JP2022131694A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can cause heating elements to generate heat in accordance with the size of a sheet.SOLUTION: A fixing device comprises a heater 50 that heats a toner image formed on a sheet S. The heater 50 includes a plurality of rows of heating elements 51 (51a, 51b), a first electrode 52, and second electrodes 53 (53a, 53b). The plurality of rows of heating elements 51 (51a, 51b) extend in a main scanning direction (direction Y(-)) of the sheet S and consist of a plurality of heating element small pieces 54 (heating element small piece 54a, heating element small piece 54b, heating element small piece 54c, ...). The first electrode 52 is arranged between the plurality of heating elements 51 (51a, 51b) and extends in the main scanning direction of the sheet S. The second electrodes 53 (53a, 53b) are arranged on the opposite side of the first electrode 52 with respect to the plurality of heating elements 51 (51a, 51b) and extend in the main scanning direction of the sheet S.SELECTED DRAWING: Figure 5

Description

The present invention relates to a fixing device and an image forming apparatus.

Patent Literature 1 discloses a heating device in which a plurality of resistance heating elements and power supply wiring patterns connected to both longitudinal ends of each resistance heating element are arranged on a ceramic substrate.

JP 2017-73196 A

In the heating device disclosed in Patent Document 1, wiring patterns for power supply are connected to both ends in the longitudinal direction of a resistance heating element on a ceramic substrate. Therefore, the power supply range of the resistance heating element cannot be adjusted to the size of the sheet.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device capable of generating heat from a heating element according to the size of a sheet.

A fixing device according to the present invention includes a heater that heats a toner image formed on a sheet, and the heater includes a plurality of rows of heating elements, a first electrode, and a second electrode. The plurality of rows of heating elements extend in the main scanning direction of the sheet and are composed of a plurality of heating element pieces. The first electrode is arranged between the plurality of rows of heating elements and extends in the direction. The second electrode is arranged opposite to the first electrode with respect to the plurality of heating elements and extends in the direction.

According to the fixing device of the present invention, the heating element can generate heat according to the size of the sheet.

1 is a diagram showing a multi-function peripheral including a fixing device according to an embodiment of the invention; FIG. 1 is a block diagram showing the configuration of an image forming apparatus including a fixing device according to the exemplary embodiment; FIG. 2 is a cross-sectional view showing the configuration of the fixing device according to the exemplary embodiment; FIG. (a) to (c) are diagrams showing the structure and temperature distribution of a heater used in a general fixing device. (a) to (d) are diagrams showing the structure of a heater used in the fixing device according to this embodiment. 3 is a block diagram showing components that control the fixing device according to the embodiment; FIG. 4 is a flowchart showing control of the fixing device according to the embodiment; FIG. 5 is a diagram showing a comparison of temperature distribution between a heater used in the fixing device according to the present embodiment and a heater used in a general fixing device;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In addition, in the present embodiment, X-, Y-, and Z-axes that are orthogonal to each other are shown in the drawing. The Z axis is parallel to the vertical plane and the X and Y axes are parallel to the horizontal plane.

In this embodiment, the Z-axis direction may be described as a "main scanning direction". Also, the Y-axis direction may be described as a "sub-scanning direction". The X-axis direction may be described as "a direction perpendicular to the main scanning direction and the sub-scanning direction".

The configuration of the multifunction machine 1 will be described with reference to FIG. FIG. 1 is a diagram showing a multifunction machine 1 including a fixing device 16 according to this embodiment. Also, with reference to FIG. 2, the configuration of the image forming apparatus 3 including the fixing device 16 according to the present embodiment will be described. FIG. 2 is a block diagram showing the configuration of the image forming apparatus 3 including the fixing device 16 according to this embodiment.

As shown in FIG. 1 , the multifunction machine 1 includes a document reading device 2 and an image forming device 3 . The multi-function machine 1 is, for example, an MFP (Multi Function Printer) that combines functions such as a scanner, a copier, a printer, a copier, and a facsimile.

The document reading device 2 has, for example, a document tray, a document feeding section, a document conveying section, a document reading section, an optical member, a document discharge section, and a document discharge tray.

The image forming apparatus 3 includes a printer control section 10, a printer driving section 11, a sheet tray 12, a sheet feeding section 13, a sheet conveying section 14, an image forming section 15, and a fixing section 16 (fixing device 16). , a sheet ejection portion 17 , and a sheet ejection tray 18 .

The printer control section 10 controls the operation of each section of the image forming apparatus 3 . The printer control section 10 may function as a control section that controls the operation of each section of the MFP 1 . A specific example of the printer control unit 10 is a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), or an ASIC (Application Specific Integrated Circuit).

The printer driving section 11 drives each section of the image forming apparatus 3 . The printer driving section 11 may be a driving section that operates each section of the multifunction machine 1 . Specific examples of the printer driver 11 are electric motors, electromagnetic solenoids, hydraulic cylinders, and pneumatic cylinders.

Sheet tray 12 stacks sheets S thereon. The sheet S is an example of a recording medium. The sheet tray 12 may include a tray and an elevating member. The sheet feeding unit 13 picks up the sheets S stacked on the sheet tray 12 and feeds them. A specific example of the sheet feeding unit 13 is a pickup roller.

The sheet conveying section 14 conveys the sheet S fed from the sheet tray 12 . The sheet conveying section 14 has a conveying path. The conveying path starts from the sheet tray 12 and extends to the sheet discharge section 17 via the image forming section 15 and the fixing section 16 . The sheet conveying section 14 may include a conveying roller and a registration roller in the conveying path.

A plurality of transport rollers may be arranged in the transport path, and transport the sheet S. The registration rollers adjust the timing of conveying the sheet S to the image forming section 15 . The sheet conveying portion 14 conveys the sheet S from the sheet tray 12 to the sheet discharging portion 17 via the image forming portion 15 and the fixing portion 16 .

The image forming unit 15 forms a toner image (not shown) on the sheet S by electrophotography based on the document image data. The document image data indicates an image of the document G, for example.

The fixing unit 16 heats and presses the toner image developed on the sheet S to fix the toner image on the sheet S. As shown in FIG.

The sheet discharge unit 17 discharges the sheet S to the outside of the housing of the multifunction machine 1 (image forming apparatus 3). A specific example of the sheet discharge unit 17 is a discharge roller.

The sheet ejection tray 18 stacks the sheets S ejected by the sheet ejection portion 17 .

Next, a detailed configuration of the fixing device 16 according to this embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the configuration of the fixing device 16 according to this embodiment.

As shown in FIG. 3 , the fixing device 16 includes a fixing belt 30 , a pressure member 31 , a heater 32 , a heater holding member 33 , a stay sheet metal 34 , a stay sheet metal holding portion 35 , and a fixing belt holding portion 36 . and

The fixing belt 30 heats the sheet S (FIG. 1) on which a toner image is formed in the image forming section 15 shown in FIG.

The fixing belt 30 shown in FIG. 3 is endless. Fixing belt 30 has a substantially cylindrical shape. Fixing belt 30 has flexibility.

The fuser belt 30 further has multiple layers. Fixing belt 30 has, for example, a polyimide layer containing polyimide, an elastic layer containing an elastic material such as silicone rubber, and a release layer. A release layer is formed on the outer peripheral surface of the polyimide layer. The release layer is, for example, a heat-resistant film made of fluororesin.

The pressure member 31 is driven to rotate and is pressed against the fixing belt 30 to cause the fixing belt 30 to rotate. The pressing member 31 has a substantially cylindrical shape and is arranged to face the fixing belt 30 . An example of the pressure member 31 is a pressure roller.

The pressure member 31 has a cylindrical core bar, a cylindrical elastic layer, and a release layer. The elastic layer is formed on the cored bar. The release layer is formed so as to cover the surface of the elastic layer.

The cored bar is made of, for example, stainless steel or aluminum. The elastic layer has elasticity and is made of silicone rubber, for example. The release layer is made of, for example, fluororesin.

The heater 32 is connected to a power source (not shown) and generates heat. A heater 32 heats the fixing belt 30 . The heater 32 is arranged at a position facing the inner peripheral surface of the fixing belt 30 .

The heater 32 is, for example, a planar heater or an elongated thin plate heater. The heater 32 is, for example, a ceramic heater, and has a ceramic substrate and a resistance heating element 44 . The thickness of heater 32 is, for example, 1 mm. The heater 32 receives pressure from the pressure member 31 via the fixing belt 30 .

A nip portion N is formed at the contact portion between the fixing belt 30 and the pressure member 31 by pressing the pressure member 31 against the fixing belt 30 . When the pressure member 31 is pressed against the fixing belt 30 , the heater 32 is pressed against the inner circumferential surface of the fixing belt 30 . Therefore, the fixing belt 30 is heated by the heater 32, and the toner image formed on the sheet S (FIG. 1) passing through the nip portion N is fixed on the sheet S. As shown in FIG.

The heater holding member 33 holds the heater 32 that guides the fixing belt 30 so as to be rotatable and heats the fixing belt 30 .

The stay sheet metal 34 reinforces the heater holding member 33 . The stay sheet metal 34 is, for example, an elongated metallic stay member. The stay metal plate 34 may be formed in a U-shape, a U-shape, or a V-shape.

The stay sheet metal holding portion 35 holds the stay sheet metal 34 so as to be fixed to the heater holding member 33 .

The fixing belt holding portion 36 guides the fixing belt 30 so as to be rotatable.

Next, referring to FIGS. 4A to 4C, the structure of a heater 40 used in a general fixing device will be described. FIG. 4A is a schematic plan view showing the structure of a heater 40 used in a general fixing device. FIG. 4(b) is a IVB-IVB sectional view of the heater 40 taken along the dashed line L shown in FIG. 4(a). FIG. 4(c) is a diagram showing the temperature distribution in the direction Z of the heater 40 when the resistance heating element 44 is heated.

As shown in FIG. 4A, the heater 40 has a heater base material 41, a glaze layer 42, electrodes 43 (electrodes 43a and 43b), a resistance heating element 44, and an overcoat layer 45. As shown in FIG.

The heater 40 is arranged to face the inner circumferential surface of a fixing belt of a general fixing device (not shown), and heats the fixing belt.

The glaze layer 42 serves, for example, as a heat storage layer. The glaze layer 42 is laminated on the heater base material 41 .

The resistance heating element 44 heats the fixing belt by generating heat. A resistive heating element 44 is laminated on the glaze layer 42 .

The electrodes 43 a and 43 b are connected to the resistance heating element 44 and supply electric power to the resistance heating element 44 .

The electrode 43 a is arranged on one side of the resistance heating element 44 in the Z direction and extends in the Y direction in parallel with the resistance heating element 44 . The electrode 43b is arranged on the side opposite to the electrode 43a with respect to the resistance heating element 44 and extends in the direction Y in parallel with the resistance heating element 44 .

That is, the electrodes 43a and 43b are arranged so as to sandwich both sides of the resistance heating element 44 in the Z direction.

The overcoat layer 45 coats the electrodes 43 a , 43 b and the resistance heating element 44 . The overcoat layer 45 is laminated on the electrodes 43 a , 43 b and the resistance heating element 44 .

In FIG. 4C, the horizontal axis indicates the position of the heater 40 in the Z direction, and the vertical axis indicates the temperature at the position of the heater 40 in the Z direction.

As shown in FIG. 4C, the temperature rises from the ends of the heater 40 in the Z direction toward the center, and the temperature is highest at the center of the resistance heating element 44 . Then, the temperature of the heater 40 decreases from the central portion in the direction Z toward the end portions.

The temperature difference between the ends of the heater 40 in the direction Z and the center thereof is the temperature difference Tg.

Next, the fixing device 16 according to the present embodiment will be described with reference to FIGS. 5A to 7 in addition to FIGS. 1 to 3. FIG. FIG. 5A is a schematic plan view showing the configuration of the heater 50 used in the fixing device 16. FIG. FIG. 5(b) is an enlarged plan view showing the area surrounded by the dotted line A of the heater 50. FIG. FIG. 5(c) is a VC-VC cross-sectional view of the heater 50 shown in FIG. FIG. 5(d) is a diagram comparing the temperature distribution of the heater 50 used in the fixing device 16 according to this embodiment with the temperature distribution of the heater 40 according to the comparative example of FIG. 4(a).

As shown in FIG. 5A, the fixing device 16 includes a heater 50 that heats the toner image formed on the sheet S (FIG. 1). The heater 50 includes multiple rows of heating elements 51 (51a, 51b), first electrodes 52, and second electrodes 53 (53a, 53b). A plurality of rows of heating elements 51 (51a, 51b) extend in the main scanning direction (direction Y(−)) of the sheet S, and a plurality of heating element pieces 54 (heating element pieces 54a, heating element pieces 54b, heating element pieces 54c) are arranged. , …). The first electrode 52 is arranged between the plurality of rows of heating elements 51 (51a, 51b) and extends in the main scanning direction of the sheet S. As shown in FIG. The second electrodes 53 (53a, 53b) are arranged on the side opposite to the first electrodes 52 with respect to the plurality of heating elements 51 (51a, 51b) and extend in the main scanning direction of the sheet S. As shown in FIG.

The main scanning direction is a direction (direction Y) that is parallel to the heater 50 and orthogonal to the conveying direction (direction Z) of the sheet S. The conveying direction (direction Z) of the sheet S may be described as a “sub-scanning direction”.

In principle, the “multiple rows of heating elements 51 (51a, 51b)” are described as “heating elements 51”, and if necessary, they are described as “heating elements 51a” or “heating elements 51b”. There is

"Plural heating element pieces 54 (heating element pieces 54a, heating element pieces 54b, heating element pieces 54c, . . . )" are basically described as "heating element pieces 54", They may be described as a small piece 54a,” a “heating element piece 54b,” and a “heating element piece 54c.”

"Second electrode 53 (53a, 53b)" is described as "second electrode 53" in principle, and may be described as "second electrode 53a" or "second electrode 53b" as necessary. There is

The heater 50 is arranged to face the inner peripheral surface of the fixing belt 30 ( FIG. 3 ) of the fixing device 16 and heats the fixing belt 30 . One example of heater 50 is a ceramic heater. A plurality of rows of heating elements 51 , a plurality of rows of first electrodes 52 , and a plurality of rows of second electrodes 53 are formed on a facing surface T of the heater 50 that faces the conveyed sheet S.

The heating elements 51a and 51b extend in the main scanning direction of the sheet S. As shown in FIG. The heating element 51 is, for example, a resistance heating element such as Ag/Pd (silver palladium), RuO ₂ (ruthenium oxide), Ta ₂ N (tantalum nitride).

As shown in FIG. 5B, the heating elements 51a and 51b of the heater 50 each consist of a plurality of heating element pieces 54 (heating element pieces 54a, heating element pieces 54b, heating element pieces 54c, . . . ). may

The heating elements 51a and 51b may be divided into heating element pieces 54 (heating element pieces 54a, heating element pieces 54b, heating element pieces 54c, . . . ) in the main scanning direction of the sheet S, respectively.

The first electrode 52 is arranged between the heating element 51a and the heating element 51b and extends in the main scanning direction of the sheet S. As shown in FIG. The first electrode 52 may be connected to a power supply (not shown).

The second electrode 53a is arranged on the side opposite to the first electrode 52 with respect to the heating element 51a, and extends in the main scanning direction of the sheet S. As shown in FIG. The second electrode 53b is arranged on the opposite side of the heating element 51b to the first electrode 52 and extends in the main scanning direction of the sheet S. As shown in FIG. The second electrode 53 may be connected to a power supply (not shown).

A power source (not shown) selectively energizes the second electrode 53a and the first electrode 52 according to the size of the sheet S, and supplies power to some or all of the heating element pieces 54 according to the size of the sheet S. be able to.

According to the present embodiment, the heating element 51 can generate heat according to the size of the sheet S, so that power consumption can be reduced and the life of the heating element 51 can be extended.

The first electrode 52 may have a higher potential than the second electrode 53 . Also, the second electrode 53 may be a ground electrode or a reference electrode. A ground or reference electrode is at earth potential. In this case, a potential difference is generated between the first electrode 52 and the second electrode 53 and current flows from the first electrode 52 to the second electrode 53 . Therefore, the heating element 51 can generate heat throughout the main scanning direction.

Also, the potential of the second electrode 53 may be higher than that of the first electrode 52 . The first electrode 52 may be a ground electrode or a reference electrode. In this case, a potential difference is generated between the first electrode 52 and the second electrode 53 and current flows from the second electrode 53 to the first electrode 52 . Therefore, the heating element 51 can generate heat throughout the main scanning direction.

According to this embodiment, with respect to the plurality of rows of heating elements 51 extending in the main scanning direction of the sheet S, the sheet S power can be supplied in the conveying direction of

Next, the first electrode 52 or the second electrode 53 of the heater 50 may be connectable to the heating element piece 54 selected from among the plurality of heating element pieces 54 . The first electrode 52 or the second electrode 53 may be capable of energizing a selected heating element piece 54 among the plurality of heating element pieces 54 . The first electrode 52 or the second electrode 53 may be capable of supplying electric power supplied from the power source to the selected heating element piece 54 among the plurality of heating element pieces 54 .

As shown in FIG. 6 , the fixing device 16 may further include a power supply section 60 and a power control section 61 . The power supply unit 60 supplies power to the first electrode 52 or the second electrode 53 connected to the selected heating element piece 54 . The power control unit 61 selects a heating element piece 54 to which electric power is to be supplied from among the plurality of heating element pieces 54, and supplies power to only the first electrode 52 or the second electrode 53 connected to the selected heating element piece 54. Control the power supply unit 60 to supply power.

Specifically, the first electrode 52 and the second electrode 53 may be divided in the main scanning direction of the sheet S at a plurality of locations.

For example, according to different sizes of sheets S such as B5 sheet S, A4 sheet S, A3 sheet S, etc., the power control unit 61 controls the power supply to supply power to the heating element piece 54 corresponding to each sheet S. It controls the supply unit 60 .

That is, when fixing the toner image on the A4 sheet S, the power control unit 61 supplies power to the first electrode 52 and the second electrode 53 of the heating element pieces 54 at positions corresponding to the width of the A4 sheet S in the main scanning direction. The power supply unit 60 is controlled to supply the . The power supply unit 60 supplies power only to the heat generating piece 54 at the portion corresponding to the width of the A4 sheet S in the main scanning direction, so that only the heat generating piece 54 at that portion generates heat.

According to this embodiment, power can be supplied to the selected heating element piece 54 according to the type of the sheet S. FIG.

Further, according to the present embodiment, wasteful power consumption of the fixing device 16 can be suppressed.

Next, a specific configuration of the heater 50 will be described in detail with reference to FIG. 5(c). As shown in FIG. 5C, the heater 50 further includes a heater base material 55, a glaze layer 56, and an overcoat layer 57 in addition to the heating element 51, first electrode 52, and second electrode 53 described above. Prepare. A glaze layer 56 is laminated to the heater substrate 55 . The first electrode 52 is laminated on the glaze layer 56 . The second electrode 53 is laminated on the glaze layer 56 . A plurality of rows of heating elements 51 are laminated on the glaze layer 56 . The overcoat layer 57 is laminated on the first electrode 52 , the second electrode 53 , and the multiple rows of heating elements 51 .

The heater base material 55 is, for example, an insulating ceramic substrate such as alumina or aluminum nitride, and has a plate shape with a low heat capacity.

The glaze layer 56 is laminated on the heater base material 55 and formed on the facing surface T (FIG. 5(a)) of the heater base material 55, and is made of a glass material such as amorphous glass. The glaze layer 56 is formed by printing a thick film of glass paste and then baking it. The glaze layer 56 is provided to eliminate unevenness on the facing surface T of the heater base material 55 and facilitate lamination of the first electrode 52 , the second electrode 53 , and the plurality of rows of the heating elements 51 .

The glaze layer 56 has a heat storage property, partially stores the heat of the heating element 51, and also serves to prevent the temperature of the heating element 51 from rising excessively.

The first electrode 52 and the second electrode 53 are made of, for example, resinate Au to which rhodium, vanadium, bismuth, silicon, or the like is added as additive elements. The first electrode 52 and the second electrode 53 may be formed by printing a resinate Au paste as a thick film and then firing it. The first electrode 52 and the second electrode 53 may be formed by a thin film forming technique such as sputtering. The first electrode 52 and the second electrode 53 may be configured by laminating a plurality of Au layers.

The heating element 51 is made of, for example, ruthenium oxide, which has a higher resistivity than the materials forming the first electrode 52 and the second electrode 53 . The heating element 51 is formed by printing a thick film of a paste such as ruthenium oxide and then firing it. Note that the heating element 51 may be formed by a thin film forming technique such as sputtering.

The overcoat layer 57 protects the heating element 51 , the first electrode 52 and the second electrode 53 and covers substantially the entire heating element 51 , the first electrode 52 and the second electrode 53 .

Overcoat layer 57 is made of a glass material such as amorphous glass. The softening point of this glass material is, for example, about 700.degree. The overcoat layer 57 may be formed by printing a thick film of glass paste and then baking it.

The material of the overcoat layer 57 is not limited to amorphous glass, and may be an insulating material such as SiC (Silicon Carbide), SiN (Silicon Nitride), TiN (Titanium Nitride). : titanium nitride), DLC (Diamond-Like Carbon), ta-C (Tetrahedral Amorphous Carbon), and the like.

Since the overcoat layer 57 can have a flat surface on the side of the heater 50 facing the sheet S, the heater 50 can be brought into contact with the sheet S favorably. Furthermore, since the overcoat layer 57 has heat dissipation properties, by improving the heat dissipation properties of the heater 50, the print quality on the sheet S and the durability of the heating element 51 can be improved.

Next, the temperature distribution of the heater 50 will be described with reference to FIG. 5(d). FIG. 5(d) is a view showing the configuration of the facing surface T of the heater 50 with the temperature distribution superimposed thereon. The solid line shown in FIG. 5(d) indicates the temperature distribution of the heater 50 when the heating elements 51a and 51b are provided as in this embodiment. The dotted line shown in FIG. 5(d) indicates the temperature distribution of the heater 40 when one resistance heating element 44 is provided as in the comparative example described in FIGS. 4(a) to 4(c).

As shown in FIG. 5D, in the case of the temperature distribution of the comparative example indicated by the dotted line, both ends of the resistance heating element 44 in the sub-scanning direction (direction Z) have a larger temperature drop than the central portion. On the other hand, the temperature drop at both end portions in the sub-scanning direction of the heater 50 according to the present embodiment with respect to the central portion is suppressed to be smaller than in the comparative example.

Furthermore, in the case of the comparative example, the temperature difference between the maximum temperature and the minimum temperature of the resistance heating element 44 in the sub-scanning direction (direction Z) is large. On the other hand, the temperature difference Tg between the maximum temperature and the minimum temperature in the sub-scanning direction of the heater 50 of this embodiment is kept small compared to the comparative example.

According to this embodiment, the temperature distribution of the heater 50 can be made flat. Therefore, damage caused by the temperature difference Tg between the high temperature portion and the low temperature portion of the heater 50 can be suppressed.

Next, control of the fixing device 16 will be described with reference to FIG. FIG. 7 is a flowchart showing control of the fixing device 16 according to this embodiment.

As shown in FIG. 7, the flowchart includes steps S10 to S12. Specifically, it is as follows.

In step S<b>10 shown in FIG. 7 , the power control section 61 controls the power supply section 60 to supply power only to the first electrode 52 or the second electrode 53 . The process proceeds to step S12n.

In step S<b>12 , the power supply unit 60 supplies power to the first electrode 52 or the second electrode 53 connected to the selected heating element piece 54 . Then the process ends.

Next, the relationship between the configuration of the heater 50 according to the present embodiment and thermal stress will be described with reference to FIGS. 8B to 8D respectively show the configuration of the heater 50 according to this embodiment. FIG. 8(a) is a diagram showing the thermal stress generated in each heater 50 of FIGS. 8(b) to (d).

In the fixing device 16 according to this embodiment, the width Wa of the first electrode 52 in the sub-scanning direction and the width Wa of the first electrode 52 and the heater A ratio of the distance Wb from the end of the electrode 50 in the sub-scanning direction to the end of the second electrode 53 in the sub-scanning direction may be defined.

As shown in FIGS. 8B to 8D, the width Wa of the first electrode 52 in the sub-scanning direction is the sub-scanning direction of the heater 50 and the upstream side of the first electrode 52 in the conveying direction of the sheet S. The distance from the side edge to the side edge of the first electrode 52 on the downstream side of the sheet S in the conveying direction is shown.

The distance Wb from the end of the heater 50 in the sub-scanning direction to the end of the second electrode 53 in the sub-scanning direction is the side end of the heater 50 on the downstream side in the conveying direction of the sheet S in the sub-scanning direction of the heater 50 . , to the downstream end of the sheet S in the conveying direction in the sub-scanning direction of the second electrode 53a.

When the heating element 51 generates heat, the heat exerts a thermal stress on the heater 50 . If the thermal stress exceeds the threshold, the heater 50 will fail.

As shown in FIGS. 8B to 8D, the thermal stress applied to the heater 50 is different.

Therefore, the width Wa of the first electrode 52 in the sub-scanning direction and the sub-scanning direction width Wa of the first electrode 52 and the sub-scanning It is preferable to define a ratio of the distance Wb from the end of the direction to the end of the second electrode 53a in the sub-scanning direction.

Similarly, the width Wa of the first electrode 52 in the sub-scanning direction and the sub-scanning direction width Wa of the first electrode 52 and the sub-scanning direction of the heater 50 are such that the thermal stress generated in the heater 50 by the heat generated by the heating elements 51 a and 51 b is less than the thermal stress that damages the heater 50 . It is preferable to define a ratio of the distance Wb from the end in the scanning direction to the end in the sub-scanning direction of the second electrode 53b.

According to this embodiment, it is possible to prevent the heater 50 from being damaged due to thermal stress caused by the heat generated by the heating element 51 .

The ratio (Wa/Wb) of the width Wa of the first electrode 52 in the sub-scanning direction to the distance Wb from the end of the heater 50 in the sub-scanning direction to the end of the second electrode 53 in the sub-scanning direction is 1. to 4.

Data A shown in FIG. 8(a) indicates the thermal stress applied to the heater 50 in the case of the configuration of the heater 50 shown in FIG. 8(b). The ratio (Wa/Wb) shown in FIG. 8(b) is less than one. At this time, since the thermal stress generated in the heater 50 by the heat generated by the heating elements 51a and 51b exceeds the threshold value, the heater 50 may be damaged due to the thermal stress.

Data C shown in FIG. 8(a) indicates the thermal stress that the heater 50 receives when the heater 50 has the configuration shown in FIG. 8(d). The ratio (Wa/Wb) shown in FIG. 8(d) is greater than four. At this time, since the thermal stress generated in the heater 50 by the heat generated by the heating elements 51a and 51b exceeds the threshold value, the heater 50 may be damaged due to the thermal stress.

Data B shown in FIG. 8(a) indicates the thermal stress that the heater 50 receives when the heater 50 has the configuration shown in FIG. 8(c). The ratio (Wa/Wb) shown in FIG. 8(c) is between 1 and 4, and is 1 or more and 4 or less. At this time, the thermal stress generated in the heater 50 by the heat generated by the heating elements 51a and 51b is below the threshold. Therefore, the heater 50 is less likely to be damaged due to thermal stress.

According to this embodiment, it is possible to prevent the heater 50 from being damaged due to thermal stress caused by the heat generated by the heating element 51 .

The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist of the present invention. In order to facilitate understanding, the drawings schematically show each component mainly, and the thickness, length, number, etc. of each component illustrated are different from the actual ones due to the convenience of drawing. . In addition, the material, shape, dimensions, etc. of each component shown in the above embodiment are examples and are not particularly limited, and various changes are possible within a range that does not substantially deviate from the effects of the present invention. be.

INDUSTRIAL APPLICABILITY The present invention can be used in the fields of fixing devices and image forming apparatuses.

1 MFP 3 Image forming device 16 Fixing device 50 Heater 51 Heating element 52 First electrode

Claims (10)

A fixing device including a heater for heating a toner image formed on a sheet,
The heater is
a plurality of rows of heating elements extending in the main scanning direction of the sheet and made up of a plurality of heating element pieces;
a first electrode disposed between the plurality of rows of heating elements and extending in the main scanning direction;
and a second electrode arranged on the side opposite to the first electrode with respect to the plurality of rows of heating elements and extending in the main scanning direction. The fixing device according to claim 1, wherein the first electrode has a higher potential than the second electrode. 3. The fixing device of claim 2, wherein the second electrode is a ground electrode or a reference electrode. The fixing device according to claim 1, wherein the second electrode has a higher potential than the first electrode. 5. The fixing device of claim 4, wherein the first electrode is a ground electrode or a reference electrode. the first electrode or the second electrode is connectable to a heating element piece selected from among the plurality of heating element pieces,
a power supply unit that supplies power to the first electrode or the second electrode connected to the selected heating element piece;
A heating element piece to which the electric power is to be supplied is selected from among the plurality of heating element pieces, and the electric power is supplied only to the first electrode or the second electrode connected to the selected heating element piece. The fixing device according to claim 5, further comprising a control section that controls the power supply section. The heater is
further comprising a heater base material and a glaze layer,
The glaze layer is laminated on the heater base material,
The first electrode is laminated on the glaze layer,
The second electrode is laminated on the glaze layer,
The plurality of rows of heating elements are laminated on the glaze layer,
The fixing device according to any one of claims 1 to 6, further comprising an overcoat layer laminated on the first electrode, the second electrode, and the plurality of rows of heating elements. The width of the first electrode in the sub-scanning direction and the distance from the end of the heater in the sub-scanning direction are such that the thermal stress generated in the heater by the heat generated by the heating element is less than the thermal stress that damages the heater. 8. The fixing device according to any one of claims 1 to 7, wherein a ratio of the distance to the end of the second electrode in the sub-scanning direction is defined. 9. The fixing device of claim 8, wherein the ratio is between 1 and 4. An image forming apparatus comprising the fixing device according to claim 1 .

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