JP6252452B2 - 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, 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, thereby forming a toner image. Is fixed on the recording medium.

  For example, Patent Document 1 discloses a fixing belt (refer to “Fixing film 20” in Patent Document 1) and a cap member (“driven ring 28” and “driven ring 34” in Patent Document 1) attached to an end of the fixing belt. ) And an elastic member (see “elastic ring 27” and “elastic member 33” in Patent Document 1) interposed between the end portion of the fixing belt and the cap member. ing.

  In the fixing device having such a configuration, there is a case where it is determined whether or not the fixing belt is rotating normally by detecting the rotation of the cap member by rotating the cap member following the rotation of the fixing belt. is there. Further, there is a case where the fixing belt is rotated in accordance with the rotation of the cap member by rotating the cap member by the driving source.

Japanese Patent Laid-Open No. 10-48777

  In the fixing device configured as described above, if slip occurs between the end portion of the fixing belt and the elastic member, the cap member cannot be rotated following the rotation of the fixing belt, and the rotation of the cap member is detected. It becomes difficult to determine whether or not the fixing belt is rotating normally. Further, when slip occurs between the end portion of the fixing belt and the elastic member as described above, the fixing belt cannot be rotated following the rotation of the cap member, which may lead to rotation failure of the fixing belt. .

  In view of the above circumstances, an object of the present invention is to suppress occurrence of slip between an end portion of a fixing belt and an elastic member.

  The fixing device of the present invention includes a fixing belt that rotates about a rotation shaft, a pressure rotating body that presses against the fixing belt to form a fixing nip, a cap member that is attached to an end of the fixing belt, An elastic member interposed between the end portion of the fixing belt and the cap member, and the elastic member has a concavity and convexity continuous in a circumferential direction on a surface in contact with the end portion of the fixing belt. A shape is provided.

  By adopting such a configuration, the end portion of the fixing belt is less likely to slip with respect to the elastic member as compared with a case where the surface of the elastic member that contacts the end portion of the fixing belt is smooth. Accordingly, it is possible to suppress the occurrence of slip between the end portion of the fixing belt and the elastic member.

  The fixing device may further include a rotation detection unit that detects rotation of the cap member, and the cap member may be rotated following the rotation of the fixing belt.

  By adopting such a configuration, it is possible to determine whether or not the fixing belt is normally rotated through detection of the rotation of the cap member.

  A detected piece projects from the outer peripheral portion of the cap member, and the rotation detecting unit includes a light emitting unit that emits light toward the detected piece, and a light receiving unit that receives light from the light emitting unit. It may be a PI sensor provided.

  By adopting such a configuration, it is possible to detect the rotation of the cap member with a simple configuration.

  The fixing device may further include a drive source for rotating the cap member, and the fixing belt may be rotated by the rotation of the cap member.

  By adopting such a configuration, it is possible to suppress the rotation failure of the fixing belt.

  The fixing device may further include a drive gear connected to the drive source, and a driven gear that meshes with the drive gear may be provided on an outer peripheral portion of the cap member.

  By adopting such a configuration, the cap member can be rotated with a simple configuration.

  In the cap member, at least a portion where the driven gear is provided may be formed of an elastic material.

  By adopting such a configuration, even if the rotation shaft of the fixing belt is displaced with the rotation of the fixing belt, the driving gear and the driven gear are not easily disengaged. Therefore, the cap member can be reliably rotated by the drive source.

  The elastic member is provided so as to be rotatable about the rotation axis, and the uneven shape is formed such that another convex portion is disposed on the opposite side of the one convex portion across the rotation shaft. Also good.

  By adopting such a configuration, when the fixing belt is deformed into an ellipse with the formation of the fixing nip, the fixing belt can be securely gripped by the one convex portion and the other convex portion. It becomes.

  The elastic member is provided so as to be rotatable around the rotation axis, and the concave and convex shape is formed such that one concave portion is arranged on the opposite side of the one convex portion across the rotation shaft. good.

  By adopting such a configuration, when the fixing belt is deformed into an ellipse with the formation of the fixing nip, it is possible to suppress the rotational driving force of different sizes from being applied to the fixing belt from a plurality of convex portions. Is possible.

  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 suppress the occurrence of slip between the end portion of the fixing belt and the elastic member.

1 is a schematic diagram illustrating an outline of a configuration of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. 1 is a side view showing a fixing device according to an embodiment of the present invention. FIG. 3 is a side sectional view showing the vicinity of the front end portion of the fixing belt in the fixing device according to the embodiment of the present invention. It is VV sectional drawing of FIG. FIG. 3 is a side sectional view showing the vicinity of the rear end portion of the fixing belt in the fixing device according to the embodiment of the present invention. It is VII-VII sectional drawing of FIG. 1 is a block diagram illustrating a control system for a fixing device according to an embodiment of the present invention. FIG. 6 is a cross-sectional view showing the vicinity of a front end portion of a fixing belt in a fixing device according to another different embodiment of the present 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 stored in a lower portion 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. 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 with reference to FIGS.

  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. Arrows Fr in FIGS. 3, 4, and 6 indicate the front side (front side) of the fixing device 18. 4 and 6 indicate the inner side in the front-rear direction, and the arrow O in FIGS. 4 and 6 indicates the outer side in the front-rear direction.

  As shown in FIGS. 2 and 3, the fixing device 18 is disposed above the fixing belt 21, a pressure roller 22 (pressure rotator) disposed below the fixing belt 21, and the fixing belt 21. An IH fixing unit 23 (not shown in FIG. 3), a support member 24 disposed on the inner diameter side of the fixing belt 21, and a reinforcing member 25 disposed on the left side of the support member 24 on the inner diameter side of the fixing belt 21. A pressing pad 26 (pressing member) disposed below the support member 24 on the inner diameter side of the fixing belt 21, and a support pad 24 and a pressing pad 26 disposed from the left side to the lower side on the inner diameter side of the fixing belt 21. The sliding contact member 27, the magnetic shielding member 28 disposed above the support member 24 on the inner diameter side of the fixing belt 21, and the magnetic shielding member 28 disposed on the inner diameter side of the fixing belt 21. Guide member 30, a first cap member 31 mounted on the front end portion 21 a of the fixing belt 21, and a first elastic member 32 interposed between the front end portion 21 a of the fixing belt 21 and the first cap member 31. A second cap member 33 attached to the rear end portion 21b of the fixing belt 21, a second elastic member 34 interposed between the rear end portion 21b of the fixing belt 21 and the second cap member 33, and a second member. And a rotation detection unit 35 disposed above the cap member 33.

  The fixing belt 21 is an endless thin belt having flexibility, and has a long cylindrical shape in the front-rear direction. 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 and a release layer that covers the base material layer. The base material layer of the fixing belt 21 is formed of a metal such as nickel or stainless steel or a resin such as PI (polyimide). The release layer of the fixing belt 21 is formed of a fluorine resin such as PFA, for example. The fixing belt 21 may include an elastic layer between the base material layer and the release layer. This elastic layer is made of, for example, silicon rubber.

  The pressure roller 22 has a long cylindrical shape in the front-rear direction. As shown in FIG. 2, the pressure roller 22 is in pressure contact with the fixing belt 21, and a fixing nip 37 is formed between the fixing belt 21 and the pressure roller 22. The paper and the toner image are heated and pressurized by passing the paper through the fixing nip 37, and the toner image is fixed on the paper.

  The pressure roller 22 is rotatably supported by a fixing frame (not shown). The pressure roller 22 includes, for example, a cylindrical cored bar 38, an elastic layer 39 provided around the cored bar 38, and a release layer (not shown) that covers the elastic layer 39. ing. The cored bar 38 of the pressure roller 22 is made of a metal such as stainless steel or aluminum. A transmission gear 40 (see FIG. 3) is fixed to the rear end portion of the cored bar 38 of the pressure roller 22. The elastic layer 39 of the pressure roller 22 is formed of, for example, silicon rubber or silicon sponge. The release layer of the pressure roller 22 is formed of, for example, a fluorine resin such as PFA. Note that the pressure roller 22 is not shown in FIGS. 4 and 6.

  As shown in FIG. 2, the IH fixing unit 23 includes a case member 41 and an IH coil 42 (heat source) accommodated in the case member 41. The IH coil 42 is disposed on the outer diameter side of the fixing belt 21, and is provided in an arc shape along the outer periphery of the fixing belt 21.

  The support member 24 extends in the front-rear direction and penetrates the fixing belt 21. The support member 24 is formed by combining a pair of L-shaped sheet metals, for example, and has a rectangular cross-sectional shape. A support protrusion 43 protruding downward is provided at the lower right corner of the support member 24.

  As shown in FIG. 3, the front and rear end portions of the support member 24 are fixed to fixing members 44 arranged respectively in front and rear of the fixing belt 21. The fixing member 44 is fixed to, for example, a fixing frame (not shown) or forms a part of the fixing frame. A ring-shaped detent member 45 is fixed to both front and rear ends of the support member 24. The detent member 45 is disposed on the inner side in the front-rear direction than the fixed member 44. As shown in FIGS. 4 and 6, an annular protrusion 46 is provided on the inner surface in the front-rear direction of the detent member 45.

  As shown in FIG. 2, the reinforcing member 25 includes a first reinforcing portion 47 that extends in the vertical direction, and a second reinforcing portion 48 that is bent from the lower end of the first reinforcing portion 47 toward the right side. The cross section is substantially L-shaped.

  The pressing pad 26 extends in the front-rear direction. The upper surface of the pressing pad 26 is fixed to the lower surface of the support member 24. Thereby, the pressing pad 26 is supported by the support member 24. The lower surface of the pressing pad 26 presses the fixing belt 21 toward the lower side (pressure roller 22 side) from the inner diameter side. The pressing pad 26 is sandwiched between the support protrusion 43 of the support member 24 and the second reinforcement portion 48 of the reinforcement member 25.

  The sliding member 27 has a sheet shape, for example. The sliding contact member 27 includes a first contact portion 50 that extends in the up-down direction, and a second contact portion 51 that is bent toward the right side from the lower end of the first contact portion 50. The first contact portion 50 is sandwiched between the left side portion of the support member 24 and the first reinforcement portion 47 of the reinforcement member 25. The second contact portion 51 is sandwiched between the lower surface of the pressing pad 26 and the fixing belt 21. When the fixing belt 21 rotates, the fixing belt 21 slides with respect to the pressing pad 26 and the second contact portion 51.

  The magnetic shielding member 28 includes a curved plate portion 52 that curves in an arc shape toward the upper side, and a flat plate portion 53 that extends downward from both left and right ends of the curved plate portion 52. The magnetic shielding member 28 is made of a non-magnetic and highly conductive material such as oxygen-free copper. The magnetic shielding member 28 prevents the magnetic field generated by the IH coil 42 from penetrating the support member 24.

  The guide member 30 is provided so as to cover the upper side of the magnetic shielding member 28. The guide member 30 is formed of, for example, a magnetic material, and has a function of heating the fixing belt 21 by generating heat by the action of a magnetic field generated by the IH coil 42. The guide member 30 includes an attachment portion 54 attached to each flat plate portion 53 of the magnetic shielding member 28 and a connection portion 55 that connects the attachment portions 54 and curves in an arc shape toward the upper side. The connecting portion 55 guides (stretches) the fixing belt 21 from the inner diameter side.

  The first cap member 31 is made of an elastic material (for example, heat resistant rubber such as silicon rubber). As shown in FIG. 4, FIG. 5, etc., the first cap member 31 includes a first main body portion 63 that covers an outer side in the front-rear direction of the front end portion 21 a of the fixing belt 21, and an end on the outer diameter side of the first main body portion 63. And a cylindrical first flange portion 64 that extends inward in the front-rear direction and covers the outer diameter side of the front end portion 21 a of the fixing belt 21.

  The first main body 63 of the first cap member 31 is provided substantially perpendicular to the rotation axis A of the fixing belt 21. The first main body 63 is provided with a circular communication hole 65 in the front-rear direction, and the support member 24 passes through the communication hole 65. The protrusion 46 of the detent member 45 is in contact with the outer surface 66 of the first main body 63 in the front-rear direction. Thereby, the movement to the front-back direction outer side of the 1st cap member 31 is controlled. A plurality of ribs 67 protrude from the inner surface of the first main body 63 in the front-rear direction. The plurality of ribs 67 are provided radially about the rotation axis A of the fixing belt 21.

  The first flange portion 64 of the first cap member 31 is provided substantially parallel to the rotation axis A of the fixing belt 21. The first flange portion 64 is provided with an interval from the outer peripheral surface of the fixing belt 21. A driven gear 68 is provided on the outer peripheral portion of the first main body portion 63 and the first flange portion 64 (which also corresponds to the outer peripheral portion of the entire first cap member 31). The driven gear 68 meshes with a drive gear 69 provided above the first cap member 31.

  The first elastic member 32 is made of heat resistant rubber such as silicon rubber, for example. The first elastic member 32 has a cylindrical shape. The first elastic member 32 is configured to rotate around the rotation axis A together with the fixing belt 21 and the first cap member 31.

  The outer peripheral surface of the first elastic member 32 is in contact with the inner peripheral surface of the first flange portion 64 of the first cap member 31. The outer peripheral surface of the first elastic member 32 is not bonded to the inner peripheral surface of the first flange portion 64 of the first cap member 31.

  The inner peripheral surface of the first elastic member 32 is in contact with the outer peripheral surface of the front end portion 21 a of the fixing belt 21. The inner peripheral surface of the first elastic member 32 is not bonded to the outer peripheral surface of the front end portion 21 a of the fixing belt 21. On the inner peripheral surface of the first elastic member 32, an uneven shape 71 continuous in the circumferential direction is provided. The concavo-convex shape 71 is composed of a plurality of convex portions 72 and concave portions 73 provided alternately. The convex portion 72 and the concave portion 73 are provided at equiangular intervals (for example, at intervals of 30 degrees). In the concavo-convex shape 71, the other convex portion 72 is necessarily arranged on the opposite side of the one convex portion 72 across the rotation axis A, and the other concave portion 73 is necessarily located on the opposite side of the one concave portion 73 across the rotational axis A. It is formed to be arranged. That is, the concavo-convex shape 71 is formed such that the convex portions 72 and the concave portions 73 face each other with the rotation axis A interposed therebetween.

  The second cap member 33 is made of, for example, a heat resistant resin such as a liquid crystal polymer or PPS (polyphenylene sulfide). As shown in FIGS. 6, 7, and the like, the second cap member 33 includes a second main body portion 74 that covers the outer side in the front-rear direction of the rear end portion 21 b of the fixing belt 21, and an outer diameter side of the second main body portion 74. And a cylindrical second flange portion 75 that extends inward in the front-rear direction from the end portion and covers the outer diameter side of the rear end portion 21 b of the fixing belt 21.

  The configuration of the second main body portion 74 of the second cap member 33 is the same as the configuration of the first main body portion 63 of the first cap member 31. Therefore, the same number as each part of the 1st main-body part 63 of the 1st cap member 31 is attached | subjected to each part of the 2nd main-body part 74 of the 2nd cap member 33, and description is abbreviate | omitted.

  A detected piece 76 projects from the outer peripheral portion of the second flange portion 75 of the second cap member 33 (which also corresponds to the outer peripheral portion of the entire second cap member 33). A plurality of pieces to be detected 76 are provided at equal angular intervals (in this embodiment, six at intervals of 60 degrees). Other configurations of the second flange portion 75 of the second cap member 33 are the same as the configurations of the first flange portion 64 of the first cap member 31. Therefore, the same number as each part of the 1st flange part 64 of the 1st cap member 31 is attached | subjected to each part of the 2nd flange part 75 of the 2nd cap member 33, and description is abbreviate | omitted.

  The second elastic member 34 is configured to rotate about the rotation axis A together with the fixing belt 21 and the second cap member 33. The configuration of the second elastic member 34 is the same as the configuration of the first elastic member 32. Therefore, the same number as each part of the 1st elastic member 32 is attached | subjected to each part of the 2nd elastic member 34, and description is abbreviate | omitted.

  The rotation detection unit 35 is, for example, a PI sensor (Photo Interrupter Sensor). The rotation detection unit 35 includes a light emitting unit 77 that emits light toward the detected piece 76 provided on the second cap member 33, and a light receiving unit 78 that receives light from the light emitting unit 77.

  Next, a control system for the fixing device 18 will be described.

  As shown in FIG. 8, the fixing device 18 is provided with a control unit 81 (CPU). The control unit 81 is connected to a storage unit 82 composed of a storage device such as a ROM and a RAM, and the control unit 81 is connected to the fixing device 18 based on a control program and control data stored in the storage unit 82. It is configured to control each part.

  The control unit 81 is connected to the rotation detection unit 35, and when the rotation detection unit 35 detects the rotation of the second cap member 33, a detection signal is output from the rotation detection unit 35 to the control unit 81. Yes.

  The control unit 81 is connected to the IH coil 42. A current flows through the IH coil 42 based on a drive command signal from the control unit 81, so that the IH coil 42 generates a magnetic field, and an eddy current is generated in the fixing belt 21 due to the action of the magnetic field. Is configured to generate heat. That is, the fixing belt 21 can be heated by the IH coil 42.

  The control unit 81 is connected to a drive unit 84 configured by a motor or the like, and the drive unit 84 is connected to the transmission gear 40. When the drive unit 84 rotates the transmission gear 40, the pressure roller 22 is configured to rotate integrally with the transmission gear 40. That is, the pressure roller 22 can be rotated by the drive unit 84.

  The control unit 81 is connected to a drive source 85 configured by a motor or the like, and the drive source 85 is connected to a drive gear 69. When the drive source 85 rotates the drive gear 69, the first cap member 31 that meshes the driven gear 68 with the drive gear 69 rotates. That is, the first cap member 31 can be rotated by the drive source 85.

  In the configuration as described above, when the toner image is fixed on the paper, the transmission gear 40 is rotated by the drive unit 84. Along with this, the pressure roller 22 rotates integrally with the transmission gear 40 (see arrow B in FIG. 2), and the fixing belt 21 pressed against the pressure roller 22 rotates following the rotation of the pressure roller 22. (See arrow C in FIG. 2).

  Further, at the same time as the transmission gear 40 is rotated by the drive unit 84 as described above, the drive gear 69 is rotated by the drive source 85. When the drive gear 69 rotates in this way, the first cap member 31 that meshes the driven gear 68 with the drive gear 69 rotates. Accordingly, the rotation of the first cap member 31 is transmitted to the fixing belt 21 via the first elastic member 32, and the fixing belt 21 rotates following the rotation of the first cap member 31. That is, the fixing belt 21 rotates following the rotation of the first cap member 31 simultaneously with the rotation of the pressure roller 22. By adopting such a configuration, it is possible to suppress the rotation failure of the fixing belt 21.

  Further, when the toner image is fixed on the paper, a current is passed through the IH coil 42. Along with this, the IH coil 42 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. In this state, when the sheet passes through the fixing nip 37, the sheet and the toner image are heated and pressurized to fix the toner image on the sheet.

  When the fixing belt 21 rotates as described above, the rotation of the fixing belt 21 is transmitted to the second cap member 33 via the second elastic member 34, and is driven by the rotation of the fixing belt 21. Rotates. When the second cap member 33 rotates in this way, the optical path from the light emitting unit 77 of the rotation detecting unit 35 to the light receiving unit 78 is continuously opened and closed by the detected piece 76 of the second cap member 33, and the light receiving unit 78 receives light. The amount switches continuously between High and Low. Accordingly, the rotation detection unit 35 detects the rotation of the second cap member 33, and a detection signal is output from the rotation detection unit 35 to the control unit 81. In this case, the control unit 81 determines that the fixing belt 21 is rotating.

  On the other hand, when the rotation of the fixing belt 21 is stopped, the second cap member 33 also does not rotate. Therefore, the optical path from the light emitting unit 77 of the rotation detecting unit 35 to the light receiving unit 78 is not opened and closed by the detected piece 76 of the second cap member 33, and the amount of light received by the light receiving unit 78 is held high or low. The Therefore, the rotation detection unit 35 does not detect the rotation of the second cap member 33, and no detection signal is output from the rotation detection unit 35 to the control unit 81. In this case, the control unit 81 determines that the fixing belt 21 is not rotating. Thus, in the present embodiment, it is possible to determine whether or not the fixing belt 21 is rotating normally through detection of the rotation of the second cap member 33.

  By the way, in the fixing device 18 configured as described above, when a slip occurs between the rear end portion 21b of the fixing belt 21 and the second elastic member 34, the second cap member 33 is moved by the rotation of the fixing belt 21. It becomes impossible to rotate, and it becomes difficult to determine whether or not the fixing belt 21 is rotating normally through detection of the rotation of the second cap member 33. Further, when slip occurs between the front end portion 21 a of the fixing belt 21 and the first elastic member 32, the fixing belt 21 cannot be rotated by the rotation of the first cap member 31, and the rotation of the fixing belt 21 is stopped. There is a risk of failure.

  However, in the present embodiment, the concave and convex shape 71 continuous in the circumferential direction on the inner peripheral surfaces of the first and second elastic members 32 and 34 (surfaces in contact with the outer peripheral surfaces of the front and rear end portions 21a and 21b of the fixing belt 21). Is provided. Therefore, compared to the case where the inner peripheral surfaces of the first and second elastic members 32 and 34 are smooth, the front and rear end portions 21a and 21b of the fixing belt 21 slip relative to the first and second elastic members 32 and 34. It becomes difficult. Accordingly, it is possible to suppress the occurrence of slip between the front and rear end portions 21a and 21b of the fixing belt 21 and the first and second elastic members 32 and 34.

  In the fixing device 18 of the present embodiment, when the pressure roller 22 is brought into pressure contact with the fixing belt 21 to form the fixing nip 37, the fixing belt 21 is crushed in the pressing direction (vertical direction in the present embodiment). And deformed into a horizontally long ellipse (see FIG. 2). Therefore, the rotational driving force from the first cap member 31 is transmitted through the contact area (see R portion in FIG. 5) between the left and right side portions (ellipse long axis side portion) of the fixing belt 21 and the first elastic member 32. It is transmitted to the fixing belt 21. At this time, if the front end 21a of the fixing belt 21 and the first elastic member 32 are in continuous contact with each other in the circumferential direction, a difference in circumferential length between the front end 21a of the fixing belt 21 and the first elastic member 32 (fixing belt). The difference between the outer peripheral length of the front end portion 21a of 21 and the inner peripheral length of the first elastic member 32) causes a shift in the phase of the front end portion 21a of the fixing belt 21 and the first elastic member 32, resulting in poor rotation of the fixing belt 21. There is a risk of connection.

  However, in this embodiment, the uneven | corrugated shape 71 continuous in the circumferential direction is provided in the internal peripheral surface of the 1st elastic member 32 as mentioned above. Therefore, the convex portion 72 of the concavo-convex shape 71 bends the phase shift between the front end portion 21 a of the fixing belt 21 and the first elastic member 32 caused by the difference in the circumferential length between the front end portion 21 a of the fixing belt 21 and the first elastic member 32. Can be absorbed. In this respect as well, it is possible to suppress the rotation failure of the fixing belt 21.

  Further, a detected piece 76 projects from the outer periphery of the second cap member 33, and a light emitting portion 77 that emits light toward the detected piece 76 and a light receiving portion that receives light from the light emitting portion 77. 78, the rotation sensor 35 is a PI sensor. By adopting such a configuration, it is possible to detect the rotation of the second cap member 33 with a simple configuration.

  The fixing device 18 includes a drive gear 69 connected to the drive source 85, and a driven gear 68 that meshes with the drive gear 69 is provided on the outer periphery of the first cap member 31. By adopting such a configuration, the first cap member 31 can be rotated with a simple configuration.

  The first cap member 31 is entirely formed of an elastic material including a portion where the driven gear 68 is provided. By adopting such a configuration, even if the rotation axis A of the fixing belt 21 is displaced with the rotation of the fixing belt 21, the engagement between the drive gear 69 and the driven gear 68 is difficult to disengage. Therefore, the first cap member 31 can be reliably rotated by the drive source 85.

  In addition, the uneven shape 71 of the first and second elastic members 32 and 34 is formed such that the other protrusion 72 is necessarily disposed on the opposite side of the rotation axis A of the one protrusion 72. By adopting such a configuration, when the fixing belt 21 is deformed into an elliptical shape with the formation of the fixing nip 37, the fixing belt 21 is surely secured by the one convex portion 72 and the other convex portion 72 described above. It becomes possible to grip.

  In the present embodiment, the description has been given of the case where the uneven shape 71 of the first elastic member 32 is formed so that the other protrusion 72 is always arranged on the opposite side of the rotation axis A of the one protrusion 72. . On the other hand, in another different embodiment, as shown in FIG. 9, the first elastic member 32 is arranged such that one concave portion 73 is always disposed on the opposite side of the one convex portion 72 across the rotation axis A. An uneven shape 71 may be formed. By adopting such a configuration, when the fixing belt 21 is deformed into an elliptical shape with the formation of the fixing nip 37, the plurality of convex portions 72 of the concave and convex shape 71 of the first elastic member 32 are changed to the fixing belt 21. It is possible to suppress the application of rotational driving forces of different sizes. The same applies to the second elastic member 34 in that the concave-convex shape 71 may be formed so that the single concave portion 73 is always disposed on the opposite side of the convex portion 72 across the rotation axis A. is there.

  In the present embodiment, the case where the outer peripheral surface of the first elastic member 32 is not bonded to the inner peripheral surface of the first flange portion 64 of the first cap member 31 has been described. On the other hand, in another different embodiment, the outer peripheral surface of the first elastic member 32 may be bonded to the inner peripheral surface of the first flange portion 64 of the first cap member 31. The same applies to the relationship between the outer peripheral surface of the second elastic member 34 and the inner peripheral surface of the second flange portion 75 of the second cap member 33.

  In the present embodiment, the case where the entire first cap member 31 is formed of an elastic material has been described. However, in other different embodiments, only the portion of the first cap member 31 where the driven gear 68 is provided is elastic. It may be formed of a material.

  In the present embodiment, the case where the first cap member 31 is formed of an elastic material has been described. However, in another different embodiment, the first cap member 31 is formed of a heat resistant resin such as liquid crystal polymer or PPS (polyphenylene sulfide). It may be formed.

  In the present embodiment, the drive unit 84 that rotates the pressure roller 22 and the drive source 85 that rotates the first cap member 31 are provided separately. However, in other different embodiments, the drive unit that rotates the pressure roller 22. The first cap member 31 may be rotated using 84.

  In the present embodiment, the case where the configuration of the present invention is applied to the fixing device 18 in which the fixing belt 21 slides with respect to the pressing pad 26 and the sliding contact member 27 has been described. The configuration of the present invention may be applied to a fixing device 18 that rotates the fixing belt 21 together with one or a plurality of rollers disposed on the inner diameter side of the belt 21.

  Although the case where the IH coil 42 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.

1 Printer (image forming device)
18 fixing device 21 fixing belt 21a front end portion (of fixing belt) 21b rear end portion (of fixing belt) 22 pressure roller (pressure rotating body)
31 1st cap member 32 1st elastic member 33 2nd cap member 34 2nd elastic member 35 rotation detection part 37 fixing nip 68 driven gear 69 drive gear 71 uneven shape 72 convex part 73 concave part 76 detected piece 77 light emitting part 78 light reception 85 Drive source A Rotating shaft (of fixing belt)

Claims (9)

A fixing belt that rotates about a rotation axis;
A pressure rotator that presses against the fixing belt to form a fixing nip; and
A cap member attached to an end of the fixing belt;
An elastic member interposed between the end portion of the fixing belt and the cap member,
The elastic member is provided with a concavo-convex shape continuous in the circumferential direction on a surface that contacts the end portion of the fixing belt ,
The fixing device according to claim 1, wherein the uneven shape is constituted by convex portions and concave portions provided alternately in the circumferential direction . A rotation detection unit that detects rotation of the cap member;
The fixing device according to claim 1, wherein the cap member rotates following the rotation of the fixing belt. On the outer peripheral portion of the cap member, a detected piece protrudes.
The said rotation detection part is a PI sensor provided with the light emission part which light-emits toward the said to-be-detected piece, and the light-receiving part which light-receives the light from the said light emission part. Fixing device. A drive source for rotating the cap member;
The fixing device according to claim 1, wherein the fixing belt rotates following the rotation of the cap member. A drive gear connected to the drive source;
The fixing device according to claim 4, wherein a driven gear that meshes with the drive gear is provided on an outer peripheral portion of the cap member.   The fixing device according to claim 5, wherein at least a portion of the cap member where the driven gear is provided is formed of an elastic material. The elastic member is provided to be rotatable around the rotation shaft,
The uneven shape is any one of the preceding claims, characterized in that it is formed so as to be arranged the other of the convex portion on the opposite side of the axis of rotation of one of said protrusions The fixing device according to 1. The elastic member is provided to be rotatable around the rotation shaft,
The uneven shape, in any one of claims 1 to 6, characterized in that one of said recesses to sandwich the rotation axis of one of the convex portions opposite side are formed so as to be arranged The fixing device described.   An image forming apparatus comprising the fixing device according to claim 1.

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