JP2016114810A - Fixation device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress contact of an end face in a rotation shaft direction outer side of a fixation roller with an outer side member, and prevent the fixation roller from being worn out and damaged.SOLUTION: A fixation device 18 according to the present invention comprises: a fixation roller 22 that is provided rotatably around a rotation shaft A; a pressure member 23 that comes into pressure-contact with the fixation roller 22 to form a fixation nip N, and is rotatably provided; ring bodies 25 and 26 to be mounted in an inner periphery of end parts 22a and 22b of the rotation shaft direction outer side of the fixation roller 22; and outer side members 27 and 28 that have at least one part provided on the fixation roller 22 and the rotation shaft direction outer side of the ring bodies 25 and 26. End faces 25Fr and 26Rr on the rotation shaft direction outer side of the ring bodies 25 and 26 protrude outwardly on the rotation shaft direction further than end faces 22Fr and 22Rr on the rotation shaft direction outer side of the fixation roller 22.SELECTED DRAWING: Figure 2

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.

  For example, Patent Document 1 discloses a fixing roller (see “Heating Roller 2” in Patent Document 1) that is rotatably provided, and a pressure member that is rotatably provided to form a fixing nip by being pressed against the fixing roller. And a ring body (see “Ring 11” in Patent Document 1) that is attached to the inner periphery of the outer end of the fixing roller in the rotational axis direction. An apparatus is disclosed.

JP-A-6-308847

  In the fixing device of Patent Document 1, the ring body is completely inserted into the outer end of the fixing roller in the rotation axis direction. Therefore, the end surface of the fixing roller in the rotation axis direction may come into contact with a member (hereinafter referred to as “outer member”) provided outside the fixing roller in the rotation axis direction, which may lead to wear or damage of the fixing roller.

  In view of the above circumstances, an object of the present invention is to prevent the fixing roller from being worn and damaged by suppressing the contact between the outer end surface of the fixing roller in the rotation axis direction and the outer member.

  The fixing device of the present invention includes a fixing roller that is rotatably provided around a rotation axis, a pressure member that is pressed against the fixing roller to form a fixing nip, and is rotatably provided, and the rotation of the fixing roller. A ring body mounted on the inner periphery of the axially outer end, and an outer member provided at least partially on the outer side in the rotational axis direction of the fixing roller and the ring body, and the rotation of the ring body An end surface on the outer side in the axial direction protrudes outward in the rotational axis direction from an end surface on the outer side in the rotational axis direction of the fixing roller.

  By adopting such a configuration, it is possible to suppress contact between the outer end surface of the fixing roller in the rotation axis direction and the outer member, and to prevent the fixing roller from being worn or damaged.

  The outer member includes a main body provided on the outer side in the rotation axis direction of the fixing roller and the ring body, and extends from the main body portion toward the inner side in the rotation axis direction. And a flange portion that covers the outer periphery of the end portion.

  By adopting such a configuration, it becomes possible to directly regulate the displacement of the outer end of the fixing roller in the rotation axis direction by the flange portion of the outer member. Along with this, it is possible to suppress the rotation axis of the fixing roller from being inclined with respect to a predetermined direction.

  The ring body is provided on the inner circumference of the outer end of the fixing roller in the rotation axis direction, and is provided on the outer side in the rotation axis direction of the fixing roller and the small diameter portion, than the small diameter portion. A large-diameter portion having a large outer diameter, and the outer member extends from the main body portion toward the inner side in the rotational axis direction, the main body portion provided on the outer side in the rotational shaft direction of the large-diameter portion, And a flange portion that covers the outer periphery of the large-diameter portion.

  By adopting such a configuration, not only the contact between the outer end surface of the fixing roller in the rotation axis direction and the outer member, but also the contact between the outer peripheral surface of the end portion of the fixing roller in the rotation axis direction and the outer member is suppressed. Is possible. Accordingly, it is possible to more effectively prevent the fixing roller from being worn and damaged.

  The outer member is a drive gear connected to a drive source, a key projects from an inner peripheral surface of the drive gear, and the key can be inserted through the fixing roller and the ring body. A groove may be provided, and an edge portion of the key groove of the ring body may protrude inward from an edge portion of the key groove of the fixing roller.

  By adopting such a configuration, the rotational driving force transmitted from the drive gear can be received by the ring body instead of the fixing roller. Along with this, it is possible to prevent the fixing roller from cracking from the keyway.

  The ring body may be thicker than the fixing roller.

  By adopting such a configuration, it is possible to increase the rigidity of the ring body, and it is possible to suppress deformation of the ring body when the end surface on the outer side in the rotation axis direction of the ring body contacts the outer member. It becomes.

  The ring body may be formed of a material having heat resistance.

  By adopting such a configuration, it is possible to suppress thermal deformation and the like of the ring body.

  The ring body may be fixed to the outer end of the fixing roller in the rotational axis direction by press fitting, welding, or punching.

  By adopting such a configuration, the ring body can be securely fixed to the outer end of the fixing roller in the rotation axis direction.

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

  According to the present invention, contact between the outer end surface of the fixing roller in the rotation axis direction and the outer member can be suppressed, and wear and breakage of the fixing roller can be prevented.

1 is a schematic diagram illustrating an outline of a printer according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to a first embodiment of the present invention. FIG. 3 is a side view showing a heat roller and a rear ring body in the fixing device according to the first embodiment of the present invention. It is IV-IV sectional drawing of FIG. FIG. 6 is a cross-sectional view illustrating a front portion of a fixing device according to a second embodiment of the present invention.

<First Embodiment>
First, the overall configuration of an electrophotographic printer 1 (image forming apparatus) will be described with reference to FIG. Hereinafter, the front side of the sheet in FIG. Arrows Fr, Rr, L, R, U, and Lo appropriately attached to the drawings indicate the front side, rear side, left side, right side, upper side, and lower side of the printer 1, respectively.

  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 4 is disposed on the upper surface of the printer main body 2. 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 stored below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the 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 20 is provided at the downstream end of the conveyance path 15. A reverse path 21 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 20 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 with reference to FIGS. 2 and 3 indicates the inner side in the front-rear direction, and the arrow O attached to FIGS. 2 and 3 indicates the outer side in the front-rear direction.

  As shown in FIG. 2, the fixing device 18 includes a heat roller 22 (fixing roller), a press roller 23 (pressure member) provided on the lower side (outer diameter side) of the heat roller 22, and the heat roller 22. A heater 24 (heat source) provided on the inner diameter side, a front ring body 25 mounted on the inner periphery of the front end portion 22a (end portion on the outer side in the front-rear direction) of the heat roller 22, and a rear end portion 22b (front and rear portions) of the heat roller 22 The rear ring body 26 attached to the inner periphery of the outer end of the direction), the front bearing 27 (outer member) that supports the front end 22a of the heat roller 22, and the outer periphery of the rear end 22b of the heat roller 22. And a rear bearing 29 that is provided on the front side (front-rear direction inner side) of the drive gear 28 and pivotally supports the rear portion of the heat roller 22. In FIG. 2, only the press roller 23 and the heater 24 are displayed in a side view, and the other members are displayed in cross section.

  The heat roller 22 has a long cylindrical shape in the front-rear direction. The heat roller 22 is provided to be rotatable around a rotation axis A extending in the front-rear direction. That is, in the present embodiment, the front-rear direction is the rotation axis direction of the heat roller 22.

  The heat roller 22 includes, for example, a cylindrical core material made of a metal such as aluminum or iron, an elastic layer that is provided around the core material and made of silicon rubber, etc., covers the elastic layer, and is made of fluorine such as PFA. And a release layer made of a resin.

  As shown in FIGS. 3 and 4, a second keyway 31 is provided at the rear end 22 b of the heat roller 22. The second keyway 31 is provided from the rear end surface 22Rr of the heat roller 22 toward the front side (front-rear direction inner side). The edge of the second keyway 31 is U-shaped.

  The press roller 23 (see FIG. 2) has a long cylindrical shape or columnar shape in the front-rear direction. The press roller 23 is in pressure contact with the heat roller 22, and a fixing nip N is formed between the heat roller 22 and the press roller 23. The press roller 23 is rotatably provided.

  The press roller 23 is, for example, a cylindrical or columnar core material made of a metal such as aluminum or iron, an elastic layer that is provided around the core material and is made of silicon rubber, and the elastic layer. And a release layer made of a fluororesin.

  The heater 24 has a long shape in the front-rear direction. The heater 24 is composed of, for example, a halogen heater or a ceramic heater. The heater 24 is disposed in the center of the internal space of the heat roller 22.

  Each of the ring bodies 25 and 26 has a cylindrical shape whose axial direction is the front-rear direction. Each of the ring bodies 25 and 26 is formed of a heat-resistant material (for example, a metal such as aluminum, iron, or SUS, or a heat-resistant resin such as polyimide, PPS (polyphenylene sulfide), or PEEK (polyether ether ketone)). Yes. The thickness of each ring body 25, 26 is thicker than the thickness of the heat roller 22.

  The outer peripheral surfaces of the ring bodies 25 and 26 are fixed to the inner peripheral surfaces of the front and rear end portions 22a and 22b of the heat roller 22 by press-fitting, welding, or punching. Here, “punching” is a method of fixing a plurality of members by forming dents from the front surface side or the back surface side at the same location of the plurality of members in a state where the plurality of members are overlapped.

  A front end surface 25Fr (end surface in the front-rear direction) of the front ring body 25 projects forward (outward in the front-rear direction) from a front end surface 22Fr (end surface in the front-rear direction) of the heat roller 22. The rear end surface 26Rr (end surface in the front-rear direction) of the rear ring body 26 projects rearward (outer direction in the front-rear direction) from the rear end surface 22Rr (end surface in the front-rear direction) of the heat roller 22. That is, each ring body 25, 26 is not entirely inserted into the heat roller 22, but is partially inserted into the heat roller 22.

  As shown in FIGS. 3 and 4, the rear ring body 26 is provided with a first key groove 32 so as to overlap the second key groove 31 of the heat roller 22. The first keyway 32 is provided from the rear end surface 26Rr of the rear ring body 26 toward the front side (inward in the front-rear direction). The edge of the first key groove 32 is U-shaped. The edge (U-shaped portion) of the first key groove 32 is inward (the width direction and length of the first key groove 32) than the edge (U-shaped portion) of the second key groove 31 of the heat roller 22. Projecting toward the center point P in the direction).

  As shown in FIG. 2, the front bearing 27 includes an annular first main body portion 41 and a cylinder extending from the outer diameter side end portion of the first main body portion 41 toward the rear side (in the front-rear direction). And a first flange portion 42 having a shape.

  The first main body 41 of the front bearing 27 is provided on the front side (front-rear direction outer side) of the heat roller 22 and the front ring body 25. This prevents the heat roller 22 and the front ring body 25 from dropping off. A first through hole 43 is provided in the central portion of the first main body 41 along the front-rear direction, and the heater 24 passes through the first through hole 43.

  The first flange portion 42 of the front bearing 27 covers the outer periphery of the front end portion 22 a of the heat roller 22. An annular front fixing portion 44 projects from the outer periphery of the first flange portion 42, and the front fixing portion 44 is fixed to a fixing frame (not shown).

  The drive gear 28 includes an annular second main body 51, a cylindrical second flange 52 extending from the outer diameter side end of the second main body 51 toward the front side (front-rearward direction inner side), It has.

  A gear portion 54 is provided on the outer peripheral surfaces of the second main body portion 51 and the second flange portion 52 of the drive gear 28. The gear unit 54 is connected to a drive source 55 configured by a motor or the like via a gear train (not shown).

  The second main body 51 of the drive gear 28 is provided on the rear side (front-rear direction outer side) of the heat roller 22 and the rear ring body 26. This prevents the heat roller 22 and the rear ring body 26 from dropping off. A second through hole 53 is provided in the central portion of the second main body 51 along the front-rear direction, and the heater 24 passes through the second through hole 53.

  The second flange portion 52 of the drive gear 28 covers the outer periphery of the rear end portion 22 b of the heat roller 22. As shown in FIG. 4, a key 56 projects from the inner peripheral surface of the second flange portion 52. The key 56 is inserted into the second key groove 31 of the heat roller 22 and the first key groove 32 of the rear ring body 26. Thereby, the relative rotation of the heat roller 22 and the rear ring body 26 with respect to the drive gear 28 is restricted. The key 56 is not in contact with the second key groove 31 of the heat roller 22 and is in contact with the first key groove 32 of the rear ring body 26.

  As shown in FIG. 2, the rear bearing 29 has a cylindrical shape whose axial direction is the front-rear direction. A bearing hole 61 is provided in the center portion of the rear bearing 29 along the front-rear direction, and the heat roller 22 passes through the bearing hole 61. An annular rear fixing portion 62 is provided on the outer periphery of the rear bearing 29, and the rear fixing portion 62 is fixed to a fixing frame (not shown).

  In the fixing device 18 configured as described above, when the toner image is fixed on the paper, the driving gear 28 is rotated by the driving source 55. When the drive gear 28 rotates in this way, the heat roller 22 and the ring bodies 25 and 26 rotate around the rotation axis A coaxially with the drive gear 28. When the heat roller 22 rotates as described above, the press roller 23 that presses against the heat roller 22 follows the heat roller 22 and rotates. Even if the heat roller 22 rotates as described above, the front bearing 27 and the rear bearing 29 do not rotate and remain stopped.

  In addition, when the toner image is fixed on the paper, the heater 24 is operated. When the heater 24 operates in this manner, the heat roller 22 is heated by the radiant heat radiated from the heater 24. In this state, when a sheet holding an unfixed toner image passes through the fixing nip N, the sheet and the toner image are heated and pressurized to fix the toner image on the sheet.

  As described above, the fixing device 18 of the present embodiment employs a method (so-called “roller fixing method”) in which a toner image is fixed on a sheet by a pair of rollers 22 and 23. When such a method is adopted, the most effective means for improving energy saving is to reduce the thickness of the heat roller 22 as a member to be heated to reduce its heat capacity. However, when the thickness of the heat roller 22 is reduced in this way, the rigidity of the heat roller 22 is reduced (factor 1).

  In the fixing device 18 of this embodiment, when the heat roller 22 and the press roller 23 are brought into pressure contact with each other to form the fixing nip N, the cross section of the heat roller 22 is deformed into an elliptical shape by the pressure from the press roller 23. Along with this, the contact between the heat roller 22 and the front bearing 27 becomes non-uniform (factor 2).

  In the present embodiment, the first main body portion 41 of the front bearing 27 is provided on the front side of the heat roller 22. If the front end surface 22Fr of the heat roller 22 contacts the first main body portion 41 of the front bearing 27, the first main body portion 41 of the front bearing 27 and the front end surface 22Fr of the heat roller 22 slide with the rotation of the heat roller 22. Rub (Factor 3).

  When the above-described factors 1 to 3 occur in a complex manner, the wear of the heat roller 22, particularly the wear of the front end surface 22 Fr of the heat roller 22, may be severely damaged. However, in the present embodiment, as described above, the front end face 25Fr of the front ring body 25 protrudes more forward than the front end face 22Fr of the heat roller 22. Therefore, the contact between the front end face 22Fr of the heat roller 22 and the first main body 41 of the front bearing 27 can be suppressed, and the occurrence of the factor 3 can be suppressed. Accordingly, it is possible to prevent the heat roller 22 from being worn and damaged.

  In addition, since the wear and breakage of the heat roller 22 can be prevented in this way, the heat roller 22 (for example, the thickness is thinner than the conventional heat roller (for example, a heat roller having a thickness of 0.5 mm or more)). It is possible in some cases to use a heat roller 22) of 0.1 mm to 0.3 mm. Along with this, the heat capacity of the heat roller 22 can be further reduced, and further energy saving can be achieved.

  Further, the front bearing 27 includes a first flange portion 42 that covers the outer periphery of the front end portion 22 a of the heat roller 22, and the drive gear 28 includes a second flange portion 52 that covers the outer periphery of the rear end portion 22 b of the heat roller 22. . By adopting such a configuration, the first and second flange portions 42 and 52 can directly restrict the displacement of the front and rear end portions 22a and 22b of the heat roller 22. In connection with this, it becomes possible to suppress that the rotating shaft A of the heat roller 22 inclines with respect to a predetermined | prescribed direction (this embodiment front-back direction).

  Moreover, since each ring body 25 and 26 is attached to the inner periphery of the front and rear end portions 22a and 22b of the heat roller 22, the front and rear end portions 22a and 22b of the heat roller 22 are reinforced, and deformation of the heat roller 22 is suppressed. It becomes possible to do.

  Further, the edge of the first key groove 32 of the rear ring body 26 protrudes inward from the edge of the second key groove 31 of the heat roller 22. By adopting such a configuration, the rotational driving force transmitted from the drive gear 28 can be received by the rear ring body 26 instead of the heat roller 22. Along with this, it is possible to prevent the heat roller 22 from cracking from the second keyway 31.

  Moreover, the thickness of each ring body 25 and 26 is thicker than the thickness of the heat roller 22. By adopting such a configuration, it is possible to increase the rigidity of the ring bodies 25 and 26, and to suppress the deformation of the ring bodies 25 and 26.

  Further, by making the thickness of each ring body 25, 26 thicker than the thickness of the heat roller 22 as described above, the contact area between the front end surface 25Fr of the front ring body 25 and the first main body portion 41 of the front bearing 27 and the rear It is possible to increase the contact area between the rear end surface 26Rr of the side ring body 26 and the second main body 51 of the drive gear 28. Accordingly, the force applied from the front ring body 25 to the front bearing 27 and the force applied from the rear ring body 26 to the drive gear 28 can be dispersed. Therefore, it is possible to suppress wear and breakage of the front bearing 27 and the drive gear 28.

  Moreover, since each ring body 25 and 26 is formed with the material which has heat resistance, it becomes possible to suppress the thermal deformation etc. of each ring body 25 and 26. FIG.

  The outer peripheral surfaces of the ring bodies 25 and 26 are fixed to the inner peripheral surfaces of the front and rear end portions 22a and 22b of the heat roller 22 by press-fitting, welding, or punching. By adopting such a configuration, the ring bodies 25 and 26 can be reliably fixed to the front and rear end portions 22a and 22b of the heat roller 22.

  In the present embodiment, the case where the outer peripheral surfaces of the ring bodies 25 and 26 are fixed to the inner peripheral surfaces of the front and rear end portions 22a and 22b of the heat roller 22 by press fitting, welding, or punching has been described. On the other hand, in other different embodiments, the outer peripheral surfaces of the ring bodies 25 and 26 may be fixed to the inner peripheral surfaces of the front and rear end portions 22a and 22b of the heat roller 22 by other different means such as adhesion.

  In this embodiment, the case where only a part of the outer member (the front bearing 27 and the drive gear 28) is provided on the front and rear end portions 22a and 22b of the heat roller 22 in the front and rear direction has been described. On the other hand, in other different embodiments, the entire outer member may be provided on the front and rear ends of the front and rear end portions 22a and 22b of the heat roller 22.

  Although the case where the heater 24 is used as a heat source has been described in the present embodiment, an IH coil or the like may be used as a heat source in other different embodiments.

  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.

<Second Embodiment>
Next, a fixing device 71 according to the second embodiment of the present invention will be described with reference to FIG. An arrow I attached to FIG. 5 indicates the inner side in the front-rear direction, and an arrow O attached to FIG. 5 indicates the outer side in the front-rear direction. Since the configuration other than the front ring body 72 and the front bearing 73 is the same as that of the first embodiment, the description thereof is omitted.

  The front ring body 72 includes a small diameter portion 76 and a large diameter portion 77 having an outer diameter larger than that of the small diameter portion 76. A step 78 is formed between the small diameter portion 76 and the large diameter portion 77 in the front ring body 72, and the front end surface 22 Fr (end surface in the front-rear direction) of the heat roller 22 is locked by the step 78. .

  The small-diameter portion 76 of the front ring body 72 is attached to the inner periphery of the front end portion 22a (end portion on the outer side in the front-rear direction) of the heat roller 22. The outer peripheral surface of the small diameter portion 76 is fixed to the inner peripheral surface of the front end portion 22 a of the heat roller 22.

  The large diameter portion 77 of the front ring body 72 is provided on the front side (front and rear direction outer side) of the heat roller 22 and the small diameter portion 76. The front end surface 77Fr (end surface in the front-rear direction) of the large-diameter portion 77 projects forward (outward in the front-rear direction) from the front end surface 22Fr (end surface in the front-rear direction) of the heat roller 22.

  Since the other configuration of the front ring body 72 is the same as that of the front ring body 25 of the first embodiment, the description thereof is omitted.

  The front bearing 73 includes an annular first main body portion 81, a cylindrical first flange portion 82 that extends from the outer diameter side end portion of the first main body portion 81 toward the rear side (inward in the front-rear direction), and It is equipped with. The first main body portion 81 is provided on the front side (front-rear direction outer side) of the large-diameter portion 77 of the front ring body 72. The first flange portion 82 covers the outer periphery of the large diameter portion 77 of the front ring body 72.

  Since other configurations of the front bearing 73 are the same as those of the front bearing 27 of the first embodiment, the same reference numerals as those of the front bearing 27 of the first embodiment are attached to the respective portions of the front bearing 73. The description is omitted.

  As described above, the front bearing 73 extends from the first main body 81 to the rear side of the first main body 81 provided on the front side (front-rear direction outer side) of the large-diameter portion 77 of the front ring body 72, And a first flange portion 82 that covers the outer periphery of the large-diameter portion 77 of the front ring body 72. By adopting such a configuration, it is possible to suppress not only the contact between the front end surface 22Fr of the heat roller 22 and the front bearing 73, but also the contact between the outer peripheral surface of the front end portion 22a of the heat roller 22 and the front bearing 73. Become. Along with this, wear and breakage of the heat roller 22 can be more effectively prevented.

  Particularly in the present embodiment, the inner peripheral portion of the front bearing 73 is not in contact with the heat roller 22 at all, and is in contact with only the front ring body 72. Therefore, wear and breakage of the heat roller 22 can be more reliably prevented.

1 Printer (image forming device)
18 Fixing device 22 Heat roller (Fixing roller)
22a Front end portion (of heat roller) 22b Rear end portion of (heat roller) 22Fr Front end surface of (heat roller) 22Rr Rear end surface of (heat roller) 23 Press roller (pressure member)
25 Front ring body 25Fr Front end surface (front ring body) 26 Rear ring body 26Rr Rear end surface (rear ring body) 27 Front bearing (outer member)
28 Drive gear (outer member)
31 1st keyway 32 2nd keyway 41 1st body part 42 1st flange part 51 2nd body part 52 2nd flange part 55 Drive source 56 key 71 Fixing device 72 Front ring body 73 Front bearing (outer member)
76 Small-diameter portion 77 Large-diameter portion 81 First main body portion 82 First flange portion A Rotating shaft N (heat roller) N Fixing nip

Claims (8)

A fixing roller provided rotatably around a rotation axis;
A pressure member provided in a rotatable manner to form a fixing nip by pressing against the fixing roller;
A ring body mounted on the inner periphery of the outer end of the fixing roller in the rotational axis direction;
An outer member provided at least partly on the outer side in the rotational axis direction of the fixing roller and the ring body,
The fixing device according to claim 1, wherein an end surface of the ring body on the outer side in the rotational axis direction protrudes outward in the rotational axis direction from an end surface on the outer side in the rotational axis direction of the fixing roller. The outer member is
A main body provided on the outer side in the rotational axis direction of the fixing roller and the ring body;
2. A flange portion extending from the main body portion toward the inner side in the rotation axis direction and covering an outer periphery of an end portion of the fixing roller on the outer side in the rotation axis direction. Fixing device. The ring body is
A small-diameter portion mounted on the inner periphery of the outer end of the fixing roller in the rotational axis direction;
A large-diameter portion provided outside the fixing roller and the small-diameter portion in the rotation axis direction, and having a larger outer diameter than the small-diameter portion,
The outer member is
A main body provided outside the large-diameter portion in the rotational axis direction;
The fixing device according to claim 1, further comprising a flange portion that extends inward in the rotation axis direction from the main body portion and covers an outer periphery of the large diameter portion. The outer member is a driving gear connected to a driving source, and a key protrudes from an inner peripheral surface of the driving gear.
The fixing roller and the ring body are provided with a key groove through which the key can be inserted,
The fixing device according to claim 1, wherein an edge of the key groove of the ring body protrudes inward from an edge of the key groove of the fixing roller.   The fixing device according to claim 1, wherein a thickness of the ring body is larger than a thickness of the fixing roller.   The fixing device according to claim 1, wherein the ring body is formed of a material having heat resistance.   The fixing device according to claim 1, wherein the ring body is fixed to an end portion on the outer side in the rotation axis direction of the fixing roller by press-fitting, welding, or punching.   An image forming apparatus comprising the fixing device according to claim 1.

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