JP3933996B2 - Defrost heater and cooling device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defrosting heater used in a cooling storage device or a cooling device such as a freezer or a refrigerator, and more particularly to a defrosting heater suitable for a cooling storage device using a combustible gas as a refrigerant of a cooling mechanism.
[0002]
[Prior art]
A conventional refrigerator defrost heater will be described with reference to FIGS.
As shown in FIG. 6, the conventional refrigerator 21 forms a refrigerator compartment with a box-shaped main body 21a and a door 21b having a handle 21d attached to the front portion of the main body 21a via a packing 21c. A shelf 21e and the like are provided inside the refrigerator compartment.
In the cooling mechanism in the refrigerator 21, the refrigerant gas compressed by the compressor 22 becomes high-temperature and high-pressure, and the high-temperature and high-pressure refrigerant gas exchanges heat with the outside air in the condenser 23 to be liquefied and flows into the expansion mechanism 24. The refrigerant gas liquefied by the expansion mechanism 24 is decompressed, evaporated by the evaporator 25, and cooled by exchanging heat with the air in the refrigerator compartment through the protective plate 25a.
[0003]
And if a cooling mechanism is drive | operated for a fixed time, frost will adhere to the outer wall of the evaporator 25 by cooling of the air in a refrigerator compartment. Therefore, the operation is automatically switched to the defrosting operation and the defrosting heater 26a is energized to supply power. The frost adhering to the outside of the evaporator 25 is melted by the heat radiated from the defrosting heater 26 by energization, becomes water droplets, etc., flows out of the refrigerator 21 through the drain hole 27 and is removed.
[0004]
Conventionally, a defrost heater called LT valve with a structure in which a filament wound with a nichrome wire is inserted into an opaque quartz tube, lead wires are joined to both ends of the filament, and sealed with a silicone rubber cap or the like is widely used. It had been.
Recently, a defrosting heater 26a called a Colts lamp shown in FIG. 7 is also used. In this Colts lamp, molybdenum foils 7a and 7b are welded to both ends of a tungsten wire filament 12 wound in a coil shape, and molybdenum wires 6a and 6b joined to inner ends of external lead wires 8a and 8b, respectively, are welded thereto. The heating element thus obtained is inserted into the transparent quartz glass tube 1. 8c and 8d are insulation coatings for introducing the lead wires 8a and 8b. In the defrosting heater 26a of this Colts lamp, the end of the quartz glass tube 1 is melt-sealed with the molybdenum foils 7a and 7b after the inside air is replaced with an inert gas.
[0005]
The problem that chlorofluorocarbon (hereinafter referred to as CFC), which has been widely used as a refrigerant for a conventional cooling device, has caused environmental degradation such as ozone layer destruction and global warming has been highlighted. From this point of view, the abolition of CFC, which has been widely used as a refrigerant for cooling devices in recent years, has become an extremely important environmental problem theme.
Therefore, conversion to the use of hydrocarbons (hereinafter referred to as HC), which is flammable as a refrigerant gas but has very little influence on global warming, has been studied. For example, it is disclosed that propane (R290) and isobutane (R600a), which are HC, can be applied to household refrigerators in p281 to p291 of the 11R-11F commission B1 / 2 proceedings in Belgium in February 1993 Has been.
[0006]
[Problems to be solved by the invention]
The former nichrome wire type LT valve used as a defrosting heater has a temperature of the heating element itself of 500 ° C. or more and the space between the opaque quartz tube in which the heating element is inserted and the external atmosphere are completely Not sealed. Therefore, the heating element may become an ignition source for the combustible refrigerant gas leaked to the outside from the cooling device.
[0007]
In the latter Colts lamp, both ends of the transparent quartz glass tube are melt-sealed, so that the internal heating element and the external atmosphere are completely cut off, and the heating element does not become an ignition source. However, since the temperature of the heating element is as high as 1500 ° C to 2000 ° C, the surface temperature of the transparent quartz glass tube exceeds 400 ° C. Therefore, when using an HC refrigerant with extremely low ozone depletion, such as isobutane with an ignition temperature as low as 460 to 495 ° C., if isobutane leaks from the cooling mechanism, the Colts lamp itself may become an ignition source. .
As described above, all the conventional defrost heaters have a problem that they cannot be used due to the danger of ignition and explosion with respect to the combustible refrigerant gas.
[0008]
Therefore, an attempt has been made to reduce the power consumption of one Colts lamp and to lower the surface temperature of the transparent quartz glass tube by about 100 ° C. from the ignition temperature of isobutane in a safe state of 360 ° C. or less. In this case, since the power consumption is small, the defrosting capability is insufficient, so a method of using two Colts lamps has been studied.
On the other hand, the nichrome wire and tungsten wire used in the conventional defrost heater have a specific resistance value of the material, and it is a wire to increase the resistance value of the heating element so as to reduce the power consumption of one Colts lamp. There is no other way but to make the diameter narrower or longer. Since the mechanical strength is lowered, there is a limit to the wire diameter of the heating element, and the resistance value is generally increased by increasing the wire diameter. In that case, the size of the defrost heater becomes large.
However, the size of the defrosting heater used in the refrigerator is limited by the internal space of the refrigerator. There is a problem that it is very difficult to set the surface temperature of the quartz glass tube to 360 ° C. or less within such limited dimensions.
[0009]
The present invention provides a defrosting heater capable of obtaining sufficient power consumption with a single heater and capable of reducing the surface temperature of a quartz glass tube to 360 ° C. or less despite the small size, and the same. An object is to provide a cooling device.
[0010]
[Means for Solving the Problems]
  Defrosting of the present inventionheaterThe compressorAndContractorAnd bulgeZhang mechanismAnd steamConnect the generator to the circulation path with a refrigerant line in sequence.ConfiguredCooling systemToA defrosting heater disposed in the vicinity of the evaporator so as to vaporize and remove frost generated outside the evaporator, which is disposed inside a refrigerator having a cooling mechanism enclosing a combustible refrigerant, A defrosting heater is a heating element formed of a sintered body containing a carbonaceous material.Sealed insideQuartz glass tubeThe heating element is formed by mixing and sintering a composition having shapeability and substantially containing residual carbon after sintering, and at least one metal compound or metalloid compound. The energy radiation density from the surface of the heating element (power consumption per unit radiation area: hereinafter watt density) is 2 to 20 W / cm ² And the surface temperature of the quartz glass tube is 360 degrees or less,It is characterized by that.
[0011]
  According to the defrost heater of this configuration, since the heating element is sealed in the quartz glass tube, even when a flammable refrigerant gas leaks, the heating element does not come into direct contact with the heating element. It cannot be a fire source. AlsoSintering comprising a carbon-based material formed by mixing and sintering a composition having formability and substantially containing residual carbon after sintering and at least one metal compound or metalloid compound bodyThe specific resistance value of the heating element formed by the above can be selected within a large range by adjusting its composition. Therefore, it is possible to create a defrosting heater in which power consumption and the temperature of the heating element can be freely selected.
[0012]
  Furthermore, there is an exact correlation between the temperature of the heating element and the surface temperature of the quartz glass tube. As a result, a heater having a surface temperature of the quartz glass tube of 360 ° C. (which is said to be safe) lower by about 100 ° C. than the ignition temperature of the flammable refrigerant (R600a) can be realized. As a result, it is possible to provide a safe defrosting heater that does not cause ignition or explosion caused by the defrosting heater when flammable refrigerant gas leaks.
  Further, the oxidation of the heating element can be prevented by replacing the oxidizing gas, which is the internal gas at the time of assembly, with an inert gas or by applying a vacuum. furtherFormed by mixing and sintering a composition having formability and substantially containing residual carbon after sintering, and at least one metal compound or metalloid compound,A heating element formed of a sintered body containing a carbon-based material is a manufacturing method in which extrusion molding is performed and fired, so that heating elements having various cross-sectional shapes such as thin and thin objects and thick and thick objects can be freely created.
[0013]
The inventor has studied various lamp-type heaters using a sintered body containing a carbon-based material. Among them, a sintered body composed of one or more of carbonaceous materials, oxides of compounds, oxides of metalloid compounds, carbides, nitrides, borides, silicides, etc., which are conductors, and their A device with a different mixing ratio or a heat generating element formed from a carbon-based material with a different shape or cross-sectional area was prototyped and evaluated. As a result, it was confirmed that a heating element having a specific resistance value of several thousand to several million μΩ · cm can be produced.
[0014]
In the defrost heater having the above configuration, the energy radiation density from the surface of the heating element (power consumption per unit radiation area: watt density) is 2 to 20 W / cm.²It is preferable to use a heating element.
Watt density (W / cm) obtained by dividing the power consumption of the heating element (W number) by the surface area of the heating element²) And the surface temperature (° C.) of the heating element have a little variation. It has been found that this relationship does not change even when the material of the heating element, the cross-sectional shape, or the light emission length changes, and correlates only with the watt density.
Of course, it has also been confirmed that there is an accurate correlation between the surface temperature of the heating element and the surface temperature of the encapsulated quartz glass tube. That is, when the diameter of the quartz glass tube is determined and a defrosting heater having a desired surface temperature of the quartz glass tube is obtained, it has been found that a desired heating element can be designed from the watt density.
[0015]
  As mentioned aboveFormed by mixing and sintering a composition having formability and substantially containing residual carbon after sintering, and at least one metal compound or metalloid compound,A defrost heater using a sintered body containing a carbon-based material as a heating element can arbitrarily select a watt density, so that the surface temperature of the quartz glass tube of the defrost heater can be kept below a predetermined temperature. For example, when isobutane is used as a refrigerant, the safe temperature at which the refrigerant does not ignite even if the refrigerant leaks is 360 ° C. or less, and the watt density of the heating element that can obtain the necessary power consumption at the temperature is 2 to 20 W / cm.², More preferably 3-15 W / cm²It is.
[0016]
  Also,What is important in the heater of the present invention is that in order to realize a defrost heater having a desired power consumption and a surface temperature of the quartz glass tube with the light emission length of the defrost heater and the diameter of the quartz glass tube determined, a heating element That is, the surface area of the heating element can be freely changed and the specific resistance value of the heating element can be freely changed.Formed by mixing and sintering a composition having shapeability and substantially containing residual carbon after sintering, and at least one metal compound or metalloid compound,Since the heating element formed of a sintered body containing a carbon-based material is made by an extrusion molding method or the like, the surface area can be changed by changing the die shape and size of the extruded portion. In addition, in order to obtain a change in the specific resistance value, as a result of experimental studies on many materials, a mixture of a carbon-based material and a metal compound or metalloid compound is sintered to obtain a wide range of specific resistance values. It was found that a heating element with high strength and long-term reliability can be made.
[0017]
The metal compound or metalloid compound contains at least one of metal carbide, metal boride, metal silicide, metal nitride, metal oxide, metalloid nitride, metalloid oxide, metalloid carbide. Is preferred. In order to realize the watt density, metal carbide, metal boride, metal silicide, metal nitride, metal, as an additive material that increases specific resistance and has little characteristic fluctuation during heat generation compared to carbon-based materials. In a heating element made by sintering a material in which at least one of oxide, semi-metal nitride, semi-metal oxide, and semi-metal carbide is mixed, the specific resistance value of the heating element is several thousand to several million μΩ. -It was confirmed that it can be changed within the range of cm.
[0018]
The composition containing substantially residual carbon after sintering in the mixed material before sintering preferably contains a resin as a component. When fired by including a resin, it is carbonized, and a sintered body with a high bending strength can be realized in the process. Further, by selecting the type of the resin material, it is possible to form a heating element in which the fired carbon contains carbon having a large specific resistance value such as non-graphitizable carbon.
More preferably, the composition containing carbon substantially after sintering contains at least one carbon powder of carbon black, graphite, and coke powder. The component that controls the conduction mechanism of the heating element is carbon, and there are various types of materials, but materials whose characteristics do not easily change even when used for a long time at elevated temperatures are carbon black, graphite and coke. This can be realized by using at least one of the powders.
[0019]
Furthermore, in the defrosting heater having the above-described configuration, it is preferable that a reflection film that reflects light radiated from the heating element in a predetermined direction is formed on at least a part of the inner wall or the outer wall of the quartz glass tube. The defrost heater is to quickly remove frost adhering to the periphery of the evaporator, and the carbon-based heating element whose emissivity is 0.85 close to a black body (emissivity is 1.0) depends on radiant energy. Since heating is the main component, it is important to concentrate the radiant light in the direction of the evaporator. When a reflective film is formed on the surface of the quartz glass tube, most of the emitted light can be irradiated toward the evaporator, so that an energy efficient defrosting heater can be realized.
[0020]
In the defrosting heater having the above-described configuration, it is preferable that a substance that decomposes odor is deposited on at least a portion of the outer wall of the quartz glass tube. Since various foods are stored in the refrigerator, an unpleasant odor tends to accumulate. A function of removing unpleasant gas in the refrigerator or the like can be added by applying a substance that decomposes odor.
A method for forming a substance that decomposes odor is a powder of molecular sieve having an adsorption function, a platinum compound as a catalyst component, a sol of alumina or silicon dioxide as an adhesive component, and a slurry-like material mixed with water in the quartz glass tube. It is preferably formed by coating and baking.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a defrosting heater suitable for a refrigerator according to the present invention will be described with reference to the accompanying drawings.
[0022]
Example 1
FIG. 1 is a cross-sectional view of a defrosting heater 26 according to a first embodiment of the present invention that is employed for a refrigerator.
In the defrosting heater 26 shown in FIG. 1, a heating element 2 formed of a sintered body containing a carbon-based material is enclosed inside a transparent quartz glass tube 1. Specifically, the coil-like portions 5a and 5b of the internal lead wires 3a and 3b are screwed into the both ends of the heating element 2 with a close fitting, and are electrically connected. Spring portions 4a and 4b for applying a tensile tension to the heating element 2 are provided at intermediate portions of the internal lead wires 3a and 3b. The other end portions of the internal lead wires 3a and 3b are welded to the other end portions of the molybdenum foils 7a and 7b to which the molybdenum wires 6a and 6b are welded to form a heating element block. The heating element block is inserted into the quartz glass tube 1 to melt and seal the quartz glass tube 1 in the portions of the molybdenum foils 7a and 7b.
[0023]
At the time of sealing, the inside of the quartz glass tube 1 is replaced with nitrogen, argon, or a mixed gas thereof. The inner ends of the lead wires 8a and 8b, the outer circumferences of which are covered with the insulators 8c and 8d, are welded to the molybdenum wires 6a and 6b taken out from the sealing portion to the outside of the quartz glass tube 1, respectively. Caps 9a and 9b formed of a silicone resin for protecting the sealing portion of the quartz glass tube 1 from humidity are respectively bonded and fixed with a silicone resin adhesive.
The defrosting heater 26 configured in this manner is basically mounted near the evaporator 25 of the refrigerator 21 having the same shape as the conventional one as shown in the cross section of FIG.
[0024]
Conservation of the global environment is the current proposition of product development, and non-flammable CFCs and HFCs that are also used in refrigerators destroy the ozone layer. Therefore, refrigerators that use refrigerant gas with less destruction of the ozone layer. Is required. As a concrete measure, refrigerators using isobutane gas that hardly destroys the ozone layer as a refrigerant have been developed.
However, isobutane gas is a flammable gas, and its ignition temperature is 460 to 495 ° C., and it is said that the temperature zone where no ignition occurs even if isobutane gas leaks outside the cooling mechanism is 360 ° C. or less. Therefore, there is a demand for the surface temperature of the quartz glass tube 1 of the defrost heater 26 for heating and removing frost attached to the evaporator in the refrigerator to be 360 ° C. or lower.
[0025]
Even with a conventional nichrome wire or tungsten wire filament, a heater having a surface temperature of the quartz glass tube 1 of 360 ° C. or less can be manufactured unless the light emission length is limited. In reality, however, the installation space for the defrost heater in the refrigerator is limited, and in order to efficiently defrost, it is required to supply the power consumption of the heating element, which is the minimum heating energy, and it is small in size. In addition, it has been difficult to realize a defrost heater that can supply sufficient power consumption.
[0026]
The inventors have studied a defrost heater using a sintered body of a carbon-based material that satisfies these conditions as a heating element. Initially, if the power consumption is satisfied, the surface temperature of the quartz glass tube 1 is 360 ° C. As described above, power consumption cannot be supplied if the surface temperature is satisfied. Therefore, as a result of examining the relationship between the power consumption and the surface temperature of the quartz glass tube 1 in detail, the watt density (the value obtained by dividing the power consumption W of the heating element by the surface area of the heating element: W / cm)²) And the surface temperature of the heating element 2 and the surface temperature of the heating element 2 and the surface temperature of the quartz glass tube 1 were found to have good linear relationships, respectively. It has also been found that this linear relationship shows an accurate linear relationship with a value expressed only by the surface area, regardless of the cross-sectional shape of the heating element 2, such as a round bar, plate shape, length of the heating element, or the like.
For example, when the diameter of the quartz glass tube 1 is 10 mm and the surface temperature of the quartz glass tube 1 is 360 ° C., the watt density is 8 W / cm.²Met. The value of the watt density varies with the diameter of the quartz glass tube 1, and it has been found that the temperature becomes a smaller watt density when the tube becomes thinner and a larger watt density when the tube becomes thicker.
[0027]
From these results, the watt density of the heating element 2 that can be used in the refrigerator using isobutane as the refrigerant gas is 2 to 20 W / cm.², More preferably 3-15 W / cm²It was found from the experimental results that
In order to realize a heating element for a defrost heater that can be used in a refrigerator by using the correlation between the watt density of the heating element 2 and the surface temperature of the quartz glass tube 1, the specific resistance value of the heating element 2 can be changed freely. It is an indispensable condition. It has been found that a sintered body containing a carbon-based substance is preferable as a heating element material capable of this.
[0028]
An example of a method for producing a heating element formed of a sintered body containing the carbonaceous material of the present invention will be described. This manufacturing method is close to that of the embodiment disclosed in the publication of International Publication No. WO 98/59526, which is the prior application of the present applicant. That is, as a resin component, a carbon-based substance is added to a mixed resin of 45 parts by weight of chlorinated vinyl chloride resin (T-741 manufactured by Nippon Carbide) and 15 parts by weight of furan resin (Hitafuran (trademark) tree VF-302 manufactured by Hitachi Chemical Co., Ltd.). As a plasticizer, a composition containing 10 parts by weight of natural graphite powder (average particle size of 5 μm manufactured by Nippon Graphite Co., Ltd.) and a mixture of 30 parts by weight of boron nitride (average particle size of 2 μm manufactured by Shin-Etsu Chemical Co., Ltd.) as a resistance value adjusting component As a starting material, 20 parts by weight of diallyl phthalate monomer is added and kneaded to prepare a slurry mixture. This slurry-like mixture was drawn and extruded using a die having a circular cross-sectional shape, and then fired in a nitrogen gas atmosphere to obtain a columnar carbon-based heating element.
[0029]
As a material of the resistance adjusting component that changes the specific resistance value as a result of the study, nitrides such as titanium nitride, zirconium nitride, vanadium nitride, niobium nitride, tantalum nitride, and chromium nitride are preferable in addition to boron nitride. Further, carbides such as silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, molybdenum carbide, and tungsten carbide are also preferable. Further borides such as titanium boride, zirconium boride, niobium boride, tantalum boride, chromium boride and molybdenum boride, or titanium silicide, zirconium silicide, niobium silicide, tantalum silicide, chromium silicide, molybdenum silicide, and silicide Silicides such as tungsten are also preferred. In addition, oxides such as silicon dioxide, aluminum oxide, magnesium oxide, calcium oxide, or mixtures thereof, or metals such as kaolinite, halloysite, mica, montmorillonite, clay minerals such as chlorite, or metalloid compounds are effective. Can be used for For example, in the case of using kaolinite as a main component, a heating element having a specific resistance value of 100,000 to 2 million μΩ · cm could be created. These materials can be used alone, but it is preferable to use a mixture of a plurality of materials.
[0030]
Since clay minerals are layered compounds, slip properties are added when used in combination with other oxides, nitrides, carbides, silicides, or borides. Use of a slurry-like mixture to which slipperiness is added is effective in production because the extruded product becomes homogeneous and the die is less likely to wear.
[0031]
Various materials other than metal materials were also examined as heating element materials. For example, a large number of rod-like heating elements obtained by mixing various semiconductor materials such as silicon carbide powder with an oxide material, extruding, firing, and changing the components were prepared. In addition, a thin plate (thickness 0.5 mm or less) heating element could not be made. That is, no suitable heating element other than a sintered body containing a carbon-based material has been found as a heating element suitable for the purpose of realizing a wide range of specific resistance values of the present invention.
[0032]
In carbon-based materials, the carbon component in the heating element becomes a conductive component, but the conductivity varies depending on the carbon component generation history. Carbon black and thermosetting resin-decomposed carbon are called non-graphitizable carbon and have a high conductivity. On the other hand, graphite, coke, etc. are materials that are said to be easily graphitized carbon and have high electrical conductivity. That is, the specific resistance value can also be changed by selecting a carbon component. The heating element of the present invention contains graphite, coke, carbon black or the like, and it is possible to obtain non-graphitizable carbon in which graphitization hardly occurs even in a high temperature state during lighting and resistance value hardly changes.
[0033]
FIG. 3 shows a conventional LT lamp in which a nichrome wire is inserted in an opaque quartz glass tube, a conventional Colts lamp in which a tungsten filament is sealed in a quartz glass tube and an inert gas is sealed inside, and the carbon-based material of the present invention. It is the graph which compared each radiation intensity between the wavelengths of 1-14 micrometers of the carbon lamp which sealed the sintered compact containing in a quartz glass tube, and sealed the inert gas inside. In FIG. 3, the characteristic curve of the product of the present invention (hereinafter abbreviated as carbon transparent bulb) in which a carbon heating element (color temperature of the heating element: 1100 ° C.) is enclosed in a quartz glass transparent bulb is shown by a thick solid curve. Indicates. A curve indicated by a dotted line in FIG. 3 shows the characteristics of a Colts lamp (hereinafter abbreviated as “Cortz red bulb”) in which a conventional tungsten filament (color temperature of a heating element: 2000 ° C.) is enclosed in a quartz glass tube. A curve indicated by a thin solid line in FIG. 3 represents the characteristics of a conventional nichrome wire heater (color temperature of heating element: 800 ° C.) inserted into an opaque bulb (hereinafter abbreviated as “LT opaque bulb”). Each lamp has a power consumption of 300 W and a heat generating part with a length of 315 mm.
[0034]
As shown in FIG. 3, the peak wavelength of the emitted light of the carbon transparent bulb is about 2.1 μm, the peak wavelength of the emitted light of the Colts red bulb is about 1.6 μm, and the peak wavelength of the emitted light of the LT opaque bulb is about 2.8 μm respectively.
[0035]
FIG. 4 is a graph showing the total radiation intensity in the wavelength region of 2.5 to 8.0 μm and the total radiation intensity amount in the wavelength region of 1.38 to 14.08 μm.
As shown in FIG. 4, the heater of the carbon transparent bulb has the largest total radiant intensity, and the radiant intensity is about 40% greater than that of other conventional heaters in the wavelength range of 1.38 to 14.08 μm. This is because the emissivity of carbon itself is 0.85, which is close to that of a black body, whereas the emissivity of a conventional heater such as a nichrome wire or a tungsten wire is 0.5 or less.
[0036]
FIG. 5 is a graph showing the infrared absorption characteristics of water. As shown in FIG. 5, water has a strong absorption band with respect to infrared rays having wavelengths of about 2.9 μm and 6 μm, and when irradiated with infrared rays of this wavelength, it absorbs resonance between OH of water molecules. Vibration occurs and temperature rises. In other words, it can be seen that a heater having a peak wavelength in the vicinity of 2.9 μm, which is a water absorption band, and a heater having a large radiation intensity is most effective for defrosting the refrigerator evaporator.
That is, as can be seen from the characteristics of FIGS. 3 to 5, the carbon transparent bulb of the present invention has a peak wavelength very close to 2.9 μm and a large amount of radiant intensity in the vicinity thereof. is there.
[0037]
In the defrosting heater of Example 1 described above, the coiled portions 5a and 5b at the other end portions of the internal lead wires 3a and 3b were directly screwed and joined to both ends of the heating element 2 as shown in FIG. However, since the heating element 2 is at a high temperature, a small amount is generated during lighting, but impurities and impure gas are generated. If the heating element 2 is used for a long period of time, the coil-like portions 5a and 5b may be discolored to change temperature characteristics. Therefore, it is preferable to coat the surface of the internal lead wires 3a and 3b including the coiled portions 5a and 5b or the spring portions 4a and 4b with a corrosion resistant material.
The surface of the internal lead wires 3a and 3b using molybdenum wire is preferably coated with gold in order to obtain stable conductivity, and the best result is obtained by electroplating gold on a nickel base plating. Indicated. However, the above-described plating for improving conductivity is not limited to gold plating, and it has been found that a compound film such as chromium, rhodium, or titanium nitride also works effectively.
As a material for the internal lead wires 3a and 3b, a tungsten wire can be used in the same manner in addition to the molybdenum wire.
[0038]
Example 2
FIG. 2 is a cross-sectional view of the defrost heater 26b according to the second embodiment of the present invention. The defrosting heater of Example 2 is different from that described in Example 1 in that a reflective film is provided. Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
In FIG. 2, a reflective film 11 formed of a material that reflects radiation light from the heating element 2 is formed on the outer peripheral surface of the quartz glass tube 1 in which the heating element 2 of the defrosting heater 26 b of Example 2 is enclosed. Provided. The material of the reflective film 11 is preferably a material having a high reflectance in the near infrared region, and preferably a gold thin film or a titanium nitride thin film is used. The reflective film is usually made by sputtering, but in the case of a thin gold film, a thin paste of organic gold compound (generally called a resinate) is applied as a main component, followed by drying and firing. It is suitable for mass production.
In the defrosting heater 26b of Example 2, the reflective film 11 is provided on the outer surface of the quartz glass tube 1, but the same effect can be obtained even if it is provided on the inner surface.
[0039]
According to the defrost heater 26b of the second embodiment, most of the radiation light such as infrared rays emitted from the heating element 2 is emitted upward, which is the direction of the evaporator, so that a defrost heater with high thermal efficiency can be realized. .
[0040]
Further, it is more preferable to apply a substance having a deodorizing function to a part of the outer periphery of the reflective film 11 because the odor component in the refrigerator is decomposed into an odorless component. As a specific example of a substance having a deodorizing function, water is preferably added to a fine powder having an adsorption function such as molecular sieve, a platinum material, for example, a catalyst component such as chloroplatinic acid, and a sol component of alumina or silicon dioxide as an adhesive component. There is a slurry. The slurry containing the substance having the deodorizing function is applied to about a half circumference of the quartz glass tube 1 and dried and baked. The substance having the deodorizing function exhibits a catalytic function by the heat of the heating element 2, and decomposes various odorous gases generated in a refrigerator or the like into odorless component gases.
[0041]
The present invention is not limited to the configurations of the first and second embodiments. That is, the heating element 2 has the same effect not only in the rod shape but also in various shapes such as a plate shape.
Moreover, although the Example demonstrated the defrost heater for refrigerators, the function of the defrost heater of this invention is not restrict | limited to the defrost heater used for refrigerators, and it is for commercial use refrigeration equipment, a freezer room, or a refrigerator room. It can be effectively applied to a defrosting heater of many cooling devices such as a cooling cycle device, a cooling device for various beverage foods and water.
[0042]
【The invention's effect】
As described in detail in the above embodiments, the defrosting heater of the present invention forms a sintered body containing a carbon-based material that can be adjusted to a desired specific resistance value as a heating element, and the heating element is placed inside the quartz glass tube. Enclosed. Thereby, even when the watt density of the heating element of the defrost heater is adjusted and the surface temperature of the quartz glass tube is set low, radiation of large heating energy can be realized. As a result, in a refrigerator having a cooling mechanism using a flammable refrigerant such as isobutane gas as a refrigerant, even if the flammable gas leaks into the refrigerator, the defrost heater by the heating element is ignited by an ignition explosion. There is no possibility of becoming a source, and the power consumption of the defrost heater can be freely designed by selecting the surface area, specific resistance and quartz glass tube diameter of the heating element.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a defrosting heater of Example 1 used for a refrigerator of the present invention.
FIG. 2 is a cross-sectional view of a defrosting heater of Example 2 used for a refrigerator of the present invention.
FIG. 3 is a graph comparing the radiation intensities of LT lamps, Colts lamps, and carbon lamps at wavelengths of 1 to 14 μm.
FIG. 4 is a graph showing the total radiation intensity in the wavelength range of 2.5 to 8.0 μm and the total radiation intensity in the range of 1.38 to 14.08 μm for each of the LT lamp, the Colts lamp, and the carbon lamp.
FIG. 5 is a graph showing infrared absorption characteristics with respect to the wavelength of water.
FIG. 6 is a cross-sectional view showing a configuration of a refrigerator provided with a defrosting heater according to the present invention.
FIG. 7 is a sectional view of a conventional defrosting heater used for a refrigerator.
[Explanation of symbols]
1 Quartz glass tube
2 Heating element
3a, 3b Internal lead wire
4a, 4b Spring part
5a, 5b Coil part
6a, 6b Molybdenum wire
7a, 7b Molybdenum foil
8a, 8b Lead wire
8c, 8d insulation coating
9a, 9b cap
11 Reflective film
21 Refrigerator
21a body
21b door
21c packing
21d handle
21e shelf
22 Compressor
23 Condenser
24 Expansion mechanism
25 Evaporator
25a Protection plate
26, 26b Defrost heater
27 Drain hole

Claims (12)

Compressor coagulation condenser and Rise Zhang mechanism and evaporator and circulation like connected configured to cooling systems in the refrigerator of the cooling device having a cooling mechanism encapsulating flammable refrigerant sequentially in the refrigerant conduit A defrosting heater disposed in the vicinity of the evaporator so as to vaporize and remove frost generated outside the evaporator,
Comprising a quartz glass tube sealed inside the heating element formed of a sintered body containing carbon Motokei material,
The heating element is formed by mixing and sintering a composition having shapeability and substantially containing residual carbon after sintering, and at least one metal compound or metalloid compound,
The energy radiation density from the surface of the heating element (power consumption per unit radiation area: watt density) is ² to 20 W / cm ² , and the surface temperature of the quartz glass tube is 360 degrees or less.
A defrosting heater characterized by that. The metal compound is
The defrosting heater according to claim 1 , comprising at least one of metal carbide, metal boride, metal silicide, metal nitride, and metal oxide. The metalloid compound is
The defrost heater according to claim 1 , comprising at least one of a metalloid nitride, metalloid oxide, and metalloid carbide. The defrost heater according to any one of claims 1 to 3 , wherein the composition containing carbon substantially after sintering contains a resin. The defrosting heater according to any one of claims 1 to 4 , wherein the composition containing substantially residual carbon after sintering contains at least one carbon powder of carbon black, graphite, and coke powder. Energy radiation density from the surface of the heating element (power consumption per unit radiation area: hereinafter referred to as watt density),
It is 3-15W / cm < ² >. The defrost heater in any one of Claims 1-5 characterized by the above-mentioned. According to any one of claims 1 to 6, characterized in that the reflective film that reflects light radiated from the heating element to at least a portion of the inner wall or outer wall of the quartz glass tube in a predetermined direction is formed Defrost heater. The defrosting heater according to any one of claims 1 to 7, wherein a substance that decomposes an odor generating substance is attached to at least a part of an outer wall of the quartz glass tube of the defrosting heater. The substance that decomposes the odor generating substance is
The silica glass tube is coated with a slurry-like substance in which molecular sieve powder having an adsorbing function, a platinum compound as a catalyst component, an alumina or silicon dioxide sol as an adhesive component, and water are mixed and deposited. The defrosting heater according to claim 8 , wherein the defrosting heater is provided. A refrigerator or refrigerator-freezer using the defrost heater according to any one of claims 1 to 9 . A food storage, wherein the defrost heater according to any one of claims 1 to 9 is used. Joshimohi according to any of the claims 1-10 - data - cooling device characterized by using the.

Images