JPS6142179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting device for removing frost generated in coolers of refrigerators, air conditioners, and the like.

In general, refrigerator coolers or air conditioning equipment coolers are affected by water vapor generated from the items stored in the refrigerator, damp air that enters the refrigerator when the door is opened, or air from outside and indoors. Frost formation occurs due to the temperature difference between the When frost adheres to the cooler, the heat exchange efficiency of the cooler decreases and the cooling capacity decreases. Therefore, in refrigerators, as shown in FIG.
The defrosting heater 2 is attached to the heat exchange fin 3 attached to the
is installed, and every time the refrigerator is operated for a certain period of time, the operation of the refrigerator's cooling device is stopped, the defrosting heater 2 is energized, and the defrosting heater 2 is heated to perform defrosting, thereby preventing the cooling capacity from decreasing. is prevented. In the case of air conditioning equipment, when frost occurs, the operation of the air conditioning equipment is stopped for a certain period of time, and the frost is melted using heat from the outside air to perform defrosting. Refrigerator defrost heater 2
Conventionally, a heater has been used in which a metal heater wire such as a nichrome wire or a nickel/copper wire is housed in a protective tube such as an aluminum pipe.

This conventional defrosting heater 2 is a heater that does not have a self-temperature control function, and has the characteristic of maintaining a constant amount of heat regardless of the amount of frost attached to the cooler and the frost distribution state. The time when defrosting is completed differs for each part. In other words, defrosting is delayed in areas where a large amount of frost has adhered. Conventionally, in order to detect when defrosting has been completed, a temperature detection device such as a thermistor is installed at the part of the cooler 1 that is the latest to complete defrosting, and the temperature is detected while defrosting. Defrosting is considered complete when the temperature is reached. Furthermore, in consideration of cases where the amount of frost increases due to seasonal changes, or when the distribution of frost changes due to differences in the arrangement of stored items, sufficient defrosting should be carried out in both cases. We had no choice but to set defrosting conditions such as temperature and time to ensure that For this reason, the temperature of the portions of the cooler 1 where the amount of frost is small and defrosting is completed quickly increases unnecessarily as the energization time increases. That is, heater 2
As shown in FIG. 2, there is a large temperature difference in the temperature of each part of the cooler 1 at the time when the power supply to the cooler 1 is finished. In FIG. 2, curves 4, 5, and 6 indicate the temperature distribution of the defrosting heater 2, refrigerant pipe 1a, and heat exchange fin 3 at the upper, middle, and lower positions of the cooler 1, respectively. Curve 4 in Figure 2
If the temperature of the cooler 1 becomes unnecessarily high as shown in 5 and 5, it will take a longer time to lower the temperature of the cooler 1 when the cooling operation is restarted after defrosting, and the power consumption will increase. It had the disadvantage of becoming larger. Furthermore, there is a drawback that the electric power required to heat the defrosting heater 2 is unnecessarily large. Another disadvantage is that the temperature of foods stored in the refrigerator tends to rise.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a defrosting device that can defrost efficiently.

In order to achieve the above-mentioned object, the present invention includes at least a conductive material such as carbon, an organic material,
A heater that has a self-temperature control function consisting of a power supply electrode material, and the temperature at which the specific resistance value of the heater increases rapidly, that is, the operating setting temperature is 30 to 110 degrees Celsius.
A heater within the range of 1 is used as a defrosting heater, and defrosting completion is detected using changes in the characteristics of the heater itself, and defrosting is ended.

First, a heater having a self-temperature control function will be explained. FIG. 3 shows a cutaway perspective view of this heater. In FIG. 3, 7 and 7' are electrical conductors for power supply, such as tinned copper wires, arranged in parallel with each other, and 8 is electrical conductor for power supply 7, 7'.
9 is an insulating coating made of urethane rubber, and 10 is a flame-retardant coating made of polyethylene. It is. Next, the operation of this heater 2' will be explained. When a rated voltage is applied between the power supply electric conductors 7 and 7' of the heater 2', the power supply electric conductor 7 is moved from the power supply electric conductor 7 to the heater part 8, which has a self-temperature control function and is made of a mixture of organic material and carbon, and has a self-temperature control function. A current flows to 7', and the heater section 8 generates heat due to Joule heat. The organic material thermally expands due to the temperature rise due to this heat generation, and the fixed resistance of the heater section 8 increases accordingly, and the resistance value increases rapidly as the softening temperature determined by the organic material used is approached. FIG. 4 shows changes in the resistance value of the heater section 8, with the resistance value on the vertical axis and the temperature on the horizontal axis. In FIG. 4, the curve 11 is the heater part 8.
12 shows the resistance change characteristics, and 12 shows the operating setting temperature. Since the specific resistance value of the heater section 8 rapidly increases as the temperature rises, the current decreases, and the temperature rise stops and stabilizes at a constant temperature determined by the organic material.

As described above, if the heater 2' having a self-temperature control function is used as a heater for a defrosting device, the defrosting completion detection can be appropriately performed by the heater 2' itself without separately providing another defrosting completion detection element. be able to. When a heater 2' with a self-temperature control function with an operating temperature setting of 65°C is installed in the cooler 1 of the refrigerator shown in Figure 1, the temperature distribution in each part of the cooler 1 when defrosting is completed is shown. It is shown in FIG.
In FIG. 5, a curve 13 is the temperature of the heater 2' having a self-temperature control function, a curve 14 is the temperature of the refrigerant pipe 1, a curve 15 is the surface temperature of the heat exchange fin 3, and the temperature distribution in each part of the cooler 1. However, compared to the results obtained by the conventional defrosting device shown in FIG. 2, it can be seen that the temperature is uniform and there are no areas that become unnecessarily high temperature.

Next, a device for detecting the completion of defrosting using the heater 2' having a self-temperature control function will be described. FIG. 6 shows temporal changes in the current flowing through the defrosting heater 2' having a self-temperature control function and changes in the temperature of the cooler 1. In FIG. 6, the horizontal axis shows the time since the start of electricity supply to the defrosting heater 2', the vertical axis shows the current flowing through the defrosting heater 2', and the temperature of the cooler 1, and the curve 16 shows the heater current. , curve 17 shows the temperature of the cooler. Immediately after the defrosting heater 2' is energized, an inrush current flows and the temperature rapidly rises, and accordingly the heater current 16 begins to decrease, the temperature of each part of the cooler 1 rises, and defrosting is started. When defrosting of each part of the cooler 1 is started, the rate of decrease of the heater current 16 decreases due to the heat of melting the frost, and the current value becomes approximately constant at point A. When defrosting is completed, the heater current 16 begins to decrease again at point B. In FIG. 6, point B is the point at which defrosting is completed, and 19 indicates the decreasing slope of the heater current after defrosting is completed. Although the time during which the heater 2' is energized varies depending on the amount of frost, the heater current shows a constant current decreasing slope after defrosting is completed. Defrosting completion detection in the defrosting device according to the present invention is performed using this phenomenon.

Next, the block diagram of the defrosting device according to the present invention is shown in Fig. 7.
As shown in the figure. In Fig. 7, 20 is a defrosting heater;
21 is a switch for supplying power to the defrosting heater 20; 22;
23 is a current detection circuit for detecting the current flowing through the defrosting heater 20; 23 is an arithmetic processing circuit equipped with instructions for processing the detection signal generated by the current detection circuit 22; , a control circuit for cutting off the power supply switch 21 to the defrosting heater 20; 18 is a power source; In this device, when the power supply switch 21 is closed, current flows from the power supply 18 to the defrosting heater 20 via the power supply switch 21. When current flows through the defrosting heater 20, the defrosting heater 20 generates heat. The current flowing through the defrosting heater 20 is then supplied to the current detection circuit 22. The current detection circuit 22 detects the current I _T flowing through the defrosting heater 20 at time T.
and the current I _(T+ 〓 _T) at time (T+ΔT), and supplies a signal corresponding to the current I _T and I _(T+ 〓 _T) to the arithmetic processing circuit 23. Arithmetic processing circuit 23
stores the input signal, and the current I _T
and the difference between current I _(T+ 〓 _T) ( _IT − I _(T+ 〓 _T) ) or the decreasing slope of current I _T ( _IT − I _(T+ 〓 _T) )/Δ
Find T by calculation, for example, decreasing slope (I _T −I ₍
After _T+ 〓 _T) )/ΔT becomes a value smaller than the predetermined value a, the decreasing slope (I _T −
When I _(T+ 〓 _T) )/ΔT increases and reaches a value b larger than the value a, an output signal is generated and this output signal is supplied to the control circuit 24. That is,
The arithmetic circuit 23 calculates the decreasing slope (I _T −I _(T+ 〓 _T) )/Δ
Detecting that T has become smaller than the value a,
It is detected that _the current I _T has passed through point A shown in FIG _.
When -I _(T+ 〓 _T) )/ΔT reaches the value b, it is assumed that point B shown in FIG. 6 has been reached, and an output signal is generated. The output signal of the arithmetic circuit 23 is sent to the control circuit 24.
When the power is supplied to the power supply switch 2, the control circuit 24
Release 1. When the power supply switch 21 is opened, the current supplied to the defrosting heater 20 is cut off, and defrosting ends. Note that the current I _T flowing through the heater 20 has a decreasing slope of a value a near point C shown in FIG. 6, and a value b near point D;
After a predetermined time has elapsed after the power supply switch 21 is closed, the current detection circuit 22
detects the current I _T and the length is calculated by the arithmetic circuit 23, so that the power supply switch 21 will not be opened near point D. As described above, the defrosting device according to the present invention detects a change in the current flowing through the defrosting heater 20, and when defrosting is completed, cuts off the current flowing through the defrosting heater to end defrosting.
Note that the operating temperature setting of the heater 2', which has a self-temperature control function, can be changed by changing the organic material of the heater material.
Good results were obtained when the temperature was 110°C. If a heater whose operating temperature is below this temperature range is used as a defrosting heater, it will take a long time to complete defrosting, and for example, in the case of a refrigerator, the temperature of food in the freezer compartment will rise. There is a drawback. Furthermore, when a heater exceeding the upper limit of the above temperature range is used, the temperature of the cooler becomes unnecessarily high and the temperature distribution becomes uneven, similar to the conventional defrosting heater, and the improvement effect is small.

As described above, according to the present invention, it has a self-temperature control function made of a kneaded material of at least a semiconductive organic material and carbon, and the operating temperature is set at 30°C.
By using a heater in the range of ℃ to 110℃ as a defrosting heater, it becomes possible to detect the completion of defrosting by using the change characteristics of the current flowing through the defrosting heater itself, and also to detect the completion of defrosting. This can prevent unnecessary temperature rises in the cooler at times. As a result, the power consumed by the defrosting heater of the refrigerator is reduced, and the power consumption during recooling is also greatly reduced. Further, since a separate detection element is not required to detect the completion of defrosting, the structure is simplified and the number of manufacturing steps is reduced.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the structure of a cooler in a refrigerator, Fig. 2 is a characteristic diagram showing the temperature distribution of each part of the cooler when defrosting is completed when a conventional defrosting heater is used, and Fig. 3 is a partially cutaway perspective view of the defrosting heater used in the defrosting device of the present invention, FIG. 4 is a characteristic diagram of the defrosting heater, and FIG. 5 is a diagram showing defrosting in the defrosting device of the present invention. A characteristic diagram showing the temperature distribution of each part of the cooler at the time of completion of defrosting when a heater is used, FIG. 6 is a characteristic diagram showing changes in current and temperature flowing through the defrosting heater in the defrosting device of the present invention, FIG. 7 is a block diagram showing the configuration of a defrosting device according to the present invention. 1... Cooler, 2', 20... Defrost heater.

Claims (1)

[Claims] 1. A defrosting device for removing frost adhering to the cooler of a refrigerator or air conditioner, which includes at least two electrical conductors for power supply arranged in parallel with each other,
The heater has a heater part made of a mixture of an organic material and carbon that covers these power supply electric conductors and is arranged between the power supply electric conductors, and an insulating coating part that covers the heater part. 1. A defrosting device comprising a heater having a self-temperature control function in which the fixed resistance value of the part increases rapidly at a certain temperature within the range of 30°C to 110°C.