Image heating apparatus and image forming apparatus
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- CANON KK
- Filing Date
- 2022-04-12
- Publication Date
- 2026-08-03
Smart Images
Figure 0007898913000001 
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Abstract
Description
Technical Field
[0001] The present invention relates to an image heating device mounted on an image forming apparatus such as a copying machine or a printer that forms an image by an electrophotographic method.
Background Art
[0002] As an image heating device mounted on an image forming apparatus, a film heating type image heating device excellent in power saving property is known. The film heating type image heating device forms a fixing nip for sandwiching and conveying a recording material between a film and a pressure roller together with a heater, and fixes an unfixed toner image on the recording material by the heat of the heater while applying pressure at this fixing nip. The film is configured in a cylindrical shape, and inside thereof, a film guide, an inner surface sliding portion of a flange member, etc. are arranged together with a heater, and the rotation of the film driven by the rotation of the pressure roller is guided (Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In a film heating type image heating device, good separation property of the recording material from the film is required together with the stability of the rotation of the film.
[0005] An object of the present invention is to provide a technique capable of improving the stability of the rotation of the film and the separation property of the recording material from the film in a film heating type image heating device.
Means for Solving the Problems
[0006] In order to achieve the above object, the image heating device in the present invention includes a cylindrical film, and A heater is placed in the internal space of the film, A roller that contacts the outer surface of the film and forms a nip between itself and the film, A film guide that guides the inner surface of the film which rotates in accordance with the rotation of the roller, A flange member that guides the regions at both ends in the longitudinal direction of the film, among the inner surface of the film that rotates in accordance with the rotation of the roller, Equipped with, In an image heating device that heats an image formed on a recording material that is gripped and conveyed by the nip by the rotation of the roller using the heat of the heater, When viewed in the longitudinal direction, the position where the portion of the flange member that protrudes most towards the upstream side in the transport direction of the recording material contacts the inner surface of the film is defined as the first position. When viewed in the longitudinal direction, the second position is defined as the position where a first imaginary line passing through the first position and parallel to the nip intersects with the surface of the flange member facing the inner surface of the film, downstream of the nip in the conveying direction. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film facing the inner surface of the film in the film guide, upstream of the nip in the transport direction, is defined as the third position. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film guide downstream of the nip in the transport direction is defined as the fourth position. On the first virtual line, in the direction along the first virtual line, The first distance between the intersection point of the second imaginary line perpendicular to the center and the first imaginary line and the first position is longer than the second distance between the intersection point and the second position, and the third distance between the intersection point and the third position is longer than the distance between the intersection point and the fourth position position Longer than the fourth distance between them Ku, On the first imaginary line, the first gap between the first position and the third position is narrower than the second gap between the second position and the fourth position. The film guide comprises a base portion having a recess for housing the heater, a first rib protruding from the upstream side of the base portion in the transport direction, and a second rib protruding from the downstream side of the base portion in the transport direction. The first rib has a larger protrusion from the base in the conveying direction and a larger protrusion from the base in the direction perpendicular to the conveying direction than the second rib.Characterized by the following. In order to achieve the above object, the image forming apparatus according to the present invention An image forming unit that forms an image on a recording material, A fixing unit that fixes the image formed on the recording material to the recording material, In an image forming apparatus having It is characterized in that the fixing unit is the image heating device of the present invention.
Effect of the Invention
[0007] According to the present invention, in an image heating device using a film heating method, it is possible to improve the rotational stability of the film and the separability of the recording material from the film.
Brief Description of the Drawings
[0008] [Figure 1] Schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention [Figure 2] Schematic cross-sectional view of the image heating device of the present invention [Figure 3] Schematic diagram of the image heating device of the present invention [Figure 4] Schematic cross-sectional view of the image heating device of the present invention [Figure 5] Schematic cross-sectional view of the image heating device of the comparative example [Figure 6] Schematic cross-sectional view of a configuration example of a film guide
Mode for Carrying Out the Invention
[0009] Hereinafter, with reference to the drawings, modes for carrying out this invention will be exemplarily and specifically described based on examples. Note that dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus 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.
[0010] (Example 1) 1. Configuration of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus 1 shown in FIG. 1 is a laser printer that forms an image on a recording material P using an electrophotographic method.
[0011] When the image forming apparatus 1 receives a print signal, the scanner unit 3 emits laser light modulated according to the image information, and scans the surface of a photosensitive drum (electrophotographic photoreceptor) 5 charged to a predetermined polarity by a charging roller 4. As a result, an electrostatic latent image is formed on the photosensitive drum 5 as an image carrier. By supplying toner charged to a predetermined polarity from a developing roller 6 to this electrostatic latent image, the electrostatic latent image on the photosensitive drum 5 is developed as a toner image (developer image). On the other hand, recording materials (recording papers) P stacked in a paper feed cassette 7 are fed one by one by a pickup roller 8 and conveyed toward a registration roller pair 10 by a conveyance roller pair 9. Further, the recording material P is conveyed from the registration roller pair 10 to the transfer position at a timing when the toner image on the photosensitive drum 5 reaches the transfer position formed by the transfer roller 11 as a transfer member. The toner image on the photosensitive drum 5 is transferred to the recording material P in the process of the recording material P passing through the transfer position. The device configuration responsible for the process until the above unfixed toner image is formed on the recording material P corresponds to the image forming unit of the present invention.
[0012] Thereafter, the recording material P is heated using the heat of a heater in a fixing device (image heating device) 2 as a fixing unit (image heating unit), and the toner image is fixed to the recording material P. The recording material P carrying the fixed toner image is discharged to a tray above the image forming apparatus 1 by conveyance roller pairs 12 and 13.
[0013] The image forming apparatus 1 of this embodiment has a maximum paper passing width of 216 mm in a direction orthogonal to the conveyance direction of the recording material P, and can print 60 sheets per minute at a conveyance speed of 300 mm / sec for LTR-size recording materials P.
[0014] 2. Configuration of Fixing Device (Image Heating Device) Figure 2 is a side cross-sectional view of the fixing device 2 of this embodiment. The fixing device 2 consists of a film F (shown as a dashed line in Figure 2), a heater 21, a film guide G, a pressure roller 22, a metal stay 23, and a flange E (internal sliding portion E1). The film F is a flexible cylindrical (endless) member. The heater 21, film guide G, metal stay 23, and the internal sliding portion E1 of the flange E are arranged inside the film F (the internal space of the film F, which is the region facing the inner circumferential surface of the film F). The pressure roller 22 is arranged outside the film F (the region facing the outer circumferential surface of the film F). The heater 21, as a heating element, is positioned to contact the inner surface of the film F. The film guide G also serves as a heater holder, providing thermal insulation support for the heater 21 while guiding the inner surface of the film F. The pressure roller 22 is positioned together with the heater 21 to form a fixing nip portion N between itself and the outer surface of the film F. The metal stay 23 presses the film guide G so that contact is formed between the heater 21 and the pressure roller 22 via the film F. The flanges E, acting as flange members, are positioned at both ends of the film F in the longitudinal direction, and the internal sliding portions E1 are inserted longitudinally into the inside of the longitudinal ends of the film F from both sides in the longitudinal direction, guiding both ends of the film F in the longitudinal direction from the inner surface of the film F. The longitudinal configuration of the flanges E will be described later.
[0015] Here, the longitudinal direction of the film F is along the central axis of the cylindrical shape of the film F, and coincides with the longitudinal direction of the heater 21, the metal stay 23, the film guide G, the longitudinal direction (rotation axis direction) of the pressure roller 22, and the width direction of the recording material P which is perpendicular to the conveying direction of the recording material P.
[0016] Film F is a heat-resistant film formed in a tubular shape, with a heat-resistant resin such as polyimide as its base layer. Furthermore, to prevent toner adhesion and ensure separation from the recording material P, a release layer is formed on the surface of film F by coating it with a heat-resistant resin with excellent release properties, such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. For improved image quality, a 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, film F has an outer diameter of 24 mm, a base layer made of polyimide with a thickness of 70 μm, and an elastic layer... The molded part is made of silicone rubber with a thickness of 200 μm, and the release layer is made of PFA with a thickness of 15 μm.
[0017] The heater 21 is a low-heat-capacity ceramic heater, with a resistive heating element formed on the substrate. When current is applied, the resistive heating element heats up, generating heat for the fixing heat treatment. A temperature sensing element (not shown), such as a thermistor, is installed on the opposite side of the fixing nip portion N of the heater 21, and the current supply to the heater 21 is controlled based on the detected temperature.
[0018] Film guide G is made of heat-resistant resin or composite materials of heat-resistant resin with ceramics, metal, glass, etc. Examples of heat-resistant resins include PPS (polyphenylene sulfide), PAI (polyamide-imide), PI (polyimide), and PEEK (polyether-amide). Examples include terketones and liquid crystal polymers. The film guide G is designed to stabilize the rotational trajectory of the film F while suppressing sliding resistance with the film F, and is directed toward the inner surface of the film F. Multiple ribs Ra and Rb are provided so as to protrude radially. The film guide G supports the heater 21 and has guide surfaces on both sides of the heater 21 in the direction of rotation of the film F that guide the inner surface of the film F. The film guide G comprises a base GB having a recess GR as a housing for holding the heater 21, a first rib Ra provided on the upstream side of the base GB in the direction of transport of the recording material P, and a second rib Rb provided on the downstream side. The base GB is provided on the side facing the inner surface of the film F such that the recess GR extends in the longitudinal direction of the film. The base GB also has convex film guide surfaces BaS and BbS on both sides of the recess GR in the direction of transport of the recording material P (direction of rotation of the film F) that guide the inner surface of the film F. The ribs Ra and Rb each have convex film guide surfaces RaS and RbS that are connected to the film guide surfaces BaS and BbS of the base GB and guide the inner surface of the film F. In this embodiment, the amount of overhang from the base GB toward the inner surface of the film F is greater for the upstream rib Ra than for the downstream rib Rb. The configuration of ribs Ra and Rb in the longitudinal direction of the film and their overhang configuration will be described later.
[0019] Figure 6 is a schematic cross-sectional view of an example configuration of the film guide G. As an example of the film guide G, as shown in Figure 6(A) for film guide G1, the ribs Ra and Rb may be configured to protrude from the upper surface of the base GB (the side opposite to the side with the recess GRB). In this configuration, the upstream rib Ra is further away from the fixing nip N in the recording material transport direction than the downstream rib Rb, has a greater thickness in the same direction, and also has a greater height (protrusion amount) from the base GB. As another example, as shown in Figure 6(B) for film guide G2, the ribs Ra and Rb may be configured to protrude from the sides of the base GB (both sides in the recording material transport direction). In this configuration, the upstream rib Ra protrudes a greater amount from the base GB in the recording material transport direction than the downstream rib Rb, and also has a greater height (protrusion amount) from the base GB. The configuration shown in Figure 6 is merely an example; other configurations may be adopted, for example, by using the configuration shown in Figure 6(A) for the upstream rib in the recording material transport direction and the configuration shown in Figure 6(B) for the downstream rib.
[0020] The heater 21 is fixedly supported by the film guide G, and the outer circumference of the film guide G, including the heater 21, is smaller than the inner circumference of the film F. Therefore, the film F is fitted onto the film guide G, including the heater 21, with ample clearance.
[0021] The pressure roller 22 has an elastic layer made of a material such as silicone rubber on a core metal 24 made of a material such as iron, stainless steel, or aluminum. In addition, the surface of the pressure roller 22 is coated with a heat-resistant resin with excellent release properties, such as tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, to form a release layer in order to prevent toner from adhering to it. In this embodiment, the outer diameter of the pressure roller 22 is 24 mm.
[0022] The metal stay 23 is a metal plate bent into a U-shape, and biases the film guide G, including the heater 21, toward the pressure roller 22 with a predetermined pressure. As a result, the film F is pressed against the pressure roller 22, and a fixing nip portion N is formed between the film F and the pressure roller 22.
[0023] The pressure roller 22 receives power from a motor (not shown) and rotates in the direction of the arrow. As the pressure roller 22 rotates, the film F follows and rotates in the direction of the arrow. At the fixing nip section N, the recording material P is clamped and conveyed from upstream to downstream, and heat is applied to the film F, thereby fixing the unfixed toner image on the recording material P.
[0024] Figures 3(A), 3(B), and 3(C) are front views of the fixing device 2 of this embodiment (schematic front views of the fixing device 2 as seen in the direction of transport of the recording material P), and in Figures 3(B) and 3(C) the fill The diagram of part F is omitted. Figures 3(A) and 3(B) are front views of the recording material P as seen from the upstream side of transport, and Figure 3(C) is a front view of the recording material P as seen from the downstream side of transport.
[0025] As shown in Figures 3(B) and 3(C), the metal stay 23 is biased by pressure springs 25 installed at both ends in the longitudinal direction to move the film guide G toward the pressure roller 22, thereby transmitting the spring pressure of the pressure springs 25 toward the pressure roller 22.
[0026] The flange E comprises a semicircular inner sliding portion E1 and an end contact portion E2 provided at the longitudinal outer end of the inner sliding portion E1, and is made of a heat-resistant material. The inner sliding portion E1 has a semicircular outer surface that forms a convex film guide curved surface E1S (see Figure 2), and the cylindrical end of the film F is fitted so as to surround this outer surface. The inner sliding portion E1 restricts the rotational trajectory of the film F by allowing the inner surface of the film F to slide along its outer surface. The outer circumference of the inner sliding portion E1 (the circumference of the film guide curved surface E1S) is made larger than the outer circumference of the film guide G (the circumference of the areas of the film guide curved surfaces RaS and RbS that do not overlap with the film guide curved surface E1S + the circumferences of the film guide curved surfaces BaS and BbS). Furthermore, the internal sliding portion E1 guides the longitudinal regions of the inner surface of the film F, and the film guide G guides the inner surface of the film F from a location longitudinally inward of the internal sliding portion E1. In other words, the flange E guides the inner surface of the film F from both longitudinally outward sides of the region guided by the film guide G, in a manner that extends radially beyond the film guide G. Therefore, the rotational trajectory of the film F is determined solely by the outer circumference length of the internal sliding portion E1. On the other hand, the end contact portion E2 receives the outer end surface of the cylindrical end of the film F with its inner surface, thereby suppressing the longitudinal movement of the film F during rotation.
[0027] As described above, the film guide G has a base GB that holds the heater 21, and ribs Ra and Rb that protrude from the base GB, respectively. Multiple ribs Ra and Rb are arranged in a row at regular intervals in the longitudinal direction. That is, the film guiding curved surface of the film guide G is formed over the entire longitudinal direction of the film in the base GB, while in the ribs Ra and Rb it is formed intermittently in the longitudinal direction of the film.
[0028] In this embodiment, the same number of ribs Ra on the upstream side and the same number of ribs Rb on the downstream side are provided, and their longitudinal arrangement is configured to coincide with each other. That is, as shown in Figures 3(B) and 3(C), when viewed in the direction of recording material transport, the multiple ribs Ra on the upstream side and the multiple ribs Rb on the downstream side are arranged to overlap each other. Note that the arrangement configuration of the multiple ribs Ra on the upstream side and the multiple ribs Rb on the downstream side is not limited to the above configuration. For example, they may be arranged to be offset from each other in the longitudinal direction, the spacing between them does not have to be constant, the amount of overhang may differ, and furthermore, the number of ribs may differ between the upstream and downstream sides.
[0029] As described above, the base GB has film guide curved surfaces BaS and BbS on both sides in the recording material transport direction relative to the recess GR that houses the heater 21. The ribs Ra and Rb each have convex film guide curved surfaces RaS and RbS that extend from the base GB in a direction along the inner circumferential surface of the film F and face the inner circumferential surface of the film F. That is, the film guide G has an upstream guide curved surface on the upstream side in the recording material transport direction relative to the heater 21, where the film guide surface BaS and the film guide curved surface RaS are connected, and a downstream guide curved surface on the downstream side, where the film guide surface BbS and the film guide curved surface RbS are connected.
[0030] The film guide surface of the film guide G may be configured such that, when viewed in the longitudinal direction of the film F (Figure 2), it has a radius of curvature smaller than the diameter of the film F when the circumference of the film F forms a perfect circle, or smaller than the radius of curvature of the guide surface of the inner sliding portion E1 of the flange E. Alternatively, the curved surface may not have a constant radius of curvature, but rather a curved surface whose radius of curvature gradually changes. In other words, the shape of the curved surface is arbitrary as long as the stability of the rotation guidance of the film F, which will be described later, is ensured (it does not hinder rotation).
[0031] Furthermore, the upstream rib Ra may be configured to have a greater protrusion height from the base GB (larger protrusion in the direction perpendicular to the recording material transport direction and the longitudinal direction) and a larger protrusion from the fixing nip N in the recording material transport direction compared to the downstream rib Rb. Also, in this embodiment, the external shapes of the multiple ribs Ra are configured to be the same when viewed in the longitudinal direction of the film, but they may be configured to have different external shapes. The same applies to the multiple ribs Rb. Also, in this embodiment, the longitudinal thickness of the ribs Ra and Rb is configured to be approximately the same, but they may be different. In other words, the configuration and arrangement of each rib Ra and Rb may be set arbitrarily as long as the stability of the rotation guidance of the film F described later is ensured (without hindering rotation).
[0032] 3. Film Guide Configuration Figure 4(A) is a partial cross-sectional view of the fixing device, viewed in a direction perpendicular to the recording material transport direction, showing the positional relationship between the upstream rib Ra and the downstream rib Rb of the film guide G in this embodiment, and the film F (dashed line) restricted by the inner sliding portion E1 of the flange E. In the figure, position Fa, as the first position, is the point upstream of the fixing nip portion N in the recording material transport direction, where the inner sliding portion E1 of the flange E restricts the inner surface of the film F at the furthest upstream point in the recording material transport direction. That is, position Fa is the position where the portion of the inner sliding portion E1 of the flange E that protrudes furthest upstream in the recording material transport direction contacts the inner surface of the film F. The horizontal line L is a first imaginary line passing through position Fa and parallel to the fixing nip portion N, which is the contact area between the film F and the pressure roller 22, or to the recording material transport direction. Furthermore, position Fb, as the second position, is the intersection of the horizontal line L and the region on the outer surface of the inner sliding portion E1 of the flange E that restricts the inner surface of the film F on the downstream side in the recording material transport direction relative to the fixing nip portion N. Note that, at least when the fixing device is driven, the film F deforms slightly, being pulled downstream in the recording material transport direction, due to its driven rotation relative to the pressure roller 22. As a result, the inner surface of the film F is in contact with and restricted by the inner sliding portion E1 only at position Fa, and not at position Fb. That is, position Fb is the position where the horizontal line L intersects with the outer surface of the inner sliding portion E1 of the flange E that faces the inner surface of the film F, downstream in the recording material transport direction from the fixing nip portion N. Furthermore, in the figure, position Ea is the upstream end in the recording material transport direction where the inner surface of the film F is restricted by the inner sliding portion E1 of the flange E. The horizontal line M is a virtual line passing through position Ea and parallel to the fixing nip portion N. When viewed in the longitudinal direction of the film F, the film guide surface E1S of flange E has a horizontal line L passing through its center of curvature, and both the upstream and downstream ends in the recording material transport direction extend further toward the fixing nip section N than the horizontal line L. In other words, both ends of the film guide surface E1S are located closer to the fixing nip section N than the horizontal line L in directions perpendicular to the recording material transport direction and the longitudinal direction of the film (vertical direction in this embodiment).
[0033] Figure 4(B) is a partial cross-sectional view of the fixing device, in which the film guide G and the inner sliding portion E1 of the flange E are omitted from Figure 4(A). In the figure, the first distance, La, represents the distance from the intersection of the fixing nip portion N and the center line C on the horizontal line L to the regulating position Fa of the inner sliding portion E1 of the flange E. The center line C of the fixing nip portion N is a second imaginary line that extends in a direction perpendicular to both the recording material transport direction and the film longitudinal direction (vertical direction in this embodiment) and passes through the center of the width of the fixing nip portion N in the recording material transport direction. The second distance, Lb, represents the distance from the intersection of the fixing nip portion N and the center line C on the horizontal line L to the regulating position Fb of the inner sliding portion E1 of the flange E. In this embodiment, distance La is 13 mm and Lb is 11 mm, meaning that the inner sliding portion E1 of the flange E is offset 1 mm upstream of the fixing nip portion N. The purpose of the fret is to reduce the radius of curvature of the film F on the downstream side of the fixing nip section N in the direction of recording material transport, thereby improving the separation from the recording material P.
[0034] Figures 4(C) to 4(F) are partial cross-sectional views of the fixing device, in which the inner sliding portion E1 of flange E is omitted from the illustration in Figure 4(A).
[0035] Figure 4(C) shows the distances Wa and Wb from the intersection of the center line C of the fixing nip N with a virtual line parallel to the recording material transport direction, when viewed in the longitudinal direction of the film (direction perpendicular to the recording material transport direction), to the outer surfaces of ribs Ra and Rb. Specifically, the third distance Wa represents the distance from the intersection of the horizontal line L and the center line C of the fixing nip N to position Ga, which is the third position, where the horizontal line L intersects with the region on the outer surface of the film guide G that faces the inner surface of the film F upstream of the fixing nip N in the recording material transport direction. The fourth distance Wb represents the distance from the intersection of the horizontal line L and the center line C of the fixing nip N to position Gb, which is the fourth position, where the horizontal line L intersects with the region on the outer surface of the film guide G that faces the inner surface of the film F downstream of the fixing nip N in the recording material transport direction. The film F is supported at both ends by flanges E, maintaining a certain degree of tension and a cylindrical shape throughout its entire longitudinal direction. Therefore, at least along the horizontal line L, the film guide G does not come into contact with the inner surface of the film F, even at its longitudinal center.
[0036] Figure 4(D) shows the heights Ya and Yb of the outer surfaces of ribs Ra and Rb perpendicular to the fixing nip N when viewed in the longitudinal direction of the film. In this embodiment, the distance Wa in the width direction is 12 mm and the distance Wb is 9.5 mm, and the distance Ya in the height direction is 16 mm and the distance Yb is 13 mm. As described above, the offset amount due to the inner sliding part E1 of flange E is 1 mm, so this offset is canceled out by the configuration in which the upstream rib Ra protrudes, and the clearance between the film F and the upstream rib Ra does not increase. Therefore, the upstream rib Ra absorbs the impact when the recording material P enters the film, and buckling of the film F is prevented.
[0037] In the above explanation, the center line passing vertically through the center of the width of the fixing nip section N in the recording material transport direction was used as the reference point. However, the various positional relationships may also be defined based on the center line passing vertically through the center of the width of the recess GR of the heater 21 and the film guide G in the same direction. Furthermore, in this embodiment, the positional relationships of each component were defined based on the assumption that the film (heater, film guide) and the pressure roller are arranged vertically as a normally assumed installation state of the fixing device (image forming apparatus). However, the system is not limited to this arrangement. For example, in the case of an arrangement where the film and the pressure roller are arranged horizontally, it goes without saying that the positional relationships of each component will be defined based on this arrangement. That is, in this case, the positional relationships defined in the vertical direction will be defined in the horizontal direction, and the positional relationships defined in the horizontal direction will be defined in the vertical direction.
[0038] Here, the effect of preventing buckling of the film F in the fixing device according to this embodiment will be explained in comparison with the comparative example. Figure 5(A) is a partial cross-sectional view of a fixing device according to the comparative example, in which the rib R of the film guide G is made smaller in the direction of the rotation center of the film F than the inner sliding portion E1 of the flange E, thereby preventing the rib R from damaging the film F. In this fixing device, the inner sliding portion E1 of the flange E is not offset, and the fixing device according to this embodiment is more advantageous in terms of the separation of the film F and the recording material P. Figure 5(B) shows a configuration in the fixing device shown in Figure 5(A) in which the inner sliding portion E1 of the flange E is offset upstream of the fixing nip portion N in order to reduce the radius of curvature of the film F downstream of the fixing nip portion N and improve the separation from the recording material P. However, in this configuration, the clearance between the film F and the rib R widens on the upstream side of the fixing device. Therefore, as shown in Figure 5(C), if the recording material P bounces and penetrates the fixing nip portion N, as shown in Figure 5(D), the impact of the penetration of the recording material P may cause buckling in the longitudinal center of the film F.
[0039] Such buckling is likely to occur more significantly in image forming apparatuses that require higher speeds in recent years. Furthermore, depending on the thinning of the film, there is a concern that in extreme cases, it may lead to film breakage. In contrast, as described above, the fixing apparatus according to this embodiment is configured such that the clearance between the film F and the upstream rib Ra does not widen, due to the configuration in which the upstream rib Ra protrudes. The configuration of the upstream rib Ra will be described in more detail below.
[0040] Figure 4(E) shows the gap Xa on the upstream side in the recording material transport direction between rib Ra and film F, and the gap Xb on the downstream side in the recording material transport direction between rib Rb and film F, in the section between horizontal line L and horizontal line M, when viewed in the longitudinal direction of the film. In the rotational trajectory of film F, from position Ea to the fixing nip section N, there is no restriction by the inner sliding part E1 of flange E, so film F can change its trajectory relatively freely. Therefore, buckling of film F is unlikely to occur. In contrast, in the section between horizontal line L and horizontal line M, film F is restricted by the inner sliding part E1 of flange E, so buckling due to intrusion of the recording material is likely to occur.
[0041] In this embodiment, from this perspective, in the section between horizontal lines L and M where buckling of the film F is likely to occur, the gap Xa, which is the first gap, is made narrower than the gap Xb, which is the second gap. This makes it possible to reduce the bending of the film F when the recording material P enters the upstream side in the recording material transport direction. On the other hand, on the downstream side, by ensuring clearance between the film F and the film guide G, the overall increase in the sliding resistance of the film F is suppressed.
[0042] Here, the gaps Xa and Xb during the rotation of the film F can be measured, for example, by shining the laser beam of a laser measuring instrument onto a hole made in a part of the film F.
[0043] Figure 4(F) shows the areas Sa and Sb of the regions enclosed by the boundary on the inner surface of the film F from the intersection with the horizontal line L to the fixing nip N, the boundary on the guide surfaces of the ribs Ra and Rb from the intersection with the horizontal line L to the fixing nip N, and the horizontal line L, when viewed in the longitudinal direction of the film. In this embodiment, the area Sa of the upstream region, which is formed by dividing the film into upstream and downstream sides in the recording material transport direction by the above boundary and the horizontal line, is smaller than the area Sb of the downstream region. This makes it possible to reduce the bending of the film F on average when the recording material P enters the fixing nip N on the upstream side in the recording material transport direction. Furthermore, on the downstream side, by ensuring clearance between the film F and the film guide G, the overall increase in the sliding resistance of the film F is suppressed.
[0044] Furthermore, the areas Sa and Sb of the film F during rotation can also be measured, for example, by shining the laser beam of a laser measuring instrument onto a hole made in a part of the film F.
[0045] As described above, according to this embodiment, by configuring the upstream rib of the film guide to protrude more than the downstream rib, it is possible to prevent buckling of the film caused by the intrusion of recording material.
[0046] It should be noted that the heater configuration in the present invention is not limited to the configuration of the above embodiment. For example, an IH fuser that heats the conductive layer of the film by electromagnetic induction, or a film The present invention can also be suitably applied to fusers and the like, in which a halogen heater is positioned in the center of the internal space.
[0047] The disclosure of embodiments of the present invention includes the following configurations. (Composition 1) A cylindrical film and A heater is placed in the internal space of the film, A roller that contacts the outer surface of the film and forms a nip between itself and the film, A film guide that guides the inner surface of the film which rotates in accordance with the rotation of the roller, A flange member that guides the regions at both ends in the longitudinal direction of the film, among the inner surface of the film that rotates in accordance with the rotation of the roller, Equipped with, In an image heating device that heats an image formed on a recording material that is gripped and conveyed by the nip by the rotation of the roller using the heat of the heater, When viewed in the longitudinal direction, the position where the portion of the flange member that protrudes most towards the upstream side in the transport direction of the recording material contacts the inner surface of the film is defined as the first position. When viewed in the longitudinal direction, the second position is defined as the position where a first imaginary line passing through the first position and parallel to the nip intersects with the surface of the flange member facing the inner surface of the film, downstream of the nip in the conveying direction. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film facing the inner surface of the film in the film guide, upstream of the nip in the transport direction, is defined as the third position. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film guide downstream of the nip in the transport direction is defined as the fourth position. An image heating device characterized in that, on the first virtual line, the first distance between the intersection point of the first virtual line and a second virtual line perpendicular to the center of the nip in a direction along the first virtual line, and the first position, is longer than the second distance between the intersection point and the second position, and the third distance between the intersection point and the third position is longer than the fourth distance between the intersection point and the fourth distance. (Configuration 2) The image heating device according to configuration 1, characterized in that, on the first imaginary line, the first gap between the first position and the third position is narrower than the second gap between the second position and the fourth position. (Composition 3) The image heating device according to configuration 1 or 2, characterized in that, when viewed in the longitudinal direction, the two regions, which are separated into an upstream and downstream side in the transport direction and enclosed by the boundary from the intersection point with the first imaginary line on the inner surface of the film to the nip, the boundary from the intersection point with the first imaginary line on the outer surface of the film guide to the nip, and the first imaginary line, have an area on the upstream side in the transport direction that is smaller than the area on the downstream side in the transport direction. (Composition 4) The flange member has guide curved surfaces that guide the inner surfaces of both ends of the film in the longitudinal direction, The image heating device according to any one of configurations 1 to 3, characterized in that the center of curvature of the guide surface is located downstream of the center of the nip in the transport direction. (Composition 5) When viewed in the longitudinal direction, the guide surface has a first imaginary line passing through its center of curvature, and its upstream end and downstream end in the transport direction are, respectively, aligned in the transport direction and the longitudinal direction. The image heating device according to configuration 4, characterized in that, in directions perpendicular to each of the directions, it is located closer to the nip than the first imaginary line. (Composition 6) The image heating device according to any one of configurations 1 to 5, characterized in that the film guide supports the heater and has guide surfaces on both sides of the film in the rotational direction relative to the heater that guide the inner surface of the film. (Composition 7) The aforementioned film guide is A base portion having a recess for housing the heater, The first rib protruding from the upstream side in the conveying direction of the base portion, A second rib protruding from the downstream side in the conveying direction of the base portion, It has, The image heating device according to any one of configurations 1 to 6, characterized in that the first rib, when viewed in the longitudinal direction, protrudes more from the base portion toward the inner surface of the film than the second rib. (Composition 8) The image heating apparatus according to configuration 7, characterized in that the amount of protrusion from the base portion in the conveying direction and the amount of protrusion from the base portion in a direction perpendicular to the conveying direction are both larger than that of the second rib. (Composition 9) The first ribs are provided on the base portion so as to be arranged in a plurality along the longitudinal direction, The image heating device according to configuration 7 or 8, characterized in that the second ribs are provided on the base portion in a plurality of arrangements in the longitudinal direction. (Composition 10) The heater is in contact with the inner surface of the film, The image heating device according to any one of configurations 1 to 9, characterized in that the roller forms the nip together with the heater. (Composition 11) 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 10. [Explanation of Symbols]
[0048] F...Film, G...Film guide, N...Fixer nip, E, E1, E2...Flange, R, Ra, Rb...Film guide rib
Claims
1. A cylindrical film and A heater is placed in the internal space of the film, A roller that contacts the outer surface of the film and forms a nip between itself and the film, A film guide that guides the inner surface of the film which rotates in accordance with the rotation of the roller, A flange member that guides the regions at both ends in the longitudinal direction of the film, among the inner surface of the film that rotates in accordance with the rotation of the roller, Equipped with, In an image heating device that heats an image formed on a recording material that is gripped and conveyed by the nip by the rotation of the roller using the heat of the heater, When viewed in the longitudinal direction, the position where the portion of the flange member that protrudes most towards the upstream side in the transport direction of the recording material contacts the inner surface of the film is defined as the first position. When viewed in the longitudinal direction, the second position is defined as the position where a first imaginary line passing through the first position and parallel to the nip intersects with the surface of the flange member facing the inner surface of the film, downstream of the nip in the conveying direction. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film facing the inner surface of the film in the film guide, upstream of the nip in the transport direction, is defined as the third position. When viewed in the longitudinal direction, the position where the first imaginary line intersects the outer surface of the film guide downstream of the nip in the transport direction is defined as the fourth position, On the first imaginary line, the first distance between the intersection point of the first imaginary line and the second imaginary line perpendicular to the center of the nip in the direction along the first imaginary line, and the first position, is longer than the second distance between the intersection point and the second position, and the third distance between the intersection point and the third position is longer than the fourth distance between the intersection point and the fourth position. On the first imaginary line, the first gap between the first position and the third position is narrower than the second gap between the second position and the fourth position. The film guide has a base portion having a recess for housing the heater, and the base portion It has a first rib protruding from the upstream side in the conveying direction and a second rib protruding from the downstream side in the conveying direction of the base portion, The image heating device is characterized in that the first rib has a larger protrusion from the base in the conveying direction and a larger protrusion from the base in a direction perpendicular to the conveying direction than the second rib.
2. The image heating apparatus according to claim 1, wherein, when viewed in the longitudinal direction, the two regions, which are separated into an upstream and a downstream side in the transport direction and enclosed by the boundary from the intersection point with the first imaginary line on the inner surface of the film to the nip, the boundary from the intersection point with the first imaginary line on the outer surface of the film guide to the nip, and the first imaginary line, are characterized in that the area of the upstream region in the transport direction is smaller than the area of the downstream region in the transport direction.
3. The heater is in contact with the inner surface of the film, The image heating apparatus according to claim 1, characterized in that the roller forms the nip together with the heater.
4. 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 the image heating device described in claim 1.