Fixing device

Abstract

Even if the fixing belt fluctuates, the contact between the fixing belt and the external heating roller remains stable. [Solution] In the belt region V2 between the steering roller 410 and the external heating roller 360, which is part of the belt region V1 of the fixing belt 310 pushed inward from the outside by the external heating roller 360, an internal roller 411 is provided that extends outward from the inside, opposite to the external heating roller 360. By extending the fixing belt 310 in the opposite direction to the external heating roller 360 due to the internal roller 411, the contact area of ​​the fixing belt 310 heated by the external heating roller 360 is secured, and the heating efficiency of the fixing belt 310 by the external heating roller 360 can be improved. In addition, by applying opposite tension to the fixing belt 310 due to the external heating roller 360 and the internal roller 411, the influence of fluctuations on the contact area due to the oscillation of the steering roller 410 is suppressed, and the belt posture in the contact area remains almost unchanged and stable.

Description

Technical Field

[0001] The present invention relates to a fixing device suitable for use in an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction peripheral.

Background Art

[0002] An image forming apparatus includes a fixing device that heats and presses an unfixed toner image formed on a recording material to fix it to the recording material. As a fixing device, a so-called belt heating type fixing device using a fixing belt has been proposed (Patent Document 1). The fixing device described in Patent Document 1 includes a heating roller (inner support roll) that heats the fixing belt from the inner peripheral surface side, and an externally mounted roller (outer support roll) that is externally mounted so as to push the fixing belt from the outer peripheral surface side toward the inner side in order to heat the fixing belt.

[0003] Also, in a belt heating type fixing device, belt deviation control is performed to suppress the deviation of the fixing belt in the longitudinal direction (width direction) (Patent Document 2). In belt deviation control, as the steering roller that stretches the fixing belt swings, the fixing belt reciprocates in the longitudinal direction, and the longitudinal position of the fixing belt is kept within a predetermined range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventionally, when the rotating fixing belt fluctuates due to belt deviation control or the like, there has been a risk that the contact between the fixing belt and the externally mounted roller is unstable.

[0006] In view of the above problems, the present invention aims to provide a fixing device that can stabilize the contact between the fixing belt and the external roller even when the rotating fixing belt fluctuates. [Means for solving the problem]

[0007] A fixing device according to one embodiment of the present invention is a fixing device for fixing a toner image formed on a recording material to the recording material, comprising: an endless rotatable belt; a pressurizing rotating body that pressurizes the belt from the outside to form a nip portion for gripping and conveying the recording material between itself and the belt; a plurality of tensioning members that tension the belt from the inside; and an outer roller that extends the belt from the outside to the inside, wherein the plurality of tensioning members include a heating roller for heating the belt; a nip portion forming member that is positioned between the pressurizing rotating body and the belt and forms a nip portion for gripping and conveying the recording material between itself and the belt; and a tensioning roller that contacts the belt between the heating roller and the nip portion forming member, wherein the belt is stretched across the belt by the heating roller and the tensioning roller, and the outer roller extends the belt region between the outer roller and the tensioning roller in the opposite direction to the outer roller, from the inside to the outside. [Effects of the Invention]

[0008] According to the present invention, even if the rotating endless belt fluctuates, the contact between the belt and the outer roller can be stably maintained. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing a suitable image forming apparatus using the fixing device of this embodiment. [Figure 2] A schematic diagram showing the fixing device of the first embodiment. [Figure 3] A schematic diagram showing a portion of the fixing device as viewed from the longitudinal direction. [Figure 4] A schematic diagram showing a portion of the fixing device as viewed from downstream in the transport direction. [Figure 5] A schematic diagram showing the position of the internal roller. [Figure 6] A schematic diagram showing the contact area. [Figure 7] A schematic diagram showing a heating unit of a comparative example that does not have an internal roller. [Figure 8] A schematic diagram showing the heating unit of this embodiment, which is equipped with an internal roller. [Figure 9] A graph showing the surface temperature of the fixing belt in this embodiment and in comparative examples. [Figure 10] A schematic diagram showing the fixing device of the second embodiment. [Figure 11] A schematic diagram showing the fixing device of the third embodiment. [Figure 12] A perspective view showing the cleaning roller. [Figure 13] A diagram illustrating the positional relationship between the cleaning roller and the fixing belt. [Figure 14] A schematic diagram showing the cleaning roller of this embodiment and the cleaning roller of a comparative example. [Figure 15] A perspective view showing another embodiment of the cleaning roller. [Modes for carrying out the invention]

[0010] [First Embodiment] <Image forming apparatus> This embodiment will be described. First, the configuration of an image forming apparatus suitable for using the fixing device of this embodiment will be described with reference to FIG. 1. The image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd provided corresponding to four colors of yellow, magenta, cyan, and black. This embodiment is a tandem type image forming apparatus 1 in which the image forming units Pa, Pb, Pc, and Pd are arranged along the rotation direction of the intermediate transfer belt 204. The image forming apparatus 1 forms a toner image (image) on a recording material in accordance with an image signal from an external host device such as a document reading device 2 connected to the apparatus main body 3 of the image forming apparatus 1 or a print server communicably connected to the apparatus main body 3. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

[0011] As shown in FIG. 1, the image forming apparatus 1 includes a document reading device 2 and an apparatus main body 3. The document reading device 2 reads a document placed on the document table glass 21, and the light irradiated from the light source 22 is reflected by the document and imaged on the CCD sensor 24 through an optical system member 23 such as a lens. When such an optical system unit is scanned in the direction of the arrow under the control of the reader control unit, the document is read line by line and converted into an electric signal data series. The image signal obtained by the CCD sensor 24 is sent to the apparatus main body 3, and image processing is performed in the control unit 30 in accordance with each image forming unit described later. Further, the control unit 30 also receives an external input from an external host device such as a print server as an image signal. [

[0012] [ [ The apparatus main body 3 includes a plurality of image forming units Pa, Pb, Pc, and Pd, and in each image forming unit, image formation is performed based on the above-described image signal. That is, the image signal is converted into a laser beam PWM (pulse width modulation control) by the control unit 30. The polygon scanner 31 as an exposure device scans a laser beam corresponding to the image signal. Then, the photosensitive drums 200a to 200d as image carriers of the respective image forming units Pa to Pd are irradiated with the laser beam. [

[0013] [ [Note that the image forming unit Pa forms a toner image of the corresponding color of yellow (Y), the image forming unit Pb forms a toner image of magenta (M), the image forming unit Pc forms a toner image of cyan (C), and the image forming unit Pd forms a toner image of black (Bk). Since these image forming units Pa to Pd have substantially the same configuration, the image forming unit Pa that forms a yellow (Y) toner image will be described as an example below, and the descriptions of the other image forming units Pb to Pd will be omitted. In the image forming unit Pa, a toner image is formed on the surface of the photosensitive drum 200a based on an image signal.

[0014] The charging roller 201a charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for electrostatic latent image formation. An electrostatic latent image is formed on the surface of the photosensitive drum 200a charged to a predetermined potential by the laser beam from the polygon scanner 31. The developing device 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back surface of the intermediate transfer belt 204 and applies a primary transfer bias of the opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. The photosensitive drum 200a after transfer is cleaned on its surface by the cleaner 207a.

[0015] Also, the toner image on the intermediate transfer belt 204 is conveyed to the next image forming unit, and the toner images of each color formed in the respective image forming units Pa to Pd in the order of yellow (Y), magenta (M), cyan (C), and black (Bk) are sequentially transferred, and a four-color image is formed on its surface. Then, the toner image that has passed through the image forming unit Pd, which is the most downstream in the rotation direction of the intermediate transfer belt 204, is conveyed to the secondary transfer unit T2 composed of the secondary transfer roller pair 205 and 206. And in the secondary transfer unit T2, a secondary transfer electric field of the opposite polarity to the toner image on the intermediate transfer belt 204 is applied, and the toner image is secondarily transferred from the intermediate transfer belt 204 to the recording material.

[0016] The recording material is housed in a cassette 9. The recording material fed from the cassette 9 is transported to a registration unit 208, which consists of, for example, a pair of registration rollers, and waits in the registration unit 208. Subsequently, the registration unit 208 is controlled in timing to align the toner image on the intermediate transfer belt 204 with the position of the paper, and then transports the recording material to the secondary transfer unit T2.

[0017] The recording material onto which the toner image has been transferred in the secondary transfer unit T2 is transported to the fuser unit 8, where heat and pressure are applied to fix the toner image to the recording material. The recording material that has passed through the fuser unit 8 is discharged to the discharge tray 7. When image formation is performed on both sides of the recording material, once the transfer and fixing of the toner image to the first side (front) of the recording material is complete, the front and back sides of the recording material are reversed via the inversion transport unit 10, and the transfer and fixing of the toner image to the second side (back) of the recording material is performed before it is discharged to the discharge tray 7.

[0018] The control unit 30 controls the entire image forming apparatus 1 described above. The control unit 30 can perform various settings based on input from the operation unit 4 of the image forming apparatus 1. The operation unit 4 may be a touch panel or the like with a display unit, and accepts input for starting various programs such as "image forming jobs" and various data inputs in response to user touch operations. Although not shown in the figures, such a control unit 30 has a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each part while reading programs corresponding to control procedures stored in ROM. Working data and input data are stored in RAM, and the CPU performs control by referring to the data stored in RAM based on the aforementioned programs, etc.

[0019] <Fusing device> Next, the fixing device 8 of this embodiment will be described with reference to Figures 2 to 9. In this embodiment, a fixing device 8 using a belt heating method with a fixing belt 310 is employed. In Figure 2, the recording material on which the toner image has been formed is transported from right to left. As shown in Figure 2, the fixing device 8 has a heating unit 300 and a pressure roller 330.

[0020] <Pressure roller> The pressure roller 330, which functions as a pressurized rotating body, is a roller in which an elastic layer is formed on the outer circumference of the rotating shaft, and a release layer is formed on the outer circumference of the elastic layer. The rotating shaft is made of stainless steel, the elastic layer is made of conductive silicone rubber to a thickness of 5 mm, and the release layer is made of PFA (polytetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) to a thickness of 50 μm. The pressure roller 330 is axially supported by the fixing frame 380 of the fixing device 8, a gear is fixed to one end in the direction of the rotation axis, and is connected to the motor M0 via the gear, and is rotationally driven by the motor M0.

[0021] The pressure roller 330 is positioned between the pad 320 and the fixing belt 310, and applies pressure to the fixing belt 310. This forms a fixing nip section N1 between the fixing belt 310 and the pressure roller 330. In the fixing nip section N1, the recording material carrying the toner image is held and transported, and heat and pressure are applied at this time to fix the toner image to the recording material. For example, the rotation speed of the fixing belt 310 is "630 mm / s", the pressure applied by the pressure roller 330 is "1000 N", and the target temperature of the fixing belt 310 is "200 °C".

[0022] The fixing frame 380 is provided with a heating unit positioning section 381, a pressure frame 383, and a pressure spring 384. The stay 382 of the heating unit 300 is inserted into the concave heating unit positioning section 381, and the stay 382 is fixed to the heating unit positioning section 381 by fixing means (not shown). After the stay 382 is fixed, the pressure frame 383 moves due to a drive source (not shown) and a cam, causing the pressure roller 330 to pressurize the fixing belt 310 between itself and the pad 320.

[0023] The heating unit 300 includes a fixing belt 310, a pad 320 as a nip-forming member, a stay 382, ​​a heating roller 340, an inner roller 411, a steering roller 410, and an external heating roller 360. The fixing belt 310 is rotatably stretched by the pad 320, heating roller 340, inner roller 411, and steering roller 410 located on the inside, and pressurized by the pressure roller 330 located on the outside. In this embodiment, with respect to the rotation direction of the fixing belt 310, the heating roller 340, external heating roller 360, inner roller 411, and steering roller 410 are arranged in order from upstream to upstream on the upstream side of the pad 320.

[0024] <Fixing belt> The fixing belt 310 is a thin-walled, endless belt member that possesses thermal conductivity and heat resistance. The fixing belt 310 has a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. For example, the base layer is made of polyimide resin (PI) with a thickness of 60 μm, the elastic layer is made of silicone rubber with a thickness of 300 μm, and the release layer is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) with a thickness of 30 μm.

[0025] <pad> The pad 320 is held by the stay 382 and pressurized by the pressure roller 330. The pad 320 is positioned inside the fixing belt 310, sandwiching the fixing belt 310 between the pressure roller 330 and the pad 320, forming a fixing nip portion N1 that grips and transports the recording material between the pad and the fixing belt 310. The pad 320, as a pad member, is made of, for example, LCP (liquid crystal polymer) resin, and at least a portion that slides against the fixing belt 310 is formed in a planar shape. A lubricating member 370 is disposed between the pad 320 and the fixing belt 310. The lubricating member 370 is, for example, a PI (polyimide) coated with PTFE (polytetrafluoroethylene) and formed to a thickness of "100 μm". Preferably, this PI sheet has many protrusions, for example, at "1 mm" intervals and with a height of "100 μm", in order to reduce the contact area with the fixing belt 310 and reduce sliding resistance.

[0026] <Stay> The stay 382 that holds the pad 320 is made of a metal such as stainless steel or iron, and its cross-section (transverse plane) is formed in a substantially rectangular shape perpendicular to the longitudinal direction that intersects the rotational direction of the anchoring belt 310. The strength of the stay 382 is ensured by forming it using a drawn material of, for example, SUS304 (stainless steel) with a thickness of "3 mm" that is formed into a hollow shape with a substantially rectangular cross-section. However, the stay 382 is not limited to being formed using a drawn material; for example, it may be formed by combining multiple sheet metals and fixing these sheet metals in a substantially rectangular shape by welding or other means. The stay 382 may be made of a metal other than stainless steel or iron, or even a material other than metal, as long as sufficient strength is ensured.

[0027] A lubricant is applied to the inner surface of the fixing belt 310, and together with the lubricating member 370, the lubricant allows the fixing belt 310 to slide smoothly against the pad 320 when it rotates. For example, a silicone oil with a viscosity of "100 cSt" can be used as the lubricant. Although a pad 320 is used to form the fixing nip portion N1 that fixes the toner image to the recording material, this is not the only option, and a rotating body such as a roller may be used instead of the pad 320.

[0028] <Heating roller> The heating roller 340 is positioned inside the fixing belt 310 and, together with the pad 320, steering roller 410, and inner roller 411, tensions the fixing belt 310 from the inside. As described above, since a lubricant is applied to the inner circumferential surface of the fixing belt 310, the heating roller 340 tensions the fixing belt 310 via the lubricant. The heating roller 340 is formed in a cylindrical shape from a metal such as aluminum or stainless steel. From the viewpoint of thermal conductivity, the heating roller 340 is formed from, for example, an aluminum pipe with an outer diameter of "80 mm" and a thickness of "1 mm".

[0029] A halogen heater 350 is installed inside the heating roller 340 to heat the heating roller 340. While one halogen heater 350 may suffice, it is desirable to have multiple heaters rather than just one, considering the control of the temperature distribution in the longitudinal direction (rotation axis direction) of the heating roller 340. In this embodiment, the fixing belt 310 is heated by the heating roller 340 and an external heating roller 360, which will be described later. The temperature of the fixing belt 310 is adjusted by the control unit 30 (see Figure 1) to a predetermined target temperature according to the type of recording material, based on temperature detection by a thermistor (not shown). Note that the halogen heater 350 is not the only heater used to heat the heating roller 340; other heaters, such as a carbon heater, may also be used.

[0030] A gear is fixed to one end of the heating roller 340 in the direction of its rotation axis, and is connected to the motor M1 via the gear. When the heating roller 340 is rotated by the motor M1, a driving force is applied to the fixing belt 310, causing the fixing belt 310 to rotate. The drive transmission from the motor M1 may be by means other than a gear, such as a mechanism using a pulley and belt, or a mechanism that presses a roller driven by the motor M1 from the outside. The heating roller 340 may also be rotated by the motor M0 that drives the pressure roller 330 described above.

[0031] <Steering roller> The steering roller 410, acting as a tensioning roller, is a tensioning member that tensions the anchoring belt 310 together with the pad 320, heating roller 340, and inner roller 411, and rotates in accordance with the anchoring belt 310. With respect to the rotational direction of the anchoring belt 310, the steering roller 410 tensions the anchoring belt 310 downstream of the inner roller 411 (described later) and upstream of the pad 320. The steering roller 410 is formed in a cylindrical shape from a metal such as aluminum or stainless steel. For example, the steering roller 410 is a cylindrical member made of SUS303 (stainless steel) with an outer diameter of "40 mm" and a thickness of "1 mm", and both ends in the longitudinal direction are rotatably supported by bearings (not shown).

[0032] The steering roller 410 is provided so as to be able to swing with respect to the rotation axis direction (longitudinal direction) of the heating roller 340. As the steering roller 410 swings relative to the heating roller 340, the anchoring belt 310 reciprocates in the longitudinal direction. The steering roller 410 has a pivot axis in the center in the longitudinal direction and swings around this pivot axis as the center of rotation. When the steering roller 410 swings, a tension difference is created in the anchoring belt 310 between one end and the other end in the longitudinal direction, causing the anchoring belt 310 to reciprocate in the longitudinal direction. By causing the anchoring belt 310 to reciprocate in this way, the rotating anchoring belt 310 is prevented from getting too close to the longitudinal end relative to the heating roller 340 (so-called belt bias control).

[0033] The operation of the steering roller 410 will be explained using Figures 3 and 4. As shown in Figure 3, for example, when one end (front) of the steering roller 410 moves upward (in the direction of arrow A), the other end (rear) of the steering roller 410 moves downward (in the direction of arrow B). As a result, the anchoring belt 310 moves from the rear to the front. On the other hand, when the front of the steering roller 410 moves downward (in the direction of arrow B), the rear of the steering roller 410 moves upward (in the direction of arrow A). As a result, the anchoring belt 310 moves from the front to the rear. Note that the direction in which both ends (front and rear) of the steering roller 410 move is not limited to the vertical direction (arrows AB direction) described above.

[0034] As shown in Figure 4, to detect the longitudinal position of the fixing belt 310, photosensors 500a and 500b are positioned at both ends of the fixing belt 310 in the longitudinal direction. Photosensors 500a and 500b are transmissive photosensors having an illuminated element (not shown) and a light-receiving element, respectively, positioned opposite each other. The control unit 30 (see Figure 1) detects the presence or absence of the fixing belt 310 by determining whether the light-receiving element of each of the photosensors 500a and 500b is receiving light emitted from the illuminated element. If the fixing belt 310 enters between the illuminated element and the light-receiving element, the light emitted from the illuminated element is blocked by the fixing belt 310 and is not received by the light-receiving element, so the control unit 30 can detect the presence of the fixing belt 310 at either the position of the photosensors 500a or 500b.

[0035] For example, suppose the fixing belt 310 moves from the back to the front, and one end of the fixing belt 310 reaches the photosensor 500a. In this case, the control unit 30 detects that the fixing belt 310 is on the photosensor 500a side, and determines that the fixing belt 310 is shifted towards the front. Therefore, in order to move the fixing belt 310 from the front to the back, the control unit 30 controls the front of the steering roller 410 to move upward (in the direction of arrow A). Suppose the fixing belt 310 moves from the front to the back, and the other end of the fixing belt 310 reaches the photosensor 500b. In this case, the control unit 30 detects that the fixing belt 310 is on the photosensor 500b side, and determines that the fixing belt 310 is shifted towards the back. Therefore, in order to move the fixing belt 310 from the back to the front, the control unit 30 controls the front of the steering roller 410 to move downward (in the direction of arrow B). In this way, the steering roller 410 moves back and forth in a seesaw-like motion, causing the anchor belt 310 to move longitudinally. Note that the photosensors 500a and 500b are not the only options for detecting the longitudinal position of the anchor belt 310; for example, a flag sensor or a CCD line sensor may also be used.

[0036] The movement of the steering roller 410 described above is switched according to the position of the anchoring belt 310, which moves back and forth in the longitudinal direction, thereby realizing a steering function in which the longitudinal position of the anchoring belt 310 is kept within a predetermined range. The steering roller 410 may be configured to swing using a drive source such as a motor, or it may be configured to swing using self-centering. Furthermore, the pivot point of the steering roller 410 may be the center in the longitudinal direction, as in this embodiment, or it may be at the end in the longitudinal direction.

[0037] In this embodiment, the steering roller 410 also functions as a tension roller, applying a predetermined tension to the anchoring belt 310 by biasing it from the inside outwards with a spring (not shown) supported by the anchoring frame 380. The tension applied by the spring is, for example, 40N. By applying tension to the anchoring belt 310 with the steering roller 410, the anchoring belt 310 follows the pad 320.

[0038] Furthermore, the tensioning member positioned at the location of the steering roller 410 is not limited to the steering roller 410 having a steering function, but may be a roller without a steering function. For example, it may be a tension roller that simply applies tension to the fixing belt 310, or a roller that moves to change the trajectory of the fixing belt 310 depending on the type of recording material. Alternatively, it may be a tensioning member that simply tensions the fixing belt 310.

[0039] <External heating roller> In this embodiment, in order to efficiently raise the temperature of the fixing belt 310 in a short time, an external heating roller 360 is provided in addition to the heating roller 340. The external heating roller 360 contacts the outer circumferential surface of the fixing belt 310 to heat the fixing belt 310. The external heating roller 360 is formed in a cylindrical shape from a metal such as aluminum or stainless steel, and a halogen heater 351 is disposed inside it. The external heating roller 360 is heated to a predetermined temperature by the halogen heater 351, which acts as the heating element. From the viewpoint of thermal conductivity, the external heating roller 360 is formed from, for example, an aluminum pipe with an outer diameter of "50 mm" and a thickness of "1 mm".

[0040] The external heating roller 360, acting as an outer roller, contacts the outer circumferential surface of the fixing belt 310 between the heating roller 340 and the steering roller 410. In this embodiment, the external heating roller 360 contacts the fixing belt 310 downstream of the heating roller 340 and upstream of the inner roller 411 with respect to the rotational direction of the fixing belt 310, causing the fixing belt 310 to protrude from the outside to the inside. As a result, the external heating roller 360 obtains contact pressure to abut the fixing belt 310 and efficiently heat the fixing belt 310. The external heating roller 360 rotates in a manner driven by the fixing belt 310.

[0041] While a single halogen heater 351 may be used to heat the external heating roller 360, it is desirable to have multiple heaters rather than just one, considering the control of the temperature distribution along the longitudinal direction of the external heating roller 360. Furthermore, the external heating roller 360 may be heated using a heater other than a halogen heater 351, such as a carbon heater. Alternatively, an electromagnetic induction heating device may be used, which is provided on the outside of the external heating roller 360 and has an excitation coil that generates a magnetic field by applying an electric current to induce heating of the external heating roller 360, and a magnetic core that covers the excitation coil.

[0042] <Internal roller> In this embodiment, in addition to the pad 320, heating roller 340, and steering roller 410 described above, an inner roller 411 is also provided, which tensions the anchoring belt 310 from the inside. The inner roller 411 is made of a metal such as aluminum or stainless steel. In this embodiment, the inner roller 411 is a cylindrical member made of SUS303 (stainless steel) with an outer diameter of "3 mm", and its end is rotatably supported by a bearing (not shown), and it rotates in conjunction with the rotation of the anchoring belt 310.

[0043] As shown in Figure 5, the external heating roller 360 is positioned to push the fixing belt 310 from the outside inward towards the heating roller 340, and is in contact with the belt region V1 that is stretched across the fixing belt 310 by the heating roller 340 and the steering roller 410. As the fixing belt 310 is pressed by the external heating roller 360, the tension surface (V1) formed between the heating roller 340 and the steering roller 410 is pushed inward compared to the virtual tension surface that would exist if the external heating roller 360 were not present. That is, on the side where the heating roller 340 and the steering roller 410 each contact the fixing belt 310, the fixing belt 310 is pushed inward beyond the tangent line Q1 that contacts both the heating roller 340 and the steering roller 410.

[0044] On the other hand, the inner roller 411 is positioned to push the fixing belt 310 toward the external heating roller 360. The inner roller 411 extends the belt region V2 between the external heating roller 360 and the steering roller 410 from the inside outwards, opposite to the external heating roller 360, within the belt region V1 that is extended inwards beyond the tangent Q1 by the external heating roller 360. To do this, the inner roller 411 is positioned outside of the tangent Q2 on the side where the external heating roller 360 and the steering roller 410 are in contact with the fixing belt 310, among the two tangents (Q2, Q2') that are in contact with and intersect the external heating roller 360 and the steering roller 410.

[0045] Furthermore, it is preferable that the inner roller 411 be positioned inside the outer tangent Q3 that contacts the outer heating roller 360 and the steering roller 410. This is because when the inner roller 411 is positioned outside the tangent Q3, the amount of winding of the anchoring belt 310 around the steering roller 410 is reduced, decreasing the sliding resistance between the steering roller 410 and the anchoring belt 310, and making it more difficult for the anchoring belt 310 to move in the longitudinal direction when the steering roller 410 oscillates.

[0046] As shown in Figure 6, the external heating roller 360 presses against the fixing belt 310, thereby securing a contact area N2 for heating the fixing belt 310 on the heating roller 340, while also securing a contact area N3, which is a heating area for heating the fixing belt 310 in the belt area V1. For example, if the external heating roller 360 is not provided, the rotational length (winding amount) of the contact area N2 is "130 mm", but by providing the external heating roller 360 and pressing against the fixing belt 310, the rotational length of the contact area N2 is secured to "160 mm". The internal roller 411 presses against the fixing belt 310, making the rotational length of the contact area N3 longer compared to the case where the internal roller 411 is not provided. For example, if the internal roller 411 is not provided, the rotational length of the contact area N3 is "8 mm", but by providing the internal roller 411 and pressing against the fixing belt 310, the rotational length of the contact area N3 is secured to "15 mm". By ensuring contact areas N2 and N3 in this way, the fixing belt 310 can be efficiently heated by the heating roller 340 and the external heating roller 360.

[0047] Next, the change in the length of the contact region N3 and the temperature change of the anchoring belt 310 in response to the oscillation of the steering roller 410 will be explained using Figures 7 to 9. Figure 7 shows a heating unit of a comparative example without the inner roller 411, and Figure 8 shows the heating unit of this embodiment with the inner roller 411. Figure 9 is a graph showing the length of the contact region N3 and the surface temperature (temperature of the outer circumferential surface) of the anchoring belt 310. The surface temperature of the anchoring belt 310 shown in Figure 9 is the temperature in the longitudinal direction of the anchoring belt 310. Here, the longitudinal length "0 mm" is the position of the end on one end side (front side) in the longitudinal direction of the anchoring belt 310, and the "longitudinal length" on the horizontal axis indicates the position away from that end side (back side) in the longitudinal direction. In order to measure the surface temperature of the fixing belt 310, approximately 8.5 W / mm of power was applied to the halogen heater 350 of the heating roller 340 and approximately 2.2 W / mm of power was applied to the halogen heater 351 of the external heating roller 360, resulting in a temperature of approximately 225°C for both the heating roller 340 and the external heating roller 360.

[0048] In the comparative example shown in Figure 7, the length of the contact area N3 between the external heating roller 360 and the fixing belt 310 changes as the steering roller 410 oscillates. In Figure 7, length "N3A" represents the maximum length of the contact area N3 when it is longest due to the oscillation of the steering roller 410, and length "N3B" represents the minimum length of the contact area N3 when it is shortest due to the oscillation of the steering roller 410.

[0049] As shown in Figure 9, when the front of the steering roller 410 moves upward, the front contact area N3 between the external heating roller 360 and the fixing belt 310 becomes the maximum length "N3A", while the rear contact area N3 between the external heating roller 360 and the fixing belt 310 becomes the minimum length "N3B". Similarly, when the rear of the steering roller 410 moves upward, the rear contact area N3 between the external heating roller 360 and the fixing belt 310 becomes the maximum length "N3A", while the front contact area N3 between the external heating roller 360 and the fixing belt 310 becomes the minimum length "N3B".

[0050] In the comparative example, when the steering roller 410 is oscillated 10 mm up and down, the variation in the contact area N3 between the external heating roller 360 and the anchoring belt 310 becomes ±2.5%, as shown in Figure 9. This variation in the contact area N3 is the difference between the maximum length N3A and the minimum length N3B. Because the contact area N3 varies, in the comparative example, there is a difference of approximately 8°C between the front side (0 mm) and the back side (350 mm) in the longitudinal direction. In other words, the surface temperature of the anchoring belt 310 can become uneven in the longitudinal direction due to the oscillation of the steering roller 410.

[0051] In contrast, in this embodiment, even if the steering roller 410 is moved 10 mm up and down, the fluctuation in the contact area N3 between the external heating roller 360 and the anchoring belt 310 is approximately ±0%. This is because, as shown in Figure 8, the internal roller 411 contacts and extends against the anchoring belt 310 in the belt area V2 downstream of the contact area N3, so that the posture of the anchoring belt 310 in the contact area N3 remains almost unchanged and stable. In other words, fluctuations in the contact area N3 due to the oscillation of the steering roller 410 are suppressed. Because fluctuations in the contact area N3 are suppressed, in this embodiment, there is only a difference of approximately 1°C between the front side (0 mm) and the back side (350 mm) in the longitudinal direction. In other words, the surface temperature of the anchoring belt 310 is less likely to become uneven in the longitudinal direction due to the oscillation of the steering roller 410. Therefore, in the contact region N3, heat is stably supplied from the external heating roller 360 to the fixing belt 310.

[0052] As described above, in this embodiment, an internal roller 411 is provided that extends from the inside outwards, opposite to the external heating roller 360, in the belt region V2 between the external heating roller 360 and the steering roller 410, which is part of the belt region V1 of the fixing belt 310 that has been pushed from the outside inwards toward the heating roller 340 by the external heating roller 360. As the fixing belt 310 is pushed in by the external heating roller 360, a contact region N2 with the heating roller 340 and a contact region N3 with the external heating roller 360 are secured. Furthermore, as the fixing belt 310 extends in the opposite direction to the external heating roller 360 by the internal roller 411, a longer rotational length of the contact region N3 is secured compared to the case where the internal roller 411 is not provided. By securing a longer contact region N3, the heating efficiency of the fixing belt 310 by the external heating roller 360 can be further improved. Furthermore, since the external heating roller 360 and the internal roller 411 apply opposing tension to the anchoring belt 310, the influence of fluctuations on the contact region N3 due to the oscillation of the steering roller 410 is suppressed, and the posture of the anchoring belt 310 in the contact region N3 remains almost unchanged and stable. Even if the steering roller 410 oscillates, the belt posture in the contact region N3 remains almost unchanged and stable, making it less likely for temperature unevenness to occur in the longitudinal direction of the anchoring belt 310.

[0053] [Second Embodiment] Next, the fixing device of the second embodiment will be described with reference to Figure 10. In the fixing device 80 of the second embodiment, a roller member such as a cylindrically formed nip-forming roller 390 is used instead of a pad 320 to form a fixing nip section N1 for fixing the toner image to the recording material. The nip-forming roller 390 may also be a heating roller with a halogen heater 391 disposed inside. In the fixing device 80 of the second embodiment, the same reference numerals are used for components that are the same as those in the first embodiment described above, and their illustration and description are omitted or simplified.

[0054] As shown in Figure 10, in the fixing device 80 of the second embodiment, with respect to the rotation direction of the fixing belt 310, the steering roller 410, the inner roller 411, the outer heating roller 360, and the heating roller 340 are arranged in order from upstream to downstream of the pad 320. The outer heating roller 360 is positioned to push the fixing belt 310 from the outside inward toward the heating roller 340. On the side where the heating roller 340 and the steering roller 410 contact the fixing belt 310, the fixing belt 310 extends inward from the tangent line Q1 that contacts both the heating roller 340 and the steering roller 410.

[0055] The inner roller 411 is positioned to push the fixing belt 310 toward the external heating roller 360. The inner roller 411 extends the belt region V2 between the external heating roller 360 and the steering roller 410 inward from the outside, opposite to the external heating roller 360, within the belt region V1 that is extended inward beyond the tangent Q1 by the external heating roller 360, from the inside outward. To do this, the inner roller 411 is positioned outside the tangent Q2 on the side where the external heating roller 360 and the steering roller 410 contact the fixing belt 310.

[0056] Furthermore, it is preferable that the inner roller 411 be positioned inside the outer tangent Q3 that contacts the outer heating roller 360 and the steering roller 410. This is because when the inner roller 411 is positioned outside the tangent Q3, the amount of winding of the anchoring belt 310 around the steering roller 410 is reduced, decreasing the sliding resistance between the steering roller 410 and the anchoring belt 310, and making it more difficult for the anchoring belt 310 to move in the longitudinal direction when the steering roller 410 oscillates. In the anchoring device 80 shown in Figure 10, the steering roller 410, the outer heating roller 360, and the heating roller 340 are arranged such that the tangent Q3 is approximately the same as the tangent Q1.

[0057] In this embodiment, including the fixing device 8 of the first embodiment described above, it is preferable that the external heating roller 360 does not sandwich the fixing belt 310 between itself and the heating roller 340, as shown in Figure 10, for example. It is also preferable that the internal roller 411 does not sandwich the fixing belt 310 between itself and the external heating roller 360. That is, the external heating roller 360 is arranged so as not to form a nip portion between itself and the fixing belt 310, and the internal roller 411 is arranged so as not to form a nip portion between itself and the external heating roller 360. This is because if the above-mentioned nip portion is formed, the resistance will increase when the fixing belt 310 moves in the longitudinal direction due to the oscillation of the steering roller 410, and there is a risk that the fixing belt 310 will deform.

[0058] As described above, in the second embodiment, as in the first embodiment described above, an internal roller 411 is provided that causes the fixing belt 310 to extend in the opposite direction from the external heating roller 360. This further improves the heating efficiency of the fixing belt 310 by the external heating roller 360, and also makes it less likely for temperature unevenness to occur in the longitudinal direction of the fixing belt 310 even when the steering roller 410 swings, thus achieving the same effects as in the first embodiment described above.

[0059] [Third Embodiment] In the fuser device 8(80) described above, a small amount of toner may remain on the surface (outer surface) of the fuser belt 310 after the toner image has been fixed to the recording material. The surface of the fuser belt 310 is cleaned, for example, by a cleaning web (not shown), but toner that cannot be completely removed by this cleaning web may adhere from the fuser belt 310 to the surface of the external heating roller 360, causing the surface of the external heating roller 360 to become dirty. In addition, if the recording material is paper, paper dust may adhere to the surface of the external heating roller 360 via the fuser belt 310. If the surface of the external heating roller 360 is dirty with toner, paper dust, or other deposits, the heat transfer efficiency from the external heating roller 360 to the fuser belt 310 may decrease, or the lifespan of the external heating roller 360 may be shortened.

[0060] Furthermore, in the belt heating type fixing device 8(80), as described above, a lubricant is applied to the inner circumferential surface of the fixing belt 310 in order to suppress the sliding resistance between the pad 320 and the fixing belt 310. A portion of this lubricant flows from the inner circumferential surface to the outer circumferential surface at the end of the fixing belt 310, and is likely to adhere from the fixing belt 310 to the external heating roller 360. That is, in the fixing belt 310, pressure is generated by the pad 320 and the pressure roller 330 at the fixing nip portion N1. Therefore, a force acts on the lubricant applied to the inner circumferential surface of the fixing belt 310, pushing it outwards from the inner circumferential surface towards the end (outside). Also, when belt siding control is performed using the steering roller 410, the fixing belt 310 reciprocates in the longitudinal direction. As a result, some of the lubricant that has moved to the end of the fixing belt 310 is carried by its surface tension from the inner surface to the outer surface via the edge of the fixing belt 310, and the lubricant adheres to the external heating roller 360. If this lubricant adhering to the external heating roller re-adheres to the outer surface of the fixing belt 310, it will cause a decrease in the image quality of the toner image fixed to the recording material. In the fixing device 8(80) of this embodiment, an inner roller 411 is provided to secure a contact area N3 between the external heating roller 360 and the fixing belt 310 and to ensure stable contact, which can result in a large amount of lubricant adhering to the end of the external heating roller 360.

[0061] In light of the above, it has been conventionally proposed to provide a scraping member that contacts the outer edge of the fixing belt 310 to remove lubricant that has flowed from the inner surface to the outer surface of the fixing belt 310. However, installing a scraping member in addition to the external heating roller 360 requires a larger space for installation, and the fixing device 8 (80) described above would become larger, making it difficult to adopt in light of the current demand for miniaturization.

[0062] If a scraping member is not installed, some of the lubricant adhering to the end of the outer surface of the fixing belt will adhere to the end of the external heating roller 360. The lubricant adhering to the end of the external heating roller 360 will spread widely from the end to the center, and the widely spread lubricant will re-adhere from the external heating roller 360 to the outer surface of the fixing belt 310. This could potentially degrade the image quality of the toner image fixed to the recording material. In addition, conventionally, the adhesion of lubricant to the cleaning roller could potentially reduce the cleaning capacity and durability of the cleaning roller. Therefore, a cleaning roller 600 is provided to remove the adhering substances and lubricant from the external heating roller 360. The cleaning roller 600 will be described with reference to Figures 11 to 15. In the fixing device 800 of the third embodiment, the same reference numerals are used for components that are the same as those in the first embodiment described above, and their illustration and description are omitted or simplified.

[0063] <Cleaning roller> As shown in Figure 11, the cleaning roller 600, acting as a cleaning member, contacts the surface of the external heating roller 360 to clean its surface (outer circumferential surface). The length of the cleaning roller 600 in the longitudinal direction (direction of the rotation axis) is longer than the length of the external heating roller 360, so the cleaning roller 600 can clean the entire longitudinal area of ​​the external heating roller 360. The cleaning roller 600 is biased toward the external heating roller 360 by a compression spring 700 acting as a biasing part, and is supported by the fixing frame 380 so as to be able to rotate driven by the external heating roller 360 while in contact with the surface of the external heating roller 360 under pressure.

[0064] The cleaning roller 600 is provided downstream of the contact area N3 formed by the fixing belt 310 and the external heating roller 360 with respect to the rotational direction of the external heating roller 360. As will be described in detail later, the cleaning roller 600 has a removal roll section for removing deposits such as toner and paper dust that have adhered to the surface of the external heating roller 360. In addition to the removal roll section, the cleaning roller 600 also has a recovery roll section for recovering lubricant that has adhered to the surface of the external heating roller 360.

[0065] As shown in Figure 12, the cleaning roller 600 of this embodiment has a rotating shaft 600a made of a metal such as aluminum or stainless steel, a removal roller section 602, and recovery roller sections 601a and 601b. In this embodiment, the removal roller section 602 and the recovery roller sections 601a and 601b are mounted on the rotating shaft 600a so as to be rotatable together with the rotating shaft 600a, and rotate in accordance with the external heating roller 360 to clean the surface of the external heating roller 360.

[0066] The removal roller section 602, which serves as the removal unit, is provided to remove toner, paper dust, and other deposits adhering to the surface of the external heating roller 360. The removal roller section 602 is a roll-shaped member formed by winding, for example, a nonwoven fabric with a thickness of "100 μm" around the rotating shaft 600a. The removal roller section 602 is in contact with a predetermined area (first area) of the external heating roller 360. The predetermined area (first area) of the external heating roller 360 referred to here is the area corresponding to the image forming area where a toner image can be formed on the largest size recording material passing through the fixing nip section N1 with respect to the longitudinal direction (rotation axis direction) of the external heating roller 360.

[0067] The recovery roller sections 601a and 601b are arranged adjacent to the removal roller section 602 in the longitudinal direction of the external heating roller 360. The recovery roller sections 601a and 601b, as recovery sections, are provided to recover lubricant adhering to the surface of the external heating roller 360 from the end of the outer circumferential surface of the fixing belt 310 described above. Similar to the removal roller section 602, the recovery roller sections 601a and 601b are roll-shaped members formed by winding, for example, a nonwoven fabric with a thickness of "100 μm" around the rotating shaft 600a. With respect to the external heating roller 360, the recovery roller sections 601a and 601b are in contact with the region (second region) closer to the end (first region) than the region (first region) where the removal roller section 602 is in contact (first region), respectively.

[0068] As the nonwoven fabric, for example, a nonwoven fabric with a thickness of approximately 50-150 μm is used, which is a mixture of heat-resistant aramid fibers and polyethylene terephthalate (PET) fibers in a weight ratio of 3:7. The recovery roller sections 601a and 601b preferably use a nonwoven fabric with a smaller fiber diameter than the removal roller section 602 to facilitate lubricant recovery, thereby increasing the amount of lubricant recovered per unit area compared to the removal roller section 602. The removal roller section 602 may be made of a porous material such as silicone rubber or felt, which is excellent at toner recovery and can increase the driving force when the external heating roller 360 is driven into rotation. Furthermore, it is preferable that the removal roller section 602 be made of a conductive material. This is because if the surface of the external heating roller 360 becomes charged due to friction with the removal roller section 602, the surface of the fixing belt 310 in contact with the external heating roller 360 will also become charged, and the charged fixing belt 310 will come into contact with the toner on the recording material, causing image defects such as distortion of the toner image.

[0069] <About voids> In this embodiment, a gap T is formed between the removal roller section 602 and the recovery roller sections 601a and 601b in the longitudinal direction. By forming a gap T, the movement of lubricant recovered by the recovery roller sections 601a and 601b is restricted so that it does not move to the removal roller section 602. Preferably, the gap T is formed with a length in the longitudinal direction of "1 mm or more and 5 mm or less". The gap T may be made larger than "5 mm" in the longitudinal direction. However, in such a case, the length in the longitudinal direction of the recovery roller sections 601a and 601b may be shortened, and the amount of lubricant that can be recovered by the recovery roller sections 601a and 601b (recovery amount) will decrease, so it is preferable to form it to be "5 mm or less". If the recovery amount by the recovery roller sections 601a and 601b is small, the usable time of the cleaning roller 600 will be shortened and the cleaning roller 600 will need to be replaced frequently, which is undesirable as it will increase the running costs of the fixing device 800 and increase downtime.

[0070] As shown in Figure 13, the void T is formed on the outer side (outside) of the image region 603, which is the corresponding region to the image forming region that can form a toner image on the largest size recording material passing through the fixing nip N1, with respect to the longitudinal direction of the external heating roller 360. That is, the removal roller portion 602 is formed with a longitudinal length longer than the longitudinal length of the image region 603, and is provided so that both ends are located in the region outside the image region 603 with respect to the longitudinal direction. Since toner remaining on the fixing belt 310 and paper dust from the recording material tend to adhere to the image region 603 after the toner image has been fixed to the recording material, the removal roller portion 602 that removes toner and paper dust adhering to the image region 603 is provided so as to cover the entire area of ​​the image region 603 in the longitudinal direction.

[0071] With respect to the removal roller section 602 described above, the recovery roller sections 601a and 601b are each positioned such that one end on the side of the removal roller section 602 (removal side) is located outside the image area 603 in the longitudinal direction. Furthermore, the recovery roller sections 601a and 601b are each positioned such that one end on the side of the removal roller section 602 is located outside the image area 603 (first area) and inside the belt movement areas 604a and 604b (second area) in the longitudinal direction. In addition, the other end of the recovery roller sections 601a and 601b opposite to the end on the side of the removal roller section 602 is located outside the belt movement areas 604a and 604b in the longitudinal direction.

[0072] The belt movement regions 604a and 604b are the regions in which the ends of the anchoring belt 310, which reciprocates due to the oscillation of the steering roller 410, make contact with the external heating roller 360. That is, when the anchoring belt 310 reciprocates in the longitudinal direction due to belt-side control, one end and the other end of the anchoring belt 310 move within the belt movement regions 604a and 604b of the external heating roller 360, respectively. As the lubricant flows from the inner circumferential surface to the outer circumferential surface via the edge of the anchoring belt 310, the lubricant adheres to the belt movement regions 604a and 604b of the external heating roller 360. In order to recover the lubricant that has adhered to the belt movement regions 604a and 604b of the external heating roller 360, the recovery roller sections 601a and 601b are provided so as to cover the belt movement regions 604a and 604b in the longitudinal direction. Therefore, in this embodiment, the gap T is formed between the image region 603 and the belt movement regions 604a and 604b with respect to the external heating roller 360 in the longitudinal direction.

[0073] The effects obtained by the cleaning roller 600 of this embodiment described above will be explained with reference to Figure 11 and Figure 14. Figure 14 shows the cleaning roller 600 of this embodiment and the cleaning rollers 611, 612, 613, and 614 of Comparative Examples 1 to 4 for comparison.

[0074] The cleaning roller 611 of Comparative Example 1 does not have the recovery roller sections 601a and 601b described above, and only has a removal roller section 602 that removes toner, paper dust, etc., adhering to the image area 603. In the case of the cleaning roller 611 of Comparative Example 1, because it does not have the recovery roller sections 601a and 601b, it is not possible to recover the lubricant adhering to the belt movement areas 604a and 604b of the external heating roller 360. As a result, the lubricant adhering to the end of the external heating roller 360 is pushed and spread to the removal roller section 602 as it passes through the contact area N3, and is spread over a wide area from the end to the center of the external heating roller 360 via the removal roller section 602. The lubricant that has been spread over a wide area then re-adheres from the external heating roller 360 to the outer surface of the fixing belt 310. When the re-adhered lubricant reaches the fixing nip section N1, it adheres to the recording material when fixing the toner image to the recording material, and the image quality of the fixed toner image is reduced.

[0075] In Comparative Example 2, the cleaning roller 612 does not have the above-described gap T formed between the removal roller section 602 and the recovery roller sections 601a and 601b. When the cumulative number of recording materials that have passed through the fixing nip section N1 (referred to as the number of sheets passed) is small, the lubricant can be recovered by the recovery roller sections 601a and 601b, so the lubricant is not spread over a wide area from the edges to the center of the external heating roller 360. However, when the gap T is not formed, as the number of sheets passed increases, the lubricant recovered by the recovery roller sections 601a and 601b is more easily transmitted to the removal roller section 602. Therefore, the lubricant is spread over a wide area from the edges to the center of the external heating roller 360 via the removal roller section 602. The lubricant that has been spread over a wide area then reattaches to the outer surface of the fixing belt 310 from the external heating roller 360. When the re-adhered lubricant reaches the fixing nip N1, it adheres to the recording material when fixing the toner image to the recording material, degrading the image quality of the fixed toner image.

[0076] The cleaning roller 613 of Comparative Example 3 has a gap T formed in it, similar to the cleaning roller 600 of this embodiment, but the position of the gap T is different from that of the cleaning roller 600 of this embodiment. In the cleaning roller 613 of Comparative Example 3, the gap T is formed within the image area 603. In other words, the removal roller section 602 is provided so that both ends in the longitudinal direction are located within the image area 603, and the recovery roller sections 601a and 601b are provided so that one end on the side of the removal roller section 602 is located within the image area 603 in the longitudinal direction. In the case of the cleaning roller 613 of Comparative Example 3, the image quality of the toner image may deteriorate due to the adhesion of lubricant to the recording material with fewer sheets of paper than the cleaning roller 600 of this embodiment. This is because the lubricant recovered by the recovery roller sections 601a and 601b is more likely to penetrate into the image area 603 of the external heating roller 360, which affects the image quality of the toner image. In this way, the lubricant that has entered the image area 603 reattaches to the outer surface of the fixing belt 310 from the external heating roller 360. When the reattached lubricant reaches the fixing nip N1, it adheres to the recording material when fixing the toner image to the recording material, and the image quality of the fixed toner image deteriorates.

[0077] The cleaning roller 614 of Comparative Example 4 has a gap T formed in the same way as the cleaning roller 600 of this embodiment. However, it differs from the cleaning roller 600 of this embodiment in that, in the recovery roller sections 601a and 601b, one end on the removal roller section 602 side and the other end opposite to the other end in the longitudinal direction are located within the belt movement areas 604a and 604b. In the case of the cleaning roller 614 of Comparative Example 4, there are areas in the belt movement areas 604a and 604b where the lubricant cannot be recovered by the recovery roller sections 601a and 601b. When the lubricant in the unrecoverable area passes through the contact area N3, it spreads from the end of the external heating roller 360 towards the center and re-adheres to the outer surface of the fixing belt 310 from the external heating roller 360. When the re-adhered lubricant reaches the fixing nip section N1, it adheres to the recording material when fixing the toner image to the recording material, and the image quality of the fixed toner image deteriorates.

[0078] In the cleaning roller 600 of this embodiment, as described above, the recovery roller sections 601a and 601b are provided to cover the belt movement areas 604a and 604b in the longitudinal direction. Therefore, there are no areas in the belt movement areas 604a and 604b where the lubricant cannot be recovered by the recovery roller sections 601a and 601b. In addition, a gap T is formed between the removal roller section 602 and the recovery roller sections 601a and 601b in the longitudinal direction. Consequently, the recovery roller sections 601a and 601b can recover lubricant over the entire belt movement area 604a and 604b, and even if the number of sheets of paper passed increases and the amount of recovered lubricant increases, the gap T restricts the movement of lubricant from the recovery roller sections 601a and 601b to the removal roller section 602.

[0079] Table 1 below shows the number of sheets of paper passed through the toner image obtained by experimentation until a decrease in image quality appeared, for the case in which the cleaning roller 600 of this embodiment is installed, the case in which the cleaning roller is not installed, and the case in which the cleaning rollers of Comparative Examples 1 to 4 described above are used. In the experiment, the toner image was fixed to the largest size recording material (for example, 320 mm x 450 mm).

[0080] [Table 1]

[0081] As shown in Table 1, when a cleaning roller for cleaning the surface of the external heating roller 360 was not provided, or in the case of the cleaning roller 611 of Comparative Example 1, a decrease in the image quality of the toner image occurred when the number of sheets of paper passed through exceeded "5,000 sheets". In the case of the cleaning roller 612 of Comparative Example 2 and the cleaning roller 613 of Comparative Example 3, a decrease in the image quality of the toner image occurred when the number of sheets of paper passed through exceeded "2,000,000 sheets". In contrast, in the case of the cleaning roller 600 of this embodiment, a decrease in the image quality of the toner image occurred when the number of sheets of paper passed through exceeded "5,000,000 sheets". From the above results, the cleaning roller 600 of this embodiment is superior to the case where no cleaning roller is provided and to Comparative Examples 1 to 4.

[0082] As described above, in the cleaning roller 600 of this embodiment, a gap T is formed between the removal roller section 602 and the recovery roller sections 601a and 601b in the longitudinal direction. The removal roller section 602 is provided to remove deposits such as toner and paper dust adhering to the surface of the external heating roller 360, and the recovery roller sections 601a and 601b are provided to recover lubricant adhering to the surface of the external heating roller 360 from the ends of the outer circumferential surface of the fixing belt 310. The gap T formed between the removal roller section 602 and the recovery roller sections 601a and 601b restricts the movement of lubricant recovered by the recovery roller sections 601a and 601b so that it does not move to the removal roller section 602. By restricting the movement of lubricant with the gap T, it becomes difficult for the lubricant recovered by the recovery roller sections 601a and 601b to penetrate into the image area 603 of the external heating roller 360, which affects the image quality of the toner image. Therefore, the lubricant does not re-adhere from the external heating roller 360 to the outer surface of the fixing belt 310. In this way, by using the cleaning roller 600 described above, the lubricant does not re-adhere to the outer surface of the fixing belt 310, so that the lubricant does not adhere to the recording material when fixing the toner image to the recording material, and the image quality of the fixed toner image is not reduced.

[0083] In the cleaning roller 600 described above, the movement of lubricant from the recovery roller sections 601a and 601b to the removal roller section 602 is restricted by the gap T, but this is not limited to this. For example, a restricting roller section that restricts the movement of lubricant may be provided. Figure 15 shows a cleaning roller 6001 having a restricting roller section.

[0084] As shown in Figure 15, the cleaning roller 6001 has a rotating shaft 600a, a removal roller section 602, recovery roller sections 601a and 601b, and limiting roller sections 605a and 605b. The removal roller section 602 and the recovery roller sections 601a and 601b may have the same configuration as the cleaning roller 600 shown in Figure 12 above, so their explanation is omitted here. The limiting roller sections 605a and 605b are rubber roller sections formed of rubber that is less permeable to lubricant compared to the removal roller section 602 and the recovery roller sections 601a and 601b. In other words, the limiting roller sections 605a and 605b absorb less lubricant per unit area than the removal roller section 602 and the recovery roller sections 601a and 601b.

[0085] The restricting roller sections 605a and 605b, acting as limiting parts, are provided between the removal roller section 602 and the recovery roller sections 601a and 601b in the longitudinal direction. In this embodiment, the restricting roller sections 605a and 605b are provided on the rotating shaft 600a so as to be rotatable together with the rotating shaft 600a, but the cleaning roller 6001 does not come into contact with the surface of the external heating roller 360 when it is pressurized by the compression spring 700 (see Figure 11). By providing the restricting roller sections 605a and 605b, the movement of lubricant recovered by the recovery roller sections 601a and 601b is restricted so that it does not move to the removal roller section 602. By preventing the restricting roller sections 605a and 605b from contacting the surface of the external heating roller 360, in addition to limiting the movement of lubricant due to the material of the restricting roller sections 605a and 605b, the lubricant that accumulates on the outer surface of the recovery roller sections 601a and 601b due to centrifugal force from rotation is prevented from moving along the outer surface of the restricting roller sections 605a and 605b to the removal roller section 602.

[0086] In the above-described embodiment, an example was given in which the cleaning roller 600 is applied when the inner roller 411 is provided. However, the cleaning roller 600 may also be applied when the inner roller 411 is not provided. When the inner roller 411 is provided, as described above, the contact area N3 between the fixing belt 310 and the external heating roller 360 can be secured and stable contact can be achieved. However, if the contact area N3 becomes wider, the lubricant is more likely to move from the fixing belt 310 to the external heating roller 360. In view of this, it is preferable to apply the cleaning roller 600 when the inner roller 411 is provided, as this effectively suppresses the re-adhesion of the lubricant to the fixing belt 310. [Explanation of Symbols]

[0087] 8(80, 800)... Fixing device, 310... Belt (fixing belt), 320... Tensioning member (nip part forming member, pad member, pad), 330... Pressurizing rotating body (pressure roller), 340... Tensioning member (heating roller), 351... Heating section (heater, halogen heater), 360... Outer roller (external heating roller), 390... Tensioning member (nip part forming member, roller member, nip forming roller), 410... Tensioning section Material (tension roller, steering roller), 411...internal roller, 600 (6001)...cleaning member (cleaning roller), 600a...rotating shaft, 601a, 601b...recovery section (recovery roller section), 602...removal section (removal roller section), 605a, 605b...restriction section (restriction roller section), 700...biasing section (compression spring), N1...nip section (fixing nip section), T...gap, V1 (V2)...belt area

Claims

1. A fixing device for fixing a toner image formed on a recording material to the recording material, An endless, rotatable belt, A pressurizing rotating body that applies pressure to the belt from the outside to form a nip section that grips and transports the recording material between itself and the belt, Multiple tensioning members that tension the belt from the inside, The belt comprises an outer roller that extends from the outside inward, The aforementioned plurality of tensioning members are, A heating roller for heating the aforementioned belt, A nip-forming member is positioned between the pressurizing rotating body and the belt, and forms a nip portion that holds and conveys the recording material between itself and the belt. The heating roller and the nip-forming member include a tension roller that contacts the belt, The belt is stretched between the heating roller and the tensioning roller, and the outer roller extends inward from the outer tangent line that contacts the heating roller and the tensioning roller, and the belt region between the outer roller and the tensioning roller is provided with an inner roller that extends inward from the inside to the outside, opposite to the outer roller. A fixing device characterized by the following features.

2. The inner roller is provided on the outside of the two tangent lines that contact and intersect the outer roller and the tension roller, and which are on the side where the outer roller and the tension roller contact the belt. The fixing device according to feature 1.

3. The inner roller is provided inward from the outer tangent line that contacts the outer roller and the tension roller. The fixing device according to feature 2.

4. The tension roller is a steering roller that is pivotably mounted relative to the heating roller in order to reciprocate the belt in the direction of the heating roller's rotation axis. The fixing device according to feature 1.

5. The inner roller does not clamp the belt between itself and the outer roller. The fixing device according to feature 1.

6. Having a heating section for heating the outer roller, The fixing device according to feature 1.

7. The heating element is a heater located inside the outer roller. The fixing device according to feature 6.

8. With respect to the rotation direction of the belt, the heating roller, the outer roller, the inner roller, and the tensioning roller are provided in order from upstream of the nip portion forming member. The fixing device according to feature 1.

9. The nip portion forming member is a pad member in which at least a portion that slides on the belt is formed in a planar shape. The fixing device according to feature 1.

10. The nip-forming member is a roller member that is rotatably mounted on the belt. The fixing device according to feature 1.

11. The tension roller is a tension roller that applies tension to the belt. The fixing device according to feature 1.

12. The system includes a cleaning member that contacts the surface of the outer roller and cleans the surface of the outer roller, The cleaning member has a removal unit that removes deposits adhering to the first region of the outer roller, and a recovery unit that is disposed adjacent to the removal unit in the direction of the rotation axis of the outer roller and recovers the belt lubricant adhering to the second region of the outer roller that is on the end side of the first region in the direction of the rotation axis. With respect to the rotation axis direction, a gap is formed between the recovery unit and the removal unit to restrict the movement of lubricant from the recovery unit to the removal unit. The fixing device according to feature 1.

13. The aforementioned void restricts the movement of lubricant from the recovery section to the removal section. The fixing device according to feature 12.

14. The first region is a corresponding region of the outer roller that corresponds to an image forming region capable of forming a toner image on the largest size recording material passing through the nip portion in the direction of the rotation axis, The recovery unit has one end on the removal unit side located outside the corresponding area with respect to the rotation axis direction. The fixing device according to feature 12.

15. The tension roller is a steering roller that is pivotably mounted relative to the heating roller in order to reciprocate the belt in the direction of the heating roller's rotation axis. The recovery unit has an end opposite to the one end in the direction of the rotation axis that is located outside the moving area of ​​the heating roller, which is in contact with the end of the belt that reciprocates due to the oscillation of the steering roller. The fixing device according to feature 14.

16. The cleaning member has a rotating shaft, The removal unit and the recovery unit are provided on the rotating shaft and rotate together with the rotating shaft. The fixing device according to feature 12.

17. The removal section and the recovery section are made of nonwoven fabric. The fixing device according to feature 12.

18. The recovery unit recovers a larger amount of lubricant per unit area than the removal unit. The fixing device according to feature 12.

19. The aforementioned gap has a length of 1 mm or more and 5 mm or less in the direction of the rotation axis. The fixing device according to feature 12.

20. The system includes a cleaning member that contacts the surface of the outer roller and cleans the surface of the outer roller, The cleaning member is A removal unit for removing deposits adhering to the first region of the outer roller, A recovery unit for recovering the belt lubricant adhering to the second region of the outer roller, which is closer to the end of the first region, with respect to the rotation axis direction of the outer roller, With respect to the rotation axis direction, a limiting unit is disposed between the removal unit and the recovery unit, and has a limiting unit that restricts the movement of lubricant from the recovery unit to the removal unit. The limiting section absorbs less lubricant per unit area than the removal section and the recovery section. The fixing device according to feature 1.

21. The cleaning member is provided with a biasing unit that biases it toward the heating roller, The removal unit and the recovery unit contact the surface of the outer roller while being biased by the biasing unit. The limiting portion does not come into contact with the surface of the outer roller when biased by the biasing portion. The fixing device according to claim 20.

22. The cleaning member has a rotating shaft, The removal unit, the recovery unit, and the limiting unit are provided on the rotating shaft and rotate together with the rotating shaft. The fixing device according to claim 20.

23. The removal unit and the recovery unit are nonwoven fabrics wrapped around the rotating shaft. The fixing device according to feature 22.

24. The limiting portion is a rubber roller provided on the rotating shaft. The fixing device according to feature 23.

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