Image forming apparatus and fixing device

Abstract

To provide a fixing device that, after installation of a new web, can accurately take up the web.SOLUTION: A fixing device 30 fixing an unfixed toner image to a recording material comprises: a web 201 that recovers toner; a take-up roller 203 that takes up the web 201; a contact member 221 that is in contact with an outer surface of the web 201 and movable according to the position of the outer surface of the web 201; a variable resistor 225 in which a resistance value can be changed depending on the position of the contact member 221; a control unit 151 that calculates, from the resistance value of the variable resistor 225, information on the resistance value; a storage unit 152 that stores information; and a take-up motor 240 that takes up the web 201. After a new web 201 is installed, the storage unit 152 stores first information detected by the time the take-up motor 240 rotates once, and after the new web 201 is installed, controls the amount of rotation of the take-up motor according to the first information.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

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

[0003] The fixing device has a pair of rotors, including a heating rotor that applies heat to unfixed toner and is driven to rotate, and a pressure rotor that applies pressure to the heating rotor to form a fixing nip between the heating rotor and the pressure rotor, which is also driven to rotate. When a recording material with unfixed toner on it is conveyed to the fixing nip, the heat of the heating rotor and the pressure of the pressure rotor are applied to the recording material, and the unfixed toner is fixed to the recording material.

[0004] In a fixing device, excessive heat from the heating rotor may be transferred to unfixed toner, resulting in hot offset, in which the toner adheres to the surface of the heating rotor without being fixed to the recording material. The toner (hot offset toner) remaining on the surface of the heating rotor due to hot offset may adhere to subsequent paper, resulting in poor image quality.

[0005] Therefore, a configuration in which a web unit is installed to remove hot offset toner is used (Patent Document 1).The hot offset toner can be removed and cleaned from the heating rotor using a web made of nonwoven fabric or the like.

[0006] The web used to clean the surface of the heating rotor is wound up by the rotation of the web winding roller. The larger the amount of web wound up, the larger the outer diameter of the wound web. Therefore, the rotational speed of the winding roller when winding up the web is changed depending on the outer diameter of the wound web.

[0007] A method is known in which a variable resistor is used to detect the position of a contact member that contacts the outer surface of a wound web, and the rotation amount of the winding roller is controlled based on the position of the contact member estimated by the variable resistor.

[0008] On the other hand, the web is a consumable item, and when the remaining amount of unused web falls below a specified amount, the web must be replaced. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2001-282029 Summary of the Invention [Problem to be solved by the invention]

[0010] A known configuration uses a variable resistor in the web unit to control the rotation amount of the take-up roller according to the position of a contact member that contacts the outer surface of the take-up roller. The position of the contact member can be detected by calculating a voltage value from the resistance value of the variable resistor.

[0011] When the web falls below a specified amount, a new web is installed, and after the new web is installed, the resistance of the variable resistor is returned to the resistance value before the web was used.

[0012] However, due to the hysteresis component of the variable resistor, the initial voltage value before and after the new web installation may differ, and if the web is wound up using the initial voltage value before the new web installation, there is a risk of a discrepancy in the amount of web wound up.

[0013] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a fixing device that can wind up a web with high precision. [Means for solving the problem]

[0014] a pressure rotating member that applies pressure to the heating rotating member to form a fixing nip portion and sandwich and transport the recording material having the unfixed toner thereon through the fixing nip portion, thereby fixing an unfixed toner image to the recording material; a web that collects toner that has not been fixed to the recording material and adheres to the surface of the heating rotating member; a take-up roller that takes up the web used to collect the toner that has adhered to the surface of the heating rotating member; a contact member that contacts the outer surface of the web taken up by the take-up roller and is movable according to the position of the outer surface of the web taken up by 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 control unit that calculates information about the resistance value from the resistance value of the variable resistor; a memory unit that stores the information; and a take-up motor that rotates the take-up roller to take up the web. detecting that a new web has been attached when a difference between the current value calculated by the control unit and the previous value stored in the storage unit is equal to or greater than a predetermined value; The storage unit stores first information calculated by the control unit, and the control unit controls the rotation amount of the winding motor based on the first information. [Effects of the Invention]

[0015] According to the present invention, it is possible to wind up the web with high precision. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Figure 2] FIG. 2 is a schematic cross-sectional view of a fixing device and a web unit. [Figure 3] FIG. 2 is a schematic diagram showing a web unit. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of an outer diameter detection unit. [Figure 5] FIG. 2 is a diagram illustrating a detection circuit for a variable resistor. [Figure 6] FIG. 10 is a diagram showing the relationship between the detected voltage and the rotation angle of the variable resistor. [Figure 7] 10 is a flowchart in a first control example. [Figure 8] 10 is a flowchart for correcting a hysteresis component. [Figure 9] 10A and 10B are diagrams showing the relationship between the detected voltage and the rotation angle of the variable resistor before and after web replacement. [Figure 10] 10 is a flowchart in a second control example. [Figure 11] FIG. 2 is a schematic cross-sectional view of a roller pair fixing device and a web unit. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Image forming device> Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 100. As shown in Fig. 1, the image forming apparatus 100 has four image forming units for yellow, magenta, cyan, and black arranged along the direction of movement of an intermediate transfer belt 6. First, the process of forming a toner image on the intermediate transfer belt 6 will be explained using the yellow image forming unit PY as an example.

[0018] The surface of the photosensitive drum 3, which is rotated by the charger 2, is uniformly charged (charging). Then, the exposure device 5 irradiates the surface of the photosensitive drum 3 with a laser in accordance with input image data, forming an electrostatic latent image on the surface of the photosensitive drum 3 (exposure). Then, the development device 1 forms a yellow toner image on the photosensitive drum (development). The primary transfer roller 24 applies a voltage of the opposite polarity to the potential polarity of the yellow toner image to the intermediate transfer belt 6. This transfers the yellow toner on the photosensitive drum 3 to the intermediate transfer belt 6 (primary transfer). Any remaining yellow toner on the photosensitive drum surface is scraped off by the toner cleaner 4 and removed from the surface of the photosensitive drum 3. This series of processes is repeated for magenta PM, cyan PC, and black PK. As a result, a full-color toner image is formed on the intermediate transfer belt 6.

[0019] The toner image on the intermediate transfer belt 6 is transported to a secondary transfer portion n2 formed by a pair of secondary transfer rollers 11 and 14. In synchronization with the transport of the toner image, recording material A is taken out one by one from a recording material cassette 10 and fed to the secondary transfer portion n2. Then, the toner image on the intermediate transfer belt 6 is transferred onto the recording material A (secondary transfer).

[0020] The recording material A onto which the toner image has been transferred is transported to the fixing device 30, where it is fixed by heat and pressure (fixing). The recording material A onto which the toner image has been fixed is discharged onto the discharge tray 8.

[0021] Image forming apparatus 100 can also form monochrome images. When forming monochrome images, only the black image forming station PK is driven among the multiple image forming stations.

[0022] Now, we will explain double-sided printing, in which images are formed on both sides of a recording material. After recording material A with an image formed on one side is discharged from fixing device 30, it is guided to paper path 18 by flapper 7. When recording material A is transported from paper path 18 to reversing path 19, it is switched back and transported on reversing path 19. After that, recording material A passes through double-sided path 20 and is transported to paper path 21. At this time, recording material A is in an inverted state. After that, recording material A is transported again to secondary transfer section n2, where a toner image is transferred and fixed by fixing device 30. Then, recording material A with double-sided printing performed is discharged to output tray 8.

[0023] This process, which starts from charging and ends when the recording material A with the fixed toner image is discharged onto the discharge tray 8, is called an image forming process (print job). The period during which image formation is being performed is called an image forming process (print job).

[0024] <Fixing device> Next, the fixing device 30 of this embodiment will be described with reference to FIG.

[0025] This embodiment employs a fixing device that uses an endless, rotatable fixing belt 310. In Fig. 2, the recording material is conveyed in the direction indicated by the arrow α. The fixing device 30 has a heating rotor 300 that has the fixing belt 310, and a pressure rotor 330 that contacts the fixing belt 310 and applies pressure to it, thereby forming a nip N with the fixing belt 310.

[0026] The heating rotator 300 has a 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 circumferential surface of the fixing belt. The fixing belt 310 is stretched between the fixing pad 380 and the heating roller 340.

[0027] The heating roller 340 is cylindrical and made of metal such as aluminum or stainless steel. In this embodiment, it is made of 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. The halogen heater 341 heats the heating roller 340 to a predetermined temperature. The heating roller 340, heated by the heat of the halogen heater 341, heats the fixing belt 310. 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 by electromagnetic induction heating (IH), for example. The heating roller 340 is driven to rotate in the direction of arrow R2 by being driven by a motor (not shown).

[0028] The fixing belt 310 has excellent thermal conductivity and heat resistance, and is a thin, endless belt with an inner diameter of, for example, 120 mm. In this embodiment, the fixing belt 310 has a three-layer structure consisting of a base layer, an elastic layer on the outside of the base layer, and a release layer on the outside of the elastic layer. The base layer is 60 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt is rotated by the pressure rotor 330 (described later) pressing the fixing pad 380 via the fixing belt 310 and rotating it. Furthermore, since the heating roller 340 is rotated by receiving drive from a motor, the fixing belt 310 is also rotated by the rotation of the heating roller 340.

[0029] Fixing pad 380 is disposed on the inner circumferential surface of fixing belt 310 so as to face pressure rotor 330 with fixing belt 310 sandwiched therebetween. In this embodiment, a lubricant such as a lubricating sheet containing silicone oil or silicone oil is interposed between fixing pad 380 and fixing belt 310 to enable fixing belt 310 and fixing pad 380 to slide smoothly against each other. For this reason, oil such as silicone oil is applied to the inner circumferential surface of fixing belt 310.

[0030] The pressure rotor 330 has a cylindrical aluminum core, an elastic layer with a thickness of 1 mm on the outside of the core, and a release layer for enhancing separation from the toner on the outside of the elastic layer.

[0031] Furthermore, pressure rotator 330 is rotated in the direction of arrow R1. Therefore, fixing belt 310 sandwiched between pressure rotator 330 and fixing pad 380 is rotated in response to the rotation of pressure rotator 330.

[0032] The pressure rotor 330 can be moved by a contact / separation mechanism that moves the pressure rotor 330 so that it can contact or separate 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 rotor 330. The frame 385 is rotated around a rotation axis 332 by receiving drive from a drive motor (not shown). When the drive motor (not shown) rotates the frame 385 around the rotation axis 332 clockwise on the paper, the pressure rotor 330 moves in the direction of arrow P. As a result, the pressure rotor 330 contacts the fixing pad 380 (contact state) in a direction perpendicular to the recording material conveyance direction α, sandwiching the fixing belt 310 therebetween. This forms a fixing nip N. In this embodiment, a total pressure of 2000 N is applied, and the width of the fixing nip N is 24 mm. When the frame 385 is rotated counterclockwise on the paper surface about the rotation axis 332, the pressure rotator 330 is separated from the fixing belt 310 (separated state).

[0033] As explained above, the recording material carrying the unfixed toner image is sandwiched and conveyed by the heating rotor 300 and the pressure rotor 330 in the fixing nip N, where heat and pressure are applied to fix the toner image.

[0034] As described above, the present embodiment is configured as a so-called belt fixing device using an endless fixing belt 310, but the present invention is not limited to this. As shown in Fig. 10, the fixing device may be configured in such a way that a heating rotator 300 and a pressure rotator 330 are a pair of rollers that perform fixing on the recording material.

[0035] <Web Unit> Next, the web unit 200 or the collection roller 204 will be described with reference to FIG. 2 or FIG.

[0036] The fixing device fixes the toner on the recording material to the recording material using heat and pressure. If excessive heat is applied to the toner on the recording material, the toner on the recording material will melt excessively, and will not be fixed to the recording material, but will instead adhere to the heating rotor 300. This phenomenon is called hot offset. If the toner that has adhered to the heating rotor 300 due to hot offset is not collected, the heating rotor 300 will continue to rotate, causing the hot offset toner to adhere to and be fixed on the subsequent paper. This can result in image defects in the area where the hot offset toner has fixed.

[0037] Therefore, a web unit 200 for recovering toner that has been hot offset is known. The web unit 200 recovers toner that has adhered to the heating rotator 300. This prevents image defects caused by hot offset.

[0038] The web unit 200 includes a web 201 , a supply roller 202 , a take-up roller 203 , and a pressure roller 205 .

[0039] The collection roller 204 contacts the surface of the fixing belt 310 and is rotated by the rotation of the roller. The offset toner is melted by heat applied in the fixing nip N and adheres to the surface of the fixing belt 310. The collection 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 collection roller 204.

[0040] The toner that has moved to the surface of the recovery roller 204 is collected from the recovery roller 204 by a web 201 made of nonwoven fabric or the like. The web unit 200 has a pressure roller 205 for pressing the web 201 against the recovery roller 204. The pressure roller 205 presses the web 201 against the recovery roller 204, forming a predetermined nip width. The toner that has moved to the recovery roller 204 is collected by the web 201.

[0041] The web 201 used for toner recovery is taken up by the take-up roller 203. In this embodiment, the take-up roller 203 takes up the web at a frequency of 0.2 mm per four sheets of A4 paper, for example. One end of the web 201 is taken up by the take-up roller, and the other end is taken up by the supply roller 202. The supply roller has unused web 201 wound around it, and when the web 201 is taken up by the take-up roller 203, unused web 201 is supplied from the supply roller 202. As a result, unused web 201 is supplied to the contact area between the web 201 and the recovery roller 204, and toner adhering to the surface of the fixing belt 310 is recovered.

[0042] The web 201 is made of nonwoven fabric or the like, with a total length of approximately 50 m. After the recording material has been fixed, when 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 of the image forming apparatus 100 calls a service technician, who then replaces the web unit 200 with a new one. The longer the life of the web unit 200, the fewer times the user will need to call a service technician, so it is preferable that the web unit 200 has a long life. A new web here refers to a web that has never been used to collect toner.

[0043] The reason why the web 201 collects toner via the collection roller 204 will be explained. The web 201 is made of nonwoven fabric or the like. Therefore, if the web 201 were to come into direct contact with the fixing belt 310 without the collection roller 204, the surface of the fixing belt 310 would be more susceptible to deterioration. If the surface of the fixing belt 310 were to deteriorate quickly, the belt would need to be replaced more frequently, which would increase the amount of work required. Therefore, by collecting toner via a metal collection roller, the web 201 does not come into direct contact with the fixing belt 310, thereby extending the life of the fixing belt 310. Furthermore, unevenness on the surface of the fixing belt 310 affects the gloss of the image formed on the recording material. If the web 201 were to come into direct contact with the surface of the fixing belt 310, unevenness would occur on the surface of the fixing belt 310. This could result in uneven gloss in the image formed on the recording material. Therefore, by using a configuration in which the toner is collected via the collection roller 204 and the web 201 does not come into direct contact with the surface of the fixing belt 310, gloss unevenness can be suppressed.

[0044] [Web unit contact mechanism] The web unit 200 has a mechanism (not shown) for moving the web 201 into contact with or away from the collection roller 204. The collection roller 204 also has a mechanism (not shown) for moving the web 201 into contact with or away from the fixing belt 310. When a print job has not been accepted by the control unit 151, the collection roller 204 is in a state separated from the fixing belt 310. When a print job has been accepted, the collection roller 204 comes into contact with the fixing belt 310, and the surface temperature of the collection roller 204 rises. This makes it easier for toner on the surface of the fixing belt 310 to be transferred to the collection roller 204. When the surface temperature of the collection roller 204 becomes sufficiently high, the web 201 comes into contact with the collection roller 204 one second before the recording material is transported to the fixing nip portion. Until the print job is completed, the web 201 remains in contact with the collection roller 204, and the collection roller 204 remains in contact with the fixing belt 310.

[0045] When the print job is completed, the web 201 is separated from the collection roller after the last recording material of the print job has passed through the fixing nip portion N.

[0046] [Controlling the rotation amount of the winding roller according to the outer diameter of the wound web] The winding roller 203 is rotated to wind up the used web 201. As the used web 201 is wound, the amount of web 201 wound onto the winding roller 203 gradually increases, and the outer diameter of the web 201 wound by the winding roller 203 increases. If the rotational speed of the winding roller 203 is kept constant, the larger the outer diameter of the wound web 201, the greater the amount of web 201 wound up. Therefore, unless the rotational speed of the winding roller 203 is controlled in accordance with the outer diameter of the wound web 201, it is impossible to keep the amount of web 201 wound constant. If the rotational speed of the winding roller 203 is kept constant without taking the outer diameter of the wound web 201 into consideration, the amount of web 201 wound up gradually increases, resulting in unnecessary use of the web 201 and a shortened lifespan of the web 201.

[0047] Therefore, it has been conventional to control the rotation amount of the winding roller 203 in consideration of the outer diameter of the wound web 201.

[0048] <Winding mechanism using a variable resistor and motor> The following describes how the amount of web 201 to be wound is controlled in accordance with the outer diameter of the wound web 201. First, with reference to Figure 4, the mechanism by which the variable resistor 225 converts the outer diameter of the wound web 201 into a resistance value via the contact member 221 in this embodiment will be described.

[0049] The fixing device 30 has an outer diameter detection unit 220 that detects the outer diameter of the wound web. Figure 4 is a schematic diagram showing an example of the configuration of the outer diameter detection unit 220 in this embodiment. Also, Figure 4(a) shows a state in which the web unit 200 is unused and the web 201 is not wound around the winding roller 203. Figure 4(b) shows a state in which the outer diameter of the web 201 wound around the winding roller 203 has increased as a result of the web 201 being wound around the winding roller 203 in the direction of arrow A.

[0050] The contact member 221 of the outer diameter detection unit 220 shown in FIG. 4 has a lever 221a that is biased to contact the outer surface of the wound web 201, and a portion 221b that contacts the link gear 222. The lever 221a of the contact member 221 rotates in the direction of arrow B shown in FIG. 4(b) in accordance with the outer diameter of the wound web 201. This causes 221b of the contact member 221 to rotate in the direction of arrow C, causing the link gear 222 to rotate in the direction of arrow D. The gear portion of the link gear meshes with a 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 a gear portion 224 of the variable resistor 225. The gear shaft of the gear portion 224 of the variable resistor 225 is a D-cut shaft and is engaged with a rotating portion 225a of the variable resistor 225. Therefore, when stepped gear 223 rotates in the direction of arrow E, rotating portion 225a of variable resistor 225 rotates in the direction of arrow G. In other words, when web 201 is wound by winding roller 203 and the outer diameter of web 201 increases, rotating portion 225a of variable resistor 225 rotates in the direction of arrow G. The resistance value of variable resistor 225 can be changed by the amount of rotation of rotating portion 225a.

[0051] [Calculate the detection voltage Vsns from the resistance value of the variable resistor] The relationship between the rotating portion 225a of the variable resistor 225 and the resistance value will be described using Figure 5. Figure 5 is a diagram showing a detection circuit for the variable resistor 225 in this embodiment. The variable resistor 225 has terminals 1, 2, and 3. Terminals 1 to 3 of the variable resistor 225 shown in Figure 5 correspond to terminals 1 to 3 of the variable resistor 225 shown in Figure 4. Terminal 2 is connected to the rotating portion 225a. The resistance value R12 between terminals 1 and 2 or the resistance value R23 between terminals 2 and 3 changes depending on the angle (amount of rotation) of the rotating portion 225a.

[0052] Terminals 1 to 3 of variable resistor 225 are connected to control board 150, terminal 1 is connected to GND, terminal 2 is connected to a terminal of control unit 151 as detection voltage Vsns, and terminal 3 is connected to a 3.3V power supply.

[0053] In this embodiment, the total resistance value of the variable resistor between R1 and R3 is set to 10 kΩ, and the angle (amount of rotation) of the rotating portion 225a of the variable resistor 225, the resistance value R12 between terminals 1 and 2, and the resistance value R23 between terminals 2 and 3 are changed. R13=R12+R23=10kΩ...Formula 1 holds true.

[0054] Next, an example of calculating information related to the resistance value of the variable resistor 225 will be shown. In this embodiment, the voltage value is calculated from the resistance value of the variable resistor 225. However, this is not limiting. A method of calculating the current value from the resistance value is also acceptable. In addition, the resistance value of the variable resistor 225 may be stored in the storage unit 152. However, since the resistance value has the characteristic of changing depending on the temperature of the external environment, it is preferable to store the voltage value or the current value in the storage unit 152.

[0055] Since the resistance value is set by variable resistor 225 and terminal 3 is connected to the 3.3V power supply, detection voltage Vsns is input to control unit 151 connected to terminal 2. The detection voltage Vsns is a voltage obtained by dividing the 3.3V power supply by R12 and R23, and is calculated by the following formula. Vsns=3.3V×(R12)÷(R12+R23)...Equation 2 As a result, by using the detection voltage Vsns, the outer diameter of the web 201 wound around the winding roller 203 can be obtained as an electrical detection signal.

[0056] [Relationship between detection voltage and outer diameter of web] The relationship between the rotation angle of the variable resistor 225 and the output voltage value in this embodiment will be described using FIG. 6. In this embodiment, the outer diameter of the winding roller 203 is Φ12 mm, and is Φ50 mm when the winding roller 203 runs out of web 201 (when the web 201 reaches the end of its life). The point at which the web 201 begins to be used at the time of factory shipment is designated as (1), and the rotational angle of the rotating part 225a of the variable resistor 225 at this time is designated as 45°. The detected voltage value at (1) is designated as Va. As the web 201 is subsequently used, the outer diameter of the wound web 201 increases, and the resistance value (between R1 and R2) of the variable resistor 225 also increases. This increases the detected voltage Vsns, and when the web 201 reaches the end of its life, it reaches (2). The rotational angle of the rotating part 225a of the variable resistor 225 at (2) is designated as 315°, and the detected voltage is designated as Vb. The characteristic line connecting (1) and (2) is defined as TYP, and control unit 151 controls the rotation amount of take-up motor 240 (described later) along TYP.

[0057] The storage unit 152 stores data related to the web 201. The data includes Va, which is the detected voltage at the time of shipping from the factory, and Vb, which is the detected voltage at the end of the life (the voltage value at the end of the life).

[0058] In this embodiment, Vb and Vb' (described later) refer to the time when the web 201 to be wound up runs out, and Vb is calculated from the detected voltage Va at the time of shipment from the factory (as will be described later, Vb' is calculated from Va'). Therefore, depending on the amount of toner collected by the web 201, the time when the web 201 to be wound up actually runs out and the time when the detected voltage Vsns becomes equal to or greater than Vb may not necessarily coincide.

[0059] In this embodiment, Vb and Vb', which will be described later, refer to the time when the web 201 to be wound up runs out, but are not limited to this. They may also be values ​​that prompt the user to replace the web 201 when the web 201 falls below a predetermined amount.

[0060] [The web is wound up by the winding motor] Using FIG. 3, we will explain how the control unit 151 controls the take-up motor 240 based on the acquired voltage value. 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 obtain the detected voltage value Vsns using Equation 2. The control unit 151 is also connected to the take-up motor 240. The "take-up motor 240" here refers to 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 detected voltage value Vsns. Specifically, in this embodiment, if the take-up roller 203 can rewind 0.2 mm of the web 201 in one rotation, it is possible to recover toner from the surface of the fixing belt 310 and reduce the risk of image defects on subsequent sheets. Therefore, the desired amount of the web 201 to be rewound in one rotation of the take-up roller 203 is 0.2 mm. As the outer diameter of the wound web 201 increases, the rotation amount of the winding motor 240 is decreased so that the amount of web 201 wound by the winding roller 203 becomes 0.2 mm. At this time, the control unit 151 controls the rotation amount of the winding motor 240 in accordance with the obtained value of Vsns, and rotates the winding motor 240.

[0061] In this embodiment, a stepping motor is used as the winding motor 240. The control unit 151 controls the number of pulses input to the stepping motor, thereby controlling the amount of rotation of the stepping motor and controlling the amount of web 201 to be wound up.

[0062] Furthermore, as the winding motor 240 winds up the web 201, the unused web 201 gradually runs out, and the time to replace the web 201 approaches. By storing Vb, which is the voltage value for prompting the user to replace the web 201, in the memory unit 152, it is possible to determine whether the detected voltage value Vsns has reached Vb. This makes it possible to determine when it is time to replace the web 201.

[0063] The web 201 is a consumable item. When the wound web 201 runs out, it must be replaced with a new web 201. Usually, the entire web unit 200 is replaced, not just the web 201. Therefore, when it is time to replace the web unit 201, the user calls a service technician to replace the web 201 with a new web 201. When the web 201 is replaced with a new web, the wound web 201 runs out and the outer diameter of the wound portion of the web 201 also disappears. Because the contact member 221 is biased against the outer surface of the wound web 203, Vsns returns to near Va, which is the value at the start of use.

[0064] [Detected voltage deviation due to hysteresis component] In this embodiment, the image forming apparatus 100 detects Va, which is the voltage value at the time of shipment from the factory. Therefore, when Va is detected, it indicates a state in which the web 201 has never been replaced. Va is also the voltage value in a state in which no used web 201 is wound around the winding roller 203. In this embodiment, the winding roller 203 has a voltage of Φ12, so Va is the voltage value at Φ12. Therefore, the winding roller 203 winds the web 201 based on Va until the web 201 attached at the time of shipment from the factory is used up.

[0065] Storage unit 152 stores Va at the time of shipment from the factory. However, this is not limited to this. Storage unit 152 may store Va when image forming apparatus 100 is first powered on after image forming apparatus 100 is installed at a user-specified installation location.

[0066] Even after the factory-installed web 201 is used up and a new web 201 is installed in the fixing device 30, the web 201 continues to be wound based on Va. Va and the initial voltage value after the new web 201 is installed may differ due to the hysteresis component of the variable resistor 225. The hysteresis component of the variable resistor 225 is caused by the spring flexibility of the rotating portion 225a of the variable resistor 225 and backlash of one or more gears, such as the stepped gear 223, connected to the variable resistor 225. When the web 201 is replaced, the rotating portion 225a is reversed from the rotated position corresponding to the outer diameter of the wound web 201 and returns to the rotation angle at the start of use. However, the detected voltage value may differ due to the hysteresis component.

[0067] FIG. 6 shows cases where the initial voltage value after a new web 201 is attached differs. For example, assume that the voltage value at the start of use of the web 201 at the time of factory shipment is (1). The end of the web 201's life is at position (2), and the web 201 is consumed by moving from (1) to (2). After the voltage value and rotation angle reach (2), the web 201 is replaced with a new web 201. At this time, the contact member 221 is in contact with the outer surface of the take-up roller 203. Although the outer diameter is Φ12, FIG. 6 shows a case where the detected voltage differs from (1) due to a hysteresis component. Note that (3) indicates a case where the detected voltage is higher than (1), and the characteristic line drawn from (3) parallel to TYP is designated as MAX. When the detected voltage is lower, a characteristic line similar to MAX is drawn, designated as MIN. Since the deviation of the detected voltage due to the hysteresis component of the variable resistor 225 is ±30 mV, the characteristic line deviating by +30 mV is set to MAX, and the characteristic line deviating by −30 mV is set to MIN.

[0068] In this embodiment, the amount of change in voltage value due to the hysteresis component of variable resistor 225 is ±30 mV. The web 201 is wound around take-up roller 203 for several hundred revolutions. The voltage value varies within a range of several volts relative to the outer diameter of the wound web 201. This means that the amount of change in voltage value per revolution of the web is several mV. Therefore, the deviation of ±30 mV, which is the amount of change in voltage value due to the hysteresis component, cannot be ignored.

[0069] As shown in Figure 6, if the initial voltage value after the new web 201 is installed is 30 mV higher than (1), the outer diameter of the web 201 is mistakenly determined to be larger than the actual diameter. As a result, the amount of web 201 taken up is reduced, which may result in insufficient toner collection and poor image quality. Also, if the initial voltage value after the new web 201 is installed is lower than (1), the outer diameter of the web 201 is mistakenly determined to be smaller than the actual diameter. As a result, the amount of web 201 taken up is increased, which may result in a shortened lifespan of the web 201.

[0070] Therefore, in this embodiment, after the new web 201 is attached, the web 201 is wound up in consideration of the hysteresis component of the variable resistor 225.

[0071] [Winding control after web replacement] [Control example 1] Control example 1 in this embodiment will be described with reference to FIGS.

[0072] Fig. 7 is a flowchart showing the process for attaching a new web 201 in this embodiment. Fig. 8 is a flowchart showing the process for detecting the initial voltage after the new web 201 is attached in this embodiment. Fig. 9 is a diagram showing the relationship between the detected voltage value Vsns before and after the attachment of the new web 201 and the rotation angle of the variable resistor 225 in this embodiment.

[0073] First, the flow of attaching a new web 201 will be described with reference to Fig. 7. As described above, the web 201 is a consumable item, so a new web 201 is attached when the amount of web 201 being wound becomes less than a predetermined amount. The description will be given with reference to the flowchart in Fig. 7.

[0074] S101 When the image forming apparatus 100 is powered on, the control unit 151 obtains the detection voltage Vsns from the resistance value of the variable resistor 225. The control unit 151 also reads the voltage value Va at the time of shipment from the factory and the voltage value Vb at the end of the life stored in the storage unit 152. After reading Va and Vb, the process proceeds to S102.

[0075] In this embodiment, the voltage value Vb at the end of the service life is also used as a voltage value that prompts the user to replace the web 201. When Vsns reaches Vb, a notification is issued to the user urging them to replace the web 201. This allows the user to know when it is time to replace the web 201.

[0076] S102 Here, the image forming apparatus is in a standby state, which means that it is waiting for a print job.

[0077] S103 The control unit 151 determines whether the print job has been accepted. If it is determined that the print job has been accepted, the process proceeds to S104, and if it is determined that the print job has not been accepted, the process returns to S102.

[0078] S104 The image forming apparatus 100 starts the print job and proceeds to S105.

[0079] S105 The control unit 151 obtains the detected voltage value Vsns from the resistance value of the variable resistor 225 .

[0080] S106 The control unit 151 compares Vb with Vsns obtained in S105. If Vsns is equal to or greater than Vb, the process proceeds to S107, and if Vsns is smaller than Vb, the process proceeds to S113.

[0081] S107 If Vsns is equal to or greater than Vb, this means that there is little or no remaining web 201. Therefore, a new web 201 must be installed. Therefore, the control unit 151 interrupts the print job and proceeds to S108.

[0082] S108 The control unit 151 displays a message on the operation unit 40 prompting the user to replace the web 201 .

[0083] S109 When the web 201 is replaced by the user or a service person, the process proceeds to S110.

[0084] S110 After the web 201 is replaced, the control unit 151 acquires the detected voltage value Vsns. The memory unit 152 stores the threshold value Vth. The threshold value Vth is a value used by the control unit 151 to determine whether a new web 201 has been attached to the fixing device 30. The threshold value Vth is a value that takes into account the amount of change due to a hysteresis component in Vsns that is first obtained after the new web 201 is attached.

[0085] When the new web 201 is properly attached, the control unit 151 obtains the detected voltage Vsns before the web 201 is first wound. The detected voltage Vsns at this time returns to near Va, excluding any voltage changes due to the hysteresis component of the variable resistor 225.

[0086] Let us assume that a new web 201 was not properly attached and the used web 201 was replaced with a new web 201. After the web 201 is replaced, the voltage Vsns obtained initially becomes greater than the threshold value Vth. In this case, the control unit 151 determines that the web 201 was not properly replaced and returns to S107. After the web 201 is replaced, if the voltage value Va', which is the first information described below, is equal to or less than the threshold value Vth, it is determined that the web 201 was properly replaced and the process proceeds to S111. This allows the user to recognize that the web 201 has been replaced with a new one.

[0087] The threshold value Vth is a value that takes into consideration the hysteresis component of the variable resistor 225 after the new web 201 is attached, and in this embodiment, Vth is set to 0.6 V. Furthermore, it is preferable that Vth be a value that ensures the attachment of a new web 201. Therefore, it is preferable that Vth be in the range of 0.42 V to 0.6 V.

[0088] Alternatively, the control unit 151 may calculate the difference between the current voltage value stored in the memory unit 152 and the previous voltage value stored in the memory unit 152, and if the difference is equal to or greater than a predetermined value, the control unit 151 may detect that a new web 201 has been attached. In this case, the previous voltage value is the value detected in S105. The current voltage value is the value detected in S110. In this embodiment, the control unit 151 determines that a new web 201 has been attached if the difference between the current voltage value and the previous voltage value is equal to or greater than 2.0 V. However, the difference is not limited to 2.0 V or greater, and may not be equal to or greater than 2.0 V, depending on the value of the detected voltage Vsns. In order for the control unit 151 to detect that a new web 201 has been attached, the memory unit 152 stores the calculated voltage value each time the voltage value is calculated by the control unit 151.

[0089] S111 In S111, after the new web 201 is attached, Va' (first information), which is the initial voltage value after attachment, and Vb' (second information), which is the voltage value at the end of the life after attachment, are newly set. The setting of Va' and Vb' will be described later in [Setting Va' and Vb'].

[0090] S112 The print job is resumed. The rotation rate of take-up motor 240 at this time is controlled based on the first information. Specifically, when Va' is 0.45V, a characteristic line "after installation" is drawn as shown in FIG. 9. Control unit 151 controls the rotation rate of take-up motor 240 along this characteristic line "after installation." The characteristic line "after installation" is drawn from Va' so that it is parallel to TYP shown in FIG. 6.

[0091] S113 Steps S106 to S112 are repeated until the control unit 151 determines that the print job has ended. If it is determined that the print job has ended, the process proceeds to step S114.

[0092] S114 The control unit 151 stops detecting the detected voltage value Vsns.

[0093] S115 The print job of the image forming apparatus 100 is stopped.

[0094] S116 The image forming apparatus 100 transitions to a standby state.

[0095] [Va' and Vb' settings] The flow of setting Va' and Vb' will be described with reference to FIG.

[0096] S201 The detected voltage Vsns is detected, and the value at that time is stored in the memory unit 152 as the initial voltage value Va' after the new web 210 is attached. Note that Va' is calculated from the time the new web 201 is attached until the take-up roller 203 makes one rotation. The outer diameter of the take-up roller 203 hardly changes until the take-up roller 203 makes one rotation. This allows the memory unit 152 to store a voltage value Va' corresponding to the initial outer diameter of the take-up roller 203 for the new web 201. However, since the web 201 is made of a nonwoven fabric or the like, its surface has irregularities. Therefore, there is a risk of slight errors in the outer diameter occurring before the take-up roller 203 makes one rotation. Therefore, in this embodiment, the control unit 151 calculates Va' between the time the new web 201 is replaced and the time the take-up roller 203 starts rotating for the first time. This reduces errors that occur before the take-up roller 203 makes one rotation, allowing for accurate calculation of Va'.

[0097] S202 In order to calculate the amount of change in the detected voltage due to the hysteresis component of the variable resistor 225, the control unit 151 calculates the amount of change ΔV in the detected voltage. ΔV is ΔV=Va'―Va···Equation 3 It is calculated using the above formula 3.

[0098] S203 The control unit 151 calculates Vb'. The voltage value Vb' to be detected after the new web 201 is attached is calculated by shifting it by ΔV, and stored in the storage unit 152. Vb' is Vb'=Vb+ΔV...Equation 4 and is calculated as follows.

[0099] In this embodiment, as shown in Figure 9, assume that a hysteresis component of ΔV = 30 mV occurs before and after attaching the new web 201. As a result, Va' = 0.45 V (Va + 30 mV). The second information Vb' is also shifted by the hysteresis component ΔV, so Vb' = Vb + ΔV = 2.58 V + 30 mV = 2.61 V.

[0100] Thereafter, control unit 151 controls the rotation amount of take-up motor 240 based on the characteristic line connecting first information Va', which is a detected voltage value taking into account the hysteresis component of variable resistor 225, and second information Vb'.

[0101] The control unit 151 also reviews the detected voltage value relative to the outer diameter of the winding roller 203. When the first information Va' is given, the control unit 151 determines that the outer diameter is Φ12 mm, and when the second information Vb' is given, the control unit 151 determines that the outer diameter is Φ50 mm.

[0102] [Effect of detecting the outer diameter of the web using a variable resistor] The outer diameter of the web 201 being wound increases slightly because the web 201 is thin. Therefore, in this embodiment, a variable resistor 225 is used in the web unit 200 to acquire the detected voltage Vsns. Because the detected voltage Vsns is an electrical signal, the detected voltage Vsns can also be changed in response to minute changes in the outer diameter of the web 201 being wound. This allows the control unit 151 to precisely control the rotation amount of the winding motor 240.

[0103] As a specific example, when the resistance value of the variable resistor 225 is small, the amount of wound web 201 is small and the outer diameter is also small. Therefore, the rotation amount of the winding roller 203 is increased. On the other hand, when the resistance value of the variable resistor 225 is large, the amount of wound web 201 is large and the outer diameter is also large. Therefore, the rotation amount of the winding roller 203 is reduced. In this case, the rotation amount of the winding roller 203 can be precisely set according to the position of the contact member 221. Therefore, the web 201 can be wound with high precision. As a result, the life of the web 201 can be extended.

[0104] Although the variable resistor 225 in this embodiment is a rotary type variable resistor 225 in which a slider rotates, other types of variable resistor 225 may be used. For example, the variable resistor 225 may be a sliding type variable resistor 225 in which the rotating portion 225a is a sliding type.

[0105] [Effect of using Va' in post-exchange control] The greater the detected voltage Vsns, the smaller the rotation amount of the winding motor 240 is made, and conversely, the smaller the detected voltage Vsns, the greater the rotation amount of the winding motor 240 is made.

[0106] If the initial voltage value Va at the time of shipment from the factory is used as the initial voltage value after the new web 201 is attached, there is a risk that the position of the contact member 221 will be misidentified due to the hysteresis component of the variable resistor 225. As a result, the initial voltage value before and after the attachment of the new web 201 may differ.

[0107] For example, if the initial voltage value after replacement is 30 mV higher than before replacement, the outer diameter of the wound web 201 may be mistakenly recognized as being larger than the actual outer diameter. This may result in the amount of web 201 wound by take-up motor 240 being less than the amount of web 201 that is actually required. As a result, the toner on the surface of fixing belt 310 may not be sufficiently collected, and offset toner may adhere to the subsequent paper, resulting in poor image quality.

[0108] Similarly, if the initial voltage value after replacement is 30 mV lower than before replacement, the outer diameter of the wound web 201 will be erroneously recognized as smaller than the actual outer diameter. This may cause the amount of web 201 wound by the winding motor 240 to exceed the amount of web 201 that is actually required. This may result in excessive winding of the web 201, which may shorten the life of the web 201.

[0109] However, in this embodiment, after the new web 201 is attached, the first information Va' is calculated and used to control the winding of the web 201. The position of the contact member 221 remains almost constant from the time the new web 201 is attached until the take-up roller 203 makes one rotation. Furthermore, because the web 201 is thin, the take-up roller 203 only winds the web 201 a few times when the web unit 200 is new. Because the outer diameter of the take-up roller 203 is Φ12, after the new web 201 is attached, the memory unit 152 stores the position of the contact member 221 when the outer diameter is Φ12, corresponding to the first information Va'. At this time, the rotation angle of the rotating portion 225a of the variable resistor 225 is 45°. After the new web 201 is attached, the control unit 151 controls the rotation amount of the take-up motor 240 based on the first information Va'. This makes it possible to suppress erroneous recognition of the position of the contact member 221 due to the hysteresis component of the variable resistor 225 after the new web 201 is attached.

[0110] By suppressing erroneous recognition, the web can be wound up with high accuracy.

[0111] In this embodiment, the first information Va' uses the voltage value detected first after the new web 201 is attached. However, this is not limited to this. After the web 201 is replaced with a new one, the contact member 221 moves by the thickness of the web 201 as the take-up roller 203 rotates once. Therefore, if the voltage is detected between the time the web 201 is replaced with a new one and the time the take-up roller 203 rotates once, the position of the contact member 221 of the new web 201 can be detected.

[0112] In addition, although the take-up roller 203 having a diameter of 12 mm is used in this embodiment, the take-up roller 203 is not limited to a diameter of 12 mm, as long as it is a roller for taking up the web 201 after use.

[0113] [Effect of using Vb' in post-exchange control] In S203 of FIG. 8, the control unit 151 calculates the voltage value Vb' (second information) at the end of the life after the attachment of the new web 201 from the first information Va'. The calculation method is as described above in S203. Furthermore, when the take-up roller 203 finishes winding the web 201 used in this embodiment and there is no more web 201 to wind, the outer diameter of the wound web 201 is approximately Φ50. Therefore, in this embodiment, the time when the wound web 201 is Φ50 is defined as the time when the take-up roller 203 finishes winding the web 201 and there is no more web 201 to wind.

[0114] Vb' is shifted by ΔV from the voltage value Vb at the end of the life before the attachment of the new web 201. As a result, the voltage value at Φ50 shifts by ΔV before and after the attachment of the new web 201.

[0115] Therefore, by calculating the second information Vb' taking ΔV into consideration, the voltage value at Φ50 after replacement can be calculated with high accuracy. In this embodiment, if the detected voltage value Vsns becomes equal to or greater than the second information Vb' after the new web 201 is attached, it is assumed that there is no more web 201 to be wound. Therefore, a message can be displayed on the operation unit 40 to prompt the user to attach a new web 201. This allows the user to know when to replace the web 201 even after the new web 201 has been attached.

[0116] For ease of understanding, Va and Vb are assumed to be the voltage values ​​at the time of shipment from the factory. However, this is not limited to this. After each installation of a new web 201, the control unit 151 calculates ΔV and performs control using Va' and Vb' that take ΔV into account.

[0117] As described above, the fixing device of this embodiment can wind up the web 201 with high precision.

[0118] [Control example 2] Next, a control example 2 in this embodiment will be described with reference to FIG. 10. FIG. 10 is a flowchart showing a control example in this embodiment in which replacement of the new web 201 is manually detected. The only difference from the control example 1 described so far is S310 in FIG. 10. In control example 1, the threshold value Vth was used to automatically detect that the web 201 has been replaced with a new web 201. In control example 2, after the web 201 has been replaced with a new web 201, the user manually notifies the user using the operation unit 40.

[0119] The following description will be made with reference to Fig. 10. S301 to S309 correspond to S101=S109 in control example 1, and the contents are the same, so the description will be omitted.

[0120] S310 A determination is made as to whether a notification of the attachment of the new web 201 has been made on the operation unit 40. This means that the user has actually selected and executed the notification of the completion of attachment of the new web 201 using the operation keys on the operation unit 40. If the user selects the notification of the completion of attachment of the new web 201 on the operation unit 40 after the new web 201 has been attached, the operation unit 40 transmits a signal indicating the completion of attachment of the new web 201 to the control unit 151. The control unit 151 receives the signal indicating the completion of attachment of the new web 201. Then, the flow proceeds to S311 in the flowchart. If the notification of the completion of web 201 replacement has not been selected, the flow returns to S307.

[0121] S311 to S316 correspond to S111 to S116 in control example 1, respectively, and have the same content, so a description thereof will be omitted. [Explanation of symbols]

[0122] 30 Fixing device 40 Control section 100 Image forming device 150 control board 151 Control Unit 152 Storage section 200 web units 201 Web 202 Supply roller 203 Winding roller 204 Collection Roller 205 Pressure roller 220 Outer diameter detection unit 221 Contact member 225 variable resistor 240 Winding motor 300 Heating Rotor 310 Fixing belt 330 Pressurized Rotating Body 340 Heating Roller α Conveying direction

Claims

1. a heating rotor for heating unfixed toner carried on a recording material; a pressure rotating body that applies pressure to the heating rotating body to form a fixing nip portion, and that sandwiches and conveys a recording material carrying unfixed toner into the fixing nip portion, thereby fixing the unfixed toner image onto the recording material; a web for collecting toner that has not been fixed to the recording material and adheres to the surface of the heating rotary body; a take-up roller that takes up the web used to collect the toner adhering to the surface of the heating rotary body; a contact member that contacts an 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 depending on the position of the contact member; a control unit that calculates information about the resistance value from the resistance value of the variable resistor; a storage unit that stores the information; a winding motor that rotates the winding roller to wind the web; detecting that a new web has been attached when a difference between the current value calculated by the control unit and the previous value stored in the storage unit is equal to or greater than a predetermined value; the storage unit stores first information calculated by the control unit; The control unit controls the rotation amount of the winding motor based on the first information. A fixing device characterized by:

2. 2. The fixing device according to claim 1, wherein the first information is calculated from the time when the new web is attached until the take-up roller makes one rotation.

3. 3. The fixing device according to claim 1, wherein the first information is calculated from the time when the new web is attached to the take-up roller until the take-up roller starts to rotate.

4. a heating rotor for heating unfixed toner carried on a recording material; a pressure rotating body that applies pressure to the heating rotating body to form a fixing nip portion, and that sandwiches and conveys a recording material carrying unfixed toner into the fixing nip portion, thereby fixing the unfixed toner image onto the recording material; a web for collecting toner that has not been fixed to the recording material and adheres to the surface of the heating rotary body; a take-up roller that takes up the web used to collect the toner adhering to the surface of the heating rotary body; a contact member that contacts an 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 depending on the position of the contact member; a control unit that calculates information about the resistance value from the resistance value of the variable resistor; a storage unit that stores the information; a winding motor that rotates the winding roller to wind the web; an operation unit for transmitting a signal to the control unit; When the control unit receives a signal, the storage unit stores first information calculated by the control unit; The control unit controls the rotation amount of the winding motor based on the first information. A fixing device characterized by:

5. The heating rotor includes a rotatable endless fixing belt and 5. The fixing device according to claim 1, further comprising a heating roller that contacts an inner peripheral surface of the fixing belt and applies heat to the fixing belt.

6. 6. The fixing device according to claim 1, further comprising a recovery roller that recovers toner that has not been fixed to the recording material and adheres to the heating rotor from the heating rotor, and the web recovers toner that has adhered to the recovery roller from the recovery roller.

7. The fixing device according to any one of claims 1 to 6, characterized in that the contact member has a lever that contacts the outer surface of the web wound around the winding roller, and the lever is connected to the variable resistor via one or more gears.

8. 8. The fixing device according to claim 1, wherein the variable resistor has a rotating portion that rotates in accordance with the movement of the contact member, and the resistance value can be changed according to the amount of rotation of the rotating portion.

Images