JP2000283635A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ignition from a defrost heater even when combustible refrigerant leaks into a refrigerator by setting the temperature of the defrost heater lower than the ignition temperature of isobutane. SOLUTION: The refrigerator comprises an evaporator disposed in the refrigerator body, and a defrost heater for the evaporator located below the evaporator wherein the heater wire 15 of the defrost heater is arranged in a hermetically sealed sheath tube 17 filled with an insulating material 18 and fins 19 for accelerating heat transfer are provided on the outer circumference of the sheath tube 17. The defrost heater is constituted by providing a core body with fins coated with a conductive film, i.e., a heating material. In a refrigerator comprising a finned evaporator, a defrost heater is constituted by coating the fins of the evaporator with an insulating film and a circuit pattern of conductive film, i.e., a heating material. Furthermore, surface temperature of the defrost heater is set lower than the ignition temperature of refrigerant using combustible refrigerant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrost heater for a refrigerator using a flammable refrigerant.

[0002]

2. Description of the Related Art A conventional refrigerator is disclosed in Japanese Patent Application Laid-Open No. Hei 8-1056.
The refrigerator disclosed in Japanese Patent Publication No. 80 will be described with reference to FIGS. 2, 3, and 4. FIG. FIG. 2 is a sectional perspective view of an evaporator portion of the refrigerator, FIG. 3 is a sectional view of a principal part of a defrost heater, and FIG. 4 is a front view and a side view of a principal part around the evaporator. The refrigerant of the refrigerator uses HFC134a (1, 2, 2, 2-tetrafluoroethane).

In FIG. 2, 1 is a refrigerator main body, 2 is a freezing room, and 3 is a refrigerator room. Reference numerals 4 and 5 denote suction ports from the freezer compartment 2 and the refrigerator compartment 3, from which air in the freezer compartment 2 and the refrigerator compartment 3 is sucked and passed through the passages 4 ′ and 5 ′, and the evaporator installed at the back of the freezer compartment. Sent to 6. Reference numeral 7 denotes a defrost heater provided at a lower portion of the evaporator 6, and both ends of the defrost heater 7 are provided with caps 8.
It has. Reference numeral 10 denotes an upper surface cover (hereinafter, ceiling cover) attached so as to cover the upper part of the defrost heater 7.
The ceiling cover 10 prevents defrosting water dropped from the evaporator 6 during defrosting from coming into contact with the high-temperature defrosting heater 7 to generate an evaporation sound. Reference numeral 12 denotes a fan for sending air cooled by the evaporator 6 to the freezing compartment 2, and reference numeral 13 denotes a drain for discharging defrost water dropped from the evaporator 6 to the outside of the refrigerator during defrosting.

As the defrost heater 7, a glass tube heater shown in FIG. 3 is used. A heater wire 15 is accommodated in a glass tube 14, and electricity is generated through an insulated cord 16 to generate heat. The heater wire is insulated and waterproof at both ends by the cap 8 and the code wire 16. As shown in FIG. 4, the evaporator 6 is brazed at an entrance 30 and an entrance 32 of an accumulator 31.

FIG. 5 shows another conventional refrigerator. FIG. 5 is a front view and a side view of a main part around an evaporator. In FIG. 5, the defrost heater 7 is fixed by a sheath heater 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. 33 is a heater installed in the gutter 25.

[0006]

Although the refrigerant HFC134a currently used in refrigerators has no ozone depleting ability, it has a global warming effect of about 1,300 times as high as the carbon dioxide ratio. In recent years, there has been an increasing social demand for a hydrocarbon-based refrigerant such as isobutane or propane, which has a small global warming effect.

[0007] Isobutane, which has a high refrigeration cycle efficiency due to its thermophysical properties, is considered promising for refrigerators. However, since isobutane is flammable, it is necessary to prevent refrigerant leakage from the refrigeration cycle. Preventing ignition is an important issue. Since the surface temperature of the current glass tube heater may exceed the ignition temperature of isobutane in the air, there has been a problem that the surface temperature of the heater must be reduced from the viewpoint of safety.

Further, since the temperature of the heater wire is higher than the surface temperature of the glass tube, if the cap 8 and the glass tube 14 are not completely sealed, the leaked refrigerant enters the glass tube and is ignited by the bare heater wire. There is a problem that there is a fear.

In the refrigerator shown in FIG. 5, defrosting can be performed by using a sheath heater to lower the surface temperature of the heater, but the heater must be arranged on the front and back of the evaporator. Therefore, in order to prevent the refrigerant from leaking into the refrigerator, the pipe connection 3
When 0 and 31 are provided in the main body 1, the evaporator 6 is rigidly (immovably) fixed, and the heater 7 on the back side of the evaporator 6 is fixed.
May be unable to be replaced in the event of a failure.

Further, since the frost adhering to the evaporator is heated from the inside, the frost may fall as a lump during defrosting.
3 is required separately, and increase in the number of parts and installation space cannot be avoided. Furthermore, since the heater 7 is installed over the entire front and back of the evaporator 6, the ventilation resistance of the evaporator 6 is increased by the heater 7 during the normal cooling operation of the refrigerator, and the fan 12
There was a problem that the air volume was reduced due to the

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and the temperature of the defrosting heater does not rise to a temperature higher than the ignition temperature of isobutane as a refrigerant. It is an object of the present invention to provide a safe refrigerator that does not ignite by a defrost heater even if the gas leaks into the refrigerator.

[0012]

In order to solve the above problems, the present invention mainly employs the following configuration.

[0013] In a refrigerator comprising an evaporator provided inside the refrigerator main body and a defrost heater located below the evaporator to melt frost attached to the evaporator, a heater wire of the defrost heater is provided. A refrigerator is provided in a heat sink tube filled and sealed with an insulating material, and a fin for promoting heat transfer is provided around the heat sink tube.

Further, in a refrigerator comprising an evaporator provided inside the refrigerator main body and a defrost heater located below the evaporator to melt frost attached to the evaporator, a fin is provided on the core main body. A refrigerator, wherein the refrigerator comprises a conductive film as a heating element provided on the fins to constitute the defrost heater.

Further, in a refrigerator provided with an evaporator having fins provided inside the refrigerator body, an insulating film and a circuit pattern of a conductive film as a heating element are applied to the fin of the evaporator. Refrigerator that constitutes a defrost heater.

In the above refrigerator, a flammable refrigerant is used as the refrigerant, and the surface temperature of the defrost heater is set lower than the ignition temperature of the refrigerant.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A defrost heater according to an embodiment of the present invention will be described with reference to the drawings. Here, the same components as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a sectional view of a main part of a defrost heater according to a first embodiment of the present invention, and FIG. 6 is a front view and a side view of a main part around an evaporator of a refrigerator of the present invention. Here, 17 is a sheath tube, 18 is an insulating material, and 19 is a fin. A heater wire 15 filled with an insulating material 18 is housed in a sheath tube, and both ends are insulated and sealed by caps 8.
Electricity is supplied through 6 to perform heating. Fins 19 are provided on the outer periphery of the sheath tube 17 to promote heat transfer with the surrounding air.

When power is supplied to the defrost heater 7, the temperature of the sheath tube 17 and the fins 19 rises, and the frosted evaporator 6 is heated by radiation and natural convection, and the frost adhering to the evaporator is melted. It is. Fins 19 are provided on the defrost heater 7, and the surface area is greatly increased. Therefore, even when the surface temperature of the defrost heater is reduced as compared with the conventional glass tube heater, the heating amount required for the defrost is approximately the same as the conventional. Can be transmitted to the evaporator. Therefore, even if a flammable refrigerant such as isobutane leaks due to breakage of a pipe or the like, there is no danger of ignition because the ignition temperature does not reach the defrosting heater surface. The temperature of the defrost heater is a minimum ignition temperature of isobutane of about 4
By setting the temperature at about 300 ° C., which is 100 ° C. lower than 00 ° C., safety is enhanced.

Further, 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 from the heater wire 15 comes into contact and ignites. Further, since the heater 7 is installed below the evaporator 6 similarly to the glass tube heater, the replacement operation can be easily performed in the event of a failure.

Further, a PTC (Position) is used as a heater.
liveTemperatureCoefficie
t) A configuration may be employed in which the safety of the defrost heater is further increased by using a heater such as a heater whose temperature does not rise above a predetermined temperature.

Further, since the heater wire 15 is in the insulating material 18 and insulation is ensured, the heater wire 15 is folded back at one end as shown in FIG.
May be taken out from one of the caps 8. With this configuration, only one cap 8 to be waterproofed and insulated from the outside of the heater can be provided, and the reliability against water intrusion can be increased. Further, since the two cord wires 16 can be pulled out from one end of the heater 7 at a time, the wiring when stored in the refrigerator can be shortened as compared with the case where it is drawn out from both ends shown in FIG. The performance is improved.

The fins 19 of the defrost heater 7 may be independent fins as shown in FIG. 7, or may be of a configuration in which the fins are spirally wound around the sheath tube 17 as shown in FIG. You may. Defrost heater 7
Is a flat container 34 having fins 19 as shown in FIG.
The same effects as those described above can be obtained even if a heater wire 15 connected and sealed is used.

Each of the above-described defrost heaters 7 is an evaporator 6
Is installed separately from the evaporator 6 below, so that during the normal cooling operation of the refrigerator, the ventilation resistance does not increase unlike the conventional refrigerator shown in FIG. be able to.

Another embodiment of the defrost 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. An insulating film 24 is formed on the surface of the fin 19 provided on the core 20, a conductive film 21 is further applied on the insulating film 24, and electricity is supplied by the cord wire 16 to constitute the defrost heater 7.

The defrost heater has the same function as the above-mentioned finned defrost heater tube, and can increase the surface area and lower the fin surface temperature by the fins. A defrost heater that is less expensive than when a sheath tube heater is used can be provided.

Another embodiment of a defrost heater will be described with reference to FIG. 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 part of the fin 23 on the near side is shown as being transmitted through the conductive film 21.
The insulating film 24 and the conductive film 21 are sequentially applied on the fins 23, and a circuit pattern is drawn to form a defrost heater. 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 limited to a small area.

Since the fins 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 flammable refrigerant such as isobutane, so that defrosting can be performed safely. Alternatively, although not shown, fin 2
3 may have a configuration in which the conductive film 21 is applied to both surfaces.

Further, the present invention relates to a conventional refrigerant HFC134.
The present invention may be applied to a defrost heater of a refrigerator using a, and it is possible to lower the heater surface temperature as compared with the related art, thereby reducing the power consumption required for defrost.

As described above, according to the embodiment of the present invention, the following configuration examples and those having functions or actions are included.

In a refrigerator having an evaporator provided inside a refrigerator main body and a defrost heater located below the evaporator and melting frost attached to the evaporator, a heater wire of the defrost heater is insulated. This is provided in a tube filled with a material, and fins for promoting heat transfer are provided in the heater tube.

When defrosting is performed using such a defrost heater, the surface area of the defrost heater that exchanges heat with the surrounding air by the fins increases, so that the surface temperature of the defrost heater is reduced as compared with the conventional glass tube heater. Even in this case, the same amount of heat required for defrosting as in the conventional case can be transmitted to the evaporator. Therefore, even if a flammable refrigerant such as isobutane leaks, the ignition temperature does not reach the defrost heater surface, and there is no danger of ignition. Further, since the heater wire 15 is filled and sealed with the insulating material 18 and is not exposed,
There is no danger of ignition due to contact of the leaked refrigerant. The safety of the defrost heater may be further increased by using a heater whose temperature does not rise above a predetermined temperature, such as a PTC heater, as the heater.

Further, in a refrigerator having an evaporator provided inside the refrigerator body and a defrost heater located below the evaporator and melting frost attached to the evaporator, the defrost heater comprises: A conductive film as a heating element is applied to a main body having fins. In other words, a conductive film is applied to the surface of the fin provided on the core, and the wire is energized by a cord wire to constitute a defrost heater. The defrost heater has the same function as the above-mentioned finned defrost heater tube, and can increase the surface area by the fins and lower the fin surface temperature. A defrost heater that is less expensive than the case of using a heater can be provided.

Further, in a refrigerator provided with an evaporator having fins provided inside the refrigerator body, a defrost heater formed by applying a conductive film as a heating element insulated from the fins to the fins of the evaporator is provided. It is provided. That is, an insulating film and a conductive film are sequentially applied on the fins of the evaporator heat transfer tube to form a defrost 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 sufficiently lower than the ignition temperature of a flammable refrigerant such as isobutane, so that defrosting can be performed safely. Also, unlike the prior art, there is no need for a space for installing a defrost heater, a ceiling cover, and the like below the evaporator.

[0034]

According to the present invention, since the defrosting is performed by the sealed sheathed tube heater with fins, the surface area of the defrosting heater that exchanges heat with the surrounding air by the fins is increased. Even if the surface temperature of the frost heater is lowered, the same amount of heat required for defrosting as before can be transmitted to the evaporator, and even if a flammable refrigerant such as isobutane leaks, Since the ignition temperature is not reached, there is no danger of ignition. Further, installation and replacement of the evaporator can be easily performed as in the conventional case.

According to another embodiment of the present invention, the above-mentioned finned defrost heater tube is provided by using a defrost heater formed by applying a conductive film to the surface of a fin provided on a core. A defrost heater having the same function can be provided at low cost.

According to another embodiment of the present invention, a conductive film is applied, a defrosting heater is formed on the evaporator fins, and the evaporator is directly heated from the fins. The temperature of the film can be sufficiently lowered from the ignition temperature of a flammable refrigerant such as isobutane, so that defrosting can be performed safely.

[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 diagram illustrating an example of a conventional defrost heater.

FIG. 4 is a diagram showing a main part around a conventional evaporator.

FIG. 5 is a diagram showing a main part around an evaporator in another conventional example.

FIG. 6 is a diagram showing a configuration around an evaporator according to the 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 defrost heater according to the present embodiment.

FIG. 9 is a diagram showing still another configuration example of the defrost heater according to the present embodiment.

FIG. 10 is a diagram illustrating a fin configuration example of a defrost heater according to the present embodiment.

FIG. 11 is a diagram showing a configuration in which the evaporator heat transfer tube fin according to the embodiment of the present invention is used as a defrost heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerator main body 2 Freezer room 3 Refrigerating room 6 Evaporator 7 Defrosting heater 8 Cap 10 Ceiling cover 12 Cooling fan 14 Glass tube 15 Heater wire 16 Code wire 17 Sheath tube 18 Insulating material 19 Defrosting heater fin 20 Core 21 Conductive film 22 evaporator heat transfer tube 23 evaporator tube fin 24 insulating film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Taichi, Inventor Store Network 800, Tomita, Odai-cho, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture Inside the Cooling and Refrigerating Business Dept., Hitachi, Ltd. F-term in Ritsumeikan Machinery Research Laboratory (reference) 3L046 AA05 BA01 CA07 MA04

Claims (4)

[Claims] 1. An evaporator provided inside a refrigerator body,
A defrost heater positioned below the evaporator to melt frost attached to the evaporator, wherein a heater wire of the defrost heater is provided in a tube filled and sealed with an insulating material; A refrigerator characterized by providing fins for promoting heat transfer on the outer periphery of a tube. 2. An evaporator provided inside the refrigerator body,
A defrosting heater positioned below the evaporator to melt frost adhering to the evaporator, wherein a fin is provided on the core body, and a conductive film as a heating element is applied to the fin. A refrigerator comprising the defrost heater. 3. A refrigerator provided with an evaporator having fins provided inside a refrigerator body, wherein a fin of the evaporator is coated with an insulating film and a circuit pattern of a conductive film as a heating element on the insulating film. A refrigerator comprising a defrost heater. 4. The refrigerator according to claim 1, wherein a flammable refrigerant is used as the refrigerant, and a surface temperature of the defrost heater is lower than an ignition temperature of the refrigerant.