JP2006202583A - Heating roll and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating roll taking a short time to raise the temperature of the surface of the heating roll to a set temperature even with simple structure, excellent in power consumption efficiency, and easy to manufacture, and a method of manufacturing the heating roll. <P>SOLUTION: This heating roll has a rotation shaft 11, a porous ceramic heat insulating layer 12 formed on the surface of the rotation shaft 11, a porous ceramic resistance heating element 13 formed on the surface of the heat insulating layer 12, and inorganic binders contained in the heat insulating layer 12 and the resistance heating element 13 are identical ones. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention particularly relates to a toner fixing heating roll used in an electrophotographic image forming apparatus and a method of manufacturing the heating roll.

  In the fixing process of an electrophotographic image forming apparatus, a method of applying pressure and heat energy to a toner image via a fixing heating roller or a fixing belt, making the toner in a semi-molten state and penetrating the recording paper, and fixing the toner Have taken.

  Conventionally, as a heating element for fixing, a heating element such as a halogen lamp is attached inside a cylindrical body made of metal such as aluminum, and a heating element or roll that heats the generated cylinder by heat transfer or heat radiation. 2. Description of the Related Art There is known a heating roller that uses a body itself as a heating element, and heats the roll body directly by energizing it to raise the temperature. A heating roller that directly generates heat from a roll body is frequently used in that the temperature rise time is short and the energy efficiency is high.

  The electrophotographic image forming apparatus needs to have a fixed temperature on the surface of the fixing heating body during use. When starting to use a new electrophotographic image forming apparatus, it is necessary to wait until the surface of the fixing heating body reaches its set temperature after turning on the power. Not only is the efficiency low, but there is a problem that the user is frustrated.

  In order to solve these problems, Japanese Patent Application Laid-Open No. 2004-22285 discloses a resistance exothermic porous ceramic base portion, an electrode portion for supplying power to the base portion, and an outermost peripheral surface of the base portion. In addition, there is disclosed a heating element mainly including a coating layer having heat resistant, insulating and non-adhesive properties. According to this heating element, the base portion of the resistance heating element can be rapidly heated to a predetermined set temperature, and the power consumption efficiency is excellent.

Japanese Patent Application Laid-Open No. 2-137871 discloses an electrophotographic apparatus for passing a transfer means between a heating roll and a pressure roll that rotate in close contact with each other, and fixing a subject image on the transfer means. The heating roller has a rotating shaft, a heat insulating layer stratified on the surface of the rotating shaft, and a resistance heating layer laminated on the surface of the heat insulating layer, and the heat insulating layer. A heat fixing roll device of an electrophotographic apparatus in which hollow or porous hard particles are dispersed is disclosed. According to this heat fixing roll device, the rigidity of the heat insulating layer can be improved, deformation and deterioration due to temperature change of the heating roll can be prevented, and the durability of the heating roll is improved.
JP 2004-22285 A (Claim 1) JP-A-2-137871 (Claim 1)

  However, the heating element described in Japanese Patent Application Laid-Open No. 2004-22285 has no insulation effect although an insulating layer exists between the shaft shaft or the pipe and the resistance heating element. For this reason, it cannot be said that it is enough for heating a heating body rapidly. Further, the heat fixing roll device described in JP-A-2-137871 has a heat insulating layer between the rotating shaft and the resistance heat generating layer. This heat insulating layer is made of glass or ceramic based on silicon rubber or heat resistant resin. Since a large number of hollow sphere particles are mixed, dispersed, and molded, there is a risk of particle cracking when mixing the base and particles, or a process for forming a large number of adhesive layers is required. There are still problems in production.

  Accordingly, an object of the present invention is to provide a heating roll and a heating roll that are simple in structure and have a short heating time until the heating roll surface is set to a set temperature, excellent in power consumption efficiency, and easy to manufacture. It is to provide a manufacturing method.

  In such a situation, the present inventors have intensively studied, and as a result, have a hollow cylindrical porous ceramic heat insulating layer and a porous ceramic resistance heating element formed on the surface of the heat insulating layer, and the heat insulating layer. The heating roll with the same inorganic van binder contained in the resistance heating element has a short heating time until the heating roll surface is set to a set temperature, is excellent in power consumption efficiency, is easy to manufacture, and is further insulated. The layer and the resistance heating element can be integrated without using an adhesive, and the strength and the like have been found, and the present invention has been completed.

  That is, the present invention comprises a rotating shaft, a porous ceramic heat insulating layer stratified on the surface of the rotating shaft, and a porous ceramic resistance heating element stratified on the surface of the heat insulating layer, The inorganic van binder included in the resistance heating element provides a heating roll that is the same.

  The present invention also includes a step of forming a first raw material mixture containing an inorganic binder and a second raw material mixture containing an inorganic binder and a conductive filler to obtain a two-layer structure, a drying step, The present invention provides a method for producing a heating roll having a firing step, wherein the inorganic binder used in the first raw material mixture and the second raw material mixture is the same.

  Since the heat roll of this invention provided the heat insulation layer between the rotating shaft and the resistance heat generating body, the temperature rising time which makes the heat roll surface the predetermined preset temperature is short, and it is excellent in power consumption efficiency. Moreover, since the same inorganic binder is mix | blended, a heat insulation layer and a resistance heating element can be integrated even if it does not use an adhesive agent, and it is excellent also in intensity | strength. Further, since the heat insulating layer has an insulating function, a separate process for forming the insulating layer on the surface of the rotating shaft can be omitted. In addition, according to the method in which the first raw material mixture and the second raw material mixture are subjected to two-layer extrusion molding, a two-layer structure integrated product can be easily produced in one step.

  A heating roll in an embodiment of the present invention has a rotating shaft, a porous ceramic heat insulating layer stratified on the surface of the rotating shaft, and a porous ceramic resistance heating element stratified on the surface of the heat insulating layer. The heat insulating layer and the inorganic vaninder included in the resistance heating element are the same, and the heating roll includes a first raw material mixture containing an inorganic binder, and a second raw material mixture containing an inorganic binder and a conductive filler. It is obtained by a production method having a step of obtaining a molded article having a two-layer structure, a drying step and a firing step.

  The first raw material mixture forms a porous ceramic heat insulating layer after firing. In addition, the inorganic binder used in the first raw material mixture becomes a ceramic component after firing, and has a function of bonding heat-resistant inorganic materials to each other. The inorganic binder is not particularly limited, and examples thereof include glass frit, colloidal silica, silica sol, alumina sol, sodium silicate, and water glass. Among these, the glass frit has high strength and good adhesion between two layers. Is preferable. Moreover, these inorganic binders can be used singly or in combination of two or more.

  The first raw material mixture contains a heat-resistant inorganic material as necessary in order to increase strength and heat resistance. The heat-resistant inorganic material refers to a fibrous or particulate material that does not substantially melt and deform in each step of kneading, molding and firing. The fibrous heat-resistant inorganic material is not particularly limited. For example, alumina silica fiber, glass fiber, alumina fiber, carbon fiber, silica fiber, zirconia fiber, gypsum whisker, slag wool, silicon carbide fiber, potassium titanate whisker, Examples thereof include aluminum borate whisker, fused silica fiber, rock wool and the like. Among these, alumina silica fiber and glass fiber are preferable in terms of high strength and low cost. These fibrous heat-resistant inorganic materials can be used alone or in combination of two or more. Further, the length and diameter of the fibrous heat-resistant inorganic material are not particularly limited, but the length is preferably 3 mm or less in consideration of dispersibility in the mixture or kneaded material, and the diameter is about 1 to 15 μm. Is preferable in that the porosity of the fired porous ceramic heat insulating layer can be further increased.

  The particulate heat-resistant inorganic material is not particularly limited, for example, clay, talc, silica, alumina, calcium carbonate, calcium oxide, magnesium oxide, zirconia, titania, kaolin, zeolite, silicon nitride, aluminum nitride, aluminoborosilicate, Particulate matter such as aluminosilicate can be mentioned. In addition, these particulate heat-resistant inorganic materials can be used individually by 1 type or in combination of 2 or more types. The maximum length of the particulate heat-resistant inorganic material is not particularly limited, but considering the dispersibility in the mixture or kneaded material, it is preferably 3 mm or less, and the diameter is about 1 to 15 μm after firing. This is preferable in that the porosity of the porous ceramic heat insulating layer can be further increased.

  The amount of the heat-resistant inorganic material used is not particularly limited, but is preferably 0 to 500 parts by weight, particularly preferably 0 to 200 parts by weight, and more preferably 30 to 100 parts by weight with respect to 100 parts by weight of the inorganic binder. When the amount used exceeds 500 parts by mass, the strength of the fired porous ceramic heat insulating layer becomes insufficient.

  The first raw material mixture further contains an organic binder as necessary in order to improve handling properties such as plasticity adjustment and strength improvement of the mixture in the kneading and molding stages, and also improves the internal porosity. Therefore, a water-resistant organic material is contained as necessary. Organic binders also include what are usually called thickeners. The organic binder and the water-resistant organic material are burned out in the baking process.

  The organic binder is not particularly limited. For example, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, phenol resin, polyacrylate ester, sodium polyacrylate, acrylic resin, vinyl acetate resin, polyvinyl alcohol resin, etc. Is mentioned. These organic binders can be used singly or in combination of two or more.

  As for the usage-amount of an organic binder, 0-100 mass parts is preferable normally with respect to 100 mass parts of inorganic binders, 10-50 mass parts is especially preferable, and also 15-25 mass parts is preferable. When the amount used exceeds 100 parts by mass, unnecessary organic components increase and the strength is lost.

  The water-resistant organic material is not particularly limited, and examples thereof include water-resistant synthetic resins such as polypropylene, polyethylene, polystyrene, acrylic resin, and phenol resin, wood, bamboo, and other natural organic materials. The shape of the water-resistant organic material is not particularly limited, and may be fibrous or particulate. These water resistant organic materials may be foamed internally. These water-resistant organic materials can be used alone or in combination of two or more.

  The diameter of the fibrous material of the water-resistant organic material and the diameter of the particulate material are usually in the range of 1 to 2000 μm, preferably 5 to 1000 μm, more preferably 10 to 500 μm.

  The amount of the water-resistant organic material used is appropriately determined as necessary in consideration of the target internal porosity of the target porous ceramic heat insulating layer. For example, the amount is usually based on 100 parts by mass of the inorganic binder. It is 0-300 mass parts, Preferably it is 0-150 mass parts, More preferably, it is 0-100 mass parts. When the usage-amount of a water-resistant organic material exceeds 300 mass parts, it is unpreferable at the point which the intensity | strength of porous ceramics becomes remarkably low. However, the amount of the water-resistant organic material used is determined in relation to the amount of the inorganic material used, and the total amount of the water-resistant organic material and the inorganic material ranges from 0 to 500 parts by mass with respect to 100 parts by mass of the inorganic binder. preferable.

  The first raw material mixture can be used in the molding step as it is, but it is preferable to obtain a kneaded product by a kneading step before the molding step. The kneading step is a step of mixing a predetermined amount of a heat-resistant inorganic material, an inorganic binder, an organic binder, a water-resistant organic material and other additives with water to make the mixture a uniform plastic material. The amount of water used in the kneading step is appropriately adjusted so that the mixture is suitable for the molding step, which is a subsequent step, but is generally 50 to 200% by mass with respect to the total mass of each solid component. The kneading apparatus used in the kneading step is not particularly limited, and a known apparatus can be used. Specific examples include a pressure kneader, a double-arm kneader, and a high-speed mixer.

  The second raw material mixture forms a porous ceramic resistance heating element after firing. The second raw material mixture is different from the first raw material mixture in that it further contains a conductive filler. That is, the material used in the second raw material mixture is the same as the raw material used in the first raw material mixture. Among these, the inorganic binder is the same as the inorganic binder used in the first raw material mixture. Is used.

  The conductive filler used in the second raw material mixture is not particularly limited. For example, graphite, carbon black, iron, copper, aluminum, stainless steel, zinc, gold, silver, platinum, silicon nitride and their alloys, titanium oxide Metal oxides such as zinc oxide and tin oxide, or non-conductive substance particles coated with metal particles or a metal plating layer. Of these, graphite has excellent conductivity and high strength. It is preferable in that it can be performed. These conductive fillers may be powder, sphere, or fiber. Moreover, these electrically conductive fillers can be used individually by 1 type or in combination of 2 or more types.

  The amount of the conductive filler to be used is appropriately determined in consideration of the volume resistivity of the porous ceramic resistance heating element, but is usually preferably 5 to 500 parts by weight, particularly preferably 10 to 100 parts by weight with respect to 100 parts by weight of the inorganic binder. 100 parts by mass is preferred. When the conductive filler is less than 5 parts by mass, the volume resistivity becomes too high, and when it exceeds 500 parts by mass, the volume resistivity becomes unnecessarily low and the strength is also unfavorable. The volume resistivity of the porous ceramic resistance heating element is usually 0.01 to 100,000 Ω · cm.

  The second raw material mixture can be used in the molding step as it is, but it is preferable to obtain a kneaded product by a kneading step before the molding step. The kneading step is a step of mixing a predetermined amount of conductive filler, heat-resistant inorganic material, inorganic binder, organic binder, and other additives with water to make the mixture a uniform plastic material. The amount of water and the kneading apparatus used in the kneading step are the same as in the kneading step of the first raw material mixture.

  The forming step is a step of obtaining a two-layered molded body from the first raw material mixture and the second raw material mixture. The two-layered molded body is obtained by subjecting the first raw material mixture and the second raw material mixture to extrusion molding. A method of obtaining, a method of obtaining a molded body having a two-layer structure by extruding a first raw material kneaded material that has undergone a kneading step and a second raw material kneaded material that has undergone a kneading step, a first raw material mixture or a first material having undergone a kneading step A raw material kneaded product is extruded to obtain a molded body, and then the second raw material mixture or the second raw material kneaded material is laminated on the surface of the molded body for extrusion molding, or the first raw material mixture or the kneading step is passed. A method of obtaining a molded body having a two-layer structure by extruding the first raw material kneaded material to obtain a molded body, and then immersing or applying the second raw material mixture or a slurry thereof on the surface of the molded body. Among these, the first raw material kneaded material and the kneading worker that have undergone the kneading step The second raw material kneaded product and a method to obtain a molded product of two-layer extrusion molding to the two-layer structure which has undergone is, by one step, preferably at a stroke in that an integrated product of a two-layer structure can be easily manufactured. Further, in the molding process, the rotating shaft may be integrally incorporated simultaneously with the molding, or a molded body having a hollow portion may be obtained so that the rotating shaft is fitted in a subsequent process of the molding process.

  As a method for obtaining a two-layered molded article by subjecting the first raw material kneaded product after the kneading step and the second raw material kneaded product after the kneading step to a two-layer structure, a known two-layer extruder is used. Can do. A two-layer extruder having a cross head structure having a double nozzle portion at the tip can be used. That is, the second raw material kneaded material is supplied from the axial direction of the double nozzle, the first raw material kneaded material is supplied from the side orthogonal to the axial direction, and the surface of the first raw material kneaded material from the portion where the two raw materials intersect. A two-layered molded body in which the second raw material kneaded material is laminated is extruded through the double nozzle portion at the tip. In this case, the rotary shaft (shaft) can be disposed at the center of the two-layer extruder, and the rotary shaft and the molded body can be integrated together.

  After the molding process, the process proceeds to the drying process. The drying step is usually a step of drying at room temperature or heating temperature to remove moisture and cure the molded body to obtain its shape. The heating temperature in the drying step is usually 200 ° C. or lower, preferably about 100 ° C., where water is gently evaporated and easily evaporated. Moreover, although drying time is suitably determined by the shape of a molded object, heating temperature, etc., it is 0.5 to 12 hours normally.

  After the drying process, the process proceeds to the firing process. The firing step is preferably performed by dividing the preliminary firing step and the final firing step. The preliminary firing step is performed in order to prevent the occurrence of cracks due to the rapid disappearance of the particulate organic matter in the final firing step at a high temperature, and is usually performed at a temperature of 150 to 400 ° C. in the atmosphere. The pre-baking time is appropriately determined depending on the shape of the molded body, the heating temperature, and the like, but is usually 12 to 72 hours.

  The final firing step is usually performed at a high temperature of 400 to 1000 ° C., and the remaining particulate organic matter and organic binder are completely disappeared, and the inorganic binder is melted to integrate the whole. When carbon black, metal particles, or other materials that may be oxidized or denatured at 400 ° C. or higher are used as the conductive filler, it is preferably performed in a reducing atmosphere. The heating time in the final firing step is appropriately determined depending on the shape of the molded body, the heating temperature, the used material components, the blending ratio, and the like, but is usually 0.5 to 24 hours.

  In the firing step, since the inorganic binders of the first raw material mixture and the second raw material mixture are the same, the fired body is heated at the interface portion between the porous ceramic heat insulating layer and the porous ceramic resistance heating element formed on the surface thereof. The molten inorganic binder is integrated with both heat-resistant inorganic materials. For this reason, the porous ceramic heat insulating layer and the porous ceramic resistance heating element are firmly bonded without using an adhesive. The surface of the fired porous ceramic resistance heating element that has undergone the firing process can be further subjected to painting, surface coating, and other secondary processing.

  The thickness in the radial direction of the inner layer porous ceramic heat insulating layer and the outer layer porous ceramic resistance heating element is not particularly limited, but the thickness of one side of the ring-shaped cross section of the outer layer porous ceramic resistance heating element is usually 0. The thickness ratio in the cross-section of the inner porous ceramic heat insulating layer and the outer porous ceramic resistance heating element is 1: 1 to 10 for the outer layer: inner layer. When the outer layer: inner layer ratio is less than 1: 1, the heat insulating effect is insufficient, and when the outer layer: inner layer ratio exceeds 1:10, it is not preferable in that the production becomes difficult.

  Both the internal porosity of the porous ceramic heat insulating layer and the porous ceramic resistance heating element obtained through the firing step are 20 to 90%, preferably 40 to 85%. If the internal porosity of the porous ceramic resistance heating element is less than 20%, sufficient power efficiency and temperature increase rate cannot be obtained, and if it exceeds 90%, it is difficult to maintain sufficient strength. If the internal porosity of the porous ceramic heat insulating layer is less than 20%, a sufficient heat insulating effect cannot be obtained, and it becomes difficult to maintain a sufficient strength of 90%.

The bulk density of the porous ceramic heat insulating layer and the porous ceramic resistance heating element are both 0.2 to 1.95 g / cm ³ , preferably 0.4 to 1.5 g / cm ³ . If the bulk density of the porous ceramic resistance heating element exceeds 1.95 g / cm ³ , sufficient power efficiency and temperature increase rate cannot be obtained, and if it is less than 0.2 g / cm ³ , the strength is not sufficient. If the bulk density of the porous ceramic heat insulating layer exceeds 1.95 g / cm ³ , the heat insulating effect is insufficient, and if it is less than 0.2 g / cm ³ , it is difficult to maintain sufficient strength.

  The porous ceramic resistance heating element is conductive, and its volume resistivity is usually 0.01 to 100,000 Ω · cm, preferably 0.1 to 10,000 Ω · cm, more preferably 0.1 to 100,000 Ω · cm. 1000 Ω · cm. When the volume resistivity is less than 0.01 Ω · cm, since the resistance is small, it is difficult to control the temperature to a predetermined temperature, and the power consumption increases. On the other hand, if it exceeds 100,000 Ω · cm, the necessary heat generation cannot be obtained because of the large resistance.

  A hollow part of the fired body obtained by a method in which the rotary shaft is not integrally formed is attached through the rotary shaft. The method for mounting the rotating shaft is not particularly limited, and can be performed by a known method. Further, in the heating roll of the present invention, the roll-shaped porous ceramic resistance heating element is resistance exothermic, and can be heated to raise its temperature by passing an electric current through the porous ceramic resistance heating element. Energization is performed by passing an electric current in the length direction of the porous ceramic resistance heating element. Moreover, since the porous ceramic resistance heating element has an NTC characteristic having a negative temperature coefficient, it is possible to suppress a temperature rise in a portion that is not in contact with the heating object, and a temperature difference between the paper passing portion and the non-paper passing portion is reduced. No heating roll can be obtained.

  As a method of passing an electric current in the length direction of the porous ceramic resistance heating element, a conductive paste or the like is applied to both side end surfaces of the roll-shaped porous ceramic resistance heating element or inside the resistance heating element and in the vicinity of both side ends, After firing, the conductive paste portion and the metal electrode plate are brought into contact with each other to provide an electrode, and a power source may be connected to the electrode.

  A coating layer is usually formed on the outermost peripheral surface of the porous ceramic resistance heating element that is the outer layer. As this coating layer, those having surface suitability as a heating roll such as heat resistance, insulation and non-adhesiveness are preferable. As a method of forming the coating layer, a known method can be used, for example, a method of sticking a sheet-like material whose main component is a fluororesin such as PFA or PTFE, fluororubber, silicon rubber, or the like, glass, Examples thereof include a method of coating an inorganic insulator such as alumina. As a method of coating the inorganic insulator, the inorganic insulator is applied to a fired body having a porous ceramic resistance heating element on the outermost peripheral surface, and further, the inorganic insulator is applied in the form of a fired method or a molded body. Examples include a method of firing. Although the thickness of a coating layer is suitably set by the use which uses a roll-shaped heating body, it is about several dozen micrometers-5 mm, for example.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

(Production of first raw material mixture and kneaded product)
100 parts by mass of alumina silica fiber and glass fiber as the heat resistant inorganic material, 75 parts by mass of glass frit as the inorganic binder, 14 parts by mass of methyl cellulose as the organic binder, and 43 parts by mass of polyethylene as the water resistant organic material, 90 parts by mass of water The added aqueous mixture was kneaded with a double-arm kneader for about 20 minutes to obtain a plastic kneaded product.

(Production of second raw material mixture and kneaded product)
Alumina silica fiber and glass fiber 50 parts by weight as heat resistant inorganic material, 100 parts by weight of glass frit as inorganic binder, 18 parts by weight of methyl cellulose as organic binder, 60 parts by weight of polyethylene as water resistant organic material and 25 parts by weight of graphite as conductive filler An aqueous mixture obtained by adding 90 parts by mass of water to this mixture was kneaded with a double-arm kneader for about 20 minutes to obtain a plastic kneaded product.

(Molding, drying and firing process)
Using the two-layer extrusion molding apparatus, the two plastic kneaded materials are obtained by using the inner layer 12 derived from the first raw material mixture having an outer diameter of 16 mm × inner diameter of 8 mm × length of 220 mm and an outer diameter of 20 mm × inner diameter of 16 mm × length of 230 mm. Two layers of the outer layer 13 derived from the mixture of two raw materials and a roll-shaped molded body having a hollow two-layer structure having a length of 230 mm were extruded by two layers and dried at 100 ° C. for 3 hours to obtain a molded body cured. This molded body was heated at 600 ° C. for 48 hours to burn off methylcellulose and polyethylene, and an inorganic binder was fused to obtain a roll-shaped heating body in which inorganic components were integrated.

(Evaluation method of heating roll)
Separately from the obtained roll-shaped heating body, the outer layer resistance heating element and the inner layer porous ceramic heat insulating layer were extruded and fired to obtain respective cylindrical bodies. The resistance heating element was prepared by applying a conductive paint (Dotite D-550, manufactured by Fujikura Kasei Co., Ltd.) to both end faces to prepare a volume resistivity measuring test specimen. The resistivity was measured. The bulk density and porosity were then measured. The bulk density and porosity of the inner porous ceramic heat insulating layer were also measured in the same manner. The results are shown in Table 1.

  About one obtained roll-shaped heating body, the SUS rotating shaft 11 having an outer diameter of 8 mm and a length of 260 mm is press-fitted into the hollow portion of the roll-shaped heating body, and the inner surface of the outer layer 13 of the roll-shaped heating body 10. And silver paste was apply | coated to the part 5 mm from both ends, and the phosphor bronze electrode 15 was closely_contact | adhered and arrange | positioned only to the part of the outer layer 13 of both ends. The periphery of the electrode 15 was sealed with PPS resin. Further, a PFA coating layer 14 having a thickness of 30 μm was formed by spray coating on the outer peripheral surface of the roll-shaped heating body to produce a heating roll. For the reference numerals, see FIG.

  Using a Minolta A4 monochrome copier, under the conditions of paper feed speed of 13 ppm and fixing temperature of 200 ° C., the temperature rise speed, power consumption, resistance value, and temperature difference between the paper-passing part and the non-paper-passing part are measured by the following methods. did. The results are shown in Table 1.

Bulk density (g / cm ³ ): Calculated from the mass of the test piece and the volume calculated from the shape dimensions.
Porosity (%): A test piece having a predetermined size is cut out, and the volume calculated from the shape and size of the test piece and the pore volume obtained by using an air comparison type hydrometer 1000 type (manufactured by Tokyo Science Co., Ltd.) Calculated as a 100-minute value.
-Volume resistivity (ohm * cm, 20 degreeC): It computed by the average cross-sectional area method according to JISH0505 from the dimension and resistance value of the test body.
Resistance value (Ω, 20 ° C.): The resistance value between the electrodes of the test specimen was measured.
-Rate of temperature increase (seconds): The time required for temperature increase to 200 ° C. when an applied voltage of 650 W was applied was measured.
Power consumption: Applying a voltage of 650 W to the heating roll to raise the temperature from room temperature to 200 ° C., repeating the cycle of maintaining the temperature for 60 seconds in total, including the temperature rise, 10 times. The average value was obtained.
・ Temperature difference between the paper-passing part and the non-paper-passing part: temperature difference between the paper-passing part and the non-paper-passing part when a postcard size (small size paper) is passed for A4 size. The strength of the resistance heating element of the outer layer of the obtained heating element and the strength of the porous ceramic heat insulating layer of the inner layer were evaluated as “B” when there was no problem even in actual evaluation, and “C” when the two layers were idle.

Examples 2 and 3
The second raw material mixture was prepared in the same manner as in Example 1 except that the composition shown in Table 1 was used. The results are shown in Table 1.

Comparative Example 1
The second raw material mixture was prepared in the same manner as in Example 1 except that the composition shown in Table 1 was used. That is, the same procedure as in Example 1 was performed except that 70 parts by mass of colloidal silica was used as the solid content instead of 75 parts by mass of the glass frit used in the porous ceramic heat insulating layer. The results are shown in Table 1.

Comparative Example 2
Instead of a heating roll equipped with a rotating shaft, a PFA coating layer having a thickness of 30 μm was formed on the surface of an aluminum shaft pipe by coating. This was carried out in the same manner as in Example 1 except that a halogen lamp heat source was attached to the hollow portion of the shaft pipe and then fixed and a roll-shaped heating body was produced. A 100-volt power source was connected to both electrodes of the halogen lamp, and the temperature increase rate, power consumption, and temperature difference between the sheet passing portion and the non-sheet passing portion were measured in the same manner as in Example 1. The results are shown in Table 1.

  As is apparent from Table 1, Examples 1 to 3 are excellent in power consumption efficiency because the heating time for bringing the heating roll surface to a predetermined set temperature is short. Moreover, since the same inorganic binder was mix | blended, the heat insulation layer and the resistance heating element were able to be integrated even if it did not use an adhesive agent. Further, since the heat insulating layer has an insulating function, a separate process for forming the insulating layer on the surface of the rotating shaft can be omitted. Moreover, since the first raw material mixture and the second raw material mixture were subjected to two-layer extrusion molding, a two-layer structure integrated product could be easily produced in one step. In addition, since the heating body of the present invention has NTC characteristics, the temperature rise of the non-sheet passing portion is suppressed even when a small size paper is passed, and heat damage is caused to the pressure roller and the fixing belt. It turns out that there is nothing.

The schematic block diagram of the heating roll obtained in the Example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heating roll 11 Rotating shaft 12 Porous ceramic heat insulation layer 13 Porous ceramic resistance heating element 14 Coating layer 15 Electrode 16 Sealing material

Claims (9)

  Included in the heat insulating layer and the resistance heating element, comprising: a rotating shaft; a porous ceramic heat insulating layer formed on the surface of the rotating shaft; and a porous ceramic resistance heating element formed on the surface of the heat insulating layer. A heating roll characterized in that the inorganic binder is the same.   The heating roll according to claim 1, further comprising a coating layer formed on the surface of the resistance heating element.   The heating roll according to claim 1 or 2, wherein the inorganic binder is a glass frit. The heat insulating layer is a fired body containing as a main component 100 parts by mass of an inorganic binder and 0 to 500 parts by mass of a heat-resistant inorganic material, and has an internal porosity of 20 to 90% and a bulk density of 0.2 to The heating roll according to any one of claims 1 to 3, wherein the heating roll is a porous ceramic of 1.95 g / cm ³ . The resistance heating element is a fired body containing 100 parts by mass of an inorganic binder, 0 to 500 parts by mass of a heat-resistant inorganic material, and 5 to 300 parts by mass of a conductive filler, and has an internal porosity of 20 The porous ceramic material according to any one of claims 1 to 4, which is a porous ceramic having a volume resistivity of 0.01 to 100,000 Ω · cm and a bulk density of 0.2 to 1.95 g / cm ³ . The heating roll according to item 1.   The heating roll according to any one of claims 1 to 5, wherein the resistance temperature characteristic of the resistance heating element has an NTC characteristic, and a heating current is passed in a length direction of the resistance heating element.   It has a step of forming a first raw material mixture containing an inorganic binder and a second raw material mixture containing an inorganic binder and a conductive filler to obtain a two-layer molded body, a drying step, and a firing step. And the inorganic binder used by this 1st raw material mixture and this 2nd raw material mixture is the same thing, The manufacturing method of the heating roll characterized by the above-mentioned.   The first raw material mixture contains 100 parts by weight of an inorganic binder and 0 to 500 parts by weight of a heat-resistant inorganic material as main components, and the second raw material mixture comprises 100 parts by weight of the inorganic binder, a heat-resistant inorganic material. The method for producing a heating roll according to claim 7, comprising 0 to 500 parts by mass of a material and 5 to 300 parts by mass of a conductive filler as main components.   The method for producing a heating roll according to claim 7 or 8, wherein the molding is two-layer extrusion molding.

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