JP7512615B2 - Fixing device and image forming apparatus - Google Patents

Description

The present invention relates to a fixing device and an image forming device.

In recent years, in image forming devices such as copiers, printers, and facsimiles, images are formed by image forming processes such as electrophotographic recording, electrostatic recording, and magnetic recording, and an unfixed toner image is formed on a recording medium by an image transfer method or a direct method. As a fixing device for fixing an unfixed toner image, a fixing process is known in which the toner image formed on the recording medium is heated and pressurized in a nip between an endless belt-like fixing member (fixing belt) and a pressure roller to perform the fixing process.

The fixing member has built-in components such as a heating component such as a halogen lamp and a nip forming component. If the outer diameter of the fixing member is small or the built-in components are large, the fixing member and the built-in components may come into contact with each other. To prevent this contact, regulating members that regulate the travel range of the fixing member are arranged at both ends of the fixing member in the width direction, and the fixing member can travel stably by being lifted up by the regulating members.

However, conventional restricting members have a portion that comes into strong contact with the fixing member when the fixing member is lifted, and friction with this portion causes wear on the inner surface of the fixing member, ultimately causing the end of the fixing member to break.

In this regard, a technique has been proposed in which the flange portion of the regulating member, which contacts the inner surface of the fixing member to regulate the radial trajectory, is inclined with respect to the axial direction of the fixing member (for example, Patent Document 1).

More specifically, this technology makes the angle of inclination of the top surface side, which is the part facing the nip part with respect to the longitudinal axis of the fixing member, larger than that of the side surface side, which is closer to the nip part than the top surface side, thereby matching the shape of the flange part to the trajectory of the running fixing member, avoiding the application of force locally and suppressing wear.

However, the inventors discovered that when using fixing members made of materials such as Ni or SUS, which have higher rigidity (i.e., a larger Young's modulus) than resin materials such as polyimide, the wear of the fixing members cannot be effectively suppressed using conventional techniques.

The running path of a fixing member with a large Young's modulus is different from that of a fixing member with a smaller Young's modulus, and the fixing member comes into strong contact with the flange portion on the side.

Therefore, when using the restricting member of the conventional technology, it was unavoidable that the fixing member, which has a large Young's modulus, would wear locally and break.

Therefore, there is a need for a fixing device that can suppress damage caused by wear of the fixing member, even when a fixing member with a relatively large Young's modulus is used.

In order to solve the above problems, the present invention provides a fixing device comprising: a rotatable endless fixing member having a Young's modulus of 70 to 300 GPa; a pressure member that contacts an outer peripheral surface of the fixing member to form a nip portion; and a regulating member that is disposed at both ends of the fixing member, contacts an inner surface of the fixing member, and has a flange portion that is inclined more in a direction away from the inner surface of the fixing member than in a first region that is farthest from the nip portion, and a second region near the nip portion is inclined more in a direction away from the inner surface of the fixing member, the flange portion having a cylindrical shape cut out along the nip portion, and when the downstream side of the cut-out shape with respect to the rotation of the fixing member is defined as a downstream lower end and the upstream side of the cut-out shape is defined as an upstream lower end, the downstream lower end is disposed in the second region, a part of the cylindrical shape is disposed in the first region, and another part of the cylindrical shape is disposed in the second region, and the second region is inclined toward an axis that passes through the center of the arc of the flange portion and is parallel to the rotation axis of the pressure member,
The fixing device provides a fixing member in which an inclination angle toward the axis is 0° in the first region and a maximum inclination angle is 1° to 3° in the second region, and when a straight line passing through the axis and the downstream lower end is called a line J and a straight line passing through the axis and the upstream lower end is called a line K, the inclination angle begins to incline toward the axis from the intersection of the line K and the flange portion, and the inclination angle reaches its maximum inclination angle at a position where the line K is rotated 30° downstream around the axis, and the maximum inclination angle is maintained toward the lower end of the flange portion.

The present invention provides a fixing device that suppresses damage caused by wear of the fixing member, even when a fixing member with a relatively large Young's modulus is used.

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus. FIG. 13 is a diagram showing a restricting member according to the prior art. FIG. 11 is a longitudinal sectional view taken along the axial direction of a regulating member and its vicinity in a fixing device according to a conventional technique. 4 is a cross-sectional view of the fixing device shown in FIG. 3 along line AA, showing a running path of a fixing member. 5A and 5B are diagrams illustrating a regulating member of the fixing device according to the first embodiment. 11 is a graph showing the relationship between the maximum inclination angle θ1MAX of the inclination angle θ1 of the normal line M of the flange portion and the amount of wear of the inner surface of the fixing member that comes into contact with the flange portion. 13A and 13B are diagrams illustrating a regulating member of a fixing device according to a second embodiment. 11 is a graph showing the relationship between the maximum inclination angle θ2MAX of the inclination angle θ2 of the normal M2 of the flange portion and the amount of wear of the inner surface of the fixing member that comes into contact with the flange portion. 13A and 13B are diagrams illustrating a regulating member of a fixing device according to a third embodiment. 10 is a graph showing the relationship between the maximum curvature xMAX of the flange portion and the amount of wear of the inner surface of the fixing member that comes into contact with the flange portion.

The fixing device and image forming device according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiment shown below, and can be modified within the scope of what a person skilled in the art can imagine, including other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[Image forming apparatus]
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

The image forming device 100 shown in FIG. 1 is a tandem color printer in which imaging units that form multiple color images are arranged side by side along the direction in which the belt is stretched. Note that the present invention is not limited to this type, and can also be applied to copiers, facsimile machines, and other devices in addition to printers.

The image forming device 100 employs a tandem structure in which photoconductor drums 20Y, 20C, 20M, and 20Bk are arranged side by side as image carriers capable of forming images corresponding to the colors separated into yellow, cyan, magenta, and black.

In the image forming device 100, the visible images formed on each of the photosensitive drums 20Y, 20C, 20M, and 20Bk are primarily transferred to an intermediate transfer body (hereinafter referred to as transfer belt 11), which is an endless belt that can move in the direction of arrow A1 while facing each of the photosensitive drums. By executing this primary transfer process, the images of each color are superimposed and transferred, and then, by executing a secondary transfer process to the recording medium (e.g., a recording sheet, etc.) S, they are transferred all at once.

Around each photoconductor drum, devices are arranged to perform image formation processing in accordance with the rotation of the photoconductor drum. Taking photoconductor drum 20Bk, which forms black images, as an example, charging device 30Bk, developing device 40Bk, primary transfer roller 12Bk, and cleaning device 50Bk, which perform image formation processing, are arranged along the direction of rotation of photoconductor drum 20Bk. An optical writing device 8 is used for writing using writing light Lb, which is performed after charging.

In the overlapping transfer onto the transfer belt 11, the visible images formed on the photoconductor drums 20Y, 20C, 20M, and 20Bk are transferred and overlapped at the same position on the transfer belt 11 as the transfer belt 11 moves in the A1 direction. For this reason, the transfer is performed with shifted timing from the upstream side to the downstream side in the A1 direction by applying a voltage to the primary transfer rollers 12Y, 12C, 12M, and 12Bk arranged opposite the photoconductor drums 20Y, 20C, 20M, and 20Bk across the transfer belt 11.

The photoconductor drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the A1 direction. The photoconductor drums 20Y, 20C, 20M, and 20Bk are provided in image stations for forming yellow, cyan, magenta, and black images, respectively.

The image forming device 100 has four image stations that perform image formation processing for each color, a transfer belt unit 10 that is arranged above and facing each of the photoconductor drums 20Y, 20C, 20M, and 20Bk and that includes a transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12Bk, a secondary transfer roller 5 that is arranged opposite the transfer belt 11 and rotates in conjunction with the transfer belt 11, a belt cleaning device 13 that is arranged opposite the transfer belt 11 and cleans the transfer belt 11, and an optical writing device 8 that is arranged below and facing these four image stations.

The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, and a rotating polygon mirror as a deflection means. The optical writing device 8 is configured to emit writing light Lb corresponding to each color to each of the photoconductor drums 20Y, 20C, 20M, and 20Bk to form electrostatic latent images on the photoconductor drums 20Y, 20C, 20M, and 20Bk. For convenience, the writing light Lb is labeled in FIG. 1 only for the image station for black images, but the same is true for the other image stations.

The image forming apparatus 100 is provided with a sheet feeding device 61 as a paper feed cassette that holds recording medium S to be transported between the photosensitive drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11. In addition, a pair of registration rollers 4 is provided that feeds the recording medium S transported from the sheet feeding device 61 toward the transfer section between each photosensitive drum and the transfer belt 11 at a predetermined timing that matches the timing of the formation of a toner image by the image station. In addition, a sensor is provided to detect when the leading edge of the recording medium S has reached the pair of registration rollers 4.

The image forming apparatus 100 is also provided with a fixing device 200 as a roller fixing type fixing unit for fixing the toner image onto the recording medium S to which the toner image has been transferred, and a discharge roller 7 for discharging the fixed recording medium S to the outside of the main body of the image forming apparatus 100. The upper part of the main body of the image forming apparatus 100 is also provided with a paper discharge tray 17 for stacking the recording medium S discharged to the outside of the main body of the image forming apparatus 100 by the discharge roller 7. The lower side of the paper discharge tray 17 is also provided with toner bottles 9Y, 9C, 9M, and 9Bk filled with toner of each color, yellow, cyan, magenta, and black.

The transfer belt unit 10 includes the transfer belt 11, primary transfer rollers 12Y, 12C, 12M, and 12Bk, as well as a drive roller 72 and a driven roller 73 around which the transfer belt 11 is wound.

The driven roller 73 also functions as a tension applying means for the transfer belt 11, and for this reason, the driven roller 73 is provided with a biasing means using a spring or the like. The transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, 12Bk, the secondary transfer roller 5, and the belt cleaning device 13 constitute the transfer device 71.

The sheet feeding device 61 is disposed at the bottom of the main body of the image forming device 100, and has a feeding roller 3 that contacts the upper surface of the topmost recording medium S. The feeding roller 3 is rotated counterclockwise in the figure to feed the topmost recording medium S toward the pair of registration rollers 4.

The belt cleaning device 13 equipped to the transfer device 71 has a cleaning brush and a cleaning blade arranged to face and contact the transfer belt 11, though detailed illustration is omitted. The belt cleaning device 13 cleans the transfer belt 11 by scraping off and removing foreign matter such as residual toner on the transfer belt 11 with the cleaning brush and cleaning blade.

The belt cleaning device 13 also has a discharge means for removing and disposing of residual toner removed from the transfer belt 11.

[Fixing device]

Figure 2 is a diagram showing a typical regulating member 210. Figure 3 is a vertical cross-sectional view along the axial direction near the regulating member 210 of a typical fixing device 200. Figure 4 is a diagram showing the running trajectory of the fixing member 211 in the cross-sectional view of the fixing device 200 shown in Figure 3 taken along line AA.

As shown in Figures 2 to 4, the fixing device 200 includes a rotatable endless belt-like fixing member 211, a heat source 221 for heating the fixing member 211, a non-rotating nip forming member 223 arranged inside the fixing member 211, a heat transfer assisting member 222 for assisting the heat transfer of the fixing member 211, and a pressure roller 203 (hereinafter also referred to as a counter rotating body) that abuts against the outer peripheral surface of the fixing member 211 and is arranged opposite the nip forming member 223 to form a nip portion N between the fixing member 211 and the pressure roller 203. The recording medium S carrying an unfixed image is passed through the nip portion N to perform fixing.

The fixing member 211 is directly heated by radiant heat from the inner circumference side by multiple heat sources 221 such as halogen heaters. A pressure roller 203 (hereinafter also referred to as a counter rotating body) is provided as a pressure member that forms a nip portion N between the fixing member 211 and the pressure roller 203, and the recording medium S carrying an unfixed image is passed through the nip portion N to perform fixing.

The fixing member 211 has inside thereof a nip forming member 223 arranged opposite the pressure roller 203, a heat transfer assisting member 222 that covers the surface of the nip forming member 223 that faces the inner surface of the fixing member 211, and a stay member 224 that holds the nip forming member 223 against the pressure force from the pressure roller 203.

The nip forming member 223 forms a nip N between the pressure roller 203 and the fixing member 211, and slides indirectly between the inner surface of the fixing member 211 and the heat transfer assisting member 222.

The fixing device 200 passes the recording medium S carrying the toner image through the nip portion N, melting the toner on the recording medium with heat and fixing it to the recording medium with pressure.

The contact surface of the heat transfer assisting member 222 with the fixing member 211 is coated with a sliding coating having a low coefficient of friction. Examples of the sliding coating include a fluorine coating and a glass coating such as diamond-like carbon (DLC) that has high wear resistance.

A lubricant is applied to the contact surface of the heat transfer auxiliary member 222 with the fixing member 211. Suitable lubricants are fluorine grease or silicone oil, which have a high heat resistance. Fluorine grease is a gel-like lubricant made by dispersing a thickener in fluorine oil, which serves as a base oil, and because it has a higher viscosity than oil, it is effective in preventing leakage from sliding parts.

The heat transfer assistance member 222 is provided to prevent heat from accumulating locally and to actively transfer heat in the longitudinal direction to reduce temperature non-uniformity in the longitudinal direction.

For this reason, the material for the heat transfer assistance member 222 is preferably one that allows heat transfer in a short time, such as copper, aluminum, or silver, which have high thermal conductivity. Of these, copper is the most preferable when considering the overall cost, availability, thermal conductivity characteristics, and workability.

In this embodiment, the surface of the heat transfer assistant member 222 that directly contacts the fixing member 211 becomes the nip forming surface.

The fixing member 211 is formed as an endless belt or film using a metal belt such as nickel or SUS or a resin material such as polyimide. The surface layer of the fixing member 211 has a release layer such as a PFA or PTFE layer, which provides release properties so that toner does not adhere to it. An elastic layer formed of a silicone rubber layer or the like may be provided between the base material of the fixing member 211 and the PFA or PTFE layer. If there is no silicone rubber layer, the heat capacity is reduced and the fixing property is improved, but when the unfixed image is crushed and fixed, the minute irregularities on the belt surface are transferred to the image, and a problem may occur in which an citrus peel-like uneven gloss (citrus peel image) remains in the solid part of the image. To improve this, it is necessary to provide a silicone rubber layer of 100 [μm] or more. The deformation of the silicone rubber layer absorbs the minute irregularities and improves the citrus peel image.

As described above, a sliding coating can be applied to the surface of the fixing member 211 that slides against the heat transfer auxiliary member 222. In this case, a material such as polyimide or polyamide-imide can be selected taking into consideration heat resistance and abrasion resistance.

The fixing member 211 is heated directly by radiant heat from the inner surface of the heat source 221 in areas other than the nip portion N.

The pressure roller 203 has an elastic rubber layer on a core metal, and a release layer (PFA or PTFE layer) is provided on the surface to provide releasability. The pressure roller 203 rotates by a driving force transmitted via gears from a driving source such as a motor provided in the image forming apparatus. The pressure roller 203 is also biased toward the fixing member 211 by a spring or the like, and has a predetermined nip width as the elastic rubber layer is crushed and deformed.

The pressure roller 203 may be a hollow roller, and may have a heat source such as a halogen heater. The elastic rubber layer may be solid rubber, but if there is no heater inside the pressure roller 203, sponge rubber may be used. Sponge rubber is more preferable because it has better insulation properties and is less likely to lose heat to the fixing belt.

The fixing member 211 rotates together with the pressure roller 203. In the case of FIG. 3, the pressure roller 203 rotates by a drive source, and the driving force is transmitted to the belt at the nip portion N, causing the fixing member 211 to rotate. The fixing member 211 rotates while being sandwiched in the nip portion N, and is guided by the regulating members 210 at both ends outside the nip portion and travels.

The regulating members 210 are arranged at both axial ends of the fixing member 211, which is formed in a sleeve shape, and regulate the running trajectory of the fixing member 211.

Figure 2 (A) is a front view of the regulating member 210, Figure 2 (B) is a view of the regulating member 210 as viewed from the X1 arrow, and Figure 2 (C) is a view of the regulating member 210 as viewed from the X2 arrow.

As shown in FIG. 2, the regulating member 210 includes an axial regulating portion 210A having a disk shape cut out along the nip surface N in a front view, and a flange portion 210B provided on the flat surface of the axial regulating portion 210A and having a cylindrical shape cut out along the nip surface N.

As shown in FIG. 3, the regulating member 210 is disposed at the axial end of the fixing member 211, and is fitted into the fixing member 211 so that the inner surface of the fixing member 211 contacts the flange portion 210B, and the axial end of the fixing member 211 contacts the axial regulating portion 210A.

The travel trajectories Ca, Cb, and Cc shown in FIG. 4 indicate the travel trajectories in the area La inside the nip area Ln shown in FIG. 3, the area Lb intermediate between the nip area Ln and the flange portion 210B, and the area Lc on the flange portion 210B.

These running trajectories show the running trajectories when using a fixing member 211 that has a larger Young's modulus than a conventional fixing member made of a general resin, such as a fixing member made of polyimide.

The Young's modulus of a conventional resin fixing member is approximately 3 to 10 GPa. In this resin fixing member, the rate of deformation from area La to area Lc is greater for change σ1 in the top surface direction than for change σ2 in the side surface direction.

Fixing members 211 that have a larger Young's modulus than typical resin fixing members include those made of, for example, Ni or SUS (Stainless Used Steel), and the Young's modulus of these fixing members 211 is approximately 200 GPa.

As shown in FIG. 4, the travel path of the fixing member 211, which has a large Young's modulus, is greatly deformed toward the outside of the fixing member 211, but the degree of deformation is greater for the change σ2 in the side direction than for the change σ1 in the top direction. This point will be explained below.

The fixing member 211 is heated by a heat source 221 such as a halogen heater, and is pressurized by the pressure roller 203 and a heat transfer auxiliary member 222 held by a stay member 224 fixed to a side plate (not shown), and rotates in response to the driving force of the pressure roller 203.

The inner surface of the longitudinal end of the fixing member 211 is lifted by the inner surface regulating surface of the flange portion 210B, i.e., the surface that contacts the fixing member 211, so that the fixing member 211 does not come into contact with the built-in heat source 221 or stay member 224, and the movement of the fixing member 211 is stabilized.

When a highly rigid material such as SUS or Ni is used as the base layer of the fixing member 211, the deflection when the same load is applied is smaller than when a resin material is used. In this embodiment, Ni with a Young's modulus of 204 GPa was used as the base layer. Therefore, even when the fixing member 211 is suspended by the flange portion 210B, the displacement amount δ1, which is the difference between the trajectory Cc of the fixing member 211 in the longitudinal direction near the top surface that contacts the inner regulating surface of the flange portion 210B and the trajectories Ca and Cb on the inner side in the longitudinal direction that are not in contact with the inner regulating surface, is small.

Meanwhile, near the upstream and downstream sides of the fixing member 211, the trajectories bulge outward while the radius of curvature in the upstream and downstream directions gradually decreases from trajectory Ca on the inside of the longitudinal nip boundary to trajectories Cb and Cc on the outside of the nip boundary. This is because, in the case of Ca, the sleeve trajectory near the nip surface is constrained by the nip and distorted, but in the case of trajectories Cb and Cc on the outside of the nip boundary, the constraint of the nip surface gradually weakens in the order of Cb and Cc, so the distortion decreases and the sleeve tries to restore to a perfect circular shape with lower distortion energy. As a result, the displacement amount δ2 near the upstream and downstream sides is larger than the displacement amount δ1.

As a result, the fixing member 211 is not parallel to the inner regulating surface of the flange portion 210B near the upstream and downstream, and rubs strongly against the inner regulating surface of the flange portion 210B at the longitudinal center side, accelerating wear on the inner surface of the fixing member 211, which may ultimately cause the end of the fixing member 211 to tear and become unusable.

There is no particular limit to the method for measuring Young's modulus, but it can be measured or compared, for example, by a tensile test on a plate-shaped test piece according to the JIS standard.

The fixing device 200 including the regulating member 210 of each embodiment described below is suitable for a base layer made of a material with a relatively high Young's modulus, such as NI or SUS, when the fixing member 211 is composed of an inner coating layer, a base layer, an elastic layer, and a release layer, in that order from the inside.

More specifically, each regulating member 210 is suitable for a fixing member 211 with a Young's modulus of 70 to 300 Gpa and a thickness of 30 to 50 μm.

[First embodiment]
Fig. 5 is a diagram showing the regulating member 210 of the fixing device 200 according to the present embodiment. Fig. 5(A) is a front view of the regulating member 210, Fig. 5(B) is a plan view of the regulating member 210, i.e., a view seen from the arrow X1, Fig. 5(C) is a side view of the regulating member 210 in the downstream direction, i.e., a view seen from the arrow X2, and Fig. 5(D) is a graph showing the inclination angle θ1 of the normal line M on the downstream side of the flange portion 210B toward the axis G direction.

As shown in FIG. 5, the inclination angle θ1 of the normal line M of the flange portion 210B, which is inclined toward the axis G passing through the center of the arc of the flange portion 210B in a front view, increases from the top surface portion, which is the first region, toward the lower end of the downstream side surface portion, which is the second region.

More specifically, the regulating member 210 has a flange portion 210B that is inclined at a greater angle away from the inner surface of the fixing member 211 as it approaches a second region near the nip portion from a first region farthest from the nip portion.

More preferably, in a front view, when a straight line passing through the downstream lower end of flange portion 210B and axis G is defined as line J, and a straight line obtained by rotating line J 120° counterclockwise around axis G is defined as line K, normal line M starts to incline toward axis G from near the intersection point between line K and flange portion 210B (this intersection point is defined as 0°), and in the vicinity of the portion located most downstream (where -φ1=30° when counterclockwise is defined as positive), inclination angle θ1 reaches a maximum inclination angle θ1MAX, and the maximum inclination angle θ1MAX is maintained toward the lower end of flange portion 210B.

Figure 6 is a graph showing the relationship between the maximum inclination angle θ1MAX of the inclination angle θ1 of the normal line M of the flange portion 210B and the amount of wear of the inner surface of the fixing member 211 that contacts the flange portion 210B.

In FIG. 6, the vertical axis indicates the amount of wear (μm) of the fixing member 211 and the contact width (mm) between the fixing member 211 and the flange portion 210B after printing 300,000 sheets of recording media over an assumed product life, and the horizontal axis indicates the value (angle) of the maximum inclination angle θ1MAX.

The contact width between the fixing member 211 and the flange portion 210B was measured by applying grease to the surface of the flange portion 210B and observing the shape of the grease when it peeled off.

As shown in FIG. 6, the larger the maximum inclination angle θ1MAX, the smaller the amount of scraping at the position on the inner surface of the fixing member 211 corresponding to the vicinity of A in FIG. 5(C) tends to be. Also, the larger the maximum inclination angle θ1MAX, the wider the contact width starting from the vicinity of A in FIG. 5(C).

This means that the larger the maximum inclination angle θ1MAX, the wider the contact width becomes, making it possible to lower the maximum surface pressure and reduce the amount of wear on the fixing member 211.

On the other hand, when the maximum inclination angle θ1MAX exceeds 2.5°, the amount of wear on the inner surface of the fixing member 211 starts to increase. This is because the starting point of contact between the fixing member 211 and the flange portion 210B is near B in Figure 5 (C), and wear on the part of the fixing member 211 corresponding to this part increases.

Therefore, the maximum inclination angle θ1MAX is preferably 1° to 3°, and more preferably 2.5°.

As described above, in the fixing device 200 of this embodiment, at least on the downstream side, the inclination angle θ1 of the normal line M of the flange portion 210B is larger in the second region than in the first region.

Therefore, even when a fixing member 211 with a relatively large Young's modulus is used, it is possible to suppress wear of the fixing member 211.

Second Embodiment
Fig. 7 is a diagram showing the regulating member 210 of the fixing device 200 according to the present embodiment. Fig. 7(A) is a front view of the regulating member 210, Fig. 7(B) is a plan view of the regulating member 210, i.e., a view seen from the arrow X1, Fig. 7(C) is a side view of the regulating member 210 in the upstream direction, i.e., a view seen from the arrow X3, and Fig. 7(D) is a graph showing the inclination angle θ2 of the normal line M2 on the upstream side of the flange portion 210B toward the axis G.

In this embodiment, the normal line M1 on the downstream side of the flange portion 210B is the same as the normal line M of the flange portion 210B in the first embodiment.

As shown in FIG. 7, the inclination angle θ2 of the normal M2 of the flange portion 210B, which is inclined toward the axis G passing through the center of the arc of the flange portion 210B in a front view, increases from the top surface portion, which is the first region, toward the lower end of the upstream side surface portion, which is the second region.

More specifically, the regulating member 210 has a flange portion 210B that is inclined at a greater angle away from the inner surface of the fixing member 211 as it approaches a second region near the nip portion from a first region farthest from the nip portion.

More preferably, in a front view, when a straight line passing through the downstream lower end of flange portion 210B and axis G is defined as line J, and a straight line obtained by rotating line J 120° counterclockwise around axis G is defined as line K, normal line M2 starts to incline toward axis G from near the intersection point between line J and flange portion 210B (this intersection point is defined as 0°), and the inclination angle θ2 reaches a maximum inclination angle θ2MAX near the portion located most upstream (where φ2 = 30° when counterclockwise is defined as positive), and the maximum inclination angle θ2MAX is maintained toward the lower end of flange portion 210B.

Figure 8 is a graph showing the relationship between the maximum inclination angle θ2MAX of the inclination angle θ2 of the normal line M2 of the flange portion 210B and the amount of wear of the inner surface of the fixing member 211 that contacts the flange portion 210B.

In FIG. 8, the vertical axis indicates the amount of wear (μm) of the fixing member 211 and the contact width (mm) between the fixing member 211 and the flange portion 210B after printing 300,000 sheets of recording media over an assumed product life, and the horizontal axis indicates the value (angle) of the maximum inclination angle θ2MAX.

Furthermore, the maximum inclination angle θ1MAX of the normal M1 of the flange portion 210B is 2.5°.

The contact width between the fixing member 211 and the flange portion 210B was measured by applying grease to the surface of the flange portion 210B and observing the shape of the grease when it peeled off.

As shown in FIG. 8, the larger the maximum inclination angle θ2MAX, the smaller the amount of scraping at the position on the inner surface of the fixing member 211 corresponding to the vicinity of A in FIG. 7(C) tends to be. Also, the larger the maximum inclination angle θ2MAX, the wider the contact width starting from the vicinity of A in FIG. 7(C).

This means that the larger the maximum inclination angle θ2MAX, the wider the contact width becomes, making it possible to lower the maximum surface pressure and reduce the amount of wear on the fixing member 211.

On the other hand, when the maximum inclination angle θ2MAX exceeds 2.5°, the amount of wear on the inner surface of the fixing member 211 starts to increase. This is because the starting point of contact between the fixing member 211 and the flange portion 210B is near B in Figure 7(C), and wear on the part of the fixing member 211 corresponding to this part increases.

Therefore, the maximum inclination angle θ2MAX is preferably 1° to 3°, and more preferably 2.5°.

As described above, in the fixing device 200 of this embodiment, the inclination angle θ1 of the downstream normal M1 of the flange portion 210B and the inclination angle θ2 of the upstream normal M2 are larger in the upstream second region and the downstream second region than in the first region on the upstream and downstream sides.

Therefore, even when a fixing member 211 with a relatively large Young's modulus is used, it is possible to more efficiently suppress wear of the fixing member 211.

[Third embodiment]
9A and 9B are diagrams showing the regulating member 210 of the fixing device 200 according to the present embodiment. Fig. 9A is a front view of the regulating member 210, Fig. 9B is a plan view of the regulating member 210, i.e., a view taken along the X1 arrow, Fig. 9C is a graph showing the curvature 1/R1 of the normal line M1 on the downstream side of the flange portion 210B, Fig. 9D is a graph showing the curvature 1/R2 of the normal line M2 on the upstream side of the flange portion 210B, and Fig. 9E is a side view of the regulating member 210 in the upstream direction.

As shown in FIG. 9, the curvature 1/R1 of the normal line M1 of the flange portion 210B of the restricting member 210 and the curvature 1/R1 of the normal line M1 increase from the top surface portion, which is the first region, toward the lower end of the downstream side surface and the lower end of the upstream side surface, which are the second region.

More specifically, the regulating member 210 has a flange portion 210B that is inclined with a greater curvature in a direction away from the inner surface of the fixing member 211 as it approaches a second region near the nip portion from a first region farthest from the nip portion.

More preferably, when viewed from the front, the straight line passing through the downstream lower end of flange portion 210B and axis G is defined as line J, and the straight line obtained by rotating line J 120° counterclockwise around axis G is defined as line K. The curvature 1/R1 of normal line M1 begins to increase near the intersection point between line K and flange portion 210B (this intersection point is defined as 0°), and the curvature 1/R1 reaches a maximum curvature 1/R1MAX near the portion located most downstream (where -φ1=30° when counterclockwise is defined as positive), and the maximum curvature 1/R1MAX is maintained toward the lower end of flange portion 210B.

The curvature 1/R2 of the normal line M2 begins to increase near the intersection of the straight line J and the flange portion 210B (this intersection is set to 0°), and the curvature 1/R2 reaches a maximum curvature 1/R2MAX near the portion located most upstream (where φ2 = 30°, assuming counterclockwise direction to be positive), and the maximum curvature 1/R2MAX is maintained toward the lower end of the flange portion 210B.

Figure 10 is a graph showing the relationship between the maximum curvature xMAX of the curvature x = 1/R1 = 1/R2 of the normal line M1 and normal line M2 of the flange portion 210B and the amount of wear of the inner surface of the fixing member 211 that contacts the flange portion 210B.

In FIG. 10, the vertical axis indicates the amount of wear (μm) of the fixing member 211 after printing 300,000 sheets of recording media over the expected product life, and the horizontal axis indicates the maximum curvature xMAX.

As shown in FIG. 10, the larger the maximum curvature xMAX, the smaller the amount of wear at the position on the inner surface of the fixing member 211 corresponding to the vicinity of A in FIG. 9(E) tends to be.

On the other hand, when the maximum curvature xMAX exceeds 0.01, the amount of wear on the inner surface of the fixing member 211 begins to increase. This is because the contact area between the fixing member 211 and the flange portion 210B is largest at approximately x = 0.01, and conversely, when x is further increased, the contact area becomes narrower, accelerating wear.

Therefore, the maximum curvature xMAX is 0 in the first region, and is preferably 0.005 to 0.02 in the downstream and upstream second regions, and more preferably xMAX = 0.01.

In this embodiment, both the downstream side and the upstream side of the second region have a curvature, but it is also possible to have a curvature on only one of them.

As described above, in the fixing device 200 of this embodiment, the curvature 1/R1 of the normal M1 on the downstream side of the flange portion 210B and the curvature 1/R2 of the normal M2 on the upstream side are larger in the upstream second region and the downstream second region than in the first region on the upstream and downstream sides.

Therefore, even when a fixing member 211 with a relatively large Young's modulus is used, it is possible to more efficiently suppress wear of the fixing member 211.

The method for setting the straight lines K and J in each of the above embodiments is not limited to the conditions in each embodiment.

3 Feeding roller 4 Registration roller pair 7 Discharge roller 8 Device 9Bk Toner bottle 9C Toner bottle 9M Toner bottle 9Y Toner bottle 10 Transfer belt unit 11 Transfer belt 13 Belt cleaning device 17 Paper discharge tray 20Bk Photoconductor drum 20C Photoconductor drum 20M Photoconductor drum 20Y Photoconductor drum 30Bk Charging device 40Bk Developing device 50Bk Cleaning device 61 Sheet feeding device 71 Transfer device 72 Drive roller 73 Driven roller 100 Image forming device 200 Fixing device 203 Pressure roller 210 Regulating member 210A Axial direction regulating portion 210B Flange portion 211 Fixing member 221 Heat source 222 Heat transfer auxiliary member 223 Nip forming member 224 Stay member

JP 2018-116268 A

Claims (2)

a rotatable, endless fixing member having a Young's modulus of 70 to 300 Gpa;
a pressure member that contacts an outer peripheral surface of the fixing member to form a nip portion;
a regulating member disposed at each end of the fixing member, in contact with an inner surface of the fixing member, the regulating member having a flange portion inclined more in a direction away from the inner surface of the fixing member in a second region adjacent to the nip portion than in a first region farthest from the nip portion;
Equipped with
The flange portion is
a cylindrical shape has a portion cut out along a nip portion, and when the downstream side of the cut-out shape with respect to the rotation of the fixing member is defined as a downstream lower end portion and the upstream side of the cut-out shape is defined as an upstream lower end portion, the downstream lower end portion is disposed in the second region, a part of the cylindrical shape is disposed in the first region, and another part of the cylindrical shape is disposed in the second region, and the second region is inclined toward an axis that passes through an arc center of the flange portion and is parallel to the rotation axis of the pressure member,
The tilt angle inclined toward the axis is 0° in the first region, and the maximum tilt angle in the second region is 1° to 3°;
When a straight line passing through the shaft and the downstream lower end is a straight line J, and a straight line passing through the shaft and the upstream lower end is a straight line K,
The fixing device begins to incline toward the axis from the intersection of the straight line K and the flange portion, and the inclination angle reaches its maximum at a position where the straight line K is rotated 30° downstream around the axis, and the maximum inclination angle is maintained toward the lower end of the flange portion. An image forming apparatus comprising the fixing device of claim 1 .

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