JP2006134747A - Heating body, heating device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To strengthen strength of a heating body using a carbon based resistance heating element. <P>SOLUTION: This heating body is composed of at least a substrate 3b, the carbon based resistance heating element manufactured by heat treating a raw material containing at least an organic substance in a non-oxidizing atmosphere to carbonize the organic substance by using carbon as a conductive material, and electrodes 3c, 3d to feed the carbon based resistance heating element 3a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heating body used in a heating device that heats a material to be heated to a predetermined temperature, and a heating device including the heating body. In particular, in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, a heating apparatus suitable for use as a heating and fixing apparatus that heats a recording material on which an unfixed toner image is formed and supported to fix the image as a permanently fixed image It is about. The present invention also relates to an image forming apparatus equipped with the heating device.

  In general, in various types of information, video equipment, and the like, an image forming apparatus that specifically substantiates an image in an intangible information format on a recording material such as paper is used as its final output form.

  In such an image forming apparatus such as a copying machine, a coloring agent or the like is fixed on a recording material according to an image pattern by drawing or drawing, scanning or recording an object, or generating an image generated by communication transfer or the like. By doing so, an appropriate image is reproduced on the recording material.

  Further, in this image forming apparatus, fine toner powder is used as a colorant, and in order to stably fix the toner arranged in an image pattern on the recording material, a heating method is used for simplicity and the like. Widely used.

  Conventionally, a heat roller type fixing device has been widely used as a fixing device as a heating device. However, such a fixing device takes a long time to start operation and consumes a relatively large amount of power. Inconvenience occurred.

  In other words, this fixing device has a structure in which a halogen lamp is disposed inside a metal roller, and the halogen lamp generates heat to heat the entire metal roller. Since it takes time until it becomes possible, the time required for start-up of the operation is slow, and the entire metal roller having a relatively large heat capacity is always heated, so that power consumption is also increased.

  Therefore, a resistance heating element pattern is directly formed on a ceramic substrate having excellent heat resistance and durability to form a heating element, which is used as a heat source, and through a thin heat resistant film. A heating device of a film heating system that uniformly heats a recording material by bringing it into contact with a recording material on which an unfixed toner image is formed and supported has been proposed and disclosed in Patent Document 1.

  Further, as disclosed in Patent Document 2, as a film heating type heating device, the film is loosely fitted on a film guide, and the pressure roller as a pressure unit is driven to drive the film to the pressure roller. There is also a tension-free type that is driven in response to this. In this type, this method is often adopted because the number of parts is small.

  According to such a film heating type heating apparatus, since the heat capacity of the heating body and the film itself is small, it is possible to shorten the time required to raise the temperature up to a predetermined temperature and to reduce power consumption.

  Patent Document 3 discloses a carbon-based resistance heating element having any necessary specific resistance value and shape and a manufacturing method thereof.

Patent Document 4 discloses a fixing device using such a carbon resistance heating element.
JP-A-63-313182 JP-A-4-44075 Japanese Patent No. 3173800 JP 2002-372880 A

  In recent years, copying machines and printers using an electrophotographic system have greatly increased the number of printable sheets per unit time, and the speed of image forming apparatuses has been increased. At the same time, in order to achieve on-demand, so-called first printout time (hereinafter abbreviated as FPOT), which shortens the output time of the first sheet, is also being promoted.

  In order to shorten the FPOT, there is a method using a carbon resistance heating element that has a quick rise in heat generation, but the strength of the carbon resistance heating element itself is weak, and it breaks down when a large pressure is applied to the fixing device. I had to do it.

  Accordingly, an object of the present invention is to increase the strength of a heating body using a carbon-based resistance heating element.

  In addition, with regard to a heating device using a heating body using a carbon resistance heating element and an image forming apparatus using the heating device, the reliability and durability of the apparatus is improved by increasing the strength of the heating body using the carbon resistance heating element. The purpose is to improve the properties.

  A typical configuration of the heating body according to the present invention for achieving the above object is that the heating body used in a heating device for heating a material to be heated uses at least a base material and carbon as a conductive material, and at least Heating comprising: a carbon-based resistance heating element manufactured by heat-treating a raw material containing an organic substance in a non-oxidizing atmosphere of carbon to carbonize the organic substance; and an electrode for supplying power to the carbon-based resistance heating element The body.

  That is, the presence of the base material makes it possible to increase the strength of the heating body itself using the carbon resistance heating element.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is a laser beam printer using a transfer type electrophotographic process.

  Reference numeral 101 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier. For example, an organic photosensitive drum in which a photosensitive layer such as an organic photoconductor is formed on the outer peripheral surface of a conductive drum base such as aluminum. The photosensitive drum 101 is driven to rotate at a predetermined speed in the clockwise direction of the arrow.

  Reference numeral 102 denotes a charging roller as charging means. The charging roller 102 uniformly charges the photosensitive drum surface to a predetermined polarity and potential. The printer of this example is uniformly charged to a predetermined negative potential.

  Reference numeral 103 denotes a laser exposure apparatus. The laser exposure apparatus 103 outputs a laser beam L modulated in accordance with a time-series electric digital pixel signal of image information input from an external device (host device) such as an image scanner / computer (not shown), and a photosensitive drum 101. The uniformly charged surface is subjected to scanning exposure. This scanning exposure attenuates or eliminates the charge in the exposed bright portion of the photosensitive drum surface, and an electrostatic latent image corresponding to the image information scanned and exposed on the photosensitive drum surface is formed.

  Reference numeral 104 denotes a developing device. The electrostatic latent image formed on the surface of the photosensitive drum is visualized as a toner image by the developing device. In the case of a laser beam printer, a reversal development method is generally used in which toner is attached to the exposed bright portion of an electrostatic latent image for development. Reference numeral 104a denotes a developing sleeve, 104b denotes a developing blade, 104c denotes a developing bias application power source, and t denotes one-component magnetic toner.

  Reference numeral 107 denotes a paper feed cassette in which recording materials (transfer materials) P are stacked and stored. Based on the paper feed start signal, the paper feed roller 108 is driven and the recording material P in the paper feed cassette 107 is separated and fed. The fed recording material P passes through the sheet path 109 → registration roller 110 → top sensor 111 and is introduced at a predetermined control timing into a transfer portion T which is a contact nip portion between the photosensitive drum 101 and the transfer roller 112. Is done. In other words, when the leading end portion of the toner image on the photosensitive drum 101 reaches the transfer position T, the conveyance timing of the recording material P is controlled by the registration roller 110 so that the leading end portion of the recording material P also reaches. Further, the image writing timing to the photosensitive drum 101 is controlled based on the recording material leading edge detection signal from the top sensor 111.

  The recording material P introduced into the transfer portion T is nipped and conveyed by the transfer portion T. During this time, a transfer bias having a predetermined potential opposite to the toner charging polarity is applied to the transfer roller 112 from the transfer bias applying power source 112a. The As a result, the toner image on the photosensitive drum surface side is electrostatically transferred sequentially onto the recording material surface at the transfer portion T.

  At the transfer portion T, the recording material P that has received the transfer of the toner image is separated from the surface of the photosensitive drum, is conveyed through the sheet path 113 to the fixing device 114 that is a heating device, and undergoes heat fixing processing of the toner image. .

  On the other hand, the surface of the photosensitive drum after separation of the recording material (after transfer of the toner image to the recording material) is cleaned by the cleaning blade 105a of the cleaning device 105 after removing the transfer residual toner and paper dust and the like, and repeatedly. It is used for image creation.

  Further, the recording material P that has passed through the fixing device 114 passes through the sheet path 115 and is discharged from the discharge port 116 onto the discharge tray 117 on the upper surface of the printer.

  In the printer of this example, the photosensitive drum 101, the charging roller 102, the developing device 104, and the cleaning device 105 are configured as a process cartridge 106 that is detachable / replaceable with respect to the printer body. is there.

(2) Fixing device 114
FIG. 2 is a schematic cross-sectional view of a main part of the fixing device 114 in this embodiment. FIG. 3 is a perspective model view of the main part. The fixing device 114 is a tensionless type film heating type heating device disclosed in Japanese Patent Application Laid-Open Nos. 4-44075 to 44083, Japanese Patent Application Laid-Open No. 4-20420 to 204984, and the like.

  A tensionless type film heating type heating device uses an endless belt-like or cylindrical heat-resistant film as a flexible member, and at least part of the circumference of the film is always tension-free (in a state where no tension is applied). The film is a device that is driven to rotate by the rotational driving force of the pressure member.

  Reference numeral 1 denotes a stay as a heating body support member / film guide member, which is made of a heat-resistant resin having a semi-circular saddle-shaped cross section with a longitudinal direction in a direction crossing the recording material conveyance direction a on the conveyance path surface of the recording material P. It is a member. In this example, a high heat-resistant liquid crystal polymer was used as the material of the stay 1. 4A is a front view of the stay 1, and FIG. 4B is a bottom view (bottom view).

  Reference numeral 3 denotes a heating body, which is fixedly supported by being fitted into a groove 1a provided on the lower surface of the stay 1 along the length of the stay. The heating element 3 uses a carbon-based resistance heating element. The configuration of the heating element 3 will be described in detail in the next item (3).

  Reference numeral 2 denotes a cylindrical film having excellent heat resistance as a flexible member, and is externally fitted to the stay 1 that supports the heating body 3. The inner peripheral length of the film 2 and the outer peripheral length of the stay 1 including the heating body 3 are larger than the film 2 by, for example, about 3 mm. Therefore, the film 2 is loosely fitted with a margin in the peripheral length. .

  In order to reduce the heat capacity and improve the quick start property, the film 2 has a total thickness of about 100 μm or less and has PTFE, PFA, FEP having heat resistance, releasability, strength, durability, etc. Or a composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of polyimide, polyamideimide, PEEK, PES, PPS or the like. In this example, the heat resistant film 2 was coated with a polyimide film of 50 μm, PTFE of 10 μm, and a layer thickness of 60 μm. The inner peripheral surface side of the film 2 is coated with grease in order to improve slidability.

  Reference numeral 4 denotes a reinforcing member having a transverse U-shaped rigidity. The inside of the stay 1 is inserted and arranged. In FIG. 3, the pressure member 4 is omitted.

  The stay 1, the heating body 3, the film 2, the reinforcing member 4, and the like constitute a heating member (heating assembly) 1A.

  Reference numeral 6 denotes an elastic pressure roller as a pressure member. The pressure roller 6 of this example is a core metal 6a made of iron, stainless steel, aluminum, or the like having an outer diameter of 13 mm, coated with a silicone foam having a length of 240 mm and a thickness of 3 mm as a heat-resistant elastic layer 6b. It is. Then, the film 2 is sandwiched between the heating member 1 on the heating member 1A side and pressed with a predetermined pressing force against the elasticity of the heat resistant elastic layer 6b to form a fixing nip portion N having a predetermined width. ing. The nip width is a dimension of the fixing nip portion N in the recording material conveyance direction a.

  The pressure roller 6 is driven to rotate at a predetermined peripheral speed in the counterclockwise direction indicated by an arrow by transmitting the driving force of the driving mechanism M to a drive gear G provided at the end of the metal core. When the pressure roller 6 is driven to rotate, a rotational force acts on the film 2 by a frictional force between the pressure roller 6 and the outer surface of the film in the fixing nip N, and the inner surface of the film 2 is a heating body in the fixing nip N. 3, while being in close contact with and sliding on the surface of a carbon-based resistance heating element (described later), the outer periphery of the stay 1 is driven to rotate in the direction of the arrow in the direction of the arrow at substantially the same peripheral speed as that of the pressure roller 6. The stay 1 also serves as a guide member for the film 2 that is driven to rotate.

  Then, in a state where the temperature of a carbon-based resistance heating element, which will be described later, of the heating element 3 rises to a predetermined level and the rotational peripheral speed of the film 2 is stabilized by the rotation of the pressure roller 6, the heating element 3 A recording material P to be image-fixed as a material to be heated is introduced from a transfer portion T into a fixing nip N formed by the pressure roller 6. Then, when the recording material P is nipped and conveyed together with the film 2 through the fixing nip portion N, the heat of the heating body 3 is applied to the recording material P through the film 2 and an unfixed visible image (toner on the recording material P). The image (t) is heat-fixed on the surface of the recording material P. The recording material P that has passed through the fixing nip N is separated from the surface of the film 2 and conveyed.

(3) Heating body 3
5 and 6 are a perspective model view and an exploded perspective model view of the heating element 3 in this embodiment. This heating body 3 is an elongated member having a longitudinal direction as a longitudinal direction with respect to the conveyance direction a of the recording material P as a material to be heated, and contains at least an organic substance using the base material 3b and carbon as a conductive material. A carbon resistance heating element (hereinafter also abbreviated as a heating element) 3a manufactured by heat-treating the raw material to be heated in a non-oxidizing atmosphere of carbon to carbonize the organic substance, and an electrode for supplying power to the heating element 3a It consists of 3c and 3d.

  With respect to the carbon-based resistance heating element 3a, the raw material containing organic matter is heat-treated at a predetermined temperature in a non-oxidizing atmosphere of carbon to suppress decomposition and disappearance due to carbon oxidation, and carbonization and graphitization of the raw material. The carbon in the heat-treated product can be controlled as a resistance heating element to have a structure having appropriate resistance value and resistance temperature characteristics. By using such a carbon resistance heating element, it is possible to reduce the temperature rise of the non-sheet passing portion of the heating device. The startup time of the apparatus can be shortened. Along with this, it is possible to realize a reduction in cost by improving the throughput of the image forming apparatus, specifications such as FPOT, and using heat-resistant grade down parts.

  In this embodiment, as the organic substance to be carbonized in particular, an organic substance that exhibits a carbonization yield of 5% or more by baking in a non-oxidizing atmosphere, for example, a reduced pressure environment or a vacuum, or an inert gas such as nitrogen gas or argon. Used, chlorinated vinyl chloride resin, polyvinyl chloride, polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride-polyvinyl acetate copolymer, polyamide and other thermoplastic resins, phenol resin, furan resin, epoxy resin, Saturated polyester resin, thermosetting resin such as polyimide, lignin, cellulose, tragacanth gum, gum arabic, natural polymer substance having condensed polycyclic aromatics such as sugars in the basic structure of the molecule, and naphthalene not contained above Basic structure of condensed polycyclic aromatics such as formalin condensate of sulfonic acid and copna resin Synthetic polymer materials having the like.

  The non-oxidizing atmosphere of carbon is an atmosphere or a vacuum reduced from the normal pressure, or in a nitrogen gas or an inert gas. Oxidation can be reliably prevented, and a carbon-based resistance heating element can be stably produced.

  The carbonization yield here is the weight ratio of the weight of the carbonized material (composite such as graphite or amorphous carbon) remaining by heat treatment in a non-oxidizing atmosphere to the organic material before heat treatment. In addition, when heat treatment is performed in an oxidizing atmosphere, depending on the type of organic material used, oxidation generally starts from a temperature of 500 ° C. to 700 ° C., so carbon does not decompose or burn, and the temperature can be raised further. Sufficient carbonization does not proceed (components other than carbon are not sufficiently decomposed and graphitization does not proceed), so that a stable carbonized material that can use carbon as a resistance heating element cannot be obtained. The kind and amount of the composition to be used are appropriately selected depending on the shape of the heating element, and can be used as one kind or a mixture of several kinds.

Carbon powder may be mixed in advance with organic matter. Examples of the carbon powder here include carbon black, graphite, coke, etc., depending on the resistance value and shape of the heating element. It is possible to use. In this case, electrons flow in the carbon powder mixed beforehand and in the organic material carbonized by heat treatment. Usually, when only the composition is heat-treated, there are few things that obstruct the electrons flowing through the carbon, the resistance value becomes too low (1.0 × 10 ⁻³ Ω · cm or less), and current easily flows. Therefore, it becomes difficult to design the energization circuit and control the energization of the heating element.

  As a countermeasure, it is necessary to reduce the cross-sectional area of the heating element and increase the resistance value, which limits the shape of the heating element. Therefore, it is desirable to heat-treat the mixture obtained by mixing an insulating or semiconductive substance with respect to the organic substance in the previous period. Insulating and semiconducting materials are preferably metal carbides, metal borides, metal silicides, metal nitrides, metal oxides, semimetal nitrides, semimetal oxides, and semimetal carbides, depending on the resistance value and shape of the heating element. It is selected and one kind or a mixture of several kinds can be used. The above mixture has not only carbon but also insulation and semi-conducting substances that inhibit the conduction of electrons that flow through the carbon, so the resistance value can be easily controlled and the shape that the heating element can take Of freedom.

  That is, an organic substance to be carbonized by heat treatment, and at least one or several kinds of insulating or semiconductive substances are mixed with this organic substance, and after molding this, a carbon-based resistance is obtained by a heat treatment in a non-oxidizing atmosphere of carbon. By making the heating element 3, it is possible to more easily control the resistance temperature characteristics, resistance value, shape of the heating element, and the like, and a heating and fixing device capable of stably suppressing the temperature rise of the non-sheet passing portion. Can be provided.

  Such a carbon-based resistance heating element 3a uses a crystallite or a polycrystal of graphite, and is filled with at least an insulating or semiconductive conductivity inhibiting substance except for a contact surface between crystallites. In the temperature range below the maximum use temperature of the heating device, the conduction of electrons between crystallites is due to contact between crystallites or conduction due to the tunneling effect of electrons between crystallites than other conduction between crystallites. Is also dominant.

  Further, boron nitride, alumina, silicon carbide, boron carbide or the like is recommended as the insulating material or semiconductive material. By using such a substance, the resistance value of the heating element can be easily controlled.

  Moreover, it is preferable that the heat processing temperature at the time of the heat processing of the said carbon-type resistance heating element is 850 degreeC or more and 1750 degrees C or less. By performing heat treatment at the above temperature, the resistance change rate of the carbon resistance heating element can be made near zero or negative, and the resistance value of the carbon resistance heating element can be adjusted to a practical resistance value. Therefore, it is possible to provide a heat fixing device that suppresses the temperature rise of the non-sheet passing portion and does not have excessive or insufficient power.

  In general, the resistance value of a heating element of a film heating type fixing device in a laser beam printer is in the range of 3Ω or more and 250Ω or less considering that it is connected to a general household power source. desirable. If it is 250Ω or more, it is difficult to obtain electric power necessary for fixing, and if it is 3Ω or less, the energization control mechanism for the heating element becomes complicated.

  The heat generating element made in this way is characterized by high on-off and high on-off speeds and high responsiveness.

  In this embodiment, the heating element 3a is made by mixing and dispersing chlorinated vinyl chloride resin, graphite and boron nitride, firing at 1500 ° C. after molding, length 250 mm × width 5 mm × thickness 0.5 mm, total resistance value. 30Ω.

  The base material 3b is installed on the side opposite to the side in contact with the film 2 of the heating element 3a in order to increase the strength of the heating element 3a itself. In this embodiment, the substrate 3b is a liquid crystalline wholly aromatic polyester resin. The size is 250 mm long × 5 mm wide × 0.5 mm thick and is the same as the heating element 3a.

  The heating element 3a and the base material 3b are each molded and fired independently, and then bonded with a thermosetting resin or the like. Depending on the material of the base material and the firing temperature of the base material, the heating element 3a and the base material 3b may be At the same time, it can be molded, baked and bonded.

  Further, depending on the configuration of the fixing device, the heating element 3a may be simply placed on the substrate 3b without being bonded. In this example, the heating element 3a and the base material 3b were each molded separately, and then bonded with an epoxy resin.

  As a result, the size of the heating element 3 (3a + 3b) used in this example is 250 mm long × 5 mm wide × 1 mm thick.

  In this embodiment, the power supply electrodes 3c and 3d are formed by forming silver palladium screen printing patterns on both longitudinal end surfaces of the heat generating element 3a.

  The heating element 3 has the heating element 3a exposed to the outside and is fitted into the groove 1a on the lower surface of the stay 1 to be fixedly supported. FIG. 7 is a bottom view of the stay 1 in which the heating body 3 is fitted and fixedly supported in the groove 1a. The heating body 3 is disposed on the stay 1 so that the direction perpendicular to the recording material conveyance direction a is the longitudinal direction.

  Reference numeral 5 denotes a temperature detection element (temperature detection element) that detects the temperature of the heating element 3a of the heating element 3. In this embodiment, an external contact type thermistor separated from the heating body 3 is used as the temperature detection element 5. The external contact type thermistor 5 is provided with a heat insulating layer on a support, for example, and a chip thermistor element is fixed on the support, and the element is directed downward (on the back side of the heating element) to the back side of the heating element by a predetermined pressure. It is configured to abut. A high heat-resistant liquid crystal polymer was used as the support, and ceramic paper was laminated as the heat insulating layer.

  In this embodiment, as shown in FIG. 8, the thermistor is provided in the through hole 1 b provided in the bottom surface of the heating body insertion groove 1 a of Ste-1, and the corresponding through hole 3 b 1 provided in the base material 3 b of the heating body 3. 5 is inserted and directly contacted with the back surface of the heating element 3a of the heating element 3.

  By adopting the above configuration, it is possible to shorten the time until the target fixing temperature is reached, and quick start is possible.

  FIG. 9 is a block diagram of a power supply control circuit system as power supply control means for the heating element 3. Reference numerals 7 and 8 denote power supply connectors, which are fitted to the power supply electrodes 3c and 3d on both ends of the heating element 3a of the heating body 3 fixedly supported on the stay 1, and are respectively connected to the power supply electrodes 3c and 3d. The electrical contacts on the 7 and 8 sides are in contact. The power feeding connectors 7 and 8 are connected to the power feeding unit via a power feeding cable.

  The heating element 3a is heated between the electrodes 3c and 3d from the commercial power supply (AC power supply) 13 via the triac 12, and the effective heat generation full length region in the longitudinal direction generates heat and rapidly rises in temperature. The temperature of the heating element 3 a is detected by the thermistor 5, and the output of the thermistor 5 is taken into the power supply control unit (CPU) 11 via the analog / digital converter (A / D) 10. Based on the detected temperature information, the control unit 11 controls the temperature of the heating element 3a by controlling the power supplied to the heating element 3a of the heating element 3 by the triac 12 by phase control or wave number control. That is, when the temperature detected by the thermistor 5 is lower than a predetermined set temperature (fixing temperature), the temperature of the heating element 3a is increased. When the temperature detected by the thermistor 5 is higher than the predetermined temperature, the temperature of the heating element 3a is decreased. As described above, by controlling the electric power supplied to the heating element 3a, the temperature of the heating element 3a at the time of fixing is kept at a predetermined constant temperature. In this embodiment, the output is changed in 21 steps from 5 to 100% from 0 to 100% by phase control. The output of 100% is when the heating element is fully energized.

  Here, the paper width is a recording material dimension in a direction orthogonal to the recording material conveyance direction a on the plane of the recording material P. In the printer of this embodiment, the recording material passing is used as the center reference of the recording material center, and the center in the longitudinal direction of the heating body 3 of the fixing device is the conveyance center of recording materials of various sizes. In FIG. 9, O is the recording material center sheet passing reference line (virtual line). A is a sheet passing portion (maximum sheet passing portion) of a recording material having the maximum sheet width that can be used for this printer, and substantially corresponds to the effective total heat generation region in the longitudinal direction of the carbon-based resistance heating element 3a. B is a sheet passing portion (minimum sheet passing area) of a recording material having a minimum sheet width that can be used for the printer. C is a non-sheet passing portion generated in the recording material conveyance path surface when a recording material (small size paper) having a paper width smaller than that of the recording material having the maximum paper width is passed. The area width of the non-sheet passing portion C differs depending on the size of the small size paper that has been passed.

  The thermistor 5 for detecting the temperature of the heating element 3a is arranged corresponding to the heating element portion corresponding to the minimum sheet passing portion B which becomes the recording material passing area regardless of the recording material having a large or small paper width. It is set up.

(4) Cracking test of heating element 3a The heating element 3 was actually passed through the fixing device 114. The fixing device 114 is configured to apply a total applied pressure of 127.4 N (13 kgf) at both ends in the longitudinal direction in order to secure 7 mm as the nip width of the fixing nip portion N in the above configuration. In order to make the nip width along the length of the fixing nip portion N straight, the pressure roller 6 is bent due to the applied pressure at the center portion. Therefore, the stay 1 is crowned so that the pressure roller 6 is bent. It is common to correct. In this embodiment, a crown shape is provided 0.5 mm below the central portion, and the nip width along the length of the fixing nip portion N is 7 mm straight.

  As a comparative example, a heating element that is not provided with the base material 3b and is made of only the carbon resistance heating element 3a is incorporated in the fixing device 114, and 100 sheets are passed under the conditions of a process speed of 120 mm / s and a throughput of 20 ppm. went.

  Regarding the heating element 3 of Example 1, since the heating element 3a is provided with the base material 3b, the heating element 3a was not cracked. This is because the strength of the base material 3b itself is increased, so that the heat generating element 3a is destroyed even if a stress of 0.5 mm due to the crown shape of the stay 1 and a stress in the transport direction applied during paper feeding are applied. I never did.

  Cracks occurred in the heating element of only the heating element 3a of the comparative example. This is because the strength of the heating element 3a itself is so weak that it could not withstand the stress of 0.5 mm due to the crown shape of the stay 1 and the stress in the conveying direction applied during the sheet passing, and it was destroyed. When the bending strength of the heating element 3 (3a + 3b) of Example 1 was measured, it was 1.6 times the bending strength of the heating element of the comparative example (only the carbon resistance heating element 3a).

  From this result, it can be seen that the heating element 3 in which the base material 3b is installed on the carbon-based resistance heating element 3a has increased strength.

  Since the strength of the heating element 3 itself is increased by installing the base material 3b on the carbon-based resistance heating element 3a in this way, it is not broken even when it is incorporated in a fixing device and a large pressure is applied. is there.

  In the present embodiment, the material of the substrate 3b is a liquid crystalline wholly aromatic polyester, but the material is not limited to this as long as the same effect can be obtained. For example, PEEK, PES, etc., liquid crystal wholly aromatic polyester glass fiber mixed strengthening type, glass balloon, glass fiber mixed strengthening type and the like can be mentioned.

  Example 2 of the present invention will be described below. The feature of this example is that in Example 1, the base material 3b of the heating element 3 is replaced with liquid crystalline wholly aromatic polyester, and polyphenylene sulfide (PPS) is used. Otherwise, the same as in Example 1. Therefore, the entire configuration, description of the heating element, and configuration diagram are omitted.

  In the heating element 3 of this embodiment, the carbon-based resistance heating element 3a is prepared by mixing and dispersing chlorinated vinyl chloride resin, graphite and boron nitride, heat-treating at 1500 ° C. after molding, and length 250 mm × width 5 mm × thickness. The total resistance value was set to 0.5 mm.

  The base material 3b is installed on the opposite side in contact with the film 2 in order to increase the strength of the heating element 3a itself. In this example, PPS was used. The size is 250 mm long × 5 mm wide × 0.5 mm thick and is the same as the carbon-based resistance heating element 3a.

  In this example, the heating element 3a and the base material 3b were each molded separately, and then bonded with an epoxy resin. As a result, the size of the heating element 3 (3a + 3b) used in this example is 250 mm long × 5 mm wide × 1 mm thick.

  The heating body 3 was actually assembled into the fixing device 114 as Example 2 and paper was passed. In Example 2, since the throughput is higher than that in Example 1, it is necessary to widen the width of the fixing nip portion N to ensure the fixing property. The fixing device requires 8 mm as the width of the fixing nip portion N in order to ensure the same level of fixing performance as in the first embodiment. In order to ensure a nip width of 8 mm, a total pressure 147N (15 kgf) is applied at both ends in the longitudinal direction. In order to make the nip width along the length of the fixing nip portion N straight, the pressure roller 6 is bent due to the applied pressure at the center portion. Therefore, the stay 1 is crowned so that the pressure roller 6 is bent. It is common to correct. In this embodiment, a crown shape is provided 0.7 mm below the central portion, and the nip width along the length of the fixing nip portion N is 8 mm straight.

  Although 100 sheets were passed under the above conditions at a process speed of 120 mm / s and a throughput of 22 ppm, there was no problem because the heating element 3a of the heating element 3 did not break.

  Regarding the heating element 3 of Example 2, the heating element 3a is provided with a base material 3b (PPS) having a higher bending strength than the base material 3b (liquid crystalline wholly aromatic polyester) of the heating element 3 of Example 1. For this reason, the heating element 3a was not broken even when the stress of 0.7 mm due to the crown shape of the stay 1 larger than that of Example 1 and the stress in the conveyance direction applied during the sheet passing were applied. It is. The bending strength of the heating body 3 of Example 2 is 2.5 times the bending strength of the heating body of the comparative example.

  From this result, it can be seen that the strength of the carbon-based resistance heating element 3a on which the substrate 3b is installed is increased. If a stronger material is selected, the strength can be further increased, and the pressing force of the fixing device can be further increased.

  In the present embodiment, the material of the base material 3b is PPS, but the material is not limited to this as long as the same effect can be obtained. Further, the mixed material and the material ratio of the carbon-based resistance heating element 3a are not limited to this as long as the same effect can be obtained.

Embodiment 3 of the present invention will be described below. The feature of this example is that the base material 3b of the heating element 3 in Example 1 is replaced with liquid crystalline wholly aromatic polyester, and aluminum oxide (Al ₂ O ₃ ), which is an inorganic compound, is used. Since this is the same as that of the first embodiment, the entire configuration, description of the heating element, and configuration diagram are omitted.

  In this embodiment, the carbon-based resistance heating element 3a is a mixture of chlorinated vinyl chloride resin, graphite, and boron nitride, dispersed, heat-treated at 1500 ° C. after molding, length 250 mm × width 5 mm × thickness 0.5 mm, The total resistance value was 30Ω.

  The base material 3b is installed on the side opposite to the side in contact with the film 2 in order to increase the strength of the heating element 3a itself. In this embodiment, aluminum oxide was used. In this example, the heating element 3a and the base material 3b were each molded separately, and then bonded with an epoxy resin.

  As a result, the size of the heating element 3 (3a + 3b) used in this example is 250 mm long × 5 mm wide × 1 mm thick.

  Using the heating body 3 as Example 3, the fixing device 114 was actually assembled and paper was passed. In the third embodiment, since the process speed and the throughput are increased as compared with the first embodiment, it is necessary to widen the width of the fixing nip portion N to ensure the fixability. In the fixing device 114, the width of the fixing nip portion N needs to be 9 mm in order to ensure the same level of fixing performance as in the first embodiment. In order to secure a width of 9 mm at the fixing nip N, a total pressure 196N (20 kgf) is applied at both ends in the longitudinal direction. In order to make the nip width along the length of the fixing nip portion N straight, the pressure roller 6 is bent due to the applied pressure at the center portion. Therefore, the stay 1 is crowned so that the pressure roller 6 is bent. It is common to correct. In this embodiment, a crown shape is provided 0.9 mm below the central portion, and the nip width along the length of the fixing nip portion N is set to a straight 9 mm.

  Although 100 sheets were passed under the above conditions at a process speed of 140 mm / s and a throughput of 25 ppm, there was no problem because the carbon resistance heating element 3a of the heating element 3 did not break.

  Regarding the heating element 3 of Example 3, the heating element 3a is provided with a base material 3b (aluminum oxide (Al2O3)) having a higher bending strength than the base material 3b (PPS) of the heating element 3 of Example 2. In addition, the heating element 3a was not broken even when a stress of 0.9 mm due to the crown shape of the stay 1 larger than that of Example 1 and a stress in the conveyance direction applied during the sheet passing were applied. The bending strength of the heating body 3 of Example 3 is 3.3 times the bending strength of the heating body of the comparative example.

  From this result, it can be seen that the heating element 3 in which the base material 3b is installed on the carbon-based resistance heating element 3a has increased strength. If a stronger material is selected, the strength can be further increased, and the pressing force of the fixing device can be further increased.

In this embodiment, the base material 3b is made of aluminum oxide (Al ₂ O ₃ ), but the material is not limited to this as long as the same effect can be obtained. For example, mullite _{(3Al 2 O 3 · 2SiO 2} ), cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2), steatite (Mg · SiO _2), and the like.

[Others]
1) Other desired functional layers such as a heat-resistant lubricant layer can be added to the film sliding surface of the heating element 3a as necessary.

  2) The heating body 3 according to the present invention is not limited to use as a heating source in the film heating type fixing device of the embodiment, and can be widely used as a heating source of a heating device for heating a material to be heated. Of course.

  3) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but also an image heating device that presupposes an image, and a recording medium that carries the image is reheated to improve the surface properties such as gloss. It can also be used as an image heating device. Further, for example, it is also effective to use as a heating device such as a heat press device for removing wrinkles such as banknotes, a heat laminating device, a heat drying device for evaporating water content such as paper.

  4) When the heating device is a film heating type heating device, the driving method of the film 2 which is a flexible member is not limited to the pressing member driving method of the embodiment. A driving roller may be provided on the inner peripheral surface of the endless flexible member and driven while applying tension to the flexible member. Thus, it is possible to adopt a device configuration that travels and moves while feeding it out. The pressure member 6 is not limited to a roller body, and may be a rotating belt body. The temperature detection element 5 is not limited to a thermistor. Various types of contact type or non-contact type can be used.

1 is a configuration explanatory diagram of an image forming apparatus in Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view of a main part of the heat fixing device in Example 1. It is a perspective model figure of the principal part similarly. (A) is a front model figure of a stay, (b) is a bottom model figure. It is a perspective model figure of a heating body. It is a disassembled perspective model figure of a heating body. It is a bottom model figure of the stay which fixedly supported the heating body. It is an enlarged cross-sectional model view of the fixing nip portion of the heat fixing device. It is a block diagram of the electric power feeding control circuit system with respect to a heating body.

Explanation of symbols

  1 .... Long stay, 2 .... Heat resistant film, 3 .... Heating body, 3a ... Carbon-based resistance heating element, 3b ... Base material, 3c ... electrode, 3d ... electrode, 4.Pressure member 5 ..Temperature sensing element (temperature sensing element) 6 ..Pressure roller 11 ..CPU 12 ..Triac 13 ..AC power supply 101 .Organic photosensitive drum 102 ..Charging roller 103. ..Laser exposure device, 104 ..developing device, 105 ..cleaning device, 105a ..cleaning blade, 1112 ..transfer roller, 114 ..fixing device, P ..recording material, t..toner

Claims (8)

In a heating element used in a heating device for heating a material to be heated,
A carbon-based resistance heating element manufactured by carbonizing at least a base material, carbon as a conductive material, and heat-treating a raw material containing at least an organic substance in a non-oxidizing atmosphere of carbon; A heating element comprising an electrode for supplying power to a resistance heating element.   The carbon-based resistance heating element includes an organic substance to be carbonized by heat treatment, and at least one kind or a mixture of insulating or semiconductive substances mixed with the organic substance, and after molding this, in a non-oxidizing atmosphere of carbon The heating element according to claim 1, wherein the heating element is heat-treated.   3. The heating body according to claim 1, wherein the non-oxidizing atmosphere of carbon is an atmosphere or vacuum that is lower than a chamber pressure, nitrogen gas, or an inert gas.   The heating body according to claim 1, wherein the base material is a liquid crystalline wholly aromatic polyester.   The heating body according to claim 1, wherein the base material is polyphenylene sulfide.   The heating body according to claim 1, wherein the substrate is an inorganic compound.   A heating member fixedly supported by the support member; a flexible member having one surface in contact with and sliding on the heating member and the other surface in contact with the material to be heated; and the flexible member and the heated surface on the heating member. In the heating apparatus which transfers the heat | fever of a heating body to a to-be-heated material via a flexible member because a material moves together, the said heating body is a heating body in any one of Claims 1-6. A heating device characterized by.   8. An image forming apparatus comprising: an image forming unit that forms an image on a recording material; and an image heating and fixing unit that heat-fixes the image on the recording material. The heating device according to claim 7 as the image heating and fixing unit. An image forming apparatus comprising: