JP7136688B2 - heater and fuser - Google Patents

Description

The disclosed embodiments relate to heaters and fixing devices.

A heater provided with a protective layer that physically or chemically protects a heat generating portion on a substrate is known.

JP-A-2009-9720

However, in the heater described above, there is a concern that the protective layer may peel off from the substrate or the heat-generating portion due to the difference in thermal expansion coefficient.

One aspect of the embodiments has been made in view of the above, and an object thereof is to provide a heater and a fixing device in which the protective layer is less peeled off.

A heater according to one aspect of an embodiment includes a substrate, a heat generating portion, an electrode, and a protective layer. The substrate has a first side. The heat generating portion is located on the first surface. An electrode is positioned on the first surface and electrically connected to the heat generating portion. The protective layer includes a void region having a plurality of voids at an edge in a thickness direction facing the substrate, and covers the first surface.

The heater and the fixing device according to one aspect of the embodiment cause less peeling of the protective layer.

FIG. 1 is a schematic diagram (front view) showing a printer according to an embodiment. FIG. 2 is a cross-sectional view schematically showing the fixing device according to the embodiment. FIG. 3 is a bottom view schematically showing the heater according to the embodiment. FIG. 4 is a sectional view taken along line IV-IV of FIG. 5 is a cross-sectional view taken along line VV of FIG. 3. FIG. 6 is a partially enlarged view of FIG. 4. FIG. 7 is a partially enlarged view of FIG. 5. FIG. FIG. 8 is a cross-sectional view schematically showing a heater according to a first modified example of the embodiment; FIG. 9 is a cross-sectional view schematically showing a heater according to a second modified example of the embodiment;

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below. In each figure, "Fr" indicates "front", "Rr" indicates "rear", "L" indicates "left", "R" indicates "right", and "U" indicates "Upper" is indicated and "D" indicates "Lower".

[Overall Configuration of Printer]
A printer 1 as an example of an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram (front view) showing the printer 1. FIG.

The printer 1 includes an apparatus main body 2 having a substantially rectangular parallelepiped appearance. The printer 1 has a paper feed cassette 3 in the lower part of the device main body 2 for storing sheets S (medium) such as plain paper. The printer 1 has a paper discharge tray 4 on the upper surface of the device main body 2 . Note that the sheet S is not limited to being made of paper, and may be made of resin or the like.

The printer 1 also includes a paper feeding device 5 , an image forming device 6 , and a fixing device 7 . The paper feeder 5 is positioned at the upstream end of the transport path 8 extending from the paper feed cassette 3 to the paper discharge tray 4 . The imaging device 6 is positioned in the middle of the transport path 8 . The fixing device 7 is positioned downstream of the transport path 8 .

The imaging device 6 includes a toner container 10 , a drum unit 11 and an optical scanning device 12 . The toner container 10 contains, for example, black toner (developer). The drum unit 11 includes a photosensitive drum 13 , a charging device 14 , a developing device 15 and a transfer roller 16 . The transfer roller 16 contacts the photosensitive drum 13 from below to form a transfer nip. The toner may be a two-component developer in which toner and carrier are mixed, or may be a one-component developer composed of magnetic toner.

A control device (not shown) of the printer 1 appropriately controls each device and executes image forming processing as follows. The charging device 14 charges the surface of the photosensitive drum 13 . The photosensitive drum 13 receives scanning light emitted from the optical scanning device 12 and carries an electrostatic latent image. The developing device 15 uses the toner supplied from the toner container 10 to develop the electrostatic latent image on the photosensitive drum 13 into a toner image. The sheet S is fed from the sheet feeding cassette 3 to the conveying path 8 by the sheet feeding device 5, and the toner image on the photosensitive drum 13 is transferred onto the sheet S passing through the transfer nip. The fixing device 7 fixes the toner image on the sheet S. As shown in FIG. After that, the sheet S is ejected onto the paper ejection tray 4 .

[Fixing device]
Next, the fixing device 7 will be described with reference to FIGS. 2 to 5. FIG. FIG. 2 is a cross-sectional view schematically showing the fixing device 7. As shown in FIG. FIG. 3 is a bottom view schematically showing the heater 23. FIG. FIG. 4 is a sectional view taken along line IV-IV of FIG. FIG. 5 is a cross-sectional view taken along line VV of FIG.

As shown in FIG. 2 , the fixing device 7 includes a fixing belt 21 , a pressure roller 22 and a heater 23 . The fixing belt 21 and the pressure roller 22 are positioned inside the housing 20 (see FIG. 1). The heater 23 is a heat source for heating the fixing belt 21 .

<Fixing belt>
The fixing belt 21, which is an example of a fixing member, is an endless belt and has a substantially cylindrical shape elongated in the front-rear direction (axial direction). The surface layer of the fixing belt 21 is made of, for example, a heat-resistant and elastic synthetic resin material such as polyimide resin. The fixing belt 21 is arranged inside and above the housing 20 . A pair of substantially cylindrical caps (not shown) are attached to both ends of the fixing belt 21 in the axial direction. A belt guide (not shown) for holding the substantially cylindrical shape of the fixing belt 21 may be provided inside the fixing belt 21 .

A pressing member 24 is positioned inside the fixing belt 21 . The pressing member 24 has a substantially square tubular shape that is elongated in the axial direction. The pressing member 24 axially penetrates the fixing belt 21 (and the cap) and is supported by the housing 20 . The fixing belt 21 described above is rotatably supported with respect to the pressing member 24 . The pressing member 24 is made of, for example, a metal material.

<Pressure roller>
The pressure roller 22, which is an example of a pressure member, has a substantially cylindrical shape elongated in the front-rear direction (axial direction). The pressure roller 22 is positioned inside the housing 20 and below. The pressure roller 22 includes a metal core 22A and an elastic layer 22B such as silicone sponge laminated on the outer peripheral surface thereof. Both ends of the cored bar 22A in the axial direction are rotatably supported by the housing 20 . A drive motor (not shown) is connected to the cored bar 22A via a gear train or the like, and the pressure roller 22 is rotationally driven by the drive motor. The fixing device 7 includes a pressure adjusting section (not shown) that moves the pressure roller 22 up and down to adjust the contact pressure of the pressure roller 22 against the fixing belt 21 . A pressure area N is formed between the fixing belt 21 and the pressure roller 22 by pressing the pressure roller 22 against the fixing belt 21 . Further, the pressurized region N is from a position on the upstream side in the conveying direction of the sheet S where the pressure is 0 Pa to a position on the downstream side in the conveying direction of the sheet S where the pressure again becomes 0 Pa via a position where the maximum pressure is applied. pointing to the area.

<Heater>
The heater 23, which is an example of a heater, is a substantially rectangular plate member elongated in the front-rear direction (axial direction). As shown in FIG. 2, the heater 23 is fixed to the lower surface of the pressing member 24 via the holding member 25 . The holding member 25 has a semicircular cross-section perpendicular to the axial direction and is elongated in the axial direction. The holding member 25 is curved along the lower inner surface of the fixing belt 21 . The holding member 25 is made of, for example, a heat-resistant material.

As shown in FIGS. 3-5, the heater 23 includes a substrate 30, a heat insulating layer 31, and a heat generating contact portion 32. As shown in FIG. The substrate 30 is fixed to the bottom surface of the holding member 25 . The heat insulating layer 31 is located on the lower surface as the first surface of the substrate 30 . The heat generating contact part 32 is located on the first surface of the substrate 30 and located on the lower surface of the heat insulating layer 31 .

In this specification, the "passing direction (second direction)" is a direction that intersects the axial direction (first direction) and is the direction in which the sheet S passes through the pressure area N of the fixing device 7 ( direction). Also, in the following description, the terms "upstream" and "downstream" and like terms refer to the concept of "upstream" and "downstream" and like terms in the direction of passage.

The heater 23 is held on the lower surface of the holding member 25 . A heating contact portion 32 of the heater 23 faces the pressure roller 22 and is a portion that contacts the inner surface of the fixing belt 21 . A contact area between the fixing belt 21 and the pressure roller 22 is a pressure area N. FIG. The heater 23 is positioned corresponding to the pressure area N with the fixing belt 21 interposed therebetween (see FIG. 2), and has a function of heating the fixing belt 21 . Note that the housing 20 shown in FIG. 1 may have a temperature sensor (not shown) for detecting the surface temperature of the fixing belt 21 or the temperature of the heater 23 .

As shown in FIGS. 3 to 5, the substrate 30 is made of an electrically insulating material such as ceramic and has a substantially rectangular plate shape elongated in the axial direction. Both upper and lower surfaces of the substrate 30 are substantially smooth.

The heat insulating layer 31 is laminated (film-formed) on the first surface (entire lower surface) of the substrate 30 . The heat insulating layer 31 is made of, for example, a material having electric insulation and low thermal conductivity, such as ceramic or glass. The heat insulating layer 31 has a function of regulating the transfer of heat generated at the heat generating contact portion 32 to the substrate 30 .

The heat generating contact 32 is located on the first surface of the substrate 30 . Specifically, the heat generating contact portion 32 is laminated on one surface (lower surface) of the heat insulating layer 31 arranged on the substrate 30 . Heat-generating contact portion 32 includes heat-generating portion 40 , electrode 50 , and protective layer 60 .

The heat generating portion 40 includes a plurality of heat generating portions 41-43. The heat generating part 40 is located on the lower surface of the heat insulating layer 31 . As shown in FIG. 3, the plurality of heat generating portions 41 to 43 are composed of a plurality of resistance heating elements 45 arranged in a row in the axial direction. Each of the plurality of resistance heating elements 45 has a substantially rectangular shape elongated in the passing direction. All resistive heating elements 45 may have approximately the same size. The heat generating portions 41 to 43 are made of a conductive material such as a metal having a higher resistance value than the electrode 50, for example.

The heating portion 41 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-to-rear width of the first size sheet S passing through the pressing area N. As shown in FIG. The heating portion 42 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-to-rear width of the second size sheet S passing through the pressing area N. As shown in FIG. The heating portion 43 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-to-rear width of the third size sheet S passing through the pressing area N. As shown in FIG.

The plurality of resistance heating elements 45 may have the same dimension in the axial direction and the same dimension in the passing direction. In this specification, the term "same size" does not require that the size be exactly the same, but means that a slight manufacturing error is allowed.

As shown in FIG. 3, electrode 50 includes a plurality of electrodes 51-54. The plurality of electrodes 51 to 54 are made of, for example, a conductive material (having a lower resistance value than the resistance heating element 45) such as metal. A plurality of electrodes 51 to 54 are positioned on the bottom surface of the heat insulating layer 31 . A plurality of electrodes 51 to 54 are electrically connected to both sides of the heating portions 41 to 43 in the passage direction. Specifically, the electrode 50 includes a plurality of (for example, three) individual electrodes 51 to 53 respectively connected to the plurality of heat generating portions 41 to 43, and a common electrode 54 commonly connected to the heat generating portions 41 to 43. including.

The individual electrode 51 is connected to the downstream end portion (right end portion) of each resistance heating element 45 that constitutes the heating portion 41 . Similarly, the other individual electrodes 52 and 53 are connected to the downstream ends of the resistance heating elements 45 that constitute the heating portions 42 and 43, respectively. On the other hand, the common electrode 54 is connected to the upstream ends (left ends) of all the resistance heating elements 45 .

In this specification, the individual electrodes 51 to 53 and the common electrode 54 may be referred to as the "electrode 50" in the following description. Similarly, in the description below common to the heat generating units 41 to 43, the heat generating unit 40 may be referred to.

Each of the electrodes 51-54 has lead portions 51B-54B and electrode end portions 51A-54A. The lead portions 51B to 54B are portions extending from the portions (connection portions 51C to 54C) connected to the heat generating portions 41 to 43, respectively, toward the electrode terminal portions 51A to 54A, respectively. In other words, the lead portions 51B to 54B are located between the axial outer ends of the heat generating portions 41 to 43 and the electrode terminal portion 54A. The electrode terminal portions 51A to 54A are connected to the tip portions of the lead portions 51B to 54B, respectively. The electrode terminal portions 51A to 54A are terminals for electrically connecting to an external device such as a power source.

Specifically, the lead portion 51B of the individual electrode 51 extends to one side (upper side) in the axial direction from the connection portion 51C with the heat generating portion 41 . The electrode terminal portion 51A is connected to the end portion of the lead portion 51B and is bent upstream (to the left). A lead portion 52B of the individual electrode 52 and a lead portion 53B of the individual electrode 53 extend to one side (upper side) in the axial direction from connection portions 52C and 53C with the heat generating portions 42 and 43, respectively. The electrode terminal portions 52A and 53A are connected to lead portions 52B and 53B, respectively. The electrode terminal portion 52A is located axially inside the electrode terminal portion 51A, and the electrode terminal portion 53A is located axially inside the electrode terminal portion 52A. On the other hand, the lead portion 54B of the common electrode 54 extends to one side (upper side) in the axial direction from the connection portion 54C with the heat generating portions 41-43. The electrode terminal portion 54A is connected to the lead portion 54B. The electrode terminal portion 54A is located axially inward of the electrode terminal portion 53A.

As shown in FIGS. 4 and 5, the protective layer 60 covers the heating portion 40 and the electrodes 50 (excluding the electrode terminal portions 51A to 54A). The protective layer 60 is made of, for example, a material such as ceramic that has electrical insulation properties and a small sliding frictional force with respect to the fixing belt 21 . A first surface 60</b>C of the protective layer 60 constitutes a sliding surface that contacts the inner surface of the fixing belt 21 . In addition, the protective layer 60 is laminated so as to cover the first surface of the substrate 30 even in a portion where the heating portion 40 and the electrode 50 are not laminated.

For manufacturing the heater 23 described above, for example, a film forming technique such as sputtering, a printed circuit board manufacturing technique, a screen printing technique, or a combination of these techniques can be used. For example, the heat insulating layer 31 and the heat generating contact portion 32 (heat generating portion 40, electrode 50, protective layer 60) may be deposited on the substrate 30 by sputtering. Further, for example, the heat-insulating layer 31 and the heat-generating contact portion 32 may be formed on the substrate 30 by repeating processes such as exposure, development, etching, peeling, lamination, etc. using a photomask, which is a manufacturing technology for printed circuit boards. good. Further, for example, the heat insulating layer 31 and the heat generating contact portion 32 may be formed by applying (screen printing) an electrically insulating paint or a conductive paint onto the substrate 30 . With these manufacturing methods, the heat insulating layer 31, the heat generating portion 40, and the electrodes 50 can be formed with high accuracy.

The electrodes 50 of the heater 23, the drive motor, etc. are electrically connected to a power source (not shown) via various drive circuits (not shown). The heater 23 (electrode 50), drive motor, temperature sensor, etc. are electrically connected to the controller of the printer 1 through various circuits. The control device controls connected devices and the like.

[Function of Fixing Device]
Here, mainly referring to FIG. 2, the operation (fixing process) of the fixing device 7 will be described.

First, the control device drives and controls the drive motor and the heater 23 . The pressure roller 22 is rotated by receiving the driving force of the drive motor, and the fixing belt 21 is rotated following the pressure roller 22 (see solid-line thin arrow in FIG. 2). Each resistance heating element 45 generates heat by passing current in the passing direction between the plurality of electrodes 50 sandwiching the heating portion 40 . Thereby, the pressure area N of the fixing belt 21 is heated.

At this time, the control device controls the heating units 41 to 43 (see FIG. 3) that generate heat according to the size of the sheet S. FIG. For example, when the maximum size sheet S that can be processed by the fixing device 7 passes through the pressure area N (see FIG. 2), the control device supplies power to all the heat generating units 41 to 43, 41-43 are exothermed. Further, for example, when a medium size sheet S smaller than the maximum size passes through the pressure area N, the control device heats the heat generating portions 41 and 42, and the small size sheet S smaller than the medium size is pressed. When passing through the pressure region N, the heating portion 41 is caused to generate heat. Accordingly, it is possible to match the size of the sheet S and heat only the necessary portion of the fixing belt 21 (pressing area N). As a result, excessive temperature rise of the fixing belt 21 can be reduced.

The temperature sensor detects the surface temperature of the fixing belt 21 and sends a detection signal to the control device through the input circuit. When the control device receives a detection signal from the temperature sensor indicating that the set temperature (for example, 150 to 200° C.) has been reached, the control device controls the heater 23 so as to maintain the set temperature while performing the image forming process already described. Start execution. The sheet S to which the toner image has been transferred enters the housing 20, and the fixing belt 21 heats the toner (toner image) on the sheet S passing through the pressure area N while rotating forward about its axis. The pressure roller 22 presses the toner on the sheet S passing through the pressure area N while rotating about its axis. Then, the toner image is fixed on the sheet S. Then, the sheet S on which the toner image has been fixed is delivered to the outside of the housing 20 and ejected onto the paper ejection tray 4 .

By the way, the heater 23 is subjected to thermal stress caused by temperature changes. In particular, the protective layer 60 covering the heat-generating portion 40 and the electrodes 50 may peel off at the interface with the heat-generating portion 40 and the electrodes 50 due to the difference in thermal expansion coefficient between the heat-generating portion 40 and the electrodes 50. . Therefore, as shown in FIG. 4, the fixing device 7 (heater 23) according to the present embodiment has a void region 60A having a plurality of voids 70 at the end of the protective layer 60 facing the heat generating portion 40. Since the stress generated in the protective layer 60 is relaxed in the vicinity of the interface with the heat-generating portion 40, the peeling of the protective layer 60 is less.

As shown in FIG. 4 , the protective layer 60 in contact with the heat generating portion 40 has a void region 60A at the end facing the heat generating portion 40 . The void region 60A has an area ratio of the voids 70 of 10% or more and 35% or less, and may be 16% or more and 29% or less. With such a configuration, peeling of the protective layer 60 from the heat generating portion 40 can be reduced while ensuring a contact area with the heat generating portion 40 . Here, the area ratio of the voids 70 refers to the area ratio of the voids 70 measured by image processing in an enlarged photograph (SEM) of the cross section of the heater 23 cut in the thickness direction. Specifically, a predetermined area 65 (with respect to the thickness h2 of the protective layer 60, the thickness h1 from the end face 60B = 0.1 x h2 (for example, the thickness h1 = 9.6 µm), the width L1 = 20 x h2 (for example, , width L1 = 190 μm)), the outline of the void 70 is traced, and the area ratio measured by dividing the total area of the void 70 by the area of the area 65 is measured for each different area 65 (for example, five locations ), and the average value is defined as the area ratio of the voids 70 in the void region 60A.

In addition, the void region 60A may have voids 70 with an average diameter of 10 μm or less, for example, 1 μm or more and 5 μm or less, further 2.63 μm or more and 3.81 μm or less. With such a configuration, peeling of the protective layer 60 from the heat generating section 40 can be reduced while ensuring a contact area between the protective layer 60 and the heat generating section 40 . Here, the average diameter of the void region 60A is obtained by measuring the diameters of the voids 70 having a diameter of 1 μm or more in the predetermined area 65 and averaging the measured values. The diameter of the void 70 is defined as the equivalent diameter of a circumscribed circle that circumscribes the outer shape of the void 70 .

Here, as the thickness h2 of the protective layer 60 increases, the stress generated at the interface with the heat generating portion 40 tends to increase. Therefore, the void region 60</b>A may have voids 70 whose average diameter is 10% or less of the thickness h<b>2 of the protective layer 60 . With such a configuration, the stress generated in the protective layer 60 can be relaxed, and peeling of the protective layer 60 from the heat generating portion 40 can be reduced.

Moreover, as shown in FIG. 5 , the protective layer 60 in contact with the electrode 51 as an example of the electrode 50 may have a void region 60A at the end facing the electrode 51 . With such a configuration, the stress generated in the protective layer 60 can be relaxed in the vicinity of the interface with the electrode 50, so peeling of the protective layer 60 is reduced. That is, even when the material forming the electrode 50 and the material forming the protective layer 60 have different coefficients of thermal expansion, the void region 60</b>A can relax the stress generated in the protective layer 60 .

The thickness h4 of the protective layer 60 shown in FIG. 5 may be the same as or different from the thickness h2 of the protective layer 60 shown in FIG. The thickness h3 and width L2 of the area 66 used for measuring the porosity of the void region 60A and the average diameter of the voids 70 can be defined based on the thickness h4 as in the case of the area 65 shown in FIG. .

Next, the voids 70 of the protective layer 60 will be further described with reference to FIGS. 6 and 7. FIG. 6 is a partially enlarged view of FIG. 4. FIG.

As shown in FIG. 6 , the void region 60A may have voids 71 that do not face the surface 401 of the heat generating portion 40 . In other words, the void 71 may be separated from the surface 401 of the heat generating portion 40 . Since the void 71 does not face the surface 401 of the heat generating portion 40 , the stress of the protective layer 60 is less likely to be transmitted to the interface with the heat generating portion 40 . Moreover, the stress in the protective layer 60 can be relieved by deformation of the voids 71 not facing the heat generating portion 40 . Moreover, the contact area between the heat generating portion 40 and the protective layer 60 does not decrease due to the presence of the voids 71, and the bonding strength between the heat generating portion 40 and the protective layer 60 does not decrease. Therefore, peeling of the protective layer 60 from the heat generating portion 40 can be reduced.

Moreover, the void region 60A may have voids 72 facing the surface 401 of the heat generating portion 40 . In other words, void 72 may be in contact with surface 401 of heat generating portion 40 . With such a configuration, the heat generated in the heat generating portion 40 can be stored directly in the voids 72 . As a result, the time required to raise the temperature of the heat generating portion 40 can be shortened, improving thermal responsiveness.

Moreover, the void region 60A may have a void 73 that communicates with the first concave portion 401a located on the surface 401 of the heat generating portion 40 . In other words, the void 73 is accommodated inside the first recess 401a. With such a configuration, not only the stress of the protective layer 60 but also the stress of the heat generating portion 40 generated at the edge of the first concave portion 401a can be relaxed. Therefore, peeling of the protective layer 60 from the heat generating portion 40 can be further reduced.

As shown in FIG. 6, the voids 70 of the protective layer 60 facing the heat generating portion 40 may include all of the one or more voids 71 to 73, or may include only some of them.

7 is a partially enlarged view of FIG. 4. FIG. As shown in FIG. 7, the electrode 50 may have a first electrode 50a and a second electrode 50b laminated in the thickness direction of the heater 23. As shown in FIG. Since the electrode 50 has the first electrode 50a and the second electrode 50b, it is possible to cope with an increase in current amount, for example. That is, the first electrode 50a can realize a fine wiring pattern, and the second electrode 50b can reduce the wiring resistance of the electrode 50 itself.

Also, the void region 60A may have voids 74 that do not face the surface of the electrode 50, that is, the surface 501 of the first electrode 50a. Such a configuration makes it difficult for the stress of the protective layer 60 to be transmitted to the interface with the electrode 50 . In addition, deformation of the voids 74 not facing the electrode 50 can relieve stress in the protective layer 60 . Moreover, the contact area between the electrode 50 and the protective layer 60 does not decrease due to the presence of the void 74, and the bonding strength between the electrode 50 and the protective layer 60 does not decrease. Therefore, peeling of the protective layer 60 from the electrode 50 can be reduced.

Also, the void region 60A may have a void 77 facing the second electrode 50b through an exposed portion 501b where a portion of the first electrode 50a is not located. With such a configuration, voids 77 having a thermal conductivity lower than that of the first electrode 50a are partially located, and heat transmitted through the protective layer 60 or the first electrode 50a is stored in the voids 77. As a result, the heat of the exothermic part 40 is less likely to be dissipated through the first electrode 50a.

The void region 60A may also have a void 78 that communicates with the second recess 502a located on the surface 502 of the second electrode 50b. With such a configuration, not only the protective layer 60 but also the stress of the electrode 50, especially the second electrode 50b generated at the edge of the second recess 502a can be relaxed. Therefore, peeling of the protective layer 60 from the electrode 50 can be further reduced.

In addition, as shown in FIG. 7, the voids 70 of the protective layer 60 facing the electrodes 50 may include all of the one or more voids 74, 77, 78, or may include only some of them. Also, the void region 60A may have a void 75 facing the surface 501 of the electrode 50 (first electrode 50a). Also, the void region 60A may have a void 76 that communicates with the third recess 501a located on the surface 501 of the first electrode 50a.

<First modification>
Although the heater 23 according to the embodiment described above has been described as having the end surface 60B of the protective layer 60 in contact with the heat generating portion 40 or the electrode 50, the present invention is not limited to this. FIG. 8 is a cross-sectional view schematically showing a heater according to a first modified example of the embodiment; As shown in FIG. 8, an intermediate layer 80 may be provided between the protective layer 60 and the heat generating portion 40. FIG. With such a configuration, the protective layer 60 is separated from the heat-generating portion 40 via the intermediate layer 80, specifically, the intermediate layer 80 is separated from the protective layer 60, or the intermediate layer 80 is damaged. and the exothermic portion 40 can be reduced.

As the material of the intermediate layer 80, an electrically insulating ceramic such as silicon nitride _{( Si3N4} ) or silicon oxide ( _SiO2 ) can be used. Also, an electrically insulating resin material that enhances the adhesion between the protective layer 60 and the heat generating portion 40 may be used. Although FIG. 8 shows an example in which the intermediate layer 80 is provided between the protective layer 60 and the heat-generating portion 40, the intermediate layer 80 may be provided between the protective layer 60 and the electrode 50 (see FIG. 9). reference).

<Second modification>
Although the heater 23 according to the embodiment described above has been described assuming that the first surface 60C of the protective layer 60 is in contact with the fixing belt 21, the present invention is not limited to this. FIG. 9 is a cross-sectional view schematically showing a heater according to a second modified example of the embodiment; As shown in FIG. 9, the protective layer 60 may have a coating layer 90 on the outer surface (first surface 60C) side. The coating layer 90 can be made of, for example, a resin material that has a smaller sliding frictional force on the fixing belt 21 than the protective layer 60 and has electrical insulation. Although FIG. 9 shows an example having the intermediate layer 80 and the covering layer 90, the intermediate layer 80 may not be provided and only the covering layer 90 may be provided. FIG. 9 shows an example in which the coating layer 90 is positioned to face the electrode 50 with the protective layer 60 interposed therebetween. may have.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the scope of the invention. For example, in the above-described fixing device 7 according to the present embodiment, the heating units 41 to 43 correspond to three sizes of sheets S, but the present invention is not limited to this. The heating part 40 (resistance heating element 45) may be formed so as to correspond to two or more sizes of sheets S. As shown in FIG. Further, in the fixing device 7 according to the present embodiment, the sheet S is configured to pass through the center of the pressure region N in the axial direction. It may be configured such that the sheet S passes through the position. Further, in the fixing device 7 according to the present embodiment, an example in which the drawer portions 51B to 54B extend long in the axial direction has been shown, but the present invention is not limited to this. For example, the drawer portions 51B to 54B may have portions extending upstream (left side) or downstream (right side).

Further, in the present embodiment, the direction in which the heat generating portions 41 to 43 extend is the lateral direction of the substrate 30, but the configuration is not limited to this. For example, the individual electrodes 51 to 53 and the common electrode 54 may be formed in a comb shape, and the heating portion 40 may be extended in the longitudinal direction between the comb-shaped individual electrodes 51 to 53 and the common electrode 54. .

Further, in the fixing device 7 according to the present embodiment, the pressure roller 22 is rotationally driven and the fixing belt 21 is driven to rotate. It may be driven to rotate.

Further, in the fixing device 7 according to the present embodiment, the pressure roller 22 is raised and lowered (moved in a direction toward or away from the fixing belt 21), but the present invention is not limited to this. For example, the fixing belt 21 may be moved toward or away from the pressure roller 22 .

In addition, in the description of the present embodiment, as an example, the case where the present invention is applied to the monochrome printer 1 has been shown, but the present invention is not limited to this, and can be applied to, for example, color printers, copiers, facsimiles, multifunction machines, and the like. may apply.

Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and representative embodiments so shown and described. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and equivalents thereof.

1 Printer (image forming device)
7 fixing device 21 fixing belt (fixing member)
22 pressure roller (pressure member)
23 heater (heater)
30 substrate 31 heat insulating layer 40-43 heat generating part 45 resistance heating element 51-53 individual electrode (electrode)
54 common electrode (electrode)
60 protective layer 60A void region 70 void 80 intermediate layer

Claims (7)

a substrate having a first surface;
a heat generating portion positioned on the first surface;
an electrode located on the first surface and electrically connected to the heat generating portion;
a protective layer that includes a void region having a plurality of voids at an edge in a thickness direction facing the substrate and covers the first surface ;
an intermediate layer disposed between the electrode or the heat generating portion and the protective layer and in contact with the void region;
with
The heater, wherein the intermediate layer contains silicon nitride . The intermediate layer is arranged between the heat generating portion and the protective layer,
The heater according to claim 1 , wherein the void region has the void facing the heat generating portion. The heat generating part has a first recess on the surface,
The heater according to claim 2 , wherein the void region has the void communicating with the first recess. the intermediate layer is disposed between the electrode and the protective layer;
the electrode has a second recess on the surface,
The heater according to any one of claims 1 to 3 , wherein the void region has the void communicating with the second recess. The heater according to claim 2 or 3 , wherein the plurality of voids have the voids that do not face the surface of the heat generating portion. The electrode includes a first electrode in contact with the protective layer and a second electrode arranged on the opposite side of the protective layer with the first electrode interposed therebetween,
6. The heater according to claim 2, 3 or 5 , wherein the void region has the void facing the second electrode through an exposed portion where a portion of the first electrode is not located. a fixing member that heats the toner on the medium while rotating about its axis;
a pressing member that presses the toner on the medium while rotating about an axis;
and the heater according to any one of claims 1 to 6 , which is disposed corresponding to the pressure member with the fixing member interposed therebetween, and heats the fixing member.

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