Image heating device and imaging device

Abstract

The present disclosure relates to an image heating device and an imaging device. In the image heating device, a plurality of heating members included in a heater include a first group of heating members and a second group of heating members that are symmetrically arranged with respect to a conveyance reference position of a recording material. A control section supplies power to the first group of heating members and the second group of heating members via a first common circuit and a second common circuit. A temperature detection section includes a first temperature detection element and a second temperature detection element. The first temperature detection element is configured to detect the temperature of one of the heating members included in the first group of heating members, and the second temperature detection element is configured to detect the temperature of one of the heating members included in the second group of heating members. The first temperature detection element is placed on one side with respect to the conveyance reference position in a width direction, and the second temperature detection element is placed on the other side with respect to the conveyance reference position in the width direction.

Description

Technical Field

[0001] The present invention relates to an imaging apparatus using an electrophotographic system, such as a printer, a copying machine, etc. The present invention also relates to an image heating device and a gloss applying device, etc., where the image heating device is, for example, a fixing unit installed in the imaging apparatus, and the gloss applying device improves the gloss value of the toner image by reheating the toner image fixed on the recording material. Background Art

[0002] A film heating system fixing device is known as a fixing device used in an electrophotographic system imaging apparatus. In the film heating system fixing device, the problem of high temperature in the non-sheet feeding portion is known, which will be described below. This high temperature in the non-sheet feeding portion is a phenomenon in which, when an imaging apparatus using such a fixing device continuously prints small-sized sheets, the temperature of the area in the longitudinal direction of the sheet that is not passed through by the sheet in the clamping portion gradually increases. When the temperature of the non-sheet feeding portion becomes too high, various components in the device (such as heaters, fixing films, pressure rollers, etc.) will be damaged. In addition, when printing a large-sized sheet in a state where high temperature appears in the non-sheet feeding portion, a thermal offset phenomenon of the toner may occur in the area corresponding to the non-sheet feeding portion of the small-sized sheet.

[0003] A fixing device having the configuration described in Japanese Patent Application Laid-Open No. 2017-54071 has been proposed as a technique for suppressing such high temperature in the non-sheet feeding portion. That is, this is a fixing device having a heater in which a heat generating member (hereinafter referred to as a divided heater) divided along the longitudinal direction is arranged on a substrate. Using this configuration enables the heating resistors on the heater to be divided into a plurality of heating regions (hereinafter referred to as "heating blocks HB") in the longitudinal direction of the heater, and the heat distribution of the heater can be switched according to the size of the recording material. Therefore, even in the case of feeding small-sized sheets, the high temperature in the non-sheet feeding portion can be suppressed.

[0004] In addition, Japanese Patent Application Laid-Open No. 2017-54071 also proposes a configuration in which the circuit for supplying power to a plurality of heat generating members is shared. That is, this is a configuration in which a shared driver is used to supply power to a plurality of heating blocks arranged symmetrically with respect to the center of the sheet in the lateral direction. Adopting this configuration can achieve size reduction, cost reduction, and energy saving of the device. Summary of the Invention

[0005] In the case of using a fixing device that utilizes the above-described divided heater, temperature control needs to be performed for each drive circuit. That is, a temperature detection element needs to be arranged in at least one of each group of heating blocks HB that are powered through the same drive, and the temperature detection result from the temperature detection element needs to be used to perform control for determining the power to be applied to the drive circuit, i.e., temperature control control. From the viewpoints of function and cost, a thermistor is used as the temperature detection element here.

[0006] Now, there is a situation where the resistance value of the heating member constituting the heater varies, and particularly when there is a variation in the resistance distribution in the longitudinal direction, the lateral variation in fixing performance due to the variation in the heating distribution may become large in some cases. In this case, depending on the layout of the temperature detection element, it may be difficult to perform precise temperature control control, and the occurrence of misfixing or thermal deviation may result.

[0007] An object of the present invention is to provide an image heating device capable of performing high-precision temperature control control.

[0008] To solve the above problems, an image heating device according to the present invention includes:

[0009] A heater including a plurality of heating members arranged in the width direction of a recording material, the width direction being orthogonal to the conveying direction of the recording material;

[0010] A nip forming portion that forms a nip for nipping the recording material;

[0011] A temperature detection portion that detects the temperature of the heater; and

[0012] A control portion that controls the power to be supplied to the plurality of heating members based on the temperature detected by the temperature detection portion,

[0013] wherein the image heating device heats an image formed on the recording material nipped by the nip by the heat of the heater,

[0014] wherein the plurality of heating members have a first heating member group and a second heating member group,

[0015] Among them, the first heating member group includes a plurality of heating members symmetrically arranged with respect to the conveyance reference position of the recording material in the width direction, and the second heating member group includes a plurality of heating members symmetrically arranged with respect to the conveyance reference position. The plurality of heating members of the second heating member group are placed at positions different from those of the plurality of heating members of the first heating member group in the width direction.

[0016] Among them, the temperature detection section includes a first temperature detection element and a second temperature detection element. The first temperature detection element is used to detect the temperature of one of the heating members included in the first heating member group, and the second temperature detection element is used to detect the temperature of one of the heating members included in the second heating member group.

[0017] Among them, when heating and forming an image on the recording material at the clamping portion, the control section supplies power to the first heating member group via a first common circuit to maintain the detected temperature detected by the first temperature detection element at a control target temperature, and supplies power to the second heating member group via a second common circuit to maintain the detected temperature detected by the second temperature detection element at a control target temperature.

[0018] Among them, the first temperature detection element is placed on one side with respect to the conveyance reference position in the width direction, and

[0019] Among them, the second temperature detection element is placed on the other side with respect to the conveyance reference position in the width direction.

[0020] In addition, to solve the above problems, an imaging device according to the present invention includes:

[0021] An imaging section that forms an image on a recording material; and

[0022] A fixing section that fixes the image formed on the recording material to the recording material.

[0023] Among them, the fixing section is the image heating device of the present invention.

[0024] As described above, according to the present invention, the accuracy of temperature control of the image heating device can be improved.

[0025] Referring to the accompanying drawings, other features of the present invention will become apparent from the following description of exemplary embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1is a schematic cross-sectional view of an imaging apparatus according to the first embodiment;

[0027] Figure 2 is a schematic cross-sectional side view of a fixing apparatus according to the first embodiment;

[0028] Figures 3A to 3C is a diagram showing the configuration of a heater according to the first embodiment;

[0029] Figure 4 is a circuit diagram of a circuit according to the first embodiment;

[0030] Figure 5A and Figure 5B is a schematic cross-sectional view of a thermistor according to the first embodiment;

[0031] Figure 6 is a schematic plan view of a heater and a thermistor according to the first embodiment;

[0032] Figure 7 is a schematic plan view of a heater and a thermistor according to Comparative Example 1;

[0033] Figures 8A to 8D is a longitudinal distribution diagram of the resistance value of a heater and the temperature of a heating member according to Comparative Example 1;

[0034] Figure 9A and Figure 9B is a longitudinal distribution diagram of the resistance value of a heater and the temperature of a heating member according to the first embodiment;

[0035] Figure 10A and Figure 10B is a longitudinal temperature distribution diagram of the surface of a fixing film according to the first embodiment;

[0036] Figure 11A and Figure 11B is a schematic plan view of a heater according to the first embodiment;

[0037] Figure 12 is a schematic plan view of a heater according to the first embodiment;

[0038] Figures 13A to 13D is a longitudinal distribution diagram of the resistance value of a heater and the temperature of a heating member according to the second embodiment;

[0039] Figure 14A and Figure 14B is a longitudinal temperature distribution diagram of the surface of a fixing film according to the second embodiment; and

[0040] Figures 15A to 15C is a diagram showing the configuration of a heater according to the third embodiment. DETAILED DESCRIPTION

[0041] Hereinafter, a description of embodiments (examples) of the present invention will be given with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments may be appropriately changed according to the construction of the apparatus to which the present invention is applied, various conditions, etc. Therefore, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention to the following embodiments.

[0042] First Embodiment

[0043] Figure 1 FIG. 1 is a schematic cross-sectional view of an image forming apparatus using electrophotographic recording technology according to an embodiment of the present invention. Examples of the image forming apparatus to which the present invention can be applied include copying machines, printers, etc. using an electrophotographic system or an electrostatic recording system. An arrangement applied to a laser printer will be described here, which uses an electrophotographic system to form an image on a recording material P such as recording paper.

[0044] Overall Configuration of the Image Forming Apparatus

[0045] Figure 1 FIG. 2 is a schematic cross-sectional view of an example of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus includes an image forming section A that forms a toner image on a recording material, a recording material feeding section B that feeds the recording material away to the image forming section A, and a fixing section (fixing device) C that performs heat fixing of the toner image onto the recording material. The image forming section A includes an electrophotographic photosensitive member, which is a drum-shaped member (hereinafter referred to as "photosensitive drum") 101 serving as an image carrier member. The photosensitive drum 101 is rotatably supported by an image forming apparatus main member M that constitutes the image forming apparatus. A charging roller 102, a laser scanner 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are sequentially arranged around the outer peripheral surface of the photosensitive drum 101 in the rotation direction of the photosensitive drum. The recording material feeding section B includes a feeding roller 11. The feeding roller 11 is rotated in the direction of the arrow at a predetermined time by a conveyance drive motor (not shown in the figure), and feeds the recording material P stacked and accommodated in the cassette 7 away to the conveyance path.

[0046] The imaging device according to the first embodiment has a control section (not shown in the figure), which controls the imaging section A, the recording material feeding section B, the fixing device C, etc. The control section is composed of a central processing unit (CPU) and memories such as a read-only memory (ROM) and a random access memory (RAM), and various types of programs required for imaging are stored in the memories. The control section receives a print signal from an external device such as a host computer, and executes a predetermined imaging control sequence based on the print signal. Therefore, the drum motor is rotationally driven, and the photosensitive drum 101 rotates in the arrow direction at a predetermined circumferential speed (processing speed). The surface of the rotating photosensitive drum 101 is uniformly charged to a predetermined potential of the same polarity as the toner (negative polarity here) by the charging roller 102. The laser scanner 3 scans the charged surface on the surface of the photosensitive drum 101 with a laser beam L based on the image information, thereby exposing the surface of the photosensitive drum 101. By this exposure, the charge of the exposed portion is removed, and thus an electrostatic latent image is formed on the surface of the photosensitive drum 101.

[0047] The developing device 4 includes a developing roller 41 and a toner container 42 that houses toner. The toner is rubbed by a member such as a urethane blade (not shown in the figure) so as to be charged to a predetermined polarity (negative polarity in the first embodiment). The developing device 4 applies a negative voltage to the developing roller 41 through a developing voltage power source (not shown in the figure), and thus the toner adheres to the electrostatic latent image on the surface of the photosensitive drum 101 by the potential difference, thereby developing the electrostatic latent image into a toner image T. A positive voltage opposite to the toner polarity is applied to the transfer roller 5, and thus the toner image T formed on the surface of the photosensitive drum 101 is transferred to the recording material P by the potential difference with the transfer voltage. In addition, the conveyance drive motor provided in the recording material feeding section B is rotationally driven, and the feeding roller 11 feeds the recording material P out of the cassette 7 to the conveyance roller 8. The recording material P is conveyed by the conveyance roller 8, passes through the top sensor 9, and is conveyed to the transfer nip portion between the surface of the photosensitive drum 101 and the outer peripheral surface of the transfer roller 5. The recording material P onto which the toner image formed on the surface of the photosensitive drum 101 has been transferred is conveyed along the conveyance guide 10 to the fixing device C. The toner image on the recording material P is heated and pressed at the fixing device C, and thus is thermally fixed to the recording material P. The recording material P onto which the toner image T has been thermally fixed is sequentially conveyed by the conveyance roller 12 and the discharge roller 13, and is discharged onto the discharge tray 14 on the upper portion of the device main body M. The transfer residual toner remaining on the surface of the photosensitive drum 101 after transferring the toner image to the recording material P is removed by the cleaning blade 61 of the cleaning device 6, and accumulates inside the cleaning device 6. Continuous printing is performed by repeating the above operations. In the case of A4 size, the imaging device according to the first embodiment can perform printing at a printing speed of 70 sheets per minute. Although the details are omitted here, the imaging device according to the first embodiment is provided with a reverse conveyance path that enables double-sided imaging, and is configured such that the recording material P on which an image has been formed on one side is returned to the upstream side of the imaging section A by being folded back by the reversely rotating discharge roller 13.

[0048] Structure of the fixing device

[0049] Figure 2is a schematic cross-sectional side view of a fixing device C serving as an image heating device according to a first embodiment. The fixing device C according to the first embodiment has a basic structure: a heater 1100, a heater holder 29, a metal brace 22, a fixing film 25 serving as a fixing member, and a pressure roller 26. The heater holder 29 is a holding member that holds (supports) the heater 1100 serving as a heating member on the inner side of the fixing film 25. The fixing device C holds a recording material P at a clamping portion N between the fixing film 25 and the pressure roller 26, and thermally fixes a toner image T onto the recording material P using the heat of the heater 1100. The fixing film is formed in a cylindrical shape and serves as a heating rotating member, and the pressure roller serves as a pressure rotating member (pressure member). The clamping portion N is formed by the heater 1100 and the pressure roller 26 with the fixing film 25 therebetween. The recording material P is conveyed while being clamped at the clamping portion N by the rotation of the pressure roller 26 and the driven rotation of the fixing film 25. Although it is configured in this embodiment that the heater 1100 is in direct contact with the inner surface of the fixing film 25, a heat conductive member or the like may be interposed between the heater 1100 and the inner surface of the fixing film 25. Among the components of the fixing device C according to this embodiment, the components involved in forming the clamping portion N constitute a clamping portion forming part. A power application control portion 421 connected to a commercial alternating current (AC) power supply supplies power to the fixing device C according to a signal from a CPU 420.

[0050] Pressure roller

[0051] The pressure roller 26 has an elastic layer 262 on the outer circumference of a core portion 261, and a surface layer 263 on the outer circumference of the elastic layer 262. The outer diameter of the pressure roller 26 is approximately 25 mm. A metal material such as aluminum or iron is used to form the core portion 261 in a solid or hollow form. In the first embodiment, aluminum is used as the solid metal material. The elastic layer 262 is made of heat-resistant silicone rubber, and the heat-resistant silicone rubber is made conductive by adding a conductive material such as carbon. The surface layer 263 that contacts the outer surface portion of the fixing film 25 is a release tube that is 10 μm to 80 μm thick and is made of a fluororesin such as tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (tetrafluoride) (PTFE), or tetrafluoroethylene hexafluoropropylene copolymer (tetrafluoride, hexafluoride) (FEP). From the perspective of preventing charging during sheet passage, the surface layer 263 is preferably made conductive. In the first embodiment, the surface layer 263 of the pressure roller 26 has a structure in which carbon is added as a conductive material to a 30-μm-thick PFA tube.

[0052] Fixing film

[0053] The fixing film 25 has a cylindrical shape with a diameter of 24 mm. The fixing film 25 is flexible and is loosely fitted around the outside of the heater holder 29. FromFigure 2 As can be seen from the cross-sectional structure shown by the circle, the fixing film 25 has a multi-layer structure including a base layer 251, an elastic layer 252, and a surface layer 253 in this order from the inside. Generally, a resin material with low heat capacity and heat resistance (such as polyimide, polyamide-imide, polyether ether ketone (PEEK), polyether sulfone (PES), etc.) is used as the material for the base layer 251. There are also cases where a metal material such as stainless steel is used. Since it is necessary to satisfy the quick start characteristic with a small heat capacity while also satisfying the mechanical strength, the base layer 251 is preferably used with a thickness of at least 18 μm and not exceeding 150 μm. The base layer 251 according to the first embodiment is a cylindrical polyimide base layer with a thickness of 70 μm. The elastic layer 252 is made of an elastic material, and silicone rubber is a representative of such material. Providing this elastic layer 252 enables the toner image T to be wrapped and uniformly heated, so that a good image without unevenness can be obtained. Silicone rubber itself has low thermal conductivity, and therefore, heat conductive fillers such as alumina, metal silicon, silicon carbide, zinc oxide, etc. are added to endow the elastic layer 252 with high thermal conductivity. In a high-speed machine such as the first embodiment, the addition amount of the heat conductive filler is appropriately adjusted to preferably ensure a thermal conductivity of at least 0.9 W / m·K. In the first embodiment, alumina and metal silicon are added as heat conductive fillers to the rubber material of the elastic layer 252 so that its thermal conductivity is 1.5 W / m·K. In addition, the thickness of the elastic layer 252 is 270 μm. The surface layer 253 serving as a release layer requires high wear resistance and high release ability with respect to the toner. Fluorine resins such as PFA, PTFE, FEP, etc. are used as the material for the surface layer. The layer forming means includes forming a coating obtained by baking a resin dispersion, or forming a pipe layer. There are also cases where additives such as carbon or ion conductive materials are added to the fluorine resin to be used to endow the fluorine resin with conductivity. For the surface layer 253 according to the first embodiment, PFA is used as the fluorine resin, no conductive material is added, and the pipe layer is formed to be 20 μm thick.

[0054] Heater holder

[0055] The heater 1100 is held by a heater holder 29 made of a heat-resistant resin material such as liquid crystal polymer, etc. The heater holder 29 also serves as a guide for guiding the rotation of the fixing film 25.

[0056] Heater

[0057] Reference will be made to Figures 3A to 3CDescribe the heater 1100 configured as a feature of the first embodiment. The heater 1100 includes a substrate 1105 made of ceramic, and a heating resistor (heating member) disposed on the substrate 1105 and generating heat when powered on. On one side of the sliding surface layer 2 of the face (first face) of the substrate 1105 on the N side of the clamping portion that contacts the fixing film 25, a surface protective layer 1108 made of glass is provided to the substrate to ensure slidability with respect to the fixing film 25. On the face (second face) of the substrate 1105 opposite to the first face on the N side of the clamping portion, a surface protective layer 1107 made of glass is provided to the substrate for insulation of the heating resistor. The electrode E13 is exposed at the second face, and the heating resistor is electrically connected to an AC power source by contacting the electrode E13 with an electrical contact C13 for feeding power.

[0058] Figure 3A and Figure 3B is a view showing the configuration of the heater 1100 according to the present embodiment. Figure 3A is in Figure 3B a cross-sectional view of the heater 1100 taken at the conveyance reference position X of the recording material P shown in. Figure 3B is a plan view of each layer of the heater 1100. Figure 3C is a plan view of a heater holder that holds the heater 1100. In the present embodiment, the conveyance reference position X is set at a substantially middle position in the width direction of the recording material P (the longitudinal direction of the substrate 1105) orthogonal to the conveyance direction of the recording material P through the fixing device C, but the setting position is not limited to any specific position.

[0059] The heater 1100 is composed of a substrate 1105, a sliding surface layer that contacts the fixing film 25 provided on the first face side of the substrate 1105, a back surface layer 1 provided on the second face side of the substrate 1105 on the side opposite to the first face side, and a back surface layer 2 that covers the back surface layer 1. The heater 1100 has a plurality of heating blocks, and each heating block is composed of a first conductor (conductor AE) 1101, a second conductor (conductor BE) 1103, and a heating member 1102 arranged in the back surface layer 1 along the longitudinal direction of the substrate 1105. A total of five heating blocks HB11 to HB15 are formed in the heater 1100 according to the present embodiment by a plurality of heating members 1102a-1 to 1102b-5 arranged in the width direction of the recording material P (the longitudinal direction of the substrate 1105) orthogonal to the conveyance direction of the recording material P.

[0060] Figures 3A to 3CThe heater 1100 shown is divided in the longitudinal direction of the substrate 1105 (in the width direction of the recording material P orthogonal to the conveyance direction of the recording material P) into heating blocks HB11 to HB15 that are laterally symmetric with respect to the center of the heater 1100 (symmetric with respect to the conveyance reference position X). The positions where the heating blocks HB are divided respectively correspond to "A5 size", "B5 size", and "A4 size". That is, the width of the heating block HB13 is 150 mm, which is substantially the same as the short side of the A5 size. The widths of the heating blocks HB12 to HB14 are 182 mm, which is substantially the same as the short side of the B5 size. The widths of the heating blocks HB11 to HB15 are 210 mm, which is substantially the same as the short side of the A4 size. Further, among these heating blocks HB, "heating block HB13" is the 1st heating group, "heating block HB12 and heating block HB14" are the 2nd heating group, and "heating block HB11 and heating block HB15" are the 3rd heating group. Power feeding to each heating group is respectively performed by the same driver (common circuit).

[0061] In the lateral direction of the heater 1100 (the direction orthogonal to the longitudinal direction of the heater 1100), the heating members 1102 in each heating block are arranged to be divided into a heating member 1102a on the upstream side in the passing direction of the recording material P and a heating member 1102b on the downstream side. Further, the first conductor 1101 is divided into a conductor 1101a connected to the heating member 1102a and a conductor 1101b connected to the heating member 1102b.

[0062] The heater 1100 is divided into five heating blocks HB11 to HB15. That is, the heating member 1102a is divided into five, namely 1102a-1 to 1102a-5. In the same manner, the heating member 1102b is divided into five, namely 1102b-1 to 1102b-5. Further, the second conductor 1103 is also divided into five, namely 1103-1 to 1103-5.

[0063] A surface protective layer 1107 that insulates and covers the surfaces of the heating member 1102, the first conductor 1101, and the second conductor 1103 is provided on the back surface layer 2 of the heater 1100. In this first embodiment, glass is used as the surface protective layer 1107. The surface protective layer 1107 does not cover the electrodes E11 to E15, E18-1, and E18-2 that come into contact with the electrical contacts C11 to C15, C18-1, and C18-2 for power feeding. The electrodes E11 to E15 are electrodes for supplying power to the heating blocks HB11 to HB15 via the second conductors 1103-1 to 1103-5. The electrodes E18-1 and E18-2 are electrodes for supplying power to the heating blocks HB11 to HB15 via the first conductors 1101a and 1101b.

[0064] By providing the electrodes on the back surface of the heater 1100 in this manner, it is no longer necessary to provide a conductive pattern on the substrate 1105 to supply power to the second conductors 1103-1 to 1103-5, and thus the length of the substrate 1105 in the lateral direction can be reduced. Therefore, an increase in the size of the heater 1100 can be suppressed. Note that, as Figure 3B shown, the electrodes E12 to E14 are arranged in the longitudinal direction of the substrate 1105 in the region where the heat generating member is provided.

[0065] The heater 1100 according to the first embodiment can form various heat distribution patterns by independently controlling a plurality of heat generating blocks. Therefore, the heat distribution pattern can be set according to the size of the recording material P. In addition, the heat generating member 1102 is formed of a material having a positive temperature coefficient (PTC) characteristic. Therefore, even when the boundary between the end of the recording material P and the heat generating block does not match, the high temperature at the non-sheet feeding portion can be suppressed to the maximum extent.

[0066] The surface protection layer 1108 having slidability is provided at the sliding surface layer 2 on the side of the sliding surface of the heater 1100 (the surface in contact with the fixing film 25). In this first embodiment, glass is used for the surface protection layer 1108. Providing this surface protection layer 1108 enables smooth sliding between the heater 1100 and the fixing film 25.

[0067] Reference will be made to Figure 3C describe the heater holder 29. The heater holder 29 according to the present embodiment is provided with opening portions HC11 to HC15, HC18-1 and HC18-2 to supply power to the electrodes E11 to E15, E18-1 and E18-2 formed on the back surface layer 1. The electrical contacts C11 to C15, C18-1 and C18-2 supply power to the electrodes through these opening portions. Opening portions H212-12, H212-13 and H212-15 for arranging the thermal switch 520 and opening portions H213-12, H213-13 and H213-15 for arranging the thermistor 510 are also provided to the heater holder 29.

[0068] Thermistor

[0069] Next, the thermistor 510, which is a characteristic configuration of the first embodiment, will be described. The thermistor 510 is an example of a temperature detection element used by the temperature detection section in the control configuration of the fixing device C or the imaging device to detect and measure the temperature of the heater 1100. In particular, its purpose is to perform desired temperature control by reflecting its measurement results in the power application control of the heater 1100. From the perspective of temperature control, the thermistor 510 is preferably arranged in at least one of the heating blocks HB belonging to the heating group that is fed power from the same driver.

[0070] Now, reference will be made to Figure 5A and Figure 5B to describe the configuration of the thermistor 510. As Figure 5A and Figure 5B shown, the thermistor 510 is composed of a thermistor chip 51, an insulating film 52, an elastic member 53, and a heat-resistant member 54. The thermistor chip 51 that performs temperature detection has the characteristic that its resistance value changes depending on the temperature, and it is an element that can detect the temperature by measuring its resistance value. The insulating film 52 made of a material such as polyimide ensures the insulation of the thermistor chip 51 by covering around the thermistor chip 51. The elastic member 53 is arranged to achieve stable contact between the thermistor chip 51 and the temperature detection object, and ceramic paper or the like is used. The heat-resistant member 54 is made of a heat-resistant material such as liquid crystal polymer (LCP). The thermistor 510 is placed such that the insulating film 52 contacts the surface (surface protective layer 1107) of the heater 1100 on the side opposite to the face where the nip portion N is formed with the pressure roller 26.

[0071] Power application control circuit of the heater

[0072] Figure 4It is a circuit diagram of the control circuit 1400 that controls the heater 1100. The power control (power application control) of the heater 1100 is performed by turning on / off the power supply to the heater 1100 through the triac elements 1411 to 1413. The triac elements 1411 to 1413 each operate according to the Fuser 1 to Fuser 3 signals from the CPU 420. The control circuit 1400 of the heater 1100 has a circuit configuration that enables power supply to the five heating blocks HB11 to HB15 through the three triac elements 1411 to 1413. Specifically, the power application control of the heating block HB13 (1st heating group) is performed by the triac element 1411. In addition, the power application control of the heating blocks HB12 and HB14 (2nd heating group) is performed by the triac element 1412, and the power application control of the heating blocks HB11 and HB15 (3rd heating group) is performed by the triac element 1413. At this time, the 2nd heating group serving as the first heating member group and the 3rd heating group serving as the second heating member group each have multiple heating blocks HB for one drive circuit. That is, power is supplied to each of the heating members included in the group via one common drive circuit (first common circuit, second common circuit). Note that in Figure 4 the drive circuits of the triac elements 1411 to 1413 are omitted.

[0073] The zero-crossing detection section 1421 is a circuit that detects the zero-crossing of the AC power supply 1401 and outputs a ZeroX signal to the CPU 420. The ZeroX signal is used as a reference signal for phase control etc. of the triac elements 1411 to 1413.

[0074] The relay 1440 is provided as a component for cutting off the power supply to the heater 1100 when the heater 1100 overheats due to equipment failure etc. The three thermal switches 520-11, 520-13, and 520-14 are located on the DC circuit connected to the 24V power supply. The construction is such that when any one of the three thermal switches 520-11, 520-13, and 520-14 is opened, the 24V applied to the relay 1440 is cut off and the relay 1440 is opened, thereby cutting off the AC circuit. Note that although the case of using thermal switches is described as an example of a safety element in this embodiment, a temperature fuse or other element that can detect abnormal heating of the heater and cut off the power supply to the heater can be used.

[0075] Arrangement positions of the thermistor and the thermal switch according to Comparative Example 1

[0076] Figure 7is a schematic plan view showing the arrangement positions of the thermistor 510 and the thermal switch 520 according to Comparative Example 1. As Figure 7 shown, regarding the thermistor 510 of Comparative Example 1, the thermistors 510-11, 510-12, and 510-13 are respectively arranged in the heating blocks HB11, HB12, and HB13. In Comparative Example 1, these three thermistors 510-11, 510-12, and 510-13 perform temperature control. Regarding the thermal switch 520, the thermal switches 520-11, 520-12, and 520-13 are respectively arranged in the heating blocks HB11, HB12, and HB13. That is, the fixing device according to Comparative Example 1 is configured such that the thermistors 510-11, 510-12, and 510-13 are arranged unilaterally (one-sidely) on the same right side or the same left side with respect to the center of the recording material in the width direction (on either the right side or the left side) in the heating block HB.

[0077] Problems of Comparative Example 1

[0078] The fixing device according to Comparative Example 1 is configured such that the thermistor is arranged on one side (biased to either the right side or the left side) with respect to the center of the sheet, and thus, when there is a change in the resistance value of the heater 1100, the lateral difference in fixing ability may become large. Therefore, due to the fixing ability, there may be occurrence of defective images such as misfixing, thermal offset, etc. A feasible measure to solve this problem is to improve the product quality so that, for example, the change in the resistance distribution of the heater is suppressed within a predetermined range, but this will inevitably lead to an increase in costs such as the selection and management of the heater in order to meet the quality requirements for use as an imaging device.

[0079] Resistance change of the heater

[0080] will refer to Figure 8A and Figure 8C to describe the resistance change of the heating member. Due to its manufacturing method, the resistance change in the heating member tends to have a uniform resistance distribution in the longitudinal direction. As an example of the resistance distribution of a heater with large resistance non-uniformity, Figure 8A shows the resistance distribution (resistance non-uniformity) of the heating member 1102 of the heater AH, and Figure 8C shows the resistance distribution (resistance non-uniformity) of the heating member 1102 of the heater BH.

[0081] As Figure 8A shown, the resistance value of the heating member of the heater AH continuously changes in the longitudinal direction, where Figure 8A the resistance on the right side is high. That is, this is with respect to the resistance distribution that is uniform in the longitudinal direction when there is no resistance non-uniformity (Figure 8A The thick solid line extending horizontally in the middle) has a resistance distribution with an inclination Figure 8A The thick solid line extending obliquely in the middle). When using such a heater and supplying power to the heating blocks HB of the same heating group, since the heating members are connected in parallel to the electrodes, the heating members with lower resistance values will generate a larger amount of heat. Specifically, the amount of heat generated by the heating block HB12 will be greater than that of the heating block HB14, and the amount of heat generated by the heating block HB11 will be greater than that of the heating block HB15.

[0082] As Figure 8C shown, the resistance values of the heating members of the heater BH continuously change in the opposite direction with respect to the resistance values of the heater AH. That is, Figure 8C The resistance is low on the right side in the middle. Therefore, when using the heater BH, the amount of heat generated by the heating block HB12 will be less than that of the heating block HB14, and the amount of heat generated by the heating block HB11 will be less than that of the heating block HB15.

[0083] As described above, due to its manufacturing method, the heating members 1102 of the heater 1100 tend to have a uniform resistance distribution in the longitudinal direction. The heating members 1102 are formed on a substrate 1105 made of ceramics by techniques such as screen printing. When transferring the heating members 1102 to the substrate 1105 in screen printing, the coating amount of the heating members 1102 is determined by moving a squeegee along the longitudinal direction of the heater 1100. In the case of forming the heating members 1102 by screen printing in this way, the thickness of the heating members 1102 is uneven in the screen printing direction, that is, in the longitudinal direction of the heater 1100, and therefore, resistance unevenness tends to occur easily.

[0084] Temperature control of Comparative Example 1

[0085] Figure 8B And Figure 8D show the temperature control of the fixing unit according to Comparative Example 1 in the case of using the above heaters AH and BH. Figure 8B And Figure 8D show Figure 7 the temperature distribution of the heating members in the case of performing temperature control using the thermistors 510-11, 510-12, and 510-13 in the fixing device of the comparative example shown in Figure 8B show the temperature distribution of the heating members in the case of performing temperature control using the heater AH, and Figure 8DShows the temperature distribution of the heating member when the heater BH is used. In Comparative Example 1, temperature control is performed using the thermistors 510-11, 510-12, and 510-13, and thus the temperature of the heater 1100 is controlled to a predetermined temperature at the arrangement positions P510-11, P510-12, and P510-13 of the thermistors.

[0086] When the heater AH is used, the resistance value of the heating member 1102 in the regions of the heating blocks HB11 and HB12 is lower than that in the heating blocks HB14 and HB15. Therefore, as Figure 8B shown, the temperature of the heating member in the heating blocks HB14 and HB15 becomes lower than the temperature of the heating member in other regions. That is, when the heater AH is used, since the thermistor 510-11 is arranged in the heating block HB11, temperature control is performed to a predetermined temperature at the arrangement position (P510-11) of the thermistor 510-11. In addition, since the thermistor 510-12 is arranged in the heating block HB12, temperature control is performed to a predetermined temperature at P510-12 in the same manner. At the same time, in the heating blocks HB14 and HB15, the resistance value of the heating member is high and the generated heat is small, and furthermore, temperature control is performed at the heating blocks HB12 and HB11, and thus the temperature of the heating member drops even further. Therefore, it may not be possible to supply a sufficient amount of heat required for fixing, and incorrect fixing may occur.

[0087] On the contrary, when the heater BH is used, the resistance value of the heating member 1102 in the regions of the heating blocks HB11 and HB12 is higher than that in the heating blocks HB14 and HB15. Therefore, when the heater BH is used, since temperature control is performed at the thermistors 510-11 and 510-12, the temperature of the heating member in the heating blocks HB14 and HB15 becomes higher than the temperature of the heating member in other regions, as Figure 8D shown. Therefore, the heat for fixing becomes excessive, and thermal offset may occur.

[0088] The film surface temperature in Comparative Example 1

[0089] Next, with reference to Figure 10A and Figure 10BDescribe the longitudinal temperature distribution on the surface of the fixing film 25 according to Comparative Example 1. The longitudinal temperature distribution on the surface of the fixing film 25 is characterized by having a smoother temperature change compared to the longitudinal temperature distribution of the heat generating member 1102. The reason is that the thermal conductivity of the heater 1100 and the fixing film 25 in the longitudinal direction is higher than the thermal conductivity of the fixing film 25 in its thickness direction. That is to say, this is because when the heat from the heat generating member 1102 is transmitted in the thickness direction of the substrate 1105 of the heater 1100 and the fixing film 25, heat is supplied in the longitudinal direction. Note that Figure 10A and Figure 10B the shown temperature TL is the threshold temperature for misfixing, and the temperature TH is the threshold temperature for thermal deviation. When the surface temperature of the fixing film 25 drops below the temperature TL, misfixing occurs, and when the surface temperature exceeds the temperature TH, thermal deviation occurs.

[0090] In the case of performing temperature control on the fixing device according to Comparative Example 1 using the heater AH, the longitudinal temperature distribution on the surface of the fixing film 25 is shown by Figure 10A the solid line in. Compared with Figure 8B , the longitudinal temperature distribution of the heat generating member 1102 according to Comparative Example 1 makes the temperatures at both the heating block HB14 and the heating block HB15 lower. Therefore, heat supply in the longitudinal direction is not performed in the area of the heating block HB15, and the surface temperature of the fixing film 25 becomes lower in the area of the heating block HB15. As a result, the surface temperature of the fixing film 25 drops below the temperature TL (the threshold temperature for misfixing), and misfixing occurs.

[0091] On the contrary, in the case of performing temperature control on the fixing device according to Comparative Example 1 using the heater BH, the longitudinal temperature distribution on the surface of the fixing film 25 is conceptually shown by Figure 10B the solid line in. Compared with Figure 8D , the longitudinal temperature distribution of the heat generating member 1102 according to Comparative Example 1 makes the temperatures at both the heating block HB14 and the heating block HB15 higher. Therefore, the heat excessively supplied to the area of the heating block HB15 cannot be diverted to other heating blocks HB, and the surface temperature of the fixing film 25 becomes higher at the area of the heating block HB15. As a result, the surface temperature of the fixing film 25 exceeds the temperature TH (the threshold temperature for thermal deviation), and thermal deviation occurs.

[0092] As described above, in the case of using the heater 1100 having a resistance distribution (such as the heater AH or the heater BH) in the fixing device according to Comparative Example 1, it is possible to occur misfixing or thermal deviation.

[0093] The arrangement positions of the thermistor and the thermal switch according to the first embodiment

[0094] On the other hand, the problem of Comparative Example 1 can be solved by using the fixing device according to the first embodiment of the present invention. Figure 6 The arrangement positions of the thermistor 510 and the thermal switch 520 according to the first embodiment are shown. As Figure 6 shown, in the first embodiment, the thermistors 510-11, 510-13, and 510-14 are respectively arranged in the heating blocks HB11, HB13, and HB14. That is, the thermistor 510-11 serving as the second temperature detection element is placed on the left side (the other side) with respect to the conveyance reference position X to detect the temperature of the heating block HB11 in the 3rd heating group (heating blocks HB11 and HB15) serving as the second heating member group. In addition, the thermistor 510-14 serving as the first temperature detection element is placed on the right side (one side) with respect to the conveyance reference position X to detect the temperature of the heating block HB14 in the 2nd heating group (heating blocks HB12 and HB14) serving as the first heating member group. In the first embodiment, the temperature control is performed by these three thermistors 510-11, 510-13, and 510-14. That is, the temperature control is performed so that the temperatures detected by the thermistors 510-11, 510-13, and 510-14 are maintained at a predetermined control target temperature. Regarding the thermal switch, the thermal switches 520-11, 520-13, and 520-14 are respectively arranged in the heating blocks HB11, HB13, and HB14. That is, the thermal switch 520-11 serving as the second safety element is placed corresponding to the heating block HB11 in the heating blocks included in the 3rd heating group, and the thermistor 510-11 is placed correspondingly in this heating block. In addition, the thermal switch 520-14 serving as the first safety element is placed corresponding to the heating block HB14 in the heating blocks included in the 2nd heating group, and the thermistor 510-14 is placed correspondingly in this heating block.

[0095] Temperature control according to the first embodiment

[0096] Figure 9A Shows the temperature distribution of the heating member 1102 in the case where the thermistor temperature control is performed using the heater 1100 having the Figure 8A shown resistance distribution in the first embodiment of the present invention. In the first embodiment of the present invention, the temperature control is performed using the thermistors 510-11, 510-13, and 510-14, and therefore the temperature control is performed to a predetermined temperature at the Figure 6 arrangement positions P510-11, P510-13, and P510-14 of the shown thermistors.

[0097] The difference point in the temperature of the heating member 1102 compared to Comparative Example 1 is Figure 8B with Figure 9Abetween and Figure 8D and Figure 9B The difference between them, that is, the temperature difference in the regions of the heating blocks HB12 and HB14. In this first embodiment, temperature control is performed by the thermistor 510-14 arranged in the heating block HB14, and thus the temperature of the heating block HB14 is controlled to a predetermined temperature. At the same time, the temperature of the heating member 1102 in the heating block HB12 is higher when the heater AH is used and lower when the heater BH is used, compared with the temperature of the heating member 1102 in the heating block HB14. In Comparative Example 1 and this first embodiment, the temperatures in other regions are the same.

[0098] The film surface temperature of the first embodiment

[0099] will be referred to Figure 10A and Figure 10B to describe the longitudinal temperature distribution of the surface of the fixing film 25 according to this first embodiment.

[0100] When temperature control is performed on the fixing device according to the first embodiment using the heater AH, the longitudinal temperature distribution of the surface of the fixing film 25 is shown by the Figure 10A dashed line in. As Figure 10A shown, the surface temperature of the fixing film 25 in the regions of the heating blocks HB14 and HB15 according to the first embodiment is higher than the surface temperature of the fixing film 25 in the same regions according to Comparative Example 1. This is because in the first embodiment, temperature control is performed by the thermistor 510-14 arranged in the heating block HB14, and thus, compared with Comparative Example 1, the temperature of the heating member 1102 in the heating block HB14 is higher, and this heat is also transferred to the region of the heating block HB15. Therefore, in this first embodiment, different from Comparative Example 1, the surface temperature of the fixing film also exceeds the temperature TL in the region of the heating block HB15, and thus incorrect fixing does not occur. As described above, by using this first embodiment, the occurrence of incorrect fixing can be suppressed when the heater AH is used.

[0101] On the other hand, when temperature control is performed on the fixing device according to the first embodiment using the heater BH, the longitudinal temperature distribution of the surface of the fixing film 25 is conceptually shown by the Figure 10B dashed line in. As Figure 10BAs shown, the surface temperature of the fixing film 25 in the regions of the heating blocks HB14 and HB15 according to the first embodiment is lower than the surface temperature of the fixing film 25 in the same regions according to Comparative Example 1. This is because in the first embodiment, temperature control is performed by the thermistor 510-14 disposed in the heating block HB14, and thus, compared with Comparative Example 1, the temperature of the heating member 1102 in the heating block HB14 is lower, and the heat of the heating block HB15 is also transferred to the region of the heating block HB14. Therefore, in this first embodiment, different from Comparative Example 1, the surface temperature of the fixing film is also lower than the temperature TH in the region of the heating block HB15, and thus thermal deviation does not occur. As described above, according to this first embodiment, the occurrence of thermal deviation can also be suppressed when using the heater BH.

[0102] As described above, the fixing device according to the first embodiment can exhibit an operation effect that cannot be obtained by the comparative example.

[0103] Note that although the positions where the thermistors 510 are disposed in this first embodiment are the three heating blocks HB11, HB13, and HB14, this is not restrictive as long as the thermistors 510 are disposed in the heating group including a plurality of heating blocks HB without being adjacent to each other. For example, the positions where the thermistors 510 are disposed can be the heating blocks HB12, HB13, and HB15.

[0104] In addition, although the first embodiment has been described by way of the example of the heater 1100 in which the heating members 1102a and 1102b are disposed in the conveying direction of the recording material P, the form of the heating member is not limited as long as the heating blocks HB are divided in the width direction of the recording material P in the heater 1100. In addition, in this first embodiment, the structure in which the electrodes E11 to E15, E18-1, and E18-2 are formed on the back surface of the recording material passing region of the heater 1100 has been shown, but this is not restrictive.

[0105] In Figure 11A and Figure 11B examples of the above structure are shown. Figure 11AThe heater 1100 therein is divided into these five heating members 1102-1 to 1102-5, and the heating area is divided into these five heating blocks HB11 to HB15. According to their respective drive circuits, the heating blocks HB are grouped into three heating groups, namely, the 1st heating group (heating block HB13), the 2nd heating group (heating blocks HB12 and HB14), and the 3rd heating group (heating blocks HB11 and HB15). The 1st heating group is the heating area including the conveyance reference position X of the recording material P. The 2nd heating group is the heating area having heating blocks HB divided into left and right two parts with the conveyance reference position X of the recording material P therebetween, and is arranged adjacent to the 1st heating group on the side away from the conveyance reference position X of the recording material P of the 1st heating group. The 3rd heating group is the heating area having heating blocks HB divided into left and right two parts with the conveyance reference position X of the recording material P therebetween, and is arranged adjacent to the 2nd heating group on the side away from the conveyance reference position X of the recording material P of the 2nd heating group.

[0106] Now, the heating members 1102-1 to 1102-5 have a form that is folded multiple times in the width direction of the heater 1100, as Figure 11A shown. In addition, the heating members 1102-1 to 1102-5 receive power supply from the electrodes E21 to E24 through the conductors 1101a and 1101b-1 to 1101b-5, and generate heat. The thermistor 510 is arranged relative to the heater 1100 at the Figure 11B position shown. That is, the thermistor 510-11 is arranged in the area of the heating block HB11, the thermistor 510-13 is arranged in the area of the heating block HB13, and the thermistor 510-14 is arranged in the area of the heating block HB14. Therefore, the effects of this embodiment can be exhibited. Note that, in this case, the thermistors can also be arranged in the heating blocks HB12, HB13, and HB15 in the same manner.

[0107] In addition, although the case where there are three heating groups has been described in this embodiment, the same advantages can also be exhibited in a fixing device in which the heating area is divided into more parts. An example is shown in Figure 12 . As Figure 12As shown, the heating group (n) consists of a heating block HB(n) and HB(n)x supplied with power by the same driver, and the heating blocks HB(n) and HB(n)x are arranged to be divided into left and right parts with respect to the conveyance reference position X of the recording material P. Further, the heating group (n + 1) consists of a heating block HB(n + 1) and HB(n + 1)x supplied with power by the same driver, and the heating blocks HB(n + 1) and HB(n + 1)x are arranged to be divided into left and right parts with respect to the conveyance reference position X of the recording material P. Further, the heating group (n + 1) is arranged to be adjacent to the heating group (n) on the side away from the conveyance reference position X of the recording material P. Here, the thermistor 510 is arranged at Figure 12 the position shown. That is, the thermistor 510-(n) is arranged in the heating block HB(n), and the thermistor 510-(n + 1) is arranged in the heating block HB(n + 1)x. Therefore, regardless of the longitudinal change in the heater resistance, even in a fixing device using a heater 1100 divided into more divided parts, good fixing performance can be satisfied.

[0108] In addition, although in this first embodiment the thermistor 510 is placed such that its insulating film 52 contacts the heater 1100, the placement position is not particularly limited as long as the thermistor chip 51 can detect the temperature of the area of the heating block HB.

[0109] Further, although in this first embodiment it is configured such that the thermistor 510 and the thermal switch 520 are arranged in the same heating block HB, from the perspective of saving space, the thermistor 510 and the thermal switch 520 can be arranged in different heating blocks HB under the same drive. For example, it can be configured such that the thermistor 510 is arranged in the heating blocks HB11 and HB14, and the thermal switch 520 is arranged in the heating blocks HB12 and HB15. According to this layout, the thermistor 510 and the thermal switch 520 can be effectively arranged. Therefore, the size and cost of the heater 1100 can be reduced.

[0110] Second Embodiment

[0111] In the second embodiment, the configuration of a fixing device applied in the case where the longitudinal resistance distribution of the heater 1100 is large will be described, and the fixing device has a unit for detecting the resistance distribution of the heater. The difference between the second embodiment and the first embodiment lies only in the resistance distribution of the heater 1100 and the detection unit for detecting the resistance distribution and its control method. Other configurations are the same as those in the first embodiment, and thus repeated descriptions will be omitted. Items not particularly described in the second embodiment are the same as those in the first embodiment.

[0112] Resistance Change of the Heater in the Second Embodiment

[0113] Figure 13A and Figure 13C shows the resistance non-uniformity of the heating element 1102 of "heater CH" and "heater DH", and the heaters represent the heater 1100 with large resistance non-uniformity used in the second embodiment. Figure 13A shows the resistance non-uniformity of "heater CH", and Figure 13C shows the resistance non-uniformity of "heater DH". The resistance value of heater CH becomes higher as it goes to the right, while the resistance value of heater DH becomes lower as it goes to the right, and the respective resistance distributions are larger than those of heater AH and heater BH in the first embodiment.

[0114] Next, the detection unit for detecting the heater resistance in the second embodiment will be described. In the fixing device according to the second embodiment, the resistance value distribution of the heating element 1102 pre-measured during the manufacture of the heater 1100 is stored in a storage unit such as a fixing memory.

[0115] Although the device for pre-measuring the resistance value distribution of the heating element 1102 in the second embodiment is shown here as a detection unit (acquisition part) for detecting the resistance distribution, other devices can also be used. For example, a device for comparing the thermistor temperature at startup or a device for comparing the input power during temperature control can be used.

[0116] will be described with reference to Figure 13B and Figure 13D the fixing control according to the second embodiment. In the fixing device according to the second embodiment, Figure 13B shows the temperature control device in the case of using heater CH, and Figure 13D shows the temperature control device in the case of using heater DH.

[0117] In the case of using heater CH, the temperature control temperature of the thermistor 510-11 is set to be higher than the temperature control temperature of the thermistor 510-13, and the temperature control temperature of the thermistor 510-14 is set to be lower than the temperature control temperature of the thermistor 510-13, as Figure 13B shown. The set value of the temperature control temperature is preferably set such that the temperature difference between the heating blocks HB11 and HB12 predicted from the resistance distribution of the heating element 1102 and the temperature difference between the heating blocks HB14 and HB15 do not exceed a predetermined value.

[0118] In the second embodiment, the temperature control temperatures of the thermistors 510-11 and 510-14 are determined according to the following process. The heater resistance distribution data stored in the fixing memory is used to calculate the predicted value of the temperature of the heating member 1102 when the same power is input to all of the heating groups No. 1 to No. 3 ( Figure 13B as indicated by the dashed line in). At this time, the average value of the predicted value T11a of the temperature of the heating member 1102 at P510-11 and the temperature control temperature T13 at P510-13 is calculated to obtain T11b. Here, the difference between the predicted value T11a and T11b is the same as the difference between T11b and the temperature control temperature T13. This T11b is set as the temperature control temperature (control target temperature) of the thermistor 510-11. In the same manner, for the thermistor 510-14, the average value of the predicted value T14a of the temperature of the heating member 1102 at P510-14 and the temperature control temperature T13 at P510-13 is calculated to obtain T14b. At this time, the difference between the predicted value T14a and T14b is the same as the difference between T14b and the temperature control temperature T13. This temperature T14b is set as the temperature control temperature (control target temperature) of the thermistor 510-14.

[0119] In addition, in the same manner as when using the heater CH, the above process is also used to determine the temperature control temperatures of the thermistors 510-11 and 510-14 when using the heater DH. When using the heater DH, the temperature control temperature of the thermistor 510-11 is set to be lower than the temperature control temperature of the thermistor 510-13, and the temperature control temperature of the thermistor 510-14 is set to be higher than the temperature control temperature of the thermistor 510-13, as Figure 13D shown.

[0120] Next, the longitudinal temperature distribution on the surface of the fixing film 25 according to the second embodiment will be described with reference to Figure 14A and Figure 14B . When performing temperature control on the fixing device according to the second embodiment using the heater CH, the longitudinal temperature distribution on the surface of the fixing film 25 is shown by the dashed line in Figure 14A . As shown in Figure 14A , in the second embodiment, the surface temperature of the fixing film is higher than TL in the entire longitudinal region, and misfixing does not occur. In addition, when performing temperature control on the fixing device according to the second embodiment using the heater DH, the longitudinal temperature distribution on the surface of the fixing film 25 is shown by the dashed line in Figure 14B . As shown in Figure 14B , in the second embodiment, the surface temperature of the fixing film is lower than TH in the entire longitudinal region, and thermal offset does not occur.

[0121] As described above, the variation in the longitudinal temperature distribution of the fixing film 25 can be reduced by using the fixing device according to the second embodiment. Therefore, the occurrence of misfixing and thermal deviation can be suppressed. Further, the temperature difference between the heating blocks HB can be reduced, specifically, the temperature difference between the heating blocks HB11 and HB12 and between the heating blocks HB14 and HB15. Therefore, for example, the occurrence of defective images such as uneven gloss caused by the temperature difference between the heating blocks HB can be suppressed.

[0122] Third Embodiment

[0123] The fixing device according to the third embodiment is characterized in that the thermistor 510 that performs temperature detection is a printed thermistor formed on the substrate 1105 of the heater 1100, and a plurality of printed thermistors are formed in each individual heating block HB. Other configurations are the same as those in the first embodiment, and thus repeated descriptions will be omitted. Items not particularly described in the third embodiment here are the same as those in the first and second embodiments.

[0124] Reference will be made to Figure 15B the arrangement positions of the thermistors according to the third embodiment. The heater 1100 according to the third embodiment is provided with a sliding surface layer 1 and a sliding surface layer 2 covering the sliding surface layer 1 on the sliding surface side in contact with the fixing film 25, and a printed thermistor is provided in the sliding surface layer 1. A plurality of printed thermistors for detecting the temperatures of the heating blocks HB11 to HB15 are formed in the sliding surface layer 1 of the heater 1100. In Figure 15B it, the plurality of thermistors are represented by T11-1C, T11-3C, T11-1E to T11-3E, T12-4C, and T12-3E to T12-5E, respectively. A material having a large positive or negative temperature coefficient of resistance (TCR) is sufficient as the material for the thermistor. In the present third embodiment, a material having a negative temperature coefficient (NTC) characteristic (where the TCR is negative) is thinly printed on the substrate 1105 to form the thermistor.

[0125] Next, the thermistor layout in each of the heating blocks HB will be described. In the present third embodiment, two or more thermistors are placed in each of the heating blocks HB11 to HB15, as Figure 15BAs shown. For example, two thermistors T11-1C and T11-1E are arranged in the heating block HB11, and the conductive patterns ET11-1C and ET11-1E for detecting resistance and the common conductive pattern EG11 are configured to detect the temperature of the thermistors. The thermistor T11-1C is a thermistor for detecting the temperature at the central region of the heating block HB11, and is placed at approximately the middle part of the heating block HB11 with respect to the width direction of the recording material P. In addition, the thermistor T11-1E is an end portion thermistor for detecting the temperature at the end portion region of the heating block HB11, and is placed at the position farthest from the conveyance reference position X in the region of the heating block HB11 with respect to the width direction of the recording material P. In this way, the thermistors T11-1C, T11-3C, and T12-4C for detecting the temperature at the central region are placed in the heating blocks HB11, HB13, and HB14. In addition, the end portion thermistors T11-1E to T11-3E and T12-3E to T12-5E for detecting the temperature of the end portion region are placed in the respective heating blocks HB11 to HB15.

[0126] In this third embodiment, the temperature control thermistors for performing temperature control on the heating blocks HB belonging to each heating group are set in each heating group. The thermistor T11-3C is set as the temperature control thermistor in the 1st heating group, the thermistor T12-4C is the temperature control thermistor in the 2nd heating group, and the thermistor T11-1C is the temperature control thermistor in the 3rd heating group. Therefore, in the third embodiment, the temperature control thermistors for performing temperature control on the heating blocks HB belonging to the respective heating groups are placed at positions laterally spaced apart across the conveyance reference of the recording material P in adjacent heating groups. Therefore, even when there are changes in the resistance value of the heater 1100, the occurrence of misfixing and thermal deviation can be suppressed.

[0127] Note that in this third embodiment, it is sufficient that the temperature control thermistors of adjacent heating groups are placed laterally spaced apart from each other across the conveyance reference, and this does not apply to the thermistors whose purpose is temperature detection. For example, supplementary functions can be given, such as changing the temperature control temperature using the detection result of the thermistor T12-5E arranged in the region of the heating block HB15.

[0128] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims will be given the broadest interpretation so as to cover all such modifications as well as equivalent structures and functions.

Claims

1. An image heating device, the image heating device comprises: a heater, the heater including a plurality of heating members arranged along the width direction of a recording material, the width direction being orthogonal to the conveying direction of the recording material; a clamping portion forming part, the clamping portion forming part forming a clamping portion for clamping the recording material; a temperature detection part, the temperature detection part detecting the temperature of the heater; and a control part, the control part controlling the power to be supplied to the plurality of heating members based on the temperature detected by the temperature detection part, wherein the image heating device heats an image formed on the recording material clamped by the clamping portion by the heat of the heater, wherein the plurality of heating members have a first heating member group and a second heating member group, wherein the first heating member group includes a plurality of heating members symmetrically arranged with respect to a conveyance reference position of the recording material in the width direction, and the second heating member group includes a plurality of heating members symmetrically arranged with respect to the conveyance reference position, and the plurality of heating members of the second heating member group are placed at positions different from those where the plurality of heating members of the first heating member group are placed in the width direction, wherein the temperature detection part includes a first temperature detection element and a second temperature detection element, the first temperature detection element being used to detect the temperature of one of the heating members included in the first heating member group, and the second temperature detection element being used to detect the temperature of one of the heating members included in the second heating member group, wherein, when heating an image formed on the recording material at the clamping portion, the control part supplies power to the first heating member group via a first common circuit to maintain the detected temperature detected by the first temperature detection element at a control target temperature, and supplies power to the second heating member group via a second common circuit to maintain the detected temperature detected by the second temperature detection element at a control target temperature, wherein the first temperature detection element is placed on one side with respect to the conveyance reference position in the width direction, and wherein the second temperature detection element is placed on the other side with respect to the conveyance reference position in the width direction.

2. The image heating device according to claim 1, wherein, the first heating member group and the second heating member group are adjacent to each other in the width direction.

3. The image heating device according to claim 1 or 2, wherein, the clamping portion forming part includes a cylindrical film on which the heater is placed on the inner side, and a pressure member in contact with the outer surface portion of the film, and wherein the clamping portion is formed between the film and the pressure member by the heater and the pressure member via the film.

4. The image heating device according to claim 3, wherein, the first temperature detection element and the second temperature detection element are placed in contact with the surface of the heater on the side opposite to the surface forming the clamping portion with the pressure member.

5. The image heating device according to claim 1 or 2, wherein, the first temperature detection element and the second temperature detection element are thermistors.

6. The image heating device according to claim 1 or 2, wherein, the heater includes a substrate, and a plurality of heating members are formed on the substrate, and wherein, the first temperature detection element and the second temperature detection element are printed thermistors formed on the substrate.

7. The image heating device according to claim 1 or 2, the image heating device further comprises: an acquisition section that acquires a resistance distribution of the heater in the width direction, wherein, the control section controls the power to be supplied to the plurality of heating members based on the resistance distribution acquired by the acquisition section and the temperature detected by the temperature detection section.

8. The image heating device according to claim 7, wherein, the control section controls the power to be supplied to the plurality of heating members while maintaining the temperature difference between the first heating member group and the second heating member group within a predetermined value.

9. The image heating device according to claim 1 or 2, the image heating device further comprises: a plurality of safety elements, wherein, the plurality of safety elements includes: a first safety element that is placed corresponding to one of the heating members included in the first heating member group, and a second safety element that is placed corresponding to one of the heating members included in the second heating member group.

10. The image heating device according to claim 9, wherein, the first safety element is placed corresponding to the heating member to which the first temperature detection element included in the heating members included in the first heating member group corresponds, and wherein, the second safety element is placed corresponding to the heating member to which the second temperature detection element included in the heating members included in the second heating member group corresponds.

11. The image heating device according to claim 9, wherein, the first safety element is placed corresponding to a heating member different from the heating member to which the first temperature detection element included in the heating members included in the first heating member group corresponds, and wherein, the second safety element is placed corresponding to a heating member different from the heating member to which the second temperature detection element included in the heating members included in the second heating member group corresponds.

12. The image heating device according to claim 1 or 2, wherein, the first temperature detection element is placed to detect the temperature at the central region in the width direction of one of the heating members included in the first heating member group, and wherein, the second temperature detection element is placed to detect the temperature at the central region in the width direction of one of the heating members included in the second heating member group.

13. The image heating device according to claim 12, wherein, The temperature detection section further includes a temperature detection element for detecting the temperature at an end portion region in the width direction of each of the plurality of heating members.

14. An imaging device, the imaging device comprising: an imaging section that forms an image on a recording material; and a fixing section that fixes the image formed on the recording material to the recording material, wherein the fixing section is the image heating device according to claim 1 or 2.

Images