Conveying device, image forming device

Abstract

To prevent faulty heating of a recording medium.SOLUTION: A fixing device has a heater 22 for heating a sheet P, and an end side thermistor 25A and a center side thermistor 25B that detect the temperature of the heater 22. The heater 22 has a substrate 30 and a resistance heating element 31. When a direction orthogonal to a direction in which the sheet P is conveyed, the direction along a surface of the sheet P is defined as a conveyance orthogonal direction X, and a middle position of the resistance heating element 31 in the conveyance orthogonal direction X as a reference position X0, the heater 22 has a large heat distribution amount area on one side in the conveyance orthogonal direction X with respect to the reference position X0, and a small heat distribution amount area on the other side on the opposite side of one side. The end side thermistor 25A is provided at a position farther from the reference position X0 than the center side thermistor 25B in the conveyance orthogonal direction X. The end side thermistor 25A is provided in the small heat distribution amount area, and a paper feed detection sensor 29 is provided in the large heat distribution amount area.SELECTED DRAWING: Figure 9

Description

[Technical Field]

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

[0002] In a fixing device as a heating device, when heating is started using the heater (heating element) while the device is in a cold state, such as when the device is started up, the ends of the heater and fixing belt (rotating member) tend to radiate heat to other members, so their temperatures do not easily rise.

[0003] If the fixing operation is performed when the temperature at the end of the fixing belt has not risen sufficiently, the end of the paper that has passed through the fixing nip will not be heated sufficiently, which will result in poor fixing of the image.

[0004] In addition, in an image forming apparatus equipped with a fixing device, misalignment in the direction perpendicular to the transport direction of the recording medium may occur due to misalignment when the user sets the recording medium in the paper feed tray or misalignment during transport.

[0005] For example, in the image heating device of Patent Document 1 (Japanese Patent No. 5924867), a left paper width sensor and a right paper width sensor are provided inside the vicinity of the boundary lines on both sides in the width direction of the paper passing area for normal-sized recording media. Alternatively, a temperature detection element is provided instead of the paper width sensor. Depending on the detection state of the paper width sensor or temperature detection element, deviation to either side in the width direction of the passing recording material is detected.

[0006] Although the paper width sensor described in Patent Document 1 can detect misalignment of the paper, it cannot detect the temperature inside the fixing device and therefore cannot prevent the aforementioned fixing failure. Furthermore, in a configuration with a temperature detection element, the device cannot detect an abnormality unless the paper is misaligned and the temperature of the fixing belt or other components on one side of the temperature detection element rises to an abnormal temperature. This poses the problem of wasting paper and toner until the device detects the abnormality. Thus, the configuration described in Patent Document 1 leaves room for improvement as a configuration for preventing fixing failure (insufficient heating of the recording medium) due to insufficient temperature of the rotating members. Summary of the Invention [Problem to be solved by the invention]

[0007] The object is to prevent defective heating of a recording medium. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a conveying device for conveying a recording medium, the conveying device including a heating device for heating a recording medium and a recording medium detection member for detecting the recording medium, the heating device including a heating element for heating the recording medium, a first temperature detection member and a second temperature detection member for detecting the temperature of the heating element, a rotating member; and a pressing member that presses the rotating member; and the pressure member has an elastic layer, the heating element has a base material and a heat generating element, and a direction perpendicular to the direction in which the recording medium is transported and along the surface of the recording medium is defined as a transport-orthogonal direction; The center position of the elastic layer in the direction perpendicular to the conveyance direction is When the reference position is taken as a reference position, the heating element has a large heat distribution area on one side in the transport orthogonal direction with respect to the reference position and a small heat distribution area on the other side opposite to the one side, and in the transport orthogonal direction, the first temperature detection member is provided at a position farther from the reference position than the second temperature detection member, and the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area. With respect to the reference position, the side of the heat generating element that is longer in the direction perpendicular to the conveyance direction is the large heat distribution area, and the side of the heat generating element that is shorter in the direction perpendicular to the conveyance direction is the small heat distribution area. It is characterized by: [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent defective heating of the recording medium. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. [Figure 2] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 3] FIG. [Figure 4] FIG. 10 is a diagram illustrating power supply to a heater. [Figure 5] FIG. 4 is a plan view of a heater having a different resistive heating element shape from that of FIG. 3. [Figure 6] FIG. 6 is a plan view of a heater having a resistance heating element with a different shape from those in FIGS. 3 and 5. [Figure 7] FIG. 10 is a diagram showing the arrangement of thermistors in an image forming apparatus different from that of the present embodiment. [Figure 8] 8 is a diagram showing a case where a sheet is misaligned in the image forming apparatus of FIG. 7. FIG. [Figure 9] FIG. 2 is a diagram showing the arrangement of a thermistor and a paper passing detection sensor in the image forming apparatus of the present embodiment. [Figure 10] FIG. 2 is a cross-sectional view showing the configuration of a thermistor. [Figure 11] FIG. 11 is a cross-sectional view showing a configuration of a thermistor different from that in FIG. 10. [Figure 12] 1A and 1B are diagrams showing a sheet-passing detection sensor, in which (a) is a front view showing the entire sheet-passing detection sensor, and (b) is a side view showing the rotational movement of a shielding member. [Figure 13] FIG. 10 is a diagram showing a state in which the paper is misaligned in one direction. [Figure 14] FIG. 10 is a diagram showing a state in which the paper is misaligned in another direction. [Figure 15] FIG. 10 is a plan view showing a modified example of the heater. [Figure 16] FIG. 10 is a plan view showing a modified example of the heater. [Figure 17] FIG. 10 is a plan view showing a modified example of the heater. [Figure 18]FIG. 2 is a side cross-sectional view of a fixing device having a first highly thermally conductive member. [Figure 19] 1A and 1B are diagrams showing the temperature distribution in the arrangement direction of the fixing belt, in which FIG. 1A is a plan view of the heater, and FIG. 1B is a diagram showing the temperature distribution of the fixing belt. [Figure 20] FIG. 6 is a diagram showing divided regions of the heater in FIG. 5. [Figure 21] FIG. 21 is a diagram showing divided regions having a different shape from that shown in FIG. 20. [Figure 22] FIG. 7 is a diagram showing divided regions of the heater in FIG. 6. [Figure 23] FIG. 2 is a perspective view of a heater, a first high thermal conductive member, and a heater holder. [Figure 24] FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity members. [Figure 25] 10A and 10B are plan views of a heater showing different examples of the arrangement of first high thermal conductivity members. [Figure 26] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of first high thermal conductivity members. [Figure 27] 3 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIG. 2. [Figure 28] FIG. 2 is a perspective view of a heater, a first highly thermally conductive member, a second highly thermally conductive member, and a heater holder. [Figure 29] FIG. 3 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. [Figure 30] 3A to 3C are plan views of a heater showing examples of different arrangements of the first and second high thermal conductive members. [Figure 31] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 32] FIG. 1 illustrates the atomic crystal structure of graphite. [Figure 33] 30 is a plan view showing a heater in which the arrangement of the second high thermal conductive members is different from that in FIG. 29. FIG. [Figure 34] 27. FIG. 30 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIGS. [Figure 35] 10 is a partial cross-sectional view of a fixing device in which a first highly thermally conductive member is provided between a heat insulating member and a heater. FIG. [Figure 36] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 37] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 38] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 39] FIG. 2 is a schematic diagram illustrating the configuration of an image forming apparatus different from that in FIG. [Figure 40] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 41] FIG. 41 is a plan view of a heater in the fixing device of FIG. 40. [Figure 42] FIG. 2 is a perspective view of a heater and a heater holder. [Figure 43] FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. [Figure 44] FIG. 2 is a diagram showing the arrangement of a thermistor and a thermostat. [Figure 45] FIG. 10 is a view showing a groove portion of the flange. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted. In the following description, an image forming apparatus that conveys paper as a recording medium and forms an image on the paper will be described as the conveying device of the present invention. In addition, a fixing device will be exemplified as a heating device provided in the image forming apparatus.

[0012] FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

[0013] The image forming apparatus 100 shown in FIG. 1 includes four imaging units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming apparatus main body. Each imaging unit 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains a different color developer: yellow, magenta, cyan, or black. These color developers correspond to the color separation components of a color image. Each imaging unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoconductor 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 photoconductor 2. The developing device 4 supplies toner as a developer to the surface of the photoconductor 2 to form a toner image. The cleaning device 5 cleans the surface of the photoconductor 2.

[0014] The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7 as a recording medium supply unit, 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 photoconductor 2 to light and forms an electrostatic latent image on that surface. The paper feed device 7 has a paper feed tray 16, a paper feed roller 17, and a paper pass detection sensor 29. The paper feed device 7 supplies paper P as a recording medium to a paper transport path 14 as a transport path for the recording medium. The transfer device 8 transfers the toner image formed on each photoconductor 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. The imaging units 1, photoconductors 2, charging devices 3, exposure device 6, transfer device 8, etc. constitute image forming means for forming an image on paper.

[0015] The transfer device 8 has 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 multiple rollers. The primary transfer rollers 12 transfer the toner images on the photoconductors 2 to the intermediate transfer belt 11. The secondary transfer rollers 13 transfer the toner images transferred onto the intermediate transfer belt 11 to paper P. Each of the multiple primary transfer rollers 12 contacts the photoconductors 2 via the intermediate transfer belt 11. This brings the intermediate transfer belt 11 and each photoconductor 2 into contact with each other, forming a primary transfer nip between them. Meanwhile, the secondary transfer roller 13 contacts one of the rollers stretching the intermediate transfer belt 11 via the intermediate transfer belt 11. This forms a secondary transfer nip between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0016] Further, a pair of timing rollers 15 is provided on the paper transport path 14 between the paper feeder 7 and the secondary transfer nip (secondary transfer roller 13). A pair of rollers such as the timing rollers 15 provided on the paper transport path 14 is a transport member for transporting the paper P on the paper transport path 14.

[0017] Next, the printing operation of the image forming apparatus will be described with reference to FIG.

[0018] When a command to start a printing operation is issued, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the charging device 3 charges the surface of the photoconductor 2 to a uniform high potential. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the original document read by the document reading device or the print information instructed to be printed from the terminal. This reduces the potential of the exposed area, forming an electrostatic latent image. Toner is then supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2.

[0019] The toner images formed on each photoconductor 2 rotate with the rotation of the photoconductor 2 and reach the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred to the intermediate transfer belt 11, which rotates counterclockwise in FIG. 1, so that they overlap one another. 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) with the rotation of the intermediate transfer belt 11. The toner images are then transferred to the paper P transported at the secondary transfer nip. This paper P is supplied from the paper feed tray 16. The paper P supplied from the paper feed device 7 is temporarily stopped by the timing roller 15 and then transported to the secondary transfer nip in time with the toner image on the intermediate transfer belt 11 reaching the secondary transfer nip. In this way, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoconductor 2 is removed by the cleaning devices 5.

[0020] The paper P onto which the toner image has been transferred is transported to a fixing device 9, which fixes the toner image onto the paper P. The paper P is then discharged outside the apparatus by a paper discharge device 10, completing the series of printing operations.

[0021] Next, the configuration of the fixing device will be described.

[0022] As shown in FIG. 2 , the fixing device 9 according to this embodiment includes a fixing belt 20, a pressure roller 21 as a counter rotating member or pressure member, a heater 22 as a heating element, a heater holder 23 as a holding member, a stay 24 as a support member, and a thermistor 25 as a temperature detection member. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer surface of the fixing belt 20 and forms a fixing nip N between the fixing belt 20 and the pressure roller 21. 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 contacts the back surface of the substrate 30 and detects its temperature. The fixing member provided in the fixing device is one example of a rotating member provided in a heating device. The fixing device 9 according to this embodiment includes the fixing belt 20 as a specific example of the fixing member.

[0023] 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, etc. This longitudinal direction is also perpendicular to the paper conveyance direction, i.e., the direction along the surface of the paper. Hereinafter, this direction will be referred to as the "transfer-orthogonal direction." Note that this "transfer-orthogonal direction" is also the belt width direction of the fixing belt 20 or the axial direction of the pressure roller 21, and is also the width direction of the paper being conveyed.

[0024] The fixing belt 20 has a base layer made of a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of a fluororesin such as PFA or PTFE and having a thickness of 5 to 50 μm is formed on the outermost surface of the fixing belt 20 to enhance durability and ensure releasability. A 50 to 500 μm thick elastic layer made of rubber or the like may be provided between the substrate and the release layer. The fixing belt 20 of this embodiment is a rubberless belt that does not have an elastic layer. The substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with a sliding layer made of polyimide, PTFE, or the like.

[0025] The pressure roller 21 has an outer diameter of, for example, 25 mm and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, 3.5 mm. To improve the release properties of the surface of the elastic layer 21b, it is desirable to form the release layer 21c, which is a fluororesin layer having a thickness of, for example, about 40 μm.

[0026] The pressure roller 21 is urged toward the fixing belt 20 by the urging means, so that the pressure roller 21 is pressed against the heater 22 via the fixing belt 20. As a result, a fixing nip N is formed between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of the arrow in FIG. 2, the fixing belt 20 is rotated accordingly.

[0027] The heater 22 is disposed so as to be in contact with the inner circumferential surface of the fixing belt 20. In this embodiment, the heater 22 comes into contact with the pressure roller 21 via the fixing belt 20 and serves as a nip forming member that forms a fixing nip N between the pressure roller 21 and the fixing belt 20. The fixing belt 20 is also a member to be heated by the heater 22. In other words, the heater 22 heats the paper P that is passed through the fixing nip N via the fixing belt 20.

[0028] 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 substrate 30, a resistance heating element 31 provided on the substrate 30, an insulating layer 32 covering the resistance heating element 31, and the like. The heater 22 is in contact with the inner circumferential surface of the fixing belt 20 on the insulating layer 32 side, and heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the insulating layer 32. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (the fixing nip N side) of the substrate 30. However, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the substrate 30. In this case, the heat from the resistance heating element 31 is transferred to the fixing belt 20 via the substrate 30, so the substrate 30 is preferably made of a material with high thermal conductivity, such as aluminum nitride. Furthermore, by forming the base material 30 from a material with high thermal conductivity, it is possible to heat the fixing belt 20 sufficiently even if the resistance heating element 31 is placed on the opposite side of the base material 30 from the fixing belt 20 side.

[0029] The heater holder 23 and the stay 24 are disposed on the inner circumferential side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends thereof in the direction perpendicular to the conveyance direction are supported by both side plates of the fixing device 9. By supporting the heater holder 23 and the heater 22 by the stay 24, 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. This ensures that the fixing nip 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 smaller than that of the base material 30.

[0030] The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity, such as LCP or PEEK, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to heat the fixing belt 20 efficiently.

[0031] The heater holder 23 has a recess 23b for holding the heater 22.

[0032] 2, the heater holder 23 is integrally provided with guide ribs 26 that guide the fixing belt 20. A plurality of guide ribs 26 are provided on the upstream side and downstream side of the heater holder 23 in the paper transport direction, in the direction perpendicular to the transport direction.

[0033] The guide rib 26 is formed in a generally fan shape. The guide rib 26 is provided along the inner peripheral surface of the fixing belt 20 and has an arc-shaped or convex curved guide surface 260 extending in the circumferential direction of the belt.

[0034] Heater holder 23 has an opening 23a penetrating in the thickness direction. A thermistor 25 and a thermostat (described later) are provided in this opening 23a. These thermistor 25 and thermostat are pressed against the rear surface of substrate 30 by a spring to detect the temperature of heater 22. Note that fixing device 9 is provided with end-side thermistor 25A and center-side thermistor 25B (described later), which are referred to as thermistors 25.

[0035] In the fixing device 9 according to this embodiment, when a printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate accordingly. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the guide surface 260 of the guide rib 26, thereby allowing the fixing belt 20 to rotate stably and smoothly. Furthermore, power is supplied to the resistance heating element 31 of the heater 22, thereby heating the fixing belt 20. Then, when the temperature of the fixing belt 20 reaches the fixing temperature, which is a predetermined target temperature, as shown in FIG. 2 , a sheet of paper P carrying an unfixed toner image is conveyed to the fixing nip N between the fixing belt 20 and the pressure roller 21, whereby the unfixed toner image is heated and pressurized and fixed to the sheet of paper P.

[0036] Next, a more detailed configuration of the heater provided in the fixing device will be described with reference to Fig. 3. Fig. 3 is a plan view of the heater according to this embodiment.

[0037] 3, a plurality of (four) resistance heating elements 31, power supply lines 33A and 33B as conductors, and first and second electrode portions 34A and 34B are provided on the surface of plate-shaped substrate 30. However, the number of resistance heating elements 31 is not limited to that in this embodiment. Hereinafter, power supply lines 33A and 33B will also be referred to as power supply lines 33, and first electrode portion 34A or second electrode portion 34B will also be referred to as electrode portion 34.

[0038] 3 is the direction perpendicular to the transport direction and is also the arrangement direction of the multiple resistance heating elements 31. The up-down direction Y in FIG. 3 is the transport direction of the paper, which is a direction intersecting the arrangement direction, particularly a direction perpendicular to the arrangement direction in this embodiment, and is a direction different from the thickness direction of the base material 30. The paper transport direction Y is also the widthwise direction of the heater 22.

[0039] The multiple resistance heating elements 31 form a heating section 35 divided into multiple sections in the cross-machine direction. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode portions 34A, 34B via power supply lines 33A, 33B. The pair of electrode portions 34A, 34B is provided at one end of the substrate 30 in the cross-machine direction, i.e., the left end in FIG. 3 . The power supply lines 33A, 33B are made of a conductor with a lower resistance value than the resistance heating elements 31. To ensure insulation between the resistance heating elements 31, the gap between adjacent resistance heating elements 31 is preferably 0.2 mm or more, more preferably 0.4 mm or more. Furthermore, if the gap between adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap. Therefore, to suppress temperature unevenness across the cross-machine direction, the gap is preferably 5 mm or less, more preferably 1 mm or less.

[0040] The resistance heating element 31 is made of a material having a PTC (positive temperature coefficient of resistance) characteristic, and is characterized in that as the temperature rises, the resistance value rises and the heater output decreases.

[0041] The PTC characteristics of the resistance heating element 31 and the configuration of the heating section 35, which is divided in the direction perpendicular to the conveyance direction, prevent excessive temperature rise of the fixing belt 20 when small-size paper is passed through. In other words, when paper narrower than the overall width of the heating section 35 is passed through, the paper does not absorb heat from the fixing belt 20 in the area outside the paper width, causing the temperature of the resistance heating element 31 corresponding to that area to rise. Because the voltage applied to the resistance heating element 31 is constant, when the temperature of the resistance heating element 31 outside the paper width rises, its resistance value also rises. This relatively reduces the heater output, i.e., the amount of heat generated, and suppresses temperature rise at the edge. Furthermore, electrically connecting multiple resistance heating elements 31 in parallel suppresses temperature rise in non-paper passing areas while maintaining printing speed. The heating elements constituting the heating section 35 may be other than resistance heating elements with PTC characteristics. Furthermore, the resistance heating elements may be arranged in multiple rows in the paper conveyance direction of the heater 22.

[0042] The resistance heating element 31 can be formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the substrate 30 by screen printing or the like, and then firing the substrate 30. In this embodiment, the resistance value of the resistance heating element 31 is set to 80 Ω at room temperature. In addition to the materials mentioned above, the resistance heating element 31 may also be made of resistance materials such as silver alloy (AgPt) or ruthenium oxide (RuO2). The power supply line 33 and the electrode portion 34 can be made of silver (Ag) or silver palladium (AgPd) by screen printing or the like. The power supply line 33 is made of a conductor with a lower resistance value than the resistance heating element 31.

[0043] The substrate 30 is preferably made of ceramics such as alumina or aluminum nitride, which have excellent heat resistance and insulation properties, or non-metallic materials such as glass or mica. In this embodiment, an alumina substrate is used, which is 8 mm wide in the paper transport direction, 270 mm wide in the direction perpendicular to the transport direction, and 1.0 mm thick. Alternatively, the substrate 30 may be made of a conductive material such as a metal laminated with an insulating material. Aluminum and stainless steel are preferred metal materials for the substrate 30 because they are low-cost. By constructing the substrate 30 from a stainless steel plate, cracks due to thermal stress can be suppressed. Furthermore, to improve the uniform heating of the heater 22 and enhance image quality, the substrate 30 may be made of a highly thermally conductive material such as copper, graphite, or graphene.

[0044] The insulating layer 32 is made of heat-resistant glass having a thickness of, for example, 75 μm. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulating and protecting them and maintaining sliding properties with the fixing belt 20.

[0045] FIG. 4 is a diagram showing a power supply circuit to the heater according to this embodiment.

[0046] As shown in Fig. 4, in this embodiment, a power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power source 200 and electrode portions 34A, 34B of the heater 22. The power supply circuit is also provided with a triac 210 that controls the amount of power supplied. The amount of power supplied to each resistance heating element 31 is controlled by a control unit 220 via the triac 210 based on the temperatures detected by the thermistors 25A, 25B. The control unit 220 is configured as a microcomputer including a CPU, ROM, RAM, I / O interface, etc. The control unit 220 may be provided in the fixing device or in the image forming apparatus main body.

[0047] In this embodiment, an end thermistor 25A serving as a first temperature detection member is disposed at one end of the heater 22 in the cross-machine direction, and a center thermistor 25B serving as a second temperature detection member is disposed in a central region of the heater 22 in the cross-machine direction, which is within the minimum sheet passing width. Furthermore, a thermostat 27 serving as a power cutoff device for cutting off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 exceeds a predetermined temperature is disposed at the other end of the heater 22 in the cross-machine direction. The thermistor 25 and the thermostat 27 contact the back surface of the heater substrate to detect its temperature. Hereinafter, the end thermistor 25A and the center thermistor 25B will also be referred to as thermistors 25.

[0048] In this embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the direction perpendicular to the transport direction, but they may be provided on different sides. The shape of the resistance heating element 31 is not limited to that of this embodiment. For example, as shown in FIG. 5, the resistance heating element 31 may be rectangular. Alternatively, as shown in FIG. 6, the resistance heating element 31 may be formed of a linear portion that is folded back to form a substantially parallelogram shape. As shown in FIG. 5, the portion of the block-shaped resistance heating element 31 that extends toward the power supply line 33 (the portion extending in the paper transport direction) may be part of the resistance heating element 31, or may be made of the same material as the power supply line 33.

[0049] However, in a heating device equipped with a rotating member, if the recording medium is conveyed while the temperature of the rotating member is not sufficiently raised, the recording medium may be heated improperly. In other words, in the fixing device described above, the end side of the fixing belt in the direction perpendicular to the conveyance direction may not be heated sufficiently, resulting in the problem of improper fixing of the image on the paper.

[0050] First, when such poor fixing occurs, there is a problem of temperature sagging at the edges of the paper. For example, when an image forming apparatus is started up from a cold state, the edges of the fixing belt 20 in the direction perpendicular to the conveyance direction rise in temperature more slowly than the center. As a result, the edges of the paper passing through the fixing nip N are not heated sufficiently compared to the center, resulting in poor fixing at the edges. Hereinafter, this problem will be referred to as Problem 1.

[0051] Figure 7 shows an image forming apparatus with a different thermistor arrangement from this embodiment. The dotted line in Figure 7 indicates the center position of the paper in the direction perpendicular to the conveyance direction. The dashed-dotted line in Figure 7 indicates the temperature distribution of the heater substrate in the direction perpendicular to the conveyance direction. Note that the fixing belt also shows a similar temperature trend. For convenience, the heater is shown in Figure 7 simply, and only the area where the resistance heating element on the heater is located is shown.

[0052] The fixing device in Fig. 7 has a center thermistor 25B in the center of the paper in the direction perpendicular to the conveyance direction, and end thermistors 25A on one side and the other side. These end thermistors 25A detect the temperature at both ends of the fixing belt 20 in the direction perpendicular to the conveyance direction, and can heat both ends of the fixing belt 20 in the direction perpendicular to the conveyance direction to a sufficient temperature. This prevents the above-mentioned fixing failure, which solves the above-mentioned problem 1.

[0053] However, the configuration shown in FIG. 7 has a problem in that poor fixing occurs when the paper is misaligned in the direction perpendicular to the transport direction. In other words, misalignment in the direction perpendicular to the transport direction occurs on the paper conveyed to the fixing device due to misalignment when the paper is set in the paper feed tray or misalignment during transport. Specifically, as shown in FIG. 8, for example, if the paper P is misaligned to the right in FIG. 8, the right edge of the paper P passes through a low-temperature area of ​​the fixing belt 20 outside the thermistor 25A, and the paper P is not sufficiently heated in this area. This causes a problem in that the image on the paper P does not fix properly. Hereinafter, this problem will be referred to as problem 2.

[0054] Furthermore, when such poor fixing occurs, toner and paper are wasted. Therefore, the challenge is to detect the abnormality as early as possible on the device side. This challenge will be referred to as Challenge 3 below.

[0055] The configuration of this embodiment that solves these problems will be described with reference to FIG.

[0056] 9, an end thermistor 25A as a first temperature detection member, a center thermistor 25B as a second temperature detection member, and a paper passing detection sensor 29 as a recording medium detection member are provided at positions corresponding to heating region D, which is the main heat generation region of heater 22. Heating region D is the region where resistance heating elements 31 are provided in the orthogonal transport direction X, and is also the heating region of heater 22 in the orthogonal transport direction. Heating region D is the region that includes the gaps between resistance heating elements 31, such as those of heater 22 in FIG. 5, for example.

[0057] In this embodiment, the end side thermistor 25A and the center side thermistor 25B are provided in the fixing device 9, and the paper passing detection sensor 29 is provided in the paper feed tray 16 (see FIG. 1) of the paper feed device 7. In other words, the positions of the end side thermistor 25A, the center side thermistor 25B, and the paper passing detection sensor 29 in the orthogonal transport direction shown in FIG. 9 indicate the positions of each device in the orthogonal transport direction X.

[0058] The conveying device of this embodiment is an image forming apparatus equipped with a fixing device having an end-side thermistor 25A and a center-side thermistor 25B, and a paper feeder having a paper feed detection sensor 29. However, the conveying device of this embodiment is not limited to this. For example, a heating device equipped with a heating element may also be the conveying device of this embodiment. In other words, the heating device may be configured as a conveying device equipped with a first temperature detection member, a second temperature detection member, and a recording medium detection member. The fixing device 9 of this embodiment is one aspect of a heating device. Alternatively, the recording medium detection member may be provided at an appropriate position from the time the recording medium is loaded into the image forming apparatus until it is ejected from the apparatus. Alternatively, the conveying device of this embodiment may be a combination of a fixing device within an image forming apparatus and another device having a recording medium detection member.

[0059] The configuration of the thermistor 25 will be described in more detail with reference to Figure 10. Note that the end-side thermistor 25A and the center-side thermistor 25B in this embodiment have the same configuration except for their positions in the direction perpendicular to the conveyance direction. However, they do not necessarily have to have the same configuration.

[0060] As shown in FIG. 10, the thermistor 25 has a holder 251, an elastic member 252, a temperature detection element 253 as a temperature detection section, a spring 254 as a biasing member, and an insulating sheet 255.

[0061] The holder 251 is made of a resin material such as LCP. A temperature detection element 253 is provided on the surface of the holder 251 facing the heater substrate via an elastic member 252. The elastic member 252 is made of a material with lower thermal conductivity and rigidity than the holder 251, and has elasticity and heat insulation properties. The insulating sheet 255 is made of an insulating material such as PI (polyimide) and is provided to cover the holder 251, the elastic member 252, and the temperature detection element 253. The holder 251 is biased toward the heater 22 by a spring 254, so that the temperature detection element 253 contacts the heater 22 via the insulating sheet 255. Two wires 256 connected to the temperature detection element 253 extend from the holder 251, and each wire 256 is covered with an insulating coating. In consideration of heat resistance, the coating of the wires 256 is desirably 0.4 mm or more in thickness. In addition, if the thickness of the coating is 0.4 mm or less, multiple coatings may be stacked.

[0062] Thermistor 25 may also be a non-contact temperature detection member. For example, as shown in Fig. 11, non-contact thermistor 25 has a holder 251, a temperature detection element 253, and an insulating sheet 255. As an example, thermistor 25 is disposed downstream of fixing nip N in Fig. 2 in the paper transport direction. However, thermistor 25 may also be disposed downstream of fixing nip N.

[0063] Temperature detection element 253 is provided in holder 251 and faces the outer peripheral surface of fixing belt 20 via insulating sheet 255. Two wires 256 held by holder 251 are connected to temperature detection element 253 on one side and extend outside the thermistor 25 on the other side. This thermistor 25 does not require as much heat resistance as a contact-type thermistor, so holder 251 can be made of a material with lower heat resistance, or the elastic member can be omitted. Also, no biasing member for biasing temperature detection element 253 is required.

[0064] Alternatively, the first temperature detection member and the second temperature detection member may detect the temperature of another member in contact with the heater 22. For example, a first high thermal conductivity member 28 (see FIG. 18 ), which will be described later, may be provided between the heater 22 and thermistor 25, and thermistor 25 may detect the temperature of first high thermal conductivity member 28. "Thermistor 25 detects the temperature of heater 22" may thus mean that thermistor 25 detects the temperature of heater 22 via another member.

[0065] 12(a) and 12(b) show an example of the paper-passing detection sensor 29. As shown in Fig. 12(a), the paper-passing detection sensor 29 has a light-blocking member 291, a shaft 292, a light-emitting unit 293, and a light-receiving unit 294.

[0066] 12(b), the light blocking member 291 rotates around the shaft 292. Abutment portion 291a, which is one end of the light blocking member 291, is disposed on the paper passage path inside the image forming apparatus, particularly on the paper passage path inside the paper feed tray 16 in this embodiment. When a sheet is transported in the direction of the arrow in FIG. 12(b), the abutment portion 291a abuts against the sheet, causing the light blocking member 291 to rotate.

[0067] By switching between the solid line position in FIG. 12(b) where the light-shielding member 291 is not pressed by the paper and the dotted line position in FIG. 12(b) where the light-shielding member 291 rotates as it is pressed by the paper, the other end 291b of the light-shielding member 291 shown in FIG. 12(a) switches between a state in which it blocks light from the light-emitting unit 293 and a state in which it does not block light. In other words, the detection state can be switched depending on whether paper is being passed through. The light-emitting unit 293, the other end 291b, and the light-receiving unit 294 form a photocoupler unit 299. The range H where the contacted portion 291a in the orthogonal direction to the conveyance direction is provided is the paper-passage detection area H of the paper-passage detection sensor 29. The dotted line H0 in FIG. 12(a) indicates the center position of the paper-passage detection area H in the orthogonal direction to the conveyance direction.

[0068] 12 shows an example of a transmission type optical sensor as the paper passing detection sensor 29, but a reflection type optical sensor may also be used. Other suitable mechanisms can be used as the recording medium detection member, such as a push button type detection sensor in which a button is pressed by paper being transported on the transport path, or a magnetic sensor in which the detection state is changed by the rotation of a rotating member pressed by paper being transported on the transport path.

[0069] 9, in this embodiment, end-side thermistor 25A is provided on the end side of maximum paper passing area E, and center-side thermistor 25B is provided on the center side of maximum paper passing area E. In other words, end-side thermistor 25A is provided at least in the area on the end side when maximum paper passing area E is divided into thirds, and center-side thermistor 25B is provided at least in the area on the center side when maximum paper passing area E is divided into thirds. In this embodiment, particularly, temperature detection element 253 of end-side thermistor 25A is provided near the end of maximum paper passing area E, and temperature detection element 253 of center-side thermistor 25B is provided at the same position as reference position X0.

[0070] The maximum paper passing area E is the area through which a sheet of paper of the maximum width passes without misalignment when passed through the fixing device 9. Hereinafter, the paper passing area E for the maximum width sheet P1 will be referred to as the maximum paper passing area E as the maximum passing area for the recording medium.

[0071] The reference position X0 in this embodiment is the center position of a sheet of paper placed without misalignment on a transport path in a paper feeder or image forming apparatus in a direction perpendicular to the transport direction. Furthermore, in this embodiment, this reference position X0 is also the center position of the heating area D. Incidentally, the center position of the heating area D coinciding with the reference position X0 does not necessarily mean that the positions exactly match, but also means that there may be some degree of error. This also applies to other embodiments described later, such as when the reference position X0 matches the center position of the elastic layer of the pressure roller.

[0072] The heating area D is set larger than the paper passing area E. This makes it possible to mitigate the temperature drop at the end of the paper passing area E. In addition, the end-side thermistor 25A, the center-side thermistor 25B, and the paper passing detection sensor 29 are set within the maximum paper passing area E.

[0073] The length of the region of the substrate 30 on the right side in FIG. 9 relative to the reference position X0 is longer than the length of the region on the left side. In other words, the length of the right side of the substrate 30 in FIG. 9 is longer because the electrode portions are arranged biased to one side. For this reason, the region of the substrate 30 on the right side in FIG. 9 relative to the reference position X0 has a larger heat capacity than the region on the left side. As a result, the temperature of the heater 22 on the right side in FIG. 9 relative to the reference position X0 is lower than the temperature on the left side. The region on the right side in FIG. 9 relative to the reference position X0 is the small heat distribution region of this embodiment, and the region on the left side in FIG. 9 relative to the reference position X0 is the large heat distribution region of this embodiment.

[0074] This "large heat distribution area" refers to the area on the high temperature side of the heater 22 relative to the reference position X0, and the "small heat distribution area" refers to the area on the opposite side of the "large heat distribution area" on the low temperature side of the heater 22. This temperature of the heater 22 refers to the temperature measured in the direction perpendicular to the conveyance direction when the heater 22 is caused to generate heat alone.

[0075] The paper passing detection sensor 29 is provided in an area on the end side of the maximum paper passing area E, on the opposite side of the end side thermistor 25A with respect to the reference position X0.

[0076] In this embodiment, the end thermistor 25A detects the temperature of the heater at the end of the maximum paper passing area E, and controls the power supply to the heater 22 based on the detection result. This allows the end area of ​​the fixing belt 20 to be heated to a sufficient temperature, and the end side of the paper in the direction perpendicular to the paper transport direction to be sufficiently heated. Therefore, poor fixing due to temperature sagging at the end side of the paper in the direction perpendicular to the paper transport direction can be prevented. In other words, Problem 1 can be solved.

[0077] 13, if the position of the paper P1 in the direction perpendicular to the transport direction is misaligned to the right in FIG. 13, the paper passing detection sensor 29 goes into a non-detecting state and the paper misalignment can be detected. This prevents fixing problems in the fixing device and solves Problem 2. Furthermore, even when printing continuously, the misalignment of the paper can be detected from the first sheet, and the paper misalignment can be detected early, solving Problem 3.

[0078] 14, if the position of the sheet P1 is shifted in the opposite direction to that of the sheet P1 in FIG. 13, the sheet P1 will be shifted toward the high heat distribution area. In other words, the sheet P1 will be positioned on the side where the amount of heat generated by the heater 22 is greater, and therefore poor fixing of the image onto the sheet P1 will not occur. Therefore, problems 2 and 3 can be solved.

[0079] In this manner, in this embodiment, even if the position of the sheet P1 is shifted in either direction as shown in FIGS. 13 and 14, problems 2 and 3 can be solved.

[0080] As described above, by arranging the end-side thermistor 25A and the sheet-passing detection sensor 29 in this embodiment, all of the problems 1 to 3 can be solved, and fixing defects in the fixing device can be effectively prevented.

[0081] Next, a modified example of the heater 22 will be described.

[0082] In the embodiment shown in FIG. 15, the reference position X0, which is the center position of the sheet of paper passing through in the orthogonal direction to the transport direction, is also the center position of the elastic layer 21b of the pressure roller 21 in the orthogonal direction to the transport direction. Furthermore, the center position D0 of the heating region D is located at a position different from the reference position X0. In other words, in the embodiment shown in FIG. 15, the length of the heating region D is longer on the side where the center position D0 of the heating region D is located relative to the reference position X0 than on the side where the center position D0 is not located. Therefore, in this embodiment, the left side of FIG. 15 is the high heat distribution region, and the right side of FIG. 15 is the low heat distribution region. In this embodiment, the first electrode portion 34A and the second electrode portion 34B are located on both sides of the orthogonal direction to the transport direction, and the center position of the substrate 30 in the orthogonal direction to the transport direction coincides with the reference position X0.

[0083] In the embodiment shown in FIG. 16, the reference position X0, which is the center position of the paper sheet in the direction perpendicular to the conveyance direction, coincides with the center position of the heating area D and the center position of the substrate 30.

[0084] The heater 22 in Fig. 16 has independent heat generating portions at the center and end sides in the orthogonal transport direction. Specifically, among the multiple resistance heating elements 31 arranged on the substrate 30 in the orthogonal transport direction, a first heat generating portion 35A consisting of the resistance heating elements 31 other than those at both ends and a second heat generating portion 35B consisting of the resistance heating elements 31 at both ends are configured so that heat generation can be controlled independently. Specifically, each of the resistance heating elements 31 other than those at both ends that constitute the first heat generating portion 35A is connected via a first power supply line 33A to a first electrode portion 34A provided on one end side of the substrate 30 in the orthogonal transport direction. Furthermore, each of the resistance heating elements 31 that constitute the first heat generating portion 35A is connected via a second power supply line 33B to a second electrode portion 34B provided on the end side opposite to the first electrode portion 34A. On the other hand, each of the resistance heating elements 31 at both ends constituting the second heating section 35B is connected via a third power feed line 33C or a fourth power feed line 33D to a third electrode section 34C (different from the first electrode section 34A) provided on one end side of the substrate 30 in the direction perpendicular to the transport direction. Furthermore, each of the resistance heating elements 31 at both ends is connected to the second electrode section 34B via a second power feed line 33B, similar to each of the resistance heating elements 31 of the first heating section 35A. In other words, the second electrode section 34B is connected by merging the power feed lines (second power feed line 33B) extending from all of the resistance heating elements 31.

[0085] When a voltage is applied to the first electrode portion 34A and the second electrode portion 34B, the resistance heating elements 31 except those at both ends are energized, and only the first heating portion 35A generates heat. On the other hand, when a voltage is applied to the second electrode portion 34B and the third electrode portion 34C, the resistance heating elements 31 at both ends are energized, and only the second heating portion 35B generates heat. Furthermore, by applying a voltage to all of the electrode portions 34A to 34C, it is possible to cause both (all) of the resistance heating elements 31 in the first heating portion 35A and the second heating portion 35B to generate heat. For example, when a relatively small sheet of paper, such as A4 size (paper width: 210 mm) or less, is fed, only the first heating portion 35A generates heat. However, when a relatively large sheet of paper, such as A4 size (paper width: 210 mm), is fed, both the first heating portion 35A and the second heating portion 35B generate heat, thereby achieving a heating region according to the paper width.

[0086] In this embodiment, a large heat distribution area is arranged on the left side of Fig. 16 with respect to reference position X0, and a small heat distribution area is arranged on the right side of Fig. 16. That is, in this embodiment, the surface area of ​​the conductors arranged on substrate 30 is larger in the area on the left side of Fig. 16 with respect to reference position X0 than in the area on the right side of Fig. 16. These conductors refer to resistance heating element 31, power supply lines 33A to 33D, and electrode portions 34A to 34C, and in this embodiment in particular, the heat generation amount of heater 22 is larger on the left side of Fig. 16 where two electrode portions 34A and 34C are arranged, and this side becomes the large heat distribution area.

[0087] 16, in addition to the configuration in which a high heat distribution area and a low heat distribution area are provided due to differences in the surface area of ​​the electrode portion, a configuration in which the area of ​​the resistance heating element 31 is non-uniform in the direction perpendicular to the transport direction can also be used, as shown in FIG. 17. That is, with respect to the center position D0 of the heating area D, the resistance heating element 31 on the right side in FIG. 17 has a larger area than the resistance heating element 31 on the left side. More specifically, the width of the resistance heating element 31 in the transport direction increases the further to the right in FIG. 17. Furthermore, in this embodiment, the center position D0 of the heating area D is located at the same position as the reference position X0 of the paper P. With this configuration, the right side of FIG. 17 with respect to the reference position X0 can be made a high heat distribution area, and the opposite side can be made a low heat distribution area.

[0088] In each of the heaters 22 described above, fixing defects in the fixing device can be prevented by arranging the paper-passage detection sensor 29 in the large heat distribution area and the end-side thermistor 25A in the small heat distribution area. When the reference position X0 coincides with the center position of the elastic layer 21b in the direction perpendicular to the transport direction as shown in Fig. 15, the large heat distribution area and the small heat distribution area may be formed by making the length of the base material 30 non-uniform with respect to the reference position X0 as shown in Fig. 9, or by making the surface area of ​​the conductor non-uniform with respect to the reference position X0 as shown in Fig. 16.

[0089] The paper passing detection sensor 29 is preferably located upstream of the fixing device 9 in the paper transport direction. This allows for detection of an abnormality due to paper position misalignment (Problem 2) before the fixing device 9 performs the image fixing operation on the toner on the paper. In this way, it is preferable to locate the paper passing detection sensor 29 further upstream in the paper transport direction, as this allows for earlier detection of an abnormality. In particular, as in this embodiment, providing the paper passing detection sensor 29 in the paper feeder allows for earlier detection of an abnormality, which is more preferable.

[0090] Furthermore, by providing the sheet passing detection sensor 29 outside the fixing device 9, the sheet passing detection sensor 29 does not need to be replaced when the fixing device 9 is replaced. Therefore, the cost of replacing the fixing device 9 can be reduced.

[0091] The configuration of this embodiment is particularly suitable for application to a fixing device equipped with a fixing belt 20 that does not have an elastic layer. In other words, in such a fixing device, the amount of heat transfer in the longitudinal direction of the fixing belt 20 is small, and temperature sagging is likely to occur at the end sides of the fixing belt 20. Therefore, it is suitable to apply the above-described configuration of this embodiment.

[0092] Next, as an embodiment different from the fixing device of FIG. 2, an embodiment in which a highly heat-conductive member is disposed between the heater holder 23 and the heater 22 will be described with reference to FIG.

[0093] The first high thermal conductivity member 28 is made of a material having a higher thermal conductivity than the base material 30. 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, for example, copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 with respect to the heater holder 23 and the first high thermal conductivity member 28 can be improved.

[0094] Next, a method for calculating the thermal conductivity will be described. When calculating the thermal conductivity, first, the thermal diffusivity of the object is measured, and then the thermal conductivity is calculated using the measured thermal diffusivity.

[0095] The thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (trade name: ai-Phase Mobile 1u, ai-Phase Corporation).

[0096] To convert the thermal diffusivity to thermal conductivity, the density and specific heat capacity values ​​are required. A dry-type automatic densitometer (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used to measure the density. A differential scanning calorimeter (product name: DSC-60, manufactured by Shimadzu Corporation) was used to measure the specific heat capacity, using sapphire as a reference material with a known specific heat capacity. In this example, the specific heat capacity was measured five times, and the average value at 50°C was used. When the density and specific heat capacity are ρ and C, respectively, the thermal conductivity λ can be calculated from the thermal diffusivity α obtained from the thermal diffusivity measurement using the following equation (1):

[0097]

number

[0098] As with the previously described embodiments, an image forming apparatus equipped with the fixing device of this embodiment also experiences problems 1 to 3. However, by arranging end-side thermistor 25A and center-side thermistor 25B in contact with first high thermal conductivity member 28 and by arranging paper passing detection sensor 29, problems 1 to 3 can be resolved and poor fixing of images to paper can be prevented.

[0099] However, openings may also be similarly provided in first high thermal conductivity member 28 and a second high thermal conductivity member described below, so that thermistor 25 and thermostat are pressed against the back surface of substrate 30. By providing first high thermal conductivity member 28, it is possible to suppress temperature unevenness in the longitudinal direction of heater 22. Therefore, an inexpensive thermistor with low heat resistance can be used for thermistor 25.

[0100] 19A and 19B are diagrams showing the temperature distribution of the fixing belt 20 in the direction perpendicular to the conveyance direction. (a) shows the arrangement of the heater 22. (b) shows the vertical axis representing the temperature T of the fixing belt 20, and the horizontal axis representing each position on the fixing belt 20 in the direction perpendicular to the conveyance direction.

[0101] As shown in FIGS. 19(a) and 19(b), the heater 22 has a plurality of resistance heating elements 31 divided in the cross-transport direction, forming divided regions B between the resistance heating elements 31. In other words, the heater 22 has a plurality of resistance heating elements 31 arranged at intervals B. Hereinafter, the range B of the divided region will be referred to as interval B. In interval B, the area occupied by the resistance heating elements 31 is smaller than in other regions, resulting in a smaller amount of heat generation. As a result, the temperature of the fixing belt 20 in interval B is lower than in other regions, causing temperature unevenness in the cross-transport direction of the fixing belt 20. Furthermore, in an expanded divided region C (hereinafter simply referred to as region C) including the area surrounding interval B, which is a divided region, the temperatures of the heater 22 and the fixing belt 20 are also lower. Note that the temperature of the heater 22 is also lower in interval B. Herein, as shown in the enlarged view of FIG. 19(a), interval B refers to the cross-transport direction region including all of the divided regions into which the resistance heating elements 31, which are the main heat-generating portions of the heater 22, are divided in the cross-transport direction. In addition to the gap B, an area including a range corresponding to the connection portion 311 of the resistance heating element 31 is defined as area C. This connection portion 311 refers to the portion of the resistance heating element 31 that extends in the paper transport direction and is connected to each of the power supply lines 33A and 33B.

[0102] As shown in Fig. 20, even in a heater 22 having a rectangular resistance heating element 31 as shown in Fig. 5, the temperature in the gap B is lower than in other parts. Also in a heater 22 having a resistance heating element 31 shaped as shown in Fig. 21, the temperature in the gap B is lower than in other parts. Furthermore, as shown in Fig. 22, even in a heater 22 having a resistance heating element 31 shaped as shown in Fig. 6, the temperature in the gap B is lower than in other parts. However, by overlapping adjacent resistance heating elements 31 in the direction orthogonal to the transport direction as in Figs. 19, 21 and 22, the temperature drop in the gap B relative to other parts can be suppressed.

[0103] In this embodiment, the above-mentioned first highly thermally conductive member 28 is provided to suppress the temperature drop in the above-mentioned interval and to suppress temperature unevenness in the direction perpendicular to the conveyance direction of the fixing belt 20. The first highly thermally conductive member 28 will be described in more detail below.

[0104] 18, first high thermal conductivity member 28 is disposed between heater 22 and stay 24 in the left-right direction of FIG. 18, and is particularly sandwiched between heater 22 and heater holder 23. That is, first high thermal conductivity member 28 has one surface abutting against the back surface of base material 30 and the other surface abutting against heater holder 23.

[0105] The stay 24 supports the heater holder 23, the first high thermal conductivity member 28, and the heater 22 by bringing the contact surfaces of two vertical portions 24a extending in the thickness direction of the heater 22 and the like into direct contact with the heater holder 23. In the paper conveyance direction (the up-and-down direction in FIG. 18 ), the contact surfaces are provided outside the range in which the resistance heating element 31 is provided. This makes it possible to suppress heat transfer from the heater 22 to the stay 24, and allows the heater 22 to heat the fixing belt 20 efficiently.

[0106] As shown in Fig. 23, first high thermal conductivity member 28 is made of a plate material with a thickness of 0.3 mm, a length of 222 mm in the direction perpendicular to the transport direction, and a width of 10 mm in the paper transport direction. In this embodiment, first high thermal conductivity member 28 is made of a single plate material, but it may be made of multiple members. Note that Fig. 23 omits the illustration of guide rib 26 from Fig. 18.

[0107] The first high thermal conductivity member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is attached thereto, thereby sandwiching and holding the first high thermal conductivity member 28 between the heater holder 23 and the heater 22. In this embodiment, the width of the first high thermal conductivity member 28 in the cross-conveyance direction is set to be approximately the same as the width of the heater 22 in the cross-conveyance direction. Movement of the first high thermal conductivity member 28 and the heater 22 in the cross-conveyance direction is restricted by both side walls (cross-conveyance direction restricting portions) 23b1 that form the recess 23b in the cross-conveyance direction. In this manner, restricting positional deviation of the first high thermal conductivity member 28 in the cross-conveyance direction within the fixing device 9 improves heat conduction efficiency within a target range in the cross-conveyance direction. Movement of the first high thermal conductivity member 28 and the heater 22 in the paper transport direction is restricted by both side walls (paper transport direction restricting portions) 23b2 that form the recess 23b in the paper transport direction.

[0108] The range in the cross-machine direction in which the first high thermal conductivity members 28 are provided is not limited to the above. For example, as shown in FIG. 24, the first high thermal conductivity members 28 may be provided only in the range corresponding to the heat generating portions 35 in the cross-machine direction (see the hatched area in FIG. 24). Alternatively, as shown in FIG. 25, the first high thermal conductivity members 28 may be provided only in the entire area at a position corresponding to the interval B in the cross-machine direction. Note that for convenience, in FIG. 25, the resistance heating element 31 and the first high thermal conductivity members 28 are shown shifted in the vertical direction in FIG. 25, but they are actually positioned at approximately the same position in the paper transport direction. However, this is not limiting, and the first high thermal conductivity members 28 may be provided on a portion of the resistance heating element 31 in the paper transport direction, or may be provided so as to cover the entire paper transport direction as shown in FIG. 26 described below.

[0109] 26, the first high thermal conductivity members 28 may be provided not only at a position corresponding to the interval B in the transverse direction, but also across the resistance heating elements 31 on both sides that sandwich the interval B. "Across the resistance heating elements 31" means that the first high thermal conductivity members 28 at least partially overlap with the resistance heating elements 31 on both sides in the transverse direction. Note that the first high thermal conductivity members 28 may be provided to correspond to all of the intervals B of the heaters 22, or may be provided only at positions corresponding to some of the intervals B, such as by providing the first high thermal conductivity members 28 at only one position of the interval B as shown in FIG. 26. Here, "provided at a position corresponding to the interval B in the transverse direction" means that the first high thermal conductivity members 28 at least partially overlap with the interval B in the transverse direction.

[0110] Due to the pressure of the pressure roller 21, the first highly thermally conductive member 28 is sandwiched between the heater 22 and the heater holder 23 and is in close contact with these members. The first highly thermally conductive member 28 comes into contact with the heater 22, improving the thermal conduction efficiency of the heater 22 in the cross-conveyance direction. Furthermore, by providing the first highly thermally conductive member 28 at a position corresponding to the interval B between the heaters 22 in the cross-conveyance direction, the thermal conduction efficiency in the interval B can be improved. This increases the amount of heat transferred to the area of ​​the interval B in the cross-conveyance direction, thereby raising the temperature in the area of ​​the interval B in the cross-conveyance direction. This reduces temperature unevenness of the heater 22 in the cross-conveyance direction. This reduces temperature unevenness of the fixing belt 20 in the cross-conveyance direction. This reduces uneven fixing and glossiness of the image fixed to the paper. Alternatively, there is no need for the heater 22 to provide extra heating to ensure sufficient fixing performance in the area of ​​the interval B, thereby achieving energy savings in the fixing device 9. In addition, by providing the first high thermal conductivity member 28 over the entire area of ​​the heat generating section 35 in the direction perpendicular to the conveying direction, the heat transfer efficiency of the heater 22 can be improved over the entire area that is the main heating area by the heater 22, i.e., the image forming area of ​​the paper being passed through, and temperature unevenness of the heater 22 and therefore the fixing belt 20 in the direction perpendicular to the conveying direction can be suppressed.

[0111] In particular, in this embodiment, the combination of the configuration of the first high thermal conductivity member 28 and the resistance heating element 31 having the PTC characteristic described above can effectively suppress excessive temperature rise in the non-paper passing area when small size paper is passed. In other words, the PTC characteristic suppresses the amount of heat generated by the resistance heating element 31 in the non-paper passing area, and the heat of the non-paper passing area with an increased temperature can be efficiently transferred to the paper passing area, effectively suppressing excessive temperature rise in the non-paper passing area.

[0112] Furthermore, it is preferable to arrange the first highly thermally conductive member 28 around the gap B, since the temperature there is also low due to the small amount of heat generated in the gap B. For example, in this embodiment, by providing the first highly thermally conductive member 28 at a position corresponding to region C (see FIG. 20), the heat transfer efficiency in the orthogonal transport direction in the gap B and its periphery is particularly improved, and temperature unevenness in the orthogonal transport direction of the heater 22 can be further suppressed. Particularly in this embodiment, the first highly thermally conductive member 28 is provided over the entire heat generating portion 35 in the orthogonal transport direction. This makes it possible to further suppress temperature unevenness in the orthogonal transport direction of the heater 22 (fixing belt 20).

[0113] Next, a different embodiment of the fixing device will be described.

[0114] As shown in Fig. 27, fixing device 9 of this embodiment has second high thermal conductivity member 36 between heater holder 23 and first high thermal conductivity member 28. Second high thermal conductivity member 36 is provided at a different position from first high thermal conductivity member 28 in the left-right direction of Fig. 27, which is the stacking direction of components such as heater holder 23, stay 24, and first high thermal conductivity member 28. More specifically, second high thermal conductivity member 36 is provided overlapping first high thermal conductivity member 28. Note that, unlike Fig. 18, Fig. 27 shows a cross section in the orthogonal transport direction where the thermistor 25 is not arranged. In other words, Fig. 27 shows a cross section in which second high thermal conductivity member 36 is arranged.

[0115] The second high thermal conductivity member 36 is made of a material having 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 of a graphite sheet having a thickness of 1 mm. However, the second high thermal conductivity member 36 may also be formed of a plate material such as aluminum, copper, or silver.

[0116] As shown in Figure 28, a plurality of second high thermal conductive members 36 are arranged in the cross-convex direction, each of which is partially provided in the cross-convex direction. The portion of the recess 23b of the heater holder 23 where the second high thermal conductive members 36 are provided is one level deeper than the remaining portion. A gap is provided between the second high thermal conductive member 36 and the heater holder 23 on both sides of the cross-convex direction. This suppresses heat transfer from both ends of the second high thermal conductive member 36 in the cross-convex direction to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that the guide ribs 26 of Figure 18 are not shown in Figure 28.

[0117] 29, the second high thermal conductivity members 36 (see hatched areas) are provided in positions corresponding to the interval B in the direction perpendicular to the transport direction so as to overlap at least a portion of the adjacent resistance heating elements 31, and in this embodiment in particular, are provided over the entire area of ​​the interval B. However, although FIG. 29 and FIG. 33 described below show the case where the first high thermal conductivity members 28 are provided only in areas corresponding to the heat generating portions 35 in the direction perpendicular to the transport direction, as mentioned above, this is not limited to this.

[0118] In this embodiment, in addition to the first high thermal conductivity member 28, a second high thermal conductivity member 36 is provided at a position corresponding to the interval B in the cross-transport direction, overlapping at least a portion of adjacent resistance heating elements 31. This particularly improves the heat transfer efficiency in the cross-transport direction at the interval B, thereby further suppressing temperature unevenness in the cross-transport direction of the heater 22. Most preferably, as shown in FIG. 30 , the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are provided only over the entire area of ​​the position corresponding to the interval B. This particularly improves the heat transfer efficiency in the position corresponding to the interval B compared to other areas. For convenience, FIG. 30 illustrates the resistance heating elements 31, the first high thermal conductivity member 28, and the second high thermal conductivity member 36 offset from one another in the vertical direction, but they are actually positioned at approximately the same position in the paper transport direction. However, this is not a limitation, and the first high thermal conductivity member 28 and the second high thermal conductivity member 36 may be provided at a portion of the resistance heating elements 31 in the paper transport direction.

[0119] In one embodiment of the present invention different from the above, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are formed from 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 graphene surface, that is, in the orthogonal transport direction rather than the thickness direction. This makes it possible to effectively suppress temperature unevenness in the heater 22 and the fixing belt 20 in the orthogonal transport direction.

[0120] Graphene is a flaky powder. As shown in Figure 31, graphene is made of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, and is 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 the same number of carbon atoms form a polycyclic ring in which five-membered and six-membered rings are condensed into a cage shape, and examples thereof include C 60 , C 70 and C 80 Fullerenes or other closed cage structures with three-coordinated carbon atoms.

[0121] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD).

[0122] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet (described later), may be measured using, for example, a transmission electron microscope (TEM).

[0123] Furthermore, graphite, which is a multilayered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 32, graphite has a crystalline structure in which layers of fused six-membered rings of carbon atoms are laid out in a planar fashion, and these layers are stacked on top of each other. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. Covalent bonds have a stronger bonding strength than van der Waals bonds, resulting in a large anisotropy between intralayer and interlayer bonds. 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 first high thermal conductivity member 28 or the second high thermal conductivity member 36 in the direction perpendicular to the transport direction is greater than in the thickness direction (i.e., the stacking direction of the members), thereby suppressing heat transfer to the heater holder 23. This effectively suppresses temperature unevenness in the heater 22 in the direction perpendicular to the transport direction and minimizes heat leakage toward the heater holder 23. Furthermore, by making the first high thermal conductivity member 28 or the second high thermal conductivity member 36 out of graphite, the first high thermal conductivity member 28 or the second high thermal conductivity member 36 can have excellent heat resistance, preventing oxidation up to approximately 700 degrees.

[0124] The physical properties and dimensions of the graphite sheet can be changed as appropriate depending on the functions required of first high thermal conductivity member 28 or second high thermal conductivity member 36. For example, the anisotropy of thermal conduction can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. Furthermore, in order to increase the speed of fixing device 9, a thin graphite sheet may be used to reduce the heat capacity of fixing device 9. Furthermore, if the width of fixing nip N or heater 22 is large, the width of first high thermal conductivity member 28 or second high thermal conductivity member 36 in the direction perpendicular to the conveyance direction may be increased accordingly.

[0125] From the viewpoint of increasing the mechanical strength, the number of layers of the graphite sheet is preferably at least 11. The graphite sheet may partially include a single layer portion and a multi-layer portion.

[0126] The second high thermal conductivity members 36 need only be arranged in positions corresponding to interval B (and further area C) in the perpendicular transport direction and overlap at least a portion of the adjacent resistance heating elements 31, and are not limited to the arrangement shown in Figure 29. For example, as shown in Figure 33, the second high thermal conductivity members 36A are arranged to protrude beyond the base material 30 on both sides of the paper transport direction. The second high thermal conductivity members 36B are arranged in the range in the paper transport direction where the resistance heating elements 31 are arranged. The second high thermal conductivity members 36C are arranged in part of interval B.

[0127] As shown in FIG. 34, in this embodiment, a gap is provided between the first high thermal conductivity member 28 and the heater holder 23 in the thickness direction (left-right direction in FIG. 34). Specifically, a recess 23b (see FIG. 28) for accommodating the heater 22, first high thermal conductivity member 28, and second high thermal conductivity member 36 of the heater holder 23 has a recess 23c as a heat insulating layer that makes the depth of the recess 23b deeper than the remaining portion that accommodates the first high thermal conductivity member 28. This partial region is part or all of the area other than the portion where the second high thermal conductivity member 36 is provided in the perpendicular direction to the conveyance direction, and is a partial region in the paper conveyance direction. This minimizes the contact area between the heater holder 23 and the first high thermal conductivity member 28. This suppresses heat transfer 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, in the cross section in the direction perpendicular to the transport direction where second high thermal conductivity member 36 is provided, second high thermal conductivity member 36 abuts against heater holder 23 as in FIG. 27 of the above-described embodiment.

[0128] 34, which is the paper conveyance direction, the relief portion 23c is provided over the entire area where the resistance heating element 31 is provided. This particularly suppresses heat transfer from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that, in addition to a configuration in which a space is provided as the heat insulating layer, such as the relief portion 23c, a configuration in which a heat insulating member with a lower thermal conductivity than the heater holder 23 is provided may also be used.

[0129] Furthermore, in the above description, second high thermal conductivity member 36 is provided as a member different from first high thermal conductivity member 28, but this is not limiting. For example, the portion of first high thermal conductivity member 28 corresponding to interval B may be made thicker than the other portions.

[0130] 35, a heat insulating member 39 may be provided between first high heat conductive member 28 and heater holder 23. In FIG. 35, thermistor 25 comes into contact with first high heat conductive member 28 through opening 23a of heater holder 23 and opening 39a of heat insulating member 39.

[0131] In an image forming apparatus equipped with the fixing device of the embodiment of Figure 27, Figure 34 or Figure 35, as in the above-mentioned embodiment, by arranging end-side thermistor 25A, center-side thermistor 25B and paper-passing detection sensor 29, problems 1 to 3 can be solved and poor fixing of the image to the paper can be prevented.

[0132] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0133] Furthermore, in addition to the fixing device described above, the present invention can also be applied to fixing devices such as those shown in Figures 36 to 38. The configuration of each fixing device shown in Figures 36 to 38 will be briefly described below.

[0134] First, in the fixing device 9 shown in FIG. 36, a pressure roller 84 is disposed on the opposite side of the fixing belt 20 from the pressure roller 21 side. The pressure roller 84 is a counter rotating member that rotates opposite the fixing belt 20, which is a rotating member. This pressure roller 84 and heater 22 are configured to sandwich and heat the fixing belt 20. Meanwhile, on the pressure roller 21 side, a nip forming member 45 is disposed on the inner periphery of the fixing belt 20. The nip forming member 45 is supported by a stay 24. The fixing nip N is formed by the nip forming member 45 and the pressure roller 21 sandwiching the fixing belt 20.

[0135] 37, the above-mentioned pressure roller 84 is omitted, and in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22, the heater 22 is formed in an arc shape to match the curvature of the fixing belt 20. The rest of the configuration is the same as that of the fixing device 9 shown in FIG.

[0136] Finally, the fixing device 9 shown in FIG. 38 will be described. The fixing device 9 includes a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as an opposing member. The heating assembly 92 includes the heater 22, the first high thermal conductivity member 28, the heater holder 23, the stay 24, and the heating belt 120 as a rotating member, as described in the previous embodiment. The fixing roller 93 is an opposing rotating member that rotates opposite the heating belt 120 as a rotating member. The fixing roller 93 includes a solid iron core 93a, an elastic layer 93b formed on the surface of the core 93a, and a release layer 93c formed on the outer surface of the elastic layer 93b. A pressure assembly 94 is provided on the side of the fixing roller 93 opposite the heating assembly 92. The pressure assembly 94 includes a nip forming member 95 and a stay 96, and a pressure belt 97 is rotatably disposed so as to enclose the nip forming member 95 and the stay 96. Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93, and the image is fixed by applying heat and pressure. Arrow J in Figure 38 indicates the rotation direction of the pressure belt.

[0137] In the image forming apparatus equipped with the fixing device shown in Figures 36 to 38 above, by arranging end-side thermistor 25A, center-side thermistor 25B, and paper-passing detection sensor 29, problems 1 to 3 can be solved and poor fixing of the image onto the paper can be prevented.

[0138] Furthermore, the device equipped with the conveying device having the first and second temperature detection members and recording medium detection member of the present invention is not limited to the image forming apparatus described in the above embodiment. That is, it may be an image forming apparatus equipped with a drying device that dries ink applied to paper, or a heating device such as a laminator that thermocompresses a film as a covering member onto the surface of a sheet such as paper, or a heat sealer that thermocompresses a seal portion of a packaging material. Applying the present invention to the conveying device installed in such an apparatus can also prevent improper heating of the recording medium.

[0139] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0140] 39, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 15 and the like, a paper feeder 7, a fixing device 9, a paper discharge device 10, and a reading section 51. Paper feeder 7 includes a plurality of paper feed trays 16, each with a corresponding paper passage detection sensor 29 and paper feed roller 17, and each paper feed tray 16 stores paper of a different size.

[0141] In this embodiment, the sheet passing detection sensor 29 is provided in the sheet feeding tray 16, but it may also be provided near the upstream side of the timing roller 15 on the conveying path.

[0142] The reading unit 51 reads an image of the document Q. The reading unit 51 generates image data from the read image. The paper feeder 7 stores a plurality of sheets of paper P and sends the sheets of paper P to a conveyance path. The timing rollers 15 convey the sheets of paper P on the conveyance path to the image forming means 50.

[0143] 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 discharging device. The toner image represents, for example, an image of the original Q. The fixing device 9 applies heat and pressure to the toner image to fix the toner image 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 outside the image forming apparatus 100.

[0144] Next, the fixing device 9 of this embodiment will be described. Descriptions of the configurations common to the fixing devices of the above-described embodiments will be omitted as appropriate.

[0145] As shown in FIG. 40, 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.

[0146] A fixing nip N is formed between the fixing belt 20 and the pressure roller 21. The nip width of the fixing nip N is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

[0147] The fixing belt 20 has a polyimide base and a release layer, but does not have an elastic layer. The release layer is made of a heat-resistant film material such as fluororesin. The outer diameter of the fixing belt 20 is approximately 24 mm.

[0148] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a release layer 21c. The pressure roller 21 has an outer diameter of 24 to 30 mm, and the elastic layer 21b has a thickness of 3 to 4 mm.

[0149] The heater 22 includes a base material, a heat insulating layer, a conductive layer including a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width Y of the heater 22 in the paper transport direction is 13 mm.

[0150] As shown in FIG. 41, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. In this embodiment, as shown in the enlarged view of FIG. 41, the resistance heating elements 31 are divided into divided regions in the direction perpendicular to the transport direction, with intervals B formed therebetween (although FIG. 41 only illustrates the intervals B within the enlarged view, in reality, intervals B are provided between all of the resistance heating elements 31). The resistance heating elements 31 form three heat generating portions 35A-35C. By energizing the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By energizing the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heat generating portion 35B is made to generate heat, and when performing a fixing operation on large-sized paper, all of the heat generating portions are made to generate heat.

[0151] As shown in Figure 42, the heater holder 23 holds the heater 22 and the first high thermal conductivity 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 that is approximately parallel to the base material 30 and is recessed toward the stay 24 side more than the other surfaces of the heater 22, wall portions 23d2 provided inside the heater holder 23 on both sides (or one side) of the heater holder 23 in the direction perpendicular to the conveyance direction, and wall portions 23d3 provided inside the heater holder 23 on both sides in the paper conveyance direction. The heater holder 23 has guide ribs 26. The heater holder 23 is made of LCP (liquid crystal polymer).

[0152] As shown in FIG. 43, the connector 60 includes a housing made of resin (for example, LCP), and a plurality of contact terminals provided inside the housing.

[0153] The connector 60 is attached so as to sandwich the heater 22 and heater holder 23 together from the front and back sides. In this state, each contact terminal comes into contact (pressure-welded) with each electrode portion of the heater 22, electrically connecting the heat generating portion 35 to a power supply provided in the image forming apparatus via the connector 60. This enables power to be supplied from the power supply to the heat generating portion 35. Note that, to ensure connection with the connector 60, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0154] The flanges 53 are provided on both sides of the fixing belt 20 in the direction perpendicular to the conveyance direction, and hold both ends of the fixing belt 20 from the inside of the belt. The flanges 53 are fixed to the housing of the fixing device 9. The flanges 53 are inserted into both ends of the stays 24 (see the arrow directions from the flanges 53 in Figure 43).

[0155] The attachment direction of the connector 60 to the heater 22 and heater holder 23 is the paper feed direction of the heater (see the arrow direction from the connector 60 in Figure 43). When the connector 60 is attached to the heater holder 23, a convex portion on one of the connector 60 and the heater holder 23 may engage with a concave portion on the other, with the convex portion moving relatively within the concave portion. The connector 60 is attached to the heater 22 and heater holder 23 on one side in the direction perpendicular to the feed direction, opposite the side on which the drive motor for the pressure roller 21 is provided.

[0156] 44, thermistors 25 are provided on the central side and the end side of the fixing belt 20 in the direction perpendicular to the conveyance direction, facing the inner circumferential surface of the fixing belt 20. The heater 22 is controlled based on the temperatures of the central side and the end side of the fixing belt 20 in the direction perpendicular to the conveyance direction detected by the thermistors 25.

[0157] Thermostats 27 are provided facing the inner circumferential surface of the fixing belt 20, at the center and end sides of the fixing belt 20 in the direction perpendicular to the conveyance direction. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold, the power supply to the heater 22 is stopped.

[0158] Flanges 53 are provided on both ends of the fixing belt 20 in the direction perpendicular to the conveyance direction to hold the respective ends of the fixing belt 20. The flanges 53 are made of LCP (liquid crystal polymer).

[0159] 45, a slide groove 53a is provided in the flange 53. The slide groove 53a extends in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21. An engagement portion of the housing of the fixing device 9 engages with the slide groove 53a. The engagement portion moves relatively within the slide groove 53a, allowing the fixing belt 20 to move in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21.

[0160] In an image forming apparatus equipped with the above-described fixing device 9, as in the previously described embodiment, problems 1 to 3 can be solved by arranging an end-side thermistor 25A, a center-side thermistor 25B, and a paper-passing detection sensor 29, thereby preventing poor fixing of the image onto the paper.

[0161] Recording media include paper P (plain paper), as well as cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, plastic film, prepreg, copper foil, etc.

[0162] In the present application, the terms "sensing" and "detection" are synonymous. [Explanation of symbols]

[0163] 7. Paper feeder (recording medium supply unit) 9 Fixing device (heating device) 14 Paper transport path (recording medium transport path) 16 Paper tray 20 Fixing belt (rotating member) 21 Pressure roller (pressure member) 21b Elastic layer 22 Heater (heating element) 25A End thermistor (first temperature detection element) 25B Center thermistor (second temperature detection element) 29 Paper passing detection sensor (recording medium detection member) 100 Image forming device (conveyor device) D Heating area of ​​the heater (heating area of ​​the heating element) D0 Center position of the heater's heating area (center position of the heating area of ​​the heater in the direction perpendicular to the conveyance direction) E Maximum paper passing area (maximum passing area) H Paper passing detection area of ​​the paper passing detection sensor (recording medium detection area of ​​the recording medium detection member) N Fixing nip (nip part) P Paper (recording medium) X: Orthogonal to conveying direction X0 Reference position Y Paper transport direction (recording medium transport direction) [Preliminary Technology Documents] [License]

[0164] [License 1] Patent No. 5924867

Claims

1. a heating device for heating the recording medium; a recording medium detection member that detects the recording medium, the heating device includes a heating element for heating the recording medium, a first temperature detection member and a second temperature detection member for detecting the temperature of the heating element, a rotating member, and a pressing member for pressing the rotating member; the pressure member has an elastic layer, the heating element has a substrate and a heating element, A direction perpendicular to the direction in which the recording medium is conveyed and along the surface of the recording medium is defined as a conveyance perpendicular direction, and the center position of the elastic layer in the conveyance perpendicular direction is defined as a reference position. the heating element has a large heat distribution area on one side in the direction perpendicular to the transport direction with respect to the reference position, and a small heat distribution area on the other side opposite to the one side, In the perpendicular direction to the conveyance direction, the first temperature detecting member is provided at a position farther from the reference position than the second temperature detecting member, the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area, A conveying device characterized in that, relative to the reference position, the side of the heat generating element that is longer in the direction perpendicular to the conveying direction is the large heat distribution area, and the side of the heat generating element that is shorter in the direction perpendicular to the conveying direction is the small heat distribution area.

2. a heating device for heating the recording medium; a recording medium detection member that detects the recording medium, the heating device has a heating element for heating the recording medium, and a first temperature detection element and a second temperature detection element for detecting the temperature of the heating element; the heating element has a substrate and a heating element, A direction perpendicular to the direction in which the recording medium is conveyed and along the surface of the recording medium is defined as a conveyance perpendicular direction, and the center position of the conveyed recording medium in the conveyance perpendicular direction is defined as a reference position. the heating element has a large heat distribution area on one side in the direction perpendicular to the transport direction with respect to the reference position, and a small heat distribution area on the other side opposite to the one side, In the perpendicular direction to the conveyance direction, the first temperature detecting member is provided at a position farther from the reference position than the second temperature detecting member, the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area, A conveying device characterized in that, relative to the reference position, the side of the heat generating element that is longer in the direction perpendicular to the conveying direction is the large heat distribution area, and the side of the heat generating element that is shorter in the direction perpendicular to the conveying direction is the small heat distribution area.

3. a heating device for heating the recording medium; a recording medium detection member that detects the recording medium, the heating device has a heating element for heating the recording medium, and a first temperature detection element and a second temperature detection element for detecting the temperature of the heating element; the heating element has a substrate and a heating element, A direction perpendicular to the direction in which the recording medium is conveyed and along the surface of the recording medium is defined as a conveyance perpendicular direction, and the center position of the heat generating element in the conveyance perpendicular direction is defined as a reference position. the heating element has a large heat distribution area on one side in the direction perpendicular to the transport direction with respect to the reference position, and a small heat distribution area on the other side opposite to the one side, In the perpendicular direction to the conveyance direction, the first temperature detecting member is provided at a position farther from the reference position than the second temperature detecting member, the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area, The heating element has a conductor including the heating element on the substrate, A conveying device characterized in that, with respect to the reference position, the side where the area of ​​the conductor is larger is the large heat distribution area, and the side where the area of ​​the conductor is smaller is the small heat distribution area.

4. a heating device for heating the recording medium; a recording medium detection member that detects the recording medium, the heating device includes a heating element for heating the recording medium, a first temperature detection member and a second temperature detection member for detecting the temperature of the heating element, a rotating member, and a pressing member for pressing the rotating member; the pressure member has an elastic layer, the heating element has a substrate and a heating element, A direction perpendicular to the direction in which the recording medium is conveyed and along the surface of the recording medium is defined as a conveyance perpendicular direction, and the center position of the elastic layer in the conveyance perpendicular direction is defined as a reference position. the heating element has a large heat distribution area on one side in the direction perpendicular to the transport direction with respect to the reference position, and a small heat distribution area on the other side opposite to the one side, In the perpendicular direction to the conveyance direction, the first temperature detecting member is provided at a position farther from the reference position than the second temperature detecting member, the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area, The heating element has a conductor including the heating element on the substrate, A conveying device characterized in that, with respect to the reference position, the side where the area of ​​the conductor is larger is the large heat distribution area, and the side where the area of ​​the conductor is smaller is the small heat distribution area.

5. a heating device for heating the recording medium; a recording medium detection member that detects the recording medium, the heating device has a heating element for heating the recording medium, and a first temperature detection element and a second temperature detection element for detecting the temperature of the heating element; the heating element has a substrate and a heating element, A direction perpendicular to the direction in which the recording medium is conveyed and along the surface of the recording medium is defined as a conveyance perpendicular direction, and the center position of the conveyed recording medium in the conveyance perpendicular direction is defined as a reference position. the heating element has a large heat distribution area on one side in the direction perpendicular to the transport direction with respect to the reference position, and a small heat distribution area on the other side opposite to the one side, In the perpendicular direction to the conveyance direction, the first temperature detecting member is provided at a position farther from the reference position than the second temperature detecting member, the first temperature detection member is provided in the small heat distribution area, and the recording medium detection member is provided in the large heat distribution area, The heating element has a conductor including the heating element on the substrate, A conveying device characterized in that, with respect to the reference position, the side where the area of ​​the conductor is larger is the large heat distribution area, and the side where the area of ​​the conductor is smaller is the small heat distribution area.

6. 6. The image forming apparatus according to claim 1, wherein the recording medium detection member is provided upstream of the heating device on a conveyance path of the recording medium.

7. 7. The conveying device according to claim 6, further comprising a recording medium supply unit that loads the recording medium and supplies the recording medium onto the conveying path, The image forming apparatus includes a recording medium detection member provided in the recording medium supply unit.

8. An image forming apparatus comprising the conveying device according to claim 1 .

9. 9. The image forming apparatus according to claim 8, wherein the heating device has a rotating member. The image forming apparatus wherein the rotating member does not have an elastic layer.

Images