JP7486048B2 - Heating body, heating device, fixing device and image forming apparatus - Google Patents

Description

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

The fixing device, which acts as a heating device installed in an image forming device such as a copier or printer, is provided with a planar heating element equipped with a resistive heating element.

For example, the following Patent Document 1 discloses a planar heating element that includes a first heating sheet and a second heating sheet having a resistive heating element, and an insulating sheet provided between these heating sheets.

The problem with the above heaters is that the amount of heat generated by the conductor connecting the resistance heating element and the power supply section can cause the amount of heat generated by the heater to be uneven in the longitudinal direction.

There was an issue with temperature deviation occurring in the heating element along its length.

In order to solve the above problems, the present invention provides a heating element comprising a substrate, a plurality of conductor layers formed by stacking directly or indirectly on the substrate, and an insulating layer formed by an edge member and provided between the conductor layers, wherein at least one of the conductor layers has a resistance heating element, at least one of the conductor layers has a power supply section that supplies power to the resistance heating element, has a conductor section that connects the conductor layers, has the power supply section, and is characterized in that the heating element is provided in a first conductor layer in which the resistance heating element is not provided, a second conductor layer that is provided farther from the substrate than the first conductor layer and has the resistance heating element, a first insulating layer provided between the first conductor layer and the second conductor layer, and a second insulating layer formed on the second conductor layer .

According to the present invention, it is possible to suppress temperature deviation in the longitudinal direction of the heating body.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a fixing device. FIG. FIG. FIG. FIG. FIG. FIG. 2 is an exploded perspective view showing the configuration of a conductor layer of a heater. 4A to 4E are cross-sectional views showing a manufacturing process of the heater. FIG. 4 is a diagram showing power supply to a heater. FIG. 1 is a perspective view of a heater different from that of the present invention. FIG. 12 is a perspective view showing only a conductor layer of a heater according to an embodiment different from that of FIG. 11 . 13A and 13B are diagrams showing the layer structure of the heater in FIG. 12, in which FIG. 13A is a diagram seen from the direction of an arrow D1 in FIG. 12, and FIG. 13B is a diagram seen from the direction of an arrow D2 in FIG. 13A to 13E are cross-sectional views showing a manufacturing process of the heater of FIG. 12. FIG. 13 is a perspective view showing only the conductor layer of a heater according to an embodiment different from that of FIG. 12 . 16A and 16B are diagrams showing the layer structure of the heater in FIG. 15, in which FIG. 16A is a diagram seen from the direction of an arrow D1 in FIG. 15, and FIG. 16B is a diagram seen from the direction of an arrow D2 in FIG. FIG. 16 is a diagram showing power supply to each heat generating portion of the heater in FIG. 15 . FIG. 16 is a perspective view showing only the conductor layer of a heater according to an embodiment different from that of FIG. 15 . 19A and 19B are diagrams showing the layer structure of the heater in FIG. 18, in which FIG. 19A is a diagram seen from the direction of an arrow D1 in FIG. 18, and FIG. 19B is a diagram seen from the direction of an arrow D2 in FIG. FIG. 19 is a diagram showing power supply to each heat generating portion of the heater in FIG. 18. FIG. 20 is a perspective view showing only the conductor layer of a heater according to an embodiment different from that of FIG. 18 . 22A and 22B are diagrams showing the layer structure of the heater in FIG. 21, in which FIG. 22A is a diagram seen from the direction of an arrow D1 in FIG. 21, and FIG. 22B is a diagram seen from the direction of an arrow D2 in FIG. FIG. 22 is a diagram showing power supply to each heat generating portion of the heater in FIG. 21. FIG. 13 is a diagram showing the configuration of another fixing device. FIG. 13 is a diagram showing the configuration of another fixing device. FIG. 13 is a diagram showing the configuration of still another fixing device.

Below, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts are given the same reference numerals, and duplicate explanations will be appropriately simplified or omitted. In the following explanation of each embodiment, a fixing device that fixes an image on paper as a recording medium will be described as an example of a heating device. However, the heating device and the fixing device do not necessarily have to be the same, and the heating device may be one of the devices equipped in the fixing device.

The monochrome image forming device 1 shown in FIG. 1 is provided with a photoconductor drum 10. The photoconductor drum 10 is a drum-shaped rotating body capable of carrying toner as a developer on its surface, and rotates in the direction of the arrow in the figure. Around the photoconductor drum 10 are a charging roller 11 that uniformly charges the surface of the photoconductor drum 10, a developing device 12 equipped with a developing roller 7 that supplies toner to the surface of the photoconductor drum 10, and a cleaning blade 13 for cleaning the surface of the photoconductor drum 10.

An exposure unit is disposed above the photoconductor drum 10. Laser light Lb emitted by the exposure unit based on image data is irradiated onto the surface of the photoconductor drum 10 via the mirror 14.

In addition, a transfer means 15 equipped with a transfer charger is disposed opposite the photoreceptor drum 10. The transfer means 15 transfers the image on the surface of the photoreceptor drum 10 onto the paper P.

The paper feed section 4 is located at the bottom of the image forming device 1 and is made up of a paper feed cassette 16 that contains paper P as a recording medium, a paper feed roller 17 that conveys the paper P from the paper feed cassette 16 to the conveying path 5, and the like. A registration roller 18 is disposed downstream of the paper feed roller 17 in the conveying direction.

The fixing device 9 includes a fixing belt 20 that is heated by a heating member described below, a pressure roller 21 that can apply pressure to the fixing belt 20, and the like.

The basic operation of the image forming device 1 will be described below with reference to FIG. 1.

When the printing operation (image forming operation) starts, first the surface of the photoconductor drum 10 is charged by the charging roller 11. Then, a laser beam Lb is irradiated from the exposure section based on image data, and the potential of the irradiated area is reduced to form an electrostatic latent image. Toner is supplied from the developing device 12 to the surface of the photoconductor drum 10 on which the electrostatic latent image has been formed, and the image is visualized as a toner image (developer image). Any toner remaining on the photoconductor drum 10 after transfer is removed by the cleaning blade 13.

When the printing operation is started, the paper feed roller 17 of the paper feed section 4 rotates at the bottom of the image forming device 1, sending the paper P stored in the paper feed cassette 16 to the transport path 5.

The paper P sent to the transport path 5 is timed by the registration roller 18 and transported to the transfer section, which is the opposing part between the transfer means 15 and the photosensitive drum 10, at a timing that faces the toner image on the surface of the photosensitive drum 10, and the toner image is transferred by applying a transfer bias by the transfer means 15.

The paper P with the transferred toner image is transported to the fixing device 9, where it is heated and pressurized by the heated fixing belt 20 and pressure roller 21, fixing the toner image to the paper P. The paper P with the fixed toner image is then separated from the fixing belt 20, transported by a pair of transport rollers provided downstream of the fixing device 9, and discharged to a paper output tray provided outside the device.

Next, we will explain the configuration of the fixing device 9 in more detail.

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 an opposing member or pressure member that contacts the outer peripheral surface of the fixing belt 20 to form a nip portion N, and a heating unit 19 that heats the fixing belt 20. The heating unit 19 also includes a planar heater 22 as a heating body, a heater holder 23 as a holding member that holds the heater 22, and a stay 24 as a support member that supports the heater holder 23. The fixing belt 20, the pressure roller 21, the heater 22, the heater holder 23, and the stay 24 extend in a direction perpendicular to the paper surface of FIG. 2 (see the direction of the double-headed arrow B in FIG. 3). Hereinafter, this direction will be referred to as the longitudinal direction of each member (or the axial direction of the pressure roller 21), and the longitudinal direction of the fixing device 9 and the heating unit 19. This longitudinal direction is also the width direction of the paper passed through the fixing device 9. However, the longitudinal direction of the heater 22 and each member, device, and unit does not necessarily have to coincide.

The fixing belt 20 is composed of an endless belt member, and has a cylindrical base made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of fluorine-based resin such as PFA or PTFE with a thickness of 5 to 50 μm is formed on the outermost layer 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 base and the release layer. The base of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal base such as nickel (Ni) or SUS. The inner surface of the fixing belt 20 may be coated with polyimide, PTFE, or the like as a sliding layer. The fixing belt 20 is a heated member that is heated by the heater 22.

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. In order to improve the release properties of the surface of the elastic layer 21b, it is desirable to form a release layer 21c made of a fluororesin layer having a thickness of, for example, about 40 μm.

The pressure roller 21 and the fixing belt 20 are pressed against each other by a spring as a biasing member. This forms a nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 also functions as a drive roller that is rotated by a driving force transmitted from a drive means provided in the image forming apparatus body. On the other hand, the fixing belt 20 is configured to rotate in response to the rotation of the pressure roller 21. When the fixing belt 20 rotates, the fixing belt 20 slides against the heater 22. Therefore, a lubricant such as oil or grease may be interposed between the heater 22 and the fixing belt 20 to improve the sliding property of the fixing belt 20.

The heater 22 contacts the inner surface of the fixing belt 20 in the longitudinal direction at a position corresponding to the pressure roller 21.

The heater 22 includes a base material 50 and a heating section 60 made of a resistive heating element (the detailed configuration will be described later). By passing electricity through the heating section 60 to generate heat, the fixing belt 20 can be heated from the inside.

Unlike this embodiment, the heat generating section 60 may be provided on the opposite side of the substrate 50 from the fixing belt 20 side (the heater holder 23 side). In that case, since the heat from the heat generating section 60 is transferred to the fixing belt 20 via the substrate 50, it is desirable that the substrate 50 be made of a material with high thermal conductivity such as aluminum nitride. Furthermore, in the configuration of the heater 22 according to this embodiment, an insulating layer may be further provided on the surface of the substrate 50 opposite the fixing belt 20 (the heater holder 23 side).

The heater 22 may be in non-contact with the fixing belt 20 or indirectly contact with the fixing belt 20 via a low-friction sheet or the like, but in order to increase the efficiency of heat transfer to the fixing belt 20, it is preferable to have the heater 22 in direct contact with the fixing belt 20 as in this embodiment. The heater 22 can also be in contact with the outer peripheral surface of the fixing belt 20, but since there is a risk that the fixing quality will decrease if the outer peripheral surface of the fixing belt 20 is damaged by contact with the heater 22, it is preferable that the surface with which the heater 22 contacts is the inner peripheral surface of the fixing belt 20.

The heater holder 23 and the stay 24 are disposed inside the fixing belt 20. The stay 24 is made of a metal channel material, and both ends are supported by both side walls of the fixing device 9. The stay 24 supports the surface of the heater holder 23 opposite the heater 22 side, so that the heater 22 and the heater holder 23 are maintained without being significantly deflected by the pressure force of the pressure roller 21, and a nip portion N is formed between the fixing belt 20 and 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 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, and the fixing belt 20 can be heated efficiently.

When the printing operation starts, power is supplied to the heater 22, which causes the heat generating section 60 to generate heat and heat the fixing belt 20. The pressure roller 21 is also rotated and the fixing belt 20 starts to rotate. Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, the paper P carrying the unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (nip portion N) (see the direction of arrow A in FIG. 2), and the unfixed toner image is heated and pressurized to be fixed to the paper P.

Figure 3 is a perspective view of the fixing device, and Figure 4 is an exploded perspective view of the fixing device.

As shown in Figures 3 and 4, the device frame 40 of the fixing device 9 includes a first device frame 25 consisting of a pair of side walls 28 and a front wall 27, and a second device frame 26 consisting of a rear wall 29. The pair of side walls 28 are arranged at one end side and the other end side in the longitudinal direction, and both end sides of the fixing belt 20, the pressure roller 21, and the heating unit 19 are supported by the side walls 28. Each side wall 28 is provided with a plurality of engagement protrusions 28a, and the first device frame 25 and the second device frame 26 are assembled by each engagement protrusion 28a engaging with an engagement hole 29a provided in the rear wall 29.

Each side wall portion 28 is provided with an insertion groove 28b for inserting the rotating shaft of the pressure roller 21. The insertion groove 28b opens on the rear wall portion 29 side and is a butt portion that does not open on the opposite side. A bearing 30 that supports the rotating shaft of the pressure roller 21 is provided at the end on the butt portion side. The pressure roller 21 is rotatably supported by the side wall portions 28 by mounting both ends of the rotating shaft to the bearings 30.

A drive transmission gear 31 is provided as a drive transmission member on one end of the rotation shaft of the pressure roller 21. The drive transmission gear 31 is arranged in a state where it is exposed outside the side wall portions 28 when the pressure roller 21 is supported by the side wall portions 28. As a result, when the fixing device 9 is mounted on the image forming apparatus main body, the drive transmission gear 31 is connected to a gear provided on the image forming apparatus main body, and is in a state where it can transmit drive force from the drive source. Note that the drive transmission member that transmits drive force to the pressure roller 21 may be a pulley that stretches a drive transmission belt or a coupling mechanism, in addition to the drive transmission gear 31.

A pair of end support members 32 that support the fixing belt 20, heater holder 23, stay 24, etc. are provided at both longitudinal ends of the heating unit 19. Each end support member 32 is provided with a guide groove 32a. The end support members 32 are assembled to the side wall portion 28 by inserting the guide groove 32a along the edge of the insertion groove 28b of the side wall portion 28.

A pair of springs 33 are provided between each end support member 32 and the rear wall portion 29 as biasing members. Each spring 33 biases the stay 24 and the end support members 32 toward the pressure roller 21, so that the fixing belt 20 is pressed against the pressure roller 21, and a nip is formed between the fixing belt 20 and the pressure roller 21.

As shown in FIG. 4, one end of the rear wall 29 constituting the second device frame 26 in the longitudinal direction is provided with a hole 29b as a positioning portion for positioning the fixing device body relative to the image forming device body. On the other hand, the image forming device body is provided with a protrusion 101 as a positioning portion. When the protrusion 101 is inserted into the hole 29b of the fixing device 9, the protrusion 101 and the hole 29b fit together, and the fixing device body is positioned in the longitudinal direction relative to the image forming device body. Note that no positioning portion is provided on the end side opposite the end side where the hole 29b of the rear wall 29 is provided. This prevents the longitudinal expansion and contraction of the fixing device body due to temperature changes from being restricted.

Figure 5 is a perspective view of the heating unit 19, and Figure 6 is an exploded perspective view of the heating unit 19.

As shown in Figs. 5 and 6, the heater holder 23 has a rectangular storage recess 23a on the fixing belt side (the surface on the near side in Figs. 5 and 6) for storing the heater 22. The storage recess 23a is formed to have approximately the same shape and size as the heater 22, but the longitudinal dimension L2 of the storage recess 23a is set to be slightly longer than the longitudinal dimension L1 of the heater 22. In this way, the storage recess 23a is formed to be slightly longer than the heater 22, so that the heater 22 and the storage recess 23a do not interfere with each other even if the heater 22 expands in the longitudinal direction due to thermal expansion. In addition, the heater 22 is held in the storage recess 23a by being sandwiched together with the heater holder 23 by a connector, which will be described later, as a power supply member.

The pair of end support members 32 have a C-shaped belt support portion 32b that is inserted inside the fixing belt 20 to support the fixing belt 20, a flange-shaped belt regulation portion 32c that contacts the end face of the fixing belt 20 to regulate longitudinal movement (deviation), and support recesses 32d into which both end sides of the heater holder 23 and the stay 24 are inserted to support them. With the belt support portions 32b inserted into both end sides, the fixing belt 20 is supported in a so-called free belt manner in which no tension is generated in the circumferential direction (belt rotation direction) when the belt is not rotating.

As shown in Figures 5 and 6, a positioning recess 23e is provided as a positioning portion at one end of the heater holder 23 in the longitudinal direction. The fitting portion 32e of the end support member 32 shown on the left side of Figures 5 and 6 fits into this positioning recess 23e, thereby positioning the heater holder 23 and the end support member 32 in the longitudinal direction. On the other hand, the end support member 32 shown on the right side of Figures 5 and 6 does not have the fitting portion 32e, and is not positioned in the longitudinal direction relative to the heater holder 23. In this way, by positioning the heater holder 23 relative to the end support member 32 only on one side in the longitudinal direction, even if the heater holder 23 expands and contracts in the longitudinal direction due to temperature changes, the expansion and contraction is not restricted.

As shown in FIG. 6, steps 24a are provided on both longitudinal ends of the stay 24 to restrict movement of the stay 24 relative to each end support member 32. Each step 24a abuts against the end support members 32 to restrict longitudinal movement of the stay 24 relative to the end support members 32. However, at least one of these step portions 24a is disposed with a gap (backlash) between it and the end support members 32. In this way, by disposing at least one step portion 24a with a gap between it and the end support members 32, even if the stay 24 expands and contracts in the longitudinal direction due to temperature changes, the expansion and contraction is not restricted.

As shown in FIG. 7, the heater 22 has a substrate 50, a substrate-side insulating layer 51 provided on the substrate 50, a first conductor layer 52 having heating portions 60B1, 60B2, etc. provided on the substrate-side insulating layer 51, a first insulating layer 53 covering the first conductor layer 52, a second conductor layer 54 having heating portions 60A, etc. provided on the first insulating layer 53, and a second insulating layer 55 covering the second conductor layer 54. In this embodiment, the substrate 50, substrate-side insulating layer 51, first conductor layer 52 (heat generating portion 60B), first insulating layer 53, second conductor layer 54 (heat generating portion 60A), and second insulating layer 55 are laminated in this order toward the fixing belt 20 side (nip portion N side). Heat generated from the heat generating portion 60 of the first conductor layer 52 is transferred to the fixing belt 20 via the first insulating layer 53 and the second insulating layer 55, and heat generated from the heat generating portion 60 of the second conductor layer 54 is transferred to the fixing belt 20 via the second insulating layer 55 (see FIG. 2).

The substrate 50 is a longitudinal plate made of a metal material such as stainless steel (SUS), iron, or aluminum. In addition to metal materials, ceramics, glass, etc. can also be used as the material for the substrate 50. When an insulating material such as ceramics is used for the substrate 50, the substrate-side insulating layer 51 between the substrate 50 and the first conductor layer 52 can be omitted. On the other hand, metal materials are excellent in durability against rapid heating and are easy to process, making them suitable for reducing costs. Among metal materials, aluminum and copper are particularly preferred because they have high thermal conductivity and are less likely to cause temperature unevenness. Stainless steel also has the advantage of being cheaper to manufacture than these.

Each of the insulating layers 51, 53, and 55 is made of an insulating material such as heat-resistant glass. Alternatively, ceramic or polyimide (PI) may be used as the material.

As shown in FIG. 8, the first conductor layer 52 has second heating portions 60B1 and 60B2 consisting of a resistive heating element 69, second electrode portions 61B1 and 61B2 as a power supply portion (second power supply portion), and a power supply line 62 as a conductor portion.

Hereinafter, the direction intersecting the longitudinal direction B of the heater 22 (in this embodiment, the direction perpendicular to the longitudinal direction and different from the thickness direction of the heater 22 or the substrate 50) is referred to as the transverse direction Y of the heater 22 or the substrate 50. In this embodiment, the transverse direction Y is also the same as the paper transport direction (see arrow A in Figure 2) or the opposite direction.

As shown in FIG. 8, the second conductor layer 54 has a first heating portion 60A consisting of a resistive heating element 69, and first electrode portions 61A1, 61A2 as a power supply portion (first power supply portion). Hereinafter, the first heating portion 60A and the second heating portions 60B1, 60B2, etc. are also referred to as the heating portion 60, and the first electrode portions 61A1, 61A2 and the second electrode portions 61B1, 61B2, etc. are also referred to as the electrode portions 61.

The resistance heating element 69 is formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the substrate 50 by screen printing or the like, and then firing the substrate 50. In addition to these, the material of the resistance heating element 69 may be a resistance material such as a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ).

The power supply line 62 is made of a conductor with a resistance value smaller than that of the resistive heating element 69. Materials such as silver (Ag) or silver palladium (AgPd) can be used as the material for the power supply line 62 and the electrode portion.

The first electrode portions 61A1, 61A2 and the second electrode portions 61B1, 61B2 are supplied with power from the power source 64 via a connector, which will be described later. By supplying power to the first electrode portions 61A1, 61A2, electricity can be passed through the first heating portion 60A, causing the resistive heating element 69 to generate heat. In addition, by supplying power to the second electrode portions 61B1, 61B2, electricity can be passed through the second heating portions 60B1, 60B2, causing the resistive heating element 69 to generate heat.

A switch 65A serving as a switching unit is provided between the first electrode unit 61A1 and the power supply 64. By turning switch 65A on and off, it is possible to switch between applying and not applying a voltage to the first heating unit 60A. In addition, a switch 65B serving as a switching unit is provided between the second electrode unit 61B1 and the power supply 64. By turning switch 65B on and off, it is possible to switch between applying and not applying a voltage to the second heating units 60B1 and 60B2.

As shown in FIG. 9(a), a connector 70 serving as a power supply member is connected to the electrode portion 61.

The connector 70 has a resin housing 71, a number of contact terminals 72 provided on the housing 71, and a harness 73. Each contact terminal 72 is made of a leaf spring. A power supply harness 73 is connected to each contact terminal 72, and power is supplied from the power source 64 described above.

In this embodiment, the side surfaces X1 and X2 (side surfaces on both sides in the longitudinal direction) of each conductor layer are used as power supply positions, and the contact terminals 72 are connected to the side surfaces X1 and X2. By connecting on the side surfaces as in this embodiment, it is not necessary for each electrode portion to be exposed in the stacking direction. Therefore, the degree of freedom in the layout of each conductor layer is increased, and the heater 22 can be made smaller. However, as shown in FIG. 9(b), a power supply line 62 connecting the first electrode portion 61A2 and the second electrode portion 61B2 in the stacking direction is provided, and the second electrode portion 61B2 is extended in the longitudinal direction and partially exposed from the insulating layers 53 and 55 (in other words, an insulating layer is not formed in a part of the upper area of the second electrode portion 61B2 in the stacking direction), and this exposed portion X3 may be used as a power supply position and connected to the contact terminal 72. As shown in FIG. 9(c), the first electrode portion 61A2 and the second electrode portion 61B2 may be extended in the longitudinal direction and partially exposed from the insulating layers 53 and 55, and these exposed portions X4 and X5 may be connected to the contact terminals 72 as power receiving positions.

As shown in FIG. 8, the first heat generating section 60A and the second heat generating sections 60B1 and 60B2 have different heat generating regions in the longitudinal direction. Specifically, the first heat generating section 60A is provided at the center in the longitudinal direction, and the second heat generating sections 60B1 and 60B2 are provided at positions corresponding to both ends in the longitudinal direction.

By turning on only switch 65A, a voltage is applied to the first heating section 60A, and the heater 22 can heat the resistance heating element 69 in an area corresponding to the width of small-sized paper (e.g., A4 size, paper width: 210 mm). By turning on switches 65A and 65B, a voltage is applied to the first heating section 60A and the second heating sections 60B1 and 60B2, and the heater 22 can heat the resistance heating element 69 in an area corresponding to the width of large-sized paper.

As described above, the heater 22 of this embodiment has a laminated structure in which the conductor layer on which the heat generating portion 60, the electrode portion 61, and the power supply line 62 are provided are divided into multiple layers. This allows the area of each layer to be kept small. Therefore, the short-side length of the electrode portion 61 and the power supply line 62 can be made long and the long-side length can be made short.

However, unlike this embodiment, in a configuration in which the heating portion, power terminal, power supply line, etc. are all provided on the same layer, if you try to miniaturize the heater, the layout constraints mean that the power supply line needs to be made thin and long, which increases the resistance of the power supply line.

For example, in the case of the heater 22' shown in FIG. 10, when all the heating parts 60A, 60B, the electrodes 61A to 61C, and the power supply lines 62A to 62C are provided on the same plane, the power supply lines 62A to 62C are long and thin in order to connect the electrodes 61A to 61C to the resistance heating element 69. In this case, due to an increase in the resistance of the power supply lines 62A to 62C, the amount of heat generated from the power supply lines 62A to 62C when the heater 22 is energized becomes relatively large compared to the amount of heat generated from the resistance heating element 69, and cannot be ignored. Furthermore, since the current values flowing through the power supply lines 62A to 62C differ in the longitudinal direction, the amount of heat generated also varies in the longitudinal direction, which causes a longitudinal deviation in the amount of heat generated by the heater 22. Furthermore, the longitudinal deviation in the amount of heat generated by the heater 22 may cause unevenness in the image or uneven fixing of the paper on which the fixing device 9 performs the fixing operation.

In contrast, in this embodiment, the multi-layer structure described above allows the power supply line to be thicker and shorter, and the amount of heat generated can be relatively small. This makes it possible to suppress temperature deviation in the longitudinal direction of the heater 22. This makes it possible to reduce the size of the heater 22 and thus the fixing device 9, and also suppresses problems caused by temperature deviation in the longitudinal direction of the heater 22, specifically, uneven images on the paper and uneven fixing. Furthermore, the joint between the resistance heating element and the power supply line or electrode portion can be made wider, which has the advantage of suppressing poor joints at the joints.

Next, we will explain the specific manufacturing method of the heater 22.

First, as shown in FIG. 11(a), an insulating material is coated on the surface of the substrate 50 (the surface on the side of the nip portion N). For example, glass coating is performed. This forms the substrate-side insulating layer 51. Then, as shown in FIG. 11(b), a paste material constituting the heating portion, the electrode portion, and the power supply line is screen-printed on the surface of the substrate-side insulating layer 51 to form the first conductor layer 52 (power supply line 62C is shown in FIG. 11b). Next, as shown in FIG. 11(c), an insulating material is coated on the upper part of the substrate-side insulating layer 51 to the same height as the first conductor layer 52, and further insulating material is coated on the upper part and the upper part of the first conductor layer 52 to form the first insulating layer 53. Furthermore, as shown in FIG. 11(d), a paste material constituting the heating portion and the electrode portion is screen-printed on the surface of the first insulating layer 53 to form the second conductor layer 54 (resistance heating element 69 is shown in FIG. 11d). Then, an insulating material is coated to the same height as the second conductor layer 54, and the upper part of the second conductor layer 54 and the upper part of the first conductor layer 52 are further coated with an insulating material to form the second insulating layer 55. In this manner, the heater 22 can be manufactured. If the conductor layer is divided into three or more layers, the process of forming the conductor layer by screen printing and the process of coating the surface of the conductor layer with an insulating material to form the insulating layer can be repeated.

Next, we will explain the modified layer structure of the heater 22 in order.

Figure 12 is a perspective view of the heater 22 of this embodiment, showing only the conductor layer. Figure 13 is a diagram showing the layer structure of the heater 22 of this embodiment, where (a) is a view from the direction of the arrow D1 in Figure 12, and (b) is a view from the direction of the arrow D2 in Figure 12. However, Figure 13 also shows the base material and insulating layer. Figure 12 is a diagram showing the arrangement of the resistive heating element, electrode parts, etc. in the heater 22, and the thickness of the resistive heating element differs from that of the actual heater 22. Also, the length of the power supply wires connecting each conductor layer is exaggerated and shown to be longer than the actual length.

As shown in FIG. 12, the heater 22 of this embodiment has a first conductor layer 52 and a second conductor layer 54 as conductor layers. The first conductor layer 52 is provided with electrode portions 61A to 61C. The second conductor layer 54 is provided with a first heat generating portion 60A and a second heat generating portion 60B.

The first electrode 61A and the first heating part 60A are connected via a power supply line 62A1 as a conductor, and the first heating part 60A and the third electrode part (third power supply part) 61C are connected via a power supply line 62A2 as a conductor. The second electrode 61B and the second heating part 60B are connected via a power supply line 62B1 as a conductor, and the second heating part 60B and the third electrode part 61C are connected via a power supply line 62B2 as a conductor.

As shown in FIG. 13, similar to the above-described embodiment, a substrate-side insulating layer 51 is provided between the substrate 50 and the first conductor layer 52, a first insulating layer 53 is provided between the first conductor layer 52 and the second conductor layer 54, and a second insulating layer 55 is provided on top of the second conductor layer 54.

Each power supply line 62 is provided at the same height as the first insulating layer 53 and connects each electrode portion 61 of the first conductor layer 52 to each heating portion 60 of the second conductor layer 54.

As shown in FIG. 12, in the longitudinal direction, the first heating section 60A has a heating area corresponding to the width of large-size paper, and the second heating section 60B has a heating area corresponding to the width of small-size paper. The first electrode section 61A is connected to a power source 64 via a switch 65A, and the second electrode section 61B is connected to the power source 64 via a switch 65B. As in the previous embodiment, by turning on or off each switch 65A, 65B, the application of voltage to each heating section 60A, 60B can be switched on or off, and the heater 22 can cause the heating section corresponding to each paper width to generate heat.

As described above, in this embodiment, the heat generating section 60 and the electrode section 61 are provided on different conductor layers, and the conductor layers are connected to each other by a power supply line. This allows the area of each conductor layer to be kept small. Also, each electrode section 61 can be made thick and short, and each power supply line 62 only needs to be provided with a length and width sufficient to connect the different layers. Therefore, the amount of heat generated by the power supply line and the electrode section can be kept relatively small, and the longitudinal temperature deviation occurring in the heater 22 can be suppressed. This allows the heater 22 and thus the fixing device 9 to be made smaller, and also suppresses problems caused by the longitudinal temperature deviation of the heater 22, specifically, uneven images on the paper and uneven fixing.

The manufacturing method of the heater 22 of the embodiment shown in FIG. 12 will be described with reference to FIG. 14. As shown in FIG. 14(a), first, glass coating is performed on the surface of the substrate 50 (the surface on the side of the nip portion N) to form the substrate-side insulating layer 51. Then, as shown in FIG. 14(b), a paste material constituting the heating portion and the electrode portion is screen-printed on the surface of the substrate-side insulating layer 51 to form the first conductor layer 52 (FIG. 14b shows the third electrode portion 61C). Next, as shown in FIG. 14(c), glass coating is performed on the portion at the same height as the first conductor layer 52 where the conductor portions such as the heating portion and the electrode portion are not provided. Then, as shown in FIG. 14(d), a paste material constituting the power supply line (FIG. 14d shows the power supply line 62A2 and the power supply line 62B2) is screen-printed on the upper portion of the first conductor layer 52. After that, as shown in FIG. 14(e), glass coating is performed on the portion other than where the power supply line is provided to form the first insulating layer 53. Then, as shown in FIG. 14(f), the first heating portion 60A and the second heating portion 60B are screen-printed on the first insulating layer 53 to form the second conductor layer 54. Then, as shown in FIG. 14(g), glass coating is performed to the same height as the second conductor layer 54. Finally, as shown in FIG. 14(h), the second insulating layer 55 is formed on the top of the second conductor layer 54 to manufacture the heater 22. If the conductor layer has three or more layers, the heater 22 can be manufactured by repeating the steps of FIG. 14(d) to FIG. 14(g) after the step of FIG. 14(g).

Figure 15 is a perspective view of the heater 22 of the next embodiment, showing only the conductor layer. Figure 16 shows the layer structure of the heater 22 of this embodiment, where (a) is a view from the direction of the arrow D1 in Figure 15, and (b) is a view from the direction of the arrow D2 in Figure 15. Also, Figure 17 is a diagram showing the power supply to each heat generating portion.

In the next embodiment, each heat generating portion is provided on a different layer. Specifically, as shown in FIG. 15, a first heat generating portion 60A is provided on the second conductor layer 54, and a second heat generating portion 60B is provided on the third conductor layer 56. All of the electrode portions 61A to 61C are provided on the first conductor layer 52, similar to the embodiment in FIG. 12.

As in the previous embodiment, the first electrode 61A and the first heat generating part 60A are connected via a power supply line 62A1, and the first heat generating part 60A and the third electrode 61C are connected via a power supply line 62A2. The second electrode 61B and the second heat generating part 60B are connected via a power supply line 62B1, and the second heat generating part 60B and the third electrode 61C are connected via a power supply line 62B2.

As shown in FIG. 16(a), the power supply line 62A1 is provided across the first insulating layer 53, the second conductor layer 54, and the second insulating layer 55, and connects the first electrode portion 61A of the first conductor layer 52 and the first heating portion 60A of the third conductor layer 56. The power supply line 62B1 is provided at the same height as the first insulating layer 53, and connects the second electrode portion 61B of the first conductor layer 52 and the second heating portion 60B of the second conductor layer 54. Also, as shown in FIG. 16(b), the power supply line 62A2 is provided across the first insulating layer 53, the second conductor layer 54, and the second insulating layer 55, and connects the third electrode portion 61C of the first conductor layer 52 and the first heating portion 60A of the third conductor layer 56. The power supply line 62B2 is provided at the same height as the first insulating layer 53, and connects the third electrode portion 61C of the first conductor layer 52 and the second heating portion 60B of the second conductor layer 54. In addition, a third insulating layer 57 is provided between the third conductor layer 56 and the inner surface of the fixing belt.

As shown in FIG. 17, in the longitudinal direction, the first heating section 60A has a heating area corresponding to the width of large-sized paper, and the second heating section 60B has a heating area corresponding to the width of small-sized paper. The first electrode section 61A is connected to a power source 64 via a switch 65A, and the second electrode section 61B is connected to the power source 64 via a switch 65B. As in the previous embodiment, by turning on or off each switch 65A, 65B, the application of voltage to each heating section 60A, 60B can be switched on or off, and the heater 22 can cause the heating section corresponding to each paper width to generate heat.

As in this embodiment, the first heat generating section 60A and the second heat generating section 60B can be provided on different layers. By arranging the first heat generating section 60A and the second heat generating section 60B on top of each other, it is possible to reduce the width of the heater 22 in the short direction. In this way, by dividing the conductor layer into multiple parts, the area of each conductor layer can be reduced. In addition, each electrode section 61 can be made thick and short, and each power supply line 62 can be provided with a length and width sufficient to connect different layers. Therefore, the heat generation amount of the power supply line and the electrode section can be kept relatively small, and the temperature deviation in the longitudinal direction of the heater 22 can be suppressed. This makes it possible to reduce the size of the heater 22 and thus the fixing device 9, and to suppress problems caused by the temperature deviation in the longitudinal direction of the heater 22, specifically, image unevenness and fixing unevenness on the paper.

Figure 18 is a perspective view of the heater 22 of the next embodiment, showing only the conductor layer. Figure 19 shows the layer structure of the heater 22 of this embodiment, where (a) is a view from the direction of the arrow D1 in Figure 18, and (b) is a view from the direction of the arrow D2 in Figure 18. Also, Figure 20 is a diagram showing the power supply to each heat generating portion.

As shown in FIG. 18, in this embodiment, in addition to the first heating section 60A and the second heating section 60B, a third heating section 60C is provided.

The first conductor layer 52 is provided with a fourth electrode portion 61D and a fifth electrode portion 61E. The second conductor layer 54 is provided with a first electrode portion 61A, a second electrode portion 61B, and a third heat generating portion 60C. The third conductor layer 56 is provided with a third electrode portion 61C. The fourth conductor layer 58 is provided with a first heat generating portion 60A and a second heat generating portion 60B. In this manner, in this embodiment, the heat generating portions 60 and the electrodes are arranged separately on multiple conductor layers.

The fourth electrode portion 61D and the third heating portion 60C are connected via a power supply line 62C1, and the third heating portion 60C and the fifth electrode portion 61E are connected via a power supply line 62C2. The power supply lines 62C1 and 62C2 are provided at the same height as the first insulating layer 53 (see Figures 19a and 19b), and connect the electrodes 61D and 61E of the first conductor layer 52 to the third heating portion 60C of the second conductor layer 54.

As shown in FIG. 19(a), the power supply lines 62A1 and 62B1 are provided across the second insulating layer 55, the third conductor layer 56 and the third insulating layer 57, and connect the first electrode portion 61A and the second electrode portion 61B of the second conductor layer 54 to the first heating portion 60A and the second heating portion 60B of the fourth conductor layer 58, respectively. As shown in FIG. 19(b), the power supply lines 62A2 and 62B2 are provided at the same height as the third insulating layer 57, and connect the first heating portion 60A and the second heating portion 60B of the fourth conductor layer 58 to the third electrode portion 61C of the third conductor layer 56. In addition, a fourth insulating layer 59 is provided between the fourth conductor layer 58 and the inner surface of the fixing belt.

As shown in FIG. 20, in the longitudinal direction, the first heating section 60A has a heating area corresponding to the large size paper width, and the second heating section 60B has a heating area corresponding to the medium size paper width. And the third heating section 60C has a heating area corresponding to the small size paper width. The first electrode section 61A is connected to the power supply 64 via the switch 65A, and the second electrode section 61B is connected to the power supply 64 via the switch 65B. Also, the third electrode section 61C is connected to the power supply 64 via the switch 65C. As in the previous embodiment, by turning on and off each of the switches 65A to 65C, the application of voltage to each of the heating sections 60A to 60C can be switched, and the heater 22 can heat the heating section corresponding to each paper width. In other words, in this embodiment, the heater 22 can form heating areas corresponding to three types of paper widths.

In this way, in a configuration with three heat generating parts, the conductor layer can be divided into multiple layers. Also, specific heat generating parts can be provided on the same layer or on different layers. In this way, the layer configuration of the heat generating parts and electrode parts can be selected as appropriate, and as long as space allows, even more conductor layers can be stacked.

In this embodiment, too, by dividing the conductor layer into multiple layers, the area of each conductor layer can be kept small. Furthermore, each electrode portion 61 can be made thick and short, and each power supply line 62 only needs to be long and wide enough to connect different layers. Therefore, the amount of heat generated by the power supply line and electrode portion can be kept relatively small, and the longitudinal temperature deviation occurring in the heater 22 can be suppressed. This makes it possible to reduce the size of the heater 22 and thus the fixing device 9, and to suppress problems caused by the longitudinal temperature deviation of the heater 22, specifically, uneven images on the paper and uneven fixing.

In the next embodiment, as shown in FIG. 21, the first heating portion 60A to the third heating portion 60C are provided on different layers. Specifically, the third heating portion 60C and the electrodes 61A to 61D are provided on the first conductor layer 52. The second heating portion 60B is provided on the second conductor layer 54, and the first heating portion 60A is provided on the third conductor layer 56.

The third heating element 60C is connected to the fourth electrode element 61D and the third electrode element 61C, which are provided on the same layer. As in the above-described embodiment, the first electrode element 61A and the first heating element 60A are connected via a power supply line 62A1, and the first heating element 60A and the third electrode element 61C are connected via a power supply line 62A2. The second electrode element 61B and the second heating element 60B are connected via a power supply line 62B1, and the second heating element 60B and the third electrode element 61C are connected via a power supply line 62B2.

22(a), the power supply line 62A1 is provided across the first insulating layer 53, the second conductor layer 54, and the second insulating layer 55, and connects the first electrode portion 61A of the first conductor layer 52 and the first heating portion 60A of the third conductor layer 56. The power supply line 62B1 is provided at the same height as the first insulating layer 53, and connects the second electrode portion 61B of the first conductor layer 52 and the second heating portion 60B of the second conductor layer 54. As shown in FIG. 22(b), the power supply line 62A2 is provided across the first insulating layer 53, the second conductor layer 54, and the second insulating layer 55, and connects the third electrode portion 61C of the first conductor layer 52 and the first heating portion 60A of the third conductor layer 56. The power supply line 62B2 is provided at the same height as the first insulating layer 53, and connects the third electrode portion 61C of the first conductor layer 52 and the second heating portion 60B of the second conductor layer 54.

As shown in FIG. 23, in this embodiment, the first heating section 60A has a heating area corresponding to the large paper width, the second heating section 60B has a heating area corresponding to the medium paper width, and the third heating section 60C has a heating area corresponding to the small paper width in the longitudinal direction. The first electrode section 61A is connected to the power supply 64 via the switch 65A, and the second electrode section 61B is connected to the power supply 64 via the switch 65B. The third electrode section 61C is connected to the power supply 64 via the switch 65C. As in the previous embodiment, the ON/OFF of each switch 65A to 65C switches between the application of voltage to each heating section 60A to 60C, and the heater 22 can generate heat in the heating section corresponding to each paper width. In other words, in this embodiment, the heater 22 can form heating sections corresponding to three different paper widths.

In this embodiment, too, by dividing the conductor layer into multiple layers, the area of each conductor layer can be kept small. Furthermore, each electrode portion 61 can be made thick and short, and each power supply line 62 only needs to be long and wide enough to connect different layers. Therefore, the amount of heat generated by the power supply line and electrode portion can be kept relatively small, and the longitudinal temperature deviation occurring in the heater 22 can be suppressed. This makes it possible to reduce the size of the heater 22 and thus the fixing device 9, and to suppress problems caused by the longitudinal temperature deviation of the heater 22, specifically, uneven images on the paper and uneven fixing.

In particular, in this embodiment, as shown in FIG. 21, in a cross section cut in the longitudinal direction of the heater 22 (a cross section cut in the longitudinal direction at the position where the first electrode portion 61A in the short direction is arranged), the heater 22 is symmetrical on one side and the other side with respect to the longitudinal center position H1 of the entire heat generating region H of the heater 22 (which is also the center position of the heater 22 and the center position of the paper being passed in this embodiment). That is, the arrangement of the heat generating portion 60, the electrode portion 61, and the power supply line 62 of the heater 22 is symmetrical on one side and the other side with respect to the center position H1. This makes it possible to suppress the temperature deviation between one side and the other side of the heater 22 in the longitudinal direction, and to make the temperature of the heater 22 more uniform in the longitudinal direction. In particular, in this embodiment, as shown in FIG. 23, the heat generating portion 60 is symmetrical on one side and the other side with respect to the longitudinal center position. This makes it possible to suppress the temperature deviation between one side and the other side of the heater 22 in the longitudinal direction, and to make the temperature of the heater 22 more uniform in the longitudinal direction. The entire heating region H refers to the region of all the resistive heating elements 69 provided in the heater 22 in the longitudinal direction of the heater 22, from the position Ha on one side in the longitudinal direction to the position Hb on the other side in the longitudinal direction.

In addition, when each heating portion 60 is provided on a different layer, it is preferable to provide the heating portion 60 with a larger heating area, in other words, a longer longitudinal length, at a position farther in the stacking direction than the layer on which the electrode portion 61 is provided. For example, as shown in FIG. 21, the electrode portions 61A to 61D of the heater 22 are provided at the height of the first conductor layer 52. In contrast, the widths of the third heating portion 60C to the second heating portion 60B to the first heating portion 60A in the longitudinal direction become larger as they are farther away from the first conductor layer 52. In contrast, if the widest first heating portion 60A is provided on the intermediate second conductor layer 54 and the second heating portion 60B is provided on the third conductor layer 56, it is necessary to secure a space in the second conductor layer 54 on which the first heating portion 60A is provided for the power supply lines 62B1 and 62B2 connected to the second heating portion 60B to pass through in the stacking direction. In other words, it is necessary to arrange the power supply lines 62B1 and 62B2 to avoid the first heating section 60A, which is the widest, and this increases the size of the heater 22. Therefore, by configuring the heating section 60 so that the width increases the farther it is from the power supply section 61 in the stacking direction, as in this embodiment, the heater 22 can be made smaller, which is preferable.

In addition to the fixing devices described above, the present invention can also be applied to fixing devices such as those shown in Figures 24 to 26. Below, we will briefly explain the configuration of each fixing device shown in Figures 24 to 26.

First, the fixing device 9 shown in FIG. 24 has a pressure roller 90 disposed on the opposite side of the fixing belt 20 from the pressure roller 21 side, and is configured so that the fixing belt 20 is sandwiched and heated by this pressure roller 90 and heater 22. On the other hand, on the pressure roller 21 side, a nip forming member 91 is disposed on the inner circumference of the fixing belt 20. The nip forming member 91 is supported by a stay 24, and the fixing belt 20 is sandwiched between the nip forming member 91 and the pressure roller 21 to form a nip portion N.

Next, in the fixing device 9 shown in FIG. 25, the pressure roller 90 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. 24.

Finally, in the fixing device 9 shown in FIG. 26, in addition to the fixing belt 20, a pressure belt 92 is provided, and a heating nip (first nip portion) N1 and a fixing nip (second nip portion) N2 are separately configured. That is, a nip forming member 91 and a stay 93 are arranged on the opposite side of the pressure roller 21 from the fixing belt 20 side, and the pressure belt 92 is arranged rotatably so as to include the nip forming member 91 and the stay 93. Then, a sheet of paper P is passed through the fixing nip N2 between the pressure belt 92 and the pressure roller 21, and the image is fixed by heating and pressurizing it. The rest of the configuration is the same as the fixing device 9 shown in FIG. 2.

In these fixing devices 9, the heater 22 has a layered structure as described above, which allows the heater 22 to be made smaller and suppresses deviations in the amount of heat generated in the longitudinal direction of the heater 22.

In addition, devices equipped with a heating device to which the heating element of the present invention is applied are not limited to fixing devices as 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 heating devices such as laminators that thermocompression bond a film as a covering member to the surface of a sheet such as paper, and heat sealers that thermocompression bond the seal portion of a packaging material. By applying the heating element of the present invention to such devices, the heating element can be made smaller and the temperature deviation in the longitudinal direction of the heating element can be suppressed.

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)
19 Heating unit 20 Fixing belt (rotating member, fixing member)
21 Pressure roller (opposing member, pressure member)
22 Heater (heating body)
31 Drive transmission gear (drive transmission member)
40: Device frame 50: Base material 51, 53, 55, 57, 59: Insulating layer 52, 54, 56, 58: Conductive layer 60: Heat generating portion 61: Electrode portion (power supply portion)
62 Power supply line (conductor part)
64 Power supply 65A to 65C Switch (switching part)
69 Resistance heating element 70 Connector (power supply member)
A: Paper feed direction B: Longitudinal direction H: Total heating area of heater H1: Center position of heater P: Paper (recording medium or heated object)
Y: Short side of heater

JP 2013-186402 A

Claims (10)

A substrate;
A plurality of conductor layers formed by laminating directly or indirectly on the substrate;
A heating body including an insulating layer formed of an insulating material and provided between the conductor layers,
At least one of the conductor layers has a resistive heating element;
At least one of the conductor layers has a power supply portion that supplies power to the resistance heating element,
A conductor portion connecting the conductor layers to each other is provided,
a first conductor layer having the power supply portion and not having the resistance heating element;
a second conductor layer provided on a side farther from the base material than the first conductor layer and having the resistive heating element;
a first insulating layer provided between the first conductor layer and the second conductor layer;
and a second insulating layer formed on the second conductor layer . a third conductor layer having the resistive heating element;
2. The heating element according to claim 1 , further comprising a third insulating layer formed on the third conductor layer,
The second insulating layer is a heating element provided between the second conductive layer and the third conductive layer. a first heating portion and a second heating portion each having a different resistance heating element;
3. The heating body according to claim 1 or 2, comprising: a first power supply part connected to the first heat generating part, a second power supply part connected to the second heat generating part, and a third power supply part connected to the first heat generating part and the second heat generating part,
A heating element in which the conductor portion connecting the first heating portion and the first power supply portion and the conductor portion connecting the second heating portion and the second power supply portion are provided at different positions in a direction intersecting the longitudinal direction of the heating element. The heating element according to any one of claims 1 to 3, wherein the resistive heating elements provided on the conductor layer are arranged symmetrically on one side and the other side with respect to a longitudinal center position of the entire heat generation area formed by all the resistive heating elements of the heating element. The heating element according to claim 1 , wherein the power supply portion provided on the side surface of the conductor layer contacts a power supply member. The heating element according to claim 1 , wherein the length of the resistance heating element in the longitudinal direction increases as the resistance heating element moves away from the conductor layer having the power supply portion in the stacking direction. The heating element according to claim 1 , wherein the insulating layer is not formed on a part of the power supply portion. A heating device comprising the heating element according to any one of claims 1 to 7 . A fixing device comprising the heating device according to claim 8 , for fixing toner on a recording medium by heat. An image forming apparatus comprising the fixing device according to claim 9 .

Images