Patent Application
20100084394
The present invention relates to a heat generating unit used for a heat source and a heating apparatus using such a heat generating unit, and in particular, relates to a heat generating unit having a heat generating element that is mainly composed of a carbon-based substance and formed into a film-sheet shape and a heating apparatus using such a heat generating unit.
A conventional heat generating unit having an elongated shape to be used as a heat source has a structure in which a coil shaped tungsten wire or a rod-shaped or plate-shaped carbon-based sintered body is sealed in a cylinder-shaped glass tube as a heat generating element. Examples of heating apparatuses using such a heat generating unit include: various apparatuses that require heat sources, such as electronic apparatuses including copying machines, facsimiles and printers, and electric appliances including electric heating apparatuses, cooking apparatuses and drying apparatuses.
Heat generating units have been widely used in the various apparatuses as heat sources. For this reason, there have been various demands for a heat generating unit so as to meet specifications of the function, shape, structure and the like of an apparatus to which the heat generating unit is applied. For example, those demands include to provide a high temperature as a heat source, to maintain a specified temperature, to have a wide temperature adjusting range, to allow an input power to be converted to heating energy with high efficiency, to uniformly heat an object to be heated, to have directivity so that heating is applied only in a specified direction, to have little rush current upon application of power, to have a quick temperature rise up to a predetermined temperature, and to have a structure capable of miniaturizing the heat generating unit, which is easily detachably attached.
In order to satisfy the above-mentioned demands, various heat generating units have been proposed. For example, as a conventional heat generating unit that carries out a heating process to a high temperature, a structure has been proposed in which a tape-shaped heat generating element, formed by allowing carbon fibers to be impregnated with a resin to be secured, is sealed in a glass tube (for example, see JP-A No. 2004-193130). Patent Document 1: JP-A No. 2004-193130
In the conventional heat generating unit having a structure as described above, carbon fibers are aligned in the longitudinal direction and joined to be fixed into a tape shape with a resin so that a heat generating element is formed. In the conventional heat generating element formed in this manner, since the carbon fibers are kept in a connected state, it exerts superior thermal conductivity in a direction in parallel with the carbon fibers (direction of carbon fibers); however, when subjected to a machining process so as to adjust resistance or the like, the thermal conductivity in the direction of carbon fibers deteriorates abruptly since the carbon fibers are cut partially. Moreover, since the thermal conductivity in a direction orthogonal to the direction of carbon fibers is low, temperature variations tend to occur in the respective heat generating units serving as heat sources, resulting in a problem with reliability. Moreover, cracks tend to develop from the cut portions of the carbon fibers forming the starting points, resulting in a problem of short service life.
Moreover, since the heat generating element of the conventional heat generating unit has a structure formed by joining carbon fibers to be fixed by a resin, it has no pliability with the result that it is difficult to satisfy various specifications required for a heat source used in a heating apparatus.
The present invention has been devised to solve the above-mentioned problems with the conventional heat generating element, and its objective is to provide a heat generating unit that has a small size with high efficiency and high directivity, and carries out a uniform heating process with a fast temperature rise, and a heating apparatus using such a heat generating unit.
In order to solve the above-mentioned problems and achieve the object of the present invention, a heat generating unit according to a first aspect of the present invention includes: a heat generating element that is formed into a film shape by using a material containing a carbon-based substance, and has an equivalent thermal conductivity in a plane direction; a power supply part that supplies power to two opposing ends of the heat generating element; and a container that encloses the heat generating element and the power supply part. In the heat generating unit configured as described above, since the heat generating element, mainly composed of a carbon-based material and formed into a film-sheet shape, has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, the entire surface is allowed to generate heat upon application of power so that a heat source having a fast temperature rise is achieved.
In a heat generating unit according to a second aspect of the present invention, the heat generating element includes an applied-power heat-generating portion in which a current flows to generate heat and radiate heat, and a conducted heat-generating portion in which heat is generated to radiate the heat due to thermal conduction from the applied-power heat-generating portion. In the heat generating unit configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, not only the power-applied heat-generating portion, but also the conducted heat-generating portion is allowed to generate heat with high efficiency.
In a heat generating unit according to a third aspect of the present invention, the heat generating element has a structure in which wide width portions and narrow width portions are sequentially and alternately disposed in a longitudinal direction. In the heat generating unit configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, the wide width portions and the narrow width portions are respectively allowed to generate heat with high efficiency.
In a heat generating unit according to a fourth aspect of the present invention, a hole is formed in each of the wide width portions of the heat generating element to prepare a power-applied heat-generating passage so that the heat generating element has a wide width portion which has a different resistance value per unit length in the power-applied heat-generating passage. In the heat generating unit configured as described above, it becomes possible to easily and reliably set a desired temperature distribution.
In a heat generating unit according to a fifth aspect of the present invention, the power supply part has a holding block that holds the heat generating element, with a heat resistant member being formed on at least one side of the holding portion in the heat generating element. In the heat generating unit configured as described above, the heat generating element is reliably held by the power supply part so that it is possible to achieve a heat source with high reliability.
In a heat generating unit according to a sixth aspect of the present invention, the power supply part has a holding block that holds the heat generating element, with a convex portion being formed on one portion of the holding portion of the holding block. In the heat generating unit configured as described above, the heat generating element is reliably held by the power supply part so that it is possible to achieve a heat source with high reliability.
In a heat generating unit according to a seventh aspect of the present invention, the heat generating element is formed by using a material having pliability, flexibility and elasticity. In the heat generating unit configured as described above, a machining process of the heat generating element, an assembling process into an apparatus, and a designing process of the apparatus can be easily carried out.
In a heat generating unit according to an eighth aspect of the present invention, at least one portion of areas in the longitudinal direction in the heat generating element is configured so as to have a different resistance value per unit length in the longitudinal direction. In the heat generating unit configured as described above, it becomes possible to easily and reliably set a desired temperature distribution.
In a heat generating unit according to a ninth aspect of the present invention, the container is configured by using either a glass tube or a ceramic tube having a heat resistant property. In the heat generating unit configured as described above, it becomes possible to structurally protect the heat generating element with the heat resistant container.
In a heat generating unit according to a tenth aspect of the present invention, at least one portion of a cross-sectional shape orthogonal to the longitudinal direction of the heat generating element is formed into a curved face. In the heat generating unit configured as described above, the heat generating element can be easily designed in accordance with service objectives.
In a heat generating unit according to an eleventh aspect of the present invention, at least one portion of the container in the longitudinal direction is formed into a curved face. In the heat generating unit configured as described above, a degree of freedom in designing can be expanded in accordance with service objectives.
In a heat generating unit according to a twelfth aspect of the present invention, at least one of the ends of the tube-shaped container is sealed at the power supply part, with the container being filled with an inert gas. In the heat generating unit configured as described above, it becomes possible to prevent the heat generating element from being oxidized and consequently to provide a longer service life.
In a heat generating unit according to a thirteenth aspect of the present invention, the heat generating element has a film sheet shape in which a plurality of film sheet materials are laminated in a thickness direction with one another, with a void being formed therebetween, by using a material having a conductivity of 200 W/m·K or more. In the heat generating unit configured as described above, since the heat generating element, mainly composed of a carbon-based material and formed into a film-sheet shape, has a structure in which a plurality of film sheet materials are laminated in a thickness direction, and consequently exerts the same thermal conductivity in respective plane directions, that is, a so-called two dimensional isotropic thermal conductivity, the entire surface is allowed to generate heat upon application of power so that a heat source having a fast temperature rise is achieved.
In a heat generating unit according to a fourteenth aspect of the present invention, the heat generating element is formed into a film sheet shape with a thickness of 300 μm or less. In the heat generating unit configured as described above, it becomes possible to easily design the heat generating element in accordance with service objectives, and also to achieve a heat source with high directivity.
In a heat generating unit according to a fifteenth aspect of the present invention, the heat generating element is formed by using a graphite film obtained by subjecting a polymer film, or a polymer film to which a filler is added, to a heating treatment at a temperature of 2400° C. or more. In the heat generating unit configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, a heat generating process is carried out with high efficiency.
In a heat generating unit according to a sixteenth aspect of the present invention, at least one portion of an outer shape, a hole shape and a cut-in shape of the heat generating element is formed by a laser machining process. The heat generating unit formed as described above, is allowed to have a desired shape with superior machining precision, and a stable resistance value can be obtained.
A heating apparatus according to a seventeenth aspect of the present invention includes: a heat generating unit that includes: a heat generating element that is formed into a film shape by using a material containing a carbon-based substance, and has an equivalent thermal conductivity in a plane direction; a power supply part that supplies power to two opposing ends of the heat generating element; and a container that encloses the heat generating element and the power supply part, wherein reflective means is disposed at a position opposite to the heat generating element. In the heating apparatus configured as described above, since the heat generating unit and the reflective means for reflecting radiated heat from the heat generating unit are installed, the heating apparatus is provided with a heat source with high efficiency.
In a heating apparatus according to an eighteenth aspect of the present invention, the heat generating element includes an applied-power heat-generating portion in which a current flows to generate heat and radiate heat, and a conducted heat-generating portion in which heat is generated to radiate the heat due to thermal conduction from the applied-power heat-generating portion. In the heating apparatus configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, not only the power-applied heat-generating portion, but also conducted heat-generating portion is allowed to generate heat so that the heating apparatus is provided with a heat source with high efficiency.
In a heating apparatus according to a nineteenth aspect of the present invention, the heat generating element has a structure in which wide width portions and narrow width portions are sequentially and alternately disposed in a longitudinal direction. In the heating apparatus configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, the wide width portions and the narrow width portions are respectively allowed to generate heat so that the heating apparatus is provided with a heat source with high efficiency.
In a heating apparatus according to a twentieth aspect of the present invention, a hole is formed in each of the wide width portions of the heat generating element to prepare a power-applied heat-generating passage so that the heat generating element has a wide width portion which has a different resistance value per unit length in the power-applied heat-generating passage. In the heating apparatus configured as described above, it becomes possible to easily and reliably set a desired temperature distribution.
In a heating apparatus according to a twenty-first aspect of the present invention, the reflective means is a reflective plate having a cross-sectional face in a longitudinal direction, formed into a curved shape. In the heating apparatus configured as described above, it becomes possible to heat an object to be heated, by radiated heat from the heat generating element with high efficiency.
In a heating apparatus according to a twenty-second aspect of the present invention, the reflective means is a reflective plate having a cross-sectional face in a longitudinal direction, with a convex portion protruding toward the heat generating element being formed at one portion of the reflective plate. In the heating apparatus configured as described above, since the reflective plate prevents the heat generating element from being heated, it is possible to realize a heating state as specified at the time of designing.
In a heating apparatus according to a twenty-third aspect of the present invention, the reflective means is a reflective film formed on the heat generating unit. In the heating apparatus configured as described above, it becomes possible to heat an object to be heated, by radiated heat from the heat generating element with high efficiency.
A heating apparatus according to a twenty-fourth aspect of the present invention includes: a heat generating unit that includes: a heat generating element that is formed into a film shape by using a material containing a carbon-based substance, and has an equivalent thermal conductivity in a plane direction; a power supply part that supplies power to two opposing ends of the heat generating element; and a container that encloses the heat generating element and the power supply part, wherein a tube member is disposed so as to surround a periphery of the heat generating unit. The heating apparatus, configured in this manner, can be applied to an electronic apparatus having a toner fixing mechanism, a cooking appliances and the like.
In a heating apparatus according to a twenty-fifth aspect of the present invention, the heat generating element includes an applied-power heat-generating portion in which a current flows to generate heat and radiate heat, and a conducted heat-generating portion in which heat is generated to radiate the heat due to thermal conduction from the applied-power heat-generating portion. In the heating apparatus configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, not only the power-applied heat-generating portion, but also conducted heat-generating portion is allowed to generate heat so that the heating apparatus is provided with a heat source with high efficiency.
In a heating apparatus according to a twenty-sixth aspect of the present invention, the heat generating element has a structure in which wide width portions and narrow width portions are sequentially and alternately disposed in a longitudinal direction. In the heating apparatus configured as described above, since the heat generating element has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, the wide width portions and the narrow, width portions are respectively allowed to generate heat so that the heating apparatus is provided with a heat source with high efficiency.
In a heating apparatus according to a twenty-seventh aspect of the present invention, a hole is formed in each of the wide width portions of the heat generating element to prepare a power-applied heat-generating passage so that the heat generating element has a wide width portion which has a different resistance value per unit length in the power-applied heat-generating passage. In the heating apparatus configured as described above, it becomes possible to easily and reliably set a desired temperature distribution.
A heating apparatus according to a twenty-eighth aspect of the present invention, further includes: a control circuit that carries out an electrical controlling process on the heat generating unit, wherein the control circuit is provided with one of circuits or at least two or more of combined circuits, selected from an ON/OFF control circuit, a duty factor control circuit, a phase control circuit and a zero-cross control circuit. The heating apparatus configured as described above makes it possible to form a heat source having a desired temperature distribution with high precision.
In accordance with the present invention, it is possible to provide a heat generating unit that has a small size with high efficiency and high directivity, and carries out a uniform heating with a fast temperature rise, and a heating apparatus using such a heat generating unit.
Hereinafter, embodiments of a heat generating unit and a heating apparatus using such a heat generating unit in accordance with the present invention will be described with reference to attached drawings.
Referring to
In the heat generating unit of embodiment 1, an elongated heat generating element 2 is placed inside a glass tube 1 made of transparent quartz glass, and the heat generating element 2 is extended in a longitudinal direction along the glass tube 1. Moreover, the two ends of the glass tube 1 are fused and adhered to be formed into flat plates, and the heat generating element 2 is sealed inside the glass tube 1 together with an inert gas, such as an argon gas, a nitrogen gas, or a mixed gas of an argon gas and a nitrogen gas. The argon gas, nitrogen gas or the mixed gas of the argon gas and nitrogen gas, that is, the inert gas sealed inside the glass tube 1, is used so as to prevent oxidation of the heat generating element 2 made of a carbon-based substance, when used under high temperatures.
As shown in
The first internal lead wire member 11A is configured by a coil portion 5 that is wound around the outer circumferential face of the holding block 3 (holding block 3 on the left side in
In embodiment 1, a first power supply part 10A is configured by the holding block 3, the molybdenum foil 8, the external lead wire 9 and the first internal lead wire member 11A, and a second power supply part 10B is configured by the holding block 3, the molybdenum foil 8, the external lead wire 9 and the second internal lead wire member 11B.
Note that the spring portion 6 of the first internal lead wire member 11A is used for applying a tension to the heat generating element 2, and designed so that the heat generating element 2 is always placed at a desired position. In other words, the heat generating element 2 is disposed substantially on the center axis of the glass tube 1 so as not to come in contact with the glass tube 1. Moreover, by forming the spring portion 6 between the internal lead wire 7 and the coil portion 5, it becomes possible to absorb a change in the heat generating element 2 due to expansion and contraction.
In the case where the elongation percentage of the material of the heat generating element 2 or the elongation percentage derived from the shape of the heat generating element 2 is large relative to the change due to the expansion and contraction of the heat generating element 2, it is not necessary to install the spring portions 6 on the respective internal lead wire members on the two ends of the heat generating element 2.
In the heat generating unit of embodiment 1, the coil portion 5 is wound around the outer circumferential face of each holding block 3 to be adhered thereto; however, no coil portion is wound around on substantially half of the outer circumferential face of the holding block 3 to be kept in an exposed state. Therefore, heat transmitted from the heat generating element 2 is emitted from the holding block 3.
The heat generating unit of embodiment 1 is exemplified by a structure with the internal lead wire members 11A and 11B having different structures that are placed on the two ends of the heat generating element 2; however, the heat generating unit of the present invention may have structural members having the same structure as the first internal lead wire member 11A, attached to the two ends of the heat generating element 2, and these structures may be altered on demand in accordance with the specification or the like of the heating apparatus in which the heat generating unit is used. By placing the first internal lead wire member 11A having the spring portion 6 on either one of the ends of the heat generating element 2, the positional regulation and the change absorption of the heat generating element 2 can be obtained; however, a further effect can be expected when the first internal lead wire members 11A are installed on the two ends of the heat generating element 2.
Note that in the heating apparatus, in the case where the heat generating unit is assembled with its longitudinal direction being aligned to the vertical direction, if the spring portion 6 is placed above the heat generating element 2, the spring portion 6 heated by the temperature of the heat generating element 2 exceeds its elastic limitation and a failure to absorb the heat expansion may be caused; therefore, the spring portion 6 is preferably disposed below the heat generating element 2.
Moreover, the heat generating unit in embodiment 1 is exemplified by a structure in which the coil portion 5 of the first internal lead wire member 11A, the spring portion 6 and the internal lead wire 7, as well as the coil portion 5 of the second internal lead wire member 11B, the holding portion 4 and the internal lead wire 7, are integrally formed; however, needless to say, even when the respective members are formed with different members, the same effects can be obtained as long as they are respectively joined to one another electrically.
The heat generating element 2 used in embodiment 1 is formed by cutting a film sheet, and has a structure in which wide width portions 2A and narrow width portions 2b are alternately disposed sequentially in the longitudinal direction. As shown in
The heat generating element 2 of embodiment 1 has a thickness (t) of 100 μm, a maximum width (W1) of 6 mm, a minimum width (W2) of about 2 mm and a length (L) of 250 mm (see
The heat generating element 2 of embodiment 1 has a structure including a portion through which a current flows by applied power to generate heat (hereinafter, this portion is referred to as a power-applied heat-generating portion 20) and a portion which generates heat with thermal conduction from the power-applied heat-generating portion 2C (hereinafter, this portion is referred to as a conducted heat-generating portion 2D). The heat generating element configured as described above has the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity. In the case where the thermal conductivity of the heat generating element is less than 200 W/m·K, that is, the two dimensional isotropic thermal conductivity is poor, heat conduction from the power-applied heat-generating portion 2C to the conducted heat-generating portion 2D becomes smaller. As a result, the temperature difference between the power-applied heat-generating portion 2C and the conducted heat-generating portion 2D becomes larger, with the result that temperature irregularities occur in the heat generating element.
The heat generating element 2, used in the heat generating unit of embodiment 1 in accordance with the present invention, is mainly composed of a carbon-based substance, has a structure in which a plurality of film sheet materials are laminated with a void formed between the respective layers in the thickness direction so as to have superior two dimensional isotropic thermal conduction, and is formed by a material with a film sheet shape having a thermal conductivity of 200 W/m·K or more. Therefore, the heat generating element 2, which has the power-applied heat-generating portion 2C and the conducted heat-generating portion 2D, forms a heat source without temperature irregularities because of heat generation and heat conduction thereof.
The film sheet material that is a material for the heat generating element 2 is a highly oriented graphite film sheet having a heat resistant property, formed by heating a polymer film or a polymer film with a filler added thereto at a high temperature, for example, in an atmosphere of 2400° C. or more, to be fired into graphite, and has a thermal conductivity of 600 to 950 W/m·K in its plane direction. In the case of a film sheet obtained through processes in which powder mainly made from natural graphite is molded and fired and then formed into a film sheet shape through a rolling process, the sheet generally has a thermal conductivity of 200 to 400 W/m·K; however, the heat generating element 2 used in embodiment 1 of the present invention has a superior two dimensional isotropic thermal conductive property with a thermal conductivity of 600 to 950 W/m·K in its plane direction, as described above.
The two dimensional isotropic thermal conductive property as used herein refers to thermal conduction that is exerted in all directions, within a face defined by the orthogonal X-axis and Y-axis. Therefore, the two dimensional isotropic property of the present invention is not intended to be limited only by one direction (X-axis direction) of carbon fiber directions in a heat generating element in which, for example, the carbon fibers are formed side by side in the same direction, or by two directions (X-axis direction and Y-axis direction) of carbon fiber directions in a heat generating element formed by knitting the carbon fibers in crossing directions.
The film sheet material serving as the material for the heat generating element 2 used in the present invention has a laminated structure in which the layer surface in the plane direction has various facial shapes, such as a flat face, a concave/convex face or a waving face, with a void being formed between the respective opposing layers. In the laminated structure of this film sheet material, the image of the formation states of the voids formed between the respective layers is similar to a cross-sectional shape of a pie obtained through processes in which a pie dough is formed by bending the material so as to be overlapped with one after another a plurality of times (for example, several ten times, several hundred times) and the pie dough is baked. Consequently, the film sheet material that is the material for the heat generating element 2 of the present invention is allowed to have a superior two dimensional isotropic thermal conductive property in the thermal conductivity in its plane direction, as described earlier.
The polymer film used for the film sheet material produced as described above may be at least one kind of polymer film selected from the group consisting of polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzooxazole, polybenzobisoxazole, polypyromellitic imide (pyromellitic imide), polyphenylene isophthalic amide (phenylene isophthalic amide), polyphenylene benzoimidazole (phenylene benzoimidazole), polyphenylene benzobisimidazole (phenylene benzobisimidazole), polythiazole and polyparaphenylenevinylene. Moreover, the material for the filler to be added to the polymer film include: phosphoric acid ester-based, calcium phosphate-based, polyester-based, epoxy-based, stearic acid-based, trimellitic acid-based, metal oxide-based, organic tin-based, lead-based, azo-based, nitroso-based and solfonylhydrazide-based compounds. More specifically, examples of phosphoric acid ester-based compounds include: tricresyl phosphate, (trisisopropylphenyl)phosphate, tributyl phosphate, triethyl phosphate, trisdichloropropyl phosphate and trisbutoxyethyl phosphate. Examples of calcium phosphate-based compounds include: calcium dihydrogen phosphate, calcium hydrogen phosphorous and calcium triphosphate. Examples of polyester-based compounds include: polymers and the like between adipic acid, a zelaic acid, sebacic acid as well as phthalic acid and glycols as well as glycerins. Moreover, examples of stearic acid-based compounds include: dioctyl sebacate, dibutyl sebacate, and acetyltributyl citrate. Examples of metal oxide-based compounds include: calcium oxide, magnesium oxide and lead oxide. Examples of trimellitic acid-based compounds include: dibutyl fumarate and diethyl phthalate. Examples of lead-based compounds include: lead stearate and lead silicate. Examples of azo-based compounds include: azodicarboxylic amide and azobisisobutylonitrile. Examples of nitroso-based compounds include: nitrosopentamethylene tetramine and the like. Examples of solfonylhydrazide-based compounds include: p-toluenesulfonyl hydrazide.
The film sheet materials are laminated, and subjected to a heating treatment at 2400° or more in an inert gas, and by adjusting the pressure in the gas treatment atmosphere generated during the graphite-forming process, a heat generating element having a film sheet shape is produced. Moreover, if necessary, by subjecting the film-sheet shaped heat generating element to a rolling process, a film-sheet shaped heat generating element having a better quality can be obtained. The film-sheet shaped heat generating element thus manufactured is used for a heat generating element 2 in the heat generating unit of the present invention.
Note that the amount of addition of the filler is preferably set in a range from 0.2 to 20.0% by weight, and more preferably, from 1.0 to 10.0% by weight. The optimal amount of addition differs depending on the thickness of a polymer material, and in the case where the thickness of the polymer material is thin, the amount of addition is set to a larger amount, while in the case where the thickness is thick, the amount of addition may be set to a smaller amount. The role of the filler is to keep the film after the heating treatment in a uniform foamed state. In other words, the added filler generates a gas during the heating process, and voids resulting from the gas generation serve as passages so that decomposition gases from the film inner portion are allowed to gently pass therethrough. Thus, the filler is effectively used for forming the uniformly foamed state.
The film sheet material, produced as described above, is generally processed into a desired shape by a punching mold of Thomson type or a laser machining process. In the case where, as one example of the laser machining process, a laser machining process mainly using a heat machining function of a CO2 laser (wavelength: 10,600 nm) or the like is used with a thermal conductivity in a plane direction of the heat generating element 2 being set to 200 W/m·K or more, the heat is absorbed by the heat generating element to cause a failure to carry out the machining process. However, in the case where a laser machining process mainly using a non-heat machining function, such as a laser machining process using a wavelength from 1064 to 380 nm, for example, a short-wavelength laser machining process having a nominal length of 1064 nm, is used, it becomes possible to carry out a preferable machining process to obtain a desired shape with high precision.
In particular, upon forming the heat generating element 2 of embodiment 1, the inventors have confirmed that, by using the second high harmonic wave laser process with a nominal wavelength of 532 nm, a preferable machining process can be carried out with high precision. The material for the heat generating element 2 of embodiment 1 is a film sheet material, that is, a highly oriented graphite film sheet having a heat resistant property formed by heating a polymer film or a polymer film with a filler added thereto at a high temperature, for example, in an atmosphere of 2400° C. or more, to be fired into graphite. Moreover, the material forming the heat generating element 2 has a thermal conductivity of 600 to 950 W/m·K in its plane direction. In the case where the heat generating element 2 made from such a material is processed into a complicated shape, such as a shape having the thickness (t) of 100 μm, the maximum width (W1) of 6 mm, the minimum width (W2) of about 2 mm and the length (L) of 250 mm, the second high harmonic wave laser process with a nominal wavelength of 532 nm is preferably used. As described above, as the laser wavelength in the laser machining process becomes shorter, the thermal treatment becomes closer to a chemical treatment so that the effects of heat to the heat generating element 2 becomes smaller, and the generations of soot and burrs due to the treatment can be reduced, thereby making it possible to carry out a machining process with high precision. However, all the outer shapes of the heat generating element 2 are not necessarily required to be subjected to the laser machining process, and only either one of the wide width portion and the narrow width portion may be subjected to the laser machining process. For example, in the case where the wide width portion is determined by the element shape, only the narrow width portion may be subjected to the laser machining process, and needless to say, these processes may be properly selected on demand depending on the material shape or the like of the heat generating element.
Moreover, needless to say, the laser machining method may be selected on demand from machining methods having a laser machining wavelength (from 1069 to 380 nm) mainly utilizing the aforementioned non-heat machining function, depending on the material of the heat generating element 2, that is, the thermal conductivity in a plane direction and the shape. Furthermore, needless to say, the above-mentioned laser machining method used for processing the above-mentioned heat generating element 2 may be adopted in a heat generating unit of another embodiment to be described later, so as to carry out a hole-forming process of an area of the wide width portion of the heat generating element 22 shown in (b) of
Hereinafter, a specific structure of the heat generating unit in accordance with embodiment 1 will be described.
Each of the holding blocks 3 attached to the two ends of the heat generating element 2 has a substantially column shape, and is divided into two semi-column shapes. The heat generating element 2 is placed between the inner wall faces serving as the opposing faces of the semi-column-shaped holding blocks 3 divided into two portions, and the coil portion 5 of the first internal lead wire member 11A or the second internal lead wire member 11B is wound around the outer circumferential face of the holding block 3 so that the heat generating element 2 is held therein. With this arrangement, the holding blocks 3 support the two end portions of the heat generating element 2, while being electrically connected thereto. The holding blocks 3 made from a conductive material dissipate heat of the heat generating element 2 so that it exerts a heat releasing effect so as not to transmit high temperature to the coil portion 5 of the first internal lead wire member 11A or the second internal lead wire member 11B. For example, graphite is preferably used as the material for the holding blocks 3. However, any material may be used as the material for the holding blocks 3, as long as it is a material having a superior conductive property, such as a metal material. Moreover, the shape of the holding blocks 3 is not limited to a column shape, but may be formed into a shape such as a rectangular shape so as to be easily produced. Furthermore, the holding blocks 3 may have a shape in which the heat radiating effect is enhanced, for example, such a shape as to have a cooling fin or the like.
In embodiment 1, as has been described by the structural example having two divided holding blocks 3, a structure having a plurality of divided holding blocks so as to hold the heat generating element may be used, or a single integrated member, with slits, each having a thickness of each of the heat generating elements, being formed so that the heat generating elements 2 can be inserted therein, may be used with the same effects.
In embodiment 1 shown in
The heat generating element 2 is a member having elasticity in the thickness direction. Therefore, the heat generating element 2 having the above-mentioned structure is depressed by the opposing face of the holding block 3A so that the heat generating element 2 is deformed within its elastic range to form concave/convex portions. As a result, even when the heat generating element 2 generates a large contraction force due to a high temperature, the heat resistant member 12 serves as a wedge against the heat generating element 2 so that it is possible to reliably prevent the heat generating element 2 from coming off from the holding block 3A. Moreover, another structure may be prepared in which a convex portion or a concave/convex portion having a size not more than the thickness of the heat generating element 2 is formed at least one portion of the opposing inner wall face of the holding block 3A. With this arrangement, it becomes possible to prevent the heat generating element 2 from coming off from the holding block 3A.
In the heat generating unit of embodiment 1 having the above-mentioned structure, when power is supplied to the external lead wires 9 drawn out from the two sides thereof, a current is allowed to flow through the heat generating element 2 so that heat is generated by the resistance of the heat generating element 2. At this time, since the heat generating element 2 is mainly made from a carbon-based substance, infrared rays are emitted from the heat generating element 2.
By changing the surface shape of the heat generating element 2 in the heat generating unit of embodiment 1, the heat radiating state thereof can be changed. For example, even when the heat generating unit is formed by the same film sheet material, radiating energy thereof can be increased by reducing the thickness, with the width being widened, even in the case where no change is made on the resistance value.
As described earlier, the dimensions of the heat generating element 2 (see
The belt-shaped heat generating element 2 that is extended in the longitudinal direction is preferably designed so as to have a ratio of 5/1 or more between the length in the width direction and the length in the thickness direction. The length in the width direction is made five times or more larger than the length in the thickness direction so that the quantity of heat released from the surfaces forming the width direction is made substantially larger than the quantity of heat released from the surfaces forming the thickness direction; thus, it becomes possible to utilize the heat generating element 2 as a heat source having high directivity.
The heat generating element 2, which is mainly composed of a carbon-based substance and configured by using a film sheet-shaped material having a two dimensional isotropic thermal conductive property, has a positive characteristic (PTC) in which the resistance value increases as the temperature becomes higher, with a high heat-generating efficiency being exerted. For this reason, the time required for achieving a rated temperature from the start of heating is extremely short. Therefore, although a rush current occurs upon lighting on, the rush current is just two times as high as the equilibrium current although it depends on the temperature in the equilibrium state, and such a rush current as 10 times as high, as in the case of a heat generating element made of a tungsten wire is not generated. Therefore, the heat generating element 2 in the heat generating unit of embodiment 1 has a characteristic that hardly causes flickers. Moreover, the life of the heat generating element 2 is about 10000 hours although it depends on the service temperature of the heat generating element 2. The life is about two times longer than that of a heat generating element made of a tungsten wire.
At least one kind of polymer film particularly selected from the aforementioned film sheet materials, or the polymer film to which the aforementioned filler is added, is subjected to a heating treatment at 2400° C. or more in an inert gas, and the pressure in the gas treatment atmosphere generated during the graphite-forming process is controlled. By carrying out these controlling processes, it is possible to produce a heat generating element 2 that has a two-dimensional isotropic thermal conductive property and a positive characteristic (PTC) in which the resistance value increases as the temperature becomes higher in the temperature characteristic. The heat generating element 2 produced in this manner makes it possible to ensure stability in the generated temperature, and also to provide a stable heat source with high reliability that can carry out a stable self-input controlling operation in response to a thermal variation, in the case where an input voltage is supplied as a constant voltage.
In (a) of
The heat generating element 22, shown as a front view in (b) of
The shape of the heat generating element 23, shown in a front view of (c) of
Note that the positions of the holes to be formed are not limited to one row, and a plurality of positions of the holes may be prepared by taking into consideration an object to be heated and the specification and the like of an apparatus in which it is assembled; moreover, a plurality of holes, formed in a plurality of rows or at random, may be prepared.
The shape of each hole is not necessarily formed into a round shape as shown in (c) of
The shape of a heat generating element 24, as shown by a perspective view in (d) of
The shape of a heat generating element 25, as shown by a perspective view in (e) of
The shape of a heat generating element 26, as shown by a perspective view in (f) of
The shape of a heat generating element 27, as shown by a perspective view in (g) of
The shape of a heat generating element 28, as shown by a perspective view in (h) of
Moreover, in the same manner as in the heat generating element 23 shown in (c) of
The heat generating element 29 shown in (i) of
In the heat generating unit in accordance with embodiment 1 of the present invention, a heat generating element, which is mainly composed of a carbon-based substance, is made into a film-sheet shape, and has substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity. In particular, the heat generating unit of embodiment 1 uses a heat generating element that is formed into a film-sheet shape having a thermal conductivity of 200 W/m·K or more, with a thickness of 300 or less. For this reason, the heat generating unit of embodiment 1 makes it possible to generate heat uniformly. Moreover, in the heat generating unit of embodiment 1, since the heat generating element has pliability, flexibility and elasticity, it is possible to carry out machining processes, such as cutting out, hole-forming, bending, and cutting and raising processes, thereon, so that the heat generating element is allowed to have a high degree of freedom in designing.
In the above-mentioned embodiment 1, a description has been given by exemplifying a structure in which the heat generating element is inserted in a transparent quartz glass tube, with a gas being sealed in the glass tube, and used under a high temperature. However, a container other than the glass tube may be used for the heat generating element in the heat generating unit of the present invention. The film-sheet-shaped heat generating element, which is mainly composed of a carbon-based substance, and has two dimensional isotropic thermal conduction and properties, such as pliability, flexibility and elasticity, with a thermal conductivity of 200 W/m·K or more and a thickness of 300 μM or less, has an amount of oxidation smaller than that of other carbon-based materials for the heat generating element, not only when used under a high temperature (about 1100° C.), but also when used around 800° C., so that the resulting composition structure is sufficiently durable for practical use. This is because the film-sheet-shaped heat generating elements are closely molded. Therefore, the material for the container for the heat generating element can be selected in association with the service temperature of the heat generating element. For example, when the heat generating element is used at 180° C. or less, a container made from a silicon material may be used, and when used at 250° C. or less, a container made from a fluorine resin may be used, while, when used at 800° C. or less, the insulating material may be selected from materials, such as a mica material, ceramics, crystallized glass, a quartz tube and heat resistant glass, within a permissible range of heat resistant temperatures. It is not necessary to fill the container with a gas under the service temperature of 800° C. or less, and the structure and shape of the heat generating unit can be designed freely in accordance with service objectives. Thus, in the case of the heat generating unit to be used under the service temperature of 800° C. or less, it becomes possible to greatly widen the degree of freedom in designing, and also to reduce the costs.
Note that, with respect to the tube shape in embodiment 1, a description has been given as a substantially round shape in its cross section; however, the present invention is not limited to the substantially round shape, and a square shape or a polygonal shape, such as a hexagonal shape, may be used in accordance with the specification and objectives of the heat generating unit; moreover, an elliptical shape may be used with the same effects as those of the heat generating unit of embodiment 1.
Moreover, in the heat generating unit of embodiment 1 of the present invention, needless to say, since the heat generating element has superior pliability, flexibility and elasticity, the heat generating unit can be formed into a tube shape, a rectangular shape, a curved shape with a bent portion being formed in the longitudinal direction, an annular shape with a round portion, and the like.
Hereinafter, heat generating units in accordance with embodiment 2 of the present invention will be described with reference to (a) to (d) of
The heat generating units of embodiment 2 are different from the heat generating units of embodiment 1 only in the shapes of the heat generating elements, and the other portions are the same as those of embodiment 1. Therefore, descriptions will be given on the shapes of the heat generating elements in the heat generating units of embodiment 2, and the descriptions of embodiment 1 will be applied to the other structural components.
In each of the heat generating elements of the heat generating units of embodiment 2, an attempt is made not to make the temperature distributions in the longitudinal direction and the width direction of the heat generating element uniform, but to make the temperature distributions different from each other. In each of the heat generating elements of the heat generating units of embodiment 2, an area having a different resistance value per unit length is formed in at least one portion in the length direction. The heat generating element of embodiment 2 is a modified example of the heat generating element 2 that has been described with reference to
In a heat generating element 201 shown in (a) of
As shown in (a) of
In a heat generating element 202 shown in (b) of
In the heat generating element 202 shown in (b) of
In a heat generating element 203 shown in (c) of
In a heat generating element 204 shown in (d) of
Not limited to the pattern shapes shown in (a) to (e) of
In particular, the heat generating element in the heat generating unit of the present invention, mainly composed of a carbon-based substance, has a two-dimensional isotropic thermal conductive property and superior pliability, flexibility and elasticity, and is formed into a film-sheet shape having a thermal conductivity of 200 W/m·K or more, with a thickness of 300 μm or less. For this reason, the heat generating element in the heat generating unit of the present invention makes it possible to carry out machining processes, such as cutting out, hole-forming, bending, and cutting and raising processes, thereon, so that the heat generating element is allowed to have a structure that can be altered on demand in accordance with the structure of the heat generating unit.
Referring to (a) to (d) of
The heat generating unit of embodiment 3 differs from the heat generating unit of embodiment 1 in the shape of the heat generating element, the other structures are the same as those of embodiment 1. Therefore, the shape of the heat generating element in the heat generating unit of embodiment 3 will be described, and with respect to the other components, the descriptions of embodiment 1 will be applied.
In each of the heat generating elements of the heat generating units of embodiment 3, an attempt is made not to make the temperature distributions in the longitudinal direction and the width direction of the heat generating element uniform, but to make the temperature distributions different from each other. In each of the heat generating elements of the heat generating units of embodiment 3, an area having a different resistance value per unit length is formed at least one portion in the length direction. The heat generating element of embodiment 3 is a modified example of the heat generating element 22 that has been described with reference to (b) of
In a heat generating element 301 shown in (a) of
In the heat generating element 301 shown in (a) of
In a heat generating element 302 shown in (b) of
In the heat generating element 302 shown in (b) of
In a heat generating element 303 shown in (c) of
In a heat generating element 304 shown in (d) of
Not limited to the pattern shapes shown in (a) to (e) of
Hereinafter, heat generating units in accordance with embodiment 4 of the present invention will be described with reference to
The heat generating units of embodiment 4 are different from the heat generating units of embodiment 1 in the shapes of the heat generating elements, and in that the heat generating elements have curved faces. In the heat generating units of embodiment 4, those heat generating elements, described in embodiment 1, the widths of which are further widened are utilized. In order to insert each of the heat generating elements of embodiment 4 into a quartz glass tube serving as a heat resistant tube, at least one portion of each heat generating element in its cross-sectional shape in a direction (width direction) orthogonal to the longitudinal direction is formed into a curved face so that the heat generating element, even if it has a wide width, can be easily housed in the heat resistant tube.
As shown in
In the heat generating unit of embodiment 4, since those members that are other than the heat generating element in the heat generating unit of embodiment 1 have the same structures as those of embodiment 1, those members having the same functions and structures as those of embodiment 1 are indicated by the same reference numerals, and the same detailed descriptions as those of embodiment 1 are applied thereto.
As shown in
Heat generating bodies 402, 403 and 404, shown in (a), (b) and (c) of
In the heat generating element 402 shown in (a) of
Moreover, the heat generating element 402, shown in (a) of
In the heat generating element 403 shown in (b) of
In the heat generating element 404 shown in (c) of
The heat generating element in the heat generating unit in accordance with embodiment 4 of the present invention is mainly composed of a carbon-based substance and has a film-sheet shape. Therefore, the heat generating element in the heat generating unit of embodiment 4 has a so-called two dimensional isotropic thermal conductivity that exerts substantially the same thermal conductivity in a plane direction. Since the heat generating element in the heat generating unit of embodiment 4 is made from a material that has superior pliability, flexibility and elasticity, and can be machined with high precision, various modifications can be made as shown by the heat generating elements used in embodiment 4. In the heat generating elements in embodiment 4, in the case where the maximum width is larger than the inner diameter of the heat resistant tube, a curved face can be formed so that the heat generating element may be disposed along the inner wall face of the heat resistant tube. Moreover, even in the case where the maximum width is smaller than the inner diameter of the heat resistant tube, the heat generating elements having various shapes with curved faces as described in embodiment 4 can be used for the purpose of concentration and diffusion of heat radiation from the heat generating elements.
In the heat generating unit of embodiment 4, by forming curved portions in the heat generating element, the shape (diameter) of a heat resistant tube used for housing the heat generating element is made free from regulations caused by the shape of the heat generating element. As a result, the heat generating unit of the present invention has a structure capable of variably changing a heat capacity; thus, for example, by miniaturizing the heat resistant tube without changing the heat generating element to make the heat capacity smaller, it is possible to start the temperature rise earlier so that designing processes suitable for purposes can be carried out.
Moreover, by disposing the heat generating element close to the inner wall face of the heat resistant tube, it is possible to raise the inner wall temperature of the heat resistant tube and consequently to increase heat radiation from the heat resistant tube.
Furthermore, the heat generating element formed with curved faces may be inserted in a heat resistant tube, with the pattern shape in the longitudinal direction and the pattern shape in the width direction being combined with each other, so that a heat generating unit is formed; thus, it becomes possible to properly set not only the temperature distribution in the longitudinal direction, but also the temperature distribution in the circumferential direction. As a result, the present invention makes it possible to form a three-dimensional temperature distribution, and consequently to greatly widen the service range of the heat generating unit of the present invention. In the conventional heat generating unit, the three-dimensional temperature distribution is formed by using a plurality of heat generating units; however, in accordance with the present invention, the same structure can be formed by using only one heat generating unit so that it is possible to save space and also to reduce costs.
Hereinafter, a heating apparatus in accordance with embodiment 5 of the present invention will be described with reference to (a) to (c) of
In the heating apparatus of embodiment 5, the heat generating units of embodiments 1 to 4 are used as heat radiating sources. (a) to (c) of
Referring to (a) to (c) of
The heating apparatus, shown in (a) of
In addition to the heat generating unit 50 serving as the heat radiating source shown in (a) to (c) of
In the heating apparatus of embodiment 5, the heat generating element 2 used for the heat generating unit 50, which is mainly composed of a carbon-based substance, is made into a belt shape by using a film-shaped material having substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity. For this reason, the amount of heat, released from the plane portion of the heat generating element 2, exerts a greater value remarkably in comparison with the amount of heat released from the width face portion (face forming the thickness). In other words, the heat generating element 2 is a heat radiating body having directivity. Therefore, by placing the reflective plate 51 at a position opposite to the plane portion of the heat generating element 2, heat rays, emitted from the back face of the heat generating element 2, are reflected by the reflective plate 51 so that it becomes possible to efficiently heat an object to be heated that is placed in front of the reflective plate 51.
In the heating apparatus shown in (a) of
In the heating apparatus shown in (b) of
In the heat radiating source of the heating apparatus arranged as shown in (b) of
As described above, in the heating apparatus shown in (b) of
Moreover, in the heating apparatus shown in (b) of
As described above, by installing the reflective plates 51 and 53 serving as the reflective means in the heat generating units 50 and 52, it is possible to configure a heating apparatus having high radiation efficiency.
Additionally, as the shape of the reflective face of the reflective plates 51 and 53 shown in (a) and (b) of
Moreover, as the shape of the convex portion 53A of the reflective plate 53 shown in (b) of
The heat generating units 50 and 52 shown in (a) and (b) of
Moreover, as the material for the reflective plates 51 and 53, aluminum, aluminum alloys, various kinds of stainless steels and the like may be used. Needless to say, it is preferable to apply a surface treatment, such as coating of a reflective material having a high reflective efficiency to the reflective faces of the reflective plates 51 and 53 so as to improve the reflectance of the reflective plates 51 and 53.
Note that, with respect to the cross-sectional shape orthogonal to the longitudinal direction (extending formation direction) in the reflective plates 51 and 53, the present invention is not limited to the parabolic line shape, and any shapes capable of at least applying radiated heat to the back face of the heat generating element so as to heat the object to be heated placed on the front face side of the heat generating element, such as, for example, curved face shapes and polygonal shapes capable of diffused reflection, may be used.
The heating apparatus shown in (c) of
In the heating apparatus shown in (c) of
As described above, by forming the reflective film 55 serving as the reflective means on the back face of the glass tube 1, it becomes possible to configure a small-size heating apparatus with high radiating efficiency.
Hereinafter, a heating apparatus in accordance with embodiment 6 of the present invention will be described with reference to
The copying machine serving as the heating apparatus of embodiment 6 uses the heat generating unit (see
Since the heating apparatus of embodiment 6 is a copying machine, the tube member 61 surrounding the heat generating unit 60 is a toner fixing roller. Hereinafter, the tube member 61 is described as a toner fixing roller 61.
The toner fixing roller 61 is designed to be in contact with a pressure roller 62 so as to rotate together therewith. A sheet of paper 64 with toner 63 having a predetermined shape supported thereon is inserted between the toner fixing roller 61 and the pressure roller 62, and heated and pressed so as to be fixed thereon. Therefore, in order to efficiently fix the toner 63 on the paper that has been passed through the gap between the toner fixing roller 61 and the pressure roller 62, the curved face on the convex side of the heat generating element 401 is disposed so as to face an area including the opposing faces (toner fixing area) between the toner fixing roller 61 and the pressure roller 62. Here, the direction in which the curved face on the convex side of the heat generating element 401 faces is set so that it is directed to the upstream side of the toner fixing area, that is, the front side area from the toner fixing area of the toner fixing roller 61. By placing the heat generating element 401 in this manner, a heating process is carried out on the toner fixing roller 61, with a portion on the upstream side of the toner fixing area being included therein; thus, the amount of heat accumulation is increased in this portion so that the amount of heat released from the heat generating element 401 can be effectively used for the toner fixing process.
In the heating apparatus of embodiment 6, the tube member serving as the toner fixing roller 61 that is disposed so as to surround the heat generating unit 60 is allowed to radiate heat released from the heat generating unit 60 in a desired direction, and an area facing the center of the curved face on the convex side of the heat generating element 401 is allowed to form the center of heat radiation. The description has been given by exemplifying this tube member (61) as a single member; however, the tube member (61) may also be configured by combining a plurality of members.
In the copying machine serving as the heating apparatus of embodiment 6, by effectively arranging the heat generating unit 60 having directivity in this manner, it becomes possible to provide a heat radiating source with high efficiency.
Next, a temperature controlling method for the heating apparatus of embodiment 6 will be described with reference to
Power supplied from the power supply 67 is controlled in the control part 66 in accordance with an instruction by the user, and applied to the heat generating unit 60. Upon application of power, the heat generating element 401 of the heat generating unit 60 is heated to a high temperature to raise the temperature of the toner fixing roller 61 to a predetermined temperature (toner fixing temperature). A sensor unit 65 is attached to the toner fixing roller 61 so as to detect the temperature of the toner fixing roller 61. The sensor unit 65 feeds back the detected temperature of the toner fixing roller 61 to the control part 66 so that the control part 66 controls the power supplied to the heat generating unit 60 to adjust the temperature of the toner fixing roller 61.
As described above, upon controlling the power to be applied to the heat generating unit, the heating apparatus of embodiment 6 makes it possible to add the detected temperature as another condition to controlling conditions. Moreover, upon controlling the temperature, one of processes, such as an ON/OFF control by using a temperature detection means such as a thermostat, a phase control of the input power supply by using a temperature sensor that detects an accurate temperature, a duty factor control and a zero-cross control, is independently carried out, or some of these are carried out in combination so that it becomes possible to achieve a heating apparatus capable of carrying out the temperature control with high precision.
Therefore, in accordance with the heating apparatus of embodiment 6 arranged as described above, the directivity control is carried out by properly disposing the heat generating element and the applied power control is carried out by the detected temperature so that a heating operation with superior radiation characteristics and a temperature control with high precision are available.
In the heating apparatus of embodiment 6, a description has been given by exemplifying the heat generating unit (see
Moreover, a description has been given by exemplifying a copying machine as the heating apparatus of embodiment 6; however, the heat generating unit of the present invention can be used for a heat radiating source for fixing toner also in an electronic apparatus, such as a facsimile and a printer, and the same effects can be obtained. In the case where the mechanism is used for fixing toner in an electronic apparatus, such as a copying machine, a facsimile and a printer, the heat generating unit to be used as a heat radiating source is used in a manner so as to be surrounded by a tube member referred to as a roller.
Furthermore, in addition to electronic apparatuses, such as a copying machine, a facsimile and a printer, the heating apparatuses of the present invention also include electric heating apparatuses, such as a heating stove, cooking apparatuses, such as a cooking and heating device, drying machines for foods and the like, and other apparatuses that require heating processes to a high temperature in a short period of time.
In the heating apparatus of the present invention, the roller serving as a tube member that surrounds the heat generating unit has a structure in which the inner side is formed by a metal material and the outer side is coated with a silicon resin, with driving gears and the like for use in driving being attached to the two sides of the roller. In order to enhance the absorbing property for heat and the like, a ceramic material, a far infrared paint or the like may be applied to the inner side of the roller. Moreover, from the viewpoints of heat-releasing and heat-absorbing properties and strength, the tube member may be configured by a plurality of metal members, such as aluminum, iron and the like, so as to obtain higher heating efficiency.
In the case where the heat generating unit of the present invention is used as a heat source for a cooking apparatus, the heat generating unit is disposed in a manner so as to be surrounded by a tube member. The tube member is a tube-shaped heat resistant pipe made of a single member or a plurality of members. In the case where the heat generating unit having a heat generating element surrounded by a quartz glass tube, as it is, is used as a heat source for a cooking apparatus, the quartz glass tube tends to cause erroneous permeation due to alkali metal ions and the like, contained in seasonings and the like, such as salt and soy source, that are used in cooking processes, and subsequent damages, with the result that the heat generating unit serving as the heat source has a shortened service life. For this reason, by designing the heat generating unit so as to be surrounded by a tube member that is a heat resistant pipe, it becomes possible to prolong the service life of the heat generating unit.
Note that, by using crystallized glass having superior light transmittance, ceramics having a high amount of radiation of far infrared rays and the like as the tube member, the applications of the apparatus can be widened.
With respect to the positional relationship between the heat generating unit and an object to be heated, needless to say, by directing the heating center of the heat generating element to the heating object side, it becomes possible to heat the heating object with high efficiency.
As described above, in the heat generating unit of the present invention, a heat generating element, which is mainly composed of a carbon-based substance, is made into a film sheet shape having substantially the same thermal conductivity in a plane direction, that is, a so-called two dimensional isotropic thermal conductivity, and has pliability, flexibility and elasticity. Moreover, the heat generating element has a thermal conductivity of 200 W/m·K or more and a thickness of 300 μm or less. The heat generating element having such an arrangement makes it possible to easily carry out machining processes, such as cutting out, hole-forming, bending, and cutting and raising processes, thereon, so that the heat generating element is easily formed into a shape in which a cross-sectional shape orthogonal to the longitudinal direction thereof has a curved face. Furthermore, the heat generating element, formed in the heat generating unit of the present invention, can be modified into various shapes, such as a pipe shape, a plate shape, a curved shape with a pipe shape being bent in the longitudinal direction, a shape with a pipe shape being formed into a round shape, in accordance with the shape of a container (heat resistant pipe), and can also be modified with high precision in accordance with the service objectives, and assembled into the apparatus.
Moreover, in the heat generating unit of the present invention, the heat generating element is formed into a mode in accordance with the service objectives so that heat radiation can be exerted with high efficiency from a plane portion or a curved face portion of the heat generating element.
Furthermore, in the heat generating unit of the present invention, the heat generating element has two dimensional isotropic thermal conduction and is formed into a film-sheet shape having properties such as pliability, flexibility and elasticity; therefore, not only a power-applied heat-generating portion in which a current is allowed to flow to generate heat, but also portions other than the power-applied portion are allowed to generate heat by heat conduction from the power-applied heat-generating portion. Therefore, the heat generating element can be formed into a structure having a complicated pattern (shape) so that it becomes possible to eliminate irregularities in the heat generating temperature due to a slight difference in thicknesses caused by a machining process and consequently to increase the degree of margin in machining precision.
Moreover, in the heat generating unit of the present invention, the tube-shaped heat resistant tube (glass tube 1 shown in
As described in embodiment 5, in the heating apparatus shown in (a) of
Moreover, as described in embodiment 5, in the heating apparatus shown in (b) of
Moreover, in the heating apparatus shown in (b) of FIG. 10, a reflective plate is disposed on the back face side of the heat generating element of the heat generating unit so that the heat generating element is not irradiated with heat rays that are reflected by the reflective plate; therefore, it is possible to prevent a temperature rise due to secondary heating of the heat generating element by the reflective plate, and consequently to achieve a heating apparatus with stable specifications that is free from deviations. In the heat generating element used in the heat generating unit, its rate of change in resistance is varied depending on the temperatures of the heat generating element itself. Moreover, in most cases, the ratings of the heat generating unit are set only by taking into consideration the self-heat radiation of the heat generating unit. In the case where the heat generating unit, set in this manner, is assembled into a heating apparatus, the temperature of the heat generating element rises by heat rays from the reflective plate due to the shape of the reflective plate to cause the ratings of the heating apparatus to change. Since the heating apparatus of the present invention is designed so as to prevent the heat generating element from being irradiated by the reflective plate, it is possible to prevent the ratings of the heat generating unit from being influenced by the reflective plate, and consequently to easily design a heating apparatus reliably provided with predetermined desired specifications.
As described in embodiment 5, in the heating apparatus shown in (c) of
Moreover, in the heating apparatus of the present invention, as described in embodiment 6, the heat generating element of the present invention may be installed, with a tube member covering the heat generating unit being disposed. With this structure, foreign matters, generated by the object to be heated or the like, such as meat juice, seasonings and the like, are shield by the tube member to be prevented from directly coming into contact with the heat generating unit. With this arrangement, it is possible to prevent damages and disconnections due to degradation of the surface of the heat generating unit, and consequently to provide a heating apparatus with a longer service life.
Moreover, in the heating apparatus of the present invention, in the case where the heat generating unit is used, for example, as a heat source of an electronic apparatus, such as a copying machine or the like, by using the tube member covering the heat generating unit as a toner fixing roller, it becomes possible to provide a structure in which a portion of the toner fixing roller to come in contact with paper can be heated with high efficiency.
Furthermore, in the heating apparatus of the present invention, by using a structure in which at least one portion of the heat generating element is covered with a heat resistant tube, it becomes possible to raise the temperature of the heat generating element to a higher level, and consequently to provide a heating apparatus that can alter the heating distribution.
The heat generating unit and the heating apparatus of the present invention uses a heat generating element that is mainly composed of a carbon-based substance, and made by a film shaped material that has a two dimensional isotropic thermal conductivity, as well as pliability, flexibility and elasticity, and also has a thermal conductivity of 200 W/m·K or more, with a thickness of 300 μm or less, and this heat generating element has a high radiating rate of 80% or more.
Although the invention has been shown and described in detail with respect to preferred modes, the contents of the disclosure of these preferred modes can be modified in detailed portions of the structures, and the combinations and the change in the order of the respective components can be devised without departing from the scope and spirit of the invention.
Since the heat generating unit in accordance with the present invention has a small size with high efficiency, it can be applied widely as heat sources, and a heating apparatus using the heat generating unit makes it possible to carry out a heating with high efficiency, and is effectively applied.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-023851 | Feb 2007 | JP | national |
| 2007-324418 | Dec 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/050960 | 1/24/2008 | WO | 00 | 7/30/2009 |
