Patent Publication Number: US-8995870-B2

Title: Belt cleaning device and image forming apparatus having the same

Description:
INCORPORATION BY REFERENCE 
     This application claims priority to Japanese Patent Application No. 2013-40159 filed on Feb. 28, 2013, the entire contents of which are incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a belt cleaning device and an image forming apparatus having the same. 
     Electrophotographic image forming apparatuses have various structures and types, one of which is an intermediate transfer type in which a color image is formed. The image forming apparatus of the intermediate transfer type is configured so that toner images of respective colors are transferred to an intermediate transfer belt (primary transfer), after which the corresponding toner images are transferred to recording paper again (secondary transfer), and the image is fixed to the recording paper by thermocompression. Since toner remains on the intermediate transfer belt after the toner images are transferred to the recording paper, there is a need to remove the remaining toner prior to the next image forming process. For this reason, the image forming apparatus is provided with a belt cleaning device for removing the toner remaining on the intermediate transfer belt. 
     Typical belt cleaning devices electrically adsorb the toner remaining on the intermediate transfer belt to a surface of a collection roller, and scrape off the toner with a cleaning blade. In this configuration, paper dust may become stuck in a contact portion between the collection roller and the cleaning blade, causing defects in cleaning on the collection roller and the intermediate transfer belt, and generating vertical black stripes on the image. Further, a technique for resolving a similar problem with a cleaning unit of a photoreceptor may include a technique for thrusting the cleaning blade in a direction of a rotating shaft of the photoreceptor to remove foreign materials such as paper dust. 
     SUMMARY 
     A belt cleaning device according to an aspect of the present disclosure includes a collection roller, a cleaning blade, a sealing member, a first thrust mechanism, and a second thrust mechanism. 
     The collection roller is rotated by a rotational driving force from a drive source, and electrically adsorbs and collects remaining toner on an intermediate transfer belt. 
     The cleaning blade extends along a rotating shaft of the collection roller, and a tip of which comes into contact with a surface of the collection roller under pressure and scrapes off the toner adsorbed to the surface of the collection roller rotated by the driving force from the drive source. 
     The sealing member extends along the rotating shaft of the collection roller, and a tip of which softly comes into contact with the surface of the collection roller and prevents counterflow of the toner scraped off by the cleaning blade. 
     The first thrust mechanism thrusts the collection roller in a direction of the rotating shaft of the collection roller by the rotational driving force transmitted to the collection roller. 
     The second thrust mechanism thrusts the cleaning blade in the direction of the rotating shaft of the collection roller in a thrust cycle shorter than that of the collection roller based on the first thrust mechanism by the rotational driving force transmitted to the collection roller. 
     A image forming apparatus according to another aspect of the present disclosure includes an intermediate transfer unit, and an image forming unit, and the belt cleaning device. 
     The intermediate transfer unit includes an intermediate transfer belt. 
     The image forming unit are disposed to face the intermediate transfer belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front cross-sectional view showing a structure of an image forming apparatus according to an embodiment of the present disclosure. 
         FIG. 2A  is a perspective view showing an appearance of the intermediate transfer unit when viewed from above, and  FIG. 2B  is a perspective view showing an appearance of the intermediate transfer unit when viewed from below. 
         FIG. 3  is a partial cross-sectional view showing surroundings of an intermediate transfer cleaning unit in the intermediate transfer unit. 
         FIG. 4A  is a perspective view of the belt cleaning device, and  FIG. 4B  is a perspective view of the belt cleaning device when viewed from an angle different from that of  FIG. 4A . 
         FIG. 5A  is a perspective view showing surroundings of the thrust mechanism of the belt cleaning device, and  FIG. 5B  is a perspective view showing a state in which the surroundings of the thrust mechanism of the belt cleaning device are viewed from an angle different from  FIG. 5A . 
         FIG. 6  is a partial perspective view showing the intermediate transfer cleaning unit. 
         FIG. 7  is a perspective view showing a thrust cam gear thrusting a cleaning blade. 
         FIG. 8  is a perspective view showing a group of thrust cam gears thrusting a collection roller. 
         FIG. 9  is a partial perspective view showing the intermediate transfer cleaning unit at a separate angle. 
         FIG. 10  is a view for describing a thrusting operation of the cleaning blade. 
         FIG. 11  is a view for describing a thrusting operation of the cleaning blade. 
         FIG. 12  is a view for describing a thrusting operation of the cleaning blade. 
         FIG. 13  is a view for describing a thrusting operation of the collection roller. 
         FIG. 14  is a view for describing a thrusting operation of the collection roller. 
         FIG. 15  is a view for describing a thrusting operation of the collection roller. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a belt cleaning device and an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.  FIG. 1  is a front cross-sectional view showing a structure of an image forming apparatus according to an embodiment of the present disclosure. 
     An image forming apparatus  1  according to an embodiment of the present disclosure is a multifunction device combining a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus  1  includes an apparatus main body  11  that is equipped with an operation unit  47 , an image forming unit  12 , a fixing unit  13 , a paper feed unit  14 , a document conveying unit  6 , and an image reading unit  5 . 
     The operation unit  47  receives instructions, such as an instruction to implement an image forming operation and an instruction to implement a document reading operation, from an operator with regard to various operations and processes which can be implemented by the image forming apparatus  1 . 
     When the image forming apparatus  1  performs the document reading operation, the image reading unit  5  optically reads an image of a document fed by the document conveying unit  6  or a document placed on a document table glass  161  to generate image data. The image data generated by the image reading unit  5  is stored in an internal hard disk drive (HDD) or a networked computer. 
     When the image forming apparatus  1  performs the image forming operation, the image forming unit  12  forms toner images on recording paper P as a recording medium fed from the paper feed unit  14  based on the image data generated by the document reading operation, the image data received from the networked computer, or the image data stored in the internal HDD. Image forming units  12 M,  12 C,  12 Y, and  12 Bk of the image forming unit  12  are each equipped with a photosensitive drum, a developing device supplying toner to the photosensitive drum, a toner cartridge (not shown) containing the toner, a charging device, an exposure device, and a primary transfer roller  126 . 
     When color printing is carried out, the image forming unit  12 M for magenta, the image forming unit  12 C for cyan, the image forming unit  12 Y for yellow, and the image forming unit  12 Bk for black of the image forming unit  12  form the toner images on the photosensitive drums  121  based on images composed of respective color components constituting the image data by charging, exposure, and developing processes, and cause the toner images to be transferred to an intermediate transfer belt  125  stretched on a driving roller  125   a  and a driven roller  125   b  by the primary transfer rollers  126 . 
     The intermediate transfer belt  125  has an image carrying surface which is set to an outer circumferential surface thereof and to which the toner images are transferred, and is driven in contact with circumferential surfaces of the photosensitive drums  121  by the driving roller  125   a . The intermediate transfer belt  125  endlessly runs between the driving roller  125   a  and the driven roller  125   b  while being synchronized with each photosensitive drum  121 . 
     The toner images of the respective colors which are transferred to the intermediate transfer belt  125  are superimposed on the intermediate transfer belt  125  by adjusting transfer timing, thereby becoming a color toner image. A secondary transfer roller  210  causes the color toner image formed on the surface of the intermediate transfer belt  125  to be transferred to the recording paper P, which is conveyed from the paper feed unit  14  along a conveying path  190 , at a nip zone N at which the intermediate transfer belt  125  is sandwiched between the secondary transfer roller  210  and the driving roller  125   a . Afterwards, the fixing unit  13  causes the toner image on the recording paper P to be fixed to the recording paper P by thermocompression. The recording paper P on which the color image undergoing the fixing process is formed is ejected to an eject tray  151 . 
     A portion of the intermediate transfer belt  125  which is stretched on the driven roller  125   b  is provided with a belt cleaning device  120 . The belt cleaning device  120  collects toner remaining on the outer circumferential surface of the intermediate transfer belt  125 . 
     Further, in addition to the belt cleaning device  120 , the intermediate transfer belt  125 , the primary transfer roller  126 , the driving roller  125   a , and the driven roller  125   b  are mounted on an intermediate transfer unit  50 . 
     Next, the intermediate transfer unit  50  will be described.  FIG. 2A  is a perspective view showing an appearance of the intermediate transfer unit  50  when viewed from above, and  FIG. 2B  is a perspective view showing an appearance of the intermediate transfer unit  50  when viewed from below. 
     The intermediate transfer unit  50  is mounted above the image forming unit  12  in the apparatus main body  11 . As shown in  FIG. 2A , the intermediate transfer belt  125 , the primary transfer roller  126 , the driving roller  125   a , the driven roller  125   b , and the belt cleaning device  120  are mounted on the intermediate transfer unit  50  as described above. 
     The intermediate transfer unit  50  is equipped with a casing  51 . Each mechanism with which the intermediate transfer unit  50  is equipped is mounted in the casing  51 . The casing  51  is made up of an upper surface portion  51   c  and lateral surface portions  51   a  and  51   b  provided for edges of the upper surface portion  51   c . The driving roller  125   a  is rotatably supported on one end of the casing  51 , and the driven roller  125   b  is supported on the other end of the casing  51 . 
     In the state in which the intermediate transfer belt  125  is stretched between the driving roller  125   a  and the driven roller  125   b  supported in this way, an upper part and both lateral parts of the intermediate transfer belt  125  are covered by the casing  51  made up of the upper surface portion  51   c  and the lateral surface portions  51   a  and  51   b . As shown in  FIG. 2B , a lower portion of the intermediate transfer belt  125  is kept exposed from the casing  51 . In the state in which the intermediate transfer unit  50  is mounted in the apparatus main body  11 , the image forming units for respective colors are arranged in the apparatus main body  11  below the portion of the exposed intermediate transfer belt  125 . 
     Next, an internal constitution of the intermediate transfer unit  50  will be described.  FIG. 3  is a side cross-sectional view showing surroundings of the driven roller  125   b  and the belt cleaning device  120  in the intermediate transfer unit  50 .  FIG. 4A  is a perspective view of the belt cleaning device  120 , and  FIG. 4B  is a perspective view of the belt cleaning device  120  when viewed from an angle different from that of  FIG. 4A . 
     A tension roller applying tension to the intermediate transfer belt  125 , the primary transfer rollers  126  of respective colors ( FIG. 1 ), and the belt cleaning device  120  are installed in the casing  51  of the intermediate transfer unit  50 , in addition to the intermediate transfer belt  125 , the driving roller  125   a , and the driven roller  125   b  described above. 
     The belt cleaning device  120  according to the embodiment of the present disclosure comes into contact with the portion of the outer circumferential surface of the intermediate transfer belt  125  that is kept stretched on the driven roller  125   b , and electrically adsorbs and collects the toner remaining on the outer circumferential surface. 
     The belt cleaning device  120  has a brush roller  1221 , a collection roller  1222 , a sealing member  1232 , a cleaning blade  1231 , a toner reservoir  124 , and a toner conveying screw  127 . 
     The brush roller  1221  comes into contact with the outer circumferential surface of the intermediate transfer belt  125  stretched on the driven roller  125   b , and collects the toner remaining on the outer circumferential surface using electric adsorption. The brush roller  1221  is formed by winding an unwoven fabric formed of, for instance, a resinous filament around the entire circumference of a rotating shaft  711  thereof. The rotating shaft  711  of the brush roller  1221  extends in a direction of a rotating shaft of the driven roller  125   b , and is rotatably supported on the casing  51 . The brush roller  1221  is rotated around a rotating shaft  1221   a  in a direction (i.e. a direction of an arrow D 2  shown in  FIG. 3 ) that is opposite to a rotational direction of the driven roller  125   b  (i.e. a direction of an arrow D 1  shown in  FIG. 3 ). 
     The collection roller  1222  is made of, for instance, a metal, comes into contact with a surface of the brush roller  1221 , and electrically collects the toner that the brush roller  1221  has collected from the brush roller  1221 . A rotating shaft  721  of the collection roller  1222  extends in the direction of the rotating shaft of the brush roller  1221 , and is rotatably supported on the casing  51 . The collection roller  1222  is rotated around the rotating shaft  721  in the same direction (i.e. a direction of an arrow D 3  shown in  FIG. 3 ) as the rotational direction of the brush roller  1221 . 
     The sealing member  1232  is made of a flexible material such as urethane, and is fixed and attached to the toner reservoir  124 . The sealing member  1232  is installed so that a top thereof is softly in contact with a surface of the collection roller  1222 . The sealing member  1232  is set to very weakly bring a top end thereof into contact with the surface of the collection roller  1222 , compared to the cleaning blade  1231 . The toner that is scraped off from the surface of the collection roller  1222  by the cleaning blade  1231 , is prevented from flowing back to the side of the brush roller  1221  at a contact position at which the top of the sealing member  1232  and the surface of the collection roller  1222  are in contact with each other while allowing passage of the toner sticking to the surface of the collection roller  1222 . 
     The cleaning blade  1231  is formed of a tabular member, and extends in the direction of the rotating shaft of the collection roller  1222 . The cleaning blade  1231  is mounted on the casing  51  so that, when viewed from the side shown in  FIG. 3 , a tip thereof is in contact with the surface of the collection roller  1222 . The cleaning blade  1231  scrapes off the toner which the collection roller  1222  has collected from the surface of the collection roller  1222 . The scraped off toner falls and accumulates in the toner reservoir  124 . 
     The toner reservoir  124  is provided with a toner conveying screw  127 . The toner conveying screw  127  extends in the direction of the rotating shaft of the collection roller  1222 , and its rotating shaft  1271  is rotatably supported on the casing  51 . A toner conveying blade  1272  is installed on a circumferential surface of the rotating shaft  1271  of the toner conveying screw  127  in a spiral shape. The toner in the toner reservoir  124  is gathered in a waste toner tank (not shown) disposed at a predetermined position in a direction of the rotating shaft  1271  by the toner conveying blade  1272 . Thereby, the remaining toner on the outer circumferential surface of the intermediate transfer belt  125  is collected. 
     The belt cleaning device  120  is provided with a thrust mechanism  20 . 
     Next, the thrust mechanism provided for the belt cleaning device  120  will be described.  FIG. 5A  is a perspective view showing surroundings of the thrust mechanism of the belt cleaning device  120 , and  FIG. 5B  is a perspective view showing a state in which the surroundings of the thrust mechanism of the belt cleaning device  120  are viewed from an angle different from  FIG. 5A .  FIG. 6  is a perspective view selectively showing the belt cleaning device  120  and main portions of the thrust mechanism.  FIG. 7  is a perspective view of a thrust cam gear.  FIG. 8  is an exploded perspective view showing a first gear and each thrust adjusting gear of a first thrust mechanism.  FIG. 9  is a perspective view showing an end of the belt cleaning device  120  which becomes a side at which the thrust mechanism is not provided. 
     The belt cleaning device  120  includes the thrust mechanism  20  that independently thrusts the cleaning blade  1231  and the collection roller  1222  in a rotating shaft direction of the collection roller  1222 . The thrust mechanism  20  is equipped with a first thrust mechanism  20 A and a second thrust mechanism  20 B. 
     The first thrust mechanism  20 A is a mechanism that thrusts the collection roller  1222  in an extending direction of a rotating shaft  1224  of the collection roller  1222  (i.e. a rotating shaft direction). 
     The second thrust mechanism  20 B is a mechanism that thrusts the cleaning blade  1231  in the rotating shaft direction of the collection roller  1222  in a thrust cycle shorter than that of the collection roller  1222  caused by the first thrust mechanism  20 A. 
     The first thrust mechanism  20 A will be described. The first thrust mechanism  20 A is equipped with a first thrust cam gear  250 . The first thrust cam gear  250  has a plurality of gears to be described below, and thrusts the collection roller  1222  in a predetermined thrust cycle. The first thrust cam gear  250  is rotated by a driving force from a drive source that is, for instance, a motor supplying a driving force to each drive train of the belt cleaning device  120 . 
     The first thrust mechanism  20 A is equipped with a gear guide  25  in addition to the first thrust cam gear  250 . The first thrust cam gear  250  is equipped with a first gear  21  and thrust adjusting gears  23  and  24 . 
     The first gear  21  has a predetermined number of teeth, and is mounted on the rotating shaft  1224  of the collection roller  1222 . The first gear  21  is engaged with a driving gear  131  that integrally corotates with a rotating shaft  130  of the drive source, and is integrally rotated along with the rotating shaft  1224  by the driving force from the drive source, thereby rotating the collection roller  1222 . As shown in  FIG. 8 , one side of the first gear  21  which is located in the rotating shaft direction is formed with a cam follower  211  sliding on a cam  231  (to be described below) formed on the thrust adjusting gear  23 , and the other side of the first gear  21  is formed with a cam follower  212  sliding on a cam  241  (to be described below) formed on the thrust adjusting gear  24 . 
     The cam follower  211  is shaped of an arc having a lowermost part  211   a  and an uppermost part  211   b  that is formed by connecting to the lowermost part  211   a  and is formed at a position shifted from the lowermost part  211   a  in a rotational direction of the cam follower  211  by a half circumference. Thus, when the cam follower  211  makes one rotation along with the first gear  21 , a height of the cam follower  211  varies from the lowest value to the highest value, and returns to the lowest value again after the variation to the highest value. The cam follower  212  is configured similarly to the cam follower  211 . However, with regard to a rotational direction position of the first gear  21 , a portion at which the height of the cam follower  212  has the highest value is located on the rear of the first gear  21  with respect to a portion at which the height of the cam follower  211  has the lowest value. To this end, the uppermost and lowermost parts of the cam followers  211  and  212  are set to reciprocal heights. 
     The thrust adjusting gears  23  and  24  are mounted in a state in which they are loosely fitted around the rotating shaft  1224  of the collection roller  1222 . The thrust adjusting gear  23  is arranged on a side of the first gear  21  which is a side of the collection roller  1222 . The thrust adjusting gear  24  is disposed on the other side of the first gear  21  which is the opposite side of the side on which the thrust adjusting gear  23  is arranged. 
     Further, the thrust adjusting gears  23  and  24  have a predetermined number of teeth that is different from the number of teeth of the first gear  21 . The thrust adjusting gears  23  and  24  are engaged with the driving gear  131  of the drive source, and are rotated independently of the rotating shaft  1224  by the driving force from the drive source. In other words, the thrust adjusting gears  23  and  24  run idle relative to the rotating shaft  1224 . 
     As shown in  FIG. 8 , a side of the thrust adjusting gear  23  which is a side facing the first gear  21  is provided with a cam  231  that slides in contact with the cam follower  211  of the first gear  21 . The cam  231  has, for instance, a shape similar to that of the cam follower  211 , and is shaped in an arc having a lowermost part  231   a  and an uppermost part  231   b  that is formed by connecting to the lowermost part  231   a  and is formed at a position shifted from the lowermost part  231   a  in a rotational direction of the thrust adjusting gear  23  by a half circumference. 
     A side of the thrust adjusting gear  24  which is a side facing the first gear  21  is provided with a cam  241  that has, for instance, a shape similar to that of the cam  231  and has a lowermost part  241   a  and an uppermost part  241   b.    
     As shown in  FIGS. 5A and 6 , the gear guide  25  supports the thrust adjusting gears  23  and  24  with the thrust adjusting gears  23  and  24  sandwiched from both sides in the rotating shaft direction, and restricts the thrust adjusting gears  23  and  24  to move in the rotating shaft direction of the collection roller  1222 . In other words, the gear guide  25  fixes positions at which the thrust adjusting gears  23  and  24  are arranged in the rotating shaft direction of the collection roller  1222 . 
     As the first gear  21  slides in contact with the cam follower, the cams  231  and  241  of the respective thrust adjusting gears  23  and  24  shift the first gear  21  between the thrust adjusting gears  23  and  24  in the rotating shaft direction of the collection roller  1222 . Detailed movements of the cam and the cam follower will be described below. 
     The second thrust mechanism  20 B will be described. The second thrust mechanism  20 B is equipped with a cam follower  1234  attached to one end of the cleaning blade  1231 , and a cam gear (second thrust cam gear)  22 . 
     The cam follower  1234  extends from one end of the cleaning blade  1231  toward the cam gear  22 , and is configured so that a tip thereof is in contact with the cam  221  provided for a side of the cam gear. 
     The cleaning blade  1231  is mounted on the casing  51  so as to freely move in the rotating shaft direction of the collection roller  1222 . As shown in  FIG. 9 , in a longitudinal direction of the cleaning blade holder  1233  holding the cleaning blade  1231 , a compression spring  1235  is mounted on the other end of the cleaning blade  1231  which is opposite to the side at which the belt cleaning device  120  is arranged. An end of the cleaning blade holder  1233  is provided with a support shaft  1236  that causes the cleaning blade holder  1233  and the cleaning blade  1231  held thereto to be supported on the casing  51 . The compression spring  1235  is mounted on the support shaft  1236  in such a manner that one end thereof is mounted on the cleaning blade holder  1233  and that the other end thereof is mounted on the casing  51 . Thereby, the compression spring  1235  biases the cleaning blade holder  1233  in a direction in which the cam follower  1234  presses the cam  221  of the cam gear  22  to be described below. 
     The cam gear  22  is rotatably supported on the casing  51 , and is engaged with the first gear  21  of the first thrust mechanism  20 A, thereby being rotated by the driving force from the drive source. As shown in  FIG. 7 , the cam  221  is formed on a face of the cam gear  22  which faces the cam follower  1234 . The cam  221  comes into contact with the cam follower  1234 , changes a push-in amount of the cleaning blade  1231  in the rotating shaft direction of the collection roller  1222 , and thrusts the cleaning blade  1231  in a predetermined thrust cycle. Similar to each of the cams  231  and  241  of the thrust adjusting gears  23  and  24 , the cam  221  is shaped in an arc having a lowermost part  221   a  and an uppermost part  221   b  that is formed by connecting to the lowermost part  221   a  and is formed at a position shifted from the lowermost part  221   a  in a rotational direction of the cam gear  22  by a half circumference. However, a height of the cam  221  from the lowermost part  221   a  to the uppermost part  221   b , i.e., an amount of movement when the cleaning blade  1231  is thrust in its longitudinal direction by the cam  221 , is appropriately determined as a value suitable for removal of paper dust at a contact portion of the cleaning blade  1231  which comes into contact with the surface of the collection roller  1222 . In the present embodiment, the thrust cycle in which the cam  221  thrusts the cleaning blade  1231  when the cam gear  22  makes one rotation is shorter than that in which the first thrust mechanism  20 A thrusts the collection roller  1222  when the first gear  21  makes one rotation. 
     Next, a thrusting operation of the cleaning blade  1231  based on the thrust mechanism  20  having the aforementioned constitution will be described.  FIGS. 10 to 12  are views for describing a thrusting operation of the cleaning blade  1231 . 
     The cam  221  is displaced by rotation of the cam gear  22 , and the cam follower  1234  sliding in contact with the cam  221  performs an operation following the displacement of the cam  221 . Thereby, the cleaning blade  1231  performs a thrusting operation. As shown in  FIG. 10 , when the cam follower  1234  comes into contact with the lowermost part  221   a , and the displacement of the cam  221  of the cam gear  22  is in a state of the minimum value, the cleaning blade  1231  is located at the rightmost end in the longitudinal direction thereof, i.e., in the rotating shaft direction of the collection roller  1222 . 
     When the driving gear  131  of the drive source is rotated from here, the first gear  21  engaged with the driving gear  131  is rotated, and the collection roller  1222  initiates thrust movement in its rotating shaft direction. Then, due to rotation of the cam gear  22  engaged with the first gear  21 , as shown in  FIG. 11 , depending on an amount of the rotation of the cam gear  22 , an amount of displacement of the cam  221  is changed to gradually increase in a direction of an arrow A. The cleaning blade  1231  is thrust in the direction of the arrow A by a distance corresponding to the displacement of the cam  221 . 
     When the cam gear  22  is further rotated from the state shown in  FIG. 11 , the cam follower  1234  comes into contact with the uppermost part  221   b  as shown in  FIG. 12 , and the amount of displacement of the cam  221  becomes the maximum value. Then, the cleaning blade  1231  moves to the leftmost position in the direction of the arrow A. 
     Further, when the cam gear  22  is further rotated from the state shown in  FIG. 12 , the amount of displacement of the cam  221  turns into a decrease, and the result returns to the state shown in  FIG. 10 , i.e., the state in which the amount of displacement of the cam  221  becomes the minimum value. In other words, in the present embodiment, when the cam gear  22  makes one rotation from the state shown in  FIG. 10 , the cleaning blade  1231  performs the thrust movement reciprocating between the position of the rightmost end shown in  FIG. 10  and the position of the leftmost end shown in  FIG. 12 . In this way, the cleaning blade  1231  performs the thrusting operation in the same cycle as the rotation cycle of the cam gear  22 . According to the rotation of the cam gear  22 , the states shown in  FIGS. 10 to 12  are repeated. 
     Since the cleaning blade  1231  comes into contact with the collection roller  1222  under strong pressure in order to scrape off the toner stuck to the surface of the collection roller  1222 , an effect of removing foreign materials is low if the cleaning blade  1231  is not thrust relatively rapidly. Therefore, for example, the first gear  21  and the cam gear  22  are adapted to have the same number of teeth. In this case, whenever the collection roller  1222  makes one rotation, the cleaning blade  1231  is reciprocated once by the thrust movement. In other words, the rotation cycle of the collection roller  1222  and the thrust cycle of the cleaning blade  1231  are made identical. Thereby, the cleaning blade  1231  is relatively rapidly thrust on the surface of the collection roller  1222  in its rotating shaft direction, and the foreign materials stuck to the contact portion of the cleaning blade  1231  and the collection roller  1222  are kept removed. However, the thrust cycle of the cleaning blade  1231  is not limited to the foregoing, and may be appropriately changed. 
     Next, a thrusting operation of the collection roller  1222  will be described.  FIGS. 13 to 15  are views for describing a thrusting operation of the collection roller  1222 . 
     Here, in the present embodiment, an example in which the number of teeth of the first gear  21  is 20, and the number of teeth of each of the thrust adjusting gears  23  and  24  is 19 is shown. 
     When the first gear  21  is engaged with the rotated driving gear  131  and is thereby rotated by receiving the driving force of the drive source, the collection roller  1222  is rotated along with its rotating shaft  1224  in the first thrust mechanism  20 A, as described above. In this case, the thrust adjusting gears  23  and  24  engaged with the driving gear  131  are also rotated at the same time. When the cams  231  and  241  are displaced with the rotation of the thrust adjusting gears  23  and  24 , the first gear  21 , the rotating shaft  1224 , and the collection roller  1222  are thrust in the rotating shaft direction by an amount of movement of the cam followers  211  and  212  of the first gear  21  which slide on the cams  231  and  241  in contact with the cams  231  and  241 . 
     For example, as shown in  FIG. 13 , the uppermost part of the cam follower  211  of the first gear  21  and the lowermost part of the cam  231  of the thrust adjusting gear  23  are adapted to be in contact with each other, and the uppermost part of the cam follower  211  of the first gear  21  and the uppermost part of the cam  241  of the thrust adjusting gear  24  are adapted to be in contact with each other. In this case, the first gear  21  is shifted to a position of the leftmost end in a direction of an arrow shown in  FIG. 13 . 
     When the first gear  21  and the thrust adjusting gears  23  and  24  are rotated with the rotation of the driving gear  131  from the state shown in  FIG. 13 , since the number of teeth of the first gear  21  is 20, and the number of teeth of each of the thrust adjusting gears  23  and  24  is 19, a contact state of the cam follower  211  of the first gear  21  and the cam  231  of the thrust adjusting gear  23  and a contact state of the cam follower  212  of the first gear  21  and the cam  241  of the thrust adjusting gear  24  are not maintained by a difference between an amount of rotation of the first gear  21  and an amount of rotation of each of the thrust adjusting gears  23  and  24 , and a place at which the cam follower  211  comes into contact with the cam  231  and a place at which the cam follower  212  comes into contact with the cam  241  are changed depending on the rotation amounts of the first gear  21  and the thrust adjusting gears  23  and  24 . For this reason, the contact state of the cam follower  211  of the first gear  21  and the cam  231  of the thrust adjusting gear  23  and the contact state of the cam follower  212  of the first gear  21  and the cam  241  of the thrust adjusting gear  24  are changed to, for instance, the state shown in  FIG. 14 , and the first gear  21  is shifted to the right side farther than the position of the leftmost end shown in  FIG. 13 . 
     When the first gear  21  and the thrust adjusting gears  23  and  24  are further rotated with the rotation of the driving gear  131  from the state shown in  FIG. 14 , the uppermost part  211   b  of the cam follower  211  of the first gear  21  and the uppermost part  231   b  of the cam  231  of the thrust adjusting gear  23  come into contact with each other, and the lowermost part of the cam follower  212  of the first gear  21  and the uppermost part of the cam  241  of the thrust adjusting gear  24  come into contact with each other as shown in  FIG. 15 , the first gear  21  is shifted to a position of the rightmost end. 
     For this reason, when the first gear  21  and the thrust adjusting gears  23  and  24  are rotated with the rotation of the driving gear  131 , the first gear  21  performs thrust movement reciprocating between the position of the leftmost end and the position of the rightmost end between the respective arranged positions of the thrust adjusting gears  23  and  24  in an extending direction of the rotating shaft  1224 . In this case, the thrust movement of the first gear  21  is guided by mechanical contact of the cams  231 , 241  and the cam followers  211 , 212 . As such, the first gear  21 , the rotating shaft  1224 , and the collection roller  1222  can be thrust with the amounts of movement accurately corresponding to amounts of displacement of the cam followers  211  and  212  and amounts of displacement of the cams  231  and  241 . 
     Further, when the first gear  21  and the thrust adjusting gears  23  and  24  are rotated with the rotation of the driving gear  131  in this way, the cam gear  22  engaged with the first gear  21  is also rotated. As such, the cleaning blade  1231  also performs the thrust movement shown in  FIGS. 13 to 15 . 
     The sealing member  1232  is formed of, for instance, a very thin urethane sheet having a thickness of about t0.1 to t0.2, and comes into contact with the surface of the collection roller  1222 . As such, the thrust cycle of the collection roller  1222  is short like the aforementioned cleaning blade  1231 , and an excess load is applied to the sealing member  1232 . As a result, deflection takes place at the sealing member  1232 , and a gap is generated between the collection roller  1222  and the sealing member  1232 . There is a possibility of toner falling through the gap. Accordingly, it is necessary for the collection roller  1222  to be thrust at a relatively slow speed to the extent that no load is given so as to act as the sealing member  1232 . 
     In the present embodiment, as described above, since the number of teeth of the first gear  21  is 20, and the number of teeth of each of the thrust adjusting gears  23  and  24  is set to be one less at 19, whenever the first gear  21  is rotated 20 times, the collection roller  1222  performs the thrust movement reciprocated once in its rotating shaft direction. In other words, the collection roller  1222  is thrust in a cycle 20 times to its own rotation cycle. In this case, for example, if the number of teeth of the cam gear  22  is set equal to that of the first gear  21  at 20, the cleaning blade  1231  can be thrust in a short cycle that is 1/20 of the thrust cycle of the collection roller  1222 . The numbers of teeth of the first gear  21  and the thrust adjusting gears  23  and  24  shown herein is merely one example. The thrust cycle of the collection roller  1222  can be adjusted by changing each of the numbers of teeth. 
     Thus, (1) without applying an excessively great load to the sealing member  1232  by thrusting the collection roller  1222  at a relatively slow speed, it is possible to clean the foreign materials such as the toner and the paper dust stuck to the contact portion of the sealing member  1232  and the collection roller  1222 , and (2) it is possible to perform the thrust movement on the cleaning blade  1231  at an adequate speed at which the foreign materials such as the toner and the paper dust stuck between the cleaning blade  1231  and the surface of the collection roller  1222  can be removed. 
     As described above, in the belt cleaning device  120  according to the present embodiment, the thrust cycles of the cleaning blade  1231  and the collection roller  1222  can be individually optimized, and the foreign materials stuck to the contact portions between the cleaning blade  1231  and the collection roller  1222  and between the sealing member  1232  and the collection roller  1222  can be efficiently cleaned. Thereby, it is possible to prevent toner from scattering and falling from the belt cleaning device  120 . 
     The sealing member  1232  is installed in contact with the surface of the collection roller  1222 . When the foreign materials such as paper dust are stuck to such a contact portion, the toner scraped off by the cleaning blade may flow back toward the collection roller and cause toner to scatter and fall. However, unlike the cleaning blade  1231 , the sealing member  1232  is very weakly in contact with the surface of the collection roller  1222 . As such, if the foreign materials are stuck to such a contact portion, it is difficult to clean the foreign materials. Since the sealing member  1232  is fixed to the case of the intermediate transfer cleaning unit, the thrust movement of the sealing member  1232  is mechanically complicated. Further, as the sealing member  1232  itself is thrust, the toner may be scattered from a gap of the contact portion. 
     For example, to realize a constitution in which the sealing member  1232  formed of a soft material having flexibility is thrust with its tip maintained in contact with the surface of the collection roller  1222 , a complicated mechanism is required. However, in the present embodiment, since the side of the collection roller  1222  is thrust rather than the sealing member  1232 , the thrust mechanism  20  can be made into a relatively simple constitution. Further, if the collection roller  1222  is thrust relative to the sealing member  1232  at a thrust speed at which proper cleaning performance is obtained by the cleaning blade  1231 , a load applied to the sealing member  1232  is increased. However, in the present embodiment, since the thrust cycle of the collection roller  1222  is set to be longer than that of the cleaning blade  1231 , the removal of the paper dust between the sealing member  1232  and the surface of the collection roller  1222  can be accurately performed without applying a great load to the sealing member  1232 , while the proper cleaning performance is secured by the cleaning blade  1231 . 
     Accordingly, according to the embodiment, without complicating the structure of the belt cleaning device  120 , image defects caused by poor cleaning, or the toner scattering and falling from the intermediate transfer cleaning unit can be more reliably prevented than in the related art. 
     The present disclosure is not limited to the constitution of the embodiment, and various modifications are possible. For example, one embodiment of the image forming apparatus according to the present disclosure has been described using a multifunction peripheral. However, this is merely one example. For example, another image forming apparatus such as a printer, a copier, or a facsimile device may be used. 
     Further, in the embodiment, the constitution and processing shown in the embodiment using  FIGS. 1 to 15  are merely one embodiment of the present disclosure, and the contents of the present disclosure are not intended to limit to the constitution and processing. 
     Various modifications and alterations of this disclosure will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein.