JP3955412B2 - refrigerator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defrosting heater for a refrigerator using a flammable refrigerant.
[0002]
[Prior art]
A refrigerator disclosed in JP-A-8-105680 as a conventional refrigerator will be described with reference to FIGS. 2 is a cross-sectional perspective view of the evaporator part of the refrigerator, FIG. 3 is a cross-sectional view of the main part of the defrost heater, and FIG. 4 is a front view and a side view of the main part around the evaporator. HFC134a (1, 2, 2, 2-tetrafluoroethane) is used as the refrigerant of the refrigerator.
[0003]
In FIG. 2, 1 is a refrigerator main body, 2 is a freezer compartment, 3 is a refrigerator compartment. Reference numerals 4 and 5 denote suction ports from the freezer compartment 2 and the refrigerator compartment 3, from which the air in the refrigerator compartment 2 and the refrigerator compartment 3 is sucked, and via the passages 4 'and 5', an evaporator installed on the back of the freezer compartment 6 is sent. 7 is a defrost heater installed in the lower part of the evaporator 6, and both ends of the defrost heater 7 are provided with caps 8. Reference numeral 10 denotes an upper surface cover (hereinafter referred to as a ceiling cover) that is attached so as to cover the upper portion of the defrost heater 7, and the defrost water dripped from the evaporator 6 at the time of defrosting becomes high temperature. This prevents the generation of evaporating noise in contact with the defrosting heater 7. 12 is a fan that sends the air cooled by the evaporator 6 to the freezer compartment 2, and 13 is a drain that discharges the defrost water dripped from the evaporator 6 to the outside of the refrigerator during defrosting.
[0004]
A glass tube heater shown in FIG. 3 is used as the defrosting heater 7. A heater wire 15 is housed in the glass tube 14, and is energized through an insulated cord wire 16 to generate heat. The heater wire is insulated and waterproofed at both ends by the cap 8 and the cord wire 16. As shown in FIG. 4, the evaporator 6 is connected by brazing at an inlet / outlet 30 and an inlet / outlet 32 of an accumulator 31.
[0005]
FIG. 5 shows another conventional refrigerator. FIG. 5 is a front view and a side view of main parts around the evaporator. In FIG. 5, the defrost heater 7 is a sheath heater fixed so as to contact the corners of the fins 23 of the evaporator 6, and is installed on both the front and back surfaces of the evaporator 6. Reference numeral 33 denotes a heater installed in the bowl 25.
[0006]
[Problems to be solved by the invention]
Refrigerant HFC134a currently used in refrigerators has no global warming action about 1,300 times the carbon dioxide ratio, although it does not have the ability to destroy the ozone layer. Therefore, isobutane has no ozone layer destruction ability and low global warming action. In recent years, an alternative to hydrocarbon refrigerants such as propane and propane has been socially demanded.
[0007]
Isobutane, which has high refrigeration cycle efficiency due to its thermophysical properties, is considered promising for refrigerators. However, because isobutane is flammable, it should prevent refrigerant leakage from the refrigeration cycle and ignite from electrical components in the unlikely event of refrigerant leakage. Prevention has become an important issue. Since the surface temperature of the current glass tube heater sometimes exceeds the ignition temperature of isobutane in the air, there has been a problem that the heater surface temperature has to be lowered for safety.
[0008]
In addition, since the heater wire temperature is higher than the glass tube surface temperature, if the cap 8 and the glass tube 14 are not completely sealed, there is a risk that leaked refrigerant may enter the glass tube and ignite with the exposed heater wire. There is a problem.
[0009]
In the refrigerator shown in FIG. 5, a sheath heater is used to perform defrosting by lowering the heater surface temperature. However, the heater must be arranged on the front and back of the evaporator. Therefore, when the pipe connection portions 30 and 31 are provided in the main body 1 to prevent the refrigerant from leaking into the refrigerator, the evaporator 6 is rigidly fixed (so that it cannot be moved), and the heater 7 on the back side of the evaporator 6 There is a risk that it cannot be replaced in the event of a failure.
[0010]
Moreover, since it heats from the inside of the frost adhering to an evaporator, frost may fall as a lump during defrosting, and the haze heater 33 for melting the lump of frost which fell to the hail 25 is needed separately. The increase in the number of parts and installation space is inevitable. Further, since the heater 7 is installed over the entire front and back of the evaporator 6, there is a problem that the air flow resistance of the evaporator 6 is increased by the heater 7 during the normal cooling operation of the refrigerator, and the air volume by the fan 12 is decreased.
[0011]
The object of the present invention is to solve the above-mentioned problems of the prior art, and the defrost heater temperature does not rise above the ignition temperature of the isobutane refrigerant, so that the flammable refrigerant should be stored in the refrigerator. An object of the present invention is to provide a safe refrigerator that is not ignited by a defrosting heater even if it leaks into the oven.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention mainly adopts the following configuration.
[0013]
In a refrigerator comprising: an evaporator provided inside a refrigerator body; and a defrost heater positioned below the evaporator to melt frost attached to the evaporator,
Using a flammable refrigerant as the refrigerant,
A heater wire is provided in the pipe of the defrost heater, and a fin for heat transfer promotion is spirally wound around the outer circumference of the pipe, and the surface temperature of the defrost heater is determined from the ignition temperature of the refrigerant. Refrigerator to lower .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The defrost heater which concerns on embodiment of this invention is demonstrated based on drawing. Here, the same components as those of the conventional example are denoted by the same reference numerals and description thereof is omitted. FIG. 1 is a cross-sectional view of a main part of the defrosting heater according to the first embodiment of the present invention, and FIG. 6 is a front view and a side view of the main part around the evaporator of the refrigerator of the present invention. Here, 17 is a sheath tube, 18 is an insulating material, and 19 is a fin. Heater wires 15 filled with an insulating material 18 are accommodated in a sheath tube, both ends are insulated and sealed with caps 8, and energized from the outside via the cord wires 16 to perform heating. Fins 19 are provided on the outer periphery of the sheath tube 17 to promote heat transfer with the surrounding air.
[0018]
When the defrost heater 7 is energized, the temperature of the sheath tube 17 and the fins 19 rises, the frosted evaporator 6 is heated by radiation and natural convection, and the frost attached to the evaporator is melted. Since the fin 19 is provided in the defrost heater 7 and the surface area is greatly increased, even when the defrost heater surface temperature is lowered as compared with the conventional glass tube heater, the heating amount required for defrosting to the same level as the conventional one is reduced. Can be transmitted to the evaporator. Therefore, even if a flammable refrigerant such as isobutane leaks due to a broken pipe or the like, the ignition temperature is not reached on the surface of the defrost heater, so there is no risk of ignition. The temperature of the defrost heater is set to about 300 ° C., which is 100 ° C. lower than the lowest ignition temperature of isobutane, which is about 400 ° C., thereby improving safety.
[0019]
Furthermore, since the heater wire 15 is filled and sealed with the insulating material 18 and is not exposed, there is no danger that the refrigerant leaking into the heater wire 15 will come into contact and ignite. Moreover, since the heater 7 is installed in the lower part of the evaporator 6 like a glass tube heater, replacement | exchange work can be easily performed at the time of a failure.
[0020]
Furthermore, it is good also as a structure which raised the safety | security of the defrost heater further by using the heater which does not rise in temperature more than predetermined temperature like a PTC (Positive Temperature Coefficient) heater as a heater.
[0021]
Further, since the heater wire 15 is in the insulating material 18 and insulation is reliably performed, as shown in FIG. 7, the heater wire 15 is folded back at one end, and the cord wire 16 is taken out from one cap 8. Also good. With this configuration, there is only one cap 8 to be waterproofed and insulated from the outside of the heater, and the reliability against water intrusion can be increased. Further, since two cord wires 16 can be pulled out from one end of the heater 7, the wiring when housed in the cabinet can be shortened compared to the case where it is pulled out from both ends shown in FIG. Improves.
[0022]
The fin 19 of the defrosting heater 7 may be an independent fin as shown in FIG. 7, or may be one that is easy to manufacture as a configuration in which the fin is wound spirally around the sheath tube 17 as shown in FIG. . Further, the defrosting heater 7 can obtain the same effects as those described above even when a flat container 34 having fins 19 and a heater wire 15 is connected and sealed as shown in FIG.
[0023]
Since all the defrosting heaters 7 described above are installed separately from the evaporator 6 below the evaporator 6, during the normal cooling operation of the refrigerator, the ventilation resistance is as in the case of the conventional refrigerator shown in FIG. 5. Efficient cooling can be performed without increasing.
[0024]
An embodiment of another defrosting heater will be described with reference to FIG. In FIG. 10, 20 is a core, 21 is a conductive film, and 24 is an insulating film. The defrost heater 7 is configured by forming an insulating film 24 on the surface of the fin 19 installed on the core 20, applying a conductive film 21 on the insulating film 24, and energizing the cord wire 16.
[0025]
The defrost heater has the same function as the above-described defrost heater pipe with fins, can increase the surface area by using the fins, can reduce the fin surface temperature, and has a simple structure. It is possible to provide a defrosting heater that is less expensive than the case of using.
[0026]
Furthermore, it demonstrates based on FIG. 11 as embodiment of another defrost heater. In FIG. 11, 22 is a heat transfer tube of the evaporator 6, 23 is a fin of the evaporator heat transfer tube 22, 21 is a conductive film, and 24 is an insulating film. In FIG. 11, for the sake of explanation, the lower portion of the front fin 23 is shown through the conductive film 21. However, the insulating film 24 and the conductive film 21 are formed on the fin 23 of the evaporator heat transfer tube 22. Are applied in order, and a defrost heater is formed by drawing a circuit pattern. Since the thermal resistance of the fins 23 increases due to the formation of the circuit pattern, and the performance as the original heat exchanger decreases, the circuit pattern portion is suppressed to a small area.
[0027]
Since the fin 23 in the frosted state can be directly heated, the temperature of the conductive film serving as a heater can be sufficiently lower than the ignition temperature of a combustible refrigerant such as isobutane, and defrosting can be performed safely. Alternatively, although not shown, the conductive film 21 may be applied to both surfaces of the fin 23.
[0028]
In addition, the present invention may be applied to a refrigerator defrost heater using a conventional refrigerant HFC134a, and the heater surface temperature can be lowered as compared with the conventional one to reduce the power consumption required for defrosting.
[0029]
As described above, according to the embodiment of the present invention, the following configuration examples and functions and functions are included.
[0030]
In a refrigerator provided with an evaporator provided inside the refrigerator main body and a defrost heater positioned below the evaporator to melt frost attached to the evaporator, the heater wire of the defrost heater is filled with an insulating material. The heat pipe is provided with a fin for promoting heat transfer.
[0031]
If defrosting is performed using such a defrosting heater, the surface area of the defrosting heater that exchanges heat with the surrounding air is increased by fins, so even when the defrosting heater surface temperature is lowered compared to the conventional glass tube heater, The amount of heating required for defrosting to the same extent as before can be transmitted to the evaporator. Therefore, even if a flammable refrigerant such as isobutane leaks, it does not reach the ignition temperature on the surface of the defrost heater, so there is no danger of ignition. Furthermore, since the heater wire 15 is filled and sealed with the insulating material 18 and is not exposed, there is no danger of the refrigerant leaking into the heater wire 15 coming into contact and igniting. Moreover, you may make the safety | security of a defrost heater still higher by using what does not rise in temperature more than predetermined temperature like a PTC heater as a heater.
[0032]
Moreover, the refrigerator provided with the evaporator provided in the refrigerator main body, and the defrost heater which melt | dissolves the frost adhering to the said evaporator located under this evaporator, The said defrost heater has a fin. A conductive film as a heating element is applied to the main body. That is, the defrosting heater is configured by applying a conductive film on the surface of the fin installed on the core and energizing the cord wire. The defrost heater has the same function as the above-described defrost heater pipe with fins, can increase the surface area by using the fins, can reduce the fin surface temperature, and has a simple structure. It is possible to provide a defrosting heater that is less expensive than the case of using.
[0033]
Further, in a refrigerator provided with an evaporator having fins provided inside the refrigerator body, a defrosting heater is provided which is formed by applying a conductive film as a heating element insulated from the fins to the fins of the evaporator. is there. That is, an insulating film and a conductive film are sequentially applied on the fins of the evaporator heat transfer tube to form a defrosting heater on the evaporator fins. Since the evaporator can be directly heated from the fins, the temperature of the conductive film serving as a heater can be made sufficiently lower than the ignition temperature of a combustible refrigerant such as isobutane, and defrosting can be performed safely. Moreover, the installation space, such as a defrost heater and a ceiling cover, becomes unnecessary under the evaporator like the past.
[0034]
According to the present invention, defrosting with a finned sealed sheath tube heater increases the surface area of the defrost heater that exchanges heat with the surrounding air by the fins. Even when the temperature is lowered, the amount of heat required for defrosting can be transmitted to the evaporator, and even if a flammable refrigerant such as isobutane leaks, it will not reach the ignition temperature on the surface of the defrost heater. Therefore, there is no danger of fire. Furthermore, installation and replacement of the evaporator can be easily performed as in the conventional case.
[0035]
According to another embodiment of the present invention, the defrost heater formed by applying a conductive film to the surface of the fin installed on the core is used and has the same effect as the above-described defrost heater tube with fins. The defrost heater which makes can be provided at low cost.
[0036]
According to another embodiment of the present invention, a conductive film is applied, a defrost heater is formed on the evaporator fin, the evaporator is directly heated from the fin, and the temperature of the conductive film serving as the heater is increased. Can be sufficiently lowered from the ignition temperature of a combustible refrigerant such as isobutane, and defrosting can be performed safely.
【The invention's effect】
According to the present invention, the defrost heater temperature does not rise above the ignition temperature of the isobutane refrigerant, and a safe refrigerator that is not ignited by the defrost heater even if flammable refrigerant leaks into the refrigerator. It can be.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a defrost heater according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration around an evaporator in a conventional refrigerator.
FIG. 3 is a view showing an example of a conventional defrost heater.
FIG. 4 is a view showing a main part around a conventional evaporator.
FIG. 5 is a view showing a main part around an evaporator in another conventional example.
FIG. 6 is a diagram showing a configuration around an evaporator according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a configuration example of a defrost heater according to the present embodiment.
FIG. 8 is a diagram showing another configuration example of the defrosting heater according to the present embodiment.
FIG. 9 is a diagram showing still another configuration example of the defrosting heater according to the present embodiment.
FIG. 10 is a diagram illustrating a fin configuration example of the defrosting heater according to the present embodiment.
FIG. 11 is a diagram showing a configuration in which an evaporator heat transfer tube fin according to an embodiment of the present invention is used as a defrost heater.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Refrigerator body 2 Freezer compartment 3 Refrigerating compartment 6 Evaporator 7 Defrost heater 8 Cap 10 Ceiling cover 12 Cooling fan 14 Glass tube 15 Heater wire 16 Cord wire 17 Sheath tube 18 Insulating material 19 Defrost heater fin 20 Core 21 Conductive film 22 Evaporator Heat Transfer Tube 23 Evaporator Tube Fin 24 Insulating Film

Claims (1)

In a refrigerator comprising: an evaporator provided inside a refrigerator body; and a defrost heater positioned below the evaporator to melt frost attached to the evaporator,
Using a flammable refrigerant as the refrigerant,
A heater wire is provided in the pipe of the defrost heater, and a fin for heat transfer promotion is spirally wound around the outer circumference of the pipe, and the surface temperature of the defrost heater is determined from the ignition temperature of the refrigerant. A refrigerator characterized by being lowered .

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