JP7713155B2 - 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 device.

The fixing device is provided with a planar heater having a resistance heating element on a substrate as a heating member 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), a resistive heating element divided into multiple parts is provided on a substrate.

In the heating device, the amount of heat generated by the heating element is smaller in the divided areas between the resistance heating elements than in other areas. This causes a problem in that the fixing member (rotating member) is not heated sufficiently in the positions corresponding to the divided areas.

The objective is to sufficiently heat the portion of the rotating member that corresponds to the division area between the resistive heating elements.

In order to solve the above problems, the present invention provides a heating device comprising a rotating member, a planar heating member having a base material and a plurality of resistive heating elements, and one or more temperature detection members having a temperature detection element, wherein the plurality of resistive heating elements are arranged at intervals on the base material, the temperature detection element and the dividing regions between the resistive heating elements are provided at the same position in the arrangement direction of the plurality of resistive heating elements, and the device further comprises a cut-off device having a thermal deformation member, which cuts off the flow of current to the heating element by deformation of the thermal deformation member, and the cut-off device is provided at a position corresponding to the outside of the dividing region of one of the resistive heating elements on both sides that sandwich the dividing region in which the temperature detection member is arranged, in the arrangement direction of the plurality of resistive heating elements .

The heating device of the present invention can sufficiently heat the portion of the rotating member that corresponds to the divided area between the resistive heating elements.

FIG. 1 is a schematic diagram 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. 4 is a diagram showing power supply to a heater. FIG. 4 is a plan view of a heater having a resistive heating element with a different shape from that of FIG. 3 . FIG. 6 is a plan view of a heater having a resistive heating element having a different shape from those in FIGS. 3 and 5 . 5A and 5B are diagrams showing temperature distribution in the arrangement direction of a fixing belt, in which FIG. 5A is a plan view of a heater, and FIG. 5B is a diagram showing temperature distribution of 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 in FIG. 8 . FIG. 7 is a diagram showing divided regions of the heater in FIG. 6 . FIG. 2 is a diagram showing the arrangement of thermistors and thermostats in an array direction. 11A and 11B are side cross-sectional views of a fixing device showing modified examples of the arrangement of the thermistor. FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 4 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 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. 18 is a plan view of a heater in the fixing device of FIG. 17. 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. 4 is a diagram showing a groove portion of a flange. FIG. 2 is a perspective view showing a configuration of a thermistor. FIG. 2 is a cross-sectional view showing a configuration of a thermostat.

The present invention will be described below with reference to the attached drawings. In each drawing for explaining the present invention, components such as parts and components having the same function or shape are given the same reference numerals as far as they can be distinguished, and the description will be omitted after the first description. In the following description, a fixing device that fixes a toner image by heat will be exemplified as an example of a heating device.

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

The image forming device 100 shown in FIG. 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 developer of a different color, 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 feeder 7, a transfer device 8, a fixing device 9, 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 feeder 7 supplies paper P as a recording medium to a 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 an 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 a plurality of 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 the paper P. Each of the plurality of primary transfer rollers 12 contacts the photoconductors 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoconductor 2 come into contact with each other, and a primary transfer nip is formed between them. Meanwhile, the secondary transfer roller 13 contacts one of the rollers that stretch the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

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).

Next, the printing operation of the image forming device will be described with reference to FIG.

When an instruction to start a printing operation is given, in each of the imaging units 1Y, 1M, 1C, 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the surface of the photoconductor 2 is charged to a uniform high potential by the charging device 3. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the original document read by the original 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.

The toner images formed on each photoconductor 2 rotate with the rotation of each 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 transferred to the paper P that has been transported at the secondary transfer nip. This paper P is supplied from the paper supply device 7. The paper P supplied from the paper supply device 7 is stopped once by the timing roller 15, and then transported to the secondary transfer nip in accordance with the timing at which the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is carried on the paper P. After the toner image is transferred, the toner remaining on each photoconductor 2 is removed by each cleaning device 5.

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

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

2, the fixing device 9 according to the present embodiment includes a fixing belt 20 as a rotating member or fixing member, a pressure roller 21 as a counter 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, and the like. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form 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 (the surface on the left side in FIG. 2) and detects the temperature of the substrate 30. The direction perpendicular to the paper surface of FIG. 2 is the longitudinal direction of the fixing belt 20, the pressure roller 21, the heater 22, the heater holder 23, the stay 24, and the like, and hereinafter, this direction will be simply referred to as the longitudinal direction. This longitudinal direction is also 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 fluororesin such as PFA or PTFE with a thickness of 5 to 50 μm is formed on the outermost surface of the fixing belt 20 to enhance durability and ensure releasability. An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the substrate and the release 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 polyimide, PTFE, or the like as a sliding layer.

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 releasability, it is desirable to form a release layer 21c made of a fluororesin layer having a thickness of, for example, about 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 driven to rotate by the 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.

The heater 22 is a planar heating member provided 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 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 the heat generated by the resistance heating element 31 is transferred to the fixing belt 20 through 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 (fixing nip N side) of the substrate 30, but conversely, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the substrate 30. In that case, since the heat of the resistance heating element 31 is transferred to the fixing belt 20 through 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 the stay 24 are disposed on the inner periphery of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends thereof are supported by both side plates of the fixing device 9. The heater holder 23 and the heater 22 are supported by the stay 24, so that the heater 22 can reliably receive the pressing force of the pressure roller 21 when the pressure roller 21 is pressed against the fixing belt 20. This allows the fixing nip N to be 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.

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 a thickness, abuts against the heater holder 23 from the opposite side to the pressure roller 21 (left side in the figure). This makes it possible to suppress the deflection of the heater holder 23 due to the pressure from the pressure roller 21 (particularly the deflection in the longitudinal direction in this embodiment). However, the above-mentioned abutment is not limited to the case where the stay 24 abuts against the heater holder 23 directly, but also includes the case where the stay 24 abuts against the heater holder 23 via another member. "Abutment through 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 where at least a part of the other member corresponds, and the other member abuts against the heater holder 23. In addition, "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 the deflection of the heater holder 23 against the pressure force from the pressure roller 21.

Next, we will explain how to calculate the thermal conductivity. When calculating the thermal conductivity, first, the thermal diffusivity of the target object is measured, and then the thermal conductivity is calculated using this thermal diffusivity.

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

In order 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, and sapphire was used 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 obtained from the thermal diffusivity α obtained from the thermal diffusivity measurement by the following formula (1).

The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat of the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, the transfer of heat 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 provided with guide sections 26 that guide the fixing belt 20. The guide sections 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 belt rotation direction of the heater 22. The upstream and downstream guide sections 26 are arranged at intervals along the longitudinal direction of the heater 22. Each guide section 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 peripheral surface of the fixing belt 20.

The heater holder 23 has multiple openings 23a in the longitudinal direction. The openings 23a are openings that penetrate the heater holder 23 in the thickness direction. The thermistor 25 and a thermostat, which will be described later, are provided in the openings 23a. The thermistor 25 and the thermostat are pressed against the back surface of the substrate 30 by a spring 29.

In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is rotated and the fixing belt 20 starts 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, so that the fixing belt 20 rotates stably and smoothly. In addition, the fixing belt 20 is heated by supplying power to the resistance heating element 31 of the heater 22. Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, a sheet P carrying an unfixed toner image is conveyed between the fixing belt 20 and the pressure roller 21 (fixing nip N), so that the unfixed toner image is heated and pressurized to be fixed to the sheet 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, a plurality of (four) resistive heating elements 31, power supply lines 33A and 33B as conductors, a first electrode portion 34A, and a second electrode portion 34B are provided on the surface of a plate-shaped substrate 30. 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 paper surface of FIG. 2) is also the arrangement direction X of the multiple resistance heating elements 31 as shown in FIG. 3. Hereinafter, this direction will also be referred to simply as the arrangement direction. In addition, the vertical direction Y in FIG. 3, which is a direction that intersects with the arrangement direction (a direction perpendicular to the paper surface of FIG. 2) and is different from the thickness direction of the substrate 30, will also be referred to as the direction that intersects with 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 short side direction of the heater 22, or the transport direction of the paper passed through the fixing device 9.

The heating section 35 is divided into multiple parts in the arrangement direction by the multiple resistance heating elements 31. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode parts 34A, 34B provided at one end of the substrate 30 in the arrangement direction (the left end in FIG. 3) via power supply lines 33A, 33B. The power supply lines 33A, 33B are made of a conductor having a smaller resistance value than the resistance heating element 31. From the viewpoint of ensuring 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. In addition, if the gap between adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap. For this reason, from the viewpoint of suppressing temperature unevenness across the arrangement direction, the above gap is preferably 5 mm or less, and more preferably 1 mm or less.

The resistive heating element 31 is made of a material with PTC (positive temperature coefficient of resistance) properties, and has the characteristic that its resistance value increases (heater output decreases) as the temperature increases.

The resistance heating element 31 has PTC characteristics, and the configuration of the heating section 35 divided in the arrangement direction makes it possible to suppress the phenomenon in which the temperature in the heating area by the heating section 35 and the non-paper passing area becomes higher than the paper passing area (hereinafter referred to as non-paper passing area temperature rise). This occurs when a paper with a paper passing width shorter than the length of the heating section 35 (hereinafter referred to as small size paper) is passed through. In other words, when a paper with a width smaller than the entire width of the heating section 35 is passed through, the heat of the fixing belt 20 is not taken by the paper in the area outside the paper width, so the temperature of the resistance heating element 31 corresponding to that part rises. In other words, since 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 its resistance value rises. In this case, if the resistance heating element 31 has PTC characteristics, the output (heat generation amount) of the resistance heating element 31 outside the paper width relatively decreases, and the end temperature rise is suppressed. Furthermore, by electrically connecting multiple resistance heating elements 31 in parallel, it is possible to suppress temperature rise in non-paper passing areas while maintaining the printing speed. The heating elements constituting the heating section 35 may be other than resistance heating elements having PTC characteristics. The resistance heating elements may also be arranged in multiple rows in the crossing direction of the heaters 22. Here, the heating section 35 is set to a length corresponding to the maximum paper passing width or an appropriate length corresponding to the width of a specified paper type. The specified paper type is, for example, standard paper such as A4 or B4.

The resistance heating element 31 can be formed, for example, by applying a paste prepared by mixing 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 80Ω at room temperature. In addition to the above-mentioned materials, the material of the resistance heating element 31 may be a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO ₂ ). The material of the power supply line 33 and the electrode portion 34 may be formed by screen printing or the like using silver (Ag) or silver palladium (AgPd). The power supply line 33 is made of a conductor having a smaller resistance value than the resistance heating element 31.

As the material of the substrate 30, ceramics such as alumina and aluminum nitride, which have excellent heat resistance and insulation, and non-metallic materials such as glass and mica are preferred. In this embodiment, an alumina substrate having a width of 8 mm in the cross direction of the array, a width of 270 mm in the array direction, and a thickness of 1.0 mm is used. Alternatively, the substrate 30 may be formed by laminating an insulating material onto a conductive material such as a metal. As the metal material of the substrate 30, aluminum and stainless steel are preferred because of their low cost. By forming the substrate 30 from a stainless steel plate, cracks due to thermal stress can be suppressed. In addition, the substrate 30 may be formed from a material with high thermal conductivity such as copper, graphite, and graphene in order to improve the thermal uniformity of the heater 22 and enhance image quality.

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 while maintaining their sliding properties 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, a power supply circuit for supplying power to each resistive 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 control unit 220 controls the amount of power supplied to each resistive heating element 31 via the triac 210 based on the temperature detected by the thermistor 25. The control unit 220 is configured with a microcomputer including a CPU, ROM, RAM, an I/O interface, etc. The control unit 220 may be provided in the fixing device 9 or in the image forming apparatus main body.

FIG. 23 shows an example of a specific configuration of the thermistor.
As shown in FIG. 23, the thermistor 25 includes a temperature detection element 25a, a frame 25b, conductive wires 25c, and a heat-resistant film 25d.

The frame 25b is made of an insulating material, and in this embodiment, is made of a resin material. The frame 25b is provided with an opening 25e, which is a hole that penetrates the frame 25b.

The thermal element 25a is held in the approximate center of the width of the opening 25e by a pair of lead wires extending from the inside of the frame 25b. The outer periphery of the thermal element 25a is covered with infrared absorbing glass. In addition to the configuration of this embodiment, the thermal element may be configured as appropriate using known thermistors such as diode-type thermistors, bead-type thermistors, chip thermistors, thin film thermistors, etc.

Two conductors 25c extend from one end of the frame 25b to the outside for supplying power to the thermistor 25 from the outside. The conductors 25c are electrically connected to the heat-sensitive element 25a via a metal plate and lead wires provided inside the frame 25b.

The heat-resistant film 25d is attached to the bottom surface of the frame 25b (the surface on the back side of the paper in FIG. 23) and covers the bottom side of the opening 25e. The heat-resistant film 25d is made of, for example, polyimide resin.

As shown in Fig. 4, the fixing device 9 has a thermostat 27 as a cutoff device. As shown in Fig. 24, the thermostat 27 has a bimetal 27a as a thermal deformation member, a first cover member 27b, a base member 27c, a pressing pin 27d, a second cover member 27f, a fixed terminal 27g, and a pressed terminal 27h. The lower side of Fig. 24 is the heater 22 side (the right side of Fig. 2).

The first lid member 27b is an insulating member. The first lid member 27b is attached to the base member 27c so as to cover the heater side portion of the base member 27c. A first space 27j is formed between the first lid member 27b and the base member 27c.

The bimetal 27a is made by stacking two metal materials with different thermal expansion coefficients. However, it is not necessarily limited to metal materials, as long as materials with different thermal expansion coefficients are used. For example, the bimetal 27a may be made by pairing two plastic materials with different thermal expansion coefficients, or a plastic material and a metal material.

The bimetal 27a is disposed in the first space 27j. As shown in FIG. 24, when the bimetal 27a is at or below a predetermined temperature, the bimetal 27a is convex toward the heater.

A second lid member 27f is provided to cover the portion of the base member 27c opposite the heater side. A second space 27k is formed between the base member 27c and the second lid member 27f.

A through hole 27e is provided on the inside of the base member 27c, connecting the first space 27j and the second space 27k. The pressure pin 27d is held by the base member 27c so that it can move up and down within the through hole 27e.

A fixed terminal 27g and a pressed terminal 27h are provided in the second space 27k. The pressed terminal 27h can be opened and closed in the directions of the double arrows in FIG. 24, with a fulcrum 27h1 as a fulcrum. As shown in FIG. 24, one end of the pressed terminal 27h is in contact with the fixed terminal 27g, and the two are electrically connected.

The lower surface 27b1 of the first cover member 27b in FIG. 24 is the heat-sensitive surface and faces the heater. Heat is transferred from the heater to the bimetal 27a via the first cover member 27b.

When excessive heat is generated due to a heater failure or the like, the temperature of the bimetal 27a rises and exceeds the predetermined temperature described above. This causes the bimetal 27a to thermally deform into a convex shape toward the upper side of FIG. 24. This causes the bimetal 27a to press one end of the pressing pin 27d toward the upper side of FIG. 24. The other end of the pressing pin 27d then protrudes further toward the second space 27k and presses the pressed terminal 27h. This causes the pressed terminal 27h to rotate around the fulcrum 27h1, and the pressed terminal 27h and the fixed terminal 27g are separated from each other. This causes the conductive state between the pressed terminal 27h and the fixed terminal 27g to be released.

When the conductive state between the pressed terminal 27h and the fixed terminal 27g is released, the fixing device 9 cuts off the power supply to the heater 22. This stops excessive heating by the heater.

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 be provided on different sides. 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. As shown in FIG. 5, the portion extending from the block-shaped resistive heating element 31 toward the power supply line 33, that is, the portion extending in the arrangement crossing 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 FIG. 7(a) and FIG. 7(b), the multiple resistance heating elements 31 provided in the heater 22 are arranged at intervals. In other words, the multiple resistance heating elements 31 are divided in the arrangement direction. In the divided area B, which is the part between the resistance heating elements 31, the area occupied by the resistance heating elements 31 is smaller than the other parts, and the amount of heat generated is smaller. As a result, the temperature of the fixing belt 20 in the divided area B is smaller than the other parts, causing temperature unevenness in the arrangement direction of the fixing belt 20. In addition, the temperature of the heater 22 and the fixing belt 20 is also lower in the expanded divided area C including the area around the divided area B. The temperature of the heater 22 is also lower in the divided area B. Here, as shown in the enlarged view of FIG. 7(a), the divided area B means an arrangement direction area including the entire part into which the resistance heating element 31, which is the main heat generating part of the heater 22, is divided in the arrangement direction. In addition to the divided area B, an area including a range corresponding to the connection part 311 of the resistance heating element 31 is defined as the expanded divided area C. This connection portion 311 refers to the portion of the resistive heating element 31 that extends in the cross-arrangement direction and is connected to each of the power supply lines 33A and 33B.

As shown in FIG. 8, in the heater 22 having the rectangular resistive heating element 31 shown in FIG. 5, the temperature of the divided region B is lower than the other parts. Also in the heater 22 having the resistive heating element 31 shaped as shown in FIG. 9, the temperature of the divided region B is lower than the other parts. Furthermore, as shown in FIG. 10, in the heater 22 having the resistive heating element 31 shaped as shown in FIG. 6, the temperature of the divided region B is lower than the other parts. However, by overlapping adjacent resistive heating elements 31 in the arrangement direction as in FIG. 7, FIG. 9, and FIG. 10, the temperature drop in the other parts of the divided region B can be suppressed.

In this way, the temperature of the fixing belt 20 drops in the position corresponding to the divided region B in the arrangement direction compared to other parts. Therefore, even if the fixing belt 20 reaches the fixing temperature in other parts and the fixing operation starts, the temperature of the fixing belt 20 does not reach the fixing temperature in the position corresponding to the divided region B, and the toner image on the paper P may not be heated sufficiently in the position corresponding to the divided region B. This may also cause a fixing offset.

In this embodiment, as shown in FIG. 11, the temperature detection element 25a of thermistor 25A as the temperature detection member is provided at a position corresponding to divided region B in the arrangement direction. The temperature detection element 25a of thermistor 25B as the other temperature detection member is disposed outside the divided region. More specifically, all of the temperature detection elements 25a are disposed at positions corresponding to divided region B. Note that "disposed at corresponding positions" means that the multiple resistive heating elements are disposed at the same position in the arrangement direction X.

In this way, by arranging the temperature detection element 25a of the thermistor 25A at a position corresponding to the divided region, it is possible to detect the temperature of the part of the heater 22 where the temperature is particularly low. Therefore, by the control unit controlling the current supply to the heater 22 based on the detection result of the thermistor 25A, heating by the heater 22 can be continued until the divided region B of the heater 22 reaches a sufficient temperature, that is, until the divided region B of the fixing belt 20 reaches the fixing temperature. In this way, in the arrangement direction of the heater 22, the temperature detection element 25a of the thermistor 25A is deliberately arranged at a position corresponding to the divided region B where the area of the resistance heating element 31 is smaller than the other parts, so that the fixing belt 20 can be heated to a sufficient temperature in the divided region B. Therefore, the above-mentioned fixing offset can be prevented.

In particular, in this embodiment, the temperature detection element 25a of the thermistor 25A is disposed at a position corresponding to the divided region B at the center of the arrangement direction, which is the middle of the three divided regions B. In addition to the thermistor 25A, the temperature detection element 25a of the thermistor 25B is disposed outside the divided region B in the arrangement direction. In other words, the temperature detection element 25a of the thermistor 25B is disposed at a position different from the divided region B in the arrangement direction. The temperature detection element 25a of the thermistor 25B is disposed at a position facing the resistance heating element 31 at the end side of the arrangement direction. In other words, the temperature detection element 25a of the thermistor 25B is disposed at the end side of the center position D0 of the heat generation region D of the heater 22, rather than the temperature detection element 25a of the thermistor 25A. The heat generation region D of the heater 22 is the main heat generation region of the heater 22, and is the region where the resistance heating element 35 in the arrangement direction is disposed. However, this heat generation region D also includes the divided region B.

By providing a thermistor 25B that detects the outside of the divided region B, it is possible to detect the temperature of the portion of the heater 22 where the temperature is relatively high. Therefore, by controlling the power supply to the heater 22 based on the detection result of thermistor 25B, it is possible to prevent the fixing belt 20 from overheating.

In particular, in this embodiment, the temperature detection element 25a of thermistor 25A is placed at a position corresponding to divided region B at the center of the arrangement direction. In other words, the temperature detection element 25a of thermistor 25A is placed closer to the center of heat generation region D in the arrangement direction than the temperature detection element 25a of thermistor 25B. This makes it possible to detect the temperature of the region where the temperature is low, particularly at the center, which is important for image fixability, and is therefore preferable from the perspective of ensuring the fixability of the fixing device 9. In addition, by using thermistor 25B to detect the temperature outside divided region B of the resistance heating element 31 at the end of the arrangement direction, it is possible to effectively suppress excessive heating at the end of the arrangement direction of the fixing belt 20 when small size paper is passed through.

In addition, in the heater 22 having an even number (four in this embodiment) of resistive heating elements 31, as in this embodiment, by providing the temperature detection element 25a of the thermistor 25A at a position corresponding to the central divided area B of the odd number (three in this embodiment) of divided areas B, it is possible to detect the temperature of the area where the temperature is low, particularly in the center side which is important for the fixability of the image, which is preferable from the viewpoint of ensuring the fixability of the fixing device 9. In addition, by providing the temperature detection element 25a of the thermistor 25B at a position corresponding to the two resistive heating elements 35 sandwiching this central divided area B, that is, the resistive heating elements 35 other than the two innermost of the four, it is possible to effectively suppress excessive temperature rise at the end side of the arrangement direction of the fixing belt 20 when small size paper is passed through.

In this embodiment, the thermostat 27 is provided at a position corresponding to the second resistive heating element 31 from the right in FIG. 11 in the arrangement direction. In other words, the thermostat 27 is disposed at a position corresponding to either one of the resistive heating elements 31 (the second resistive heating element 31 from the right in FIG. 11) on both sides of the divided region B in which the temperature detection element 25a of the thermistor 25A is disposed (the second resistive heating element 31 from the right in FIG. 11), and at a position corresponding to the outside of the divided region B. In this way, by disposing the thermistor 25A at a position corresponding to the divided region B, there is more space outside the divided region B, so that the thermistor 25A and the thermostat 27 can be disposed in correspondence with the same resistive heating element 31 (the second resistive heating element 31 from the right in FIG. 11 in this embodiment). Therefore, when it is necessary to place a thermistor and a thermostat corresponding to the same resistive heating element 31 for reasons of space or temperature detection, the placement of the thermistor 25A in this embodiment is advantageous in terms of placing the thermostat 27.

However, the above arrangement of the thermistor 25A, thermistor 25B, and thermostat 27 is an example, and the number and arrangement are not limited to this. For example, the temperature detection element 25a of the thermistor 25A can be arranged at a position corresponding to the divided area B on the end side of the arrangement direction, and the temperature detection element 25a of thermistor 25B can be arranged at a position corresponding to the resistance heating element 31 on the center side of the arrangement direction, in the opposite manner to FIG. 11. When passing paper such as large size paper (e.g. paper other than A4 paper, etc.), the temperature tends to be lower on the end side of the arrangement direction of the fixing belt 20, so by arranging the temperature detection element 25a at a position corresponding to the divided area B on the end side of the arrangement direction, the end side of the arrangement direction of the fixing belt 20 can be sufficiently heated when passing large size paper, etc. Therefore, hot offset on the end side of the arrangement direction can be effectively suppressed. In addition, by providing the temperature detection element 25a at a position corresponding to the resistance heating element 31 on the center side of the arrangement direction, the temperature outside the divided area on the center side, which tends to be higher, can be detected, which is advantageous in terms of safety of the fixing device 9. Also, only a temperature detection member with a temperature detection element disposed at a position corresponding to the divided region may be provided, or three or more temperature detection members may be provided. Also, a temperature detection element of a temperature detection member may be disposed at a position corresponding to divided region B on the end side of the arrangement direction, or a temperature detection element of another temperature detection member may be disposed at a position corresponding to the outside of divided region B of resistance heating element 31 on the center side of the arrangement direction. Also, multiple cutoff devices may be provided, or a cutoff device may be provided on the end side of the arrangement direction from the viewpoint of suppressing an excessive rise in temperature of fixing belt 20 due to an increase in end temperature when small size paper is passed.

The arrangement of the thermistor in the cross array direction is not limited to this. For example, as shown in FIG. 12, in this embodiment, the thermistor 25 is provided upstream of the center position NA of the fixing nip N in the cross array direction in the rotation direction of the fixing belt 20, in other words, on the entrance side of the fixing nip N. The entrance side of the fixing nip N is an area that is particularly susceptible to heat loss by the paper P, so by thermistor 25 detecting the temperature of this area, the fixability of the fixing device 9 can be ensured and the above-mentioned fixing offset can be effectively suppressed.

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

In addition to the fixing device described above, the present invention can also be applied to fixing devices such as those shown in Figures 13 to 15. The configuration of each fixing device shown in Figures 13 to 15 will be briefly described below.

First, in the fixing device 9 shown in FIG. 13, a pressure roller 44 is disposed 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 as a rotating member. This pressure roller 44 and the 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 circumference 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 FIG. 14, the pressure roller 44 described above 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. The rest of the configuration is the same as that of the fixing device 9 shown in FIG. 13.

Finally, the fixing device 9 shown in FIG. 15 will be described. The fixing device 9 is composed of 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 has the heater 22, 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 outside 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 side. The pressure assembly 94 has a nip forming member 95 and a stay 96 arranged therein, and a pressure belt 97 arranged rotatably 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 pressurized to fix the image.

The fixing devices in Figures 13 to 15 above also have the same feature that the amount of heat generated by the heater 22 is small in the divided area B between the resistance heating elements 31 of the heater 22. Therefore, as in the above-mentioned embodiment, by providing a temperature detection element of the temperature detection member at a position corresponding to the divided area B of the heater 22, it is possible to sufficiently heat the portion of the rotating member corresponding to the divided area. This ensures sufficient fixability of the image and prevents problems such as fixing offset.

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, and further to 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 thermocompress the seal portion of a packaging material. By applying the present invention to such devices, the portion corresponding to the divided area of the rotating member can be sufficiently heated.

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 machine of these.

For example, as shown in FIG. 16, the image forming apparatus 100 of this embodiment includes an image forming means 50 including a photosensitive drum, a paper transport section including a pair of timing rollers 15, a paper feeder 7, a fixing device 9, a paper discharge device 10, and a reading section 51. The paper feeder 7 includes multiple paper feed trays, each of which stores 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 feed device 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 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 replenishing device, a transfer roller, a cleaning device, and a charge removing device. The toner image represents, for example, an image of the original Q. The fixing device 9 heats and pressurizes 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 device 100.

Next, the fixing device 9 of this embodiment will be described. Descriptions of configurations common to the fixing device of the previous embodiment will be omitted as appropriate.

As shown in FIG. 17, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, etc.

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 including a resistive heating element, and an insulating layer, and is formed with a total thickness of 1 mm. The width Y of the heater 22 in the cross-arrangement direction is 13 mm.

As shown in FIG. 18, the conductor layer of the heater 22 includes multiple resistive heating elements 31, power supply lines 33, and electrode portions 34A to 34C. In this embodiment, as shown in the enlarged view of FIG. 18, the multiple resistive heating elements 31 are divided in the arrangement direction to form divided regions B. However, while FIG. 18 illustrates divided regions B only in the enlarged view, in reality, divided regions are provided between all of the resistive heating elements 31. The resistive heating elements 31 form three heating portions 35A to 35C. By passing electricity through the electrode portions 34A and 34B, the heating portions 35A and 35C generate heat. By passing electricity through the electrode portions 34A and 34C, the heating portion 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heating portion 35B can be made to generate heat, and when performing a fixing operation on large-sized paper, all of the heating portions can be made to generate heat.

As shown in FIG. 19, the heater holder 23 holds the heater 22 in its recess 23b. The recess 23b is provided on the heater 22 side of the heater holder 23. The recess 23b is composed of a surface 23b1 that is approximately parallel to the substrate 30 and is recessed toward the stay 24 side more than the other surfaces of the heater 22, a wall portion 23b2 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 a wall portion 23b3 provided on the inside of the heater holder 23 on both sides in the intersecting direction of the arrangement. The heater holder 23 has a guide portion 26. The heater holder 23 is formed of LCP (liquid crystal polymer).

As shown in FIG. 20, the connector 60 includes a housing made of resin (e.g., LCP) and a number of contact terminals provided within the housing.

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 the power source provided in the image forming apparatus via the connector 60. This makes it possible to supply power from the power source to the heat generating portion 35. Note that at least a portion of each electrode portion 34 is not covered by an insulating layer and is exposed in order to ensure connection with the connector 60.

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 20).

The attachment direction of the connector 60 to the heater 22 and heater holder 23 is the cross direction of the heater arrangement. This cross direction is the direction of the arrow from the connector 60 in FIG. 20. 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, and the convex portion may 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 of the pressure roller 21 is provided.

As shown in FIG. 21, thermistors 25 are provided on the center and end sides of the fixing belt 20 in the arrangement direction, facing the inner circumferential surface of the fixing belt 20. The heater 22 is controlled based on the temperatures of the center and end sides of the fixing belt 20 in the arrangement direction detected by the thermistors 25. Note that one of these thermistors 25 is provided at a position corresponding to the divided area between the resistive heating elements of the heater 22, as in the above-mentioned embodiment.

Thermostats 27 are provided on the center side and end side of the arrangement direction of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold value, the supply of electricity 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 arrangement direction. The flanges 53 are made of LCP (liquid crystal polymer).

As shown in FIG. 22, 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. This engagement portion moves relatively within the slide groove 53a, allowing the fixing belt 20 to move in the direction in which it approaches and separates from the pressure roller 21.

In the fixing device 9 described above, by providing a temperature detection element of the thermistor 25 at a position corresponding to the divided area B of the heater 22, the portion of the fixing belt 20 corresponding to the divided area can be sufficiently heated. This ensures sufficient fixability of the image and prevents problems such as fixing offset.

In particular, in the case of an image forming apparatus that performs image forming operations using a single color toner, hot offset is less likely to occur compared to an image forming apparatus that performs image forming operations using multiple color toners. Therefore, even if the heating member is controlled based on the detection results of a temperature detection element arranged at a position corresponding to the divided area as in the present invention, there is an advantage that hot offset is less likely to occur in an image forming apparatus that uses a single color toner.

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 member)
23 Heater holder (holding member)
24 Stay (support member)
25A thermistor (temperature detection element)
25B Thermistor (other temperature sensing element)
25a Temperature detection element 27 Thermostat (shutoff device)
30: substrate 31: resistive heating element 35: heating section 220: control section B: divided area D: heating area of heater N: fixing nip (nip section)
X: Arrangement direction of multiple resistance heating elements Y: Intersecting direction of the arrangement

JP 2019-164328 A

Claims (10)

A rotating member;
a planar heating member having a base material and a plurality of resistive heating elements;
A heating device comprising one or more temperature detection members having a temperature detection element,
The plurality of resistive heating elements are arranged at intervals on the base material,
the temperature detection element and the dividing region between the resistance heating elements are provided at the same position in an arrangement direction of the plurality of resistance heating elements ,
Further comprising a cut-off device having a thermal deformation member,
The thermal deformation member is deformed to cut off the current supply to the heating member,
A heating device characterized in that the blocking device is provided at a position corresponding to the outside of the divided area of one of the resistive heating elements on both sides of the divided area in which the temperature detection member is arranged, in the arrangement direction of the multiple resistive heating elements . 2. The heating device according to claim 1 , wherein the thermal deformation member is a bimetal. A rotating member;
a planar heating member having a base material and a plurality of resistive heating elements;
A heating device comprising one or more temperature detection members having a temperature detection element,
The plurality of resistive heating elements are arranged at intervals on the base material,
the temperature detection element and the dividing region between the resistance heating elements are provided at the same position in an arrangement direction of the plurality of resistance heating elements ,
Further comprising another temperature sensing member having a temperature sensing element,
A heating device characterized in that the temperature detection element of the other temperature detection member is provided at a position opposite the resistive heating element in the arrangement direction of the multiple resistive heating elements, and at a position different from the dividing area between the resistive heating elements . 4. The heating device according to claim 3, wherein the temperature detection element of the other temperature detection member is arranged closer to an end of the heat generation region of the heating member in an arrangement direction of the plurality of resistive heating elements than the temperature detection element of the first temperature detection member. A rotating member;
a planar heating member having a base material and a plurality of resistive heating elements;
A heating device comprising one or more temperature detection members having a temperature detection element,
The plurality of resistive heating elements are arranged at intervals on the base material,
the temperature detection element and the dividing region between the resistance heating elements are provided at the same position in an arrangement direction of the plurality of resistance heating elements ,
When the resistance heating elements are an even number in the arrangement direction of the plurality of resistance heating elements, the temperature detection element of the temperature detection member is disposed at the same position as a central divided region of the plurality of divided regions in the arrangement direction of the plurality of resistance heating elements,
a temperature sensing member having a temperature sensing element;
the temperature detection element of the other temperature detection member is provided at a position opposite to the resistance heating body in the arrangement direction of the plurality of resistance heating bodies and at a position different from a dividing region between the resistance heating bodies,
a temperature detection element of said another temperature detection member being disposed at the same position as any one of said resistance heating elements other than the two resistance heating elements sandwiching said central divided region therebetween; A heating device as described in any one of claims 1 to 4, wherein when there is an even number of the resistive heating elements in the arrangement direction of the multiple resistive heating elements, the temperature detection element of the temperature detection member is positioned at the same position as a central divided area among the multiple divided areas in the arrangement direction of the multiple resistive heating elements. a counter rotating member that contacts the rotating member to form a nip between the counter rotating member and the rotating member ,
The heating device according to claim 1 , wherein the temperature detection member is provided closer to the entrance side of the nip portion than a center position of the nip portion when the upstream side of the nip portion in the rotation direction of the rotating member is defined as a nip entrance side. A fixing device for fixing a toner image on a recording medium by heating the toner image with the heating device according to claim 1 . An image forming apparatus comprising the fixing device according to claim 8 . 10. The image forming apparatus according to claim 9 , wherein an image is formed using only a single color toner.