JP7086672B2 - Heater and fixing device - Google Patents

Description

The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic recording type copier or a printer, and a heater mounted on the fixing device.

As a fixing device mounted on an electrophotographic recording type image forming device, a device using a film is known. This fixing device has a tubular film and a heater that contacts the inner surface of the film. Since the fixing device using a film has a low heat capacity, it has advantages such as a short warm-up time of the device and low power consumption.

The heater has a substrate made of a material such as ceramic and a heating element (heating element) provided on the substrate. The temperature of the heater is detected by a temperature detection element such as a thermistor, and the control unit controls the power supply to the heat generation resistor according to the output of the temperature detection element.

As a configuration of the temperature detection element, there is a configuration in which a temperature detection element provided independently of the heater is pressed against the heater via an insulating sheet. In addition, there is also a heater-integrated configuration in which the temperature detection element and the conductive line electrically connected to the temperature detection element are provided on the substrate of the heater by a coating method such as screen printing. In the heater-integrated type, the temperature detection element, the conductive line, and the heating element are protected by a glass film for insulation. The heater-integrated type has the advantage that the temperature detection element is printed on the substrate, so that there is little variation in responsiveness and the temperature detection accuracy is high.

Further, there is also a proposal to provide a temperature detecting element on the sliding surface side of the heater with the film in order to accurately detect the temperature of the fixing nip portion (Patent Document 1). Further, in Patent Document 1, in order to reduce the size of the heater, the heat generation resistor is provided on the surface of the substrate opposite to the surface on which the temperature detection element is provided.

Japanese Unexamined Patent Publication No. 2017-54071

However, in the above-mentioned heater configuration, the thickness of the portion provided with the temperature detecting element or the conductive line from the surface of the substrate may be thicker than that of the other portions, and the surface of the heater may be uneven. According to the studies by the present inventors, it has been found that when the conductive line on the heater substrate is formed parallel to the transport direction of the recording material, fixing failure and gloss streaks may occur. The reason is that the heat and pressure applied to the toner image become non-uniform due to the stepped portion on the surface of the heater generated by the conductive line.

Further, as a result of detailed examination, it was found that in the connection portion where the temperature detection element and the conductive line overlap, unevenness tends to be larger than in other portions, and fixing failure and gloss streaks are likely to occur remarkably.

An object of the present invention is to provide a heater and a fixing device capable of suppressing the occurrence of image defects such as fixing defects and gloss streaks.

The present invention for solving the above-mentioned problems includes a substrate, a heating element provided on the substrate, a temperature detecting element provided on the substrate, and a conductive line connected to the temperature detecting element. In a heater having a temperature detecting element and a protective layer covering the conductive line and used in a fixing device for fixing a toner image formed on the recording material to the recording material, the temperature detecting element and the conductive line The connecting portion is provided with an overlapping portion in which both are overlapped in the thickness direction of the heater, the conductive line is a line having a substantially constant width over the extending direction thereof, and the heater is provided in the longitudinal direction thereof. In the cross section when cut in parallel with the temperature detecting element and on the surface passing through the temperature detecting element, the temperature detecting element does not overlap next to the overlapping portion in the longitudinal direction , and the overlapping portion is formed from the surface of the substrate. A gradient relaxation portion having a step smaller than the step to the surface is provided , and in the cross section when the heater is cut in a plane parallel to the short side and passing through the temperature detection element, the short side direction. Next to the overlapping portion in the above, the temperature detecting element does not overlap because the width of the conductive line is larger than the constant width, and there is a step rather than a step from the surface of the substrate to the surface of the overlapping portion. It is characterized in that a small gradient relaxation portion is provided .
Further, in the present invention, the substrate, the heating element provided on the substrate, the temperature detecting element provided on the substrate, the conductive line connected to the temperature detecting element, and the temperature detecting element. In a heater having a protective layer covering the conductive line and used for a fixing device for fixing a toner image formed on the recording material to the recording material, the temperature detecting element and the connection portion of the conductive line are connected to the heater. An overlapping portion is provided in which both are overlapped in the thickness direction of the heater, and the conductive line is a line having a substantially constant width over the extending direction, and the heater is parallel to the lateral direction thereof and In the cross section when cut on the surface passing through the temperature detection element, the temperature detection element does not overlap next to the overlapping portion in the lateral direction, and a step from the surface of the substrate to the surface of the overlapping portion. A gradient relaxation portion having a smaller step than the above is provided, and in the cross section when the heater is cut parallel to the longitudinal direction and on the surface passing through the temperature detecting element, next to the overlapping portion in the longitudinal direction. Is provided with a gradient relaxation portion in which the temperature detection elements do not overlap because the width of the conductive line is larger than the constant width, and the step is smaller than the step from the surface of the substrate to the surface of the overlapping portion. It is characterized by being.

According to the present invention, it is possible to provide a heater and a fixing device capable of suppressing the occurrence of image defects such as fixing defects and gloss streaks.

Sectional view of image forming apparatus Cross-sectional view of the fixing device The figure of the heater which concerns on Example 1. The figure of the connection part of the thermistor and a conductive line which concerns on Example 1. Diagram of heater according to comparative example The figure of the connection part of the thermistor and a conductive line which concerns on a comparative example. The figure which showed the image defect which occurs in the comparative example The figure of the connection part of the thermistor and a conductive line which concerns on the modification of Example 1. The figure of the heater which concerns on Example 2. The figure of the connection part of the thermistor and a conductive line which concerns on Example 2. The figure of the connection part of the thermistor and a conductive line which concerns on the modification of Example 2. The figure which showed the other configuration of a heater

[Example 1]
FIG. 1 is a cross-sectional view of an electrophotographic recording type image forming apparatus. The photosensitive drum 1 is rotationally driven in the direction of the arrow, and its surface is uniformly charged by the charging roller 2. Next, the surface of the charged photosensitive drum 1 is scanned by the laser scanner 3 with the laser beam L corresponding to the image information. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 1. The electrostatic latent image is developed by the toner supplied from the developer 4. The toner image formed on the photosensitive drum 1 is transferred to the recording material P fed from the paper feed cassette 6 at the transfer nip portion which is the pressure contact portion between the transfer roller 5 and the photosensitive drum 1. The recording material P to which the toner image is transferred is conveyed to the fixing device 7, and the toner image is heat-fixed to the recording material in the fixing device 7. After that, the recording material P is discharged onto the paper ejection tray. The toner remaining on the photosensitive drum 1 after the transfer is recovered by the cleaner 8.

(Structure of fixing device 7)
Next, the fixing device 7 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the fixing device. The fixing device 7 has a film unit 10 and a pressure roller 20, and a fixing nip portion N for sandwiching and transporting the recording material P is formed between the film unit 10 and the pressure roller 20. The film unit 10 has a tubular film 11 and a heater 12 that comes into contact with the inner surface of the film 11. The fixing device 7 further has a heater holder 13 that holds the heater 12, and a metal stay 14 that is urged by a pressure spring (not shown) and presses the heater holder 13 against the pressure roller 20.

The film 11 has a base layer and a release layer formed on the outside of the base layer. The base layer is formed of a heat-resistant resin such as polyimide, polyamide-imide, PEEK, or a metal such as SUS (stainless steel). The release layer is a mixed or single layer of a fluororesin such as PTFE, PFA, FEP, or a heat-resistant resin having good releasability such as a silicone resin. Further, an intermediate layer made of heat-resistant rubber such as silicone rubber may be provided between the base layer and the release layer. The film 11 of this embodiment has a SUS base layer having a thickness of 30 μm, a silicone rubber layer (elastic layer) having a thickness of 200 μm, and a release layer made of PFA having a thickness of 20 μm. The outer diameter of the film 11 was 24 mm, and the length in the longitudinal direction (width direction of the recording material P) was 240 mm.

The heater holder 13 holds the heater 12 and also has a guide function for guiding the rotation of the film 11. The heater holder 13 is made of a heat-resistant resin such as a liquid crystal polymer.

The metal stay 14 is a component that reinforces the heater holder 13. In order to withstand the load when the heater holder 13 is pressed against the pressure roller 20, a highly rigid metal such as SUS is used for the metal stay 14.

The pressure roller 20 has a core metal 21 and an elastic layer 22 formed on the outside of the core metal. A mold release layer such as PFA or PTFE may be provided on the outside of the elastic layer 22. When the core metal 21 receives power from a motor (not shown), the pressure roller 20 rotates in the direction of the arrow. As the pressure roller 20 rotates, the film 11 also rotates in a driven manner. The pressure roller 20 of this embodiment has an elastic layer 22 made of silicone rubber having a thickness of 3.5 mm and a release layer made of PFA having a thickness of 70 μm. The outer diameter of the pressure roller 20 was 25 mm, and the length in the longitudinal direction was 230 mm.

The fixing device 7 fixes the image formed on the recording material P to the recording material by the heat from the heater 12 via the rotating film 11.

(Structure of heater 12)
The heater configuration of this embodiment will be described with reference to FIG. The heater 12 has a substrate 30 and a heating element 31 provided on the substrate 30. Further, the heater 12 has the temperature detection elements 331 to 333 provided on the surface of the substrate 30 opposite to the surface on which the heating element 31 is provided, and the side opposite to the surface of the substrate 30 on which the heating element 31 is provided. It has a conductive line 34 which is provided on the surface of the surface and is electrically connected to the temperature detecting element 33.

FIG. 3A is a diagram showing the back surface side of the heater 12, that is, the surface of the heater 12 opposite to the sliding surface of the film 11. A heating element (heating element) 31 and an electrode 32 are formed on the alumina substrate 30 by screen printing, and the heating element 31 is covered with a first protective layer 35 (material is glass). A connector (not shown) is connected to the electrode 32, and the heat generation resistor 31 generates heat by the electric power supplied from the power source. The material of the substrate 30 may be a ceramic material such as aluminum nitride or a metal whose surface is covered with an insulating layer.

FIG. 3B is a diagram showing the sliding surface side of the heater 12. Thermistors 331 to 333 and conductive lines 34 as temperature detecting elements are formed by screen printing on the sliding surface side of the heater 12. Since the conductive line 34 is connected to the control circuit 9 in the image forming apparatus via a connector (not shown), the temperature detected by the thermistors 331 to 333 can be known. The conductive line 34 has a region 34a inclined with respect to both the longitudinal direction (longitudinal direction of the heater 12) D1 and the lateral direction (minor direction of the heater 12) D2 of the substrate 30. By forming the conductive line 34 in the oblique direction, it is possible to suppress the occurrence of image defects. The line X indicates the center of the heater 12 in the lateral direction D2. Further, the angle A is an inclination angle of the region 34a with respect to the direction D1. Further, in the fixing device, the direction D2 is the recording material transport direction.

In the middle of the region 34a of the conductive line 34 arranged in the diagonal direction, the thermistors 331, 332, and 333 are respectively parallel to the direction D1 (so that the long side of the thermistor is parallel to the direction D1). Have been placed. The reason for arranging in this way is to prevent image defects from occurring due to a step generated at the connection portion between the thermistors 331, 332, and 333 and the conductive line 34. Details will be described later. As shown in FIG. 4A, the thermistors 331 to 333 have a long side and a short side when the heater 12 is viewed from a direction perpendicular to the sliding surface.

The thermistors 331 to 333 and the conductive line 34 are also covered with a second protective layer 36 made of glass. The second protective layer 36 also plays a role of protecting the thermistors 331 to 333 and the conductive line 34 from wear caused by rubbing against the film 11. Therefore, a glass material having better wear resistance than the first protective layer 35 is used. The material of the resistance heating element 31 is Ag / Pd, and the material of the electrode 32 and the conductive line 34 is Ag.

The connection portion between the thermistor 332 and the conductive line 34 will be described with reference to FIGS. 4 (a) to 4 (c). FIG. 4A is an enlarged view of the vicinity of the thermistor 332, and the line widths of the thermistor 332 and the conductive line 34 are both W1. W1 is 0.5 mm. However, the line width of the conductive line 34 at the connection portion with the thermistor 332 is W2, which is wider than W1. This is also to prevent image defects from occurring due to the step generated at the connection portion between the thermistor 332 and the conductive line 34, and the details will be described below. W2 is 0.7 mm. In this embodiment, both are connected so that the thermistor 332 overlaps from above the conductive line 34. The overlapping portion OLP of both is shown by the shaded portion in FIG. 4 (a).

FIG. 4B is a cross-sectional view taken along the line L1 shown in FIG. 4A. h0 is the height of the substrate 30, h1 is the height of the overlapping portion OLP of the conductive line 34 and the thermistor 332 as the first height, and h2 is the height of the conductive line 34 as the second height. ing.

Further, g0 is the height of the second protective layer 36 in an empty portion on the substrate 30, g1 is the height of the second protective layer 36 above the overlapping OLP portion, and g2 is above the conductive line 34 portion. The height of the second protective layer 36 is shown. The thermistor 332 and the conductive line 34 are set to have the same thickness, and both have a thickness of 7 μm. Therefore, h1-h0 = 14 μm and h2-h0 = 7 μm. Further, the difference in height g0 to g2 (step size) of the second protective layer 36 is substantially the same as the difference in height h0 to h2 (step size).

In the L1 cross section, as a gradient relaxation portion having a height (second height) h2 between the substrate 30 having a height h0 and the overlapping portion OLP having a height (first height) h1. There is a conductive line 34. Therefore, the change in height from the surface of the substrate 30 to the surface of the overlapping portion OLP is gradual, and the change in the height of the surface of the second protective layer 36 in the direction D1 is also gradual. The thickness of the second protective layer 36 is set to 20 μm.

As shown in FIG. 4B, in the cross section of the line L1, in the vicinity of the thermistor 332, there is no region that changes from the height h0 to the height h1 without passing through the region of the height h2. When the height h0 changes to the height h1, a conductive line 34 having a second height h2 always exists between the two as a gradient relaxation portion. The heater 12 of this example has a cross-sectional structure in the line L1 similar to that in the vicinity of the thermistor 332 in the region near the thermistor 331 and the region near the thermistor 333. It should be noted that the cross-sectional structure of the line L1 in the vicinity of all thermistors does not necessarily have to be the above-mentioned structure. The structure in the vicinity of at least one thermistor that needs to suppress the change in the height of the surface of the second protective layer 36 may be the above-mentioned structure. Further, in this embodiment, the length L34 in the direction D1 of the portion of the conductive line 34 that is the gradient relaxation portion (excluding the portion that is the overlapping portion OLP) is 0.5 mm or more.

FIG. 4 (c) is a cross-sectional view taken along the line F1 shown in FIG. 4 (a). As described above, the line width W2 of the connection portion of the conductive line 34 with the thermistor 332 is wider than the width W1. Therefore, in the cross section of the line F1, in the vicinity of the thermistor 332, there is no region that changes from the height h0 to the height h1 without passing through the region of the height h2. When the height h0 changes to the height h1, a conductive line 34 having a second height h2 always exists between the two as a gradient relaxation portion. Therefore, the change in the height of the surface of the second protective layer 36 in the direction D2 is also gradual.

The heater 12 of this example has a cross-sectional structure in the line F1 similar to that in the vicinity of the thermistor 332 in the region near the thermistor 331 and the region near the thermistor 333. It should be noted that the cross-sectional structure at the line F1 in the vicinity of all thermistors does not necessarily have to be the above-mentioned structure. The structure in the vicinity of at least one thermistor that needs to suppress the change in the height of the surface of the second protective layer 36 may be the above-mentioned structure. Further, in this embodiment, the length F34 in the direction D2 of the portion of the conductive line 34 that is the gradient relaxation portion (excluding the portion that is the overlapping portion OLP) is 0.1 mm or more.

The heater 12 of this example has a total of three thermistors, but if a heater having one thermistor or a heater having four or more thermistors is also provided with the above-mentioned gradient relaxation portion, the second protective layer 36 is provided. The change in the height of the surface of the can be made gentle.

Next, the heater of the comparative example will be described with reference to FIG. The heater of Comparative Example 1 shown in FIG. 5 also has three thermistors. The arrangement location of the three thermistors is the same as that of the heater 12 of the first embodiment, and the thickness of the thermistor, the conductive line and the thickness are also the same as those of the first embodiment.

The thermistors 334, 335, and 336 of the heater shown in FIG. 5 are arranged so that the long side of the thermistor is parallel to the direction D2. Further, the thermistor and the conductive line 34 are connected so that the two connection positions of the thermistor and the conductive line 34 are arranged in a direction parallel to the direction D2.

Next, the connection portion between the thermistor 335 and the conductive line 34 in Comparative Example 1 will be described with reference to FIG. 6 (a) is an enlarged view of the vicinity of the thermistor 335 of the heater of Comparative Example 1, FIG. 6 (b) is a sectional view taken along line L2 of FIG. 6 (a), and FIG. 6 (c) is FIG. 6 (a). It is sectional drawing in line F2. The line widths of the thermistor 335 and the conductive line 34 are both W1.

PH1 and PH2 show a path in which the height changes from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Since the conductive line 34 as the gradient relaxation portion having the second height h2 exists in the path PH1, the height change from the substrate height h0 to the height h1 of the overlapping portion OLP is gradual. However, since the path PH2 does not have a gradient relaxation portion and directly changes from the substrate height h0 to the height h1 of the overlapping portion OLP, the height gradient becomes large. Therefore, even on the surface of the second protective layer 36 corresponding to the path PH2, the height suddenly changes from the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the overlapping portion OLP portion. do. For this reason, fixing defects and glossy streaks due to the size of the unevenness on the surface of the second protective layer 36 are likely to occur.

The path PH3 and the path PH4 also show a path in which the height changes from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. In both the path PH3 and the path PH4, there is no gradient relaxation portion, and the height directly changes from the substrate height h0 to the height h1 of the overlapping portion OLP, so that the gradient is large. Along with the magnitude of this gradient, even on the surface portion of the second protective layer 36 corresponding to the paths PH3 and PH4, the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the overlapping portion OLP portion. The height changes suddenly. For this reason, fixing defects and glossy streaks due to the size of the unevenness on the surface of the second protective layer 36 are likely to occur.

As described above, in Comparative Example 1, in both the directions D1 and D2, there is a region where the height h0 changes to the height h1 without passing through the region of the height h2. There is a part where the gradient relaxation part does not exist. Further, the heater of Comparative Example 1 does not have a gradient relaxation portion even in a direction other than the in-plane directions D1 and D2 in which the thermistor and the conductive line are installed (for example, the direction D3 shown in FIG. 6A). There is an area. On the other hand, between the region of the height h0 and the region of the height h1 of the heater 12 of the first embodiment, in all the directions other than the directions D1 and D2 in the plane where the thermistor and the conductive line are installed. , There is a gradient relaxation section that is a region of height h2.

Next, the effect of the heater of this example was verified under the conditions shown below. The recording material P used was plain paper "HP Laser Jet 90 g" and glossy paper "HP Brochure Paper 200 g". The image after the toner image formed on the recording material P was heated and fixed on the recording material P was compared between the case where the heater of this example was used and the case where the heater of the comparative example was used. When plain paper was used as the recording material P, the transport speed was set to 300 mm / sec, and when glossy paper was used, the transport speed was set to 75 mm / sec.

The results are shown in Table 1. When the heater of Comparative Example 1 was used, image defects occurred on both plain paper and glossy paper, but when the heater of this example was used, a good image was obtained over the entire area of the recording material P. Was done.

In Comparative Example 1, as shown in FIG. 7, the toner image T is insufficiently fixed or has a low gloss in the regions Y1, Y2, and Y3 corresponding to the installation positions of the thermistors 334, 335, and 336. Glossy streaks occurred.

By using the heater configuration of this embodiment as described above, it is possible to suppress the occurrence of image defects. The reason will be explained below.

The reason why the image defect occurs in the comparative example is that the heat and pressure locally applied to the toner image are insufficient due to the large step of the heater sliding surface in the overlapping portion OLP of the conductive line and the thermistor.

As described above, in the present embodiment, in the direction D1 and the direction D2, a gradient relaxation portion is always provided so as not to cause a large step around the overlapping portion OLP of the conductive line and the thermistor. Then, as described above, the generation of the region where the heat and pressure applied to the toner image locally are insufficient is suppressed. As a result, the effect of suppressing the occurrence of image defects can be obtained.

In the apparatus configuration of this embodiment, it has been confirmed that when the height of one step exceeds about 10 μm, the frequency of image defects increases. In Example 1, since the height of one step (h1-h2) is about 7 μm, the effect of suppressing image defects was obtained. Therefore, it is preferable to provide a gradient relaxation portion so that the step is 10 μm or less.

Next, a modified example of this embodiment will be given. FIG. 8 shows two examples in which the connection directions of the thermistor and the conductive line differ from those of the first embodiment by 90 °.

(Modification 1)
Modification 1 shown in FIG. 8A has a configuration in which the periphery of the connection portion between the thermistor 332 and the conductive line 34 of the first embodiment is rotated by 90 °.

The cross sections of the direction D1 and the direction D2 including the overlapping portion OLP are configured to be interchanged with those of the first embodiment, and the effects obtained in the respective cross sections are the same as those of the first embodiment.

(Modification 2)
Modification 2 shown in FIG. 8B has a configuration in which the relationship between the line width of the thermistor and the conductive line at the connection portion is different from that of Example 1 and Modification 1.

In the second modification, the line width of the thermistor 332 is set to W3, which is wider than the line width W1 of the conductive line 34. In this configuration, it is the conductive line 34 that functions as the gradient relaxation section in the transport direction as in Example 1 and Modification 1, but it is Example 1 and the modification that functions as the gradient relaxation section in D1. Unlike 1, it is a thermistor 332. Since the thickness of the thermistor and the conductive line is the same, the same effect as that of the first embodiment and the first modification can be obtained.

In the above example, a part of the conductive line and the thermistor functioned as a gradient relaxation part. However, as the gradient relaxation portion, for example, an insulator having a second height or the like can be used.

As described above, the heater of this embodiment includes a substrate, a heating element provided on the substrate, a temperature detection element provided on the substrate, a conductive line connected to the temperature detection element, and temperature detection. It has a protective layer that covers the element and the conductive line. This heater is used in a fixing device that fixes a toner image formed on a recording material to the recording material. The connection portion between the temperature detecting element and the conductive line is provided with an overlapping portion in which both are overlapped. In the cross section when the heater is cut parallel to the longitudinal direction and on the surface passing through the temperature detection element, the gradient relaxation in which the step is smaller than the step from the surface of the substrate to the surface of the overlapping portion next to the overlapping portion. A part is provided. Further, in the cross section when the heater is cut parallel to the lateral direction and on the surface passing through the temperature detection element, there is a step next to the overlapping portion rather than a step from the surface of the substrate to the surface of the overlapping portion. A small gradient relaxation section is provided.

(Example 2)
Next, Example 2 will be described. The feature of this embodiment is that the gradient relaxation portion is always provided only in the direction D1. Unlike the first embodiment, the direction D2 has a configuration in which a gradient relaxation portion does not exist or a portion thereof does not exist.

The basic configuration and operation of the image forming apparatus 100 and the image heating apparatus 7 are the same as those in the first embodiment. Only the shape on the sliding surface side of the heater 12 mounted on the image heating device 7 is different.

(Characteristics of heater)
The characteristics of the heater used in the second embodiment will be described. FIG. 9A shows the back surface side of the substrate 30, and has the same shape as that of the first embodiment shown in FIG. 3A. FIG. 9B shows the sliding surface side, and has the same configuration as that of the first embodiment shown in FIG. 3B except for the portion described below. The difference from the first embodiment will be described with reference to FIG.

FIG. 10A is an enlarged view of the vicinity of the thermistor 338, and the line widths of the thermistor 338 and the conductive line 34 are both W1. In the second embodiment, W1 is 0.5 mm, and unlike the first embodiment, the line width of the conductive line 34 at the connection portion with the thermistor 338 is also W1. Others are the same as in Example 1. 10 (b) is a cross-sectional view taken along the line L3 shown in FIG. 10 (a), which is exactly the same as FIG. 4 (b) described in the first embodiment. FIG. 10 (c) is a cross-sectional view taken along the line F3 shown in FIG. 10 (a).

As described above, in the second embodiment, the line widths of the thermistor 338 and the conductive line 34 at the connection portion are the same W1, and both are exactly overlapped with each other. Therefore, unlike the cross section of the line F1 of the first embodiment shown in FIG. 4C, the cross section of the line F3 does not have a gradient relaxation portion. Therefore, in Example 2, in the cross section of the line F3, the change in height on the surface of the second protective layer 36 is steeper than in Example 1.

When the confirmation was performed under the same conditions as the effect confirmation of Example 1, neither fixing failure nor gloss streaks occurred in Example 2. This result shows that if there is a gradient relaxation portion in the direction D1, image defects can be avoided. The reason is as follows.

In the second embodiment, although there is a sharp step in the direction D2, the contact pressure with respect to the inner peripheral surface of the film is lowered, the pressure is lower than the other portions, and the heat transfer is deteriorated only for a moment. Therefore, the influence on the image is small, and image defects such as fixing defects and gloss streaks do not occur.

As described above, it is preferable to provide the conductive line 34 so that the gradient relaxation portion appears at least in the cross-sectional structure of the line L3.

Next, as a modification of the present embodiment, there is a configuration in which the gradient relaxation portion is always provided in the direction D1 although there is a portion in the direction D2 in which the gradient relaxation portion does not exist. FIG. 11 shows two examples of the modification of the second embodiment, the modification 3 and the modification 4.

(Modification 3)
In the modified example 3 shown in FIG. 11A, the thermistor 338 is diagonally arranged, and the two connecting portions with the conductive line 34 are also diagonally arranged. However, as shown in the figure, the thermistor 338 is not a rectangle but a parallelogram. Further, the shape near the connection portion of the conductive line 34 is also a parallelogram shape, and the overlapping portion OLP is also a parallelogram shape. By doing so, a part of the conductive line 34 always exists as the gradient relaxation portion in the direction D1.

On the other hand, in the direction D2, the conductive line 34 or the thermistor 338 is present as the gradient relaxation portion in most parts, but the gradient relaxation portion is not present at the points PA and PB in the figure. However, since it is limited to the above two points, the influence on the image is smaller than that in Example 2, and no image defect occurs in the confirmation under the same conditions as before.

(Modification example 4)
Modification 4 shown in FIG. 11B has a configuration in which the relationship between the width of the thermistor 338 and the conductive line 34 at the connection portion is opposite to that of modification 3. In the direction D1, a part of the thermistor 338 always exists as a gradient relaxation portion.

On the other hand, in the direction D2, the conductive line 34 or thermistor 338 is present as the gradient relaxation portion in most of the parts, but the gradient relaxation portion is not present at the points of PC and PD in the figure. However, since it is limited to the above two points, the influence on the image is smaller than that in Example 2, and no image defect occurs in the confirmation under the same conditions as before.

The shape of the resistance heating element 31 is not limited to the shapes shown in the present embodiment and the modified examples. For example, as shown in FIG. 12, a plurality of resistance heating elements 31 may be provided in the longitudinal direction of the heater, and each resistance heating element 31 may be independently controlled. The resistance heating element 31 shown in FIG. 12 is divided into five regions. Then, each resistance heating element 31 can be independently controlled by inputting electric power from an external power source via the electrodes 32 provided in each region. A thermistor is provided for each region on the sliding surface side of the heater with the film 11.

12 Heater 31 Resistance heating element 331 to 339 Thermistor 34 Conductive line

Claims (4)

With the board
A heating element provided on the substrate and
The temperature detection element provided on the substrate and
The conductive line connected to the temperature detection element and
The temperature detecting element, the protective layer covering the conductive line, and the
In a heater used for a fixing device that has a toner image formed on a recording material and fixes the toner image on the recording material.
The connection portion between the temperature detecting element and the conductive line is provided with an overlapping portion in which both are overlapped in the thickness direction of the heater .
The conductive line is a line having a substantially constant width over the stretching direction.
In the cross section when the heater is cut in a plane parallel to the longitudinal direction and passing through the temperature detecting element, the temperature detecting element does not overlap next to the overlapping portion in the longitudinal direction , and the substrate is not overlapped. A gradient relaxation portion is provided in which the step is smaller than the step from the surface of the above to the surface of the overlapping portion .
In the cross section when the heater is cut parallel to the lateral direction and on the surface passing through the temperature detection element, the width of the conductive line is constant next to the overlapping portion in the lateral direction. A heater characterized in that the temperature detection elements do not overlap due to being larger than the width, and a gradient relaxation portion having a step smaller than the step from the surface of the substrate to the surface of the overlapping portion is provided . Cylindrical film and
A heater that contacts the inner surface of the film and
In a fixing device for fixing a toner image formed on a recording material by the heat of the heater through the film to the recording material.
The fixing device according to claim 1 , wherein the heater is the heater, and the side of the protective layer of the heater comes into contact with the inner surface of the film . With the board
A heating element provided on the substrate and
The temperature detection element provided on the substrate and
The conductive line connected to the temperature detection element and
The temperature detecting element, the protective layer covering the conductive line, and the
In a heater used for a fixing device that has a toner image formed on a recording material and fixes the toner image on the recording material.
The connection portion between the temperature detecting element and the conductive line is provided with an overlapping portion in which both are overlapped in the thickness direction of the heater.
The conductive line is a line having a substantially constant width over the stretching direction.
In the cross section when the heater is cut parallel to the lateral direction and on the surface passing through the temperature detecting element, the temperature detecting element does not overlap next to the overlapping portion in the lateral direction. A gradient relaxation portion having a smaller step than the step from the surface of the substrate to the surface of the overlapping portion is provided.
In the cross section when the heater is cut in a plane parallel to the longitudinal direction and passing through the temperature detection element, the width of the conductive line is wider than the constant width next to the overlapping portion in the longitudinal direction. The heater is characterized in that the temperature detection elements do not overlap due to the large size, and a gradient relaxation portion having a step smaller than the step from the surface of the substrate to the surface of the overlapping portion is provided. Cylindrical film and
A heater that contacts the inner surface of the film and
In a fixing device for fixing a toner image formed on a recording material by the heat of the heater through the film to the recording material.
The fixing device according to claim 3, wherein the heater is the heater, and the side of the protective layer of the heater comes into contact with the inner surface of the film.

Images