Fixing device

Abstract

To provide a fixing device that can prevent lubricant applied to the inner surface of the fixing belt from spreading to and adhering to the outer surface. [Solution] The amount of lubricant impregnated into the application roller 233 differs between the central region T1 and the end region T2. ​​The amount of lubricant per unit length in the end region T2 is less than the amount of lubricant per unit length in the central region T1. Even if some of the lubricant is pushed out from the central region T1 to the end region T2 of the fixing belt 201 when the fixing belt 201 rotates, the lubricant is absorbed into the end region T2. ​​In order to absorb the lubricant that has moved from the central region T1 when the fixing belt 201 rotates into the end region T2, the amount of lubricant in the end region T2 is always less than the amount of lubricant in the central region T1. This prevents the lubricant from wrapping around the edge of the fixing belt 201 from the inner surface to the outer surface and adhering to it, and this can be suppressed by the application roller 233.

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 applies heat and pressure to a recording material on which a toner image is formed to fix the toner image on the recording material. As a fixing device, there has been proposed a belt heating type fixing device having an endless fixing belt, a heating roller provided inside the fixing belt for heating the fixing belt, a pad that contacts the inner peripheral surface of the fixing belt, and a pressure roller that presses the fixing belt against the pad to form a fixing nip portion that applies heat and pressure to the recording material (Patent Document 1). In the belt heating type fixing device, in order to suppress the sliding resistance between the non-rotating pad and the rotating fixing belt, a lubricant is applied to the inner peripheral surface of the fixing belt by an application roller impregnated with silicone oil as a lubricant.

[0003] Further, in the device described in Patent Document 1, in order to remove the lubricant that is pushed out from the central region to the end region of the fixing belt and wraps from the inner peripheral surface to the outer peripheral surface through the edge of the fixing belt, a scraping member that contacts the edge of the fixing belt to remove the lubricant is provided. This is because if the lubricant adheres to the outer peripheral surface of the rotating fixing belt, the lubricant adheres to the recording material passing through the fixing nip portion, and the image quality of the toner image fixed on the recording material deteriorates.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventionally, a large amount of lubricant was removed by the scraping member, and when image formation was performed on the recording material for a long period of time, the removed lubricant could adhere to other components such as the pressure roller, potentially degrading the image quality of the toner image. In addition, because the lubricant continuously moves and is removed from the central region to the edge region of the fixing belt, the amount of lubricant in the central region of the fixing belt may decrease as the operating time of the fixing belt increases, potentially leading to increased sliding resistance between the pad and the fixing belt.

[0006] In view of the above problems, the present invention aims to provide a fixing device that can suppress the lubricant applied to the inner surface of the fixing belt from spreading to and adhering to the outer surface. [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 fixing belt; a tension roller for tensioning the fixing belt; a nip portion forming member provided on the inside of the fixing belt and forming a nip portion for fixing a toner image to the recording material; a pressurizing rotating body positioned between the fixing belt and the nip portion forming member and for pressurizing the fixing belt; and a lubricant application member extending in a width direction intersecting the transport direction of the recording material on the inside of the fixing belt and contacting the inner circumferential surface of the fixing belt to apply a lubricant to the inner circumferential surface, wherein the lubricant application member has a first region with respect to the width direction and a second region provided at both ends of the first region, wherein the amount of lubricant contained per unit length is less than the amount of lubricant contained per unit length in the first region. [Effects of the Invention]

[0008] According to the present invention, the lubricant applied to the inner surface of the fixing belt can be prevented from spreading to and adhering to the outer surface by the lubricant application member. [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. [Figure 3] A schematic diagram showing the area where lubricant is applied. [Figure 4] A diagram illustrating the lubricant application area. [Figure 5] A schematic diagram showing another embodiment of the coating roller. [Figure 6] A schematic diagram showing yet another embodiment of the coating roller. [Modes for carrying out the invention]

[0010] <Image forming apparatus> This embodiment will now 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 Figure 1. The image forming apparatus 100 has four types of image forming units 120 arranged along the direction of movement of the intermediate transfer belt 115: a yellow image forming unit 120a, a magenta image forming unit 120b, a cyan image forming unit 120c, and a black image forming unit 120d. First, the process of forming a toner image on the intermediate transfer belt 115 will be described using the yellow image forming unit 120a as an example.

[0011] In Figure 1, the surface of the rotating photosensitive drum 111 is uniformly charged by the charger 112 (charging). Subsequently, the exposure unit 113 irradiates the surface of the photosensitive drum 111 with a laser according to the input image data, forming an electrostatic latent image on the surface of the photosensitive drum 111 (exposure). Then, the developing unit 114 forms a yellow toner image on the photosensitive drum 111. The primary transfer roller 117 applies a voltage to the intermediate transfer belt 115 with a polarity opposite to the potential polarity of the yellow toner image. As a result, the yellow toner on the photosensitive drum 111 is transferred to the intermediate transfer belt 115 (primary transfer). Any yellow toner that remains on the surface of the photosensitive drum 111 without being transferred is removed from the surface of the photosensitive drum 111 by a drum cleaner (not shown). This series of processes is carried out similarly in the magenta image forming unit 120b, the cyan image forming unit 120c, and the black image forming unit 120d. As a result, a full-color toner image is formed on the intermediate transfer belt 115.

[0012] The toner image on the intermediate transfer belt 115 is transported to the secondary transfer section N2, which is formed by the secondary transfer outer roller 116 and the secondary transfer inner roller 118. In accordance with the timing of the toner image transport, recording material P is taken out one sheet at a time from the recording material cassette 103 and fed to the secondary transfer section N2. Then, the toner image on the intermediate transfer belt 115 is transferred to the recording material P (secondary transfer). The recording material P with the toner image transferred to it is transported to the fixing device 200, where it is fixed by heat and pressure (fixing). The recording material P with the toner image fixed is discharged to an output tray (not shown).

[0013] The image forming apparatus 100 can also perform monochrome image formation. When forming a monochrome image, only the black image forming unit 120d among the multiple image forming units 120 is driven.

[0014] When image formation is performed on both sides of the recording material P, once the transfer and fixing of the toner on the first side (first surface) is complete, the recording material P is guided to the transport path 134 by a flapper 132 located inside the image forming apparatus after fixing. The recording material P is then transported to the inversion unit 136. When the inversion sensor 135 detects the rear end of the recording material P, the flapper 133 switches the transport direction of the recording material P to the inversion path 137. The image forming apparatus 100 then transports the inverted recording material P back to the image forming unit 120 and further to the fixing device 200 via the inversion path 137. After printing on both sides is complete, the recording material P is guided to the discharge path 139 by the flapper 132 and discharged to the outside.

[0015] The process from this charging stage to the discharge of the recording material P, on which the toner image has been fixed, into the output tray is defined as the image forming process (print job). The period during which image formation is taking place is defined as the image forming process (print job in progress).

[0016] The control unit 180 includes a display screen and selection keys. The control unit 180 displays the status of the image forming apparatus 100 on the display screen and accepts operation instructions from the operator via the selection keys.

[0017] The control board 150 has a control unit 151 and a memory 152, and controls each unit in the image forming apparatus 100 described above. Based on detection signals input from each sensor and information stored in the memory 152, the control unit 151 outputs output signals to each electrical component in order to operate the electrical component at the desired timing and with the required control amount. Therefore, it is the control unit 151 that actually controls the electrical components. The memory 152 stores information data necessary for controlling each unit, and the control unit 151 reads and writes the information data stored in the memory 152.

[0018] <Fusing device> Next, the configuration of the fixing device 200 of the present embodiment will be described with reference to FIG. 2. The fixing device 200 of the present embodiment is a fixing device using a belt heating method. In FIG. 2, the recording material P is conveyed in the conveyance direction from right to left (direction of arrow A). The fixing device 200 includes a heating unit 210 having a heat source, and a pressure roller 202 as a pressure rotating body that forms a fixing nip portion N together with the heating unit 210. The heating unit 210 includes a fixing belt 201 as an endless and rotatable heating rotating body, a pad 203, a heating roller 204, a steering roller 205, and a lubricant application unit 230.

[0019] <Fixing Belt> The fixing belt 201 has a length of "360 mm" in the longitudinal direction (width direction intersecting the conveyance direction of the recording material P), has thermal conductivity, heat resistance, etc., and has a thin cylindrical shape. In the present embodiment, it has a three-layer structure in which a base layer, an elastic layer is formed on the outer periphery of the base layer, and a release layer is formed on the outer periphery thereof. The base layer has a thickness of "60 μm" and is made of polyimide resin (PI), the elastic layer has a thickness of "300 μm" and is made of silicone rubber, and the release layer has a thickness of "30 μm" and is made of PFA (ethylene tetrafluoride·perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt 201 is stretched by the pad 203, the heating roller 204, and the steering roller 205.

[0020] <Pad> The pad 203 is disposed on the inner peripheral side of the fixing belt 201, and is a nip portion forming member that forms a fixing nip portion N of a predetermined length in the conveyance direction (direction of arrow A) of the recording material P by being in pressure contact with the pressure roller 202 through the fixing belt 201. The cross section is substantially rectangular, and it is a member that is long along the longitudinal direction of the fixing belt 201. The material of the pad 203 requires heat resistance, and LCP (liquid crystal polymer) resin is used.

[0021] A sliding sheet 207, whose surface is coated with PTFE (polytetrafluoroethylene), and silicone oil are interposed between the pad 203 and the fixing belt 201, allowing the fixing belt 201 to slide smoothly against the pad 203. In this embodiment, silicone oil is used as a lubricant, but the invention is not limited to this, and grease or the like may also be used.

[0022] <Stay> A stay 206 is positioned inside the anchoring belt 201. The stay 206 is positioned inside the pad 203. The stay 206 is a rigid reinforcing member that is long in the longitudinal direction of the anchoring belt 201 and backs up the pad 203. It is made of 3mm thick extruded SUS304 (stainless steel), and its strength is ensured by forming the cross-section into a hollow "square" shape. The stay 206 prevents deflection when the pad 203 is pressed against by the pressure roller 202, thereby ensuring the applied pressure at the anchoring nip section N. Note that the material of the stay 206 is not limited to stainless steel as long as strength can be ensured.

[0023] <Heating roller> The heating roller 204, which serves as the tension roller (first roller), is made of a stainless steel pipe with a thickness of "1 mm," and a halogen heater (not shown) is placed inside it to generate heat up to a predetermined temperature. The fixing belt 201 is heated by the heating roller 204 and controlled to a predetermined target temperature according to the type (basis weight) of the recording material P, based on temperature detection by a thermistor (not shown). The heating roller 204 may also be configured to be rotationally driven. By rotating the heating roller 204 at a speed faster than the pressure roller, it is possible to increase the tension of the fixing belt 201 from the fixing nip section N to the heating roller 204 in the direction of belt rotation. By doing so, the curvature on the downstream side of the fixing nip section N increases in the direction of belt rotation, and the separation performance of the recording material P can be improved.

[0024] <Steering Roller> The steering roller 205, acting as a second roller, suspends the fixing belt 201 and is supported by the steering frame 213. The steering frame 213 is provided so as to be tiltable relative to the frame of the heating unit 210 with the pivot axis 212 as the fulcrum, thereby changing the alignment of the steering roller 205 with respect to other suspension members. This generates a tension difference between the front and rear of the fixing belt 201, controlling the position of the fixing belt 201 in its longitudinal direction. By moving the fixing belt 201 back and forth in the longitudinal direction in this way, the rotating fixing belt 201 is prevented from moving too far towards the end in the longitudinal direction relative to the heating roller 204 (so-called belt alignment control). The steering roller 205 is biased by a spring 211 supported by the steering frame 213 and also serves as a tension roller that applies a predetermined tension to the fixing belt 201. The axial direction of the pivot axis 212 is the same as the conveying direction of the recording material P. As a result, the steering roller 205 rotates, causing at least one end of the steering roller 205 to move vertically downward and upward.

[0025] Furthermore, the steering roller 205 also plays a role in suppressing uneven gloss caused by the edge of the recording material P. In this embodiment, a force of approximately "2000N" is applied to the fixing belt 201 at the fixing nip section N. When fixing unfixed toner to the recording material P, the part of the fixing belt 201 that contacts the edge of the recording material P is subjected to greater stress than the part that does not contact the edge. The contact area where the edge of the recording material P repeatedly contacts the fixing belt forms a recessed shape compared to the non-contact area where the edge of the recording material P does not contact. This recess created on the surface of the fixing belt 201 by the edge of the recording material P is called a paper edge scratch.

[0026] When fixing unfixed toner to the recording material P, the fixing device 200 applies pressure and heat to the recording material P. At this time, the surface condition of the fixing belt 201 is reflected in the gloss of the image surface after fixing. If there are irregularities on the surface of the fixing belt 201, the state of these irregularities will be reflected in the gloss of the image surface, resulting in uneven gloss (gloss unevenness) on the image surface. Therefore, if unfixed toner is fixed to the recording material P with paper edge scratches on the surface of the fixing belt 201, gloss unevenness resembling straight lines will occur on the image surface. In this embodiment, in order to suppress paper edge scratches on the surface of the fixing belt 201, the fixing belt 201 is moved back and forth in the longitudinal direction. By doing so, the number of times the fixing belt 201 contacts the edge of the recording material P is distributed in the longitudinal direction, thereby suppressing paper edge scratches.

[0027] Although not shown in the diagram, a belt position detection unit is provided to detect the position of the fixing belt 201 in the longitudinal direction. The belt position detection unit has an arm attached to the end of the fixing belt 201 that abuts against the fixing belt 201 from the outside to the inside in the longitudinal direction. By detecting the position of this arm with a sensor such as a photointerrupter, the position of the fixing belt 201 in the longitudinal direction can be detected. In order to accurately detect the position of the fixing belt 201 in the longitudinal direction, the direction in which the arm applies force to the fixing belt 201 is from the outside to the inside in the longitudinal direction. In addition, in order to apply force in this direction, the rotation axis of the arm is perpendicular to the longitudinal direction. Therefore, the arm that detects the position of the fixing belt 201 in the longitudinal direction rotates in the longitudinal direction around the rotation axis. By controlling the belt's position according to the detection results of the photointerrupter, it is possible to prevent the fixing belt 201 from coming off the components that suspend it (pad 203, heating roller 204, steering roller 205). In addition, the fixing belt 201 can be actively moved in the longitudinal direction to prevent edge damage.

[0028] <Pressure roller> The pressure roller 202 is a roller with an elastic layer formed on the outer circumference of its shaft and a release layer formed on the outer circumference of the elastic layer. The shaft is made of stainless steel, the elastic layer is made of conductive silicone rubber with a thickness of 5 mm, and the release layer is made of PFA as a fluororesin with a thickness of 50 μm. The pressure roller 202 is pivotally supported on the fixing frame 380 of the fixing device 200, and a gear is fixed to one end, which is connected to the drive source M to rotate it. The fixing belt 201 is driven to rotate clockwise (arrow R direction) by being sandwiched between the rotating pressure roller 202 and the pad 203.

[0029] As described above, a pad 203, a heating roller 204, and a steering roller 205 are arranged on the inner circumferential surface of the fixing belt 201, suspending the fixing belt 201. The fixing belt 201 is held between the pressure roller 202 and the pad 203, and rotates as the pressure roller 202 is rotationally driven. The fixing belt 201 stores heat from the heating roller 204. When the recording material P carrying the unfixed toner image is held and conveyed by the pressure roller 202 and the fixing belt 201 at the fixing nip section N, the heat and pressure necessary for fixing are applied. As a result, the toner image is fixed onto the recording material P.

[0030] <Lubricant application area> The lubricant application section 230 includes a lubricant container 231 containing silicone oil (hereinafter referred to as lubricant), a metal pumping roller 232, and an application roller 233 in contact with the pumping roller 232. The application roller 233 extends in the width direction inward of the fixing belt 201. The application roller 233 is in contact with the inner circumferential surface of the fixing belt 201 with a force of "3.0N" by a compression spring (not shown) and is supported on the frame of the heating unit 210 so as to be rotatable driven by the fixing belt 201. The application roller 233 as a lubricant application member is, for example, a roll-shaped member with a longitudinal length of "365 mm" made by winding a nonwoven fabric that can be impregnated with lubricant around a rotating shaft 233a to a thickness of "100 μm". As for the nonwoven fabric, for example, a nonwoven fabric with a thickness of about 50-150 μm is used, which is made by mixing aramid fibers and polyethylene terephthalate (PET) fibers, which have excellent heat resistance, in a weight ratio of 3:7.

[0031] The pumping roller 232, acting as a lubricant supply member, is supported on the frame of the heating unit 210 so as to be rotatable driven by the application roller 233, with a portion of it being immersed in the lubricant contained in the lubricant container 231. As the pumping roller 232 rotates, it pumps lubricant from the lubricant container 231. As the application roller 233 rotates, it applies the lubricant pumped up by the pumping roller 232 to the inner surface of the fixing belt 201. That is, when the fixing belt 201 is rotating, the lubricant supplied from the pumping roller 232 is held by the application roller 233 and applied to the fixing belt 201. On the other hand, when the fixing belt 201 is not rotating, a portion of the lubricant held by the application roller 233 is returned to the lubricant container 231 via the pumping roller 232.

[0032] The lubricant interposed between the pad 203 and the fixing belt 201 may deteriorate as the fixing device 200 operates and may decrease due to leakage to the outside. When the lubricant between the pad 203 and the fixing belt 201 decreases, the sliding resistance between the pad 203 and the fixing belt 201 increases, which may cause problems such as poor rotation of the fixing belt 201. Therefore, as described above, lubricant is supplied to the inner circumferential surface of the fixing belt 201 by the lubricant application section 230. This maintains the lubricant interposed between the pad 203 and the fixing belt 201, preventing an increase in sliding resistance and allowing the fixing belt 201 to rotate stably for a longer period of time.

[0033] <Degradation of image quality due to lubricant> As in this embodiment, a lubricant is used in the fixing device 200 using the fixing belt 201. As described above, the lubricant is applied to the inner circumferential surface of the fixing belt 201 by the application roller 233. At the fixing nip section N, pressure is generated by the pad 203 and the pressure roller 202, so a force acts on the lubricant applied to the inner circumferential surface of the fixing belt 201, pushing it toward the longitudinal end of the fixing belt 201. As a result, the lubricant is exposed from the longitudinal end of the fixing belt 201.

[0034] Furthermore, in this embodiment, a steering roller 205 is used to reciprocate the fixing belt 201 in the longitudinal direction. Here, if there is lubricant exposed from the longitudinal end of the fixing belt 201, there is a risk that the lubricant will wrap around to the outer surface of the fixing belt 201 and adhere to the outer surface. Then, because the fixing belt 201 rotates in the direction of arrow R in Figure 2, the lubricant adhering to the outer surface of the fixing belt 201 will reach the fixing nip section N. If this happens, the lubricant will adhere to the recording material P conveyed to the fixing nip section N, and image defects will occur, such as a decrease in the image quality of the toner image in the area where the lubricant has adhered. Therefore, it is necessary to suppress the adhesion of lubricant to the outer surface of the fixing belt 201.

[0035] <Recovery mechanism> Therefore, in view of the above points, in this embodiment, a recovery mechanism 220 is provided to suppress the lubricant from flowing from the inner surface to the outer surface of the fixing belt 201. The recovery mechanism 220 is arranged at both ends in the longitudinal direction of the fixing belt 201. It may also be arranged at one end, but it is preferable to arrange it at both ends so that the lubricant leaking from both ends of the fixing belt 201 can be recovered. The recovery mechanism 220 includes a scraping member 221 that contacts the end of the fixing belt 201, a dripping member (not shown) for dripping lubricant, and a support member 223 that allows the scraping member 221 to follow the reciprocating movement of the fixing belt 201.

[0036] The scraping member 221 and the dripping member are positioned between the heating roller 204 and the steering roller 205 in the rotational direction of the fixing belt 201. The scraping member 221 and the dripping member are movable around the support member 223 as a pivot axis. The axial direction of the support member 223 is parallel to the rotational axis direction of the heating roller 204. The scraping member 221 applies force to the fixing belt 201 in the direction from the outer circumferential surface side toward the inner circumferential surface side of the fixing belt 201. As a removal member, the scraping member 221 contacts the edge of the outer circumferential surface side of the fixing belt 201 and removes the lubricant that has moved from the inner circumferential surface to the outer circumferential surface of the fixing belt 201. The lubricant removed from the outer circumferential surface by the scraping member 221 is collected by a receiving member (not shown) via the dripping member. This establishes a suitable path for collecting the lubricant applied to the inner circumferential surface of the fixing belt 201, making it possible to suppress lubricant leakage from the fixing belt 201.

[0037] As mentioned above, in this embodiment, the fixing belt 201 is moved back and forth in the longitudinal direction using the steering roller 205. As the fixing belt 201 moves back and forth in the longitudinal direction, the lubricant is collected at both ends of the fixing belt 201 in the longitudinal direction and may wrap around from the inner surface to the outer surface via the edge of the fixing belt 201 due to surface tension. Conventionally, a large amount of lubricant was removed by the scraping member 221, and when image formation was performed on the recording material P for a long period of time, the removed lubricant may adhere to other components such as the steering roller 205 and the pressure roller 202, which could lead to a decrease in the image quality of the toner image. In addition, since the lubricant is continuously moved and removed from the inner surface to the outer surface of the fixing belt 201, as the continuous operation time of the fixing belt 201 increases, the amount of lubricant on the inner surface of the fixing belt 201 decreases, which could lead to an increase in the sliding resistance between the pad 203 and the fixing belt 201.

[0038] Therefore, in this embodiment, we propose a lubricant application section 230 that prevents the lubricant applied to the inner circumferential surface of the fixing belt 201 by the application roller 233 from easily flowing from the inner circumferential surface to the outer circumferential surface. The lubricant application section 230 of this embodiment will be described below with reference to Figures 3 and 4. In Figure 3, the positions of the lubricant container 231 and the pumping roller 232 of the lubricant application section 230 are shown shifted from their original positions in order to make the explanation easier to understand. Also, in Figure 4, the lubricant container 231 and the pumping roller 232 of the lubricant application section 230 are omitted from the illustration.

[0039] As described above, the lubricant application section 230 includes a lubricant container 231, a pumping roller 232, and an application roller 233. As shown in Figure 3, the application roller 233 has a central region T1 (first region) and end regions T2 (second regions) adjacent to both ends of the central region T1, as areas into which lubricant can be impregnated. The longitudinal length of the central region T1 is "L1 (mm)", and the longitudinal length of the end regions T2 is "L2 (mm)". The lubricant pumped up from the lubricant container 231 by the pumping roller 232 is supplied to the central region T1 of the application roller 233. To this end, the pumping roller 232 is formed to have a longitudinal length of "L1 (mm)" similar to the application roller 233 and is arranged to contact the entire central region T1 of the application roller 233. In other words, the contact area that is contacted by the pumping roller 232 is the central area T1, and the area that is not contacted by the pumping roller 232 is the end area T2.

[0040] When the fixing belt 201 rotates, the application roller 233 is supplied with lubricant to its central region T1 by the pumping roller 232. Subsequently, as the application roller 233 rotates in conjunction with the rotation of the fixing belt 201, some of the lubricant moves from the central region T1 to the end region T2 of the application roller 233 and penetrates there. In this way, the lubricant is impregnated into the central region T1 and the end region T2 of the application roller 233, making it possible to apply lubricant to the inner circumferential surface of the fixing belt 201 along its longitudinal direction.

[0041] In this embodiment, the amount of lubricant impregnated into the coating roller 233 differs between the central region T1 and the end region T2. ​​The coating roller 233 is pre-impregnated in the central region T1 and the end region T2 with different amounts of lubricant using a predetermined method. If the amount of lubricant impregnated into the central region T1 is "S1(g)" and the amount of lubricant impregnated into the end region T2 is "S2(g)", then the amount of lubricant impregnated per unit length in the central region T1 of the coating roller 233 is "S1 / L1(g / mm)". The amount of lubricant impregnated per unit length in the end region T2 of the coating roller 233 is "S2 / L2(g / mm)", which is less than "S1 / L1(g / mm)". These "amounts of lubricant" per unit length are less than the maximum amount of impregnation (impregnation possible) per unit length that the nonwoven fabric wrapped around the coating roller 233 can absorb.

[0042] Table 1 shows the experimental results of the relationship between the amount of lubricant impregnated in the central region T1 "S1 / L1 (g / mm)" and the amount of lubricant impregnated in the end region T2 "S2 / L2 (g / mm)", and the amount of lubricant exposed at the longitudinal end of the anchoring belt 201 D (g) (Verification Experiment 1). [Table 1]

[0043] In this verification experiment 1, the longitudinal length "L1" of the central region T1 was set to "260 mm", and the longitudinal length "L2" of the end region T2 was set to "40 mm (80 mm total for both sides)". The longitudinal reciprocating movement range of the fixing belt 201 by the steering roller 205 was set to "20 mm". In the experiment, with the pressure on the fixing belt 201 and the pressure roller 202 released, the surface temperature of the heating roller 204 was set to "200°C", and the fixing belt 201 was rotated continuously for a predetermined time. At that time, the amount of lubricant impregnated in the central region T1 and the amount of lubricant impregnated in the end region T2 before the rotation of the fixing belt 201 were varied (Examples 1 to 3), and the weight of the lubricant exposed at the longitudinal end of the fixing belt 201 was measured.

[0044] As can be seen from Table 1, by making the amount of lubricant in the end region T2 "S2 / L2 (g / mm)" less than the amount of lubricant in the central region T1 "S1 / L1 (g / mm)", the exposure of lubricant to the longitudinal end of the anchor belt 201 can be suppressed compared to the conventional example. Furthermore, the smaller the amount of lubricant in the end region T2 "S2 / L2 (g / mm)", and the larger the difference with the amount of lubricant in the central region T1, the less lubricant can be exposed to the longitudinal end of the anchor belt 201. This is because a large amount of lubricant that moves from the central region T1 is absorbed by the end region T2. ​​In this embodiment, in order to absorb the lubricant that moves from the central region T1 when the anchor belt 201 rotates into the end region T2, the amount of lubricant in the end region T2 is always less than the amount of lubricant in the central region T1. Furthermore, as shown in Example 3, when pre-impregnating the fixing belt 201 with lubricant using a predetermined method, it is preferable to set the amount of lubricant in the end region T2 before rotation of the fixing belt 201 to "0g".

[0045] Next, the longitudinal length of the end region T2 will be explained using Figure 4. In Figure 4, the upper panel shows the fixing belt 201 shifted to the left, and the lower panel shows the fixing belt 201 shifted to the right. As shown in Figure 4, the longitudinal length of the fixing belt 201 is denoted as "Lb (mm)" and the longitudinal length of the coating roller 233 is denoted as "Lc (mm)". In this case, the difference between the longitudinal lengths of the fixing belt 201 and the coating roller 233 is expressed as "1 / 2 (Lb - Lc)" on one side. The fixing belt 201 also moves back and forth in the longitudinal direction as the steering roller 205 tilts. If the length of this movement is denoted as "L (mm)", then the longitudinal length of the end region T2 of the coating roller 233, "L2 (mm)", is in the relationship "1 / 2 (Lb - Lc) + L2 > L". By satisfying this relationship, even when the fixing belt 201 moves back and forth in the longitudinal direction, the end of the fixing belt 201 will be in contact with the end region T2 of the coating roller 233. This prevents the lubricant from being exposed at the longitudinal end of the fixing belt 201.

[0046] Table 2 shows the results of an experimental verification of the relationship between the longitudinal length "L2 (mm)" of the end region T2, the reciprocating movement length "L (mm)" of the anchoring belt 201, and the amount of lubricant exposed D (g) at the longitudinal end of the anchoring belt 201 (Verification Experiment 2). [Table 2]

[0047] In this Verification Experiment 2, the longitudinal length of the fixing belt 201, "Lb," was set to "340 mm," the longitudinal length of the coating roller 233, "Lc," was set to "340 mm," and the difference in the longitudinal lengths of the fixing belt 201 and the coating roller 233 was set to "0." In this case, the relationship between the longitudinal length "L2" of the end region T2 of the coating roller 233 and the travel length "L" of the fixing belt 201 was verified. In the experiment, using the conditions of Examples 1 to 3 of Verification Experiment 1, with the pressure on the fixing belt 201 and the pressure roller 202 released, the surface temperature of the heating roller 204 was set to "200°C," the fixing belt 201 was rotated continuously for a predetermined time, and the weight of the lubricant exposed at the longitudinal end of the fixing belt 201 was measured.

[0048] As can be seen from Table 2, by making the longitudinal length "L2" of the end region T2 of the coating roller 233 greater than the reciprocating movement length "L" of the fixing belt 201, the exposure of lubricant to the longitudinal end of the fixing belt 201 can be suppressed. The reason why lubricant is exposed to the longitudinal end of the fixing belt 201 is that when the fixing belt 201 moves back and forth, it scrapes up the lubricant adhering to the inner surface of the fixing belt 201 and the surface of the heating roller 204. Therefore, by making the longitudinal length "L2" of the end region T2 for absorbing lubricant greater than the reciprocating movement distance "L" of the fixing belt 201, it is possible to suppress the exposure of lubricant scraped up toward the longitudinal end by the fixing belt 201 from the longitudinal end.

[0049] As described above, in this embodiment, the amount of lubricant impregnated into the coating roller 233 differs between the central region T1 and the end region T2 in the longitudinal direction. The amount of lubricant per unit length in the end region T2 is less than the amount of lubricant per unit length in the central region T1. This ensures that even if some of the lubricant is pushed out from the central region T1 to the end region T2 of the fixing belt 201 when the fixing belt 201 rotates, the lubricant is absorbed by the end region T2. ​​In order to absorb the lubricant that has moved from the central region T1 when the fixing belt 201 rotates into the end region T2, the amount of lubricant in the end region T2 is always less than the amount of lubricant in the central region T1. In this way, the coating roller 233 can suppress the lubricant from being pushed out from the central region T1 to the end region T2 of the fixing belt 201 and from wrapping around the edge of the fixing belt 201 from the inner surface to the outer surface and adhering to it. Therefore, when fixing the toner image to the recording material P, no lubricant adheres to the recording material P, and the image quality of the fixed toner image is not reduced.

[0050] [Other embodiments] Next, another embodiment of the coating roller will be described with reference to Figure 5. As shown in Figure 5, in the coating roller 400, a gap T3 is formed between the central region T1 and the end region T2 in the longitudinal direction. By forming the gap T3, the movement of the lubricant from the central region T1 to the end region T2 is restricted, so that even if the fixing belt 201 is rotated for a long time, the lubricant can continue to impregnate the end region T2.

[0051] The gap T3 is preferably formed with a longitudinal length of "1 mm or more and 3 mm or less". The longitudinal length of the gap T may be greater than "3 mm". However, in such a case, the longitudinal length of the end region T2 may be shortened, and the amount of lubricant that can be recovered in the end region T2 (recovered amount) will decrease, so it is preferable to form it to "3 mm or less". If the recovered amount in the end region T2 is small, the time until it exceeds the amount that can be impregnated in the end region T2 will be shortened, and the time until the lubricant is exposed to the longitudinal end of the anchor belt 201 will be shortened, which is undesirable.

[0052] Table 3 shows the experimental results of the relationship between the amount of lubricant impregnated in the central region T1 "S1 / L1 (g / mm)" and the amount of lubricant impregnated in the end region T2 "S2 / L2 (g / mm)", and the amount of lubricant exposed D (g) at the longitudinal end of the anchoring belt 201, in the case where a gap T3 is provided (Verification Experiment 1). [Table 3]

[0053] In this Verification Experiment 3, similar to Verification Experiment 1 described above, the longitudinal length "L1" of the central region T1 was set to "260 mm", and the longitudinal length "L2" of the end region T2 was set to "40 mm (80 mm total for both sides)". In addition, the longitudinal reciprocating movement range of the fixing belt 201 by the steering roller 205 was set to "20 mm". In the experiment, with the pressure on the fixing belt 201 and the pressure roller 202 released, the surface temperature of the heating roller 204 was set to "200°C", and the fixing belt 201 was rotated continuously for a predetermined time. At that time, the amount of lubricant impregnated in the central region T1 and the amount of lubricant impregnated in the end region T2 before the rotation of the fixing belt 201 were varied (Examples 7 to 9), and the weight of the lubricant exposed at the longitudinal end of the fixing belt 201 was measured. Note that the conventional example and Example 7 are cases where no gap T3 is provided, and the results are the same as the conventional example and Example 1 in Table 1 above. Example 8 is a case where a gap T3 is provided, but the gap T3 is smaller than "1 mm".

[0054] As can be seen from Example 9 in Table 3, when the amount of lubricant in the end region T2 of the anchoring belt 201 before rotation is "0g (g / mm)", providing a gap T3 makes the exposed amount D "0g". In other words, there is no exposure of lubricant to the longitudinal end of the anchoring belt 201. This is because the movement of lubricant from the central region T1 to the end region T2 is restricted by the gap T3. Also, the lubricant that has moved from the central region T1 is absorbed in the end region T2.

[0055] As in Example 8, when the amount of lubricant in the end region T2 is close to "0 (g / mm)" (0.03 (g / mm)), compared to the conventional example and Example 7, the end region T2 can absorb more lubricant that has moved from the central region T1, thus reducing the amount of exposure D. However, compared to Example 9, exposure of lubricant at the longitudinal end of the anchoring belt 201 may occur. This is because the gap T3 is narrow, making it impossible to completely restrict the movement of lubricant from the central region T1 to the end region T2, and also because the end region T2 cannot absorb as much lubricant that has moved from the central region T1 compared to when the amount of lubricant in the end region T2 is "0 (g / mm)".

[0056] As described above, in the coating roller 400 of this embodiment, a gap T3 is formed between the central region T1 and the end region T2 in the longitudinal direction. This gap T3 formed between the central region T1 and the end region T2 restricts the movement of lubricant so that the lubricant in the central region T1 does not move to the end region T2. ​​As a result, even if the fixing belt 201 is rotated for a long time, the coating roller 233 can prevent the lubricant from wrapping around from the inner surface to the outer surface of the fixing belt 201 via the edge and adhering to it.

[0057] The coating rollers 233 and 400 described above are roll-shaped members formed by winding a nonwoven fabric impregnable with lubricant around a rotating shaft, but are not limited to this. Figure 6 shows yet another embodiment of the coating roller. As shown in Figure 6, the coating roller 500 has a bag-shaped portion 501 formed from nonwoven fabric bonded to a long holder 500a, and a foamed material 502 (502a, 502b) of felt or silicone rubber is disposed inside the bag-shaped portion 501 (inside the bag-shaped portion). The coating roller 500 is supported by the frame of the heating unit 210 (see Figure 2) in a non-rotating state. A thin stainless steel plate 503 is provided in the middle of the coating roller 500 as a pressing portion, and the coating roller 500 is brought into contact with the inner circumferential surface of the fixing belt 201 by the elastic force of the thin stainless steel plate 503. At this time, the foam material 502 is pressed against the coating roller 500, and the lubricant that is pre-impregnated in the foam material 502 is applied to the inner surface of the fixing belt 201.

[0058] The foam material 502 impregnable with lubricant in the coating roller 500 includes a first foam material 502a located in the longitudinal direction corresponding to the central region T1 described above, and a second foam material 502b located in the longitudinal direction corresponding to the end regions T2 adjacent to both ends of the central region T1. Lubricant is supplied to the foam material 502a from the pumping roller 232 (see Figure 2). The amount of lubricant in the first foam material 502a and the second foam material 502b is the same as the amount of lubricant in the central region T1 and the end regions T2 described above. In other words, the amount of lubricant in the first foam material 502a and the second foam material 502b is different.

[0059] The first foam material 502a and the second foam material 502b may be arranged with the above-mentioned gap T3 between them, as shown in Figure 6, or they may not have the gap T3 between them. However, because the coating roller 500 has the first foam material 502a and the second foam material 502b, it is easier to create the gap T3 between them compared to the coating rollers 233 and 400 described above.

[0060] In the above-described embodiment, the lubricant is supplied to the coating rollers 233 (400, 500) by the pumping roller 232, but this is not the only configuration. The lubricant container 231 and the pumping roller 232 do not need to be provided. However, if this is the case, it is necessary to impregnate the central region T1 with a sufficient amount of lubricant when impregnating the coating rollers 233 (400, 500) with lubricant using a predetermined method.

[0061] In the embodiment described above, a recovery mechanism 220 is shown, but the recovery mechanism 220 is not required. This is because, as described above, the application rollers 233, 400, and 500 can suppress the exposure of lubricant to the longitudinal end of the fixing belt 201. However, if there is lubricant exposed from the longitudinal end of the fixing belt 201 even after suppressing the exposure of lubricant, it is preferable to provide the recovery mechanism 220 to prevent the lubricant from flowing around to the outer surface of the fixing belt 201 and adhering to the outer surface. [Explanation of symbols]

[0062] 200... Fixing device, 201... Fixing belt, 202... Pressure rotating body (pressure roller), 203... Nip part forming member (pad), 204... Tension roller (first roller, heating roller), 205... Second roller (steering roller), 221... Removal member (scraping member), 231... Lubricant container, 232... Lubricant supply member (pumping roller), 233... Lubricant application member (application roller), 233a... Rotating shaft, 500a... Holder, 501... Bag-shaped part, 502 (502a, 502b)... Foam material, 503... Pressing part (stainless steel sheet), T1... First region (central region), T2... Second region (end region), T3... Gap

Claims

1. A fixing device for fixing a toner image formed on a recording material to the recording material, An endless fixing belt, A tension roller for tensioning the aforementioned fixing belt, A nip-forming member is provided on the inside of the fixing belt and forms a nip portion for fixing a toner image to the recording material, A pressing rotating body is positioned between the nip portion forming member and the fixing belt, and pressurizes the fixing belt. The fixing belt is provided with a lubricant application member that extends in a width direction intersecting the direction of transport of the recording material, and contacts the inner circumferential surface of the fixing belt to apply a lubricant to the inner circumferential surface, The lubricant application member has a first region in the width direction and a second region provided at both ends of the first region, wherein the amount of lubricant contained per unit length is less than the amount of lubricant contained per unit length in the first region. A fixing device characterized by the following features.

2. A lubricant container that holds the lubricant, The system includes a lubricant supply member that contacts the first region of the lubricant application member and supplies the lubricant from the lubricant container to the first region, The fixing device according to feature 1.

3. The lubricant application member has a gap formed between the first region and the second region in the width direction. The fixing device according to feature 1.

4. The tension roller is the first roller, The fixing belt is stretched together with the first roller, and a second roller is provided so as to be tiltable relative to the first roller in order to reciprocate the fixing belt in the direction of the rotation axis of the first roller, When the length of the fixing belt in the width direction is Lb (mm), the length of the lubricant application member in the width direction is Lc (mm), the distance traveled in the width direction of the fixing belt as it reciprocates due to the tilting of the second roller is L (mm), and the length of the second region in the width direction is L2 (mm), the relationship 1 / 2(Lb - Lc) + L2 > L is satisfied. The fixing device according to feature 1.

5. The lubricant application member is provided so as to be rotatable in accordance with the fixing belt, The lubricant application member is a nonwoven fabric wrapped around the rotating shaft. The fixing device according to feature 1.

6. The lubricant application member comprises a bag-shaped portion formed from a nonwoven fabric, a holder for holding the bag-shaped portion, and a foamed material disposed within the bag-shaped portion held by the holder and capable of impregnating with lubricant. The fixing device according to feature 1.

7. The lubricant application member is equipped with a pressing part that presses it toward the fixing belt, The fixing device according to feature 1.

8. The system includes a removal member that contacts the edge of the fixing belt in the width direction and removes lubricant that moves from the inner circumferential surface to the outer circumferential surface of the fixing belt. The fixing device according to feature 1.

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