JP2020106699A - Heater and fixing device - Google Patents

Abstract

To provide a heater and a fixing device that reduce deterioration of electrodes.SOLUTION: A heater according to an embodiment comprises: a substrate; a plurality of heating parts; a first electrode; and a second electrode. The substrate has a long shape having a first surface. The plurality of heating parts are located on the first surface. The first electrode is located on the first surface and electrically connected to the plurality of heating parts. The second electrode is located on the first surface and overlaps the first electrode in plan view.SELECTED DRAWING: Figure 4

Description

The disclosed embodiments relate to heaters and fusing devices.

There is known a fixing device that heats a heat generating portion on a substrate connected to an electrode by supplying electric power from outside via a terminal. The fixing device controls the temperature by controlling the current based on the temperature of the substrate detected by the thermistor.

JP, 2016-6499, A

However, in the fixing device described above, when a large current is supplied from the terminal, there is a concern that the electrode locally deteriorates in a portion where the contact resistance between the terminal and the electrode increases and the electrode deteriorates.

One aspect of the embodiment is made in view of the above, and an object thereof is to provide a heater and a fixing device in which deterioration of an electrode is small.

A heater according to an aspect of the embodiment includes a substrate, a plurality of heat generating parts, a first electrode, and a second electrode. The substrate has an elongated shape having a first surface. The plurality of heat generating parts are located on the first surface. The first electrode is located on the first surface and is electrically connected to the plurality of heat generating portions. The second electrode is located on the first surface and overlaps the first electrode in plan view.

In the heater and the fixing device according to one aspect of the embodiment, the deterioration of the electrodes is small.

FIG. 1 is a schematic view (front view) showing a printer according to an embodiment. FIG. 2 is a 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 partially enlarged view of FIG. FIG. 5 is a sectional view taken along line VV of FIG. FIG. 6 is a sectional view taken along line VI-VI of FIG. FIG. 7A is a sectional view schematically showing a heater according to a first modified example of the embodiment. FIG. 7B is a sectional view schematically showing a heater according to a second modification of the embodiment. FIG. 7C is a sectional view schematically showing a heater according to a third modified example of the embodiment. FIG. 7D is a sectional view schematically showing a heater according to a fourth modification of the embodiment. FIG. 7E is a cross-sectional view schematically showing a heater according to a fifth modified example of the embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below. In addition, "Fr" shown in each figure shows "front", "Rr" shows "rear", "L" shows "left", "R" shows "right", and "U" shows. "Up" is shown and "D" shows "down".

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

The printer 1 includes an apparatus main body 2 having a substantially rectangular parallelepiped appearance. The printer 1 has, at a lower portion of the apparatus main body 2, a paper feed cassette 3 that stores a sheet S (medium) such as plain paper. The printer 1 has a paper discharge tray 4 on the upper surface of the apparatus body 2. The sheet S is not limited to paper and may be 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 feeding device 5 is located at the upstream end of the conveyance path 8 extending from the paper feeding cassette 3 to the paper ejection tray 4. The image forming device 6 is located in the middle of the transport path 8. The fixing device 7 is located on the downstream side of the transport path 8.

The image forming device 6 includes a toner container 10, a drum unit 11, and an optical scanning device 12. The toner container 10 stores, 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 the lower side to form a transfer nip. The toner may be a two-component developer in which toner and carrier are mixed, or a one-component developer made of magnetic toner.

A control device (not shown) of the printer 1 appropriately controls each device and executes an image forming process as follows. The charging device 14 charges the surface of the photoconductor drum 13. The photoconductor drum 13 receives the scanning light emitted from the optical scanning device 12 and carries an electrostatic latent image. The developing device 15 develops the electrostatic latent image on the photosensitive drum 13 into a toner image using the toner supplied from the toner container 10. The sheet S is sent out from the sheet feeding cassette 3 to the conveyance path 8 by the sheet feeding device 5, and the toner image on the photosensitive drum 13 is transferred to the sheet S passing through the transfer nip. The fixing device 7 fixes the toner image on the sheet S. After that, the sheet S is discharged to the paper discharge tray 4.

[Fixing device]
Next, the fixing device 7 will be described with reference to FIGS. FIG. 2 is a sectional view schematically showing the fixing device 7. FIG. 3 is a bottom view schematically showing the heater 23. FIG. 4 is a partially enlarged view of FIG. FIG. 5 is a sectional view taken along line VV of FIG. FIG. 6 is a sectional view taken along line VI-VI 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 located 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 that is long in the front-rear direction (axial direction). The surface layer of the fixing belt 21 is made of, for example, a synthetic resin material having heat resistance and elasticity such as polyimide resin. The fixing belt 21 is arranged above the inside of 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. The inside of the fixing belt 21 may have a belt guide (not shown) for holding the substantially cylindrical shape of the fixing belt 21.

A pressing member 24 is located inside the fixing belt 21. The pressing member 24 has a substantially rectangular tube shape that is long 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 is rotatably supported by the pressing member 24. The pressing member 24 is made of, for example, a metal material.

<Pressure roller>
The pressure roller 22 as an example of the pressure member has a substantially cylindrical shape that is long in the front-rear direction (axial direction). The pressure roller 22 is located below the inside of the housing 20. The pressure roller 22 includes a metal cored bar 22A and an elastic layer 22B such as a silicone sponge laminated on the outer peripheral surface thereof. Both ends in the axial direction of the cored bar 22A 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 unit (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. When the pressure roller 22 is pressed against the fixing belt 21, the pressure area N is between the fixing belt 21 and the pressure roller 22. Further, the pressurizing region N is a position from an upstream position in the transport direction of the sheet S having a pressure of 0 Pa to a downstream position in the transport direction of the sheet S having a pressure of 0 Pa via a position having the maximum pressure. Pointing to the area.

<Heater>
The heater 23, which is an example of a heater, is a substantially rectangular plate member that is long 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 orthogonal to the axial direction and a long shape 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 resin material.

As shown in FIGS. 3 to 6, the heater 23 includes a substrate 30, a heat insulating layer 31, and a heat generation contact portion 32. The substrate 30 is fixed to the lower 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 generation contact portion 32 is located on the first surface of the substrate 30, and is located on the lower surface of the heat insulating layer 31 or on the first surface of the substrate 30 located at the exposed portion 59 exposed without the heat insulating layer 31 being arranged. ..

In the present specification, the “passing direction (width direction)” is a direction intersecting the axial direction (length direction), and the direction in which the sheet S passes through the pressure area N of the fixing device 7 (conveyance). Direction). Further, in the following description, the terms “upstream” and “downstream” and similar terms refer to “upstream” and “downstream” in the passage direction and similar concepts.

The heater 23 is held on the lower surface of the holding member 25. The heat generation contact portion 32 of the heater 23 is a portion that faces the pressure roller 22 and contacts the inner surface of the fixing belt 21. The heater 23 receives the fixing belt 21 pressed against the pressure roller 22, so that the contact area between the fixing belt 21 and the pressure roller 22 is the pressure area N. The heater 23 is located corresponding to the pressure region N with the fixing belt 21 interposed therebetween (see FIG. 2) and has a function of heating the fixing belt 21. 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 6, the substrate 30 is, for example, a substantially rectangular plate shape that is long in the axial direction (length direction) and is made of an electrically insulating material such as ceramic. Both upper and lower surfaces of the substrate 30 are substantially smooth.

The heat insulating layer 31 as an example of the coating layer is laminated (deposited) on the first surface (lower surface) of the substrate 30. The heat insulating layer 31 is made of, for example, a material having an electrical insulating property and low thermal conductivity, such as ceramic or glass. The heat insulating layer 31 has a function of restricting transfer of heat generated in the heat generating contact portion 32 to the substrate 30.

The heat generation contact portion 32 is located on the first surface of the substrate 30. Specifically, the heat generation contact portion 32 is laminated on one surface (lower surface) of the heat insulating layer 31 arranged on the substrate 30 and on the first surface (lower surface) of the substrate 30 exposed without the heat insulating layer 31 being arranged. Has been done. The heat generation contact portion 32 includes a heat generation portion 40, an electrode 50, and a protective layer 60.

The heat generating section 40 includes a plurality of heat generating sections 41 to 43. The heat generating portion 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 line in the axial direction. Each of the plurality of resistance heating elements 45 has a substantially rectangular shape elongated in the passing direction. All the resistance heating elements 45 may have substantially the same size. The heat generating parts 41 to 43 are made of, for example, a conductive material such as metal having a higher resistance value than the electrode 50.

The heat generating portion 41 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-back width of the first size sheet S passing through the pressure area N. The heat generating portion 42 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-rear width of the second size sheet S passing through the pressure area N. The heat generating portion 43 is composed of a plurality of resistance heating elements 45 arranged in a range corresponding to the front-rear width of the third size sheet S passing through the pressurizing region N.

The resistance heating elements 45 may have the same size in the axial direction and the same size in the passing direction. In the present specification, the "same size" does not require that the sizes are exactly the same, but means that a slight error in manufacturing is allowed.

As shown in FIG. 3, the electrode 50 includes a plurality of wiring electrodes. The electrode 50 is made of, for example, a conductive material such as a metal (having a resistance value lower than that of the resistance heating element 45). The electrode 50 is located on the lower surface of the heat insulating layer 31 and on the lower surface of the substrate 30 located at the exposed portion 59. The plurality of wiring electrodes are electrically connected to both sides of the heat generating portions 41 to 43 in the passing direction. Specifically, the electrode 50 includes a plurality (for example, three) of individual electrodes 51 to 53 that are respectively connected to the plurality of heat generating portions 41 to 43, and a common electrode 54 that is commonly connected to the heat generating portions 41 to 43. including.

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

It should be noted that in the present specification, the individual electrodes 51 to 53 and the common electrode 54 may be referred to as “electrode 50 ”in the following description, which is common. Similarly, in the following description common to the heat generating units 41 to 43, it may be referred to as a "heat generating unit 40".

Each of the wiring electrodes (individual electrodes 51 to 53 and common electrode 54) has lead portions 51B to 54B and electrode terminal portions 51A to 54A. The lead-out parts 51B to 54B are parts extending from the parts connected to the heat generating parts 41 to 43 (connecting parts 51C to 54C) toward the electrode terminal parts 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, respectively. 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. The electrode terminal portions 51A to 54A are located in the exposed portion 59 located axially above the heat generating portions 41 to 43.

Specifically, the lead-out portion 51B of the individual electrode 51 extends from the connecting portion 51C with the heat generating portion 41 to one side (upper side) in the axial direction. The electrode terminal portion 51A is connected to the end of the lead-out portion 51B and is bent to the upstream side (left side). The lead-out portion 52B of the individual electrode 52 and the lead-out portion 53B of the individual electrode 53 extend from the connecting portions 52C and 53C with the heat generating portions 42 and 43, respectively, to one side (upper side) in the axial direction. The electrode terminal portions 52A and 53A are connected to the lead portions 52B and 53B, respectively. The electrode terminal portion 52A is located axially inside of the electrode terminal portion 51A, and the electrode terminal portion 53A is located axially inside of the electrode terminal portion 52A. On the other hand, the lead-out 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 to 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. 5 and 6, the protective layer 60 covers the heat generating 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 having an electric insulating property and a small sliding friction force with respect to the fixing belt 21. The first surface 60C of the protective layer 60 constitutes a sliding surface that contacts the inner surface of the fixing belt 21. The protective layer 60 is laminated so as to cover the first surface of the substrate 30 even in a portion where the heat generating portion 40 and the electrode 50 are not laminated. The protective layer 60 may be a single layer as illustrated, or may be a laminate of two or more layers. In addition, in FIG. 5, the end portion 60A of the protective layer 60 is not limited to the illustrated position, and for example, the protective layer 60 may not be located at a position where the heat insulating layer 31 is not located.

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 formed 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 steps such as exposure, development, etching, peeling, and stacking using a photomask which is a manufacturing technique of a printed circuit board. Good. Further, for example, the heat insulating layer 31 and the heat generation contact portion 32 may be formed by applying (screen printing) an electrically insulating paint or a conductive paint on the substrate 30. With these manufacturing methods, the heat insulating layer 31, the heat generating portion 40, and the electrode 50 can be accurately formed.

The electrode 50 of the heater 23, the drive motor, and the like are electrically connected to a power supply (not shown) via various drive circuits (not shown). Further, the heater 23 (electrode 50), the drive motor, the temperature sensor and the like are electrically connected to the control device of the printer 1 via various circuits. The control device controls the connected device or the like.

[Function of fixing device]
Here, the operation (fixing process) of the fixing device 7 will be described mainly with reference to FIG.

First, the control device drives and controls the drive motor and the heater 23. The pressure roller 22 rotates by receiving the driving force of the drive motor, and the fixing belt 21 rotates following the pressure roller 22 (see the solid thin arrow in FIG. 2). Each resistance heating element 45 generates heat by passing a current in the passing direction between the plurality of electrodes 50 sandwiching the heating portion 40. As a result, 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. 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 electric power to all the heat generating parts 41 to 43, and all the heat generating parts. 41-43 are made to generate heat. Further, for example, when the medium-sized sheet S smaller than the maximum size passes through the pressure area N, the control device causes the heat generating portions 41 and 42 to generate heat, and the small-sized sheet S smaller than the medium size is added. When passing through the pressure region N, the heat generating part 41 is caused to generate heat. As a result, only the required portion of the fixing belt 21 (pressurizing region N) can be heated according to the size of the sheet S. 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 via the input circuit. When the control device receives the detection signal indicating that the temperature has reached the set temperature (for example, 150 to 200° C.) from the temperature sensor, the control device controls the heater 23 so as to maintain the set temperature while performing the above-described image forming process. Start execution. The sheet S onto which the toner image has been transferred enters into 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 the axis. The pressure roller 22 presses the toner on the sheet S passing through the pressure area N while rotating around the axis. Then, the toner image is fixed on the sheet S. Then, the sheet S on which the toner image is fixed is sent out of the housing 20 and discharged to the paper discharge tray 4.

By the way, when a large current is supplied to the electrode 50, the heater 23 may be locally overheated at the portion where the contact resistance increases. For example, in the electrode 50 in which the terminals (electrode terminal portions 51A to 54A) and the lead-out portions 51B to 54B are formed of different materials, there is a concern that the electrode 50 may deteriorate due to overheating of the contact portion. Therefore, as shown in FIGS. 4 to 6, in the fixing device 7 (heater 23) according to the present embodiment, the electrode 50 having the first electrode 50a and the second electrode 50b overlapping the first electrode 50a in plan view is provided. By being located, the electric capacity of the electrode 50 increases. That is, the electric resistance of the electrode 50 can be reduced, and the electrode 50 is less likely to deteriorate.

As shown in FIGS. 4 to 6, the electrode 50 has a first electrode 50a and a second electrode 50b. The second electrode 50b is located on the lower surface of the heat insulating layer 31. The first electrode 50a is located so as to cover the second electrode 50b from the lower surface side of the heat insulating layer 31 and to be in close contact with the second electrode 50b. By electrically connecting the first electrode 50a and the second electrode 50b, the electric capacity of the entire electrode 50 can be increased, and the electrode 50 is less likely to deteriorate. The first electrode 50a is composed of, for example, an aluminum electrode containing aluminum. The second electrode 50b is composed of, for example, a silver electrode containing silver.

Further, among the electrodes 50, the electrode terminal portions 51A to 54A do not have the first electrode 50a, and only the second electrode 50b is located. Further, as described above, the electrode terminal portions 51A to 54A are located on the lower surface (first surface) of the substrate 30 without the heat insulating layer 31 interposed therebetween. The lower surface of the substrate 30 is more uneven than the lower surface of the heat insulating layer 31. Therefore, the electrode terminal portions 51A to 54A located on the substrate 30 without the heat insulating layer 31 have improved bonding strength with the substrate 30. Therefore, even if a terminal (not shown) of the connector is inserted into and removed from the electrode terminal portions 51A to 54A, the electrode terminal portions 51A to 54A are difficult to peel off. Further, even if heat is generated by the current flowing through the electrode terminal portions 51A to 54A, since the heat insulating layer 31 is not provided and heat is not easily accumulated, deterioration of the electrode 50 due to overheating hardly occurs.

Further, the arithmetic surface roughness Ra of the electrode terminal portions 51A to 54A can be made larger than the arithmetic surface roughness Ra of the first electrode 50a. By roughening the surfaces of the electrode terminal portions 51A to 54A, the terminals (not shown) of the connector connected to the electrode terminal portions 51A to 54A are less likely to fall off. Here, the arithmetic surface roughness Ra means, for example, the arithmetic average roughness Ra measured according to JIS B 0601 (2013). A contact-type surface roughness meter or a non-contact-type surface roughness meter can be used for the measurement, and for example, OLYMPUS LEXT OLS4000 can be used. As the measurement conditions, for example, the measurement length may be 0.4 mm, the cutoff value may be 0.08 mm, the spot diameter may be 0.4 μm, and the scanning speed may be 1 mm/sec. The measurement points can be set arbitrarily, and the average value can be defined as the arithmetic surface roughness Ra.

Further, the substrate 30 and the electrode terminal portions 51A to 54A may include a glass component. The glass component is, for example, silicon oxide (SiO ₂ ). Since the substrate 30 and the electrode terminal portions 51A to 54A contain the glass component, they have the same composition. Therefore, the bonding strength between the substrate 30 and the electrode terminal portions 51A to 54A is improved. The substrate 30 may include the glass component over the entire surface of the substrate 30, for example, only the exposed portion 59 where the electrode terminal portions 51A to 54A are located may include the glass component.

Further, as shown in FIG. 4, the common electrode 54 has a first portion 55a in which the first electrode 50a extends in the length direction of the substrate 30 from the electrode terminal portion 54A as an example of the common terminal. The individual electrodes 51 to 53 have second portions 55b extending in the width direction of the substrate 30 from the electrode terminal portions 51A to 53A, which are examples of individual terminals. By arranging the common electrode 54 and the individual electrodes 51 to 53, particularly the first portion 55a and the second portion 55b in this way, the wiring distance of the common electrode 54 can be reduced by reducing the wiring distance of the common electrode 54. Therefore, the deterioration of the electrode 50 can be reduced.

Further, as shown in FIG. 4, the width w4 of the first portion 55a of the common electrode 54 is larger than the widths w1 to w3 of the second portion 55b of the individual electrodes 51 to 53. Therefore, in the common electrode 54, the electrical resistance of the first portion 55a can be particularly reduced, and the deterioration of the electrode 50 can be reduced. It should be noted that the common electrode 54 can reduce the deterioration of the electrode 50 because, for example, the heater 23 according to the present embodiment may flow a current that is nearly three times that of the individual electrodes 51 to 53. Here, the width w4 of the first portion 55a refers to the width direction of the substrate 30 in the portion where the first electrode 50a and the second electrode 50b overlap each other in plan view at the end portion of the first portion 55a of the common electrode 54. Say the length. In addition, the widths w1 to w3 of the second portion 55b are the lengths of the substrate 30 in a portion where the first electrode 50a and the second electrode 50b overlap each other in plan view at the end portion of the second portion 55b of each individual electrode 51 to 53. Say the length along the direction. The widths w1 to w3 of the second portion 55b may be the same or different from each other, but if the widths w1 to w3 are different, the temperature control of the heater 23 becomes complicated.

Further, the heat insulating layer 31 is located between the substrate 30 and the first portion 55 a and the second portion 55 b. Therefore, for example, diffusion of silver atoms originating from the second electrode 50b located in the first portion 55a and the second portion 55b is suppressed, and a reaction layer having high electric resistance is hard to be generated. Therefore, the deterioration of the electrode 50 can be reduced.

Further, as shown in FIGS. 3 to 5, in the common electrode 54, the first electrode 50a and the second electrode 50b are mutually in plan view from the first portion 55a to the connecting portion 54C via the lead-out portion 54B. They are located so that they overlap. Similarly, in the individual electrodes 51 to 53, the first electrode 50a and the second electrode 50b respectively overlap each other in a plan view from the second portion 55b to the connecting portions 51C to 53C via the lead-out portions 51B to 53B. Is located in.

In the connection parts 51C to 54C, as shown in FIG. 6, the first electrode 50a has a contact part 56 with the heat generating part 40. The heat generating portion 40 covers a part of the electrode 50 so that the contact portion 56 is located on the lower surface (outer surface) of the first electrode 50a. On the other hand, the second electrode 50b is located on the lower surface of the heat insulating layer 31 so as to overlap the contact portion 56 in a plan view. By arranging the first electrode 50a and the second electrode 50b in this way, it is possible to reduce the influence of the voltage drop due to the wiring resistance to the heat generating portion 40.

<First Modification>
In the heater 23 according to the above-described embodiment, the contact portion 56 between the first electrode 50a and the heat generating portion 40 is described as being located on the lower surface (outer surface) of the first electrode 50a, but the present invention is not limited to this. FIG. 7A is a sectional view schematically showing a heater according to a first modified example of the embodiment. In addition, in FIG. 7A and other drawings described later, the cross-section is viewed from the same viewpoint as FIG. 6. As shown in FIG. 7A, a part of the heat generating portion 40 may be positioned so as to be sandwiched between the first electrode 50a and the second electrode 50b. In such a case, the contact portion 56 will be located between the first electrode 50a and the second electrode 50b. Even when the first electrode 50a and the second electrode 50b are positioned as described above, the influence of the voltage drop due to the wiring resistance to the heat generating portion 40 can be reduced.

<Second and third modified examples>
Although the heater 23 according to the above-described embodiment is described as being positioned so that the first electrode 50a covers the second electrode 50b, the present invention is not limited to this. 7B and 7C are cross-sectional views schematically showing heaters according to second and third modifications of the embodiment. As shown in FIG. 7B, the first electrode 50a may be positioned so as to be stacked on the lower surface of the second electrode 50b. Further, as shown in FIG. 7C, the first electrode 50a and the second electrode 50b may be located apart from each other. Even when the first electrode 50a and the second electrode 50b are positioned as described above, the influence of the voltage drop due to the wiring resistance to the heat generating portion 40 can be reduced.

<Fourth and fifth modifications>
The heater 23 according to the above-described embodiment has been described as the first electrode 50a being located on the lower surface of the second electrode 50b, but the present invention is not limited to this. 7D and 7E are cross-sectional views schematically showing heaters according to fourth and fifth modifications of the embodiment. As shown in FIG. 7D, the first electrode 50a extends from the end of the heat generating portion 40 onto the lower surface of the heat insulating layer 31 where the heat generating portion 40 is not located, and the second electrode 50b is the lower surface (outer surface of the first electrode 50a). ) May be located so that it may cover. Further, as shown in FIG. 7E, the electrode 50 may be located on the lower surface of the heat generating portion 40 and apart from the lower surface of the heat insulating layer 31. Even when the first electrode 50a and the second electrode 50b are positioned as described above, the influence of the voltage drop due to the wiring resistance to the heat generating portion 40 can be reduced.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit thereof. For example, in the heater 23 according to the above-described embodiment and each modified example, the arrangement of the first electrode 50a and the second electrode 50b may be replaced with each other. Further, the heat insulating layer 31 may be located on the entire surface of the first surface of the substrate 30 without the exposed portion 59.

Further, in the above-described fixing device 7 according to the present embodiment, the heat generating portions 41 to 43 correspond to the sizes of the three types of sheets S, but the present invention is not limited to this. The heat generating section 40 (resistance heating element 45) may be configured to correspond to the sizes of the two or more types of sheets S. Further, in the fixing device 7 according to the present exemplary embodiment, the sheet S is configured to pass through the center of the pressure area N in the axial direction, but the present invention is not limited to this. The sheet S may pass 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 in the axial direction is shown, but the present invention is not limited to this. For example, the drawer portions 51B to 54B may have a portion that extends to the upstream side (left side) or the downstream side (right side).

Further, in the fixing device 7 according to the present exemplary embodiment, the pressure roller 22 is rotationally driven and the fixing belt 21 is driven to rotate, but the present invention is not limited to this, and the fixing belt 21 is rotationally driven to rotate the pressure roller 22. It may be driven to rotate.

Further, in the fixing device 7 according to the present exemplary embodiment, the pressure roller 22 is moved up and down (moved 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.

Further, in the description of the present embodiment, the case where the present invention is applied to the monochrome printer 1 is shown as an example, but the present invention is not limited to this, and the present invention is applied to, for example, a color printer, a copying machine, a facsimile, or a multifunction peripheral. You may apply.

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

1 Printer (image forming device)
7 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (pressure member)
23 Heater
30 substrate 31 heat insulation layer 40 to 43 heat generating portion 45 resistance heating element 50 electrode 50a first electrode 50b second electrode 51 to 53 individual electrode 54 common electrode 60 protective layer

Claims (9)

An elongated substrate having a first surface,
A plurality of heat generating portions located on the first surface,
A first electrode located on the first surface and electrically connected to the plurality of heat generating parts;
A heater provided on the first surface, the second electrode overlapping the first electrode in a plan view. The heating portion includes a plurality of resistance heating elements arranged in the length direction of the substrate,
The first electrode includes a common electrode that connects all the resistance heating elements and a common terminal, and a plurality of individual electrodes that connect each of the plurality of heat generating portions and a plurality of individual terminals,
The common electrode has a first portion extending from the common terminal in the length direction of the substrate,
The heater according to claim 1, wherein each of the plurality of individual electrodes has a second portion that extends from the plurality of individual terminals in a width direction that intersects a length direction of the substrate. The heater according to claim 2, wherein the width of the first portion is larger than the width of the second portion. The heater according to claim 2 or 3, further comprising a coating layer located between the substrate and the first portion and the second portion. The heater according to claim 4, wherein the common terminal and the individual terminal are located on the first surface without interposing the coating layer. The surface roughness Ra of the said common terminal and the said individual terminal is larger than the surface roughness Ra of the said 1st electrode, The heater as described in any one of Claims 2-5. The heater according to any one of claims 2 to 6, wherein the substrate, the common terminal, and the individual terminal include a glass component. The first electrode has a contact portion with the heat generating portion,
The said 2nd electrode is located so that it may overlap with the said contact part by planar view, The heater as described in any one of Claims 1-7. A fixing member that heats the toner on the medium while rotating around the axis,
A pressing member for pressing the toner on the medium while rotating around an axis;
A fixing device comprising: the heater according to any one of claims 1 to 8, which is arranged corresponding to the pressing member with the fixing member interposed therebetween, and heats the fixing member.

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