JP6134288B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines and printers include a fixing device that fixes a toner image onto a recording medium such as paper. A heat roller system is widely used for this fixing device. The hot roller method is a method of forming a fixing nip using a pair of rollers. The pair of rollers is formed of a metal such as aluminum or iron, for example.

  On the other hand, in order to shorten the warm-up time, the fixing method is moving from the heat roller method to the belt method. The belt method is a method of forming a fixing nip using a fixing belt. The fixing belt has a smaller heat capacity than the pair of rollers, and is formed of a metal such as SUS.

  For example, Patent Document 1 discloses a fixing belt, a pressure member that presses against the fixing belt to form a fixing nip, and a heat source that is disposed on the radially inner side of the fixing belt (see “heating unit 25” in Patent Document 1). ), A reflecting member that reflects radiant heat from the heat source (see “reflecting plate 22” in Patent Document 1), and a supporting member that supports the reflecting member (see “Main body 23a” in Patent Document 1). An apparatus is disclosed.

JP 2012-128075 A

  In the fixing device as described in Patent Document 1, the reflection member and the support member may be screwed. However, when the reflecting member and the supporting member are screwed, when there is a difference in the linear expansion coefficient between the reflecting member and the supporting member, the reflecting member or the supporting member having a lower strength (usually the reflecting member) is deformed during heating. There's a problem.

  Further, in a fixing device as described in Patent Document 1, a heat source, a reflection member, and a support member must be inserted into a flexible fixing belt at the time of assembly. Therefore, there is a problem that it is difficult to assemble the fixing device.

  In view of the above circumstances, an object of the present invention is to prevent the deformation of the reflecting member and the supporting member, and to facilitate the assembly of the fixing device.

  The fixing device according to the present invention includes a fixing belt that is rotatably provided around a rotation shaft, a pressure member that is pressed against the fixing belt to form a fixing nip, and is rotatably provided, and a radial direction of the fixing belt A heat source that is disposed on the inside and radiates radiant heat; a reflecting member that reflects radiant heat radiated from the heat source toward an inner peripheral surface of the fixing belt; and a support member that supports the reflecting member from the fixing nip side. And a pressing member having a contact portion that contacts the reflective member from the opposite side of the fixing nip and a holding portion that holds the heat source.

  As described above, the abutting portion of the pressing member is brought into contact with the reflecting member from the side opposite to the fixing nip, so that the reflecting member can be sandwiched between the supporting member and the abutting portion. It is possible to fix the reflecting member to the support member without stopping. Therefore, even when there is a difference between the linear expansion coefficients of the reflecting member and the supporting member, it is possible to suppress deformation of the reflecting member or the supporting member with weaker strength during heating. Further, since the holding portion of the pressing member holds the heat source as described above, the heat source, the reflection member, and the support member can be easily inserted into the fixing belt. Therefore, it is possible to facilitate the assembly of the fixing device.

  The reflection member may be disposed between the heat source and the support member, and may be curved or bent so as to be convex toward the heat source side.

  By adopting such a configuration, it is possible to widen the area of the fixing belt that is directly heated by the heat source. Therefore, it is possible to quickly raise the temperature of the fixing belt.

  The reflection member is provided on the downstream side of the first reflection unit in the recording medium conveyance direction, and is provided on the downstream side of the first reflection unit in the recording medium conveyance direction. A second reflecting portion that is inclined toward the support member toward the downstream side in the direction, a third reflecting portion that is provided along the recording medium conveyance direction, and that connects the first reflecting portion and the second reflecting portion; The contact portion may be in contact with the third reflecting portion.

  Since the reflecting member includes the third reflecting portion in this manner, the distance between the heat source and the reflecting member can be easily increased, so that the temperature rise of the reflecting member can be suppressed. Moreover, since the contact portion contacts the third reflecting portion, it is possible to reliably prevent the position of the reflecting member from being displaced.

  The pressing member may include a main body plate having the contact portion and the holding portion, and both side plates provided on both sides of the main body plate, and the both side plates may be fixed to the support member.

  By adopting such a configuration, the pressing member can be reliably fixed to the support member.

  The contact portion may be provided at one end portion of the main body plate in the rotation axis direction, and the holding portion may be provided at the other end portion of the main body plate in the rotation axis direction.

  By adopting such a configuration, it is possible to separate the contact portion that contacts the reflecting member and the holding portion that holds the heat source as much as possible. Along with this, it is possible to suppress contact between the reflecting member and the heat source when the fixing device is assembled.

  The support member includes an engagement portion that engages with an end portion of the reflecting member in the rotation axis direction, and the contact portion at least partially overlaps the position of the engagement portion and the rotation axis direction. May be.

  By adopting such a configuration, it is possible to sandwich the reflecting member between the engaging portion and the contact portion. Therefore, it is possible to reliably prevent the displacement of the reflecting member.

  The heat source may include a radiating portion that radiates radiant heat, and a held portion that is disposed outside the radiating portion in the rotation axis direction and is placed on the holding portion.

  By adopting such a configuration, the temperature of the pressing member is less likely to increase due to heat transfer from the heat source as compared to the case where the radiating unit is placed on the holding unit.

  The held portion may have a horizontal columnar shape, and the holding portion may be curved in an arc shape toward the lower side.

  By adopting such a configuration, the held portion can be reliably held by the holding portion.

  The fixing device may further include a pressing member that is supported by the support member and presses the fixing belt toward the pressing member.

  By adopting such a configuration, it is possible to reliably fix the toner image on the paper in the fixing nip.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, it is possible to prevent the reflection member and the support member from being deformed and to facilitate the assembly of the fixing device.

1 is a schematic diagram illustrating an outline of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device of a printer according to an embodiment of the present invention. 1 is a perspective view showing a fixing device of a printer according to an embodiment of the present invention. 1 is an exploded perspective view showing an upper frame portion and a fixing belt in a fixing device of a printer according to an embodiment of the present invention. FIG. 3 is an exploded perspective view showing a heater, a reflecting member, a supporting member, a pressing member, and a pressing member in the fixing device of the printer according to the embodiment of the present invention. FIG. 3 is an exploded perspective view illustrating a support member and a pressing member in the fixing device of the printer according to the embodiment of the present disclosure. FIG. 3 is a front view showing a heater, a reflecting member, a supporting member, a pressing member, and a pressing member in the fixing device of the printer according to the embodiment of the present invention. FIG. 3 is a plan view showing a heater, a reflecting member, a supporting member, and a pressing member in the fixing device of the printer according to one embodiment of the present invention. FIG. 3 is a perspective view showing a heater, a reflecting member, a supporting member, and a pressing member in the fixing device of the printer according to the embodiment of the present invention. FIG. 3 is an exploded perspective view showing a reflecting member, a supporting member, and a pressing member in the fixing device of the printer according to the embodiment of the present invention. It is sectional drawing which shows the fixing device which concerns on other different embodiment of this invention.

  First, the overall configuration of the printer 1 (image forming apparatus) will be described with reference to FIG.

  The printer 1 includes a box-shaped printer main body 2, and a paper feed cassette 3 that stores paper (recording medium) is accommodated in a lower portion of the printer main body 2. A paper discharge tray is disposed on the upper surface of the printer main body 2. 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is accommodated below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the paper discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A paper transport path 15 is provided inside the printer main body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing device 18, and a paper discharge unit 19 is provided at the downstream end of the conveyance path 15. A reverse path 20 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 18 is executed. Then, when image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the electrostatic latent image is developed by the developing device 12 into a toner image with toner.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 16 is conveyed to the transfer unit 17 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit 17. Is transcribed. The sheet on which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18 where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 19 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the fixing device 18 will be described in detail. Hereinafter, for convenience of explanation, the front side of the sheet in FIG. 2 is defined as the front side (front side) of the fixing device 18. An arrow Y in FIG. 2 indicates the sheet conveyance direction (in this embodiment, the left-right direction). An arrow Fr appropriately attached to each drawing indicates the front side (front side) of the fixing device 18. An arrow I appropriately attached to each figure indicates an inner side in the front-rear direction, and an arrow O appropriately attached to each figure indicates an outer side in the front-rear direction.

  As shown in FIG. 2 and the like, the fixing device 18 includes a box-shaped fixing frame 21, a fixing belt 22 accommodated in the upper part of the fixing frame 21, and a pressure roller 23 accommodated in the lower part of the fixing frame 21. (Pressure member), a heater 24 (heat source) disposed radially inside the fixing belt 22, a reflecting member 25 disposed below the heater 24 on the radially inner side of the fixing belt 22, and the fixing belt 22 A support member 26 disposed below the reflecting member 25 on the radially inner side, a pressing member 27 disposed below the support member 26 on the radially inner side of the fixing belt 22, and both front and rear ends of the fixing belt 22. And the pressing members 28 (only the pressing member 28 on the rear side is shown in FIG. 2).

  The fixing frame 21 is formed of sheet metal. As shown in FIG. 3 and the like, the fixing frame 21 includes an upper frame portion 31 and a lower frame portion 32 that are connected to each other.

  The upper frame portion 31 of the fixing frame 21 includes a pair of front and rear upper end plates 33 and a top plate 34 that connects the upper end portions of the upper end plates 33.

  As shown in FIG. 4 and the like, a heater mounting plate 35 is fixed to the outer surface of each upper end plate 33 of the upper frame portion 31. A belt mount 36 is fixed to the inner surface of each upper end plate 33. An arcuate belt support portion 37 is provided at the end of each belt mount 36 on the inner side in the front-rear direction. An annular meandering control ring 38 is provided on the outer periphery of the belt support portion 37.

  A pair of front and rear first thermistors 40 are fixed to the top plate 34 of the upper frame portion 31. As shown in FIG. 3 and the like, each first thermistor 40 is in contact with the central portion and the rear portion of the outer peripheral surface of the fixing belt 22.

  The lower frame portion 32 of the fixing frame 21 includes a pair of front and lower lower end plates 41 and a bottom plate 42 that connects lower portions of the lower end plates 41.

  A swing frame 43 is provided inside each lower side end plate 41 of the lower frame portion 32 in the front-rear direction. A support shaft 44 is provided on the right end side of each swing frame 43, and each swing frame 43 swings around each support shaft 44 as a fulcrum. An input gear 45 is provided coaxially with each support shaft 44 on the rear side (front-rear direction outer side) of the lower lower end plates 41 on the rear side. The input gear 45 is connected to a drive source 46 configured by a motor or the like.

  As shown in FIG. 2 and the like, a second thermistor 47 is fixed to the lower frame portion 32. The second thermistor 47 is in contact with the outer peripheral surface of the pressure roller 23. The lower frame portion 32 is provided with an entry guide 48 and a discharge guide 49.

  The fixing belt 22 has a substantially cylindrical shape that is long in the front-rear direction. The fixing belt 22 has flexibility and is endless in the circumferential direction. The fixing belt 22 includes, for example, a base material layer and a release layer that covers the base material layer. The base material layer of the fixing belt 22 is formed of a metal such as SUS, for example. The base material layer of the fixing belt 22 may be formed of a resin such as PI (polyimide). The release layer of the fixing belt 22 is formed of, for example, a PFA tube. In each figure, each layer (base material layer, release layer) of the fixing belt 22 is displayed without being particularly distinguished.

  At both front and rear ends of the fixing belt 22, belt support portions 37 (see FIG. 4 and the like) provided on each belt mounting base 36 of the upper frame portion 31 are inserted. As a result, the fixing belt 22 is rotatably supported by the upper frame portion 31. The fixing belt 22 is rotatable around a rotation axis A (see FIG. 4) extending in the front-rear direction. That is, in the present embodiment, the front-rear direction is the rotation axis direction of the fixing belt 22. Both front and rear end faces of the fixing belt 22 are disposed on the inner side in the front-rear direction of a meandering restriction ring 38 provided on each belt mount 36 of the upper frame portion 31. As a result, the meandering (moving outward in the front-rear direction) of the fixing belt 22 is restricted.

  The pressure roller 23 (see FIG. 2 and the like) has a substantially cylindrical shape that is long in the front-rear direction. The pressure roller 23 includes, for example, a cylindrical core member 50, an elastic layer 51 provided around the core member 50, and a release layer (not shown) that covers the elastic layer 51. ing. The core material 50 of the pressure roller 23 is made of metal such as iron, for example. The elastic layer 51 of the pressure roller 23 is made of, for example, silicon rubber. The release layer of the pressure roller 23 is formed by, for example, a PFA tube.

  The pressure roller 23 is disposed on the lower side (outside) of the fixing belt 22. The pressure roller 23 is in pressure contact with the fixing belt 22, and a fixing nip 52 is formed between the fixing belt 22 and the pressure roller 23. The paper conveyance direction is, for example, the conveyance direction when the paper passes through the fixing nip 52. The pressure roller 23 is rotatably supported at the longitudinal center of the swing frame 43 of the fixing frame 21 (in this embodiment, the center in the left-right direction). The swing frame 43 swings around the support shaft 44. By moving, the pressure roller 23 moves up and down, and the pressure of the fixing nip 52 is switched.

  As shown in FIG. 3, a drive gear 53 is fixed to the rear end portion of the pressure roller 23. The drive gear 53 meshes with the input gear 45 and is connected to the drive source 46 via the input gear 45.

  The heater 24 (see FIG. 5 and the like) is composed of, for example, a halogen heater. As shown in FIG. 2 and the like, the lower end portion (end portion on the fixing nip 52 side) of the heater 24 is the upper end portion (end portion on the side away from the fixing nip 52) of the pressing member 27, the support member 26, and the reflecting member 25. ) Above (side away from the fixing nip 52). Both front and rear end portions of the heater 24 are attached to a heater mounting plate 35 (see FIG. 4 and the like) of the upper frame portion 31 of the fixing frame 21. As shown in FIG. 5 and the like, thermostats 54 are connected to both front and rear ends of the heater 24.

  The heater 24 includes a radiating portion 55 and held portions 56 arranged on both front and rear sides (front and rear direction outside) of the radiating portion 55. The radiating unit 55 is configured to generate heat and emit radiant heat when the heater 24 is energized. The held portions 56 are provided at both front and rear ends of the heater 24. The held portion 56 has a horizontal columnar shape and is provided with a larger diameter than the radiating portion 55.

  The reflection member 25 has a long shape in the front-rear direction. The reflecting member 25 is made of a metal such as bright aluminum, for example. The reflection member 25 is disposed between the heater 24 and the support member 26. The upper surface of the reflecting member 25 (the surface on the heater 24 side) is a reflecting surface (mirror surface) that reflects the radiant heat radiated from the radiating portion 55 of the heater 24 toward the inner peripheral surface of the fixing belt 22. The reflection member 25 is disposed so as to cover the upper side (the heater 24 side) of the support member 26, and prevents the support member 26 from being directly irradiated with radiant heat radiated from the radiating portion 55 of the heater 24. The temperature rise of the member 26 is suppressed.

  As shown in FIG. 2 and the like, the reflecting member 25 includes a first reflecting portion 61, a second reflecting portion 62 provided on the left side of the first reflecting portion 61 (downstream side in the sheet transport direction), and a first reflecting portion. 61 and a third reflecting portion 63 that connects the second reflecting portion 62.

  The first reflecting portion 61 is inclined downward (to the support member 26 side) toward the right side (upstream side in the sheet conveyance direction). The second reflecting portion 62 is inclined downward (supporting member 26 side) toward the left side (downstream side in the sheet conveyance direction). The third reflector 63 is provided along the left-right direction (paper transport direction). The third reflecting portion 63 is opposed to the radiating portion 55 of the heater 24 with an interval.

  The reflection member 25 is bent so as to be convex toward the upper side (the heater 24 side). In other words, the reflection member 25 is bent so as to be concave toward the lower side (the support member 26 side). Therefore, a recess 66 is formed below the reflecting member 25 (on the support member 26 side) so as to be surrounded by the first reflecting portion 61, the second reflecting portion 62, and the third reflecting portion 63.

  As shown in FIG. 5 and the like, engagement pieces 64 that extend horizontally toward the right side (upstream side in the sheet transport direction) are provided at both front and rear ends of the first reflecting portion 61. Engagement pieces 65 that extend horizontally toward the left side (downstream side in the sheet conveyance direction) are provided at both front and rear ends of the second reflecting portion 62.

  The support member 26 has a shape that is long in the front-rear direction. The support member 26 includes an upstream stay 71 and a downstream stay 72. The upstream stay 71 and the downstream stay 72 are made of sheet metal such as SECC (galvanized steel sheet), for example. The upper part of the support member 26 is inserted into a recess 66 formed on the lower side of the reflection member 25.

  As shown in FIGS. 5 to 7 and the like, the upstream stay 71 has an upstream base plate 73 extending in the vertical direction, and a lower end portion of the upstream base plate 73 toward the right side (upstream side in the sheet conveyance direction). An upstream support plate 74 that is bent, an upstream guide plate 75 that is bent from the right end portion of the upstream support plate 74 toward the upper right side, and an upper end projecting upward from both front and rear ends of the upstream guide plate 75; An upstream fixing piece 76 extending outward in the front-rear direction.

  A pair of front and rear fixing protrusions 77 are provided on the left side surface (the inner surface in the left-right direction) of each upstream side fixing piece 76. An engagement groove 78 (engagement portion) is provided at the end of each upstream side fixing piece 76 on the inner side in the front-rear direction.

  As shown in FIG. 5 to FIG. 7 and the like, the downstream stay 72 has a downstream base plate 80 extending in the up-down direction and a lower end portion of the downstream base plate 80 toward the left side (downstream in the sheet transport direction). A downstream support plate 81 to be bent, a downstream guide plate 82 to be bent from the left end portion of the downstream support plate 81 toward the upper left side, and an upward projection from both front and rear end portions of the downstream guide plate 82; And a downstream fixing piece 83 extending outward in the front-rear direction.

  The downstream base plate 80 is fixed to the upstream base plate 73 by a plurality of screws 84 provided at intervals in the front-rear direction. A plurality of fitting holes 85 are provided at the lower end portion of the downstream base plate 80 at intervals in the front-rear direction.

  A fixing projection 86 is provided on the right side surface (the inner surface in the left-right direction) of each downstream side fixing piece 83. An engagement groove 87 (engagement portion) is provided at an end of each downstream side fixing piece 83 on the inner side in the front-rear direction.

  As shown in FIGS. 8 and 9, the first reflecting portion 61 and the second reflecting portion 62 of the reflecting member 25 are provided in the engaging grooves 78 and 87 provided in the upstream stay 71 and the downstream stay 72. The engaging pieces 64 and 65 provided in the are engaged. With such a configuration, the reflecting member 25 is supported by the support member 26 from the lower side (the fixing nip 52 side).

  As shown in FIG. 6 and the like, the pressing member 27 has a plate shape that is long in the front-rear direction. The pressing member 27 is formed of a heat resistant resin such as LCP (Liquid Crystal Polymer).

  A plurality of fitting protrusions 88 are provided on the upper surface of the pressing member 27 at intervals in the front-rear direction. Each fitting protrusion 88 is fitted in each fitting hole 85 provided in the downstream base plate 80 of the downstream stay 72 of the support member 26.

  7 and the like, the upper surface of the pressing member 27 is the lower surface of the support member 26 (specifically, the lower surface of the upstream support plate 74 of the upstream stay 71 and the lower surface of the downstream support plate 81 of the downstream stay 72). ). Accordingly, the pressing member 27 is supported by the support member 26, and warping (deformation due to the fixing load) of the pressing member 27 is suppressed.

  As shown in FIG. 2 and the like, the lower surface of the pressing member 27 is inclined downward (on the pressure roller 23 side) from the right side (upstream side in the paper transport direction) to the left side (downstream side in the paper transport direction). ing. The lower surface of the pressing member 27 presses the fixing belt 22 toward the lower side (pressure roller 23 side).

  A sheet member 90 is interposed between the lower surface of the pressing member 27 and the inner peripheral surface of the fixing belt 22. The sheet member 90 is made of, for example, a fluorine resin such as PTFE, and has a lower friction coefficient than the pressing member 27. A lubricant (grease) may be applied between the lower surface of the pressing member 27 and the inner peripheral surface of the fixing belt 22.

  As shown in FIGS. 9, 10, etc., each pressing member 28 includes a main body plate 91 and both side plates 92 provided on both the left and right sides of the main body plate 91.

  The main body plate 91 of each pressing member 28 extends in the horizontal direction. A substantially rectangular abutting portion 93 is provided at an end of the main body plate 91 on the inner side in the front-rear direction. The contact portion 93 protrudes inward in the front-rear direction from the center in the left-right direction of the edge on the inner side in the front-rear direction of the main body plate 91. The contact portion 93 is in contact with the front and rear end portions of the third reflection portion 63 of the reflection member 25 from the upper side (the side opposite to the fixing nip 52). As shown in FIG. 8 and the like, the contact portion 93 partially overlaps with the engagement grooves 78 and 87 of the support member 26 in the front-rear direction.

  As shown in FIG. 9, FIG. 10, and the like, a notch portion 94 having a rectangular shape in plan view is provided in the center portion in the front-rear direction of the main body plate 91. A holding portion 95 is provided at the outer end in the front-rear direction of the main body plate 91 on the outer side in the front-rear direction of the notch portion 94. The holding portion 95 is curved in an arc shape toward the lower side (the fixing nip 52 side). A held portion 56 of the heater 24 is placed (held) on the holding portion 95. Rectangular slits 96 are formed on the left and right edges of the main body plate 91.

  Each side plate 92 of each pressing member 28 is bent downward from the left and right edge portions of the main body plate 91. Each side plate 92 is provided with a projecting piece 97 projecting upward from the front to the rear.

  A first circle-shaped first fixing hole 98 is provided on the inner side in the front-rear direction of each side plate 92 so as to partially overlap the protruding piece 97. A fixing projection 77 on the inner side in the front-rear direction of the upstream stay 71 of the support member 26 is engaged with the first fixing hole 98 of the right side plates 92. A laterally long second fixing hole 99 is provided on the outer side in the front-rear direction of each side plate 92 so as to partially overlap the protruding piece 97. A fixing protrusion 77 on the outer side in the front-rear direction of the upstream stay 71 of the support member 26 is engaged with the second fixing hole 99 of the right side plates 92. The fixing protrusions 86 of the downstream stay 72 of the support member 26 are engaged with the second fixing holes 99 of the left side plates 92. With the configuration as described above, each side plate 92 is fixed to the support member 26.

  In the fixing device 18 configured as described above, when the toner image is fixed on the paper, the drive source 46 is driven. When the drive source 46 is driven in this way, the rotation of the drive source 46 is transmitted to the pressure roller 23 via the input gear 45 and the drive gear 53, and the pressure roller 23 is moved as shown by an arrow B in FIG. Rotate. When the pressure roller 23 rotates in this way, as indicated by an arrow C in FIG. 2, the fixing belt 22 that is in pressure contact with the pressure roller 23 is driven to rotate in the direction opposite to the pressure roller 23. When the fixing belt 22 rotates in this way, the fixing belt 22 slides with respect to the pressing member 27 and the sheet member 90.

  Further, when fixing the toner image on the paper, the heater 24 is operated (lighted). When the heater 24 operates in this way, radiant heat is radiated from the radiating portion 55 of the heater 24. A part of the radiant heat radiated from the radiating portion 55 of the heater 24 is directly irradiated and absorbed on the inner peripheral surface of the fixing belt 22 as indicated by an arrow D in FIG. Further, another part of the radiant heat radiated from the radiating portion 55 of the heater 24 is reflected toward the inner peripheral surface of the fixing belt 22 by the upper surface of the reflecting member 25 as shown by an arrow E in FIG. It is absorbed by the inner peripheral surface of the fixing belt 22. Due to the above operation, the fixing belt 22 is heated by the heater 24. When the paper passes through the fixing nip 52 in this state, the toner image is heated and melted, and the toner image is fixed on the paper.

  In the present embodiment, as described above, the method in which the fixing belt 22 is directly heated by the heater 24 is employed. However, in the region where the reflecting member 25 and the support member 26 are present (region on the fixing nip 52 side), the heater 24 is used. Therefore, the fixing belt 22 cannot be directly heated. Therefore, there is a problem that the heating efficiency of the fixing belt 22 is lowered.

  However, in the present embodiment, the reflecting member 25 is provided with the first reflecting portion 61 and the second reflecting portion 62 to form the reflecting member 25 in an umbrella shape, and at the center in the left-right direction of the support member 26 (upstream base plate 73). In addition, the height of the downstream base plate 80) is made higher than the height of the left and right side portions (the upstream guide plate 75 and the downstream guide plate 82) of the support member 26 (see FIG. 2 and the like). By adopting such a configuration, it is possible to widen the area of the fixing belt 22 that is directly heated by the heater 24. Therefore, the heating efficiency of the fixing belt 22 can be increased.

  The reflecting member 25 further includes a third reflecting portion 63 that connects the first reflecting portion 61 and the second reflecting portion 62. Therefore, the distance between the heater 24 and the reflecting member 25 can be easily increased, and the temperature rise of the reflecting member 25 can be suppressed.

  On the other hand, when the height of the central portion in the left-right direction of the support member 26 is made higher than the heights of the left and right side portions as described above, the portion having the same height on the upper surface of the support member 26 decreases. It becomes difficult to place the heater 24 on the heater 26. As a result, the fixing device 18 may be difficult to assemble. Therefore, in the present embodiment, the fixing device 18 is assembled by the following method.

  First, the reflecting member 25 is placed on the support member 26 while the engaging pieces 64 and 65 of the reflecting member 25 are engaged with the engaging grooves 78 and 87 of the supporting member 26. Next, the fixing protrusions 77 and 86 of the support member 26 are engaged with the first and second fixing holes 98 and 99 of the both side plates 92 of each pressing member 28. Thereby, each side plate 92 is fixed to the support member 26, and each pressing member 28 is attached to both front and rear ends of the support member 26. Accordingly, the abutting portions 93 of the pressing members 28 abut on both front and rear end portions of the third reflecting portion 63 of the reflecting member 25 from above. Thereby, the position shift of the reflection member 25 is prevented reliably.

  Next, the held portion 56 of the heater 24 is placed on the holding portion 95 of each pressing member 28. In this state, the heater 24, the reflection member 25, the support member 26 and the pressing member 27 are inserted into the fixing belt 22.

  In this embodiment, as described above, when the fixing device 18 is assembled, the held portion 56 of the heater 24 is placed (held) on the holding portion 95 of each pressing member 28. Therefore, it is possible to facilitate the assembly of the fixing device 18.

  Further, in the fixing device 18 configured as described above, when the reflection member 25 and the support member 26 are screwed, the reflection member having a lower strength than the support member 26 due to the difference in linear expansion coefficient between the reflection member 25 and the support member 26. 25 may be deformed during heating. Therefore, in the present embodiment, the reflection member 25 is supported from the lower side (fixing nip 52 side) by the support member 26, and the contact portions 93 of the pressing members 28 are arranged at both front and rear ends of the third reflection portion 63 of the reflection member 25. It is made to contact | abut from the upper side (opposite side to the fixing nip 52). By adopting such a configuration, the reflection member 25 can be sandwiched between the support member 26 and the contact portion 93, and the reflection member 25 can be supported by the support member 26 without screwing the reflection member 25 and the support member 26. It becomes possible to fix to. Therefore, it is possible to prevent the reflecting member 25 from being deformed during heating.

  Each pressing member 28 includes a main body plate 91 having a contact portion 93 and a holding portion 95, and both side plates 92 provided on both sides of the main body plate 91, and the both side plates 92 are fixed to the support member 26. ing. By adopting such a configuration, each pressing member 28 can be securely fixed to the support member 26.

  The contact portion 93 is provided at an end portion on the inner side in the front-rear direction of the main body plate 91, and the holding portion 95 is provided at an end portion on the outer side in the front-rear direction of the main body plate 91. By adopting such a configuration, the contact portion 93 that contacts the third reflection portion 63 of the reflection member 25 and the holding portion 95 on which the held portion 56 of the heater 24 is placed (held) are separated as much as possible. It becomes possible. Accordingly, it is possible to prevent the reflecting member 25 and the heater 24 from coming into contact with each other when the fixing device 18 is assembled.

  Further, the support member 26 includes engagement grooves 78 and 87 with which the engagement pieces 64 and 65 of the reflection member 25 are engaged, and the contact portion 93 is partially located in the front-rear direction with respect to the engagement grooves 78 and 87. Overlapping. By adopting such a configuration, it is possible to sandwich the reflecting member 25 between the engagement grooves 78 and 87 and the contact portion 93. For this reason, it is possible to reliably prevent the displacement of the reflecting member 25.

  The heater 24 includes a radiating portion 55 that radiates radiant heat, and a held portion 56 that is disposed outside the radiating portion 55 in the front-rear direction and is placed on the holding portion 95. By adopting such a configuration, the temperature of each pressing member 28 is less likely to rise due to heat transfer from the heater 24 as compared to the case where the radiating portion 55 is placed on the holding portion 95.

  Further, the held portion 56 has a horizontal columnar shape, and the holding portion 95 is curved in an arc shape toward the lower side. By adopting such a configuration, the held portion 56 can be reliably held by the holding portion 95.

  Further, the fixing device 18 includes a pressing member 27 that presses the fixing belt 22 toward the lower side (the pressure roller 23 side). By adopting such a configuration, it is possible to reliably fix the toner image on the paper in the fixing nip 52.

  In the present embodiment, since the fixing belt 22 is heated by the heater 24, the heat capacity of the member heated by the heater 24 can be reduced as compared with the case where the fixing roller is heated by the heater 24. Accordingly, it is possible to shorten the warm-up time of the fixing device 18.

  In the present embodiment, the case where the reflecting member 25 is bent so as to be convex toward the upper side (the heater 24 side) has been described. On the other hand, in other different embodiments, the reflecting member 25 may be curved so as to be convex toward the upper side (the heater 24 side). In still another different embodiment, as shown in FIG. 11, the reflecting member 25 is provided along the vertical direction (direction intersecting (orthogonal) with the sheet conveyance direction) and on the right side of the support member 26. The first plate unit 101 disposed on the upstream side of the paper conveyance direction and the vertical direction (direction intersecting (orthogonal to) the paper conveyance direction) and the left side of the support member 26 (paper conveyance) A second plate portion 102 disposed on the downstream side in the direction, and a third plate portion 103 that connects the first plate portion 101 and the upper end portion of the second plate portion 102 (the end portion on the side away from the fixing nip 52). , May be provided. By adopting such a configuration, the reflecting member 25 has a U-shape, and the space formed on the lower side (the supporting member 26 side) of the reflecting member 25 can be increased. Accordingly, the degree of freedom in the layout of the support member 26 can be increased.

  In this embodiment, the case where the 1st reflection part 61 and the 2nd reflection part 62 of the reflection member 25 were connected by the 3rd reflection part 63 was demonstrated. On the other hand, in other different embodiment, the 1st reflection part 61 and the 2nd reflection part 62 of the reflection member 25 may be directly connected without the 3rd reflection part 63 being interposed. In this case, since the reflecting member 25 is substantially V-shaped, it is preferable that the contact portion 93 of each pressing member 28 is also V-shaped in accordance with the shape of the reflecting member 25. By adopting such a configuration, it is possible to prevent the displacement of the reflecting member 25 more reliably.

  In the present embodiment, the case where one heater 24 is arranged on the inner side in the radial direction of the fixing belt 22 has been described. On the other hand, in other different embodiments, a plurality of heaters 24 may be arranged inside the fixing belt 22 in the radial direction.

  In the present embodiment, the case where a halogen heater is used as the heater 24 has been described. However, in another different embodiment, a ceramic heater or the like may be used as the heater 24.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible.

1 Printer (image forming device)
18 Fixing Device 22 Fixing Belt 23 Pressure Roller (Pressure Member)
24 Heater (heat source)
25 Reflecting member 26 Supporting member 27 Pressing member 28 Pressing member 52 Fixing nip 55 Radiating part 56 Held part 61 First reflecting part 62 Second reflecting part 63 Third reflecting part 78, 87 Engaging groove (engaging part)
91 Body plate 92 Both side plates 93 Abutting part 95 Holding part A Rotating shaft

Claims (10)

A fixing belt provided rotatably around a rotation axis;
A pressure member provided in a rotatable manner to form a fixing nip by pressing against the fixing belt;
A heat source that is disposed radially inside the fixing belt and emits radiant heat;
A reflecting member that reflects radiant heat radiated from the heat source toward an inner peripheral surface of the fixing belt;
A support member for supporting the reflecting member from the fixing nip side;
A fixing device comprising: a pressing member having a contact portion that contacts the reflective member from a side opposite to the fixing nip; and a holding portion that holds the heat source.   The fixing device according to claim 1, wherein the reflection member is disposed between the heat source and the support member, and is curved or bent so as to be convex toward the heat source side. The reflective member is
A first reflecting portion that is inclined toward the support member toward the upstream side in the conveyance direction of the recording medium;
A second reflecting portion provided on the downstream side of the first reflecting portion in the recording medium conveyance direction and inclined toward the support member toward the downstream side in the recording medium conveyance direction;
A third reflecting portion provided along the conveyance direction of the recording medium and connecting the first reflecting portion and the second reflecting portion;
The fixing device according to claim 2, wherein the contact portion is in contact with the third reflection portion. The holding member is
A main body plate having the contact portion and the holding portion;
Both side plates provided on both sides of the main body plate,
The fixing device according to claim 1, wherein the both side plates are fixed to the support member. The contact portion is provided at one end of the main body plate in the rotation axis direction,
The fixing device according to claim 4, wherein the holding portion is provided at the other end portion of the main body plate in the rotation axis direction. The support member includes an engaging portion with which an end portion of the reflecting member in the rotation axis direction is engaged,
The fixing device according to claim 1, wherein the abutting portion at least partially overlaps the engaging portion and a position in the rotation axis direction. The heat source is
A radiating part that radiates radiant heat; and
The fixing device according to claim 1, further comprising: a held portion that is disposed outside the radiating portion in the rotation axis direction and is placed on the holding portion. . The held portion has a horizontal columnar shape,
The fixing device according to claim 7, wherein the holding portion is curved in an arc shape toward the lower side.   The fixing device according to claim 1, further comprising a pressing member that is supported by the support member and presses the fixing belt toward the pressing member side.   An image forming apparatus comprising the fixing device according to claim 1.

Images