JP2002372363A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety in case that defrosting operation is carried out under a circumstance where ignitable refrigerant has leaked out in a refrigerator in which the ignitable refrigerant is used. SOLUTION: There is provided a cooling chamber 19 having an evaporator 10 of a freezing cycle where the ignitable refrigerant is applied, and a pipe heater 26 for defrosting the evaporator 10. A part of the pipe heater 26 is installed near the lower-most piping 20 of the evaporator 10, and a straight pipe part of the pipe heater 26 is brought into contact with a fin 25 of the evaporator 10. A surface temperature of the pipe heater 26 is lowered while defrosting efficiency is raised; thereby, the ignitable refrigerant is prevented from catching fire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, Japanese Patent Application Laid-Open No. 8-54172 discloses a refrigerator using a flammable refrigerant.

Hereinafter, the conventional refrigerator will be described with reference to the drawings. FIG. 10 is a longitudinal sectional view of a main part of a conventional refrigerator. 10, 1 is a refrigerator main body, 2 is a freezing room inside the refrigerator main body 1, 3 is a refrigerator room inside the refrigerator main body 1, 4 is a freezing room door, 5 is a refrigerator room door, 6 is a freezing room 2 , A partition wall for partitioning the refrigerator compartment 3, a refrigerator compartment inlet 7 for sucking air in the refrigerator compartment 2, a refrigerator compartment suction port 8 for sucking air in the refrigerator compartment 3, a discharge port 9 for discharging cool air, and a reference numeral 10. Evaporator, 11 is a fan for circulating cool air, 12 is evaporator 1
Evaporator partition wall separating 0 and freezer compartment 2, 13 is a tub, 14 is a drain port, 15 is a defrosting tube heater in which a coiled nichrome wire is covered with a glass tube, and 16 is a defrosting water heater. A roof for preventing the evaporation noise generated when it comes into direct contact with the frost tube heater 15, and 17 is a metal bottom plate provided between the tub 13 and the defrost tube heater 15 and insulated and held. .

Next, the operation will be described. When cooling the freezer compartment 2 or the refrigerator compartment 3, the refrigerant flows through the evaporator 10 to cool the evaporator 10. Fan 11 in the same way
, The heated air of the freezing room 2 or the cold room 3 is sent from the freezing room suction port 7 or the cold room suction port 8 to the cooling chamber 20, and the heat is exchanged by the evaporator 10 to be cooled and the cooling is performed from the discharge port 9. The wind is sent into the freezer compartment 2, and cool air is sent from the freezer compartment 2 to the refrigerator through a communication port (not shown). Here, the air that exchanges heat with the evaporator 10 is highly humidified by the inflow of high-temperature outside air due to the opening and closing of the freezer compartment door 4 and the refrigerating compartment door 5 and the evaporation of the moisture of the stored food in the freezer compartment 2 and the refrigerating compartment 3. Since the air is turbid, the moisture in the air becomes frost and forms frost on the evaporator 10 having a lower temperature than the air.

As described above, when the evaporator 10 becomes frosted, as the amount of frost increases, the heat transfer between the surface of the evaporator 10 and the air that exchanges heat is hindered, and the air flow decreases due to the ventilation resistance. Insufficient cooling occurs due to a decrease in heat transfer rate.

[0006] Therefore, the evaporator 10 is heated by the heat rays radiated by energizing the nichrome wire of the defrosting tube heater 15.
The frost that has arrived near the tub 13 and the drain 14 is melted into water.

A part of the defrost water thus melted falls directly into the tub 13, and the rest falls into the tub 13 by the roof 16, avoiding the defrosting tube heater 15, and is discharged from the drain port 14 to the outside of the refrigerator. Drained to At this time, the defrosting tube heater 15
The heat rays radiated to the tub 13 are partially reflected by the bottom plate 17 and scattered toward the evaporator 10.

[0008]

However, in the above-described conventional construction, in the refrigeration cycle using the flammable refrigerant, the flammable refrigerant has a relatively large latent heat, so that the piping portion of the evaporator 10 in which the flammable refrigerant accumulates. In this case, the amount of heat becomes considerably larger than that of the other pipes, so that defrosting is insufficient, defrosting occurs, and heat transfer is hindered by frost remaining during the cooling operation after the completion of defrosting, and uncooling occurs.

In general, the temperature of the glass surface is extremely high, not to mention the surface of the nichrome wire of the defrosting tube heater 15, so that the flammable refrigerant communicates with the inside of the refrigerator such as the evaporator 10. When leaking from a certain pipe, there is a problem that the risk of causing a fire and explosion due to energization of the defrosting tube heater 15 and causing a catastrophe is extremely high.

SUMMARY OF THE INVENTION In view of the above problems, the present invention prevents disasters caused by explosion by preventing explosion due to ignition of combustible refrigerant when defrosting is performed in an environment in which combustible refrigerant has leaked into the installation atmosphere of the defrosting means. It is an object of the present invention to provide a refrigerator using a combustible refrigerant provided with a defrosting means for preventing frost and preventing uncooling due to frost residue.

[0011]

According to a first aspect of the present invention, there is provided a cooling chamber provided with an evaporator of a refrigeration cycle using a combustible refrigerant and a defrosting means for defrosting the evaporator. The defrosting means is a pipe heater in which a heater wire made of a metal resistance material is covered with an insulator having good thermal conductivity, and a surface of the insulator is covered with a metal film, and a part of the pipe heater is evaporated. It is installed in contact with the fins of the vessel, and heat conduction from the pipe heater to the evaporator is promoted, so that defrosting of the evaporator can be promoted. Further, since the metal surface of the pipe heater and the evaporator are in contact with each other, heat is exchanged with each other, and the temperature difference between the surface of the pipe heater and the surface of the evaporator is reduced. Has the effect of being able to.

According to a second aspect of the present invention, in the first aspect of the present invention, a part of the pipe heater is installed near the lowermost pipe of the evaporator. When heating the evaporator and the surroundings of the evaporator, the lowermost piping section of the evaporator having a large heat capacity is easy to accumulate flammable refrigerant with large latent heat, and it is easy to receive heat. Disappears. Furthermore, the improvement of the defrosting efficiency has the effect that the operating time of the pipe heater can be shortened and the surface temperature of the pipe heater can be reduced.

According to a third aspect of the present invention, in the first or second aspect, the surface temperature of the pipe heater is set to be lower than the ignition temperature of the flammable refrigerant. It has the effect that the flammable refrigerant does not ignite even if defrosting is performed at the time of leakage.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) Embodiment 1 according to the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 1 is a longitudinal sectional view of a main part of a refrigerator according to Embodiment 1 of the present invention. As shown in FIG. 1, reference numeral 18 denotes a heating type defrosting unit for defrosting frost adhering to the evaporator 10 and its surroundings, and 19 denotes an evaporator 10 and a fan 1.
1, a cooling chamber in which the roof 16 and the defrosting means 19 are installed. Reference numeral 20 denotes a lowermost pipe of the evaporator 10, and a defrosting means 18 is installed near the lowermost pipe 20.

With respect to the refrigerator configured as described above,
The operation will be described below. After an elapse of an arbitrary time, the fan 11 stops to remove the frost on the evaporator 10, and after the refrigerant circulation of the evaporator 10 stops, the defrosting means 18
Is activated, the completion of the defrosting is detected by the defrosting completion detecting means (not shown), and the operation of the defrosting means 18 is stopped, thereby completing the defrosting. Here, when the fan 11 is stopped, the liquid of the flammable refrigerant in the evaporator 10 collects in the largest amount in the lowest pipe 20 of the evaporator 10 by its own weight. Thereafter, by the operation of the defrosting means 18, the flammable refrigerant having a large latent heat accumulated in the lowermost pipe 20 in a large amount evaporates.

At this time, the defrosting means 18 is connected to the lowermost pipe 20
, A large amount of the flammable refrigerant accumulated inside the lowermost pipe 20 is promoted in evaporation. The combustible refrigerant evaporated in this way moves as a high-temperature gas to the pipe above the evaporator 10. The high-temperature gas of the combustible refrigerant that has moved to the upper pipe of the evaporator 10 absorbs heat from the frost through the pipes and the fins and liquefies because the upper pipe of the evaporator 10 has a low temperature due to frost. Necessary heat to evaporator 1
Defrosting is performed by absorbing heat from the upper frost.

At this time, since the flammable refrigerant has a large latent heat, it is liquefied and a large amount of heat is removed from the frost, so that defrosting is promoted.

The flammable refrigerant that has been liquefied again accumulates in the lowest pipe 19 of the evaporator 10 by its own weight.

Thus, the defrost of the evaporator 10 is performed by the thermosiphon phenomenon. Further, in addition to the defrosting by the thermosiphon, the direct heat reception from the defrosting means 18 melts the frost on the evaporator 10 and peripheral parts and walls, and also warms and convections the surrounding air, thereby causing the evaporator 10 to degrade. The entire defrost is performed.

As described above, the periphery of the evaporator 10 and the evaporator 1
0 indicates that the entire surface is uniformly defrosted by the thermosiphon effect of the combustible refrigerant in the pipe and the direct thermal effect of the defrosting means 18, and that the defrosting efficiency is improved. By reducing the operation time of the means 18, the defrosting means 18
Before the surface temperature of the defrosting means 18 reaches the ignition temperature of the combustible refrigerant, the defrosting completion detecting means (not shown) detects the completion of the defrosting and the defrosting is completed.

(Embodiment 2) Embodiment 2 according to the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 2 is a longitudinal sectional view of a main part of a refrigerator according to a second embodiment of the present invention. As shown in FIG.
Numeral 0 is the same heat exchange area and the shape is smaller in the depth direction or in the height direction than in the refrigerator with the door facing the front.

With respect to the refrigerator configured as described above,
The operation will be described below. At the time of defrosting, since the distance from the defrosting means 18 to the upper part of the evaporator 10 is reduced, the defrosting means 18 from the defrosting means 18 to the upper part of the evaporator 10 is reduced.
Is transferred early, and the difference in heat transfer time between the upper and lower portions of the evaporator 10 is reduced. From this, the defrost of the evaporator and the surroundings is performed more uniformly, and the defrost efficiency is improved, so there is no frost residue,
Further, the operation of the defrosting means 18 for a short time completes the defrosting.

(Embodiment 3) Embodiment 3 according to the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 3 is a longitudinal sectional view of a main part of a refrigerator according to Embodiment 3 of the present invention. As shown in FIG. 3, reference numeral 21 denotes a cooling chamber suction port in which the suction air from the freezing chamber suction port 7 and the suction air from the refrigeration chamber suction port 8 merge and suck into the cooling chamber 19; 8 is a damper for controlling the flow of air in the refrigerator compartment flowing into the refrigerator compartment suction port 8 in the refrigerator 8
Reference numeral 23 denotes a communication port for sending low-temperature air from the freezer compartment to the refrigerator compartment 3 to cool the refrigerator compartment.

Regarding the refrigerator configured as described above,
The operation will be described below. Fan 11 just before defrosting
Is stopped for a predetermined time and the gunpa 22 is opened. Thereafter, the damper 22 is closed, the defrosting means 18 is operated to perform defrosting, and the defrosting completion detecting means (not shown) detects the completion of defrosting, and the defrosting is completed.

Here, if the flammable refrigerant leaks into the refrigerator due to the stop of the fan 11 and the opening of the damper 22 immediately before the defrosting, the flammable refrigerant has a higher specific gravity than the air. Represents air having a low specific gravity, and the combustible refrigerant having a high specific gravity accumulates in the refrigerator compartment 3 through the cooling chamber suction port 21;
What leaks into the freezer compartment 2 also accumulates in the refrigerator compartment 3 through the communication port 23.

Thereafter, since the damper 22 is closed, the convection is eliminated and the combustible refrigerant accumulated in the refrigerator compartment 3 does not flow back into the cooling compartment 19. Then, the defrosting means 18 operates, but since the cooling chamber 19 in which the defrosting means 18 is installed has an air atmosphere, the defrosting is completed without igniting the combustible refrigerant.

(Embodiment 4) Embodiment 4 of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 4 is a sectional view of a main part according to a fourth embodiment of the present invention. As shown in FIG. 4, reference numeral 24 denotes an evaporator pipe forming the evaporator 10, in which a flammable refrigerant is sealed, 25 denotes fins forming the evaporator 10, and 26 denotes a metal. Reference numeral 27 denotes a pipe heater in which a heater wire made of a resistance material is covered with an insulator having good thermal conductivity, and the surface of the insulator is covered with a metal film. Reference numeral 27 denotes a straight pipe portion of a pipe heater 26 in contact with the evaporator 10. is there.

With respect to the refrigerator configured as described above,
The operation will be described below. Pipe heater 2 for defrosting
The heater wire of No. 6 is energized to heat the surface of the pipe heater 26. The heat heated by the pipe heater 26 is transferred from the portion of the evaporator 10 in contact with the straight pipe portion 27 to the entire evaporator 10 by heat conduction, and the heat transferred to the entire evaporator 10 is evaporated by air and radiation. Transfer heat around the vessel.

The heat generated in the portion of the pipe heater 26 other than the straight pipe 27 heats the evaporator 10 and the vicinity of the evaporator 10 by heat transfer and radiation via air.

As described above, the defrosting of the evaporator 10 is performed by the direct heat transfer from the pipe heater 26 and the thermosiphon of the flammable refrigerant in the pipe by the heat transfer, and is made up of the metal surface of the pipe heater 26 and the metal. Since the evaporator 10 is in contact, the temperature difference between the surface of the pipe heater 26 and the evaporator 10 becomes small.

Accordingly, the surface temperature of the pipe heater 26 is not heated to a temperature higher than the temperature at which the frost of the evaporator 10 melts, and the defrosting is completed before the temperature reaches the ignition temperature of the combustible refrigerant.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 5 is a longitudinal sectional view of a main part of a refrigerator compartment according to a fifth embodiment of the present invention. As shown in FIG. 5, reference numeral 28 denotes a heater wire made of a metal resistance material, which is one of the constituent elements of the defrosting means 18, and has the same calorific value, a larger diameter, and a longer overall length as combustible than the conventional one. It is designed to be lower than the ignition temperature of the ionic refrigerant, and is formed in a spiral shape.
Reference numeral 29 denotes one of the components of the defrosting means 18, which is a glass tube having a heater wire 28 installed therein. Further, L is the length of the heater wire 28 after the spiral shape is formed, D is the diameter of the spiral of the heater wire 28, L is the same as the conventional one, and D is large.

With respect to the refrigerator configured as described above,
The operation will be described below. When the heater wire 28 is energized during defrosting, the calorific value per unit length is reduced as compared with the related art, and becomes lower than the ignition temperature of the combustible refrigerant. However, since the calorific value is the same as in the past, defrosting is performed in the conventional manner. From this, defrosting is performed below the ignition temperature of the flammable refrigerant while maintaining the same defrosting ability as before.

In this embodiment, the defrosting means 18 is a glass tube heater in which the heater wire 28 is covered with a glass tube 29. However, any defrosting means using the heater wire 28 can achieve the same effect. Is obtained.

(Embodiment 6) Embodiment 6 of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 6 is a longitudinal sectional view of a main part of a refrigerator according to a sixth embodiment of the present invention. As shown in FIG. 6, reference numeral 31 denotes second defrosting means.

With respect to the refrigerator configured as described above,
The operation will be described below. At the time of defrosting, power is supplied to the defrosting means 18 and the second defrosting means 31, and the defrosting means 18 generates half the amount of heat in the conventional case, and the second defrosting means also generates half the amount of the conventional state. I do. From this, the total heat generation is equal to or higher than the conventional one, so that the defrosting ability higher than the conventional one is ensured.
Since the heat value per unit is halved, the surface temperatures of the defrosting means 18 and the second defrosting means 31 are reduced, and defrosting is performed below the ignition temperature of the combustible refrigerant.

In this embodiment, the second defrosting means 3
1 is installed in the evaporator 10, but is similarly installed by installing the evaporator 10 at a position where the defrosting by the defrosting means 18 and the second defrosting means 31 is equivalent depending on the shape and the frosting state of the evaporator 10. The effect is obtained.

(Embodiment 7) Embodiment 7 of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 7 is a diagram showing the relationship between the resistance change coefficient R of the heater wire 28 and the surface temperature according to the seventh embodiment of the present invention. As a general characteristic of the heater wire 28, the resistance increases as the surface temperature increases. Here, the resistance change coefficient R is a value obtained by dividing a resistance value when the surface temperature of the heater wire 28 rises by an initial value at a low temperature.

Regarding the refrigerator configured as described above,
The operation will be described below. During defrosting, the heater wire 28 is energized and the heater wire 28 is heated by the hot wire resistance method.
Measure the resistance. Then, the resistance change coefficient R is constantly calculated, and the surface temperature is calculated from the relationship between the resistance change coefficient R of the heater wire 28 and the surface temperature T. At this time, when the calculated surface temperature of the heater wire 28 becomes lower than the ignition temperature of the flammable refrigerant, the power supply to the heater wire 28 of the defrosting means 18 is cut off. Thereafter, when the surface temperature of the heater wire 28 decreases to an arbitrary low temperature, the energization is started. By this repetition, the surface temperature of the heater wire 28 is reliably controlled to be lower than the ignition temperature of the flammable refrigerant to perform defrosting.

In this embodiment, the relationship between the resistance change coefficient R and the surface temperature T is as shown in FIG. 7, but since the characteristics differ depending on the material used for the heater wire, the characteristics of the heater wire used are changed. A similar effect can be obtained by grasping.

Embodiment 8 Embodiment 8 of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 8 is a schematic diagram of a main part according to an eighth embodiment of the present invention. As shown in FIG.
Is a voltage variable device that controls a voltage applied to the heater wire 28, which is a component of the first embodiment.

Regarding the refrigerator configured as described above,
The operation will be described below. In the defrosting, the power supply to the heater wire 28 is started after an elapse of an arbitrary time, and the completion of the defrosting is detected by a defrosting completion detecting means (not shown), and the heater wire 28 is defrosted.
The power supply to is stopped, and the defrosting ends. When the surface temperature of the heater wire 28 becomes lower than the ignition temperature of the flammable refrigerant, the voltage applied to the heater wire 28 is reduced by the voltage variable device 32.

(Embodiment 9) Embodiment 9 of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

FIG. 9 is a sectional view of a main part of a refrigerator according to a ninth embodiment of the present invention. As shown in FIG.
The piping in which the flammable refrigerant, which is a component of the above, is enclosed is installed inclined downward.

With respect to the refrigerator configured as described above,
The operation will be described below. At the time of defrosting, the combustible refrigerant in the piping repeats condensation and evaporation above and below the evaporator 10 due to a thermosiphon phenomenon. At this time, the combustible refrigerant condensed at the upper part of the evaporator 10 moves to the lowest pipe 20 through the inclined pipe. At this time, evaporator 1
The inclination of the 0 pipe promotes the movement of the liquid refrigerant from the upper part of the evaporator to the lowermost pipe 20, so that the thermosiphon phenomenon is actively performed, and the defrosting by the thermosiphon is promoted.

[0055]

As described above, the present invention comprises a defrosting means for defrosting an evaporator of a refrigeration cycle using a flammable refrigerant, and the defrosting means comprises a heater wire made of a metal resistive material having a heat conductive property. The pipe heater is covered with a good insulator and the surface of the insulator is covered with a metal film.Since a part of the pipe heater is installed in contact with the fins of the evaporator, it can accelerate the defrosting of the evaporator. The temperature difference between the surface of the pipe heater and the surface of the evaporator is reduced, and the surface temperature of the pipe heater can be reduced.

Also, since a part of the pipe heater is installed near the lowest pipe of the evaporator, the lowermost pipe of the evaporator having a large heat capacity is easily received by the flammable refrigerant having a large latent heat, so that the defrosting is easy. Can be made uniform, defrosting efficiency is improved, and frost residue is eliminated. Further, the operation time of the pipe heater can be reduced, and the surface temperature of the pipe heater can be reduced.

Further, since the surface temperature of the pipe heater is set to be lower than the ignition temperature of the flammable refrigerant, ignition of the flammable refrigerant can be prevented even if defrosting is performed when the flammable refrigerant leaks.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a refrigerator according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part of a refrigerator according to a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a main part of a refrigerator according to a third embodiment of the present invention.

FIG. 4 is a schematic external view of a main part according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a main part according to a fifth embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a main part of a refrigerator compartment according to a sixth embodiment of the present invention.

FIG. 7 is a characteristic diagram of main parts according to a seventh embodiment of the present invention.

FIG. 8 is a schematic diagram of a main part according to an eighth embodiment of the present invention.

FIG. 9 is a schematic external view of a main part according to a ninth embodiment of the present invention.

FIG. 10 is a longitudinal sectional view of a main part of a conventional refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerator main body 2 Freezer room 3 Refrigerator room 10 Evaporator 18 Defrosting means 19 Cooling room 20 Lowest piping 21 Cooling room suction port 24 Evaporator piping 25 Fin 26 Pipe heater 28 Heater wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Nishimura 2-3-1-2 Nojihigashi, Kusatsu-shi, Shiga Prefecture Inside Matsushita Refrigerating Machinery Co., Ltd. No. 1-2 Matsushita Refrigeration Co., Ltd. F term (reference) 3L046 AA05 AA07 BA04 CA04 MA06 MA01 MA04

Claims (3)

[Claims] An evaporator for a refrigeration cycle using a flammable refrigerant, and a cooling chamber provided with defrosting means for defrosting the evaporator, wherein the defrosting means includes a heater wire made of a metal resistance material. A refrigerator comprising a pipe heater covered with an insulator having good thermal conductivity and a surface of the insulator covered with a metal film, and a part of the pipe heater is installed in contact with a fin of an evaporator. 2. The refrigerator according to claim 1, wherein a part of the pipe heater is installed near the lowest pipe of the evaporator. 3. The refrigerator according to claim 1, wherein the surface temperature of the pipe heater is lower than the ignition temperature of the flammable refrigerant.