JP2009237089A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high speed and high function of the device by making it attainable to start up the device in a shorter time even in a cold state due to a low temperature environment by reducing heat loss during the start up. <P>SOLUTION: In a rigid stay 20 for applying pressure, which is disposed inside a film 16 and reinforces a film guide 18, the surface 20a of a part opposite at least the film 16 is formed so as to have a mirror face. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image heating apparatus for heating a material to be heated.

  In general, electrophotographic image forming apparatuses are widely used in copying machines, laser beam printers, and the like. In the electrophotographic method, an electrostatic force is used to form an image of toner particles on a recording material such as recording paper by a transfer method or a direct method, and the toner image is recorded on the recording material by a fixing device as an image heating device. A stable image is formed by being melted and fixed thereon.

  As a fixing device, a heat roller method is widely used, but recently, a film heating method device has been put into practical use.

  As a heat roller system, a pressure roller pair of a fixing roller (heating roller) and a pressure roller is a basic configuration, and an unfixed toner image is fixed to a recording material surface by heat and pressure as follows. . First, as the pressure roller pair rotates, the fixing roller is heated from the inside by a halogen heater or the like to keep the surface temperature at a predetermined fixing temperature. Then, a recording material on which an unfixed toner image to be image-fixed is formed and carried is introduced into a fixing nip portion (heating nip portion) which is a mutual pressure contact portion of the pressure roller pair, and is nipped and conveyed, and the heat of the fixing roller, An unfixed toner image is fixed on the surface of the recording material by heat and pressure by the pressure applied at the fixing nip.

  In a film heating type fixing device (heating device), an unfixed toner image is fixed to a recording material surface by heat and pressure as follows.

  First, a heat-resistant film (fixing film) as a flexible moving member is sandwiched between a ceramic heater as a heating body and an elastic pressure roller as a pressure member, and a nip portion (fixing nip portion, contact portion) ). Then, by introducing a recording material that forms and carries an unfixed toner image to be fixed as an image to be heated between the film in the nip portion and the pressure roller, the recording material is nipped and conveyed together with the film, Then, the unfixed toner image is fixed on the surface of the recording material by heat and pressure.

  In this film heating type fixing device, an on-demand type device can be configured by using a ceramic heater and a low heat capacity member as a film. That is, in the film heating type fixing device, it is only necessary to energize a ceramic heater as a heat source to generate heat to a predetermined fixing temperature only when image formation is performed by the image forming apparatus, and has the following advantages. . For example, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is significantly small (power saving).

  In recent years, with the increase in speed and color of image forming apparatuses, in film heating type heat fixing apparatuses, metals such as stainless steel and nickel are used as the base layer of the film member, and an elastic layer is further provided on the metal base layer. A heat fixing device using a provided film member has been proposed. (See Patent Documents 1 to 4).

  Using a metal with higher thermal conductivity than the resin as the base layer of the film member instead of the conventional heat-resistant resin increases the thermal conductivity of the film member and makes the heat of the fixing heater more efficient. In other words, it is transmitted to the recording material and adapted to increase the speed of the image forming apparatus.

Further, uniform fixing is achieved by providing an elastic layer on the base layer of the film member for the toner image transferred in multiple color images. This is because the elastic layer is deformed along the toner layer, so that the toner that is unevenly placed on the image is enveloped by the elastic layer and uniformly heat is applied.

In such a heat fixing apparatus of the film heat fixing system, there is a concern that an offset phenomenon occurs in which toner adheres to the film member and is transferred again to the recording material. In order to prevent this offset phenomenon, it has been proposed to provide a surface release layer having a fluororesin such as a PFA resin on the base layer or the elastic layer of the film member (see Patent Document 5).
JP 2003-045615 A JP 2003-156554 A Japanese Patent Laid-Open No. 10-10893 Japanese Patent Laid-Open No. 11-15303 JP-A-9-011362

  However, in the above-described film heating type fixing device, a shorter start-up time is required as the speed and functionality of the device are increased, and thus further improvement in thermal efficiency has been a problem.

  In other words, from the viewpoint of thermal efficiency of transferring heat to the recording material, the conventional example described above is deprived of heat in addition to the portions necessary for directly heating the recording material, such as a reinforcing member, and heat loss (loss) is lost. ) Was a concern. In particular, this effect is considered to be significant when starting up from a cold state in a low-temperature environment where the temperature of each member is low.

  The present invention has been made in view of the circumstances as described above, reduces heat loss during startup, enables a shorter startup time even in a cold state in a low-temperature environment, and increases the speed and speed of the apparatus. The goal is to achieve functionality.

In order to achieve the above object, the present invention provides:
A rotating body having flexibility;
A support member that has a sliding surface that slides with an inner peripheral surface of the rotating body, is provided inside the rotating body, and supports the rotating body;
A reinforcing member that is provided inside the rotating body and reinforces the supporting member;
A pressure member that forms a nip portion with the sliding surface of the support member via the rotating body;
Have
In an image heating apparatus that heats the recording material by nipping and conveying the recording material on which the developer image is formed in the nip portion,
A surface of at least a portion of the reinforcing member facing the inner peripheral surface of the rotating body is formed in a mirror state.

  According to the present invention, heat loss at the time of start-up can be reduced, a shorter start-up time can be achieved even in a cold state in a low-temperature environment, and high speed and high functionality of the apparatus can be achieved.

  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.

[Embodiment 1]
(1) Image Forming Apparatus FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus shown in FIG. 1 is a full-color image printer using an electrophotographic process.

  In FIG. 1, reference numeral 101 denotes an electrophotographic photosensitive drum (image carrier) composed of an organic photosensitive member or an amorphous silicon photosensitive member, which is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined process speed (peripheral speed). .

  The photosensitive drum 101 is subjected to a uniform charging process with a predetermined polarity and potential by a charging device 102 constituted by a charging roller or the like in the rotation process.

  Next, a scanning exposure process of target image information by the laser beam 103 output from the laser optical box (laser scanner) 110 is subjected to the charging process surface.

  The laser optical box 110 outputs a laser beam 103 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generator such as an image reading device (not shown) to output a photosensitive drum. The surface is subjected to scanning exposure. By this scanning exposure, an electrostatic latent image corresponding to target image information scanned and exposed on the surface of the photosensitive drum 101 is formed.

  Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

  In the case of full-color image formation, scanning exposure and latent image formation are performed on a first color separation component image of a target full-color image, for example, a yellow component image. The latent image is developed as a yellow toner image (developer image) by the operation of the yellow developing device 104Y in the four-color developing device 104. The yellow toner image is transferred onto the surface of the intermediate transfer drum 105 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105. The surface of the photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is cleaned by the cleaner 107 after removal of adhered residues such as transfer residual toner.

  The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above is sequentially executed for each color separation component image (second to fourth color separation component images) of the target full-color image. In this embodiment, a magenta component image is developed as a second color separation component image as a magenta toner image by the operation of the magenta developer 104M, and a cyan component image is developed as a third color component image in the cyan developer 104C. As a result, the cyan toner image is developed. Further, a black component image is developed as a fourth color component image as a black toner image by the operation of the black developing device 104BK.

  In this manner, four color toner images of yellow toner image, magenta toner image, cyan toner image, and black toner image are sequentially superimposed and transferred onto the surface of the intermediate transfer drum 105, and the color toner corresponding to the target full-color image. An image is synthesized and formed.

The intermediate transfer drum 105 has a middle-resistance elastic layer and a high-resistance surface layer on a metal drum. The intermediate transfer drum 105 is in contact with or close to the photosensitive drum 101 at the same peripheral speed as the photosensitive drum 101. It is rotationally driven in the direction. By applying a bias potential to the metal drum of the intermediate transfer drum 105, the toner image on the photosensitive drum 101 side is transferred to the surface of the intermediate transfer drum 105 due to the potential difference from the photosensitive drum 101.

  The color toner image synthesized and formed on the surface of the intermediate transfer member 105 is transferred from the feeding unit to the secondary transfer unit T2 in the secondary transfer unit T2, which is a contact nip portion between the rotating intermediate transfer drum 105 and the transfer roller 106. The image is transferred to the surface of the recording material P fed in at the control timing. The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images sequentially from the surface of the intermediate transfer drum 105 to the recording material P side.

  The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105 and introduced into a fixing device 100 as an image heating device. The recording material P introduced into the fixing 100 is nipped and conveyed at a fixing nip portion described later, whereby an unfixed toner image undergoes a heat fixing process, and a color image is formed on the recording material P. Thereafter, the recording material P is discharged as an image formed product to a discharge tray (not shown) outside the apparatus.

  After the color toner image is transferred to the recording material P, the intermediate transfer drum 105 is cleaned by the cleaner 108 after removal of adhering residues such as transfer residual toner and paper dust. The cleaner 108 is always held in a non-contact state with the intermediate transfer drum 105, and is in contact with the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Retained.

  Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and recording is performed on the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The contact state is maintained via the material P.

  A mono-color image print mode such as a monochrome image can also be executed. A double-sided image print mode or a multiple image print mode can also be executed.

  In the double-sided image print mode, the recording material P on which the first-side image has been printed that has left the fixing device 100 is turned upside down through a recirculation conveyance mechanism (not shown) and sent again to the secondary transfer portion T2. Then, the toner image is transferred to the second side, introduced again into the fixing device 100, and the toner image is fixed to the second side, whereby a double-sided image print is output.

  In the multiple image print mode, the recording material P that has been printed on the first image from the fixing device 100 is sent to the secondary transfer portion T2 again without being turned upside down via a recirculation conveyance mechanism (not shown). Then, the second toner image is transferred to the surface on which the first image has been printed, and is again introduced into the fixing device 100 and undergoes the second toner image fixing process to output a multiple image print.

(2) Fixing device 100
The fixing device 100 according to the present embodiment is basically heated by a film heating method or a pressure roller driving method (tensionless type) disclosed in JP-A-4-44075 to 44083, JP-A-4-204980 to 204984, and the like. Device. In such a heating device, a cylindrical heat-resistant film (fixing film) is used as a flexible member.

FIG. 2 is a schematic front view showing the fixing device 100 of the present embodiment. FIG. 3 is a schematic longitudinal sectional view showing the fixing device 100 of the present embodiment. Here, in FIG. 2, 3, the intermediate part of the apparatus main body is abbreviate | omitted. FIG. 4 is a schematic cross-sectional view showing the fixing device 100 of the present embodiment.

  Reference numeral 15 denotes a heating assembly (film unit), and 19 denotes an elastic pressure roller as a pressure member. A nip portion (fixing nip portion) N as a contact portion is formed by pressure contact between the heating assembly 15 and the elastic pressure roller 19. It is formed.

(A) Heating assembly 15
The heating assembly 15 is an assembly of a cylindrical heat-resistant fixing film (hereinafter referred to as a film) 16, a heater (heating body) 17, a film guide 18, a pressurizing rigid stay 20, an annular flange member 25, and the like. Here, the film 16 constitutes a rotating body (flexible moving member, flexible sleeve) having flexibility. The film guide 18 has a sliding surface that slides with the inner peripheral surface of the film 16, and constitutes a support member that is provided inside the film 16 and supports the film 16. The pressurizing rigid stay 20 constitutes a reinforcing member that is provided inside the film 16 and reinforces the film guide 18. The annular flange member 25 constitutes a film displacement movement restricting means. Here, the nip portion N is formed between the elastic pressure roller 19 and the sliding surface sliding with the inner peripheral surface of the film 16 of the film guide 18 through the film 16. it can.

  The film 16 is composed of a base layer made of a heat-resistant resin-based material or a metal material, a heat-resistant elastic layer as an intermediate layer, and a composite layer film in which a peripheral layer is coated with a fluororesin to form a release layer. Can be used.

  Here, examples of the heat-resistant resin constituting the base layer include polyimide, polyimide amide, PEEK (polyether ether ketone), PES (polyether sulfone), and PPS (polyphenylene sulfide) having a thickness of 20 to 100 μm. Moreover, as a metal material which comprises a base layer, 15-50 micrometers thick SUS (stainless steel), Ni, etc. can be illustrated. Examples of the heat resistant elastic layer include silicon rubber and fluoro rubber having a thickness of 50 to 500 μm. Moreover, as a fluororesin which comprises a mold release layer, 5-40 micrometers PTFE, PFA, FEP, etc. can be illustrated. Here, PTFE is polytetrafluoroethylene, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, and FEP is a tetrafluoroethylene hexafluoropropylene copolymer.

  In the present embodiment, a SUS film having a diameter of 20 mm in which silicon rubber is formed on the outer peripheral surface and PTFE is coated is used.

  The heater 17 is a member that has a low heat capacity and rapidly increases the temperature by energization, with the direction intersecting (substantially orthogonal) the recording material conveyance direction (recording material passing direction, arrow R direction) as the longitudinal direction. In this embodiment, a ceramic heater is applied as the heater 17. Here, the direction intersecting the recording material conveyance direction is the same direction as the rotation axis direction (bus line direction) of the film 16 and is the longitudinal direction of the heating assembly 15.

  Basically, the heater 17 is electrically connected to the substrate, the energization heating resistor layer formed on the substrate surface, the insulating layer covering the substrate surface on which the energization heating resistor layer is formed, and the energization heating resistor layer. It is a surface heating type heater having a low heat capacity as a whole, having a power supply electrode portion that is conducted and formed on the substrate surface.

Here, the substrate may be made of insulating ceramics such as alumina and aluminum nitride, heat resistant resin such as polyimide, PPS, and liquid crystal polymer. In addition, the energization heating resistor layer is formed on a substrate surface by Ag / Pd (silver), which is formed by coating and baking in a linear or thin strip shape having a thickness of about 10 μm and a width of about 1 to 5 mm by means of screen printing or the like. Palladium), RuO ₂ , Ta ₂ N, or the like. Further, the insulating layer is preferably composed of a glass coat or the like. The power supply electrode portion is electrically connected to the energization heating resistor layer and is formed on the substrate surface, and is configured such that a voltage is applied from the power supply circuit via the power supply connector.

  The heater 17 is formed on the outer surface of the film guide 18 along the longitudinal direction of the film guide 18 along the longitudinal direction of the film guide 18 with the heater surface side as the film contact sliding surface. Are fixedly held by being exposed to the outside. Here, the heater surface side means the substrate surface side on which the energized heat generating resistance layer and the insulating layer (glass coat) are formed in the heater 17. Further, the heater fitting groove 18a of the film guide 18 forms (configures) the nip portion N of the sliding surface on which the film guide 18 slides with the film 16 so that the heater 17 forms (configures) the nip portion N. ). Here, the heater 17 and the heater fitting groove 18a may be provided so as to constitute at least a part of the nip portion N.

  The heater 17 is supplied with power from the AC power supply (not shown) to the energized heat generating resistor layer, and the energized heat generating resistor layer generates heat over the entire length, so that the temperature rises rapidly and steeply. The temperature rise of the heater 17 is detected by a temperature detection element (not shown) arranged on the back side of the heater. A control circuit unit (not shown) controls the electric power supplied from the AC power source to the energization heating resistor layer of the heater 17 based on the detection result of the temperature detection element arranged on the back side of the heater by phase, wave number control, etc. The temperature of the heater 17 is controlled to a predetermined fixing temperature.

  The temperature control configuration of the heater 17 is not limited to the above configuration. For example, it may be based on temperature information detected by temperature detection means such as the surface temperature of the elastic pressure roller 19 or a temperature sensor such as a thermistor disposed at an arbitrary position on the inner surface of the film 16 in the nip N. Based on this temperature information, the surface temperature of the film 16 required for fixing the toner image T on the recording material P as the material to be heated in the nip portion N is set as the target set temperature so that it can be maintained. The energization amount of the heater 17 to the energization heat generating resistance layer can also be controlled.

  The film guide 18 is a heat- and heat-insulating member having a substantially semi-circular cross-sectional shape having a longitudinal direction in the direction intersecting the recording material conveyance direction. The film guide 18 backs up the film 16, pressurizes the nip portion N, and the heater 17. It supports the support of the film and the stability of conveyance during rotation of the film 16.

  The film guide 18 is made of a material having good insulation and heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, fluororesin, LCP resin, and mixed resin thereof. It is done. Here, examples of the fluororesin include PFA, PTFE, FEP and the like. The LCP resin is a liquid crystal polymer.

  The cylindrical film 16 is loosely fitted on a film guide 18 on which a heater 17 is fixedly supported.

  The annular flange member 25 is fitted to the end portion side of the film guide 18 to regulate the end portion of the film 16.

  The pressurizing rigid stay 20 is inserted into the insertion portion 18b (inner portion in the recording material conveyance direction) of the film guide 18 on the inner surface side of the film 16, and both end portions thereof are outside the both end portions of the film guide 18 in the longitudinal direction. Protrudes towards. The pressurizing rigid stay 20 will be described in detail in the section (d) below.

(B) Elastic pressure roller 19
An elastic pressure roller (hereinafter referred to as a pressure roller) 19 as a pressure member is a core metal 19a provided with an elastic layer 19b such as silicone rubber to reduce the hardness, and both ends of the core metal 19a are connected to the apparatus. A bearing is rotatably held between the front side and the rear side chassis side plate (not shown). In the pressure roller 19, a fluororesin layer such as PTFE, PFA, or FEP may be further provided on the outer periphery in order to improve surface properties.

  In the present embodiment, the heating assembly 15 is disposed above the pressure roller 19 with the lower surface side of the film guide 18 facing downward. Then, the pressure springs 22 and 22 are respectively contracted between the spring receiving members 23 and 23 added to both ends of the pressing rigid stay 20 and the spring receiving members 21 and 21 on the apparatus chassis side plate side. A pressing force is applied to the pressurizing rigid stay 20.

  As a result, the lower surface of the film guide provided with the heater 17 and the pressure roller 19 are pressed against each other with the film 16 against the elasticity of the elastic layer 19b of the pressure roller 19, and a nip having a predetermined width as a contact portion. Part N is formed. The heater 17 exists in the nip portion N. The film 16 is backed up at the nip N by a film guide 18 and a heater 17.

  In this example, the ceramic heater 17 as the heating body and the film guide 18 that supports the ceramic heater 17 have a sliding surface that slides on the fixing film 16 as a moving member, and supports the fixing film 16. It is a member.

(C) Device Operation In FIG. 4, the pressure roller 19 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the film 16 by a frictional force between the pressure roller 19 and the outer surface of the film 16 by the rotation of the pressure roller 19. As a result, the film 16 rotates around the film guide 18 in the clockwise direction indicated by the arrow while sliding with the inner surface in close contact with the lower surface of the heater 17 at the nip portion N (pressure roller driving method). The film 16 is in a rotating state having a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 19.

  In order to reduce the mutual sliding frictional force between the lower surface of the heater 17 and the inner surface of the film 16 in the nip portion N, a lubricant such as heat-resistant grease is provided between the lower surface of the heater 17 and the inner surface of the film 16 in the nip portion N. Intervene.

  The rotation of the pressure roller 19 is started based on the print start signal, and the heater 17 starts to heat up.

  The rotation peripheral speed of the film 16 by the rotation of the pressure roller 19 becomes steady, and the toner t is placed between the film 16 and the pressure roller 19 in the nip portion N while the temperature of the heater 17 rises to a predetermined temperature. The supported recording material P is introduced with the toner image carrying surface side of the film 16 side. As a result, the recording material P is brought into close contact with the lower surface of the heater 17 through the film 16 at the nip portion N and moves and passes through the nip portion N together with the film 16.

  During the moving and passing process, the heat of the heater 17 is applied to the recording material P through the film 16 and the toner image t is heated and fixed on the surface of the recording material P. The recording material P that has passed through the nip portion N is separated from the surface of the film 16 and conveyed.

(D) Pressurizing rigid stay 20
FIG. 5 is a schematic cross-sectional view of the pressurizing rigid stay 20.

  The pressurizing rigid stay 20 is generally made of iron, SUS, aluminum or the like as a metal that is inexpensive, has high workability, and is excellent in strength. As shown in FIG. 5, the shape is excellent in strength, reduces the heat capacity, and further includes a temperature detection element and a safety element inside, so that “U-shaped”, “U-shaped”, It has an arched cross-sectional shape. Here, in the pressurizing rigid stay 20, both end portions 20 b of the arch-shaped cross-sectional shape constitute contact portions that come into contact with the film guide 18 when inserted into the film guide 18. Then, the pressurizing rigid stay 20 having an arch-shaped cross-sectional shape is formed by connecting the curved portion 20c to both end portions 20b. When the heating assembly 15 is configured, as shown in FIG. 4, both end portions 20b are respectively provided upstream and downstream of the nip portion N so as to sandwich the nip portion N in the recording material conveyance direction.

  The plate thickness of the pressurizing rigid stay 20 is preferably a thickness that can achieve both prevention of deflection with applied pressure and reduction in heat capacity. In addition, the size and shape are not particularly defined as long as a member such as a temperature detecting member can be included as required and the size does not contact the inner surface of the film.

  On the other hand, the surface 20a (the hatched portion shown in FIG. 5) of the pressurizing rigid stay 20 facing the film 16 side is mirror-finished by chemical polishing, physical polishing, gloss plating treatment, vapor deposition, coating, etc. Mirror surface state). Here, it is sufficient that the surface of at least the portion (region) facing the film 16 side (the inner peripheral surface side of the film 16) of the pressurizing rigid stay 20 is formed in a mirror state.

  In general, the glossiness of the mirror surface is that of bright-treated steel such as bright aluminum by bright annealing or the like, which is a heat treatment that prevents high-temperature oxidation and decarburization of the surface and maintains the surface gloss state from the viewpoint of absorption and reflection of radiant heat. A glossiness higher than the glossiness is preferred. By obtaining a glossiness like a mirror surface, it is possible to realize extremely high radiant heat reflection. Here, in terms of the glossiness of the mirror surface in terms of emissivity, it is 0.2 or less, preferably 0.05 or less. When the emissivity is large, the amount of absorption due to radiant heat is increased, the effect of suppressing heat loss is weakened, and as a result, the thermal efficiency is degraded.

  The pressurizing rigid stay 20 according to the present embodiment can be manufactured as follows, for example.

  For example, a steel sheet having a thickness of 1.6 mm as a plate-like member is deformed (bent or the like) and cut with a press or the like to obtain a molded body having a desired size and shape. In addition, there is a case where a portion that is a contact portion with a film guide requiring high accuracy is individually cut.

  The molded body thus obtained is subjected to a mirror finishing process at least on the part facing the film. Thereby, the pressurizing rigid stay of the present embodiment is obtained.

  Examples of the mirror finishing treatment include gloss plating such as “bright nickel-chrome plating”, mirror polishing by chemical polishing / physical polishing, wet (bright) polishing, or coating by vapor deposition of gold, or a combination of these. Is preferred. Alternatively, the surface roughness of the member itself may be reduced by “mirror finish”, “titanium mirror finish” or the like to increase the smoothness, and a film such as glass may be coated thereon to obtain a mirror finish. . On the other hand, a desired shape may be obtained by processing a member on a sheet metal that has been mirror-finished in advance.

(Example)
A steel plate having a thickness x of 1.6 mm was deformed and cut with a press machine to obtain a shape having a height h1: 9 mm, a height h2: 14 mm, and a width w: 15 mm. After that, the surface facing the film is polished with “bright nickel-chrome plating” and “# 1000 buffing”
, And physical polishing by “wet polishing” was performed to obtain a rigid stay for pressurization of this example.

  By adopting the above shape, the closest distance (A in FIG. 4) between the film and the pressurizing rigid stay was 2.5 mm. In addition, the surface emissivity ε of the mirror surface portion of the pressurizing rigid stay of this example was as extremely low as 0.01, and a mirror surface with extremely good gloss was obtained.

  The pressurizing rigid stay manufactured as described above was applied as the pressurizing rigid stay 20 of the fixing device of the image forming apparatus shown in FIGS.

  Table 1 shows the evaluation results when an image is output after a predetermined start-up time from the cold state in a low temperature environment. Also shown is the result when the device is made faster. However, when the speed of the apparatus was increased, the control temperature was set high in order to ensure fixability.

As comparative examples, steel sheets shown below as comparative examples 1 to 3 were used in which a pressurizing rigid stay was formed without applying a mirroring treatment.
Comparative Example 1: A commonly used electrogalvanized steel sheet.
Comparative Example 2: A steel sheet whose surface was mud to improve absorption of radiant heat, which was blackened by carbon coating.
Comparative Example 3: A bright stainless steel plate as a general glossy plate such as bright aluminum or bright stainless steel.

  As can be seen from Table 1, in Comparative Example 1, there is no problem such as an image defect at the start-up time of 15 seconds, but when the start-up time is shortened to 8 seconds, a fixing defect occurs and the image defect is became. In the case where the speed was further increased, image defects similarly occurred.

  In Comparative Example 2, even when the start-up time was 15 seconds, a slight fixing failure occurred, and the image defect was Δ level. Furthermore, when the start-up time was shortened to 8 seconds or when the speed was increased, an image defect occurred.

  In Comparative Example 3, there is no problem when the start-up time is 15 seconds, but when the start-up time is shortened to 8 seconds, a slight fixing failure occurs, resulting in an image defect Δ. When the speed was further increased, fixing failure occurred and x level image failure occurred.

  On the other hand, in the case of this example, even when the start-up time was shortened to 8 seconds or even when the speed was further increased, a good image without image failure due to fixing failure could be obtained.

FIG. 6 is a result of confirming the temperature change when measuring the temperature of each part at the time of startup from the cold state in a low temperature environment (10 ° C.) as a confirmation of the effect with respect to the present embodiment. FIG. 6 shows a setup time (8 to 15 seconds) in which image evaluation was actually performed in order to clarify the difference.
On the other hand, a comparison was made when the heater back surface was set to 200 ° C. and rotated for a relatively long time of 120 seconds. The temperature measurement point is the closest point (B in FIG. 4) between the surface on the upstream side of the nip portion of the film and the film on the film side of the pressurizing rigid stay.

  For temperature measurement, measurement was performed by attaching an infrared radiation thermometer and a thermocouple. Since the measurement by attaching the thermocouple may have an effect of responsiveness or the like, the influence was measured individually, and after correcting each, the actual member temperature was confirmed.

  As can be seen from FIG. 6, the film directly heated from the heater may have a low heat capacity, and rapidly rises to the vicinity of the temperature control temperature as it starts up. On the other hand, it can be seen that the pressurizing rigid stay having a large heat capacity and indirectly heated is basically difficult to raise the temperature.

  Further, it can be confirmed that there is a difference between the temperature increase of the film and the temperature increase of the rigid stay for pressurization in this example and the comparative example. As the tendency, it can be seen that the higher the temperature rise of the pressurizing rigid stay, the lower the temperature of the film. From these trends, it is considered that the amount of heat used for raising the temperature of the pressurizing rigid stay becomes a loss and the rate of temperature rise of the film is slow.

In general, the following factors can be considered as factors for increasing the temperature of the pressurizing rigid stay.
-Heat transfer by increasing the temperature of the contact part that is in contact with the heater side via the film guide.
Convective heat transfer due to the temperature rise of the air layer interposed in the space between the film and the pressurizing rigid stay accompanying the temperature rise of the film.
・ Temperature rise due to radiant heat from the film by approaching the heated film.

  Of these, in a short time range such as when starting up, radiation that directly radiates and exchanges heat rather than the effect of convection heat transfer due to heat transfer at the contact area or air layer temperature rise. The influence of heat is great. In general, the effect of heat transfer by radiant heat is greater when the temperature difference between the target members is larger. Therefore, as can be seen from FIG. 6, it is understood that the temperature difference between the film and the pressurizing rigid stay is large when starting from the cold state, and the influence of this radiant heat becomes significant. This can be confirmed from a temperature rise experiment in a vacuum chamber.

  Therefore, as described above, a part of the heat accompanying the temperature rise of the film is used as the radiant heat for raising the temperature of the rigid stay for pressurization. It seems that the rate of temperature rise is slow.

  In addition, the film temperature is in an equilibrium state with a set temperature relatively quickly by temperature control, whereas the temperature of the pressurizing rigid stay is not in an equilibrium state in a short time. That is, the temperature of the pressurizing rigid stay is considerably different between the image output from the cold state and the image output in the hot state such as during intermittent printing. However, the fixability significantly affects the film temperature, but hardly affects the temperature of the pressurizing rigid stay. For this reason, even if the temperature of the pressurizing rigid stay is different, it is possible to ensure a certain fixing property by controlling the film temperature.

  Here, paying attention to the rise time of 8 to 15 seconds in which the image evaluation was performed, it can be seen that the film temperature of the comparative example is still in the process of raising the temperature, particularly in the vicinity of 8 seconds.

That is, in the case of startup from a cold state in a low-temperature environment, the comparative example cannot maintain a sufficient temperature to secure the amount of heat necessary for fixing, so if the startup time is shortened to 8 seconds, An image defect occurs due to a fixing defect. Therefore, when the speed of the apparatus is increased, a larger amount of heat is required, so that it is considered that image defects have occurred remarkably.

  On the other hand, in this embodiment, since the film facing portion of the pressurizing rigid stay is a mirror surface, the temperature rise of the pressurizing rigid stay can be suppressed by reflecting the radiant heat of the film, and the heat loss of the film can be reduced. For this reason, the film temperature is rapidly increased.

  Therefore, even when the start-up time is shortened to 8 seconds as in this embodiment, the film temperature can be sufficiently raised, and a sufficient amount of heat necessary for fixing can be secured. For this reason, it is possible to obtain a good image having no image defect due to a fixing failure even when the speed of the apparatus is increased.

  As described above, the present embodiment is characterized by using a pressurizing rigid stay in which the surface facing the film 16 is mirror-finished. As a result, it is possible to suppress the temperature rise of the pressurizing rigid stay that does not directly contribute to the fixing property due to the radiant heat from the film, and to suppress the heat loss at the time of start-up and improve the thermal efficiency. it can. As a result, it is possible to quickly raise the temperature of the film at the time of start-up, and it is possible to ensure a sufficient amount of heat necessary for fixing before passing paper.

  Therefore, even when the start-up time is shortened or the speed of the apparatus is increased, it is possible to obtain a good image without image defects such as fixing failure when outputting an image from a cold state in a low temperature environment.

  In particular, the mirror surface can suppress the exchange of heat due to radiation, so that it is effective in suppressing heat loss particularly when starting from a cold state where the temperature difference is large.

  In addition, since a new member is not required to achieve efficiency, such as providing a heat insulating member between the film and the pressurizing rigid stay, the configuration can be simplified.

(Modification)
This modification is intended to further shorten the startup time by downsizing the apparatus and reducing the amount of heat.

  That is, the diameter of the film and the pressure roller is reduced with respect to the above embodiment, and the pressure rigid stay is formed in a shape having a height h1: 8 mm, a height h2: 12 mm, and a width w: 15 mm. The distance between the film and the film was 1.0 mm.

  Also in this modification, the image is output by applying as a pressurizing rigid stay of the fixing device of the image forming apparatus shown in FIGS.

  As a comparative example, an electrogalvanized steel sheet was used that was formed into the same shape as that of the modified example without using a mirror finish (Comparative Example 4).

  Table 2 shows the evaluation results when an image is output after a predetermined start-up time from the cold state in the low temperature environment using the heating device of this modification. Also shown is the result when the device is made faster. However, when the speed of the apparatus was increased, the control temperature was set high in order to ensure fixability.

  As can be seen from Table 2, in Comparative Example 4, there is no problem such as an image defect at the start-up time of 10 seconds, but when the start-up time is shortened to 5 seconds, a fixing defect occurs and the image defect is became. In the case where the speed was further increased, image defects similarly occurred.

  On the other hand, in the case of this modification, even when the start-up time was shortened to 5 seconds or when the speed was further increased, a good image without image failure due to fixing failure could be obtained.

  Also in this modification, when the film surface temperature and the temperature of the pressurizing rigid stay were confirmed, in Comparative Example 4, the temperature rise of the pressurizing rigid stay was larger and the film temperature tended to be lower. .

  Therefore, by making the film facing surface portion of the pressurizing rigid stay a mirror surface, it is possible to suppress the temperature rise of the pressurizing rigid stay at the time of start-up and to improve the thermal efficiency with respect to the temperature rise of the film. As a result, even when starting up from a cold state in a low-temperature environment, it is possible to prevent the occurrence of image defects such as fixing defects, and to increase the speed of the apparatus.

  In addition, since the closest distance between the film and the pressurizing rigid stay can be reduced, it is possible to reduce the size such as a smaller diameter and realize a lower heat capacity.

  Therefore, it is possible to further shorten the startup time.

  As described above, according to the present embodiment, the film heating type image heating apparatus is configured as described above, and in particular, even when starting up from a code state in a low temperature environment, It is possible to suppress the heat loss by suppressing the temperature rise in the portion not directly related to the heating. As a result, a shorter start-up time can be achieved.

  Therefore, even when the speed of the apparatus is increased, it is possible to obtain a good image without image defects such as fixing defects. Further, since heat loss can be suppressed, power saving can be achieved.

  On the other hand, since the proximity distance between the rotating body (film) and the reinforcing member (pressurizing rigid stay) can be shortened, downsizing is also possible.

  Furthermore, compared with the structure etc. which arrange | position a heat insulation member inside a rotary body (film), the improvement of thermal efficiency can be achieved with a simple structure. Therefore, the cost can be reduced and the assembly process can be simplified.

[Embodiment 2]
FIG. 7 is a schematic cross-sectional view of the main part of the fixing device according to the second embodiment of the present invention.

  The fixing device of the present embodiment is characterized in that, in addition to the fixing device of the first embodiment, a cover body 30 as a cover member that covers the film 16 is provided on the outer surface (outer periphery) side of the film 16. In the present embodiment, the cover body 30 has a shape substantially opposite to the film 16 and is provided so as to be disposed close to the film 16.

  The surface 30a of the portion of the cover body 30 facing the film 16 is a mirror surface (mirror surface state) like the surface 20a of the pressurizing rigid stay 20 described above.

  In the present embodiment, a gloss-plated steel plate having a thickness of 0.5 mm is processed by a press machine, and a cover 30 is obtained as a molded body having a desired shape and surface property by mirror finishing.

  The cover body 30 may be a member in which at least the surface (part) facing the film 16 is a mirror surface, and the material such as a metal such as a steel plate or a heat resistant resin is not particularly limited. . Further, a heat insulating member or the like having poor thermal conductivity is preferable because it can prevent diffusion of heat to the outer surface side that is opposite to the film surface side through the cover body 30.

  The shape of the cover body 30 is preferably a shape that reduces the escape of reflected heat from the opening such as the entrance / exit of the nip. In the present embodiment, the film surface is substantially reflected on the film surface to reflect the radiant heat from the film 16 to the film side. The shape was opposed.

  By setting it as such a structure, the spreading | diffusion of the heat to the outer peripheral side by the radiant heat of the film 16 can be suppressed. Therefore, in addition to the effect of the first embodiment, the effect that the film temperature can be raised more rapidly than the case of the first embodiment is obtained.

  That is, the radiant heat toward the outside of the film 16 is reflected by the cover body 30 having a mirror surface and returned to the film side, so that heat loss can be reduced and the film itself can rise faster than the open system. Can be warmed. As a result, the start-up time can be shortened, and even when the speed of the apparatus is increased, a good image free from image defects can be obtained.

  Further, when a heat insulating member is used as the cover body 30, it is possible to suppress the temperature rise of the cover body (housing) itself, so that it is not necessary to provide a protective member for heat protection, and the configuration is simplified. Can be Therefore, the cost can be reduced and the assembly process can be simplified.

  In this embodiment, image evaluation was performed in the same manner as in Embodiment 1. As a result, even when the speed was increased, no defective image was generated, and a good fixed image was obtained.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a schematic front view of a fixing device according to a first embodiment of the present invention. 1 is a schematic longitudinal sectional view of a fixing device according to Embodiment 1 of the present invention. 1 is a schematic cross-sectional view of a fixing device according to Embodiment 1 of the present invention. It is a schematic cross-sectional view of the pressurizing rigid stay according to the first embodiment of the present invention. It is a figure which shows the temperature change of each part in the Example of Embodiment 1 of this invention. FIG. 6 is a schematic cross-sectional view of a fixing device according to a second embodiment of the present invention.

Explanation of symbols

16 Film 18 Film Guide 19 Elastic Pressure Roller 20 Pressing Rigid Stay 20a Surface 100 Fixing Device N Nip Portion

Claims (7)

A rotating body having flexibility;
A support member that has a sliding surface that slides with an inner peripheral surface of the rotating body, is provided inside the rotating body, and supports the rotating body;
A reinforcing member that is provided inside the rotating body and reinforces the supporting member;
A pressure member that forms a nip portion with the sliding surface of the support member via the rotating body;
Have
In an image heating apparatus that heats the recording material by nipping and conveying the recording material on which the developer image is formed in the nip portion,
The image heating apparatus according to claim 1, wherein at least a surface of a portion of the reinforcing member facing the inner peripheral surface of the rotating body is formed in a mirror state. A cover member that covers the rotating body on an outer peripheral side of the rotating body;
The image heating apparatus according to claim 1, wherein a surface of at least a portion of the cover member facing the rotating body is formed in a mirror state.   The image heating apparatus according to claim 1, wherein a heater is provided at a portion of the sliding surface of the support member where the nip portion is formed.   The image heating apparatus according to claim 3, wherein the heater is a ceramic heater.   5. The image heating apparatus according to claim 1, wherein an emissivity of the surface of the reinforcing member formed in a mirror surface state is 0.2 or less. The reinforcing member has a contact portion that comes into contact with the supporting member when the supporting member and the reinforcing member are assembled.
6. The image according to claim 1, wherein the contact portions are provided upstream and downstream of the nip portion so as to sandwich the nip portion in the recording material conveyance direction. Heating device.   The said reinforcement member has comprised the shape where the plate-shaped member was bent, and is provided with the curved part which connects the said contact part provided in the upstream and the downstream of the said nip part, respectively. Image heating device.

Images