JP2015018139A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent slipping from occurring between a pressure member and a fixing belt, while reducing durability of the fixing belt.SOLUTION: A fixing apparatus 18 includes: a rotatable fixing belt 21 having a paper-passing area R1 where a recording medium passes and a non-paper-passing area R2 formed outside the paper-passing area R1; a pressure member 22 which comes into pressure contact with outer peripheral surfaces of the paper-passing area R1 and the non-paper-passing area R2, to form a fixing nip 32 with the paper-passing area R1; a pressing member 25 which is in contact with the inner peripheral surface of the paper-passing area R1 and presses the paper-passing area R1 against the pressure member 22; and an elastic member 27 which is in contact with the inner peripheral surface of the non-paper-passing area R2, and presses the non-paper-passing area R2 against the pressure member 22. Hardness of the elastic member 27 is lower than that of the pressing member 25.

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, an electrophotographic image forming apparatus such as a printer or a copying machine forms a toner image on the surface of a recording medium such as paper, and then heats and pressurizes the recording medium and the toner image by a fixing device. Is fixed on the recording medium.

  In the fixing device described above, a flexible fixing belt, a pressure member that presses against the outer peripheral surface of the fixing belt to form a fixing nip, and an inner peripheral surface of the fixing belt are contacted with each other. There is a so-called “sliding belt type” fixing device that includes a pressing member that presses toward the pressing member side. In such a sliding belt type fixing device, the pressure member is rotated by a driving source connected to the pressure member, so that the fixing belt is rotated by the rotation of the pressure member, and the fixing belt is pressed. Usually, it is slid with respect to the member.

  By the way, in the sliding belt type fixing device, when the operation of fixing the toner image on the recording medium is repeated, the pressing member wears at the portion where the fixing belt and the pressing member are in sliding contact, and the sliding load of the fixing belt (fixing belt) The load necessary for sliding the member with respect to the pressing member increases. Further, when a sheet having a low friction coefficient (for example, a sheet having a smooth surface) passes through the fixing nip, the sheet easily slips with respect to the fixing belt or the pressure member. When these factors are combined, a slip occurs between the pressure member and the fixing belt, and it becomes impossible to rotate the fixing belt following the rotation of the pressure member, thereby causing a problem of image defects. is there.

  Therefore, Patent Document 1 discloses a configuration in which the pressing roller is brought into contact with the inner peripheral surface of the non-sheet passing region of the fixing belt to increase the driving force of the fixing belt (following property of the fixing belt with respect to the pressure member). ing.

JP 2012-255870 A

  In Patent Document 1, a pressing roller is formed of PPS (polyphenylene sulfide) which is a highly rigid resin material. For this reason, when the pressing roller is brought into contact with the inner peripheral surface of the non-sheet passing area of the fixing belt, stress concentrates on a part of the non-sheet passing area of the fixing belt, and the durability of the fixing belt may be reduced.

  Accordingly, an object of the present invention is to prevent the occurrence of slip between the pressure member and the fixing belt without lowering the durability of the fixing belt in consideration of the above circumstances.

  The fixing device of the present invention includes a sheet passing area through which a recording medium passes, and a non-sheet passing area provided outside the sheet passing area, the fixing belt provided rotatably, the sheet passing area, and the paper passing area. A pressure member that is in pressure contact with the outer peripheral surface of the non-sheet passing region and forms a fixing nip with the sheet passing region; and a pressure member that is in contact with the inner peripheral surface of the sheet passing region and that is the pressure member A pressing member that presses toward the side, and an elastic member that contacts an inner peripheral surface of the non-sheet passing region and presses the non-sheet passing region toward the pressing member. The hardness is lower than the hardness of the pressing member.

  As described above, the elastic member is brought into contact with the inner peripheral surface of the non-sheet passing area of the fixing belt, so that the non-sheet passing of the fixing belt can be performed more than when the rigid body is brought into contact with the inner peripheral surface of the non-sheet passing area of the fixing belt. It becomes difficult for stress to concentrate on a part of the region. As a result, the fixing belt is not easily damaged, and the durability of the fixing belt can be improved.

  Further, as described above, the non-sheet passing area of the fixing belt is pressed toward the pressure member side by the elastic member, so that the driving force of the fixing belt (the fixing belt followability with respect to the pressure member) can be increased. It becomes. Therefore, it is possible to prevent the occurrence of slip between the pressure member and the fixing belt.

  Furthermore, by making the hardness of the elastic member lower than the hardness of the pressing member as described above, the elastic member becomes easier to deform than the pressing member. Accordingly, the contact area between the non-sheet passing region of the fixing belt and the elastic member can be increased, and the contact pressure (surface pressure) between the non-sheet passing region of the fixing belt and the elastic member can be decreased. Therefore, it is possible to reduce the stress applied to the contact portion between the non-sheet passing region of the fixing belt and the elastic member while sufficiently securing the driving force of the fixing belt.

  The elastic member is configured to rotate following the rotation of the fixing belt, and the frictional force between the non-sheet passing region and the elastic member is a frictional force between the sheet passing region and the pressing member. It may be larger than.

  By rotating the elastic member in accordance with the rotation of the fixing belt as described above, it is possible to prevent the fixing belt from rubbing against the elastic member. As a result, cracks are less likely to occur at the end of the fixing belt, and the durability of the fixing belt can be further improved.

  Further, by making the frictional force between the non-sheet passing region of the fixing belt and the elastic member larger than the frictional force between the sheet passing region of the fixing belt and the pressing member, the non-sheet passing region of the fixing belt and the elastic member It is possible to prevent slippage between the two. Therefore, the elastic member can be reliably rotated following the rotation of the fixing belt.

  A support member that supports the pressing member and the elastic member; and a bearing that is interposed between the support member and the elastic member. The support member, the elastic member, and the bearing include the fixing belt. It may be provided so as to cover the opening formed at the end of the.

  By adopting such a configuration, the lubricant applied to the inner peripheral surface of the fixing belt leaks to the outside of the fixing belt through the opening, and toner, paper powder, etc., pass through the opening. Can be prevented from entering the inside.

  A cap member attached to an end of the fixing belt, and rotated by the rotation of the fixing belt; and a detent member disposed outside the cap member in the rotation axis direction of the fixing belt. May be.

  By rotating the cap member following the rotation of the fixing belt as described above, it is possible to prevent the fixing belt from rubbing against the cap member. As a result, cracks are less likely to occur at the end of the fixing belt, and the durability of the fixing belt can be further improved. Further, the meandering of the fixing belt can be restricted by disposing a detent member on the outer side of the cap member in the rotation axis direction of the fixing belt.

  A cap member attached to an end of the fixing belt and rotating in accordance with the rotation of the fixing belt, and a detection mechanism for detecting the rotation of the cap member may be further provided.

  By adopting such a configuration, it is possible to reliably detect the rotation state of the fixing belt through the rotation detection of the cap member. Therefore, a situation in which the fixing belt is heated while the fixing belt is not rotating can be avoided.

  The pressing member may include a pressing portion that presses the paper passing area toward the pressing member, and a sliding contact portion that is interposed between the pressing portion and the paper passing area. .

  By adopting such a configuration, it is possible to reduce the sliding load of the fixing belt.

  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 occurrence of slip between the pressure member and the fixing belt without reducing the durability of the fixing belt.

1 is a schematic diagram illustrating an outline of a configuration of a printer according to a first embodiment of the present invention. 1 is a side cross-sectional view showing a fixing device in a printer according to a first embodiment of the present invention. It is III-III sectional drawing of FIG. It is IV-IV sectional drawing of FIG. FIG. 6 is a side sectional view showing a fixing device in a printer according to a second embodiment of the present invention.

<First Embodiment>
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 transferred to. 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 with reference to FIGS.

  Hereinafter, for convenience of explanation, the left side in FIG. 2 is defined as the front side (front side) of the fixing device 18. An arrow Fr in FIG. 2 indicates the front side (front side) of the fixing device 18. An arrow I in FIG. 2 indicates the inner side in the front-rear direction, and an arrow O in FIG. 2 indicates the outer side in the front-rear direction.

  As shown in FIG. 2 and the like, the fixing device 18 includes a fixing belt 21, a pressure roller 22 (pressure member) disposed on the lower side (outside) of the fixing belt 21, and an upper side (outside) of the fixing belt 21. IH fixing unit 23, a supporting member 24 disposed inside the fixing belt 21, a pressing member 25 disposed below the supporting member 24 inside the fixing belt 21, and the fixing belt 21. A guide member 26 disposed on the upper side of the support member 24 on the inner side, elastic rollers 27 (elastic members) inserted into the front and rear end portions 21 a and 21 b of the fixing belt 21, and front and rear end portions 21 a and 21 b of the fixing belt 21. And a cap member 28 to be mounted on each.

  The fixing belt 21 is a flexible thin-walled belt and has a long cylindrical shape in the front-rear direction. The fixing belt 21 is formed with an outer diameter of 20 mm to 50 mm, for example. The fixing belt 21 is provided to be rotatable about 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 fixing belt 21.

  The fixing belt 21 includes, for example, a base material layer, an elastic layer provided around the base material layer, and a release layer that covers the elastic layer. The base material layer of the fixing belt 21 is formed of, for example, Ni (nickel) having a thickness of 30 μm to 50 μm, or formed of a polyimide resin having a thickness of 50 μm to 100 μm. When the base material layer of the fixing belt 21 is formed of a polyimide resin, a metal powder such as Cu (copper), Ag (silver), or Al (aluminum) may be mixed in the polyimide resin. The elastic layer of the fixing belt 21 is formed of, for example, silicon rubber having a thickness of 100 μm to 500 μm. The release layer of the fixing belt 21 is formed of, for example, a fluorine resin such as PFA having a thickness of 30 μm to 50 μm. In each figure, each layer (base material layer, elastic layer, release layer) of the fixing belt 21 is displayed without being particularly distinguished.

  On the inner peripheral surface of the fixing belt 21, a coating made of, for example, polyimide, polyamideimide, PTFE, or the like is applied to a portion that slides with respect to the pressing member 25. On the inner peripheral surface of the fixing belt 21, a lubricant composed of, for example, fluorine grease or silicon oil is applied to a portion that slides with respect to the pressing member 25.

  The fixing belt 21 includes a sheet passing area R1 (area through which the maximum size sheet passes) and a non-sheet passing area R2 provided outside the sheet passing area R1 (on both sides before and after the sheet passing area R1). Non-region). Opening portions 31 are formed in the front and rear end portions 21a and 21b of the fixing belt 21, respectively.

  The pressure roller 22 is rotatably supported by a fixing frame (not shown). The pressure roller 22 has a long cylindrical shape in the front-rear direction. The pressure roller 22 is in pressure contact with the outer peripheral surfaces of the sheet passing region R1 and the non-sheet passing region R2 of the fixing belt 21, and a fixing nip 32 is provided between the sheet passing region R1 of the fixing belt 21 and the pressure roller 22. Is formed.

  The pressure roller 22 includes, for example, a cylindrical core member 33, an elastic layer 34 provided around the core member 33, and a release layer (not shown) that covers the elastic layer 34. ing. The core material 33 of the pressure roller 22 is formed of a metal such as stainless steel or aluminum. A drive gear 35 is fixed to the rear end portion of the core member 33 of the pressure roller 22. The drive gear 35 is connected to a drive source 36 constituted by a motor or the like. The elastic layer 34 of the pressure roller 22 is formed of, for example, silicon rubber or silicon sponge. The release layer (not shown) of the pressure roller 22 is made of, for example, a fluorine resin such as PFA.

  The IH fixing unit 23 includes a case member 37 and an IH coil 38 (heat source) accommodated in the case member 37. The IH coil 38 is provided in an arc shape along the outer periphery of the fixing belt 21. The IH coil 38 is provided on the upper side of the fixing belt 21 (the side opposite to the fixing nip 32). The IH coil 38 is configured to generate a magnetic field when a high-frequency current flows.

  The support member 24 extends in the front-rear direction. The support member 24 penetrates the fixing belt 21. The support member 24 includes a fixed portion 40 and shaft portions 41 provided on both front and rear sides of the fixed portion 40.

  The fixing portion 40 of the support member 24 extends in the front-rear direction. The fixing portion 40 is disposed from the front end side to the rear end side of the sheet passing region R1 of the fixing belt 21. Both front and rear end portions of the fixing portion 40 are disposed in the non-sheet passing region R2 of the fixing belt 21. As shown in FIG. 3, the fixing portion 40 has a rectangular cross section.

  As shown in FIG. 2, each shaft portion 41 of the support member 24 extends in the front-rear direction. An end portion on the inner side in the front-rear direction of each shaft portion 41 is connected to the fixing portion 40 of the support member 24. A portion on the inner side in the front-rear direction of each shaft portion 41 is inserted into the non-sheet passing region R <b> 2 of the fixing belt 21. A portion on the outer side in the front-rear direction of each shaft portion 41 protrudes to the outer side in the front-rear direction of the fixing belt 21 through each opening 31. A ring-shaped detent member 42 is fixed to the outer portion of each shaft portion 41 in the front-rear direction. An end portion of each shaft portion 41 on the outer side in the front-rear direction is fixed to a fixing frame (not shown). As shown in FIG. 4, each shaft portion 41 has a circular shape in cross section.

  As shown in FIG. 2, the pressing member 25 extends in the front-rear direction, and is disposed from the front end side to the rear end side of the sheet passing region R <b> 1 of the fixing belt 21. Both front and rear ends of the pressing member 25 are disposed in the non-sheet passing region R2 of the fixing belt 21. The pressing member 25 includes a pressing portion 43 and a sliding contact portion 44 disposed on the lower side of the pressing portion 43. The hardness of the pressing member 25 (in this embodiment, the hardness of the entire pressing member 25 when the pressing portion 43 and the sliding contact portion 44 are regarded as an integral body) is 60 ° to 70 ° in Asker C hardness.

  The pressing portion 43 of the pressing member 25 is made of a heat resistant resin such as LCP (Liquid Crystal Polymer). An elastomer layer such as silicon rubber may be provided on the lower surface of the pressing portion 43 (the surface on the sliding contact portion 44 side). The upper surface of the pressing portion 43 is fixed to the lower surface of the fixing portion 40 of the support member 24. Thereby, the pressing member 25 is supported by the support member 24. The lower surface of the pressing portion 43 presses the sheet passing region R1 of the fixing belt 21 toward the lower side (pressure roller 22 side) via the sliding contact portion 44. As shown in FIG. 3, the pressing portion 43 has a substantially rectangular cross section. A fixing protrusion 45 is provided on the right surface of the pressing portion 43.

  The sliding contact portion 44 of the pressing member 25 has, for example, a sheet shape. A right end portion of the sliding contact portion 44 is fixed to a fixing protrusion 45 of the pressing portion 43. The sliding contact portion 44 is interposed between the pressing portion 43 and the sheet passing region R1 of the fixing belt 21, and is in contact with the inner peripheral surface of the sheet passing region R1 of the fixing belt 21. When the fixing belt 21 rotates, the sheet passing region R1 of the fixing belt 21 slides with respect to the sliding contact portion 44. That is, the fixing device 18 of the present embodiment is a “sliding belt type”. The sliding contact portion 44 is made of, for example, a fluorine-based resin such as PTFE, and has a smaller friction coefficient than the pressing portion 43. The sliding contact portion 44 reduces the sliding load of the fixing belt 21 (the load necessary for sliding the fixing belt 21 with respect to the pressing member 25).

  The guide member 26 is supported by the support member 24. The guide member 26 is curved in an arc shape toward the upper side (side away from the pressure roller 22). The outer peripheral surface of the guide member 26 is in contact with the inner peripheral surface of the fixing belt 21. The guide member 26 is formed of a material that generates heat by a magnetic field generated by the IH coil 38 (for example, a magnetic shunt metal such as an Fe—Ni alloy).

  As shown in FIGS. 2 and 4, each elastic roller 27 has a cylindrical shape. Each elastic roller 27 is made of, for example, silicon rubber and has elasticity. In this embodiment, each elastic roller 27 is formed of silicon rubber, and the sliding contact portion 44 of the pressing member 25 is formed of a fluorine-based resin. Thereby, the frictional force between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27 is larger than the frictional force between the sheet passing region R1 of the fixing belt 21 and the sliding contact portion 44 of the pressing member 25. ing. Each elastic roller 27 has an Asker C hardness of 20 ° to 50 °. The hardness of each elastic roller 27 is lower than the hardness of the pressing member 25 (Asker C hardness 60 ° to 70 °). The outer diameter of each elastic roller 27 is slightly smaller than the inner diameter of the fixing belt 21. Each elastic roller 27 is disposed on the outer side in the front-rear direction than the pressing member 25.

  Each elastic roller 27 is rotatably supported by each shaft portion 41 of the support member 24 via a bearing 46. That is, each bearing 46 is interposed between each shaft portion 41 of the support member 24 and each elastic roller 27. The shaft portions 41, the elastic rollers 27, and the bearings 46 of the support member 24 are provided so as to cover the openings 31 formed at the front and rear end portions 21 a and 21 b of the fixing belt 21.

  The outer peripheral surface of each elastic roller 27 is in contact with the inner peripheral surface of the non-sheet passing region R2 of the fixing belt 21, and the non-sheet passing region R2 of the fixing belt 21 is directed downward (to the pressure roller 22 side). Pressing. The outer peripheral surface of each elastic roller 27 is not in contact with the inner peripheral surface of the sheet passing region R <b> 1 of the fixing belt 21. Each elastic roller 27 is configured to rotate following the rotation of the fixing belt 21.

  As shown in FIG. 2, each cap member 28 includes an annular main body portion 47 and a flange portion 48 that protrudes inward in the front-rear direction from the outer diameter side end portion of the main body portion 47. .

  The main body portion 47 of each cap member 28 is disposed outside the front and rear end portions 21 a and 21 b of the fixing belt 21 in the front and rear direction. A circular through hole 49 is provided in the center portion of the main body 47 in the front-rear direction, and each shaft portion 41 of the support member 24 is loosely inserted into the through hole 49. A detent member 42 fixed to each shaft portion 41 of the support member 24 is disposed outside the main body portion 47 in the front-rear direction. Thereby, the movement to the front-back direction outer side of each cap member 28 is controlled.

  The flange portion 48 of each cap member 28 is provided so as to cover the outer diameter side of the front and rear end portions 21 a and 21 b of the fixing belt 21. The inner peripheral surface of the flange portion 48 is in contact with the outer peripheral surfaces of the front and rear end portions 21 a and 21 b of the fixing belt 21. Each cap member 28 is configured to rotate following the rotation of the fixing belt 21.

  In the above configuration, when the toner image is fixed on the paper, the drive gear 35 is rotated by the drive source 36. When the drive gear 35 is thus rotated, the pressure roller 22 rotates integrally with the drive gear 35 (see arrow B in FIG. 3). Along with this, the fixing belt 21 in pressure contact with the pressure roller 22 rotates following the rotation of the pressure roller 22 (see arrow C in FIG. 3). Accordingly, each elastic roller 27 and each cap member 28 are rotated following the rotation of the fixing belt 21.

  Further, when the toner image is fixed on the paper, a high frequency current is passed through the IH coil 38. Along with this, the IH coil 38 generates a magnetic field, an eddy current is generated in the fixing belt 21 by the action of the magnetic field, and the fixing belt 21 generates heat. Further, the guide member 26 generates heat by the magnetic field generated by the IH coil 38, and the fixing belt 21 is heated by the guide member 26. In this state, when the sheet passes through the fixing nip 32, the sheet and the toner image are heated and pressurized to fix the toner image on the sheet.

  When the operation of fixing the toner image on the sheet is repeated in this way, the sliding contact portion 44 of the pressing member 25 is worn, and the sliding load of the fixing belt 21 is increased. Further, when a sheet having a low friction coefficient (for example, a sheet having a smooth surface) passes through the fixing nip 32, the sheet easily slips with respect to the pressure roller 22 and the fixing belt 21. When these factors are combined, slip occurs between the pressure roller 22 and the fixing belt 21, and the fixing belt 21 cannot be rotated following the rotation of the pressure roller 22, causing image defects. There is a fear.

  However, in the present embodiment, the non-sheet passing region R2 of the fixing belt 21 is pressed downward (pressure roller 22 side) by the elastic rollers 27, so that the driving force (pressure roller) of the fixing belt 21 is pressed. The followability of the fixing belt 21 with respect to the belt 22 can be increased. Therefore, it is possible to prevent a slip from occurring between the pressure roller 22 and the fixing belt 21.

  Further, since each elastic roller 27 is in contact with the inner peripheral surface of the non-sheet passing region R2 of the fixing belt 21, the fixing is performed more than when the rigid body is brought into contact with the inner peripheral surface of the non-sheet passing region R2 of the fixing belt 21. The stress is less likely to concentrate on a part of the non-sheet passing region R2 of the belt 21. As a result, the fixing belt 21 is not easily damaged, and the durability of the fixing belt 21 can be improved.

  Further, since the hardness of each elastic roller 27 is lower than the hardness of the pressing member 25, each elastic roller 27 is more easily deformed than the pressing member 25. Accordingly, the contact area between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27 is increased, and the contact pressure (surface pressure) between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27 is decreased. be able to. Therefore, it is possible to reduce the stress applied to the contact portion between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27 while sufficiently securing the driving force of the fixing belt 21.

  Further, since each elastic roller 27 is rotated following the rotation of the fixing belt 21, it is possible to prevent the fixing belt 21 from rubbing against each elastic roller 27. As a result, the front and rear end portions 21a and 21b of the fixing belt 21 are hardly cracked, and the durability of the fixing belt 21 can be further improved.

  Further, the frictional force between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27 is made larger than the frictional force between the sheet passing region R1 of the fixing belt 21 and the sliding contact portion 44 of the pressing member 25. Therefore, it is possible to prevent a slip from occurring between the non-sheet passing region R2 of the fixing belt 21 and each elastic roller 27. Therefore, each elastic roller 27 can be reliably rotated following the rotation of the fixing belt 21.

  The shaft portions 41, the elastic rollers 27, and the bearings 46 of the support member 24 are provided so as to cover the openings 31 formed at the front and rear end portions 21 a and 21 b of the fixing belt 21. Therefore, the lubricant applied to the inner peripheral surface of the fixing belt 21 leaks to the outside of the fixing belt 21 through each opening 31, and toner, paper dust, and the like pass through each opening 31. It is possible to prevent intrusion into the inside.

  Further, since each cap member 28 is rotated following the rotation of the fixing belt 21, it is possible to prevent the fixing belt 21 from rubbing against each cap member 28. As a result, the front and rear end portions 21a and 21b of the fixing belt 21 are hardly cracked, and the durability of the fixing belt 21 can be further improved. Further, since each detent member 42 is disposed outside the main body 47 of each cap member 28 in the front-rear direction, the meandering of the fixing belt 21 can be restricted.

  Although the case where the pressing member 25 includes the pressing portion 43 and the sliding contact portion 44 has been described in the present embodiment, the pressing member 25 may include only the pressing portion 43 in other different embodiments.

  In the present embodiment, the case where driving is input from the driving source 36 to the pressure roller 22 has been described. On the other hand, in another different embodiment, driving may be input from the driving source 36 to both the pressure roller 22 and the fixing belt 21.

  Although the case where the IH coil 38 is used as a heat source has been described in the present embodiment, a heater such as a halogen heater or a ceramic heater may be used as a heat source in another different embodiment.

  In the present 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, and a multifunction peripheral. May be.

<Second Embodiment>
Next, a fixing device 51 according to a second embodiment of the present invention will be described with reference to FIG. In addition, since it is the same as that of 1st Embodiment about structures other than each cap member 52 and the detection mechanism 53, the same reference number as 1st Embodiment is attached | subjected to FIG. 5, and description is abbreviate | omitted.

  Each cap member 52 is attached to both front and rear end portions 21 a and 21 b of the fixing belt 21. Each cap member 52 includes an annular main body 54 and a flange 55 that protrudes inward in the front-rear direction from the radial center of the main body 54.

  The main body portion 54 of each cap member 52 is disposed outside the front and rear end portions 21 a and 21 b of the fixing belt 21 in the front and rear direction. A circular through hole 56 is provided in the front-rear direction at the center of the main body 54, and each shaft 41 of the support member 24 is loosely inserted into the through hole 56. A first connection gear 57 is provided on the outer periphery of the main body portion 54.

  The flange portion 55 of each cap member 52 is inserted into the front and rear end portions 21 a and 21 b of the fixing belt 21. The flange portion 55 is rotatably supported by the shaft portions 41 of the support member 24 via bearings 66. The flange portion 55 is provided with an elastic roller 27 that is inserted into the front and rear end portions 21 a and 21 b of the fixing belt 21.

  A detection mechanism 53 is provided on the rear upper side of the rear cap member 52. The detection mechanism 53 includes a second connection gear 58, a pulse plate 59 provided on the rear side of the second connection gear 58, a connection shaft 60 that connects the second connection gear 58 and the pulse plate 59, and a rear of the pulse plate 59. And a sensor 61 disposed on the upper side.

  The second connection gear 58 meshes with the first connection gear 57 of the rear cap member 52. On the pulse plate 59, light shielding portions 62 are arranged in the circumferential direction. The sensor 61 is, for example, a PI sensor (Photo Interrupter Sensor), and includes a light emitting unit 64 and a light receiving unit 65.

  In the configuration as described above, when the fixing belt 21 rotates, each elastic roller 27 rotates following the rotation of the fixing belt 21, and each cap member 52 rotates following the rotation of each elastic roller 27. To do. When each cap member 52 rotates, the first connection gear 57 of the rear cap member 52 rotates, and the second connection gear 58 that meshes with the first connection gear 57 of the rear cap member 52 rotates. The rotation of the second connection gear 58 is transmitted to the pulse plate 59 via the connection shaft 60, and the pulse plate 59 rotates. When the pulse plate 59 rotates, the light emitted from the light emitting unit 64 of the sensor 61 toward the light receiving unit 65 is intermittently blocked by the light blocking unit 62 of the pulse plate 59, and thus the amount of light received by the light receiving unit 65 of the sensor 61. Alternately switch between High and Low. Thereby, the detection mechanism 53 detects the rotation of the rear cap member 52.

  On the other hand, if the fixing belt 21 is stopped, the cap members 52 are also stopped, and the detection mechanism 53 does not detect the rotation of the rear cap member 52.

  As described above, the rotation state of the fixing belt 21 can be reliably detected through the rotation detection of the rear cap member 52. Therefore, it is possible to avoid a situation in which the fixing belt 21 is heated by the IH coil 38 when the fixing belt 21 is not rotating.

1 Printer (image forming device)
18 Fixing Device 21 Fixing Belt 21a (Fixing Belt) Front End 21b (Fixing Belt) Rear End 22 Pressure Roller (Pressure Member)
24 support member 25 pressing member 27 elastic roller (elastic member)
28 Cap member 31 Opening portion 32 Fixing nip 42 Locking member 43 Pressing portion 44 Sliding contact portion 46 Bearing 51 Fixing device 52 Cap member 53 Detection mechanism R1 Paper passing area R2 Non-paper passing area A Rotating shaft of (fixing belt)

Claims (7)

A fixing belt provided rotatably, having a sheet passing area through which the recording medium passes, and a non-sheet passing area provided outside the sheet passing area;
A pressure member that presses against an outer peripheral surface of the sheet passing area and the non-sheet passing area and forms a fixing nip between the sheet passing area;
A pressing member that contacts an inner peripheral surface of the sheet passing area and presses the sheet passing area toward the pressing member;
An elastic member that contacts an inner peripheral surface of the non-sheet-passing region and presses the non-sheet-passing region toward the pressure member side;
The fixing device according to claim 1, wherein a hardness of the elastic member is lower than a hardness of the pressing member. The elastic member is configured to rotate following the rotation of the fixing belt,
The fixing device according to claim 1, wherein a frictional force between the non-sheet passing region and the elastic member is larger than a frictional force between the sheet passing region and the pressing member. A support member that supports the pressing member and the elastic member;
A bearing interposed between the support member and the elastic member,
The fixing device according to claim 1, wherein the support member, the elastic member, and the bearing are provided so as to cover an opening formed at an end portion of the fixing belt. A cap member attached to an end of the fixing belt, and rotated by the rotation of the fixing belt;
The fixing device according to claim 1, further comprising a detent member disposed outside the cap member in a rotation axis direction of the fixing belt. A cap member attached to an end of the fixing belt, and rotated by the rotation of the fixing belt;
The fixing device according to claim 1, further comprising a detection mechanism that detects rotation of the cap member. The pressing member is
A pressing portion that presses the sheet passing area toward the pressure member;
The fixing device according to claim 1, further comprising a sliding contact portion interposed between the pressing portion and the sheet passing area.   An image forming apparatus comprising the fixing device according to claim 1.

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