Fixing device and image forming apparatus

Abstract

To extend the life of a slide member in slide contact with an outer peripheral surface of a fixing rotating body and increase the wear resistance of the fixing rotating body.SOLUTION: A fixing device is provided with a fixing belt 21 (fixing rotating body) that has a release layer 21c formed on an outer peripheral surface and heats and fixes a toner image on a sheet P. The fixing device is also provided with a pressure roller 31 (pressure rotating body) that is in contact with the fixing belt 21 to form a fixing nip through which the sheet is conveyed, and a refresh roller 28 (slide member) that is in slide contact with the release layer 21c of the fixing belt 21. The fixing belt 21 has spherical silica 21c2 added to the release layer 21c.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fixing device that heats and fixes a toner image on a sheet, and to an image forming apparatus including the fixing device, such as a copying machine, a printer, a facsimile, or a combination machine thereof. [Background technology]

[0002] Conventionally, in fixing devices installed in image forming devices such as copiers and printers, a technique has been known in which the outer peripheral surface of a fixing rotor such as a fixing roller is brought into sliding contact with the outer peripheral surface of the fixing rotor to polish the outer peripheral surface of the fixing rotor, in order to reduce the problem of scratches on a sheet passing through the fixing nip due to the roughness of the outer peripheral surface of the fixing rotor (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 2 discloses a technology in which a release layer formed on the outer peripheral surface of a fixing roller (fixing rotor) has fillers such as carbon, alumina, silicon carbide, magnesium oxide, and iron oxide dispersed in PFA resin, in order to improve the wear resistance of the fixing roller (fixing rotor). Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional fixing devices, it has been difficult to achieve a good balance between improving the wear resistance of the fixing rotor and extending the life of the sliding member that comes into sliding contact with the outer circumferential surface of the fixing rotor.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a fixing device and an image forming apparatus in which the sliding contact member that comes into sliding contact with the outer circumferential surface of the fixing rotor has a long life and the fixing rotor has high wear resistance. [Means for solving the problem]

[0006] The fixing device of this invention comprises a fixing rotor having a release layer formed on its outer peripheral surface which heats and fixes a toner image on a sheet, a pressure rotor which contacts the fixing rotor to form a fixing nip through which the sheet is transported, and a sliding member which comes into sliding contact with the release layer of the fixing rotor, and the fixing rotor has a release layer to which spherical silica has been added. Effect of the Invention

[0007] According to the present invention, it is possible to provide a fixing device and an image forming apparatus in which the sliding contact member that comes into sliding contact with the outer circumferential surface of the fixing rotor has a long life and the fixing rotor has high wear resistance. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a fixing device. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing a fixing belt. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing the refreshing roller. [Diagram 5] 1A is an enlarged view showing the surface layer of a refreshing roller, and FIG. 1B is an enlarged view showing the release layer of a fixing belt. [Figure 6] 1A is an enlarged view showing a surface layer of a refreshing roller, and FIG. 1B is an enlarged view showing a release layer of a fixing belt, as comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an image forming apparatus as a multifunction machine having a copy function and a printer function, reference numeral 2 denotes a writing unit that emits laser light based on input image information, reference numeral 3 denotes an original transport unit that transports an original D to an original reading unit 4, reference numeral 4 denotes an original reading unit that reads image information of the original D, and reference numeral 7 denotes a paper feed unit in which sheets P such as paper are stored. Additionally, reference numeral 9 denotes a registration roller (timing roller) that adjusts the timing of transporting sheet P, 11Y, 11M, 11C, and 11BK denote photosensitive drums on which toner images of each color (yellow, magenta, cyan, and black) are formed, and 12 denotes a charging unit that charges each of the photosensitive drums 11Y, 11M, 11C, and 11BK. Further, reference numeral 13 denotes a developing unit which develops the electrostatic latent images formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, reference numeral 14 denotes a primary transfer bias roller which transfers the toner images formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK onto the sheet P in a superimposed manner, and reference numeral 15 denotes a cleaning unit which collects untransferred toner on each of the photosensitive drums 11Y, 11M, 11C, and 11BK. In addition, reference numeral 16 denotes an intermediate transfer belt cleaning section that cleans the intermediate transfer belt 17, reference numeral 17 denotes the intermediate transfer belt onto which multiple color toner images are transferred in superimposed order, reference numeral 18 denotes a secondary transfer bias roller for transferring the color toner image on the intermediate transfer belt 17 onto the sheet P, and reference numeral 20 denotes a fixing device that fixes the toner image (unfixed image) on the sheet P. Reference numeral 65 denotes an operation display panel for displaying information relating to the printing operation (image forming operation) and for carrying out operations.

[0011] A normal color image forming operation (printing operation) in the image forming apparatus will be described below. When the image forming apparatus 1 is used as a copier, the user places an original D on the original platen, inputs necessary information such as printing conditions into the operation display panel 65, and presses the copy button. As a result, the document D is transported from the document table in the direction of the arrow in the figure by the transport rollers of the document transport unit 3, and placed on the contact glass 5 of the document reading unit 4. Then, the image information of the document D placed on the contact glass 5 is optically read by the document reading unit 4.

[0012] More specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating it with light emitted from an illumination lamp. The light reflected by the document D is then imaged on a color sensor via a group of mirrors and a lens. The color image information of the document D is read by the color sensor for each color separation light of RGB (red, green, blue), and then converted into an electrical image signal. Furthermore, based on the RGB color separation image signal, the image processing unit performs processing such as color conversion processing, color correction processing, and spatial frequency correction processing to obtain color image information of yellow, magenta, cyan, and black.

[0013] In addition, when the image forming apparatus 1 is used as a printer, the user inputs necessary information such as image information and printing conditions from an external input device such as a personal computer that is communicatively connected to the image forming apparatus 1, and the information is acquired by the control unit of the image forming apparatus 1.

[0014] Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. Then, from the writing unit 2, laser light (exposure light) based on the image information of each color is emitted toward the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK, respectively.

[0015] Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate in the counterclockwise direction in FIG. 1. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging unit 12 (charging process). Thus, a charging potential is formed on the photoconductor drums 11Y, 11M, 11C, and 11BK. After that, the charged surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams. In the writing unit 2, laser light corresponding to each color is emitted from four light sources in response to an image signal. Each laser light passes through a separate optical path for each color component: yellow, magenta, cyan, and black (this is the exposure process).

[0016] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor drum 11Y from the left side of the drawing. At this time, the laser light of the yellow component is scanned in the direction of the rotation axis (main scanning direction, width direction) of the photoconductor drum 11Y by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photoconductor drum 11Y after it has been charged by the charging unit 12.

[0017] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the second photoconductor drum 11M from the left on the paper, forming an electrostatic latent image corresponding to the magenta component. The laser light corresponding to the cyan component is irradiated onto the surface of the third photoconductor drum 11C from the left on the paper, forming an electrostatic latent image of the cyan component. The laser light corresponding to the black component is irradiated onto the surface of the fourth photoconductor drum 11BK from the left on the paper, forming an electrostatic latent image of the black component.

[0018] Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color are formed reach positions facing the developing unit 13. Then, toner of each color is supplied from each developing unit 13 onto the photoconductor drums 11Y, 11M, 11C, and 11BK, and the latent images on the photoconductor drums 11Y, 11M, 11C, and 11BK are developed (this is the developing process). Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the developing process reach the portions facing the intermediate transfer belt 17. Here, primary transfer bias rollers 14 are provided at the respective facing portions so as to abut against the inner peripheral surface of the intermediate transfer belt 17. Then, at the positions of the primary transfer bias rollers 14, the toner images of the respective colors formed on the photoconductor drums 11Y, 11M, 11C, and 11BK are transferred onto the intermediate transfer belt 17 in order, superimposed thereon (this is the primary transfer process).

[0019] After the transfer process, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK each reach a position facing the cleaning unit 15. Then, the cleaning unit 15 collects untransferred toner remaining on the photoconductor drums 11Y, 11M, 11C, and 11BK (this is the cleaning process). Thereafter, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through a charge removing section, and a series of image forming processes on the photoconductor drums 11Y, 11M, 11C, and 11BK are completed.

[0020] Meanwhile, the intermediate transfer belt 17 onto which the toners of the respective colors on the photoconductor drums 11Y, 11M, 11C, and 11BK are transferred (carried) in an overlapping manner travels in a clockwise direction in the drawing and reaches a position facing the secondary transfer bias roller 18. Then, at the position facing the secondary transfer bias roller 18, the color toner images carried on the intermediate transfer belt 17 are transferred onto the sheet P (secondary transfer process). Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and the series of transfer processes on the intermediate transfer belt 17 is completed.

[0021] In the present embodiment, an elastic intermediate transfer belt can also be used as the intermediate transfer belt 17. As the elastic intermediate transfer belt, for example, one in which a flexible elastic layer is laminated on a rigid base layer that provides comparative flexibility can be used. In order to prevent the intermediate transfer belt 17 from meandering, a guide member for preventing deviation may be provided on the inner peripheral surface of the intermediate transfer belt 17 . In the figure, the intermediate transfer belt cleaning unit 16 is arranged so as to clean the outer peripheral surface of the intermediate transfer belt 17, but an intermediate transfer belt cleaning unit that cleans the inner peripheral surface of the intermediate transfer belt 17 may be provided separately. The intermediate transfer belt cleaning unit 16 may have a cleaning means in the shape of a blade or a brush. A collecting means for receiving the toner and the like removed by the cleaning means may be provided. A dish-shaped tray or the like may be used as the collecting means.

[0022] Here, the sheet P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is conveyed from the paper feed section 7 via the registration rollers 9 and the like. Specifically, the sheet P fed by the feed roller 8 from the feed unit 7 storing the sheet P passes through a conveyance guide and is then guided to the registration roller 9. The sheet P that has reached the registration roller 9 is conveyed in a timely manner toward the secondary transfer nip.

[0023] Then, the sheet P onto which the full-color image has been transferred is guided by a conveyor belt to a fixing device 20. In the fixing device 20, the color image (toner image) is fixed onto the sheet P at a fixing nip (nip portion) between a fixing belt 21 and a pressure roller 31 (fixing process). Then, the sheet P after the fixing process is discharged as an output image to the outside of the apparatus main body 1 by a paper discharge roller, and a series of image forming processes (printing operations) is completed.

[0024] Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG. As shown in FIG. 2, the fixing device 20 is composed of a fixing belt 21 as a fixing rotor, a heating roller 22, a nip forming member 23 (sliding pad), a lubricant supply roller 24, a tension roller 25, a heater 26 as a heating means, a refresh roller 28 as a sliding contact member, an opposing roller 29, a reinforcing roller 27, an external recovery member 38, an internal recovery member 40, a temperature sensor 41, a pressure roller 31 as a pressure rotor, and the like.

[0025] Here, the fixing belt 21 as a fixing rotator heats the toner image on the sheet P to fix it on the sheet P. Referring to FIG. 3 and the like, the fixing belt 21 is an endless belt having a multi-layer structure in which an elastic layer 21b and a release layer 21c (surface layer) are sequentially laminated on a base layer 21a made of a resin material such as polyimide. The elastic layer 21b of the fixing belt 21 can be formed of an elastic material such as fluororubber, silicone rubber, and foamed silicone rubber having a layer thickness of about 90 μm. The release layer 21c of the fixing belt 21 can be formed of PFA (tetrafluoroethylene perfluoroalkylvinylether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like having a layer thickness of about 20 μm. By providing the release layer 21c on the outer circumferential surface (surface layer) of the fixing belt 21, the releasability (peelability) for the toner (toner image) is ensured. Fixing belt 21 is stretched and supported by three roller members (heating roller 22, lubricant supply roller 24, and tension roller 25) and nip forming member 23, and rotates (runs) in the direction of the arrow (clockwise) in Fig. 2. By using fixing belt 21 with low heat capacity as the fixing member, the temperature rise characteristic of the device is improved. Here, in the present embodiment, three roller members 22, 24, and 25 are used to stretch and support fixing belt 21, but the number of roller members is not limited to this. In the present embodiment, spherical silica 21c2 is added to the release layer 21c (surface layer) formed on the outer circumferential surface of the fixing belt 21, which will be described in detail later with reference to FIGS.

[0026] The heating roller 22 is a roller member having a hollow structure made of a metal material such as aluminum or stainless steel, and a heater 26 (heat source) serving as a heating means is fixedly installed in the inside of the cylinder without rotating. By setting the thickness of the heating roller 22 to be relatively thin, the heat capacity of the heating body is reduced, improving the temperature rise characteristics of the device (the rise time is shortened).

[0027] The heater 26 (heating means) installed inside the heating roller 22 is a halogen heater, and both ends thereof are fixed to the side plates of the fixing device 20. Then, when the main switch of the image forming apparatus main body 1 is turned on, power is supplied to the heater 26 from a power supply unit (not shown). Then, the heating roller 22 is heated by radiant heat from the heater 26, the output of which is controlled by the control unit 90, and further, heat is applied to the toner image T on the sheet P from the surface of the fixing belt 21 heated by the heating roller 22. The output control of the heater 26 is performed based on the detection result of the belt surface temperature by a temperature sensor 41 that faces the surface of the fixing belt 21 without making contact with it. More specifically, an AC voltage is applied to the heater 26 for a current-carrying time that is determined based on the detection result of the temperature sensor 41 (thermopile). By controlling the output of the heater 26 in this way, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature). In this embodiment, one heater 26 is provided inside the heating roller 22, but a plurality of heaters may be provided. In this embodiment, the temperature sensor 41 is disposed at a position opposite to the heating roller 22 with the fixing belt 21 interposed therebetween.

[0028] 2, nip forming member 23 is in sliding contact with the inner circumferential surface (sliding surface) of fixing belt 21, and is in pressure contact with pressure roller 31 via fixing belt 21 to form a fixing nip. Nip forming member 23 has a surface facing pressure roller 31 (a surface that is in sliding contact with fixing belt 21) formed in a flat shape. This makes the shape of the nip portion approximately parallel to the image surface of sheet P, and improves the adhesion between fixing belt 21 and sheet P, thereby improving fixability. Furthermore, since the curvature of fixing belt 21 at the exit side of the nip portion is large, sheet P sent out from the nip portion can be easily separated from fixing belt 21. In this embodiment, the shape of nip forming member 23 that forms the nip portion is formed to be flat, but the shape of nip forming member 23 that forms the nip portion can also be formed to be concave. That is, the opposing surface of nip forming member 23 (the surface that slides against fixing belt 21) can also be formed to be concave so as to follow the curvature of pressure roller 31. In that case, sheet P is sent out from the nip portion so as to follow the curvature of pressure roller 31, so that it is possible to prevent a problem in which sheet P after the fixing process is attracted to fixing belt 21 and is not separated.

[0029] In addition, the material for forming the nip forming member 23 may be a resin material or a metal material, but a resin material (such as a liquid crystal polymer, polyamideimide, polyimide, etc.) that has sufficient rigidity so as not to bend significantly even when subjected to the pressure of the pressure roller 31 and has heat resistance and heat insulation properties is preferable. In addition, the opposing surface of the nip forming member 23 is preferably coated with a low-friction material (such as diamond-like carbon, PTFE, molybdenum disulfide, graphite, etc.) to reduce sliding resistance with the fixing belt 21. In the present embodiment, heater 26 is used as a heating means for heating fixing belt 21. However, by using a ceramic heater or the like as nip forming member 23, nip forming member 23 can be configured to function as a heating means as well. In that case, the facing surface of nip forming member 23 may be made of an inorganic material such as glass or ceramics, or may have a resin coating formed on the outermost surface.

[0030] In this embodiment, a reinforcing roller 27 that reinforces the strength of nip forming member 23 that forms the nip portion is fixed to the inner peripheral surface side of fixing belt 21. Although not shown, reinforcing roller 27 is formed so that its length in the width direction (the direction perpendicular to the paper surface of FIGS. 1 and 2) is equal to that of nip forming member 23, and both ends in the width direction are held non-rotatably by a frame (housing) of fixing device 20. Reinforcing roller 27 abuts against pressure roller 31 via nip forming member 23 and fixing belt 21, thereby preventing the nip forming member 23 from being significantly deformed by the pressure of pressure roller 31 at the nip portion. In order to satisfy the above-mentioned functions, reinforcing roller 27 is preferably made of a metal material with high mechanical strength, such as stainless steel or iron.

[0031] The lubricant supply roller 24 is disposed downstream of the heating roller 22 (downstream in the belt rotation direction) and upstream of the fixing nip (nip forming member 23) so as to abut against the inner circumferential surface of the fixing belt 21. The lubricant supply roller 24 is rotated clockwise in FIG. 2 in accordance with the rotation of the fixing belt 21. The lubricant supply roller 24 is impregnated with a lubricant (for example, silicone oil, silicone grease whose base oil is silicone oil, fluorosilicone oil, fluorosilicone grease whose base oil is fluorosilicone oil, fluorine oil, fluorine grease whose base oil is fluorine oil, or a combination of any two or more of these). The lubricant is supplied (applied) from the lubricant supply roller 24 to the inner circumferential surface of the fixing belt 21, thereby reducing the sliding resistance between the nip forming member 23 and the fixing belt 21.

[0032] In this embodiment, a blade-shaped internal recovery member 40 that comes into sliding contact with the inner circumferential surface of the fixing belt 21 is provided downstream of the lubricant supply roller 24 and upstream of the fixing nip. The internal recovery member 40 optimizes the amount of lubricant supplied to the inner circumferential surface of the fixing belt 21 by the lubricant supply roller 24. Further, a pad-shaped external recovery member 38 that comes into sliding contact with the outer peripheral surface of the fixing belt 21 is provided on the entrance side of the fixing nip. The external recovery member 38 removes foreign matter such as lubricant and paper powder adhering to the outer peripheral surface of the fixing belt 21.

[0033] The tension roller 25 is disposed downstream (in terms of the belt rotation direction) of the fixing nip (nip forming member 23) and upstream of the heating roller 22 so as to abut against the inner circumferential surface of the fixing belt 21. Although not shown, the tension roller 25 is biased by a compression spring so as to apply tension to the fixing belt 21 . The tension roller 25 is rotated in the clockwise direction in FIG. 2 in accordance with the rotation of the fixing belt 21.

[0034] The refresh roller 28 as a sliding contact member is disposed downstream of the tension roller 25 (downstream in the belt rotation direction) and upstream of the heating roller 22 so as to abut against the outer circumferential surface of the fixing belt 21. The counter roller 29 is disposed so as to sandwich the fixing belt 21 between itself and the refreshing roller 28 . The refreshing roller 28 is configured to generate frictional resistance between itself and the fixing belt 21 and to be in sliding contact with the fixing belt 21. Therefore, the refreshing roller 28 rotates at a linear velocity slower than the linear velocity of the fixing belt 21 while slipping against the fixing belt 21. This makes it possible to smooth out the roughness of the outer peripheral surface (release layer 21c) of the fixing belt 21, thereby reducing the problem that the fixing belt 21 scratches the sheet P passing through the fixing nip. The refreshing roller 28 will be described in detail later with reference to FIGS.

[0035] The pressure roller 31 is a pressure rotating body that forms a fixing nip through which the sheet P is conveyed by pressing the pressure roller 31 against the nip forming member 23 via the fixing belt 21. The pressure roller 31 as the pressure rotating body mainly comprises a core 32 made of a metal material, an elastic layer 33 formed on the outer peripheral surface of the core 32 via an adhesive layer, and a surface layer 34 (release layer) formed on the outer peripheral surface of the elastic layer 33. The elastic layer 33 of the pressure roller 31 has a layer thickness of about several mm and is formed of an elastic material such as foamed silicone rubber, fluororubber, or silicone rubber having insulating properties. The surface layer 34 of the pressure roller 31 has a layer thickness of about several tens of μm to several hundreds of μm and is formed of a low-friction material such as PFA (PFA tube) having electrical conductivity. By providing a release layer having electrical conductivity as the surface layer 34 of the pressure roller 31, the release property (peelability) for the toner (toner image) is ensured, and the problem of the sheet P being electrostatically attracted to the pressure roller 31 and the separation property being reduced can be reduced.

[0036] In addition, in this embodiment, the driving means for driving the fixing device 20 is composed of a driving motor 70 connected to the shaft portion of the pressure roller 31, a gear train (not shown) that transmits drive from a driving gear installed on the motor shaft of the driving motor 70 to the shaft portion of the heating roller 22, and the like.

[0037] The fixing device 20 configured as above operates as follows. When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (power is supplied) to the heater 26 from the power supply unit. When a print command (job command) is input, the pressure roller 31 and the heating roller 22 are rotated in the directions of the arrows in FIG. 2 by the drive motor 70, and the fixing belt 21, the lubricant supply roller 24, and the tension roller 25 are rotated in the directions of the arrows in FIG. 2 (clockwise direction). After that, the sheet P is fed from the paper feed section 7, and the toner image on the intermediate transfer belt 17 is carried on the sheet P as an unfixed image at the position of the secondary transfer bias roller 18. The sheet P carrying the unfixed image (toner image) is transported in the direction of the dashed arrow in FIG. 2, and is fed into the fixing nip between the fixing belt 21 and the pressure roller 31, which are in a pressure contact state. The toner image is fixed on the surface of the sheet P by the heating of the fixing belt 21 and the pressing force of the fixing belt 21 (nip forming member 23) and the pressure roller 31. Thereafter, the sheet P sent out from the fixing nip by the rotating fixing belt 21 and pressure roller 31 is conveyed in the direction of the dashed arrow.

[0038] The characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) in this embodiment will be described in detail below. As previously explained using Figure 2 etc., the fixing device 20 in this embodiment is provided with a fixing belt 21 as a fixing rotor, a pressure roller 31 as a pressure rotor, a nip forming member 23, a refresh roller 28 as a sliding contact member, and the like. The fixing belt 21 has a release layer 21c (see FIGS. 3 and 5(B)) formed on its outer peripheral surface, and functions as a fixing rotator that heats and fixes a toner image on the sheet P. The fixing belt 21 is an endless belt member in which a base layer 21a, an elastic layer 21b, and a release layer 21c are laminated in this order from the inner peripheral surface side. The fixing belt 21 is in contact with the pressure roller 31 via the nip forming member 23 that is in sliding contact with the inner peripheral surface of the fixing belt 21. The pressure roller 31 functions as a pressure rotating member that forms a fixing nip through which the sheet P is transported by coming into contact with the fixing belt 21 (fixing rotating member). The nip forming member 23 is in sliding contact with the inner circumferential surface of the fixing belt 21 and abuts against the pressure roller 31 (pressure rotating body) via the fixing belt 21. The refreshing roller 28 functions as a sliding contact member that comes into sliding contact with the release layer 21c (outer circumferential surface) of the fixing belt 21 (fixing rotary body).

[0039] Now, referring to FIG. 5(B), in the fixing belt 21 (fixing rotatable body) of the present embodiment, spherical silica 21c2 is added to the release layer 21c. Specifically, the release layer 21c is formed by adding 5 to 10 wt % of spherical silica 21c2 having an average particle size of 1 to 2 μm to a PFA layer 21c1 made of tetrafluoroethylene perfluoroalkylvinylether copolymer resin (PFA). Incidentally, "spherical silica" is made by heating and melting high purity powder in the air to form spherical particles of submicrons to 100 microns. In the present specification, "spherical silica" is defined to include not only perfect spheres with a sphericity of 100%, but also silica close to a sphere with a sphericity of less than 100% but 60% or more.

[0040] On the other hand, as shown in FIG. 4, the refreshing roller 28 serving as a sliding contact member is a roller member in which a surface layer 28b made of an elastic material is formed on a core metal 28a. 5(A), a silicone rubber layer 28b1 to which an abrasive 28b2 such as alumina is added is formed on the outer circumferential surface (surface layer 28b). In other words, the surface layer 28b of the refreshing roller 28 is formed by adding the abrasive 28b2 to the silicone rubber layer 28b1. 5, the surface layer 28b of the refreshing roller 28 comes into sliding contact with the release layer 21c of the fixing belt 21. As shown in FIG.

[0041] In this manner, in the fixing device 20 of the present embodiment, spherical silica 21c2 is added to the release layer 21c of the fixing belt 21, and therefore the wear resistance of the fixing belt 21 can be improved while the life of the refresh roller 28 (sliding contact member) can be extended, compared to the case where the release layer 121c of the fixing belt shown as a comparative example in Figure 6 (B) has non-spherical filler 121c2 made of carbon, alumina, silicon carbide, magnesium oxide, iron oxide, etc. dispersed in the PFA layer 121c1. This is because the spherical silica 21c has physical properties sufficient to increase the durability of the fixing belt 21, and its shape can reduce the sliding resistance with the refreshing roller 28. Also, compared to non-spherical filler, the spherical silica 21c is more likely to slide off the release layer 21c rather than get caught by the surface layer 28b of the refreshing roller 28 when the sliding resistance with the refreshing roller 28 becomes large. Therefore, wear deterioration of the release layer 21c of the fixing belt 21 is reduced, and problems such as a decrease in toner releasability causing abnormalities in the fixed image and a shortened replacement cycle of the fixing belt 21 are alleviated. Also, wear deterioration of the surface layer 28b of the refreshing roller 28 is reduced, and problems such as a decrease in the function of preventing scratches on the sheet P conveyed to the fixing nip by leveling the surface roughness of the fixing belt 21 and a shortened replacement cycle of the refreshing roller 28 are alleviated.

[0042] Furthermore, as a result of extensive efforts and repeated experiments and simulations, the inventors of the present application have discovered that by adding 5 to 10 wt % of spherical silica 21c2 having an average particle size of 1 to 2 μm to the release layer 21c, it is possible to achieve a better balance between improving the wear resistance of the fixing belt 21 and extending the life of the refreshing roller 28. In addition, it has been found that the use of the PFA layer 21c1 as a binder for the release layer 21c can improve the function of the spherical silica 21c2 described above.

[0043] As described above, the fixing device 20 in this embodiment is provided with a fixing belt 21 (fixing rotor) having a release layer 21c formed on its outer peripheral surface, which heats and fixes a toner image on a sheet P. Also provided are a pressure roller 31 (pressure rotor) which contacts the fixing belt 21 to form a fixing nip through which the sheet P is conveyed, and a refresh roller 28 (sliding member) which comes into sliding contact with the release layer 21c of the fixing belt 21. The fixing belt 21 has spherical silica 21c2 added to the release layer 21c. This extends the life of the refresh roller 28 that is in sliding contact with the outer circumferential surface of the fixing belt 21, and also increases the abrasion resistance of the fixing belt 21.

[0044] In this embodiment, the pressure roller 31 (roller member) is used as the pressure rotating body, but a pressure belt (belt member) can also be used as the pressure rotating body. Furthermore, in this embodiment, the fixing belt 21 is used as the fixing rotor, but a fixing roller can also be used as the fixing rotor. In addition, in this embodiment, the present invention is applied to a fixing device 20 of a thermal heater type that uses a heater 26 as a heating means, but the application of the present invention is not limited to this, and the present invention can also be applied, for example, to a fixing device of an electromagnetic induction type (IH type) that uses an electromagnetic induction coil as a heating means, or a fixing device of a resistance heating type that uses a resistance heating element as a heating means. In these cases, the same effects as those of this embodiment can be obtained.

[0045] It is clear that the present invention is not limited to the present embodiment, and that the present embodiment may be modified as appropriate within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention.

[0046] In this specification, the term "sheet" is not limited to paper, but is defined to include all sheet-like recording media, such as coated paper, label paper, and OHP sheets. [Explanation of symbols]

[0047] 1 Image forming apparatus (image forming apparatus main body), 21 Fixing belt (fixing rotor), 21a base layer, 21b elastic layer, 21c release layer, 21c1 PFA layer (binder), 21c2 Spherical silica (filler), 22 Heating roller, 23 Nip forming member, 24 Lubricant supply roller, 25 tension roller, 26 heater (heating means), 27 Reinforcing roller, 28 Refresh roller (sliding contact member), 28a Core metal, 28b surface layer, 28b1 Silicone rubber layer (binder), 28b2 Abrasives (fillers), 29 Counter roller, 31 Pressure roller (pressure rotating body), 38 External recovery components, 40 Internal recovery parts, 41 temperature sensor (temperature detection means), P sheet (recording medium).

[0048] The present invention can also be embodied in the following combinations of Supplementary Notes 1 to 6. (Appendix 1) a fixing rotor having a release layer formed on its outer circumferential surface, which heats and fixes a toner image on a sheet; a pressure rotating member that forms a fixing nip through which a sheet is conveyed by contacting the fixing rotating member; a sliding contact member that is in sliding contact with the release layer of the fixing rotor; Equipped with The fixing device is characterized in that the fixing rotor has a release layer containing spherical silica. (Appendix 2) 2. The fixing device according to claim 1, wherein the release layer contains 5 to 10 wt % of spherical silica having an average particle size of 1 to 2 μm. (Appendix 3) 3. The fixing device according to claim 1, wherein the release layer is made of tetrafluoroethylene perfluoroalkylvinylether copolymer resin to which the spherical silica has been added. (Appendix 4) The fixing rotatable body is an endless fixing belt in which a base layer, an elastic layer, and the release layer are laminated in this order from the inner circumferential surface side, The fixing device according to any one of claims 1 to 3, further comprising a nip forming member that is in sliding contact with an inner peripheral surface of the fixing belt and abuts against the pressure rotating body via the fixing belt. (Appendix 5) 5. The fixing device according to claim 1, wherein the sliding contact member is a refresh roller having an outer circumferential surface formed with a silicone rubber layer containing an abrasive. (Appendix 6) An image forming apparatus comprising the fixing device according to any one of claims 1 to 5. [Prior art documents] [Patent documents]

[0049] [Patent Document 1] JP 2017-9656 A [Patent Document 2] JP 2000-89600 A

Claims

1. a fixing rotor having a release layer formed on its outer circumferential surface, which heats and fixes a toner image on a sheet; a pressure rotating member that forms a fixing nip through which a sheet is conveyed by contacting the fixing rotating member; a sliding contact member that is in sliding contact with the release layer of the fixing rotor; Equipped with The fixing device is characterized in that the fixing rotor has a release layer containing spherical silica.

2. 2. The fixing device according to claim 1, wherein the release layer contains 5 to 10 wt % of spherical silica having an average particle size of 1 to 2 μm.

3. 3. The fixing device according to claim 1, wherein the release layer is made of a tetrafluoroethylene-perfluoroalkylvinylether copolymer resin to which the spherical silica has been added.

4. The fixing rotatable body is an endless fixing belt in which a base layer, an elastic layer, and the release layer are laminated in this order from the inner circumferential surface side, 3. The fixing device according to claim 1, further comprising a nip forming member that is in sliding contact with an inner circumferential surface of the fixing belt and abuts against the pressure rotating member via the fixing belt.

5. 3. The fixing device according to claim 1, wherein the sliding contact member is a refresh roller having an outer circumferential surface formed with a silicone rubber layer containing an abrasive.

6. 3. An image forming apparatus comprising the fixing device according to claim 1.

Images