Image forming device

Abstract

This application provides an image forming apparatus capable of suppressing temperature unevenness in a fixing device. The image forming apparatus of one embodiment includes an image forming unit, a cylindrical body, a first heating element group, a second heating element group, and a heating element unit. The image forming unit forms an image on a sheet. The cylindrical body is film-shaped and contacts the sheet moving in a first direction to fix the image. The first heating element group has a plurality of first heating element elements arranged in a second direction orthogonal to the first direction, spaced apart by first non-heated regions. The second heating element group has a plurality of second heating element elements arranged in the second direction, spaced apart by second non-heated regions, with the second non-heated regions and the first non-heated regions positioned at different locations in the second direction. The second heating element group and the first heating element group are arranged in the first direction. The heating element unit contacts the inner surface of the cylindrical body at a first surface with the second direction as its long side and the first direction as its short side.

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus. Background Technology

[0002] Image forming apparatuses that form images on sheets (paper) have been used. These apparatuses include a fixing device that fixes a toner (recording agent) onto the sheet. There is a need for image forming apparatuses capable of suppressing temperature unevenness in the fixing device. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an image forming apparatus capable of suppressing temperature unevenness in the fixing device.

[0004] An image forming apparatus according to an embodiment includes: an image forming unit for forming an image on a sheet; a film-like cylindrical body for contacting the sheet moving in a first direction to fix the image; and a heating element unit for contacting the inner surface of the cylindrical body at a first surface, the first surface having a second direction orthogonal to the first direction as its long side and the first direction as its short side. The heating element unit includes: a first heating element group having a plurality of first heating element elements arranged in the second direction with a first non-heating region between them; and a second heating element group having a plurality of second heating element elements arranged in the second direction with a second non-heating region between them, the second non-heating region and the first non-heating region being disposed at different positions in the second direction, and the second heating element group and the first heating element group being arranged in the first direction. Attached Figure Description

[0005] Figure 1 This is a simplified configuration diagram of the image forming apparatus according to an embodiment.

[0006] Figure 2 This is a hardware configuration diagram of an image forming apparatus.

[0007] Figure 3 This is a front sectional view of the fixing device.

[0008] Figure 4 This is a front sectional view of the heating element unit.

[0009] Figure 5 This is a bottom sectional view of the heating element unit.

[0010] Figure 6 This is a bottom view of the heating element unit.

[0011] Figure 7 This is a bottom sectional view of the heating element unit in a modified embodiment.

[0012] Explanation of reference numerals in the attached figures

[0013] S: Sheet; 1: Image forming apparatus; 3: Image forming unit; 30: Fixing apparatus; 35: Cylindrical film (cylindrical body); 40: Heating element unit; 41: First surface; 50: First heating element group; 51, 53: End heating element; 52: Central heating element; 55: First heating element; 57: First non-heating area; 60: Second heating element group; 61, 64: End heating element; 62, 63: Central heating element; 65: Second heating element; 67: Second non-heating area. Detailed Implementation

[0014] The image forming apparatus of the embodiment will now be described with reference to the accompanying drawings.

[0015] Figure 1 This is a simplified configuration diagram of the image forming apparatus according to an embodiment.

[0016] The image forming apparatus 1 performs the process of forming an image on a sheet S. The sheet S can be paper. The image forming apparatus 1 includes a housing 10, a scanner unit 2, an image forming unit 3, a sheet supply unit 4, a conveying unit 5, a tray 7, a flipping unit 9, a control panel 8, and a control unit 6.

[0017] The outer casing 10 forms the shape of the image forming apparatus 1.

[0018] The scanner unit 2 reads the image information of the object to be copied as the brightness of light and generates an image signal. The scanner unit 2 outputs the generated image signal to the image forming unit 3.

[0019] The image forming unit 3 forms a toner image based on an image signal from the scanner unit 2 or an external source. The toner image is an image formed using toner or other materials. The image forming unit 3 transfers the toner image onto the surface of the sheet S. The image forming unit 3 heats and pressurizes the toner image on the surface of the sheet S to fix the toner image onto the sheet S.

[0020] The sheet supply unit 4, in coordination with the image forming unit 3, supplies sheets S one by one to the conveying unit 5 during the timing of forming a toner image. The sheet supply unit 4 has a sheet receiving unit 20 and a pick-up roller 21.

[0021] The sheet receiving section 20 stores sheets S of specified sizes and types.

[0022] Pick-up roller 21 picks up sheets S one by one from sheet receiving section 20. Pick-up roller 21 supplies the picked-up sheets S to conveying section 5.

[0023] The conveying unit 5 conveys the sheet S supplied from the sheet supply unit 4 to the image forming unit 3. The conveying unit 5 has a conveying roller 23 and a alignment roller 24.

[0024] The conveying roller 23 conveys the sheet S supplied by the pick-up roller 21 to the alignment roller 24. The conveying roller 23 causes the leading edge of the sheet S in the conveying direction to abut against the alignment clamping part RN, which serves as the clamping part of the alignment roller 24.

[0025] The alignment roller 24 aligns the front end of the sheet S in the conveying direction by flexing it at the alignment clamping part RN. The alignment roller 24 conveys the sheet S according to the timing of the toner image transfer onto the sheet S by the image forming unit 3.

[0026] The image forming unit 3 will be described.

[0027] The image forming unit 3 has multiple image forming sections F, a laser scanning unit 26, an intermediate transfer belt 27, a transfer section 28, and a fixing device 30.

[0028] The image forming unit F has a photosensitive drum D. The image forming unit F forms a toner image corresponding to the image signal on the photosensitive drum D. Multiple image forming units FY, FM, FC, and FK respectively form toner images using yellow, magenta, cyan, and black toners.

[0029] An electric charge makes the surface of the photosensitive drum D charged. The developer contains a developer including yellow, magenta, cyan, and black toners. The developer develops the electrostatic latent image on the photosensitive drum D in order to form toner images of various colors on the photosensitive drum D.

[0030] The laser scanning unit 26 scans the charged photosensitive drum D with laser L to expose the photosensitive drum D. The laser scanning unit 26 uses different lasers LY, LM, LC, and LK to expose the photosensitive drum D in the image forming sections FY, FM, FC, and FK of various colors to form electrostatic latent images.

[0031] The toner image is transferred onto the surface of the photosensitive drum D in one pass through the intermediate transfer belt 27.

[0032] The transfer unit 28 transfers the toner image that was first transferred on the intermediate transfer belt 27 to the surface of the sheet S at the secondary transfer position.

[0033] The fixing device 30 heats and pressurizes the toner image transferred to the sheet S to fix the toner image onto the sheet S.

[0034] The flipping unit 9 flips the sheet S to form an image on the back side of the sheet S. The flipping unit 9 flips the sheet S discharged from the fixing unit 30 in both directions via a switchback mechanism. The flipping unit 9 then conveys the flipped sheet S toward the alignment roller 24.

[0035] The tray 7 holds the sheet S that is ejected to form the image.

[0036] The control panel 8 is part of the input section where the operator inputs information for operating the image forming apparatus 1. The control panel 8 has a touch panel and various physical keys.

[0037] The control unit 6 controls each part of the image forming apparatus 1.

[0038] Figure 2 This is a hardware configuration diagram of the image forming apparatus according to the embodiment. The image forming apparatus 1 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, etc., connected via a bus, and executes a program. By executing the program, the image forming apparatus 1 functions as a device including a scanner unit 2, an image forming unit 3, a sheet supply unit 4, a transport unit 5, a flipping unit 9, a control panel 8, and a communication unit 90.

[0039] CPU 91 functions as control unit 6 by executing programs stored in memory 92 and auxiliary storage device 93. Control unit 6 controls the operation of each functional unit of image forming apparatus 1.

[0040] The auxiliary storage device 93 is constructed using storage devices such as magnetic hard disk devices and semiconductor storage devices. The auxiliary storage device 93 stores information.

[0041] The communication unit 90 is configured to include a communication interface for connecting its own device to an external device. The communication unit 90 communicates with the external device through the communication interface.

[0042] The fixing device 30 will be described in detail.

[0043] Figure 3 This is a front sectional view of the fixing device. The fixing device 30 includes a pressure roller 31 and a heating roller 34. A fixing clamping portion FN is formed between the pressure roller 31 and the heating roller 34.

[0044] In this application, the z-direction, x-direction, and y-direction are defined as follows: The z-direction is the direction in which the heating roller 34 and the pressure roller 31 are arranged. The +z-direction is the direction from the heating roller 34 toward the pressure roller 31. The x-direction (first direction) is the conveying direction of the sheet S in the fixing clamping part FN, and the +x-direction is the downstream side of the conveying direction of the sheet S. The y-direction (second direction) is the direction orthogonal to the z-direction and the x-direction, and is the axial direction of the cylindrical film 35 of the heating roller 34.

[0045] The pressure roller 31 applies pressure to the toner image of the sheet S that enters the fixing clamping section FN. The pressure roller 31 has a mandrel 32 and an elastic layer 33. The configuration of the pressure roller 31 is not limited to the above and can be configured in various ways.

[0046] The mandrel 32 is formed into a cylindrical shape from a metal material such as stainless steel. The elastic layer 33 is formed from an elastic material such as silicone rubber. The elastic layer 33 has a certain thickness on the outer peripheral surface of the mandrel 32. The release layer can also be a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), located on the outer peripheral surface of the elastic layer 33.

[0047] The pressure roller 31 is driven by a motor to rotate. If the pressure roller 31 rotates with the fixing clamping part FN formed, the cylindrical film 35 of the heating roller 34 rotates passively. The pressure roller 31 conveys the sheet S along the conveying direction W by rotating with the sheet S present at the fixing clamping part FN.

[0048] The heating roller 34 heats the toner image on the sheet S that enters the fixing clamping section FN. The heating roller 34 includes a cylindrical film (cylindrical body) 35, a heating element unit 40, a heat transfer component 48, a support component 36, a support bar 38, and a temperature sensing element 80. The configuration of the heating roller 34 is not limited to the above and can be configured in various ways.

[0049] The tubular film 35 contacts a sheet moving in the x-direction to fix the image. The tubular film 35 is a film-shaped tubular body. From the inner peripheral side, the tubular film 35 has a base layer, an elastic layer, and a release layer in sequence. The base layer is formed of a material such as nickel (Ni). The elastic layer is formed of an elastic material such as silicone rubber. The release layer is formed of a material such as PFA resin.

[0050] The heating element unit 40 is located inside the cylindrical membrane 35. The heating element unit 40 is formed as a rectangular plate with the y-direction as its longer side and the x-direction as its shorter side. In both the x and y directions, the direction closer to the center of the heating element unit 40 is sometimes referred to as the inner side, and the direction farther from the center of the heating element unit 40 is referred to as the outer side. The first surface 41 of the heating element unit 40 in the +z direction is in contact with the inner surface of the cylindrical membrane 35 through a grease.

[0051] Figure 4 for Figure 5 The image shows a front sectional view of the heating element unit at line IV-IV. The heating element unit 40 includes a substrate 44, a first heating element group 50, a second heating element group 60, and a wiring group 70. Sometimes, the first heating element group 50 and the second heating element group 60 are collectively referred to as heating element groups 50 and 60.

[0052] The substrate 44 is formed of a metallic material such as stainless steel or a ceramic material such as aluminum nitride. The substrate 44 is formed into a rectangular plate shape with the y-direction as the long side and the x-direction as the short side. The insulating layer 45 is formed in the +z direction of the substrate 44 using a glass material or the like. Alternatively, the insulating layer can be formed in the -z direction of the substrate 44 in the same way as the insulating layer 45 formed in the +z direction of the substrate 44.

[0053] The heating element assemblies 50 and 60 have heating element elements formed of silver / palladium alloy or TaSiO2, etc. The heating element assemblies 50 and 60 are energized through the wiring assembly 70, thereby generating heat. The heating element assemblies 50 and 60 and the wiring assembly 70 are arranged in the +z direction of the insulating layer 45. The protective layer 46 is formed of a glass material or the like to cover the heating element assemblies 50 and 60 and the wiring assembly 70. Alternatively, the protective layer may be formed in the -z direction of the substrate 44, similar to the protective layer 46 formed in the +z direction of the substrate 44.

[0054] like Figure 3 As shown, the heat transfer component 48 is formed of a metal material with high thermal conductivity, such as copper. The shape of the heat transfer component 48 is identical to the shape of the substrate 44 of the heating element unit 40. The heat transfer component 48 is configured to contact at least a portion of the second surface 42 in the -z direction of the heating element unit 40. For example, the heat transfer component 48 contacts the entire second surface 42 of the heating element unit 40.

[0055] The support member 36 is formed of a resin material such as a liquid crystal polymer. The support member 36 is configured to cover both sides of the heating element unit 40 in the -z and x directions. The support member 36 supports the heating element unit 40 across the heat transfer member 48. Rounded chamfers are formed at both ends of the support member 36 in the x direction. The support member 36 supports the inner circumferential surface of the cylindrical film 35 at both ends of the heating element unit 40 in the x direction.

[0056] The support bar 38 is formed of a material such as steel plate. The cross-section of the support bar 38 perpendicular to the y-direction is U-shaped. The support bar 38 is installed in the -z direction of the support member 36 such that the opening of the U-shape is blocked by the support member 36. The support bar 38 extends in the y-direction. The two ends of the support bar 38 in the y-direction are fixed to the housing 10 of the image forming apparatus 1.

[0057] The temperature sensing elements 80 include a heater thermometer 82, a thermostat 88, and a membrane thermometer 84. The heater thermometer 82 and the thermostat 88 are located in the -z direction of the heating element unit 40, separated by a heat transfer component 48. The heater thermometer 82 measures the temperature of the heating element unit 40 through the heat transfer component 48. If the temperature of the heating element unit 40 detected by the heat transfer component 48 exceeds a predetermined temperature, the thermostat 88 cuts off the power supply to the heating element assemblies 50 and 60. The membrane thermometer 84 contacts the inner circumferential surface of the cylindrical membrane 35 to measure the temperature of the cylindrical membrane 35.

[0058] The heating element groups 50 and 60 and the wiring group 70 are described in detail.

[0059] Figure 5 for Figure 4 The image shows a bottom sectional view of the heating element unit at the VV line. The first heating element group 50 and the second heating element group 60 extend in the y direction and are arranged in the x direction. The first heating element group 50 is arranged in the -x direction, and the second heating element group 60 is arranged in the +x direction.

[0060] The first heating element group 50 has a plurality of first heating element elements 55 (51, 52, 53). Each first heating element element 55 is formed in a rectangular shape with its longer side in the y-direction and its shorter side in the x-direction. For example, the lengths of the plurality of first heating element elements 55 in the y-direction and x-direction are the same. The plurality of first heating element elements 55 are arranged in the y-direction. A first non-heating region 57 is disposed between adjacent first heating element elements 55. Heating elements are not formed in the first non-heating region 57. The plurality of first heating element elements 55 and the first non-heating region 57 are arranged alternately in the y-direction.

[0061] The second heating element group 60 has a plurality of second heating element elements 65 (61, 62, 63, 64). Each second heating element element 65 is formed in a rectangular shape with its longer side in the y-direction and its shorter side in the x-direction. For example, the lengths of the plurality of second heating element elements 65 in the y-direction and x-direction are the same. The plurality of second heating element elements 65 are arranged in the y-direction. A second non-heating region 67 is disposed between adjacent second heating element elements 65. Heating elements are not formed in the second non-heating region 67. The plurality of second heating element elements 65 and the second non-heating region 67 are arranged alternately in the y-direction.

[0062] For example, the lengths of the first heating element 55 and the second heating element 65 in the y and x directions are the same. Similarly, the lengths of the first non-heating region 57 and the second non-heating region 67 in the y direction are the same. The length of the first non-heating region 57 in the y direction is much shorter than the length of the second heating element 65 in the y direction. The length of the second non-heating region 67 in the y direction is much shorter than the length of the first heating element 55 in the y direction.

[0063] The wiring group 70 has multiple individual electrodes 71, multiple individual terminals 72, a common electrode 73, and a common terminal 74.

[0064] Multiple individual electrodes 71 are individually configured for each of the multiple first heating element 55 and the multiple second heating element 65. The individual electrodes 71 are disposed on the outer side of the first heating element 55 and the second heating element 65 in the x-direction. The individual electrode 71 of the first heating element 55 is disposed along the end edge of the first heating element 55 in the -x direction and is connected to the first heating element 55. The individual electrode 71 of the second heating element 65 is disposed along the end edge of the second heating element 65 in the +x direction and is connected to the second heating element 65.

[0065] A separate terminal 72 is disposed at the center of the separate electrode 71 in the y-direction. For example... Figure 4 As shown, the individual terminal 72 extends from the individual electrode 71 in the +z direction. The +z end of the individual terminal 72 is exposed on the first surface 41 of the heating element unit 40.

[0066] Figure 6 This is a bottom view of the heating element unit (viewed from the +z direction to the -z direction). Multiple individual terminals 72 are arranged corresponding to multiple individual electrodes 71. The multiple individual terminals 72 are exposed on the first surface 41 of the heating element unit 40.

[0067] like Figure 5 As shown, a common electrode 73 is configured for multiple first heating element elements 55 and multiple second heating element elements 65. The common electrode 73 extends linearly along the y-direction. The common electrode 73 is disposed inside the multiple first heating element elements 55 and multiple second heating element elements 65 in the x-direction. The common electrode 73 is connected to the +x-direction end edge of the multiple first heating element elements 55. The common electrode 73 is connected to the -x-direction end edge of the multiple second heating element elements 65.

[0068] The common terminal 74 extends from the +y end of the common electrode 73 toward the +z direction. For example... Figure 6 As shown, the +z-direction end of the common terminal 74 is exposed on the first surface 41 of the heating element unit 40. The common terminal 74 is connected to a power supply (not shown).

[0069] like Figure 5 As shown, multiple individual terminals 72 are connected to a power supply (not shown) via multiple triacs 76-79. Control unit 6 (see reference) Figure 2 Multiple three-terminal bidirectional thyristor switches 76-79 can be independently controlled to turn on / off. As a result, the first heating element group 50 and the second heating element group 60 can generate heat independently.

[0070] Of the plurality of first heating elements 55, the first heating element 52 located at the center in the y-direction is the central heating element 52. The central heating element 52 is connected to the first three-terminal bidirectional thyristor switch 76. Of the plurality of first heating elements 55, the first heating elements 55 located at both ends in the y-direction are the end heating elements 51 and 53. The end heating elements 51 and 53 are connected to the second three-terminal bidirectional thyristor switch 77. The control unit 6 independently controls the on / off state of the first three-terminal bidirectional thyristor switch 76 and the second three-terminal bidirectional thyristor switch 77. Thus, the central heating element 52 and the end heating elements 51 and 53 can heat up independently. The pair of end heating elements 51 and 53 heat up in the same manner.

[0071] Of the plurality of second heating elements 65, the second heating element 65 disposed at the center in the y-direction is the central heating element 62, 63. The central heating element 62, 63 is connected to the third three-terminal bidirectional thyristor switch 78. Of the plurality of second heating elements 65, the second heating elements 65 disposed at both ends in the y-direction are the end heating elements 61, 64. The end heating elements 61, 64 are connected to the fourth three-terminal bidirectional thyristor switch 79. The control unit 6 independently controls the on / off state of the third three-terminal bidirectional thyristor switch 78 and the fourth three-terminal bidirectional thyristor switch 79. Thus, the central heating elements 62, 63 and the end heating elements 61, 64 can heat up independently. The pair of central heating elements 62, 63 heat up in the same way. The pair of end heating elements 61, 64 heat up in the same way.

[0072] Various sizes of sheets S are used in the image forming apparatus 1. The sheet S is transported in the x-direction by aligning the center of the sheet S in the y-direction with the center of the fixing unit 30 in the y-direction. The control unit 6 heats the heating element assemblies 50 and 60 so that the temperature of the tubular film 35 in the area through which the sheet S passes reaches a predetermined fixing temperature. In the area through which the sheet S passes, the sheet S absorbs heat from the tubular film 35. In the area where the sheet S does not pass, the temperature of the tubular film 35 and the heating element unit 40 rises. When a large number of sheets S pass through the fixing unit 30 per unit time, the heat generated by the heating element assemblies 50 and 60 increases. In the area where the sheet S does not pass, the temperature rise of the tubular film 35 and the heating element unit 40 increases.

[0073] When the sheet S is wider in the y-direction, the control unit 6 heats the entire first heating element group 50 and the entire second heating element group 60. Conversely, when the sheet S is narrower in the y-direction, the control unit 6 heats only the central heating element element 52 of the first heating element group 50 and the central heating elements 62 and 63 of the second heating element group 60. Since the first heating element group 50 includes three or more first heating element elements 55, it is possible to heat only the central heating element element 52. The same applies to the second heating element group 60.

[0074] As described above, when the sheet S has a small width in the y-direction, the control unit 6 only heats the central heating element 52 and the central heating elements 62 and 63. Therefore, the temperature rise of the cylindrical membrane 35 and the heating element unit 40 is suppressed in the region at the y-direction end where the sheet S does not pass. Figure 3 As shown, the temperature rise of the support member 36, which supports the heating element unit 40 across the heat transfer member 48, is suppressed. The temperature of the support member 36, which is made of resin material, is suppressed below its heat resistance temperature. In addition, malfunctions of the cylindrical diaphragm 35 and the temperature sensing element 80 are suppressed.

[0075] Further detailed explanations are provided for heating element groups 50 and 60.

[0076] exist Figure 5 In the first heating element group 50 shown, the first heating element 55 heats up, while the first non-heating region 57 does not. This results in temperature unevenness in the y-direction of the first heating element group 50. Consequently, temperature unevenness also occurs in the y-direction of the cylindrical film 35 and the sheet S. As a result, the image fixed on the sheet S exhibits uneven gloss. The same applies to the second heating element group 60.

[0077] The first non-heating region 57 of the first heating element group 50 and the second non-heating region 67 of the second heating element group 60 are arranged at different positions in the y-direction. The first non-heating region 57 and the second non-heating region 67 are not arranged adjacent to each other in the x-direction. The second heating element 65 is arranged in the +x direction of the first non-heating region 57, and the first heating element 55 is arranged in the -x direction of the second non-heating region 67. The heating element groups 50 and 60 can generate heat throughout the entire y-direction. As a result, temperature unevenness in the fixing device 30 is suppressed.

[0078] In the y-direction of the first heating element group 50, the central temperature of the first non-heating region 57 is the lowest, and the central temperature of the first heating element 55 is the highest. In the y-direction of the second heating element group 60, the central temperature of the second non-heating region 67 is the lowest, and the central temperature of the second heating element 65 is the highest.

[0079] In the y-direction, the center of the first non-heating region 57 and the center of the second heating element 65 are positioned at the same location. The centers of the first non-heating region 57 and the second heating element 65 in the y-direction are adjacent to each other in the x-direction. Similarly, in the y-direction, the center of the second non-heating region 67 and the center of the first heating element 55 are positioned at the same location. The centers of the second non-heating region 67 and the center of the first heating element 55 in the y-direction are adjacent to each other in the x-direction. Thus, the temperature of the heating element assemblies 50 and 60 is equalized in the y-direction. Temperature unevenness in the fixing device 30 is suppressed.

[0080] In the y-direction, the end of the second heating element group 60 is positioned further outward than the end of the first heating element group 50. At the y-direction ends of the heating element groups 50 and 60, only the second heating element group 60 can generate heat. Therefore, in the region at the y-direction end where the sheet S does not pass, the temperature rise of the cylindrical membrane 35, the heating element unit 40, the heat transfer component 48, and the support component 36 is suppressed.

[0081] Alternatively, in the opposite embodiment, the end of the first heating element group 50 may be positioned further outward than the end of the second heating element group 60 in the y direction.

[0082] A plurality of first heating elements 55 have a central heating element 52 disposed at the center in the y-direction and end heating elements 51, 53 disposed at their ends in the y-direction. The central heating element 52 and the end heating elements 51, 53 are capable of heating independently of each other. Similarly, a plurality of second heating elements 65 have a central heating element 62, 63 disposed at the center in the y-direction and end heating elements 61, 64 disposed at their ends in the y-direction. The central heating element 62, 63 and the end heating elements 61, 64 are capable of heating independently of each other.

[0083] When the sheet S has a small width in the y-direction, only the central heating element 52 of the first heating element group 50 and the central heating elements 62 and 63 of the second heating element group 60 can generate heat. As a result, the temperature rise of the cylindrical membrane 35, heating element unit 40, heat transfer component 48, and support component 36 is suppressed in the region at the end of the sheet S that does not pass through in the y-direction.

[0084] As detailed above, the image forming apparatus 1 of the embodiment includes an image forming unit 3, a fixing device 30, a cylindrical film 35, a heating element unit 40, a first heating element group 50 and a second heating element group 60, a plurality of first heating element elements 55, and a plurality of second heating element elements 65. The image forming unit 3 forms an image on a sheet S. The fixing device 30 fixes the image to the sheet S. The cylindrical film 35 is included in the fixing device 30 and is film-shaped. The heating element unit 40 is included in the fixing device 30 and contacts the inner surface of the cylindrical film 35 at a first surface 41 with the y-direction as its long side. The first heating element group 50 and the second heating element group 60 are included in the heating element unit 40 and are arranged in the x-direction. The first heating element group 50 and the second heating element group 60 are capable of heating independently of each other. The plurality of first heating element elements 55 are included in the first heating element group 50 and are arranged alternately with the first non-heated region 57 in the y-direction. Multiple second heating element elements 65 are included in the second heating element group 60 and are arranged alternately with the second non-heating region 67 in the y-direction. The second non-heating region 67 and the first non-heating region 57 are arranged at different positions in the y-direction.

[0085] Therefore, the heating element assemblies 50 and 60 can generate heat along the entire y-direction, suppressing temperature unevenness in the fixing device 30.

[0086] Figure 7 For equivalent to Figure 4 A bottom sectional view of the heating element unit of a modified embodiment at a portion of the VV line. Sometimes, descriptions of points in the modified embodiment that are identical to those in the original embodiment are omitted.

[0087] Compared to the above-described embodiments, in a modified example, the lengths of the first heating element 55 and the second heating element 65 in the y-direction are shorter, while the lengths of the first non-heating region 57 and the second non-heating region 67 in the y-direction are longer. The lengths of the plurality of first heating elements 55 and the plurality of second heating elements 65 in the y-direction may be the same, but they may also be different. The lengths of the plurality of first non-heating regions 57 and the plurality of second non-heating regions 67 in the y-direction are the same, but they may also be different. The length of the first non-heating region 57 in the y-direction is slightly shorter than the length of the second heating element 65 in the y-direction. The length of the second non-heating region 67 in the y-direction is slightly shorter than the length of the first heating element 55 in the y-direction.

[0088] The ends of the first heating element 55 and the second heating element 65 in the y-direction are arranged adjacent to each other in the x-direction. In the y-direction, the ends of the first heating element 55 and the second heating element 65 overlap. The region where the ends of the first heating element 55 and the second heating element 65 are arranged adjacent to each other in the x-direction is designated as R. The length of region R in the y-direction is set such that the temperature of region R is not excessively high compared to the temperatures of other regions. For example, the length of region R in the y-direction is shorter than the length (width) of the first heating element 55 and the second heating element 65 in the x-direction. For example, the length of region R in the y-direction is shorter than the length (width) of the common electrode 73 in the x-direction.

[0089] In the region where the first heating element 55 is formed, the temperature is highest at the center in the y-direction and lowest at the ends in the y-direction. The same applies in the region where the second heating element 65 is formed. Because the ends of the first heating element 55 and the second heating element 65 in the y-direction are arranged adjacent to each other in the x-direction, the temperatures of the heating element assemblies 50 and 60 are equalized in the y-direction. This suppresses temperature unevenness in the fixing device 30.

[0090] The heating element unit 40 in this embodiment has two rows of heating element groups: a first heating element group 50 and a second heating element group 60. Alternatively, the heating element unit 40 may also have three or more rows of heating element groups.

[0091] The first heating element group 50 of the embodiment has three first heating element elements 55, and the second heating element group 60 has four second heating element elements 65. In contrast, the first heating element group 50 may also have four or more first heating element elements 55, and the second heating element group 60 may also have three or five or more second heating element elements 65.

[0092] The image forming apparatus 1 in this embodiment is a type of image processing apparatus, and the fixing apparatus 30 is a type of heating apparatus. In contrast, the image processing apparatus can also be a desaturating apparatus, and the heating apparatus can also be a desaturating section. The desaturating apparatus performs a process of desaturating (eliminating) an image formed on a sheet using a desaturating toner. The desaturating section heats the desaturating toner image formed on the sheet passing through the clamping section to desaturate it.

[0093] According to at least one embodiment described above, the second non-heating region 67 and the first non-heating region 57 are arranged at different positions in the y-direction. This suppresses temperature unevenness in the fixing device 30.

[0094] While several embodiments of the invention have been described, these embodiments are merely illustrative and not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and likewise within the scope of the invention as described in the claims and its equivalents.

Claims

1. An image forming apparatus comprising: An image forming unit forms an image on a sheet; A membrane-like tubular body contacts the sheet moving in a first direction to fix the image; as well as The heating element unit contacts the inner surface of the cylindrical body at its first surface, wherein the first surface has a second direction orthogonal to the first direction as its long side and the first direction as its short side. The heating element unit has: The first heating element group has a plurality of first heating element elements, which are arranged in the second direction with a first non-heating region between them; as well as The second heating element assembly has a plurality of second heating element elements arranged in the second direction with a second non-heating region between them. The second non-heating region and the first non-heating region are positioned at different locations in the second direction. The second heating element assembly and the first heating element assembly are arranged in the first direction. The first heating element group and the second heating element group are heated by being energized through the wiring group. When the region where the ends of the first heating element and the ends of the second heating element are arranged adjacently in the first direction is defined as region R, The length of the region R in the second direction is shorter than the lengths of the first heating element and the second heating element in the first direction, and the length of the region R in the second direction is shorter than the length of the common electrode of the wiring group in the first direction.

2. The image forming apparatus according to claim 1, wherein, In the second direction, the center of the first non-heating region and the center of the second heating element are located at the same position. In the second direction, the center of the second non-heating region and the center of the first heating element are located at the same position.

3. The image forming apparatus according to claim 1 or 2, wherein, In the second direction, the end of the second heating element group is positioned further outward than the end of the first heating element group.

4. The image forming apparatus according to claim 1 or 2, wherein, The plurality of first heating elements have a central heating element disposed at the center of the second direction and end heating elements disposed at the ends of the second direction. The central heating element and the end heating element can generate heat independently of each other.

Images