JPS589351B2 - Reiki Yakukino Chiyaku Kenchi Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frost detection circuit for a cooler that automatically detects frost on a cooler such as a refrigerator and automatically starts defrosting.

Conventionally, the removal of frost that has adhered to the cooler has been carried out periodically using a long-term timer. Therefore, even if the cooling efficiency of the cooler decreases due to heavy frost formation, defrosting will continue until a certain period of time has elapsed. On the other hand, there is a drawback that the defrosting device is operated periodically even when there is no frost.

In order to eliminate these drawbacks, a method has been proposed that automatically detects frost formation by detecting the temperature of the air in the cooler coil and its vicinity and taking advantage of the fact that the temperature difference between the two increases due to frost formation. There is.

However, due to temperature difference, when cooling starts after turning on the power and completing defrosting, there is a time delay in the fall of the air temperature with respect to the fall of the coil temperature, so the temperature difference between the two is equivalent to that at the time of frosting. This has the disadvantage of causing malfunctions that are even more widespread than those described above.

For this reason, a timer for about one hour is used to shut off the frost formation detection circuit until cooling is stabilized to prevent malfunctions at the start of cooling, but the timer still has the disadvantage that it is expensive and takes up a lot of space.

This invention was made in consideration of the above points, and defrosts using a memory circuit that is set when the cooling compressor motor is shifted from operation to stop, and an AND circuit of the output of a differential amplifier. By starting, it is intended to eliminate the drawbacks of the conventional ones mentioned above.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 1 is a first temperature sensor for detecting the temperature of the cooler coil, 2 is a second temperature sensor for detecting the temperature of the air cooled by the cooler, and NTC thermistor. etc. are used, and are connected to the DC power supply 5 via voltage dividing resistors 3 and 4, respectively.

Both the intersections of the first and second temperature sensors 1 and 2 and the voltage dividing resistors 3 and 4 become inputs a and b of the first operational amplifier 6, and the first and second temperature sensors 1 and 2, i.e. Detects the temperature difference between the cooler and the air.

Further, one end d of the input of the second operational amplifier 7 receives a signal from the second temperature sensor 2 that detects the air temperature, and the other end e
The intersection of resistors 8 and 9 connected to the DC power supply 5 terminal is connected to the resistor 9, and by making the resistor 9 variable, the air temperature, that is, the temperature inside the refrigerator is adjusted.

10 is a flip-flop circuit whose output Q is at a low potential (hereinafter referred to as "L") after the power is turned on and reset, but the output f of the second differential amplifier 7 changes from "L" to a high potential (
(hereinafter referred to as "H"), it becomes a set signal, and the output Q becomes "H" and maintains that state until a reset signal comes.

11 is an AND circuit which receives the output c of the first differential amplifier 6 and the output Q of the flip-flop 10, and both inputs are "H".
”, the output also becomes “H”, and the transistor 12
The defrosting drive relay 13 is operated via the .

Further, a signal at the completion of defrosting in which the output of the AND circuit 11 switches from "H" to "L" is applied to the reset of the flip-flop 10.

A transistor 14 is controlled by the output f of the second differential amplifier 7, and controls the compressor motor 16 via the contact 15S of the relay 15 to adjust the temperature inside the refrigerator.

17 is a heater for defrosting, and relay 13 is the output of the frost detection circuit.
It is connected to the AC power supply 18 via the contact 13S.

Note that contacts 13S and 15S in FIG. 1 are relays 13 and 15.
1 indicates a state where it is not driven.

Next, the operation will be explained.

In the above configuration, when the DC power source 5 and the AC power source 18 are applied, each part changes as shown in FIG. 2.

That is, in FIG. 2, A indicates the change in temperature T1 of the first temperature sensor 1 of the cooler coil and temperature T2 of the second temperature sensor 2 of the air, and the temperature T2 is higher than the set temperature determined by the resistor 9. If so, the compressor motor 16 is operated to continue cooling.

When the air is cooled, the resistance value of the second temperature sensor 2 becomes NT.
In the case of a C thermistor, when the temperature reaches the set temperature, the potential of the input d of the second differential amplifier 7 becomes higher than the potential of the input e determined by the resistor 9, and the output f also changes from "L" to "H". ”, and the relay 15 is connected via the transistor 14.
7 to stop the compressor motor 16.

When the air temperature in the refrigerator increases due to the stop of the compressor motor 16, the resistance value of the second temperature sensor 2 decreases, the potential of the input d decreases, and the output f of the second differential amplifier 7 becomes "L".
”, the compressor motor 16 is operated again for cooling.

In this way, the temperature T2 inside the refrigerator is kept constant, but as frost builds up on the cooler, the heat exchange efficiency of the cooler decreases, so the temperature T2 is kept constant.
2 increases, the temperature T1 of the cooler coil decreases, and the temperature difference between the two (T2-T1) increases as shown in B in FIG. 2 in proportion to frost formation.

As shown in E of FIG. 2, the output Q of the flip-flop 10 changes when the compressor motor 16 stops operating after the power supplies 5 and 18 are applied, that is, the output f of the second differential amplifier 7 changes from "L" to " The output Q changes from "L" to "H" and remains in that state until a reset signal is received at the completion of defrosting.

On the other hand, at the start of operation, the drop in air temperature T2 is delayed compared to the temperature drop in the cooler coil due to the internal volume and heat transfer, and the temperature difference (T2 - T1) is The value is equal to or greater than .

When the temperature difference (T2-T1) is large, the potentials Va and Vb of the inputs a and b of the first differential amplifier 6 become (Va>Vb), and the output c becomes "H".

However, since the defrosting operation is performed by using the output c and the output Q of the flip-flop 10 via the AND circuit 11, at the start of operation, the output Q of the flip-flop 10 is "L" as described above. Therefore, the temperature difference (T2
1; Defrosting is not performed even if T1) is large.

The defrosting operation starts at time t when the flip-flop 10 is set.
When the temperature difference (T2'rt) becomes large after 1, that is, at time t2 when frost formation on the cooler is large, both the two inputs of the AND circuit 11 become "H", the output 5 also becomes "H". '', the relay 13 is driven via the transistor 12, and its contact 13S disconnects the compressor motor 16 and energizes the defrosting heater 17.

When defrosting starts, for example, input b side and transistor 12
A clamp circuit on the input b side consisting of a series circuit of a diode (with input b side as an anode) 19 and a low resistor 20 is inserted between the collectors of Since the potential Vb on the b side is kept at a low potential, defrosting is completed when the temperature T1 of the cooling coil becomes below the potential at point b.

If the potential at point b when the transistor 12 is on is set to an appropriate value by the low resistor 20, the cooler can be defrosted effectively.

When T1 reaches the defrosting completion temperature, the output C of the first differential amplifier 6 becomes "L", and the output of the AND circuit 11 also becomes "H".
to "L", cutting off the drive of the relay 13, and at the same time, the clamp circuit on the input b side is also turned off, temperature regulating operation begins, and cooling begins.

At this time, the flip-flop 10 is reset by the change in the output of the AND circuit 11, that is, from "H" to "L", and the output Q
holds "L" until it is set by the transition signal from operation to stop of the compressor smoker 16, so the temperature difference (
Malfunctions due to large T2-T1) are also prevented.

After the compressor smoker 16 shifts from operation to stop at time t4, the cooling operation and stop are repeated until the temperature difference (T2-T1) is large, that is, the cooling capacity is reduced due to frost formation.

In the above description, NTC thermistors were used as the first and second temperature sensors 1 and 2, but various other temperature sensors may be used.

Further, as the flip-flop 10, a thyristor or other memory circuit that utilizes a holding characteristic or other memory circuits may be used.

Furthermore, output stage transistors 12, 14 and relay 13
, 15, etc. can be controlled by a thyristor, and the defrosting heater 17 may be one that allows hot gas to flow into the cooler.

Furthermore, it goes without saying that the present invention is applicable not only to refrigerators but also to other cooling devices such as freezers and showcases.

As explained in detail above, this invention uses a memory circuit that is set when the compressor motor stops operating and is reset when defrosting is completed, and a temperature difference between the cooler temperature and the air temperature. An AND circuit is provided to obtain the AND of both outputs, and the output of this AND circuit is used to drive the defrosting heater, ensuring reliable frost detection without malfunctions even when cooling is started. This enables efficient cooler operation and provides the ideal cooling air temperature.

Furthermore, since the memory circuit and the AND circuit can be integrated circuits, the invention can be constructed compactly and economically, and the practical value of this invention is extremely great.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a timing chart showing the operation of each part of the embodiment of FIG. In the figure, 1 and 2 are the first and second temperature sensors, and 6 and 7 are the first temperature sensors.
, a second differential amplifier, 10 a flip-flop, 11 an AND circuit, 16 a combinator motor, and 17 a defrosting heater.

Claims (1)

[Claims] 1 a first temperature sensor that detects the temperature of the cooler coil;
A second temperature sensor detects the temperature of the cooled air, a circuit detects a temperature difference between the two temperature sensors, and a compressor motor for the cooler, and the temperature detected by the second temperature sensor is a predetermined value. In the cooler, the compressor motor is operated to perform cooling when the temperature exceeds 100%, and the compressor motor is operated to perform defrosting when the temperature difference between the first and second temperature sensors reaches a certain value. a memory circuit that is set when the temperature is stopped and reset when defrosting is completed, and an AND circuit that performs a logical product between the output of this memory circuit and the output of the temperature difference detection circuit, and uses the output to start defrosting. A frost detection circuit for a cooler, comprising: