Image heating apparatus and image forming apparatus

Abstract

To provide an image heating device capable of suppressing film deformation. [Solution] The image heating device comprises a film, a heater for heating the film, a roller that contacts the outer surface of the film and forms a nip portion between itself and the film, and a regulating member 201 disposed in the internal space of the film and regulating the rotational shape of the film, the regulating member 201 having a plurality of first regulating portions 320 arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, the regulating member 201 further having a second regulating portion 330 disposed between the plurality of first regulating portions 320 in the generatrix direction, the upstream end of the second regulating portion 330 is located downstream of the upstream end of the first regulating portion 320 in the transport direction, and in directions perpendicular to the generatrix direction and the transport direction, the distance from the nip portion to the tip of the second regulating portion 330 is greater than the distance from the nip portion to the upstream end of the film in the transport direction.

Description

Technical Field

[0001] The present invention relates to an image heating device and an image forming apparatus.

Background Art

[0002] As an image heating device used in an electrophotographic image forming apparatus, a film heating type image heating device excellent in power saving performance and transition to a fixable state in a short time is known. The film heating type image heating device includes a rotatable film, a heater that contacts the film to heat the film, a roller that abuts on the outer peripheral surface of the film to form a nip portion, and the like. A recording material carrying an unfixed toner image is heated while being sandwiched and conveyed at the nip portion, whereby the toner image on the recording material is fixed to the recording material.

[0003] As a film heating type image heating device, a configuration is known in which a regulating member (guide member) that regulates the rotation shape of the film while guiding the rotation of the film is provided in the internal space of the film. For example, Patent Document 1 discloses a regulating member provided with guide ribs for regulating the rotation shape of the film. Further, Patent Document 2 discloses a regulating member having a semi-arc-shaped outer surface extending in the generatrix direction of the film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] If the contact area of ​​the regulating member with the film is excessively large, heat from the film is absorbed by the regulating member, increasing the frictional resistance acting on the film, which is undesirable. On the other hand, in a configuration where the regulating member only partially contacts the film in the direction of the film's generatrix, the film may deform or break due to uneven heat distribution in the direction of the film's generatrix.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide an image heating device that suppresses deformation of the film. [Means for solving the problem]

[0007] To achieve the above-mentioned objectives, the image heating device according to this application is: A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member disposed in the internal space of the film and restricting the rotational shape of the film, the restricting member having a plurality of first restricting portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion arranged between the plurality of first regulating portions in the direction of the busbar, In the aforementioned transport direction, the upstream end of the second restricting section is downstream of the upstream end of the first restricting section. Located, In the direction perpendicular to the busbar direction and the transport direction, the distance from the nip portion to the tip of the second restricting portion is greater than the distance from the nip portion to the upstream end of the film in the transport direction. Furthermore, in order to achieve the above-mentioned objectives, the image heating device according to this application is A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member disposed in the internal space of the film and restricting the rotational shape of the film, the restricting member having a plurality of first restricting portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion that extends along the direction of the generatrix from one of the plurality of first regulating portions to an adjacent first regulating portion. The second regulating section is characterized in that it is provided at the same position as the upstream end of the film in the transport direction in a direction perpendicular to the busbar direction and the transport direction. [Effects of the Invention]

[0008] According to the present invention, an image heating device capable of suppressing deformation of the film can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of an image forming apparatus according to the first embodiment. [Figure 2] This is a schematic cross-sectional view of the image heating device according to the first embodiment. [Figure 3] This is an explanatory diagram of the configuration of the image heating device according to the first embodiment. [Figure 4] This diagram shows how the fixing film deforms. [Figure 5] This is an explanatory diagram of the buckling deformation of the fixing film. [Figure 6] This figure shows an example of a fixing film that has buckled and deformed. [Figure 7] This is an explanatory diagram of the starting point of buckling deformation in the fixing film. [Figure 8] This is an explanatory diagram of the film guide relating to the comparative example and the first embodiment. [Figure 9] It is an explanatory diagram of a film guide according to a modification example. [Figure 10] It is an explanatory diagram of a film guide according to a second embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, modes for carrying out this invention will be exemplarily and specifically described based on the embodiments. However, dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment should be appropriately changed according to the configuration of the device to which the invention is applied and various conditions. That is, it is not intended to limit the scope of this invention to the following embodiments. Also, not all of the features described in the following embodiments are essential for the solution means of the invention.

[0011] <First Embodiment> An example in which the present invention is applied to an electrophotographic laser beam printer will be described as a first embodiment. The image forming apparatus 1 according to the first embodiment receives a print signal, which is image information transmitted from an external device such as a personal computer (not shown), and forms an image on a recording material P using electrophotographic image formation.

[0012] (1. Configuration of Image Forming Apparatus) FIG. 1 is a schematic cross-sectional view of the image forming apparatus 1 according to the first embodiment. The external device and the image forming apparatus 1 are connected via a control unit 400 in the image forming apparatus 1. When the control unit 400 receives a print signal from the external device, the image forming apparatus 1 executes an image forming operation.

[0013] The image forming operation of the image forming apparatus 1 will now be described. First, when a laser beam modulated according to image information is emitted from the scanner unit 21, the surface of the photosensitive drum 19, which has been charged to a predetermined polarity potential by the charging roller 16, is scanned. This forms an electrostatic latent image on the photosensitive drum 19. Toner is supplied to this electrostatic latent image from the developing roller 17, and the electrostatic latent image on the photosensitive drum 19 is developed as a toner image as a visible image.

[0014] The recording material P is stored in a paper feed cassette 11 and is fed one sheet at a time by a paper feed roller 12 and transported to a registration roller pair 14 by a transport roller pair 13. The arrows in Figure 1 indicate the transport direction of the recording material P. The recording material P is transported from the registration roller pair 14 to the transfer nip in time with the timing when the toner image on the photosensitive drum 19 reaches the transfer nip formed by the photosensitive drum 19 and the transfer roller 20. The toner image on the photosensitive drum 19 is transferred to the recording material P as it passes through the transfer nip. This series of operations is performed by the image forming unit of the image forming apparatus 1. Toner that remains on the photosensitive drum 19 without being transferred to the recording material P at the transfer nip is scraped off by a drum cleaner 18 in preparation for the next image formation.

[0015] Subsequently, the recording material P is heated and pressurized by the image heating device 2, which acts as a fixing device (fixing unit), and the toner image is heat-fixed to the recording material P. The heat source of the image heating device 2 is controlled by the control unit 400 to maintain the temperature necessary to fix the unfixed toner image to the recording material P. The recording material P, which carries the fixed toner image, is discharged to the paper output tray 35 at the top of the image forming apparatus 1 by the transport roller pair 26 and the paper output roller pair 27. The discharge of the completed recording material P from the image forming apparatus 1 is detected by the paper output detection sensor 28, which is a detection means provided near the paper output roller pair 27. The image forming process is completed when the paper output detection sensor 28 detects the discharge of the recording material P. The paper output detection sensor 28 may also have a full load detection function that detects when the number of recording materials P loaded in the paper output tray 50 is below a specified number.

[0016] The main body of the image forming apparatus 1 has a process cartridge 3 that is detachably attached. The process cartridge 3 consists of a developing unit containing a developing roller 17, a photosensitive drum 19 and toner, and a cleaning unit including a charging roller 16 and a drum cleaner 18. The image forming apparatus 1 is also equipped with a motor 33 that drives the image forming apparatus 1, the image heating device 2, the process cartridge 3, etc.

[0017] In this embodiment, the maximum paper feed width of the image forming apparatus 1, which is the width in the direction perpendicular to the transport direction of the recording material P, is 216 mm [LTR size]. By transporting the recording material P at a transport speed of 233 mm / second, the image forming apparatus 1 can print 42 LTR size sheets per minute and 40 A4 size sheets [210 mm x 297 mm] per minute. Furthermore, the image forming apparatus 1 is capable of forming images on both sides of the recording material P (referred to as double-sided printing).

[0018] Double-sided printing is performed in the following manner: Once the first toner image is formed on the front surface of the recording material P, the recording material P passes through the image heating device 2, and after the rear end of the recording material P passes the position of the flapper 29 for transport path switching, the position of the flapper 29 is switched to the double-sided transport side.

[0019] Simultaneously with the switching of the flapper 29, the rotation direction of the paper discharge roller pair 27 is reversed by a reverse clutch (not shown) that determines the rotation direction of the paper discharge roller pair 27. The recording material P is drawn into the image forming apparatus 1 by the reverse-rotating paper discharge roller pair 27 and transported to the double-sided transport path 30. The recording material P, which has been inverted so that the second surface of the recording material P becomes the surface on which the image is formed, is transported to the double-sided transport path 30. The internal double-sided transport roller pair 31 and the main unit re-feed roller pair 32 transport the material back to the transport roller pair 13 and the registration roller pair 14. Then, a toner image is formed on the side of the recording material P opposite to the side where the image was formed after it passed through the double-sided transport path 30.

[0020] The process from the registration roller pair 14 onward is the same as the image formation process described above. That is, a toner image is formed on the second side of the recording material P, and after the recording material P passes through the image heating device 2 again, the recording material P is discharged from the image forming apparatus 1 by the paper discharge roller pair 27 and stacked so that the second side faces the paper discharge tray 35. Duplex printing has seen increased demand in recent years due to growing environmental awareness.

[0021] (2. Configuration of the image heating device) The configuration of the image heating device 2 according to the first embodiment will be described. The image heating device 2 heats the image formed on the recording material P while conveying the recording material in the conveying direction D1 with a fixing nip N which serves as a nip section. In the following description, the direction parallel to the conveying direction of the recording material P in the image heating device 2 is the X direction, the direction parallel to the generatrix direction and rotation axis of the fixing film 202 of the image heating device 2 is the Y direction, and the direction perpendicular to the planar fixing nip N is the Z direction. The X, Y, and Z directions intersect each other (orthogonal in this embodiment).

[0022] Figure 2 is a schematic cross-sectional view of the image heating device 2 according to the first embodiment, showing the image heating device 2 as viewed in the Y direction. Figure 3 is an explanatory diagram of the configuration of the image heating device 2 according to the first embodiment, showing the image heating device 2 as viewed in the Z direction. In Figure 3, some components such as the fixing film 202 and the heater 300 that constitute the image heating device 2 are shown as transparent, and some components are omitted from the illustration.

[0023] The image heating device 2 comprises a rotatable fixing film 202 as an endless belt, a heater 300 for heating the fixing film 202, and a pressure roller 208 that forms a fixing nip N together with the heater 300 via the fixing film 202. Furthermore, the image heating device 2 comprises a film guide 201 that holds the heater 300 and guides the rotation of the fixing film 202, and metal stays 204 that hold both ends of the fixing film 202. The heater 300, film guide 201, and metal stays 204 are arranged in the internal space of the fixing film 202.

[0024] The fixing film 202 is a thin, tubular, multi-layered, high-heat-resistant film made of a heat-resistant resin or metal. The fixing film 202 has its generatrix direction (longitudinal direction) parallel to the Y direction and is configured to rotate about a rotation axis parallel to the Y direction.

[0025] The fixing film 202 has a base layer made of a heat-resistant resin such as polyimide, or a metal such as stainless steel. Furthermore, the surface of the fixing film 202 is provided with a release layer made of a high-performance fluororesin such as PFA, which has excellent heat resistance and release properties to prevent toner adhesion. In addition, to improve image quality, a highly heat-resistant rubber such as silicone rubber may be formed as an elastic layer between the base layer and the release layer. In this embodiment, a fixing film 202 with an outer diameter of 24 mm and an elastic layer is used.

[0026] The pressure roller 208 is a roller having a core metal 209 made of a material such as iron or aluminum, and an elastic layer 210 made of a highly heat-resistant rubber material such as silicone rubber. With this configuration, the pressure roller 208 has a hardness appropriate for a pressure member, and a fixing nip N corresponding to the image heating device 2 can be obtained. In this embodiment, a pressure roller 208 with an outer diameter of 25 mm and an elastic layer with a thickness of 4 mm is used.

[0027] The pressure roller 208 rotates in the direction of arrow R1 (counterclockwise in Figure 2) by receiving rotational driving force from the motor 33. As the pressure roller 208 rotates, the fixing film 202 rotates in the direction of arrow R2 (clockwise in Figure 2). The pressure roller 208 has its generatrix direction (longitudinal direction) parallel to the Y direction and is configured to rotate around a rotation axis parallel to the Y direction.

[0028] The heater 300 is a heating source that contacts the inner surface of the fixing film 202 and generates heat to heat the fixing film 202. The heater 300 is made of ceramic as its base material, with the Y direction as its longitudinal direction. In this embodiment, the heater 300 uses a ceramic substrate 305 made of alumina or similar material, which has high electrical insulation properties, excellent thermal conductivity, and low heat capacity. In this embodiment, a ceramic substrate 305 made of alumina (Al2O3) as its base material was used.

[0029] On the side of the ceramic substrate 305 facing away from the fixing nip N, an electrical heating resistance layer 302 made of silver palladium or the like is formed by screen printing or the like, along the longitudinal direction of the heater 300 (ceramic substrate 305). Furthermore, in order to ensure the insulation of the electrical heating resistance layer 302, the electrical heating resistance layer 302 is covered with a thin protective glass layer 307 with a thickness of about 50 μm.

[0030] A sliding glass layer 308 with a thickness of approximately 10 μm is formed on the surface of the ceramic substrate 305 facing the fixing nip N side, in order to ensure sliding properties with the fixing film 202. A fluorine-based grease (not shown) with excellent heat resistance is applied to the sliding glass layer 308 to enhance sliding properties with the fixing film 202. In other words, the sliding glass layer 308 constitutes the contact surface of the heater 300 with respect to the fixing film 202.

[0031] The current-conducting heat-retaining resistance layer 302 generates heat when AC is supplied from the heater electrode 301 located at the longitudinal end of the heater 300. Due to the heat generated by the current-conducting heat-retaining resistance layer 302, the entire heater 300, including the ceramic substrate 305, protective glass layer 307, and sliding glass layer 308, rapidly rises in temperature.

[0032] The rise in temperature of the heater 300 is detected by a thermistor 310, which is a temperature sensing element located on the back of the heater 300 (on the side of the protective glass layer 307), and the information is fed back to the control unit 400 (control circuit). The power supplied to the energized heating resistance layer 302 is controlled so that the temperature of the heater 300 detected by the thermistor 310 is maintained at a predetermined fixing temperature.

[0033] Furthermore, the heater 300 is provided with a safety element 312 that activates when the heater 300 overheats and cuts off the power supplied to the energizing heat resistance layer 302. The safety element 312 is, for example, a thermoswitch or a thermal fuse, and is positioned either directly on the heater 300 or with a gap between it and the heater 300.

[0034] The heater 300 is held in a film guide 201, which is a heater holding member made of heat-resistant resin. The heater 300 heats the recording material P, which is held between the fixing film 202 and the pressure roller 208 at the fixing nip N, by heating the fixing film 202.

[0035] The film guide 201 is positioned in the internal space of the fixing film 202 and is a restricting member that guides the rotation of the fixing film 202 and restricts the rotational shape of the fixing film 202. Here, the rotational shape of the fixing film 202 is the shape of the fixing film 202 when it is rotated in accordance with the pressure roller 208. When the fixing film 202 rotates, various external forces are applied to the fixing film 202, so it rotates in a deformed shape from when it is stopped. The film guide 201 is configured to contact the fixing film 202 and restrict the rotational shape of the fixing film 202 in order to suppress excessive deformation of the fixing film 202. The film guide 201 is a component whose longitudinal direction is in the Y direction.

[0036] The film guide 201 has multiple guide ribs 320 as restricting parts that control the rotational shape of the fixing film 202. The multiple guide ribs 320 are provided on both the upstream and downstream sides of the conveying direction D1 with respect to the fixing nip N, and are arranged along the generatrix direction (Y direction) of the fixing film 202. In addition, flanges 315 are fixed to the film guide 201 as film holding members that hold both ends of the fixing film 202.

[0037] The guide ribs 320 are formed in a smooth, semi-circular curved shape that conforms to the rotational trajectory of the fixing film 202, in order to guide the rotation of the fixing film 202 along the inner surface of the fixing film 202. In the transport direction D1, the guide ribs 320 upstream of the fixing nip N protrude upstream, and the guide ribs 320 downstream of the fixing nip N protrude downstream. In other words, the guide ribs 320 are protrusions that extend upstream and downstream from the fixing nip N in the transport direction D1. The smooth semi-circular shape and the amount of protrusion are not limited to those shown in the figure, and should be configured to be optimal according to the specifications of the image forming apparatus 1 and the image heating apparatus 2.

[0038] The guide rib 320 prevents the fixing film 202 from contacting the film guide 201 and metal stay 204 over a wide area, thereby reducing the contact area. Furthermore, even if the fixing film 202 does come into contact with the guide rib 320, the small contact area reduces frictional resistance, enabling smooth and stable driven rotation.

[0039] The metal stay 204, under pressure not shown, presses the film guide 201 toward the pressure roller 208. While the recording material P is held and conveyed at the fixing nip N, heat from the heater 300 is applied through the fixing film 202, thereby fixing the unfixed toner image on the recording material P.

[0040] (3. Buckling deformation of the fixing film) Next, we will explain the buckling deformation of the fixing film 202. Films like the fixing film 202 used in the film heating method are made thin using high-performance resins or metals to reduce heat capacity and achieve energy saving and quick transition to a state where fixing is possible, and may undergo buckling deformation.

[0041] The fixing film 202 is supported at both longitudinal ends by flanges 315, and is held between a heater 300 and a pressure roller 208 over almost its entire longitudinal area so that a fixing nip N is formed. A specific example of buckling deformation occurring in the longitudinal center of the fixing film 202 in this state will be described below.

[0042] The following explains the state of the fixing film 202 during rotation and the reason for buckling deformation. Figures 4(a) to 4(c) show how the fixing film 202 deforms. Figures 5(a) to 5(c) are explanatory diagrams of the buckling deformation of the fixing film 202.

[0043] In the first embodiment of the film heating type image heating device 200, the recording material P is transported by the rotational drive of a pressure roller 208, and the fixing film 202 is driven to rotate by the pressure roller 208 and the transported recording material P. In such an image heating device 200, in order to prevent wrinkles from occurring as a deformation phenomenon of the printed recording material P, a predetermined transport force is applied to the recording material P as it passes through the fixing nip N to ensure stable transport of the recording material P.

[0044] Wrinkles can occur when force acts from the edge to the center of the recording material P in the width direction (direction perpendicular to the transport direction D1) as it passes through the fixing nip N. When the recording material P becomes compressed and passes through the fixing nip N in that compressed state, wrinkles occur in the recording material P. Thus, wrinkles are a phenomenon that is more likely to occur in the central part where the material is compressed. Even if wrinkles do not occur, the transport of the recording material P as it passes through the fixing nip N becomes unstable, and the unfixed toner image may come into contact with the fixing film 202 before the fixing nip N, causing distortion of the toner image. To stabilize the transport of the recording material P as it passes through the fixing nip N, such deformation can be avoided by applying a transport force to the recording material P in a direction that pulls the recording material P from the center toward the edges.

[0045] As a concrete measure, the aforementioned transport force can be obtained by shaping the fixing nip N such that the width in the transport direction D1 is equal to or wider at both ends in the longitudinal direction of the fixing nip N than at the center. One example of this is to make the outer diameter of the pressure roller 208 wider at the ends than at the center in the longitudinal direction, and to make the peripheral speed of the pressure roller 208 at the ends faster than at the center. By creating a transport force such that the ends of the recording material P are transported faster than the center, a force is applied in a direction that pulls the recording material P from the center to the ends, thereby achieving stable transport of the recording material P. The fixing film 202 receives a force in the transport direction D1 from the recording material P that is transported with such a transport force.

[0046] On the other hand, both ends of the fixing film 202 are supported by flanges 315. During rotation, the fixing film 202 as a whole is driven to rotate by these forces, bending downstream in the direction of transport of the recording material P, starting from the part supported by the flanges 315. Figures 4(a) to 4(c) show the state of the fixing film 202 as viewed from above in the Z direction of the image heating device 2. Similar to Figure 3, Figures 4(a) to 4(c) show the longitudinal arrangement relationship of the fixing film 202 and the heater 300 that constitute the image heating device 2, so some components such as the fixing film 202 are shown as transparent, and some components are omitted from the illustration.

[0047] Figure 4(a) shows the state in which the fixing film 202 has stopped rotating. When the fixing film 202 has stopped rotating and is not receiving a force in the transport direction D1 from the recording material P, the fixing film 202 is stretched straight in the longitudinal direction (general direction) and is not deformed.

[0048] Figure 4(b) shows the fixing film 202 rotating and bending by a deflection amount Lb. In Figure 4(b), the outline of the fixing film 202 before deformation (the state in Figure 4(a)) is shown by a dotted line. The deflection amount Lb is the amount by which the central part bends downstream in the transport direction D1 from both ends of the longitudinal side which are restricted by the flange 315. Due to the force received from the recording material P, the fixing film 202 bends in an arc shape so that it is convex downstream in the transport direction D1. Thus, during the image forming operation, the fixing film 202 may rotate with its longitudinal central part bent downstream in the transport direction D1.

[0049] The shape of the flange 315, which holds the ends of the guide rib 320 and the fixing film 202, is designed to prevent the inner surface of the fixing film 202 from contacting the guide rib 320 even if it is slightly deformed, taking into account the state in which the fixing film 202 is bent. However, it is difficult to completely prevent the fixing film 202 from contacting the guide rib 320 with the shape of the flange 315 alone, and depending on the image forming conditions, the fixing film 202 may rub strongly against the guide rib 320.

[0050] Figure 4(c) shows the fixing film 202 rotating and bending with a deflection amount Lc greater than the deflection amount Lb, causing it to contact the guide rib 320. In Figure 4(c), the outline of the fixing film 202 before deformation (the state shown in Figure 4(a)) is shown by a dotted line. When the fixing film 202 contacts the guide rib 320, heat is absorbed from the fixing film 202 by the guide rib 320 through the contact area. This can cause temperature unevenness in the longitudinal direction of the fixing film 202, potentially worsening fixing performance and uniformity due to heat unevenness. Furthermore, As the fixing film 202 continues to rotate while in contact with the guide rib 320, there is a risk that wear and deformation may occur on the inner surface of the fixing film 202.

[0051] Furthermore, the factors that cause temperature unevenness and deformation in the fixing film 202 are not limited to those mentioned above; temperature unevenness can also occur due to the image pattern formed during the image forming operation. Next, we will explain examples of how image patterns can cause temperature unevenness and deformation.

[0052] The heater 300 of the image heating device 200 is generally designed to generate heat uniformly along its length. During the fixing operation, the surface temperature of the fixing film 202 in contact with the recording material P decreases as heat is absorbed by the recording material P. At this time, the amount of decrease in surface temperature differs depending on whether or not there is a toner image. In areas with a toner image, more heat is required to melt the toner, so the decrease in temperature is greater.

[0053] Specific examples of temperature unevenness and bending in the fixing film 202 caused by the image pattern will be explained using Figures 5(a) to (c). In this example, we compare pattern P1, in which a character image is formed over the entire surface of the recording material P, and pattern P2, in which a toner image long in the transport direction D1 is formed at both ends in the width direction of the recording material P. Figure 5(a) shows pattern P2, in which a toner image long in the transport direction D1 is formed at both ends in the width direction of the recording material P.

[0054] Figure 5(b) is a graph showing the surface temperature difference [°C] of the fixing film 202 and the surface temperature difference [°C] of the pressure roller 208 when recording materials P with patterns P1 and P2 are passed through continuously and the image forming operation is performed a predetermined number of times. Here, the surface temperature difference is the difference in surface temperature between the edges and the center in the longitudinal direction, and is the value obtained by subtracting the surface temperature of the center from the surface temperature of the edges. In other words, the surface temperature difference represents how much lower the surface temperature of the longitudinal edges is compared to the longitudinal center. Figure 5(b) shows, from left to right, the surface temperature difference of the fixing film 202 when pattern P1 is printed, the surface temperature difference when pattern P2 is printed, and the surface temperature difference of the pressure roller 208 when pattern P1 is printed and the surface temperature difference when pattern P2 is printed.

[0055] As shown in Figure 5(b), the surface temperature difference of the fuser film 202 during pattern P1 printing was approximately 0°C, and the surface temperature difference during pattern P2 printing was approximately -6°C. Similarly, the surface temperature difference of the pressure roller 208 during pattern P1 printing was approximately 0°C, and the surface temperature difference during pattern P2 printing was approximately -4°C. Thus, the surface temperature difference between the fuser film 202 and the pressure roller 208 is larger during pattern P2 printing compared to pattern P1 printing. In other words, when printing images with toner images in the same position consecutively, the decrease in surface temperature at the toner image is greater than at the area without a toner image.

[0056] The elastic layer 210 of the pressure roller 208 is made of silicone rubber and expands in response to temperature. Therefore, when the temperature of both ends of the pressure roller 208 decreases, the center expands more than the ends. As a result, the pressure roller 208 becomes thicker in the center compared to the ends.

[0057] Figure 5(c) is a graph showing the outer diameter profile of the pressure roller 208, with the outer diameter profile when pattern P1 is printed shown by a dotted line and the outer diameter profile when pattern P2 is printed shown by a solid line. In the graph of Figure 5(c), the vertical axis is the outer diameter [mm] of the pressure roller 208, and the horizontal axis is the longitudinal position [mm] of the pressure roller 208 (distance from one end in the longitudinal direction). As shown in Figure 5(c), it can be seen that the outer diameter at both ends in the longitudinal direction of the pressure roller 208 is smaller when pattern 2 is printed compared to when pattern 1 is printed.

[0058] When the outer diameter of the central part becomes larger than the outer diameter of the edges, the peripheral speed of the central part becomes faster than the peripheral speed of the edges, so the central part of the fixing film 202 that is rotated by the pressure roller 208 also becomes faster than the edges. This will result in the film being subjected to a force that causes it to rotate rapidly. When subjected to such a force, the fixing film 202 may deform in its longitudinal center and rub strongly against the guide rib 320, as shown in Figure 4(c).

[0059] When the fixing film 202 rubs strongly against the guide ribs 320, buckling deformation may occur between the guide ribs 320 aligned in the Y direction, causing greater bending and deformation. Figures 6(a) and (b) show examples of fixing film 202 that have undergone buckling deformation.

[0060] Buckling deformation will be explained in more detail. Buckling deformation refers to a phenomenon in which, when the load (force that causes bending) applied to a structure (in this embodiment, the anchoring film 202) increases, it deforms significantly and changes in state (a dynamic change from a reversible change to an irreversible change) when it exceeds a certain load value, resulting in a large deflection.

[0061] The fixing film 202 is a cylindrical structure formed from a thin-walled high-performance resin such as polyimide or a metal such as stainless steel to achieve low heat capacity, and its buckling strength is not large. To increase the buckling strength, it is conceivable to make the fixing film 202 thicker, but this is not suitable for the image heating device 2 that uses a film heating method for the following reasons.

[0062] If the fixing film 202 is made of a metal material such as stainless steel, increasing its thickness increases the risk of cracking due to repeated stress as it passes through the fixing nip N. If the fixing film 202 is made of a high-performance resin such as polyimide, increasing its thickness reduces its thermal conductivity. Therefore, it is difficult to increase the buckling strength by increasing the thickness of the fixing film 202.

[0063] Furthermore, as a film guide 201 that prevents buckling deformation of the fixing film 202, a configuration could be considered in which, instead of providing guide ribs, the deformation of the fixing film 202 is restricted by a surface that extends straight in the longitudinal direction. In such a configuration, the inner surface of the fixing film 202 comes into planar contact with the film guide 201, preventing buckling deformation, but causing more heat to be lost to the film guide 201. As a result, the heater 300 will need to be lit more often to compensate for the lost heat, which ultimately increases power consumption and contradicts energy-saving principles. In addition, there is concern that the frictional resistance acting on the fixing film 202 will increase.

[0064] Furthermore, to suppress buckling deformation of the fixing film 202, it is conceivable to increase the number of guide ribs 320. However, if the fixing film 202 has more opportunities to come into contact with the guide ribs 320, the concern about temperature unevenness in the fixing film 202 also increases. Therefore, it is not desirable to excessively increase the number of guide ribs 320.

[0065] Next, we will explain in more detail the buckling deformation of the fixing film 202. Buckling deformation is a phenomenon that occurs when the fixing film 202 is rotating. Therefore, we installed an industrial fiberscope upstream of the transport direction D1 of the image heating device 2 and observed the fixing film 202.

[0066] Figure 7 is an explanatory diagram of the starting point of buckling deformation of the fixing film 202. Buckling deformation occurs upstream of the fixing nip N in the transport direction D1, and the starting point of buckling deformation is near the position where the width of the fixing film 202 in the transport direction D1 (X direction) is maximum. In Figure 7, the position where the width of the fixing film 202 in the transport direction D1 is maximum is shown as the starting point K. The starting point K can also be described as the upstream end of the fixing film 202 in the transport direction D1. The reason why buckling deformation occurs near the starting point K is that the width W of the fixing film 202 changes from the point where it widens to its maximum width (from the highest point of the fixing film 202 in the figure) to the point where the width W narrows. This is because it is a point of change in the part that changes in that way.

[0067] At the moment buckling deformation occurs, the anchoring film 202 is rotating, so the buckling deformation that occurs near the starting point K is observed to have occurred in the region shown as region A in Figure 7, which is the region downstream from the starting point K in the rotational direction R2 of the anchoring film 202. When buckling deformation occurs consistently, it is observed that the width of the anchoring film 202 in the transport direction D1 is deformed around the starting point K, which is its maximum width W. The anchoring film 202 that has undergone buckling deformation rotates and moves while buckling, and enters the anchoring nip N.

[0068] Buckling deformation can sometimes be resolved when the deformed portion enters the fixing nip N, as the fixing nip N restricts the rotational trajectory of the fixing film 202. However, repeated entry into the fixing nip N while buckling deformation is present can cause plastic deformation of the fixing film 202, leaving traces of the buckling deformation on the film. When a toner image is fixed to the fixing film 202 with traces of buckling deformation, these traces are transferred to the recording material P. Furthermore, continued use in such a state may cause the fixing film 202 to crack and break at the buckled portion.

[0069] As the fixing film 202 continues to rotate, the buckling deformation spreads not only to region A but also upstream in the direction of rotation (R2 direction) from the starting point K. The range in which buckling deformation occurs upstream of the starting point K of the fixing film 202 in the direction of rotation is approximately a distance HT (see Figure 7) from the starting point K in the Z direction. Here, distance HT is the same distance HN as the distance from the fixing nip N to the starting point K in the Z direction.

[0070] (4. Detailed structure of the film guide) In the first embodiment, a sub-guide rib 330 is provided on the film guide 201 as a configuration to suppress buckling deformation of the fixing film 202. The detailed configuration of the film guide 201 according to the first embodiment will be described below.

[0071] Figures 8(a) to 8(d) are explanatory diagrams of the film guide 201 according to the comparative example and the first embodiment. Figure 8(a) is a perspective view of the film guide 201 according to the comparative example. Figure 8(b) is a diagram showing the FF cross-sectional view and HH cross-sectional view of Figure 8(a) together. Both the FF cross-section and the HH cross-section are cross-sections passing through the guide rib 320 when the film guide 201 is viewed in the longitudinal direction.

[0072] In the comparative example, multiple guide ribs 320 (13 in the illustrated example) are arranged longitudinally on both the upstream and downstream sides of the conveying direction D1. All of the multiple guide ribs 320 have the same shape, and the cross-sectional shape of the film guide 201 is the same in the FF section and the HH section. In this configuration, as described above, there is a risk of buckling deformation of the fixing film 202 occurring between guide ribs 320 that are adjacent to each other in the longitudinal direction.

[0073] Therefore, in the first embodiment, in addition to the guide rib 320, a plurality of sub-guide ribs 330 are provided on the film guide 201 to restrict the rotational shape of the fixing film 202 and suppress buckling deformation. Figure 8(c) is a perspective view of the film guide 201 according to the first embodiment. Figure 8(d) is a diagram showing the RR cross section and the QQ cross section of Figure 8(c) together. The RR cross section is a cross section passing through the guide rib 320 when the film guide 201 is viewed in the longitudinal direction, and the HH cross section is a cross section passing through the sub-guide rib 330 when the film guide 201 is viewed in the longitudinal direction.

[0074] The film guide 201 includes a heater holding section 340 that holds the heater 300, and a plurality of guide ribs 320 and a plurality of sub-guide ribs 330 that restrict the rotational shape of the fixing film 202. The film guide 201 has two types of restricting parts: a guide rib 320 as a first restricting part and a sub-guide rib 330 as a second restricting part. The guide rib 320 is provided on the upstream and downstream sides of the transport direction D1 with respect to the heater holding part 340 and the fixing nip N, while the sub-guide rib 330 is provided only on the upstream side of the transport direction D1 with respect to the heater holding part 340 and the fixing nip N.

[0075] The sub-guide rib 330 is a protruding portion that extends upstream of the fixing nip N in the transport direction D1, and is a restricting portion that restricts the rotational shape of the fixing film 202. The sub-guide rib 330 is provided between two guide ribs 320 in the longitudinal direction of the film guide 201. The amount of protrusion of the sub-guide rib 330 upstream in the transport direction D1 is different from the amount of protrusion of the guide rib 320 upstream in the transport direction D1. In other words, as shown in Figure 8(c), on the upstream side of the film guide 201 in the transport direction D1, guide ribs 320 and sub-guide ribs 330 with different protrusion amounts are arranged alternately in the Y direction. In the first embodiment, the multiple sub-guide ribs 330 are arranged such that one or more sub-guide ribs 330 are adjacent in the Y direction to all guide ribs 320 provided on the upstream side of the transport direction D1.

[0076] The sub-guide rib 330, like the guide rib 320, is formed in a curved shape that is convex on the upstream side in the conveying direction D1. This shape prevents it from contacting the inner surface of the fixing film 202 at an angle, thereby suppressing the risk of hindering the rotation of the fixing film 202 or damaging it. Furthermore, the sub-guide rib 330 is configured to have a smaller protrusion amount in the conveying direction D1 than the guide rib 320. The protrusion amount of the guide rib 320 and the sub-guide rib 330 can be defined, for example, as the distance from the center of the heater 300 to the upstream end of the rib in the conveying direction D1. However, the reference position for the protrusion amount is not limited to the center of the heater 300, but may be, for example, the upstream end of the fixing nip N. In other words, in the conveying direction D1, the upstream end of the sub-guide rib 330 is located downstream of the upstream end of the guide rib 320.

[0077] As described above, the film guide 201 according to the first embodiment is provided with ribs of two different sizes, each with a different amount of protrusion in the direction opposite to the transport direction D1. With this configuration, even if the fixing film 202 bends and contacts the guide rib 320, and the fixing film 202 attempts to deform further, it will contact the sub-guide rib 330, thus suppressing deformation of the fixing film 202. Therefore, it is possible to prevent the fixing film 202 from buckling. In addition, since the sub-guide rib 330 is located downstream of the guide rib 320 in the transport direction D1, if the deformation of the fixing film 202 is not large, the fixing film 202 will only contact the guide rib 320 and not the sub-guide rib 330. Therefore, it is possible to prevent heat from being drawn away from the fixing film 202 by the sub-guide rib 330, thus suppressing the occurrence of heat unevenness in the fixing film 202.

[0078] Furthermore, since buckling deformation of the fixing film 202 mainly occurs upstream of the fixing nip N in the conveying direction D1, in the first embodiment, the sub-guide rib 330 is not provided downstream of the conveying direction D1, but only upstream of the conveying direction D1.

[0079] Next, the detailed configuration of the sub-guide rib 330 will be described. As mentioned above, the upstream ends of the guide rib 320 and the sub-guide rib 330 are located at different positions in the transport direction D1. As shown in Figure 8(d), in the transport direction D1, the distance from the center of the heater 300 to the upstream end of the guide rib 320 is denoted as distance d1, and the distance from the center of the heater 300 to the upstream end of the sub-guide rib 330 is denoted as distance d2. Distance d1 can also be described as the protrusion amount of the guide rib 320, and distance d2 as the protrusion amount of the sub-guide rib 330. In the first embodiment, distance d2 is smaller than distance d1. In this case, the distance d3 from the upstream end of the sub-guide rib 330 to the upstream end of the guide rib 320 in the transport direction D1 is equal to d1-d2. Distance d3 is equal to the distance from the upstream end of the guide rib 3 This corresponds to the difference in protrusion between 20 and the sub-guide rib 330.

[0080] When the distance d3 is large, that is, when the protrusion amount of the sub-guide rib 330 is small, the effect of suppressing buckling deformation is reduced. On the other hand, when the distance d3 is small, that is, when the protrusion amount of the sub-guide rib 330 is large, the effect of suppressing buckling deformation is increased, but the opportunities for the fixing film 202 to come into contact with the sub-guide rib 202 increase, raising concerns about image defects such as vertical streaks due to uneven heat. In order to suppress buckling deformation while suppressing the occurrence of image defects, it is preferable that the distance d2, which is the protrusion amount of the sub-guide rib 330, be a value in the range of 5 to 20% less than the distance d1, which is the protrusion amount of the guide rib 320. In other words, it is preferable that the distance d2 be in the range of 80 to 95% of the distance d1. Also, it is preferable that the distance d3 be in the range of 0.5 to 2.0 mm.

[0081] Next, the length (height) of the guide rib 320 and sub-guide rib 330 in the Z direction (direction perpendicular to the anchoring nip N) will be described. As shown in Figure 7, the starting point K of buckling deformation is the position where the width of the anchoring film 202 in the transport direction D1 is at its maximum width W, or near thereto, when viewed in a cross section perpendicular to the generatrix direction of the anchoring film 202. Therefore, in order to more effectively suppress buckling deformation, it is preferable that the sub-guide rib 330 is formed to extend in the Z direction to the starting point K or the region A near thereto.

[0082] In the first embodiment, the sub-guide rib 330 is configured such that the distance H1 from the fixing nip N to the tip of the sub-guide rib 330 in the Z-axis direction is greater than the distance HN (the distance from the fixing nip N to the starting point K in the Z direction). In other words, the sub-guide rib 330 is formed to extend beyond the starting point K in the Z direction. With this configuration, deformation of the fixing film 202 at or near the starting point K can be suppressed by the sub-guide rib 330. In the first embodiment, the guide rib 320 is also formed to extend beyond the starting point K in the Z direction, similar to the sub-guide rib 330. In other words, the distance H2 from the fixing nip N to the tip of the guide rib 320 in the Z-axis direction is greater than the distance HN.

[0083] Furthermore, the distance d3, which corresponds to the difference in protrusion between the sub-guide rib 330 and the guide rib 320, and the distance H1, which corresponds to the height of the sub-guide rib 330, are not limited to the ranges described above. These vary depending on the specifications of the image heating device 2, the outer diameter of the fixing film 202, the design of the film guide 201, and so on.

[0084] Next, we will describe the evaluation test that assessed the buckling deformation suppression effect of the configuration of the first embodiment. In the evaluation test, the same paper feeding test was performed using the comparative example and the film guide 201 of the first embodiment shown in Figures 8(a) and (b). In the evaluation test, the pattern P2 shown in Figure 5(a) was printed continuously, and the presence or absence of buckling deformation of the fixing film 202 and the presence or absence of transfer of buckling deformation marks to the recording material P were checked. The check for buckling deformation marks was performed by feeding a full halftone through every 10 prints of pattern P2.

[0085] The presence or absence of buckling deformation was confirmed using an industrial fiberscope installed upstream of the image heating device 2 in the transport direction D1. The results of the evaluation test are shown in Table 1. In Table 1, the state of the fixing film 202 at a predetermined number of sheets [sheets] is indicated by symbols. [Table 1] The symbols in the table indicate the following ranks: ◎ indicates that the fixing film 202 is rotating without deformation. ○ indicates that rotational movement is occurring with slight buckling deformation, but there are no problems. △ indicates that rotational movement is occurring with noticeable buckling deformation, as shown in Figure 6, and there are concerns. × indicates that buckling deformation marks are visible in the full-screen halftone image.

[0086] In the comparative example, the fixing film 202 did not deform up to 10 sheets of paper, and at 15 and 20 sheets of paper, slight buckling deformation that was not problematic was observed. However, at 25 and 30 sheets of paper, buckling deformation was clearly recognizable, raising concerns about continuing to use the fixing film 202. Furthermore, at 40 sheets of paper, the buckling deformation marks were recognizable as a full-screen halftone image.

[0087] On the other hand, in the first embodiment, the fixing film 202 did not deform up to 10 sheets of paper, and at 15 sheets of paper, slight buckling deformation that was not problematic was observed. Furthermore, even at 50 sheets of paper, the buckling deformation in the fixing film 202 was still slight and not problematic. In addition, no buckling deformation marks were recognized in the full-surface halftone image.

[0088] Based on the above, this evaluation test revealed that the configuration of the first embodiment can suppress buckling deformation of the fixing film 202 compared to the configuration of the comparative example. In other words, it was found that the buckling deformation suppression effect of the fixing film 202 can be obtained by providing the subguide rib 330.

[0089] Next, as a modification of the first embodiment, a film guide 201 with a different configuration from the first embodiment will be described. Figures 9(a) and 9(b) are explanatory diagrams of the modified film guide 201. It is desirable to select which configuration to adopt for the first embodiment and the modified embodiment according to the specifications and form of the image forming apparatus 1 and the image heating apparatus 2.

[0090] [Position of sub-guide ribs in the longitudinal direction of the film guide] First, as a first modification, we will describe a configuration in which the arrangement position of the sub-guide rib 330 in the Y direction differs from that of the first embodiment. Figure 9(a) is a perspective view of the film guide 201 of the first modification.

[0091] In the first embodiment, the sub-guide ribs 330 were also positioned at both ends of the film guide 201 in the longitudinal direction, but in the first modification, the sub-guide ribs 330 are positioned only in the center of the film guide 201 in the longitudinal direction. Here, in the center of the film guide 201 in the longitudinal direction The central region refers to the area near the longitudinal center. In the illustrated example, four sub-guide ribs 330 are provided in the longitudinal center of the film guide 201.

[0092] Buckling deformation of the fixing film 202 occurs in the central part in the longitudinal direction. Therefore, even if the sub-guide rib 330 is installed only in the central part and only the guide rib 320 is provided at both ends, a buckling deformation suppression effect can be obtained compared to the comparative example.

[0093] [Position of sub-guide ribs in the conveying direction] Next, as a second modification, a configuration in which the arrangement position of the sub-guide rib 330 in the Z direction differs from that of the first embodiment will be described. Figure 9(b) is a perspective view of the film guide 201 of the second modification.

[0094] In the first embodiment, the sub-guide rib 330 was positioned only on the upstream side of the film guide 201 in the transport direction D1. However, in the second modification, the sub-guide rib 330 is also positioned on the downstream side of the film guide 201 in the transport direction D1. In other words, in the second modification, the regulating portion of the film guide 201 is positioned symmetrically with respect to the center line of the transport direction D1.

[0095] The guide rib 320 on the upstream side of the film guide 201 in the transport direction D1 is designated as the first restricting section, and the sub-guide rib 330 as the second restricting section. The guide rib 320 located on the downstream side of the film guide 201 in the transport direction D1 is designated as the third restricting section, and the sub-guide rib 330 as the fourth restricting section. In this case, the third and fourth restricting sections each protrude downstream of the fixing nip N in the transport direction D1. Furthermore, in the transport direction D1, each restricting section is configured such that the downstream end of the fourth restricting section is located upstream of the downstream end of the third restricting section. The height of the third restricting section in the Z direction is the same as that of the first restricting section, and the height of the fourth restricting section in the Z direction is the same as that of the second restricting section.

[0096] The film guide 201, molded from resin, is a component that requires high dimensional accuracy along its entire length, including the surface accuracy of the surface where the fixing film 202 and heater 300 are installed and the metal stays that ensure strength are mounted. Therefore, by providing the sub-guide rib 330 on the downstream side in the transport direction D1, the uniformity of the resin flow during mold molding of the film guide 201 can be ensured, and high dimensional accuracy can be obtained. From this viewpoint, it is preferable that the upstream sub-guide rib 330 and the downstream sub-guide rib 330 in the transport direction D1 have a symmetrical shape with respect to the center line of the film guide 201.

[0097] [Maximum width of recording material supported] Next, as a third modification, we will describe a configuration in which the position (amount of protrusion) of the upstream end of the sub-guide rib 330 in the transport direction D1 is changed.

[0098] In the first embodiment, an image forming apparatus 1 was described that supports LTR / A4 size as the maximum paper width for recording material P. However, when supporting A3 / LDR size as the maximum paper width, the total length of the fixing film 202 increases, resulting in a greater amount of deflection downstream. Therefore, in the third modified example, the rib configuration with two levels of protrusion is changed to a rib configuration with three or more levels of protrusion, following the deflection of the fixing film 202.

[0099] In the modified example 3, the distance d3, which is the difference in the amount of protrusion between the sub-guide rib 330 and the guide rib 320 in the longitudinal center, is configured to be smaller than the distance d3, which is the difference in the amount of protrusion between the sub-guide rib 330 and the guide rib 320 at the longitudinal end. With this configuration, the effect of suppressing buckling deformation is enhanced at the sub-guide rib 330 in the longitudinal center where the deflection of the fixing film 202 is large, while the opportunity for the sub-guide rib 330 to contact the fixing film 202 in the area where the deflection is small at the longitudinal end can be reduced. At this time, the distance d3 is, for example, from the longitudinal center to the longitudinal The configuration may also involve a continuous or gradual decrease towards the ends.

[0100] In the first embodiment and each of the modified examples, the guide ribs 320 and sub-guide ribs 330 were integrally formed with respect to the film guide 201, but the configuration is not limited to this. For example, each rib may be configured to be detachably attached to the film guide 201, or the regulating member (guide member) having each rib may be configured separately from the heater holding member having the heater holding portion 340.

[0101] As described above, according to the configuration of the first embodiment and its modified form, even when the fixing film 202 bends significantly downstream in the transport direction D1, the sub-guide rib 330 suppresses the bending of the fixing film 202, making it possible to prevent buckling deformation caused by bending. Furthermore, since the contact area of ​​the fixing film 202 with the film guide 201 can be kept small, the heat from the fixing film 202 being absorbed by the film guide 201 can be suppressed, and power consumption can be reduced.

[0102] <Second Example> Next, a second embodiment of the present invention will be described. The configuration of the film guide 201 in the second embodiment differs from that of the first embodiment. Hereinafter, only the differences in the configuration of the second embodiment from that of the first embodiment will be described. Components in the configuration of the second embodiment that are the same as those in the configuration of the first embodiment will be denoted by the same reference numerals and their description will be omitted.

[0103] Figures 10(a) to 10(e) are explanatory diagrams of the film guide 201 according to the second embodiment. Figure 10(a) is a perspective view of the film guide 201 according to the second embodiment. Figure 10(b) is a cross-sectional view SS of Figure 10(a). Figure 10(c) is a cross-sectional view VV of Figure 10(a).

[0104] The second embodiment is configured in which multiple bridge members 322 are provided as regulating parts instead of sub-guide ribs 330. The bridge members 322 are regulating parts that extend along the generatrix direction (Y direction) of the fixed film 202, from one guide rib 320 to the adjacent guide rib 320, bridging the gaps between the guide ribs 320 of the film guide 201. All of the multiple bridge members 322 are provided on the upstream side of the transport direction D1 of the film guide 201. In other words, the film guide 201 according to the second embodiment is provided with guide ribs 320 as first regulating parts and bridge members 322 as second regulating parts.

[0105] The cross-sectional shape of the bridge member 322 in the direction perpendicular to the longitudinal direction (Y direction) is circular. The bridge member 322 can be molded integrally with the film guide 201, or it can be a separate member attached to the guide rib 320. The SS cross section is the cross section passing through the guide rib 320 when the film guide 201 is viewed in the longitudinal direction, and the VV cross section is the cross section passing through the bridge member 322 when the film guide 201 is viewed in the longitudinal direction.

[0106] With this configuration, the bridge member 322 can contact the fixing film 202 over substantially the entire area between the guide ribs 320 in the longitudinal direction of the film guide 201. Therefore, the configuration of the second embodiment can suppress the occurrence of thermal unevenness in the longitudinal direction of the fixing film 202 compared to the configuration of the first embodiment.

[0107] Next, the position of the bridge member 322 will be described. It is preferable that the bridge member 322 be positioned considering the starting point K of buckling deformation (the point where the width of the fixing film 202 in the transport direction D1 is maximum), similar to the first embodiment. Therefore, the bridge member 322 is positioned in the Z direction at the same position as the starting point K (the upstream end of the fixing film 202 in the transport direction D1), and at least a part of it overlaps within region A. In other words, in the Z direction, If H3 is the distance from the anchoring nip N to one end of the bridge member 322 closer to the anchoring nip N, then distance H3 is smaller than distance HN. Also, if H4 is the distance from the anchoring nip N to the other end of the bridge member 322 further from the anchoring nip N in the Z direction, then distance H4 is larger than distance HN. This configuration enhances the effect of suppressing buckling deformation.

[0108] In the second embodiment, as shown in Figure 10(c), the upstream end of the bridge member 322 is located downstream of the upstream end of the guide rib 320 in the transport direction D1. In other words, the bridge member 322 is positioned recessed downstream of the guide rib 320 in the transport direction D1. However, the configuration of the bridge member 322 is not limited to this.

[0109] For example, in the transport direction D1, the upstream end of the bridge member 322 may be located upstream of the upstream end of the guide rib 320. That is, the bridge member 322 may be positioned to protrude upstream of the guide rib 320 in the transport direction D1. The reason for the configuration of the second embodiment is that, compared to the first embodiment, the longitudinal distance of the contact portion where the bent fixing film 202 contacts the regulating portion is longer, making it less likely for partial heat unevenness in the longitudinal direction to occur. Figure 10(d) is a VV cross-sectional view showing an example of a configuration in which the bridge member 322 protrudes upstream of the guide rib 320 in the transport direction D1.

[0110] Furthermore, the cross-sectional shape of the bridge member 322 in a section perpendicular to the Y direction may be elliptical rather than circular. Figure 10(e) is a VV cross-sectional view showing an example where the cross-sectional shape of the bridge member 322 is elliptical. In this example, the cross-sectional shape of the bridge member 322 is an ellipse with the Z direction as the longitudinal direction and the X direction as the short direction. The cross-sectional shape of the bridge member 322 is preferably such that the surface in contact with the inner surface of the bent fixing film 202 is a smooth surface, and a cross-section that contacts the fixing film 202 at a corner is undesirable. In other words, the surface of the bridge member 322 facing the inner circumferential surface of the fixing film 202 is preferably a curved surface that is convex towards the upstream side in the transport direction D1.

[0111] Furthermore, while the second embodiment provides bridge members 322 between all guide ribs 320, the configuration is not limited to this. For example, similar to the first embodiment, bridge members 322 can be provided only in the longitudinal center of the film guide 201, and not at the ends. It is also conceivable to vary the position and cross-sectional shape of the bridge members 332 in the longitudinal direction.

[0112] Based on the above, according to the configuration of the second embodiment, even when the fixing film 202 bends significantly downstream in the transport direction D1, the bridge member 322 acting as a restricting part suppresses the bending of the fixing film 202, making it possible to prevent buckling deformation caused by bending.

[0113] As with the first embodiment, it is desirable to optimize the detailed configuration of the bridge member 322 according to the specifications of the image heating device 2 and the form of the fixing film 202 and film guide 201. Even with the configuration in which the bridge member 322 is provided as described above, the effect of suppressing buckling deformation of the fixing film 202 can be obtained, as with the first embodiment.

[0114] This embodiment includes the following configuration. (Composition 1) A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member is disposed within the internal space of the film and restricts the rotational shape of the film. A regulating member having a plurality of first regulating portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion arranged between the plurality of first regulating portions in the direction of the busbar, In the aforementioned transport direction, the upstream end of the second restricting section is located downstream of the upstream end of the first restricting section. An image heating device characterized in that, in the direction perpendicular to the busbar direction and the transport direction, the distance from the nip portion to the tip of the second regulating portion is greater than the distance from the nip portion to the upstream end of the film in the transport direction. (Configuration 2) The regulating member has a plurality of the second regulating parts, The image heating apparatus according to configuration 1, characterized in that the first regulating section and the second regulating section are arranged alternately in the direction of the busbar. (Composition 3) The image heating apparatus according to configuration 2, characterized in that the second regulating section is provided such that one or more of the second regulating sections are adjacent to all of the first regulating sections in the direction of the busbar. (Composition 4) The image heating device according to configuration 1 or 2, characterized in that the second regulating portion is provided only in the central part of the regulating member in the direction of the generatrix. (Composition 5) The regulating member has a plurality of third regulating portions arranged along the generatrix direction of the film on the downstream side in the transport direction relative to the nip portion, and a fourth regulating portion positioned between the plurality of third regulating portions in the generatrix direction, In the aforementioned transport direction, the upstream end of the fourth restricting section is located upstream of the downstream end of the third restricting section. The image heating device according to any one of configurations 1 to 4, characterized in that, in the direction perpendicular to the busbar direction and the transport direction, the distance from the nip portion to the tip of the fourth restricting portion is greater than the distance from the nip portion to the upstream end of the film in the transport direction. (Composition 6) The image heating device according to any one of configurations 2 to 5, characterized in that, in the transport direction, the distance from the upstream end of the second restricting portion provided in the central part of the restricting member in the direction of the busbar to the upstream end of the first restricting portion is smaller than the distance from the upstream end of the second restricting portion provided at the end of the restricting member in the direction of the busbar to the upstream end of the first restricting portion. (Composition 7) The image heating device according to any one of configurations 1 to 6, characterized in that, in the transport direction, the distance from the center of the heater to the upstream end of the second restricting section is within the range of 80 to 95% of the distance from the center of the heater to the upstream end of the first restricting section. (Composition 8) The image heating apparatus according to any one of configurations 1 to 7, characterized in that, in the transport direction, the distance from the upstream end of the second restricting section to the upstream end of the first restricting section is within the range of 0.5 to 2.0 mm. (Composition 9) The image heating device according to any one of configurations 1 to 8, characterized in that the second restricting portion is formed in a curved shape that is convex on the upstream side in the conveying direction. (Composition 10) The image heating apparatus according to any one of configurations 1 to 9, characterized in that the regulating member is a heater holding member that holds the heater. (Composition 11) The image heating device according to any one of the configurations 1 to 10, characterized in that the film is formed of a heat-resistant resin or metal. (Composition 12) A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member disposed in the internal space of the film and restricting the rotational shape of the film, the restricting member having a plurality of first restricting portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion that extends along the direction of the generatrix from one of the plurality of first regulating portions to an adjacent first regulating portion. The image heating device is characterized in that the second regulating section is provided at the same position as the upstream end of the film in a direction perpendicular to the busbar direction and the transport direction. (Composition 13) The image heating device according to configuration 12, characterized in that the second regulating portion is provided in the central part of the regulating member in the direction of the generatrix. (Composition 14) The image heating device according to configuration 12 or 13, characterized in that the second regulating section is provided between all of the plurality of first regulating sections. (Composition 15) The image heating device according to any one of the configurations 12 to 14, characterized in that the surface of the second regulating portion facing the inner circumferential surface of the film is a curved surface that is convex toward the upstream side in the transport direction. (Composition 16) The image heating apparatus according to any one of the configurations 12 to 15, characterized in that the regulating member is a heater holding member that holds the heater. (Composition 17) The image heating device according to any one of the configurations 12 to 16, characterized in that the film is formed of a heat-resistant resin or metal. (Composition 18) An image forming unit that forms an image on the recording material, A fixing unit that fixes the image formed on the recording material to the recording material, In an image forming apparatus having, An image forming apparatus characterized in that the fixing unit is an image heating device according to any one of the configurations 1 to 17. [Explanation of Symbols]

[0115] 2…Image heating device, 201…Film guide (regulating member), 202…Fixing film (film), 208…Pressure roller (roller), 300…Heater, 320…Guide rib (first regulating section), 330…Sub-guide rib (second regulating section), N…Fixing nip, P…Recording material

Claims

1. A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member disposed in the internal space of the film and restricting the rotational shape of the film, the restricting member having a plurality of first restricting portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion arranged between the plurality of first regulating portions in the direction of the busbar, In the aforementioned transport direction, the upstream end of the second restricting section is located downstream of the upstream end of the first restricting section. An image heating device characterized in that, in the direction perpendicular to the busbar direction and the transport direction, the distance from the nip portion to the tip of the second regulating portion is greater than the distance from the nip portion to the upstream end of the film in the transport direction.

2. The regulating member has a plurality of the second regulating parts, The image heating apparatus according to claim 1, characterized in that the first regulating section and the second regulating section are arranged alternately in the direction of the busbar.

3. The image heating apparatus according to claim 2, characterized in that the second regulating section is provided such that one or more of the second regulating sections are adjacent to all of the plurality of first regulating sections in the direction of the busbar.

4. The image heating device according to claim 1, characterized in that the second regulating portion is provided only in the central part of the regulating member in the direction of the generatrix.

5. The regulating member has a plurality of third regulating portions arranged along the generatrix direction of the film on the downstream side in the transport direction relative to the nip portion, and a fourth regulating portion positioned between the plurality of third regulating portions in the generatrix direction. In the aforementioned transport direction, the upstream end of the fourth restricting section is located upstream of the downstream end of the third restricting section. The image heating device according to claim 1, characterized in that, in the direction perpendicular to the busbar direction and the transport direction, the distance from the nip portion to the tip of the fourth restricting portion is greater than the distance from the nip portion to the upstream end of the film in the transport direction.

6. The image heating apparatus according to claim 2, characterized in that, in the transport direction, the distance from the upstream end of the second restricting portion provided in the central part of the restricting member in the direction of the busbar to the upstream end of the first restricting portion is smaller than the distance from the upstream end of the second restricting portion provided at the end of the restricting member in the direction of the busbar to the upstream end of the first restricting portion.

7. The image heating apparatus according to claim 1, characterized in that, in the transport direction, the distance from the center of the heater to the upstream end of the second restricting section is within the range of 80 to 95% of the distance from the center of the heater to the upstream end of the first restricting section.

8. The image heating apparatus according to claim 1, characterized in that, in the transport direction, the distance from the upstream end of the second restricting section to the upstream end of the first restricting section is within the range of 0.5 to 2.0 mm.

9. The image heating device according to claim 1, characterized in that the second restricting portion is formed in a curved shape that is convex on the upstream side in the conveying direction.

10. The image heating apparatus according to claim 1, characterized in that the regulating member is a heater holding member that holds the heater.

11. The image heating device according to claim 1, characterized in that the film is formed of a heat-resistant resin or metal.

12. A rotatable cylindrical film, A heater is placed in the internal space of the film and heats the film, A roller that contacts the outer surface of the film and forms a nip portion between itself and the film for transporting the recording material in the transport direction, A restricting member disposed in the internal space of the film and restricting the rotational shape of the film, the restricting member having a plurality of first restricting portions arranged along the generatrix direction of the film on the upstream side in the transport direction relative to the nip portion, An image heating device comprising the nip portion, which heats the image formed on the recording material while transporting the recording material, The regulating member further has a second regulating portion that extends along the direction of the generatrix from one of the plurality of first regulating portions to an adjacent first regulating portion. The image heating device is characterized in that the second regulating section is provided at the same position as the upstream end of the film in the transport direction in a direction perpendicular to the busbar direction and the transport direction.

13. The image heating device according to claim 12, characterized in that the second regulating portion is provided in the central part of the regulating member in the direction of the generatrix.

14. The image heating device according to claim 12, characterized in that the second restricting section is provided between all of the plurality of first restricting sections.

15. The image heating device according to claim 12, characterized in that the surface of the second regulating portion facing the inner circumferential surface of the film is a curved surface that is convex toward the upstream side in the transport direction.

16. The image heating apparatus according to claim 12, characterized in that the regulating member is a heater holding member that holds the heater.

17. The image heating device according to claim 12, characterized in that the film is formed of a heat-resistant resin or metal.

18. An image forming unit that forms an image on the recording material, A fixing unit that fixes the image formed on the recording material to the recording material, In an image forming apparatus having, An image forming apparatus characterized in that the fixing unit is an image heating device according to any one of claims 1 to 17.

Images