Fixing device and image forming apparatus

Abstract

To provide a fixation device and an image formation apparatus which can suppress the occurrence of lubrication failure due to such a state that abrasion powder generated when an inner surface of a belt brought into pressure-contact with a rotor is worn buries irregularities of the belt inner surface.SOLUTION: A fixation device comprises: an endless belt; holding means which is arranged in the belt and holds the belt so as to be brought into pressure-contact with a rotor in a pressure-contact part; and a surface roughening processing part which is provided so as to be adjacent to the downstream side along the movement direction of the belt in the pressure-contact part of the holding means and is applied with surface roughening processing holding abrasion powder of the belt inner surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fixing device and an image forming apparatus. [Background technology]

[0002] Conventionally, as a technique relating to a fixing device, for example, the one disclosed in Patent Document 1 has already been proposed.

[0003] Patent Document 1 discloses a configuration in which the surface roughness Ra of the inner surface of the belt is set to 0.3 μm to 1.5 μm in order to facilitate retention of a lubricant between the belt and the sliding member (paragraph

[0043] ). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-154074 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to suppress poor lubrication caused by wear powder generated by wear of the inner surface of a belt that is pressed against a rotating body filling in irregularities on the inner surface of the belt. [Means for solving the problem]

[0006] The invention described in claim 1 comprises a rotatable endless belt, a holding means for holding the sheet heating element so as to press the belt against a rotating body at a pressure contact portion; a surface roughening treatment portion provided adjacent to the downstream side of the pressure contact portion of the holding means along the moving direction of the belt, the surface roughening treatment being performed to hold wear powder on the inner surface of the belt; Equipped with picture, The surface roughness of the roughened surface portion is greater than that of the inner surface of the belt. This is a fixing device.

[0008] Claim 2 The invention described in the above-mentioned embodiment is characterized in that the surface roughness Ra of the roughened surface treatment portion is 0.5 to 1.0 μm. Claim 1 The fixing device according to the present invention is

[0009] Claim 3 The invention described in is a fixing device as described in claim 1, in which the roughening treatment section sets the surface roughness by adjusting at least one of the surface roughness of a mold that molds the holding means from synthetic resin, the pouring speed of the synthetic resin, and the molding temperature.

[0010] Claim 4 In the invention described in the above, the surface roughening treatment section adjusts the surface roughness of a mold for molding the holding means from a synthetic resin, thereby setting the surface roughness. Claim 3 The fixing device according to the present invention is

[0011] Claim 5 The invention described in the above relates to a belt having at least a base layer, an adhesive layer, and a surface layer, 2. The fixing device according to claim 1, wherein the base layer contains a highly heat conductive filler having a low coefficient of friction.

[0012] Claim 6 The invention described in is characterized in that the highly thermally conductive filler is made of carbon nanotubes. Claim 5 The fixing device according to the present invention is

[0013] Claim 7 The invention described in the above relates to an image forming means for forming an image on a recording medium, A fixing unit for fixing the image formed on the recording medium; Equipped with As the fixing means Claims 1 to 6 2. An image forming apparatus using the fixing device according to claim 1. Effect of the Invention

[0014] According to the invention described in claim 1, it is possible to suppress poor lubrication caused by wear powder generated by wear of the inner surface of the belt that is pressed against the rotating body filling in the unevenness of the inner surface of the belt, thereby making it possible to suppress the occurrence of poor lubrication.

[0015] Also, claim 1 According to the invention described in the above, the roughened portion can reliably hold the wear powder on the inner surface of the belt, compared to a case in which the surface roughness of the roughened portion is smaller than that of the inner surface of the belt.

[0016] Claim 2 According to the invention described in the above, the roughened surface treatment portion can hold wear powder on the inner surface of the belt more reliably than when the surface roughness Ra is less than 0.5 or exceeds 1.0 μm.

[0017] Claim 3 According to the invention described in the above, the roughened surface portion can be formed more easily than in the case where the roughened surface portion is formed after molding the holding means from a synthetic resin.

[0018] Claim 4 According to the invention described in the above, the roughened surface treatment can be formed much easier than when the pouring speed or molding temperature of the synthetic resin used to mold the holding means is adjusted.

[0019] Claim 5 According to the invention described in the above, the base layer can have improved thermal conductivity compared to a case where the base layer is made of only the material that forms the base layer.

[0020] Claim 6 According to the invention described in the above, the wear resistance of the belt can be improved compared to the case where the highly thermally conductive filler is made of carbon fiber.

[0021] Claim 7 According to the invention described in Claims 1 to 6In comparison with the case where no fixing device described in any one of the above is used, it is possible to suppress poor lubrication caused by wear powder generated by wear of the inner surface of the belt that is pressed against the rotating body filling in the irregularities on the inner surface of the belt, thereby making it possible to extend the life of the fixing device. [Brief description of the drawings]

[0022] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus to which a fixing device according to a first embodiment of the present invention is applied. [Diagram 2] 1 is a cross-sectional view showing a fixing device according to a first embodiment of the present invention; [Diagram 3] FIG. 2 is a cross-sectional view showing a heating belt. [Figure 4] FIG. 2 is a plan view showing the heat generating portion of the ceramic heater. [Diagram 5] 1 is a cross-sectional view showing a configuration of a main part of a fixing device according to a first embodiment of the present invention. [Figure 6] 1 is a cross-sectional view showing a configuration of a main part of a fixing device according to a first embodiment of the present invention. [Figure 7] 2 is an enlarged cross-sectional view showing a nip portion of the fixing device according to the first embodiment of the present invention. [Figure 8] 1 is a graph showing the relationship between bearing characteristic numbers and dynamic friction coefficients. [Figure 9] 1 is a schematic cross-sectional view showing a main part of a fixing device according to a first embodiment of the present invention. [Figure 10] FIG. 4 is an explanatory diagram showing a transition state from fluid lubrication to mixed lubrication. [Figure 11] 4A to 4C are schematic diagrams showing the wear state of the inner surface of the heating belt. [Figure 12] 1 is a schematic cross-sectional view showing a main part of a fixing device according to a first embodiment of the present invention. [Figure 13] 3 is a schematic cross-sectional view illustrating the operation of the fixing device according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] [Embodiment 1] FIG. 1 shows an image forming apparatus to which the fixing device according to the first embodiment is applied.

[0025] <Overall configuration of image forming apparatus> The image forming apparatus 1 according to the first embodiment is configured as, for example, a color printer. The image forming apparatus 1 includes a plurality of image forming devices 10 that form toner images developed with toner constituting a developer 4, an intermediate transfer device 20 that holds the toner images formed by each image forming device 10 and transports them to a secondary transfer position where they are finally secondarily transferred onto a recording paper 5 as an example of a recording medium, a paper feed device 50 that stores and transports the required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20, and a fixing device 40 that fixes the toner image on the recording paper 5 that has been secondarily transferred by the intermediate transfer device 20. The plurality of image forming devices 10 and the intermediate transfer device 20 constitute an image forming section 2 that forms an image on the recording paper 5. In addition, 1a in the figure indicates the device body of the image forming apparatus 1, and this device body 1a is formed by a support structure member, an exterior cover, etc. In addition, the two-dot chain line in the figure indicates the main transport path along which the recording paper 5 is transported within the device body 1a.

[0026] The imaging device 10 is composed of four imaging devices 10Y, 10M, 10C, and 10K that are dedicated to forming toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four imaging devices 10 (Y, M, C, and K) are arranged in a line at an angle in the internal space of the device main body 1a.

[0027] The four image forming devices 10 are composed of image forming devices 10 (Y, M, C) for the colors yellow (Y), magenta (M), and cyan (C), and a black (K) image forming device 10K. The black image forming device 10K is disposed on the most downstream side along the moving direction B of the intermediate transfer belt 21 of the intermediate transfer device 20. The image forming apparatus 1 has, as image forming modes, a full-color mode in which the color image forming devices 10 (Y, M, C) and the black (K) image forming device 10K are operated to form a full-color image, and a black-and-white mode in which only the black (K) image forming device 10K is operated to form a black-and-white (monochrome) image.

[0028] As shown in FIG. 1, each imaging device 10 (Y, M, C, K) has a rotating photosensitive drum 11 as an example of an image carrier, and around this photosensitive drum 11, various devices as examples of toner image forming means, such as those described below, are mainly arranged. The main devices are a charging device 12 that charges the image-forming peripheral surface (image bearing surface) of the photosensitive drum 11 to a required potential, an exposure device 13 that irradiates the charged peripheral surface of the photosensitive drum 11 with light based on image information (signal) to form an electrostatic latent image (for each color) with a potential difference, developing devices 14 (Y, M, C, K) that develop the electrostatic latent image with toner of developer 4 of the corresponding color (Y, M, C, K) to form a toner image, primary transfer devices 15 (Y, M, C, K) that transfer each toner image to an intermediate transfer device 20, and drum cleaning devices 16 (Y, M, C, K) that remove and clean any toner and other deposits that remain on and adhere to the image bearing surface of the photosensitive drum 11 after the primary transfer.

[0029] The photoconductor drum 11 has an image bearing surface formed on the peripheral surface of a grounded cylindrical or columnar base material, the peripheral surface having a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoconductor drum 11 is supported so as to rotate in the direction indicated by the arrow A by power transmitted from a drive device (not shown).

[0030] The charging device 12 is composed of a contact-type charging roll that is arranged in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 performs reversal development, the charging voltage is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. Note that the charging device 12 may also be a non-contact charging device such as a scorotron that is arranged in a non-contact state on the surface of the photosensitive drum 11.

[0031] The exposure device 13 is an LED print head that forms an electrostatic latent image by irradiating the photoconductor drum 11 with light corresponding to image information using LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photoconductor drum 11. Note that the exposure device 13 may be one that deflects and scans laser light configured according to the image information along the axial direction of the photoconductor drum 11.

[0032] Each of the developing devices 14 (Y, M, C, K) is configured by arranging a developing roll 141 that holds the developer 4 and transports it to a development area facing the photosensitive drum 11 inside a housing 140 in which an opening and a developer 4 storage chamber are formed, stirring and transporting members 142 and 143 such as two screw augers that stir the developer 4 and transport it to pass through the developing roll 141, and a layer thickness regulating member 144 that regulates the amount (layer thickness) of the developer held on the developing roll 141. A developing voltage is supplied from a power supply device (not shown) between the developing roll 141 and the photosensitive drum 11 in the developing device 14. In addition, the developing roll 141 and the stirring and transporting members 142 and 143 are rotated in the required direction by the power transmitted from a drive device (not shown). Furthermore, a two-component developer containing a non-magnetic toner and a magnetic carrier is used as the four color developers 4 (Y, M, C, K).

[0033] The primary transfer device 15 (Y, M, C, K) is a contact type transfer device equipped with a primary transfer roll that rotates in contact with the periphery of the photosensitive drum 11 via the intermediate transfer belt 21 and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage showing a polarity opposite to the charge polarity of the toner is supplied from a power supply device (not shown).

[0034] The drum cleaning device 16 is composed of a container-shaped main body 160 with a portion open, a cleaning plate 161 that is arranged so as to come into contact with the peripheral surface of the photosensitive drum 11 after primary transfer with a required pressure to remove and clean adhering matter such as residual toner, and a sending member 162 such as a screw auger that collects the adhering matter such as toner removed by the cleaning plate 161 and conveys it to a collection system (not shown). A plate-shaped member (for example, a blade) made of a material such as rubber is used as the cleaning plate 161.

[0035] 1, the intermediate transfer device 20 is disposed so as to be located above each of the image forming devices 10 (Y, M, C, K). The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21 that rotates in the direction indicated by the arrow B while passing through a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), a plurality of belt support rolls 22-27 that support the intermediate transfer belt 21 in a desired state from its inner surface and rotatably, a secondary transfer device 30 as an example of a secondary transfer means that is disposed on the outer peripheral surface (image bearing surface) side of the intermediate transfer belt 21 supported by the belt support roll 25 and secondarily transfers the toner image on the intermediate transfer belt 21 to the recording paper 5, and a belt cleaning device 28 that removes and cleans toner, paper powder, and other deposits that remain and adhere to the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0036] An endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used as the intermediate transfer belt 21. The belt support roll 22 is configured as a drive roll that is rotated by a drive unit (not shown) and also serves as an opposing roll of the belt cleaning device 28, the belt support roll 23 is configured as a surface finishing roll that forms the image forming surface of the intermediate transfer belt 21, the belt support roll 24 is configured as a tension applying roll that applies tension to the intermediate transfer belt 21, the belt support roll 25 is configured as an opposing roll that faces the secondary transfer device 30, and the belt support rolls 26 and 27 are configured as driven rolls that support the running position of the intermediate transfer belt 21.

[0037] 1, the secondary transfer device 30 is a contact type transfer device including a secondary transfer roll 31 that rotates in contact with the circumferential surface of the intermediate transfer belt 21 and is supplied with a secondary transfer voltage at a secondary transfer position, which is the outer circumferential surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. A DC voltage having the same polarity as or opposite to the charge polarity of the toner is supplied as a secondary transfer voltage from a power supply device (not shown) to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20.

[0038] The fixing device 40 is configured by arranging, inside a housing 41 in which an inlet and an outlet for the recording paper 5 are formed, a heating belt 42 which rotates in the direction indicated by the arrow and is heated by a heating means so that the surface temperature is maintained at a predetermined temperature, and a pressure roll 43 which rotates in contact with the heating belt 42 at a predetermined pressure in a state substantially along the axial direction of the heating belt 42. In the fixing device 40, the contact portion where the heating belt 42 and the pressure roll 43 come into contact with each other is a fixing processing portion which performs the required fixing process (heating and pressure application). The fixing device 40 will be described in detail later.

[0039] The paper feeder 50 is disposed so as to be located below the imaging devices 10 (Y, M, C, K). This paper feeder 50 is mainly composed of one (or more) paper containers 51 that contain stacks of recording paper 5 of desired sizes, types, etc., and feeders 52, 53 that feed the recording paper 5 one sheet at a time from the paper container 51. The paper container 51 is attached so as to be able to be pulled out, for example, from the front side (the side that the user faces during operation) of the device main body 1a.

[0040] Examples of the recording paper 5 include thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or OHP sheets, etc. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is as smooth as possible, and for example, coated paper in which the surface of plain paper is coated with a resin or the like, or so-called thick paper with a relatively large basis weight such as art paper for printing can be suitably used.

[0041] Between the paper feed device 50 and the secondary transfer device 30, there is provided a paper feed conveying path 56 consisting of one or more paper conveying roll pairs 54 and conveying guides 55 for conveying the recording paper 5 sent out from the paper feed device 50 to the secondary transfer position. The paper conveying roll pair 54 arranged at a position immediately before the secondary transfer position in the paper feed conveying path 56 is configured as, for example, a roll (registration roll) for adjusting the conveying timing of the recording paper 5. In addition, between the secondary transfer device 30 and the fixing device 40, there is provided a paper conveying path 57 for conveying the recording paper 5 sent out from the secondary transfer device 30 after the secondary transfer to the fixing device 40. Furthermore, in a portion near the paper discharge port formed in the device main body 1a of the image forming device 1, there is provided an output conveying path 59 including a paper output roll pair 59a for discharging the recording paper 5 sent out from the fixing device 40 by the exit roll 36 after the fixing to a paper output section 58 at the top of the device main body 1a.

[0042] 1, reference numeral 200 denotes a control device that comprehensively controls the operation of the image forming apparatus 1. The control device 200 includes a central processing unit (CPU), read only memory (ROM), random access memory (RAM), or a bus connecting the CPU and ROM, etc., not shown, a communication interface, etc. Furthermore, reference numeral 201 denotes a communication unit that allows the image forming apparatus 1 to communicate with external devices, and reference numeral 202 denotes an image processing unit that processes image information input via the communication unit 201.

[0043] <Operation of the image forming device> Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

[0044] Here, we will first explain the operation in full-color mode, in which the four image creating devices 10 (Y, M, C, K) are used to form a full-color image composed of a combination of toner images of four colors (Y, M, C, K).

[0045] When the image forming apparatus 1 receives image information and command information requesting a full-color image forming operation (printing) from a personal computer or image reading device (not shown) via the communication unit 201, the control device 200 starts the four image creating devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc.

[0046] 1, in each imaging device 10 (Y, M, C, K), first, each photoconductor drum 11 rotates in the direction indicated by the arrow A, and each charging device 12 charges the surface of each photoconductor drum 11 to a required polarity (negative polarity in the first embodiment) and potential. Next, the exposure device 13 irradiates the surface of the charged photoconductor drum 11 with light emitted based on an image signal obtained by converting image information input to the image forming device 1 into each color component (Y, M, C, K) by the image processing unit 202, and forms an electrostatic latent image of each color component composed of a required potential difference on the surface.

[0047] Next, each image forming device 10 (Y, M, C, K) develops the electrostatic latent image of each color component formed on the photoconductor drum 11 by supplying toner of the corresponding color (Y, M, C, K) charged to the required polarity (negative polarity) from the developing roll 141 and electrostatically attaching it to the electrostatic latent image of each color component. Through this development, the electrostatic latent image of each color component formed on each photoconductor drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed with the toner of the corresponding color.

[0048] Next, when the toner images of each color formed on the photosensitive drum 11 of each image creating device 10 (Y, M, C, K) are transported to the primary transfer position, the primary transfer device 15 (Y, M, C, K) performs primary transfer of the toner images of each color in such a manner that they are superimposed in order onto the intermediate transfer belt 21 rotating in the direction indicated by arrow B of the intermediate transfer device 20.

[0049] In addition, in each of the imaging devices 10 (Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. This makes each of the imaging devices 10 (Y, M, C, K) ready for the next image formation operation.

[0050] Next, the intermediate transfer device 20 conveys the primarily transferred toner image to the secondary transfer position by the rotation of the intermediate transfer belt 21. Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 56 in accordance with the image creation operation. In the paper feed path 56, a pair of paper feed rolls 54 as registration rolls feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0051] At the secondary transfer position, the secondary transfer device 30 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed in the intermediate transfer device 20, the belt cleaning device 28 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other deposits remaining thereon after the secondary transfer.

[0052] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and then transported to the fixing device 40 via a paper transport path 57. In the fixing device 40, the recording paper 5 after the secondary transfer is introduced into and passes through a contact portion between the rotating heating belt 42 and pressure roll 43, thereby performing the necessary fixing process (heating and pressurization) to fix the unfixed toner image onto the recording paper 5. Finally, the recording paper 5 after fixing is discharged by a paper discharge roll pair 59a to, for example, a paper discharge section 58 installed at the top of the device main body 1a.

[0053] By the above operation, the recording paper 5 is outputted on which a full-color image formed by combining four color toner images is formed.

[0054] <Configuration of the fixing device> FIG. 2 is a cross-sectional view showing the fixing device according to the first embodiment.

[0055] As shown in FIG. 2, the fixing device 40 is roughly divided into a heating unit 44 having a heating belt 42 as an example of a rotating endless belt, and a pressure roll 43 as an example of a rotating body pressed against the heating unit 44. Between the heating belt 42 and the pressure roll 43, a fixing nip portion N as an example of a pressure contact portion is formed, which is an area through which a recording paper 5 as an example of a recording medium holding an unfixed toner image T as an example of an unfixed image passes. The recording paper 5 is transported with the center along a direction intersecting the transport direction as a reference (so-called center register). As shown in FIG. 1, the fixing device 40 is arranged so that the heating belt 42 and the pressure roll 43 face each other in a substantially horizontal direction in a paper transport path 57 that transports the recording paper 5 from below to above along a vertical direction, in order to perform a fixing process on the recording paper 5 transported along the extension direction, but in FIG. 2, the heating belt 42 and the pressure roll 43 are illustrated along the vertical direction for convenience.

[0056] As shown in FIG. 2, the heating unit 44 includes a heating belt 42, a ceramic heater 45 arranged inside the heating belt 42 and serving as an example of a planar heating means (planar heating element) for heating the heating belt 42, a holding member 46 arranged inside the heating belt 42 and serving as an example of a holding means for holding the ceramic heater 45 so as to be pressed against the surface of the pressure roll 43 via the heating belt 42, and a support member 47 arranged inside the heating belt 42 and serving as an example of a supporting means for supporting the holding member 46 so as to be pressed against the pressure roll 43.

[0057] The ceramic heater 45, which is an example of a planar heat generating means, does not need to have a planar heat generating portion, and even if the heat generating portion is formed linearly, it is sufficient as long as the lower end surface (heating surface) of the ceramic heater 45 that heats the heating belt 42 is planar. In addition, the lower end surface (heating surface) of the ceramic heater 45 does not need to be flat, and may be curved.

[0058] The heating belt 42 is made of a flexible material and is configured as an endless belt with a thin-walled cylindrical free shape before installation. As shown in FIG. 3, the heating belt 42 includes a base layer 421 disposed on the ceramic heater 45 side, an elastic layer 423 coated on the surface of the base layer 421 via an adhesive layer 422, and a surface layer 424 coated on the surface of the elastic layer 423 directly or via an adhesive layer (not shown). The heating belt 42 does not necessarily include all of the base layer 421, the adhesive layer 422, the elastic layer 423, and the release layer 424, and may be configured from the base layer 421 and the surface layer 424. The base layer 421 is formed mainly from a heat-resistant synthetic resin such as polyimide, polyamide, or polyimideamide. The elastic layer 422 is made of an elastic material such as heat-resistant silicone rubber or fluororubber. The surface layer 423 is formed of perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), etc. The heating belt 42 can have a thickness set to, for example, about 50 to 200 μm.

[0059] The base layer 421 is mainly composed of a heat-resistant synthetic resin such as polyimide, polyamide, or polyimideamide, and is mixed with a filler such as carbon nanotubes, carbon fiber, or glass fiber as necessary to improve the thermal conductivity and other properties of the heating belt 42. As the filler, carbon nanotubes are desirable from the viewpoints of high thermal conductivity, low dynamic friction coefficient, and abrasion resistance.

[0060] The back surface (inner surface) of the heating belt 42 is composed of a base material layer 421. As described above, the base material layer 421 of the heating belt 42 is made of a heat-resistant synthetic resin such as polyimide, polyamide, polyimideamide, etc., mixed with a filler such as carbon nanotubes, carbon fiber, or glass fiber. The back surface of the heating belt 42 has a required surface roughness Ra. The surface roughness Ra of the back surface of the heating belt 42 is, for example, about 0.3 to 1.5 μm. The surface roughness Ra complies with JIS B 0601.

[0061] As shown in Figures 4 and 5, the ceramic heater 45 comprises a ceramic substrate 451, first to third heat generating portions 4521-4523 formed in a linear manner along the longitudinal direction on the surface of the substrate 451, first to third electrodes 4531-4533 for individually supplying electricity to the first to third heat generating portions 4521-4523, a common electrode 454 that commonly supplies electricity to the other ends of the first to third heat generating portions 4521-4523, and a covering layer 455 made of glass or the like that covers at least the surfaces of the first to third heat generating portions 4521-4523.

[0062] 2, the holding member 46 is made of a heat-resistant synthetic resin integrally molded into a required shape by, for example, injection molding, etc. Examples of heat-resistant synthetic resins include liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyether sulfone (PES), polyamide imide (PAI), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and composite materials thereof.

[0063] The holding member 46 has a support frame portion 461 (see FIG. 5) made of a long and narrow rectangular frame corresponding to the planar shape of the ceramic heater 45, which supports the ceramic heater 45 so as to press the ceramic heater 45 against the pressure roll 43 via the heating belt 42 in the fixing nip portion N. The holding member 46 is disposed to have a length longer than the entire length of the heating belt 42 in the longitudinal direction.

[0064] 2, the holding member 46 is provided with a first guide portion 462 having a curved cross-sectional shape that guides the heating belt 42 to the fixing nip portion N on the upstream side along the rotation direction of the heating belt 42 of the fixing nip portion N. The lower end surface 463 of the support member 46 is formed in a flat shape. The lower end surface 463 of the support member 46 is formed to form approximately the same plane as the surface of the ceramic heater 45. In addition, the holding member 46 is provided with a second guide portion 464 having a curved cross-sectional shape that contacts the inner surface of the heating belt 42 that has passed through the fixing nip portion N and guides the heating belt 42 to return to an approximately free shape at a position adjacent to the downstream side along the rotation direction of the heating belt 42 of the fixing nip portion N.

[0065] In addition, the holding member 46 has contact portions 465, 466 on the upstream and downstream sides along the rotation direction of the heating belt 42, which hold the tips of the vertical plate portions 471, 472 of the support member 47 in abutting contact with the surface opposite the fixing nip portion N.

[0066] 2, the support member 47 is made of a metal plate material such as stainless steel, aluminum, or steel. The support member 47 is formed to have a substantially U-shaped cross section on the upstream and downstream sides along the rotation direction of the heating belt 42 of the fixing nip portion N, and is made of vertical plate portions 471 and 472 disposed substantially perpendicular to the surface of the ceramic heater 45, and a horizontal plate portion 473 disposed along the horizontal direction so as to connect the base ends of the vertical plate portions 471 and 472.

[0067] 5, the temperature of the fixing nip portion N of the heating belt 42 is detected by a temperature sensor 49 arranged so as to contact the surface of the ceramic heater 45 opposite to the fixing nip portion N. As described above, the ceramic heater 45 has first to third heat generating parts 4521 to 4523 having different heat generating regions along the longitudinal direction. Therefore, a plurality of temperature sensors 49 (for example, three) are arranged along the longitudinal direction of the ceramic heater 45 corresponding to the first to third heat generating parts 4521 to 4523. The heating belt 42 is heated so that the fixing nip portion N reaches a required fixing temperature (for example, about 200° C.) according to the size of the recording paper 5 by controlling the energization of the first to third heat generating parts 4521 to 4523 of the ceramic heater 45 by a temperature control circuit (not shown) based on the detection result of the temperature sensor 49.

[0068] 2, the pressure roll 43 has a columnar or cylindrical core metal 431 made of metal such as stainless steel, aluminum, or iron (thin-walled high-tensile steel pipe), an elastic layer 432 made of a heat-resistant elastic material such as silicone rubber or fluororubber coated relatively thickly on the outer periphery of the core metal 431, and a release layer 433 made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like coated thinly on the surface of the elastic layer 432. Note that a heating means (heat source) made of a halogen lamp or the like may be disposed inside the pressure roll 43 as necessary.

[0069] The pressure roll 43 has both ends of a core metal 431 along its longitudinal direction (axial direction) rotatably supported by a frame of an apparatus housing (not shown) of the fixing device 40 via bearing members. The pressure roll 43 is pressed against the heating unit 44 with a required pressure. The pressure roll 43 is driven to rotate at a required speed in the direction of arrow C by a driving device via a driving gear (not shown) attached to one end along the axial direction of the core metal 431, which also serves as a rotation shaft. The heating belt 41 is pressed against the pressure roll 43, which is driven to rotate.

[0070] 6, in the fixing device 40 configured as described above, the ceramic heater 45 is pressed against the pressure roll 43 via the heating belt 42, and the heating belt 42 rotates in the counterclockwise direction in the figure as the pressure roll 43 rotates. A lubricant 48 such as silicone oil or grease is applied to the inner peripheral surface of the heating belt 42 in order to reduce sliding resistance with the ceramic heater 45. The lubricant 48 is supplied in a state in which it is applied to the inner peripheral surface of the heating belt 42 in advance. The lubricant 48 may also be configured to be supplied by a lubricant supplying member (not shown) made of felt or the like that is arranged to hold the lubricant 48 and contact the inner peripheral surface of the heating belt 42.

[0071] Here, when looking microscopically at the fixing nip portion N where the heating belt 42 and the ceramic heater 45 are in pressure contact, it can be said to have a bearing structure in which the heating belt 42 moves while being pressed against the surface of the fixedly arranged ceramic heater 45 with a required pressing force via a film of lubricant 48, as shown diagrammatically in FIG. 7.

[0072] A technical field known as tribology is known as a field that studies interactions such as those occurring when two objects, such as the ceramic heater 45 and the heating belt 42, slide against each other relative to each other through a film of lubricant 48.

[0073] In tribology, a curve called the Stribeck curve is used to explain the lubrication state between two surfaces in relative motion. The Stribeck curve is a curve that was derived by measuring the coefficient of friction as a function of load (stress), sliding speed, and temperature (appears as a change in the viscosity of the lubricant) for friction in sliding and rolling bearings, and deriving the relationship shown in Figure 8. The horizontal axis is the value of the bearing characteristic number calculated as η·N / Pm when the pressure load acting on the two objects is Pm, the relative speed of the two objects is N, and the viscosity of the lubricant is η, and the vertical axis shows the dynamic friction coefficient.

[0074] As shown in Figure 8, in the region of fluid lubrication where a layer of lubricant 48 exists between two objects, if sufficient lubricant 48 is initially supplied and the film thickness is large, the dynamic friction coefficient tends to increase due to an increase in shear force caused by the viscosity of the lubricant 48 (numerals on the horizontal axis). In the region of mixed lubrication, which is located between boundary lubrication where two objects are in direct contact and fluid lubrication, if the bearing characteristic number (η·N / Pm) decreases due to a decrease in the film thickness of the lubricant 48, the friction coefficient increases rapidly and transitions to boundary lubrication, where the value is approximately constant. The dynamic friction coefficient is lowest in the boundary region between fluid lubrication and mixed lubrication.

[0075] The conditional equation for fluid lubrication derived from the Reynolds equation is as follows: L√(ηUKw / P) ≥ 3√(R1 2 +R2 2 ) Here, the first term indicates the film thickness of the lubricant, and the second term indicates the roughness of the sliding portion. The roughness of the sliding portion is determined by the surface roughness R1 of the inner surface of the heating belt 42 and the surface roughness R2 of the ceramic heater 45.

[0076] In this embodiment, R3=√(R1 2 +R2 2 ), R3 is set to 0.7 μm≧R3<≧0.1 μm. If R3 is less than 0.1 μm, the drive torque at the time of starting may become excessively large, which may cause rotation failure of the heating belt 42. If R3 exceeds 0.7 μm, the stick-slip phenomenon may occur, which may cause abnormal noise.

[0077] As shown in FIG. 7, the fixing device 40 can be regarded as a fluid lubricated sliding bearing in which the heating belt 42 is pressed against the surface of the ceramic heater 45 via a film of the lubricant 48. Meanwhile, the inner surface of the heating belt 42 is not flat, but has a required surface roughness Ra, as shown in FIG. 9. Therefore, when the fixing device 40 is continuously used, among the unevenness of the inner surface of the heating belt 42, the convex portion 42a comes into contact with the surface of the ceramic heater 45 and is partially worn. Then, in the fixing device 40, as shown in FIG. 10(b), the average film thickness of the lubricant 48 increases, the shear force caused by the viscosity of the lubricant increases, the coefficient of kinetic friction increases, and the slope of the Stribeck curve becomes larger in the positive direction.

[0078] 11, when the fixing device 40 is used continuously, wear powder 42b generated by the wear of the convex parts on the inner surface of the heating belt 42 accumulates in the concave parts on the inner surface of the heating belt 42. When the wear powder 42b accumulates in the concave parts on the inner surface of the heating belt 42, the lubricant 48 applied to the inner surface of the heating belt 42 is attracted to and held in the concave parts of the heating belt 42 due to the capillary phenomenon of the wear powder 42b consisting of fine particles. The lubricant 48 attracted to and held in the concave parts of the heating belt 42 does not contribute to the lubrication between the ceramic heater 45 and the heating belt 42.

[0079] As a result, when the fixing device 40 is continuously used, the thickness of the lubricant 48 decreases as the lubricant 48 decreases, and the slope of the Stribeck curve becomes negative (shifts to the right in FIG. 8).

[0080] 10(c) and (d), as the fixing device 40 continues to be used, the film thickness of the lubricant 48 further decreases, the inner surface of the heating belt 42 partially comes into contact with the inner surface of the ceramic heater 45, the lubrication changes from fluid lubrication to mixed lubrication, the coefficient of dynamic friction increases rapidly, and the contact portion of the heating belt 42 undergoes minute deformation while repeatedly slipping, causing a stick-slip phenomenon, which causes abnormal noise. When the stick-slip phenomenon occurs and abnormal noise occurs, the fixing device 40 must be replaced.

[0081] Therefore, in conventional fixing devices, it has already been proposed to set the surface roughness Ra of the inner surface of the belt to 0.3 μm to 1.5 μm in order to make it easier to retain a lubricant between the heating belt and the sliding member (see, for example, paragraph

[0043] of Patent Document 1).

[0082] However, simply setting the surface roughness Ra of the inner belt surface to 0.3 μm to 1.5 μm in this manner will gradually wear out the inner surface of the heating belt 42, which is pressed against the ceramic heater 45 in the fixing nip N, during continuous use of the fixing device 40, and as described above, will sooner or later cause the stick-slip phenomenon and will not be able to effectively prevent the generation of abnormal noise, causing the fixing device 40 to reach the end of its life, making it necessary to replace the entire fixing device 40 with a new one.

[0083] Therefore, in order to prevent poor lubrication caused by wear powder 42b generated by wear of the inner surface of the heating belt 42 pressed against the pressure roll 43 filling recesses in the inner surface of the heating belt 42, the fixing device 40 of this embodiment 1 is configured to have a roughening treatment section that is adjacent to the downstream side in the movement direction of the heating belt 42 from the pressure contact section of the holding means and is subjected to a roughening treatment to hold the wear powder on the inner surface of the heating belt 42.

[0084] To explain further, as shown in Figure 6, the fixing device 40 of this embodiment 1 is provided with a second guide portion 464, whose cross-sectional shape that contacts the inner surface of the heating belt 42 is formed into a curved shape, located adjacent to the downstream side of the fixing nip portion N of the holding member 46 in the rotational direction of the heating belt 42.

[0085] The second guide portion 464 of the holding member constitutes a roughening treatment portion in which the surface roughness Ra of the surface 464a in contact with the inner surface of the heating belt 42 is set to be larger than the surface roughness Ra of the heating belt 42. The surface 464a of the second guide portion 464 is set to, for example, about 0.5 to 2.0 μm, preferably 0.5 to 1.0 μm, and more preferably 0.5 to 0.8 μm. The second guide portion 464 of the holding member 46 is provided adjacent to the downstream side along the moving direction of the heating belt 42 from the outlet of the fixing nip portion N, and unlike the fixing nip portion N, no pressure contact force acts on the second guide portion 464. Therefore, even if the surface roughness Ra of the surface 464a of the second guide portion 464 is set to be larger than that of the heating belt 42, it does not promote wear of the inner surface of the heating belt 42, or even if wear occurs, it is extremely small compared to the wear in the fixing nip portion N.

[0086] The roughened surface treatment portion 464a of the holding member 46 is formed at the same time as the holding member 46 is molded by injection molding or the like by performing a roughening process (roughening process) so that the surface roughness Ra of a portion of a mold for molding the holding member 46 that corresponds to the roughened surface treatment portion 464a has a required surface roughness Ra value. The roughened surface treatment portion 464a of the holding member 46 is provided three-dimensionally not only in the moving direction of the heating belt 42 but also in all directions such as directions intersecting the moving direction.

[0087] <Operation of the fixing device> In the fixing device according to embodiment 1, it is possible to prevent poor lubrication caused by wear powder generated by wear on the inner surface of the belt that is pressed against the rotating body filling in the irregularities on the inner surface of the belt, as follows.

[0088] 2, in the fixing device 40 according to the first embodiment, during the fixing operation, the ceramic heater 45 is energized to heat the ceramic heater 45, and the pressure roll 43 is rotated by a driving device (not shown) in the direction of the arrow C. At that time, the heating belt 42 is pressed against the pressure roll 43 and rotates counterclockwise in the figure.

[0089] In the image forming apparatus 1, as shown in FIG. 1, when the ceramic heater 45 of the fixing device 40 reaches the required fixing temperature, the recording paper 5 is fed from the paper feeding device 50, and the toner image on the intermediate transfer belt 21 is secondarily transferred to the recording paper 5 at the secondary transfer position of the intermediate transfer device 20.

[0090] 2, the recording paper 5 onto which the unfixed toner image T has been transferred is transported to a fixing nip portion N where a heating belt 42 and a pressure roll 43 are in pressure contact with each other. The recording paper 5 introduced into the fixing nip portion N is heated and pressurized in the fixing nip portion, where the toner image is fixed onto the recording paper to become a permanent image.

[0091] 6, in the fixing device 40, the heating belt 42 held by a holding member 46 is pressed against the pressure roll 43, and the heating belt 42 is rotated counterclockwise in accordance with the rotation of the pressure roll 43. The heating belt 42 moves while being supported by the surface of the ceramic heater 45 in a state similar to that of a sliding bearing via the lubricant 48 applied to the inner surface of the heating belt 42.

[0092] When the fixing nip portion N, which is the pressure contact portion between the ceramic heater 45 and the heating belt 42, is viewed microscopically, it can be said to be fluid lubrication with a layer of lubricant 48 interposed between the ceramic heater 45 and the heating belt 42, as shown diagrammatically in FIG. 7.

[0093] 11, during continuous use of the fixing device 40, the convex portion on the inner surface of the heating belt 42 partially comes into contact with the surface of the ceramic heater 45, and the inner surface of the heating belt 42 is worn down, generating wear powder 42b. The wear powder 42b generated by the wear on the inner surface of the heating belt 42 moves in the moving direction of the heating belt 42 as the heating belt 42 moves.

[0094] In the fixing device 40 according to the first embodiment, as shown in Fig. 6, the roughening process portion 464a of the holding member 46 is provided adjacent to the downstream side of the fixing nip portion N along the moving direction of the heating belt 42. The surface roughness Ra of the roughening process portion 464a of the holding member 46 is set to be larger than the surface roughness Ra of the inner surface of the heating belt 42. Therefore, the wear powder 42b generated by wearing the inner surface of the heating belt 42 inside the fixing nip portion N moves downstream with the movement of the heating belt 42 as shown in Fig. 13, and comes into contact with the roughening process portion 464a of the holding member 46, and the wear powder 42b is scraped off from the inner surface of the heating belt 42 due to the surface roughness Ra of the roughening process portion 464a.

[0095] The abrasion powder 42b on the inner surface of the heating belt 42 scraped off by the surface roughening treatment portion 464a of the holding member 46 remains and is held by the surface roughening treatment portion 464a of the holding member 46.

[0096] The wear powder 42b on the inner surface of the heating belt 42 held by the roughening treatment portion 464a of the holding member 46 is located downstream of the fixing nip portion N along the movement direction of the heating belt 42, i.e., downstream of the exit of the fixing nip portion N, and is therefore not subjected to the pressure force of the pressure roll 43.

[0097] Therefore, the wear powder 42b on the inner surface of the heating belt 42 held in the roughening treatment portion 464a of the holding member 46 is not filled into the roughening treatment portion 464a by the pressing force acting on the heating belt 42, but is held in a state attached to the downstream side of the roughening treatment portion 464a along the movement direction of the heating belt 42.

[0098] 11, the wear powder 42b held by the roughened surface treatment portion 464a of the holding member 46 is prevented from accumulating and adhering to the recesses on the inner surface of the heating belt 42. Since the roughened surface treatment portion 464a of the holding member 46 has a larger surface roughness Ra than the inner surface of the heating belt 42, there are many roughened surface treatment portions 464a in which the individual recesses themselves are extremely small.

[0099] As a result, even if wear powder 42b is retained in the roughened surface treatment portion 464a of the retaining member 46, the individual recesses of the roughened surface treatment portion 46 are extremely small, and the effect of the wear powder 42b captured in the individual recesses of the roughened surface treatment portion 46 absorbing the lubricant 48 is extremely small.

[0100] Therefore, in the fixing device 40 of this embodiment 1, even if the inner surface of the heating belt 42 wears and generates wear powder 42b during continuous use, the wear powder 42b accumulates in recesses on the inner surface of the heating belt 42 and absorbs the lubricant 48, thereby preventing the fluid lubrication of the heating belt 42 from being hindered and causing poor lubrication.

[0101] Therefore, even with continuous use, the fixing device 40 according to this embodiment 1 can maintain fluid lubrication as shown in Figures 10(a) and (b) for a long period of time, suppressing the generation of abnormal noises associated with the stick-slip phenomenon caused by insufficient lubrication, and enabling the fixing device 40 to have a long life.

[0102] In the above embodiment, the case where the present invention is applied to a heating belt as an endless belt has been described, but the present invention is not limited to this, and it is of course possible to apply the present invention to a pressure belt as well. Similarly, the rotating body is not limited to a pressure roll, and may be a pressure belt.

[0103] In the above embodiment, the application to a heating belt has been described, but the present invention is not limited to this, and it goes without saying that the heating member may be a heating roll.

[0104] Furthermore, although the present invention has been described using an electrophotographic image forming apparatus, the present invention is not limited to electrophotographic image forming apparatuses and can also be applied, for example, to an inkjet image forming apparatus that contacts a transported sheet of paper holding an image of an undried layer of ink (unfixed ink image) and fixes the unfixed ink image onto the sheet of paper. [Explanation of symbols]

[0105] 1...Image forming device 1a…Device body 40...Fixing device 42…Heating belt 43...Pressure roll 45…Ceramic heater 452…heat generating part 46…Retaining member 464a…Roughening treatment section

Claims

1. A rotatable endless belt; a holding means for holding the sheet heating element so as to press the belt against a rotating body at a pressure contact portion; a surface roughening treatment portion provided adjacent to the downstream side of the pressure contact portion of the holding means along the moving direction of the belt, the surface roughening treatment being performed to hold wear powder on the inner surface of the belt; Equipped with The surface roughening treatment portion has a surface roughness greater than that of the inner surface of the belt.

2. 2. The fixing device according to claim 1, wherein the surface roughness of the roughened surface treatment portion is 0.5 to 1.0 μm.

3. 2. The fixing device according to claim 1, wherein the surface roughening treatment section sets the surface roughness by adjusting at least one of the surface roughness of a mold for molding the holding means from synthetic resin, the pouring speed of the synthetic resin, and the molding temperature.

4. The fixing device according to claim 3 , wherein the surface roughening treatment section adjusts the surface roughness of a mold for molding the holding means from a synthetic resin, thereby setting the surface roughness.

5. The belt includes at least a base layer, an adhesive layer, and a surface layer. The fixing device according to claim 1 , wherein the base layer contains a highly heat conductive filler having a low coefficient of friction.

6. 6. The fixing device according to claim 5, wherein the highly thermally conductive filler is made of carbon nanotubes.

7. an image forming means for forming an image on a recording medium; A fixing unit for fixing the image formed on the recording medium; Equipped with 7. An image forming apparatus comprising the fixing device according to claim 1 as said fixing means.

Images