Fixing apparatus and image forming apparatus

Abstract

Even if wear particles adhere to the lubricant-coated member, the system will suppress deterioration of the sliding properties between the belt and the pressure pad, thereby suppressing paper jams or image defects. [Solution] The fixing device F1 includes a pressure pad 303 that forms a nip portion N by applying pressure to a pressure roller 305 via the belt 301 and contacts the inner circumferential surface of the belt 301, a coating roller 401 that supplies lubricant to the inner circumferential surface of the belt 301, and a scraping member 501 that recovers the lubricant supplied to the inner circumferential surface of the belt 301 by the coating roller 401 from the end in the longitudinal direction perpendicular to the rotational direction of the belt 301, and the scraping member 501 supplies the recovered lubricant to the inner circumferential surface of the belt 301.

Description

Technical Field

[0001] The present invention relates to a fixing device that heats a toner image on a recording material and an image forming apparatus including this fixing device.

Background Art

[0002] In an electrophotographic image forming apparatus, generally, a nip portion is formed by a belt heated by a heating body and a pressure member, and a transfer material carrying a toner image is conveyed while being pressure-heated at the nip portion, thereby fixing the toner image on the transfer material. A fixing device is used. In particular, in recent fixing devices, a flat fixing pad is pressed against a pressure member via a belt to form a flat nip, and a technique for printing a high-quality image while reducing paper stress such as wrinkles or unevenness on the transfer material is adopted. In such a fixing device, it is important to continuously maintain good slidability between the belt and the fixing pad, and a lubricant application member for continuously applying a lubricant to the inner peripheral surface of the belt is provided.

[0003] However, the lubricant applied to the inner peripheral surface of the belt gradually leaks to the outside from the end surface of the belt in the process of continuous use of the fixing device. As a result, the amount of lubricant applied to the inner peripheral surface of the belt or the contact portion of the fixing pad that contacts the inner peripheral surface of the belt decreases in the process of continuous use of the fixing device.

[0004] In addition, when the amount of lubricant contained in the lubricant application member decreases, it becomes impossible to sufficiently apply the lubricant to the inner peripheral surface of the belt. In this case, since good slidability cannot be ensured, the rotational load of the belt increases, and there is a concern that paper jams may occur because the transfer material cannot be conveyed. In addition, there is a concern that the rotational speed of the belt may lag behind the rotational speed of the pressure member, resulting in image defects such as toner images being disturbed in the conveyance direction.

[0005] In contrast, Patent Document 1 discloses a fixing device that maintains the lubrication state of the sliding part by preventing lubricant from leaking out from the end of the belt by providing a lubricant scraping member at the end of the belt. Furthermore, the fixing device of Patent Document 1 also prevents the depletion of lubricant contained in the lubricant coating member by returning the lubricant scraped off by the scraping member to the lubricant coating member. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-036812 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in Patent Document 1, continuous use of the fixing device causes wear debris from the inner surface of the belt or the contact portion of the fixing pad that contacts the inner surface of the belt to adhere to the lubricant application member. When wear debris adheres to the lubricant application member, the lubricant that is scraped off by the scraping member and returned to the lubricant application member cannot be adequately applied to the inner surface of the belt.

[0008] Specifically, when lubricant is returned from the scraping member to the lubricant application member, the lubricant application member absorbs the lubricant through gaps where wear particles are not adhering. However, due to the wear particles adhering to the surface, it becomes unable to adequately release the absorbed lubricant. Furthermore, the lubricant application member is also unable to adequately release the lubricant it contains because it is hindered by the wear particles adhering to its surface.

[0009] Thus, Patent Document 1 has the problem that, with continued use of the fixing device, the lubricant ceases to circulate to the inner surface of the belt or the contact portion of the fixing pad that contacts the inner surface of the belt, resulting in deterioration of the belt's sliding properties and causing paper jams or image defects.

[0010] The object of the present invention is to provide a fixing device and an image forming device that can suppress deterioration of the sliding properties between the belt and the pressure pad, even when wear particles adhere to the lubricant coating member, thereby suppressing the occurrence of paper jams or image defects. [Means for solving the problem]

[0011] The fixing device according to the present invention comprises a rotatable endless belt, a heating element for heating the belt, a pressurizing member positioned opposite the belt, a pressurizing pad that forms a nip portion by applying pressure to the pressurizing member via the belt and contacts the inner circumferential surface of the belt, a lubricant supplying member for supplying lubricant to the inner circumferential surface of the belt, and a lubricant recovery member for recovering the lubricant supplied to the inner circumferential surface of the belt by the lubricant supplying member from the longitudinal end perpendicular to the rotational direction of the belt, wherein the fixing device fixes a toner image formed on a recording material by heating and pressurizing the recording material at the nip portion, and the lubricant recovery member supplies the recovered lubricant to the inner circumferential surface of the belt. [Effects of the Invention]

[0012] According to the present invention, even if wear particles adhere to the lubricant-coated member, deterioration of the sliding properties between the belt and the pressure pad can be suppressed, thereby suppressing the occurrence of paper jams or image defects. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of an image forming apparatus according to Embodiment 1 of the present invention. [Figure 2] This is a schematic diagram of a fixing device according to Embodiment 1 of the present invention. [Figure 3] This diagram shows the configuration of the lubricant recovery member of the fixing device according to Embodiment 1 of the present invention. [Figure 4] This is a schematic diagram of a part of the fixing device according to Embodiment 1 of the present invention. [Figure 5]It is a schematic diagram of a conventional fixing device shown for comparison with the fixing device according to Embodiment 1 of the present invention. [Figure 6] It is a diagram showing the relationship between the number of durable sheets of the fixing device according to Embodiment 1 of the present invention and the weight of the lubricant. [Figure 7] It is a schematic diagram of the fixing device according to Embodiment 2 of the present invention. [Figure 8] It is a diagram showing the relationship between the number of durable sheets of the fixing device according to Embodiment 2 of the present invention and the weight of the lubricant.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings.

[0015] (Embodiment 1) <Configuration of the Image Forming Apparatus> The configuration of the image forming apparatus 1 according to Embodiment 1 of the present invention will be described in detail while referring to FIG. 1.

[0016] The image forming apparatus 1 exemplifies a full-color image forming apparatus here. The image forming apparatus 1 has an image reading unit 2 and a device main body 3.

[0017] The image reading unit 2 reads an image of a document and outputs an image signal of the read image to the device main body 3. The image reading unit 2 includes a document table glass 21, a light source 22, an optical system member 23, and a CCD sensor 24.

[0018] A document is placed on the document table glass 21.

[0019] The light source 22 irradiates light on the document placed on the document table glass 21 while moving in the direction of the arrow in FIG. 1.

[0020] The optical system member 23 is a lens or the like, and forms an image of the reflected light irradiated from the light source 22 and reflected by the document on the CCD sensor 24.

[0021] The CCD sensor 24 obtains an image signal by converting the reflected light imaged by the optical system component 23 into a series of electrical signal data for each line, and outputs the obtained image signal to the main unit 3 of the device.

[0022] The optical system unit, comprising the light source 22, optical system component 23, and CCD sensor 24 described above, scans the document in the direction of the arrow in Figure 1, converting the image of the document into a line-by-line sequence of electrical signal data.

[0023] The main body of the device 3 houses various components that perform image processing to form an image on the transfer material P, which is used as a recording material, based on the image signal input from the image reading unit 2.

[0024] <Configuration of the main device> The configuration of the main body 3 of the image forming apparatus 1 according to an embodiment of the present invention will be described in detail with reference to Figure 1.

[0025] The main body of the device 3 comprises a paper output tray 7, a paper feed cassette 8, a paper feed cassette 9, a control unit 30, an exposure device 31, an image forming unit Pa, an image forming unit Pb, an image forming unit Pc, an image forming unit Pd, and an intermediate transfer belt 204. The main body of the device 3 also comprises a secondary transfer roller 205, a secondary transfer roller 206, a registration unit 208, and a fixing device F1. The image forming units Pa, Pb, Pc, and Pd constitute the image forming means.

[0026] The output tray 7 is loaded with transfer material P transported from the fuser unit F1.

[0027] The paper feed cassette 8 contains the transfer material P.

[0028] The paper feed cassette 9 contains the transfer material P.

[0029] The control unit 30 controls the operation of the entire image forming apparatus 1 and performs image processing, etc. The control unit 30 controls the operation of the exposure apparatus 31 by controlling the image signal input from the CCD sensor 24 or the image signal received from an external host device (not shown), such as a print server, using PWM (pulse width modulation).

[0030] The exposure apparatus 31 is, for example, a polygon scanner. The exposure apparatus 31 forms an electrostatic latent image on the photosensitive drum 200a of the image forming unit Pa by irradiating it with a laser and scanning it, under the control of the control unit 30. The exposure apparatus 31 forms an electrostatic latent image on the photosensitive drum 200b of the image forming unit Pb by irradiating it with a laser and scanning it, under the control of the control unit 30.

[0031] The exposure apparatus 31, under the control of the control unit 30, irradiates and scans the charged photosensitive drum 200c of the image forming unit Pc with a laser to form an electrostatic latent image on the photosensitive drum 200c. The exposure apparatus 31, under the control of the control unit 30, irradiates and scans the charged photosensitive drum 200d of the image forming unit Pd with a laser to form an electrostatic latent image on the photosensitive drum 200d.

[0032] The image forming unit Pa forms a yellow (Y) toner image on the photosensitive drum 200a. The image forming unit Pa comprises the photosensitive drum 200a, a primary charger 201a, a developer 202a, a transfer roller 203a, and a cleaner 207a.

[0033] The photosensitive drum 200a is charged by the primary charger 201a. An electrostatic latent image is formed on the photosensitive drum 200a by the exposure device 31, and a toner image is formed on it by the developer 202a.

[0034] The primary charger 201a prepares the photosensitive drum 200a for forming an electrostatic latent image by charging its surface to a predetermined potential.

[0035] The developing unit 202a develops the electrostatic latent image formed on the photosensitive drum 200a by the exposure device 31 to form a toner image on the photosensitive drum 200a.

[0036] The transfer roller 203a applies a primary transfer bias with opposite polarity to the toner by discharging from the inside of the intermediate transfer belt 204, thereby transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204.

[0037] The cleaner 207a cleans the surface of the photosensitive drum 200a after the toner image has been transferred onto the intermediate transfer belt 204.

[0038] The image forming unit Pb forms a magenta (M) toner image on the photosensitive drum 200b. The image forming unit Pb comprises the photosensitive drum 200b, the primary charger 201b, the developer 202b, the transfer roller 203b, and the cleaner 207b. Note that the configurations of the photosensitive drum 200b, the primary charger 201b, and the developer 202b are the same as those of the photosensitive drum 200a, the primary charger 201a, and the developer 202a, respectively, so their descriptions are omitted. Similarly, the configurations of the transfer roller 203b and the cleaner 207b are the same as those of the transfer roller 203a and the cleaner 207a, respectively, so their descriptions are omitted.

[0039] The image forming unit Pc forms a cyan (C) toner image on the photosensitive drum 200c. The image forming unit Pc comprises the photosensitive drum 200c, the primary charger 201c, the developer 202c, the transfer roller 203c, and the cleaner 207c. The configurations of the photosensitive drum 200c, the primary charger 201c, and the developer 202c are the same as those of the photosensitive drum 200a, the primary charger 201a, and the developer 202a, respectively, so their descriptions are omitted. Similarly, the configurations of the transfer roller 203c and the cleaner 207c are the same as those of the transfer roller 203a and the cleaner 207a, respectively, so their descriptions are omitted.

[0040] The image forming unit Pd forms a black (Bk) toner image on the photosensitive drum 200d. The image forming unit Pd comprises the photosensitive drum 200d, the primary charger 201d, the developer 202d, the transfer roller 203d, and the cleaner 207d. Note that the configurations of the photosensitive drum 200d, the primary charger 201d, and the developer 202d are the same as those of the photosensitive drum 200a, the primary charger 201a, and the developer 202a, respectively, so their descriptions are omitted. Similarly, the configurations of the transfer roller 203d and the cleaner 207d are the same as those of the transfer roller 203a and the cleaner 207a, respectively, so their descriptions are omitted.

[0041] On the intermediate transfer belt 204, toner images are transferred by transfer rollers 203a, 203b, 203c, and 203d, forming four-color toner images. The intermediate transfer belt 204 then transports the formed four-color toner images to the secondary transfer section, which is formed by secondary transfer rollers 205 and 206.

[0042] The secondary transfer rollers 205 and 206, acting as transfer means, constitute a secondary transfer roller pair. The secondary transfer rollers 205 and 206 are subjected to a secondary transfer electric field with opposite polarity to the toner image formed on the intermediate transfer belt 204, thereby secondary transferring the toner image formed on the intermediate transfer belt 204 to the transfer material P conveyed by the register unit 208. The secondary transfer rollers 205 and 206 then convey the transfer material P, on which the toner image has been secondary transferred, to the fixing device F1.

[0043] The register unit 208 temporarily holds the transfer material P supplied from the paper feed cassette 8 or paper feed cassette 9, and then, in conjunction with the timing when the toner image formed on the intermediate transfer belt 204 is transported to the secondary transfer roller pair, it transports the held transfer material P to the secondary transfer roller pair.

[0044] The fuser unit F1 is a belt-heating type fuser unit. The fuser unit F1 heats and pressurizes the toner image that has been secondarily transferred to the transfer material P, which is conveyed by the secondary transfer rollers 205 and 206, thereby fixing the toner image to the transfer material P. The fuser unit F1 then conveys the transfer material P with the fixed toner image to the output tray 7.

[0045] In the image forming apparatus 1 having the above configuration, in the case of a double-sided job, after the transfer and fixing of the toner image to the first surface of the transfer material P is completed, the front and back of the transfer material P are reversed by the reversal unit. Then, after the transfer and fixing of the toner image to the second surface of the transfer material P is completed, the image forming apparatus 1 discharges the transfer material P and stacks it on the output tray 7.

[0046] <Configuration of the fixing device> The configuration of the fixing device F1 according to Embodiment 1 of the present invention will be described in detail with reference to Figures 2 to 4.

[0047] In Figures 2 and 4, the X direction is the conveying direction of the transfer material P, the Y direction is the longitudinal direction of the belt 301, and the Z direction is the pressing direction of the pressure roller 305. The opposite direction to the pressing direction is the vertical direction. Also, in Figure 2, the support portion 501c of the scraping member 501 is omitted, and the scraping member 501 is located further back than the belt 301.

[0048] Furthermore, in Figure 3, Figure 3(a) is a view of the scraping member 501 from the Z direction (downward in Figure 2), and Figure 3(b) is a view of the scraping member 501 from the right direction in Figure 3(a).

[0049] Furthermore, for the sake of clarity, Figure 4 omits the description of the opposite side of the belt 301 in the X direction.

[0050] The fixing device F1 includes a belt 301, a stay 302, a pressure pad 303, a pressure roller 305, a halogen heater 306, a heating roller 307, a steering roller 308, a coating roller 401, and a scraping member 501.

[0051] The belt 301 is endless and rotatable. The belt 301 has thermal conductivity and heat resistance, and is thin-walled. The belt 301 is stretched by a pressure pad 303, a heating roller 307, and a steering roller 308. The belt 301 is heated by the heating roller 307.

[0052] Belt 301 has a three-layer structure, consisting of a base layer (not shown), an elastic layer covering the outer surface of the base layer, and a release layer covering the outer surface of the elastic layer, all stacked from the inside outwards. The base layer is 80 μm thick and made of polyimide resin (PI). The elastic layer is 300 μm thick and made of silicone rubber. The release layer is 30 μm thick and made of a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin). The inner surface of belt 301 is composed of the base layer, and the outer surface of belt 301 is composed of the release layer.

[0053] The stay 302 supports the pressure pad 303. The stay 302 is made of a metal such as stainless steel. The stay 302 is provided to ensure the strength of the pressure pad 303 and to uniformly press the pressure pad 303 against the pressure roller 305.

[0054] The pressure pad 303 forms a nip portion N by applying pressure to the pressure roller 305 via the belt 301, and is also pressed by the pressure roller 305 via the belt 301. The pressure pad 303 is a metal plate made of SUS (stainless steel). The contact portion 303a of the pressure pad 303 that abuts the inner circumferential surface of the belt 201 is coated with PTFE (polytetrafluoroethylene) with a thickness of 30 μm. 500 mg of lubricant is pre-applied to the contact portion 303a of the pressure pad 303 to ensure sliding properties until the lubricant is discharged from the application roller 401. Silicone oil is used as an example of the lubricant.

[0055] The pressure roller 305, acting as a pressurizing member, is positioned opposite the belt 301 and together with the belt 301 forms a nip section N. The pressurizing force (NF) at the nip section N during printing is exemplified here as 1600N. The width of the nip section N in the X direction is exemplified here as 24.5mm. Furthermore, the width of the nip section N in the Y direction is exemplified here as 326mm.

[0056] The pressure roller 305 is axially supported at both ends in the longitudinal direction by a fixing frame (not shown) of the fixing device F1, and a gear (not shown) is fixed to one end in the longitudinal direction and connected to the drive source M1 via the gear. The pressure roller 305 rotates when a driving force is transmitted from the drive source M1 via the gear. The pressure roller 305 applies pressure to the pressure pad 303 via the belt 301 when driven by the drive source (not shown).

[0057] The pressure roller 305 is a roller formed by laminating a core metal layer, an elastic layer covering the outer surface of the core metal layer, and a release layer covering the outer surface of the elastic layer. The core metal layer, which is the shaft, has a diameter of 72 mm and is made of SUS (stainless steel). The elastic layer has a thickness of 8 mm and is made of conductive silicone rubber. The release layer has a thickness of 100 μm and is made of a fluororesin such as PFA (polytetrafluoroethylene perfluoroalkoxyethylene copolymer resin).

[0058] The halogen heater 306 is located inside the heating roller 307 and is capable of generating heat up to a predetermined temperature.

[0059] The heating roller 307, which serves as the heating element, is a stainless steel pipe with a thickness of 1 mm. The heating roller 307 is in contact with the inner circumferential surface of the belt 301, and the halogen heater 306 generates heat, thereby heating the belt 301.

[0060] The steering roller 308 is positioned inside the belt 301 and is in contact with the inner circumferential surface of the belt 301. The steering roller 308 has a pivot point at one end or near the center in the longitudinal direction, and by rotating, it generates a tension difference between the front and rear of the belt 301, thereby controlling the position of the belt 301 in the Y direction. The steering roller 308 has a diameter of 20 mm and is made of hollow stainless steel. The steering roller 308 may also have a rubber material or the like on its surface to improve its grip on the belt 301.

[0061] The coating roller 401, which serves as a lubricant supply member, has a structure in which a nonwoven fabric is wound around a shaft made of SUS, and it absorbs lubricant more easily than the inner circumferential surface of the belt 301. The nonwoven fabric of the coating roller 401 contains approximately 10g of lubricant, similar to the lubricant applied to the surface of the pressure pad 303, uniformly distributed throughout. The coating roller 401 contacts the inner circumferential surface of the belt 301 and continuously applies lubricant to the inner circumferential surface of the belt 301, and also continuously supplies lubricant to the contact portion 303a of the pressure pad 303 via the inner circumferential surface of the belt 301. Here, the diameter of the coating roller 401, including the nonwoven fabric, is exemplified as 20mm.

[0062] The scraping member 501, which serves as a lubricant recovery member, is a metal plate with a thickness of 1 mm and made of SUS (stainless steel). The scraping member 501 is positioned downstream of the nip portion N and upstream of the coating roller 401 in the rotational direction of the belt 301. The scraping member 501 scrapes and recovers the lubricant that is about to leak out from the longitudinal end of the belt 301, and applies the recovered lubricant to the inner surface of the belt 301 by dripping it between the nip portion N on the inner surface of the belt 301 and the coating roller 401.

[0063] The scraping member 501 comprises a tip portion 501a, a scraping portion 501b, and a support portion 501c.

[0064] The tip portion 501a, which serves as a dripping portion, is located at the tip of the scraping portion 501b in the inclined direction. The tip portion 501a is located closer to the center in the longitudinal direction than the longitudinal end of the belt 301. The tip portion 501a drips the lubricant scraped off by the scraping portion 501b onto the inner circumferential surface of the belt 301.

[0065] The scraping section 501b is positioned inclined with respect to the opposite direction to the vertical Z direction and also inclined toward the pressure roller 305. The scraping section 501b contacts the longitudinal end of the belt 301 and scrapes off the lubricant that would otherwise leak out from the longitudinal end of the belt 301.

[0066] The support portion 501c is fixed to the sheet metal (not shown) that supports the heating roller 307 and the pressure roller 305 with screws or the like, thereby fixing the scraping member 501 to the sheet metal.

[0067] In the scraping member 501 described above, the length L3 in the width direction of the tip portion 501a is smaller than the lengths L1 and L2 in the width direction of the scraping portion 501b (L1 and L2 > L3). Also, the length in the width direction of the scraping portion 501b decreases as it approaches the tip portion 501a (L1 > L2).

[0068] Furthermore, if the lubricant leaks out only from one end of the belt 301 in the longitudinal direction due to a bias in the direction of leakage, the scraping member 501 is provided only at that one end of the belt 301 in the longitudinal direction. On the other hand, if the lubricant leaks from both ends of the belt 301 in the longitudinal direction, a pair of scraping members 501 are provided at both ends of the belt 301 in the longitudinal direction.

[0069] In the fixing device F1 having the above configuration, the belt 301 can slide smoothly against the pressure pad 303 by applying a lubricant to its inner circumferential surface. In this way, the lubricant is interposed between the inner circumferential surface of the belt 301 and the contact portion 301a of the pressure pad 303, thereby improving the sliding properties of the belt 301 against the pressure pad 303.

[0070] Furthermore, the fixing device F1 is set so that the longitudinal length of the belt 301 is greater than or equal to the longitudinal length of the coating roller 401, in order to prevent the lubricant discharged from the coating roller 401 from adhering to components other than the belt 301. If the longitudinal length of the belt 301 is less than the longitudinal length of the coating roller 401, the coating roller 401 may discharge lubricant on the outside of the longitudinal direction of the belt 301 when the belt 301 moves longitudinally due to the rotation of the steering roller 308. In this case, there is a risk that the lubricant may adhere to components other than the belt 301.

[0071] Furthermore, the fixing device F1 is configured such that the longitudinal length of the coating roller 401 is greater than the longitudinal length of the release layer exposed on the outer surface of the pressure roller 305.

[0072] Furthermore, the fixing device F1 is configured such that the longitudinal length of the coating roller 401 is greater than or equal to the longitudinal length of the pressure pad 303, and both longitudinal ends of the coating roller 401 are positioned outside the longitudinal ends of the nip portion N. As a result, both longitudinal ends of the coating roller 401 are positioned further outward in the longitudinal direction than both longitudinal ends of the pressure pad 303, so that the lubricant discharged from the coating roller 401 can be sufficiently supplied to the entire longitudinal area of ​​the contact portion 301a of the pressure pad 303.

[0073] Furthermore, the tip 501a of the scraping member 501 is located longitudinally inward from the longitudinal end of the coating roller 401. This allows the scraping member 501 to adequately return the lubricant recovered from the belt 301 to the coating roller 401.

[0074] <Operation of the fixing device> The operation of the fixing device F1 according to Embodiment 1 of the present invention will be described in detail with reference to Figures 2 to 6.

[0075] The fixing device F1 fixes the toner image to the transfer material P by heating the toner image while gripping and transporting the transfer material P, which is carried by the secondary transfer rollers 205 and 206, in the nip section N.

[0076] Furthermore, when the coating roller 401 is heated, it discharges lubricant by concentration diffusion near the interface between the surface of the nonwoven fabric and the inner surface of the belt 301, which has less lubricant, thereby applying lubricant to the inner surface of the belt 301. The lubricant applied to the inner surface of the belt 301 comes into contact with the contact portion 303a of the pressure pad 303 as the belt 301 rotates, and is also applied to the contact portion 303a of the pressure pad 303.

[0077] The lubricant applied to the inner surface of the belt 301 is depleted as the belt 301 rotates repeatedly. In this case, the lubricant near the surface of the nonwoven fabric on the application roller 401 moves to the inner surface of the belt 301 due to concentration diffusion and is reapplied to the inner surface of the belt 301.

[0078] Furthermore, the lubricant near the surface of the nonwoven fabric on the coating roller 401 is reduced as it is discharged from the coating roller 401 onto the inner circumferential surface of the belt 301. In this case, the lubricant inside the nonwoven fabric of the coating roller 401 moves to the surface of the coating roller 401 due to concentration diffusion. Through the repetition of these processes, the coating roller 401 can continuously apply lubricant to the inner circumferential surface of the belt 301.

[0079] The lubricant applied to the inner surface of the belt 301 moves towards the longitudinal end of the belt 301 as the belt 301 moves repeatedly in the longitudinal direction due to the rotational movement of the steering roller 308. Furthermore, the lubricant that has moved to the longitudinal end of the belt 301 may leak out of the belt 301 and leak onto the pressure roller 305 or the outer surface of the belt 301. The scraping member 501 scrapes off the lubricant that is about to leak out of the longitudinal end of the belt 301 with its scraping portion 501b.

[0080] The lubricant scraped off by the scraping portion 501b remains attached to the scraping member 501 due to the surface tension of the lubricant and moves along the slope of the scraping portion 501b toward the longitudinal center (moving in the O1 direction). The lubricant that moves along the slope of the scraping portion 501b toward the longitudinal center then reaches the tip portion 501a.

[0081] The lubricant that reaches the tip 501a gradually accumulates there, and when it exceeds a predetermined weight, it drips from the tip 501a onto the inner surface of the belt 301 due to gravity (moving in the O2 direction). At this time, since the plate width L3 of the tip 501a is narrower than the plate widths L1 and L2 of the scraping portion 501b, the weight per unit area of ​​the lubricant that reaches the tip 501a is greater than the weight per unit area of ​​the lubricant scraped off by the scraping portion 501b. As a result, the lubricant that reaches the tip 501a is more likely to drip due to gravity. The lubricant that drips onto the inner surface of the belt 301 then adheres to the inner surface of the belt 301.

[0082] The lubricant adhering to the inner circumferential surface of the belt 301 reaches the coating roller 401 as the belt 301 rotates (moves in the O3 direction) because the scraping member 501 is positioned downstream of the nip portion N and upstream of the coating roller 401 in the rotational direction of the belt 301. The lubricant that reaches the coating roller 401 is then incorporated into the nonwoven fabric of the coating roller 401 and supplied to the coating roller 401.

[0083] Even when a lubricant is present between the belt 301 and the pressure pad 303, wear progresses because the inner surface of the belt 301 and the contact portion 301a of the pressure pad 303 rub against each other for a long period of time. As a result, the polyimide resin (PI) of the base layer of the belt 301 that is in contact with the pressure pad 303 and the PTFE coating on the contact portion 301a of the pressure pad 303 wear down, generating wear debris. This wear debris mainly adheres to the surface of the coating roller 401. When wear debris adheres to the surface of the coating roller 401, the lubricant contained in the nonwoven fabric cannot be applied to the inner surface of the belt 301 because it is obstructed by the wear debris.

[0084] Furthermore, the inner surface of the belt 301 has higher surface energy than the contact portion 303a of the pressure pad 303 and the surface of the coating roller 401 with wear particles adhering to it, due to the absence of PTFE. As a result, the lubricant adheres more easily to the inner surface of the belt 301 than to the contact portion 303a of the pressure pad 303 and the surface of the coating roller 401 with wear particles adhering to it. Consequently, the lubricant adheres well to the inner surface of the belt 301, while being repelled and less absorbed by the coating roller 401 with wear particles adhering to it.

[0085] In contrast, by supplying the lubricant recovered by the scraping member 501 to the inner circumferential surface of the belt 301, lubricant can be applied to the inner circumferential surface of the belt 301 even if wear particles are adhering to the application roller 401. Furthermore, the lubricant applied to the inner circumferential surface of the belt 301 can also be applied to the contact portion 303a of the pressure pad 303 via the inner circumferential surface of the belt 301 as the belt 301 rotates.

[0086] Next, the results of the comparative experiment will be explained in detail with reference to Figures 5 and 6. In Figure 6, the vertical axis shows the weight of the lubricant applied to the inner surface of the belt 301, and the horizontal axis shows the number of sheets of paper passed through.

[0087] As a comparative experiment, the weight change of lubricant adhering to the inner surface of the belt 301 was compared between the fixing device F1 according to this embodiment and the fixing device G shown in Figure 5, which has a configuration in which the lubricant recovered by the scraping member 2501 is directly returned to the application roller 401.

[0088] For the comparative experiment, 500 mg of silicone oil was applied as a lubricant to the contact portion 303a of the pressure pad 303, and an unused application roller 401 containing 10 g of lubricant was installed. A3 plain paper with a basis weight of 100 g was fed through the belt at a speed of 100 sheets per minute, and the weight change of the lubricant on the inner surface of the belt 301 was measured. The rotation speed of the belt 301 and the pressure roller 305 was set to 450 mm / s.

[0089] In both fixing devices F1 and G, in the initial state, no lubricant is applied to the inner surface of the belt 301, while 500 mg of lubricant is applied to the contact portion 303a of the pressure pad 303. Thus, in the initial state of both fixing devices F1 and G, the weight of lubricant is 500 mg, as shown in Figure 6, because the belt 301 is in contact with the pressure pad 303. Subsequently, the application roller 401 is heated and rotated to discharge the lubricant, applying approximately 2 g of lubricant to the inner surface of the belt 301.

[0090] The weight of the lubricant on the inner surface of the belt 301 gradually decreases until the number of belts it can withstand reaches 400,000, due to factors such as adhesion to the surface of the heating roller 307, adhesion to the surface of the steering roller 308, or penetration into the back side of the pressure pad 303 (stay 302 side).

[0091] Furthermore, the weight of lubricant on the inner surface of the belt 301 in the fixing device G decreases sharply after 400K sheets, when wear particles begin to adhere to the surface of the coating roller 401. In the fixing device G, lubricant is directly dripped onto the coating roller 401 from the scraping member 501, allowing the lubricant to be absorbed into the nonwoven fabric through gaps where wear particles are not adhering to the coating roller 401. On the other hand, the lubricant absorbed into the nonwoven fabric of the fixing device G moves to the interface between the wear particles adhering to the surface of the coating roller 401 and the nonwoven fabric due to concentration diffusion, making it difficult to discharge onto the surface of the coating roller 401.

[0092] In contrast, with the fixing device F1, wear particles adhere to the coating roller 401, preventing the lubricant originally contained in the coating roller 401 from being discharged, resulting in a significant decrease in lubrication after 400K sheets. However, with the fixing device F1, the lubricant recovered by the scraping member 501 can be circulated on the inner surface of the belt 301 by applying it to the inner surface of the belt 301. Therefore, the fixing device F1 can maintain lubricant on the inner surface of the belt 301 better than the fixing device G.

[0093] In this embodiment, a scraping member 501 is provided to supply the recovered lubricant to the inner circumferential surface of the belt 301. This prevents deterioration of the sliding performance between the belt 301 and the pressure pad 303 even if wear particles adhere to the coating roller 401, thereby suppressing paper jams or image defects.

[0094] In this embodiment, the shape of the scraping member 501 can be any shape as long as it can collect the lubricant from the longitudinal end of the belt 301 and supply it to the inner circumferential surface of the belt 301.

[0095] In this embodiment, the lubricant recovered by the scraping member 501 was returned to the coating roller 401 via the belt 301. However, the invention is not limited to this, and the lubricant recovered by the scraping member 501 may also be returned to the coating roller 401 via a member other than the belt 301 that is less likely to absorb lubricant.

[0096] (Embodiment 2) The configuration of the image forming apparatus according to Embodiment 2 of the present invention is the same as that shown in Figure 1, so its description will be omitted.

[0097] <Configuration of the fixing device> The configuration of the fixing device F2 according to Embodiment 2 of the present invention will be described in detail with reference to Figure 7.

[0098] In Figure 7, parts that have the same configuration as those in Figure 2 are denoted by the same reference numerals, and their descriptions are omitted.

[0099] In Figure 7, the X direction is the transport direction of the transfer material P, the Y direction is the width direction of the transfer material P perpendicular to the transport direction, and the Z direction is the pressurizing direction.

[0100] The fixing device F2 includes a belt 301, a stay 302, a pressure pad 303, a pressure roller 305, a halogen heater 306, a heating roller 307, a steering roller 308, a coating roller 401, and a scraping member 1501.

[0101] The scraping member 1501 is a metal plate with a thickness of 1 mm and made of SUS (stainless steel). The scraping member 1501 is positioned upstream of the nip portion N in the rotational direction of the belt 301. Note that the configuration of the scraping member 1501 is the same as that of the scraping member 501, so its description is omitted.

[0102] Furthermore, if the lubricant leaks out only from one end of the belt 301 in the longitudinal direction due to a bias in the direction of leakage, the scraping member 1501 is provided only at that one end of the belt 301 in the longitudinal direction. On the other hand, if the lubricant leaks from both ends of the belt 301 in the longitudinal direction, a pair of scraping members 1501 are provided at both ends of the belt 301 in the longitudinal direction.

[0103] In the fixing device F2 having the above configuration, the lubricant recovered by the scraping member 1501 can be resupplied to the belt 301 and then quickly resupplied to the contact portion 303a of the pressure pad 303 at the nip portion N. The lubricant resupplied to the pressure pad 303 by the scraping member 1501 can also be resupplied to the coating roller 401 after passing through the nip portion N. In this way, even if wear debris adheres to the surface of the coating roller 401, the lubricant can be quickly resupplied to the inner circumferential surface of the belt 301 and the contact portion 303a of the pressure pad 303.

[0104] <Operation of the fixing device> The operation of the fixing device F2 according to Embodiment 2 of the present invention will be described in detail with reference to Figure 7.

[0105] The lubricant adhering to the inner circumferential surface of the belt 301 reaches the nip portion N as the belt 301 rotates, because the scraping member 1501 is positioned upstream of the nip portion N in the direction of rotation of the belt 301. The lubricant that reaches the nip portion N is applied to the contact portion 303a of the pressure pad 303 and also reaches the application roller 401 as the belt 301 rotates. The lubricant that reaches the application roller 401 is then contained in the nonwoven fabric of the application roller 401 and supplied to the application roller 401.

[0106] Note that the operation of the fixing device F2 in this embodiment, other than the operation of the fixing device F1, is the same as that of the fixing device F2, so its explanation will be omitted.

[0107] <Comparative experiment> A comparative experiment of the fixing device F2 according to Embodiment 2 of the present invention will be described in detail with reference to Figures 7 and 8. In Figure 8, the vertical axis shows the weight of the lubricant applied to the inner surface of the belt 301, and the horizontal axis shows the number of sheets of paper passed through.

[0108] As a comparative experiment, the weight change of lubricant adhering to the inner surface of the belt 301 was compared between the fixing device F2 according to this embodiment and the fixing device G shown in Figure 5, which directly returns the lubricant recovered by the scraping member 501 to the application roller 401. The results of the comparative experiment for fixing device G have already been explained in Embodiment 1 above, so that explanation will be omitted. Also, the experimental conditions for the comparative experiment are the same as those for the comparative experiment in Embodiment 1 above, so that explanation will also be omitted.

[0109] In the fixing device F2, in the initial state, no lubricant is applied to the inner surface of the belt 301, while 500 mg of lubricant is applied to the contact portion 303a of the pressure pad 303. Therefore, the weight of lubricant in the initial state of the fixing device F2 is 500 mg, as shown in Figure 8, because the belt 301 is in contact with the pressure pad 303. Subsequently, approximately 1000 mg of lubricant is applied to the contact portion 303a of the pressure pad 303 by heating and rotating the application roller 401, which discharges the lubricant.

[0110] In the fixing device F2, wear particles adhere to the coating roller 401, preventing the lubricant originally contained in the coating roller 401 from being discharged, resulting in a significant decrease in lubrication after 400K sheets. However, in the fixing device F2, the lubricant recovered by the scraping member 1501 can be circulated on the inner surface of the belt 301 by applying it to the inner surface of the belt 301. Therefore, the fixing device F2 can maintain lubricant on the inner surface of the belt 301 better than the fixing device G.

[0111] In this embodiment, a scraping member 1501 is provided to supply the recovered lubricant to the inner circumferential surface of the belt 301. This prevents deterioration of the sliding performance between the belt 301 and the pressure pad 303 even if wear particles adhere to the coating roller 401, thereby suppressing paper jams or image defects.

[0112] In this embodiment, the shape of the scraping member 1501 can be any shape as long as it can collect the lubricant from the longitudinal ends of the inner circumferential surface of the belt 301 and supply it to the longitudinal central part of the inner circumferential surface of the belt 301.

[0113] In this embodiment, the lubricant recovered by the scraping member 1501 was returned to the coating roller 401 via the belt 301. However, the invention is not limited to this, and the lubricant recovered by the scraping member 1501 may also be returned to the coating roller 401 via a member other than the belt 301 that is less likely to absorb lubricant.

[0114] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0115] F1 Fixing device F2 Fixing device N Nip section Pa Image Forming Unit Pb Image Forming Unit PC image forming section Pd Image Forming Unit 1. Image forming apparatus 205 Secondary Transfer Roller 206 Secondary Transfer Roller 301 Belt 303 Compression Pad 303a Contact part 305 Pressure Roller 308 Steering Roller 401 Application roller 501 Scraping member 501a Tip 501b Scraping section 501c support part 1501 Scraping member

Claims

1. A rotatable endless belt, A heating element for heating the aforementioned belt, A pressurizing member positioned opposite the belt, The pressure pad, which applies pressure to the pressure member via the belt to form a nip portion and contacts the inner circumferential surface of the belt, A lubricant supply member that supplies lubricant to the inner circumferential surface of the belt, A lubricant recovery member that recovers the lubricant supplied to the inner circumferential surface of the belt by the lubricant supply member from the end in the longitudinal direction perpendicular to the rotational direction of the belt, It has, A fixing device for fixing a toner image formed on a recording material by heating and pressurizing the recording material in the aforementioned nip section, The lubricant recovery member is The recovered lubricant is supplied to the inner surface of the belt. A fixing device characterized by the following features.

2. The lubricant recovery member is Located downstream of the nip portion and upstream of the lubricant supply member in the aforementioned rotational direction, The fixing device according to feature 1.

3. The lubricant recovery member is Located upstream of the nip portion in the aforementioned rotational direction, The fixing device according to feature 1.

4. The lubricant recovery member is The lubricant supplied to the inner circumferential surface of the belt by the lubricant supply member is recovered from both ends of the belt in the longitudinal direction. A fixing device according to any one of claims 1 to 3.

5. The lubricant supply member is Compared to the inner circumferential surface of the aforementioned belt, it is more likely to absorb lubricant. A fixing device according to any one of claims 1 to 3.

6. The longitudinal ends of the lubricant supply member are Located further outward in the longitudinal direction than both ends of the nip portion in the longitudinal direction, A fixing device according to any one of claims 1 to 3.

7. The aforementioned pressure pad is The belt has a contact portion covered with PTFE (polytetrafluoroethylene) that contacts the inner circumferential surface of the belt, The inner circumferential surface of the aforementioned belt is Formed from polyimide resin, A fixing device according to any one of claims 1 to 3.

8. The lubricant recovery member is The plate-shaped member comprises a scraping portion for scraping lubricant from the longitudinal end of the belt, and a dripping portion for dripping the lubricant scraped off by the scraping portion onto the inner circumferential surface of the belt. The scraping section is, It is inclined with respect to the vertical, The aforementioned dropping part is, It is provided at the tip of the scraping portion in the inclined direction, The length of the dropping portion in the plate width direction is smaller than the length of the scraping portion in the plate width direction. A fixing device according to any one of claims 1 to 3.

9. A fixing device according to any one of claims 1 to 3, Image forming means for forming a toner image, A transfer means for transferring the toner image formed by the image forming means onto a recording material, It has, The fixing device is The toner image transferred to the recording material by the transfer means is fixed to the recording material. An image forming apparatus characterized by the following:

Images