JP2004263889A - Defrosting heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defrosting heater having high safety in the defrosting heater used for a refrigerator using a combustible refrigerant. <P>SOLUTION: A cap 22 is formed with inside space 23a of a first glass tube 23, and holes 22b extending to the outside from respective spaces 24a surrounded by a second glass tube 24 and the first glass tube 23, and a valve 25 is arranged for blocking up the holes 22b. The valve 25 acts as a check valve for releasing pressure to the outside when the inside of the defrosting heater 20 is applied with high pressure, and preventing the intrusion of the combustible refrigerant from the outside under low pressure. Thus, even if the combustible refrigerant leaked out of a refrigerating cycle is filled in the outside of the defrosting heater 20, since the combustible refrigerant does not intrude inside the defrosting heater 20, ignition is not caused, and the defrosting heater is safe. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a defrost heater for removing frost adhering and accumulating on a cooler of a refrigeration cycle, such as a refrigerator, in which a flammable refrigerant is sealed, and a method of assembling the heater.
[0002]
[Prior art]
BACKGROUND ART Various types of defrosting heaters conventionally used in refrigerators are known (for example, see Patent Document 1).
[0003]
Hereinafter, the conventional defrost heater will be described with reference to the drawings.
[0004]
FIG. 4 is a longitudinal sectional view of a main part of a conventional refrigerator. In FIG. 4, the refrigerator main body 1 includes a freezer compartment 2, a refrigerator compartment 3, a freezer compartment door 4, a refrigerator compartment door 5, a partition wall 6 for separating the freezer compartment 2 from the refrigerator compartment 3, and a freezer compartment for sucking air in the freezer compartment 2. Suction port 7, refrigeration chamber suction port 8 for sucking air in refrigeration chamber 3, discharge port 9 for discharging cool air, evaporator 10, fan 11 for circulating cool air, evaporator partition wall separating evaporator 10 and freezer compartment 2. 12 are provided. Below the evaporator 10, a defrost heater 15 in which a coil made of nichrome wire is covered with a glass tube, to prevent evaporation noise generated when defrost water is directly dropped onto the defrost heater 15 and comes into contact therewith. 16 and a metal bottom plate 17 are provided, and the defrost water collected in the tub 13 is drained through a drain port 14.
[0005]
The operation of the defrost heater configured as described above will be described below. When cooling the freezer compartment 2 or the refrigerator compartment 3, the refrigerant flows through the evaporator 10 to cool the evaporator 10. Similarly, by the operation of the fan 11, the heated air in the freezing room 2 or the cooling room 3 is sent from the freezing room suction port 7 or the refrigerating chamber suction port 8 to the cooling chamber 20, and the heat is exchanged by the evaporator 10 for cooling. Then, the cooling air is sent from the discharge port 9 into the freezing compartment 2, and cool air is sent from the freezing compartment 2 to the refrigerating compartment through a communication port (not shown).
[0006]
Here, the air that exchanges heat with the evaporator 10 has high humidity due to 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 moisture contained in the preserved food in the freezer compartment 2 and the refrigerator compartment 3. Because the air is oxidized, the moisture in the air becomes frost and forms frost and accumulates on the evaporator 10 at a lower temperature than the air. In addition, the heat transfer is impaired and the air flow decreases as a result of the ventilation resistance, so that the heat transmission rate decreases and insufficient cooling occurs.
[0007]
Therefore, before the cooling becomes insufficient, the nichrome wire of the defrost heater 15 is energized. When energization of the nichrome wire is started, heat rays are radiated from the nichrome wire to the evaporator 10 and peripheral components. At this time, a part of the heat ray radiated to the bottom plate 17 is reflected by the heater wire from the shape of the bottom plate 17, and the other part is reflected toward the evaporator 10 and other peripheral parts.
[0008]
As a result, the frost that has arrived near the evaporator 10, the tub 13, and the drain 14 is melted into water.
[0009]
A part of the defrosted water thus melted falls directly into the tub 13, and the other falls into the tub 13 by the roof 16, avoiding the defrost heater 15, and is drained out of the refrigerator through the drain 14.
[0010]
[Patent Document 1]
JP-A-8-54172
[Problems to be solved by the invention]
However, in the above-described conventional configuration, generally, the temperature of the glass surface is extremely high, not to mention the surface of the nichrome wire of the defrost heater 15, and the bottom plate 17 is located near the defrost heater 15 and the defrost heater Since a part of the heat ray radiated from 15 is reflected again to the defrost heater 15, the temperature of the glass tube rises abnormally and becomes higher than the ignition temperature of the combustible refrigerant.
[0012]
From this, when the flammable refrigerant is used as the refrigerant, even if the flammable refrigerant leaks from a pipe installed in a portion communicating with the evaporator 10 or the inside of the refrigerator, the energization of the defrost heater -15 is performed. Therefore, there is a problem that it must be prevented from becoming an ignition source.
[0013]
In view of the above problems, an object of the present invention is to provide a defrost heater with high safety even when defrosting is performed in an environment in which a flammable refrigerant has leaked into an installation atmosphere of a defrost heater.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is directed to a defrost heater that removes, by heating, frost adhered and deposited on an evaporator of a refrigeration cycle in which a flammable refrigerant is sealed, wherein the defrost heater includes a glass tube, A heater wire made of a metal resistor installed inside the glass tube, a plug formed with a lead wire insertion hole and covering both ends of the glass tube, and connected to the end of the heater wire through the lead wire insertion hole. And a valve for allowing the gas in the internal space of the glass tube expanded due to a rise in temperature to flow out to the outside. This alleviates the pressure rise in the glass tube and prevents the glass tube from bursting. Furthermore, even if the flammable refrigerant leaks and enters the glass tube and ignites, the flame is blocked by the valve and does not propagate outside the glass tube, so safety is ensured.
[0015]
Next, an invention according to claim 2 is a defrost heater for removing frost adhering and accumulating on an evaporator of a refrigeration cycle in which a flammable refrigerant is sealed, by heating, wherein the defrost heater is connected to a first glass tube. A second glass tube installed so as to cover the outer periphery of the first glass tube, a heater wire made of a metal resistor installed inside the first glass tube, and a lead wire insertion hole formed therein; A plug for covering both ends of the first glass tube and the second glass tube, and a lead wire connected to an end of the heater wire through the lead wire insertion hole; The gas in the expanded inner space of the first glass tube and the gas in the space formed by the outer peripheral surface of the first glass tube, the inner peripheral surface of the second glass tube, and the plug are discharged to the outside. It is provided with a valve to make it run.
[0016]
This alleviates the pressure rise in the glass tube and prevents the glass tube from bursting. Furthermore, even if the flammable refrigerant leaks and enters the first glass tube and ignites, the flame is blocked by the valve and does not propagate to the outside of the first glass tube.
[0017]
Similarly, even if the combustible refrigerant enters the space formed by the outer peripheral surface of the first glass tube, the inner peripheral surface of the second glass tube, and the plug and ignites, the flame is blocked by the valve. Since it is not transmitted to the outside, safety is ensured.
[0018]
Next, according to a third aspect of the present invention, in the first or second aspect of the invention, the stopper is provided with a predetermined hole in advance, and the hole is closed with the valve. This provides a simple configuration in which only a valve is installed in the hole, does not complicate the shape of the plug, and can realize low cost.
[0019]
Next, according to a fourth aspect of the present invention, in the third aspect of the invention, the minimum cross-sectional area of the hole is set to a size such that even if a flammable refrigerant ignites in the glass tube, the flame cannot propagate. Therefore, even if the flammable refrigerant leaks, the flammable refrigerant enters the glass tube and ignites, and even if the valve is missing, the flame cannot propagate through the minimum cross-sectional area of the hole, so safety is reduced. Secured.
[0020]
Next, according to a fifth aspect of the present invention, in the third aspect of the invention, the valve is deformed when the pressure inside the glass tube becomes equal to or higher than a predetermined pressure, and releases the pressure inside the glass tube to the outside. is there. As a result, the pressure in the glass tube can be kept at a certain level or less, and breakage of the glass tube and removal of the plug when the heater is energized can be prevented.
[0021]
Further, even if the flammable refrigerant leaks and is ignited by the heater wire in the glass tube, the flame cannot propagate through the valve, so that safety is ensured.
[0022]
Next, according to a sixth aspect of the present invention, in the first or second aspect, the stopper is provided with a predetermined hole in advance, a cylinder is inserted into the hole, and an opening of the cylinder is provided. Is closed by the valve. Thereby, mounting and positioning of the valve are facilitated, workability is improved, and cost can be reduced.
[0023]
Next, in the invention according to claim 7, in the invention according to claim 1 or 2, the valve releases pressure outside the defrost heater when the inside of the glass tube is at a high pressure, and Is a check valve that closes when the pressure is low and keeps the inside of the glass tube at a low pressure. This can prevent the flammable refrigerant from entering the inside of the glass tube through the valve, and does not ignite inside the glass tube, thereby ensuring higher safety.
[0024]
Next, according to an eighth aspect of the present invention, in the first or second aspect, the diameter of the lead wire insertion hole is smaller than the diameter of the lead wire.
[0025]
As a result, the lead wire insertion hole is sealed with no gap by the lead wire, and even if the flammable refrigerant leaks, it cannot flow into the vicinity of the heater wire through the lead wire insertion hole, so that safety is ensured.
[0026]
Next, according to a ninth aspect of the present invention, in the invention according to the eighth aspect, a sleeve is attached to the lead wire, and then the sleeve is assembled by passing the sleeve through the lead wire insertion hole. The wire can be easily passed through a lead wire insertion hole smaller than the diameter of the lead wire, thereby improving workability and reducing cost.
[0027]
Next, according to a tenth aspect, in the invention according to any one of the first to eighth aspects, the outside of the glass tube is covered with a metal tube. As a result, it is possible to prevent the metal tube from forming an outer shell and directly spraying water on the glass tube.
[0028]
Next, according to an eleventh aspect, in the invention according to the tenth aspect, the surface of the metal pipe is colored. Thereby, the radiation from the metal pipe increases, and the defrosting performance is improved. Further, since the rise in the temperature of the tube surface can be suppressed, it is effective as a means for reducing the surface temperature to the ignition temperature of the combustible refrigerant.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a defrost heater according to the present invention will be described with reference to the drawings.
[0030]
(Embodiment 1)
FIG. 1 is a cross-sectional view of a main part showing a defrost heater according to Embodiment 1 of the present invention.
[0031]
As shown in FIG. 1, the defrost heater 20 includes a heater wire 21 in which a resistance wire is formed in a coil shape, and the vicinity of both ends of the heater wire 21 has a linear connection end 21a instead of a coil shape. The first glass tube 23 that covers the heater wire 21 has a cylindrical shape with an outer diameter of about 10.5 mm and both ends are open.
[0032]
The second glass tube 24 covering the first glass tube 23 has a cylindrical shape with an outer diameter of about 20 mm and both ends opened.
[0033]
The heater wire 21 is connected to a lead wire 26 via a conductive sleeve 28.
[0034]
The stopper 22 made of silicone rubber covers the open ends of the first glass tube 23 and the second glass tube 24. The lead wire 26 is connected to the heater wire 21 through a lead wire insertion hole 22 a provided in the stopper 22. The stopper 22 is provided with an internal space 23 a of the first glass tube 23 and a hole 22 b communicating from the space 24 a surrounded by the first glass tube 23 and the second glass tube 24 to the outside of the stopper 22. Hole 22b has a minimum cross-sectional area of 7.1 square millimeters or less.
[0035]
The rubber valve 25 is attached to the hole 22b via a cylinder 27. The valve 25 acts as a check valve that opens only in one direction with a predetermined pressure difference.
[0036]
FIG. 2 is a schematic diagram of a refrigeration system of a refrigerator using a defrost heater according to an embodiment of the present invention. In FIG. 2, a flammable refrigerant is sealed inside a refrigeration cycle in which a compressor 60, a condenser 61, a decompression mechanism 62 and the evaporator 10 are functionally connected.
[0037]
The operation of the defrost heater configured as described above will be described below. The operation of the compressor 60 cools the evaporator 10 of the refrigerating cycle, and the air in the refrigerator passes through the cooled evaporator 10 by the fan 11 that operates simultaneously with the operation of the compressor 60, and exchanges heat with the evaporator 10. Cooled air is discharged into the refrigerator. Then, after an arbitrary operation time of the compressor 60 has elapsed, the operation of the compressor 60 is also stopped. At this time, the heater wire 21 is simultaneously energized through the lead wire 26 to cause the defrost heater 20 to generate heat.
[0038]
When the heater wire 21 generates heat, a part of the radiant heat ray is directly transmitted to the outside, but the other part is transmitted to the first glass tube 23 and the second glass tube 24, and the surface of the second glass tube 24 becomes a flammable refrigerant. The temperature rises to below the ignition temperature of, and heat is radiated to the outside to safely defrost peripheral components.
[0039]
At this time, in the internal space 23a of the first glass tube 23 and the space 24a surrounded by the first glass tube 23 and the second glass tube 24, the gas inside expands due to a rise in temperature. Since the gas is discharged from the valve 25 to the outside, the glass tube is not broken or the stopper 22 does not come off due to an increase in the internal pressure. In this state, when the power supply to the heater wire 21 is stopped and cooling is started again, the inside of the glass tube is depressurized due to the temperature drop. However, the inside of the defrost heater 20 is depressurized because the outside air is prevented by the valve 25. Keep. Therefore, even if the flammable refrigerant is present around the defrost heater 20, the flammable refrigerant hardly flows into the defrost heater 20 and the possibility of ignition can be extremely reduced.
[0040]
Even if the combustible refrigerant flows into the glass tube for some reason and the ignition is caused by the heater wire 21, the valve 25 is opened slightly when the pressure becomes equal to or higher than a predetermined pressure, thereby preventing the internal pressure from rising too much. Only because the flame is shut off by the valve, it is possible to prevent the flame from propagating to the outside.
[0041]
Also, even if the valve is missing for some reason, the flame is set to a size that does not allow the flame to pass through the hole 22b, so that the flame cannot be transmitted to the outside, and higher safety is secured. In the present embodiment, the minimum cross-sectional area of the hole 22b is set to 7.1 square millimeters or less.
[0042]
The valve 25 is attached to the stopper 22 via the cylinder 27. If the rubber valve 25 is directly attached to the rubber stopper 22, the position of the valve 25 is difficult to determine, which causes a variation in valve opening pressure. There remains a problem in terms of assembly workability. Therefore, by attaching the valve 25 to the cylinder 27, the valve opening pressure is stabilized, and the assembling workability is improved. Further, since the valve opening pressure of the valve 25 can be changed by changing the dimensions of the mounting portion of the valve 27 in the cylinder 27, it is easy to set the optimum valve opening pressure based on the calorific value of the heater, the internal volume of the glass tube, and the like. .
[0043]
As shown in FIG. 3, the diameter d of the lead wire insertion hole 22 a of the plug 22 is configured to be smaller than the diameter D of the lead wire 26. Therefore, after assembling, the lead wire 26 is held in a state of being tightened by the stopper 22, and outside air does not flow through this portion.
[0044]
Since the lead wire 26 is made of a soft coating such as silicon rubber, it is difficult to pass through the lead wire insertion hole 22a as it is. Therefore, first, the sleeve 28 is attached to the tip of the lead wire 26. The sleeve 28 is passed through the lead wire insertion hole 22a to facilitate the assembly.
[0045]
In the above-described embodiment, the description has been given of the case where the glass tube has a double structure. However, if the surface temperature of the glass tube is equal to or lower than the ignition point of the flammable refrigerant, the structure may be single. Can adapt.
[0046]
In the above-described embodiment, the outside of the surface of the glass tube is exposed, but the outside of the glass tube may be covered with a metal tube. As a result, it is possible to prevent the metal tube from forming an outer shell and directly spraying water on the glass tube.
[0047]
Furthermore, if the surface of the metal tube is colored (for example, black), the radiation from the metal tube increases, and the defrosting performance is improved. In addition, since the rise in the temperature of the tube surface can be suppressed, it is effective as a means for reducing the surface temperature to the ignition temperature of the combustible refrigerant.
[0048]
Further, in the above-described embodiment, a refrigerator is described as an example of an apparatus to which the defrost heater is applied. However, the present invention is not limited to this, and may be a so-called cooling storage provided with an evaporator. It can be widely applied to showcases and vending machines equipped with a refrigeration cycle filled with a flammable refrigerant.
[0049]
【The invention's effect】
As described above, the invention according to claim 1 is a defrosting heater that removes, by heating, frost adhering and accumulating on an evaporator of a refrigeration cycle in which a flammable refrigerant is sealed. A heater wire formed of a metal resistor, a plug having a lead wire insertion hole formed therein and covering both ends of the glass tube, and a lead wire connected to the end of the heater wire through the lead wire insertion hole. Since the valve is provided in the stopper with a valve for allowing gas in the internal space of the glass tube expanded due to a rise in temperature to flow out, even if ignition occurs inside the glass tube, the valve prevents flame propagation to the outside. Can be prevented.
[0050]
According to a second aspect of the present invention, there is provided a defrosting heater for removing frost adhered and deposited on an evaporator of a refrigeration cycle in which a flammable refrigerant is sealed by heating, the first glass tube and the first glass. A second glass tube installed so as to cover the outer periphery of the tube, a heater wire made of a metal resistor installed inside the first glass tube, and a lead wire insertion hole formed in the first glass tube and the first glass tube; A plug that covers both end openings of the second glass tube, and a lead wire that is connected to an end of the heater wire through the lead wire insertion hole, wherein the first plug that expands due to a rise in temperature is attached to the plug. A valve is provided for allowing gas in the internal space of the glass tube and gas in the space formed by the outer peripheral surface of the first glass tube, the inner peripheral surface of the second glass tube, and the plug to flow out. Therefore, even if ignition occurs inside the glass tube, The flame propagation to the outside can be prevented Te.
[0051]
According to a third aspect of the present invention, in the first or second aspect of the invention, the stopper is provided with a predetermined hole in advance and the hole is closed by the valve, so that the structure is simple. Thus, the inside and outside of the glass tube can be physically blocked, and the shape of the plug is not complicated, and a low-cost defrost heater can be realized.
[0052]
According to a fourth aspect of the present invention, in the third aspect of the invention, the minimum cross-sectional area of the hole is set to a size such that the flame cannot propagate even if the flammable refrigerant ignites in the glass tube. Therefore, safety can be ensured even if the stopper is missing.
[0053]
According to a fifth aspect of the present invention, in the third aspect of the invention, the valve is deformed when the pressure inside the glass tube becomes equal to or higher than a predetermined pressure, and releases the pressure inside the glass tube to the outside. The pressure in the glass tube can always be kept below a certain level, and the breakage of the glass tube and the removal of the plug when the heater is energized can be prevented.
[0054]
According to a sixth aspect of the present invention, in the first or second aspect of the invention, the stopper is provided with a predetermined hole in advance, a cylinder is inserted into the hole, and an opening of the cylinder is provided. Is closed by the valve, thereby stabilizing the valve opening pressure. In addition, since the valve opening pressure of the valve can be changed by changing the dimensions of the mounting portion of the valve in the cylinder, it is easy to set the optimum valve opening pressure based on the calorific value of the heater, the internal volume of the glass tube, and the like. Further, since the valve can be easily mounted, workability is improved and cost can be reduced.
[0055]
The invention according to claim 7 is the invention according to claim 1 or 2, wherein the valve releases pressure to the outside of the defrost heater when the inside of the glass tube is at a high pressure, and When the pressure is low, the valve closes to provide a check valve that keeps the inside of the glass tube at a low pressure, so that the flammable refrigerant leaked to the outside hardly enters the inside of the glass tube, and extremely high safety is achieved. Can have.
[0056]
The invention according to claim 8 is the invention according to claim 1 or 2, wherein the diameter of the lead wire insertion hole is smaller than the diameter of the lead wire, so that At the same time, it is possible to prevent the flame from propagating to the outside even if ignition occurs inside the glass tube.
[0057]
According to a ninth aspect of the present invention, in the invention of the eighth aspect, a sleeve is attached to the lead wire, and then the sleeve is assembled by passing the sleeve through the lead wire insertion hole. The cost can be improved.
[0058]
According to a tenth aspect of the present invention, in the invention according to any one of the first to eighth aspects, the outside of the glass tube is covered with a metal tube. As a result, it is possible to prevent the metal tube from forming an outer shell and directly spraying water on the glass tube.
[0059]
The invention according to claim 11 is the invention according to claim 10, wherein the surface of the metal tube is colored. Thereby, the radiation from the metal pipe increases, and the defrosting performance is improved. Further, since the rise in the temperature of the tube surface can be suppressed, it is effective as a means for reducing the surface temperature to the ignition temperature of the combustible refrigerant.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of a first embodiment of a defrost heater according to the present invention. FIG. 2 is a schematic diagram of a refrigeration system of a refrigerator using the defrost heater of the first embodiment. Exploded view of defrost heater [Figure 4] Schematic vertical sectional view of refrigerator equipped with conventional defrost heater [Explanation of reference numerals]
Reference Signs List 20 defrost heater 21 heater wire 22 plug 22a lead wire insertion hole 22b hole 23 first glass tube 24 second glass tube 25 valve 26 lead wire 27 cylinder 28 sleeve

Claims (11)

In a defrost heater that removes frost adhering and accumulating on an evaporator of a refrigeration cycle containing a combustible refrigerant by heating,
The defrost heater includes a glass tube, a heater wire made of a metal resistor installed inside the glass tube, a plug having a lead wire insertion hole formed therein to cover both ends of the glass tube, and the lead wire insertion hole. And a lead wire connected to the end of the heater wire through
A defrost heater characterized in that a valve is provided on the stopper so that gas in the internal space of the glass tube expanded due to a rise in temperature flows out to the outside. In a defrost heater that removes frost adhering and accumulating on an evaporator of a refrigeration cycle containing a combustible refrigerant by heating,
The defrost heater includes a first glass tube, a second glass tube installed so as to cover an outer periphery of the first glass tube, and a metal resistor installed inside the first glass tube. A wire, a plug having a lead wire insertion hole formed therein and covering both end openings of the first glass tube and the second glass tube, and a lead connected to the end of the heater wire through the lead wire insertion hole. With a line,
The plug was formed by the gas in the internal space of the first glass tube expanded by the temperature rise, and the outer peripheral surface of the first glass tube, the inner peripheral surface of the second glass tube, and the plug. A defrost heater characterized by having a valve for allowing gas in the space to flow out. The defrost heater according to claim 1 or 2, wherein a predetermined hole is provided in the stopper in advance, and the hole is closed by the valve. 4. The defrost heater according to claim 3, wherein the minimum cross-sectional area of the hole is set to a size that does not allow the flame to propagate even if the flammable refrigerant ignites in the glass tube. 5. 4. The defrost heater according to claim 3, wherein the valve is deformed when the pressure inside the glass tube becomes equal to or higher than a predetermined pressure, and releases the pressure inside the glass tube to the outside. 5. The defrost heater according to claim 1 or 2, wherein a predetermined hole is provided in advance in the stopper, a cylinder is inserted into the hole, and an opening of the cylinder is closed with the valve. . The valve is a check valve that releases pressure to the outside of the defrost heater when the inside of the glass tube is at a high pressure, and closes when the inside of the glass tube is at a low pressure to keep the inside of the glass tube at a low pressure. The defrost heater according to claim 1 or 2, characterized in that: 3. The defrost heater according to claim 1, wherein a diameter of the lead wire insertion hole is smaller than a diameter of the lead wire. 4. The method for assembling a defrost heater according to claim 8, wherein a sleeve is attached to the lead wire, and then the sleeve is assembled by passing the sleeve through the lead wire insertion hole. The defrost heater according to any one of claims 1 to 8, wherein the outside of the glass tube is covered with a metal tube. The defrost heater according to claim 10, wherein the surface of the metal tube is colored.

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