Patent Publication Number: US-2022214635-A1

Title: Image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile machine and a multi-function printer including the plurality of those functions. 
     Description of the Related Art 
     Hitherto, there has been known an image forming apparatus including a fixing unit configured to fix a tonner image which has been formed on a recording material by utilizing an electro-photographic system or the like on the recording material by heating the recording material on which the tonner image has been formed. As the fixing unit, there has been known one including a fixing roller having a heat source therein and a pressure roller configured to nip a recording material by being in pressure contact with the fixing roller for example (see Japanese Patent Application Laid-Open No. 2004-212409). 
     Here, there is a possibility that foreign substances such as toner adhere on the fixing roller. Due to that, Japanese Patent Application Laid-Open No. 2004-212409 is arranged such that a metallic cleaning roller is brought into contact with the fixing roller to clean a surface of the fixing roller and a web is brought into contact with the cleaning roller to clean the cleaning roller. 
     Here, there is also a demand of suppressing a consumption amount of the web in the arrangement of cleaning the cleaning roller by the web. However, in a case of the arrangement of Japanese Patent Application Laid-Open No. 2004-212409, it is difficult to suppress the consumption amount of the web because the fixing roller, the cleaning roller and the web are kept in contact with each other. 
     Although it is conceivable to separate the cleaning roller, i.e., a collecting roller, from a rotary member such as the fixing roller to that end, there is also a possibility that if the cleaning roller is kept in contact with the web, the cleaning roller adheres with the web by toner left on the cleaning roller. If the cleaning roller adheres with the web, there is a possibility that the web is drawn out so as to be wound up by the cleaning roller in driving the web next. 
     SUMMARY OF THE INVENTION 
     The present disclosure aims at providing an image forming apparatus configured to be able to suppress the cleaning roller from adhering with the cleaning web while separating the cleaning roller from the rotary member in the arrangement in which the cleaning web for cleaning the cleaning roller is provided. 
     According to one aspect of the present invention, an image forming apparatus includes an image forming unit configured to form a tonner image on a recording material, first and second rotary members cooperatively forming a nip portion configured to nip and convey the recording material while heating and fixing the tonner image onto the recording material, a cleaning mechanism including a collecting roller coming into contact with the first rotary member to collect toner on the first rotary member and a cleaning web coming into contact with the collecting roller to clean the collecting roller, the cleaning mechanism being configured to clean the first rotary member by bringing the cleaning web into contact with the collecting roller that is in contact with the first rotary member and rotates together with the first rotary member, and, a separating mechanism configured to separate the cleaning web from the collecting roller when the collecting roller is separated from the first rotary member. 
     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 section view illustrating a schematic configuration of an image forming apparatus of a present exemplary embodiment. 
         FIG. 2  is a section view illustrating a schematic configuration of a fixing unit of the present exemplary embodiment. 
         FIG. 3  illustrates a mechanism for contacting/separating a web and an intermediate cleaning roller of the present exemplary embodiment. 
         FIG. 4A  illustrates a total contact state in which a fixing roller, the intermediate cleaning roller and the web of the present exemplary embodiment are in contact with each other. 
         FIG. 4B  illustrates an intermediate contact state in which the fixing roller is in contact with the intermediate cleaning roller and intermediate cleaning roller is separated from the web of the present exemplary embodiment. 
         FIG. 4C  illustrates a total separation state in which the fixing roller, the intermediate cleaning roller and the web of the present exemplary embodiment are totally separated. 
         FIG. 5  is a control block diagram of the fixing unit of the present exemplary embodiment. 
         FIG. 6  is a table indicative of a cleaning operation mode of the present exemplary embodiment. 
         FIG. 7  is a flowchart indicating one example of a cleaning operation of the present exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An exemplary embodiment will be described with reference to  FIGS. 1 through 7 . At first, a schematic configuration of an image forming apparatus of the present exemplary embodiment will be described with reference to  FIG. 1 . Image forming apparatus 
     The image forming apparatus  100  is an electro-photographic type full-color printer including four image forming portions Pa, Pb, Pc and Pd provided corresponding to four colors of yellow, magenta, cyan and black. In the exemplary embodiment, the image forming apparatus is configured to be a tandem type printer in which the image forming portions Pa, Pb, Pc and Pd arrayed along a rotation direction of an intermediate transfer belt  6  described later. The image forming apparatus  100  forms a tonner image, i.e., an image, on a recording material in accordance to an image signal received from a document reading apparatus connected with an apparatus body  100   a  of the image forming apparatus  100  or a host device such as a personal computer communicably connected with the apparatus body  100   a . The recording material may be a sheet of paper, a plastic film and a sheet member such as a cloth. 
     While the apparatus body  100   a  includes the image forming portions Pa, Pb, Pc and Pd, each of the image forming portions forms an image based on the image signal described above. That is, the image signal is converted into a laser beam to which PWM (pulse-width modulation control) has been executed by a control portion  200 . A laser scanner  5  serving as an exposing unit scans the laser beam corresponding to the image signal. Then, a photosensitive drum  3  serving as an image bearing member of the respective image forming portions Pa through Pd is irradiated with the laser beam. 
     Note that Pa denotes the image forming portion of yellow (Y), Pb denotes that of magenta (M), Pc denotes that of cyan (C) and Pd denotes that of black (Bk). The respective image forming portions form images of the corresponding colors. Because the configurations of the image forming portions Pa through Pd are approximately the same, so that the image forming portion Pa of yellow will be described in detail below and descriptions of the other image forming portions will be omitted here. In the image forming portion Pa, a tonner image is formed on a surface of the photosensitive drum  3  based on the image signal, as follows. 
     A charging roller  2  serving as a primary charger charges the surface of the photosensitive drum  3  to a predetermined potential to be ready to form an electrostatic latent image. The electrostatic latent image is formed on the surface of the photosensitive drum  3  charged at the predetermined potential by the laser beam from the laser scanner  5 . A developer  1  forms the tonner image by developing the electrostatic latent image on the photosensitive drum  3  by toner. 
     Here, the toner used in the present exemplary embodiment contains paraffin or wax composed of polyolefin and silicon oil serving as a releasing agent. Specifically, the toner in which such wax component and pigment are finely dispersed within grinded toner is used. Note that the toner may be arranged so as to use polymerized toner containing such wax component. While the toner containing wax as a releasing agent will be illustrated in the following description, the same applies to a case where silicon oil is used as the releasing agent as described above. 
     A primary transfer roller  24  discharges electricity from a back of the intermediate transfer belt  6  to apply a primary transfer bias with a polarity reverse to that of the toner to transfer the tonner image on the photosensitive drum  3  onto the intermediate transfer belt  6  at a primary transfer portion n 1 . The intermediate transfer belt  6  is configured to rotate with an equal peripheral speed with the photosensitive drum  3  in a direction of an arrow A by being stretched by tension rollers  13 ,  14  and  15 . The surface of the photosensitive drum  3  is cleaned by a cleaner  4  after transferring the tonner image onto the intermediate transfer belt  6 . 
     The tonner image on the intermediate transfer belt  6  is conveyed to the next image forming portion and the tonner images of the respective colors formed by the respective image forming portions are transferred onto the surface of the intermediate transfer belt  6  sequentially in order of Y, M, C and Bk to form four color images. Then, the tonner image which has passed through the image forming portion Pd of Bk located at a most downstream in the rotation direction of the intermediate transfer belt  6  is conveyed to a secondary transfer portion n 2  composed of a secondary transfer roller pair  11  and  14 . Then, a secondary transfer electric field having a polarity reverse to that of the tonner image on the intermediate transfer belt  6  is applied to the secondary transfer portion n 2  to secondarily transfer the tonner image onto the recording material S. 
     The tonner image secondarily transferred is formed onto the recording material S while leaving certain margins from edges of four sides. A margin at a leading edge is around 2 to 3 mm in the present exemplary embodiment. Note that transfer residual toner and other foreign substances left on the intermediate transfer belt  6  are removed by a cleaning web  23  which is formed of a nonwoven fabric in a belt cleaner  22  and which is rubbed against the surface of the intermediate transfer belt  6 . 
     The recording material S stored in and fed from a cassette  10  is conveyed to a registration portion  12  composed of a pair of registration rollers for example and stands by at the registration portion  12 . Then, the registration portion  12  conveys the recording material S to the secondary transfer portion n 2  while controlling conveyance timing to adjust the tonner image on the intermediate transfer belt  6  with the recording material S. A configuration including the respective image forming portions Pa through Pd, the intermediate transfer belt  6  and others and until when the tonner image is secondarily transferred onto the recording material as described above will be referred to as an image forming unit  150  for forming the tonner image on the recording material. 
     The recording material S onto which the tonner image has been transferred at the secondary transfer portion n 2  is conveyed to a fixing unit  9  and is heated and pressed there to fix the tonner image borne on the recording material S to the recording material S. The recording material S that has passed through the fixing unit  9  is discharged onto a discharge tray  8 . Note that in a case where images are to be formed on both surface of the recording material S, front and back surfaces of the recording material S are reversed at a reverse conveyance portion  21  after finishing transferring and fixing the tonner image onto a first face, i.e., the front surface, of the recording material S. Then, a tonner image is transferred and fixed onto a second face, i.e., the back surface, of the recording material S. After that, the recording material S is stacked on the discharge tray  8 . 
     Fixing Unit 
     Next, a schematic configuration of the fixing unit  9  of the present exemplary embodiment will be described with reference to  FIG. 2 . As described later, the fixing unit  9  of the present exemplary embodiment includes a configuration of fixing the tonner image formed on the recording material by using toner containing releasing agent by applying heat and pressure to the tonner image. 
     The fixing unit  9  including a cleaning unit  60  is disposed within a casing  31  (see  FIG. 1 ) supported within the apparatus body  100   a . The fixing unit  9  includes a fixing roller  40  serving as a first rotary member or as a fixing rotary member, a counter roller  41  serving as a second rotary member or as a pressing rotary member and the cleaning unit  60  serving as a cleaning mechanism for cleaning a surface of the fixing roller  40 . The cleaning unit  60  is disposed above the fixing roller  40 . In the fixing unit  9  constructed as described above, the counter roller  41  is in pressure contact with the fixing roller  40  with a total pressure of about 784 [N], i.e., about 80 [kg] and forms a heating nip portion n 3  for heating while nipping and conveying the recording material S. 
     That is, the counter roller  41  that is in contact with the fixing roller  40  forms the heating nip portion n 3  to heat the image, i.e., the tonner image, on the recording material. Thus, the fixing roller  40  and the counter roller  41  cooperatively form the nip portion for nipping the recording material and for heating and fixing the tonner image onto the recording material. That is, the fixing unit  9  fixes the non-fixed tonner image secondarily transferred onto the recording material S in the image forming unit  150  to the recording material S while nipping and conveying the recording material S by the heating nip portion n 3  between the fixing roller  40 , that comes into contact with an image surface, and the counter roller  41 . 
     The fixing roller  40  is the fixing rotary member that comes into contact with the tonner image to fix the tonner image onto the recording material S. According to the present exemplary embodiment, the fixing roller  40  includes a cylindrical core metal  40   b  made of aluminum and an elastic layer  40   c  of 3 mm thick for example which is disposed around an outer circumferential face of the core metal  40   b . The fixing roller  40  is formed into a cylindrical roller having 60 mm in diameter for example. An under layer of the elastic layer  40   c  is a HTV (high-temperature vulcanized) silicon rubber layer, and a RTV (room-temperature vulcanized) or an LTV (low-temperature vulcanized) silicon rubber layer serving as a heat resistant elastic layer that comes into contact with the image surface is disposed around an outer circumferential face of the HTV silicon rubber layer. A fluorine-based resin, e.g., a PFA tube in the present exemplary embodiment, serving as a heat resistant releasing layer  40   d  is coated on the elastic layer  40   c  to improve releasability from toner. 
     The fixing roller  40  also includes a fixing roller heater  40   a  serving as a heating portion for heating the fixing roller  40 . The fixing roller heater  40   a  is disposed unrotatably at a center part of the core metal  40   b  of the fixing roller  40  and is a halogen heater of a predetermined rated power that heats the fixing roller  40  such that a surface temperature of the fixing roller  40  converges to a predetermined temperature. A set temperature of the fixing roller heater  40   a  may be changed under control of a fixing unit control portion  202  (see  FIG. 5 ) described later. According to the present exemplary embodiment, the fixing unit  9  includes a temperature detection sensor  42   a  serving as a temperature detection member for detecting the surface temperature of the fixing roller  40 . The fixing unit control portion  202  controls the fixing roller heater  40   a  such that the surface temperature of the fixing roller  40  converges to the predetermined temperature based on an output of the temperature detection sensor  42   a.    
     Note that it is possible to arrange so as to heat the fixing roller  40  by including a heater in an intermediate cleaning roller  62  described later and by heating the intermediate cleaning roller  62  itself. In this case, the fixing unit control portion  202  may control the heater of the intermediate cleaning roller  62  based on the output of the temperature detection sensor  42   a.    
     The counter roller  41  is disposed so as to face the fixing roller  40  and forms the heating nip portion n 3  together with the fixing roller  40  as described above. According to the present exemplary embodiment, the counter roller  41  includes a cylindrical core metal  41   b  made of aluminum and an elastic layer  41   c  of 1 mm thick for example disposed around an outer circumferential face of the core metal  41   b . The counter roller  41  is formed into a cylindrical roller having 60 mm in diameter for example. An under layer of the elastic layer  41   c  is a HTV silicon rubber layer, and a RTV (room-temperature vulcanized) or an LTV (low-temperature vulcanized) silicon rubber layer serving as a heat resistant elastic layer that comes into contact with the image surface is disposed around an outer circumferential face of the HTV silicon rubber layer. A fluorine-based resin, e.g., a PFA tube in the present exemplary embodiment, for example serving as a heat resistant releasing layer  41   d  is coated on the elastic layer  41   c  to improve releasability from toner. 
     The counter roller  41  also includes a counter roller heater  41   a  serving as a heating portion for heating the counter roller  41 . The counter roller heater  41   a  is disposed unrotatably at a center part of the core metal  41   b . The counter roller heater  41   a  is a halogen heater of a predetermined rated power that heats the counter roller  41  such that a surface temperature of the counter roller  41  converges to a predetermined temperature. According to the present exemplary embodiment, the fixing unit  9  includes a temperature detection sensor  42   b  for detecting the surface temperature of the counter roller  41 . The fixing unit control portion  202  controls the counter roller heater  41   a  such that the surface temperature of the counter roller  41  converges to the predetermined temperature based on an output of the temperature detection sensor  42   b.    
     According to the present exemplary embodiment, releasability against sharp melt toner is improved further by combining the fixing roller  40  and the counter roller  41  having the layer structure as described above. Still further, in order to fix images on both surfaces, a releasing layer  41   d  having a high toner releasing effect is provided not only on the surface of the fixing roller  40  but also on the surface of the counter roller  41 . 
     Both ends of the fixing roller  40  and the counter roller  41  are rotatably supported by ball bearings not illustrated. The fixing roller  40  and the counter roller  41  rotate in directions of arrows K and L, respectively, as gears not illustrated fixed to one axial end portion of the respective rollers are linked with each other by a gear mechanism not illustrated and are integrally and rotationally driven by a fixing roller motor  211  (see  FIG. 5 ). Note that a motor for driving the counter roller  41  may be separately provided so as to drive the fixing roller  40  and the counter roller  41  with different motors. 
     As described above, the temperature detection sensor  42   a  composed of a thermistor and others is disposed within the casing  31  so as to detect the surface temperature of the fixing roller  40  by being in contact with the surface of the fixing roller  40 . The temperature detection sensor  42   a  is disposed upstream of the heating nip portion n 3  in the rotation direction of the fixing roller  40 . The temperature detection sensor  42   a  is connected with the fixing unit control portion  202  (see  FIG. 5 ). The fixing unit control portion  202  adjusts a power supplied to the fixing roller heater  40   a  such that the surface temperature of the fixing roller  40  detected by the temperature detection sensor  42   a  converges to the predetermined temperature, e.g., about 165° C. 
     Cleaning Unit 
     Next, the cleaning unit  60  will be described with reference to  FIGS. 2 through 4C . Note that  FIG. 3  is a schematic diagram illustrating a contacting/separating mechanism  32  that brings the intermediate cleaning roller  62  into contact with or in separation from a web roller  63  and is a view when the contacting/separating mechanism  32  in  FIGS. 2 and 4A through 4C  is seen from a back side of the drawings.  FIGS. 4A through 4C  are schematic diagrams illustrating contact and separation states of the intermediate cleaning roller  62  and the web roller  63 . 
     The cleaning unit  60  is what cleans the surface of the fixing roller  40  and includes a metallic intermediate cleaning roller  62  serving as a collecting roller, a web, i.e., a cleaning web,  61  serving as a cleaning member, the contacting/separating mechanism  32  and others. The intermediate cleaning roller  62  cleans the fixing roller  40  by coming into contact with the fixing roller  40 . Specifically, the intermediate cleaning roller  62  collects toner on the fixing roller  40  by coming into contact with the fixing roller  40 . The web  61  cleans the intermediate cleaning roller  62  by coming into contact with the intermediate cleaning roller  62 . The contacting/separating mechanism  32  is configured to move the intermediate cleaning roller  62  and the web  61 . 
     In a case of the present exemplary embodiment as described above, it is possible to put the intermediate cleaning roller  62  and the web  61  into three states as illustrated in  FIGS. 4A through 4C  by operating the contacting/separating mechanism  32 . Firstly,  FIG. 4A  illustrates a total contact state, i.e., a first contact state, in which the fixing roller  40  is brought into contact with the intermediate cleaning roller  62  and the intermediate cleaning roller  62  is brought into contact with the web  61 .  FIG. 4B  illustrates an intermediate contact state, i.e., a second contact state, in which the fixing roller  40  is brought into contact with the intermediate cleaning roller  62  and the intermediate cleaning roller  62  is separated from the web  61 .  FIG. 4C  illustrates a total separation state in which the fixing roller  40 , the intermediate cleaning roller  62  and the web  61  are separated, respectively. These states will be described in detail below. 
     As illustrated in  FIGS. 2 and 4A , the intermediate cleaning roller  62  is disposed between the fixing roller  40  and the web  61  during the cleaning operation of the cleaning unit  60 . The intermediate cleaning roller  62  is rotationally driven by the fixing roller  40  and collects toner and foreign substances on the fixing roller  40 . The web  61  is rubbed against the intermediate cleaning roller  62  to clean the toner and foreign substances collected by the intermediate cleaning roller  62 . That is, the cleaning unit  60  cleans the fixing roller  40  by bringing the intermediate cleaning roller  62  into contact with the fixing roller  40  and by bringing the web  61  into contact with the intermediate cleaning roller  62  that rotates together with the fixing roller  40 . Because the intermediate cleaning roller  62  executes the indirect contact of the web  61  with the fixing roller  40 , the intermediate cleaning roller  62  suppresses a phenomenon of stripes otherwise caused on an output image as the fixing roller  40  is scratched by being rubbed by the foreign substances restrained by the web  61 . 
     As illustrated in  FIG. 2 , the web  61  serving as a cleaning member is a nonwoven sheet of about  5  meters long in total wound into a roll. A feed end portion  61   a  of the web  61  is fixed to a roll core and is removably supported by a support shaft  64  supported to a web frame  70  (see  FIG. 3 ). The support shaft  64 , i.e., the feed roller, which is one example of a mount portion is mounted rotatably in a rewind direction in a state in which an unused part of the web  61  is wound up. 
     A winding end portion  61   b  of the web  61  is removably held around a driving shaft  65  supported by the web frame  70 . A web feed motor  210  is connected at one end of the driving shaft  65  to wind up the web  61 . The web  61  is bridged over the web roller  63  serving as a pressing member, and a part bridged over the web roller  63  is rubbed against the intermediate cleaning roller  62 . That is, as the web feed motor  210  rotates in a winding direction, the winding end portion  61   b  is wound by the driving shaft  65  serving as a winding roller, the web  61  is pulled from the feed end portion  61   a  via the web roller  63  and the support shaft  64  is driven and is rotated. Thereby, the web  61  is gradually wound up in a direction of an arrow B in  FIG. 2 . Then, the intermediate cleaning roller  62  is rubbed by the web  61  by this winding operation of the web  61 . 
     The web roller  63  presses the web  61  against the intermediate cleaning roller  62 . That is, the web roller  63  presses the web  61  against the intermediate cleaning roller  62  to rub the intermediate cleaning roller  62  with the web  61 . It is preferable to widen a circumferential nip width between the web roller  63  and the intermediate cleaning roller  62  in order to improve cleaning ability of the web  61 . To that end, the web roller  63  is configured to be an elastic roller of a heat resistant silicon sponge of  30  mm in diameter wrapped around the shaft  63   a  (see  FIG. 3 ). The silicon sponge is then coated with a PFA tube composed of fluorocarbon resin of around 100 μm thick to prevent adhesion of toner. As illustrated in  FIG. 3 , the shaft  63   a  of the web roller  63  is supported movably in a direction of the intermediate cleaning roller  62 , through a bearing  71 , to a long hole  70   b  formed through the web frame  70  serving as a first support member of the cleaning unit  60 . The shaft  63   a  of the web roller  63  is urged by a web roller pressing spring  72  serving as a pressure spring having an end portion fixed to the web frame  70  through the bearing  71 . 
     The intermediate cleaning roller  62  serving as an intermediate cleaning member has an outer diameter of  20  mm for example and is a metallic roller such as stainless steel (e.g., SUS 303) having higher affinity with melted toner than the fixing roller  40  having the release layer. Due to that, the toner and the foreign substances adhered from the recording material to the fixing roller  40  are collected from the fixing roller  40  to the intermediate cleaning roller  62 . As illustrated in  FIG. 3 , the intermediate cleaning roller  62  is rotatably supported by a rotation shaft  62   a  having both ends supported by an intermediate support arm  67  serving as a second support member. The intermediate cleaning roller  62  is also enabled to move between a state in which the intermediate cleaning roller  62  comes into contact with the fixing roller  40  and a state in which the intermediate cleaning roller  62  is separated from the fixing roller  40  as the intermediate support arm  67  is operated by the contacting/separating mechanism  32  as described later. The intermediate support arm  67  is urged in a direction of the fixing roller  40  by an intermediate cleaning roller pressing spring  69 . 
     Contacting/Separating Mechanism 
     Next, the contacting/separating mechanism  32  serving as a moving unit will be described with reference to  FIG. 3  and  FIGS. 4A through 4C . The contacting/separating mechanism  32  is configured to be able to move the intermediate cleaning roller  62  and the web  61  and to shift the intermediate cleaning roller  62 , the web  61  and the fixing roller  40  in the three states of the “total contact state”, “intermediate contact state” and “total separation state” as illustrated in  FIGS. 4A through 4C  described above. 
     The contacting/separating mechanism  32  includes the intermediate support arm  67  serving as the second support member supporting the intermediate cleaning roller  62 , the web frame  70  serving as the first support member supporting the web  61  and a contacting/separating cam  74  serving as a separating mechanism. The intermediate support arm  67  and the web frame  70  are supported swingably centering on a common swing shaft  70   a . The web frame  70  is formed integrally with a web arm  73 , and the web roller  63  is urged in the direction of the fixing roller  40  by a spring  75  bridged between the web arm  73  and a frame not illustrated. 
     The contacting/separating cam  74  is provided abuttably with a contact portion  73   a  of the web arm  73  and is driven by a web contacting/separating motor  209 . A spring  75  urges the web arm  73  in a direction in which the contact portion  73   a  abuts with the contacting/separating cam  74 . The contacting/separating cam  74  is formed eccentrically and moves the contact portion  73   a  in a direction inverse to the urging direction of the spring  75  as the contacting/separating cam  74  is rotated clockwise in  FIG. 3  centering on a rotation shaft  74   a  by the web contacting/separating motor  209 . Thereby, the web frame  70  integrated with the web arm  73  swings counterclockwise in  FIG. 3  centering on the swing shaft  70   a  and separates the web roller  63  and the web  61  supported by the web frame  70  from the intermediate cleaning roller  62 . 
     Meanwhile, the contacting/separating cam  74  moves the contact portion  73   a  in the same direction with the urging direction of the spring  75  as the contacting/separating cam  74  is rotated counterclockwise in  FIG. 3  centering on the rotation shaft  74   a  by the web contacting/separating motor  209 . Thereby, the web frame  70  integrated with the web arm  73  swings clockwise in  FIG. 3  centering on the swing shaft  70   a  and brings the web roller  63  and the web  61  supported by the web frame  70  come into contact with the intermediate cleaning roller  62 . 
     The pressing spring  69  is bridged between the intermediate support arm  67  and a frame not illustrated, and the intermediate cleaning roller  62  is urged in the direction of the fixing roller  40  by the spring  69 . The intermediate support arm  67  also includes an abutment portion  67   c  butting against a restrict portion  73   b  provided on the web arm  73  integrated with the web frame  70 . The restrict portion  73   b  restricts the rotational move of the intermediate cleaning roller  62  in the direction of the fixing roller  40  caused by the intermediate support arm  67  by coming into contact with the abutment portion  67   c  of the intermediate support arm  67 . 
     The abutment portion  67   c  is disposed so as to butt against the restrict portion  73   b  after when the web  61  is separated from the intermediate cleaning roller  62  as the web frame  70  is moved by the contacting/separating cam  74  from the total contact state. 
     In the state in which the restrict portion  73   b  butts against the abutment portion  67   c , the intermediate support arm  67  swings centering on the swing shaft  70   a  together with the web frame  70  as the restrict portion  73   b  abuts with the abutment portion  67   c  because the contacting/separating cam  74  is driven in the same direction further, i.e., clockwise in  FIG. 3 . Then, the intermediate support arm  67  is moved in a direction in which the intermediate cleaning roller  62  is separated from the fixing roller  40 . That is, when the web roller  63  is separated from the intermediate cleaning roller  62 , the web frame  70  comes into contact with the intermediate support arm  67  and moves the intermediate support arm  67  such that the intermediate cleaning roller  62  is separated from the fixing roller  40  along with the move of the web roller  63  of the web frame  70  in a direction of separating from the intermediate cleaning roller  62 . Meanwhile, when the contacting/separating cam  74  is rotationally driven in a direction inverse to that, the intermediate support arm  67  is moved in a direction in which the intermediate cleaning roller  62  comes into contact with the fixing roller  40  by an urging force of the spring  69 . 
     The cleaning unit  60  is put into the three states as described above by the contacting/separating mechanism  32  constructed as described above. That is, the fixing roller  40  is in contact with the intermediate cleaning roller  62  and the intermediate cleaning roller  62  is also in contact with the web  61  in the total contact state as illustrated in  FIG. 4A . In this state, the restrict portion  73   b  of the web arm  73  is separated from the abutment portion  67   c  of the intermediate support arm  67 , and the intermediate cleaning roller  62  is pressed against the fixing roller  40 . At this time, the web roller  63  presses the intermediate cleaning roller  62  with 40 N through the web  61 . Still further, the spring  69  urges the both ends of the intermediate cleaning roller  62  toward the fixing roller  40  and presses the intermediate cleaning roller  62  against the fixing roller  40  with a force of 60 N. 
     By adopting the abovementioned contact relationship, the residual toner and the foreign substances adhering on the fixing roller  40  are collected first by the intermediate cleaning roller  62  that is rotationally driven by the fixing roller  40 . After that, because the web  61  is pressed by the web roller  63  and is rubbed against the intermediate cleaning roller  62 , the residual toner and the foreign substances collected by the intermediate cleaning roller  62  are cleaned and are removed by the web  61 . 
     That is, as the fixing roller  40  is rotated in the state in which the web roller  63  is in contact with the intermediate cleaning roller  62  through the web  61 , the residual toner and others are collected onto the intermediate cleaning roller  62  from the fixing roller  40  as the intermediate cleaning roller  62  is rotationally driven by the fixing roller  40 . Then, the collected residual toner and the foreign substances are cleaned by the web  61 . In this case, the web  61  in contact with the intermediate cleaning roller  62  is gradually wound up in the direction of the arrow B in  FIG. 2 , and a new part of the web comes into contact with the intermediate cleaning roller  62  before the web is saturated by toner. 
     During such cleaning operation, the web  61  is gradually wound up in the direction of the arrow B with a rate of 0.5 mm per recording material of A4 size along with the rotation of the web feed motor  210 . According to the present exemplary embodiment, the web  61  is moved intermittently per recording material of A4 size. A speed for winding up the web  61  is set such that a new part thereof comes into contact with the intermediate cleaning roller  62  before a preceding part being in contact with the intermediate cleaning roller  62  saturates with toner. The feed end portion  61   a  of the web  61  is rotationally driven as the web  61  is wound up to the winding end portion  61   b  and supplies a non-used part of the web  61  gradually to the contact portion with the intermediate cleaning roller  62 . 
     The intermediate contact state illustrated in  FIG. 4B  is a state in which the fixing roller  40  is in contact with the intermediate cleaning roller  62  and the web  61  is separated from the intermediate cleaning roller  62 . That is, the cleaning unit  60  is configured to be able to switch to a state in which the intermediate cleaning roller  62  is in contact with the fixing roller  40  and is rotated together with the fixing roller  40  in a state in which the web  61  is separated from the intermediate cleaning roller  62 . As the web contacting/separating motor  209  rotates the contacting/separating cam  74 , the web arm  73  pivots centering on the swing shaft  70   a  as described above and moves the web  61  and the web roller  63  integrally from the total contact state or the separation state to the intermediate contact state. In the intermediate contact state, the restrict portion  73   b  of the web arm  73  is kept being separated from the abutment portion  67   c  of the intermediate support arm  67 , and the intermediate cleaning roller  62  is pressed against the fixing roller  40  with the force of 60 N. 
     Here, in a state in which the intermediate cleaning roller  62  is not fully warmed up, the residual toner collected from the fixing roller  40  coagulates on the intermediate cleaning roller  62  or viscosity of the residual toner increases. There is a case where such residual toner cannot be fully cleaned by rubbing the web  61 . In such a case, there is a possibility that the residual toner is transferred again to the fixing roller  40 . Or, there is a possibility that the web  61  adheres with the intermediate cleaning roller  62  by the viscosity of the residual toner and the web  61  is drawn out and is sagged in driving the web  61 . 
     According to the present exemplary embodiment, temperature of the intermediate cleaning roller  62  can be readily controlled because it is possible to bring only the intermediate cleaning roller  62  into contact with the fixing roller  40  including the fixing roller heater  40   a  in the intermediate contact state. Therefore, it is possible to warm up the intermediate cleaning roller  62  before bringing the web  61  into contact with the intermediate cleaning roller  62  and to suppress the problem caused by the collected residual toner described above. 
     In the total separation state illustrated in  FIG. 4C , the fixing roller  40 , the intermediate cleaning roller  62  and the web  61  are separated from each other. When the web contacting/separating motor  209  rotates the contacting/separating cam  74 , the web arm  73  pivots centering on the swing shaft  70   a  as described above and moves the web  61  integrally with the web roller  63  from the total contact state to the intermediate contact state and further to the total separation state. That is, the contacting/separating cam  74  can separate the web  61  from the intermediate cleaning roller  62  when the intermediate cleaning roller  62  is separated from the fixing roller  40 . 
     In the total separation state, the restrict portion  73   b  of the web arm  73  is in contact with the abutment portion  67   c  of the intermediate support arm  67 , so that the rotational move of the intermediate cleaning roller  62  in the direction of the fixing roller  40  caused by the intermediate support arm  67  is restricted. Still further, the intermediate support arm  67  restricted by the abutment portion  67   c  rotationally moves in a direction of separating the intermediate cleaning roller  62  from the fixing roller  40  along with the rotation of the web arm  73 . 
     At this time, the fixing roller  40  takes a clearance of around 2 mm from the intermediate cleaning roller  62 . In a case of heating the fixing roller  40  from a normal temperature, e.g., 20° C., when a surface temperature of the fixing roller  40  is 100° C., temperature of the intermediate cleaning roller  62  is around 40° C. due to an influence of heat radiation from the fixing roller  40 . Still further, when the fixing roller  40  is left by around 5 minutes in a state in which the surface temperature of the fixing roller  40  is 140° C. which is a lowest temperature in a case of passing the recording material through the fixing unit  9  of the present exemplary embodiment, temperature of the intermediate cleaning roller  62  rises up to about 90° C. 
     Because the fixing roller  40  is completely separated from the intermediate cleaning roller  62  in the total separation state, none of the residual toner and the foreign substances which have adhered on the surface of the fixing roller  40  deposit on the intermediate cleaning roller  62 . Therefore, it is not necessary to execute the winding operation for rubbing the intermediate cleaning roller  62  with the web  61 , and no unused portion of the web  61  is consumed. Still further, because the intermediate cleaning roller  62  is completely separated from the web  61 , it is possible to suppress the toner and the foreign substances collected by the web  61  from adhering again to the intermediate cleaning roller  62  in a case where no winding operation of the web  61  is executed. It is also possible to suppress the web  61  from sticking with the intermediate cleaning roller  62  by the melted toner or the like. 
     Still further, as described in detail later, there are cases where the cleaning operation by the cleaning unit  60  is executed and not executed during a fixing operation of fixing a tonner image on a recording material in the present exemplary embodiment. That is, the fixing unit control portion  202  can execute a first mode of putting the intermediate cleaning roller  62  and the web  61  into the total separation state during the fixing operation and a second mode of putting the intermediate cleaning roller  62  and the web  61  into the total contact state during the fixing operation. 
     Still further, the states are shifted from the total separation state to the total contact state via the intermediate contact state in shifting to a standby state by which an image can be formed in the present exemplary embodiment. That is, in starting the image forming apparatus by turning power on or in returning from a sleep mode, the image forming apparatus shifts to the standby state by which an image can be formed from a stop mode or the sleep mode of the image forming apparatus. The sleep mode is a mode in which power consumption is lowered than that in the standby state. Normally, the fixing unit  9  is kept in the total separation state before shifting to the standby state. Therefore, in a case where the image forming apparatus shifts to the standby state and the cleaning operation is to be performed during the fixing operation, while the fixing unit  9  is put into the total contact state from the total separation state, the intermediate contact state is included in the middle thereof in the present exemplary embodiment. That is, the fixing unit control portion  202  can execute a third mode of bringing the intermediate cleaning roller  62  into contact with the fixing roller  40  while separating the web  61  from the intermediate cleaning roller  62  and of putting the intermediate cleaning roller  62  and the web  61  into the intermediate contact state from the total separation state. 
     Here, the toner adhering on the fixing roller  40  is solidified in low temperature. If the intermediate cleaning roller  62  comes into contact with the fixing roller  40  in a state in which the toner is solidified, there is a case where a lump of the solidified toner scratches the surface of the fixing roller  40  at the contact portion where the intermediate cleaning roller  62  is in contact with the fixing roller  40 . Due to that, the surface temperature of the fixing roller  40  is desirable to be a temperature exceeding a glass transition temperature of a base resin in the toner in use in shifting from the total separation state to the intermediate contact state in which the intermediate cleaning roller  62  is brought into contact with the fixing roller  40 . That is, it is preferable for the fixing unit control portion  202  to meet the following conditions in a case of shifting from the total separation state to the intermediate contact state. Specifically, the state is shifted to the intermediate contact state in a case where the fixing roller  40  is heated up by the fixing roller heater  40   a  in the total separation state and the surface temperature of the fixing roller  40  detected by the temperature detection sensor  42   a  exceeds the predetermined temperature. 
     In the same manner, it is desirable to arrange such that the temperature of the intermediate cleaning roller  62  exceeds the glass transition temperature of the base resin in the toner also in shifting to the total contact state in which the web  61  is brought into contact with the intermediate cleaning roller  62 . That is, it is preferable for the fixing unit control portion  202  described later to meet the following conditions in shifting from the intermediate contact state to the total contact state. Specifically, the state is shifted to the total contact state in a case where the intermediate cleaning roller  62  is heated up by the fixing roller heater  40   a  through the fixing roller  40  in the intermediate contact state and a surface temperature of the intermediate cleaning roller  62  exceeds a predetermined temperature. The abovementioned predetermined temperature is the glass transition temperature of the toner in the present exemplary embodiment. The base resin of the toner used in the present exemplary embodiment is polyester and the glass transition temperature thereof is about 80° C. 
     In the present exemplary embodiment, it is possible to increase the temperature of the intermediate cleaning roller  62  around to 100° C. which exceeds the glass transition temperature of the toner by about 9 seconds by bringing the intermediate cleaning roller  62  into contact with the fixing roller  40  when the temperature of the fixing roller  40  reaches 165° C. by heating the fixing roller  40  from the normal temperature state. Still further, because the temperature of the intermediate cleaning roller  62  is around 90° C. in a state in which the fixing roller  40  is left for five minutes when the surface temperature of the fixing roller  40  is 140° C., it is possible to immediately bring the intermediate cleaning roller  62  into contact with the fixing roller  40 . This arrangement makes it possible to execute the cleaning operation by the intermediate cleaning roller  62  and the web  61  instantly in a case where the cleaning operation needs to be executed in passing a recording material through the fixing unit  9  for example. Still further, in a case of heating up the fixing roller  40  from the normal temperature, the temperature of the intermediate cleaning roller  62  is around 50° C. in a state where the surface temperature of the fixing roller  40  reaches 140° C., and when the intermediate cleaning roller  62  is brought into contact with the fixing roller  40  in this state, the temperature of the intermediate cleaning roller  62  reaches around 80° C. in around 6.7 seconds. 
     That is, the surface temperature of the intermediate cleaning roller  62  is predictable from the surface temperature of the fixing roller  40  and from a time during which the intermediate cleaning roller  62  is continuously in contact with the fixing roller  40 . Note that a thermistor serving as a temperature detecting unit may be provided on the intermediate cleaning roller  62  to detect the surface temperature of the intermediate cleaning roller  62 , and the shifts from the total contact state, the intermediate contact state and the total separation state may be executed based on a temperature detected by the thermistor. 
     Control Portion 
     Next, a control system related to the fixing unit  9  of the present exemplary embodiment will be described with reference to  FIG. 5 .  FIG. 5  is a block diagram illustrating a control system of controlling the contacting/separating operations of the cleaning unit  60  in the present exemplary embodiment. That is, the image forming apparatus  100  (see  FIG. 1 ) is provided with the control portion  200  of a whole system integrally controlling the respective units. The control portion  200  of the whole system is connected with an operating panel  201  serving as an operating portion and the fixing unit control portion  202 . The user can make various settings, e.g., setting of a type of a recording material or the like, to the image forming apparatus  100  through the operating panel  201 . 
     Each of the control portion  200  and the fixing unit control portion  202  includes a CPU (Central Processing Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory). The CPU controls the respective units while reading out a program corresponding to a control procedure stored in the ROM. The RAM stores operational data and input data, and the CPU controls while making reference to the data stored in the RAM based on the program or the like described above. 
     The fixing unit control portion  202  is connected with a cleaning unit control portion  203 , a remaining amount detection sensor  205 , the temperature detection sensor  42   a , the fixing roller heater  40   a , the fixing roller motor  211  and others. The fixing unit control portion  202  is also connected with the temperature detection sensor  42   b  and the counter roller heater  41   a . The cleaning unit control portion  203  controls the cleaning unit  60 . 
     The remaining amount detection sensor  205  is a sensor for detecting a remaining amount of the web  61 . For instance, the remaining amount detection sensor  205  detects a radius of the roll of the web  61  on a feed side. Specifically, the remaining amount detection sensor  205  includes a flag being in contact with an outer circumference of the roll and detects the remaining amount of the web  61  by detecting a moving amount of the flag. It is possible to detect the remaining amount of the web  61  by detecting the moving amount of the flag in the radius direction while bringing the flag into contact with the outer circumferential face of the roll because the radius of the roll of the web  61  decreases as the web  61  is used. 
     The fixing unit control portion  202  controls the following controls in accordance to an instruction of the control portion  200  of the whole system based on detection signals from the temperature detection sensors  42   a  and  42   b . That is, the fixing unit control portion  202  controls the cleaning unit  60  through the cleaning unit control portion  203  and controls the fixing roller heater  40   a , the fixing roller motor  211  and the counter roller heater  41   a , respectively. 
     The cleaning unit control portion  203  is connected with a home position sensor  208 , the web contacting/separating motor  209  and a web feed motor  210 . The home position sensor  208  detects a home position of the web roller  63 . The web contacting/separating motor  209  is a motor for rotating the contacting/separating cam  74  as described above to bring/separate the web  61  into contact with/from the intermediate cleaning roller  62  and to bring/separate the intermediate cleaning roller  62  into contact with/from the fixing roller  40 . The web feed motor  210  is a motor for rotating the driving shaft  65  serving as a winding roller for winding the web  61 . 
     The cleaning unit control portion  203  rotates the contacting/separating cam  74  by driving the web contacting/separating motor  209  while determining a position of the web roller  63  to the intermediate cleaning roller  62  by the home position sensor  208 . In conjunction with that operation, the cleaning unit control portion  203  brings/separates the web  61  into contact with/from the intermediate cleaning roller  62  while winding the web  61  by driving the web feed motor  210 . According to the present exemplary embodiment, the home position sensor  208  is attached on the shaft of the contacting/separating cam  74 , and a photo-interrupter that reacts, i.e., turns ON, in the total separation state described above is used. 
     Cleaning Operation Mode 
     Next, a cleaning operation mode for executing the cleaning operation in the present exemplary embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a table illustrating various operating conditions in the image forming apparatus and responses whether or not the cleaning operation is to be executed. That is, according to the present exemplary embodiment, there are cases where the cleaning operation by the cleaning unit  60  is executed and not executed depending on sheet passing conditions during a fixing operation in fixing a tonner image on a recording material. 
     In the table, the conditions marked with round black marks indicate whether or not the cleaning operation is executed as indicated in a rightmost “determination” column. That is, the table indicates that the cleaning operation is executed under such condition if a row is marked with “execute” and that no cleaning operation is executed under such condition if a row is marked with “not execute”. 
     Such condition includes a “use condition” and a “sheet passing condition”. The “sheet passing condition” includes a “normal sheet passing condition”, a “high production mode” and a “high gross mode”. The high production mode” includes a “first grammage condition” and a “second grammage condition” and the “high gloss mode” includes a “first temperature condition” and a “second temperature condition”. 
     Firstly, as the “use condition”, the table describes various types of recording materials that are to be passed through the fixing unit and a case in returning from an abnormal stop such as jamming. Note that passing the recording material, i.e., the various sheets in the table, through the fixing unit will be referred to “sheet passing” hereinafter. Then, as the “sheet passing condition”, the table describes the “normal sheet passing condition” in which temperature of the fixing roller  40  is selected by adjusting to a sheet type to be used and grammage and combinations of grammages and temperatures in the “high production mode” and the “high gross mode” described later. 
     Receiving an instruction to execute the cleaning operation from the control portion  200 , the fixing unit control portion  202  drives the web contacting/separating motor  209  through the cleaning unit control portion  203 . Then, the fixing unit control portion  202  operates the cleaning unit  60  so as to shift from the total separation state to the total contact state via the intermediate contact state. The “use condition” is a condition determined by sheet setting selected by the user or whether returning from an abnormality is present. A method for setting information such as the sheet type and the grammage through the operating panel  201  is well known in setting the sheet in particular. 
     Due to a late improvement of toner, it is a general practice to determine temperature of the fixing roller  40  corresponding to grammage of a recording material to be passed like the “normal sheet passing condition” described above. In such a “sheet passing condition”, an amount of residual toner adhering on the fixing roller  40  is reduced. Therefore, the cleaning operation is not selected and the cleaning unit  60  takes the total separation state in a case where the “normal sheet passing condition” is selected except of a “recycled sheet” and an “embossed sheet”. 
     However, due to a late demand of increasing a speed of an image forming operation, some image forming apparatus has a mode of passing a sheet in the high production mode even in a case where the image forming apparatus is loaded mixedly with thin and thick sheets. In such “high production mode”, there is a case where the fixing operation is executed consecutively with the same surface temperature of the fixing roller  40  for recording materials largely different in terms of heat capacities due to different grammages. In such a case, a heat quantity becomes excessive for toner on a thin sheet having a low grammage in particular, and there is a case where excessively melted toner is separated from a lump of toner fused on the recording material side and adheres on the surface of the fixing roller  40  (called as “hot offset” hereinafter). Therefore, it is desirable to execute the cleaning operation in a case where sheets of paper containing a sheet type with grammage that is passed at a higher temperature than that of the “normal sheet passing condition” and is desirable to apply the cleaning operation preferentially to a sheet with low grammage in particular. 
     The fixing unit control portion  202  executes the second mode described above in a case where a plurality of sheets having different grammages is consecutively passed through the heating nip portion n 3  and in a case where the plurality of recording materials includes a recording material having a grammage less than a first grammage and a recording material having a grammage more than a second grammage greater than the first grammage. That is, the fixing unit control portion  202  puts the fixing unit  9  into the total contact state to execute the cleaning operation of the fixing roller  40 . 
     A fixing arrangement applied in the present exemplary embodiment instructs the fixing unit control portion  202  to execute the cleaning operation from the control portion  200  by setting the “first grammage condition” in a case of including recording materials having grammages of less than 91 g/m 2  (gsm) and of 256 g/m 2  (gsm) or more. This arrangement has been determined from results of an experiment in which the hot offset has occurred in a recording material of grammage of less than 91 g/m 2  (gsm) with a surface temperature of the fixing roller  40  by which toner can be melted and fixed to a sheet having grammage of 256 g/m 2  or more. Meanwhile, no cleaning operation is required for recording materials of the “second grammage condition” of 91 g/m 2  or more and less than 256 g/m 2  (gsm), except of a recycled sheet and an embossed sheet. Note that 91 g/m 2  corresponds to the first grammage and 256 g/m 2  corresponds to the second grammage, respectively. 
     In the same manner, there is a case of including the “high gross mode” for acquiring further glossiness. In the “high gross mode”, a temperature of the fixing roller  40  is increased more than a normal fixing temperature to melt toner on a recording material more than a normal fixing state to smooth a surface of the toner. In such a case, the cleaning operation may be required because a heat quantity becomes excessive in the same manner as described above and hot offset toner may adhere on the surface of the fixing roller  40 . 
     The fixing unit control portion  202  can execute the fixing operation in a normal temperature condition, a first high temperature condition and a second high temperature condition, respectively. The normal temperature condition is the “normal sheet passing condition” in the table in  FIG. 6  in which the surface temperature of the fixing roller  40  is set at a first temperature. The first and second high temperature conditions are the “high gross mode” in the table in  FIG. 6 . The first high temperature condition is the “first temperature condition” in the table in  FIG. 6  in which the surface temperature of the fixing roller  40  is set at a second temperature higher than the first temperature. The second high temperature condition is the “second temperature condition” in the table in  FIG. 6  in which the surface temperature of the fixing roller  40  is set at a third temperature higher than the second temperature. 
     Then, in a case where the recording material is a plain sheet of paper, the first mode is executed in a case of executing the fixing operation in the “normal sheet passing condition”, and the second mode is executed in a case of executing the fixing operation in the “first temperature condition”. Still further, in a case where the recording material is a plain sheet of paper, the second mode is executed also in a case of executing the fixing operation in the “second temperature condition”. That is, in the case of the plain sheet of paper, no cleaning operation is executed in the “normal sheet passing condition” and the cleaning operation is executed in the high gloss mode. 
     Still further, in a case where surface irregularity of a recording material is smaller than that of a plain sheet of paper, i.e., in a case of a gloss sheet, a film and a resin sheet, and in a case of executing the fixing operation in the “normal sheet passing condition” and the “first temperature condition”, the first mode is executed. Meanwhile, in a case of executing the fixing operation in the “second temperature condition” in this case, the second mode is executed. That is, in a case where the recording material is a gloss sheet, a film or a resin sheet, no cleaning operation is executed in the “normal sheet passing condition” and the “first temperature condition”, and the cleaning operation is executed in the “second temperature condition”. 
     The fixing arrangement applied in the present exemplary embodiment determines whether or not the cleaning operation is to be executed by setting a sheet passing condition higher than the surface temperature of the fixing roller  40  in the “normal sheet passing condition” by 10° C. or more as the “first temperature condition” and a sheet passing condition higher than the surface temperature of the fixing roller  40  by 15° C. or more as the “second temperature condition”. In a case of a plain sheet of paper such as a fine paper which is a normal sheet, the cleaning operation is instructed to be executed in the “first temperature condition” and the “second temperature condition”. Meanwhile, in a case of a gloss sheet such as a coated sheet having better surface nature, i.e., surface smoothness is higher, than the plain sheet of paper, a film and a resin sheet including an OHT sheet, the cleaning operation is instructed to be executed in the “second temperature condition”. It is because excessively melted toner is liable to remain on the surface of the fixing roller  40  because adhesiveness between the surface layer of the fixing roller  40  and the recording material drops in the sheet having the large surface irregularity. 
     Still further, in a case of a sheet having large surface irregularity such as an embossed sheet and a recycled sheet, the adhesiveness between the surface layer of the fixing roller  40  and the recording material is low even in temperature setting of the “normal sheet passing condition”, so that enough heat may not be conducted to the toner. In such a case, the toner may adhere on the surface of the fixing roller  40  as the toner may not be fully melted on the recording material. Still further, if the surface temperature of the fixing roller  40  is set higher than the “normal sheet passing condition”, excessively melted toner remains as described above. Due to that, the control portion  200  instructs to execute the cleaning operation regardless of the “sheet passing condition” in the condition of using the recycled sheet, the embossed sheet and the like. That is, the fixing unit control portion  202  executes the second mode in the fixing operation in a case where the recording material is the recycled sheet or the embossed sheet. 
     Still further, in a state in which the recording material stops within the fixing unit  9  due to abnormality such as a conveyance failure, i.e., in a jammed state, there is a case where the toner on the recording material is cooled and is solidified between the recording material and the fixing roller  40 , thus remaining on the surface of the fixing roller  40 . There is also a case where the toner before being melted on the fixing roller  40  adheres on the fixing roller  40  in removing the recording material, i.e., in treating a jam. Therefore, it is desirable to execute the cleaning operation even after the jammed state. 
     Therefore, according to the present exemplary embodiment, the control portion  200  instructs to execute the cleaning operation in the “case of returning from abnormality” after the occurrence of a process for the abnormal stop such as a jam treatment and before when no cleaning operation has been executed yet. In such a case, it is desirable to execute the cleaning operation immediately even during a starting control of shifting the fixing roller  40  to a predetermined temperature regardless of the “sheet passing condition”. That is, the fixing unit control portion  202  puts the intermediate cleaning roller  62  and the web  61  into the total contact state to execute the cleaning operation to clean the fixing roller  40  when the image forming apparatus  100  executes a return operation to resume the fixing operation after being stopped due to the abnormality. 
     While a method for selecting the “use condition” and the “sheet passing condition” has been described by exemplifying the case where the user inputs them through the operating panel  201  or the like, any method may be adopted as long as the method enables to set the similar conditions such as printing setting from a personal computer, automatic setting in the image forming apparatus or the like. 
     One Example of Cleaning Operation 
     Next, one example of the cleaning operation of the present exemplary embodiment will be described by using  FIG. 7  and with reference to  FIG. 5 . When the image forming apparatus  100  or the fixing unit  9  is started at first, the fixing unit control portion  202  confirms whether the home position sensor  208  is turned ON in Step S 1 . In a case where the home position sensor  208  is OFF, i.e., No in Step S 1 , the fixing unit control portion  202  operates the web contacting/separating motor  209  such that the intermediate cleaning roller  62  and the web  61  are put into the total separation state in Step S 2 . In the total separation state, the home position sensor  208  is turned ON. 
     Next, the fixing unit control portion  202  operates the fixing roller motor  211  to start to rotate the fixing roller  40  in Step S 3 . When the fixing roller  40  starts to rotate, the fixing unit control portion  202  starts temperature control of the fixing roller  40  based on detection results of the fixing roller heater  40   a  and the temperature detection sensor  42   a  based on an instruction from the control portion  200  in Step S 4 . 
     The fixing unit control portion  202  determines whether no cleaning operation has been executed right after the abovementioned jammed state, i.e., after treating a jam, in Step S 5 . If no cleaning operation has been executed yet, i.e., Yes in Step S 5 , the fixing unit control portion  202  shifts to the cleaning operation automatically. 
     In the cleaning operation, the fixing unit control portion  202  waits until when a surface temperature of the fixing roller  40  increases to 165° C. or more which is higher than a glass transition temperature of a base resin of toner to be used in Step S 6 . Then, when the surface temperature of the fixing roller  40  increases to 165° C. or more, i.e., Yes in Step S 6 , the fixing unit control portion  202  shifts the state to the intermediate contact state in which the intermediate cleaning roller  62  is brought into contact with the fixing roller  40  by operating the web contacting/separating motor  209  in Step S 7 . That is, the fixing unit control portion  202  brings the intermediate cleaning roller  62  into contact with the fixing roller  40  in a case where a temperature detected by the temperature detection sensor  42   a  is higher than a predetermined temperature in cleaning the fixing roller  40 . The fixing unit control portion  202  waits for  12  seconds for example as a standby time in the state in which the intermediate cleaning roller  62  is in contact with the fixing roller  40  in Step S 8 . This standby time, i.e., a predetermined time, is a time for increasing the surface temperature of the intermediate cleaning roller  62  to 100° C. or more which is higher than the glass transition temperature of the base resin. After waiting for  12  seconds, the fixing unit control portion  202  operates the web contacting/separating motor  209  to shift to the total contact state in which the fixing roller  40  comes into contact with the intermediate cleaning roller  62  and the intermediate cleaning roller  62  comes into contact with the web  61 , respectively in Step S 9 . That is, the cleaning unit  60  brings the web  61  into contact with the intermediate cleaning roller  62  after bringing the intermediate cleaning roller  62  into contact with the fixing roller  40  in cleaning the fixing roller  40 . The fixing unit control portion  202  brings the web  61  into contact with the intermediate cleaning roller  62  after an elapse of a predetermined period after bringing the intermediate cleaning roller  62  into contact with the fixing roller  40 . 
     The total contact state enables to clean the surface of the fixing roller  40  as the web  61  sweeps the residual toner and the foreign substances collected by the intermediate cleaning roller  62  from the fixing roller  40 . The fixing unit control portion  202  operates the web feed motor  210  to execute an operation of winding the web  61  such that a new part of the web  61  comes into contact with the intermediate cleaning roller  62  before a part of the web  61  being in contact with the intermediate cleaning roller  62  is saturated by the foreign substances such as the toner in Step S 10 . Then, after finishing the cleaning operation in Step S 11 , the fixing unit control portion  202  operates the web contacting/separating motor  209  to shift the state to the total separation state in Step S 13  via the intermediate contact state in Step S 12 . 
     Meanwhile, even if the cleaning operation has been executed after treating the jam, i.e., No in Step S 5 , the control portion  200  determines whether the cleaning operation is necessary in Step S 14 . In a case where the cleaning operation is necessary, i.e., Yes in Step S 14 , the fixing unit control portion  202  shifts to the cleaning operation. A criterion of the determination whether the cleaning operation is necessary is made based on the conditions in the table illustrated in  FIG. 6  for example. 
     In the cleaning operation, in a case where the surface temperature of the fixing roller  40  is 140° C. or more, i.e., Yes in Step S 15 , the fixing unit control portion  202  shifts to the intermediate contact state in Step S 16 . Then, in a case where a time during which the temperature of the fixing roller  40  is kept at 140° C. or more is less than 5 minutes, i.e., No in Step S 17 , the fixing unit control portion  202  waits for 6.7 seconds for example in Step S 18  and shifts to the total contact state in Step S 19 . In a case where the time during which the temperature of the fixing roller  40  is kept at 140° C. or more is more than 5 minutes, i.e., Yes in Step S 17 , the fixing unit control portion  202  shifts immediately to the total contact state in Step S 19 . 
     This arrangement makes it possible to bring the intermediate cleaning roller  62 , the fixing roller  40  and the web  61  into contact in a state in which the surface temperature of the intermediate cleaning roller  62  is higher than the glass transition temperature of the base resin of the toner to be adopted. During the cleaning operation, the web  61  is gradually wound up in the direction of the arrow B (see  FIG. 2 ) along with the rotation of the web feed motor  210  at a rate of 0.5 mm per A4 paper in Step S 20 . 
     After finishing the cleaning operation in Step S 21 , the fixing unit control portion  202  operates the web contacting/separating motor  209  to shift the state via the intermediate contact state in Step S 22  to the total separation state in Step S 23 . 
     The fixing unit control portion  202  determines whether the process is to be stopped or not in Step S 24  in the case where the state has been put into the total separation state in Steps S 13  and S 23  and in the case where the cleaning operation is determined to be unnecessary, i.e., No in Step S 14 , after the cleaning operation as described above. For instance, the fixing unit control portion  202  determines whether the fixing operation has been made on a final recording material of an image forming job. In a case of stopping the process or in the case where the fixing operation has been made on the final recording material for example, i.e., Yes in Step S 24 , the fixing unit control portion  202  stops the temperature control of the fixing roller  40  in Step S 25  and stops the rotation of the fixing roller  40  in Step S 26 . Thereby, the abovementioned process is stopped. Meanwhile, the process returns to Step S 5  in a case where the fixing unit control portion  202  determines not to stop the process because the recording material is not the final recording material for example, i.e., No in Step S 24 . 
     As described above, the present exemplary embodiment enables to adjust the temperature of the intermediate cleaning roller  62  in the intermediate contact state and to collect the foreign substances by the web  61  in the total contact state. The present exemplary embodiment enables to prolong a life of the web  61  and to stabilize the cleaning ability because it is not always necessary to bring the web  61  into contact with the intermediate cleaning roller  62 . 
     Specifically, the present exemplary embodiment enables to suppress the web  61  from adhering with the intermediate cleaning roller  62  in such arrangement of suppressing a consumption amount of the web  61 . That is, the cleaning unit  60  can move the intermediate cleaning roller  62  and the web  61  to the total separation state and also to the total contact state. Therefore, it is possible to execute the fixing operation while being in the total separation state depending on conditions and to suppress the consumption amount of the web  61 . Still further, because the intermediate cleaning roller  62  and the web  61  are thus put into the total separation state so as not execute the cleaning operation during the fixing operation, it is possible to suppress the intermediate cleaning roller  62  and the web  61  from adhering with each other by the toner during that time. Accordingly, it is possible to suppress the web  61  from being drawn out in a next operation. 
     The present exemplary embodiment also enables to shift the intermediate cleaning roller  62  and the web  61  to the intermediate contact state in which the intermediate cleaning roller  62  is brought into contact with the fixing roller  40  and the web  61  is separated from the intermediate cleaning roller  62 . For instance, there is a case where the intermediate cleaning roller  62  is cool in shifting to a standby state in returning from a sleep state. In such a case, there is a possibility that the fixing roller  40  cannot be fully cleaned by the intermediate cleaning roller  62 . Therefore, the present exemplary embodiment shifts the state into the intermediate contact state in which the intermediate cleaning roller  62  is brought into contact with the fixing roller  40  in shifting to the standby state to bring the web  61  into contact with the intermediate cleaning roller  62  after warming up the intermediate cleaning roller  62 . Then, the present exemplary embodiment executes the cleaning operation. 
     Other Embodiments 
     While the fixing unit has been described to have a configuration of fixing a non-fixed tonner image onto a sheet, i.e., a recording material, the fixing unit may be a heating processing unit that heats a recording material borne with a fixed image or a semi-fixed image to modify surface nature of the image. Still further, while the intermediate cleaning roller has been brought into contact with the fixing roller in the present exemplary embodiment, the intermediate cleaning roller may be brought into contact with a pressing rotary member such as a pressure roller. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     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 Application No. 2020-005982, filed Jan. 17, 2020 which is hereby incorporated by reference herein in its entirety.