JP2010014904A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely separate the paper sheet from the fixing roller or belt. <P>SOLUTION: In a first nip 140 in the fixing device 100, the toner image is heated, pressed, and fixed on the paper sheet P. In the second nip 142, the curvature of the fixing roller 110 is deformed by the separator 134 so that the front surface side of the paper sheet P is separated from the fixing roller 110 by this deformed curvature. At the downstream of the second nip 142, the fixing belt 120 is contacted and pressed by the driven roller 150 and the curvature of the fixing belt 120 is deformed so that the back surface side of the paper sheet P is separated from the fixing belt 120 by this deformed curvature. The paper sheet P separated from the fixing roller 110 and the fixing belt 120 is carried to the paper sheet eject tray. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes a toner image on a sheet, and an image forming apparatus such as a copying machine, a facsimile, and a printer including the fixing device.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a printer includes a fixing device for fixing a toner image on a sheet. The fixing device includes a fixing roller having a heat source such as a halogen lamp, and a fixing belt that presses the fixing roller. In a first nip portion formed between the fixing roller and the fixing belt, an unfixed toner image is fixed on the sheet by heating and pressurizing the conveyed sheet.

  Here, in the first nip portion, the fixing belt is softer than the fixing roller, and the shape thereof is deformed into an arc shape along the fixing roller, so that the fixing roller and the sheet are likely to be poorly separated. The paper separation failure means that the paper that has passed through the first nip portion is transported without being normally separated while being wound around the fixing roller. In particular, poor separation tends to occur on coated paper with high surface smoothness, thin paper with low rigidity, and the like.

  Therefore, Patent Document 1 discloses an image forming apparatus in which a separation member for separating the sheet from the fixing roller is provided on the inner peripheral surface of the fixing belt on the downstream side of the first nip portion. According to this image formation, the curvature of the fixing roller is deformed at the time of pressure contact, and the second nip portion is formed between the separation member and the fixing roller, so that the sheet can be reliably separated (peeled) from the roller. it can.

JP 2008-107382 A (page 6, FIG. 3)

  However, in Patent Document 1, since the deformation of the curvature of the fixing roller by the second nip portion acts only on one surface (front surface) of the paper, the paper is separated from the fixing roller, but is separated from the fixing belt. In some cases, the sheet is conveyed while the sheet is wound around the fixing belt. In particular, in the case of duplex printing, since a toner image is also formed on the back side of the paper, the paper often wraps around the fixing belt. As a result, there is a risk of causing image defects such as paper wrinkles, image misalignment, and gloss unevenness.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, and to provide a fixing device and an image forming apparatus that reliably separate a sheet from a fixing roller and a fixing belt.

  In order to solve the above-mentioned problems, an image forming apparatus according to claim 1 is a fixing device for fixing a toner image formed on a sheet, and has a heating mechanism inside and a fixing device provided rotatably. A roller, a fixing belt that is pressed against the fixing roller and rotates as the fixing roller rotates, and is disposed inside the fixing belt. The nip portion is disposed between the fixing roller and the fixing belt by pressing the fixing belt against the fixing roller. And a curvature of the fixing roller which is disposed downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt, and presses the fixing belt against the fixing roller. The first separating member that separates the sheet from the fixing roller by deforming the sheet and the downstream of the first separating member in the rotation direction of the fixing belt and outside the fixing belt. By the fixing belt pressed against deforming the curvature of the fixing belt it is intended and a second separating member for separating the sheet from the fixing belt.

  In the present invention, the paper on which the toner image is formed by the image forming unit is conveyed to the fixing device. In the nip portion of the fixing device, the toner image is heated and melted by the heating mechanism, and is pressed by the fixing roller and the fixing belt, and is fixed to the paper on the paper.

  The sheet on which the toner image is fixed is conveyed downstream of the nip portion. On the downstream side of the nip portion, the fixing roller is pressed against the first separation member, and the curvature of the surface of the fixing roller is deformed. For this reason, the conveyed sheet is separated from the fixing roller on the surface side of the sheet by deformation of the curvature of the fixing roller.

  Further, on the downstream side of the first separating member, the fixing belt is pressed against the second separating member, and the curvature of the fixing belt is deformed. Therefore, the back side of the sheet that has passed through the first separation member is separated from the fixing belt by the deformation of the curvature of the fixing belt by the second separation member.

  The fixing device according to claim 2 is the second pressing member according to claim 1 or 2, wherein the second pressing member is disposed downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt. The second pressing member presses the second separation member via the fixing belt.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the axial length of at least one of the second separating member and the second pressing member is substantially the same as the axial length of the fixing belt. It is provided to become.

  According to a fourth aspect of the present invention, in the fixing device according to the first or second aspect, at least one of the second separating member and the second pressing member is provided in plural along the axial direction of the fixing belt. is there.

  According to a fifth aspect of the present invention, there is provided the fixing device according to any one of the first to fourth aspects, wherein the first driving unit that rotationally drives the fixing roller, the second driving unit that rotationally drives the second pressing member, and the first driving unit. And a control unit that controls driving of the driving unit and the second driving unit, and the control unit controls the second driving unit in synchronization with the driving of the first driving unit.

  An image forming apparatus according to a sixth aspect includes an image forming unit that forms a toner image on a sheet, and a fixing device that fixes the toner image on the sheet on which the toner image is formed by the image forming unit. A fixing roller having an internal heating mechanism and rotatably provided by a driving unit, a fixing belt that is pressed against the fixing roller and rotates as the fixing roller rotates, and is disposed inside the fixing belt. Is pressed against the fixing roller to form a nip portion between the fixing roller and the fixing belt, and is located downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt. A first separating member that separates the sheet from the fixing roller by deforming the curvature of the fixing roller by pressing the fixing belt against the fixing roller, and fixing more than the first separating member. And a second separating member that is disposed downstream of the fixing belt and outside the fixing belt, and separates the sheet from the fixing belt by pressing the fixing belt and deforming the curvature of the fixing belt. It is.

  According to the first aspect of the present invention, the second separation member is provided on the downstream side of the first separation member, and the fixing belt is pressed against the second separation member to deform the curvature. It can be efficiently separated from the fixing belt. Thereby, the separation performance of the fixing device can be improved.

  According to the second aspect of the invention, the second separation member can be prevented from idling by pressing the second separation member through the fixing belt by the second pressing member provided inside the fixing belt. Accordingly, it is possible to prevent the fixing belt from being worn out due to the idling of the second separation member, and it is possible to improve the durability of the fixing belt. As a result, the replacement time of the fixing belt can be delayed and the cost can be reduced.

  According to the invention of claim 3, since the axial length of the second separation member is set to be substantially the same as the axial length of the fixing belt, the fixing belt can be uniformly pressed and the paper The curvature deformation of the fixing belt can be applied to the entire width direction (direction perpendicular to the conveying direction). Thereby, the paper can be reliably separated from the fixing belt.

  According to the fourth aspect of the present invention, since the plurality of second separating members are provided, the fixing belt can be pressed uniformly, and the curvature deformation of the fixing belt can be applied to the entire width direction of the sheet. Thereby, the paper can be reliably separated from the fixing belt.

  According to the fifth aspect of the present invention, even when the load of the fixing belt is increased by the pressing of the second pressing member and the rotation of the fixing belt is prevented, the second driving unit independently performs the second pressing. Since the member rotates, the load on the fixing belt can be reduced. Thereby, rotation unevenness of the fixing belt can be suppressed.

  According to the sixth aspect of the present invention, the second separation member is provided on the downstream side of the first separation member, and the curvature is deformed by pressing the fixing belt by the second separation member. Can be efficiently separated from the fixing belt. Thereby, the separation performance of the fixing device provided in the image forming apparatus can be improved.

  Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

[First Embodiment]
<Configuration of image forming apparatus>
FIG. 1 is a diagram showing a configuration of an image forming apparatus 500 according to an embodiment of the present invention. The image forming apparatus 500 includes an image reading unit 30, an image forming unit 10, a paper feeding unit 50, and a fixing device 100. The image reading unit 30 is provided on the upper part of the image forming apparatus main body 8 and includes an automatic document feeder 32 and a scanning exposure device 34. The automatic document feeder 32 transports the document M placed on the document table to the scanning exposure device 34 by a transport mechanism.

  The optical system of the scanning exposure device 34 scans and exposes one or both side images of the conveyed document M, and reads the image of the document M scanned and exposed by a line image sensor 36 composed of a CCD (Charge Coupled Device). The image signal photoelectrically converted by the line image sensor 36 is supplied to the image forming unit 10 after being subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown).

  The image forming unit 10 is referred to as a tandem color image forming unit, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer member 40, and the like.

  The image forming unit 10Y is a unit that forms a yellow (Y) color image. The drum-shaped photoconductor 11Y having an electrostatic latent image formed on the surface thereof, a charging unit 12Y disposed around the drum-shaped photoconductor 11Y, It has an exposure unit 14Y, a developing unit 16Y, a primary transfer unit 18Y, and a cleaning unit 20Y.

  The image forming unit 10M is a unit that forms a magenta (M) color image. The drum-shaped photoconductor 11M on the surface of which an electrostatic latent image is formed, a charging unit 12M disposed around the drum-shaped photoconductor 11M, and exposure. It has a portion 14M, a developing portion 16M, a primary transfer portion 18M, and a cleaning portion 20M.

  The image forming unit 10 </ b> C is a unit that forms a cyan (C) color image. The drum-shaped photoconductor 11 </ b> C on which an electrostatic latent image is formed, a charging unit 12 </ b> C disposed around the drum-shaped photoconductor, and exposure 14C, developing unit 16C, primary transfer unit 18C, and cleaning unit 20C.

  The image forming unit 10K is a unit for forming a black (K) color image. The drum-shaped photoconductor 11K having an electrostatic latent image formed on the surface thereof, a charging unit 12K disposed around the drum-shaped photoconductor 11K, and exposure. It has a section 14K, a developing section 16K, a primary transfer section 18K, and a cleaning section 20K.

  The cleaning units 20Y, 20M, 20C, and 20K of each unit remove residual toner on the photoconductors 11Y, 11M, 11C, and 11K with a cleaning blade (not shown) at the timing when, for example, primary transfer or secondary transfer described later is completed. To do.

  The intermediate transfer body 40 is stretched and supported by a plurality of rollers, and is controlled to move to each transfer position by the rotation of the plurality of rollers. The toner images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the moving intermediate transfer member 40 by the primary transfer portions 18Y, 18M, 18C, and 18K of each unit, and the intermediate transfer member. A color toner image in which the toners of the respective colors are overlaid on 40 is formed.

  The paper feed unit 50 selects the paper feed tray 28 selected by the user based on a control signal (paper feed tray selection information) from a control unit 80 (see FIG. 4) described later. The paper P stored in the selected paper feed tray 28 is separated into a single paper P by the paper feed roller 52 and fed to the resist roller 56 in a stopped state via a plurality of paper feed rollers 54. Is done. The fed paper P is temporarily stopped by the registration roller 56, and the registration roller 56 starts to rotate at the timing when the leading edge of the paper P and the toner image on the intermediate transfer body coincide with each other. The color toner image is transferred onto the paper P (secondary transfer) and conveyed to the fixing device 100.

<Configuration of fixing device>
FIG. 2 is a cross-sectional view illustrating a configuration of the fixing device 100. FIG. 3A is a perspective view schematically showing the fixing device 100, and FIG. 3B is a top view schematically showing the fixing belt 120 and the driven roller 150 of the fixing device 100. The fixing device 100 includes a fixing roller 110, a fixing belt 120, and a driven roller 150 that is an example of a second separation member.

  The fixing roller 110 has a metal core 112, an elastic layer 114, and a surface layer 116. The cored bar 112 has a cylindrical shape and is made of aluminum, iron, or the like. The elastic layer 114 is made of, for example, silicon rubber having high heat resistance, and is provided so as to cover the outer peripheral surface of the cored bar 112. The surface layer 116 is made of a releasable material made of a fluororesin such as PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene), and is provided so as to cover the outer peripheral surface of the elastic layer 114.

  A heater 148 made of a halogen lamp or the like for heating the toner image is installed inside the cored bar 112 of the fixing roller 110. The heater 148 is controlled by the controller 80 (see FIG. 4) so that the surface temperature of the fixing roller 110 becomes a predetermined temperature. The fixing roller 110 is rotated in the rotation direction D1 by a drive motor 146 (not shown) (see FIG. 4).

  The fixing belt 120 is pressed against the fixing roller 110 and rotates as the fixing roller 110 rotates, and includes a belt main body 122, a sliding member 124, and a fixing belt unit 170. The fixing belt unit 170 is provided inside the sliding member 124, and includes a pressing member (first pressing member) 126, a separation member (first separation member) 134, and a support member 133 made of a sheet metal that supports them. Composed.

  The belt body 122 is an endless belt and is made of a heat resistant resin such as PI (polyimide), PA (polyamide), or PIA (polyamideimide).

  The sliding member 124 is made of glass wool coated with a fluororesin such as PTFE and contains a heat-resistant lubricant. The sliding member 124 is provided on the inner peripheral surface side of the belt main body 122 and slidably supports the belt main body 122.

  The pressing member 126 is made of, for example, silicon rubber, and is disposed inside the belt main body 122. A compression spring 132 is attached to the back side of the pressing member 126 via a base metal plate 128 and a base member 130, and the pressing member 126 is biased toward the fixing belt 120 by the compression spring 132. The urging pressing member 126 presses (presses) the fixing belt 120 via the belt main body 122. At this time, since the pressed fixing roller 110 is harder than the fixing belt 120, the fixing belt 120 is elastically deformed according to the shape of the outer peripheral surface of the fixing roller 110. Between the elastically deformed fixing belt 120 and the fixing roller 110, a first nip portion 140 for fixing the toner image on the paper P is formed.

  The separation member 134 is made of a rigid body such as PPS (polyphenylene sulfide), PI (polyimide), PA (polyamide), iron, or aluminum, and is downstream of the pressing member 126 with respect to the rotation direction D2 of the belt body 122. It is disposed inside the fixing belt 120. An elastic member 136 made of rubber or the like is attached to the back surface side of the separation member 134, and the separation member 134 is urged toward the fixing belt 120 by the elastic member 136. The biased separation member 134 presses (presses) the fixing roller 110 via the belt body 122. At this time, since the pressed fixing roller 110 is softer than the separating member 134, the curvature of the fixing roller 110 is elastically deformed according to the shape of the outer peripheral surface of the separating member 134. A second nip portion 142 that separates the sheet P from the fixing roller 110 is formed between the elastically deformed fixing belt 120 and the belt main body 122.

  The driven roller 150 elastically changes the curvature of the fixing belt 120 by pressing the fixing belt 120, and is downstream of the separating member 134 and outside the belt body 122 with respect to the rotation direction D <b> 2 of the belt body 122. Be placed. As shown in FIGS. 3A and 3B, the driven roller 150 has an axial length shorter than the axial length of the fixing belt 120, and the diameter thereof is the diameter of the fixing belt 120. It is comprised from the roller which makes a smaller cylindrical shape, for example, consists of materials, such as the above-mentioned polyimide and silicon rubber. In this example, the driven roller 150 is disposed at a substantially central portion in the axial direction of the fixing belt 120 so that the axis of the driven roller 150 is parallel to the axis of the fixing belt 120.

  One ends of shaft portions 152 and 152 are attached to both ends of the driven roller 150, and the other ends of the shaft portions 152 and 152 are rotatably supported by bearing portions 154 and 154. A compression spring 156 is attached to the opposite side of the bearing portion 154 from the driven roller 150, and the bearing portion 154 is biased toward the fixing belt 120 by the compression spring 156. The biased driven roller 150 presses (presses) the fixing belt 120 by the bias of the compression spring 156 to elastically deform the curvature of the fixing belt 120. The driven roller 150 pressed against the fixing belt 120 is rotated in the rotation direction D3 following the rotation of the fixing belt 120 in the rotation direction D2 (see FIG. 2).

<Block Configuration of Image Forming Apparatus>
Next, a block configuration of the image forming apparatus 500 will be described. FIG. 4 is a diagram illustrating an example of a block configuration of the image forming apparatus 500. The image forming apparatus 500 includes a control unit 80, an image reading unit 30, an image forming unit 10, an operation display unit 90, a memory unit 88, and a fixing device 100.

  The image reading unit 30 converts image information composed of analog signals read by the scanner into a digital image signal and outputs the digital image signal to the control unit 80 or the like. The image forming unit 10 outputs an image based on image data stored in, for example, a job reservation content data file in the memory unit 88 according to an instruction from the control unit 80 and applies toner to the paper P supplied from the paper supply unit 50. The image is transferred to form an image.

  The operation display unit 90 includes an operation unit 94 and a display unit 92. For example, a touch panel in which the operation unit 94 and the display unit 92 are combined together is used. The operation unit 94 detects input information (input position) input by the user on the operation screen displayed on the display unit 92, generates a detection signal based on the detected input information, and supplies the detection signal to the control unit 80. The display unit 92 includes, for example, a liquid crystal display or an organic EL (Electro Luminescence) display. The display unit 92 performs a predetermined display process according to an image signal based on the detection signal of the operation unit 94 supplied from the control unit 80.

  The memory unit 88 is configured by, for example, an HDD (Hard disk drive) or a semiconductor memory. The memory unit 88 includes, for example, image data read from the image reading unit 30, document / image data from a computer (not shown) connected to the image forming apparatus 500, operation screen data displayed on the operation display unit 90, and the like. Remembered.

  The control unit 80 includes a CPU (Central Processing Unit) 82, a ROM (Read Only Memory) 84, and a RAM (Random Access Memory) 86. The ROM 84 stores a program for operating the image forming apparatus 500. The RAM 86 is used as a temporary storage area for programs read from the ROM 84 and input information from the display unit 92 and the like. The CPU 82 reads a program held in the ROM 84 and executes processing according to the program.

  The fixing device 100 includes a drive motor 146 and a heater 148. The drive motor 146 is an example of a first drive unit, and rotates the fixing roller 110 at a predetermined speed and timing based on a drive signal supplied from the control unit 80. The heater 148 is an example of a heating mechanism. The heater 148 heats the fixing roller 110 based on a control signal supplied from the control unit 80, detects the temperature by a sensor or the like, and keeps the surface temperature of the fixing roller 110 constant by feedback control. To maintain.

<Operation of fixing device>
Next, an example of the operation of the fixing device 100 described above will be described. 5A and 5B are diagrams illustrating the operation of the fixing device 100. FIG. When the sheet P on which the toner image is formed is conveyed to the fixing device 100, the drive motor 146 is driven by the drive signal supplied from the control unit 80, and the fixing roller 110 rotates in the rotation direction D1 (clockwise). Along with this rotation, the belt main body 122 pressed against the fixing roller 110 slides on the surface of the sliding member 124 and rotates in the rotation direction D2 (counterclockwise), and the paper P is conveyed to the first nip portion 140. Is done.

  In the first nip portion 140, as shown in FIG. 5A, the toner images formed on both sides of the paper P are heated by the heaters disposed inside the fixing roller 110 and are passed through the fixing belt 120. The toner image is fixed on the paper P by being pressed by the pressing member 126. The sheet P on which the toner image is fixed is conveyed from the first nip 140 to the second nip 142 by the rotation of the fixing roller 110 and the fixing belt 120.

  In the second nip portion 142, as shown in FIG. 5B, the curvature of the surface of the fixing roller 110 is changed by the pressing of the separation member 134, and the sheet P that has passed through the first nip portion 140 is transferred to the fixing roller. The surface P <b> 1 is separated from the fixing roller 110 by the deformation of the curvature of 110. At this time, although the paper P that has passed through the second nip portion 142 is separated from the fixing roller 110 by the separation member 134, only the curvature of the surface of the fixing roller 110 on the surface side of the paper P is obtained at the second nip portion 142. Only the front surface of the paper P is separated because of the change, and the back surface P2 of the paper P may not be separated from the fixing belt 120 in some cases.

  In this example, as shown in FIG. 5B, the curvature of the surface of the fixing belt 120 is elastically deformed in the inner direction of the fixing belt 120 by a driven roller 150 provided on the downstream side of the second nip portion 142. Therefore, the curvature of the fixing belt 120 in the vicinity T on the downstream side of the second nip portion 142 is smaller than that in the case where the driven roller 150 is not installed (broken line), so the sheet P that has passed through the second nip portion 142 is The fixing belt 120 is easily separated from the fixing belt 120 due to deformation of the curvature of the fixing belt 120. The paper P separated from the fixing belt 120 is conveyed to the paper discharge tray 68 side (see FIG. 1).

  As described above, according to the present embodiment, the driven roller 150 is provided on the downstream side of the separation member 134, and the fixing belt 120 is pressed by the driven roller 150 to deform the curvature. Can be efficiently separated from the fixing belt 120. Thereby, the separation performance of the fixing device 100 can be improved.

(Modification 1)
Next, a driven roller 150A, which is a modified example of the driven roller 150 described above, will be described. 6A and 6B are diagrams showing the configuration of the driven roller 150A. As the driven roller 150A, a roller having the same size, shape, etc. as the driven roller 150 of the first embodiment described above is used. In this example, three driven rollers 150 </ b> A are arranged at a predetermined interval along the axial direction of the fixing belt 120. A shaft portion 152 connects the driven roller 150A on the left end side and the driven roller 150A on the center side, and between the driven roller 150A on the center side and the driven roller 150A on the right end side.

  One ends of shaft portions 152, 152 are attached to the outer end faces of the driven roller 150A on one end side and the other end side, and the other ends of the shaft portions 152, 152 are rotatably supported by bearing portions 154, 154. . A compression spring 156 is attached to the opposite side of the bearing portion 154 from the driven roller 150 </ b> A, and the bearing portion 154 is biased toward the fixing belt 120 by the compression spring 156. The driven roller 150 </ b> A presses (presses) the fixing belt 120 by the urging force of the compression spring 156 to elastically deform the curvature of the fixing belt 120. The driven roller 150A pressed against the fixing belt 120 is driven to rotate clockwise as the fixing belt 120 rotates counterclockwise.

  According to this modification, since the axial length of the driven roller 150 is set to be substantially the same as the axial length of the fixing belt 120, the fixing belt 120 can be uniformly pressed and the width of the paper P The curvature deformation of the fixing belt 120 can be applied to the entire direction. Thereby, the paper P can be reliably separated from the fixing belt 120.

(Modification 2)
FIGS. 7A and 7B are diagrams showing the configuration of the driven roller 150B. The driven roller 150B has the same diameter as the driven roller 150 of the first embodiment described above, and the axial length of the driven roller 150B is the axis of the fixing belt 120 (in the direction orthogonal to the circumferential direction of the fixing belt 120). It is set to a length substantially the same as the length of (width).

  One ends of shaft portions 152, 152 are attached to both ends of the driven roller 150B, and the other ends of the shaft portions 152, 152 are rotatably supported by bearing portions 154, 154. A compression spring 156 is attached to the opposite side of the bearing portion 154 from the driven roller 150B, and the bearing portion 154 is biased toward the fixing belt 120 by the compression spring 156. The driven roller 150 </ b> B presses (presses) the fixing belt 120 by the urging force of the compression spring 156 to elastically deform the curvature of the fixing belt 120. The driven roller 150B pressed against the fixing belt 120 is driven to rotate clockwise, for example, as the fixing belt 120 rotates counterclockwise.

  According to this modification, the driven roller 150B is provided substantially the same as the shaft length of the fixing belt 120, so that the fixing belt 120 can be uniformly pressed and the curvature of the fixing belt 120 is deformed in the entire width direction of the paper P. Can act. Thereby, the paper P can be reliably separated from the fixing belt 120.

[Second Embodiment]
Hereinafter, a fixing device 200 according to a second embodiment of the present invention will be described with reference to the drawings. Note that components common to the image forming apparatus 500 and the fixing apparatus 100 described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment described above, in order to prevent the paper P from being wrapped around the fixing belt 120, the driven roller 150 is pressed against the fixing belt 120 to change the curvature of the surface of the fixing belt 120, thereby changing the paper P. Was separated from the fixing belt 120 efficiently.

  However, since the fixing belt 120 itself is soft and has a surface coated, the driven roller 150 may slip and slip by simply pressing the driven roller 150. As a result, friction occurs at the contact portion between the driven roller 150 and the fixing belt 120, and the durability of the fixing belt 120 may be reduced. Further, since the driven roller 150 is idled, the conveyance efficiency of the paper P is lowered, so that image defects such as paper wrinkles, image misalignment, and light unevenness may occur. Therefore, in the present embodiment, the fixing device 200 is provided with a backup roller 160 for preventing the driven roller 150 from idling.

  FIG. 8 is a cross-sectional view showing a configuration of a fixing device 200 according to the second embodiment of the present invention. FIG. 9A and FIG. 9B are diagrams illustrating the configuration of the fixing device 200.

  The backup roller 160 is an example of a second pressing member, and is disposed on the downstream side of the pressing member 126 with respect to the rotation direction D <b> 2 of the fixing belt 120 and inside the fixing belt 120 facing the driven roller 150. The The backup roller 160 is a roller having an outer shape slightly smaller than the driven roller 150, and is made of, for example, a material such as polyimide or silicone as described above.

  As shown in FIGS. 9A and 9B, one ends of shaft portions 162 and 162 are attached to both ends of the backup roller 160, and the other ends of the shaft portions 162 and 162 are bearing portions 164 and 164, respectively. Is rotatably supported by the shaft. A compression spring 166 is attached to the opposite side of the bearing portion 164 from the driven roller 150, and the bearing portion 164 is elastically biased toward the fixing belt 120 by the compression spring 166.

  The backup roller 160 biased by the compression spring 166 presses the driven roller 150 from the inside of the fixing belt 120 via the belt body 122. As a result, the driven roller 150 and the fixing belt 120 are pressed against each other, and the surface of the driven roller 150 is in close contact with the surface of the belt body 122.

  When the driven roller 150 has the shape described in the first and second modifications, it is preferable to use a backup roller 160 corresponding to the driven roller 150 in the first and second modifications. For example, when there are three driven rollers 150, three backup rollers 160 are prepared, and when the driven roller 150 has the axial length of the fixing belt 120, the backup roller 160 also has an axial length. Use things.

  As described above, according to the second embodiment, the idle rotation of the driven roller 150 can be prevented by the backup roller 160 provided inside the fixing belt 120 so as to face the driven roller 150. Thereby, wear of the fixing belt 120 due to idling of the driven roller 150 can be prevented, and durability of the fixing belt 120 can be improved. As a result, the replacement time of the fixing belt 120 can be delayed and the cost can be reduced.

[Third Embodiment]
Hereinafter, a fixing device 300 according to a third embodiment of the present invention will be described with reference to the drawings. Note that the same reference numerals are given to components common to the image forming apparatus 500 and the fixing apparatuses 100 and 200 described in the first and second embodiments described above, and detailed description thereof is omitted.

  FIG. 10 is a cross-sectional view showing a configuration of a fixing device 300 according to the third embodiment of the present invention. The sliding member 124 is formed to have a shorter circumferential length than the second embodiment, and is arranged in a state where the backup roller 160 is in contact with the inner peripheral surface of the belt main body 122 facing the driven roller 150. Is done. The backup roller 160 is urged toward the driven roller 150 by a compression spring 166 (see FIG. 9B) and presses (presses) the driven roller 150 from the inside of the fixing belt 120 via the belt main body 122. At this time, it is preferable to press to such an extent that rotation of the fixing belt 120 and the driven roller 150 is not hindered.

  As a result, the driven roller 150 and the fixing belt 120 are pressed against each other, and the surface of the driven roller 150 is in close contact with the surface of the belt body 122. The backup roller 160 rotates in the rotation direction D2 as the fixing belt 120 rotates while pressing the driven roller 150.

  As described above, according to the third embodiment, similarly to the second embodiment, the driven roller 150 is idled by the backup roller 160 provided inside the fixing belt 120 so as to face the driven roller 150. Can be prevented.

  In the case where the load on the fixing belt 120 becomes heavy due to the pressing of the backup roller 160 and the rotation of the fixing belt 120 is hindered, a second drive motor may be installed on the backup roller 160. The second drive motor is driven in synchronization with the drive motor 146 based on the drive signal from the control unit 80. The backup roller 160 is driven to rotate in synchronization with the fixing roller 110 by the drive of the second drive motor. As a result, the load on the fixing belt 120 can be reduced, and uneven rotation of the fixing belt 120 can be suppressed.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention.

  The present invention can be suitably applied to an image forming apparatus including a fixing device that fixes a toner image onto a sheet.

1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a configuration of a fixing device. FIG. 3 is a diagram illustrating a configuration of a fixing device. 1 is a diagram illustrating a block configuration of an image forming apparatus. FIG. 6 is a diagram illustrating an operation of the fixing device. FIG. 10 is a diagram illustrating a configuration of a first modification of the fixing device. FIG. 10 is a diagram illustrating a configuration of a second modification of the fixing device. FIG. 6 is a cross-sectional view illustrating a configuration of a fixing device according to a second embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of a fixing device. FIG. 9 is a cross-sectional view illustrating a configuration of a fixing device according to a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming part 80 ... Control part 100, 200, 300 ... Fixing device 110 ... Fixing roller 120 ... Fixing belt 134 ... Separation member 140 ... 1st nip part 142 ... second nip 146 ... drive motor 148 ... heater 150 ... driven roller 160 ... backup roller 500 ... image forming apparatus P ... paper

Claims (6)

A fixing device for fixing a toner image formed on paper,
A fixing roller having a heating mechanism inside and rotatably provided;
A fixing belt that is pressed against the fixing roller and rotates as the fixing roller rotates;
A first pressing member that is disposed inside the fixing belt and presses the fixing belt against the fixing roller to form a nip portion between the fixing roller and the fixing belt;
The fixing belt is disposed downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt, and the curvature of the fixing roller is deformed by pressing the fixing belt against the fixing roller. A first separating member for separating the paper from the fixing roller by:
The sheet is disposed downstream of the first separating member in the rotation direction of the fixing belt and outside the fixing belt, and deforms the curvature of the fixing belt by pressing the fixing belt. And a second separating member that separates from the fixing belt. A second pressing member disposed downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt;
The fixing device according to claim 1, wherein the second pressing member presses the second separation member via the fixing belt. The length in the axial direction of at least one of the second separation member and the second pressing member is provided to be substantially the same as the axial length of the fixing belt. Alternatively, the fixing device according to claim 2. The fixing device according to claim 1, wherein a plurality of at least one of the second separation member and the second pressing member are provided along the axial direction of the fixing belt. . A first drive unit that rotationally drives the fixing roller;
A second drive unit that rotationally drives the second pressing member;
A control unit that controls driving of the first driving unit and the second driving unit;
The fixing device according to claim 1, wherein the control unit controls the second driving unit in synchronization with the driving of the first driving unit. An image forming unit that forms a toner image on paper;
A fixing device for fixing the toner image on the paper on which the toner image is formed by the image forming unit;
The fixing device includes:
A fixing roller having a heating mechanism inside and rotatably provided by a driving unit;
A fixing belt that is pressed against the fixing roller and rotates as the fixing roller rotates;
A first pressing member that is disposed inside the fixing belt and presses the fixing belt against the fixing roller to form a nip portion between the fixing roller and the fixing belt;
The fixing belt is disposed downstream of the first pressing member in the rotation direction of the fixing belt and inside the fixing belt, and the curvature of the fixing roller is deformed by pressing the fixing belt against the fixing roller. A first separating member for separating the paper from the fixing roller by:
The sheet is disposed downstream of the first separating member in the rotation direction of the fixing belt and outside the fixing belt, and deforms the curvature of the fixing belt by pressing the fixing belt. An image forming apparatus comprising: a second separation member that separates from the fixing belt.

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