Fixing apparatus and image forming apparatus

Abstract

To provide a fixing device that suppresses variations in the clearance between a separation member disposed over a longitudinal direction and a fixing belt, and thereby can prevent the occurrence of separation failure and damage to the fixing belt.SOLUTION: A fixing device 9 comprises: a fixing belt 20; a heating body 22; a pressure roller 21 that forms a nip part N with the fixing belt 20; and a holding member 66 that has a holding part 66a disposed inside the fixing belt 20, and rotatably holds the fixing belt 20, wherein a recording medium P is conveyed through the nip part N. The fixing device has a separation member 40 that separates the recording medium P from the fixing belt 20. The separation member 40 has an urging member 42 that urges the separation member in a direction to approach the fixing belt 20, and a contact part 41 that is in contact with the fixing belt 20. A contact position of the contact part 41 with the fixing belt 20 is outside a passage area R of the recording medium P and is a position facing the holding part 66a of the belt holding member 66 with the fixing belt 20 therebetween.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In image forming apparatuses such as copiers, printers, and facsimiles, an image is formed by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording, and an unfixed toner image is formed on a recording medium (e.g., paper, etc.) by an image transfer method or a direct method. As a fixing device for fixing the unfixed toner image, a device that heats and presses the toner image formed on the recording medium at a nip portion between a fixing member and a pressure roller to perform a fixing process is known.

[0003] As a fixing device used in an electrophotographic image forming apparatus, from the viewpoint of energy saving, a thin belt member (fixing belt) with a low heat capacity is used as a fixing member. For example, a configuration in which a nip portion is formed via a fixing belt between a heating body disposed on the inner surface of the fixing belt and a pressure roller as the pressure roller is known.

[0004] In the above configuration, there is a problem that a temperature difference occurs between the fixing belt whose temperature rapidly decreases due to its small heat capacity and the heating body having a larger heat capacity than the fixing belt, and the fixing belt is likely to have a deformation habit. Also, the fact that the flat heating body is pressed inside the cylindrical fixing belt is also a factor contributing to the deformation habit of the fixing belt.

[0005] When a deformation habit occurs in the fixing belt, the fluctuation of the orbit becomes large during driving, and the distance from a member fixedly arranged near the fixing belt also fluctuates. For example, when a separating member for separating the recording medium after the fixing process from the fixing belt is provided, there is a risk of causing separation failure due to the unstable separation distance from the fixing belt, or a risk of causing damage by contacting the fixing belt.

[0006] In contrast, Patent Document 1 discloses a configuration in which a separating member is integrally provided with respect to a flange near the contact point between the fixing belt, which is a flexible member, and the flange, which is a restricting member, downstream from the nip portion in the recording material transport direction from the fixing belt. Furthermore, as a configuration that can maintain a constant relative distance between the fixing belt and the separating member, a configuration is disclosed in which a roller is provided on the separating member as a contact member that contacts the fixing belt, and the separating member is biased via the roller. [Overview of the project] [Problems that the invention aims to solve]

[0007] In Patent Document 1, the outer circumferential shape and trajectory of the anchoring belt are restricted at the flanges at both longitudinal ends of the anchoring belt, but not at the central part in the longitudinal direction. Therefore, it is difficult to maintain a constant distance from members arranged over the entire longitudinal area. To achieve good separation of recording media of various sizes, especially small-sized recording media, it is preferable to arrange the separation member in a region that includes the central part in the longitudinal direction of the fixing belt.

[0008] Therefore, the present invention aims to provide a fixing device that can suppress fluctuations in the separation distance between the separating member and the fixing belt, which are arranged along the longitudinal direction, thereby preventing the occurrence of separation failures and damage to the fixing belt. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides a fixing device comprising: a rotatable endless fixing belt; a heating element for heating the fixing belt; a pressure roller for forming a nip portion with the fixing belt; and a belt holding member for rotatably holding the fixing belt, having holding portions disposed inside the fixing belt at both longitudinal ends of the fixing belt, wherein a recording medium is conveyed by passing through the nip portion, and further comprising a separation member for separating the recording medium from the fixing belt, wherein the separation member has a biasing member for biasing it in a direction toward the fixing belt, and a contact portion for contacting the fixing belt, wherein the contact portion is provided convex toward the fixing belt on the side of the separation member facing the holding portion of the belt holding member via the fixing belt, and the contact position of the contact portion with respect to the fixing belt is outside the passage area of ​​the recording medium and at a position facing the holding portion of the belt holding member via the fixing belt. the law of nature, The fixing belt, at the contact position of the abutment portion, has a state in which its inner circumferential surface is not in contact with the holding portion, and when the separating member is pushed toward the fixing belt side, it contacts and is restricted by the holding portion opposite to the abutment portion. It is characterized by the following: [Effects of the Invention]

[0010] The present invention aims to provide a fixing device that can suppress fluctuations in the separation distance between the separating member and the fixing belt, which are arranged along the longitudinal direction, thereby preventing the occurrence of separation failures and damage to the fixing belt. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the image forming apparatus. [Figure 2] This is a cross-sectional view showing an example of the schematic configuration of a fixing device to which the present invention is applied. [Figure 3] This is a cross-sectional view showing the schematic configuration of a fixing device according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing the configuration of the longitudinal end of a fixing device according to one embodiment of the present invention. [Figure 5] This is a cross-sectional view showing the schematic configuration of a fixing device according to one embodiment of the present invention. [Figure 6]It is a schematic diagram showing the configuration of the longitudinal end portion of the fixing device according to an embodiment of the present invention. [Figure 7] It is a perspective view showing an example of a belt support member. [Figure 8] It is a cross-sectional view showing the schematic configuration of a fixing device according to an embodiment different from FIG. 2. [Figure 9] It is a perspective view of a heater, a first high thermal conductivity member, a second high thermal conductivity member, and a heater holder. [Figure 10] It is a plan view of the heater showing the arrangement of the first high thermal conductivity member and the second high thermal conductivity member. [Figure 11] It is a plan view of the heater showing an example of a different arrangement of the first high thermal conductivity member and the second high thermal conductivity member. [Figure 12] It is a diagram showing the atomic crystal structure of graphene. [Figure 13] It is a diagram showing the atomic crystal structure of graphite. [Figure 14] It is a plan view showing a heater in which the arrangement of FIG. 10 is different from that of the second high thermal conductivity member. [Figure 15] It is a cross-sectional view showing the schematic configuration of a fixing device according to an embodiment different from FIGS. 2 and 8. [Figure 16] It is a schematic configuration diagram of an image forming apparatus different from FIG. 1. [Figure 17] It is a cross-sectional view showing the schematic configuration of a fixing device according to another embodiment. [Figure 18] It is a plan view of the heater in the fixing device of FIG. 17. [Figure 19] It is a perspective view of a heater and a heater holder. [Figure 20] It is a perspective view showing the mounting state of a connector to a heater. [Figure 21] It is a diagram showing the arrangement of a thermistor and a thermostat. [Figure 22] It is a diagram showing the groove portion of a belt holding member.

Embodiments for Carrying Out the Invention

[0012] The fixing apparatus and image forming apparatus according to the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited to the embodiments shown below, and other embodiments, additions, modifications, and deletions can be made within the scope of what a person skilled in the art can conceive. Any embodiment that achieves the function and effect of the present invention is included within the scope of the present invention.

[0013] [Image forming apparatus] Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus of this embodiment includes a fixing device according to the present invention, which will be described later.

[0014] The image forming apparatus 100 shown in Figure 1 comprises four detachable image forming units 1Y, 1M, 1C, and 1Bk attached to the main body of the image forming apparatus. Each image forming unit 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains different colored developers: yellow, magenta, cyan, and black. These colored developers correspond to the color separation components of a color image. Each image forming unit 1Y, 1M, 1C, and 1Bk comprises a drum-shaped photoreceptor 2 as an image carrier, a charging device 3, a developing device 4, and a cleaning device 5. The charging device 3 charges the surface of the photoreceptor 2. The developing device 4 supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image. The cleaning device 5 cleans the surface of the photoreceptor 2.

[0015] The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7, a transfer device 8, a fixing device 9 as a heating device, and a paper discharge device 10. The exposure device 6 exposes the surface of each photoreceptor 2 and forms an electrostatic latent image on its surface. The paper feed device 7 supplies the recording medium (hereinafter also referred to as "paper") P to the paper transport path 14. The transfer device 8 transfers the toner image formed on each photoreceptor 2 to the paper P. The fixing device 9 fixes the toner image transferred to the paper P to the surface of the paper P. The paper discharge device 10 discharges the paper P outside the apparatus. Each image forming unit 1, photoreceptor 2, charging device 3, exposure device 6, transfer device 8, etc., constitutes an image forming means for forming an image on paper.

[0016] The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer body, four primary transfer rollers 12 as primary transfer members, and a secondary transfer roller 13 as a secondary transfer member. The intermediate transfer belt 11 is stretched by a plurality of rollers. The primary transfer rollers 12 transfer the toner image on each photoreceptor 2 to the intermediate transfer belt 11. The secondary transfer rollers 13 transfer the toner image transferred on the intermediate transfer belt 11 to the paper P. Each of the plurality of primary transfer rollers 12 is in contact with the photoreceptor 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoreceptor 2 are in contact with each other, and a primary transfer nip is formed between them. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretches the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0017] Furthermore, a pair of timing rollers 15 are provided in the paper transport path 14, between the paper feed device 7 and the secondary transfer nip (secondary transfer roller 13).

[0018] Next, the printing operation of the image forming apparatus described above will be explained with reference to Figure 1. When a print operation is initiated, in each image unit 1Y, 1M, 1C, and 1Bk, the photoreceptor 2 is driven to rotate clockwise as shown in Figure 1, and the surface of the photoreceptor 2 is charged to a uniform high potential by the charging device 3. Next, based on the image information of the original document read by the document reader or the print information instructed from the terminal, the exposure device 6 exposes the surface of each photoreceptor 2. As a result, the potential of the exposed area decreases, and an electrostatic latent image is formed. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoreceptor 2.

[0019] The toner images formed on each photoreceptor 2 rotate with the rotation of each photoreceptor 2 and reach the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred sequentially onto the intermediate transfer belt 11, which rotates counterclockwise as shown in Figure 1. The toner images transferred onto the intermediate transfer belt 11 are then transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates. At the secondary transfer nip, the toner images are transferred to the paper P that has been transported. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 7 is stopped by the timing roller 15, and then transported to the secondary transfer nip in time with the toner images on the intermediate transfer belt 11 reaching the secondary transfer nip. Thus, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoreceptor 2 is removed by the cleaning devices 5.

[0020] The paper P onto which the toner image has been transferred is transported to the fuser unit 9, where the fuser unit 9 fixes the toner image onto the paper P. After that, the paper P is discharged from the device by the paper discharge unit 10, completing the series of printing operations. In addition to paper P (plain paper), recording media on which the image is formed include cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheets, plastic film, prepreg, copper foil, etc.

[0021] [Fusing device] Next, an example of the configuration of a fixing device to which the present invention is applied will be described. The fixing device 9 shown in Figure 2 comprises a fixing belt 20, a pressure roller 21 as a pressure roller, a heater 22 as a heating element, a heater holder 23, a stay 24 as a support member, a thermistor 25 as a temperature sensing member, and a first high thermal conductivity member 28, etc. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer circumferential surface of the fixing belt 20, forming a nip portion N between it and the fixing belt 20. The heater 22 heats the fixing belt 20. The heater holder 23 holds the heater 22. The stay 24 supports the heater holder 23. The thermistor 25 detects the temperature of the first high thermal conductivity member 28.

[0022] The direction perpendicular to the plane of the paper in Figure 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, first high heat conductive member 28, etc. Hereafter, this direction will simply be referred to as the longitudinal direction. This longitudinal direction is also the width direction of the conveyed paper, the belt width direction of the fixing belt 20, and the axial direction of the pressure roller 21.

[0023] The fixing belt 20 has, for example, a tubular base made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer with a thickness of 5 to 50 μm made of a fluororesin such as PFA or PTFE is formed on the outermost layer of the fixing belt 20 to enhance durability and ensure release properties. An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the base and the release layer. The fixing belt 20 can also be configured without an elastic layer, having a release layer as a surface layer on a cylindrical base via an adhesive layer. However, without an elastic layer, the overall rigidity of the belt is low, and it is prone to deformation when stopped. The substrate of the fixing belt 20 is not limited to polyimide; it may also be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni) or SUS. The inner circumferential surface of the fixing belt 20 may be coated with a sliding layer such as polyimide or PTFE.

[0024] The pressure roller 21 has, for example, an outer diameter of 25 mm. The pressure roller 21 has, from the inside out, a core metal 21a as the first layer, an elastic layer 21b as the second layer, and a surface layer 21c as the third layer. The solid core metal 21a is made of a conductive material, and in this embodiment, it is made of iron. The elastic layer 21b is made of a non-conductive material, and in this embodiment, it is made of silicone rubber with a thickness of 3.5 mm. By making the elastic layer 21b a non-conductive layer, it is not necessary to add materials such as fillers to impart conductivity to the elastic layer 21b, and its elasticity and stretchability can be ensured.

[0025] The pressure roller 21 is biased toward the fixing belt 20 by the biasing means, causing the pressure roller 21 to press against the heater 22 via the fixing belt 20. This forms a nip portion N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is also configured to be rotationally driven by a driving means, and as the pressure roller 21 rotates in the direction of the arrow in Figure 2, the fixing belt 20 rotates in conjunction with it.

[0026] The heater 22 is a planar heating element provided longitudinally across the width direction of the fixing belt 20. The heater 22 is composed of a plate-shaped base material 30, a resistance heating element 31 provided on the base material 30, and an insulating layer 32 covering the resistance heating element 31. The heater 22 is in contact with the inner circumferential surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the insulating layer 32. However, this contact may be made via a conductive member such as a sliding sheet. By applying an AC voltage from a power source to the heater 22, the resistance heating element 31 mainly generates heat. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (nip portion N side) of the base material 30, but conversely, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the base material 30. In that case, the heat from the resistance heating element 31 will be transferred to the fixing belt 20 via the base material 30, so it is desirable that the base material 30 be made of a material with high thermal conductivity, such as aluminum nitride. Furthermore, by making the base material 30 of a material with high thermal conductivity, it is possible to sufficiently heat the fixing belt 20 even if the resistance heating element 31 is placed on the opposite side of the base material 30 from the fixing belt 20 side.

[0027] The heater holder 23 and the stay 24 are positioned on the inner circumference side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends are supported by the side plates of the fixing device 9. The heater holder 23 and heater 22 are supported by the stay 24, so that the heater 22 can reliably receive the pressing force of the pressure roller 21 when the pressure roller 21 is pressed against the fixing belt 20. As a result, a nip portion N is stably formed between the fixing belt 20 and the pressure roller 21. In this embodiment, the thermal conductivity of the heater holder 23 is set to be lower than that of the base material 30.

[0028] Furthermore, the statement that the stay 24 supports the heater holder 23 means that the portion of the stay 24 that extends in the direction of pressure applied by the pressure roller 21 (left-right direction in the figure), or the portion that has thickness, contacts the heater holder 23 from the side opposite to the pressure roller 21 (left side in the figure). This suppresses the deflection of the heater holder 23 due to the pressure applied by the pressure roller 21 (in this embodiment, especially deflection in the longitudinal direction). However, the above contact is not limited to cases where the stay 24 directly contacts the heater holder 23, but also includes cases where it contacts via another member. "Contact via another member" refers to a state in which, in the left-right direction in the figure, another member is sandwiched between the stay 24 and the heater holder 23, and at least a part of it contacts the other member, and the other member contacts the heater holder 23. Furthermore, the phrase "extending in the direction of pressure" as described above is not limited to the same direction as the pressure direction of the pressure roller 21, but also includes cases where the stay 24 extends in a direction with a certain angle from the pressure direction of the pressure roller 21. In these cases as well, it is of course possible for the stay 24 to suppress the deflection of the heater holder 23 against the pressure applied from the pressure roller 21.

[0029] Since the heater holder 23 is prone to becoming hot due to the heat from the heater 22, it is desirable that it be made of a heat-resistant material. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to efficiently heat the fixing belt 20.

[0030] Furthermore, the heater holder 23 is provided with guide sections 26 for guiding the fixing belt 20. The guide sections 26 are provided on the upstream side (below the heater 22 in Figure 2) and the downstream side (above the heater 22 in Figure 2) of the heater 22 in the direction of belt rotation. Multiple guide sections 26 on the upstream and downstream sides are arranged at intervals along the longitudinal direction of the heater 22. Each guide section 26 is formed in a substantially fan shape and has an arc-shaped or convex curved belt-facing surface 260 that extends in the circumferential direction of the belt so as to face the inner circumferential surface of the fixing belt 20.

[0031] The heater holder 23 has a plurality of openings 23a in the longitudinal direction. The openings 23a are openings that penetrate the heater holder 23 in the thickness direction. Thermistors 25 and thermostats described later are provided in these openings 23a. These thermistors 25 and thermostats are pressed against the back surface of the first high heat conductive member 28 by pressure from a spring 29. However, the first high heat conductive member 28 (and the second high heat conductive member described later) may also be provided with openings in a similar manner, so that the thermistors 25 and thermostats are pressed against the back surface of the base material 30.

[0032] The first high thermal conductivity member 28 is made of a material with a higher thermal conductivity than the base material. In this embodiment, the first high thermal conductivity member 28 is made of plate-shaped aluminum. Alternatively, the first high thermal conductivity member 28 may be made of other materials such as copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 relative to the heater holder 23 and the first high thermal conductivity member 28 can be improved.

[0033] Next, we will explain the method for calculating the thermal conductivity described above. When calculating thermal conductivity, first, the thermal diffusivity of the object in question is measured, and this thermal diffusivity is used to calculate the thermal conductivity. Thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (product name: ai-Phase Mobile 1u, manufactured by i-Phase Co., Ltd.). To convert the above thermal diffusivity to thermal conductivity, the values ​​of density and specific heat capacity are required. For density measurement, a dry automatic densimeter (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used. For specific heat capacity measurement, a differential scanning calorimetry device (product name: DSC-60, manufactured by Shimadzu Corporation) was used, and sapphire was used as a reference material with a known specific heat capacity.

[0034] In this example, specific heat capacity measurements were performed five times, and the average value at 50°C was used. If the density and specific heat capacity are ρ and C, respectively, then the thermal conductivity λ can be obtained from the thermal diffusivity α obtained in the above thermal diffusivity measurement using the formula: λ = ρ × C × α.

[0035] In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate in response. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the belt-facing surface 260 of the guide section 26, so that the fixing belt 20 rotates stably and smoothly. Also, power is supplied to the resistance heating element 31 of the heater 22, so that the fixing belt 20 is heated. When the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in Figure 2, the paper P on which the unfixed toner image is carried between the fixing belt 20 and the pressure roller 21 (nip section N), so that the unfixed toner image is heated and pressurized and fixed to the paper P. The fixing belt 20 is the heated member that is heated by the heater 22.

[0036] <First Embodiment> A first embodiment of the fixing device according to the present invention is shown in Figures 3 and 4. Figure 3 is a cross-sectional view showing the schematic configuration of the fixing device according to this embodiment, and Figure 4 is a schematic diagram showing the configuration of the longitudinal end of the fixing device according to this embodiment. Although Figure 4 shows only one end, the other end has a similar configuration. Detailed illustrations and explanations of configurations similar to those in Figure 2 are omitted.

[0037] The fixing device of this embodiment includes a rotatable endless fixing belt 20, a heating element (heater) 22 for heating the fixing belt 20, a pressure roller 21 that forms a nip portion N between itself and the fixing belt 20, and a belt holding member 66 that has holding portions 66a disposed inside the fixing belt 20 at both longitudinal ends of the fixing belt 20 and rotatably holds the fixing belt 20, and the fixing device is such that a recording medium (paper P) is conveyed by passing through the nip portion N, and includes a separating member 40 for separating the recording medium (paper P) from the fixing belt 20. The separating member 40 has a biasing member 42 that biases it in a direction that brings it closer to the fixing belt 20, and a contact portion 41 that contacts the fixing belt 20. The contact position of the contact portion 41 with respect to the fixing belt 20 is outside the passage area R of the recording medium (paper P) and is opposite to the holding portion 66a of the belt holding member 66 via the fixing belt 20.

[0038] The fixing belt 20 is slidably held at the inner surfaces of both ends by the holding portion 66a of the belt holding member 66. Figure 7 shows an external perspective view of an example of a belt retaining member 66. The belt retaining member 66 shown in Figure 7(A) has a retaining portion 66a with a C-shaped cross-section and a notch, a restricting portion (flange portion) 66b, and an opening 66c. The belt retaining member 66 shown in Figure 7(B) is cylindrical with a continuous retaining portion 66a. The belt retaining member 66 is a member that is integrally formed, for example, by resin injection molding.

[0039] The retaining portion 66a is inserted into the inner circumference of the fixing belt 20 and supports the fixing belt 20. The restricting section 66b restricts the longitudinal (widthwise) movement of the anchoring belt 20. The ends of the heater 22 and heater holder 23, etc., which are arranged inside the fixing belt 20, are fixed to each side plate 68 through the opening 66c. Alternatively, these may be fixed to the belt holding member 66.

[0040] Since only both ends of the fixing belt 20 are held by the belt holding member 66, the fixing belt 20 is in a deformable state between both ends (the longitudinal center), except for the nip portion N. Therefore, when the fixing operation stops (when left under pressure), the fixing belt 20 deforms to spread out to the left and right, as shown by the solid line in Figure 3. On the other hand, the fixing belt 20a, shown by the dashed line, represents the trajectory of the fixing belt when it is sufficiently heated and a sufficient amount of time has elapsed since the start of operation. The fixing belt starts rotating from the deformed state shown by the solid line (reference numeral 20) at the beginning of operation, and gradually becomes the stable trajectory (reference numeral 20a) of normal rotation. When the trajectory of the anchoring belt 20 changes, the contact portion 41 that abuts the surface of the anchoring belt 20 is displaced in accordance with the anchoring belt 20, causing the separating member 40 to rotate and maintaining a constant distance from the anchoring belt 20.

[0041] In the configuration of this embodiment, since there is no member to restrict the deformation of the anchoring belt 20, a similar change in trajectory occurs throughout the entire longitudinal direction. The contact portion 41 of the separating member 40 is provided only at both ends in the longitudinal direction, but by following the change in trajectory at both ends, the separating member 40 as a whole, which is integrally provided along the longitudinal direction (width direction) of the anchoring belt 20, follows the displacement and makes it possible to maintain a constant distance from the anchoring belt 20.

[0042] As shown in Figure 4, the pressure roller 21 and the belt holding member 66 are arranged without overlapping in the longitudinal direction. This prevents the formation of areas on the fixing belt 20 that are in contact with both the pressure roller 21 and the belt holding member 66, thereby mitigating stress concentration.

[0043] The separation member 40 is provided along the longitudinal direction and has a length that exceeds the passage area of ​​the recording medium (hereinafter also referred to as the "paper passage area"). The material constituting the separation member 40 is not particularly limited and can be, for example, resin or metal. The separating member 40 has a pivot shaft 40a fixed to the side plate 68 that rotatably supports the main body.

[0044] In this embodiment, a leaf spring is used as the biasing member 42, but it is not particularly limited to any member that biases the separating member 40 toward the fixing belt 20. One end of the biasing member 42 is fixed to a support portion (not shown) provided on the side plate 68.

[0045] The separating member 40 has contact portions 41 at both ends in the longitudinal direction that are located outside the paper feeding area R and opposite the holding portion 66a of the belt holding member 66 via the fixing belt 20, and are provided in a convex shape toward the fixing belt 20. When the transport of paper P stops due to a jam or the like within the fixing device, a paper removal operation is performed. However, during this removal operation, the separating member 40 may be excessively pushed towards the fixing belt 20, potentially causing damage to the fixing belt 20. In contrast, in this embodiment, the pushing of the separating member 40 is restricted by the holding portion 66a facing the contact portion 41, thus preventing excessive pushing and the resulting damage to the fixing belt 20.

[0046] Furthermore, at the contact point with the contact portion 41 of the fixing belt 20, the inner circumferential surface does not come into contact with the holding portion 66a during normal fixing operation (rotation). By having the contact portion 41 come into contact with a portion that would not normally come into contact with the holding portion 66a, wear of the fixing belt 20 can be suppressed, thereby extending the lifespan of the component. Furthermore, since the contact portion 41 contacts the fixing belt 20 outside the paper feeding area R, the occurrence of image unevenness due to friction in the image area is prevented, and image quality is maintained.

[0047] The contact portion 41 of the separating member 40 is preferably made of an elastic material that can be elastically deformed. By constructing the contact portion 41 from an elastic material, wear on the surface of the fixing belt 20 can be prevented, and the load can be distributed when pressed against the holding portion 66a, thereby preventing the fixing belt 20 from becoming indented. The preferred material for the contact portion 41 is not particularly limited as long as it has low abrasion resistance, but examples include foams such as resins and nonwoven fabrics. Furthermore, while the shape of the contact portion 41 is not particularly limited, it is preferable to have a large contact area with the anchoring belt 20. By increasing the contact area between the contact portion 41 and the anchoring belt 20, the surface pressure on the contact surface is reduced, preventing deformation and thus preventing damage to the anchoring belt 20.

[0048] Because the contact portion 41 lightly contacts the circumferential surface of the fixing belt 20, the gap between the leading edge of the separating member 40 in the paper feeding area R and the fixing belt 20 is maintained at an optimal gap for separating the paper P. "Light contact" refers to contact that does not cause significant deformation or displacement of the contact points. The biasing force applied by the biasing member 42 to the separating member 40 is set such that the fixing belt 20 does not deform significantly when the contact portion 41 contacts the circumferential surface of the fixing belt 20.

[0049] In this embodiment, the fixing device, with the above configuration, suppresses fluctuations in the separation distance between the separation member 40, which is arranged along the longitudinal direction, and the fixing belt 20, thereby preventing separation failures and damage to the fixing belt 20. Furthermore, since the movement of the contact portion 41 is restricted by the holding portion 66a of the belt holding member 66, abnormal displacement of the separation member 40 is prevented, and damage to the fixing belt can be prevented. Moreover, since the contact portion 41 contacts the outside of the paper feeding area R of the fixing belt 20, the image quality is not reduced. It is preferable that the contact portion 41 of the separation member 40 be located outside the area where the heating element of the heater 22 is arranged in the longitudinal direction. This reduces the influence of heat absorption from the contact area.

[0050] The heating element (heater) 22 is positioned in the nip section N. The heater 22, supported by the heater holder 23, acts as the nip-forming member, and the nip section N is formed by the opposing pressure rollers 21 via the fixing belt 20. By arranging the heater 22 in the nip section N, a difference in cooling time occurs after the fixing operation, making the fixing belt 20 more prone to deformation. However, with the configuration of this embodiment, the separation member 40 is displaced in accordance with the trajectory fluctuations of the deformed fixing belt 20, and the separation distance between the fixing belt 20 and the separation member 40 can be kept constant, thus maintaining good separation of the paper P.

[0051] The heating element (heater) 22 can be a planar or plate-shaped member. Using a flat plate-shaped member reduces the heat capacity and improves the heating rate, leading to energy savings. However, a flat plate-shaped heater 22 makes the fixing belt 20 more prone to deformation, and the deformation becomes more pronounced. In contrast, with the configuration of this embodiment, the separation distance between the fixing belt 20 and the separation member 40 can be kept constant, thus maintaining good separation of the paper P.

[0052] As described above, the fixing belt 20 is preferably composed of a belt-shaped member made of a resin material. However, using a resin base material results in lower rigidity and a tendency to deform compared to a metal base material. In contrast, with the configuration of this embodiment, the separation distance between the fixing belt 20 and the separation member 40 can be kept constant, thus maintaining good separation of the paper P.

[0053] The formation of the nip portion N may be in a manner in which pressure is applied toward the heater 22 side to which the pressure roller 21 is fixed, or in a manner in which pressure is applied toward the pressure roller 21 side to which the heater 22 is fixed. However, from the viewpoint of suppressing fluctuations in the separation distance between the fixing belt 20 and the separating member 40 and maintaining separation performance, it is preferable that the pressure roller 21 applies pressure. For example, the system is equipped with a pressure means that applies pressure to the pressure roller 21 to press it against the fixing belt 20, and the nip portion N can be formed by the pressure means applying pressure to the pressure roller 21.

[0054] As described above, the fixing belt 20 is a component that rotates in conjunction with the rotation of the pressure roller 21. Because it rotates in conjunction with the pressure roller 21, it is necessary to provide a large gap between the fixing belt 20 and each component housed inside it. This makes the fixing belt 20 more susceptible to deformation, but according to the configuration of this embodiment, the separation distance between the fixing belt 20 and the separation member 40 can be kept constant, so the separation of the paper P is maintained well.

[0055] Furthermore, it is preferable that the outer diameter of the fixing belt 20 is larger than the outer diameter of the pressure roller 21. By increasing the outer diameter of the fixing belt 20, the nip width of the nip section N and the width of the heating element (heater) 22 disposed in the nip section can also be increased, thereby improving productivity and enabling the equipment to accommodate high production capacity. It is preferable that the heater 22 has a heating element divided into multiple sections in the longitudinal direction, but in order to achieve such a configuration, it is necessary to widen the width of the heater 22. The degree of deformation that occurs in the fixing belt 20 changes depending on the width of the heater 22 or the width of the nip portion N relative to the outer diameter of the fixing belt 20. However, with the configuration of this embodiment, the separation distance between the fixing belt 20 and the separation member 40 can be kept constant, so the separation of the paper P is maintained well.

[0056] The pressure roller 21 has a depressurization mechanism for moving from a pressing state to a depressurized state against the fixing belt 20. In the pressed state, the pressure roller 21 presses against the fuser belt 20 with the pressure necessary to transfer the toner image onto the paper P. By operating the pressure release mechanism to the depressurized state, deformation of the fuser belt 20 can be reduced, jammed paper caught between the pressure roller 21 and the fuser belt 20 can be easily removed, and the compression set of the elastic layer 21b of the pressure roller 21 can be alleviated.

[0057] <Second Embodiment> A second embodiment of the fixing device according to the present invention is shown in Figures 5 and 6. Figure 5 is a cross-sectional view showing the schematic configuration of the fixing device according to this embodiment, and Figure 6 is a schematic diagram showing the configuration of the longitudinal end of the fixing device according to this embodiment. Although Figure 6 shows only one end, the other end has a similar configuration. Detailed illustrations and explanations of configurations similar to those shown in Figures 2 to 4 are omitted.

[0058] In this embodiment, the contact portion 41 is formed integrally with the separating member 40. Furthermore, while the shape of the contact portion 41 is not particularly limited, it is preferable to have a large contact area with the anchoring belt 20. By increasing the contact area between the contact portion 41 and the anchoring belt 20, the surface pressure on the contact surface is reduced, preventing deformation and thus preventing damage to the anchoring belt 20. The contact portion 41 is preferably made of a low-friction material in order to prevent wear on the surface of the fixing belt 20 that it contacts. Furthermore, while the shape of the contact portion 41 is not particularly limited, it is preferable to minimize the contact area with the fixing belt 20 to the extent that the effect can be obtained.

[0059] In this embodiment, the biasing member 42 is a torsion spring (torsion coil spring). Similar to the first embodiment, the biasing force applied by the biasing member 42 to the separating member 40 is set such that the fixing belt 20 does not deform when the contact portion 41 contacts the circumferential surface of the fixing belt 20.

[0060] [Other embodiments] The following describes different embodiments of fixing apparatuses and image forming apparatuses to which the present invention is applied. The fixing device 9 in Figure 8 has a second high-temperature conductive member 36 between the heater holder 23 and the first high-temperature conductive member 28. The second high-temperature conductive member 36 is provided at a different position from the first high-temperature conductive member 28 in the stacking direction (left-right direction in Figure 8) of the components such as the heater holder 23, stay 24, and first high-temperature conductive member 28. More specifically, the second high-temperature conductive member 36 is provided superimposed on the first high-temperature conductive member 28. Note that Figure 8 differs from Figure 2 in that it shows a cross-section where the second high-temperature conductive member 36 is arranged in the alignment direction and the thermistor 25 is not provided.

[0061] The second high thermal conductivity member 36 is made of a material with a higher thermal conductivity than the base material 30, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 36 is formed from a graphite sheet with a thickness of 1 mm. However, the second high thermal conductivity member 36 may also be made from a plate material such as aluminum, copper, or silver.

[0062] As shown in Figure 9, multiple second high-heat-conducting members 36, each partially provided in the arrangement direction, are arranged in the arrangement direction. The portion of the recess 23b of the heater holder 23 where the second high-heat-conducting member 36 is provided is made one step deeper than the other portions. The second high-heat-conducting member 36 has a gap between it and the heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from the second high-heat-conducting member 36 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that the guide portion 26 shown in Figure 2 is omitted in Figure 9.

[0063] As shown in Figure 10, the second high thermal conductivity member 36 (see hatched area) is provided in the arrangement direction at a position corresponding to the interval B, overlapping at least a portion of the adjacent resistance heating element 31, and in this embodiment in particular, it is provided over the entire interval B. However, although Figure 10 (and Figure 14 described later) shows the case in which the first high thermal conductivity member 28 is provided only in the region corresponding to the heating element 35 in the arrangement direction, as mentioned above, it is not limited to this.

[0064] As in this embodiment, by providing a second high-heat-conducting member 36 in addition to the first high-heat-conducting member 28 at a position corresponding to the spacing B in the arrangement direction, overlapping at least a portion of the adjacent resistance heating elements 31, the heat transfer efficiency in the arrangement direction at the spacing B can be particularly improved, and temperature unevenness in the arrangement direction of the heater 22 can be further suppressed. Furthermore, most preferably, as shown in Figure 11, the first high-heat-conducting member 28 and the second high-heat-conducting member 36 are provided only in the entire area at the position corresponding to the spacing B. This makes it possible to particularly improve the heat transfer efficiency at the position corresponding to the spacing B compared to other areas. Note that in Figure 11, for convenience, the resistance heating elements 31, the first high-heat-conducting member 28, and the second high-heat-conducting member 36 are shown shifted vertically in Figure 11, but they are arranged at approximately the same position in the arrangement intersection direction. However, this is not limited to this, and the first high-heat-conducting member 28 and the second high-heat-conducting member 36 may be provided in a part of the arrangement intersection direction of the resistance heating elements 31, or they may be provided so as to cover the entire arrangement intersection direction.

[0065] In an embodiment different from the above, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are made of the graphene sheet. This makes it possible to form the first high thermal conductivity member 28 and the second high thermal conductivity member 36 with high thermal conductivity in a predetermined direction along the surface of the graphene, that is, in the alignment direction rather than the thickness direction. Therefore, temperature unevenness in the alignment direction of the heater 22 and the fixing belt 20 can be effectively suppressed.

[0066] Graphene is a flaky powder. As shown in Figure 12, graphene consists of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, usually a single layer. The single layer of carbon may contain impurities. Graphene may also have a fullerene structure. A fullerene structure is generally recognized as a compound in which an equal number of carbon atoms form a polycyclic structure fused in a cage-like manner with 5-membered and 6-membered rings, such as C60, C70, and C80 fullerenes or other closed cage-like structures having 3-coordinate carbon atoms.

[0067] Graphene sheets are artificial materials and can be fabricated, for example, by chemical vapor deposition (CVD).

[0068] Commercially available graphene sheets can be used. The size and thickness of the graphene sheet, as well as the number of layers of the graphite sheet described later, can be measured, for example, by a transmission electron microscope (TEM).

[0069] Furthermore, graphite with multiple layers of graphene exhibits high thermal conductivity anisotropy. As shown in Figure 13, graphite has a crystalline structure in which layers of condensed six-membered rings of carbon atoms are spread out in a planar manner, and these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. The covalent bonds have a stronger bonding force than van der Waals bonds, and there is a large anisotropy between the bonds within a layer and the bonds between layers. In other words, by constructing the first high thermal conductivity member 28 or the second high thermal conductivity member 36 from graphite, the heat transfer efficiency in the arrangement direction of the first high thermal conductivity member 28 or the second high thermal conductivity member 36 becomes larger than in the thickness direction (i.e., the stacking direction of the members), and heat transfer to the heater holder 23 can be suppressed. Therefore, temperature unevenness in the arrangement direction of the heater 22 can be efficiently suppressed, and the heat flowing out to the heater holder 23 can be minimized. Furthermore, by constructing the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 from graphite, it is possible to provide the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 with excellent heat resistance that prevents oxidation up to approximately 700 degrees Celsius.

[0070] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the function required of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36. For example, the anisotropy of its thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. In addition, to increase the speed of the fixing device 9, a thinner graphite sheet may be used to reduce the heat capacity of the fixing device 9. Furthermore, if the width of the nip section N or the heater 22 is large, the width of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 in the alignment direction may be increased accordingly.

[0071] From the viewpoint of increasing mechanical strength, it is preferable that the graphite sheet has 11 or more layers. Furthermore, the graphite sheet may partially consist of single-layer and multi-layer sections.

[0072] The second high-heat-conductivity member 36 is provided in a position corresponding to the spacing B (and further to region C) in the arrangement direction, overlapping at least a portion of the adjacent resistance heating element 31, and is not limited to the arrangement shown in Figure 10. For example, as shown in Figure 14, the second high-heat-conductivity member 36A is provided so as to protrude from the base material 30 on both sides in the direction of the arrangement intersection. The second high-heat-conductivity member 36B is provided in the range where the resistance heating element 31 is provided in the direction of the arrangement intersection. The second high-heat-conductivity member 36C is provided in a portion of the spacing B.

[0073] Furthermore, as shown in Figure 15, in this embodiment, a gap in the thickness direction (left-right direction in Figure 15) is provided between the first high heat conductive member 28 and the heater holder 23. In other words, in a part of the recess 23b (see Figure 9) of the heater holder 23 for arranging the heater 22, the first high heat conductive member 28, and the second high heat conductive member 36, a relief portion 23c is provided as an insulating layer in a part of the direction of the intersection of the arrangement, in the part other than the part where the second high heat conductive member 36 is provided in the arrangement direction, making the depth of the recess 23b deeper than the other part that receives the first high heat conductive member 28. This minimizes the contact area between the heater holder 23 and the first high heat conductive member 28. Therefore, heat transfer from the first high heat conductive member 28 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20. In the cross-section where the second high-heat-conducting member 36 in the arrangement direction is provided, the second high-heat-conducting member 36 abuts against the heater holder 23, as shown in Figure 8 of the embodiment described above.

[0074] Furthermore, in this embodiment in particular, relief portions 23c are provided over the entire area where the resistance heating element 31 is provided in the direction of array crossing (up and down direction in Figure 15). This suppresses heat transfer, especially from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. In addition to a configuration that provides space as in the relief portion 23c, a configuration in which an insulating material with a lower thermal conductivity than the heater holder 23 is provided may also be used as the insulating layer.

[0075] Furthermore, although the above description describes the second high-thermal-conductivity member 36 as a different member from the first high-thermal-conductivity member 28, the explanation is not limited to this. For example, the portion of the first high-thermal-conductivity member 28 corresponding to the gap B may be made thicker than the other portions.

[0076] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Figure 1, but may also be a monochrome image forming apparatus, a copier, a printer, a facsimile, or a combination device thereof.

[0077] For example, as shown in Figure 16, the image forming apparatus 100 of this embodiment comprises an image forming means 50 consisting of a photosensitive drum, a paper transport unit consisting of a pair of timing rollers 15, a paper feed device 7, a fuser 9, a paper discharge device 10, and a reading unit 51. The paper feed device 7 is equipped with multiple paper trays, each tray accommodating paper of different sizes.

[0078] The reading unit 51 reads the image of the original document Q. The reading unit 51 generates image data from the read image. The paper feed device 7 receives multiple sheets of paper P and feeds the paper P to the transport path. The timing roller 15 transports the paper P on the transport path to the image forming means 50.

[0079] The image forming means 50 forms a toner image on the paper P. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a static elimination device. The toner image shows, for example, an image of the original document Q. The fixing device 9 heats and pressurizes the toner image to fix it to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming device 100.

[0080] Furthermore, a fixing device 9 of another embodiment will be described. Configurations common to the fixing device of the previously described embodiment will be omitted from the description as appropriate. As shown in Figure 17, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, a first high heat conductive member 28, and the like.

[0081] A nip section N is formed between the fixing belt 20 and the pressure roller 21. The nip width of the nip section N is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

[0082] The fixing belt 20 comprises a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material, for example, made of fluororesin. The outer diameter of the fixing belt 20 is approximately 24 mm.

[0083] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a surface layer 21c. The outer diameter of the pressure roller 21 is formed to be 24-30 mm, and the thickness of the elastic layer 21b is formed to be 3-4 mm.

[0084] The heater 22 includes a base material, a heat insulating layer, a conductor layer containing a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width Y in the direction of the arrangement intersection of the heaters 22 is 13 mm.

[0085] As shown in Figure 18, the conductor layer of the heater 22 comprises a plurality of resistive heating elements 31, a power supply line 33, and electrode sections 34A to 34C. In this embodiment as well, as shown in the enlarged view of Figure 18, the plurality of resistive heating elements 31 are divided in the direction of arrangement to form a spacing B as a divided region (however, although spacing B is only shown in the enlarged view in Figure 18, in reality spacing B is provided between all resistive heating elements 31). The resistive heating elements 31 constitute three heating sections 35A to 35C. By energizing the electrode sections 34A and 34B, heating sections 35A and 35C generate heat. By energizing the electrode sections 34A and 34C, heating section 35B generates heat. For example, when performing a fixing operation on small-sized paper, heating section 35B is heated, and when performing a fixing operation on large-sized paper, all heating sections can be heated.

[0086] As shown in Figure 19, the heater holder 23 holds the heater 22 and the first high heat conductive member 28 in its recess 23d. The recess 23d is provided on the heater 22 side of the heater holder 23. The recess 23d is composed of a surface 23d1 substantially parallel to the base material 30 that is recessed on the stay 24 side than the other surfaces of the heater 22, a wall portion 23d2 provided on the inside of the heater holder 23 on both sides (or one side) in the arrangement direction of the heater holder 23, and a wall portion 23d3 provided on the inside of the heater holder 23 on both sides in the direction of the arrangement intersection. The heater holder 23 has a guide portion 26. The heater holder 23 is made of LCP (liquid crystal polymer).

[0087] As shown in Figure 20, the connector 60 comprises a housing made of resin (e.g., LCP) and a plurality of contact terminals provided inside the housing.

[0088] The connector 60 is attached by sandwiching the heater 22 and the heater holder 23 together from the front and back sides. In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 22, thereby electrically connecting the heating element 35 and the power supply provided in the image forming apparatus via the connector 60. This makes it possible to supply power from the power supply to the heating element 35. Note that each electrode portion 34 is exposed, at least a portion of which is not covered by the insulating layer, in order to ensure connection with the connector 60.

[0089] The belt holding members 66 are provided on both sides of the fixing belt 20 in the direction of arrangement and hold both ends of the fixing belt 20 from the inside of the belt. The belt holding members 66 are fixed to the housing of the fixing device 9. The belt holding members 66 are inserted into both ends of the stay 24 (see the direction of the arrows from the belt holding members 66 in Figure 20).

[0090] The mounting direction of the connector 60 to the heater 22 and heater holder 23 is the direction in which the heaters intersect (see the direction of the arrow from the connector 60 in Figure 20). When the connector 60 is mounted to the heater holder 23, a protrusion on one side of the connector 60 and the heater holder 23 may engage with a recess on the other side, and the protrusion may move relative to the other within the recess. The connector 60 is mounted to the heater 22 and heater holder 23 on one side in the arrangement direction, on the side opposite to the side where the drive motor for the pressure roller 21 is provided.

[0091] As shown in Figure 21, thermistors 25 are provided opposite the inner circumferential surface of the fixing belt 20, at the center and end sides in the direction of alignment of the fixing belt 20. The heater 22 is controlled based on the temperatures of the center and end sides of the fixing belt 20 detected by the thermistors 25.

[0092] Thermostats 27 are provided on the center side and end side of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. If the temperature of the fixing belt 20 detected by the thermostats 27 exceeds a predetermined threshold, the power supply to the heater 22 is stopped.

[0093] Belt retaining members 66 are provided at both ends of the fixing belt 20 in the direction of arrangement to hold each end of the fixing belt 20. The belt retaining members 66 are made of LCP (liquid crystal polymer).

[0094] As shown in Figure 22, the belt holding member 66 is provided with a slide groove 66d. The slide groove 66d extends in the direction in which the fixing belt 20 moves toward and toward the pressure roller 21. The engaging portion of the housing of the fixing device 9 engages with the slide groove 66d. As this engaging portion moves relative to the slide groove 66d, the fixing belt 20 can move toward and toward the pressure roller 21. [Explanation of symbols]

[0095] 1. Image forming apparatus 9 Fixing device 20 Fixing belt 21 Pressure roller 22 Heater (heating element) 23 Heater holder 26 Guide section 40 Separation member 41 Contact part 42. Biasing member 66 Belt holding member 66a Holding part 68 Side panel N Nip section [Prior art documents] [Patent Documents]

[0096] [Patent Document 1] Japanese Patent Publication No. 2006-153948

Claims

1. A fixing device comprising: a rotatable endless fixing belt; a heating element for heating the fixing belt; a pressure roller for forming a nip portion with the fixing belt; and a belt holding member having holding portions disposed inside the fixing belt at both longitudinal ends of the fixing belt and rotatably holding the fixing belt, wherein a recording medium is conveyed by passing through the nip portion, It has a separating member that separates the recording medium from the fixing belt, The separating member has a biasing member that biases it in a direction that brings it closer to the fixing belt, and a contact portion that contacts the fixing belt, The contact portion is provided convex toward the fixing belt on the side of the belt holding member facing the holding portion via the fixing belt, the separating member is provided convex toward the fixing belt. The contact position of the contact portion with respect to the fixing belt is outside the passage area of ​​the recording medium and is opposite to the holding portion of the belt holding member via the fixing belt. The fixing belt, at the contact position of the abutment portion, has a state in which its inner circumferential surface is not in contact with the holding portion, and when the separating member is pushed toward the fixing belt side, it contacts and is restricted by the holding portion opposite to the abutment portion. A fixing device characterized by the following features.

2. The fixing device according to claim 1, characterized in that the heating element is disposed in the nip portion.

3. The fixing device according to claim 1 or 2, characterized in that the heating element is a planar or plate-shaped member having a base material, a heating element provided on the base material, and a high thermal conductivity member on the side of the base material where the heating element is provided.

4. The fixing device according to claim 3, characterized in that the contact portion of the separating member is located outside the area where the heating element is installed in the longitudinal direction.

5. The fixing device according to any one of claims 1 to 4, characterized in that the fixing belt rotates in conjunction with the rotation of the pressure roller.

6. The fixing device according to any one of claims 1 to 5, characterized in that the fixing belt is a belt-shaped member made of a resin material.

7. The fixing device according to any one of claims 1 to 6, characterized in that the pressure roller has a depressurization mechanism for moving from a pressing state to a depressurization state with respect to the fixing belt.

8. The fixing device according to any one of claims 1 to 7, characterized in that the contact portion of the separating member is made of an elastic material that can be elastically deformed.

9. The fixing device according to any one of claims 1 to 8, characterized in that the outer diameter of the fixing belt is larger than the outer diameter of the pressure roller.

10. The fixing device according to any one of claims 1 to 9, further comprising a pressurizing means for pressurizing the pressure roller and pressing it against the fixing belt, wherein the nip portion is formed by the pressurizing means pressing the pressure roller.

11. The fixing device according to any one of claims 1 to 10, characterized in that the fixing belt has a surface layer on a cylindrical substrate via an adhesive layer.

12. The fixing device according to any one of claims 1 to 11, characterized in that the heating element has a plurality of heating elements divided in the longitudinal direction.

13. An image forming apparatus characterized by comprising a fixing device according to any one of claims 1 to 12.

Images