Image forming apparatus and fixing device

Abstract

To provide a configuration that can accurately take up a web according to the position of an outer surface of a web that is taken up.SOLUTION: A fixing device 30 that fixes an unfixed toner image to a recording material has: a web 201 that recovers a toner that is not fixed to the recording material and attached to a surface of a heating rotating body 300; a take-up roller 203 that takes up the web 201 used for the recovery of the toner attached to the surface of the heating rotating body 300; a contact member 221 that is movable according to the position of an outer surface of the web 201 that is taken up by the take-up roller 203; a variable resistor 225 that can change a resistance value depending on the position of the contact member 221; a take-up motor 240 that rotates the take-up roller 203 to take up the web 201; and a control unit 151 that controls the take-up motor 240 according to the resistance value of the variable resistor.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a fixing apparatus for forming a toner image on a recording material.

Background Art

[0002] An image forming apparatus has a fixing apparatus that fixes an unfixed toner image on a recording material to the recording material.

[0003] The fixing apparatus includes a heating rotating body that applies heat to unfixed toner and is rotationally driven, and a pressing rotating body that forms a fixing nip portion between the heating rotating body by pressing the heating rotating body and is rotationally driven. When a recording material with unfixed toner on the fixing nip portion is conveyed, the heat of the heating rotating body and the pressure by the pressing rotating body are applied to the recording material, and the unfixed toner is fixed to the recording material.

[0004] There is a risk that hot offset may occur in the fixing apparatus, where the heat of the heating rotating body is excessively transmitted to the unfixed toner and adheres to the surface of the heating rotating body without being fixed to the recording material. The toner (hot offset toner) remaining on the surface of the heating rotating body due to hot offset may adhere to the subsequent paper, resulting in image defects.

[0005] Therefore, a configuration in which a web unit is mounted to remove hot offset toner is used (Patent Document 1). The hot offset toner can be removed from the heating rotating body and cleaned by a web made of non-woven fabric or the like.

[0006] The web used for cleaning the surface of the heating rotating body is wound up by the rotation of the winding roller. The more the wound web is, the larger the outer diameter of the wound web becomes. Therefore, the rotation amount of the winding roller when winding up the web is changed according to the outer diameter of the wound web.

[0007] In a conventional web unit, a solenoid is used to change the amount of rotation of a take-up roller when taking up a web according to the outer diameter of the wound web (Patent Document 1). A method of controlling the amount of web taken up according to the outer diameter of the wound web has been adopted by the web unit using a solenoid.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In a conventional web unit using a solenoid, a lever driven by the solenoid rotates a take-up roller via a gear to take up the web. When taking up a desired amount of web using a solenoid, due to its configuration, a large error in the amount of web taken up occurs.

[0010] Also, even if an error occurs, a large amount of the web is taken up so as not to fall below the amount of web taken up required for cleaning. Therefore, in a conventional web unit, there is a risk that the consumption amount of the web increases due to a large error occurring.

[0011] Therefore, an object of the present invention is to provide a fixing device capable of accurately taking up a web.

Means for Solving the Problems

[0012] The fixing device according to the present invention includes a heating rotating body that heats unfixed toner carried on a recording material, a pressure rotating body that forms a fixing nip portion by pressing the heating rotating body, and sandwiches and conveys a recording material carrying unfixed toner in the fixing nip portion to fix an unfixed toner image on the recording material, and recovers toner that is not fixed on the recording material and adheres to the surface of the heating rotating bodya recovery roller and recovering the toner attached to the recovery roller from the recovery roller A web, a take-up roller for taking up the web used for recovering toner adhering to the surface of the heating rotator, a contact member that contacts the outer surface of the web wound around the take-up roller and is movable according to the position of the outer surface of the web wound around the take-up roller, a variable resistor connected so that its resistance value can be changed according to the position of the contact member, a take-up motor for taking up the web by rotating the take-up roller, and a control unit for controlling the rotation amount of the take-up motor according to the resistance value of the variable resistor. and the contact member includes a first lever configured to contact the outer surface of the web and swing based on the outer diameter of the take-up roller, and a second lever configured to rotate as the first lever swings, and the second lever is rotatably connected to a gear mechanism including a stepped gear configured to rotate the rotating portion of the variable resistor It is characterized by this.

Advantages of the Invention

[0013] According to the present invention, it becomes possible to accurately wind up the web.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0015] <Image forming apparatus> FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus 100. As shown in FIG. 1, four types of image forming units, namely yellow, magenta, cyan, and black, are arranged along the moving direction of the intermediate transfer belt 6 in the image forming apparatus 100. First, the process of forming a toner image on the intermediate transfer belt 6 will be described taking the yellow image forming unit PY as an example.

[0016] The surface of the photosensitive drum 3 that is rotationally driven by the charger 2 is uniformly charged (charging). Then, the surface of the photosensitive drum 3 is irradiated with a laser according to the image data input by the exposure device 5, and an electrostatic latent image is formed on the surface of the photosensitive drum 3 (exposure). Then, a yellow toner image is formed on the photosensitive drum by the developing device 1 (development). The primary transfer roller 24 applies a voltage of a polarity opposite to that of the yellow toner image to the intermediate transfer belt 6. As a result, the yellow toner on the photosensitive drum 3 is transferred to the intermediate transfer belt 6 (primary transfer). Note that the yellow toner remaining on the surface of the photosensitive drum without being transferred is scraped off by the toner cleaner 4 and removed from the surface of the photosensitive drum 3. This series of processes is similarly performed for magenta PM, cyan PC, and black PK. As a result, a full-color toner image is formed on the intermediate transfer belt 6.

[0017] The toner image on the intermediate transfer belt 6 is conveyed to the secondary transfer unit n2 formed by the secondary transfer roller pair 11 and 14. In accordance with the timing of conveyance of the toner image, the recording material A is taken out one by one from the recording material cassette 10 and fed to the secondary transfer unit n2. Then, the toner image on the intermediate transfer belt 6 is transferred to the recording material A (secondary transfer).

[0018] The recording material A onto which the toner image has been transferred is conveyed to the fixing device 30, and is fixed by receiving heat and pressure in the fixing device 30 (fixing). The recording material A onto which the toner image has been fixed is discharged to the paper discharge tray 8.

[0019] The image forming apparatus 100 can also perform monochrome image formation. During monochrome image formation, only the black image forming unit PK among the plurality of image forming units is driven.

[0020] Double-sided printing, in which images are formed on both sides of a recording material, will be described. After the recording material A on which an image has been formed on one side is discharged from the fixing device 30, it is guided to the paper path 18 by the flapper 7. When the recording material A is conveyed from the paper path 18 to the reverse path 19, it is conveyed in a switchback manner on the reverse path 19. Thereafter, the recording material A passes through the double-sided path 20 and is conveyed to the paper path 21. At this time, the recording material A is in a state of being reversed front to back. Thereafter, the recording material A is conveyed to the secondary transfer unit n2 again, and when the toner image is transferred, the toner image is fixed by the fixing device 30. Then, the recording material A on which double-sided printing has been performed is discharged to the discharge tray 8.

[0021] This process from charging to the recording material A on which the toner image has been fixed being discharged to the discharge tray 8 is defined as an image forming process (print job). Also, the period during which image formation is being performed is defined as during the image forming process (during the print job).

[0022] <Fixing device> Next, the fixing device 30 of the present embodiment will be described with reference to FIG. 2.

[0023] In the present embodiment, a fixing device using an endless rotatable fixing belt 310 is employed. In FIG. 2, the recording material is conveyed in the direction indicated by the arrow α. The fixing device 30 includes a heating rotator 300 having the fixing belt 310, and a pressure-applying rotator 330 that forms a nip portion N with the fixing belt 310 by contacting and applying pressure to the fixing belt 310.

[0024] The heating rotator 300 includes the fixing belt 310, a steering roller 350, a fixing pad 380 which is a pad member, and a heating roller 340. The fixing pad 380 and the heating roller 340 are in contact with the inner peripheral surface of the fixing belt. Also, the fixing belt 310 is stretched by the fixing pad 380 and the heating roller 340.

[0025] The heating roller 340 is formed in a cylindrical shape from a metal such as aluminum or stainless steel. In this embodiment, it is formed from an aluminum pipe with an outer diameter of 80 mm. A halogen heater 341 is installed inside the heating roller 340 as a means for heating the fixing belt 310. By the halogen heater 341, the heating roller 340 is heated to a predetermined temperature. The fixing belt 310 is heated by the heating roller 340 heated by the heat of the halogen heater 341. The fixing belt 310 is controlled to a predetermined target temperature according to the basis weight of the recording material to be fixed, based on the temperature detection result by a fixing temperature detection sensor (not shown). Note that the heating means is not limited to a halogen heater, and may be configured to generate heat for the heating roller 340 by electromagnetic induction heating (IH), for example. Also, the heating roller 340 is rotationally driven in the direction of arrow R2 by receiving drive from a motor (not shown).

[0026] The fixing belt 310 is excellent in heat conductivity and heat resistance, and its shape is, for example, an endless belt with a thin wall and an inner diameter of 120 mm. In this embodiment, the fixing belt 310 has a three-layer structure in which a base layer, an elastic layer outside the base layer, and a release layer outside the elastic layer are formed. 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 uses PFA (ethylene tetrafluoride·perfluoroalkoxyethylene copolymer resin) as a fluororesin. By the pressure rotating body 330, which will be described later, pressing and rotationally driving the fixing pad 380 via the fixing belt 310, the fixing belt is rotationally driven passively. Also, since the heating roller 340 is rotationally driven by receiving drive from a motor, the fixing belt 310 is also rotationally driven passively by the rotational drive of the heating roller 340.

[0027] The fixing pad 380 is disposed on the inner peripheral surface of the fixing belt 310 so as to face the pressure-applying rotating body 330 with the fixing belt 310 interposed therebetween. In this embodiment, a lubricant such as a lubricating sheet containing silicone oil or silicone oil is interposed between the fixing pad 380 and the fixing belt 310 so that the fixing belt 310 and the fixing pad 380 can slide smoothly with respect to each other. Therefore, the inner peripheral surface of the fixing belt 310 is in a state where oil such as silicone oil is applied thereto.

[0028] The pressure-applying rotating body 330 has a cylindrical core metal made of aluminum, an elastic layer with a thickness of 1 mm on the outside of the core metal, and a release layer for enhancing the separability from the toner on the outside of the elastic layer.

[0029] Further, the pressure-applying rotating body 330 is rotationally driven in the direction of arrow R1. Therefore, the fixing belt 310 sandwiched between the pressure-applying rotating body 330 and the fixing pad 380 is rotationally driven as a follower with respect to the rotational drive of the pressure-applying rotating body 330.

[0030] The pressure-applying rotating body 330 is movable by a contact / separation mechanism that moves the pressure-applying rotating body 330 into contact with or away from the fixing belt 310. The contact / separation mechanism includes a frame 385 and a drive motor (not shown). The frame 385 is supported by the image forming apparatus 100. The frame 385 supports the pressure-applying rotating body 330. The frame 385 is rotated about the rotation shaft 332 as the rotation axis by receiving drive from a drive motor (not shown). When the frame 385 is rotated counterclockwise on the paper surface about the rotation shaft 332 by a drive motor (not shown), the pressure-applying rotating body 330 is moved in the direction of arrow P. As a result, the pressure-applying rotating body 330 is brought into contact with the fixing pad 380 across the fixing belt 310 in a direction perpendicular to the conveyance direction α of the recording material (contact state). Thereby, the fixing nip portion N is formed. In this embodiment, it is pressed with a total pressure of 2000 N, and the width of the fixing nip portion N is 24 mm. When the frame 385 is rotated clockwise on the paper surface about the rotation shaft 332, the pressure-applying rotating body 330 is in a state of being separated from the fixing belt 310 (separation state).

[0031] As described above, the recording material carrying the unfixed toner image by the heating rotator 300 and the pressing rotator 330 is nipped and conveyed at the fixing nip portion N, heat and pressure are applied, and fixing is performed.

[0032] In the present embodiment, as described above, it is a configuration of a so-called belt fixing device using the endless fixing belt 310, but it is not limited thereto. As shown in FIG. 10, a fixing device configured to perform fixing on the recording material by a roller pair in which the heating rotator 300 and the pressing rotator 330 are in a roller shape may be used.

[0033] <Web unit> Subsequently, the web unit 200 or the recovery roller 204 will be described with reference to FIG. 2 or FIG. 3.

[0034] The fixing device fixes the toner on the recording material by heat and pressure. When excessive heat is applied to the toner on the recording material, the toner on the recording material dissolves excessively and is not fixed on the recording material, and the toner adheres to the heating rotator 300. This phenomenon is called hot offset. If the toner adhering to the heating rotator 300 due to hot offset is not recovered, since the heating rotator 300 rotates, the hot-offset toner adheres to and is fixed on the subsequent paper. Then, there is a risk that the area where the hot-offset toner is fixed becomes an image defect.

[0035] Therefore, a web unit 200 for recovering the hot-offset toner is known. The web unit 200 recovers the toner adhering to the heating rotator 300. Thereby, image defects due to hot offset are suppressed.

[0036] The web unit 200 includes a web 201, a supply roller 202, a winding roller 203, and a pressing roller 205.

[0037] The recovery roller 204 contacts the surface of the fixing belt 310 and is rotated passively. The offset toner adheres to the surface of the fixing belt 310 in a melted state by being heated at the fixing nip portion N. The recovery roller 204 used in this embodiment is a roller with an outer diameter of 20 mm and is made of stainless steel SUS303, which has a higher affinity for the melted toner than the release layer on the surface of the fixing belt 310. Therefore, the melted toner is moved to the surface of the recovery roller 204.

[0038] The toner that has moved to the surface of the recovery roller 204 is recovered from the recovery roller 204 by a web 201 made of a non-woven fabric or the like. The web unit 200 has a pressing roller 205 for pressing the web 201 against the recovery roller 204. The web 201 is pressed against the recovery roller 204 by the pressing roller 205 to form a predetermined nip width. The toner that has moved to the recovery roller 204 is recovered by the web 201.

[0039] The web 201 used for toner recovery is wound up by a winding roller 203. In this embodiment, for example, the winding roller 203 winds up the web at a frequency of 0.2 mm per 4 sheets of A4 paper. One end of the web 201 is wound up by the winding roller, and the other end is wound by a supply roller 202. The supply roller winds up the unused web 201. When the web 201 is wound up by the winding roller 203, the unused web 201 is supplied from the supply roller 202. As a result, the unused web 201 is supplied to the contact portion between the web 201 and the recovery roller 204, and the toner adhering to the surface of the fixing belt 310 is recovered.

[0040] The web 201 is made of a non-woven fabric or the like with a total length of approximately 50 m. When the fixing of the recording material is performed and the web 201 for collecting toner runs out, it must be replaced with a new web. Therefore, when the web 201 for collecting toner runs out, the user who uses the image forming apparatus 100 calls a service technician, and the service technician replaces the web unit 200 with a new one. The longer the life of the web unit 200, the fewer times the user needs to call the service technician. Therefore, it is preferable that the life of the web unit 200 is longer.

[0041] Explain the reason why the web 201 collects toner via the collection roller 204. The web 201 is made of a non-woven fabric or the like. Therefore, if the web 201 is directly abutted against the fixing belt 310 without passing through the collection roller 204, the deterioration of the surface of the fixing belt 310 will easily progress. If the deterioration of the surface of the fixing belt 310 progresses rapidly, the replacement frequency will increase, resulting in increased labor. Therefore, by collecting the toner via a collection roller made of metal, the web 201 does not directly contact the fixing belt 310, and the life of the fixing belt 310 can be extended. In addition, the unevenness on the surface of the fixing belt 310 is reflected in the gloss of the image formed on the recording material. If the web 201 directly abuts against the surface of the fixing belt 310, unevenness will occur on the surface of the fixing belt 310. Then, there is a risk that gloss unevenness will occur in the image formed on the recording material. Therefore, by collecting the toner via the collection roller 204 and configuring the web 201 not to directly abut against the surface of the fixing belt 310, gloss unevenness can be suppressed.

[0042] [Web Unit Contact Mechanism] The web unit 200 has a mechanism (not shown) for the web 201 to contact or separate from the recovery roller 204. The recovery roller 204 also has a mechanism (not shown) for contacting or separating from the fixing belt 310. When no print job is received by the control unit 151, the recovery roller 204 is in a state separated from the fixing belt 310. When a print job is received, the recovery roller 204 contacts the fixing belt 310 and the surface temperature of the recovery roller 204 rises. As a result, the toner on the surface of the fixing belt 310 is more easily transferred to the recovery roller 204. When the surface temperature of the recovery roller 204 becomes high enough, the web 201 contacts the recovery roller 1 second before the recording material is conveyed to the fixing nip portion. The web 201 contacts the recovery roller 204 until the print job is completed, and the recovery roller 204 is in a state of contacting the fixing belt 310.

[0043] When the print job is completed, when the last recording material that has passed through the fixing nip portion N after the print job is completed, the web 201 is separated from the recovery roller.

[0044] [Control the rotation amount of the take-up roller according to the outer diameter of the wound web] The web 201 is wound up by rotating the take-up roller 203 to wind up the used web 201. As the used web 201 is wound up, the amount of the web 201 wound up by the take-up roller 203 gradually increases, and the outer diameter of the web 201 wound up by the take-up roller 203 becomes larger. Then, if the rotation amount for rotating the take-up roller 203 is kept constant, the larger the outer diameter of the wound web 201, the more the web 201 is wound up. Therefore, unless the rotation amount for rotating the take-up roller 203 is controlled according to the outer diameter of the wound web 201, the amount of the web 201 wound up cannot be made constant. If the rotation amount of the take-up roller 203 is kept constant without considering the outer diameter of the wound web 201, the amount wound up gradually increases, so the amount of the web 201 used increases wastefully, and the life of the web 201 becomes short.

[0045] Therefore, conventionally, the rotation amount of the take-up roller 203 has been controlled in consideration of the outer diameter of the web 201 wound up. It is a web unit using a solenoid.

[0046] <Web unit using a solenoid which is a conventional example> Conventionally, by using a solenoid, the rotation amount of the take-up roller 203 has been controlled according to the outer diameter of the wound-up web 201. When controlling the rotation amount of the take-up roller 203 using a solenoid, the take-up amount is controlled by regulating the amount of operation of the solenoid once according to the outer diameter of the wound-up web 201.

[0047] The web is wound up by rotating the web take-up roller 203 through a gear by a lever moved by a solenoid. When winding up a desired amount of web using a solenoid, a large error occurs in the amount of web 201 wound up due to its configuration.

[0048] One of the reasons for the large error in the amount of web 201 wound up is "contact between levers". When winding up a desired amount of web using a solenoid, many levers must be used. Specifically, three levers are required: a lever [1] that moves with the outer diameter of the wound-up web 201, a lever [2] that moves with the operation of the solenoid, and a lever [3] that regulates the amount of movement of the lever [2] with the movement of the lever [1]. These levers are in contact with each other.

[0049] As the outer diameter of the wound-up web 201 changes, the position where the levers contact gradually changes. The change in the position where the levers contact is minute. Therefore, it is difficult to consider the change in the position where the levers contact. As a result, an error occurs in the amount of web 201 wound up. That is, it was necessary to reduce the error by a configuration with less contact between levers.

[0050] In addition, the web 201 is made of a non-woven fabric or the like and is thin, so the outer diameter of the wound web 201 changes slightly. Therefore, in order to wind up the web 201 with a desired amount of accuracy, it is necessary to accurately detect the outer diameter of the wound web 201. However, since there were processing limitations in the components conventionally used to detect the outer diameter of the wound web 201, the error when detecting the outer diameter of the wound web 201 was large.

[0051] In this embodiment, even if an error occurs, the web 201 is wound up with a large amount of the generated error so as not to fall below the winding amount of the web required for cleaning. Therefore, in the conventional web unit 200, the consumption amount of the web 201 increases by the amount of the large error generated, and the life of the web is shortened.

[0052] Therefore, in this embodiment, a configuration is adopted in which a variable resistor 225 and a winding motor 240 are used to accurately wind up a desired amount of the web 201. The following is a detailed description thereof.

[0053] <Control of Web Winding> [Detection of Outer Diameter of Web] Using FIG. 4, a mechanism in which the variable resistor 225 converts the outer diameter of the wound web 201 in this embodiment into a resistance value via the contact member 221 will be described. The fixing device 30 has an outer diameter detection unit 220 that detects the outer diameter of the wound web. FIG. 4 is a schematic diagram showing an example of the configuration of the outer diameter detection unit 220 in this embodiment. Further, FIG. 4(a) shows a state in which the web unit 200 is not in use and the web 201 is not wound around the winding roller 203. FIG. 4(b) shows a state in which the outer diameter of the web 201 wound around the winding roller 203 has increased as the web 201 is wound around the winding roller 203 in the direction of arrow A.

[0054] The contact member 221 of the outer diameter detection unit 220 shown in FIG. 4 has a portion 221a that is biased into contact with the outer surface of the wound web 201 and a portion 221b that contacts the link gear 222. According to the outer diameter of the wound web 201, 221a of the contact member 221 rotates in the direction of arrow B shown in FIG. 4(b). Then, 221b of the contact member 221 rotates in the direction of arrow C, rotating the link gear 222 in the direction of arrow D. The gear portion of the link gear meshes with the stepped gear 223, and when the link gear 222 rotates in the direction of arrow D, the stepped gear 223 rotates in the direction of arrow E. The stepped gear 223 meshes with the gear portion 224 of the variable resistor 225. The gear shaft of the gear portion 224 of the variable resistor 225 is the D cut shaft and engages with the rotating portion 225a of the variable resistor 225. Therefore, when the stepped gear 223 rotates in the direction of arrow E, the rotating portion 225a of the variable resistor 225 rotates in the direction of arrow G. That is, when the web 201 is wound by the winding roller 203 and the outer diameter of the web 201 increases, the position of the contact member 221 also changes, and the rotating portion 225a of the variable resistor 225 rotates. Therefore, when the web 201 is wound by the winding roller 203 and the outer diameter of the web 201 increases, the resistance value of the variable resistor 225 increases. The resistance value of the variable resistor 225 can be changed according to the rotation amount of the rotating portion 225a.

[0055] [Obtain the detection voltage Vsns from the resistance value of the variable resistor] With reference to FIG. 5, the relationship between the rotating portion 225a of the variable resistor 225 and the resistance value will be described. FIG. 5 is a diagram showing the detection circuit of the variable resistor 225 in the present embodiment. The variable resistor 225 has terminals 1, 2, and 3. Terminals 1 to 3 of the variable resistor 225 shown in FIG. 5 correspond to terminals 1 to 3 of the variable resistor 225 shown in FIG. 4. Terminal 2 is connected to the rotating portion 225a. The resistance value of the resistance value R12 between terminals 1 and 2 or the resistance value R23 between terminals 2 and 3 is changed according to the angle (rotation amount) of the rotating portion 225a.

[0056] The terminals 1 to 3 of the variable resistor 225 are connected to the control board 150. Terminal 1 is connected to GND, terminal 2 is connected to the terminal of the control unit 151 as the detection voltage Vsns, and terminal 3 is connected to the 3.3V power supply, respectively.

[0057] In this embodiment, the total resistance value R1-3 of the variable resistor is set to 10 kΩ, and the angle (rotation amount) of the rotating part 225a of the variable resistor 225, the resistance value R12 between terminals 1-2, and the resistance value R23 between terminals 2-3 are changed. At this time, R13 = R12 + R23 = 10 kΩ ··· Equation 1 holds.

[0058] Also, since the resistance value is set by the variable resistor 225 and terminal 3 is connected to the 3.3V power supply, the detection voltage Vsns is input to the control unit 151 connected to terminal 2. The detection voltage Vsns is the voltage obtained by dividing the 3.3V power supply by R12 and R23, and is obtained by the following equation. Vsns = 3.3V × (R12) ÷ (R12 + R23) ··· Equation 2

[0059] As a result, by using the detection voltage Vsns, the position of the contact member 221 can be obtained as an electrical detection signal.

[0060] The web 201 is wound by the take-up roller 203. When the outer diameter of the web 201 increases, the resistance value of the variable resistor 225 increases. As the resistance value of the variable resistor 225 increases, the detection voltage Vsns increases.

[0061] [Relationship between Detection Voltage and Outer Diameter of Web] Using FIG. 6, the relationship between the outer diameter of the wound web 201 and the rotation angle of the variable resistor 225 will be described. In this embodiment, the outer diameter of the take-up roller 203 is 12 mm in diameter, and when the web 201 that the take-up roller 203 winds up runs out (when the web 201 reaches the end of its life), it is 50 mm in diameter. Also, the rotation angle of the variable resistor 225 is set from 45° to 315°. That is, the angle of the variable resistor 225 at the start of using the web 201 is 45°, and the rotation angle of the variable resistor 225 at the time when the web 201 reaches the end of its life is 315°.

[0062] Using FIG. 7, the relationship between the rotation angle of the variable resistor 225 and the output voltage value in this embodiment will be described. The start point of using the web unit 200 at the time of factory shipment is set as (1), and at this time, the rotation part 225a of the variable resistor 225 is 45°. Also, let the detected voltage value at (1) be Va. After that, as the web 201 is used, the outer diameter of the wound web 201 becomes larger, and the resistance value (between R1-2) of the variable resistor 225 also becomes larger. As a result, the detected voltage Vsns also increases, and when the web 201 reaches the end of its life, it reaches (2). At (2), the rotation angle of the rotation part 225a of the variable resistor 225 is 315°, and the detected voltage is set as Vb.

[0063] The memory 152 stores the information data of the web 201. Among that information, it includes Va which is the detected voltage at the time of factory shipment and Vb which is the detected voltage at the time when the end of the life is reached.

[0064] [The web is wound up by the take-up motor] The control unit 151 is electrically connected to the terminals of the variable resistor 225, and can obtain the resistance value of the variable resistor 225. Therefore, the control unit 151 can acquire Vsns using the formula shown in Equation 2. Also, the control unit 151 is connected to the take-up motor 240. The "take-up motor 240" mentioned here is a motor for rotating the take-up roller 203. The control unit 151 controls the rotation amount of the take-up motor 240 based on the acquired detection voltage Vsns. Specifically, in this embodiment, if the web 201 can be wound by 0.2 mm in one rotation operation of the take-up roller 203, the toner on the surface of the fixing belt 310 can be recovered, and the possibility of image defects on the subsequent paper can be suppressed. Therefore, the desired amount of the web 201 to be wound in one rotation operation of the take-up roller 203 is 0.2 mm. As the outer diameter of the wound web 201 increases so that the amount of the web 201 wound by the take-up roller 203 becomes 0.2 mm, the rotation amount of the take-up motor 240 is decreased. At this time, the control unit 151 controls the rotation amount of the take-up motor 240 according to the obtained value of Vsns, and rotates the take-up motor 240.

[0065] In this embodiment, the take-up motor 240 uses a stepping motor. By the control unit 151 controlling the number of input pulses to the stepping motor, the rotation amount of the stepping motor is controlled, and the amount of the web 201 to be wound is controlled.

[0066] Also, as the take-up motor 240 winds the web 201, the unused web 201 gradually runs out, and the time to replace the web 201 approaches. By the memory 152 storing Vb which is the voltage value at the end of the life of the web 201, it is possible to check whether the detection voltage Vsns has reached Vb. Thereby, the time to replace the web 201 can be determined.

[0067] When the web 201 is replaced with a new web, the web 201 wound up by the take-up roller 203 disappears, and thus the outer diameter of the web 201 wound up by the take-up roller 203 also disappears. Since the contact member 221 is biased against the outer surface of the wound-up web 203, Vsns returns to the value Va at the start of use.

[0068] In this embodiment, after the resistance value R12 of the variable resistor 225 is converted into the detection voltage Vsns, until the take-up roller 203 rotates, the configuration is such that the levers do not contact each other. With this configuration, the error generated by the contact between the levers as described above can be suppressed as compared with the conventional case. As a result, the error in the amount of the web 201 to be wound up is reduced, and the consumption amount of the web 201 can be suppressed. As a result, the life of the web 201 can be extended.

[0069] [Effect of detecting the outer diameter of the web using a variable resistor] Since the outer diameter of the wound-up web 201 slightly increases because the web 201 is thin, in this embodiment, the variable resistor 225 is used in the web unit 200, and the detection voltage Vsns is obtained. Since the detection voltage Vsns is an electrical signal, the detection voltage Vsns can also be changed in response to a slight change in the outer diameter of the wound-up web 201. Therefore, the control unit 151 can finely control the rotation amount of the take-up motor 240.

[0070] As a specific example, when the resistance value of the variable resistor 225 is small, the wound-up web 201 is less and the outer diameter is also small. Therefore, the rotation amount of the take-up roller 203 is increased. On the other hand, when the resistance value of the variable resistor 225 is large, the wound-up web 201 is more and the outer diameter is also large. Therefore, the rotation amount of the take-up roller 203 is decreased. At this time, the rotation amount of the take-up roller 203 can be finely set according to the position of the contact member 221. Therefore, the web 201 can be wound up accurately. As a result, the life of the web 201 can be extended.

[0071] So far, the variable resistor 225 of the present embodiment uses a rotary variable resistor 225 in which the slider rotates, but other types of variable resistors 225 may be used. For example, the rotating part 225a may be a slide-type variable resistor 225.

[0072] [Effect when using a configuration with a variable resistor and a winding motor] The position of the contact member 221 is converted into a resistance value by the variable resistor 225. A voltage is detected from the converted resistance value, and the winding motor 240 controls the winding roller 203 based on the detected voltage. Compared with the configuration using a conventional solenoid, the configuration using the variable resistor 225 and the winding motor 240 of the present embodiment has a configuration with less contact between the levers. Therefore, errors due to contact between the levers are suppressed, and the generated errors can be reduced. As a result, the web 201 can be wound accurately and the life of the web 201 can be extended.

[0073] [Effect of the control unit controlling the winding motor 240 using the detected voltage Vsns] The control unit 151 controls the rotation amount of the winding motor 240. At this time, the control unit 151 uses the detected voltage Vsns instead of the resistance value R12 obtained from the variable resistor 225. The variable resistor 225 is made of metal. In general, metals tend to have a higher electrical resistivity as the temperature increases. Therefore, the resistance value R12 obtained from the variable resistor 225 changes depending on the temperature of the external environment. For example, when the control unit 151 controls the rotation amount of the winding motor 240 using the resistance value R12, the rotation amount changes depending on the temperature of the external environment. As a result, the error in the amount of the web 201 to be wound becomes large. However, it can be said that the detected voltage Vsns obtained from Equation 2 depends less on the temperature of the external environment than the resistance value R12. Therefore, the control unit 151 controls the winding motor 240 using the detected voltage Vsns. Thereby, the web 201 can be wound accurately.

[0074] [Modification example] Next, a modified example in the present embodiment will be described with reference to FIGS. 8 and 9. Note that descriptions of the same configurations as those described so far will be omitted.

[0075] FIG. 8 is a diagram showing the relationship between the rotation angle of the variable resistor 225 and the detection voltage Vsns in the modified example, and FIG. 9 is a diagram showing the relationship between the rotation angle of the variable resistor and the detection voltage Vsns in the modified example.

[0076] As shown in FIG. 8, it represents a state where the equation X obtained from the rotation angle of the variable resistor 225 and the detection voltage Vsns is not linear. FIG. 9 shows the corrected linear relationship of the equation obtained from the rotation angle of the variable resistor 225 and the detection voltage Vsns.

[0077] As shown in FIG. 8, the relationship between the rotation angle of the variable resistor 225 and the detection voltage Vsns may not be linear. At the time of factory shipment, the memory 152 stores five points including the detection voltage value Va at the start of use of the web unit 200 of the variable resistor 225, the detection voltage value Vb at the end of life, and the intermediate points Vc, Vd, and Ve among them. The control unit 151 reads and writes information data to and from the memory 152. The control unit 151 linearly corrects the equation X as shown in FIG. 9 from the obtained five-point information. Further, the control unit 151 controls the driving amount of the take-up motor 240 based on the linearly corrected equation X, so that the take-up motor 240 accurately winds up the web 201.

[0078] When the characteristics of the rotation angle of the variable resistor 225 and the detection voltage Vsns are not linear, the difference before and after the detection voltage Vsns becomes small in the region where the slope is small. Therefore, even a slight detection error may misdetect the outer diameter of the web take-up roller 214, and the accuracy of the driving amount of the web driving motor 240 may decrease. However, by performing linear correction, the detection error can be reduced.

[0079] As described above, according to the present embodiment described above, even if the equation X derived from the rotation amount of the variable resistor 225 and the detection voltage is not linear, the web 201 can be wound up accurately. As a result, the life of the web 201 can be extended.

[0080] In this embodiment, linear correction is performed using the detection voltage value Va, the detection voltage value Vb at the end of the life, and the information of five points including the intermediate points Vc, Vd, and Ve among them. However, the number of points of the detection voltage value is arbitrary, and correction may be performed based on more points of information. Also, in this embodiment, the intervals between Va and Vd are made equal at the rotation amount of the variable resistor 225, and the voltage is detected, but arbitrary intervals may be used.

Explanation of Signs

[0081] 30 Fixing device 100 Image forming apparatus 150 Control board 151 Control unit 152 Memory 200 Web unit 201 Web 202 Supply roller 203 Take-up roller 204 Recovery roller 205 Pressing roller 220 Outer diameter detection unit 221 Contact member 225 Variable resistor 240 Take-up motor 300 Heating rotating body 310 Fixing belt 320 Fixing pad 330 Pressing rotating body 340 Heating roller 341 Halogen heater

Claims

1. A heating rotating body that heats unfixed toner carried on a recording material, a pressurizing rotating body that forms a fixing nip portion by pressurizing the heating rotating body, sandwiches and conveys a recording material with unfixed toner carried on the fixing nip portion, and fixes an unfixed toner image on the recording material, a recovery roller that recovers toner that is not fixed on the recording material and adheres to the surface of the heating rotating body, a web that recovers the toner adhering to the recovery roller from the recovery roller, a winding roller that winds up the web used for recovering the toner adhering to the surface of the heating rotating body, a contact member that contacts the outer surface of the web wound around the winding roller and is movable according to the position of the outer surface of the web wound around the winding roller, a variable resistor connected so that its resistance value can be changed according to the position of the contact member, a winding motor that winds up the web by rotating the winding roller, a control unit that controls the rotation amount of the winding motor according to the resistance value of the variable resistor, and has, the contact member includes a first lever configured to contact the outer surface of the web and swing based on the outer diameter of the winding roller, and a second lever configured to rotate as the first lever swings, the second lever is rotatably connected to a gear mechanism including a stepped gear configured to rotate a rotating portion of the variable resistor A fixing device characterized by the above.

2. The heating rotating body has a rotatable endless fixing belt, and a heating roller that abuts against the inner peripheral surface of the fixing belt and supplies heat to the fixing belt. The fixing device according to claim 1, characterized by this.

3. The control unit acquires a voltage from the resistance value of the variable resistor, and controls the rotation amount of the winding motor according to the acquired voltage. The fixing device according to claim 1 or 2, characterized by this.

4. The motor is a stepping motor The fixing device according to any one of claims 1 to 3, characterized by this.

5. The rotating portion is configured to rotate as the lever swings, and the rotation angle of the rotating portion corresponds to the rotation angle of the variable resistor The fixing device according to any one of claims 1 to 4, characterized by this.

6. The gear mechanism consists of a first gear that contacts the second lever and a second gear that contacts the rotating portion of the variable resistor The fixing device according to any one of claims 1 to 5, characterized in that...

7. The second gear is a stepped gear The fixing device according to claim 6, characterized in that...

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