JP2016090765A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that can suppress an increase in temperature at the ends without using a machine configuration.SOLUTION: There is provided an image heating device including 40 conveying, while holding, a sheet P carrying a toner image T at a nip part N to heat the toner image, and including: a cylindrical first rotor 41; a slide-contact member 46 that is fixedly provided to be in slide-contact with an inner face of the first rotor; a heating element 43 that is fixedly provided on the inside of the first rotor; a reflecting member 42 that is fixedly provided on the inside of the first rotor and reflects radiation heat from the heating element to the inner face of the first rotor; and a second rotor 44 that is in contact with the slide-contact member with the first rotor therebetween to form a nip part N with the first rotor, where when the angle from the horizontal direction of a lateral face 47 at the center part 42a in the longitudinal direction of the reflecting member with respect to a transverse section of the reflecting member is α, and the angle from the horizontal direction of the lateral face 47 at both ends in the longitudinal direction is β, the relationship α>β is satisfied.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine, a printer, a fax machine, or a multifunction machine thereof.

  Various types of fixing devices that heat and fix an unfixed toner image carried on a sheet (hereinafter referred to as paper) as a recording medium as a fixed image are known.

  Patent Documents 1 and 2 disclose an on-demand fixing device with a short warm-up time. An on-demand fixing device includes an endless fixing belt (fixing film) as a fixing member, a pressure roller as a rotating body, a heater as a fixed member, and the like. The heater is installed inside the fixing belt, presses against the pressure roller via the fixing belt to form a nip portion, and heats the fixing belt at the position of the nip portion. The toner image on the paper conveyed toward the nip portion is fixed by receiving heat and pressure at the nip portion.

  Patent Document 3 discloses a fixing device using a fixing belt (endless belt) in which a heating unit (halogen lamp) is provided as a fixing member and using a pressure roller. Specifically, a pressure member (pressure pad) as a fixing member is fixed so as to be in sliding contact with the inner peripheral surface of the fixing belt while being urged toward the nip portion by a spring. As a result, the pressure member is pressed against the pressure roller via the fixing belt to form a nip portion. The toner image on the paper conveyed toward the nip portion is fixed by receiving heat and pressure at the nip portion.

  Here, in the fixing device, a non-sheet-passing rise that occurs when a sheet (small size sheet) having a sheet passing width smaller than the maximum sheet passing width that can be introduced and used is continuously passed and heat fixing is performed. Temperature (edge temperature rise) occurs. That is, when small-size paper is continuously fed, heat consumed for heating the paper is compensated by the temperature control system at the fixing belt and the pressure roller, and maintained at a predetermined temperature. On the other hand, in the non-sheet passing portion, heat is not consumed due to heating of the sheet but is stored, and the temperature of the non-sheet passing portion is higher than that of the sheet passing portion maintained at a predetermined temperature. .

  In order to suppress this non-sheet-passing temperature rise (edge temperature rise), Patent Document 3 discloses that a heat amount adjusting member is disposed between the halogen heater and the fixing belt, and the amount of radiant heat supplied from the heater to the fixing belt is reduced. A technique for changing according to the paper size is shown.

JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP 2010-032973 A

  As an advantage of the belt (film) type fixing device, there is a reduction in warm-up time due to a low heat capacity of the fixing member. However, in the fixing device using a halogen heater as a heat source, as disclosed in Patent Document 3, the technique of changing the lighting ratio of the halogen heater between the longitudinal central portion and the end portion is a paper size. However, there is a problem that the response is not good.

  An object of the present invention is to solve the above-mentioned problems, and is to provide an image heating apparatus that can suppress the temperature rise at the end without using a mechanical configuration.

  In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention is an image heating apparatus that heats a toner image by sandwiching and conveying a sheet carrying a toner image at a nip portion. A first rotating body, a sliding contact member fixed so as to be in sliding contact with the inner surface of the first rotating body, a heating element fixed inside the first rotating body, and the first A reflecting member that is fixed inside the rotating body and reflects radiant heat from the heating element toward the inner surface of the first rotating body, and abuts against the sliding contact member via the first rotating body. A second rotator that forms the nip portion with the first rotator, and the angle from the horizontal direction of the side surface at the longitudinal center of the reflecting member with respect to the cross section of the reflecting member. If α is the angle from the horizontal direction of the side surface at both ends of the longitudinal axis, β satisfies the relationship α> β. The features.

  ADVANTAGE OF THE INVENTION According to this invention, edge part temperature rising can be suppressed, without using a machine structure.

FIG. 3 is an enlarged schematic cross-sectional view of a main part of the fixing device in the embodiment. 1 is a schematic diagram of an image forming apparatus in an embodiment. FIG. 3 is a longitudinal front view of the main part of the fixing device, omitting midway parts. It is a disassembled perspective view of a heating unit. FIG. 3 is a schematic diagram of a layer configuration of a fixing belt. It is a perspective view of a reflecting plate. It is composition explanatory drawing of the longitudinal center part of a reflecting plate. It is composition explanatory drawing of the longitudinal end part of a reflecting plate. It is explanatory drawing of the fixing belt longitudinal temperature distribution in an Example and a comparative example.

  Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.

[Example]
(1) Image Forming Unit FIG. 2 is a schematic configuration diagram of an example of the image forming apparatus 1 in which the image heating apparatus according to the present invention is mounted as the fixing device 40. This image forming apparatus 1 is an intermediate transfer type, tandem four-color full-color electrophotographic laser printer, which can form a full-color toner image on a sheet P and print it out. The sheet P is a recording material (recording medium) on which a toner image can be formed, and examples thereof include plain paper, glossy paper, resin sheet, cardboard, postcard, envelope, and OHP sheet. Hereinafter referred to as paper. Since the printer configuration other than the fixing device 40 is known, only the following printer configuration will be briefly described.

  An image forming unit 2 includes four image forming units 3 (3Y, 3M, 3C, 3K) and an intermediate transfer belt unit 10. Each image forming unit 3 includes a rotating drum type photosensitive member 4, a charging member 5, a laser scanner 6, a developing device 7, a primary transfer member 8, a photosensitive member cleaner 9, and the like, and includes yellow (Y) color, magenta (M), cyan (C), and black (K) toner images are formed. Then, the four color toner images are sequentially superposed on the intermediate transfer belt 11 from the photoreceptor 4 of each image forming unit 3 in a predetermined manner and primarily transferred to form a full color toner image on the intermediate transfer belt 11. .

  The full-color toner image is secondarily transferred onto the paper P at a secondary transfer nip portion that is a pressure contact portion between the intermediate transfer belt 11 and the secondary transfer roller 12. The sheet P is separated and fed from the sheet cassette 19 or 20 or the multi-feed tray 21 and is introduced into the secondary transfer nip portion from the transport mechanism 22 including the registration roller pair 22a at a predetermined control timing. Then, the paper P that has undergone the secondary transfer of the toner image is introduced into the fixing device 40 and undergoes heat-pressure fixing of the toner image.

  The paper P exiting the fixing device 40 is routed to the first path 14 side or the second path 15 side by the flapper 13 according to the mode selection in advance. The paper P introduced into the first path 14 is discharged to the face down tray 16 on the upper surface side of the apparatus. The paper P introduced into the second path 15 is discharged to the face-up tray 17 on the side surface side of the apparatus.

  In the double-sided image forming mode, the first-side image-formed paper P that has exited the fixing device 40 is once introduced into the first path 14 and then switched back and introduced into the third path (recirculation path) 18. Is done. Then, it is conveyed again through the conveying mechanism 22 in a state where the front and back are reversed with respect to the secondary transfer nip portion of the image forming unit 2. As a result, the paper on which the double-sided image is formed is discharged to the face-down tray 16 or the face-up tray 17.

  In the image forming apparatus 1 of the present example, the conveyance of the paper P in the apparatus is performed by so-called central reference conveyance. This paper transport is a form in which the center line in the width direction of the paper is aligned with the center in the width direction of the paper transport path regardless of the width of the paper that can be used (passable) in the apparatus. That is.

(2) Fixing Device (2-1) Overall Schematic Configuration The fixing device 40 of this embodiment is an image heating device of a belt heating method and a pressure roller driving method (tensionless type). FIG. 1 is an enlarged schematic cross-sectional view of the main part of the fixing device 40, and FIG.

  Here, in this embodiment, regarding the fixing device 40 or its constituent members, the front side is a surface viewed from the paper inlet side, the back surface is the opposite surface (paper outlet side), and the left and right sides are the front of the device. Left (one end side) or right (the other end side) when viewed from the side. Up and down are up or down in the direction of gravity. The upstream side and the downstream side are the upstream side and the downstream side in the paper transport direction a. The longitudinal direction (or the width direction) and the paper width direction are directions substantially parallel to the direction orthogonal to the paper transport direction a on the paper transport path surface. The short direction is a direction substantially parallel to the paper transport direction a on the paper transport path.

  The fixing device 40 includes a heating unit (belt unit) 4A including a fixing belt (fixing member: endless belt) 41 as a cylindrical (endless) first rotating body. Further, a pressure roller 44 is provided as a second rotating body that forms a nip portion N between the fixing belt 41 and sandwiches and conveys the paper P carrying the toner image T. Moreover, it has the housing | casing 60 which accommodated them.

  FIG. 4 is an exploded perspective view of the heating unit 4A. The heating unit 4A includes a cylindrical flexible fixing belt 41, a pressing member (pressure member, pressure pad, backup member) 46 as a sliding contact member, a heater 43 as a heating element, a reflecting plate (reflecting member) 42) and left and right flange members 49L and 49R. In the above, members other than the left and right flange members 49L and 49R are members that are long in the left-right direction.

  The fixing belt 41 is a cylindrical heat-resistant member as a heating member that transmits heat. In the present embodiment, as shown in the schematic diagram of the layer structure of FIG. 5, the fixing belt 41 is arranged in order from the inner peripheral surface side to the outer peripheral surface side, an inner surface coat layer 41d, a base material layer 41a, an elastic layer 41b, and a surface layer ( This is a four-layer composite structure in which release layers 41c are sequentially stacked. It is a thin and flexible member in which the thickness of the entire four layers is set to 1 mm or less. The fixing belt 41 has a substantially cylindrical shape due to its elasticity in a free state.

  The diameter of the fixing belt 41 is set to be 15 to 120 mm. In this embodiment, the inner diameter is set to 25 mm. The length (width) W41) of the fixing belt 41 is 350 mm.

  In order to improve the quick start property, the base material layer 41a can use a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more. For example, a cylindrical metal film such as SUS or nickel can be used. In this example, a cylindrical nickel metal film having a thickness of 30 μm and a diameter of 25 mm was used.

  The elastic layer 41b can use a rubber material having a thickness of 1000 μm or less, preferably 500 μm or less in order to reduce the heat capacity and improve the quick start. For example, silicone rubber, fluorine rubber and the like can be mentioned. In this example, a silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K, and a thickness of 300 μm was used.

  For the release layer 41c, a fluororesin material having a thickness of 100 μm or less, preferably 20 to 70 μm can be used. For example, examples of the fluororesin layer include PTFE, FEP, PFA, and the like. In this example, a PFA tube having a thickness of 30 μm was used.

  Since the inner surface coating layer 41d is in sliding contact with the pressing member 46, a heat-resistant resin layer, ceramics, metal, or the like can be used. Examples include engineering plastics and diamond-like carbon (DLC). For example, polyimide, polyimide amide, PEEK, polytetrafluoroethylene resin (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin ( PFA).

  The pressing member 46 is a highly rigid member such as an aluminum material or a steel material, and is inserted through the fixing belt 41. As will be described later, the pressing member 46 comes into pressure contact with the pressure roller 44 via the fixing belt 41 to form a nip portion N where the paper P is nipped and conveyed. The length of the pressing member 46 is longer than that of the fixing belt 41, and both left and right end portions protrude outward from the left and right end portions of the fixing belt 41, respectively.

  An upward reflecting plate 42 is disposed on the pressing member 46. The length (width W42) of the reflecting plate 42 is 330 mm in this embodiment. A halogen heater 43 as a heater (heat source, heating means, heating element) is disposed inside the reflection plate 42. Other heating elements (heating bodies) such as a carbon heater can also be used. The reflection plate 42 reflects the radiant heat from the heater 43 toward the inner surface of the fixing belt 41.

  The left and right flange members 49 </ b> L and 49 </ b> R are fitted to both ends of the pressing member projecting outward from the left and right ends of the fixing belt 41. That is, the left and right end portions of the pressing member 46 are fitted into the hole portions 49b formed in the left and right flange members 49L and 49R, respectively.

  Each of the left and right flange members 49L and 49R includes a flange portion 49a that regulates the end portion of the fixing belt 41 and an arcuate guide portion 49c that guides the inner peripheral surface of the end portion of the fixing belt 41. In a state where the left and right flange members 49L and 49R are respectively attached to both end portions of the pressing member, the guide portion 49c is fitted inside the left and right end portions of the fixing belt 41.

  Further, the metal ports 43a at the left and right end portions of the heater 43 are fitted into the sockets (connectors) 62 disposed on the left and right flange members 49L and 49R, respectively, and are electrically connected to the sockets 62. .

  The fixing belt 41 is loosely fitted on the outside of the pressing member 46, the reflecting plate 42, the heater 43, and the left and right guide portions 49c between the flange portions 49a of the left and right flange members 49L and 49R.

  The assembly (assembly) of the fixing belt 41, the pressing member 46, the reflection plate 42, the heater 43, the reflection plate 42, and the left and right flange members 49L and 49R is the heating unit 4A.

  In the pressure roller 44, an elastic layer 44b made of foamable silicone rubber, silicone rubber, fluorine rubber, or the like is formed on the outer peripheral surface of a hollow cored bar 44a. Further, a release layer 44c such as PFA or PTFE may be provided on the outer peripheral surface of the elastic layer 44b. A shaft portion 44d is mounted substantially concentrically and integrally on both left and right ends of the core metal 44a. The pressure roller 44 of this embodiment has an outer diameter of 30 mm, a thickness of the elastic layer 44b of 300 μm, and a length (width W44) of the roller portion of 330 mm.

  The pressure roller 44 is disposed such that left and right shaft portions 44d are rotatably held (both supported) via bearing members 61 between the left and right side plates 60L and 60R of the housing 60, respectively. ing. A drive gear G is disposed substantially concentrically and integrally at the end of the right shaft 44d.

  The heating unit 4 </ b> A is arranged between the left and right side plates 60 </ b> L and 60 </ b> R of the housing 60, with the pressing member 46 side facing downward, arranged substantially parallel to the pressure roller 44 on the upper side of the pressure roller 44. That is, the vertical groove portions 49d (FIG. 4) respectively provided in the left and right flange members 49L and 49R of the heating unit 4A are vertically connected to the vertical guide slits 60L-a and 60R-a provided in the left and right side plates 60L and 60R, respectively. Engage with the edge. Accordingly, the left and right flange members 49L and 49R are held so as to be slidable in the vertical direction with respect to the left and right side plates 60L and 60R, respectively.

  A predetermined pressing force F is applied to the pressure receiving portions 49e of the left and right flange members 49L and 49R by the pressure springs 63, respectively. In this embodiment, a pressing force F of 160N (total pressure 320N) is applied to the pressure receiving portions 49e of the flange members 49L and 49R. As a result, a pressing force acts on the pressing member 46, and the fixing belt 41 is pressed against the upper surface of the pressure roller 44 by the pressing member 46 with a predetermined pressing force. By this pressure contact, a nip portion N having a predetermined width is formed between the fixing belt 41 and the pressure roller 44 in the short direction.

  A driving force of a motor (drive source) M controlled by the control unit 100 is transmitted to the drive gear G through a drive transmission mechanism (not shown). As a result, the pressure roller 44 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction of the arrow R44 in FIG.

  A rotational force (rotational torque) acts on the fixing belt 41 by a frictional force at the nip portion N between the pressure roller 44 and the outer surface of the fixing belt 41 due to the rotational driving of the pressure roller 44. As a result, the fixing belt 41 slides with its inner surface in close contact with the surface (downward surface) of the pressing member 46 at the nip portion N while rotating the pressure roller 44 in the clockwise direction indicated by the arrow R41 in FIG. It is driven and rotated at the corresponding peripheral speed. The pressing member 46 also functions as a rotation guide member for the fixing belt 41.

  In order to make the driven rotation of the fixing belt 41 smooth, a lubricant (not shown) can be interposed (applied) in the sliding contact portion between the fixing belt 41 and the pressing member 46. The seat portions 49a of the left and right flange members 49L and 49R are moved by receiving the belt end portion on the near side when the rotating fixing belt 31 is moved left or right along the length of the pressing member 46. regulate. Further, the guide portions 49c of the flange members 49L and 49R are arranged on both ends of the fixing belt 41 so that the circumferential shape of both ends of the fixing belt 41 is regulated when the fixing belt is driven by the pressure roller 44. Guide the inner surface.

  The heater 43 receives heat from the power supply unit 101 controlled by the control unit 100 through the sockets 62 and 62 and generates heat. The radiant heat of the heater 43 reaches the inner surface of the fixing belt 41 directly and by being reflected by the reflecting plate 42, and the fixing belt 41 is heated from the inside.

  Reference numeral 45a denotes a first temperature sensor disposed at the longitudinal center of the fixing belt 41, which detects (measures) the surface temperature of the sheet passing area of the fixing belt 41 through which the paper of any size is passed. Reference numeral 45b denotes a second temperature sensor disposed at the end of the fixing belt 41, and fixing when a sheet (small size sheet) having a width smaller than the maximum sheet passing width usable in the apparatus is passed (introduced). The surface temperature of the non-sheet passing region of the belt 41 is detected. In this example, the first and second temperature sensors 45a and 45b are both contact thermistors. The temperature detection information of the first and second temperature sensors 45 a and 45 b is input to the control unit 100.

  The configuration of the fixing device 40 is summarized as follows. In this device, the paper P carrying the toner image T is nipped and conveyed by the nip portion N to heat the toner image. It has a fixing belt 41 as a cylindrical first rotating body. A pressing member 46 is provided as a sliding contact member fixed so as to be in sliding contact with the inner surface of the fixing belt 41. A heater 43 is provided as a heating element fixed inside the fixing belt 41. A reflecting plate 42 is provided as a reflecting member that is fixed inside the fixing belt 41 and reflects radiant heat from the heater 43 toward the inner surface of the fixing belt 41.

  A pressure roller 44 is provided as a second rotating body that abuts against the pressing member 46 via the fixing belt 41 and forms a nip portion N with the fixing belt 41.

(2-2) Fixing Operation The control unit 100 starts the motor M based on the image formation start signal and starts to rotate the pressure roller 44. In addition, power supply from the power supply unit 101 to the heater 43 is started. As a result, the fixing belt 41 is driven and rotated from the inside by the radiant heat of the heater 43. Based on the temperature information detected by the first temperature sensor 45a, the control unit 100 raises the power supplied to the heater 43 so that the surface temperature of the fixing belt 41 is raised to a predetermined fixing temperature and the fixing temperature is maintained. The surface temperature of the fixing belt 41 is controlled to control the temperature.

  In this fixing device state, the sheet P carrying the unfixed toner image T from the image forming unit 2 side is introduced into the fixing device 40 and is nipped and conveyed by the nip portion N. As a result, the toner image T and the paper P are heated and pressed by the heat of the fixing belt 41 and the nip pressure, whereby the toner image T is fixed to the paper P as a fixed image. The sheet P sandwiched and conveyed by the nip N is separated from the surface of the fixing belt 41 at the sheet exit of the nip N and is discharged and conveyed from the fixing device 40.

  The pressing member 46 slidably contacting the inner peripheral surface of the fixing belt 41 has a concave shape so that the surface facing the pressure roller 44 (fixing belt slidable contact surface) follows the curvature of the pressure roller 44 as shown in FIG. Is formed. Accordingly, since the paper P is sent from the nip portion N so as to follow the curvature of the pressure roller 44, the occurrence of a situation in which the paper P after the fixing process is not attracted to and separated from the fixing belt 41 is suppressed. can do.

(2-3) Reflector (2-3-1) Reflector of Example The details of the reflector (reflective member) 42 in the configuration of this example will be described. As shown in FIG. 6, the reflecting plate 42 has a three-part configuration including a central portion 42a and both end portions 42b with respect to the longitudinal direction. And in the cross section of the reflecting plate 42, the angle from the horizontal direction of the side surface (side wall surface) 47 of the reflecting plate 42 is defined as an angle α at the longitudinal central portion 42a of the reflecting plate 42 and an angle β at both end portions 42b. Then, a relationship of α> β is established.

  The configuration of the reflecting plate 42 in the longitudinal center portion 42a and both end portions 42b will be specifically described with reference to FIGS. FIG. 7 shows a reflector structure in the longitudinal center portion 42a. Here, as shown in FIG. 7A, in the cross section of the reflection plate 42, the distance from the halogen heater 43 to the bottom surface 48 of the reflection plate 42 is s, and the distance from the inner peripheral surface 41e of the fixing belt 41 is the distance. d, the length of the side surface 47 of the reflector 42 is l, and the length of the bottom surface 48 is m.

  The radiation heat from the halogen heater 43 is reflected by the side surface 47 of the reflecting plate 42 and is condensed at an angle α of the side surface 47, where W is the condensing range when the light is condensed on the inner peripheral surface 41e of the fixing belt 41. The condition for minimizing the range Wα is when the following expression (1) is satisfied.

2 tan α = (d + s−l sin α) / (m + s−2 l cos α) (1) Formula The fixing belt 41 receives the smaller the light receiving area on the inner peripheral surface 41 e of the fixing belt 41 that receives the radiant heat from the halogen heater 43. The large amount of heat is widely known in the heat transfer theory of radiation.

  In this embodiment, in the relationship of the expression (1), specifically, the distance s = 5 mm from the halogen heater 43 to the bottom surface 48 of the reflecting plate 42, the distance d = 15 mm to the inner peripheral surface 41 e of the fixing belt 41, and the side surface 47. The length 1 is 10 mm. Further, the length m of the bottom surface 48 of the reflecting plate 42 is set to 6 mm, and the angle α of the side surface 47 is set to 80 °. As a result, it has been confirmed by experiments that the condensing range Wα when the light is condensed on the inner peripheral surface of the fixing belt 41 is minimized.

  FIG. 8 shows the configuration of the reflecting plate at the longitudinal end portion 42b of the reflecting plate. Here, as shown in FIG. 8A, the condensing range when the radiant heat from the halogen heater 43 is reflected by the side surface 47 and condensed on the inner peripheral surface 41 e of the fixing belt 41 is W. In this case, the condition that the light collection range Wβ is maximized at the angle β of the side surface 47 is that the radiation beam from the halogen heater 43 incident on the uppermost portion of the side surface 47 is in the horizontal direction, and the following (2) Satisfy the formula.

s = lsin β (2) Formula In this example, in the relationship of the formula (2), the distance s = 5 mm from the halogen heater 43 to the bottom surface 48 of the reflector 42, and the length l = 10 mm of the side surface 47, The angle β of the side surface 47 is set to 30 °. As a result, it has been confirmed by experiments that the light collection range Wβ when the light is condensed on the inner peripheral surface of the fixing belt 41 is maximized.

  That is, in this region, the radiant heat from the halogen heater 43 is not condensed on the inner peripheral surface 41e of the fixing belt 41 by the side surface 47, and the heating efficiency of the fixing belt 41 is reduced.

  FIGS. 7B and 8B illustrate the reflection of radiant heat from the halogen heater 43 on the bottom surface 48 of the reflector 42. When the angle of the side surface 47 is α, the condensing range when the light is condensed on the inner peripheral surface 41e of the fixing belt 41 is Lα, and when the angle of the wall surface 47 is β, the light is collected on the inner peripheral surface of the fixing belt 41. Let Lβ be the light collection range when light is emitted. In this case, it has been confirmed by experiments that Lα and Lβ have the relationship of the following expression (3).

L_α / L_β = (90−α) / (90−β) (3) In this embodiment, as described above, α = 80 ° and β = 30 ° are set in the relationship of equation (3). Therefore, the relationship is L_α / L_β = 1/6. Therefore, even in the condensing range L when the reflection of the radiant heat from the halogen heater 43 on the bottom surface 48 of the reflecting plate 42 is condensed on the inner peripheral surface 41e of the fixing belt 41, the longitudinal central portion 42a is formed at both end portions 42b. It was confirmed that high-efficiency heat transfer was achieved.

  Here, the angle β from the horizontal direction of the side surface 47 at both longitudinal ends of the reflecting plate 42 is continuous or intermittent from the angle α to the angle β at the longitudinal central portion 42a as it goes toward the longitudinal both ends of the reflecting plate 42. Can be changed.

  In the above embodiment, specific operating conditions are described below. In the present embodiment, the pressurizing condition of the flange members 49L and 49R is 320N in total pressure, the rotation speed of the fixing belt 41 and the pressure roller 44 is 250 mm / s, and the input power to the heater 43 is 800W. .

  First, when the sheet passing size of the output sheet (recording sheet) P is input, as shown in Table 1, the non-sheet passing portion region L with respect to the longitudinal length (350 mm) of the fixing belt 41 is set in the control unit 100. It is determined.

  As shown in Table 1, when the paper size to be used is A4R, the length of the non-sheet passing portion region Lb is 70 mm. In this embodiment, the longitudinal central region 42a of the reflector 42 is provided with an A4R size of 210 mm.

(2-3-2) Comparison with Comparative Example FIG. 9 shows the effects of the fixing device of this embodiment and the fixing device of the comparative example. In the fixing device of the comparative example, the reflecting plate 42 has both end portions 42b having the same shape as the central portion 42a (FIG. 7). FIG. 9 is a longitudinal temperature distribution diagram of the fixing belt 41. In the fixing device of the comparative example, the non-sheet passing portion temperature rise that occurs when 2000 sheets of A4R sheets are continuously fed at a speed of 50 ppm reaches 220 ° C. On the other hand, the fixing device of this embodiment obtained a result that the surface temperature of the fixing belt 41 in the non-sheet-passing area was reduced by 25 ° C. at the maximum as compared with the fixing device of the comparative example.

  As described above, the reflection of the radiant heat from the halogen heater 43 on the reflection plate 42 with respect to the cross section of the reflection plate 42 is highly efficient (narrow-angle irradiation) in the longitudinal central portion 42a of the reflection plate 42. This is because the portion 42b has low efficiency (wide-angle irradiation). Thereby, the temperature rise of the both end portions 42b is suppressed during continuous paper feeding.

  From the above, regarding the transverse cross section of the reflecting plate 42, the angle from the horizontal direction of the side surface 47 of the reflecting plate 42 is the angle α at the longitudinal central portion 42a of the reflecting plate 42 and the angle β at both longitudinal end portions 42b. Then, the structure which becomes a relationship of (alpha)> (beta) is provided. Thereby, the effect which suppresses non-paper passing part temperature rise (edge part temperature rise) simply could be confirmed, without providing a mechanical structure.

[Other matters]
Here, the present invention is not limited to the embodiment described above, and within the scope of the technical idea of the present invention, the embodiment can be changed as appropriate, other than suggested in the embodiment. it is obvious. Further, the number, position, shape, and the like of the constituent members are not limited to the form of the embodiment, and can be set to a suitable number, position, shape, and the like in carrying out the present invention.

  1) For example, in the embodiment, the first rotating body 41 has been described as an apparatus using a cylindrical belt that is driven to rotate by the rotational driving of the second rotating body 44 as a driving rotating body. However, the present invention is not limited to this, and the first rotating body 41 can be in the form of a cylindrical driving rotating body having rigidity.

  2) The 2nd rotary body 44 can also be made into the form of the endless belt body which can rotate.

  3) The image heating apparatus of the present invention is not limited to use as a fixing apparatus that heats and presses the unfixed toner image T carried on the sheet P as in the embodiment and heat-fixes it as a fixed image. It is also effective as a heat treatment apparatus that adjusts the surface properties of an image such as improving the glossiness by heating and pressing an image (fixed image or semi-fixed image) once fixed or assumed on a sheet.

  4) The image forming unit of the image forming apparatus is not limited to the electrophotographic system. The image forming unit may be an electrostatic recording system or a magnetic recording system. Further, it is not limited to the transfer method, and a configuration in which an unfixed image is formed directly on a sheet may be used.

  40..Image heating device, 41..First rotating body, 46..Sliding contact member, 43..Heat generating element, 42..Reflective member, 44..Second rotating body, 47..Reflecting member Side, N · Nip, T · Toner image, P · Sheet

Claims (4)

An image heating apparatus that heats a toner image by nipping and conveying a sheet carrying a toner image at a nip portion,
A cylindrical first rotating body;
A sliding contact member fixed to be in sliding contact with the inner surface of the first rotating body;
A heating element fixed inside the first rotating body;
A reflecting member fixed inside the first rotating body and reflecting radiant heat from the heating element toward the inner surface of the first rotating body;
A second rotating body that contacts the sliding contact member via the first rotating body and forms the nip portion between the first rotating body, and
With respect to the cross section of the reflecting member, α satisfies the relationship of α> β, where α is the angle from the horizontal direction of the side surface at the longitudinal center of the reflecting member, and β is the angle from the horizontal direction of the side surface at both longitudinal ends. Image heating device.   The angle from the horizontal direction of the side surface at the both longitudinal ends changes continuously or intermittently from the angle α at the longitudinal central portion toward the angle β as it goes toward the longitudinal both ends of the reflecting member. The image heating apparatus according to claim 1.   The image heating apparatus according to claim 1, wherein the first rotating body is an endless belt having flexibility.   The image heating apparatus according to claim 1, wherein the second rotating body is driven.