Heating device, and image forming apparatus

Abstract

To provide a heating device and an image forming apparatus that can improve heating performance at a facing part where two resistance heating elements face each other.SOLUTION: A heating device 32 comprises: a substrate that is longer in one direction; a resistance heating element 42A and a resistance heating element 42B that are arranged on the substrate with an interval in the longitudinal direction of the substrate; a connection part 43A and a connection part 43B that sandwich the resistance heating element 42A in a width direction of the substrate orthogonal to the longitudinal direction; and a conductive first extension part 51 that extends along an outer periphery surrounding the resistance heating element 42A in the longitudinal direction from the connection part 43A to the connection part 43B, at an end of the resistance heating element 42A facing the resistance heating element 42B, and is laminated on the resistance heating element 42A in a thickness direction of the substrate 41.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a heating device and an image forming apparatus. [Background technology]

[0002] An electrophotographic image forming apparatus includes a heating device for heating a fixing member such as a fixing belt. For example, the heating device includes a substrate that is elongated in one direction and a plurality of resistance heating elements arranged on the substrate along the longitudinal direction of the substrate.

[0003] When the heating device includes a plurality of the resistive heating elements, the heating performance of the opposing portion where the two resistive heating elements face each other in the heating device is reduced. In response to this, a heating device that improves the heating performance of the opposing portion by reducing the electrical resistance of each end of the resistive heating element included in the opposing portion is known as a related art (see Patent Document 1). Specifically, in the heating device according to the related art, a notch portion is formed on both sides in the width direction of the substrate at each end of the resistive heating element included in the opposing portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-17877 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the heating device according to the related art, the outer sides (cut-out portions) in the width direction at each end of the resistive heating element included in the opposing portion do not generate heat, and therefore the heating performance of both ends in the width direction of the opposing portion cannot be sufficiently improved.

[0006] An object of the present invention is to provide a heating device and an image forming apparatus that can improve the heating performance in the opposing portion where two resistance heating elements face each other. [Means for solving the problem]

[0007] A heating device according to one aspect of the present invention includes a substrate, a first resistive heating element and a second resistive heating element, a first conductor and a second conductor, and an extension portion. The substrate is elongated in one direction. The first resistive heating element and the second resistive heating element are arranged on the substrate at an interval in the longitudinal direction of the substrate. The first conductor and the second conductor sandwich the first resistive heating element in a width direction of the substrate perpendicular to the longitudinal direction. The extension portion is conductive, and extends from the first conductor to the second conductor at an end of the first resistive heating element facing the second resistive heating element along an outer periphery surrounding the longitudinal direction of the first resistive heating element. The extension portion is laminated in a thickness direction of the substrate perpendicular to the longitudinal direction and the width direction of the first resistive heating element.

[0008] According to another aspect of the present invention, there is provided an image forming apparatus including a fixing member and the heating device, the fixing member fixing a toner image onto a sheet, and the heating device heating the fixing member. Effect of the Invention

[0009] According to the present invention, it is possible to improve the heating performance in the opposing portion where two resistance heating elements face each other. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a fixing device of the image forming apparatus according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing a configuration of a heating device according to an embodiment of the present invention. [Figure 4]FIG. 4 is a diagram showing the configuration of a heating device according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing a configuration of the opposing portion of the heating device according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the configuration of a first extension portion and a second extension portion of the heating device according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing a modified example of the heating device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0012] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the configuration of the image forming apparatus 100.

[0013] For ease of explanation, the vertical direction in the installed state (as shown in FIG. 1) in which image forming apparatus 100 can be used is defined as up-down direction D1. Also, the front-rear direction D2 is defined with the left side of image forming apparatus 100 shown in FIG. 1 as the front (front face). Also, the left-right direction D3 is defined with the front face of image forming apparatus 100 in the installed state as the reference.

[0014] The image forming apparatus 100 is a printer having a print function for forming an image based on image data. The present invention can be applied to fax machines, copy machines, multifunction machines, and the like that form images by electrophotography.

[0015] 1, the image forming apparatus 100 includes an image forming unit 1 and a sheet conveying unit 2. The image forming unit 1 and the sheet conveying unit 2 are housed in a housing 101 of the image forming apparatus 100. The housing 101 is formed in a substantially rectangular parallelepiped shape. A sheet receiving unit 102 is formed at the top of the housing 101, to which a sheet on which an image is formed by the image forming apparatus 100 is discharged.

[0016] The image forming unit 1 is capable of forming an image on a sheet by electrophotography based on image data input from an information processing device such as an external personal computer. As shown in FIG. 1, the image forming unit 1 includes a photoconductor drum 11, a charging device 12, an optical scanning device 13, a developing device 14, a transfer roller 15, a cleaning device 16, and a fixing device 17.

[0017] The photoconductor drum 11 is rotatably supported by a housing 101. The photoconductor drum 11 receives a rotational driving force transmitted from a motor (not shown) and rotates in the direction of the arrow shown in FIG.

[0018] The charging device 12 charges the surface of the photoconductor drum 11 .

[0019] The optical scanning device 13 irradiates light based on image data onto the charged surface of the photoconductor drum 11. An electrostatic latent image is formed on the surface of the photoconductor drum 11 by the optical scanning device 13.

[0020] The developing device 14 uses a developer containing toner to develop the electrostatic latent image formed on the surface of the photoconductor drum 11. A toner image is formed on the surface of the photoconductor drum 11 by the developing device 14.

[0021] The transfer roller 15 transfers the toner image formed on the surface of the photoconductor drum 11 onto a sheet that is being transported by the sheet transport section 2 toward the fixing device 17 .

[0022] The cleaning device 16 cleans the surface of the photoconductor drum 11 after the toner image has been transferred by the transfer roller 15 .

[0023] The fixing device 17 heats the sheet onto which the toner image has been transferred, thereby fixing the toner image onto the sheet.

[0024] The sheet conveying section 2 conveys a sheet on which an image is formed by the image forming section 1. As shown in FIG 1, the sheet conveying section 2 includes a paper feed cassette 21, a sheet conveying path 22, a paper feed unit 23, a pair of registration rollers 24, and a pair of paper discharge rollers 25.

[0025] The paper feed cassette 21 accommodates sheets on which an image is formed by the image forming unit 1. As shown in FIG. 1, the paper feed cassette 21 is provided at the bottom of the housing 101. For example, the paper feed cassette 21 accommodates sheet materials such as paper, coated paper, postcards, envelopes, and overhead projector sheets. The paper feed cassette 21 has a lift plate that lifts up multiple sheets accommodated therein. In the paper feed cassette 21, the posture of the accommodated sheet is adjusted so that the sheet is positioned at the center of the paper feed cassette 21 in the left-right direction D3.

[0026] The sheet transport path 22 is a passageway through which the sheet travels from the paper feed cassette 21 to the sheet receiving section 102 via the transfer roller 15 and the fixing device 17. The sheet transport path 22 is provided with a plurality of roller pairs including a registration roller pair 24 and a paper discharge roller pair 25. In the sheet transport path 22, the sheet discharged from the paper feed cassette 21 by the plurality of roller pairs is transported in a transport direction D4 (see FIG. 1 ) toward the sheet receiving section 102. The sheet transport path 22 is formed by a pair of transport guide members provided in the housing 101. In the sheet transport path 22, the sheet is transported so as to move along the center of the sheet transport path 22 in the left-right direction D3.

[0027] The paper feed unit 23 sends out the sheets stored in the paper feed cassette 21 one by one to the sheet transport path 22. The paper feed unit 23 includes a pickup roller, a paper feed roller, and a retard roller. The pickup roller rotates while contacting an upper surface of the topmost sheet among the multiple sheets lifted by the lift plate of the paper feed cassette 21, thereby sending the sheet to the paper feed roller. The paper feed roller rotates while contacting an upper surface of the sheet sent out by the pickup roller, thereby sending the sheet to the sheet transport path 22. The retard roller is provided so as to be biased from the underside of the paper feed roller toward the paper feed roller. When multiple sheets are sent out by the pickup roller in an overlapping state, the retard roller separates the sheets other than the topmost sheet from the overlapping multiple sheets.

[0028] The pair of registration rollers 24 transports the sheet to the transfer position in accordance with the timing at which the toner image formed on the surface of the photosensitive drum 11 is transported to the transfer position by the transfer roller 15 by the rotation of the photosensitive drum 11 .

[0029] The pair of paper discharge rollers 25 discharges the sheet on which the toner image has been fixed by the fixing device 17 to a sheet receiving section 102 .

[0030] [Configuration of fixing device 17] Next, the configuration of the fixing device 17 will be described with reference to Fig. 2. Here, Fig. 2 is a cross-sectional view showing the configuration of the fixing device 17.

[0031] As shown in FIG. 2, the fixing device 17 includes a fixing belt 31, a heating device 32, a first support portion 33, a second support portion , and a pressure roller .

[0032] The fixing belt 31 is heated by a heating device 32. The fixing belt 31 comes into contact with a sheet in a heated state, thereby fixing the toner image transferred to the sheet to the sheet. As shown in FIG. 2, the fixing belt 31 is endless. The fixing belt 31 is flexible. The fixing belt 31 has a base layer, an elastic layer provided on the outer peripheral surface of the base layer, and a release layer provided on the outer peripheral surface of the elastic layer. The base layer is made of a material such as polyimide or nickel alloy. The elastic layer is made of a material such as silicone rubber. The release layer is made of a fluorine-based resin material such as PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin). The fixing belt 31 is long along the left-right direction D3. The size of the fixing belt 31 in the left-right direction D3 is determined according to the maximum size of a sheet on which an image can be formed by the image forming apparatus 100. The fixing belt 31 is an example of a fixing member of the present invention.

[0033] The pressure roller 35 is provided at a position where it can come into contact with the outer peripheral surface 31A (see FIG. 2) of the fixing belt 31. Specifically, as shown in FIG. 2, the pressure roller 35 is provided below the fixing belt 31. The pressure roller 35 is long along the left-right direction D3. The pressure roller 35 includes a shaft portion 35A and an elastic layer 35B. The shaft portion 35A is formed in a cylindrical shape from a metal material. The elastic layer 35B is formed on the outer periphery of the shaft portion 35A from an elastic material such as silicone rubber. The surface of the elastic layer 35B is coated with PFA or the like. The shaft portion 35A is rotatably supported by a pair of bearing portions. The pair of bearing portions are supported by the housing of the fixing device 17 so as to be movable along a direction perpendicular to the shaft portion 35A and toward the heating device 32. The pair of bearing portions are biased toward the heating device 32 by a biasing member (not shown). As a result, the pressure roller 35 rotatably supported by the pair of bearings is also biased toward the heating device 32. The pressure roller 35 receives a rotational driving force supplied from a motor (not shown) and rotates in a rotational direction D5 (see FIG. 2).

[0034] The heating device 32 heats the fixing belt 31. As shown in Fig. 2, the heating device 32 is provided inside an inner circumferential surface 31B (see Fig. 2) of the fixing belt 31, at a position facing the pressure roller 35 with the fixing belt 31 interposed therebetween. The heating device 32 is elongated in the left-right direction D3, and extends across both outer sides of the fixing belt 31 in the left-right direction D3. The heating device 32 is pressed by the pressure roller 35 that is biased by the biasing member.

[0035] The first support portion 33, together with the second support portion 34, supports the heating device 32 which is pressed by the pressure roller 35. As shown in FIG. 2, the first support portion 33 is provided on the inside of the inner circumferential surface 31B of the fixing belt 31. The first support portion 33 is elongated in the left-right direction D3 and extends across both outsides of the fixing belt 31 in the left-right direction D3. A recess 33A corresponding to the shape of the heating device 32 is formed in the bottom of the first support portion 33. The heating device 32 is fitted into the recess 33A.

[0036] The second support section 34 supports the heating device 32 pressed by the pressure roller 35 together with the first support section 33. As shown in FIG. 2, the second support section 34 is provided inside the inner circumferential surface 31B of the fixing belt 31, at a position facing the pressure roller 35 with the first support section 33 interposed therebetween. The second support section 34 is long in the left-right direction D3 and extends across both outer sides of the fixing belt 31 in the left-right direction D3. Both ends of the second support section 34 in the left-right direction D3 are fixed so as not to move in the biasing direction of the biasing member that biases the pressure roller 35. As a result, the second support section 34 supports the heating device 32 pressed by the pressure roller 35 and the first support section 33.

[0037] As the pressure roller 35 is biased by the biasing member, a fixing nip portion 36 (see FIG. 2) is formed between the fixing belt 31 and the pressure roller 35, where the toner image transferred to the sheet is fixed to the sheet. In this specification, the region where the fixing belt 31 and the pressure roller 35 contact each other is defined as the fixing nip portion 36. Note that a lubricant such as Si grease and fluorine grease is applied between the heating device 32 and the inner circumferential surface 31B of the fixing belt 31.

[0038] The fixing belt 31 is sandwiched between the heating device 32 and the pressure roller 35. When the pressure roller 35 rotates in a rotation direction D5, the fixing belt 31 rotates along a belt rotation direction D6 (see FIG. 2) following the rotation of the pressure roller 35.

[0039] The first support portion 33 includes a pair of guide portions 33B, 33C (see FIG. 2) that contact an inner circumferential surface 31B of the fixing belt 31 to guide the running of the fixing belt 31. The pair of guide portions 33B, 33C are provided on both ends of the first support portion 33 in the front-rear direction D2. The fixing belt 31 is guided by the pair of guide portions 33B, 33C to run along a predetermined running path.

[0040] The second support portion 34 may be biased toward the pressure roller 35. In this case, the pressure roller 35 does not need to be biased by the biasing member.

[0041] [Configuration of heating device 32] Next, the configuration of the heating device 32 according to the embodiment of the present invention will be described with reference to Fig. 2 to Fig. 4. Fig. 3 is a cross-sectional view showing the configuration of the heating device 32. Fig. 4 is a view showing the configuration of the heating device 32, as viewed from below. In Fig. 4, each of the opposing parts 50 is indicated by a dashed line.

[0042] 3 and 4, the heating device 32 includes a substrate 41, four resistance heating elements 42 (42A to 42D), connection portions 43A to 43B provided for each resistance heating element 42, electrode portions 44X1 to 44X2, wiring portions 45X1 to 45X3, electrode portions 44Y1 to 44Y2, wiring portions 45Y1 to 45Y3, a protective layer 46, and a sensor 47.

[0043] The substrate 41 is a flat member that is long in the left-right direction D3. The substrate 41 is made of a material that is excellent in heat resistance, electrical insulation, and low heat capacity. For example, the substrate 41 is made of ceramic such as alumina. For example, the substrate 41 is formed to have a thickness of 0.5 to 1.0 mm (millimeters).

[0044] The size of the substrate 41 in the left-right direction D3 is larger than that of the fixing belt 31. The substrate 41 is disposed so as to extend on both outer sides of the fixing belt 31 in the left-right direction D3. Therefore, both end portions of the substrate 41 in the left-right direction D3 protrude outward from the fixing belt 31 in the left-right direction D3.

[0045] As shown in FIG. 2 and FIG. 3, the lower surface of the substrate 41 faces the inner circumferential surface 31B of the fixing belt 31. As shown in FIG. 3 and FIG. 4, on the lower surface of the substrate 41, four resistance heating elements 42 (42A to 42D), connection parts 43A to 43B provided for each resistance heating element 42, electrode parts 44X1 to 44X2, wiring parts 45X1 to 45X3, electrode parts 44Y1 to 44Y2, and wiring parts 45Y1 to 45Y3 are arranged. In addition, the facing area of ​​the lower surface of the substrate 41 facing the inner circumferential surface 31B of the fixing belt 31 is covered with a protective layer 46 (see FIG. 3). The protective layer 46 is made of an electrically insulating material such as glass. For example, the protective layer 46 is formed to a thickness of 20 to 50 μm (micrometers).

[0046] As shown in FIG. 2 and FIG. 3, the upper surface of the substrate 41 faces the bottom surface of the recess 33A of the first support portion 33. As shown in FIG. 3, a sensor 47 is disposed on the upper surface of the substrate 41. The sensor 47 outputs an electric signal according to the temperature of the heating device 32. The electric signal output from the sensor 47 is input to a control unit (not shown). The control unit controls the driving of the heating device 32 based on the electric signal input from the sensor 47. Note that a separate sensor may be provided to detect the temperature of the fixing belt 31. In this case, the control unit may control the driving of the heating device 32 using the sensor.

[0047] 4, each of the resistance heating elements 42 is formed in a long strip shape in the left-right direction D3, which is the longitudinal direction of the substrate 41. For example, each of the resistance heating elements 42 is formed to have a width of 5 to 15 mm (millimeters) along the front-rear direction D2, which is the width direction of the substrate 41. Each of the resistance heating elements 42 is also formed to have a thickness of 5 to 15 μm (micrometers) in the thickness direction (up-down direction D1) of the substrate 41 perpendicular to the left-right direction D3 and the front-rear direction D2. Each of the resistance heating elements 42 generates heat in response to power supply from a power source (not shown) that outputs an AC voltage. For example, each of the resistance heating elements 42 is formed of a material such as silver-palladium (Ag / Pd).

[0048] As shown in FIG. 4, the four resistance heating elements 42 are arranged side by side along the left-right direction D3 on the substrate 41. Each of the resistance heating elements 42 is arranged with a gap between it and the other adjacent resistance heating elements 42 in the left-right direction D3. For example, each of the resistance heating elements 42 is arranged with a gap of 0.3 to 1.0 mm (millimeters) between it and the other adjacent resistance heating elements 42. The row of the four resistance heating elements 42 has a size smaller than that of the fixing belt 31 in the left-right direction D3. The row of the four resistance heating elements 42 is arranged inside the facing region on the lower surface of the substrate 41. The row of the four resistance heating elements 42 is arranged such that a center portion in the left-right direction D3 faces a center portion in the left-right direction D3 of a sheet passing through the fixing nip portion 36.

[0049] As shown in FIG. 4, each of the resistance heating elements 42 is sandwiched between a connection portion 43A and a connection portion 43B in the width direction of the substrate 41 (front-rear direction D2).

[0050] The connection portion 43A is electrically connected to the front end of the resistance heating element 42 in the front-rear direction D2. As shown in FIG. 4, the connection portion 43A is provided along the front end of the resistance heating element 42 in the front-rear direction D2. The connection portion 43A extends across both ends of the resistance heating element 42 in the left-right direction D3. The connection portion 43A is formed in a long strip shape in the left-right direction D3. For example, the connection portion 43A is formed to have a width of 1 to 2 mm (millimeters) along the width direction (front-rear direction D2) of the substrate 41. The connection portion 43A is formed to have a thickness of 20 to 40 μm (micrometers) in the thickness direction (up-down direction D1) of the substrate 41. That is, the resistance heating element 42 is thinner in the thickness direction (up-down direction D1) of the substrate 41 than the connection portion 43A. The connection portion 43A is formed of a conductor such as a metal material having a higher conductivity than the resistance heating element 42.

[0051] The connection portion 43B is electrically connected to a rear end portion of the resistance heating element 42 in the front-rear direction D2. As shown in Fig. 4, the connection portion 43B is provided along the rear end portion of the resistance heating element 42 in the front-rear direction D2. The connection portion 43B also extends across both ends of the resistance heating element 42 in the left-right direction D3. The connection portion 43B has the same shape and is made of the same material as the connection portion 43A.

[0052] The electrode portions 44X1 to 44X2 are connected to the power source. As shown in FIG. 4, the wiring portion 45X1 electrically connects the electrode portion 44X1 to the connection portion 43A corresponding to the resistive heating element 42A arranged on the rightmost side among the four resistive heating elements 42. The wiring portion 45X2 electrically connects the connection portion 43B corresponding to the resistive heating element 42A to the connection portion 43B corresponding to the resistive heating element 42D arranged on the leftmost side among the four resistive heating elements 42. The wiring portion 45X3 electrically connects the connection portion 43A corresponding to the resistive heating element 42D to the electrode portion 44X2. As shown in FIG. 4, in the substrate 41, an electric path is formed from the electrode portion 44X1 to the electrode portion 44X2 via the wiring portion 45X1, the resistive heating element 42A, the wiring portion 45X2, the resistive heating element 42D, and the wiring portion 45X3. The electrode portions 44X1-44X2 and the wiring portions 45X1-45X3 are formed of the same material (conductor) as the connection portion 43A. When the electrode portions 44X1-44X2 are connected to the power supply, a current flows through the resistance heating element 42A and the resistance heating element 42D, causing the resistance heating element 42A and the resistance heating element 42D to generate heat.

[0053] The electrode portions 44Y1-44Y2 are connected to the power supply separately from the electrode portions 44X1-44X2. As shown in Fig. 4, the wiring portion 45Y1 electrically connects the electrode portion 44Y1 to a connection portion 43A corresponding to the resistive heating element 42B, which is adjacent to the resistive heating element 42A on the left side of the resistive heating element 42A among the four resistive heating elements 42. The wiring portion 45Y2 electrically connects the connection portion 43B corresponding to the resistive heating element 42B to a connection portion 43B corresponding to the resistive heating element 42C, which is adjacent to the resistive heating element 42B on the left side of the resistive heating element 42B among the four resistive heating elements 42. The wiring portion 45Y3 electrically connects the connection portion 43A corresponding to the resistive heating element 42C to the electrode portion 44Y2. 4, an electric path is formed on the substrate 41 from the electrode portion 44Y1 through the wiring portion 45Y1, the resistive heating element 42B, the wiring portion 45Y2, the resistive heating element 42C, and the wiring portion 45Y3 to the electrode portion 44Y2. The electrode portions 44Y1-44Y2 and the wiring portions 45Y1-45Y3 are made of the same material (conductor) as the connection portion 43A. When the electrode portions 44Y1-44Y2 are connected to the power source, a current flows through the resistive heating element 42B and the resistive heating element 42C, causing the resistive heating element 42B and the resistive heating element 42C to generate heat.

[0054] In image forming apparatus 100, the resistance heating element 42A and the resistance heating element 42D are switched on and off depending on the size in the left-right direction D3 of the sheet passing through fixing nip portion 36. Specifically, image forming apparatus 100 uses a switch (not shown) that can switch between conduction and interruption of an electrical path from electrode portion 44X1 via the power source to electrode portion 44X2, to switch on and off the generation of heat from resistance heating element 42A and resistance heating element 42D.

[0055] The number of resistance heating elements 42 arranged on substrate 41 along the longitudinal direction of substrate 41 may be three, or may be five or more. Furthermore, resistance heating elements 42 are not limited to being elongated strip-shaped (rectangular) in the longitudinal direction of substrate 41 (left-right direction D3), and may be formed in a parallelogram shape.

[0056] However, when a plurality of resistance heating elements 42 are arranged side by side along the longitudinal direction of the substrate 41 as in the heating device 32, the heating performance of the facing portion 50 (see FIG. 4) where the two resistance heating elements 42 face each other is reduced. In response to this, a heating device that improves the heating performance of the facing portion 50 by reducing the electrical resistance of each end of the resistance heating elements 42 included in the facing portion 50 is known as a related art. Specifically, in the heating device according to the related art, a notch is formed on both sides in the width direction (front-rear direction D2) of the substrate 41 at each end of the resistance heating elements 42 included in the facing portion 50.

[0057] However, in the heating device of the related technology, both outer sides (cut-out portions) of the width direction (front-to-back direction D2) of the substrate 41 at each end of the resistive heating element 42 included in the opposing portion 50 do not generate heat, and therefore the heating performance of both ends in the width direction of the opposing portion 50 cannot be sufficiently improved.

[0058] In contrast, in the heating device 32 according to the embodiment of the present invention, as described below, it is possible to improve the heating performance in the facing portion 50 where the two resistance heating elements 42 face each other.

[0059] Specifically, in the heating device 32, a first extension portion 51 and a second extension portion 52 are provided at each end of the resistance heating element 42 included in the facing portion 50.

[0060] [Configuration of the first extension portion 51 and the second extension portion 52] Hereinafter, the first extension portion 51 and the second extension portion 52 provided on the resistance heating element 42A will be described with reference to Fig. 5 and Fig. 6. Here, Fig. 5 is an enlarged view of a facing portion 50 including an end portion of the resistance heating element 42A, out of the three facing portions 50 shown in Fig. 4. Also, Fig. 6 is a cross-sectional view taken along the line VI-VI in Fig. 5.

[0061] The following description also applies to the first extending portion 51 and the second extending portion 52 provided on each of the resistance heating elements 42B to 42D.

[0062] The first extension portion 51 is conductive. As shown in FIG. 5 and FIG. 6, the first extension portion 51 extends from the connection portion 43A to the connection portion 43B at an end of the resistance heating element 42A facing the resistance heating element 42B along an outer periphery surrounding the longitudinal direction (left-right direction D3) of the substrate 41 in the resistance heating element 42A. The first extension portion 51 is laminated on the resistance heating element 42A in the thickness direction (up-down direction D1) of the substrate 41. The resistance heating element 42A is an example of the first resistance heating element of the present invention. The resistance heating element 42B is an example of the second resistance heating element of the present invention. The connection portion 43A is an example of the first conductor of the present invention. The connection portion 43B is an example of the second conductor of the present invention.

[0063] Specifically, the first extension portion 51 is formed on a surface of the resistive heating element 42A opposite to the surface that contacts the substrate 41 (the lower surface of the resistive heating element 42A in the vertical direction D1) (see FIG. 6). The first extension portion 51 is formed so as to protrude from the connection portion 43A of the resistive heating element 42A to the lower surface of the resistive heating element 42A in the vertical direction D1 (see FIG. 5). This makes it possible to avoid the occurrence of a step in the resistive heating element 42A (see FIG. 7) compared to a configuration in which the first extension portion 51 is formed on the surface of the resistive heating element 42A that contacts the substrate 41 (the upper surface of the resistive heating element 42A in the vertical direction D1) (see FIG. 7).

[0064] For example, the first extending portion 51 is formed of the same material (conductor) as the connecting portion 43A. This makes it possible to form the first extending portion 51 together with the connecting portion 43A at the same time that the connecting portion 43A (pattern) is printed on the substrate 41.

[0065] For example, the first extending portion 51 is formed in a rectangular shape that is long in the width direction (front-rear direction D2) of the substrate 41. For example, the first extending portion 51 is formed with a width of 1 to 3 mm (millimeters) in the longitudinal direction (left-right direction D3) of the substrate 41. Moreover, the first extending portion 51 is formed with a length of 1 to 4 mm (millimeters) in the width direction (front-rear direction D2) of the substrate 41.

[0066] The second extension portion 52 is conductive. As shown in Fig. 5 and Fig. 6, the second extension portion 52 extends from the connection portion 43B toward the connection portion 43A at an end of the resistance heating element 42A facing the resistance heating element 42B along an outer periphery surrounding the longitudinal direction (left-right direction D3) of the substrate 41 of the resistance heating element 42A. The second extension portion 52 is laminated in the thickness direction (up-down direction D1) of the substrate 41 with respect to the resistance heating element 42A.

[0067] The second extending portion 52 is formed to be symmetrical with respect to a plane (plane of symmetry) that passes through the center of the resistance heating element 42A in the front-rear direction D2 and is perpendicular to the front-rear direction D2 (see FIGS. 5 and 6).

[0068] By providing the first extension portion 51 and the second extension portion 52 at the end of the resistance heating element 42A facing the resistance heating element 42B, a second current path is formed that has a smaller electrical resistance than the first current path between the connection portion 43A and the connection portion 43B via the resistance heating element 42A. The second current path is a current path between the first extension portion 51 and the second extension portion 52 via the resistance heating element 42A. In addition, in FIG. 6, the current flowing along the second current path is indicated by a thick line with an arrow. This makes it easier for a current to flow along the width direction (front-back direction D2) of the substrate 41 at the end of the resistance heating element 42A facing the resistance heating element 42B. Therefore, the current flowing through the end of the resistance heating element 42A facing the resistance heating element 42B increases, and the amount of heat generated at the end becomes greater than other parts of the resistance heating element 42A.

[0069] Furthermore, in heating device 32, unlike the heating device according to the related art, an increase in the amount of heat generated at the end of resistive heating element 42A facing resistive heating element 42B is realized without providing a notch on both sides in the width direction (front-rear direction D2) of substrate 41 at the end. That is, in heating device 32, both sides in the width direction (front-rear direction D2) of substrate 41 at the end of resistive heating element 42A facing resistive heating element 42B also generate heat in response to energization.

[0070] Therefore, in the heating device 32, it is possible to improve the heating performance in the facing portion 50 where the two resistance heating elements 42 face each other, as compared with the heating device according to the related art.

[0071] The distance between the first extending portion 51 and the second extending portion 52 may be adjusted as desired so that a desired amount of heat is obtained at the end of the resistance heating element 42A that faces the resistance heating element 42B.

[0072] Furthermore, the shape of the first extending portion 51 and the second extending portion 52 is not limited to a rectangular shape, and may be a triangular shape, a parallelogram shape, an elliptical shape, or the like.

[0073] In addition, the second extending portion 52 does not have to be formed so as to be symmetrical with respect to a plane (symmetric plane) that passes through the center of the resistance heating element 42A in the front-rear direction D2 and is perpendicular to the front-rear direction D2. In addition, the heating device 32 does not have to be provided with the second extending portion 52.

[0074] Also, as shown in FIG. 7, the first extension portion 51 and the second extension portion 52 may be formed on the surface of the resistive heating element 42A that comes into contact with the substrate 41 (the upper surface of the resistive heating element 42A in the vertical direction D1).

[0075] [Notes on the invention] The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0076] <Appendix 1> a first resistive heating element and a second resistive heating element arranged on the substrate at a distance from each other in the longitudinal direction of the substrate; a first conductor and a second conductor sandwiching the first resistive heating element in a width direction of the substrate perpendicular to the longitudinal direction; and a conductive extension portion extending from the first conductor to the second conductor at an end of the first resistive heating element facing the second resistive heating element along an outer periphery surrounding the longitudinal direction of the first resistive heating element, the extension portion being stacked in a thickness direction of the substrate perpendicular to the longitudinal direction and the width direction relative to the first resistive heating element.

[0077] <Appendix 2> 2. The heating device according to claim 1, wherein the extension is formed on a surface of the first resistive heating element opposite to a surface that contacts the substrate.

[0078] <Appendix 3> 3. The heating device of claim 2, wherein the extension is formed from the same material as the first conductor.

[0079] <Appendix 4> 4. The heating device according to claim 3, wherein the first resistive heating element is thinner in the thickness direction than the first conductor.

[0080] <Appendix 5> The heating device according to any one of Appendices 1 to 4, wherein the extension portion is a first extension portion, and the heating device is provided with a conductive second extension portion that extends from the second conductor to the first conductor at an end of the first resistive heating element facing the second resistive heating element along an outer periphery surrounding the longitudinal direction of the first resistive heating element, and the second extension portion is laminated in the thickness direction with respect to the first resistive heating element.

[0081] <Appendix 6> 6. An image forming apparatus comprising: a fixing member for fixing a toner image onto a sheet; and a heating device according to any one of claims 1 to 5 for heating the fixing member. [Explanation of symbols]

[0082] 1 Image forming section 2 Sheet transport section 11 Photoconductor drum 12 Charging device 13 Optical scanning device 14 Developing device 15 Transfer roller 16 Cleaning equipment 17 Fixing device 21 Paper feed cassette 22 Sheet transport path 23 Paper feed unit 24 Registration Roller Pair 25 Paper ejection roller pair 31 Fixing belt 32 Heating device 33 Support part 34 Pressing member 35 Pressure Roller 41 Substrate 42 Resistance heating element 43 Connection 44 Electrode section 45 Wiring section 46 Protective layer 47 Sensors 48 Power supply 100 Image forming device

Claims

1. A substrate that is long in one direction; a first resistive heating element and a second resistive heating element disposed on the substrate at an interval in a longitudinal direction of the substrate; a first conductor and a second conductor sandwiching the first resistive heating body in a width direction of the substrate perpendicular to the longitudinal direction; a conductive extension portion extending from the first conductor toward the second conductor along an outer periphery surrounding the longitudinal direction of the first resistive heating element at an end portion of the first resistive heating element facing the second resistive heating element; Equipped with The extension portion is stacked in a thickness direction of the substrate, which is perpendicular to the longitudinal direction and the width direction of the first resistive heating element.

2. the extension portion is formed on a surface of the first resistive heating element opposite to a surface that contacts the substrate; The heating device according to claim 1 .

3. The extension portion is formed of the same material as the first conductor. The heating device according to claim 2.

4. The first resistive heating element has a thickness smaller than that of the first conductor in the thickness direction. The heating device according to claim 3.

5. The extension portion is a first extension portion, The heating device includes: a second conductive extension portion extending from the second conductor toward the first conductor at an end of the first resistive heating element facing the second resistive heating element along an outer periphery surrounding the longitudinal direction of the first resistive heating element, The second extension portion is laminated on the first resistance heating element in the thickness direction. The heating device according to claim 1 .

6. a fixing member for fixing the toner image onto the sheet; a heating device according to any one of claims 1 to 5 for heating the fixing member; An image forming apparatus comprising:

Images