JP7733352B2 - Heating device, fixing device, image forming apparatus - Google Patents

Description

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

The fixing device is equipped with a planar heater consisting of a base material and a resistance heating element as a heating element for heating the fixing belt, which acts as a rotating member. In such a fixing device, it is important to make the temperature of the fixing belt uniform in its longitudinal direction (the direction in which the multiple resistance heating elements are arranged) and to heat the toner on the recording medium uniformly.

For example, in Patent Document 1 (JP 2019-164328 A), multiple divided resistance heating elements are provided on a substrate. The resistance heating elements have PTC characteristics. In this fixing device, when a small-sized recording medium is passed through and the temperature of the resistance heating element corresponding to the non-paper passing area rises, the resistance of the resistance heating element increases due to the PTC characteristics, and the amount of heat generated by this resistance heating element is suppressed. Therefore, the amount of heat generated by the heater in the non-paper passing area is suppressed, preventing excessive temperature rise in the non-paper passing area of the fixing belt.

However, in a configuration where the resistance heating element is divided into multiple parts like this, the amount of heat generated by the heating element in the divided areas, which are the spaces between the resistance heating elements, is smaller than in other areas. This causes the temperature of the rotating element to be lower in these areas, resulting in uneven temperature distribution of the fixing belt.

The objective is to suppress temperature variations in the direction of arrangement of multiple resistance heating elements on a rotating member.

In order to solve the above-mentioned problems, the present invention provides a heating device comprising: a rotating member; a planar heating element having a base material and a plurality of resistance heating elements; a holding member that holds the heating element; and a first high thermal conductivity member having a higher thermal conductivity than the base material, wherein the plurality of resistance heating elements are arranged on the base material at intervals in the longitudinal direction of the heating element , and the first high thermal conductivity member is provided between the holding member and the heating element at a position where at least a portion of the first high thermal conductivity member overlaps with the spacing between the resistance heating elements in the arrangement direction of the plurality of resistance heating elements, and the heating device further comprises a second high thermal conductivity member having a higher thermal conductivity than the base material between the holding member and the first high thermal conductivity member, wherein a plurality of second high thermal conductivity members are provided in the arrangement direction of the plurality of resistance heating elements, and each of the second high thermal conductivity members is provided at a position where it overlaps with the spacing between the resistance heating elements in the arrangement direction of the plurality of resistance heating elements .

The heating device of the present invention can suppress temperature variations in the direction in which multiple resistance heating elements are arranged on the rotating member.

FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. FIG. FIG. 10 is a diagram illustrating power supply to a heater. FIG. 4 is a plan view of a heater having a different resistive heating element shape from that of FIG. 3 . FIG. 6 is a plan view of a heater having a resistance heating element with a different shape from those of FIGS. 3 and 5. 5A and 5B are diagrams showing temperature distribution in the arrangement direction of the fixing belt, in which FIG. 5A is a plan view of a heater, and FIG. 5B is a diagram showing temperature distribution in the fixing belt. FIG. 6 is a diagram showing divided regions of the heater in FIG. 5 . FIG. 9 is a diagram showing divided regions having a different shape from that shown in FIG. 8; FIG. 7 is a diagram showing divided regions of the heater in FIG. 6; FIG. 2 is a perspective view of a heater, a first high thermal conductive member, and a heater holder. FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity member. 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; FIG. 2 is a perspective view of a heater, a first high thermal conductive member, a second high thermal conductive member, and a heater holder. FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity member and the second high thermal conductivity member. FIG. 16 is a plan view showing a heater in which the arrangement of the second high thermal conductive member is different from that in FIG. 15 . FIG. 14 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIGS. 2 and 13 . FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 2 is a schematic configuration diagram of an image forming apparatus different from that shown in FIG. 1 . 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. FIG. 23 is a plan view of a heater in the fixing device of FIG. 22. FIG. 2 is a perspective view of a heater and a heater holder. FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. FIG. 2 is a diagram showing the arrangement of a thermistor and a thermostat. FIG. 10 is a view showing a groove portion of a flange. 10A and 10B are plan views of a heater showing different examples of the arrangement of first high thermal conductivity members. FIG. 10 is a plan view of the heater showing yet another example of the arrangement of the first high thermal conductivity members. 10A to 10C are plan views of the heater showing examples of different arrangements of the first high thermal conductivity member and the second high thermal conductivity member. FIG. 1 illustrates the atomic crystal structure of graphene. FIG. 1 illustrates the atomic crystal structure of graphite.

The present invention will now be described with reference to the accompanying drawings. In each of the drawings used to explain the present invention, components such as parts and components having the same function or shape will be assigned the same reference numerals as far as possible to distinguish them, and once they have been described, their description will be omitted.

Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention.

The image forming device 100 shown in Figure 1 has four imaging units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming device 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 has 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.

The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7, a transfer device 8, a fixing device 9 as a heating device, and a paper discharge device 10. The exposure device 6 exposes the surface of each photoconductor 2 to light and forms an electrostatic latent image on that surface. The paper feed device 7 supplies paper P as a recording medium to the paper transport path 14. 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. Each imaging unit 1, photoconductor 2, charging device 3, exposure device 6, transfer device 8, etc. constitute image forming means for forming an image on paper.

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 each photoconductor 2 to the intermediate transfer belt 11. The secondary transfer roller 13 transfers the toner images transferred on the intermediate transfer belt 11 to paper P. Each of the multiple primary transfer rollers 12 contacts the photoconductor 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.

In addition, a pair of timing rollers 15 are provided along the paper transport path 14, from the paper feeder 7 to the secondary transfer nip (secondary transfer roller 13).

Next, the printing operation of the image forming device will be explained with reference to Figure 1.

When a command to start a printing operation is received, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in Figure 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, forming a toner image on each photoconductor 2.

The toner images formed on each photoconductor 2 rotate as the photoconductor 2 rotates, reaching the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred onto 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) as the intermediate transfer belt 11 rotates. The toner images are then transferred to the paper P transported through the secondary transfer nip. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 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 formed on the paper P. After the toner image is transferred, any remaining toner on each photoconductor 2 is removed by the cleaning devices 5.

The paper P with the transferred toner image is transported to the fixing device 9, which fixes the toner image to the paper P. The paper P is then ejected from the device by the paper ejection device 10, completing the printing process.

Next, we will explain the configuration of the fixing device.

As shown in FIG. 2, the fixing device 9 according to this embodiment includes a fixing belt 20 as a rotating member or fixing member, a pressure roller 21 as an opposing rotating member or pressure member, a heater 22 as a heating member, a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature detection member, and a first high thermal conductivity member 28. 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 detects the temperature of the first high thermal conductivity member 28. The direction perpendicular to the plane of the paper in Figure 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, first high thermal conductivity member 28, etc., and hereinafter this direction will be simply referred to as the longitudinal direction. Note that this longitudinal direction also corresponds to the width direction of the paper being transported, the belt width direction of the fixing belt 20, and the axial direction of the pressure roller 21.

The fixing belt 20 has a cylindrical substrate made of polyimide (PI) with 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 elastic layer made of rubber or other material may be provided between the substrate and the release layer. The substrate of the fixing belt 20 is not limited to polyimide; it may also be a heat-resistant resin such as PEEK or a metal substrate such as nickel (Ni) or SUS. The inner surface of the fixing belt 20 may be coated with a sliding layer made of polyimide, PTFE, or other material.

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 this 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 release properties, it is desirable to form a release layer 21c made of a fluororesin layer with a thickness of, for example, 40 μm on the surface of the elastic layer 21b.

When the pressure roller 21 is urged toward the fixing belt 20 by the urging means, the pressure roller 21 is pressed against the heater 22 via the fixing belt 20. This forms a fixing nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is also configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of the arrow in Figure 2, the fixing belt 20 is rotated accordingly.

The heater 22 is a planar heating element arranged longitudinally across the width of the fixing belt 20. The heater 22 is composed of a plate-shaped substrate 30, a resistance heating element 31 arranged on the substrate 30, and an insulating layer 32 covering the resistance heating element 31. The heater 22 is in contact with the inner surface of the fixing belt 20 on the insulating layer 32 side, and heat generated by 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 arranged 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 alternatively be arranged on the heater holder 23 side of the substrate 30. In this case, because heat from the resistance heating element 31 is transferred to the fixing belt 20 via the substrate 30, it is desirable that the substrate 30 be made of a material with high thermal conductivity, such as aluminum nitride. Furthermore, by constructing the substrate 30 from a material with high thermal conductivity, it is possible to sufficiently heat the fixing belt 20 even if the resistance heating element 31 is placed on the opposite side of the substrate 30 from the fixing belt 20 side.

The heater holder 23 and stay 24 are positioned on the inner periphery of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends are supported by both side plates of the fixing device 9. By supporting the heater holder 23 and 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 lower than that of the base material 30.

Note that the stay 24 supporting the heater holder 23 means that the stay 24, which has a portion extending in the pressure direction of the pressure roller 21 (left-right direction in the figure) or a portion with thickness, abuts against the heater holder 23 from the side opposite the pressure roller 21 (left side in the figure). This prevents the heater holder 23 from bending (particularly in the longitudinal direction in this embodiment) due to the pressure from the pressure roller 21. However, the above-mentioned abutment does not necessarily mean that the stay 24 abuts against the heater holder 23 directly, but also includes abutment via another member. "Abutment via another member" refers to a state in which another member is sandwiched between the stay 24 and the heater holder 23 in the left-right direction in the figure, and the stay 24 abuts against the other member at a position corresponding to at least a portion of the other member, and the other member abuts against the heater holder 23. Furthermore, "extending in the pressure direction" does not necessarily mean the same direction as the pressure direction of the pressure roller 21, but also includes extending in a direction at a certain angle from the pressure direction of the pressure roller 21. Even in these cases, the stay 24 can of course suppress bending of the heater holder 23 against the pressure force from the pressure roller 21.

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, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to efficiently heat the fixing belt 20.

The heater holder 23 is also provided with guide portions 26 that guide the fixing belt 20. The guide portions 26 are provided on the upstream side (below the heater 22 in FIG. 2) and downstream side (above the heater 22 in FIG. 2) of the heater 22 in the belt rotation direction. The upstream and downstream guide portions 26 are arranged at intervals along the length of the heater 22. Each guide portion 26 is formed in a roughly fan shape, and has a belt-facing surface 260 that is arc-shaped or convexly curved and extends in the belt circumferential direction so as to face the inner circumferential surface of the fixing belt 20.

The heater holder 23 has multiple openings 23a in the longitudinal direction. The openings 23a penetrate the heater holder 23 in the thickness direction. The thermistor 25 and a thermostat (described later) are provided in these openings 23a. The thermistor 25 and thermostat are pressed against the back surface of the first high thermal conductivity member 28 by a spring 29. However, similar openings may also be provided in the first high thermal conductivity member 28 (and the second high thermal conductivity member (described later)), so that the thermistor 25 and thermostat are pressed against the back surface of the substrate 30.

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

Next, we will explain how to calculate the above thermal conductivity. When calculating thermal conductivity, first measure the thermal diffusivity of the object in question, and then use this thermal diffusivity to calculate the thermal conductivity.

Thermal diffusivity was measured using a thermal diffusivity/thermal conductivity measuring device (product name: ai-Phase Mobile 1u, ai-Phase Corporation).

To convert the thermal diffusivity to thermal conductivity, the density and specific heat capacity values are required. A dry automatic density meter (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. If 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):

In the fixing device 9 according to this embodiment, when a printing operation is initiated, the pressure roller 21 is driven to rotate, and the fixing belt 20 begins to rotate. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the belt-facing surface 260 of the guide portion 26, 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 a predetermined target temperature (fixing temperature), as shown in FIG. 2 , a sheet of paper P bearing an unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (fixing nip N), where the unfixed toner image is heated and pressurized to be fixed to the sheet of paper P. The fixing belt 20 is a heated member that is heated by the heater 22.

Figure 3 is a plan view of the heater according to this embodiment.

As shown in FIG. 3, the surface of the plate-shaped substrate 30 is provided with multiple (four) resistive heating elements 31, power supply lines 33A and 33B as conductors, and first and second electrode portions 34A and 34B. However, the number of resistive heating elements 31 is not limited to this embodiment.

In this embodiment, the longitudinal direction of the heater 22, etc. (the direction perpendicular to the plane of the paper in Figure 2) is also the arrangement direction X of the multiple resistance heating elements 31, as shown in Figure 3. Hereinafter, this direction will also be simply referred to as the arrangement direction. Furthermore, the vertical direction Y in Figure 3, which is a direction that intersects the arrangement direction (a perpendicular direction in this embodiment) and is different from the thickness direction of the substrate 30, will also be referred to as the direction that intersects the arrangement direction of the multiple resistance heating elements 31, or simply as the inter-arrangement direction. The inter-arrangement direction Y is the direction along the surface of the substrate 30 on which the resistance heating elements 31 are provided, and is also the widthwise direction of the heater 22 or the transport direction of paper passed through the fixing device 9.

The multiple resistance heating elements 31 form a heating section 35 divided into multiple sections in the arrangement direction. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode portions 34A, 34B provided at one end of the substrate 30 in the arrangement direction (the left end in Figure 3) via power supply lines 33A, 33B. 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, and 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 arrangement direction, the gap is preferably 5 mm or less, and more preferably 1 mm or less.

The resistance heating element 31 is made of a material with PTC (positive temperature coefficient of resistance) characteristics, and is characterized by an increase in resistance (decreasing heater output) as the temperature increases.

The PTC characteristics of the resistance heating element 31 and the divided heating section 35 configuration in the array 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, the temperature of the resistance heating element 31 outside the paper width rises, and when its resistance value increases, the output (heat generation amount) decreases relatively, suppressing temperature rise at the edge. Furthermore, by electrically connecting multiple resistance heating elements 31 in parallel, temperature rise in non-paper passing areas can be suppressed while maintaining printing speed. The heating elements that make up 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 cross-arrangement direction of the heaters 22.

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 described above, the resistance heating element 31 may also be made of resistance materials such as silver alloy (AgPt) or ruthenium oxide (RuO ₂ ). 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.

Preferred materials for the substrate 30 are ceramics such as alumina and aluminum nitride, which have excellent heat resistance and insulation, or non-metallic materials such as glass and mica. In this embodiment, an alumina substrate is used that is 8 mm wide in the cross-array direction, 270 mm wide in the array direction, and 1.0 mm thick. Alternatively, the substrate 30 may be constructed by laminating an insulating material onto a conductive material such as a metal. 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 thermal uniformity of the heater 22 and enhance image quality, the substrate 30 may be constructed from a material with high thermal conductivity, such as copper, graphite, or graphene.

The insulating layer 32 is made of heat-resistant glass, for example, 75 μm thick. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulating and protecting them while maintaining sliding contact with the fixing belt 20.

Figure 4 shows the power supply circuit to the heater in this embodiment.

As shown in FIG. 4, in this embodiment, the power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting the AC power source 200 and the electrode portions 34A, 34B of the heater 22. The power supply circuit also includes a triac 210 that controls the amount of power supplied. The amount of power supplied to each resistance heating element 31 is controlled by the control unit 220 via the triac 210 based on the temperature detected by the thermistor 25. The control unit 220 is configured as a microcomputer including a CPU, ROM, RAM, I/O interface, etc.

In this embodiment, the thermistors 25 are disposed in the central region of the heaters 22 in the arrangement direction, which is within the minimum paper passing width, and at one end of the heaters 22 in the arrangement direction. Furthermore, at one end of the heaters 22 in the arrangement direction, a thermostat 27 is disposed as a power cut-off device that cuts off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 reaches or exceeds a predetermined temperature. The thermistors 25 and thermostat 27 contact the first high thermal conductivity member 28 to detect its temperature.

In this embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the arrangement direction, but they may also be provided on different sides. Furthermore, the shape of the resistive heating element 31 is not limited to that of this embodiment. For example, as shown in FIG. 5, the resistive heating element 31 may be rectangular, or as shown in FIG. 6, the resistive heating element 31 may be made of a linear portion that is folded back to form a substantially parallelogram shape. Furthermore, as shown in FIG. 5, the portion extending from the block-shaped portion of the resistive heating element 31 toward the power supply line 33 (the portion extending in the intersecting direction) may be part of the resistive heating element 31, or may be made of the same material as the power supply line 33.

Figure 7 shows the temperature distribution in the arrangement direction of the fixing belt 20. (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 in the arrangement direction of the fixing belt 20.

As shown in Figures 7(a) and 7(b), the multiple resistance heating elements 31 provided in the heater 22 are divided in the arrangement direction, forming divided regions B between the resistance heating elements 31. In other words, the multiple resistance heating elements 31 provided in the heater 22 are arranged at intervals B. Hereinafter, the range B as a 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 arrangement 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 the 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. Here, as shown in the enlarged view of Figure 7(a), interval B refers to the arrangement direction region including all of the areas into which the resistance heating elements 31, the main heat-generating portions of the heater 22, are divided in the arrangement direction. Additionally, in addition to the spacing B, the area including the range corresponding to the connection portion 311 of the resistance heating element 31 is referred to as region C. This connection portion 311 refers to the portion of the resistance heating element 31 that extends in the cross-array direction and is connected to each of the power supply lines 33A and 33B.

As shown in Figure 8, even in a heater 22 having a rectangular resistance heating element 31 as shown in Figure 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 Figure 9, the temperature in the gap B is lower than in other parts. Furthermore, as shown in Figure 10, even in a heater 22 having a resistance heating element 31 shaped as shown in Figure 6, the temperature in the gap B is lower than in other parts. However, by overlapping adjacent resistance heating elements 31 in the arrangement direction as in Figures 7, 9, and 10, the temperature drop in the other parts of the gap B can be suppressed.

In this embodiment, the aforementioned first high thermal conductivity member 28 is provided to suppress temperature drops in the above-mentioned intervals and to suppress temperature unevenness in the alignment direction of the fixing belt 20. The first high thermal conductivity member 28 will be described in more detail below.

As shown in FIG. 2, the first high thermal conductivity member 28 is disposed between the heater 22 and the stay 24 in the left-right direction of FIG. 2, and is particularly sandwiched between the heater 22 and the heater holder 23. In other words, one surface of the first high thermal conductivity member 28 abuts against the back surface of the substrate 30, and the other surface abuts against the heater holder 23.

The stay 24 supports the heater holder 23, the first high thermal conductivity member 28, and the heater 22 by abutting the abutment surfaces 24a1 of two vertical portions 24a extending in the thickness direction of the heater 22 and other components against the heater holder 23. In the cross-array direction (the vertical direction in Figure 2), the abutment surfaces 24a1 are located outside the area where the resistance heating element 31 is located. This suppresses heat transfer from the heater 22 to the stay 24, allowing the heater 22 to efficiently heat the fixing belt 20.

As shown in Figure 11, the first high thermal conductivity member 28 is made of a plate material with a thickness of 0.3 mm, a length in the array direction of 222 mm, and a width in the direction crossing the array of 10 mm. In this embodiment, the first high thermal conductivity member 28 is made of a single plate material, but it may also be made of multiple members. Note that the guide portion 26 from Figure 2 is not shown in Figure 11.

The first high thermal conductivity member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is attached from above, 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 arrangement direction is set to be approximately the same as the width of the heater 22 in the arrangement direction. Movement of the first high thermal conductivity member 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement direction restriction portions) 23b1 that form the recess 23b. In this way, restricting misalignment of the first high thermal conductivity member 28 in the arrangement direction within the fixing device 9 improves heat conduction efficiency within a targeted range in the arrangement direction. Furthermore, movement of the first high thermal conductivity member 28 and the heater 22 in the cross-arrangement direction is restricted by both side walls (arrangement cross-direction restriction portions) 23b2 that form the recess 23b in the cross-arrangement direction.

The range in the array direction in which the first high thermal conductivity members 28 are provided is not limited to the above. For example, as shown in FIG. 12, the first high thermal conductivity members 28 may be provided only in the range corresponding to the heat-generating portions 35 in the array direction (see the hatched area in FIG. 12). Alternatively, as shown in FIG. 28, the first high thermal conductivity members 28 may be provided only in the entire area at a position corresponding to the spacing B in the array direction. For convenience, FIG. 28 shows the resistance heating element 31 and the first high thermal conductivity members 28 offset vertically in FIG. 28, but they are actually positioned at approximately the same position in the cross-array direction. However, this is not limited to this. The first high thermal conductivity members 28 may be provided only in a portion of the resistance heating element 31 in the cross-array direction, or may be provided so as to cover the entire cross-array direction as shown in FIG. 29 (described later). Furthermore, as shown in FIG. 29, the first high thermal conductivity members 28 may be provided in addition to the position corresponding to the spacing B in the array direction, spanning both resistance heating elements 31 on either side of the spacing B. "Provided across the resistance heating elements 31 on both sides" means that the first high thermal conductivity members 28 at least partially overlap with the resistance heating elements 31 on both sides in the arrangement 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 they 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 corresponding to the interval B as shown in Figure 29. Here, "provided at a position corresponding to the interval B in the arrangement direction" means that the first high thermal conductivity members 28 at least partially overlap with the interval B in the arrangement direction.

The pressure of the pressure roller 21 causes the first high thermal conductivity member 28 to be sandwiched between the heater 22 and the heater holder 23, bringing them into close contact with these members. Contact between the first high thermal conductivity member 28 and the heater 22 improves the thermal conduction efficiency in the heater 22's arrangement direction. Furthermore, by positioning the first high thermal conductivity member 28 in the arrangement direction at a position corresponding to the spacing B between the heaters 22, the thermal conduction efficiency at spacing B can be improved, increasing the amount of heat transferred to the position at spacing B in the arrangement direction and raising the temperature at spacing B in the arrangement direction. This reduces temperature unevenness in the heater 22's arrangement direction. This reduces temperature unevenness in the fixing belt 20's arrangement direction. This reduces uneven fixing and glossiness of the image fixed to the paper. Alternatively, there is no need for extra heating by the heater 22 to ensure sufficient fixing performance at the spacing, thereby achieving energy savings in the fixing device 9. Furthermore, by providing the first high thermal conductivity member 28 over the entire heat generating section 35 in the arrangement direction, the heat transfer efficiency of the heater 22 is improved over the entire area that is primarily heated by the heater 22 (i.e., the image forming area on the paper being fed), and temperature unevenness in the arrangement direction of the heater 22 and, by extension, the fixing belt 20 can be suppressed.

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 characteristics described above effectively prevents excessive temperature rise in non-paper passing areas when small-size paper is passed through. In other words, the PTC characteristics reduce the amount of heat generated by the resistance heating element 31 in non-paper passing areas, and the heat from the non-paper passing areas where the temperature has risen can be efficiently transferred to the paper passing areas, effectively preventing excessive temperature rise in non-paper passing areas.

It is also preferable to place the first high thermal conductivity member 28 around gap B, as the temperature there is low due to the small amount of heat generated in gap B. For example, in this embodiment, by providing the first high thermal conductivity member 28 at a position corresponding to region C (see Figure 8), the heat transfer efficiency in the arrangement direction at gap B and its periphery is particularly improved, and temperature unevenness in the arrangement direction of the heaters 22 can be further suppressed. In particular, in this embodiment, the first high thermal conductivity member 28 is provided across the entire heat-generating section 35 in the arrangement direction. This makes it possible to further suppress temperature unevenness in the arrangement direction of the heaters 22 (fixing belt 20).

Next, we will explain different embodiments of the fixing device.

As shown in FIG. 13, the fixing device 9 of this embodiment has a second high thermal conductivity member 36 between the heater holder 23 and the first high thermal conductivity member 28. The second high thermal conductivity member 36 is provided at a different position from the first high thermal conductivity member 28 in the stacking direction (left-right direction in FIG. 13) of components such as the heater holder 23, stay 24, and first high thermal conductivity member 28. More specifically, the second high thermal conductivity member 36 is provided overlapping the first high thermal conductivity member 28. Note that, unlike FIG. 2, FIG. 13 shows a cross section in which the second high thermal conductivity member 36 is arranged in the arrangement direction and the thermistor 25 is not arranged.

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

As shown in FIG. 14, multiple second high thermal conductive members 36 are arranged in the arrangement direction, each partially spaced in the arrangement 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 portions. A gap is provided between the second high thermal conductive members 36 and the heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from the second high thermal conductive members 36 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that the guide portion 26 from FIG. 2 is not shown in FIG. 14.

As shown in Figure 15, the second high thermal conductivity members 36 (see hatched areas) are provided in positions corresponding to the interval B in the arrangement direction, overlapping at least a portion of adjacent resistance heating elements 31, and in this embodiment in particular, are provided across the entire interval B. However, while Figure 15 (and Figure 16 described below) shows a case where the first high thermal conductivity members 28 are provided only in areas corresponding to the heat generating portions 35 in the arrangement direction, as mentioned above, this is not limited to this.

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 spacing B in the array direction, overlapping at least a portion of adjacent resistance heating elements 31. This particularly improves the heat transfer efficiency in the array direction at spacing B, thereby further suppressing temperature unevenness in the array direction of the heaters 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 corresponding to spacing B. This particularly improves the heat transfer efficiency in the area corresponding to spacing 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 positioned at approximately the same position in the cross-array 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 only over a portion of the resistance heating elements 31 in the cross-array direction, or may be provided so as to cover the entire area in the cross-array direction.

In one embodiment of the present invention, which is 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 allows the first high thermal conductivity member 28 and the second high thermal conductivity member 36 to be formed with high thermal conductivity in a predetermined direction along the graphene surface, i.e., in the arrangement direction rather than the thickness direction. This effectively suppresses temperature unevenness in the arrangement direction of the heater 22 and the fixing belt 20.

Graphene is a flaky powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in FIG. 31 . A graphene sheet is a sheet of graphene, typically a single layer. Impurities may be included in the single layer of carbon. Graphene may also have a fullerene structure. Fullerene structures are generally recognized as compounds in which the same number of carbon atoms form a polycyclic ring structure in which five- and six-membered rings are fused together in a cage-like fashion, such as C ₆₀ , C ₇₀ , and C ₈₀ fullerenes, or other closed cage structures with three-coordinate carbon atoms.

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

Commercially available graphene sheets can be used. The size and thickness of the graphene sheets, as well as the number of layers of the graphite sheets described below, can be measured, for example, using a transmission electron microscope (TEM).

Furthermore, graphite, which is made by multilayering graphene, has a large thermal conductivity anisotropy. As shown in Figure 32, graphite has layers in which the condensed six-membered ring layer planes of carbon atoms extend in a planar fashion, forming a crystalline structure in which these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. 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 arrangement direction of the first high thermal conductivity member 28 or the second high thermal conductivity member 36 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 arrangement direction of the heater 22 and minimizes heat leakage toward the heater holder 23. Furthermore, by constructing the first high thermal conductivity member 28 or the second high thermal conductivity member 36 from graphite, the first high thermal conductivity member 28 or the second high thermal conductivity member 36 can be endowed with excellent heat resistance, being resistant to oxidation up to approximately 700 degrees.

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

From the perspective of increasing mechanical strength, it is preferable that the number of layers of the graphite sheet be 11 or more. The graphite sheet may also contain some single-layer and multi-layer portions.

The second high thermal conductivity members 36 need only be arranged in positions corresponding to interval B (and further to area C) in the array direction so as to overlap at least a portion of adjacent resistance heating elements 31, and are not limited to the arrangement shown in FIG. 15. For example, as shown in FIG. 16, the second high thermal conductivity members 36A are arranged to protrude beyond the substrate 30 on both sides in the cross array direction. The second high thermal conductivity members 36B are arranged in the range in the cross array direction where the resistance heating elements 31 are arranged. The second high thermal conductivity members 36C are arranged in part of interval B.

Also, as shown in FIG. 17 , 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. 17 ). That is, a recess 23c is provided as a heat insulating layer in a portion of the recess 23b (see FIG. 14 ) for arranging the heater 22, first high thermal conductivity member 28, and second high thermal conductivity member 36 of the heater holder 23, except for the portion where the second high thermal conductivity member 36 is provided in the array direction. This recess 23b is deeper than the remaining portion that receives the first high thermal conductivity member 28. 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 where the second high thermal conductivity member 36 is provided in the arrangement direction, the second high thermal conductivity member 36 abuts against the heater holder 23, as in Figure 13 of the above-mentioned embodiment.

In particular, in this embodiment, relief portions 23c are provided across the entire area where the resistance heating elements 31 are provided in the cross-array direction (the vertical direction in Figure 17). 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 like relief portions 23c as a heat insulating layer, a configuration in which an insulating member with a lower thermal conductivity than the heater holder 23 is provided may also be used.

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

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications can of course be made without departing from the spirit of the present invention.

In addition to the fixing devices described above, the present invention can also be applied to fixing devices such as those shown in Figures 18 to 20. Below, we will briefly explain the configuration of each fixing device shown in Figures 18 to 20.

First, in the fixing device 9 shown in Figure 18, a pressure roller 44 is arranged on the opposite side of the fixing belt 20 from the pressure roller 21 side. The pressure roller 44 is an opposing rotating member that rotates opposite the fixing belt 20, which is a rotating member. This pressure roller 44 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 arranged on the inner periphery of the fixing belt 20. The nip forming member 45 is supported by the stay 24. The nip forming member 45 and the pressure roller 21 sandwich the fixing belt 20 to form a fixing nip N.

Next, in the fixing device 9 shown in Figure 19, the aforementioned pressure roller 44 is omitted, and the heater 22 is formed in an arc shape to match the curvature of the fixing belt 20 in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22. Otherwise, it has the same configuration as the fixing device 9 shown in Figure 18.

Finally, the fixing device 9 shown in Figure 20 will be described. The fixing device 9 comprises 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, first high thermal conductivity member 28, heater holder 23, stay 24, and 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 is composed of 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 opposite side of the fixing roller 93 from 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, where it is heated and pressed to fix the image.

In the fixing devices shown in Figures 18 to 20, the amount of heat generated by the heater 22 decreases at the interval B between the resistance heating elements 31 of the heater 22, resulting in temperature unevenness in the arrangement direction of the heater 22 and fixing members. Therefore, as in the previously described embodiment, by providing the first high thermal conductivity member 28 and the second high thermal conductivity member at positions corresponding to the interval B between the resistance heating elements 31 of the heater 22, temperature unevenness in the heater 22 and the rotating members can be reduced. This reduces uneven gloss and fixing of images on paper sheets passed through the fixing device. Alternatively, there is no need for extra heating by the heater 22 to ensure sufficient fixing performance at the interval between the resistance heating elements 31, thereby achieving energy savings in the fixing device 9.

Furthermore, the present invention is not limited to the fixing device described in the above embodiment, but can also be applied to heating devices such as drying devices that dry ink applied to paper, laminators that thermocompression bond a film as a covering member to the surface of a sheet such as paper, and thermocompression bonding devices such as heat sealers that thermocompression bond the seal portion of packaging material. By applying the present invention to such devices, temperature unevenness in the arrangement direction of the heating element or rotating element can be suppressed.

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 copier, a printer, a facsimile, or a combination of these.

For example, as shown in FIG. 21, the image forming apparatus 100 of this embodiment includes an image forming means 50 consisting of a photosensitive drum or the like, a paper transport unit consisting of a pair of timing rollers 15 or the like, a paper feeder 7, a fixing device 9, a paper discharge device 10, and a reading unit 51. The paper feeder 7 includes multiple paper feed trays, each of which accommodates paper of a different size.

The reading unit 51 reads the image of the document Q. The reading unit 51 generates image data from the read image. The paper feeder 7 stores multiple sheets of paper P and sends the sheets P to the transport path. The timing rollers 15 transport the sheets P on the transport path to the image forming means 50.

The image forming unit 50 forms a toner image on the paper P. Specifically, the image forming unit 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a static eliminator. The toner image represents, for example, an image on the original Q. The fixing device 9 applies heat and pressure to the toner image to fix it to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P outside the image forming apparatus 100.

Next, we will explain the fixing device 9 of this embodiment. Descriptions of components common to the fixing device of the previous embodiment will be omitted where appropriate.

As shown in FIG. 22, 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-thermal-conductivity member 28, and the like.

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.

The fixing belt 20 has a polyimide base and a release layer, and 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.

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.

The heater 22 includes a base material, a heat insulating layer, a conductor layer containing a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width Y of the heater 22 in the cross-array direction is 13 mm.

As shown in FIG. 23, the conductor layer of the heater 22 includes multiple resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. In this embodiment, as shown in the enlarged view of FIG. 23, the multiple resistance heating elements 31 are divided into divided regions in the arrangement direction, forming intervals B (although FIG. 23 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 passing current through electrode portions 34A and 34B, heat generating portions 35A and 35C are generated. By passing current through electrode portions 34A and 34C, heat generating portion 35B is generated. For example, when performing a fixing operation on small-size paper, heat generating portion 35B is generated, and when performing a fixing operation on large-size paper, all of the heat generating portions are generated.

As shown in Figure 24, the heater holder 23 holds the heater 22 and 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 substrate 30 and is recessed toward the stay 24 side relative to the other surfaces of the heater 22, wall portions 23d2 provided on the inside of the heater holder 23 on both sides in the arrangement direction of the heater holder 23 (or on one side), and wall portions 23d3 provided on the inside of the heater holder 23 on both sides in the cross-arrangement direction. The heater holder 23 has a guide portion 26. The heater holder 23 is made of LCP (liquid crystal polymer).

As shown in Figure 25, the connector 60 includes a housing made of resin (e.g., LCP) and multiple contact terminals provided within the housing.

The connector 60 is attached so that it sandwiches the heater 22 and heater holder 23 from both the front and back sides. In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 22, electrically connecting the heat generating portion 35 to the power supply provided in the image forming device 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 by an insulating layer and is exposed.

The flanges 53 are provided on both sides of the fixing belt 20 in the arrangement 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 direction from the flanges 53 in Figure 25).

The connector 60 is attached to the heater 22 and heater holder 23 in the direction that intersects the heater arrangement (see the arrow direction from the connector 60 in Figure 25). When attaching the connector 60 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, allowing the convex portion to move relatively within the concave portion. The connector 60 is attached to the heater 22 and heater holder 23 on one side of the arrangement direction, opposite the side on which the drive motor for the pressure roller 21 is installed.

As shown in FIG. 26, thermistors 25 are provided facing the inner circumferential surface of the fixing belt 20, at the center and end of the fixing belt 20 in the arrangement direction. The heater 22 is controlled based on the temperatures detected by the thermistors 25 at the center and end of the fixing belt 20 in the arrangement direction.

A thermostat 27 is provided facing the inner circumferential surface of the fixing belt 20, at both the center and end of the fixing belt 20 in the arrangement direction. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold, power to the heater 22 is stopped.

Flanges 53 that hold each end of the fixing belt 20 are provided on both ends of the fixing belt 20 in the alignment direction. The flanges 53 are made of LCP (liquid crystal polymer).

As shown in Figure 27, a slide groove 53a is provided on the flange 53. The slide groove 53a extends in the direction in which the fixing belt 20 moves toward and away from the pressure roller 21. An engagement portion on the housing of the fixing device 9 engages with the slide groove 53a. This engagement portion moves relative to the pressure roller 21 within the slide groove 53a, allowing the fixing belt 20 to move toward and away from the pressure roller 21.

In the fixing device 9 described above, by providing a first high thermal conductivity member and a second high thermal conductivity member at positions corresponding to the spacing B between the resistance heating elements of the heater 22, it is possible to suppress temperature unevenness in the arrangement direction of the heater 22 and the fixing belt 20. This makes it possible to suppress uneven gloss and fixing of images on paper passed through the fixing device. Alternatively, there is no need to apply extra heat to ensure sufficient fixing performance in the spacing between the resistance heating elements, thereby realizing energy savings in the fixing device 9.

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

1 Image forming apparatus 9 Fixing device (heating device)
20 Fixing belt (rotating member or fixing member)
21 Pressure roller (opposing rotating member or pressure member)
22 heater (heating element)
23 heater holder (holding member)
23b: Recessed portion 23b1: Side wall (arrangement direction restricting portion)
23b2 Side wall (array crossing direction regulation portion)
23c Relief portion (heat insulating layer)
24 Stay (support member)
25 Thermistor (temperature detection element)
28 First high thermal conductive member 30 Base material 31 Resistive heating element 35 Heat generating portion 36 Second high thermal conductive member B Gap (divided region)
N Fixing nip (nip portion)
X: Arrangement direction of multiple resistance heating elements Y: Intersecting direction of arrangement

Japanese Patent Application Laid-Open No. 2019-164328

Claims (14)

A rotating member;
a planar heating element having a base material and a plurality of resistance heating elements;
a holding member for holding the heating member;
a first high thermal conductive member having a thermal conductivity higher than that of the base material,
the plurality of resistance heating elements are arranged on the base material at intervals in the longitudinal direction of the heating member ,
the first high thermal conductivity member is provided between the holding member and the heating member, and at a position where at least a part of the first high thermal conductivity member overlaps with the interval between the resistance heating elements in an arrangement direction of the plurality of resistance heating elements ,
a second high thermal conductive member having a higher thermal conductivity than the base material is further provided between the holding member and the first high thermal conductive member,
a heating device characterized in that the second high thermal conductivity members are provided in multiple positions in the arrangement direction of the multiple resistance heating elements, and each of the second high thermal conductivity members is provided at a position in the arrangement direction of the multiple resistance heating elements that overlaps with the spacing between the resistance heating elements . The heating device of claim 1, wherein the first high thermal conductivity member is disposed across the resistance heating elements on both sides of the gap. The heating device according to claim 1 or 2, wherein the first high thermal conductivity member is provided over the entire area of the spacing between the resistance heating elements in the arrangement direction of the multiple resistance heating elements. the second high thermal conductive member is provided at a position where it at least partially overlaps with the first high thermal conductive member in the arrangement direction of the plurality of resistance heating elements,
The heating device according to claim 1 , wherein the second high thermal conductivity member has a thermal conductivity in an arrangement direction of the plurality of resistance heating elements that is greater than a thermal conductivity in a thickness direction of the second high thermal conductivity member. The heating device of claim 4, wherein the second high thermal conductivity member is a graphite sheet. When a direction intersecting the arrangement direction of the plurality of resistance heating elements and along the surface of the base material on which the resistance heating elements are provided is defined as an arrangement intersecting direction,
The heating device according to claim 1 , further comprising a heat insulating layer between the holding member and the first high thermal conductivity member at a position where the heat resistive heating element at least partially overlaps with the heat resistive heating element in the crossing direction. A heating device according to any one of claims 1 to 6, wherein the first high thermal conductivity member is provided over the entire area in which the resistance heating elements are arranged in the arrangement direction of the multiple resistance heating elements. The heating device described in any one of claims 1 to 7, wherein the first high thermal conductivity member is made of a metal material. The heating device of claim 8, wherein the first high thermal conductivity member is aluminum. A heating device according to any one of claims 1 to 9, wherein the substrate is stainless steel. A heating device according to any one of claims 1 to 10, wherein the holding member has an arrangement direction restricting portion that restricts movement of the first high thermal conductivity member in the arrangement direction of the multiple resistance heating elements. A heating device according to any one of claims 1 to 11, wherein the resistive heating element has PTC characteristics. A fixing device that heats and fixes heat on a recording medium using the heating device described in any one of claims 1 to 12. An image forming apparatus equipped with the fixing device according to claim 13.