JP2006092785A - Plate heating element and image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plate heating element preventing abrasion on a heating film even when there are ridge lines of a base material of the plate heating element inside a nip, a plate heating element which is hardly broken during transport, inspection and assemblage, and a durable film heating type image heating device using the plate heating element. <P>SOLUTION: This plate heating element has the base material 23a, and a resistance heating element 23b and a surface protecting layer 23f, which are placed on the base material, and is used for a heater for heating a material to be heated, at least one of the ridge lines A-B in the longitudinal direction on the surface protecting layer 23f of the base material 23a being coated by a protecting layer 23f'. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plate-like heating element having a base material, a resistance heating element and a surface protection layer provided on the base material, and used for a heating device that heats a heated material. The present invention also relates to an image heating apparatus using the plate-like heating element as a heat source.

  For example, in an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile using an electrophotographic process or an electrostatic recording process, a recording material (transfer paper, printing paper, photosensitive paper, static As a fixing device that heats and fixes an unfixed toner image formed and supported on an electric recording paper or the like as a permanently fixed image, an image heating device of various methods and configurations such as a heat roller method, a film heating method, and an electromagnetic induction heating method. It has been known.

  Among these, the film heating type image heating apparatus has a short warm-up time and is suitable for use as an inexpensive fixing apparatus. In particular, it is suitable for use as a low-cost, short rise time, excellent on-demand fixing device used in a color image forming apparatus.

  The image heating apparatus of the film heating system is a plate-like heating element (heating element) that is generally supported by a fixed ceramic heater, and a heat-resistant resin film or metal that moves while in contact with the plate-like heating element. A flexible member such as a film (hereinafter referred to as a heating film), a plate-like heating element and an elastic roller that forms a nip portion via the heating film, and a heating film and an elastic roller at the nip portion. A recording material carrying an image between them is nipped and conveyed and heated. In the image heating apparatus having such a configuration, the heat capacity of the heating film is very small. Therefore, after power is applied to the plate-like heating element, the temperature of the nip portion is raised to a predetermined image heatable temperature in a short time. It is possible.

  On the other hand, a film heating type image heating apparatus is advantageous from the viewpoint of shortening the warm-up time, but has sufficient fixing properties and gloss to meet the recent demand for higher speed and higher image quality for color image forming apparatuses. Getting a feeling is getting harder.

  In order to satisfy the conditions for increasing the fixing property and glossiness, it is preferable that the position of the plate-like heating element can be freely set with respect to the nip. Due to the generated burrs, the inner surface on the heated film side is scraped, resulting in a problem of increasing sliding resistance.

In Patent Document 1, in a film heating type image heating apparatus, the pressure is rapidly changed in the downstream portion of the fixing nip. According to this method, not only the pressure roller can be prevented from being soiled, but also an effect for high speed and high image quality (high gloss) is recognized.
Japanese Patent Laid-Open No. 2003-337481

  However, if the ridge line of the base plate of the plate-shaped heating element is strongly pressed against the heating film on the downstream side of the nip, or conversely, the ridge line on the base material becomes strong on the upstream side, thereby causing slip or wear. It became such a problem.

  Further, the plate-like heating element used in this type of film heating type image heating apparatus has a thickness of 100 microns or less, and therefore has a disadvantage that it is easily damaged during transportation, inspection, and assembly, and needs to be handled with care. Met.

  Accordingly, an object of the present invention is to provide a plate-like heating element devised so as not to cause wear on the heating film even when the ridge line of the substrate of the plate-like heating element exists in the nip.

  Another object of the present invention is to provide a plate-like heating element that is not easily damaged during transportation, inspection, and assembly.

  Another object of the present invention is to provide a durable film heating type image heating apparatus using the plate-like heating element.

  A typical configuration of the plate-like heating element according to the present invention for achieving the above object includes a base material, a resistance heating element and a surface protective layer provided on the base material, A plate-like heating element used in a heating device for heating a heating material, wherein at least one of the ridge lines in the longitudinal direction on the surface protection layer side of the substrate is covered with a protection layer. .

  In order to achieve the above object, a typical configuration of the image heating apparatus according to the present invention includes a plate-like heating element, a flexible member that moves in contact with the plate-like heating element, and the plate-like heating element. And a support holder that holds the flexible member, and an elastic roller that forms a nip portion with the plate-like heating element via the flexible member, and the flexible member of the nip portion In the image heating apparatus for sandwiching and conveying a recording material carrying an image between the elastic roller and the elastic roller, the plate-like heating element is the plate-like heating element, and at least the longitudinal direction of the plate-like heating element An image heating apparatus, wherein one ridge line in a direction exists in the nip of the nip portion.

  According to the plate-shaped heating element having the above-described configuration, the ridge line of the base material itself does not contact the flexible member by covering the longitudinal ridge line of the base material with the protective layer. Therefore, the slidability with respect to the flexible member is improved, and a configuration that does not increase the sliding torque can be realized, and the arrangement of the plate-like heating elements necessary for achieving both durability and high speed can be realized. It became possible to set freely.

  Further, an image heating apparatus using the plate-shaped heating element having the above-described configuration and having at least one ridge line in the longitudinal direction of the plate-shaped heating element is present in the nip of the nip portion. As a result, the image is melted by receiving heat from the flexible member, and at the ridgeline of the plate-like heating element, the image is satisfactorily smoothed against unevenness of the recording material. Heatability and gloss can be ensured.

  In particular, by adopting a configuration in which the plate-like heating element is arranged to be inclined with respect to the normal line of the elastic roller axis, the pressure distribution in the nip is inclined to improve the image quality by shifting from the heating peak. It became possible to plan.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The first embodiment will be described below.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus in which an image heating device according to the present invention is mounted as a fixing device. The image forming apparatus of this example is an inline type (tandem type) four-color full-color laser beam printer using a transfer type electrophotographic process.

  Y, M, C, and Bk are first to fourth process stations (hereinafter referred to as image forming units) that form toner images of yellow, magenta, cyan, and black, respectively. They are arranged in parallel from top to bottom.

  Each image forming unit includes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1, a primary charger 2, a laser scanner unit 3, and a developing device that are rotationally driven in a clockwise direction at a predetermined process speed. 4. It has a cleaning device 5 and the like.

  Reference numeral 7 denotes an endless belt (hereinafter referred to as a conveyance belt) as an electrostatic adsorption conveyance member for a recording material. The conveyor belt 7 is suspended between an upper drive roller 8, a lower suction facing roller 9, and two tension rollers 10 and 11. A conveying belt portion between the driving roller 8 and the suction facing roller 9 is disposed in the vertical direction across the image forming portions. Reference numeral 6 denotes a transfer roller, which is brought into pressure contact with the photosensitive drum 1 of each image forming unit via the conveyance belt 7.

  In each image forming unit, the photosensitive drum 1 is rotationally driven, and the primary charger 2 uniformly performs primary charging processing with a predetermined polarity and potential. The charged surface is exposed to light by the laser scanner unit 3, and an electrostatic latent image corresponding to image information is formed on each photosensitive drum 1. The electrostatic latent image is developed as a toner image by the developing device 4.

  By such a process, yellow, magenta, cyan, and black toner images, which are color separation component images of full-color images, are formed on the surfaces of the photosensitive drums 1 of the respective image forming units Y, M, C, and Bk. The

  On the other hand, a recording material P (hereinafter referred to as a transfer material) P in a paper feed cassette 12 disposed in the lower part of the printer is separated and fed one by one by a paper feed roller 13 at a predetermined control timing. The transfer material P is transported upward by the transport rollers 14 and 15, and is introduced into the suction portion between the lower end portion of the transport belt 7 and the suction roller 17 by the registration roller 16 at a predetermined control timing. The suction roller 17 is brought into pressure contact with the suction counter roller 9 via the conveyance belt 7. When a voltage is applied to the suction roller 17 from the suction bias power source 17a, a charge is applied to the transfer material P introduced into the suction portion. The transfer material P becomes electrostatically attracted to the belt surface by polarizing the transport belt.

  The transfer material P is transported upward by the rotation of the transport belt 7, and passes through the transfer portions of the first to fourth image forming portions Y, M, C, and Bk in the transport process. The yellow, magenta, cyan, and black toner images respectively formed on the photosensitive drum surface are sequentially superposed and transferred. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the transfer material P. The transfer of the toner image from the photosensitive drum 1 to the transfer material P is performed electrostatically by applying a transfer bias to the transfer roller 6 from the transfer bias power source 6a.

  Further, in each image forming section, the photosensitive drum 1 after the transfer of the toner image onto the transfer material P is subjected to repeated image formation by removing residual deposits such as transfer residual toner by the cleaning device 5.

  The transfer material P, which has been transferred to the upper end of the conveying belt 7 after receiving the superimposed transfer of the four toner images, is separated from the surface of the conveying belt 7 and sent to the fixing device 18 that is an image heating device to heat and fix the toner image. After receiving, it is discharged and conveyed as a full-color print.

(2) Fixing device 18
FIG. 2 is an enlarged schematic cross-sectional view of the main part of the fixing device 18. The fixing device 18 is a film heating type, pressure roller driving type (tensionless type) heating device using a cylindrical (sleeve-like) thin film (fixing film) as a flexible member.

  Reference numeral 20 denotes a heating unit (heating rotator unit), and 30 denotes a pressure roller (elastic roller) having elasticity. The fixing nip portion N is formed by the pressure contact between both 20 and 30.

  The heating unit 20 has a longitudinal direction in the drawing (a direction intersecting the recording material conveyance direction on the recording material conveyance path surface) as a longitudinal direction, and has heat resistance and slidability such as liquid crystal polymer, phenol resin, PPS, and PEEK. A support holder 22 formed of a heat-resistant resin provided, and a plate-like heating element (heating body) disposed by being fitted and fixed in a concave groove provided along the length of the support holder in the center portion on the outer surface side of the support holder 22 ) 23, a metal fixing stay (rigid pressure stay) 24 having a U-shaped cross section, which is disposed on the inner surface side of the support holder 22 and holds the support holder, and the support holder 22 and the plate-like heat generation described above. It consists of a cylindrical heating film 21 or the like as a flexible member that is loosely fitted on the assembly of the body 23 and the fixing stay 24.

  The pressure roller 30 is formed of a core bar 31 made of aluminum or iron, an elastic layer 32 on the outer side thereof, and a release layer 33 that covers the surface of the elastic layer 32. The elastic layer 32 is a solid rubber layer formed of silicon rubber or the like, or a sponge rubber layer formed by foaming silicon rubber in order to have a heat insulation effect, or a hollow filler is dispersed in the silicon rubber layer, so that the inside of the cured product is dispersed. There is a bubble rubber layer that has a bubble part and improved heat insulation. The release layer 33 is a fluorine resin such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP), or a GLS latex coating. The releasable layer 43 may be a tube coated or a surface coated with a paint.

  The pressure roller 30 is fixedly disposed by rotatably supporting both ends of the core metal 21 between unillustrated apparatus side plates. The heating unit 20 is arranged in parallel to the pressure roller 30 with the plate-like heating element 23 side facing the pressure roller 30, and both ends of the fixing stay 24 are added with springs (not shown) or the like. By pressing the elastic layer 32 of the pressure roller 30 against the elasticity of the pressure roller 30 with a predetermined pressure F in the direction of the pressure roller by the pressure means, a plate-like heat is generated on the pressure roller 30 via the heating film 21. The body 23 is inserted into the elastic layer 32 of the pressure roller 30 in a predetermined manner to form the fixing nip portion N.

  The pressure roller 30 is rotationally driven in the counterclockwise direction indicated by the arrow by the driving means M (pressure roller drive type). A moving force acts on the heating film 21 by the contact frictional force at the fixing nip N between the pressure roller 30 and the heating film 21 due to the rotational driving of the pressure roller 30, and the inner surface side of the cylindrical heating film 21 is fixed. The outer periphery of the assembly of the support holder 22, the plate-like heating element 23, and the fixing stay 24 is driven to rotate in the clockwise direction indicated by the arrow while sliding in close contact with the surface of the plate-like heating element 23 at the nip portion N.

  The pressure roller 30 is rotationally driven, and the cylindrical heating film 21 is driven and rotated, and the plate-like heating element 23 is energized. The plate-like heating element 23 is heated to a predetermined temperature. In the state in which the temperature is adjusted to the temperature, the transfer material P, which is a recording material carrying the unfixed toner image T, is introduced between the heating film 21 and the pressure roller 30 in the fixing nip N. The transfer material P is nipped and conveyed through the fixing nip N together with the heating film 21 with the toner image carrying surface side in close contact with the outer surface of the heating film 21 in the fixing nip N. In this nipping and conveying process, the heat of the plate-like heating element 23 is applied to the transfer material P via the heating film 21, and the unfixed toner image T on the transfer material P is heated and pressurized on the transfer material P to be melt-fixed. Is done. The transfer material P that has passed through the fixing nip N is separated from the heating film 21 by curvature.

  Specifically, the cylindrical heating film 21 constituting the heating rotator is a heat-resistant and heat-insulating polyimide, polyamideimide, PEEK, PES, PPS, PFA, PTFE, FEP, or other resin film or nickel, A metallic film such as iron or stainless steel is used as the base layer 21a, and an elastic layer 21b made of a material having good heat resistance and thermal conductivity, such as silicone rubber, fluorine rubber, and fluorosilicone rubber, and fluorine resin and silicone resin. The release layer 21c made of a material having good release properties and heat resistance, such as fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP, etc. is sequentially formed.

The thickness of the elastic layer 21b is preferably 10 to 500 μm, and more preferably 50 to 300 μm from the viewpoint of achieving both image quality and high-speed warm-up characteristics. The elastic layer 21b has a hardness of 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less. The thermal conductivity of the elastic layer 21b lambda is preferably ^{2.5 × 10 -1 ~8.4 × 10 -1} W / m · ℃. When the thermal conductivity λ is smaller than the above range, the thermal resistance is too large, and the temperature rise in the release layer 21c that is the surface layer of the heating film 21 is slow. When the thermal conductivity λ is larger than the above range, the hardness of the elastic layer 21b becomes too high or compression set tends to occur. More preferably, 3.3 × 10 ^{−1 to} 6.3 × 10 ⁻¹ W / m · ° C. is good.

In addition, the thickness of the releasable layer 21c is preferably 1 to 100 μm from the viewpoints of releasability, manufacturing stability, and heat conduction characteristics. The heating film 21 used in this example has a thickness as the base layer 21a. On a polyimide endless belt formed in a cylindrical shape of 50 μm, a silicone rubber layer as an elastic layer 21b was formed to a thickness of 250 μm by a ring coating method. For the silicone rubber layer, a thermal conductivity of about 8.0 × 10 ⁻¹ W / m · K was used, and as the silicone rubber, a material belonging to a class having a high thermal conductivity was used. Further, a PFA resin tube having a thickness of 30 μm was coated on the silicone rubber layer as the releasable layer 21 c to form a heating film (resin sleeve) 21.

(3) Plate-like heating element 23
FIG. 3 is an explanatory diagram of a configuration of an example of the plate-like heating element 23. This plate-like heating element 23 is basically applied to a flat plate heater base material made of ceramics such as alumina or aluminum nitride, and to the surface of the base material by means of screen printing or the like in a linear or narrow strip shape. And heating and baking, such as Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N resistance heating element pattern, and surface protection such as glass covering the substrate surface on which the resistance heating element pattern is formed A layer and an electrode pattern that is electrically connected to the resistance heating element pattern and is formed on the substrate surface and to which a voltage is applied from a power supply circuit via a power supply connector. This is a surface heating type ceramic heater. More specifically, a: a long and thin flat plate-like base material 23a made of, for example, Al ₂ O ₃ or AlN, whose longitudinal direction is a direction intersecting (orthogonal) with the recording material conveyance direction PF in the fixing nip N. ,
b: Along with the length of the base material on the surface side of the base material 23a, an electric resistance material such as Ag / Pd (silver palladium), for example, is applied by pattern printing to a thickness of about 10 μm and a width of 1 to 5 mm by screen printing or the like and fired. Two parallel heating element patterns 23b,
c: First and second feeding electrode patterns 23c formed on the base material surface on one end side of the two parallel resistance heating element patterns 23b and electrically connected to the resistance heating element pattern 23b, respectively.・ 23d,
d: Conductive electrode pattern 23e formed on the substrate surface by electrically connecting the other end of the parallel two-line resistance heating element pattern 23b in series.
e: Covering the resistance heating element pattern 23b, the first and second feeding electrode patterns 23c and 23d, and the conductive electrode pattern pattern 23e to provide insulation and slidability. A surface protective layer 23f, such as a glass having a thickness of about 10 μm,
f: a temperature detection element 23g such as a thermistor disposed in close contact with a substantially central portion in the longitudinal direction of the base material on the back side of the base material 23a;
Etc.

  Then, as shown in FIG. 4, this plate-like heating element 23 has a heating film adhesion sliding surface on the surface side where the surface protective layer 23f is provided, and is along the length of the support holder at the center on the outer surface side of the support holder 22. The plate-like heating element surface is exposed to the outside in the plate-like heating element fitting groove formed and fixed and held.

  Reference numeral 50 denotes a power feeding connector, which is fitted to the first and second electrode patterns 23b and 23c of the plate-like heating element 23 fixedly held by the support holder 22, and is connected to the electrode patterns 23b and 33c, respectively. The electrical contact on the 50 side is in contact.

  51 is an AC power source, 52 is a control circuit unit (CPU), and 53 is a triac. The plate-shaped heating element 23 is fed from the AC power source 51 to the resistance heating element pattern 23b via the triac 53, the power feeding connector 50, and the first and second electrode patterns 23c and 23d. The temperature rises quickly and steeply by generating heat over the entire length.

  The temperature rise of the plate-like heating element 23 is detected by the temperature detecting element 23g, and electrical information of the detected temperature is input to the control circuit unit 52. The control circuit unit 52 controls the triac 53 based on the input detected temperature information and controls the electric power supplied from the AC power source 51 to the resistance heating element pattern 23b by phase, wave number control, etc. The temperature is controlled to a predetermined fixing temperature.

  The temperature control configuration of the plate-like heating element 23 is not limited to the above, and the temperature of the pressure roller 30 or the temperature of a thermistor (not shown) disposed at an arbitrary position such as the inner surface of the heating film 21 of the fixing nip N. Based on the temperature information detected by the detection means, the surface temperature of the heating film 21 required for fixing the toner image T on the recording material P in the fixing nip N is set as a target set temperature and is maintained. As a result, the energization amount to the resistance heating element pattern 23b of the plate-like heating element 23 can be controlled.

  Here, in the following, upstream and downstream mean upstream and downstream in the recording material conveyance direction or heating film movement direction in the fixing nip portion.

  As described above, the surface heating type plate-like heating element 23 in FIG. 3 provides insulation and slidability on the resistance heating element pattern 23b and the electrode patterns 23c, 23d, and 23e formed on the surface of the substrate 23a. For this purpose, the glass layer 23f side as a surface protection layer provided by covering them is used as a heating film sliding surface as shown in FIG. The base material ridge line portions A and B in the longitudinal direction of the heating element are covered with a protective layer 23f ′ obtained by extending the glass layer 23f. A is a base material ridge line portion on the upstream side in the sliding movement direction of the heating film 21 with respect to the plate-like heating element 23, and B is a base material ridge line portion on the downstream side.

  The resistance heating element pattern 23b, the electrode patterns 23c, 23d, and 23e, and the glass layer 23f are formed on the base material 23b by screen printing, and the base edge portions A and B are formed on the glass layer as shown in FIGS. In order to obtain a plate-like heating element 23 in a form in which 23f is covered with an extended protective layer 23f ', a resistance heating element pattern and an electrode pattern are printed on a plurality of large plate bases, and then the substrate is temporarily attached. It can be manufactured using thixotropy by printing a glass layer at intervals in what has been divided into final dimensions. Or when forming a glass layer by printing in multiple times, you may divide | segment in the middle of the printing of glass, and may perform the printing applied to a ridgeline after that. Alternatively, the glass layer is printed on the entire surface of the substrate before the division, and after the division, the ridgelines A and B are covered with the protective layer 23f ′ obtained by extending the glass layer 23f by heating to the melting point of the glass again. It becomes possible to make it form.

  FIG. 5 shows a back surface (back surface) heating type plate-shaped heating element 23 in which a surface opposite to the surface on which the resistance heating element pattern 23 b of the base material 23 b is formed is a heating film sliding surface. This back surface heating type plate-like heating element 23 is used as a heat source of an image heating apparatus using a metal sleeve as the heating film 21. When glass is used as the sliding layer of the plate-like heating element 23, the sleeve is heavily worn due to friction with the metal sleeve, and slipping occurs. The sliding layer 23h is formed by covering a conductive resin. On the sliding surface side of the heating plate 23 of the plate-like heating element 23, the base material ridge line portions A and B in the longitudinal direction of the plate-like heating element are covered with a protective layer 23h ′ obtained by extending the sliding layer 23h. A is a base material ridge line portion on the upstream side in the sliding movement direction of the heating film 21 with respect to the plate-like heating element 23, and B is a base material ridge line portion on the downstream side.

  Then, as shown in FIG. 6, the back side of the plate-like heating element 23 on which the sliding layer 23h is provided is the heating film contact sliding surface, and the support holder 22 is arranged along the length of the support holder at the center on the outer surface side. The plate-like heating element is inserted into the groove for fitting the plate-like heating element so that the back side of the plate-like heating element is exposed and fixed and held.

  In order to obtain the plate-like heating element 23 in the form in which the base material ridge portions A and B are covered with the protective layer 23h ′ obtained by extending the sliding layer 23h as described above, the sliding is the same as in the first embodiment. In the case where the layer 23h is a thermosetting resin, it can be manufactured using thixotropy by printing the resin at intervals after dividing the substrate.

  This is shown in FIG. (A) is the one in which the sliding layer 23h is printed on a plurality of large plate bases, and a cut is made for division, and the scribe lines are shown by dotted lines. (B) is obtained by dividing this by a scribe line. In this state, the ridge lines A and B are not covered. By heating again from this state and setting the temperature to be equal to or higher than the melting temperature of the resin of the sliding layer 23h, the substrate ridge line portions A and B are moved to the sliding layer 23h as shown in FIG. Thus, a form covered with a protective layer 23h 'extended from the above can be completed.

  In the case where the sliding layer 23h is a thermoplastic resin, a ridgeline is obtained by dividing the plurality of large plate substrates after providing the sliding layer and then heating again to melt the resin layer. It is possible to complete a form in which the resin of the part is melted and the base material ridge line parts A and B are covered with the protective layer 23h ′ obtained by extending the sliding layer 23h.

  As described above, in the plate-like heating element in which the longitudinal ridge lines A and B of the substrate are covered with the protective layers 23 f ′ and 23 h ′, the longitudinal ridge lines A and B of the substrate do not contact the inner surface of the heating film 21. Therefore, problems such as shaving on the inner surface of the heating film 21 due to burrs generated on the ridgelines A and B, increasing the sliding resistance, and shortening the life of the heating film 21 are solved. Thereby, it is possible to freely set the position of the plate-like heating element 23 with respect to the fixing nip portion.

  Further, the plate-like heating element in which the longitudinal ridge line of the base material is covered with the protective layers 23f ′ and 23h ′ in this way is not easily cracked and is strong against cracking. Normally, this type of plate-like heating element is divided using laser scribing or a cut by a diamond cutter, and a shell-like crack is generated at that time. Starting from this crack, there is a problem that the crack progresses into the ceramic substrate and eventually leads to breakage. However, the strength can be remarkably increased by covering the longitudinal ridges of the substrate 23a with the protective layers 23f 'and 23h' of glass or resin as described above.

  Further, this type of plate-like heating element 23 is usually used as assembled as the heating unit 20 as described above, but at that time, it may be broken by an impact in handling. However, if the longitudinal ridge line of the base material 23a is covered with the protective layers 23f ′ and 23h ′ as in this embodiment, this problem is also reduced.

  The film heating type fixing device 18 shown in FIG. 2 has a plate-like heating element 23 as a plate-like heating element 23 of the surface heating type or the backside heating type in which the longitudinal ridges of the base material 23a are made of glass or resin protective layers 23f 'and 23h'. The ridgeline of the plate-like heating element 23 enters the fixing nip portion N at least on the downstream side in the conveyance direction PF of the recording material P. Thus, after the toner image T on the recording material P is sufficiently heated and softened before the ridge line, the surface of the toner image is smoothed by squeezing the downstream ridge line of the plate-like heating element 23. As a result, the fixing property and the glossiness are improved. In general, the smoothness of the surface of the toner image makes it difficult to peel off when the external force is applied, and the effect of pushing it into the fibers of the recording material (paper) can be obtained. Therefore, the fixability is expected to be improved.

  In the present embodiment, the configuration in which the ridge line on the downstream side in the moving direction of the heating film of the plate-like heating element 23 is in the fixing nip portion N has been described, but conversely, the ridge line may be in the fixing nip portion N on the upstream side. In that case, an effect can be obtained as a solution to the problem that water vapor accumulated in the unfixed loose toner is heated and blows off the toner. That is, another configuration of the present embodiment may be to heat the air in the toner after the vapor pressure suddenly rises, to apply a binding force to the toner and then to heat the toner.

  It goes without saying that the plate-like heating element 23 may have a downstream ridge line and an upstream ridge line in the heating nip moving direction in the fixing nip portion N.

  The second embodiment will be described below. Since the configuration of the image forming apparatus including the fixing device of the present embodiment is the same as that described with reference to FIG. 1 of the first embodiment, the description thereof will be omitted. Constituent members / portions common to the fixing device of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  In the fixing device of this embodiment, the heating film 21 as a flexible member uses a heating film (metal sleeve) based on stainless steel. The plate-like heating element 23 is of the back surface heating type shown in FIG. 5, and is pressed against the pressure roller 30 via the heating film 21 based on the stainless steel.

  As shown in FIG. 8, the plate-like heating element 23 is pressed in the pressing direction F toward the rotation center of the pressure roller 30 in a cross section perpendicular to the rotation axis of the pressure roller 30. The normal direction U of the sliding surface of the plate-like heating element 23 and the support holder 22 with the inner surface of the heating film 21 in the fixing nip N is not parallel to the pressing direction F to the pressing roller 30, and the fixing nip In the portion N, the sliding surface of the plate-like heating element 23 and the support holder 22 is inclined from the surface of the pressure roller 30 to the inside in an increasing amount from the entrance to the exit in the conveyance direction PF of the recording material P. ing.

  In this embodiment, since the heating film 21 based on stainless steel is used, the rigidity is higher than that of the heating film 21 based on polyimide. For this reason, as shown in FIG. 9, the shape of the heating film 21 on the upstream side of the fixing nip portion is a shape in which the heating film 21 is curved toward the pressure roller 30. The inner surface of the heating film 21 and the plate-like heating element 23 form a narrower film inner surface nip portion N ′ different from the fixing nip N formed by the contact between the heating film 21 and the pressure roller 30. It becomes.

  Therefore, in the present embodiment, the plate-like heating element 23 is arranged so that the upstream end J of the plate-like heating element 23 is inside the recording material inlet of the fixing nip N and outside the film inner surface nip N ′. Arranged. Further, the center line C1 of the plate-shaped heating element 23 in the recording material conveyance direction PF is upstream from the center line C2 of the fixing nip portion N in the recording material conveyance direction near the entrance of the recording material P in the conveyance direction PF. The downstream end K of the plate-like heating element 23 is located at the downstream end of the film inner surface nip N ′.

  As described above, the normal direction U of the sliding surface in the heating film 21 including the plate-like heating element 23 and the support holder 22 is not parallel to the pressing direction F to the pressing roller 30, and the sliding surface is inclined. In addition, since one of the end portions K is in the fixing nip portion N, similar to the effect in the first embodiment, in the fixing nip portion N, simultaneously with the heating by the plate-like heating element 23, FIG. As shown, the fixing pressure distribution has a peak value at the outlet side (sliding surface end portion K) position of the fixing nip portion N.

  As a result, the toner is supplied with heat from the heating film 21 in the fixing nip portion N, and is exposed to a higher fixing pressure in the downstream portion where the temperature becomes highest, that is, in a sufficiently softened or melted state. Therefore, compared with the first embodiment, it is possible to ensure sufficient fixability and image quality even under higher speed conditions without increasing the pressure F.

  The third embodiment will be described below. Since the configuration of the image forming apparatus including the fixing device of the present embodiment is the same as that described with reference to FIG. 1 of the first embodiment, the description thereof will be omitted. Constituent members / portions common to the fixing device of the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  A third embodiment is shown in FIG. An enlarged view of the fixing nip N in this case is shown in FIG. The plate-like heating body 23 used in this example is of the surface heating type or the backside heating type described in the first embodiment. The left side of FIG. 11 is the downstream side of the nip, and an arch-shaped protrusion 22a is provided at this portion in the nip of the support holder 22 so as to increase the pressure.

  It is sufficient that the protrusion 22a has a height of about 100 to 200 microns.

  In FIGS. 11 and 12, the plate-like heating body 23 is arranged so that the normal line coincides with the direction F of the pressing force. However, the plate-like heating body 23 is inclined as in FIGS. 8 to 10 of the second embodiment. May be arranged.

  Furthermore, the thickness of the downstream part of the protective layer 23h 'or the sliding layer 23h of the surface heating type or the backside heating type plate-like heating body itself may be increased and provided with a protrusion.

  FIG. 13 shows a configuration in which the protrusion a is provided by increasing the thickness of the downstream portion of the sliding layer 23h of the back surface heating type plate-like heating body. As a method of increasing the sliding layer thickness in the heating downstream portion in order to provide the protrusion a, it can be achieved by widening the screen printing mesh or printing this portion a plurality of times. Alternatively, a heat resistant resin such as LCP or PPS may be thermally welded to the plate-like heating element 23 later. FIG. 14 shows a heat fixing device using this plate-like heating body.

  When the protrusion 22 a is provided on the support holder 22, the effect of the height of the protrusion varies due to the variation in the thickness of the plate-like heating element 23. This appears as a difference in fixability and gloss between machines. However, if the plate-like heating body itself is provided with the protrusions a, it is possible to eliminate the influence of pressure variation due to the fitting step with the support holder-22.

(Other)
1) In the surface heating type plate-like heating element 23 of FIGS. 3 and 4, the covering 23f ′ of the base 23a with the protective layer on the longitudinal ridge line on the surface protective layer 23f side is upstream or downstream in the heating film moving direction. It is also possible to adopt a form in which only one of the sides is provided.

  Also, in the backside heating type plate-like heating element 23 of FIGS. 5 and 6, the covering 23h ′ with the protective layer of the longitudinal ridge line on the sliding layer 23H side of the base material 23a is upstream of the moving direction of the heating film or Only one of the downstream sides may be used.

  2) The image heating device of the present invention is a hypothetical fixing device that temporarily fixes an unfixed image on a recording material, or a surface modification that modifies image surface properties such as gloss by reheating a recording material carrying a fixed image. Image heating devices such as quality devices.

  3) Of course, the plate-like heating element 23 may be a ceramic heater having a structure different from that of the embodiment in the form of resistance heating element and electrode pattern. A plate-like heating element using nichrome wire or the like may be used as the resistance heating element.

  4) In the embodiment, the flexible member is a cylindrical member (flexible sleeve), which is driven and rotated by driving a pressure roller. However, a driving roller is provided inside the endless film to drive the driving roller. Therefore, any rotation means such as rotating the film can be obtained. Further, the flexible member may be a long end-like web-like member wound in a roll, and the image heating device may be configured such that the flexible member is fed out and moved through a plate-like heating element.

1 is a schematic view of an example of an image forming apparatus in a first embodiment. FIG. 3 is a cross-sectional model view of a fixing device (image heating device). Structure explanatory drawing of an example of a surface heating type plate-shaped heat generating body. FIG. 4 is an enlarged cross-sectional model view of a fixing nip portion of a fixing device using the surface heating type plate-like heating element of FIG. 3. Structure explanatory drawing of an example of a back surface heating type plate-shaped heating element. FIG. 6 is an enlarged cross-sectional model view of a fixing nip portion of a fixing device using the back surface heating type plate-shaped heating element of FIG. 5. Manufacturing point explanatory drawing of the back surface heating type plate-shaped heating element of FIG. FIG. 9 is an enlarged cross-sectional model view of a fixing nip portion of a fixing device according to a second embodiment. Enlarged model of the upstream side of the fixing nip Illustration of pressure distribution in the fixing nip FIG. 10 is a schematic cross-sectional view of a fixing device according to a third embodiment. The enlarged cross-sectional model figure of a fixing nip part. The expansion cross-sectional model figure of the plate-shaped heat generating body in a 3rd Example. FIG. 14 is an enlarged cross-sectional model view of a fixing nip portion of a fixing device using the plate-like heating element of FIG. 13.

Explanation of symbols

  18 .. Fixing device (image heating device), 20.. Heating unit (heating rotator unit), 30.. Pressure roller (elastic roller), 21.. Heating film (flexible member), 22. Holder, 23 .... Plate heating element (heating element), 23a ... Heater base material, 23b ... Resistance heating element, 23f ... Surface protection layer, 23f '... Dynamic layer, 23h '.. Base material edge covering protective layer, P..Recording material, T..Toner image, PF..Recording material conveying direction, N..Fixing nip, C1..Plate heating element. 23 width direction center line, C2,... Fixing nip N width direction center line, U .. sliding surface normal direction

Claims (8)

  A plate-like heating element having a base material, a resistance heating element and a surface protection layer provided on the base material, and used in a heating device for heating a material to be heated. A plate-like heating element, wherein at least one of the longitudinal ridges on the surface protective layer side is covered with a protective layer.   A base material, a resistance heating element and a surface protection layer provided on the base material, and a slide provided on a surface of the base material opposite to the side on which the resistance heating element and the surface protection layer are provided. A heating element for heating a material to be heated, wherein at least one of the longitudinal ridges on the sliding layer side of the substrate is covered with a protective layer. A plate-like heating element.   The plate-like heating element according to claim 1 or 2, wherein the substrate is ceramic.   The plate-like heating element according to any one of claims 1 to 3, wherein the covering protective layer of the ridge line is resin or glass. A plate-like heating element, a flexible member that moves while in contact with the plate-like heating element, a support holder that holds the plate-like heating element and the flexible member, and the flexible member through the flexible member An image that includes a plate-like heating element and an elastic roller that forms a nip portion, and heats the recording material that holds the image between the flexible member of the nip portion and the elastic roller, and heats the recording material. In the heating device,
The plate-like heating element according to any one of claims 1 to 4, wherein at least one ridge line in the longitudinal direction of the plate-like heating element exists in the nip of the nip portion. An image heating device.   The image heating apparatus according to claim 5, wherein the plate-like heating element is inclined with respect to a normal line of the axis of the elastic roller in a cross section perpendicular to the rotation axis of the elastic roller.   In a cross section perpendicular to the rotation axis of the elastic roller, the sliding amount of the plate-shaped heating element increases from the surface of the elastic roller to the inside from the entrance to the exit direction of the recording material. The image heating apparatus according to claim 4, wherein the image heating apparatus is inclined in a direction.   In a cross section perpendicular to the rotation axis of the elastic roller, the sliding amount of the plate-shaped heating element increases from the surface of the elastic roller to the inside from the entrance to the exit direction of the recording material. Inclining in the direction, and two ridges upstream and downstream of the plate-like heating element are present in the nip of the nip portion, and have a protrusion toward the elastic roller on the downstream side of the plate-like heating element. The image heating apparatus according to claim 4.