of the collecting portion  50  and is disposed substantially at a fixing position. The tube-shaped portion  43  is fixed integrally to the upper engaging portion  41  and the lower engaging portion  42  by a fixing means such as welding (bonding in this embodiment). As a result, the communicating member  40  is sealed so that the toner is not leaked from the inside to the outside thereof. In this embodiment, the upper engaging portion  41  is connected to the discharging portion  35  of the cleaning device  30  so as to be mountable to and dismountable from the discharging portion  35  when the belt unit  10  is mounted in the apparatus main assembly  110 . Further, in this embodiment, the upper engaging portion  41  is disconnected form the discharging portion  35  of the cleaning device  30  when the belt unit  10  is dismounted form the apparatus main assembly  110 . On the other hand, in this embodiment, the lower engaging portion  42  is substantially fixed to the feeding portion  52  of the collecting portion  50 . 
     Here, the belt unit  10  is supported by an unshown supporting frame provided in the apparatus main assembly  110 . In this embodiment, when the belt unit  10  is mounted in the apparatus main assembly  110 , the discharging portion  35  of the cleaning device  30  communicates with the upper engaging portion  41  of the communicating member  40  held by the apparatus main assembly  110 , so that the discharge opening  35   a  and the upper opening  41   a  communicate with each other. In this embodiment, the cleaning device  30  is provided with a shutter member  36  capable of opening and closing the discharge opening  35   a  of the cleaning device  30 . The shutter member  36  opens the discharge opening  35   a  in interrelation with a mounting operation of the belt unit  10  into the apparatus main assembly  110  when the upper engaging portion  41  of the communicating member  40  engages with the discharging portion  35  of the cleaning device  30 . Further, the shutter member  36  closes the discharge opening  35   a  in interrelation with a dismounting opening of the belt unit  10  from the apparatus main assembly  110  when the engagement between the upper engaging portion  41  and the discharging portion  35  is eliminated. 
     The tube-shaped portion  43  is constituted by a bellows-shaped elastic member which is capable of expansion and contraction with movement of the upper engaging portion  41  and which is provided with a feeding path  43   a  formed therein so as to guide the toner, toward the lower opening  42   a , received through the upper opening  41   a . The tube-shaped portion  43  is capable of expanding to until bellows stretch with respect to a vertical direction and is capable of contracting until the bellows collapse and overlap with since the tube-shaped portion  43  is constituted by the bellows-shaped elastic member. In this embodiment, the tube-shaped portion  43  is formed of a rubber material as an elastic material. However, the material of the tube-shaped portion  43  is not limited to the rubber material, but for example, an arbitrary material such as a resin material when sufficient expansion and contraction property and durability can be obtained. 
     The cleaning blade  32  contacts the intermediary transfer belt  11  in an elastically deformed state and scrapes off the toner of the intermediary transfer belt  11 . The toner scraped off of the intermediary transfer belt  11  id dropped in the cleaning device  30 . The toner dropped in the cleaning device  30  is fed to the discharge opening  35   a  provided at the front-side end portion of the cleaning device  30  with respect to the longitudinal direction of the cleaning device  30  by the feeding screw  34  disposed so as to extend along the longitudinal direction of the cleaning device  30 . The toner fed to the discharge opening  35   a  passes through the inside of the tube-shaped portion  43  of the communicating member  40  through the discharge opening  35   a  by free fall, and is discharged toward an inside of the feeding portion  52  of the collecting portion  50  provided in the apparatus main assembly  110 . Then, the toner discharged in the feeding portion  52  is accommodated in the collecting container  51  of the collecting portion  50  attached to the apparatus main assembly  110 . 
     6. Operation of Communicating Member 
     Next, an operation of the communicating member  40  in this embodiment will be further described.  FIG. 9  is a perspective view showing a state in which the steering unit  1  swings and the tube-shaped portion  43  of the communicating member  40  is expanded.  FIG. 10  is a perspective view showing a state in which the steering unit  1  swings and the tube-shaped portion  43  of the communicating member  40  is contracted. 
     When a shift of the intermediary transfer belt  11  is generated by a fluctuation of a load on the belt unit  10  depending and distortion of the image forming apparatus  100 , a use environment, a use condition such as continuous output of images with a thin density, and the like, a steering force is exerted on the steering unit  1 . As a result, the steering unit  1  is swung about the steering axis J in a range of a predetermined angle θ° and corrects the shift of the belt. At this time, the cleaning device  30  is constituted so as to be swingable integrally with the steering unit  1  about the steering axis J in a range of ±1.5°. For example, in the case of the image forming apparatus  100  capable of printing an image on A3-size paper, the width of the intermediary transfer belt  11  is 297 mm or more. For that reason, in this case, end portions of the steering unit  1  and the cleaning device  30  with respect to the longitudinal direction move in the vertical direction in an amount of ±(297/2)×tan(1.5°)≈±3.9 mm or more. Here, in consideration of variation of manufacturing and installation conditions, the case where the end portions of the steering unit  1  and the cleaning device  30  with respect to the longitudinal direction move within a range of ±5 mm was investigated. As a result thereof, it turned out that in this case, when reaction force is 50 gf or less, there is no problem about belt shift correcting power of the steering unit  1 . That is, it turned out that from the viewpoint of the belt shift correcting power of the steering unit  1 , a spring constant, with respect to an expansion and contraction direction of the tube-shaped portion  43  constituted by the bellow-shaped elastic member may desirably be 0.098 N/mm or less. This spring constant may preferably be as small as possible. In this embodiment, the spring constant is 0.098 N/mm or less. 
     For example, in the case where the intermediary transfer belt  11  shifts toward a rear side as shown in  FIG. 9 , the steering unit  1  swings so that a front side thereof moves upward about the steering axis J in the vertical direction in order to correct this belt shift. At that time, the tube-shaped portion  43 , of the communicating member  40 , constituted by the bellows-shaped elastic member expands without substantially exerting a load on the steering operation and is capable of maintaining the communication between the discharge opening  35   a  and the receiving opening  50   a.    
     Further, in the case where the intermediary transfer belt  11  shifts toward a front side as shown in  FIG. 10 , the steering unit  1  swings so that a rear side thereof moves upward about the steering axis J in the vertical direction in order to correct this belt shift. At that time, the tube-shaped portion  43 , of the communicating member  40 , constituted by the bellows-shaped elastic member contracts without substantially exerting the load on the steering operation and is capable of maintaining the communication between the discharge opening  35   a  and the receiving opening  50   a.    
     Here, the case where a path portion which constitutes a delivering portion of the toner from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110  and which corresponds to the tube-shaped portion  43  of the communicating member  40  in this embodiment is constituted by a rigid member will be considered. Further, similarly as in the above-described example, it is assumed that the end portions of the steering unit  1  with respect to the longitudinal direction (the rotational axis direction of the steering roller  13 ) move in the vertical direction in the amount (distance) of ±3.9 mm or more. In this case, in order to maintain the communication between the path portion and the collecting portion  50  in the case where the longitudinal end portions of the steering unit  1  move upward in the vertical direction, there is a need that the path portion has a length of about 5 mm or more in consideration of the variations of the manufacturing and installation conditions. Further, in order to accommodate the path portion in the case where the longitudinal end portions of the steering unit  1  swing downward in the vertical direction, a space (an accommodating region of the path portion) of 5 mm or more is needed in the collecting portion  50 . For that reason, there is a possibility that a structure of the delivering portion from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110  is upsized and thus leads to upsizing of the image forming apparatus  100 . Further, in the case of such a structure, in order to suppress the load on the steering operation, there is a need that a gap is formed between the path portion and the collecting portion  50  and a sealing member for sealing the gap is separately provided. 
     On the other hand, according to this embodiment, the tube-shaped portion  43  of the communicating member  40  is constituted by the bellows-shaped elastic member capable of expansion and contraction, so that there is no need to provide the accommodating region for the communicating member  40  in the collecting portion  50  provided in the apparatus main assembly  110 . For that reason, downsizing of the structure of the toner delivering portion from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110  can be realized, so that downsizing of the image forming apparatus  100  can be realized. That is, according to this embodiment, the tube-shaped portion  43  of the communicating member  40  is constituted by the bellow-shaped elastic member, and therefore, the length of the communicating member  40  and the space occupied by the collecting portion  50  can be minimized, so that the downsizing of the image forming apparatus  100  can be realized. Further, the tube-shaped portion  43  of the communicating member  40  is capable of expansion and contraction, and therefore, the upper engaging portion  41 , the lower engaging portion  42  and the tube-shaped portion  43  can be sealed by bonding or the like. For that reason, there is no need that a sealing member is separately provided for suppressing leakage of the toner from the delivering portion of the toner from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110 , or necessity thereof can be reduced. 
     As described above, according to this embodiment, downsizing of the structure of the toner delivering portion from the cleaning device  30  swingable together with the steering roller  13  toward the collecting portion  50  disposed at the predetermined position can be realized. By this, downsizing of the image forming apparatus  100  can be realized. 
     Embodiment 2 
     Another embodiment of the present invention will be described. Basic constitutions and operations of an image forming apparatus in this embodiment are the same as those of the image forming apparatus in Embodiment 1. Accordingly, in the image forming apparatus of this embodiment, elements having the same or corresponding functions and constitutions as those of the image forming apparatus in Embodiment 1 are represented by the same reference numerals or symbols as those in Embodiment 1, and will be omitted from detailed description. 
     In Embodiment 1, the image forming apparatus  100  employed the automatic belt center alignment type. However, the present invention is not limited to application to the image forming apparatus employing the automatic belt center alignment type, but is applicable when the image forming apparatus is an image forming apparatus in which a cleaning device is swingable together with a steering roller. In this embodiment, the image forming apparatus  100  detects an end portion position of the intermediary transfer belt  11  with respect to a widthwise direction by a sensor and corrects the belt shift by controlling an attitude of the steering roller  13  by a drive control device on the basis of a detection result of the end portion position of the intermediary transfer belt  11 . Further, in this embodiment, in the image forming apparatus  100  having such a constitution, a communicating member  40  similar to that in Embodiment 1 is applied to the toner delivering portion which is swingable together with the steering roller  13  and which delivers the toner from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110 . 
       FIG. 11  is a perspective view of the belt unit  10  in this embodiment and a neighborhood of the belt unit  10 . Parts (a) and (b) of  FIG. 12  are schematic structural views for illustrating a sensor unit and a steering driving portion which are described later.  FIG. 13  is a sectional side view of the communicating member  40  and a neighborhood of the communicating member  40 .  FIG. 14  is a perspective view of the belt cleaning device  30  and a periphery thereof. 
     The belt unit  10  includes a unit frame  71  as a first supporting member and a swingable frame  72  as a second supporting member. The secondary transfer opposite roller  12  and the first and second idler rollers  14  and  15  of the stretching rollers, and the respective primary transfer rollers  16  are rotatably supported by the unit frame  71 . Further, the front-side end portion of the rotation shaft of the steering roller  13  of the stretching rollers is rotatably supported by the swingable frame  72 . Further, the rear-side end portion of the rotation shaft of the steering roller  13  is rotatably supported by a steering arm  81  (part (a) of  FIG. 12 ). Further, a rear-side end portion of the swingable frame  72  is rotatably held by the rear-side end portion of the rotation shaft of the steering roller  13  and is supported by the steering arm  81  (part (b) of  FIG. 12 ) through the steering roller  13 . 
     Further, a steering shaft  73  ( FIG. 13 ) which is a swing shaft (rotation shaft) provided at a front-side end portion of the swingable frame  72  is rotatably supported by a steering shaft supporting portion  74  ( FIG. 13 ) provided on the unit frame  71 . An axis of the steering shaft  73  constitutes a steering axis J′. As a result, the swingable frame  72  is swingable relative to the unit frame  71  (the secondary transfer opposite roller  12 ). 
     The steering arm  81  (part (a) of  FIG. 12 ) is supported by the unit frame  71  so as to be rotatable about the arm rotation shaft  82  provided on the rear side plate of the unit frame  71 . On the rear side plate of the unit frame  71 , an eccentric cam  83  (part (a) of  FIG. 12 ) is provided. The steering arm  81  is urged by a steering spring  84  as an urging means so as to contact this eccentric cam  83 . The eccentric cam  83  is rotationally driven by a steering motor  85  as a driving source, and an angular position of the steering arm  81  with respect to a swing direction is determined depending on a stop position thereof. In this embodiment, the steering driving portion  80  is constituted by the steering arm  81 , the eccentric cam  83 , the steering spring  84 , the steering motor  85  and the like. 
     Further, the belt unit  10  is provided with a sensor unit  90  as a position detecting means for detecting a position of an end portion (front-side end portion in this embodiment) of the intermediary transfer belt  10  with respect to the widthwise direction of the intermediary transfer belt  11 . In this embodiment, the sensor unit  90  is constituted by including a sensor flag  91  and a plurality of photo-interrupters  92 . The sensor flag  91  is supported by the swingable frame  72  so as to be rotatable (swingable) about a flag rotation shaft  91   c . At one end portion of the sensor flag  91 , a rotatable detecting roller  91   a  is provided, and at the other end portion of the sensor flag  91 , a light-blocking portion  91   b  for light-blocking the photo-interrupters  92  depending on an angular position thereof with respect to a rotational direction is provided. The sensor flag  91  contacts the front-side end portion of the intermediary transfer belt  11  and is rotated with generation of the belt shift. Then, the light-blocking portion  91   b  light-blocks the photo-interrupters  92  depending on a feeding position of the intermediary transfer belt  11  with respect to the widthwise direction and thus is capable of detecting the feeding position. A controller  120  (part (b) of  FIG. 12 ) actuates the steering motor  85  depending on an output signal of the photo-interrupters  92  and swings the steering roller  13 . As a result, a widthwise position of the intermediary transfer belt  11  is corrected with circulatory movement of the intermediary transfer belt  11 . 
     In this embodiment, the steering unit  1  is constituted by the steering roller  13 , the swingable frame  72 , the steering driving portion  80 , the sensor unit  90 , the controller  120  and the like which are described above. 
     In this embodiment, similarly as in Embodiment 1, the cleaning device  30  is held by the steering unit  1  (specifically by the swingable frame  72 ) so as to be swingable together with the steering unit  1 . In this embodiment, the discharging portion  35  provided with the discharge opening  35   a  is provided at the front-side longitudinal end portion of the cleaning device  30 . In this embodiment, similarly as in Embodiment 1, in the apparatus main assembly  110 , the feeding portion  52  which constitutes, together with the collecting container  51 , the collecting portion  50  and which is provided with the receiving opening  50   a  is provided. In this embodiment, similarly as in Embodiment 1, the discharge opening  35   a  of the cleaning device  30  and the receiving opening  50   a  of the collecting portion  50  are caused to communicate with each other by the communicating member  40 . The structure of the communicating member  40  in this embodiment is substantially the same as that of the communicating member  40  in Embodiment 1. However, the shape and the like of the upper engaging portion  41  are adapted to the discharging portion  35  of the cleaning device  30  in this embodiment. 
     When the shift of the intermediary transfer belt  11  generates due to a fluctuation of the load on the belt unit  10  during the image formation, the widthwise end portion position of the intermediary transfer belt  11  is detected by the sensor unit  90 . On the basis of information thereof, the controller  120  causes the steering driving portion  80  to swing the steering roller  13  about the steering axis J′ in a range of a predetermined angle θ°, and thus corrects the belt shift. At that time, the tube-shaped portion  43 , of the communicating member  40 , constituted by the bellows-shaped elastic member expands and contracts without substantially exerting a load on the steering operation and is capable of maintaining the communication between the discharge opening  35   a  and the receiving opening  50   a.    
     Further, also in this embodiment, similarly as in Embodiment 1, downsizing of the structure of the toner delivering portion from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110  can be realized, so that downsizing of the image forming apparatus  100  can be realized. Further, also in this embodiment, similarly as in Embodiment 1, there is no need that a sealing member is separately provided for suppressing leakage of the toner from the delivering portion of the toner from the cleaning device  30  toward the collecting portion  50  provided in the apparatus main assembly  110 , or necessity thereof can be reduced. 
     As described above, the present invention is also applicable to the constitution in which the steering unit  1  is driven by the actuator as in this embodiment, so that an effect similar to the effect of Embodiment 1 can be obtained. 
     In this embodiment, the steering unit  1  swings the steering roller  13  by moving vertically one end portion of the steering roller  13  with respect to the rotational axis direction of the steering roller  13 , but for example, a constitution in which the steering roller  13  is swung by moving opposite end portions thereof in opposite directions to each other may also be employed. 
     Embodiment 3 
     Next, Embodiment 3 of the present invention will be described. 
     (Image Forming Apparatus) 
       FIG. 15  is an illustration of an image forming apparatus  1100  in this embodiment. As shown in  FIG. 15 , the image forming apparatus  1100  is a tandem color digital printer of an intermediary transfer type in which four image forming portions  1109  are provided along an intermediary transfer belt  1101 . 
     Photosensitive drums  1103  as four image bearing members are electrically charged uniformly at their surfaces by charging rollers  1104 , respectively. Into laser scanners  1105 , image signals for yellow, magenta, cyan and black are inputted, respectively, and drum surfaces are irradiated with laser light (beams) depending on the image signals, and electric charges are neutralized, so that latent images are formed. The latent images formed on the drum surfaces are developed with toners of yellow, magenta, cyan and black, respectively, by developing devices  1106 . The toner images formed on the drums by development are successively primary-transferred onto the surface of the intermediary transfer belt  1101  by primary transfer rollers  1107 . Transfer residual toners on the photosensitive drums  1103  are collected by drum cleaners  1108 . 
     On the other hand, a recording material P such as paper fed from a cassette sheet feeding portion  1120  by a sheet feeding roller pair  1121  is conveyed toward a registration roller pair  1122  and then are conveyed toward a secondary transfer portion T 2  in synchronism with the toner images on the intermediary transfer belt  1101 . The toner images on the intermediary transfer belt  1101  are transferred onto the recording material P at the secondary transfer portion T 2  by an inner secondary transfer roller  1110  and an outer secondary transfer roller  1111 , and then is sent toward a fixing device  1130 . The recording material P sent to the fixing device  1130  is discharged to an outside of the image forming apparatus  1100  after the toner images are fixed on the recording material P by the fixing perspective view  1130  under application of heat and pressure. Transfer residual toner on the intermediary transfer belt  1101  which is not transferred onto the recording material P at the secondary transfer portion T 2  is collected by an intermediary transfer belt cleaner unit  1102 . 
     (Intermediary Transfer Unit) 
     Parts (a), (b) and (c) of  FIG. 16  are illustrates of an intermediary transfer unit  1200 . The intermediary transfer unit  1200  is a belt feeding device including the intermediary transfer belt  1101  as an intermediary transfer member which is stretched by a plurality of stretching rollers and which is rotated and fed by the stretching rollers. The intermediary transfer belt  1101  is an endless belt member using polyimide or the like. The intermediary transfer belt  1101  is stretched by a driving roller  1110 , a steering roller  1112 , stretching rollers  1113  and  1114  and primary transfer rollers  1107  which are rotatably supported by a part of a frame  1201  and are integrally assembled, and these component parts constitute the intermediary transfer unit  1200 . The driving roller  1110  as a first roller also functions as an inner secondary transfer roller forming the secondary transfer portion T 2 . The steering roller  1112  as a second roller is urged so as to press the intermediary transfer belt  1101  from an inner surface thereof by a compression spring  1213  and also functions as a tension roller for imparting tension to the intermediary transfer belt  1101 . 
     As shown in part (a) of  FIG. 16 , the primary transfer rollers  1107  form primary transfer portions T 1  in combination with the photosensitive drums  1103  through the intermediary transfer belt  1101  and form a color image by superposing and transferring toner images of yellow, magenta, cyan and black on the intermediary transfer belt  1101 . On the other hand, during monochromatic image formation, as shown in part (b) of  FIG. 16 , the primary transfer rollers  1107  for yellow, magenta and cyan, the intermediary transfer belt  1101  and the photosensitive drums  1103  for yellow, magenta and cyan are separated from each other by an unshown raising and lowering mechanism, and then the photosensitive drums  1103  for yellow, magenta and cyan are stopped. Then, a monochromatic toner image is formed on the intermediary transfer belt  1101  by the primary transfer roller  1107  for black and the photosensitive drum  1103  for black which form the primary transfer portion T 1  through the intermediary transfer belt  1101 . In a stand-by state of the image forming apparatus  1100 , as shown in part (c) of  FIG. 16 , the primary transfer roller  1107  for black and the stretching roller  1114  are also moved, so that the intermediary transfer belt  1101  is placed in a state of being completely separated from the four photosensitive drums  1103 . 
     (Steering Mechanism) 
       FIG. 17  is a perspective view of a steering mechanism of the intermediary transfer unit  1200 , and parts (a), (b) and (c) of  FIG. 18  are illustrates of an operation of the steering mechanism. 
     A steering unit as the steering mechanism includes the steering roller  1112 , a steering roller supporting member  1211  rotatably supporting the steering roller  1112 , and a rotation shaft  1214 . The steering unit is pivotably supported by the frame  1201  through the rotation shaft  1214 . The steering unit is provided downstream of the frame  1201  with respect to a mounting direction of the intermediary transfer unit  1200 . 
     The steering roller  1112  is supported at opposite end portions thereof by the steering roller supporting member  1211  constituting the steering unit so that the steering roller  1112  is rotated with rotation of the intermediary transfer belt  1101 . At the opposite end portions of the steering roller  1112 , sliding ring portions  1212  of which rotation is restricted. In this embodiment, the sliding ring portions  1212  include bearings  1212   a  and also function as bearing members of the steering roller  1212 . Further, the sliding ring portions (bearing members)  1212  are slidably supported in an arrow X direction by the steering roller supporting members  1211 , so that the steering roller  1112  is surged against the intermediary transfer belt  1101  by the compression springs  1213 . The sliding ring portions  1212  are provided at the end portions of the steering roller  1112  with respect to an axial direction of the steering roller  1112 . The steering roller supporting member  1211  is pivotably supported by the frame  1201  through the rotation shaft  1214 . The rotation shaft  1214  pivotably supports the steering roller supporting member  1211  constituting the steering unit about an axis crossing an axis of the steering roller  1112  relative to the frame  1201  as a frame member. 
     A state shown in part (a) of  FIG. 18  is a state in which the intermediary transfer belt  1101  is stretched with a good balance with respect to a center of the steering roller  1112  with respect to the axial direction of the steering roller  1112 . From the state shown in part (a) of  FIG. 18 , when a shift of the intermediary transfer belt  1101  toward a leftward direction (one direction of the axial direction) generates as shown in part (b) of  FIG. 18 , a frictional force generates between the intermediary transfer belt  1101  and each of the sliding ring portions  1212  provided at the opposite end portions. At this time, bearing widths between the intermediary transfer belt  1101  and the opposite sliding ring portions  1212  are different from each other on left and right sides, so that the frictional force on the left side (one side with respect to the axial direction) is larger than the frictional force on the right side (the other side with respect to the axial direction), and thus the steering roller  1112  is pivoted in a direction in which the left side of the steering roller  1112  lowers. As a result, the driving roller  1110  and the steering roller  1112  go out of alignment, so that the intermediary transfer belt  1101  generates a belt shift toward the right side at a winding portion of the steering roller  1112  around the intermediary transfer belt  1101 , and thus the shift of the belt position is corrected. Further, as shown in part (c) of  FIG. 18 , in the case where the shift toward the right direction (the other direction of the axial direction) occurs, the frictional force between the intermediary transfer belt  1101  and the sliding ring portion  1212  on the right side (the other side with respect to the axial direction) becomes large, so that the steering roller  1112  pivots in a direction in which the right side of the steering roller  1112  lowers. As a result, the intermediary transfer belt  1101  generates the belt shift toward the left side (one side with respect to the axial direction) at a winding portion of the steering roller  1112  around the intermediary transfer belt  1101 , so that the shift of the belt position is corrected. 
     In the intermediary transfer unit  1200 , in general, when the intermediary transfer belt  1101  is rotationally driven, the belt shift occurs in one direction by influences such as a deviation of alignment of the stretching rollers and a slight longitudinal distribution of a roller diameter. However, when a balance of the frictional forces between the intermediary transfer belt  1101  and the opposite sliding ring portions  1212  is gradually changed correspondingly and the steering roller  1112  is pivoted, a shifting speed of the intermediary transfer belt  1101  is gradually decreased and settles in a steering pivot attitude in which the belt shift is balanced. 
     (Intermediary Transfer Belt Cleaner Unit) 
       FIG. 19  is an illustration of a mounting state of the intermediary transfer belt cleaner unit  1102 . The steering unit pivotably supported by the frame  1201  includes the intermediary transfer belt cleaner unit  1102  as a cleaning unit for cleaning the intermediary transfer belt  1101  in contact with the intermediary transfer belt  1101  at a position opposing the steering roller  1112 . 
     The intermediary transfer belt cleaner unit  1102  includes a cleaning blade  1031  as a cleaning member for collecting the toner in contact with the intermediary transfer belt  1101  and includes a discharge opening  1035  which is provided on one end side thereof with respect to the axial direction of the steering roller  1112  and which permits discharge of the toner through the discharge opening  1035 . The intermediary transfer belt cleaner unit  1102  is fixed to the steering unit and is provided together with the intermediary transfer unit  1200  so as to be mounted to and dismounted from the image forming apparatus  1100 . 
     The intermediary transfer belt cleaner unit  1102  causes a free end of the cleaning bade  1031  to contact the intermediary transfer belt  1101  at a position opposing the steering roller  1112  so as to form a contact pressure by elastic deformation of the cleaning blade  1031 , and causes the cleaning blade  1031  to collect the transfer residual toner on the intermediary transfer belt  1101 . As described above, the steering roller  1112  is rotatably supported at opposite end portions thereof by the sliding ring portions (bearing members)  1212  and is slidably supported by the steering roller supporting member  1211  via the compression springs  1213 . The intermediary transfer belt cleaner unit  1102  is fixed to the sliding ring portions  1212  at opposite end portions thereof, so that the intermediary transfer belt cleaner unit  1102  is integrated with the steering roller  1112  and pivoted together with the steering roller supporting member  1211 . That is, the cleaning blade  1031  is press-contacted to the intermediary transfer belt  1101  at a certain position so as to always maintain a parallel state even in the case where the steering roller  1112  is pivoted by generation of the shift of the intermediary transfer belt  1101 , and thus is capable of stably maintain a friction state with the intermediary transfer belt  1101 . 
     Further, a cleaner container  1034  supporting the cleaning blade  1031  includes a first projection  1034   a  and a second projection  1034   b , which are used for connection with an intermediary feeding unit (described later). 
     The first projection  1034   a  is a contact portion for moving a connecting member  1302  to a predetermined position against an elastic force of a bellows pipe (bellows-shaped pipe) in contact with the connecting member  1302  by movement of the intermediary transfer unit  1200  in the mounting direction. The second projection  1034   b  is an engaging portion engaging with the connecting member  1302  with a mounting operation of the intermediary transfer unit  1200  after the connecting member  1302  is moved to the predetermined position. Specifically, the first projection  1034   e  contacts the connecting member  1032  ( FIG. 27 ) on an intermediary feeding unit side described latera by the movement of the intermediary transfer unit  1200  in the mounting direction (an arrow direction of  FIG. 27 ), and presses downward the connecting member  1302  with respect to a direction (arrow Z direction of  FIG. 22 ) crossing the mounting direction. The second projection  1034   b  engages with the connecting member  1302  pushed downward by the first projection  1034   a  and connects the intermediary transfer belt cleaner unit  1102  and the intermediary feeding unit, so that positioning of the intermediary transfer belt cleaner unit  1102  with respect to a direction (arrow Z direction of  FIG. 22 ) crossing the mounting direction is carried out. 
       FIG. 20  is a sectional view of the intermediary transfer belt cleaner unit  1102  and an intermediary transfer belt cleaner supporting portion. The transfer residual toner on the intermediary transfer belt  1101  is scraped off by the cleaning blade  1031  supported by the cleaner container  1034  and is collected in the cleaner container  1034 . The collected toner collected in the cleaner container  1034  drops by self-weight thereof in a collected toner feeding path  1032  provided in the cleaner container  1034 . The collected toner dropped in the collected toner feeding path  1032  provided in the cleaner container  1034  is fed toward one end portion (frontward direction in  FIG. 20 ) with respect to a longitudinal direction of the cleaner container  1034  by a connected toner feeding screw  1033  provided in the connected toner feeding path  1032 . Thereafter, the collected toner reaches the discharge opening  1035  provided at one end portion (the end portion with respect to the frontward direction in  FIG. 20 ) with respect to the longitudinal direction of the cleaner container  1034  and passes through an intermediary feeding unit  1300  (described later), and then is accommodated in a collected toner box (not shown) provided in an image forming apparatus main assembly. 
     The intermediary transfer belt cleaner unit  1102  and the steering unit are supported by the frame of the intermediary transfer unit through the rotation shaft  1214  as described above, but are subjected to a force substantially in the direction of gravitation by self-weights, the belt tension and elastic reaction force of the cleaning blade  1301 . When an excessive bending force generates in the frame  1201  ( FIG. 17 ) supporting the rotation shaft  1214 , the frame  1201  is deformed, so that the intermediary transfer belt cleaner unit  1102  and the steering unit are displaced downward so as to sag. As a result, the displacement leads to inconveniences such as a lowering in belt shift returning power due to prevention of the steering operation and an image defect due to that a desired belt tension is not imparted. 
     Therefore, in this embodiment, the intermediary transfer belt cleaner unit  1102  and the steering unit are supported substantially horizontally by a supporting portion  1036  provided into image forming apparatus  1100  through a cleaning blade holder  1037  bearing the cleaning blade  1031 . 
     The supporting portion  1036  is provided on an apparatus main assembly of the image forming apparatus  1100  and supports the steering unit pivotably around an axis crossing an axis of the steering roller  1112  relative to the frame of the image forming apparatus  1100 . The supporting portion  1036  point-contacts the cleaning blade holder  1037  coaxially with the rotation shaft  1214  so as not to prevent the pivot of the steering roller  1112 . The supporting portion  1036  slides with the cleaning blade holder  1037  when the intermediary transfer unit  1200  is mounted in and dismounted from the image forming apparatus  1100 , and therefore it is desirable that a material high in sliding properly, such as polyacetal (POM) is used. 
     (Intermediary Feeding Unit) 
       FIG. 21  is a perspective view of the intermediary transfer unit  1200  including the intermediary transfer belt cleaner unit  1102 , and of the intermediary feeding unit  1300  and the supporting portion  1036  in a state in which these units are portion are mounted in the image forming apparatus  1100 .  FIG. 22  is a perspective view of the intermediary feeding unit  1300 . 
     The intermediary feeding unit  1300  includes a connecting member  1302 , a feeding pipe  1303 , a bellows pipe  1304  and a feeding screw  1305 . The connecting member  1302  is supported slidably in an arrow Z direction by a connecting member guide  1301  provided in the image forming apparatus  1100 . Here, the arrow Z direction is a pivoting direction of the steering unit and is also an expansion and contraction direction of the bellows pipe  1304 , and is a direction crossing the mounting direction (arrow direction of  FIG. 27 ) of the intermediary transfer unit  1200 . The connecting member  1302  connects the discharge opening  1035  of the cleaner container  1034  and the bellows pipe  1304 . The feeding pipe  1303  is provided in the image forming apparatus  1100  and is provided with the feeding screw  1305  therein. The bellows pipe  1304  is a bellows-shaped tube-like member constituted by a rubber. This bellows pipe  1304  is engaged with the connecting member  1302  and is connected with the feeding pipe  1303  provided in the image forming apparatus  1100 . The bellows pipe  1304  is an elastic member capable of deformation (expansion and contraction) in the arrow Z direction in order to connect the feeding pipe provided in the image forming apparatus  1100  and the intermediary transfer belt cleaner unit  1102  pivotably supported by the intermediary transfer unit  1200 . The bellows pipe  1304  may desirably have small elastic reaction force so as not to prevent the pivot of the intermediary transfer belt cleaner unit  1102 . In this embodiment, the bellows pipe  1304  is capable of expansion and contraction in the arrow Z direction in  FIG. 22 . Specifically, the bellows pipe  1304  is expanded and contracted by ±5.5 mm in the arrow Z direction at the time of maximum pivot of the steering roller  1112  and the intermediary transfer belt cleaner unit  1102 , and the elastic reaction force at that time is set at 50 gf or less. 
     Further, the connecting member  1302  includes a first receiving portion  1302   a  contacting the first projection  1034   a  provided on the cleaner container  1034  and a second receiving portion  1302   b  engaging with the second projection  1034   b  provided on the cleaner container  1304 . The first receiving portion  1302   a  contacts the first projection  1034   a  provided on the cleaner container  1034  and is pushed downward in the direction (arrow direction of  FIG. 27 ) crossing the mounting direction by movement of the first projection  1034   a  in the mounting directions (arrow direction of  FIG. 27 ). The second receiving portion  1302   b  is pushed downward to a position where the second receiving portion  1302   b  is engageable with the second projection  1034   b  moved in the mounting direction by pushing downward the connecting member  1032  by the first projection  1034   a . The second perspective viewing portion  1032   b  connects the discharge opening  1035  of the intermediary transfer belt cleaner unit  1102  and the bellows pipe of the intermediary feeding unit  1300  by being engaged with the second projection  1034   b  moved in the mounting direction, and is in a state in which the second receiving portion  1302   b  is movable by following the pivot of the intermediary transfer belt cleaner unit  1102 . 
     Further, in a state in which the intermediary transfer unit  1200  including the intermediary transfer belt cleaner unit  1102  is not mounted in the image forming apparatus  1100 , a position of the connecting member  1302  engaged with the bellows pipe  1304  with respect to the arrow Z direction is determined in the following manner. That is, the position of the connecting member  1302  with respect to the arrow Z direction is determined by a relationship between the self-weight of the connecting member  1302  and the elastic reaction force determined by a rubber hardness and a thickness of the bellows pipe  1304 . The self-weight of the connecting member  1302  and the elastic reaction force of the bellows pipe  1304  are set so that the position of the first receiving portion is between an uppermost position and a lowermost position of the first projection  1034   a  provided on the cleaner container  1034  in a center alignment range of the pivot of the intermediary transfer belt cleaner unit  1102 . In other words, the following constitution is employed. That is, the steering roller  1112  is pivotable between a first pivot angle and a second pivot angle. For example, when a pivot angle of the steering roller  1112  is the first pivot angle, an end portion position where the discharge opening  1035  of the cleaner container  1034  is provided is the uppermost position. On the other hand, when the pivot angle of the steering roller  1112  is the second pivot angle, the end portion position where the discharge opening  1035  of the cleaner container  1034  is provided is the lowermost position. Further, in the case where the pivot angle of the steering roller  1112  is the first pivot angle, the bellows pipe  1304  is expanded and, by a restoring force thereof, the bellows pipe  1304  is constituted so that the steering roller  1112  receives a force in a direction in which the steering roller  1112  moves toward the second pivot angle. Further, in the case where the pivot angle of the steering roller  1112  is the second pivot angle, the bellows pipe  1304  is contracted (compressed) and, by the restoring force thereof, the bellows pipe  1304  is constituted so that the steering roller  1112  receives a force in a direction in which the steering roller  1112  moves toward the first pivot angle. By employing such a constitution, for example, even at any pivot angle of the steering roller  1112 , it is possible to avoid that the bellows pipe  1304  is always contracted (compressed) or is always expanded. 
     (Guiding Rail) 
     As shown in  FIG. 23 , the image forming apparatus  1100  includes four image forming portions  1109  which are juxtaposed and is provided with an opening  1140  at one side surface, and the intermediary transfer unit  1200  is integrally mountable in and dismountable from an inside of a casing of the image forming apparatus  1100  through the opening  1140 . At this one side surface of the image forming apparatus  1100 , an openable member  1115  openable relative to the image forming apparatus  1100  is provided, and the opening  1140  is opened by opening the openable member  1115 . Incidentally, in this embodiment, this openable member  1115  is provided with an outer secondary transfer roller  1111  opposing a driving roller (inner secondary transfer roller)  1110  of the intermediary transfer unit  1200  and with one of a registration roller pair  1122 . Accordingly, by opening the openable member  1115 , a feeding path which is a transfer-receiving member is also opened. 
       FIG. 24  is an illustration of the image forming apparatus  1100  as seen from the opening  1140  side. As shown in  FIG. 24 , in a casing (apparatus main assembly) of the image forming apparatus  1100 , side plates  1151  and  1152  which oppose each other are connected by a plurality of stays  1153 . The intermediary transfer unit  1200  is provided with guiding ribs (first portions-to-be-guided)  1201  and  1203  on side surfaces on opposite sides of a frame  1201  with respect to an axial direction of stretching rollers. On inner wall surfaces of the side plates  1151  and  1152  of the image forming apparatus  1100 , guiding rails (first guiding portions)  1161  and  1162  for holding the guiding rib  1202  and  1203 , respectively, are provided opposed to the guiding rib  1202  and  1203 . Further, in the image forming apparatus  1100  shown in  FIG. 23 , the four image forming portions  1109  containing the photosensitive drums  1103  are disposed below the intermediary transfer unit  1200 , and are rotationally driven by a driving unit  1170  provided on one side plate  1152  through a coupling  1171  as shown in  FIG. 24 . Accordingly, when the intermediary transfer unit  1200  is mounted and dismounted, as shown in  FIG. 23 , the intermediary transfer unit  1200  passes through above the image forming portions  1109  in an arrangement direction of the image forming portions  1109 . 
       FIG. 25  is a perspective view showing a state in which the intermediary transfer unit  1200  is mounted on the guiding rail  1162 . In actuality, the guiding rail  1161  is disposed at an opposing position to the guiding rail  1162 , but a side surface of the intermediary transfer unit  1200  is displayed, and therefore, in  FIG. 25 , the guiding rail  1161  is not shown. 
       FIG. 26  is an illustration of the guiding rail  1162 . At the opposing position to the guiding rail  1162 , as described above, the guiding rail  1161  is disposed, but is not shown also in  FIG. 26 . A position of a first guiding rail  1161   a , with respect to the arrow Z direction of  FIG. 28 , which is described later and which is provided on the guiding rail  1161  disposed at the opposing position to the guiding rail  1162  is the same as a position of a first guiding rail  1162   a  provided on the guiding rail  1162 . A second guiding rail  1161   b  which is not shown in  FIG. 26  guides a guiding projection  1215 , and therefore is different in position with respect to the arrow Z direction of  FIG. 28 , from a second guiding rail  1162   b  for guiding a guiding projection  1216 . However, together with the second guiding rail  1162   b  for guiding the guiding projection  1216 , the second guiding rail  1161   b  for guiding the guiding projection  1215  not only restricts the pivot of the cleaner but also eliminates the restriction of the pivot at the same timing. 
     The intermediary transfer unit  1200  is supported by engaging guiding ribs  1202   a ,  1202   b ,  1203   a  and  1203   b  provided on opposite side surfaces of the frame  1202  with the first guiding rails  1161   a  and  1162   a  provided on the guiding rails  1161  and  1162  on the image forming apparatus  1100  side. As a result, an attitude of the intermediary transfer unit  1200  during mounting and dismounting thereof is regulated, so that an inconvenience such that the intermediary transfer belt  1101  is damaged is prevented by avoiding contact with peripheral members such as the image forming portions  1109  disposed below the intermediary transfer belt  1101  and the stay  1153  disposed above the intermediary transfer belt  1101 . 
     On the other hand, in the intermediary transfer unit  1200 , attitudes of the steering unit and the intermediary transfer belt cleaner unit  1102  which are provided pivotably relative to the frame  1201  are not sufficiently regulated by the guiding ribs  1202   a ,  1202   b ,  1203   a  and  1203   b . That is, when the steering roller  1112  is pivoted depending on the shift position of the intermediary transfer belt  1101 , end portions of the steering unit and the intermediary transfer belt cleaner unit  1102  on the shift direction side of the intermediary transfer belt  1101  lower. Then, there is a liability that during the mounting and dismounting of the intermediary transfer unit  1200 , the steering unit and the intermediary transfer belt cleaner unit  1102  contact the image forming portions  1109  disposed below the intermediary transfer unit  1200 . Or, there is a liability that positions of the first projection  1034   a  and the second projection  1034   b  provided on the cleaner container  1034  vary and thus improper connection between the intermediary transfer belt cleaner unit  1102  and the connecting member  1302  occurs. 
     Therefore, in this embodiment, as shown in  FIGS. 19 and 26 , at opposite end portions of the intermediary transfer belt cleaner unit  1102 , guiding projections (second portions-to-be-guided)  1215  and  1216  are provided, respectively. As shown in  FIG. 19 , the guiding projection  1215  is provided on one side of the intermediary transfer belt cleaner unit  1102  with respect to the longitudinal direction (axial direction of the steering roller  1112 ). The side where this guiding projection  1215  is provided is a side where the intermediary transfer belt cleaner unit  1102  is connected with the intermediary feeding unit  1300  shown in  FIG. 21 . On the other hand, the guiding projection  1216  is provided on the other side of the intermediary transfer belt cleaner unit  1102  with respect to the longitudinal direction. 
     Further, the guiding rails  1161  and  1162  are provided in the second guiding rails (second guiding portions)  1161   b  and  1162   b , respectively, engaging with the guiding projections  1215  and  1216 , respectively. Here, the second guiding rails  1161   b  and  1162   b  engage with the guiding projections  1215  and  11216  during passing of the steering unit and the intermediary transfer belt cleaner unit  1102  from a mounting start position on the opening  1140  side of the image forming apparatus  1100  through above the image forming portions  1109  and regulate the attitudes of the steering unit and the intermediary transfer belt cleaner unit  1102 . However, the second frames  1161   b  and  1162   b  eliminate engagement thereof with the guiding projections  1215  and  1216  of the intermediary transfer belt cleaner unit  1102  at a position A in front of a mounting position (mounting completion position) after the steering unit and the intermediary transfer belt cleaner unit  1102  pass through above the image forming portions  1109 . As a result, at the mounting position of the intermediary transfer unit  1200 , the attitudes of the steering unit and the intermediary transfer belt cleaner unit  1102  are pivotable, so that steering against the shift of the intermediary transfer belt  1101  is enabled. 
     (Connecting Process Between Intermediary Transfer Belt Cleaner Unit and Connecting Member) 
     A connecting process unit connection between the intermediary transfer belt cleaner unit  1102  and the connecting member of the intermediary feeding unit  1300  during the mounting of the intermediary transfer unit  1200  in the image forming apparatus  1100  is completed will be described. In the following description, the process until the connection is completed will be described in stages. 
     (Connecting Process Position  1 ) 
       FIG. 27  is an illustration of the intermediary transfer belt cleaner unit  1102  and the intermediary feeding unit  1300  in a state (connecting process position  1 ) before connection therebetween is started. In the connecting process position  1  shown in  FIG. 27 , the intermediary transfer belt cleaner unit  1102  supported pivotably by the frame  1201  are guided at the guiding projections  1215  and  1216  by the guiding rails  1161   b  and  1162   b . For this reason, the intermediary transfer belt cleaner unit  1102  supported pivotably relative to the frame  1201  is regulated in pivot attitude by the second guiding rails  1161   b  and  1162   b  provided on the guiding rails  1161  and  1162 . Further, the position of the connecting member  1302  of the intermediary feeding unit  1300  with respect to the arrow Z direction is a position where the elastic reaction force of the bellows pipe  1304  and the self-weight of the connecting member  1302  are balanced with each other as described above. In this embodiment, the connecting member  1302  is positioned above a connecting position shown in  FIG. 29  by a predetermined distance d (mm). That is, the connecting member  1302  is disposed so that a second receiving portion  1302   b  thereof is positioned above the second projection  1034   b  provided on the cleaner container  1034  by the predetermined distance d in the figure. Accordingly, when the intermediary transfer unit  1200  is intended to be mounted in the image forming apparatus  100  as it is, improper connection thereof with the intermediary transfer belt cleaner unit  1102  can occur. 
     (Connecting Process Position  2 ) 
     Therefore, before the second projection  1034   b  and the second receiving portion  1302   b  start engagement therebetween, at a connecting process position  2  shown in  FIG. 28 , the first projection  1034   a  provided on the cleaner container  1034  contacts the first receiving portion  1302   a  provided on the connecting member  1302  by movement of the intermediary transfer unit  1200  in the mounting direction and thus pushes downward the connecting member  1302  in the arrow Z direction crossing the mounting direction. As a result, the second receiving portion  1302   a  of the connecting member  1302  and the second projection  1034   b  of the cleaner container  1034  are positionally aligned with each other, so that engagement therebetween is carried out with reliability.  FIG. 28  shows a state (connecting process position  2 ) in which the first projection  1034   a  provided on the cleaner container  1034  contacts the first perspective viewing portion  1302   a  provided on the connecting member  1302  by movement of the intermediary transfer unit  1200  in the mounting direction and thus pushes downward the connecting member  1302  in the arrow Z direction. By the contact between the first projection  1034   a  and the first receiving portion  1302   a , the bellows pipe  1304  engaging with the connecting member  1302  is contracted (compressed) downward in the arrow Z direction. As a result, positional alignment of the second receiving portion  1302   b  of the connecting member  1302  with the second projection  1304   b  of the cleaner container  1304  in the arrow Z direction can be carried out. 
     (Connection Completion Position) 
       FIG. 29  is an illustration showing a state in which the second projection  1034   b  of the cleaner container  1034  and the second receiving portion  1302   b  are engaged with each other and connection between the intermediary transfer belt cleaner unit  1102  and the intermediary feeding unit  1300  is completed. After the first projection  1034   a  contacts the first receiving portion  1302   a  and pushes downward the connecting member  1302  in the arrow Z direction, as shown in  FIG. 29 , the second projection  1034   b  provided on the cleaner container  1034  engages with the second receiving portion  1302   b  provided on the connecting member  1302 . Then, after the second projection  1034   b  engages with the second receiving portion  1032   b , by further movement of the intermediary transfer belt cleaner unit  1102 , the first projection  1034   a  separates from the first receiving portion  1302   a  and contact between the first projection  1034   a  of the cleaner container  1034  and the first receiving portion  1302   a  of the connecting member  1032  is eliminated. In addition, by the movement of the intermediary transfer belt cleaner unit  1102  in the mounting direction after the second projection  1034   b  engages with the second receiving portion  1302   b , as shown in  FIG. 29 , the discharge opening  1035  of the cleaner container  1034  and the bellows pipe  1304  are connected with each other. Further, at a connection completion position shown in  FIG. 29 , the supporting portion  1036  on the image forming apparatus side contacts a cleaning blade holder  1037  as shown in  FIG. 20  and supports pivotably the intermediary transfer belt cleaner unit  1102  of which support by the guiding projections  1215  and  1216  is eliminated. 
     Incidentally, engagement of the guiding projections  1215  and  1216  provided on the cleaner container  1034  with the guiding rails  1161   b  and  1162   b  provided on the guiding rails  1161  and  1162  is eliminated after the second projection  1034   b  engages with the second receiving portion  1032   b . As a result, the pivot of the intermediary transfer belt cleaner unit  1102  in a state in which the mounting of the intermediary transfer belt cleaner unit  1102  into the image forming apparatus  1100  is completed is not prevented. 
     As described above, according to this embodiment, in a mounting process of the intermediary transfer belt cleaner unit into the image forming apparatus, the bellows pipe capable of expansion and contraction between the cleaner container and the intermediary feeding unit is pushed downward in the direction of gravitation by the first projection of the cleaner container through the connecting member and thereafter connection thereof with the cleaner container is completed by the second projection. For that reason, the intermediary transfer belt cleaner unit capable of mounting is and demounting from the image forming apparatus can be reliably connected, in the mounting process thereof with the bellows pipe which is provided on the image forming apparatus side and which is capable of expansion and contraction. 
     Embodiment 4 
     In Embodiment 3 described above, the constitution in which the position, with respect to the arrow Z direction, of the guiding projections (second portions-to-be-guided)  1215  and  1216  provided on the cleaner container  1034  is restricted to the same position (level) until the second projection  1034   b  engages with the second receiving portion  1302   b  was described as an example, but the present invention is not limited thereto. 
     In this embodiment, a constitution in which the position, with respect to the arrow Z direction, of the guiding projection (second portion-to-be-guided)  1215  provided on the cleaner container  1034  is restricted to a position (level) below the other guiding projection  1216  before the first projection  1034   a  contacts the first receiving portion  1302   a . In the following, the constitution will be described using parts (a) and (b) of  FIG. 30 . Part (a) of  FIG. 30  is an illustration of a guiding rail  1162  on a rear side of an apparatus main assembly in this embodiment, in which the guiding rail  1162  includes a second guiding groove  1162   b . Part (b) of  FIG. 30  is an illustration of a guiding projection  1161  on a front side of the apparatus main assembly in this embodiment, in which the guiding rail  1161  includes a second guiding groove  1161   b.    
     In this embodiment, as shown in part (a) of  FIG. 30 , the guiding rail  1162  on the rear side of the apparatus main assembly is provided with the second guiding groove  1162   b  as a second guiding portion. Further, as shown in part (b) of  FIG. 30 , the guiding rail  1161  on the front side of the apparatus main assembly is provided with the second guiding groove  1161   b  as a second guiding portion. In the above-described Embodiment 3, as the second guiding portions, the guiding rails for restricting the positions of the guiding projections from below with respect to the arrow Z direction were described as an example, but in this embodiment, the guiding grooves for restricting the positions of the guiding projections from above and below with respect to the arrow Z direction are used. For this reason, shapes of the guiding projections  1215  and  1216  as the second portions-to-be-guided provided at opposite end portions of the intermediary transfer belt cleaner unit  1102  are different from those in Embodiment 3 and are cylindrical shapes capable of being restricted (regulated) from above and below with respect to the arrow Z direction by the guiding grooves are shown in parts (a) and (b) of  FIG. 30 . 
     The guiding rail  1161  shown in part (b) of  FIG. 30  is provided on one side of the image forming apparatus  1100  shown in  FIG. 24  with respect to an axial direction (direction of an axis  1112   a  shown in  FIG. 17 ) of the steering roller  1112 . Further, the guiding rail  1162  shown in part (b) of  FIG. 30  is provided opposed to the guiding rail  1161  with respect to the axial direction of the steering roller  1112  and is disposed on the other side opposite to the above-described one side of the image forming apparatus  1100  shown in  FIG. 24 . Incidentally, the other side of the image forming apparatus  1100  where the guiding rail  1162  is provided is a rear side Rr of the image forming apparatus  1100  where a driving unit  1170  is provided as shown in  FIG. 24 . Further, the above-described one side of the image forming apparatus  1100  where the guiding rail  1161  is provided is a side where the intermediary feeding unit  1300  ( FIG. 21 ) including the bellows pipe  1304  and the connecting member  1302  is provided, and is a front side Fr of the apparatus main assembly opposite from the rear side Rr of the apparatus main assembly where the driving unit  1700  is provided. 
     The guiding groove  1161   b  on the above-described one side (front side Fr of the apparatus main assembly) shown in part (b) of  FIG. 30  has a range in which one side of the intermediary transfer belt cleaner unit is pivoted downward relative to the other side of the intermediary transfer belt cleaner unit in a process in which the intermediary transfer unit  1200  is mounted in the image forming apparatus  1100 . That is, the guiding groove  1161   b  has a range in which the guiding projection  1215  on one side is pivoted downward relative to the guiding projection  1216  on the other side shown in part (a) of  FIG. 30 . In this embodiment, the range in which the guiding groove  1161   b  causes the intermediary transfer belt cleaner unit to pivot is set at a range from a position G where the intermediary transfer belt cleaner unit passes through above the image forming portions  1109  to a position C where the support of the guiding projections  1215  and  1216  is eliminated and where the position C is located in front of a mounting position (mounting completion position) A. Incidentally, the position C where the support of the guiding projections  1215  and  1216  is eliminated is similar to the position where the support of the guiding projections is eliminated in the above-described Embodiment 3. 
     As shown in part (b) of  FIG. 30 , the guiding groove  1161   b  of the guiding rail  1162  on the front side Fr of the apparatus main assembly gradually changes the position of the guiding projection  1215  from the position G where the intermediary transfer belt cleaner unit  1102  passes through above the image forming portions  1109  toward below with respect to a height direction. At this time, as shown in part (a) of  FIG. 30  the guiding groove  1162   b  of the guiding rail  1162  on the rear side Rr of the apparatus main assembly does not change the position of the guiding projection  1216  with respect to the height direction even when the intermediary transfer belt cleaner unit  1102  passes through the position G where the intermediary transfer belt cleaner unit  1102  passes through above the image forming portions  1109 . As a result, the guiding projection  1215  on the front side Fr of the apparatus main assembly is lower in position with respect to the height direction than the guiding projection  1216  on the rear side Rr of the apparatus main assembly. Further, as shown in part (b) of  FIG. 30 , the guiding groove  1161   b  of the guiding rail  1161  on the front side Fr regulates (restricts) the position of the guiding projection  1215  so that the pivot position (attitude) of the intermediary transfer belt cleaner unit  1102  is a lower end at the position C in a center alignment range. Further, the pivot attitude is maintained by the self-weight of the intermediary transfer belt cleaner unit  1102 , so that even when the intermediary transfer belt cleaner unit  1102  is in a pivotable position, the intermediary transfer belt cleaner unit  1102  is capable of reliably engaging with the intermediary feeding unit  1300  including the bellows pipe  1304  and the connecting member  1302 . 
     In this embodiment, as described above, the position, with respect to the height direction, of the one guiding projection (second portion-to-be-guided)  1215  provided on the intermediary transfer belt cleaner unit  1102  is regulated to the position below the other guiding projection  1216 , and therefore, by further movement of the intermediary transfer belt cleaner unit  1102  in the mounting direction, the first projection  1034   a  contacts the first receiving portion  1302   a  and pushes downward the connecting member  1302 . A subsequent operation is similar to the operation in the above-described Embodiment 3, and therefore, will be omitted from description in this embodiment. 
     Incidentally, in Embodiment 4, a constitution in which the guiding grooves  1161   b  and  1162   b  were provided as the second portion-to-be-guided for guiding the guiding projections provided on the intermediary transfer belt cleaner unit (cleaner container) was described as an example. That is, in  FIG. 4 , a constitution in which the guiding grooves for restricting the movement of the guiding projections  1215  and  1216  toward above and below with respect to the height direction in the pivot direction of the steering unit and the intermediary transfer belt cleaner unit was described as an example. However, the second portions-to-be-guided for guiding the guiding projections provided on the cleaner container is not limited thereto, but may also be guide-shaped members such as guiding rails for restricting at least movement (downward movement by self-weight) of the guiding projections toward a lower side. 
     As described above, also in this embodiment, in a mounting process of the intermediary transfer belt cleaner unit into the image forming apparatus, the bellows pipe capable of expansion and contraction between the cleaner container and the intermediary feeding unit is pushed downward in the direction of gravitation by the first projection of the cleaner container through the connecting member and thereafter connection thereof with the cleaner container is completed by the second projection. For that reason, the intermediary transfer belt cleaner unit capable of mounting is and demounting from the image forming apparatus can be reliably connected, in the mounting process thereof with the bellows pipe which is provided on the image forming apparatus side and which is capable of expansion and contraction. 
     Other Embodiments 
     The present invention was described above based on the specific embodiments, but is not limited to the above-described embodiments. 
     In the above-described embodiments, the endless belt is the intermediary transfer belt but may also be a photosensitive (member) belt, (photosensitive member), an electrostatic recording dielectric member belt (electrostatic recording dielectric member) or a feeding belt (recording material carrying member). 
     Further, in the above-described embodiments, the communicating member is held in the apparatus main assembly of the image forming apparatus, but for example, may also be mountable in and dismountable from the apparatus main assembly, together with the belt unit. 
     Further, the present invention is not limited to application to the constitution in which the belt feeding device (belt unit) is mountable in and dismountable from the apparatus main assembly of the image forming apparatus but may also be applicable to a constitution in which the belt feeding device is not readily dismounted from the apparatus main assembly. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent No. 2018-108093 filed on Jun. 5, 2018, Na 2018-118301 filed on Jun. 21, 2018, and Na 2018-118715 filed on Jun. 22, 2018, which are hereby incorporated by reference herein in their entirety.