JP5020775B2 - Image heating apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system and an electrostatic recording system, and an image heating apparatus applied to the image forming apparatus.

  Conventionally, many image forming apparatuses such as electrophotographic copying machines and printers are heat-fixing apparatuses as image heating apparatuses, such as contact-heating type heat roller fixing apparatuses with good thermal efficiency and safety, and energy-saving types. The film heating system is used.

  A heat roller fixing type heat fixing device is basically composed of a heating roller (fixing roller) as a heating rotator and an elastic roller as a pressure rotator pressed against the heating roller, and is not fixed as follows. The image is fixed by heat and pressure as a permanent image on a recording material as a material to be heated.

  That is, as a heated material in which a pair of rollers (heating roller, elastic roller) is rotated to form and carry an unfixed image (hereinafter, referred to as a toner image) in a fixing nip portion that is a pressure nip portion of the two roller pairs. The recording material is introduced, and is nipped and conveyed at the fixing nip portion. As the recording material passes through the fixing nip portion in this manner, the toner image is fixed to the recording material as a permanent image by heat and pressure by the heat from the heating roller and the pressure applied to the fixing nip portion. Here, examples of the recording material include a transfer material (transfer material sheet), electrostatic recording paper, electrofax paper, and printing paper.

  A film heating type heat fixing device has been proposed in, for example, Patent Documents 1 to 4 and the like.

  In the film heating method, a heat-resistant film (flexible sleeve) as a heating rotator is brought into close contact with a heating element such as a ceramic heater fixedly arranged by a pressing rotator (elastic pressure roller) and slid. Transport. Then, a recording material carrying an image of a toner image is introduced into a fixing nip portion, which is a pressure nip portion formed by a heating body and a pressure rotating body, with the film interposed therebetween, and is conveyed along with the film. As a result, the toner image is fixed on the recording material as a permanent image by the heat from the heating body applied through the film and the pressing force of the fixing nip portion.

  With reference to FIG. 7, a schematic configuration of a film heating type heat fixing apparatus will be described.

  The film heating and fixing apparatus includes a heating member (heating body, hereinafter referred to as a heater) 211 and a pressure rotating body (hereinafter referred to as a pressure roller) 220. Here, the heater 211 is fixedly supported by a stay holder (support body) 212. The pressure roller 220 is pressed against the heater 211 so that a nip portion (fixing nip portion) N having a predetermined nip width is formed with a heat-resistant thin film (hereinafter referred to as a fixing film) 213 interposed therebetween. Is provided.

  The heater 211 is heated and adjusted to a predetermined temperature by energization. The fixing film 213 is conveyed and moved in the direction of the arrow a shown in FIG. 7 while being in close contact with and sliding on the surface of the heater 211 at the fixing nip N by the driving force (not shown) or the rotational force of the pressure roller 220. It is. The fixing film 213 is provided in a cylindrical shape, an endless belt shape, or a roll-ended end web shape.

Since the fixing film 213 rotates while rubbing against the internal heating heater 211 and the stay holder 212, a small amount of lubricant such as heat resistant grease is interposed on the surfaces of the heater 211 and the stay holder 212. As a result, the fixing film 213 can rotate smoothly.

  In a state where the heater 211 is heated and adjusted to a predetermined temperature and the fixing film 213 is conveyed and moved in the direction of the arrow, an unfixed toner image t is fixed between the fixing film 213 and the pressure roller 220 in the fixing nip N. The recording material P on which is formed and supported is introduced. Then, the recording material P is brought into close contact with the surface of the fixing film 213 and is nipped and conveyed together with the fixing film 213 at the fixing nip portion N.

  In the fixing nip portion N, the recording material P / toner image t is heated by the heater 211 via the fixing film 213, and the toner image t on the recording material P is heated and fixed. The recording material portion that has passed through the fixing nip N is peeled off from the surface of the fixing film 213 and conveyed.

A ceramic heater is generally used as the heater 211 as a heating member. This is because the energization heating resistor layer 2112 is formed on the surface of the ceramic substrate 2111 (the surface facing the fixing film 213) along the longitudinal direction of the substrate by screen printing or the like. The protective layer 2113 is covered. Here, the longitudinal direction of the substrate is the axial direction of the pressure roller 220 and is perpendicular to the drawing (cross section) of FIG. The ceramic substrate 2111 is a substrate of electrical insulation, good thermal conductivity, and low heat capacity such as alumina. The energization heating resistance layer 2112 is made of silver palladium (Ag / Pb) .Ta ₂ N or the like.

  In the heater 211, when the energization heat generating resistance layer 2112 is energized, the energization heat generation resistance layer 2112 generates heat, and the entire heater rapidly rises in temperature. The temperature rise of the heater 211 is detected by the temperature detecting means 214 disposed on the back surface of the heater, and fed back to an energization control unit (not shown). The energization control unit controls energization to the energization heating resistor layer 2112 so that the heater temperature detected by the temperature detection unit 214 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 211 is heated and adjusted to a predetermined fixing temperature.

  The fixing film 213 has a thickness as thin as 20 to 70 μm in order to efficiently apply the heat of the heater 211 to the recording material P as the material to be heated in the fixing nip portion N. The fixing film 213 has a three-layer structure of a film base layer, a primer layer, and a releasable layer. The film base layer side is a heater side, and the releasable layer side is a pressure roller side. The film base layer is made of polyimide, polyamideimide, PEEK, or the like, which has higher insulation than the glass protective layer 2113 of the heater 211, and has heat resistance and high elasticity. Further, the film base layer maintains the mechanical strength such as the tear strength of the entire fixing film 213. The primer layer is formed as a thin layer having a thickness of about 2 to 6 μm. The releasable layer is a toner offset prevention layer for the fixing film 213, and is formed by coating a fluororesin such as PFA, PTFE, FEP or the like having good releasability to a thickness of about 10 μm.

  The pressure roller 220 foams heat-resistant rubber or heat-resistant rubber on the cored bar 221 to form an elastic layer 222, and is coated or coated with a fluororesin having a good releasability on the adhesive layer 223. It is formed and configured as a coated release layer 224. Here, the cored bar 221 is made of Al, Fe, or the like. The heat-resistant rubber that forms the elastic layer 222 is made of insulating silicone rubber, fluorine rubber, or the like. The fluororesin that forms the release layer 224 is made of PFA, PTFE, FEP, or the like.

  The stay holder 212 is formed of a heat-resistant plastic member, for example, and holds the heater 211 and also serves as a conveyance guide for the fixing film 213.

In the film heating type heating apparatus using such a thin fixing film 213, the pressure roller 220 having the elastic layer 222 is in pressure contact with the heater 211, so that the heater 211 has high rigidity. It becomes flat according to the flat lower surface of 211. As a result, a fixing nip portion N having a predetermined width is formed. With this configuration, heat fixing that can be quick started by heating only the fixing nip portion N is realized.
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980

  Along with the recent increase in the speed of image forming apparatuses, a metal thin film having high thermal conductivity has been adopted as a fixing film of the film heating type heat fixing apparatus shown in the above conventional example. In particular, a thin metal film produced by a spinning method, which is a rotational plastic working method disclosed in Japanese Patent Application Laid-Open No. 2003-275834, is excellent in thermal conductivity and durability (strength) and is widely adopted.

  However, the metal film manufactured by the above spinning method has a spiral groove M as shown in FIG. 8 formed on the inner surface of the film during the spinning process. There is a concern that such problems will occur.

  When the metal film having spiral grooves as shown in FIG. 8 is rotated and slid, the metal film moves in a certain direction along the spiral grooves, that is, has a property of approaching the certain direction. Due to this approaching property, the metal film abuts and is regulated by a film position regulating member (hereinafter referred to as a flange) such as a flange provided at both ends in the heat fixing device.

  The distance between the flanges at both ends is set slightly larger than the metal film length in consideration of the length of the metal film and the tolerance of various parts. Therefore, on the side where the metal film approaches, the end of the metal film and the flange are in close contact with no gap, and on the opposite side, there is a gap between the end of the metal film and the flange. For this reason, there is almost no seepage of grease on the side closer to the metal film, and the seepage of grease tends to occur from the gap on the side opposite to the side closer to the metal film.

  Further, the spiral groove on the inner surface of the metal film has a function of conveying a lubricant such as grease by the rotational movement of the metal film, and moves the grease in a direction opposite to the direction in which the metal film in the longitudinal direction approaches. Therefore, the grease is more likely to ooze out at the end portion on the opposite side of the metal sleeve.

  For these reasons, grease tends to ooze out more easily than a configuration using a conventional PI film or the like.

  This exudation of grease affects the output image quality. That is, in the heating and fixing apparatus of the film heating method shown in the conventional example, the fixing film is grounded or biased from the end in the longitudinal direction via conduction means such as a conductive elastic ring (rubber ring). The polarity opposite to that of the toner is prevented and the offset image is prevented. Therefore, when grease adheres to the conductive elastic ring, there is a concern that the electrical connection with the metal film becomes unstable and image defects such as an offset image occur.

In order to prevent the offset caused by the adhesion of grease to the conductive elastic ring, it is also possible to adopt a conductive brush that is not easily affected by the adhesion of grease instead of the conductive elastic ring as a conduction means to the fixing film. It is done. However, in this case, there is a concern that the cost will increase significantly.

  Further, a method of bringing a cleaning member such as a cleaning pad into contact with the conductive elastic ring is conceivable, but there is a concern that the apparatus may be increased in size or cost.

  When using a flexible sleeve manufactured by a spinning method, the present invention prevents offset due to the deviation of the flexible sleeve due to the spiral shape of the inner surface and the grease seepage due to the conveying action of the grease, The object is to obtain a good image.

In order to achieve the above object, the present invention provides:
A flexible sleeve that slides on the heater, which is manufactured by a spinning process, and has a metal flexible sleeve having a spiral groove on a surface that slides on the heater, and a pressure roller. In the image heating apparatus for heating the developer image on the recording material by passing the recording material on which the developer image is formed through a nip portion formed therebetween,
A conductive elastic member provided so as to be in contact with the flexible sleeve, and a conductive means for preventing the flexible sleeve from being opposite in polarity to the developer image formed on the recording material,
The conductive elastic member is characterized in that, among the end portions in the axial direction of the pressure roller, the flexible sleeve is provided at an end portion on a side closer to the axial direction.

  According to the present invention, when a flexible sleeve manufactured by a spinning method is used, the offset due to the deviation of the flexible sleeve due to the spiral shape of the inner surface and the seepage of grease due to the grease conveying action is prevented. As a result, a good image can be obtained.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

(1) Image Forming Apparatus FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier, and a photosensitive material such as OPC, amorphous Se, or amorphous Si is formed on a cylindrical substrate such as aluminum or nickel.

  The photosensitive drum 1 is rotationally driven in the direction of arrow R shown in FIG. 1, and first, the surface thereof is uniformly charged by a charging roller 2 as a charging device. Next, scanning exposure is performed with a laser beam E that is ON / OFF controlled according to image information, and an electrostatic latent image is formed. This electrostatic latent image is developed and visualized by the developing device 4. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and image exposure and reversal development are often used in combination.

The visualized toner image (developer image) is transferred from the photosensitive drum 1 onto the recording material P conveyed at a predetermined timing by a transfer roller 5 as a transfer device. At this time, the recording material P is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5 with a constant pressure. The recording material P to which the unfixed toner image is transferred is conveyed to a heat fixing device 6 as an image heating device, and is fixed as a permanent image by passing through the heat fixing device 6. On the other hand, the residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

  By repeating the above operation, image formation can be performed one after another. The image forming apparatus according to the present exemplary embodiment can perform printing at a printing speed of 600 dpi, 22 sheets / minute (LTR vertical feed: process speed of about 150 mm / sec).

(2) Heat Fixing Device FIG. 2 is a diagram showing a schematic configuration of the heat fixing device 6 of the present embodiment, where (a) is a sectional view and (b) is a front view. FIG. 3 is a schematic view showing the main part of the heat fixing device 6 of this embodiment, (a) is a cross-sectional view showing the layer structure of the fixing film 13, and (b) is a method for grounding the fixing film 13. FIG.

  As shown in FIG. 2, the heat fixing device 6 includes a fixing member 10 as a heating unit and a pressure roller (a pressure rotating body, a pressure member) 20. The fixing member 10 includes a heater 11 as a heater (heating body, heating element), a fixing film 13 as a flexible sleeve that slides on the heater 11, and a heat insulating stay holder 12. .

  The fixing film 13 of the present embodiment is manufactured by a spinning method, and has a spiral (spiral) groove M as shown in FIG. 8 on the inner surface (the surface that slides on the heater 11). It is a metal sleeve (film). As shown in FIG. 3A, the fixing film 13 has a release layer 133 such as PFA, PTFE, and FEP directly on the surface of a thin metal element tube (SUS element tube) 131 such as SUS or via a primer layer. Is a composite layer film coated or tube-coated. Here, the metal element tube 131 is a conductive layer provided in the lower layer of the release layer 133 having an exposed portion that is partially exposed on the surface of the fixing film 13. The release layer 133 is a resin layer provided as the outermost layer in contact with the pressure roller 20. SUS is stainless steel, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, PTFE is polytetrafluoroethylene, and FEP is a tetrafluoroethylene hexafluoropropylene copolymer.

  When the release layer 133 is directly formed on the surface of the metal element tube 131, the surface may be subjected to a surface treatment such as a blast treatment. The fixing film 13 preferably has a thickness of 100 μm or less in order to enable a quick start, and has a sufficient strength to constitute a long-life heat fixing device 6 and has a durability of 20 μm or more. Is required.

  Therefore, the thickness of the fixing film 13 is optimally 20 μm or more and 100 μm or less. In this embodiment, a fixing film 13 is used in which a SUS blank having an outer diameter of 18 mm and a thickness of 27 μm is coated with a 15 μm thick PFA tube by heat welding. The fixing film 13 is slidable (slidable) with respect to the heater 11.

  The fixing film 13 is grounded via a diode 101 as a rectifying element (self-bias element) in order to prevent image defects such as offset. In this embodiment, the following method is applied as the grounding method. As shown in FIGS. 2B and 3B, the conductive elastic member provided at the end of the pressure roller 20 with the metal base tube 131 exposed on the surface of the end of the fixing film 13. It is made to contact with the conductive elastic ring 31 as.

Here, the conductive elastic ring 31 is, as a feature of the present embodiment, the end of the pressure roller 20 in the axial direction at the end on the offset side where the fixing film 13 is offset in the axial direction of the pressure roller 20. Has been placed. When the fixing film 13 rotates and slides, the fixing film 13 moves along the spiral groove M in the arrow Y direction (a constant direction) shown in FIG. A conductive elastic ring 31 is provided on the side closer to the end of the pressure roller 20 in the axial direction.

  The conductive elastic ring 31 is grounded via the diode 101 and the safety resistor 102. In this way, the fixing film 13 is prevented from having a reverse polarity to the toner on the recording material P, and an offset image is prevented. Here, the conductive elastic ring 31, the diode 101, and the safety resistor 102 constitute a conduction means. The fixing film 13 may be grounded without passing through the diode 101. Further, by providing a bias applying means and applying a bias to the fixing film 13, it is possible to prevent the fixing film 13 from having a reverse polarity to the toner on the recording material P, thereby preventing an offset image.

The heater 11 is a heater provided inside the fixing film 13, and an energization heating resistance layer 112 made of silver palladium or the like is formed on an Al ₂ O ₃ or AlN substrate 111 having high thermal conductivity, and further from above. The thin glass protective layer 113 is covered. The surface or back surface of the heater 11 on which the energization heating resistor layer 112 is formed is brought into contact with the fixing film 13 to heat the nip portion where the toner image on the recording material P is melted and fixed.

  The heat insulating stay holder 12 is a holder for holding the heater 11 and preventing heat radiation in the direction opposite to the nip portion, and is formed of liquid crystal polymer, phenol resin, PPS, PEEK, or the like. A fixing film 13 is loosely fitted on the heat insulating stay holder 12 with a margin, and the fixing film 13 is rotatably arranged in the direction of the arrow shown in FIG.

  Further, since the fixing film 13 rotates while rubbing against the internal heater 11 and the heat insulating stay holder 12, the frictional resistance between the heater 11 and the heat insulating stay holder 12 and the fixing film 13 needs to be kept small. . For this reason, a small amount of lubricant such as heat resistant grease is interposed on the surfaces of the heater 11 and the heat insulating stay holder 12. Thereby, the fixing film 13 can be smoothly rotated.

  The pressure roller 20 foams heat-resistant rubber or heat-resistant rubber on a core metal 21 to form an elastic layer 22, and is coated with RTV silicone rubber that is primed as an adhesive layer 23 and has adhesiveness. Further, a release layer 24 is formed. Here, the core metal 21 is made of Al, Fe, or the like. The heat-resistant rubber that forms the elastic layer 22 is made of insulating silicone rubber, fluorine rubber, or the like. Further, the release layer 24 constitutes a conductive layer provided as the outermost layer in the pressure roller 20, and covers or covers a tube in which a conductive agent such as carbon is dispersed in a fluororesin such as PFA, PTFE, or FEP. Constructed by coating. In the following description, the longitudinal direction refers to the axial direction of the pressure roller 20.

The release layer 24 preferably has a resistance value of 10 ⁹ Ω / □ or less in order to prevent charge-up due to rubbing against the fixing film 13 or the recording material P. On the other hand, the release layer 24 preferably has a resistance value of 10 ⁶ Ω / □ or more in order to prevent offset due to a decrease in toner retention of the recording material due to leakage of transfer charge.

  In the present embodiment, a pressure roller having a roller outer diameter of 18 mm and a roller hardness of 40 ° (Asker-C 600 g load) is used.

The pressure roller 20 is sufficiently pressed (pressed) in the direction of the fixing member 10 by pressure means (not shown) so as to form nip portions necessary for heat fixing from both ends in the longitudinal direction. Then, the pressure roller 20 is rotationally driven in the direction of the arrow shown in FIG. 2A by rotational driving (not shown) from the end in the longitudinal direction through the cored bar 21. Thereby, the fixing film 13 is driven to rotate in the direction of the arrow shown in FIG. Note that a driving roller (not shown) may be provided inside the fixing film 13 and the driving roller may be rotationally driven to rotate the fixing film 13 and the pressure roller 20 to be driven.

  In this way, the recording material P on which an unfixed toner image is formed (carrying) is nipped and conveyed by the nip portion formed between the fixing member 10 (fixing film 13) and the pressure roller 20. Is heated by. As a result, the toner image on the recording material is fixed to the recording material P as a permanent image.

  Next, a specific experimental example will be described.

  FIG. 4 is a schematic configuration diagram showing a comparative example of the heat fixing device, and shows a case where a conductive elastic ring 31 is provided on the opposite side of the pressure roller 20 in the axial direction with respect to the present embodiment.

Table 1 shows a case where the conductive elastic ring 31 is provided on the side closer to the fixing film 13 as in this embodiment, and the case where the conductive elastic ring 31 is provided on the opposite side as shown in FIG. The result of the level comparison is shown. The offset was confirmed using a low-temperature, low-humidity environment and high-resistance paper (Xx (manufactured by Xerox) 4200 left paper).

  From Table 1, it can be seen that when the conductive elastic ring 31 is provided on the side opposite to the side on which the fixing film 13 is approached, up to 5,000 sheets have less grease oozing and no offset image is observed. However, it has been found that the amount of the grease oozing from the vicinity of 10,000 sheets passes, the grease starts to adhere to the conductive elastic ring 31, and an offset image starts to be generated.

  On the other hand, in the configuration of this example, even when 750,000 sheets were passed, the conductive elastic ring 31 was not soiled due to the grease oozing out, and a good image without an offset image was obtained. In the present embodiment, the structure of the insulating PFA tube is used for the surface layer of the metal sleeve and the conductive PFA tube is used for the surface layer of the pressure roller. However, the surface layer of the metal sleeve is conductive and the surface layer of the pressure roller is insulating. The same effect can be obtained.

  As described above, in this embodiment, in the configuration in which a metal film manufactured by spinning processing is used as the fixing film 13, the conductive elastic ring 31 is provided on the side where the film is offset by the spiral groove on the inner surface. With such a configuration, the sliding grease on the inner surface of the fixing film oozes out, adheres to the conductive elastic ring 31, and an offset image generated by causing an electrical contact failure with the fixing film can be prevented. As described above, according to this embodiment, it is possible to prevent an offset image due to the adhesion of grease or the like of the conductive elastic ring 31 and to obtain a good output image.

  In Example 2 of the present invention, a configuration in which a silicone rubber foam is used as the conductive elastic ring 31 as shown in FIG. 5 will be described.

  FIG. 5 is a schematic configuration diagram for explaining the conductive elastic ring 31 of the present embodiment. FIG. 5A shows a plan view and a side view, and FIG. The enlarged view of the surface of the elastic elastic ring 31 (foam) is shown. The process speed of the image forming apparatus of this embodiment was 180 mm / s, 30 sheets / minute (LTR longitudinal feed), and the main body life was 150,000 sheets. In the present embodiment, constituent parts different from those in the first embodiment will be described, and description of constituent parts similar to those in the first embodiment will be omitted.

  In the configuration of the first embodiment, if the life of the image forming apparatus is about 70,000 sheets, a sufficient offset prevention effect can be obtained over the life of the apparatus. However, if the apparatus life exceeds 100,000 sheets, the conductive elastic ring 31 is used. There is a concern that paper dust or toner adheres to the surface. When paper dust or toner adheres to the conductive elastic ring 31, there is a concern that a connection failure with the fixing film 13 occurs and an offset image is generated.

  Therefore, as in this embodiment, by using a conductive silicone rubber foam as the conductive elastic ring 31, paper powder, toner, and the like can be absorbed into the foamed cell, so that the electrical connection with the fixing film 13 is achieved. Can be held for a long time. Therefore, although the cost of the conductive elastic ring 31 is slightly increased, the generation of the offset image can be prevented for a longer period than in the case of the first embodiment.

Table 2 shows the result of comparison of the offset image level due to durability in the configuration of the present embodiment and the configuration of the first embodiment. The offset was confirmed using a low-temperature, low-humidity environment and high-resistance paper (Xx (manufactured by Xerox) 4200 paper) as in the previous example.

  From Table 2, when conductive silicone rubber is used as the conductive elastic ring 31 as in Example 1, the following can be seen. That is, in the first embodiment, no offset image is generated up to 75,000 sheets, but dirt such as paper dust starts to adhere to the conductive elastic ring 31 from the vicinity of 100,000 sheets to pass through the fixing film. It can be seen that the contact becomes unstable and offset begins to occur.

  On the other hand, in the configuration of this embodiment, even when 150,000 sheets are passed, no dirt such as paper dust or toner adheres to the conductive elastic ring 31 and the contact with the fixing film 13 is maintained. No offset image was found. In this embodiment, an example in which a conductive silicone rubber foam is used as the conductive elastic ring 31 has been described, but the same effect can be obtained even when a conductive fluororubber foam is used.

  As described above, by using a conductive silicone rubber or fluororubber foam as the conductive elastic ring 31, not only the adhesion of grease to the conductive elastic ring 31 but also the adhesion of paper powder, toner, etc. is reduced. be able to. Accordingly, it is possible to prevent the occurrence of an offset image due to a defective electrical contact with the fixing film 13 over a long period of time.

  FIG. 6 is a schematic configuration diagram for explaining the conductive elastic ring 31 according to the third embodiment of the present invention.

  In this embodiment, a configuration in which a conductive elastic ring 31 in which a conductive PFA tube 32 is coated on a conductive silicone rubber (surface layer) as shown in FIG. 6 will be described. The process speed of the image forming apparatus of this embodiment was 200 mm / s, 35 sheets / minute (LTR longitudinal feed), and the main body life was 2 million sheets. In the present embodiment, constituent parts different from those in the first and second embodiments will be described, and the description of the same constituent parts as those in the above embodiment will be omitted.

  As in this example, the surface layer of the conductive elastic ring 31 is coated with a fluororesin such as a conductive PFA tube, so that the releasability is improved, and the fixing film 13 The durability of the contact portion can be ensured.

Table 3 shows the result of comparing the offset image level due to durability in the configuration of the present embodiment and the configuration of the second embodiment. The offset was confirmed using a low-temperature, low-humidity environment and high-resistance paper (Xx4200 untreated paper) as in the previous example.

  From Table 3, when a conductive silicone rubber foam is used as the conductive elastic ring 31 as in Example 2, the following can be seen. That is, in the second embodiment, offset images are not generated up to 150,000 sheets, but dirt such as paper dust and toner starts to adhere to the conductive elastic ring 31 from around 200,000 sheets. It can be seen that the contact becomes unstable and offset begins to occur.

  On the other hand, in the configuration of this embodiment, even when 250,000 sheets are passed, no dirt such as paper dust or toner adheres to the conductive elastic ring 31 and the contact with the fixing film 13 is maintained. Generation of offset images was not observed. In this embodiment, the conductive elastic ring 31 is covered with a conductive PFA tube. However, the same applies to a configuration in which a conductive PTFE or FEP tube is coated or a conductive fluororesin is coated. The effect of was obtained.

As described above, by covering or coating the surface layer of the conductive elastic ring 31 with the conductive fluororesin tube, not only the adhesion of grease to the conductive elastic ring 31 but also the adhesion of paper powder, toner, etc. is reduced. be able to. Accordingly, it is possible to prevent the occurrence of an offset image due to a defective electrical contact with the fixing film 13 over a long period of time.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a schematic configuration diagram of a heat fixing device according to a first embodiment of the present invention, where (a) is a cross-sectional view and (b) is a front view. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram illustrating a main part of a heat fixing device according to a first embodiment of the present invention, where (a) illustrates a layer configuration of a fixing film, and (b) illustrates a grounding method of the fixing film. FIG. 2 is a schematic configuration diagram illustrating a comparative example of a heat fixing device in Embodiment 1. FIG. 5 is a diagram illustrating a schematic configuration of a conductive elastic ring according to a second embodiment. FIG. 5 is a diagram illustrating a schematic configuration of a conductive elastic ring according to a third embodiment. 1 is a schematic configuration diagram of a conventional film heat fixing device. The figure which shows the metal film manufactured by the spinning process.

Explanation of symbols

6 Heat Fixing Device 10 Fixing Member 11 Heater 13 Fixing Film 20 Pressure Roller 31 Conductive Elastic Ring 101 Diode 102 Safety Resistance

Claims (4)

A flexible sleeve that slides on the heater, which is manufactured by a spinning process, and has a metal flexible sleeve having a spiral groove on a surface that slides on the heater, and a pressure roller. In the image heating apparatus for heating the developer image on the recording material by passing the recording material on which the developer image is formed through a nip portion formed therebetween,
A conductive elastic member provided so as to be in contact with the flexible sleeve, and a conductive means for preventing the flexible sleeve from being opposite in polarity to the developer image formed on the recording material,
An image heating apparatus, wherein the conductive elastic member is provided at an end of the pressure roller in an axial direction where the flexible sleeve is shifted toward the axial direction. .   The image heating apparatus according to claim 1, wherein the conductive elastic member is formed of a conductive silicone rubber or fluororubber foam.   The image heating apparatus according to claim 1, wherein the conductive elastic member has a surface layer coated with a conductive fluororesin. An image heating apparatus according to any one of claims 1 to 3, comprising:
An image forming apparatus, wherein a recording material onto which a developer image formed on an image carrier is transferred is nipped and conveyed by the nip portion to fix an image on the recording material.

Images