Patent Publication Number: US-11378903-B2

Title: Image forming apparatus having long-life fixing device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 35 U.S.C. 0.371 as a National Stage of PCT International Application No. PCT/KR2018/01117, filed on Sep. 20, 2018, in the Korean Intellectual Property Office, which claims the priority benefit of Korean Patent Application No. 10-2018-0008229, filed on Jan. 23, 2018, in the Korean Intellectual Property Office. The disclosures of PCT International Application No. PCT/KR2018/011117 and Korean Patent Application No. 10-2018-0008229 are incorporated by reference herein in their entireties. 
     BACKGROUND ART 
     Generally, an electrophotographic image forming apparatus such as a laser printer forms a developer image corresponding to a predetermined image onto a printing medium, and then permanently fixes the image onto the printing medium by applying heat and pressure to the developer image using a fixing device. 
     The fixing device includes a pair of rollers, that is, a fixing roller to generate heat to be applied to the printing medium and a pressing roller to apply a predetermined pressure to the printing medium. 
    
    
     
       DISCLOSURE 
       Description of Drawings 
         FIG. 1  is a perspective view of a fixing device according to an example; 
         FIG. 2  is a perspective view of the fixing device of  FIG. 1  in disassembled state; 
         FIG. 3  is a cross-sectional view taken on line III-III of  FIG. 1 ; 
         FIG. 4A  is a perspective view of a flange member according to an example; 
         FIG. 4B  is a front view of a flange member according to an example; 
         FIG. 5  is a perspective view of a rotation ring member according to an example; 
         FIG. 6  is a side view of a flange member provided with a rotation ring member according to an example; 
         FIG. 7  is a front view of a flange member according to another example; 
         FIG. 8  is a front view of a flange member according to another example; 
         FIG. 9  is a front view of a flange member according to another example; and 
         FIG. 10  is a brief cross-sectional view illustrating an image forming apparatus including a fixing device according to an example. 
     
    
    
     MODE FOR INVENTION 
     Meanwhile, many fixing devices provided for a high-speed, low-energy image forming apparatus recently use a fixing belt instead of the fixing roller, which is an endless belt having relatively small heat capacity. Such fixing belt is not provided with a rotation axis and instead rotated with pressing contact and driving of the pressing roller. 
     However, the fixing device using the fixing belt has shorter service life, as fatigue crack is generated on both ends of the fixing belt due to repetitive rotation of the fixing belt. 
     Accordingly, a fixing device is necessary, which has an extended service life by suppressing fatigue cracks of the both ends on the fixing belt. 
     Examples of the disclosure will now be described in greater detail with reference to the accompanying drawings. Examples described herein may be modified into various different forms and used. In order to more clearly describe the features of the examples, detailed description of the matters known to those skilled in the art pertinent to the examples will be omitted. 
     Throughout the description, when a portion is stated as being “connected” to another portion, it intends to include an example where the portions are “directly connected”, and also an example where the portions are “electrically connected” while having another element therebetween. Further, throughout the description, when a portion is stated as “comprising (including)” an element, unless specified to the contrary, it intends to mean that the portion may additionally include another element, rather than excluding the same. 
     Further, the term “image forming apparatus” used herein refers to a device that prints printing data generated at a terminal such as a computer onto a recording medium. Examples of such image forming apparatus may include a copy machine, a printer, a fax machine or a multi-function printer (MFP) implementing a combination of the functions of the above into one device. Further, the image forming apparatus may refer to any device that is capable of performing an image forming job, including printer, scanner, fax machine, multi-function printer (MFP) or display, for example. 
     Further, the elements with the same functions within the same scope of the present disclosure appearing in the drawings of the respective examples will be referred to by the same reference numerals. 
       FIG. 1  is a perspective view of a fixing device according to an example, and  FIG. 2  is a perspective view of the fixing device of  FIG. 1  in disassembled state.  FIG. 3  is a cross-sectional view taken on line III-III of  FIG. 1 . 
     Referring to  FIGS. 1 to 3 , the fixing device  1  according to an example includes a pressing roller  10 , a fixing belt  20 , a pressing member  30 , a pair of rotation ring members  40 , a pair of flange members  100  and a heat source  60 . 
     The pressing roller  10  is configured to exert a predetermined pressure to a printing medium P and may have a roller shape. The pressing roller  10  may include a shaft  11  formed from a metal material such as aluminum or steel, and an elastic layer  13  that is elastically deformed to form a fixing nip N between the fixing belt  20  and itself. The elastic layer  13  may be formed from a silicon rubber. Although not illustrated in  FIGS. 1 to 3 , the pressing roller  10  may be configured to be rotated with a power received from a driving source such as a motor. The configuration of the pressing roller being rotated with the driving source will not be specifically explained herein, as it is same as, or similar to the driving configuration of the related pressing roller. 
     The fixing belt  20  may apply a predetermined heat to the printing medium P; and likewise the related heating roller, may be heated by the heat source  60  and deliver the heat to the printing medium P passing through the fixing nip N. Accordingly, the fixing belt  20  may be configured to face the pressing roller  10  and form a fixing nip N in cooperation with the pressing roller  10 , through which the printing medium P passes. The fixing belt  20  may be configured to be rotated by the pressing roller  10 . When the pressing roller  10  is rotated, the fixing belt  20  may be rotated by friction force between the fixing belt  20  and the pressing roller  10 . A length of the fixing belt  20  in an axis direction may be greater than a length of the pressing roller  10  in an axis direction. The fixing belt  20  may be configured as a single layer of metal, heat-resistant polymer, or the like, or, may be configured by adding an elastic layer and a protecting layer to a basic layer formed from metal or heat-resistant polymer. The fixing belt  20  that is same as, or similar to the fixing belt used in the related belt-type fixing device may be used, and the fixing belt  20  will not be redundantly explained herein. 
     The pressing member  30  may be provided on an inner side of the fixing belt  20 , and may support an inner surface of the fixing belt  20  as the fixing belt  20  forms the fixing nip N by a contact with the pressing roller  10 . The pressing member  30  may have a greater length than that of the pressing roller  10 . Accordingly, when the fixing nip N is formed by the pressing roller  10  contacting the fixing belt  20 , bending on both ends of the fixing belt  20  due to the pressing roller  10  is not occurred. Specifically, the pressing member  30  may include a guide member  31  that guides the fixing belt  20  in contact with the inner surface of the fixing belt  20 , and a support member  32  disposed above the guide member  31  to press and support the guide member  31 . 
     The guide member  31  is brought into contact with an inner surface of the fixing belt  20  and forms a fixing nip N, and guides the fixing belt  20  to run smoothly near the fixing nip N. The guide member  31  may be formed as a U-shaped channel in cross-section, which has a roughly flat bottom, with the support member  32  being provided on an inner side thereof. A heat disconnect member  35  may be coupled with both sides of the guide member  31 . 
     The support member  32  may reinforce the guide member  31  to minimize the bending distortion of the guide member  31 . The support member  32  may be formed as a channel having a U-shaped cross-section, which has a roughly flat bottom, and provided on an inner side of the guide member  31 . Not only the U-shape having a flat bottom, the support member  32  may also be configured as other structure with a high area moment of inertia, such as I-shaped beam, H-shaped beam, or the like. 
     The heat disconnect member  35  may prevent the heat generated from the heat source  60  from directly being radiated to the guide member  31 . For the above, the heat disconnect member  35  may be provided above the guide member  31  and the support member  32  to cover the guide member  31  and the support member  32 . Specifically, the heat disconnect member  35  may be provided under the heat source  60  and above the support member  32  inserted into the guide member  31 . 
     As illustrated in  FIG. 3 , when a lower surface of the pressing member  30 , i.e., when the lower surface  31   a  of the guide member  31  is in contact with the inner surface of the fixing belt  20 , the fixing nip N is formed between the portion of the fixing belt  20  supported by the lower surface  31   a  of the guide member  31  and an upper portion of the pressing roller  10  which is in contact therewith. Accordingly, when the pressing roller  10  is rotated, the fixing belt  20  is rotated by friction with the pressing roller  10 . 
     A pair of rotation ring members  40  may be provided on both ends of the fixing belt  20 , supporting both ends of the fixing belt  20  and controlling a movement of the fixing belt  20  in the direction of a center axis thereof. A pair of rotation ring members  40  may be provided to minimize generation of fatigue crack on both ends of the fixing belt  20  when the fixing belt  20  is rotated by the pressing roller  10 . 
     A pair of flange members  100  may rotatably support a pair of rotation ring members  40 . Accordingly, when the fixing belt  20  is rotated by friction force with the pressing roller  10 , the fixing belt  20  may be rotated via a pair of rotation ring members provided between the fixing belt  20  and the flange member  100  rather than being rotated in direct frictional contact with the flange member  100 . 
     Regarding a position of the fixing nip N to form an image, the fixing belt  20  may be in a linear movement along a printing medium transfer direction A, and the rotation ring members  40  in a rotating movement and supporting inner surfaces of both ends of the fixing belt  20  may be in a circular movement. 
     When thrust force is generated by the axial meandering force during the rotation of the fixing belt  20 , the rotation ring members  40  that support both ends of the fixing belt  20  repeat pulling up the fixing belt  20 , which are linearly moving in the printing medium transfer direction A, along the rotation direction of the rotation ring members  40  and then dropping the fixing belt  20 . In this example, the fixing belt  20  may be bent or may flutter. Such bending or fluttering of the fixing belt  20  may occur at a portion where the fixing nip N is formed, and the fixing belt  20  may have fatigue crack generated on an end of the fixing belt  20  due to the bending or fluttering phenomenon at the portion where the fixing nip N is formed. 
     While supporting the inner surface of the fixing belt  20  and rotating, an ideal expectation is that the rotation ring members  40  are rotated at the same velocity as that of the fixing belt  20 . However, when the phenomenon described above occurs, that is, when the rotation ring members  40  rotating at the fixing nip N pull up the fixing belt  20 , which are linearly moving in the printing medium transfer direction A, along the rotation direction of the rotation ring members  40  and then drop the fixing belt  20 , the rotation velocity of the rotation ring members  40  is delayed from that of the fixing belt  20 . When this difference in rotation velocity occurs between the rotation ring members  40  and the fixing belt  20 , slip occurs at a position where the rotation ring members  40  are in contact with the fixing belt  20  and both ends of the fixing belt  20  are worn out due to friction with the rotation ring members  40 . 
     In order to minimize fatigue crack on both ends of the fixing belt  20 , the rotation ring members  40  may be inclined on the flange member  100  in which case the area opposite the fixing nip N area of the fixing belt  20  is relatively protruded than the fixing nip N area. Accordingly, the rotation ring members  40  may minimize friction with the ends of the fixing belt  20  as they are not brought into contact with an area where the linear movement of the fixing belt  20  meets the circular movement of the rotation ring members  40 . Constitution of the flange member  100  and the rotation ring members  40  will be further explained below. 
     The heat source  60  may be provided within the fixing belt  20 , and generates a heat to heat the fixing belt  20  up to a fixing temperature. The heat source  60  may be provided above the pressing member  30  between a pair of flange members  100 . The heat source  60  may be inserted into the fixing belt  20  through a through hole  121  provided in the flange member  100 . For the heat source  60 , a halogen lamp, a ceramic heater or the like may be used. An electric wire for supplying electric power may be connected to the heat source  60 . However, in  FIG. 2 , the electric wire is omitted for convenience of illustration. Because a heat source used in the related fixing device may be used also for the heat source  60 , it will not be further explained below. 
     Although the constitution in which the heat source  60  is provided above the pressing member  30  to heat the fixing belt  20  by radiation, other examples are possible. For example, the heat source  60  may be configured to directly heat the fixing belt  20 . In other words, a ceramic heater may be provided as the heat source  60  on a lower surface  31   a  of the guide member  31  near the fixing nip N, in which case the ceramic heater may directly heat the inner surface of the fixing belt  20 . For another example of the heat source  60 , a surface heating element (not illustrated) may be used. The surface heating element is an electric resistance material that generates heat upon supply of electric currents, and may be a layer sandwiched between an outer surface and an inner surface of the fixing belt  20 . 
       FIGS. 4A and 4B  are perspective diagram and front diagram of a flange member according to an example. 
     Referring to  FIGS. 4A and 4B , the flange member  100  may include a stationary body  120 , a rotation ring support  110  and a protrusion  130 . 
     The stationary body  120  may be fastened to a frame of the fixing device or to an inner frame of a main body  201  of the image forming apparatus. The stationary body  120  may be formed in a roughly rectangular shape, and have the rotation ring support  110  provided on a front side, and a fastening groove  125  provided on both sides to receive the frame  90  therein ( FIGS. 1 and 2 ). According to an example, the stationary body  120  is fixed to the frame  90  by the fastening groove  125  by way of example. However, a method for fastening the stationary body  120  to the frame  90  is not limited hereto. The stationary body  120  may be fastened to the frame  90  with various methods including screw fastening. 
     The rotation ring support  110  may be eccentrically formed from a center of the stationary body  120 . A through hole  121  for receiving the heat source  60  may be formed under the rotation ring support  110 . Two fastening grooves  123  to fixedly receive the pressing member  30  may be provided under the through hole  121 . Both ends of the pressing member  30 , or more specifically, both ends of the guide member  31  may be provided with two fastening bars  33  which are inserted into the two fastening grooves  123  of the flange member  100 . 
     The rotation ring support  110  may be extended perpendicularly from a front side of the stationary body  120  and rotatably support the rotation ring member  40 . The rotation ring support  110  may be formed in various shapes that can support load of the rotation ring member  40  during rotation of the fixing belt  20  while supporting the rotation of the rotation ring member  40 .  FIG. 4A  illustrates the rotation ring support  110  formed in a circular arc shape to provide a space thereunder. Accordingly, a space for installation of the heat source  60  may be provided under the rotation ring support  110 . In this example, the rotation ring support  110  may be formed in a circular arc shape which is larger or smaller than a semicircle. According to an example, the rotation ring support  110  may be in a roughly semicircular shape. However, the present disclosure is not limited to a specific example, and accordingly, the rotation ring support  110  may be formed in various shapes. 
     A plurality of ribs  110   a  may be configured to minimize friction between an inner support  41  of the rotation ring member  40  and the rotation ring support  110  of the flange member  100 . A plurality of ribs  110   a  may reduce friction between the rotation ring member  40  and the flange member  100 , because an inner surface of the inner support  41  of the rotation ring member  40  are not entirely in contact with an outer surface of the rotation ring support  110 . 
     Specifically, a plurality of ribs  110   a  may be configured to prevent the inner support  41  of the rotation ring member  40  from a plane-contact with an outer surface of the rotation ring support  110 , in which case the outer surface of the rotation ring support  110  may support the inner surface of the inner support  41  of the rotation ring member  40  by line-, or point-contact. 
     Further, the flange member  100  may be provided with a protrusion  130  to improve service life of the fixing belt  20  during rotation of the rotation ring member  40 . 
     The protrusion  130  may be configured to reduce friction generated between the fixing belt  20  and the rotation ring member  40  where bending or fluttering phenomenon occurs during rotation of the rotation ring member  40 . The protrusion  130  may support the rotation ring member  40  to be inclined in a contact area where the fixing nip N is formed between the fixing belt  20  and the pressing roller  10 , in which case the rotation ring member  40  is not brought into contact with the fixing belt  20 . 
     A plurality of protrusions  130  may be configured to allow the rotation ring member  40  to be disposed on the flange member  100  while a lower end thereof are inclined toward the direction of flange member  100 . Specifically, a plurality of protrusions  130  may be formed on the stationary body  120  of the flange member  100  to support the rotation ring member  40  by line- or point-contact. In this example, a plurality of protrusions  130  may be formed on a surface of the stationary body  120  of the flange member  100  to stably support the rotation ring member  40 . As illustrated in  FIG. 4B , six protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be provided on the stationary body  120  of the flange member  100 . 
     The protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be formed in a spherical shape or in a column shape having a semicircular or circular cross-section. A plurality of protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be in point-contact with the rotation ring member  40 . In this example, the protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may not be disposed in the fixing nip N area, but disposed in the remainder area, to support the rotation ring member  40  in an inclined state. 
     A portion where the protrusions  130  are not formed may correspond to an area where the fixing belt  20  is brought into contact with the pressing roller  10 , and more specifically, it indicates a lower end of the flange member  100 . 
     A plurality of protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may protrude to an higher height as they are distanced farther away from the lower end of the flange member  100 . In the order of remote distance from the lower end of the flange member  100 , there may be a first protrusion  130   a , a second protrusion  130   b , a third protrusion  130   c , a fourth protrusion  130   d , a fifth protrusion  130   e  and a sixth protrusion  130   f . The first protrusion  130   a  formed on an upper end opposite the lower end of the flange member  100  may be protruded to the greatest height. The height of the sixth protrusion  130   f  may be lowest. The second protrusion  130   b , the third protrusion  130   c , the fourth protrusion  130   d , the fifth protrusion  130   e , and the sixth protrusion  130   f  which become nearer to the lower end of the flange member  100  from the first protrusion  130   a  may have sequentially decreasing heights. 
     Meanwhile, the protrusions disposed on positions laterally symmetrical to each other may have the same height in order to prevent the rotation ring member  40  from being tilted laterally. Specifically, the second protrusion  130   b , the third protrusion  130   c , and the fourth protrusion  130   d  may have heights to support the rotation ring member  40  from being tilted laterally. 
     The protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be laterally symmetrical to each other to stably support the rotation ring member  40 . The first to sixth protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be in different shapes from each other, but not limited hereto. The first to sixth protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be formed in the same shape or formed in a lateral symmetry with each other. 
     Leading ends of the protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  may be processed into a convex form for a stable contact with a side support  43  of the rotation ring member  40 . Although  FIGS. 4A and 4B  provide an example in which the protrusions are formed in a rounded shape, the shape of the protrusions  130  may not be limited hereto. The protrusions  130  may be formed in various shapes that can stably support the side support  43  of the rotation ring member  40 . For example, the shape of the protrusions  130  may include cone, polypyramid, truncated cone, truncated polypyramid, or the like. In this case, the protrusions  130  may support the side support  43  of the rotation ring member  40  by point-contact. 
       FIG. 5  is a perspective view of a rotation ring member according to an example. 
     Referring to  FIG. 5 , the rotation ring member  40  may be extended and formed in a perpendicular direction to the inner support  41  that supports the inner surface of the fixing belt  20 , and may include a side support  43  that prevents a movement of the fixing belt  20  in the direction of a center axis thereof. 
     The inner support  41  of the rotation ring member  40  may be formed in a ring shape, and the side support  43  may be extended in a perpendicular direction from one end of the inner support  41  to an outer side of the inner support  41  by a predetermined length. 
     An inner diameter of the inner support  41  of the rotation ring member  40  may be sized to be inserted into an outer side of the rotation ring support  110  of the flange member  100 . 
     In order to reduce friction between the rotation ring member  40  and the rotation ring support  110  of the flange member  100 , the rotation ring member  40  may be formed from a material having less friction. 
     A width W of the side support  43  extending from the inner support  41  of the rotation ring member  40  may be greater than a depth of the fixing belt  20 , in which case the fixing belt  20  rotating with the rotation ring member  40  is prevented from riding over the side support  43 . 
     The inner support  41  that supports an inner surface of the fixing belt  20  may be formed from a material having a greater friction than the side support  43  that supports an end of the fixing belt  20 . The surface of the inner support  41  may be rough while the surface of the side support  43  may be smooth, which may improve the difference in velocity between the rotation ring member  40  and the fixing belt  20 . 
     For the greater surface roughness of the inner support  41  than that of the side support  43 , a groove extending in parallel to a rotation axis direction of the fixing belt  20  may be provided, which may be included in the inner support  41  to be more specific. 
     Further, a plurality of protrusions  130  may be configured to reduce friction generated between the side support  43  of the rotation ring member  40  and a side of the stationary body  120  of the flange member  100  during rotation of the rotation ring member  40 . A plurality of protrusions  130  may be configured to prevent the side support  43  of the rotation ring member  40  from an entire plane-friction with the stationary body  120  of the flange member  100 . 
     In this case, the protrusions  130  may support the rotation ring member  40 , while being in line-contact with the side support  43  of the rotation ring member  40 . Accordingly, a plurality of protrusions  130  may stably support the side support  43  of the rotation ring member  40 , and minimize friction with the stationary body  120  of the flange member  100  during rotation of the rotation ring member  40 . 
     According to an example, operation of the fixing device  1  will be explained below. 
     When the pressing roller  10  is rotated, the fixing belt  20  in contact with the pressing roller  10  may be rotated by friction force with the pressing roller  10 . In this example, both ends of the fixing belt  20  may be supported by a pair of rotation ring members  40 . Further, a pair of rotation ring members  40  may be in the state of being inserted in the rotation ring support  110  of a pair of the flange members  100 . Accordingly, when the fixing belt  20  is subjected to the friction force from the rotating pressing roller  10 , the fixing belt  20  may be rotated, while being supported by the rotation ring support  110  of a pair of flange members  100  and a pair of rotation ring members  40 . 
     In this example, because the rotation ring members  40  according to an example are rotated in the inclined state with respect to the flange member  100 , the circularly-moving rotation ring members  40  do not meet the linearly-moving fixing belt  20  at a lower end where the fixing nip N is formed. Accordingly, little friction force is exerted by the rotation ring members  40  onto the ends of the fixing belt  20 . 
     Further, because the protrusions  130  are provided on the flange member  100  in the present disclosure, friction force between the rotation ring support  110  of the flange member  100  and the inner support  41  of the rotation ring members  40  is very little. 
     If the fixing belt  20  and the rotation ring members  40  do not rotate at same velocity and the fixing belt  20  performs relative movement with respect to the rotation ring members  40 , the relative velocity of the fixing belt  20  to the rotation ring members  40  is considerably slower than the relative velocity of the rotation ring member  40  rotating with respect to the rotation ring support  110  of the flange member  100 . Accordingly, fatigue crack generated from the rotation of the fixing belt  20  with respect to the flange member  100  may be reduced. 
     Printing service life has been tested in order to confirm life extension effect of the belt-type fixing device  1  according to an example. As a result, the fixing device  1  according to an example, when used, exhibited an effect of four times longer life extension than the related fixing device. Further, when the fixing device  1  according to an example is used, crack is not generated on the fixing belt  20 . 
       FIG. 6  is a side view of a flange member provided with a rotation ring member according to an example. 
     Referring to  FIG. 6 , when the rotation ring member  40  is inserted into the rotation ring support  110  of the flange member  100 , the rotation ring member  40  may be rotated with respect to the rotation ring support  110 . In this example, the rotation ring member  40  may be rotated with respect to a center of the rotation ring support  110  of the flange member  100  as a center of rotation. 
     The rotation ring member  40  may be inclined on the flange member  100  in which case the area opposite the contact area having the fixing nip N formed between the fixing belt  20  and the pressing roller  10  is relatively protruded than the contact area having the fixing nip N. In other words, the rotation ring member  40  may be inclined in which case it is further protruded on an upper end of the flange member  100  than on a lower end. 
     When the rotation ring member  40  is inserted into the rotation ring support  110  of the flange member  100 , the rotation ring member  40  may be rotated in the inclined state with respect to the flange member  100  by rotation of the fixing belt  20 . In this example, the circularly-moving rotation ring member  40  may not meet the linearly-moving fixing belt  20  at a lower end where the fixing nip N is formed. As the rotation ring member  40  is inclined and is thus less protruded on a portion where the fixing nip N is formed than the remainder portion, the force of the rotation ring member  40  may not be applied to the ends of the fixing belt  20 . Accordingly, the fixing belt  20  may be rotated without bending or fluttering. 
     The rotation ring member  40  may be supported in the inclined state by the protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f  protruded from the stationary body  120  of the flange member  100 . The first protrusion  130   a  may be most protruded on an upper end of the flange member  100 . The third protrusion  130   c  and the fifth protrusion  130   e , which are positioned nearer to the portion formed with the fixing nip N than the first protrusion  130   a , may be less protruded than the first protrusion  130   a  in that order. 
     Accordingly, when the rotation ring member  40  is inserted into the rotation ring support  110  of the flange member  100 , the rotation ring member  40  may be inclined by the presence of a plurality of protrusions  130   a ,  130   b ,  130   c ,  130   d ,  130   e ,  130   f , in which case an upper end may be relatively protruded than a lower end formed with the fixing nip N. 
     When the fixing belt  20  is rotated, the fixing belt  20  may perform a linear movement in a printing medium transfer direction A at a portion where the fixing nip N is formed, and the rotation ring member  40  that is rotated while supporting an inner surface of both ends of the fixing belt  20  may perform a circular movement. 
     In this example, as the rotation ring member  40  is inclined and the flange member  100  is further protruded at the upper end thereof than at the lower end, the rotation ring member  40  that is rotated while supporting both ends of the fixing belt  20  may not be brought into contact with the fixing belt  20  that is linearly moved in a printing medium transfer direction A, at the fixing nip N portion. In other words, the rotation ring members  40  are not brought into contact with a portion where the linear movement of the fixing belt  20  meets the circular movement of the rotation ring member  40 . Accordingly, the ends of the fixing belt  20  are not subjected to force. As a result, bending phenomenon and fluttering phenomenon of the fixing belt  20  may be reduced and difference in rotation velocity between the rotation ring member  40  and the fixing belt  20  during rotation may be decreased, and therefore, wearing phenomenon due to slip on the contact surface between the fixing belt  20  and the rotation ring member  40  may be decreased. 
       FIG. 7  is a front view of a flange member according to another example. 
     Referring to  FIG. 7 , the flange member  101  according to another example is similar to the flange member  100  described above. For example, the stationary body  120  and the rotation ring support  110  of the flange member  101  may be same as those of the flange member  100  described above. Accordingly, these elements will not be described repeatedly. 
     As illustrated in  FIG. 7 , one single protrusion  131  may be protruded on the flange member  101 . The protrusion  131  may be disposed nearer to an upper end opposite a lower end of the flange member  101  where the fixing nip N is formed. The protrusion  131  may be protruded convexely in a direction of facing the rotation ring member  40 . 
     The rotation ring member  40  may be inclined by the protrusion  131  formed on an upper end of the flange member  101 , in which case the rotation ring member  40  is further protruded at the upper end thereof than at the lower end. 
     Further, the protrusion  131  may extend laterally, in which case the rotation ring member  40  may be prevented from being tilted laterally. A front end of the protrusion  131  may be extended laterally to be stably in line-contact with the side support  43  of the rotation ring member  40 . In this case, the protrusion  131  may support the side support  43  of the rotation ring member  40  by line-contact. 
       FIG. 8  is a front view of a flange member according to another example. 
     Referring to  FIG. 8 , the flange member  102  according to another example is similar to the flange member  100  described above in terms of the fact that it  102  also includes the stationary body  120  and the rotation ring support  110 . 
     As illustrated in  FIG. 8 , the flange member  100  may include a friction reduction member  132  instead of the protrusions  130  protruding thereon. The friction reduction member  132  may be configured as a separate member between the rotation ring member  40  and the flange member  102 . The friction reduction member  132  may be formed from plastic mold or film, sponge, or fabric which can reduce friction. 
     The friction reduction member  132  may be formed in a circular arc shape that encloses the rotation ring support  110 . The friction reduction member  132  may be formed on a portion corresponding to a portion formed with the fixing nip N, except the lower end of the flange member  100 . 
     The rotation ring member  40  may be inclined by the friction reduction member  132 , in which case the rotation ring member  40  may be further protruded at the upper end than at the lower end. 
       FIG. 9  is a front view of a flange member according to another example. 
     Referring to  FIG. 9 , a plurality of friction reduction members  133   a ,  133   b ,  133   c ,  133   d ,  133   e ,  133   f  may be provided on a surface of the stationary body  120  of the flange member  100  to stably support the rotation ring member  40 . As illustrated in  FIG. 9 , six friction reduction members  133   a ,  133   b ,  133   c ,  133   d ,  133   e ,  133   f  may be provided on the stationary body  120  of the flange member  103 . 
     A plurality of friction reduction members  133   a ,  133   b ,  133   c ,  133   d ,  133   e ,  133   f  may be in contact with the rotation ring member  40 . In this example, the friction reduction members  133   a ,  133   b ,  133   c ,  133   d ,  133   e ,  133   f  may not be disposed in the fixing nip N area, but disposed in the remainder area, to support the rotation ring member  40  in an inclined state. 
     The portion where the friction reduction members  133   a ,  133   b ,  133   c ,  133   d ,  133   e ,  133   f  are not formed, may correspond to an area where the fixing belt  20  and the pressing roller  10  are in contact with each other, and specifically, to the lower end of the flange member  103 . 
       FIG. 10  is a brief cross-sectional view illustrating an image forming apparatus including a fixing device according to an example. 
     Hereinbelow, referring to  FIG. 10 , the image forming apparatus  200  including a belt-type fixing device  1  according to an example will be explained. 
     Referring to  FIG. 10 , the image forming apparatus  200  includes a main body  201 , a printing medium feed device  210 , an image forming device  220 , a belt-type fixing device  1 , and a discharge device  250 . 
     The main body  201  may form an appearance of the image forming apparatus  200 , and contain and support therein the printing medium feed device  210 , the image forming device  220 , the belt-type fixing device  1 , and the discharge device  250 . 
     The printing medium feed device  210  may be provided within the main body  201  and may supply the printing medium P to the image forming device  220 , and may include a feeding cassette  211  and a pickup roller  212 . A feeding cassette  211  may load a predetermined number of printing mediums and a pickup roller  212  may pick up the loaded the printing mediums from the feeding cassette  211  one by one to supply the same to the image forming device  220 . 
     A plurality of transfer rollers  215  to move the printing medium P picked up from the pickup roller  212  may be provided between the pickup roller  212  and the image forming device  220 . 
     The image forming device  220  is configured to form a predetermined image onto the printing mediums P supplied from the printing medium feed device  210  and may include an exposure device  221 , a developing cartridge  230 , and a transfer roller  240 . The exposure device  221  may emit a predetermined light corresponding to printing data according to a printing command. The developing cartridge  230  may be provided on one side of an image bearing member  231  on which electrostatic latent image is formed by the light generated from the exposure device  221 , and may include a developing roller  232  for developing the electrostatic latent image formed on the image bearing member  231  into a developer image by supplying a developer to the image bearing member  231 . Further, the developing cartridge  230  may store a predetermined developer, and include a developer supply roller  233  for supplying a developer to the developing roller  232 , or the like. The transfer roller  240  may be rotated while facing the image bearing member  231  of the developing cartridge  230 , and may transfer the developer image formed on the image bearing member  231  to the printing medium P. 
     The belt-type fixing device  1  may fix the developer image onto the printing medium P by applying heat and pressure, while the printing medium P transferred with the developer image is passed through the image forming device  220 . Because constitution and operation of the belt-type fixing device  1  are described above, it will not be specifically explained below. 
     The discharge device  250  is configured to discharge the printing medium P formed with image out of the image forming apparatus  200  after the printing medium is passed through the belt-type fixing device  1 , and may be formed with a pair of discharge rollers which are rotated while facing each other. 
     The belt-type fixing device  1  according to the example described above may fix a developer image transferred onto a printing medium P onto the printing medium P. Further, because both ends of the fixing belt  20  of the belt-type fixing device  1  according to an example may be supported by a pair of rotation ring members  40 , fatigue crack on both ends of the fixing belt  20  generated from rotation of the fixing belt  20  directly contacted with the flange member  100  may be minimized. 
     As described above, the present disclosure may be applied to S path-type image forming apparatus, and also C path-type image forming apparatus. 
     While the present disclosure has been particularly shown and described with reference to examples thereof, it is to be understood that the present disclosure is not limited to the examples thereof, it will be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure.