Patent Publication Number: US-11392063-B2

Title: Imaging system with cleaning member for endless belt

Description:
BACKGROUND 
     Some imaging systems include a gloss control device which controls gloss of a toner image formed on a printing medium. The gloss control device includes an endless belt which conveys a printing medium, a heating roller which heats the endless belt, a pressing roller which presses the endless belt against the heating roller, and a cooling structure which cools the endless belt having passed between the heating roller and the pressing roller. The printing medium which is conveyed on the endless belt passes between the heating roller and the pressing roller to be heated and pressed and is cooled by the cooling structure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of an example imaging system with an example fixing assembly. 
         FIG. 2  is a schematic diagram of the example fixing assembly of the example imaging system illustrated in  FIG. 1 . 
         FIG. 3  is a schematic diagram of a tensioning member and a cleaning roller of an example fixing assembly, illustrated with a first gear connected to the tensioning member and a second gear connected to the cleaning roller. 
         FIG. 4  is a schematic diagram illustrating an example of a gear group further including third and fourth gears. 
         FIG. 5  is an enlarged partial view of example fixing assembly of  FIG. 2 , illustrating the cleaning roller and the tensioning member of the example fixing assembly. 
         FIG. 6  is an enlarged view of the cleaning roller and the endless belt of  FIG. 5 . 
         FIG. 7A  is a graph showing an example relationship of a difference of stress and speed associated with the endless belt, relative to a lifespan of the endless belt. 
         FIG. 7B  is a graph showing an example relationship of a cleaning efficiency, relative to a difference between stress and speed difference to the endless belt. 
         FIG. 8  is a graph showing an example relationship of a printing medium cleaning efficiency relative to a contact area of a cleaning roller with respect to the endless belt. 
         FIG. 9A  is a schematic diagram illustrating an example of a toner image on the endless belt. 
         FIG. 9B  is a schematic diagram illustrating another example of a toner image on the endless belt. 
         FIG. 10  is a diagram illustrating a cleaning roller, a tensioning member, an endless belt, and a printing medium according to a modified example. 
         FIG. 11  is a diagram illustrating an example of a state in which a cleaning roller according to another modified example presses the endless belt inwardly. 
         FIG. 12  is a diagram illustrating an example of a state in which the cleaning roller of  FIG. 11  presses the endless belt further inwardly. 
         FIG. 13  is a diagram illustrating an example of a fixing assembly including a cleaning roller and an endless belt according to still another modified example. 
         FIG. 14  is a diagram illustrating the fixing assembly including the cleaning roller of  FIG. 13  as viewed from a direction different from  FIG. 13 . 
         FIG. 15  is a schematic diagram of a fixing assembly according to another modified example. 
         FIG. 16  is a schematic diagram of a fixing assembly according to another modified example. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. 
     An imaging system may include various devices relating to an imaging operation. In some examples, an imaging system may include an imaging apparatus such as a printer. In some examples, an imaging system may include a gloss control device to be mounted in or to be operable with an imaging apparatus. An example imaging system includes both an imaging apparatus and a gloss control device, and may include various devices relating to an imaging operation. 
     As illustrated in  FIG. 1 , an example imaging system  1  forms a color image by using respective colors of magenta, yellow, cyan, and black. The example imaging system  1  includes a recording medium conveying device  10 , a plurality of developing devices  20 , a transfer device  30 , a plurality of photoreceptors  40 , a fixing device  50 , and a fixing assembly  60 . The recording medium conveying device  10  may convey a printing medium P. As an example, the printing medium P may be paper. 
     The photoreceptor  40  may form an electrostatic latent image, and the developing device  20  may develop the electrostatic latent image. The transfer device  30  may secondarily transfer a toner image onto the printing medium P. In some examples, the fixing device  50  fixes the toner image to the printing medium P, and the fixing assembly  60  includes a gloss control device which controls the gloss of the toner image. In some examples, the fixing device  50  may be a primary fixing device which performs a first fixing operation on the printing medium P, and the fixing assembly  60  may be a secondary fixing device which performs a second fixing operation on the printing medium P. 
     The example recording medium conveying device  10  includes a feeding roller  11  which may convey the printing medium P having an image formed thereon along a conveying path R 1 . The printing medium P is stacked and stored on a cassette C and is picked up and conveyed by the feeding roller  11 . The example feeding roller  11  is provided in the vicinity of an outlet (e.g. the exit) of the cassette C, for the printing medium P. The recording medium conveying device  10  may convey the printing medium P to a secondary transfer region R 2  through the conveying path R 1  at a timing at which the toner image transferred to the printing medium P reaches the secondary transfer region R 2 . 
     In the example imaging system  1 , one developing device  20  is provided for each color. Each developing device  20  includes a developing roller  21  which carries toner on the photoreceptor  40 . In the example developing device  20  toner and carrier may be adjusted to a predetermined mixing ratio and the toner and the carrier may be mixed and stirred so as to uniformly disperse the toner. The developer may be carried on the developing roller  21 . The developing roller  21  may rotate so that the developer is conveyed to a region facing the photoreceptor  40 . The toner in the developer carried on the developing roller  21  may be transferred to the electrostatic latent image of the photoreceptor  40  to develop the electrostatic latent image. 
     The transfer device  30  may convey the toner image formed by the developing device  20  and the photoreceptor  40  to the secondary transfer region R 2 . In some examples, an image developed by the photoreceptor  40  is transferred to the transfer device  30 . The example transfer device  30  includes a transfer belt  31 , tension rollers  32   a ,  32   b ,  32   c , and  32   d , a primary transfer roller  33 , and a secondary transfer roller  34 . The example transfer belt  31  is tensioned by the tension rollers  32   a ,  32   b ,  32   c , and  32   d . In the example imaging system  1 , one primary transfer roller  33  is provided for each color. Each primary transfer roller  33  sandwiches the transfer belt  31  along with each photoreceptor  40 . The secondary transfer roller  34  sandwiches the transfer belt  31  along with the tension roller  32   d.    
     The example transfer belt  31  is an endless belt which may be moved in a circulating manner by the tension rollers  32   a ,  32   b ,  32   c , and  32   d . The primary transfer roller  33  may press against the photoreceptor  40  from the inner peripheral side of the transfer belt  31 . The secondary transfer roller  34  presses against the tension roller  32   d  from the outer peripheral side of the transfer belt  31 . In some examples, the photoreceptor  40  is a photosensitive drum. In the example imaging system  1 , one photoreceptor  40  is provided for each color. The plurality of photoreceptors  40  are arranged side by side along the movement direction of the transfer belt  31 . One developing device  20 , one exposure unit  41 , one charging device  42 , and one cleaning device  43  are provided for each photoreceptor  40 , at a position facing the outer peripheral surface of the associated photoreceptor  40 . 
     The example imaging system  1  includes a process cartridge  2  which may include the developing device  20 , the photoreceptor  40 , the charging device  42 , and the cleaning device  43 , and the example imaging system  1  may further include an apparatus body  3  to and from which the process cartridge  2  is attached and detached (e.g., separated). The process cartridge  2  may be attachable to and detachable (e.g., separable) from the apparatus body  3  through a door of the apparatus body  3  that may be opened to insert or withdraw the process cartridge  2  into and from the apparatus body  3 . 
     In some examples, the charging device  42  uniformly charges the outer peripheral surface of the photoreceptor  40  to a predetermined potential. The charging device  42  is, for example, a charging roller which may rotate to follow the rotation of the photoreceptor  40 . The exposure unit  41  may expose the outer peripheral surface of the photoreceptor  40  charged by the charging device  42  in response to the image formed on the printing medium P. A potential of a portion exposed by the exposure unit  41  in the outer peripheral surface of the photoreceptor  40  may change, so that an electrostatic latent image is formed on the outer peripheral surface of the photoreceptor  40 . 
     In the example imaging system  1 , one toner tank  25  is disposed to face each of the plurality of developing devices  20 . For example, toners of magenta, yellow, cyan, and black are stored in the respective toner tanks  25 . The toner may be supplied from each toner tank  25  to the associated developing device  20 . Each developing device  20  may develop the electrostatic latent image by the supplied toner and form a toner image on the outer peripheral surface of the photoreceptor  40 . The toner image formed on the outer peripheral surface of the photoreceptor  40  may be primarily transferred to the transfer belt  31  and the toner remaining on the outer peripheral surface of the photoreceptor  40  after the primary transferring operation may be removed by the cleaning device  43 . 
     In some examples, the fixing device  50  fixes the toner image which is secondarily transferred from the transfer belt  31  onto the printing medium P to the printing medium P. The example fixing device  50  includes a heating roller  51  to heat the printing medium P and fix the toner image to the printing medium P, and a pressing roller  52  to press against the heating roller  51 . The heating roller  51  and the pressing roller  52  may each have a cylindrical shape. 
     In some examples, a heat source such as a halogen lamp may be provided inside the heating roller  51 . Furthermore, a heat source such as a halogen lamp may be provided inside the pressing roller  52 . A nip portion N 1  which is a fixing region of the printing medium P may be provided between the heating roller  51  and the pressing roller  52 . When the printing medium P passes through the nip portion N 1 , the toner image may be melted and fixed to the printing medium P. 
     In some examples, the fixing assembly  60  smoothes the toner on the printing medium P to which the toner image is melted and fixed by the fixing device  50  so that the image of the printing medium P becomes glossy. The fixing assembly  60  may increase the glossiness of the image by melting and pressing minute (or fine) unevenness of the toner formed on the printing medium P so as to smooth the toner. The fixing assembly  60  is further described further below. The example imaging system  1  may include discharging rollers  45  and  46  which discharge the printing medium P of which the gloss of the image has been controlled by the fixing assembly  60 , to the outside of the imaging system  1 . 
     An example image forming method carried out by the example imaging system  1  will be described. In some examples, when an image signal of a target recording image is input to the imaging system  1 , the feeding roller  11  rotates so that the printing medium P stacked on the cassette C is picked up and the printing medium P is conveyed along the conveying path R 1 . The charging device  42  uniformly charges the outer peripheral surface of the photoreceptor  40  to a predetermined potential on the basis of the image signal. The exposure unit  41  irradiates the outer peripheral surface of the photoreceptor  40  with a laser beam so that an electrostatic latent image is formed on the outer peripheral surface of the photoreceptor  40 . 
     In some examples, the developing device  20  performs a developing operation by forming a toner image on the photoreceptor  40 . For example, the toner image is primarily transferred from each photoreceptor  40  to the transfer belt  31  in a region in which each photoreceptor  40  faces the transfer belt  31 . For example, the toner images respectively formed on the plurality of photoreceptors  40  may be sequentially layered (or superimposed) on the transfer belt  31  so that a single composite toner image is formed. The composite toner image is secondarily transferred to the printing medium P conveyed from the recording medium conveying device  10  in the secondary transfer region R 2  in which the tension roller  32   d  faces the secondary transfer roller  34 . 
     The printing medium P to which the composite toner image is secondarily transferred is conveyed from the secondary transfer region R 2  to the fixing device  50 . In some examples, the fixing device  50  may melt and fix the composite toner image to the printing medium P by conveying the printing medium P to pass through the nip portion N 1  while applying heat and pressure to the printing medium P. For example, the printing medium P to which the composite toner image is melted and fixed may be conveyed to the fixing assembly  60 . The fixing assembly  60  smoothes the toner by melting and pressing the toner of the composite toner image again (e.g., re-melting). 
     The fixing assembly  60  may harden the toner by cooling the printing medium P having a smoothened composite toner image. Accordingly, the fixing assembly  60  may increase the glossiness of the image of the printing medium P so that the image of the printing medium P has a surface similar to a photo image, to obtain a high-quality image. The printing medium P of which the image quality is increased by the fixing assembly  60  may be discharged to the outside of the imaging system  1  by the discharging rollers  45  and  46 . 
     With reference to  FIG. 2 , the example fixing assembly  60  includes an endless belt  61  which conveys the printing medium P, heating member  62  and tensioning member  63  which are rotation bodies for tensioning the endless belt  61 , a pressing member  64  which is a rotation body for pressing the printing medium P, a cleaning member  65  that cleans the endless belt  61 , and a cooling member  66  that cools the endless belt  61 . As an example, the heating member  62  may be a roll-shaped heating roller, or the heating member  62  may be a belt-shaped heating belt. 
     In some examples, the printing medium P which passes through the outer surface of the heating member  62  is loaded on the endless belt  61 . As an example, the endless belt  61  includes an outer surface  61   b  on which the printing medium P is loaded and an inner surface  61   c  which contacts the outer peripheral surface of the heating member  62  and the outer peripheral surface of the tensioning member  63 . In some examples, the heating member  62 , the tensioning member  63 , and the cooling member  66  are located inside the endless belt  61 , and the pressing member  64  and the cleaning member  65  are located outside the endless belt  61 . 
     The heating member  62  may heat the endless belt  61  and generate a high-temperature region inside the imaging system  1 . The cooling member  66  may cool the endless belt  61  and generates a low-temperature region inside the imaging system  1 . As an example, the high-temperature region may be a region including the heating member  62  and may include a portion of the endless belt  61  heated by the heating member  62 . Meanwhile, the low-temperature region may be a region including the cooling member  66  and may include, for example, a portion of the endless belt  61  cooled by the tensioning member  63 , the cleaning member  65 , and the cooling member  66 . 
     In some examples, the heating member  62  may include a free belt which is operated by receiving power from the outside of the fixing assembly  60 . In some examples, a nip portion N 2  which is a fixing region of the printing medium P, is formed between the heating member  62  and the pressing member  64 . A contact pressure is generated between the heating member  62  and the pressing member  64  so that the nip portion N 2  is formed by this contact pressure. As an example, the nip portion N 2  is a re-melting portion which re-melts a toner image P 1  of the printing medium P. In this case, the printing medium P may pass through the nip portion N 2  so that the toner image P 1  of the printing medium P becomes smooth. 
     The tensioning member  63  is, for example, a rotatable tension roller. The tensioning member  63  may be, for example, a support roller which supports the endless belt  61  from the inside of the endless belt  61 , where the endless belt  61  moves in a circumferential direction along the outer peripheries of the heating member  62  and the tensioning member  63 . As an example, the printing medium P is conveyed along the endless belt  61  through the nip portion N 2  and the low-temperature region of the cooling member  66 , toward the outside of the fixing assembly  60 . 
     The pressing member  64  may be for example, a pressing roller which is formed in a roller shape. In some examples the pressing member may have a shape other than a roller shape. As an example, the surface hardness of the pressing member  64  may be equal to or greater than 45, and equal to or less than 80 in terms of the hardness of ASKER-C. The heating member  62  may be, for example, a rigid body and the surface hardness of the heating member  62  may be equal to or less than the surface hardness of the pressing member  64 . 
     The cooling member  66  may include, for example, at least one of a heat sink which contacts the inner surface  61   c  of the endless belt  61  or a fan which blows air to the endless belt  61 . The cooling member  66  may include, for example, at least one of a peltier device or a heat pipe. The cooling member  66  may cool and harden the toner image P 1  of the printing medium P smoothed while passing through the nip portion N 2 . 
     The cleaning member  65  is, for example, a cleaning roller which presses the outer surface  61   b  of the endless belt  61  toward the inside of the endless belt  61 . In some examples, the cleaning member  65  is a rotatable cleaning roller. The example cleaning member  65  is disposed between the heating member  62  and the tensioning member  63  so that the endless belt  61  moving from the nip portion N 2  toward the tensioning member  63  through the cooling member  66  is pressed inwardly. In some examples, the cleaning member  65  is disposed on the upstream side of the tensioning member  63  in the movement path of the endless belt  61 . 
     In some examples, the cleaning member  65  is provided at a position in which the outer surface  61   b  of the endless belt  61  is urged toward the inside of the endless belt  61  and a concave portion  61   d  in a portion of the endless belt  61  that is adjacent the cleaning member  65 . As an example, components do not exist inside the endless belt  61  in alignment with the cleaning member  65  (e.g., at the side opposite of the endless belt, relative to the cleaning member  65 ). Accordingly, the concave portion  61   d  is formed in a portion pressed by the cleaning member  65  in the endless belt  61  and stress to the endless belt  61  by the cleaning member  65  is suppressed. 
     The example cleaning member  65  includes a drive roller which rotates in a direction D 2  following a movement direction D 1  of the endless belt  61 . The cleaning member  65  may rotate by receiving a driving force from a drive source such as a motor. In some examples, the cleaning member  65  frictionally contacts the outer surface  61   b  of the endless belt. For example, the cleaning member  65  may be movable with respect to the endless belt  61  and may contact the outer surface  61   b  of the endless belt  61  with a friction force. In some examples, the endless belt  61  includes a contact region A which comes into surface-contact with a surface  65   b  of the cleaning member  65  and the contact region A extends in the direction D 2 . 
     In some examples, the rotation speed of the cleaning member  65  in the direction D 2  may be different from the movement speed of the endless belt  61  in the direction D 1 . In some examples, the adhesion (or adhesion characteristic) of the surface  65   b  of the cleaning member  65  is greater than the adhesion (or adhesion characteristic) of the outer surface  61   b  of the endless belt  61 . Accordingly, foreign matter such as toner adhering to the outer surface  61   b  of the endless belt  61  can be more efficiently scraped off, for example by adhering more easily to the cleaning member  65  than to the endless belt  61 . In some examples, the rotation speed of the cleaning member  65  is slower than the movement speed of the endless belt  61 . For example, the rotation speed of the cleaning member  65  may be adjustable by controlling the drive source of the cleaning member  65 . 
     The fixing assembly  60  may include a blade  67  which contacts the surface  65   b  of the cleaning member  65 . The blade  67  may scrape off foreign matter adhering to the surface  65   b  by contacting the surface  65   b  of the rotating cleaning member  65 . In some examples, the cleaning member  65  is disposed at the lower side of the endless belt  61  in the direction of gravity, to cause the foreign matter scraped off by the cleaning member  65  and the blade  67 , to fall down in the direction of gravity. 
     For example, the cleaning member  65  is provided at a position adjacent to the tensioning member  63  and separated from the tensioning member  63 . As an example, the endless belt  61  passes through the upper side of the cleaning member  65  in the direction of gravity and is curved downward in the direction of gravity as it goes from the cleaning member  65  toward the tensioning member  63 . 
     In some examples, the endless belt  61  which extends downward in the direction of gravity as it goes from the cleaning member  65  toward the tensioning member  63  is curved along the outer peripheral surface  63   b  of the tensioning member  63  and extends from the tensioning member  63  toward the heating member  62 . The fixing assembly  60  may include a spring which urges the tensioning member  63  in a direction D 3  opposite to the heating member  62 , to increase the tension of the endless belt  61  passing through the tensioning member  63 , the heating member  62 , and the cleaning member  65 . 
       FIG. 3  is a diagram illustrating an example in which the tensioning member  63  and the cleaning member  65  are enlarged. With reference to  FIG. 3 , the fixing assembly  60  may include a first gear  68  which is connected to the tensioning member  63  and a second gear  69  which is connected to the cleaning member  65  and engages with the first gear  68 . The tensioning member  63  is connected to the cleaning member  65  through the first gear  68  and the second gear  69 . As an example, the driving force of the tensioning member  63  is transmitted to the cleaning member  65  through the first gear  68  and the second gear  69 . 
     In some examples, the diameter of the second gear  69  connected to the cleaning member  65  is larger than the diameter of the first gear  68  connected to the tensioning member  63 , and the number of teeth of the second gear  69  is greater than the number of teeth of the first gear  68 . In this case, the rotation speed of the cleaning member  65  is slower than the rotation speed of the tensioning member  63  and the movement speed of the endless belt  61 . A difference in speed of the rotation speed of the cleaning member  65  with respect to the movement speed of the endless belt  61 , allows the cleaning member  65  to clean the outer surface  61   b  of the endless belt  61 . 
       FIG. 4  illustrates an example in which a third gear  70  and a fourth gear  71  are further provided in addition to the first gear  68  and the second gear  69 . In this example, the third gear  70  is connected to the first gear  68 , the fourth gear  71  is connected to the second gear  69 , and the cleaning member  65  is connected to the tensioning member  63  through the second gear  69 , the fourth gear  71 , the third gear  70 , and the first gear  68 , in order to suitably change the number of gears connecting the tensioning member  63  and the cleaning member  65 . 
       FIG. 5  is a diagram illustrating an example of the printing medium P passing through the endless belt  61  and the cleaning member  65 .  FIG. 6  is an enlarged view of the endless belt  61  passing through the surface  65   b  of the cleaning member  65 . The printing medium P is conveyed along the endless belt  61 , is separated from the cleaning member  65 , and is further conveyed to the outside of the fixing assembly  60 . The contact region A of the endless belt  61  with respect to the cleaning member  65  extends from one end (e.g., a first end) A 1  to the other end (e.g., a second end) A 2  in the direction D 2  and the endless belt  61  comes into surface-contact with the cleaning member  65  between the first end A 1  and the second end A 2 . The second end A 2  provides an exit of the contact region where the endless belt  61  is separated from the cleaning member  65 . 
     A first line L 1  connecting the first end A 1  of the contact region A in the direction D 2  and a center  65   c  of the cleaning member  65  forms an angle θ 1  with a second line L 2  connecting the second end A 2  of the contact region A in the direction D 2  and the center  65   c  of the cleaning member  65 . The angle θ 1  may be, for example, greater than 0° and equal to or less than 90°. The cleaning member  65  may be disposed so that the angle θ 1  corresponding to a wound angle of the endless belt  61  with respect to the cleaning member  65  is greater than 0° and equal to or less than 90°. The angle θ 1  may be associated with an arc portion of the endless belt  61  that is wound about the cleaning member  65  (e.g., the arc portion of the endless belt  61  that is in contact with the cleaning member  65 ). 
     An operation of the example imaging system  1  with the above-described configuration will be described.  FIG. 7A  shows a graph of a relationship between the stress and speed difference of the cleaning member  65  with respect to the endless belt  61  and the life (or lifespan) of the endless belt  61 .  FIG. 7B  shows a graph of a relationship between the cleaning efficiency of the endless belt  61  by the cleaning member  65  and the stress and speed difference of the cleaning member  65  with respect to the endless belt  61 . 
     With reference to  FIGS. 7A and 7B , as the stress or speed difference with respect to the endless belt  61  increase, the life of the endless belt  61  is shortened, but the cleaning efficiency for the endless belt  61  is improved. The wear of the endless belt  61  can be prevented when the stress and speed difference with respect to the endless belt  61  decreases, thus extending the life of the endless belt  61 . When the stress and speed difference with respect to the endless belt  61 , decrease, the cleaning efficiency of the cleaning member  65  may be deteriorated. 
     Therefore, in the above-described example, since the cleaning member  65  presses the endless belt  61  inward, the area of the contact region A of the cleaning member  65  with respect to the endless belt  61  is widened (or increased). In this case, with reference to the graph of  FIG. 8 , the cleaning efficiency of the endless belt  61  by the cleaning member  65  can be improved while extending the life of the endless belt  61  by suppressing the stress of the cleaning member  65  with respect to the endless belt  61  and by widening the contact region A. 
     The cleaning member  65  may be a rotatable cleaning roller. The endless belt  61  may include the contact region A which comes into surface-contact with the surface  65   b  of the cleaning member  65 , and the contact region A may extend along the direction D 2  corresponding to the rotation direction (or rotational direction) of the cleaning member  65 . Accordingly, the contact region A is widened (or increased) while suppressing the stress of the cleaning member  65  with respect to the endless belt  61  to extend the life of the endless belt  61  and to improve the cleaning efficiency. 
     As described above, the angle θ 1  corresponding to the angle formed by the line L 1  connecting the first end A 1  of the contact region A in the direction D 2  and the center  65   c  of the cleaning member  65  and the line L 2  connecting the second end A 2  of the contact region A in the direction D 2  and the center  65   c  of the cleaning member  65 , may be greater than 0° and equal to or less than 90°. Accordingly, the endless belt  61  may be pressed by the cleaning member  65  and the endless belt  61  may be prevented from being excessively deformed. Further, the adhesion of the surface  65   b  of the cleaning member  65  may be greater than the adhesion of the outer surface  61   b  of the endless belt  61 . For example, the adhesion of the surface  65   b  of the cleaning member  65  may be set to an adhesion in which foreign matter such as toner or paper dust sandwiched between the surface  65   b  and the outer surface  61   b  of the endless belt  61  adheres to the surface  65   b  when the endless belt  61  is separated from the cleaning member  65 . Accordingly, the adhesion of the surface  65   b  of the cleaning member  65  may be an adhesion for allowing foreign matter to adhere to the surface  65   b , in order to more reliably remove the foreign matter adhering to the endless belt  61  by the cleaning member  65 . 
     The cleaning member  65  may be a drive roller which rotates by receiving a driving force in order to change the rotation speed of the cleaning member  65  by controlling the drive source of the cleaning member  65 . The cleaning member  65  rotates in the movement direction of the endless belt  61 , and the rotation speed of the cleaning member  65  may be different from the movement speed of the endless belt  61  in order to further improve the cleaning efficiency due to a speed difference of the cleaning member  65  with respect to the endless belt  61 . 
     The cleaning member  65  may be disposed at the lower side of the endless belt  61  in the direction of gravity. Accordingly, foreign matter scraped off from the endless belt  61  by the cleaning member  65  can fall by gravity, and the falling foreign matter can be more easily stored when a foreign matter collection container is disposed below the endless belt  61  in order to simplify a configuration that stores the foreign matter. 
     As described above, the example imaging system  1  may include the first gear  68  which is connected to the tensioning member  63  and the second gear  69  which is connected to the cleaning member  65  and engages with the first gear  68 . The tensioning member  63  may be a rotatable tension roller and the number of teeth of the second gear  69  may be different from the number of teeth of the first gear  68 . In this case, the cleaning member  65  can be connected to the tensioning member  63  by the first gear  68  and the second gear  69  and a rotational driving force can be transmitted from the tensioning member  63  to the cleaning member  65 . 
     Accordingly, the tensioning member  63  and the cleaning member  65  can be operated in an interlocked manner. The number of teeth of the second gear  69  may be different from the number of teeth of the first gear  68 . Accordingly, the rotation speed of the cleaning member  65  is different from the rotation speed of the tensioning member  63  and the movement speed of the endless belt  61 , thus resulting in a speed difference between the cleaning member  65  and the tensioning member  63  or the endless belt  61 , in order to improve the cleaning efficiency by using the driving force from the tensioning member  63 . 
     With reference to  FIGS. 9A and 9B , in a phenomenon called curl, the printing medium P having the toner image P 1  formed thereon may be curved or curled. The curl may be caused by, for example, a difference in thermal expansion coefficient between the toner image P 1  and the printing medium P or a curvature of the nip portion N 2 . The printing medium P may be curved in a U-shape and a case in which the printing medium P is curved in an inverse U-shape. The printing medium may tend to curve in a U-shape as the image density of the toner image P 1  increases, and the printing medium may tend to curve in an inverse U-shape as the image density of the toner image P 1  decreases. 
     With reference to  FIGS. 10 and 11 , the imaging system may include an image density acquiring unit  81  which acquires image density of the image surface of the printing medium P and a position control unit  82  which controls the position of the cleaning member  65  with respect to the endless belt  61 . In some examples, according to the position control unit  82 , the cleaning member  65  may contact the endless belt  61  when the image density of the printing medium P acquired by the image density acquiring unit  81  is equal to or greater than a predetermined value and the cleaning member  65  may be separated from the endless belt  61  when the image density of the printing medium P is less than the predetermined value. As an example, the position control unit  82  may include a cam mechanism which changes the position of the cleaning member  65  with respect to the endless belt  61 . 
     Since the cleaning member  65  contacts the endless belt  61  during the passage of the printing medium P having high image density and formed in a U-shape, the printing medium P curled in a U-shape is corrected. Since the cleaning member  65  is separated from the endless belt  61  during the passage of the printing medium P having low image density, the printing medium P passes between the cleaning member  65  and the endless belt  61  and is separated from the tensioning member  63 . Since the adhesion of the printing medium P with respect to the endless belt  61  is low when the image density of the printing medium P is low, the printing medium P is more easily separated from the tensioning member  63 . 
     As described above, in the examples illustrated in  FIGS. 10 and 11 , the cleaning member  65  may contact the endless belt  61  and be separated therefrom, to control the position of the cleaning member  65  in response to the curl state occurring in the printing medium P, for example, the image density state of the toner image P 1 . 
     In the examples illustrated in  FIGS. 10 and 11 , the example imaging system  1  includes the image density acquiring unit  81  which acquires the image density of the image surface of the printing medium P having the toner image P 1  fixed thereto and the cleaning member  65  may contact the endless belt  61  when the image density acquired by the image density acquiring unit  81  is equal to or greater than a predetermined value and may be separated from the endless belt  61  when the image density acquired by the image density acquiring unit  81  is less than the predetermined value, in order to correct the curl of the printing medium P. 
     With reference to  FIGS. 11 and 12 , the cleaning member  65  may be movable with respect to the endless belt  61  and the above-described angle θ 1  may be changeable when the pressing amount (e.g., pressure or biasing force) of the cleaning member  65  with respect to the endless belt  61  is adjusted. Since the pressing amount of the cleaning member  65  with respect to the endless belt  61  can be adjusted in response to the image density acquired by the image density acquiring unit  81 , for example, the degree of curl of the printing medium P, may be corrected more accurately. 
     For example, when the cleaning member  65  is located at the side opposite to the conveying side (the sheet conveying side) of the printing medium P, the cleaning member  65  may be separated from the endless belt  61  when the rotation of the endless belt  61  stops. Further, the cleaning member  65  may contact the endless belt  61  when the printing medium P does not pass through the nip portion N 2  and may be separated from the endless belt  61  when the printing medium P passes through the nip portion N 2 . For example, the cleaning member  65  may contact the endless belt  61  in a non-sheet-passing state and the cleaning member  65  may be separated from the endless belt  61  in a sheet-passing state. The cleaning member  65  is separated from the endless belt  61  in the sheet-passing state to convey the printing medium P more smoothly, and the cleaning member  65  contacts the endless belt  61  in a non-sheet-passing state to perform a cleaning operation more intensively. 
     With reference to  FIGS. 13 and 14 , the cleaning member  65  may be tiltable with respect to the extension direction of the axis X 1  of the tensioning member  63 . The tensioning member  63  may be a tension roller which is rotatable about the axis X 1  and the cleaning member  65  may extend in the extension direction of the axis X 1 . In some examples, the imaging system  1  may include a meandering detection member  83  that detects the meandering of the endless belt  61 . When the meandering detection member  83  detects the deviation (meandering) of the endless belt  61 , the cleaning member  65  is tilted, to correct the deviation of the endless belt  61 . 
     As described above, in the examples illustrated in  FIGS. 13 and 14 , the cleaning member  65  is tiltable with respect to the extension direction of the axis X 1 . An angle θ 2  corresponding to a tilting angle of the cleaning member  65  with respect to the axis X 1  may be, for example, ±10°, but is appropriately changeable. Accordingly, the meandering of the endless belt  61  may be prevented when the cleaning member  65  contacting the endless belt  61  is tilted. 
     With reference to  FIG. 15 , a fixing assembly  90  according to a modified example includes a cleaning member  95  that is disposed on the downstream side of the tensioning member  63  in the movement path of the endless belt  61 . With reference to  FIG. 16 , a fixing assembly  100  according to still another modified example includes a cleaning member  105  that is disposed at the upper side of the endless belt  61  in the direction of gravity. With reference to the example of  FIG. 16 , in a case in which the cleaning member  105  is located at the conveying side (the sheet conveying side) of the printing medium P, the cleaning member  105  may contact the endless belt  61  when the printing medium P does not pass through the nip portion N 2  and may be separated from the endless belt  61  when the printing medium P passes through the nip portion N 2  and the rotation of the endless belt  61  stops. As in the above-described examples, the position of the cleaning member with respect to the endless belt can be appropriately changed. 
     It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail.