JP2012022042A - Image heating device and endless belt for image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device which don't require a large-scale special device for detection of breakage and control after the breakage of a fixing film including a heat generator which generates heat by electric conduction.SOLUTION: A patterned heat generator which is formed of a series of single lines and is distributed throughout an effective heating area of the fixing film is provided in an endless film-shaped fixing member.

Description

  The present invention relates to an image heating apparatus used in an image forming apparatus such as a copying machine and a printer, and an endless belt for the image heating apparatus. Examples of the image heating device include a fixing device that heats and fixes an unfixed image formed on a recording material as a fixed image, and a glossiness increasing device that increases the glossiness of an image by heating the image fixed on the recording material. Can be mentioned.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a recording material, and an image is formed by fixing the toner image by heating and pressurizing it with a fixing device. As such a fixing device, in recent years, from the viewpoint of energy saving, as a fixing method with high heat transfer efficiency and quick start-up of the device, a heating element formed such that a resistance heating element made of a substance that generates heat when energized rotates together with the core roller. A roller has been proposed (Patent Document 1). This type of heating roller has good electric / thermal conversion efficiency, and can quickly raise the surface temperature of the heating roller to a predetermined temperature after energization of the resistance heating element, thereby shortening the rise time of the fixing device. It becomes.

  When using a rotatable endless belt for the fixing device and providing a resistance heating element that generates heat when energized in the endless belt itself, for example, when handling a jam that occurs in the paper feed conveyance mechanism or replacing the image forming unit, etc. It is necessary to pay attention to the breakage of the film constituting the endless belt. That is, the film member is accidentally damaged, or the film base material is damaged, for example, pinholes such as pinholes are not found by visual inspection. Etc. occur. If the fixing process is continued in a state where the film is torn, problems such as poor fixing due to pressure drop at the film breakage part and damage to other members of the fixing device due to the breakage part occur. Further, in a system using a fixing film having a heat generating layer in the film itself, current concentrates on the heat generating layer other than the fractured portion, and an excessive temperature rise occurs partially.

  Therefore, as a method for solving these problems, it has been proposed to attach a film breakage detection means to detect breakage (Patent Document 2). However, since the film breakage detection means is newly provided to detect the breakage, the function cannot be performed when the film breaks outside the detectable range. If detection is possible in all parts, the apparatus becomes large and the cost increases. Further, since control such as stopping the heater temperature control or stopping the film drive is performed after the film break is detected, there is a time lag from the break to the end of the control, and an undesired product is produced during that time.

JP-A-1-177576 JP 2002-021952 A

  The present invention is a further improvement of the above prior art. The purpose of the image heating apparatus and image heating apparatus is that it is possible to detect breakage of an endless belt without using a special detection means, and that is convenient for preventing excessive temperature rise after break and stopping driving. It is to provide a belt for use.

  In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention includes an endless belt having a heating element that is flexible and rotatable and generates heat when energized, and the belt. And an opposing member that forms a nip portion, and an image heating apparatus that heats an image by sandwiching and conveying a recording material that holds an image at the nip portion, wherein the heating element is a series of single wires. Thus, the pattern is distributed over the entire effective heat generation area of the belt.

  In addition, a typical configuration of an endless belt for an image heating apparatus includes an endless belt having a heating element that is flexible and can be rotated, and generates heat when energized, and the belt and an opposite end forming a nip portion. A belt for use in an image heating apparatus that sandwiches and conveys a recording material that holds an image at the nip portion and heats the image, wherein the heating element is a series of single wires, The pattern is distributed over the entire effective heat generation area of the belt.

  According to the present invention, the breakage of the endless belt can be detected without using a special detection means, and the heater temperature is cut off at the same time as the breakage, so that an excessive temperature rise can be prevented promptly. Then, it becomes possible to quickly stop driving the image heating unit or the image forming unit.

(A) is element explanatory drawing of the fixing device concerning this invention, (B) is a perspective view of 1st Embodiment which comprised the heat generating body of the fixing film by a series of single wires. 1 is a schematic view of a color electrophotographic printer equipped with a fixing device according to the present invention. FIG. 3 is a schematic cross-sectional view of the fixing device according to the present invention during a sheet passing operation. FIG. 3 is a development view of a fixing film in the first embodiment. FIG. 5 is a flowchart illustrating an operation of the fixing device according to the first embodiment. It is a graph which shows the temperature transition of the fixing film in 1st Embodiment. It is an expanded view of the fixing film in 2nd Embodiment which comprised the heat generating body with a series of single wires. It is an expanded view of the fixing film in 3rd Embodiment which comprised the heat generating body with a series of single wires. 2 is a schematic diagram of a layer configuration of a fixing film in Comparative Example 1. FIG. 2 is a schematic plan view of a fixing film in Comparative Example 1. FIG. 2 is a schematic configuration diagram of a fixing device in Comparative Example 1. FIG. FIG. 10 is a flowchart showing the operation of the fixing device in Comparative Example 1. 6 is a graph showing a temperature transition of a fixing film in Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

<< First Embodiment >>
(Image forming device)
FIG. 2 is a cross-sectional view showing a schematic configuration along the recording material conveyance direction of a color electrophotographic printer which is an example of an image forming apparatus in which the image heating apparatus according to the present invention is mounted as a fixing device. The printer 1 according to the present embodiment forms an image on the recording material P by performing an image forming operation in accordance with input image information from an external host device 200 that is communicably connected to a control circuit unit (control board: CPU) 100. Can be output. The external host device 200 is a computer, an image reader, a facsimile, or the like. The control circuit unit 100 exchanges signals with the external host device 200. It also controls image forming sequence by exchanging signals with various image forming devices on the printer side. The recording material P includes plain paper, resin sheet, cardboard, OHP sheet (overhead projector sheet), envelope, postcard, label, and the like.

  In the printer, first to fourth image forming portions Y, M, C, and Bk are arranged in a horizontal direction from the left side to the right side in the drawing (in-line configuration, tandem type). Each of the image forming units is a laser exposure type electrophotographic process mechanism, and has the same configuration except that the color of the developer (toner) contained in the developing device is different. That is, each of the image forming units Y, M, C, and Bk is a drum type electrophotographic photosensitive member (image carrier: hereinafter referred to as a drum) 2 that is driven to rotate at a predetermined speed in the counterclockwise direction indicated by an arrow. Have Around each drum 2, a primary charger 3, a laser scanner 4, a developing device 5, a primary transfer blade 6, and a cleaner 7 are disposed as process means acting on the drum 2.

  An intermediate transfer belt unit 8 is disposed below the image forming portions Y, M, C, and Bk. The unit 8 includes an endless and flexible intermediate transfer belt (hereinafter referred to as a belt) 9, a driving roller 10, a tension roller 11, and a secondary transfer counter roller 12 that suspends the belt 9. . The primary transfer blades 6 of the respective image forming portions Y, M, C, and Bk are arranged inside the belt 9 and correspond to each other via an ascending belt portion between the tension roller 11 and the driving roller 10 of the belt 9. The drum 2 is pressed against the lower surface of the drum 2. A contact portion between each drum 2 and the belt 9 is a primary transfer portion. A secondary transfer roller 13 is in pressure contact with the secondary transfer counter roller 12 via a belt 9. A contact portion between the belt 9 and the secondary transfer roller 13 is a secondary transfer portion. The belt 9 is circulated and moved by the driving roller 10 in a clockwise direction indicated by an arrow at a speed corresponding to the rotational speed of the drum 2.

  In the present embodiment, the first image forming unit Y contains a yellow (Y) developer in the developing device 5 and forms a Y color toner image on the drum 2. The second image forming unit M stores a magenta (M) developer in the developing unit 5 and forms an M toner image on the drum 2. In the third image forming unit C, cyan (C) developer is accommodated in the developing device 5, and a C color toner image is formed on the drum 2. The fourth image forming unit Bk contains a black (Bk) developer in the developing unit 5 and forms a Bk color toner image on the drum 2.

  The control circuit unit 100 causes each of the image forming units Y, M, C, and Bk to perform an image forming operation based on the color separation image signal input from the external host device 200. As a result, Y, M, C, and Bk color toner images are formed on the surface of the drum 2 that rotates in each of the image forming units Y, M, C, and Bk at predetermined control timings. . The electrophotographic image forming principle and process for forming a toner image on the drum 2 are well-known and will not be described.

  The toner images formed on the surfaces of the drums 2 of the image forming units Y, M, C, and Bk are respectively transferred to the primary transfer unit in the rotation direction and the forward direction of the drums 2 and the rotation speed of the drums 2. Are sequentially superimposed and transferred onto the outer surface of the belt 9 which is rotationally driven at a speed corresponding to the above. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 9 by superimposing the four toner images of the Y, M, C, and Bk colors.

  On the other hand, at a predetermined paper feed timing, each of the selected levels of the upper and lower cassette paper feed units 14A and 14B in which recording materials P (hereinafter referred to as sheets) P of various sizes are stacked and accommodated. The paper feed roller 15 of the paper feed cassette is driven. As a result, the sheets P stacked and stored in the paper feed cassette at that level are separated and fed one by one and conveyed to the registration roller 18 through the conveyance path 16. When manual sheet feeding is selected, the sheet feeding roller 19 is driven. As a result, the sheets P stacked and set on the multi-feed tray 20 are separated and fed one by one and conveyed to the registration roller 18 through the conveyance path 16. The registration roller pair 18 receives the sheet P once and corrects it straight when the sheet is skewed. Then, the registration roller pair 18 sends the sheet P to a secondary transfer portion that is a pressure contact portion between the belt 9 and the secondary transfer roller 13 in synchronization with the toner image on the belt 9. As a result, the full-color composite toner image on the belt 9 is secondarily transferred onto the surface of the sheet P at the secondary transfer portion.

  The sheet P exiting the secondary transfer portion is separated from the surface of the belt 9 and introduced into the fixing device 21. The fixing device 21 melts and mixes toner images of a plurality of colors on the sheet P and fixes them as fixed images on the sheet surface.

  The surface of the belt 8 after separation of the sheet at the secondary transfer portion is cleaned by removing residual deposits such as secondary transfer residual toner by the belt cleaner 22 and repeatedly used for image formation.

  In the monochrome print mode, only the fourth image forming unit Bk that forms a black toner image is controlled in image forming operation.

  In the case of the single-sided printing mode, the sheet P that has exited the fixing device 21 is switched by the switching flapper 23 in accordance with a pre-designation, and is discharged to the face-up discharge tray 25 disposed on the side of the printer. Alternatively, the paper is discharged to a face-down paper discharge tray 28 disposed on the upper surface of the printer. In the case of paper discharge to the tray 25, the sheet P that has exited the fixing device 21 travels straight through the lower surface side of the flapper 23 that has been converted to the first posture, and the first paper discharge roller 24 causes the sheet P to move onto the tray 25. The image is discharged upward. In the case of paper discharge to the tray 28, the sheet P that has exited the fixing device 21 is guided upward through the upper surface side of the flapper 23 that has been changed to the second posture, and is transported upward by the transport path 26. Then, the second paper discharge roller 27 discharges the image onto the tray 28 downward.

  In the double-sided printing mode, the sheet P having undergone image formation and fixing on the first surface exiting the fixing device 21 is guided upward through the upper surface side of the flapper 23 that has been converted to the second posture. It is conveyed upward by the path 26. When the trailing edge reaches the reversal point R during the conveyance of the sheet P, the conveyance path 26 is switched to the reverse conveyance drive. As a result, the sheet P is switched back and enters the double-sided conveyance path 29. Then, it enters the conveyance path 16 again from the double-sided conveyance path 29 and is re-conveyed to the secondary transfer unit in a state where the front and back sides are reversed. As a result, the sheet P receives image transfer on the second surface. The sheet P that has exited the secondary transfer portion is introduced into the fixing device 21. The double-side printed sheet P exiting the fixing device 21 is routed by the switching flapper 23 according to a pre-designation and discharged to the tray 25 or 28 as in the single-sided printing mode. The portion constituted by the flapper 23, the switchback transport path 26, etc. is an example of the reversing means.

(Fixing device)
Next, the fixing device 21 will be described with reference to FIG. In addition to the fixing film 41 which is an endless belt for an image heating apparatus having a heating element that is flexible and rotatable and generates heat when energized, the fixing apparatus 21 includes a support stay 42, a pressure member 43, A pressure roller 44 and a thermistor 45 are provided. The support stay 42 is desirably made of a material that is not easily bent even when a high pressure is applied. In this embodiment, SUS304 is used.

  The pressurizing member 43 is preferably made of a material with little heat conduction to the support stay 42 from the viewpoint of energy saving, and for example, heat resistant glass or heat resistant resin such as polycarbonate is used. The pressure member 43 is pressed against the upper surface of the pressure roller 44 through the fixing film 41 with a predetermined pressing force, and a fixing nip N having a predetermined width is formed. The applied pressure in this embodiment is 156.8N at one end and the total applied pressure is 313.6N (32 kgf).

  The support stay 42 and the pressure member 43 are provided with a sheet-like heat insulating member 46 for preventing the heat of the fixing film 41 from being transferred. The heat insulating member 46 is made of a porous silicon sponge and has a thickness of 500 μm. Grease is applied to the inner surface of the fixing film 41 to reduce the frictional force between the heat insulating member 46 and the inner surface of the fixing film 41 and reduce the wear on the inner surface of the fixing film 41.

  The pressure roller 44 as an opposing member that forms a nip portion with the fixing film 41 has a multilayer structure in which a silicone rubber layer having a thickness of about 3 mm and a PFA resin tube having a thickness of about 40 μm are sequentially laminated on a stainless steel core. It is said that. Both end portions of the metal core of the pressure roller 44 are rotatably supported by bearings between side plates on the back side and the near side of the apparatus frame (not shown).

  The thermistor 45 is installed so as to elastically contact the inner surface of the fixing film 41, and has a function of detecting the temperature of the inner surface of the fixing film 41. Specifically, a thermistor is attached to the tip of a stainless steel arm (not shown), and the thermistor 45 is always fixed even when the movement of the fixing film 41 becomes unstable due to elastic swinging of the arm. The state in contact with the inner surface of the film 41 is maintained.

  The thermistor 45 is connected to a control circuit unit (CPU) as control means via an A / D converter (not shown). This control circuit section samples the output from the thermistor 45 at a predetermined cycle, and reflects the obtained temperature information in the energization control to the heating element of the fixing film 41. That is, the control circuit unit determines the energization control content to the heating element based on the output of the thermistor 45 and controls the energization supplied to the heating element of the fixing film 41. Note that the above control in the fixing device of the present embodiment is controlled so that the temperature detected by the thermistor 45 is constant at 160 ° C. in consideration of the temperature for fixing the toner image on the recording material.

  The pressure roller 44 is rotationally driven in the direction of the arrow at a predetermined peripheral speed. The fixing film 41 in pressure contact with the pressure roller 44 is driven by the pressure roller 44 and rotates at a predetermined speed. The pressure roller 44 is driven to rotate, and the cylindrical fixing film 41 is driven to rotate. Then, the heating element of the fixing film 41 is energized. Then, when the temperature of the fixing film 41 rises to the set temperature and is adjusted in temperature, the sheet P carrying an unfixed toner image is introduced into the fixing nip portion N.

  In the fixing nip portion N, a sheet (recording material) holding the image is nipped and conveyed to heat the image. As a result, the toner image carrying surface side of the sheet P is brought into close contact with the outer surface of the fixing film 41, and the sheet P moves together with the fixing film 41. At the same time, heat from the heating element of the fixing film 41 is applied to the sheet P. The toner image T is melted and fixed.

(Layer structure of fixing film and method for producing heat generation layer)
The fixing film 41 is a cylindrical and endless film member. As shown in FIG. 1A, the base layer 41a, the heat generating layer 41b, the elastic layer 41c, and the release layer 41d are sequentially formed from the inner surface side to the outer surface side. It has a four-layer composite structure. The base layer 41a can be made of a heat-resistant material having a thickness of 100 μm or less, preferably 20 μm or more and 50 μm or less in order to reduce the heat capacity and improve the quick start property. For example, resin films such as polyimide, polyimide amide, PEEK, PTFE, PFA, and FEP, and metal films such as SUS and nickel can be used. In this embodiment, a cylindrical polyimide film having a thickness of 30 μm and a diameter of 25 mm was used. In addition, when using the material which has electroconductivity as the base layer 41a, it is necessary to provide insulating layers, such as a polyimide, between the base layer 41a and the heat generating layer 41b. As the elastic layer 41c, a silicone rubber having a rubber hardness of 10 degrees (JIS-A), a thermal conductivity of 1.3 W / m · K, and a thickness of 300 μm was used.

  The release layer 41d was a PFA tube having a thickness of 20 μm. A PFA coat may be used as the release layer, and the PFA tube and the PFA coat can be used properly according to the required thickness, mechanical and electrical strength. The release layer 41d is bonded to the elastic layer 41c with an adhesive made of silicone resin.

  The heat generating layer 41b has a heat generating pattern by a series of resistance heat generating elements in which a conductor containing silver / palladium alloy is applied on the base layer 41a with a uniform thickness. The coating for specifically forming the heating pattern of the heating element composed of a series of single wires formed on the heating layer 41b is performed as follows, for example. That is, the cylindrical body shown in FIG. 1B is installed in the vertical direction (gravity direction) so that the cylindrical body can be displaced in the vertical direction while rotating at a constant moving speed, and applied to the side of the cylindrical body. A fixed nozzle as a device is opposed in a non-contact state or in contact. Then, a conductor containing silver / palladium alloy is discharged from the fixed nozzle, and a heat generation pattern having a constant thickness corresponding to the moving speed is formed on the base layer 41a of the fixing film. The thickness of this series of heat generation patterns is preferably 5 μm to 20 μm. Regarding the heat generating layer 41b, if the space adjacent to the heat generating pattern portion is in an empty state, the layer thickness unevenness of the heat generating layer 41b occurs. Therefore, the insulator is further coated so as to fill the space adjacent to the heat generating pattern portion. Is more preferable.

  Thus, the total resistance value in the heating region of the fixing film 41 on which the heat generating layer 41b is formed is 10.0Ω. Therefore, the power in the heating region of the fixing film 41 when 100 V is applied is 1000 W. The resistance value may be determined as appropriate depending on the amount of heat generated as a fixing device.

(Longitudinal size of fixing device such as effective heat generation area)
FIG. 1A is a view for explaining the longitudinal relationship of the fixing device 40. The length of the base layer 41a is 326 mm, the length of the elastic layer 41c and the release layer 41d is 316 mm, and the length of the silicone rubber layer of the pressure roller 44 is 312 mm. Are symmetrical. The heat generating layer 41b has a shape as shown in FIG. 1 (B) and FIG. FIG. 1B is a schematic view of the fixing film 41 used in this embodiment, and FIG. 4 is a development view thereof. In the schematic view and the developed view, the release layer 41d and the elastic layer 41c are omitted, and the pattern of the heat generating layer 41b is shown.

  The heat generating layer 41b is formed on the base layer 41a over the entire region of 326 mm in the longitudinal direction, and the heat generating pattern is formed by one line shape (a series of single lines), and the line-shaped energized portion is the fixing region of the fixing film. It is in a spiral shape that covers the entire surface layer. This heat generation pattern has a length of 750 mm. Further, at both ends of the heat generating layer 41b, the heat generating layer 41b and the power feeding layer 41e are in contact with each other at both left and right ends, thereby energizing the heat generating layer 41b. In this embodiment, the line width of the spiral heat generating layer is 5 mm, and the interval between adjacent lines is 0.5 mm.

  The heat generating layer 41b is divided into an effective heat generating region 41ba that is a region that requires image heating in the longitudinal direction and a region of the power feeding layer 41e that is a non-heated region. The region of the electrode part 41e in which the extent of heat generation is suppressed even if heat is generated is not included in the effective heat generation region.

  The effective heat generation area 41ba has a length (corresponding to W in FIG. 4) of 307 mm, which is 5 mm longer on one side than the maximum length 297 mm of the longitudinal sheet (recording material) in the image forming apparatus of this embodiment. This prevents a cold offset at the end of the sheet due to the temperature of the fixing film 41 at the portion facing the recording material end being lower than that at the center due to heat transfer from the effective heat generation area 41ba to the outside. Because.

(Feeding layer and feeding member)
In FIG. 1B, one end of a heating element composed of a series of single wires formed on the heating layer 41b is on one end side in the longitudinal direction of the fixing film 41 and rotates with the fixing film 41. It is electrically connected to 41e (left side). The other end of the heating element is electrically connected to the ring-shaped second power supply layer 41e (on the right side) which is on the other end side in the longitudinal direction of the fixing film 41 and rotates together with the fixing film 41.

  Here, the power supply member 51 fixed to the rotating power supply layer 41e provided at the left and right ends in the longitudinal direction comes into contact. The circumferential position of the pair of power supply members 51 is the position of the fixing nip portion in FIG. 1A, but the present invention is not limited to this and can be any circumferential position.

  The power supply layer 41e, which is a non-heated region for energizing the effective heat generation region 41ba from the power supply member 51, is a ring-shaped resistor in which a conductive material is uniformly applied on the base layer 41a with a thickness of about 30 μm. The total resistance value of the power feeding layer 41e is about 0.1Ω, which is about 1% of the effective heat generation area 41ba. Therefore, the amount of heat generated in the power supply layer 41e, which is a non-heated area with respect to the effective heat generation area 41ba, is about 1%, so that an excessive temperature rise does not occur in the power supply layer 41e, which is a non-heated area through which the sheet does not pass. Further, the release layer 41d of the fixing film 41 does not peel off.

  In the power supply member 51, since the conductive carbon power supply member 51a is pressed against the fixing film 41 by the conductive leaf spring 51b, the heat generation layer 41b and the power supply member 51 are kept electrically connected even while the fixing device is driven. The heating element 41b is electrically and stably connected to the power source.

(Configuration and operation of comparative example)
As a comparative example for the fixing device of this embodiment, a fixing film 91 as shown in FIGS. 9 and 10 was used. As shown in FIG. 9, the layer structure of the fixing film 91 is similar to the fixing film 41 used in this embodiment, in order from the inner surface side to the outer surface side, a base layer 91a, a heat generating layer 91b, an elastic layer 91c, a release layer. The layer 91d has a four-layer composite structure.

  Further, as shown in FIG. 10, the heat generating layer is provided over the entire fixing region of the fixing film 91. FIG. 10 is a schematic view in which the elastic layer 91c and the release layer 91d of the fixing film 91 are omitted. The heat generating layer 91b has a thickness of about 30 μm. Further, at both ends of the heat generation layer 91b, the heat generation layer 91b and the power supply layer 41e are in contact, and electricity is supplied from the power supply member 51 to the heat generation layer 91b via the power supply layer 41e.

  FIG. 11 is a schematic view showing a fixing device 90 (hereinafter referred to as Comparative Example 1) using the fixing film 91. In Comparative Example 1, a rubber blade attached at a position 1 mm away from the inner surface of the fixing film 91, a detection flag 92 that detects elastic wave vibration due to minute vibration of the rubber blade, and the film is broken based on the detection information. A breakage detecting means 93 for determining is provided. And it has the control means 94 which controls the electric power feeding from an electric power feeding part based on the detection information of the fracture | rupture detection means 93. FIG. The rubber blade of the detection flag 92 is configured to detect breakage over the entire length, and is installed at a position separated from the fixing film 91. This is because if the film is always in contact with the fixing film 91, the heat capacity increases due to the deterioration of the durability caused by scraping of the inner surface of the film or the number of members that contact the fixing film, and the rise time to the target temperature increases. It is because it ends up. The power supply mechanism of Comparative Example 1 is as shown in FIG. 1A and is the same power supply mechanism as that of the present embodiment.

  The operation of the image forming apparatus using the fixing device 90 of Comparative Example 1 will be described. FIG. 12 is a flowchart showing the operation of the fixing device 90. First, when the printing operation is started, the fixing film 91 is rotated by receiving the drive from the pressure roller 44 (1), and an AC voltage of 100 V is applied to the heater, that is, the heat generating layer 91b of the fixing film 91 (2) to fix. The temperature of the film 91 rises and the fixing process starts. Then, the vibration state of the fixing film is detected by the detection flag 92 (3), and the film is judged to be broken (4). When the fixing film 91 is ruptured, the crack portion formed by the rupture comes into contact with the rubber blade of the detection flag 92 to generate elastic wave vibration. Therefore, the rupture detection means 93 determines the film rupture from the vibration information. To do.

  When it is determined by the detection flag 92 that the film is broken, the CPU 96 stops the energization to the energization control means 94 (5a), and the fixing film driving means (not shown) is stopped (6). The operation ends (7).

  If it is determined by the detection flag 92 that the film is not broken, printing is continued (5b), and the operation ends (7).

  FIG. 13 is a graph showing the detected temperature transition of the thermistor 45 when the film is broken in Comparative Example 1. In Comparative Example 1, there is a great influence on the direction of breakage that occurs. For example, in the case of breakage occurring in the longitudinal direction, the breakage portion makes contact with the rubber blade as a surface, and elastic wave vibration increases, so breakage detection is easy. Therefore, energization is stopped immediately after the film breakage is detected, and the temperature of the fixing film is lowered.

  On the other hand, in the break that occurs perpendicularly to the longitudinal direction, the breakage portion comes into contact with the rubber blade as a point, and the elastic wave vibration becomes small, so that detection becomes difficult. In these cases, the rupture cannot be detected unless the film rupture has progressed to some extent after the film rupture has occurred. For this reason, when a break occurs perpendicular to the longitudinal direction, the fixing film is energized and heated until the break proceeds and can be detected, and the temperature of the film rises. Further, even when a break occurs in the longitudinal direction, the resistance of the heat generating layer 91b changes due to the break, and thus a partial abnormal temperature occurs.

(Operation of this embodiment apparatus)
Next, the operation of the image forming apparatus using the fixing device 21 of the present embodiment will be described. FIG. 5 is a flowchart showing the operation of the fixing device 21 in this embodiment. FIG. 5 is a flowchart showing the operation of the fixing device 21. First, when the printing operation is started, the fixing film 41 is rotated by receiving a drive from the pressure roller (1), an AC voltage of 100 V is applied to the heater (2), and the temperature of the fixing film rises to fix processing. Starts. Then, the presence or absence of breakage of the fixing film is detected from the heater energization information (3). When the fixing film 41 is broken, the driving of the fixing film is stopped (4a), and the operation is finished (5). That is, when the detection means 95 (FIG. 3) for detecting current information flowing through the heating element of the fixing film 41 detects that a current signal cannot be obtained, the CPU 96 stops driving the apparatus for image heating. When the fixing film 41 is not broken, the printing is continued (4b) and the operation is finished (5).

  As a result, energization of the heating element consisting of a single wire is cut off when the film breaks, so that the heater can be quickly de-energized, and the film break can be detected based on the energization information. Can do. At that time, “fixing film is broken” is displayed on an operation display panel (not shown) to notify the user of the film breakage.

  FIG. 6 is a graph showing the detected temperature transition of the thermistor 45 when the film is broken in this embodiment. In the present embodiment, the outer surface of the fixing film 41 is comprehensively covered with the spiral heat generation pattern, so that it is possible to deal with any case where the fixing film 41 is broken in the longitudinal direction or the longitudinal vertical direction. In Comparative Example 1, since the heater was stopped after the film break was detected, the temperature increased even after the film was broken. However, in this embodiment, since the heat generation pattern is composed of one line, the energization to the heater, that is, the heat generation layer 41b can be stopped immediately after the film breaks, and the film temperature is lowered. .

  Thus, by using this embodiment, the film breakage can be easily detected with the conventional mechanism, and the heater temperature control is cut off simultaneously with the breakage, so that an excessive temperature rise can be prevented immediately. In addition, the wiring of the heater layer that covers the entire film comprehensively makes it possible to cope with both longitudinal and lateral breaks of the film.

<< Second Embodiment >>
Next, a second embodiment of the fixing device according to the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

In this embodiment, a fixing film 41 as shown in FIG. 7 is used. In this development view, the release layer 41d and the elastic layer 41c are omitted, and the pattern of the heat generating layer 41b is shown. The fixing film 41 is a cylindrical endless film member. As shown in FIG. 1 (A), the base layer 41a, the heat generating layer 41b, the elastic layer 41c, and the release layer 41d are sequentially formed from the inner surface side to the outer surface side. It has a four-layer composite structure.
The fixing film 41 in the present embodiment is configured in one line shape such that the heat generation pattern of the heat generating layer 41b is longer than the length in the longitudinal direction, and the line-shaped energized portion is the fixing region of the fixing film. It has a lightning pattern that covers the entire surface. The heat generating layer 41b and the power feeding layer 41e are in contact with each other on the left and right sides so that power is fed. In the present embodiment, the line width of the lightning pattern heating layer is 5 mm, and the interval between adjacent lines is 0.5 mm. By using this configuration and performing the same control as in the first embodiment, it is possible to obtain the same effect as in the first embodiment.

<< Third Embodiment >>
Next, a third embodiment of the fixing device according to the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted. In this embodiment, a fixing film 41 as shown in FIG. 8 is used. FIG. 3 is a development view of a fixing film 41 used in the present embodiment. In this development view, the release layer 41d and the elastic layer 41c are omitted, and the pattern of the heat generating layer 41b is shown. The fixing film 41 is a cylindrical endless film member. As shown in FIG. 1 (A), the base layer 41a, the heat generating layer 41b, the elastic layer 41c, and the release layer 41d are sequentially formed from the inner surface side to the outer surface side. It has a four-layer composite structure.

  The fixing film 41 in the present embodiment is configured in one line shape such that the heat generation pattern of the heat generating layer 41b is longer than the length in the longitudinal direction, and the line-shaped energized portion is the fixing region of the fixing film. The zigzag shape covers the entire surface. Further, the heat generation layer 41b and the power supply layer 41e are configured to contact each other on the left and right sides to supply power. In this embodiment, the line width of the zigzag heat generating layer is 5 mm, and the interval between adjacent lines is 0.5 mm. By using this configuration and performing the same control as in the first to second embodiments, it is possible to obtain the same effect as in the first embodiment.

(Modification)
In the above-described embodiment, the apparatus for image heating is stopped when the current signal cannot be obtained by the detection unit that detects the current information flowing through the heating element, but the image forming unit that performs image formation before image heating It can also be applied to an image heating apparatus comprising That is, the driving of the image forming unit may be stopped when a current signal cannot be obtained by a detection unit that detects current information flowing through the heating element.

  Further, in the above-described embodiment, the power supply layer 41e to which the end portions of the heating elements having a pattern shape that is a series of single wires and distributed over the entire effective heat generation area of the fixing film 41 is electrically connected. Although the fixing film 41 itself is provided, the present invention is not limited to this. That is, the power feeding layer may be provided separately from the fixing film 41, and the power feeding layer may be configured as a ring-shaped separate member that rotates in conjunction with the fixing film 41.

  As a backup member in the nip portion, a fixed pressure pad or a fixed pressure sheet having a smaller heat capacity may be used instead of the pressure roller 44. In this case, heat absorbed by the backup member side is used. The heat efficiency can be improved.

41a ... Fixing film base layer, 41b ... Fusing film heat generating layer, 41c ... Fusing film elastic layer, 41d ... Fixing film release layer, 41e ... Fusing film feeding layer, 44 ... Pressure Roller 51 ・ ・ Power supply member

Claims (8)

An endless belt having a heating element that is flexible and rotatable and generates heat when energized;
An opposing member forming the belt and a nip portion,
An image heating apparatus that heats an image by nipping and conveying a recording material that has an image at the nip portion,
The image heating apparatus according to claim 1, wherein the heating element is a series of single wires and has a pattern shape distributed over the entire effective heating area of the belt.   One end of the heating element is on one end side in the longitudinal direction of the belt and is connected to a ring-shaped first feeding layer that rotates together with the belt, and the other end of the heating element is the other end side in the longitudinal direction of the belt. The image heating apparatus according to claim 1, wherein the image heating apparatus is connected to a ring-shaped second power feeding layer that rotates together with the belt.   The image heating apparatus according to claim 1, wherein a pattern shape of the heating element is a spiral shape.   The image heating apparatus according to claim 1, wherein a pattern shape of the heating element is a lightning pattern.   The image heating apparatus according to claim 1, wherein a pattern shape of the heating element is a zigzag shape. Detecting means for detecting current information flowing in the heating element;
6. An image heating apparatus according to claim 1, further comprising a drive stop unit that stops driving of the apparatus for image heating when a current signal is not obtained by the detection unit. . An image forming unit that forms an image before image heating is provided.
Detecting means for detecting current information flowing in the heating element;
The image heating apparatus according to claim 1, further comprising: a drive stop unit that stops driving the image forming unit when a current signal is not obtained by the detection unit. An endless belt having a heating element that is flexible and rotatable and generates heat when energized;
An opposing member forming the belt and a nip portion,
An endless belt for an image heating device used in an image heating device that heats an image by nipping and conveying a recording material that has an image at the nip portion,
An endless belt for an image heating apparatus, wherein the heating element is a series of single wires and has a pattern shape distributed over the entire effective heating area of the belt.