Fixing device and image forming apparatus

Abstract

To provide a fixation device and an image formation device that can suppress an image defect or paper jamming caused by a foreign matter falling from a separation pawl.SOLUTION: In an image formation device making a recording sheet pass through a fixation nip formed by pressing a fixation belt to a pressure roller, and fixing a toner image on the recording sheet, a separation pawl 200, which is disposed in a fixation nip downstream in a rotation direction of the pressure roller and separates the recording sheet from the pressure roller, has: a separation part 201 that faces the pressure roller, and has a wedge-like external shape protruding toward the fixation nip; and a supporting part 202 that is lower in a releasing property than the separation part 201, is away from the pressure roller further than the separation part 201, and has the separation part 201 anchored. The separation part 201 has a protrusion part 401 in an external surface getting to the supporting part 202 from a tip end part protruding toward the fixation nip.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a fixing device and an image forming apparatus, and in particular to a technology for preventing foreign matter adhering to a separation claw that separates a recording sheet discharged from a fixing nip from a rotating body from growing into a lump and causing poor fixing or image degradation. [Background technology]

[0002] An electrophotographic image forming apparatus is equipped with a fixing device that thermally fixes a toner image onto a recording sheet. The fixing device presses a fixing member, such as a fixing roller or a fixing belt, against a pressure member, such as a pressure roller or a pressure pad, to form a fixing nip. When the recording sheet passes through the fixing nip, the toner image carried by the recording sheet is melted by the high-temperature fixing member and pressed onto the recording sheet.

[0003] Thereafter, when the recording sheet leaves the fixing nip, if the recording sheet wraps around a rotating body such as a fixing member or a pressure roller, a paper jam occurs, so a separation claw is provided to separate the recording sheet from the rotating body. For example, as shown in Fig. 9(a), a separation claw 9 has been proposed that is made of a base member (supporting portion) 902 made of a hard material and having a wedge-shaped tip, and a fluororesin layer (separating portion) 901 that covers the surface of the base member 902 facing the sheet discharge path (see Patent Document 1).

[0004] Since the fluororesin layer 901 has high releasability, the recording sheet discharged from the fixing nip can be smoothly separated from the fixing member and the pressure member. Also, by configuring the separation claw 9 with two parts, the support part 902 and the separation part 901, the cost of the separation claw 9 can be reduced and its strength can be improved.

[0005] Furthermore, as shown in FIG. 9(b), by providing a coating layer 903 made of fluororesin on a surface 904 of the base member 902 opposite to the surface on which the fluororesin layer 701 is provided and facing the fixing belt (not shown), it is possible to prevent wear and contamination of the fixing belt due to contact and sliding of the tip of the separation claw 9 against the fixing belt. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-164389 A Summary of the Invention [Problem to be solved by the invention]

[0007] When the separation claw separates the recording sheet from a rotating body such as a fixing member or a pressure roller, the wedge-shaped tip of the separation claw comes into contact with the recording sheet and scrapes off paper dust and toner (hereinafter referred to as "foreign matter") from the surface of the recording sheet. The scraped off foreign matter may be carried by air currents generated by the rotation of the rotating body and the transport of the recording sheet, and may be dispersed, and may adhere to the outer surface of the separation section facing the rotating body.

[0008] If the foreign matter adhering to the separation section moves further onto the support section, it will remain on the support section and accumulate, growing into a lump, since the support section does not have a high releasability. When the foreign matter grows to a certain size, it will fall onto the fixing member or pressure roller, causing image defects and paper jams. Such problems are particularly likely to occur at the end of the product's life.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a fixing device and an image forming apparatus that can suppress image defects and paper jams caused by foreign objects falling from the separation claws. [Means for solving the problem]

[0010] In order to achieve the above object, a fixing device according to one embodiment of the present disclosure is a fixing device that fixes a toner image by passing a recording sheet through a fixing nip formed by pressing a pressure body against a rotating body, and includes a separation claw that is arranged vertically above the rotating body and separates the recording sheet from the rotating body downstream of the fixing nip in the rotational direction of the rotating body, the separation claw having a separation portion having a first outer surface facing the rotating body and a second outer surface facing a sheet transport path after separation, and a support portion that supports the separation portion, the separation portion having a higher releasability than the support portion, The first outer surface and the second outer surface intersect at an acute angle to form a sharp portion, and the first outer surface has a step portion that forms a boundary between the separation portion and the support portion from the sharp portion along the rotation direction of the rotor, and the step portion is set back more in the support portion than in the separation portion with respect to the rotor, and when, in a side view, a virtual line that is tangent to the first outer surface at a corner position of the step portion is defined as a first virtual line, and a virtual line that is perpendicular to the first virtual line at a corner position of the step portion is defined as a second virtual line, the step portion is inclined so as to turn back toward the upstream side in the rotation direction of the rotor with respect to the second virtual line. the separation portion has a side surface provided at an end portion in the axial direction of the rotor, and the side surface has a second step portion different from the step portion on the way from the end portion on the upstream side in the rotation direction of the rotor to the boundary with the support portion along the rotation direction of the rotor, and the second step portion is provided so that the support portion is narrower than the separation portion in the axial direction of the rotor. It is characterized by:

[0011] Also , the separation unit is A side surface provided at the end of the rotor in the axial direction Side The surface is characterized by having a convex portion along the rotation direction of the rotor from the upstream end of the rotor in the rotation direction to the boundary with the support portion.

[0013] Moreover, it is preferable that the step portion is provided so that the support portion is narrower than the separation portion in the axial direction of the rotor.

[0014] Furthermore, the outer surface constituting the step of the support may be disposed at a position farther from the rotor than a tangent plane at a position on the outer surface of the rotor that is closest to the sharp portion.

[0015] Moreover, the support portion may be press-fitted into the separation portion, so that the separation portion is fixed so as to cover the support portion.

[0016] The separating portion may also be a release layer formed on the surface of the supporting portion.

[0017] In addition, the separation section is preferably made of any one of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), and ethylene-chlorotrifluoroethylene resin (ECTFE).

[0018] Moreover, the support portion is preferably made of any one of polyetheretherketone (PEEK), polyetherketone (PEK), liquid crystal polymer (LCP) and polyphenylsulfide (PPS).

[0019] The pointed portion may have a constant width in the axial direction of the rotor, and may have a tip portion whose cross section perpendicular to the axial direction forms an acute angle.

[0020] The width of the sharp portion in the axial direction of the rotor may be gradually reduced as the sharp portion approaches the rotor.

[0021] The separation claws may be disposed so that their sharp points do not come into contact with the rotating body.

[0022] It is also preferable that a plurality of separation claws are arranged along the axial direction of the rotor. Furthermore, a fixing device according to another embodiment of the present disclosure is a fixing device that fixes a toner image by passing a recording sheet through a fixing nip formed by pressing a pressure body against a rotating body, and includes a separation claw that is arranged vertically above the rotating body and separates the recording sheet from the rotating body downstream of the fixing nip in the rotation direction of the rotating body, the separation claw having a separation portion having a first outer surface facing the rotating body and a second outer surface facing a sheet transport path after separation, and a support portion that supports the separation portion, the separation portion having higher releasability than the support portion, the first outer surface and the second outer surface intersect at an acute angle to form a sharp portion, the first outer surface has a convex portion on the way from the sharp portion to the boundary with the support portion along the rotation direction of the rotating body, and the convex portion has a quadrangular pyramid shape having an apex. The apex of the quadrangular pyramid faces the outer circumferential surface of the rotor via a space.It is characterized by:

[0023] An image forming apparatus according to an embodiment of the present disclosure includes the fixing device according to an embodiment of the present disclosure, and uses the fixing device to thermally fix a toner image onto a recording sheet. Effect of the Invention

[0024] In this way, the separation part, which has higher releasability than the support part, has a convex part on its outer surface from the tip part protruding toward the fixing nip to the support part, so that the convex part can cause foreign matter such as paper dust and toner scraped off from the recording sheet by the tip part to fall from the separation claw before the foreign matter reaches the support part along the outer surface. Therefore, it is possible to prevent the foreign matter from reaching the support part, accumulating, and growing into a lump, and it is possible to prevent the lump-shaped foreign matter from falling onto the rotating body and causing image defects or paper jams. [Brief description of the drawings]

[0025] [Figure 1] 1 is a diagram showing a main configuration of an image forming apparatus 1 according to an embodiment of the present disclosure. [Diagram 2] 1 is a diagram showing a main configuration of a fixing device 100 according to an embodiment of the present disclosure. [Diagram 3] 2 is a diagram illustrating an example of the arrangement of a separation claw 200 in the fixing device 100. FIG. [Figure 4] 1A shows the front, side and back of the separation claw 200, (b) is an overall view showing the step formed by the separation portion 201 and support portion 202 of the separation claw 200 and an enlarged view 412 of the dashed area 411 in the overall view, and (c) is an overall view of the step formed by the separation portion 201 and support portion 202 of the separation claw 200 seen from a different perspective than (b) and an enlarged view 422 of the dashed area 421 in the overall view. [Diagram 5] 13 is a diagram illustrating a mechanism by which a foreign object 501 falls from an outer surface 403 of a separation section 201 due to a convex portion 401. FIG. [Figure 6]1A is a diagram for explaining the positional relationship between the support portion 202 and the pressure roller 211, and FIG. 1B is a diagram for explaining how the separation claw 200 scrapes off foreign matter from the recording sheet S. FIG. [Figure 7] 13(a) to 13(d) are diagrams showing the shapes of convex portions 703, 711, and 731 according to modified examples of the present disclosure, respectively. [Figure 8] 11 is a diagram showing a main configuration of a fixing device 100 according to a modified example of the present disclosure. [Figure 9] 1A and 1B are diagrams showing the main configuration of a separation claw according to the prior art. [Figure 10] 1A is a front view illustrating how a foreign object 1001 attached to the tip 404 of the separation claw 200 moves from the outer surface 402 to the side due to friction with the recording sheet, and FIG. 1B is an external perspective view illustrating how the foreign object 1001 moves along the side and then falls off at a step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present disclosure will be described with reference to the drawings. [1] Configuration of image forming apparatus 1 First, the image forming apparatus according to the present embodiment will be described.

[0027] 1, image forming apparatus 1 is a so-called tandem type color printer, and includes a fixing section 100, an image creating section 110, and a secondary transfer section 120. Image creating section 110 includes image creating units 111Y, 111M, 111C, and 111K that form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively.

[0028] Each of the imaging units 111Y, 111M, 111C, and 111K includes a photoconductor drum, a charging device, a developing device, a primary transfer roller, and a cleaning device, and uses the charging device to uniformly charge the outer circumferential surface of the photoconductor drum. The exposure device 112 forms an electrostatic latent image by irradiating the outer circumferential surface of the photoconductor drum with laser light modulated according to the image to be formed.

[0029] Developer supply unit 113 has detachably mounted toner bottles 114Y, 114M, 114C, and 114K containing toner of each color, YMCK, and supplies toner to the developing device. The developing device develops the electrostatic latent image by supplying toner to the outer circumferential surface of the photosensitive drum. The primary transfer roller electrostatically transfers the toner image from the outer circumferential surface of the photosensitive drum onto the outer circumferential surface of intermediate transfer belt 115 (primary transfer).

[0030] In this case, a color toner image is formed by primarily transferring the toner images of each color, YMCK, so that they overlap each other on the outer circumferential surface of the intermediate transfer belt 115. When forming a monochrome toner image, only a toner image of one color is transferred onto the outer circumferential surface of the intermediate transfer belt 115.

[0031] Intermediate transfer belt 115 is an endless belt member that is looped around drive roller 116, driven roller 117, and primary transfer roller, and travels in the direction of arrow A. Drive roller 116 and secondary transfer roller 118 form secondary transfer section 120. Drive roller 116 and secondary transfer roller 118 are pressed against each other to form a secondary transfer nip. Intermediate transfer belt 115 transports a toner image carried on its outer circumferential surface to the secondary transfer nip by traveling in the direction of arrow A.

[0032] A stack of recording sheets is stored in the paper feed tray 119. A stack of recording sheets may also be placed on the manual feed tray 121. A recording sheet is transported from the paper feed tray 119 or the manual feed tray 121 to the secondary transfer nip in accordance with a user's designation, in time with the toner image being transported to the secondary transfer nip. A secondary transfer bias is applied to the secondary transfer roller 118, and the toner image is electrostatically transferred from the outer circumferential surface of the intermediate transfer belt 115 onto the recording sheet (secondary transfer).

[0033] The recording sheet onto which the toner image has been secondarily transferred is transported to a fixing unit 100, where the toner image is thermally fixed. A switching claw 122 switches the transport direction of the recording sheet onto which the toner image has been thermally fixed. When an image is to be formed on the back side of the recording sheet as well, the switching claw 122 guides the recording sheet to a double-sided reversing path 123. A reversing roller 124 reverses the transport direction of the recording sheet guided to the double-sided reversing path 123.

[0034] At this time, a part of the recording sheet is once sent onto switchback tray 125, and then pulled back into image forming apparatus 1. The recording sheet whose transport direction has been reversed is transported again to the secondary transfer nip, where a toner image is secondarily transferred to the rear surface, and the toner image is thermally fixed. In the case of single-sided printing or when images have been formed on both sides, switching claw 122 guides the recording sheet to discharge rollers 126. Discharge rollers 126 discharge the recording sheet onto discharge tray 127. [2] Configuration of fixing device 100 Next, the configuration of the fixing device 100 will be described.

[0035] 2, fixing device 100 includes pressure roller 211, fixing belt 212, and fixing pad 213. Pressure roller 211 is in pressure contact with fixing pad 213 with fixing belt 212 sandwiched therebetween, and a fixing nip is formed by this pressure contact. Fixing belt 212 is wound around fixing pad 213 and heating roller 214, and travels in the direction of arrow C following pressure roller 211 rotating in the direction of arrow B. This causes the recording sheet to be transported in the direction of arrow D.

[0036] Heating roller 214 incorporates heater 215 such as a halogen lamp, and is heated by turning on heater 215. When the temperature of heating roller 214 rises due to this heating, fixing belt 212 is heated by heated heating roller 214 and also rises in temperature. When pressure roller 211 presses the recording sheet against heated fixing belt 212, the toner carried by the recording sheet is melted and thermally fixed.

[0037] Separation claw 200 is fixed on the sheet discharge side of the fixing nip so that its wedge-shaped tip is in a non-contact position with a small gap from the outer circumferential surface of pressure roller 211, or in a position in contact with the outer circumferential surface of pressure roller 211, and separates the recording sheet from the outer circumferential surface of pressure roller 211 so that the recording sheet does not wrap around pressure roller 211. Separation claw 200 includes separation section 201 disposed at a position facing the discharge path of the recording sheet, and support section 202 for fixing separation claw 200 in the position described above.

[0038] As shown in Fig. 3, three separation claws 200 are arranged along the axial direction of the pressure roller 211. Needless to say, the number of separation claws 200 is not limited to three, and may be any number other than three. Generally, if the recording sheet is stiff, such as thick paper, it is difficult for it to wind around the pressure roller 211, and if the recording sheet is weak, such as thin paper, it is easy for it to wind around the pressure roller 211. In addition, since the ease of winding varies depending on the size of the recording sheet, it is desirable to design the number of separation claws 200 assuming the case in which the recording sheet is most likely to wind around.

[0039] Furthermore, it goes without saying that the configuration of the fixing device 100 is not limited to the above, and as shown in Fig. 8, a roller member 801 may be used instead of the fixing pad 213, or a pressure roller may be directly pressed against the fixing roller. Also, a pressure pad may be pressed against the fixing roller. As long as the fixing nip is formed by pressing a pressure member against the fixing rotor, the fixing rotor may be a fixing belt or a fixing roller, and the pressure member may be a pressure roller or a pressure pad. [3] Configuration of separation jaw 200 Next, the structure of the separation claw 200 will be described.

[0040] As described above, separation claw 200 includes separation portion 201 and support portion 202. Separation claw 200 is disposed near the exit of the fixing nip and is continuously exposed to high temperatures during image formation, so it is necessary to use a heat-resistant resin material. Separation portion 201 desirably has high releasability so that toner from the recording sheet is less likely to adhere to it by rubbing against the high-temperature recording sheet leaving the fixing nip.

[0041] For this reason, in this embodiment, a fluororesin is used as the material for the separation unit 201. As a fluororesin, tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) has particularly high releasability, and is therefore more advantageous in preventing the accumulation and adhesion of toner and paper powder. In addition to PFA, other examples include tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), and ethylene-chlorotrifluoroethylene resin (ECTFE).

[0042] Examples of PFA and FEP include Teflon (registered trademark) manufactured by DuPont-Mitsui Co., Ltd., examples of FEP and ETFE include Aflon (registered trademark) manufactured by Asahi Glass Co., Ltd., examples of COP and PVDF include Kynar (registered trademark) manufactured by Atofina Japan Co., Ltd., and examples of ECTFE include Halar (registered trademark) manufactured by Ausimont K.K.

[0043] Furthermore, by adding a low-density filler such as aramid fiber, talc, mica, or graphite to the fluororesin, it is possible to reduce wear of the pressure roller 211 caused by contact with or rubbing against the separation part 201. Also, materials other than fluororesin, such as silicone resin, may be used as the material for the separation part 201.

[0044] As shown in Fig. 4(a), the separating section 201 has an outer surface 402 facing the transport path of the recording sheet that has left the fixing nip and been separated from the pressure roller 221, and an outer surface 403 facing the pressure roller 211, and these outer surfaces are continuous with a wedge-shaped outer surface that protrudes toward the fixing nip. The wedge-shaped outer surface has a certain width in the axial direction of the pressure roller 211, and has an acute-angled tip portion 404 that protrudes toward the fixing nip in a cross section perpendicular to the axial direction (see Fig. 4(a) <side view>). The tip portion 404 is a sharp-pointed portion in terms of its shape.

[0045] In the separating portion 201, the width of the outer surfaces 402, 403 in the axial direction of the pressure roller 211 gradually decreases as the outer surface 402 approaches the pressure roller 211. The outer surface 402 has a function of guiding the transport of the recording sheet separated from the pressure roller 221. By having such a shape, the separating portion 201 can reduce the area that can come into contact with the pressure roller 211, so that toner and paper powder are less likely to adhere to the separating portion 201 and are less likely to accumulate on the support portion 202.

[0046] The support portion 202 is narrower than the separation portion 201 in the axial direction of the pressure roller 211, and is snapped into the separation portion 201 by being pressed into the separation portion 201. By this snapping, the separation portion 201 is fixed so as to cover the support portion 202.

[0047] Resin materials such as polyether ether ketone (PEEK), polyether ketone (PEK), liquid crystal polymer (LCP), polyphenylsulfide (PPS), etc., or metal materials such as aluminum, etc. may be used for the support portion 202. These materials have heat resistance and sufficient rigidity (mechanical strength).

[0048] The outer surface 405 of the support part 202 facing the pressure roller 211 is set back from the outer surface 403 of the separation part 201 facing the pressure roller 211, forming a step portion when viewed from the pressure roller 211. The outer surface 403 of the separation part 201 has higher releasability than the outer surface 405 of the support part 202, and even if paper powder or toner (hereinafter referred to as "foreign matter") moves downstream along the rotation direction of the pressure roller 211 on the outer surface 403 of the separation part 201, it cannot go beyond the step portion and reach the outer surface 405 of the support part 202, and does not necessarily adhere to the outer surface 405 of the support part 202. Therefore, it is possible to suppress the growth of the foreign matter into a lump on the outer surface 403 of the support part 202.

[0049] Further, the corner 401 of the step is convex in the sense that it is not flat, and in this sense, it can be said that the outer surface 403 of the separating section 201 has the convex portion 401 on the way from the tip 404 to the boundary with the support section 202 along the rotation direction of the pressure roller 211. As illustrated in Fig. 5, when an air flow is generated around the separation claw 200 or the separation claw 200 vibrates with the rotation of the pressure roller 211 or the conveyance of the recording sheet, the foreign matter 501 attached to the outer surface 403 of the separating section 201 may move along the outer surface 403. When the foreign matter 501 reaches the convex portion 401 due to this movement, the contact area between the foreign matter 501 and the outer surface 403 is reduced because the outer surface 403 at the convex portion 401 has a convex shape.

[0050] Since outer surface 403 of separation section 201 has high releasability and foreign matter 501 does not easily adhere thereto, the foreign matter does not accumulate and grow into a lump. Therefore, the contact area between foreign matter 501 and outer surface 403 is small, and foreign matter 501 is in a state where it is easy to separate from outer surface 403. For this reason, when the contact area between foreign matter 501 and outer surface 403 decreases, foreign matter 501 is no longer able to maintain contact with outer surface 403 and falls off.

[0051] As described above, since the outer surface 405 of the support part 202 is recessed from the outer surface 403 of the separation part 201, the fallen foreign matter 501 moves to the outer circumferential surface of the pressure roller 211 or other places without adhering to the outer surface 405 of the support part 202. Since the foreign matter 501 does not grow into a lump and is small, even if it falls onto the outer circumferential surface of the pressure roller 211, there is no risk of damaging the pressure roller 211, causing fixing failure, degrading the image, or causing a paper jam.

[0052] Therefore, since the amount of foreign matter 501 on the outer surface 405 of the support part 202 can be reduced, it is possible to prevent the foreign matter from growing into a lump on the outer surface 405 of the support part 202 and then falling onto the outer peripheral surface of the pressure roller 211 due to air currents, vibration of the separation claws 200, its own weight, etc., which would result in wear on the pressure roller 211, poor fixing, and deterioration of the image.

[0053] As shown in Fig. 6(a), the separation claw 200 is disposed such that an outer surface 405 of the support portion 202 forming a step with an outer surface 403 of the separation portion 201 is located at a position receding from the pressure roller 211 relative to a tangent plane 602 at a position 601 on the outer peripheral surface of the pressure roller 211 that is closest to the tip of the separation claw 200. As shown in Fig. 6(b), a foreign object 611 scraped off by the separation claw 200 from the recording sheet S transported in the direction of the arrow E rubs against the outer peripheral surface of the pressure roller 211 rotating in the direction of the arrow F at a position on the outer peripheral surface of the pressure roller 211 that is closest to the tip of the separation claw 200.

[0054] Due to this rubbing, the foreign matter 611 is subjected to a rubbing force along the tangent plane at that position and is scattered. Therefore, if the support part 202 is disposed at a position set back from the tangent plane 602 as seen from the pressure roller 211, the outer surface 405 of the support part 202 is out of the way of the movement of the foreign matter 611, so that the foreign matter 611 is less likely to adhere to the outer surface 405.

[0055] 4(b) and 4(c), in addition to the outer surface facing pressure roller 211, outer surface 413 of separating portion 201 and outer surface 414 of supporting portion 202, which come into contact with the outer surface facing pressure roller 211 and the outer surface facing the recording sheet, also form steps. When foreign matter scraped off by separation claw 200 is pressed against the tip of separation claw 200 by the rotation of pressure roller 211, a force moving the foreign matter in the axial direction of pressure roller 211 can be exerted.

[0056] 10(a) and 10(b), foreign matter scraped off by separation claw 200 from a recording sheet may also move to the side of separation claw 200. On the other hand, if outer surface 413 of separation portion 201 and outer surface 414 of support portion 202 form a step even at the side, and outer surface 414 of support portion 202 is set back from outer surface 413 of separation portion 201, foreign matter can be dropped at the step portion as shown in FIG. 10(b), and therefore foreign matter can be prevented from adhering to and accumulating on outer surface 414 of support portion 202.

[0057] Therefore, it is possible to prevent the above-mentioned problems caused by the foreign matter growing into lumps on the outer surface 414 of the support portion 202 and dropping onto the outer circumferential surface of the pressure roller 211.

[0058] Moreover, a step portion can be similarly provided on the side surface opposite to the illustrated side surface 413. Furthermore, not only can steps be provided on both the outer surface 403 and the side surface 413 of the separation unit 201, but even if a step is provided on only one of the outer surface 403 or the side surface 413 of the separation unit 201, it is possible to obtain an effect of reducing adhesion of foreign matter to the outer surface 405 or the side surface 414 of the support unit 202, as compared to a configuration in which a step is not provided on either the outer surface 403 or the side surface 413 of the separation unit 201. [4] Variations While the present disclosure has been described above based on the embodiments, it goes without saying that the present disclosure is not limited to the above-described embodiments, and the following modified examples can be implemented. (4-1) In the above embodiment, an example was described in which the outer surface of separation portion 201 and the outer surface of support portion 202 form a step to prevent the accumulation of foreign matter. However, it goes without saying that the present disclosure is not limited to this, and the following may be used instead.

[0059] 7(a), a convex portion 703 may be provided at a position closer to the tip 702 of the separation claw 200 than the boundary 701 between the separation portion 201 and the support portion 202. Even in this case, foreign matter adhering to the separation portion 201 moves toward the support portion 202 and falls from the separation claw 200 when it reaches the convex portion 703, so that it is possible to prevent the foreign matter adhering to the support portion 202 from growing into a lump.

[0060] It should be noted that, with respect to the portion of outer surface 403 of separating section 201 facing pressure roller 211, from convex portion 703 to boundary 701, convex portion 703 cannot prevent the foreign matter from moving from separating section 201 to support section 202. In this sense, it is desirable to shorten distance L1 from convex portion 703 to boundary 701.

[0061] As shown in FIG. 7(b), the convex portion 711 provided on the outer surface 403 of the separating section 201 facing the pressure roller 211 has a shape that protrudes toward the pressure roller 211. Specifically, as shown in FIG. 7(c), the convex portion 711 may have a triangular prism shape having an edge line 721 along the axial direction of the pressure roller 211. In this way, foreign matter can be dropped from the edge line 721. Alternatively, the convex portion 711 may have a quadrangular pyramid shape having an apex 722. In this case, foreign matter can be dropped from the four edge lines.

[0062] Furthermore, the convex portion does not have to have a ridge line, and may be, for example, a semi-cylindrical portion as shown in Fig. 7(d) . Even if the cross section is arc-shaped like convex portion 731, if the size and shape of the foreign object are the same, the contact area with the foreign object is smaller on the arc-shaped curved surface than on a flat surface, and therefore, the effect of dropping the foreign object from outer surface 403 of separation section 201 can be obtained.

[0063] In addition, the three-dimensional shape with an arc-shaped cross section includes a semi-cylindrical shape, a hemispherical shape, etc., but any shape is acceptable as long as the outer surface is curved. Also, the greater the curvature, the greater the effect of dropping foreign objects.

[0064] 7(b) and (d), foreign matter adhering to the portion of the outer surface 403 of the separating portion 201 extending from the boundaries 712, 732 between the separating portion 201 and the supporting portion 202 to the convex portions 711, 731 cannot be dropped from the separating claws 200 by the convex portions 711, 731. For this reason, it is desirable to make the distances L2, L3 from the boundaries 712, 732 between the separating portion 201 and the supporting portion 202 to the convex portions 711, 731 short in the same manner as the distance L1 shown in FIG. (4-2) In the above embodiment, an example was described in which separation section 201 has outer surface 402 facing the sheet transport path after separation, outer surface 403 facing pressure roller 211, and side surface 413 provided at the end of pressure roller 211 in the axial direction. However, it goes without saying that the present disclosure is not limited to this, and the following may be used instead.

[0065] For example, the separation section 201 may not have the outer surface 403 facing the pressure roller 211, and may have only the outer surface 402 facing the sheet transport path and the side surface 413. Foreign matter scraped off from the recording sheet S by the separation claw 200 mainly scatters toward the side surface 413, and may not scatter much onto the surface of the separation claw 200 facing the pressure roller 211 because the gap between the tip 404 and the pressure roller 211 is narrow.

[0066] In such a case, there is little practical problem even if there is no outer surface 403 facing the pressure roller 211, and it is effective to simply provide a protrusion on the side surface 413 to prevent foreign matter from moving from the side surface 413 to the support part 202.

[0067] In addition, when there is space between the tip 404 and the pressure roller 211, and when the rotation of the pressure roller 211 causes a large amount of foreign matter to scatter toward the outer surface 403 facing the pressure roller 211 and a small amount of foreign matter to scatter toward the side surface 413, by providing outer surfaces 402, 403 and providing a convex portion on outer surface 403 without providing side surface 413, it is possible to prevent foreign matter from accumulating on support portion 202. (4-3) In the above embodiment, an example has been described in which separation portion 201 is a member formed separately from support portion 202. However, it goes without saying that the present disclosure is not limited to this, and separation portion 201 may be a coating layer (release layer) applied to the surface of support portion 202. (4-4) In the above embodiment, the image forming apparatus 1 has been described as a tandem color printer, but the present disclosure is not limited to this, and may be a color printer other than a tandem printer, or a monochrome printer. In addition, the image forming apparatus 1 may be a copying machine equipped with a scanner, or may be a facsimile machine equipped with a facsimile communication function.

[0068] Furthermore, even if the image forming apparatus 1 is a multi-function peripheral (MFP) that combines these functions, the above-mentioned effects can be obtained by applying the present disclosure. [Industrial Applicability]

[0069] The fixing device and image forming apparatus of the present disclosure are useful as devices that can prevent foreign matter attached to the separation claws that separate the recording sheet discharged from the fixing nip from the rotating body from growing into lumps and causing fixing problems, image degradation, etc.

[0070] The present disclosure relates to a fixing device and an image forming apparatus, and in particular to the techniques thereof. [Explanation of symbols]

[0071] 1. Image forming device 100.................................................... Fixing device 200, 9………………………………………… Separation claw 201………………………………………… Separation section 202……………………………………………………support part 211...................................................................Pressure roller 212....................................................................Fusing belt 401, 703, 711, 731……………Convex part 402, 403, 405, 413, 414...Outer surface 501, 611……………………………………Foreign object 602…………………………………………Tangential plane

Claims

1. A fixing device in which a toner image is fixed by passing a recording sheet through a fixing nip formed by pressing a pressure body against a rotating body, a separation claw disposed vertically above the rotating body and configured to separate the recording sheet from the rotating body downstream of the fixing nip in the direction of rotation of the rotating body; The separation claws are a separation unit having a first outer surface facing the rotating body and a second outer surface facing a sheet transport path after separation; A support portion that supports the separation portion, The separation part has higher releasability than the support part. the first outer surface and the second outer surface intersect at an acute angle to form a sharp point; the first outer surface has a step portion that forms a boundary between the separation portion and the support portion from the sharp portion along a rotation direction of the rotor, the step portion being such that the support portion is set back from the rotor more than the separation portion; when viewed from the side, a virtual line tangent to the first outer surface at a corner of the step portion is defined as a first virtual line, and a virtual line perpendicular to the first virtual line at the corner of the step portion is defined as a second virtual line, the step portion is inclined so as to turn back toward the upstream side in the rotation direction of the rotor with respect to the second virtual line, the separation portion has a side surface provided at an end portion in an axial direction of the rotor, the side surface has a second step portion different from the step portion, along the rotation direction of the rotor from an end portion on the upstream side in the rotation direction of the rotor to a boundary with the support portion; The second step is provided such that the support portion is narrower than the separation portion in the axial direction of the rotor. A fixing device comprising:

2. The outer surface constituting the step portion of the support portion is disposed at a position farther from the rotor than the tangent plane at the position closest to the sharp point on the outer surface of the rotor.

2. The fixing device according to claim 1,

3. The support portion is press-fitted into the separation portion, so that the separation portion is fixed so as to cover the support portion.

3. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller.

4. The separating portion is a release layer formed on the surface of the supporting portion.

4. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing surface.

5. The separation section is made of any one of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVDF), vinyl fluoride resin (PVF), and ethylene-chlorotrifluoroethylene resin (ECTFE).

5. The fixing device according to claim 1, wherein:

6. The support is made of any one of polyetheretherketone (PEEK), polyetherketone (PEK), liquid crystal polymer (LCP), and polyphenylsulfide (PPS).

6. The fixing device according to claim 1, wherein

7. The pointed portion has a constant width in the axial direction of the rotor, and has a tip portion with an acute angle in a cross section perpendicular to the axial direction.

7. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing surface.

8. The width of the sharp portion in the axial direction of the rotor gradually decreases as the sharp portion approaches the rotor.

8. The fixing device according to claim 7,

9. The separation claws are positioned so that their sharp points do not come into contact with the rotating body.

9. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing surface.

10. A plurality of separation claws are arranged along the axial direction of the rotor.

10. The fixing device according to claim 1,

11. A fixing device in which a toner image is fixed by passing a recording sheet through a fixing nip formed by pressing a pressure body against a rotating body, a separation claw disposed vertically above the rotating body and configured to separate the recording sheet from the rotating body downstream of the fixing nip in the direction of rotation of the rotating body; The separation claws are a separation unit having a first outer surface facing the rotating body and a second outer surface facing a sheet transport path after separation; A support portion that supports the separation portion, The separation part has higher releasability than the support part. the first outer surface and the second outer surface intersect at an acute angle to form a sharp point; the first outer surface has a convex portion extending from the sharp portion to a boundary with the support portion along a rotation direction of the rotor, The convex portion has a quadrangular pyramid shape having a vertex, The apex of the quadrangular pyramid faces the outer circumferential surface of the rotor via a space. A fixing device comprising:

12. A fixing device according to any one of claims 1 to 11, The toner image is thermally fixed onto the recording sheet using the fixing device.

1. An image forming apparatus comprising:

Images