Patent Publication Number: US-9411272-B2

Title: Heating device, fixing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2014-152311 filed Jul. 25, 2014. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a heating device, a fixing device, and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided a heating device including: 
     a transparent endless pressurizing member that pressurizes a heating target; 
     a contact member that transmits light which is emitted from a light source to heat the heating target, and comes in contact with an inner circumferential surface of the pressurizing member; 
     a support member that supports the contact member within the pressurizing member; and 
     a reflection section that is provided between the contact member and the support member, and reflects light toward a side opposite to the support member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is an entire configuration diagram that schematically shows an image forming apparatus according to a first exemplary embodiment; 
         FIG. 2  is a schematic configuration diagram showing a fixing device according to the first exemplary embodiment; 
         FIG. 3  is an exploded view of major components of the fixing device according to the first exemplary embodiment; 
         FIG. 4A  is a longitudinal cross-sectional view showing an exploded state of the major components of the fixing device according to the first exemplary embodiment; 
         FIG. 4B  is a longitudinal cross-sectional view showing an assembled state of the major components of the fixing device according to the first exemplary embodiment; 
         FIG. 5  is an explanatory diagram showing the assembled state of the major components of the fixing device according to the first exemplary embodiment; 
         FIG. 6  is an explanatory diagram that schematically shows a state where laser beams are incident, scattered and reflected in the fixing device according to the first exemplary embodiment; 
         FIG. 7  is a graph representing a total absorptance by a lens wall surface and a reflectance of the lens wall surface according to the first exemplary embodiment; 
         FIG. 8A  is a longitudinal cross-sectional view showing an exploded state of major components of a fixing device according to a second exemplary embodiment; 
         FIG. 8B  is a longitudinal cross-sectional view showing an assembled state of the major components of the fixing device according to the second exemplary embodiment; 
         FIG. 9  is an explanatory diagram that schematically shows a state where laser beams are incident, scattered and reflected in the fixing device according to the second exemplary embodiment; 
         FIG. 10  is a schematic configuration diagram showing a fixing device according to a third exemplary embodiment; and 
         FIG. 11  is a schematic configuration diagram showing a fixing device according to a modification example. 
     
    
    
     DETAILED DESCRIPTION 
     [First Exemplary Embodiment] 
     Examples of a heating device, a fixing device and an image forming apparatus according to a first exemplary embodiment will be described. 
     Entire Configuration 
       FIG. 1  shows an image forming apparatus  10  according to the first exemplary embodiment. The image forming apparatus  10  includes, for example, a transport unit  12  that transports sheet P, an image forming unit  14  that forms a toner image G by using toner T on the transported sheet P, and a fixing device  20  that fixes the toner image G on the sheet P. The sheet P is an example of a recording medium. The toner T is an example of a developer and a heating target. The toner image G is an example of a developer image. The image forming unit  14  is an example of a developer image forming unit. The image forming unit  14  is configured to perform a charging process, an exposing process, a developing process, a transferring process and a cleaning process. 
     Configuration of Major Components 
     Next, the fixing device  20  will be described. 
     As shown in  FIG. 2 , the fixing device  20  includes a facing roll  22  as an example of a transport unit that transports the sheet P to which the toner T adheres, and a heating unit  30  as an example of a heating device that irradiates the toner T on the sheet P with laser beams Bm as an example of light to heat the toner T. 
     Facing Roll 
     The facing roll  22  is, for example, a housing made from stainless steel, and is disposed such that a predetermined pressurizing force acts between the facing roll and a transparent tube  44 , to be described below. The facing roll  22  is driven to be rotated by, for example, a non-illustration gear and motor, and is configured such that the sheet P interposed between the transparent tube  44  and the facing roll is transported. 
     Heating Unit 
     A pressurizing member used in the present exemplary embodiment has an endless shape and a rotatable shape. The endless shape includes a cylindrical shape and a hollow shape. As shown in  FIG. 2 , the heating unit  30  includes the transparent tube  44  as an example of the pressurizing member, a light irradiation unit  32  as an example of a light source, a lens pad  34  as an example of a contact member, and support frames  36  and  38  as examples of support members that support the lens pad  34 . The heating unit  30  includes a reflection film  42  as an example of a reflection section, and a liquid coating unit that coats an inner circumferential surface of the transparent tube  44  with a transparent liquid. 
     Light Irradiation Unit 
     The light irradiation unit  32  includes a laser array  52 , and a collimating lens  54 . Plural laser light sources  56  are arranged in the laser array  52 . The collimating lens  54  is an optical member that renders each laser beam Bm emitted from each laser light source  56  into parallel light. 
     Lens Pad 
     The lens pad  34  is an elongated lens member that extends in a longitudinal direction of the laser array  52 . As the material of the lens pad  34 , a heat-resistant material may be generally selected among materials used for a lens, and an optical transparent plastic resin may be used. As the optical transparent plastic resin, a material that contains poly(diethylene glycol bis(allyl carbonate)) (PADC), and polymethyl methacrylate (PMMA), polystyrene (PSt) is used. As the optical transparent plastic resin, a material that contains a polymer (MS resin) consisting of a methyl methacrylate unit and a styrene unit, polycarbonate resin, cycloolefin resin, and fluorene resin is used. 
     The lens pad  34  transmits the plural laser beams Bm from the laser array  52 , and condenses the laser beams toward a transmission direction. The lens pad  34  is disposed such that an optical axis K is located in a center in a transport direction of the sheet P. 
     In the following description, for example, a longitudinal direction of the laser array  52  is described as a Z direction, a direction which is perpendicular to the Z direction and in which the laser beams Bm are applied is described as a Y direction, and a direction which is perpendicular to the Z direction and the Y direction and in which the sheet P is transported is described as an X direction. A rotation direction of the transparent tube  44  is described as an R direction. When it is necessary to distinguish one side of the X direction, the Y direction, or the Z direction from the other side thereof, in a front view along the longitudinal direction of the lens pad  34 , an upper side is described as a Y side, a lower side is described as a −Y side, a right side is described as an X side, a left side is described as a −X side, a back side is described as a Z side, and a front side is described as a −Z side. 
     As shown in  FIG. 3 , the lens pad  34  includes a light incident surface  34 A, and a light emission surface  34 B. The light incident surface  34 A is formed in a convex arc shape on the Y side when viewed in the Z direction, is disposed in a light incident region of the transparent tube  44 , and comes in contact with the inner circumferential surface of the transparent tube  44 . 
     The light emission surface  34 B is formed in a convex arc shape on the −Y side when viewed in the Z direction, is disposed in a light emission region of the transparent tube  44 , and comes in contact with the inner circumferential surface of the transparent tube  44 . In the present exemplary embodiment, for example, it is assumed that a portion where the light emission surface  34 B and the transparent tube  44  come in contact with each other is a contact portion N (see  FIG. 2 ). 
     The lens pad  34  includes side surfaces  34 C along a Z-Y surface between the light incident surface  34 A and the light emission surface  34 B. Positioning grooves  34 D whose cross sections have a rectangular shape and are recessed from the side surfaces  34 C by one step are integrally formed on parts of the side surfaces  34 C. The lens pad  34  is supported and held within the transparent tube  44  through the support frames  36  and  38 . 
     Support Frame 
     As shown in  FIG. 3 , the support frame  36  is, for example, an elongated member which is long in the Z direction, and includes a semi-circular guide portion  36 A that protrudes toward the −X side when viewed in the Z direction, and a rectangular convex portion  36 B that protrudes toward the X side from a portion of the −Y side rather than a center of the guide portion  36 A in the Y direction. The support frame  36  is made from a material that absorbs the laser beams Bm (see  FIG. 2 ), and is made from, for example, stainless steel. 
     The guide portion  36 A includes a curved surface  36 D disposed on the −X side when viewed in the Z direction, and a flat surface  36 E disposed on the X side. The curved surface  36 D has a radius corresponding to a radius of the inner circumferential surface of the transparent tube  44 . A concave portion  36 C that is opened to the −X side is formed in a portion of the curved surface  36 D. The liquid coating unit  46  is received in the concave portion  36 C. 
     The convex portion  36 B has a size capable of being fitted into the positioning groove  34 D on the −X side of the lens pad  34 . By fitting the convex portion  36 B into the positioning groove  34 D, the lens pad  34  is positioned in the support frame  36 . Although the detailed description will be described below, the reflection film  42  is formed on surfaces of the flat surface  36 E and the convex portion  36 B. 
     For example, the support frame  38  has the same configuration (material, shape, and size) as those of the support frame  36  except for the concave portion  36 C. For this reason, some parts of the support frame  38  will be assigned the same reference numerals as those of the support frame  36 , and the description thereof will not be described. The convex portion  36 B of the support frame  38  has a size capable of being fitted into the positioning groove  34 D on the X side of the lens pad  34 . The reflection film  42  is formed on surfaces of the flat surface  36 E and the convex portion  36 B of the support frame  38 . 
     Here, the lens pad  34 , the support frame  36  and the support frame  38  have a cylindrical shape as a whole in an assembled state. Thus, the lens pad  34 , the support frame  36  and the support frame  38  may be arranged inside the transparent tube  44 . The support frame  36  and the support frame  38  support the lens pad  34  within the transparent tube  44 . 
     Holding Member 
     As shown in  FIG. 3 , a holding member  64  is provided at ends of the support frame  36  and the support frame  38  on the Z side, and a holding member  66  is provided at ends of the support frame  36  and the support frame  38  on the −Z side. For example, since the holding member  64  and the holding member  66  have the same configuration, the holding member  66  will be described, and the holding member  64  will not be described. 
     The holding member  66  includes, for example, a cylindrical lid  66 A with the Z direction as an axial direction, a stepped portion  66 B that protrudes toward the −Z side from a center of the lid  66 A and has a diameter smaller than the lid  66 A, and a prismatic supporting shaft  66 C that protrudes from the stepped portion  66 B toward the −Z side. The supporting shaft  66 C protrudes toward the Z side or the −Z side from an end cap  72  to be described below, and is supported by a non-illustration bracket. 
     Transparent Tube 
     In the present exemplary embodiment, the term “transparent” of the transparent tube  44  means that a transmittance is sufficiently high in a wavelength region of the laser beams Bm. That is, any transparent tube may be used as long as the transparent tube  44  transmits the laser beams Bm. In order to improve light utilization efficiency or in order to suppress heating of the lens pad  34 , the higher a transmittance is, the better the transparent tube is. The transmittance may be, for example, 90[%] or more, and preferably, 95[%] or more. 
     The transparent tube  44  includes, for example, a base material layer for maintaining a required strength, an elastic layer laminated on the base material layer, and a releasing layer laminated on the elastic layer. The base material layer, the elastic layer and the releasing layer will not be shown. The transparent tube  44  is not limited to a three-layer structure. 
     Examples of a material of the base material layer include polyvinylidene fluoride (PVDF), polyimide (PI), polyethylene (PE), polyurethane (PU), and polydimethylsiloxane (PDMS). Examples of the material of the base material layer include polyetheretherketone (PEEK), polyethersulfone (PES), fluorinated ethylene propylene (FEP), and ethylene tetrafluoroethylene copolymer (ETFE). Examples of the material of the base material layer include chlorotrifluoroethylene (CTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and polytetrafluoroethylene (PTFE). The base material layer may be made from a material selected from a group consisting of mixtures of the aforementioned materials. 
     The elastic layer is made from LSR silicone rubber, HTV silicone rubber or RTV silicone rubber, and any elastic layer may be used as long as the elastic layer transmits the laser beams Bm and has elasticity that absorbs unevenness of the sheet P or a difference in grade of the toner image G. 
     The releasing layer is made from fluororesin, for example, tetrafluoroethylene copolymer (PTFE), tetrafluoroethylene-perfluoroalkoxy ethylene copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Any releasing layer may be used as long as the releasing layer transmits the laser beams Bm and prompts the transparent tube  44  to be released from the toner image G formed on the sheet P. The releasing layer has a function of providing a desirable glossiness to the fixed image (toner image G) by cooperating with the elastic layer. 
     End Cap 
     The end caps  72  are respectively provided on the Z side and the −Z side of the transparent tube  44 . The end cap  72  on the −Z side is not shown in  FIG. 3 . 
     Each of the end caps  72  includes a cylindrical portion  72 A that is fitted into the inner circumferential surface of the transparent tube  44  on the Z side or the inner circumferential surface on the −Z side, and a gear  72 B that is integrally provided on one side of the cylindrical portion  72 A in the Z direction. The stepped portion  66 B is inserted into the cylindrical portion  72 A. While the stepped portion  66 B is inserted into the cylindrical portion  72 A, the end caps  72  and the transparent tube  44  are relatively moved (are rotatably moved) with respect to the holding members  64  and  66 . The gear  72 B is driven to be rotated by a non-illustration motor, and supplies rotation driving force to the transparent tube  44 . 
     As described above, for example, the facing roll  22  and the transparent tube  44  shown in  FIG. 2  respectively include independent driving sources, but a non-illustration one-way clutch is provided at any one of the facing roll and the transparent tube. 
     Liquid Coating Unit 
     As shown in  FIG. 2 , the liquid coating unit  46  is made from, for example, a felt material, and comes in contact with the inner circumferential surface of the transparent tube  44 . Silicone oil as an example of a transparent liquid is infiltrated into the liquid coating unit  46 . Thus, the inner circumferential surface of the transparent tube  44  is coated with the silicone oil by rotating the transparent tube  44 . 
     Reflection Film 
     Next, the reflection films  42  will be described. 
     The reflection films  42  shown in  FIG. 4A  are made from, for example, white paint containing fine particles of titanium oxide. Surfaces of the convex portions  36 B and surfaces of the flat surfaces  36 E of the support frames  36  and  38  are coated with the reflection films  42 . The material of the reflection film  42  is not limited to the titanium oxide, and may be selected from materials having characteristics that reflect the laser beams Bm of the light irradiation unit  32  (see  FIG. 2 ). 
     As shown in  FIG. 4B , the convex portions  36 B of the support frames  36  and  38  are fitted into the positioning grooves  34 D of the lens pad  34 . Thus, the reflection films  42  are formed between the optical axis K and the support frames  36  and  38 . In other words, the reflection films  42  are formed on the surfaces of the support frames  36  and  38  close to the lens pad (that is, a side close to the optical axis K). 
     As shown in  FIGS. 3 and 5 , after the lens pad  34  is held by the support frames  36  and  38 , the lens pad  34  on the Z side and the −Z side is held by the holding members  64  and  66 . The liquid coating unit  46  (see  FIG. 3 ) is attached to the concave portion  36 C. Subsequently, these members are inserted into the transparent tube  44 , and the end caps  72  are respectively attached to both ends of the holding members  64  and  66  and the transparent tube  44 . Thereafter, the transparent tube is supported by the non-illustration bracket, and, thus, the transparent tube  44  may be rotatably supported. 
     Operation 
     Next, an operation of the first exemplary embodiment will be described. 
     As shown in  FIG. 2 , in the heating unit  30 , the laser beams Bm emitted from the light irradiation unit  32  are transmitted through the transparent tube  44 , and are incident on the light incident surface  34 A of the lens pad  34 . The laser beams Bm incident on the light incident surface  34 A are condensed in the lens pad  34 , are transmitted through the light emission surface  34 B and the transparent tube  44 , and are applied to the toner T on the sheet P during the transporting. The toner T (toner image G) on the sheet P is heated and melted by absorbing the condensed laser beams Bm, and is fixed on the sheet P by receiving pressurizing force F from the facing roll  22 . 
     As shown in  FIG. 6 , among the laser beams Bm incident on the lens pad  34 , laser beams which are not absorbed by the toner T are scattered on the sheet P to become scattered light beams A (indicated by arrow A). Among the scattered light beams A, some scattered light beams travel toward the support frames  36  and  38 . Here, since the reflection films  42  are formed on the support frames  36  and  38 , the scattered light beams A traveling toward the support frames  36  and  38  are reflected toward opposite sides to the support frames  36  and  38  by the reflection films  42  to become reflected light beams B (indicated by arrow B). The reflected light beams travel in the lens pad  34 . Thus, since the scattered light beams A are prevented from being absorbed by the support frames  36  and  38 , temperatures of the support frames  36  and  38  are prevented from increasing. The convex portions  36 B of the support frames  36  and  38  (see  FIG. 4A ) are not shown in  FIG. 6 . 
       FIG. 7  shows graphs G 1 , G 2  and G 3  that represent a relationship between a reflectance of a lens wall surface and a total absorptance by the lens wall surface. The reflectance of the lens wall surface refers to a ratio of an amount of the laser beams Bm reflected from the reflection films  42  to an amount of the laser beams Bm incident on the reflection films  42  (see  FIG. 2 ). A unit of the reflectance of the lens wall surface is denoted by %. The reflectance of the lens wall surface refers to a reflectance of single reflection in the reflection film  42 . 
     The total absorptance by the lens wall surface is a ratio of an amount of the laser beams Bm absorbed by the support frames  36  and  38  to a total amount of the laser beams Bm incident on the lens pad  34 . A unit of the total absorptance by the lens wall surface is denoted by %. 
     It is assumed that an opening width of the light incident surface  34 A of the lens pad  34  shown in  FIG. 6  in the X direction is d. The opening width d is a space between the reflection films  42  facing each other in the X direction. It is assumed that a height of the lens pad  34  in the Y direction is h. Here, in  FIG. 7 , the graph G 1  represents a result when d=15 [mm] and h=30 [mm], the graph G 2  represents a result when d=10 [mm] and h=30 [mm], and the graph G 3  represents a result when d=5 [mm] and h=30 [mm]. 
     As may be seen from the graphs G 1 , G 2  and G 3  shown in  FIG. 7 , when the reflectance of the lens wall surface is increased, the total absorptance by the lens wall surface is decreased. Even with the same reflectance of the lens wall surface, as the opening width d (see  FIG. 6 ) becomes wide, the total absorptance by the lens wall surface is decreased. This is because as the opening width d becomes wide, the number of times the laser beams Bm (see  FIG. 6 ) are incident on the lens wall surface decreases. 
     Here, for example, in the graph G 2 , when the reflectance of the lens wall surface is 70[%], the total absorptance by the lens wall surface is approximately 40[%]. When the reflectance of the lens wall surface is 95[%], the total absorptance by the lens wall surface is approximately 10[%]. That is, when the reflectance of the reflection film  42  (see  FIG. 2 ) is set to 95[%], an absorbing amount of the scattered light beams A (see  FIG. 6 ) is approximately a quarter of that in the case where the reflectance is 70[%]. Since a difference between the absorbing amounts becomes a difference between temperature rises of the support frames  36  and  38  (see  FIG. 2 ), when the reflection film  42  having a reflectance of 95[%] is used, the temperature rises of the support frames  36  and  38  are suppressed compared to the case where the reflection film  42  having a reflectance of 70[%] is used. 
     As shown in  FIG. 4A , in the heating unit  30 , the reflection films  42  are formed on the support frames  36  and  38  through coating, and are integrally formed with the support frames  36  and  38 . For this reason, positions of the reflection film  42  are prevented from being deviated from the support frames  36  and  38  compared to the case where the reflection films  42  and the support frames  36  and  38  are separately provided. Since the positions of the reflection film  42  are prevented from being deviated, the scattered light beams A (see  FIG. 6 ) are prevented from being incident on the support frames  36  and  38 , and the temperature rises of the support frames  36  and  38  are suppressed. 
     In the fixing device  20  shown in  FIG. 2 , since the laser beams Bm are reflected from the reflection film  42 , the temperature rises of the support frames  36  and  38  are suppressed. For this reason, the support frames  36  and  38  are prevented from heating the transparent tube  44  and the sheet P to more than a set temperature, and the toner T is prevented from being heated (overheated) to more than the set temperature. Thus, since adhesion force of the sheet P and the toner T to the transparent tube  44  is prevented from increasing, fixing failure of the toner image G on the sheet P caused by the overheating of the toner T by the transparent tube  44  is suppressed. 
     In the image forming apparatus  10  shown in  FIG. 1 , since the fixing failure of the toner image G in the fixing device  20  is suppressed, an image defect caused by the fixing failure is suppressed. 
     [Second Exemplary Embodiment] 
     Next, examples of a heating device, a fixing device and an image forming apparatus according to a second exemplary embodiment will be described. Components and portions that are basically the same as those in the first exemplary embodiment are assigned the same reference numerals as those in the first exemplary embodiment, and the description thereof will not be described. 
       FIG. 8A  shows reflection films  82  according to the second exemplary embodiment. The second exemplary embodiment has a difference from the first exemplary embodiment in that the reflection films  82  are formed instead of the reflection films  42  (see  FIG. 2 ) in the image forming apparatus  10 , the fixing device  20  and the heating unit  30  according to the first exemplary embodiment (see  FIG. 1 ), and other configurations are the same as those in the first exemplary embodiment. 
     The reflection films  82  shown in  FIG. 8A  are made from, for example, aluminum. The reflection films  82  are deposited on the surfaces of the side surfaces  34 C of the lens pad  34  and the surfaces of the positioning grooves  34 D by using a known metal deposition method. The material of the reflection film is not limited to aluminum, and may be selected from materials having characteristics that reflect the laser beams Bm (see  FIG. 2 ) of the light irradiation unit  32  (see  FIG. 2 ). The surface of the deposited reflection film  82  approaches a mirror surface state. 
     As shown in  FIG. 8B , the convex portions  36 B of the support frames  36  and  38  are fitted into the positioning grooves  34 D of the lens pad  34 . Thus, the reflection films  82  are formed between the support frames  36  and  38  and the lens pad  34 . In other words, the reflection films  82  are formed on the surfaces of the lens pad  34  close to the support frames  36  and  38 . 
     Operation 
     Next, an operation of the second exemplary embodiment will be described. 
     As shown in  FIG. 9 , some scattered light beams A travel toward the support frames  36  and  38 . Here, since the reflection films  82  are formed on the support frames  36  and  38 , the scattered light beams A traveling toward the support frames  36  and  38  are reflected toward opposite sides to the support frames  36  and  38  by the reflection films  82  to become reflected light beams B. The reflected light beams travel in the lens pad  34 . Thus, since the support frames  36  and  38  are prevented from absorbing the scattered light beams A to be overheated, the temperature rises of the support frames  36  and  38  are suppressed. The convex portions  36 B of the support frames  36  and  38  (see  FIG. 8A ) are not shown in  FIG. 9 . 
     As shown in  FIG. 8A , in the heating unit  30 , the reflection films  82  are formed by being deposited on the lens pad  34 , and are integrated with the lens pad  34 . For this reason, compared to the case where the reflection film  82  and the support frames  36  and  38  are separately provided, the positions of the reflection film  82  are prevented from being deviated from the support frames  36  and  38 . Thus, the scattered light beams A (see  FIG. 9 ) are prevented from being incident on the support frames  36  and  38 , and the temperature rises of the support frames  36  and  38  are suppressed. 
     [Third Exemplary Embodiment] 
     Next, examples of a heating device, a fixing device and an image forming apparatus according to a third exemplary embodiment will be described. Components and portions that are basically the same as those in the first exemplary embodiment are assigned the same reference numerals as those in the first exemplary embodiment, and the description thereof will not be described. 
       FIG. 10  shows a heating unit  90  as an example of the heating device according to the third exemplary embodiment. The third exemplary embodiment is different from the first exemplary embodiment in that the heating unit  90  is provided instead of the heating unit  30  in the image forming apparatus  10 , the fixing device  20  and the heating unit  30  (see  FIG. 1 ), and other configurations are the same as those in the first exemplary embodiment. The heating unit  90  has a difference from the heating unit  30  according to the first exemplary embodiment in that a cover member  92  as an example of an absorbing member is added, and other configurations are the same as those in the first exemplary embodiment. 
     The cover member  92  is, for example, a member with the Z direction as a longitudinal direction and the X direction as a lateral direction, and an X-Y cross section thereof has a semi-circular shape. A through hole  93  through which the laser beams Bm pass is formed in the cover member  92 . The through hole  93  is a hole that has a width in the X direction greater than a beam diameter of the laser beams Bm and extends in the Z direction. The cover member  92  is made from, for example, aluminum, and a black alumite process is performed on a surface of the cover member disposed to face the transparent tube  44 . The process on the surface disposed to face the transparent tube  44  of the cover member  92  is not limited to the black alumite process, and may be selected from processes using materials having characteristics that absorb the laser beams Bm. 
     The cover member  92  has a convex shape on the Y side, faces the transparent tube  44  in a diametrical direction of the transparent tube  44 , and is disposed between the light irradiation unit  32  and the transparent tube  44  such that the through hole  93  does not block traveling of the laser beams Bm. The cover member  92  covers the transparent tube  44  when viewed in the Y direction. 
     Operation 
     Next, an operation of the third exemplary embodiment will be described. 
     In the heating unit  90  shown in  FIG. 10 , among the laser beams Bm incident on the lens pad  34 , scattered light beams (not shown) scattered from the sheet P travel toward the support frames  36  and  38 , and are reflected from the reflection films  42  to become reflected light beams B. The reflected light beams travel in the lens pad  34 . The reflected light beams B travel from an opening end (the Y side in the drawing) of the lens pad  34  toward the outside. 
     Here, since the cover member  92  is provided in a traveling direction of the reflected light beams B, the reflected light beams B are absorbed by the cover member  92 . Thus, the light beams reflected from the sheet P are prevented from being incident on a member other than the cover member  92  within the fixing device  20  (heating unit  90 ). Since the reflected light beams B are prevented from being incident on the member other than the cover member  92  within the fixing device  20  and being reflected toward the support frames  36  and  38  again, the toner T is prevented from being overheated by the reflected light beams B traveling toward the outside of the lens pad  34 . 
     The present invention is not limited to the aforementioned exemplary embodiments. 
     MODIFICATION EXAMPLE 
     As in the fixing device  20  shown in  FIG. 2 , the fixing device is not limited to the device using the transparent tube  44 , but may be a fixing device  100  having a heating unit  110  as an example of the heating device as shown in  FIG. 11 . The fixing device  100  includes the heating unit  110 , and the facing roll  22 . 
     The heating unit  110  includes the light irradiation unit  32 , a lens pad  114  as an example of the contact member, support frames  116  and  118  as examples of the support members that support the lens pad  114 , and reflection films  122  as an example of the reflection section. The heating unit  110  includes a fixing belt  124  as an example of the pressurizing member. 
     The fixing belt  124  is made from a material that transmits the laser beams Bm, and is held by plural support rolls  126  to be circulated. The light irradiation unit  32  is disposed inside the fixing belt  124 . 
     The lens pad  114  transmits the laser beams Bm and condenses the laser beams toward the transmission direction. The lens pad  114  includes a light incident surface  114 A on which the laser beams Bm are incident, and a light emission surface  114 B from which the laser beams Bm are emitted. The light emission surface  114 B comes in contact with an inner circumferential surface of the fixing belt  124 . The lens pad  114  is supported by the support frames  116  and  118 . 
     The reflection films  122  are made from, for example, white paint containing fine particles of titanium oxide, and are formed on surfaces of the support frames  116  and  118  close to the lens pad  114  through coating. Lower surfaces of the support frames  116  and  118  are also coated with the reflection films  122 . The lower surfaces of the support frames  116  and  118  are surfaces facing the fixing belt  124 . 
     Here, in the fixing device  100  and the heating unit  110 , since the laser beams Bm are reflected from the reflection films  122 , the temperature rises of the support frames  116  and  118  are suppressed. Thus, since the support frames  116  and  118  are prevented from overheating the fixing belt  124 , adhesion force of the sheet P to the fixing belt  124  is prevented from increasing, and the fixing failure of the toner image G on the sheet P caused by the overheating of the toner T by the fixing belt  124  is suppressed. 
     ANOTHER MODIFICATION EXAMPLE 
     The heating unit  30  or  110  is not limited to the fixing device  20  or  100  that fixes the toner T on the sheet P. For example, the heating unit  30  or  110  may preliminarily heat a liquid developer adhering to the sheet P by a liquid developing method before the fixing. The heating unit  30  or  110  may be used as a drying device for removing moisture in the sheet P. 
     The support frames  36  and  38  or the support frames  116  and  118  are not limited to the pair of two support frames. One support frame or plural (for example, three or more) support frames may be used. The support frames  36  and  38  or the support frames  116  and  118  may have a shape different from that in the aforementioned exemplary embodiments as long as the support frames have surfaces coming in contact with the lens pad  34  or  114 . 
     The lens pad  34  or  114  is not limited to one lens pad, and plural lenses arranged at a space in an optical axial direction may be used. 
     As mentioned above, the material of the reflection film is not limited to aluminum or white paint containing titanium oxide as long as the reflection films  42 ,  82  or  122  reflect the laser beams Bm. For example, the reflection film may be made from gold. The reflection section is not limited to the reflection films  42 ,  82  or  122  formed on the surfaces of the members, and a member that is independently disposed from the contact member and the support members may be used such as a reflection plate. 
     The cover member  92  may be provided on the heating unit  30  according to the second exemplary embodiment or the heating unit  110  according to the modification examples in addition to the heating unit  30  according to the first exemplary embodiment. 
     The facing roll  22  may be made from aluminum or another metal as well as from stainless steel. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.